An austenitic stainless steel cemented carbide and a method of manufacturing the same

Abstract

The application discloses an austenitic stainless steel cemented carbide and a preparation method thereof. The austenitic stainless steel cemented carbide comprises the following components in percentage by mass: 35-50% of titanium carbide powder, 10-20% of tungsten carbide powder, 30-55% of 304 austenitic stainless steel powder and 2-5% of molybdenum powder. The FSSS particle size of the titanium carbide powder is 0.8-3.0 microns, the FSSS particle size of the tungsten carbide powder is 0.4-3.0 microns, the FSSS particle size of the 304 austenitic stainless steel powder is 1.0-3.0 microns, and the FSSS particle size of the molybdenum powder is 2.0-5.0 microns. The austenitic stainless steel cemented carbide has good oxidation resistance, corrosion resistance and high-temperature thermal stability, and is a new material with higher strength, wear resistance and toughness. The service life of the austenitic stainless steel cemented carbide is more than three times that of conventional materials. The austenitic stainless steel cemented carbide is suitable for the preparation of core parts of a plastic engineering machinery double-screw extruder. The preparation process of the austenitic stainless steel cemented carbide is equivalent to that of conventional cemented carbide, and the austenitic stainless steel cemented carbide has the characteristics of low cost, controllable quality and batch production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel-bonded carbide, in particular to an austenitic stainless steel-bonded carbide and a preparation method thereof. BACKGROUND

[0002] The plastic engineering machinery double-screw extruder is the main equipment for engineering plastic processing and manufacturing, and its working environment is to crush, stir and convey high-viscosity and high-strength engineering plastics at a high temperature of 200-300 DEG C. In addition to high temperature, it also has high corrosiveness, and the working environment is harsh. The core components in contact with high-temperature engineering plastics are the double-screw barrel and the spiral block installed on the screw for crushing, stirring and conveying, which requires the two core components to have the characteristics of high corrosion resistance, high wear resistance, high temperature stability, high toughness and high strength. The screw is usually more than 2m long, and can only use high-speed steel, special steel or stainless steel materials prepared by pyrometallurgy with poor rigidity, and the spiral block installed on the screw also requires light weight to prevent the screw from bending and deforming. At present, the double-screw barrel and the spiral block in the industry are mainly made of Stellite alloy, nickel-based alloy, high-speed steel and stainless steel. However, these three materials need to be frequently unloaded, installed and debugged due to poor wear resistance, resulting in low production efficiency, which has been criticized by the industry. In addition, Stellite alloy and nickel-based alloy also have the problems of high cost and limited use range, and high-speed steel has the problem of poor corrosion resistance.

[0003] A steel-bonded carbide and a preparation method and application thereof are provided in Chinese patent CN112301295B. The main components are titanium carbide 35-45%, reduced iron powder 40-50%, reduced molybdenum powder 2-5%, reduced nickel powder 2-5%, manganese powder 10-15% and chromium powder 0-3%, i.e. the Cr content is only 0-5.45% in the binder phase except for the hard phase, which is far less than the 13% required for stainless steel and oxidation resistance, and can only be used at room temperature and in a non-corrosive environment. Chinese patent CN103215483B discloses a high-strength industrial cutter for rolling steel, which contains 5-10% carbon powder. In use, carbon elements are easily combined with oxygen to form carbonate, which leads to the lack of a protective layer in the alloy and easy oxidation and corrosion. Chinese patent CN103114232A discloses that La2O3 can react with impurities and oxide films on the interface of metal powder to purify the interface, thereby improving the wettability of the binder phase and the hard phase and increasing the density of the alloy. However, the Ni content in the composition is only 1.0-2.0%, which is insufficient to wet 48-50% TiC to provide sufficient toughness. SUMMARY

[0004] In view of the above technical problems in the related art, the present application provides an austenitic stainless steel-bonded carbide and a preparation method thereof, which can solve the above problems.

[0005] To achieve the above technical purposes, the technical scheme of the present application is as follows:

[0006] An austenitic stainless steel cemented carbide comprises the following components in mass percentage: titanium carbide powder 35-50%, tungsten carbide powder 10-20%, 304 austenitic stainless steel powder 30-55%, and molybdenum powder 2-5%, wherein the FSSS particle size of the titanium carbide powder is 0.8-3.0 μm, the FSSS particle size of the tungsten carbide powder is 0.4-3.0 μm, the FSSS particle size of the 304 austenitic stainless steel powder is 1.0-3.0 μm, and the FSSS particle size of the molybdenum powder is 2.0-5.0 μm.

[0007] Further, the mass percentage of the titanium carbide fine powder with an FSSS particle size less than 1 μm in the entire titanium carbide powder is ≥20%.

