ZA200200796B - Installation for continuously monitoring ferrous products derived from casting. - Google Patents

Abstract

The invention concerns an installation (1) for continuously monitoring ferrous products derived from casting, comprising a controlled gas torch (20) transversely mobile to the ferrous product (B), said gas torch including a visual inspection device enabling direct observation of a zone of the surface in the sampling bath. The invention is characterised in that it further comprises a device for analysing images and identifying defects appearing in the field of vision of the visual inspection device. Said monitoring installation can be adapted on oxyacetylene cutting plants so as to make the oxyacetylene cutting completely automatic. It can be followed by a scarfing installation automatically cutting along the detected defects.

Description

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The present invention relates to an installation for continuously monitoring iron and steel castings.

Iron and steel castings such as slabs, blooms, or steel billets, for example, and regardless of whether they are obtained by casting ingots or by continuous casting, are generally transformed into flat or long products by being hot-rolled. The person skilled in the art generally seeks to extract maximum penefit from the heat of & recently-cast casing when performing such rolling operations.

Nevertheless, in the vicinity of their surfaces, such castings can present defects that are not necessarily visible, such as cracks, seams, biow holies, cas inclusions, etc. and that run the risk of remaining in the rclled products, or even of becoming amplified and thus of leading to the products being rejected, not to mention any possible damage to the surfaces cf the cylinders in the rolling mill.

Theat is why it is generally necessary, prior to rolling, to examine castings to determine whether they are suitable for being rolled directly or whether they need prior treatment to eliminate or repair the defects they present.

In traditicnal techniques, examination to detect defects requires prior cooling of the iron or steel casting. i

To illustrate the state of the art, reference can be made to document EP-A—0 512 972 which describes a method of monitoring butt welds between metal strips, in which method a temperature map of the weld and the surrounding zone is drawn up, and the measured temperature profiles are compared with at least one reference temperature profile. That method of monitoring welds is thus based on a temperature mapping technique.

About ten years ago, a technique was developed for observing a molten bath produced by a blowtorch while avoiding exposure of the material under visual observation to splashing and smoke from the surroundings.

Thus, document EP-A—-0 336 807 in the name of the

Applicant describes a blowtorch with an integrated visual observation system. Such a blowtorch comprises a body containing an optical system for visual observation placed inside the central oxygen feed duct, the surface area of the main orifice corresponding substantially to that embraced by the viewing angle of the objective lens of the observation system.

Although that technique has produced considerable advances over prior arrangements, the human eye remains necessary for performing visual observation of the zone of the deseaming bath, and the use of cassettes for recording purposes requires additional management that is difficult for the user to implement.

In general, defects are analyzed almost always a posteriori on iron and steel products such as slabs after they have been cut up and cooled down. Consequently, although the presence of defects can indeed be detected, it is often by then too late to act on the casting line in order to perform an appropriate adjustment.

To illustrate the state of the art, reference can be made to the article entitled "Enhancement of penetrant- inspection images", from NASA Tech Brief, February 1992, page 189, Springfield VA (USA). That article describes a method of recognizing defects in a welding bead by analyzing images of the defects illuminated by a source of ultraviolet (UV) light for revealing fluorescent particles deposited on the defects. That constitutes a non-destructive inspection technique suitable for use only in a metallurgical analysis laboratory, and it is unsuitable for transposing to monitoring continuous casting because of the need to illuminate the defects with a UV source and the need to use a camera which, to say the least, would be hindered by the smoke given off by the blowtorch, and would quite possibly completely unusable in the vicinity of continuous castings.

Finally, the technological background is illustrated by document US—A—1 728 972 which describes a traditional blowtorch having no visual observation system and mounted on moving equipment.

Tt can thus be seen that there is a major need for equipment capable of monitoring iron and steel castings directly and continuously.

A specific object of the invention is to resolve that problem by designing such an installation for continuous monitoring that makes automatic processing possible, thus providing the possibility of acting on a casting line so as to avoid the stream of metal being diverted, to avoid intermediate storage with associated handling, and to avoid producing defective products.

Another object of the invention is to design a continuous monitoring installation which is also compatible with techniques for automatically deseaming or oxygen cutting.

