Melting steel.

Discussion in 'General foundry chat' started by Ironsides, Oct 12, 2020.

  1. Ironsides

    Ironsides Silver

    On my youtube channel I get asked so many times, will my furnace melt steel? I always say no because I tried to melt ball bearing races a long time ago and the result was a blob of badly oxidized steel in the crucible. So this week I came across this video by PatJ making an attempt to melt steel in his fuel fired crucible furnace. It was no surprise to see it fail. PatJ is an expert in building high temperature furnaces so this means that it is impossible to melt steel in a backyard furnace.

     
  2. Peter, my foundry mentor told (as I recall from a few years ago) that steel was impossible as it becomes a burning foamy mass in a liquid petroleum gas fired furnace fed by a 210Kg gas cylinder. Assuming you could reach temperature, then you'd need those single use clay crucibles and cover flux made from crushed glass like the Sheffield steel makers. Mild steel begins to melt at 1400 deg C and I know Peter made monel castings an alloy which begins to melt at 1350 deg C. so a gas fired furnace can get close.
     
  3. Jason

    Jason Gold

    If anyone can pull it off, it's Pat.
     
  4. It's not so much reaching the melting temps as keeping the air from the steel as it ignites and burns, that's why they use bottom pour crucibles with cover flux.
     
  5. metallab

    metallab Copper

    Use electric arc melting. It goes quick (100g steel melts in about 4 minutes) and costs way less energy than a gas or oil fires furnace, because the latter barely reaches the required temperature of 1500 C.
    I did it for small quantities (up till 100g) using a DC welder set to 140A and a graphite crucible. I made soms stainless steel castings.

    Another option (I never tried) is injecting oxygen in the forced air supply. Rental oxygen cylinders can be used or also abandoned medical zeolite based oxygen generators.

    Here a Youtube video of a more upscaled attempt to melt steel with a garage EAF.

     
    Last edited: Oct 12, 2020
  6. 6BBA8F32-C402-45EC-BB11-0B9B8EEC97FA.jpeg In 2001 a university prof from my Alma Mater, Iowa State, and a Texas blacksmith teamed up to make not just steel, but real Damascus Steel (NOT the folded imitation foisted off as “Damascus”) identical to the fabled steel of yore. They worked in a “backyard“ furnace using period clay closed crucibles to make ingots of steel that were allowed to solidify in the crucible. Once cooled, the crucible is broken open and the “wootz “ is forged. That is how it was done at the time of the crusades. I have a print version of the article that used to be available free online but is now, sadly locked up. Your local library (remember libraries?) probably has a copy of the actual 2001 publication. A copy of the article was in a bin next to my bed—-bed time reading:



    Here is a more recent and less detailed description by the professor: https://www.mse.iastate.edu/news/john-verhoeven/

    General article on wootz. https://en.wikipedia.org/wiki/Wootz_steel
    Denis
     
    Last edited: Oct 13, 2020
    DavidF likes this.
  7. Ironsides

    Ironsides Silver

    I read that description by the professor and now I why these videos on youtube used this method ( bottle glass and leaves added to the crucible ). All of them got a ingot to forge but when taken up to forging temperature the ingots crumbled with the first blow with the hammer. What those people don't realize is that the leaves they added to the crucible carbonize and will be absorbed by the steel. Also they were using graphite crucibles which is another place where steel can absorb carbon. So what they got was a low carbon cast iron and if you try to forge cast iron it will crumble.

    So how do I know how quickly carbon dissolves in steel? I used a home made induction furnace for two years melting steel to make cast iron. So what you need to do is copy their method as you have a working furnace and fill the crucible with steel and see if you can forge the end product. You will find that your efforts are doomed to failure. If you want to be serious about melting steel preheating the combustion air will give you the extra temperature to get to steel pouring temperatures. This is how scrap steel was melted in an industrial scale using a reverbatory furnace with high preheat to the combustion air. I think most of those furnaces have disappeared because of EPA issues. Around where I live they all use arc furnaces to melt scrap steel.

    Metallab was right the only way to melt steel is to use electricity.
     
    Mark's castings likes this.
  8. OMM

    OMM Silver

    Using electricity is the best way but not the most efficient and very difficult to achieve in a home situation. A glass or rock slag needs to protect the metal until just before pour. Diesel fuel has the most kilowatts at the cheapest price for most people. The blast furnace is the cheapest if you can get your hands on coke. You can get lime stone anywhere pretty cheap.

    Mini mills work around the clock using AC electricity, then converting it to DC electricity. They get huge discount for their arc furnaces in off peak times. If I can sign a contract with only $0.02 per kilowatt hour from 7 PM to 7 AM, I'd be all over it. I would pull electricity all night long in to batteries and then sell it back to them during the day at $.78 per kilowatt saying I generated this through solar and wind turbines.
     
  9. metallab

    metallab Copper

    Well, electricity is also dirt cheap compared to, say, 50 years ago, but in the near future the rates will be flexible. In peak hours you will pay a lot more and in low hours you pay less. And in a 'home situation', current residential electricity (in the EU) is usually single phase 230V x 25 or 35 A and if you pay more fixed subscrption fee you get three phase 3x 25 or 3x35 A. However newer homes have standard three phase. I have single phase, so I can only use a 200A welder to melt 100g of steel. But in the future with electric cars residentials require much more power to charge their cars. And when you do not charge your car, a 400-600 Amp welder or a 30kW indunction furnace can be used and the latter are becoming more affordable. And (both hobby and commercial / industrial) induction melting and even arc melting is much more efficient in primary energy than fuel based furnaces.
    And the blast furnace is still cheap, but within ten years most of them will be phased out due to high CO2 emissions and the inefficient preprocessing of ore to sinter and pellets and coking of coal, both processes take additional (usually carbon based) energy.
    DRI (Direct reduced iron) by the COREX or MIDREX processes are much more favorable, even when all energy used is comes from coal. Companies like Primetals now build steel mills with much more efficient technology. And, despite the EAF being more than a hundred years old, it is getting used more and more in the steel industry and not only in minimills. Particularly in areas with renewable energy. And steel is so easy to recycle, that we barely need additional iron ore.
     

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