FRACTURE SPLITTING CONNECTING ROD STEEL, FRACTURE SPLITTING CONNECTING ROD, AND PRODUCTION METHOD THEREFOR

摘要

Provided are a fracture splitting connecting rod that, in addition to having an enhanced strength due to the use of tempered martensite for the metallographic microstructure, has an improved fracture splittability and is free of the production of quench cracking during quenching; a fracture splitting connecting rod steel that is a material for the production of this fracture splitting connecting rod; and a production method therefor. The fracture splitting connecting rod steel has a DI value calculated using formula (1) below of 55 to 200 mm and has a total area percentage for tempered martensite and bainite of at least 80 area% with reference to the metallographic microstructure as a whole. The [ ] in formula (1) represents the content of each particular element in mass%. DI (mm) = 1.16 × ([C]/10)^1/2 × (0.7 × [Si] + 1) × [5.1 × {[Mn] - 1.2 - (55/32 × [S])} + 5] × (0.35 × [Cu] + 1) × (0.36 × [Ni] + 1) × (2.16 × [Cr] + 1) × (3 × [Mo] + 1) × 25.4 ... (1)