Extruded Graphite

Properties of Extruded Graphite

Extruded graphite has distinctive characteristics which makes it suitable for many industrial applications. Some of the extruded graphite properties are detailed below:

· Excellent Thermal Properties

Extruded graphite has an extraordinary thermal conductivity – typically 100 to 200 W/m·K at room temperature. This high conductivity allows efficient heat transfer. This makes it perfect for thermal management. Moreover, its low coefficient of thermal expansion (CTE), about 1.8-5.0 × 10^-6/°C between 100-600°C provides outstanding thermal shock resistance. You can depend on it to stay stable despite rapidly changing temps.

· Low Electrical Resistance

The extruded graphite shows excellent electrical conductivity. It’s electrical resistance is 6.0-8.0 μΩ·m. This makes it a favored material for electrodes in electric arc steel manufacturing and many electronic uses. Its ability to efficiently conduct electricity while going through high temperatures differentiates it from many other industry materials.

· High Flexural and Compressive Strength

Extruded graphite with 8-15 GPa Young’s modulus gives flawless dimensional stability under load. It also has excellent mechanical resilience. It offers up to 90 MPa compressive strength and 20-50 MPa flexural strength. This combination allows extruded graphite to carry on structural integrity in high-stress environments. For example, continuous EG casting molds can operate ideally at 1500°C.

· Low Ash Content

High-purity extruded graphite has remarkably low ash content usually below 50 ppm. This extraordinary purity is quantified per ASTM C561 standard test methods. The minimal impurities result in a material with superior thermal conductivity (≥ 120 W/m·K at 20°C) and electrical resistivity (≤ 8 μΩ·m).

For the manufacturing of semiconductors where trace contaminants can greatly affect device performance, this low ash content is very important.

· High Corrosion Resistance

Extruded graphite shows exceptional chemical inertness. It resists attack from most organic solvents and stays stable in pH 0-14 ranges. Its corrosion resistance is particularly noteworthy in high-temp environments as it outperforms many ceramics and metals.

For example, in phosphoric acid production, extruded graphite heat exchangers operate successfully at up to 85% concentrations and 180°C temperature. This resistance gives reduced maintenance costs and extended service life in corrosive industrial processes.

Available Extruded Graphite Grades

Extruded graphite comes in many grades, each tailored for specific applications. Knowing these grades is very important for selecting the right material.

1. Isostatic Graphite (IG 1 to IG 6)

Isostatic graphite grades (IG 1 to IG 6) are known for their uniform properties and high purity.

IG 1 has the highest density (≥1.85 g/cm³) and smallest grain size (≤3 μm) which makes it perfect for semiconductors. As you go to IG 6, grain size rises (≤20 μm) and density drops (≥1.75 g/cm³).

IG 3 and IG 4 are commonly used in EDM electrodes due to balanced features such as electrical resistivity of 10-12 μΩ·m and flexural strengths around 70 MPa.

Here’s a detailed comparison of these grades:

Table 1: Isostatic graphite grade 1 to grade 6 properties.

2. Molded Graphite (MG 1, MG 2)

The MG series are molded graphite grades. MG 1 has higher density (≥1.75 g/cm3) and strength (compressive strength ≥90 MPa) than MG 2 (compressive strength ≥70 MPa, density ≥1.65 g/cm3).

These extruded graphite grades offer good machinability and moderate conductivity. You’ll see MG grades used in continuous casting molds and EDM electrodes where thermal conductivity (120-140 W/m·K) makes sure of good heat dissipation.

Here’s a detailed comparison of these grades:

Table 2: Molded graphite grade 1 and grade 2 properties

3. Vibration-Molded Graphite Grades (VG1-VG3)

The VG series represents vibration-molded graphite grades which offers a balance between cost-effectiveness and performance.

With a flexural strength of ≥45 MPa, VG 1 shows the finest grain size (≤10 μm) and highest density (≥1.82 g/cm³) in this series. VG 2 and VG 3 have progressively larger grain sizes (≤15 μm and ≤20 μm) and lower densities (≥1.77 g/cm³ and ≥1.72 g/cm³, respectively).

These grades are particularly suitable for applications requiring moderate electrical resistivity (12-15 μΩ·m) and good thermal conductivity (110-130 W/m·K). You’ll find VG grades commonly used in high-temperature furnace components, EDM electrodes and continuous casting.

Below table shows a detailed comparison of these grades:

Table 3: Vibration-molded graphite grade 1 to grade 3 properties.

