Cracks in the heat-affected zone of welds in cylinders made from Q345R+32168 composite sheets
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Our company has newly manufactured a batch of equipment using Q345R+32168 composite plate cylinders; during rolling, numerous cracks appeared in the heat-affected zone of the welds on these cylinders (Φ2000X50+4). The Q345R+32168 composite plate cylinder is preheated before welding; during welding, a low current and low heat input are used. After welding, the cylinder is kept at a constant temperature to allow slow cooling. Before straightening, the entire cylinder is heated for annealing, and it is then straightened while still in a hot state (around 200 degrees). Cracks appear along the entire weld area in the heat-affected zone. Experts, do you think there might be something wrong with the material? I’m dying of anxiety.
Are there any photos? Is it a composite layer or the heat-affected zone of the base layer? Preheat during welding, use a low current and low wire energy during the welding process, and maintain heat retention for slow cooling after welding. Is it being welded as a base layer or a composite layer?
Both the composite layer and the base layer are cracked; the base layer on the outer surface is even cracked at the center of the weld. (The photo has been attached)
Strangely, our company has carried out welding of spherical tanks using composite steel plates, and the welding quality was excellent – this issue did not occur. Could it be that there is a problem with the welding materials or the steel plates?
It has already turned into a crack; it’s no longer just a fissure. As can be seen from the diagram, the cause of cracking is likely stress concentration resulting from the fusion transition at the weld seam and the shape between the weld beads, which serves as the origin of cracking. This type of cracking tends to occur easily after welding composite sheet materials.
The welding stress is too high, which makes cracking likely during rounding; we have encountered this issue as well
When welding Q345R together with S32168, cracks are inevitable.
If it is confirmed that the base material, welding materials, and welding process are correct, then the problem lies in the forming process: 1. No pre-bending? 2 Is the temperature at the school too low? 3 Is the surface of the front weld on the school circle polished flat? In short, strive to reduce the local stress at the weld during alignment.
Also, when welding the base material, the stainless steel at the groove must be thoroughly cleaned.
First, check whether the welding process and welding materials are incorrect, and then examine the quality of the welding materials. Samples were taken from the cracked area for chemical composition analysis, and weld metal from the base material was collected, indicating that welding problems are widespread in the base material.
For composite plate tube sections with this diameter and thickness, it is generally not necessary to consider post-weld straightening of the longitudinal welds; instead, weld deformation is controlled through welding techniques and welding sequence.