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Metal injection molding vacuum sintering furnace
With the latest iPhones, small high-performance car engines, gearboxes or other machinery, there is a demand for system miniaturization, and the public is looking forward to more economical production techniques. Specifically, in notebook computers and mobile phones, many precision parts are used, and if these parts use complex MIM parts, the assembly cost can be reduced.
After 20 to 30 years of development, there are more and more types of materials (metal injection molding, MIM) for complex MIM (ie “metal powder injection molding”) products, which are widely used in different industries. The high material properties brought about by the improvement of MIM process technology and integration make high-quality parts put forward higher requirements for the accuracy of dimensional tolerances, which are increasing year by year.
Intense market competition and technical limitations have forced parts manufacturers to find ways to reduce costs. Technological optimization, advancement to reduce the cost of production equipment, and optimization of material selection are the key factors driving the rapid growth of the MIM industry.
In addition to the purchase cost of expensive raw materials (particulate metal powder, polymer binder, etc.), high temperature sintering is one of the main costs of the MIM process. Therefore, the selection of excellent brand degreasing furnace and sintering furnace equipment is the key to increase the market competitiveness of MIM production.
MIM sintering furnace type:
The MIM sintering furnaces that appear on the market are mainly divided into vacuum batch furnaces and atmosphere continuous furnaces. Both furnace types can remove the MIM product during the molding process by heating the product in the furnace, as well as dissolve the residual polymer after degreasing.
Manufacturers of MIM materials with similar surface shapes of parts after mass production are suitable for the use of continuous atmosphere furnaces. In the case of short-cycle high-density sintering, the cost is relatively low. If the annual output is 150-200 tons of small and medium-scale production, the continuous atmosphere furnace is not economical, and the equipment needs to be shut down for a long time during maintenance, and the production flexibility is poor.
Using a vacuum sintering furnace, the investment is small and the production flexibility is high. It is more beneficial to produce products with different shapes and sizes and materials with different characteristics for large changes in orders. The production line composed of multiple vacuum furnaces not only has stable output but also leaves room for production switching. Different production processes (heated temperature curves) can be used for production at the same time. In addition, vacuum furnaces can produce better temperature distribution in the furnace, with high temperature uniformity, which can produce high-quality products. For some high-quality products (such as medical use), in addition to the high cleanliness of the atmosphere gas, the process and parameter adjustment functions of the equipment are also required. It is also necessary to reduce the vibration of the product when the product is sintered. Therefore, only vacuum can be used. Sintering furnace.
Structure of vacuum sintering furnace
The basic structure of the furnace body is as follows: the metal furnace shell is made of double-layer water-cooled stainless steel material, and the built-in circulating water is cooled to ensure that the heater, insulation material and heating chamber have uniform and sufficient heat resistance. The graphite heating element is distributed around the heating chamber to provide the most suitable heating power to the product evenly. The front door and the rear of the furnace body are provided with heating zones to ensure the temperature uniformity of the front and rear ends of the furnace body. The thermal insulation lining of the furnace body consists of several layers of graphite felts.
Gas purging function in the furnace: evenly flushed process gas flows from the outside of the heating chamber to the inside of the heating chamber, which can effectively prevent the adhesive from evaporating and adhering to the product again, which can also prevent impurities from adhering to the heating chamber. And contaminate the furnace.
(1) Economy of vacuum sintering furnace
A key consideration for vacuum sintering furnaces for the production of MIM materials is the economical use of process gas and electricity. The two kinetic energies (process gas and electricity) used in the sintering process account for more than 50% of the total cost. In the process of degreasing and sintering without impurities, the gas with the minimum flow rate must be used to achieve the partial pressure adjustment function in the furnace, so as to meet the requirements of nitrogen and hydrogen ratio and extremely low oxygen content in the furnace.
(2) Removal of binder
During the sintering process of MIM products, the sintering furnace and auxiliary equipment (such as gas outlet, pump specifications, heating chamber, etc.) will adhere to the products in the furnace and volatilize the binder. The adhesion amount of the binder varies according to the different loading amount of the product in the furnace and the content rate of the brown polymer remaining after the product is sintered. The amount of cleaning this adhesion is relatively large, which shortens the cleaning and maintenance of the equipment. The time of maintenance work has a great influence.
In order to achieve long-term sustainable management of equipment and reduce the workload of equipment maintenance, it is necessary to set up a pipe debinding system that can effectively protect important components in the furnace.
On the latest vacuum MIM furnaces, a gas split system and a binder separation system are installed. Efficient exhaust air inside the heating chamber is achieved by a powerful pump unit consisting of a rotary pump and a mechanical pump. The high-speed flow of process cleaning gas at high temperature, after the absorbed and evaporated binder is saturated, is discharged through the piping below the furnace body. When flowing through the cooling pipe, the binder in the vaporized state is rapidly cooled, and a part of the binder is condensed. As a result, 20% to 25% of the adhesive gradually sticks in the pipeline, accumulates gradually, and is finally collected in the pipeline, and then the colloid accumulated in the pipeline is discharged by the screw motor (plunger).
By applying alternating cooling and heating, the binder can be further coagulated and removed. The water-cooled two-section pipe can not only condense the adhesive, but also solidify the condensate. The heating coil wound on the pipe can soften the solidified adhesive before the plunger is cleaned, and accelerate the discharge of the adhesive.
After passing through this horizontally arranged pipeline, the gas still contains about 75% binder. In order to protect the product from damage in a safe and economical way and to obtain a wide range of cleaning, a special filtration system is required in the upper part (in front of the pump). With reference to the binder used and various process parameters, the filtration system is equipped with a three-layer exhaust gas capture device: the first stage captures heavy particles, passes through a large filter surface area, and condense volatile substances and liquids; the second and third stages, with Two parallel filter elements remove aggressive chemicals and fine particles. The setting rate of the binder in the first stage is controlled with water and a cooling agent. With modular design, the equipment can be easily disassembled, and the operation of replacing the filter element is simple and quick. When multiple filters are configured together, the filtration capacity can be increased when installed in parallel, and multi-stage filtration can be achieved when directly connected in series, so as to obtain cleaner exhaust.
Selection of vacuum heat treatment equipment: The RVS vacuum sintering furnace provided by SIMUWU is a high-quality product for processing MIM process. It has the characteristics of good temperature uniformity, high temperature control accuracy, and efficient glue removal system. SIMUWU specializes in the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries. SIMUWU provides a professional team of engineers who can solve various problems encountered in the production process and are committed to giving customers the most convenient and efficient experience.
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