Abstract:
A method for attaching an insert to a substrate includes: rubbing the insert against the substrate; forming a heat-affected zone in the substrate; forming plasticized substrate material from friction resulting from the rubbing; moving the insert to a first depth in the heat-affected zone in the substrate; moving the insert to a second depth in the heat-affected zone in the substrate where the first depth is deeper than the second depth; flowing the plasticized material against the insert; and releasing the insert.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure is related to a wear-resistant insert used in such machinery like road paving and mining equipment, and more particularly to a method of joining the wear-resistant insert with a base substrate component using a method of friction welding. 
       BACKGROUND 
       [0002]    Wear-resistant inserts, herein also referred to as inserts, are commonly brazed or press fit into place to improve wear resistance of road paving or mining equipment. These types of ground engaging elements are high wear parts and so assembling them into machinery in a cheap, yet efficient and sturdy manner, is desired. The inserts are intended to withstand substantial and repetitive forces when used with any ground-engaging tool. For example, the rotor drum of an asphalt reclaimer may include many smaller cutter bits that often are brazed into their respective piece holders. The asphalt reclaimers pulverize the asphalt layer and mix it with the underlying base. The reclaimers can add asphalt emulsions or other binding agents during pulverization or during a separate mix pass. Softer metallic materials do not exhibit the required theoretical strength properties for the purpose of such heavy-wear use with a rotary workpiece or rotor drum. To address that limitation, the design of the parts can be made to avoid or limit the need for such assembly components, but that approach generally involves more machining operations and more parts to produce the desired assembly. 
         [0003]    One problem which may arise when working in the field of ground-engaging road paving or mining equipment is that wear-resistant inserts are often brazed or press-fit into a base component. However, over time, the braze tends to wear out or the insert starts to wear away the base material around it and the insert falls out. Brazing is also time-consuming. This may cause inefficiencies and failures of expensive equipment and slows down processes that rely on multiple small moving parts to be working seamlessly together. 
         [0004]    Alternative approaches have been applied to product assembly, such as the friction welding methods like that disclosed in U.S. Pat. No. 8,708,628, where a component for use with a rotary tool is inserted through a surface of a workpiece made of a material showing friction-induced plasticity and rotated in a first direction while an axial force is applied onto the component. Better methods of friction welding may be desired to create stronger “welds.” 
         [0005]    A problem which may also arise in friction-welding two separate parts together is that the resultant piece often does not produce the desired wear resistance that is needed for repetitive use in heavy machinery. Parameters like cost, efficiency and a first life-cycle of a machine come into play. Achieving a longer-lasting wear-resistant insert and method to better join two components is desired to provide enhanced mechanical traction retention of the wear-resistant insert. 
         [0006]    And yet another problem that may arise is that when welding a wear-resistant insert and a wear base component together, a stress concentration often referred to as a stress riser, occurs on an object where the stress is concentrated. This can lead to a mechanical defect with either or both the wear-resistant insert and the base-wear component which in turn can cause a material to fail. For example, a propagating crack can cause a material to fail when a concentrated stress exceeds the material&#39;s strength. Further, fatigue cracks often start at stress risers, so removing such defects increases the fatigue strength. 
         [0007]    Many of these and other shortcomings of the prior art are addressed by the various embodiments desirable in the present disclosure. 
       SUMMARY 
       [0008]    In some embodiments, an insert may be provided. The insert may include: a body, having an engaging portion and a free portion located opposite the engaging portion; a side portion of the body defining a retention cavity, the retention cavity being located closer to the engaging portion than the free portion; a junction between the retention cavity on a side of the portion defining a rounded surface; and a protrusion extending from a surface on the engaging portion. 
         [0009]    In some embodiments, a ground engaging element for a machine is provided. The ground engaging element may include: a substrate; an insert having a body, which has an engaging portion and a free portion located opposite the engaging portion; a side portion of the body defining a retention cavity, the retention cavity being located closer to the engaging portion than the free portion; a junction between the retention cavity on a side of the portion defining a rounded surface; and a protrusion extending from a surface on the engaging portion; and wherein the insert is embedded into the substrate and the substrate material is located in the retention cavity. 
