Development and production practice of hot-rolled wire rod of TH550-NQ-Ⅱ weather-resistant welding wire steel
Tangshan iron and steel co.,ltd.uses the existing technology and equipment to produce and trial-produce TH550-NQ-Ⅱ weather-resistant welding wire steel wire rod.Terminal control of converter smelting components:C 0.03％～0.07％,P≤0.012％,S≤0.025％;LF refining for 40～65 min,soft argon blowing time 10 min;Con-tinuous casting adopts the whole process of protective pouring,electromagnetic stirring of crystallizer and electric stirring at the end,and the casting speed is controlled at 2.1 m/min.The soaking section temperature of the heating furnace is 1000～1150 ℃,the initial rolling temperature is 1010～1050 ℃,the finishing rolling inlet temperature is 900～930 ℃,the finishing rolling temperature is 930～960 ℃,the spinning temperature is 870～890 ℃,and the finishing rolling speed is 94～98 m/s.The tensile strength of φ 6.5 mm T550-NQ-Ⅱ wire rod in hot rolled state is 487～506 MPa,the elongation after breaking is 42.4％～50.2％,and the area shrinkage is 80.5％～85.2％.The metallographic structure is mainly ferrite(F)+pearlite(P),and the finished product has good stability,the fin-ished product size meets the C-level accuracy and the surface quality is good.The product quality fully meets the us-er's requirements.
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