批量试制X90螺旋埋弧焊管的性能研究

Research on Batch Manufacturing X90 SAWH Pipes

为综合研究X90管线钢管的性能,选用国内某钢厂轧制的X90M卷板,利用预精焊工艺批量试制了X90MΦ1 219 mm×16.3 mm螺旋埋弧焊管400 t,在对应卷板的头中尾位置的18根钢管取样,采用金相分析、扫描电镜(SEM)断口分析、夏比V型缺口冲击试验、拉伸、弯曲、硬度等试验,研究了X90钢管的性能。试验结果表明:内外焊缝区组织均为针状铁素体,热影响区组织为粒状贝氏体和贝氏体铁素体,在原奥氏体晶界和贝氏体板条内部存在块状或条状的(马氏体-奥氏体)M-A组元;HAZ冲击功存在一定的离散性,出现了一个单值较低(67 J)的试样,SEM断口分析呈现典型的解理断裂特征。这与HAZ的冲击功缺口经过多个不同的HAZ亚区有关,因此应重点研究不同的HAZ的位置的韧性变化规律,以提高HAZ的冲击功稳定性;焊接接头抗拉强度800~850 MPa,断裂位置多在HAZ;焊接接头弯曲试验表明,面弯和背弯试样表面均完好无裂纹;焊接接头不同位置的硬度也能满足标准要求。预精焊批量试制的X90螺旋埋弧焊管各项性能均能满足《天然气输送管道用X90钢级螺旋缝埋弧焊管技术条件》标准要求,为X90钢级管线钢管的成功开发奠定基础。

400 t SAWH （Submerged-arc Helical Welding） pipes were manufactured by Tack-Final welding process to investigate the weld ability of X90 pipeline steel. Metallographic analysis, SEM （ scanning electron microscope） fractographic analysis, Charpy impact test , tensile test, bending test, and hardness test were performed. Metallographic analysis showed that the microstructure of inside and outside wel-ded seam was acicular ferrite, and CGHAZ （ Coarse Grain Heat Affected Zone） was coarsening with blocky or elongated martensite-austenite constituent （M-A） at prior austenite grain boundaries or bainite-ferrite strip. The toughness of HAZ was discrete and low-value toughness occasionally appeared with typical cleavage fracture by SEM fractographic analysis. This is related to the different fracture toughness of HAZ subregion, so it is necessary to study the microstructure transformation and brittleness mechanism of HAZ sub-region. The tensile test confirmed that the strength of welded joint was between 800 to 850 MPa, which was fractured at HAZ. The bending test and hardness tests showed the X90 pipes can meet the standard requirements. The X90 SAWH pipes manufactured by the tack-final welding process can meet the standard requirements, which will lay the foundation of practical application.