大线能量焊接用海工钢的夹杂物与组织

Investigation on inclusions and microstructure of offshore steel for high heat input welding

海洋工程领域对可大线能量焊接且低温韧性优良的厚钢板需求迫切。宝钢通过微合金化技术及调质工艺,开发出了满足大线能量焊接的E550级海洋工程用钢。通过冶炼、轧制、调质试验、焊接热模拟试验、电镜观察统计及金相观察,研究了大线能量焊接用海工钢H1夹杂物、显微组织及力学性能,并与宝钢现有海工钢E550进行了对比。研究结果表明,H1中夹杂物为Al2O3、MnS、Al2O3-Ti3O5、Al2O3-MnS、TiN-MnS、Al2O3-Ti3O5-MnS;E550中夹杂物为Al2O3、CaO·xAl2O3(CAx)、CaO-CaS、CAx-CaS、CAx-CaS-TiN。H1力学性能满足E550级海工钢要求,且满足50和100kJ/cm线能量焊接要求。其HAZ韧性改善的机理为,低硅低铝质量分数有利于减少局部脆性区;钛质量分数的降低,有利于抑制TiC脆化,提高HAZ韧性。

In the field of ocean engineering,there is an urgent demand for thick steel plate with high heat input welding and excellent low-temperature toughness.Through microalloying technology and quenching and tempering process,Baosteel has developed E550 grade ocean engineering steel for high heat input welding.The inclusions and microstructure of the offshore steel for high heat input welding were investigated by smelting,rolling,quenching and tempering,thermal simulating test,SEM observation statistical analysis of inclusions and metallographic observation.The results were compared with the existing offshore steel E550 in Baosteel.The results show that the inclusions of the developed offshore steel H1 are Al2O3,MnS,Al2O3-Ti3 O5,Al2O3-MnS,TiN-MnS,Al2O3-Ti3 O5-MnS.The inclusions of the E550 are Al2O3,CAx,CaO-CaS,CAx-CaS,CAx-CaS-TiN.The mechanical properties of steel H1 can meet the requirements of E550 grade offshore steel and can meet the requirements for 50 kJ/cm and 100 kJ/cm weld heat input.The mechanism of HAZ toughness improvement is as follows,low silicon and low aluminum content are beneficial to reduce local brittle zone;Ti content reduction is beneficial to inhibit TiC embrittlement and improve HAZ toughness.