In recent years, the demand for lightweight materials is increasing, magnesium alloy as a structural material because of its small specific gravity, high specific strength and stiffness, good thermal and electrical conductivity, good machinability, excellent damping and electromagnetic shielding, easy to process and shape and recycling, so widely used in automotive, electronics, communications and other industries, known as the “21st century green engineering materials”. It is widely used in automotive, electronics, communication and other industries.
in short, how many magnesium alloy manufacturing process method exist on industry? today let’s discuss more, keep reading.
Magnesium alloys Stages
Mg alloy materials in the liquid, solid and semi-solid stages all show significantly different physical properties, the use of these characteristics, the generation of solidification processing, plastic processing and semi-solid processing and a variety of metal thermal processing forming methods
|Material||Manufacturing Process Methods|
|Casting Magnesium Alloy||Die Casting, Sand Casting, Investment Casting,Gravity Die Casting|
|Deform Magnesium Alloy||For plastic processing (rolling, forging, extrusion, stamping)|
For magnesium alloy, the forming process can be mainly divided into liquid forming process and solid forming process. The liquid forming mainly includes gravity die casting, low pressure die casting, high pressure die casting, semi-solid casting, etc. Solid state forming is also called plastic processing forming, including extrusion, forging, rolling, etc.
Liquid molding process
Gravity Die Casting
Magnesium alloy can be produced by different gravity casting methods, such as sand casting, fusion casting, metal mold casting, semi-metal mold casting, shell casting, etc.. Among them, sand casting of magnesium alloy has gone through the development stage of common clay sand, water glass sand and self-hardening resin sand. The use of self-hardening resin sand molding core making process can improve the quality of castings, simplify the process procedures, is conducive to the realization of mechanized automation of production and improve mold life, and reduce harmful gases, is the direction of large and complex castings towards precision. Investment casting, also known as lost wax method, is usually coated with several layers of refractory materials on the surface of the wax mold, and after it hardens and dries, the wax mold will be melted away and made into a shell, then roasted, and then poured, and the castings are obtained. Because the obtained casting has high dimensional accuracy and surface finish, it is also called “investment casting”.
Low pressure Die casting
Magnesium alloy generally has small heat capacity, large solidification interval, easy to produce cracks, uneven filling, segregation and coarse organization and other casting defects, and it is difficult to produce large, thin-walled or complex structure of the casting. The use of low-pressure casting smooth filling and sequential solidification characteristics can produce high-quality magnesium alloy castings.
Die casting is the main and most widely used forming process for magnesium alloy. Magnesium alloy has excellent die-casting process performance: magnesium alloy liquid viscosity is low, good fluidity, easy to fill the complex cavity. Here you can find Magnesium alloy die casting.
Lost Foat casting
Lost Foam casting is a nearly no margin, precise molding of new casting technology, it has many advantages, such as, the sand does not need binder, castings and sand disposal system is very simple, easy to achieve clean production; castings without parting surface and draft angle, can make the structure of the casting high; processing and assembly time is reduced, casting costs can be reduced by 10%-30%, etc..
Preliminary experimental research shows that the characteristics of magnesium alloy is very suitable for Lost Foam casting process, because the magnesium alloy Lost foam casting in addition to the above characteristics, but also has the following unique advantages.
① magnesium alloy in the pouring temperature, foam mold sample decomposition products are mainly hydrocarbons, benzene and styrene and other aerosol substances, they have a natural protective effect on the liquid magnesium alloy that is highly susceptible to oxidation during the punch molding;
②The use of dry sand negative pressure molding to avoid the contact between the magnesium alloy liquid and the moisture in the sand and the resulting casting defects;
③Compared with the currently commonly used magnesium alloy die-casting process, its investment costs are greatly reduced, dry sand good yielding to reduce the tendency of thermal cracking when the magnesium alloy solidification shrinkage; metal liquid slower and smooth filling speed to avoid the involvement of gas, so that the casting can be heat treatment to further improve its mechanical properties. Therefore, Lost foam casting of magnesium alloy has a great prospect of application.
Semi-solid forming is a new, advanced process method, compared with the traditional liquid forming, has the advantages of low forming temperature, long mold life, improved production conditions and environment, refining grain, reducing porosity, loosening shrinkage, improving tissue denseness, and improving the quality of castings.
Semi-solid forming can be divided into rheoforming and thixoforming. At present, in the preparation of semi-solid slurry, domestic and foreign scholars have invented different preparation processes, all aiming to obtain the ideal semi-solid tissue with fine, rounded primary particles uniformly suspended in the liquid phase, and then combine different processes for forming to give full play to the advantages of semi-solid forming. Among them, semi-solid thixoforming injection molding is the most mature, with the advantages of simple process, high degree of automation, has been widely used in the production of magnesium alloy.
Solid state forming process
Magnesium alloy plasticity is poor, suitable for extrusion molding, generally for warm extrusion and hot extrusion, extrusion temperature is usually 300 ~ 450 ℃. Magnesium alloy extrusion has the following advantages: can refine the grain, by retaining the extrusion fiber structure can improve the strength, can obtain excellent surface quality and good dimensional accuracy. At present, magnesium alloy tube, bar, profile, strip and other products are mainly used in extrusion forming. But magnesium alloy extrusion also exists extrusion speed is slow, deformation resistance, extrusion processing due to the formation of weave structure caused by the anisotropy of material mechanical properties and other disadvantages.
Magnesium alloy forging generally has two ways: free forging and die forging. Commonly used to forge magnesium alloys are ZK series and AZ series magnesium alloy. The mechanical properties of magnesium alloy forgings usually depends on the degree of strain hardening produced during the forging process. The lower the forging temperature, the more significant the strain hardening effect, however, the forgings are prone to cracking when the temperature is too low, and oxidation is severe when it is too high. A new technology developed on the traditional forging process, precision forging, can form high-precision, complex-shaped forgings with flow lines distributed along the geometry of the forging, while increasing the load-bearing capacity of the forgings. In addition, magnesium alloy forging temperature range is narrow, the thermal conductivity is twice that of steel, contact die cooling fast, easy to lead to plasticity reduction, deformation resistance increases, filling performance decreases, so suitable for isothermal forging forming. Precision stamping and forging forming technology is a new process that combines stamping forming and forging forming, which is a promising process applicable to magnesium alloy forming. Mainly heated magnesium alloy billet in the heating die for stamping and forging, using ordinary mechanical forging machine tools can be, its technical key is the forming die and forming process design, and die temperature, deformation rate and deformation speed and other parameters control. Compared with die-casting and semi-solid forming process, this technology has the advantages of high production efficiency, high yield and low cost.
Strip and plate of magnesium alloy is generally produced by rolling forming method. Rolling process can refine the grain, improve the organization of magnesium alloy, significantly improve the mechanical properties of magnesium alloy. Rolling temperature is the key parameter in the rolling process of magnesium alloy. If the rolling temperature is too low, the high stress concentration can lead to twin nucleation and shear fracture; if the rolling temperature is too high, the grains can easily grow and make the plate more hot and brittle.
What is the most popular fabrication process applied to magnesium alloys?
Hot Chamber Die Casting and Gravity die Casting are the most popular Fabrication process for Mg alloys; Because of the advantages of magnesium alloy, so now there are constantly new processes, gradually more and more lightweight products also have the use of magnesium alloy.