Sintered steel is a type of metal that has undergone a sintering process, in which powdered metal is heated below its melting point until the particles form a molecular bond. Metals such as iron, copper, and aluminum are commonly turned into sintered steel. Sintered steels normally possess resistance to high temperature and slow deformation rate.
There are three main stages in producing sintered steel: powdering, molding, and compacting. The first step involves turning steel ore into powder. Grinding, atomization, chemical reaction, and centrifugal disintegration are four ways of producing metal powder.
The powder is transferred into a mold press. Metal products with intricate shapes and details can be manufactured more efficiently with this method because the particles conform to the mold better. The mold is then pressurized and compacted. Heat is added to fuse the particles. In some cases, the sintered metal may be re-pressed to reduce porosity.
Although easy to shape, sintered steel can be difficult to machine. The uneven particles create an abrasive surface that accelerates the wear on machining tools. To increase machinability, additives like phosphorous, sulfur, and tellurium are mixed with the base metal to create a smoother surface.
Unlike traditional metallurgy, where steel is melted into a more or less liquid state before being shaped, sintered steel is forged while still in a powdered form. By not having to be melted, several phases are eliminated from the conventional process. This reduces manufacturing time, which can be crucial for high volume production.
A relatively low temperature is needed to sinter steel. As a result, tungsten and other metals with high melting temperatures are frequently turned into sintered steel. Metals that do not easily alloy from melting can be combined through sintering. Titanium carbide, a tough metal used in machining tips and spacecraft exteriors, is manufactured using this method.
Gaps between the particles created during sintering increase the steel's porosity. This attribute allows for the production of sintered stainless steel filters, which can be used to filter air and chemicals. Moreover, since sintered stainless steel can withstand tremendous heat, it is often applied in environments under extreme conditions.
In motorcycles, sintered copper steel is regularly used as a brake pad component. It provides relatively more stopping power and heat resistance compared to organic brake pads. The ability to remain durable after repeated breaking has made it popular among motorcycle enthusiasts. Ball bearings made from sintered steel are often found in industrial machines. Spaces inside the bearings retain liquid, which help keep them properly lubricated.