| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel for cold forging suitable for forming a near-net shape in which the generation of cracking in a region with a severe working ratio is prevented, reduction in the yield caused by the increase of a cutting allowance is prevented, also, low O and low S are attained for the prevention of cracking caused by inclusions, and there is no deterioration in machinability therefor or there is no need of incorporating poisonous lead for supplementing this. SOLUTION: For realizing high cold forgeability, not only the content of S and the content of oxygen are reduced, but the number of oxide inclusions of certain dimensions or above present in the steel as shown by <=80 in the axis of abscissas, i.e., in the thick type (heavey) ones of >=8μm of D series oxide inclusions based on the ASTM-D method, the number of the ones of 0.5 grade is made to <=10 pieces, also, the ones of >=1.0 grades are not allowed to contain, and furthermore, its hardness is made to <=90 HRB.
|
