Zinc alloy die-casting process advantages and disadvantages
The zinc alloy die casting is a zinc alloy of the group consisting of adding other elements. Often increases the alloy elements such as aluminum, copper, magnesium, cadmium, lead, titanium. Zinc alloy has a low melting point, good fluidity, easy welding, brazing and plastic processing, corrosion in the atmosphere, maimed materials to facilitate recycling and remelting; creep strength is low, prone to natural aging cause dimensional changes. Preparation of melting, die-casting or pressure processing. Manufacturing process can be divided into cast zinc alloy and the deformation zinc alloy.
The main element of the zinc alloy, aluminum, copper and magnesium. Zinc alloy according to the machining process can be divided into two types of deformation and cast zinc alloy cast zinc alloy fluidity and good corrosion resistance, suitable for die-casting instrumentation, automotive parts shell and so on.
First, the zinc alloy is characterized by
1. Than significant.
Casting performance, complex shapes can be die-casting, precision parts, thin-walled castings smooth surface.
3. Surface treatment: electroplating, spray, spray paint.
Melting and die-casting iron absorption, pressure-type non-corrosive, non-stick mold.
5 has good mechanical properties at room temperature and abrasion resistance.
A low melting point, melting at 385 ℃ easily die casting.
Should be noted that the process of problem:
A poor corrosion resistance. When the alloy composition, impurity elements such as lead, cadmium, tin exceeds the standard, resulting castings aging deformation occurred, the performance of the volume swell, the mechanical properties, particularly the ductility was significantly decreased, a long time or even rupture.
Very small solubility of lead, tin, cadmium and zinc alloy, and thus concentrated at the grain boundaries as a cathode, the aluminum-rich solid solution as an anode, electrochemical corrosion in the presence of steam (electrolyte), contributed intergranular. Die casting due to intergranular corrosion and aging.
2. Aging role
Zinc Alloy composed mainly composed of a zinc-rich solid solution containing Al and Cu, and Zn-containing Al-rich solid solution, their solubility increases with the decrease in temperature lower. However, due to the solidification speed of the die casting fast to room temperature, the solubility of the solid solution is substantially saturated. After a certain time, this over-saturation phenomenon will be gradually lifted, so that the castings to the shape and dimensions of slightly changing from.
3. Zinc alloy die castings should not be used in the work environment of high temperature and low temperature (0 ° C or less). Zinc alloy with good mechanical properties at room temperature. However, in the high temperature tensile strength and low temperature impact properties are significantly decreased.
Second, zinc alloy type
Zamak 3: good flowability and mechanical properties.
Castings used in the mechanical strength of the less demanding, such as toys, lamps, decorations, some electrical items.
Zamak 5: good flowability and good mechanical properties.
Used for mechanical strength castings have certain requirements, such as auto parts, electrical and mechanical parts, mechanical parts, and electrical components.
Zamak 2: Particular requirements for mechanical properties, high hardness requirements, dimensional accuracy requirements of general machinery parts.
ZA8: good flowability and dimensional stability, but poor fluidity.
Applied to the die casting small size, high accuracy and mechanical strength requirements of the workpiece, such as electrical parts.
Superloy: mobility, the applied casting thin-walled, large-size, high precision, complex shape of the workpiece, such as electrical components and their box body.
The different zinc alloys have different physical and mechanical properties and offers a choice of space, such as the design of the die casting.
Third, zinc alloy selection
Choose what kind of zinc alloy, mainly from three aspects to consider
Die casting itself uses, the need to meet the performance requirements. Include:
(1) The mechanical properties, tensile strength, the maximum resistance in the material is broken;
Elongation, which is a measure of the material brittle and plastic;
Hardness is the resistance of the material pressed into the surface of the hard objects or friction caused by the plastic deformation.
(2) The state of the environment: Operating temperature, humidity, workpiece contact media and air tightness requirements.
(3) the accuracy requirements: accuracy and dimensional stability can be achieved.
Process performance: (1) the casting process;
(2) mechanical processing technology;
(3) surface treatment processes.
3.3 economy: the cost of raw materials and production equipment requirements (including smelting equipment, die casting machines, molds, etc.), as well as the cost of production.