DE8519599U1 - Probe for high temperature inspection of surface defects of metallic bodies - Google Patents

Description

Probe for checking surface defects of metallic bodies at high temperatures

The invention relates to a probe which enables the measurement of surface defects of metallic bodies at high temperatures in general and in particular of the products of the continuous casting process (slabs, blooms or semi-finished products and billets), which, according to the state of the art, is an important step for direct rolling, which consists in rolling continuously cast products without first cooling them.

Methods for solving the problem are known to those skilled in the art, based on the use of a sensor (a coil) that operates on the Foucault current or eddy current principle or the electromagnetic resonance principle.

When the measurements are carried out, the sensor must be kept at a temperature of 60 to 70°C and sufficiently close to the surface to be examined to ensure that it remains within the limits of sensitivity while scanning the slabs lengthwise and widthwise, the temperature of which may exceed 1000 ⁰ C. A device is therefore necessary which protects the probe and enables it to operate under these conditions.

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According to the invention, it is a container for the sensor/ which consists of the following sensibly assembled elements:

- a frame that holds the different parts together and creates connections for operating the probe;

- a protective housing (containing the sensor and creating an environment in which a cooling fluid circulates) with a surface facing the surface to be examined and acting as a window through which the magnetic flux passes from and to the sensor and consisting of at least one sheet of heat-resistant dielectric material, the thickness of which is such that the distance between the probe and the surface under examination is kept within the sensitivity limits of the probe;

- a system for supplying and returning a fluid, the purpose of which is to maintain the probe at a temperature not exceeding 60-70 ⁰ C.

Preferably, at least two sheets of dielectric material are used for the side facing the workpiece to be examined: these sheets are given a mirror finish on the outward-facing side; they are kept at a distance from each other so that an air gap is created.

The only figure shows a practical example of an embodiment, which, due to its original structural solution, has led to surprisingly satisfactory results.

It comprises a frame 1 made of stainless steel; a tubular chamber made of refractory material 2, which forms the outer side heat grid housing; an axial tube made of stainless steel for the passage of cooling air and

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connecting wires; an inner frame made of heat-resistant dielectric material (Teflon) connected to the axial tube and made up of two parts: the upper part (4) with an inverted tapered hole in the middle to facilitate the connection to the axial tube, through which air passes and then tapers on the outside towards the bottom, so that after assembly by screwing against the lower part 5, a seat remains that holds the sensor (circuit 6 + coil 7 + ferrite cores); in the upper part of the inner frame there are two holes: one for the connecting wires of a thermocouple 9 and one for the circuit connecting wires 10; two tracks of heat-resistant dielectric material (quartz) with the reference numeral 11 are provided, which are inserted into the side

which rests against the workpiece to be examined and forms a window through which the magnetic flux passes from and to the coil, so that the maximum distance between the probe and the surface to be examined is 22 mm: These tracks have a mirror finish on the outward-facing side and have a stepped recess on the mating surfaces so that an air gap 12 is formed. The thickness of the two overlapping tracks is 10 mm.

A probe was therefore proposed for controlling surface defects of metallic bodies at high temperatures, in particular of continuously cast products. This consists of a device which enables a sensor, for example a coil operating on the eddy current or magnetic resonance principle, to be positioned at a distance from the workpiece being tested within the sensitivity limits.

Claims (2)

C 3553 Lw/GE - Case 151
Protection claims A probe for the high-temperature control of surface defects in metallic bodies based on the Foucault current or eddy current principle or on the electromagnetic resonance principle, with cooling of the sensor structures, a frame holding the various parts together and having connections for actuating the probe, characterized in that, in particular for products cast in continuous casting, a supply and discharge structure;3) for a fluid which keeps the probe at a temperature of not more than 60-70 ⁰ C is provided; a protective housing (4; 5) is provided which contains the sensor (6, 7, 8) and creates an environment ⁱⁿ which a cooling fluid circulates, the cooling fluid is forcibly passed under the sensor (6; 7), the side facing the workpiece to be examined, which is designed as a window in a manner known per se and which allows the magnetic flux to pass from and to the sensor (6, 7), consists of at least one disk of heat-resistant dielectric material. 2. Probe according to claim 1, characterized in that the outer frame (1) is made of metal; the outer side protective housing is made of fireproof Material (2) consists; " the inner frame is made of heat-resistant dielectric material (4; 5; 11) which is axially connected to the tube through which the cooling fluid is guided (3) and consists of two parts (4; 5), the upper part (4) of which has a hole tapering in the middle to facilitate the connection to the axial tube (3) through which the cooling fluid passes and on the outside -2- side is tapered towards the bottom in such a way that after assembly by screwing against the lower part (5) a seat is formed which retains the sensor; that in the upper part of the inner frame two holes are provided for passing the circuit wires; that the window through which the magnetic flux passes from and to the sensor (6) is formed from a number of discs of refractory dielectric material (11) which allows the electromagnetic waves to pass through, the discs of the window having a mirror finish on the outside and being kept at a distance from one another and the cooling fluid flow between sensor (6) and window (11; 12) is positively guided. 20 25 30 35 iH <<·