LIP FOR EXCAVATOR BUCKET

Abstract

A cast lip for an excavator bucket composed of a ferrous alloy having at least seven percent chromium by weight, between 3%-6% nickel by weight, and =0.12% carbon by weight, and a mainly martensitic structure.

Description

EXCAVATOR BUCKET LIP RELATED APPLICATIONS This application claims the benefit of priority of U.S. provisional patent application No. 62 / 824,949, filed on March 27, 2019, which is incorporated in its entirety by reference. FIELD OF DISCLOSURE This disclosure relates to a lip for an excavator bucket for use on excavating machines such as draglines, electric cable shovels, front shovels, hydraulic excavators and the like. BACKGROUND TO THE DISCLOSURE Excavating machines, such as those used in mining and construction operations, include buckets that are driven into the ground to scoop up a load of earth. The bucket is generally defined by a back wall, a bottom wall, and side walls, creating a cavity with an open front to receive the excavated material. The front edge of the bottom wall has a lip to which soil preparation tools such as teeth, adapters, and / or guards are typically attached. These attachments protect the lip from wear and break up the soil more effectively during excavation. The lips are formed from steel plates (called plate lips) or by a casting process (called cast lips). COMPENDIUM OF DISCLOSURE In a first example, a cast lip for excavation equipment is composed of a ferrous alloy that has at least 7% chromium, by weight, and a primarily martensitic structure. In another example, a cast lip for excavation equipment is composed of a ferrous alloy that has at least 7% chromium, at least 3% nickel and 0.12% or less carbon, and a primarily martensitic structure. In another example, a cast lip for excavation equipment is composed of a ferrous alloy having at least 10% chromium, at least 3% nickel and 0.12% or less carbon, and optionally 3% or less of one or more of manganese, silicon and / or molybdenum, and a primarily martensitic structure. 7C! II Π / l 7Π7 / E / YΙΛΙ In another example, a cast lip for excavation equipment is composed of a ferrous alloy that has between 10%-15% chromium, between 3%-6% nickel and 0.12% or less carbon, and a primarily martensitic structure. In another example, a cast lip for excavation equipment is composed of a ferrous alloy that has between 10%-15% chromium, between 3%-6% nickel, and <0.10% each of carbon, manganese, silicon and molybdenum, and a primarily martensitic structure. In another example, a cast lip for excavation equipment is composed of a ferrous alloy that has 7% to 10% chromium, at least 3% nickel and 0.12% or less carbon, and a primarily martensitic structure. In another example, a cast lip for excavation equipment is composed of a ferrous alloy that has between 7-9% chromium, and 0.12% or less carbon, and a primarily martensitic structure. In another example, a cast lip for excavation equipment is composed of an alloy that has the same composition as a CA6NM alloy, and a primarily martensitic structure. In another example, a cast lip for excavation equipment is composed of a low-carbon stainless steel that has a primarily martensitic structure. In another example, a lip made of any of the mentioned alloys is formed by sand casting and / or air tempering processes. In another example, a cast lip having any of the mentioned alloys includes an inner surface and an outer surface, where the outer surface includes grooves, which, for example, can reduce the overall weight of the lip. In another example, a cast lip made of any of the alloys mentioned includes a curved portion at least near each end of the lip so that the lip ends bend upward and generally align with the side walls of the bucket. Such a lip is suitable for use with an electric cable shovel, although other uses are possible. Optionally, the outer surface of the lip includes grooves. Each of the disclosure examples mentioned is suitable for use as a cast lip for a large excavator bucket such as those found on draglines, electric cable shovels, front-end loaders, and hydraulic excavators. Such lips extend across the width of the bucket to form the primary digging edge. Such lips may, for example, weigh up to approximately 30,000 pounds, and / or may have a maximum thickness of approximately nine inches or more. 7C! II Π / I 7Π7 / Β / YΙΛΙ Lips according to this disclosure may provide improvements in yield strength, fatigue strength and / or strength limits with respect to welds, hardness and / or service life compared to current cast low-alloy steel lips. In an example of a process for manufacturing cast lips according to this disclosure, one of the mentioned ferrous alloys is melted, the molten alloy is poured into a sand mold to shape the alloy into a lip structure for use with excavation equipment, the alloy is hardened to give it a primarily martensitic structure, and then the lip is tempered to give it hardness. In one example, the lip is air-tempered. A lip cast in accordance with this disclosure may be repaired, rebuilt, secured to the ladle, and / or fitted with accessories by welding processes. In one example, the welding is achieved using a welding material that is the same as or similar to the alloy of the base