         [0010]    In some embodiments, a method for attaching an insert to a substrate is provided. The method may include: rubbing the insert against the substrate; forming a heat-affected zone in the substrate; forming plasticized substrate material from friction resulting from the rubbing; moving the insert to a first depth in the heat-affected zone in the substrate; moving the insert to a second depth in the heat-affected zone in the substrate, wherein the first depth is deeper than the second depth; flowing the plasticized material against the insert; and releasing the insert. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a partially cut-away diagram of a ground-engaging machine that includes at least one friction welded wear-resistant insert in accordance with aspects of the present disclosure. 
           [0012]      FIG. 2  is a side view of an exemplary design of a wear-resistant insert with aspects of the present disclosure. 
           [0013]      FIG. 3  is a side view of an exemplary design of a wear-resistant insert with aspects of the present disclosure. 
           [0014]      FIG. 4  is a side view of an exemplary design of a wear-resistant insert with aspects of the present disclosure. 
           [0015]      FIG. 5  is a side view of an exemplary design of a wear-resistant insert with aspects of the present disclosure. 
           [0016]      FIGS. 6-8  are side cross-sectional views of the presently disclosed wear-resistant insert entering a base wear component. 
           [0017]      FIG. 9  is a top view of an embodiment showing orbital friction welding that can be utilized according to the present disclosure. 
           [0018]      FIG. 10  is a top view of an embodiment showing linear friction welding that can be utilized according to the present disclosure. 
           [0019]      FIG. 11  is a flow chart illustrating a method of friction welding the insert and base substrate together. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    In one aspect of the present disclosure, friction may be used to generate heat in order to make a base substrate material that is referred to herein as a “plasticized” substrate material so that a wear-resistant insert may be inserted inside the base substrate material. Plasticized, however, and can mean a plasticized, a semi-plasticized material, molten, molten-like, or other material that is softened or will flow as a result of being heated. Once the insert is placed in the base material, the base material and insert will cool and thus be permanently joined. In some embodiments where no melting occurs, friction welding is not actually a welding process in the traditional sense, but a forging technique. However, due to the similarities between these techniques and traditional welding, the term “friction weld” has become common. The insert could be rotated, rubbed, and/or simultaneously pressed into the base by a welding tool that is similar to a friction stir welding machine, mill, or lathe. Frictional heat is generated at the contact point or area between the surfaces caused by the rubbing of the insert on the surface of the base material. Specifically, once a desired depth has been achieved, the insert could be slowly lifted to a second more shallow depth in the substrate to allow a better flow of the plasticized material into any cavities in the insert and/or generally encompassing the engaging end of the insert. Rotation could then be stopped to allow the base material to solidify. Quenching may be done during or at the end of the process to promote high hardness or any other desired qualities of the base material and/or insert. 
         [0021]    In one aspect, it may be desirable to enhance the shape or material strength of the wear-resistant insert. For example, a shape of the insert may be selected to reduce any concentrated stress that could exceed the material&#39;s cohesive strength. More specifically, the shape of the insert could also be produced in a way that would reduce the likelihood of the generation of stress risers, which may include, but is not limited to, the use of rounded edges (also termed rounded surfaces) and fillets to reduce such potential for stress concentration. The wear-resistant insert may be made of carbide, ceramic, metal or another material with similar properties that are capable of use in friction welding. The wear-resistant insert may also be coated with a coating material that may promote friction to improve heating of the base material. The coating material may provide an alloying agent to the base material to further ensure higher hardness and wear resistance. In other embodiments, the coating may provide corrosion resistance or any other desired function. 
         [0022]    The shape of the insert and/or the coating material applied to the insert may provide enhanced mechanical fraction retention of the wear-resistant insert. The process may be done with manually controlled equipment or automated equipment. It is contemplated that friction welding can be achieved in many ways, which may include, but is not limited to, spinning, orbital, or linear friction stir welding. 
