What factors determine the temperature of aluminum die casting die
The temperature of aluminum die casting die shall be determined according to the shape of the casting, the material of the molten metal and other conditions.
As we all know, in continuous casting, the mold temperature rises and falls once every time the injection is made. In such a continuous and repeated lifting cycle, the temperature changes considerably. Therefore, which time temperature is used as the reference point for measuring the mold temperature? The ideal reference point is the surface temperature of the mold cavity before the metal liquid is about to be filled as the control reference of the mold temperature. But it is difficult to measure this temperature. Generally speaking, the surface temperature of the mold cavity after the casting is taken out is taken as the measurement benchmark of the mold temperature, which is called the mold temperature.
For general die-casting dies, it is better to take out the casting in continuous casting and the temperature of the cavity surface is about 40% of the alloy melting point (for example, if the alloy melting point is 600 ℃, the mold temperature is about 240 ℃; if the alloy melting point is 375 ℃, the mold temperature is about 150 ℃). However, the mold temperature of thin-wall castings should be slightly increased; Heavy wall castings should be slightly reduced.
High temperature of molten metal makes it easy to cast. However, if the temperature of molten metal is too high, the gas content will increase, and pinholes and pores will be easily formed; Moreover, the shrinkage cavity increases after filling the mold cavity, and the defects of shrinkage cavity and surface shrinkage pit are easy to occur; What is more serious is that it shortens the service life of the mold and melting batch, increases the melting cost and other adverse factors. In this way, the temperature of molten metal should be low, but it should not be too low, otherwise the fluidity is poor and the casting forming is difficult.
In addition, when the filling process is carried out on a low-power die-casting machine, the temperature of the molten metal should also be higher. For castings where the mold temperature is not easy to rise and inserts such as motor rotors have great resistance to the flow of the molten metal, the temperature of the molten metal should also be higher.
Application technology of release agent for aluminum die casting die
Aluminum alloy die-casting, including aluminum, magnesium and zinc alloy series die-casting products, is widely used in automotive, telecommunications, motorcycles, home appliances and other industries. Mold release agent for aluminum alloy die casting is an auxiliary agent that must be used in the production process. Due to the different volume size, structure complexity and post-processing requirements of products, the requirements for release agent are also different.
The zinc alloy material is heated and melted (aluminum melting point 660.4 ℃), injected into the mold cavity under high pressure in the liquid state, and the top part of the mold is opened for ejection in a short time. In order to ensure the smooth demoulding of products, the mold cavity surface must be sprayed with release agent before injection. The release agent for aluminum alloy die casting must meet the following requirements:
1. Oil. As an effective material for metal to metal isolation, organic silicone oil is an ideal choice. This silicone oil must have the characteristics of high temperature resistance and not affect the post-processing performance (such as aluminum product coating).
2. Water based. Because the mold is in a high temperature state, any solvent based release agent is not suitable. With water as the dispersion medium, the water evaporates rapidly in the high temperature environment, and the effective demoulding material is evenly distributed on the surface of the mold cavity. Uniform film formation, strong adhesion, high temperature erosion resistance, good demoulding performance.
3. Emulsion. Select appropriate emulsifier to emulsify silicone oil to prevent its carbonization at high temperature. To keep the surface of products and mold cavity clean.
4. No corrosion to castings and mold equipment. The wheel Gallery of casting products shall be clear, and the surface shall be smooth without trace, which will not affect the coating. Volatiles are smoke-free, non-toxic, do not pollute the environment and do not damage the health of operators.
What is the performance of aluminum die casting die
1. low density: the density of plastic is small, which is of great significance for reducing the weight of mechanical equipment and saving energy, especially for vehicles, ships, aircraft and spacecraft.
2. high specific strength and stiffness: the good strength of plastic is not as high as that of metal, but the density of plastic is small, so the specific strength（ σ b/ ρ)、 Specific stiffness (e/ ρ) Quite high. In particular, reinforced plastics made of various high-strength fibrous, flaky and powdered metal or non-metal fillers have higher specific strength and stiffness than metals.
3. good chemical stability: most plastics have good resistance to acid, alkali, salt, water and gas. Under normal conditions, they do not react with these substances.
4. good electrical insulation, heat insulation and sound insulation performance.
5. good wear resistance and self lubrication: the plastic has small friction coefficient, good wear resistance, good self lubrication, high specific strength and low transmission noise. It can work effectively in liquid medium, semi dry or even dry friction conditions. It can be made into machine parts such as bearings, gears, cams and pulleys. It is very suitable for occasions with low speed and low load.
6. strong bonding ability.
7. good forming and coloring performance.
What aspects should be considered in the design of aluminum die casting die
Before making the aluminum die-casting die, we must first design its structure and specific production requirements, so as to ensure the smooth development of the production work and the good development of the aluminum die-casting die. In order to achieve this goal, these things should be considered when designing.
