US2274056A - Extruded anode - Google Patents

Description

Feb. 24, 1942.

BY ROLLI HG lNGOTS ARE MILLED HND CHIPPED I NGOT BOOQ HEATED AND FORGED 2 BLOOMS REHEAT AND FORGE H EATEI? AND RGLLE'D AND ROLLED ,ovAL Auooes G. F. GEIGER EXTRUDED ANODE Filed June 25, 1940 3 Sheets-Sheet 1 av ax-r-RusmN INGOT'S GO TO PRESS DIRETLY FROM THE MOULD HEATED- ANODES VARIOUS SHAPES INVENTOR. GEORGE FGE/GE/S G. F. GEIGER l=eb. 24, 1942.

EXTRUDED ANODE Filed June 25, 1940 :5 Sheets- Sheet 2 IN V EN TOR. I GEORGE F GE /6E/? ATTORNEY Y I Feb. 24,- 1942.

ca. FL GEIGER EXTRUDED ANQDE Fi led June 25, 1940 3 Sheets-Shee,t 3

. INVENTOR.

GEO/FGEEGE/GE/P a am ATTORNEY Patented Feb. 24, 1942 EXTRUDED ANODE George Fellmuth Geiger, Radburn, N. J., assignor to The International Nickel Company, Inc.,

a New York, N. Y., a corporation of Delaware Application June 25. 1940, SerialNo. 342,228 In Canada May 29, 1940 2 Claims. (01. 148-2) The present invention relates to extruded anodes, and, more particularly, to extruded nickel anodes. v

Since the inception of the nickel plating industry, the workers intimately connected therewith have constantly striven to improve the anodes employed. Efiorts have been made to imsame structural characteristics as rolled nickel anodes, slightly less uniform distribution of the provethe uniformity of corrosion and the upper limit of acceptable corrosion. In addition, efforts have been made to control the amount of sludge produced and the amount of loose nickel produced during corrosion by control of the com.- position of the anodes. Among the satisfactory solutions to these various problems has been the rolled nickel anodes now available to the art. These rolled anodes, from a technical viewpoint are highly satisfactory from the standpoint of activity, the upper limit of acceptable corrosion, the amount of loose nickel and the amount of sludge produced during corrosion. From a manufacturing standpoint the multiplicity of opera- .tions required to reduce the cast ingot to an anode of suitable size is a drawback. This will be readily appreciated when the process of producing rolled anodes is reviewed. As those skilled in the art well know. the metal for an anode is first cast as an ingot. The ingots are then milled and chipped. The chipped ingots are then heated and forged to provide two blooms. At times however, a reheat is necessary. The blooms are again heated and rolled and the operations repeated as often as is necessary to obtain the required reduction in cross section to provide an anodeof suitable dimensions. It has been dis.- covered that anodes comparing favorably in every respect 'from a chemical and an electrochemical standpoint can be produced by a very much simpler process than the prior art rolling process.

It is an object of the present invention to produce anodes having the valuable characteristics of roll 6. anodes by a simplified process.

It is a other object of' the present invention to produce carbon-containing and carbon-free nickel anodes having the desirable characteristics of rolled nickel anodes.

It is a further object of the present invention to provide nickel anodes having improved surface characteristics, good corrosion, and high eniciency.

It is likewise within the purview of the present invention to provide oxygen-free anodes havin the desirable characteristics of rolled nickel anodes. I

The present invention also contemplates the nickel oxide and slightly less uniformity of grain size.

It is also within the contemplation of the present invention to provide nickel anodes having the valuable characteristics of rolled nickel anodes from cast and/or forged billets.

Other objects and advantages will become ap parent from the following description in which:

Fig. 1 is a diagrammatic flow sheet in asomewhat pictorial manner of the prior art process of producing rolled anodes;

Fig. 2 is a diagrammatic flow sheet clearly illustrating in a pictorial manner the simplicity of the process of the present invention as compared with the conventional process for producing rolled anodes;

Fig. 3 is a photomicrograph of transverse edge of a hot rolled nickel anode;

Fig. 4 is a photomicrograph of a transverse edge of an extruded nickel anode;

Fig. 5 is a photomicrograph of a longitudinal edge of a hot rolled nickel anode;

Fig. 6 is a' photomicrograph of a longitudinal edge of an extruded nickel anode;

Fig. 7 is a photomicrograph of a transverse center of a rolled nickel anode;

Fig. 8 is a photomicrograph .of a transverse center of an extruded nickel anode;

Fig. 9 is a photomicrograph of a longitudinal center ofa rolled nickel anode; and

Fig. 10 is a photomicrographof a longitudinal center of an extruded nickel anode.

