Powder High-Speed ​​Steel

Abstract

To provide powder high speed steel which is excellent in abrasion resistance and softening resistance.SOLUTION: A metallic structure of powder high speed steel contains a matrix 4, a primary carbide 4, and an eutectic carbide 6. The primary carbide 4 and the eutectic carbide 6 are dispersed in a matrix 2. An element ratio AR calculated by the following expression of the powder high speed steel is 15 or more and 40 or less. AR=(Cr%+Mo%+0.5 W%+V%) / (Mn%+Si%+Al%). In the expression, Cr% represents a mass content of Cr, Mo% represents a mass content of Mo, W% represents a mass content of W, V% represents a mass content of V, Mn% represents a mass content of Mn, Si% represents a mass content of Si%, and Al% represents a mass content of Al.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This specification discloses a powder metallurgically obtained high speed steel. [Background technology]

[0002] High-speed steel is used in cutting tools. High-speed steel is also called "high-speed tool steel." High-speed steel obtained by powder metallurgy is called "powdered high-speed steel." Powdered high-speed steel is also called "powdered high-speed steel" or "sintered high-speed steel."

[0003] Cutting tools require wear resistance. Powder high-speed steels intended to improve wear resistance are disclosed in Japanese Patent Laid-Open Publication Nos. 2001-294986 and 2015-160957. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-294986 A [Patent Document 2] JP 2015-160957 A Summary of the Invention [Problem to be solved by the invention]

[0005] The powder high-speed steel described in JP 2001-294986 A has insufficient wear resistance, and the powder high-speed steel described in JP 2015-160957 A has room for improvement in terms of softening resistance.

[0006] The applicant's intention is to provide a powder high speed steel having excellent wear resistance and softening resistance. [Means for solving the problem]

[0007] The preferred powder high speed steel is C: 1.00% by mass or more and 1.90% by mass or less, Si: 0.10% by mass or more and 1.00% by mass or less, Mn: 0.10% by mass or more and 1.00% by mass or less, Cr: 2.0 mass% or more and 7.0 mass% or less, Mo: 2.0% by mass or more and 7.0% by mass or less, W: 3.0% by mass or more and 15.0% by mass or less, V: 2.0% by mass or more and 5.0% by mass or less, Co: 0.0% by mass or more and 15.0% by mass or less, Al: 0.000 mass% or more and 0.500 mass% or less and N: 0.000 mass% or more and 0.100 mass% or less The balance is Fe and unavoidable impurities. This high-speed steel contains primary carbides and eutectic carbides in its metal structure. The element ratio AR calculated by the following formula is 15 or more and 40 or less. AR = (Cr% + Mo% + 0.5W%+ V%) / (Mn% + Si% + Al%) In this formula, Cr% represents the mass content of Cr, Mo% represents the mass content of Mo, W% represents the mass content of W, V% represents the mass content of V, Mn% represents the mass content of Mn, Si% represents the mass content of Si, and Al% represents the mass content of Al. [Effects of the Invention]

[0008] This powder high-speed steel has excellent wear resistance and softening resistance. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a photomicrograph showing the metal structure of a powder high-speed steel according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] The high-speed steel according to this embodiment is obtained by powder sintering. In other words, this alloy is a sintered body. The powder is typically obtained by atomization. This powder high-speed steel is obtained through heat treatment. Typical heat treatments include annealing, quenching, and tempering.

[0011] [composition] This powder high-speed steel is C: 1.00% by mass or more and 1.90% by mass or less, Si: 0.10% by mass or more and 1.00% by mass or less, Mn: 0.10% by mass or more and 1.00% by mass or less, Cr: 2.0 mass% or more and 7.0 mass% or less, Mo: 2.0% by mass or more and 7.0% by mass or less, W: 3.0% by mass or more and 15.0% by mass or less, V: 2.0% by mass or more and 5.0% by mass or less, Co: 0.0% by mass or more and 15.0% by mass or less, Al: 0.000 mass% or more and 0.500 mass% or less and N: 0.000 mass% or more and 0.100 mass% or less The remainder is Fe and unavoidable impurities.

