The graphite crucibles should be tempered before use. Heat the empty graphite crucible for a temperature of about 260 degree celsius and hold it for 20 minutes. Then work the crucible to red heat. Turn off the heat and leave the furnace crucible to cool slowly. This process takes off any moisture in the furnace crucible.
What is the melting temperature of a graphite crucible?
The melting temperature of a silicon carbide crucible is up to 1600 degree celsius. Clay graphite on the other hand has a melting temperature ranging from 850 degree celsius to 1600 degree celsius. Graphite crucibles are for melting precious metals such as gold, silver, platinum, palladium.
What are the advantages of graphite crucible?
As the graphite has a great heat performance, the time spent on melting is short, therefore saving energy. The graphite crucible is suitable for foundries, jewelry industry and other industries where metal melting and casting is necessary.
Do you have to heat up clay graphite crucibles?
I've heard that you have to heat up clay graphite crucibles more carefully. I've only worked with silicon graphite ones, and used them for bronze. I've only cracked one so far. They tend to last hundreds of castings.
What metals can be melted in a crucible?
Metals such as nickel and zirconium are also used as melting crucibles. Graphite crucible can withstand the high temperature of metals and has a good resistance to chemical erosions and thermal shock. Graphite crucibles are most especially ideal for melting precious metals, aluminium, copper, etc.
How do you temper graphite in the crucible?
After first use — The crucible should be heated to 600°C (1110°F) on low power and then to bright red heat on full power or to the desired temperature, however the slow heating phase to 200°C (390°F) should be adopted whenever the crucible has been allowed to cool off for extended periods.
How do you season a new graphite crucible?
1:265:15Seasoning (tempering) Graphite Crucibles with Borax - YouTubeYouTubeStart of suggested clipEnd of suggested clipAnd what I'm doing is seasoning the crucibles. So I have filled the crucible about a third of theMoreAnd what I'm doing is seasoning the crucibles. So I have filled the crucible about a third of the way full full of borax a little little one in there right. Now as soon as it's melted. He's melting a
How do you fire graphite in the crucible?
1:009:11How to Temper a Graphite Clay Crucible for Metal Casting at homeYouTubeStart of suggested clipEnd of suggested clipBecause water will flash boil. And it will flash foil inside. So this was sitting in a bunch of rainMoreBecause water will flash boil. And it will flash foil inside. So this was sitting in a bunch of rain water. And I you know let it air dry for 20 minutes and went through in the furnace.
How do you season a new crucible?
4:4313:18Learning How To Prepare A Crucible Before Using It For The First TimeYouTubeStart of suggested clipEnd of suggested clipMake sure the crucible is nice and safe inside. We're going to get some borax powder.MoreMake sure the crucible is nice and safe inside. We're going to get some borax powder.
How do you condition a crucible?
4:0311:58How to Clean Out a Crucible - Melting Down Gold and Silver - YouTubeYouTubeStart of suggested clipEnd of suggested clipYou can use the flame to sort of push down the flux and push it out of the crucible.MoreYou can use the flame to sort of push down the flux and push it out of the crucible.
How do you initially heat a crucible?
0:031:31Heating a substance in a crucible - YouTubeYouTubeStart of suggested clipEnd of suggested clipHe's in a crucible is a useful technique for reactions where you need to heat something to a veryMoreHe's in a crucible is a useful technique for reactions where you need to heat something to a very high temperature crucibles are made of a ceramic material which can withstand very high temperatures.
Do graphite crucibles burn?
The main use of graphite crucibles is in the casting process. They are ideal for melted metal processes because they are non-reactive and able to survive extremely high temperatures. Casting and melt forming production require vessels that can survive the burning and heating process.
What is the melting point of a graphite crucible?
Graphite Crucibles Properties (Theoretical)Molecular Weight12.01AppearanceBlack solidMelting Point3652 - 3697 °C (sublimes)Boiling Point4200 °CDensity1.8 g/cm39 more rows
How long does a crucible last?
The Crucible is a test every recruit must go through to become a Marine. It tests every recruit physically, mentally and morally and is the defining experience of recruit training. The Crucible takes place over 54-hours and includes food and sleep deprivation and over 45 miles of marching.
Why do you have to tilt the crucible during charring?
