SU1595928A1 - Method of inspecting heat treatment of steel articles - Google Patents

Abstract

The invention relates to the control of heat treatment of steel and can be used in mechanical engineering in the manufacture of shafts. The purpose of the invention is to increase accuracy. SUMMARY OF THE INVENTION The essence of the invention is that in a known acoustic method for monitoring the tempering of products, including recording and analyzing acoustic signals arising during cooling in quenching liquid, a signal corresponding to bubble boiling frequencies is selected.

Description

The invention relates to the control of heat treatment of steel and can be used in mechanical engineering in the manufacture of shafts.

The purpose of the invention is accuracy.

The essence of the invention is that, according to the acoustic method of controlling the quality of quenching of products by recording and analyzing the spectrum of acoustic signals emitted during phase transformations in a thermally convertible product — a quenching medium in the quenching cooling process, a signal is extracted from the acoustic spectrum bubble boiling frequencies, by the presence of which the duration of the cooling process necessary for obtaining high quality hardening is judged.

I Using the proposed acoustic quality control method for quenching allows one to determine the period of bubble boiling by direct measurement, which provides a significant decrease in the quality of control.

Example 1. A steel cylindrical reference sample of steel and 12X18K, 9T size (30x150 mm) was used as a quenched product. A chromel-alumel thermocouple was installed on the sample surface. The sample was heated in an oven to Tj. Then it was immersed in a tank with an aqueous solution of CaCl.i (from 16%). In the same tank was installed

A waveguide-type acoustic sensor with a C-21 piezoceramics sensitive element. In order to increase the sensitivity of the sensor and match it with the secondary electronic equipment, a matching device was used, which is a differential amplifier, built-in. According to the K284UD1A.10 chip.

At the time of immersion, the hardening medium began to boil on the surface of the specimen, accompanied by an acoustic signal, fixed by an acoustic sensor. Bandwidth The jalchik provided for the passage of an acoustic signal with frequencies corresponding to sound emission at n | whisker boiling. The choice of the transmission band was achieved by a low-jq frequency filter embedded in the amplifier and tuned to a cut-off frequency of 10 kHz. The signal was recorded using a H071.2 type recorder and visually monitored using a 25-millimeter voltmeter VZ-42 quadrant. xy

In the process of cooling, the intensity of the .. Bubble boiling signal reached a maximum, after which it decreased. w; ala until the complete disappearance, Qi. At this point, the sample was removed from the quenching tank for further processing. At the same time, the same recorder H071.2 sent a signal from a thermocouple located on the surface of the sample. By the characteristic fracture on the obtained curve: cooling of the vehicle, the end of the pressure boil was determined.

A comparative analysis of the signals of the Thermocouple T (C) and the acoustic sensor IC G) showed that the acoustic sensor recorded the moment of the end of Bubble Boiling, the accuracy of determining this moment was determined by the instrumental error of the applied electronic devices and was equal to 5%.

Example 2. Hardening was subjected to, Shafts of steel 40X size 0 60k750 mm heated to TO 820 ° С In a quenching 1 tank of 5000x4500xZOOOOmm size filled with 3 /, 4 with a water solution of HJaCli (15%) pH9, were placed acoustically, A wave-type wave sensor with a sensitive element from piezoelectric ceramics TsGS-21, the sensor was constructively combined with a differential amplifier with a passband of 40

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0

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bubble boiling, and the output was connected with the exponential device, made in the form of a siren and a light beacon. In the process of bubble boiling, mack was in the on state. At the moment of stopping the boiling, the ma- chine was turned off, and the siren was turned on, which served as a signal to the crane operator on the lifting of the quenching tank product. As a result of the experimental hardening of a batch of 7 shafts, no cracks were found on the cracks, the hardness was satisfactory (HRC 58), and the deformation was within the normal range. At the same time, the quality control of quenching was performed according to the maximum of the acoustic emission signal arising during phase transformations in the product. Of the two hardened parts, both were rejected due to the formation of cracks. Further hardening according to the method prototype stopped.

As a control, a batch of parts was tempered according to the technology, at which the moment of the end of bubble boiling was determined by the empirical relationship between the terry of heat exchange at boiling. In three of the eight cases, cracks were recorded on the surface of the parts.

Thus, an experienced pryuver on full-scale products has confirmed the improvement in the quality control of quenching by the proposed method.

Simplification of the measurement of the bubble boiling period was achieved by eliminating the laborious calculation of the approximate duration of the bubble boiling due to the empirical relationship of the m. At the same time, it was no longer necessary. measurement of geometrical dimensions, thermophysical properties of full-scale products,

The accuracy of determining the period of bubble boiling according to the pre- This method is increased by 6-10 times, since the empirical ratio is within 30-50% and more, and the error of electronic devices that measure the moment of the end of bubble boiling is 5%. In addition, the hardening of steel products using the proposed control method increases the yield of finished products and improves the performance characteristics of heat-treated products.

The proposed method is simple, low-cost recording of the spectrum of acoustic guitars during implementation allows one to conduct the signals of a predetermined frequency of a stationary control of the measurements and, during the cooling process, to obtain almost instantaneous information-bubble boiling in a liquid and

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Claims (1)

F. R. R. Ula inventions A method for controlling heat Botko formed ^from steel products, comprising registration of the spectrum of the acoustic signals in predetermined frequency oscillations during cooling by quenching with nucleate boiling in the liquid and 5 determining the duration of the cooling process upon reaching the maximum acoustic signal, characterized in that, in order to Ιθ.) Of increasing accuracy, acoustic signals are recorded that correspond to the vibration frequencies of the bubble boiling of the liquid.