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Company Profile

 

As a ceramic and carbon company, we have excellent quality control and products covering various applications such as semi-conductor,high-temperature furnaces, non-ferrous,pigment,magnetic powder, rubber,break pads and more. We have a dedicated research and development team committed to technological innovation and developing new products to meet customer demands. We have flexible production capabilities to provide customized refractory material solutions according to customer needs. With these competitive advantages, we strive to become your trusted and reliable supplier of refractory materials.

 

Why Choose Us

Factory

The founder,Mr Tang,open the first factory in Zibo and produce graphite molds and synthetic graphite powder. For Mr tang once worked for a state-owned graphite company, he has much experience in graphite application. Gotrays grow quickly in business.

Quality Control

Our team is experienced bringing wide knowledge to every order we received. We train our employee to ensure they posses the skills and qualifications to deliver outstanding results.

 

High Quality

We are committed to producing and providing high-quality product. We take advanced production techniques and strict quality control measures to ensure our products have excellent performance, stable chemical composition, and reliable service life.

 

Professional Team

We value environmental protection and sustainable development, focusing on developing and producing eco-friendly materials. We actively adopt energy-saving and emission-reducing production processes, promote recycling and resource utilization to minimize our impact on the environment.

 

 

 

Graphite Crucibles

 

What is Graphite Crucible？

Graphite crucibles serve as essential vessels for melting and casting metals like gold, silver, aluminum, and brass. They are prized for their excellent thermal conductivity, ability to withstand high temperatures, and resistance to thermal expansion under extreme conditions. Their durability against rapid heating and cooling makes them a preferred choice for metal casting. Additionally, graphite crucibles are highly resistant to chemical corrosion from acids and alkaline solutions, ensuring long-term stability.
Graphite is sourced from naturally occurring crystalline carbon and is processed by integrating it with fire-resistant materials such as clay or carbon dioxide. This combination enhances its properties for high-temperature applications.

 

Benefits of Graphite Crucible
 

Thermal Stability

Graphite crucibles can withstand temperatures ranging from 3,000 to 5,000 degrees Celsius without undergoing significant structural changes. This exceptional thermal stability ensures consistent performance even under extreme conditions.

Low Thermal Expansion

Graphite exhibits minimal thermal expansion, meaning it maintains its shape and integrity when exposed to rapid temperature changes. This property prevents cracking or warping of the crucible and enhances its longevity.

Oxidation Resistance

Graphite is highly resistant to oxidation, even at high temperatures. This characteristic prevents the crucible from reacting with oxygen in the air, ensuring the purity of the materials being processed.

Low Wettability

Graphite has low wettability, meaning molten metals do not readily adhere to its surface. This property facilitates easy removal of the solidified metal from the crucible, simplifying the casting and recycling processes.

 

Graphite crucibles can be roughly divided into four categories

 

 

Pure graphite crucible. The carbon content is generally greater than 99.9%, and it is made of pure artificial graphite material. It is only recommended to use carefully for electric furnaces.

 

Clay graphite crucible. It is made of natural graphite powder mixed with clay and other oxidation-resistant materials. It is suitable for factories with low labor cost and low operating rate.

 

ilicon carbide graphite crucible. It is made of natural graphite powder, silicon carbide, aluminum oxide, etc. and added with an anti-oxidation layer. Suitable for high temperature smelting, popular demand.

 

The silicon carbide graphite crucible is formed by isostatic pressing, and the crucible is pressed by an isostatic pressing machine. The service life is generally 2-4 times that of the rotary formed silicon carbide graphite crucible. It is the most suitable for aluminum and zinc oxide. Due to the high cost of isostatic pressing, there is generally no small crucible.

 

 

How Graphite Crucibles are Used?

Graphite crucibles are highly suited for casting due to their inert nature. They excel in thermal performance, enabling the rapid melting of metals and improving production efficiency. Their resistance to both chemical attack and corrosion ensures that they maintain their integrity under various workshop conditions, contributing to their longevity and reliability.

