JP2005270997A - Method for removing surface foreign matter of pickling hot rolled steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently removing, without impairing productivity, foreign matters that remain sticking to the surface of a pickling hot rolled steel sheet after pickling, that come from hardly dissolving metallic pieces peeled and stuck from a metallic roll at the time of mechanical descaling prior to a pickling process, or that come from rubber pieces peeled and stuck from a dewatering rubber roll arranged in the front and the rear of a pickling tank. <P>SOLUTION: The pickling hot rolled steel sheet is processed by shot blasting for the purpose of removing foreign matters stuck to the surface. The pickling hot rolled steel sheet can be the one passed through a mechanical descaling device including a tension leveler before pickling or the one passed through a rubber lining roll or a plastic lining roll. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a method for refining a hot-rolled steel sheet whose surface scale has been removed by pickling (hereinafter simply referred to as “pickled hot-rolled steel sheet”), in particular, the efficiency of removing foreign matter adhering to the surface of the pickled hot-rolled steel sheet after pickling. Relates to a method of removing the target.

  Hot-rolled steel sheets are shipped as a raw material for construction, etc. with a black skin, that is, they are shipped with a hot-rolled scale attached to the surface, as well as being subjected to the next cold-rolling process and further surface treatment processes such as plating. . For these steps, it is necessary to remove the hot-rolled scale in advance, and pickling with so-called hydrochloric acid or the like is performed as a means for that purpose.

  The purpose of this pickling is to completely remove the surface scale of the hot-rolled steel sheet, and to achieve a surface state in which the subsequent cold rolling and subsequent surface treatment are satisfactorily performed. Foreign matter remains on the surface of the rolled steel sheet, and causes cold-faced surface defects called gouges during cold rolling, or pinhole generation on the plated surface. The main constituent material of the foreign material roll is peeled and adhered from the metal roll constituting the bridle roll or tension leveler when the metal strip comes into contact with the bridle or tension leveler at a high surface pressure during mechanical descaling prior to the pickling process. It has been found that the hardly soluble metal piece or the rubber lining roll for draining disposed before and after the pickling tank is a peeled and attached rubber piece or the plastic piece that is peeled and attached to a plastic roll lined with urethane or the like. Yes.

  Therefore, the surface of the pickled hot-rolled steel sheet is visually inspected at the end of the pickling process, and when there is a high possibility that the foreign matter is attached, the line speed is reduced to a very low speed to find the foreign matter attached portion. It temporarily stops at the adhering portion and is removed by grinding work with a grinder. Such inspection and further removal of foreign matter by a grinder not only significantly impairs the smooth operation of the pickling line but also requires a large number of work steps, which is a problem in terms of productivity and cost reduction.

  As a means for uniformly descaling in the width direction of the hot-rolled sheet, Patent Document 1 discloses that a plurality of shot projectors are arranged in the width direction, the projection speed is adjusted independently, and the remaining scale is eliminated. Means for shortening the pickling time are disclosed.

Japanese Patent Laid-Open No. 7-9024

  However, the means described in Patent Document 1 is only to perform shot blasting uniformly before pickling, and adheres to the steel plate surface during descaling, particularly mechanical descaling, and remains on the steel plate surface after pickling. It is irrelevant to the removal. Unlike the conventional technique, the present invention is a hardly soluble metal piece peeled and adhered from a metal roll at the time of mechanical descaling prior to the pickling process, or for draining water disposed before and after the pickling tank. Proposal of a method for efficiently removing foreign matters that are derived from rubber pieces, etc., from which the rubber lining roll has been peeled off and adhered to the surface of pickled hot-rolled steel sheets after pickling without impairing productivity. It is.

  The method for removing surface foreign matter from a pickled hot rolled steel sheet according to the present invention is performed by shot blasting a pickled hot rolled steel sheet having foreign matters attached to the surface. The pickling hot-rolled steel sheet to which the invention is applied can be a sheet obtained by passing a mechanical descaling device including a tension leveler before pickling, or a sheet obtained by passing a rubber lining roll or a plastic lining roll.

  The surface foreign matter removal method for pickled hot rolled steel sheets according to the present invention is a pickling line for pickling hot rolled steel sheets that are judged to have foreign matters remaining while operating the pickling line at a normal line speed. Since different shot blasting equipment is mechanically processed by so-called off-line, productivity is not hindered, and the foreign matter on the surface of the pickled hot-rolled steel sheet can be removed with very few man-hours.

