SU748916A1 - Method of controlling the surface heating of ingots - Google Patents

Description

(54) METHOD OF MANAGING SURFACE HEATED PREPARATIONS

-, ...

The invention relates to electrothermal and can be used in surface heating, for example, induction to accelerate to reach a predetermined temperature with a permissible unevenness in the thickness of the workpiece.

A known method of controlling a fire (heating by heating, during which during heating and holding, necessary for temperature equalization, over the cross section of the workpiece, the average temperature of the workpiece 1 is maintained at a certain level.

With this control method, the total heating and holding time is longer than the minimum possible, since overheating of the middle part of the workpiece over the final temperature allows creating a large amount of heat in the workpiece during the heating interval, which significantly reduces the temperature equalization time across the workpiece section.

A known method of controlling the surface heating of the workpieces, mainly induction, in which a power source is turned on for heating the workpiece, then it is turned off and the workpiece is kept in the heating zone, while aligning

temperature over the section of the workpiece, during heating and holding, control the temperature of the surface and center of the workpiece when these temperatures reach a finite value with a given temperature difference

J over the cross section of the workpiece unload the workpiece from the heating zone 2.

This method allows to obtain the minimum possible time of the whole heating cycle. However, if it is necessary to obtain higher heating accuracy

10 cross-section, control in two intervals: the heating-shutter speed does not allow to achieve the desired. The temperature difference over the cross section is higher than the allowable one.

The purpose of the invention is to reduce the temperature difference over the cross section of the workpiece at

15 maintaining a minimum total time of heating-exposure.

To do this, additionally control the temperature at a point located at a depth equal to one third of the radius of the workpiece,

20 after the end of the exposure, the power source is re-enabled to further equalize the temperature, and the workpiece is unloaded when the surface temperature is reached and the control unit is additionally controlled by the f64K {i) i upper limit, k the center temperature - the lower acceptable value.

FIG. 1 shows the curves of the temperature variation over the section of the workpiece; in fig. 2 koHe4Hoe temperature distribution across the thickness of the workpiece.

The control method is implemented as follows., .. „.,

The control is performed in three intervals - heating-shutter-heating, while controlling the temperature at three points: on the surface of the blank T, at a depth equal to 1/3 of the radius of the blank T and in the center of the blank TU. In the first control interval, the maximum allowable power and temperature of the surface Tp, overheat on D of a given final temperature T, aj

On the east. In the interval, the power supply is disconnected and temperature equalization is performed. Through the cross section, the temperature of the sensor decreases below the lower limit Tjo, g-, where is the allowable final temperature difference across the section, and the center temperature has not reached the desired one.

In the third interval, the power source is switched on again and the surface temperatures are raised to the upper permissible limit tjoj +. In this case, the temperature of all layers of the workpiece does not go beyond the permissible temperatures.

The workpiece is unloaded while the temperature of the center of the lower permissible value is reached, and the surface and point temperatures located at a depth equal to 1/3 of the workpiece radius reach the upper permissible value

TS ". +.

Instead of the switching line, as in the case of 2 interval controls in this method, we have a switching surface in the space of temperatures Tn, Tc, and T / vi. The corresponding function (Tp, Tc, Trtt) is twtbiBaieTc or o practically. Moreover, at the moments of transition from one interval to another, this function passes through zero.

The implementation of the method is simplified if the permissible dBs of the maximum allowable value is due to irreversible processes in the billet, flashing, etc. In this case, one of the controlled temperatures Tp TMAI.

The practical implementation of the described method was carried out on an IN-220-58 / 140 furnace with a capacity of 2,200 kW.

On a billet with a diameter of 480 mm from alloy D1, heating is carried out for the shortest possible time with a tolerance of ± 1 ° C from the specified final temperature of 46 ° C.

In view of this, fW) it is impossible to withstand such a small temperature tolerance over the cross section of the workpiece with a minimum time of the entire heating cycle with a 2 interval control, heating is carried out at 3 intervals. At the end of the first interval, the surface temperature Tp is 495 ° M, the center of the TC 431 ° C and Tut 473 ° C.

During5 | second interval, the power source is disconnected.

Temperatures at the end of the second interval

9next Т „452 ° С, Тц 458 ° С, ТмНбЗ С.

During the third interval, the power source power is maximum.

The workpiece is unloaded at the following temperatures TC 461 ° C, TC 459 ° C. .

The total heating time + shutter speed -f heating is 20.2 + 2.2 + 0.25 22.65 minutes.

The total time by a known heating method is 25.14 minutes, and the allowable

the temperature difference was ± 10 ° С. Therefore, the use of the proposed method has reduced the total heating time by 11%.

Claims (2)

Invention Formula The method of controlling surface heating blanks, mainly induction, which includes a source power to heat the workpiece, then turn it off and hold the workpiece in the heating zone, while partially equalizing the temperature over the cross section of the workpiece, during heating and holding the temperature of the surface and the center of the workpiece, when these temperatures reach a final value with a predetermined difference in cross section of the workpiece, the workpiece is unloaded from the heating zone, characterized in that, in order to reduce the temperature difference over the cross section of the workpiece while maintaining the minimum total heating time, the temperature is additionally controlled at a point located at a depth equal to one third of the workpiece radius, after the end of the exposure, re-energize the power source to further equalize the temperature over the cross section, and the workpiece is unloaded at stizhenii surface temperature and further Controlled point upper permissible value and a center temperature - lower allowable value. Sources of information taken into account during the examination 1. US Patent No. 2988623, cl. 219-10.75, 1966.  2. USSR inventor's certificate in LGG 2421154/07, cl. H 05 B 5/04, 1976. Tj6 HlfOH. tfit (o HiCOf /. f.KOH . I ntfOHi  If i I / OH / fg fig i