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What Is The Difference Between Cold Chamber Die Casting And Hot Chamber Die Casting?

As a widely used processing method, die casting is characterized by applying high pressure to the molten metal and quickly filling it into the cavity of the mold to form metal parts. This equipment, and its mold making, are relatively expensive and are more suitable for producing high-volume products. Commonly used metals for die casting are aluminum, zinc, magnesium, copper, tin, lead and their alloys. In fact, different types of die casting techniques are used with different metals. Die casting techniques are divided into hot chamber die casting and cold chamber die casting. What is the difference between these two die casting technologies, Xiaobian will take you to understand them.

Hot Chamber Die Casting VS Cold Chamber Die Casting

What is Hot Chamber Die Casting?

Hot chamber die casting, also called gooseneck die casting, because the part of the injection gate is very similar to the gooseneck shape. Its shot chamber and shot punch are immersed directly in a pool of molten metal, filling the mold under pressure. There is no air in the pressure chamber. During the injection process, less gas enters, the molten metal flows in a closed pipe, there are fewer impurities in the oxide inclusions, the temperature fluctuation is small, and the quality of the molten metal is higher. Hot chamber die casting is suitable for the production of thin-walled parts. Thin-walled parts refer to metal material parts with a wall thickness of less than 1mm. It is light in weight and compact in structure, making it easier to form an ideal shape during processing.

What is cold chamber die casting?

The biggest difference between cold chamber die casting and hot chamber die casting is that the shot chamber and punch are not immersed in the molten metal, but the molten metal is scooped into the shot chamber. The earliest cold chamber die casting machine came out in 1920, which followed the injection method of the hot chamber die casting machine. The cold chamber die casting machine is also divided into vertical die casting and horizontal die casting according to the structure and arrangement of the pressure chamber. The vertical die-casting mold is placed parallel to the ground and fed from the side. The horizontal die-casting machine is perpendicular to the ground and generally feeds from the bottom of the side mold.

How To Choose Metal Materials?

The methods of hot chamber die casting and cold chamber die casting are different, and the metal materials selected are also different.

Physical properties of three commonly used alloys
MaterialDensity
g/cm^3
tensile strength
Mpa
specific strength
σb/p
Elastic modulus E
10^4MPa
Hardness
BHN
melting point
°C
Zinc alloy6.7280~440527.0565~140385
Aluminum alloy2.7110~270577.1575~120660
magnesium alloy1.8250~3431914.4160~75650

In terms of hardness, zinc alloy>aluminum alloy>magnesium alloy

In terms of strength, zinc alloy>magnesium alloy>aluminum alloy

Material Selection For Hot Chamber Die Casting

Metal materials with low melting point are more suitable for hot chamber die casting, and small die castings are more suitable for hot chamber die casting, and the production efficiency is also higher.

Zinc alloy: Zinc alloy is the most commonly used hot-chamber die-casting material. Zinc alloy is actually an alloy based on zinc and added with other elements, such as aluminum, copper, beauty, cadmium, lead, titanium, etc. Why do we choose zinc alloy for hot chamber die casting?

First, the melting point of zinc alloy is low, its density is 6.7 g/cm3, and the melting point is 382-386°

Second, zinc alloy has good fluidity, low melting point, easier die-casting, complex shape, thin-walled precision parts.

Third, various surface treatments can be performed, such as electroplating, spraying, painting, polishing, sandblasting, electrophoresis, etc.

Fourth, it will not attract iron during die casting and melting, and will not stick to the mold

Fifth, it has good corrosion resistance, suitable for auto parts, etc.

Material selection for cold chamber die casting

Cold chamber die casting is suitable for die casting of high melting point parts. During the operation, the injection chamber and punch are not immersed in the molten metal, and then the molten metal is poured into the injection chamber quantitatively.

Aluminum alloy: Aluminum alloy is the most suitable metal material for cold chamber die casting. Its melting point is around 660°C. The density is about 2.63~2.7g/cm. First: It has good thermal conductivity, electrical conductivity, and corrosion properties, and can be welded. Second: It has good filling properties and can be cast into various complex shapes Third: Aluminum alloy is lighter in weight and easier to install, which can save time and effort in installation or handling. Fourth: It has strong corrosion resistance and oxidation resistance. It also has good thermal and electrical conductivity, polishing optical properties and suitable mechanical properties.

Magnesium alloy: This should be a special one. It can be used for hot chamber die casting or cold chamber die casting. Depending on the thickness of the casting wall, magnesium alloys with small size, thin walls and complex shapes are suitable for hot chamber die casting. Wall thickness, relatively large small and medium parts, mass production is more suitable for cold chamber die casting.

First, magnesium alloy melt has low viscosity and good fluidity, which can quickly fill complex mold cavities

Second, the production efficiency can be 40% higher than that of aluminum alloy die castings, or even 50%, and can even reach twice that of die casting aluminum.

Third, compared with aluminum, it is even lighter in weight, good in quality, and not easy to age.

The above is how to choose metal materials for hot chamber die casting and cold chamber die casting.

