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A2 & A4 Stainless Steel Screws, Fasteners and Fixings 

Stainless steel, like many other steels, are available in a number of differing grades that can be used within screws, nuts, bolts and fasteners.

There are a number of grades of stainless steel, with A2 (304) and A4 (316) being the most popular.

There is Type 301, a highly ductile steel for formed products, which also rapidly hardens during mechanical working. Type 301 has good weldability, as well as better resistance and fatigue strength than A2.

Following that, there’s Type 302 which boasts the same corrosion resistance as A2 stainless steel, but with slightly higher strength due to additional carbon. 

Then there is Type 303, which is an easier machining version of A2 due to an addition of sulfur and phosphorus. It’s also known as “A1” in accordance to ISO 3506.

Type 309 holds a better temperature resistance than A2.

Type 321 is similar to A2, but with a lower risk of weld decay due to an addition of titanium.

There is also the 400 series, including 409, 420 and 440 as well as many more. 409 is the cheapest type within the 400 series and is used for car exhausts, whilst 420 is surgical steel and 490 is known as razor blade steel.

Stainless Steel Hex BoltA2 Stainless Steel

A2 stainless steel differs from its counterparts like standard carbon steel, due to the fact that it is an alloy, a mixture of two or more metals.

The steel must contain at least 10.5% chromium to be considered or called stainless, and this chromium makes the metal more corrosion resistant, and less likely to stain than other steels. The corrosion resistance is created by the steel forming a layer of chromium oxide.

Stainless steel can be paired with molybdenum, titanium, nickel and copper for enhanced or increased properties in areas such as strength, corrosion resistance and formability.

With fasteners often found in a number of industries, including hospitality, stainless steel is also popular for fasteners due to the low levels of distortion it provides.

A2 stainless steel is made of 18% chromium and 8% nickel and sometimes referred to as type 304.

A4 Stainless Steel

Visually, there is no discernable difference between A2 and A4 stainless steel as they are polished using the exact same process – but there are characteristics that provide a difference between the two steels.

A4 stainless steel is made of 16% chromium, 10% nickel and 2% molybdenum.

It is typically known as marine grade stainless steel due to its resistance to salt water corrosion, and can be found in a number of constructions in contact with water.

A4 is exceptionally resistant to salt spray, making it a common choice in marine and naval applications. 

It also makes the fasteners easier to fabricate, clean, finish and weld.

Whilst A4 is more expensive than A2, it can be more cost-effective over a longer period of time – especially when being used outside.

If you require more information or would like to order a product in stainless steel, please call us.

You can see all materials and finishes here.

 

Specials and non standard fixings

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Fastener Terminology Glossary

There are a number of confusing names and terms within the Fastener industry, so we have created a handy terminology glossary to help.

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