According to the invention, this problem is resolved by an installation for continuously monitoring iron and steel castings, the installation comprising a gas blowtorch placed facing a face of the optionally traveling casting to generate a monitor bath therein, said torch being movable under control transversely to the travel direction and comprising a body having a central oxygen feed duct having a visual observation system arranged therein enabling a zone of said face concerned by the monitor bath to be observed directly; and apparatus for analyzing images and automatically recognizing any defects that appear in the field of view of the visual observation system.

Automatic recognition of defects thus makes it possible for a complete map of the iron or steel casting to be drawn up automatically in the context of the

4 oo installation being used directly at the outlet from a casting line. This makes it possible to automate the entire monitoring installation with monitoring being performed continuously on a hot casting.

Provision can be made for the continuous monitoring installation to comprise a plurality of gas torches each placed facing a respective face of the iron or steel casting so as to enable a plurality of faces and edges of said casting to be inspected simultaneously at a plurality of locations, if necessary. This makes it possible in particular to inspect the top and bottom faces simultaneously together with the side faces of a cast slab or billet.

Preferably, the apparatus for analyzing images and for recognizing defects comprises means for analyzing differences of shade over the inspected area so as to detect the presence of a defect, means for analyzing dimensional parameters of a located defect, and means for comparing said parameters with preestablished parameters in order to identify the type of defect in question. In particular, the dimensional parameters analyzed are selected from the group comprising: perimeter profile; area; position of barycenter; and depth of defect; together with any measurement necessary for obtaining better definition.

This provides analysis of the characteristics of the detected defect that is very fine and accurate, thus helping to understand the causes that have led to such defects being created, and consequently helping to take action on the casting line.

In an advantageous embodiment, the continuous monitoring installation is followed by a deseaming installation, the action of the deseaming installation being controlled as a function of any defect previously detected and recognized by the monitoring installation, for the purpose of automatically deseaming the zone containing said defect.

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In another embodiment, the gas blowtorch fitted with the visual observation system is an oxygen cutting torch.

This makes it possible to view a groove of cut and any defects therein for the purpose of automatically regulating cutting parameters.

In a variant, the gas blowtorch fitted with the visual observation system is a deseaming torch. This makes it possible to regulate said torch automatically as a function of the disappearance of defects. It is thus possible to implement a working unit that is extremely flexible, enabling a deseaming and/or monitoring operation to be performed in fully automatic manner.

According to another advantageous characteristic, the visual observation system comprises a camera connected to at least one optical fiber passing through the body of the torch. Naturally, in some situations, for example when oxygen cutting very thick plates, it is possible to omit such a camera insofar as a single optical fiber suffices to monitor the narrow field under inspection which is restricted to the width of the line of cut.

Also preferably, the apparatus for analyzing images and recognizing defects is connected to a processor unit comprising a computer and a printer.

Advantageously, the apparatus for analyzing images and recognizing defects is connected to the casting controller to enable action to be taken on casting parameters as a function of any defects that are detected and recognized. Such action performed directly on the casting line makes it possible very quickly to counter the phenomena which have given rise to the detected defects. This possibility for taking action constitutes a considerable practical advantage over conventional observation techniques performed on cold products which result in any action taken on a casting line being very late.

Other characteristics and advantages of the invention will appear more clearly on reading the following description and on observing the accompanying drawings relating to particular embodiments, in which: + Figure 1 is a perspective view showing an installation for continuous monitoring of a single face in accordance with the invention and acting on a slab which in this case is moving; - Figure 2 is a diagrammatic plan view of the

Figure 1 installation; - Figure 3 is a fragmentary view showing more clearly the structure of the blowtorch together with its visual observation system; - Figure 4 is an end view of the outlet zone from the blowtorch body; - Figure 5 is a diagram showing a variant of the preceding monitoring installation, in which two monitor blowtorches are used to inspect two opposite faces of an iron or steel casting; 20 . Figure 6 is a plan view on a larger scale showing the monitor bath and the zone of the field of view observed by the system fitted to the blowtorch of the monitoring installation; . Figure 7 is a diagrammatic view of the field of view zone showing three typical defects that have been located and recognized, while Figure 8 shows how the various gauge lines are organized to determine certain dimensional parameters of defects that have been located; and - Figure 9 is a diagrammatic view of the continuous monitoring installation of the invention in association with a processor unit.