material. In another example, the lip and the welding material are each a ferrous chromium alloy. In yet another example, the lip is composed of a CA6NM alloy and the welding material is type 309 stainless steel. BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a perspective view of an excavator bucket with a lip in accordance with this disclosure. Figure 2 is a top perspective view of a fused lip. Figure 3 is the bottom perspective view of a fused lip. Figure 4 is a perspective view of a second excavator bucket with a lip in accordance with this disclosure. Figure 5 is a perspective view of another example of a cast lip in accordance with this disclosure with attached soil preparation tools. DETAILED DESCRIPTION OF PREFERRED EXAMPLES This disclosure relates to cast lips for excavator buckets such as those used on draglines, electric cable shovels, front shovels, hydraulic excavators and the like. Cast lips are large steel structures that span the width of an excavator bucket, typically a large mining machine, to form its primary digging edge. Lips can be formed by casting the entire lip in a mold or by casting lip segments that are then welded together to form a complete lip. For example, cast lips can weigh anywhere from approximately 6,500 pounds to approximately 29,000 pounds. 7?! II Π / l 7Π7 / Β / YΙΛΙ Lip segments are typically smaller; for example, an end segment might weigh approximately 2,000 pounds. Cast lips tend to have a maximum thickness of approximately 9 inches or more. They often range from approximately 4 to 16 inches in maximum thickness, although other variations are possible. The thickness dimension is the distance between the inner and outer faces of the lip. Cast lips may include forward-projecting points for mounting digging teeth. The points are usually cast integrally with the lip or lip segments. The points may also be cast separately and welded to the front of the lip. Sometimes, such points can also be provided by means of adapters welded to the lip. In other examples, the adapters with points are mechanically attached to the lip. This is often the case with the lips of an electric cable shovel.For decades, cast lips have been made of low-alloy steels due to their high elasticity and hardness, and their low manufacturing cost. Cast lips for excavation equipment are typically manufactured using a sand casting process in which molten steel is poured into a sand mold. As with any large steel casting, it is extremely difficult to produce a lip casting without defects. It is not uncommon for large castings to have some defects in the as-cast state. Typical defects can include inclusions, hot tears, cracks, porosity, and so on. It is common practice in the steel foundry business to repair these defects by welding, provided the repairs do not impair the functionality of the finished part. Welding on cast lips is also common for other purposes. For example, due to their size, cast lips are sometimes cast in segments (usually two or three segments) that are welded together to form a single lip. The cast lip is then welded to the bucket.Tips, adapters, and protectors are sometimes welded to the lip. Sometimes, add-ons such as protrusions and similar components are welded to the lip to secure wear parts. Damage to the lip during use, usually at the front end, is also often repaired and / or rebuilt using welding processes. While in some cases weld repairs on low-alloy cast lips are made with weld filler materials that roughly match the elasticity of the lip material, repair welds are very often made with softer iron-based weld materials, such as E70 series carbon steel filler materials. When weld repairs can undergo subsequent heat treatment (as sometimes occurs with repairs to castings in foundries), the use of matching materials can be advantageous in terms of fatigue strength and wear resistance. If repair welds cannot undergo subsequent heat treatment, a non-matching filler material may be used. The use of materials of Non-matching filler is a welding engineering technique that can be extremely useful in preventing hydrogen-assisted cracking when welding hardened steels, especially when post-weld heat treatment is not possible. For the same reason, non-matching filler materials are also preferred for fabrication welds, such as lip welds on ladles. These fabrication welds can be quite thick, and the associated stresses can be significant. Using non-matching filler materials limits the magnitude of these stresses, greatly increasing the likelihood of producing good, crack-free fabrication welds. However, using a softer welding material makes the lip more susceptible to damage in those areas during use.For example, softer material is less able to withstand the high and cyclic loads commonly applied during excavation, and / or the high level of abrasion that usually occurs in excavation. This disclosure relates to a cast lip for excavation equipment that is composed of a ferrous alloy having a relatively high chromium content. For example, the cast lip may be composed of a ferrous alloy having at least 7% chromium by weight and preferably 10% or more. All percentages of components stated herein are by weight. A ferrous alloy is one that has at least 50% iron. The lip also preferably