JP2631262B2 - Manufacturing method of cold die steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold die having high hardness and high toughness which is particularly suitable for use in electric discharge machining such as wire cutting when cold working under severe conditions or processing into a tool. The present invention relates to a method for producing steel.

[0002]

2. Description of the Related Art Conventionally, dies and punches for cold forging,
JIS SKD11 is widely used as a cold working alloy tool steel used for die-cutting applications and the like. These SKD11 are quenched from 1000-1050 ° C as a heat treatment method, and then 150-200 ° C.
In general, it is used in HRC61 or higher. However, these conventional SKD11s have high hardness but insufficient toughness. With the recent severer working of cold working methods or the spread of electric discharge machining methods such as wire cutting, SKK11 has been developed.
The cases that cannot be dealt with by D11 are increasing. For example, in a die for cold forging, there is a problem in that the tool life is shortened due to seizure, and in the case of punching, a crack is generated during electric discharge machining due to the wire cutting. Under such circumstances, various cold work tool steels have been proposed, such as adding various components based on the composition of SKD11. However, it is difficult for these to have sufficient hardness and toughness as a tool used for severe cold working or electric discharge machining as described above.

[0003]

SUMMARY OF THE INVENTION The present invention has a high hardness which can sufficiently cope with recent severe use conditions and can be used stably for a long period of time without causing a decrease in strength or cracking. An object of the present invention is to provide a method for producing a cold die steel having high toughness and excellent electric discharge machining property.

[0004]

Means for Solving the Problems The present inventors have conducted various studies for the purpose of solving the above problems. As a result, while maintaining an appropriate balance between carbon and carbide forming elements to reduce the primary eutectic carbides, the toughness is increased, and the composition range of each component is specified.
By quenching at temperatures below ℃ and then performing high temperature tempering at temperatures from 450 ° C to 550 ° C to increase the secondary hardening hardness, the life and electrical discharge machinability of cold die steel are greatly improved. This led to the present invention.

According to the present invention, C: more than 0.9 to less than 1.3%,
i: more than 0.5 to 2.0%, Mn: 0.1 to 2.0%, Cr: 5.0 to 1
Contains less than 1.0%, Mo: 1.3-4.0%, V: 0.1-less than 0.35%, or further contains REM: 0.001-0.5%,
Cu: 0.1-2.0%, W: 0.1-3.0%, Co: 0.1-5.0%,
Ti: 2.0% or less, Zr: one or more of 2.0% or less, and / or S: 0.20% or less, Pb: 0.40% or less, Se: 0.30% or less, Bi: 0.50% or less, Te: 0.30% %
Hereinafter, a steel material containing one or more of Ca: 0.002 to 0.010% (each wt%) and the balance of Fe and impurities is quenched at 1060 ° C or lower, and thereafter 450 ° C or higher to 550 ° C.
A method for producing cold die steel, characterized by tempering at the following temperature.

