Selection of alkaline low-hydrogen electrodes and fluxes to reduce the content of hydrogen diffusion in the weld metal; improve the selection of base material and welding material matching; in the technical conditions permitting, the use of good toughness of the material (such as a lower strength level of welding material), or the implementation of the "soft" cover to reduce the residual stress on the surface; if necessary, the base material and welding material before manufacturing Chemical analysis, mechanical properties and weldability, crack susceptibility test of the base material and weld material before manufacturing, if necessary.
2. Strictly in accordance with the correct test process specifications for welding operations
Mainly including: strictly according to the specifications for welding rod drying; choosing the appropriate welding specification and line energy, reasonable current, voltage, welding speed, interlayer temperature and the correct welding sequence; spot welding inspection process; good double-sided welding root cleaning, etc.; carefully clean the bevel and wire, remove oil, rust and moisture.
3. Choose a reasonable welding structure to avoid excessive constraint stress; correct bevel form and welding sequence; reduce the peak residual stress of welding.
4. Preheating before welding, slow cooling after welding, controlling the interlayer temperature and post-welding heat treatment, is poor weldability of high-strength steel and unavoidable forms of high constraint structure, to prevent cold cracking effective method. Preheating and slow cooling can slow down the cooling rate (extended △ t 800 ~ 500 ℃ residence time), improve the organizational state of the joint, reduce the tendency to harden, and reduce tissue stress; post-weld heat treatment can eliminate residual stresses in welding, reduce the content of diffusion hydrogen in the weld. In most cases, the stress relief heat treatment should be carried out immediately after welding.
5. Hammering immediately after welding, so that the residual stress is dispersed to avoid causing high-stress areas, is one of the effective methods to prevent cold cracking when local patch welding.
6. In the root of the weld and the stress is a more concentrated weld surface, (the heat-affected zone is subject to lower constraint stress), using a lower strength level of the electrode, often in the high degree of constraint to achieve good results.
7. The use of inert gas-shielded welding, the maximum control of the weld hydrogen content, reduces cold cracking sensitivity, so TIG, MIG welding should be vigorously promoted.
