Hot Crack Tendency of 09CuPCrNi-A Steel

Hot cracks are generated at high welding temperatures. When crystallized, the eutectic with low melting point forms a liquid film, which will lead to cracking under the action of stress, hot cracks are mainly closely related to S, Ni, Mn, etc.

316L and 09CuPCrNi-A steel have a certain tendency of thermal cracking when welding, the main reasons are:
①The thermal conductivity of 316L stainless steel is smaller than that of 09CuPCrNi-A steel, but the coefficient of linear expansion is much larger, so greater stress will be generated in the joint after welding;

② 316L contains more Cr, Ni and other elements, and 09CuPCrNi-A contains higher S and P contents. 316L is easy to form low melting point eutectic with S and P near the seam. For example, the melting point of Ni-Ni3S2 is 644°C, and the melting point of Ni-Ni3P is 880°C. The existence of these eutectics with low melting point can promote the formation of hot cracks. Since 09CuPCrNi-A steel contains 0.093% P element, it is easy to weld with Ni forms a eutectic with a low melting point, leading to generation of hot cracks.

When 09CuPCrNi-A steel welding, the use of small welding heat input, multi-layer welding and reasonable welding sequence will help reduce the tendency of thermal cracks.