Bayview BOOM

How to Harden Tin/Bismuth Alloy?

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hi

sorry if non-iron posts are not allowed here. 

I need a low-toxicity, low-melting point metal (before casting), to cast hardware parts. 
After casting, the parts must not crack under torque or impact, and should remain hard up to 100 deg C. 

My plan is to make a Tin/Bismuth alloy, since low-toxicity, low-melting point. 
I've heard a tiny amount of silver can make this alloy less brittle. 

Any suggestions? Could be a different alloy, or a hardening process. 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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Yes: provide the specs!  How much torque?  How much impact?  

In general if there was a cheap easy to make/cast alloy that was as good as more expensive ones; there would be a ton of things made from them and it would be easy to recycle them!  If you can't find such alloys in common use---there is a reason for it!

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On ‎12‎/‎31‎/‎2018 at 9:34 PM, ThomasPowers said:

 

the cast object will be approx 4" x 1/2" x 1/4". 

torque: hand-tightening with a wrench, as in nuts and bolts. 

impact: roughly, dropped from 20 feet while mounted to a 2 lb weight (sorry, i don't have exact force rating)

i plan to start with "pure" metal powders or ingot, and combine in the melting pot. 

i'm not trying to recycle anything. i didn't mention "cheap". 

i don't know if there are or aren't such alloys in existence. I guess you're saying it's impossible?

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So you are ok if it's 5000 US Dollars apiece? Good to know as that opens up some of the weirder stuff!  (Unfortunately non-toxic closes a lot of avenues...)

I mentioned recycling as part of "if there was such an alloy it would be commonly used for a lot of things and so easy to find..."  Have you found an item with a similar use case that you could then determine the alloy used?

I think  the low temp is the biggest issue, most of the high strength alloys are higher temp stuff. (Though the zinc alloys are fairly low melting---but not like tin/bismuth!)

Have you looked at some of the potmetal alloys?  Or Zinc/aluminum alloys (like ZAMAK) I think your best bet is going to be with these alloys!

Note that "nuts and bolts" can be tightened to hundreds of foot pounds torque or 1/2 a foot pound of torque. so still not narrowing it down much.  

You know what you want; we have to play 20 questions to figure it out.  I'm sure it's annoying to both ends. (You ever looked into the cost of hiring a metallurgy consultant?)

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Thx for suggestions!

Re tightening with a wrench: Whatever is the average range for people of average strength, with average consumer tools. I think that narrows it down sufficiently. If you still feel there are totally different metal options at the margins of that range, plz share both options. 

The similar use-case is steel or aluminum nuts and bolts, but i believe that's neither low-melting-temp nor low-toxicity. 

Not trying to hire a consultant, this is a DIY project. 

Thx!

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Head bolts on a car engine vs bolting together a bed frame.  Both fairly common tasks for people---though the car engine repair was a lot more popular in the 60's and 70's...So replace that with changing a tire.

I'm sorry but asking us is asking for a metallurgy consult; just you are less assured at getting good answers! I was at the local big used bookstore today and they had a shelf of books on various alloy types and their properties for DIY types to research in.

Is there any environmental issues with the item?  Some alloys do NOT play nice with other alloys if there is moisture or salty environments involved.

Still think that, barring environment,  Zamak alloys might be a good place to start.

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many thx for suggestions, i will look into them. 

my project is more toward the bedframe end of the spectrum, not car engine repair. But i'm interested in options at both ends of the spectrum. 

no direct contact with salt or water, just the amount salt or moisture that is in the outside-air in San Francisco on an average day. 

I assumed this forum is for asking questions and sharing wisdom, not a "hire me" website. My bad. 

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When you are asking people to help you it behooves you to make it as easy for them as possible. So clear concise questions that can have specific answers.  Time is all we are given so treat it as a precious resource!

For instance San Francisco is rather famed for moisture in the air, (fog rain), and high chlorine content as it's on the seacoast---well bay coast. Also will this be brought inside on un-average days or will it likely be exposed to them as well?

If this will be screwed/bolted into steel I don't think ZAMAK would be a good choice for SF due to environmental issues unless the item will be protected.

I'm afraid I have to go spend my time elsewhere.  Good Luck

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Posted (edited)

i totally understand guys need to make a living! Wish i could help with that. 

this won't be brought inside on unaverage days, but again, no direct contact with salt or water, other than sea-air. Will not be in direct contact with steel, although there will be stainless steel a few inches away. 

Many thx for your questions, which help me clarify what i need. 

cheers and happy new year. Thx!

Edited by Bayview BOOM

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Just a bit of info about the project: 

We are a nonprofit mentoring org for disadvantaged teens. Our goal is to give our apprentices a taste of professional methods and materials, in a safe, simple way. That's why "low-temp" and "non-toxic". 

 

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The problem is that your questions are way to vague to give concise answers, there are simply far too many variables. If you asked a question like I want to use a low temp, low toxicity metal alloy to cast door hinges for custom outdoor cabinets with doors weighing 20 pounds, which ones would you suggest? That would be a lot more helpful than the way you have been asking. Unless this is some secret squirrel program where you cannot divulge specifics, it will be very hard to help you. We can only point you into the direction of books or other reference materials where you will have to come up with the answers to your questions.

