How heating coils are manufactured?

Heating coils (used in furnaces, appliances, and industrial heaters) are typically made from high-resistance alloys like FeCrAl (Kanthal) or NiCr (Nichrome). We manufacture high quality heating coils according to customer needs. mad  Below is a detailed manufacturing process:

1. Material Selection:

– FeCrAl (Ferritic Chromium-Aluminum) – For high-temp applications (up to 1500°C). 

  – *Grades*: Kanthal A-1, AF, D, APMT, 0Cr25Al5, 0Cr23Al5, etc.

– NiCr (Nickel-Chromium) – For lower temps (<1200°C), better ductility. 

  – *Grades*: Nichrome 80/20 (80% Ni, 20% Cr), Nichrome 70/30, Nichrome 60/15, Nichrome 25/20, etc

2. Wire Production:

A. Melting & Casting

– Raw materials (Fe, Cr, Al, Ni) are melted in an Electric Arc Furnace (EAF) or Vacuum Induction Melting (VIM) for high-purity alloys. 

– Molten metal is cast into ingots or rods. 

B. Hot Rolling

– Ingots are heated and rolled into thick wires (5–10 mm diameter). 

C. Cold Drawing & Annealing

1. Cold Drawing:

   – Wire is pulled through progressively smaller dies to reach the desired diameter (e.g., 0.5–3 mm). 

   – Lubricants reduce friction. 

2. Intermediate Annealing (Softening):

   – After several drawing passes, the wire becomes brittle. 

   – It is heated (800–1000°C) in an inert atmosphere to restore ductility. 

3. Final Diameter Achieved:

   – Precision drawing ensures uniform thickness (±0.02 mm tolerance). 

3. Coil Formation:

A. Coiling Process

– The wire is wound around a mandrel (metal rod) to form a helix. 

– Coiling Machines (CNC or mechanical) control: 

  – Coil Diameter (matches mandrel size). 

  – Pitch (Spacing Between Loops) – Affects heat distribution. 

  – Tension – Too much tension can deform the wire. 

 B. Stress Relief Annealing

– After coiling, the wire is heated to 600–900°C to relieve internal stresses and prevent cracking. 

4. Surface Treatment

Pre-Oxidation (Stabilization)

– The coil is heated to 1000–1200°C in air to form a protective Al₂O₃ (for FeCrAl) or Cr₂O₃ (for NiCr) layer. 

– This prevents rapid oxidation during actual use. 

Optional Coatings

– Siliconizing – Improves corrosion resistance. 

– Ceramic Coating – For extreme environments (e.g., semiconductor furnaces). 

5. Quality Control & Testing

– Resistance Check (Ohm/meter) – Ensures uniform electrical properties. 

– Visual Inspection – No cracks, deformations, or inconsistent winding. 

– High-Temp Cycling Test – Verifies durability under repeated heating/cooling. 

6. Final Assembly & Installation

– Coils are mounted in: 

  – Ceramic Insulators (for high-temp furnaces). 

  – Mica or Fiberglass Supports (for household appliances). 

– Terminals are welded or crimped for electrical connections. 

 Comparison: FeCrAl vs. NiCr Coil Manufacturing: 

Applications of Manufactured Heating Coils: 

– Industrial: Furnaces, kilns, heat treatment systems. 

– Consumer: Toasters, hair dryers, electric stoves. 

– Automotive/Aerospace: Glow plugs, cabin heaters. 

 Conclusion: 

The manufacturing of heating coils involves: 

1. Wire production (melting, rolling, drawing).
2. Coil forming (winding, annealing).
3. Surface treatment (pre-oxidation).
4. Testing & assembly.

FeCrAl coils are preferred for high-temperature, long-life applications, while NiCr is used where better ductility and lower temps are needed.