Lip for excavator bucket

Abstract

A cast lip for a digging bucket, the cast lip being composed of a ferrous alloy having at least 7 wt% chromium, 3-6 wt% nickel and < 0.12 wt% carbon and having a primary martensitic structure.

Description

[0001] This application is a divisional application of the invention patent application filed on March 26, 2020, with application number 202080022903.3 and invention title "Lip for Excavator Bucket".

[0002] Related applications

[0003] This application claims priority to U.S. Provisional Patent Application No. 62 / 824,949, filed March 27, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0004] This disclosure relates to a lip for a digging bucket used in excavators such as dragline excavators, cable shovels, front shovels, and hydraulic excavators. Background Technology

[0005] Excavators, such as those used in mining and construction operations, include a bucket that engages the ground to collect large quantities of earthen material. The bucket is generally defined by a rear wall, bottom wall, and side walls, which define a cavity with an open front for receiving the excavated material. The leading edge of the bottom wall has a lip, to which ground engagement tools, such as teeth, adapters, and / or guards, are typically attached to protect the lip from wear and to better break up the ground during excavation. The lip is formed from plate steel (called a plate lip) or by a casting method (called a cast lip). Summary of the Invention

[0006] In the first example, the casting lip of the excavation equipment is made of an iron alloy having at least 7% by weight chromium and a primary martensitic structure.

[0007] In another example, the casting lip used in excavation equipment is made of an iron alloy having at least 7% chromium, at least 3% nickel, and 0.12% or less carbon and having a primary martensitic structure.

[0008] In another example, the casting lip for the excavating equipment is made of an iron alloy having at least 10% chromium, at least 3% nickel, and 0.12% or less carbon, and optionally 3% or less manganese, silicon, and / or molybdenum, and having a primary martensitic structure.

[0009] In another example, the casting lip used in excavation equipment is made of an iron alloy with 10%-15% chromium, 3%-6% nickel and 0.12% or less carbon and a primary martensitic structure.

[0010] In another example, the casting lip used in excavation equipment is made of an iron alloy having 10%-15% chromium, 3%-6% nickel, and ≤0.10% of each of carbon, manganese, silicon, and molybdenum, and having a primary martensitic structure.

[0011] In another example, the casting lip used in excavation equipment is made of an iron alloy having 7% to 10% chromium, at least 3% nickel, and 0.12% or less carbon and having a primary martensitic structure.

[0012] In another example, the casting lip used in excavation equipment is made of an iron alloy with 7%-9% chromium and 0.12% or less carbon and a primary martensitic structure.

[0013] In another example, the casting lip used for excavation equipment is made of an alloy with the same composition as CA6NM alloy and a primary martensitic structure.

[0014] In another example, the casting lip used in excavation equipment is made of low-carbon stainless steel with a primary martensitic structure.

[0015] In another example, the lip having any of the above alloys is formed by sand casting and / or air hardening methods.

[0016] In another example, a cast lip having any of the aforementioned alloys includes an inner surface and an outer surface, wherein the outer surface includes a groove, which, for example, can reduce the overall weight of the lip.

[0017] In another example, a cast lip having any of the aforementioned alloys includes a curved portion at least near each end of the lip, thereby curving the ends of the lip upwards and generally aligning them with the sidewall of the bucket. Such a lip is suitable for application with cable shovels, although other applications are possible. Optionally, the outer surface of the lip includes grooves.

[0018] The examples described above are each suitable for use as cast lips for excavating buckets found in large digging buckets, such as dragline excavators, cable shovels, front shovels, and hydraulic excavators. Such lips extend across the width of the bucket, forming the primary digging edge. Such lips can, for example, weigh up to about 30,000 pounds and / or have a maximum thickness of about nine inches or more.

[0019] Compared to current low-alloy steel cast lips, the lip according to this disclosure can provide improvements in terms of weld strength, fatigue strength and / or endurance limit with respect to weld, hardness and / or wear life.

[0020] In one example of a method for manufacturing a casting lip according to this disclosure, one of the aforementioned ferroalloys is melted, the molten alloy is fed into a sand mold to shape the alloy into a lip structure for excavating equipment, the alloy is hardened to give it a primary martensitic structure, and then the lip is tempered to obtain toughness. In one example, the lip is air-hardened.

[0021] The casting lip according to this disclosure can be repaired, rebuilt, fastened to the bucket and / or equipped with attachments by welding. In one example, welding is achieved using a welding material that is the same as or similar to the alloy base material.

[0022] In another example, both the lip and the welding material are ferrochrome alloys. In yet another example, the lip is made of CA6NM alloy and the welding material is type 309 stainless steel. Attached Figure Description

[0023] Figure 1 It is a perspective view of an excavating bucket having a lip according to this disclosure.

