Alloy For High-Stress Gouging Abrasion

Abstract

The present invention relates to a manganese steel alloy having a heat-treated microstructure comprising: (a) an alloy composition of: manganese: 12 to 30 wt %; carbon: 1.0 to 2.0 wt %; chromium: 4.5 to 7.0 wt %; molybdenum: 0.0 to 3.0 wt %; and iron and impurities: balance, and (b) an austenitic ferrous matrix; and (c) formed refractory particles dispersed throughout the austenitic ferrous matrix such that ≥10% of the formed refractory particles are located within crystallites of the austenitic ferrous matrix, as opposed to being located at grain boundaries between the crystallites, wherein the formed refractory particles are compounds of carbides and/or borides and/or nitrides of any one or more of chromium, zirconium, hafnium, tantalum, molybdenum, and tungsten. The invention further relates to equipment adapted for high-stress gouging abrasion that includes the manganese steel alloy of the invention, and a method of producing the manganese steel alloy of the invention.

Claims

1. A manganese steel alloy having a heat-treated microstructure comprising: (a) an alloy composition of: manganese: 12 to 30 wt %; carbon: 1.0 to 2.0 wt %; chromium: 4.5 to 7.0 wt %; molybdenum: 0.0 to 3.0 wt %; and iron and impurities: balance, and (b) an austenitic ferrous matrix, and (c) formed refractory particles dispersed throughout the austenitic ferrous matrix such that ≥10% of the formed refractory particles are located within crystallites of the austenitic ferrous matrix, as opposed to being located at grain boundaries between the crystallites, wherein the formed refractory particles are compounds of carbides and/or borides and/or nitrides of any one or more of chromium, zirconium, hafnium, tantalum, molybdenum, and tungsten, and wherein ≥50%, of the formed refractory particles are chromium carbides and/or borides and/or nitrides.

2. The manganese steel alloy according to claim 1, wherein additional carbon and/or boron and/or nitrogen are added to the composition during manufacture.

3. The manganese steel alloy according to claim 1, wherein the alloy composition comprises manganese between about 12 wt % and 26 wt %.

4. The manganese steel alloy according to claim 1, wherein the alloy composition comprises carbon between about 1.25 wt % and 1.50 wt %.

5. The manganese steel alloy according to claim 1, wherein the alloy composition comprises chromium between about 5 wt % and 6 wt %.

6. (canceled)

7. The manganese steel alloy according to claim 1, wherein the alloy composition comprises molybdenum between about 0.5 wt % and 2.0 wt %.

8. (canceled)

9. The manganese steel alloy according to claim 1, wherein the impurities include one or more of: silicon: ≤1.00 wt %; sulphur: ≤0.20 wt %; nickel: ≤0.15 wt %; boron: ≤0.10 wt %; tungsten: ≤0.10 wt %; phosphorus: ≤0.05 wt %; copper: ≤0.05 wt %; titanium: ≤0.05 wt %; and vanadium: ≤0.05 wt %.

10. (canceled)

11. The manganese steel alloy according to claim 1, wherein the alloy composition carbon is selected based on the concentration of manganese to control properties the microstructure including one or more of: increasing a rate of formed refractory particles forming throughout the austenitic ferrous matrix, opposed to being localized at grain boundaries; decreasing a rate of formed refractory particles forming at grain boundaries of the austenitic ferrous matrix; increasing a rate of formed refractory particles forming with smooth surfaces; reducing a rate of formed refractory particles forming with coarse surfaces; and/or reducing a rate of grain growth within the austenitic ferrous matrix.

12. The manganese steel alloy according to claim 1, wherein the formed refractory particles comprise a maximum of 1.0 wt % titanium carbides, niobium carbides and/or vanadium carbides.

13. The manganese steel alloy according to claim 1 wherein the manganese steel alloy is a cast alloy.

14. The manganese steel alloy according to claim 13, wherein the manganese steel alloy is a casting that is heat-treated by solution treatment and quenching.

15. The manganese steel alloy according to claim 14, wherein the solution treatment occurs at a temperature between about 1000° C. and 1250° C.