[0008] Further, the composition of the 304 austenitic stainless steel is Fe x Ni y Cr z , and the subscripts x, y and z are the mass percentages of the elements, wherein y is greater than 8 and z is greater than 17.5.

[0009] A preparation method of an austenitic stainless steel cemented carbide comprises the following steps:

[0010] S1. Weighing titanium carbide powder, tungsten carbide powder, 304 austenitic stainless steel powder and molybdenum powder, and mixing and ball-milling the powders with paraffin powder and alcohol medium to obtain a mixture;

[0011] S2. Drying the obtained mixture;

[0012] S3. Pressing the dried mixture to obtain a compact;

[0013] S4. Vacuum sintering the compact of the mixture in S3 at 1350-1480 ℃ to remove the paraffin forming agent and densify the alloy, thereby obtaining an austenitic stainless steel cemented carbide containing TiC-Mo solid solution and TiC-WC solid solution.

[0014] Further, in step S1, Co powder with a mass M5 is weighed and used to replace the 304 austenitic stainless steel powder with the same mass to further improve the strength and toughness of the alloy, wherein M5≤10% (M1+M2+M3+M4).

[0015] Further, in the step S1 of weighing the titanium carbide powder with a mass M1, the tungsten carbide powder with a mass M2, the 304 austenitic stainless steel powder with a mass M3 and the molybdenum powder with a mass M4, the Ni powder with a mass M6 is weighed and used to replace the 304 austenitic stainless steel powder with the same mass to further improve the strength and toughness of the alloy, wherein M6≤10% (M1+M2+M3+M4).

[0016] Further, in the step S1 of weighing the titanium carbide powder with a mass M1, the tungsten carbide powder with a mass M2, the 304 austenitic stainless steel powder with a mass M3 and the molybdenum powder with a mass M4, the La2O3 powder with a mass M7 is weighed and used to replace the 304 austenitic stainless steel powder with the same mass to further improve the strength and toughness of the alloy, wherein M7≤0.5% (M1+M2+M3+M4).

[0017] Further, the paraffin powder is 3.0-5.0% of the total mass of the titanium carbide powder, the tungsten carbide powder, the 304 austenitic stainless steel powder and the molybdenum powder.

[0018] The austenitic stainless steel steel-bonded hard alloy has the advantages that the austenitic stainless steel steel-bonded hard alloy has good oxidation resistance, corrosion resistance and high-temperature thermal stability, is a new material with higher strength, wear resistance and toughness, has a service life 3 times longer than that of conventional materials, is suitable for the preparation of core parts of a plastic engineering machinery double-screw extruder, and has the characteristics of low cost, controllable quality and batch production. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0020] The present application will be further described in detail below according to the drawings.

[0021] Figure 1 is a metallographic photo of the steel-bonded hard alloy of Example 2 of the present application;

[0022] Figure 2 is a metallographic photo of the steel-bonded hard alloy of Example 3 of the present application;

[0023] Figure 3 is a metallographic photo of the steel-bonded hard alloy of Example 1 of the present application;

[0024] Figure 4 is a metallographic photo of the steel-bonded hard alloy of Comparative Example 3 of the present application.

[0025] Fig. (Note: to highlight the characteristics of hard phase, Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 are taken after removing the binder phase):

[0026] 1, TiC-Mo solid solution; 2, TiC grain; 3, TiC-WC solid solution. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0028] Embodiment 1:

[0029] Titanium carbide powder with FSSS particle size of 2.5 μm, tungsten carbide powder with FSSS particle size of 1.5 μm, 304 austenitic stainless steel powder with FSSS particle size of 2.5 μm, molybdenum powder with FSSS particle size of 3.5 μm, and fine powder with FSSS particle size less than 1 μm in the TiC powder account for 25%.

[0030] The mass proportions of the raw materials are as follows: the mass proportion of titanium carbide powder is 40% (the mass of titanium carbide powder is 40 kg, of which the fine powder with FSSS particle size less than 1 μm accounts for 40*25%=10 kg); the mass proportion of tungsten carbide powder is 15% (the mass of tungsten carbide powder is 15 kg); the mass proportion of 304 austenitic stainless steel powder is 41% (the mass of 304 austenitic stainless steel powder is 41 kg); the mass proportion of molybdenum powder is 4.0% (the mass of molybdenum powder is 4 kg); and the total weight of the powder is 100 kg. Then, 4.2 kg of paraffin powder with an additional mass proportion of 4.2% is weighed, and mixed with 45 L of alcohol medium at a ball-to-powder ratio of 3:1 for ball milling for 50 h, and then vacuum dried to obtain a mixed material.

