The cause of formation and treatment of the surface scar defect of aluminum alloy extruded products

- Mar 09, 2019-

scratch

scratch
Scratches generally show as the continuous or semi-continuous furrow scars parallel to the extrusion direction, which are caused by the contact or friction between the extrusion material and the mold or between the extrusion material and each other. It is likely that the products from the mold hole outflow process and mold (or die pad) contact, not smooth guide road and other mutual contact and friction scars, or porous extrusion is to install guide road, products to separate and mutual friction scars.
If it is the contact scar between the extrusion material and the tool is need to design the appropriate mold, the mold pad dressing;
(2) the contact between the extrusion material scars, need to install the appropriate guide (graphite liner) in the work table and the discharge table using soft high-temperature resistant materials isolated extrusion products.
scratch
The abrasion of aluminum alloy extruded products is generally caused by the friction between the extruded materials in the process of moving and other operations and the contact with other objects. It is to pile up the scar that squeezes each other between extrusion material to produce, have fine and successive line or dot scar, accompanied by twinkling burnish, shape each different. Sometimes improper packing can cause damage during transit.

The thick paper can be sandwiched between the extrusion material and the extrusion material; Improve the material of professional spreader and fixture, use specific material rack and special material to make the rack; Finally pay attention to finished product packaging, reasonable packaging to reduce unnecessary losses.

Crack (tear)

Crack (tear)
Aluminum alloy extrusion products crack (tear) injury is the surface of the extrusion products to produce micro-cracks, or the edge parts and thickness of the big difference between the zigzag crack (crack). Eye microscopic examination can be found in the cracks, large in a certain interval outside the occurrence, especially in the alloy composition of high strength alloy more. Due to the reason of friction force, the metal deformation is uneven because the metal is subject to the action of adhesive stress, when the tensile stress accumulated to exceed the breaking strength of the metal will produce cracks. When the temperature is high, the metal's ability to resist damage decreases, and when the deformation speed increases, the tensile stress increases and the crack tendency increases.
Ingot, mould, extrusion process and equipment can be studied to see if these problems have been noticed.
In high Mg alloy, Na content was reduced as much as possible.
Improve the design of structure or welded cavity. The corner radius of the extruded product section should be as large as possible, especially the high component content.
The heating temperature of the ingot should be even, and the extrusion temperature and speed should be reduced. When changing the alloy, the extrusion speed should be adjusted in time, and the starting speed of extrusion should be relatively slow. After normal extrusion, the appropriate metal speed should be adjusted in time.
Equipment, heating furnace design control and instrumentation should be accurate, to prevent the actual metal temperature on the high; Strictly control the speed control system to ensure the accuracy, and at the same time should often overhaul and maintenance of extrusion and related equipment