Welding procedure qualification
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How to weld 09MnNiD low-temperature steel? Our factory is currently manufacturing a low-temperature pressure vessel made of 09MnNiD material; the operating temperature is -39 degrees Celsius, the plate thickness is 26 mm, and the diameter is 2600 mm. What welding materials should be used by experts? How should the welding process be formulated?
09MnNiD is likely to be a ferritic low-temperature steel; its microstructure consists mainly of ferrite with a small amount of pearlite, and it is generally used in the normalized state. 09MnNiD is generally not suitable for dissimilar metal joints. When welding ferritic low-temperature steels by shielded metal arc welding, high-toughness electrodes made of low-carbon steel or C–Mn steel with the same composition as the base material can be used; the weld metal retains sufficient impact toughness at -30°C. It is more reliable to use low-nickel electrodes with W(Ni) = 0.5%–1.5%, such as W707Ni. Its heat input is kept below 20 kJ/cm. In submerged arc welding, a neutral flux can be used in combination with Mn–Mo wire, or an alkaline flux can be used with Ni-containing wire; alternatively, C–Mn steel wire can be used with an alkaline non-fusing flux. Trace amounts of Ti and B alloying elements are introduced into the weld through the flux, thereby ensuring that the weld metal possesses good low-temperature toughness. The welding heat input should be kept between 25–50 kJ/cm. This is a welding process between pearlitic steel and austenitic stainless steel; wire rod A302 or wire H1Cr24Ni13 can be used for this purpose