Powder metallurgy corrosion resistant precipitation hardened high speed steel

Abstract

The application provides a powder metallurgy corrosion-resistant precipitation-hardened high-speed steel, which comprises the following components in percentage by mass: Si: 0.5%-1.2%; Cr: 2.0%-15.0%; Co: 8.0%-16.0%; W: 0%-5.0%; Mo: 18.0%-25.0%; (Mo+W / 2): 18.0%-27.0%; the balance is iron and impurities, and the steel mainly consists of an iron-based cubic solid solution matrix and an intermetallic compound (IMC) mu phase in the matrix, wherein the mu phase is of the (Fe,Co)7(Mo+W / 2)6 type. The powder metallurgy corrosion-resistant precipitation-hardened high-speed steel prepared by the application has fine mu phase size and uniform distribution, and has excellent comprehensive performance, especially outstanding corrosion resistance and tempering softening resistance, and can meet the requirements of different working conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to a precipitation hardening high speed steel, in particular to a powder metallurgy corrosion resistant precipitation hardening high speed steel. BACKGROUND

[0002] In the field of aerospace and marine chemical industry, tools or parts not only need to bear working stress load and impact, but also need to withstand the corrosion of moisture, acid or other corrosive media. In order to be suitable for these working conditions and have a long service life, the material must have good strength and toughness matching and corrosion resistance.

[0003] Precipitation hardening steel is a carbon-free ferritic martensitic precipitation hardening tool alloy. Due to the low content of C in the composition, no carbide is precipitated, and the structure is mainly ferritic matrix and Fe-Co-Mo-W intermetallic compound (i.e. IMC). The hardening effect is due to the precipitation of IMC particles during aging process. This kind of precipitation hardening high speed steel has good grindability and resistance to temper softening, and good dimensional stability.

[0004] However, due to the limitation of the slow cooling and solidification characteristics of the steel liquid in the process of using traditional casting and forging process to prepare the precipitation hardening high speed steel, the alloy composition is easy to segregate during solidification. This undesirable structure cannot be effectively solved by hot processing, which will adversely affect the performance of the alloy, resulting in low levels of strength, toughness, grindability and other properties of the high speed steel, which is difficult to meet the requirements of high-end machining and manufacturing on material performance and service life. The corrosion resistance of the existing precipitation hardening steel is also difficult to meet the use in high-end field. SUMMARY

[0005] Therefore, the present application provides a powder metallurgy precipitation corrosion resistant hardening high speed steel with good structure and excellent performance.

[0006] To achieve the above purpose, the technical scheme of the present application is as follows:

[0007] A powder metallurgy corrosion resistant precipitation hardening high speed steel, characterized in that the steel comprises the following chemical components in mass percentage:

[0008] Si: 0.5%-1.2%;

[0009] Cr: 2.0%-15.0%;

[0010] Co: 8.0%-16.0%;

[0011] W: 0%-5.0%;

[0012] Mo: 18.0%-25.0%;

[0013] (Mo+W / 2): 18.0%-27.0%;

[0014] balance: iron and impurities;

[0015] and the intermetallic compound (i.e. IMC phase) in the precipitation hardening high speed steel is μ phase, and the type of μ phase is (Fe,Co)7(Mo+W / 2)6.

[0016] The present application can promote the precipitation of μ phase when the precipitation hardening high speed steel is prepared by adopting the powder metallurgy process through the reasonable design of alloy components and proportion, thereby improving the temper softening resistance and corrosion resistance of the steel.

[0017] Specifically, the Co in the precipitation hardening high speed steel in the present application is dissolved in the matrix to make the alloy become a martensitic steel, thereby increasing the hardness and strength of the alloy by one level compared with ferrite alloy, and the increase of Co content can appropriately reduce the toughness of the steel, and the Co content in the present application is in the range of 8.0%-16.0%, preferably 10.0%-16.0%.

[0018] W has a high melting point, which can increase the strength and temper stability of the steel, and the high temperature creep resistance, and increase the temper softening resistance of the steel, so that the surface layer of the steel has less temperature rise and less hardness drop during processing and use, and the W content in the present application is in the range of 0%-5.0%, preferably 0%-3.0%.

