Induction heating in the forging industry

For details, please purchase the mechanical worker (thermal processing) 2007 issue 5 or the PDF file at the bottom of the download page.

Induction heating of 5-1 steel blue brittle blanking and warm forging

The temperature range of steel in the induction heating cold specification is just the temperature range of blue brittle cutting and warm forging.

Taking 45 steel as an example, its mechanical properties change at different temperatures: tensile strength σb decreases slightly from room temperature to 300 °C, and between 300 and 450 °C, there is a rising peak, which is the blue-brittle zone. After the blue brittle area, the drop is more severe: σb is about 200MPa at 650°C, and about 100Mpa at 800°C, and the plasticity index increases obviously.

......

The deformation temperature of warm forging is generally between room temperature and hot forging temperature. The ferrous metal warm forging temperature range is generally 200 to 850 °C.

The typical warm forging temperature of steel billets is shown in Table 5-1 below. Typical warm forging temperature of steel billets...

5-2 Average resistivity ρ2 and relative permeability μr of cold gauge steel

1, the average resistivity ρ2

The average resistivity ρ2 value refers to the integral average value of the electrical resistivity of each point of the steel from the initial temperature (20 ° C) to the initial forging temperature. Engineeringly, the sum of the temperatures of several points before the initial forging temperature can be divided by the number of points as its average resistivity.

Table 5-2 Relationship between resistivity and temperature of several steels (×10-6Ωm)

......

Figure 5-1 Approximate average resistivity of steel between initial temperature and Curie temperature...

2. Relative magnetic permeability μr

The relative permeability during induction heating is a very complex variable. In order to determine the permeability, it is necessary to refer to the magnetization curve B = f (H) of the steel. Generally, the magnetic field strength of induction heating is H>4×104A/m. When H>4×103A/m, the magnetization curves of various steels are very small, so it is possible to compile an average magnetization curve 1 — — B=f(H)

2, 3, 4 - H2 = f(H)

(The three curves multiply the H2 value by 109, 1010, 1011, respectively)

5 —— μ= f(H)

Figure 5-2 Average magnetization curve of steel...

5-3 Current frequency and heating time of steel cold gauge

1, the frequency is selected according to the formula (2-3)

≤f≤

The frequency can be obtained by substituting the average resistivity ρ2 and the relative magnetic permeability μr of the steel in the cold state into the above equation.

According to the frequency determined by the above formula, the following problems are encountered in the design of the sensor parameters: the density of the inductors calculated at a lower frequency is higher, in order to arrange the number of turns of the coils within a certain length, An intermediate frequency transformer can be used to reduce the intermediate frequency voltage of the thyristor inverter, to be divided by the inductor coil, or to adopt a multilayer coil scheme. However, in engineering, the calculated number of turns of the coil can be arranged by appropriately increasing the frequency. Since the increase in frequency causes an increase in heating time (the length of the inductor is also prolonged), the effect of heat loss due to the increase in the length of the inductor can be tolerated due to the cold state.

......

5-4 Parameter Calculation of Cold State Standard Solenoid Sensor*

Cold state specification sensor design ideas: find ρ2, μr

Where: r2=1.37 × and X2m = . The rest of the calculations are the same as the thermal specifications.

Example: The piston of the internal combustion engine is formed by two parts: the first part heats the surface temperature of the blank from the initial temperature to 80-120 ° C, takes 100 ° C, the billet exits the sensor, and immediately enters the commercial water. In the base graphite lubricant tank, the surface of each blank is dip coated with about 0.5 g of lubricant, and then enters the second part of the inductor to continue heating to a warm extrusion temperature, and the heated billet is sent to a press for intermediate temperature extrusion molding.

Billet material: 20Cr; billet specification: φ45.5×66; mass: 0.842kg; extrusion temperature: 650±10°C, heating beat: 5s; heart surface temperature difference: ≤30°C.

The calculation steps are as follows:

......

`

* The calculation of the sensor parameter design example in this paper is completed by Comrade Wang Xin and Wang Haiyan.

H2 = 3.67 × 102 × =1.97 × 109

H=0.19×105 (A/m)

Rr=30

When calculating the unit power, the length a2 of the blank in the inductor has not been determined. At this time, it can be preset according to the experience, and after obtaining μr and △2, the a2 value is obtained according to the formula of the shortest heating time, and the value of a2 is re-established with the value of a2. Calculate μr.

......

The following contents: Induction heating of aluminum alloy and sensor design and parameter calculation, induction heating of aluminum alloy isothermal forging die, induction heating of aluminum and aluminum alloy with temperature.

· The copyright of this article is jointly owned by China Metalworking Online and the author, and may not be reproduced without written permission. Please contact the editorial department of this website for reprinting .

Air-Fluid Threaded Brass Pneumatic Fittings in many different styles, Those Brass Air Hose Fittings are machined from quality brass bar stock or forgings. They work well with air, water, oil, oxygen, nitrogen and argon. Available in most popular styles and sizes, the fittings all have NPT, PT, BSPP threaded connections. Plating: Nickel, Chrome, Silver, Zinc, Gold, Brass, As Per Customer Requirement. Maximum Pressure = up to 800 psi

BSP Taper Plug with Hexagonal Socket , Reducing Nipple, BSP Male Tee, Male Branch Tee, Reducing Bush, Brass Elbow Equal Female.

China Air-Fluid Manufacturer, Supplier, Exporter, OEM for High Pressure Misting Cooling Fittings , Pneumatic Fittings, Nickel Plated Brass Push-fit Fittings, Plastic Push In Fittings, One Touch Tubing Fittings, Push-To-Connect Tubing Fittings. Nickel-Plated Brass Push-To-Connect Fittings