US1876582A

US1876582A - Coating and heat treating

Info

Publication number: US1876582A
Authority: US
Publication date: 1932-09-13
Anticipated expiration: 1949-09-13

Description

Sept. 13, 1932.

AL 0. AUSTIN COATING AND HEAT TREATING Original Filed May 25, 192:

l /Z BY A TTORNEY Patented Sept. 13, 1932 umTEosTATEs PATENT OFFICE ARTHUR o. AUSTIN, or NEARBARBEBTON, omqassronon, BY'MESNE AssIGnMEN'rs, TO THE OHIO BRASSHCOMPA'NY; or MANSFIELD, 01110, A CORPORATION or NEW JERSEY COATING AND HEAT TREATING;

Original application filed. May as; iazsysemi memos- Divided andthis application filed September 14, 1m. 7 Serial No; ao5,a7s-.

This invention relates to a method andapparatus for coating and heat treating metal articles and has for its object the provisionof a method and apparatus in which a uniform.

coating may be economically applied tothe articles and in which difficulties that heretoexperienced are largely fore have been avoided. a v v The invention also, includes heat treatment of articles simultaneously .with the coat ng operation. In the accompanying drawing there is illustrated apparatus by means in per which the present invention maybe formed. This apparatus together with the process comprised in the invention, is described in the following specification, the invention being more particularly pointed out in the appended claims.

In the drawing: r I The figure is a. vertical sectional view showing one. form of apparatus-for practicing the p esentinvention. i

"This application is a division Of'flPPllCfltion, Serial Number 32,709, filed May 25, 1925. 1

This invention deals with new and im proved methods of galvanizing and heat treating articles. In galvanizing, tinning or coating articles wlth lead or other material, it is generally desirable toform a umfornr coat which amalgamates with the material covered and acts as a water protection.

While the invention applies particularly to galvanizingor the process of coating steel ,'f

grey iron and malleable castings with zinc, it applies to coat ng with some other metals such as tin. In the process of. galvanizing,

it'is customar to clean'thearticleb sand H y y temperature WVhere the bath is atlow temgalvanized or tinned is placed inthe-bath,an 1

amalgamation takes place. Where articles are simply clean and bright, it is generally necessary to dip the articles in a flux such as zinc chloride or sprinkle the articles with ammonium chloride commonly known as salammoniac. If thegalvanizing or tinning bath is not very hot, an amalgamation usually takes place without much difii'culty, providing the usual pains'are taken. Where the 'culties. Where abatn of high temperature is used, there is'a tendency to oxidizethe surface of the article to be galvanized or tinned ifamalgamation does not'take place in a very short time such as may happen if there. is a small amount of air or gas entrapped. This makes it exceedingly difiicult to use a high temperature bath on'many classes of ware which are galvanized or tinned. If the hot bath comes incontact on one side of the metal to be coated and an air or gas pocket exists onthe opposite side of a thin section, the surface may become oxidized or the flux driven oil so thatamalgamation will not take place readily unless more flux is applied or considerablc'length of time is allowed.

Where the surface becomes oxidized or the -fiux is driven off before amalgamation takes place, a bare spot, or pinhole in the galvanizing or tinning usually results.

One object of the present invention is to get awayfrom this difficulty. This is accomplished by placingthe article to be coated in a molten bath which has a relatively low perature, the tendency to drive off the fluxbe- 'fore amalgamation takes place is not so great and the tendency to oxidize the surface is also reduced so that amalgamation takes place with a minimum amount of fluxing and without the formation of bare spots or pinholes. After amalgamation takes place, the

surface of the article to begalvanized or.

to transfer the articles galvanized to a bath which is much hotter. This is frequently quite important when a thin uniform coat is desired or where large production is desirable. In order to insure uniformity, steps may be taken so that temperature is finally raised to the desired value. This can be readily done in one of several ways, depending upon the conditions.

