US3334994A - Electrolytic manganese addition agent - Google Patents

Description

United States Patent 3,334,994 ELECTROLYTIC MANGANESE ADDITION AGENT Robert M. Fowler, Washington, D.C., assignor to Union Carbide Corporation, a corporation of New York No Drawing. Filed Dec. 11, 1963, Ser. No. 329,871 1 Claim. (CI. 75-53) This invention relates to the production of ferrous and non-ferrous manganese bearing alloys and more particularly to an improved means for introducing electrolytic manganese into a molten metal heat.

Electrolytic manganese has a very high purity level and is an important alloying addition agent to both ferrous metal heats and non-ferrous metal heats such as copper and aluminum.

Electrolytic manganese is commonly produced in a diaphragm cell by electrowinning of manganese onto a cathode from an electrolyte (catholyte) composed of manganese sulfate, ammonium sulfate and usually a smoothing agent such as potassium sulfate or boric acid which improves the quality of the manganese which is deposited on the cathode. The chemistry of electrolytic manganese diaphragm compartment cells, as well as the operating practice form no part of the subject invention, but if a detailed discussion is desired reference may be had to US. Patent 2,286,148 issued to Mantell; US. Patent 2,361,143 issued to Leute et al. and Bureau of Mines Report No. 463.

The cathode or cathodes on which the electrolytic manganese is plated out in a diaphragm cell are generally sheetlike in shape and are fabricated from stainless steel, although Hastelloy 1 alloys, titanium, and palladium-titanium cathodes have also been commercially employed.

After completion of the electrowinning process in the cell, the cathodes are removed from the cell and the adhering deposited manganese is stripped from the cathodes by flexing them and the deposits still remaining after the flexing operation are hammered with a mallet in an attempt to strip 100% of the deposited manganese from the cathode.

In present day practice, the thus stripped electrolytic manganese is then collected and placed in bags or cans in definite weight amounts, fifty pounds being common. These bags or cans of electrolytic manganese are supplied to the metallurgical industry for use directly as addition agents to ferrous and non-ferrous metal heats.

The above discussed conventional process for producing electrolytic manganese and the manner of using it, unfortunately is not completely satisfactory. For convenience sake, the inherent drawbacks will be discussed in connection with the production of electrolytic manganese for use as an addition agent to molten steel but this is in no way to be construed as a limitation of the inventive concept to be disclosed hereinafter.

The principal disadvantages associated with present commercial practice from a production standpoint are:

(1) Relatively low efliciency in the manganese electrowinning process.

(2) The cost of maintaining the cathode sheets such as stainless steel or a Hastelloy alloy in a highly polished condition in order to facilitate the removal of the plated manganese.

(3) Extreme precise operating control of the cell is necessary primarily due to the fact that the extent of the manganese removed from the catholyte must be limited to prevent the plated manganese from adhering so tightly to the cathode that it cannot be stripped.

(4) Loss of some plated manganese during the stripping and recovery operation due to tight adherence to the cathode, and additional loss due to the generation of 7 3,334,994 Patented Aug. 8, 1967 fines as a result of the stripping and subsequent handling operations.

From a use standpoint the principal disadvantage encountered in the present commercial practice is the loss of manganese as fines in the slag upon addition to the heat resulting in low recoveries and erratic manganese analysis of the finished alloy.

Accordingly, the object of the subject invention is to provide an electrolytic manganese addition agent which in being produced and in use avoids or greatly minimizes the above enumerated disadvantages of the prior art.

The object of the invention is accomplished by electroplating manganese on both sides of an expendable cathode strip chosen from the group consisting of steel, aluminum and copper. In the practice of the invention, after the selected cathode strip has been plated in the conventional manner, it is removed from the cell and conventionally washed, dried and degassed at which time it is ready for shipment to the ultimate user.

Through the simple expedient of starting with a cathode sheet of a predetermined thickness and careful control of the quantity of manganese deposited, a sheet of addition agent will be provided from which a piece may be cut which contains an exact amount of electrolytic manganese and cathode material and which is ready for immediate use in that form as an alloy addition agent in ferrous and non-ferous metallurgical processes.

It should be readily apparent that the process benefits which are realized in supplying and using electrolyte manganese addition agents in such a manner as compared to the prior art are many including the following:

. (1) The use of cathodes in sheet form on which maximum adherence is obtained increases plating efficiency since the well known treeing effect is minimized and accordingly plated out manganese metal is less likely to fall into the catholyte with an accompanying reduction in plating rate and current efliciency.

(2) Similarly, the use of cathodes in sheet form on which maximum adherence is obtained and the concurrent reduction in the likelihood of any plated out manganese falling into the cell tends to lower the sulfur content of the plated out manganese and thus provides better control of the sulfur content in alloy addition agents so produced.

