Explosion-proof deep-hardened crawler track shoes

Abstract

Method for manufacturing a caterpillar track shoe (20), comprising: Casting a crawler track shoe (20) made of manganese steel, wherein the crawler track shoe (20) has at least one drive lug (44) arranged on a top surface (39) and at least one wear surface (43, 46, 48) arranged on the at least one drive lug (44), Solution treatment of the caterpillar track shoe (20) to form fully austenitic manganese steel, Attaching an explosive material (52) to at least one wear surface (43, 46, 48) and Ignition of the explosive material (52).

Description

Technical area

[0001] The present disclosure relates generally to track shoes and, more particularly, to explosive deep-hardened track shoes. background

[0002] A mobile tracked machine or vehicle uses tracks attached to both sides of the machine to propel the machine or vehicle. The tracks each comprise a chain with links pinned together to form a loop extending around a drive sprocket and one or more idler wheels, and ground engaging shoes connected to each pair of track links. A ground engaging shoe, along with a pair of track links, may commonly be referred to as a track shoe. In some embodiments, the track shoe is a cast and / or forged component constructed of steel. During operation, each track shoe encounters forces caused by the weight of the machine and the torque of the engine arranged to drive the machine. The forces are transferred through the track shoes into the ground surface, creating traction to propel the machine.

[0003] Over time, the forces acting on the track shoes can cause localized wear and plastic deformation, which can lead to a shortened track shoe life. Steel track shoes are sometimes hardened using heat treatment processes, such as quenching and tempering, to resist wear and extend the life of the track shoes. Typically, multiple heat treatment steps are used to achieve a minimum hardness at specific depths below the surface of the track shoes. An example of such a hardening process is disclosed in U.S. Patent 7,040,080 to Okawa et al., issued May 9, 2006. However, hardening processes that involve multiple tempering and / or other heat treatment steps require high energy inputs and are expensive, ultimately increasing the price of the track shoes for the end user.

[0004] DE 25 35 519 A1 describes the production of frost-resistant steels, in particular the production of steels containing carbon, manganese, silicon, chromium, niobium, boron, iron and, as admixtures, sulfur and phosphorus.

[0005] From CN 1 03 160 679 A, ​​an explosion hardening process of high-manganese steel for a lining plate and a movable cone and a fixed cone of a cone crusher is known.

[0006] US 2 823 082 A relates to tread elements which, when pivotally connected, form endless chains for earth-working machines or the like and are made by casting from austenitic manganese steel.

[0007] The disclosed track shoes are directed to overcoming one or more of the problems set forth above. Summary of Revelation

[0008] According to one aspect, the present disclosure relates to a method for manufacturing a track shoe. The method comprises casting a track shoe from manganese steel, the track shoe having at least one drive link disposed on a top surface and at least one wear surface disposed on the at least one drive link. The method further comprises solution treating the track shoe to form a fully austenitic manganese steel, applying explosive material to the at least one wear surface, and detonating the explosive material.

[0009] According to another aspect, the present disclosure relates to a track shoe comprising a ground-engaging shoe formed entirely from austenitic manganese steel, a ground-engaging surface disposed on a bottom surface of the ground-engaging shoe, an upper surface opposite the bottom surface, at least one drive plate disposed on the top surface, and at least one hardened wear surface disposed on the top surface. The at least one wear surface is hardened by explosive deep hardening and is disposed on the at least one drive plate. Short description of the drawings Fig. 1 is a side view of an exemplary disclosed mobile machine or vehicle, Fig. 2 is a perspective view of an exemplary disclosed track shoe used in conjunction with the mobile machine of Fig. 1 can be used, Fig. 3 is a plan view of the crawler shoe of the Fig. 2, Fig. 4 is a perspective view of a second exemplary disclosed track shoe used in conjunction with the mobile machine of Fig. 1 can be used, and Fig. 5 is a flow chart showing an exemplary disclosed method for manufacturing crawler shoes used to manufacture the crawler shoes of the Fig. 2 to 4 can be used. Detailed description

[0010] The Fig. 1 illustrates a mobile tracked vehicle or machine 10 having an engine 12 supported by a frame and configured to drive a track subframe 14. The mobile machine 10 may be any machine capable of performing work associated with an industry, such as mining, construction, agriculture, or any other known industry. For example, the machine 10 may be a material handling machine, such as a backhoe, dragline, hydraulic excavator, grader, loader, or any other material handling machine.

