High-speed steel and preparation method thereof

Abstract

The invention provides high-speed steel and a preparation method thereof, the high-speed steel relates to the technical field of tool steel, and the high-speed steel comprises the following chemical components in percentage by mass: 1.00%-2.00% of carbon, 4.00%-8.00% of chromium, 3.00%-6.00% of molybdenum, 2.00%-5.00% of vanadium, 3.00%-6.50% of tungsten, 4.00%-10.00% of cobalt, 0.01%-0.30% of zirconium, 0.10%-0.40% of silicon and the balance of iron and impurities. According to the high-speed steel, the problems that in traditional cast-forged high-speed steel, core eutectic carbide segregation is serious, and eutectic carbide particles are coarse can be solved, and the problems that existing high-vanadium high-speed steel is coarse in MC carbide particles, poor in grindability and low in grinding machining efficiency can also be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of tool steel, in particular to a high-speed steel and also to a preparation method of the high-speed steel. Background Art

[0002] High-speed steel is a high-alloy tool steel that has excellent wear resistance, hardness and heat resistance under high temperature and high speed conditions. High-speed steel is a complex steel type. In addition to carbon, it contains a lot of alloying elements, such as tungsten, molybdenum, chromium, vanadium and other carbide-forming elements. These elements give high-speed steel excellent mechanical properties. Traditional high-speed steel is generally prepared by traditional casting technology or electroslag remelting technology.

[0003] The traditional casting technology is used to prepare high-speed steel. Although the process is simple and the cost is low, the slow solidification speed easily leads to segregation of carbon and alloy elements, resulting in the formation of intergranular carbide network. In addition, this type of high-speed steel is prone to stress concentration during use, and is brittle and has poor toughness.

[0004] Electroslag remelting technology is a refining metallurgical technology. The use of electroslag remelting technology to prepare high-speed steel can significantly improve the low-magnification structure of high-speed steel, improve the quality of steel, reduce the sulfur and phosphorus content in the molten steel, and improve the purity of the molten steel. However, this method has high energy consumption, low production efficiency, and will produce fluorides during the production process, which is harmful to the environment and human body.

[0005] The high vanadium high speed steel prepared by the existing preparation method has the following main shortcomings:

[0006] 1. The eutectic carbide segregation in the core of high vanadium high-speed steel is relatively serious, and the eutectic carbide particles are coarse, some of which exceed 20μm.

[0007] 2. In the process of preparing high-vanadium high-speed steel, it is usually necessary to increase the vanadium content in its alloying elements. Generally, the vanadium content is controlled above 2.45% (by mass percentage). The main purpose is to improve the wear resistance of high-vanadium high-speed steel. However, this high-vanadium high-speed steel has poor grindability and low grinding efficiency due to its coarse MC (M represents metal element) carbide particles. Summary of the invention

[0008] In view of this, the present invention aims to provide a high-speed steel, in particular a high-vanadium high-speed steel, and to make it have excellent performance.

[0009] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0010] A high-speed steel, whose chemical components, measured by mass percentage, include: C: 1.00%-2.00%, Cr: 4.00%-8.00%, Mo: 3.00%-6.00%, V: 2.00%-5.00%, W: 3.00%-6.50%, Co: 4.00%-10.00%, Zr: 0.01%-0.30%, Si: 0.10%-0.40%, and the balance is iron and impurities.

[0011] Furthermore, the chemical components of the high-speed steel include, by mass percentage, Nb: 0.10% to 2.00%.

[0012] Furthermore, the chemical components of the high-speed steel include, by mass percentage: C: 1.00% to 2.00%, Cr: 4.00% to 8.00%, Mo: 3.00% to 6.00%, V: 2.00% to 5.00%, W: 3.00% to 6.50%, Co: 4.50% to 8.50%, Zr: 0.01% to 0.25%, Si: 0.10% to 0.40%, and the remainder is iron and impurities.

[0013] Furthermore, the Nb content is between 0.10% and 1.20%.

[0014] The impurities include at least one of O, S and P, and O≤0.01%, S≤0.060%, and P≤0.030%.

[0015] Furthermore, the carbides in the high-speed steel include MC carbides, M2C carbides, M6C carbides and M23C6 carbides, the type of the MC carbides is (V, Nb, Zr)C, the type of the M2C carbides is (W, Mo, Cr, V, Fe)2C, the type of the M6C carbides is (W, Mo, Fe)6C, and the type of the M23C6 carbides is (Cr, Fe)23C6.