[0012] [Metal structure] The metal structure of powder high-speed steel includes a matrix and numerous metal carbides dispersed in the matrix. The matrix is ​​based on Fe. In the matrix, other elements are solid-solved in Fe. Metal carbides are compounds of C and other elements. Metal carbides include primary carbides and eutectic carbides. In this specification, primary carbides refer to carbides other than eutectic carbides that are formed during the solidification or quenching process. In this specification, eutectic carbides refer to a composite phase that is formed during the quenching process. In this composite phase, multiple carbides exist in layers, or carbides and solid solutions exist in layers.

[0013] A micrograph of this metal structure is shown in Figure 1. This photograph was obtained by etching powdered high-speed steel with Vilela etching solution. In this metal structure, multiple primary carbides 4 and multiple eutectic carbides 6 are dispersed in a matrix 2. The primary carbides 4 are shown only in white. These primary carbides 4 are mainly M16C or M1C, where M1 is Cr, Mo, V, W, Fe, or Co. The eutectic carbides 6 are shown alternating white and black. These eutectic carbides 6 are composite phases consisting of multiple carbides or carbides and solid solutions. The white side is mainly M16C, and the black side is mainly Fe solid solution or M23C, where M2 is Cr, Mo, V, W, Fe, or Co.

[0014] [element] The elements contained in the powder high speed steel will be described in detail below.

[0015] [Carbon (C)] C combines with other elements to form carbides. These carbides can contribute to the wear resistance of powder high-speed steel. C also dissolves in Fe, the base of the matrix, and contributes to the hardness of the powder high-speed steel. From these viewpoints, the C content is preferably 1.00 mass% or more, more preferably 1.10 mass% or more, and particularly preferably 1.20 mass% or more. Excess C leads to the formation of excessive carbides, which impairs the toughness of the powder high-speed steel. From this viewpoint, the C content is preferably 1.90 mass% or less, more preferably 1.80 mass% or less, and particularly preferably 1.75 mass% or less.

[0016] [Silicon (Si)] Si contributes to deoxidation in the steelmaking process. Si also contributes to hardenability. From these viewpoints, the Si content is preferably 0.10 mass% or more, and particularly preferably 0.20 mass% or more. Excessive Si inhibits the workability of powder high-speed steel. From the viewpoint of workability, the Si content is preferably 1.00 mass% or less, more preferably 0.90 mass% or less, and particularly preferably 0.80 mass% or less.

[0017] [Manganese (Mn)] Mn contributes to hardenability. From this viewpoint, the Mn content is preferably 0.10 mass% or more, more preferably 0.20 mass% or more, and particularly preferably 0.30 mass% or more. Excess Mn inhibits the workability of powder high-speed steel. From this viewpoint, the Mn content is preferably 1.00 mass% or less, more preferably 0.90 mass% or less, and particularly preferably 0.80 mass% or less.

[0018] Chromium Cr forms primary carbides and eutectic carbides. Of these, the primary carbides contribute to the wear resistance of powder high-speed steel. Furthermore, Cr dissolves in the matrix of the powder high-speed steel structure, contributing to corrosion resistance. From these viewpoints, the Cr content is preferably 2.0% by mass or more, more preferably 2.2% by mass or more, and particularly preferably 2.3% by mass or more. Excessive Cr leads to the formation of excessive eutectic carbides. Excessive eutectic carbides impair the wear resistance and softening resistance of powder high-speed steel. Excessive eutectic carbides also lead to crevice corrosion. From the viewpoints of wear resistance, softening resistance, and corrosion resistance, the Cr content is preferably 7.0% by mass or less, more preferably 4.0% by mass or less, and particularly preferably 3.0% by mass or less.

[0019] [Molybdenum (Mo)] Mo forms fine primary carbides and eutectic carbides in powder high-speed steel. Of these, the primary carbides contribute to the hardness and wear resistance of the powder high-speed steel. Furthermore, Mo dissolves in the matrix of the powder high-speed steel structure, contributing to corrosion resistance. From these viewpoints, the Mo content is preferably 2.0 mass% or more, more preferably 2.5 mass% or more, and particularly preferably 3.0 mass% or more. Excess Mo leads to the formation of excessive primary carbides, which impairs the toughness of the powder high-speed steel. From this viewpoint, the Mo content is preferably 7.0 mass% or less, more preferably 6.5 mass% or less, and particularly preferably 6.0 mass% or less.

