Issues related to the heat-affected zone of welds
Thread Content
For the boiler we have designed, the minimum spacing between the openings in the header is 81, and the diameter of the convection tubes is 51 mm. Some experts have asked whether the heat-affected zones of the welds on two adjacent tubes overlap; please discuss this. If the design cannot be changed, how can this be controlled?
They do not overlap; the net dimension of the two tubes is 81–51 = 30 mm. After deducting 4 mm for the welds, this becomes 30–4–4 = 22 mm. According to section 7.3.5 of \"GB T16508-1996 Calculation of Strength of Pressured Components in Shell and Tube Boilers\", the net distance between the weld edges must be at least 6 mm. This requirement does not apply to water tube boilers, but it can still serve as a reference! As long as the strength is sufficient, there’s no need to worry about the heat-affected zone!
It depends on the welding method used. I came across this information in a book, but the figures aren’t entirely accurate; it’s for reference only: the HAZ for manual arc welding is about 2 mm, while it’s around 27 mm for resistance welding. Everyone is welcome to point out any mistakes
Under normal circumstances, the heat-affected zone at the edge of a single weld is usually only 2 or 3 mm. In the situation described by the poster, the heat-affected zones will not overlap, unless a groove is created and the angle is very large.