JPS59183359A - Method for testing quality of steel material - Google Patents

Abstract

PURPOSE:To enable a material quality test even in a thickness direction, by passing a steel material through a plurality of piercing type testing coils excited in different frequencies or passing the same through a single piercing type testing coil alternately excited in plural mutually different frequencies. CONSTITUTION:A steel pipe P to be tested is conveyed while inserted through self-induction piercing type testing coils H, M, L. Each of the coils H, M, L is one arm among four arms constituting each of bridges 1H, 1M, 1L which are, in turn, connected to oscillators 2H, 2M, 2L respectively applying different exciting frequencies and preamplifiers 3H, 3M, 3L. An eddy current is generated to the steel pipe P so as to reach a depth position corresponding to each frequency and the impedances of the coils H, M, L are changed. Non-equilibrium voltage is inputted to an operation circuit 7 through BPF 4H, 4M, 4L, amplifiers 5H, 5M, 5L and phase regulators 6H, 6M, 6L. By this method, the quality changes in the pipe axial direction and the wall thickness direction can be detected with high accuracy.

Description

[Detailed Description of the Invention] Kihachi January relates to a material testing method for steel bars, wire rods, steel pipes, etc. with circular cross sections, and more specifically, an electromagnetic method that can test the material in both the axial direction and the thickness direction. This paper proposes a material testing method using induction testing.

Electromagnetic induction testing is an old method for non-destructive testing of steel materials. There are two methods for this electromagnetic induction test: a method that uses a weak magnetic field and a method that uses a strong magnetic field. The induced voltage of the test coil is determined using changes in the magnetic flux density when the coil is exposed to abnormalities in the material, such as tissue abnormalities and hardness abnormalities.

When performing a material test on a steel material using this electromagnetic induction wiping, the steel material must be inserted through a penetrating test coil.

This is done by moving the steel material and the test coil completely relative to each other, but by measuring the impedance or induced voltage within the steel material, it is possible to detect material abnormalities in the axial direction of the steel material. It was impossible to detect abnormalities in the thickness direction.

If the steel material is heat treated, for example quenched, the steel type,
Although it varies depending on the quenching, f'1~ method, quenching conditions, etc., the structure of steel materials differs in the thickness direction, that is, on the outside and inside, and the hardness may differ due to this. Therefore, for steel materials that have been subjected to such heat treatment, it is desirable to carry out a material test to detect differences in hardness in the thickness direction.

Raikou 811 was created in view of this despicable situation, and uses one or more shell-type test piece coils excited at different frequencies, and the depth of inspection in the thickness direction of each coil is imprinted. Was it possible to test paulownia texture in the thickness direction? The purpose is to provide a method for testing the material properties of materials.

The in-quality test method of the steel frame phase according to the present invention uses electromagnetic
A steel frame of 11 paulownia (') passes through the through-type test coil of the game-only test roll.
In the l-sen test method, multiple through-type test coils are
1-1. Exciting each test coil at a different frequency 2.
It is characterized by

Using one through-type test coil, the test coil was
It is characterized by being alternately excited at multiple different frequencies. The method of the present invention is described below based on the drawings) 41 Basically,
U month.

FIG. 1 is a diagram illustrating an apparatus for carrying out the Wooden Lee 1 method. PI-j in the figure is a steel pipe that is the test material, and the steel pipe is supported by a transport device (not shown) so that it can be inserted through three self-induction type page-through test coils I, M, and L. , transported.

Each of the above coils H, M, and L is a bridge IH, ], M,
One of the four sides configuring LL, and the bridge I
f-i, IM, LL are the excitation frequency H for the coils H, M, and L.
Oscillator 2T-], 2M, 2L and bridge IH, which give f 2Mf, L f ('Hf>Mf>Lf),
niJ device width amplifier 3H that amplifies the unbalanced components of IM and LL.

Connected to 3M and 3L.

The oscillators 2H, 2M, and 2L magnetize the coils H, M, and L at I5h (frequency) If, Mf, and Lf, so that the steel pipe P has a depth 'V corresponding to the frequencies Hf, Mf, and Lf.
An eddy current is generated in ct, and this eddy current and coil H'
, M, LK The impedance of the coils H, M, and L becomes '[-f' due to the interaction with the flowing current. Coil H2Δ4. from bridge IH, 1M, LL. The unbalanced vomit pressure according to the impedance of L is corrected, and the preamplifiers 3H, 3M, and 3LK amplify the force by 1 and increase +p% by f1. (2i% is pan 1: bass filter 4H, 41
The double "+" noise due to other excitation frequency components is removed at vl, 4L, and the amplifier 5) (, 5M, 5LVc, l:
5 m width, <x It is input to the arithmetic circuit 7VC via phase checkers 6H, 6M, and 6L.

