JPH0575822B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is capable of producing H _R C71 by normal quenching and tempering.
The present invention relates to a high-speed tool steel that can obtain the above ultra-high hardness and a manufacturing method. [Prior art] There are few examples of high-speed tool steels that have a superhardness of H _R C71 or higher. "Speed Tool Steel", JP-A-57-181367, "Sintered High-V High-Speed Tool Steel and Its Manufacturing Method", JP-A-58-181848, "Nitride-Containing Sintered High-V High-Speed Tool Steel and Its Manufacturing Method" There is only a partial disclosure in "Manufacturing method". [Problems to be solved by the invention] However, when trying to obtain H _R C71 using conventional techniques, it is necessary to contain large amounts of expensive alloying elements such as W, Mo, and V, or to use hard substances such as TiN. It is necessary to disperse a large amount, making the material expensive and having poor grindability. There were problems such as a decrease in toughness. For example, in the example disclosed in Japanese Patent Publication No. 57-2142, only alloys No. 5, 11, and 13 (Tables 1 and 2) can achieve a superhardness of H _R C71 or higher. However, these are W + 2Mo amount (No. 5, 11)
Alternatively, it can be seen that it is an alloy system with a significantly high V content (No. 13). Furthermore, even in the embodiment disclosed in JP-A-57-181367, it is necessary to contain 20% or more of V.
A superhardness of H _R C71 or higher has not been achieved (Figure 2).
Furthermore, even in JP-A-58-181848, superhardness of H _R C71 or higher is not achieved unless 15% or more of TiN is dispersed. Therefore, the present invention provides that even if the content of alloying elements such as W, Mo, V, etc. or hard substances such as TiN is relatively small, a superhardness of H _R C71 or higher can be obtained by normal quenching and tempering. The aim is to provide high-speed tool steel. [Means for solving the problem] The present invention provides Ceq=0.06Cr+0.033W+0.063Mo+
When 0.2V, C is in the range of 1.7 to 2.8%, and
Satisfies 0≦C-Ceq≦0.6, and further contains Cr3~10%,
W1~20%, Mo1~11% (18≦W+2Mo
≦24), V1~5.5%, Co15% or less, Si2% or less,
One or more selected from the group of nitrides, carbonitrides, and carbides of Ti, V, Zr, Nb, Hf, and Ta on a high-speed tool steel matrix consisting of 1% or less Mn and the balance Fe and impurities. and at least one of the nitrides and carbonitrides,
The above problem is solved by uniformly dispersing hard particles whose total weight is 2 to 12% of the total weight. Moreover, the present invention
The above-mentioned high-speed tool steel substrates include those containing the above-mentioned elements and further containing 2% or less Ni and 0.1% or less N. [Operation] In the present invention, the content of C is the most important component. C is Cr, W, which is contained at the same time.
It forms carbides such as Mo, V, M ₆ C, and MC, and has the effect of imparting wear resistance, as well as increasing the hardness of the martensite base through quench hardening heat treatment, and further increasing the amount of secondary hardening through tempering. . Equilibrium carbon amount at which the above carbide-forming elements Cr, W, Mo, V and C combine in just the right amount to form carbide.
