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通过连续冷却相转变行为研究,成功试制了20 mm厚屈服强度450 MPa级耐候钢板,并对钢板的显微组织、力学性能、耐腐蚀性能及焊接性能进行了分析。连续冷却相变行为和钢板试制结果表明:精轧温度约为850℃、累计压下率不小于0.6、轧后冷速为15~30℃/s、终冷温度不大于579℃可以得到以多边形铁素体(晶粒尺寸为3~10μm)和退化珠光体为主并含有少量马奥岛(M-A组元)的钢板,其屈服强度和抗拉强度分别为458和557 MPa,伸长率不小于28%,-60℃冲击功不小于287 J,其优异的低温冲击韧性与钢板有效晶粒尺寸较小以及大角度晶界所占比例较高有关。72 h亚硫酸氢钠和氯化钠溶液周期性浸润试验结果显示,试制钢板的耐蚀性能比Q345B分别提高了约49%和40%。对试制钢板进行线能量为30 k J/cm的埋弧焊焊接试验,得到的焊接接头热影响区熔合线处-40℃冲击功为156 J。
Based on the study of the continuous cooling phase transformation behavior, the weathering steel plate with a yield strength of 450 MPa at 20 mm thickness was successfully manufactured and the microstructure, mechanical properties, corrosion resistance and weldability of the steel plate were analyzed. The results of continuous cooling and phase transformation and plate trial showed that the finish rolling temperature was about 850 ℃, the cumulative reduction rate was not less than 0.6, the cooling speed after rolling was 15-30 ℃ / s and the final cooling temperature was not more than 579 ℃. Ferrite (grain size of 3 ~ 10μm) and degenerate pearlite and a small amount of MAO island (MA component) steel, the yield strength and tensile strength were 458 and 557 MPa, the elongation is not Less than 28%, - 60 ℃ impact energy is not less than 287J, its excellent low temperature impact toughness and the effective size of the plate smaller grain size and high angle grain boundaries accounted for a higher proportion. The results of periodic wetting test of sodium bisulfite and sodium chloride solution for 72 h showed that the corrosion resistance of trial steel was improved by about 49% and 40% respectively compared with that of Q345B. The submerged arc welding test of 30 kJ / cm of the test steel was carried out. The impact energy at -40 ℃ of the fusion line in the heat affected zone of the welded joint was 156J.