Solution annealing of stainless steel
When welding metals undesirable structures can be created, which have a negative result on the welded material
The most well-known effect is the formation of chromium carbides with some types of stainless steel. Chromium carbides develop in the critical temperature range of about 500 to 900 degrees. In this range carbons are extracted from the structure matrix. As a result, the material loses its homogeneity and reduces corrosion resistance because of so-called precipitates. These can be dissolved by annealing at extremely high temperatures. Hence the term solution annealing.
In case of solution annealing, temperatures lie between 1,100°C to 1,200°C. By force cooling the workpiece adequately using forced air or water quenching, the secretion of chromium carbides in the critical range is being prevented.
Each material has its own specific characteristics. The so-called Time Temperature Transformation Diagram or CCT diagram shows the maximum required critical temperature range after the solution annealing process.
Due to annealing at high temperatures, an oxide layer is being formed on the workpiece. It is therefore often customary to bead blast or pickle workpieces which have been treated using solution annealing.