Varestraint test: soldification cracks during welding occur in the brittleness temperature range (BTR) if a critical strain ε is exceeded there (Division 9.4)
Source: BAM
The use of high-strength steels is a key element in resource efficiency and the use of renewable energies - for example in the installation of wind turbines. Even during welding, such materials are subjected to high stresses in lightweight applications. Various test methods are available for assessing the susceptibility of materials to so called solidification cracking during welding. In the widely used Varestraint test a specimen is subjected to a bending load during welding. The resulting crack length is selected as a criterion for the cracking susceptibility. Unfortunately, the crack length does not characterize the material behavior alone but depends to varying degrees on the individual test parameters used, which makes the interpretation of the results difficult. In addition, the crack length is not comparable under different test conditions. To overcome these disadvantages, we have developed a novel evaluation methodology that decouples the machine influence from the material behavior. The measured crack length is related to the maximum possible value specified by welding speed and deformation time. This relative crack length is calculated numerically, considering the orientation of the cracks. Experiments on two high-alloy martensitic welding consumables show that, in contrast to the conventional evaluation, a comparison of different welding parameters becomes possible. Furthermore, the strain rate proved to be a suitable crack criterion in agreement with prominent solidification cracking theories.
Assessment of the Solidification Cracking Susceptibility of Welding Consumables in the Varestraint Test by Means of an Extended Evaluation Methodology
Arne Kromm, Maximilian Thomas, Thomas Kannengießer, J. Gibmeier, F. Vollert
published in Advanced Engineering, Page 2101650
BAM Component Safety und Weld Mechanics