JPS6045367B2 - Hot flaw detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot flaw detection method, and more particularly to a hot flaw detection method that enables direct rolling.

In recent years, energy conservation has become a major issue due to the depletion of oil resources.

The steel industry, which consumes a large amount of thermal energy, is also trying to implement direct rolling of hot steel materials as an energy-saving measure. However, in the conventional hot rolling process, since hot flaw detection is difficult, the heated steel billet is cooled first and then visually inspected, and the flaws are removed before being reheated and rolled. There was a problem that a large amount of thermal energy was required for reheating. Therefore, if hot flaw detection and defect removal are possible, the energy required for reheating can be saved, but this hot flaw detection method has not yet been established, although various proposals have been made. Not put into practical use. For example, hot flaw detection devices that use television cameras, infrared cameras, radiation thermometers, etc. have been proposed, but since all of them perform hot flaw detection, scales and other formation irregularities that occur on hot chips can cause defects in the flaws. It was difficult to detect defects because the defects were hidden or it was difficult to distinguish between the defective portion and these irregularities due to the signal level. An object of the present invention is to provide a hot flaw detection method that easily removes these formation irregularities using inexpensive equipment, facilitates hot flaw detection, and is highly accurate and can easily detect even small flaws. It is in.

Embodiments of the hot flaw detection method of the present invention will be described below with reference to the drawings.

FIG. 1 is an equipment layout diagram in a hot billet rolling process to which the method of the present invention is applied;
2 is a hot scarf, 3 is a preparative slab shear, 4 is a hot flaw detection device, and arrow P indicates the traveling direction of the hot steel billet.

The specific configuration of the hot flaw detection device 4 is as shown in FIG. 2, for example.

In the figure, 6 is a hot steel billet, 7 is a tape roller group for transferring the steel billet 6, and above the hot steel billet 6 is a water spray nozzle 8 attached to a water spray nozzle header 9. A compressed air injection nozzle 13 attached to a compressed air nozzle header 14, and a television camera 10 are arranged. The television camera 10 is connected to a video recorder 11 and a monitor television 12. Furthermore, the shaded area 15 is the hot steel piece 6
A hatched area 16 indicates a location where water impinges on the surface, a television camera field of view on the same surface, and a hatched area 17 indicates an air impingement location on the same surface. When performing hot flaw detection now, after hot scarfing the flaw detection of the hot steel piece 6, the scale is removed within a short time and then flaw detection is performed immediately.

This will be explained in more detail. First, the surface of the hot steel billet 6 rolled in the blooming mill 1 is treated with a solvent in the hot scarf 2 .

On the surface after the solvent has been applied, the scratches that were not removed by the solvent and the slag generated by the scarf remain without being sufficiently removed, and the high temperature caused by the solvent causes oxidation to progress due to the solvent atmosphere and oxygen in the atmosphere. , a quadratic scale is occurring. The surface condition becomes uneven due to the surface adhesion of slag and secondary scale caused by the scarf, and even though there are no scratches on the surface, brightness and darkness occur, making it appear as if there are scratches. Also, flaws that could not be completely removed by the hot scarf may be hidden by these. For this purpose, wear a scarf. It is necessary to remove the secondary scale. To remove these, we conducted experiments using (a) wire brush only, (b) water jet only, and (c) combination of wire brush and water jet, and the results showed that it is difficult to remove them with wire brush alone. The heat causes wire brushing. The tip of the tube becomes bent and becomes useless, but it has been found that it can be easily and completely removed just by spraying water. The scale removal method using water jetting described above is carried out, for example, in the following manner (a) to (f). (B) Water pressure: 3kgIcIt1 nozzle flat spray/shape Collision angle: 100 inclination from vertical, distance from nozzle tip to hot steel billet: 350Twt1 Spray width (d)
: 90mm 1 water amount: 26'Iminl per nozzle Nozzle pitch (e): 45? . b) The arrangement of the nozzles is as shown in Fig. 3, and the nozzles 8 are arranged so that about half of each spray width (d) is covered by about half of another nozzle, with the mutual thread angle 15; , spray width (d) 90T
Two stages of scale removal can be performed within the range of rrIn.

→ The television camera was installed perpendicular to the surface of the hot steel slab, and the distance between the center of the water collision point and the center of the television camera's field of view was 1 m.

This distance needs to be such that the cooling part in the water injection recovers heat and almost no rescaling occurs after scale removal. -) The surface temperature of the hot steel piece is preferably about 1,000 to 1,100°C after scale removal and reheating by water injection, but when flaws are detected with the television camera 10, 800'C or higher is sufficient.