In the casting process, the application of heat is crucial to reduce the tensile and yield strengths of metal alloys. The melting points of different metals vary, and successful casting depends on both the alloy's temperature and the crucible's heat resistance. Graphite crucibles are adept at withstanding these high temperatures, making them ideal for a wide range of metal alloys.

Graphite crucibles come in a vast array of shapes, classified by a letter system starting with A. These shapes are further detailed by subcategories based on dimensions like inner diameter (ID or d), outer diameter (OD or D), and height (H), as well as the crucible's design. For example, the illustrated crucible features a cylindrical form with a flat base and lacks any spout or lid.

Graphite crucibles come in a wide variety of shapes, reflecting their diverse applications. They can range from cylindrical forms with or without spouts to cup-like designs, and some may feature a rim or lid, among other configurations.

Over time, graphite crucibles have become indispensable in metalworking. They are available in various sizes, from small units akin to teacups to large vessels capable of holding several tons of molten metal, and can even be integrated into furnace systems.

Graphite crucibles are versatile tools utilized in fuel-fired, electric, and induction furnaces, as well as for transferring and handling molten metals. They must be engineered to meet the specific temperature, chemical, and mechanical demands of each particular process.

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What Metals Can Be Melted In Graphite Crucibles?

 

The specific metal being melted dictates the appropriate crucible type needed. The crucible's design and construction must withstand the highest melting temperatures of the metal and maintain its integrity. This requirement is influenced by both the chemical and physical interactions between the metal and the crucible.

 

Copper
Copper-based alloys melted in fuel-fired furnaces are typically processed using silicon carbide graphite crucibles, chosen for their resistance to thermal shock.

 

luminum
Crucibles used for processing aluminum and its alloys are typically made from carbon or ceramic-bonded clay graphite and silicon carbide. This is because aluminum melts at temperatures ranging from 400°C (750°F) to 1600°C (2912°F).

 

Gold
Graphite crucibles designed for melting gold are crafted from high-quality graphite to ensure excellent thermal shock resistance, stability, oxidation resistance, and mechanical strength. They are engineered to endure temperatures exceeding 2000°C (3632°F).

 

Silver
Graphite crucibles used for melting silver share similar characteristics with those for gold and can endure temperatures above 2000°C (3632°F). These crucibles are constructed from natural graphite, maintaining their chemical and physical integrity. They exhibit minimal thermal expansion and offer resistance to rapid temperature changes, making them suitable for high-temperature applications.

 

Brass
Brass has a low melting point and must be heated rapidly before the component metals oxidize. For working with brass, a graphite crucible is ideal due to its durability and ability to heat up quickly.

 

The Process Of Making Graphite Crucible

 

The graphite crucible graphite pendant was dried and inspected according to the semi-finished product standard. Qualified products into the glazing process brush glazing, glazing layer dry before firing into the kiln. The purpose of sintering is to increase the density and mechanical strength of crucible and improve product quality.

 

(1) Preheating and baking stages: Kiln temperature for 100 300 ℃ or less, from the process of graphite crucible to remove residual water. The opening skylight should be opened and the heating speed should be slow, especially when the residual water in the graphite crucible's graphite box exceeds 3%, the temperature should be strictly controlled, which is prone to crucible cracks and explosion accidents.

 

(2) The low temperature sintering stage: 4 0 0 ℃ and 6 0 0 ℃. The low temperature stage of crucible sintering. As the kiln temperature increases, the bound water in the crucible begins to decompose and remove. A1203 and Si02, the main components, once formed a free state in the clay: the glaze layer on the surface of the crucible has not been melted, the heating speed should still be slow, if the heating speed is too fast and uneven, it is also prone to explosion and collapse.

