JPH0539552A - Powdery steel for high speed tool and its production - Google Patents

Abstract

PURPOSE:To provide powdery steel for high speed tool having high high-temp. temper softening resistance capable of corresponding to the speeding-up of the using conditions of a tool and combining high wear resistance and high toughness. CONSTITUTION:This is powdery steel for high speed tool constituted of, by weight, >1.5 to 2.2% C, <=1.0% Si, <=0.6% Mn, 3.0 to 6.0% Cr, W and/or Mo by 20 to 30% W+2Mo as well as >=1W/2Mo, <=5.0% V, 2.0 to 7.0% Nb as well as >=0.5 Nb/V and preferably 4.0 to 15.0% Co as well and the balance Fe with inevitable impurities and in which C-ceq satisfies the relationship of -0.20 to 0.05 (where Ceq=0.24+0.033.W+0.063.Mo+0.2.V+0.1.Nb) as well as the density of carbide of 2 to 5mum is regulated to 10000 to 30000 pieces/mm<2>. Furthermore, the relationship of <=2 Nb/V and >6 Nb+V are preferably satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used for cutting tools and forging tools, and particularly under high-speed use conditions where hardness and wear resistance at high temperatures are required, it is possible to obtain not only excellent wear resistance but also high toughness. The present invention relates to a powder high speed tool steel having the same and a manufacturing method thereof.

[0002]

2. Description of the Related Art High-speed tool steels used for cutting tools and forging tools are required to satisfy the two requirements of high hardness and excellent wear resistance and toughness. As a method of improving the toughness of the molten high speed tool steel, a method of adding a trace amount of an element such as Nb and refining the crystal grains to improve the toughness (for example, JP-A-58-73753 and JP-A-58-11).
No. 7863), and a method of uniformly refining MC type carbide mainly composed of Nb by adding Nb and rare earth elements in combination (Japanese Patent Publication No. 61-896).

On the other hand, the most general method for improving wear resistance is to increase the amount of carbide in powder high speed tool steel in which carbide is uniformly and finely distributed and crystal grains can be refined. is there. For example, Japanese Examined Sho 57-2142
And JP-A-55-148747, the amount of M ₆ C type carbides mainly containing W and Mo is increased by mainly increasing the W equivalent, and the wear resistance is improved by increasing the hardness. Is. Further, in the powder high speed tool steel, it is considered to contain Nb for the purpose of refining the crystal grains and further preventing the crystal grains from being coarsened even if the quenching temperature is raised {Metall. Trans. 19A (1988) P1395 to 1401, Japanese Patent Laid-Open No. 1-212736}.

[0004]

However, the above-mentioned Japanese Patent Laid-Open No. 58-58
-73753 and 58-117863 melted high speed tool steels have Nb
When N is excessively added, coarse NbC carbides mainly composed of Nb are crystallized, and M ₆ C type carbides mainly composed of W and Mo are also
Since a coarse carbide is crystallized during solidification, there is a problem that the effect of improving the toughness by refining the crystal grains is diminished and the toughness is rather lowered. Further, in the above powder high-speed tool steel, the amount of carbide and the hardness of the tool have been increased for the purpose of improving wear resistance, but the toughness is lowered, and the tool is broken or chipped. Was a problem.

Further, Japanese Patent Laid-Open No. 55-148747 proposes a powder high-speed steel containing Nb.
The main purpose is to add b as a substitute for V to form a hard carbide. Furthermore, Metall.Trans.1
The high speed tool steel disclosed in 9A (1988) P1395 to P1401 and Japanese Patent Laid-Open No. 1-212736 makes it possible to increase the quenching temperature without coarsening the crystal grains by adding Nb. According to the inventor's idea, the alloying element amount, particularly the W equivalent, is low, so that the high temperature temper softening resistance is insufficient under severe tool use conditions, and the carbide content is also small, so that the wear resistance is insufficient. Is.

Therefore, it has been difficult for the conventional high-speed tool steel described above to meet the recent tool usage conditions in which high speed is required. Therefore, the present invention remarkably enhances the high temperature tempering softening resistance characteristics that can correspond to the speeding up of tool use conditions, and increases the carbide density of 2 to 5 μm to further enhance wear resistance, and high toughness powder high speed. The challenge is to provide tool steel.

[0007]

In recent years, as the use conditions of tools have become faster, increasing the hardness of the tools has become an important factor. The present inventor also actually used a tool such as an end mill and analyzed the relationship between the tool life and the material factor.As a result, the life was improved by hardness, especially since the tool became hot during use, It has been found that the reversion softening resistance property is the most important, and further the wear resistance is improved by adjusting the carbide grain size.

