Powder metallurgy high-speed steel with high abrasive wear resistance and adhesive wear resistance

Abstract

The invention discloses powder metallurgy high-speed steel with high abrasive wear resistance and adhesive wear resistance. C, S, Mo and W elements are added into Fe, the proportion of the four elements is adjusted, the content of aluminum, oxygen and manganese in the powder preparation process is strictly controlled, B-type inclusions are made to be 0 grade, about 15 wt% of S-doped (Mo, W) 6 (C, S) phases with the size being 2-3 micrometers are formed in the alloy, compared with a conventional M6C phase, the alloy has the same hardness and abrasive particle abrasion performance, due to the fact that the S element is doped, the self-lubricating effect is generated, and the service life of the alloy is prolonged. And in the process of dual friction, the friction coefficient is lower, and the adhesive wear resistance is more excellent. In addition, a proper amount of Cr and V elements are added to form a VC phase of 1-2 microns and Cr23C6 of 0.5-1 micron, and the finally prepared high-speed steel has high abrasive wear resistance and also has high adhesive wear resistance. The service life of a powder metallurgy cold press forming die or a blanking forming die made of the material is prolonged by more than 1.5 times compared with that of conventional powder metallurgy high-speed steel.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials and relates to a preparation method for improving the wear resistance of powder metallurgy high-speed steel. Background Technology

[0002] Powder metallurgy high-speed steel is a high-performance high-speed steel or directly formed tool material produced using powder metallurgy technology. Powder metallurgy high-speed steel possesses excellent toughness and machinability, good red hardness, high compressive strength, and high wear resistance. It also features high alloy content, high purity, no segregation, fine carbide particles, and isotropic properties, thus finding wide application. It can be used as milling cutters, hobs, gear shapers, gear shaving cutters, twist drills, machine taps, reamers, and precision high-speed stamping dies. Different applications require different performance characteristics of high-speed steel, thus requiring different alloy composition designs. When used in screws, barrels, and stamping dies, high resistance to abrasive wear and adhesive wear is required. However, current powder high-speed steels typically do not simultaneously possess resistance to both adhesive and abrasive wear, and can only meet single performance requirements. For example, K390, CPM10V, and ASP2053, although they have excellent resistance to abrasive wear, have poor resistance to adhesive wear. Therefore, developing new powder high-speed steel materials that take into account both frictional properties to meet the urgent needs of stamping or punching dies has become a problem that must be solved. Summary of the Invention

[0003] The purpose of this invention is to prepare a powder high-speed steel material with both anti-adhesive wear and anti-abrasive wear properties through composition design and powder metallurgy process. The main idea is to add C, S, Mo, and W elements to Fe, rationally design the proportions of these four elements, and strictly control the contents of aluminum, oxygen, and manganese during powder preparation to achieve a B-type inclusion level of 0. This allows the formation of approximately 15 wt% S-doped (Mo,W)6(C,S) phase with a size of 2-3 micrometers in the alloy. Compared to the conventional M6C phase, this phase has the same hardness and abrasive wear properties, but due to the S doping, it exhibits a self-lubricating effect, resulting in a lower coefficient of friction during mating friction and demonstrating superior anti-adhesive wear performance. In addition to the above four elements, appropriate amounts of Cr and V elements are also added to form a 1-2 micrometer VC phase and a 0.5-1 micrometer Cr phase. 23 C6, the high-speed steel ultimately produced, has high resistance to abrasive wear as well as high resistance to adhesive wear.

[0004] A powder metallurgical high-speed steel that combines resistance to both abrasive and adhesive wear. The main alloying element contents are as follows: C content is 1.30-1.35%, Mo and W content are both 5%-6%, S content is 0.05-0.06%, V content is 3.5-4.0%, Cr content is 4-5%, Co content is 3-4%, Mn content is 0-0.15%, Si content is 0-0.15%, and the Mo and W contents are the same, the Mn and Si contents are the same, the S content is 1% of the W or Mo content, and the balance is Fe and impurity elements, of which the impurity element Al content is less than 5ppm, O content is less than 30ppm, P content is less than 0.1%, and the powder particle size is less than 120 micrometers.

