Study On Physical Simulation Of Welding Heat Affected Zones On New High Cr Ferritic Heat-resistant Steel

As global electric power consumption increases fast in recent years, in order to solve the increasingly prominent problem of inadequate energy and environmental pollution, thermal power generating units around the world are transforming from sub-critical parameters to the super (super-) critical parameters. 9~12% ferritic heat-resistant steel has gradually become the primary election material used for main power plant equipment and timber replacement materials for its excellent strength and toughness, oxidation resistance, corrosion resistance, and high creep strength.In this paper, the SHCCT curve of new high Cr ferritic heat-resistant steel was made by thermal simulation and quantitative metallographic method, and studied the organization structure and morphology of precipitation at different cooling rates for testing steel. Orthogonal test was used to investigate the influences of heat input and preheat temperature on the microstructure and mechanical properties of heat affected zone (HAZ) of testing steel. Moreover, the HAZ includes coarse grain heat affected zone (CGHAZ), fine grain heat affected zone (FGHAZ), critical heat affected zone (ICHAZ), super-critically reheated coarse-grained HAZ (SRCGHAZ) and inter-critically reheated coarse-grained HAZ (IRCGHAZ).Test results showed that testing steel CGHAZ was constructed of lath martensite and delta ferrite. The brittle dioxide layer could also be observed in the interface between lath martensite and delta ferrite under different cooling rates, and the thickness of carbon layer decreased with the cooling rate increasing. The CGHAZ impact energy at room temperature was low under the different welding process, but the ICHAZ had high impact energy at room temperature. Saturated martensite and brittleδferrite existed in the CGHAZ microstructure was the main reason for its low impact energy at room temperature, andδferrite content was higher, the worse the toughness. For ICHAZ, some fine precipitation which distributed uniformly in the martensite lath was able to stabilize the martensitic matrix, and the ICHAZ toughness was improved attributed to these fine precipitation. CGHAZ showed the highest hardness, and the ICHAZ hardness was the minimum, compared with CGHAZ, the IRCGHAZ hardness decreased a lot.