Patent Description:
In recent years, the application of thermoformed component in automobile industry has become very important. Especially, with respect to safety structural parts of automobile, it has irreplaceable advantages in some parts with high strength and complex shape. The materials used for thermoformed components are divided into those with coating and those without coating. The main purpose of the coating is to prevent the oxidation of the steel plate surface during the hot stamping process. The formed components can be directly coated and welded for use. At present, the materials without coating must be subject to surface shot peening after thermoforming to remove the oxide layer generated on the surface, otherwise it will affect the subsequent coating and welding of parts. The surface of materials hot-dipped with aluminum coating cannot be phosphated normally after thermoforming. The adhesion of paint film after electrophoresis depends entirely on the surface morphology of the coating. During the use of existing materials, there will be the problem that the coating adhesion cannot meet the use.

For example, the Chinese patent document with the publication number of <CIT>, entitled "process for manufacturing stamped products, and stamped products prepared from the same" discloses a thermoforming material coated with aluminum or aluminum alloy and its manufacturing method. The method specifically controls the thickness and five-layer structure of the coating to ensure the welding performance of thermoformed component.

For another example, the Chinese patent document with the publication number of <CIT>, entitled "hot-stamping forming component, pre-coating steel-plating plate for hot-stamping forming, and hot-stamping forming process" discloses a hot-stamping formed component. In the technical solution disclosed in the patent document, the thickness of the coating is reduced and the protective effect of the coating is also reduced. Therefore, the fluctuation of the thermoforming process is easy to affect the surface performance of the component, thus affecting the subsequent service performance.

For another example, the Chinese patent document with the publication number of <CIT>, entitled "coated steel strip, methods of making the same, methods of using the same, stamping blanks prepared from the same, stamped products prepared from the same, and articles comprising such stamped products" discloses a hot stamped product of coated steel strip and a method. The technical solution disclosed in the patent document includes heating, transferring and cooling, but does not involve the hot stamping process, which will lead to the unstable quality of stamped products, such as shrinkage and cracking. The furnace atmosphere during the heating process is not controlled, which leads to the change of furnace atmosphere during the heating, especially the large change of oxygen content, which makes the appearance color of products easy to change. In the actual production, it is found that the appearance color of stamped products obtained from the same incoming materials under the same process is quite different. Moreover, the published patent applications <CIT>, <CIT> and <CIT> disclose steel sheets according to prior art.

An object of the present invention is to provide a thermoformed component having excellent coating adhesion. The thermoformed component has good paintability, good coating adhesion and good corrosion resistance, and is very suitable for automotive parts, such as front and rear doors, left and right anti-collision rods/beams, front and rear bumpers, A-pillar reinforcing plates, B-pillar reinforcing plates, floor middle channels, etc..

To achieve the above object, the present invention provides a thermoformed component having excellent coating adhesion, comprising a substrate layer and an aluminum coating coated on at least one surface of the substrate layer, wherein the average roughness Ra of a surface of the thermoformed component is between <NUM> and <NUM>, the peak-to-valley height Rt is between <NUM> and <NUM>, and the roughness peak count Rpc is greater than or equal to <NUM>, wherein the mass percentage of chemical elements of the aluminum coating is: Si: <NUM>~<NUM>%, Fe: <NUM>~<NUM>%, Mg: <NUM>~<NUM>%, Zn: <NUM>~<NUM>%, and a balance of Al and other unavoidable impurities, wherein the aluminum coating comprises a diffusion layer adjacent to the substrate layer and an alloy layer on the surface of the aluminum coating, wherein the ratio of the thickness of the diffusion layer to the total thickness of the aluminum coating is <NUM>-<NUM>; wherein the mass percentage of chemical elements of the substrate layer is: C: <NUM> -<NUM>%, Si: <NUM>~<NUM>%, Mn: <NUM> ~<NUM>%, P≤<NUM>%, S≤<NUM>%, Al<<NUM>%, Ti≤<NUM>%, B: <NUM>~<NUM>%, Cr: <NUM> ~<NUM>%, Nb≤<NUM>%, V≤<NUM>%, and a balance of Fe and other unavoidable impurities.

In the technical solution of the present invention, the aluminum coating comprises aluminum phase and aluminum silicon phase. In the heating process, the aluminum in the aluminum coating diffuses to the substrate layer, and the iron in the substrate layer diffuses to the aluminum coating to form Al<NUM>Fe<NUM>Si phase. The formation of new phase leads to a significant increase in surface roughness. With the further diffusion of iron and aluminum, Fe<NUM>Al<NUM> phase is formed, and the surface roughness is basically maintained. Finally, FeAl alloy is completely formed in the aluminum coating, while the surface roughness decreases slightly.

