What is Stress Relief Cracking in Welding?
Stress relief cracking (SRC) is a type of cracking that can occur in the weld metal or heat-affected zone during post-weld heat treatment or high-temperature service. The main cause of SRC is the presence of residual stresses in the material, which can lead to crack initiation and propagation.
There are two main types of stress relief cracking: thermal fatigue cracking and creep-fatigue cracking. Thermal fatigue cracking typically occurs at lower temperatures (<400°C) and is caused by the repeated heating and cooling cycles of the material during welding. Creep-fatigue cracking typically occurs at higher temperatures (>600°C) and is caused by the combination of high temperatures and mechanical stresses acting on the material.
To avoid stress relief cracking, it is important to carefully control the welding process and heat treatment parameters. Additionally, the use of low-alloy steels and proper weld design can help to minimize the risk of stress relief cracking.
What is stress relief in steel?
Stress relief is a heat treatment process that is used to remove residual stresses from a material. The process involves heating the material to a specific temperature and then allowing it to cool slowly. This helps to relieve the stresses that can lead to cracking during high-temperature service or post-weld heat treatment.
There are two main types of stress relief: annealing and normalizing. Annealing is typically used for low-carbon steels and involves heating the material up to its critical temperature before cooling it slowly in a furnace. Normalizing is typically used for high-carbon steels and involves heating the material up to 50°C above its critical temperature before cooling it in the air.
Both annealing and normalizing help to reduce the risk of stress relief cracking by relieving the residual stresses in the material. Additionally, they can also improve the toughness and ductility of the material, making it less susceptible to cracking.
How do you reduce welding stresses to prevent cracking?
There are a few ways to reduce welding stresses to prevent cracking:
- Use low-carbon steels: Low-carbon steels have a lower risk of stress relief cracking than high-carbon steels.
- Control the welding process: Carefully controlling the welding process can help to minimize the residual stresses in the material.
- Use proper weld design: Proper weld design can help to distribute the stresses more evenly, which can reduce the risk of cracking.
- Heat treat properly: Proper heat treatment is essential for relieving residual stresses in the material.
Corrosionpedia – What is a Stress-Relief Cracking? – Definition from Corrosionpedia
The Mechanism of Stress-Relief Cracking in a Ferritic Alloy Steel
Mechanisms of stress relief cracking in a ferritic steel – ScienceDirect
Stress Relaxation Cracking (SRC), a Dangerous Failure in Petrochemical Reformers