High-carbon steel truck bushings

Abstract

The exemplary bushing (204) has three radial sections, including an inner section (410) proximal to the central bore of the bushing (204), an outer section (404) distal from the central bore, and a core section (406) between the inner section (410) and the outer section (404). The core section (406) has a lower hardness than either the inner section (410) or the outer section (404) of the bushing (204). The bushing (204) may be formed using high-carbon steel and, in some cases, may have a spheroidal cementite crystal structure. A rough bushing may be formed using high-carbon steel, followed by a direct hardening process and an induction hardening process on the inner surface (412) proximal to the central bore of the bushing (204). Induction hardening on the inner surface (412) may harden the outer portion (404) while tempering the core portion (406) of the bushing (204).

Description

[Technical Field]

[0001] This disclosure relates to high-carbon steel track bushings. More specifically, this disclosure relates to track bushings made of high-carbon steel that are hardened to achieve improved wear life. [Background technology]

[0002] Tracked machinery is widely used in construction, mining, forestry, and other similar industries. The undercarriage of such tracked machinery utilizes track assemblies rather than wheels to provide ground-engagement propulsion. Such track assemblies can be preferred in environments where generating sufficient traction is a concern, such as those frequently found in the aforementioned industries. Specifically, instead of rolling across the work surface on wheels, tracked machinery utilizes one or more track assemblies, including a ground-engagement track shoe that moves around one or more rotatable track engagement elements such as a drive sprocket, idler, tensioner, and rollers, and an infinite loop of coupling track links defining the outer surface and supporting the inner surface.

[0003] A typical track chain assembly design includes track pins fixed or rotatably coupled to a pair of chain links, as well as bushings rotatably positioned between the links and around the track pins. Such track chain assemblies can operate in extremely harsh environments where the track joints may be exposed to various abrasive mixtures of water, dust, sand, rocks, or other minerals or chemical elements. The bearing interface between the track pins and bushings encounters high contact stresses, which can lead to failure due to gouging. Gouging is a major failure mode for track chain assemblies and can limit their lifespan in many applications. Furthermore, the operation of the track chain assembly can cause wear on track chain components such as bushings.

[0004] During operation, track bushings can be subjected to excessive loads. Different surfaces of the track bushing, such as the inner diameter and end ring surface, may require increased strength and toughness to withstand the loads that may be imposed on the track bushing. Track bushings are typically made of low-carbon or medium-carbon steel. Furthermore, track bushings may be tempered to create track bushings of the desired hardness. However, the production of track bushings can be a time-consuming, labor-intensive, and costly process. Moreover, the final bushings may not provide sufficient wear resistance and toughness when produced by conventional methods.

[0005] One example of bushing manufacturing, as described in U.S. Patent No. 9,616,951 (hereinafter referred to as '951'), involves placing a hard metal alloy slurry on the surface or in an undercut or channel, and then fusing it to form a metallic bond with the iron-based alloy. However, this requires additional processing steps such as undercutting and the addition of the metal alloy slurry. Furthermore, this process of slurry addition and fusing may limit the thickness of the hard outer layer, such as about 1 mm to 2 mm, as described in '951'.

[0006] The exemplary embodiments of this disclosure are intended to overcome the aforementioned shortcomings. [Overview of the Initiative]

[0007] In exemplary embodiments of the present disclosure, a method for manufacturing a bushing includes performing direct hardening of a rough bushing. The rough bushing is formed from a high-carbon steel having a carbon content of more than 0.8% by weight. Furthermore, the high-carbon steel includes a cementite crystalline structure. The method further includes performing induction hardening on the inner surface of the rough bushing to form a hardened inner portion of the bushing and a soft core portion of the bushing.

[0008] In another exemplary embodiment of the present disclosure, the bushing includes an outer surface and an inner surface opposite the outer surface, the inner surface defining a channel having substantially constant diameter, the channel passing substantially through the center of the bushing from a first end of the bushing to a second end of the bushing opposite the first end. The bushing further has an inner portion including the inner surface, an outer portion including the outer surface, and a core portion positioned between the inner and outer portions. In this bushing, the core portion is softer than the inner portion, and the core portion is softer than the outer portion.

[0009] In yet another exemplary embodiment of the present disclosure, a track chain assembly comprises a plurality of components including a plurality of track shoes, a plurality of links, and a plurality of bushings. At least one bushing includes an inner portion, an outer portion, and a core portion between the inner and outer portions. The core portion is softer than the inner portion, and the core portion is softer than the outer portion. Furthermore, the outer portion is at least 5 mm thick and has a hardness greater than 55 HRC, and the core portion has a hardness less than 52 HRC. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram of an exemplary system including a truck-type machine having one or more components formed according to an exemplary embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic diagram of an exemplary portion of a track chain assembly for the undercarriage of an exemplary track-type machine as shown in Figure 1, according to an exemplary embodiment of the present disclosure. [Figure 3] Figure 3 is a schematic diagram of an exemplary bushing, part of the truck chain shown in Figure 2, according to an exemplary embodiment of the present disclosure. [Figure 4] Figure 4 is a cross-sectional view of an exemplary bushing according to an exemplary embodiment of the present disclosure. [Figure 5] Figure 5 is another cross-sectional view of a particular bushing according to an exemplary embodiment of the present disclosure. [Figure 6]FIG. 6 is a flowchart showing an exemplary method for forming the exemplary bushing of FIG. 4 according to an exemplary embodiment of the present disclosure. [Figure 7] FIG. 7 is a flowchart showing another exemplary method for forming the exemplary bushing of FIG. 4 according to an exemplary embodiment of the present disclosure. **DETAILED DESCRIPTION**

[0011] Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or similar parts.