Application Fields Of Die Casting Parts

Whether using hot chamber die casting or cold chamber die casting, high-precision parts can be cast to meet the needs of various industries. Its main application range is very wide, and it is even expanding its application range, such as the automotive industry, electric motors Manufacturing, computer, construction, hardware, shipbuilding, aerospace, lighting, and even the makeup industry, LOGO nameplates, perfume bottle caps, etc.

Advantages of Hot Chamber Die Casting and Cold Chamber Die Casting

Advantages of Hot Chamber Die Casting

Hot chamber die casting has many advantages. Its injection cylinder and pressure chamber are vertically distributed. The pressure chamber enters the molten metal in the crucible of the furnace. There is no air in the pressure chamber, so less gas enters. The molten metal is in a closed pipe. Flowing, there are fewer opportunities for oxidizing impurities, and the quality of the molten metal will be higher. This kind of hot chamber die casting is more used for the production of thin-walled die casting parts. Generally, the hot chamber die casting machine does not have a pressurized hydraulic cylinder, because the components of the pressure chamber need to be immersed in the molten metal for a long time, so it is more suitable for the pressure chamber. Components erode small parts such as zinc alloys.

  • The production efficiency of hot chamber die casting is higher because no additional procedures such as pouring are required
  • Easier to automate the process of die casting
  • When filling the mold cavity, the molten metal flows in the closed channel, impurities are not easily involved, and the quality of die-casting parts is better
  • Reduce metal waste, reduce costs, and be more environmentally friendly

Advantages of Cold Chamber Die Casting

Cold chamber die casting follows the injection method of hot chamber die casting machine, but its injection chamber and injection punch are not immersed in the molten metal, and the molten metal is poured into the injection chamber quantitatively. Cold chamber die casting can even produce denser die cast parts than hot chamber die casting. Different cold chamber die casting machines certainly have different advantages.

Vertical cold chamber die casting machine

  • Fewer materials are used on the production site, and small machines account for the majority, reducing the use of factory area
  • The pressure chamber is placed vertically, and the metal liquid enters the pressure chamber. During the injection process, less gas is involved and the quality of the parts is better.

 

Horizontal cold chamber die casting

  • Suitable for die casting of various non-ferrous alloys
  • More complete models
  • Fewer production operations, more convenient production, high efficiency, and easier automation

Hot chamber die casting and cold chamber die casting have their own advantages, but hot chamber die casting has a higher degree of automation than cold chamber die casting, less material loss, and higher production efficiency than cold chamber die casting. However, the currently widely used aluminum alloy die-casting parts have a high melting point, so they can only be produced on a cold-chamber die-casting machine. They have their own points of attention. Aluminum alloy die castings are not suitable for heat treatment, and zinc alloy die castings are not suitable for surface spraying.

Process Flow Of Die Casting Machine

Hot chamber die casting

Hot-chamber die-casting injection and injection punch are immersed in molten metal. How does hot chamber die casting work?

The molten metal is poured into the pressure chamber first, and the injection punch moves down slowly to seal the side holes so that air cannot enter. The injection punch injects at high speed, pushes the molten metal, passes through the gooseneck, the nozzle, and the shunt, fills the mold from the inner gate, and solidifies into a casting. Raise the injection punch, and the molten metal from the nozzle and gooseneck flows back into the pouring pot. Finally, open the mold and take out the part.

Cold chamber die casting

Cold chamber die casting The shot chamber and punch are not immersed in molten metal, and molten metal is then scooped into the shot chamber. The furnace is only used for thermal insulation. As with hot chamber die casting, first close the mold, pour the molten metal into the pressure chamber, the upper punch sinks at a lower injection rate, enters the pressure chamber, and then changes to a higher injection rate to press down. The upper and lower punches extrude the molten metal to the nozzle at high speed; the molten metal is filled from the inner gate to the inner cavity of the mold from the nozzle, the flow divider, and the sprue. Complete casting.

Precautions

Whether it is cold chamber die casting or hot chamber die casting, the whole machine must be well grounded, and the safety protection device cannot be simplified.

Pay attention to check whether the outer casing of the wire is damaged. If the wire is found to be damaged, it must be replaced immediately.

Before turning on the power, all junction boxes must be closed, and it is forbidden to touch electrical parts after turning on the power.

Operators must be strictly trained employees. When entering the die-casting workshop, they must wear protective equipment.

It is strictly forbidden to go to the product in the mold with bare hands, it is strictly forbidden to stand on the parting surface of the die-casting machine, and it is strictly forbidden to beat the various parts of the machine.

When shutting down, the pump must be stopped and the power supply must be turned off to prevent others from accidentally touching

It is strictly forbidden to rinse the die-casting machine with water to avoid rust and short circuit of the equipment.

Regarding cold chamber die casting and hot chamber die casting, it is clearer through the comparison below

Hot Chamber Die Casting Cold Chamber Die Casting
The molten metal is connected to the machineMolten metal is introduced into the shot chamber from an external source
Suitable for metals with low melting pointsSuitable for metals with high melting point
higher production efficiencyProduction efficiency is low
Less pressure is required during die castingApply high pressure to molten metal
Short machine lifelonger machine life

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