Regarding heat treatment: welding between Q345R, 30mm, 15CrMoR, and 10mm.
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Question 1: Is heat treatment required? 2. If so, but what if the heat treatment temperature for 15CrMoR is higher than that of Q345R?
1. Heat treatment is required. 2. It is necessary to carry out heat treatment at the temperature appropriate for 15CrMoR.
Then isn’t the Q345R material affected?
The recommended temperature for post-weld heat treatment of 15CrMoR according to JB/T4709 is ≥600. However, welding manuals state that CrMo steel has a tendency to develop reheat cracks; therefore, during post-weld heat treatment, the temperature range sensitive to reheat cracks, namely 500–700, should be avoided； The heat treatment annealing temperature for Q345R is 620±20°C; therefore, an annealing temperature of 600–650°C is chosen. The holding time is 1 hour for every 25 mm of the effective thickness of the workpiece, with a minimum holding time of 3 hours.
In other words, it means increasing the heat treatment time according to the heating treatment temperature for Q345R – that’s how it can be understood, right? .
Obviously, heat treatment should be carried out at the higher temperature of the two
Treat it according to strict and high requirements. . . If necessary.
4.4.5 When welding steel of different grades together, the post-weld heat treatment temperature shall be set according to the grade with the higher post-weld heat treatment temperature, provided that this temperature does not exceed the lower transformation point Ac1 of either grade. Excerpted from: GB/T 30583-2014 Code for Post-Weld Heat Treatment of Pressure Equipment
For the top floor 8#, that makes sense. :handshake
The 8th floor is correct; that’s what the standards specify. However, it should be taken into account that the temperature for 15CrMoR is generally above 650°C, which causes a significant decrease in the strength of Q345R. Therefore, this factor must be considered when purchasing Q345R plates; otherwise, low strength can lead to problems.
It is heat treatment at the highest temperature permitted for Q345R; by extending the heat treatment time, the same effects as those achieved with 15CrMoR can be obtained! (What the regular teacher says in class)