[0019] Mo has the same effect as W, can completely replace W, and the price is lower than W. On the other hand, the higher the Mo content, the higher the initial precipitation temperature of μ phase, and the larger the particle size of μ phase, and the Mo content in the present application is in the range of 18%-25.0%, preferably 18.0%-22.0%.

[0020] The Cr added to the steel has two effects: one is to coarsen the particles, so that the red hardness is reduced and the machinability is improved; on the other hand, part of Cr is dissolved in the matrix, which can improve the corrosion resistance and hardenability of the steel. In the present application, the Cr content is in the range of 2.0%-15.0%, preferably 2.0%-12.0%.

[0021] Si is not a carbide forming element, but is used as a deoxidizer and matrix strengthening element, which can improve the strength and hardness of the steel, but too much Si will reduce the plasticity and toughness of the matrix, and the Si content in the present application is controlled in the range of 0.5%-1.2%, preferably 0.5%-1.0%.

[0022] As a limitation of the above-mentioned manner, the powder metallurgy corrosion-resistant precipitation hardening high speed steel comprises the following chemical components by mass percentage:

[0023] Si: 0.5%-1.0%;

[0024] Cr: 2.0% - 12.0%;

[0025] Co: 10.0% - 16.0%;

[0026] W: 0% - 3.0%;

[0027] Mo: 18.0% - 22.0%;

[0028] (Mo + W / 2): 18.0% - 23.5%;

[0029] the balance being iron and impurities.

[0030] In order to achieve better comprehensive performance, the chemical components in the powder metallurgy corrosion-resistant precipitation-hardening high-speed steel should be controlled within the required range.

[0031] Further, at least 80% of the volume fraction of the μ phase has a particle size ≤ 1.5 μm.

[0032] Further, the maximum particle size of the μ phase is not more than 6.0 μm.

[0033] Further, the volume fraction of the μ phase in the powder metallurgy corrosion-resistant precipitation-hardening high-speed steel is 15-27%.

[0034] Further, the hardness of the powder metallurgy corrosion-resistant precipitation-hardening high-speed steel is above 63 HRC, and the impact toughness value of the unnotched sample is above 12.0 J.

[0035] In the present application, the powder metallurgy process is used to prepare the precipitation-hardening steel, which can solve the problem of element segregation and obtain a uniform microstructure. The main steps of the powder metallurgy process for preparing the precipitation-hardening high-speed steel include: atomization powdering → hot isostatic pressing forming. The steel liquid is rapidly cooled into powder, and the alloy elements in the steel liquid completely solidify without segregation. After the powder is consolidated into a material, the microstructure is fine and uniform. Compared with the precipitation-hardening high-speed steel produced by traditional casting or electroslag process, the performance is greatly improved.

[0036] The present application also provides a preparation method for the powder metallurgy corrosion-resistant precipitation-hardening high-speed steel as described above, and the preparation method specifically comprises the following steps:

[0037] s1. preparing a precipitation-hardening steel liquid according to the above chemical composition requirements and transferring it to a ladle;

[0038] s1.1. maintaining the superheat of the steel liquid by heating the protective slag covering the upper surface of the steel liquid in the ladle; and stirring the steel liquid by introducing inert gas at the bottom of the ladle;

[0039] s1.2. The molten steel is flowed into the preheated tundish through the flow guide pipe at the bottom of the ladle at a stable flow rate, and a protective slag is applied to the upper surface of the molten steel when the molten steel enters the tundish and covers the lower end surface of the flow guide pipe;

[0040] s1.3. The tundish is continuously compensated and heated to maintain the superheat of the molten steel;

[0041] s1.4. After the molten steel enters the atomization chamber from the tundish, inert gas is used for atomization and powder preparation, and the obtained metal powder is settled at the bottom of the atomization chamber and then enters the powder storage tank with a protective atmosphere, and the metal powder is screened through a protective screening device and then enters the powder storage tank for storage;

[0042] s1.5. Under the protection of inert gas, the metal powder in the powder storage tank is transferred to the hot isostatic pressing jacket, and after the metal powder is vibrated and packed tightly, the hot isostatic pressing jacket is subjected to vacuum degassing treatment, the end part is subjected to sealing welding treatment, and then hot isostatic pressing treatment is carried out to make the metal powder completely dense and solidified, and the powder metallurgy process is completed.

