Part four: extrusion crack, Aluminum extrusion defect analysis and quality control method

Part four: extrusion crack, Aluminum extrusion defect analysis and quality control method

Extrusion crack, Aluminum extrusion defect analysis and quality control method

Extrusion crack causes and solutions

Extrusion crack

This is a small arc-shaped crack at the edge of the lateral test piece of the extruded product, and periodically cracks at a certain angle along the longitudinal direction thereof, and is hidden under the skin when the crack is slight, and the outer surface layer forms a serrated crack in severe cases, which seriously damages the continuity of the metal.

The extrusion crack is formed by the tearing of the metal surface layer during the extrusion process by the excessive tensile stress of the mold wall.

The main causes of extrusion cracks:

1. The extrusion speed is too fast; the additional tensile stress on the metal surface is increased to cause cracks in the profile.

2. The extrusion temperature is too high, the tensile strength of the metal surface decreases, and cracks occur under the action of friction

3. The extrusion speed fluctuates too much;

4. The temperature of the extruded line felt is too high;

5. When the porous die is extruded, the die is arranged too close to the center, so that the supply of the center metal is insufficient, so that the difference between the center and the edge velocity is too large;

6. The aluminum ingot homogenization is not good. 

Solutions for extrusion crack:

1. Strictly implement various heating and extrusion specifications;

2. Timely inspection of instruments and equipment to ensure normal operation;

3. Modify the mold design, careful processing, especially the design of the mold bridge, welding chamber and angular radius should be reasonable;

4. Minimize the sodium content in high-magnesium aluminum alloys;

5. The billet is homogenized to improve its plasticity and uniformity.

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