The reasons for limiting the composition range of each component in the present invention are as follows. C: C is an essential element that increases the hardness of martensite, forms special carbides by high-temperature tempering and contributes to secondary hardening, and further forms carbides with Cr, Mo and V and contributes to wear resistance. It is. This C content is correlated with the Cr content, but 0.9
If it is less than 0% (weight), the quenching and tempering hardness is low, and the wear resistance decreases. Conversely, if it is more than 1.3% (weight), the toughness decreases. . Si: Si is effective for increasing the high temperature tempering hardness and improves the toughness without lowering the hardness. In order to obtain these effects, it is necessary to contain it in an amount exceeding 0.5%, but if it exceeds 2.0% (weight), hot workability,
Decreases toughness. Mn: Mn acts as a deoxidizing and desulfurizing agent, improving the cleanliness of the steel and improving the hardenability. For this reason, 0.1% (weight) or more is contained, but if it exceeds 2% (weight), processability is impaired. Cr: Cr forms a solid solution in the matrix at the time of quenching to enhance hardenability and form Cr carbide, thereby improving wear resistance.
At less than 5% (weight), such an effect is small, and conversely 11%
% (Weight) or more deteriorates toughness. Mo: Mo is an element that is effective in forming a solid solution in the matrix at the time of quenching and forming carbides to improve wear resistance, and to enhance quenching and tempering resistance. In order to exhibit such an effect, in particular, in order to obtain a high hardness of HRC62 or more by high-temperature tempering, it is necessary to contain 1.3% (weight) or more, but even if it exceeds 4% (weight), the effect is not increased. Not so much, the hot workability deteriorates. V: V prevents the austenitic crystal grains of the matrix from becoming coarse and forms fine carbides, thereby contributing to the improvement of wear resistance and hardenability. If these effects are less than 0.1% (weight), they cannot be expected, and if 0.35% or more, workability deteriorates. REM, Cu, Ni, W, Co, Nb, Ti, Zr: These elements contribute to the improvement of strength and toughness.
If contained in large amounts, it reduces hot workability and toughness.
REM: 0.001-0.5%, Cu: 0.1-2.0%,
W: 0.1-3.0%, Co: 0.1-5.0%, Ti: 2.0% or less,
Zr: 2.0 or less (% by weight). Each of these elements may be used alone or in combination of two or more. S, Pb, Se, Bi, Te, Ca: All of these elements are effective in improving machinability, and are workable in finishing after machining and plastic working (forging, etc.). However, if the content is too large, the hot workability and toughness decrease, so that S: 0.20% or less, Pb: 0.40% or less, respectively.
Se: 0.30% or less, Bi: 0.50% or less, Te: 0.30% or less, Ca: 0.002 to 0.010% (each weight%). One or two or more of these elements may be contained.

[0007] In the production method of the present invention, a steel material having each of the above-mentioned compositions is annealed, then quenched at a temperature of 1060 ° C or less, and then 45%.
It is manufactured by tempering at a high temperature of 0 ° C to 550 ° C. The quenching temperature at this time is preferably performed at a high temperature within 1000 to 1060 ° C. The thus produced cold die steel is used for applications such as cold dies, punches, and die cutting. The method of the present invention employs high-temperature tempering, whereby residual stress during quenching is removed, a stable structure is obtained, and the secondary hardening hardness is increased, and both hardness and toughness are excellent. The tool life is extended without causing cracking even when the tool generates heat due to galling or electric discharge machining, and the workability is greatly improved. Further, the surface treatment property when TiC or the like is physically deposited on the tool surface is also improved. These advantages of high-temperature tempering are not sufficiently exhibited when the tempering temperature is lower than 450 ° C. On the other hand, if the temperature exceeds 550 ° C., a predetermined hardness cannot be obtained.

[0008]

Next, the present invention will be described in detail with reference to examples.
A steel material having a composition shown in Table 1 is hardened at a quenching temperature shown in Table 2,
Thereafter, it is tempered at the tempering temperature shown in Table 2 to obtain a cold die steel of the present invention. It should be noted that JIS SKD11, SKD12 and other conventionally used conventional steels manufactured by the conventional method were melted as comparative steels, and the hardness, Charpy impact value,
Tests were made on bending fold, seizure load, specific wear, residual stress, and wire cutability. Table 2 shows the test results of these characteristic values. Charpy impact value is 15x for φ30mm material
Cutting to 15 x 60mm and quenching (oil cooling) tempering (air cooling)
A test piece was prepared by forming a notch having a center depth of 2 mm, a surface roughness of 0.25 or less, and a radius of 10 mm. The residual stress is φ200
X 300mml material is quenched (maintain air temperature for 15 minutes at heating temperature)
Tempering (air cooling x 2 times at heating temperature for 2 hours), electrolytic polishing of 20mm square, 0.5mm depth in the center of the surface layer,
The polished surface was measured by the X-ray method (longitudinal direction), and other test conditions were as follows. (A) Flexural bending strength: For a test piece of φ8 × 130 mm, the distance between fulcrums is 100 mm, and the load at one point at the center is shown as the breaking load when the test piece breaks. (B) Specific wear amount: Using a Ohkoshi type rapid friction tester, the mating material SCM415 (HB190), friction speed 2.9 m / sec, friction distance 2
00 mm and a friction load of 6.5 kg. (C) Seizure load: Using SCM415 (annealed) as the mating material, friction speed 30 to 100 mm / sec, contact surface pressure 5 to 50 k
gf / mm ² , oil-based lubricating oil. (D) Wire cutability: 10mm due to wire cut
The length is cut and the number of cracks on the cut surface is 100 μ or more.