Amplifiers 5H, 5M, 5Ll''i bridges], H, LM
, is for aligning the signal levels from the IL,
Phase adjusters 6H, 6M, 61- are oscillators 2H, 2M
, amplifiers 5H and 5 in synchronization with the output frequency of 2L.
This is to synchronously adjust the M and 5L outputs.

A case in which the method is implemented using the above-mentioned apparatus will be explained in detail.

ii1 For the oscillators 2H, 2M, and 2L, predetermined excitation frequencies f1f, , Mfu, and Lfo, which are derived from the following fl+ formula showing the relationship between the excitation frequency f and the penetration depth δ, are set in advance, and the oscillators 2H, 2M, and , 2L [7] To excite coils H, M, L, bridge IH, LM,
The above frequencies Hfu, Mft, , Lfo are given to LL.

δ-1/u ・(1) 1,, iji, δ
: Penetration depth, where the density of AC magnetic flux is 37% VC of the surface.
This is the place to drop off.

π: Circumference f: Excitation frequency μ: Magnetic permeability (H/m) σ: ;18 military rate (17 m) Here, the penetration depth δ is determined according to the desired depth by separating the material and obtaining a high layer 6, excitation frequency f is set to high frequency Hf
By setting it to o, the outside of the Lie tube P, which is shallower than the penetration depth δ, is detected. By setting the excitation frequency f to a medium frequency Mfo, the central part of the steel pipe P in the mechanical direction has a low frequency vf:
, Lfo, the inside of the ρ knowledge tube P can be detected to a large extent.

Next VC': J With the bridges LH, LM', and IL in the air center, the bridges LH, LM', and IL are balanced, and then the structure and hardness are the same in the entire wall thickness direction.
= Coil the sample (preferably the same steel as t<M4A) 1. Insert into M and L. 71. As a result, bridges IFI, LM, and LL become unbalanced, and bridges IH, LM, and LL receive signals Hf+, Mft, and L.
Output f+. Bridges LH, LM, and IL send these @ signals Hf+, Mft, and Lf+ to 111 amplifiers 3H, 3M, and 3L.

The Mini device expanders 3H, 3M, and 3L are input ports HL
, Mf, , u+ to a level that can be processed, and the amplified signals are amplified by bandpass filters 4H, 4M, 4L+ &11#jl units 5H, 5M.
, 5L K input. The amplifiers 5H and 5M.

5L adjusts the VC so that each input signal has the same level of 1, the output is B, 9, and the level is suitable for input to the arithmetic circuit 7.

Arithmetic (4-way 7 has input value amplifier 5I (, 5M, 5
LK The outer hardness lower limit voltage Eo, which was determined using the set gain, copper drawing, quenching conditions, conveyance speed, etc., and the outer hardness upper limit electric ratio Igo2. Central product hardness] - Limit Shimoda E old, central part hardness upper limit voltage EtJ-Mz, inner hardness lower limit voltage 1-1-E, Nihon-based amplifier 5H, 5M
, 5L input signal Hf,.

Mf+, Lf+ electric EHf1. EMf+, I
Below (2) for issue Lf1.

(3) , (Condition f of formula 41: If satisfied, it is set to determine that the steering is abnormal.

EO, <EHf, < Eo2 −+2+1ih
++ < EMfl <, EM2 ... (3
)】=1. <Eu, riEI□...(4
)Arithmetic circuit 7) If the above settings are not satisfied, the operator will be notified by means of an inexpensive warning means as shown in the figure.

After doing the quasi (iiiI), the inside of the coil L (, M, L is the test material @iI shadow, P is j↓B, and the structure and hardness inside the steel pipe P are constant. The output is stable or the impedance changes abnormally, and the bridge I
H.

IM and IL are the signals Hf', , M
Output f′, , Lf′,. The @No.Hf',
, Mf', , Lf' are old building amplifiers 3H.

3M, 31-, band pass filter 4H, 4M, 4L,
'Amplifier 5H.

5M, 5L, and phase adjusters 6H, 6M, and 6L, and are input to the arithmetic unit 7. The P-device 7 phase adjuster 6H,
The output values from 6M and 6L are EHf', , EMf
It is determined whether or not ', , ELf' satisfy the above conditions, and if they are not satisfied, the operator is notified by an alarm means (not shown). Second, we will explain the example of End of End 4]. For each oscillator, l:Hfo=200H
Each coil H, M, LK was excited by applying a frequency of 3 (JHz, Lfo = 3Hz), and a tin screw P which had been hardened by Hs was inserted into the outer surface of the coil. Amplifiers 5H, 5M, 5L voltages for each position in the axial direction (complementary axis) on the outside, center, and inside (
Blood 7 (11Ilb) is shown in FIG. Figure 3 shows the results of measurements of the long-cruel hardness of the same steel that was cut on the outside, center, and inside. The ○ and ×2 openings in the diagram are largely on the outside,
The central part, the inner part] represents the 18th fruit.

