JPS58117863A - High speed tool steel with high wear resistance and toughness - Google Patents

Abstract

PURPOSE:To obtain a high speed tool steel for a cold working tool with superior wear resistance and toughness by regulating the W content of a high speed tool steel and by adding Mo, Ni, etc. CONSTITUTION:The composition of a high speed tool steel for a cold working tool is composed of 0.6-0.8% C, 0.6-2.0% Si, 5.2-6.0% Cr, <2% W, <3% Mo (W+2Mo=4-6%), 0.5-2.2% V, <1.5% Mn, <2.0% Ni, <5% Co, <0.1% N and the balance Fe. To the composition may be added <=0.2% in total of one or more among Ti, Zr, Nb, Hf and Al and <0.05B. Hard carbides of Cr, W, Mo, V, etc. enhance the wear resistance, and Ni improves the toughness, so a high- speed tool steel with high wear resistance and toughness is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-speed tool steel for cold working tools having excellent wear resistance and high toughness.

Conventionally, JIS8KH9 was used as high-speed tool steel for cold work tools.
Class materials were used, but due to their low toughness, tools that are subject to strong impact will break quickly.

This caused chipping, significantly reducing its useful life.

In addition, a high-speed tool steel called Matrix Chair, which has improved toughness of 5KH9 class, is also used, and has been found to be quite effective in some applications.

However, the hardness of H [around 60 and the Charpy @ Hayabusa value is 5~
For cold-opening forging dies and cold extrusion dies, which require extremely high toughness such as -m/cJ or higher, matrix high-speed tool steels still do not have sufficient toughness and have a short service life.

In order to solve this problem, one of the inventors invented a high-speed tool steel with excellent properties (% Kosho 55-4
No. 9148). This high-speed tool steel has a H)061 rating of 6
Since a Charpy force value of 9 m/- or more can be obtained,
This multi-layered tool has been shown to be extremely effective. This steel can reasonably be expected to have a hardness of HRCso~62, so it can be said that it has excellent wear resistance. Nowadays, as the conditions become more and more severe, there is a demand for even better abrasion resistance. Also,
Small diameter materials may have high toughness of 6Kg m/- or more, but when it comes to large diameter materials of 100-2 or more, a certain degree of decrease in toughness is avoided as usual with ordinary high-speed tool steel. I can't.

The present invention has even better wear resistance than the invention steel of Japanese Patent Publication No. 55-49148, and has the same high toughness.
Moreover, it is an object of the present invention to provide a daytime speed tool steel that exhibits little decrease in toughness even when used as a large-diameter material.

The reasons for restricting the composition of each element are described below.

C has the effect of imparting wear resistance by combining with W, Mo, and V contained at the same time to form a hard carbide. Also, it has the effect of increasing the hardness of martensite by being dissolved in the matrix during quenching. However, if it is contained in excess, it may become martensite brittle or cause macroscopic segregation during agglomeration, resulting in a decrease in toughness.
In order to find the appropriate content of C, careful and extensive experiments are required.

Summarizing the results of many experiments in the present invention, the appropriate CI) content is 0.6 to 0.8 tai, and if it is less than 0.6 tai, the desired hardness and Me abrasion resistance cannot be obtained, and 0.8% If it exceeds this, the desired high toughness cannot be obtained.

Moreover, the content of W, Mo, and V added simultaneously within the appropriate carbon content range of 0.6 to 0.8% means that unless the carbon content is controlled more strictly, the desired high-resistance umbrella, High toughness cannot be obtained. That is, in the steel of the present invention, Ceq 2α24+0065Mo(%
) t-1033Lν (%) + 0.2 V (%), the C content is C-Ceq +005 to -0.10g
must be managed so that

For the above reasons, the C-containing lid is limited to C0.6 to 0.8%, preferably a65 to 175%.

8i improves the tempering hardness, and this effect is particularly great when the content of W, Mo, and V is small as in the present invention. In order to effectively activate the effect of 81 with the component system of the present invention, K needs to be at least 0.6% of 8i, but on the contrary, 2.
．． If the Si content exceeds 0%, the machinability is reduced, so the Si content is limited to 0.6 to 2.0%, preferably 08 to 16%.

Cr is an important constituent element in the present invention. Conventional high-speed tool steels contain 55 to 4.5% Cr, but based on many experimental facts in the present invention, Cr is used in fields that require high toughness such as the steel of the present invention. It has been discovered that when the Cr content is 5.2 to 6.0%, the wear resistance is further improved and the toughness of large-diameter materials is less reduced than that of conventional materials. Moreover, this C
The effect of r will not be fired sufficiently unless it is in C and 81 or the above component range.

If the Cr content is less than 5.2%, the above effects will not be sufficient;
If the Cr content exceeds excellent, the toughness decreases, so the Cr content was limited to 5.2 to 6 t%.

W and 1vlo have the effect of imparting temper hardening and wear resistance. However, if its content increases, it will remain as segregated undissolved carbides after quenching, reducing toughness, so it is desirable to contain it as little as possible while taking tempering hardness into consideration.

In the application of the steel of the present invention, a hardness of 6.2 or higher in terms of H is required, and this hardness cannot be obtained if W+2Mo is less than 4.

Also, if it exceeds 6%, the Charpy impact value is 6ky m/cd.
Since higher toughness cannot be obtained, W+2 Mo is 4 to 6
Limited to 俤. W and Mo have almost the same effect in terms of weight percent and stoichiometric amount. However, in the component yarn of the steel of the present invention, the effect of Mo was greater than that of W, so W
2% or less, Mo5% or less, W+2M.

is 4 to 6 excellent, preferably W1 excellent or less, MO21 to 29%
and W+2Mo was limited to 45 to 6%.

