Please send us your inquiry about the customization of other furnace types or related questions about vacuum furnace. We will reply you immediately. Thank you.
Downloads
All documents in the overview
News & Press
All news at a glance
Request
Send us a message
Email: contact@vacfurnace.com
Tel : +86-21-50878190
Wechat : 2210154395
Address: NO.1299, XinJinQiao Road, Pudong New Area, Shanghai, China.
MIM metal powder injection molding
Analysis of common defects in metal powder injection molding (MIM)
Metal powder injection molding (MIM) is a new molding technology developed by the combination of powder metallurgy and polymer injection molding, which is a molding method of injecting the plasticized mixture of binder and metal powder into a specific mold.Especially suitable for mass production of small, complex shape and large amount of metal products, especially complex structure, small volume, special requirements of precision metal parts, difficult to use traditional processing means and high processing cost, metal powder injection molding can reduce the processing cost.
The production process of metal powder injection molding (MIM) products is as follows: powder + binder → mixing → granulating → injection molding → degreasing (MIM degreasing furnace) → sintering (MIM sintering furnace) → subsequent treatment → forming products.
In the process of producing MIM cemented carbide parts, improper material selection and operation control in any link may cause cemented carbide parts to cause defects, so how to avoid such defects?
1. Powder selection.MIM cemented carbide powder metallurgy not only needs to meet the basic requirements of particle size distribution and particle size, but also requires a high purity of powder, and cannot choose powder containing impurities. If the powder contains sulfur, phosphorus, silicon and other elements, these substances will form pores in the sintering process, resulting in product defects.
2. Feeding production process.Cemented carbide powder mixing at the appropriate binder, mixed with cemented carbide powder and binder mix, mixing process, must strictly control the temperature to avoid caking agent, the condition of uneven distribution of volatile and make the mixture made after feeding has good rheological properties and viscosity value, avoid the defects in the later part.
3. Forming green parts.This is also a key link in the production of cemented carbide parts. To avoid product defects, it is necessary to pay attention to the reasonable control of mold temperature, feeding amount, injection pressure, pressure holding time, and injection speed during the injection process, so as to effectively avoid the occurrence of defects in the injection of fresh green.
4. Degreasing.The degreasing of cemented carbide green, in the degreasing process, if the degreasing furnace heating rate is too fast, will cause the crack defects of cemented carbide parts, can be used to degrease the method of heating step by step.
5. Sintering process.The density of cemented carbide is high, and the product is easy to be deformed due to its gravity during liquid phase sintering.Suitable supporting devices can be used. For larger products, materials with similar shrinkage rate can be selected as the supporting plate. In addition, the time of liquid phase sintering should be shortened as much as possible.
The common defects of metal powder injection parts are as follows.
1. Undernote: Undernote refers to the incomplete injection products caused by insufficient pressure of the injection molding machine or poor fluidity of the injection materials, etc., which fail to fill the entire mold cavity.The causes of insufficient injection are poor material fluidity, too small product wall thickness, too low mold temperature and too short injection time, which can be solved by measures such as improving material fluidity or changing materials, increasing wall thickness, increasing mold temperature, increasing injection pressure and extending injection time.
2. Weld mark: the material is divided into several flows in the mold cavity during the injection process and then merged together. There may be linear marks at the confluence, that is, the weld mark, which affects the appearance quality and even mechanical strength of the product.The causes of weld mark are too low injection pressure, too slow injection speed, too low material temperature and too many flowing parts. Measures such as increasing injection pressure, speeding up injection speed, increasing material temperature and mould temperature, and appropriately reducing diverging can be taken to solve the problem.
3. Air cavitation.In the process of injection, the air in the mold cavity has no time to be discharged, so it is wrapped by the material or compressed into the inner wall of the mold to form air cavitation, causing underinjection on the surface of the product, affecting the appearance quality and even mechanical strength of the product.The original cavitation is caused by bad exhaust, improper gate position, too fast injection speed and too large change in product thickness, which can be solved by measures such as adding vent or deepening vent, changing gate position, appropriately slowing down injection speed, extending pressure holding time and avoiding sharp change in product thickness.
4. Deformation.Deformation refers to the bending or distortion of molded products after cooling, which directly affects the appearance and dimension accuracy of the products, and even causes the products to be scrapped.The causes of deformation are uneven cooling, too hot and premature jacking, too thin and unreasonable structure, and internal residual stress of the product, which can be solved by measures such as uniform cooling of mold channel, prolongation of holding time and timely jacking out of the product, improvement of wall thickness and structural design of the product, and improvement of forming conditions.
Metal powder injection molding (MIM) can form cemented carbide products with complex shapes. With the problem of defect control solved, the improvement of MIM technology gradually expands the application scope of cemented carbide, greatly promoting the development of the whole cemented carbide industry.
The most important parts of the MIM production line are feeding, injection machines, and the selection of degreasing and vacuum sintering furnaces.
SIMUWU catalytic degreasing furnace USES nitric acid or oxalic acid to remove POM by the degreasing method of nitrogen atmosphere charging and washing, which is safe and reliable. Compared with solvent degreasing, it has the advantages of larger yield and smaller performance.
The following are the degreasing furnace specifications of different specifications:
In addition, the SIMUWU vacuum sintering furnace has nitrogen, argon and hydrogen gas in different atmospheres, which can be customized according to different processes.
The use temperature of MIM sintering generally does not exceed 1300℃, and the equipment with the highest temperature of 1400℃ can be designed.Or customize SIMUWU standard RVS-M series vacuum debinding and sintering furnace.
dimension
(mm)
(C)
pressure
(Pa)
rising rate
(pa/h)
uniformity
(C)
capacity
(kg)
Copyright: SIMUWU Vacuum Furnace
Related products:
MIM sintering Furnace
Catalytic debinding furnace
Vacuum debinding&sintering furnace