[0020] [Tungsten (W)] W forms fine primary carbides and eutectic carbides in powder high-speed steel. Of these, the primary carbides contribute to the hardness and wear resistance of the powder high-speed steel. From this viewpoint, the W content is preferably 3.0% by mass or more, more preferably 3.5% by mass or more, and particularly preferably 4.0% by mass or more. Excess W leads to the formation of excessive primary carbides, which impairs the toughness of the powder high-speed steel. From this viewpoint, the W content is preferably 15.0% by mass or less, more preferably 14.5% by mass or less, and particularly preferably 13.0% by mass or less.

[0021] [Vanadium(V)] V forms fine and hard primary carbides and eutectic carbides in powder high-speed steel. Therefore, V contributes to the hardness and wear resistance of the powder high-speed steel. From these viewpoints, the V content is preferably 2.0 mass% or more, more preferably 2.3 mass% or more, and particularly preferably 2.5 mass% or more. Excess V inhibits the workability of the powder high-speed steel. From this viewpoint, the V content is preferably 5.0 mass% or less, more preferably 4.7 mass% or less, and particularly preferably 4.5 mass% or less.

[0022] [Cobalt (Co)] Co contributes to the hardness and corrosion resistance of the powder high-speed steel. From this viewpoint, the Co content is preferably 0.5 mass% or more, more preferably 0.8 mass% or more, and particularly preferably 1.0 mass% or more. From the viewpoint of low cost, the Co content is preferably 15.0 mass% or less, more preferably 13.0 mass% or less, and particularly preferably 10.0 mass% or less. The powder high-speed steel may have a composition that is substantially free of Co. Even a powder high-speed steel that is substantially free of Co can achieve the above-mentioned effects of this powder high-speed steel.

[0023] [Aluminum (Al)] Al is present in the powder high-speed steel as an oxide. This oxide impairs the toughness of the powder high-speed steel. From the viewpoint of toughness, the Al content is preferably 0.500% by mass or less, and particularly preferably zero. The inclusion of Al as an unavoidable impurity is acceptable. On the other hand, Al can contribute to the wear resistance of the powder high-speed steel. For example, when the cutting edge of a cutting tool separates from a workpiece, an oxynitride film is formed at the wear point of the cutting edge due to frictional heat. In tools containing Al, this oxynitride film has high hardness. This oxynitride film can contribute to the wear resistance of the cutting edge. In other words, Al can contribute to the wear resistance of the powder high-speed steel. From the viewpoint of wear resistance, Al may be intentionally added. The Al content is preferably 0.001% by mass or more, more preferably 0.003% by mass or more, and particularly preferably 0.005% by mass or more. Even if Al remains as an unavoidable impurity, it can contribute to wear resistance if its content is appropriate. The Al content may be less than 0.001% by mass when toughness is emphasized, or may be 0.001% by mass or more when wear resistance is emphasized. Whether the Al content is less than 0.001% by mass or 0.001% by mass or more depends on the content of Al contained as an impurity in the raw materials, and can be adjusted by selecting the type of raw material used.

[0024] Nitrogen N causes coarsening of primary carbides. N also generates nitrides. These primary carbides and nitrides impair the toughness of powder high-speed steel. From the viewpoint of toughness, N is preferably an unavoidable impurity, and ideally, the N content is 0.000 mass%. Practically, the N content is preferably 0.100 mass% or less, and particularly preferably 0.080 mass% or less. On the other hand, primary carbides and nitrides can contribute to the wear resistance of powder high-speed steel. From the viewpoint of wear resistance, the inclusion of a certain amount of N is acceptable. From the viewpoint of wear resistance, the N content is preferably 0.010 mass% or more, more preferably 0.050 mass% or more. In other words, if the N content is 0.050 mass% or more and 0.080 mass% or less, both toughness and wear resistance are achieved. The N content may be less than 0.050 mass% when toughness is emphasized, or the N content may be 0.081 mass% or more when wear resistance is emphasized. The N content can be achieved, for example, by selecting the type of atomizing gas (nitrogen, argon, etc.). Even if N remains as an unavoidable impurity, it can contribute to wear resistance if its content is appropriate.

