CN119403636A

CN119403636A - Tungsten carbide and titanium carbide reinforced manganese steel

Info

Publication number: CN119403636A
Application number: CN202380050989.4A
Authority: CN
Inventors: 拉蒂法·梅尔克
Original assignee: Sandvik SRP AB
Current assignee: Sandvik SRP AB
Priority date: 2022-07-01
Filing date: 2023-06-29
Publication date: 2025-02-07
Also published as: WO2024003234A1; AU2023298082A1; EP4299210A1

Abstract

A composite material comprising at least one reinforcing region comprising tungsten carbide (WC) and titanium carbide (W, ti) C and a manganese steel matrix, a manganese steel region surrounding each of the reinforcing regions, and an interface layer between each of the reinforcing regions and the manganese steel region, characterized in that the average grain size of the (W, ti) C particles in each of the reinforcing regions is between 0.2 and 2 μm and the average grain size of the WC particles in each of the reinforcing regions is between 20 and 30 μm.

Description

Tungsten carbide and titanium carbide reinforced manganese steel

Technical Field

The present invention relates to a composite material based on reinforced manganese steel, a wear part manufactured therefrom and a method of manufacturing the same.

Background

One particular class of wear resistant steels is commonly referred to as manganese steels or hatfield steels (HATFIELD STEEL). These materials are suitable for applications requiring high toughness and moderate wear resistance, including for example, use as wear parts for crushers that are subjected to intense wear and dynamic surface pressures due to rock crushing action. Wear occurs when rock material contacts the wear part and strips material from the wear part surface. In addition, the surface of the wear part is subjected to significantly high surface pressures that lead to fatigue and breakage of the wear part.

Manganese steel or hatfield steel is generally characterized by having a certain amount of manganese, typically in an amount of more than 11% by weight. However, manganese steel has a problem in that it is generally too soft for wear parts in modern crushers subjected to extreme operating conditions, which means that the service life of the wear parts is reduced and the maintenance costs are increased. Accordingly, the problem to be solved is to provide manganese steel with enhanced wear resistance.

One known solution is to use particles with increased hardness to strengthen at least a portion of the manganese steel. WO 20200222662 discloses a composite material, however, the problem with such a material is that an optimal balance between wear resistance and impact resistance is not provided, and the more important problem is that the bond between the reinforcing particles and the manganese steel matrix is weak and the bond between the reinforcing region and the non-reinforcing region is weak, which leads to reduced wear resistance and premature failure of the wear resistant component.

Accordingly, the problem to be solved is to provide a composite material that can be used for wear parts having an optimal balance between wear resistance and impact resistance, wherein the bond between the reinforcing particles and the manganese matrix and the bond between the reinforcing and non-reinforcing regions are improved so as to reduce defects and cracks that would lead to premature failure of the wear parts.

Additional composites are disclosed in US 2018/369905 and CN 111482579.

Definition of the definition

A "catalyst" is a metal powder or mixture of metal powders that undergoes melting and forms a composite zone matrix during the reaction of self-propagating high temperature synthesis (SHS). The basic function of the catalyst is to reduce the amount of energy dissipated during SHS.

A "compact" is a densified powder composition.

Disclosure of Invention

It is an object of the present invention to provide a new and improved composite material for wear parts. The object is achieved by providing a composite material comprising at least one reinforcing region comprising a core-edge titanium tungsten carbide (W, ti) C, tungsten carbide (WC) and a manganese steel matrix, a manganese steel region surrounding each of the reinforcing regions, and an interface layer between each of the reinforcing regions and the manganese steel region, characterized in that the average grain size of the (W, ti) C particles in each of the reinforcing regions is between 0.2-2 μm, preferably between 1-2 μm, and the WC particles in each of the reinforcing regions is between 20-30 μm, preferably between 20-25 μm.

