Patent Publication Number: US-2023149993-A1

Title: Cell phone frame and method for manufacturing the same

Description:
TECHNICAL FIELD 
     The present invention relates to the technical field of cell phone accessories, more particularly, to a cell phone frame and a method for manufacturing the same. 
     BACKGROUND ART 
     The advent of the age of intelligence has witnessed an increasing demand of people for cell phones. Cell phone manufacturers are trying their best in innovating and redesigning various features of cell phones to attract consumers. Many processes and methods have been tried in manufacturing a cover plate, an important part of a cell phone, which, however, has often been ended up with failures, therefore, the choice of method is extremely critical because it directly affects the yield and production efficiency. 
     A steel-aluminum composite plate is advantageous by combining the high strength and good plasticity of steel and good electrical conductivity, thermal conductivity, corrosion resistance, and low density of aluminum. Steel-aluminum composite plates are common in subway contact rails in rail transit, vehicle body materials of automobiles and high-speed trains, and bearing shell materials of engines. A variety of heat sinks and cookware made of steel/aluminum composite materials have been launched in the market because of the good thermal conductivity of aluminum. In addition, the steel-aluminum composite plate has a wide application in many fields such as machinery, ships, nuclear energy, and electric power. Especially with the development of smartphones and 5G technology, the steel-aluminum composite plate has also been applied to the production of the smartphone frame because of its unique properties. 
     However, due to the great difference in material properties (deformation resistance, plasticity, thermal conductivity, melting point, etc.) between steel and aluminum materials, manufacturing a steel-aluminum composite plate is challenging. In the process of rolling to produce a steel/aluminum composite plate, it is difficult to achieve the high bonding strength of the final composite plate due to the different properties of steel and aluminum. 
     SUMMARY OF THE INVENTION 
     The present invention provides a cell phone frame to solve the problem of the low bonding strength of the cell phone frame in the prior art. 
     The present invention provides a cell phone frame, including:
         a composite plate, the composite plate enclosing a receiving space for receiving a cell phone, the composite plate including a first plate and a second plate, wherein a first side surface of at least one of the first plate and the second plate is provided with striations, the first side surface of the second plate and the first side surface of the first plate are rolled to connect, and the striations of which adjacent striations have a pitch of 0.005 mm to 0.03 mm account for more than 90% of all the striations.       

     According to the cell phone frame provided in an embodiment of the present invention, a side of the composite plate facing the receiving space is provided with a recess extending along a length direction of the composite plate. 
     According to the cell phone frame provided in an embodiment of the present invention, the cell phone frame includes two composite plates, a first end of the composite plate forms a first bent portion towards the receiving space, a second end of the composite plate forms a second bent portion towards the receiving space, and the two composite plates are connected by the first bent portion and the second bent portion. 
     According to the cell phone frame provided in an embodiment of the present invention, the striations of which adjacent striations have a pitch of 0.01 mm to 0.02 mm account for more than 90% of all the striations. 
     According to the cell phone frame provided in an embodiment of the present invention, the striations of which adjacent striations have a pitch of 0.01 mm to 0.02 mm account for more than 80% of all the striations. 
     According to the cell phone frame provided in an embodiment of the present invention, the striations of which adjacent striations have a pitch of 0.01 mm to 0.02 mm account for more than 70% of all the striations. 
     According to the cell phone frame provided in an embodiment of the present invention, the striations of which adjacent striations have a pitch of 0.01 mm to 0.02 mm account for more than 50% of all the striations. 
     According to the cell phone frame provided in an embodiment of the present invention, the first side surface of the first plate has a roughness of 0.8 Ra to 4.0 Ra. 
     According to the cell phone frame provided in an embodiment of the present invention, the first side surface of the second plate has a roughness of 4 Ra to 10 Ra. 
     According to the cell phone frame provided in an embodiment of the present invention, the first plate has a greater hardness than the second plate. 
     According to the cell phone frame provided in an embodiment of the present invention, the first plate is a stainless steel plate, and the second plate is an aluminum plate. 
     According to the cell phone frame provided in an embodiment of the present invention, the composite plate has a shear strength τ=a*b*K1*K2*σ soft , a is a length of the first plate, b is a width of the first plate, K1 is a roughened area ratio of the first plate, and a value range of K1 is 1.5 to 3; K2 is a degree of bonding between the first plate and the second plate, a value range of K2 is 0.15 to 0.3, and when K1*K2&gt;1, a product of K1 and K2 takes a value of 1; σ soft  is a yield strength of the second plate, and a value range of σ soft  is 350 MPa to 412 MPa. 
     According to the cell phone frame provided in an embodiment of the present invention, the first plate has an elongated shape, and a length direction of the striations and a width direction of the first plate is at a preset angle. 
     The present invention provides a method for manufacturing a cell phone frame, including steps of:
         roughening the first side surface of the first plate and/or the first side surface of the second plate;       

     Rolling the first plate and the second plate asynchronously to obtain the composite plate;
         treating the composite plate by a bending process; and   welding the composite plate treated by a bending process to obtain a cell phone frame.       

     According to the method for manufacturing a cell phone frame provided in an embodiment of the present invention, the step of roughening the first side surface of the first plate and/or the first side surface of the second plate includes:
         rubbing the first side surface of the first plate and/or the first side surface of the second plate with a roughening friction roller to form the striations; and   removing debris from a surface of the first plate and/or the second plate.       

     According to the method for manufacturing a cell phone frame provided in an embodiment of the present invention, after the step of removing debris from a surface of the first plate and/or the second plate, further including:
         acquiring a number of striations per unit area of the first side surface of the first plate or the first side surface of the second plate;   determining that the number of striations per unit area of the first side surface of the first plate or the first side surface of the second plate is smaller than a corresponding preset value, and controlling a lifting component to increase a height of the roughening friction roller.       

     According to the method for manufacturing a cell phone frame provided in an embodiment of the present invention, the step of rolling the first plate and the second plate asynchronously includes:
         heating the first plate and the second plate; and   rolling the heated first plate and the heated second plate asynchronously so that the first side surface of the second plate and the first side surface of the first plate are rolled to connect and produce the composite plate.       

     According to the method for manufacturing a cell phone frame provided in an embodiment of the present invention, after the step of rolling the heated first plate and the heated second plate asynchronously, further including:
         subjecting the composite plate to a solid solution treatment; and   subjecting the composite plate to aging treatment after the solid solution treatment.       

     According to the method for manufacturing a cell phone frame provided in an embodiment of the present invention, the solution treatment is performed at 480° C. to 540 ° C. for 45 min to 65 min; the aging treatment is performed at 160° C. to 200° C. for 5 h to 7 h. 
     According to the method for manufacturing a cell phone frame provided in an embodiment of the present invention, the first plate and the second plate feature a thickness ratio of 1.5:1.0; a differential speed ratio of the roller corresponding to the first plate to the roller corresponding to the second plate is 1:1.05, and a reduction rate of the asynchronous rolling is 20% to 40%. 
