crucible materials - Smelting, Melting, Foundry, and Casting

Since you asked a very commonly asked and answered question, and also posted this in the gallery not the forums casting section I will assume you are very green, have not read anything yet, and do not want to kill yourself?

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If that is true I suggest you read a lot before even getting started to light a fire. Welcome to the forum I will relocate this post for you.

Steve I don't know that casting your own metal crucible is covered as it's generally not a good way to go...

However Platinum is definitely the best!   Works to high heats and is very inert. (and can be bought premade---just google platinum crucibles!)   Of course casting a metal crucible will be MUCH more expensive than buying a non-metallic one that would work far better in most cases; but since that cost doesn't play a part in the question I knew that you could handle the cost of platinum on top of the cost of casting your own.

Note that you will want to have separate crucibles for each metal/alloy to prevent cross contamination.

As usual our local curmudgeons are trying to gently steer you along in a safer and more practical direction.

Casting metal is very dangerous.  Get some hands on assistance and training from someone who has actually done it successfully for a couple of years (and still has all their parts intact).  Training by watching YouTube does not qualify.

As far as crucibles go, how are you going to cast a crucible if you don't already have a crucible to heat the metal up in?  Kind of horse before the cart there.  Not to mention, that as Thomas said, non-metallic crucibles are a better choice.  Crucibles are a consumable in a foundry in any case, so a cheaper, time tested alternative is a better choice.  Suggest you Google search graphite crucibles for info on suppliers and crucible types.

Sorry; it's just the question set off all the warning signs for someone getting in over their head. Lead is often cast out of a cast iron ladle---but I don't know anybody who spends a ton of money casting their own when such are available cheap...  Al; well I'd suggest you read through the Dave Gingery series on casting Al and go with what he suggests.  Copper is getting into the higher temp metals and is a pain to cast due to it's uptake of oxygen.  BTW have you spent time on the backyard metal casting forums?  A site dedicated to casting rather than smithing?  Me I do small casts usually for knife fittings and use my coal forge as the heat source and stainless steel creamers as disposable crucibles. Usually get at least 1 pour for them before they scale to danger zone.  Fire control is paramount to keep it reducing. I like to use petrobond for the molds.  I took an out of hours brass casting class from a University arts school to learn the safety aspects and basics.  I strongly recommend folks learning from other folks who know as it's easy to not know what you are missing from books and the web...

The way we usually get these questions is "Hi I want to save money by spending 100 times more to do something myself that is easily found and purchased with a much better safety factor"  Or even "Please help me damage/maim/disfigure myself and risk high legal bills cause I have to blame someone else when I screw up"  Hence our caution.

If your casting volumes are pretty small (a pound or two at a shot) there are now some fairly inexpensive electric smelters available from places like Amazon.  The units are generally chinese made (what isn't these days?) but do give reasonable service without the fuss.  You would simply buy spare crucibles which fit the specific machine for each metal you want to melt.

The lead you mentioned is generally considered to be a bad idea these days for obvious health reasons.  Think twice on that one.

No use reinventing the wheel with a "home brew" set-up if you really don't need to.  Counting your labor it will cost you more to roll your own and will take much longer to be pouring liquid.

If your shots are larger, there are commercial crucibles available.  Again, no benefit to reinventing the wheel so it's better to save your cigarette money until you can buy something standard.

For some real fun, look up "fixturing metal".  Those are the specialty metals which melt at very low temperatures..often hot water is enough...which can be cast and re-cast.  Fun to play with when you are just experimenting.  Your molds can even be plastic (the right plastic, of course) because the temps are so low.  Vacuum formed candy molds often work for example.

The 'correct term' is often relative to the region it is being used in. There are several terms that can be considered correct.

And if its correct terms you want to use, then the word playing has absolutely no business what so ever anywhere near working with molten metal. Playing with molten metal is how people get hurt. 

To ThomasPowers:  no sir, I don't.  I've not got around to reading Longfellow yet. Maybe I should...

words are all we have to communicate with in a forum situation.  Games and word play in a forge can kill.  Also as you yourself stated something about paying attention, but you started this thread in the gallery section of this forum's feedback and support section, where a fast glance would have shown you its for reporting issues with the software.  If you pay that little attention in the shop you are dead. either way your comments are big flags, and this is not our first rodeo

I think I had better clarify things a bit.  I have not yet started anything at this time.  It is far to early into bthe plannig stage of my project to do anything but ask questions and do research.  the clkiosest thing to this kinda of work i have done thus faris melting wax to make candles. im nowhere near any kind of actual fabrication point yet. soi rest asurde bthat i have not yet tried anything of this nature yet. appologies if iu have givenb any impressions to the otherwise.

