Research On Properties Interface Factors Of High-frequencey Induction Brazing Joint Of1Cr12Mo Stainless Steel

1Cr12Mo stainless steel is on the basis of AISI403steel adding Moelement to improve the heat resistance, temper resistance and the secondaryhardening effect, also improved the mechanical properties at roomtemperature and has a satisfactory corrosion resistance, fatigue strength andshock resistance, are widely used in the dynamic and static blades, girdle,spring pieces and Embedded gland of gas turbine and steam turbine usedunder550℃. This kind of material of steam turbine rotor dynamic leaf andbrace welding at present mainly adopts the silver based filler metals andartificial flame brazing. And the joint performance in the high temperaturediffer with parent metal greatly. Also the working condition is poor, the lowefficiency, big joint heat affected zone, and brazing temperature and jointquality is not easy to control.According to the problems above, this paper selects high frequencyinduction brazing which is of the high heating speed, high energy utilizationrate, and easy to automatic control to study the microstructure andmechanical properties of1Cr12Mo stainless steel joint under differentprocess conditions. According to the form of the brazed joint, a highfrequency induction brazing experiment platform was constructed first.Then completed the choice of induction power supply, design andmanufacture of the induction coil, the way of measuring temperature andchoice of temperature measuring system, design and manufacture of the gasprotection device, etc.On this basis, choose three different types of solder, the silver based(BAg45CuZn), nickel based (BNi82CrSiB) and copper based (Cu58MnCo)to do the wetting test and shear strength test, respectively. Then determine the most suitable solder. Based on the results of comprehensive evaluation,finally Ni82CrSiB was chosen as solder because of its good surface forming,stable welding process and high joint strength.After choosing BNi82CrSiB as the solder, the wettability of it and themicrostructure and mechanical properties of joint were studied in differentprotective atmosphere, heating rate and process conditions such as brazingtemperature and holding time. The influence of different process factors onthe microstructure and mechanical properties of joints was analyzed. Byusing the optical microscope, scanning electron microscopy (SEM),transmission electron microscopy (TEM) and energy dispersivespectrometer (EDS), microstructure of brazing seam, mutual diffusionbetween the solder and the parent and the generating mechanism of thesecond phase under different process conditions was studied. Also analysisthe correlation between joint performance and the microstructure.On the basis of experimental analysis and research, temperature andjoint organization and performance of1Cr12Mo stainless steel highfrequency induction brazing can be accurately control through theoptimization of process. The research results show that with the increase oftemperature and holding time, the strength of the brazed joint was increased,but too high temperature will lead to the parent metal melting anddegradation of the joint performance. The optimized process parameters forthe argon gas flow25L/min, the heating current is600A, the brazingtemperature is1120℃, holding time is90s. In this process, the good jointorganization can be get and the mechanical performance is outstanding.