JPH0569911B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is capable of producing H _R C72 by normal quenching and tempering.
The present invention relates to a high-speed tool steel that can obtain the above-mentioned ultra-high hardness and a method for producing the same. [Prior art] There are few examples of high-speed tool steels that have a superhardness of H _R C72 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, in order to obtain H _R C72 or higher using conventional techniques, it is necessary to contain large amounts of expensive alloying elements such as W, Mo, and V, or to use hard materials such as TiN. It is necessary to disperse a large amount of the material, which causes problems such as the material becomes expensive, the grindability deteriorates, and the toughness decreases. For example, in the example disclosed in Japanese Patent Publication No. 57-2142, only alloy No. 11 (Tables 1 and 2) can achieve a superhardness of H _R C72 or higher; is an alloy system with a significantly high W+2Mo content of 49.7%. Furthermore, even in the embodiment disclosed in JP-A No. 57-181367, it is necessary to contain 25% or more of V.
A superhardness higher than H _R C72 has not been obtained (Figure 2).
Furthermore, even in JP-A-58-181848, superhardness of H _R C72 or higher is not achieved unless 15% or more of TiN is dispersed. Therefore, the present invention aims at achieving a superhardness of H _R C72 or higher through normal quenching and tempering even if the content of alloying elements such as W, Mo, and V or hard substances such as TiN is relatively small. The aim is to provide high-speed tool steel. [Means for solving the problems] The present invention is a powder metallurgy product in which Ceq=
When 0.06Cr + 0.033W + 0.063Mo + 0.2V,
In the range of C2.0 to 3.5%, and 0.1≦C-Ceq≦0.6
Satisfied, and additionally Cr3~10%, W1~20%, Mo1
~11% (18≦W＋2Mo≦24), V5.6～15
%, Co15% or less, Si2% or less (preferably Si0.8~
2%), Mn 1% or less (preferably Mn 0.25-1.0
%), one or more types of nitrides, carbonitrides, and carbides of Ti, V, Zr, Nb, Hf, and Ta are added to the high-speed tool steel matrix consisting of residual Fe and impurities in a total of 2 to 12 The problem mentioned above is solved by uniformly dispersing the %. In addition, in the present invention, for the reasons described later, Ni2% or less and N0.1 are added to the high-speed tool steel substrate.
% or less may be added as appropriate. [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 theoretically known that Ceq is expressed as 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 the C content and the equilibrium carbon content Ceq, C-Ceq, is adjusted to be negative (for example, in JIS SKH59,
Almost -0.3, even -0.05 in AISIM42). In the present invention, even if the amount of W, Mo, V or dispersed particles such as TiN is relatively small, a superhardness of H _R C72 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, C-Ceq does not become negative as in the past in the range of 18≦W + 2Mo≦24, but 0.1≦C-Ceq ≦
It was newly discovered that it is sufficient to contain C so as to satisfy 0.6. If C-Ceq is less than 0.1, a superhardness of H _R C72 or higher cannot be obtained unless large amounts of W, Mo, V, and TiN are contained as described above.
Conversely, when C-Ceq exceeds 0.6, stable retained austenite increases significantly during quench hardening heat treatment,
In addition, since the decomposition temperature of retained austenite shifts to the high temperature side, even if secondary hardening is performed by tempering, H _R
It becomes impossible to obtain a superhardness of C72 or higher. That is,
In the range of 18≦W+2Mo≦24, 0.1≦C−Ceq≦0.6
The purpose of this application can be achieved only under these conditions. 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
At least 2.0% of C is required in order to satisfy 0.1≦C-Ceq≦0.6.
On the other hand, even if the above conditions are met, the C content remains
If it exceeds 3.5%, the toughness will decrease significantly, so C
The content is in the range of 2.0 to 3.5%, and 0.1≦C-Ceq
It was limited to ≦0.6. Furthermore, if the Cr content is more than 6% and less than 10%, the lower limit of the C content is set at 2.25%.
It is best to limit it to Cr has the effect of increasing quench hardenability, but 3
If the content of Cr is less than 1%, this effect will be small, and if it exceeds 10%, the amount of retained austenite will increase and the hardness of quenching and tempering will decrease, so the content of Cr was limited to 3 to 10%. In particular, in order to obtain a superhardness of H _R C72 or higher even when heat treated in a quenching furnace with a slow cooling rate such as vacuum quenching, the Cr content is preferably more than 6% and less than 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 the wear resistance, and solid solution in the matrix during quench hardening heat treatment, which precipitates as fine carbide during tempering heat treatment and increases the degree of secondary hardening. The stability of the present invention
To achieve the purpose of obtaining superhardness of H _R C72 or higher, W + 2Mo should be set in the range of W1~20% and Mo1~11%.