[0025] [Iron (Fe)] The powder high-speed steel is an Fe-based alloy. This powder high-speed steel has excellent toughness. From the viewpoint of toughness, the Fe content is preferably 60 mass % or more, more preferably 70 mass % or more, and particularly preferably 75 mass % or more.

[0026] [impurities] In addition to the aforementioned N, powder high-speed steel may contain unavoidable impurities. A typical example of such an impurity is oxygen (O). O causes the formation of inclusions (oxides). The inclusions can become the starting point for fracture. From the viewpoint of suppressing fracture, the O content is preferably 0.030 mass% or less, and more preferably 0.020 mass% or less. The O content can be achieved, for example, by selecting the type of atomizing gas (nitrogen, argon, etc.).

[0027] [Element ratio] As mentioned above, Cr, Mo, W, and V can form primary carbides. These primary carbides contribute to the wear resistance of powder high-speed steel. However, when a tool made from this powder high-speed steel is subjected to machining, such as cutting, heat is generated, causing Cr, Mo, W, and V to oxidize. This oxidation adversely affects wear resistance. Mn, Si, and Al have weaker bonding strength with C than Cr, Mo, W, and V. Therefore, Mn, Si, and Al oxidize preferentially over Cr, Mo, W, and V. Oxides of Mn, Si, and Al can exist as a protective film on the friction surface of the tool. This protective film contributes to the wear resistance and softening resistance of the powder high-speed steel.

[0028] In this specification, the first equivalent E1 is calculated by the following formula (1). E1 = Cr% + Mo% + 0.5W%+ V% (1) In this formula (1), Cr% represents the mass content of Cr, Mo% represents the mass content of Mo, W% represents the mass content of W, and V% represents the mass content of V. This first equivalent E1 correlates with the wear resistance due to primary carbides. Since the contribution of W to wear resistance is about half that of Cr, W is multiplied by a coefficient of "0.5" in the above formula (1). This first equivalent E1 also correlates with the softening resistance due to primary carbides.

[0029] In this specification, the second equivalent E2 is calculated by the following formula (2). E2 = Mn% + Si% + Al% (2) In this formula (2), Mn% represents the mass content of Mn, Si% represents the mass content of Si, and Al% represents the mass content of Al. This second equivalent E2 correlates with the wear resistance attributable to the protective film. This second equivalent E2 also correlates with the softening resistance attributable to the protective film.

[0030] In this specification, The element ratio AR is calculated by the following formula (3). AR = (Cr% + Mo% + 0.5W%+ V%) / (Mn% + Si% + Al%) (3) This element ratio AR is the ratio between the first equivalent E1 and the second equivalent E2. The element ratio AR is preferably 15 or more and 40 or less. In powder high-speed steel having an element ratio AR within this range, both the wear resistance due to the primary carbides and the wear resistance due to the protective film can be achieved. From the viewpoint of the wear resistance due to the primary carbides, the element ratio AR is more preferably 16 or more, and particularly preferably 17 or more. From the viewpoint of the wear resistance due to the protective film, the element ratio AR is more preferably 35 or less, and particularly preferably 30 or less. In powder high-speed steel having an element ratio AR within this range, both the softening resistance due to the primary carbides and the softening resistance due to the protective film can be achieved. The reason why excellent softening resistance is achieved when the ratio of the first equivalent E1 to the second equivalent E2 is appropriate is not clear in detail, but it is presumed to be due to the pinning effect of the oxide protective film.

[0031] [Maximum diameter of primary carbide DM] The maximum diameter DM of the primary carbides is preferably 2.0 μm or more. In powder high-speed steel having a maximum diameter DM of 2.0 μm or more, fine carbides having a diameter of less than 2.0 μm and coarse carbides having a diameter of 2.0 μm or more are present. The fine carbides contribute to the toughness of the powder high-speed steel, while the coarse carbides contribute to the wear resistance of the powder high-speed steel. From the viewpoint of wear resistance, the maximum diameter DM is more preferably 2.5 μm or more, and particularly preferably 3.0 μm or more. Excessive primary carbides impair toughness and cause chipping of tools, etc. From the viewpoint of toughness, the maximum diameter DM is preferably 10.0 μm or less, more preferably 8.0 μm or less, and particularly preferably 7.0 μm or less. As is clear from FIG. 1, the amount of primary carbides is greater than the amount of eutectic carbides. By controlling the maximum diameter DM of the primary carbides, toughness and wear resistance can be efficiently achieved.

