4.Casting deformation
(1) characteristics:
① Overall deformation or local deformation; ② the geometric drawing of the die casting is inconsistent.
(2) Causes:
① The structure of the casting is poor; ② the casting is too early opened, the rigidity of the casting is not enough; ③ the ejector pin is not set properly, and the force is uneven when it is ejected; ④ when the thickness of the gate is too thick, it is easy to deform when the gate is cut off; ⑤ when the resistance is large due to the local surface roughness, the product is deformed when it is ejected; when the local temperature of the mold is too high, the product is not fully solidified, and the force is large when it is ejected, which causes the product to deform.
(3) Treatment method:
① Improve the casting structure; ② reasonably adjust the pressure maintaining and mold opening date; ③ reasonably set the ejection position and ejector number, preferably using 4 pieces, in an open place; ④ change the gate position, so that the gate has a point, reduce the gate thickness, so as to ensure the casting quality of the product, so that the product is not easy to deform when the gate is cut off; ⑤ strengthen the mold surface treatment, reduce the stripping resistance; ⑥ locally The temperature of the die is controlled to keep the heat balance of the die.
5 Flow marks and patterns
(1) characteristics:
There are striations on the surface of the casting which are consistent with the flow direction of the liquid metal, and there are obvious non directional striations which are different from the color of the metal matrix, and there is no development trend.
(2) Causes:
① The metal liquid entering into the mold cavity first forms a very thin and incomplete metal layer, which is made up by the later metal liquid; ② the mold temperature is too low, and the mold temperature is uneven; ③ the cross-sectional area of the internal sprue is too small and the position is improper to produce splashing; ④ the pressure acting on the metal liquid is insufficient; ⑤ the pattern: the amount of paint is too much.
(3) Treatment method:
① Increase the temperature of liquid metal 620% ~ 650 ℃; ② increase the mold temperature to maintain the heat balance of 200 ~ C ~ 250 “(2); ⑧ thicken the cross-sectional area of the internal sprue to change the inlet position; ④ adjust the filling speed and the stroke length of injection time; ⑤ select the appropriate coating and adjust the amount of contrast concentration.
6 Casting cold insulation
(1) characteristics
The surface of die-casting has obvious, irregular and linear lines (penetration and non penetration) with small, narrow and long shape. Some of the joint edges are smooth, which may develop under the action of external force.
(2) Causes:
① The two streams of metal are butted with each other, but they are not fully fused and there is no inclusion between them, and the bonding force of the two streams of metal is very weak; ② the pouring temperature or the temperature of the die casting die is low; ③ the alloy is not properly selected, and the fluidity is poor; ④ the position of the runner is not right or the flow path is too long; ⑤ the filling speed is low, and the injection pressure ratio is low.
(3) Treatment method:
① Increase the pouring temperature and mold temperature properly; ② increase the injection specific pressure and shorten the filling time; ③ increase the injection speed and increase the cross-sectional area of the inner gate; ④ improve the exhaust and filling conditions; ⑤ select the alloy correctly and improve the alloy fluidity.