Recasting a broken casting.

[100model]

I tried to straighten a casting for my electric saw and it broke. So I cast another part and made a video about it. At the moment it is summer where I live and my green sand tends to dry out before the mold has been completed so I added lots of water to make up another mold. It was way too much water because the two halves of the mold stuck together even though plenty of parting dust was used. Adding too much water can cause blowholes in castings and I never vented this mold but every thing was OK so it shows that my sand has plenty of porosity and does not need venting.

 

[GreenTwin]

Perfect pour technique; crucible as low as possible, correct pour temperature, and great casting (as usual).

Its a joy to watch someone cast that knows what they are doing.

Nice !

.

 

[bluejets]

I'd tend to be more than hesitant at using anything from car rims given the possibility of them containing magnesium.
Why, I'll let you all find out for yourselves....suffice to say, rather spectular fireworks at time of meltdown.

 

[GreenTwin]

I have used car rims, and it is my understanding that most are some variant on the alloy 356 aluminum.
Generally speaking, many seem to use car rims with good results in backyard casting, with the biggest problem being cutting them up, or melting them in a large scrapper furnace.

I think the test for magnesium is to use some sort of acetic material, like lemon juice, or perhaps vinegar (I forget exactly what should be used).

Aluminum will not be affected by something acetic, but magnesium will bubble/gas.

.

 

[Richard Hed]

I have used car rims, and it is my understanding that most are some variant on the alloy 356 aluminum.
Generally speaking, many seem to use car rims with good results in backyard casting, with the biggest problem being cutting them up, or melting them in a large scrapper furnace.

I think the test for magnesium is to use some sort of acetic material, like lemon juice, or perhaps vinegar (I forget exactly what should be used).

Aluminum will not be affected by something acetic, but magnesium will bubble/gas.

.

couldn't you also take a small peice and heat with a blowtorch till it melts? If not alum, it will burn.

 

[wce4]

I have used car rims, and it is my understanding that most are some variant on the alloy 356 aluminum.
Generally speaking, many seem to use car rims with good results in backyard casting, with the biggest problem being cutting them up, or melting them in a large scrapper furnace.

I think the test for magnesium is to use some sort of acetic material, like lemon juice, or perhaps vinegar (I forget exactly what should be used).

Aluminum will not be affected by something acetic, but magnesium will bubble/gas.

.

Test for magnesium with vinegar. Pour a little vinegar on it, it will bubble if it's magnesium.

 

[bluejets]

Throw some in a crusible with enough heat or existing molten metal and you'll have glorious fireworks.

Think you need to be responsible here and show others who have no idea, that adding magnesium content can be rather dangerous instead of passing it off as " ah....no worries bloke, I do it all the time".

 

[GreenTwin]

I am a big follower of John Campbell and his 10 rules for good castings.
I think his rule No.01 is to use a known metal/alloy for the melt, not some random metal.

I use near 356 alloy ingots that are derived from automotive engine blocks.
They work well when I do aluminum casting, and produce consistent results.

As I understand magnesium (I have never run across it), it is not so much an explosion issue, but rather a very hot fire that can burn through the crucible, through the bottom of the furnace, and down into the ground.
I am not aware of anything that can extinguish a magnesium fire.

So if you are not using a known scrap, or even if you are, it is a good idea to have the furnace located out away from the house, and away from anything combustible, so if you ever get into some free-burning situation, you just step back, and let it burn itself out.

Here is a video of what I think is magnesium or some magnesium-based additive.
There are various grades of magnesium additive used to make ductile iron, and depending upon the percentage of magnesium, you can get a mild reaction, or a severe one.
I have been looking for Nickle-Mag4, which is suppose to have a mild reaction.

I have been told that the way to use magnesium-based additives is to put then in a pocket that is at the bottom of a ladle (not in a crucible) and use some small steel pieces to cover the additive that is in the pocket. The molten iron is then poured in next to the basin, and the level rises up and floods the basin. The steel pieces slow the reaction down a bit.