Advantageously, this particular selected grain size range provides an optimal balance between wear resistance and impact resistance. If the weight% and grain size of (W, ti) C and WC in each of the strengthening zones are too high, the composite will be too brittle and the material will be more susceptible to failure because the manganese steel between the hard metal grains in the matrix is insufficient to provide the required toughness. If the weight% and grain size of (W, ti) C and WC in each of the reinforcing regions are too low, the composite material will have low hardness and thus will not have sufficient wear resistance.

Preferably, the composite material comprises between 80-98 wt.% of (W, ti) C and between 0% -30% WC in each of the reinforcement zones. Preferably between 90-98 wt% of (W, ti) C and 20% -30% of WC, respectively, more preferably between 94-98 wt% and 25% -30% of (W, ti) C and WC, respectively. Advantageously, this provides an optimal balance between wear resistance and impact resistance. If the weight% of (W, ti) C and WC in each of the reinforcement zones is too high, the composite will be too brittle and more prone to failure. If the weight% of (W, ti) C and WC in each of the reinforcing regions is too low, the composite material will have low hardness and thus will not have sufficient wear resistance.

Preferably, the composition of the manganese steel in the manganese steel zone has a chemical composition by weight of carbon of 0.5 to 2.0%, manganese of 11 to 22%, silicon of 0.2 to 1.0%, chromium of 1 to 2%, nickel of at most 0.6%, molybdenum of at most 0.5%, and the balance Fe. Advantageously, the steel composition is characterized by the addition of suitable amounts of microalloying elements, such as chromium, nickel and molybdenum, which lead to a high yield strength and a high hardness, resulting in an increase of the wear resistance of the manganese steel.

Preferably, the vickers hardness of the reinforced region is between 900-1400 HV1 and the hardness of the manganese steel region is between 300-400 HV1 prior to work hardening. Advantageously, the increased hardness in the reinforced areas makes the material more wear resistant.

Preferably, the thickness of each of the interface layers is greater than 150 μm, preferably greater than 100 μm, more preferably greater than 90 μm. Advantageously, the thickness of the interface layer, or the thickness of the contact area between manganese and the composite zone, is indicative of the reaction propagation rate and the increase in heat generated due to the high combustion temperature that occurs upon contact between the molten manganese steel and the insert. If the thickness is too large, the thermal conductivity in the composite region increases, resulting in faster heat dissipation into the interior of the composite region, and thus in a high nucleation rate of (W, ti) C and WC particles. If the thickness is too small, the thermal conductivity is small, which facilitates growth, whereby nucleation of (W, ti) C and WC particles is less.

Preferably, the interfacial layer is free of defects. Advantageously, the absence of any defects in the interfacial layer means that there is a good bond between each of the manganese steel region and the reinforcing region and thus the structural integrity of the composite material is improved, which means that the life of the wear resistant component in which the material is used is increased. Furthermore, the absence of any pores indicates that the composition has the ability to absorb excess heat and gases from the SHS process and thus indicates that the synthesis reaction has been successful.

Preferably, the binding rate between (W, ti) C and WC grains in the reinforced zone and the manganese steel is >99%, preferably >99.5%, more preferably >99.9%. Advantageously, a good bond results in an excellent bond between the composite region and the manganese steel, thereby avoiding the formation of defects such as holes and cracks, and thus an increase in wear resistance. If there is a 100% bond, this means that there are no cracks or holes between the composite zone and the manganese steel.

Preferably, the volume of each of the reinforcing regions is between 30-75cm ³. The volumes were determined using XRD. Advantageously, this dimension provides an optimal balance between wear resistance and impact resistance.

Preferably at least 90%, more preferably at least 95% of the (W, ti) C has a core-edge structure with a circular shape with a composition gradient from the centre to the outside of the particle, wherein the core is Ti-rich and the shell is W-rich. The WC grains in the enhanced region have irregular prismatic shapes including triangular to rectangular shapes. Advantageously, the rounded core-edge structure of (W, ti) C and the different prismatic shape of WC will assist crack deflection and prevent crack propagation, thereby improving ductility and high wear resistance of the reinforced region. Advantageously, the prismatic shape of the WC will assist crack deflection and prevent crack propagation, thereby improving ductility and high wear resistance of the reinforced region. At the same time, the core-edge shape will help reduce stress concentrations under load.

