The quenching sensor of induction hardening equipment is a key heating element that uses the eddy current principle to complete the surface quenching of parts and strengthen the surface. There are many types of parts for surface heating, and the shape is very different, so the design of the sensor is different. Generally, the size of the sensor mainly considers the diameter, height, cross-sectional shape, cooling water channel and water spray hole of the induction coil. The idea is as follows.
1. The diameter of the sensor
The shape of the inductor is determined according to the surface contour of the heated part, which requires a certain gap between the induction ring and the part, and it is uniform throughout.
When heating the outer circle, the inner diameter D of the sensor = D0 + 2a ; when heating the inner hole, the outer diameter D of the sensor = D0-2a . Where D0 is the outer diameter or inner hole diameter of the workpiece, and a is the gap between the two. Take 1.5 to 3.5mm for shaft parts , 1.5 to 4.5mm for gear parts , and 1 to 2mm for inner hole parts . If the medium frequency heating quenching is performed, the gap is slightly different, the general shaft parts are 2.5 ~ 3mm , and the inner hole is 2 ~ 3mm .
2. The height of the sensor
The height of the inductor is mainly determined by the power P0 setting of the heating equipment , the diameter D of the workpiece and the determined specific power P setting:
( 1 ) For short-axis parts heating at one time, in order to prevent overheating of sharp corners, the height of the induction ring should be less than the height of the parts.
( 2 ) When the long-axis parts are locally cooled by heating once, the height of the induction coil is 1.05 to 1.2 times the length of the quenching zone .
( 3 ) When the height of the single-turn induction coil is too high, the heating of the workpiece surface is uneven, the intermediate temperature is much higher than the temperature on both sides, and the higher the frequency, the more obvious it is. Therefore, double-turn or multi-turn induction coils are used instead.
3. The cross-sectional shape of the induction coil
There are many cross-sectional shapes of the induction ring, such as round, square, rectangular, plate type (outside welded cooling water pipe), etc. When the quenching area is the same, it is the most material-saving to bend into a rectangular cross-section induction ring, and the heat transmission layer is uniform and round The worst cross-section, but easy to bend. The materials selected are mostly brass tubes or copper tubes, the wall thickness of the high-frequency induction ring is 0.5mm , and the intermediate frequency induction ring is 1.5mm .
4. Cooling water circuit and water spray hole
Considering that heat is generated due to eddy current loss, each component needs to be cooled by water. For copper pipes, direct water cooling can be used. The copper plate manufacturing part can be made into a sandwich or an externally welded copper pipe to form a cooling water path; During spray cooling, the diameter of the water spray holes of the induction ring is mostly 0.8 to 1.0mm , and the intermediate frequency heating is 1 to 2mm ; the angle of the continuous heating and quenching of the water spray holes of the induction ring is 35 ° to 45 ° , and the hole distance is 3 to 5mm . At the same time, the heating and quenching water spray holes should be staggered, and the hole spacing should be evenly arranged. In general, the total area of the water spray holes should be smaller than the area of the water inlet pipe to ensure that the pressure of the water spray and the water inlet pressure meet the requirements.
It should be noted that in order to solve the circular effect of the heating of the inner hole, a ferrite (high frequency quenching) or silicon steel (intermediate frequency quenching) piece can be stuck on the induction ring to make a gate-shaped magnet, driving the current along the gap of the magnet ( The outer layer of the induction loop) flows through. In order to prevent the part that should not be hardened from being heated, the magnetic short-circuit ring shield can be made of steel ring or soft magnetic material. In addition, during induction heating, the gap between the induction ring and the sharp corner should be appropriately increased to prevent local overheating.