(3) Since no stripping of the plated out electrolytic manganese from the cathode is necessary, there is an increase in the recovery of metal plated. In current practice, one to three percent of the plated manganese cannot be stripped and must be redissolved in the anolvte solution.

(4) In order to obtain maximum adherence of the manganese concentration in the plating bath is at a lower level than previously employed and this provides a greater manganese removal from the solution. Accordingly, less solution need be processed through a plant for a given amount of electrolytic manganese produced.

(5) Since stripping is not required there is a reduction in direct labor costs and a saving in that the hammer and other items necessary for stripping are not needed.

(6) Since no stripping operation is performed there is no generation of manganese fines with concurrent handling loss and thus the quantity of manganese metal recovered is increased.

The introduction of electrolytic manganese into a heat in the form of a plating on a metal which is the same as the metal constituting the heat has the following advantages:

(1) An addition agent of controlled composition, free from impurities is insured.

(2) The thus produced alloy agent being in sheet form has sufiicient weight to penetrate the slag more readily then the flakes, chips and fines of electrolytic manganese which are presently used and accordingly less manganese is lost to the slag by oxidation and therefore higher recoveries of added manganese are achieved.

The subject invention will be more fully illustrated by the following example.

Example A catholyte containing about 12.5 g./l. manganese and 160 g./l. ammonium sulfate, was continuously produced in the cathode compartment of a diaphragm electrolytic cell employing lead-silver anodes and steel cathodes, each cathode having a length of 44 inches, a width of 24 inches and a thickness of 24 gage (U.S. Standard Plate). The electrolyte feed to the cell contained 31 g./l. of manganese and 128 g./l. of ammonium sulfate. The cathode current density was about 35 amperes per square foot and catholyte pH was about 8.6. Under these conditions a metallic manganese deposit 4; inch thick was deposited in 48 hours. This deposit evidenced a plating efiiciency of 63% which compares very favorably with the presently achieved plating efiiciency of 59 to 60% in commercial practice.

The thus deposited metallic manganese was excellent in appearance and was tightly adherent to the cathode strip. The cathode strip was sheared into strips two inches wide with negligible loss of plated manganese due to the generation of fines. The two inch wide strips were ready to be broken into smaller pieces which would have the desired weight for direct addition to a molten steel heat.

In the practice of the invention, the preferred limits for the steel cathode thickness are in the range of from 26 gage to inch and a 24 gage material has been found to give excellent performance. The thickness of the plated manganese is controlled by the plating time which is preferably from 16 hours to 72 hours which in the above example would produce respectively a manganese plating of inch and inch. As indicated in the example, the use of 24 gage cathode plate with a 48 hour plating line produces a manganese deposit about inch thick on each side of the cathode resulting in an alloy addition agent containing about 82% (by weight) manganese and 18% steel. A 72 hour plating time under the same conditions produced an addition agent containing about 88% manganese and 12% steel.

With respect to the production of alloy addition agents for use with molten steel heats the desirable composition ranges are from 75 to 90% manganese and 25 to steel.

When an aluminum cathode is employed, the preferred cathode thickness ranges from 30 gage to A inch and the plating time is controlled to give a manganese thickness which will result in an alloy addition agent which will have a desired composition, and preferably this is about manganese and 40% aluminum. Under the operating conditions given in the foregoing example, a inch aluminum cathode plate after a 48 hour plating time will have a A; inch deposit on each side and the composition of the plated cathode is approximately 60% manganese and 40% aluminum.

When a copper cathode is employed, the preferred cathode thickness ranges from 24 gage to 4 inch and the plating time is controlled to give a manganese thickness which will result in an alloy addition agent which will have a desired composition, and preferably this is about 50% manganese and 50% copper. Under the operating conditions given in the foregoing example, a inch copper cathode after a 48 hour plating time will have a 43 inch deposit on each side and the composition of the plated cathode is approximately 50% manganese and 50% copper.

As previously indicated, in use, the alloy addition agent of known composition is divided into smaller pieces of known weight and as such are introduced directly into a molten metal heat. It has been found that loss of manganese to the slag is reduced to a minimum when each piece of alloy addition agent has a weight of at least about 2 ounces.

I claim:

A method of using an addition agent by introducing it into a ferrous molten metal bath in solid form, said addition agent consisting of an electrolytic manganese plated strip of steel having a weight composition of between about to manganese and about 25 to 10% steel, wherein said addition agent is produced by electroplating a steel sheet with manganese using a plating bath in which the manganese concentration is less than that normally employed for manganese deposition so as to provide a maximum adherence of electroplated manganese to the steel sheet.

References Cited UNITED STATES PATENTS 2,191,479 2/1940 Hopkins 75 X 2,398,614 4/1946 Bradt 204-45 2,501,532 3/1950 Meng 75-53 x 2,637,896 5/1953 Nachtman 29-493 2,717,370 9/1955 Dean 204-45 HYLAND BIZOT, Primary Examiner.