Preferably, the distance between two adjacent enhancement zones is between 0.5 and 50 μm, preferably between 0.5-10 μm, more preferably between 0.5-5 μm. Advantageously, this provides an optimal balance between wear resistance and impact resistance. If the enhancement zones are spaced too far apart, the wear resistance will not be high enough. If the reinforcement interval is too close, the impact resistance will not be high enough.

Another aspect of the invention relates to a wear part comprising a composite material as described above or below. Advantageously, the presence of the strengthening zone within the manganese zone will improve the wear resistance and thus the service life of the wear resistant component, thereby increasing the profitability.

Another aspect of the invention relates to a method of manufacturing a composite material as described above or below comprising the steps of a) mixing together 65-98 wt.% tungsten, 3-90 wt.% titanium, 3-20 wt.% carbon and 0-80% catalyst powder, b) pressing the mixed powders together to form at least one compact, c) positioning and optionally fixing the at least one compact inside a mould, d) pouring molten cast manganese steel into the mould to surround the at least one compact to initiate a self-propagating high temperature synthesis (SHS) reaction to manufacture a casting, e) heat treating the casting, f) quenching the casting, wherein in step b) the powder is pressed at a pressure between 400-700MPa, preferably between 500-600MPa, more preferably between 550-600 MPa.

Advantageously, if this pressing pressure is used, the compact has a low density, which enables the manganese steel to penetrate more easily between WC and (W, ti) C grains and thereby results in improved bonding between WC and TiC grains and the manganese steel. Furthermore, it avoids the creation of defects that would lead to premature failure of the wear parts in which the composite is used.

Preferably, the catalyst is selected from Fe, mn, ni, mo, cr, W, al or a mixture thereof. Advantageously, the addition of a specific amount of catalyst will contribute to a strong stability of the austenitic phase in the microstructure on the basis of good mechanical properties and high attrition resistance. The catalyst addition will also act as a grain growth inhibitor resulting in a fine microstructure.

Drawings

Figure 1 is a line drawing showing the composition of the composite material.

Fig. 2 shows an SEM image taken of the enhancement region, with low magnification on the left and high magnification on the right.

Fig. 3 shows SEM images taken of the interface layer, with low magnification on the left and high magnification on the right.

Fig. 4 shows SEM images of the composite material.

Fig. 5 shows a perspective view of the wear part.

FIG. 6 shows a defect in sample E.

Detailed Description

Fig. 1 shows a composite material 2 comprising at least one reinforcing zone 4, said reinforcing zone 4 comprising a matrix of tungsten titanium carbide (W, ti) C and tungsten carbide (WC), a manganese steel zone 6, said manganese steel zone 6 surrounding each of said reinforcing zones 4, and an interface layer 8, said interface layer 8 being located between each of said reinforcing zones 4 and said manganese steel zone 6. In each of the strengthening zones, (W, ti) C and WC function to strengthen the manganese steel matrix.

The average grain size of the (W, ti) C particles in each of the reinforcing zones (4) is between 0.2 and 2. Mu.m, preferably between 1 and 2. Mu.m. The WC particles in each of said enhancement zones (4) have an average grain size between 20-30 μm, preferably between 20-25 μm.

The average grain size of the (W, ti) C and WC grains was determined by Scanning Electron Microscope (SEM) analysis, where the analysis was performed from several different regions of the sample, and the grain size was determined using Image J software. The average particle size is then calculated.

In one embodiment, the density of the enhancement zone is between 4.5 and 7.5g/cm ³, preferably between 6 and 7g/cm ³.

In one embodiment, the density of the enhancement zone is between 83% and 96% of theoretical density, preferably between 85% and 94%.