[0016] Furthermore, the volume fraction of the MC carbide, the M2C carbide and the M6C carbide in the high-speed steel is between 12% and 20%.

[0017] Furthermore, the volume fraction of the MC carbide is between 4% and 4.97%, and at least 80% of the volume fraction of the MC carbide has a particle size of ≤6 μm, and the maximum particle size of the MC carbide is not greater than 10 μm.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] Compared with existing materials, the high-speed steel described in the present invention improves the problems of serious core eutectic carbide segregation and coarse eutectic carbide particles in traditional cast and forged high-speed steels, and can also improve the problems of coarse carbide particles, poor grindability and low grinding efficiency of high-vanadium high-speed steel MC.

[0020] In the high-speed steel of the present invention, chromium, molybdenum, vanadium and tungsten are all essential carbide-forming elements. These metal elements combine with carbon to form high-hardness alloy carbides, wherein tungsten and molybdenum participate in the formation of M6C carbides, vanadium and niobium participate in the formation of MC carbides, and chromium participates in the formation of M23C6 carbides. When these carbides are precipitated from the liquid phase, they are wear-resistant phases, which can improve the wear resistance of the material. When these carbides are precipitated from the solid phase, they become strengthening phases, which can enhance the strength and hardness of the material, thereby improving the overall performance of the material.

[0021] Carbon is an alloying element necessary for forming carbides. In the present invention, the contents of the alloying elements tungsten, molybdenum, chromium and vanadium and carbon are selected according to the target hardness, wear resistance requirements and the carbide carbon ratio formula [Cp=0.033*W+0.063*Mo+0.06*Cr+0.2*V, wherein Cp represents the total content of carbide-forming elements, and W (tungsten), Mo (molybdenum), Cr (chromium) and V (vanadium) represent the contents of tungsten, molybdenum, chromium and vanadium, respectively].

[0022] In the present invention, the Cr content is controlled between 4.00% and 8.00%. If the Cr content is too low, the hardenability cannot be guaranteed, and if the Cr content is too high, coarse M23C6 eutectic carbides will appear.

[0023] In the present invention, increasing the content of molybdenum and tungsten is beneficial to attracting vanadium to participate in the formation of M2C eutectic carbide, which can reduce its presence in MC pre-eutectic carbide, thereby refining MC pre-eutectic carbide, and is beneficial to improving the red hardness of the material. The red hardness of the material is a key factor in determining the life of high-speed cutting tools and an important factor in distinguishing high-speed steel from general tool steel. In the present invention, the content of Mo is controlled between 3.00% and 6.00%, and the content of W is controlled between 3.00% and 6.50%. If the content of molybdenum and tungsten is too low, the red hardness cannot be guaranteed, and if it is too high, coarse eutectic carbide will be formed.

[0024] Vanadium forms high-hardness MC carbide particles in the high-speed steel, which can significantly improve the hardness, wear resistance and thermal stability of the steel. In the present invention, the V content is controlled between 2.00% and 5.00%. If the vanadium content is too low, the wear resistance cannot be guaranteed, and if it is too high, coarse MC pro-eutectic carbides are easily formed, resulting in reduced grindability.

[0025] Niobium and zirconium are stronger carbide-forming elements and participate in the formation of MC carbides. In the present invention, 1% niobium corresponds to 0.13% carbon, and 1% zirconium corresponds to 0.15% carbon. The MC carbides formed have a higher precipitation temperature, which is beneficial to inhibit the solidification segregation of eutectic carbides and to refine carbides, thereby improving the wear resistance and toughness of the material and improving the grindability of the material.

[0026] In the present invention, the content of Nb is controlled between 0.1% and 2.00%, and the content of Zr is controlled between 0.01% and 0.30%. If the content of niobium and zirconium is too low, pro-eutectic carbides cannot be formed, and if the content is too high, coarse MC pro-eutectic carbides are easily formed, resulting in reduced grindability.

[0027] Cobalt is a non-carbide forming element and does not participate in the formation of carbides. It can improve the thermal conductivity of the material and inhibit the precipitation and growth of carbides, thereby refining the carbide size, significantly improving the hardness and red hardness of the steel, and improving the grindability of the material. In the present invention, the cobalt content is controlled between 4.00% and 10.00%. Too low a cobalt content cannot guarantee red hardness, and too high a cobalt content is disadvantageous to the cost.

