Analysis and prevention of sticking occurring during hot rolling of ferritic stainless steel

Sticking phenomena occurring during hot rolling of a modified STS 430J1L ferritic stainless steel were investigated in this study by using a pilot-plant-scale rolling machine. As the rolling pass proceeded, the Fe–Cr oxide layer formed in a reheating furnace was destroyed, and the destroyed oxides infiltrated into the rolled steel to form a thin oxide layer in the surface region. The sticking did not occur in the surface region containing oxides, whereas it occurred in the surface region without oxides by the separation of the rolled steel at high temperatures. This indicated that the resistance to sticking increased by the increase in the surface hardness when a considerable amount of oxides were formed in the surface region, and that the sticking could be evaluated by the volume fraction and distribution of oxides formed in the surface region. The lubrication and the increase of the rolling speed and rolling temperature beneficially affected to the resistance to sticking because they accelerated the formation of oxides on the steel surface region. In order to prevent or minimize the sticking, thus, it was suggested to increase the thickness of the oxide layer formed in the reheating furnace and to homogeneously distribute oxides along the surface region by controlling the hot-rolling process.