Design and commissioning of the induction hardening tooling for automobile wheel hubs (part 2)
2. Induction coil design model
FIG. 11 is the model designed for the inner hole quenching inductor, and FIG. 12 is the model designed for the outer circle quenching inductor. The gap of conductive copper pipe is 2mm, insulation board must be installed. A 2mm thick PTFE insulation board is used here.
FIG. 11 Inner hole quenching Induction coil model
FIG. 12 Model of the cylindrical quench Induction coil
3. Induction coil welding
(1) The common solder for inductor brazing is pure copper, brass, silver copper, and phosphorus copper. Generally, brass is used for welding, and the choice of flux is also very important.
(2) Before welding, the base material must be cleaned to remove the oxide film and oil stains on the surface of the base material, so as to improve the brazing quality.
(3) The lap joint method and the assembly gap will affect the welding quality of the inductor, so the design and splitter should be well budgeted. The partial process of the external flange inductor from the welding of simple parts to the completion of the overall brazing and the completion of the installation of the magnetic body is shown in Figure 13.
FIG. 13 Welding process of the external flange Induction coil
In the welding process must pay attention to:
(1) when welding two parts to be heated evenly, the required welding parts to be fixed, welding spot should be evenly spread out and piled up, uneven or welding spot is too thin will cause welding defects, may cause leakage inductor, etc..
(2) in the welding of the effective ring, to fix the contact plate on the bracket so that the welding of effective ring components can reach the required size and perpendicularity and centerline deviation requirements.
(3) Inner flange (outer circle) quenching inductor, bevel effective ring Angle must be well designed, otherwise, it will cause insufficient cooling and damage the inductor.
(4) The magnetic conducting body can be cemented with 504 adhesives. Finally, the conductive tube of the inductor needs to be wound and fixed with a glass fiber cloth.
4. Induction coil shaping
The formed Induction coil entity is shown in Figure 14 and Figure 15.
Figure 14 The formed Induction coil entity 01
Figure 15 The formed Induction coil entity 02
The forming Induction coil needs to conduct the quality inspection, which mainly includes the following points:
(1) Appearance and geometric dimension inspection
The perpendicularity of the end face of the contact plate and the effective ring, the matching size of the contact plate, etc.
(2) Weld quality
Whether leakage occurs when the test pressure reaches the required pressure.
Whether the design matches the flatness of the contact plate surface, the clearance between the effective ring and the workpiece, the inlet and outlet pipe of the inductor, etc.
Product commissioning and acceptance
(1) The quenching machine is selected for the installation of inductors and auxiliary devices, as shown in Figure 16.
Figure 16 Induction coil and auxiliary installation
(1) The installation of the tooling must pay attention to the proximity of the inductor and transformer, the bolts should be locked.
(2) Pay attention to the effective ring and the perpendicularity of the product when installing the inductor, the inductor cannot tilt, otherwise, it will affect the quenching quality of the product.
(3) the external flange needs to install the product pressure sleeve as a heat absorption device, this relative to some auxiliary external spray way more stable.
Check the circular run-out of the workpiece when it rotates on the fixture. Runout of general tooling circle ≤0.3mm.
(2) Quenching equipment power supply matching is 250kW/8 ~ 30kHz.
(3) Adjust the quenching equipment, determine the appropriate quenching process, to meet the product’s quenching technical requirements.
External flange products: power input ratio 98%, heating time 7.4s, cooling time 14s, quenching fluid concentration 1.5% ~ 2.5%.
Internal flange products: power input ratio 98%, heating time 7.7s, cooling time 20s, quenching fluid concentration 1.5% ~ 2.5%.
Shanghai Haofton water-soluble quench liquid was used and its concentration was measured by refractometer.
2. Adjustment of cooling device
(1) Ensure the cooling pressure, where the quenching liquid cooling pressure is 0.25 ~ 0.4mpa, and the sensor cooling pressure is 0.5 ~ 0.8mpa.
(2) Adjust the position of the cooling device so that the cooling water cannot be blocked or blocked.
(3) The cooling water has two parts, one is the quenching fluid, the other is the system cooling water. Heat exchangers are commonly used for temperature cooling.
Quenching liquid temperature is generally not more than 35℃, too high a temperature will cause insufficient cooling, thus the product quality problems. The cooling water temperature of the system is the soft water of the cooling appliances. This temperature is generally controlled at 30℃ and must not be lower than the room temperature, otherwise, it will make the surface of the cooling appliances condensation of water, easy to damage the appliances.
3. Product inspection method
The inspection of heat treatment products requires wire cutting and pre-grinding of metallographic samples.
4. Product tempering process
The tempering of the induction quenching workpiece includes self-tempering, induction tempering, and furnace tempering. The product is tempered in the furnace.
Tempering temperature depends on the technical requirements of the workpiece. When the general hardness is above 52HRC, the tempering temperature is 180 ~ 200℃, and the tempering time is 1.5h. For hardness requirements above 56HRC, the tempering temperature can be used 160℃, tempering time 1.5h.
The product tempering process was finally determined to be tempering temperature 165℃, tempering time 2.5h.
FIG. 17 and FIG. 18 show the product samples successfully debugged.
FIG. 17 Quenching sample for outer flange
FIG. 18 Quenching sample for inner flange
The hardness of the surface and the depth of the effective hardening layer meet the technical requirements of Vickers hardness tester. The product heat treatment, from the design of the tooling sensor to the product commissioning, has been successfully completed.
The structure, shape, and size of the Induction coil is the core problem of induction quenching technology, which has a direct impact on the quality, production efficiency, and energy consumption of parts. Therefore, an appropriate inductor is an important way to make induction quenching obtain high quality, high efficiency, and energy-saving.
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