550MPa-grade steel plate and manufacturing method of 550MPa-grade steel plate

[0014] According to the 550MPa grade steel plate of the embodiment of the present invention, its chemical composition is: C: 0.08-0.1%, Si: 0.25-0.35%, Mn: 1.78-1.88%, P: 0-0.015%, S : 0-0.005%, Als: 0.017-0.027%, Cr: 0.23-0.33%, V: 0.05-0.07%, Nb: 0.05-0.06%, Ca: 0.001-0.0025%, Ti: 0.01-0.02%, and the rest Iron and unavoidable impurities.

[0015] The 550MPa grade steel plate adds a small amount of expensive alloying elements such as Nb, V, Ti, etc., the production cost is low, and the machinability is good.

[0017] The manufacturing method of the 50MPa grade steel plate according to the embodiment of the present invention includes: step 1, heating process: heating the slab in a walking heating furnace, the temperature of the continuous casting slab out of the furnace is 1210-1250°C, and the heating time is 200-400 Minutes; step 2, rolling process: if the thickness of the steel plate is 10mm to 30mm, then the controlled rolling is carried out after the heating process is completed, the first stage rolling is completed in a four-roll reversible roughing mill, and the thickness of the starting rolling is the thickness of the slab, The rolling temperature of the first stage is 1190~1230℃, the rolling speed of the first stage is 1m / s, and the reduction rate of single pass in the first stage of high temperature elongation rolling is ≥10%; the second stage is rolled in a four-roll reversible The finish rolling mill is completed, the thickness of the second-stage rolling of the steel plate...

[0020] The thickness of the steel plate is 16mm, the steel type is Q550D, the chemical composition of the steel is: C: 0.088, Si: 0.27, Mn: 1.85, P: 0.009, S: 0.004, Als: 0.021, Cr: 0.283, V: 0.062, Nb: 0.058, Ca: 0.0019, Ti: 0.017; the rest are iron and unavoidable impurities. The thickness of the slab is 250mm, the heating temperature is 1228°C, the heating time is 297 minutes, the rolling start temperature is 1202°C in the rough rolling stage, the rolling speed is 1m / s, the reduction rate in the high temperature extension stage is 11-24%; the finishing rolling stage The starting rolling thickness is 48mm, the starting rolling temperature is 998°C, the finishing rolling temperature is 897°C, the effective rolling pass is 6 passes, and the reduction amount in the 6th pass of finishing rolling is limited to 2mm, and the final cooling of ACC is set to 570°C, the cooling rate is 21K / S, the cooling strategy calculated by the ACC model is: the water volume of the upper spray beam ...