JPH0443956A - Heat resistance type eddy current detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a heat-resistant eddy current detector used for quality evaluation of high-temperature steel materials, and more specifically, the present invention relates to a heat-resistant eddy current detector used for quality evaluation of high-temperature steel materials. This invention relates to a heat-resistant eddy current detector that monitors cracks occurring at the corners of slabs.

(Prior art) Is there still no technology available for measuring the depth of oscillation marks on continuous slabs during continuous casting using an eddy current detector?
Regarding a device for detecting surface flaws in hot steel materials, there is a Japanese Utility Model Application Publication No. 60-88261.

The heat-resistant eddy current flaw detection device proposed in Japanese Utility Model Application No. 60-88261 is intended for flaw detection on steel materials at temperatures of about 900°C, and its conceptual diagram is shown in FIG. In the heat-resistant eddy current flaw detection device shown in FIG. 2, a detection coil 21 is covered with a coating material 22 having high thermal conductivity, the detection coil 21 and the coating material 22 are fixed in a housing 23, and the coating material 22, the housing 23, and the electrically insulating material cooling water jacket 24 formed between
Basically, the coating material 22 is cooled by flowing cooling water from the supply port 25 to the drain port 26 in the direction of arrow a.

Furthermore, since the eddy current flaw detection device utilizes mutual induction between the alternating magnetic flux induced by the detection coil 21 and the steel material 28, a heat-resistant electrical insulating material 27 is placed between the detection coil 21 and the steel material 28. .

The magnitude of the signal from the steel material obtained by an eddy current detector is affected by the distance between the end face of the detection coil and the surface of the steel material, so -
Quantitatively, the spacing is maintained to be equal to or less than the diameter of the detection coil. In addition, as a characteristic of the eddy current detector, the separation performance (resolution) when multiple defects exist is determined by the diameter of the detection coil. It is difficult to separate and detect.

(Problem to be solved by the invention) The heat-resistant eddy current flaw detection device proposed in Utility Model Application Publication No. 60-88261 is intended for flaw detection on steel materials of about 900"C. It is inappropriate for the purpose of measuring the oscillation mark depth of a continuous slab and feeding back this measurement result to the control of casting conditions.In addition, the pitch of the oscillation marks is l Omm.
In order to detect this, the diameter of the detection coil is l.
It is necessary that it is less than 0aun, therefore,
In order to obtain a sufficient signal from the steel material, the distance between the end face of the detection coil and the surface of the steel material must be 10 mm or less. For this reason as well, ensuring heat resistance is important. Furthermore, heat transfer from the steel material to the detector can be thought of as radiation or convection, but quantitatively the amount of heat transferred by radiation is larger, and the amount of radiant heat is proportional to the fourth power of the absolute temperature, so 900℃ and 1
At 300°C, there is a three-fold difference, and therefore it is necessary to focus on preventing temperature rise due to radiation from the detector.

(Means for Solving the Problem) The present invention blocks heat transfer from the steel material, and even at a high temperature of 1300°C, the distance between the end face of the detection coil and the steel surface is reduced to 10
The first invention provides a heat-resistant eddy current detector that can be used to detect defects or displacements in high-temperature steel materials. This is a heat-resistant eddy current detector that forms a water film between the surface of the current detector that faces the high-temperature steel material and the high-temperature steel material, and blows gas onto this water film.

A second invention is a heat-resistant eddy current detector according to claim (1), wherein cooling water is pumped into a housing that holds a detection coil of the eddy current detector.

A third aspect of the invention is the heat-resistant eddy current detector according to claim (2), wherein the housing on the surface facing the high-temperature steel material of the detection coil of the eddy current detector is made of a heat-resistant electrical insulating material.

(effect) Hereinafter, the effects of the present invention will be explained.

The reason why a water film is formed between the surface of the high-temperature eddy current detector facing the high-temperature steel material and the high-temperature steel material is as follows. In other words, the latent heat of vaporization of water is 540ca compared to the specific heat.
The evaporation of water has a large heat removal effect of 1/g. Utilizing this heat removal effect, a water film is formed between the eddy current detector and the surface of the steel material in order to prevent heat transfer from the steel material at a temperature of 1300° C. or higher. Further, the reason for blowing gas onto the water film is to prevent the water film from spreading, hold the water film directly below the eddy current detector, and enhance the effect of preventing heat transfer to the eddy current detector. The gas to be blown onto the water film is not particularly limited. Note that although there is volume expansion due to evaporation of the water film, changes in the distance between the eddy current detector and the steel surface can be ignored because the structure does not trap water vapor.

The reason why the cooling water is pumped into the housing that holds the detection coil of the eddy current detector is that by pumping the cooling water into the housing, there is a slight heat transfer through the water film and the electrical insulation material, and the temperature of the housing increases. This is to protect the detection coil from heat transfer from the housing. In this case, the detection coil is made of, for example, water-resistant and heat-resistant resin, and the surface in contact with the cooling water is finished smooth to eliminate pressure loss of the flowing water and improve cooling efficiency. Note that part or all of the resin may be replaced with a metal having good thermal conductivity.

The reason why we made the housing of the eddy current detector's detection coil, which faces the high-temperature steel material, from a heat-resistant material with high electrical insulation is as follows.
By using a heat-resistant electrical insulating material, unnecessary eddy currents are generated in the housing in front of the detection coil when the eddy current detector is in operation, and in order to transmit the signal from the steel material to the detection coil without damaging it. This is to block heat transfer from the

(Example) Examples of the present invention will be described below.