[0024] Figure 2 This is a top-view perspective view of the casting lip.

[0025] Figure 3 This is a bottom-view perspective view of the casting lip.

[0026] Figure 4 It is a perspective view of another excavating bucket having a lip according to this disclosure.

[0027] Figure 5 This is a perspective view of another example of a casting lip according to this disclosure, with a ground engagement tool attached. Detailed Implementation

[0028] This disclosure relates to casting lips for excavating buckets, such as those used in dragline excavators, cable shovels, front shovels, hydraulic excavators, etc.

[0029] A cast lip is a large steel structure that extends across the width of the bucket used on excavators, typically large mining machines, thus forming its primary digging edge. The lip can be formed by casting the entire lip in a mold or by casting lip segments and welding these segments together to form a complete lip. For example, a cast lip can weigh from approximately 6,500 pounds to approximately 29,000 pounds. Lip segments are typically smaller; as an example, an end segment can weigh approximately 2,000 pounds. Cast lips tend to have a maximum thickness of approximately 9 inches or more. Typically, they range from approximately 4 to 16 inches in maximum thickness, but other variations are possible. The thickness dimension is the distance between the inner and outer surfaces of the lip. A cast lip may include a forward-projecting nose for mounting digging teeth. The nose is typically cast integrally with the lip or lip segments. The nose may also be cast separately and welded to the front of the lip. Sometimes, such a nose can be fitted by an adapter welded to the lip. In other instances, an adapter with a nose is mechanically attached to the lip. This is typically the case for cable snare lips. For decades, cast lips have been made of low-alloy steel because of its high strength and toughness and low manufacturing cost.

[0030] Cast lips for excavating equipment are typically manufactured using sand casting, in which molten steel is fed into a sand mold. As with any large steel casting, producing a defect-free lip casting is very difficult. It is not uncommon for large castings to have some defects in the as-cast state. Typical defects can be inclusions, hot tears, cracks, porosity, etc. A common practice in steel foundries is to repair such defects by welding, as long as the repair does not impair the function of the finished part. Welding to cast lips is also common for other purposes. For example, given the size of the cast lips, they are sometimes cast in sections (typically two or three sections), which are then welded together to form a single lip. Cast lips are welded to the bucket. Noses, adapters, and guards are sometimes welded to the lip. Attachments, such as bosses, are sometimes welded to the lip to secure worn parts. Damage to the lip caused during use is also typically repaired and / or rebuilt by welding, typically along the front end.

[0031] Although in some cases weld repairs on low-alloy casting lips are performed with filler materials that roughly match the strength of the lip material, softer iron-based filler materials, such as E70 series carbon steel filler materials, are most commonly used for weld repairs. When the weld repair can undergo post-weld heat treatment (as is sometimes the case with casting repairs in foundries), using a matching material offers advantages in fatigue and wear resistance. If the weld repair cannot undergo post-weld heat treatment, an undermatched filler material can be used. Using an undermatched filler material is a welding engineering technique that is extremely helpful in preventing hydrogen-assisted cracking when welding hardenable steels, especially when post-weld heat treatment is not feasible. For the same reason, fabrication welding, such as welding the lip to the bucket, is also preferred. These fabrication welds can be thick, and the associated stresses can be extremely high. Using an undermatched filler material will limit the magnitude of these stresses, thereby significantly increasing the likelihood of producing a good, crack-free fabrication weld. However, using a softer filler material makes the lip more susceptible to damage in these locations during service. For example, softer materials are less able to withstand the higher cyclic loads typically applied during excavation and / or the high levels of wear typically encountered during excavation.

[0032] This disclosure relates to a cast lip for excavating equipment, the lip being composed of an iron alloy having a relatively high level of chromium. In one example, the cast lip may be composed of an iron alloy having at least 7% by weight, and preferably 10% or more, of chromium. All component percentages provided herein are by weight. The iron alloy is an alloy containing at least 50% iron. The lip also preferably has greater than or equal to 3% nickel and less than or equal to 0.12% carbon. Other elemental combinations are also possible. The lip will be hardened to have a primary martensitic structure to provide sufficient strength for use as a lip for geotechnical equipment.

[0033] In another example, the casting lip for the excavating equipment is made of an iron alloy having at least 10% chromium, at least 3% nickel, and less than or equal to 0.12% carbon, and optionally less than or equal to 3% manganese, silicon, and / or molybdenum, and having a primary martensitic structure.

[0034] In another example, the casting lip used in excavation equipment is made of an iron alloy having 10%-15% chromium, 3%-6% nickel, and less than or equal to 0.12% carbon and having a primary martensitic structure.

