Standard martensitic stainless steels are: 410, 414, 416, 416(Se), 420, 431, 440A, 440B and 440C, which are magnetic; the corrosion resistance of these steels comes from "chromium", which ranges from 11.5 to 18%. The higher the chromium content, the higher the carbon content is required to ensure the formation of martensite during heat treatment. The above three 440 types of stainless steel are rarely considered for applications requiring welding, and filler metals of 440 composition are not easy to obtain.
Improvements to standard martensitic steels contain additives such as nickel, molybdenum, vanadium, etc., mainly used to increase the limited allowable operating temperature of standard steels to above 1100K. When these elements are added, the carbon content also increases. As the carbon content increases, the problem of avoiding cracking in the hardened heat-affected zone of the weld becomes more serious.
Martensitic stainless steel can be welded in the annealed, hardened and tempered states. Regardless of the original state of the steel, a hardened martensitic zone will be produced adjacent to the weld after welding. The hardness of the heat-affected zone mainly depends on the carbon content of the parent metal. As the hardness increases, the toughness decreases, and this area becomes more prone to cracking. Preheating and controlling the interlayer temperature are the most effective ways to avoid cracking. To obtain the best properties, post-weld heat treatment is required.
ASME SA268 TP410 High Pressure Tube