The present invention has been made in consideration of this finding, and the following three points are the basic technical ideas. In order to maximize the temper softening resistance, it has been found that it is effective to regulate W + 2Mo, W / 2Mo and C-Ceq within a specific range in terms of chemical composition. That is, it is effective to increase the amount of W + 2Mo to disperse hard carbides and increase the amount of alloying elements dissolved in the matrix. In addition, increase the amount of W
When / 2Mo ≧ 1, high tempering hardness can be obtained and high Mo
A higher temper softening resistance is obtained than the materials of the system.
The amount of C needs to be determined in consideration of the amounts of other carbide forming elements, and is adjusted by C-Ceq. In order to obtain a high tempering softening resistance, it is necessary to regulate C-Ceq and secure the amount of C that forms a solid solution in the matrix.

[0009] When many quenching temperatures are used as a solid solution of many alloying elements in the matrix, the crystal grains become coarse. However, by containing Nb and controlling the Nb / V ratio, Prevents coarsening of crystal grains, secures fine crystal grains, and prevents deterioration of toughness. Nb forms MC carbides like V, but in order to form fine NbC of 1 μm or less, which is effective for preventing coarsening of crystal grains,
It must contain more Nb than V in atomic ratio.
In weight ratio, Nb / V should be 0.5 or more.

Further, an important point in the present invention is that it has been found that it has an effect of increasing the density of carbides of 2 to 5 μm in improving wear resistance. To improve wear resistance,
Effective carbides are medium grain carbides of 2-5 μm, with a minimum carbide density of 10,000 / mm ^{2 for} this size. If it is less than that, tool wear remarkably progresses and the life becomes short. If the medium-grain carbide density of 2-5 μm exceeds 30,000 / mm ² , the carbides will start to be connected and the toughness will be significantly reduced.Therefore, the medium-grain carbide density of 2-5 μm will be 10,000-30,000 / mm.
²

It has been found that the above properties can be satisfied for the first time by satisfying the following component balance. That is, the present invention uses C by weight.
More than 1.5% and 2.2% or less, Si ≦ 1.0%, Mn ≦ 0.6%, Cr 3.0
~ 6.0%, W or 20 to 30% at W + 2Mo and W / 2Mo≥1, V≤5.0%, Nb 2.0 to 7.0%, but Nb /
V ≧ 0.5, balance of Fe and inevitable impurities, and C
-Ceq is -0.20 to 0.05 (Ceq = 0.24 + 0.033 ・ W + 0.063 ・ Mo
The powder high speed tool steel is characterized by satisfying the relationship of + 0.2V + 0.1 · Nb) and having a carbide density of 2 to 5 μm of 10,000 to 30,000 pieces / mm ² .

The present invention also has a weight ratio of more than C 1.5% to 2.2.
% Or less, Si ≦ 1.0%, Mn ≦ 0.6%, Cr3.0 to 6.0%, W or 20 to 30% of Mo with W + 2Mo, and W / 2Mo ≧ 1,
V ≦ 5.0%, Nb 2.0 to 7.0%, but Nb / V ≧ 0.5, Co 4.0
~ 15.0%, the balance Fe and inevitable impurities, C
-Ceq is -0.20 to 0.05 (Ceq = 0.24 + 0.033 ・ W + 0.063 ・ Mo
The powder high speed tool steel is characterized by satisfying the relationship of + 0.2V + 0.1 · Nb) and having a carbide density of 2 to 5 μm of 10,000 to 30,000 pieces / mm ² .

In the present invention, if Nb is excessively large with respect to V, coarse NbC is likely to occur and the toughness deteriorates. Therefore, it is preferable to satisfy the relationship of Nb / V ≦ 2. Further, in order to improve wear resistance, Nb + V>
It is preferable that the relationship of 6 is satisfied.

Further, the manufacturing method of the present invention uses C 1.5 by weight.
% To 2.2% or less, Si ≦ 1.0%, Mn ≦ 0.6%, Cr 3.0 to 6.
0%, W or 20 to 30% with Mo + W2 Mo and W /
2Mo ≧ 1, V ≦ 5.0%, Nb 2.0-7.0%, but Nb / V ≧ 0.
5, or in addition to this, contains Co ≤ 15.0%, with the balance being F
e and inevitable impurities, C-Ceq is -0.20 ~
0.05 (However, Ceq = 0.24 + 0.033 ・ W + 0.063 ・ Mo ＋ 0.2V +
After the alloy powder satisfying the relationship of 0.1 · Nb) is sintered to obtain a sintered body, before hot working or during hot working, 11
A method for producing a powder high-speed tool steel, which comprises performing a heat treatment at 00 ° C to 1200 ° C.