Longfellow's "The Village Blacksmith"  is one of the "classic" mentions of blacksmithing in American literature, Melville's "Moby Dick" has another when he describes the forging of the harpoon with great detail on the materials used and the properties they were believed to have.  Of course the stories of the smith Reginn are the well known northern European works as are tales of Wayland the smith who even gets mentioned in Beowulf!  Child Ballad #44 has even been set to contemporary music with a "Coal Black Smith" being one of the two protagonists.

One of the two most common jokes about blacksmithing:  "When I nod my head hit it!" is about the problem of miscommunication in a blacksmith's shop.  (The other joke being "doesn't take me long to look at a horse shoe".)  Jargon is a method of precisely specifying things specific to a craft or area of knowledge; it does have a local bias at times which can get down to a single person---or such a person and the students they had and the  students their students had...usw.  Learning the "language" is a part of learning a craft. (My wife has been teaching spinning for over 40 years now and her first class is just over terminology and students are expected to take notes!)

As we don't know where you are at we can't make allowances for jargon shift, yearling black wolf...

Something to consider is the forum you chose to participate in. Iforge is represented by some 40,000 people in about 120+ countries around the world. If everyone here insists on using terminology from home the quality and value of communications goes in the dumper. One person could be looking for a kowalski and end up in the lee instead or just get funny looks when he gets upset by someone jumping up on his project.

Does any of that make sense? Could be because two terms are Polish and Korean while the other two are regional or dialectic.

One of the truly wonderful benefits of Iforge is how folks from around the world are developing a universal language and terminology so we can trade knowledge, techniques, tricks and help solve problems. We're all learning from each other, the smart ones listen and don't make excuses nor . . . Nevermind.

Frosty The Lucky.

Mingte supply professional and honest service.

Blackwolf, a graphite or fused silica crucible is relatively cheap online, and the way to go. Homemade crucibles are delicate, risky, and if you go with most metals, melty, and can cause nasty inclusions in your casting, amongst other issues.

Other reccomendations - read up. The gingery books and the online sites like backyardmetalcasting.com, etc. Good PPE is a must. Stay away from zinc containing metals until experienced. But most importantly, seek experienced help. And not "that guy from youtube that put molten aluminum in an ant bed/watermelon/swimming pool." Try the local blacksmithing group, colleges, or sculpting groups. You'll save yourself a lot of grief, and quite possibly a lot of skin.

And to be fair, Lee is about every third word/name in Korean, Frosty. And Kim is most of the rest.

I don't plan on melting iron/steel for some time to come. The hottest melt temp I'll be dealing with initially is aluminum. And the only casting I'll be doing is simple plates type shapes.  As for losing skin: not gonna say it won't happen. That's a biton the arrogant side I think.  In stead I will account as much for Murphy's Law as I can and implement safety measures that many here might consider overkill. I don't plan on putting any part of my skin close enough to be harmed by the molten metal.  I can't say I won't mess up, I'm human after all, but I can say I won't be one of those beginner level idiot cowboys that think watching a few YouTube videos makes them experts.  Expertise is something earned by training, work, devotion to this craft, and experience.  I don't yet have the time put into it to be an expert and I'll be the first to admit it about myself.

Close enough to be seriously injured by molten al is within about 30' of the melt in a well designed foundry area. 212f. water expands 1,600x when it's phase changes to 212f steam. The greater the temperature of the steam the larger the expansion and al melts around 1,100f. One drop of water is enough to splash 15lbs of molten al better than 30'. I had some run down my back and I was almost that far from the badness. Fortunately I was really sweating and my shirt was untucked so it road a barrier of steam down my spine and didn't go down my pants. Mr. Harding 86ed the kid in class who knocked the bottom out of the mold for the fun of it.

Here's another little tidbit to keep in mind. A steam explosion driven by 10 lbs. of molten iron is about the same as detonating 1 case of 40% dynamite. That's a crucible a little larger than a good size coffee mug. If you're pouring you will NOT get away.

No synthetic clothing in a hot shop!

Take a class and learn casting the right way and don't expect me to encourage your experimenting. I don't dislike you so I won't try talking you into a Darwin award.

Frosty The Lucky.

Graphite crucibles are the perfect tool for metal casting because of their thermal conductivity, high-temperature resistance, low thermal expansion coefficient for high-temperature applications, and anti-strain characteristics to rapid heating and cooling. They also have great chemical stability and are resistant to acids and alkaline solutions.

Natural graphite, a crystalline form of carbon that occurs in nature, is used to make graphite, which is then combined with carbon dioxide or a lump of clay that resists fire. Petroleum pitch and coke, byproducts of oil refining, are processed to produce synthetic graphite; because of this, it has a lower sulfur concentration and a higher, purer, fixed carbon content.