[0005] The method for preparing powder metallurgy high-speed steel that combines resistance to abrasive wear and adhesive wear, as described above, is characterized by the following specific preparation steps: 1) Prepare spherical metal powders using vacuum atomization or non-vacuum atomization powder preparation technology; 2) The powder prepared in step 1) is sintered and densified according to conventional hot isostatic pressing process to obtain a dense sintered ingot. 3) The dense sintered ingot obtained in step 2) is subjected to hot deformation operations such as forging or hot rolling to obtain the required blank. Then the hot-deformed block is annealed and cooled in the furnace after annealing. 4) Perform performance heat treatment on the hot-deformed and annealed block using oil quenching or vacuum quenching. The holding time is based on the size of the block and is 1 min / mm. After holding, quench the block. Then temper the quenched block material, repeating the tempering process three times to obtain the finished product.

[0006] Further, in step 2), the sintering temperature is 1140-1160℃, the pressure is 100-110MPa, and the holding time is 60-90 minutes.

[0007] Further, the temperature of the heat deformation in step 3) is 1080℃-1140℃.

[0008] Furthermore, the annealing temperature in step 3) is 860-880℃, and the holding time is 120-150 minutes.

[0009] Further, the quenching and holding temperature in step 4) is 1150-1175℃.

[0010] Furthermore, the tempering process in step 4) is 550-560℃, with a holding time of 60-90min.

[0011] Further, the typical reinforcing phase of the finished product described in step 4) is a 2-3 micrometer (Mo,W)6(C,S) phase, accounting for approximately 15 wt%; a 1-2 micrometer VC phase, accounting for approximately 3 wt%; and a 0.5-1 micrometer Cr phase.23 C6 phase, accounting for approximately 2.5 wt%.

[0012] The powder high-speed steel prepared by the above process has abrasive wear resistance comparable to K390 and CPM10V, but its adhesive wear resistance is more than doubled.

[0013] The principle of this invention: The strengthening phases of powder high-speed steel are typically carbides, such as vanadium carbide, chromium carbide, molybdenum carbide, and tungsten carbide formed by adding carbon, vanadium, chromium carbide, molybdenum carbide, and tungsten carbide to iron. These carbides have high hardness and can provide excellent resistance to abrasive wear, but their resistance to adhesive wear is relatively poor. To improve the resistance to adhesive wear, an appropriate amount of MoS2 with good self-lubricating properties is mixed in before sintering the atomized powder. This method has some effect, but it is difficult to mix evenly in batch preparation, and the mixing process easily causes powder oxidation. This invention discovers that by adding four elements—C, Mo, W, and S—to Fe, and under strict control of type B inclusions and Mn, and through reasonable proportion control of the four elements, S-doped (Mo,W)6(C,S) can be formed. This phase possesses the high wear resistance of carbides and the self-lubricating properties of sulfides. Based on this, by adding an appropriate amount of V, the prepared powder high-speed steel exhibits the same wear amount as traditional powder high-speed steel under the same friction conditions, but with a significantly reduced coefficient of friction, demonstrating excellent anti-adhesive wear performance. It should be noted that the sulfur (S) added in this invention is a beneficial element. During powder solidification, it is incorporated into (Mo,W)₆C to form the (Mo,W)₆(C,S) phase. This differs from the effect of adding S to traditional mold steel to form MnS and improve machinability. Furthermore, in traditional casting and forging processes for high-speed steel or mold steel, S is a harmful element because it readily reacts with Fe to form hot-brittle FeS. However, in powder metallurgy for high-speed steel, due to the rapid cooling rate during powder preparation, S does not have enough time to react with Fe to form the FeS phase. Instead, it precipitates as B-type inclusions, i.e., the Al₂O₃ phase. Therefore, this invention, on the one hand, strictly controls the Al content to below 5 ppm, thus eliminating the formation of B-type inclusions during powder solidification. This ensures that all S is incorporated into the (Mo,W)₆C phase, which is preferentially formed during solidification, thereby forming the (Mo,W)₆(C,S) phase. On the other hand, controlling the content of Si and Mn, with both at equal levels, helps to fix residual oxygen in the melt and reduce the formation of B-type inclusions. Additionally, it should be noted that the contents of Mo, W, and V should be optimized. Although vanadium carbide has high wear resistance, if its content is too high, it is prone to precipitating first during solidification, affecting the formation of (Mo,W)6C and thus preventing the formation of the (Mo,W)6(C,S) phase. The ratio of Mo to W should also be controlled; when their mass ratio is the same, the (Mo,W)6C phase is more easily formed. Excessive Mo or W content will result in the formation of single Mo6C and WC carbides.

