Mn对中碳钢连铸坯高温物理性能的影响

120 t转炉-LF-VD-连铸工艺生产37Mn5钢的280 mm×380 mm连铸坯易出现纵向裂纹。用Gleeble1500D热模拟试验机试验和分析了在1300～800℃时37Mn5钢(%:0.34～0.38C、1.30～1.55Mn)和45钢(%:0.42～0.50C、0.50～0.80Mn)280 mm×380 mm连铸坯的热塑性和力学性能,以及室温和1300℃之间加热和冷却时的膨胀-收缩效应。与45钢比较,得出≤950℃时37Mn5钢连铸坯的热塑性较低,在相变范围的体积变化较45钢铸坯大,导致37Mn5钢铸坯出现纵向裂纹。因此应降低37Mn5钢铸坯在540～870℃范围内的加热和冷却速度,以避免产生纵向裂纹。

Effect of Mn on Physical Properties of Concasting Bloom of Medium Carbon Steel at High Temperature

The longitudinal crack of 37Mn5 steel 280 mm×380 mm concasting bloom produced by 120 t converter-LF -VD-bloom caster process often occurs in production.The hot plasticity and mechanical properties of 280 mm×380 mm concasting bloom of 37Mn5 steel(%:0.34～0.38C,1.30～1.55Mn)and 0.45C steel(%:0.42～0.50C,0.50～0.80Mn)at 1 300～800℃and their dilatometric-shrinking effect during heating and cooling between ambient and 1 300℃have been tested and analyzed by using Gleeble 1500D thermal simulation machine.It is obtained that as compared with 0.45C steel bloom,at≤950℃the hot plasticity of 37Mn5 steel bloom is lower and the change of volume at phase transformation range is larger than that of 0.45C steel bloom led to occurrence of longitudinal crack.Therefore heating and cooling speed of 37Mn5 steel bloom between 870℃and 540℃should be slowed down to avoid occurrence of longitudinal crack.