Huizhou Shuangcheng Hardware Co., Ltd., an aluminum alloy parts die casting factory

Chemical heat treatment: refers to a heat treatment process in which the atoms of chemical elements are infiltrated into the surface layer of the workpiece with the help of the ability of atomic diffusion at high temperatures to change the chemical composition and structure of the surface layer of the workpiece, so as to achieve a specific structure and performance of the steel surface layer. Chemical heat treatment can be divided into carburizing, nitriding, cyaniding and metallizing according to the different types of elements

Carburizing: Carburizing refers to the process of penetrating carbon atoms into the surface layer of steel. It also makes the low carbon steel workpiece have the surface layer of high carbon steel. After quenching and low temperature tempering, the surface layer of the workpiece has high hardness and wear resistance, while the central part of the workpiece still maintains the toughness and plasticity of low carbon steel

Nitriding: also known as nitriding, refers to the process of penetrating nitrogen atoms into the surface layer of steel. The purpose is to improve the hardness and wear resistance of the surface layer as well as the fatigue strength and corrosion resistance. At present, gas nitriding is widely used in production

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Cyanide: also known as carbonitriding, refers to the process of infiltrating carbon atoms and nitrogen atoms into steel at the same time. It makes the steel surface have the characteristics of carburizing and nitriding

Metallizing: refers to the process of penetrating metal atoms into the surface layer of steel. It is to alloy the surface layer of steel, so that the workpiece surface has some characteristics of alloy steel and special steel, such as heat resistance, wear resistance, oxidation resistance, corrosion resistance, etc. In production, aluminizing, chromizing, boronizing and siliconizing are commonly used

Die casting process scheme design

As we all know, most of the die casting industry is based on customized processing with supplied samples and drawings. Now, Dongguan die casting will analyze the main steps of die casting mold opening design for your reference

The design steps of die casting die are as follows:

1. Process analysis of die castings, including alloy, casting structure and technical analysis of die castings

2. Process scheme design, including determination and setting of parting surface, gate position, pouring and overflow system, cavity quantity, core pulling scheme and quantity, die casting ejection scheme, die casting machine selection, etc

3. Pouring and overflow system design. Dongguan die-casting includes the determination of process parameters, the calculation of inner gate size, the determination of the shape and size of the gating system and the calculation of the location and size of the slag ladle in the exhaust slot

4. Structure design of die-casting die. Including the design of insert, cavity, core pulling, ejection, cooling water, heating pipe, etc

5. Design of general drawing of die-casting die

6. Design of die-casting die parts

Equipment performance

Air hole, shrinkage cavity and cold shut in die castings are also the main reasons for air leakage of die castings, and equipment performance plays a crucial role in casting production. For products with strict air tightness requirements, appropriate die-casting models must be selected

At present, the die-casting machine basically adopts three-stage injection in aluminum alloy die-casting production. During the first stage injection, the injection punch moves at a slower speed, which is conducive to extruding the gas in the pressure chamber; In the second stage of injection, the ingate speed is extremely fast, and the aluminum liquid basically fills the mold cavity. At the same time, if the position of the secondary injection rate comes too early, the casting is prone to defects such as air holes. If the starting position of the secondary injection rate is too late, the casting is prone to cold shut and other defects. Generally, it is better to choose the starting position of the second stage injection velocity at the point where the molten metal in the cup just reaches the entrance of the ingate. Therefore, this stage is the key to the generation of pores, so the higher the speed is, the easier it is to generate vortex and form pores

For example, there are many kinds of defects that cause the air leakage of the CG125 right crankcase body die casting on the motorcycle engine. Theoretically, any defect of the die casting may cause the air leakage of the casting. In actual production, the most common locations of poor air tightness are A, B and C as shown in Figure 3. There are many causes of such problems, so we should grasp the main cause to adjust, so that air leakage can be significantly improved. It is an effective method to adjust the die casting process curve

In order to reduce the shrinkage cavity in the casting and fill the air leakage channel, the air in the pressure chamber shall be discharged as much as possible. In this process, the main idea of controlling the porosity of die castings is to control the injection velocity of the first and second stages and the switching point of the first and second stages. On the premise of meeting the requirements of casting forming or surface quality, the primary injection speed shall be as low as possible, and the high speed shall be started when the aluminum alloy reaches the ingate. Through the improvement of the above process, the air tightness of the box is greatly improved