Correct selection and use of electrodes directly affect the chemical composition and properties of welds, which is an important link in the preparation of large diameter seamless steel pipe welding. Selection of suitable electrodes requires a comprehensive consideration of various factors, sometimes testing and validation before final determination. The following aspects should be considered: performance requirements of weld metal, shape of electrode, rigidity and position of weld metal, crack resistance of weld metal, processability, equipment and construction conditions, and economic rationality.
Large diameter seamless steel pipes of large forgings are mainly heat treated by direct forging of large forgings, so the internal quality of smelting, ingot and forging casting process must be considered in heat treatment process as long as these factors are: non-uniform chemical composition has various smelting defects; rough and very uneven grain; more gas and impurities; greater forging stress and heat treatment should be considered. Power. The purpose of heat treatment after forging large forgings is to prevent white spot and hydrogen embrittlement, improve the internal structure of forgings, eliminate forging stress, reduce hardness and improve cutting performance, so as to make them have good mechanical properties or prepare for subsequent heat treatment.
The forging of large-caliber seamless steel pipe belongs to large-scale casting forgings. The main difference between large diameter seamless steel pipe and welded pipe lies in the different forming process. Ordinary steel pipes, such as tap pipes, are usually welded by bending plates. You can find the weld at the top; the thicker diameter is usually the spiral weld. Seamless steel pipes are usually formed by laminating molten steel through annular slits and then stretching to avoid welding. In terms of performance, compared with ordinary steel pipe, the pressure bearing capacity is greatly improved, so it is often used in high-pressure equipment. For example, pipeline connection of hydraulic equipment. Welded joint of common steel pipe is its weak link, and welding quality is also the main factor affecting its overall performance. People living in the North usually experience freezing pipes or heating pipes in winter. Usually where welding explodes. Welded pipe is not seamless steel pipe. The seamlessness of seamless steel tube in seamless steel tube production process is mainly realized by reducing tension.  Tension reduction is a continuous rolling process of hollow base metal without mandrel. On the premise of guaranteeing the welding quality of the main pipe, the pipeline tension reduction process is to heat the whole welded pipe to 950 degrees Celsius or higher, and then roll it into various external diameters and walls (24) through the tension reducer. Number of shock absorbers. Hot-rolled steel pipes produced by this process are essentially different from ordinary high frequency welded pipes. After heating in the heating furnace, the metallographic structure and mechanical properties of the weld bead and the matrix can be exactly the same. In addition, large diameter is not controlled automatically by multi-channel reducer, so the dimensional accuracy of steel tube (especially the roundness and wall thickness accuracy) is better than that of steel tube. Similar seamless tubes.