Short-time heat treatment of press hardened steel for laser assisted clinching

Abstract

Clinching of high strength steels is currently difficult due to their relative low ductility. Hence a new method has been developed to clinch these steel grades. This could be achieved by heating the sheets locally at the joint by a laser during the clinching process. The short-time tempering behaviour of the press hardened steel 22MnB5 has been investigated by dilatometry respectively calorimetry experiments. Different stages of the tempering process have been identified depending on heating rates up to 1000 K s−1. Characteristic tempering reactions were shifted to higher temperatures with increasing heating rate. Based on these results, suitable short-time heat treatment parameters have been selected and transferred to the clinching process. Thereby the press hardened steel 22MnB5 has been successfully clinched with laser assistance for the very first time. The laser assisted clinched joint has been characterised by metallographic analysis and hardness testing. It could be shown, that in the clinching joint only a slight strength loss occurs due to the introduced laser heat.

Review of the Quench Sensitivity of Aluminium Alloys: Analysis of the Kinetics and Nature of Quench-Induced Precipitation

“…The methodology for heating and cooling DSC described in Section 2 has been applied to analyse a range of solid-solid phase transformations in other metallic alloy systems. For instance, quench-induced precipitation in magnesium alloys [123] and the tempering of steels have been analysed [221,222]. Recently, the DSC method for the analysis of solid-solid phase transformation kinetics was successfully adapted for use with high-temperature alloys up to 1100 • C [122].…”

Clinching for sheet materials

“…High-strength steels can be clinched if the ductility at the site of the joint can be improved by localized heating. Reich et al [ 212 ] proposed a laser assisted clinching method to solve this problem. With this new method, the overlap section is heated locally by a laser during the clinching process.…”

Enhancement of the tensile shear strength for joining low-ductility aluminium to high-strength steel by using electrically-assisted mechanical clinching (EAMC)

“…For this purpose, many studies utilized various pre-heating methods for MC of low-ductility materials, for example, electrical resistance, electric furnace, induction, convection, flame heating, laser, and friction assisted clinching. [13][14][15][16][17][18][19][20][21][22] These heating-assisted methods were facing challenges involving high energy consumption, thermal distortions, and high initial investment.…”