[zinc Die casting Summit] knowledge of die casting zinc alloy industry chain is necessary!

SMM10 March 22: at the 2020 Zinc Die casting Industry chain Summit Forum held by SMM, Cheng Chujun, Technical Director of Foshan Guihe Metal Trading Co., Ltd., delivered a keynote speech on "Segmentation Die casting Industry requirements for Zinc Alloy quality and Technology".

Cheng Chujun said that zinc alloy is an alloy synthesized by adding other metals on the basis of zinc, and the main addition elements of zinc alloy are aluminum, copper and magnesium. Zinc alloy according to the processing technology to die-casting, widely used in building hardware, bathroom accessories, door and window hardware, smart locks, electronics, electrical appliances, leather goods, toys, accessories, auto parts and so on.

The characteristics of zinc alloy include low melting point, high specific gravity, good fluidity, good casting and processing performance, can be die-cast complex shapes and precision parts, so that the casting surface is smooth, but also can carry out surface treatment. Electroplating, spraying, painting, melting, die casting does not absorb iron, does not corrode the mold, does not stick mold, has good room temperature mechanical properties and wear resistance, the melting point begins to melt at 385 degrees, and is easy to be formed by die casting.

The role of elements in Zinc Alloy

Zinc alloy composition, effective elements: aluminum, magnesium, copper; harmful impurity elements: lead, cadmium, tin, iron.

The role of aluminum: 1. Improve the casting properties of the alloy, increase the fluidity of the alloy, effectively refine the grains, cause solid solution strengthening and improve the mechanical properties.

two。 Reduce the reaction ability of zinc to iron and reduce the erosion of iron materials such as mold gooseneck crucibles.

The function of magnesium: 1. Reduce intergranular corrosion. Refine the microstructure of the alloy so as to increase the strength of the alloy. Improving the wear resistance of the alloy

The function of copper: 1. Increase the hardness and strength of the alloy. Improve the wear resistance of the alloy. Reduce intergranular corrosion

Impurity elements of iron: 1. Iron reacts with aluminum to form FeAI3 intermetallics, resulting in the loss of aluminum and the formation of scum.

two。 Hard spots are formed in die castings, affecting post-processing and polishing

3. Increase the brittleness of the alloy

Analysis of Common defects in Die Castings

The design of the die casting itself is unreasonable, such as wall thickness, shape, fillet, demoulding angle, hole, etc., but the die casting machine has insufficient injection force and clamping force, improper casting pressure and filling speed, casting size, projection area and die casting machine capacity mismatch and other performance problems.

The problems in the design and manufacture of die-casting die: mold matching, grinding, machining accuracy, the influence of moving parts on the size of castings, the layout of cooling water and so on.

The problems of die casting process include the selection of parting surface, gating system design, exhaust slot, die casting process parameters and improper coating.

Alloy materials and smelting problems: improper composition of alloy raw materials, ratio of new and old materials, smelting process, etc.

Die casting operator operation problems: material temperature, mold temperature control, process parameter control, spray, pick-up, production cycle and so on. Incorrect one of the above factors or incorrect combination of several factors will lead to defects.