It is logically known that Ceq is the following formula. Ceq = 0.06 (%Cr) + 0.033 (%W) + 0.063 (%Mo) + 0.2 (%V) In conventional high-speed tool steel, the difference between C content and equilibrium carbon content Ceq, C- Ceq is adjusted to be negative (for example, approximately -0.3 for SKH59, -0.05 for AISIM42). In the present invention, even if the amount of W, Mo, V and the amount of dispersed particles such as TiN is relatively small, a superhardness of H _R C71 or higher can be obtained and a large number of As a result of experiments and studies regarding the alloy system, when Ceq=0.06Cr+0.033W+0.063Mo+0.2V, in the range of 18≦W+2Mo≦24, 0≦C-
We have newly discovered that it is sufficient to contain C so that Ceq≦0.6 is satisfied. If C-Ceq is less than 0, a superhardness of H _R C71 or higher cannot be obtained unless large amounts of W, Mo, V, and TiN are contained as described above. On the other hand, when C-Ceq exceeds 0.6, stable retained austenite increases significantly during quench hardening heat treatment, and the decomposition temperature of retained austenite shifts to a high temperature side, so even if secondary hardening is performed by tempering, H _R It becomes impossible to obtain superhardness of C71 or higher. That is, in the range of 18<W+2Mo≦24, 0≦C−Ceq
The purpose of the present application can be achieved only under the condition of ≦0.6. As mentioned above, C should be appropriately changed depending on the amounts of Cr, W, Mo, and V contained at the same time. Cr, W, Mo, V of the present invention described below
In order to satisfy 0≦C-Ceq≦0.6, C must be at least 1.7%.
On the other hand, even if the above conditions are met, the C content remains
If it exceeds 2.8%, the decrease in toughness will be significant, so C
The content is in the range of 1.7 to 2.8%, and 0≦C-Ceq
It was limited to ≦0.6. Cr has the effect of increasing quench hardenability, but 3
If the Cr content is less than 10%, this hardening will be small, whereas if it exceeds 10%, the amount of retained austenite will increase and the quenching/tempering hardness will decrease, so the Cr content was limited to 3 to 10%. As mentioned above, W and Mo combine with C to form M ₆ C
It has the effect of forming carbide in the mold and increasing its wear resistance, and solid solution in the matrix during quenching and hardening heat treatment, which precipitates as fine carbide during tempering heat treatment and increases the degree of secondary hardening. In order to achieve the purpose of stably obtaining a superhardness of H _R C71 or higher according to the present invention, W +
It is necessary to contain 2Mo amount of 18% or more.
However, if the amount of W + 2Mo exceeds 24%, the material not only becomes expensive but also has poor toughness.
The content of W+2Mo was limited to 18 to 24%.
In addition, in the present invention, an equal amount (atomic percent) of W
and Mo have almost equivalent effects. Like W and Mo, V also combines with C to form MC type carbide, which has the effect of increasing wear resistance. It also contributes to secondary hardening during tempering, but since the MC type carbide is stable, the amount of solid solution in the matrix is small.
It does not have as great an effect as W or Mo. Therefore, increasing the V content more than necessary will only reduce the grindability and toughness, so in the present invention, the upper limit of the V content is set at 5.5%. On the other hand, 1%
If the V content is less than 1%, the MC type carbide will not crystallize and the wear resistance will be insufficient. Therefore, the V content was limited to 1 to 5.5%. Co dissolves in the matrix and has the effect of increasing tempering hardness and high-temperature hardness. However, if it is contained in a large amount, the toughness will decrease significantly, so the content of Co
Limited to 15% or less. Since Si acts as a deoxidizer and further increases the hardness of the base, it is contained in an amount of 2% or less. Mn also has a deoxidizing effect and also has the effect of increasing quench hardness, so it is contained in an amount of 1% or less. Ni has the effect of increasing the toughness of the base, but 2
If it exceeds 2%, the amount of retained austenite will increase extremely and the tempering hardness will decrease. Therefore, in the present invention, the content should be appropriately within the range of 2% or less. Note that high-speed tool steel contains a trace amount of Ni, and the range of Ni 0.25% or less is treated as an impurity amount by JIS. N has the effect of increasing the hardness of the base, and the effect of forming a solid solution in the MC type carbide to form an MCN type carbonitride, thereby increasing the welding resistance. However, since the upper limit of the amount that can be contained industrially is 0.1%, in the present invention, it is appropriately contained within the range of 0.1%. In addition, in high-speed tool steel, usually N0.05
% or less may be contained as an impurity amount. Nitride, carbide of Ti, V, Zr, Nb, Hf, Ta,
Dispersing carbonitrides has the effect of increasing hardness. Furthermore, as in the present invention, if the C content is 0 to 0.6 higher than the equilibrium carbon content (Ceq), the austenite crystal grains will become coarse during the quench hardening process.
