Carbon and Alloying Steels

Carbon and alloying steels are the most commonly used metals

The structural makeup and controlled processing of these steels make them suitable for many different functions.

Basic product shapes include plate, sheet, bar, wire, tube, castings, and forgings.

Increasing the percentages of these elements in steels, increases the properties they impart.

Effects of Elements in Steels

Different elements are added to steels to given the steel different properties.

The elements pass on properties such as harden- ability, strength, hardness, toughness, wear resistance, etc.

Some properties are beneficial while others are detrimental.

Effects of Elements in Steels Boron: Improves hardenability without the loss of (or even with some

improvement in) machinability and formability.

Calcium: Deoxidizes steels, improves toughness, and may improve formability and machinability.

Carbon: improves hardenability, strength, hardness, and wear resistance; it reduces ductility, weldability, and toughness.

Cerium: controls the shape of inclusions and improves toughness in high-strength low alloy steels; it deoxidizes steels.

Chromium: improves toughness, hardenability, wear and corrosion resistance, and high-temperature strength; it increases the depth of the hardness penetration resulting from heat treatment by promoting carburization.

Cobalt: improves strength and hardness at elevated temperatures.

Effects of Elements in Steels

Copper: improves resistance to atmospheric corrosion and, to a lesser extent, increases strength with little loss in ductility; it adversely affects the hot-working characteristics and surface quality.

Lead: improves machinability; it causes liquid-metal embrittlement.

Magnesium: has the same effects as cerium.

Manganese: improves hardenability, strength, abrasion resistance, and machinability; it deoxidizes the molten steel, reduce shot shortness, and decreases weldability.

Molybdenum: improves hardenability, wear resistance, toughness, elevated-temperature strength, creep resistance, and hardness; it minimizes temper embrittlement.

Effects of Elements in Steels Nickel: improves strength, toughness, and corrosion resistance; it

improves hardenability.

Niobium (columbium): imparts fineness of grain size and improves strength and impact toughness; it lowers transition temperature and may decrease hardenability.

Phosphorus: improves strength, hardenability, corrosion resistance, and machinability; it severely reduces ductility and toughness.

Selenium: improves machinability.

Silicon: improves strength, hardness, corrosion resistance, and electrical conductivity; it decreases magnetic-hysteresis loss, machinability, and cold formability.

Effects of Elements in Steels Sulfur: Improves machinability when combined with manganese; it lowers

impact strength and ductility and impairs surface quality and weldability.

Tantalum: has effects similar to those of niobium.

Tellurium: improves machinability, formability, and toughness.

Titanium: improves hardenability; it deoxidizes steels.

Tungsten: has the same effects as cobalt.

Vanadium: improves strength, toughness, abrasion resistance, and hardness at elevated temperatures; it inhibits grain growth during heat treatment.

Zirconium: has the same effects as cerium

Carbon Steels Carbon steels are group by

their percentage of carbon content per weight. The higher the carbon content the greater the hardness, strength and wear resistance after heat treatment.

Low-carbon steel, also called

mild steels, has less than 0.30% carbon. Used in everyday industrial products like bolts, nuts, sheet, plate and tubes.

High Carbon Steel Nails

Carbon Steels

Medium-carbon steel has 0.30% to 0.60% carbon. Used for jobs requiring higher strength such as machinery, automotive equipment parts, and metalworking equipment.

High-carbon steel has more than 0.60% carbon. Used parts that require the highest strength, hardness, and wear resistance. Once manufactured they are heat treated and tempered

Alloy Steels

Alloy steels are steels that contain significant amounts of alloying elements.

High strength low alloy steels Microalloyed steels Nanoalloyed steels

Alloy Steels

High-strength, low-alloy steels (HSLA) steels were developed to improve the ratio of strength to weight. Commonly used in

automobile bodies and in the transportation industry (the reduced weight makes for better fuel economy ).

Microalloyed steels Provide superior properties without the use of heat treating. When cooled carefully these steels develop enhanced and consistent strength.

Stainless Steels

Stainless steels are primarily know for their corrosion resistance, high strength, and ductility and chromium content.

Stainless Steels

The reason for the name stainless is due to the fact that in the presence of oxygen, the steel develops a thin, hard, adherent film of chromium. Even if the surface is scratched, the protective film is

rebuilt through passivation.▪ For passivation to occur there needs to be a minimum chromium

content of 10% to 12% by weight.

Stainless Steels

Stainless steels tend to have lower carbon content since increased carbon content lowers the corrosion resistance of stainless steels.

Since the carbon reacts with chromium it decreases the available chromium content which is needed for developing the protective film.

Stainless Steels Using stainless steels as reinforcing bars, has become a new

trend, in concrete structures such as highways buildings and bridges.

It is more beneficial than carbon steels because it is resistant to corrosion from road salts and the concrete itself.

corrosion in concrete

Tool and Die Steels

Tool and die steels are alloyed steels design for high strength, impact toughness, and wear resistance at normal and elevated temperatures.

High-speed steels Maintain their hardness and strength at elevated operating temperatures. There are two basic types the M-series and T-series

Tool and Die Steels

M-series contain 10 % molybdenum and have higher abrasion resistance than T- series

T- Series contain 12 % to 18 % tungsten. They undergo less distortion in heat treatment and are less expensive than the M-series. M- series steel drill

bits coated with titanium

Tool and Die Steels

Dies are tools used for drawing wire, and for blanking, bending, cutting, machine forging, and embossing. . H-series (Hot-working steels) for use at elevated

temperatures. They have high toughness and high resistance to wear and cracking.

S-series (shock resisting steels) designed for impact toughness.