Stainless steels are materials of primary importance in precision machining. Characterised by exceptional corrosion resistance, they are ideal for highly reliable components, especially where aggressive agents such as acids, bases and salts are involved. In this article we explore the different types of stainless steel used in precision machining and the main production processes associated with them.
Stainless steels: an overview of the most common grades
Stainless steels are alloys based on iron, chromium and other elements, including nickel and molybdenum. Their key feature is corrosion resistance, thanks to a passive layer of chromium oxide that forms on the surface. This is why stainless steels are widely used in many sectors, from the food industry to chemical, medical and aerospace.
The stainless steels most used in precision machining include:
- AISI 304: the most common austenitic stainless steel, known for its ductility, formability and weldability. It is used for pipes, valves, components for chemical and food plants and many general applications.
- AISI 303: more machinable than AISI 304, it is used for mechanical parts requiring high precision, such as gears.
- AISI 316: thanks to its high corrosion resistance, even in marine and saline environments, AISI 316 is used in critical applications such as components for the chemical, oil and shipbuilding industries.
- AISI 420: known for its hardness and wear resistance, this martensitic stainless steel is used for blades, knives and other cutting tools.
- AISI 431: although difficult to machine, AISI 431 is used for components requiring high resistance to corrosion and fatigue, such as springs.
Production processes: from raw material to finished product
Stainless steel is produced through several stages, including:
- Forging: hot plastic deformation shapes the metal into the required form.
- Casting: molten metal is poured into moulds to obtain the shape of the component.
- Rolling: the metal is rolled to the required shape and thickness.
- Extrusion: the metal is extruded through a die to produce profiles of different shapes.
The most suitable process depends on several factors, including the shape of the component, the desired material properties and the production quantities required.