Fastener SuperStore carries a wide range of 300 Series & 400 Series Stainless Steel products. The primary differences between the two involve corrosion resistance vs. hardness. 300 Series Stainless Products are classified as austenitic and provide stronger corrosion resistance, while 400 Series Stainless Products are classified as martensitic, and offer greater hardness and strength.

Here is a breakdown on what makes each type unique.

300 Series Stainless Steel

300 Series Stainless Steels are non-magnetic. They generally contain between 18% - 30% chromium & 6% - 20% nickel. 300 Series is the most commonly used type of stainless steel. We carry 300 Series products in the three specific grades below.

303 Stainless Steel

Good resistance to mildly corrosive atmospheres, but less resistant than Grade 304 (18-8), due to the addition of sulfur. The sulfur improves the machinability of parts created with 303 stainless. Not recommended for marine or other wet environments, as these will result in rapid pitting corrosion. Commonly used in parts for electronics.

304 Stainless Steel , also known as
18-8 Stainless Steel, also known as
A2 Stainless Steel (when referencing metric products)

The most common type of stainless steel worldwide, 304 / 18-8 / A2 offers excellent corrosion resistance (better than 303 and 400 Series), and high tensile strength. It contains at least 18% chromium and 8% nickel, as well as small amounts of carbon and manganese. It is not hardened, however, making 410 Stainless a better option for some applications, such as self-drilling screws being used in metals.

316 Stainless Steel, also known as
A4 Stainless Steel (when referencing metric products)

Often referred to as "Marine Grade", 316 Stainless is differentiated from other 300 Series grades by the addition of 2% - 3% molybdenum, an element that is extremely corrosion resistant. It also provides high tensile strength. It is second to 304 as the most common austenitic stainless steel grade.


400 Series Stainless Steel

400 Series Stainless Steels are magnetic. The grades that we carry are typically made of 11.5% - 14% chromium and 1% manganese, along with carbon, phosphorus, sulfur, silicon and nickel. They provide less corrosion resistance but significantly more hardness and strength than other types of stainless steel. We carry 400 Series products in the two specific grades below.

410 Stainless Steel

Because of its additional hardness, 410 is commonly used for self-drilling screws, particularly when they are being installed into other metals. (18-8 stainless self-drilling screws are suitable for wood installations but can deform or break under the pressure of going into another metal material.)

420 Stainless Steel

A slight modification to 410 stainless, 420 stainless contains higher carbon levels and is capable of being hardened to a greater strength than other varieties of stainless steel, including 410.

See below for links to categories offering each of the types of stainless steel.

Parts available in 420 Stainless Steel