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Thread: Ideas for zinc castings
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8th Nov 2015, 07:47 AM #1Diamond Member
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Ideas for zinc castings
I have recently acquired a large amount of zinc swarf and want to have a go at doing some casting. Does anyone have any ideas of what i can make out of zinc?
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8th Nov 2015, 09:57 AM #2Member: Blue and white apron brigade
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While not exactly the material of choice these days, in the past Zn has been used to make things like pulleys, machinery part covers, some toys, electrical boxes, and motor vehicle parts like door and window handles, fuel inlet system parts(carbys), and maker emblems/badges.
f it's fine enough, mixed with sulhuur it makes a decent rocket propellant!
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11th Nov 2015, 11:24 AM #3Novice
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You could cast some pattern letters, or dissolve it in HCl acid to make soldering flux (killed spirits), or add a bit to lead to make solder (eutectic or wiping lead), or an ingot for use as a sacrificial anode for a boat.
John
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11th Nov 2015, 07:23 PM #4
Read a bit about Zinc castings not so long ago -- I think in response to someone wanting Zinc hardware for a cabinet.
The key point I recall was that no one casts pure zinc. Commercial Zinc castings are always an alloy, where the alloying elements and amounts are selected to obtain particular properties in the alloy.
Something to bear in mind.
Would also be worthwhile checking the precautions one needs to take against zinc fumesregards from Canmore
ian
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9th Dec 2015, 11:51 AM #5Most Valued Member
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9th Dec 2015, 11:59 AM #6Banned
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9th Dec 2015, 06:53 PM #7Philomath in training
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How about zinc anodes for boat (corrosion) protection?
Michael
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15th Dec 2015, 11:30 PM #8Diamond Member
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One of the problems with melting swarf (and aluminium drink cans) is that because of the high surface area to volume ratio you can easily end up oxidising half of your stock.
To reduce the dross problem, and it is a chicken and egg situation, you need to have a fair bit of molten material in your crucible into which you can plunge and completely submerse compacted blocks of swarf. As has already been said watch out for the fumes.
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16th Dec 2015, 09:43 AM #9Most Valued Member
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[QUOTE=bob ward;1899504 which you can plunge and completely submerse compacted blocks of swarf.[/QUOTE]
Wouldnt that be sort of scary to do....trapped moisture, centre very cold?
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18th Dec 2015, 10:03 AM #10Diamond Member
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Any melting stock you are uncertain of re containing water or volatiles needs to be pre-heated before it is added to the pot. Mostly this is done by placing it near the flame outlet.
A good source of info on DIY metal casting is alloyavenue.com
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18th Dec 2015, 10:33 AM #11
I have a YouTube video called Foundry Myths.
In this video
1. A red hot crucible is plunged into a tin of water.
2. Water is dripped into a crucible containing molten aluminium.
3. Molten aluminium is poured into a tin of water. Nice abstract art.
Nothing disastrous happened.
Comments?
Heating the compressed swarf was my first thought as well. Where I worked back in the early 80's they had an aluminium foundry that was worked constantly. The result was machined on site. Mostly pistons. None of the swarf was reused because of the oxidation issue. The ingots were left on the side to preheat before adding to the crucible. The foundry ran on diesel. Somebody noticed a pool of it slowly running across the concrete towards the foundry, from a leak one day. A bit of excitement ensued. If my memory is correct (35yrs) it did ignite, but was quickly dealt with.
When I start casting aluminium I intend to reuse the swarf. This compression idea should be ideal. Press into a bit of pipe, knock it out, warm it up and toss it in the foundry.
Dean
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18th Dec 2015, 02:15 PM #12Diamond Member
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18th Dec 2015, 02:59 PM #13
I guess he was trying to dispel some myths he had heard of. Not knowing much about the subject myself, I thought I would ask. Never hurts to clear things up. Maybe it was his attempt at fame.
Dean
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31st Dec 2015, 10:47 PM #14Diamond Member
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Back in the 1970s I briefly worked as a furnaceman at Comalco in Tasmania, and during my induction, (which was the most thorough induction that I had till I returned to Comalco on a project in 2005ish) we were shown photos of an accident where the furnaceman had plunged a sampling ladle straight through the flux layer into the molten aluminium. The ladle had been stored outside overnight, where it had collected some light rain or dew, and the operator failed to adhere to the correct procedure which was to empty any water from the ladle bowl, and then place a the ladle on top of the fluxing crust to dry completely before plunging it into the molten layer below the crust, in order to collect a sample of the furnace contents for analysis. They estimated that no more than 2 desert spoonfuls of water were probably injected below the crust into the molten Al below, but the result was the complete emptying of the furnace contents, about ten tonnes of molten aluminium on top of the unfortunate operator. That was the last mistake he ever made, and if I remember correctly, I think that the molten aluminium not only turned the water to steam, which expands by a factor around 1600 times, but the hot aluminium also strips the oxygen from the water in order to make aluminium oxide, some hydrogen which possibly also explodes, but the reaction releases lots of energy, which in this case shifted ten tonnes of hot material onto the unfortunate furnace operator.
As I understand it, molten aluminium is best kept well away from water unless you have the expertise and the equipment to do it safely.
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1st Jan 2016, 09:46 AM #15Most Valued Member
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I used to do work for Castalloy (new owned by Harley Davidson) and the induction film they showed us was basically a small cube (1.5 metre) bunker with with sleepers on all sides and top except the front (for viewing and allowing filming). The bunker was destroyed...totally!!! when water was placed in the molten alloy. Cant quite recall how this was done but it was nothing like those utube vids. Also if I recall correctly it can occur with cold objects fall into the molten alloy.
As far as I recall there is the real chance of secondary explosion (hydrogen??) which is of most concern, caused by whatever it was ...a reaction as the water vapourising etc etc and molten alloy.????
it was eye opener to see it.
When working in the plant I always hoped the foundary men were obeying the rules.
cold water bottles cans etc were a definite no no in the plant other than the canteen
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