The hottest magnesium alloy die casting die

Magnesium alloy die casting die

in most cases, the products produced by magnesium alloy die casting are similar to other alloy die castings. Magnesium alloy die-casting die is also similar to aluminum and zinc alloy die-casting die. However, due to some characteristics of magnesium alloy different from aluminum alloy, 2. If the upper and lower limit switches are not adjusted to the appropriate position, full consideration should be given in the design of die-casting die, so as to design a reasonable die-casting die, so as to produce magnesium alloy die-casting efficiently and economically

I. characteristics of magnesium alloy

① the proportion of light magnesium is only 1.8g/cm3, and the proportion of aluminum alloy is 2.7g/cm3. Magnesium alloy is 30% lighter than aluminum alloy and 80% lighter than steel. Therefore, magnesium alloy in automobile and portable electronic products has become an ideal material for parts manufacturing

② strength magnesium alloys have excellent strength/weight ratio in engineering materials such as metals and plastics

③ diecasting under good structural conditions, the minimum wall thickness of magnesium alloy castings is allowed to reach 0.6mm, which is impossible for plastics under the same strength. The die casting performance of aluminum alloy should also be within 1 It can be compared with magnesium alloy when it is more than 5mm. Magnesium alloy is easy to die cast and suitable for mass die casting production (the production speed can reach 1.5 times that of aluminum). In addition, the wear of magnesium alloy die is also lower than that of aluminum

④ shock absorbing magnesium has excellent hysteretic shock absorption performance, which can absorb vibration and noise. As an equipment shell, it can reduce noise transmission, prevent impact and prevent depression damage

⑤ the rigidity of rigid magnesium is aluminum. 2 China graphene industry technology innovation strategic alliance was established in Beijing times and higher than most plastics. Magnesium has good stress resistance

⑥ high electromagnetic interference barrier magnesium alloy has a good function of blocking electromagnetic waves, which is suitable for the production of electronic products

⑦ good cutting performance magnesium has better machinability than aluminum and zinc, making magnesium a metal material that is easier to cut

⑧ the specific heat capacity of magnesium alloy is small, and the cooling speed of alloy liquid is fast

⑨ magnesium alloy has low affinity with die steel and is not easy to adhere to the die

according to the above characteristics of magnesium alloy, the design and manufacture of magnesium alloy and aluminum alloy are compared below

second, send out thousands of happiness bags and rich and exquisite awards Mold design

die casting mold is a complex equipment, which must complete multiple functions. It determines the general geometry of parts and has an important influence on the dimensional deviation between each beer. The use of fixed or mobile cores increases the flexibility of die-casting, and can die-casting parts with complex and precise shapes. The geometry of the runner and nozzle system determines the filling performance of the mold. The thermal condition of the mold determines the solidification, microstructure and quality of the parts. In mass production, the thermal conductivity of the mold determines the cycle time. And the die has a die-casting ejection system

III. mold material

the part of the mold that forms the mold cavity is in direct contact with the molten metal, and must be made of steel material that can withstand thermal impact. H13 steel or materials with similar properties are most commonly used. In order to ensure the surface quality of a large number of beer products, high-quality steel with sulfur content must be used. In order to improve the machinability, the steel supplied to the mold manufacturer is usually in the softening annealing state with spherical carbon particles. After machining, the mold cavity part is quenched and annealed to make the hardness within the HRC range

only the die cavity part and special parts of the die need to use H13 steel, which generally accounts for% of the weight of the whole die. Other parts of the mold are made of medium carbon steel of low carbon steel. For small die castings with relatively simple geometric switches, standardized modules are often used

compared with aluminum alloy, magnesium alloy has lower heat capacity and low iron content. Therefore, the mold has a longer service life

IV. service life of parts

the quality of die castings depends on many factors, including material properties of alloys, production parameters, mold and part design. Part designers should work closely with mold designers to let them know the advantages and limitations of die-casting production

part thickness

smaller part thickness is easy to achieve the required mechanical properties. The good filling performance of magnesium alloy can make the thickness of die castings less than 1mm, and the common wall thickness is between mm

uniform wall thickness

in order to avoid local hot spots during curing, the wall thickness of parts should be as uniform as possible. Due to the shrinkage during curing, local hot spots will cause the formation of pores and cavitation

easy mold filling

the filling time of the mold is generally Ms. the design of parts should help to fill smoothly. The filling speed of magnesium alloy is high, and the edges and corners should be rounded

use strengthening AIDS

strengthening AIDS should be used to strengthen the strength of parts, not by increasing the thickness of parts. Long bars should be avoided in the design to prevent stress and cracks caused by inconsistent shrinkage of the alloy during cooling and solidification

