FI89511C - Method and apparatus for machining steel bands - Google Patents

Description

1 89511

METHOD AND APPARATUS FOR COATING STEEL STRIPS -FÖRFARANDE OCH ANORDNING FÖR BETNING AV STÄLBAND

The invention relates to a method as defined in the preamble of claim 1 and to an apparatus as defined in the preamble of claim 4 for pickling steel strips.

The methods used heretofore process hot and cold rolled steel strip in continuous annealing and pickling lines. In this case, the strip is unwound with a reel unwinder and joined together with the end of the preceding coil in the welding machine. In order to avoid standing of the equipment and thus over-pickling of the previous strip, the strip is received in the strip storage during the strip stop in the unwinding group. The incoming strip is first annealed in an annealing furnace, cooled with air and water, and dehydrated in a pickling plant. Various methods have been used in the industry for pickling hot-rolled and cold-rolled strip, the best known method being pickling with a neutral electrolyte and its associated acid mixing treatments. In this case, a mixture of nitric and hydrofluoric acid is used as the acid mixture. The corresponding welds are then cut off so that a skein of approximately the same length as at the feed end of the apparatus is re-formed. This method has disadvantages, such as high hardware and labor costs and a large space requirement.

Compared to the use of other pickling methods, especially with regard to the passing of the strips through the equipment, a general technical misconception arose that the materials used hitherto could lead to damage to the strip. In particular, it was feared that the stone coatings of the pickling tubs could lead to scratching of the strips 35 or similar damage, especially in the pickling of stainless steel strips.

On the other hand, however, lining materials for pickling equipment are 2> 39511, which can withstand the chemical stress of the treatment chemicals, as well as withstand the mechanical load. Although rock and ceramic liners to date are resistant to chemical stress, they lead to damage to the surface of the goods to be pickled quickly or are themselves less mechanically loaded.

The object of the invention is to provide a method which avoids the above-mentioned disadvantages.

It is a further object of the invention to provide an apparatus for carrying out a method by which the risk of damage to the goods to be pickled is reduced as far as possible.

In the method according to the invention, the belt coming from the unwinder is initially pushed through at least one pre-descaler, pickling compartments and one rinsing device until it reaches the processing line at the end of the winding device or transverse winder. through the processing equipment or transversely by means of a dividing device are cut into plates. According to the invention, the pre-heat-treated noble-25 steel strip is guided continuously in coils through the apparatus as a steel strip, and the stainless steel strip is passed from the coil unloader directly to the pre-descaler and to at least one pickling compartment without further heat treatment.

Preferably, the strip passes through a plurality of pickling sections with different pickling agents. In this case, the strip can be treated with sulfuric acid in one compartment and a mixture of nitric and hydrofluoric acid in the next compartment.

The concentration of sulfuric acid is 250 to 600 g / l, preferably 300 to 450 g / l. The temperature of this pickling acid is 60 to 95 ° C, preferably 70 to 90 ° C.

In the acid mixture, the concentration of nitric acid may be 100 to 250 g / l, preferably 100 to 200 g / l, and the concentration of hydrofluoric acid is 10 to 100 g / l, preferably 20 to 80 g / l, based on hydrofluoric acid. of the existing total of 5. In this case, the temperature of the acid mixture is 30 to 70 ° C, preferably 40 to 65 ° C.

In order to implement the method according to the invention, it has been proposed to use at least one axially adjustable strip-guided reel unloading device, at least one pickling compartment, one rinsing device and one winding device and / or preferably one transverse distributor, the pickling part comprising at least one longitudinal part consisting of a load-bearing structure made of steel, fiberglass-reinforced plastic or propylene and a lining of an acid- and wear-resistant material on top of a base layer of PVC and / or coal. According to the invention, the upper layer of the liner consists of a graphite-20 filled and / or alumina filled polyester resin.

According to a further feature of the invention, the at least two pickling baths are each provided with at least one pickling compartment, a brush washing machine being arranged between the pickling baths.

Further details of the invention will be described in more detail in connection with the accompanying drawing, which shows an application example of the actual apparatus. In the schematic representation 30 Fig. 1 schematically shows the apparatus with its main equipment, Fig. 2 shows a longitudinal section of the apparatus from the head of one pickling section and the beginning of the next pickling section, 35 Fig. 3 shows a longitudinal section of two pickling tubs with intermediate brush washing machines, 4 89511 and Figure 5 shows a longitudinal section of the bottom of the cover bath.

shown in 5 Figure 1, the apparatus includes a substantially spool vehicle device 1, the trend of machine 2, the mechanical esihilseenpoistolaite, e.g. sand blower 3, a pair of longitudinally extending flat peittausammetta 4 between them, together with the brush a washing machine 5, the return-10 a flushing device 7, a drying unit 8 and the winding device 9. Ke lanpurkulaitteen 1 and between the orienting machine 2 there is a traction device 10 consisting of two overlapping rollers in succession and two opposite guide rollers 11.

