The medium frequency dual frequency induction heating of aluminum alloy forgings is continuous heating from bottom to top by using a circular inductor and spraying quenching water at the same time. Cold roll, piston, cement grinding wheel, etc. Especially for long forgings, due to the limited length, the quenching machine cannot be used for vertical lifting. Special sensors and transformers can be used for shaft crawling or sliding along the guide rails, only for horizontal placement.
Aluminum alloy forgings shall be supported by rotary table. The forged product is supported by its own weight and rotates on the supporting wheel. The inner and outer circles can be freely retracted, and the fixed position of the sensor can be retracted from the gap with the ring heating surface. When local heating occurs, the gap between inductance and heating surface will change due to expansion and contraction. The change of the gap will affect the heating speed and temperature.
With the heating and expansion of the coil, the sensor moves synchronously to maintain the stability of the gap between the sensor and the heating surface. Therefore, when heating the inner and outer rings of the large coil, there will always be positioning inductors and rings for guidance, and the equipment will move forward or backward with the expansion and contraction of the circuit heating surface.
Large forging medium frequency quenching, the two sides of the tread bulge, the bulge height exceeds the gap distance between the sensor and the tread, and the sensor bead cannot be inserted into the tread. This kind of aluminum alloy forgings can adopt the split type separation sensor buckle sensor to separate the sensor from the running wheel, and then take it out for quenching or directly spray quenching. Open the sensor and remove the operating wheel.
Aluminum alloy forgings can adjust the structure, hardness and mechanical properties of the base metal through heat treatment, but after all, they are ultra-high carbon materials, which have a greater quenching tendency than forged steel rolls and are difficult to withstand excessive quenching. From the operating conditions, this type of roll does not depend on the hardening matrix, but mainly relies on a large amount of carbon dioxide to ensure high temperature wear resistance. The matrix of the roll must be pearlite structure after high temperature tempering, because it does not have good heat resistance cracking when hardened into martensite or bainite matrix.
The heat treatment of aluminum alloy forgings is carried out after rough machining. The actual heat treatment process usually includes tempering and spray quenching+tempering.
The normalized heating temperature is 850-930 ℃. If air cooling is required when static air cooling is used, it can also be sprayed to facilitate cooling. After normalizing, the sheet structure is formed by tempering at 500~650 ℃. Massive and strip pearlite+primary eutectic carbide+granular secondary carbide.
The positive tempering process is mainly used for forging semi steel rolls. The surface hardness of the roll body is 38-42, and the strength can reach 850 mpa. The process is easy to operate and install, with low quenching stress, and can meet the hardness requirements of ordinary rolls. The disadvantage is that you will see some network carbide, especially when the normalizing temperature is high. The network carbide produced at this time is thin and not completely continuous, but it will still damage the strength and plastic toughness of the roll, thus reducing the roll properties.