NIOBIUM CARBIDE REINFORCED MANGANESE STEEL

Abstract

A composite material has at least one reinforcing zone including niobium carbide (NbC) and a manganese steel matrix. A manganese steel zone surrounds the at least one reinforcing zone and an interface layer is positioned between the reinforcing zone and the manganese steel zone. An average grain size of the NbC particles in the at least one reinforcing zone is between 2-5 m.

Claims

1. A composite material comprising: at least one reinforcing zone including niobium carbide (NbC) and a manganese steel matrix; a manganese steel zone surrounding the at least one reinforcing zone; and an interface layer positioned between the reinforcing zone and the manganese steel zone, wherein an average grain size of the NbC in the at least one reinforcing zone is between 2-5 m.

2. The composite material according to claim 1, wherein the wt % of NbC in the at least one reinforcing zone is between 60-98.

3. The composite material according to claim 1, wherein a composition of the manganese steel in the manganese steel zone has the chemical composition by weight of: carbon: 0.5 to 2.0%; manganese: 11 to 22%; silicon: 0.2 to 1.0%; chromium: 1 to 2%; nickel: up to 0.6%; molybdenum: up to 0.5%; and a balance of iron.

4. The composite material according to claim 1, wherein a hardness of the at least one reinforcing zone is between 600-1000 HV1 and the hardness of the manganese steel zone is between 200-300 HV1 before work hardening.

5. The composite material according to claim 1, wherein a thickness of the interface layer is between 90-295 m.

6. The composite material according to claim 1, wherein the interface layer 8 is free of defects.

7. The composite material according to claim 1, wherein wettability between the NbC grains and the manganese steel in the at least one reinforcing zone is >99%.

8. The composite material according to claim 1, wherein the at least one reinforcing zone has a volume of between 30-75 cm.sup.3.

9. The composite material according to claim 1, wherein at least 90% of the NbC grains in the at least one reinforcing zone has a square prismatic shape, wherein a square prismatic shape is a cuboid having two square faces and two rectangular faces, 12 edges and 8 vertices and wherein a percentage of grains having the square prismatic shape is calculated by counting from a SEM fracture surface image.

10. The composite material according to claim 1, wherein there are a plurality of reinforcing zones and a distance between two neighbouring reinforcing zones is between 1-5 mm.

11. A wear part comprising the composite material according to claim 1.

12. A method of producing a composite material according to claim 1, the method comprising the steps of: a) mixing together 50-90 wt % niobium, 6-20 wt % carbon and 0-40 wt % catalysis powders; b) compacting the mixed powders together to form at least one compact; c) positioning and optionally fixing the at least one compact into an interior of a mold; d) pouring molten casting manganese steel into the mold to surround the at least one compact to initiate a self-propagating high temperature synthesis reaction to produce a cast; e) heat treating the cast; and f) quenching the cast, wherein in step b) the powders are compacting with a pressure of between 450-700 MPa.

13. The method according to claim 12, wherein the catalysis is selected from iron, cobalt, nickel, molybdenum, chromium, tungsten, aluminum, or a mixture thereof.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0024] FIG. 1: Shows a line drawing of the composition of the composite material.

[0025] FIG. 2: Shows an SEM image taken of the reinforced zone with low magnification on the left and high magnification on the right.

[0026] FIG. 3: Shows an SEM image taken of the interface layer with low magnification on the left and high magnification on the right.

[0027] FIG. 4: Shows an SEM image of the composite material

[0028] FIG. 5: Shows a perspective drawing of a wear part.

[0029] FIG. 6: Shows an SEM image of a comparative sample having pores in the interface layer (left picture) and reinforced zone (right picture).

DETAILED DESCRIPTION

[0030] FIG. 1 shows a composite material 2 comprising at least one reinforcing zone 4 comprising niobium carbide (NbC) and a manganese steel matrix; a manganese steel zone 6 that surrounds each of the reinforcing zones 4; and an interface layer 8 positioned between each of the reinforcing zones 4 and the manganese steel zone 6. In each of the reinforcing zones, the NbC acts to reinforce the manganese steel matrix.

[0031] The average grain size of the NbC particles in each of the reinforcing zone(s) (4) is between 2-5 m, preferably between 2-4 m, most preferably between 2-3 m.

[0032] The average grain size of the NbC grains is measured by Scanning Electron Microscopy (SEM) analysis where several and different areas from the samples were analysed and particle sizes were measured. Then, the average particle size was calculated.