     According to the method for manufacturing a cell phone frame provided in an embodiment of the present invention, before the step of treating the composite plate by a bending process, further including:
         straightening the composite plate.       

     According to the method for manufacturing a cell phone frame provided in an embodiment of the present invention, the step of straightening the composite plate includes:
         straightening the composite plate in a thickness direction; and       

     Straightening the composite plate in a width direction. 
     According to the method for manufacturing a cell phone frame provided in an embodiment of the present invention, before the step of welding the composite plate treated by a bending process, further including:
         shearing the composite plate treated by a bending process.       

     According to the cell phone frame provided in an embodiment of the present invention, the first side surface of the first plate is roughened to form striations, which increases the area of the first plate and the second plate subjected to rolling, so that a composite plate produced by combining the first plate and the second plate has a higher bonding strength, thereby ensuring that the cell phone frame is firmer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To explain the technical solutions of the present invention or the prior art more clearly, the following will briefly introduce the drawings necessary for the description of the embodiments or the prior art. Apparently, the drawings in the following description illustrate only some embodiments of the present invention, other drawings may be obtained by those of ordinary skills in the art based on these drawings without inventive work. 
         FIG.  1    is a schematic view showing a structure of a first plate according to an embodiment of the present invention; 
         FIG.  2    is a schematic cross-sectional view of a composite plate according to an embodiment of the present invention; 
         FIG.  3    is a partially enlarged structural view at A in  FIG.  2    according to an embodiment of the present invention; 
         FIG.  4    is a schematic view showing a structure of a cell phone frame according to an embodiment of the present invention; 
         FIG.  5    is a schematic view showing a structure of the composite plate treated by a bending process according to an embodiment of the present invention; 
         FIG.  6    is a first schematic view showing a structure of a composite plate roughening device according to an embodiment of the present invention; 
         FIG.  7    is a second schematic view showing the structure of the composite plate roughening device according to an embodiment of the present invention; 
         FIG.  8    is a flow chart showing a method for manufacturing a cell phone frame according to an embodiment of the present invention; 
         FIG.  9    is a first schematic view showing how to treat the composite plate by a bending process according to the embodiment of the present invention; 
         FIG.  10    is a second schematic view showing how to treat the composite plate by a bending process according to the embodiment of the present invention; 
         FIG.  11    is a third schematic view showing how to treat the composite plate by a bending process according to the embodiment of the present invention; 
         FIG.  12    is a fourth schematic view showing how to treat the composite plate by a bending process according to the embodiment of the present invention; 
         FIG.  13    is a fifth schematic view showing how to treat the composite plate by a bending process according to the embodiment of the present invention; 
         FIG.  14    is a schematic view showing how to straighten the composite plate according to an embodiment of the present invention. 
     
    
    
     Reference signs:  1 . unwinding device;  2 . camera;  3 . roughening friction roller;  4 . dedusting roller;  5 . first plate;  6 . chamber;  7 . partition;  8 . control terminal;  9 . controller;  10 . lifting component;  11 . support roller;  12 . dust collector;  13 . air jet port;  14 . striation;  15 . tension control means;  16 . second plate;  17 . first speed sensor;  18 . second speed sensor;  19 . third speed sensor;  20 . first straightening means;  21 . second straightening means;  22 . first bent portion;  23 . second bent portion;  24 . bending machine;  25 . composite plate;  26 . cell phone frame. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The implementation of the present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments. The following embodiments illustrate the present invention, without limiting the scope of the present invention. 
     In the description of the embodiments of the present invention, it should be noted that such terms as “center”, “longitudinal”, “transverse”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer” and others indicating directional or positional relations are based on the positions or positional relations shown in the drawings, intended only to facilitate the description rather than indicate or imply that the device or element must have a specific orientation or must be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present invention. In addition, such terms as “first”, “second”, and “third” are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance. 
     In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and defined, such terms as “connection” and “coupling” should be understood in a broad sense. For example, the connection may be a fixed connection, a detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate. For those of ordinary skill in the art, the specific meanings of the above-mentioned terms in the embodiments of the present invention can be interpreted depending on specific situations. 
     In the embodiments of the present invention, unless otherwise clearly defined and specified, a first feature being “on” or “under” a second feature may include direct contact between the first and second features, or indirect contact through an intermediate. Moreover, the first feature being “on”, “above” and “over” the second feature may indicate that the first feature is directly above or obliquely above the second feature, or simply the level of the first feature is higher than that of the second feature. The first feature being “below”, “under” and “beneath” the second feature may indicate that the first feature is directly below or obliquely below the second feature, or simply the level of the first feature is lower than the second feature. 
     In the description of this specification, descriptions with reference to such terms as “one embodiment”, “some embodiments”, “examples”, “specific examples”, or “some examples” indicate that specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic representations of the above-mentioned terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials, or characteristics can be combined in any one or more embodiments or examples as appropriate. In addition, those skilled in the art can combine different embodiments or examples and the features of the different embodiments or examples described in this specification without contradicting each other. 
     A composite plate, a composite plate roughening device, and a method for manufacturing according to embodiments of the present invention will be described below with reference to  FIGS.  1  to  14   . 
     As shown in  FIGS.  1  to  5   , the cell phone frame  26  includes the composite plate  25 , wherein the composite plate  25  encloses a receiving space for receiving the cell phone, the receiving space is shaped to fit the cell phone, and the width of the composite plate  25  is adapted to the thickness of the cell phone. The composite plate  25  includes a first plate  5  and a second plate  16 , the first side surface of the first plate  5  is provided with striations  14 , the first side surface of the second plate  16  and the first side surface of the first plate  5  are rolled to connect, and the striations  14  of which adjacent striations  14  have a pitch of 0.005 mm to 0.03 mm account for more than 90% of all the striations. It&#39;s tested that the shear strength of the composite plate is between 210 MPa and 245 MPa when the striations  14  of which adjacent striations  14  have a pitch of 0.005 mm to 0.03 mm account for more than 90% of all the striations. 
     It should be noted here that the number of the composite plate  25  may be one, in which case an end-to-end connection of the composite plate  25  forms a closed frame. Certainly, the number of the composite plates  25  may be two, three, or more, in which case the composite plates  25  are sequentially connected to form a closed frame. 
     According to the composite plate  25  provided in the embodiment of the present invention, the first side surface of the first plate  5  is roughened so that the first side surface of the first plate  5  is provided with the striations  14 , which increases the area of the first plate  5  and the second plate  16  subjected to rolling, hence the composite plate  25  produced by combining the first plate  5  and the second plate  16  has higher bonding strength, thereby ensuring that the cell phone frame  26  is firmer. 
     According to the embodiment of the present invention, one side of the composite plate  25  facing the receiving space is provided with a recess extending along the length direction of the composite plate  25 . The cell phone has its edge snapped into the recess when placed in the receiving space so that the cell phone frame  26  is secured around the cell phone. The cross section of the recess is C-shaped or U-shaped, and can be shaped as appropriate according to a profile of the edge of the cell phone. 
