When welding some base materials and for some service conditions, preheating and/or post weld heat treatment may be a requirement. These types of thermal treatments are generally required in order to ensure suitable weld integrity and will typically prevent or remove undesirable characteristics in the completed weld. Any form of heat treatment is costly since it demands extra equipment, extra time, and extra handling. For these reasons, heat treatment should only be undertaken after careful consideration of the advantages it may offer. In certain cases heat treatment will be mandatory, as with heavy sections of low alloy steels, whereas in other cases, it will be a justifiable precaution against early failure in service. Preheating During Welding provides the following benefits:
- Reduces the levels of thermal stress.
- Provides compensation for high heat losses.
- Minimizes the rate of weld hardening.
- Reduced porosity in the weld.
- Reduced hydrogen cracking.
- Improved microstructure of heat affected zone