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Why does the aluminum coil have curling problems after cooling at high temperatures?
Nov 07, 2018

In the process of aluminum coil production, in order to help change its shape, we need to heat it at high temperature. It will be softer at high temperature, and its shape is more prone to some changes. After that, it can be lowered to maintain a certain hardness, but in some cases, after the high-temperature cooling is completed, the aluminum coil will have some curling problems. What is the reason? The aluminum coil will be bent when it is cooled. The reason is: under the condition of general air cooling, the heat transfer coefficient of the parts of the aluminum coil in contact with the air is flat, but because the wall thickness or shape is different, the heat dissipation speed of each part is not balanced. The heat dissipation rate of the thick wall portion or the hollow tube is slower than that of the thin wall portion, and finally it causes a phenomenon of being bent to a hollow portion or a thick wall portion when it is cooled.


The reasons and process of bending are as follows:


1. The temperature of the thin-walled part decreases rapidly, firstly, the contraction force is generated, and the temperature of the thick-walled part or the hollow tube part is slow, and there is almost no contraction force;


2. The thin-walled part has a small cross-sectional area, and the contraction force generated is small, or is eliminated by the traction force of the tractor;


3. Leaving the tractor, the temperature continues to drop;


4. The thick-walled part or the hollow tube has a large cross-sectional area, and gradually produces a large contraction force as the temperature decreases. The temperature of the thin-walled part has been greatly reduced, and the contraction force or contraction force is no longer generated;


5. The shrinkage force received on the cross section of the aluminum coil is not uniform, and is bent toward the thick wall portion or the hollow tube portion along the extrusion direction.


The above is a description of the method of curling up the aluminum coil after high temperature cooling. I hope it can help everyone.