[0011] The undercarriage 14 may have parallel track assemblies 16 arranged on opposite sides of the machine 10 and driven by the engine 12 via respective drive wheels 18 (in the Fig. 1, only one track assembly 16 and one drive sprocket 18 are shown). Each track assembly 16 may include a plurality of track shoes 20 connected together by pins 22 to form an endless track. The endless track of the track shoes 20 may be wrapped around the corresponding drive sprockets 18, one or more idler sprockets 24, and at least one idler pulley 26. The drive sprockets 18 may engage the pins 22 (or bushings disposed around the pins 22), drive plates, or other elements of the track shoes, thereby transmitting torque from the engine 12 to the track assemblies 16. The idler sprockets 24 and idler pulleys 26 may guide the track assemblies 16 around the drive sprockets 18 along a generally elliptical trajectory.A tensioner 18 may be arranged between the idler 24 and the drive wheel 18 to force the track links apart and thereby maintain a desired tension of the track assembly 16. The track shoes 20 may be configured to transfer the torque of the drive wheels 18 into the ground as a linear drive or traction force 30. The weight of the machine may be transferred from the drive wheel 18, the idler 24, and the track rollers 26 through the track shoes 20 into the ground as a load-bearing force 32.

[0012] The Fig. 2 shows an exemplary track shoe 20 engaging a track roller 26. The track shoe 20 may include one or more pairs of spaced-apart links 34 that are generally parallel to one another. Each link 24 may have at least one pin bore 26 formed at one end thereof for connecting to links of other track shoes, thereby forming a track. The track shoe 20 may include a ground engaging shoe 38, and the links 34 may be disposed on a top surface 39 of the ground engaging shoe 38, rigidly connecting the links 34 to one another. A ground engaging surface 40 may be disposed on a bottom surface 41 of the ground engaging shoe 38 opposite the links 34. The ground engaging shoe 38 and the links 34 are integrally formed as a single cast and / or forged component in this example.In further embodiments, the members 34 and the ground-engaging shoe 38 may be formed separately and joined together by any suitable known process, such as welding and / or, if desired, threaded fasteners. The ground-engaging shoe 38 may have any known external geometry. For example, the ground-engaging shoe 38 may be generally plate-shaped, have transverse ribs or webs, apertures, and / or any conventionally known features.

[0013] The ground engaging shoe 38 may have a track roller track 42 disposed on its top surface 39. The track roller track 42 may be disposed between the links 34 and extend over the track shoe 20. A wear surface 43 may be disposed on a track roller track 42 that engages the track roller 26. The track roller tracks 42 and wear surfaces 43 of all track shoes 20 within a particular track assembly 16 may form a substantially continuous smooth surface upon which the track rollers 26 may roll. The weight of the machine 10 may be transferred from the track rollers 26 via the wear surface 43, thereby applying a load 32 to the wear surface 43. Over time, the load 32 may cause plastic deformation of the track shoe 20 at the wear surface 43. The wear surface 43 may be flat, curved or have any suitable shape for engagement with the roller 26.For example, the roller 26 may have a curvature (C) (see . Fig. 2), and the wear surface 43 may be shaped with a similar curvature. As the machine 10 moves, additional rolling and / or sliding forces between the wear surface 43 and the track roller 26 may create frictional wear of the wear surface 43. Coarse debris, such as gravel, dirt, sand, or other ground material, may accumulate or deposit between the roller 26 and the wear surface 43, causing additional wear and / or abrading of the wear surface 43.

[0014] In the example of Fig. 2, the track shoe 20 includes a pair of drive plates 44 disposed on a top surface 39 of the ground engaging shoe 38 and engaging the drive wheels 18 of the track assembly 16. The drive plates 44 may be disposed between the links 34 on either side of the wear surface 43. In other embodiments, the drive plates 44 may be disposed at other positions on the track shoes, with fewer or more drive plates 44 being provided. The drive plates 44 may contact openings, pockets, or teeth of the drive wheel 18 of the track assembly 16 to receive torque from the engine 12 and provide the traction force 30 to the track shoe 20 to move the machine 10. The drive plates 44 may include one or more wear surfaces 46 that contact the drive wheels 18.As the machine 10 moves, the wear surfaces 46 experience abrasion and / or wear from the forces transmitted by the drive wheels 18, which may be exacerbated if coarse debris accumulates or is deposited between the drive plates 44 and the drive wheels 18.

