X80大应变管线钢焊接热影响区疲劳性能的研究

为了研究X80大应变管线钢焊接热影响区疲劳性能,采用MTS和INSTRON万能力学试验机测得了全壁厚X80大应变钢管焊接接头的疲劳寿命及焊接热影响区的疲劳裂纹扩展速率,并采用Gleeble-3500热模拟试验研究了焊接热循环不同峰值温度对组织和性能的影响。结果表明,焊接接头的疲劳性能显著降低,在相同的疲劳寿命条件下,其疲劳裂纹应力降低约100 MPa以上;疲劳裂纹均在焊趾处萌生,并向内沿热影响区扩展;而疲劳裂纹在热影响区的扩展速率随其通过的不同区域而变化。经焊接热循环后,热影响区呈现弱化趋势,强度最低点出现在细晶区,然而细晶区良好的塑韧性有利于抑制疲劳裂纹扩展,改善疲劳性能。

Research on Fatigue Performance of X80 Large Strain Pipeline Steel Heat Affected Zone

In order to know the fatigue performance of X80 large strain pipeline steel heat affected zone, the fatigue life of full-thickness X80 large strain pipeline steel welded joint and fatigue crack propagation rate of welding heat affected zone were investigated using MTS and INSTRON universal mechanical testing machine, and the influence of different peak temperature of welding thermal cycle on microstructure and mechanical properties were studied by using Gleeble-3500 thermal simulation experiment. The results indicated that the fatigue life of welded joint decreases remarkably. Under same fatigue life conditions, the fatigue stress of welded joint reduced by more than 100 MPa;The fatigue cracks generate at the toe of weld, and propagate along heat affected zone. While, the fatigue crack propagation rate changes when it grows in different heat affected zone. After welding thermal cycle, the heat affected zone shows a trend of weakening, and lowest strength appears at fine grain heat affected zone. However, the excellent ductility and toughness of fine grain benefit to inhibit fatigue crack propagation, and improve the fatigue properties.