[0033] Each interface layer 8 comprises NbC and manganese steel and can be distinguished from the reinforcing zones 4 as the shape and size of the NbC grains are different. The interface layer(s) 8 can be distinguished from the reinforcing zone(s) 4 can either: comparing the geometry and/or comparing the average grain size. If the geometry is being compared, the reinforcing zone(s) 4 comprise >90% NbC grains having a square prismatic geometry whereas the interface layer(s) 8 comprise <5% NbC grains having a square prismatic geometry. A NbC grain is considered to have square prismatic geometry if the grains have 4 sharp edges. If the grain size is being compared the average NbC grain size of in the interface layer(s) 8 is at least 5% less than the average NbC grain size on the reinforcing zone(s) 4.

[0034] FIG. 2 shows a Scanning Electron microscope image using MIRA3 TESCAN equipment. A secondary electron detector (SE) with a high voltage of 15 KV and a working distance of 9 mm configuration were used. SEM image of the NbC grains in the reinforcing zone 4. FIG. 3 shows an SEM image of the NbC grains in the interface layer 8. The different NbC grain geometry and size can be clearly be seen when comparing these two figures.

[0035] In one embodiment the wt % of NbC in each of the reinforcing zones 4 is between 60-90%, more preferably between 80-91%, even more preferably between 80-90%.

[0036] In one embodiment, the composition of the manganese steel in manganese steel zone 6 has the chemical composition by weight of: carbon: 0.5 to 2.0%; manganese: 11 to 22%; silicon: 0.2 to 1.0%; chromium: 1 to 2%; nickel: up to 0.6%, molybdenum: up to 0.5% and a balance of Fe.

[0037] In one embodiment, the chemical composition of the manganese steel in each of the reinforcing zones 4 has the 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.

[0038] In one embodiment, the hardness of the reinforcing zones 4 is between 600-1000HV1, preferably between 750-1000. The hardness of the manganese steel zone 6 is between 200-300 HV1.

[0039] Hardness is measured using Vickers hardness mapping on polished samples using a 1 kg. and a holding time of 15 seconds. A micro-hardness tester, Matsuzawa, model MXT was used. Hardness measurement profiles are performed starting from the non-reinforce zone, moving to the interface layer and then to the reinforced zone.

[0040] In one embodiment, the interface layer 6 is between 90-300 m wide, preferably between 130-200. FIG. 4 shows an SEM image taken at 15.0 kV, 563 magnification of the reinforced zone 4, the manganese steel zone 6 and the interface layer 8. The width of the interface layer 6 is measured from a start point 10, which is defined as being adjacent to the manganese steel zone 6 and the point at where the NbC grains are present. The end point 12 for measuring where the interface layer 8 ends, and therefore where the reinforcing zone 8 starts is considered to be where the average grain size of the NbC grains has increased by 20% compared average NbC grains measured at the start point 10 and/or where the percentage of NbC grains having a square prismatic shape increases above 90%.

[0041] In one embodiment, the interface layer 8 is free of defects. Defects are considered to be cracks or pores.

[0042] In one embodiment, the wettability between the NbC grains and the manganese steel in the reinforcing zones 4 is >99%, preferably >99.5%, more preferably >99.9%, most preferably 100%. Wettability is measured by a Scanning Electron Microscope where the contact area and the bonding between the NbC grains and the manganese steel have been evaluated.

[0043] In one embodiment each of the reinforcing zones 4 has a volume of between 30-75 cm.sup.3. For example, but not limited to the reinforcing zone(s) 4 could have a length of between 100-200 mm, preferably between 100-150 mm, a width of between 20-30 mm, preferably between 20-25 mm and a thickness between 15-30 mm, preferably between 15-25 mm.

[0044] In one embodiment >95%, preferably >98%, more preferably >99% of the NbC grains in the reinforcing zones 4 have a square prismatic shape. Preferably, the NbC grains are uniformly distributed in the manganese steel in the reinforcing zone(s).

[0045] In one embodiment, there are a plurality of reinforcing zones 4 with its interface zone 8 and the distance between two neighbouring reinforcing zones 4 with its interface layer 8 is between 1-5 mm, preferably between 1-3 mm, more preferably between 1-2 mm.

[0046] FIG. 5 shows an example of a wear part 14 comprising the composite material 2 as described hereinabove or hereinafter. For example, the wear part 2 could be, but not limited to, a cone crusher or a stationary jaw crusher or a mobile jaw crusher that is configured to crush material or other material/rock processing unit. The reinforcing zone(s) 4 are positions on the wear parts 14 in the locations that are most subjected to high wear, for example on a crushing zone 18 of a cone crusher 16.