     According to the embodiment of the invention, the striations  14  of which adjacent striations  14  have a pitch of 0.01 mm to 0.02 mm account for more than 90% of all the striations. The more uniform the striations  14  are and the smaller the pitch between two adjacent striations  14  is, the greater the number of the striations  14  per unit area is, the larger the area subjected to rolling of the first plate  5  and the second plate  16  is, and thus the higher the bonding strength is of the composite plate  5  formed by bonding the first plate  5  and the second plate  16 . It&#39;s tested that the shear strength of the composite plate is between 200 MPa and 230 MPa when the striations  14  of which adjacent striations  14  have a pitch of 0.01 mm to 0.02 mm account for more than 90% of all the striations. 
     According to an embodiment of the invention, the striations  14  of which adjacent striations  14  have a pitch of 0.01 mm to 0.02 mm account for more than 80% of all the striations. It&#39;s tested that a shear strength of the composite plate is between 190 MPa and 225 MPa when the striations  14  of which adjacent striations  14  have a pitch of 0.01 mm to 0.02 mm account for more than 80% of all the striations. 
     According to an embodiment of the invention, the striations  14  of which adjacent striations  14  have a pitch of 0.01 mm to 0.02 mm account for more than 70% of all the striations. It&#39;s tested that a shear strength of the composite plate is between 185 MPa and 220 MPa when the striations  14  of which adjacent striations  14  have a pitch of 0.01 mm to 0.02 mm account for more than 70% of all the striations. 
     According to an embodiment of the invention, the striations  14  of which adjacent striations  14  have a pitch of 0.01 mm to 0.02 mm account for more than 50% of all the striations. It&#39;s tested that a shear strength of the composite plate is between 170 MPa and 210 MPa when the striations  14  of which adjacent striations  14  have a pitch of 0.01 mm to 0.02 mm account for more than 50% of all the striations. 
     According to an embodiment of the present invention, as shown in  FIG.  5   , the cell phone frame  26  includes two composite plates  25 , a first end of the composite plate  25  is formed with a first bent portion  22  towards the receiving space, and a second end of the composite plate  25  is formed with a second bent portion  23  towards the receiving space. Two modes are possible for connecting two composite plates  25 . For convenience of description, the two composite plates  25  are referred to as a first composite plate and a second composite plate, respectively. The two modes for connecting the two composite plates  25  are described below. 
     Mode 1: 
     The first bent portion  22  of the first composite plate is welded to the first bent portion  22  of the second composite plate, and the second bent portion  23  of the first composite plate is welded to the second bent portion  23  of the second composite plate. 
     It should be noted here that the first bent portion  22  of the first composite plate and the first bent portion  22  of the second composite plate may be equal lengthwise or not. The second bent portion  23  of the first composite plate and the second bent portion  23  of the second composite plate may be equal lengthwise or not, but a total length of the first bent portion  22  of the first composite plate and the first bent portion  22  of the second composite plate is equal to a total length of the second bent portion  23  of the first composite plate and the second bent portion  23  of the second composite plate. 
     Mode 2: 
     The first bent portion  22  of the first composite plate is welded to the second bent portion  23  of the second composite plate, and the second bent portion  23  of the first composite plate is welded to the first bent portion  22  of the second composite plate. 
     It should be noted here that the first bent portion  22  of the first composite plate and the second bent portion  23  of the second composite plate may be equal lengthwise or not. The second bent portion  23  of the first composite plate and the first bent portion  22  of the second composite plate may be equal lengthwise or not, but a total length of the first bent portion  22  of the first composite plate and the second bent portion  23  of the second composite plate is equal to a total length of the second bent portion  23  of the first composite plate and the first bent portion  22  of the second composite plate. 
     According to an embodiment of the invention, the striations  14  are straight striations, and the straight striations are arranged at intervals, and the pitch between two adjacent striations  14  may be consistent or not. 
     Herein, it should be noted that the striation  14  of the embodiment of the present invention refers to a groove formed in the first side surface of the first plate  5  and/or the first side surface of the second plate  16 , and a depth of the groove is determined by the pressure applied to the roughening friction roller  3  when it works. 
     According to an embodiment of the invention, the striations  14  of which adjacent striations  14  have a pitch of 0.005 mm to 0.03 mm account for more than 90% of all the striations. The more uniform the striations  14  are and the smaller the pitch between two adjacent striations  14  is, the greater the number of the striations  14  per unit area is, the larger the area subjected to rolling of the first plate  5  and the second plate  16  is, and thus the higher the bonding strength is of the composite plate  25  formed by bonding the first plate  5  and the second plate  16 . 
     According to an embodiment of the present invention, the first plate  5  has an elongated shape, there is a preset angle between a length direction of the striations  14  and a width direction of the first plate  5 , and the preset angle in this embodiment may be, but is not limited to, 70° to 82°. The striations  14  of the first plate  5  serve to increase the contact area between the first plate  5  and the second plate  16  during rolling. 
     According to an embodiment of the present invention, the hardness of the first plate  5  is greater than the hardness of the second plate  16 ; since the hardness of the second plate  16  is smaller, the second plate  16  is deformed during rolling, and the second plate  16  enters the grooves of the striations  14  of the first plate  5 ; after the first plate  5  is cooled, the pitch of the striations  14  is reduced, and the second plate  16  is closely attached to the first plate  5  in the grooves of the striations  14 , forming an interference fit, thereby bonding the first plate  5  and the second plate  16  tightly. 
     Herein, HV refers to Vickers hardness in kg/mm2. Vickers hardness is defined as the ratio of a load to an area of indentation formed on a surface of a specimen when a positive tetragonal diamond indenter is pressed into the surface of the specimen with the load and held for a while before unloading the test force. 
     According to the embodiment of the present invention, the first plate  5  is a stainless steel plate, and the second plate  16  is an aluminum alloy plate; however, the materials of the first plate  5  and the second plate  16  are not limited thereto, and can be selected as appropriate. Herein, the stainless steel plate may be a stainless steel plate containing various alloy components and a stainless steel plate containing various non-metal elements, or a stainless steel plate with various metallographic structures; certainly, the first plate  5  may also be a steel plate coated with a plating layer on a surface; the aluminum alloy plate may be an aluminum alloy plate containing various alloys and various proportions of components. 
     According to the embodiment of the present invention, the hardness of the first plate  5  is HV 270 to HV 330, the hardness of the second plate  16  is HV 50 to HV 70, the roughness of the first side surface of the first plate  5  is 0.8 Ra to 4.0 Ra, the roughness of the first side surface of the second plate  16  is 4 Ra to 10 Ra, where Ra is an arithmetic average roughness. 
     According to an embodiment of the present invention, the shear strength of the composite plate  25  is τ=a*b*K1*K2*σ soft , wherein a is a length of the first plate  5 , b is a width of the first plate  5 , K1 is a roughened area ratio of the first plate  5 , and a value range of K1 is 1.5 to 3; K2 is a degree of bonding between the first plate  5  and the second plate  16 , a value range of K2 is 0.15 to 0.3, and when K1*K2&gt;1, a product of K1 and K2 takes a value of 1; σ soft  is a yield strength of the second plate  16 , and a value range of σ soft  is 350 MPa to 412 MPa. MPa is the unit of pressure, M denotes Mega, and Pa denotes Pascal. 
