does a gas forge really damage carbon in steel, i saw this disription of a knife on ebay that said somthing along those lines.
the person also said that char coal and coal burning do the opposite and add carbon to the metal to make it stronger.

Edited September 6, 200817 yr by Drenched_in_flame

It can if it's not adjusted properly, just like coal, coke or charcoal.

In fact, if you haven't coked your coal properly it's possible to introduce sulfur and phosphorus into a billet potentially doing un-good things.

Frosty

Steel doesn't know what is getting it hot, gas or coal. The damage can come from overheating the steel with either. Sulfur in coal can cause problems with a forge weld, but as far as introducing anything into the steel from the fire, that is next to impossible. I would recommend you read some material on metallurgy and disregard a lot of the "alchemy and legends" that pass for factual information in the knifemaking world.

The carburization/decarburization that happens during normal forging (in coal or gas) is usually far too shallow to really affect the end product. It might affect a blade's edge, but really any grinding should remove it.

Every set up instruction I have come across emphasizes a carburizing flame(reducing)- fuel rich- to avoid damaging the steel by oxidizing- also, overcooking can do it as well. In welding, new weldors are cautioned against that hissing needle sharp cone which is tempting as "hotter". "Just off feather" is essential there as well.mike

Our company sends out a wide variety of parts for heat treatment. The heat treat suppliers all use natural gas for a fuel source (except in vacuum furnaces, which are electrically heated). By modifying the air/fuel mix, they can alternately reduce, increase, or maintain the carbon level in plain steels. In most cases, they want to leave the carbon as specified so the flame is neutral but for example, in a case hardening application, they will increase the carbon and add other gases to the mix (ammonia is one type) to impart a hard case to a prescribed depth. This industrial processing is very repeatable but the average blacksmith cannot control his fire so closely, so most get some level of decarburization or scaling while forging. To answer your question, a gas forge would actually be easier to control than coal or coke if you pay attention to the fuel mix because it would not tend to change much, once set.

i am new to gas forging as well...but it does seem that gas is the fuel of choice for bladesmiths the world over...not quite as traditional as coal but from what i've heard (when talking about forging blades) gas has a number of advantages that make it optimal...

as far as "adding carbon to make the steel stronger" goes...thats not really true...adding carbon will make the steel *harder* not stronger...which will mean it can hold a better edge...but also mean it is more brittle...bladesmithing (as far as i've been informed) is about striking a balance between flexibility and edge-holding capacity...the more carbon you have in the steel the better an edge it will hold...but the less flexible it will be...as with most things in this world...its a compromise :)