Sheet Metal Information and Types
What is sheet metal? According to MSN Encarta Dictionary, sheet metal is metal that has been formed into a sheet by being pressed between rollers until it is thinner than plate but thicker than foil. Sheets can vary in thickness. As long as the surface area is greater than the thickness of the material, it is by definition, a sheet. However, by this definition, sheets of metal can be 6 inches thick and still be called a sheet. However, most common thicknesses are less than ¼” thick. Generally, when a sheet of metal reaches a critical thickness, it is called a plate. Usually this includes sheets of metal that are 3/16” or thicker. Plates are categorized by their thickness and labeled by it as well. Quarter inch steel hot rolled plate is just called, ¼” HRS (Hot Rolled Steel). Sheets of metal thinner than 3/16” are categorized by thickness as well, but the actual thickness is converted into simpler numbers referred to as “gauges”. I do not know who came up with this system, but most likely it is from England. Thus, the thickness of thinner sheets of metal are called by their gauge. The following table breaks down numbers
10 gauge steel = .135”
11 gauge steel = .120”
12 gauge steel = .104”
13 gauge steel = .090”
14 gauge steel = .075”
16 gauge steel = .060”
18 gauge steel = .048”
20 gauge steel = .036”
22 gauge steel = .030”
24 gauge steel = .024”
26 gauge steel = .018”
This is just for steel. The numbers change slightly with aluminum – but as you have noticed, as the thickness decreases, the unit in gauges increases. And this is just for our standard system. There is a whole other system of metric measurements that are less commonly used in America.
Aluminum is a whole branch of sheet metal by itself. There are so many different types of Aluminum; certainly too many to list here.
How many types are there?
There are as many types of sheet metal as there are types of metal. If an alloy can be stretched out into a sheet, that is all it takes to be sheet metal. Sheet metal are categorized by their thickness as I discussed, but then further categorized by hardness, method of manufacturing, tensile strength, alloy composition, and quality.
VIP works with a wide variety of sheet metal types, but here are the most common.
CRS (Cold Rolled Steel) – CRS is pressed into a sheet in a cold state at the steel foundry. It has a more homogeneous composition than Hot rolled steel (HRS), which allows better heat conductivity and is easier to machine. Most of our steel sheets are CRS as well as our bar stock that the machine shop uses.
HRS (Hot Rolled Steel) – HRS is formed into a sheet in a molten state and rolled flat while still hot. HRS is usually of less quality than CRS, is more difficult to machine due to variable composition in the metal. Most often, VIP uses HRS for thick plate. Olea uses 3/16” HRS plate for their base plates on most of their kiosks. Also, the base for the mailboxes is 3/16” HRS. Thin HRS is very rare – I have never worked with anything thinner than 12 gauge HRS.
Aluminum – This metal comes in many forms, but the most common type is 5052-H32, which is really an Aluminum alloy. Aluminum alloys are mixtures of aluminum with other metals, often with copper, zinc, manganese, silicon, or magnesium. There are way too many to list. VIP uses, 5052-H32, 6061-T6, 6061-T4, 2024-T0 for most of our parts. The number after the 4 digit code is the tensile strength or temper of the alloy. T0 is soft, T6 is full hard.
The International Alloy Designation System is the most widely accepted naming scheme for wrought alloys. Each alloy is given a four-digit number, where the first digit indicates the major alloying elements.
1000 series are essentially pure aluminum with a minimum 99% aluminum content by weight and can be work hardened.
2000 series are alloyed with copper, can be precipitation hardened to strengths comparable to steel. Formerly referred to as duralumin, they were once the most common aerospace alloys, but were susceptible to stress corrosion cracking and are increasingly replaced by 7000 series in new designs.
3000 series are alloyed with manganese, and can be work-hardened.
4000 series are alloyed with silicon. They are also known as silumin.
5000 series are alloyed with magnesium, derive most of their strength from work hardening. It is suitable for cryogenic applications and low temperature work. However is susceptible to corrosion above 60°C.
6000 series are alloyed with magnesium and silicon, are easy to machine, and can be precipitation-hardened, but not to the high strengths that 2000, and 7000 can reach.
7000 series are alloyed with zinc, and can be precipitation hardened to the highest strengths of any aluminum alloy.
8000 series is a category mainly used for lithium alloys.
Stainless Steel (CRES) – Stainless Steel is an alloy based on chromium and steel and is categorized by its resistance to corrosion. The same gauge thickness apply as regular steel. Stainless is much harder than regular steel and is not easy to work with in some respects. The laser loves it and has no problem cutting it. It is difficult to punch, and difficult to weld.
For more information on sheet metal go to http://en.wikipedia.org