Abstract:Abstract:Hot-rolled wire rod SAE8620 has been successfully developed by using the process flow: converter smelting→LF refining→RH→ continuous casting(casting slab size:320 mm x 425 mm)→breakdown rolling→finishing and checking→ high speed wire rod rolling and reasonable chemical composition design. At?the?same?time, the over-cooling Austenite continuous cooling transformation behavior of steel SAE8620 has been studied. The results show that the rod SAE8620 has excellent hot-rolled microstructure?and?properties, and the heat treatment performance meets the requirements of steel 20CrNiMo in accordance with Alloy Structure Steels GB/T 3077, the end hardenability test results meet the requirements of 20CrNiMoH in accordance with Structural Steels Subject to End-quench Hardenability Requirement GB/T 5216-2004. The addition of Cr, Mo, and Ni alloy elements can effectively inhibit the transformation of over-cooling Austenite to ferrite and pearlite, and promote the transformation of Bainite and Martensite. When the cooling rate is greater than 1.0℃/s, Bainite will begin to form in the metallographic structure, and the proportion has increased dramatically with the increase of cooling rate; when the cooling rate is greater than 5.0℃/s, Martensitic will form in the metallographic structure.