C-276 alloy liquid metal poor mobility, joint bevel angle needs more; weld metal melting depth, easy to form incomplete penetration thickness of the blunt edge of the connector to be smaller, welding heat input can not be too small; but not by increasing the welding current to improve its process characteristics, the welding current exceeds the recommended range not only makes the puddle overheating, increasing the sensitivity of the thermal cracks, and the deoxidizer in the weld metal was evaporated, pores, in order to prevent weld and heat affected zone grain growth and carbide precipitation, generally requires the use of a smaller amount of welding heat input Welding Alloys C-276. So using medium should be in the Welding Assembly current, welding speed faster by reducing the residence time at high temperature to control the amount of welding heat input; again C-276 alloy the linear expansion coefficient is large, has a higher thermal cracking susceptibility, the welding is easy to produce heat cracks, such as solidification cracking, the multilateral crack and high temperature loss plastic cracks, and to ensure that the first floor of the weld bead appearance appear before a convex shape and can effectively prevent thermal cracks filled crater. Welding generally no warm-up, but when the base metal temperature is below 15 ° C, to address both sides of the connector 250 ~ 300mm wide area heated to 15 to 20 ° C to avoid condensation of moisture causes the pore in the weld. Low interpass temperature should be controlled in order to prevent the weld and heat-affected zone grain growth and carbide precipitation, generally no more than 90 ° C; easily occur depleted Cr grain boundaries in the region due to the sensitizing temperature, poor Mo phenomenon, leading to intergranular corrosion and stress corrosion tends to occur, the welding area should be avoided in the long residence time at high temperature, pay attention to the rapid cooling can prevent the corrosion tendency, rapid cooling welding, weld gas is too late to escape, it is easy to form pores. Groove and in the vicinity of the oxide layer is thoroughly cleaned before welding, various paints, oils, etc., the generation of holes can be prevented.
Hardenability 15CrMo steel of Cr, Mo, C and other Brazing Alloy elements, the increase in carbon equivalent, so that the hardenability of the steel tendency is more obvious, weldability deteriorates. Under specific cooling rate in the weld thermal cycle, the weld and heat affected zone are likely to form a crack-sensitive tissue. Reheat cracking 15CrMo heat resistant steel containing Cr, Mo, Mn and Si, and other carbide forming elements, and have a certain degree of superheat zone reheat cracking tendency. Prevention measures are: (1) strictly control the content of the base metal and weld materials of Mn and Si alloying elements; (2) selection of plastic Welding Material is higher than the base metal; (3) an appropriate increase in the temperature between the preheat temperature and layer Road; (4) using a small line of energy, limit the width of the overheated zone, inhibiting grain coarsening; (5) try to shorten the the reheat cracking sensitive temperature interval holding time in the heat treatment process; (6) the rational design of joint form to reduce the structure of the binding. Temper brittleness Harmful residual elements such as higher levels of P, S, and joints long the temperature range of 370 ~ 565 â„ƒ run, will lead to temper brittleness.