And visually, a magnesium fire is extremely bright, and without the right eye protection, you can damage your eyes (same applies to melting and pouring gray iron due to the IR radiation).

The important thing with backyard casting is to not panic.
I see folks that sometimes panic, and start throwing water on molten metal, which can and will cause an explosion.
Keep your cool, step back, turn off the burner/fuel, and don't do anything foolish that will make the situation more dangerous.

The group in this video actually train a lot before they do these events, and they practice what to do when things don't go as planned. They take safety very seriously.
They even have post-even safety meetings, to discuss what went right and wrong.

I don't think the reaction needs to be anywhere near as big as the one in the video below in order to make ductile iron. He seems to add quite a large amount of additive too, and I am not sure what the correct ratio is, but I would guess it depends on the percentage of magnesium in the additive.

.

 

[100model]

Think you need to be responsible here and show others who have no idea, that adding magnesium content can be rather dangerous instead of passing it off as " ah....no worries bloke, I do it all the time".

The leftovers from my last melt were aluminium rims which did not burn at that time and the rest for this melt were bicycle rims which I have melted many times because they are easier to cut up for melting. Aluminium car rims are the best alloy to melt and do not contain magnesium. I did melt VW crankcases in a crucible just to see what would happen years ago and I knew they were a magnesium alloy. There were no problems so I just let it burn out. Magnesium alloys are a dark grey compared to aluminium and feel a lot lighter. If you do have a magnesium fire just fill the crucible with sand to eliminate oxygen and it will go out.

 

[bluejets]

The leftovers from my last melt were aluminium rims which did not burn at that time and the rest for this melt were bicycle rims which I have melted many times because they are easier to cut up for melting. Aluminium car rims are the best alloy to melt and do not contain magnesium. I did melt VW crankcases in a crucible just to see what would happen years ago and I knew they were a magnesium alloy. There were no problems so I just let it burn out. Magnesium alloys are a dark grey compared to aluminium and feel a lot lighter. If you do have a magnesium fire just fill the crucible with sand to eliminate oxygen and it will go out.

Actually they can and do contain magnesium.
Where do you think the term " mag wheels" came from?

We have also come across alloy containing magnesium in motorcycle engine crankcase.
Point being, it's not all " she'll be right bloke".
Personally I couldn't care less what you think is ok or what you shove in your oven, it's the upcoming inexperienced future model engineers who need to at least be given the word of warning.

 

[L98fiero]

Actually they can and do contain magnesium.
Where do you think the term " mag wheels" came from?

We have also come across alloy containing magnesium in motorcycle engine crankcase.
Point being, it's not all " she'll be right bloke".
Personally I couldn't care less what you think is ok or what you shove in your oven, it's the upcoming inexperienced future model engineers who need to at least be given the word of warning.

It's just a guess, but the likely source of magnesium rims is in very high end rims where the minor difference in weight makes a difference or at least the perceived difference, most 'consumer grade' 'mags' are aluminum. That said, if you aren't sure, test it before use.

 

[GreenTwin]

I got into backyard metal casting in about 2011, and I have seen countless folks melt and use aluminum rims for casting things, and never a mention of problems with magnesium.

Safety is No.01, and the point that some rims may contain magnesium is a very good point, but to be fair, I would say running across a typical auto cast rim with magnesium in it would be pretty rare.
Test your rims though, as well as other non-ferrous scrap, because better safe than sorry.

The problem I do see over and over again is someone using something like aluminum cans with moisture in them, or pouring into a mold/container that has moisture or ice in it.
These situations cause very dangerous explosions, and ytube is full of people doing this.

Another explosion danger I see is people using concrete to make furnaces in lieu of refractory material. A concrete furnace will explode violently.

So I think "inexperienced future model engineers" should prioritize backyard casting dangers, with moisture-caused explosions ranking No.01, and magnesium fire danger being subjectively a No.05 or less, because there is no explosion.

