JFE TECHNICAL REPORT

No.15 Special Issue on “Steel Bar and Wire Rod”

Development of Free Cutting Steel without Lead Addition to Replace AISI12L14


MURAKAMI Toshiyuki     TOMITA Kunikazu     SHIRAGA Tetsuo

Abstract

AISI12L14(JIS SUM24L) is Pb-added free cutting steel containing 0.3% Pb and 0.3% S. Customers need Pb-free free cutting steel from the viewpoint of global environmental problems. Since it has long been known that the machinability of S-added free cutting steels is improved as the size of sulfide inclusions becomes larger, the improvement of machinability was studied from this viewpoint. Firstly, the chemical compositions of the developed steel were designed by the calculated phase diagram to have a wide temperature range of solidification which results in the formation of large size of sulfide inclusions. Based on the results, machinability test and hot forging test were actually conducted to confirm the chemical compositions. Crystallization of large sulfide inclusions was first attained with Cr addition and increment of S content. The authors have developed a new Pb-free free cutting steel with excellent machinability in a wide range from low cutting speed such as drilling to high one such as turning.

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