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Thread: Lead grade for casting keel

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    Default Lead grade for casting keel

    Salvage companies sell impure lead (with bits of steel, etc.) for about 45 cents a pound. Pure lead costs 75 cents. Is the contaminated lead suitable for casting a keel for a boat that'll live in saltwater?

    For a large keel c. 7500 lbs., the cost difference is considerable.

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    Default Re: Lead grade for casting keel

    Bits of steel will float to the top as dross when the lead is melted down.

    Be nice to know what you'br actually got, though.

    Keels don't want to be pure lead (tensile strength 1160 psi). It want's to be allowed with a few percent antimony to harden it up (3% alloy has tensile strength of some 4700 psi; 5% alloy has a tensile stength of some 6360 psi).

    Adding tin to lead makes (according to wikipedia) the molten metal more fluid and the resulting alloy more tough with greater resistance to wear.

    Lead tire weights are alloyed with antimony. Stuff like like old lead pipe, lead roof flashing, old X-ray shielding, etc. is likely pure lead. Bullets tend to be alloyed with maybe 2% tin and up to 8% antimony. Old printing type metal might vary from 3-18% tin and from 11-28% antimony. Linotype metal is 3% tin, 11% antimony with the remainder lead.
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    Default Re: Lead grade for casting keel

    So, is it practical to get a sample of lead assayed (is that the word?) for its composition or do you just have to guess based on where your stuff came from?

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    Default Re: Lead grade for casting keel

    Thanks Nicholas, good info .I cast my keel from wheel weighs but I would be happier had it been stronger .The low tensile strength x the mass can make things floppy.
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    Default Re: Lead grade for casting keel

    Since it wouldn't be possible to cast a large keel in one go, would the best course to be to assay each molten batch and then adjust the alloy (i.e. add tin and antimony as needed) before pouring?

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    Default Re: Lead grade for casting keel

    Quote Originally Posted by PeterSibley View Post
    Thanks Nicholas, good info .I cast my keel from wheel weighs but I would be happier had it been stronger .The low tensile strength x the mass can make things floppy.
    I'm not sure I'd trust my numbers...I got them via Google (worth every penny I paid for it).

    This book, Engineering Properties and Applications of Lead Alloys seems like it would be useful...but at c. $270 a copy, just wee bit pricey. Inter-library (the big building with all the books) loan might be your friend there.

    Googling also suggests that the plates in lead/acid batteries, these days is being alloyed with calcium and/or aluminum as a replacement for antimony. Seems like that might not be such a good idea in a salt-water marine environment, what with electrolysis and suchlike.

    Also notices that one of the things the tin does is to improve the wetting-out properties of the molten metal and improve its bonding with copper and steel. Something to consider if casting keel bolts in place.
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    Default Re: Lead grade for casting keel

    Quote Originally Posted by Chip-skiff View Post
    Since it wouldn't be possible to cast a large keel in one go, would the best course to be to assay each molten batch and then adjust the alloy (i.e. add tin and antimony as needed) before pouring?
    You really should cast it in one go, or the dross on each pour will prevent the next pour from bonding. I have seen a keel like this, one stack of 1 inch thick slabs that came apart when the keel bolts were changed out.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Lead grade for casting keel

    Quote Originally Posted by Chip-skiff View Post
    Since it wouldn't be possible to cast a large keel in one go, would the best course to be to assay each molten batch and then adjust the alloy (i.e. add tin and antimony as needed) before pouring?
    My pour was 5400 pound and really very simple and easy .... once I'd stack the ingots in the pot !
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    Default Re: Lead grade for casting keel

    Quote Originally Posted by Nicholas Carey View Post
    I'm not sure I'd trust my numbers...I got them via Google (worth every penny I paid for it).

    This book, Engineering Properties and Applications of Lead Alloys seems like it would be useful...but at c. $270 a copy, just wee bit pricey. Inter-library (the big building with all the books) loan might be your friend there.

