Steel vs cast iron? metallurgical question

[RainsFire]

IT seems to be a craze lately to make your own steel, and its something I really want to try at least once. but I guess something I don't get is what is the difference between cast iron and steel? is it just part of the process where you don't let it oxidize? or is it a heat thing, anyway.. any help would be lovely.

Thanks guys, Kenon.

[irnsrgn]

wrought iron has no carbon, old mild steel had .03% carbon, .35% is the start of high carbon steel, bearing races generally have 1.0% carbon. cast iron has as much as 3 to 4% carbon much of it in a free state, picture a glass full of marbles representing iron molecules and you fill in the void with black pepper representing the carbon. Mild steel has a tensile strength of around 60,000, cast iron is around 36,000 and is brittle, it will break before it gives or bends. Pig Iron called that because of the way it was originally cast it looked like a bunch of piglets nursing their mother, has much more carbon before it is refined into usable cast iron. Cast iron is refined into mild and other steels by removing a lot of the carbon and having other alloys incorporated into it.

[Ice Czar]

^

a bit more

Iron and Steel - LoveToKnow 1911

[R Funk]

Cast Iron is the natural product of a blast furnace. The carbon in the coke or charcoal used to fuel the blast furnace get absorbed by molten iron. Typical carbon content is 3% to 4%.

To produce steel, the carbon is burned out the cast iron in the "basic oxygen process" which is basically a large crucible in which oxygen is injected to burn out the carbon to a 0.1% to 1% level.

Historical Steel production processes included processes to add carbon to wrought iron.

Wrought iron has essentially no carbon content but appear fiborous due to fibers of silica or slag.

[matt87]

Wrought iron was produced in a bloomery historically; tall hollow structure with air draft from the bottom. Light a charcoal fire inside and add charges of iron ore, flux and charcoal at regular intervals. Sustain for a many hours. The product is a bloom, a sponge of iron plus slag and a few other impurities. Heat to welding heat and squeeze together. Heat, hammer together etc. over and over. Each time, more impurities are removed and you get a more homogenous product.

[RainsFire]

oh, so cast iron would melt at a lower temp right? because of its high carbon temp.. so hmn... this is very interesting, I have a plan for a furnace small runs, totally controlable, high temp, and no molten refractory waste.. Should work, and I think it'll be one of the first wvo powered steel smelters.

thanks guys!

[Ice Czar]

Originally Posted by RainsFire

wvo powered

Id be very interested in that design
Im working on adapting a slightly cooler forge\furnace design
Dasifier (top stage is woodgas, bottom stage producer gas, modifications that are about include employing superheated compressed air, personally looking at adapting low-swirl combustion and or a secondary fuel source (methane\natural gas) in a modified cyclone furnace)

[RainsFire]

hmn, very cool design. I had never thought of pumping heat from a solid fuel source into a seperate melting furnace, that could make things even more controllable as far as the enviorment being absorbed go..

what I'm shooting for is to eliminate the need for refractory around the bloom, because it seems to always corrupt the steel unless you use really expensive refined crucibles..

I'm thinking of starting the melt with a thermite reaction, which would knock out alot of the time consumption for the initial heat, not to mention it can yield really controllable alloy's. but ya..

I'm thinking a charcoal "crucible" or bed for the ingot to land on.. so instead of consuming refractory components, all it will consume would be carbon..

but I dont know, I'm still toying with design and like the idea of taking something like a bloomery, and combining it with a crucible melt with wvo as its heat source, best of both worlds so to speak..

anyway, maybe we should collaborate, all I'm really doing is messing around with hotter fire and trying to figure out something cool for my senior project for highschool..
making steel would definately be a first for my crummy school..

[Ice Czar]

well when it comes to making a cupola or furnace able to melt steel thats like learning to run before you can crawl

Im currently aiming slightly lower, melting bronze, and a basic forge
Im already experimenting with gasifiers as quickly as I can eat the conents of the food cans to make them

Looking to perfect a design at a slightly smaller scale with cheap materials before investing in serious tube, slip rolling steel and applying high quality refractory coatings'

When it comes to gasifiers its the superficial velocity (pdf) that matters. The Dasifier or Twin Fire Gasifier is somewhat unique in that the bottom stage is creating producer gas (largely carbon monoxide) for a second stage close coupled combustion, downdraft gasifiers are the best bet for "cleanable" gas (to run motors), updraft gasifiers for the highest efficiency, but a basic twin fired (pdf) can do between 460 and 520C with wood. (860F to 968) add a higher superficial velocity with compression it can melt brass, superheat the compressed secondary air and....its sounds like this

[RainsFire]

ya, I've been thinking of doing some alum castings.. and my parents used to do lost wax bronze castings, so they are fairly knowledgeable in that area.

also, today during our oil collection trip we got permission from a hotel owner who is removing an incinerator from the basement to pick up the firebrick they had removed.. Is about 3pickup truck loads of soft white non asbestos firebrick, most of it in good shape, and another load of broken brick for grog..

so I'm going to see just how much heat that stuff can stand, and maybe form the basis of my smelting furnace out of it..
we could have a fireproof yellow brick road.. or a shop made entirely out of firebrick..
well anyway, let me know how it goes this is something I am really interested in and you seem pretty knowledgeable about it.