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)