某电厂氨气输送管道上的SUS304不锈钢三通多次出现裂纹，通过宏观观察、渗透检测、化学成分分析、硬度测试、力学性能测试、金相检验等方法，分析了该三通裂纹产生的原因。结果表明：由于三通成型后没有进行规范的固溶热处理，导致显微组织中存在较多的形变马氏体和弥散分布的碳化物，增加了材料的硬度和脆性，加之三通成型内应力没有充分释放，三通在应力最大的肩部产生了裂纹。

A SUS304 stainless steel tee in an ammonia gas pipeline cracked several times. By using macroscopic observation, penetration testing, chemical composition analysis, hardness testing, mechanical property testing, metallographic examination and so on, the causes for cracks of the tee were analyzed. The results show that:the solid solution treatment of the tee was not enforced normatively, which generated much deformed martensite and dispersed distributed carbide in the microstructure, and the hardness and brittleness of the material were increased; in addition, the internal stress of the tee during forming didn't release completely, as a result of that, the cracks generated on the shoulder of the tee under the maximum stress.