BR112016015487B1 - composite metal product and method for centrifugally melting a composite metal product - Google Patents

Abstract

COMPOSITE METAL PRODUCT This is a centrifugally cast composite metal product that has a geometric axis of rotation symmetry and a mass of at least 5 kg, comprising a host metal and refractory particles of insoluble solid of a refractory material in a non-uniform distribution across the host metal. The particles have a density that is up to 30% of the host metal's density at its melting temperature.

Description

FIELD OF TECHNIQUE

[0001] The present disclosure relates to a method for centrifugal casting of a composite metal product, in which the finished product typically ranges in mass from 20 to 5,000 kg, so that it has a host metal matrix, typically a matrix of ferrous metal and comprising an outer surface layer, nominally 1 to 20 mm thick, of hard insoluble refractory particles for improved wear resistance.

[0002] The present disclosure also relates to centrifugally cast composite metal products.

[0003] In the context of the present disclosure, the term "refractory particles" is understood to include particles of high melting point carbides and/or nitrides and/or borides of any one or more than one of the nine titanium transition metals, zirconium, hafnium, vanadium, niobium, tantalum, chromium molybdenum and tungsten dispersed in a rigid host metal, which acts as a binding phase. Each such refractory particle is a particle of a refractory material and is referred to herein as a “refractory material”. Typically, the host metal is a ferrous metal alloy. The host metal can also be nickel-based and cobalt-based superalloys.

[0004] In the context of the present disclosure, it is understood that the term "insoluble" means, for all purposes and purposes, that the refractory material is not soluble in the host metal at melting temperatures, typically in a range of 1,200 to 1,600° C for ferrous host metals. There may be limited solubility. However, the refractory particles are essentially distinct from the host metal to the extent that there is negligible partitioning of the elements in the refractory material particles to the host metal during the casting method and in the solidified product.

DISCLOSURE SUMMARY

[0005] In a first aspect, modalities of a centrifugally cast composite metal product are disclosed that have a geometric axis of rotation symmetry and a mass of at least 5 kg, typically at least 10 kg and more typically at least 20 kg and comprising a host of metal and solid insoluble particles of a refractory material in a non-uniform distribution throughout the host metal, wherein the particles have a density that is up to 30%, typically up to 20% of the host's density of metal at its melting temperature.

[0006] The composite metal product comprises two distinct zones along the solidified material, namely, a zone of insoluble solid particles of the refractory material and a region at least substantially free of refractory particle of the host metal, in which the refractory particles are essentially distinct from the host metal to the extent that there is no negligible partitioning of elements in the particles of material refractory to the host metal at the melting temperature and solidified product.

[0007] The feature of the invention of solid particles of refractory material that are insoluble in the host metal at the melting temperature and after solidification distinguishes the invention from prior art proposals, such as JPS632864, for the addition of ferroalloys (a) Fe-W, (b) Fe-Mo and (c) Fe-Cr to a ferrous host alloy that respectively form (a) tungsten carbide, (b) molybdenum carbide and (c) chromium carbide, which are soluble to varying degrees in the host metal at common melting temperatures. As a consequence, in these systems, the % by volume of hard insoluble refractory carbides in the microstructure is substantially reduced and dissolved tungsten and/or molybdenum and/or chromium can adversely influence the physical and chemical properties of the host metal at room temperature in an amount unknown, (eg, reduced stiffness and a different response to heat treatment).

[0008] In some embodiments, the refractory particles may have a density that is higher than that of the host metal, in which case, there will be a higher concentration of the refractory particles toward an outer surface of the composite centrifugally cast metal product.

[0009] In some embodiments, the refractory particles may have a density that is lower than that of the host metal, in which case there will be a higher concentration of refractory particles towards an internal surface of the product.

[0010] In some embodiments, the non-uniform distribution of refractory particles may comprise a first concentration of refractory particles in an outer or inner surface layer of the product that is greater than a second concentration of refractory particles in another layer in the product.

[0011] In some embodiments, the first concentration of refractory particles in the outer surface layer of the product may be at least 50% by volume, typically at least 60% by volume, typically at least 70% by volume, and more typically 50 120% by volume greater than the nominal volume percentage of the refractory material in the product.

[0012] In some embodiments, the first concentration of refractory particles in the outer surface layer of the product may be at least 10%, typically at least 20%, typically less than 40%, and more typically in a range of 10 to 40% by volume of the total volume of the outer surface layer.

[0013] In some embodiments, the second concentration of refractory particles in the outer layer of the product may be in a range of 2 to 4.5% by volume, typically 2 to 3.5% by volume of the total volume of the other layer.

[0014] In some embodiments, the outer or inner surface layer of the product may extend for at least 5%, typically at least 20%, more typically at least 25% of the radial thickness of the product from the outer or inner surface .

[0015] In some embodiments, the outer or inner surface layer of the product may extend for less than 50%, typically less than 40%, more typically less than 30%, and more typically less than 20 % of radial product thickness from outer or inner surface.

[0016] In some embodiments, the outer or inner surface layer of the product may extend for at least 10 mm, typically at least 20 mm, typically less than 50 mm, typically 1 to 50, and more typically 5 to 20 mm from the outer or inner surface.

[0017] In some embodiments, the first concentration of refractory particles in the outer surface layer of the product may be in a range of at least 5% by volume, typically at least 10% by volume, typically 5 to 90% by volume, and, more typically 10 to 40% by volume of the total volume of particles.

[0018] In some embodiments, the overall concentration of refractory particles in the product may be at least 5% by volume, typically at least 10% by volume, and more typically in a range of 5 to 50% by volume of the total volume of the product.

[0019] In some modalities, the general concentration of refractory particles in the product may be in a range of 5 to 40% by volume of the total volume of the product.

[0020] In some modalities, the general concentration of refractory particles in the product can be in a range of 5 to 20% by volume of the total volume of the product.

[0021] In some embodiments, the refractory particles can be carbides and/or borides and/or nitrides of one or more of a transition metal where the particles are a chemical mixture (as opposed to a chemical mixture) of the carbides and/ or transition metal borides and/or nitrides. In other words, in the case of carbides, the refractory particles can be of the type described as (M1, M2)C or (M1, M2, M3)C, where “M” is a transition metal. An example that is discussed further in this document is (Nb,Ti,W)C.

[0022] The host metal may be any suitable host metal. The host metal can be a ferrous alloy, such as stainless steel or an austenitic manganese steel or cast iron. The host metal can be a non-ferrous host metal, such as titanium or a titanium alloy.

[0023] In some embodiments, the host metal may be an alloy comprising any of the following alloys:

[0024] (a) Hadfield steel for use, for example, in hoods of rotary crushers;

[0025] (b) 420C stainless steel for use, for example, in stub shafts in slurry pumps; and

[0026] (c) high chromium white cast iron.

[0027] As used in some modalities, Hadfield steel can comprise:

[0028] 1.0 to 1.4% by weight of C,

[0029] 0.0 to 1.0% by weight of Si,

[0030] 10 to 15% by weight of Mn,

[0031] 0.0 to 3.0% by weight of Mo,

[0032] 0.0 to 5.0% by weight of Cr,

[0033] 0.0 to 2.0% by weight of Ni,

[0034] where the remainder is Fe and incidental impurities.

[0035] As used in some embodiments, 420C stainless steel may comprise:

[0036] 0.3 to 0.5% by weight of C,

[0037] 0.5 to 1.5% by weight of Si,

[0038] 0.5 to 3.0% by weight of Mn,

[0039] 0.0 to 0.5% by weight of Mo,

[0040] 10 to 14% by weight of Cr,

[0041] 0.0 to 1.0% by weight of Ni,

[0042] where the remainder is Fe and incidental impurities.

