加氢反应器全焊缝高温持久断口分析

Analysis on Stress Rupture of Weld Seams on Hydrogenation Reactors

运用OM、SEM对两种典型加氢反应器全焊缝高温持久试样的断口形貌和组织进行分析,探讨高温持久断裂的机理。试验结果表明,持久性能好的试样断口为脆性断裂,缩颈小,难变形;而持久性能差的试样为延性断口,表现为颈缩大,易变形。另外,断口附近组织中的裂纹多形成于柱状晶区,且多萌生于晶界、大颗粒碳化物或夹杂物等处,而在等轴晶区中裂纹的数量较少。因此,增大等轴晶比例,减少夹杂物和大颗粒碳化物将有利于提高加氢反应器焊缝的高温持久性能。

The fracture morphology after stress-rupture of two typical weld seams of hydrogenation reactors and the microstructure close to the fracture were observed with optical microscope（ OM） and scanning electron microscope（ SEM）, and the mechanism of stress rupture was discussed as well. The results show that the fracture morphology of high stress-rupture property displays a brittle fracture with little necking, which means hard deformability at high temperature.Inversely, the low stress-rupture fracture morphology is ductile fracture with heavy necking that exhibits an easily deforming behavior. In the vicinity of fracture, micro-cracks normally initiate at the grain boundaries, larger carbides and inclusions,and the number of micro-cracks in the columnar grains area is much higher than that in equiaxed grain zone. Therefore, to increase the proportion of equiaxed grain zone and to reduce inclusions may contribute to the enhancement of stress-rupture properties at high temperature for the weld seams on hydrogenation reactors.