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Automotive hub induction hardening tool design and processing debugging

Automotive hub induction hardening tool design and processing debugging

Inductor design is very important before the surface induction heat treatment of automotive wheel products. The quality of inductor production directly affects the debugging and processing of products and has a great influence on the quenching quality of products. The induction heat treatment of a certain product is analyzed and discussed from inductor design to product commissioning.

Overview

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

The author has been engaged in the induction heat treatment of automobile wheel hub for nearly 10 years. The induction heat treatment process of external flange and internal flange is analyzed and combed below for the reference of colleagues and common discussion.

Product drawing analysis

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

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FIG. 1 Outer flange structure

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FIG. 2 Internal flange structure

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 wall thickness of the caliber is 10mm, and the quenching area is 40mm long. Inner flange (outer circle): main channel shaft diameter, shaft height, base circle size and overall structure, etc. The product is solid shaft, main channel diameter 33.8mm, shaft height 71.1mm, base circle diameter 60mm, quenching area length 52mm.

Technical requirements

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

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FIG. 3 Outer flange

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FIG. 4 Neflin

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

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

(2) External flange testing technical requirements

Point A and f are tested in the direction of pattern AngleDs= 1.9 ~ 3.2 mm; B and eDs= 2.2 ~ 3.7 mm; C, d pointsDsAcuity 2.4 mm.

(3) Internal flange testing technical requirements

Test points A, B, E and H in the direction of pattern AngleDs= 1.9 ~ 3.7 mm; D pointDs= 2.2 ~ 3.7 mm; The g-spotDsAcuity 1.5 mm; Point cDsAcuity 2.4 mm; F pointDs= 2 ~ 6 mm.

Draw product sensor drawings

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

Determine the material and size of the sensor

Inductor consists of active ring, conductive plate, contact plate and accessories made of various materials.

  • (1) Conductive contact plate, effective ring, conductive plate. Made of T2 pure copper and brazed with brass electrode.
  • (2) The inlet and outlet water pipe adopts round copper pipe with outer diameter of 12mm and wall thickness of 2mm; Square copper pipe 14mm x 14mm x 2mm.
  • (3) Effective circle. Outer flange square copper pipe 8mm×10mm×1.5mm; Inner flange square copper pipe 12mm x 15mm x 2mm.

Sensor design and manufacture

Sensor design drawing

The sensor design is shown in Figure 5.

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FIG. 5 Sensor design pattern

(1) According to the product structure, design and measure the sensor pattern, and mark the name of each component.

(2) Contact plate. See Figure 6.

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FIG. 6 Contact plate

The contact plate shall be reliable, tight and firm in connection with the quenching transformer. The thickness of the contact plate should be > 1.57D (D is the current penetration depth), but it should be <12mm. The thickness of the contact plate should be 10mm.

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

The punching diameter of the compression bolts 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, otherwise it will lead to improper connection with the transformer.

In addition, the power on the inductor is distributed along the length of the conductor, so the conductive plate should be wide rather than narrow.

(3) Inductor effective circle design. In order to ensure the quality of sensor fabrication, some necessary molds must be prepared.

The effective ring is made by winding the mandrel mold (see Figure 7). After the copper tube is annealed, winding the mandrel should be smaller than the diameter of the inductor after winding the finished product.

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Figure 7 Winding mandrel mold

For external flanges, the width of the copper tube of the effective ring of the inductor is 10mm, the diameter of the product shoulder is 47.5mm, and the diameter of the mandrel can be 35mm. The inner flange products are also made by mandrel winding. The diameter of the induction ring at the R Angle of the product can be selected as 63mm, and this section of the induction ring should be processed into an inclined plane at a certain Angle to improve the quenching efficiency at the R Angle. Other parts of the effective ring according to the size of the drawing wound.

(4) Parameter determination. The inductor’s extra-round quenching and internal hole quenching, the height difference between the effective ring and the workpiece, and the gap between the effective ring and the workpiece should be determined according to the frequency of the on-site quenching equipment, as shown in Table 1 ~ Table 4.

Table 1 Height difference between effective ring and workpiece during inner hole heating

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Table 2 Clearance between effective ring and workpiece during heating of inner hole

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Table 3 Height difference between the effective circle and the workpiece when the outer circle is heated simultaneously

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Table 4 Clearance between effective ring and workpiece during outer circle heating

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According to the above data, the product parameters are selected as follows :① Inner flange (inner hole quenching). Based on the shape of the hardened layer required by the technical requirements, the overall height of the product is 64.6mm, and the length of the quenching area is 40mm, so the total height of the effective ring is set as 44mm, and the gap between the effective ring and the workpiece is 2mm. ② External flange (external round quenching). Based on the shape of hardened layer required by the technical requirements, the height of the product flange plate above the plane is 71mm, and the length of the quenched area is 52mm. The height of the effective ring is set at 54mm, and the clearance between the effective ring and the workpiece is 3mm.

(5) Magnetic conductors. The magnet (see Figure 8) can improve the sensor heating efficiency and heat the product rounded corners better.

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Figure 8. Magnetic conductor

Its size calculation: C =(0.2 ~ 0.75) A, generally C ≥3mm. Therefore, the width of the outer flange is 3mm magnetic guide, and the width of the inner flange is 4mm magnetic guide.

(6) Liquid injector. The outer flange injector is shown in Figure 9, and the inner flange injector is shown in Figure 10. The hole spacing is 3.5 ~ 4.0mm, the aperture is 1.2 ~ 1.6mm, the aperture should be small rather than large. In addition, the inner flange injector can also be fitted with a quick change connector.

