“burns out” is where my confusion comes in. That explanation might make sense as far as the body that got cubed into the Lincoln in James Bond’s “Goldfinger”…
What I find myself wondering most about are property determining alloys. Some alloys are added to enhance threadability for example, while others to create hardness. At the temperatures necessary to melt the work, it’s not like you can just pick the right solvent, as you can in a chem lab, to wash out the undesirables…at least I don’t think you can.
“Somebody with more experience can probably correct me”
That might be me. I spent 25 years in the scrap business. Contaminants do not “burn” out but most can be removed. Carbon, of course, is critical but nowadays can be added by coke injection or removed by blowing air or oxygen through the melt. Sulfur, Phosphorous, and Chromium can be removed by fluxing with limestone. The problem contaminants are copper and nickle. To reduce the level the mill must dilute it. The best practice is to buy from reliable sources such as large scrap procesors. These yards will be equipped to shred mixed items such as electrical appliances , switch gear and the like so that the metals are separated and recovered.The most common problem, electric motors, are worth enough that they can be separated and sold as an item. Nickle might come from aaaaarmor plate, not that common, and some tool steels. Again the sophisticated yard will separate these for sale as a more valuable item.
High scrap prices bring all kinds of wannabes into the business and their lack of experience and priciples lead to low quality. In addition since the mid 1980s when the length restrictions were removed on trucks some new product moved to trucks. previously 50 and 60 foot items moved almost exclusively by rail. Mills wanted scrap by rail as that assured a supply of eqiipment for their products. That coupled with the ridiculous PSR fad were the name of the game is drive customers away leads to these newbies and amateurs being able to deliver by truck and so lower quality scrap will get in. Melt shop people know what they are doing so I doubt that it is a big problem.
The iron ore is milled to a powder finer than talcum, and then goes thru a flotation process that separates the metalics from the country rock. The concentrate can be mixed with clay in a kiln to form taconite pellets. Knowing the composition of the mines output, steel companies can choose which mine to buy from.
I guess American steel producers don’t get much scrap from the Alang shipbreakers in India. I would guess the scrap from shipbreakers would be of a rather high quality. Maybe even higher quality if it war vessels being scrapped.
tdmidget - Thank you for your insightful reply. I was thinking of those processes when I said “burned out”, but I also see how that is absolutely the wrong way to describe it.
Be careful here. The issue I remember with radioactive contamination was for very specific circumstances: use of steel for construction of diagnostic and test equipment that could be thrown off by the relatively small residual atmospheric concentration of nuclides in all steel processed since the era of above-ground weapons testing – leading at the time of realization to finding pre-WWII sources of scrap, notably sunken warships in the Pacific, that were free of the problem.
I do not know if modern cost-effective processes can remove those elements from scrap; I suspect that careful sourcing and treatment of virgin ores could provide ‘new’ alloy steels without this low level of nuclear contamination, but perhaps not at economical scale at all points in the required processing.
If there is, or has been, a concern with actual ‘health’ levels of radioactive contamination of scrap (e.g. with americium from older smoke detectors and the like) I’d like to know more details.
Deep wells, such as oil&gas or brine, may have radioactive scale from trace minerals that accumulate on the pipe. Pipe pulled from the well must be tested for NORM
The usual iron ore mineral is hematite. Magnatite is another that has Fe++ in addition to Fe+++. Magnatite can be seperated out by running the flotation slurry over magnets. Other metal elements often associated with iron mines are those close to Fe in the periodic table like Mn, Cr, Ti. They are probably more like trace elements in the big Lake Superior mines. Nevertheless there may be mines with lots more. I recollect that the Tahwas Mine in the Adirondacks had considerable Ti, although there may have been some segregation of ore bodies.
Be careful here. The issue I remember with radioactive contamination was for very specific circumstances: use of steel for construction of diagnostic and test equipment that could be thrown off by the relatively small residual atmospheric concentration of nuclides in all steel processed since the era of above-ground weapons testing – leading at the time of realization to finding pre-WWII sources of scrap, notably sunken warships in the Pacific, that were free of the problem.
I do not know if modern cost-effective processes can remove those elements from scrap; I suspect that careful sourcing and treatment of virgin ores could provide ‘new’ alloy steels without this low level of nuclear contamination, but perhaps not at economical scale at all points in the required processing.
If there is, or has been, a concern with actual ‘health’
Are there actually situations where scrap iron or steel is melted down and directly made into a product? My understanding was that scrap iron could be recycled but the result would be blended with iron ore / taconite pellets to produce useable iron/steel.
Removing radioactive material from a rail car is not really that difficult but it is a pain in the you know what. The rail scale is setup with radiation detectors which are very sensitive. If an alarm was tripped the car was moved back and forth very slowly three times to make sure it was a “true” reading. If it is true its just a matter of magging it out of the car and spreading it out on the ground to locate it with a hand held detector. Usually a few magloads of scrap until you find it and then put it in an end loader a moving it to an appointed quarantied area and have an outside contractor take care of it. When an alarm was set off the whole department was aware so there was no chance of contaminated scrap being used. I worked in a “mini-mill” which only uses scrap metal, so I cannot comment on iron ore.
I can’t comment on steel, but cast iron can be totally scrap. There may be small amounts of minor ingredients added to get the pour to the specific formula, but it will be 99% or so scrap.
I’ll reply to several people here. I don’t post very often since I’ve been on moderation for about 10 years and I’m tired of not being able to have a prompt response.
nyc ohio, much cast iron is 100 % scrap due to the lesser demand for it these days. An exception would be high volume items like engine castings which would use a high percentage of pig iron.
murphy siding- Crushed autos are bound for a shredder. There a large hammermill will reduce them to fist size pieces easily separated by magnets. This is a prime feedstock for arc furnaces.
Overmod- radioactive materials in steel are a real concern when quantities of highly radioactive materials are involved. The incidents which brought this to attention involved aged medical machines palmed off to third world countries where they were never used for the intended purpose. These usually involved cancer treatment equipment that used Cobalt 60 as a source. One incident in Brazil resulted in several fatalities when children played with the luminous pellets form such a machine. It came to light in the U.S. when cast iron table bases cast in Mexico and contaminated with Cobalt 60 were detected at a military base in the US. Americium 241 is not a real threat because it is produced in tiny quantities in fission reactions. A ton of spent fuel contains about 100 grams of it. The only common use for it is in smoke detectors and 100 grams is probably a years supply for the U.S.
However the Nuclear regulartory Commission and the nuclear power industry subscribe to ALARA which means “as low as reasonably achievable”. Therefore they perform as though it is the end of the world. ALARA is on the whole a very good standard but should not be used to establish fear in the general population.
I have been away from the scrap industry for 25 years but when I was invilved the procedure for radioactive scrap was " Your car no xxxxxxx has been rejected for radioactivity. Have it removed within 48
To deliver say 22 tons of scrap 200 miles if we’re talking bales I would be charging between 3 to 3.50 a mile loaded for it. It breaks down to about less than 2 cents per pound to ship to the mill. That’s figuring on coming back empty for another load.