     A specific embodiment of the invention is described below in connection with  FIGS.  1 ,  2  and  3   . In  FIGS.  1  and  2   , the composite plate  25  includes the first plate  5 , which is a stainless steel plate, and the second plate  16 , which is an aluminum alloy plate. The first side surface of the stainless steel plate is provided with the striations  14 , wherein the striations  14  are straight striations arranged at intervals. The striations  14  of which adjacent ones have a pitch of 0.02 mm account for more than 90% of all the striations  14 . The stainless steel plate has an elongated shape, an angle of 78° is included between the length direction of the striations  14  and the width direction of the stainless steel plate, the hardness of the stainless steel plate is I-IV  300 , and the roughness of the first side surface of the stainless steel plate is 2 Ra. 
     A thickness ratio of the stainless steel plate to the aluminum alloy plate is 1.5:1.0, and the roughness of the first side surface of the aluminum alloy plate is 3 Ra. The first side surface of the aluminum alloy plate and the first side surface of the stainless steel plate are rolled to connect to form the composite plate  25 , wherein the shear strength of the composite plate  25  is τ=a*b*K1*K2*σ soft , a is the length of the stainless steel plate, b is the width of the stainless steel plate, K1 is the roughened area ratio of the stainless steel plate, and K1 takes a value of 2; K2 is the degree of bonding between the stainless steel plate and the aluminum alloy plate, and K2 takes a value of 0.2; when K1*K2&gt;1, the product of K1 and K2 is 1; σ soft  is the yield strength of aluminum alloy plate, and σ soft  takes a value of 380 MPa. 
     Embodiments of the present invention provide a composite plate  25  in which the first side surface of the first plate  5  and/or the first side surface of the second plate  16  are roughened so that the first side surface of the first plate  5  and/or the first side surface of the second plate  16  are provided with the striations  14  to increase the area of the first plate  5  and the second plate  16  subjected to rolling, hence the composite plate  25  produced after the first plate  5  and the second plate  16  are combined has a higher bonding strength and thus a stronger bonding. The composite plate  25  produced by rolling according to the embodiment of the present invention has a high shear forth and features a strong bonding, which satisfies the design requirement. The resulting composite plate  25  has a strong bonding strength and is suitable to be machined as a cell phone frame, in which case, it satisfies the requirement of minimal signal shielding for a cell phone and a low ratio of strength to weight. 
     The present invention also provides a composite plate roughening device, as shown in  FIGS.  6  and  7   , for use in the manufacture of the composite plate according to any of the embodiments described above. The composite plate roughening device includes a roughening means, the roughening means includes a machine body, a first driving member and at least one roughening friction roller  3  rotatably disposed on the machine body, and the roughening friction roller  3  is configured for rubbing the first side surface of the first plate  5  or the first side surface of the second plate  16 . there is a preset angle between an axis of the roughening friction roller  3  and a first direction, and the preset angle is 70° to 82° in this embodiment. The first driving member is configured for driving the roughening friction roller  3  to rotate axially, and the first driving member includes a first motor and a first transmission member, wherein a rotating shaft of the first motor is connected to the roughening friction roller  3  via the first transmission member, the first transmission member can be a combination of a belt and a pulley, a combination of a gear and a chain, or a combination of a plurality of gears, and the specific structure of the first transmission member is not limited by examples herein, as long as the roughening friction roller  3  can be driven to rotate. 
     Herein, it should be noted that as shown in  FIG.  6   , a second direction is a left-right direction in  FIG.  6   , and the first direction is a front-rear direction in  FIG.  6   . When the roughening means works, the first plate  5  or the second plate  16  moves in the second direction and comes into contact with the roughening friction roller  3 , and the rotating roughening friction roller  3  rubs the first side surface of the first plate  5  or the first side surface of the second plate  16 , so that the first side surface of the first plate  5  or the first side surface of the second plate  16  is provided with the striations  14 . 
     According to an embodiment of the present invention, the roughening friction roller  3  includes a steel wire brush roller, the steel wire brush roller includes a cylindrical roller body and plurality of steel wire brushes wrapping an outer peripheral surface of the cylindrical roller body, each composed of plurality of brush filaments. The hardness of the brush filament of the steel wire brush roller is HRC  55  to HRC  60 , the pressure applied to the steel brush roller when it works is 1 MPa to 1.5 MPa, the diameter of the steel brush roller is 250 mm to 400 mm, the steel wire brush roller rotates at a speed of 400 r/min to 600 r/min, the length of the brush filament is 10 mm to 40 mm, the density of the brush filaments is more than 60%, and the diameter of the brush filament is 0.3 mm to 0.5 mm. The pressure applied to the steel wire brush roll when it works determines the depth and number of the striations  14 , and the diameter of the brush filament determines the width of the striation  14 . The pressure applied to the steel brush roller when it works and the diameter of the brush filament are determined as appropriate. 
     HRC in the examples of the present invention refers to Rockwell hardness, which was proposed by S. P. Rockwell in  1921 . The hardness value of a metal material measured with a Rockwell hardness tester is represented by “HR” rather than a physical unit. HRC is a hardness obtained by using a 150 Kg load and a diamond cone indenter for very hard materials, for example, quenched steel, etc. It is measured by pressing a steel ball or a diamond indenter vertically into a surface of a material to be tested to generate a dent under a specified external load, and calculating the Rockwell hardness as per a formula, i.e., HR=(K−H)/C, according to a depth of the dent after the load is released. The Rockwell hardness value is displayed on a dial of a durometer and can be read directly. 
     According to an embodiment of the present invention, the roughening friction roller  3  includes a grinding wheel with a mesh number of 40 to 120, the pressure applied to the grinding wheel when it works is 0.1 MPa to 0.5 MPa, and the diameter of the grinding wheel is 200 mm to 400 mm. The pressure applied to the grinding wheel when it works determines the depth and number of the striations  14 , and the mesh number of the grinding wheel determines the width of the striation  14 . 
     According to an embodiment of the present invention, the roughening means further includes a dedusting component, the dedusting component includes a dedusting roller  4  rotatably disposed on the machine body and having an axis extending in the first direction, and a second driving member. The roughening friction roller  3  and the dedusting roller  4  are successively arranged at intervals along the second direction, two support rollers  11  rotatably connected to the machine body are disposed above each of the roughening friction roller  3  and the dedusting roller  4 , and the two support rollers  11  are spaced apart. The support roller  11  is configured for cooperating with the roughening friction roller  3  and the dedusting roller  4 , so as to limit the first plate  5  or the second plate  16  subjected to the roughening treatment and ensure that the roughening friction roller  3  and the dedusting roller  4 , respectively, have good contact with the plate. The second driving member is configured for driving the dedusting roller  4  to rotate axially and includes a second motor and a second transmission member, and a rotating shaft of the second motor is connected to the dedusting roller  4  via the second transmission member. The second transmission may be a combination of a belt and a pulley, a combination of a gear and a chain, or a combination of a plurality of gears. The dedusting roller  4  is a brush roller to remove debris from the surface of the first plate  5  or the second plate  16  upon contact with the first side surface of the first plate  5  or the first side surface of the second plate  16 . 
