Introduction

Stainless steel contain Chromium as the principle alloying element other than ferrous. Chromium in the presence of oxygen forms a thin layer around the metal, thus shielding it from outside environment. Stainless steels contain a minimum of 10.5% Chromium. There are over 150+ grades of stainless steel which are divided into 5 types based on internal structure of the metal at room temperature. Austenitic, Ferritic, Martensitic, Duplex and Precipitation hardened are the 5 types of stainless steels. Austenitic grades constitute roughly 70% of the total consumption of stainless steel. Austenitic stainless steels have BCC (Body-Centered Cubic) structure and are non-magnetic. This grade of stainless steel cannot be hardened by heat treatment but can be work hardened. AISI 304 is one of the most versatile grades within the austenitic grades. The grade finds applications in a variety of industries due to its excellent properties.

Composition

AISI 304 is also known as 18/8 Stainless steel. This name has been derived from the composition of Chromium and Nickel elements present in the alloy. Nickel amounts to about 8% and Chromium accounts for about 18%. A few suffixes used with 304 stainless steel with the major alterations in chemical composition are shown in below table-

Properties of 304/304L

Chemical Properties (as per Standard EN 10088-3:2014)

Mechanical Properties (as per Standard EN 10088-3:2014)

Characteristics

Strengths

• The grade has excellent forming characteristics. It can be drawn without any intermediate heat-softening process.
• It has good retention of properties especially toughness at cryogenic temperatures
• No post weld annealing is required to restore the corrosion resistance in most of the cases. The low carbon 304L grade can be used where carbide precipitation needs to be kept low.
• The grade offers good resistance to most of the oxidising acids and is easy to clean and sterilise.

Weakness

• Machinability of 304 is inferior to carbon steels. It is readily machined provided slower speeds and high feed rates with cutting fluids are used.
• 304 is susceptible to stress corrosion cracking. It has inferior corrosion in chloride and saline environments. Chloride ions cause localised pitting corrosion which compromises structural rigidity of the product.

Applications

• Kitchen sinks, consumer durables
• Chemical containers, including for transport
• Food processing equipment, particularly in beer brewing, milk processing, and wine making
• Fasteners and flange manufacturing
• Architectural applications such as roofing and cladding, doors and windows
• Automotive and aerospace components
• Heat exchangers

Other Trade names of AISI 304 & 304L

About Ambica Steels Limited

Ambica Steels Limited is one of the leading manufacturers of Stainless Steel in India. The company has over 5 decades of experience in stainless steel manufacturing and currently caters to customers across 6 continents.

Below is a size chart for the products offered by the company-

About Author

Aniruddha Bauskar is responsible for New Business Development and Sales at Ambica Steels Limited. He likes reading and writing articles on various industries including Steel, Automobile and FMCG. You can find him on LinkedIn.