US2368339A - Process for producing aluminum brasses - Google Patents

Description

Jan, 3o, 1945. M.' L. woon I lRooEss FOR PRODUCING ALUMINUM BRAssEs Filed Jue 2o, 1944 HYD/9065M- Hyokasfm- Inval? or By Maur/ce L. Wood Patented4 Jan. 30, 1945 Maurice L. Wood, Waterbury, Conn., assignor to ,Chase Brass & Copper Co. Incorporated, Wa-

terbury, Conn., .a corporation of Connecticut Application June 20, 1944, Serial -N0. 541,240

(Ci. 'l5-10) 1 Claim.

The present invention relates to improvements in process for producing :brasses which contain aluminum.

One object of the present invention is to provide an improved process of producing highquality :brass which contains aluminum in addition to the usual copper and zinc, so that products made of such aluminum-brass will possess physical qualities enabling them to withstand severe distortion without developing defects.

With the above and other objects in view, as will appear to those skilled in the art from the present disclosure, this inventionv includes all features in 4the said/disclosure which are novel over the prior art. l

In the description and claims, the various parts and steps are identified by specific terms'for convenience, lbut they are intended to be as generic in their application as the -prior art will permit.

In the accompanying drawing form part of the present disclosure, in which one wa of car--y rylng out the invention is shown for illustrative purposes: u

Fig. 1 is a schematic view in central vertical section of an electrical induction furnace suitable for carrying out the present invention, and schematically illustrating one stage of the process; and

Fig. 2 is a view similar to Fig. 1 but schematically illustrating a later stage of the process.

Referring to the drawing, the electric induction furnace I has an outer metal casing I I provided with a refractory lining I2 so as to provide a main chamber I3 which is in communication with two Wdepending chambers in the form of loops I4 and I5. The top of the furnace is, provided with a charging-door I6, a skimming-door I1, and a'pouring-spout I8. All of'the construction of the furnace I0 thus far described is of well-known construction. A pipe I9 is screwthreadedly engaged in an opening opening into the interior top-portion 2l of the furnace. Except when molten metal is being, poured out of the furnace through the pouring-spout I8, the spout is kept closed by a removable closure-block -22 of asbestos or other suitable material.

In carrying out my process when starting with the furnace empty, suflicient-aluminum-containing brass-in molten condition is poured into the furnace through the charging-door I6 to fill the loops I4 and I5 and occupy the lower portion of scrap such, for example, as tube-ends, extrusion-l butts, billet-gates, saw-chips, etc., are also introduced into the furnace through the chargingdoor I6, or solid pieces of cathode copper, ingot aluminum and slab zinc may be used with or without the piecesv of aluminum brass mentioned. With all furnace openings closed by the parts I6,

I1 'and 22, hydrogen-containing gas is fed `of all pieces of solid brass which extend above the surface of the molten brass. The hydrogencontaining gas is introduced under sufficient pressure to maintain the upper interior 2 I, above the molten brass, filled with it, so that the gas leaks out of all openings and crevices such, for example, as exist around the charging-door I6, the skimming-door Il, and the closure-:block 22, although the arrows adjacent the closure-block 22 are the only arrows used to indicate escape of the gas from the furnace. The escaping gas is preferably disposed of iby lighting it at the places where it escapes from the furnace so that the escaping gas burns outside of the furnace. The hydrogen-containing gas should lbe substantially free of oxygen and of sulfur and of any compound containing oxygen orsulfur, such as Water vapor, carbon dioxide, carbon monoxide, hydrogen-sulphide. While hydrogen or any suitable hydrocarbon that can be introduced into the furnace to form gas could be used, I find the Well-known hydrocarbon gas propane to :be convenient and` economical for the purpose.

Alternating electric current, acting on the induction principle upon the molten brass occupying .the closed loops I4 and I5, as is well understood in the art, heats the molten brass in the loops, and Iby electric action and by convection, causes molten Ibrass from the loops It and I5 to be circulated up into the main-body of moltenbrass mixture,l and part of the latter circulates down into thefloops where the heating takes place.

Finally, after. all of the Ibrass becomes molten, there is present in the furnace a molten material or mixture or alloyl consisting substantially of copper, zinc, aluminum and small particles of Y aluminum-oxide, with or without any minor percentage of elements such for example, as antimony-or arsenic. Itl is the small particles of aluminum-oxide which lare believed to lbe the cause of the defects in products made of the alloy.' During the time that the unmolten scrap was being heated to raise it to the melting temperation which occurs, partie ture, the hydrogen-containing gas is thus maintained in contact with the surfaces of the solid piecesy of brass, as fwell as with ythe surface of the molten portion of the brass, and finally, after all of the brass becomes molten, the hydrogen-i containing gas continues to be maintained in contact with the surface of the molten brass, and after several minutes, depending upon the amount of brass being melted, and the rate of heat development by the particular furnace used, the temperature of the molten brass rises from its melting-point of about 1750" F. up to about 2300 F. to 2350 F. As the superheating above the melting-point proceeds, and the temperature rises from about 2000 F. up to 2300 F. or aibove, zinc is vaporized from the brass in increasing 'substantial amounts, so as to produce a' substantial quantity of zinc vapor, which is indicated in Fig. 2 in the form of what may be referred to as a "blanket of zinc vapor 23, which is in contact with the surface of the superheated molten brass. After the brass has been raised tothe neighborhood of 2300 F. for several minutes, the process is complete, and the brass becomes largely freed of the harmful aluminum-oxide particles. The superheated brass is then poured out of the furnace in a usual and well-known Way to make .products therefrom.