[0043] As used in some embodiments, high chromium white cast iron may comprise:

[0044] 1.5 to 4.0% by weight of C,

[0045] 0.0 to 1.5% by weight of Si,

[0046] 0.5 to 7.0% by weight of Mn,

[0047] 0.0 to 1.0% by weight of Mo,

[0048] 15 to 35% by weight of Cr,

[0049] 0.0 to 1.0% by weight Ni,

[0050] where the remainder is Fe and incidental impurities.

[0051] The composite metal product can be any product that is adapted to be centrifugally cast and requires high wear and high stiffness properties. Examples of such products include a rotary crusher cover for a primary, secondary or tertiary crusher, a slurry pump shaft sleeve, rollers for use in crushers (including large diameter rollers that are on the order of 1 m in diameter with radial wall thicknesses in a range of 300 to 400 mm) and other crusher and pump components.

[0052] In a second aspect, embodiments are disclosed in which the composite metal product of the first aspect may be a rotary crusher cover for a primary, secondary or tertiary crusher.

[0053] In a third aspect, embodiments are disclosed wherein the composite metal product of the first aspect may be a slurry pump shaft sleeve.

[0054] In a fourth aspect, embodiments of a method for centrifugally casting a composite metal product having a geometric axis of rotation symmetry and a mass of at least 5 kg, typically at least 10 kg, and more typically, are disclosed at least 20 kg and comprising a host metal and a non-uniform dispersion of refractory particles of insoluble solid of a refractory material, the method comprising:

[0055] (a) form a slurry comprising solid particles of the refractory material dispersed in a liquid host metal, wherein the refractory particles comprise 5 to 50% by volume, typically 5 to 40% by volume of the total volume of the slurry wherein the refractory particles are insoluble at a melting temperature and wherein the refractory particles have a density that is up to 30%, typically up to 20% of the metal host density at the melting temperature; and

[0056] (b) pouring the slurry into a mold for the composite metal product and centrifugally melting the product in the mold and obtaining a non-uniform distribution of refractory particles of insoluble solid throughout the host metal.

[0057] In some embodiments, step (a) may comprise forming the refractory particles in situ in the molten host metal and dispersing the particles into a molten form of the host metal.

[0058] In some embodiments, step (a) may comprise adding refractory particles to a molten form of the host metal.

[0059] In some embodiments, steps (a) and (b) can be performed in an inert environment, such as an inert gas atmosphere.

[0060] In some embodiments, step (b) may comprise preparing the mold by forming an inert environment inside the mold.

[0061] In some embodiments, step (b) may comprise rotating the mold around the geometric axis subsequent to and/or pouring the slurry into the mold to cause a concentration of refractory particles on or near the external surface or in a internal surface of or near the composite metal product, which is greater than the concentration of particles elsewhere in the product.

[0062] In some embodiments, step (b) may comprise rotating the mold in a G Factor from 10 to 120, in which the G Factor is the centrifugal force acting on a rotating body divided by the gravitational force.

[0063] In some embodiments, step (b) may comprise rotating the mold at a peripheral speed of 2.5 to 25 m/s.

[0064] In some embodiments, step (b) may comprise rotating the mold long enough to obtain non-uniform distribution of solid particles throughout the host metal.

[0065] In some embodiments, step (b) may comprise rotating the mold until the host metal has solidified.

[0066] In some embodiments, step (b) may comprise pouring the slurry into the mold at a melting temperature in a range of 1200 to 2000 °C, typically in a range of 1350 to 1650 °C.

[0067] In some embodiments, the method may comprise selecting production parameters to form the slurry in step (a) that has a fluidity required for processing in step (b).

[0068] The production parameters may comprise any one or more of the particle size, reactivity, density and solubility of the refractory materials, as described in the international patent application PCT/AU2011/000092 (W02011/094800) in the name of the present assignee . The disclosure in the International Application is incorporated herein by reference. Density and solubility of refractory materials are discussed below.

[0069] The density of the refractory material of the particles, compared to the density of the host metal in the liquid state, is a parameter to be considered during the method of the present disclosure to control the dispersion of refractory particles in the hot host metal,

[0070] The nominal density of a host ferrous liquid metal at 1400 °C is 6.9 grams/cc. When refractory particles in the form of tungsten carbide (WC) particles with a density of 15.7 grams/cc at 25 °C are added to a host ferrous metal to form the slurry, the WC particles will if submerged to the bottom of the slurry. When refractory particles in the form of titanium carbide (TiC) particles, with a density of 4.8 grams/cc at 1400 °C, are added to the same host ferrous metal, the TiC particles will float to the top of the slurry. fluid. Refractory particles in the form of niobium carbide (NbC), with a density of 7.7 grams/cc at 1400 °C, are significantly close to the density of the host ferrous liquid metal at 6.9 grams/cc and are less prone to the segregation described above in the liquid host ferrous metal than TiC or WC.

TiC with a density of 4.9 grams/cc at 25°C is completely soluble in NbC, which has a density of 7.8 grams/cc at 25°C. Therefore, refractory particles with densities in the range of 4.9 to 7.8 grams/cc at 25 °C can be obtained by selecting (Nb,Ti)C particles with the required contents of niobium and titanium.

[0072] Tungsten carbide (WC) with a density of 15.7 grams/cc at 25 °C, is mainly soluble in NbC, TiC and (Nb,Ti)C. Therefore, refractory particles with densities in the range of 4.8 to 15.7 grams/cc at 25 °C can be obtained by selecting (Nb,Ti,W)C particles with the required contents of niobium, titanium and tungsten .

[0073] All refractory particles described through the formula (Nb,Ti,W)C are insoluble in liquid ferrous host metals at melting temperatures ranging from 1200 to 1600 °C.

[0074] Niobium carbide and titanium carbide have similar crystal structures and are isomorphic.

[0075] It is evident from the above that to select the ratio of Nb:Ti required in a chemical compound of (Nb,Ti)C or the ratio of Nb:Ti:W required in a chemical compound of (Nb,Ti) ,W)C can yield a refractory material with a required density of up to 20% of the host ferrous metal density.

[0076] The addition of refractory particles that are, for all purposes and purposes, insoluble, (i.e., that have minimal solid solubility in a liquid metal host), to produce a centrifugal smelting of a composite metal product in accordance with with the method of the present disclosure produces a product that exhibits physical and chemical properties that are very similar to the host metal with substantially improved wear resistance due to the presence of a controlled dispersion of a high % by volume of hard refractory material particles in the microstructure of the host metal.

[0077] For example, the solubility of a refractory material in the form of (Nb,Ti,W)C in liquid host metals in the form of (a) liquid Hadfield steel and (b) liquid 420C stainless steel and (c) white cast iron with high liquid chromium content at elevated temperatures is negligible (<0.3% by weight). The addition of (Nb,Ti,W)C with the necessary densities to these three host metal alloys, followed by centrifugal casting of a composite metal product and standard heat treatment procedure for each host metal produces microstructures in the product comprising a dispersion of primary niobium-titanium-tungsten carbides in the host metals that are substantially free of niobium, titanium and tungsten, i.e. there is negligible partitioning of the transition metals in the refractory material slurry particles to the liquid host metal.

[0078] Consequently, there is negligible influence of particulate refractory materials on the physical properties (eg melting point) and chemical properties (eg response to heat treatment) of the host metal.

[0079] In addition to the above, in particular, the Applicant has found that to provide a composite metal product with a microstructure that includes niobium carbide particles and/or particles of a chemical (as opposed to a physical) mixture of two or more than two of niobium carbide, titanium carbide and tungsten carbide dispersed in a matrix of a host metal considerably improves the wear resistance of the carbide material without negatively affecting the contribution of other metal forming elements. alloy has relative to other composite metal product properties.

