EA033878B1 - Composite metal product - Google Patents

Abstract

The invention provides a centrifugally cast composite metal product having an axis of rotation, an axially extended exterior surface and a mass of at least 5 kg, comprising a ferrous alloy matrix and 5-50 vol.% of insoluble solid particles of a refractory material distributed in a ferrous alloy, wherein the particles of a refractory material are carbides and/or borides and/or nitrides of one or more than one transition metal wherein the particles of a refractory material form radial layers of the product and are included in an exterior surface layer of the product that extends less than 50% of the radial thickness of the product from the exterior surface of the product, wherein a non-uniform distribution of the refractory particles in the radial thickness of the product is formed, where the non-uniform distribution of the refractory particles comprises a first concentration of particles in one layer of the product that is higher than a second concentration of particles in another layer in the product.

Description

FIELD OF THE INVENTION

The present invention relates to a centrifugal casting method for a composite metal product, wherein the final product typically varies in weight in the range of 20-5000 kg, has a matrix of a base metal, usually a matrix of an alloy based on iron, and contains an outer surface layer with a nominal thickness of 1-20 mm, consisting of solid insoluble refractory particles for increased wear resistance.

The present invention also relates to centrifugally cast composite metal products.

In the context of the present invention, the term “refractory particles” means the inclusion of particles of carbides and / or nitrides and / or borides with a high melting point of one or more of one of nine transition metals, such as titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium , molybdenum and tungsten dispersed in a viscous base metal, which acts as a binder phase. Each of these refractory particles is a particle of a refractory material and is referred to herein as a refractory material. Typically, the base metal is an iron-based alloy. The base metal may also be nickel and cobalt-based superalloys.

In the context of the present invention, the term insoluble means for all intents and purposes that the refractory material does not dissolve in the base metal at casting temperatures, typically in the range of 1200-1600 ° C, for base metals of an iron-based alloy. Limited solubility may be present. However, refractory particles differ significantly from the base metal in that there is a slight distribution of the elements of the particles of the refractory material over the base metal during casting and in the cured product.

SUMMARY OF THE INVENTION

In a first aspect, embodiments of a centrifugally cast composite metal article having a rotational symmetry axis and a mass of at least 5 kg, typically at least 10 kg and more often at least 20 kg and containing a base metal and insoluble solid particles of a refractory material in an inhomogeneous distribution over the base metal, wherein the particles have a density that is within 30%, usually within 20% of the density of the base metal at its casting temperature.

A composite metal product contains two different zones in the cured material, namely, the zone of insoluble solid particles of the refractory material and the region of the base metal, which contains almost no refractory particles, while the refractory particles differ significantly from the base metal in that there is a slight distribution of the elements of the particles of the refractory material on base metal at casting temperature and in the cured product.

A distinctive feature of this invention is that solid particles of a refractory material are insoluble in the base metal at casting temperature and after curing, and this distinguishes this invention from prior art proposals such as JPS632864, in which ferroalloys are added to the base metal of an iron-based alloy. (a) Fe-W, (b) Fe-Mo, and (c) FeCr to form respectively (a) tungsten carbide, (b) molybdenum carbide, and (c) chromium carbide, which are soluble to various degrees in the base metal at a usual rate Aturi casting. As a result, in these systems, the volume percent (%) of solid insoluble refractory carbides in the microstructure is significantly reduced, and dissolved tungsten, and / or molybdenum, and / or chromium can adversely affect the physical and chemical properties of the base metal at room temperature to an unknown degree (for example, a decrease in viscosity and another reaction to heat treatment).

In some embodiments, the implementation of the refractory particles may have a density that is higher than the density of the base metal, and in this case there will be a higher concentration of refractory particles towards the outer surface of the centrifugal cast composite metal product.

In some embodiments, the implementation of the refractory particles may have a density lower than the density of the base metal, and in this case there will be a higher concentration of refractory particles towards the inner surface of the product.

In some embodiments, the non-uniform distribution of the refractory particles may include a first concentration of refractory particles in the outer or inner surface layer of the article, which is higher than the second concentration of refractory particles in another layer in the article.

In some embodiments, the first concentration of the refractory particles in the outer surface layer of the article may exceed at least 50 vol.%, Usually at least 60 vol.%, Usually at least 70 vol.% And more often 50-120 vol. .% nominal volume percent of refractory material in the product.

In some embodiments, the first concentration of refractory particles in the outer surface layer of the article may be at least 10%, usually at least 20%,

- 1,033878 is usually less than 40% and more often in the range of 10-40 vol.% Of the total volume of the outer surface layer.

In some embodiments, the second concentration of refractory particles in another layer of the product may be in the range of 2-4.5 vol.%, Usually 2-3.5 vol.% Of the total volume of the other layer.

In some embodiments, the outer or inner surface layer of the article may have a thickness of at least 5%, usually at least 20%, more often at least 25% of the radial thickness of the article in the direction from the outer or inner surface.

In some embodiments, the outer or inner surface layer of the article may have a thickness of at least 50%, usually at least 40%, more often at least 20% of the radial thickness of the article in the direction from the outer or inner surface.

In some embodiments, the outer or inner surface layer of the article may extend at least 10 cm, usually at least 20 mm, usually less than 50 mm, usually 1-50 mm, and more often 5-20 mm from the outer or inner surface .

In some embodiments, the first concentration of refractory particles in the outer surface layer of the article can be at least 5 vol.%, Usually at least 10 vol.%, Usually 5-90 vol.% And more often 10-40 vol.% Of the total particles.

In some embodiments, the implementation of the total concentration of refractory particles in the product may be at least 5 vol.%, Usually at least 10 vol.% And more often in the range of 550 vol.% Of the total volume of the product.

In some embodiments, the implementation of the total concentration of refractory particles in the product may be in the range of 5-40 vol.% Of the total volume of the product.

In some embodiments, the implementation of the total concentration of refractory particles in the product may be in the range of 5-20 vol.% Of the total volume of the product.

In some embodiments, the refractory particles may be carbides and / or borides and / or nitrides of one or more transition metals, the particles being a chemical mixture (but not a physical mixture) of carbides and / or borides, and / or nitrides of transition metals. In other words, in the case of carbides, the refractory particles can be of the type described as (M ₁ , M ₂ ) C or (M ₁ , M ₂ , M ₃ ) C, where M is a transition metal. Hereinafter, particles of the type (Nb, Ti, W) C are described as an example.

The base metal may be any suitable base metal. The base metal may be an iron-based alloy, such as stainless steel or austenitic manganese steel or cast iron. The base metal may be a non-ferrous metal such as titanium or a titanium alloy.

In some embodiments, the base metal may be an alloy comprising any of the following alloys:

(a) Hadfield steel for use, for example, in gowns of gyration crushers;

(b) 420C stainless steel for use, for example, in shaft sleeves in slurry pumps; and (c) high chromium white cast iron.

As used in some embodiments, the Hadfield steel may contain

1.0-1.4 wt.% C,

0.0-1.0 wt.% Si,

10-15 wt.% Mn,

0.0-3.0 wt.% Mo,

0.0-5.0 wt.% Cr,

0.0-2.0 wt.% Ni, while the remaining components are Fe and random impurities.

As used in some embodiments, 420C stainless steel may comprise

0.3-0.5 wt.% C,

0.5-1.5 wt.% Si,

0.5-3.0 wt.% Mn,

0.0-0.5 wt.% Mo,

10-14 wt.% Cr,

0.0-1.0 mass /% Ni, with the remaining components being Fe and random impurities.