From the comparison of both figures, it is clear that the output voltage represents the hardness.
-y-1 It is smooth. In other words, due to quenching, the axial direction of the steel pipe is approximately 500 cm away from #! Degree is 46 HRC
The hardness is higher than the hardness at the axial position after 111, and the output voltage is high corresponding to fLK. Regarding the central part, the hardness is lower than the outer hardness at an axial position of about 500 Cym, or the hardness is about 30 HRC, as in the case of the outer hardness, and the front and rear axial rotation 1
In m? ilf! The output voltage is higher to correspond to this power. In addition, medium heat G+
＞B! Regarding the inner output voltage, which will be explained next,
Since the hardness at the depth corresponding to the frequency from the side surface (1) is measured, the outer hardness is detected for the central part, and the outer hardness and the central hardness for the inner part are detected with force 2 including people. There is. Therefore, for the inside, the axial rotation is 11
At a distance of about 500 cm, the hardness is 18H], while the output voltage is slightly higher and is currently 717. It can be seen that when performing a material test on a steel pipe that has a change in li degree, the deterioration in hardness can be detected and output with high accuracy.

Hardness at the outside, center, and inside of the steel pipe in the above example <M
The correlation between the A axis) and the output voltage (vertical axis) is shown in Figures 4 and 5.
It is shown in FIG. The black circles in the figure are astronomical values. From each figure, the output 'voltage shows a positive correlation with the hardness at the outer and central parts of the wood fiber example7, and as mentioned above, the output 'voltage' shows a positive correlation with the hardness7.
Because it is detected in a state that includes the hardness of the center, the output voltage increases as the hardness decreases, showing a negative correlation, and the hardness and output voltage are very different. I understand that.

Although the coil used in the present invention is a self-refining type coil, it is of course possible to use a mutual J-research type coil. Although the above embodiment uses three coils, it is also possible to use one coil for time-sharing VC for a plurality of excitation magnetic layer wave numbers. FIG. 7 shows an embodiment in that case, and the same signs as in the first example are given the same sign. In this embodiment, the oscillators 2H, 2M
, 2L power is applied to the multiplexer 8, the timing control circuit 10 outputs the timing signal, the three inputs of the multiplexer 8 are sequentially selected and outputted, and the 2L power is applied to the bridge l, The steel pipe P is excited by the coil C.

The n11 tube P oscillates Krj, 2H, 2M, 2L (
The D output frequencies I&Hf, Mf, LflC'''r are excited alternately.The unbalanced portion of the bridge 1 is amplified by the preamplifier 3 common to the three frequencies, and input to the multiplexer 9. .

The timing multiplexer 9 has l from the timing control circuit 10.
A timing signal similar to that described in section 1 is applied, and during the period when the outputs of the oscillators 2H, 2M, and 2L are selected by the multiplexer 8, the inputs from the preamplifier 3 are passed through the respective band-pass filters. 48.4M and 4L respectively.

This method also has the advantage of not only achieving the same effect as the embodiment described in 111, but also making it easier to commercialize electrical, electrical, and electronic circuits.

As detailed above, the method of the present invention applies different excitation frequencies to the coil to detect material abnormalities in the wall thickness direction. The material change is also high.

[Brief explanation of drawings]

FIGS. 1 and 7 are diagrams showing the apparatus for carrying out the method of the present invention, FIGS. 2 and 3 are graphs showing the output voltage and hardness, respectively, and FIGS. Figure 6 is a correlation diagram between the 4i history and the output voltage at the outside, center, and inside, respectively. ■)...Copper tube H, M,,L...Through type test coil L
H, LM, LL...Bridge 2H, 2M, 2L-
Oscillator 5) 1.5M, 5L...Amplifier 7--When operating circuit H'RC) 16 18 20 2224 section foot (
HRC) 6 Figure

Claims (1)

[Scope of Claims] 1. In a method for testing the quality of steel materials in which the steel material is passed through a through-type test coil for electromagnetic induction testing, a plurality of shell-through test coils are used and each test coil is excited at a different frequency. Characteristic material testing method for steel H. 2 Steel material is passed through electromagnetic induction test l+1 coil a
1. A method for testing the quality of steel materials, characterized in that a dog-shaped test coil is used and the test coil is alternately excited at a plurality of different frequencies.