Although this allows flaw detection even when the flaw is low, it tends to be difficult to detect small flaws. The distance from the outlet of the hot scarf fire 2 to the water collision point 15 is 207T1. However, there is no difference in the way the secondary scale comes off between the hot scarf shear 2 and the blooming slab shear 3 at any position during the transfer of the hot steel billet 6. The distance between the hot scarfing furnace 2 and the blooming slab shear 3 is 50W1, and the time required from the start of hot scarving until the slab is transferred to the blooming slab shear 3 is approximately 2 minutes, and if it is within 3 minutes, the pressure is low. It is thought that scale removal by water injection is easy. It was also confirmed that it became difficult to remove the scale by low-pressure water jetting if more than 5 minutes had passed after starting the hot scarfing. Of course, it can be removed by high-pressure water jetting (for example, 100 to 150 k91d), such as the deska song performed at the front of the rolling mill. →
The air nozzle blows compressed air at a pressure of 5k91cT1 onto the flaw detection surface to cut off the flow of water caused by water jet collision and prevent water and steam generated from heat from entering the television camera field of view 16.

Furthermore, the flaw detection surface is cooled to emphasize the difference in brightness between the flawed area and the normal area. The specifications of the nozzle used are as follows. Nozzle conical spray type, collision angle: 45 degrees tilt from vertical, distance from nozzle tip to hot steel surface: 350W$L1 spray diameter: 120 degrees, air volume: 1400' Imjnl
The spray shape arrangement in this case is as shown in Fig. 4, and the nozzle pitch (f) is 10h0.
00 was made into two stages by even 50 TWL, and the middle of the preceding nozzle pitch was arranged so that the succeeding nozzle covered it.

Although not shown in FIG. 2, a shielding plate is also provided between the nozzles 8 and 13 to prevent water from splashing. After removing scale by water injection as described above, flaw detection begins immediately.

This flaw detection is performed using a television camera 10 housed in a water-cooled jacket. This television camera 10 is equipped with a zoom lens that is remotely controlled to set the field of view and adjust the focus, and the aperture can also be controlled remotely (this aperture can also be automatically apertured). After the video signal from the television camera 10 is recorded on the video recorder 11,
It is reproduced on the monitor television 12 at an arbitrary speed that is easy to inspect, and is detected for flaws. If it is determined that there is a flaw as a result of this flaw detection, an instruction is given using a light pen, and the signal is delayed to the flaw removal process (as shown in the figure). Note that the following changes may be made to the embodiments described above.

For example, in the above embodiment, flaw detection was performed using a television camera, but since scale removal and scar removal are performed after scarfing, detection can be easily performed using an infrared camera, radiation thermometer, rotating mirror method, etc. The specifications of the water injection nozzle and compressed air injection nozzle described in the embodiments do not have any meaning per se, and can be changed as appropriate to effectively remove scale and scarf slag.

In addition, when removing scale using low-pressure water injection, the scale cracks due to the difference in the coefficient of thermal expansion between the scale and the base material of the steel billet, and the scale peels off due to the dynamic pressure caused by water. It's effective.

Further, in the embodiment, an example of draining water and cooling the steel piece surface by air injection was given, but it can be said that injection of nitrogen gas, argon gas, etc. is more effective in terms of preventing surface oxidation.

Further, in the drawings, for simplicity, it is shown that scale removal and flaw detection are performed only on a part of the surface of the hot steel billet, but it goes without saying that scale removal and flaw detection may be performed over the entire surface.

The same applies not only to the top surface but also to both side surfaces and the bottom surface.
Furthermore, it goes without saying that flaw detection using a television camera may be performed using an unmanned automatic flaw determination device rather than visual inspection of a monitor television image.

As is clear from the above description, according to the hot flaw detection method of the present invention, scale can be easily removed without expensive equipment such as high pressure water equipment, brush equipment, grinding wheel equipment, etc. Removal provides excellent effects such as accurate and easy flaw detection.

[Brief explanation of the drawing]

Figures 1 to 4 show examples of the present invention; Figure 1 is an equipment layout diagram, Figure 2 is a configuration diagram showing an example of a hot flaw detection device, Figure 3 is a nozzle layout diagram, and Figure 3 is a nozzle layout diagram. Figure 4 shows the spray shape layout. 2...hot scarf, 4...hot flaw detection device, 6...hot steel piece, 8...water injection nozzle, 101... ...TV camera.

Claims (1)

[Claims] 1. A hot flaw detection method characterized by performing flaw detection immediately after hot scarfing the flaw detection surface and removing scale and scarf slag using low pressure water within a short time.