As used in some embodiments, high chromium white cast iron may contain

1.5-4.0 wt.% C;

0.0-1.5 wt.% Si,

0.5-7.0 wt.% Mn,

0.0-1.0 wt.% Mo,

15-35 wt.% Cr,

- 2 033878

0.0-1.0 wt.% Ni, while the remaining components are Fe and random impurities.

A composite metal product may be any product that is adapted for centrifugal casting and which requires high wear resistance and high viscosity. Examples of such products include a gyration crusher mantle for primary, secondary or tertiary crushing, a slurry pump shaft sleeve, rolls for use in crushers (including large diameter rolls that have a diameter of about 1 m and a radial wall thickness in the range of 300-400 mm) and others elements of crushers and pumps.

In a second aspect, embodiments are disclosed in which the composite metal product according to the first aspect may be a mantle of a gyration crusher for primary, secondary or tertiary crushing.

In a third aspect, embodiments are disclosed in which the composite metal product according to the first aspect may be a shaft sleeve of a slurry pump.

In a fourth aspect, embodiments of a centrifugal casting method of a composite metal product having an axis of rotational symmetry and a mass of at least 5 kg, typically at least 10 kg and more often at least 20 kg and containing a base metal and a non-uniform distribution of insoluble solid refractory particles of refractory are disclosed material, the method includes:

(a) the formation of a suspension containing solid particles of refractory material dispersed in a liquid base metal, while the concentration of refractory particles is 5-50 vol.%, usually 5-40 vol.% of the total volume of the suspension, while the refractory particles are insoluble at temperature castings and refractory particles have a density that is within 30%, usually within 20% of the density of the base metal at the casting temperature; and (b) pouring the suspension into a mold for a composite metal product, centrifugally casting the product into a mold, and obtaining an inhomogeneous distribution of insoluble solid refractory particles over the base metal.

In some embodiments, step (a) may include forming in situ refractory particles in the molten base metal and dispersing the particles in the molten base metal.

In some embodiments, step (a) may include adding refractory particles to the molten base metal.

In some embodiments, steps (a) and (b) may be performed in an inert atmosphere, for example in an inert gas atmosphere.

In some embodiments, step (b) may include preparing the mold by creating an inert atmosphere within the mold.

In some embodiments, step (b) may include rotating the mold around an axis after and / or while pouring the suspension into the mold in order to cause an increase in the concentration of refractory particles on the outer surface or near the outer surface, or on the inner surface or near the inner surface of the composite a metal product that is higher than the concentration of particles elsewhere in the product.

In some embodiments, step (b) may include rotating the mold at 10-120 g-factor units, wherein the g-factor is a centrifugal force acting on a rotating body divided by gravitational force.

In some embodiments, step (b) may include rotating the mold at a peripheral speed of 2.5-25 m / s.

In some embodiments, step (b) may include rotating the mold for a time sufficient to obtain an inhomogeneous distribution of the solid particles over the base metal.

In some embodiments, step (b) may include rotating the mold until the base metal has cured.

In some embodiments, step (b) may include pouring the slurry into the mold at a casting temperature in the range of 1200-2000 ° C, typically in the range of 1350-1650 ° C.

In some embodiments, the method may include selecting production parameters to form a slurry in step (a) that has the desired flow for processing in step (b).

Production parameters may include one or more of particle size, reactivity, density and solubility of refractory materials, as described in international patent application PCT / AU2011 / 000092 (WO2011 / 094800) in the name of the present applicant. The disclosure of this international application is incorporated herein by cross-reference. The density and solubility of a refractory material are discussed below.

The parameter to be considered during the implementation of the method according to the present invention is the density of the refractory particle material relative to the density of the base metal in the liquid state to control the dispersion of the refractory particles in the hot base metal.

- 3 033878

The nominal density of the basic liquid metal based on iron at 1400 ° C is 6.9 g / cm ³ . When refractory particles in the form of particles of tungsten carbide (WC) with a density of 15.7 g / cm ³ at 25 ° C are added to the base metal based on iron to form a suspension, WC particles will settle to the bottom of the suspension. When refractory particles in the form of particles of titanium carbide (TiC) with a density of 4.8 g / cm ³ at 1400 ° C are added to the same base metal based on iron, TiC particles will float to the surface of the suspension. Refractory particles in the form of niobium carbide (NbC) having a density of 7.7 g / cm ³ at 1400 ° C are very close in density to the base iron-based liquid metal having a density of 6.9 g / cm ³ and are less prone to the segregation described above in the base liquid iron-based metal than TiC or WC.

TiC with a density of 4.9 g / cm ³ at 25 ° C is completely soluble in NbC, which has a density of 7.8 g / cm ³ at 25 ° C. Thus, refractory particles with a density in the range of 4.9-7.8 g / cm ³ at 25 ° C can be obtained by selecting (Nb, Ti) C particles with the desired content of niobium and titanium.

Tungsten carbide (WC) with a density of 15.7 g / cm ³ at 25 ° C is mainly soluble in NbC, TiC and (Nb, Ti) C. Thus, refractory particles with a density in the range of 4.8-15.7 g / cm ³ at 25 ° C can be obtained by sampling (Nb, Ti, W) C particles with the required content of niobium, titanium and tungsten.

All refractory particles described by the formula (Nb, Ti, W) C are insoluble in basic iron-based liquid metals at casting temperatures in the range of 1200-1600 ° C.

Niobium carbide and titanium carbide have similar crystalline structures and are isomorphic.

From the above it follows that the choice of the required ratio of Nb: Ti in the chemical compound (Nb, Ti) C or the required ratio of Nb: Ti: W in the chemical compound (Nb, Ti, W) C can provide a refractory material with the desired density within 20 % of the density of the base metal based on iron.

The addition of refractory particles, which are insoluble for all purposes and purposes (i.e., minimally soluble in the base liquid metal), to obtain a centrifugally cast casting of a composite metal product in accordance with the method of the present invention provides an article having physical and physical properties similar to that of the base metal chemical properties, with significantly improved wear resistance due to the presence in the microstructure of the base metal of a controlled dispersion with high volume percentage of refractory material particles.

For example, the solubility of a refractory material in the form of (Nb, Ti, W) C in liquid base metals in the form of (a) Hadfield liquid steel, (b) 420C liquid stainless steel, and (c) liquid high-chromium white cast iron at elevated temperatures is negligible ( <0.3 wt.%). Adding (Nb, Ti, W) C with the required densities to these three main metal alloys followed by centrifugal casting of the composite metal product and the standard heat treatment procedure for each base metal provides microstructures containing a dispersion of primary niobium-titanium-tungsten carbides in the base metals that mainly do not contain niobium, titanium and tungsten, that is, there is a small distribution of transition metals contained in particles of a suspension of refractory m Therians by molten parent metal.

Thus, particles of a refractory material slightly affect the physical properties (e.g., melting point) and chemical properties (e.g., reaction to heat treatment) of the base metal.

In addition to the foregoing, in particular, the applicant has found that providing a composite metal product with a microstructure comprising niobium carbide particles and / or particles of a chemical (but not physical) mixture of two or more than two of niobium carbide, titanium carbide dispersed in a base metal matrix tungsten carbide, significantly improves the wear resistance of solid metal material without compromising the beneficial effect of other alloy components on other properties of the composite metal product and I.

