AU2008212058B2

AU2008212058B2 - Profiled steel decking sheets

Info

Publication number: AU2008212058B2
Application number: AU2008212058A
Authority: AU
Inventors: Neil Tooley
Original assignee: BlueScope Steel Ltd
Current assignee: BlueScope Steel Ltd
Priority date: 2002-03-14
Filing date: 2008-09-08
Publication date: 2011-09-08
Anticipated expiration: 2023-03-06
Also published as: AU2008212058A1; AU2008212058C1

Abstract

- 16 A method of manufacturing profiled steel decking sheets on a roll forming line is disclosed. A profiled steel 5 decking sheet is also disclosed. The method is characterised by (i) forming a coating on at least one surface of the strip upstream of a first roll-former stand, the coating being selected to reduce the glare of the profiled steel decking sheets produced by the method; 10 and (ii) at least partially drying the coating before the strip reaches the first roll-former stand. The decking sheet includes: one upstanding rib or a plurality of parallel upstanding ribs that extend along the length of the sheet, pans that separate the rib or ribs, and a 15 coating (i) on the pans or (ii) on the rib or ribs or (iii) on the pans and on the rib or ribs, that reduces the overall glare of the sheet and highlights the presence of the ribs. 2758570_1 (GHMatters) P45276.AU.2

