JPS60247158A - Hot flaw detection apparatus - Google Patents

Abstract

PURPOSE:To efficiently perform the flaw detection of an elongated member with high sensitivity, in the electromagnetic induction of a steel round bar or a steel pipe in a hot state, by magnetically saturating a steel material to be inspected and detecting a flaw by a flaw detection coil block. CONSTITUTION:In a process for producing a wire material or a steel bar being a steel material 1 to be inspected under heating, the steel material 1 is allowed to pierce through doughnut shaped magnetization coils 5, 5' and a ring shaped flaw detection coil block 2, and the magnetization coils 5, 5' or the like are supported by a basket shaped support material 6 or a stand 3. The steel material 1 receives DC or AC excitation by the magnetization coils 5, 5' and magnetically saturated. Next, a flaw is detected by a flaw detection coil 2 formed by winding up a plurality of electromagnetic induction type flaw detection windings while the output signal from the flaw detection coil 2 is compensated on the basis of the temp. signal of the steel material 1 to perform flaw detection. Because the steel material to be inspected is magnetically saturated to perform flaw detection, a dummy signal is not picked up even at high temp. such as a Curie point and flaw detection can be performed with good accuracy regardless of the effect of temp.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hot flaw detection device for elongated ferromagnetic materials such as round steel bars and steel pipes.

[Conventional technology]

In electromagnetic induction flaw detection in warm or hot conditions of ferromagnetic materials such as round steel bars and steel pipes, changes in magnetic properties such as magnetic permeability that depend on the temperature of the liquid deep flaw inspection material are a problem. Generally, magnetic permeability or magnetic susceptibility decreases as the temperature rises, and at the Curie point (Tc), the spontaneous magnetization function disappears and the ferromagnetic material becomes a paramagnetic material. The horizontal axis shows the steel temperature expressed as the ratio T/Tc between Curie point Tc and the steel temperature T, and the vertical axis shows the ratio of magnetic strength, that is, the magnetization strength at room temperature. The relationship between the two is shown in FIG. 8 by taking the ratio I/Io to the magnetization strength. Further, although not shown, the electrical conductivity tends to increase as the temperature rises, and as a result, there is a problem in that the flaw detection sensitivity and the phase of the flaw detection output in electromagnetic induction flaw detection change depending on the temperature of the material to be flaw tested.

It was also found that there is a problem in that electromagnetic induction flaw detection detects false signals near the Curie point even though there are no flaws on the surface of the steel material. FIG. 7 shows a graph in which the temperature T of the material to be tested is plotted on the horizontal axis and the intensity En (relative value) of the detected pseudo signal is plotted on the vertical axis. This pseudo signal becomes an undesirable interference factor for flaw detection equipment that detects flaws.

As the temperature of the ferromagnetic material rises and approaches the Curie point, the spontaneous magnetization characteristic decreases, and in this process the magnetic domain structure is destroyed irregularly, and the pseudo signal En is thought to be due to the Barkhausen effect that occurs at this time. It will be done. From a microscopic point of view, the effect does not disappear immediately even after exceeding one point.

FIG. 9 shows an example of the temperature characteristics of this pseudo signal, which changes depending on the composition of various steel materials. Note that the average specific heat (Kcal/Kg deg, ) of the steel material varies depending on the steel material temperature, as shown in FIG. 10, and the steel material temperature versus pseudo signal characteristic and the steel material temperature versus average specific heat characteristic have a strong correlation. This relationship is shown in FIG.

Next, it is best to perform forced water cooling on the surface of wire rods and steel materials that are subjected to rolling or drawing in warm or hot conditions to prevent overheating of the processing rolls and ensure durability. When the material to be tested is rolled and rolled using jigs and tools, the material to be tested is locally cooled. The heating that is performed immediately before processing is often not uniform along the length of the steel material. Generally, it is often seen that a low-temperature part exists over the entire circumference of the tip of the steel material and over a certain lengthwise range.

Since the magnetic permeability and electrical conductivity are different between the low-temperature part and the high-temperature part, even if the same flaw exists, the relative sensitivity and relative phase angle when it is detected will show different values.

This not only impairs the reliability of flaw detection, but also results in the detection of false signals corresponding to temperature differences with non-uniform distribution.

It has been found that it is effective to deal with such defects by applying a direct current or alternating current magnetic field to the steel material to be inspected to magnetically saturate the flaw detection surface area of the steel material. That is, it has been found that the problem can be solved by focusing on the A2 transformation point and the specific heat around it, which are unique to each steel type, and adjusting and controlling the signal and the excitation current of the magnetizing coil using this as a parameter. Fig. 12 shows an actual measurement example in which a false signal detected by electromagnetic induction flaw detection was reduced by increasing the magnetizing current when the temperature of the low carbon steel material was at or around the Curie point. This figure shows the measurement results at a steel material surface temperature of approximately 730°C, with the magnetization current (■) on the horizontal axis, and the relative pseudo-noise signal amplitude (En).
is taken on the vertical axis.

