High-voltage Pulse Discharge Heated Refined Grain Process

Low carbon steel and low carbon microalloy steel were researched in this paper, These materials were austenitized and then followed by water-quenching to obtain packet martensitic microstructure. Then the martensite sheet was cold-rolled by reduction in thickness above 60%. Finally the cold-rolled specimens were quickly annealed by high-voltage electroplusing. The mechanical properties of these materials were measured on Shimadzu testing machine. All the micro structures were observed by transmission electron microscopy. The influence of different quenching temperature and the parameter of discharge on the material's microstructure and properties were discussed. The influence of high-voltage electroplusing on grain refinement was also studied. The results showed that the grain size of these materials could be greatly refined, and the mechanical properties of these samples also improved greatly. The grain size of low carbon microalloy steel with the length of 200mm was refined from 6μm to less than 200nm, its tensile strength was improved from 350MPa to 841MPa, percentage elongation reached to 13%. The tensile strength of the same material with the length of 400mm was improved to 956MPa, percentage elongation also reached to 13%. The grain size of low carbon steel with the length of 200mm was refined from 6μm to less than 200nm and its tensile strength was improved from 300MPa to 874MPa, percentage elongation reached to 12%.