Figures 1 and 2 show a continuous monitoring installation 1 of the invention for inspecting one face of an iron or steel casting, e.g. a slab or a billet, directly after it has been cast. This figure shows a slab B moving on rollers R, however the invention is not limited to monitoring a moving casting, and it applies equally well to monitoring a stationary casting. The monitoring installation 1 has a stand 2 surmounted by a turret 3 that can be turned about a vertical axis 3.1 and that is capable of turning through 360° about said axis.

The turret 3 caries a first cantilevered arm 4 which is connected to a second arm 5 via a hinge 6 about a vertical axis 6.1. The angle between the arms 4 and 5 is determined by a controlled actuator which is constituted in this case by a hydraulic cylinder 7 (in a variant, the cylinder could be replaced by a hydraulic motor mounted coaxially about the hinge). The arm 5 is terminated by a hinge 8 about a vertical axis 8.1 and supporting a fork 9 having a torch support 10 hinged thereto. This hinge is about a horizontal axis 10.1, and the fork 9 can turn through a range of at least 180° about the vertical axis 8.1

A gas blowtorch 20 is secured to the support 10, with the axis of said torch being inclined in this case relative to the vertical, e.g. at an angle of 30°. The gas torch 20 serves to provide a "monitor" bath referenced 100 in the face Bl of the slab B. The visual observation system which is included in the gas torch 20 serves specifically to inspect a zone of the monitor bath 100 in order to detect and recognize any defects that are to be found therein.

The line of impact of the flame from the gas torch 20 on the face Bl of the slab B is shown as following a sinusoidal path T. Naturally, this path is fully configurable as a function of requirements. The gas torch 20 which is placed facing the face Bl of the traveling casting B in order to generate the monitor bath 100 therein can be moved in controlled manner transversely to the travel direction (reference 200) .

The torch 20 is moved by controlling a motor for driving the turret 3 about its axis 3.1, by controlling the actuator 7, and by controlling the rotation mechanism included in the hinge 8 about the vertical axis 8.1. The various angular parameters can be varied in application of a predetermined relationship so as to fix a desired path for the point of impact on the face of the casting under inspection. Since the travel speed of the casting is known, and since the exact position in three dimensions of the gas torch 20 is also known, it is possible to determine the exact location of the monitor bath 100 on the inspected face. Thus, when a defect is detected on said face by means of the visual observation system and associated apparatus for image analysis and automatic recognition of defects, it is possible to determine exactly the location of the defect, and consequently to control automatic removal of the defect by deseaming and to deliver accurate information in time and at the right moment. This also makes it possible to help understanding how the defect was created and to draw up a classification of manufactured products.

Figures 3 and 4 show the structure of the gas blowtorch 20 more clearly. There can be seen the fork 9 from which the torch support 10 is itself supported together with the gas torch 20. The support block 10 which is hinged about the axis 10.1 is extended by feed and cooling pipes 11 and 12 leading to a torch body which is constituted in this case by two complementary blocks 21 and 22 assembled together by a ring 26. The torch body 21, 22 presents a central oxygen feed duct 23 having a visual observation system 15 located therein, represented in this case by a set of optical fibers. The central oxygen feed duct 23 is extended downstream by a nozzle 24 which opens out through an outlet orifice 25.

The upstream portion 21 of the torch body is fitted with means 27 for cooling the torch body. It also has grooves 28, 29 serving to feed oxygen and gas respectively via associated axial channels passing through the downstream portion 22 of the torch, said gas being natural gas, for example. A disk 30 is provided at the outlet from the torch body, and Figure 4 shows clearly the plurality of outlet orifices: thus, there can be seen around the central orifice 25 (with the end of the optical fiber 15 behind it), orifices 31 which correspond to heating jets, and a few orifices 32 which represent the option of blowing out a priming powder, e.g. iron, particularly for the purpose of welding stainless steel slabs. Figure 3 also shows the presence of a camera 16 associated with the optical fibers 15 and integrated in the support 10 for the torch body.

For fuller understanding of the structure of such a gas blowtorch with an integrated visual observation system, reference can usefully be made to above-cited document EP—-A—0 336 807 which is incorporated herein by reference.