[0028] Silicon is a residual element, which is beneficial to improving the fluidity of molten steel. In the present invention, the silicon content is controlled between 0.10% and 0.4%.

[0029] Sulfur and phosphorus are residual harmful elements and are generally controlled below 0.030%. Since sulfur can improve grindability, for high-vanadium steel that is difficult to grind, the sulfur content can be controlled below 0.060%.

[0030] The high-speed steel of the present invention can generate a new steel type with 0.01-0.3% zirconium by rationally proportioning its chemical components, when the preparation components include Zr, and fine pre-eutectic carbides ZrC containing Zr (zirconium) can be detected by testing. When the preparation components include Nb and Zr, a new steel type containing 0.1-2% niobium and 0.01-0.3% zirconium can be generated, and fine pre-eutectic carbides (Nb, Zr) C containing Nb (niobium) and Zr (zirconium) can be detected by testing. The addition of these new components makes V in the prepared deposited ingot mainly exist in the eutectic carbide M2C, and decompose into fine M6C and MC in the heating process before forging, thereby giving the high-speed steel excellent wear resistance, good grindability and toughness.

[0031] It should be noted that wear resistance refers to the ability of a material to resist wear during friction and abrasion, that is, when a material is subjected to friction, its surface wears slowly. Grindability refers to the difficulty of a material in the grinding process and the degree of wear on the grinding tool during the grinding process. Toughness refers to the ability of a material to absorb energy and undergo plastic deformation without being destroyed when subjected to external forces, especially dynamic loads such as impact or stretching, before breaking.

[0032] At the same time, another object of the present invention is to provide a method for preparing high-speed steel, the method for preparing the high-speed steel as described above, and the method for preparing the high-speed steel comprises:

[0033] S1. Prepare high-speed steel liquid according to the chemical composition requirements of the above high-speed steel, excluding zirconium;

[0034] S2, slag making and deoxidation, adjust the temperature of the molten steel to a superheated degree between 100℃ and 150℃, add zirconium, stir evenly and then skim off the slag;

[0035] S3. The molten steel is transferred to a preheated tundish, and the molten steel is subjected to gas atomization treatment to deposit atomized powder to form a deposited ingot of high-speed steel.

[0036] Furthermore, in step S3, the temperature of the preheated tundish is between 600° C. and 800° C.; after step S3, the preparation method further comprises:

[0037] S4, performing a first annealing on the deposited ingot;

[0038] S5, heating and forging the deposited ingot, with the forging temperature being between 950° C. and 1100° C.;

[0039] S6. Perform a second annealing on the deposited ingot.

[0040] The method for preparing high-speed steel of the present invention is used to prepare the aforementioned high-speed steel. By reasonably matching alloy elements with a suitable preparation method, the core structure of the prepared high-speed steel is fine and uniform, and the grindability is good, and the grinding efficiency is high.

[0041] It should be noted that, when the preparation components include both Nb and Zr, Nb is not added in step S1. Specifically, in step S2, Nb and Zr are added together.

[0042] In the preparation method of this embodiment, in step S1, alloy elements other than niobium and zirconium are added when preparing molten steel, and in step S2, niobium and zirconium are added after slag making and deoxidation and adjusting the temperature of the molten steel to a superheat degree between 100°C and 150°C. Adding niobium and zirconium too early, especially zirconium, is prone to burnout, thereby reducing the yield.

[0043] In order to improve the performance of the prepared high-speed steel, the present invention has made breakthrough innovations in both alloy design concepts and preparation processes. While limiting specific chemical components and ratios, the present invention preferably adopts a rapid solidification process to reduce alloy element segregation based on the design characteristics of the chemical components, so that the performance of the finally prepared high-speed steel is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0045] Figure 1 The microstructure image of W6Mo5Cr4V3 high-speed steel prepared by casting and forging process for comparative example (1 / 4D, longitudinal, 100 times);

[0046] Figure 2 The microstructure image of W6Mo5Cr4V3 high-speed steel prepared by casting and forging process for comparative example (1 / 4D, longitudinal, 500 times);

[0047] Figure 3 This is a microstructure picture of the high-speed steel described in Example 7 of the present invention (1 / 4D, longitudinal, 100 times);

[0048] Figure 4 This is a microstructure image of the high-speed steel described in Example 7 of the present invention (1 / 4D, longitudinal, 500 times). DETAILED DESCRIPTION

[0049] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0050] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0051] The present embodiment relates to a high-speed steel, and in particular to an easy-to-grind high-performance high-speed steel, which has excellent wear resistance, thermal stability and processing performance, and is suitable for preparing high-precision tools and complex processing workpieces.