Generally speaking, the simplified process for producing the anodes, and, more particularly, nickel anodes having the valuable characteristics of hot rolled nickel anodes involves the fusion of a melt having a suitable composition which is cast preferably in ingots somewhat smaller than those heretofore employed in the hot rolling production of nickel anodes. The casting is then introduced into an extrusion press of suitable size and having a die of suitable contour and the anodes extruded directly from the press.

The advantages in simplification of the manufacturing process for producing nickel anodes having the valuable characteristics of nickel anodes will become manifest from a study of the flow sheet depicted in Fig. l. As will be readily appreciated by those skilled in the art there are a minimum of 9 or 10 steps in the process of producing rolled nickel anodes. These steps include millin chipping and heating the ingot followed shapes.

by forging the blooms. The blooms are then heated again, rolled, say on a 24 inch mill, reheated and rolled again, for example, on a 14 inch mill. These latter rolling operations are repeated as often as necessary to produce anodes having the required dimensions.

A further drawback of the rolling process is the inflexibility of the process with respect to the shape of the anode produced. The hot rolling process as practiced by the industry at the present time produces but one shape anode, to wit: the so-called "oval anode, without a change from one pass to another or a roll change. Such a roll change is much more expensive than a die change as required in the extrusion process of the present invention. On the other hand in direct contrast to this disadvantage of the hot rolling process, the process of the present invention is very flexible as is well understood by those skilled in the art. The die by which the form of the extruded anode is controlled may be designed to produce anodes of various and diverse Thus rounds, flats and in addition various other shapes such as prismatic, half-round, half-oval and many other unusual shapes may be produced in one operation. As the hot rolling process is carried out at the present time anodes cannot be produced in the latter unusual shapes without considerable expense. In addition to these manufacturing advantages the improved extruded anode provides a certain other advantage. Thus the over-hauling of the ingot prior to hot rolling is eliminated since practically all of the outer skin of the ingot is left in the extrusion press. Furthermore the surface of the anode is devoid of certain defects which are common in hot rolled nickel anodes.

The novel anode described herein possesses certain advantages over the conventional cast anodes of the prior art processes. For example, the extruded anodes of the present invention come from the press in a surface condition which is a considerable improvement over that of cast anodes. The surface of the extruded anodes is smoother and free from mold pulls. Furthermore the extruded anode is free from slag inclusions, has a more homogeneous structure and a more uniform composition than the cast anodes now available to industry. From the foregoing it will be readilyappreciated that the process of the present invention represents a long stride forward in the technical progress of electroplatmg.

In order thatthose skilled in the art may have a better understanding of the principles of the present invention the following discussion of the metallurgical, electrochemical and plating characteristics of the new extruded anode made from oxidized nickel will be given together with a brief discussion of similar characteristics of hot rolled nickel anodes as well as the cast anodes available to the industry at the present time.

The drawings, Figs. 3 to 10, provide means for differentiating between the crystal structure of the new extruded anode and the prior art hot rolled anode. For comparison of the crystal structure of the prior art anode and the new ex- .truded anode, sections of the transverse edge,

the longitudinal edge, the transverse center and the longitudinal center of representative anodes were taken and polished and etched in the usual manner. The crystal structure of the transverse edge of a hot rolled nickel anode is depicted at an enlargement of about 100 magnifications in Fig. 3. As those skilled in the art will readily appreciate, the grain size is uniform and relatively large. Furthermore, as is clearly shown in .Fig. 3, the distribution of oxides and similar conand that the distribution of oxide formations likewise is not as uniform as in the hot rolled anode. The uniform distribution of grain size and oxide formation characteristic of. hot rolled nickel anodes is readily appreciated by an inspection of Fig. 5 However, in striking contrast to the homogeneity of the hot rolled nickel anode, the banded structure of the extruded anode is manifest in the photomicrograph Fig. 6, as will be clearly seen. This is a photomicropragh of a section taken from a longitudinal edge of an extruded nickel anode. The distribution of grain size is not uniform and the striations of oxides are manifest. Further evidence of these differences between the crystalline structure ,of the prior art hot rolled nickel anodes and the novel extruded anode may be readily appreciated by those skilled in the art, from an inspection of Figs. 7, 8, 9 and 10.

In view of the non-uniformity of distribution of oxides and the non-uniformity of grain size it is surprising that uniform corrosion and production of only small amounts of loose nickel and sludge are characteristic of the new extruded anode. Those skilled in the art will appreciate the importance of this discovery when it is borne in mind that the experts have taught that uniformity of distribution of the oxide inclusions is necessary to smooth corrosion and similar desirable characteristics of nickel anodes.

It has been found that after de-skinning the new extruded nickel anode the degree of activity of the anode is practically the same as that of a similarly de-skinned hot rolled nickel anode. As those skilled in the art know, it is customary to subject nickel anodes to a de-skinning process in which about 3% by weight of the anode is removed in a preliminary electrolytic treatment.