It was conventional wisdom that the martensitic structure becomes rough and the toughness is extremely reduced. It consists of one or more selected from the following, and contains at least one of the nitrides and carbonitrides, and is uniformly dispersed so that the total weight of the nitrides and carbonitrides is 2 to 12% of the total weight. The inventors have discovered that this drawback can be overcome by tightening the material, and that even if the quench hardening treatment is performed at a high austenitizing temperature just below the melting start temperature, a significantly finer structure can be obtained. That is, dispersing the nitrides, carbides, and carbonitrides is C
The defects caused by the content being higher than the Ceq amount are successfully compensated for, and the object of the present invention is achieved. However, if it is less than 2%, the above effect will be small;
On the other hand, if it exceeds 12%, the effect not only becomes saturated, but also the grindability and toughness are significantly reduced.
It was limited to 2-12%. As a method for uniformly dispersing nitrides, carbides, and carbonitrides in a substrate,
High-speed tool steel powder with the above chemical composition is produced by atomizing water, gas, oil, etc.
The most suitable method is to mix this powder with nitride, carbide, or carbonitride powder, then mold and sinter it. In addition, upon mixing, it is preferable to add and mix carbon powder such as graphite powder or black carbon at the same time for the purpose of adjusting the final carbon content after sintering and improving sinterability. Furthermore, when one or more of Cr, Ni, Mo, W, Cu, Co, and Fe powders are simultaneously mixed in a total of 5 wt % or less, there is an effect of improving sinterability. [Example] Next, the present invention will be explained in more detail with reference to Examples. Example 1 Powders having a total of 22 base powder compositions shown in Table 1 were produced by a water atomization method. After further crushing this powder and classifying it with a 350 mesh sieve, TiN, TiC, TiCN with an average particle size of 1 to 10μ,
NbC, NbN, VN, ZrN, TaC, HfC, HfN,
HfCN, VC, VCN, NbCN, ZrCN, ZrC,
TaN and TaCN powders were mixed in the proportions shown in Table 1. Furthermore, after adding carbon powder in an amount equal to the oxygen content of the powder, the mixture was wet mixed using a ball mill for 36 hours, dried, and then molded using a cold isostatic press at a pressure of 6 t/cm ² . This molded body is heated to 1200 to 1250℃ in a vacuum.
The material was sintered using a hot isostatic press, followed by true densification using a hot isostatic press. High speed tool steel thus obtained (Table 1
After annealing No. 1 to No. 22), quenching and tempering were performed and the hardness was measured. Quenching was performed by immersing in a salt bath heated to 1,200 to 1,260°C and cooling in oil, and tempering was performed in the air at 560°C x (1+1+1) hours. The hardness after tempering is also listed in Table 1, but for steels of the present invention No. 1 to No. 22, all
A superhardness of H _R C71 or higher was obtained.

〔Effect of the invention〕

As stated above, the high speed tool steel of the present invention is
Even if the content of alloying elements such as W, Mo, and V or hard substances such as TiN is relatively low, a superhardness of H _R C71 or higher can be obtained through normal quenching and tempering, and excellent cutting durability can be achieved. It is the most suitable cutting tool material.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the quenching-tempering hardness of alloy No. 3 in Table 1, Figure 2 is a diagram showing the quenching-tempering hardness of alloy No. 4 in Table 1, FIGS. 3 and 4 are diagrams showing the results of cutting tests using serious cutting tools made from the steel of the present invention and the conventional steel.

