Semi-solid rolling process of steel strips

Semi-solid metal forming (SSF) is recognized as a new forming technology, which has been paid more and more attention by the researchers all over the world. The semi-solid rolling process (Rheo-rolling) combines the fabrication of slurry with continuously rolling as an important neoteric means to achieve near-shape forming. In this paper, an original device of semi-solid rolling has been designed and manufactured to prepare the spring steel–60Si2Mn and stainless steel–1Cr18Ni9Ti. The semi-solid slurry is successfully fabricated by electromagnetic stirring and rolled into the strips with the thickness of 3–5 mm, the width of 70 mm and the length of 1000 mm. The effects of the stirring parameters, including stirring power and time, on the solid fraction and microstructure of steel, have been investigated through electromagnetic stirring process. The experimental results show that the semi-solid slurry with the solid phase diameter of 50–150 μm and the solid fraction (fs) of 5–65% can be obtained by electromagnetic stirring. The highest ultimate tensile strength and elongation obtained for 60Si2Mn strip with 60% solid fraction are 860 MPa and 13.4%, respectively. For 1Cr18Ni9Ti strip with 60% solid fraction, the highest ultimate tensile strength and elongation are 1022 MPa and 40.6%, respectively. With increasing the solid fraction, the properties of semi-solid rolled products become better. The method of grooved rolling can ameliorate the stress state at the edge of rolled strip, which is beneficial to improve the homogenization of microstructure.