     In the working process of the roughening means, the first side surface of the first plate  5  or the first side surface of the second plate  16  is roughened by the roughening friction roller  3 , and then the debris is removed from the surface of the first plate  5  or the second plate  16  by the dedusting roller  4 , so as to ensure that the roughened surface of the first plate  5  or the roughened second plate  16  is clean, and then the subsequent work such as rolling is performed. 
     Herein, it should be noted that only one dedusting roller  4  is provided in this embodiment, but two or more dedusting rollers  4  may be provided as appropriate. The debris includes, but is not limited to, metal debris and dust, but may be other substances. 
     According to an embodiment of the present invention, the dedusting component further includes a dust collector  12  provided at an outer periphery of at least one of the roughening friction roller  3  and the dedusting roller  4 , and air jet ports  13 . The dust collector  12  is connected to a negative pressure device via a pipeline, and the dust collector  12  can suck up the dust near the roughening friction roller  3  and the dedusting roller  4  to prevent air pollution. The air jet ports  13  are disposed in the machine body on a side of the dedusting roller  4  facing away from the roughening friction roller  3 . The air jet port  13  is connected to an air supply device via a pipeline, and the air supply device provides a high-speed air flow to the air jet ports  13 . In this embodiment, the air jet ports  13  are arranged in two rows up and down, and the two rows of air jet ports  13  are spaced at a certain distance to facilitate the passage of the first plate  5  or the second plate  16 . When the first plate  5  or the second plate  16  passes through the space between the upper and lower rows of air jet ports  13 , the air jet ports  13  jet a high-speed air flow to the first plate  5  or the second plate  16  to remove debris from the surface of the first plate  5  or the second plate  16  and ensure a clean surface of the first plate  5  or the second plate  16  so that the camera  2  can capture a clear image, facilitating subsequent rolling and other processes. 
     According to an embodiment of the present invention, the roughening means further includes a housing, wherein the machine body is disposed inside the housing, partitions  7  are arranged at intervals inside the housing to divide the interior of the housing into a plurality of chambers  6 , and the roughening friction roller  3  and the dedusting roller  4  are respectively positioned in corresponding chambers  6 . The partition  7  between two adjacent chambers  6  is provided with through holes (not shown) which facilitate the passage of the first plate  5  or the second plate  16 . Because of the partitions  7  inside the housing, the interior of the housing is divided into a plurality of smaller chambers  6 , which enhances the dedusting effect of the dust collector  12 . 
     According to an embodiment of the present invention, the roughening means further includes a lifting component  10  connected to the roughening friction roller  3  for changing the height of the roughening friction roller  3 . The outer diameter of the roughening friction roller  3  is reduced if the roughening friction roller  3  rubs the first plate  5  or the second plate  16  for a period of time, so the number of striations  14  formed in the roughening process falls short of the design requirement. Therefore, it is necessary to increase the height of the roughening friction roller  3  by the lifting component  10  so that the roughening friction roller  3  is in full contact with the first side surface of the first plate  5  or the first side surface of the second plate  16 . In this embodiment, the lifting component  10  is a lead screw component composed of a servo motor and a lead screw, a sliding block of the lead screw component is connected to the roughening friction roller  3 , and the servo motor drives the lead screw to rotate, thereby pushing the roughening friction roller  3  to slide up and down and then changing the height of the roughening friction roller  3 . Certainly, the type of the lifting component  10  is not limited thereto, as long as the roughening friction roller  3  can be driven. 
     According to an embodiment of the present invention, the composite plate roughening device further includes a detection means, and the detection means includes a control terminal  8 , a controller  9 , and a camera  2 . The camera  2  is positioned below the first plate  5  or the second plate  16 , and the camera  2  faces towards the first side surface of the first plate  5  or the first side surface of the second plate  16 , that is, the camera  2  is oriented upwards. The camera  2  is configured to acquire image information of the first side surface of the first plate  5  or the first side surface of the second plate  16 . The controller  9  is electrically connected to the lifting component  10 , and the controller  9  is configured for controlling the lifting component  10  to start and stop. The control terminal  8  is electrically connected to the controller  9  and the camera  2 , respectively, and the control terminal  8  is configured for determining that the number of striations per unit area of the first side surface of the first plate  5  or the first side surface of the second plate  16  is greater than a corresponding preset value or determining that the number of striations per unit area of the first side surface of the first plate  5  or the first side surface of the second plate  16  is smaller than the corresponding preset value, and controlling the lifting component  10  to increase the height of the roughening friction roller  3 . 
     According to an embodiment of the present invention, the composite plate roughening device further includes an unwinding means  1  provided at a side of the roughening friction roller  3  facing away from the dedusting roller  4  for winding the first plate  5  or the second plate  16  and releasing the first plate  5  or the second plate  16  under the traction of the driving component, and a tension control means  15 . The tension control means  15  is provided on the side of the dusting roller  4  facing away from the roughening friction roller  3 , and the tension control means  15  is configured for driving the first plate  5  or the second plate  16  to move in the second direction and to tension it as appropriate. The tension control means  15  is composed of a plurality of cylindrical bars and a driving motor, wherein the driving motor is connected to the cylindrical bars, the first plate  5  or the second plate  16  is clamped between the cylindrical bars and driven to move along the second direction by rotating the cylindrical bars. Driven by the tension control means  15 , the first plate  5  or the second plate  16  is released from the unwinding means  1  with a preset tension and sequentially passes through the roughening friction roller  3  and the dedusting roller  4 . 
     An embodiment of the invention is described below in connection with  FIGS.  6  and  7   . In  FIGS.  6  and  7   , the composite plate roughening device includes the roughening means, the detection means, the unwinding means  1 , and the tension control means  15 , wherein the unwinding means  1 , the roughening means and the tension control means  15  are successively arranged along the second direction, namely, the unwinding means  1  is positioned left to the roughening means, and the tension control means  15  is positioned right to the roughening means. 
     The roughening means includes the machine body, the first driving member, two roughening friction rollers  3 , the dedusting component, the housing, and the lifting component  10 , wherein the machine body is disposed inside the housing, the two roughening friction rollers  3  are rotatably disposed on the machine body, the roughening friction rollers  3  are configured for rubbing the first side surface of the first plate  5  or the first side surface of the second plate  16 , there is a preset angle between the axis of the roughening friction rollers  3  and the first direction, and the preset angle is 80° in this embodiment. The first driving member includes the first motor and the first transmission member, wherein the rotating shaft of the first motor passes through the first transmission member and the roughening friction roller  3 , and the first transmission member can be a combination of a belt and a pulley, a combination of a gear and a chain, or a combination of a plurality of gears. 
