火焰切割及正火热处理对20控Cr碳钢管性能影响试验研究

Test and Research of Effects of Flame Cutting and Normal Heat Treatment to Properties of 20+Cr Carbon Steel Pipe

20控Cr优质碳钢管广泛应用于核电站管路系统和化学工业炉上有蒸汽冲刷的管道系统,在管件加工、配管过程中不可避免地采用了高效、便捷的火焰切割方法。通过对20控Cr碳钢管在火焰切割与锯切后的化学成分、力学性能、金相试样对比发现,火焰切割将带来-20℃冲击功不满足技术要求、晶粒长大、铁素体与珠光体偏析等系列问题,火焰切割影响范围超过30 mm。正火(890~930℃)热处理校正工艺工程应用试验表明,经过正火热处理校正后,可将受到火焰切割影响的-20℃冲击功数值恢复到正常水平;同时,粗大的晶粒得以细化,晶粒度在8~9之间,碳化物分布均匀化。

20+Cr carbon steel pipes are widely used in the pipeline of the nuclear power plant and the pipeline, which is eroded by steam, of chemical industrial furnace. The highly efficient and convenient flame cutting technology is often used in pipe matching and machining. By comparing the chemical compositions, mechanical properties and metallurgical constitution for both flame cutting and sawing on 20+Cr carbon steel pipes, it had been revealed that flame cutting will bring in several problems, such as unqualified-20 ℃impact energy, coarse grains and the segregation of ferrite and pearlite. The heat-affected zone by flame cutting will be as large as 30mm. The heat treatment experiment of normalization under temperature of 890~930℃indicated that after normalizing heat treatment,-20℃impact energy of the steel had been recovered to the normal level. In addition, the coarse grains would be refined to grain size of grade 8-9 and carbides homogeneously distributed.