Arranged between the orienting machine 2 and the sand blower 3 15, two cutting machines 12, 13 are arranged in succession, as well as another traction device 14 consisting of two overlapping rollers.

Between the drying device 8 and the winding device 9 there is a belt guide 11 'consisting of two guide rollers arranged opposite each other 20 on each side 20 of the strip to be pickled, and a retracting machine 18 consisting of two overlapping rolls.

At least one of the pickling baths 4 consists of at least two successive pickling compartments 25 6, between which the strip 14 is guided between two press rolls 15 (Fig. 2), the upper of which is used and assists in feeding the strip 14 forward. Our pickling 4 or each of the pickling compartments 6 is provided with a partially removable cover 16 and a bottom part 17 rising on the inlet and outlet side 30, which forms a dam for the pickling hook in the bath 4 or in the pickling compartment. The shape of this base part 17 is to be understood as meaning that the outlet-side part extends downwards in the direction of travel of the strip and the inlet-side part extends upwards. In this case, the inlet-side part forms with the corresponding part of the lid 16 a guide funnel 19 for guiding the beginning of the strip, which beginning has a tendency to settle between the press rolls 15.

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Our pickling 4 or pickling compartment 6 is assembled from a load-bearing structure and lining made of an acid- and wear-resistant material. The load-bearing structure consists of steel lined with chlorinated PVC or fiberglass-reinforced plastic or plain plastic, such as polypropylene. It has a layer of coal on top and a polyester resin filled with alumina or graphite is used as the top layer.

The amount of filler in the alumina may be 10 to 100% by weight, but preferably 20 to 50% by weight. The filler for graphite has values of 50 to 400% by weight, preferably 80 to 200% by weight.

15 This combination of polyester resin matrix and filler gives a material which, on the other hand, has sufficient resistance to the chemical and mechanical stresses of pickling, but which cannot damage stainless steel strips.

The return rinsing device 7 comprises, as shown in Fig. 4, a brush washing machine 5 'and rinsing devices 20 or 20' connected in front of and after it. Overlapping press rollers 15, at least the upper one of which is used, are arranged on the inlet and outlet side of each rinsing device or between the rinsing devices 20 or 20 'and the brush washing machine 5', respectively, as between the pickling compartments 6. Arranged in the rinsing devices 20, 20 'are lower and upper spray pipes 21 or 22, between which the strip 14 to be treated is guided in the direction A-30. The bottom of the rinsing device 20, 20 'is formed of plates 23 provided in the same way or in the same way as the lining of the pickling tubs 4 and each rising in the direction of movement A of the strip 14. The lower spray tubes 21 are between the plates 23 and below their upper surface. at the beginning of the introduction, to protect.

6 89511 In addition, the lower injection pipes 21 also ensure the formation of a water film between the belt and the underside of the lining material so that the tape slides over this water film does not touch the bottom of the bath tub 5 at all or only slightly. This also helps to avoid mechanical damage both to the goods to be pickled and to the equipment itself.

To guide the strip 14 into the press rolls 15, a funnel 24 is arranged on the outlet side, in the same way as in the pickling compartments 10 6, which in this case is formed from a base and a cover plate.

The brush washing machine 5 'between the rinsing devices 20, 20' successively comprises two overlapping rollers, a support roller 25 and a brush roller 26, the first roller pair having a support roller 25 at the bottom and the second at the top and the lower roller deflected relative to the upper roller 14 in the direction of travel . To prevent damage to the brush roll 26 when feeding the beginning of the belt, the first brush roll 20 must be raised and the second lowered. For the same purpose, the upper of each press roll 15 must also be lifted. The distance between each roll 25, 26 and between the first roll pair and the previous press roll pair 15 and between the second roll pair and the next press-25 roll pair 15 are each provided with a hopper 27 or 28 or 29 corresponding to the hopper 24.

In this embodiment, pairs of press rolls 15 and 15 'are connected to the outlet side of the second rinsing device 20', with a funnel 30 corresponding to the funnel 24 being interposed between each pair of press rolls 15, 15 '30.

The rinsing device is a series return rinsing device in which the rinsing agent is passed from the third stage to the second stage, from where it is led to the first stage, i. to a brush washer 5 '. From this, the rinsing agent 35 is fed to the stage preceding the rinsing device 20 and from there to the brush washing machine between each pickling bath 4. The rinsing or detergent used flows 7) to a collection tank (not shown) 9511, from which it is in any case recycled to the rinsing or washing process via a cleaning device.

The brush washing machine 5 5 between the pickling baths 4 corresponds to the previously described brush washing machine 5, which is provided with the same parts as in Fig. 3 with the same reference numerals.

