US1378052A - Process of coating steel sheets with aluminum - Google Patents

Description

V adhere to" the I oial precautions are taken. If to remedy UNITED srarrs PATENT": orrice.

MENTS, TO WHEELING STEEL & IRON COMPANY, OF

A. CORPORATION OF WEST VIRGINIA.

WHEELING, WEST VIRGINIA,

PROCESS OF COATING STEEL SHEETS WITH AL'UMINUM,

No Drawing.

To all whom it may concern:

Be it known that I, SAMUEL PEAGOCK. a citizen of the United States. residing at Wheeling, in the county of Ohio and State of West Virginia, have invented certain new and useful Improvements in Processes of Coating Steel Sheets with Aluminum; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled 1n the art to which it appertains to make and use the same.

This invention relates to a process of coating thin steel sheets with aluminum and has for its object to provide a procedure which will be more efiicient in action and less costly to carry out than those which have been heretofore proposed.

With these'and other objects in view the invention consists in the novel steps and combinations of steps constituting the process, all as will be more fully hereinafter disclosed and particularly pointed out in the claims.

In order that the precise invention may be the more clearly understood, it is said: It is well known that thin sheets of steel after being descaled or cleaned according to well known procedures are now commonly immersed in a bath of molten tin, inorder to convert them into the tin plate of commerce. The tin of the coating, however, is a largeitem of cost when it is considered that these sheets are treated by the million, and in addition, said coating entails other well known objections not necessary to mention. A

It is therefore the object of this invention more specifically stated, to coat said sheets with aluminum and thus obviate many of the objections that are now met with in the tin coating processes.

But in coating said sheets by dipping them into a molten bath of aluminum, the

relatively high temperature of about 700? C. of the latter causes many practical d fliculties in obtaining a good coating, which greatly increase the cost of the procedure. 1

That is to say, the differences in temperature between the steel and aluminum are considerable and the coating is not apt to steel throughout,-:unless spe- Specification of Letters Patent.

Application filed November 9, 1920. Serial No. 422,812.,

Patented May 17, 1921.

this objection, we pass the steelsheets through the molten aluminum slowly enoughfor the steel sheets to reach the temperature of the bath, and to form an alloy film to hold the coating, the process will be found to be too slow to be commercial.

On the other hand, a rapid passage of the steel sheets through the molten bath will result in a coating consisting of a solidified, or frozen la er, almost devoid, of a film of alloy to hold it to the sheet, and possessing a considerable structure.

In carrying out this invention, I avoid the foregoing objections by employing 011 top of the molten aluminum a molten layer of an anhydrous double alkali aluminum porosity .due to a crystalline,

chlorid such as AlNaCh, which has a melting point of about 200 C. I further employ the usual apparatus for coating with tin, consisting of a series of submerged guide and traction rolls to carry the steel sheets into and out of the aluminum bath. The double aluminum sodium chlorid layer or bath is preferably maintained at about 300 C. on top of the aluminum by means of cooling coils. The steel sheets being freed from their oxids, or cleaned, are now heated up in a non-oxidizing atmosphere, or out of contact with the air, to a temperature of say 250 C. or 300 C. or higher, whereupon they are carried through the said double chlorid layer into the aluminum bath. Said double aluminum alkali chlorid is found to readily deposit a firmly adhering film on the. steel sheets as they pass into the aluminum, and the molten aluminum readily coats said filmwith a firmly adhering film of aluminum, as said sheets pass therethrough, with the result that the finonv the molten aluminum, however, -all contact with the air is avoided and thewcoating is thereforegreatly improved. Again, as is well known in coating procedures of this kind it-is very desirable to pass the coated,

sheets throu h palm oil as they leave the apparatus. t is found that instead of having a single double chlorid bath, two may be provided. The one is positioned on that side of the machine at which the steel plates enter the bath of aluminum, and the other Y is positioned on the exit side of the maplates therewith, as they leave the apparatus. 1

It is obvious that those skilled in the art may vary the details of the procedure without departing from .the spirit of the invention, and therefore it is not desired to be limited to the above disclosure except as may be required by the claims.

What is .claimed is:

1. The process ofcoating steel sheets with aluminum which consists in first passing said sheets through a molten bath of a double aluminum alkali metal chlorid, and then through a molten bath of aluminum} substantially as described.

2. Tlidprocessof coating steel sheets with aluminum which consists in first depriving said sheets of any oxid coating they may have, then passing said sheets through a substantially as described.

i said baths in the order named, substantially as described.

4. The process of coating steel sheets with aluminum which consists in floating a molf ten bath of a double aluminum alkali metal chlorid upon a molten bath of aluminum; maintaining the temperature of said first named bath below that of saidsecond named bath; heating said sheets to the approximate temperature of said first named bath; and passing said sheets through said baths in the order named, substantially a described.

5. The process of coating steel s eets with aluminum which consists in floating a molten bath of a double aluminum alkali metal chlorid upon a molten bath of aluminum; maintaining'the temperature of said first named bath below that of said second named bath; passing said sheets through said baths in the order named; and thin passing the coated sheets through a bat In testimony whereof I afiix my signature.

SAMUEL PEACOCK.

of palm oil,