Abstract
The microstructure and properties of shielded metal arc welding (SMAW) joint of P91 heat-resistant steel annealed at different holding time were observed and analyzed. The results show that the martensite and residual austenite structures in the weld zone and coarse grain heat affected zone (CGHAZ) were transformed with the extension of holding time. After 760°C+4h annealing, a large number of white rod-shaped precipitates appeared in the weld zone. The main components of precipitates were Fe, Cr, Mn, V, Si, and a small amount of oxides appeared. After 760°C+5h annealing treatment, relatively fine white granular precipitation appeared in the weld zone, and a large number of oxides and some precipitates have been dissolved. After 760°C+6h annealing treatment, the precipitated phases were composed of Fe-Cr, Fe3Si, Ni-Cr-Fe, Fe2MnAl. Compared with the annealing treatment for 5h, the microstructure of the precipitated phase is fine and uniform, dispersion distribution of second phase particles, and the material mechanics is relatively stable.
Highlights
P91 heat-resistant steel is a kind of improved type martensite 9 Cr1Mo steel[1,2]
Researchers have carried out related studies on the welding process and post-welding heat treatment process of P91 heat-resistant steel[12,13]
The microstructure of coarse grain heat affected zone (CGHAZ) of P91 heat-resistant steel shielded metal arc welding (SMAW) butt joint without annealing treatment is mainly composed of martensite and residual austenite
Summary
P91 heat-resistant steel is a kind of improved type martensite 9 Cr1Mo steel[1,2]. The steel is fabricated by adding V, Nb, N and other strengthening elements in the steel containing Cr and Mo elements. The microstructure of P91 heat resistant steel is mainly martensite and some ferrite. It has excellent performance in high temperature environment. Researchers have carried out related studies on the welding process and post-welding heat treatment process of P91 heat-resistant steel[12,13]. From the point of view of the actual production and installation of thermal power supercritical units and supercritical units, the relationship between the holding time of P91 heat-resistant steel at different heat treatment temperatures and the change of joint structure and properties is very important. The results will be to optimize the heat treatment process of P91 heat-resistant steel provide important research basis
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