JPS645100B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a cold die steel having high hardness and high toughness, which is particularly suitable for use in severe cold working conditions or electrical discharge machining of wire cuts and the like when processing into tools. Traditionally, cold working alloy tool steel used for cold forging dies, punches, cutting dies, etc.
JIS SKD11 is commonly used. These SKD11 are heat treated from 1000 to 1050℃ and then heated to 150℃.
It is generally tempered at ~200℃ and used with an HRC of 61 or higher. However, these conventional
Although SKD11 has high hardness, it does not have sufficient toughness.
As cold working methods become more severe in recent years and electric discharge machining methods such as wire cutting become more widespread, there are an increasing number of cases that cannot be handled with SKD11. For example, with dies for cold forging, tool life may be reduced due to seizure.
With cutting dies, cracking during electrical discharge machining due to the wire cut has become a problem. In response to this situation, various cold work tool steels have been proposed, such as those based on the composition of SKD11 and with the addition of various ingredients. However, these tools cannot be said to have sufficient hardness and toughness as tools used in severe cold working or electrical discharge machining as described above. The present inventors have developed a material with high hardness and high toughness that can fully cope with today's harsh usage conditions and can be used stably for a long period of time without decreasing strength or cracking. With the aim of providing cold die steel with excellent properties, various studies were conducted. As a result, by maintaining an appropriate balance between carbon and carbide-forming elements and reducing the amount of primary eutectic carbides, toughness is increased, and
By identifying the composition range of each component and subjecting it to high-temperature tempering at 450°C or higher to increase secondary hardening hardness, the lifespan and electrical discharge machinability of cold die steel can be greatly improved. This knowledge led to the present invention. That is, the present invention contains 0.9<C<1.3 0.5<Si≦2.0 0.1≦Mn≦2.0 5.0≦Cr<11.0 1.3≦Mo≦4.0 0.1≦V<0.35 (each % by weight), and further contains 0.001 as necessary. ≦REM≦0.5 0.1≦Cu≦2.0 0.1≦W≦3.0 0.1≦Co≦5.0 0<Ti≦2.0 0<Zr≦2.0 (each weight%) One or more of the following, and further as necessary. Contains one or more of the following: 0<S≦0.20 0<Pb≦0.40 0<Se≦0.30 0<Bi≦0.50 0<Te≦0.30 0.002≦Ca≦0.010 (each weight%), with the remainder being Fe and It is a cold die steel that consists of impurities and has a hardening effect at high temperatures below 1060°C and a tempering effect at 450 to 550°C. The reason for limiting the composition range of each component in the present invention is as follows. C: C is an essential element that increases the hardness of martensite, forms special carbides through high-temperature tempering, and contributes to secondary hardening, and also forms carbides with Cr, Mo, and V, contributing to wear resistance. It is. The amount of C has a correlation with the amount of Cr, but if it is less than 0.90%, the hardness after quenching and tempering will be low and the wear resistance will decrease.
On the other hand, if it exceeds 1.3%, the toughness decreases, so 0.9<C
<1.3. Si: Si is effective in increasing high temperature tempering hardness.
It also improves toughness without reducing hardness. In order to obtain these effects, it is necessary to contain more than 0.5%, but if it exceeds 2.0%, hot workability and toughness will decrease. Mn: Mn acts as a deoxidizing and desulfurizing agent, improving the cleanliness of steel and improving hardenability. For this purpose, it is made to contain 0.1% or more, but
If it exceeds 2%, workability will be impaired. Cr: During quenching, Cr dissolves into the matrix to improve hardenability and forms Cr carbide, improving wear resistance. However, if it is less than 5%, this effect is small, and conversely if it is 11% or more When this happens, the toughness deteriorates. Mo: Mo is an effective element for improving wear resistance by forming a solid solution in the matrix during quenching and forming carbides, and for increasing quenching and tempering resistance. In order to exhibit such effects and obtain a high hardness of HRC62 or higher through high-temperature tempering,
It is necessary to contain 1.3% or more, but even if it exceeds 5%, the effect will not increase much and hot workability will deteriorate. V: V prevents the austenitic crystal grains of the matrix from becoming coarser, forms fine carbides, and contributes to improving wear resistance and hardenability. These effects are
If it is less than 0.1%, it cannot be expected, and if it is more than 0.35%, workability deteriorates. REM, Cu, W, Co, Ti, Zr: Each of these elements contributes to improving strength and toughness, but if contained in large amounts, hot workability and toughness decrease, so REM: 0.001 to 5 %,
Cu: 0.1~2.0%, W: 0.1~3.0%, Co: 0.1~
5.0%, Ti: 2.0% or less, Zr: 2% or less.
Each of these elements may be contained alone or in combination. S, Pb, Se, Bi, Te, Ca: All of these elements are effective in improving machinability, and improve workability during finishing after machining and plastic working (forging, etc.) However, if it is too large, it will reduce hot workability and toughness, so S: 0.20% or less, Pb: 0.40% or less, and Se: 0.30.
% or less, Bi: 0.50% or less, Te: 0.30% or less,
Ca: 0.002 to 0.010%. Each of these elements is 1
A species or two or more kinds may be contained. Steel materials whose component compositions are specified within the above ranges are annealed, quenched at a high temperature, and then tempered at a high temperature. The present invention is quenched at a high temperature of 1060℃ or less, and
It is a cold die steel that exhibits excellent physical properties through high-temperature tempering treatment at a temperature of ~550°C.This high-temperature tempering removes residual stress during quenching and creates a stable structure, as well as secondary hardening. The hardness increases, and both hardness and toughness are excellent, and the tool life is extended without causing galling when used as a tool, or cracking when the tool is heated due to electrical discharge machining, etc., and the tool life is extended. Sexuality will greatly improve. Furthermore, TiC on the tool surface
Surface treatment properties are also improved when physical vapor deposition is performed. These advantages of high-temperature tempering are not fully exhibited when the tempering temperature is lower than 450°C. Next, the present invention will be explained in detail with reference to examples. Example Inventive steel with the composition shown in Table 1 and JIS SKD11, which has been conventionally used as comparative steel,
SKD12 and other materials were melted and tested for hardness, shear py impact value, bending transverse rupture strength, seizure load, specific wear amount, residual stress, and wire cuttability. The test results of these characteristic values are shown in Table 2. The test conditions are as follows. (a) Bending transverse rupture strength...for a φ8×130mm test piece,
The distance between the supporting points is 100mm, and the load is applied at one point at the center.The breaking load is shown when the test piece breaks. (b) Specific wear amount...Mating material SCM415 (HB190), friction speed 2.9m/sec, by Okoshi type rapid wear tester.
The friction distance was 200 mm and the friction load was 6.5 kg. (c) Seizing load: SCM415 (annealed) was used as the mating material, the friction speed was 30 to 100 mm/sec, the contact surface pressure was 5 to 50 Kgf/mm ² , and the lubricant was oil-based. (d) Wire cutting property... due to wire cutting
Cut to a length of 10mm, and indicate the number of cracks with a length of 100μ or more on the cut surface.