Description

- 1 PROFILED STEEL DECKING SHEETS The present invention relates to profiled steel decking sheets that are suitable for use as formwork in 5 the construction of composite concrete slabs. Composite concrete slabs include profiled steel decking sheets, concrete that has been poured onto and set on the sheets, and reinforcement (such as mesh or bars) 10 embedded in the concrete. The present invention relates particularly, but by no means exclusively, to profiled steel decking sheets that are used as formwork in the construction of composite 15 concrete slabs that form the floors of buildings. Conventional profiled steel decking sheets include a plurality of upstanding parallel ribs that extend along the length of the sheets and are separated by 20 flat pans. The sheets are usually roll-formed from zinc coated, high tensile steel strip in base metal thicknesses of 0.6-1.0 mm. The strip may have a spangled surface. The ribs are provided to resist downward 25 deflection of the profiled steel decking sheets in response to the weight of wet concrete poured onto the sheets during on-site construction of composite concrete slabs. 30 When the concrete hardens and reaches a sufficient compressive strength, the profiled steel decking sheets provide reinforcement for the composite concrete slabs. In addition, the ribs mechanically interlock the concrete and the profiled steel decking 35 sheets. According to the present invention there is 2758570_1 (GHMatters) P45276 AU.2 -2 provided a roller coater assembly for forming a coating on at least one surface of a steel strip which includes a roll for picking up the coating from a reservoir, an applicator roll for transferring the coating from the 5 pick-up roll to a surface of the strip and thereby forming the coating on the strip surface. Preferably the applicator roll has a series of raised lands that extend around the circumference of the 10 roll at spaced intervals along the length of the roll whereby the lands define surfaces for transferring the coating from the pick-up roll to the strip to form a series of spaced apart lengthwise extending coating bands on sections of the strip that form the pans of the 15 profiled steel decking sheets. Preferably the applicator roll is adapted to be driven by contact with the strip and the pick-up roll is adapted to be driven by contact with the applicator roll. 20 Preferably the roller coater assembly further includes a pressure roll for contacting the opposite surface of the strip to that contacted by the applicator roll to force the strip against the applicator roll. 25 Preferably the roller coater assembly further includes a scraper member for scraping coating from the pick-up roll upstream of the applicator roll and thereby controlling the coating thickness on the pick-up roll. 30 Preferably the scraper member is adjustable. In the context of this patent specification the term "coating" can mean ink or paint. The term "ink" can 35 be interchanged with the term "paint". Preferably the strip is made from zinc coated, 275S5701 (GHMatters) P45276.AU.2 -3 steel strip. Preferably the coating is fast drying. 5 Preferably the coating has non-slip characteristics when dry. Preferably the dried coating is chemically inert with respect to concrete. 10 A preferred coating is water based and contains an organic resin and is free of heavy metals. The organic resin of the coating may be 15 substantially thermoplastic in nature. However the final properties of the coating may be enhanced by providing sites for cross-linking of the polymer chains. The coating may be an acrylic, and more 20 particularly may be a styrinated acrylic. The coating may contain a small volume of organic solvent to assist rapid drying. However, the total organic solvent content must be such that the coating 25 remains non-flammable and non-explosive. The coating may contain between 15% and 65% volume solids. 30 Preferably a dried coating on the strip has gloss of less than 40 gloss units as measured by a BYK Gardner Micro-Tri-Gloss Glossmeter in accordance with ASTM D523:1999 - Standard Test Method for Specular Gloss. 35 More preferably the dried coating has gloss of less than 30 gloss units. 2758570.1 (GHMatter) P45278 AU.2 -4 In addition to reducing glare of the profiled steel decking sheets, the coated pans highlight the location of the uncoated rib or ribs of the sheets. 5 Preferably the colour of the coating is selected to highlight the location of the uncoated rib or ribs of the sheets. The present invention is described further by 10 reference to the accompanying drawings, of which: Figure 1 is a side elevation of one embodiment of a roll forming line in accordance with the present invention; 15 Figure 2 is a side elevation of a preferred embodiment of a roller coater assembly that forms part of the line shown in Figure 1; 20 Figure 3 is a front elevation of the roller coater assembly; Figure 4 is a front elevation of an applicator roll that forms part of the roller coater assembly; 25 Figure 5 is a front elevation of a pick-up roll that forms part of the roller coater assembly; Figure 6 is a perspective view of part of one 30 embodiment of a preferred embodiment of a profiled steel decking sheet in accordance with the present invention that can be formed in the roll forming line shown in Figure 1; 35 Figure 7 is a side elevation of another embodiment of a roll forming line in accordance with the present invention; and 2758570_1 (GHMatters) P45270.AU.2 - 5 Figure 8 is a section along the line 8-8 of Figure 7. 5 The preferred embodiment of the profiled steel decking sheet shown in Figure 6 is representative of a general type of decking sheet that includes a series of parallel upstanding ribs 3 separated by flat pans 5. 10 An alternative profile may include just one major upstanding rib in the profile. The present invention is not limited to the particular profile shown in Figure 6 and extends to the 15 general type of decking sheet. The particular profile of the sheet shown in Figure 6 is a standard profile marketed by the applicant under the Registered trade mark BONDEK. 20 The sheet is formed from zinc coated, high tensile steel strip. The sheet is characterised in that the pans 5 are 25 coated with a low glare coating and the ribs 3 are not coated ie the surface of the ribs 3 is the surface of the zinc coated steel. The coated pans 5 substantially reduce the 30 overall glare resulting from the sheet. In addition, selectively coating the pans 5 and leaving the ribs 3 uncoated has the effect of highlighting the location of the ribs 3. At one level, the location of 35 the ribs 3 is highlighted by the difference between the glare of the ribs 3 and the glare of the pans 5. At another level, the location of the ribs 5 is further 2758570.1 (GHMatters) P45276.AU.2 - 6 highlighted by appropriate selection of the colour of the coating. The applicant retained an external consultant to 5 carry out test work on the profiled steel decking sheets shown in Figure 6 and a standard uncoated sheet. The external consultant made gloss measurements of three sample sheets. 10 Two of the sheets were in accordance with Figure 6, with one of the sheets having a series of scratches as would be expected in the field. The sheets were coated with a blue coloured "ink". The "ink" was water based and 15 was selected on the basis of being able to dry quickly to form a non-slip low glare surface. The third sheet was an uncoated sheet, ie a standard sheet formed from zinc coated, steel strip - as 20 supplied to the building industry. Gloss is a measurement of reflection of illuminated light and therefore provides an indication of the extent of glare resulting from a surface. 25 Gloss measurements were made with a BYK Gardner Micro-Tri-Gloss GloBsmeter in accordance with ASTM D523:1999 - Standard Test Method for Specular Gloss. A 60 degree gloss reading geometry was used according to the 30 above standard. For each sheet, 25 measurements were taken evenly to provide a good representation of the gloss and a variation in gloss over each sheet. Results are expressed 35 below in terms of gloss units. The results are summarised in Tables 1 and 2. 27585701 (GHMatters) P45276.AU.2 - 7 Table 1. Gloss (Gloss Units) Uncoated Coated sheet Coated sheet sheet (bare (unscratched) (scratched) steel) Mean (Gloss 121.8 8.4 22.7 Units) Std Dev 21.5 6.7 15.3 5 Table 2. Reduction in gloss(%) Coated sheet Coated sheet (unscratched) (scratched) Percentage 93.1 81.4 reduction (%) The unscratched and scratched coatings of the Figure 6 sheets reduced gloss by 93 and 81 percent 10 respectively when compared to the bare steel sheet. Hence, the blue coating would reduce glare significantly at building sites. The coated profiled steel decking sheet shown in 15 Figure 6 can be manufactured on the roll forming line shown in Figure 1. The roll forming line shown in Figure 1 includes an uncoiler 23 that holds a coil 25 of zinc coated steel 20 strip so that the strip 71 can be unwound from the coil as a flat sheet and passed successively to and thereafter through a roller coater assembly 11 and a series of conventional roll-former stands 9. 