Soft felt is the classic form of high-temperature furnace insulation: flexible roll material that can be cut, wrapped, and fitted to chamber geometry on site. It remains the most direct insulation route for many industrial furnaces.
AYD CarboniteX® soft felt starts from selected rayon-based long-fiber precursor felt, processed through impregnation, carbonization, graphitization, and deep purification on AYD’s own production line. Standard thicknesses are 5 mm and 10 mm, with widths from 1100 to 1400 mm. Two purity grades are available: graphitized and semiconductor grade, with semiconductor-grade ash below 20 ppm and GDMS verification. The same soft felt also serves as source material for long-fiber rigid felt (IRL) through solidified winding.
From continuous roll to fiber structure.
From fiber to finished roll. Six steps, fully internal.
Starting from selected rayon long-fiber precursor felt, processed through needle-punching, impregnation, carbonization, graphitization, and deep purification, all on AYD’s own production line. Key parameters are logged, and each roll is traceable to its specific batch.
Two purity grades, from industrial to semiconductor.
CarboniteX® soft felt is offered in two purity grades: Graphitized (ash ≤ 500 ppm, general industrial furnaces) and Semiconductor Purified (ash < 20 ppm, GDMS-verified). Both share the same processing chain, differing only at the final purification step.
SOFT FELTRayon-Based Long-Fiber Soft Felt · 12 properties × 2 grades Expand
| Property | Unit | GraphitizedAYD/SF-G | Semi GradeAYD/SF-P | Note |
|---|---|---|---|---|
| Processing Temp | °C | 2000–2200 | 2200 | Vacuum |
| Carbon Content | wt% | ≥ 99 | ≥ 99.99 | |
| Ash | ppm | ≤ 500 | ≤ 20 | |
| Bulk Density | g/cm³ | 0.08–0.13 | ||
| Thermal Cond. (700°C) | W/(m·K) | 0.04 | 0.02 | Vacuum |
| Thermal Cond. (900°C) | W/(m·K) | 0.061 | 0.039 | |
| Thermal Cond. (1300°C) | W/(m·K) | 0.133 | 0.198 | |
| Thermal Cond. (1500°C) | W/(m·K) | 0.173 | 0.226 | |
| Compressive Strength | MPa | 0.10–0.16 | ||
| Thickness | mm | 5 / 10 | Customizable | |
| Width | mm | 1100–1400 | Cut-to-size | |
| Roll Length | m | 5 mm: 40–50 / 10 mm: 20–30 | ||
Max service temperature up to 3000°C in vacuum. Higher thickness, narrower widths (for tight chamber wrapping), and ultra-low ash (< 0.1 wt%) are available on request. Semiconductor grade ships with a GDMS report and per-batch COA.
Trace impurities are measured by GDMS.
Semiconductor-grade soft felt ships with a third-party GDMS analysis report per batch, with focused control over B, Al, Fe, Mg, elements that can affect crystal growth yield.
Soft felt’s dual application.
Soft felt is both a standalone product and a process precursor for rigid felt. The two usage modes serve two distinct customer scenarios.
Hand-Wrapped Furnace Insulation
For industrial furnaces with flexible hot-zone dimensions (MIM sintering, vacuum heat treatment, brazing), soft felt is an efficient, direct insulation solution. Roll material is hand-cut, wrapped, and secured to the chamber geometry on site.
- Shipped as full roll. Cut to size on site
- Flexible structure conforms to complex chamber geometry
- Supplements rigid felt as outer radiation-shield layer
- Lower purchase cost and shorter installation cycle than rigid felt
Source Material for Long-Fiber Rigid Felt
Soft felt is binder-impregnated, tension-wound on a heated mandrel, and final-cured to form long-fiber rigid felt (IRL), one of the two AYD rigid felt process routes (Path B, Solidified Winding). This structure is often specified for large-format cylinders requiring high fracture toughness, such as 12-inch Si CZ hot zones.
- Long-fiber architecture retains high fracture toughness after winding
- Superior radiation shielding vs short-fiber systems
- Single-piece large-format cylinder winding
- Soft felt to rigid felt, closed internal loop
There is no “better.” Only “more suitable.”
The matrix below helps customers select between soft felt and rigid felt based on hot-zone dimensions, purity requirements, operating cycles, and maintenance frequency. AYD supplies both; our engineering team recommends configurations based on the specific application.
| Dimension | Soft Felt | Rigid Felt |
|---|---|---|
| Structure | Flexible roll, long-fiber non-woven | Structural component, machinable to precise geometry |
| Installation | Hand-wrapped, wound, cut to size | Modular structural assembly |
| Dimensional Stability | Possible thermal drift over long cycles | Geometrically stable across multiple campaigns |
| Erosion Resistance | May shed fibers under sustained gas flow | Dense surface, resists argon erosion |
| Service Life | Shorter; requires periodic replacement | Longer; spans multiple process cycles |
| Typical Applications | Industrial furnace wrapping, supplemental radiation shield | SiC PVT, 12-inch CZ, fiber drawing for precision hot zones |
| Selection Guidance | Industrial scenarios with flexible hot-zone dimensions where periodic maintenance is acceptable | Semiconductor-grade precision, long service life, low maintenance frequency, critical process consistency |
For many industrial furnace applications, a hybrid “rigid-inside, soft-outside” (or vice versa) configuration captures the strengths of both materials. AYD’s engineering team recommends configurations based on furnace type, energy targets, and maintenance strategy.
Downloads
From furnace wrapping to large-format rigid felt.
Share your furnace type, operating temperature, hot-zone dimensions, purity requirement, and procurement scale. Standard roll specifications: quote within 24 hours. Semiconductor grade or rigid felt customization: engineering response within 24 hours.