         [0023]    Referring to  FIG. 1 , a road asphalt reclaimer  20  is illustrated.  FIG. 1  shows the asphalt reclaimer  20  with an exposed region  22  that has the cover or housing that typically would cover a rotor drum  24  removed to better illustrate the rotor drum  24 . In particular, an example of a ground-engaging tool such as a rotor drum  24  may include multiple welded wear resistant inserts  40  on a rotor drum  24  used to pulverize asphalt  26 . For example, an insert  40  may be a cutter bit. The wear-resistant insert  40  and the substrate  62  may interface and may be permanently joined by friction welding. The base substrate  62  may be pre-manufactured to be shaped to receive a specific insert  40  or may not be pre-manufactured to fit with the insert  40  and can be adjusted or adapted to receive any sized insert  40 . 
         [0024]    Referring now to  FIGS. 2-5 , in preferred embodiments a typically unaltered insert  40  is shown. The insert  40  in  FIGS. 2-8  is shaped differently than the insert  40  of  FIG. 1 , as inserts  40  in accordance with the present disclosure may vary in shape. The insert  40  may be designed with enhancements. These enhancements can be achieved through configuring the shape and/or material strength of the wear-resistant insert  40  depending on the potential use and ultimately ensure a longer lifecycle of the insert  40 . For example, an insert  40  might have rounded edges or a special coating to prevent any concentrated stress (not pictured and also referred to as a stress riser) that could cause material failure by exceeding the material&#39;s cohesive strength. 
         [0025]    In one aspect shown in  FIG. 2 , an insert  40  may be elongated with engaging portions and free portions such as a free end  42  and an engaging end  44 . The engaging end  44  includes an engaging end surface  46  that can interface with the substrate  62  and substrate surface  64 , as further explained below with respect to  FIGS. 6-8 . In one aspect, the insert  40  may include at least one protrusion  48  near the engaging end  44  such that the protrusion  48  is centered to be able to localize and generate a sufficient amount of heat necessary for developing a heat-affected area on the substrate  62 . In one aspect, a rounded edge  52  instead of a squared or sharp corner may cause an object to experience less likelihood of a local increase in the intensity of a stress field. 
         [0026]    In one aspect shown in  FIG. 3 , an insert  40  may include at least one type of a retention cavity  49 . Specifically, a retention cavity  49  can be also referred to as a pre-drilled or otherwise formed hole  50  on the engaging end  44  of the insert  40 . The retention cavity  49  can also be referred to as a retention groove  54  to form a stepped or castellated portion  58  on the engaging end  44  of the insert  40 . The groove  54  can encircle the insert  40  or run along the periphery of the insert  40 . A retention cavity  49  can be located closer to an engaging end  44  than the free end  42  and where there is a junction between the retention cavity  49  on a side of the portion defining a rounded surface or rounded edge  52 . 
         [0027]    In an aspect seen in  FIG. 4 , an insert  40  may be configured to include a retention cavity  49  such as a second groove  60  near the engaging end  44 . The second groove  60  is defined by a stepped or castellated portion  58 , rounded edges  52  and fillets  56 . The insert  40  may also include a plurality of holes  50  located in close proximity to the first groove  54  and second groove  60 . The insert  40  may also include a plurality of protrusions  48  located at selected locations near the engaging end  44  of the insert  40 . 
         [0028]    The physical shape of an insert  40  to be used in a friction welding process can be any shape, whether the shape be cylindrical (as illustrated in  FIGS. 2-4 ), shaped like teeth or cutters ( FIG. 1 ), spherical (not pictured), or can be a quadrilateral shaped tile, as shown in  FIG. 5 . For example, brazing or friction welding may be performed on a thin tile insert  40  and then brazed onto the front of a rotor blade. Further, a plurality of protrusions  48 , holes  50  or rounded edges  52  may be included on the insert  40  as seen here in  FIG. 5 . 
         [0029]    The friction-welding of an insert  40  will be described hereinafter with reference to  FIGS. 6, 7 and 8 . The friction-welding method and the related methods of operation may be controlled in response to one or more operational parameters such as material strength, force needed, pressure needed, time constraints, and other parameters. 
