Key Differences  

1. Frequency Range & Heating Depth  

- MF Induction:  

- Frequency: 1–10 kHz  

- Heating Depth：  Deep penetration (2–10 mm).  

- Effect: Uniform through-thickness heating, ideal for thick-walled pipes (≥10 mm).  

- HF Induction:  

- Frequency: 10–50 kHz  

- Heating Depth:   Shallow penetration (0.5–2 mm).  

- Effect :  Rapid surface heating, suited for thin-walled pipes (≤10 mm).  

2. Temperature Control & Uniformity  

- MF:  

- Lower thermal gradient ( ΔT ≈ 30–50°C   between inner/outer walls).  

- Reduces risk of cracks/oxidation in critical alloys (e.g., stainless steel).  

- HF:  

- High thermal gradient (ΔT ≈ 100–200°C).  

- Risk of overheating/burning thin walls.  

3. Efficiency & Quality  

- MF:  

- Slower bend rate (0.5–1.5°/s) but superior dimensional accuracy (meets ASME B16.49 ovality ≤3%).  

- Minimal spring back, better surface finish.  

- HF:  

- Faster bend rate (1.5–3°/s), but higher risk of deformation/ovality.  

- Cost-effective for simple bends.  

4. Industry Preference  

- MF Dominates: 90%+ of heavy industrial bending (power plants, pipelines) due to reliability and compliance with strict standards (ASME/API).  

- HF Niche: Repairs, thin-wall tubing, or budget-limited scenarios.  

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How to Choose between MF and HF  

- Use MF If:  

- Pipe wall thickness >10 mm or diameter >DN 200.  

- Material is  stainless steel, duplex, or high-alloy.  

- Precision bending (e.g., nuclear/offshore applications) is required.  

- Use HF If:  

- Thin walls (<10 mm), small pipes (<DN 200).  

- Rapid, low-cost bending for non-critical systems.  

> Modern Trend: Advanced MF systems (with IGBT inverters, 1–20 kHz adaptive frequency) now dominate  both thick and thin-wall bending, replacing HF in most industrial applications.