Similar to W and Mo, (2) not only contributes to secondary hardening during tempering, but also remains as a hard VC carbide when quenched, and has the effect of imparting wear resistance. If (2) is less than 0.5%, the above effect will be small, and if it exceeds 2.2%, undissolved carbonized '#J'jIk will increase too much and the toughness will decrease, so the Vt/-) content will be 05 ~2.2%, preferably 08
It was limited to ~2.0 well.

In addition to being added as a deoxidizing agent, the content of pigeon is 1.5% or less for the purpose of improving hardenability, so the content of pigeon is 15% or less.
Limited to the following.

Since N1 is contained in an amount of 2.0% or less for the purpose of increasing flexibility, the Ni content is limited to 2.0% or less.

CO has the effect of relatively reducing the decrease in toughness and increasing the tempering hardness, but if it is contained in excess of 5 qb, the decrease in toughness becomes large, so the Co content was limited to SS or less.

Normally, the content of N is about 0.02%, but since it is effective to contain 0.1% or less for the purpose of increasing the tempering hardness, the N content is limited to 0.1% or less.

Although the purpose of the present invention can be achieved even without the inclusion of Ti, Zr, NJ Hf #At, the addition of Ti
, Zr, Nb.

When one or more of Hf and At are contained in total at most 0.2 Ti, it has the effect of making the crystal grains finer and further improving the toughness.
The total amount of one or more types of t was limited to 0.2% or less.

Although the purpose of the present invention can be sufficiently achieved without specifically containing B, it has been found that containing 130.05% or less improves hardenability and refines grains, so Bo,
Limited to o5chi or less.

Examples are shown below.

Example 1 Among the many experimental results related to the present invention, representative ones are shown in Table 1.

A to E are according to the present invention @, F-I are comparative steels, and J is J.K.
The steel invented in No. 49148 is already in industrial use. K is JIS 8KH9. The heat treatment hardness shown in Table 1 is determined by heating a sample processed to 100°C x 6rm in a melt bath at 1160°C xeo seconds, cooling it in oil, and then heating it twice in a 560°C x 1 hour x 2 times. This is the measurement result after returning it. Also, the Charpy impact value is 10R.
-C notch Charpy impact test results.

The heat treatment conditions were the same as those for the hardness test above.

As a result, all of the steels of the present invention had a high hardness of HFtC62 or higher, and a Charpy impact value of 6 Kfm/- or higher. Comparative steel F has a low C @ cap and cannot obtain iaJ hardness. Similarly, G has a high V content but a low C content, so the C-Ceq decreases and high hardness cannot be obtained. H has a low Si content and cannot be expected to have high hardness. Engineering is tVio
The content is low and high hardness cannot be obtained. Conventional steel J has low hardness. K has a low Charpy impact value.

Example 2 The same steel as shown in Table 1 of Example 1 was used to conduct the Okoshi Nigishi test. The results are shown in FIG. Invention steel A
It was confirmed that -E has less reduction in bank wear than conventional steel and 1C, and has almost the same level of wear resistance as conventional steel K (5KH9).

Example 3 Invention steel B and conventional vI/4 shown in Table 1 shown in Example 1
A 100×100×1 round bar was prepared with the same composition as J. This was heated in a salt bath at 1160° C. for 10 minutes, cooled, and then tempered twice at 560° C. for 1 hour in an electric resistance furnace. From the center of this demon sample 10)
When an L-C notch Charpy impact test piece was taken and tested, the Charpy value of the invention steel B was 56.
m/- and hardness was HRC59.2. The Charpy value of conventional steel J is 58 Kf-m/7 and the hardness is HRC565.
Met.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the results of the Okoshi type abrasion test. Cow 1r! rU 1"+1.'l'"I'Jri'l°°・ Tono+
Q 1lll L') 2 15' Takayu, I &Q's High School Worker 4゜urall^, Juruh ・ 1 ・ s＋＋++, If ”: ”'I affiliated pearl company f・ノ, and Nori Kawano Ignari theory! (...1... Toichi East 4; Mito ``1 (Enter 1111) IWI'l 11th 2shi; 11.゛f'r' Group Stock Company Monthly Telephone j [[Correct to 284-4642 .

Claims (1)

[Claims] tC06-Q, 8%, 8i0.6-2.0%, Cr5.
2~At)%, W2% or less 1M03qb or less
Below, Ni 2.0% or less, Co 5% or less, NO, 1%
High wear resistance and high toughness consisting of the balance Fe and impurities.
L tool steel. 2Cα65~0.75% lSi [18~16%, Cr5
．． 2-60%lW1chi or less, Mo2 or less -29% and W+2Mo is 4.5-6, ■08-2.0%, Mn
ts4 or less, NI2.0% or less, Co5% or less. The high wear-resistant, high-toughness, high-speed tool steel according to claim 1, comprising NO, the balance being Fe and impurities of 1% or less. ! ,, C0.6-0.8%, SiO, 6-2.0%
, (, r5.2~to%, w2 俤 or less, Mo 3%
Below, Tekatsu W+2Mo is 4~6%, vO,s~2.
2'%, Mn 15% or less, Ni 2.0% or less,
Co55S or less, N01 or less + Ti, Zr, Nb,
A high-wear, high-toughness, high-speed tool steel consisting of a total of 0.2% or less of one or more of Hf and At, 0.05% or less of B, and the balance Fe and impurities.