Analysis on Metallographic Structure and Surface Defect of Heat-resistant Austenitic Stainless Steel 309S

A research was carried out to investigate the as-cast,as-rolled and as-annealed metallographic structure as well as as-annealed mechanical property and surface defects of heat-resistant austenitic stainless steel coil 309S which was produced with smelting-rolling-annealing and pickling process.The results show that under the above three conditions,the steel is composed of austenite and high temperature residual ferrite that could not be eliminated by heat treatment.For the as-rolled and as-annealed structure,there is low content of ferrite near the surface and high content of ferrite in the core along the thickness direction.The product's mechanical properties are not affected by the high temperature residual ferrite.Fine grinding of the continuously cast slab can avoid surface defect of the product.