US1675646A - Method of zinc coating ferrous metal - Google Patents

Description

July 3, 1928. 1,675,546-

J. G. FIVTZ GERALD METHOD OF ZINC GOATING FERROUS METAL Filed March so, 1925 Patented July 3, 1928.

UNITED STATES y 1,615,646 lrA'rErrr-I OFFICE.

`JOSEPH G. FITZ GERALD, OF CANTON, OHIO, ASSIGNOB, BY DIRECT AND MESNE ASSIGN- MENTS, TO CENTRAL ALLOY STEEL CORPORATION, OF CANTON, OHIOQA CORPORA- 'rIoN 0F NEW Yom; i

nia'rnon oFlzINc coATKINe rannous METAL Application filed Harel! 30, 1925.v Serial No. 19,381.. l

The invention relates to the process of coating ferrous metal with a film of zinc, which is commonly called` galvanizing when applied to the zinc coating of steel or iron sheets. One object of the improvement is to cause such a coating to adhere so tightly to the ferrous metal that'it will not become detached or scale therefrom during bending, breaking or deep drawing operations; and another object of the improvement is to so control the crystallization of the zinc coating as to present a uniform velvety gray `frosted appearance to the surface of the sheet.

Ordinary galvanized sheets present a bright surface of large granular spangles variegated in appearance and of different sizes and shapes, which may have so little adhe.

ordinarily used in a .galvanizing process, be-v fore it is passed-through molten spelter, the pores of the ferrous metal will open up to such an extent that when it is bathed in the molten spelter, the same will find its way into the pores and amalgamate more intimately with the ferrousbase; and the same super-heating of the sheet, and the resultingsuperheatin of the spelter, results in a thinner coatin g o the same being applied'to the sheet. I have, also discovered that the adhesion of such a coating is increased by a slow and gradual cooling of the same,` extended through af considerable period of time; and that tllis treatment also reduces the size, the appearance, and the character of the zspangles, which.'may be reduced to-such a. minute size as to present a uniform velvety gray frosty appearance, instead of the bright flaky appearance4 of the ordinary .galzanized s eet. v

By thus superheating the sheet in lead and spelter baths successively, and then control ling the degree and the rate of the cooling conditions, I lhave found that a galvanized sheet can be produced with a coating so tight as to adhere, without scalin during forming operations, orwhen su jected Ato high temperatures and also with a uniform velvety gray surface which is desirable for spe'- elevation section, somewhat diagrammatic,

of apparatus which may be used for carrying out the improved process. Such apparatus may include al cleaning tank A, a galvanizing pot B Lw-ith a hood C therefor, a heat maintaining and cooling tunnel D, finishing rolls E, leveling rolls'Fand' a porcupinev cooling ,ta-ble G. v

vSteel or iron `sheets may be cleaned for galvanizing by a weak solution 2 of hydrochloric or muriat-ic acid in the tank'A, and then carried byrolls 3 between'guides 4 and 4 to feed-in rolls 5, which. direct them downward through a salammoniac flux 6 in a trough' 7 directly into a bath of molten lead 8, all in accordance with common and well known practice.

The molten lead' bath may have a'depth of some thirty or thirty-six inches on top of which floats a layer of molten spelter 9, which ma be molten zinc, together with 'such additionsof tin, antimony, and the like,

as may be desired, according to the particular character of thecoating desired. It will be understood that the flux trough 7 extends downward into the molten lead, so that the sheets vpass through the lfluir into the lead without coming into contact with the'spelter. For the purpose of the present invention, the molten lead is maintained at a temperature .of from 850 to 950 F. preferably about 900 F., which is from 50 to 100 higher than common' -galvanizing practice; the pu ose of which is not only to su rheat the bo y of the sheets before passing the same through the spelter, but to open or enlarge the pores of the ferrous metal so that the s Iter` and iron will amalgamate more comp etely. y