[0015] The Fig. 3 shows a top view of the track shoe 20. The wear surfaces 46 may be disposed on the front and rear sides of the drive plates 44 so that the machine 10 can be driven in forward and reverse directions. In this example, the drive plates 44 are located adjacent to the wear surfaces 43, but in other embodiments, they may be disposed elsewhere. The idler rollers 26 may also be configured to engage or slide against the inner surfaces of the drive plates 44 as they move along the wear surface 43, thereby assisting in guiding the track assembly 16 along a desired trajectory around the idler wheel 24 and the drive sprocket 18.

[0016] In other embodiments, the drive wheels 18 may alternatively engage the pins 22 to provide the traction force 30 to the track shoes 20. For example, Fig. 4 shows a second exemplary track shoe 20 having pairs of spaced links 34 arranged generally parallel to each other. Each link 34 may have at least one pin bore 36 formed at one end thereof. The links 24 may be configured to connect to links 34 of adjacent track shoes by aligning the pin bores 36 of adjacent links and inserting pins 22 through the pin bores 36, thereby forming a track. It is contemplated that further configurations are possible.

[0017] The track shoes 20 may include a wear surface 48 disposed on at least one link 34. The wear surface 48 may be configured to engage elements associated with the drive sprocket 18, the idler wheel 24, and / or the track roller 26 of the track assembly 16. The wear surface 48 may be disposed on a top surface 39 of the ground engagement shoe 38 of the track shoe 20. In this example, in addition to passing through the track rollers 26, the load bearing elements 32 may also pass through a hub 50 of the track roller 26 to the track shoe 20, rolling over the wear surface 48 of each link 34. The wear surface 48 may be flat or configured to conform to the shape of the hub 50, the idler wheel 24, and / or the drive sprocket 18. Over time, the load-bearing forces 32 can cause wear and / or plastic deformation of the wear surfaces 48.Wear may be increased if coarse debris accumulates or deposits between the wear surfaces 48 and the hub 50, the impeller 24 and / or the drive wheel 18.

[0018] To withstand the load-bearing forces 32 without cracking or breaking, the crawler shoes 20 are formed from a high-strength metal, namely manganese steel. Manganese steel can be cast to produce crawler shoes 20 with suitable shapes and dimensions, but can be brittle after casting. Consequently, crawler shoes cast from manganese steel can be solution-treated to impart an austenitic grain structure to the metal, which improves overall hardness. Chromium can be added to the manganese steel prior to casting to promote faster work hardening of the austenitic manganese steel. Because austenitic manganese steel is also soft, the crawler shoes 20 can experience plastic deformation near the wear surfaces 43, 46, and 48 during operation.Instead of subjecting the track shoes 20 to costly and time-consuming heat treatment processes, an explosion-based deep hardening process is used to harden specific areas of the track shoes 20, such as the wear surfaces 43, 46, and 48. Explosion-based deep hardening can locally harden the austenitic manganese steel to resist wear and pre-harden the steel, reducing plastic deformation during operation. Reducing wear and plastic deformation can increase the uptime of the track shoes and reduce the overall cost to the end user. Methods for forming and hardening track shoes formed from manganese steel are discussed in the following section with reference to the . Fig. 5 described. Industrial applicability

[0019] The track shoes of the present disclosure can be used on any mobile tracked machine or vehicle. However, the disclosed track shoes may be particularly applicable to large machines where the forces passing through the track assembly are significant and may affect the longevity of the track shoes. This may be particularly important for high-cost machines that operate around the clock, where downtime and the cost of replacing track shoes are costly for the owner. Methods for manufacturing and hardening track shoes made of manganese steel will now be described with reference to the Fig. 5 described.

