Manufacturing
An iron-based powder mix is the initial material for manufacturing of sintered components. Properties of the final component can be easily tailored by using different alloying elements and other additives. The powder mix also contains a solid lubricant, which is primarily added to reduce friction between the powder mass and surfaces of the compaction tool.
The most common compaction method is axial pressing in a steel or carbide die, usually under pressures of 400-800 MPa. It is possible to press parts with complicated shapes in a single operation and with a high production rate, up to 25 parts per minute. The part receives its predetermined shape after compaction, but not its final dimensions.
Sintering is a heat treatment from which the pressed parts gain strength. The parts are heated in a controlled atmosphere to a temperature that is below the melting point of the main metal. For iron-based alloys this is usually at 1100-1150 °C, for between 15 and 60 minutes, depending on the application. The main mechanisms of sintering are surface and volume diffusion.
The parts are transported on a belt through three furnace zones; dewaxing, where the lubricant is burned off, sintering and cooling. During sintering, a minor dimensional change takes place, which gives the component its final dimensions. Properties of the component can be steered by changing the cooling rate. |
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Various optional post-sintering process steps are available for sintered components. Hardening operations, for example, are carried out in the same way as for conventional steel, so all treatments applicable to a given alloy are also applicable for sintered material.
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