In addition and as described above, in particular, the applicant has found that it is possible to control the particle density of a chemical mixture of two or more than two of niobium carbide, titanium carbide and tungsten carbide to a sufficient degree relative to the density of the base metal, which forms the matrix of the composite metal product. This ability to control density is an important discovery in relation to centrifugal castings made of solid metal material.

In particular, thanks to this discovery, it is possible to obtain centrifugally cast castings of a composite metal product with a controlled inhomogeneous distribution, i.e., segregation of particles in parts of the castings. This is important for the end use of castings, when it is desirable to have a concentration of particles with high wear resistance near the surface of the castings made of solid metal material.

In addition, the applicant has found that the inclusion in the molding of a composite metal product of particles of niobium carbide and / or particles of a chemical mixture of two or more than two of niobium carbide, titanium carbide and tungsten carbide in the range of 5-50 vol.%, Usually 5-40 vol.%, more often

- 4 033878

5-20 vol.% Of the total volume of the composite metal product dispersed in the base metal, which forms the matrix of the composite metal product, does not significantly affect the corrosion resistance and viscosity of the iron-based material in the base metal. Thus, the present invention provides the ability to achieve high wear resistance of a composite metal product without losing other desirable properties of the material.

Thus, in a fifth aspect, there is provided a method for centrifugally casting a composite metal product having an axis of rotational symmetry and a mass of at least 5 kg and containing a base metal and a non-uniform distribution of insoluble solid refractory particles of a refractory material, the method comprising adding (a) niobium or (b) two or more than two of niobium, and titanium, and tungsten in a melt containing a base metal in a form that provides solid refractory particles of niobium carbide are insoluble at a temperature of casting, and / or solid refractory particles of a chemical mixture of two or more than two of niobium carbide, and titanium carbide, and tungsten carbide, insoluble at casting temperature, while the concentration of solid refractory particles is in the range of 5-50 vol.%, usually 5-40 vol.%, more often 5-20 vol.% of the total volume of the product, centrifugal casting of the product in the form and obtaining a heterogeneous distribution of insoluble solid particles on the base metal.

The terms chemical mixture of niobium carbide and titanium carbide and niobium / titanium carbide are herein understood as synonyms. In addition, the term chemical mixture in this context means that niobium carbides and titanium carbides are present in the mixture not in the form of particles of carbides of one metal, but in the form of particles of niobium / titanium carbides, (Nb, Ti) C.

The terms chemical mixture of niobium carbide, and titanium carbide, and tungsten carbide and niobium / titanium / tungsten carbide are herein understood as synonyms. In addition, the term chemical mixture in this context means that niobium carbides, and titanium carbides, and tungsten carbides are present in the mixture not in the form of particles of carbides of one metal, but in the form of particles of niobium / titanium / tungsten carbides (Nb, Ti, W) C.

Niobium carbide, and titanium carbide, and tungsten carbide each have a Vickers hardness of about 25 GPa, which is about 10 GPa higher than the hardness of chromium carbides (nominally 15 GPa). Thus, composite metal products having a microstructure containing 5-50 vol.%, Usually 5-40 vol.%, Usually 5-20 vol.% Niobium carbide and / or niobium / titanium carbide and / or niobium carbide / titanium / tungsten, have excellent wear resistance. The applicant has concluded that niobium carbides and titanium carbides and tungsten carbides and niobium / titanium carbides and niobium / titanium / tungsten carbides are substantially chemically inert with respect to other components of the composite metal article, therefore, these components provide receipt of the product with the properties due to which they were selected. For example, chromium added to a cast iron alloy also forms chromium carbides and provides corrosion resistance.

Niobium and titanium and tungsten can be added to the molten base metal to form a suspension in any suitable form, taking into account the requirement for the formation of insoluble solid particles of niobium carbides and / or niobium / titanium carbides and / or niobium / titanium / tungsten carbides in a composite metal product .

For example, the method may include adding niobium to the melt in the form of ferro-niobium, for example, ferro-niobium particles. In this situation, ferro-niobium is dissolved in the melt and the resulting free niobium and carbon are chemically combined to form insoluble solid niobium carbides in the melt.

The method may also include adding niobium to the melt in the form of elemental niobium.

The method may also include adding niobium and titanium to the melt in the form of ferro-niobium-titanium.

The method may also include adding niobium and titanium and tungsten to the melt in the form of ferroniobium-titanium-tungsten.

The method may also include adding niobium to the melt in the form of particles of niobium carbide.

The method may also include adding niobium and titanium to the melt in the form of insoluble solid particles of niobium / titanium carbides.

The method may also include adding niobium and titanium and tungsten to the melt in the form of insoluble solid particles of niobium / titanium / tungsten carbides.

In each of these cases, the cured metal alloy can be formed from a suspension of niobium carbide particles and / or niobium / titanium / tungsten carbides suspended in the melt. If the mass fraction of these carbides in the molten suspension is too high, the flow properties of the suspension can be significantly impaired, resulting in poor-quality castings.

The insoluble solid particles of niobium / titanium carbides can be any suitable chemical mixture of the general formula (Nb _x , Ti _y ) C.

The insoluble solid particles of niobium / titanium / tungsten carbides can be any suitable chemical mixture of the general formula (Nb _x , Ti _y , W _z ) C. For example, nio

- 5,033,878 biya / titanium / tungsten may be (Nb ₀ .25, Tio.5o, W ₀ .25) C.

Niobium and / or titanium and / or tungsten can be added to the melt to obtain insoluble solid particles of niobium carbide and / or niobium / titanium carbides and / or niobium / titanium / tungsten carbides in an amount in the range of 12-33 wt. % niobium carbides, or niobium / titanium carbides, or niobium / titanium / tungsten carbides, based on the total weight of the cast material.

Niobium, and / or titanium, and / or tungsten can be added to the melt to obtain insoluble solid particles of niobium carbide and / or niobium / titanium carbides and / or niobium / titanium / tungsten carbides in an amount in the range of 12-25 wt. % niobium carbides, or niobium / titanium carbides, or niobium / titanium / tungsten carbides, based on the total weight of the cast material.

The number of particles of niobium carbide and / or niobium / titanium carbides and / or niobium / titanium / tungsten carbide in the microstructure of the cured solid metal material may depend on the system.

The applicant considers, in particular, solid composite metal products, which include base metals in the form of iron-based alloys, such as iron-based alloys, described as high-chromium white cast irons, stainless steels and austenitic manganese steels (such as Hudfield steels). For iron-based alloys, the amount of insoluble solids of the 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 may be in the range of 5-50 vol.%, Usually 5-40 vol.%, More often 5-20 vol.% Of the total volume of the cast composite metal product.

The particle size of niobium carbide and / or niobium / titanium carbide and / or niobium / titanium / tungsten carbide can be in the range of 1-150 μm in diameter.

The method may include mixing the suspension with an inert gas or magnetic induction or any other suitable means for dispersing particles of niobium carbide and / or niobium / titanium carbides and / or niobium / titanium / tungsten carbides in suspension.

The method may include adding particles of niobium carbide and / or particles of niobium / titanium / tungsten carbides to the molten base metals from an iron-based alloy under inert conditions, such as an argon pad, to reduce the oxidation state of niobium and / or niobium carbide / titanium / tungsten when added to the melt.