The method according to the invention takes place, in so far as it has not already been described, in such a way that, at the beginning of the processing of the spool in the reel-10 unwinding device 1, the reel unwinding device 1 is operated at least until To control the central part of the strip, the reel unwinding device 1 can be adjustable in a direction perpendicular to the direction of passage of the strip. Then, the drive unit 10 to push the strip in the direction of arrow A towards the barrier. The tape guide 11 prevents lateral passage of the tape. The cutting device 12 cuts off the beginning of the strip, which is tongue-shaped when the strip comes from the rolling mill. The cutting device 20 13 then cuts the edges of the beginning of the strip obliquely so that the beginning of the strip tapers conically to promote the guidance of the strip. The beginning of the strip thus has a trapezoidal shape, it being preferred that the top side or end of the trapezoid is at least half the width of the strip 25 and the angle between the direction of travel of the strip and the trapezoidal side is 10 ° to 80 °, preferably 30 ° to 60 '.

The same pickling agent or different substances can be used in the pickling baths 4 or pickling compartments 6. In this case, the pickling agent is led from the exit side of the strip to the pickling bath 4 or the pickling compartment 6 and is led away from the inlet side of the strip so that it flows against the movement of the strip 14. The circulation of the pickling agent in the pickling bath or pickling section takes place at least once and at most 20 times per hour, preferably 5-10 times per hour.

After leaving the return rinsing device 7 and the drying 8 -19511 device 8, the rollers or rollers on the side of the belt guide 11 'lead to the belt 14 winding device 9, where the belt 14 is braked by two overlapping rollers of the retraction unit 18.

Of course, additional processing steps, such as cold rolling, longitudinal or transverse division, or belt grinding, are conceivable and installable in similar equipment. Any transverse divider 10 which cuts the pickled finished product into sheets can replace the winding device 9. A longitudinal divider which divides the belt into narrower belts and a grinding device can be arranged before the winding device 9. A device rinse with water. In particular for the acid-pickling of ferritic stainless steel strip, this can be cooled by means of an externally arranged heat exchanger. 20 Finally, a rolling mill can be connected before the winding device, where the thickness of the strip is reduced.

To prevent steam or dust from escaping from the individual treatment devices, air or steam can be sucked in by a fan.

The lining material may, as shown in Figure 5, consist of plates formed sawtooth-shaped in the direction of travel of the strip and mounted with an acid-resistant putty. In this figure, reference numeral 27 denotes sawdust-shaped artificial resin stones in the direction of travel of the strip, reference numeral 28 denotes the underlying carbon stones, and reference numeral 29 denotes a support structure.

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Claims (8)

9 o 9 511 A method for pickling steel strips, wherein the strip from the reel unwinder 5 is initially pushed through at least one pre-descaling device, pickling compartments and one rinsing device until it reaches the processing line at the end of the winding device or transverse splitter. with other used processing rollers through the processing equipment or by means of a transverse distributor is cut into sheets, characterized in that the pre-heat-treated stainless steel strip (14) is wound from the disc (4). Method according to Claim 1, characterized in that the strip is treated, as is known per se, in a plurality of pickling baths with a plurality of pickling compartments, in at least one of which is treated with a mixture of nitric and hydrofluoric acid, and optionally treated with sulfuric acid before acid treatment. A method according to claim 1, characterized in that after the treatment in the pickling bath and before the next pickling bath, the strip is treated in a brush washer (5) with brushes made of plastic and having an abrasive material such as silicon carbide or Al 2 O 3, and after pickling 7), wherein the series rinsing device (7) removes the washing water delivered by the brush washing machine (5). Apparatus for carrying out the method according to claim 1, using at least one axially adjustable strip-guided reel unloading device, at least one pickling compartment, one rinsing device and one winding device and / or one transverse distributor, the covering part comprising at least one splitting part -5 va, preferably a flat pickling, consisting of a load-bearing structure made of steel, fiberglass-reinforced plastic or propylene and a lining of an acid- and wear-resistant material on top of a PVC and / or coal base layer, characterized in that , that the upper layer (31) of the liner consists of a graphite-filled and / or alumina-filled polyester resin. Apparatus according to claim 4, characterized in that the upper layer 15 of the liner consists of an Al 2 O 3 -filled polyester resin, in which the amount of the Al 2 O 3 filler is 10 to 100% by weight, preferably 20 to 50% by weight. Apparatus according to claim 4, characterized in that the uppermost layer 20 of the liner consists of a graphite-filled polyester resin in which the proportion of graphite is 50 to 400% by weight, preferably 80 to 200% by weight. Apparatus according to one of Claims 4 to 6, characterized in that the at least one rinsing device (20, 20 ') and / or at least one brush washing machine (5, 5') are provided with the same lining material as our pickling (4). Apparatus according to Claim 7, characterized in that the brushes are made of plastic and have an abrasive material, such as, for example, silicon carbide or Al 2 O 3. n ’95. 1