Introduction to metal injection molding
Metal Injection Molding (MIM) is a forming process suitable for the production of small, three-dimensional complex shapes and products with special performance requirements. This technology is a new powder metallurgy forming technology which is formed by introducing modern plastic injection molding technology into the field of powder metallurgy.
The basic process is as follows: a variety of fine metal powders (generally less than 20 μm) are combined with a binder to form a feedstock having rheological properties. The green part is formed by injection into a mold cavity through an injection machine. After removing the binder and sintering at a high temperature, various metal parts can be obtained. The flow chart is as follows:
What is the ideal MIM metal powder?
Powder particle size, tap density and particle shape are key performance indicators that determine whether a powder can be successfully used in a MIM process. The MIM process requires very fine raw material powders (~10 μm) to ensure uniform dispersion, good rheological properties and large sintering rates.
The ideal powder for MIM is: powder particle size 2 ~ 8μm; bulk density 40% ~ 50%; tap density 50% or more; powder particles are nearly spherical, larger than the surface.
At present, MIM metal powder raw materials include iron, nickel, titanium, stainless steel, precious metals, super alloys and other materials. At the same time, it is developing in diversification, such as structural materials, functional materials, magnetic materials etc.
How to choose binder for MIM ?
Binder is the core of MIM technology, and an important difference between MIM and conventional powder metallurgy is the high binder content. The primary function of the binder is to act as a carrier for the flow of bonded metal powder particles and to maintain the shape of the workpiece after molding.
The binder for MIM should meet the following requirements:
The binder has a small contact angle with the powder, strong adhesion and does not react with the powder;
The viscosity does not change much in the range of the injection temperature, but the viscosity changes quickly during cooling, and it is not easy to stick the mold;
The amount of hydrazine is small, and a relatively low amount of binder can be used to produce a better rheology of the mixture;
How is the binder classified for MIM?
A practical binder generally consists of several components, each of which has its own unique function, which can be divided into main binders, secondary binders and additives according to functions. The binder system can be classified into a thermoplastic binder, a thermosetting binder, a gel system and a water-soluble binder, and a special system according to the main binder component and its properties in the binder system.
Among them, thermoplastic binders are the most widely used, and are classified into paraffin-based binders, oil-based binders, and polymer-based binders.
Metal Injection Molding (MIM) is a forming process suitable for the production of small, three-dimensional complex shapes and products with special performance requirements. This technology is a new powder metallurgy forming technology which is formed by introducing modern plastic injection molding technology into the field of powder metallurgy.
The basic process is as follows: a variety of fine metal powders (generally less than 20 μm) are combined with a binder to form a feedstock having rheological properties. The green part is formed by injection into a mold cavity through an injection machine. After removing the binder and sintering at a high temperature, various metal parts can be obtained. The flow chart is as follows:
What is the ideal MIM metal powder?
Powder particle size, tap density and particle shape are key performance indicators that determine whether a powder can be successfully used in a MIM process. The MIM process requires very fine raw material powders (~10 μm) to ensure uniform dispersion, good rheological properties and large sintering rates.
The ideal powder for MIM is: powder particle size 2 ~ 8μm; bulk density 40% ~ 50%; tap density 50% or more; powder particles are nearly spherical, larger than the surface.
At present, MIM metal powder raw materials include iron, nickel, titanium, stainless steel, precious metals, super alloys and other materials. At the same time, it is developing in diversification, such as structural materials, functional materials, magnetic materials etc.
How to choose binder for MIM ?
Binder is the core of MIM technology, and an important difference between MIM and conventional powder metallurgy is the high binder content. The primary function of the binder is to act as a carrier for the flow of bonded metal powder particles and to maintain the shape of the workpiece after molding.
The binder for MIM should meet the following requirements:
The binder has a small contact angle with the powder, strong adhesion and does not react with the powder;
The viscosity does not change much in the range of the injection temperature, but the viscosity changes quickly during cooling, and it is not easy to stick the mold;
The amount of hydrazine is small, and a relatively low amount of binder can be used to produce a better rheology of the mixture;
How is the binder classified for MIM?
A practical binder generally consists of several components, each of which has its own unique function, which can be divided into main binders, secondary binders and additives according to functions. The binder system can be classified into a thermoplastic binder, a thermosetting binder, a gel system and a water-soluble binder, and a special system according to the main binder component and its properties in the binder system.
Among them, thermoplastic binders are the most widely used, and are classified into paraffin-based binders, oil-based binders, and polymer-based binders.