16-18. (canceled)

19. The manganese steel alloy according to claim 13 wherein the quenching is with water.

20. The manganese steel alloy according to claim 1, wherein the manganese steel alloy is a wrought alloy.

21. Equipment adapted for high-stress gouging abrasion that includes the manganese steel alloy according to claim 1, wherein the equipment is a liner selected from cone crusher liners, gyratory crusher liners, jaw crusher liners, impact crusher liners, mill liners, and other liners used in the mining industry, or a wear part used in crusher systems and mill systems.

22. (canceled)

23. A method of producing the manganese steel alloy according to claim 1, comprising the steps of: (a) forming a melt of a manganese steel comprising heating a composition to a casting temperature, the composition comprising: manganese: 12 to 30 wt %; carbon: 1.0 to 2.0 wt %; chromium: 4.5 to 7.0 wt %; molybdenum: 0.0 to 3.0 wt %; and iron and impurities: balance, and (b) pouring the melt into a mould to form the casting; (c) allowing the casting to cool to room temperature; (d) heating the casting to a solution treatment temperature; and (e) quenching the casting.

24. The method according to claim 23, wherein the casting temperature is between about 1350° C. and 1450° C.

25. The method according to claim 23, wherein the casting temperature is within 30° C. of a liquidus temperature of the melt of manganese steel.

26. The method according to claim 23, wherein the solution treatment temperature is between about 1000° C. and 1250° C.

27-29. (canceled)

30. The method according to claim 23, wherein the quenching is with water.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0097] Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0098] FIG. 1 illustrates a microstructure of an example manganese steel casting of the invention, showing the dispersion of fine Cr-rich carbide particles; and

[0099] FIG. 2 illustrates a comparison of bulk hardness with increasing levels of cold rolling between two example manganese steel casting of the invention against two conventional manganese steels.

DETAILED DESCRIPTION

[0100] The following embodiments are described by way of example only in order to provide a more detailed understanding of certain aspects of the invention. It is to be understood that other embodiments are contemplated, and it is not intended that the disclosed invention is limited to the following description. Specifically, while the following examples have been directed to manganese steel castings with carbide refractory particles, it will be appreciated that manganese steels produced with alternative methods could demonstrate similar properties, e.g. wrought manganese steels with boride refractory particles.

[0101] The inventor has carried out extensive experimental work in relation to the manganese steel casting of the present invention to determine the limits of composition concentrations that would enable the sought carbide structures that are dispersed throughout the austenitic ferrous matrix, rather than the carbides amassing at the grain boundaries. Moreover, the inventor has further investigated varying production methodology variables in order to maximize the dispersed carbides and minimize the carbides at the grain boundaries, particularly in relation to heat-treatment of the steel.

[0102] The inventor has found that the produced manganese steel with dispersed carbides throughout the matrix possesses an increased hardness when compared to conventional manganese steels with a higher proportion of carbides localized at the grain boundaries. The manganese steel according to the invention provides further advantages in being less susceptible to cracking at grain boundaries when compared to conventional manganese steels.

[0103] A produced microstructure of an example manganese steel casting of the invention is provided in FIG. 1, illustrating the dispersion of fine Cr-rich carbide particles.

[0104] The broadest composition concentration ranges of the manganese steel casting include: [0105] manganese: 12 to 30 wt %; [0106] carbon: 1.0 to 2.0 wt %; [0107] chromium: 4.5 to 7.0 wt %; and [0108] iron and impurities: balance.

[0109] This manganese steel may also include a small concentration of molybdenum, which is known to suppress pearlite formation during the manufacturing process. The formation of pearlites in the manganese steel is undesirable as it results in a more brittle alloy. In particular, the inventor has proposed the addition of molybdenum in concentrations less than 3 wt %, preferably between about 0.5 to 2.0 wt %.