has 3% or more nickel and 0.12% or less carbon. Other elemental combinations are possible. The lip will be hardened to have a primarily martensitic structure that provides sufficient elasticity for use as a lip for earthmoving equipment. In another example, a cast lip for excavation equipment is composed of a ferrous 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% of one or more of each of manganese, silicon and / or molybdenum, and a primarily martensitic structure. In another example, a cast lip for excavation equipment is composed of a ferrous alloy that has between 10%-15% chromium, 3%-6% nickel and less than or equal to 0.12% carbon, and a primarily martensitic structure. In another example, a cast lip for excavation equipment is composed of a ferrous alloy containing 10–15% chromium, 3–6% nickel, and less than or equal to 0.10% each of carbon, manganese, silicon, and molybdenum, and has a primarily martensitic structure. A lower carbon content (i.e., <0.10%) is preferred for high lip performance, but levels as low as <0.12% are generally acceptable. In another example, a cast lip for excavation equipment is composed of an alloy that has a composition CA6NM, which is a ferrous-based alloy that includes less 7?) II π / I 7π7 / Β / YILI 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, and a hardened structure to primarily martensitic. In another example, a cast lip for excavation equipment is composed of a low-carbon stainless steel that has a primarily martensitic structure. While steels with a relatively high chromium content (such as those found in the stainless steel alloys described above) will generally provide a preferred level of the desired benefits, it may be desirable to reduce the cost of the cast lip by using a non-stainless steel alloy (i.e., one with a lower chromium content but still high enough to achieve the benefits mentioned in this disclosure). In such cases, a cast lip for excavation equipment may be composed of a ferrous alloy having 7%–10% chromium and less than or equal to 0.12% carbon, and a primarily martensitic structure. In another example, a cast lip for excavation equipment is composed of a ferrous alloy having 7%–9% chromium and less than or equal to 0.12% carbon, and a primarily martensitic structure.In addition, as mentioned previously for 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. When using chromium alloys as described above, a weld material matching or similar to the base alloy of the lip can be used. For example, if a lip is made of composition CA-6NM, filler materials of composition “410Ni-Mo” can be used. Weld deposits made with this material respond to heat treatment similarly to the base metal CA-6NM and can also achieve similar properties when properly heat-treated. Using the lips described in this disclosure and a weld material of similar composition can allow the welded area to have elasticity and abrasion resistance similar to the base alloy and thus avoid certain weaknesses found in current low-alloy cast lips.Preheating the base material around the area to be welded and heat-treating the welded area after welding can result in a welded area that generally matches the base alloy of the lip in elasticity and hardness. When post-weld heat treatment is not possible or desirable (as in the case of welding a lip to a ladle), a different austenitic stainless steel filler material, such as Type 309, can be used for the weld lips of this disclosure. While this combination is considered unique, it is noted that the use of a non-matching filler material is a known welding process. 7C! II Π / l 7Π7 / Β / YILI is commonly used when welding highly hardened steels, such as conventional low-alloy steel lips. Although this austenitic filler material is soft, it is useful for preventing hydrogen-assisted cracking, which can be a significant problem when welding high-yield-strength steels. Other benefits can also be achieved with a cast lip according to this disclosure. For example, lips according to this disclosure can provide improvements in yield strength, fatigue strength, and / or weld strength limits, hardness, and / or service life compared to current low-alloy steel cast lips. As an example, the table below compares an example of a cast lip alloy of the invention (nominally 0.03%C-0.05%Mn-0.6%Si-12.75%Cr4-0.5%Ni-0.5%Mo) to a current low-alloy steel cast lip. zc / 1 ι η / ι znz / E / YiAi Table 1: Mechanical Property vs. Improvement Mechanical Property Improvement of the lip of the invention over the current low-alloy lip Yield strength 20%-30% Fatigue strength limit (repair weld) 30%-50% Fatigue strength limit (factory weld) 75%-100% Hardness 20%-25% Service life 0%-20% A cast lip manufactured in accordance with this disclosure can maintain significant fatigue strength after welding, be lighter than conventional low-alloy cast steel lips, and / or provide improved elasticity. These advantages can offset the increased cost associated with the chromium alloys described in this disclosure by providing, for example, longer service life, less machine downtime, easier component repair and / or assembly, higher load-bearing capacity, better penetration, reduced material usage, and / or corrosion resistance. The improved mechanical properties of a