[0015]

The present invention is most characterized in that the carbide density of 2 to 5 μm is set to 10,000 to 30,000 pieces / mm ² in order to improve wear resistance while ensuring sufficient hardness and temper softening resistance. .. Such a specific size carbide density cannot be obtained only by specifying the components, and can be obtained by performing a heat treatment such as soaking before hot working or during hot working. When heat treatment such as soaking is performed, fine carbides of 2 μm or less are solid-dissolved, and the density of carbides of 2 to 5 μm can be increased by Ostwald ripening. Wear resistance is significantly improved by making the medium-grain carbide of 2 to 5 μm 10,000 pieces / mm or more, but 30,000 pieces / m
If it exceeds m ² , it is not preferable because carbides start to be connected and the toughness decreases.

The reasons for limiting the components will be described below. C forms a hard carbide with Cr, W, Mo, V, and Nb added at the same time, and contributes to the improvement of wear resistance. Further, it has a function of improving the secondary hardening by solid solution in the matrix during quenching. However, if the amount is too large, the amount of carbon solid-dissolved in the matrix increases remarkably and the toughness decreases. Therefore, the amount of C must be determined in consideration of the contents of Cr, W, Mo, V and Nb. In the present invention, the range of 1.5 to 2.2% and the value of C-Ceq are-.
The amount of C is adjusted so as to satisfy the relationship of 0.200.05. By satisfying this relationship, one condition for achieving high high temperature temper softening resistance is achieved.

Si and Mn are added as deoxidizing agents, but if added in a large amount, there is a problem such as impairing toughness.
It is limited to 0% or less and Mn 0.6% or less. Cr is added in an amount of 3 to 6% for the purpose of enhancing the hardenability and the secondary hardening of the temper. If it is less than 3%, the above effect is small. On the contrary, if it is more than 6%, the amount of M ₂₃ C ₆ type carbides mainly composed of Cr is extremely increased and the toughness of the whole is impaired. Reduce resistance.

In order to impart remarkable wear resistance, which is an object of the present invention, it is necessary to disperse a large amount of hard carbide and increase the matrix hardness. In the present invention, W, M
o Quantity is an important element for the above purposes. W or further Mo is 20 + 30% at W + 2 Mo. If it is less than 20%, the above effect is small. However, when W + 2Mo exceeds 30%,
Since the number of connected carbides increases rapidly and the amount of alloying elements that form a solid solution in the matrix is extremely increased, the toughness is significantly reduced. Therefore, W or Mo is set to 20 to 30% at W + 2Mo. Further, by increasing the W / 2Mo ratio to 1 or more, in order to remarkably improve the temper softening resistance, which is a feature of the present invention,
Other one condition (one is C-Ceq condition) can be satisfied.

V is also an element effective in increasing wear resistance. For the purpose of abrasion resistance, it is desirable to contain as much as possible. However, if it exceeds 5%, coarse MC type carbides are likely to crystallize, which impairs toughness and grindability of the tool.
Below. Nb is one of the most important elements in the present invention. When Nb is limited to a specific component range, a hard carbide mainly composed of 1 to 5 μm Nb effective for wear resistance and a fine carbide of 1 μm or less are crystallized.

The present inventor has found a range of components in which the fine NbC suppresses the growth of crystal grains and effectively suppresses the coarsening of crystal grains even if the quenching temperature is increased. This fine NbC is closely related to the Nb amount and the Nb / V ratio, and the Nb amount and the Nb / V ratio.
If the ratio is low, fine NbC is hardly crystallized,
The amount of Nb was adjusted so that Nb ≧ 2% and Nb / V ≧ 0.5. However, when Nb exceeds 7%, extremely coarse NbC is crystallized and impairs toughness and grindability, so it was set to 7% or less.
Further, if Nb is too much with respect to V, Nb carbide tends to be coarsened, so that it is desirable to satisfy Nb / V ≦ 2.

Co is an extremely effective element for improving the temper softening resistance of the steel of the present invention. It forms a solid solution in the matrix, delays the precipitation and agglomeration of carbides, and has the effect of significantly improving the hardness and strength at high temperatures, which is extremely important for applications where the contact part between the tool and the work such as cutting tools and end mills is particularly hot. It is an additive element. However, if Co exceeds 15.0%, the toughness decreases due to crystallization of the Co single phase due to solid solution, so the content was made 15.0% or less. Further, in order to remarkably improve the tempering softening resistance by adding Co, Co is preferably contained at 4% or more.

