RU1827391C - Method for heating blanks after deformation in inductor - Google Patents

Abstract

The invention relates to methods for heating a preform e inductor and under deformation. Before heating, the cold billet is wrapped in a heat insulator. As the latter, a fibrous material with a melting point above the heating temperature under deformation is used, the layer thickness is selected from the condition of ensuring isothermalness when transferring the heated preform from the inductor to the deforming device. The fibrous heat-insulator dissipates little radiation from the heated preform and at the same time contributes to the conservation of heat in the preform itself. 2 tab.

Description

The invention relates to high temperature induction heating, in particular to methods for heating a workpiece under deformation in an inductor.

The aim of the invention is to maintain the temperature of the workpiece when transferring it from the inductor to the deformation device while maintaining the resistance of the inductor and its efficiency.

The proposed method is carried out as follows.

The billet of a heat-resistant alloy in a cold state is wrapped in a cover made of a fibrous heat insulator, the melting temperature of which is higher than the heating temperature under deformation. The thickness of the fibrous heat insulator is chosen so that the degree of filling

the internal space of the inductor did not exceed 0.378. To make it more firmly attached, the cover may be wrapped with an asbestos cord. Then the workpiece in the case is placed in the inductor. If necessary, an additional seal of the heat insulator is made in the gap between the inductor and the workpiece. After checking the reliability of the insulation fastening, the inductor is turned on and the workpiece is heated. If necessary, control the heating is carried out using thermocouples, which can also be placed under the cover and secured to the workpiece by any known method. After heating is completed, the preform with the case is removed from the inductor, for example, using an ejector and transported to a deforming device. At the same time, the heat-insulating cover allows the preservation of

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thread isothermal conditions in the workpiece before deformation.

The quality of the inductor is assessed by inspecting its working part for damage to the electrical insulation or cracking of the insulating layer. The efficiency of the inductor is estimated by reducing the heating time of the workpiece as compared to heating without thermal insulation.

Example. The proposed method for protecting the inductor was tested on a special induction installation, with a power of 50 kW, a working voltage of 36 V, an inflow of 1900 A with an industrial frequency of 50 Hz; the diameter of the water-cooled inductor 460 mm; a washer with a diameter of 380 mm, a height of 270 mm, and a mass of 270 kg from a heat-resistant alloy EP962PD was used as a blank. The cold billet was wrapped in a cover made of a roll mullite-siliceous fibrous material of the MKPP-130 brand manufactured by the industry according to GOST 23619-79. Moreover, the billet was heated in the inductor with varying degrees of filling the inner space of the inductor by changing the thickness of the cover. At the same time, the heating time of the workpiece was recorded. The experimental results are summarized in table 1.

As follows from the data in Table 1, the best heating results were obtained with a degree of filling up to 0.378. When heated according to the prototype, the efficiency of the inductor decreased by more than 20%.

When transferring the workpiece from the inductor to the deforming device during heating in accordance with the proposed heating method, the temperature drop is not fixed. When transferring the workpiece from the inductor to the deforming device during heating in accordance with the prototype, the temperature on the surface of the workpiece fell below the permissible limit.

The measurement results are given in table.2.

As follows from the data in Table 2, the temperature on the surface of the workpiece during transfer to the deforming device under the thermal insulation layer remained practically unchanged, which corresponds to the isothermal process.

An inspection of the surface of the inductor was also conducted.

According to the proposed method, surface inspection showed a complete absence of damage to the electrical insulation from the micanite tape. Even the color of the tape has not changed, which indicates the complete absence of thermal radiation from the workpiece.

Claims (1)

The claims A method of heating a workpiece for deformation in an inductor, including applying thermal insulation, characterized in that, in order to maintain the temperature of the workpiece when transferring it from the inductor to the deformation device while maintaining the resistance of the inductor and its efficiency, thermal insulation is applied directly to the workpiece with a degree of filling the inner space of the inductor is 0.12-0.378, and a fibrous material with a melting point higher than the heating temperature under deformation is used as thermal insulation. 0 5 0 5 0 Table 1 Change in the efficiency of the inductor depending on the degree of filling with fibrous insulation Table 2 The temperature drop on the surface of the workpiece during transfer from the inductor to the deforming device