[0043] The above-mentioned powder metallurgy process includes non-vacuum melting, atomization and powder preparation, and hot isostatic pressing, and the whole process is protected to control the oxygen content and the morphology of precipitated phases and optimize the performance of the precipitation hardened steel.

[0044] The protective slag of the ladle has the functions of air insulation and conductive heating, and the inert gas is introduced into the ladle through the air hole at the bottom of the ladle, so that the temperature of the molten steel at different positions in the ladle is balanced, and the removal of harmful inclusions is accelerated. The flow guide pipe at the bottom of the ladle plays a role in guiding the flow of the molten steel, reducing turbulence during the flow of the molten steel, avoiding slag entrainment and preventing inclusions from entering the next process. On the other hand, the flow guide pipe prevents the molten steel from being exposed to air, preventing the oxygen content of the molten steel from rising. Preheating the tundish before the molten steel enters the tundish can prevent local condensation of the molten steel when it enters the tundish.

[0045] The powder storage tank has the functions of atmosphere protection and forced cooling, the powder protective screening device plays a protective role during powder screening and prevents powder from floating, the powder storage tank is sealingly connected with the hot isostatic pressing jacket, and the hot isostatic pressing jacket is filled with inert gas to discharge air before powder is loaded, which can prevent the oxygen content in the powder from rising.

[0046] The precipitation hardened high-speed steel of the present application is prepared by powder metallurgy process, the component design is reasonable, various effective protection measures are taken during preparation to prevent the molten steel and powder from being contaminated, and due to the specific chemical composition and the rapid condensation process of powder metallurgy, the precipitated intermetallic compound mu phase is more fine and uniform, has excellent hardness, corrosion resistance, temper softening resistance and toughness, and after solid solution and aging treatment, the hardness is above 63HRC, the unnotched impact toughness is above 12.0J, and it is suitable for use in working conditions with load and corrosive medium at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0047] The accompanying drawings, which form a part of the present application, are intended to provide further understanding of the application and are incorporated herein for a description of the application. The drawings are not intended to limit the present application and are merely used for illustrative purposes. In the drawings:

[0048] Figure 1 Microstructure of the precipitation hardening high speed steel prepared in Example 1 of the present application;

[0049] Figure 2 Microstructure of the precipitation hardening high speed steel prepared in Example 2 of the present application;

[0050] Figure 3 Microstructure of the precipitation hardening high speed steel prepared in Example 4 of the present application;

[0051] Figure 4 Microstructure of the precipitation hardening high speed steel prepared in Example 5 of the present application;

[0052] Figure 5 Microstructure of the precipitation hardening high speed steel prepared in Example 6 of the present application;

[0053] Figure 6 Microstructure of the precipitation hardening high speed steel prepared in Example 7 of the present application;

[0054] Figure 7 Microstructure of the corrosion resistant tool steel prepared in Comparative Example A of the present application;

[0055] Figure 8 Microstructure of the powder metallurgy high speed steel prepared in Comparative Example B of the present application. DETAILED DESCRIPTION

[0056] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0057] The present application will be described in detail below with reference to the accompanying drawings and embodiments.

[0058] The present application relates to a group of powder metallurgy corrosion resistant precipitation hardening high speed steels, which comprises the following chemical components in percentage by mass: Si: 0.5%-1.2%; Cr: 2.0%-15.0%; Co: 8.0%-16.0%; W: 0%-5.0%; Mo: 18.0%-25.0%; (Mo+W / 2): 18.0%-27.0%; the balance being iron and impurities; and, the intermetallic compound (i.e. IMC phase) in the precipitation hardening steel is μ phase, and the type of the μ phase is (Fe,Co)7(Mo+W / 2)6.

[0059] The present application can promote the precipitation of mu phase, improve the temper softening resistance, corrosion resistance and toughness of the steel by the reasonable design of alloy composition and ratio when the powder metallurgy process is used to prepare the precipitation hardening high speed steel.

[0060] Secondly, the present application also relates to the method for preparing the precipitation hardening high speed steel, when the traditional ingot or electroslag process is used to prepare, the segregation is easy to occur due to the slow solidification speed, which leads to the performance decline. Therefore, in order to ensure that the prepared precipitation hardening high speed steel ingot has uniform composition and organization, small mu phase and high purity, the powder metallurgy process is used to prepare the steel ingot, and then the required rod product is obtained through forging.