[0052] Based on the above design concept, the chemical components of the high-speed steel in this embodiment include, by mass percentage, C: 1.00% to 2.00%, Cr: 4.00% to 8.00%, Mo: 3.00% to 6.00%, V: 2.00% to 5.00%, W: 3.00% to 6.50%, Co: 4.00% to 10.00%, Zr: 0.01% to 0.30%, Si: 0.10% to 0.40%, and the remainder is iron and impurities.

[0053] As a preferred embodiment, the chemical components of the high-speed steel further include, by mass percentage: Nb: 0.10% to 2.00%.

[0054] As a preferred embodiment, the chemical components of the high-speed steel include, by mass percentage: C: 1.00% to 2.00%, Cr: 4.00% to 8.00%, Mo: 3.00% to 6.00%, V: 2.00% to 5.00%, W: 3.00% to 6.50%, Co: 4.50% to 8.50%, Zr: 0.01% to 0.25%, Si: 0.10% to 0.40%, and the remainder is iron and impurities.

[0055] As a further preferred embodiment, the chemical composition of the high speed steel includes a Nb content of between 0.10% and 2.00% by mass.

[0056] As a preferred implementation, the chemical composition of the high-speed steel of this embodiment further includes some inevitable impurities by mass percentage. Specifically, the impurities include at least one of oxygen (O), sulfur (S) and phosphorus (P).

[0057] Preferably, the impurities include O, and the chemical composition of the high-speed steel includes O≤0.01% by mass. Preferably, the impurities include S, and the chemical composition of the high-speed steel includes S≤0.060% by mass. Preferably, the impurities include P, and the chemical composition of the high-speed steel includes P≤0.030% by mass.

[0058] Next, the high-speed steel of this embodiment is prepared according to the following high-speed steel preparation method, which mainly includes material preparation, smelting, deoxidation temperature control slag removal, steel tapping, gas atomization, atomized steel liquid spray deposition, rotation and downward movement of the deposition tray, completion of spray deposition, standing, removing the deposited ingot, annealing the deposited ingot, heating forging, annealing, and finishing processes.

[0059] The specific preparation method is as follows:

[0060] S1. Prepare high-speed steel liquid according to the following chemical composition requirements of high-speed steel. Except for iron, the main metal elements are added in the form of alloys, and Nb and Zr are not added in this step. It should be noted that this step is smelted in an induction furnace, and the weight of the steel liquid is 1.2 tons.

[0061] S2. Slag making and deoxidation: adjust the temperature of the molten steel to a superheated degree between 100°C and 150°C, add niobium and zirconium, or add zirconium, stir evenly and then skim off the slag.

[0062] S3, transferring the molten steel to a preheated tundish, atomizing the molten steel, and allowing the atomized powder to be deposited to form a deposited ingot of the high-speed steel.

[0063] Table 1: Chemical composition of high-speed steel of various embodiments of the present invention and chemical composition of W6Mo5Cr4V3 prepared by conventional casting and forging process

[0064]

[0065]

[0066] In step S3, the temperature of the preheated tundish is between 600°C and 800°C, and the liquid level depth needs to be maintained at no less than 100 mm in this step.

[0067] Specifically, the molten steel is atomized through the ceramic nozzle below the tundish, and nitrogen is used as the gas medium during the atomization process, and the purity of nitrogen is >99.999%; the atomized molten steel is swung and sprayed to the rotating deposition tray, and the deposition tray is rotated and gradually moved down during the process, so that the distance between the deposition surface and the nozzle is maintained at any fixed distance between 30mm and 50mm, and in this embodiment, it is roughly maintained at 40mm. Before and after spray deposition, the interior of the spray deposition chamber is protected by nitrogen. After the spray deposition is completed, the diameter of the deposited ingot obtained is between 350mm and 400mm. After standing for 5min-10min, the deposited ingot is removed.

[0068] S4, annealing the deposited ingot. This step needs to be performed in a protective atmosphere furnace such as a nitrogen atmosphere.