     The roughening friction roller  3  includes the steel wire brush roller, the steel wire brush roller includes the cylindrical roller body and a plurality of steel wire brushes wrapping the outer peripheral surface of the cylindrical roller body, each composed of a plurality of brush filaments. The hardness of the brush filament of the steel wire brush roller is HRC  55 , the pressure applied to the steel wire brush roller when it works is 1.5 MPa, the diameter of the steel wire brush roller is 300 mm, the steel wire brush roller rotates at a speed of 500 r/min, the length of the brush filament is 30 mm, the density of the brush filaments is more than 60%, and the diameter of the brush filament is 0.35 mm. 
     The dedusting component includes the dedusting roller  4 , the second driving member, the dust collector  12  and the air jet port  13 , the dedusting roller  4  being rotatably disposed in the machine body, the axis of the dedusting roller  4  extending in the first direction. The roughening friction roller  3  and the dedusting roller  4  are successively arranged at intervals in the second direction, and the dedusting roller  4  is positioned right to two roughening friction rollers  3 . Two support rollers  11  rotatably connected to the machine body are disposed above each of the roughening friction roller  3  and the dedusting roller  4 , and the two support rollers  11  are spaced apart. The support roller  11  cooperates with the roughening friction roller  3  and the dedusting roller  4  to limit the first plate  5  or the second plate  16  and ensure that the roughening friction roller  3  and the dedusting roller  4  are in good contact with the plate, respectively. The second driving member is configured for driving the dedusting roller  4  to rotate axially and includes the second motor and the second transmission member, wherein the rotating shaft of the second motor is connected to the dedusting roller  4  via the second transmission member, and the second transmission member can be a combination of a belt and a pulley, a combination of a gear and a chain, or a combination of a plurality of gears. The dedusting roller  4  is a brush roller that removes debris from the surface of the first plate  5  and/or the second plate  16  by contacting the first side surface of the first plate  5  or the first side surface of the second plate  16 . 
     When working, the roughening means roughens the first side surface of the first plate  5  or the first side surface of the second plate  16  with the roughening friction roller  3 , and then removes the debris from the surface of the first plate  5  or the second plate  16  with the dedusting roller  4 , so as to ensure that the surface of the first plate  5  or the second plate  16  after roughening is clean, and then the subsequent work such as rolling is performed. 
     Three dust collectors  12  are provided, wherein two dust collectors  12  are disposed on the periphery of the roughening friction roller  3 , and the other dust collector  12  is disposed on the periphery of the dedusting roller  4 ; the dust collectors  12  are connected to the negative pressure device via a pipeline; the dust collectors  12  can suck up dust near the roughening friction roller  3  and the dedusting roller  4  to prevent air pollution. 
     A plurality of air jet ports  13  are provided, and the air jet ports  13  are provided in the machine body on a side of the dedusting roller  4  facing away from the roughening friction roller  3 , namely, the air jet ports  13  are positioned right to the dedusting roller  4 . The air jet port  13  is connected to the air supply device via a pipeline, and the air supply device provides a high-speed air flow to the air jet port  13 . In this embodiment, the air jet ports  13  are arranged in two rows up and down, and the two upper and lower rows of air jet ports  13  are spaced apart at a certain distance so as to facilitate the passage of the first plate  5  or the second plate  16 . When the first plate  5  or the second plate  16  passes through space between the upper and lower rows of air jet ports  13 , the air jet ports  13  jet a high-speed air flow to the first plate  5  or the second plate  16  to further remove debris from the surface of the first plate  5  or the second plate  16  and ensure that the surface of the first plate  5  or the second plate  16  is clean and the camera  2  can capture a clear image, and thus avoid the influence on rolling the first plate  5  and the second plate  16 . 
     Two partitions  7  are arranged at intervals inside the housing to divide the interior of the housing into three chambers  6 , two roughening friction rollers  3  are disposed in two chambers  6  in a one-to-one correspondence, and the dedusting roller  4  is disposed in the other chamber  6 . The partition  7  between two adjacent chambers  6  is provided with through holes to facilitate the passage of the first plate  5  and the second plate  16 . With the partitions  7  that divide the interior of the housing into a plurality of smaller chambers  6 , the dedusting effect of the dust collector  12  is enhanced. 
     The lifting component  10  is connected to the roughening friction roller  3  for changing the height of the roughening friction roller  3 . The brush filament will be worn after the first side surface of the first plate  5  or the first side surface of the second plate  16  are treated by the roughening friction roller  3  for a period of timewhile, and the outer diameter of the roughening friction roller  3  is reduced, as a result, the number of the striations  14  generated by the roughening treatment falls short of the design requirement. Therefore, it is necessary to increase the height of the roughening friction roller  3  with the lifting component  10  so that the roughening friction roller  3  is in full contact with the first side surface of the first plate  5  or the first side surface of the second plate  16 . In this embodiment, the lifting component  10  is a lead screw component composed of a servo motor and a lead screw, a sliding block of the lead screw component is connected to the roughening friction roller  3 , and the servo motor drives the lead screw to rotate, thereby pushing the roughening friction roller  3  to slide up and down and changing the height of the roughening friction roller  3 . Certainly, the lifting component  10  is not limited this type, and other types are possible. 
     The detection means includes the control terminal  8 , the controller  9 , and the camera  2 , wherein the camera  2  is positioned below the first plate  5  or the second plate  16  and faces the first side surface of the first plate  5  or the first side surface of the second plate  16 , and the camera  2  is configured for acquiring image information about the first side surface of the first plate  5  or the first side surface of the second plate  16 . The controller  9  is electrically connected to the lifting component  10  and configured for controlling the lifting component  10  to start and stop. The control terminal  8  is electrically connected to the controller  9  and the camera  2 , respectively, and configured for determining that the number of striations per unit area of the first side surface of the first plate  5  or the first side surface of the second plate  16  is greater than a corresponding preset value, or determining that the number of striations per unit area of the first side surface of the first plate  5  or the first side surface of the second plate  16  is smaller than the corresponding preset value, and controlling the lifting component  10  to increase the height of the roughening friction roller  3 . 
     The unwinding means  1  is provided on a side of the roughening friction roller  3  facing away from the dedusting roller  4  and configured for winding the first plate  5  or the second plate  16  and releasing the first plate  5  or the second plate  16  under the traction of the tension control means  15 . 
     The tension control means  15  is provided on a side of the dedusting roller  4  facing away from the roughening friction roller  3 , the tension control means  15  is provided right to the dedusting roller  4  and configured for driving the first plate  5  or the second plate  16  to move in the second direction. The tension control means  15  is composed of a plurality of cylindrical bars and a driving motor, wherein the driving motor is connected to the cylindrical bars, the first plate  5  or the second plate  16  is clamped between the cylindrical bars and driven to move in the second direction by rotating the cylindrical bars. Driven by the tension control means  15 , the first plate  5  or the second plate  16  is released from the unwinding means  1  with a preset tension, and the roughening friction roller  3  can be brought into good contact with the first plate  5  or the second plate  16  by tensioning the first plate  5  or the second plate  16 . 
