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1. (WO2017033773) MECHANICAL STRUCTURE STEEL FOR COLD-WORKING AND MANUFACTURING METHOD THEREFOR

Pub. No.:    WO/2017/033773    International Application No.:    PCT/JP2016/073769
Publication Date: Fri Mar 03 00:59:59 CET 2017 International Filing Date: Sat Aug 13 01:59:59 CEST 2016
IPC: C22C 38/00
C21D 8/06
C22C 38/60
Applicants: KABUSHIKI KAISHA KOBE SEIKO SHO (KOBE STEEL, LTD.)
株式会社神戸製鋼所
Inventors: SASAKI, Yuki
佐々木 雄基
KOCHI, Takuya
高知 琢哉
CHIBA, Masamichi
千葉 政道
SAKATA, Masayuki
坂田 昌之
MURAKAMI, Shogo
村上 昌吾
Title: MECHANICAL STRUCTURE STEEL FOR COLD-WORKING AND MANUFACTURING METHOD THEREFOR
Abstract:
Provided are: mechanical structure steel for cold-working capable of achieving spheroidization equal to or greater than in the past and capable of greater softening than in the past even when spheroidizing annealing time is shortened more than usual; and a manufacturing method therefor. The present disclosure is mechanical structure steel for cold-working that is characterized in: comprising C, Si, Mn, P, S, Al and N; the steel metal structure containing pro-eutectoid ferrite and pearlite; the total area ratio of the pro-eutectoid ferrite and pearlite with respect to the total structure being at least 90% and the area ratio Af of the pro-eutectoid ferrite satisfying the relationship Af ≥ A in relation to value A represented in formula (1); the mean circle equivalent diameter of bcc-Fe crystal grains being 15-30 µm; and the pearlite lamellar spacing being 0.20 µm or less on average. A = (103−128×[C(%)]) × 0.80 (%) ... (1) In formula (1), [C(%)] represents C content in mass%.