Influence of Local Weld Deformation on the Solidification Cracking Susceptibility of a Fully Austenitic Stainless Steel
For the evaluation of the solidification cracking behaviour of welded structures, the influence of the external boundary conditions needs to be considered, in addition to the metallurgical aspects. Against this background, the solidification crack formati
- PDF / 2,741,877 Bytes
- 19 Pages / 439.37 x 666.142 pts Page_size
- 87 Downloads / 286 Views
Abstract For the evaluation of the solidification cracking behaviour of welded structures, the influence of the external boundary conditions needs to be considered, in addition to the metallurgical aspects. Against this background, the solidification crack formation in a fully austenitic stainless steel under variation of external restraint was examined in this study. For this purpose, a newly developed hot cracking test (CTW test) was used for the first time, which allows application of a defined tensile load transverse to the welding direction during welding. In addition, the strains and strain rates could be determined with the help of a mechanicalelectrical measuring device in the near field of the weld pool. These values were examined both under free contraction and varied external load, i.e. under different constant cross head speeds. The Critical strain and strain rate required for the propagation of macroscopic surface cracks were determined. By means of high speed recording the authors succeeded in correlating strain and strain rate with the relative position of the weld pool. In addition, centreline crack initiation and growth were located.
Introduction A potential problem when welding austenitic steels is their distinct tendency to hot crack. This is due to the solidification behaviour of these materials. The range between liquidus and solidus temperature, i.e. the mushy zone, is the place of solidification crack formation. Here, liquid metal surrounds the already solidified material. Volume shrinkage during the liquid to solid phase transformation must be compensated for the remaining melt. Otherwise solidification cracks will occur [1, 2].
128
A. Kromm, Th. Kannengießer
For the evaluation of the hot cracking resistance of welded components, the influence of the external boundary conditions is to be considered in particular, apart from the metallurgical aspects [3]. According to Prokhorov [1] and Rappaz et al. [2], local strain rates in the vicinity of the weld pool can significantly affect hot crack formation and can thus be regarded as a suitable hot crack criterion. In addition, in the work of several authors [4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18], it was pointed out that a hot crack formation is usually connected with the occurrence of tensile stresses and strains in hot crack-sensitive areas. In the case of an external restraint, e.g. by the design specific shape of the component itself or by additional external load, these stresses/strains near the weld pool are affected and are directly associated with hot crack formation. Up to now a multiplicity of self restraint or externally loaded tests have been developed in order to evaluate the hot cracking susceptibility of materials. With the help of such tests mostly just material rankings can be provided. Transferability to component welds or quantification of hot cracking susceptibility can be achieved by determining, among other things, the hot crack critical strain and strain rate in the weld pool vicinity [9, 10]. In the presen
Data Loading...