  FIG. 1 is a conceptual diagram showing the overall configuration of a pickling line to which the present invention is applied. As shown here, the steel strip S to be pickled is paid out by the payoff reel 1 from the state wound up by the coil, and is composed of the bridle rolls 5 and 7 and the tension leveler 6 through the shear 2, the welder 3 and the looper 4. The scale is continuously fed to the mechanical descaler 8 and the scale formed on the surface of the hot-rolled steel sheet is crushed and is easily dissolved by pickling. The hot-rolled steel strip subjected to the mechanical descaling is then led to a pickling facility 17 including a pickling tank 11 and a rinsing tank 12, and scale dissolution and peeling are performed. A guide roll 15 is provided on the entrance side of the pickling tank 11, a squeeze roll 13 is provided on the exit side, and a squeeze roll 14 is also provided on the exit side of the rinse tank 12. The hot-rolled steel strip from which the scale has been melted and peeled off by the pickling equipment 17 is checked for the presence of foreign matter by the visual inspection table 18, and the outgoing steel strip processing equipment such as loopers, side trimmers and shears (these are not shown) After that, it is wound around a tension reel to form a pickled hot rolled steel sheet.

  In the above-described series of facilities, the roll disposed on the mechanical descaler 8 including the bridle rolls 5 and 7 and the tension leveler 6 is made of high-strength steel having excellent wear resistance. However, since the surface pressure applied from the steel strip at this portion is high, the surface layer of the roll peels off and is embedded in the surface layer of the steel strip S to become foreign matter. Also, the pickling tank 11 constituting the pickling equipment, the guide roll 15 provided on the entry side and the exit side of the rinse tank 12, and the squeeze rolls 13 and 15 are lined with rubber or plastic, so that the surface It is the cause that the rubber constituting the layer peels off and remains on the pickled steel strip.

  FIG. 2 is a flowchart showing the flow of materials when removing foreign substances adhering and remaining on the surface of the pickled hot-rolled steel sheet in this way. The hot-rolled steel sheet from which the scale has been removed through mechanical descaling and pickling is subjected to a visual inspection and checked for the presence of foreign matter including its possibility. This visual inspection is performed at a normal pickling line speed, and therefore it is not possible to strictly determine the presence or absence of foreign matter adhesion and the location of the adhesion. Therefore, in the present invention, there is a possibility of foreign matter adhesion by comprehensively judging the surface condition of the pickled hot-rolled steel sheet in consideration of the operation status of the entire equipment from the payoff reel 1 to the pickling tank 17. For example, the coil including the foreign substance adhering portion is limited to be identifiable as a shot blast processing target coil by a marker or the like.

  Coils that are determined to be “possibly adhered to foreign matter” by this visual inspection are sent to a shot blasting facility and subjected to shot blasting for removing foreign matter. This shot blasting process can employ the conditions used for the scale removal process by normal shot blasting. For example, about 2 to 6 projectors (wheel ablators) capable of projecting shots with a projection rate of 300 to 1200 kg / min on a steel plate with a plate passing speed of 5 to 30 m / min are arranged in the traveling direction of the steel plate. It is sufficient to perform shot blasting at a rotational speed of about 1200 to 1400 rpm. Moreover, what is necessary is just to use a shot grid about 30-60.

  The steel plate from which foreign matter has been removed by shot blasting in this way is taken up again by a coiler (attached to the subsequent stage of the shot blasting equipment), and the next step as a pickled hot rolled steel plate, that is, a cold rolling step, It is sent to the plating process.

  Using the pickling equipment having the specifications shown in Table 1, the scale removal of the hot-rolled steel sheet having a thickness of 2.3 mm was performed at a line speed of 300 m / min. The possibility of foreign matter adhesion was checked by visual inspection, and shot blasting for removing foreign matter was performed under the conditions shown in Table 2. Here, the shot blasting process was performed by shot blasting equipment in which four projectors (wheel ablators) were arranged on the upper surface side and the lower surface side of the steel plate in the longitudinal direction (through plate direction) of the steel plate. As a result, 0.8% of the pickling coil was subjected to shot blasting using a foreign matter adhering coil. As described above, in the foreign matter removal processing by the conventional grinder, four people are required for the processing, and the work efficiency is 2.5 t / h, whereas in the processing of the present invention, the work can be performed by one person. The processing speed was greatly improved to 6.7 t / h.

It is a conceptual diagram which shows the whole structure of the pickling line to which this invention is applied. It is a flowchart which shows the flow of a material when applying this invention.

Explanation of symbols

1: Payoff reel
2: Shah
3: Welder
4: Looper
5, 7: Bridle roll
6: Tension leveler
8: Mechanical descaler
11: Pickling tank
12: Rinse tank
13, 14: Drawing roll
15: Guide roll
17: Pickling equipment
18: Visual inspection table

Claims (3)

  A method for removing foreign matter on a surface of a pickled hot-rolled steel sheet, which comprises shot blasting a pickled hot-rolled steel sheet having foreign matters attached to the surface.   2. The pickling hot rolled steel sheet according to claim 1, wherein the pickled hot rolled steel sheet is obtained by passing a mechanical descaling device including a tension leveler before pickling. The pickling hot-rolled steel sheet is obtained by passing a rubber lining roll or a plastic lining roll, and the surface foreign matter removing method for the pickled hot-rolled steel sheet according to claim 1 or 2.

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