The method may include adding particles of ferro-niobium and / or ferro-titanium and / or ferro-tungsten and / or ferro-niobium-titanium-tungsten to the melt under inert conditions, such as an argon pad, to reduce the oxidation state of niobium, and / or titanium and / or tungsten when added to the melt.

In a situation where the presence of niobium / titanium / tungsten carbide particles is required in the cast composite metal product, the method may include pre-melting ferroniobium and ferro-titanium and ferro-tungsten and / or ferro-niobium-titanium-tungsten under inert conditions and forming the liquid phase, which is a homogeneous chemical mixture of iron, niobium, and titanium, and tungsten, and the curing of this chemical mixture. Then the chemical mixture can be properly treated, for example, grinding to particles of the desired size, and then added to the melt (containing carbon) under inert conditions. Iron, niobium, and titanium, and tungsten dissolve in the melt and chemically combine with carbon to form niobium / titanium / tungsten carbides in the melt.

Other aspects, features and advantages will become apparent from the following detailed description in combination with the accompanying drawings, which are part of this description and illustrate, by way of example, the principles of the disclosed invention.

Brief Description of the Drawings

Regardless of any other forms that fall within the scope of the method and the final composite metal product, as set forth in the Summary of the invention, specific embodiments of the method and the final composite metal product will be described by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is a diagram that illustrates a typical centrifugal casting method;

FIG. 2 is an SEM image of a portion of one of the samples of a centrifugally cast test cylinder 37863 (base metal A05 + 5 vol.% NbC particles) made during the experimental work associated with the invention;

FIG. 3 is an optical cross-sectional image of samples of centrifugally cast test cylinders 37628, 37629, 37630 and 37655 (base metal A05 + 5 vol.% NbC particles) made during the experimental work associated with the invention;

FIG. 4 is a graph of hardness versus distance from outer surfaces to inner surfaces of the samples described with respect to FIG. 3;

FIG. 5 is an optical cross-sectional image of samples of centrifugally cast test cylinders 37631, 37632, 37633 and 37636 (base metal A05 + 12 vol.% NbC particles) made during the experimental work associated with the invention;

- 6,033,878 of FIG. 6 is a graph of hardness versus distance from outer surfaces to inner surfaces of the samples described with respect to FIG. 5;

FIG. 7 is an optical cross-sectional image of samples of centrifugally cast test cylinders 37634 and 37635 (base metal A05 + 17 vol.% NbC particles) made during the experimental work associated with the invention;

FIG. 8 is a graph of hardness versus distance from outer surfaces to inner surfaces of the samples described with respect to FIG. 7;

FIG. 9 is an optical cross-sectional view of a sample of a centrifugally cast test cylinder A352 (base metal C21 + 10 vol.% NbC particles) made during the experimental work associated with the invention;

FIG. 10 is an optical image of a transverse section of the outer layer of the transverse section of the sample shown in FIG. 9 after sample etching;

FIG. 11 is an optical cross-sectional image of a sample of a centrifugally cast test cylinder A323 (base metal A49 + 15 vol.% NbC particles);

FIG. 12 is a graph of hardness versus distance from outer surfaces to inner surfaces of portions of the sample described with respect to FIG. eleven;

FIG. 13 is a graph of the thickness of the NbC particle-rich outer layer versus the nominal vol% NbC in the total composition of centrifugally cast cylinders of base metal A05 + NbC particles and FIG. 14 is a graph of volume% NbC in a particle-rich NbC outer layer versus nominal volume% NbC in the total composition of centrifugally cast cylinders of base metal A05 + NbC particles.

Detailed Description of Specific Embodiments

FIG. 1 was obtained from the Internet and illustrates in a diagrammatic form the main stages of centrifugal casting.

These centrifugal casting steps include forming a melt, pouring the melt into a suitable mold, and rotating the mold around a vertical axis (in the case of the arrangement shown in the drawing) at the required rotation speed to form the molded product.

In alternative arrangements, such as the arrangement used to perform the experimental work described below, the casting mold is horizontal and rotates about a horizontal axis.

In the context of the present invention, the melt, as a rule, is a suspension of solid insoluble refractory particles in the base metal, and the cast product is a composite metal product, which usually varies in weight in the range from 5 to 5000 kg, has an iron-based alloy matrix ( base metal) and contains an inhomogeneous distribution of solid insoluble refractory particles in the specified matrix, especially in the outer surface layer with a nominal thickness of 1-20 mm, consisting of solid insoluble x refractory particles which provide increased wear resistance in the surface layer.

Actual centrifugal casting conditions can be selected in any particular situation based on the required characteristics of the particular product to be cast. By way of example, casting conditions include mold rotation speed, rotation time and cooling conditions, as well as the conditions under which the casting is carried out, for example, an inert atmosphere.

Requirements for the properties of refractory particles may include a density greater or less than the density of the base metal based on iron;

hardness greater than 15 GPa;

a diameter of less than 500 microns, preferably less than 50 microns;

10-80 vol.% Refractory particles are present in the solid surface layer;

5-50 vol.%, Usually 5-40 vol.%, More often 5-40 vol.% Of refractory particles is present in the composite metal product.

Composite metal products obtained using the centrifugal casting process according to the invention include, by way of example only, the following products.

1. Slurry pump shaft bushings:

stainless steel cylinders;

size: diameter in the range of 25-400 mm, wall thickness of 10-50 mm and a length of 2000 mm;

the outer surface layer is 1-10 mm thick, containing a high concentration of solid insoluble refractory particles.

BACKGROUND OF THE INVENTION The prior art includes hardfacing of a stainless steel cylinder to a surface layer of tungsten carbide of a thickness of about 1 mm Then, to obtain a smooth surface, grinding / machining of the deposited layers is required.

The centrifugally cast sleeve of the slurry pump shaft in accordance with the invention makes it possible to produce a cylinder with a length of about 2000 mm with the required smooth hard surface layer in one

- 7 033878 casting operation. In addition, the long cylinder can be divided into sections to produce several shaft sleeves with a length of 60 to 300 mm.

2. The outer surface of the mantles of gyration crushers.

The standard composition of the mantles of gyration crushers is austenitic manganese steel (Hadfield steel). The initial hardness of the Hudfield steel is approximately 200 Brinell (HB) units, and the hardness of the surface layer of the steel structure rises to approximately 550 HB during operation, while the inner region retains lower hardness and extremely high toughness. The yield strength for Hadfield steel with a hardness of 200 HB is about 1/3 of the tensile strength. Strong plastic deformation can occur during operation to increase the hardness of the structure to 550 HB. As a result, crusher mantles quickly wear out and undergo excessive plastic deformation in the initial stages of operation. All previous attempts to improve the initial hardness and yield strength of Hadfield steel invariably led to an unexpected loss of viscosity and a high risk of rapid cracking during operation.

Centrifugal casting of the mantle of the Hadfield steel crusher in accordance with the present invention and the formation of the outer surface layer of insoluble solid refractory carbides during casting while maintaining the original composition of the Hadfield steel in the casting body provides a more wear-resistant material with minimal loss of viscosity.

3. White cast irons.

Centrifugal casting of high-chromium white cast irons with refractory particles provides composite metal products having surface layers containing a high concentration of refractory particles for improved wear resistance.

4. Mountings, tips of hammers, earthmoving equipment.

Centrifugal casting of mountings, hammer tips, and earthmoving equipment from high-chromium white cast irons with refractory particles provides a surface layer containing a high concentration of refractory particles for improved wear resistance.

Experimental work.