[0032] To measure the maximum diameter (DM), a backscattered electron image of the polished surface of the powder high-speed steel is taken using a scanning electron microscope. This backscattered electron image is then binarized using image analysis software. A field of view is randomly selected from this backscattered electron image. The outline of this field of view is rectangular, with an area of ​​5000 μm. 2The circle-equivalent diameter of each of the multiple primary carbides included in this field of view is measured. The circle-equivalent diameter is the diameter of a circle having the same area as the area of ​​the primary carbide in question in the backscattered electron image (two-dimensional image). The largest value among these circle-equivalent diameters is the maximum diameter DM.

[0033] [Area ratio of primary carbides PS] The area fraction PS of primary carbides having an equivalent circle diameter of 2.0 μm or more and 10.0 μm or less is preferably 5% or more and 20% or less. Powder high-speed steel having this area fraction PS of 5% or more has excellent wear resistance. From this viewpoint, this area fraction PS is more preferably 7% or more, and particularly preferably 8% or more. Powder high-speed steel having this area fraction PS of 20% or less has excellent toughness. From this viewpoint, this area fraction PS is more preferably 18% or less, and particularly preferably 15% or less.

[0034] Insufficient or excessively large primary carbides do not contribute to wear resistance. Furthermore, it is difficult to measure the area of ​​excessively small primary carbides. In light of these circumstances, the present inventors focused on primary carbides having a size of 2.0 μm or more and 10.0 μm or less, and measured the area fraction PS of these primary carbides.

[0035] To measure the area ratio PS, a backscattered electron image of the polished surface of the powder high-speed steel is taken using a scanning electron microscope. This backscattered electron image is then binarized using image analysis software. A field of view is randomly selected from this backscattered electron image. The outline of this field of view is rectangular, and the area is 5000 μm. 2 The area of ​​each of the primary carbides included in this field of view is measured. The areas of the primary carbides with an equivalent circle diameter of 2.0 μm or more and 10.0 μm or less are summed up, and the total value is divided by the area of ​​the field of view to calculate the area ratio PS.

[0036] [Maximum area of ​​eutectic carbide SM] Coarse eutectic carbides impair the wear resistance and softening resistance of powder high-speed steel. From the viewpoint of wear resistance and softening resistance, the maximum area SM of eutectic carbides is 30 μm 2 Preferably less than 28 μm 2 Less than 27 μm is more preferable2 The following is particularly preferable. In a metal structure containing too few eutectic carbides, the number of primary carbides is also too few. Too few primary carbides contribute little to wear resistance. From the viewpoint of wear resistance, the maximum area SM of the eutectic carbides is 5 μm. 2 More than 7 μm is preferable. 2 More preferably, 10 μm or more 2 The above is particularly preferred.

[0037] To measure the maximum area SM, a backscattered electron image of the polished surface of the powder high-speed steel is taken using a scanning electron microscope. This backscattered electron image is then binarized using image analysis software. A field of view is randomly selected from this backscattered electron image. The outline of this field of view is rectangular, and the area is 5000 μm. 2 The area of ​​each of the multiple eutectic carbides included in this field of view is measured. The area of ​​the eutectic carbide with the largest area among these eutectic carbides is the maximum area SM.

[0038] The maximum area of ​​the eutectic carbide is (1) Adjustment of Cr content (2) Adjusting the temperature of the hot isostatic pressing method described below (3) Adjustment of the quenching temperature, which will be described later This can be done by, etc.

[0039] [Powder metallurgy method] The high-speed steel according to the present invention can be obtained by powder metallurgy. In powder metallurgy, metal powder is first produced by gas atomization, water atomization, disk atomization, pulverization, or the like. This metal powder is then compressed in a high-temperature atmosphere to solidify, thereby obtaining a compact. A preferred pressing method is hot isostatic pressing (HIP). In hot isostatic pressing, powder is compressed under isostatic pressure at high temperature. Preferably, an inert gas such as argon gas or helium gas is used as the pressurizing medium.

[0040] This compact is then subjected to hot working. Further heat treatment of this compact results in powder high-speed steel. A typical heat treatment is "annealing-quenching-tempering." These heat treatments result in the formation of the desired metal carbides.