[0080] In addition and as described above, in particular, the Applicant has found that it is possible to adjust the particle density of a chemical mixture of two or more than two among niobium carbide, titanium carbide and tungsten carbide to an extent sufficient relative to the density of a host metal, which forms a matrix of the composite metal product. This opportunity for density control is an important finding in relation to centrifugal casting of carbide material.

[0081] In particular, by virtue of this finding, it is possible to produce a centrifugal casting of the composite metal product with controlled non-uniform distribution, that is, segregation of particles in parts of the castings. This is important for end user applications for foundries where it is desirable to have a concentration of high wear resistant particles close to a surface of a foundry of a carbide material.

[0082] In addition, the Applicant has found that to form composite metal product castings to include niobium carbide particles and/or particles of a chemical mixture of two or more than two among niobium carbide, titanium carbide and titanium carbide tungsten in a range of 5 to 50% by volume, typically 5 to 40% by volume, more typically 5 to 20% by volume of the total volume of the composite metal product, dispersed in a host metal, which forms a matrix of the product composite metal, does not have a significant negative impact on the corrosion resistance and stiffness of ferrous material in the host metal. Therefore, the present disclosure makes it possible to achieve a high wear resistance of a composite metal product without a loss of other desirable material properties.

[0083] Accordingly, in a fifth aspect there is provided a method for centrifugally casting a composite metal product having a geometric axis of rotation symmetry and a mass of at least 5 kg and comprising a host metal and a non-uniform distribution of refractory particles of insoluble solid of a refractory material, wherein the method comprises adding (a) niobium or (b) two or more than two of niobium and titanium and tungsten to a melt component that contains a host metal in a form that produces solid refractory particles of niobium carbide that are insoluble at a melting temperature and/or solid refractory particles of a chemical mixture of two or more than two of niobium carbide and titanium carbide and tungsten carbide that are insoluble at temperature fusion, in which the solid refractory particles are in a range of 5 to 50% by volume, typically 5 to 40% by volume, more typically 5 to 20% by volume of the total volume of the product and centrifugally melt the product in a mold and obtain a non-uniform distribution of insoluble solid particles throughout the host metal.

[0084] The terms "a chemical mixture of niobium carbide and titanium carbide" and "niobium/titanium carbide" are hereafter understood to be synonymous. Furthermore, the term "chemical mixture" is understood in the present context to mean that niobium carbides and titanium carbides are not present as single metal carbide particles in the mixture, but are present as niobium carbide particles /titanium, (Nb,Ti)C.

[0085] The terms “a chemical mixture of niobium carbide and titanium carbide and tungsten carbide” and “niobium/titanium/tungsten carbide” are hereafter understood to be synonymous. Furthermore, the term "chemical mixture" is understood in the present context to mean that niobium carbides and titanium carbides and tungsten carbides are not present as single metal carbide particles in the mixture, but are present as niobium/titanium/tungsten carbide particles, (Nb,Ti,W)C.

[0086] Niobium carbide, titanium carbide and tungsten carbide each have a Vickers hardness of approximately 25 GPa, which is about 10 GPa above the hardness of chromium carbides (nominally 15 GPa). Consequently, composite metal products that have a microstructure that contains 5 s 50% by volume, typically 5 to 40% by volume, more typically 5 to 20% by volume of niobium carbide and/or niobium/titanium carbide and/ or niobium/titanium/tungsten carbide have excellent wear resistance properties. Applicant has recognized that niobium carbides, titanium carbides, tungsten carbides, niobium/titanium carbides and niobium/titanium/tungsten carbides are substantially chemically inert towards other constituents in the composite metal product, such that such constituents provide the product with the properties for which they were selected. For example, chromium added to cast iron alloys still produces chromium carbides and provides corrosion resistance.

[0087] Niobium, titanium and tungsten can be added to a host metal fusion component to form the slurry in any suitable form, considering the requirement to form solid insoluble particles of niobium carbides and/or carbides of niobium/titanium and/or niobium/titanium/tungsten carbides in the composite metal product.

[0088] For example, the method may comprise adding the niobium to the melting component in the form of iron-niobium, e.g. iron-niobium particles. In this situation, the iron-niobium dissolves in the fusion component and the resulting free niobium and carbon chemically combine to form solid niobium carbides insoluble in the fusion component.

[0089] The method may also comprise adding the niobium to the fusion component as elemental niobium.

[0090] The method may also comprise adding niobium and titanium to the fusion component such as iron-niobium-titanium.

[0091] The method may also comprise adding niobium, titanium and tungsten to the fusion component such as iron-niobium-titanium-tungsten,

[0092] The method may also comprise adding the niobium to the melting component in the form of niobium carbide particles.

[0093] The method may also comprise adding the niobium and titanium to the melting component in the form of insoluble solid particles of niobium/titanium carbides.

[0094] The method may also comprise adding the niobium, titanium and tungsten to the melt component in the form of insoluble solid particles of niobium/titanium/tungsten carbides.

[0095] In each of these cases, the solidified metal alloy can be formed from a slurry of niobium carbide particles and/or niobium/titanium/tungsten carbides suspended in the melt component, if the weight fraction if such carbides in the molten slurry is too high, the flow properties of the slurry can be adversely affected, with the result that inconsistent melts of the slurry can be produced.

[0096] The insoluble solid particles of niobium/titanium carbides can be any suitable chemical mixture of a general formula (Nbx,Tiy)C.

[0097] The solid insoluble particles of niobium/titanium/tungsten carbides can be any suitable chemical mixture of a general formula (Nbx,Tiy,Wz)C. By way of example, the niobium/titanium/tungsten carbides can be (Nb0.25,Ti0.50,W0.25)C.

[0098] Niobium and/or titanium and/or tungsten can be added to the melting component to produce insoluble solid particles of niobium carbide and/or niobium/titanium carbides and/or niobium/titanium/tungsten carbides in a range of 12 to 33% by weight of niobium carbides or niobium/titanium carbides or niobium/titanium/tungsten carbides of the total weight of the molten product.

[0099] Niobium and/or titanium and/or tungsten can be added to the melting component to produce insoluble solid particles of niobium carbide and/or niobium/titanium carbides and/or niobium/titanium/tungsten carbides in a range of 12 to 25% by weight of niobium carbides, niobium/titanium carbides and niobium/titanium/tungsten carbides of the total weight of the composite metal melt.

[00100] The amount of niobium carbide and/or niobium/titanium carbide and/or niobium/titanium/tungsten carbide particles in the microstructure of the solidified carbide material may depend on the system.

[00101] The applicant pays particular attention to solid hard composite metal products that include host metals in the form of ferrous alloys, such as ferrous alloys described as high chromium white cast irons, stainless steels and austenitic manganese steels (such as such as Hadfield steels). For ferrous alloys, the amount of insoluble solid particles of refractory material in the form of niobium carbide and/or niobium/titanium carbides and/or niobium/titanium/tungsten carbides in the final composite metal product can be in a range of 5 to 50% by volume, typically 5 to 40% by volume, more typically 5 to 20% by volume of the total volume of the composite metal melt.

[00102] The particle size of niobium carbide and/or niobium/titanium carbide and/or niobium/titanium/tungsten carbide can be in a range of 1 to 150 µm in diameter.

[00103] The method may comprise stirring the slurry with an inert gas or magnetic induction or any other suitable means in order to disperse particles of niobium carbide and/or niobium/titanium carbides and/or niobium/titanium/tungsten carbides in the slurry.

[00104] The method may comprise adding niobium carbide particles and/or niobium/titanium/tungsten carbide particles to the fusion component of the host ferrous metals under inert conditions such as an argon blanket to reduce the extent to which the Niobium carbide and/or niobium/titanium/tungsten carbide oxidize as they are added to the melt component.

[00105] The method may comprise adding particles of iron-niobium and/or iron-titanium and/or iron-tungsten and/or iron-niobium-titanium-tungsten to the melting component under inert conditions such as an argon blanket for reduce the extent to which the niobium and/or titanium and/or tungsten oxidize as they are added to the fusion component.

