Krypsis wrote:
> On 22/06/2010 2:42 AM, Omelet wrote:
>
> Recycling steel is a wonderful concept. The problems arise because of
> the vast range of impurities in the recycled material. Even running the
> recycled steel through the smelting process doesn't guarantee that the
> iron or steel output has the correct alloying makeup. Probably this
> arises because of the exotic contaminants that are in the recycled steel
> as opposed to raw iron ore dug up from the ground.
>
> Many years back, when we were running a desert rally in the Pilbara
> region of Western Australia, I took the opportunity to visit and do
> tours of the iron ore mining and port facilities. I was amazed at the
> purity of the iron ore they were digging up, anything up to 90%. Much of
> the ore was too pure for the smelters in Japan so one of the functions
> of the loading process at the port was to grade the ore into the desired
> purity level by blending high and low grade ores. The smelter operators
> knew exactly what impurities were present and could gear the processes
> up to deal with it.


I worked in an alloy smelting plant for two summers, one of them in the
furnace room and one in the sample room. We used to take samples of the
ore that was brought to our plant by ship. The ore was unloaded from the
ship into sump trucks and we took a pailful of ore from every 5th truck,
ground it down, split it into parts and ended up with one pail of
powdered ore to send to up to the lab for analysis.

Mix recipes were then made up for the furnaces, with the amount of each
type of ore, coke and lime to go into each batch in the furnace. The
stuff was all cooked up in arc furnaces and a sample was taken from the
middle of each tap, ground into powder and thens ent to the lab for
analysis. Each batch was poured into a pan mold to set and then
transferred to cooling racks where they usually fell apart. An tag was
attached to each one to show the amount of carbon, manganese, iron,
silicon etc. Then it was was crushed up and put into drums. When an
order came in, various batches were mixed together to come up with the
proper percentages of each element in the alloy additive. They went to
steel companies to be added to the steel in order to have the proper
make-up of whatever specialized steel they were making.




> If you get an opportunity, go visit a car recycling plant and see just
> how cars are recycled. They aren't stripped into their component parts
> and graded into various levels of steel. Instead the entire care is
> shredded or just simply crushed into a block. Contaminants include glass
> and plastics, not good inputs into the steelmaking process.


As a matter of fact, I was in a car recycling yard last month looking
for a hub cap for my wife's car. The tires had been removed and the
wheel rims were used to old the bodies up off the ground (not mounted).
Various parts had been removed from some of the cars. They keep tabs of
what they have in the yard. If someone comes in looking for a particular
part for a car, like an engine, alternator, door, fenders etc. they may
go out and remove it for the person, or let him go out and get it himself.


Obviously, there is limited demand for some parts, so they don't just
buy up every old scrap car around for parts, but there really are car
part recycling centres, not just scrap car dealers.