[0012] FIG. 1 is a schematic view of an exemplary system including a track-type machine 100 having one or more components formed in accordance with an exemplary embodiment of the present disclosure. An exemplary embodiment of machine 100 includes a track-type undercarriage 120. Machine 100 may also be referred to interchangeably herein as track-type machine 100 and / or machine 100. In other embodiments, machine 100 may be any suitable machine having a track-type undercarriage 120, such as a dozer, loader, excavator, tank, backhoe, drill rig, trencher, or any other on-road or off-road vehicle.

[0013] Machine 100 includes a frame 140 having a first track chain assembly 160 disposed on its first side 110 and a second track chain assembly (not shown) disposed on its second side (not shown). The second side is in an opposing relationship with the first side 110. Together, the track assemblies are adapted to engage the ground or other surface and propel machine 100 in a rearward and / or forward direction.

[0014] Naturally, the track assemblies of machine 100 may be similar, and may even represent mirror images of each other. Therefore, only the first track chain assembly 160 is described herein. Naturally, the description of the first track chain assembly 160 may also apply to the second track chain assembly. Other embodiments may, according to this disclosure, include two or more track chain assemblies. Thus, the devices, systems, and methods disclosed herein are applicable to any suitable track-type machine or its variation. Furthermore, the components of the disclosed track-type machine 100, and their forming mechanisms, disclosed herein may also apply to other systems, such as non-track-type machines and / or other mechanical systems.

[0015] Continuing to refer to Figure 1, the first track chain assembly 160 extends around a drive sprocket 162, a front idler 164, a back idler 166, and several track rollers 168. The track chain assembly 160 includes several ground-engaging track shoes 170 for engaging with the ground or other surfaces and propelling the machine 100.

[0016] During typical operation of the undercarriage 120, the drive sprocket 162 is driven in the forward rotation direction FR by an engine or the like to drive the track chain assembly 160, and therefore the machine 100 drives the track chain assembly 160 in the forward direction F and in the reverse rotation direction RR, and therefore the machine 100 is driven in the reverse direction R. The drive sprocket 162 of the undercarriage 120 may be operated to rotate the machine 100 independently.

[0017] The undercarriage 120 and the track chain assembly 160 may include various other components as described herein. Due to the harsh operating environment and the loads on the various components of the track chain assembly, it is desirable to improve the material properties of the various components of the track chain assembly in order to improve the usable life of those components.

[0018] While machine 100 is illustrated in the context of a track-type machine, it should be understood that this disclosure is not limited thereto, and that a wide variety of other machines having tracks are also intended within this context. For example, in other embodiments, the track chain assembly 160 may be included in a conveyor system as a track for transmitting torque between rotating elements, or in any other application known to those skilled in the art. Furthermore, machines without tracks may include components disclosed herein.

[0019] According to exemplary embodiments of the present disclosure, various components of the machine 100 and its track chain assembly 160 may be formed in a manner that improves their wear resistance while maintaining and / or improving their overall toughness. Mechanisms disclosed herein can be applied to any various track chain assembly components disclosed herein to increase the surface hardness of these components while maintaining a softer core portion of these components, thereby providing improved surface wear resistance, reduced goring between parts, and high toughness.

[0020] Figure 2 is a schematic diagram of an exemplary portion 200 of a track chain assembly 160 for the undercarriage of an exemplary track-type machine 100, as shown in Figure 1, according to an exemplary embodiment of the present disclosure. As described above, when operated, the drive sprocket 162 of the track-type machine 100 can rotate the track assembly 160 around one or more idlers, or other guiding components such as a front idler 164, a back idler 166, and a plurality of track rollers 168, to facilitate the movement of the machine 100.

[0021] The track assembly 160 may further include a series of links 202 that can be coupled to one another by laterally positioned track bushings 204. As shown, the links 202 may be offset links. That is, each of the links 202 may have an inwardly offset end 206 and an outwardly offset end 208. The inwardly offset end 206 of each link 202 is coupled to the outwardly offset end 208 of each adjacent link. Furthermore, each inwardly offset end 206 of a link 202 may be coupled to the inwardly offset end 206 of an opposing link, and each outwardly offset end 208 of a link 202 may be coupled to the outwardly offset end 208 of an opposing link by the track bushings 204. However, it should be understood that the links 202 do not necessarily have to be offset links. Rather, in some embodiments, the links 202 may include inner links and outer links. In these embodiments, the ends of each opposing pair of inner links are positioned between the ends of the opposing outer links, as is known in the art.

[0022] In some embodiments, at least a portion of this disclosure relates to the formation, creation, and / or manufacture of a track bushing 204, its components, and a system in which the track bushing is used, such as a track chain assembly 160 and / or machine 100. Furthermore, the forming mechanism of the track bushing 204 may be applied to other components, such as other components of the track chain assembly 160 and / or machine 100.

[0023] Figure 3 is a schematic diagram of an exemplary bushing 204 according to an exemplary embodiment of the present disclosure. The track bushing 204 has an inner surface 302 and a thickness "T" between them. TIt may have a substantially hollow cylindrical shape, including an outer surface 304 that defines the inner surface 302 and the outer surface 304. As shown, the inner surface 302 and the outer surface 304 may have curvatures that define the round shape of the track bushing 204. The track bushing 204 also has a first end ring 306 and a second end ring 308 that define the length "L" of the track bushing 204.

[0024] The shape and dimensions of the track bushing 204 may vary depending on the application. For example, a larger track chain assembly 160 may include a larger track bushing 204 than smaller track chain assemblies 160. The thickness of various parts of the track bushing 204 (e.g., hardened surface layer, softer core portion) may also vary depending on the application of the track bushing 204.

[0025] The track bushing 204 according to the exemplary embodiments of this disclosure may be made of high-carbon steel with additional treatments disclosed herein. High-carbon steel, as used herein, includes alloy steel having a high carbon content. The carbon content of the track bushing 204 may be greater than approximately 0.8 wt% of carbon content before it is formed and before any hardening and / or tempering treatment. In other exemplary embodiments, the track bushing 204 may be greater than approximately 0.9 wt% of carbon content before it is formed and before any hardening and / or tempering treatment. For example, the track bushing may be formed from 52100 steel having a carbon content greater than 0.9 wt%, such as a carbon content of approximately 0.95 wt% to 1.1 wt%. In some exemplary embodiments, the carbon content of the track bushing 204 may be greater than approximately 1.1 wt% of carbon content, and optionally up to 2 wt% of carbon content, before it is formed and before any hardening and / or tempering treatment. Other elements present in steel include, but are not limited to, cobalt (Co), molybdenum (Mo), nickel (Ni), titanium (Ti), tungsten (W), niobium (Nb), vanadium (V), and combinations thereof.

[0026] In alternative embodiments, the track bushing 204 may be made of a high-carbon steel, such as a high-carbon alloy steel, using additional treatments disclosed herein. In these embodiments, the carbon content of the track bushing 204 may be approximately 0.4–0.8% by weight. In some cases, the track bushing 204 may have a carbon content of approximately 0.6–0.8% by weight before being formed and before any hardening and / or tempering treatments.

[0027] Track bushing 204 steel may further contain other elements such as manganese (Mn), phosphorus (P), sulfur (S), silicon (Si), chromium, and / or other materials. For example, the steel may contain approximately 0.1% to 0.6% by weight of manganese, approximately 0% to 0.1% by weight of phosphorus, approximately 0% to 0.1% by weight of sulfur, approximately 0.1% to 0.5% by weight of silicon, and / or approximately 0.6% to 3% by weight of chromium before any hardening and / or tempering treatment.

[0028] During rough bushing formation, the track bushing 204 steel may have a spheroidized cementite crystalline structure. The spheroidized cementite structure may be soft and ductile, allowing for easier formation of the track bushing 204. In exemplary embodiments, if the starting high-carbon steel does not have a spheroidized cementite structure, a spheroidizing process can be carried out. In exemplary embodiments, the spheroidizing process may be carried out at the carbon steel eutectic temperature during a multi-hour annealing. For example, the steel may be held at 700°C for 30 hours to spheroidize the steel before roughening the track bushing 204. The temperature and / or time ranges in this specification and / or throughout this disclosure are examples, and temperatures and shorter or longer periods may be used according to exemplary embodiments of this disclosure.

[0029] According to exemplary embodiments of this disclosure, the formed track bushing 204 may undergo various heat treatments, such as a direct hardening process, and then an induction hardening process on the inner surface 302 or inner diameter (ID) of the track bushing 204. This induction hardening process following the direct hardening process may result in hardened steel in areas near both the outer surface 304 and the inner surface 302 of the track bushing 204, while the core portion may be softer and more ductile, resulting in improved wear resistance and toughness. Thus, as described herein, the outer portions of the track bushing 204, such as a specific depth into the bushing 204 near the inner surface 302 and a specific depth into the bushing near the outer surface 304, may have a predominantly martensitic and / or austenitic structure, while the inner portions of the track bushing 204, away from the inner surface 302 and the outer surface 304, may have a predominantly ferritic and / or cementite crystalline structure.

[0030] Figure 4 is a cross-sectional view of an exemplary bushing 400 according to an exemplary embodiment of the present disclosure. The cross-section of this exemplary bushing 400 may be an exemplary cross-section passing through the diameter of the track bushing 204, showing the exposed surface of the cross-section without showing the curved inner surface 302.