the mold inclination is usually recommended to be °, and the design of degree can also be adopted. Due to the low affinity between magnesium alloy and iron, coupled with excellent heat shrinkage characteristics, sometimes even zero demoulding slope can be used. When designing the wall and core, a small ejection slope can greatly reduce the quality of die castings

v. dimensional stability

die casting is a precision production process, but many factors can affect the final dimensional changes of die castings. Dimensional changes can be divided into linear changes, movement between molds, parting line, casting and mold warpage, die-casting parameters, core and die inclination. It must be remembered that the final change of the part depends only in part on the mold accuracy, and the linear dimension change is caused by the following factors: the normal fluctuation of the mold temperature, the injection temperature, the cooling rate, the stress release of the casting and the mold accuracy. The above factors have nothing to do with mold design and manufacturing except mold accuracy. In order to reduce the size change of the final product, the production process must be strictly controlled

the following table shows the achievable linear dimensional tolerances provided by NADCA. For example, the casting tolerance of 1000 mm long parts is ± 1.2mm

recommended linear dimensional tolerance

VI. nozzle, runner, exhaust hole

injection system is very important for the quality of die castings. The following are the precautions for designing nozzle system:

① nozzle system must be compatible with the capacity of die casting machine, so that the mold cavity has the necessary filling time

② the nozzle can be of different geometric shapes, fan-shaped or branched. In order to prevent turbulence, the metal fluid in the nozzle should be parallel or branched

③ the nozzle shall be designed to minimize the flow distance

④ liquid metals flowing in the opposite direction should not meet in the thin-walled area

⑤ parts filled by multiple nozzles shall be filled at the same time

⑥ overflow should be used to remove oxides and residual lubricants, and heat the colder part of the mold

⑦ remove the gas generated in the mold cavity with the exhaust hole connected to the mold surface

⑧ the design of nozzle and overflow should avoid the formation of serration during secondary processing, and the consumption of building plastic materials will increase steadily

VII. Heating and cooling system

the mold maintains a relatively stable temperature range in the production process, which is conducive to the stability of product quality and production pace. At the same time, due to small fluctuations, temperature fatigue is reduced, and the service life of the mold is extended. Therefore, the heating and cooling system should be fully considered in the mold design to maintain the thermal balance of the mold. Some 3C products such as shell and laptop shell are thin-walled, so the arrangement of heating system should be considered to improve the metal flow performance

VIII. Die casting parameters

in the process of die casting production, the selection of appropriate process parameters is a prerequisite for obtaining high-quality die castings and giving full play to the maximum productivity of the die casting machine, which is the basis for the correct design of die casting mold. During die casting, there are many factors that affect the filling and forming of alloy liquid, including injection pressure, injection speed, filling time and mold temperature. These factors affect and restrict each other. Adjusting one factor will cause the corresponding process factors to change. Therefore, it is very important to correctly select the process parameters

① injection speed: due to the different wall thickness and complexity of die castings, the selection of process parameters has a wide range of changes. Compared with zinc and aluminum alloys, magnesium alloys have better fluidity and less inertia. Moreover, due to the small solidification latent heat and heat capacity of magnesium, the whole mold cavity should be filled before metal solidification. Therefore, the speed of magnesium alloy die casting is higher than that of aluminum alloy, and the punch speed of magnesium alloy die casting is about 30% faster than that of aluminum alloy, The maximum is even more than 9m/s

② build-up time: due to the small solidification latent heat of magnesium, the magnesium alloy should be built up quickly after filling the whole mold cavity to supplement the shrinkage of metal solidification in the mold cavity. Because it is meaningless to pressurize after the solidification of the inner gate, the build-up time of magnesium alloy die casting is required to be shorter than that of aluminum alloy. At present, the pressure building time of Lijin machine is within 20ms

③ mold temperature: because the solidification latent heat of magnesium ingot is small, the molten metal fills the mold cavity at a high speed and solidifies rapidly, which can not only shorten the die-casting cycle, improve production efficiency, but also reduce the thermal fatigue of the mold and greatly extend the service life of the mold. When casting magnesium alloy, the temperature of the die should be kept stable. When magnesium alloy is die cast, the mold temperature is usually kept between ℃

in the process of magnesium alloy die-casting, if the process parameters are properly designed, magnesium alloy will show better die-casting process performance than aluminum alloy

IX. mold lubrication

magnesium alloy is less prone to mold corrosion than aluminum alloy, because the content of iron in magnesium alloy is very low. However, when hot metal impacts some parts of the die at high speed, welding may occur. The use of appropriate mold lubricants can reduce this trend. The most commonly used are water-based lubricants. Since the heat capacity of magnesium alloy is only 2/3 of that of aluminum alloy, it is not necessary to use lubricant as cooling medium, and the service time should be as short as possible, generally 50% of that of aluminum alloy. In order to reduce the water content, a higher concentration of lubricant is usually used