[00106] In a situation where niobium/titanium/tungsten carbide particles are required in the composite metal cast product, the method may comprise pre-melting iron-niobium and iron-titanium and iron-tungsten and/or iron-niobium -titanium-tungsten under inert conditions and form a liquid phase which is a homogeneous chemical mixture of iron, niobium and titanium and tungsten and solidify this chemical mixture. The chemical mixture can then be processed as needed, for example by grinding it to a required particle size and then added to the melting component (which contains carbon) under inert conditions. Iron, niobium and titanium and tungsten dissolve in the fusion component and chemically combine with carbon to form niobium/titanium/tungsten carbides in the fusion component.

[00107] Other aspects, features and advantages will become apparent from the following detailed description when considered in conjunction with the accompanying drawings, which are a part of the present disclosure and which illustrate, by way of example, principles of the disclosed inventions.

DESCRIPTION OF DRAWINGS

[00108] Notwithstanding any other forms that may fall within the scope of the method and resulting composite metal product as set forth in the Summary, the specific modalities of the method and the resulting composite metal product will now be described by way of example and with reference to Attached figures, of which:

[00109] Figure 1 is a diagram illustrating a typical centrifugal casting method;

[00110] Figure 2 is an SEM image of a section of one of the samples of the centrifugally cast test cylinder "37863" (host metal of A05 + 5% by volume of NbC particles) produced during the experimental work in relation to invention;

[00111] Figure 3 comprises cross sections of optical image samples from the centrifugally cast test cylinders "37628", "37629", "37630" and "37655" (host metal of A05 + 5% by volume of particles of NbC) produced during experimental work in relation to the invention;

[00112] Figure 4 is a graph of hardness as a function of distance from external surfaces to internal surfaces of the samples described in relation to Figure 3;

[00113] Figure 5 comprises optical images of cross-sections of samples from centrifugally cast test cylinders "37631", "37632", "37633" and "37636" (host metal of A05 + 12% by volume of NbC particles) produced during experimental work in relation to the invention;

[00114] Figure 6 is a graph of hardness as a function of distance from the external surfaces to the internal surfaces of the samples described in relation to Figure 5;

[00115] Figure 7 comprises optical images of cross-sections of samples from centrifugally cast test cylinders "37634" and "37635" (host metal of A05 + 17% by volume of NbC particles) produced during experimental work in relation to the invention;

[00116] Figure 8 is a graph of hardness as a function of distance from external surfaces to internal surfaces of the samples described in relation to Figure 7;

[00117] Figure 9 is an optical image of a cross section of a sample of a centrifugally cast A352 test cylinder (host metal of C21 + 10% by volume of NbC particles) produced during experimental work in relation to the invention;

[00118] Figure 10 is an optical image of a cross section of the outer layer of the cross section of the sample shown in Figure 9 after recording the sample;

[00119] Figure 11 is an optical image of a cross section of a sample from a centrifugally cast A323 test cylinder (A49 host metal + 15% by volume NbC particles); and

[00120] Figure 12 is a graph of hardness as a function of distance from outer surfaces to inner surfaces of sections of the sample described in relation to Figure 11.

[00121] Figure 13 is a graph of the thickness of the outer layer rich in NbC particle as a function of the % in nominal volume of NbC in the total composite of centrifugally cast cylinders of host metal of A05 + NbC particles; and

[00122] Figure 14 is a graph of the % by volume of NbC in the outer layer rich in NbC particle against the % by volume of nominal NbC in the total composite of centrifugally cast host metal cylinders of A05 + NbC particles.

DETAILED DESCRIPTION OF SPECIFIC MODALITIES

[00123] Figure 1 originates from the Internet and illustrates, in diagram form, the basic steps in a centrifugal casting method.

[00124] These centrifugal casting steps include forming a molten fusion component and pouring the fusion component into a suitable mold and rotating the mold around a vertical axis (in the case of the arrangement shown in the Figure) at a required rate of rotation to form a molten product.

[00125] In alternative arrangements, such as the arrangement used to perform the experimental work described below, the casting mold is positioned horizontally and the mold is rotated around a horizontal geometric axis.

[00126] In the context of the present disclosure, typically, the molten melt component comprises a slurry of hard insoluble solid refractory particles in a host metal and the molten product is a composite metal product that typically ranges in mass from 5 kg to 5,000 kg, which has a ferrous metal matrix (the host metal) and comprises a non-uniform distribution of hard insoluble refractory particles in the ferrous metal matrix, specifically, an outer surface layer, namely 1 to 20 mm thick refractory particles hard insolubles that provide improved wear resistance in the surface layer.

[00127] Actual centrifugal casting conditions can be selected in any given situation based on the required characteristics of an actual product to be cast. Casting conditions include, by way of example, the mold rotation rate and rotation time and the cooling conditions and conditions under which the casting is conducted, for example, in an inert atmosphere.

[00128] Refractory particle property requirements may include:

[00129] • Density greater than or less than the host ferrous metal.

[00130] • Hardness in excess of 15 GPa.

[00131] • Diameter less than 500 microns, preferably less than 50 microns.

[00132] • 10 to 80% by volume of refractory particles present in the hard surface layer.

[00133] • 5 to 50% by volume, typically 5 to 40% by volume, more typically 5 to 40% by volume of refractory particles in the composite metal product.

[00134] The composite metal products produced through the centrifugal casting process of the invention include, by way of example, only the following products: 1. FLUID Slurry PUMP SHAFT SLEEVES

[00135] • Stainless steel cylinders

[00136] • Size: ranging from 25 to 400 mm in diameter, 10 to 50 mm in wall thickness and 2000 mm in length.

[00137] • Outer surface layer 1 to 10 mm thick, which contains a high concentration of hard insoluble refractory particles.

[00138] The prior art comprises face welding of a stainless steel cylinder to obtain a tungsten carbide surface layer approximately 1 mm thick. Faced layers then require grinding/machining to achieve a smooth finish.

[00139] Centrifugal casting of a slurry pump shaft sleeve according to the invention allows the fabrication of a cylinder approximately 2000 mm in length with a smooth hard surface layer in a casting operation. In addition, the long cylinder can be sectioned to yield multiple stub shafts ranging in length from 60 to 300 mm. 2. EXTERNAL SURFACE OF ROTATING CRUSHERS COVERS

[00140] The standard composition of gyratory crusher covers is austenitic manganese steel (Hadfield steel). The initial hardness of Hadfield steel is approximately 200 Brinell (HB) and the steel work surface layer hardens to approximately 550 HB during service while the interior maintains a lower hardness and extremely high stiffness. The tensile strength for Hadfield steel with a hardness of 200 HB is about 1/3 of the tensile strength. Severe plastic deformation can occur during service before work hardening to 550 HB occurs. As a result, crusher covers wear out quickly and are subjected to excessive plastic deformation in the early stages of operation. All previous attempts to improve the initial hardness and tensile strength of Hadfield steel have invariably resulted in an unacceptable loss of stiffness and a high risk of catastrophic cracking in service.

[00141] Centrifugal melting of a Hadfield steel crusher bed in accordance with the present disclosure and forming an outer surface layer of insoluble solid refractory carbides in the foundry, while maintaining the original composition of Hadfield steel in the foundry body, provides a more wear resistant material with minimal loss of stiffness. 3. WHITE CAST IRON

[00142] Centrifugal casting of high chromium white cast irons with refractory particles produces composite metal products that have surface layers that contain a high concentration of refractory particles for improved wear resistance. 4. BREAKDOWN BARS, HAMMER TIPS, GROUND COUPLING TOOLS

[00143] Centrifugal casting of high chromium white cast iron breaker bars, hammer tips and ground engaging tools with refractory particles produces a surface layer that contains a high concentration of refractory particles for improved wear resistance. EXPERIMENTAL WORK

[00144] In order to investigate the invention, the applicant has carried out extensive experimental work in relation to particles of a particular refractory material, namely NbC particles in different ferrous host metals.

[00145] Specifically, the experimental work investigated the effects of % by volume of NbC particles, wall thickness and centrifugal forces in the NbC rich zones in centrifugally cast products.

[00146] In the experimental work, fourteen cylinders were centrifugally cast in a horizontally disposed centrifugal casting arrangement.

[00147] The fourteen cylindrical shaft sleeves with different concentrations of NbC particles and a host metal with a ferrous base, as summarized below were centrifugally cast and machined and then tested.

[00148] • Four A301 cylinders (A05 host metal + 5% by volume of NbC particles of total volume).

[00149] • Four A303 cylinders (A05 host metal + 12% by volume of NbC particles of total volume).

[00150] • Four A304 cylinders (A05 host metal + 12% by volume of NbC particles of total volume).

[00151] • One A352 cylinder (C21 host metal + 10% by volume of NbC particles of the total volume).

[00152] • One A323 cylinder (A49 host metal + 15% volume NbC particles of total volume).

[00153] A05 is a eutectic high Cr content cast iron, C21 is a 420C stainless steel and A49 is a hypoeutectic high Cr content cast iron. The nominal compositions of the ferrous alloys of A05, C21 and A49 are as follows, with the amounts of each element in % by weight:

[00154] Twelve cylinders based on A05 steel with different nominal chemical compositions were centrifugally cast at various rotational speeds (RPM). 4.1. THE A301 FOUR CYLINDER CENTRIFUGAL FOUNDRY (HOST METAL OF A05 + 5% by volume of NbC particles)

[00155] Four cylinders containing 5% by volume of NbC particles in A05 high Cr eutectic cast iron host metal were centrifugally cast at various rotational speeds or centrifugal forces. The melting temperature was in a range of 1400-1500 °C. The density difference between the NbC particles and the host metal at the melting temperature was approximately 12%. Cylinder dimensions and casting conditions are in Table 1. TABLE 1. SOUNDING DIMENSIONS AND CONDITIONS OF CYLINDERS CONTAINING 5% by volume of NbC particles

[00156] Each 400 mm cylinder was sectioned into three rings of approximately 280 mm, 20 mm and 100 mm in length. The 20 mm thick rings were used for inspection and metallurgical analysis. 1.1.1 METALLURGICAL RESEARCH

[00157] Samples were prepared from each 20 mm thick ring by cutting through the thickness at two locations about 15 mm apart and forming cross sections of the rings. Each cut was made perpendicular to the outer and inner circumferences of the ring. For this reason, the sample width decreased from the outer surface to the inner surface. Samples were mounted, ground and polished following standard metallographic procedures and were then engraved with Acidified Ferric Chloride (AFC) for metallographic examination. The microstructures of the samples were examined with a scanning electron microscope. In addition, an optical stereomicroscope was used for macroscopic examination of the samples.

[00158] Analysis of the samples from the cylinders established that the foundry microstructure in each case comprised the host metal of high Eutectic Cr content of A05 and a non-uniform distribution of solid NbC particles along the host metal. Figure 2 is an SEM image of a section of one of the samples. Figure 2 shows the non-uniform distribution of NbC particles in the host metal. The Figure indicates that NbC was undetectable in the host metal. More particularly, it has been found that NbC particles are insoluble in the host metal at the melting temperature and in the molten cylinders.

[00159] Figure 3 comprises optical images of cross-sections of samples of cylinders "37628", "37629", "37630" and "37655".

[00160] Figure 3a shows that the cylinder sample “37628” had an outer layer rich in NbC particle about 2 mm thick. On the inside of the outer layer there are three layers numbered 2 through 4 in the Figure. There are boundaries between layers. Each layer is about 3 to 5 mm thick. Layers 2 to 4 form an inner region that has a lower concentration of NbC particles than the outer layer.

[00161] Figure 3b shows that the cylinder sample “37629” had a similar layered (ie banded) structure, but with more layers than shown in Figure 3a. The outer layer of high concentration NbC particle (identified by numeral 1 in Figure) is about 2 mm thick with NbC particles evenly spread throughout the sample. The outer layer 1 and the innermost layer (identified by the numeral 6 in the Figure) are the most distinct and the layers between them (ie, layers 2 to 5 in the Figure) are very similar to each other in terms of appearance, however, they are distinct layers, however, separated by boundaries. It was found that the microstructures of layers 1 and 6 are very different from each other, as well as they are different from the microstructures of layers 2 to 5. It was found that the microstructures of layers 2 to 5 are remarkably similar to each other. Each layer 1 to 6 is about 3 to 4 mm thick.

[00162] Cylinder “37630” was cast at the highest rotation speed. Figure 3c shows that the sample had three layers. Compared to the samples from the other three cylinders, this foundry had the lowest NbC particle concentration in the inner layers. The high speed of rotation forced more NbC particles into the outer layer, resulting in the thickest high concentration NbC particle layer of all castings.

[00163] Cylinder "37655" was cast at the same rotational speed as cylinder "37628" but was cast with a 5 mm thicker wall thickness. Figure 3d shows that the NbC particle-rich layer in cylinder sample “37655” was approximately 3 mm thicker in cylinder sample “37628”. This shows that even if the rotation speeds are equal, a thicker wall results in a thicker NbC particle-rich zone.

[00164] The NbC particle volume fractions (a) of the outer layer rich in NbC particle and (b) the inner layer of low concentration NbC particle were calculated from SEM images of various areas of the layers in 100x magnification. The values shown in Table 2 are the means of multiple measurements. TABLE 2. NBC PARTICLES IN EXTERNAL AND INTERNAL LAYERS

[00165] From Table 2, it is evident that the rotation speed during casting had an effect on the NbC-rich outer layer of the cast cylinders. The sample for cylinder “37630”, which was melted at the highest velocity had the highest layer thickness and the highest volume fraction of the NbC particles. The sample for cylinder “37629”, which was cast at the second highest velocity, approached in terms of volume fraction of NbC, however, the layer thickness was approximately half the layer in sample “37630”. Comparing the samples for cylinders "37628" and "37655" shows that even at the same rotational speed, if the casting wall thickness is greater (ie more material), then the outer layer rich in NbC particle and its fraction by volume of NbC particles will also be larger.

[00166] Furthermore, all four foundries had similar levels of NbC particles present in the unconcentrated NbC particle inner layers, collectively described as an inner region for each sample. Most of the NbC particles observed in the inner regions were a typical “Chinese script” morphology. A small amount of spherical and dendritic NbC particles was also observed. 1.1.2 FERRITE AND HARDNESS MEASUREMENTS

[00167] Cross-sectional Vickers hardness tests with a load of 10 kg were performed on the polished surfaces of each sample. Measurements were started at the outer diameter (OD) of each sample and then traversed by the thickness of the sample at 1 mm intervals, ending at the inner diameter (ID) of the sample.

[00168] Table 3 shows the ferrite and average hardness readings for each of the regions. The transverse hardness profiles are shown in Figure 4. TABLE 3. FERRITE AND HARDNESS MEASUREMENTS

[00169] It will be evident from Table 3 and Figure 4 that the outer layer rich in NbC particle of each of the samples was considerably harder than the inner region of the sample and that the highest hardness values were typically in the outer surface of each sample and uniformly decreased to approximately 8 mm from the outer surface and remained generally constant throughout the remainder of the sample. In addition, the ferrite measurement results for the four smelters showed a general trend of the outer layer rich in NbC particle having higher ferrite measurements than the layers forming the inner regions. Differences in ferrite content were negligible, with the outer layers rich in NbC particles ranging from 13 to 16%, while the inner regions ranged between 9 and 10%. 1.1.3 SUMMARY

[00170] • All four A301 centrifugal castings (A05 host metal + 5% by volume NbC particles) exhibited NbC segregation, resulting in the outer layers of each sample having high concentrations of NbC particles.

[00171] • All four foundries exhibited layers below the outer layer rich in NbC particle, which were marginally different from each other. Each foundry had a different amount of layers.

[00172] • The thickness and hardness of the NbC particle-rich layers and the volume fractions of NbC particles in the outer layers of the centrifugally cast cylinders depended on different casting parameters, including casting rotation rate and wall thickness .

[00173] • The specimens for cylinders “37628” and “37655” were cast at the same rotational speeds but with different mass of material, resulting in different dimensions. Sample “37655” had a slightly thicker NbC particle-rich outer layer and also contained a greater amount of layers in different bands across the thickness of the samples.

[00174] • The specimen for cylinder “37629” was similar to the specimen for cylinder “37628”, despite being cast at a higher rotational speed. The faster rotation speed did not affect the thickness of the outer layer rich in NbC particle, however, it did affect the volume fraction of NbC particles in the outer layer slightly.

[00175] • The specimen for cylinder specimen “37630” was cast at the highest rotation speed and this was directly reflected in various features. The sample had the thickest NbC particle-rich outer layer and the highest fraction of NbC particles in the outer layer. Consequently, the highest outer shell hardness recorded for that group of cylinders.

[00176] • Ferrite measurement results for foundries have shown a general trend of the outer layer rich in NbC particle having higher ferrite measurements than the layers forming the inner regions. Differences in ferrite content were negligible, with the outer layers rich in NbC particles ranging from 13 to 16%, while the inner regions ranged between 9 and 10%. 4.2. A303 FOUR Cylinder CENTRIFUGAL CASTING (A05 host metal + 12% by volume of NbC particles)

[00177] Four cylinders were cast under the same conditions as the four cylinders described in section 1.1 above, in the same host metal (A05), but with an overall NbC volume fraction of 12%. Cylinder dimensions and rotation speeds are in Table 4. TABLE 4. WORK CODES AND SIZE OF CYLINDERS CONTAINING 12% NbC VOLUME

[00178] Each 400 mm cylinder was sectioned into three rings of approximately 280 mm, 20 mm and 100 mm in length. The 20 mm thick rings were used for inspection and metallurgical analysis. The samples were prepared and tested using the same methodology described in section 1.1 above.

[00179] Figure 5 comprises optical images of samples of cylinders "37631", "37632", "37633" and "37636".

[00180] It will be evident from Figure 5 that, as was the case with the lower NbC particle volume fraction cylinders described in section 1.1 above, the NbC particles formed a non-uniform distribution in the host metal across the thickness of the smelters, with the outer layers of the samples having higher concentrations of NbC particles.

[00181] Similar to the case with the lower NbC particle volume fraction cylinders described in section 1.1 above, SEM analysis established that NbC was not detectable in the host metal. More particularly, it has been found that NbC particles are insoluble in the host metal at the melting temperature and in the molten cylinders.

The NbC particle volume fractions of the outer layers rich in NbC particle and the thicknesses of the outer layers were calculated from SEM images of various areas of the layers at 100x magnification. The values shown in Table 5 are the means of multiple measurements. TABLE 5. EXTERNAL LAYER THICKNESS AND AVERAGE % VOLUME OF NBC PARTICLES

[00183] Cross-sectional Vickers hardness tests with a load of 10 kg were performed on the polished surfaces of each sample. Measurements were started at the outer diameter (OD) of each sample and then traversed by the thickness of the sample at 1 mm intervals, ending at the inner diameter (ID) of the sample.

[00184] Table 6 shows the ferrite and average hardness readings for each of the two regions. The transverse hardness profiles are shown in Figure 6. TABLE 6. FERRITE AND HARDNESS MEASUREMENTS

[00185] It will be evident from Tables 5 and 6 and Figures 5 and 6 that the same basic results were obtained with the higher percentage by volume of the A303 cylinders and with the A301 cylinders described in section 1.1 above. 4.3. A304 FOUR Cylinder CENTRIFUGAL CASTING (A05 host metal + 17% NbC particles by volume)

[00186] Four A304 cylinders were centrifugally cast using the same conditions as the A301 and A303 cylinders described in sections 1.1 and 1.2 above, respectively, with the same host metal as A05, but with a higher volume fraction of particles of NbC. Samples were prepared and tested as described in sections 1.1 and 1.2 above. Only three cylinders were examined (the “37634” cylinder cast at 920 rpm, the “37635” cylinder cast at 1100 rpm and the “37636” cylinder cast at 1280 rpm).

[00187] Figure 7 comprises optical images of cross-sectional samples of cylinders "37634" and "37635".

[00188] It will be evident from Figure 7 that, as was the case with the lower NbC particle volume fraction cylinders described in sections 1.1 and 1.2 above, the NbC particles formed a non-uniform distribution in the host metal across the thickness of castings, where the outer layers of the samples have higher concentrations of NbC particles. The cross sections show an outer NbC particle-rich layer (or region) and an inner region of lower NbC particle concentration (which may include multiple layers separated by boundaries).

[00189] Furthermore, as was the case with the lower NbC particle volume fraction cylinders described in sections 1.1 and 1.2 above, SEM analysis established that NbC was not detectable in the host metal. More particularly, it has been found that NbC particles are insoluble in the host metal at the melting temperature and in the molten cylinders.

[00190] The test work indicated that the thicknesses of the outer layers rich in NbC particle in the samples for cylinders “37634”, “37635” and “37636” were 12 mm, 13 mm and 15 mm, respectively.

[00191] The concentrations by volume of NbC particles in the outer layers of such samples were 28% for cylinder “37634”, 25% for cylinder “37635” and 29% for cylinder “37636”.

[00192] Table 7 shows the ferrite and average hardness readings for each of the inner and outer regions of cylinder samples “37634” and “37635”. The transverse hardness profiles are shown in Figure 8. TABLE 7. FERRITE AND HARDNESS READINGS

[00193] It will be evident from Table 7 and Figures 7 and 8 that the same basic results were obtained with the higher volume percentage of the A304 cylinders and with the A301 and A303 cylinders described in sections 1.1 and 1.2 above. 4.4. A352 ONE-Cylinder CENTRIFUGAL CASTING (HOST C21 metal + 10% NbC particles by volume)

[00194] An A352 cylinder was centrifugally cast from a C21 host metal with 10% by volume of NbC particles. Samples were prepared and tested as described above.

[00195] Figure 9 comprises an optical image of a cross section of a sample of cylinder A352.

[00196] It will be evident from Figure 9 that, as was the case with the other test cylinders described above, the NbC particles formed a non-uniform distribution across the thickness of the casting, where the outer layer of the sample has a concentration higher than NbC particles.

[00197] Furthermore, as was the case with the other test cylinders described above, SEM analysis established that NbC was not detectable in the host metal. More particularly, it has been found that NbC particles are insoluble in the host metal at the melting temperature and in the molten cylinders.

[00198] As shown in Figure 9, the NbC-rich layer is a 20 mm thick layer, 50% of the total radial thickness of the sample. The sample was found to contain about 25% by volume of NbC particles.

[00199] After etching, three sublayers of the outer layer rich in NbC particle with 20 mm thickness were identified and are shown in Figure 10. Figure 10 shows that there was directional solidification through the sublayers during centrifugal casting. It was found that the columnar structure contributed significantly to the wear resistance of the foundry. 4.5. CENTRIFUGAL CASTING OF A323 ONE Cylinder (HOST metal of A49 + 15% by volume of NbC particles)

[00200] An A323 cylinder was centrifugly cast from an A119 host metal and 15% by volume of NbC particles. Samples were prepared and tested as described above. 1.5.1 METALLURGICAL RESEARCH

[00201] Figure 11 comprises an optical image of a cross section of a sample of cylinder A323. It will be evident from Figure 11 that, as was the case with the other test cylinders described above, the NbC particles formed a non-uniform distribution across the thickness of the casting, with the outer layer of the sample having a higher concentration of particles of NbC.