To verify the conformity of the invention, the applicant conducted intensive experimental work aimed at particles of a specific refractory material, namely, NbC particles in various base metals based on iron.

In particular, in the experimental work, the effects of vol% of NbC particles and wall thickness and centrifugal forces on NbC rich zones in centrifugally cast products were investigated.

In the experimental work, fourteen cylinders were centrifugally cast in a horizontally centrifugal casting device.

Fourteen cylindrical shaft sleeves with different concentrations of NbC particles and a base metal of an iron-based alloy, as described below, were centrifugally cast and machined, and then tested.

Four cylinders A301 (base metal A05 + 5 vol.% Particles of the total volume);

four cylinders A303 (base metal A05 + 12 vol.% particles of the total volume); four cylinders A304 (base metal A05 + 17 vol.% particles of the total volume); one cylinder A352 (base metal C21 + 10 vol.% particles of the total volume); one cylinder A323 (base metal A49 + 15 vol.% particles of the total volume);

A05 is high Cr eutectic cast iron, C21 is 420C stainless steel, and A49 is high Cr pre-eutectic cast iron. The nominal compositions of ferrous metal alloys A05, C21 and A49 are presented below with the amounts of each element in wt.%.

Alloy SG Mp FROM Ni Si Fe A05 27 2.0 3.0 0.5 balance C21 14 2.0 0.5 1,0 1,0 balance A49 28 1,5 1,5 2.0 1,5 balance

1. Results and discussion.

Twelve cylinders based on A05 steel with different nominal chemical compositions were centrifugally cast at various rotational speeds (rpm).

1.1. Centrifugal casting of four cylinders A301 (base metal A05 + 5 vol.% NbC particles).

Four cylinders containing 5 vol.% NbC particles in A05 base metal from high Cr eutectic cast iron were centrifugally cast at various rotational speeds or centrifugal forces. The casting temperature was in the range of 1400-1500 ° C. The difference in density between the NbC particles and the base metal at casting temperature was approximately 12%. The cylinder dimensions and casting conditions are presented in table. 1.

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Table 1

Sizes and casting conditions for cylinders containing 5 vol.% NbC particles

room cylinder ID (mm) (inner diameter) OD (mm) (outer diameter) Length (mm) Rpm 37628 91 130 400 924 37629 90.5 130 400 1100 37630 91 130 400 1285 37655 82.3 130 400 924

Each 400 mm long cylinder was cut into three rings of approximately 280, 20 and 100 mm long. Rings with a thickness of 20 mm were used for control and metallurgical analysis.

1.1.1. Metallurgical research.

Samples were prepared from each ring 20 mm thick by cutting in thickness in two places, at a distance of about 15 mm from each other, forming cross sections of the rings. Each incision was perpendicular to the outer and inner circumference of the ring. Thus, the width of the sample decreased from the outer surface to the inner surface. Samples were fixed, ground and polished following standard metallographic procedures and then etched with Acidified Ferric Chloride (AFC) for metallographic examination. The microstructures of the samples were examined using a scanning electron microscope. An optical stereo microscope was also used for macroscopic examination of samples.

An analysis of the samples obtained from the cylinders showed that the microstructure of the castings in each case contained the A05 base metal of eutectic white cast iron with a high Cr content and the inhomogeneous distribution of NbC solid particles over the base metal. FIG. 2 is an SEM image of a portion of one of the samples. In FIG. Figure 2 shows the inhomogeneous distribution of NbC particles in the base metal. The drawing shows that NbC were undetectable in the base metal. In particular, it was found that NbC particles are insoluble in the base metal at casting temperature and in cast cylinders.

In FIG. Figure 3 shows optical images of transverse sections of samples obtained from cylinders 37628, 37629, 37630 and 37655.

In FIG. 3a shows that the sample obtained from cylinder 37628 has an NbC particle-rich outer layer about 2 mm thick. On the inner side of the outer layer there are three layers, numbered in the drawing by the numbers 2-4. There are borders between the layers. Each layer has a thickness of about 3-5 mm. Layers 2-4 form an inner region having a lower concentration of NbC particles compared to the outer layer.

In FIG. 3b shows that the sample obtained from cylinder 37629 has a similar layered (i.e., banded) structure, but with more layers than shown in FIG. 3a. The outer layer with a high concentration of NbC particles (indicated by the number 1 in the drawing) has a thickness of about 2 mm, while the NbC particles are evenly distributed over the sample. The outer layer 1 and the innermost layer (indicated by the number 6 in the drawing) are most different, and the layers between them (that is, layers 2-5 in the drawing) are very similar in appearance, but, nevertheless, are different layers separated by borders. It was found that the microstructures of layers 1 and 6 are very different from each other, as well as from the microstructures of layers 2-5. It was found that the microstructures of layers 2-5 are very similar to each other. Each layer 1-6 has a thickness of 3-4 mm.

The cylinder 37630 was cast at the highest rotational speed. In FIG. 3c shows that the sample has three layers. Compared to the samples of the other three cylinders, this casting has the lowest concentration of NbC particles in the inner layers. A high rotation speed directs more NbC particles to the outer layer, resulting in the thickest layer with a high concentration of NbC particles from all castings.

Cylinder 37655 was cast at the same rotational speed as cylinder 37628, but with a wall thickness that was 5 mm larger. In FIG. 3d shows that the thickness of the NbC-rich layer in the sample obtained from cylinder 37655 was about 3.5 mm greater than the thickness in the sample obtained from cylinder 37628. This indicates that even at the same rotation speeds a thicker wall to the formation of a zone with a larger thickness rich in NbC particles.

Volume fractions of NbC particles of (a) an NbC-rich outer layer and (b) an inner layer with a low concentration of NbC particles were calculated from SEM images of different regions of the layers at 100 * magnification. The values shown in the table. 2 are average values of a plurality of measurements.

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Table 2 NbC particles in the outer and inner layers

ID Nbc-rich layer The inner layer, vol.% NbC Thickness mm % NbC 37628 2 12.9 2.0 37629 2 13.6 2.6 37630 3-5 14.2 2,4 37655 3,5 13.5 3.4

From the table. 2 that the rotation speed during casting affects the NbC particle-rich outer layer of the cast cylinders. The sample from cylinder 37630, which was cast at the highest speed, had the largest layer thickness and the highest volume fraction of NbC particles. The sample from cylinder 37629, which was cast at the second highest speed, was close in volume fraction of NbC, but the layer thickness was almost half the thickness of the layer in sample 37630. Comparison of samples from cylinders 37628 and 37655 showed that even at the same rotation speed, if the casting wall thickness is larger (i.e., more material), the NbC particle-rich outer layer and its volume fraction of NbC particles are also larger.

In addition, all four castings had similar levels of NbC particles present in the inner layers not containing concentrated NbC particles, collectively described as the inner region for each sample. Most of the NbC particles observed in the inner regions had typical Chinese handwriting morphology. A small amount of spherical and dendritic NbC particles was also observed.

1.1.2. Hardness and ferrite measurements.

Vickers hardness measurements over the cross section of a cylindrical sample (Vickers hardness traverse tests) with a load of 10 kg were carried out on the polished surfaces of each sample. Measurements were started on the outer diameter (OD) of each sample and then passed through the thickness of the sample at 1 mm intervals until completion on the inner diameter (ID) of the sample.

In the table. 3 shows data on average hardness and ferrite content for each of the two regions. The hardness profiles along the cross section of the cylindrical sample are shown in FIG. 4.

