Difference between pre weld heat treatment and preheating
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When welding some base materials and for some service conditions, preheating and/or postweld 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.
There are a number of reasons for the incorporation of these thermal treatments within the welding procedure, and we will consider some of the most common.
Preheating
Preheat, as defined within the AWS Standard Welding Terms and Definition, is “the heat applied to the base metal or substrate to attain and maintain preheat temperature”. The preheat temperature is defined by the same document as “the temperature of the base metal in the volume surrounding the point of welding immediately before welding is started. In a multipass weld, it is also the temperature immediately before the second and subsequent passes are started” (Interpass Temperature
When welding some base materials and for some service conditions, preheating and/or postweld 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.
There are a number of reasons for the incorporation of these thermal treatments within the welding procedure, and we will consider some of the most common.
Preheating
Preheat, as defined within the AWS Standard Welding Terms and Definition, is “the heat applied to the base metal or substrate to attain and maintain preheat temperature”. The preheat temperature is defined by the same document as “the temperature of the base metal in the volume surrounding the point of welding immediately before welding is started. In a multipass weld, it is also the temperature immediately before the second and subsequent passes are started” (Interpass Temperature
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