[0031] The above dried mixed material is pressed, and the mixed compact is sintered at 1430℃ in vacuum to obtain an austenitic stainless steel-bonded hard alloy of the present application. The related properties are shown in Table 1, and the microstructure is shown in Figure 3 .

[0032] Through actual use test, the service life of the plastic engineering machinery double-screw extruder for one-time molding is 3 times that of high-speed steel material.

[0033] Embodiment 2:

[0034] Select FSSS particle size 2.5 μm titanium carbide powder, FSSS particle size 1.5 μm tungsten carbide powder, FSSS particle size 2.8 μm 304 austenitic stainless steel powder, FSSS particle size 0.8 μm cobalt powder, FSSS particle size 3.5 μm molybdenum powder and FSSS particle size 0.8 μm lanthanum oxide powder, the fine powder with FSSS particle size less than 1 μm accounts for 25% in the TiC powder.

[0035] The mass proportion of the raw materials is: the mass proportion of titanium carbide powder is 40%; the mass proportion of tungsten carbide powder is 20%; the mass proportion of 304 austenitic stainless steel powder is 30.6%; the mass proportion of cobalt powder is 5.0%; the mass proportion of molybdenum powder is 4%; and the mass proportion of lanthanum oxide powder is 0.4%, and the total weight of the powder is 100 kg. Then, 3.8% of paraffin powder in addition is weighed, mixed with 38 L of alcohol medium at a ball-to-powder ratio of 4.5:1, ball milled for 25 h, and then vacuum dried to obtain a mixed material.

[0036] The above dried mixed material is pressed, and the mixed material compact is sintered at 1410 ℃ in vacuum to obtain an austenitic stainless steel-bonded hard alloy of the present application. The related properties are shown in Table 1, and the microstructure is shown in Figure 1 .

[0037] Through actual use test, the service life of the plastic engineering machinery double-screw extruder for one-time die loading is 6 times that of high-speed steel material.

[0038] Example 3:

[0039] Select FSSS particle size 2.0 μm titanium carbide powder, FSSS particle size 1.5 μm tungsten carbide powder, FSSS particle size 2.5 μm 304 austenitic stainless steel powder, FSSS particle size 1.2 μm cobalt powder, FSSS particle size 3.5 μm molybdenum powder and FSSS particle size 0.8 μm lanthanum oxide powder, the fine powder with FSSS particle size less than 1 μm accounts for 35% in the TiC powder.

[0040] The mass proportion of the raw materials is: the mass proportion of titanium carbide powder is 40%; the mass proportion of tungsten carbide powder is 15%; the mass proportion of 304 austenitic stainless steel powder is 30.65%; the mass proportion of cobalt powder is 10.0%; the mass proportion of molybdenum powder is 4.0%; and the mass proportion of lanthanum oxide powder is 0.35%. The total weight of the powder is 100 kg. Then, 4.0% of paraffin powder in addition is weighed, mixed with 42 L of alcohol medium at a ball-to-powder ratio of 4:1, ball milled for 40 h, and then vacuum dried to obtain a mixed material.

[0041] The above dried mixed material is pressed, and the mixed material compact is sintered at 1430 ℃ in vacuum to obtain an austenitic stainless steel-bonded hard alloy of the present application. The related properties are shown in Table 1, and the microstructure is shown in Figure 2 .

[0042] The practical use test shows that the service life of the plastic engineering machinery double-screw extruder is 5 times that of the high-speed steel material.

[0043] Comparative Example 1

[0044] The properties of the 304 austenitic stainless steel purchased on the market are shown in Table 1.

[0045] Comparative Example 2

[0046] The properties of the high-speed steel W6Mo5Cr4V2 are shown in Table 1.

[0047] Comparative Example 3

[0048] Titanium carbide powder with FSSS particle size of 2.5 μm, 304 austenitic stainless steel powder with FSSS particle size of 2.5 μm, molybdenum powder with FSSS particle size of 3.5 μm, and fine powder of the titanium carbide powder with FSSS particle size less than 1 μm account for 25%.

[0049] The mass proportions of the raw materials are as follows: the mass proportion of the titanium carbide powder is 55%; the mass proportion of the 304 austenitic stainless steel powder is 41%; and the mass proportion of the molybdenum powder is 4.0%. The total weight of the powders is 100 kg. An additional mass proportion of 4.2% of paraffin powder is weighed, mixed with 45 L of alcohol medium at a ball-to-powder ratio of 3:1, and subjected to ball milling for 50 h, followed by vacuum drying to obtain a mixture;

[0050] The above dried mixture is pressed, and the mixture compact is sintered at 1430°C in vacuum to obtain an austenitic stainless steel cemented hard alloy with a compactness of only 95%. The related properties are shown in Table 1, and the microstructure is shown in Figure 4 .