Each interface layer 8 comprises (W, ti) C, WC and manganese steel and can be distinguished from the reinforcing zone 4 due to the differences in the shape and size of the (W, ti) C and WC grains. The interfacial layer 8 can be distinguished from the enhancement zone 4 by comparing the geometry and/or comparing the average grain size. If the geometry is compared, the enhancement zone 4 contains >90% WC grains having an irregular prismatic geometry, while the interface layer 8 contains <5% WC grains having a rectangular prismatic geometry. WC grains are considered to have a rectangular prismatic geometry if they have 4 sharp edges. If (W, ti) C has a dark core (rich in Ti) and a light shell (rich in W), it is considered to have a core-edge structure of circular geometry. If the grain sizes are compared, the average WC grain size in interface layer 8 is at least 5% smaller than the average WC grain size on enhancement zone 4.

Fig. 2 shows a scanning electron microscope image using a MIRA3 TESCAN device. A secondary electron detector (SE) with a high voltage of 15KV and a working distance configuration of 9mm was used. SEM images of (W, ti) C and WC grains in the enhancement zone 4. Fig. 3 shows SEM images of (W, ti) C and WC grains in the interface layer 8. When comparing these two images, it is clear that the different (W, ti) C and WC grain geometries and granularities.

In one embodiment, the weight% of (W, ti) C in each of the enhancement zones 4 is between 80-98%, more preferably between 90-98%, even more preferably between 94-98%, and the weight% of WC in each of the enhancement zones 4 is between 0-30%, more preferably between 20% -30%, even more preferably between 25% -30%.

In one embodiment, the composition of the manganese steel in manganese steel zone 6 has a chemical composition by weight of carbon of 0.5 to 2.0%, manganese of 11 to 22%, silicon of 0.2 to 1.0%, chromium of 1 to 2%, nickel of at most 0.6%, molybdenum of at most 0.5%, and the balance Fe.

In one embodiment, the chemical composition of the manganese steel in each of the enhancement zones 4 has a chemical composition by weight of 1% -1.5% C, 11% -14% Mn, 0.4% -0.8% Si, 1.3% -2.0% Cr, 0.6% Ni, 0.065% P.

In one embodiment, the stiffness of the reinforcement zone 4 is between 900 and 1400 HV1, preferably between 1000 and 1400 HV1. The hardness of the manganese steel zone 6 is between 300-400 HV1.

The hardness was determined using a vickers hardness map on the polished sample using a holding time of 1kgf and 15 seconds. A microhardness tester, matsuzawa, model MXT was used. The hardness measurement profile proceeds from the non-reinforced region, moves to the interface layer, and then moves to the reinforced region.

In one embodiment, the width of the interface layer 6 is greater than 150 μm, preferably greater than 100 μm. Fig. 4 shows SEM images of the reinforcing zone 4, the manganese steel zone 6 and the interface layer 8 taken at 15.0kV, 219 magnification. The width of the interface layer 6 is measured from a starting point 10, which starting point 10 is defined as the point adjacent to the manganese steel zone 6 where (W, ti) C and WC grains are present. The end point 12 is used to determine where the interface layer 8 ends and thus where the enhancement zone 8 begins, which is considered to be the location where the average grain size of WC grains increases by 20% compared to the average WC grains determined at the start point 10 and/or where the percentage of WC grains having a triangular prism shape increases by more than 90%.

In one embodiment, the interfacial layer 8 is free of defects when measured using an optical microscope at 1000 x magnification. Defects are considered to be cracks or holes.

In one embodiment, in the reinforcing zone 4, the binding rate between the (W, ti) C grains and the manganese steel and between WC and the manganese steel is >99%, preferably >99.5%, more preferably >99.9%, most preferably 100%. The% bonding rate was determined by a scanning electron microscope in which the contact area and the bonding rate between the (W, ti) C grain or WC grain and the manganese steel were evaluated. In said reinforcing zone 4, the presence of cracks and/or defects between the (W, ti) C grains and the manganese steel and between WC and the manganese steel will reduce the% of the bonding rate.

In one embodiment, the volume of each of the reinforcing areas 4 is between 30 and 75cm ³. For example, the reinforcing section 4 may have a length of between 100 and 200mm, preferably between 100 and 150mm, a width of between 20 and 30mm, preferably between 20 and 25mm, and a thickness of between 15 and 30mm, preferably between 15 and 25mm, but is not limited thereto.

