GB1562228A - Method of detecting marking and removing surface cracks from the surface of a metal workpiece - Google Patents

Description

(54) METHOD OF DETECTING MARKING AND REMOVING SURFACE CRACKS FROM THE SURFACE OF A METAL WORKPIECE (71) We, CENTRO-MASKIN GOTE BORG AB, a Swedish joint-stock company, of 2 Dagjämningsgatan, 5402 56 Gothenburg, Sweden, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a method of detecting, marking and removing surface cracks from the surface of a metal workpiece.

It is known to remove cracks in the surface layer of steel workpieces by spot grinding prior to the processing of the workpiece, for example by rolling, in order to prevent the transfer of cracks into the processed workpiece.

The positions of surface cracks in steel workpieces to be ground are detected in different ways. The workpiece can be inspected before the grinding is commenced, and the cracks marked by chalk or the like. The depth of possible cracks cannot be determined by a superficial inspection and therefore the operator of the grinding tool must be able to observe the crack all the time until its complete elimination. Narrow cracks are sometimes very hard to detect with the naked eye, which involves the risk that the crack will not be eliminated completely and that much material will be cut unnecessarily.

According to the present invention, there is provided a method of detecting, marking and removing surface cracks from the surface of a metal workpiece, which method comprises the steps of placing the workpiece on a grinding table which moves the workpiece under inspection of an operator; detecting cracks on the surface of the workpiece; marking the cracks with ink which has a viscosity sufficiently low so that it entirely fills each crack, the ink having a high heat resistance to enable it to withstand heat developed during grinding, and being an easily seen colour or fluorescent to facilitate the observation of the ink-filled cracks; and thereupon eliminating the detected and marked cracks by grinding the surface of the workpiece until the ink is no longer visible, and the marked cracks are therefore entirely eliminated.

An ink scraper may be used to remove all excess ink from the surface of the steel workpiece, in order to make the ink-filled crack appear in a clear manner.

A spray-gun for applying ink to the steel workpiece with surface cracks may preferably be attached to a control and inspection cabin and be operated from the interior thereof. The ink-spraying may also take place at a separate examination station outside the grinding machine.

The steel workpieces, from which surface cracks are to be removed, are most so-called billets or slabs. As these may have a length of 9m and more, the inspection and marking is carried out in a step before the grinding operation is commenced.

The invention is described in greater detail in the following, by way of example and with reference to an embodiment shown.

Figure 1 is a lateral view of a grinding machine where the method according to the invention is utilized, and Figure 2 is a view from above, partly as a section of a portion of the grinding machine according to Figure 1.

The grinding machine shown in Figure 1 which is not a part of the invention, is described only in a summarizing manner.

The control and inspection cabin 1 is located near the grinding wheel 2 and near the billet or slab, and is provided with windows 12, through which the billet or slab 3 moving on the grinding table 4 past the cabin can be inspected. 5 designates drive means for the grinding table 4, and 6 designates a device for supplying the drive motor of the grinding wheel with cooling air. A device 11 on the grinding table 4 turns the billet or slab through one quarter of a revolution at a time, so that the billet or slab can be inspected on four sides. Said device 11 for turning the billet or slab is previously known and its mode of operation, therefore, is not described here.

In the embodiment shown, the marking of surface cracks in the billet or slab is effected from the control and inspection cabin 1.

The operator has a view of the billet or slab 3 through the window 12 and can detect possible surface cracks. Each crack is marked by ink, which in the embodiment shown is applied by means of a spray-gun 7 operated from the cabin 1. The spray-gun comprises an oblong mouth-pipe 13 which passes through the cabin 1 via a pivot means 8, which renders possible movement of the spray-gun 7 and its mouth-pipe 13 so that the nozzle 14 located at the end of the mouth-pipe can be moved along the entire extent of the crack while the ink is being sprayed. The nozzle 14 is preferably directed substantially perpendicular to the surface of the steel billet or slab 3 in order to facilitate the penetration of the ink into the crack and to assist in filling it completely.

Excess ink is removed from the surface of the billet or slab by means of an ink-scraper 9, which in the embodiment shown is actuated hydraulically or pneumatically.

The ink-scraper 9 comprises a scraping portion, which in the actuated position abuts the surface of the billet or slab 3 with an adjustable pressure. The ink-scraper may, in one embodiment, be movable along the billet or slab 3 by means of a suitable moving device (not shown), which may be operated mechanically, electrically, hydraulically or pneumatically. The ink-scraper may also be stationary, i.e. not movable along the surface of the billet or slab. In such an embodiment of the ink-scraper, the ink is removed by the billet or slab on the grinding table 4 passing beneath the ink-scraper.

First one side of the billet or slab 3 is inspected and marked along its entire length, whereafter the cracks marked on this side are subjected to grinding. The surface layer cracks in steel billets or slabs 3 mostly extend in an axial direction, and the operator, therefore, causes the grinding table 4 to carry out a reciprocating movement along the extent of the crack while simultaneously performing grinding.

The cracks being filled with ink, the operator can rapidly observe the complete elimination of the cracks and does not have to move the grinding table 4 with the billet or slab 3 slowly past the cabin 1 to be able to check whether the cracks have been eliminated completely. Checks of this kind were necessary previously. With grinding machines of the kind described here, the bill or slab is advanced at a speed of up to 60 m/min or higher. The slow movement of the grinding table previously necessary resulted in a substantially reduced capacity of the grinding machine.

In the embodiment shown in the cabin 1 is located to the sides of the grinding wheel 2 in view of the risk that a bursting of the grinding wheel may occur.

