Welding residual stress is caused by the welding weldment uneven temperature distribution, thermal expansion and contraction of weld metal and other causes, so along with welding construction inevitably produce residual stress. Eliminate the residual stress is the most common method tempering, heat treatment furnace will be placed weldment is heated to a certain temperature and holding a certain time, the use of materials at high temperatures reduce yield limit, so that the high places stress plastic flow, gradually reduce the elastic deformation, plastic deformation stress is reduced gradually increased leaving. PWHT on metal tensile strength, creep limit the impact of the heat treatment temperature and time related. PWHT on impact toughness of the weld metal with steel varies.
Heat treatment after welding is a new technique to eliminate the residual stress. Preheated before welding the material to a heat treatment temperature after the welding process and welding pieces of heating was continued to maintain this temperature, the soldering is completed using heat insulation cotton to its slow cooling. Although the advantages of chrome-nickel seamless pipe a lot, but in recent decades because nickel-based heat-resistant alloys and nickel 20% less heat resistant steel of a large number of development and application, and the chemical industry growing more and more requirements for stainless steel large, and the deposits of nickel and because of less concentrated in a few areas, it appeared in the world in the supply and demand of nickel contradictory aspects. Therefore, unlike many other alloy steel pipe Tianjin areas (such as large castings and forgings of steel, tool steel, heat resistant steel, etc.), especially nickel resources are relatively deficient country, carried out extensive section on behalf of nickel and other elements to Nickel scientific research and production practice, research and application in this area is relatively large number of manganese and nitrogen instead of seamless steel with heat-resistant nickel. This method can effectively reduce residual stress and improve the stress corrosion resistance of metals. Heat treatment after welding can reduce the residual stress, and heat treatment temperature is higher, the better to eliminate the residual stress.
Post weld heat treatment can effectively improve the resistance to stress corrosion seamless welding ability, after the heat treatment temperature is higher, increasing resistance to stress corrosion is more significant. With the continuation of the electrolysis reaction, the solution is close to the interface layer of the anode, the electrolyte concentration may develop into saturated or supersaturated state. After coating the coating material on the pretreatment of Tianjin Seamless Steel Tube ri indirectly affect the quality of the coating off the power attached to compete. Titanium solid solution strengthening effect is strong, but the toughness of reducing solid solution, solid solution in austenite to improve the hardenability of steel, but titanium compounds, but lower hardenability of steel.