[0035] In another example, the casting lip used in excavating equipment is made of an iron alloy having a primary martensitic structure and containing between 10% and 15% chromium, 3% and 6% nickel, and less than or equal to 0.10% of each of carbon, manganese, silicon, and molybdenum. A lower carbon content (i.e., ≤0.10%) is preferred for obtaining a high-performance lip, but at most ≤0.12% is generally acceptable.

[0036] In another example, the casting lip for excavating equipment is made of an alloy with the composition CA6NM, which is an iron-based alloy comprising less than or equal to 0.06% carbon, less than or equal to 1% manganese, less than or equal to 1% silicon, less than or equal to 0.04% phosphorus, less than or equal to 0.03% sulfur, 11.5%–14% chromium, 3.5%–4.5% nickel, and 0.4%–1% molybdenum, hardened to a primary martensitic structure. In another example, the casting lip for excavating equipment is made of low-carbon stainless steel with a primary martensitic structure.

[0037] While steels with relatively high levels of chromium (such as those found in the stainless steel alloys discussed above) would provide the generally preferred level of benefits, it may be necessary, as an alternative, to reduce the cost of casting lips by using non-stainless steel alloys (i.e., alloys with lower but still sufficiently high levels of chromium to achieve the benefits discussed herein). In such cases, casting lips for digging equipment may be composed of an iron alloy having 7%–10% chromium and less than or equal to 0.12% carbon with a primary martensitic structure. In another such example, casting lips for digging equipment may be composed of an iron alloy having 7%–9% chromium and less than or equal to 0.12% carbon with a primary martensitic structure. Additionally, as mentioned above regarding other examples, 3%–6% nickel and / or 3% or less of one or more of manganese, silicon, and / or molybdenum. Alternatively, the alloy may be limited to ≤0.1% of each of manganese, silicon, and / or molybdenum.

[0038] By using the chromium alloy described above, welding materials that match or are similar to the base alloy of the lip can be used. For example, if the lip is made of a CA-6NM composition, a filler material with a "410Ni-Mo" composition can be used. The weld deposit made with this material responds to heat treatment very similarly to the CA-6NM base metal, and similar properties can be achieved when subjected to appropriate heat treatment. Using the lip described herein and welding materials with similar compositions allows the welded area to have similar strength and wear resistance to the base alloy, thereby avoiding some of the weaknesses encountered in current low-alloy cast lips. Preheating the base material around the area to be welded and then heat-treating the welded area after welding produces a welded area that substantially matches the base alloy of the lip in terms of strength and toughness. When post-weld heat treatment is not possible or desirable (such as when machining the lip to the bucket), different austenitic stainless steel filler materials, such as type 309 filler materials, can be used for the welded lip of this disclosure. Although this combination is considered unique, it should be noted that using insufficiently matched filler material is a known welding method, often used when machining highly hardenable steels, such as the lips of conventional low-alloy steels. While this austenitic filler material is relatively soft, it can be used to prevent hydrogen-assisted cracking, which can be a major problem when welding high-strength steels.

[0039] Other benefits can also be achieved using the casting lip according to this disclosure. For example, compared to current lips made of low-alloy steel, the lip according to this disclosure can provide improvements in terms of weld strength, hardness, and / or wear life, yield strength, fatigue strength, and / or endurance limit. In one example, the table below compares an example of the casting lip alloy of the present invention (nominal 0.03% C-0.05% Mn-0.6% Si-12.75% Cr-4% Ni-0.5% Mo) with an example of a current low-alloy steel casting lip.

[0040] Table 1: Comparison of Improved Mechanical Properties

[0041]

[0042] The cast lip according to this disclosure can maintain considerable fatigue strength after welding, is lighter than conventional low-alloy cast steel lips, and / or provides improved strength. These advantages can, for example, offset the increased costs associated with the chromium alloys described herein by providing, for example, longer service life, less machine downtime, easier repair and / or component attachment, increased load capacity, better penetration, less material usage, and / or corrosion resistance.

[0043] Compared to conventional low-alloy cast lips, the improved mechanical properties of the cast lips according to this disclosure enable the use of longer, thinner lips in the same excavator. Reduced lip weight provides the machine with a larger maximum load, as the maximum load includes the weight of the bucket and attachments, as well as the load-bearing capacity contained within the load. The longer profile also facilitates bucket penetration into the ground during excavation. Such lips according to this disclosure offer a lighter and more penetrating lip, higher excavator throughput, less wear on the equipment, and / or faster cycle times. In summary, these advantages result in a more efficient excavation method. Alternatively, cast lips of the same dimensions as current low-alloy cast lips can also be used in more robust environments; for example, lips of the present invention manufactured to the same dimensions as low-alloy cast lips manufactured for normal use can be used in heavy-duty and / or ultra-heavy-duty environments.

