Understanding cases regarding the relationship between thickness of 150, preheating temperature, and heat treatment
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This post was last edited by gn_1984 on 2021-12-9 at 14:15. As the title suggests: I am currently dealing with a device that uses compressed air as its medium, at room temperature. The cylinder is made of Q345R material with a plate thickness of 30 mm, while the head is also made of Q345R material with a plate thickness of 34 mm; the thickness of the straight edges after trimming is 30 mm. All the steel plates are hot-rolled, and according to GB/T150.4-2011, the equipment does not require overall stress-relief heat treatment. The question is: There are nozzles on the head. My understanding is that when welding the nozzles to the head, if the preheating temperature before welding is ≥80°C (a preheating temperature recommended by NB/T47015 and also by HG/T20582-2020), then the fillet welds between the nozzles and the head do not require local heat treatment. However, some believe that the preheating temperature recommended in clause 8.2.5 of GB/T150.4-201, which is ≥100°C, is required in order to exempt the fillet welds between the nozzles and the head from heat treatment. Dear Haiyou, regarding the materials, thickness, preheating temperature, and heat treatment specified in the first two columns of Table 5 in Clause 8.2 of GB/T150.4-2011, what is your understanding of these aspects? It would be best to have concrete evidence to support it. Thank you.
Follow the requirement that has the higher standard; besides, you’ve already preheated it and it only needs an additional 20 degrees. The thickness specified in Table GB150 is that which requires heat treatment; if the thickness is greater than 32 and preheating is not carried out, heat treatment is necessary ； For thicknesses greater than 32 and less than or equal to 38, heat treatment is not required if preheating to over 100 degrees is done; for thicknesses greater than 38, heat treatment is necessary regardless of whether preheating is applied. That’s how it should be understood; there’s no solid evidence!
Mainly, documents such as those related to welding processes specify ≥80°C. Will changing it back to 100°C cause any problems? I don’t understand welding, nor do I know exactly how much information should be filled in the welding record, so I find it very confusing.
This post was last edited by zjq1962 on 2021-12-10 at 14:26. If the preheating temperature is set to ≥80 degrees, the welding process meets the requirements of NB/T47015; however, the NB standard does not specify any requirements regarding heat treatment. GB150 eliminates the requirement for a preheating temperature during heat treatment.
That’s true too. Going at 150 is always the right choice.
For this preheating, 150 is the specified value. In standard 47014, welding preheating only needs to be at a level not lower than 50°C above the rated temperature; there is no upper limit specified. Therefore, your welding assessment is still valid, and this meets the requirements
For this preheating, 150 is the specified value. In standard 47014, welding preheating only needs to be at a level not lower than 50°C above the rated temperature; there is no upper limit specified. Therefore, your welding assessment is still valid, and this meets the requirements