[0022]

[Examples] Table 1 shows the chemical compositions of three kinds of experimental materials produced by the method of HIP (hot isostatic pressing) of nitrogen gas atomized powder. Each material is HIP
After that, soaking in the temperature range of 1080 ℃ ~ 1190 ℃,
After about 16 mm square by forging, the forged material was annealed at 860 ° C. and austenitized at 1250 ° C. for 15 minutes, which is the highest temperature possible in a temperature range where the crystal grains do not become coarse. , 550 ℃ hot bath quenching was performed. The tempering is 5
60 ° C x 1 hour 3 times.

Quantitative determination of the carbide density of 2 to 5 μm of the sample was carried out by diamond polishing the longitudinal section of each forged material, then corroding M ₆ C type carbide with Murakami reagent, and further with 10% chromic acid aqueous solution. A sample was prepared in which electrolytic corrosion was performed and MC type was corroded by carbide. These samples were quantified for carbide by an image analysis processor. Also, hardness after tempering, grain size by intercept method (after quenching), 650 ° C
After heating and holding for 1 hour, the hardness (referred to as tempering softening resistance) when air-cooled was measured. The results are shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

Comparative Examples 1a, 2a and 3a in Table 2 are alloys having a steel composition within the range of the present invention, but the heating temperature for soaking is low, so that there is a small amount of 2-5 μm medium-grain carbides. It is a thing. It can be seen from Table 2 that when the soaking temperature is raised above 1100 ° C, the medium-grain carbides of 2 to 5 µm increase. Also, comparing the material of component No. 1 containing no Co with the components No. 2 and No. 3 containing Co, by containing Co, the components No. 2 and N are better than those containing no Co.
It can be seen that the inclusion of Co is effective for tools in which the tempering softening resistance of the sample of o.3 is high and a high temperature part is generated by cutting or the like.

1 and 2 show the carbide structures of typical samples. FIG. 1a is a sample 1c which is the steel of the present invention in Table 2.
Is polished with chrome oxide, and particles with clear contours are MC
Type carbide, MC type carbide was 4470 pieces / mm ² . Further, FIG. 1b shows that the same material was selectively corroded with M ₆ C type carbide by Murakami reagent, and the amount of M ₆ C type carbide was 14000 pieces / mm ² . In addition, FIG. 2a shows a comparison steel of Table 2, Sample 1a, which was polished with chromium oxide to emboss MC type carbides.
The number of type carbides was 690 pieces / mm ² . In addition, FIG. 2b shows that the same material was subjected to selective corrosion of M ₆ C type carbide with Murakami reagent, and the amount of M ₆ C type carbide was 7120 pieces / mm ² .

In order to evaluate the toughness of this material, a test piece of 5φ × 70 L was sampled from the above forged material, subjected to the above-mentioned quenching and tempering heat treatment, and then subjected to a bending test with a span of 50 L. In addition, a serious bite (8-15-
6-6-20-15-0.5R) was prepared, and SKD61 tempered to HRC40 was
The cutting life when a continuous cutting test was performed under the conditions shown in Table 3 was measured. In addition, each sample is connected to the partner ring SCM415,
The Ogoshi-type wear test was performed at a friction distance of 400 m, a final load of 6.8 kg, and a friction speed of 3.5 m / S to measure the specific wear amount. The results are shown in Table 4. Table 4 shows that even with the same composition, the samples of Comparative Examples 1a, 2a, and 3a having a low medium-grain carbide density of 2 to 5 μm have a large specific wear amount and insufficient wear resistance, and also have a cutting tool life. It turns out that it is also short and not preferable. Further, among the examples of the present invention, it can be seen that the samples of the components No. 2 and No. 3 containing Co are superior in the tool life and the specific wear amount to the samples of the component No. 1 containing no Co.

[0029]

[Table 3]

[0030]

[Table 4]

Example 2 Nitrogen gas atomized powder was HI
Table 5 prepared by the method of P (hot isostatic pressing)
A material having the composition shown in was produced. Each material was subjected to soaking in the temperature range of 1080 ° C to 1170 ° C after HIP in the same manner as in Example 1, and after forging to make about 16 mm square, the forged material was annealed at 860 ° C and crystallized. As much as possible within the temperature range where grains do not become coarse, only sample 11 was 1210 ° C. for 15 minutes, and other samples were austenitized at 1250 ° C. for 15 minutes, respectively, and then heat-bathed at 550 ° C. I did.
The tempering was performed three times at 560 ° C for 1 hour.

