Influence of the cooling time on the mechanical properties of welded HSS‐joints

Abstract

The influence of the cooling time t 8/5 has been examined as part of the ongoing AiF-FOSTA P1020 research project for the development of a new design approach for welded joints on highstrength steels. Four thermomechanically rolled and quenched steel grades were investigated. The temperature-time course of a MAG welding process was thermo-physically simulated in a quenching and deformation dilatometer to evaluate the material behaviour. Subsequently, the influence of the cooling time on the mechanical properties of welds was examined using a flat tensile test specimen with a centric hole. The results of the examinations form the scientific basis for a significant improvement of the current execution rules for welded joints between high-strength steels taking into account mismatching of base material and filler metal.

A new design model for welded joints

“…The authors give a detailed description of the specimen and selected tests in [1][2][3][4]. In the series of small scale tests, the influences of the base material and filler metal, the cooling time t 8/5, between 800°C and 500°C, in the interval of 5 to 20 seconds, the number of layers and the opening angle were investigated.…”

“…At least 4 tests were carried out for each parameter combination, the weld thicknesses were between 3 mm (lap joints) and 20 mm (fully penetrated butt joints). The properties of the investigated base materials and filler metals are documented in [1][2][3][4] and the detailed test program for the joints in [1].…”

“…This was done to calibrate the weld construction factor a w , which takes into account the influence of the type of joint on the load-bearing capacity. In the following article, after a short summary of the current state of research, the design model, and the results from the parameter studies on flat tensile tests are described in more detail in [2][3][4]. Subsequently, the test program on welded joints and the calibration of the weld construction factor a w are presented.…”

Influence of the execution parameters on the welds of high‐strength steels

“…The peak temperature Tmax and the cooling time t8/5 were specified in the temperature-time curve. There were examined five peak temperatures in the range from 600 to 1350 °C which represent the specific areas of the HAZ and seven cooling times t8/5 from 1.5 to 25 s. The authors presented the test results with regard to the influence of the heat input on the tensile strength of the base metals in (3). Based on these results, multiple regression models were developed to derive a functional relationship between the mechanical properties of the heat-affected zone, the peak temperature Tmax and the cooling time t8/5 (cf.…”

“…The peak temperature Tmax and the cooling time t8/5 were specified in the temperature-time curve. There were examined five peak temperatures in the range from 600 to 1350 °C which represent the specific areas of the HAZ and seven cooling times t8/5 from 1.5 to 25 s. The authors presented the test results with regard to the influence of the heat input on the tensile strength of the base metals in (3).…”