JPH06279943A - Powder high speed tool steel having high hardness and high toughness - Google Patents

Abstract

PURPOSE:To obtain a high speed tool steel with high hardness and high toughness by specifying a composition consisting of C, Si, Mn, Ni, Cr, Mo, W, V, Co, and Fe. CONSTITUTION:This steel is a powder high speed tool steel which consists of, by weight, 1-2% C, 0.1-1% Si, <=0.5% Mn, <=0.5% Ni, 2-6% Cr, 1-10% Mo, 3-13% W (where 2Mo+W=18 to 24%), 2-7% V, 5-11% Co, and the balance Fe with inevitable impurities and where Mo and W are regulated so that relations in inequality 22=14(C-Ceq)+(2Mo+W)+Co<=30 and equation Ceq=0.06Cr+0.063Mo+0.033W+0.2V are satisfied. Hardness as high as >=67 HRC can be obtained and high toughness can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder high speed tool steel useful as a material for cutting tools, dies, blades and the like, and more particularly to a powder high speed tool steel having both high hardness and high toughness. .

[0002]

2. Description of the Related Art High speed tool steel is a tool steel in which a large amount of Cr, Mo, W, V, etc. is added to further enhance hardness and wear resistance at high temperatures. It is widely used as a mold material. In addition, since high-speed tool steel produced by the usual melting method tends to segregate carbides, rapidly solidified powder is extracted from the melt of high-speed tool steel by gas atomization, etc., and is subjected to HIP sintering. (Sintered high speed steel) has also been developed. Such a powder high speed tool steel has an advantage that carbides are extremely finely and uniformly distributed to further improve the performance.

As a material for the cutting tool, a so-called Mo-based high speed tool steel such as SKH51 or SKH58 is used as a material requiring particularly toughness, and SKH57 or as a material particularly required for wear resistance. So-called Mo-Co high speed tool steels such as SKH59 (all are JIS G
4403) is generally used.

[0004]

However, the SKH
Since steel materials such as 51 and SKH58 having excellent toughness generally have low wear resistance, there is a problem that the tool life is short when cutting a hard material. On the other hand, SK
With steel materials such as H57 and SKH59 that emphasize wear resistance, the tool life is often reached early due to chipping of the blade such as chipping. Under these circumstances, the development of high-speed tool steel having high hardness and high toughness is desired.

The present invention has been made in view of such circumstances, and an object thereof is to provide a high-speed tool steel capable of obtaining a high hardness of 67 or higher in HRC and ensuring a high toughness. It is in.

[0006]

The high speed tool steel according to the present invention, which has been able to solve the above problems, has a C content of 1 to 2%,
Si: 0.1 to 1%, Mn: 0.5% or less, Ni: 0.
5% or less, Cr: 2 to 6%, Mo: 1 to 10%, W: 3 to
13% (however, 2Mo + W: 18-24%), V: 2-7%,
Co: 5 to 11%, respectively, and Mo and W are adjusted so as to satisfy the following formulas (1) and (2). The balance is Fe and inevitable impurities. is there. 22 ≦ 14 (C−Ceq) + (2Mo + W) + Co ≦ 30 (1) Ceq = 0.06Cr + 0.063Mo + 0.033W + 0.2V (2)

[0007]

The reason for limiting the steel components in the present invention will be described in detail below. C: 1-2% C combines with carbide forming elements such as Cr, Mo, W and V to form a hard composite carbide, which improves the wear resistance of the material and also forms a solid solution with the matrix to form a solid solution. It is an important element for ensuring hardness. To ensure the required hardness, C
Must be contained at 1% or more. However, if it is too much, it causes cracking during hot forging and a decrease in toughness.
Should be:

Si: 0.1 to 1% Si is an element that is added as a deoxidizer for steel and is effective for strengthening the matrix. In order to exert such an effect, it is necessary to add at least 0.1% or more, but if it is too much, the toughness is rather deteriorated, so it should be 1% or less.

Mn: 0.5% or less Mn acts effectively as a deoxidizing material like Si and has the effect of enhancing the hardenability of steel. However, if added excessively, the toughness decreases, so 0.5% was made the upper limit.

Ni: 0.5% or less Ni is an element that greatly contributes to the improvement of hardenability and the improvement of toughness due to the refinement of crystal grains. However, if added in excess, it rather impairs toughness, so its upper limit is 0. It was set to 0.5%.