Table 3

Hardness and Ferrite Measurements

Sample Region Hv10 Ferrite content (% magnetic) 37628 Outdoor 640 13,4 Internal 536 9,4 37629 Outdoor 676 16,2 Internal 557 10,4

37630 Outdoor 660 12.6 Internal 551 8.9 37655 Outdoor 608 14.2 Internal 531 9.7

From the table. 3 and FIG. Figure 4 shows that the outer layer of NbC particles of each of the samples was much harder than the inner region of the sample, and that the highest hardness values were observed, as a rule, on the outer surface of each sample and uniformly decreased to a distance of about 8 mm from the outer surface, after which they remained generally constant throughout the rest of the sample. In addition, the results of measuring the ferrite content for the four castings showed a general tendency that the NbC particle-rich outer layer has a higher ferrite content than the layers forming the inner regions. Differences in the ferrite content were minimal, from 13 to 16% in the outer layers rich in NbC particles, and from 9 to 10% in the inner regions.

1.1.3. Brief conclusions.

All four centrifugal castings A301 (base metal A05 + 5 vol.% NbC particles) showed NbC segregation, as a result of which the outer layers of each sample had high concentrations of NbC particles.

All four castings showed the presence of layers below particle-rich

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NbC outer layer, which were slightly different from each other. Each casting had a different number of layers.

The thickness and hardness of the NbC particle-rich layers and the volume fractions of the NbC particles in the outer layers of the centrifugally cast cylinders depended on various casting parameters, including the rotation speed during casting and wall thickness.

Samples for cylinders 37628 and 37655 were cast at the same rotational speeds, but different masses of material, resulting in different sizes. Sample 37655 had a slightly thicker NbC particle-rich outer layer and also contained a larger number of different banded layers across the thickness of the samples.

The specimen for cylinder 37629 was similar to the specimen for cylinder 37628 despite being cast at a higher rotational speed. A higher rotation speed did not affect the thickness of the NbC particles-rich outer layer, but slightly affected the volume fraction of NbC particles in the outer layer.

The sample for cylinder 37630 was cast at the highest rotational speed, and this directly affected some properties. The sample had the thickest NbC particle-rich outer layer and the highest volume fraction of NbC particles in the outer layer. Thus, the hardness of the outer layer was the highest for this group of cylinders.

The results of measuring the ferrite content for four castings showed a general tendency that the outer layer rich in NbC particles had a higher ferrite content than the layers forming the inner regions. Differences in the ferrite content were minimal, with a content of 13 to 16% in the outer layers rich in NbC particles and from 9 to 10% in the inner regions.

1.2. Centrifugal casting of four cylinders A303 (base metal A05 + 12 vol.% NbC particles).

Four cylinders were cast under the same conditions as the four cylinders described in section 1.1 above using the same base metal (A05), but with a higher total volume fraction of NbC particles of 12%. The dimensions of the cylinders and rotational speeds are shown in table. 4.

Table 4

Numbers and sizes of cylinders containing 12 vol.% NbC

room cylinder ID (mm) (inner diameter) OD (mm) (outer diameter) Length (mm) Rpm 37631 89 130 400 922 37632 95 130 400 1104 37633 90 130 400 1280 37863 81 130 400 925

Each 400 mm long cylinder was cut into three rings of approximately 280, 20 and 100 mm long. Rings with a thickness of 20 mm were used for control and metallurgical analysis. Samples were prepared and tested using the same procedure as described above in section 1.1.

In FIG. 5 shows optical images of samples from cylinders 37631, 37632, 37633 and 37636.

From FIG. Figure 5 shows that, as in the case of cylinders with a lower volume fraction of NbC particles described above in Section 1.1, NbC particles had an inhomogeneous distribution in the base metal over the thickness of the castings, while the outer layers of the samples had higher concentrations of NbC particles.

Similarly, as in the case of cylinders with a lower volume fraction of NbC particles described above in section 1.1, SEM analysis showed that NbC were undetectable in the base metal. In particular, it was found that NbC particles are insoluble in the base metal at casting temperature and in cast cylinders.

The volume fractions of NbC particles in the outer layers rich in NbC particles and the thickness of the outer layers were calculated by analyzing SEM images of different sections of the layers at 100 * magnification. The values shown in the table. 5 are averages of a variety of experiments.

Table 5

The thickness of the outer layer and the average vol.% Particles of NbC

Sample OD (mm) (outer diameter) ID (mm) (inner diameter) Thickness Nbc layer (mm) Volume fraction NbC layer (%) Rpm 37631 130 89 6 25,098 922 37632 130 95 7 26,027 1104 37633 130 90 min 5, Max. 7 28,989 1280 37863 130 81 5 28.45 925

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Vickers hardness was measured over a cross section of a cylindrical sample (Vickers hardness traverse tests) with a load of 10 kg on polished surfaces of each sample. Measurements were started on the outer diameter (OD) of each sample and then passed through the thickness of the sample at 1 mm intervals until completion on the inner diameter (ID) of the sample.

In the table. 6 shows data on average hardness and ferrite content for each of the two regions. The hardness profiles along the cross section of the cylindrical sample are shown in FIG. 6.

Table 6

Hardness and Ferrite Measurements

Sample Region Hv10 Ferrite content (% magnetic) 37631 Outdoor 671 12.8 Internal 515 10,4 37632 Outdoor 772 And 5 Internal 584 9.8 37633 Outdoor 821 14.6 Internal 587 10,4 37863 Outdoor 771 15,2 Internal 593 And 5

From the table. 5 and 6 and FIG. Figures 5 and 6 show that the same basic results were obtained with a higher volume percentage for cylinders A303, as for cylinders A301, described above in section 1.1.

1.3. Centrifugal casting of four cylinders A304 (base metal A05 + 17 vol.% NbC particles).

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

In FIG. 7 shows optical images of transverse sections of samples from cylinders 37634 and 37635.

From FIG. Figure 7 shows that, as in the case of cylinders with a lower volume fraction of NbC particles described in Sections 1.1 and 1.2 above, NbC particles had an inhomogeneous distribution in the base metal over the thickness of the castings, while the outer layers of the samples had higher concentrations of NbC particles. Cross sections show an NbC particle-rich outer layer (or region) and an inner region with a lower concentration of NbC particles (which may include multiple layers separated by boundaries).

Furthermore, as in the case of cylinders with a lower volume fraction of NbC particles described above in sections 1.1 and 1.2, SEM analysis found that NbC were undetectable in the base metal. In particular, it was found that NbC particles are insoluble in the base metal at casting temperature and in cast cylinders.

The test showed that the thickness of the NbC-rich outer layers in the samples for cylinders 37634, 37635 and 37636 was 12, 13 and 15 mm, respectively.

The volume concentrations of NbC particles in the outer layers of these samples were 28% for cylinder 37634, 25% for cylinder 37635, and 29% for cylinder 37636.

In the table. 7 shows the average hardness and ferrite content for each of the inner and outer regions of the samples from cylinders 37634 and 37635. The hardness profiles along the cross section of the cylindrical sample are shown in FIG. 8.

Table 7

Hardness and Ferrite Data

Sample Region Hv10 Ferrite content (% magnetic) 37634 Outer 664 12.7 Interior 546 10.9 37635 Outer 661 And 7 Interior 513 Yu, 1

From the table. 7 and FIG. Figures 7 and 8 show that the same basic results were obtained with a higher volume percentage for cylinders A304, as for cylinders A301 and A303, described above in sections 1.1 and 1.2.