【table】

[Table] From Table 2, it can be seen that all of the steels of the present invention have hardness of HRC62 or higher, high toughness, and are excellent in bending strength, wear resistance, seizure load, and wire cuttability. . Next, using test materials No. 1, 6, and 12 (SKD11), the influence of the tempering temperature after high-temperature quenching on the secondary hardening hardness and Shapey impact value was investigated. The results are shown in Table 3.

[Table] From this Table 3, No. 1 and No. 1 regarding the steel of the present invention.
In 6, the tempering temperature is 200℃, 300℃, 400℃
In the case of
Although the toughness is slightly lower than that at ℃, it still maintains high toughness. From these facts, it can be said that it is necessary to set the tempering temperature to 450°C or higher in order to provide both high hardness and high toughness. On the other hand, it can be seen that even if the conventional material is subjected to high-temperature tempering, both the hardness and the impact value are considerably inferior to the steel of the present invention.

Claims (1)

[Claims] 1 Contains the following: 1 0.9<C<1.3 0.5<Si≦2.0 0.1≦Mn≦2.0 5.0≦Cr<11.0 1.3≦Mo≦4.0 0.1≦V<0.35 (each weight%), with the remainder being Fe and impurities More than 1060
Quenching effect occurs at high temperature below ℃, 450℃~550℃
Cold die steel with tempering effect at ℃. 2 Contains 0.9<C<1.3 0.5<Si≦2.0 0.1≦Mn≦2.0 5.0≦Cr<11.0 1.3≦Mo≦4.0 0.1≦V<0.35 (each weight%), and further contains 0.001≦REM≦0.5 0.1≦Cu≦ Contains one or more of the following: 2.0 0.1≦W≦3.0 0.1≦Co≦5.0 0<Ti≦2.0 0<Zr≦2.0 (each weight%), with the remainder consisting of Fe and impurities, and is resistant to temperatures below 1060℃ Cold die steel that has a hardening effect at a high temperature of , and a tempering effect at a temperature of 450℃ to 550℃. 3 Contains 0.9<C<1.3 0.5<Si≦2.0 0.1≦Mn≦2.0 5.0≦Cr<11.0 1.3≦Mo≦4.0 0.1≦V<0.35 (each weight%), and further contains 0<S≦0.20 0<Pb≦ Contains one or more of the following: 0.40 0<Se≦0.30 0<Bi≦0.50 0<Te≦0.30 0.002≦Ca≦0.010 (each weight%), with the remainder consisting of Fe and impurities, Cold die steel that has a hardening effect at high temperatures and a tempering effect at 450℃~550℃. 4 Contains 0.9<C<1.3 0.5<Si≦2.0 0.1≦Mn≦2.0 5.0≦Cr<11.0 1.3≦Mo≦4.0 0.1≦V<0.35 (each weight%), and further contains 0.001≦REM≦0.5 0.1≦Cu≦ 2.0 0.1≦W≦3.0 0.1≦Co≦5.0 0<Ti≦2.0 0<Zr≦2.0 (each weight%) One or more of the following and 0<S≦0.20 0<Pb≦0.40 0<Se≦ Contains one or more of the following: 0.30 0<Bi≦0.50 0<Te≦0.30 0.002≦Ca≦0.010 (each weight%), with the balance consisting of Fe and impurities, and has a hardening effect at high temperatures below 1060℃ Cold die steel with a tempering effect at 450℃~550℃.