Flame Hardening vs. Induction Hardening
January 23, 2025
When it comes to strengthening metals, two effective methods are flame hardening and induction hardening. Both processes involve heating the metal to a specific temperature followed by quenching, but they differ in key aspects. Understanding these differences will help you determine which method is best suited for your project.
Induction hardening shares similarities with flame hardening, as both processes heat metal to its austenitization point before rapidly quenching it to induce hardening. However, the two methods differ significantly in execution.
Unlike flame hardening, induction hardening utilizes electromagnetic induction instead of an open flame. This method employs a coil to generate alternating magnetic fields, creating electric currents that heat the surface of the component. This approach ensures precise and controlled heating, making it highly effective for specific applications.
Induction hardening technology is used in the manufacture of automotive parts, such as crankshafts, camshafts, flywheel gear rings, axle shafts, brakes, clutches, etc. After induction treatment, the wear resistance and fatigue strength of these parts are significantly improved. While flame hardening can be used with a case depth of .127mm to 6.35mm, induction hardening can be used with a case depth of up to 10mm.
- Heating steel parts with induction is fast, taking seconds instead of minutes, thanks to the adjustable current intensity.
- Ensures even heat distribution across the steel parts surface within the range of the copper coil.
- Once the induction setup is fabricated, it can be used repeatedly for items of the same shape, making it ideal for batch hardening.
- Higher setup costs compared to flame hardening, as each item requires a custom-made copper coil designed to surround the surface to be hardened.
- Limited to relatively simple shapes, as the induction coil must match the contours of the steel surface.
Flame hardening involves heating a metal surface with a high-temperature flame and then quenching it. This process is well-suited for alloy steels, mild steels, cast iron, and medium-carbon steels, resulting in a hardened surface with improved resistance to corrosion and wear.
During the process, oxy-gas flames heat the metal to its austenitization temperature, altering the surface properties without affecting the core. The heated surface is then rapidly cooled (quenched) to create a hardened layer. Flame hardening can be applied to the entire surface or localized areas of a component.
Results depend on factors such as flame temperature, heating duration, and the quenching process's speed and intensity. The composition of the metal also influences the final hardness and durability.
Benefits of flame hardening include its cost-effectiveness and relatively short processing time. It produces a highly wear-resistant surface. However, drawbacks include increased brittleness, which can lead to cracking, and less precision compared to induction hardening.
- Suitable for hardening steel of various shapes, including irregular or small items.
- Allows selective hardening of specific areas while leaving other parts ductile.
- Achieves hardness on the surface or deeper within the steel.
- Cost-effective for small batches compared to setting up induction hardening equipment.
- Can scale to harden large items effectively.
- Slower process compared to induction hardening.
- Challenging to achieve hardness depth less than 1.5mm.
- Requires skilled workers to accurately control heat and depth.
- Risk of overheating, which can result in brittle steel or other defects.
- Less cost-competitive than induction hardening for large-scale operations.
- Open flame use may not be permissible in certain work environments.
Flame Hardening | Induction Hardening |
Steel is heated using oxy-acetylene flame, or other high intensity flame | Steel is heated using a/c current passed through an induction coil |
Temperature is gauged and controlled by the operator | Temperature is easily regulated by digitally controlling voltage |
Heating is gradual, may require holding period | Heating happens quickly |
Most effective for individual items or small batches | Work is easily automated and replicated at scale |
Not effective for hardening depth less than 1/16” | Can be used to create ultra-shallow hardened layer, <1/16” |
Low equipment and maintenance cost | High equipment and maintenance cost |
Appropriate for targeted application, flat or very large surfaces | More difficult to use on isolated surfaces, or in very large applications |
Can be used on items with irregular shape | Best used on items with basic shape |
Requires skilled labor | Can be done by unskilled labor |
Cost effective when small quantity required | Cost effective at scale |
Overheating can result in damage due to warping, scaling, and decarburization | Easy to avoid damage due to finely attuned heat |
Common Applications: Large engineered sprockets Drum sprockets Wear plates | Common Applications: Roller chain sprockets Cable sheaves and pulleys Gears |
Control variables: Gas flow Distance between flame and surface Time under heat | Control variables: Frequency of a/c current Resistance of metal composition Time under heat Shape and quantity of copper induction coil |
Hot Products
Contact Us
Enquiry hotline:
+86 135 4128 7190
Email:
Address:
No.18,14th Floor, Building 2, No. 169 Zhongli Road, Banzhuyuan Subdistrict, Xindu District, Chengdu, Sichuan, China, Code:610000