From this figure, it can be seen that by magnetizing the material to be tested, the pseudo noise signal in the vicinity of one Curie point can be drastically reduced.

[Problem that the invention seeks to solve]

The present invention efficiently performs full-surface flaw detection on elongated members with relatively small diameters, such as steel bars, steel pipes, and wire rods, without picking up pseudo-noise signals, and reliably while compensating for changes in flaw detection sensitivity due to temperature changes in the longitudinal direction of the elongated members. The aim is to make it practicable.

[Means for solving problems]

The present invention is an apparatus that performs electromagnetic induction hot flaw detection during the manufacturing process of a long, slender, high-temperature ferromagnetic material to be tested. A flaw detection coil block has a magnetization coil that magnetically saturates the flaw detection coil, and a plurality of electromagnetic induction flaw detection windings arranged in a ring around the part of the material to be detected that is magnetically saturated by the magnetization coil. It is characterized by comprising a signal processing circuit that receives a temperature signal of the flaw detection material and adjusts the output signal of the flaw detection coil block and the excitation current of the magnetization coil.

However, the structure and operation will now be explained in detail with reference to embodiments.

〔Example〕

FIG. 1 shows the structure of the detection part of the hot flaw detection device of the present invention,
ia) shows an example in which the magnetizing coil is integrated, and (bl shows an example in which the magnetization coil is divided into two parts, which is similar to the one conventionally used for cold flaw detection. First, in (al), 1 is the material to be tested, and the wire rod 10 is a flaw detection device, which together with a ring-shaped or donut-shaped magnetizing coil 5 that magnetizes the material to be tested 1 and the material to be tested 1 constitutes a magnetic circuit. The mount 6 is equipped with a support plate 3.3', a flaw detection coil block 2.The mount 6 is a cylindrical or cage-shaped body surrounding the magnetizing coil 5, and the support plate 3.3' is a flat plate with a flaw detection coil block 2 in the center. The material 1 has a hole therethrough.

The magnetizing coil 5 is excited with direct current or alternating current to magnetically saturate the material 1 to be tested. The magnetic circuit includes the material to be tested 1, the support plate 3',
It consists of a closed loop of a frame 6, a support plate 3, and a material to be tested 1. (
In bl, the magnetizing coil is divided into two pieces of 5.5', and the flaw detection coil block 2 is arranged between them. Others are the same as (al).

As shown in FIG. 2, the flaw detection coil block 2 has a plurality of grooves 11 and 12! ``The windings 14 and 15 are wound around the liquid grooves of the cylindrical bobbin 13, and these windings are connected differentially, or as shown in FIG. An excitation winding 19 is wound around the liquid groove 17 of a y' cylindrical bobbin 20 having an angle of 18 degrees, and a large number of detection windings 21a, 21b, .
. . . and 22a, 22b, . . . may be attached radially. If the material to be tested is a long and narrow member with a small diameter, a penetrating type is advantageous for full-surface flaw detection. That is, the magnetizing coil 5.5' has an annular shape, and since the material to be tested passes through it, the above-mentioned magnetic circuit is formed, and the front surface of the material to be tested can be easily magnetically saturated uniformly.

Also, the detection coil 14. ,' 15 is circular and 21
a, 2 l b, ......, 24 a, 22b,
. . . are arranged in an annular shape as a whole, and since the material to be detected passes through this, the entire surface can be easily detected. Since the detection coil is disposed in a portion of the material to be tested that is magnetized by the magnetization coil and is magnetically saturated, the above-mentioned pseudo noise signal is not picked up.

Figure 4 shows an example of coil connection when applying Figure 3,
As shown in the figure, the excitation winding 19 is connected to an oscillator 23 and an amplifier 2.
5, the detection windings 21a, 21b,
. . . is grounded at one end, connected to the multiplexer 24 at the other end, and guided to a detection circuit (not shown). The flaw detection coil block 2 is inserted from the left or right side of the figure in FIG. .Bobbin 13.20 has a water-cooled structure,
It is preferable to prevent the excitation and detection windings from being excessively heated by the material 1 to be tested.

In the steel bar manufacturing process, as shown in FIG. 5, the steel bar 30 discharged from the roughing row mill is further reduced in diameter in an intermediate row rolling mill 31, and then reduced to a product diameter in the next stage finishing row mill, such as a block mill 32. Ru. The detection section 10 of the above-mentioned flaw detection device was disposed on the exit side of the finishing row rolling mill 32 in the steel bar manufacturing process. The finish-rolled wire rods are inspected for flaws using a saw, and then passed through a putty flange device 33, then conveyed out through a coil conveyor 46, and bundled in predetermined amounts. A steel material surface thermometer 35 is installed on the outlet side of the intermediate row rolling mill 31, and the output of the temperature needle is transmitted to the signal processing device 3 together with the output of the detection section 10 of the hot flaw detection device.
6 is input.