The surface of thermoformed components after heat treatment mainly consists of Fe<NUM>Al<NUM> and FeAl alloy. At the same time, because the silicon oxide, aluminum oxide and iron oxide produced by surface oxidation cannot react with phosphating solution, that is, normal phosphating coating cannot be formed, the coating adhesion of thermoformed components is completely guaranteed by the uneven structure of the surface, that is, the roughness of thermoformed components has an important impact on the coating adhesion.

The greater the surface roughness of the aluminum coating, the greater the roughness peak count Rpc value, the different diffusion paths of iron and aluminum, and the different speed of the formation of new phase, resulting in the greater the surface roughness of the formed components after heat treatment and the better the coating adhesion.

Further, in the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the thickness of the diffusion layer is ≤ <NUM>; the total thickness of the aluminum coating is ≤ <NUM>.

Further, in the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the thickness of the diffusion layer is <NUM>~<NUM>; the total thickness of the aluminum coating is <NUM>~<NUM>.

Further, in the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the average roughness Ra of the surface of the thermoformed component is <NUM>~<NUM>.

Further, in the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the peak-to-valley height Rt of the surface of the thermoformed component is <NUM>~<NUM>.

Further, in the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the roughness peak count Rpc of the surface of the thermoformed component is <NUM>~<NUM>, such as <NUM>~<NUM>.

Further, the surface of the thermoformed component having excellent coating adhesion of an embodiment the present invention comprises Fe<NUM>Al<NUM> and FeAl alloy. Further, the surface of the thermoformed component having excellent coating adhesion of an embodiment of the present invention also comprises silicon oxide, aluminum oxide and iron oxide. Further, the surface of the thermoformed component having excellent coating adhesion of the present invention mainly consists of Fe<NUM>Al<NUM> and FeAl alloy, and also comprises silicon oxide, aluminum oxide and iron oxide. Also, the content of Fe<NUM>Al<NUM> in the surface of the thermoformed component having excellent coating adhesion of the present invention is higher than 40wt%.

Further, in the surface of the thermoformed component having excellent coating adhesion according to the present invention, the mass percentage of chemical elements of the aluminum coating is: Si: <NUM>~<NUM>%, Fe: <NUM>~<NUM>%, Mg: <NUM>~<NUM>%, Zn: <NUM>~<NUM>%, and a balance of Al and other unavoidable impurities.

Further, in the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the average weight of the aluminum coating is <NUM>~<NUM>/m<NUM> per single surface.

Further, in the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the mass percentage of chemical elements of the substrate layer further meets at least one of the following:.

Further, in the substrate layer of the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the content of Al is <NUM>-<NUM>%, and the content of Ti is <NUM>-<NUM>%, preferably <NUM>-<NUM>%.

Further, in the substrate layer of the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the content of Cr is <NUM>-<NUM>%.

Further, in the substrate layer of the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, when Nb is comprised, the content of Nb is <NUM>-<NUM>%, when V is comprised, the content of V is <NUM>-<NUM>%.

Further, in the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the mass percentage of chemical elements of the substrate layer is: C: <NUM>~<NUM>%, Si: <NUM>~<NUM>%, Mn: <NUM>~<NUM>%, P≤<NUM>%, S≤<NUM>%, Al: <NUM>-<NUM>%, Ti: <NUM>-<NUM>%, B: <NUM>~<NUM>%, Cr: <NUM>~<NUM>%, Nb: <NUM>% or <NUM>-<NUM>%, V: <NUM>% or <NUM>-<NUM>%, and a balance of Fe and other unavoidable impurities.

Further, in the thermoformed component having excellent coating adhesion according to one embodiment of the present invention, the yield strength is <NUM>~<NUM> MPa, the tensile strength is <NUM>~<NUM> MPa, and the elongation is ≥<NUM>%.

Preferably, in the microstructure of the substrate of the thermoformed component having excellent coating adhesion of the present invention, the volume percentage of martensite is ≥<NUM>%, preferably ≥<NUM>%, more preferably ≥<NUM>%.

Accordingly, another object of the present invention is to provide a manufacturing method for the above thermoformed component having excellent coating adhesion, and through the manufacturing method, thermoformed component having excellent coating adhesion can be obtained.

To achieve the above object, the present invention provides a manufacturing method for the above thermoformed component having excellent coating adhesion, comprising the following steps:.