    Googling also suggests that the plates in lead/acid batteries, these days is being alloyed with calcium and/or aluminum as a replacement for antimony. Seems like that might not be such a good idea in a salt-water marine environment, what with electrolysis and suchlike.

    Also notices that one of the things the tin does is to improve the wetting-out properties of the molten metal and improve its bonding with copper and steel. Something to consider if casting keel bolts in place.
    From your figures I think next time I'll ask my friendly local non ferrous scrap dealer for some antimony. About 250 pound of it.
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    Default Re: Lead grade for casting keel

    in 2 t of lead i put 30 kg of antimony for the new yacht. in 3 t of lead i put 70 kg of antimony for may last yacht. the 3 t keel was 20' long. it did not sag when lifted and had a nice ring to it when tapped with a metal rod.

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    Default Re: Lead grade for casting keel

    Bern, I tipped my 2 ton 3.6m long keel onto it's side and it bent from the impact as it was only supported on 2 cross timbers 2.4m apart . It bent about 10mm, I bent it back a little but had to plane the rest of the bend out.

    Antimony next time.

    Bern, where did you buy yours ?
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    Default Re: Lead grade for casting keel

    So if the lead was from a single source, it could be assayed before melting and the proper amount of antimony and tin added. And if it was from several sources (e.g. tire weights vs. lead pipe), the probable alloy content of each sort could be estimated and the alloy calculated by the weight of each type.

    It seems the proportions need not be exact, and that it'd be better to have a bit too much antimony rather than too little.

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    Default Re: Lead grade for casting keel

    Quote Originally Posted by Chip-skiff View Post
    So if the lead was from a single source, it could be assayed before melting and the proper amount of antimony and tin added. And if it was from several sources (e.g. tire weights vs. lead pipe), the probable alloy content of each sort could be estimated and the alloy calculated by the weight of each type.

    It seems the proportions need not be exact, and that it'd be better to have a bit too much antimony rather than too little.
    That's certainly what I'll be aiming for next pour.
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    Default Re: Lead grade for casting keel

    There is a good table of properties of Pb-Sb alloys here: The good news is that 1% antimony doubles the strength, 6% doubles it again and 10% only buys another 10%. Some tin will increase the strength as well. In other words,as long as you have more than 1% antimony,you are in reasonable shape.

    I have seen some interesting pictures of keel casting on this forum, and one very important detail that is not always obvious is the need to protect the legs holding the melting pot from the fire. Most of us know this, but it don't hurt as much to say it as it does to forget it.

    Calcium is not a problem. They only add fractions of 1% and you will probably lose most of it as dross anyway. The corrosion issues with respect to alloying are fairly minor compared to other metals. http://www.alchemycastings.com has some more information on the web, but I have no idea about their pricing etc.

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    Default Re: Lead grade for casting keel

    peter i got my antimony from brisbane. northern smelters is the name of the company.

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    Default Re: Lead grade for casting keel

    How is a sample of lead assayed?

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    Default Re: Lead grade for casting keel

