I'm having trouble getting my head around the provisions in AS/NZS1554.1 Structural Welding Code for preheat - wondering if somebody could shed some light?

If you go to clause 5.3 there is a method using graphs for determining the min preheat required. In section 5.4 - Weather Conditions, there is a further preheat requirement in that no preheat temp is to be below 0 Deg C unless the WPS is qualified IAW section 4. Looking at section 4 all WPS's need to be qualified IAW section 4 - even if only a written PQR & a macro examination is required to do so.

If you go to the table of essential variables - 4.11 (A)(m) it allows a 20 Deg C reduction is the preheat temp on the WPS.

Does this not then permit a -20 Deg C preheat for any WPS for which the graphs in 5.3 show a 0 Deg C preheat....?

Is this not a loop-hole/provision in the standard that needs to be addressed...?

Also the inter-run temp is not allowed to drop more than 20 DegC from that in the PQR - seems bizarre doesn't it? Normally inter-run temp is a maximum and preheat is a minimum, so long as your preheat is maintained and you do not go above the max permitted inter-run temp then who cares how much the inter-run temp drops, in fact it can be an advantage not to approach the max permitted inter-run temp to help control grain growth and maintain fracture toughness....??


Read the full thread at metalworkforums.com...