It is necessary to contain 18% or more. However, if the amount of W + 2Mo exceeds 24%, the material not only becomes expensive but also has a lower toughness, so the content of W and Mo was limited to 18 to 24% in terms of W + 2Mo. In addition,
In the present invention, equal amounts (in atomic percent) of W and Mo
has almost the same effect. Like W and Mo, V also combines with C to form MC type carbide. The hardness of this MC type carbide is H _V
2500~3000 and _M6 C type carbide hardness (H _V 1500~
1800) has significantly higher hardness. For this reason, in tools where wear resistance is particularly important, use of high speed tool steel with a high V content will improve tool life. However, even if the V content is increased more than necessary, it will only worsen the grindability, shorten the service life due to grinding burns, and reduce the toughness.
In the present invention, the upper limit of the V content is 15%.
On the other hand, if the V content is less than 5.6%, the wear resistance effect is insufficient, so the V content is limited to 5.6 to 15%. 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. Si is contained in an amount of 2% or less for the purpose of deoxidation, but especially in the Si range of 0.8 to 2%, in addition to the deoxidation effect, it has the effect of increasing the hardness of the base, and the effect of increasing oxidation resistance and corrosion resistance. appears to have the effect of improving atomization workability. If it exceeds 2%, the toughness will be significantly reduced. Mn also has a deoxidizing effect and also has the effect of increasing hardenability, so it is contained in an amount of 1% or less. especially,
When the above-mentioned Si content is high, Mn can be used to stabilize ferrite and alleviate the adverse effects of Si, which increases the _A1 transformation point, so it is preferable to include 0.25 to 1.0% of Mn. 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, so in the present invention, the content is allowed to be 2% or less. Note that high-speed tool steel usually contains a small amount of Ni,
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, the upper limit of the amount that can be contained industrially is 0.1%, so 0.1
% or less. In high-speed tool steel, N0.05% or less is usually contained as an impurity. Nitride, carbide of Ti, V, Zr, Nb, Hf, Ta,
Dispersing carbonitrides has the effect of increasing hardness. On the other hand, as in the present invention, if the C content is 0.1 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 would become rough and the toughness would be extremely reduced, but with the present invention, the martensitic structure is roughened and the toughness is extremely reduced. A total of one or more types of 2
It was discovered that this defect could be overcome by uniformly dispersing ~12% of the material, resulting in a significantly finer structure even when quench hardening was performed at a high austenitizing temperature just below the melting start temperature. did. That is, the dispersion of the nitrides, carbides, and carbonitrides effectively compensates for the drawbacks caused by the C content being higher than the Ceq content, thereby achieving the object of the present invention. However, if it is less than 2%, the above effect will be small, while if it exceeds 12%, the effect will not only be saturated, but also the grindability and toughness will be significantly reduced. was limited to 2% to 12% in total. A method for uniformly dispersing nitrides, carbides, and carbonitrides in a matrix is to produce high-speed tool steel powder with the above chemical composition by atomizing water, gas, oil, etc. The most suitable method is to mix the powder with nitride, carbide, or carbonitride powder, and then mold and sinter it. In addition, when mixing, adjust the final carbon content after sintering,
Also, for the purpose of improving sinterability, carbon powder such as graphite powder or black carbon may be added and mixed at the same time. Furthermore, Cr, Ni, Mo, W,
Mixing one or more of Cu, Co, and Fe powders in a total amount of 5% or less has the 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 21 base powder compositions shown in Table 1 were manufactured by a water atomization method. After further crushing this powder and classifying it with a 350 mesh sieve, TiN, TiCN, NbC with an average particle size of 1 to 10μ,
VN, NbN, TaC, ZrN, VC, HfC, HfN,
HfCN, ZrCN, VCN, TaN, NbCN, TaCN,
ZrC powder was 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 compact was sintered in vacuum at 1200 to 1250°C, and then subjected to true densification using hot isostatic pressing. High speed tool steel thus obtained (Table 1
After annealing No. 1 to No. 21), 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 No. 1 to No. 18 of the present invention, all
A superhardness of H _R C72 or higher was obtained. Comparative steels No. 19 and No. 20 have a base composition and hard dispersed particle content within the range of the present invention, but both have C.
- Since the Ceq is at a low level, the hardness is not as high as that of the steel of the present invention. For conventional steel No. 21, C-Ceq is low at approximately -0.13 and W + 2Mo = 16.4, so
Despite dispersing approximately 10% of TiN particles,
Only a hardness of H _R C68.9 was obtained. Furthermore, No. 1, No. 2, No. 3, No. 4 in Table 1,
Cutting tests were conducted using serious cutting tools made using No. 6 and No. 21 high-speed tool steels. The results are shown in FIGS. 1 and 2. Figure 1 shows SKD61 H _R
It is a figure which shows the result of cutting the work material tempered to C45 under the conditions of high speed and low feed. The cutting durability is in the order of high-speed tool steels that provide approximately high hardness, and all of the steels of the present invention are superior in durability to conventional steels. Figure 2 shows the results of cutting a workpiece material made from SKD61 tempered to H _R C41 under conditions of low speed and high feed. Even under these conditions, the steel of the present invention exhibits superior cutting durability compared to conventional steel. This is because, although the steel of the present invention has high hardness, it also has the toughness of the cutting edge to withstand high feed conditions.