In one embodiment, >95%, preferably >98%, more preferably >99% of the (W, ti) C grains in the enhancement zone 4 have a circular shape. Preferably, the (W, ti) C grains in the reinforcement zone are uniformly distributed in the manganese steel. In one embodiment, >95%, preferably >98%, more preferably >99% of WC grains in the reinforced region 4 have a triangular prism shape. Preferably, the TiC grains in the enhancement zone are uniformly distributed in the manganese steel.

In one embodiment, there are a plurality of reinforcing regions 4 and their interface regions 8, and the distance between two adjacent reinforcing regions 4 and their interface regions 8 is between 1-5mm, preferably between 1-3 mm, more preferably between 1-2 mm.

Fig. 5 shows an example of a wear part 14 comprising a composite material 2 as described above or below. For example, the wear part 2 may be, but is not limited to, a cone crusher configured to crush material, or a fixed jaw crusher, or a moving jaw crusher, or other material/rock processing unit. The reinforcing zone 4 is located at the most highly worn location on the wear part 14, for example on the crushing zone 18 of the cone crusher 16.

The method of manufacturing a composite material 2 as described above or below comprises the steps of a) mixing 65-98 wt%, preferably 80-98 wt% tungsten, 3-90 wt%, preferably 10-90 wt% titanium, 3-20 wt%, preferably 3-20 wt% carbon and 0-80%, preferably 10-20% catalyst powder together, b) compacting the mixed powders together to form at least one compact using a compaction pressure of between 400 and 700MPa, preferably 500-600MPa, more preferably 550-600MPa, c) positioning and optionally fixing at least one compact inside a mould, d) pouring molten cast manganese steel into the mould to surround the at least one compact to induce a self-propagating high temperature synthesis (SHS) reaction to manufacture a casting, e) heat treating the casting, and then f) quenching the casting.

Preferably, the castings are treated at a temperature between 1400-1500 ℃ and quenched with water. Preferably, the catalyst is selected from Fe, co, ni, mo, cr, W, al or a mixture thereof. The carbon may be added in the form of graphite, amorphous graphite, carbonaceous material, or mixtures thereof. For example, during casting, the compacts may be held in place using a metal fixing system, thereby holding them in place during casting.

Examples

Example 1 sample

Sample A is a comparative sample of non-reinforced manganese steel having a composition of 1% -1.5% C, 11% -14% Mn, 0.4% -0.8% Si, 1.3% -2.0% Cr, 0.6% Ni, 0.065% P.

Samples a-I are samples of composite materials made by mixing together tungsten, titanium, carbon and catalyst powders. The mixed powder is pressed to form a compact, and then the compact is placed into a mold, and then molten manganese steel (having the composition: 1% -1.5% of C, 11% -14% of Mn, 0.4% -0.8% of Si, 1.3% -2.0% of Cr, 0.6% of Ni, 0.065%) is poured into the mold to surround the compact, thereby initiating the SHS reaction, and then the casting is heat-treated at a temperature of 1450 ℃, and then quenched with water. Table 1 shows a summary of the enhanced samples:

It can be seen that if the permeability of the manganese steel is not good enough, the binding rate decreases and cracks and/or holes are caused to occur.

EXAMPLE 2 hardness

Vickers hardness was measured by a microhardness tester (Matsuzawa, model MXT) using a holding time of 1kgf and 15 seconds. The hardness measurement profile proceeds from the non-reinforced region, moves to the interface layer, and then moves to the reinforced region.

The hardness measurement results are shown in table 2 below:

it can be seen that the hardness in the enhanced region of the inventive sample was increased as compared to the comparative sample. Because of the large size of the pores, the hardness of E cannot be measured.

EXAMPLE 3 Defect

Defects were evaluated by analysis using a scanning electron microscope, in which cracks and holes were identified. The inventive samples had small holes only in the enhancement region and no defects in the interface layer. The hole visible under the light microscope at 100 times magnification is considered "large", and the hole visible under the light microscope at 1000 times magnification is considered "small".

