Numerical and experimental analysis of the effect of forced cooling on laser tube forming

In the laser forming process, a cooling time is usually considered between successive scans to increase the temperature gradient and subsequently the bending angle. In this process, cooling is usually performed at ambient temperature, which can lead to a high increase in operation time and costs. The cooling rate can lead to undesirable changes in the microstructure depending on the type of material. In this research, by introducing a simple method for applying forced cooling with water at different distances from the laser beam, its effects are investigated on the laser forming of AISI 304L tubes using the finite element method and experiments. The bending angles and microstructure of the tube after forming are analyzed. The results show that local cooling with water reduces the duration of a 1-degree bend by about 8 to 13 times compared to the cooling at ambient temperature. However, local cooling with a small offset from the beam increases the residual stress after the forming and consequently increases the probability of stress corrosion cracking. However, cooling at ambient temperature increases the likelihood of intergranular precipitation in this steel compared to local cooling. According to the results, local cooling at a certain distance from the laser beam with the least change in residual stress has high efficiencies in bending the tube and less chance of corrosion after the forming.