Materials Selection and Engineering Metals

Study Notes

Materials selection process is influenced by factors that affect both material and process.

Metals are the most commonly used class of engineering materials.
Metal alloys are formed by combining a metal with one or more other metallic and/or non-metallic materials.
The goal of alloying is to improve the properties of the base material in some desirable way.

Ferrous metals have iron as their main constituent, such as cast iron, wrought iron, and steel.
Non-ferrous metals have a metal other than iron as their main constituent, such as copper, aluminum, brass, tin, and zinc.

Ferrous alloys have iron as the base element, including steels and cast irons.
Carbon steels are basically just mixtures of iron and carbon.
Low-carbon steel has less than about 0.30% carbon, characterized by low strength but high ductility.
Medium-carbon steel contains between about 0.30% to 0.70% carbon, can be heat treated to increase strength.
High-carbon steel contains between about 0.70% to 1.40% carbon, has high strength but low ductility.
Low-alloy steels, also called alloy steels, contain less than about 8% total alloying ingredients.
Tool steels are primarily used to make tooling for use in manufacturing.
Stainless steels have good corrosion resistance, mostly due to the addition of chromium as an alloying ingredient.
Stainless steels have a chromium composition of at least 11%.

Cast iron is a ferrous alloy containing high levels of carbon, generally greater than 2%.
Gray cast iron is the most common type, with carbon in the form of graphite flakes.
The addition of magnesium to gray cast iron improves the ductility of the material, resulting in nodular cast iron.
White cast iron has carbon in the form of carbide, making the material hard, brittle, and difficult to machine.
Malleable cast iron is produced by heat treating white cast iron.

Coke is formed by heating coal to 2100°F (1150°C), then cooling it in quenching towers.
Limestone (calcium carbonate) is used to remove impurities.
Cupola or Cupola Furnace is a melting device used in foundries that can be used to melt cast iron.