SS 304 Chemical Composition and Uses

Since its very inception, stainless steel has been one of the most important substances that are used in umpteen manufacturing processes and construction works. Amongst stainless steel, one of the most versatile types of stainless steel is the stainless steel 304 (SS 304). It is made up of 18% chromium and 8% nickel, which gives it its characteristic stainless look and helps to resist corrosion. Wish to know more? Sigma Steel Pipes, one of the leading steel pipes suppliers of India, is here with anything and everything that you need to know about SS 304.

Composition of SS 304

Stainless Steel 304 is made up of 18% chromium and 8% nickel, which gives it its characteristic stainless look and helps to resist corrosion. In addition, stainless steel 304 contains smaller amounts of carbon and manganese than other types of steel, making it relatively easy to work with. This blog post will provide an overview of the properties and uses of stainless steel 304.

Why is SS 304 preferred?

Stainless steel 304 is preferred because of a lot of reasons. These include:

• Grading

Stainless steel 304 is an austenitic grade – a molecular structure made from the iron-chromium-nickel alloy blend – that can be severely deep drawn.

• Corrosion Resistant

304 has excellent corrosion resistance in many environments and when in contact with different corrosive media. Pitting and crevice corrosion can occur in environments containing chlorides. Stress corrosion cracking can occur above 60°C.

• Heat Resistance

304 has good resistance to oxidation in intermittent service up to 870°C and in continuous service to 925°C. However, continuous use at 425- 860°C is not recommended. In this instance, 304L is recommended due to its resistance to carbide precipitation. Where high strength is required at temperatures above 500°C and up to 800°C grade 304H is recommended. This material will retain aqueous corrosion resistance.

• Fabrication

Fabrication of all stainless steel should be done only with tools dedicated to stainless steel materials. Tooling and work surfaces must be thoroughly cleaned before use. These precautions are necessary to avoid cross-contamination of stainless steel by easily corroded metals that may discolor the surface of the fabricated product.

• Machinability

304 has good machinability. Machining can be enhanced by using the following rules: Cutting edges must be kept sharp. Dull edges cause excess work hardening. Cuts should be light but deep enough to prevent work hardening by riding on the surface of the material. Chip breakers should be employed to assist in ensuring the swarf remains clear of the work. The low thermal conductivity of austenitic alloys results in heat concentrating at the cutting edges. This means coolants and lubricants are necessary and must be used in large quantities.

• Weldability

Fusion welding performance for type 304 stainless steel is excellent both with and without fillers. Recommended filler rods and electrodes for stainless steel 304 are grade 308 stainless steel. For 304L the recommended filler is 308L. Heavy welded sections may require post-weld annealing. This step is not required for 304L. Grade 321 may be used if post-weld heat treatment is not possible.

Various types of SS 304

SS 304 is of many types. However, major ones include the Stainless Steel 304L and the Stainless Steel 304H.

The 304L alloy is the low-carbon version of 304. Because of its improved weldability, it is extensively used in heavy gauge components. In certain cases, some plates and pipes may be available as “dual certified” material that meets the criteria for both 304 and 304L. Grade 304L does not require post-weld annealing because the low carbon percentages increase ductility. 304L is also known as 1.4307.

304H, a high carbon content variant, is commonly used in applications at high temperatures. The increased carbon content helps preserve its strength while heated.
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