JPS62124261A - Super hard high-speed tool steel - Google Patents

Abstract

PURPOSE:To obtain the titled tool steel combining super hardness with superior machining durability by means of ordinary quench-and-temper even if content of alloying elements and hard material mentioned below is reduced, by uniformly dispersing a specific amount of hard material such as TiN, etc., into a high- speed tool steel matrix in which content of alloying elements such as W, Mo, V, etc., is limited. CONSTITUTION:A powder of high-speed tool steel having a composition satisfying 0<=C-Ceq<=0.6 when Ceq=0.06Cr+0.033W+0.063Mo+0.2V and C=1.7-2.8% and further containing 3-10% Cr, 1-20% W, 1-11% Mo, 1-5.5% V, <=15% Co, <=2% Si, and <=1% Mn and having the balance Fe with impurities is prepared, where 18<=W+2Mo<=24. Subsequently, one or more kinds among nitrides, carbides, carbonitrides of Ti, V, Zr, Nb, Hf, and Ta are mixed with the above powder by 2-12% in total, and then above-mentioned hard material is uniformly dispersed into the above tool steel matrix by means of compacting-sintering, etc., so that the titled steel can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high-speed tool steel that can obtain ultra-high hardness of HRC 71 or higher by ordinary quenching and tempering.

[Conventional technology]

There are few examples of high-speed tool steels that have a superhardness of HRC71 or higher, and are listed in Japanese Patent Publication No. 55-6096, "Hard Alloys."

JP 57-2142, ``Carbide-enriched high-speed tool steel'', JP 57-181367, ``Sintered high-V high-speed tool steel and its manufacturing method'', JP 58-181848
No. 1, “Nitride-containing sintered high-speed tool steel and its manufacturing method”
There is only partial disclosure.

[Problem that the invention seeks to solve]

However, in order to obtain an HRC of 71 or higher using conventional technology, it is necessary to contain a large amount of expensive alloying elements such as W, Mo, and V, or to disperse a large amount of hard substances such as TiN. Becomes expensive, has poor grindability,
There were problems such as a decrease in toughness. For example,
In the embodiment disclosed in No.-2142, HRC71
The superhardness above can be obtained with N o , 5, 11.
There are only 13 alloys (Tables 1 and 2) that have a W + 2 Mo content (N o.

5.11) or an alloy system with a significantly high V content (No. 13).

Furthermore, even in the embodiment disclosed in JP-A No. 57-181367, HRC is
A superhardness of 71 or higher was not obtained (Figure 2).

Furthermore, in JP-A-58-181848, 15
% or more of TiN is not dispersed, superhardness of HRC 71 or higher cannot be achieved.

Therefore, the present invention aims at achieving a superhardness of HRC 71 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 Tj and N is relatively small. The aim is to provide a high-speed tool steel that can be used.

[Means for solving problems]

In the present invention, Ceq =0.06Cr+0.033W +
0.063M.

When +0.2V, in the range of C1.7 to 2.8%,
Ka, satisfies 0≦C-Ceq≦0.6, and further Cr
3 to 10%, W 1 to 20%, Mo 1 to 11% (however, 18≦W + 2 Mo≦24), V 1 to
5.5%, Co 15% or less, Si 2% or less, Mn1
% or less, one or more types of nitrides, carbides, and carbonitrides of Ti, V, Zr, Nb, Hf, and Ta are added to a high-speed tool steel matrix consisting of residual Fe and impurities in a total of 2 to 12%.
The above problem is solved by uniformly dispersing Ni and not more than 0.12% of Ni and 0.12% or less of Ni in the high-speed tool steel matrix.

[Effect]

In the present invention, the C content is the most important component. C is Cr, W, Mo, V and M contained at the same time,
In addition to forming carbides such as C and MC to impart wear resistance, the quench hardening heat treatment increases the hardness of the martensite base and further increases the amount of secondary hardening through tempering. The above carbide-forming elements Cr, W, Mo, ■
It is theoretically known that the equilibrium carbon amount Ceq at which carbon and C combine in just the right amount to form a carbide is expressed by 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, 5KH59 So, Habo-0,3, AI
Even SIM42 is 10, OS).

