Common Materials in metal fabrication
Steels are an iron – carbon alloy, a mix of iron ore, coal, and limestone along with other various elements.
Detailed processes of making steels: http://ourworld.compuserve.com/homepages/DYaros/stlmanuf.htm
Process of making steels
- Blast Furnace
o All the raw materials are dumped into the furnace, heated to liquid (molten) state where they mix and create a “Pig Iron”.
- Refining the Pig Iron
o The pig iron is then rolled, pickled, rolled, annealed, and tempered
Standard Types of Steels
This is the most common basic steels used in any metal fabrication.
Usually following from the Pig Iron refining
These steels are most often used where standard steels cannot. Alloy steels is given to any steel that is not a carbon steel. Conventionally: they contain over 4% of Chromium which include the stainless and tool steels.
Stainless Steels – are a high alloy (lots of Chromium 4% < SS < 30%)
It can be higher in chromium but it can never be as much as 50% because steels contain a minimum of 50% Iron.
Three Types of Stainless
Austenitic grades – non magnetic to slightly magnetic after cold working
Ferritic grades – Always magnetic and contain chromium
but no nickel is present.
Martensitic grades – are magnetic and can be hardened by
quenching and tempering
Tool Steels – Used to create tools used in metal working. Specifically
hardened to withstand the punishments of high loads, forces and stresses put on them.
Heat Treating Methods for Hardness
Quenching and Tempering
Consists of minimum of 3 successive operations:
1. Heating steel above critical range (1300°F to 1600°F) for a period of time
2. Cooling rapidly by use of water, oil, or air (usually hard and brittle at this stage)
3. Termpering by reheating to a temp below critical to obtain a specific hardness, strength, toughness, etc…
Normalizing: Heated to above critical range (1300°F to 1600°F) and then air
cooled in still air.
Annealing: Heated to or above critical range and slowly cooled (usually in a
Stress Relieving: Reduces internal stresses caused by machining, cold working, or
welding by heating the steel to a temperature below the critical range and holding it there long enough to equalize the temperature throughout the piece.
Case Hardening – for use when a hardened surface may be required.
Kasonite is a common name
Other materials used:
Characteristics of Aluminum and Aluminum Alloys.—Aluminum and its alloys lose part of their strength at elevated temperatures, although some alloys retain good strength at temperatures from 400 to 500 degrees F. At subzero temperatures, however, their strength increases without loss of ductility so that aluminum is a particularly useful metal for low-temperature applications. (hence good for airplanes)
Aluminum 2024 – Aircraft Quality
Most commonly known and used alloy of 2000 series. Primarily mixed with copper for the alloying material
Aluminum 6061 – Standard Machining and Heat Treatable
Most commonly known and used alloy of 6000 series. Primarily mixed with Magnesium and Silicon for the alloying materials. Thus making it heat treatable and easily machine-able.
Brasses, Bronzes, and Copper