Common Metal Material Number Expression
A metal material number (also referred to as grade) is an algorithm-based tool used to classify various types of metals according to their chemical composition, physical and metallurgical properties. The number consists of three or four numeric digits, followed by a letter or letter combinations, constituting the system symbol of a metal material.
In the United States, the system of metal material numbers was introduced by the American Iron and Steel Institute (AISI). The first letter of the metal material number indicates the general class of steel; A for carbon steel, B for alloy steel, and R for stainless steel. The first two digits of the number indicate the general group of steels. The remainder of the number indicates the specific application of steel and its class. The following is a list of the most common metal material numbers for carbon, alloy and stainless steel in the United States:
Carbon Steel:
1010: This is a low carbon grade of steel, widely used in automotive, appliance, agricultural and other manufacturing industries. The number 1010 means 0.10 percent carbon content in the steel composition.
1020: This is a higher grade of carbon steel with 0.20 percent carbon content. It is widely used in automobile, machinery and other parts manufacturing.
1040: This is a very popular grade of low carbon steel with 0.40 percent carbon content. It is used in a variety of applications including machine tools and engineering parts.
Alloy Steel:
4130: This is a medium carbon grade of alloy steel that has 0.30 percent carbon content. It is widely used for automotive, aerospace, and agricultural applications.
4140: This is a popular alloy steel with 0.40 percent carbon content. It is widely used in automotive, appliance, agricultural and other manufacturing industries.
4340: This is a high alloy steel with 0.40 percent carbon content. It is used in specialty applications such as automotive and aerospace components.
Stainless Steel:
301: This is a general purpose grade of stainless steel and it is popularly used in automotive and aircraft applications. The number indicates 0.15 percent carbon content in the steel.
304: This is an austenitic grade of stainless steel with 0.08 percent carbon content. It is commonly used in food preparation, construction and other applications.
316: This is an austenitic grade of stainless steel with 0.08 percent carbon. It is very popular for marine and food processing applications.
The above list provides only a few of the most common metal material numbers used in the United States. There are many other grades of steel, alloy and stainless steel including those with higher carbon content and even specialty grades. All of these grades have their own distinct metal material numbers. It is important to understand the system of metal material numbers to properly identify the appropriate material for a given application.