cast lip, as described in this disclosure, may allow the use of a thinner lip on the same excavating machine compared to a conventional low-alloy cast lip. The reduced lip weight provides the machine with a higher maximum load capacity because maximum loads include the weight of the bucket and attachments, as well as the load contained within the load. A thinner profile also facilitates bucket penetration into the ground during excavation. Therefore, such a lip, as described in this disclosure, may provide lighter, better-penetrating lips, increased production from the excavating machine, less wear on the equipment, and / or faster cycle times. In short, these advantages lead to a more efficient excavation process.Alternatively, a cast lip with the same dimensions as a current low-alloy cast lip can also be used in harsher environments; for example, a lip of the invention manufactured with the same dimensions as a low-alloy cast lip manufactured for normal use could be used in a heavy-duty and / or extra-heavy-duty working environment. Each of the examples mentioned in this disclosure is suitable for use as a cast lip for a large excavator bucket such as those found on, e.g., draglines, electric cable shovels, front-end loaders, and hydraulic excavators. Such lips extend across the width of the bucket to form the primary digging edge of the bucket. The lip examples described above in this disclosure are well-suited for use on lips weighing at least 6,500 pounds, formed from lip segments weighing at least 2,000 pounds each, and / or having a maximum thickness of at least 9 inches.For example, these lips can weigh anywhere from approximately 6,500 pounds to approximately 29,000 pounds; lip segments can weigh approximately 2,000 pounds or more before being welded together to form a lip; and cast lips can have a maximum thickness ranging from approximately 4 to 16 inches, although other variations are possible. Cast lips are generally shaped in various ways to maximize elasticity, minimize weight, and / or customize the shape for a particular operation and / or the mating of wear parts. In one example, a process for manufacturing a lip for earthmoving equipment in accordance with this disclosure includes melting one of the ferrous chromium alloys mentioned, pouring the molten alloy into a sand mold to shape the alloy into a lip for use with earthmoving equipment, and hardening the alloy. The lip is preferably air-quenched in an ambient environment to form the primarily martensitic structure, although quenching is possible. Cast lips of current low-alloy steel are quenched to form the desired martensitic structure. After hardening, the cast lip is quenched to provide the desired hardness for use as a lip for earthmoving equipment. This combination of hardening and quenching can result in a combination of elasticity and hardness that is desired for a cast lip secured to an excavator bucket. With reference to Figures 1-3, an example of a cast lip 10 includes a forward portion 20, a rear portion 16, side adapters 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, 7?! II Π / l 7Π7 / Β / YΙΛΙ e.g. welded to a dragline bucket 2 on a forward portion 4 of the bucket 2 on a rear face 44 on the rear portion 16 of the lip and along the fins or side adapters 45 toward the bucket body 8. This lip construction is the one described in U.S. Patent 9,963,853, which is incorporated herein by reference. The lip 10 has an elongated construction or length 25 that extends between the opposite side walls 40 of the bucket 8 (e.g., across the width of the bucket). The lower surface 32 includes several grooves 36 separated by ridges, ribs, spacers, or other structures 35; these grooves reduce the weight of the lip while still providing the necessary elasticity. This is only one example, and other lip constructions are possible. In the illustrated example, lip 10 includes a set of prongs 26 spaced along the forward portion 20 of lip 10. The prongs 26 extend forward from the main lip structure 25 to mount soil preparation tools. The forward portion 20 of lip 10 also includes forward edges 30 between the prongs. Soil preparation parts, such as guards, are typically secured over the forward edges 30. Tooth assemblies are typically secured over the prongs 26. This lip 10 is shown secured to a dragline bucket, but it could be secured to buckets for other machines, including, for example, electric cable shovels, front shovels, and / or hydraulic excavators. With reference to Figures 4-5, an articulated cable-powered shovel bucket 102 is shown, including a housing that defines a cavity for receiving soil material with a cast lip 110 and soil preparation wear products. The lip 110 includes a forward portion 120, a rear portion 116, side adapters 145 on either side of the lip 110, an upper surface 146, and a lower surface 132. Each upper adapter or fin 145 curves upward at each end 112 for use on an articulated cable-powered shovel 102. The forward rim is covered with soil preparation assembly tools, such as tooth assemblies 107 and guards 109. The guards 109 are illustrated as an upward continuation of the fins 145. These polished lips are merely examples; virtually any other fused lip structure is possible with the present disclosure.