[0110] In particular embodiments the inventor sought to enhance the initial hardness of the manganese steel casting while also maintaining the high toughness and work-hardening capabilities typical of conventional manganese steels. In this regard, the inventor pursued compositions with a higher manganese content than that of a conventional manganese steel and adjusted the carbon and chromium contents accordingly to meet the sought properties. During this process, the inventor further found that the carbon and chromium contents could be optimized to provide greater control of the microstructure of the manganese steel, in particular to: [0111] promote the carbide particles to form throughout the ferrous matrix (opposed to being localized at the grain boundaries); [0112] produce smoother carbide particles (relative to coarser carbide particles formed in conventional manganese steels); and [0113] control the grain size of the ferrous matrix.

EXAMPLES

[0114] Two example manganese steel castings were prepared in accordance with the invention and designated as H8765ST and H8766ST. The chemical compositions of these samples are provided under Table 1. These castings were poured and moulded at about 1370-1450° C. (H8765ST around 1370° C., H8766ST around 1450° C.) and allowed to cool. It is noted that carbide particles are formed throughout the alloy structure during this cooling process, including both dispersed particles in the ferrous matrix and particles at the grain boundaries.

[0115] The castings of the invention were then solution-treated at a temperature of about 1150-1180° C. and immediately quenched in water. The selected solution-treatment temperature range, being increased over conventional solution-treatment temperatures, was selected by the inventor through an experimental process. In particular, the inventor found that an increased solution-treatment temperature promoted the dissolution of grain boundary carbides during solution-treatment; however, the inventor further observed that the increased temperature caused the grain boundaries to shift resulting in grain growth, particularly undesirable coarse grain growth. The particular temperature range was accordingly selected, further in view of the alloy composition and matrix structure, to maximize discrete fine-grain carbide particles dispersed throughout the ferrous matrix and minimize the grain boundary carbides.

[0116] Table 1 further details the chemical compositions of two comparative samples of conventional manganese steels.

TABLE-US-00001 TABLE 1 Chemical compositions of samples Comparative Comparative Sample 1: Sample 2: Sample 1: Sample 2: H8765ST H8766ST A31 H8609 K700 wt % wt % wt % wt % Mn 17.40 17.80 12.0 12.5 C 1.37 1.42 1.15 1.20 Cr 5.20 6.20 <0.01 <0.01 Fe and Base Base Base Base impurities

[0117] The samples were tested for their initial hardness (after heat treatment) and subjected to cold-rolling to compare their bulk hardness after strain. This process effectively simulates the increased hardness that could be achieved by work-hardening the samples.

[0118] The results of these cold-rolling tests, shown in FIG. 2, demonstrated that the manganese steels produced in accordance with the present invention possessed an increased initial hardness (after heat treatment) compared to the comparative samples, and were able to be work-hardened at a similar rate to the comparative samples, as demonstrated by the extracted points detailed in Table 2:

TABLE-US-00002 TABLE 2 Cold-rolling hardness of samples Hardness (HV) Comparative Comparative Reduction Sample 1: Sample 2: Sample 1: Sample 2: (%) H8765ST H8766ST A31 H8609 K700 0 232.6 272 204 196 20 462 473 −377 −366 50 680 626 −550 −550

[0119] Throughout this specification and the claims which follow, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.

[0120] The term “impurity” or “impurities” has been used in throughout the specification and the claims to refer to any compositional element that has not been explicitly defined in the alloy compositions. This may include intentional compositional additives and/or unintentional compositional contaminants from manufacturing.

[0121] Furthermore, unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

[0122] Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, other example embodiments include from the one particular value and/or to the other particular value, or to any singular value or value range between the two mentioned values. Moreover, ranges may be expressed herein as “more than”, “more than or equal to”, “less than” or “less than or equal to” a particular value. When such a range is expressed, other example embodiments include any singular value or subset value range that lies within the initial value range.

[0123] Although the invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. For example, it will be appreciated that many combinations, alterations, modifications, variations and substitutions will be apparent to those skilled in the art without departing from the scope of the present invention, and it is intended for this application to embrace all such combinations, alterations, modifications, variations and substitutions. Moreover, wherein specific integers are mentioned which have known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.