[00202] Furthermore, as was the case with the other test cylinders described above, SEM analysis established that NbC was not detectable in the host metal. More particularly, it has been found that NbC particles are insoluble in the host metal at the melting temperature and in the molten cylinders.

[00203] As will become evident from Figure 11, the outer particle-rich layer of NbC is a very distinct band along the entire outer edge of the circle. This was visible on both the macroscopic and microscopic levels.

[00204] The depth of the outer layer rich in NbC particle has been found to be consistent along the circumference at about 7 to 8 mm, ie, approximately 25 to 30% of the radial thickness of the sample. It was found, however, that the fraction in volume of NbC of this outer layer is consistent in the areas examined at approximately 28 to 31% in volume of the total volume of the outer layer.

[00205] In addition to the concentrations of NbC, it was found that the microstructures of the outer and inner layers have other significant differences. The NbC particles in the NbC particle-rich outer layer were mostly rounded without any sharp edges, whereas those in the inner layers had a variety of shapes ranging from round shapes to sharp dentrites. The matrix structure of the NbC particle-rich outer layer and the other layers can mainly be distinguished through the presence/absence of “Chinese script” type NbC particle structure in the matrix austenite dendrites. This type of NbC structure was found extensively in the inner layers, however, it was almost non-existent in the outer layer rich in NbC particles. This resulted in a difference in thermal characteristics of the NbC particle-rich outer layer and the inner layers.

[00206] A very unique microstructure was found at the boundary of the outer layer rich in NbC particle and the inner layers. The microstructures were distinguished by the NbC particles being predominantly cross-shaped (dendritic). Some particles in this region resembled a shape that was a mixture of rounded and dendritic. 1.5.2 HARDNESS AND FERRIT

[00207] Cross-sectional Vickers hardness tests with a load of 10 kg were performed on the polished surfaces of two samples. Measurements started at the outermost edges of the samples and then traversed the thickness of the castings at 1mm intervals to be finished at the innermost edges. Table 8 shows the ferrite reading and average hardness for the outer layer rich in NbC particle and the inner layers of each sample. The outer layer rich in NbC particle of each sample is described as the “outer region” in the Table and the inner layers of each sample are described as the “inner region” in the Table. The transverse hardness profiles are shown in Figure 12. TABLE 8. FERRITE AND HARDNESS MEASUREMENTS

[00208] The higher NbC particle concentration of the outer layer rich in NbC particle (the outer region) naturally resulted in a harder hardness than the inner region for each sample. The hardness results correlate with the volume fraction results, where a larger volume fraction of the 4719CC-B sample provided a greater hardness result than the 419CC-A sample. There was no significant difference in ferrite content between the two regions of each sample.

[00209] Referring to Figure 12, the cross-sectional hardness tests showed that for both samples, the hardness was highest at the outer edge of the samples (ie, the first test points for both tests) and the hardness at the The limit of the two regions was approximately 425 Vickers. The inner (volume) region maintained a consistent hardness throughout most of its thickness. CONCLUSIONS 2.4. FUNCTIONALLY GRADUATED MATERIALS

[00210] In the test work summarized above, host metals (from A05, A49 and C21) with a range of volume percentages of NbC particles were centrifugly melted and examined. The results are summarized in Table 9. TABLE 9. SUMMARY OF A300 FAMILY CENTRIFUGAL fused ALLOYS

[00211] The fraction by volume of refractory particles in the outer layers rich in NbC particle of the foundries were up to 31% by volume of the outer layer. Also, high rotation speeds increased the % by volume of NbC, however, the effects were typically very small. In the inner region of each casting, the percentage by volume of NbC particles ranged from 2 to 6%.

[00212] The relationship between the thickness of the outer layer rich in NbC particle and the % by volume of overall NbC in the product compositions and the ratio between the % by volume of NbC in the outer layer rich in NbC particle and the % by volume Overall NbC in the product compositions were analyzed and the results are shown in Figures 13 and 14, respectively.

[00213] As can be seen from the Figures:

[00214] (a) it was found that the thickness of the outer NbC-rich layer of each centrifugly cast cylinder is directly dependent on the NbC content in nominal volume in the product composition (see Figure 13); and

[00215] (b) it was found that the final NbC content in the outer layer rich in NbC particle of each centrifugally cast cylinder is dependent on the NbC content in nominal volume in the product composition, where the NbC content tends to rise level to a maximum content of approximately 28 to 30% in the outer layer for the particular A05 host metal and which is 50 to 120% by volume greater than the nominal volume percentage of the refractory material in the entire product through the NbC range % in nominal volume covered by Figure 14.

[00216] It was also found that the thickness and concentration of NbC particle in the outer layer rich in NbC particle in each of the centrifugly cast cylinders was independent of the G Factor of casting in a range from 50 to 102.

[00217] In the aforementioned description of preferred modalities, the specific terminology has been restored for clarity. However, the invention is not intended to be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents that operate in a similar manner to achieve a similar technical purpose. Terms such as "front" and "rear", "inside" and "outside", "above" and "below", "top" and "bottom" and the like are used as convenience words to provide reference points and they should not be considered limiting terms.

[00218] Reference in this descriptive report to any previous publication (or information derived therefrom) or to any matter that is known is not and should not be construed as an acknowledgment or admission or any form of suggestion that the previous publication (or information derived therefrom) or known matter forms part of the common general knowledge in the field of effort to which this descriptive report refers.

[00219] In this descriptive report, the expression "which comprises" must be understood in its "open" sense, that is, in the sense of "include" and, thus, not limited to its "closed" sense, which is the sense of “only consist of”. A corresponding meaning must be assigned to the corresponding words “comprise”, “understood” and “comprises” where they appear.

[00220] In addition, the foregoing describes only some modalities of the invention(s) and changes, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the modalities revealed, in which the modalities are illustrative rather than restrictive.

[00221] Furthermore, the invention(s) have been described in relation to what are currently considered the most practical and preferred embodiments, it should be understood that the invention should not be limited to the disclosed embodiments, but rather, are intended for cover various modifications and equivalent provisions included in the spirit and scope of the invention(s). In addition, the various modalities described above can be implemented in conjunction with other modalities, for example, aspects of one modality can be combined with aspects of another modality to realize still other modalities. Furthermore, each independent feature or component of any supplied assembly may constitute an additional modality.

[00222] By way of example, although the embodiments of the invention described above comprise different types of steel (such as stainless steel or an austenitic manganese steel) as the host metal, the invention is not limited to that type of host metal and if extends to any suitable host metal. By way of example, the host metal can contain, where the host metal contains any one or more of the transition metals, the elements Ti, Cr, Zr, Hf, V, Nb and Ta.

[00223] By way of further example, although the embodiments of the invention described above focus on NbC as the material of the insoluble solid particles of refractory material, the invention also extends to other refractory materials.

[00224] By way of further example, although the embodiments of the invention described above focus on NbC particles that have a density that is greater than that of the host metal, whereby there are higher concentrations of the refractory particles towards the outer surfaces of the composite metal products, the invention also extends to embodiments in which the refractory particles have a density that is less than that of the host metal, whereby there are higher concentrations of the refractory particles towards an inner surface of the composite metal product. .

[00225] By way of further example, although the experimental work described above was performed in centrifugly cast cylinders, it can be readily observed that the invention is not limited to that particular shape casting and extends to any shape product that may be centrifugly melted.