[0020] In a method 500, track shoes 20 may be cast from manganese steel according to a suitable casting process known in the art (step 502). According to the present disclosure, manganese steel may refer to any type of steel or manganese steel alloy for high-strength applications. In some embodiments, chromium may be added to the manganese steel prior to casting to increase the work hardening rate of manufactured track shoes 20. For example, the track shoes 20 may be made from manganese steel containing between approximately 1.0-3.5% chromium. Because the work hardening rate increases as more chromium is added, the track shoes 20 may be cast from a manganese steel containing at least 1.0% chromium to reduce plastic deformation of the track shoes 20 during operation. However, the addition of chromium may be limited to prevent carbide embrittlement of the manganese steel.

[0021] For example, manganese steel containing 14% manganese may contain approximately 1.5% chromium. It is envisioned that manganese steel containing other amounts of chromium may also be used, depending on the manganese content in the steel and the extent to which it is desired to influence the work hardening rate. It is also envisioned that other manganese steel alloys may be used.

[0022] The track shoes 20 cast from manganese steel may be brittle after casting. Consequently, the track shoes 20 are then solution treated (step 504) to increase the strength of the metal and reduce brittleness. The solution treatment may involve raising the temperature of the manganese steel to a high temperature (e.g., approximately 1000°C) for approximately 1-6 hours (depending on the size and thickness of the track shoe 20) to achieve a fully austenitic grain structure within the manganese steel alloys. Manganese steel with a fully austenitic grain structure is hard but can be considered "soft" and may be further hardened to reduce plastic deformation during service and resist surface wear during work hardening.However, further heat treatment processes, such as those traditionally used to increase metal hardness, are not desirable for hardening fully austenitic manganese steels because reheating of fully austenitic manganese steels may result in embrittlement, which may lead to failure of the track shoe 20 under the action of the load-bearing forces 22.

[0023] The track shoes 20 may then, if desired, be slightly prepared by grinding processes (step 506) before explosive material is applied to one or more wear surfaces (for example, on the wear surfaces 43, 46, and 48 of the track shoe 20). Any suitable plastic explosive or any type of explosive material may be used. For example, suitable explosive materials may include, among other ingredients, PETN, RDX, HMX, TNT, or combinations thereof. The energy waves generated by the ignition or detonation of the explosive material may increase local hardening of the manganese steel at / or near the wear surfaces to which the explosive material has been applied. With exemplary reference to the Fig. 3, explosive material 52 may be attached to the wear surface 43 contacting the idler roller 26 and / or the surfaces 46 of the drive plates 44 contacting the drive wheel 18 of the track assembly 16. The explosive material 52 may also be attached to track shoes 20 having wear surfaces on the links 34, such as the wear surfaces 48 contacting the hubs 50 of the idler rollers 26 (see Fig. 4). It is contemplated that the explosive material may be applied to any wear surfaces or other surfaces of the crawler shoe 20 that are subject to plastic deformation or surface wear.

[0024] After ignition or detonation, wear surfaces 43 and 46 may be pre-hardened and therefore better able to withstand plastic deformation and surface wear during operation. This means that the energy of the detonation can cause plastic deformation of the manganese steel at or near wear surfaces 43 and 46, making them harder than ever before. As a result, track shoes 20 may be plastically deformed (and therefore hardened) at or near wear surfaces 43 and 46 before use in track assembly 16, reducing the degree of deformation occurring during operation.Reducing plastic deformation during cold forming can reduce loosening of the track assembly 16 within the undercarriage 14, thereby reducing impact forces, vibrations, and deformations that can reduce the life of the track shoes 20 and other components of the undercarriage 14.

[0025] Step 508 may be repeated multiple times to sufficiently harden the manganese steel at a specific depth below the surface of the track shoe (step 510). With each iteration of step 508, the manganese steel may be gradually hardened deeper and deeper below the surface of the track shoe 20. Instead of a single iteration of step 508 with a larger amount of explosive material, step 508 may be repeated multiple times to prevent damage to the track shoe 20. Step 508 may be repeated as many times as desired depending on the desired depth hardness, the desired surface hardness, and the amount of explosive material used during each iteration. For example, at least two, three, or more detonations may be required to achieve sufficient hardness. However, it is contemplated that a single detonation may be sufficient in some applications.

