Influence of Selective Laser Heat Treatment Pattern Position on Geometrical Variation

Abstract

Selective laser heat treatment allows local modification of material properties and can have a wide range of applications within the automotive industry. Enhanced formability and strength are possible to achieve. As the process involves selective heating, positioning of the heat treatment pattern in local areas is vital. Pattern positioning is often suggested based on the part design and forming aspects of the material to avoid failures during manufacturing. Along with improving material properties in desired local areas, the process also produces unwanted distortion in the material. Such effects on variation should be considered and minimized. In this paper, the heat treatment pattern is offset from its original position and its effect on geometrical variation is investigated. Boron steel blanks are selectively laser heat treated with a specific heat treatment pattern and then cold formed to the desired shape. Two heat treatment pattern dimensions are examined. Geometrical variation at the blank level and after cold forming, and springback after cold forming are observed. Results show that pattern offsetting increases the effect on geometrical variation. Therefore, correct positioning of the heat treatment pattern is important to minimize its effect on geometrical variation along with enhancement in the material properties. Knowledge from this study will contribute to various stages of the geometry assurance process.

Design and Optimization of the Local Laser Treatment to Improve the Formability of Age Hardenable Aluminium Alloys

“…The variation of the mechanical properties was achieved applying a laser treatment, able to quickly heat and cool the material in a narrow area whose shape can be easily reconfigured according to the geometry of the component or the heating strategy. By changing the heating treatment pattern, the shape accuracy can be affected and both the root mean square (RMS) deviation and the springback reduced up to about 27% [21]. Alternative solutions offered by conduction or inductive heating devices are more rigid and invasive, being created according to a specific geometry and acting in areas (for example 80 mm square conductive plates in the work of Kahrimanidis et al [22]) larger than a laser spot (usually in the range 10-20 mm [23]).…”