     The composite plate roughening device provided in the embodiment of the present invention roughens the first side surface of the first plate  5  so that the first side surface of at least one of the first plate  5  and the second plate  16  is provided with the striations  14 , which increases the area of the first plate  5  and the second plate  16  subjected to rolling, hence the composite plate produced by rolling the first plate  5  and the second plate  16  has a higher bonding strength and thus a stronger bonding. The composite plate produced with the composite plate roughening device of the present invention has a high shear force and features a tight bonding, which satisfies the design requirement. The resulting composite plate has a strong bonding strength and is suitable to be machined as a cell phone frame, and it satisfies the requirement of minimal signal shielding for a cell phone and a low ratio of strength to weight. 
     The present invention also provides a method for manufacturing a cell phone frame  26  according to any of the above embodiments. As shown in  FIG.  8   , the method for manufacturing a cell phone frame includes the steps as follows. 
     Step  100 , the first side surface of at least one of the first plate  5  and the second plate  16  is rubbed by the roughening friction roller  3  to form the striations  14 ; 
     the roughening process is to form groove-like straight striations in the first side surface of at least one of the first plate  5  and the second plate  16 . 
     In the process of contacting with the first side surface of the first plate  5  or the first side surface of the second plate  16 , the roughening friction roller  3  rubs to form the striations  14 ; the roughening friction roller  3  rotates at a constant speed, and the first plate  5  and the second plate  16  move at a constant speed in the second direction, so the striations  14  formed in the first side surface of the first plate  5  and the first side surface of the second plate  16  are straight striations arranged at intervals, and there is a preset angle between the straight striations and the width direction of the first plate  5  or the second plate  16 . The striations  14  of which adjacent ones have a pitch of 0.005 to 0.03 mm account for more than 90% of all the striations  14 . The roughening treatment may be performed once, or may be performed two or more times. 
     Step  200 , the first plate  5  and the second plate  16  are asynchronously rolled to obtain the composite plate. 
     Step  300 , the composite plate  25  is treated by a bending process; 
     As shown in  FIGS.  9  to  13   , the bending process mainly includes: bending the first end of the composite plate  25  firstly by a bending machine  24  so that the first end of the composite plate  25  forms the first bent portion  22  towards the receiving space; and bending the second end of the composite plate  25  by the bending machine  24  so that the second end of the composite plate  25  forms the second bent portion  23  towards the receiving space. Finally, the composite plate  25  is sheared, and the resulting composite plate  25  treated by the bending process is U-shaped. 
     Certainly, it is possible to bend only the first end of the composite plate  25  by the bending machine  24 , and then the composite plate  25  is sheared; at this time, the composite plate  25  is L-shaped, and four L-shaped composite plates  25  are successively connected to form a rectangular cell phone frame  26 . 
     Step  400 , the composite plate  25  treated by a bending process is welded to obtain the cell phone frame  26 . 
     In this embodiment, both the first side surface of the first plate  5  and the first side surface of the second plate  16  are subjected to the roughening treatment, although only the first side surface of the first plate  5  may be subjected to the roughening treatment. 
     According to an embodiment of the present invention, the roughening friction roller includes the steel wire brush roller, the hardness of the brush filament of the steel wire brush roller is HRC  55  to HRC  60 , the pressure applied when the steel wire brush roller works is 1 MPa to 1.5 MPa, the diameter of the steel wire brush roller is 250 mm to 400 mm, the steel wire brush roller rotates at the speed of 400 r/min to 600 r/min, the length of the brush filament is 10 mm to 40 mm, and the diameter of the brush filament is 0.3 mm to 0.5 mm; 
     alternatively, the roughening friction roller includes the grinding wheel, the mesh number of the grinding wheel is 40 to 120, the pressure applied when the grinding wheel works is 0.1 MPa to 0.5 MPa, and the diameter of the grinding wheel is 200 mm to 400 mm. 
     According to an embodiment of the invention, the striations of which adjacent striations have a pitch of 0.005 mm to 0.03 mm account for more than 90% of all the striations. 
     According to an embodiment of the present invention, before rolling the first plate  5  and the second plate  16  asynchronously, the method further includes: 
     step  110 , removing debris from a surface of at least one of the first plate  5  and the second plate  16 . 
     Debris on the surface of the first plate  5  or the second plate  16  can be removed during the rotation of the dedusting roller  4 ; when the first plate  5  or the second plate  16  moves to a position between the upper and lower rows of the air jet ports  13 , the air jet ports  13  emit a high-speed air flow to the first plate  5  or the second plate  16  to further remove debris from the surface of the first plate  5  or the second plate  16  and ensure that the surface of the first plate  5  or the second plate  16  is clean and the camera  2  can capture a clear image, and thus avoid the influence on combining the first plate  5  and the second plate  16 . 
     According to an embodiment of the present invention, after the step of removing the debris from the surface of at least one of the first plate  5  and the second plate  16 , the method further includes: 
     step  120 , acquiring the number of striations per unit area of the first side surface of the first plate  5  or the first side surface of the second plate  16 ; 
     acquiring, by the camera  2 , image information of the first side surface of the first plate  5  or the first side surface of the second plate  16 , and transmitting the image information to the control terminal  8 . 
     In step  130 , the number of striations per unit area of the first side surface of the first plate  5  or the first side surface of the second plate  16  is determined to be smaller than a corresponding preset value, and the lifting component  10  is controlled to increase the height of the roughening friction roller  3 . 
     When the control terminal  8  determines that the number of striations per unit area of the first side surface of the first plate  5  or the first side surface of the second plate  16  is smaller than the corresponding preset value, the control terminal  8  sends a control instruction to the controller  9 , and the controller  9  controls the lifting component  10  to rise according to the control instruction, thereby increasing the height of the roughening friction roller  3  and bringing the roughening friction roller  3  into close contact with the first side surface of the first plate  5  or the first side surface of the second plate  16 . 
     The number of striations per unit area of the first side surface of the first plate  5  or the first side surface of the second plate  16  is determined to be greater than the corresponding preset value. The control terminal  8  calculates the number of striations per unit area according to the acquired image information, and if the number of striations per unit area of the first side surface of the first plate  5  or the first side surface of the second plate  16  is determined to be greater than the corresponding preset value, then the roughening friction roller  3  is in good contact with the first side surface of the first plate  5  or the first side surface of the second plate  16 , without the need to increase the height of the roughening friction roller  3 . 
     According to an embodiment of the invention, the step of rolling the first plate  5  and the second plate  16  asynchronously includes: 
     step  210 , heating the first plate  5  and the second plate  16 , 
     wherein an online heating method is used, specifically, an eddy current heating method is employed to heat the first plate  5  to 350° C. By means of online heating, the first side surface of the first plate  5  and the first side surface of the second plate  16  can be rolled to combine in a semi-molten state to further improve the bonding strength of the composite plate. 
     The asynchronous rolling in the embodiment of the present invention refers to rolling a stainless steel plate and an aluminum alloy plate (i.e., the first plate  5  and the second plate  16 ) into a composite plate with rollers arranged up and down at different speeds. 
