Research On TMCP Method Using In Duplex Stainless Steel 2205 Medium And Heavy Plates

The duplex stainless steel(DSS) is a kind of structural material with excellent mechanical properties and corrosion resistance, which is widely used in petrochemical industry, sea-water applications, paper manufacture, nuclear power plant construction and etc. DSS 2205 medium and heavy plates are the most popular among all DSS productions, but its cost is high due to long time and high energy consuming solution treatment. In this paper, TMCP method is used to replace solution treatment. The effects on over all properties by using TMCP method and conventional method are studied. Main conclusions of this paper can be drawn as follows:The greatest difficulties of DSS 2205 TMCP method are ensuring both good hot workability and uniform two-phase. Rolling temperature, rolling rhythm, reduction ratio and roller cooling after rolling must be studied in thermal simulations and laboratory rolling by the reference of austenitic stainless TMCP method.Thermal simulation is carried out and the impacts of five TMCP process parameters on microstructure are studied. Ferrite volume content and hardness are reduced by large compression at high temperature while increased at low temperature. Similar ferrite volume content is obtained by heat preservation after compression and conventional method. A ferrite to austenite transition happens. The amount of the transition increases when temperature drops and reduction ratio increases.Laboratory rolling is carried out and the impacts of TMCP process parameters on over all properties of plates are studied. Ferrite volume content decreases when roll bed cooling time increases. Strength, hardness, ductility and impact toughness increases with roll bed cooling time to some extents while they deteriorate if roll bed cooling time is too long. Pitting corrosion resistance decreases when roll bed cooling time increases. Compared with conventional method, ferrite volume content is too high and a significant hardening happens. Online heat treatment can significantly reduce ferrite volume content.ζphase appears and bad over all properties are obtained under shorter time of online heat treatment while similar over all properties compared with conventional method are obtained under longer time of that. The plate processed by 50% pre-rolled and 80% TMCP and longer roll bed cooling time has a similar over all properties compared with conventional method.TMCP parameters are optimized. First category: One TMCP, it requires larger reduction ratio at high temperature and appropriate roll bed cooling time before quenching. Second category: One pre-roll and one TMCP, it requires high finishing temperature and roll bed cooling time before quenching.