A graphite crucible offers a non-reactive container that can withstand the high temperatures required for melting and treating metal. Crucibles offer a reliable container that won't react with the metals or other materials burned at high temperatures. Carbon is found in graphite, which can look like flakes or sheets. Graphite can create heat-resistant, long-lasting jars and containers when combined with clay. Graphite crucibles, on the other hand, can be brittle and should be handled carefully, just like many ceramic containers.

Graphite Crucible Shapes

The main difference between several crucible types is their shape. One shape is called “bilge,” which indicates a barrel shape. In addition, graphite crucible shapes are sorted by letter of the alphabet, so the first crucible shape, or “A” shape, is a cup shape common among crucibles. Since an open cup design is simpler to produce than a barrel shape, "A" shaped crucibles may be less expensive.

Graphite crucibles sorted by letters are further broken down into subgroups based on the shape, interior diameter, outer diameter, and height of the crucible.

The kind of crucible used depends on the kind of metal being treated. The crucible's construction and design must hold the metal at its maximum melting point. The chemical and physical interactions between the metal and the crucible also affect this.

Metals Melted In Graphite Crucibles

Copper

Due to its resistance to thermal shock, a silicon carbide graphite crucible is used to process copper-based alloys that are melted in a fuel-fired furnace.

Aluminum

Carbon or ceramic-bonded clay graphite and silicon carbide are used as crucibles for the production of aluminum and aluminum alloys since these metals melt at 750 °F to °F (400 °C to °C).

Gold

Superior-grade graphite crucibles for melting gold have great mechanical strength, are resistant to oxidation and thermal shock and have thermal stability. They are also built to endure more than ° F (° C).

Silver

Similar to those used to melt gold, graphite crucibles for melting silver may sustain temperatures as high as °F ( °C). Natural graphite serves as the material for the crucible's body, retaining its chemical and physical characteristics. When melting at a higher temperature, the thermal coefficient is less, but it has strain resistance to sudden changes in temperature.

Brass

Graphite crucibles can sustain temperatures above °F and are identical to those used to melt gold. The crucible's body is made of natural graphite, which retains its chemical and physical characteristics. Although the thermal coefficient is low when melting at a high temperature, it has strain resistance to sudden changes in temperature.

Use of Graphite Crucibles

Graphite crucibles are perfect for the casting process since they are non-reactive. Their superior heat efficiency aids in speedy metal melting for shorter production cycles. In addition, graphite crucibles are strong and long-lasting because they are impervious to chemicals and corrosion and unaffected by the environment in the workshop.

A graphite crucible should be properly stored and conditioned. Before usage, a new graphite crucible needs to be in condition. After two hours at 500 degrees Fahrenheit (260 °C) in the oven, the crucible should be removed and allowed to cool slowly in a dry area. Removing moisture keeps the crucible from splitting. Crucibles should be kept dry and should be reconditioned if they become wet.

Temperatures are raised during casting to lower the tensile and yield strengths of the metal alloys used. Depending on the type of metal, different temperatures are required for melting. The temperature of the crucible and the alloy being cast are two variables that affect casting. Due to its great resistance to the effects of temperature increases, graphite crucibles can supply the right vessel for casting, regardless of the type of metal alloy.

After use, a graphite crucible needs to be thoroughly cleaned. Metal shouldn't be allowed to cool in the crucible. When reheated, residual metal can expand and cause the crucible to break. Instead, use crucible tongs that are compatible with the crucible's design. To avoid cracking, the tongs should hold the crucible without applying pressure to the sides.

Improper use or handling can cause damage to graphite crucibles. They shouldn't be used with iron-containing metals since the iron will immediately react with the carbon in the crucible, altering or destroying the metal's composition. Before being heated, a crucible should be filled with loosely packed solid metals. A closely packed crucible may fail or crack if the metals expand. Never add water or wet metals to molten metal in a crucible since doing so could result in a steam explosion or cause the crucible to fail.

Choosing the Correct Graphite Crucible Supplier

To ensure you have the most constructive outcome when purchasing graphite crucibles from a graphite crucible supplier, it is important to compare several companies using our directory of graphite crucible suppliers. Each graphite crucible supplier has a business profile page highlighting their areas of experience and capabilities, along with a contact form to directly communicate with the supplier for more information or request a quote. Review each graphite crucible business website using our patented website previewer to quickly learn what each company specializes in. Then, use our simple RFQ form to contact multiple companies with the same form.

Contact us to discuss your requirements of crucibles manufacturer(ja,es,it). Our experienced sales team can help you identify the options that best suit your needs.