[0026] The desired depth hardness and surface hardness may depend on the size of the machine 10 and the harshness of the environment in which the track shoe 20 may be used. For example, the track shoe 20 may be explosively deep hardened until it has a hardness of approximately 280 HBW (Brinell hardness tested with a tungsten carbide ball) at a depth of approximately 5 mm below one or more wear surfaces (e.g., 43, 46, and / or 48). The depth hardening may pre-harden the track shoe 20 and reduce plastic deformation during operation. The explosively deep hardening may continue until the track shoe 20 has a hardness of at least approximately 350 HBW at one or more of the wear surfaces (e.g., 43, 46, and / or 48).This surface hardening can improve the resistance of the track shoes 20 to wear caused, for example, by the grinding of coarse materials between the track rollers 26 and the wear surfaces 43. Once one or more of the wear surfaces (e.g., 43, 46, and 48) of the track shoe 20 have been sufficiently hardened, the track shoe 20 can receive its final machining (step 512) in preparation for use with the machine 10.

[0027] The method 500 can be used to manufacture and / or harden manganese steel track shoes 20 at a lower cost than traditional hardening processes. By solution treating the manganese steel only when an austenitic grain structure is achieved, the method 500 can be used to harden the manganese steel track shoes with lower energy input. The time required to harden the track shoes can also be reduced by eliminating the need to repeat lengthy heat treatment processes. The hardened track shoes 20 can also require less maintenance grinding and track adjustments, thereby reducing overall maintenance costs.Accordingly, the method 500 can reduce both the energy input and the time required to harden the manganese steel track shoes, thereby increasing the life of the track shoes and reducing the cost to the end user.

[0028] Those skilled in the art will appreciate that various modifications and variations can be made to the disclosed track shoes. Other embodiments will become apparent to those skilled in the art through consideration of the specification and practice of the disclosed track shoes. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

[1] Method for producing a crawler track shoe (20), comprising: Casting a crawler chain shoe (20) from manganese steel, wherein the crawler chain shoe (20) has at least one drive plate (44) arranged on an upper side (39) and at least one wear surface (43, 46, 48) arranged on the at least one drive plate (44), Solution treating the crawler shoe (20) to form fully austenitic manganese steel, Applying an explosive material (52) to the at least one wear surface (43, 46, 48) and Detonation of the explosive material (52). [2] The method of claim 1, further comprising re-applying an explosive material (52) to the at least one wear surface (43, 46, 48) one or more times and igniting the explosive material (52). [3] A method according to any one of the preceding claims, wherein casting the crawler shoe (20) from manganese steel comprises casting the crawler shoe (20) from a chromium-containing manganese steel. [4] Method according to one of the preceding claims, wherein: the crawler shoe (20) further comprises: laterally spaced chain links (34) and a wear surface (43) arranged between the laterally spaced chain links (34), and the application of explosive material (52) to the at least one wear surface (43, 46, 48) comprises application of explosive material (52) to the wear surface (43) between the laterally spaced chain links (34). [5] Method according to one of the preceding claims, wherein: the crawler shoe (20) further comprises: laterally spaced chain links (34) and a wear surface (48) arranged on at least one of the laterally spaced chain links (34), and the application of explosive material (52) to the at least one wear surface (43, 46, 48) comprises application of explosive material (52) to the wear surface (48) arranged on the at least one of the laterally spaced chain links (34). [6] Track shoe (20), with: a ground engagement shoe (38) made of fully austenitic manganese steel, a ground engagement surface (40) arranged on an underside of the ground engagement shoe (38), an upper side (39) opposite the underside (41), at least one drive tab (44) arranged on the upper side (39), and at least one hardened wear surface (43, 46, 48) arranged on the upper side (39), wherein the at least one wear surface (43, 46, 48) is hardened by explosion-based deep hardening and is arranged on the at least one drive plate (44). [7] The crawler shoe (20) of claim 6, wherein the ground engaging shoe (38) is formed of fully austenitic manganese steel containing chromium. [8] Crawler chain shoe (20) according to one of claims 6 to 7, wherein the crawler chain shoe (20) further comprises a roller track (42) arranged on the upper side (39) and the at least one wear surface (43) is arranged on the roller track (42). [9] Crawler chain shoe (20) according to one of claims 6 to 8, wherein the crawler chain shoe (20) further comprises laterally spaced chain links (34) arranged on the upper side (39) and the at least one wear surface (48) is arranged on the laterally spaced chain links (34).

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