[0051] In the above examples and comparative examples, the composition of the 304 austenitic stainless steel is Fe 71 Ni 11 Cr 18 (the subscript is the mass percentage of the element).

[0052] Cracking in actual use test.

[0053] Table 1

[0054]

[0055] Corrosion resistance test conditions: the test results of samples with the same appearance size after being soaked in hydrochloric acid with a pH value of 2.0 for 48 h. It can be seen from the results that Examples 1, 2 and 3 have very excellent corrosion resistance, and the corrosion rate is only 3.2% to 3.6% of that of the high-speed steel W6Mo5Cr4V2.

[0056] In summary, the austenitic stainless steel cemented carbide provided by the present application simultaneously adds TiC, WC and Mo. In tests and production, we find that WC grains can complete solid solution with fine TiC particles (as shown in Figure 1 ), eliminating fine and brittle TiC phases, generating TiC-WC solid solution 3 which is more fine than original WC grains, with size even less than 1.0 μm and round appearance. These solid solutions are uniformly and diffusely distributed in the binder phase to play the role of pinning and strengthening the binder phase. Meanwhile, the fine TiC-WC solid solution 3 itself has higher anti-spalling and grinding ability. At the edge of large TiC grains 2, TiC-Mo solid solution 1 (as shown in Figure 1 ) is generated to improve the wettability of TiC and the binder phase. Therefore, the austenitic stainless steel cemented carbide of the present application can obtain higher compactness, bending strength and wear resistance, with bending strength reaching more than 1000 MPa and compactness reaching more than 98%. In addition, the strength and toughness can be further improved by adding Co, Ni and La2O3.

[0057] Through detection and actual use test, the material has oxidation resistance, corrosion resistance and high temperature thermal stability comparable to austenitic stainless steel, with service life increased by more than 3 times compared with conventional materials, and is suitable for the preparation of double-helix machine barrel and screw block of plastic engineering machinery double-helix extruder core parts. Meanwhile, the preparation process of the material is equivalent to the conventional preparation process of conventional cemented carbide, with the characteristics of low cost, controllable quality and batch production.

[0058] The above only describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of producing an austenitic stainless steel cemented carbide, characterized in that The alloy comprises the following components in mass percentage: 35-50% of titanium carbide powder, 10-20% of tungsten carbide powder, 30-55% of 304 austenitic stainless steel powder, and 2-5% of molybdenum powder, wherein the FSSS particle size of the titanium carbide powder is 0.8-3.0 microns, the FSSS particle size of the tungsten carbide powder is 0.4-3.0 microns, the FSSS particle size of the 304 austenitic stainless steel powder is 1.0-3.0 microns, and the FSSS particle size of the molybdenum powder is 2.0-5.0 microns; the mass percentage of titanium carbide fine powder with a FSSS particle size less than 1 micron in the titanium carbide powder is greater than or equal to 20%, and the alloy comprises the following preparation steps: S1, weighing the titanium carbide powder, the tungsten carbide powder, the 304 austenitic stainless steel powder, and the molybdenum powder, and mixing and ball-milling the powders with paraffin powder and an alcohol medium to obtain a mixture; In S1, when the titanium carbide powder with a mass M1, the tungsten carbide powder with a mass M2, the 304 austenitic stainless steel powder with a mass M3, and the molybdenum powder with a mass M4 are weighed, Co powder with a mass M5 or Ni powder with a mass M6 or La2O3 powder with a mass M7 is weighed and used to replace the 304 austenitic stainless steel powder to further improve the strength and toughness of the alloy, wherein M5≤10% (M1+M2+M3+M4), M6≤10% (M1+M2+M3+M4), and M7≤0.5% (M1+M2+M3+M4); S2, drying the obtained mixture; S3, pressing the dried mixture to obtain a compact; S4, vacuum sintering the compact at 1350-1480 degrees Celsius to remove the paraffin forming agent and densify the alloy, thereby obtaining an austenitic stainless steel cemented hard alloy containing TiC-Mo solid solution and TiC-WC solid solution.

2. A method of producing an austenitic stainless steel cemented carbide according to claim 1, characterized in that 304 Austenitic stainless steel having the composition Fe x Ni y Cr z , the indices x, y, z being the mass percentages of the elements, with y greater than 8 and z greater than 17.

5.

3. The method for preparing an austenitic stainless steel bonded cemented carbide according to claim 1, characterized in that, The paraffin powder accounts for 3.0-5.0% of the total mass of the titanium carbide powder, the tungsten carbide powder, the 304 austenitic stainless steel powder, and the molybdenum powder.

4. An austenitic stainless steel cemented carbide, characterized in that The austenitic stainless steel cemented hard alloy is prepared by the method according to any one of claims 1-3.

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