Vvhen the zinc starts to volatilize in ample amounts, this fact is evidenced by a change in color of the gas which issues from the crevices of the furnace and burns, since the zinc vapor, when burning, gives what may be referred to as a chartion of zinc vapor from the zinc content of the brass tends to cause a loss thereof of about onehalf of one per cent and-therefore, in order rto get any particular percentage in the final alloy,

a one-'half per cent extra amount of zinc is added,

at the beginning to make up for the loss of zinc in the form of zinc vapor.

During the first part of the process, in which the hydrogen-containing gas is maintained in contact with the surface or surfaces of the molten and non-molten parts of the metal, from the time any of the metal reaches -a temperature of about 1000 F. or more, elemental hydrogen from cally act upon small particles of aluminum-oxide and reduce them to aluminum, :thus removing the oxygen from them and joining it to the hydrogen, which then bubbles up through the metal and out above its surface and mixes with the hydrogen-containing gas in the upper portion of the chamber and gradually works its way out through the crevices surrounding the various Y closure portions of the furnace, as previously described. After the temperature has passed to about 2000 F. and the zinc vapor starts to vaporize in suilicient amountto form the :blanket of zinc vapor 23, then hydrogen ceases to enter the metal through its surface, and such hydrogen as remains dissolved in the metal and is in exss` and not needed to redfuce aluminum-oxide particles, is now caused, as a result of the vaporization of the zinc and formation of the zinc blanket, to pass upward cuit of the surface of the molten metal and up through the blanket of zinc vapor and mixes with the hydrogen-containing gas above the zinc vapor. Of course, when the evolution of zinc vapor takes place at a very high rate, the depth of the blanket olf zinc vapor becomes very deep. in fact, it may extend up so far as to substantially occupy most of the interior space in the furnace, so that, at such a stage, there may be very little hydrogen-containing gas in the furnace, this being evidenced, as previously described, by the lburning of bluish-white flames from all crevices of the upper portion of the furnace; And while the zinc vapor at and near. the surface of molten metal, will be substantially free from h"- drogen-containing gas, except such hydrogen as is evolved from the molten metal, up near the top of the furnace there is a mixture of zinc vapor and hydrogen-containing gas in which the latter is of greater percentage, the higher the position in the furnace that is considered. If no efficient stirring action were to take place, as is accomplished by the loops I6 and l5 as heretofore described, then the rst stage of the process would take longer, in order to permit the thorough penetration and mixing of the hydrogen through the molten metal.

When aluminum-containing .brass is made in accordance with my process, even where scrap metal is employed to form all of the aluminum. brass mixture, the resultant quality of the metal' is so high that the metal when formed into various products, particularly tubes, withstands physical tests indicating its high quality. Thus, one

the hydrogen-containing gas, whether `present hydrocarbon present originally, is absorbed or Y dissolved in the metal in the form off atomic hy. drogen, Whether the metal be in molten or in non-molten condition, the rate of absorption and depth of penetration increasing with the temperature of the metal. But it takes place at av higher rate where the metal is in molterrcondition, not only because the molten metal is ordinar-ily of a. higher temperature than the unmolten metal, but also owingto the stirring acarly the eilicient stirring action brought ab upon the heated loops of molten metal I4 and I5, as previously mentioned. Thus, hydrogen ab? sorbed into the metal has opportunity to chemit by the electric action of the most serious troubles encountered is where tubes are made of aluminum-brass, and when such tubes are given what is known as s. "fiatiening test," which consists in completely fiattening a portion of tube, unless ihe metal is of high quality and free from an undue amount of aluminum-oxide particles, surface cracks will ap' pear at the most severely-stressed portions of such flattened tube-pontions. Tubes made from metal produced in accordance with my process, however, event from scrap metal, vsuccessfully withstand this flattening test' without the development of surface cracks.

The. invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential character- I claim:

The process of producing high-quality brasses l containing aluminum in addition to the usual copper and zinc contents, the said process comprising: providing an electrically-heated furnace having a melting-chamber and a vent-opening leading outwardly from an upper portion of the said melting-chamber; charging into the lower portion of the melting-chamber of the said iurnace, copper, zinc, and aluminum containing aluminum-oxide; supplying into an upper por-4 tion of the melting-chamber of the said furnace above the'said charge, a hydrogen-containing reducing-gas which is substantially free of sulphur, oxygen and water vapor; electrically-energizing the said furnace to eect the melting of the said the melting point oi' the metal mixture to cause the vaporization of sufficient of the zinc to pro- 'vide a. blanket of zinc-vapor directly over the now-super-heated molten metals and maintaining 'such condition :for a sumcient length of time to substantially free the super-heated molten metals of the remaining previously absorbed hydrogen; and maintaining the pressure of the said reducing gas in the melting-chamber of the said furnace at a point sufllciently high to cause an excess thereof to flow outwardly through the vent metals in the melting-chamber thereof while the said reducing gas is present in the said meltingchamber to cause the absorption of hydrogen into the said metals; subsequently raising the temperature of the metals to a point sumciently above

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