What Kinds of Cracks do Stainless Steel Welded Pipes Have When Welding?

  • By:Iris Liang
  • Date:2021/09/25

Stainless steel welded pipes may have many problems during the welding process, such as undercuts, pores, unfused, cracks, and so on. Then, what kind of cracks do you know when welding stainless steel welded pipes?

1. Hot crack

It refers to the welding crack generated by the metal in the weld and heat affected zone during the welding process to the high temperature range near the solidus line. Preventive measures: Strictly control the content of harmful impurities such as sulfur and phosphorus in stainless steel welded pipes and welding materials, reduce the sensitivity of hot cracks; adjust the chemical composition of weld metal, improve weld microstructure, refine grains, and improve plasticity. Reduce or disperse the degree of segregation; use alkaline welding materials to reduce the content of impurities in the weld and improve the degree of segregation.

2. Cold crack

It refers to the crack generated when the welded joint is cooled to a lower temperature, which is called cold crack. Preventive measures: Use low-hydrogen type welding materials, strictly follow the instructions in the instructions before use; remove the oil and moisture on the weldments before welding, reduce the hydrogen content in the weld; select reasonable welding process parameters and heat input to reduce The hardening tendency of the weld is immediately subjected to hydrogen elimination treatment after welding to allow hydrogen to escape from the welded joint;

3. Reheat crack

It refers to the crack generated after the stainless steel welded pipe is heated again in a certain temperature range (stress-relieving heat treatment or other heating process), which is called reheat crack.

Preventive measures: Under the premise of meeting the design requirements, select low-strength welding materials, so that the weld strength is lower than the base metal, the stress is loose in the weld, avoid cracks in the heat-affected zone; minimize welding residual stress and stress concentration; Control the welding heat input of the welded pipe, reasonably select the preheating and heat treatment temperature, and avoid the sensitive area as much as possible.

Stainless steel welded pipe should pay attention to the surrounding environment during the production process, and make timely adjustments and make records. In combination with the various conditions reflected by the manufacturers of stainless steel welded pipes, Hangao Tech (SEKO Machinery)s high-speed stainless steel welded pipe production line tube making machine uses SEKO's exclusive electromagnetic control system to control the deviated arc, which greatly improves the efficiency and quality of welding. At the same time, the eddy current flaw detector is used in combination to monitor the inner wall of the welded pipe at all times. The intelligent PLC system monitors and records the production data of the welded pipe in real time, so that the yield is greatly improved, thereby reducing the cost.                                        

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