Steel for mechanical structure for cold working, and method for producing same
A technology of mechanical structure and manufacturing method, which is applied in the field of mechanical structural steel for cold working and its manufacture, can solve the problems of coarse pearlite lamella interval, slow cooling, and no spheroidized structure. , to achieve excellent cold workability, low deformation resistance, and the effect of suppressing cracks
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Embodiment 1
[0126] Using the steel grade A shown in Table 1 above, the working temperature (equivalent to the finish rolling temperature) and the cooling rate were changed in the manner shown in Table 2 below, and samples with different pre-structures were produced, that is, rolled materials, wire-drawn materials, or processed materials. F test piece. Also, in the manufacturing conditions in Table 2, "first cooling" means cooling starting from the processing temperature and ending at a temperature range of 700 to 750°C, and "second cooling" means cooling from "first cooling" The cooling starts at the end temperature of 600-650°C, and the "third cooling" means the cooling that starts at the end temperature of "second cooling" and ends at a temperature below 400°C. In either case, after the third cooling was completed, it was left to cool to room temperature, and No. 19 and No. 20 were then further subjected to wire-drawing treatment.
[0127] In addition, in Table 2, the cooling end tempe...
Embodiment 2
[0142] Using the steel grades B to I shown in the above-mentioned Table 1, the processing Formaster test device in the laboratory was used in the same manner as in Example 1, and the processing temperature (corresponding to the finish rolling temperature) and the cooling rate were changed in the manner shown in the following Table 4, respectively. Samples with different tissues before making. The first to third cooling described in Table 4 have the same meaning as in Table 2.
[0143] 【Table 4】
[0144]
[0145] For these test pieces, the pre-structure was evaluated in the same manner as in Example 1, and the spheroidization annealing was performed in the same manner as in Example 1, and the degree of spheroidization and hardness after spheroidization annealing were evaluated. The results are shown in Table 5. In addition, the standard of the degree of spheroidization after spheroidizing annealing is 2.5 or less, and in the standard of hardness after spheroidizing anneali...
Embodiment 3
[0152] In addition, in order to investigate the degree of influence of the area ratio of pro-eutectoid ferrite, using the steel grades J to L shown in Table 1 above, the processing temperature (equivalent to (Finish rolling temperature) and cooling rate were changed as shown in Table 6 below, and samples with different pre-structures were prepared respectively. The first to third cooling described in Table 6 have the same meaning as in Table 2.
[0153] 【Table 6】
[0154]
[0155] For these test pieces, the pre-structure was evaluated in the same manner as in Example 1, and the spheroidization annealing was performed in the same manner as in Example 1, and the degree of spheroidization and hardness after spheroidization annealing were evaluated. The results are shown in Table 7. In addition, in the standard of the degree of spheroidization after spheroidizing annealing, steel grades with a C content of 0.35 to 0.45%, that is, steel grades J and K are 2.5 or less, and stee...
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Abstract
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