Furthermore, the superheating of the lead serves to superheat the spelter floating thereon to a higher temperature than in ordinary practice, and melts the, same to a thinner liquid, which not only amalgamatesv more readily with the ferrous metal, but produce a .through the molten lead and upward sheets are directed by guides 13 and 13 on an endlessiconveyor 14, which details of the apparatus may all be in accordance with common practlce. The tunnelD may be of an o(pen or a muflle type, and may be heated by irect or indirect means, as for instance electric coils, or some form of fuel, and as shown may be heated by gas flames flowing from suitable apertures or slots in transverse tubes, so that the flames may impinge the sheet if desired. The heating means are arranged so as to maintain the temperature in the end portion of the tunnel adjacent to the galvanizing pot, and so that the temperature in the tunnel will gradually decrease toward the other en ereof; the purpose of the tunnel being to control the cooling of the hot coated sheets so that the same will be gradual and will extend through a considerable ing'of the hot coated sheet, to produce a period of time. The preheatin of the sheet and the spelter by the super cated lead bath, not only more completely amalgamates the spelter coating with the ferrous body of the sheet,

`but with` the slow and gradual cooling thereof so modifies the granular structure of the rcoatingl asA to not only change the appearance t ereofsas descrlbed, but also increases the adhesion thereof to the'bod of the sheet, so that the same can be sharply or drawn deeply or subject to high temperature without detaching or scaling the 'coating from the body of the' sheet.

vThe finishing rolls E may be ordinary cold rolls for compressing the coating on and into the' ferrous metal and producing a smooth finish thereon, or wire scratchingrollsfor'making al satin finish, or brush burnshing' rolls for making abright finish,

`in accordance with the commonuse of these and other liinds of finishing rolls.

The ordinary, flattening rolls F may be used vfor straightening a vbent, Yor buckled sheet and a porcupine cooling table'G may be used for final y cooling the ysheets .for manually handlin the same for delivering them at the end o the continuous processes described herein.- A I s.

I claims. .A l,

1.' The "method of zinc coating .ferrous metal, which' consists in heating the metal to be coated to from' 850". to 950 F. and

-then coating itin a molten spelter bath to produce a tlghtcoat.

-2.A The 'method of zinc 4coating ferrous metal, which consists in heating `the metal to be'coated in a molten lead bath to from ent siste -in passing metal, which consists in heating the'metal, then coating it in a molten spelter bath, and then controlling the cooling of the hot coated sheet, to produce a tight coat of the desired character and appearance. f4. The method of zinc coating ferrous metal, which consists in heating the metal to be coated to from 850 to 950 F., then coatin it in a molten spelter bath andthen contro ling the cooling of the hot coated sheet, lto produce a tight coat of the desired character and appearance.

5. The method'of zinc coating ferrous metal, which consists in heating the metal in a molten lead bath, then coating it in a molten spelter bath, and then controlling the cooling of the hot coated sheet, -to produce a tight coat of the desired character and a earance. p

' 6. 'Flic method of zinc coating ferrous metal, which consists in 'heating the metal to be coated in a molten lead bath to from 850 to 950 F., then coating it in a molten spelter bath, and then controlling the coolling the cooling of the hot coated metal by predetermined gradations of temperature to produce the desired character and appearance of the coating.

8. The methbd of zinc coating a ferrous metal, which consists in coating the metal in a molten spelter bath, and then controlling the temperature of the cooling of the hot coated metal to produce the desired character and ap arance of the coating.

9. The method)e of zinc coating ferrous metal, which consists in coatin the metal in a moltenA spelter bath, and t en controllin the time and the temperature of the coo ing of the hot coatedl metal to produce the desired character and appearance o f the coatin 10. I netal, which consists in coating the metal in a molten spelter bath, then controlling the cooling ofthe hot coated metal by predetermined dations of temperature to pro- 'duce the', esired chracter and appearance ofthecoating, and then finishing and flattening the sheet, al1 by a continuous process.

11,. The method of 'treating galvanized' sheets immediately followin the exit of the latter from the galvanizing ath, which con# the sheets through a zone of applied heat in which they are permitted to cool tions of temperature.

v In' testimony that I claim theiabove I have hereunto subscribed mname. JOSEPH G. F Z GERALD.

gradually by predeterminedv 'gra'da-I lhe-vmethod of zinc coating ferrous

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