I would say danger No.09 is people doing casting work and furnace operation indoors, such as in a garage, and people building burners with a plastic fuel tank mounted within inches of the burner and furnace. Or a two-fer, where they have a 5 gallon plastic fuel tank mounted inches away from the burner, and they have the furnace/burner in the door of the garage, which is about a 12 on the danger scale of 1-10.

One thing that got me was not preheating steel ingot molds hot enough before pouring molten metal into them. I was well aware that there can be residual moisture on what looks like a perfectly dry ingot mold, and I did preheat my molds, but not hot enough, and I had a half-full mold of molten iron pop itself out of the mold and run down my face shield and jacket, with some of it running into my gloves (I have some good 3rd degree burn photos for those into gore). I have seen the same ingot mold "pop" in online ytube videos, but I never see anyone warning about this.

Just a few thoughts relating what I have seen over the years.

.
Edit: I have seen many folks raise the alarm flag about pouring molten metal over concrete, and from what you read, you would think that this is the most dangerous situation in the world. The reality is that pouring over concrete is routinely done by many long-time casting folks, myself included and 100model too, and I have had countless spills on concrete with all sorts of metals including iron, and never more than perhaps a very slight pop.

I did see one video of an entire crucible of hot bronze being spilled on concrete, and that did cause a pretty significant bang, causing more of a flying molten metal problem than a flying concrete problem. I have never poured over or around sand, and I would never use sand around my furnace, since it contains moisture. Many "safety" folks online repeat the mantra "you must pour over sand for safety", but I disagree with that, and would never do it.

.

 

[GreenTwin]

A few more safety concerns, while we are on safety.

I see some of what I consider very hazardous situations in some of the casting videos, and yet these items never get mentioned on the forums.
Many folks miss seeing the forest because all those trees are in the way.

Items that I consider perhaps 10 or more on the rating of hazard are as follows:

1. Using an oil fuel tank that is pressurized more than about 15 psi.
This is in my opinion a danger rating of 100 on the scale of 1-10.

2. Using a pressurized oil tank that does not have a low-pressure safety valve.
One guy had his pressure regulator fail, and it put 100 psi on his fuel tank, causing one of the fuel lines to blow off the fitting near the furnace, and causing an inferno in his driveway.

3. Using an electric heater under the fuel tank (waste oil fuel tank), inside the garage.
A thermostat failure could cause a huge fire inside of the garage.
One should not sort fuel of any type inside of a garage, in my opinion.

4. Starting a foundry furnace with the lid closed, using either a propane burner or an oil burner.
When the interior of a furnace is red hot, then a burner flame-out is not generally a problem, since the burner will automatically re-ignite when it comes back on, due to the heat inside the furnace.

When starting a furnace cold, a flame-out with a closed furnace lid can be very dangerous.
One guy on a casting forum started his atomizing oil burner with the lid closed, and he had no idea how to operate the burner, so the burner flamed out, and he launched his furnace lid like a Saturn V rocket, over the top of his house.
He used his ignorance of oil burner operation as "proof positive" that an atomizing burner is a very bad design that should never be used by anyone.

A furnace should be started with the lid open, and the lid should be kept open until the burner is operating in a stable fashion.

Be ready to quickly turn off the fuel valve if you do have a flame-out (this has happened with me occasionally, and is not big deal if you just reach down immediately and close the fuel valve; a good reason to keep your fuel valve in an accessible location that is not too near the furnace).
Don't wander off and leave your furnace/burner operating unattended.

Be wise and be safe if you do metal casting work.

.

 

[master53yoda]

I process engine aluminum engine castings into ingots about 800 lbs per month, wheels any newer than mid 80s will be 356 alloy,

There are some mag automotive parts, some transfer cases, Audi / Volkswagen engine parts, if something feels to light I cut off a bolt flange and torch it on fiber insulation, if it melts it is aluminum, if mag it will start to spark, and burn, very bright. 5500F. The few times I have had mag go off in my large furnace, I take it out with a shovel or rack and put in in the GRAVEL drive way, it can be smothered with DRY sand, don't remove the sand until it has cooled completely or it will reignite. It can also be submerged in the aluminum pool, it isolates the Mag from Oxy. and will form an alloy. The pool must be large enough for completely submerge of the Mag.

