IIW History 1948-1958

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A report on this question is to be prepared, in close collaboration with Com– mission V, by the first working group, to which a member of that Commission has been appointed. The second working group is to prepare a report on post-heat treatment. In the opinion of a large number of members, it is not necessary to lay down post-heat treatment for the purpose of stress relieving where there is no risk of brittle fracture. Post-heat treatment is then only mandatory if it contributes to improving the material, for example, by reducing the hardness of the heat– affected zones or of excessively hard welds. It i clear that, if these views are accepted, the majority of pressure vessels and boilers in carbon steel need not be post-heat treated for neither the welds nor the heat-affected zones are likely to be excessively hard. This question is of great importance from the economic point of view because, at present, many authorities require full stress relief for carbon steel pressure vessels as well as for others. It is important that this matter should be investigated so that, in the future, it may be possible to draw up precise rules sho\Ying where heat treatment after welding is necessary to improve the properties of the metal and \vhere such treatment may by omitted. The weld efficiency factor must, nevertheless, remain at roo% for, whether or not post-heat treatment is required, it has in any case no connexion with the quality of the weld. This investigation on post heat treatment is to be made in close liaison with Commission IX (Behaviour of Metals subjected to Welding) and Commission X (Residual Stresses and Stress Relieving) of the IIW. It is clear that there is no risk of Commission :S:I soon completing its pro– gramme of work. Many other points, s uch as the calcula tion of wekls on nozzles, will later be studied \vhen the problems at present on the programme have been dealt with.