[0044] The examples described above in this disclosure are each suitable for use as cast lips of large digging buckets, such as those found in dragline excavators, cable shovels, front shovels, and hydraulic excavators. Such lips extend across the width of the bucket, forming the primary digging edge of the bucket. The examples of lips discussed above in this disclosure are particularly suitable for lips weighing at least 6,500 pounds, formed from lip segments of at least 2,000 pounds and / or having a maximum thickness of at least 9 inches. For example, such lips can weigh from about 6,500 pounds to about 29,000 pounds, with lip segments weighing about 2,000 pounds or more before being welded together to form the lip, and cast lips can have a maximum thickness ranging from about 4 to 16 inches, although other variations are possible. Cast lips generally have varied shapes to maximize strength, minimize weight, and / or be customized for specific operations and / or attachment of wear parts.

[0045] In one example, a method for manufacturing a lip for earthmoving equipment according to this disclosure includes melting one of the aforementioned ferrochrome alloys, feeding the molten alloy into a sand mold to shape the alloy into a lip for earthmoving equipment, and hardening the alloy. The lip is preferably air-hardened in the ambient environment to form a primary martensitic structure, but quenching is also possible. Current low-alloy steel cast lips are quenched to form the desired martensitic structure. After hardening, the cast lip is tempered to provide the desired toughness for use as a lip for earthmoving equipment. This combination of hardening and tempering produces a combination of strength and toughness desirable for cast lips fastened in the bucket of an excavator.

[0046] See Figure 1-3An example of the cast lip 10 includes a front portion 20, a rear portion 16, ears 45 on both sides of the lip 10, an upper surface 46, and a lower surface 32. The cast lip 10 according to this disclosure is welded, for example, at the back surface 44 of the rear portion 16 to the front portion 4 of the dragline excavator bucket 2, and welded to the bucket body 8 along the wing or ears 45. This lip configuration is disclosed in U.S. Patent 9,963,853, which is incorporated herein by reference.

[0047] The lip 10 has an elongated structure or length 25 extending between the opposing sidewalls 40 of the bucket 8 (e.g., across the bucket width). The lower surface 32 includes a plurality of grooves 36 spaced apart by ridges, ribs, spacers, or other structures 35; these grooves reduce the weight of the lip while still providing the desired strength. This is just one example, and other lip configurations are possible.

[0048] In the illustrated example, the lip 10 includes a set of noses 26 spaced apart along the front portion 20 of the lip 10. The noses 26 extend forward from the main lip structure 25 for mounting ground engagement tools. The front end or front portion 20 of the lip 10 also includes a front edge 30 between the noses. Ground engagement components, such as guards, are typically secured above the front edge 30. Toothed assemblies are typically secured above the noses 26. This lip 10 is shown secured in the bucket of a dragline excavator, but it can also be secured in the buckets of other machines, including, for example, cable shovels, front shovels, and / or hydraulic excavators.

[0049] See Figure 4-5 The image shows a cable bucket 102 with a cast lip 110 and a ground engagement abrasion product, comprising a housing that defines a cavity for receiving soil material. The lip 110 includes a front portion 120, a rear portion 116, ears 145 on both sides of the lip 110, an upper surface 146, and a lower surface 132. Each ear or wing 145 is curved upward at each end 112 for use with the cable bucket 102. The front edge is covered by mounting ground engagement tools, such as toothed assemblies 107 and guards 109. The guard 109 shown extends to the wing 145.

[0050] These shown lip edges are merely examples; in fact, any other cast lip edge structure can be used in this disclosure.

Claims

1. A method for manufacturing a casting lip for an excavator bucket, the method comprising: A ferroalloy having 10%-15% chromium, 3%-6% nickel, 0.12% or less carbon and less than or equal to 3% manganese by weight is melted. Molten iron alloy is fed into a sand mold to form a lip structure; During the manufacturing process, air hardening is used to harden the iron alloy into a primary martensitic structure; and The lip is tempered; wherein the cast lip includes a body configured to extend between the opposing sidewalls of the digging bucket.

2. The method according to claim 1, wherein the iron alloy comprises 3% by weight or less of each of manganese, silicon and molybdenum.

3. The method according to claim 1 or 2, wherein the lip structure is shaped to include a plurality of forward-protruding nose portions, each for mounting a tooth component.

4. The method according to claim 1, wherein the lip structure weighs at least 6,500 pounds.

5. The method according to claim 1, wherein the maximum thickness of the lip structure is at least 9 inches.

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