Steel material for cold forging

Abstract

This steel material contains C, Si, Mn and Al as chemical components, and comprises pearlite as a metal structure. The value obtained by dividing the Mn content, in terms of atomic percentage, contained in cementite in the pearlite by the Mn content, in terms of atomic percentage, contained in ferrite in the pearlite is more than 0 but 5.0 or less.

Description

technical field [0001] The present invention relates to a steel material having a pearlite structure (a layered structure of ferrite and cementite), and in particular to a steel material capable of shortening the treatment time of cementite spheroidization treatment performed to improve cold workability. Background technique [0002] Compared with hot forging, cold forging is superior in dimensional accuracy when forming mechanical parts such as bolts, and is also superior in productivity. Therefore, as a manufacturing method of machine parts, the switch from hot forging to cold forging is progressing. However, cold forging, which is processed at room temperature, has a high deformation resistance of the steel material and a large load on the die. Therefore, steel materials for cold forging are required to be excellent in cold workability (cold forgeability). Here, being excellent in cold workability means that the deformation resistance of the steel material is small and ...

AI Technical Summary

Problems solved by technology

However, as mentioned above, in the methods described in Patent Document 1 and Patent Document 2, since the metal structure of the steel material mainly contains bainite or martensite, although the spheroidization of cementite can be promoted during the spheroidizing treatment, the Insufficient reduction of deformation resistance of steel

In addition, the method described in Patent Document 3 requires more than 10% of pseudo-pearlite as a metal structure, so the alloy composition is limited.

In addition, although the method described in Patent Document 4 can shorten the spheroidization processing time, the processing time still needs more than ten hours, and further shortening of the spheroidization processing time is required.

[0014] As mentioned above, the prior art cannot be said to have simultaneously and sufficiently realized the reduction of cementite spheroidization treatment time and the improvement of cold workability.

In addition, in the prior art, attention has not been paid to Mn and Cr contained in cementite and ferrite respectively in pearlite for the purpose of shortening the cementite spheroidizing treatment time and improving cold workability at the same time. A report on the study of the distribution ratio of alloying elements in cementite and ferrite by equalizing the content of alloying elements

Images