[0032]

[Table 5]

The obtained sample was used in the same manner as in Example 1 except that
The quantification of the carbide density of 5 μm was carried out by diamond polishing the longitudinal section of each forged material, then corroding M ₆ C type carbide with Murakami reagent, and electrolytic corrosion with 10% chromic acid aqueous solution. A sample in which carbide was corroded was prepared. These samples were processed by an image analysis processor. Further, the hardness after tempering, the crystal grain size by the intercept method (after quenching), the hardness after heating and holding at 650 ° C. for 1 hour, and the hardness upon cooling in air (tempering softening resistance) were measured. The results are shown in Table 6. In order to evaluate the toughness of this material, a test piece of 5φ × 70 L was sampled from the above forged material, subjected to the above-mentioned quenching and tempering heat treatment, and then subjected to a bending test with a span of 50 L. In addition, a serious cutting tool (8-15-6-6-20-15-0.5R) that had been subjected to the same heat treatment was produced, and SKD61 that had been tempered to HRC40 was subjected to a continuous cutting test under the conditions shown in Table 3. The cutting life at that time was measured. Also,
Each sample was subjected to the Ogoshi-type wear test at a mating ring SCM415, a friction distance of 400 m, a final load of 6.8 kg, and a friction speed of 3.5 m / S, and the specific wear amount was measured. The results are shown in Table 7.

[0034]

[Table 6]

[0035]

[Table 7]

Hereinafter, each sample will be described in detail. Samples No. 4 to No. 9 which are steels of the present invention are steels of the present invention containing Co, and the number of medium grain carbides of 2 to 5 μm is 10000 pieces / mm ^{2 to} 2000.
Steel in the range of 0 pieces / mm ² . Of the samples of the present invention, N
From No. 6 to No. 8, Nb + V exceeds 6%, and since the amount of hard MC carbide is large, it can be seen that the tool life is particularly excellent and the specific wear amount is small. Of these, No.8
It can be seen that since the Co content is small, the temper softening resistance is lower than those of No. 6 and No. 7. Further, the sample No. 9 of the present invention steel shows an excellent value of the specific wear amount in this example, but the value of Nb / V exceeds 2 and the Nb amount is large relative to the V amount, so that it is slightly coarse NbC. It is found that the transverse rupture strength is slightly lower than that of the other examples, and that the Nb / V amount is preferably 2 or less.

It can be seen that sample No. 10 has a low resistance to temper softening due to a small amount of W and Mo added, and the cutting tool life is significantly shorter than that of the sample of the present invention. Since sample No. 11 does not contain Nb, the quenching temperature cannot be increased in order to prevent the crystal grains from coarsening. Therefore, it can be seen that sufficient alloy elements cannot be solid-dissolved in the matrix, the softening resistance becomes a low value, and the cutting life of the cutting tool is remarkably shorter than that of the sample of the present invention.
Sample No. 12 is a sample in which ΔC calculated by C-Ceq is out of the range of the present invention on the positive side. It can be seen that in this sample, C is excessively solid-dissolved in the matrix, so that the transverse rupture strength is remarkably reduced, which is not preferable. Sample No. 13 is a sample in which ΔC deviates to the negative side from the range of the present invention. ΔC for this sample
Therefore, even if quenching and tempering are performed, the hardness is lower than that of the sample of the present invention, so that the tool cutting life is short and the specific wear amount is large, which is not preferable.

[0038]

EFFECTS OF THE INVENTION According to the present invention, the softening resistance property at high temperature, which has been insufficient in the past, can be significantly improved, so that the wear resistance at high temperature is remarkably improved, and the carbide grain size is 2-5 μm. It was possible to further improve the wear resistance by adjusting so that the size of the product is about the same. Further, since the crystal grains remain fine and the toughness is as high as or higher than that of the conventional one, it is possible to significantly improve the service life under the high-speed use condition of the tool.

[Brief description of drawings]

FIG. 1 is a diagram showing carbides in the structure of the steel of the present invention, and FIG. 1a is a metal microstructure photograph showing MC type carbides, and FIG. 1b.
Is a metal microstructure photograph showing M ₆ C type carbide of the same material.

