Abstract: Combining with the catalytic cracking unit in flue gas environmentat 700 ℃, this paper analyzed the high-temperature creep properties and high-temperature precipitation phase effects of AISI 300 series heat-resistant stainless steel. It investigated the feasibility of applying AISI 347 material. On this basis, the paper studied through testing the mechanical properties and metallurgical structure changes of AISI 347 pipeline including base metal and weld zone after different heat-preservation time at 700 ℃. The test results show that the plasticity and impact toughness of the 347 base material are better than that of the weld zone at high temperature; there are σ-phase and carbide precipitates in the base material and weld zone under long-term heating at 700 ℃ which mainly concentrate on the grain boundaries. With the increase of heating time, the material strength gradually increases, plasticity and toughness decrease, but the trend of deterioration of material properties is relatively flat. The above study indicates that AISI 347 stainless steel is the ideal material for catalytic cracking unit in flue gas environment at 700 ℃.

Key words: austenitic stainless steel, precipitation phases, AISI 347, high-temperature performance