TWI Industrial Member Report Summary 578/1996
A J Kinsey
Weld tests confirm that TWI nomograms can be used to derive weld procedures to avoid heat affected zone (HAZ) hydrogen cracking in C-Mn steels with tubular cored wires.
Background
Guidelines which enable a fabricator to select safe, but not over-conservative, preheat levels to avoid hydrogen cracking for given welding parameters and consumable hydrogen levels have been established for some time, most notably in the form of the TWI nomogram, or the similar guidelines incorporated in BS 5135 (and likely to be included in prEN 1011). However, much of the database on which these guidelines were developed was generated using the manual metal arc (MMA) process. Very little information exists for tubular cored wires, which give enhanced deposition rates, but interest is increasing.
In view of the growing use of this process, and to provide increased confidence to users, it is considered important to consolidate existing information by generating further data for various types of tubular cored wire. Practical experience to date has been generally satisfactory, but recent work at TWI indicated that the behaviour of such wires may be different to MMA electrodes, particularly with respect to the root concentration associated with fillet welds.
Objective
- To demonstrate the extent to which current guidelines for avoiding HAZ hydrogen cracking can be applied to tubular cored wires.