SU1370540A1 - Method of checking quality of ferromagnetic articles - Google Patents

Abstract

The invention relates to non-destructive testing and can be used for structuroscopy of ferromagnetic products. The purpose of the invention - povpienie reliability of control - is achieved due to the fact that the magnetized product magnetizing device such attachable electromagnet with ferrodatchikom is supplied alternating voltage to the coil drive ferrodatchika support its amplitude constant during magnetization, control the amount of current excitation ferrodatchika, controlled magnetizing current until the amplitude of the drive current of the ferro sensor reaches a predetermined value, after which the magnetizing current is turned off, including t and then shut down in ayut demagnetization current. The quality of the product is judged by the magnitude of the magnetizing current, at which the amplitude of the excitation current of the ferro sensor reaches a predetermined value, or by the magnitude of the coercive force. 1 3.p. f-ly, 1 ill. with (L s JV

Description

113

The invention relates to non-destructive testing and can be used for structuroscopy of ferromagnetic products.

The purpose of the invention is to increase the reliability of the control - it is achieved by choosing the optimal magnetization mode, which, in particular, eliminates the non-monotony in the nature of the dependence of the coercive force on the parameter being monitored.

The drawing shows a plot of the coercive force, determined by the demagnetization current in the constant current mode of the ferro sensor, corresponding to the induction in the product, equal to 0.42 T, on the quenching temperature of the ShKh15 steel samples (the monotonic character of the indicated dependence is seen).

The method is implemented as follows.

Place the controlled product in a magnetizing device, for example in a step-type electromagnet, with a ferro-sensor. The magnetizing current is switched on and the product is magnetized. During the magnetization, the amplitude of the alternating voltage on the excitation winding of the ferro sensor is kept constant. The magnetisation current is adjusted to the amplitude of the excitation current of the ferro sensor of a predetermined value. After that, the magnetizing current is disconnected, the demagnetization current is switched on, and then disconnected. The product quality is judged by the magnitude of the magnetization current, at which the amplitude of the ferro sensor's exciting current reaches a given value, if the primary informative parameter is the magnetic permeability in the amplitude of the even harmonics of the output EMF of the ferro sensor with a fixed value of the demagnetization current (for example, at a demagnetization current, the figure is equal to 23. ) if the primary informative parameter is residual induction; by the magnitude of the demagnetization current, at which the amplitude of the even harmonics of the EMF of the ferro sensor reaches a given (zero) value, if the primary informative parameter is the coercive force; according to the magnitude of the demagnetization current, at which the amplitude of the even harmonics of the EMF of the ferro sensor reaches a given (zero) value

after switching off the demagnetization current, or in terms of the amplitude of the even harmonics of the output EMF of the ferro sensor with a fixed value of the demagnetization current (and the demagnetization current is adjusted until the amplitude of the even harmonics of the EMF of the ferro sensor is set)

after turning off the demagnetization current, if the primary informative parameter is the relaxation force.

With two-parameter control, for example, when controlling the quality of parts made of tool steels, the quality of the product is judged by two parameters, in particular, by the magnitude of the magnetizing current, at which the excitation current amplitude of the ferro sensor reaches the specified value, and by the demagnetization current, at which the even harmonic amplitude The emf of the ferro sensor reaches zero.

The essence of the method is that they regulate the magnetization current in such a way that the amplitude a of the excitation current of the ferro sensor is constant regardless of the properties of the products being monitored. This ensures the constancy of the magnetic flux in the products, which leads to the monotonic character of the dependence of the coercive force on the parameter being monitored. The required value of the magnetic flux (induction) and the corresponding value of the excitation current of the ferro sensor, at which the coercive force is monotonically dependent, is determined experimentally. In particular, for steel SHKh15 induction should be in the range of 0.3-0.6 T.

It is advisable to carry out quality control of quenching products from ShKh15 steel in the following sequence: place an unhardened product in the measuring position, set the magnetisation current so that the induction in the product is in the above range, and fix the appropriate value of the excitation current of the ferro sensor then place the controlled value in the measuring position hardened product and increase the magnetizing current until the amplitude of the excitation current of the ferro sensor reaches the obtained th the previously set;

th value

 13705

turn off the magnetizing current and in a known way estimate the value of the coercive force of the product. The coercive force is judged, for example, by the magnitude of the demagnetization current, at which the amplitude of the even harmonics of the EMF of the ferro sensor reaches a predetermined (zero) value, or in the amplitude of the even harmonics of the output EMF of the ferro sensor with a fixed value of the demagnetization current, in particular after it is turned off.

Claims (2)

1. The method of quality control of ferromagnetic products, which consists in magnetizing the product with 0 measured voltage with an amplitude unchanged during the magnetization process, and control the magnitude of the excitation current of the ferro sensor, characterized in that, in order to increase the reliability of the control, the magnetizing current is controlled until the excitation current of the ferro sensor reaches the specified magnitude, the magnetizing current is turned off, the current is turned on and off demagnetize and measure the magnitude of the coercive force, which determines the quality of the product under test. 2. The method according to claim 1, characterized in that the current value is used as informative using, for example, a pinned magnetism at the time of reaching the romagnet with a ferro sensor, the transmitter of the setpoint value is fed to the winding of the excitation current. / UO A / cm 1b 12 eight doses. 790 830 870 zack