Ch. 7: Ferrous Metals and Alloys

Pig Iron

The iron that is the result of processing the ore, limestone, carbon, and air.

What is the recycling rate for steel in the U.S.?

71%

Precipitation-Hardening Variety

Addition of alloying elements to increase strength.

True Stainless Steels

Has a tough, corrosion-resistant oxide layer that can heal itself if oxygen is present.

Alloy Steels

Steels containing more than 1.65% manganese, 0.60% silicon, and 0.60% copper

Stainless Steels

Steels with at least 12% chromium which proofs against oxidation and corrosion.

Maraging Steels

Super-high strength containing 15-25% Nickel. Can be hot worked to yield very high yield strengths. Expensive. (more than 30% of alloying additions)

Deoxidation

The addition of deoxidizers (materials that oxygen reacts with to help remove the oxygen either by scooping out the slag or making into a solid) to purify the steel.

ASTM

American Society for Testing and Materials

Low-Alloy Steel

Containing less than 8% of total alloying additions.

Cast Irons

Gray Irons Malleable Irons Ductile Irons Compacted Graphite Iron

Types of Degassification

Vacuum induction melting (VIM) Vacuum arc remelting (VAR)

Amount of carbon content according to type (name) of steel.

last 2 digits is the decimal %. (ex. 1020 = 0.20% carbon)

Types of Tool Steels

1. Shock Resistant (S) 2. High Speed. 3. Hot-Work Steels. (H) (provide strength and hardness during high temp. applications) 4. Plastic Mold. (P) (plastic injection molding) 5. Special Purpose. (L,F) (extreme toughness and wear resistance)

Ladle Metallurgy

A variety of processes in which steel melt can be fine tuned chemically and thermally

Tool Steels

Built for a balance of strength and wear resistance

Free-Machining Stainless Steel

Built specifically for machinability. They form small chips when cut and often alloys are added to provide built-in lubrication (ex. sulfer)

Classifications of Common Ferrous Metals

Cast Irons Plain-Carbon Steels Alloy Steels

Ferritic Stainless Steels

Cheapest form of stainless Readily Weldable Limited Ductility Poor Toughness

Microalloy Steel

Contain about 0.05-0.15% of alloying elements. Provide max strength with minimum carbon.

High-Alloy Steel

Containing more than 8% of total alloying additions.

Dual-Phase Steels

Contains ferrite and high-carbon martensite. These offer same strength as HSLA steels and do not lose weldability. The faster the steel is crushed, the more energy it absorbs.

Advanced High Strength Steel (AHSS)

Dual-Phase Steels and Transformation Induced Plasticity (TRIP) Steels. Used in many automobiles because of high strength and energy absorption. Usually stamped or hydroformed to form complex parts.

High-Alloy Cast Iron

Enhanced corrosion resistance and suitable for elevated temperatures.

True or False: Cast Irons are stronger, stiffer, tougher, and more ductile over a wider temperature range than cast steels.

False. Cast Irons have better ductility, fluidity, and less shrinkage.

True or False: Nickel cannot be used in high temperature or highly corrosive environments

False. Nickel is a good choice for high temperature environments as well as highly corrosive environments.

True or False: Iron and Silicon are the two main elements used to make steel

False: Iron and Carbon are the two main elements used to make steel.

True or False: Recycling steels result in a loss of material quality

False: Recycling does not result in a loss of material quality for steels

True or False: Steel is not 100% recyclable

False: Steel is in fact 100% recyclable

Austenitic Stainless Steels

High nickel and chromium alloys. Very good formability and very strong if it is cold worked. Nonmagnetic, high corrosion resistance, increased strength, 2-3 times as much cost, may be polished to a mirror finish.

Plain-Carbon Steels

High-Carbon (greater than 0.50% carbon) Medium-Carbon (0.20% - 0.50% carbon) Low-Carbon (less than 0.20% carbon)

Bake-Hardenable Steels

Increase in strength happens after the forming operations. Material has good formability and age occurs during sheet metal forming.

Ferrous Metals and Alloys

Iron-based metals and alloys

Water-Hardening Tool Steels

Lease expensive form of tool steels that are used for small parts that are not subjected to extreme temperatures.

Alloy Steels

Low-Alloy Steel HSLA Steel Microalloyed Steel Advanced High-Strength Steel Maraging Steel Stainless Steel Tool Steel

Steel

Made from pig iron and manufactured by an oxidation process that decreases the ammount of carbon, silicon, manganese, phosphorous, and sulfur.

History-Dependent Materials

Materials whose properties depend on its past. (prior processing)

Martensitic Stainless Steels

May be susceptible to rust under certain conditions. Main property is hardness. Used in cutlery.

High Strength Low-Alloy (HSLA)

Micro-alloy (low alloy) Rely on chemical composition for properties Increased strength to weight ratio High yield strength Good weldability Good corrosion resistance

Iron

Most Important of engineering metals. It is the 4th most plentiful element in the earth's crust, and it occurs in ores. (iron ores)

Amorphous Metals

No crystal structure, grains, or grain boundaries. Isotropic material. Good corrosion resistance, and magnetic domains can move freely.

Quenched

The process by which a material is cooled

True or False: Alloy steels can operate at higher temperatures than plain-carbon steels.

True. Low carbon materials are good for higher temperatures usually.

True or False: More steel is recycled each year than all other materials combined

True. More than aluminum, glass, paper, and all others combined

Cold-Work Tool Steels

Used for larger parts that must be hardened. They can be oil or air quenched.

Transformation Induced Plasticity (TRIP) Steels

Very good for work hardening because the result of work hardening is very good in energy absorption.

Vacuum Arc Remelting (VAR)

When an electric arc melts the electrode (metal)

Vacuum Induction Melting (VIM)

When induction is used to melt the electrode (metal)