[0009]

[Table 1]

[0010]

[Table 2]

From Table 2, it can be seen that all of the steels produced according to the present invention have a hardness of HRC 62 or more, have high toughness, and are excellent in wear resistance, seizure load and wire cutability.

Next, test materials Nos. 1, 14 and 9 (SKD1
The effect of tempering temperature after high-temperature quenching on secondary hardening hardness and Charpy impact value was investigated using 1). Table 3 shows the results.

[0013]

[Table 3]

From Table 3, it can be seen that No.
Tempering temperatures of 200 ° C, 300 ° C, 4 in Nos. 1 and 14
The secondary hardening hardness at 00 ° C is not sufficient, and the desired hardness is obtained at 500 ° C, and the impact value at 500 ° C is slightly lower than that at 400 ° C, but still retains high toughness. I have. From these facts, it can be said that the tempering temperature for providing both high hardness and high toughness needs to be 450 ° C. or higher. On the other hand, it is understood that the hardness and the impact value of the conventional material are considerably inferior to those of the steel of the present invention even when subjected to high-temperature tempering.

[0015]

The tool steel produced according to the present invention is fully compatible with severe conditions, and has excellent hardness, toughness, and electric discharge machinability that can be used stably for a long period of time without causing a decrease in strength or cracking. Cold die steel.

Claims (4)

(57) [Claims] 1. C: more than 0.9 to less than 1.3%, Si: more than 0.5 to 2.0%, Mn: 0.1 to 2.0%, Cr: 5.0 to less than 11.0%, Mo: 1.3 to 4.0%, V: 0.1 to less. A steel material containing less than 0.35% (each wt%) and consisting of the balance of Fe and impurities
A method for producing cold die steel, characterized by quenching at a temperature of 450 to 550 ° C after quenching at 0 ° C or less. 2. C: more than 0.9 to less than 1.3%, Si: more than 0.5 to 2.0%, Mn: 0.1 to 2.0%, Cr: 5.0 to less than 11.0%, Mo: 1.3 to 4.0%, V: 0.1 to 2.0% Contains less than 0.35%,
REM: 0.001 to 0.5%, Cu: 0.1 to 2.0%, W:
0.1 to 3.0%, Co: 0.1 to 5.0%, Ti: 2.0% or less and Zr: 2.0% or less (each weight%).
A method for producing cold die steel, characterized by quenching at a temperature of 450 ° C. or more and 550 ° C. or less after quenching below. 3. C: more than 0.9 to less than 1.3%, Si: more than 0.5 to 2.0%, Mn: 0.1 to 2.0%, Cr: 5.0 to less than 11.0%, Mo: 1.3 to 4.0%, V: 0.1 to less. Contains less than 0.35%,
Further, S: 0.20% or less, Pb: 0.40% or less, Se: 0.30%
Below, Bi: 0.50% or less, Te: 0.30% or less and Ca:
A steel material containing one or more of 0.002 to 0.010% (each wt%) and the balance of Fe and impurities at 1060 ° C
A method for producing cold die steel, characterized by quenching below and then tempering at a temperature of 450 to 550 ° C. 4. C: more than 0.9 to less than 1.3%, Si: more than 0.5 to 2.0%, Mn: 0.1 to 2.0%, Cr: 5.0 to less than 11.0%, Mo: 1.3 to 4.0%, V: 0.1 to Contains less than 0.35%,
REM: 0.001 to 0.5%, Cu: 0.1 to 2.0%, W:
0.1 to 3.0%, Co: 0.1 to 5.0%, Ti: 2.0% or less and Zr: 2.0% or less, and S: 0.20
%, Pb: 0.40% or less, Se: 0.3% or less, Bi: 0.50%
% Or less, Te: 0.30% or less and Ca: 0.002 to 0.010%
(Each wt%), characterized in that a steel material containing one or more of the remaining Fe and impurities is quenched at 1060 ° C or less and then tempered at a temperature of 450 ° C or more and 550 ° C or less. Manufacturing method of hot die steel.