The visual observation system 15, 16 thus makes it possible to observe directly a zone of the corresponding face of the casting where the monitor bath 100 is created. As described in detail below, the monitoring installation also has apparatus for analyzing images and automatically recognizing any defects that appear in the field of view of the visual observation system 15, 16.

Naturally, other means could be used for achieving controlled displacement of the gas torch 20. Also naturally, the installation could further comprise a plurality of gas torches 20 each placed facing a corresponding face of the iron or steel casting, so as to enable a plurality of faces and edges of the casting to be inspected simultaneously.

Figure 5 thus illustrates a different support for the gas torch 20, implemented by means of a gantry 40 having a carriage 41 running therealong. Another gas torch 20 mounted on a carriage 22 travels vertically beneath the first gas torch, underneath the traveling casting B. The impact zones 100 of the two gas torches 20 on the opposite faces Bl and B2 of the casting B remain vertically in register, by ensuring that the two carriages 41 and 42 move perfectly synchronously.

In any event, the monitoring installation can be followed by a manual or an automatic deseaming installation. Automatic deseaming is clearly most advantageous since the action of the deseaming installation can be controlled fully as a function of the defects previously detected and recognized by the monitoring installation (variant not shown).

There follows a description in greater detail of the way in which any defects presented by the inspected faces of the traveling casting are analyzed and recognized.

Figure 6 shows the substantially elliptical zone of the monitor bath 100 on the inspected face of the casting. This monitor bath 100 is naturally moving continuously in a direction which corresponds substantially to the major axis of the ellipse. A portion referenced 101 of the monitor bath 100 corresponds to the field of view of the visual observation system integrated in the gas torch 20. In practice, this field of view is defined by a circle having a diameter of about 30 millimeters (mm) to about 50 mm. As will easily be understood, the end portion of the monitor bath lying in the circle corresponds to the deepest zone of the bath.

Figure 6 also shows defects D,, D,, and D, of very different shapes and sizes. Specifically, relatively large defect D, represents a macroinclusion, whereas narrow and elongate defect D, represents a seam, and substantially circular defect D, of small diameter represents a microinclusion. It is these specific different shapes that are used to identify and recognize defects viewed by the observation system.

Automatic apparatus for analyzing images and recognizing defects that appear in the field of view 101 of the visual observation system 15, 16 is used for this purpose.

With reference to Figures 7 and 8, the above- mentioned defects D,, D,, and D,; can again be seen in the zone 101. References G,, G,, and G, designate the barycenters or centers of gravity of the three defect zones D,, D,, and D,;, and each point G;, Gj, and G, is identified by its coordinates (X;,Y;), (X;,Y,), and (X3,Y5)

More precisely, the apparatus for analyzing images and recognizing defects includes means for analyzing differences of shade over the inspected area so as to detect the presence of a defect, means for analyzing dimensional parameters of a located defect, and means for comparing said parameters with preestablished parameters in order to identify the type of defect in question.

To analyze the various shades over an inspected area, it is possible to select a color shade or gray levels by using a triple-CCD system or a mono-CCD system respectively. The triple system is more accurate than the mono system, but it is also more expensive.

The dimensional parameters analyzed are preferably selected from the group comprising: perimeter profile; area; position of the barycenter (or center of gravity); and depth of the defect. Gauge lines are then used which represent measurements along predetermined axes. This is better understood with reference to Figure 8: . for the defect D, which is a macroinclusion in the form of a comet's tail, there can be seen three gauge lines L,,, L;,, and L,;. As is easy to understand, this type of defect applies only when the dimensions along all three gauge lines are large; . for defect D,, two gauge lines L,;, L,, are used which correspond to a large difference in two perpendicular directions: this shape makes it possible immediately to recognize a seam type defect; and 35 . for the defect D,, two gauge lines L,;; and L;, on substantially perpendicular axes are used making it possible to detect that distances are short along both lines, and thus to recognize a microinclusion.

Naturally, the invention is not limited to the above-specified types of defect, and it is possible to imagine characterizing a multitude of defects such as blowholes, etc., which could be defined by particular parameters relating to shape, surface area, and size.

Figure 9 shows the continuous monitoring installation as described above in association with a processor unit and a casting controller.

