Surface crack’s defect characteristics of aluminum profile: the surface of
aluminum profiles presents longitudinal fish-like repeated interstitial broken lines isolation lines, and serious direct separation.
Causes of surface crack on aluminum profiles:
(1) Extrusion coefficient of aluminum profiles is too large, extrusion temperature is too high (bar, tube and mould at three temperatures), and extrusion speed is too fast;
(2) Extrusion force is unstable, flickering, or speed difference is obvious between speeds of multiple gears,and speed shifts suddenly when shifting.
(3)When aluminum alloy profiles are extruded, the pressure on the head end (stamping) is too fast, the tail end runs at a speed without deceleration, and a large amount of aluminum infiltrates into the invisible zone;
(4)The quality of the rods is poor, the rods are overburnt, the grains are large and loose.
(5)Unreasonable design and severe imbalance of flow rate ratio of extrusion dies in produce.
Methods for eliminating surface crack of
aluminum profiles:
(1) Profiles with too large extrusion coefficient can be produced in small machines, with appropriate extrusion ratio;In addition, the three temperatures of extrusion should be strictly controlled according to the production process’s requirements, and the appropriate extrusion speed should be adopted.
(2) The operator should focuse on production, the speed is stable, the pressure cannot be high or low, and manual operation is coordinated when shifting gears;
(3)The front and back end of aluminum profile’s stop printing are invisible zone, with many impurities, poor quality and low viscosity. Therefore, the extrusion speed of the end and head of the profile should be slowed down.
(4) The surface of the
aluminum bar shall be delicate, clean and free from oil pollution, and the internal tissue shall meet the standard.
(5)The designer of extrusion dies shall design and manufacture qualified molds with uniform flow rate.
