Development of homogeneous high-strength high carbon steel wire rod using the new ED process

摘要

For the direct heat treatment method, in which microstructure control is achieved using the heat of the hot-rolled wire rod itself, various direct heat treatment processes have been developed and practically applied in the high carbon steel fieldas an alternative to the lead patenting (LP) process. The New ED process is a direct heat treatment process developed by Sumitomo Electric which is characterized by its use of hot water mixed with air as a coolant. Although many improvements have beenmade to the New ED process in order to increase quality, the goal of obtaining the quality of offline LP wire (lead patented wire) has not been achieved. This project aimed to reduce deviations in the mechanical properties and to prevent unusualmicrostructures occurring in the longitudinal direction of the wire rod. As a result, a new type of cooling device was developed featuring: (1) uniform cooling throughout an entire wire rod ring, (2) high-precision control of the coolant temperature, and(3) two cooling speeds within a single coolant tank. A homogeneous high-strength high carbon steel wire rod with properties equivalent to those of offline LP wire was therefore successfully manufactured.