Burning of Iron/Steel

[Archie Zietman]

Hello.
When you put steel or iron into the fire, and it starts burning, what exactly is going on? what makes it burn and spark, and pit and all that stuff? Also, is this what is happening to steel/iron which is being cut by a cutting torch, or is that all blowing out of the molten metal?
Thanks,
Archie

[HWooldridge]

The steel actually burns - and yes, a torch does the same thing. I am no chemist but have been told that the carbon content has a lot to do with the propensity to burn so pure iron will be harder to ignite than a piece of 1090. This theory seems to hold true because wrought iron will withstand higher temps than spring steel or other high carbon material.

A plasma arc vaporizes any conductive metal and blows it away. An oxyacet torch burns steel but won't work on metals that can't ignite.

[Glenn]

I will let the metalurgists address the chemical reaction part of the question. When the metal gets too hot, starts throwing sparks, it takes on a "burnt" look. You can do a lot of things but the best is to cut off the "burnt" part and start over.

http://www.iforgeiron.com/forum/viewtopic.php?t=418 explains plasma rather well. Plasma vaporizes the material being cut and air blows it out of the kerf. Ox/Ac turns the metal to liguid and blows (or burns) the liquid out of the kerf with Oxygen.

You can find the metal from the kerf all over the floor as dust or little "ball bearings" which sometimes make standing up difficult. I must warn you that this gets into the soles of the shoes, cuffs of your pants, pockets and etc You then track "gray" footprints all the place. "Gray" is not so bad but overnight with a little humidity and the "gray" turns to rust and THAT is a whole nother problem. Rusty foot prints on the wife's carpet (notice it is no longer your house or carpet) will get you at least a week of taking you clothes off before you are allowed into the house.

I mention the pants pockets because come time to do the laundry, you want to be sure you shook out the pants and reversed the pockets. Otherwise the "gray" gets all over everything and then turns to rust in the water. The little "ball bearings" then attach them selves to only the most obvious locations and "rust stain" the material.

This results is being ban from doing laundry at home, so start looking for the local coin operated laundry and get to know how to use the machinery. You may want to find a second location as next person doing laundry will also get some of your "rust stains" in the most obvious places on their clothes.

People say Plasma, and Ox/Ac is sometimes dangerous, but they fail to mention the dangers that remain after you leave the shop. :wink:

[Authentic Iron Works]

Archie, my understanding is that when you talk about burning things all you are talking about is bonding oxygen to other elements(combustion). For example, when you "combust" gasoline(gasoline is nothing but hydrogen and carbon ), you are mixing oxygen with hydrogen to make water(H2O) and mixing carbon with oxygen to make carbon dioxide(CO2). You are also making Carbon monoxide(CO), which is incomplete combustion. Incomplete because it could potentially bond with one more oxygen.The reason you see water dripping out of your tail pipe is because you are making water through the combustion process. The heat and the bang that drives the piston is the energy released through the bonding process.


When you take steel to a high heat(scaling heat), the oxygen is readily mixing with the Iron molecules making Iron oxide. You see this flaking off your steel when you are forging. I think the only other element in steel is carbon so I believe we are seeing the oxygen reacting with the carbon in the steel when we see it spark. And this is what is happening when we use a torch. O2 is mixing with iron and carbon creating sparks and slag. That is also why you use shielding gas with your mig welder. Shielding gas is usually co2 or argon, both are inert and will not react with the steel and in effect the gas is preventing o2 from getting into the equation. Oxygen changes steel into different elements. So, your steel is changing shape and pitting because the the steel is disappearing into new elements. I am sure this explanation can be refined, but this is basically whats happening.

So when we are heating pure iron, there is now carbon to burn, no sparkler.

This is sort of the question I had with the CLinker post. I wanted to find out what other elements were forming with oxygen and whatever to form this product.

[Authentic Iron Works]

I would like to add that I misused the word "element" and would like to substitue "compound". An element cannot be broken down further. A compound is a combination of elements.

[Quenchcrack]

If the iron is sparkling, it is definitely oxidizing. This is indicative of a temperature around 2800F - 3000F. However, it is possible to burn (and ruin) your steel at lower temperatures. This can happen at around 2500F or less. It happens because the grain boundaries of the steel can have low melting point compounds (usually involving high sulfur) that melt before the steel does and the grains just fall apart. When you look at a fracture surface of a burned steel, it will look like a cluster of rounded rock candy or sugar grains. It cannot be fixed so you may as well pitch the piece in the trash. :cry: