Abstract
In a heating process of hot stripping with an oil firing heating furnace, sulphur components in fuel heavy oil are oxidized to sulphur dioxide.
It is generally considered that sulphur dioxide in the combustion gas reacts on the heated steel by absorption and/or chemical reaction to give some influences on the sulphur content which affects the chemical and mechanical properties of rolled product.
The purpose of this work is to determine the degree of migration of sulphur component from atmosphere to heated steel, to explain a possibility and limitation of use of “high sulphur oil” as fuel in the steel heating process.
The migration of sulphur component which is supplied in the form of sulphur dioxide was investigated by a model experiment using sulphur-35 as a tracer at the following variables of the experimental condition; (1) sulphur dioxide concentration, (2) temperature, (3) heating time and (4) composition of atmosphere. The depth of diffusion of sulphur component which was originated from atmosphere was also investigated.
Above 50% of sulphur component in atmospheric gas was observed to be dombined with steel species after being heated to 1, 200°C for one hour in an atmospheric gas including 0.14% sulphur dioxide.
The steel species, however, lost most of their radioactivity by a surface treatment with an ammoniacal ammonium citrate solution to indicate the greater fraction of migrated sulphur had existed in oxidized layer (scale layer) on the surface.
The amount and distribution of migrated sulphur in the scale and steel layer appear to be very affected by concentration of sulphur dioxide in atmosphere, heating temperature and heating time.
The depth of diffusion of sulphur component into the non oxidized steel layer, measured autoradiographically, was observed to be about 0.14 mm after being heated at 1, 200°C for one hour, and it seems that the heigher the heating temperature was and the longer the heating time was, the deeper the diffusion depth is.
