Example of Silicon Carbide Advantage :

Schunk-Inex Silicon/Silicon Carbide Composite Radiant/Protective Tubes

     Mainly used in heat treating industry 
For more information, please contact C.T. Kang, Ph.D., email: 7si@7-stars-international.com 
Last revised: 12/21/96 
Click here for Chinese Version ¤¤ ¤å  BIG5
INEX Tubes

Advantages of Using Si/SiC Radiant / Protective Tubes (INEX)

Example 1: Much better creep, oxidation and carburization resistance than metallic tubes (Mainly due to the existence of SiC)

Creep Test at 1350oC (2462oF)

The INEX Si/SiC composite tube on the left was tested for 360 hours. The Alloy 600 tube on the right was tested less than one hour.

Creep test result

Example 2: Better thermal shock resistance than mullite tubes

Thermal shock test Severe Thermal Shock Test for INEX tubes
  • Test system: INBZ-1001 
  • Input: 150,000 BTU/hr 
  • Total Cycle: 5 
  • Average Heat Rate: 160oF/min 
  • Average Cool Rate: 256oF/min 
Mullite tubes failed in the first cycle of this test.

Composition of Schunk-Inex Composite Tubes

INEX tubes consist of silicon carbide (SiC) in a silicon (Si) matrix, and are made by a patented, simple fabrication process using low-cost abundant raw materials.

Key Physical Characteristics

  • Thermal Expansion: 4.2 x 10-6 in/in/°F
  • Strength vs. Temperature: 
Room Temp
8,520 PSI
1000°C (1832°F)
8,620 PSI
1250°C (2282°F)
10,097 PSI
1350°C (2462°F)
10,491 PSI

Long-Term Field Use

Both commercial and captive heat treat facilities around the world have used Si-SiC INEX composite tubes for over eight years.

Processes have included:
  • Annealing 
  • Carburizing 
  • Carbide Solution Treating 
  • Neutral Hardening 
  • Carbo-Nitriding 
  • Ferriticnitrocarburizing 
Furnace Atmospheres have included:
  • Endothermic (both lean and rich) 
  • Carbon Enriched Gasses 
  • Ammonia Enriched Gasses 
  • Nitrogen 
  • Mixed Endothermic/Ammonia (50/50) 

Standard INEX Tube Sizes

Wall thickness
Available Length
1" (25.4mm)
1/8" (3.2mm)
3/4" (~19mm)
36" (914.4mm)
2-3/8" (60.3mm)
1/8" (3.2mm)
2-1/8" (~53.9mm)
70" (1778mm)
2-3/4" (70mm)
1/8" (3.2mm)
2-1/2" (~63.6mm)
70" (1778mm)
3-1/4" (82.5mm)
1/8" (3.2mm)
3" (~76.1mm)
72" (1828.8 mm)
4-1/2" (114.3mm)
3/16" (4.8mm)
4-1/8" (~104.7mm)
96" (2438.4 mm)
5-1/8" (130.2mm)
3/16" (4.8mm)
4-3/4" (~120.6mm)
60" (1524 mm)

* Larger sizes are under development. Special customer requirements concerning size, length or wall thickness can be quoted. 

Configurations of Composite Radiant tube (CRT)

Plugged and flanged tubes

Plugged end, and end with a flange

If you have any questions, please contact C.T. Kang, Ph.D.

e-mail: 7si@7-stars-international.com
P.O. Box 512, Richland, WA 99352 USA
Tel: (509)946-2495, Fax: (509)943-9235


You can hyperlink to the following web pages and find more information about these products which are handled by Seven Stars International, LLC.

Advanced Refractory Technologies (ART) Diamond Coating Maching -- Diamond Zone 800 (Chinese Big 5), Chinese GB Code

Special Nozzles for Sandblasting, Spray Drying and Geo Jet

Odor Control Company, Inc.  (Chinese Big 5), Chinese GB Code

Electrical Conductive Sintered Alpha Silicon Carbide Components: Manufactured by Standard Ceramics, Inc.

Boron Carbide, B4C: Properties, applications and products of boron carbide

Boron Carbide Nozzles and Inserts: Advantages and product information of boron carbide nozzles and inserts. Both nozzles and insert are produced by Malyn Industrial Ceramics, Inc..

Boriding Agents: Properties, applications of two boriding agents

Schunk-Inex Si / SiC Composite Radiant Tube: High temperature Si/SiC composite radiant / protective tubes for heat treatment industry

Schunk-Inex Si / SiC Tube (Chinese Big 5), Chinese GB Code Information about INEX Si/SiC tubes written in Chinese.

MCrAlY Coatings: High temperature corrosion resistant coatings

Mechanical Seals and Seal Rings: Seal ring materials include: reaction bonded SiC, tungsten carbide, alumina and silicon nitride.

Boron Nitride, BN: Properties, applications and products of boron nitride powders

MoSi2 Heating Element

SiC: Properties, applications and products of silicon carbide

Zirconia Powders: Information of two available.ZrO2 powders

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