This diagrammatic figure shows an image analyzer 60 which receives data x, V, t from the torch support 10 corresponding respectively to the (transverse) abscissa of the torch, to its travel speed, and to the instant under consideration. The image analyzer 60 also receives visual data corresponding to each of the defects D;, i.e. the coordinates X;, Y; of their barycenters, and also the various dimensions along the gauge lines L;;, and more generally any other information that could improve defect definition.

The image analyzer 60 is associated with a recognition system, and it is connected to a processor unit 70 which comprises a computer 71 and a printer 72.

The memory of the computer 71 serves in particular to establish a supply of identity cards for the various kinds of defect that are to be recognized, as previously determined.

In this case, the image analyzer 60 also communicates with the casting controller 80 which controls continuous casting. The fact that the image analyzer and defect recognizer apparatus is connected to the casting controller 80 provides a considerable advantage in practice since this makes it possible to take action quickly and directly on casting parameters as a function of any defects that are detected and recognized. Thus, it becomes possible without any human intervention to send a control signal to the casting controller instructing it to modify certain parameters of the continuous casting operation so as to stop generating the defects which have just been detected and recognized.

This constitutes considerable progress over conventional analysis performed a posteriori on a cold product.

In a particular implementation of the invention, the gas torch 20 fitted to the visual observation system can be an oxygen cutting torch which is thus regulated automatically. Full automatization is obtained by servo- controlling the cutting parameters (speed, pressure, etc. ...) and also by observing the groove of cut.

In another possibility, the gas torch 20 fitted with the visual observation system can be a deseaming torch which is then regulated automatically as a function of any detected and recognized defect.

The invention is not limited to the embodiment described above, but on the contrary covers any variant using equivalent means to reproduce the essential characteristics specified above.

Claims (1)

1. CLAIMS 1/ An installation for continuously monitoring iron and steel castings, the installation being characterized in that it comprises:

   . a gas blowtorch placed facing a face of a traveling casting to generate a monitor bath therein, said torch being movable under control transversely to the travel direction and comprising a body having a central oxygen feed duct having a visual observation system arranged therein enabling a zone of said face concerned by the monitor bath to be observed directly; and

   . apparatus for analyzing images and automatically recognizing any defects that appear in the field of view of the visual observation system. 2/ A continuous monitoring installation according to claim 1, characterized in that it has a plurality of gas torches each placed facing a respective face of the iron or steel casting so as to enable a plurality of faces and edges of said casting to be inspected simultaneously at a plurality of locations, if necessary. 3/ A continuous monitoring installation according to claim 1 or claim 2, characterized in that the apparatus for analyzing images and for recognizing defects comprises means for analyzing differences of shade over the inspected area so as to detect the presence of a defect, means for analyzing dimensional parameters of a located defect, and means for comparing said parameters with preestablished parameters in order to identify the type of defect in question. 4/ A continuous monitoring installation according to claim 3, characterized in that the dimensional parameters analyzed are selected from the group comprising: Amended 17 March 2003

   . hl perimeter profile; area; position of barycenter; and depth of defect. 5/ A continuous monitoring installation according to any one of claims 1 to 4, characterized in that it is followed by a deseaming installation, the action of the deseaming installation being controlled as a function of any defect previously detected and recognized by the monitoring installation, for the purpose of automatically deseaming the zone containing said defect. 6/ A continuous monitoring installation according to any one

   . of claims 1 to 4, characterized in that the gas torch fitted with the visual observation system is an oxygen cutting torch, which torch is regulated automatically. 7/ A continuous monitoring installation according to any one of claims 1 to 4, characterized in that the gas torch fitted with the visual observation system is a deseaming torch, which is regulated automatically. 8/ A continuous monitoring installation according to any one of claims 1 to 7, characterized in that the visual observation system comprises a camera connected to at least one optical fiber passing through the body of the torch. 9/ A continuous monitoring installation according to any one of claims 1 to 8, characterized in that the apparatus for analyzing images and recognizing defects is connected to a processor unit comprising a computer and a printer. 10/ A continuous monitoring installation according to any one of claims 1 to 9, characterized in that the apparatus for analyzing images and recognizing defects is Amended 17 March 2003 connected to the casting controller to enable action to be taken on casting parameters as a function of any defects that are detected and recognized.

   ’ 11/ An installation for continuously monitoring iron and steel castings substantially as herein described with reference to the illustrated embodiments.

   Amended 17 March 2003