         [0030]      FIG. 6  illustrates a welding tool  74  with an end effector  76  gripping an insert  40  on the free end  42  as it first begins to spin the insert  40  in a rotational direction illustrated by Arrow A around a centered axis  80  against the substrate  62 . In alternate embodiments, the spinning may occur in a direction opposite of Arrow A. The tool  74  may be a mill or lathe, or any type of tool  74  that exerts a lot of force and can withstand the resistance of the workpieces being friction welded. The tool  74  might have an end effector  76  that is shaped to interface with and grip the insert  40 . For example, an end effector  76  might be a chuck. The tool  74  may be manually controlled equipment or automated equipment. In an aspect, the substrate  62  can be homogeneous (not pictured) or have different layers like a first substrate layer  66 , a second substrate layer  68 , or even a third substrate layer  70  into which the insert  40  might be embedded. These layers can further help achieve a desired wear-resistant weld given one layer of a substrate  62  layer might have different melting properties and densities than another substrate layer, yet in combination the two or more layers act in harmony to create the desired tough and resilient weld. 
         [0031]    In one embodiment, an engaging end  44  of the insert  40  interfaces with the substrate surface  64 , and the engaging end  44  may include a protrusion  48  purposefully centered along the axis  80 . This protrusion  48  helps to centralize the heat to create a heat-affected zone  72  in the substrate  62  as the tool  74  moves the insert  40 . The heat-affected zone  72  may soon become a plasticized state that is capable of plastically displace and fusing the insert  40  with the substrate  62 . 
         [0032]      FIG. 7  illustrates the continued operational mode of the welding tool  74  pressing the insert  40  to a first depth in the substrate  62  as the heat-affected zone  72  remains in a plasticized state. As the tool  74  continues to spin, the tool  74  presses the insert  40  in the direction illustrated by Arrow B into the substrate  62 . The heat-affected zone  72  will enlarge in the substrate  62  and can enlarge into a first substrate layer  66 , second substrate layer  68 , or third substrate layer  70 . The insert  40  may be embedded into any type of homogenous or multi-layered substrate  62 . A first depth of how far to press the insert  40  into the substrate initially might be pre-determined depending on the desired use of the insert  40 . If there are retention cavities  49 , then the insert  40  is pressed to a first depth into the substrate  62  so as to allow the retention cavities  49  to surpass the plane of the substrate surface  64 . 
         [0033]      FIG. 8  illustrates the continued operational mode of the welding tool  74  bringing the insert  40  to a second depth of a substrate  62 . In the disclosed embodiment, after the insert  40  is moved to a first desired depth within the substrate  62 , the welding tool  74  moves the insert  40  in the direction of Arrow C to a second depth which is more shallow within the substrate  62  than the first depth. This second depth may be achieved while simultaneously or after slowing the rotation of the tool  74  but the slowing is optional. This type of “pull-back” motion of the tool  74  may enhance the flow of plasticized material  73  from the heat-affected zone  72  into any number of retention cavities  49  that exist on or around the insert  40  as illustrated by Arrow D. Thus the “weld” is further strengthened and reinforced by the substrate  62  when the substrate  62  acts to permanently “grip” or “encapsulate” the insert  40  upon future cooling. 
         [0034]    In one aspect, the combined inclusion of one or more of rounded edges  52  and fillets  56  aid in minimalizing localized stress concentrations on a sharp-edged or cracked insert  40 . Once the insert  40  achieves its fixed position, then the tool  74  movement is finally stopped so as to allow the wear resistant insert  40  and the base component substrate  62  to solidify into one resultant workpiece. During the cooling and hardening period, the grooves  54 , 60  stepped or castellated portions  58 , and holes  50  provide places for plasticized material  73  to flow into the insert  40  to provide a better bond between the insert  40  and substrate  62 . 
         [0035]    Three examples of friction welding operational modes that can be used to embed a wear resistant insert  40  into the desired component substrate  62  are illustrated in  FIGS. 6-8  and  FIGS. 9-10 . 
         [0036]    Referencing back to  FIGS. 6-8 , a first operational friction welding mode known as spin-welding is illustrated. Spin-welding involves spinning an insert  40  at a high rate of rotation shown by Arrow A. Further, the welding tool  74  is gripping and spinning the insert  40  around a center axis  80  of the insert  40  against fixed base substrate  62  to create heat via friction between the insert  40  and the substrate  62 . 
