gas welding and propane.......

Date 02-13-2007 06:21

from AWS "Welding Handbook" Vol 2, 7th edition P. 366 "Hydrocarbon gasses, such as propane, butane, city gas and natural gas are not suitable for welding ferrous materials due to thier oxidizing characteristics." That is what the "Good Book" says, however this topic just came up on a blacksmithing site, and the resident Guru there claims it is possible, just trickey, but the last time He tried it it diddn't work out.

By js55

Date 02-13-2007 16:50

Isn't acetylene a hydrocarbon gas?

By js55

Date 02-13-2007 16:54

Acetylene (systematic name: ethyne) is the simplest alkyne hydrocarbon, consisting of two hydrogen atoms and two carbon atoms connected by a triple bond. Because it contains a triple bond, acetylene is an unsaturated chemical compound.

The carbon-carbon triple bond leaves the carbon atoms with two sp hybrid orbitals for sigma bonding, placing all four atoms in the same straight line, with CCH bond angles of 180°.

Acetylene was discovered in 1836 by Edmund Davy who identified it as a "new carburet of hydrogen." It was rediscovered in 1860 by French chemist Marcellin Berthelot, who coined the name "acetylene."

By RonG

Date 02-13-2007 17:10

Water contains Hydrogen so what do you get when you mix water and Carbon?

By Lawrence (*****)

Date 02-13-2007 17:19

Wet carbon :)

By Cgregory (**)

Date 02-13-2007 18:09

It depends upon the form that the carbon is in. Carbon dioxide, for example, will react with water to form carbonic acid. Other forms of carbon are considerably more stable.

By Sourdough (****)

Date 02-13-2007 23:18

rust

By billvanderhoof (****)

Date 02-14-2007 04:18

If things are hot enough (steam injected into a bed of burning coal) you get a mixture of methane and carbon monoxide. The process was used to manufacture "city" gas for ilumination and heating. The carbon monoxide was poisonous and resulted in accidental and suicide deaths. Manufactured gas has been supplanted by natural gas.
Bill

By G.S.Crisi (****)

Date 02-13-2007 22:01

Bravo, js! A fine lesson of chemistry!
I'm a chemical engineer and really appreciated it.
Giovanni S. Crisi
Sao Paulo - Brazil

By js55

Date 02-13-2007 22:23

Giovanni,
This promised to be an interesting discussion. Clearly I Googled it to sorta kick things off.

By billvanderhoof (****)

Date 02-14-2007 04:32

Getting back to the original question- when I tried this in order to get the flame hot enough to melt the steel required that the flame be more oxidizing than you would want for welding. The extra oxygen burns the carbon in the steel resulting in carbon monoxide which somehow makes the steel effervesant (like soda water). The bubbles made the steel porous and the weld useless. If you need to join steel with oxy/propane braze it. If you need to weld it get the acetylene, breaking the triple bond referred to above releases a lot of energy and makes welding easy.
Bill

By DaveBoyer (*****)

Date 02-14-2007 05:03

Besides being hotter in a neutral flame, the neutral flame is reducing in nature [this is a benifit]. In the secondary flame the carbon monoxide and hydrogen from the primary flame burn with oxygen from the surrounding air forming carbon dioxide and water vapor. This shields the weld from the surrounding air. The problem with oxy/propane mentioned By bill is the same problem the guy on the other forum described. The oxidizing nature of the other fuel gasses is a benifit when cutting.