Some parts in the workpiece in the turn and bend under the influence of alternating loads, shock loads, its surface layers under higher stress than heart. In the occasion of friction, surface layer also continued to be worn, so some parts of the surface layer made of high strength, high hardness, high abrasion resistance and high fatigue limit and other requirements, only strengthened to meet the above requirements. Surface quenching with low distortion, high productivity, are widely used in production.
According to the different heating methods, surface mainly induction heating surface hardening, flame hardening, surface hardening of electric contact heating.
• Induction heating quenching
Induction heating is the use of induced eddy currents in the workpiece the workpiece is heated. Induction surface hardening and quenching than ordinary heating has the following advantages:
1. heat the workpiece surface, quick heating, high efficiency
2. workpiece not the whole heating and small deformation
3. the workpiece heating time is short, less surface oxidation and decarburization
4. high hardness and notch sensitivity of small, fatigue strength and impact toughness and wear resistance are greatly improved. Play to potential material, material consumption, which improves your life
5. the device is compact, easy to use, good working conditions
6. ease of mechanization and automation
7. used in surface hardening can also be used in not only through heating and chemical heat treatment.
• The principle of induction heating
Piece placed on the sensor, when sensor is alternating current, and current on a sensor around the same frequency alternating magnetic field, in the workpiece to create EMF, induced current on the surface of the workpiece, Eddy. The Eddy current in the presence of the resistance of the workpiece, electrical energy turns into heat energy, the surface temperature is reached heating temperature, surface hardening can be achieved.
• Induction surface hardening properties
1. hardness: high, medium-frequency induction heating quenching workpieces, its high surface hardness than regular quenching 2~3 flats (HRC).
2. wear: wear resistance of high-frequency quenched workpiece after higher than normal quenching. This is mainly due to the hardening of Martensitic grains high carbide dispersion and high hardness, high compressive stresses on the surface of the combined results.
3. fatigue strength: fatigue strength of high and medium frequency quenching is greatly improved, the notch sensitivity decreased. Artifacts of the same material, hardened layer depth within a certain range, fatigue strength increases with the depth of hardening, but over the deep surface hardening depth is stress, thus decrease fatigue strength of hardened layer depth increased, and an increase in brittleness of the workpiece.