Claims

1. A composite material (2), comprising:

at least one strengthening zone (4), the strengthening zone (4) comprising a core-edge titanium tungsten carbide (W, ti) C, tungsten carbide (WC) and a manganese steel matrix, wherein the core is titanium-rich and the edge is tungsten-rich;

a manganese steel zone (6), said manganese steel zone (6) surrounding each of said strengthening zones (4), and

-An interface layer (8), said interface layer (8) being located between each of said reinforcing zones (4) and said manganese steel zone (6);

Wherein there are a plurality of reinforcing zones (4) and the distance between two adjacent reinforcing zones is between 1-5 mm;

Wherein the weight% of (W, ti) C in each of the enhancement zones (4) is between 80-98 and the weight% of WC in each of the enhancement zones (4) is between 20-30;

wherein the hardness of the reinforcement zone (4) is between 900-1400 HV1 and the hardness of the manganese steel zone (6) is between 300-400 HV1 prior to work hardening, wherein work hardening occurs when the manganese steel is subjected to an impact of crushing forces;

The method is characterized in that:

the average grain size of the (W, ti) C particles in each of the enhancement zones (4) is between 0.2 and 2 μm and the average grain size of the WC particles in each of the enhancement zones (4) is between 20 and 30 μm, wherein the average grain sizes of the (W, ti) C and WC grains are determined by Scanning Electron Microscope (SEM) analysis, wherein the analysis is performed from several different regions of the sample, the grain size is determined using Image J software, the average grain size is calculated from the determined grain sizes, and

Wherein the density in the enhancement zone (4) is between 83% and 96% of theoretical density.

2. The composite material (2) according to claim 1, wherein the composition of the manganese steel in the manganese steel zone (6) has the following chemical composition by weight:

0.5 to 2.0% of carbon;

11 to 22% of manganese;

0.2 to 1.0% of silicon;

1 to 2% of chromium;

Nickel up to 0.6%;

molybdenum up to 0.5%;

and the balance of Fe.

3. The composite (2) according to any one of the preceding claims, wherein the thickness of each of the interface layers (8) is greater than 150 μm, wherein the thickness is determined by Scanning Electron Microscope (SEM) analysis, wherein the analysis is performed from several different regions of the sample, the particle size is determined using Image J software, and the average particle size is calculated from the determined particle sizes.

4. The composite (2) according to any one of the preceding claims, wherein the interface layer (8) is free of defects when examined using an optical microscope at 1000 x magnification, wherein the defects are holes or cracks.

5. The composite (2) according to any one of the preceding claims, wherein the bonding rate between WC grains and manganese steel and between (W, ti) C grains and manganese steel in the strengthening zone (4) is >99%.

6. The composite (2) according to any one of the preceding claims, wherein the volume of each of the reinforcing regions is between 30-75cm ³, wherein the volume is determined using X-ray diffraction.

7. The composite (2) according to any one of the preceding claims, wherein at least 90% of WC grains in the reinforcing zone (4) have an irregular prismatic shape.

8. A wear part (14) comprising a composite material (2) according to any one of claims 1-7.

9. A method of manufacturing a composite material (2) according to any one of claims 1-7, comprising the steps of:

a) Mixing together 65-98 wt% tungsten, 3-90 wt% titanium, 3-20 wt% carbon and 0-80% catalyst powder, wherein the catalyst powder is selected from Fe, ni, mo, cr, W, al or a mixture thereof;

b) Pressing the mixed powders together to form at least one compact (20);

c) Positioning and fixing at least one green compact (20) inside a mould (22), wherein the distance between two adjacent reinforcing zones is between 1 and 5 mm;

d) Pouring molten cast manganese steel (24) into a mold (22) to surround the at least one compact (20) to initiate a self-propagating high temperature synthesis (SHS) reaction to produce a casting (26);

e) -heat treating the casting (26);

f) Quenching the casting (26);

The method is characterized in that:

in step b), the powder is pressed at a pressure between 400 and 700 mPa.