Classification of Steel 201

air-hardening

A tool material that is hardened by exposing it to air or pressurized gas. Air-hardening tool steel designations begin with “A.”

AISI

American Iron and Steel Institute. An organization that issues general classification standards for irons and steels. The AISI developed the AISI-SAE classification system with the Society of Automotive Engineers (SAE).

AISI-SAE system

A steel classification system developed by the American Iron and Steel Institute (AISI) and the Society of Automotive Engineers (SAE). The AISI-SAE system is the most common classification system for carbon steels and alloy steels in the United States.

alloy steels

A group of steels that contain added materials that change the property of the metal. Alloy steels commonly contain added chromium, manganese, molybdenum, and nickel.

alloying elements

A material that is intentionally added to a metal in order to change its properties. Alloying elements can improve the strength, ductility, hardness, and toughness of a metal.

American Iron and Steel Institute

AISI. An organization that issues general classification standards for irons and steels. The American Iron and Steel Institute developed the AISI-SAE classification system with the Society of Automotive Engineers (SAE).

American Welding Society

AWS. The non-profit organization that regulates industrial standards for welding. The American Welding Society also promotes the welding industry in the United States.

ASTM International

An organization that publishes standards on a variety of materials, products, and services, including metals. ASTM International, formerly the American Society for Testing and Materials, produces standards relevant to many steel-producing industries.

austenitic

A family of stainless steels that contain the greatest amounts of chromium, nickel, and other alloying elements. Austenitic stainless steels are the most corrosion-resistant stainless steels and offer high strength and ductility.

carbon

A common non-metallic element that is very strong and resistant to heat. Carbon is combined with iron to create steel.

carbon steels

A group of steels that contain less than 3% elements other than iron and carbon. Carbon steel, also known as plain carbon steel, is relatively common and inexpensive.

chemical composition

The type, amount, and arrangement of atoms that, when combined, compose a whole material or substance. Chemical composition can be altered whenever a change occurs at the atomic level.

chromium

A hard, shiny, gray metal that is highly resistant to corrosion and wear. Chromium is often used as an alloying element to improve corrosion resistance and hardenability.

cold-working

A tool material that is used at temperatures below its melting point. Cold-working tool steel designations begin with “A,” “O,” or “D.”

corrosion resistance

The ability of a material to resist deterioration and chemical breakdown due to surface exposure to certain conditions. Alloying chromium with steel can increase the metal’s corrosion resistance.

drills

A multi-point cutting tool used to penetrate the surface of a workpiece. Drills create round holes in workpieces.

ductile

Able to be drawn, stretched, or formed without fracturing. Ductile metals usually have low strength and hardness.

ductility

A material’s ability to be drawn, stretched, or formed without fracturing. Ductility generally increases as hardness decreases.

electric arc furnace

A type of furnace that uses electricity to melt metal. Electric arc furnaces use carbon electrodes to create electric arcs.

electrical conductivity

The ability of a material to convey electricity. Many metals have high electrical conductivity.

family

A category of stainless steels that share similar microstructures. Families of stainless steel include, austenitic, ferritic, and martensitic.

fasteners

A device that holds objects together or locates them in relation to one another. Common fasteners include screws, bolts, and rivets.

ferritic

A family of stainless steels that contain high amounts of chromium and can include small amounts of molybdenum, aluminum, and titanium. Ferritic stainless steels have high hardness but low ductility.

ferrous metals

A metal in which iron is the main ingredient. The main groups of ferrous metals are cast iron and steel.

free-machining steel

A specialized type of steel that has small amounts of alloying elements added to improve machinability. Free-machining steels include resulfurized and rephosphorized steels.

furnace

A self-contained metal structure that can be heated to exceptionally high temperatures. The type of furnace used to produce steel can affect the metal’s properties.

grade

A specific type of metal indicated by a unique designation. Grades of steel are typically distinguished by the specific amount of elements included in the metal.

hardness

A material’s ability to resist penetration, indentation, and scratching. Hardness generally increases as ductility decreases.

heat treatment

Any controlled heating and/or cooling process used to change the structure of a material and alter its physical and mechanical properties. Heat treatment processes include annealing, quenching, and tempering.

high-carbon steels

A carbon steel that contains more than 0.6% carbon. High-carbon steels are extremely strong and hard.

high-speed steel

HSS. A tool material used for machining processes with fast cutting speeds. High-speed tool steel designations begin with “M” or “T.”

high-strength low-alloy steels

HSLA steels. A group of alloy steels that contain low levels of carbon and alloying elements. High-strength low-alloy steel is strong and relatively inexpensive.

hot-working

A tool material that is used at temperatures above its melting point. Hot-working tool steel designations begin with “H.”