It is an Oxy dependent combustion it can be isolated from its Oxy source putting it out.

DO NOT USE WATER OR WET SAND, it breaks the water into hydrogen and oxy and now you have even a worse fire.

If it feels to light use the torch test.

Art B

 

[100model]

it's the upcoming inexperienced future model engineers who need to at least be given the word of warning.

So do I with every post about foundry work put endless warnings with that post and put off everyone trying it for themselves? So does everyone post endless warnings when using machine tools and other operations that could be dangerous in their workshop for beginners?

 

[GreenTwin]

I think some of what I would consider paranoia about metal casting comes from a lack of understanding of the process, the operation of the furnace, the burner, etc.
There is no doubt that backyard casting can be dangerous.
My oil burner will easily produce 250 KW, which is a significant amount of energy concentrated into a small furnace space.

There was a woman killed in this State a few years ago at a technical college, when her hair got caught in a lathe, but nobody ever talks about that on the machining forums.
The difference is that a lot of people know how to machine, and know how to safely use machine tools, and there are many people who are extremely good at machining.
I have met very very few people who actually do metal casting, and of those people, very few understand how to do it correctly and/or safely.
I think it is safe to say that backyard metal casting, especially gray iron casting, is a black art to most model engine hobby folks.

I have posted previously about a number of myths that revolve around backyard casting.
Once a myth gets set in place, it is as if it is cast in high-strength concrete.
It is very difficult to correct a casting myth; they get repeated over and over again on forums and in ytube comments, and never seem to go away.

Years ago, when I mentioned to some model engineers online that I was going to start casting engine parts in gray iron, most said in absolute terms "you are going to die; the heat will cause you to self combust".

I recall being extremely aprehensive when I started doing iron work, and had a hard time convincing the wife that this was something that could be done safely.
I got some 3rd degree burns on the hands with some early blunders, but lived to tell about it, and no permanent or significant injuries.

I would say the most dangerous thing about backyard metal casting is ignorance of the process.
So much wrong information gets posted across the internet that it is extremely difficult for most beginners to sort it out.

The folks I pay the most attention to when conversing about metal are the folks who have been making high quality metal castings for a number of years (such as 20 + years), and people who over time have proven that they can consistently and safely make castings.

I know for a fact that some of the most outspoken commenters on ytube are folks who have never done any metal casting, or folks who worked in a foundry, but never had any significant responsibilities. The comments under the casting videos say it all about the commenter.

The backyard casting hobby can be done safely, and safety is No.1 in my foundry book, but I fear getting caught in a machine far more than I fear getting injured running a foundry.

.

 

[100model]

That said, if you aren't sure, test it before use.

I watched the video and I have a similar method using a hacksaw to cut a small piece off and use a torch to see if it burns. Using a file is a better method.

 

[GreenTwin]

I just became aware of someone getting seriously injured (supposedly sent to the hospital burn unit) by building and attempting to operate a foundry oil burner.

Oil burners are not something to play around with if you don't understand how to build and operate them safely.

Some oil burner designs are what I would consider dangerous, and I would not use them.

There is no excuse for getting injured by not being familiar with an oil burner.

This reinforces my statement that the greatest danger concerning foundry work is ignorance of the process, the various types of equipment, and operation of the equipment.

.

 

[Richard Hed]

I just became aware of someone getting seriously injured (supposedly sent to the hospital burn unit) by building and attempting to operate a foundry oil burner.

Oil burners are not something to play around with if you don't understand how to build and operate them safely.

Some oil burner designs are what I would consider dangerous, and I would not use them.

There is no excuse for getting injured by not being familiar with an oil burner.

This reinforces my statement that the greatest danger concerning foundry work is ignorance of the process, the various types of equipment, and operation of the equipment.

.

Can you give us examples of dangerous ones and examples of safe ones?

 

[GreenTwin]

I will start a new thread.
We have gotten way off topic.

.