US3274679A - Process for fabricating protected metal sheets - Google Patents

Description

Sept. 27, 1966 H. E. KENNEDY PROCESS FOR FABRICATING PROTECTED METAL SHEETS Filed Dec. 19, 1963 N @uw INVENTOR w E w t K f. w m

United States Patent O "ice 3,274,679 PRUCESS FR EABRICATING PROTECTED METAL SHEETS Harold E. Kennedy, Pittsburgh, Pa., assignor to H.

Robertson Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 19, 1963, Ser. No. 331,719 4 Claims. (Cl. 29-473.1)

This invention relates to an improved process for making protected metal sheets, ,and more particularly to a process for producing protected metal from continuous strips of core metal in coil form.

The production of protected metal is described in U.S. patents of Alden W. Coffman, 2,073,334, 2,631,641 and 2,764,808 inter alia.

The object of this invention is to provide an improved method for fabricating long lengths of uniform protected metal building sheets in an eflicient manner whereby the resulting strip can be readily coiled and uncoiled.

In the accompanying drawings:

FIGURE 1 is a cross-sectional view of a typical protected metal building sheet described in the aforementioned U.S. Patents 2,073,334, 2,631,641, and 2,764,808;

FIGURE 2 is a schematic illustration of apparatus similar to that shown in the aforementioned U.S. Patents 2,631,641 and 2,764,808 for preparing protected metal sheets in long coiled strips.

Protected metal sheets A protected metal sheet is shown in FIGURE 1, comprising a metal sheet core 11, a coating of adhesive non-corrodible metal 12 and an outer fibrous wrap 13. The metal core 11 is formed from iron or steel, from about 14 gauge to about 28 gauge thickness, preferably from about 18 gauge to about 26 gauge thickness. Either cold-rolled or hot-rolled steel sheets are suitable. The non-corrodible adhesive metal coating 12 is preferably zinc, although various zinc alloys are acceptable as well as tin, cadmium, lead or other non-corrodible metals or alloys. The adhesive coating 12 becomes alloyed with the metal core 11 during the fabrication of the protected metal sheet 10.

The adhesive metal coating 12 is aflixed to the metal core 11 usually by a hot dip process wherein a film of molten adhesive coating metal is applied directly to the entire outer surface of the metal core. While the adhesive coating remains molten, the fibrous wrap 13 is pressed into the molten adhesive coating whereby the fibers of the wraps become mechanically keyed or anchored to the resulting protected metal sheet 10. The foregoing processing technology is described in Ithe aforementioned U.S. Patent 2,073,334. Subsequently the 1ibrous Wraps 13 are impregnated with a resinous or bituminous saturant which provides Weather-resistant properties for the resulting laminated building sheet.

The prior art methods for producing continuous protected metal strip have provided for chilling of the product saturant-coated strip prior to coiling in order to promote congealing of the usually tacky saturant prior to the coiling of the strip.

The present invention, contrary to the prior art suggestions, maintains the saturlant-coated strip at a high temperature level prior to the coiling operation with the totally unexpected result that the coiled strip, after aging for several days, is

(1) Virtually free of wrap-to-wrap adhesion;

(2) Virtually free of separations of the saturant-impregnated fibrous wrap 13 from the steel core 11;

(3) Presents highly uniform saturant impregnation, i.e., does not exhibit any saturant-free white-spots or light-spots.

The typical generalized processing apparatus for fabrilcating protected metal sheets will be described briefly in connection with FIGURE 2.

Typical processing apparatus is presented in FIGURE 2 wherein a coil 19 of metal core sheet 20 is positioned in uncoiling attitude at the entry point of a sequential processing system. The coil 19 preferably comprises a sheet 20 of cold-rolled steel or hot-rolled steel having a thickness from about 18 gauge through about 26 gauge. The metal core sheet 20 is delivered sequentially through a galvanizing pot 21, a pair of vertically aligned bonding rolls 22a, 2217, a saturant impregnating bath 23, saturant squeeze rolls 24 and a final take-up coil 2S.

Drive means such as sheet-engaging rollers 26 are provided for the metal core sheet 20 between the coil 19 and the galvanizing pot 21. The rollers 26 may be driven in synchronism by a suitable motive power source such as an electric motor 27.

The galvanizing bath 21 comprises preferably a container having an inventory of molten heating metal such as lead 28, a supernatant layer of molten flux 29 on one side of a vertical baille 30 and a supernatant layer of the molten adhesive metal 31 -on the other side of the vertical baille 30. A pair of exit rolls 32 is partly immersed in the molten adhesive metal 30 to regulate the -thickness of adhering molten metal on the metal core sheet 20a.