HSLA steels

High-strength low-alloy steels. An alloy steel that contains low levels of carbon and alloying elements. HSLA steel is strong and relatively inexpensive.

impurities

Any foreign element or substance unintentionally included in a material. Alloying elements are considered impurities in carbon steels.

iron

A silver-white, metallic element that is highly magnetic. Iron is alloyed with carbon to make steel.

low-carbon steels

A carbon steel that contains less than 0.3% carbon. Low-carbon steels are generally tough and ductile.

manganese

A hard, brittle, gray-white metal. Manganese is often used as an alloying element to increase hardenability, strength, and hardness.

martensitic

A family of stainless steels that contain lower amounts of chromium and small amounts of molybdenum, nickel, and carbon. Martensitic stainless steels are the strongest stainless steels.

mechanical properties

A characteristic that describes how a material responds to forces that attempt to stretch, compress, bend, dent, scratch, or break it. Mechanical properties include tensile strength, hardness, and ductility.

medium-carbon steels

A carbon steel that contains between 0.3% and 0.6% carbon. Medium-carbon steels are strong and hard.

microstructure

The shape and alignment of microscopic components in a material. Microstructure strongly influences the properties of a material.

molybdenum

A hard, silver-white metal that is strong and corrosion resistant. Molybdenum is often used as an alloying element to improve toughness, creep strength, and wear resistance.

nickel

A hard, ductile, silvery-white metal. Nickel is often used as an alloying element to increase strength, toughness, and corrosion resistance.

niobium

A ductile, platinum-gray metal with high strength and creep resistance. Niobium can be used as an alloying element or as a treatment to prevent oxidation.

nitrogen

A colorless, odorless, tasteless, inert gas that naturally exists in the atmosphere. Nitrogen can be used to prevent oxidation of certain steels.

oil-hardening

A tool material that is hardened by submerging it in oil. Oil-hardening tool steel designations begin with “O.”

oxidation

A material’s chemical reaction with oxygen. Oxidation causes rust and tarnish to form on metal surfaces.

phosphorus

A waxy, non-metallic element that can be either white or red. Phosphorus can be used as an alloying element to increase strength and corrosion resistance.

physical properties

A characteristic that describes how a material responds to environmental, thermal, electrical, and magnetic forces. Physical properties include corrosion resistance and conductivity.

plain carbon steels

A group of steels that contain less than 3% elements other than iron and carbon. Plain carbon steel, also known as carbon steel, is relatively common and inexpensive.

pounds per square inch

psi. A unit of pressure used in the US Customary System. The pounds per square inch unit measures the amount of load pressure that is applied over an area of one square inch.

precipitation hardening

A family of stainless steels that undergo heat treatment to increase hardness. Precipitation hardening stainless steels are heated until they precipitate and then cooled at a rate to prevent them from returning to their original structure.

properties

A measurable characteristic that describes the qualities or attributes of a specific material or substance. Properties determine how a material will perform in different environments.

punches

A tooling component that pushes into or penetrates a workpiece. The punch is a component of the upper half of the die that is used in many stamping operations, including drawing and punching.

reamers

A multi-point cutting tool with straight cutting edges and straight or helical flutes. Reamers are used to enlarge or smooth holes that have been previously drilled.

rephosphorized

A carbon steel that contains added phosphorus to improve machinability. Rephosphorized steel designations begin with “12.”

resulfurized

A carbon steel that contains added sulfur to improve machinability. Resulfurized steel designations begin with “11.”

SAE

Society of Automotive Engineers. An organization that writes specifications and other data used in a broad range of industries. The SAE developed the AISI-SAE classification system with the American Iron and Steel Institute (AISI).

shock-resisting

A tool material designed to withstand constant high impacts. Shock-resisting tool steel designations begin with “S.”

silicon

A lustrous, blue-gray, semi-metallic element that is hard and brittle. Silicon is often used as an alloying element to improve hardenability.

Society of Automotive Engineers

SAE. An organization that writes specifications and other data used in a broad range of industries. The Society of Automotive Engineers developed the AISI-SAE classification system with the American Iron and Steel Institute (AISI).

stainless steels

A group of alloy steels that contain 11-30% chromium. Stainless steels exhibit excellent corrosion resistance.

stamping

A metalworking operation that uses dies and punches to form or separate sheet metal into parts. Stamping is performed on a press.

steel

A metal alloy made of iron and carbon. Steels often contain small amounts of alloying elements such as manganese, phosphorus, sulfur, and silicon.

strength

A material’s ability to resist forces that attempt to break or deform it. Strength may refer to tensile, compression, yield, or shear strength.

sulfur

A brittle, yellow, non-metallic element. Sulfur may be used as an alloying element to increase machinability.

tool steels

A group of specialized alloy steels that have excellent strength, toughness, and wear resistance. Tool steels are used in cutting tools, punches, and other industrial tooling.

toughness

A material’s ability to absorb energy without breaking or fracturing. Toughness generally increases as hardness decreases.

tungsten

A dense, brittle, gray metal with excellent heat and wear resistance. Tungsten is often used as an alloying element in cutting tools.

Unified Numbering System

UNS. A common classification system that is used for both ferrous and non-ferrous metals. The Unified Numbering System uses designations that consist of a prefix letter followed by five digits.

UNS

Unified Numbering System. A common classification system that is used for both ferrous and non-ferrous metals. The UNS uses designations that consist of a prefix letter followed by five digits.

vanadium

A hard, ductile, gray metal that is very strong. Vanadium can be used as an alloying element to increase strength and creep resistance or as a treatment to prevent oxidation.

water-hardening

A tool material that is hardened by quenching, or submerging it in water. Water-hardening tool steel designations begin with “W.”

yield strength

A material’s ability to resist gradual progressive force without permanent deformation. Yield strength is measured in pounds per square inch (psi) or pascals (Pa).