    I am a chemist and spent the bulk of my career in analytical chemistry and lead-acid batteries. Analysis of an unknown lead sample would be quite expensive as you would have identify what elements you are analyzing for (qualitative analysis) and then perform quantitative analysis to determine the amount of each alloying element.
    You don't really need that level of information for casting a keel. The principle analysis tool required is a hammer. Pure lead makes a dull "thunk" when hit with a hammer. Alloying elements, which are added to increase strength and stiffness, tend to give more of a ringing when you hit the pig or ingot. Very high antimony alloys (master alloys & linotype alloys) almost ring like a bell. As has been noted elsewhere relatively small amounts of antimony have a great effect on lead ally strength and hardness but the magnitude of the increase in strength falls off rapidly as the alloy levels are increased. Also not that at very high antimony levels (more than 12%) lead can get brittle enough to break and shatter, especially if subject to high cooling rates.
    For a practical method to characterize your scrap lead using a hammer test you can make up a small ingot of scrap lead from wheel weights ( the ones with steel clips in them not the stick on variety) which is about 3 % antimony and a small amount of tin. and another ingot from roofing lead ( which is essentially pure lead). A hammer blow will show a clear difference between the two "standards" and give you a rough idea of the alloying level of your scrap lead sample.
    To increase fluidity of your casting lead some lead-free solder can be added, this is about 99 percent tin. Even a little as 1 % tin in your casting alloy will make a real difference. You can ignore calcium and other alloying materials in your scrap lead. Calcium and aluminum contentis generally less than 0.1% and will mostly end up in the dross if you melt the lead in air ( as opposed to a gas shielded pot as used in the battery industry. I've never heard of galvanic or electrolysis problems from minor alloying elements in any lead or lead-antimony-tin alloys. That is: there is no de-calcification or de-aluminization issue and the miniscule amounts of silver that might be introduced by using lead-free solder to increase the tin content will not cause "de-leadifcation" of your keel.
    Depending on how old you lead is, that is if it came from very old batteries at some point in one of its recycling reincarnations, it could contain a small amount of arsenic. This is not necessarily a safety issue. It will not leach out of the finished casting and as far as arsenic vapors coming off during melting and casting it is not an issue. Arsenic sublimes at 1137 F well above lead's melting point of 621 F. As long as you are adequately protected from the lead fumes you are totally safe from the arsenic. Note that it is not fumes of elemental lead that are the real safety issue with melting lead, lead boils at over 3,100 F so very little vapor is formed. It is the lead oxide dust that forms when lead is melted in air at normal lead melting temperatures that is the health hazard. Do not ignore massive ventilation and other methods of breathing protection when casting lead!

    /// Frank ///

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    Default Re: Lead grade for casting keel

    Quote Originally Posted by JimConlin View Post
    How is a sample of lead assayed?

    A lab that does metallurgical testing often has a spark tester that can do an accurate elemental analysis quickly for a reasonable price. It is a lot faster and easier than wet chemistry, and you don't need to know what you are looking for. There are also hand held X-ray fluorescence guns that are used for sorting alloys and looking for lead in consumer goods that can do an adequate analysis in seconds. Interpreting the data can get interesting.

    If you can cast a small ingot, Brinell hardness is the quickest and most economical test that will tell you how strong the alloy is. The link to the mechanical properties table has both strength and hardness, so you can use it to get the strength of the sample from the Brinell test. The other thing to try is a bend test. If you cut a piece say 1/4 to 1/2 inch thick, it should bend without breaking. I think Frank would have a better idea how much bend, but I'm guessing that you shoule be able to bend a 1/2 inch bar at least 90 degrees.

    I like the hammer test that Frank described best though. How much more practical can you get?

    One way to make a fairly direct comparison to a known hardness sample is to place a ball bearing on the unknown ingot, hold the known hardness sample on the ball and whack it with a mallet. The ball will dent both sides with exactly the same force, so comparing the diameters of the dents gives a good indication of the relative hardness. This works on anything softer than the ball as long as both pieces are similar materials and the hardness of both is in the same ball park, so to speak.

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    Default Re: Lead grade for casting keel

    Thanks.

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    Default Re: Lead grade for casting keel

    Thanks Frank ...very useful indeed .
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    Default Re: Lead grade for casting keel

    Preparations are underway for my smallish keel pour. The dimensions are approximately 3" high x 7" wide and 7.5' long weighing about 600 lbs. There's a centerboard slot running about half the length. I'm short about 130 lbs. of lead, but what I do have appears to be pure or mostly pure lead. I'm basing that notion of purity on the post #17 where Mr. Wentzel describes the sound the lead makes when hitting it with a hammer. I'm concerned that my cast keel is going to be too flexible for the machining and attaching. Antimony seems to be the answer to provide some stiffness and small quantities appear to have a significant effect. I have about 10 lbs of antimony, but I'm clueless how to incorporate this metal. It has a melting point nearly double that of lead. A Google search indicates that the bullet casting folks commonly make an alloy of lead, antimony and tin. However, there is some sort of flux agent that they utilize. Mr. Wentzel also describes adding lead-free solder as a source of Tin. Has anyone added antimony to their lead keels?