[0041] [Cutting tools] Hereinafter, an embodiment of a cutting tool will be described. The material of this cutting tool is the powder high-speed steel described above. That is, this powder high-speed steel has the following properties: C: 1.00% by mass or more and 1.90% by mass or less, Si: 0.10% by mass or more and 1.00% by mass or less, Mn: 0.10% by mass or more and 1.00% by mass or less, Cr: 2.0 mass% or more and 7.0 mass% or less, Mo: 2.0% by mass or more and 7.0% by mass or less, W: 3.0% by mass or more and 15.0% by mass or less, V: 2.0% by mass or more and 5.0% by mass or less, Co: 0.0% by mass or more and 15.0% by mass or less, Al: 0.000 mass% or more and 0.500 mass% or less and N: 0.000 mass% or more and 0.100 mass% or less The remainder is Fe and unavoidable impurities. This powder high-speed steel contains primary carbides and eutectic carbides in its metal structure. In this powder high-speed steel, the element ratio AR calculated by the following formula is 15 or more and 40 or less. AR = (Cr% + Mo% + 0.5W%+ V%) / (Mn% + Si% + Al%) In this formula, Cr% represents the mass content of Cr, Mo% represents the mass content of Mo, W% represents the mass content of W, V% represents the mass content of V, Mn% represents the mass content of Mn, Si% represents the mass content of Si, and Al% represents the mass content of Al. [Example]

[0042] The effects of the powder high-speed steel according to the examples will be clarified below, but the scope of the present disclosure should not be construed as being limited based on the description of these examples.

[0043] [Example 1] The molten metal was gas atomized to obtain a powder. This powder was filled into a cylindrical steel can. The steel can was vacuum degassed and then sealed. A compact was obtained by hot isostatic pressing in an argon gas atmosphere at a pressure of 200 MPa and a temperature of 1200°C. This compact was forged, rolled, hot extruded, and annealed at a forging ratio of 4 to obtain a round bar with a diameter of 50 mm. This round bar was quenched at 1100°C and tempered for three hours to obtain the powder high-speed steel according to Example 1. The tempering temperature was adjusted so that the hardness of the tempered round bar was in the range of 64 to 65 HRC. The composition of this powder high-speed steel is shown in Table 1 below. In addition to the elements listed in Table 1, this powder high-speed steel contains unavoidable impurities.

[0044] [Examples 2-20 and Comparative Examples 1-5] Powder high-speed steels of Examples 2-20 and Comparative Examples 1-5 were obtained in the same manner as in Example 1, except that the compositions were as shown in Tables 1 and 2 below and the atomizing, hot isostatic pressing and heat treatment conditions were as shown in Tables 3 and 4 below.

[0045] [Hardness retention rate PK] A hob was cut out from the round bar. The Rockwell hardness H1 of this hob was measured. Cutting was performed using this hob under the following conditions. Workpiece material: SCM420 Wet / dry: Dry Circumferential speed: 300m / s Duration: 10 hours No chipping of the blade was observed during this cutting. The Rockwell hardness H2 of the hob after this cutting was measured. The hardness retention rate PK was calculated based on the following formula. PK = (H2 / H1) * 100 The results are shown in Tables 3 and 4 below.

[0046] [Wear resistance] After the hardness retention rate PK test, the width of the wear scar formed on the cutting edge of the hob was measured. Measurements were taken on 30 hobs, and the arithmetic mean of these measurements was calculated. The results are shown in Tables 3 and 4 below.

[0047] [comprehensive evaluation] Each powder high speed steel was graded based on the following criteria: A: The width of the wear scar is 1.0 mm or less, and the hardness retention rate is 90% or more. B: The width of the wear scar is greater than 1.0 mm and not more than 1.2 mm, and the hardness retention rate is 90% or more. C: The width of the wear scar is greater than 1.2 mm and not more than 2.0 mm, and the hardness retention rate is 90% or more. D: The width of the wear scar is greater than 2.0 mm and not more than 3.0 mm, and the hardness retention rate is 90% or more. F: The width of the wear scar is greater than 3.0 mm, or the hardness reduction rate is less than 90%. The results are shown in Tables 3 and 4 below.