The new extruded nickel anode possesses several advantages as compared with the cast anode of similar or comparable composition. The surface of the extruded anode is smoother than that of a cast anode. Furthermore, the freedom from slag inclusions which is characteristic of the extruded anode is an item which the practical elec troplater will appreciate. It is manifest that such slag inclusions lower the content of available anodic material, may well be the cause of uneven corrosion and are the source of other drawbacks well known to those skilled in the art. For example, in cast nickel anodes there usually is present an increased amount of loose nickel in the regions of slag inclusions. As is well known to those skilled in the art cast anodes frequently are marred by mold-pulls. The disadvantages of these inherent defects of a cast structure are too readily appreciated by those skilled in the art to require lengthy discussion at this time.

Although lacking the homogeneity of rolled anodes, the new extruded anode has a more unianodes will be appreciated by those skilled in the art.

Carbon- Carbon- Oxygenfree bearing free Electro 99. 76 99. 70 90. 9) 0. 10 None None None 0. 25 None Trace 0. 005 0. 008 0. 003 Trace 0. 01 0. 24 0. 14 Trace 0.04 0.04 0.04 01 to 0.03

Trace 0. 001 Trace 0. 0.05 0.09 0 01 to 0. 04

The value for nickel includes incidental amounts of cobalt usually present in commercial nickel.

The ingot is cast in the usual manner and transferred directly to the cylinder of an extrusion press of suitable dimensions. The press is provided with'a die having the desired contour which may be that of a square, a circle, a rectangle, a semi-circle, a triangle, or a half-oval. In addition, anodes may be extruded having an irregular cross section. It is preferred to maintain a temperature of about 900 to about 1200 C. during the extrusion of the anode. The pressure required for extrusion depends upon the size and shape of the anode being extruded. Oval anodes having a major axis about 2 inches in length as compared with the major axis of 3% inches com? mon for rolled nickel anodes have been produced. As the extruded metal comes from the press it is quenched in a 2% alcohol-water bath. From the foregoing description of the novel process it will be readily seen that a major por tion of the operations necessary to the production of good or satisfactory rolled anodes is eliminated. Those skilled in the art will readily appreciate the economic advantages arising from the elimination of these steps in the production of rolled nickel anodes.

Etched and polished edge sections of extruded anodes indicate that the average grain diameter at the edge is about 0001330001 inch, whereas the average grain size of; rolled nickel anodes at the edges is about 00021. The average grain diameter, as indicated by sections taken from the center of extruded anodes, indicates that at this point in the extruded anode the grain size likewise is appreciably less than that of the grains or crystals which are present in the center of rolled nickel anodes. Thus, the average grain size at the center for extruded anodes, is about 0.0016, whereas the average grain size at the center for rolled. anodes is about 0.0021. From the above values, it will be seen that the average grain size throughout the rolled nickel anodes is the same, whether the section be taken from an edge or from the center. On the other hand, the foregoing values clearly show that the grains or crystals in the edges of the extruded anodes are somewhat smaller than the crystals in the center of the anode. In addition, the average grain size for the entire extruded anode is about 67% of the average grain size for the entire rolled anode.

-Although the present invention has been described in conjunction with a particular embodiment thereof, those skilled in the art will readily understand that variations and modifications are to be considered within the purview .of the specification and the scope of the appended claims.

I claim:

1. As a new article of manufacture, a hotextruded nickel electroplating anode having a banded structure along the transverse axis of said extruded nickel electroplating anode, said banded structure comprising alternate areas of nickel substantially free from inclusions and areas having relatively high concentration of inclusions, said bands being disposed in planes extendingin the longitudinal direction of said nickel electroplating anode.

2. A process for producing extruded nickel electroplating anodes, which comprises establishing a bath of molten metal having a composition providing an acceptable nickel anode, casting at least a portion of said metal in a mold to form an ingot of slightly smaller size than conventional ingots provided for subsequent reduction to blooms and billets for rolling to electroplating anodes, and subjecting said ingot to suitable pressure in an extrusion press at temperatures of about 900 C. and about 1200 C. to extrude a nickel electroplating anode substantially free from slag inclusion common to cast anodes, said extruded nickel electroplating anode having areas of mutually different grain size, the grains of said anode being largest in the region of the transverse center and smallest in the region of the surface of said anode, said extruded nickel electroplating anode having a smoother corrosion than cast nickel anodes and, in contrast to the non-uniform structure of said extruded nickel electroplating anode, corroding substantially as uniformly as rolled nickel electroplating anodes of uniform structure, and producing substantially no more loose nickel and substantially no more sludge than rolled nickel electroplating anodes of uniform structure and substantially the same analysis.

GEORGE FELLMUIH GEIGER.

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