4. Extruded Graphite Grade (EG 1)

EG 1 represents extruded graphite grade, characterized by its anisotropic properties due to the extrusion process. This anisotropy makes EG 1 particularly suitable for applications where directional properties are the major concern. For example, its widely used in large electrodes for electric arc furnaces or in certain thermal management systems where heat flow direction is very important.

Here’s a detailed table of its properties:

Table 4: Extruded graphite grade 1 properties.

Types of Extruded Graphite

Extruded graphite comes in many forms. Let’s examine the important types:

· Medium Extruded Graphite Block

This type offers a moderate density range from 1.65-1.85 g/cm³. It provides a balanced combination of electrical and thermal properties. It’s electrical resistivity is 8-12 μΩ·m and thermal conductivity is around 120-140 W/m·K.

You’ll find medium extruded graphite blocks commonly used in large electrodes and furnace linings, where their thermal stability (up to 3000°C in non-oxidizing atmospheres) is important.

· High-Density Extruded Graphite Rod

With densities usually exceeding 1.85 g/cm³, these rods provide improved conductivity and strength. Their thermal conductivity may exceed 150 W/m·K, while compressive strength can reach 100 MPa.

High-density extruded graphite rods are perfect for EDM electrodes and semiconductor manufacturing. Their fine grain structure (typically 5-10 μm) offers excellent surface finish and machinability which is important in precision applications.

· Extruded Graphite Tube

Extruded graphite tubes provide excellent uniform heat distribution and thermal shock resistance.

These tubes are perfect for chemical processing equipment and heat exchangers. They come in 5-50 mm wall thicknesses and 2 meters length. You’ll find their thermal conductivity around 100-120 W/m·K in inert atmospheres up to 2500°C. This makes them efficient in high-temperature applications.

· Extruded Fine Grain Graphite Rod

These rods feature a grain size below 20 μm. It results in increased superior surface finish and machinability.

The extruded fine grain graphite rods are perfect for precision components in optics and electronics sectors. Their fine grain structure offers electrical resistivity as low as 9 μΩ·m and 70 MPa flexural strengths. This makes them suitable for applications that require tight tolerances. For example, semiconductor manufacturing equipment mostly uses fine grain graphite rods.

· Flexible Extruded Graphite Sealing Ring

Flexible extruded graphite sealing rings are priceless in high-temperature sealing applications. These rings provide excellent sealing performance by offering a compressibility of 35-45% and a recovery rate of 15-20%. Their low friction coefficient (0.05-0.1) decreases wear and increases service life.

You’ll find these rings particularly useful in applications where temperatures can reach up to 3000°C in non-oxidizing conditions and 450°C in oxidizing environments.

· Extruded Graphite Plate

Extruded graphite plates combine uniform thickness with electrical and exceptional thermal properties.

Commonly available in thicknesses ranging from 0.5mm to 50mm, these plates offer 8-12 μΩ·m electrical resistivity and 120-140 W/m·K thermal conductivity. Their high purity (ash content <0.1%) makes them perfect for heat spreaders and fuel cells. You can expect excellent dimensional stability with a coefficient of thermal expansion as low as 1.5 × 10^-6/°C while using these plates.

· Crude Quality Extruded Graphite Rod

Crude quality extruded graphite rods provide a cost-effective solution. These rods are best for sacrificial anodes and metallurgical processes. They offer 1.55-1.65 g/cm³ density and lower purity (1500-2000 ppm ash content). You’ll find their thermal conductivity to be around 90-110 W/m·K and electrical resistivity around 18-22 μΩ·m.

While not perfect for high-precision work, they excel in applications where cost-efficiency is paramount. For example in aluminum smelting electrodes or steel production.

Common Extruded Graphite Uses

Extruded graphite finds applications across many industries due to its distinctive properties. Let’s explore important areas where you’ll commonly come across this versatile material:

· Industrial Applications

In industrial settings, extruded graphite excels in thermal management.

You’ll find it in heat sinks designed to dissipate excess heat from electronic components, with thermal conductivity ranging between 100-140 W/m·K.

Extruded graphite electrodes (typically 1.7-1.9 g/cm³ density) are commonly used in electric arc steel production. These electrodes can carry currents exceeding 100,000 amperes and can resist temperatures up to 3000°C. This makes them indispensable in modern steelmaking processes.

· Metallurgy and Foundry

Extruded graphite is a go-to material in metallurgy and foundry applications. Its low coefficient of thermal expansion (2-3 × 10^-6/°C) makes sure its dimensional stability. Due to this, you will see it used in molds for continuous casting of non-ferrous metals.