[0061] Specifically, the preparation method of the present application comprises the following steps:

[0062] s1. The molten steel of the present application is loaded into a melting ladle, and the molten steel loading weight is 1.5-8 tons;

[0063] s1.1. The graphite electrode is used to heat the protective slag covered on the upper surface of the molten steel in the ladle, the argon or nitrogen gas is introduced into the bottom of the ladle to stir the molten steel, and the molten steel overheat degree reaches 100-200℃ to open the molten steel flow guide pipe;

[0064] s1.2. The molten steel flows into the tundish preheated to 800-1200℃ through the flow guide pipe at the bottom of the ladle at a flow rate of 10-50 Kg / min, and the protective slag is applied when the molten steel enters the tundish and covers the lower end surface of the flow guide pipe;

[0065] s1.3. The tundish is continuously compensated and heated during the atomization and powder preparation process, and the overheat degree of the molten steel is maintained at 100-200℃;

[0066] s1.4. The molten steel enters the atomization chamber through the bottom of the tundish, the atomization gas injection valve is opened, nitrogen gas is used as the gas medium for atomization and powder preparation, the purity of the nitrogen gas is ≥99.999%, the oxygen content is ≤2ppm, and the outlet pressure of the gas nozzle is 1.0-5.0MPa; the molten steel is broken into droplets under the action of nitrogen gas injection, and is rapidly cooled into metal powder, flies to the bottom of the atomization chamber, and then enters the powder storage tank body with a protective atmosphere; after the atomization and powder preparation is completed, the metal powder in the powder storage tank body is cooled to room temperature, and the metal powder is screened through the protective screening device; the inert protective gas is introduced into the cavity of the protective screening device, and the powder storage tank is in a positive pressure inert gas protective atmosphere;

[0067] s1.5 Fill the metal powder in the powder storage tank into the hot isostatic pressing bag, first, inert gas is introduced into the hot isostatic pressing bag to discharge air, then the hot isostatic pressing bag and the powder storage tank are tightly connected, the filling process is carried out by vibration operation to increase the filling density of the metal powder; after completion, the hot isostatic pressing bag is subjected to vacuum degassing treatment, the hot isostatic pressing bag is heated and kept at 200-600℃ during the vacuum process, degassing is carried out to 0.01 Pa, then heating and keeping for more than 2h, then the end of the bag is subjected to sealing welding treatment, finally the bag is subjected to hot isostatic pressing treatment, the hot isostatic pressing temperature is 1100-1180℃, the pressure is ≥100MPa, the holding time is ≥1h, then the metal powder is completely densified and solidified, then the furnace is cooled, and the powder metallurgy process is completed.

[0068] s2. Open the forging blank

[0069] According to the need, the precipitation hardening high speed steel of the application is further forged and deformed to obtain a rod or a forging with a certain shape and size, and different properties are obtained by using different heat treatment systems. The heat treatment used includes annealing, solid solution and aging. The annealing treatment involves heating the rod or forging to 870-890℃, keeping for ≥2h, then cooling to below 530℃ at a speed of ≤15℃ / h, and then furnace cooling or static air cooling to below 50℃; the solid solution treatment involves preheating the annealed rod or forging at a temperature of 810-850℃, then placing it in a temperature of 1170-1200℃ for 15-40min and oil cooling after uniform temperature; then aging at a temperature of 580-650℃, keeping for 3-4h, and then air cooling to 50℃.

[0070] The powder metallurgy corrosion-resistant precipitation hardening high speed steel and its preparation of the application will be further described below with specific prepared examples and comparative examples, and corresponding performance detection.

[0071] Through the above preparation method, eight kinds of precipitation hardening high speed steels with different component compositions are obtained, and are compared with cast and forged tool steel (alloy A) and powder metallurgy tool steel (alloy B), and the results are as follows:

[0072] Table 1: Component composition comparison

[0073]

[0074] In the table, "-" means that the element is not contained or the content of the element is very small and is not analyzed.

[0075] (I) Microstructure analysis

[0076] Based on the scanning electron microscope to obtain the microstructure image, Figures 1 to 6are microstructure diagrams of the prepared precipitation hardened steel forgings of example 1, example 2, example 4, example 5, example 6, example 7 respectively, Figure 7 is a microstructure diagram of alloy A, Figure 8 is a microstructure diagram of alloy B.