[0031] As shown in the diagram, the bushing 400 has a drilling diameter T H Total thickness T T The bushing may have a channel having a substantially constant diameter that penetrates the bushing 400 substantially in the center. The bushing may have an outer surface 402 similar to the outer surface 304, and an inner surface 412 similar to the inner surface 302 of the bushing 204. The bushing 400 has a thickness T from the interface 408 to the outer surface 402. O The outer portion 404 has a thickness T from the interface 414 to the inner surface 412. I It may have an inner portion 410 having a thickness T between the inner portion 410 and the outer portion 404. CA core portion 406 having [the relevant feature] may be arranged. The core portion 406 and the outer portion 404 may intersect at an interface 408, and the core portion 406 and the inner portion 410 may intersect at an interface 414. The interfaces 408, 414 are shown as distinct interfaces for illustrative purposes, but it should be understood that the transition between the outer portion 404 and the core portion 406, and / or the transition between the inner portion 410 and the core portion, can be gradual and / or stepwise. As discussed herein, the thickness dimension is in the radial direction from a channel that substantially penetrates the bushing 400 at the center.

[0032] In some exemplary embodiments, T T may be in the range of about 7 mm to about 20 mm, and T O may be in the range of about 2 mm to about 11 mm, and T C may be in the range of about 1 mm to about 10 mm, and T I may be in the range of about 1 mm to about 6 mm, and T H may be in the range of about 30 mm to about 80 mm. In other exemplary embodiments, T T may be within the range of about 10 mm to about 15 mm, and T O may be within the range of about 5 mm to about 9 mm, and T C may be within the range of about 2 mm to about 5 mm, and T I may be within the range of about 2 mm to about 4 mm, and T H may be within the range of about 40 mm to about 60 mm. An example of the dimensions of the total thickness T T of the bushing, the perforation diameter T H the thickness T O of the outer portion, the thickness T I of the inner portion, and the thickness T C of the core portion is shown in FIG. 5 of this specification.

[0033] In some exemplary embodiments, the ratio of the thickness of the outer portion to the total thickness (T O : T T ) may be within the range of about 1:10 to about 2:3. The ratio of the thickness of the inner portion to the total thickness (T I : T TThe ratio of the core thickness to the total thickness (T) may be within the range of approximately 1:20 to approximately 1:2. C :T T The ratio can be within the range of approximately 1:20 to 2:3.

[0034] According to exemplary embodiments, the inner portion 410 and outer portion 404 of the bushing 400 may be substantially martensitic and / or austenitic in their crystalline structure. On the other hand, the core portion 406 may be cementite, ferrite, and / or pearlite in its crystalline structure. The core portion 406 may also include a martensitic crystalline structure. As disclosed herein, the inner portion 410 and outer portion 404 of the bushing 400 may be harder than the core portion 406 of the bushing 400.

[0035] In some exemplary embodiments, the inner portion 410 and the outer portion 404 may have a hardness in the range of about 55 Rockwell hardness C scale (HRC) to about 64 HRC, and the core portion 406 may have a hardness in the range of about 39 HRC to about 52 HRC. In other exemplary embodiments, the inner portion 410 and the outer portion 404 may have a hardness in the range of about 58 HRC to about 62 HRC, and the core portion 406 may have a hardness in the range of about 40 HRC to about 45 HRC.

[0036] Bushing 400 may be manufactured by forming a rough bushing using spheroidized cementite steel such as 52100 steel. Where used herein, rough bushing refers to forming a bushing using a high-carbon steel starting material such as high-carbon alloy steel before any subsequent heat treatment, hardening, tempering, or similar. High-carbon steels, including high-carbon alloy steels with cementite structures, may be easier to machine than hardened carbon steels. The rough bushing may undergo a hardening process such as direct hardening. This direct hardening may be carried out in any suitable furnace, such as an induction furnace or a gas furnace. In some cases, this direct hardening process may be a batch process in which multiple rough bushings and / or other components of machine 100 may be hardened simultaneously. The rough bushing may be quenched, for example, in oil. Any tempering process may be carried out after the hardening process, for example. The rough bushing as a whole may have a hardened martensitic structure, an austenitic structure, and / or bainite structure. In other words, a rough bushing can be cured substantially uniformly after the curing process.

[0037] The induction hardening process may be carried out on the inner surface 412 (e.g., inner diameter (ID)) of the hardened bushing. Surface heating may be carried out by inducing an electric current from an alternating magnetic and / or electric field proximal to the inner surface 412 of the bushing 400. The induction hardening process may harden a region near the inner surface 412 by surface heating. Surface hardening may form the inner portion 410 of the bushing 400. Simultaneously, induction heating may cause tempering of the core portion 406 of the bushing 400. Thus, surface hardening may cause the inner portion 410 to be reheated and quenched to produce a hard martensite and / or austenite structure, while at the same time, the core portion 406 may be tempered to transition from a hard martensite and / or austenite structure to a softer cementite structure. In this way, the soft core portion 406 is achieved while the hard inner portion 410 and outer portion 404 are achieved.

[0038] Figure 5 is another cross-sectional view of a particular bushing 500 according to an exemplary embodiment of the present disclosure. The cross-section of this bushing 500 may be an exemplary cross-section through the diameter of the track bushing 204, showing the exposed face of the cross-section without showing the curved inner surface 302. The dimensions and parameter ranges discussed herein are illustrative and not intended to limit them in any way.

