Everyone is discussing how to heat-treat the following composite plate heads: Q345R+316L

Heat treatment of composite panels is still a subject of debate; generally, the heat treatment process is chosen based on the base material and its thickness, while also taking into account the impact of heat treatment on the composite layer~

Heat treatment of composite panels is a bit troublesome! The expansion coefficients of base metals and layered metals are different! This will cause major problems for heat treatment!

Please clarify your question: what is the size and thickness of your end caps, and what is the method of forming them – hot forming or cold forming? What is the purpose of performing heat treatment? Without this information, such a question is meaningless.

The base layer must meet the specifications, while also taking into account the corrosion resistance of the composite layer.

It is quite challenging to determine the appropriate heat treatment method for such composite plate materials. If there are no requirements regarding intergranular corrosion, then treatment can be carried out as per the methods used for carbon steel; however, if such requirements do exist, then heat treatment for stainless steel usually involves either stabilization or solid solution treatment, methods that we generally try to avoid. It mainly depends on the requirements at the grassroots level.

Personally, I think it is possible to use a method of performing surface heat treatment followed by welding a corrosion-resistant layer; it is difficult to handle composite plates after they have been formed and then heat-treated

This is indeed rather troublesome, but heat treatment should still be carried out according to the substrate, trying only to minimize the time spent in the sensitization temperature range during the process

For the base material Q345R steel plate, 1) it is in a hot-rolled state, and heat treatment may not be required after the head is hot-formed； 2) The processing condition is normalizing; a) the finishing temperature for hot forming shall be no lower than the minimum normalizing temperature of the material, and no heat treatment is required after the head is hot-formed. When ordering steel plates, equipment manufacturers should request the steel mill to provide the normalizing temperature, which should then be supplied to the head manufacturing plant. b) It cannot be guaranteed that the finishing temperature of heat forming will be at or above the minimum normalizing temperature of the material; or when the design does not permit the use of heat forming as a substitute for normalizing, normalizing must be carried out after heat forming, and a report on the mechanical properties after normalizing must be provided. For the duplex material 316L, assuming that the design does not require evaluation of the mechanical properties of 316L: 1) when no resistance to intergranular corrosion is required, follow the heat treatment requirements of the base material. 2) When intergranular corrosion resistance is required, it is best not to perform heat treatment after the head’s hot forming; however, if it is normalized together with the base material, it will not become sensitized and its corrosion resistance will not be reduced. The reason is: a) The reason for the reduced intergranular corrosion resistance of austenitic stainless steels is their sensitization during hot processing through the sensitization temperature range. The reason for sensitization is the precipitation of Cr23C6 at the grain boundaries, which causes chromium depletion and thus renders the grain boundaries non-passive. Sensitization requires excess carbon as well as temperature and time. b) The carbon content of 316L is below 0.03%, and the sensitization time at 600°C is more than 8 hours (see Baidu Wenku’s “Heat Treatment Process for 18-8 Austenitic Stainless Steel”). After normalizing, air cooling is employed; the material is not held in the 500–850°C temperature range for more than 8 hours, so it does not become sensitized, which would reduce its resistance to intergranular corrosion. The issue of different coefficients of thermal expansion is something that needs to be taken into account when selecting the heat forming method for end caps, rather than during the heat treatment after heat forming. For composite panel factories, stress-relief heat treatment is also required after compounding, so there should be no problem.

The answer upstairs is more reasonable. Support one