First of all, aluminum die-casting mold with other equipment. Because it is not used independently, it needs to cooperate with the die-casting machine and materials, which are the three indispensable elements of the die-casting work. Therefore, in the design, it must consider the cooperation with the other two factors, such as whether its shape, size and thickness are compatible with the specifications of the die-casting machine, which is not within the clamping range.
Secondly, it should be convenient for installation, disassembly, operation and handling. It is better to design the aluminum die-casting mold. Do not design the aluminum die-casting mold too cumbersome. In this way, it is very inconvenient to use. At the same time, in order to facilitate its use and handling, some bolts can be installed on both sides of the upper part.
Later, more consideration should be given to the structure and bearing capacity. For example, it has high bearing capacity and can work well under high-intensity pressure without deformation or damage. At the same time, the internal structure of each part should also be reasonable.
What are the solidification methods of aluminum die casting mold
One of the characteristics of casting production is liquid forming. The transformation from liquid to solid, that is, the solidification process has a direct impact on the quality of castings. The appearance of shrinkage cavity, porosity, porosity, stress, deformation, crack and other defects is the result of unfavorable control of solidification process.
The control of solidification process, in addition to the control of the solidification environment of the casting (such as the effect of forces other than pressure and gravity, the overall cooling rate of the casting, etc.), the selection and control of the solidification mode (sequence and direction) of the casting is one of the very important contents.
Generally, the solidification methods of castings are divided into "simultaneous solidification principle" and "sequential solidification principle".
1) The principle of simultaneous solidification is to adopt technological measures to ensure that there is no temperature difference between various parts of the casting or the temperature difference is as small as possible, so as to solidify at the same time. Although this solidification principle has the advantages of solidification period, it is not easy for the casting to produce hot cracks, it is not easy to cause stress and deformation after solidification, and the riser is very small or not used at all. However, the casting is not compact, and there are shrinkage defects in the central area.
2) The principle of sequential solidification is to adopt various measures to ensure that an increasing temperature gradient is established between the part far away from the riser (or gate) and the riser (or gate) on the casting, so that the part far away from the riser solidifies first, then the part close to the riser, and then the riser itself solidifies. The advantage of this solidification principle is that it can ensure that the shrinkage cavity is concentrated in the riser to obtain a dense casting.
Rapid tooling technology for aluminum die casting die
Surface treatment: although rapid prototyping technology has not been available for a long time, it has been widely used because of its great benefits to the manufacturing industry, especially for the design and manufacturing of molds.
Zinc aluminum die-casting mold technology is mostly based on the solid model made by rapid prototyping, that is, the sample mold (mother mold) adopts the copy method (such as metal spraying, electroplating, composite material pouring, precision casting, etc.) to rapidly manufacture the main working parts of the mold (convex, concave mold or mold cavity, mold core). Its manufacturing cycle is generally 1/5 ~ 1/10 of the traditional NC cutting method, but the cost is only 1/3 ~ 1/5.
A variety of process methods have been developed according to the requirements of zinc aluminum die casting die, production cost, RP prototype material, production batch and die precision. At present, there are two kinds of rapid tooling methods: indirect tooling and direct tooling. Most of the RP based rapid tooling methods are indirect tooling. According to different materials, the molds produced by indirect molding method include soft mold, bridge mold and hard mold. Softtooling usually refers to silicone rubber mold. The prototype made by SLA, FDM, LOM or SLS technology is turned into a zinc aluminum die-casting mold, and then two-component polyurethane is poured into the mold. After curing, the required parts are obtained.
What are the characteristics of aluminum die casting die processing parts
Aluminum die-casting mold is used in industrial production to obtain various molds and tools for required products by injection molding, blow molding, extrusion, die-casting or forging molding, smelting, stamping, stretching and other methods. Aluminum die-casting mold processing is composed of different parts. What characteristics should the parts have?
1. The wear resistance of parts is one of the basic and important properties of aluminum die-casting die processing, because there is severe friction between the cavity surface and the blank during aluminum die-casting die processing, which leads to the failure of aluminum die-casting die due to wear.
2. The parts shall have high temperature resistance. When the aluminum die-casting die is processed, the temperature is higher, and the convergence hardness and strength are reduced, resulting in early wear or plastic deformation and failure of the aluminum die-casting die.
3. The parts shall have cold and hot fatigue resistance. The aluminum die-casting die is in the state of repeated heating and cooling during the working process, which makes the surface of the cavity subject to tension and pressure strain stress, causing surface cracking and spalling, increasing friction, hindering plastic deformation, and reducing dimensional accuracy, resulting in the failure of the aluminum die-casting die.
4. The parts shall have corrosion resistance. When the aluminum die-casting mold such as plastic mold is working, due to the presence of chlorine, fluorine and other elements in the plastic, HCI, HF and other strong corrosive gases are decomposed after heating, which erode the surface of the aluminum die-casting mold cavity, increase its surface roughness, and intensify wear failure.