【table】

〔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 C72 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]

FIGS. 1 and 2 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, C2.0~3.5
% range, satisfies 0.1≦C-Ceq≦0.6, and furthermore Cr3~10%, W1~20%, Mo1~11% (however,
18≦W+2Mo≦24), V5.6~15%, Co15% or less,
A high-speed tool steel matrix consisting of 2% Si or less, 1% or less Mn, residual Fe and impurities, and nitrides, carbonitrides, and carbides of Ti, V, Zr, Nb, Hf, and Ta uniformly dispersed in the matrix. 1. A superhard high-speed tool steel characterized by comprising hard particles of one or more kinds, the total amount of which is 2 to 12% of the total. 2 Powder metallurgy product, Ceq=0.06Cr+
When 0.033W + 0.063Mo + 0.2V, C2.0~3.5
% range, satisfies 0.1≦C-Ceq≦0.6, and furthermore Cr3~10%, W1~20%, Mo1~11% (however,
18≦W+2Mo≦24), V5.6~15%, Co15% or less,
A high-speed tool steel matrix consisting of Si2% or less, Mn1% or less, Ni2% or less, residual Fe and impurities, and nitrides and carbonitrides of Ti, V, Zr, Nb, Hf, and Ta uniformly dispersed in the matrix. 1. A superhard high-speed tool steel characterized by comprising hard particles comprising one or more types of hard particles and carbides, and the total amount of the hard particles is 2 to 12% of the total. 3 Powder metallurgy product, Ceq=0.06Cr+
When 0.033W + 0.063Mo + 0.2V, C2.0~3.5
% range, satisfies 0.1≦C-Ceq≦0.6, and furthermore Cr3~10%, W1~20%, Mo1~11% (however,
18≦W+2Mo≦24), V5.6~15%, Co15% or less,
A high speed tool steel matrix consisting of Si 2% or less, Mn 1% or less, N 0.1% or less, residual Fe and impurities, and nitrides of Ti, V, Zr, Nb, Hf, Ta uniformly dispersed in the matrix, 1. A superhard high-speed tool steel characterized by comprising hard particles consisting of one or more types of carbonitrides and carbides, and the total amount being 2 to 12% of the total. 4 Powder metallurgy product, Ceq=0.06Cr+
When 0.033W + 0.063Mo + 0.2V, C2.0~3.5
% range, satisfies 0.1≦C-Ceq≦0.6, and furthermore Cr3~10%, W1~20%, Mo1~11% (however,
18≦W+2Mo≦24), V5.6~15%, Co15% or less,
A high-speed tool steel matrix consisting of Si2% or less, Mn1% or less, Ni2% or less, N0.1% or less, residual Fe and impurities, and Ti, V, Zr, uniformly dispersed in the matrix,
Nitride, carbonitride, and carbide of Nb, Hf, and Ta
1. A superhard high-speed tool steel characterized by comprising one or more kinds of hard particles, the total amount of which is 2 to 12% of the total. 5 C in the high-speed tool steel matrix is 2.25-3.5%, Cr
The superhard high-speed tool steel according to any one of claims 1 to 4, wherein: is more than 6% and less than 10%. 6 Si in the high-speed tool steel matrix is 0.8-2%, Mn is
Claims 1 to 5 which are 0.25 to 1.0%
The superhard high-speed tool steel described in any of the above. 7. The superhard high-speed tool steel according to any one of claims 1 to 6, which has a hardness of HRC72 or higher after quenching and tempering. 8 When Ceq=0.06Cr+0.033W+0.063Mo+0.2V, 0.1≦C−Ceq≦ in the range of C2.0 to 3.5%
Satisfies 0.6 and further Cr3~10%, W1~20%,
Mo1~11% (18≦W＋2Mo≦24), V5.6
~15%, Co15% or less, Si2% or less, Mn1% or less, atomized powder of high speed tool steel consisting of residual Fe and impurities, Ti, Zr, V, Nb, Hf,
A method for producing ultra-hard high-speed tool steel by uniformly mixing 2 to 12% powder of one or more Ta nitrides, carbonitrides, and carbides, and then forming and sintering the mixture. . 9 When Ceq=0.06Cr+0.033W+0.063Mo+0.2V, 0.1≦C−Ceq≦ in the range of C2.0 to 3.5%
Satisfies 0.6 and further Cr3~10%, W1~20%,
Mo1~11% (18≦W＋2Mo≦24), V5.6
The atomized alloy powder contains Cr, Mo,
5 in total of one or more of W, Co, and Fe
% or less of metal powder, these two types of powder,
Furthermore, after uniformly mixing powder of 2 to 12% in total of one or more of Ti, Zr, V, Nb, Hf, and Ta nitrides, carbonitrides, and carbides, it is molded and sintered. A manufacturing method for ultra-hard high-speed tool steel.