Claims (31)

1. Centrifugal cast composite metal product having an axis of rotation and an axially extending outer surface and a mass of at least 5kg and comprising a matrix of ferrous metal and 5% to 50% by volume of solid particles of a refractory material throughout the ferrous metal matrix, refractory particles being carbides and/or borides and/or nitrides of one transition metal or refractory particles being carbides and/or borides and/or nitrides of more than one transition metal, the particles being a chemical mixture (as opposed to a physical mixture) of the carbides and/or borides and/or nitrides of more than one transition metals, characterized by the fact that the refractory particles are insoluble at a melting temperature and have a density that is within 20% of the density of ferrous metal at its melting temperature, the refractory particles being formed in radial layers of the product and including a first concentration of pair. refractory particles in an outer surface layer of the product and a second concentration of refractory particles in an inner layer of the product, the first concentration of refractory particles in the outer surface layer of the product being higher than the second concentration of refractory particles in the inner layer of product. 2. Composite metal product according to claim 1, characterized in that the first concentration of refractory particles in the outer surface layer of the product is in the range of 10% to 40%, by volume, of the total volume of the layer of external surface. 3. Composite metal product according to claim 1 or 2, characterized in that the second concentration of refractory particles in the inner layer of the product is in a range of 2% to 4.5%, by volume, of the volume total of the inner layer. 4. Composite metal product, according to any one of claims 1 to 3, characterized in that the first concentration of refractory particles is 50% to 120% by volume, higher than the nominal volume percentage of the refractory material in the product . 5. Composite metal product according to any one of claims 1 to 4, characterized in that the outer surface layer of the product extends for less than 50% of the radial thickness of the product from the outer surface of the product . 6. Composite metal product according to any one of claims 1 to 5, characterized in that the outer surface layer of the product extends from 1 mm to 50 mm from the outer surface of the product. 7. Composite metal product according to any one of claims 1 to 6, characterized in that the first concentration of refractory particles in the outer surface layer of the product is in a range of 5% to 90%, by volume, of the total volume of particles. 8. Composite metal product according to any one of claims 1 to 7, characterized in that the general concentration of refractory particles in the product is in a range of 5% to 50% by volume, typically 5% to 40 %, by volume, of the total volume of the product. 9. Composite metal product according to any one of claims 1 to 8, characterized in that it has a mass of at least 20 kg. 10. Composite metal product according to any one of claims 1 to 9, characterized in that it has a mass of at least 50 kg. 11. Composite metal product according to any one of claims 1 to 10, characterized in that it has a mass of at least 75 kg. 12. Composite metal product according to any one of claims 1 to 11, characterized in that the refractory particles have a density that is within 15% of the density of ferrous metal at its melting temperature. 13. Composite metal product according to any one of claims 1 to 12, characterized in that the ferrous metal is a ferrous alloy, such as a stainless steel or an austenitic manganese steel or a cast iron. 14. Composite metal product according to claim 13, characterized in that the ferrous alloy comprises any of the following alloys (a) Hadfield steel; (b) 420C stainless steel; and (c) high chromium white cast iron. 15. Composite metal product according to claim 13, characterized in that the ferrous alloy is Hadfield steel comprising 1.0% to 1.4% by weight of C, 0.0% to 1. 0% by weight of Si, 10% to 15% by weight of Mn, 0.0% to 3.0% by weight of Mo, 0.0% to 5.0% by weight of Cr, 0.0% to 2.0% by weight of Ni, the remainder being Fe and incidental impurities. 16. Composite metal product according to claim 13, characterized in that the ferrous alloy is a 420C stainless steel comprising 0.3% to 0.5% by weight of C, 0.5% to 1, 5% by weight Si, 0.5% to 3.0% by weight Mn, 0.0% to 0.5% by weight Mo, 10% to 14% by weight Cr, 0.0% to 1.0 wt% Ni, the remainder being Fe and incidental impurities. 17. Composite metal product according to claim 13, characterized in that the ferrous alloy is a white cast iron with a high chromium content comprising 1.5% to 4.0% by weight of C, 0, 0% to 1.5% by weight of Si, 0.5% to 7.0% by weight of Mn, 0.0% to 1.0% by weight of Mo, 15% to 35% by weight of Cr, 0.0% to 1.0% by weight of Ni, the remainder being Fe and incidental impurities. 18. Composite metal product according to any one of claims 1 to 17, characterized in that it comprises a rotary crusher cover for a primary, secondary or tertiary crusher. 19. Composite metal product according to any one of claims 1 to 17, characterized in that it comprises a slurry pump shaft sleeve. 20. Composite metal product according to any one of claims 1 to 19, characterized in that the particles have a density that is within 30% of the density of ferrous metal at its melting temperature. 21. Method for centrifugally melting a composite metal product as defined in any one of claims 1 to 20, characterized in that the method comprises (a) forming a slurry comprising solid refractory particles dispersed in a liquid ferrous metal, refractory particles being carbides and/or borides and/or nitrides of a transition metal or refractory particles being carbides and/or borides and/or nitrides of more than one transition metal, the particles being a chemical mixture (in opposition to a physical mixture) of the carbides and/or borides and/or nitrides of more than one transition metals, the refractory particles comprising 5% to 50%, by volume, of the total volume of the slurry, with the refractory particles being insoluble at a melting temperature, and the refractory particles having a density which is within 20% of the metal host density at the melting temperature; and (b) pouring the slurry into a mold for the product and centrifuging the product with a mass of at least 5 kg in the mold by rotating the mold around the axis subsequent to and/or during the pouring of the slurry into the mold and causing the refractory particles to form in radial product layers with a first concentration of refractory particles in an outer surface layer of the product and a second concentration of refractory particles in an inner layer of the product, the first concentration of particles refractory particles in the outer surface layer of the product is higher than the second concentration of refractory particles in the inner layer of the product. 22. Method for centrifugly melting a composite metal product, according to claim 21, characterized in that steps (a) and (b) are performed in an inert environment. 23. Method for centrifugally melting a composite metal product, according to claim 21 or 22, characterized in that it comprises preparing the mold by forming an inert environment within the mold. 24. Method for centrifugally melting a composite metal product, according to any one of claims 21 to 23, characterized in that step (b) comprises rotating the mold in a G-Factor from 10 to 120. 25. Method for centrifugally casting a composite metal product according to any one of claims 21 to 24, characterized in that step (b) comprises rotating the mold at a peripheral speed of 2.5 to 25 meters/second . 26. Method for centrifugally melting a composite metal product according to any one of claims 21 to 25, characterized in that step (b) comprises rotating the mold until the host metal has solidified. 27. Method for centrifugally melting a composite metal product, according to any one of claims 21 to 26, characterized in that step (b) comprises rotating the mold for sufficient time to obtain the non-uniform distribution of solid particles to the along the host metal. 28. Method for centrifugally melting a composite metal product according to any one of claims 21 to 27, characterized in that step (b) comprises pouring the slurry into the mold at a melting temperature in a range of 1,200 °C to 1650 °C, typically in a range of 1350 °C to 1550 °C. 29. Method for centrifugally melting a composite metal product according to any one of claims 21 to 28, characterized in that the composite metal product has a mass of at least 20 kg. 30. Method for centrifugally melting a composite metal product, according to any one of claims 21 to 29, characterized in that the refractory particles have a density that is within 15% of the density of the metal host at its temperature of fusion. 31. Method for centrifugally melting a composite metal product according to any one of claims 21 to 30, characterized in that it comprises adding (a) niobium or (b) two or more than two of niobium and titanium and tungsten to a melt containing the ferrous metal in a form that produces solid refractory particles of niobium carbide that are insoluble at a melting temperature and/or solid refractory particles of a chemical mixture of two or more than two of niobium carbide and titanium carbide and tungsten carbide which are insoluble at a melting temperature.

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