Regarding welder qualifications
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Why is it that when the welding process factor in a welder’s qualification changes from single-pass welding to multi-pass welding, re-examination is required, whereas no re-examination is needed when changing from multi-pass welding to single-pass welding?
Those with high technical requirements have already passed; is it still necessary to test those with lower requirements?
This post was last edited by cxd11888 on 2015-9-24 at 16:48. So why do you think the technical requirements for multi-pass welding are high? Where can I find such statements? Is it still specified in A4.3.9 on page P26 of TSG Z6002?
Is multi-pass welding accompanied by interpass grinding and pass interval grinding?
The requirements for multi-pass welding should be higher than those for single-pass welding.
According to TSG Z6002A4.3.9, multi-pass welding can be used in place of single-pass welding; there must be a reason for such a regulation. I want to know why multi-pass welding can substitute for single-pass welding !
The number of weld joints in multi-pass welding is greater than that in single-pass welding; the temperature between the layers in multi-pass welding is higher than in single-pass welding, and the weld groove is also slightly wider in multi-pass welding. The plate thickness in multi-pass welding is generally greater than that in single-pass welding. Therefore, the likelihood of defects such as lack of penetration, failure to fuse, pores, and slag inclusions is also higher compared to single-pass welding.
The number of weld joints in multi-pass welding is greater than that in single-pass welding; the temperature between the layers in multi-pass welding is higher than in single-pass welding, and the weld groove is also slightly wider in multi-pass welding. The plate thickness in multi-pass welding is generally greater than that in single-pass welding. Therefore, the likelihood of defects such as lack of penetration, failure to fuse, pores, and slag inclusions is also higher compared to single-pass welding.
“The interpass temperature for multiple weld passes is higher than that for a single pass.” This factor affects the mechanical properties of the welded joint; does it also affect the welder’s skills? Other explanations are fairly plausible.
High interlayer temperature leads to high welding stress, which in turn results in greater deformation; this is the first point； The second issue is the high residual welding stress, which can lead to stress corrosion over time. This is a negative consequence of the welder’s skills; when welding stainless steel, it is explicitly required that the interlayer temperature not exceed 100°. In such cases, some plate thicknesses cannot be welded in just one pass, and two passes are necessary. These are also some of the basic requirements for welders.