Cr20Ni80 Nichrome 80/20 - Resistance Heating Alloy Supplier of Wire, Strip & Bar | Shanghai Hangbo Alloy Group
Date: 2026年8月4日 Categories: News Views: 278
By Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier | ISO 9001:2015 | Est. 2012
Contact: sales@hangboalloy.com | hangbo@nickel-alloy.com | WhatsApp (Lisa): +86 13611656360
Quick Answer: What Is Cr20Ni80?
Cr20Ni80 (Nichrome 80/20 / GB/T 1234) is the most widely used nickel-chromium electrical resistance heating alloy, with approximately 20% chromium and 80% nickel, achieving a maximum continuous operating temperature of 1200C (2190F). It combines high electrical resistivity (~1.09 micro-ohm-m), excellent oxidation resistance (from the self-forming Cr₂O₃ scale), and good hot strength — making it the industry-standard material for industrial electric furnaces, household appliances (toasters, hair dryers), and high-temperature resistor elements. Shanghai Hangbo Alloy Group supplies Cr20Ni80 as fine wire, ribbon strip, and round bar.
Industry Pain Point: Electric furnace operators who use iron-chromium-aluminum (FeCrAl / Kanthal) heating elements for cost savings encounter a hidden lifecycle penalty: FeCrAl alloys lose hot strength above 1000C and sag under their own weight in horizontal furnaces, requiring more frequent element replacement and support ceramics. Cr20Ni80 retains significantly higher hot strength at 1100-1200C, maintaining element geometry and extending replacement intervals by 30-50% over FeCrAl elements in horizontal and vertical tube furnace configurations.
Key Properties at a Glance
| Property | Value |
|---|---|
| Grade | Cr20Ni80 / Nichrome 80/20 |
| Chemical Family | Ni-Cr Electrical Resistance Alloy |
| Density | 8.40 g/cm3 |
| Melting Point | ~1400C (~2550F) |
| Max Continuous Operating Temp. | 1200C (2190F) |
| Electrical Resistivity (20C) | 1.09 +/- 0.05 micro-ohm-m |
| Temperature Coefficient of Resistance | ~0.000085/C (very low) |
| Tensile Strength (Annealed) | >= 650 MPa |
| Elongation (Annealed) | >= 20% |
| Magnetic | Non-magnetic (paramagnetic) |
| Key Standards | GB/T 1234, ASTM B344, JIS C2520 |
Product Overview
Cr20Ni80 belongs to the "Nichrome" family of alloys, where the 80% nickel-20% chromium ratio represents the optimum balance between electrical resistivity, oxidation resistance, and cost. The alloy's performance as a heating element derives from three interconnected properties:
1. High, stable electrical resistivity (~1.09 micro-ohm-m): This value is approximately 55x higher than copper, meaning a Cr20Ni80 heating wire can generate the same heat output in a shorter length or with a larger cross-section -- simplifying element design and improving durability.
2. Low temperature coefficient of resistance: The resistivity changes by only ~0.0085% per degree Celsius. This means the resistance of the heating element remains nearly constant from cold-start to operating temperature, eliminating the current inrush surge that would trip circuit breakers or require overspecified power supplies.
3. Self-forming protective Cr₂O₃ scale: At operating temperature, the 20% chromium content forms a continuous, adherent chromium oxide layer on the element surface. This scale is:
- Protective: It prevents further oxidation of the underlying metal.
- Self-healing: If the scale is cracked by thermal cycling, chromium diffuses from the alloy matrix to re-form Cr₂O₃ at the crack site.
- Electrically insulating: The oxide prevents short-circuits between adjacent coil turns in tightly wound elements.
The "Nichrome Advantage" over FeCrAl (Kanthal):
- Higher hot strength at 1100-1200C → less sag.
- Non-magnetic → no additional inductive impedance in AC applications.
- Better ductility → can be drawn to finer wire diameters (down to 0.01 mm).
Shanghai Hangbo Alloy Group supplies Cr20Ni80 in bright-annealed wire (0.05-10 mm), cold-rolled strip/ribbon (0.1-3.0 mm thickness), and hot-rolled bar (6-50 mm). All products are certified for resistivity and surface quality per GB/T 1234.