[0039] The bushing 500 may have a total thickness of 12.8 mm with a bore diameter of 49 mm. The bushing 500 may have an outer portion 502 with a thickness of 7 mm and an inner portion 508 with a thickness of 3 mm. Between the inner portion 508 and the outer portion 502, a core portion 506 may be positioned, having a thickness of 2.8 mm at the edge of the bushing 500 and 5.3 mm near the center of the bushing 500. In exemplary embodiments, the inner portion 508 and the outer portion 502 may have a hardness in the range of about 58 HRC to about 62 HRC, and the core portion 506 may have a hardness in the range of about 40 HRC to about 45 HRC. The thicknesses of the various regions 502, 506, and 508 of the bushing 500, and their relative ratios, are within the range disclosed with reference to the bushing 400 in Figure 4.

[0040] Figure 6 is a flowchart illustrating an exemplary method 600 for forming the exemplary bushing 400 of Figure 4, according to an exemplary embodiment of the present disclosure. Method 600 may be carried out using high-carbon steel in a speroidized cementite structure (e.g., spheroidized cementite and ferrite), as discussed herein. In exemplary embodiments, the starting steel may be 52100 steel or other similar high-carbon steel. Alternatively, a medium-carbon steel may be used.

[0041] High-carbon steel, as used herein, includes alloy steels having a high carbon content. The carbon content of high-carbon steel may be greater than approximately 0.8 wt%. In other exemplary embodiments, the track bushing may contain more than approximately 0.9 wt% carbon before being formed and before any hardening and / or tempering treatment. For example, the track bushing may be formed from 52100 steel having a carbon content greater than 0.9 wt%, such as approximately 0.95 wt% to 1.1 wt%. In some exemplary embodiments, the carbon content of the track bushing 204 may be more than approximately 1.1 wt% carbon, and optionally up to 2 wt% carbon, before being formed and before any hardening and / or tempering treatment. Other elements present in the steel include, but are not limited to, cobalt (Co), molybdenum (Mo), nickel (Ni), titanium (Ti), tungsten (W), niobium (Nb), vanadium (V), and combinations thereof.

[0042] As discussed herein, high-carbon steels, such as high-carbon alloy steels, in which rough bushings are formed, may be in a spheroidized cementite crystal structure. The spheroidized cementite structure may be soft and ductile, allowing for easier formation of the track bushings 204. In exemplary embodiments, if the starting high-carbon steel is not in a spheroidized cementite structure, a spheroidizing process may be optionally carried out before starting method 600. In exemplary embodiments, the spheroidizing process may be carried out over a period of annealing for several hours at the carbon steel eutectic temperature (e.g., 725°C). For example, the steel may be held at a temperature range of 650°C to 720°C for 20 to 40 hours to spheroidize the steel before roughening the track bushings 204.

[0043] In block 602, the bushing may be formed from high-carbon steel. As discussed above, the steel may be in a spheroidized cementite structure when forming the bushing. For example, the steel may mainly consist of spheroidized cementite, ferrite, and / or pearlite. If the steel has been hardened beforehand, the steel may also contain a martensite and / or austenite crystal structure. This form of high-carbon steel is relatively soft and ductile and therefore suitable for machining. The formation of the bushing, in this case a rough bushing, may involve any various machining techniques suitable for forming the bushing. For example, a rough bushing may be formed using any type of forming, turning, milling, drilling, grinding, and / or other machining techniques.

[0044] In block 604, direct hardening of the bushing can be performed. Direct hardening may be carried out by heating the bushing to a temperature higher than the eutectic temperature. This direct hardening may be carried out in any suitable furnace, such as an induction furnace or a gas furnace. In some cases, this direct hardening process may be a batch process in which multiple rough bushings and / or other components of machine 100 can be hardened simultaneously.

[0045] The furnace process may be carried out at any suitable temperature and time. For example, the furnace process may be carried out at over 800°C for a predetermined time. In some exemplary embodiments, the furnace process may be carried out in a temperature range of about 800°C to about 950°C for a time range of about 30 minutes to about 3 hours. For example, the furnace heating process for direct curing may be carried out at 850°C for 60 minutes. After the furnace process has been carried out, the rough bushing may be quenched, for example, in oil. Alternatively, the quenching process may be in any suitable medium such as a salt bath, air, and / or water. Any tempering process may be carried out after the curing process.

[0046] After the direct hardening process, the entire rough bushing may have a hardened martensite, austenite, and / or bainite structure. In other words, at this point the rough bushing has a thickness T T The hardening may be substantially uniform throughout. As a result of the direct hardening process, the overall hardness of the bushing may be in the range of about 55 HRC to about 62 HRC. For example, the bushing may be about 60 HRC after the direct hardening process.

[0047] Hardened martensitic carbon steel offers high wear resistance and reduced goring levels, but is generally brittle and lacks ductility. Therefore, uniform hardening of the bushing during this processing stage may result in a lower toughness than desired.