2 is a diagram showing carbides in the structure of a comparative steel, and FIG.
a is a metal microstructure photograph showing MC type carbide, and FIG. 2B is a metal microstructure photograph showing M ₆ C type carbide of the same material.

Claims (7)

[Claims] 1. A weight ratio of more than C 1.5% and not more than 2.2%, Si ≦.
1.0%, Mn ≦ 0.6%, Cr 3.0-6.0%, W or even Mo
Is 20 to 30% at W + 2Mo and W / 2Mo ≧ 1, V ≦ 5.0%,
Nb 2.0 to 7.0%, but Nb / V ≧ 0.5, the balance is Fe and inevitable impurities, C-Ceq is −0.20 to 0.05 (however Ceq = 0.24 + 0.033 ・ W + 0.063 ・ Mo + 0.2V + 0.1 ・Nb) is satisfied and the carbide density of 2 to 5 μm is 10,000 to 30,000.
Powder high speed tool steel characterized in that it is pieces / mm ² . 2. A weight ratio of more than C 1.5% and 2.2% or less, Si ≦
1.0%, Mn ≦ 0.6%, Cr 3.0-6.0%, W or even Mo
Is 20 to 30% at W + 2Mo and W / 2Mo ≧ 1, V ≦ 5.0%,
Nb 2.0 to 7.0%, with Nb / V ≧ 0.5, Co ≦ 15.0%, the balance Fe and inevitable impurities, and C−Ceq −0.2.
0 to 0.05 (Ceq = 0.24 + 0.033 / W + 0.063 / Mo + 0.2V
+0.1 · Nb), the carbide density of 2 ~ 5μm is 10,
Powder high-speed tool steel characterized by 000 to 30,000 pieces / mm ² . 3. A weight ratio of more than C 1.5% and not more than 2.2%, Si ≦.
1.0%, Mn ≦ 0.6%, Cr 3.0-6.0%, W or even Mo
Is 20 to 30% at W + 2Mo and W / 2Mo ≧ 1, V ≦ 5.0%,
Nb 2.0 to 7.0%, but Nb / V ≧ 0.5, Co 4.0 to 15.0%, balance Fe and unavoidable impurities, and C-Ceq −
0.20-0.05 (however Ceq = 0.24 + 0.033 ・ W + 0.063 ・ Mo ＋ 0.
2V + 0.1 · Nb), and a carbide density of 2-5 μm
Powder high speed tool steel characterized by 10,000 to 30,000 pieces / mm ² . 4. The powder high speed tool steel according to claim 1, wherein the relationship of Nb / V ≦ 2 is satisfied. 5. The powder high speed tool steel according to claim 1, wherein the relationships of Nb / V ≦ 2 and Nb + V> 6 are satisfied. 6. A weight ratio of more than C 1.5% to 2.2% or less, Si ≦
1.0%, Mn ≦ 0.6%, Cr 3.0-6.0%, W or even Mo
Is 20 to 30% at W + 2Mo and W / 2Mo ≧ 1, V ≦ 5.0%,
Nb 2.0 to 7.0%, but Nb / V ≧ 0.5, the balance is Fe and inevitable impurities, C-Ceq is −0.20 to 0.05 (however Ceq = 0.24 + 0.033 ・ W + 0.063 ・ Mo + 0.2V + 0.1 ・After the alloy powder satisfying the relationship of Nb) is sintered to obtain a sintered body, before hot working or during hot working, 1100 ° C. to 1 ° C.
Heat treatment at 200 ℃, and the carbide density of 2 ~ 5μm 10,
A method for producing a powder high-speed tool steel, which is characterized by adjusting to 000 to 30,000 pieces / mm ² . 7. A weight ratio of more than C 1.5% and not more than 2.2%, Si ≦.
1.0%, Mn ≦ 0.6%, Cr 3.0-6.0%, W or even Mo
Is 20 to 30% at W + 2Mo and W / 2Mo ≧ 1, V ≦ 5.0%,
Nb 2.0 to 7.0%, with Nb / V ≧ 0.5, Co ≦ 15.0%, the balance Fe and inevitable impurities, and C−Ceq −0.2.
0 to 0.05 (Ceq = 0.24 + 0.033 / W + 0.063 / Mo + 0.2V
+ 0.1 · Nb) alloy powder that satisfies the relationship of 1) after sintering to obtain a sintered body, before hot working or during hot working 1
A method for producing a powder high-speed tool steel, which comprises performing a heat treatment at 100 ° C to 1200 ° C to adjust a carbide density of 2 to 5 µm to 10,000 to 30,000 pieces / mm ² .