Open crucible lid or tilt lid on crucible to allow oxygen to come in contact with sample.
How does borax treat the Crucible?
3:1515:50Crucible Tempering Revisited: To use borax or not? or something else?YouTubeStart of suggested clipEnd of suggested clipAnd now it's all over the floor borax borax and boric acid are two very common treatments thatMoreAnd now it's all over the floor borax borax and boric acid are two very common treatments that people put on the crucibles. For tempering purposes it actually says did i just wipe that on my face.
How long must you heat the contents of the crucible?
Using your crucible tongs, place the crucible and contents back on the clay triangle. Partially cover the opening of the crucible with the cover. Heat your crucible and its contents with a low flame for 5 min.
What is the melting point of a graphite crucible?
Graphite Crucibles Properties (Theoretical)Molecular Weight12.01AppearanceBlack solidMelting Point3652 - 3697 °C (sublimes)Boiling Point4200 °CDensity1.8 g/cm39 more rows
Can you melt glass in a graphite crucible?
Glass remains a piece and does not adhere to graphite. Theoretically, you can glasses in graphite crucible melt under protective atmosphere and then slowly to cool with the furnace, but it does not work with all glasses.
How do you use borax in the crucible?
3:3415:50Crucible Tempering Revisited: To use borax or not? or something else?YouTubeStart of suggested clipEnd of suggested clipSo you can click so like in a molten metal puddle you pour in borax.MoreSo you can click so like in a molten metal puddle you pour in borax.
How long does a crucible last?
The Crucible is a test every recruit must go through to become a Marine. It tests every recruit physically, mentally and morally and is the defining experience of recruit training. The Crucible takes place over 54-hours and includes food and sleep deprivation and over 45 miles of marching.
Why is graphite used to make crucible?
Graphite is used to make crucibles because it is a good conductor of heat and electricity. The fact that graphite is able to resist chemicals and has a high melting point, also graphite is a good conductor of heat makes it adopted in the making of crucibles.
What is a graphite crucible?
A graphite crucible is a container made of graphite and it is used to melt and hold metals . They can be used at temperatures of up to 1600 degrees celsius and are suitable for refining and melting precious metals and base metals and other products. The graphite crucible is the crucible of choice for many users due to its outstanding properties, which include:
What is the best material for a crucible?
The best material for crucible is graphite. Graphite is an allotrope of carbon, which is a good electrical conductor. Being the most stable form of carbon under standard conditions, it is mined naturally to produce graphite crucibles.
What needs to be checked before using a crucible?
Then work the graphite crucible till red hot. Turn off the heat and leave the crucible to cool slowly. This process takes off any moisture in the crucible. Furnace crucibles should be properly checked for cracks prior to each application.
What is a melting crucible made of?
Melting crucible can be made of graphite, clay and graphite or silicon and graphite.
Why do you preheat a crucible?
A new crucible should be preheated slowly and evenly to 600 degree celsius on low power. Subsequently, the full heat input rate should be utilized to achieve a uniform bright red condition over the whole crucible at which point the crucible should be charged immediately taking care to avoid packing metal tightly or bridging ingots across the crucible. Preventing a crucible is done for the following reasons:
Why do we not allow the crucible to become red hot?
Run the furnace for 1/2 hour at 20% of maximum power and then increase to 50% until the crucible shows signs of red heat. Loosely charge the crucible with metal. Keep the power at 50% of maximum until approximately half the crucible contains molten metal. Then increase to maximum power. In 1 kHz furnaces the crucible does not absorb power; therefore the crucible should be preheated with a charge loosely in place. Run the furnace at 20% of maximum power until the crucible shows signs of red heat. If after 1/2 hour the crucible shows no evidence of red heat, increase the power input to 50% of maximum. Hold at 50% until half the crucible contains molten metal, then increase to maximum power. crucibles are prone to thermal shock if the rate of temperature charge is too rapid. To preheat the crucible use whichever power level is smaller, 100KW or 50% maximum power input. Heat until the crucible is bright red, this should take 20–40 minutes. The crucible can be preheated with or without charge material, depending on the specific furnace conditions
What happens if you heat a crucible?