[0048] Block 606 allows for induction hardening on the inner surface of the bushing. Induction hardening on the inner surface 412 may be performed by providing a magnetic field and / or alternating electric field near the inner surface 412 to induce a current near the inner surface 412 according to Faraday's law. The magnetic field and / or alternating electric field may be generated near the inner surface 412 by inserting a coil electrically powered at a desired alternating frequency and power level into a channel substantially centrally defined by the inner surface 412 and extending adjacent to the inner surface 412. In some cases, the coil used to perform induction hardening may be shaped to heat the entire length L of the bushing simultaneously. Alternatively, the coil may be moved along the length L of the bushing (e.g., rasterized) so that the entire inner surface 412 is heated by the induced current.

[0049] The heating by this induction heating process may be localized near the inner surface 412 where the induced current is generated. Therefore, when using induction heating, there may be a temperature gradient extending within the bushing. In this case, the inner surface 412 may be the highest temperature, with a decrease in temperature extending radially within the bushing away from the inner surface 412. As a result, the region closest to the inner surface 412 is carbon steel A c1It may be heated above the temperature, and the region far from the inner surface 412 is made of carbon steel A c1 It may be heated below the temperature. c1 The temperature may be the temperature at which austenite begins to form when the carbon steel is heated. In this way, the region close to the inner surface 412 may be hardened, while the region far from the inner surface 412 may be tempered during the induction hardening process.

[0050] According to an exemplary embodiment, the power and frequency for induction curing are determined by the depth T of the inner portion 404 of the bushing 400. I It may be selected to control the depth T of the inner portion 404. I Then, the temperature during induction curing can rise to approximately 800°C to approximately 1000°C. In some exemplary embodiments, the temperature is within the depth T of the inner portion 404. I The internal temperature may rise to approximately 850°C to 950°C. For example, induction heating may be performed so that the temperature near the inner surface 412 is approximately 900°C.

[0051] As mentioned above, the depth T of the inner part 404 I When the internal temperature is in the range of approximately 800°C to approximately 1000°C, the temperature of the core portion 406 is lower than the temperature of the inner portion 404. In exemplary embodiments, the temperature inside the core portion 406 may be in the range of approximately 500°C to approximately 800°C during the induction curing process. In some exemplary embodiments, the temperature inside the core portion 406 during induction curing may be in the range of approximately 650°C to approximately 750°C. As a result, the core portion 406 may be tempered at the same time as the inner portion 404 is cured.

[0052] In exemplary embodiments, the induction curing time range may be in the range of about 3 seconds to about 3 hours. For example, the induction heating process may be carried out at 925°C for 30 seconds. After the induction heating process, the bushing may be quenched in air. Alternatively, the quenching process may be in any suitable medium such as a salt bath, oil, and / or water.

[0053] After the induction heating process, the bushing 400 may be hardened in the inner portion 404 and softened in the core portion 406. The outer portion 404 may not change substantially from when it was hardened as part of the direct hardening process of block 604. Thus, after the induction hardening process, the inner portion 410 and the outer portion 404 may have a hardness in the range of about 55 HRC to about 64 HRC, and the core portion 406 may have a hardness in the range of about 39 HRC to about 52 HRC. In other exemplary embodiments, the inner portion 410 and the outer portion 404 may have a hardness in the range of about 58 HRC to about 62 HRC, and the core portion 406 may have a hardness in the range of about 40 HRC to about 45 HRC.

[0054] It should be noted that some of the operations of Method 600 may be performed in a different order than presented, with additional elements and / or without some elements. Some of the operations of Method 600 may also be performed substantially simultaneously and therefore may finish in a different order than the operations shown above.

[0055] Figure 7 is a flowchart showing another exemplary method 700 for forming the exemplary bushing of Figure 4, according to exemplary embodiments of the present disclosure. Method 700 may be carried out in a speroidized cementite structure using high-carbon steel as discussed herein. In exemplary embodiments, the starting steel may be 52100 steel or other similar high-carbon steel. Alternatively, medium-carbon steel may be used.

[0056] As discussed herein, prior to any treatment, high-carbon steels, such as high-carbon alloy steels, may be in a spheroidized cementite crystal structure along with a ferrite crystal structure. The spheroidized cementite structure may be soft and ductile, allowing for easier formation of the track bushing 204. In exemplary embodiments, if the starting high-carbon steel is not in a spheroidized cementite structure, a spheroidizing process may be optionally carried out before starting method 700. In exemplary embodiments, the spheroidizing process may be carried out over a period of annealing for several hours at the carbon steel eutectic temperature (e.g., 725°C). For example, the steel may be held at a temperature range of 650°C to 720°C for 20 to 40 hours to spheroidize the steel before roughening the track bushing 204.

[0057] In block 702, the bushing may be formed from high-carbon steel. As discussed above, the steel may be in a spheroidized cementite structure when forming the bushing. This form of high-carbon steel is relatively soft and ductile and therefore suitable for machining. The formation of the bushing, in this case a rough bushing, may involve any various machining techniques suitable for forming the bushing. For example, a rough bushing may be formed using any type of forming, turning, milling, drilling, grinding, and / or other machining techniques.

[0058] In block 704, the bushing may be uniformly hardened to a first hardness level. As discussed herein, this can be achieved by a direct hardening process or other similar processes. The direct hardening process hardens the bushing to a first hardness level. c1 This may be carried out by heating to a temperature higher than the target temperature. This direct curing may be carried out in any suitable furnace, such as an induction furnace or a gas furnace. In some cases, this direct curing process may be a batch process in which multiple rough bushings and / or other components of machine 100 can be cured simultaneously.

