Induction hardening is a type of heat treatment in which metal parts are heated by electromagnetic induction and then quenched. It is also a type of case hardening and can be used for many steel and steel alloys to improve mechanical properties such as surface hardness and fatigue strength and resistance.Typical applications of induction hardening is the hardening of steel and cast iron. Especially parts, such as drive shafts, engine components and gears undergo the process.

IN­DUC­TION HARD­EN­ING PROCESS

Induction Hardening can be split into two steps. The first one is induction heating, in which electrically conducting metals are heated with an electromagnet. The quenching phase follows directly after to alter the surface structure of the material.

INDUCTION HEATING

Materials such as steel components are typically placed inside a water cooled copper coil where they are subject to an alternating magnetic field. They undergo electromagnetic induction by means of an electromagnet and an electronic oscillator. This oscillator sends alternating currents through the electromagnet, causing alternating magnetic fields that penetrate the material. The results are eddy currents (loops of electrical current) which heat the object within the coil above the transformation temperature. Induction hardening is a form of surface hardening in which the depth can be up to 8 mm. The deeper the currents penetrate, the higher the frequency of the alternating magnetic fields have to be.

Steels that have a ferromagnetic structure (which is inherited from the iron) can also be heated by magnetic hysteresis losses. Magnetic hysteresis losses produce heat by re-aligning magnetic domains, although it depends on the frequency of the currents, the penetration depth and the properties of the material (size, density, alloys) how much heat can be generated (Ph = (kh )(f)(Bmax)n).

INDUCTION QUENCH­ING

Directly after the induction heating process, the object has to be quenched, meaning that it has to be cooled down extremely quickly. To do that, the workpiece is typically placed in a tank of oil or water, although sometimes cold air is used. Quenching ensures that only the surface is hardened and that heat doesn’t spread into the core of the material, avoiding phase transformations from arising. Furthermore, the rapid cooling down creates a martensitic or ferritic-martensitic structure on the surface layer. These structure display higher tensile strength and low initial yielding stress than a purely ferritic structure. Quenching also reduced grain size, which is a key factor to increasing hardness of materials.

Quick Detail:

Technical Parameters

• The maximum diameter of quenching material: 300mm
• The maximum weight of the work piece: 50kg
• Work piece operating speed:1-30mm/s
• Work piece descent speed: 120mm/s
• Speed of main shaft:1-200r/min
• Motor power of main drive: 1.5kw
• Cooling method: immersion, hydrojet
• Machine Weight: 900kg
• Dimension: 1100*900*2000
• Transmission mode: mechanical rotation

Advantages of induction hardening:

• Ability to localize hardening to specific areas.
• Less distortion than alternatives such as carburizing.
• Heavy case depths achievable, 1-10mm common.
• Cheap/economical especially with parts of mass >10Kg.
• Fast process - quick turnaround.