         [0037]    Referencing  FIG. 9 , a second operational friction welding mode known as orbital friction welding is shown. Orbital friction welding is similar to spin—or rotary—friction welding where the insert  40  and the substrate  62  are rotated relative to each other but with their respective axes  80  offset. In some embodiments, the axis  80  may be offset by up to 3 mm. The path the insert  40  follows runs in a type of small orbital friction path  82  in a direction indicated by Arrow E. 
         [0038]    Referencing  FIG. 10 , a third operational friction welding mode known as linear friction can be used to embed a wear resistant insert  40  into the substrate  62 . Linear friction welding is similar to spin welding except that the welding tool  74  oscillates laterally along a linear friction path  84  as indicated by Arrow F instead of, or in addition to, spinning The speeds may be much lower in general, which may result in the pieces to be kept under pressure at all times. Linear friction welding may be use more complex machinery than spin welding, but has the advantage that parts of any shape can be joined. Another advantage is that in some instances quality of joint is better than that obtained using rotating technique. 
       INDUSTRIAL APPLICABILITY 
       [0039]    The present disclosure is applicable to any type of friction welding that is contemplated being used with a wear-resistant insert  40 . The operational mode of the friction welding process described below with reference to  FIG. 11  as well as  FIGS. 2-8  may cater to the various operational requirements of the machinery or ground-engaging tools. This can include adjustment for varying forces and pressures required to friction weld. 
         [0040]      FIG. 11  is a flowchart of the method and process for attaching an insert  40  into a substrate  62 . In Step S 10 , a welding tool  74  begins to rub an insert  40  against a substrate  62 , which over a period of time, as shown in Step S 20 , this rubbing forms a heat-affected zone  72  in the substrate  62 . In Step S 30 , as the tool  74  continues to spin, the tool  74  presses the insert  40  in a direction shown by Arrow B into the substrate  62 . The first depth of how far to press the insert  40  into the substrate  62  may be pre-determined depending on the perceived industrial use of the wear-resistant insert  40 . Step S 40  is an optional step where at any point the tool  74  can be slowed rotationally as the continued rubbing movement of the insert  40  against the substrate  62  persists. In Step S 50 , then the tool  74  moves and extends the insert to a second depth within the substrate  62 . The second depth is more shallow than the first depth. This leads directly to Step S 60 , where the plasticized material  73  flows against the insert  40 . In Step S 70 , this type of “pull-back” motion of the tool  74  set forth in Step S 50  is designed to enhance the flow of plasticized material  73  from the heat-affected zone  72  into any number of retention cavities  49 . During the cooling and hardening period, the grooves  54 , 60  stepped or castellated portions  58 , or holes  50  provide places for plasticized material  73  to flow into the insert  40  to provide a better bond between the insert  40  and substrate  62 . In Step S 80 , the friction welding process also may involve quenching the insert  40 . Quenching can use any common quenching technique to promote high hardness of the base material substrate  62  and/or insert  40 . The quenching Step S 80  may include a quench material like water or oil. In Step S 90 , the tool  74  releases the insert  40  from the end effector  76 . 
         [0041]    The method may further involve the step of coating the insert  40 , or more properly referred to as friction surfacing. Friction surfacing is a process where a coating material is applied, such as a friction-enhancing or alloy-promoting material, before the tool  74  begins to spin the insert  40  into the substrate  62 . A rod composed of the coating material is rotated under pressure, generating a plasticized layer in the rod at the interface of the engaging end surface  46  of the insert  40  with the substrate  62 . By moving a substrate  62  across the face of the rotating rod a plasticized layer is deposited between 0.2-2.5 mm thick depending on rod diameter and coating material. When coating or friction surfacing a piece, the structure might change because the temper in the steel is lost. In friction stir welding, loss of temper is minimal, and performing the coating quickly minimizes the tempering effect. However, it may be desired to coat the material to restore some of the hardness present in the material prior to the steel losing its temper. The coating material might be chrome, carbon, silicon or a material with similar properties. As such, the coating could involve multiple compositions. 
         [0042]    While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.