In the present invention, even if the amount of W, Mo, V and the amount of dispersed particles such as TiN are relatively small, a large number of alloy systems are used for the purpose of obtaining a highly practical high-speed tool steel that has a superhardness of HRC 71 or higher. After experimenting and considering, Ceq=0.06
When Cr+0.033W+0.063Mo+0.2■, in the range of 18≦W+2Mo≦24, O≦C-Ce
It has been newly discovered that it is sufficient to contain C so that q≦0.6 is satisfied. When C-Ceq is less than 0, large amounts of W, Mo, and V are present as described above.

Unless T i N is contained, superhardness of HRC 71 or higher cannot be obtained. 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.C.
A super hardness of 71 or higher cannot be obtained. That is, 18≦
W + 2 M, in the range o≦24.

The object of the present application can be achieved only under the condition of 0≦C-Ceq≦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.

In order to satisfy 0≦C-Ceq≦0.6 within the content range of Cr, W-Mo, and V of the present invention described later, C
is required to be at least 1.7%. On the other hand, even if the above conditions are met, if the C content exceeds 2.8%, the toughness will decrease significantly, so the C content should be in the range of 1.7-2.8% and O≦C-Ceq ≦0.6 and limited bit.

Cr has the effect of increasing quench hardenability, but if it is less than 3%, this effect is small; on the other hand, 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 should be 3 to 3%. Limited to 1 ku.

W and Mo combine with the aforementioned Totoku C to form an M&C type carbide, which has the effect of increasing wear resistance and solid solution in the matrix during quenching and hardening heat treatment, which precipitates as fine carbides during tempering heat treatment. It has the effect of increasing the degree of secondary hardening. In order to achieve the purpose of stably obtaining superhardness of HRC 71 or higher according to the present invention, W1 to 20%, Mo 1 to 1
W + 2 M in the range of 1%.

It is necessary to contain the amount of 18% or more. but.

If the amount of W + 2Mo exceeds 24%, the material will not only become expensive but also have lower toughness, so the content of W and Mo should be W +
The amount of 2 Mo was limited to 18-24%. In the present invention, equal amounts (atomic percent) of W and MO have approximately equivalent effects.

Like V+JW and Mo, it 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 M(, type carbide is stable, the amount of solid solution in the base is small).

W and Mo have no significant effect. Therefore, ■ If the content is increased more than necessary, it will only reduce the grindability and toughness, so in the present invention, the V content is 5.5%.
was set as the upper limit. On the other hand, if the V content is less than 1%, the MC type carbide will not crystallize, resulting in insufficient wear resistance.
It was limited 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 be significantly reduced, so the content of Co was limited to 18 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 quenching hardness, so it is contained in an amount of 1% or less.

Ni has the effect of increasing the toughness of the matrix, but if it exceeds 2%, the amount of retained austenite increases extremely and the tempering hardness decreases, so in the present invention, it is appropriately contained within the range of 2% or less. shall be. Note that high-speed tool steel contains a trace amount of Ni.

The range of Ni 0.25% or less is treated as an impurity amount in JIS.

N has the effect of increasing the hardness of the matrix and the effect of forming a solid solution in the MC type carbide to form an MCN type carbonitride to improve 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, normally about 0.05% or less of N 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, the C content is changed to the equilibrium carbon amount (Ce
It is conventional wisdom that if the value is higher than 0 to 0.6 from q), the austenite crystal grains will become coarse during the quench hardening process, the martensite structure will become rough, and the toughness will be extremely reduced. , according to the present invention, Ti, V, Zr, Nb, Hf,
This drawback can be overcome by uniformly dispersing one or more Ta nitrides, carbides, and carbonitrides in a total amount of 2 to 12%. It was discovered that even if quench hardening treatment is performed at a temperature of

That is, dispersing 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, upon mixing, it is preferable to add and mix carbon powder such as graphite powder and black carbon at the same time for the purpose of adjusting the final carbon content after sintering and improving sinterability. Furthermore, Cr, Ni, Mo, W, Cu,
Co.