Cr: 2 to 6% Cr is an element which combines with C to form a double carbide, which improves the wear resistance and which forms a solid solution in the matrix to improve the hardenability of steel. In order to exert such an effect, it is necessary to add at least 2% or more, but if added excessively, it becomes a factor that greatly impairs hot workability and toughness, so the upper limit was made 6%.

Mo: 1 to 10%, W: 3 to 13% (however, 2Mo + W: 18 to 24%) Mo and W combine with C to form a double carbide and, at the same time, form a solid solution in the matrix. It is an element that increases the wear resistance and temper softening resistance because it strengthens the matrix. In order to fully bring out such effects, the value of 2Mo + W is 18%.
The above is necessary. However, if this value becomes too large, it becomes a cause of impairing the hot workability and decreasing the toughness, so the upper limit was made 24%.

V: 2 to 7% V, like Mo and W, combines with C to form a carbide that is extremely hard and hardly solid-solved, and greatly improves wear resistance. V has the effect of refining the crystal grains and increasing the toughness. These effects are effectively exhibited by containing 2% or more. However, if added excessively, the toughness and the grindability are rather impaired, so the upper limit was made 7%.

Co: 5 to 11% Co is an element that forms a solid solution in the matrix to strengthen the matrix and greatly improve the hardness and yield strength at high temperatures. In order to exert such an effect, it is necessary to add at least 5% or more, but if added excessively, it becomes a factor that hinders the toughness, so the upper limit was made 11%.

In the present invention, in addition to satisfying the above chemical composition, it is necessary to adjust Mo and W so as to satisfy the above equations (1) and (2). In particular, "14" which constitutes the equation (1)
The requirement of “(C−Ceq) + (2Mo + W) + Co” is a parameter that influences hardness and toughness. As this value increases, hardness increases but toughness decreases. Conversely, the smaller the value, the higher the toughness, but the lower the hardness. In the present invention, in order to balance hardness and toughness at a level as high as possible as shown in Examples described later, this value is set to 22 to
It was defined as a range of 30.

The powder high-speed tool steel of the present invention contains the above elements as basic components, satisfies the above formulas (1) and (2), and the balance Fe and inevitable impurities. If a large amount of N, especially N, is contained in the impurities, hot workability may be impaired, so the content should be 0.1% or less.

The present invention will be described in more detail with reference to the following examples. However, the following examples are not intended to limit the present invention, and any modification of the present invention can be made without departing from the spirit of the preceding and following paragraphs. It is included in the technical scope.

[0018]

EXAMPLES Alloy powders having the chemical composition shown in Table 1 were produced by the gas atomizing method. Each of the obtained powders was filled in a mild steel capsule, deaerated and sealed, solidified by hot isostatic pressing (HIP), further forged and rolled into a sample. Table 2 shows the heat treatment conditions, hardness, and bending value of each of the obtained samples. The distribution of hardness and bending value in each of the obtained samples is shown in FIG.

[0019]

[Table 1]

[0020]

[Table 2]

As is clear from these results, Examples (Nos. 1 to 8) satisfying the requirements specified in the present invention.
It can be seen that in HRC, a hardness of 67 or more and a high bending value of 400 kgf / mm ² were obtained in a well-balanced manner. On the other hand, in the comparative examples (Nos. 9 to 13) that do not satisfy the requirements specified in the present invention, either the hardness or the bending value is low.

[0022]

The present invention is constituted as described above, and the chemical composition of the high speed tool steel is specified and the above (1)
By satisfying the relationship between the formula and the formula (2), a high-speed tool steel having high hardness and high toughness could be realized.

[Brief description of drawings]

FIG. 1 is a graph showing the distribution of hardness and bending value in each sample.

Claims (1)

[Claims] 1. C: 1-2% (weight%: the same applies hereinafter), S
i: 0.1 to 1%, Mn: 0.5% or less, Ni: 0.5
% Or less, Cr: 2 to 6%, Mo: 1 to 10%, W: 3 to 13
% (However, 2Mo + W: 18-24%), V: 2-7%, C
o: 5 to 11%, respectively, and Mo and W are adjusted so as to satisfy the following formulas (1) and (2), and the balance is Fe and inevitable impurities. -High toughness powder high speed tool steel. 22 ≦ 14 (C−Ceq) + (2Mo + W) + Co ≦ 30 (1) Ceq = 0.06Cr + 0.063Mo + 0.033W + 0.2V (2)