Due to the fact that the spray-gun for ink-marking the cracks as well as the ink scraper are controlled from the cabin interior, the cabin can be designed as a closed unit and provides a better work environment with respect to noise and dust particles.

The embodiment shown and described can be modified and varied within the scope of the appended claims. The colour of the ink used for marking the cracks, for example, may be a contrasting colour to that of the billet or slab surface. The spray-gun may be stationary in relation to the axial extension of the billet or slab, and the spraying may take place while the grinding table is being moved. The ink scraper may be angular or have a plough-shape relative to the bill or slab surface and thereby have better removing properties. It may also consist of two scrapers, one on each side of the spray-gun.

WHAT WE CLAIM IS: 1. A method of detecting, marking and removing surface cracks from the surface of a metal workpiece, which method comprises the steps of placing the workpiece on a grinding table which moves the workpiece under inspection of an operator; detecting cracks on the surface of the workpiece; marking the cracks with ink which has a viscosity sufficiently low so that it entirely fills each crack, the ink having a high heat resistance to enable it to withstand heat developed during grinding, and being an easily seen colour or fluorescent to facilitate the observation of the ink-filled cracks; and thereupon eliminating the detected and marked cracks by grinding the surface of the workpiece until the ink is no longer visible, and the marked cracks are therefore entirely eliminated.

2. A method as claimed in claim 1, wherein the ink is applied to the workpiece surface by spraying, and any excess ink is scraped off the workpiece prior to grinding.

3. A method of detecting, marking and removing surface cracks from the surface of a metal workpiece substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. the billet or slab through one quarter of a revolution at a time, so that the billet or slab can be inspected on four sides. Said device 11 for turning the billet or slab is previously known and its mode of operation, therefore, is not described here. In the embodiment shown, the marking of surface cracks in the billet or slab is effected from the control and inspection cabin 1. The operator has a view of the billet or slab 3 through the window 12 and can detect possible surface cracks. Each crack is marked by ink, which in the embodiment shown is applied by means of a spray-gun 7 operated from the cabin 1. The spray-gun comprises an oblong mouth-pipe 13 which passes through the cabin 1 via a pivot means 8, which renders possible movement of the spray-gun 7 and its mouth-pipe 13 so that the nozzle 14 located at the end of the mouth-pipe can be moved along the entire extent of the crack while the ink is being sprayed. The nozzle 14 is preferably directed substantially perpendicular to the surface of the steel billet or slab 3 in order to facilitate the penetration of the ink into the crack and to assist in filling it completely. Excess ink is removed from the surface of the billet or slab by means of an ink-scraper 9, which in the embodiment shown is actuated hydraulically or pneumatically. The ink-scraper 9 comprises a scraping portion, which in the actuated position abuts the surface of the billet or slab 3 with an adjustable pressure. The ink-scraper may, in one embodiment, be movable along the billet or slab 3 by means of a suitable moving device (not shown), which may be operated mechanically, electrically, hydraulically or pneumatically. The ink-scraper may also be stationary, i.e. not movable along the surface of the billet or slab. In such an embodiment of the ink-scraper, the ink is removed by the billet or slab on the grinding table 4 passing beneath the ink-scraper. First one side of the billet or slab 3 is inspected and marked along its entire length, whereafter the cracks marked on this side are subjected to grinding. The surface layer cracks in steel billets or slabs 3 mostly extend in an axial direction, and the operator, therefore, causes the grinding table 4 to carry out a reciprocating movement along the extent of the crack while simultaneously performing grinding. The cracks being filled with ink, the operator can rapidly observe the complete elimination of the cracks and does not have to move the grinding table 4 with the billet or slab 3 slowly past the cabin 1 to be able to check whether the cracks have been eliminated completely. Checks of this kind were necessary previously. With grinding machines of the kind described here, the bill or slab is advanced at a speed of up to 60 m/min or higher. The slow movement of the grinding table previously necessary resulted in a substantially reduced capacity of the grinding machine. In the embodiment shown in the cabin 1 is located to the sides of the grinding wheel 2 in view of the risk that a bursting of the grinding wheel may occur. Due to the fact that the spray-gun for ink-marking the cracks as well as the ink scraper are controlled from the cabin interior, the cabin can be designed as a closed unit and provides a better work environment with respect to noise and dust particles. The embodiment shown and described can be modified and varied within the scope of the appended claims. The colour of the ink used for marking the cracks, for example, may be a contrasting colour to that of the billet or slab surface. The spray-gun may be stationary in relation to the axial extension of the billet or slab, and the spraying may take place while the grinding table is being moved. The ink scraper may be angular or have a plough-shape relative to the bill or slab surface and thereby have better removing properties. It may also consist of two scrapers, one on each side of the spray-gun. WHAT WE CLAIM IS:

1. A method of detecting, marking and removing surface cracks from the surface of a metal workpiece, which method comprises the steps of placing the workpiece on a grinding table which moves the workpiece under inspection of an operator; detecting cracks on the surface of the workpiece; marking the cracks with ink which has a viscosity sufficiently low so that it entirely fills each crack, the ink having a high heat resistance to enable it to withstand heat developed during grinding, and being an easily seen colour or fluorescent to facilitate the observation of the ink-filled cracks; and thereupon eliminating the detected and marked cracks by grinding the surface of the workpiece until the ink is no longer visible, and the marked cracks are therefore entirely eliminated.

2. A method as claimed in claim 1, wherein the ink is applied to the workpiece surface by spraying, and any excess ink is scraped off the workpiece prior to grinding.

3. A method of detecting, marking and removing surface cracks from the surface of a metal workpiece substantially as herein described with reference to the accompanying drawings.