After the metal core sheet 20 leaves the galvanizing pot 21 it is coated with a molten adhesive metal and is identified by the numeral 20a. After the coated metal core sheet 20a passes through the nip of the bonding rolls 22a, 22h, it is coated with fibrous wraps in the form of asbestos paper 33a, 33h provided from paper coils 34a, 34b and is identified by the numeral 2Gb. After the filbrous coated metal core 2017 has become impregnated with weather-resistant saturant, it is identified by the numeral 20c.

Emerging from the galvanizing bath 21, the coated metal core sheet 20a turns over a guide roll 35 which is mounted Within a few feet of the exit rolls 32. Beyond the guide roll means 3S, the metal core sheet is maintained hot enough to prevent fusion of the molten adhesive metal coating. The coated metal core sheet 20a with its molten metal coating, passes directly unsupported from the guide roll 35 to the bonding rolls 22a, 22h. Sheets of asbestos paper 33a, 33h are withdrawn continuously from the coils 34a, 34h, respectively. The combustible content of the asbestos paper sheets is burned lby impingement with llames identified by the arrows 36, 37. The sheets of residual incombustible asbestos paper peripherally engage the bonding rolls 22a, 22b respectively and, as the asbestos passes through the nip of the bonding rolls, the molten adhesive metal coating is substantially concurrently fused and pressed into the interstices of the asbestos sheets to provide a mechanical keying or anchoring of the asbestos paper to the metal core sheet as a fibrous wrap. The resulting laminated sheet structure is identified by the numeral 2Gb.

Any excess asbestos paper at the -side edges of the laminated sheet 2Gb is removed by means of trimming devices such as abrasive edge trimmer wheels 38 or spirally grooved steel burrs.

The protected metal sheet 20b is subsequently impregnated with a suitable resinous or bituminous saturant, preferably a high flash point asphalt, contained in a molten bath 23. The impregnated protected metal sheet passes through a pair of grooved impregnating `rolls 39 and thence through one or more pair of smooth-surfaced squeeze rolls 24. Excess impregnant is collected in a tray 40 beneath the rolls 24 and returned to the molten bath 23. The coated, smooth-surfaced protected metal sheets 20c heretofore have been cooled by passing through water sprays 41.

Patented Sept. 27, 1966 i The resultant impregnated protected metal 20c is turned into a coil 25 as shown in FIGURE 2 for aging prior to further processing.

The further processing might comprise applying outer coatings of resins, asphalts and the like. The final sheets are cut to desired lengths and rolled or bent into desirable architectural shapes.

Processing condi tions The temperature of the molten metal galvanizing pot 21 is usually maintained between 800 and 950 F. when the coating metal is zinc. The molten lead inventory 28 serves to heat the metal core strip 20 to the bath temperature so that adequate zinc adhesion will occur without excessive alloying phenomenon. The metal coating of the strip 20a is maintained in a molten condition until the strip passes through the bonding rolls 22a, 22b. The asbestos-bonded metal strip 20b enters into the saturant bath 23 at a temperature between about 500 and 650 F., which is preferably about 100 F. above the temperature of the saturant bath. Since the saturant preferably is a high fiash point asphalt, the saturant bath temperature is maintained at 350 to 500 F., preferably about 420 to 450 F. The saturant-impregnated protected metal strip 20c is thence directed through the squeeze rolls 24 to remove excess saturant and thence directly to the take-up coil 25.

Between the squeeze rolls 24 and the take-up coil 25,

`the protected metal strip 20c loses some of its heat content through radiation to the surroundings. The preferred temperature at the take-up coil, according to the present invention, is from 250 to about 400 F., and preferably about 270 to 320 F.

Prior art tinued with the water being supplied through the sprays 41. It was considered essential that the asphalt saturant be cooled to minimize its sticking tendencies prior to recoiling the continuous sheet in the take-up coil 25. With the water sprays 41 directed against the upper and bottom surfaces of the continuous sheet of protected metal, the temperature at the take-up coil 25 was about 190-200 F.

'Ihe initial coils of continuous metal sheets could not be successively uncoiled because of the delaminating of the sheets. The fibrous asbestos wraps cohered; fibrous chunks of the asbestos coating were actually torn out of the asbestos wrap material. The failure was in the asbestos wrapping itself, through internal delamination; there was no failure of the asbestos-to-metal-core bond which is the result 4of the concurrent compression and fusion of the molten metal into the asbestos wraps.

