TWI Industrial Member Report Summary 43/1977
By P H M Hart and T L Brooks
The effect of plate sulphur content (in the range 0.005 to 0.030%) on the risk of heat affected zone (HAZ) hydrogen cracking in C-Mn and C-Mn-Al steels has been investigated. Implant and CTS cracking tests have been used together with hydrogen diffusivity and HAZ hardenability studies.
The results have confirmed a definite increased risk of cracking with a reduction in plate sulphur content. However, it is shown that this is primarily due to an increased hardenability rather than a hydrogen trapping mechanism. The increased hardenability was observed to arise primarily from a reduction in the number of inclusions, which it is shown are capable of nucleating the start of transformation from austenite on cooling.
The CTS test results provide further evidence of an effect of carbon equivalent on critical hardness in fillet welds.