25 The roller coater assembly 11 forms a coating on the lower surface of the flat strip as the strip moves along the line prior to the strip reaching the roll former 2758570_1 (GHMetters) P45278.AU.2 -8 stands 9. The roll coater assembly 11 is described in more detail hereinafter with reference to Figures 2 to 5. The roll-former stands 9 progressively roll form 5 a series of ribs in the coated flat strip 71 and thereby form the profile of the coated profiled decking sheet shown in Figure 6. Each roll-former stand 9 includes a pair of lubricated shaped rolls 21. 10 The roll forming line also includes a shear station 27 that shears the coated profiled steel strip into pre-determined lengths, thereby to form the Figure 6 decking sheets. 15 With reference to Figures 2 to 5, the roll coater assembly 11 includes a tray 29 that contains a reservoir of a coating (such as the "ink" used in the testwork reported above), a roll 31 that picks up coating from the tray 29, and a roll 33 that contacts the pick-up roll 31 20 and transfers coating from the pick-up roll 31 to the downwardly facing surface of the strip and thereby applies the coating on the strip. The roller coater assembly 11 further includes a 25 roll 35 that contacts the upwardly facing surface of the strip and applies downward pressure to the strip and thereby forces the strip against the applicator roll 33. The arrangement of the pick-up roll 31, the 30 applicator roll 33, and the pressure roll 35 is such that the rolls are driven by contact with the strip. Consequently, the amount of coating transferred to the strip is independent of the strip speed and variations in strip speed are taken into account directly by the rolls 35 31, 33. With particular reference to Figure 4, the 2758570.1 (GHMatters) P4527.AU.2 -9 applicator roll 33 has a series of lands 37 that extend around the circumference of the roll at spaced intervals along the length of the roll. The lands 37 define surfaces that transfer coating from the pick-up roll 31 to 5 the strip and form a series of spaced apart lengthwise extending coating bands on the sections of the strip that ultimately form the pans 5 of the profiled steel decking sheet shown in Figure 6. The arrangement is such that the applicator roll 13 does not transfer coating to the 10 sections of the strip that ultimately form the top of the ribs 3 of the Figure 6 decking sheet. The roller coater assembly 11 further includes an adjustable scraper bar 39 that is positioned in relation 15 to the pick-up roll 31 so that it removes excess coating from that roll 31 before the roll 31 rotates to the applicator roll 33. The scraper bar 39 is adjustable whereby the initial coating thickness on the pick-up roll 31 can be varied, as may be required. 20 The scraper bar 39 provides an initial coating thickness control for the roll coater assembly. Further coating thickness controls are provided by the contact between the pick-up roll 31 and the applicator roll 33 and 25 by the contact pressure of the applicator roll 33 and the strip. The described roll coater assembly 11 applies wet coatings of less than 7 micron, preferably less than 3 30 micron, on the strip. The roll forming line also includes two hot air blowers 13, 15 and a cool air blower 17 downstream of the roll coater assembly 11 that blow hot and cool air against 35 the coated strip. The first air blower 13 is positioned between the 27585701 (GHMatters) P45278.AU 2 - 10 roller coater assembly 11 and the first roll-former stand 9 and is operated to substantially dry the coating before the strip reaches the first roll-former stand 9. 5 This is an important issue for a coating that is soluble in standard roll former lubricants and would be removed as the strip passes through the roll-former stands 9 unless the coating is at least substantially dry before the strip reaches the stands 9. 10 The apparatus may include a means to enable controlled application or wiping of lubricant to prevent damage of the coating by the lubricant. 15 At a typical line speed of 50 m/min and a typical spacing of approximately 2m between the roller coater assembly 11 and the first roll-former stand 9, there is a time period of the order of 1.5 to 2 seconds only in which to substantially dry the coating. This time constraint 20 places considerable practical constraints on line design and coating selection, particularly when retrofitting the roll coater assembly 11 to existing roll forming lines where space is limited. A further constraint is that the drying process should not heat the strip to temperatures 25 in excess of 140*C in order to avoid adversely effecting the solids coalescence of the coating. The second air blower 15 is positioned between the third and fourth first roll forming stands and is 30 operated to complete the process of drying the coating. The third air blower 17 is positioned towards the end of the series of roll-formers 9 and is operated to remove any residual water/lubricant that may have 35 accumulated on the strip as it passed through the line. The roll forming line shown in Figure 1 may be 2758570_1 (GHMatters) P45278.AU.2 - 11 constructed as a green field site or the above-described roller coater assembly 11 and dryers 13, 15 of the roll forming line may be retrofitted to existing roll forming lines. 5 The coated profiled steel decking sheet shown in Figure 6 can also be manufactured on other roll forming lines, such as the roll forming line shown in Figures 7 and 8. 10 The roll forming line shown in Figures 7 and 8 includes the same basic components as the roll forming line shown in Figures 1 to 5, and the same reference numerals are used to describe the same components in both 15 groups of drawings. Specifically, the roll forming line shown in Figures 7 and 8 includes an uncoiler 23 that holds a coil of zinc coated steel strip, a roller coater assembly 11 20 for forming lengthwise extending coating bands on the sections of the strip 71 that ultimately form the pans 5 of the coated profiled steel decking sheet shown in Figure 6, and a series of roll-former stands 9 for roll forming the ribs 3 of the decking sheet. 25 The main difference between the two embodiments of the roll forming lines is the arrangement for drying the wet coating applied to steel strip by the roller coater assembly 11. 30 Specifically, in the embodiment shown in Figures 7 and 8 the coated strip 71 is passed through a heated chamber 45 before being roll formed. This is a different arrangement to the hot air blowers 13, 15 used in the 35 embodiment shown in Figures 1 to 5. With reference to Figure 8, the chamber 45 2758570.1 (GHMatters) P45276.AU.2 - 12 includes an upstream inlet end 61 for wet coated strip 71 and a downstream outlet end 63 for dried coated strip 71. The strip 71 passes through the chamber 45 with the wet coating bands (identified by the numeral 75 in Figure 8) 5 facing downwardly. The moving coated strip is supported in the chamber 45 by a series of guide rollers 47 on opposite sides of the strip, above and below the strip, within the chamber 45. The rollers are positioned so that there is no direct contact between the rollers and the wet coated 10 strip moving through the chamber 45. The chamber 45 is heated by hot air that is supplied to downstream end of the chamber 45 via ductwork 77 and flows through manifolds 49 that extend along the length of the chamber and is discharged from the upstream end of the chamber 45 via 15 ductwork 79. The manifolds 49 include openings 51 in the upper and side walls thereof that allow heated air to escape into the chamber 45 and contact the moving strip. The above-described heated chamber 45 is an 20 effective arrangement for drying the wet coating applied to steel strip by the roller coater assembly 11. Many modifications may be made to the preferred embodiments of the present invention described above 25 without departing from the spirit and scope of the invention. By way of example, whilst the preferred embodiment shown in Figures 1 to 5 includes drying the 30 coating with two hot air blowers 13, 15, the present invention is not so limited and extends to any number of hot air blowers and to the use of any other suitable drying means. One example of another suitable drying means is by infra-red radiation. Another suitable drying 35 means is the heated chamber shown in Figures 7 and 8. Another suitable drying means is provided by induction heating. 275570_1 (GHMatters) P45270.AU.2 - 13 In addition, whilst the preferred embodiments include driving the rolls 31, 33, 35 of the roll coater assembly 11 by contact with the moving strip, the present 5 invention is not so limited and extends to arrangements in which the rolls are driven independently of the moving strip. In addition, whilst the coating on the profiled 10 steel decking sheet shown in Figure 6 can be manufactured on the roll forming lines shown in Figures 1 to 5 and 7 and 8 and with the coating being applied upstream of the roll formers, the present invention is not so limited and the coating can be applied at any suitable stage in the 15 process for manufacturing steel decking sheets, ie in pre , post-, and during the roll forming stages of the process. 2758570.1 (GHMatters) P45278.AU-2

