What is the Difference Between A2 & A4 Stainless Steel
Stainless steel comes in different varieties, commonly referred to as grades. The most common grades that we come across in the fasteners industry are called A2 and A4.
The key differences (and similarities) are;
A2 STAINLESS STEEL
A2 stainless steel is often referred to as 304 or 18/8 Stainless. 18/8 refers to 18% chromium and 8% nickel content in the alloy. A2 stainless is the most common type used for the manufacture of fasteners and is suitable for general use.
A4 STAINLESS STEEL
A4 Stainless is often referred to as 316 or 18/10 stainless. As in A2 above, the numbers 18/10 refer to the chromium and nickel content- 18% chromium and 10% nickel.
A4 stainless is often used in harsh marine or chemical environments as it has greater corrosion resistance than A2, hence the term "marine grade".
The chemical composition of both A2 and A4 stainless steel are almost identical with the most notable differences being the higher nickel content and the addition of Molybdenum in A4. Molybdenum is a silvery white metal that is highly corrosion resistant, very ductile and has an extremely high melting point.
Typically, A4 grade stainless steel costs slightly more than A2 because of its enhanced chemical and production properties. The extra cost can be justified, however, because hardware made of A4 stainless steel is extra resistant to tarnish and corrosion, enabling it to last a very long time.
A4 grade fixings and fasteners offer excellent corrosion resistance. They are the standard choice for many applications in the construction, automotive, marine and engineering sectors.
COMMON PROPERTIES
Both A2 and A4 grades are classed as Austenitic stainless steel (sometimes called the 300 series). This means that they have high chemical resistance but cannot be hardened by heat treatment. They can be hardened by cold working.
Both A2 and A4 stainless steels are mostly non-magnetic although some magnetism can be induced by the cold working process, this is more noticeable in smaller items.