There are several low temp alloys, some melt as low as 117F, but they are relatively expensive. I have recorded dash temps in my car here of 225F+ during the summer, so they would not work for any application inside my car. Also , there are many high temp, highly toxic items in the workplace. Teach proper protection, and how to read an MSDS now, not later. I remember when high schools had shop classes that taught aluminum casting and we operated full size machine tools.

If you are looking into possibly doing castings with low temp alloys, that will explain some of the processes used, BUT it will not be a common professional method of doing them.  If I was looking to help disadvantaged teens I would invest in something like a 3D printer. I have been a machinist, fabricator, mechanic, etc... since I graduated high school back in 83. The advances I have seen in addative manufacturing (what industry calls 3D printing) have been phenomenal. I wish I had gotten deeper into the CNC side instead of staying a manual machinist, but CNC;s were just getting popular when I was graduating. They were like early computers and each had their own programming styles, while today it is greatly simplified programming. I know a guy who started a business with a friend and one printer. 5 years later he has 125 printers, 30 employees, and did $1,000,000 in profit last year at the age of 30. When the fidget spinner thing was getting started he shifted some production to making those. He sold 9,000 of them in 2 months at $20 each.  If you want to help disadvantaged teens, teach them the fundamentals of money, budgeting, staying out of debt, how to grow a business, how to write a proper resume, how to feed an entrepreneurial spirit - you do not have to work for someone else, how to develop ideas and be inventive. Just having some skills is just part of the process. Having an open mind that delves into things like the arts, cultures, literature, travel, etc.. will help in making your way through this world we live in today. I grew up in Fairfield, and we made many trips into the Bay Area to explore the museums (I remember when the Exploratorium was an empty warehouse with donations as entry fee), and different ares like China town, Japan town, the observatory,  the wharf, and more by walking all over the area. Field trips to Benicia to see the glass blowers, or a visit to the Crucible, can help open eyes to the possibilities out there. Today's technology can open doors we never dreamed of. A friend's kid is making $500,000 a year doing YouTube videos. Also opening up to careers that others don't think are "successful". The delivery drivers at the bakery I work at make $120,000+, and the uniform delivery folks can do $60,000+. The trick is to be able to be open to the unconventional. 

Tech in the Bay Area is a double edge sword. It provides great incomes, but has also driven the cost of living through the roof. But there are areas like Salt Lake City Utah that are growing tech centers. Again, be open to  change-moving.

Good luck with your project. If you can provide more details we can possibly get you closer to what you want to accomplish.

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33 minutes ago, BIGGUNDOCTOR said:

The problem is that your questions are way to vague

if possible, plz let me know what other specs would help. I've given dimensions, weights, temperature, humidity, and air-salt info, impact info. 

I understand your points about professional opportunities. Thanks for sharing that. No offense, but not asking for advice on my educational program. Just metallurgy.

It's ok if methods aren't conventional. 

Re expense of materials, as i mentioned above i'm not concerned with cost at this time, just methods and materials. Grateful for feedback. 

cheers!

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I dont understand how you expect to teach these kids how to do a thing you yourself clearly dont know much about?

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6 minutes ago, Steve Sells said:

I dont understand how you expect to teach these kids how to do a thing you yourself clearly dont know much about?

that's why i'm here seeking info! 

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OK you are making an object that is 4"x 1/2"x 1/4" and it has to stay solid to 100C (212F), take a 20' drop, will be used outside,  and take some amount of torque. is still vague, and too many variables.  Can you tell us exactly what it is that you are making? or a picture of what you want to make? Or what specifically you want to accomplish with the item in question.

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Just now, BIGGUNDOCTOR said:

OK you are making an object that is 4"x 1/2"x 1/4" and it has to stay solid to 100C (212F), take a 20' drop, will be used outside,  and take some amount of torque. is still vague, and too many variables.  Can you tell us exactly what it is that you are making? or a picture of what you want to make? Or what specifically you want to accomplish with the item in question.

Your question is vague. It's a widget. Does that help? Of course not, cuz what matters are the specs, not the name of the object. 

If i said "a door hinge", then that still wouldn't help. What matters are the specs: weight, torque, impact, etc. What particular specs are you looking for?

 It's a bracket that holds an object weighing about 1/2 lb. It needs to be hard enough that it won't crack or deform when dropped. It's coupling has to mate with the already-existing coupling on the object that it's supporting. It will include bolt holes to mount the object. 

It sounds like what you're really doing is questioning my overall plan, to cast a metal part. Fair enough, but i'm not seeking design advice. I'm seeking metallurgy advice. Let's assume casting is an appropriate technology for my application and go from there. If you're not willing to accept on faith that casting a metal part is an appropriate solution to my application, fair enough. 

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People have tried to help you, but you wont help yourself,  Keeping your project a secret isnt helping. You are clearly not qualified to be teaching anyone about casting anything.  Some of us got the idea your trying to get us to do a school homework assignment for you,  Since you wont cooperate and tell us anything,  this thread is now closed.

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