Comparison of Sintered Metal Powder Plasticizing Extrusion Molding and Injection Molding Processes

Comparison of Sintered Metal Powder Plasticizing Extrusion Molding and Injection Molding Processes

Today, powder metallurgy technology has developed into many branches and different processes, among which the two most representative processes are plasticizing extrusion molding and injection molding. Although both belong to powder metallurgy, they also have many differences. Today, let's take a look at the small tapes together.

First, let's take a look at the metal powder plasticizing extrusion process, which is a new process developed on the basis of metal powder envelope extrusion and other processes. It can be used to extrude copper, tungsten, hard alloys, high melting point intermetallic compounds, and ceramic materials with excellent fluidity at lower temperatures. At present, there are dedicated continuous extrusion equipment for this process. The material used in this process is a metal powder with excellent fluidity added with a certain amount of accelerator. The blank produced by this process can become the final product after being dried and sintered.

Let's take a look at another new metal component forming process - metal injection molding. It is a near net forming process that combines traditional powder metallurgy with modern plastic injection molding technology and relies on binder formulation development and feed production technology. It is a forming process with a long history but a slow development rate. The basic process of this process is to inject a mixture of metal powder and adhesive into a specific mold cavity under certain temperature and pressure conditions to obtain a blank that is close to the size and shape of the final product, and then debond and sinter the blank to obtain the final product with certain mechanical properties.

From the above description, it can be seen that powder plasticized extrusion molding and injection molding have many similar advantages, so in recent years both of these two processes have achieved rapid development. Their common advantages can be summarized in four points: near net forming, which can both form the blank closest to the final shape of the product at one time; Using traditional casting, machining, and other methods to prevent the formation of difficult to produce metal products, especially small and complex parts and elongated parts, has a great advantage; The range of materials available is quite wide, and some materials that are not good at preparing finished products using conventional methods can use these two methods; These two methods can be used as new research and development methods for new materials and products.

A significant common feature of both is the use of adhesives. From the perspective of the selection and formulation of adhesives, the adhesives used in both can be classified into three systems: wax based, methyl cellulose based, and plastic based, with similar amounts, all in the range of 8% to 20% mass ratio. From a technological point of view, it is necessary to thoroughly remove the adhesive after the blank is formed.

However, there are also significant differences between the two. In terms of raw materials, the metal powder used for plasticizing and extrusion molding has a relatively large particle size variation range, ranging from a few microns to several hundred microns; However, metal injection molding requires relatively high requirements for metal powders, with particle sizes typically between 0.5-20 microns. It has higher requirements for powder preparation methods and powder shape, so the formed product is more dense, with a smaller shrinkage rate during sintering, and higher dimensional accuracy.

If there is a difference between the two, the difference in the force exerted by the forming equipment and the material is another significant difference. The plasticizing extrusion molding uses a dedicated screw extrusion molding machine, where the material is subjected to deformation in both directions of compression and in one direction of extrusion and stretching, and the extrusion pressure generally does not exceed 300Mpa; In the injection molding machine used for injection molding, the material is subjected to a three-dimensional compressive stress during the molding process, and its deformation is a compression deformation of a three-dimensional force.

By comparing the similarities and differences between the two, we realize that both are the new development direction of powder metallurgy technology today, and can play an advantage in forming small size and complex shaped products of difficult to process materials. If the precision requirements are not particularly high, plasticizing extrusion molding process can be used to reduce production costs, The forming of products with high precision requirements can only be achieved through metal powder injection molding, which has strict requirements for powder particle size.