Microstructure And Mechanical Properties Of Hot-rolled High Alumium31OS Steel And Effect Of Alumium On Action Mechanism

310S alloy has been extensively used as ethylene cracking furnace tubes. Duringrunning the material is often destroyed by high temperature oxidation environment.Research shows that as-cast high-aluminium310S alloy has excellent hightemperature oxidation resistance, while no significant decrease of mechanicalproperties. Therefore we attempt to hot-rolling the high-aluminium310S ingots, andthen research the mechanical properties,weldability and solid solution treatmentprocess of high-aluminium310S plates. The aim of this research is that thehigh-aluminium310S plates have excellent high temperature oxidation resistance,while the mechanical properties meet the national standard of hot-rolled310S plate.310S based steels with0、2、4、6wt.%aluminium was prepared by thenon-consumption of vacuum arc furnace, and then the ingots were cogged and rolledat high temperature. Microstructures and mechanical properties of the rolled steelswith different aluminum content were investigated. The result showed that parts ofaluminum enriched as Al4C3phase appeared after hot-rolling, which is different fromthe ingots in which the Al element dissolved in the matrix phase completely. With theincreasing of aluminum content the phenomenon of Al-rich became more severe andthe amount of chromium carbide decreased and the shape of carbide transformed fromthe spherical aggregates to particles gradually. The alloy with6wt.%aluminumcontent has lots of fish-bone shaped carbide after hot-rolling, which decreased themechanical properties significantly.Room temperature mechanical properties of310S hot-rolled plates with0,2,4wt.%aluminium was tested. The result showed that the strength of plates decreasedslightly with increasing of aluminum content, and the plastic reached maximum whenthe aluminum content is2wt.%. After solution treatment at1200℃for2hours, mostof the carbides dissolved into the matrix and the strength of plates decreased, whilethe plastic increased slightly. The transient tensile experiments at800℃showed that,alloys without and with2wt.%aluminum content have the same high temperaturestrength, and the high temperature strength of the plate increased significantly and theplastic somewhat decreased when the aluminum content increased to4wt.%.Weldability of310S plates with0,2,4wt.%aluminium was tested. The resultshowed that, the mechanical property of welding joint of alloys with2,4wt.%aluminium is close to mechanical property of its’ base metal. Mechanical property ofwelding joint of alloy without aluminium is obviously lower than its base metal.High-aluminium310S alloys have excellent weldability, whose mechanical properties are meeting the requirements of the national standard of hot-rolled310S plate.