[0077] It is obvious that, Figures 1 to 6 The hardened phase in medium gray white is dispersed in the matrix, Figure 7 and Figure 8 Two kinds of precipitated phases are contained in the microstructure, one kind is bright white and large in size, and the other kind is gray white and small in size. Because the hardened phase in examples 1-7 is dispersed in the matrix in a fine and dispersed manner, the wear resistance, toughness and service life of the material can be significantly improved.

[0078] The content, particle size and composition of the precipitated phase in the high-speed steel prepared in examples 1 to 8 and alloys A and B after heat treatment are compared, as shown in table 2.

[0079] Table 2: content and chemical composition of precipitated phase

[0080]

[0081] "-" in the table indicates that the element is not contained or the content of the element is very small and is not analyzed

[0082] As can be seen from table 2, in examples 1 to 8, the detected IMC is mainly μ phase, the type is (Fe, Co)7(Mo+W / 2)6, and the main components are Fe, Co, Mo, W and a small amount of Si and other alloying elements. In alloys A and B, the detected strengthening phase is mainly Cr-rich carbide, the type is (Cr, Fe)C type carbide, the composition is mainly C, V, Cr and Fe, and contains a small amount of Mo. In addition, VC type carbide also exists in alloy B, and the composition is mainly C, V, Cr and Fe.

[0083] The volume fraction of the μ phase of the precipitation hardened high-speed steel of the present application reaches 15%-27%, the particle size is small, most of the μ phase particle size is ≤1.5 μm, and the maximum size is not more than 6.0 μm. These precipitated phases are small in size and high in dispersion, and the high-temperature aggregation resistance of the μ phase is higher than that of the carbide, so that the material has better wear resistance, toughness and service life.

[0084] The VC type carbide in the alloy B prepared by the powder metallurgy process is the finest, most of the VC type carbide is ≤1.5 μm, the maximum size is ≤5.0 μm, the volume fraction is 3.81%, but there are also a large number of (Cr, Fe) C type carbides with a size range of 5-9 μm in the structure. The coarse carbide has an adverse effect of cutting the matrix. A small amount of VC type carbide with a fine particle size exists in the A alloy produced by the ingot casting process, most of the VC type carbide is ≤1.5 μm, but there are also a large number of (Cr, Fe) C type carbides with a size range of 5-12 μm in the same structure, which has an adverse effect on the performance.

[0085] (II) Hardness and impact toughness analysis of heat treatment

[0086] In order to verify the effect of the heat treatment system on the performance of the prepared precipitation hardening high speed steel, the prepared rods are heat treated by setting different solid solution temperatures and aging temperatures, and the parameter setting is referred to GB / T 230.1 and GB / T 229.

[0087] The prepared hardened steels and alloys A and B in examples 1 to 8 are heat treated, and the obtained hardness and impact toughness comparison results are shown in Table 3.

[0088] Table 3: Comparison of mechanical properties

[0089]

[0090] As can be seen from Table 3, the hardness of the powder metallurgy corrosion-resistant precipitation hardening high speed steel of the present application is above 63 HRC, and the impact toughness value of the unnotched sample is above 12.0 J. Although the impact toughness of the precipitation hardening high speed steel of the present application is relatively low, the measured value meets the demand for toughness in the application field, so the precipitation hardening high speed steel of the present application is especially suitable for occasions with less impact load.

[0091] (III) Corrosion resistance analysis

[0092] Examples 1 to 8 and alloys A and B are immersed in 5% HNO3+1% HCl solution at room temperature for corrosion, and then the corrosion rate is measured. Then the polarization curve is measured in 1% NaCl solution, and finally the self-corrosion potential is obtained. The comparison results of the corrosion resistance are shown in Table 4, and the verification parameters are set with reference to JB / T 7901 and GB / T 17899.

[0093] Table 4: Comparison of corrosion resistance

[0094]

[0095] As can be seen from the comparative data in Table 4, the precipitation hardening steel of the present application exhibits more excellent corrosion resistance. Since the C content in the precipitation hardening steel of the present application is very small, it will not precipitate with Cr in the form of carbide, and most of the Cr elements in the steel are solid-solved in the matrix, so that higher corrosion resistance can be obtained. The precipitation hardening high-speed steel of the present application can have good strength and toughness and corrosion resistance, thereby meeting the requirements of specific working conditions.

