Determination of SH-CCT Curve and Microstructure and Properties of Heat-Affected Zone in Q420qENH Steel Composite Steel Plate Substrates
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摘要: 采用MMS-200热模拟试验机测定了Q420qENH+316L复合钢板基材Q420qENH钢在不同t8/5冷却速度下的热影响区组织,基于显微组织观察及硬度分析,得出了不同t8/5冷却速度下Q420qENH钢焊接热影响区组织及硬度的变化规律,并绘制试验钢焊接热影响区连续冷却相转变(SH-CCT)曲线。结果表明,当t8/5冷却速度在1~10 ℃/s时,试验钢转变产物为F+GB,随着冷却速度增加,晶粒尺寸及硬度无显著变化;当t8/5冷却速度在15~45 ℃/s时,试验钢转变产物为铁素体及下贝氏体,晶粒尺寸减小,硬度值增加,其中,在15 ℃/s下的Q420qENH晶粒尺寸及硬度值最大。为确保焊接接头满足性能要求,基材Q420qENH钢焊接时冷却速度应控制在1~45 ℃/s之间,对应焊接线能量应控制在7.2~48.0 kJ/cm之间。
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关键词:
- Q420qENH耐候钢 /
- SH-CCT曲线 /
- 显微组织 /
- 焊接线能量
Abstract: Using the MMS-200 thermal simulation testing machine, the microstructure of the heat-affected zone (HAZ) of the Q420qENH steel matrix in Q420qENH composite steel plates was determined under different t8/5 cooling speeds. Based on microstructural observation and hardness analysis, the microstructural and hardness changes of the weld heat-affected zone (HAZ) of Q420qENH steel were determined at different t8/5 cooling speeds, and the continuous cooling transformation (CCT) curves of the weld HAZ were plotted. The results showed that when the t8/5 cooling rate was between 1 ℃/s and 10 ℃/s, the transformation products of the test steel were F+GB, and there were no significant changes in grain size and hardness as the cooling rate increased; When the t8/5 cooling rate was between 15 ℃/s and 45 ℃/s, the transformation products of the test steel were ferrite and lower bainite, with grain size decreasing and hardness increasing. Among these, Q420qENH steel exhibited the highest grain size and hardness at a cooling rate of 15 ℃/s. To ensure that the welded joint meets performance requirements, when welding Q420qENH steel base material, the cooling rate should be controlled between 1 ℃/s and 45 ℃/s, with corresponding weld heat input controlled within a range of 7.2 kJ/cm to 48.0 kJ/cm.-
Key words:
- Q420qENH weathering steel /
- SH-CCT curve /
- microstructure /
- welding line energy
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