Aluminum gravity casting vs high pressure die casting vs low pressure casting

Introduction to gravity casting:

Gravity casting refers to the process of injecting molten aluminum into the mold by gravity under the action of the earth's gravity. In a broad sense, gravity casting can be divided into sand mold casting, metal mold (steel mold) casting, lost foam casting, etc.; Gravity casting in a narrow sense refers to metal mold casting. Metal mold casting is divided into vertical manual casting, and inclined casting is now the most widely used metal mold (steel mold) casting.

The mold is made of heat-resistant alloy steel, and the strength, size, and appearance of the cast aluminum castings are higher than those of other casting processes. The aluminum liquid of gravity casting is generally poured into the gate manually, and the mold cavity is filled, vented, cooled, and opened to obtain samples by relying on the self-weight of the metal liquid. The process flow is generally as follows: aluminum liquid melting, pouring material filling, venting, cooling, mold opening, production clearing, heat treatment, and processing.

The characteristics of aluminum alloy gravity casting parts are as follows:

1. The surface finish of the product is not high, and it is easy to produce pits after shot blasting.

2. Aluminum castings have few internal pores and can be heat treated.

3. The product has low compactness, slightly poor strength, but high elongation.

4. The cost of the mould is low and the service life of the mould is long.

5. The production efficiency is low, which increases the production cost.

6. The process is relatively simple, which is not suitable for the production of thin-walled parts.

7. Special aluminum alloy with low fluidity can be used.

When choosing which process to produce the product, it is mainly based on the wall thickness of the workpiece. When the wall thickness of the product is greater than 8mm, die casting will cause many pores to exist in the wall. Therefore, the products with thick wall thickness can be completed by the gravity casting process.

Introduction to die casting:

Pressure die casting is divided into high-pressure casting and low-pressure casting.

High-pressure casting is what we usually call die casting. The liquid aluminum is poured into the pressure chamber, the mold cavity is filled with its pressure at high speed, and the liquid aluminum is solidified under pressure to form an aluminum casting.

High pressure die casting: a casting method in which liquid or semi-solid metal or alloy, or liquid metal or an alloy containing reinforcement phase, is filled into the cavity of die casting mold at a high speed under high pressure, and the metal or alloy solidifies under pressure to form a casting. The commonly used pressure during dies casting is 4 ~ 500MPa, and the metal filling speed is 0.5-120m/s. Therefore, the filling time of liquid metal is very short, and the mold cavity can be filled in about 0.01-0.2 seconds (depending on the size of the casting). Therefore, high pressure and high speeds are the fundamental difference and important characteristics between die casting and other casting methods.

Aluminum alloy dies castings are characterized by:

1. The surface finish of the product is generally good, up to ra6.6 3 or even ra1 6。

2. Do not heat treat.

3. The product has high airtightness, high casting strength, and surface hardness, but low elongation and excessive wall thickness are easy to produce pores.

4. The mold cost is high and the service life is short.

5. High production efficiency.

6. It can produce thin-walled parts with a small machining allowance.

7. Special aluminum alloys cannot be used.

Low-pressure casting: dry compressed air is introduced into the sealed crucible (or sealed tank). Under the action of gas pressure, the liquid metal rises along the riser into the sprue, enters the mold cavity smoothly through the inner sprue, and maintains the gas pressure on the liquid level in the crucible. Until the casting is completely solidified.

Then release the gas pressure on the liquid level to make the non solidified metal liquid in the liquid riser flow back to the crucible. Re-open the mold and take out the casting. This casting method has good feeding, dense casting structure, easy to cast large, thin-walled, and complex castings without a riser, and the metal yield is 95%. No pollution, easy to realize automation. However, the equipment cost is high and the production efficiency is low. Generally used for casting non-ferrous alloys.

The features of aluminum alloy low-voltage parts are:

1. The surface difference of the product is stronger than that of the die casting than that of the gravity part

2. Aluminum castings have few internal pores and can be heat treated.

3. The product has high airtightness, the strength and surface hardness of the casting are higher than those of die casting, but the elongation is lower than that of gravity

4. The die has a low cost and low service life.

5. The production efficiency is lower than gravity and far lower than die casting.

6. The process is complex and is used to produce castings with high requirements and high quality.

7. Special aluminum alloy with low fluidity can be used.

In short, low pressure is the compromise between high pressure and gravity.

Ningbo Fuerd was founded in 1987, is leading full-service die Casting Tooling, aluminum die casting, zinc dies casting, Gravity casting manufacturer. We are a solution provider offering a wide array of capabilities and services that include engineering support, designing, molds, complex CNC machining, impregnation, tumbling, chrome, powder coating, polishing, assembly, and other finishing services. We will work with you as partners, not just suppliers.

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