Preheat

The heating of the parts of a structure to be welded before welding is started to minimize thermal shock and of slowing the cooling rate.

Related Links

Preheat | Definition of Preheat
preheat – Dictionary Definition : Vocabulary.com
Preheat | Definition of Preheat at Dictionary.com
What is Preheat?
The Grammarphobia Blog: Is preheating the same as heating?