Claims

1. A cast lip for an excavator bucket defined by at least one cast body having a length to extend between the side walls of the bucket, wherein the lip is composed of a ferrous alloy having at least 7% chromium by weight and 0.12% or less carbon by weight, and a mainly martensitic structure.

2. The cast lip of claim 1, wherein the ferrous alloy includes between 3% and 6% nickel by weight.

3. The cast lip of claim 1 or 2, wherein the ferrous alloy includes 7%-15% chromium by weight.

4. The cast lip of claim 1 or 2, which is composed of 7%-9% chromium by weight.

5. The cast lip of claim 1 or 2, which is composed of 7%-10% chromium by weight.

6. A cast lip for an excavator bucket defined by at least one cast body having a length to extend between the side walls of the bucket, wherein the cast lip is composed of a ferrous alloy having between 10%-15% chromium by weight, 3%-6% nickel by weight and 0.12% or less carbon by weight, and a mainly martensitic structure.

7. The cast lip of any of the preceding claims, wherein the ferrous alloy includes 3% or less by weight of at least one of manganese, silicon, and molybdenum.

8. The cast lip of any of the preceding claims, wherein the ferrous alloy includes 0.10% or less of each of carbon, manganese, silicon, and molybdenum by weight.

9. The cast lip of any of the preceding claims comprising a plurality of forward-projecting points, each for mounting a tooth, and a plurality of mounting areas for mounting guards between the points.

10. A cast lip for an excavator bucket defined by at least one cast body and a length to extend between the side walls of the bucket, wherein the lip comprises a plurality of forward-projecting points, each for mounting a tooth, wherein the lip is composed of a stainless steel having 0.12% or less carbon by weight, and a mainly martensitic structure.

11. The cast lip of claim 10, wherein the stainless steel includes 0.10% or less carbon by weight.

12. The cast lip of any of claims 1, 7 or 10, having the composition of a CA6NM alloy. 7C! II Π / I 7Π7 / Β / YΙΛΙ 13. The cast lip of any of the preceding claims, weighing at least 6500 pounds.

14. The cast lip of any of the preceding claims, having a maximum thickness of at least 9 inches.

15. A bucket for earthmoving equipment, wherein the bucket comprises a housing defining a cavity for receiving earth material and a lip according to any of the preceding claims.

16. A method for manufacturing a cast lip for use with excavation equipment, wherein the method comprises: melting a ferrous alloy having at least 7% chromium by weight; introducing the molten ferrous alloy into a sand mold to form a lip structure; hardening the ferrous alloy into a mainly martensitic structure; and tempering the lip.

17. The method of claim 16, wherein the hardening of the ferrous alloy is by air quenching.

18. The method of claim 16, wherein the hardening of the ferrous alloy is by cooling.

19. The method of any of claims 16-18, wherein the ferrous alloy includes between 3%-6% nickel by weight and 0.12% or less carbon by weight.

20. The method of any of claims 16-19, wherein the ferrous alloy includes 3% or less by weight of each of manganese, silicon, and molybdenum.

21. The method of any of claims 16-20, wherein the ferrous alloy includes 0.10% or less of each of carbon, manganese, silicon, and molybdenum by weight.

22. A method for manufacturing a cast lip for use with excavation equipment, wherein the method comprises: melting a stainless steel with 0.12% or less carbon by weight; introducing the stainless steel into a sand mold to form a lip structure; hardening the ferrous alloy into a mainly martensitic structure; and tempering the lip.

23. The method of any of claims 16-22, wherein the lip structure is formed to include a plurality of forward-projecting points, each to mount a tooth.

24. The method of any of claims 16-23, wherein the lip structure weighs at least 6500 pounds. 7C! II Π / I 7Π7 / Β / YΙΛΙ 25. The method of any of claims 16-23, wherein the lip structure has a maximum thickness of at least 9 inches.