 

(3) Medium temperature sintering stage: 700 ℃ 900 ℃. At this point, the amorphous A1203 in the clay can be partially transformed into y-type crystal Al203. In the case of increasing temperature in the kiln, Al203 in free state and Si0 'are combined to form hard silicate curing products (also known as baifa). The graphite and clinker in the crucible are connected and solidified as a whole. In the process of medium temperature sintering, the outer glaze layer of the graphite crucible melts gradually as the temperature increases, forming a glass glaze film, which is closed or covered on the surface of the crucible to protect the crucible from oxidation.


(4) High-temperature firing stage: The temperature of this stage is ioo-1200 cc. At this time, after the clay in the crucible is sintered and solidified at medium temperature, it will gradually transform to mullite. During this period, the rate of temperature rise should be faster than that at medium temperature (commonly known as the process of fire discharge). In the process of crucible high temperature sintering, the glaze layer is completely melted, forming a glassy glaze film, which is sealed on the surface of the crucible. If the sintering temperature exceeds the temperature limit of the glaze, it is easy to flow out of the crucible and cause oxidation of the crucible. Density, hardness, fire resistance and load softening point are very high, thermal expansion coefficient is small.

 

Sic Crucible

 

Graphite crucible fired at high temperature

The temperature of this stage temperature is iooo-1200cc. The clay in graphite crucible once sintering within the medium temperature type curing, step by step transformed into mullite, such as 3A1203+2Si07:3Al203'2Si0. (Mullite). Throughout this period, the heating rate should be faster than within the middle temperature (commonly known as the fireplace process), the chamber flame should be controlled within the neutral flame or reducing flame.

The glaze layer has been completely melted throughout the crucible in warmth sintering process, forming a glass like glaze film, close to the crucible surface. If the temperature exceeds the maximum temperature limit of sintering glaze, it simply cause the oxidization of the crucible. Therefore, within the high temperature sintering method, we should observe the glaze layer melting condition of graphite crucible and avoid the burnt and not up to the sintering.

Mullite (3A1203'2Si02), a senior Department of physical and chemical properties of refractory minerals and a stable. The density, hardness, refractoriness and softening purpose are terribly high, low coefficient of thermal growth. Within the structure of the crucible, it's an important role of consolidation and hardening. It is far-famed that, within the crucible sintering method, because of the thermal effect of plastic refractory clay, the consolidation of graphite and clinker contains a certain mechanical strength. Therefore, high and low of the sintering temperature, temperature control within the process of operation, it'll has an important influence to the quality and service lifetime of graphite crucible products.

 

How to Clean a Graphite Crucible

Allow the crucible to cool

Before attempting to clean your crucible, make sure it has cooled down to a safe temperature. Handling a hot crucible can result in burns or other injuries.

 

Remove any large debris

Using a pair of tongs or a crucible tong, carefully remove any large pieces of debris or residue from the crucible.

Scrape the crucible

Using a brass or stainless steel scraper, gently scrape the inside of the crucible to remove any stuck-on residue. Be sure to use a light touch to avoid damaging the crucible.

Clean the crucible

Once you have removed as much residue as possible, you can clean the crucible using a mild detergent and warm water. Gently scrub the inside of the crucible with a soft brush to remove any remaining debris.

Rinse and dry the crucible

Rinse the crucible thoroughly with clean water to remove any soap or residue. Then, dry it off with a clean cloth or paper towel.

 

 
Our Factory
 

 

The founder,Mr Tang,open the first factory in Zibo and produce graphite molds and synthetic graphite powder. For Mr tang once worked for a state-owned graphite company, he has much experience in graphite application. Gotrays grow quickly in business.

 

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Honor&Qualification
 

 

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FAQ
 
 

Q: Do you need to heat treat graphite crucible?

A: When you get a brand-new crucible, it needs to be heat-treated before its first use. 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.

Q: What can you melt in a graphite crucible?

