The Real World

Home enthusiasts discuss their Foundry & Casting work.

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RONALD
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The Real World

Post by RONALD »

As hobby casters, those of us who do casting of metal may do less than a couple of hundred pounds per year, as a bit of information, I posted what is going on in the real world of castings. As you can see below, the Germans are the most efficient, but the US is second, and the Chinese with many thousands of little foundries are not very efficient, tho, of course, very low cost because of cheap labor.
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ctwo
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Re: The Real World

Post by ctwo »

I think they left a zero off that last page.

Whats the general difference between gray and ductile iron?
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Harold_V
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Re: The Real World

Post by Harold_V »

ctwo wrote:I think they left a zero off that last page.

Whats the general difference between gray and ductile iron?
Gray iron contains flakes of graphite, commonly accepted as being capable of disrupting the slip plane of the iron. Results? Lower tensile strength--subject to cracking.

Ductile iron is inoculated with magnesium, which, in turn, causes the graphite to form spheres instead of flakes. The conversion is short lived---time is of the essence in pouring, as the conversion reverts back to simple graphite with time. The spheres do not disrupt the slip plane, so the resulting metal has far greater tensile strength (rivals mild steel). Ductile iron can be readily welded, unlike gray iron.

Ductile iron, depending on the alloy, also has little or no shrinkage when cast, unlike gray iron.

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steamin10
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Re: The Real World

Post by steamin10 »

Closely controlled ductile iron is used in industry, and has revolutionized' the casting industry. Often called 'nodular' iron, it is what production crankshafts are poured from for small engines of automotive and simiilar appllications. High strength, limited shrink, and realtive ease in workability compared to alloy steels, it hogs a very large shaped materials market, and serves well. Done poorly it is no better than cast radiators of days of yor, and is prone to fatigue, fracture, hard inclusions, (white iron) layering, leafing and sponge.

Modern processes, are very exact, and the formulation of casting iron, is relatively forgiving in the lessor levels, and trying at best, in higher specifications. Bottom lin is it works very well when done right.
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RONALD
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Re: The Real World

Post by RONALD »

I tried pouring ductile iron twice, and after the second pour decided it was not worth the bother; I could get the same results with bronze.

We had a rotating electric arc furnace at the school that had not been used in years, until I decided to use it. I first researched ductile iron, and then went to visit the metallurgists at Wells Mfg., in Skokie, Illinois. They, at that time, were pouring several hundred tons of iron each day. The guys gave me some inoculant, and told me how to use it.

I luckily had lots of help available, because at that time there was a night school foundry class with adults in it. I heated the iron up, but there was one problem, there was no equipment to measure the high 2800'F temperature required, so they used a chart that had Watt-Hours verses Weight on it for melting iron; bad choice!

That first pour was just too cold and as you can see, I lost many hours of work on that one. Not being one to give up, I tried a second time, and this time goosed up the Watt-Hours, and it poured correctly.

The amount of work and time, and the danger of an error, was too great to continue, I went back to bronze or aluminum.

All my later iron projects were poured at either Wells, or Artz Foundry; the cost to me was zero, all I had to do was bring in my molds.
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Harold_V
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Re: The Real World

Post by Harold_V »

One of the problems of ductile iron is that the sulfur content of the heat must be quite low, as sulfur interferes with the magnesium conversion.

Ductile iron is heads and shoulders better than gray iron, yet it possesses the same good qualities that are desirable for using gray iron. It's truly the best of two worlds.

In today's market, using bronze in place of iron wouldn't be economically feasible. That most likely wasn't true when copper was selling for $1/pound.

The big problem with casting ferrous alloys is heating. Ductile iron can't be produced from a cupola unless low sulfur coke is used. However, the discharge from the cupola can be treated to lower sulfur (it is readily removed with calcium carbide).

Modern melting is typically accomplished with induction furnaces. They don't alter the feed stock (unlike a cupola), so it's dead easy to convert scrap steel to ductile iron. That's what the semi-steel is you see marked on items such as chucks.

Harold
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RONALD
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Re: The Real World

Post by RONALD »

My dad was a forman at a company called Semi Steel in the 1940's. He supervised the making of the cores, and other molds. They did not know of Ductile Iron.

The words Semi Steel has a rather broad definition; Ductile Iron is narrowed in its definition.

I drove my truck down to H. Kramer http://hkramer.com/ in November of 2011 and purchased 500 pounds of C99700 at $5 per pound. Just a few years earlier, I had paid less than $2 per pound; it's like gold you have to save every scrap of gate, sprue, and riser. I do have several pounds of milling scrap that is not to easy to melt because it is so small it tends to oxidize.

I use the C99700 for certain parts where aluminum is not appropriate like frogs, etc. For other parts I use the A319 aluminum. I bought that for 50 cents a pound when they got rid of the foundry at the school.
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Harold_V
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Re: The Real World

Post by Harold_V »

RONALD wrote:My dad was a forman at a company called Semi Steel in the 1940's. He supervised the making of the cores, and other molds. They did not know of Ductile Iron.
Correct. Ductile iron was first created in 1943, when the International Nickel Company Research Laboratory added a copper/magnesium alloy to a ladle of gray iron. The resulting iron, when cooled, formed spheres instead of flakes. For what it's worth, they revolutionized the world of iron, for they now could pour iron that could resist tensile stresses, unlike gray iron. Ductile iron is used extensively today, for items that would not work in gray iron. Cam and crank shafts are a good example.

They play a little bit of a mind game with the consumer using the term semi-steel. It is, or it isn't steel, and semi-steel isn't. Steel has no carbon that is NOT is solution (steel must contain less than 2% carbon, as it won't stay in solution if it is higher), while gray and ductile iron do have. Semi-steel is typically produced by melting scrap steel, instead of using pig iron. I expect that's the mind game they play. Ferrosilicon is added to the heat to create gray iron. Glomag is the inoculant used to produce ductile iron.

Harold
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