The number and representation of stainless steel

Stainless steel is a metal alloy that is composed mainly of chromium,manganese and iron according to the British Stainless Steel Association.Common stainless steel alloys have at least 10.5 percent chromium.The composition and properties of stainless steel can vary and there are different types such as ferritic,martensitic,austenitic and duplex,all with different designations.

Stainless steel numbers are assigned so that you can compare different types of alloys.The numbers for stainless steel are assigned using the Unified Numbering System,or UNS.This system was originally developed by ASTM International,formerly known as the American Society for Testing and Materials.ASTM currently oversees the system and provides a numbering scheme to identify different types and grades of alloys.

The UNS system consists of four digits,which are followed by a letter in some cases.The first two digits refer to the group to which the material belongs.For stainless steel,the range is 01 to 13,with most falling in the 02,03 and 04 groups.The third digit describes the subgroup for the specific alloy and the fourth digit is information about the individual alloy.This tells you the chemistry,properties or assembly of the alloy.

For example,the stainless steel alloy 31803 is designated with a UNS of S31,803.The first two digits,31,mean the alloy is part of the 300 series stainless steel group.The third digit,8,is the subgroup and the fourth digit,03,means the specific alloy makeup.Other commonly used stainless steel alloys include 304,302,410 and 430.Their UNS designation numbers are S30400,S30200,S41000 and S43000,respectively.

The UNS system also includes other alloys such as carbon steels,tool steels,casting alloys and high temperature alloys such as cobalt,nickel,titanium and aluminum.For example,the cobalt-base alloy MAR-M-247 has been assigned the UNS number N06002 which means the material belongs to the Nickel-Base Superalloys group and the alloy MAR-M-247 is the specific alloy.

The UNS system makes it easy to compare and identify alloys.When ordering materials from a supplier,it is important to provide the correct UNS number so you will receive the correct alloy with the correct properties.Knowing the composition of stainless steel,how it is classified and the UNS numbering system will help you to make informed comparisons and ordering decisions.

Stainless steel is an alloy of iron, chromium and other metals, with a minimum of 10.5% chromium content It is highly resistant to corrosion and oxidation.

Stainless steel is usually classified by its composition. The most common classification is the AISI (American Iron and Steel Institute) system, which divides stainless steel into five major categories:

1. Austenitic stainless steel (300 series)

2. Ferritic stainless steel (400 series)

3. Martensitic stainless steel (400 series)

4. Duplex stainless steel (200 and 300 series)

5. Precipitation-hardened (PH) stainless steel (400 series)

Each of these categories is identified by a 4-digit number, followed by a letter (E, F or T) which indicates its heat treatment.

Austenitic stainless steel, also known as 300-series stainless steel, is the most common type of stainless steel. It is characterized by its good weldability, corrosion resistance and ductility. Austenitic stainless steel is commonly identified with the numbers 304, 316 or 317 and is denoted by an E for heat treatment.

Ferritic stainless steel (400 series) is less ductile than austenitic stainless steel and is mostly used in applications that require high corrosion resistance. Ferritic stainless steel is identified with the numbers 409, 430, 439 and is denoted by an F for heat treatment.

Martensitic stainless steel (400 series) is a hard, strong and tough stainless steel. It is characterized by its higher carbon content, which increases its strength and hardness. Martensitic stainless steel is commonly identified with the numbers 410, 420, 430 and is denoted by a T for heat treatment.

Duplex stainless steel is a combination of austenitic and ferritic stainless steel, which provides the best of both materials properties and is used in many high-temperature and corrosive environments. Duplex stainless steel is generally identified with the numbers 2205, 2304, 2207 and is denoted by either an E or F for heat treatment.

Finally, Precipitation-hardened (PH) stainless steel is a type of austenitic stainless steel that has been heat-treated to increase its strength and corrosion resistance. PH stainless steel is generally identified with the numbers 403, 405, 416, and is denoted by an E for heat treatment.

In summary, stainless steel is classified by its composition, and each category of stainless steel is identified with a 4-digit number and a letter that indicates its heat treatment. Stainless steel is commonly used in many industrial, construction and household applications due to its corrosion resistance, high strength, and ease of fabrication.