Anti-Oxidation Cr30Ni70 Nichrome Heating Wire (1.5mm) for 1250C Controlled Atmosphere Furnaces
High-grade Cr30Ni70 (Nickel-Chromium 70/30) electric resistance wire engineered for severe thermal environments up to 1250C (2282F). Featuring an optimized 30% Chromium matrix, this 1.5mm bright-annealed wire delivers exceptional resistance to green rot and carburizing atmospheres in controlled-gas industrial furnaces, sintering kilns, and heat-treatment lines.
Product Overview
Product Overview: Cr30Ni70 Resistance Heating Wire for Extreme Atmospheres
Cr30Ni70 (equivalent to NiCr 70/30 and Nikrothal 70) is a specialized nickel-chromium electric resistance alloy developed specifically to overcome the limitations of standard 80/20 NiCr alloys in carbon-bearing and low-oxygen operating conditions.
With an elevated 30% Chromium content, this 1.5mm precision-drawn heating wire forms a dense, self-healing chromia (Cr2O3) surface layer. It provides unmatched protection against carburization and preferential chromium oxidation (green rot) in cracked ammonia, endothermic, and nitrogen-protective atmospheres at operating temperatures up to 1250C (2282F).
Technical Specifications
| Property / Parameter | Metric Value | Imperial / Standard Value | Remarks / Tolerance |
|---|---|---|---|
| Alloy Grade | Cr30Ni70 (70% Ni, 30% Cr) | NiCr 70/30 / Nikrothal 70 Eq. | High Cr Anti-Oxidation Matrix |
| Wire Diameter | 1.5 mm | Approx. 0.059 in (14.5 AWG) | ±0.02 mm tolerance |
| Max. Continuous Operating Temp | 1250°C | 2282°F | In Controlled / Reducing Atmospheres |
| Electrical Resistivity (20°C) | 1.18 ± 0.05 μΩ·m | 710 Ω·cmf | High Ohmic Stability |
| Density | 8.10 g/cm³ | 0.293 lb/in³ | Theoretical Density |
| Melting Point | 1380°C | 2516°F | Solidus / Liquidus Zone |
| Tensile Strength (Annealed) | 650 – 850 MPa | 94 – 123 ksi | Soft Condition (M state) |
| Elongation | ≥ 25% | ≥ 25% | High Ductility for Tight Coiling |
| Delivery Condition | Bright Annealed | Soft Temper (M State) | Clean Surface, Anti-Oxidized |
| Packaging | Precision DIN Spool / Coil | DIN 200 / DIN 250 (5–15 kg/spool) | Vacuum / Moisture-Proof Pack |
Key Engineering Features
Key Engineering Features of Cr30Ni70 Anti-Oxidation Heating Wire
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Superior Resistance to Green Rot and Carburizing Atmospheres Standard Ni-Cr alloys suffer from internal chromium oxidation in low-oxygen, carbon-rich environments. The Cr30Ni70 30% Chromium formulation prevents carbide precipitation and structural embrittlement, ensuring a service life up to 3 times longer in endothermic and carbonaceous gases.
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High Thermal Stability at 1250C Operating Temperatures Maintains high mechanical strength, creep resistance, and dimensional stability during prolonged high-temperature cycles, preventing element sagging and coil deformation inside industrial furnaces.
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Stable Electrical Resistance and Low Temperature Coefficient The uniform grain structure delivers consistent batch-to-batch ohmic values (1.18 micro-ohm-meter), eliminating localized hot-spots and enabling precise closed-loop PID furnace temperature control.
Excellent Ductility for Element Coiling and Bending Supplied in a precision bright-annealed soft temper with elongation greater than or equal to 25%, allowing tight-radii coiling into spiral elements, wave shapes, or rod-supported heating cages without micro-cracking.
Industrial Applications
Industrial Applications: Where Cr30Ni70 Controlled Atmosphere Wire Excels
- Controlled Atmosphere Heat-Treating Furnaces: Heating elements for carburizing, carbonitriding, bright annealing, and neutral gas hardening lines.
- Powder Metallurgy and Sintering Kilns: High-temperature resistance zones operating with cracked ammonia (NH3) or hydrogen-nitrogen shielding atmospheres.
- Industrial Kilns and Ceramic Tube Heaters: Heavy-duty coiled heating elements for continuous high-load industrial heating equipment.
- Laboratory and Vacuum Heat Treatment Systems: Protective muffle furnaces, sealed retort heaters, and diffusion furnace heating coils.
FAQ
Frequently Asked Questions (FAQ) for Cr30Ni70 Heating Wire
- Question 1: Why choose Cr30Ni70 over standard Cr20Ni80 for controlled atmosphere furnaces?
Answer: While Cr20Ni80 is the standard alloy for air and oxidizing atmospheres, it is susceptible to "green rot" (internal oxidation) in low-oxygen or reducing carbon atmospheres between 800C and 1050C. Cr30Ni70 contains 30% Chromium, which provides superior resistance to carburization and reducing gases, ensuring stable element life in endothermic and cracked-ammonia atmospheres up to 1250C.
- Question 2: What tolerances and packaging are available for 1.5mm Cr30Ni70 wire?
Answer: Our 1.5mm Cr30Ni70 wire is manufactured with a strict diameter tolerance of +/-0.02mm. It is delivered in bright-annealed condition wound on standard DIN spools (DIN 200, DIN 250, 5kg to 15kg per spool) or precision coils protected by moisture-proof, vacuum-sealed packaging.
- Question 3: Can Cr30Ni70 wire be welded or pre-oxidized before installation?
Answer: Yes. Cr30Ni70 has excellent weldability (TIG welding is recommended using matching NiCr filler material). For optimal longevity in reducing atmospheres, we recommend pre-oxidizing the finished heating elements in clean air at 1050C for 2 to 4 hours prior to gas introduction to establish a durable protective oxide coating.
- Question 4: What is the MOQ and lead time for custom spooling of Cr30Ni70 wire?
Answer: Standard MOQ is 5 kg per batch, with sample quantities (0.5 kg) available for validation testing. Standard spooling orders ship within 7 to 12 business days with complete EN 10204 3.1 Mill Test Certificates (chemical composition and mechanical test reports included).
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