Crucibles made from extruded graphite provide excellent thermal shock resistance. Their 10-50 mm wall thicknesses make them suitable for metal melting. The EG’s high purity (ash content <0.1%) prevents contamination which makes it perfect for processing reactive metals like zirconium and titanium.

· Chemical Processing

The exceptional chemical resistance of extruded graphite makes it invaluable in the chemical processing industry.

You’ll find it used in heat exchangers where its thermal conductivity (120-140 W/m·K) makes sure of efficient heat transfer. In reactors, its ability to resist corrosive environments extends equipment lifespan. For example, in the production of phosphoric acid, extruded graphite components can operate at temperatures reaching 180°C and concentrations up to 85%.

· Energy Storage

In the rapidly growing energy storage sector, extruded graphite plays a very important role. For lithium-ion batteries, you can use extruded graphite anodes with specific capacities of 350-370 mAh/g. Its low expansion coefficient (2.3 × 10^-6/°C) makes sure of structural stability during charge-discharge cycles.

In fuel cells, extruded graphite bipolar plates with electrical conductivity exceeding 100 S/cm resist the harsh operating conditions while providing efficient current collection.

· Glass and Ceramic Industry

In the glass and ceramic industry, you’ll find extruded graphite playing an important role in high-temperature processing equipment.

Its extraordinary thermal stability (up to 3000°C in inert atmospheres) makes it perfect for molds and forming tools. For example, in glass production, extruded graphite molds with thermal conductivity of 120-140 W/m·K make sure uniform heat distribution which results in high-quality finished products.

You can also use extruded graphite components in ceramic sintering processes where their low coefficient of thermal expansion decreases warping and distortion.

Key Factors to Consider When Buying Extruded Graphite

When considering extruded graphite purchases, it is very important to check the grain quality and grade carefully. Here are some important factors to keep in mind:

A. Grain Quality and Grade

Grain quality and grade are important factors in selecting extruded graphite. They directly affect its performance and worthiness for specific uses. The size of grain usually ranges between fine (< 20 μm) to coarse (> 100 μm). Finer grains are better for surface finish and machinability. Coarser grains have higher thermal conductivity and strength.

When selecting grain quality and grade, think about what your application needs for mechanical strength, thermal conductivity and electrical resistance. For high-accuracy parts, choose fine-grained grades. Coarser grades usually suit high-temperature applications.

To check grain quality, ask for certificates of analysis and consider particle size distribution tests or microscopic tests for sensitive applications.

B. Supplier Credibility and Dependability

Picking a credible extruded graphite supplier is important for making sure of reliable supply and steady quality: While selecting a supplier you should:

• Verify their compliance with industry standards (e.g. ASTM D7219 for extruded graphite electrodes).
• Opt for ISO 9001 certified manufacturers.
• Consider their quality control actions and technical assistance.
• Assess the supplier’s performance history in your sector.

Always remember that a dependable supplier can help optimize your graphite parts as per your requirements. They also give you valuable insights on grade selection.

C. Customization Choices

When selecting extruded graphite, think about availability of customization choices. You may require specific shapes, sizes or surface treatments to meet your application needs. Seek suppliers that offers:

• Machining services:Precision cutting and shaping to tight tolerances of ±0.05mm.
• Made to order dimensions:Ability to produce non-standard sizes (e.g. blocks up to 1000mm x 1000mm x 3000mm).
• Special treatments:Options like pitch impregnation for increased density (up to 1.9 g/cm3) or silicon carbide (SiC) coating for better wear resistance.

D. Cost and Budget Factors

While focusing on quality, it is very important to balance your budget with performance requirements. Think about these things while buying extruded graphite:

• Volume discounts:Bulk orders often reduce per-unit costs by 10-15%.
• Material grade selection:Higher grades (e.g. IG-110 vs. IG-430) can cost 20-30% more but have better properties.
• Energy efficiency:Better thermal conductivity can lead to 5-10% energy savings in high-temp uses.
• Lifetime expenses:Account for longevity and maintenance; higher-grade graphite may last 30-50% longer.

Conclusion

Choosing the right extruded graphite is important for best performance in many industrial uses. By knowing the different properties, suppliers and grades, you can make a better decision according to your needs. Remember to check properties like strength, thermal conductivity and purity when selecting your graphite.

Ready to find the perfect extruded graphite for your custom needs? Contact us today for expert help and high-quality products tailored to your requirements.