In an effort to offset the delamination problems, it was concluded that the asphalt saturant should be further chilled prior to recoiling of the product sheets in order to guarantee that the saturant would be below a temperature at which it is tacky. Accordingly, an ice-and-water bath was interposed between the squeeze rolls 24 and the takeup coil 25 to provide the needed chilling capacity.

Actual temperature measurements indicated that a temperature of 100 to 110 F. could be achieved through the ice-and-water bath. Accordingly protected metal was coiled at about ll10 F. These chilled coils presented greater uncoiling problems than any coils theretofore manufactured. The wrap-to-Wrap cohesion Was excessive. Great areas of the asbestos felt from one wrap were cohered to areas of fibrous asbestos felt of the next Wrap.

In addition, there were white spots and light spots on the coiled strip where the asphalt failed to penetrate toward the metal core.

This invention Subsequently the continuous protected metal strips were fabricated acc-Ording to this invention by eliminating all cooling Water and avoiding deliberate cooling efforts between the squeeze rolls 24 and the take-up coil 25. The actual surface temperature measurement at the take-up coils was 270-290 F. The saturant-impregnated strip appeared to have moist spots of excess saturant as it approached the take-up coil after the final squeeze roll. Nevertheless the coiling proceeded smoothly and the resulting coils were stored at ambient room temperature on blocks to allow air circulation around the coils. After about four days, the temperature of the coils equalized with the room temperature and uncoiling of the coils was accomplished without difficulty. There was no noticeable wrap-to-wrap cohesion. The saturant uniformity was excellent, i.e., there were no white spots or light spots where the saturant failed `to penetrate toward the metal core.

Hereinabove, -it has been stated that the metal core sheet 11 may have a thickness from about 14 through 28 gauge. It should be apparent that the different thickness materials will dissipate their heat content at different rates in transit between the squeeze rolls 24 and the take-up coil 25. The recoiling temperature may be regulated by controlling the distance between the take-up coil 25 and the squeeze rolls 24 according to the gauge of the core sheets.

The difference in core metal gauge also may have an effect on the required aging period for the coils. The nature of the changes occurring during the so-called aging period are not clearly understood. It has been found, for example, that uncoiling of the protect metal coils which are still hot is undesirable in that the wra-ps of fibrous coating material tend to stick together and delaminate in a manner similar to that described. As a rule, to deter- .mine a suitable aging period, it has been found that Suthcient aging has occurred when the coil temperature is about equalized with ambient room temperature. This usually requires about four days Where 22-gauge coldrolled steel is used as core metal. Other gauge thicknesses may require more-or-less than four days to achieve substantial coil temperature equalization with the surroundings.

The unexpected discovery which constitutes the present invention is the fact that avoiding deliberate cooling of the protected metal strip between the squeeze rolls and the take-up coil will permit production 'of a uniform coiled product which can be readily uncoiled.

A further unexpected discovery, not heretofore appreciated 4is that the coiled protected metal as described must be aged for at least several days until the coil temperature substantially equalizes With ambient room temperature before uncoiling is attempted.

application of added processing heat energy into the moving strip of freshly-made protected metal. That is,

Vin addition to avoiding the deliberate cooling of the freshly made Strip of protected metal, extrinsic heat can be applied to the strip after application of the asphalt saturant. Electrical heating elements incorporated into the final squeeze rolls, for example, have been utilized to raise the temperature of the rolls to about 450 F. (Note: Where the saturant bath 23 is maintained at 420-450 F., the temperature of the squeeze rolls 24 will be about 400 F. as a result of their conductive heat absorption through continuing peripheral engagement with the moving strip of freshly-made protected metal.) The subsequent recoiling of the heated moving strip without further deliberate cooling resulted in especially good coiled protected metal products.

The application of added heat to the moving strip conveniently is accomplished conductively by passing the sheet between rolls such as smooth-surface squeeze rolls which are deliberately heated with hot liquids, steam, hot gases or by electrical means. Alternatively, added heat may be introduced into the moving strip through radiant ener-gy such as infra-red radiation, through induction heating, through electrical resistance heating, through corrective heating by heated gases or vapors, et cetera.

Heated rolls about to 100 F. above the temperature of the moving strip are preferred.

I claim:

1. In the process of producing a protected metal sheet from a coil of metal core sheet including the sequential steps of:

metal-coating the metal core sheet;

applying a substantially asbestos felt sheet to said metal coating while said coating is at least partially molten, thereby bonding said substantially asbestos felt sheet t-o said metal sheet; impregnating the said asbestos felt sheet with a high flash point asphalt saturant in molten condition; and recoiling the resulting protected metal sheet; the improvement comprising: recoiling the said resulting protected metal sheet at a temperature between 250 and 400 F.

