Simulated post-weld heat treatment
Thread Content
I would like to ask fellow sailors what simulated post-weld heat treatment means – does it refer to welding a specimen and then performing heat treatment on it? So, is this simulated post-weld heat treatment carried out separately on this specimen before the equipment is manufactured, or is it done after the equipment is ready and as part of the heat treatment process using the equipment itself? Recently, while working on a piece of equipment, an expert suggested that simulated heat treatment be conducted; I haven’t dealt with this before, so I would appreciate any guidance you can provide
Hehe, the several fatigue testing devices I’ve worked with all came equipped with test plates for simulating post-weld heat treatment; these were included either with the containers or with the end caps. But in order to study the material properties of the materials after welding and heat treatment, such tests can also be carried out in advance – it depends on what the experts suggest
The materials used to manufacture containers may undergo multiple processes equivalent to heat treatment during the manufacturing process, such as thermoforming. Simulated post-weld heat treatment is carried out to verify whether the various mechanical properties of the material meet the required standards after undergoing these heat treatment processes. Therefore, simulated post-weld heat treatment should be carried out before container manufacturing.
It is mainly applied to relatively thick carbon steel plates; test plates are used to simulate the thermal processes of the materials, and the simulation heat treatment time is generally determined based on the number of thermal cycles in the actual manufacturing process. Mechanical property analysis is carried out after the simulation heat treatment is completed. The main thermal cycle processes to be considered include: hot forming, welding, post-welding heat treatment, and heat treatment after on-site repairs.
1# For process equipment, simulated heat treatment should be carried out in advance; otherwise it’s not necessary
Simulated heat treatment is generally applied to new materials or materials being used for the first time.
4# is absolutely right. If necessary, for example with some particularly important equipment, heat treatment for repair during use may also need to be considered. Logically, we need to complete the production of the prototype samples and verify that they meet the required standards before using the materials from the same batch to manufacture the equipment; this ensures that the material properties will also be satisfactory once the equipment is completed. If the project timeline is tight, it is possible to carry out testing while working on the equipment as well; the difference is that there is a certain level of risk involved – if the equipment is half-finished and it turns out that the samples are not up to standard, that would be problematic. This is usually only possible when one is quite confident about the material.
What I understand by simulated post-weld heat treatment is this: for example, in the case of end caps, when welding metal plates, a test piece is welded onto those plates, and then it undergoes heat treatment along with the equipment. This is because for pressure vessels that require heat treatment, the test pieces should generally be heat-treated together with the pressure vessels; otherwise, measures must be taken to ensure that the test pieces are heat-treated using the same process as the pressure vessels.
Because after welding, steel usually requires slow cooling of the weld, which is beneficial for relieving stress and removing hydrogen from the steel； Simulated post-weld heat treatment is a process that simulates the stress-relief step after welding steel; by conducting tests on the steel properties after this simulated treatment, it is possible to assess the performance of the welds in the steel.
Broadly defined, simulated heat treatment is a comprehensive simulation of actual heat treatment, encompassing a combination of various heat treatment processes such as IRC, PWHT, and multiple rework cycles. For ultra-thick plates, the conditions for PWHT are closely related to the performance requirements of the material.
Simulated heat treatment is generally used during weld evaluation, on its own. Evaluate the performance of the weld assessment test pieces. The test plate baked along with the product is used to evaluate its performance.