Claims (1)

[Claims] 1. A powder metallurgy product, Ceq=0.06Cr+
When 0.033W + 0.063Mo + 0.2V, C1.7~2.8
%, satisfies 0≦C-Ceq≦0.6, and
Cr3~10%, W1~20%, Mo1~11% (however,
18≦W+2Mo≦24), V1~5.5%, Co15% or less,
A high-speed tool steel matrix consisting of 2% Si or less, 1% or less Mn, and the balance Fe and impurities, and nitrides, carbonitrides, and carbides of Ti, V, Zr, Nb, Hf, and Ta uniformly dispersed in the matrix. consisting of one or more selected from the group, and hard particles containing at least one of the nitrides and carbonitrides, the total weight of which is 2 to 12% of the total weight. A superhard high-speed tool steel featuring: 2 Powder metallurgy product, Ceq=0.06Cr+
When 0.033W + 0.063Mo + 0.2V, C1.7~2.8
%, satisfies 0≦C-Ceq≦0.6, and
Cr3~10%, W1~20%, Mo1~11% (however,
18≦W+2Mo≦24), V1~5.5%, Co15% or less,
A high-speed tool steel matrix consisting of Si2% or less, Mn1% or less, Ni2% or less, the balance Fe and impurities, and Ti, V, Zr, Nb, Hf, Ta uniformly dispersed in the matrix.
1 or 2 or more selected from the group of nitrides, carbonitrides, and carbides, and includes at least one of the nitrides and carbonitrides, with a total weight of 2 to 30% of the total weight. Super hard high speed tool steel characterized by consisting of 12% hard particles. 3 Powder metallurgy product, Ceq=0.06Cr+
When 0.033W + 0.063Mo + 0.2V, C1.7~2.8
%, satisfies 0≦C-Ceq≦0.6, and
Cr3~10%, W1~20%, Mo1~11% (however,
18≦W+2Mo≦24), V1~5.5%, Co15% or less,
High-speed tool steel matrix consisting of Si2% or less, Mn1% or less, N0.1% or less, balance Fe and impurities, and Ti, V, Zr, Nb, Hf, Ta uniformly dispersed in the matrix.
1 or 2 or more selected from the group of nitrides, carbonitrides, and carbides, and includes at least one of the nitrides and carbonitrides, with a total weight of 2 to 30% of the total weight. Super hard high speed tool steel characterized by consisting of 12% hard particles. 4 Powder metallurgy product, Ceq=0.06Cr+
When 0.033W + 0.063Mo + 0.2V, C1.7~2.8
%, satisfies 0≦C-Ceq≦0.6, and
Cr3~10%, W1~20%, Mo1~11% (however,
18≦W+2Mo≦24), V1~5.5%, Co15% or less,
A high speed tool steel matrix consisting of Si2% or less, Mn1% or less, Ni2% or less, N0.1% or less, the balance Fe and impurities, Ti, V, Zr uniformly dispersed in the matrix,
Consisting of one or more selected from the group of nitrides, carbonitrides, and carbides of Nb, Hf, and Ta, and containing at least one of the nitrides and carbonitrides, the total weight of which is A superhard high-speed tool steel characterized by comprising 2 to 12% of hard particles. 5. The superhard high-speed tool steel according to any one of claims 1 to 4, which has a hardness of HRC71 or higher after quenching and tempering. 6 When Ceq=0.06Cr+0.033W+0.063Mo+0.2V, in the range of C1.7 to 2.8%, 0≦C−Ceq≦
Satisfies 0.6 and further Cr3~10%, W1~20%,
Mo1~11% (18≦W+2Mo≦24), V1~
Atomized powder of high speed tool steel, containing 5.5% Co, 15% or less, Si 2% or less, Mn 1% or less, and the balance consisting of Fe and impurities, Ti, V, Zr, Nb, Hf, Ta
1 or 2 or more selected from the group of nitrides, carbonitrides and carbides, and also contains at least one of the nitrides and carbonitrides, with a total weight of 2 to 12%. A method for producing ultra-hard high-speed tool steel by uniformly mixing, forming, and sintering. 7 In addition to the atomized alloy powder and hard particle powder, metal powder of one or more of Cr, Mo, W, Co, and Fe in a total amount of 5 wt% or less is mixed uniformly, then molded and sintered. A method for producing a superhard high-speed tool steel according to claim 6.