[0048] [Table 1]

[0049] [Table 2]

[0050] [Table 3]

[0051] [Table 4]

[0052] As shown in Tables 3 and 4, the powder high-speed steels of the examples were excellent in all evaluation items. From the above evaluation results, the superiority of these powder high-speed steels is clear.

[0053] [Disclosure items] Each of the following sections is a disclosure of a preferred embodiment.

[0054] [Item 1] C: 1.00% by mass or more and 1.90% by mass or less, Si: 0.10% by mass or more and 1.00% by mass or less, Mn: 0.10% by mass or more and 1.00% by mass or less, Cr: 2.0 mass% or more and 7.0 mass% or less, Mo: 2.0% by mass or more and 7.0% by mass or less, W: 3.0% by mass or more and 15.0% by mass or less, V: 2.0% by mass or more and 5.0% by mass or less, Co: 0.0% by mass or more and 15.0% by mass or less, Al: 0.000 mass% or more and 0.500 mass% or less and N: 0.000 mass% or more and 0.100 mass% or less It contains The balance is Fe and unavoidable impurities, The metal structure contains primary carbides and eutectic carbides, A powder high-speed steel having an element ratio AR calculated by the following formula of 15 or more and 40 or less. AR = (Cr% + Mo% + 0.5W%+ V%) / (Mn% + Si% + Al%) (In this formula, Cr% represents the mass content of Cr, Mo% represents the mass content of Mo, W% represents the mass content of W, V% represents the mass content of V, Mn% represents the mass content of Mn, Si% represents the mass content of Si, and Al% represents the mass content of Al.) [Item 2] 2. The powder high-speed steel according to Item 1, wherein the primary carbides have a maximum diameter DM of 2.0 μm or more and 10.0 μm or less. [Item 3] 3. The powder high-speed steel according to item 1 or 2, wherein the area fraction PS of the primary carbides is 5% or more and 20% or less. [Item 4] 4. The powder high-speed steel according to any one of items 1 to 3, wherein the N content is 0.010% by mass or more and 0.100% by mass or less. [Item 5] The maximum area SM of the above eutectic carbide is 5 μm 2 More than 30μm 2 5. A powder high-speed steel according to any one of items 1 to 4, wherein: [Industrial Applicability]

[0055] The powder high-speed steel described above is suitable for applications in environments where frictional heat is generated, applications in environments where lubricating oil is used, etc. This powder high-speed steel can be used in a variety of applications, such as cutting tools, molds, injection molding machines, die sets, punches, hand tools, machine tools, and blades. [Explanation of symbols]

[0056] 2. Matrix 4. Primary carbides 6···Eutectic carbide

Claims

1. C: 1.00% by mass or more and 1.90% by mass or less, Si: 0.10% by mass or more and 1.00% by mass or less, Mn: 0.10% by mass or more and 1.00% by mass or less, Cr: 2.0% by mass or more and 7.0% by mass or less, Mo: 2.0% by mass or more and 7.0% by mass or less, W: 3.0% by mass or more and 15.0% by mass or less, V: 2.0% by mass or more and 5.0% by mass or less, Co: 0.0% by mass or more and 15.0% by mass or less, Al: 0.000% by mass or more and 0.500% by mass or less and N: 0.010% by mass or more and 0.100% by mass or less It contains The balance is Fe and unavoidable impurities, The metal structure contains primary carbides and eutectic carbides, A powder high-speed steel having an element ratio AR calculated by the following formula of 15 or more and 40 or less. AR = (Cr% + Mo% + 0.5W% + V%) / (Mn% + Si% + Al%) (In this formula, Cr% represents the mass content of Cr, Mo% represents the mass content of Mo, W% represents the mass content of W, V% represents the mass content of V, Mn% represents the mass content of Mn, Si% represents the mass content of Si, and Al% represents the mass content of Al.)

2. 2. The powder high-speed steel according to claim 1, wherein the maximum diameter DM of the primary carbides is 2.0 μm or more and 10.0 μm or less.

3. 3. The powder high-speed steel according to claim 1, wherein the area fraction PS of the primary carbides is 5% or more and 20% or less.

4. The maximum area SM of the eutectic carbide is 5 μm ２ 30 μm or more ２ 4. The powder high-speed steel according to claim 1, wherein:

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