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    Default Re: Lead grade for casting keel

    When the ballast keels were cast for both "Seraffyn" and "Tallisen" Lynn Pardey and my wife both put on their bikinis and collected a lot of wheel weights from local tire stores. We also had the waiters and waitresses at local eateries collecting the lead caps from wine bottles which added over a hundred pounds to one of the pours. Then, we had lead pipe from the phone company as well. A lot of lead was donated from Lord knows where too. Larry did add antimony to the pours of both keels. We were always up wind of the pour
    Jay

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    Default Re: Lead grade for casting keel

    Just a note about working with scrap lead. Besides ensuring that it is absolutely dry, thereby avoiding "steam bombs" of molten lead flying out of the pot, be very careful to ensure there are no voids or hollows in the scrap you are melting. One common mishap is melting lead pipe or tubing and bending it up to fit in the pot. The bends result in crimping the pipe or tubing at the bend. When a crimped section of pipe is added to the melted lead in the pot... instant explosion when the air in the pipe expands and has nowhere to go. (If you are lucky, the hot air will find a way out and only splatter lead, as opposed to the pipe bursting and splashing lead all over.) Similarly, adding scrap lead which has been stored outdoors, as it usually is, and has had water find its way in to a nook or cranny unnoticed will ruin your entire day. Full face protection is advised. In the event of a spatter, a face shield can save you an eye. Also, do not wear tightly laced up work boots when casting lead. Foundry men, I've been told, remove the laces entirely from their work boots. The reason is that if there is a mishap, such as a spilled ladle or a broken mold that sends molten lead downward, it very often will hit footwear. If this happens, and you certainly don't want it to happen, you will want to get your foot out of that boot as quickly as humanly possible. Common sense should stand anybody casting lead in good stead, but Darwin's Law holds that stupidity will always trump common sense at some point.

    A couple of updates on sourcing lead. These days, there are lots of environmental regulations that make finding scrap lead somewhat harder than in the past. You can pretty much forget about wheel weights these days in most places. They've either made them out of something else entirely or the government requires proof from the garages that they are recycling this "hazardous" material by showing receipts from the scrap metal collectors, who have a license to do that. I haven't heard of anybody being able to get wheel weights for keel casting in ages, in CA at least. You should forget about spent storage batteries. There is so much crud in them they really aren't worth the trouble. Busting them up is a huge PIA and you have to deal with the acid. And, again, nobody's giving away old batteries in any quantity anymore. Most outfits require a hefty return deposit, like an old fashioned Coke bottle, as required by local law. If you can find a heavily used old outdoor firing range that the owner will let you "mine," spent bullets can be an fairly good source, although if there's a lot of copper jacketed stuff in there, not to mention rocks and all sorts of other junk, even if you screen it well, you're going to be skimming off a lot of dross. (Forget indoor ranges. They have "bullet traps" and their spent bullets are clean and bring top dollar from the scrappers and you'll likely be competing for it with the shooters who cast their own bullets.)

    The absolutely best source of good ballast lead is old ballast, which, for all intents and purposes, won't require worrying about how much antimony it has in it. There are plenty of lead ballast castings about. The knackers set them aside these days because of the value of the lead and sell them for scrap. If you are nice and polite, you should be able to buy from the yards for what the wholesale scrap price is running. Alternately, if you are really adventurous, there are many boats on their last legs that go begging when the marinas try to auction them off for the back berth rent. If you know your boats, you can spot one with a lead keel and such can often be picked up for a really low bid that's orders of magnitude less than the value of the lead ballast keel. Of course, scrapping the boat is on you.
    Last edited by Bob Cleek; 07-11-2017 at 08:02 PM.

