Steel formula

[Theiananator]

I've looked everywhere, but I just can't seem to find the chemical formula for AISI 1018 steel. Can anyone help me out?

 

[Gibsons]

from http://www.efunda.com/material...Page_Title=AISI%201018

Composition
Element Weight %
C 0.15-0.20
Mn 0.60-0.90
P 0.04 (max)
S 0.05 (max)


(I assume the remainder would be Fe and trace contamintants)

dunno if this is what you were looking for though...

 

[Theiananator]

I've found that already, thanks though. But what I was looking for was the chemical formula for steel (i.e. water is H2O, carbon dioxide is CO2 etc.)

 

[Gibsons]

I'm not sure you can really ascribe a molecular formula like that to a ferrous alloy. To really understand it (I don't) I think you'll need to read up on the crystal structure of steels, like here

http://www.machinedesign.com/B...bdemat6/bdemat6_1.html
http://www.schoolscience.co.uk...steel/steelch1pg4.html

You might also want to look at some sites on the metallurgy of knife and sword making, or maybe bicycles/airplanes, they'll sometimes go into detail on the atomic structures. Interesting stuff, not that I understand it.

 

[Farmer]

Theiananator:

Gibsons is right. Steel is hardly pure (as you can see from the spectrometer readings Gibsons posted); it has no set atomic structure, the type of chemical bond that exists is called "metallic bonding" (not sure if this is the proper name, but just think "sea of electrons," as electrons move freely from one atom to another, thus the electrical conductivity of metals). You can only assume some crystalline arrangment of Fe with the elements listed above sprinkled about. I am not really sure.

 

[cirthix]

steel is an alloy, not a single pure chemical

 

[Theiananator]

Farmer and Gibsons, thanks. And cirthis, brass is an alloy and it has a chemical formula (Cu3Zn2). However, according to Gibsons and Farmer, the reason steel doesn't have a defined structure is because there are so many different types of steel.

 

[Lynx516]

That would only be correct for Alpha-Beta Brass. There are many different alloys that are called brass but with different proportions of each.

 

[Theiananator]

Touche.

 

[Bulldozer2003]

The structure of metals is not like H2O or CO2 as you are imagining. Pure metals (iron, gold, zinc) are simply clumps of atoms loosely arranged together. Alloys are the same, the atoms of all the metals are distributed randomly (usually in clumps as like metals tend to congregate) throughout the alloy, they are not molecular compounds. However, steel alloys contain carbon. Some of the C in the steel reacts and forms FeC, which is a molecular compound, however, the alloy is mostly Fe (Iron) with FeC distributed randomly, and some atomic Carbon as well. High Carbon steels (cast iron) and actually lubricate themselves because the carbon on the surface acts just like graphite lubricant. Other alloys may also have molecular compounds present, depends on the chemical potential of the various components.

 

[CowIsAlreadyTaken]

Don't make me pull a phase-diagram on ya!
You could get a chemical name from the composition provided (eg. Fe98C0.15MnO.60...), but that wouldn't help you one bit. When using steel, usually, all you're concerned about is its material properties (tensile strength, hardness, corrosion resitance, etc.)

 

[Sukhoi]

Yeah steel is just a bunch of elements thrown together, with Fe being by far the largest element.

 

[Pacemaker]

A highly simplified way of explaining alloys would be to imagine a balloon. In this case the elastic part of the balloon is Iron. When it is heated the molecules spread apart (like blowing up the balloon) this allows material to enter the spaces between the atoms (put something, a rock for instance in the balloon). Then when the material is cooled (the faster it is cooled the better, well to a degree anyway) the material caught inside changes the properties of the material (Release the air from the balloon. Now it doesn't have the same properties as before, well if a large enough object was placed there). However, it is still chemically Iron and carbon.

 

[Sukhoi]

Well the faster it is cooled the more fine the particulate matter in the iron matrix becomes, which helps to restrict dislocation motion. The higher the cooling rate the harder and stronger the steel becomes, but it loses the ductility.

Strength:

martensite > bainite > pearlite

Ductility is reversed.

 

[Mday]

Originally posted by: Theiananator
Farmer and Gibsons, thanks. And cirthis, brass is an alloy and it has a chemical formula (Cu3Zn2). However, according to Gibsons and Farmer, the reason steel doesn't have a defined structure is because there are so many different types of steel.

when you reach the study of alloys, it is no longer chemistry, per se, it is now metallurgy. Steel does not have a defined chemical structure because the structure is not a CHEMICAL bond by definition. It is a metallic bond. I do not consider any alloy to have an empirical or structural formula.

 

[gururu]

steel is basically iron that has been smelted with a small amount of carbon.