高炭素鋼線材のMn偏析におよぼす鋳片均熱処理の影響

抄録

A study has been made on the diffusion behavior of manganese in the macrosegregation spots of continuously cast bloom during soaking treatment prior to bloom rolling in order to reduce the martensite structure, which is caused by manganese segregation and reduces the wire drawability, in Stelmor-cooled high-carbon steel wire rod. Eutectoid steel samples (SWRS80B) sawed off from the middle part of a 300mm×500mm continuously cast bloom were heated at 1573 K for 0.5 to 5 h and the manganese concentration profiles were measured with EPMA.
(1) Manganese microsegregation peaks (concentration peaks) were substantially annihilated by a soaking treatment of 1573 K×1 h, even though calculations based on the previously reported diffusion constant of manganese in austenite predicted the presence of high microsegregation peaks after a soaking treatment of 1573 K×5 h.
(2) The difference between the experimental and the calculated results in the diffusion rate of manganese decreased with increase in the strain of hot rolling, and thus approximately the same diffusion constant as previous works was obtained for wire rod.
(3) It is thought that the excess vacancies, which are generated by the pores existing in the macrosegregation spots of continuously cast bloom, accelerate the volume diffusion, and thereby the soaking treatment of the continuously cast bloom has the industrial significance for the reduction of manganese microsegregation, as well as carbon and phosphorus segregation.