JPS627246B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a low-cost and efficient method for manufacturing cold forged products. For example, when performing cold forging with a high degree of workability (high area reduction rate) on difficult-to-process materials such as S45C and SCM3, first the material (hot rolled material, drawn material) is preformed by cold forging. A molded product is produced, this preformed product is spheroidized, and then cold forged at a high degree of working is performed. The spheroidizing process that precedes the cold forging of the preform is an essential process to improve the deformability of the material and reduce the forging load.
It takes a long time, up to 16 hours, and a lot of energy. Furthermore, during the cold forging of the preform, it may be necessary to carry out a spheroidizing process for about 10 hours, which poses major problems in terms of cost and efficiency. In view of the above-mentioned current situation, the present invention aims to provide an extremely low-cost manufacturing method for cold forged products that does not require the long-term spheroidization treatment described above in either preforming or cold forging of preformed products. It is something. That is, the present invention heats hot-rolled steel or drawn steel containing 0.13 to 1.50% C to 500°C to _Ac3 in the case of 0.13 to 0.765% C, and 500°C in the case of 0.765 to 1.5% C.
A preformed product is produced by preforming by warm processing in the temperature range of ~Accm, and this preformed product is then continuously processed.
600℃~ _Ac3 for C0.13~0.765%, C0.765
1 to 60 at a temperature of 600℃ to Accm for ~1.5%
The gist of the present invention is a method for producing a cold forged product, which is characterized in that the preform is held for a few minutes, then air cooled or slowly cooled, and then the preform is cold forged without being spheroidized. If preforming is carried out at a warm temperature of 500°C to Ac ₃ or Accm, the prior spheroidization treatment can be omitted if the target material is C1.50% or less, which is usually used for cold forging. can. This is because the deformability of the material is improved in the warm region, and the forging load is sufficiently reduced. Furthermore, the preformed product preformed warmly in this way is immediately heated to 600℃~Ac ₃ or Accm.
If the temperature is kept constant in the temperature range, a spheroidized structure can be obtained within a very short time. That is, a large amount of plastic strain is introduced into the preformed product by the warm working, which effectively promotes spheroidization due to constant temperature maintenance. As for cooling after constant temperature maintenance, sufficiently low hardness can be expected by air cooling or gradual cooling. As described above, according to the method of the present invention, it is possible to perform cold forging with a high degree of working without performing any spheroidizing treatment that requires a long time as in the conventional method. The reasons for limiting each requirement of the present invention will be explained in detail below. First, the C content in the material used in the method of the present invention is
The reason for setting it to 0.13 to 1.50% is as follows. C is an essential component for ensuring the strength of steel, and the content can be determined as necessary, but if it is less than 0.13%, sufficient deformability will be obtained without creating a spheroidized structure, so until the method of the present invention is applied. If it exceeds 1.50%, the deformability required for cold forging cannot be expected even if it is a spheroidized structure, and it is generally not used for cold forging. Warm processing temperature is C0.13~0.765%
500℃~Ac ₃ , 500℃~ for C0.765~1.5%
Accm, but this is because the forging load is not sufficiently reduced below 500℃, deformability is insufficient, and on the other hand,
This is because when the temperature exceeds Ac ₃ or Accm, the steel material becomes an austenitic structure, and a spheroidized structure cannot be obtained even by constant temperature maintenance described below. Regarding the constant temperature holding conditions after the above-mentioned warm processing, when the holding temperature is C0.13 to 0.765%, it is 600℃ to _Ac3 ,
In the case of C0.765 to 1.5%, it is necessary to set the temperature to 600°C to Accm. At temperatures below 600°C, it takes a long time to obtain a spheroidal structure, which impairs the economic merits of the present invention.If Ac ₃ or Accm is exceeded, the structure becomes austenitic and becomes spheroidal after cooling. Organization is not secured. Regarding the holding time, if it is less than 1 minute, spheroidization cannot be expected, and holding for more than 60 minutes is substantially unnecessary and uneconomical, so the holding time is limited to 1 to 60 minutes. Cooling after constant temperature maintenance can be done by air cooling or slow cooling.
This is because the low hardness required for cold forging can be sufficiently obtained by such cooling, and any more slow cooling is unnecessary and may lead to a disadvantage in terms of efficiency. Next, examples of the present invention will be described. Hot-rolled steel material with the components shown in Table 1 (Size: 40
mmφ×100 mm) was used as a material, and according to the method of the present invention, warm forging, constant temperature maintenance, and air cooling were performed under the conditions shown in Table 2 to obtain a preformed product. For comparison, a similar material was preformed after being spheroidized using the heat pattern shown in Figure 1a, and then spheroidized using the heat pattern shown in Figure 1b to produce a preformed product. This is a conventional example.

【table】

[Table] The degree of spheroidization, hardness and deformability of the preformed products obtained above were investigated. The degree of spheroidization is expressed in stages 1 to 6 specified by JIS, and the deformability is measured by cutting out a V-grooved compression test piece from the preform and performing a compression test (ASTM E9-
46T) and measured the critical compression ratio. The results are shown in Table 3.

【table】

[Table] In Table 3, all of the examples of the present invention (subscript 1) show values equivalent to, or even better than, the conventional examples in terms of degree of spheroidization and deformability. Regarding hardness,
Although the inventive example tends to be slightly higher, this level of difference does not affect the cold forging operation at all. As is clear from the above explanation, the method of the present invention is capable of producing cold forged products of comparable quality to conventional products, and does not require any long granulation treatment. By adopting this method, it is expected that the production cost of cold forged products will be significantly reduced, and production efficiency will also be greatly improved.

[Brief explanation of the drawing]

FIGS. 1a and 1b are graphs showing heat patterns used in the conventional spheroidizing process in the example.

Claims (1)

[Claims] 1 Hot rolled or drawn steel containing C0.13~1.50% is preformed by warm working at a temperature range of 500℃~Ac ₃ or Accm, and then heated to 600℃~Ac ₃ or Accm.
1. A method for producing a cold forged product, which comprises holding the preformed product at a temperature of Accm for 1 to 60 minutes, followed by air cooling or slow cooling, and then cold forging the preformed product without spheroidizing it.