EN
Cr30Ni70 NiCr Alloy Strip for Muffle Furnace High Temperature Heating Elements
Engineered for industrial thermal processing, DLX Cr30Ni70 NiCr alloy strip delivers superior high temperature oxidation resistance and prolonged service life in muffle furnaces, continuous annealing lines, and atmosphere-controlled heat treatment systems. Featuring a 70% nickel and 30% chromium metallurgical balance, this resistance heating ribbon forms a self-healing chromium oxide layer that withstands thermal cycling and corrosive atmospheres up to 1250C.
- Overview
- Specifications
- Features
- Applications
- Advantages
- FAQ
- Recommended Products
Cr30Ni70 (NiCr 70/30) precision resistance heating alloy strip engineered for high temperature muffle furnaces and industrial heat treatment equipment. Formulated with 30% chromium content for superior oxidation resistance up to 1250C, high electrical resistivity, and stable thermal expansion. Available in cold-rolled annealed condition with bright surface finish, custom thickness from 0.05 mm to 3.0 mm, slit widths from 2.0 mm to 250 mm, and low 5 kg minimum order quantity.
Product Overview
DLX Cr30Ni70 is a premium austenitic nickel-chromium electrical resistance heating alloy developed specifically for high-demand industrial furnace applications where standard Ni-Cr alloys face accelerated oxidation or atmospheric degradation. By optimizing the chromium concentration to 30%, this alloy forms an exceptionally stable, dense chromia (Cr2O3) protective scale on the element surface during high-temperature operation.
This protective mechanism delivers superior resistance against high-temperature oxidation, cyclic spalling, and preferential green rot attack in atmosphere-controlled muffle furnaces and sealed thermal chambers. With continuous operating capabilities up to 1250C, Cr30Ni70 ribbon elements maintain mechanical integrity and electrical stability over extended production campaigns, reducing heating element replacement downtime and lowering total lifecycle operating costs for furnace builders and thermal processing facilities.
Chemical Composition Reference
| Element | Content (%) |
|---|---|
| Nickel (Ni) | Balance (68.0 - 71.0) |
| Chromium (Cr) | 28.0 - 31.0 |
| Iron (Fe) | <= 1.0 |
| Silicon (Si) | 0.70 - 1.50 |
| Manganese (Mn) | <= 0.60 |
| Carbon (C) | <= 0.06 |
| Phosphorus (P) | <= 0.020 |
| Sulfur (S) | <= 0.015 |
Physical and Electrical Properties
| Property | Value | Unit |
|---|---|---|
| Maximum Continuous Operating Temperature | 1250 | °C |
| Electrical Resistivity at 20°C | 1.18 | μΩ·m |
| Density | 8.10 | g/cm³ |
| Melting Point | 1380 - 1400 | °C |
| Specific Heat Capacity (20°C) | 0.46 | kJ/(kg·K) |
| Thermal Conductivity (20°C) | 13.5 | W/(m·K) |
| Coefficient of Thermal Expansion (20-1000°C) | 16.5 × 10⁻⁶ | 1/K |
| Microstructure | Austenitic (Non-magnetic) | - |
Mechanical Properties in Soft Annealed Condition
| Parameter | Standard Range |
|---|---|
| Tensile Strength (Rm) | 650 - 850 MPa |
| Elongation at Break (A50) | >= 25 % |
| Hardness | 140 - 180 HV |
| Surface Finish | Bright Annealed / Pickled / Matte |
| Edge Condition | Slit Edge / Deburred / Round Edge |
Product Features: Enhanced Oxidation Resistance and Furnace Performance
Superior Chromia Layer Formation for Extended Element Life The elevated 30% chromium matrix creates an adherent, slow-growing chromium oxide barrier that resists spalling under rapid thermal cycling, significantly extending element longevity in high-temperature muffle chambers.
Exceptional Resistance to Green Rot and Carburizing Atmospheres In controlled-atmosphere furnaces where fluctuating oxygen partial pressures trigger internal oxidation (green rot), Cr30Ni70 demonstrates metallurgical stability superior to lower chromium alloys.
Consistent Electrical Resistivity and Uniform Heat Distribution Tight chemical control and advanced induction melting ensure uniform cross-sectional resistivity (1.18 microhm meter) across entire strip coils, eliminating local hot spots and premature element burnout.