[0069] S5, heating the deposited ingot for forging, the forging temperature is between 950℃ and 1100℃, in this embodiment, the forging temperature is 1050℃, and a forged bar with a diameter between 50mm and 200mm is obtained. In this step, it is also feasible to make the thickness after forging between 50mm and 100mm and the width between 80mm and 200mm.

[0070] S6. Anneal the forged bar. This step needs to be carried out in a protective atmosphere furnace such as a nitrogen atmosphere, followed by finishing, straightening, peeling, flaw detection and cutting.

[0071] By observing and testing the microstructures of Examples 1, 2, 3 and the comparative example, it was found that the red hardness of the high-speed steel prepared in Example 1 was improved due to the addition of cobalt, but the eutectic carbide was coarse. The red hardness of the high-speed steel prepared in Example 3 was also improved due to the addition of zirconium, and the eutectic carbide was better refined. In Example 2, the red hardness of the high-speed steel prepared was significantly improved due to the simultaneous addition of cobalt and zirconium, and the eutectic carbide was better refined.

[0072] By observing the microstructures of the high-speed steels of Examples 6 to 9 and testing them, it was found that when the amount of cobalt added was small, such as in Example 6, the red hardness of the prepared high-speed steel was not improved much, and when the amount of cobalt added was large, such as in Example 9, the red hardness of the prepared high-speed steel was not significantly improved compared with Example 8. Therefore, the cobalt content in this embodiment is limited to 4.00% to 10.00%.

[0073] By observing and testing the microstructures of the high-speed steels of Examples 7, 10 to 13, it was found that when the amount of zirconium added was small, such as in Example 10, the eutectic carbide refinement of the prepared high-speed steel was not obvious, and when the amount of zirconium added was large, such as in Example 13, the prepared high-speed steel was prone to nozzle clogging. Therefore, the zirconium content in this embodiment was limited to 0.01% to 0.3%.

[0074] The high-speed steels prepared in Example 4 and Example 5 were tested, and the carbides in the high-speed steels included MC carbides, M2C carbides, M6C carbides and M23C6 carbides. The type of MC carbides was (V, Nb, Zr)C, the type of M2C carbides was (W, Mo, Cr, V, Fe)2C, the type of M6C carbides was (W, Mo, Fe)6C, and the type of M23C6 carbides was (Cr, Fe)23C6.

[0075] It should be noted that MC is a pro-eutectic carbide, M2C and M6C are eutectic carbides, and M23C6 is a eutectoid carbide, wherein the volume fraction of the pro-eutectic carbide and the eutectic carbide is between 12% and 20%.

[0076] Specifically, the volume fractions of MC carbides, M2C carbides and M6C carbides are between 12% and 20%, the volume fraction of MC carbides is between 4% and 4.97%, and at least 80% of the volume fraction of MC carbides has a particle size of ≤6 μm, and the maximum particle size of MC carbides is not greater than 10 μm.

[0077] As shown in the above embodiments, the volume fraction of MC carbide in Example 7 is 4.84%, of which the volume fraction of (Nb, Zr)C containing Nb and Zr is 0.56%, and the maximum size of MC carbide is 7.6μm, which is 4.7μm smaller than that of existing materials (comparative example, cast and forged W6Mo5Cr4V3).

[0078] The forged bars of the high speed steel of Example 7 were tested for bending strength (5 samples, quenched at 1180°C and tempered at 550°C for 3 times, each for 1 hour). The bending strength was between 2800 MPa and 3100 MPa, and the average bending strength was 2985 MPa.

[0079] The forged bars of the high-speed steel of Comparative Example 3 were tested for bending strength (5 samples, quenched at 1180°C and tempered at 550°C for 3 times, each for 1 hour). The bending strength was between 3300 MPa and 3602 MPa, and the average bending strength was 3432 MPa.

[0080] The results show that the bending strength of the high-speed steel of Example 7 is about 15% higher than that of the high-speed steel of Comparative Example 3.

[0081] Gear hobs are made from the deposited ingots prepared in each embodiment of the present invention, and are ground after heat treatment. The grinding time of the high-speed steel gear hob of Example 7 is 180 minutes (the grinding time of the high-speed steel gear hob of the comparison example is 235 minutes), and the grinding efficiency is improved by more than 30%. The number of workpieces processed by a single grinding of the high-speed steel gear hob of Example 7 is 36 (the number of workpieces processed by a single grinding of the high-speed steel gear hob of the comparison example is 27), and the tool life is improved by more than 30%.