Quality management of aluminum die casting die
It is very important to check the quality of products produced in a large number of production projects. Even if such an examination is made, the results of the examination can still not be 100% trusted. This is clear only through statistical investigation. In addition, once the quality such as the destructive strength of the casting is checked, it indicates that the casting cannot be used. Therefore, for such quality, statistical methods (such as sampling inspection) must be used to estimate the quality of all production batches and judge whether these castings are qualified. For the explanation of this statistical method, let the special statistics do it.
Before the description of quality management, give a vivid example to illustrate. For example, shoot a target with an air gun, accurately aim the collimation of the air gun at the bull's-eye and fix it on the shooting platform, and shoot dozens of bullets at the bull's-eye. In this case, the bullets hit the target within a certain range. However, it is rare to hit at the same target position. After investigation, it is found that the life points are scattered in a wide range. This is the result of the change of wind and air resistance, the pulling of the shooting platform and other conditions. Then, two sets of bullets with different weights are used for the test. In this case, the hit center position of the bullet It varies with the cartridge group.
The quality of mass-produced castings should be considered in the design stage, and the allowable deviation range should be determined. The allowable range reached is similar to the hit range of the above air gun handle. For mass production castings, if the quality error is small and concentrated near the bull's-eye, it is ideal. However, as in the case of air gun shooting, the quality of mass-produced die castings also changes with the change of production conditions; If the conditions change greatly, the error will be large. Therefore, the casting quality control often focuses on the various conditions required in the production process within the range near the target center, which is the quality management work.
Introduction to dimensional accuracy and finish of aluminum die casting die
Aluminum die-casting dies have high dimensional accuracy and surface finish, and are relatively stable under certain conditions, with interchangeability. Therefore, many aluminum die-casting molds can be assembled in machines and equipment without cutting or only a small amount of processing on some parts.
During design, it is necessary to understand the accuracy and smoothness that can be achieved by the aluminum die-casting die under certain production conditions, so as to be one of the bases for selecting the aluminum die-casting die. If the aluminum die-casting die is selected in the design, and the requirements for its precision and finish are too high, it can only be achieved through a large number of cutting, and the result is unreasonable in technology and economy.
At present, there is no unified standard for the dimensional accuracy and surface finish of aluminum die-casting dies. Generally speaking, the dimensional accuracy of aluminum die-casting die is about 3-4 levels lower than that of die-casting die. The accuracy of die-casting die is usually level 3-4 (sometimes up to level 2) (according to the accuracy level of gb159-59), so the dimensional accuracy of aluminum die-casting die is within the range of level 6-8. The finish of aluminum die-casting die is about two levels lower than that of die-casting die cavity surface, generally 5-6 levels. When the mold is just used, it can reach grade 7-8 (according to gb1031-68).
The precision and finish of aluminum die-casting die depend on casting structure, die-casting die structure and manufacturing quality. The stability of precision and finish is mainly related to the service life (die-casting times) of die-casting die, process factors, operation specifications, etc. For example, the surface finish of aluminum die-casting die decreases significantly with the increase of die casting times.
Safety technical operation specification for aluminum alloy die casting workers
1、 Operators must work with certificates.
2、 Operators must wear personal protective equipment.
3、 The operator must be familiar with the structure, performance, working principle and commissioning method of the equipment to be operated, carefully read the operating instructions and operate in strict accordance with the equipment operating procedures- Dongguan die casting machine parts
IV Die casting machine operation:
1. before starting the machine, the operator must make a comprehensive inspection on the equipment, instruments, lubrication and cooling systems and the safety protection devices of the equipment to ensure that they are intact and effective.
2. the operator must wear gloves to prevent hot hands when installing inserts.
3. operators (including others) shall not enter the dangerous area during equipment operation. To prevent bumps and burns.
4. when filling the holding furnace with aluminum liquid, the operator (including others) shall keep away from the forklift and holding furnace to prevent injury caused by aluminum liquid splashing.
5、 During the process of disassembling and assembling the mold, the slings and methods shall be correctly selected, and the mold shall be checked whether there is a steel tightening device to prevent the mold from falling and damaging the equipment and personnel.
1. operation of holding furnace:
2. new furnaces and furnaces that have not been used for a long time must be dried before use to prevent people from being burned by the splashing of molten aluminum.
3. the operator shall regularly check whether the conductor is scorched, damaged or overlapped with the exposed metal part of the equipment to prevent electric shock.
4. when the holding furnace is filled with aluminum liquid, the power must be cut off.
5. when cleaning the dross of molten aluminum, the lifting sling shall be correctly selected for lifting the heating cover, and the operation shall be carried out according to the operating procedures; The heating cover shall be placed on the ground and shall not be suspended in the air all the time; When the furnace temperature is reduced and the slag is cleaned, the cleaning personnel shall wear corresponding protective articles (such as gloves and goggles); After the slag is cleaned, the heating cover shall be restored to its original position, the wiring shall be correct, and the protective cover shall be installed securely.