氨分解反应炉筒体短时间使用后发生了明显的变形,并在炉体的径向焊缝上产生了大量的轴向裂纹.对氨分解反应炉炉胆的变形和开裂从化学成分、显微组织、断口形貌、蠕变等进行了综合分析.结果表明：高温使用导致在焊缝组织的晶界和晶内析出大量脆性相并形成魏氏分布从而大大降低了材料塑韧性.计算表明反应炉内的实际应力已接近材料800～850℃蠕变极限,因此蠕变造成了筒体较大的塑性变形.随基体蠕变壁厚减薄焊缝承受着逐渐增大的拉应力,由于焊缝的变形不能及时和基体保持同步,最终在拉应力作用下沿径向焊缝多处萌生轴向裂纹后,又在应力作用下逐步扩展,最终导致反应炉的早期失效.

The deformation in furnace body and a lot of cracks in welding line were observed.The deformation and cracks of reaction furnace were analyzed by metallographic test,chemical analysis,fracture observation,creep calculation,etc.There existed large numbers of brittle phases in body and especially in welding line in use under high temperature condition,resulting in increasing brittleness.The calculation indicated that the factual stress approached the creep limit stress of 316S at 800-850 ℃,which induced the creep and deformation of body.The cracks propagated in welding line because of increasing stress and the welding line couldn’t synchro-deform at the same speed as body.As a result,the cracks gradually expanded and led to early failure of furnace.