When working with a highly complex geometry or specialized materials, a pre weld heat treatment can help reduce internal stresses and make the final product more ductile. Pre weld heat treatments a process that involves heating and cooling metals to produce changes in their physical and sometimes chemical properties.
What is the main benefit of pre heat treatment?
Preheat treatment is a necessary step in many welding applications, especially when the welded material will be used in high-pressure or vibration-prone applications. By reducing the temperature gradient between the arc and the base material, the process can help prevent thermal cracking by slowing the rate of weld puddle/pool cooling and driving out hydrogen, two major factors that can lead to failures in the weld zone and overall weld integrity.
In addition, a pre-heat can also be beneficial for difficult to weld materials by lowering the melting point of the base material and helping achieve better penetration on thick sections. It can also be helpful in avoiding weld failures due to changes in the microstructure of the steel (known as embrittlement) caused by rapid cooling which can result in brittle, non-ductile structures.
A proper preheat can be accomplished through various methods such as the use of electric welding preheaters, which are rugged ceramic mat heaters that are carefully controlled by a power console to regulate and monitor the preheat temperature. Welding codes, based on metallurgical science and the physical characteristics of the metals in question, establish minimum preheat temperatures and soak times for specific welding processes and materials.