1.4. Centrifugal casting of cylinder A352 (base metal C21 + 10 vol.% NbC particles) /

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One A352 cylinder was centrifugally cast from a C21 base metal with 10 vol.% NbC particles. Samples were prepared and tested as described above.

In FIG. 9 is an optical cross-sectional image of a sample of the cylinder A352.

From FIG. Figure 9 shows that, as with the other test cylinders described above, NbC particles have a non-uniform distribution over the thickness of the casting, with the outer layer of the sample having a higher concentration of NbC particles.

In addition, as with the other test cylinders described above, SEM analysis found that NbC were undetectable in the base metal. In particular, it was found that NbC particles are insoluble in the base metal at casting temperature and in cast cylinders.

As shown in FIG. 9, the NbC-rich layer is a layer 20 mm thick, representing 50% of the total radial thickness of the sample. It was found that the sample contained about 25 vol.% NbC particles.

After etching, three sublayers of an outer layer 20 mm thick rich in NbC particles were identified, which are shown in FIG. 10. In FIG. 10 shows that directional curing is present over the sublayers during centrifugal casting. It was found that the columnar structure significantly contributes to the wear resistance of the casting.

1.5. Centrifugal casting of a cylinder A323 (base metal A49 + 15 vol.% NbC particles).

One A323 cylinder was centrifugally cast from A49 base metal and 15 vol.% NbC particles. Samples were prepared and tested as described above.

1.5.1. Metallurgical research.

In FIG. 11 is an optical cross-sectional view of a sample of cylinder A323. From FIG. Figure 11 shows that, as with the other test cylinders described above, NbC particles have a non-uniform distribution over the thickness of the casting, with the outer layer of the sample having a higher concentration of NbC particles.

In addition, as with the other test cylinders described above, SEM analysis found that NbC were undetectable in the base metal. In particular, it was found that NbC particles are insoluble in the base metal at casting temperature and in cast cylinders.

As can be seen from FIG. 11, the NbC particle-rich outer layer is a very distinct band along the entire outer edge of the circle. This is observed both at the macroscopic and at the microscopic level.

It was found that the depth of the outer layer rich in NbC particles is constant along the circumference and is about 7-8 mm, that is, about 25-30% of the radial thickness of the sample. It was also found that the volume fraction of NbC in this outer layer is constant in the studied areas and amounts to about 28-31 vol.% Of the total volume of the outer layer.

In addition to NbC concentrations, it was found that the microstructures of the outer and inner layers have other significant differences. NbC particles in the NbC particle-rich outer layer were mostly round without any sharp edges, while in the inner layers these particles had various shapes, from round to pointed dendritic shapes. The matrix structure of the outer layer rich in NbC particles and other layers can be distinguished, first of all, by the presence / absence of the structure of NbC particles of the Chinese style type in the austenitic dendrites of the matrix. This type of NbC structure was found deep in the inner layers, but was practically absent in the outer layer rich in NbC particles. This led to a difference in the thermal properties of the NbC-rich outer layer and inner layers.

A unique microstructure was found at the interface between the NbC-rich outer layer and inner layers. The microstructure was characterized by NbC particles, which were mainly cruciform (dendritic). Some particles in this area had a shape that was a mixture of round and dendritic.

1.5.2. Hardness and ferrite content.

Vickers hardness was measured over a cross section of a cylindrical sample with a load of 10 kg on the polished surfaces of two samples. Measurements were started at the outermost edges of the samples and then passed through the thickness of the castings at 1 mm intervals until completion at the innermost edges. In the table. Figure 8 shows the average hardness and ferrite content for the NbC particle-rich outer layer and inner layers of each sample. The NbC particle-rich outer layer of each sample is described in the table as the outer region, and the inner layers of each sample are described in the table as the inner region. The hardness profiles along the cross section of the cylindrical sample are shown in FIG. 12.

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Table 8 Measurement data of hardness and ferrite content

Sample Region Hv10 Content ferrites (% magnetic) 4719SS-A Outer 455 22.9 Interior 357 21,2 4719SS-B Outer 526 19.1 Interior 355 17.6

As expected, a higher concentration of NbC particles resulted in a higher hardness of the NbC-rich outer layer (outer region) compared to the inner region of the same sample. The hardness measurements correlated with the volume fraction measurements, that is, sample 4719CC-B with a higher volume fraction of NbC showed a higher hardness than sample 419CC-A. A significant difference in the ferrite content between the two regions of each sample was not observed.

When referring to FIG. 12 it can be seen that hardness tests over the cross section of a cylindrical sample showed that for both samples the hardness was highest at the outermost edge of the samples (i.e. the first test points for both tests) and the hardness at the boundary of the two regions was about 425 Vickers units. The inner (aggregate) region maintained a constant hardness over almost the entire thickness.

2. Conclusions.

2.4. Functional gradient materials.

In the test briefly described above, base metals (A05, A49, and C21) with a variety of volume percent NbC particles were centrifugally cast and examined. The results are summarized and presented in table. 9.

Table 9

Summary table of centrifugal cast alloys of the A300 family

No. The code FMMCC Rpm G-force (G) NbC rich layer Main met., Description Nbc (about.%) Thickness (mm) Nbc (about.%) 1 A323 A49 fifteen 920 fifty 7-8 28-33 2 A301 A05 5 924 52 2 thirteen 1100 74 2 14 1285 102 3-5 14

924 52 3.5 13.5

924 52 3,5 13.5 3 AZ 03 A05 12 922 52 6 25 1104 75 7 26 1280 101 5-7 29th 925 53 5 28 4 AZ 04 A05 17 920 52 12 28 1100 74 thirteen 25 1280 101 fifteen 29th 5 AZ 52 C21 10 925 67 15-17 24

The volume fraction of refractory particles with rich NbC particles in the outer layers of the castings amounted to 31% in the volume of the outer layer. In addition, high rotation speeds increased vol.% NbC, but the effects were usually negligible. In the inner region of each casting, the volume percentage of NbC particles varied in the range of 2-6%.

The relationship between the thickness of the NbC particle-rich outer layer and the total volume percent (vol.%) NbC in the product compositions and the relationship between the vol.% NbC in the particle-rich NbC outer layer and the total vol.% NbC in the product compositions were analyzed and the results are presented in FIG. 13 and 14, respectively.

As can be seen in the drawings:

(a) it was found that the thickness of the NbC-rich outer layer of each centrifugal cast cylinder directly depends on the nominal total NbC content in the composition of the product (see Fig. 13); and (b) it was found that the final NbC content in the particle-rich NbC outer layer of each centrifugally cast cylinder depends on the nominal total NbC content in the composition

- 14 033878 composition of the product, while the NbC content tends to equalize with a maximum content of about 28-30% in the outer layer for a specific base metal A05 and is 50-120 vol.% Higher than the nominal volume percent of refractory material throughout the product over the range of nominal vol.% NbC covered by FIG. 14.

It was also found that the thickness and concentration of NbC particles in the NbC particle-rich outer layer in each of the centrifugally cast cylinders depends on the casting g-factor in the range 50102.

In the foregoing description of preferred embodiments of the invention, specific terms have been used for clarity. However, the invention should not be considered limited to the particular terms chosen, and it should be understood that each specific term applies to all technical equivalents that work in a similar way, contributing to the achievement of a similar technical goal. Terms such as front and rear, inner and outer, higher, lower, upper and lower and the like are used to conveniently provide references to points and should not be construed as limiting terms.