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    Default Re: Lead grade for casting keel

    The last big chunk of lead I bought was from a fellow who did just that, scrapped out an old sailboat. He cut up the keel and melted it into ingots, most of which were snapped up by guys who like to cast their own bullets. We have competition!

    Currently on a long-term hunt for about 2500 pounds of the stuff myself.
    Steve

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    Default Re: Lead grade for casting keel

    I found a guy not TOO far from here who has from time to time found reclaimed lead from the sheathing of old communications wires going onto a local military base. he had some wheel weights and I bought all the ones he had but as mentioned, many were not made of lead. It was still enough lead to make the purchase worthwhile though. The old sheathing have been melted down. Bob's caution about bending it is spot on but the sheathing had been cut length wise so there was no trapped air to explode. I would have been careful about it had it been closed in. I found some old drain pipe in my house that was no longer used and saved the leftover flashing when they redid my roof. An outdoor range may be the way to go... I know there are a couple not too far from my place. Maybe I'll check them out and see if they'll let me dig through a couple of times per year. I'm sure I can come up with quite a haul if I did that. I need about 10 tons for the boat I want to build so I have a long way to go. I have about 800 lbs as of now. I melt it down into a frying pan and let it cool. A cast frying pan shaped ingot weighs in around 55 lbs (for the size of pan I have). I haven't given any consideration to the antimony content even though I know it's important. I'll try the hammer ringing trick.
    Cheers all,
    Daniel
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    Default Re: Lead grade for casting keel

    Thank you all for the safety tips. I had not considered the issue of entrapped air. Fortunately, my lead is fairly uniform.



    I picked up the lead bricks for $.5/lb. Our local metal recycle places claim a similar rate, but they never have it. Ebay has vendors that are asking as low as $1.40/lb. and Rotometals is a bit more. https://www.rotometals.com/lead-ingots-wire/ I'm going to assume that lead recycled from gun ranges will be alloyed with antimony and tin so that may be the best way to go. I think I will try to see if my 10 lbs. of antimony will melt with the lead as well. Oddly enough, those lead bricks in the pic were used by a master machinest to provide ballast for his tool cabinet so he could have several heavy drawers open at the same time. He must have had some heavy tools to need 450 lbs. of ballast.

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    Default Re: Lead grade for casting keel

    Quote Originally Posted by Sailor View Post
    I found a guy not TOO far from here who has from time to time found reclaimed lead from the sheathing of old communications wires going onto a local military base. he had some wheel weights and I bought all the ones he had but as mentioned, many were not made of lead. It was still enough lead to make the purchase worthwhile though. The old sheathing have been melted down. Bob's caution about bending it is spot on but the sheathing had been cut length wise so there was no trapped air to explode. I would have been careful about it had it been closed in. I found some old drain pipe in my house that was no longer used and saved the leftover flashing when they redid my roof. An outdoor range may be the way to go... I know there are a couple not too far from my place. Maybe I'll check them out and see if they'll let me dig through a couple of times per year. I'm sure I can come up with quite a haul if I did that. I need about 10 tons for the boat I want to build so I have a long way to go. I have about 800 lbs as of now. I melt it down into a frying pan and let it cool. A cast frying pan shaped ingot weighs in around 55 lbs (for the size of pan I have). I haven't given any consideration to the antimony content even though I know it's important. I'll try the hammer ringing trick.
    Cheers all,
    Daniel
    I have a cast iron pot I used to use for melting lead for fishing weights.

    I cleaned the outside with a sanding disc on an angle grinder, and then used a cutoff wheel in a die grinder to cut 'POISON!! LEAD!!' around the outside of the pot.

    That way, if I die without remembering to destroy the pot first, some poor schmuck won't end up using it to make beans.
    Rattling the teacups.

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