In the manufacturing method of the present invention, in step (<NUM>), too low temperature of the heating furnace or too short residence time of the blank in the heating furnace will lead to insufficient diffusion of iron and aluminum, resulting in too low surface roughness and affecting the roughness of the final thermoformed component. If the temperature of the heating furnace is too high or the residence time of the blank in the heating furnace is too long, it will lead to excessive diffusion of iron and aluminum and complete formation of FeAl alloy, which will also reduce the roughness of the final thermoformed component. At the same time, the holes formed by element migration in the diffusion process will affect the surface conductivity, and cause shrinkage in the electrophoresis process, which will affect the paintability.

Further, in the manufacturing method according to one embodiment of the present invention, in step (<NUM>), the mass percentage of chemical elements of the aluminum coating solution is: Si: <NUM>~<NUM>%, Fe: <NUM>~<NUM>%, Zn: <NUM>~<NUM>%, Mg: <NUM>~<NUM>%, and a balance of Al and other unavoidable impurities.

Further, in the manufacturing method according to one embodiment of the present invention, the average weight of the aluminum coating is <NUM>~<NUM>/m<NUM> per single surface.

Further, in the manufacturing method of the present invention, in step (<NUM>), during the heating up process of blank heating, the heating rate does not exceed <NUM>/s in the range of heating up to <NUM>~<NUM> to pre-alloy zinc and aluminum in the coating and avoid damage or crack of the coating.

Further, in the manufacturing method of the present invention, in step (<NUM>), the blank is transferred to the mold within <NUM> seconds.

Further, in the manufacturing method of the present invention, in the hot stamping process of step (<NUM>), after the mold is closed, a pressure holding quenching is continued for <NUM>~<NUM>, and the pressure holding pressure applied to the blank surface is ≥<NUM> MPa. In some embodiments, the pressure holding pressure is <NUM>~<NUM> MPa.

Further, in the manufacturing method of the present invention, in step (<NUM>), the material of the mold meets the following requirement: the thermal diffusion coefficient at <NUM> is greater than <NUM><NUM>/s.

Further, in the manufacturing method of the present invention, in step (<NUM>), during stamping, the closing speed of the mold is <NUM>~<NUM>/s, so that the thermoformed component can ensure good forming performance and reduce stamping defects, such as cracking and necking.

Further, in the manufacturing method of the present invention, in step (<NUM>), the blank is cooled to <NUM>~<NUM> at a cooling rate of <NUM>~<NUM>/s to change the internal structure of the thermoformed component into the required structure, and ensure that the thermoformed component still maintains a good size and shape during the cooling process.

The present invention also includes a thermoformed component manufactured by the above method.

Compared with the prior art, the thermoformed component having excellent coating adhesion and its method have the following advantages and beneficial effects:
The thermoformed component having excellent coating adhesion of the present invention has good paintability, good coating adhesion and good corrosion resistance, and is very suitable for automotive parts, such as front and rear doors, left and right anti-collision rods/beams, front and rear bumpers, A-pillar reinforcing plates, B-pillar reinforcing plates, floor middle channels, etc..

In addition, the manufacturing method of the present invention also has the above advantages and beneficial effects.

The thermoformed component having excellent coating adhesion of the present invention and its manufacturing method will be further explained and illustrated with reference to specific examples. Nonetheless, the explanation and illustration are not intended to unduly limit the technical solution of the present invention.

The thermoformed components having excellent coating adhesion of Examples <NUM>-<NUM> and Comparative Example <NUM> are manufactured by the following step:.

Wherein, the manufacturing methods of every Examples and Comparative Example are as follows:.

A <NUM> steel plate with aluminum alloy coating was leveled by a leveling roller to obtain a plate before heat treatment and hot stamping having a surface roughness as shown in Table <NUM>, and the plate was laser blanked into a blank with a certain size and shape. The mass percentage of chemical compositions of the aluminum coating solution was Si: <NUM>%, Fe: <NUM>%, Zn: <NUM>%, Mg: <NUM>%, and a balance of Al and other unavoidable impurities. The blank entered a heating furnace. The temperature of the heating furnace was <NUM>, the residence time was <NUM> minutes, the heating rate was <NUM>/s in the range of <NUM>~<NUM>, the transferring time was <NUM> seconds, the pressure holding time was <NUM> seconds, the pressure holding pressure was <NUM> MPa, the mold closing speed was <NUM>/s, the cooling speed was <NUM>/s, the finish temperature of cooling was <NUM> and the thermal diffusion coefficient of the mold at <NUM> was <NUM><NUM>/s.