One form of apparatus for accomplishing the desired results is shown in the drawing. In this case a tube 50 is filled with a molten bath and the articles 51 are put in at the charging end 52 and discharged at the end 53. The tubular member 50 containing the molten material may be of metal or a suitable refractory. The heating may be accomplished by any suitable fuel or by electrical energy as shown. Since the incoming material enters the end 52, it will tend to lower the temperature of the bath at this point. As the material traverses toward the end 53 it will be heated up. This movement may bev tact with the air or gases except at the entering and discharging ends, so that there will be little oxidation. I

Where the refractory tube is used, the

amount of dross will be reduced to a minimum and under favorable conditions no dross will be formed. This is a very material ad-- vantage in that one of the principal objections to high temperature is the amount of dross formech As the piece is discharged from the end 53 it may be allowed to fall a considerable distance and strike several baffles 54 and 55 before falling into the quench tank 56. Striking several baffles tends to knock off any superfluous material and if time sufficient is allowed before striking the cooling bath, the surface tension will tend to form a very uniform coat. Instead of striking baffies, it is possible to allow the article to fall through a passage into which air is forced at a considerable velocity. This tends to blow off any superfluous material and the direction of the air may he used to retard the fall giving ample time to remove the superfluous material. 'ith the methods shown,

it is possible to raise the material to the de-.

sired temperature so that the article may be tinned or galvanized and at the same time, give a heattrcatment to increase the mechanical strength, hardness or reliability.

This method is applicable to the heating of articles for heat treatment as well as for the galvanizing or tinning operation.

1. Apparatus for coating metal articles comprising a container for a molten bath of coating material, means for heating the coating material in said container to higher temperatures at the point of exit of said articles than at the point of entrance, and means for excluding air from the portion of said container most highly heated.

2. Apparatus for coating metal articles, comprising a container of refractory material having a portion thereof closed at the top, means for feeding articles progressively through said container and electrical means for heating a bath of molten coating metal to different temperatures at different portions of said container.

3. Galvanizing apparatus, comprising a tank having a-covered portion and having an entrance opening at one side of said covered portion and an exit opening at the opposite side of said covered portion, a bath of melted coating metal in said tank and contacting with the cover thereof to exclude air from contact with the upper surface of said bath, means for heating the melted metal in said bath, said heating means being arranged to maintain a higher temperature adjacent the exit opening than that adjacent the entrance opening, and'means for progressively feeding articles through said bath from the en trance to the exit opening thereof.

4. Galvanizing apparatus, comprising a refractory tank having a cover for the centra1- portion thereof and having entrance and exit openings at opposite ends thereof, electrical heating elements adjacent the outer surface of the wall of said tank for heating a bath of molten metal within said tank, said heating elements being arranged to maintain a higher temperature in said bath adjacent the exit opening thereof than that adjacent the entrance opening thereof, and means for feeding a separate articles progressively through said tank from the entrance to the exit opening thereof.

5. Galvanizing apparatus, comprising a refractory tank having the top portion thereof closed between its ends, an entrance opening at one end of said tank, a plunger arranged to reciprocate in said tank adjacent said entrance opening to feed separate arti cles through said tank, said tank having an exit opening at the end thereof opposite said plunger, and electrical heating elements wound, about said tank and arranged to generate a greater amount of heat adjacent the exit opening thereof than adjacent the entrance opening thereof.

6. Apparatus for coating articles comprising a receptacle having the top thereof closed but having entrance and exit openings, molten coating metal in said receptacle, means for heating said metal to a higher temperature adjacent the exit opening than adjacent .the entrance opening, the walls of said receptacle being formed of refractory material and having electrical heating velements connected therewith.

. Apparatus for galvanizing metal articles comprising a container having a cover,

7 10 means for heatingzmc in said container to a temperature above themelting point of the zinc, the melted zincin said container being 1n contact with the cover of said container to exclude air from the surfaceof said zinc, said heating means being adapted to maintain said zinc at a higher temperature, in one portion ofsaid bath than in another, and means I for passing the articles to be galvanized through said bath from the cooler to the hotter portionthereoi i In testimony whereof I have signed my name to this; sgecification this 12th day of September, A. 1928. v-

ARTHUR 0.. AUSTIN.