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    Default How to harden tin?

    (wasn't sure correct forum. moderator, feel free to move this thread.)

    i'm melting tin for casting small hardware. The hardware will be tightened down with nuts and bolts, and mustn't be malleable or brittle.

    Is there any DIY way to harden it? Tempering, nitriding, etc...

    Going to try alloying with Bismuth and Silver. Supposedly hard recipe i found is 57%Bi/42%Sn/1%Ag

    Feel free to suggest other metals. I'm not committed to tin, bismuth, or silver. But need to keep things relatively low-toxic and low-temp. (home, indoor fab). Need to minimize shrinkage/expansion of cast part.

    thx!

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    Pewter would be the commonest use of near pure tin.Current L/F solders have around 1% silver for strength........If you want to go up a bit in the melt temp scale,consider a babbit .....tin,copper and antimony.......antimony is the traditional hardener for tin /lead mixes,a small trace of arsenic also makes the alloys heat treatable.

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    You can buy babbitt already made up with hi tin content no need to make your own mix.

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    Printers type metal.

    Type metal - Wikipedia

    Tom

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    Arsenic is highly toxic (and volatile too I think, in the molten state),steer clear of that!
    There are a number of low melting lead free alloys available with different shrinkage, hardnes, and melting temps. There is no need to re-do centuries of experimentation and scientific research.
    Look up Belmont Metals, for one good Sorce of info and premixed alloys.

    Brittania metal is the tin antimony copper alloy, a good choice actually, not Babbitt which is a family of tin lead alloys

    If you need it to be very low melting, and expanding upon cooling and curing there is of corse the chamber casting alloy cerrosafe. Expensive tho. And not very strong?

    On edit; Not very safe either, just checked, it’s got lead and cadmium.

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    True Babbit contains no lead....zero...........wheelbalance weights have arsenic and antimony for hardness.......but are being phased out

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    yes john, you are correct in that the original 1839 patent for Babbit does not call out a lead content, but in the intervening 180 years much of the "Babbit" has contained lead, as do many current alloys that call themselves such.

    to specify a lead free alloy it is just much easier to specify Brittania metal today. As it is often used in food vessels as "lead free pewter" it is usually fairly controlled chemistry, at least in the USA, EU, Japan and AUS.

    again, for the OP, Go to Belmont Metals website!

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    There is work hardening so impact

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    Some Babbit has a Nickle content..
    Probably not a lot, and I can't say how much it affects the melting point.
    But I recovered some from work, and it was some dang hard bullets that came out of that lot..

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    hi, i'm the OP. This is my new account. Thx for all the awesome replies-- i will slowly go through 'em.

    Quote Originally Posted by john.k View Post
    a small trace of arsenic also makes the alloys heat treatable.
    what do you mean "heat-treatable"? As a hardening process, after casting? How hot? How long?

    i plan to start with "pure" powder or ingot, and combine them in the melting pot. Home, indoor melting, so need low melting point.

    after casting, the alloy should be hard and heat-resistant (up to at least 100 deg C).

    thx!

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    Quote Originally Posted by BayviewBOOM View Post
    hi, i'm the OP. This is my new account. Thx for all the awesome replies-- i will slowly go through 'em.



    what do you mean "heat-treatable"? As a hardening process, after casting? How hot? How long?

    i plan to start with "pure" powder or ingot, and combine them in the melting pot. Home, indoor melting, so need low melting point.

    after casting, the alloy should be hard and heat-resistant (up to at least 100 deg C).

    thx!
    You plan to work with powders, you need to do more research.

    MOST metals are toxic. I'd dare say "all" actually, even the Iron we need for our blood. Much of that has to do with "as essential trace elements" vs any form of concentration.

    You can easily poison yourself, or those who share your space. Or not live long enough to have to care.

    Use of proven alloys, ready made, and as "shot", I'd strongly suggest, rather than either ingots or powder - can greatly reduce exposure time in processing and also cut the storage and handling risk.

    Purchase of metals as powder can also earn you a slot in Federal computers if you are not already in the databases. Not always a "good-guy one", either, even if all they do is keep one eye on yah the next forever years.

    "Casting" is not the only use powder metals have been put to, y'see.

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    Quote Originally Posted by thermite View Post

    MOST metals are toxic. I'd dare say "all" actually, even the Iron we need for our blood. Much of that has to do with "as essential trace elements" vs any form of concentration.
    Everything is toxic It all depends on concentration

    Peter

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    Quote Originally Posted by thermite View Post
    You plan to work with powders, you need to do more research.
    that's what i'm doing here.

    MOST metals are toxic. "shot", I'd strongly suggest, rather than either ingots or powder - can greatly reduce exposure time in processing and also cut the storage and handling risk.
    many thanks, i'm aware of the risks, and attending to that as well.

    Purchase of metals as powder can also earn you a slot in Federal computers if you are not already in the databases.
    If i'm not already in the database?! Many thanks, i'll keep it in mind

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    Quote Originally Posted by johnywhy View Post
    (wasn't sure correct forum. moderator, feel free to move this thread.)

    i'm melting tin for casting small hardware. The hardware will be tightened down with nuts and bolts, and mustn't be malleable or brittle.

    Is there any DIY way to harden it? Tempering, nitriding, etc...

    Going to try alloying with Bismuth and Silver. Supposedly hard recipe i found is 57%Bi/42%Sn/1%Ag

    Feel free to suggest other metals. I'm not committed to tin, bismuth, or silver. But need to keep things relatively low-toxic and low-temp. (home, indoor fab). Need to minimize shrinkage/expansion of cast part.

    thx!
    .
    reminds me of joke when old guys send apprentice to heat treat with a lead hammer to have it hardened. obviously cannot be done or rather never going to get that hard compared to tool steel.

