Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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IMPROVEMENTS IN ~IOT IMMERS ION
2 COATING OF STEEL SHEET S~JRFACES
3 FIELD OF THE INVENTION
4 The instant invention relates to lmprovements in devices
for coating steel sheet surfaces by hot immersion in continu-
6 ous coating lines.
7 BAC~CGROUND OF T~ TNVENl~TON - PRIOR ART
8 As known, it is a re~uirement for the continuous coating
9 of a cold rolled steel sheet that a forward roller located
towards the vertical line of the steel band be included within
11 the non-ferrous alloy bath. Generally, the roller used is a
1~ single roller having a diameter of about S00 mm or higher,
1. assisted by tensioning rollers of lower diameter in order to
14 maintain ~table the passage o~ the sheet against the members
draining the excess of the molten alloy which is entrained
16 from the bath by the steel band. Such a roller has an angle
17 embraced by the -~heet contacting the roller of at least 120
18 which results in a large contact surface between the sheet and
19 the roller. This large contact surface is harmful since it
tends to trap molten alloy between the roller and the sheet,
21 which causes sheet deformation since molten metal cannot
22 escape therefrom.
23 In order to solve this disadvantage, immersed rollers
24 adopt different configurations to minimize the mentioned
effect. Among the most usual configurations, holes are
26 drilled at the roller surface along with slots in order to
27 facilitate displacement of molten metal towards the holes.
28 Further, the large angle involved by the contact of a portion
29 of the sheet upon ~he roller makes the deformation produced by
alloy product accumulation on the roller mor~ notorious, which
31 is minimized by the use of nitrogen fed mechanical scrapers,
32 but the effect of nitrogen-aided scraping is more notorious in
33 the case of tensioning rollers of a lower diameter. This is
34 due to the higher angular speed of the roller, which increases
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1 as the roller diameter decreases. The higher angular speed
2 facilitates scraping due to the higher frequency of the
3 passage of each roller generatrix in front of the scraper.
4 Further, a lower embracing angle Qf tensioning rollers
disfavors marking of the sheet due to roller deformation.
6 Taking into account the above, the novelty of the present
7 invention resides in multiple forward rollers provided with
8 nitrogen-assisted mechanical ~crapers, thus obtaining, as
9 shown in the case of three rollers shown in figure 1 herein,
an improvement in the quality of material produced by this
11 process, since the possibility of deformation produced by a
12 large diameter roller involving a large angle is prevented.
: BRIEF DESCRIPTION OF THE DRAWING
14 Figure 1 is a vertical section of the apparatus of the
present invention for hot immersion coating of steel sheet
16 surfaces.
17 DETAILED DESCRIPTION OF THE PREFERRED EM30~IMENT
18 Figure 1 is a vertical section of the assembly showing
19 multiple forward rollers 1, 2 and 3 of equal diameter, which
have scraper support boxes 4, 5 and 6 to which scrapers 7, 8
21 and 9, respectively, are linked.
22 Tensioning rollers 10 and 11 mounted on parallel shafts
23 have in front of them scraper support boxes 12 and 13 contain-
24 ing scrapers 14 and 15.
2~ Cutting edges are designated with numerals 16, 17, 18, 19
2~ and 20, and correspond to rollers 1, 2, 3, 10 and 11, respec-
27 tively.
28 Conduits carrying inert gas, nitrogen in this case, 21,
29 22, 23, 24 and 25, end into the scraper support boxes 4, 5, 6,
14 and 15, respectively.
31 A description of multiple roller arrangement replacing
32 the single roller of larger diameter is shown in figure 1.
33 In contrast, in a conventional arrangement of the single
34 roller with nitrogen assisted scrapers, a sheet is forwarded
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1 towards the vertical line by means of a roller having a
2 diameter larger than 400 mm with an angle of the sheet over
3 the roller higher than 120. This causes a large contact
4 surface which is disadvantageous, since in spite of the
improvement introduced by the nitrogen-assisted scraping, any
6 deformation of the roller is reproduced on the sheet.
7 Further, scraping on smaller diameter rollers is more effec-
8 tive due to the more frequent passage of possible scales on
9 the roller through the scraper.
Due to the above, the novelty of the present invention
11 resides in the use of multiple forward rollers for attaining
12 return of the sheet towards the vertical line with a minimal
. embracement angles, by means of the cistribution of the
14 contact angle of a single roller in at least two rollers,
which allows smaller contact angles and higher scraping
16 speeds, thus eliminating marks and corrugations on the sheet
17 produced by the aforementioned large surface contact, which
18 contact is prevented by this process.
19 It is further noted that other modifications may be made
to the present invention without departing from the scope of
21 the present invention, as noted in the appended claims.
