What are the heating methods for forging surfaces?

Forgings of medium frequency double frequency induction heating, with a circular inducer set on the body, bottom-up continuous heating while water quenching. Such as cold roller, piston, cement mill wheel and so on. Especially long forgings, due to their limited length, can not be vertically lifted on the quenching machine, but can only be laid horizontally, with special sensors and transformers, crawling on the shaft or sliding along the guide rail.
Forgings shall be its bearing on the special rotary table, forgings by the great trust on the wheel rotation, and inside and outside the circle itself free expansion, the position of the sensor fixed and can be away from the heated surface gap between scale, this kind of sensor before and after expansion is mainly in the circle of local heating of shrinkage and changed the sensor and the surface of the heating clearance, clearance of change can affect heating speed and heating temperature.
In order to maintain the stability of the gap between the inductor and the heating surface, when the ring is heated and expanded, the inductor moves synchronously. Therefore, when the inner and outer surfaces of the large ring are heated, the inductor and the ring surface are always positioned by a certain positioner and the inductor can move forward or backward with the expansion of the ring heating surface.
Forgings of medium frequency hardening, as a result of tread two side convex platform, its height more than sensors and tread the gap distance, the sensor coil cannot be set into the tread, forging can be used to open like this separation, sensors, buckle on heating surface after sensors, separation after heated to a temperature sensor out walk round out open again after quenching or directly spray quenching inductor go round.
The heating method of forgings flame surface quenching is roughly similar to the induction surface heating, which is also divided into fixed method and continuous moving heating method. In the fixed method, the flame nozzle can be used to spray flame on a local surface of the forgings, and the nozzle can be removed after reaching the quenching temperature and cooled by water spraying (or cooled by compressed air). In the fixed method, the flame nozzle can also be fixed in a position (or several nozzles around the forgings) and the forgings rotate, heated to the quenching temperature with a spray nozzle cooling water.
Continuous moving heating method is to move the nozzle with cooling water nozzle on the forging heating surface, heating while cooling quenching.
Watch flames can see that it is divided into three areas: near the nozzle darker part as the flame core, is composed of oxygen and its decomposition gas, the temperature is low, its outer reduction zone for white, this is the highest flame temperature zone (up to 3100 ℃), it can quickly make the metal heating, melting, even the most outer layer for complete combustion zone, the temperature was lower than those of reduction zone.

The heat of the inner layer is conducted by the surface when the flame is heated. In order to make the forging rapidly heated to the quenching temperature in a certain depth, it is necessary to maintain the high temperature of the surface, which often makes the surface temperature too high, the grain is coarse, and even the phenomenon of burning。