What designates a material "semi-steel?"
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  1. #1
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    I've seen the term for years, and I'd like to know more about what it means. I most recently ran across the term in a description of a lathe bed material for DSG lathes:

    http://www.lathes.co.uk/dsg/page5.html

    Thanks for the input you can give me.

    Richard

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    semisteel (¦sem·i′stēl)

    (metallurgy) Low-carbon steel made by replacing about one-fourth of the pig iron in the cupola with steel scrap.

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    You see it a lot in caster wheels. I've often wondered too. Thanks, Evan.

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    In the Bison chuck catalogs, they list chucks as available in cast iron, semi-steel, and steel.

    With most machine tool elements, you typically want the vibration damping of grey cast iron, steel has a much higher yeild point, so that could be an advantage with a large chuck on a big machine?

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    Is semi-steel the same as Meehanite?

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    Gee.. And here I thought this was what Freightliner and Peterbuilt used to make their trucks.

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    Gee.. And here I thought this was what Freightliner and Peterbuilt used to make their trucks.
    Nope, it's the act of large over the road truck larceny.

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    Evan,
    AKA ductile iron

    Mudflap,
    No!

    Danley also used to sell die sets in "semi-steel. If you buy a chuck in semi-steel, make sure that the RPM matches your machine.
    JR

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    Google yielded several incorrect or useless definitions. The one Evan found is an example. Note that cast iron or "pig iron" is a high carbon iron. You do not get low carbon steel by adding 25% scrap steel to pig iron.

    The definition I believe, based on the context of semi-steel lathe chucks is:

    Anvilfire definitions (see semi-steel)

    My brief version: A mixture of cast iron and steel scrap, with better ductility and strength than plain cast iron.

    It sounds like the term is for a product with too much carbon to be called steel and too little to be called cast iron. And who knows what alloys were in the scrap? There is no set standard for the mixture, so manufacturers have a lot of leeway in using the term for their product.

    Larry

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    Also this - from the horse's mouth so to speak. Definitely not "low carbon steel"

    Old post

    John

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    The definition I found is correct in describing the process although it should have said a low carbon cast iron (instead of low carbon steel), which is what semi-steel is.

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    It sounds like the term is for a product with too much carbon to be called steel and too little to be called cast iron.
    If the vendor sells chuck in all three: cast iron, semi-steel, and steel, I still don't understand how you chose which metal is best suited...

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    If the vendor sells chuck in all three: cast iron, semi-steel, and steel, I still don't understand how you chose which metal is best suited...
    They usually give a speed rating for each do they not? Thus selection is based upon what speed your machine/work is or capable of. IIRC, they are priced accordingly with cast at bottom and steel at top. So if you are chucking hard and spinning fast and willing to spend go steel.

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    Thanks Bluchip -- that makes sense.

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    As well, the beauty part of a cast chuck is the ability to cast lightening pockets. So, if acceleration/decell is a concern for a machine (weak clutch/brake, lite HP) or wt capacity is in doubt cast can get it done lighter. It can be signifigant in 14" and up stuff where RPM is contained by the size of work and where the work will usually be weighty.

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    Yep, I'm glad they lightened the 72" chuck that I've got comming in. Now, it only weighs 10,000 pounds! BTW, it's cast steel (ASME Grade SA216 or WCC). At 300 RPM, that't over 5,000 SFM at the OD. No semi-steel here!
    JR

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    Semi-steel... that explains those HF 110 lb anvils.

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    John,

    On oldpost, your authority and Forrest both alluded to a problem in that semi steel had no specification. In JR's post I note an ASME grade spec for semi steel. That would seem to remove the objections to the term based on lack of a spec. Perhaps the Ethiopian is now a free man? Any comment?

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    Stu,
    you might want to reread JR's post.

    SA 216 is cast steel. It is even listed in the ASME piping code for high temperature pipe fittings. Not semi-steel, real steel.

    Thermo1

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    I think in old post, if the time is taken to digest what a hands on authority like Richard M. wrote about 89 years ago, it is an indictment of the concept of the creation of a cheaper way to make cast iron (lots of scrap steel to replace more expensive pig iron) and then naming it something that is misleading as respect to properties achieved in actual practice. The passing of time will not change this.

    John


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