[0047] The method for producing the composite material 2 as described hereinbefore or hereinafter comprising the steps of: a) Mixing together 50-90 wt %, preferably 77-90 niobium; 6-20 wt %, preferably 10-20 wt % carbon and 0-40 wt %, preferably 0-10 wt % catalysis powders; b) compacting the mixed powders together to form at least one compact using a compacting pressure of between 450-700 MPa, preferably 500-650 MPa more preferably 550-650 MPa; c) positioning and optionally fixing at least one compact into the interior of a mold; d) pouring molten casting manganese steel into the mold to surround the at least one compact to initiate a self-propagating high temperature synthesis (SHS) reaction to produce a cast; e) heat treating the cast; and then f) quenching the cast.

[0048] Preferably, the cast is treated at a temperature of between 1400-1500 C., the cast is quenched using water. Preferably, the catalysis is selected from Fe, Co, Ni, Mo, Cr, W, Al, or a mixture thereof. Carbon could be added in the form of graphite, amorphous graphite, a carbonaceous material or mixtures thereof. The compacts could for example be held in place using me a metallic fixation system to hold them in place during casting.

EXAMPLES

Example 1Samples

[0049] Sample A is a comparative sample of non-reinforced manganese steel having the composition 1-1.5% C, 11-14% Mn, 0.4-0.8% Si, 1.3-2.0% Cr, 0.6% Ni, 0.065% P.

[0050] Samples B-H are samples of composite materials produced by mixing together powders of niobium, carbon and a catalysis powder. The compacting the mixed powders to form compacts which were then positioned in a mold and then molten 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% was poured into the mold to surround the compacts which initiated a SHS reaction, the cast was then heat treated at a temperature of 1450 C. and then quenching with water. Table 1 shows a summary of the reinforced samples:

TABLE-US-00001 TABLE 1 Summary of samples Average NbC NbC content Compacting grain in pressure size in reinforced used reinforced zone Wettability Sample (MPa) zone (m) (wt %) (%) A (comparative) B (inventive) 620 2 90 100 C (inventive) 600 2 85 100 D (inventive) 600 2 80 100 E (inventive) 650 2.5 90 100 F (comparative) 550 1 50 5 G (inventive) 600 2 87 100 H (inventive) 600 3 70 100

[0051] It can be seen if the compacting pressure is not high enough then the wettability is reduced.

Example 2Hardness

[0052] Vickers hardness was measured by a micro-hardness tester, Matsuzawa, model MXT using 1 kgf and a holding time of 15 seconds. Hardness measurement profiles are performed starting from the non-reinforce zone, moving to the interface layer and then to the reinforced zone.

[0053] The hardness measurement results are shown in Table 2 below:

TABLE-US-00002 TABLE 2 Hardness measurement Hardness in manganese Hardness in Hardness in steel zone Interface reinforced Sample (HV1) layer zone A (comparative) 300 B (inventive) 254 614 757 C (inventive) 249 663 738 D (inventive) 257 596 724 E (inventive) 238 673 820 F (comparative) 270 630 670 G (inventive) 300 643 834 H (inventive) 250 655 963

[0054] It can be seen that the inventive samples have an increased hardness in reinforced zones compared to the comparative samples.

Example 3Wear Test

[0055] Wear was tested using a standard wear test using a lab jaw crusher. The wear test procedure consists on using fixed amount of rocks from 1 Ton up to 4 Ton of rocks. Four plates, two stationary and two moving, were placed inside the jaw crusher. Reference plates were also mounted in both positions. The reference plates are based on Weldox type of material.

[0056] The calculation of wear is based on the difference in volume loss of the test plates compared to the reference plates. All plates were weighed before and after wear test. Then volume loss is calculated using the density of 7.85 g/cm.sup.3 and 7.6 g/cm.sup.3 for the reference and test plates respectively. The total wear ratio (WR) is calculated according to ASTM G81-97a (2013).

[0057] The wear test results are shown in table 3 below:

TABLE-US-00003 TABLE 3 Wear test results Sample Wear ratio rate E 0.23 B 0.24

[0058] It can be seen that the wear rate for the inventive samples is low.

Example 4Defects

TABLE-US-00004 TABLE 4 Defects Defects in the Defects in the Sample reinforced zone interface layer A (comparative) B (inventive) none none C (inventive) none none D (inventive) none none E (inventive) none none F (comparative) pores pores G (inventive) none none H (inventive) none none

[0059] Defects were assessed by using Scanning Electron microscopy analysis where cracks and pores are identified. It can be seen that the inventive samples are free of defects. It can be seen that the comparative sample contains pores, whereas the inventive samples do not. FIG. 6 shows the pores in sample F, whereas FIG. 4 shows the absence of any pores from sample B.