Chemical Composition (wt.% per GB/T 1234)
| Element | Min | Max | Role |
|---|---|---|---|
| Nickel (Ni) | 75.0 | 79.0 | Matrix; provides hot strength and ductility |
| Chromium (Cr) | 20.0 | 23.0 | Forms protective Cr₂O₃ scale; controls resistivity |
| Iron (Fe) | -- | 1.0 | Kept low to maintain resistivity |
| Manganese (Mn) | -- | 0.6 | Deoxidizer |
| Silicon (Si) | 0.50 | 1.60 | Enhances oxidation resistance and scale adhesion |
| Carbon (C) | -- | 0.08 | Control for ductility |
| Aluminum (Al) | -- | 0.50 | Enhances scale adhesion |
| Sulfur (S) | -- | 0.015 | Minimized for hot workability |
Electrical & Physical Properties
Electrical Properties
| Property | Value |
|---|---|
| Resistivity (20C) | 1.09 +/- 0.05 micro-ohm-m |
| Temp. Coeff. of Resistance (20-500C) | ~8.5 x 10^-5 /C |
| Temperature Factor (Rt/R20 at 1200C) | ~1.06 |
Physical Properties
| Property | Value |
|---|---|
| Density | 8.40 g/cm3 |
| Melting Point | ~1400C |
| Max Continuous Temp. | 1200C |
| Thermal Conductivity (20C) | ~15 W/m-K |
| Thermal Expansion (20-1000C) | ~17.0 micro-m/m-C |
| Tensile (Annealed) | >= 650 MPa |
| Elongation (Annealed) | >= 20% |
| Magnetic | Non-magnetic |
Heat Treatment & Processing
Annealing: 900-1000C, rapid air cool or water quench. This recrystallizes cold-worked wire/strip to restore ductility for further drawing or winding into heating elements.
Stress Relief: 400-500C, 1-2 hours after coil winding to prevent spring-back and stabilize element geometry.
Pre-oxidation (Shutdown Procedure): After installing new Cr20Ni80 elements, heat to 1050C in air for 7-10 hours. This "burns in" the protective Cr₂O₃ scale before the furnace enters production service, dramatically extending element life.
Production Process
1. Fine Wire (0.05-3.0 mm)
- VIM Melting: Pure Ni cathode + LCFeCr, vacuum or inert atmosphere to prevent Cr oxidation loss. Ni +/-0.5%, Cr +/-0.3% control.
- Hot Rolling: Ingot to 5.5-8.0 mm rod.
- Multi-Pass Drawing: Progressive die drawing from rod to final diameter, with intermediate anneals (950C) after every 3-4 passes.
- Bright Annealing: Final anneal in hydrogen atmosphere for clean, oxide-free surface -- critical for uniform resistivity and coil winding.
2. Strip & Bar
- Cold Rolling (Strip): Hot-band cold-rolled with intermediate anneals to final gauge.
- Bar: Hot-rolled to diameter, surface conditioned.
Industry Applications
| Industry | Component | Why Cr20Ni80? |
|---|---|---|
| Industrial Furnaces | Box furnace elements, tube furnace windings | 1200C max temp; retains strength without sagging |
| Household Appliances | Toaster elements, hair dryer coils, oven bake elements | Stable resistance; no inrush current surge |
| Laboratory Equipment | Muffle furnace windings, tube furnace elements | Clean heating -- no contamination from element degradation |
| Resistors & Rheostats | Precision wire-wound resistors, load banks | Low temperature coefficient of resistance |
| Tobacco & Food Processing | Drying oven heating elements | Non-toxic; FDA-compliant for food contact air heating |
Quality Assurance (7-Stage)
- Melting Control: VIM, Ni +/-0.5%, Cr +/-0.3%, C <=0.05%. Resistivity verified on as-cast sample.
- Wire Drawing: Diameter +/-0.005 mm tolerance by laser micrometer. Surface inspected for drawing defects.
- Resistivity Test: 100% of lots tested per GB/T 6146 (four-point probe). Must be 1.04-1.14 micro-ohm-m.
- TCR Measurement: Temperature coefficient of resistance verified 7.5-9.5 x 10^-5/C.