MOISTURE. If moisture is on your crucible when you try to heat it—even if it’s not visible to the naked eye—it will flash boil. This will cause the item to crack or explode, which is very dangerous. You don’t know what dampness the crucible has been exposed to, so you must temper it to eliminate any moisture.
How to heat cure crucible?
You can begin by putting the container in the oven at 300 degrees for an hour. Next, temper the crucible by putting it in the furnace. Your flame should be orange and yellow.
How to keep crucible from cracking?
Some like to use Borax during the tempering process as they believe it will help prevent cracking and breaking. Any time you heat your crucible from a cooled state for an extended length of time, slowly raise the temperate to 200 degrees Fahrenheit before heating it the rest of the way.
How to clean crucibles?
CLEANING. If you acquire a crucible that’s been used, it will need to be cleaned before you use it. So, wash your crucible with water and dry with a paper towel. Ensuring all residue from other projects has been removed is important. However, doing this will add moisture to your container that will need to be removed.
Why is clay used in crucibles?
Clay is ideal because it lacks metallic properties that prevent the material from messing with the alloy of the metal you’re melting. The secret to making your crucible last is to heat-treat it properly when it’s new.
Do you need to heat treat crucibles?
Heat-treating—or “curing”—a crucible sets it so that when you use it later, it doesn’t crack or break down and expose you to extremely hazardous temperatures of melted metals or other substances.
How long should I sit a pot on top of a fire?
They can be a little prone to thermal shock so it pays to sit them on top of your fire for a wee while or , as I do, charge your pot, pre-heat the fire to 700-800 then turn her off and stand the pot inside for a couple or five minute before resatarting.
Can you let crucible metal solidify?
Another thing to keep in mind: don't let the metal solidify in the crucible and cool all the way down. It will either get stuck, or rip the inside of the crucible apart. You may be able to let it solidify, but tip it out when it's still very hot and soft, so it doesn't get the chance to harden and shrink. Link to post.
Can you keep silica out of a furnace?
If you were to keep silica out of your furnace your slag would be basic and may take up some of the Phosphorous you are concerned about. That will require running a bit hotter than what you may be used to. Almost all of the iron I have made was done this way..the slag is very viscous even at higher temps.
What happens if you exceed the temperature limit on a crucible?
Every crucible has a maximum temperature limit. If you exceed that limit the crucible will be damaged and may fail. Keep close control of crucible temperatures. Allowing molten metal to solidify in the crucible also may damage the crucible when that metal is reheated for pouring. 6.
How to avoid damage to crucible?
Avoid physical damage by charging correctly and carefully. Dropping a heavy casting or ingot into a furnace crucible may chip or crack the crucible, leading to failure. Follow proper charging practice of first loading small charge materials and then carefully lowering heavier materials on top of cushioning base.
How to protect crucibles from chemical attack?
5. Guard against chemical attack by minimizing flux usage and adding flux only after metal is fully molten. All crucibles, even those designed to resist chemical attack, can be damaged flux additives. The most effective way to minimize this damage is to add flux only after the bath is fully molten and able to dilute the material. Adding flux with the solid charge allows the concentrated flux to attack the crucible surface during the melting process. It is important also to use the minimum amount of flux that is required.
Why does my crucible crack?
Too small a base may fail to provide sufficient support, and the wrong base height in a fuel-fired furnace may cause the burner flame to create an overheated and oxidized area on the crucible. Insufficient clearances between the crucible and the furnace sides and top may cause cracking when the heated crucible expands.
How is a crucible handled?
How a crucible is handled, operated and maintained may be the difference between a crucible that consistently performs well and one that fails to meet even minimal standards . Sometimes the difference between a crucible that consistently performs well and one that fails to meet even minimal standards may have nothing to do with the crucible itself.
What causes crucibles to crack?
In a fuel-fired furnace, operating the burner with excess air and direct flame impingement on the crucible surface will produce damaging oxidation of the crucible. In all furnaces, placing ceramic fiber between the crucible and its base or wedging ceramic fiber against the top edge of the crucible also will cause oxidation and cracking in those areas. Finally, allowing a metal bath to be held at a minimal temperate for a lengthy period of time will accelerate crucible oxidation.
What caused oxidation damage to the crucible?
Fig. 4 – Direct contact with a burner flame caused this oxidation damage. The base holding the crucible was not the proper height.