The signal processing device 36 has the configuration shown in FIG.

The detection output from the flaw detection coil block 2 is sent to the signal processing device 3.
The signal is amplified and detected by the amplifier 40 of No. 6, and is applied to one input terminal of the multiplier 41. The output of the steel surface thermometer 35 is input to the equalizer 42, which makes the input-to-output relationship non-linear (changes the amplitude and phase of the flaw detection output to a functional relationship necessary to compensate for temperature changes). ) is then applied to the other input terminal of the multiplier 41. The multiplier 41 multiplies these two inputs to compensate for changes in sensitivity of the flaw detection output due to the steel material surface temperature. The output of the multiplier 41 passes through a filter 45 and is led to a recorder 46 and a printer 47, where the recorder records the temporal change in the flaw detection output, and the printer, which is equipped with a quality grading logic circuit, records the graded flaw detection results. It will be printed. These records and/or print results are input into a process computer (not shown) for final judgment or are displayed externally.

The output of the thermometer 35 is also input to an equalizer 43 to change the input/output relationship to be non-linear, and then to the DC power supply 4.
4 to adjust the output current of the DC power supply, that is, the excitation current of the magnetizing coil 5. The nonlinearization performed by the equalizer 43 is
The output current of the DC power supply 44 is adjusted in accordance with the temperature of the material to be tested so that the magnetization of the material to be tested 1 by the magnetization coil 5 is carried out so that the pseudo noise signal included in the testing output is minimized. In other words, the equalizers 42 and 43 correct the temperature signal to a desired relationship between the temperature and the necessary correction amount and output the corrected signal.

Since the required input/output characteristics of the equalizers 42 and 43 differ depending on the steel type, it is preferable to prepare a plurality of types and make one of them selectable according to the steel type. Further, the equalizer, multiplier, etc. may be replaced with a computer.

Figure 7 shows the results of hot flaw detection of wire rods using this flaw detection device. The outer diameter of the wire is 5.5cm, and the rolling speed is 75m/sec.
, the steel material surface temperature was approximately 840°C.

(al~(C1 is the flaw detection output of the device of the present invention, (d)~(f
) shows the flaw detection output of the conventional device, and as is clear from these, the device of the present invention can significantly reduce pseudo noise signals.

〔Effect of the invention〕

As explained above, according to the present invention, since the material to be tested is magnetically saturated for flaw detection, pseudo noise signals are not picked up.
The magnetizing current and flaw detection output are automatically corrected depending on the temperature of the steel material, so the influence of temperature changes on the material to be tested can be ignored.The magnetizing coil and detection coil are shaped like a ring, and the material to be tested passes through this. Advantages such as efficient flaw detection of elongated members can be obtained. In particular, the former enables high-precision hot flaw detection, which was previously impossible, in response to the trend toward low-temperature rolling operations, which will become increasingly popular in the future from the perspective of energy conservation.

[Brief explanation of drawings]

1 to 3 are explanatory diagrams showing an embodiment of the flaw detection device of the present invention, FIG. 4 is a circuit diagram showing the coil connection, FIG. 5 is a block diagram showing an example of installation of the flaw detection device, and FIG. 6 is a A block diagram showing the configuration of the signal processing circuit, and FIGS. 7 to 12 are graphs showing various characteristics. In the drawing, 1 is a material to be tested, 5 and 5' are magnetizing coils, 2 is a testing coil block, 35 is a temperature needle, and 36 is a signal processing circuit. Applicant: Minoru Aoyagi, Patent Attorney, Hara Denshi Sokki Co., Ltd. Figure 1 Figure 2 (a) Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 7 WJ Figure 8 T/Tc Figure 9 Figure 10 T 'C Figure 11 Figure 12 Oj O, 20, 30, 40, 50, 6I (A)

Claims (1)

[Claims] In an equipment that performs electromagnetic induction hot flaw detection during the manufacturing process of a slender, high-temperature ferromagnetic flaw detection material, the flaw penetrates and travels through the flaw detection material, and then magnetizes the flaw detection material. A flaw detection coil block includes a magnetization coil to be saturated, and a plurality of electromagnetic induction flaw detection windings arranged in a ring around the part of the flaw detection material that is magnetically saturated by the magnetization coil; A hot flaw detection apparatus comprising: a signal processing circuit that receives a temperature signal and adjusts an output signal of a flaw detection coil block and an excitation current of a magnetizing coil.