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FIG. 9 External flange injector

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FIG. 10 Inner flange injector

Sensor design model

Figure 11 is the model designed for the inner hole quenching inductor, figure 12 is the model designed for the outer circle quenching inductor. The gap between conductive copper pipes is 2mm. Insulation boards must be installed. Teflon insulation of 2mm thickness is used here.

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FIG. 11 Model of internal hole quenching sensor

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FIG. 12 Model of external circular quenching inductor

Sensor welding

(1) Inductor brazing commonly used filler metals are pure copper, brass, silver copper and phosphorus copper. Generally, brass is used for welding. The choice of flux is also very important.

(2) Before welding, the base metal must be cleaned to remove the oxide film and oil stains on the surface of the base metal, so as to improve the brazing quality.

(3) The lap method and assembly gap will affect the welding quality of the sensor, so it is necessary to have a good budget in the design and separation link. Part of the process of external flange sensor from simple component welding to complete brazing and magnetic guide installation is shown in FIG. 13.

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FIG. 13 Welding process of external flange sensor

In the welding process, we must pay attention to: (1) when welding, the two parts should be heated evenly, the required welding parts should be fixed, the solder joints should be spread evenly and stacked, uneven or solder joints are too thin will cause welding defects, may lead to sensor water leakage, etc. (2) When welding the effective ring, the contact plate should be fixed on the bracket, so that the welded effective ring components can reach the required size, and reach the perpendicularity and center line deviation requirements.

(4) The inner flange (outer circle) quenching inductor, the Angle of the effective bevel ring must be well designed, otherwise it will cause insufficient cooling and damage the inductor.

(5) The magnet can be bonded with 504 adhesive, and the final inductor conductive tube needs to be wound and fixed with glass fiber cloth.

Sensor forming

The sensor entity formed is shown in FIG. 14 and 15.

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Figure 14

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Figure 15

Forming sensors need to carry out quality testing, mainly including the following points:

(1) Inspection of appearance and geometry

The verticality of the end face of the contact plate and the effective ring, the size of the contact plate, etc.

(2) Weld quality

Pressure test to meet the required pressure whether leakage.

(3) The other

Contact plate surface flatness, effective ring and workpiece clearance, inductor inlet and outlet water pipe design match.

Product commissioning and acceptance

Install

(1) Select quenching machine to install inductor and auxiliary device, as shown in FIG. 16.

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FIG. 16 Inductor and auxiliary installation

Installation precautions

  • ① When installing the tooling, be sure to pay attention to the close state of the connection between the sensor and the transformer, and the bolts should be locked.
  • ② Pay attention to the verticality of the effective ring and the product when installing the inductor. The inductor can not be tilted, otherwise it will affect the quenching quality of the product.
  • ③ The external flange needs to be installed with a product pressure sleeve as a heat absorption device, which is more stable than some auxiliary external spraying methods.
  • ④ Check the circular runout of the workpiece when it rotates on the fixture. General round runout ≤0.3mm.

(2) Power supply matching of quenching equipment is 250kW/8 ~ 30kHz.

(3) Adjust the quenching equipment, determine the appropriate quenching process, to meet the quenching technical requirements of the product.

External flange products: power input ratio 98%, heating time 7.4s, cooling time 14s, quenching liquid concentration 1.5% ~ 2.5%.

Internal flange products: power input ratio of 98%, heating time of 7.7s, cooling time of 20s, quenching liquid concentration of 1.5% ~ 2.5%.

Shanghai Haofton water-soluble quench was used, and its concentration was detected by refractometer.

2. Adjustment of cooling device

(1) Ensure the cooling pressure, quenching liquid cooling pressure is 0.25 ~ 0.4mpa, sensor cooling pressure is 0.5 ~ 0.8mpa.

(2) Cooling device position adjustment, cooling water can not be blocked or blocked.

(3) Cooling water has two parts, one is quenching liquid, the other is system cooling water, heat exchanger is commonly used for temperature cooling.

Generally, the temperature of quench liquid is not greater than 35℃. Too high temperature will cause insufficient cooling, resulting in product quality problems. System cooling water temperature, is the soft water cooling electrical appliances, this temperature is generally controlled at 30℃, must not be lower than room temperature, otherwise it will make the surface of the cooling electrical appliances condensation water, easy to damage the electrical appliances.

Product inspection method

The inspection of heat-treated products requires wire cutting and pre-grinding of metallographic samples.

Product tempering process

Induction hardening workpiece tempering, there are self-tempering, induction tempering, furnace tempering. The product is tempered in furnace.

Tempering temperature depends on the technical requirements of the workpiece. General hardness requirements in 52HRC above, tempering temperature 180 ~ 200℃, tempering time 1.5h; For hardness requirements above 56HRC, the tempering temperature can be 160℃, tempering time 1.5h.

The tempering process of the product was finally determined as tempering temperature 165℃, tempering time 2.5h.

Inspection

Figure 17 and Figure 18 are the product samples successfully debugged.

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FIG. 17 Quenched sample of outer flange

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FIG. 18 Quenching sample of inner flange

Table 5 is the first test data of the debugged products.

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According to vickers hardness tester, the surface hardness and effective depth of hardened layer meet the technical requirements. The heat treatment of the product was successfully completed from the design of the tooling sensor to the commissioning of the product.

Conclusion

The structure, shape and size of inductor is the core problem of induction quenching technology, which has a direct impact on the quality, production efficiency and energy consumption of induction quenching parts. Therefore, an appropriate inductor is an important way to obtain high quality, high efficiency and energy saving induction quenching.

Author: Liu Yangwei

Source: Network Arrangement – China Pipe Sleeve Manufacturer – Yaang Pipe Industry (www.epowermetals.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@epowermetals.com

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