- Life Test (Rapid Cycle): Per GB/T 13300 -- wire held at 1150C for 2 min, cooled to ambient in 2 min. Must survive >=50 cycles without breakage.
- Tensile & Elongation: Annealed wire must meet mechanical minima for the specified diameter.
- Packaging: Spooled on plastic or wooden reels, moisture-protected. Certificate per EN 10204 3.1.
Frequently Asked Questions
Q1: What is Cr20Ni80 used for?
Industrial electric furnace heating elements, household appliance heating coils (toasters, ovens, hair dryers), laboratory muffle furnace windings, precision wire-wound resistors, and load banks.
Q2: What is the maximum operating temperature?
1200C (2190F) for continuous service in air. Above this, the Cr₂O₃ scale begins to volatilize as CrO₃, progressively consuming the element cross-section.
Q3: What is the electrical resistivity?
1.09 +/- 0.05 micro-ohm-m at 20C. This is approximately 55x the resistivity of copper. A 1 mm diameter x 1 meter length Cr20Ni80 wire has a resistance of approximately 1.39 ohms.
Q4: Cr20Ni80 vs Kanthal (FeCrAl)?
Cr20Ni80 has higher hot strength at 1100-1200C (less sag), is non-magnetic, and is more ductile. FeCrAl has higher maximum temperature (1300-1400C for Kanthal A-1), higher resistivity (1.45 micro-ohm-m), and lower cost. Cr20Ni80 for horizontal/high-stress installations; FeCrAl for vertical elements with support.
Q5: Is Cr20Ni80 magnetic?
No, it is non-magnetic (paramagnetic). This eliminates inductive impedance issues in AC-powered heating circuits.
Q6: What is Nichrome?
"Nichrome" = Nickel + Chromium. It is the generic trade name for the Ni-Cr resistance heating alloy family, of which Cr20Ni80 is the most common grade.
Q7: Price per kg?
$35-60/kg EXW (80% Ni content is the primary cost driver). Contact sales@hangboalloy.com for LME-indexed quotation.
Q8: Can it be welded?
Yes, by spot welding, TIG welding, or brazing. For element-to-lead connections, fusion welding is preferred over mechanical crimping to prevent local hot spots.
Q9: What wire diameters are available?
0.05 mm to 10 mm. Finer wire (<=0.1 mm) is typically used for precision resistors; heavier wire (>=2 mm) for industrial furnace elements.
Q10: Why pre-oxidation matters?
Heating a new element at 1050C for 7-10 hours in air forms a mature Cr₂O₃ protective scale before the element enters production. This "burn-in" extends the element life by 20-50% by providing immediate oxidation protection during the first heating cycles.
Contact Shanghai Hangbo Alloy Group
| Channel | Details |
|---|---|
| Company | Shanghai Hangbo Alloy Group Co., Ltd. - China Supplier |
| Website | www.nickel-alloy.com |
| sales@hangboalloy.com | |
| WhatsApp (Lisa) | +86 13611656360 |
| Address | Room 1508, No. 288 Shiyi Road, Baoshan District, Shanghai 200940, China |
Complete Product Range
Pure Nickel: NI200, NI201, N4, N5, N6 | Monel: 400, 401, 404, K-500, R-405 | Inconel: 600, 601, 617, 625, 690, 718, X-750, 725 | Incoloy: 800, 800H, 800HT, 825, 925, 926, A-286, 25-6HN | Hastelloy: C-276, C-22, C-2000, C-4, G-30, G-35, X, B-2, B-3, N | Nimonic: 75, 80A, 90, 95, 105, 115, 263 | Haynes: 25, 188, 230, 242, 282, 556 | Super Austenitic: Alloy 28, Alloy 31, 254SMO | Precision: 1J22, 1J46, 1J50, 1J79, 1J85, 3J21, 4J32, 4J36, 4J45 | High-Strength: 18Ni250, 18Ni300, AerMet 100, PH13-8Mo | Heating: Cr20Ni80, Cr40Ni60
Product Forms: Bars | Tubes | Plates | Forgings | Welded Pipes | Fittings | Wire (0.05-10mm) | Strip (0.02-4.0mm)
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