Claims

1. A roller coater assembly for forming a coating on at least one surface of a steel strip which includes a 5 roll for picking up the coating from a reservoir, an applicator roll for transferring the coating from the pick-up roll to a surface of the strip and thereby forming the coating on the strip surface. 10

2. The roller coater assembly defined in claim 1 wherein the applicator roll has a series of raised lands that extend around the circumference of the roll at spaced intervals along the length of the roll whereby the lands define surfaces for transferring coating from the pick-up 15 roll to the strip to form a series of spaced apart lengthwise extending coating bands on sections of the strip that form the pans of the profiled steel decking sheets. 20

3. The roller coater assembly defined in claim 2 wherein the applicator roll is adapted to be driven by contact with the strip and the pick-up roll is adapted to be driven by contact with the applicator roll. 25

4. The roller coater assembly defined in any one of the preceding claims wherein the roller coater assembly further includes a pressure roll for contacting the opposite surface of the strip to that contacted by the applicator roll to force the strip against the applicator 30 roll.

5. The roller coater assembly defined in any one of the preceding claims wherein the roller coater assembly further includes a scraper member for scraping coating 35 from the pick-up roll upstream of the applicator roll and thereby controlling the coating thickness on the pick-up roll. 2758570_1 (GHMatters) P45278.AU.2 - 15

6. The roller coater assembly defined in claim 5 wherein the scraper member is adjustable. 5

7. A roller coater assembly substantially as hereinbefore described with reference to the accompanying drawings. 2754570_1 (GHMatters) P45276AU.2