A <NUM> steel plate with aluminum alloy coating was leveled by a leveling roller to obtain a plate before heat treatment and hot stamping having a surface roughness as shown in Table <NUM>, and the plate was laser blanked into a blank with a certain size and shape. The mass percentage of chemical compositions of the aluminum coating solution was Si: <NUM>%, Fe: <NUM>%, and a balance of Al and other unavoidable impurities. The blank entered a heating furnace. The heating rate of <NUM>~<NUM> °Cwas <NUM>/s, the temperature of the heating furnace was <NUM>, the residence time was <NUM> minutes, the heated blank was transferred to a mold within <NUM> seconds, and the thermal diffusion coefficient of the mold at <NUM> was <NUM><NUM>/s. The mold closing speed was <NUM>/s, the pressure holding time was <NUM> seconds, the pressure holding pressure was <NUM> MPa, the cooling speed was <NUM>/s, and the finish temperature of cooling was <NUM> The proportion of martensite in the microstructure of the substrate of the thermoformed component is higher than <NUM>%.

A <NUM> steel plate with aluminum alloy coating was leveled by a leveling roller to obtain a plate before heat treatment and hot stamping having a surface roughness as shown in Table <NUM>, and the plate was laser blanked into a blank with a certain size and shape. The mass percentage of chemical compositions of the aluminum coating solution was Si: <NUM>%, Fe: <NUM>%, and a balance of Al and other unavoidable impurities. The blank entered a heating furnace. The temperature of the heating furnace was <NUM>, the residence time was <NUM> minutes, the heating rate of <NUM>-<NUM> was <NUM>/s, the heated blank was transferred to a mold within <NUM> seconds, the mold closing speed was <NUM>/s, the pressure holding time was <NUM> seconds, the pressure holding pressure was <NUM> MPa, the cooling speed was <NUM>/s, the finish temperature of cooling was <NUM> and the thermal diffusion coefficient of the mold at <NUM> was <NUM><NUM>/s. The proportion of martensite in the microstructure of the substrate of the thermoformed component is higher than <NUM>%.

A <NUM> steel plate with aluminum alloy coating was leveled by a leveling roller to obtain a plate before heat treatment and hot stamping having a surface roughness as shown in Table <NUM>, and the plate was laser blanked into a blank with a certain size and shape. The mass percentage of chemical compositions of the aluminum coating solution was Si: <NUM>%, Fe: <NUM>%, Zn: <NUM>%, Mg: <NUM>%, and a balance of Al and other unavoidable impurities. The blank entered a heating furnace. The temperature of the heating furnace was <NUM>, the residence time was <NUM> minutes, the heating rate was <NUM>/s in the range of <NUM>~<NUM>, the heated blank was transferred to a mold within <NUM> seconds, the mold closing speed of upper and lower molds was <NUM>/s, the pressure holding time was <NUM> seconds, the pressure holding pressure was <NUM> MPa, the thermal diffusion coefficient of the mold at <NUM> was <NUM><NUM>/s and the finish temperature of cooling was <NUM>. The proportion of martensite in the microstructure of the substrate of the thermoformed component is higher than <NUM>%.

A <NUM> steel plate with aluminum alloy coating was leveled by a leveling roller to obtain a plate before heat treatment and hot stamping having a surface roughness as shown in Table <NUM>, and the plate was laser blanked into a blank with a certain size and shape. The mass percentage of chemical compositions of the aluminum coating solution was Si: <NUM>%, Fe: <NUM>%, Mg: <NUM>%, and a balance of Al and other unavoidable impurities. The blank entered a heating furnace. The temperature of the heating furnace was <NUM>, the residence time was <NUM> minutes, the heating rate was <NUM>/s in the range of <NUM>~<NUM>, the heated blank was transferred to a mold within <NUM> seconds, the mold closing speed of upper and lower molds was <NUM>/s, the pressure holding time was <NUM> seconds, the pressure holding pressure was <NUM> MPa, the thermal diffusion coefficient of the mold at <NUM> was <NUM><NUM>/s and the finish temperature of cooling was <NUM>. The proportion of martensite in the microstructure of the substrate of the thermoformed component is higher than <NUM>%.

A <NUM> steel plate with aluminum alloy coating was leveled by a leveling roller to obtain a plate before heat treatment and hot stamping having a surface roughness as shown in Table <NUM>, and the plate was laser blanked into a blank with a certain size and shape. The mass percentage of chemical compositions of the aluminum coating solution was Si: <NUM>%, Fe: <NUM>%, and a balance of Al and other unavoidable impurities. The blank entered a heating furnace. The temperature of the heating furnace was <NUM>, the residence time was <NUM> minutes, the heating rate was <NUM>/s in the range of <NUM>~<NUM>, the heated blank was transferred to a mold within <NUM> seconds, the mold closing speed of upper and lower molds was <NUM>/s, the pressure holding time was <NUM> seconds, the pressure holding pressure was <NUM> MPa, the thermal diffusion coefficient of the mold at <NUM> was <NUM><NUM>/s and the finish temperature of cooling was <NUM>. The proportion of martensite in the microstructure of the substrate of the thermoformed component is higher than <NUM>%.