[0082] The comparative data of carbide size and bending strength of the high speed steel prepared in Example 7 and the comparative example are shown in Table 2.

[0083] Table 2. Comparison of carbide size and bending strength (Continued Table 2)

[0084]

[0085] The high-speed steel in this embodiment is prepared by the injection molding process, which can improve the uniformity, density and mechanical properties of the material. During the gas atomization process, the molten metal is rapidly solidified and formed, which can reduce the defects such as segregation, coarse carbides and shrinkage cavities that are easy to appear in the traditional ingot casting process. Segregation refers to the uneven distribution of different elements in the alloy during the solidification process, and this uneven distribution will affect the performance of the material. The high-speed steel in this embodiment is prepared by the gas atomization process, so that the elements in the prepared high-speed steel can be more evenly distributed, thereby better improving the overall performance of the prepared high-speed steel.

[0086] It should be noted that the high-speed steel of this embodiment can be prepared not only by the injection molding process, but also by the powder metallurgy process or the casting and forging process. The powder metallurgy process has the following advantages: no carbide segregation, uniform and fine carbide particles, easy grinding during the processing of tools or parts, and the processed tools or parts have good toughness and long life.

[0087] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high speed steel, characterized in that: The chemical components of the high-speed steel include, by mass percentage: C: 1.00%-2.00%, Cr: 4.00%-8.00%, Mo: 3.00%-6.00%, V: 2.00%-5.00%, W: 3.00%-6.50%, Co: 4.00%-10.00%, Zr: 0.01%-0.30%, Si: 0.10%-0.40%, and the remainder is iron and impurities.

2. The high speed steel according to claim 1, characterized in that: The chemical components of the high-speed steel further include, by mass percentage: Nb: 0.10% to 2.00%.

3. The high speed steel according to claim 2, characterized in that: The chemical components of the high-speed steel include, by mass percentage: C: 1.00%-2.00%, Cr: 4.00%-8.00%, Mo: 3.00%-6.00%, V: 2.00%-5.00%, W: 3.00%-6.50%, Co: 4.50%-8.50%, Zr: 0.01%-0.25%, Si: 0.10%-0.40%, and the remainder is iron and impurities.

4. The high speed steel according to claim 2, characterized in that: The content of Nb is between 0.10% and 1.20%.

5. The high speed steel according to claim 2, characterized in that: The impurities include at least one of O, S and P, and O≤0.01%, S≤0.060%, and P≤0.030%.

6. The high speed steel according to any one of claims 2 to 5, characterized in that: The carbides in the high-speed steel include MC carbides, M2C carbides, M6C carbides and M23C6 carbides. The type of the MC carbides is (V, Nb, Zr)C, the type of the M2C carbides is (W, Mo, Cr, V, Fe)2C, the type of the M6C carbides is (W, Mo, Fe)6C, and the type of the M23C6 carbides is (Cr, Fe)23C6.

7. The high speed steel according to claim 6, characterized in that: The volume fraction of the MC carbide, the M2C carbide and the M6C carbide in the high-speed steel is between 12% and 20%.

8. The high speed steel according to claim 7, characterized in that: The volume fraction of the MC carbide is between 4% and 4.97%, and at least 80% of the volume fraction of the MC carbide has a particle size of ≤6 μm, and the maximum particle size of the MC carbide is not greater than 10 μm.

9. A method for preparing high speed steel, characterized in that: The preparation method is used to prepare the high-speed steel according to any one of claims 1 to 8, and the preparation method comprises: S1. preparing high-speed steel liquid according to the chemical composition requirements of the high-speed steel, excluding zirconium; S2, slag making and deoxidation, adjusting the temperature of the molten steel to a superheated degree between 100°C and 150°C, adding zirconium, stirring evenly and then skimming the slag; S3, transferring the molten steel to a preheated tundish, performing gas atomization treatment on the molten steel, and allowing atomized powder to be deposited to form a deposited ingot of the high-speed steel.

10. The method for preparing high speed steel according to claim 9, characterized in that: In step S3, the temperature of the preheated tundish is between 600°C and 800°C; After step S3, the preparation method further comprises: S4, performing a first annealing on the deposited ingot; S5, heating and forging the deposited ingot, with the forging temperature being between 950° C. and 1100° C.; S6. Performing a second annealing on the deposited ingot.

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