[0096] In addition, due to the limitation of the precipitated phase particle quantity statistical image analysis software, under the above implementation conditions, the precipitation hardening steel of the present application may have individual μ phase with a size exceeding the maximum size in the structure, but due to the extremely small number, it has no substantial effect on the toughness and other mechanical properties of the precipitation hardening steel, and thus can be ignored. In addition, many more fine μ phases cannot be identified by the analysis software, and the statistical results of the volume fraction and particle size are only for comparison.

[0097] Based on the above description, it can be found that, as preferred, the precipitation hardening high-speed steel of the present application comprises the following chemical components in terms of mass percentage: Si: 0%-0.8%; Mn: 0%-0.3%; Cr: 2.0%-12.0%; Co: 10.0%-16.0%; W: 0%-3.0%; Mo: 18.0%-22.0%; (Mo+W / 2): 12.0%-25.0%; and the balance is iron and impurities. The precipitation hardening high-speed steel composed of the above components can obtain ideal structure and excellent performance to meet the requirements.

[0098] In order to achieve better comprehensive performance, each chemical component in the powder metallurgy corrosion-resistant precipitation hardening high-speed steel of the present application should be controlled within the required range. Specifically, at least 80% of the μ phase has a size of ≤1.5 μm, the maximum size of the μ phase is not more than 6.0 μm, and the volume fraction of the μ phase is 15-27%.

[0099] Due to the use of specific alloy composition design and the use of powder metallurgy process for preparation, the material has high intermetallic compound μ phase content, fine particle size, high dispersion, and high high-temperature aggregation resistance than carbide, so that the material has good toughness and better service life, and can meet the application requirements of different types, and can be used to make (1) cutting tools under high-speed cutting, cutting difficult-to-machine materials; (2) high-precision gauges; (3) corrosion-resistant parts, etc.

[0100] In summary, the powder metallurgy corrosion-resistant precipitation hardening high-speed steel of the present application has excellent mechanical properties, especially good corrosion resistance. Due to the characteristics of its alloy composition, it is different from the traditional high-speed steel strengthening mechanism, which greatly improves the anti-tempering softening capacity of the traditional high-speed steel and other tool steels.

[0101] The above merely provides the preferred embodiment 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 should be included in the protection scope of the present application.

Claims

1. A powder metallurgy corrosion resistant precipitation hardened high speed steel, characterized in that, The chemical composition includes, by mass percent: Si: 0.5% - 1.2%; Cr：2.0％-15.0％； Co: 8.0% - 16.0%; W：0％-5.0％； Mo: 18.0% - 25.0%; (Mo + W / 2): 18.0% - 27.0%; the balance being iron and impurities; and, the intermetallic compound in the powder metallurgy high speed steel is μ phase, the type of μ phase is (Fe, Co)7(Mo + W / 2)6.

2. The powder metallurgy corrosion resistant precipitation hardened high speed steel of claim 1, wherein, The chemical composition includes, by mass percent: Si: 0.5% - 1.0%; Cr：2.0％-12.0％； Co: 10.0% - 16.0%; W：0％-3.0％； Mo: 18.0% - 22.0%; (Mo + W / 2): 18.0% - 23.5%; the balance being iron and impurities.

3. Powder metallurgical corrosion resistant precipitation hardened high speed steel according to claim 1 or 2, characterized in that: At least 80% of the volume fraction of the μ phase has a particle size ≤ 1.5 μm.

4. The powder metallurgy corrosion resistant precipitation hardened high speed steel according to claim 1 or 2, characterized in that: The maximum particle size of the μ phase is no more than 6.0 μm.

5. The powder metallurgy corrosion resistant precipitation hardened high speed steel of claim 1 or 2, characterized in that: The volume fraction of the μ phase in the powder metallurgy corrosion resistant precipitation hardened high speed steel is 15 - 27%.

6. The powder metallurgy corrosion resistant precipitation hardened high speed steel of claim 1 or 2, characterized in that: The hardness of the powder metallurgy corrosion resistant precipitation hardened high speed steel is 63 HRC or more, and the unnotched impact toughness value is 12.0 J or more.

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