1. limit the steel and welding material, easy to produce bias elements and harmful impurities content, especially the content of S, P, C, because they not only form low melting point eutectic, but also promote bias. c ≤ 0.10% hot crack sensitivity can be greatly reduced. Chemical analysis of the material if necessary, low times the test (such as sulfur seal, etc.).
2. Adjust the chemical composition of the weld metal, improve the organization, refine the grain, improve plasticity, change the morphology and distribution of harmful impurities, and reduce segregation, such as the use of austenite plus less than 6% of the ferrite duplex organization.
3. Improve the alkalinity of the electrode and flux to reduce the content of impurities in the weld and improve the degree of segregation.
4. Select a reasonable bevel form, weld forming factor ψ = b / h> 1, avoid narrow and deep "pear-shaped" weld, (excessive welding current will also form a "pear-shaped" weld), to prevent columnar crystals in the center of the weld channel convergence, the formation of central segregation brittle fracture The use of multi-layer multi-pass welding, disrupting the gathering of segregation.
5. Using a smaller (appropriate) welding line energy, for austenitic (nickel-based) stainless steel should try to use a small welding line energy (no preheat, no swing or less swing, fast welding, small current), strict control of the interlayer temperature to shorten the residence time of the weld metal in the high-temperature zone.
6. pay attention to the protection of the closing arc, the closing arc should be slow and fill the arc pit to prevent the arc pit bias generated by thermal cracking.
7. try to avoid multiple reworking to prevent lattice defects from gathering to produce polygonal thermal cracking.
8. take measures to minimize joint stress, avoid stress concentration, and reduce the stiffness near the weld, properly arrange the welding sequence, and try to make most of the weld under a smaller stiffness, so that it has room for shrinkage.