2. In the process of producing a protected metal sheet from a coil of metal core sheet including the sequential steps of metal-coating the metal core sheet;

applying a substantially asbestos felt sheet to said metal coating while said coating is at least partially molten, thereby bonding said substantially asbestos felt sheet to said metal sheet;

impregnating the said asbestos felt sheet with a high tlash point asphalt in molten condition; and recoiling the resulting protected metal sheet;

the improvement comprising: rec-oiling the said resulting protected metal sheet at a temperature between 250 and 400 F., and aging the protected metal sheet coil until its temperature is substantially equalized with ambient temperature.

3. In the process of producing a protected metal sheet from a coil of metal core sheet including the sequential steps of:

metal-coating the metal core sheet;

applying a substantially asbestos felt sheet to said metal coating While said coating is at least partially molten, thereby bonding said substantially asbestos felt sheet to said metal sheet;

impregnating the said asbestos felt sheet with a high ash point asphalt in molten condition; and recoiling the resulting protected metal sheet;

the improvement comprising: heating the asphalt-impregnated, fibrous-bonded, metal-coated core sheet to a temperature between 280 to 400 F. prior to recoiling and thereafter carrying out the said recoiling between 250 and 400 F.

4. In the process of producing a protected metal sheet from a coil of metal core sheet including the sequential steps of:

metal-coating the metal core sheet;

applying a substantially asbestos felt sheet to said metal coating while said coating is at least partially molten, thereby bonding said substantially asbestos felt sheet to said metal sheet;

impregnating the said asbestos felt sheet with a high flash point asphalt in molten condition; and recoiling the resulting protected metal sheet;

the improvement comprising: passing the saturant-impregnated, brous-bonded, metal-coated core sheet between a pair of rolls in peripheral engagement therewith, maintaining the temperature of the said rolls from 10 to 100 F. above the temperature of the saturant engaged therewith, and thereafter carrying out the said recoiling between 250 and 400 F.

References Cited by the Examiner UNITED STATES PATENTS 2,631,641 3/1953 Coffman 29-528 X 2,712,174 1/ 1955 Hubbele 29-473.1 3,147,546 9/1964 Bowman et al 29-473.1 X

JOHN F. CAMPBELL, Primary Examiner.

P. M. COHEN, Assistant Examiner.

Claims (2)

1. IN THE PROCESS OF PRODUCING A PROTECTED METAL SHEET FROM A COIL OF METAL CORE SHEET INCLUDING THE SEQUENTIAL STEP OF: METAL-COATING THE METAL CORE SHEET; APPLYING A SUBSTANTIALLY ASBESTOS FELT SHEET TO SAID METAL COATING WHILE SAID COATING IS AT LEAST PARTIALLY MOLTEN, THEREBY BONDING SAID SUBSTANTIALLY ASBESTOS FELT SHEET TO SAID METAL SHEET; IMPREGNATING THE SAID ASBESTOS FELT SHEET WITH A HIGH FLASH POINT ASPHALT SATURANT IN MOLTEN CONDITION; AND RECOILING THE RESULTING PROTECTED METAL SHEET; THE IMPROVEMENT COMPRISING: RECOILING THE SAID RESULTING PROTECTED METAL SHEET AT A TEMPERATURE BETWEEN 250*AND 400*F.

3. IN THE PROCESS OF PRODUCING A PROTECTED METAL SHEET FROM A COIL OF METAL CORE SHEET INCLUDING THE SEQUENTIAL STEPS OF: METAL-COATING THE METAL CORE SHEET; APPLYIMG A SUBSTANTIALLY ASBESTOS FELT SHEET TO SAID METAL COATING WHILE SAID COATING IS AT LEAST PARTIALLY MOLTEN, THEREBY BONDING SAID SUBSTANTIALLY ASBESTOS FELT SHEET TO SAID METAL SHEET; IMPREGNATING THE SAID ASBESTOS FELT SHEET WITH A HIGH FLASH POINT ASPHALT IN MOLTEN CONDITION; AND RECOILING THE RESULTING PROTECTED METAL SHEET; THE IMPROVEMENT COMPRISING: HEATING THE ASPHALT-IMPREGNATED, FIBROUS-BONDED, METAL-COATED CORE SHEET TO A TEMPERATURE BETWEEN 280*TO 400*F. PRIOR TO RECOILING AND THEREAFTER CARRYING OUT THE SAID RECOILING BETWEEN 250*AND 400*F.

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