Several common treatment method of the zinc alloy plate die casting defects
Several common zinc alloy brands processing method of zinc alloy die casting defect plate die casting has been widely applied in all sorts of adornment, such as: furniture fittings, building decoration, bathroom accessories, lighting parts, toys, signs, car decoration, tie clips, belt buckle, metal buckle, luggage fittings, etc. , so the surface finish for the castings quality requirements higher, at the same time requirements surface treatment have good performance, and the most common defect is zinc alloy die casting surface bubbles.
Defect characterization: die casting surface has a protuberant vesicles, die casting defects existed, revealed after polishing or processing, fuel injection, or after plating bubbles.
Zinc alloy plate die casting defect reasons: one, holes cause: mainly porosity and shrinkage mechanism of stomatal tend to be rounded, and shrinkage is most irregular.
Stomatal reasons: (1) in liquid metal filling and solidification process, because the gas leaking, lead to the casting surface or the inside holes;
(2) coating volatile gas leaking out;
(3) alloy liquid air content is exorbitant, coagulation precipitation, when gas in the cavity, coating of volatile gas, alloy solidification exhalation gas, in the mold venting is not good, eventually formed in casting porosity.
Shrinkage cavity causes: 1) metal solidification process, due to the smaller or the final solidification feeding, not metal and shrinkage cavity;
(2) the thickness of the casting or casting local overheating, causing some place solidification slow, volume shrinkage when surface concave;
(3) due to the presence of porosity and shrinkage cavity, the pressure in the surface treatment of zinc alloy castings, the hole may enter the water, when painting and electroplating after baking, gas heat expansion in the hole;
Or holes in the inland waters will be steam, volume expansion, resulting in casting surface bubbles.
Intergranular corrosion cause: harmful impurities in zinc alloy composition: lead, cadmium, tin, will be gathered in the grain boundary leads to intergranular corrosion, metal substrate due to intergranular corrosion and broken, and accelerated the scourge, electroplating parts can expand by intergranular corrosion and coating jacking, casting surface bubbles.
Especially in the moist environment intercrystalline corrosion will make the die casting of shape, craze, and even broken.
Three, crack cause: water, cold insulation lines, hot crack.
Water, cold insulation lines, liquid metal in the process of filling, the first to enter the metal contact type wall premature solidification, into the liquid metal can't and have metal solidification layer after fusion is an organic whole, in the joint formation on the surface of zinc alloy castings moire, strip defects.
Shallow water lines are generally in the casting surface;
And cold insulation lines may seep into the castings.
Hot crack: (1) when the casting thickness, the solidification process to produce stress;
(2) premature ejection, metal strength is not enough;
(3) out the uneven high d mold temperatures make the coarse grains;
(4) harmful impurities.
The above factors are likely to produce cracks, water lines when zinc alloy die casting, cold insulation lines, hot crack, electroplating solution will seep into the cracks, is converted into steam when baking, pneumatic jacking electric plating formed bubbles.
Zinc alloy plate die casting defects of the solution: 1, the control of stomatal generation: the key is to reduce the amount of gas in mixed with the casting, the ideal metal flow should be accelerated by the nozzle after cone and sprue into the mold cavity, the formation of a smooth and metal flow in the same direction, the taper runner design, namely water flow should be accelerated to from the nozzle to the gate to reduce gradually, can achieve this goal.
In the filling system, mixed with liquid mixed gases is due to turbulence and metal and form pores, from liquid metal into the cavity by the casting system in the study of simulation of die casting process, obvious sprue and increasing sharp change in the cross-section of runner, will appear the metal flow turbulence and gas volume, steady liquid metal to favour gas from the runner and the cavity into the overflow tank and exhaust slot, discharge mode.
2, the shrinkage cavity: to make the die casting parts uniform heat dissipation at the same time, as far as possible in the process of solidification and solidification.
Through reasonable runner design, gate thickness and position, mold design, mold temperature control and cooling, to avoid any shrinkage cavity.
For intergranular corrosion phenomena: the main is to control harmful impurity content in the alloy materials, especially the lead & lt;
Pay attention to the waste of impurity elements.
3, for water, cold insulation lines: mold temperature can be improved, the increasing speed of gate, or in cold area increase the overflow tank insulation, to reduce the occurrence of cold across the grain.
4, for the hot crack: die casting thickness don't dramatic change in order to reduce stress;
Zinc alloy die casting technology parameters are adjusted related;
Reduce the die temperature.
All treatment method of zinc alloy plate die casting defect content is our accumulated some experience in the production for a long time, just for your reference, if you are interested in our published articles, reproduction, reprint please indicate the article source: gains sign factory