[0059] The furnace process may be carried out at any suitable temperature and time. For example, the furnace process may be carried out at over 800°C for a predetermined time. In some exemplary embodiments, the furnace process may be carried out in a temperature range of about 800°C to about 950°C for a time range of about 30 minutes to about 3 hours. For example, the furnace heating process for direct curing may be carried out at 850°C for 60 minutes. After the furnace process has been carried out, the rough bushing may be quenched, for example, in oil. Alternatively, the quenching process may be in any suitable medium such as a salt bath, air, and / or water. Any tempering process may be carried out after the curing process.

[0060] After the direct hardening process, the entire rough bushing may have a hardened martensite, austenite, and / or bainite structure. In other words, at this point the rough bushing has a thickness T T The hardening may be substantially uniform throughout. As a result of the direct hardening process, the overall hardness of the bushing may be in the range of about 55 HRC to about 62 HRC. For example, the bushing may be about 60 HRC after the direct hardening process.

[0061] Hardened martensitic carbon steel offers high wear resistance and reduced goring levels, but is generally brittle and lacks ductility. Therefore, uniform hardening of the bushing during this processing stage may result in a lower toughness than desired.

[0062] In block 706, the bushings may be optionally tempered. This tempering process may, in particular, reduce stress and mitigate microcracking that may have resulted from the oil quenching process. In exemplary embodiments, the tempering process may be performed at a temperature in the range of about 100°C to about 200°C for about 30 minutes to about 3 hours. In one embodiment, the tempering process may be performed at 150°C for 60 minutes. In some cases, this tempering process may be performed together with other components of machine 100, such as other bushings 204. The tempering process may be performed in any suitable furnace or heating chamber, such as an induction furnace and / or a gas furnace.

[0063] In block 708, the inner surface of the bushing may be surface hardened, while the core of the bushing may be tempered so that the core has a lower hardness than the outer and inner surfaces. As discussed herein, this may be done using an induction hardening process. As discussed herein, induction hardening of the inner surface 412 may be done by providing a magnetic field and / or alternating electric field near the inner surface 412 to induce a current near the inner surface 412 according to Faraday's law. The magnetic field and / or alternating electric field can be generated near the inner surface 412 by inserting a coil electrically powered at a desired alternating frequency and power level in close proximity to the inner surface 412 within the bearing hole defined by the inner surface 412. In some cases, the coil used to carry out induction hardening may be shaped to heat the entire length L of the bushing simultaneously. Alternatively, the coil may be moved along the length L of the bushing (e.g., rasterized) so that the entire inner surface 412 is heated by the induced current.

[0064] The heating by this induction heating process may be localized near the inner surface 412 where the induced current is generated. Therefore, when using induction heating, there may be a temperature gradient extending within the bushing. In this case, the inner surface 412 may be the highest temperature, with a decrease in temperature extending radially within the bushing away from the inner surface 412. As a result, the region closest to the inner surface 412 may be heated above the carbon steel eutectic temperature, while the region far from the inner surface 412 may be heated below the carbon steel eutectic temperature. In this way, the region close to the inner surface 412 may be hardened, while the region far from the inner surface 412 may be tempered during the induction hardening process.

[0065] According to an exemplary embodiment, the power and frequency for induction curing are determined by the depth T of the inner portion 404 of the bushing 400. I It may be selected to control the depth T of the inner portion 404. I Then, the temperature during induction curing can rise to approximately 800°C to approximately 1000°C. In some exemplary embodiments, the temperature is within the depth T of the inner portion 404. I The internal temperature may rise to approximately 850°C to 950°C. For example, induction heating may be performed so that the temperature near the inner surface 412 is approximately 900°C.

[0066] As mentioned above, the depth T of the inner part 404 I When the internal temperature is in the range of approximately 800°C to approximately 1000°C, the temperature of the core portion 406 is lower than the temperature of the inner portion 404. In exemplary embodiments, the temperature inside the core portion 406 may be in the range of approximately 500°C to approximately 800°C during the induction curing process. In some exemplary embodiments, the temperature inside the core portion 406 during induction curing may be in the range of approximately 650°C to approximately 750°C. As a result, the core portion 406 may be tempered at the same time as the inner portion 404 is cured.

[0067] In exemplary embodiments, the induction curing time range may be in the range of about 3 seconds to about 3 hours. For example, the induction heating process may be carried out at 925°C for 15 seconds. After the induction heating process, the bushing may be quenched in air. Alternatively, the quenching process may be in any suitable medium such as a salt bath, oil, and / or water.

[0068] After the induction heating process, the bushing 400 may be hardened in the inner portion 404 and softened in the core portion 406. The outer portion 404 may not change substantially from when it was hardened as part of the direct hardening process of block 704. Thus, after the induction hardening process, the inner portion 410 and the outer portion 404 may have a hardness in the range of about 55 HRC to about 64 HRC, and the core portion 406 may have a hardness in the range of about 39 HRC to about 52 HRC. In other exemplary embodiments, the inner portion 410 and the outer portion 404 may have a hardness in the range of about 58 HRC to about 62 HRC, and the core portion 406 may have a hardness in the range of about 40 HRC to about 45 HRC.

