Design And Commissioning Of The Induction Hardening Tooling For Automobile Wheel Hubs (part 1)

  Before the induction heat treatment on the surface of automobile hub products, the design of the inductor is very important. The quality of the inductor directly affects the debugging and processing of the product, which has a great impact on the quenching quality of the product. The induction heat treatment of a certain product is analyzed and discussed from the design of the inductor to the completion of product commissioning.


  Metals can be heated in the inductor, mainly by electromagnetic induction. The essence of electromagnetic induction is: alternating magnetic field causes an alternating electric field, an alternating electric field causes an alternating magnetic field. When an alternating current passes through the conductor, the current density on the surface of the conductor is higher, while the current density inside the conductor is lower. This phenomenon is skin effect, also known as skin effect or surface effect. In addition, there are proximity effects and ring effects, which are very important for induction heat treatment. Induction heat treatment has short heating time, less oxide skin, small deformation, energy saving and environmental protection, easy to realize mechanization and automation, so it is widely used in automobile manufacturing, tractors, construction machinery, heavy machinery, bearing industry, railway and metallurgy industries, the future development trend is very good.

  Engineers of KETCHAN ELECTRONIC have been engaged in the inductive heat treatment of automobile wheel hubs for nearly 10 years. The following is the analysis of the inductive heat treatment process of the external flange and internal flange for peer reference and joint discussion.

Product drawing analysis

  The structure of the outer flange and the inner flange is shown in Figure 1 and Figure 2 respectively.

External flange structure

FIG. 1 External flange structure

External flange structure

FIG. 2 Inner flange structure

1. Key dimensions

Outer flange (inner hole): product wall thickness, inner diameter, height, groove spacing, base circle size, and overall structure, etc.

The groove spacing of the product is 30.64mm, the diameter of the base circle is 65.25mm, the diameter of the wall is 10mm, and the quenching area is 40mm. Inner flange (outer circle) : main channel axis diameter, axis height, base circle size, and overall structure, etc. The product is a solid shaft, with a main channel diameter of 33.8mm, shaft height of 71.1mm, base circle diameter of 60mm, quenching area length of 52mm.

2. Technical requirements

The technical requirements of heat treatment are shown in Figure 3 and Figure 4.

Outer flange

FIG. 3 Outer flange


FIG. 4 Nepharan

(1) Technical requirements for quenching and tempering of internal and external flanges

Quenching surface hardness 62 ~ 65HRC, tempering surface hardness 59 ~ 63HRC. The metallographic structure is martensite grade 4 ~ 6.

(2) Technical requirements for external flange detection

Point A and Point F Ds = 1.9-3.2mm; Point B and Point E Ds= 2.2-3.7mm; Ds≥2.4mm at point C and D.

(3) Internal flange detection technical requirements

Ds = 1.9-3.7mm at point A, B, E and H detected by pattern Angle direction;D point Ds = 2.2-3.7mm;G-spot Ds acuity 1.5 mm;C point Ds acuity 2.4 mm;F point Ds=2 ~ 6mm.

3. Draw the drawing of the product inductor

According to the above size data and relevant technical requirements of the product, calculate the total height and effective ring size of the sensor, draw the design drawing of the sensor, modify it according to the actual situation, and finally determine the shape of the sensor.

4. Determine the material and size of the inductor

The inductor is composed of an effective ring, a conductive plate, a contact plate, and accessories, and is made of various materials.

(1) Conductive contact plate, effective ring, and conductive plate.Made of T2 pure copper and brazed with the brass electrode.

(2) The outside diameter and wall thickness of the inlet and outlet water pipe are 12mm and 2mm round copper pipe; Square copper tube 14mm×14mm×2mm.

(3) Effective circle.External flange square copper pipe 8mm×10mm×1.5mm; Internal flange square copper pipe 12mm×15mm×2mm.

Induction coil and manufacture

1. Induction coil design pattern

The Induction coil design is shown in Figure 5.

Induction coil design pattern

Figure 5 Induction coil design pattern

(1) Design and draw a sensor pattern according to the product structure, and mark the names of each component.

(2) Contact plate. See Figure 6.

Contact plate

FIG. 6 Contact plate

The contact plate shall be guaranteed to be reliable, close, and firm in connection with the quenched transformer. The thickness of the contact plate should be > 1.57d (d is the depth of current penetration), but it should be < 12mm. The thickness of the plate here should be 10mm.

The plate width varies according to the power of the inductor. It is generally selected within the range of 60 ~ 190mm, and the upper limit is selected when the power is large. The width of the plate here is 60mm and the length of the plate is 70mm.

The diameter of the pressing bolt holes on the contact plate is 15mm, and there are 4 bolt holes in total. The bolts can be M12. It should be noted that the position of the four fixed holes must be measured well, otherwise, the connection with the transformer will not be in place.

In addition, the power on the inductor is distributed along the length of the conductor, so the conductive plate should be wide but not narrow.

(3) Design of an effective ring of the inductor. To ensure the quality of the inductor, some necessary molds must be prepared.

The effective coil is made by winding the mandrel mold (see Figure 7). After the copper tube is annealed, the mandrel shall be wound on the mandrel. The diameter of the mandrel shall be a little smaller than that of the inductor after winding the finished product.

Die for mandrel winding

FIG. 7 Die for mandrel winding

For example, the width of the effective ring copper pipe of the inductor is 10mm, the diameter of the shoulder of the product is 47.5mm, and the diameter of the mandrel can be 35mm. The inner flange product also selects mandrel winding, in which the induction coil at R Angle of the product is wound, the diameter of the mandrel can be selected to be 63mm, and this section of induction coil should be processed into a bevel at a certain Angle, so as to improve the quenching efficiency at R Angle. Other parts of the effective circle are according to the drawing size.

(4) Parameter determination. The inductor is divided into the outer quenching and the inner quenching, the height difference between the effective ring and the workpiece, and the clearance between the effective ring and the workpiece shall be determined according to the frequency of the field quenching equipment.

According to the above data reference, the product parameter selection: inner flange (inner hole quenching). Based on the shape of the hardening layer required by the technology, the overall height of the product is 64.6mm, the quenching area is 40mm, so the total height of the effective ring is set to 44mm, the gap between the effective ring and the workpiece is 2mm. (2) External flange (quenching). Based on the shape of the hardening layer required by the technology, the height above the flange plane of the product is 71mm, and the quenching area is 52mm in length. The height of the effective ring is set as 54mm, and the clearance between the effective ring and the workpiece is 3mm.

(5) Magnetic conductivity. The magnetic flux (see Figure 8) can improve the heating efficiency of the inductor and better heat the rounded corners of the product.

Magnetic conductivity

FIG. 8 Magnetic conductivity

Its size calculation: C = (0.2-0.75) a, generally C ≥3mm.Thus, the width of the outer flange is chosen to be 3mm and the width of the inner flange is chosen to be 4mm.

(6) Spray nozzle. The external flange sprayer is shown in Figure 9, while the internal flange sprayer is shown in Figure 10. The hole spacing is 3.5 ~ 4.0mm, and the aperture is 1.2 ~ 1.6mm. The aperture should be small but not large. In addition, the inner flange sprayer can also be installed quick-change connector.

External flange spout

FIG. 9 External flange spout

Inner flange sprayer

FIG. 10 Inner flange sprayer

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