Excellent Formability for Custom Heating Element Geometries Supplied in fully soft-annealed state with high ductility (>= 25% elongation), facilitating clean bending, corrugation, punching, and wave-forming into serpentine or spiral heating elements without edge cracking.
Dimensional Precision and Low Surface Defect Rate Cold rolled on high-precision multi-roll mills to achieve tight thickness tolerances (+/- 0.005 mm) and clean, oxide-free bright surfaces ready for automated element assembly.
Product Applications: Industrial Thermal Processing and Muffle Furnaces
Industrial Laboratory and High Temperature Muffle Furnaces Primary resistance heating elements for box furnaces, tube furnaces, and ceramic sintering kilns operating between 900C and 1200C.
Controlled Atmosphere Heat Treatment Equipment Heating ribbons and folded elements for bright annealing lines, carburizing chambers, brazing furnaces, and powder metallurgy sintering belts.
Electric Heating Elements for Semiconductor and Electronic Kilns High-purity thermal zones for diffusion furnaces, ceramic substrate firing, and thick-film hybrid circuit processing.
Heavy-Duty Industrial Resistance Banks and Load Resistors Dynamic braking resistors, crane load banks, and high-capacity electrical testing load frames requiring stable high-current resistance ribbon.
Chemical and Petrochemical Thermal Processing Flange heaters, circulation heaters, and reactor trace heating jackets exposed to corrosive industrial atmospheres.
Why Choose DLX Alloy: Manufacturing Scale, Quality, and Engineering Support
Integrated Production Facility and 1200 Tons Monthly Capacity DLX operates full-process production lines spanning vacuum induction melting (VIM), electroslag remelting (ESR), hot forging, precision cold rolling, continuous bright annealing, and high-speed slitting, maintaining a monthly output capacity of 1,200 metric tons.
Comprehensive Quality Inspection and Material Traceability Every production heat undergoes optical emission spectrometry (OES) chemical analysis, micro-ohmmeter electrical resistance verification, tensile testing, dimensional laser gauging, and surface flaw inspection with mill test certificates provided for each batch.
Flexible B2B Supply Terms for Global Procurement Low trial order threshold with 5 kg minimum order quantity (MOQ) . Standard strip sizes maintained in coil stock for rapid 7 to 15 day dispatch.
Tailored Customization and Secondary Processing Custom slitting to narrow widths down to 2.0 mm, precision edge conditioning, custom coil weights (spool or pancake coil packaging), and pre-shaped heating element fabrication based on client engineering drawings.
Product Frequently Asked Questions
Q: What is the main operational difference between Cr30Ni70 and Ni80Cr20 alloy strip in muffle furnaces?
A: Cr30Ni70 contains 30% chromium compared to 20% in Ni80Cr20. This higher chromium content provides superior resistance to oxidation and atmospheric attack, particularly in muffle furnaces operating near 1100C to 1200C with intermittent atmospheres or risks of green rot. Ni80Cr20 has slightly higher maximum temperature limits, but Cr30Ni70 offers longer element service life in oxidising-to-reducing transitional furnace environments.
Q: What thickness and width specifications are available for Cr30Ni70 strip?
A: DLX manufactures Cr30Ni70 strip in thicknesses ranging from 0.05 mm to 3.0 mm and widths from 2.0 mm to 250 mm. Custom slitting and spooling options can be adjusted to match automated stamping, winding, or manual element forming equipment.
Q: How is Cr30Ni70 strip packaged for international sea and air freight?
A: Strip coils are wrapped in moisture-proof plastic film, padded with shock-absorbing foam, and packed into export-grade reinforced wooden crates with internal desiccant bags. Coils can be supplied on plastic spools, cardboard cores, or as self-supporting pancake coils with eye-to-sky or eye-to-wall pallet configurations.
Q: What is the minimum order quantity (MOQ) and lead time for custom dimensions?
A: Standard inventory coils have a minimum order quantity of 5 kg. For custom melt heats or non-standard thicknesses, the typical MOQ is 20 kg to 50 kg with production lead times between 10 and 20 business days. Expedited sampling (0.5 kg) is available for verification.
Q: Does Cr30Ni70 require pre-oxidation treatment prior to furnace installation?
A: While Cr30Ni70 forms its natural protective oxide layer during initial heating, running a controlled pre-oxidation cycle in clean air at 1050C for 2 to 4 hours prior to full load operation helps establish a uniform, dense chromia layer, optimizing service life in harsh furnace atmospheres.
