A36船板拉伸断口分层分析

Delamilation analysis of the fracture surface with A36 steel for ship plate tensile sample

A36船板拉伸试验时,断口出现批量分层。通过宏观观察、扫描电镜及能谱仪分析、光学显微观察对分层缺陷进行了深入探讨,结果表明:分层位于板厚中部,该部位存在明显偏析及夹杂物富集,氢原子在该部位聚集结合形成氢气,当内压力足够大时,局部开裂,形成白点,加上偏析及夹杂物富集使板厚中部较脆,拉伸时在Z向应力作用下形成分层。可通过严格控制冶炼工艺,强化钢液脱硫、低过热度浇注,电磁搅拌等以及提高原材料质量以减少钢中氢含量等途径加以解决。

The delamilation phenomenon occurred in batch in the center of the plate fracture during tensile test of A36 steel for ship plate.The defects of delamilation were investigated by macroscopical observation,scanning electronic microscope, X ray energy spectrometer and metallography microscope.As shown by the results,the defects of delamilation were located in the middle of thickness,where the segregation and inclusions were serious.The hydrogen gas was formed due to the hydrogen atoms were concentrated in this region.When the internal pressure was big enough,the local area was cracked to form white spots. Meanwhile the enrichment of segregation and inclusions in this area made the central thickness become fragile.Then the delamilation would occur under z-axis stress during tensile test.It could be solved by controlling the smelting process strictly,strengthening desulfurization,Low superheat casting,electromagnetic stirring etc and improving the quality of raw materials to reduce the hydrogen content in steel.