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    How about Kirksite? It's used (or was used) for metal forming and stamping dies.

    Primarily zinc I believe.

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    Quote Originally Posted by johnywhy View Post
    (wasn't sure correct forum. moderator, feel free to move this thread.)

    i'm melting tin for casting small hardware. The hardware will be tightened down with nuts and bolts, and mustn't be malleable or brittle.


    Feel free to suggest other metals. I'm not committed to tin, bismuth, or silver. But need to keep things relatively low-toxic and low-temp. (home, indoor fab). Need to minimize shrinkage/expansion of cast part.

    thx!

    The zinc based casting alloys will meet all of your requirements at 1/5 of the cost of the tin based alloys.

    Tin based alloys are used for bearings because they have low coefficients of friction with steel shafts. The alloys have 3 to 7 ksi room temperature tensile strengths and in most cases the strengths cannot be increased by heat treatment or cold working. These alloys also have a very low impact strength of around 3 foot pounds. The soft metal is a advantage in bearing applications because any grit present in the bearing during operation will bury itself in the metal rather than cause abrasive wear.

    The zinc based casting alloys have tensile strengths up to 60 ksi with impact strengths as high as 40 foot-pounds. . There are a number of alloys to choose from. The casting temperatures for sand molds are in the the 750 to 1000 deg F range depending on the alloy. The casting temperatures are only 100 to 200 deg F higher than the tin based alloys.

    The Kirksite alloy mentioned in a earlier post is also known as Zamak-2 zinc casting alloy. It is a 92 % zinc- 4% aluminum-4% copper alloy. It has a high tensile strength and a mid range impact strength. It is used in gravity fed casting. This alloy has been replaced with a 70% zinc - 27% aluminum-2.5% copper alloy called ZA-27.

    The most common zinc casting alloy in the US is Zamak-3 . It is a 96% zinc -4% aluminum alloy with 0 .1% copper and magnesium. It has a mid range tensile strength and a high impact strength. It is used in spin fed casting in permanent molds as well as gravity casting. .



    .
    Last edited by Robert R; 01-07-2019 at 03:05 AM.

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    Linotype metal - Casts great and is a eutectic metal. If my memory

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    Linotype metal is a eutectic, meaning the alloys all freeze at the same time. If my memory serves me. It is 78 percent Lead. 15 percent Tin and
    5 percent Atimony. Great metal for casting bullets.
    roger

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    Quote Originally Posted by Robert R View Post
    The zinc based casting alloys will meet all of your requirements at 1/5 of the cost of the tin based alloys.

    Tin based alloys are used for bearings because they have low coefficients of friction with steel shafts. The alloys have 3 to 7 ksi room temperature tensile strengths and in most cases the strengths cannot be increased by heat treatment or cold working. These alloys also have a very low impact strength of around 3 foot pounds. The soft metal is a advantage in bearing applications because any grit present in the bearing during operation will bury itself in the metal rather than cause abrasive wear.

    The zinc based casting alloys have tensile strengths up to 60 ksi with impact strengths as high as 40 foot-pounds. . There are a number of alloys to choose from. The casting temperatures for sand molds are in the the 750 to 1000 deg F range depending on the alloy. The casting temperatures are only 100 to 200 deg F higher than the tin based alloys.

    The Kirksite alloy mentioned in a earlier post is also known as Zamak-2 zinc casting alloy. It is a 92 % zinc- 4% aluminum-4% copper alloy. It has a high tensile strength and a mid range impact strength. It is used in gravity fed casting. This alloy has been replaced with a 70% zinc - 27% aluminum-2.5% copper alloy called ZA-27.

    The most common zinc casting alloy in the US is Zamak-3 . It is a 96% zinc -4% aluminum alloy with 0 .1% copper and magnesium. It has a mid range tensile strength and a high impact strength. It is used in spin fed casting in permanent molds as well as gravity casting. .



    .
    Thanks Robert, very useful info

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    A few more things to keep in mind.

    The zinc casting alloys can be grouped by freezing temperature range and melt viscosity. The alloys for sand casting have a wide freezing temperature range. The alloys designed for permanent molds have a narrow range.

    There is, for example, a casting processes which involves filling a metal mold , waiting for a fast freeze, and then dumping the molten center of the casting back into the crucible. This allows the caster to make a hollow part without a core. The process requires a fast freeze.

    There are silicon rubber resins available for use as zinc casting molds. The flexible molding material will also require a fast freeze alloy.

    The complexity of the casting, surface finish requirements, and the method of filling the mold will determine the melt viscosity needed for the job..

    The mechanical properties of zinc alloys are very sensitive to contamination. Zinc casting ingots can be used once without a flux. A recycled zinc alloy must be melted with a flux.

    Mixing up a batch of casting alloy using inexpensive 99% pure recycled zinc anodes and scrap aluminum will not produce a good casting. There are too many unknown ingredients.

    The fatigue strength of the zinc alloys is between 1/2 to 1/4 of their tensile strength depending on the alloy.

    Aluminum is used in the zinc alloys to strengthen the alloy, reduce grain size, reduce melting temperature, and reduce viscosity. However, the high aluminum content also reduces impact strength and may affect the dimensional stability of the casting. Alloys containing more than 1% copper will also have reduced dimensional stability as the casting ages.

    Some of the zinc alloys are better suited for chemical plating and anodizing.


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