[0014] Based on the above principles, the powder composition was designed. Experimental results show that under the same friction and wear conditions, compared with traditional high-wear-resistant powder high-speed steels such as CPM10V and S390, the wear amount is comparable, but the coefficient of friction is reduced by more than half, exhibiting excellent anti-adhesive wear performance. When used as cutting tools for blanking parts or molds for powder metallurgy pressing, its service life is more than doubled compared with conventional grades, demonstrating excellent resistance to abrasive wear and anti-adhesive wear performance. Attached Figure Description

[0015] Figure 1 The typical microstructure of the material of the present invention is shown in (a) and (b) is the elemental distribution diagram of the (Mo,W)6(C,S) phase in (a). Figure 2 Figure 1 Elemental distribution of the (Mo,W)6(C,S) phase; Figure 3 Figure 1 Distribution of the VC phase in the middle; Figure 4 Figure 1 Cr 23 Distribution diagram of C6 phase. Detailed Implementation

[0016] Example 1: Preparation of high wear-resistant and long-life powder metallurgy mold steel for powder cold pressing.

[0017] The first step involves preparing metal powder using vacuum atomization powder preparation technology. The composition ratio is as follows: C content is 1.30%, Mo and W content are both 5%, S content is 0.05%, V content is 3.5%, Cr content is 4%, Co content is 3%, Mn content is 0.15%, Si content is 0.15%, and the balance is Fe and impurity elements. Among them, the impurity elements Al content is less than 5 ppm, O content is less than 30 ppm, P content is less than 0.1%, and the particle size of the powder is less than 120 micrometers. The second step is to sinter and densify the powder prepared in step 1) according to the conventional hot isostatic pressing process. The sintering temperature is 1160℃, the pressure is 110MPa, and the holding time is 90 minutes. After sintering, a dense sintered ingot is obtained. The third step is to forge the dense sintered ingot obtained in step 2) to obtain the required powder cold-pressed blank. The forging temperature is 1080℃-1140℃. Then the block is annealed at 880℃ for 120 minutes and cooled in the furnace. The fourth step involves heat-treating the annealed block using an oil quenching process. The quenching temperature is 1150℃, and the holding time is typically 1 min / mm, depending on the block's dimensions. After holding, the block is quenched again. Subsequently, the quenched block is tempered at 550℃ for 90 minutes, repeated three times to obtain the finished product. Using this mold for cold pressing of Cu powder, its lifespan is more than twice that of commonly used molds. The parts have a smooth surface without scratches or other defects. The mold ultimately failed because the dimensions could not meet requirements, indicating excellent resistance to abrasive and adhesive wear.

[0018] Example 2: Preparation of high wear-resistant, long-life powder metallurgy high-speed steel for punching stainless steel sheets

[0019] The first step involves preparing spherical metal powder using a non-vacuum atomization powder preparation technology. The main alloying elements and their contents are as follows: C content is 1.35%, Mo and W content are both 6%, S content is 0.06%, V content is 4.0%, Cr content is 5%, Co content is 4%, Mn content is 0.1%, Si content is 0.1%, and the balance is Fe and impurity elements. Among them, the impurity elements Al content is less than 5 ppm, O content is less than 30 ppm, P content is less than 0.1%, and the particle size of the powder is less than 120 micrometers. The second step is to sinter and densify the powder prepared in step 1) according to the conventional hot isostatic pressing process. The sintering temperature is 1140℃, the pressure is 100MPa, and the holding time is 60 minutes. After sintering, a dense sintered ingot is obtained. The third step is to forge and deform the dense sintered ingot obtained in step 2) to obtain the required blank. The forging and hot deformation temperature is 1080℃-1140℃. Then, the hot-deformed block is annealed at 860℃ for 120 minutes and cooled in the furnace. The fourth step is to perform performance heat treatment on the hot-deformed and annealed block using a vacuum quenching process. The quenching temperature is 1175℃, and the holding time is usually 1min / mm depending on the size of the block. After the holding time is completed, the block is quenched. Then, the quenched block material is tempered by holding at 560℃ for 60min. The tempering process is repeated three times to obtain the finished product.

