Die-casting—a mass production and processing method that is particularly common in modern production technology and its advantages and disadvantages

What is die casting

Die casting: (also called pressure casting) is the process of quickly pressing liquid or semi-liquid alloy into the mold cavity under high pressure, and solidifying under pressure to obtain castings; commonly used injection pressure is 30～70MPa, filling speed It is about 0.5-50 m/s, and the filling time is 0.01-0.2 s.

Advantages of die casting

1) High productivity, easy to realize mechanization and automation, and can produce thin-walled castings with complex shapes. The minimum wall thickness of die-cast zinc alloy is only 0.3mm, the minimum wall thickness of die-cast aluminum alloy is about 0.5mm, and the minimum casting aperture is 0.7mm;

2) Castings have high dimensional accuracy and small surface roughness values. The dimensional tolerance level of die-casting parts can reach IT3～IT6, and the surface roughness is generally Ra0.8～3.2μm;

3) The parts that can be embedded in the die casting not only save valuable materials and machining man-hours but also replace the assembly process of the parts, which can save the assembly process and simplify the manufacturing process;

Disadvantages of die casting:

1) The filling speed of liquid metal during die-casting is high, the gas in the cavity is difficult to completely remove, the castings are prone to defects such as pores, cracks and oxidized debris, and die-castings usually cannot be heat treated;

2) The die-casting mold has a complex structure, a long manufacturing cycle, and a high cost, which is not suitable for the production of small batches of castings;

3) Die-casting machines are expensive and expensive, and are limited by the clamping force of the die-casting machine and the size of the mold. It is not suitable for the production of large-scale die-casting parts. Of course, with the improvement of the technological level, the realization of large-scale die-casting workpieces has gradually become possible;

Die casting process:

"Die-casting"—a mass production and processing method that is particularly common in modern production technology and its advantages and disadvantages

1. Inject metal

Close the mold cavity first, and inject the molten metal into the gate of the mold through the injection hole on the pressure chamber;

2. Die casting

The injection punch advances forward, and the molten metal is pressed into the mold cavity;

3. Take out the casting

After the casting is solidified, the core pulling mechanism simultaneously draws out the cores on both sides of the cavity, the front and rear molds of the mold are separated, and the thimble ejects the casting;

Remark:

1. The mold cavity is generally made of special alloy tool steel (such as 3Cr2W8V2), that is, mold steel;

2. The pouring temperature refers to the average temperature of the liquid metal when it enters the cavity from the pressure setting. Because it is inconvenient to measure the temperature of the liquid metal in the pressure chamber, it is generally expressed by the temperature in the holding furnace. In addition, the mold cavity should be maintained at 120-280 ℃ during die-casting (depending on the specific die-casting material); the pouring temperature is too high and the shrinkage is large, which makes the castings prone to cracks, large grains, and stickiness; pouring temperature is too low, It is easy to produce defects such as cold partition, surface pattern and insufficient pouring. Therefore, the pouring temperature should be considered at the same time as the pressure, the temperature of the die-casting mold, and the filling speed.

3. Die casting machine specifications are generally expressed by the size of the clamping force;

After all, Structural Die Casting is the most common metal forming process in factories nowadays, and it is also a solution for mass processing and production. It is still necessary to understand more.