[0069] It should be noted that some of the operations of Method 700 may be performed in a different order than presented, with additional elements and / or without some elements. Furthermore, some of the operations of Method 700 may be performed substantially simultaneously and therefore may finish in a different order than the operations shown above. [Industrial applicability]

[0070] This disclosure describes systems, structures, and methods for improving the wear resistance and toughness of components, such as components of a track-type machine 100. These improved components may include a bushing 204 used in a track chain assembly 160 of the machine 100. The bushing 204 disclosed herein may have a hard, wear-resistant outer and inner portion, as well as a soft core portion. The soft core portion provides a high level of toughness to the bushing 204, while the hard outer and inner portions provide a high level of wear resistance and reduce goring during operation. Although the bushing 204 and procedures from the bushing 204 are discussed in the context of track-type machines and the undercarriages of such track-type machines, the bushing 204 and the mechanism forming it are, naturally, applicable across a wide range of mechanical systems, such as any mechanical system that can benefit from the improved wear resistance of the bushing and / or other components.

[0071] As a result of the systems, apparatus, and methods described herein, consumable parts of machinery, such as bushings, may have a longer lifespan. For example, the track bushing 204 described herein may have a longer lifespan than a conventional bushing 204 not formed by the mechanism described herein. In some cases, the bushing 204 and / or other components may enable a 25% to 400% improvement in the wear life of consumable parts of the track-type machine 100. This reduces field downtime, decreases the frequency of service and maintenance, and reduces the overall cost of heavy machinery such as the track-type machine 100. Improved reliability and reduced field-level downtime also improve the user experience, allowing the machine 100 to dedicate itself to its intended purpose for a longer time and a greater proportion of its overall lifespan. Improved uptime and reduced periodic maintenance of the machine 100 may enable a more efficient allocation of resources (e.g., fewer but more reliable machines 100 on a construction site). Therefore, the technologies disclosed herein improve the efficiency of project resources (e.g., construction resources, mining resources, etc.), provide longer operating hours for project resources, and improve the financial performance of project resources.

[0072] While aspects of this disclosure have been specifically shown and described with reference to the embodiments described above, it will be understood that various additional embodiments are intended by modifications of the disclosed machines, systems, and methods without departing from the spirit and scope of the disclosed content. Such embodiments should be understood to fall within the scope of this disclosure as determined by the claims and any equivalents thereof.

[0073] The listing of value ranges in this specification is merely intended to serve as a convenient way to refer individually to the individual values ​​within those ranges unless otherwise specified herein, and each individual value is incorporated herein as if it were listed individually. Unless otherwise specified herein, all methods described herein may be carried out in any suitable order.

Claims

1. A method for manufacturing a bushing (204), The method involves hardening a rough bushing by furnace heating, wherein the rough bushing is formed from high-carbon steel having a carbon content of more than 0.8% by weight before hardening by furnace heating, and the high-carbon steel contains a spheroidized cementite crystal structure. A method comprising: performing induction heating to harden the inner surface (302) of the rough bushing to form a hardened inner portion (410) and a soft core portion (406) of the bushing (204).

2. The method according to claim 1, wherein the high-carbon steel is 52100 steel.

3. The method according to claim 1, wherein the inner portion has a hardness of at least 55 HRC and the outer portion has a hardness of at least 55 HRC.

4. The curing process by heating the aforementioned furnace is carried out The rough bushing is heated to at least 800°C for a predetermined time, The method according to claim 1, comprising rapidly cooling the rough bushing.

5. The method according to claim 1, wherein the ratio of the thickness of the inner portion (410) to the thickness of the bushing (204) is in the range of 1:20 to 1:

2.

6. Bushing (204), An outer surface (402) and an inner surface (412) facing the outer surface (402), wherein the inner surface (412) defines a channel having substantially a constant diameter, and the channel penetrates the bushing (204) substantially through its center from a first end of the bushing to a second end of the bushing (204) facing the first end, the outer surface and the inner surface, An inner portion (410) including the inner surface (412), wherein the inner portion (410) has a uniform thickness and extends along the entire inner surface (412), An outer portion (404) including the outer surface (402), wherein the outer portion (404) has a uniform thickness and extends along the entire outer surface (402), The system comprises a core portion (406) positioned between the inner portion (410) and the outer portion (404), The core portion (406) comprises an intermediate portion having a first thickness and an end portion having a second thickness. The core portion (406) has a hardness lower than that of the inner portion (410) and the outer portion (404). The bushing (204) comprises the core portion (406), the inner portion (410), and the outer portion (404), all of which are made of steel having a carbon content exceeding 0.8% by weight.

7. The inner portion has a hardness of at least 55 HRC, The aforementioned outer portion has a hardness of at least 55 HRC, The bushing according to claim 6, wherein the core portion has a hardness of less than 52 HRC.

8. The bushing according to claim 6, wherein the inner portion (410) and the outer portion (404) have a martensitic crystal structure.

9. The bushing according to claim 6, wherein the outer portion has a thickness of at least 5 mm.

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