A: Carbon-bonded and ceramic-bonded clay graphite and silicon carbide crucibles are widely use in melting and holding aluminum and aluminum alloys, aluminum-bronze, copper and copper-based alloys, cupro-nickel and nickel-bronze alloys, precious metals, zinc and zinc oxide. Crucibles also are used in melting cast iron.

Q: What is the difference between graphite and clay crucible?

A: In processes that involve frequent heating and cooling cycles, ceramic crucibles are often the preferred choice. Graphite crucibles are more susceptible to thermal shock and may crack or degrade if subjected to rapid temperature changes.

Q: What is the purpose of a graphite crucible?

A: A graphite crucible is a container used for melting and casting non-ferrous, non-iron, metals such as gold, silver, aluminum, and brass. The quality of a graphite crucible is determined by how it is manufactured, which influences its structure, density, porosity, and strength.

Q: How long should a graphite crucible last?

A: Their lifespan can be several melts, depending on the purity of the materials and the care taken during handling and charging. Graphite Crucibles: Ideal for lower melting point metals that do not react with carbon, these crucibles can last through multiple melts but are susceptible to oxidation and mechanical damage.

Q: Why don't graphite crucibles burn?

A: One of he benefits of a graphite crucible is that the carbon combines with any oxygen present to create a reducing atmosphere within the crucible, helping to protect your metal, similar to how you would cover an open crucible with a flame. Coating the interior of the crucible with a barrier would prevent that.

Q: What is the temperature of graphite crucible?

A: Graphite Crucible Temperature Range can go as high as 5000°F and can be used in furnaces and high heat processes. Graphite crucibles have many applications within the foundry, laboratory testing, valves, sprinklers, and other heavy-duty products.

Q: How do you preheat graphite crucible?

A: It is therefore recommended that where possible the crucible is pre-heated empty from cold using a maximum of 100Kw, or 50% of maximum power, whichever is smaller. Heat the crucible until it attains red heat. This should take between 20 and 40 minutes.

Q: Can you melt steel in a graphite crucible?

A: Quartz crucibles are suitable for melting iron, aluminum, stainless steel, platinum, gold, palladium, etc. Graphite crucibles are suitable for melting copper, brass, gold, silver, zinc, lead, and other non-ferrous metals and their alloys.

Q: How do you clean a graphite crucible?

A: In general, the binder on the graphite crucible is the residue of inorganic combustion. We can clean it with hydrochloric acid, most of which is soluble, and some residues containing carbon that cannot be dissolved with hydrochloric acid. Nitric acid is highly oxidizing and can be used for cleaning with proper heating.

Q: What are the benefits of graphite crucibles?

A: Graphite crucibles stand out for a range of thermal, physical, and chemical properties. Thermal Performance: Thanks to their thermal conductivity, the time for melting and energy consumption are reduced. These crucibles could bear rapid heating and cooling since they have excellent heat shock resistance.

Q: What is the difference between clay graphite crucible and silicon carbide crucible?

A: For applications demanding a cost-effective yet versatile solution, Clay Graphite crucibles stand out with their moderate price and high operating temperature. Silicon Carbide, with its excellent thermal properties, is a robust choice for environments with rapid temperature changes, though at a slightly higher cost.

Q: Can I melt glass in a graphite crucible?

A: 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. Because of the high viscosity of this glass I couldn't cast in a mold, I guess even if I try to cast most of the sample will remain in the crucible.

Q: What temperature does graphite crucible work?

A: Graphite crucible maximum temperature can go as high as 5000°F and can be used in furnaces and high heat processes. Graphite crucibles have many applications within the foundry, laboratory testing, valves, sprinklers, and other heavy-duty products.

As one of the leading graphite crucible manufacturers and suppliers in China, we warmly welcome you to wholesale high quality graphite crucible at competitive price from our factory. Contact us for more details.

Graphite Crucible For Steel, Corundum Mullite Sagger, Graphite Crucibles

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