Mixing one or more 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 15 types of base compositions shown in Table 1 were produced by a water atomization method. This powder was further crushed and classified with a 350 mesh sieve, and the average particle size was 1 to 1.
10μ TiN, TiC, T1CN, N b C, N
b N , V N , Z r N , T a C
The 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 above powder, wet-mixing using a ball mill for 36 hours, drying, and cold isostatic pressing at 6t/cn! It was molded at a pressure of This molded body was sintered in vacuum at 12Co to 1250°C, and then true densified by hot isostatic pressing.

High speed tools obtained in this way [(Table 1 No
, 1 to No. 15) were annealed, quenching and tempering were performed, and the hardness was measured. Quenching is from 12Co to 1260
After being immersed in a salt bath heated to .degree. C., the sample was cooled in oil and tempered in the atmosphere at 560.degree. C. for (1+1+1) hours. The hardness after tempering is also listed in Table 1, and in the steels of the present invention No. 1 to No. 12, superhardness of 1 to IRC71 or higher was obtained in all cases.

Comparative steel No. 13.14 has a base composition and hard dispersed particle content within the range of the present invention, but both C-Ceq
Since the hardness is at a low level, the hardness is not as high as that of the steel of the present invention.

For conventional steel No. 15, C-Ceq is approximately -0.13
and W + 2Mo = 16.4, so even though the TiN particles were dispersed by about 10%, the I
(The hardness is only RC68.9, and the first
The figure shows the alloy No.3 in Table 1 as 12Co-126.
Similarly, Fig. 2 shows the quenching-tempering hardness curve when quenching at 0°C and tempering at 5Co to 650°C.
The quenching-tempering hardness curve of No. 4 alloy is shown. Alloy No. 3 is tempered at 520-570°C) (Rc 72 or more, and the highest hardness is obtained by tempering at 540°C.
The tempering temperature range in which No. 4 alloy can obtain a hardness of HnC72 or higher is wider than that of No. 3 alloy, and the maximum hardness is also higher. However, the tempering temperature that gives the highest hardness is 56
It is moving towards the high temperature side of 0℃. This indicates that the decomposition of retained austenite is becoming increasingly difficult, and as the peak temperature moves further to the high temperature side, the maximum hardness decreases.

Furthermore, in Table 1, No, 2, NCo3, No, 4, N
o.

A serious cutting tool was made using No. 6, No. 15, and high speed tool steel, and a cutting test was conducted. The results are shown in FIGS. 3 and 4. Figure 3 shows 5KD61 I (RC45
FIG. 3 is a diagram showing the results of cutting a work material that has been tempered to a high speed and a low feed condition. In terms of cutting durability, high-speed tool steels with the highest hardness are ranked first, and all of the steels of the present invention are superior in durability to conventional steels.

FIG. 4 shows the results of cutting a workpiece material in which 5KD61 was tempered to H+tC40 under high speed and high feed conditions. 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.

Example 2 Chemical composition in weight%: C1.77%, Si 0.4%
.

Mn 0.3%, Ni 0.1%, Cr 6.3%, W
2.2%, M.

10.3%, ■2.1%, Co 6.2%, N 0.0
A 4% high speed tool steel powder was produced by water atomization method. This powder was mechanically pulverized and then classified using a 350-mesh sieve to obtain a powder of 44 μm or less. When the oxygen content of this powder was analyzed, it was found to be 45CoPPm.

Next, for the purpose of reducing surface oxides of 88% of the above powder, 8% of TiN powder with an average particle size of 1.3μ, 2% of VC powder with an average particle size of 2.1μ, and the above high speed tool steel powder, 0. 45% graphite powder and 1.55% CO grain powder (particle size: 1.2 μm) were placed in a ball mill and wet-mixed for the purpose of improving sinterability. After drying this mixed powder, it was press-molded at a pressure of 5t/aJ, and then sintered at 1220°C and 211r in vacuum. The specific gravity after sintering had almost reached the true density. Furthermore, the carbon content of the material after sintering is.

1.92%, and the oxygen content was 230 PPm.

After annealing the sintered body thus obtained,
When quenching and tempering was carried out under the conditions of 560°C and (1+1+1) hours, a hardness of HRC 72.8 was obtained.

