Investigation on Laser Bending of Duplex-2205 Sheet by Applying Forced Cooling

Abstract

This research aimed to enhance the capabilities of laser bending by exploring forced cooling and investigating other performance parameters of the bent specimen. The study focused on the feasibility of laser bending of high-strength dual-phase stainless steel (duplex-2205) and the post-bending effects on material properties. A finite element based 3D numerical model was developed and experimentally validated for laser bending. Single-scan laser bending was simulated and experimented under natural and forced cooling conditions to analyze the effects of various process parameters. The feasibility of forced cooling was studied using an aluminium alloy. An experimental setup with real-time bend angle and temperature measurement capability was established. Experimental studies were conducted for both single and multi-scan laser bending under different cooling conditions, analyzing the effects of process parameters on bend angles and material properties. In the pilot study, a 3D numerical model incorporating temperature-dependent material and heat loss by convection and radiation was developed. Experimental validation of the model showed good agreement between numerical and experimental results. Numerical simulations of single-scan laser bending revealed the bending mechanism and the influence of line energy, laser power, and scanning speed on bend angle and edge effects. The mechanical properties of the bent specimens were compared to the base material, showing increased hardness and reduced ductility. Numerical simulations of single-scan laser bending with forced cooling demonstrated significantly increased bend angles at high line energy parameters. A robust experimental setup was developed, and feasibility studies with an aluminium alloy showed reduced coating degradation and increased bend angles with forced cooling. Forced cooling assisted single-scan laser bending experiments on duplex-2205 revealed reduced maximum temperature and increased cooling rates with forced cooling. The application of forced cooling led to a significant increment (35.2%) in the bend angle on the bottom surface of the sheet. The effectiveness of forced cooling was influenced by process parameters, with lower scanning speed, intermediate beam diameter, and higher laser power being more effective. The forced cooling assisted laser-bent specimens exhibited improved hardness and tensile strength compared to naturally cooled specimens. The phase distribution showed variations at the upper surface in the scanning region, while the lower surface resembled the base material. In the forced cooling assisted multi-scan laser bending study at high line energy, experiments were conducted under various process conditions. The forced cooling significantly enhanced bend angles, with a maximum increment of 427% observed. The effect of process parameters exhibited different trends compared to natural cooling. The bend angle per scan increased with the number of scans in forced cooling, reaching a maximum bend angle per scan that was around 300% higher than that achieved in natural cooling. The microstructural analysis revealed the influence of cooling on the ratio of ferrite and austenite phases, resulting in increased hardness and tensile strength but reduced ductility. Corrosion behavior analysis indicated a decreased pitting potential in forced-cooled samples. For forced cooling assisted multi-scan laser bending at low line energy, experiments were conducted under different cooling conditions. The temperature distribution along the scanning line showed a decrease in average maximum temperature with an increase in laser power. Forced cooling resulted in a reduced heat-affected zone compared to natural cooling. The bend angle achieved in forced cooling was lower than in natural cooling for low line energy parameters but increased with laser power and line energy. The waiting time between successive scans and the number of scans required to achieve the desired bend angle was reduced in forced cooling conditions. The bent specimens exhibited improved tensile strength and hardness, with the forced cooling condition demonstrating the highest values. The microstructure showed increased ferrite content and a more refined grain structure in the forced cooling condition. This research significantly contributes to advancing laser bending technology by improving bend angles and understanding the effects of forced cooling on material properties. The findings provide valuable insights for improving manufacturing productivity and have the potential to optimize laser bending processes in various industries such as microelectronics, aerospace, and marine, where high deformation with good precision is a prime requirement.