POWDER METAL COMPONENTS

Powder metallurgy is efficient and innovative and environmentally friendly technology, where powder material is compacted in a mold and heated in controlled atmosphere, causing the materials to bond to produce finished product.

The powder metallurgy process is the blending of fine powdered materials (in this case powdered metals) and pressing these powders into a desired shape. After the desired shape has been achieved, the compressed part is heated in a controlled atmosphere, causing the material to bond.

As a powder metallurgy manufacturing company, we produce sintered metal parts of simple and complex shapes. Manufacturing powder metallurgy products in Metro Metal is the best solution to get reliable components made of ferrous and non-ferrous metals.

The Metal Sintering Process

Metro Metal’s metal sintering process, also commonly known as the powder metallurgy process, is divided into three main steps:

1. Mixing

The process starts with the mixing of powdered metals. In metal sintering, an iron-based powder mix is the initial material. Based on the properties required, alloying elements and additives are added to the mix.

Powder mixes also contain a solid lubricant. This lubricant is needed in order to reduce the friction between the powder mass and the surface of the tool used for compaction.

Mixing in the powder metallurgy process enables the creation of a uniform mixture, provides the required material properties and ensures that a minimum amount of friction occurs in the compaction stage.

2. Compaction

Normally, carbide and steel tools are used in the compaction step of the process, with the load being applied axially. The amount of powder needed is predetermined and then delivered under gravity to the tool.

A filling shoe is used to deliver the powder metal to the cavity of the die and then compacted with a force of between 400 MPa to 800MPa. After the initial compaction, the ‘green’ part formed has a density of around 85% to 95%.

This process allows for the pressing of complex parts in a single operation while maintaining a relatively high production rate – usually up to 25 parts per minute.

After being compacted, the part to be produced has its desired shape, but not yet its final dimensions. For this reason, allowances are made for shrinkage that occurs during the sintering step of the process.

Note that the compaction of powder is cable of permitting a wide range of radial aspects and design flexibility.

3. Sintering

In order for the ‘green’ part formed in the compaction step of the process to meet the required mechanical properties, parts must be sintered.

A heat treatment process, sintering is usually performed on a belt conveyor furnace in a controlled atmosphere.

Parts are now heated in the furnace to a temperature that is below the melting point of the main powdered metals used in the blending step of the process. Times for heating varies depending on the final part application, materials used and physical requirements.

During the sintering process, the powder grains of the ‘green’ part grow together through a diffusion process and bonds, resulting in an improvement in the part’s mechanical properties.

During sintering, minor shrinkage takes place (for which allowances has been taken in the compaction step), giving the part its final required dimensions. Note that the properties of the part can be adjusted by adjusting the rate at which the part is left to cool.