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Main Defects and Causes of Aluminum Alloy Extrusion Materials
Defects usually refer to areas that do not meet the ordering standards or conditions, which either affect the appearance or use of the product. They are avoidable in production and are a direct reflection of product quality.
Acceptable defects that only affect the appearance of the product and can be eliminated through subsequent finishing or processing without affecting its use, such as surface contamination, scratches and scratches that are not out of tolerance, pits, bending, twisting, flat gaps, peeling, bubbles, extrusion cracks, dimensions, etc. These defects are usually caused during extrusion and subsequent finishing, packaging, and transportation processes.
Unacceptable defects that cannot be eliminated through subsequent finishing or processing, such as coarse crystal rings, layering, shrinkage, poor welding, unqualified flaw detection, excessive oxide film, metal and non-metallic slag, heat treatment cracks, over burning or overheating, as well as excessive scratches and scratches, bending, twisting, flat gaps, peeling, extrusion cracks, dimensions, etc. Some of these defects are inherited from metallurgical quality, such as unqualified inspection, excessive oxide film, metal and non-metallic slag, etc., and some are caused by process and mold reasons in extrusion production.
Surface pollution, scratches, and bumps - weak quality awareness during production and lack of protection for product surfaces; Or there is an issue with the packaging method, which may cause collision or rubbing during rotation and transportation.
Scratches - the mold work area is not cleaned thoroughly; The working track of the press or saw machine is not cleaned thoroughly.
Pitted surface - insufficient hardness of the mold working zone; The extrusion temperature is too high; The squeezing speed is too fast.
Bending, twisting, flat clearance - mold design issues; Unreasonable extrusion temperature or extrusion speed; The quenching medium temperature is too low; Insufficient stretching or other finishing methods.
Peeling and bubbles - loose ingots; The size of the extrusion pad is unreasonable; Oil stains on the surface of the ingot or extrusion cylinder; Squeeze temperature or speed too fast.
Squeeze cracks - the extrusion temperature or speed is too fast.
Size - Unreasonable mold design; The extrusion speed control is inconsistent before and after.
Coarse crystal ring - improper control of alloy composition; Unreasonable extrusion process design; The heat treatment temperature is too high and the insulation time is too long.
Layer forming - surface defects on the ingot not cleaned by turning; Oil stains on the surface of the ingot or extrusion cylinder; Unreasonable mold design.
Shrinking tail - the squeezing speed is too fast; The temperature difference between the extrusion cylinder and the ingot is large; Less residual extrusion or less removal of the end of the product; There is oil stains on the surface of the ingot or extrusion cylinder.
Poor welding - unreasonable mold design; Insufficient tonnage of the press; Low extrusion temperature; Small extrusion coefficient; Fast extrusion speed; Oil stains on extruded blanks, tools, or molds.
Unqualified flaw detection - poor ingot quality with severe porosity, oxide film, inclusions, etc; The heat treatment process is unreasonable.
Over burning or overheating - high heating temperature and long time before extrusion; High extrusion temperature and fast speed; High heating temperature during heat treatment.
Excessive oxide film, metal and non-metallic impurities - poor metallurgical quality of ingots.
Heat treatment cracks - large product thickness, low quenching medium temperature, and fast cooling rate.
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