     Step  220 , the heated first plate  5  and the heated second plate  16  are rolled asynchronously, so that the first side surface of the second plate  16  and the first side surface of the first plate  5  are rolled to connect to form the composite plate. 
     The asynchronous rolling is applied to rolling the first plate  5  and the second plate  16 , the first plate  5  and the second plate  16  feature a thickness ratio of 1.5:1.0; a differential speed ratio of the roller corresponding to the first plate  5  to the roller corresponding to the second plate  16  is 1:1.05, and a reduction rate of the asynchronous rolling is 20% to 40%. 
     In the embodiment of the present invention, the first plate  5  is heated online, that is, the stainless steel plate is heated online, so that the striations  14  in the surface of the stainless steel plate are thermally expanded to widen and deepen the grooves of the striations  14 . The heated stainless steel plate and the aluminum alloy plate with a lower hardness are rolled to combine by the upper and lower rollers, the aluminum alloy plate is pressed into the groove in the stainless steel surface on a roughened surface where the aluminum alloy plate and the stainless steel plate are combined because of a much greater hardness of the stainless steel plate than that of the aluminum alloy plate; moreover, the stainless steel plate is cooled to shrink, and the surface of the aluminum alloy plate is heated to expand, so that the stainless steel plate and the aluminum alloy plate are closely attached on both sides of the groove to form an interference fit, thereby forming a strong bonding between the stainless steel plate and the aluminum alloy plate. 
     According to the embodiment of the present invention, after asynchronously rolling the heated first plate  5  and the heated second plate  16 , the method further includes the steps as follows. 
     Step  230 , the composite plate is subjected to a solid solution treatment, 
     wherein the solid solution treatment includes a heating stage and a cooling stage, and in the heating stage, the composite plate is put into a solid solution furnace for the solid solution treatment, the solid solution treatment is performed at 480° C. to 540° C. for 45 min to 65 min. In the cooling stage, the composite plate  5  is rapidly cooled and the composite plate is finally cooled to normal temperature. By subjecting the composite plate to the solid solution treatment, the bonding strength of the composite plate is further improved. 
     Step  240 , the composite plate after the solid solution treatment is aged. 
     An aging treatment is required after the solid solution treatment of the composite plate. The aging treatment is performed in an aging furnace at 160° C. to 200° C. for 5 h to 7 h. By aging the composite plate, the bond strength of the composite plate can be further improved. 
     According to an embodiment of the present invention, before the step of treating the composite plate  25  by a bending process, the method further includes the steps as follows. 
     Step  250 , the composite plate  25  is straightened. 
     As shown in  FIG.  14   , the composite plate  25  may bend in one direction in the case of rolling two different types of metal plates, it is then necessary to straighten the composite plate  25 , which requires a tensile force applied to the composite plate  25  in the second direction in the straightening process to prevent the resulting composite plate  25  from bending or warping. The straightening treatment is carried out by a bidirectional combined straightening machine, which is a conventional device in industrial production and will not be described in detail here. 
     According to an embodiment of the invention, the step of straightening the composite plate  25  includes the sub-steps as follows. 
     Step  251 , the composite plate  25  is straightened in a thickness direction; 
     As shown in  FIG.  14   , the thickness direction of the composite plate  25  is denoted as a third direction, which is perpendicular to the first direction and the second direction, respectively. When the composite plate  25  is straightened in the thickness direction, a tensile force is required to be applied to the composite plate  25  in the second direction to the composite plate  25  from bending. The composite plate  25  straightened in the thickness direction is conveyed at a higher speed than the composite plate  25  not straightened in the thickness direction. The straightening treatment in the thickness direction is carried out by a first straightening means  20  of the bidirectional combined straightening machine, and a first speed sensor  17  and a second speed sensor  18  are provided respectively before and behind the first straightening means  20 . The straightening treatment in the width direction is carried out by a second straightening means  21  of the bidirectional combined straightening machine, a third speed sensor  19  is provided behind the second straightening means  21 . A plurality of speed sensors are arranged to measure the speed of the composite plate  25  in different stages of the straightening process to ensure that the speed of the composite plate  25  in the straightening treatment is stable, so that the composite plate  25  straightened does not bend. 
     Step  252 , the composite plate  25  is straightened in a width direction. 
     As shown in  FIG.  14   , the composite plate  25  is straightened in the width direction, namely, the composite plate  25  is straightened in the first direction. In the process of straightening the composite plate  25  in the width direction, it is also necessary to apply a tensile force to the composite plate  25  along the second direction to prevent the composite plate  25  from bending, and the tensile force in the second direction is applied to the composite plate  25  by the tension control means of the bidirectional combined straightening machine. The composite plate  25  straightened in the width direction is conveyed at a higher speed than the composite plate  25  not straightened in the width direction. It is assumed that the composite plate  25  not straightened in the thickness direction is conveyed at a first speed V1, the composite plate  25  straightened in the thickness direction is conveyed a second speed V2, and the composite plate  25  straightened in the width direction is conveyed at a third speed V3. The value of V2/V1 is greater than 1 and smaller than or equal to 1.5, the value of V3/V2 is greater than 1 and smaller than or equal to 1.5, and the value of V2/V1 is greater than the value of V3/V2. The composite plate  25  is a stainless steel-aluminum alloy composite plate  25 , the hardness of the stainless steel plate is HV  300  and the thickness thereof is 3.5 mm originally, the hardness of the aluminum alloy plate is HV  50  and the thickness thereof is 8 mm originally, however, the thicknesses of the stainless steel layer and the aluminum alloy layer in the composite plate  25  are the same, which are both 3.2 mm. The unit tension experienced by the composite plate  25  when straightened in the width and the thickness directions is 2.5 N/mm 2 . According to the method for manufacturing a cell phone frame provided in the embodiment of the present invention, the first side surface of the first plate  5  is roughened to provide the first side surface of the first plate  5  with the striations  14 , which increases the area of the first plate  5  and the second plate  16  subjected to rolling, hence the composite plate  25  produced by combining the first plate  5  and the second plate  16  has a higher bonding strength and thus a stronger bonding. When the composite plate  25  is straightened in the thickness direction, the speed of the composite plate  25  is different in the front and the rear, so the tensile force applied to the composite plate  25  along the second direction can prevent the resulting composite plate  25  from bending or warping. The resulting composite plate  25 , if bent, often deviates from the thickness direction, so it is not necessary to apply a strong tensile force when straightening in the width direction, but a strong tensile force is necessary for straightening in the thickness direction to prevent the composite plate  25  from bending. 
     The composite plate  25  may bend in one direction in the case of rolling two different types of metal plates, it is then necessary to straighten the composite plate  25 , which requires a tensile force applied to the composite plate  25  in the second direction in the straightening process to prevent the resulting composite plate  25  from bending or warping. 
     Finally, it should be noted that the above embodiments are merely illustrative of the technical solution of the present invention, rather than limiting it; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that the technical solution disclosed in the above-mentioned embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents; such modifications and equivalents do not depart from the spirit and scope of the embodiments of the present invention in nature.