Regarding the question of whether re-evaluation is required after changing the flux
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Previously, the welding qualification for submerged arc welding in this unit was carried out using HJ431; now they want to switch to SJ101. But does changing the flux require conducting welding process qualification again? What is the basis for this? I hope everyone can help resolve this question. Additionally, the welding qualification for submerged arc welding is done using single-pass welding on one side only.
Changing the flux from HJ431 to SJ101 requires a new weld evaluation to be conducted. The flux used in submerged arc welding not only serves a protective role but also introduces a certain amount of alloying elements into the molten pool, affecting the mechanical properties and chemical composition of the joint. According to NB/T47015-2011, Clause P28 – Filling metal, item 4), the mixing ratio of the mixed flux should be adjusted; a re-evaluation is required when any important factor changes. As for the assessment of submerged arc welding, it has nothing to do with changing the flux; it only covers single-sided multi-pass welding (in single-sided multi-pass welding, the subsequent welds act as a post-heating effect on the previous welds, making it easier to achieve good mechanical properties compared to single-sided single-pass welding).
First, determine what the product welding standard is; analyze each case on its own. Taking 47014 as an example, there are no particularly detailed specifications in the standards, and the base material is also a factor involved; the documentation related to the dissemination of these standards mentions the impact of changes in flux on process evaluation. It can be considered in conjunction with one’s own products and the corresponding standards.
This post was last edited by proud on 2018-2-24 at 16:28. If the base material remains unchanged or is within the same group, and if the type of weld metal produced by flux SJ101 in combination with the wire is in the same category as that produced by flux HJ431 in combination with the wire, or if the type of weld metal produced by flux SJ101 is of a higher grade than that produced by flux HJ431, then no evaluation is required. According to NB/T47014, for example, in the following case: Q345R/16mm/symmetric joint/Welding by AW/SAW/F5A0-H10Mn2 (neutral flux HJ350)/Welding process evaluation that meets the requirements for 0°C impact testing – can this evaluation be applied to Q345R/16mm/symmetric joint/Welding by AW/SAW/F5A2-H10Mn2 (neutral flux SJ101)/-20°C impact testing, provided that the important factors and additional factors related to other general and specific welding evaluation criteria remain unchanged? Why? Answer: Applicable. Reason ①: Because neither the category number nor the group number of the base material has changed ； ②The welding materials F5A0-H10Mn2 (H10Mn2+HJ350) and F5A2-H10Mn2 (H10Mn2+SJ101) belong to the same category codes (FeMS-1-2, FeG-2); therefore, the category codes of these welding materials remain unchanged. Moreover, both HJ350 and SJ101 belong to neutral fluxes.
In other words, whether a re-evaluation of the flux is necessary depends on the type of weld metal produced by the combination of the flux and the wire. Unless the flux is neutral or active as specified in NB/T47014
It’s not necessary. The explanation on the 4th floor is very clear and well-supported.