FIG. 2 is a schematic diagram of the heat-resistant eddy current detector of the present invention, in which 1 is a detection coil, 2 is a core, 3 is a resin, 4 is a coil support, 5 is a housing, 6 is an external cooling water inlet, and 7 is a water nozzle, 8 is a compressed air inlet, 9 is an air nozzle, IO is an internal cooling water inlet, 11 is an internal cooling water outlet, 12 is an internal cooling water passage, 13 is an electrical insulating plate, 14 is an insulating plate fixing plate, 15 is a screw, 16 is a continuous cast piece, 17 is a water film, and 18 is an O-ring.

Next, the structure of the heat-resistant eddy current detector will be explained.

The core 2 is inserted into the detection coil 1, and the detection coil 1 and the core 2 are integrally molded together with the coil support 4 from resin 3. In this way, the detection coil l is covered and fixed. The integrally molded detection coil 1, core 2, resin 3, and coil support 4 are fitted into a storage space in a housing 5 having a tapered surface, and the coil support 4 is fixed to the housing 5 with screws (not shown). be done.

An external cooling water port 6 and a compressed air port 8 are provided in the upper part of the housing 5, and a water nozzle 7 and an air nozzle 9 are provided in the lower part. The water nozzle 7 and the air nozzle 9 are installed at an angle of 45° with respect to the surface of the continuous slab 16 toward the center of the heat-resistant eddy current detector. Furthermore, an internal cooling water inlet lO and an internal cooling water outlet 11 are provided in the upper part of the housing 5. The internal cooling water inlet 10 and the internal cooling water outlet 11 are connected by an internal cooling water passage 12, and the internal cooling water passage 12 is connected from the internal cooling water population 10 to the housing 5.
Among them, they are provided in this order: between the detection coil 1 and the electrical insulating plate 13, inside the housing 5, and the internal cooling water outlet II. Therefore, the internal cooling water is pumped along the → mark in the figure.

An electrically insulating plate 13 made of silicon nitride is used on the front surface of the detection coil 1 facing the continuously cast piece 16, that is, on the surface of the housing 5 facing the continuous cast piece 16.

The electrical insulating plate 13 is connected to the screw 15 via the insulating plate fixing plate 14.
and is fixed to the housing 5. O-ring 18 prevents leakage of internal and external cooling water. In addition,
For the electrical insulating plate 13, it is also possible to use an insulator such as alumina instead of silicon nitride.

When measuring the depth of the oscillation mark on the continuous cast piece 16, the distance between the detection coil l and the continuous cast piece 16 is
In order to reliably detect the signal from 6, it was set to 10 mm. Directly below the eddy current detector, a water film 17 is formed with cooling water from a water nozzle 8 installed at an angle of 45° to the surface of the continuous slab 16 toward the center of the 11% current detector. Furthermore, by blowing air from the air nozzle 9, the water film 17 was moved directly below the eddy current detector to enhance the cooling effect. Note that the excess cooling water was allowed to flow out from the end of the continuous slab 16. The inside of the housing 5 and the detection coil 1 were cooled by pumping cooling water from an internal cooling water inlet 10 to an internal cooling water passage 12. Since the electrically insulating plate 13 of silicon nitride is used on the surface of the detection coil l facing the continuous cast piece 16,
The generation of unnecessary eddy currents could be prevented. In this way, it was possible to measure the depth of the oscillation mark of the continuous cast piece at 1300°C and monitor the cracks occurring at the corners of the continuous cast piece.

(Effects of the Invention) As explained above, the present invention cools the detection coil by forming a water film between the eddy current detector and the steel material, and further cools the detection coil by pumping cooling water into the inside of the detector. Since a heat-resistant electrical insulating plate is used in the housing on the side facing the steel material of the coil, it blocks heat transfer from the steel material, and even at high temperatures of 1300°C, the distance between the end face of the detection coil and the surface of the steel material can be maintained at 10 mm. By doing the following, we will be able to provide an excellent heat-resistant eddy current detector with high detection power.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of the heat-resistant eddy current detector of the present invention, and FIG.
The figures each show a conceptual diagram of a conventional heat-resistant flaw detection device. l detection coil, 2 core, 3 resin, 4 coil support, 5-housing, 6 external cooling water inlet, 7-water nozzle, 8-compressed air inlet, 9 air nozzle, 10-internal cooling water inlet, 11 - Internal cooling water outlet, 12 Internal cooling water passage, 13 Electrical insulating plate, 14 - Insulating plate fixing plate, 15... Screw, 16 Series of slabs, 17... Water film, 1
8-・Oring, 21. -・Detection coil, 22...
- Covering material, 23 - Housing, 24 - Cooling water jacket, 25 - Supply port, 26 - Drain port, 27 - Electrical insulation material, 28 - Steel material, a... - Cooling water direction arrow. Patent applicant: Kobe Steel, Ltd. Representative Patent attorney: Akira Kanemaru

Claims (3)

[Claims] (1) In a heat-resistant eddy current detector used to detect defects and displacement in high-temperature steel materials, a water film is formed between the surface of the heat-resistant eddy current detector facing the high-temperature steel material and the high-temperature steel material. A heat-resistant eddy current detector that forms a water film and blows gas onto this water film. (2) The heat-resistant eddy current detector according to claim 1, wherein cooling water is pumped into the housing that holds the detection coil of the eddy current detector. (3) The heat-resistant eddy current detector according to claim (2), wherein the housing on the surface of the detection coil of the eddy current detector that faces the high-temperature steel material is made of a heat-resistant electrical insulating material.