〔Effect of the invention〕

As mentioned above, the high speed tool steel of the present invention is made of W, Mo.
Even if the content of alloying elements such as , V, or hard substances such as TiN is relatively low, superhardness of HRC 71 or higher can be obtained through normal quenching and tempering, and it can be used as a cutting tool material with excellent cutting durability. It is the most suitable one.

1 Brief description of the drawings Figure 1 is a diagram showing the quenching-tempering hardness of the No. 3 alloy in Table 1, and Figure 2 is a diagram showing the quenching-tempering hardness of the NCo4 alloy in Table 1. The hardness diagrams, 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.

Part 1 Enter　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

Claims (1)

[Claims] 1 Ceq=0.06Cr+0.033W+0.063
When Mo+0.2V, 0≦C-Ceq≦0.6 is satisfied in the range of C1.7 to 2.8%, and Cr3 to
10%, W1~20%, Mo1~11% (however, 18%
≦W+2Mo≦24), V1 ~ 5.5%, Co 15% or less, Si 2% or less, Mn 1% or less, remaining Fe and impurities in a high speed tool steel matrix containing Ti, V, Zr, Nb, and H.
1. A superhard high-speed tool steel characterized in that a total of 2 to 12% of one or more of Ta nitrides, carbides, and carbonitrides is uniformly dispersed therein. 2 Ceq=0.06Cr+0.033W+0.063
When Mo+0.2V, 0≦C-Ceq≦0.6 is satisfied in the range of C1.7 to 2.8%, and Cr3 to
10%, W1~20%, Mo1~11% (however, 18%
≦W+2Mo≦24), V1 to 5.5%, Co 15% or less, Si 2% or less, Mn 1% or less, Ni 2% or less, remaining F
Ti, V,
A superhard high-speed tool steel characterized in that a total of 2 to 12% of one or more of nitrides, carbides, and carbonitrides of Zr, Nb, Hf, and Ta are uniformly dispersed. 3 Ceq=0.06Cr+0.033W+0.063
When Mo+0.2V, 0≦C-Ceq≦0.6 is satisfied in the range of C1.7 to 2.8%, and Cr3 to
10%, W1~20%, Mo1~11% (however, 18%
≦W+2Mo≦24), V1 to 5.5%, Co 15% or less, Si 2% or less, Mn 1% or less, N 0.1% or less, remaining Fe and impurities in a high speed tool steel matrix containing Ti, V
, Zr, Nb, Hf, and Ta nitrides, carbides, and carbonitrides, and a total of 2 to 12% of one or more of these nitrides, carbides, and carbonitrides are uniformly dispersed therein. . 4 Ceq=0.06Cr+0.033W+0.063
When Mo+0.2V, 0≦C-Ceq≦0.6 is satisfied in the range of C1.7 to 2.8%, and Cr3 to
10%, W1~20%, Mo1~11% (however, 18%
≦W+2Mo≦24), V1 to 5.5%, Co15% or less, Si2% or less, Mn1% or less, Ni2% or less, N0
．． A total of 2 to 1% of one or more of nitrides, carbides, and carbonitrides of Ti, V, Zr, Nb, Hf, and Ta is added to a high-speed tool steel matrix consisting of 1% or less of residual Fe and impurities.
A super hard high speed tool steel characterized by uniformly dispersing 2%. 5 Ceq=0.06Cr+0.033W+0.063
When Mo+0.2V, C is in the range of 1.7 to 2.8% and satisfies 0≦C-Ceq≦0.6, and further C
r3-10%, W1-20%, Mo1-11% (however, 18≦W+2Mo≦24), V1-5.5%, Co1
High-speed tool steel consisting of 5% or less, Si 2% or less, Mn 1% or less, Ni 2% or less, N 0.1% or less, residual Fe and impurities, and a high-speed tool with appropriate additions of Ni 2% or less and N 0.1% or less. 88 to 98% of steel atomized powder and nitrides and carbides of Ti, V, Zr, Nb, Hf, Ta,
The high hardness according to any one of claims 1 to 4, which is obtained by uniformly mixing a total of 2 to 12% of one or more carbonitrides, and then molding and sintering the mixture. Speed tool steel. 6. The superhard high-speed tool steel according to any one of claims 1 to 5, which has a hardness of H_RC71 or more after quenching and tempering.