[0020] When this mold is used for punching and forming 316L stainless steel plates, its lifespan is more than 1.5 times that of commonly used molds. The parts have a smooth surface and are free of scratches and other defects. The mold eventually fails because the dimensions cannot meet the requirements, which indicates that it has excellent resistance to abrasive wear and adhesive wear.

Claims

1. A powder metallurgy high-speed steel that combines resistance to abrasive wear and adhesive wear, characterized in that, The main alloying element contents are as follows: C content is 1.30-1.35%, Mo and W content are both 5%-6%, S content is 0.05-0.06%, V content is 3.5-4.0%, Cr content is 4-5%, Co content is 3-4%, Mn content is 0-0.15%, Si content is 0-0.15%, and the Mo and W contents are the same, the Mn and Si contents are the same, the S content is 1% of the W or Mo content, and the balance is Fe and impurity elements, of which the impurity element Al content is less than 5ppm, O content is less than 30ppm, P content is less than 0.1%, and the powder particle size is less than 120 micrometers.

2. The method for preparing powder metallurgy high-speed steel with both abrasive wear and adhesive wear resistance as described in claim 1, characterized in that, The specific preparation steps are as follows: 1) Prepare spherical metal powders using vacuum atomization or non-vacuum atomization powder preparation technology; 2) The powder prepared in step 1) is sintered and densified according to conventional hot isostatic pressing process to obtain a dense sintered ingot. 3) The dense sintered ingot obtained in step 2) is subjected to hot deformation operations such as forging or hot rolling to obtain the required blank. Then the hot-deformed block is annealed and cooled in the furnace after annealing. 4) Perform performance heat treatment on the hot-deformed and annealed block using oil quenching or vacuum quenching. The holding time is based on the size of the block and is 1 min / mm. After holding, quench the block. Then temper the quenched block material, repeating the tempering process three times to obtain the finished product.

3. The method for preparing powder metallurgy high-speed steel with both abrasive wear and adhesive wear resistance according to claim 2, characterized in that, Step 2) The sintering temperature is 1140-1160℃, the pressure is 100-110MPa, and the holding time is 60-90 minutes.

4. The method for preparing powder metallurgy high-speed steel with both abrasive wear and adhesive wear resistance according to claim 2, characterized in that, Step 3) The temperature of the heat deformation is 1080℃-1140℃.

5. The method for preparing powder metallurgy high-speed steel with both abrasive wear and adhesive wear resistance according to claim 2, characterized in that, Step 3) The annealing temperature is 860-880℃, and the holding time is 120-150 minutes.

6. The method for preparing powder metallurgy high-speed steel with both abrasive wear and adhesive wear resistance according to claim 2, characterized in that, Step 4) The quenching and holding temperature is 1150-1175℃.

7. The method for preparing powder metallurgy high-speed steel with both abrasive wear and adhesive wear resistance according to claim 2, characterized in that, Step 4) The tempering process is at 550-560℃, and the holding time is 60-90 minutes.

8. The method for preparing powder metallurgy high-speed steel with both abrasive wear and adhesive wear resistance according to claim 2, characterized in that, Step 4) The typical reinforcing phase of the finished product is a 2-3 micrometer (Mo,W)6(C,S) phase, accounting for 15 wt%; a 1-2 micrometer VC phase, accounting for 3 wt%; and a 0.5-1 micrometer Cr phase. 23 C6 phase, accounting for 2.5 wt%.

Images