A <NUM> steel plate with aluminum alloy coating was leveled by a leveling roller to obtain a plate before heat treatment and hot stamping having a surface roughness as shown in Table <NUM>, and the plate was laser blanked into a blank with a certain size and shape. The mass percentage of chemical compositions of the aluminum coating solution was Si: <NUM>%, Fe: <NUM>%, and a balance of Al and other unavoidable impurities. The blank entered a heating furnace. The temperature of the heating furnace was <NUM>, the residence time was <NUM> minutes, the heating rate was <NUM>/s in the range of <NUM>~<NUM>, the oxygen content of the atmosphere in the furnace was <NUM>%, the heated blank was transferred to a mold within <NUM> seconds, the mold closing speed of upper and lower molds was <NUM>/s, the pressure holding time was <NUM> seconds, the pressure holding pressure was <NUM> MPa, the thermal diffusion coefficient of the mold at <NUM> was <NUM><NUM>/s and the finish temperature of cooling was <NUM>. The proportion of martensite in the microstructure of the substrate of the thermoformed component is higher than <NUM>%.

Table <NUM> lists the mass percentage ratio of each chemical element of the substrate layers of the thermoformed components having excellent coating adhesion of Examples <NUM>-<NUM> and the substrate layer of Comparative Example <NUM>.

To verify the application effect of the present invention and prove the components having excellent coating adhesion of Examples <NUM>-<NUM> and the comparative thermoformed component of Comparative Example <NUM> were tested in the present invention. Table <NUM> lists the test results of every Examples and Comparative Example.

As can be seen from Table <NUM>, the yield strength of each example of the present invention is <NUM>~<NUM> MPa, the tensile strength is <NUM>~<NUM> MPa, and the elongation is <NUM>~<NUM>%.

In addition, it can be seen from Table <NUM> that the surface roughness Ra of the finished product of the comparative thermoformed component of Comparative Example <NUM> after hot stamping is lower than <NUM>, Rt is less than <NUM>, Rpc is lower than <NUM>, and the paintability of the thermoformed component of Comparative Example <NUM> is poor, the coating adhesion does not meet the requirements, and its performance is far inferior to that of the thermoformed components of every Examples of the present invention. In addition, it can be seen from table <NUM> that the higher the surface roughness of the material before heat treatment and hot stamping used by the thermoformed component, the higher the product roughness after heat treatment and hot stamping, and the better the coating adhesion.

To sum up, the thermoformed component having excellent coating adhesion of the present invention has good paintability, good coating adhesion and good corrosion resistance, and is very suitable for automotive parts, such as front and rear doors, left and right anti-collision rods/beams, front and rear bumpers, A-pillar reinforcing plates, B-pillar reinforcing plates, floor middle channels, etc..

Claim 1:
A thermoformed component having excellent coating adhesion, comprising a substrate layer and an aluminum coating coated on at least one surface of the substrate layer, wherein the average roughness Ra of a surface of the thermoformed component is <NUM>~<NUM>, the peak-to-valley height Rt is <NUM>~<NUM>, and the roughness peak count Rpc is ≥<NUM>, wherein the mass percentage of chemical elements of the aluminum coating is: Si: <NUM>~<NUM>%, Fe: <NUM>~<NUM>%, Mg: <NUM>~<NUM>%, Zn: <NUM>~<NUM>%, and a balance of Al and other unavoidable impurities, wherein the aluminum coating comprises a diffusion layer adjacent to the substrate layer and an alloy layer on the surface of the aluminum coating, wherein the ratio of the thickness of the diffusion layer to the total thickness of the aluminum coating is <NUM>-<NUM>, and
wherein the mass percentage of chemical elements of the substrate layer is:
C: <NUM> -<NUM>%, Si: <NUM>~<NUM>%, Mn: <NUM>~<NUM>%, P≤<NUM>%, S≤<NUM>%, Al<<NUM>%, Ti≤<NUM>%, B: <NUM>~<NUM>%, Cr: <NUM> ~<NUM>%, Nb≤<NUM>%, V≤<NUM>%, and a balance of Fe and other unavoidable impurities.