The reference in this description to any publication of a known technical solution (or information extracted from it) or to any known topic does not constitute or should not be construed as confirmation or assumption or any form of assumption that the publication of a known technical solution (or information extracted from it) ) or a known topic forms part of general common knowledge in the field of technology of interest to which this description relates.

In this description, the word containing should be understood in its open sense, that is, in the sense of including, and in no way limiting it to a closed meaning, which is expressed by a phrase consisting only of. When used words contain, contain and contain, they should be given the appropriate meaning.

In addition, although only certain embodiments of the invention (s) are described above, it should be understood that various changes, modifications, additions and / or substitutions can be made without departing from the scope and nature of the disclosed embodiments, while the embodiments are illustrative and not restrictive.

Moreover, although this invention (s) has been described on the basis of what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent embodiments corresponding to the essence and scope of the invention (s). Also, various embodiments described above may be embodied in combination with other embodiments, for example, aspects described in one embodiment, may be combined with aspects described in another embodiment to implement further embodiments. In addition, each independent feature or component of any given assembly may constitute an additional embodiment.

By way of example, although the embodiments described above include various types of steel (such as stainless steel or austenitic manganese steel) as a base metal, the invention is not limited to this type of base metal and extends to any suitable base metal. As an example, the base metal may contain any one or more of the elements of the transition metals Ti, Cr, Zr, Hf, V, Nb and Ta.

As an additional example, although the above-described embodiments of the invention are directed to the use of NbC as insoluble solid particles of a refractory material, the invention also extends to other refractory materials.

As an additional example, although the embodiments described above are directed to NbC particles with a higher density than the density of the base metal, while higher concentrations of refractory particles are observed in the direction of the outer surfaces of the composite metal products, the invention also extends to embodiments in which the refractory particles have a lower density than the density of the base metal, with higher con entratsii refractory particles are observed in the direction of the internal surfaces of a composite metal product.

As an additional example, although the experimental work described above was carried out on centrifugally cast cylinders, it can be readily understood that the invention is not limited to this particular form of casting and extends to any form of product that can be centrifugally cast.

Claims (14)

CLAIM 1. A centrifugal cast composite metal product having an axis of rotation, an axially elongated outer surface and a mass of at least 5 kg, containing an iron-based alloy matrix and 5-50 vol.% Insoluble solid particles of refractory material distributed in - 15 033878 an iron-based alloy, wherein the particles of the refractory material are carbides and / or borides and / or nitrides of one or more transition metals and the particles are a chemical mixture, but not a physical mixture, of carbides, and / or borides and / or nitrides of transition metals, while the particles of the refractory material have a density that is within 20% of the density of the iron-based alloy at its casting temperature, the particles of the refractory material form the radial layers of the product and are included externally the surface layer of the product, which is less than 50% of the radial thickness of the product in the direction from the outer surface of the product, and an inhomogeneous distribution of refractory particles is formed in the radial thickness of the product, where the inhomogeneous distribution of refractory particles includes the first concentration of particles in the product in one layer of the product, which is higher than the second concentration of particles in another layer in the product. 2. The composite metal product according to claim 1, characterized in that the first concentration of refractory particles is contained in the outer surface layer of the product and is in the range of 10-40 vol.% Of the total volume of the outer surface layer. 3. The composite metal product according to claim 1 or 2, characterized in that the second concentration of refractory particles in another layer of the product is in the range of 2-4.5 vol.% Of the total volume of the other layer. 4. Composite metal product according to any one of the preceding paragraphs, characterized in that the first concentration of refractory particles is 50-120 vol.% Higher than the nominal volume percent of the refractory material in the product. 5. Composite metal product according to any one of the preceding paragraphs, characterized in that the outer surface layer of the product extends 1-50 mm from the outer surface of the product. 6. Composite metal product according to any one of the preceding paragraphs, characterized in that the iron-based alloy is Hadfield steel for use, for example, in gowns of gyration crushers, where Hadfield steel contains 1.0-1.4 wt.% C, 0 , 0-1.0 wt.% Si, 10-15 wt.% Mn, 0.0-3.0 wt.% Mo, 0.0-5.0 wt.% Cr, 0.0-2.0 wt.% Ni, while the remaining components are Fe and random impurities. 7. The composite metal product according to any one of claims 1 to 5, wherein the iron-based alloy is 420C stainless steel for use, for example, in shaft sleeves in slurry pumps, where 420C stainless steel contains 0.3-0.5 wt. % C, 0.5-1.5 wt.% Si, 0.5-3.0 wt.% Mn, 0.0-0.5 wt.% Mo, 10-14 wt.% Cr, 0.0 -1.0 wt.% Ni, while the remaining components are Fe and random impurities. 8. The composite metal product according to any one of claims 1 to 5, where the iron-based alloy is a high-chromium white cast iron containing 1.5-4.0 wt.% C, 0.0-1.5 wt.% Si, 0.5-7.0 wt.% Mn, 0.0-1.0 wt.% Mo, 15-35 wt.% Cr, 0.0-1.0 wt.% Ni, with the remaining components being Fe and random impurities. 9. Composite metal product according to any one of the preceding paragraphs, characterized in that it has a mass of at least 20 kg 10. The method of centrifugal casting of a composite metal product having an axis of rotation axially extending through the outer surface and a mass of at least 5 kg, comprising an iron-based alloy matrix and a non-uniform dispersion of insoluble solid refractory particles of refractory material, as defined in any one of claims 1 -9, the method includes (a) forming a suspension containing solid refractory particles dispersed in an iron-based liquid alloy, the refractory particles being carbides, and / or b the horides and / or nitrides of one or more than one transition metal and particles are a chemical mixture, but not a physical mixture of carbides and / or borides and / or nitrides of transition metals, the concentration of refractory particles is 5-50 vol.% from the total volume of the suspension, refractory particles are insoluble at the casting temperature and have a density that is within 20% of the density of the base metal at the casting temperature; and (b) pouring the suspension into the product mold and centrifugally casting the product with a mass of at least 5 kg in the mold by rotating the mold around the axis after and / or while pouring the suspension into the mold to cause the radial layers of the product to form refractory particles in radial thickness products where the outer surface layer is less than 50% of the radial thickness of the product in the direction from the outer surface of the product, with a concentration of insoluble refractory particles in one layer higher than the concentration of particles in the other layer in product, and obtaining a heterogeneous distribution of insoluble solid particles over the iron-based alloy in the product. 11. The method of centrifugal casting of a composite metal product according to claim 10, characterized in that stages (a) and (b) are carried out in an inert atmosphere. 12. The method of centrifugal casting of a composite metal product according to claim 10 or 11, characterized in that stage (b) comprises rotating the mold at 10-120 g-factor units. 13. The method of centrifugal casting of a composite metal product according to any one of claims 10-12, comprising forming a suspension by adding (a) niobium or (b) two or more - 16 033878 two of niobium, and titanium, and tungsten in the form of solid refractory particles of niobium, which are insoluble at casting temperature, and / or solid refractory particles of a chemical mixture of two or more than two of niobium, and titanium carbide, and tungsten carbide which are insoluble at casting temperature, into a melt containing an iron-based alloy. 14. The method of centrifugal casting of a composite metal product according to any one of paragraphs.10-13, where the mass of the product is at least 20 kg