US2217193A - Method of swaging blowpipe nozzles - Google Patents

Description

Oct. 8, 1940. v P R. ARONSON 2,217,193 METHOD oF swAGING BLowPIPE 'NozzLEs T Filed'Aug. 12, 1937- lNvENToR PETER R. ARONSOVN ATTORNEY Patented Oct. 8, 1940 METHOD F SWAGING BLOWPIPE NOZZLES Peter R. Aronson, Millburn, N. J., assignor to Oxweld` Acetylene Company, a

West Virginia corporation of Application August 12, 1937, serial No. V153,703

9 Claims. This invention relates to the art of metal work ing and particularly to a method of swagingv blanks of copper bar-stock provided with longi- 1 tudinally-drilled rough, oversize passages in which mandrels in the form of music wire are inserted. 'One such method is disclosed in U. S. Patent No. 1,644,157'to Elmer H. Smith. By virtue of the swaging operation, the length of the metal blank is increased, and its cross-sectional area as well as that of the rough oversize passages is reduced, the latter conforming with the cross-section of the wire mandrels. n

Blowpipe nozzles formed in accordance with prior known methods often contain structural defects, and the manner in which the swaging operations are performed makes it diiiicult to i remove the mandrels from the blanks after swaging. Often the application of intense heat to the blanks and extreme tensile stress tothe mandrels is required to eect removal. Furthermore, the nozzles produced in accordance with 5 these methods are limited in length' and vin the degree of cross-sectional reduction of the blanks and passages. These difficulties and defects are probably due to the metallurgical changes occurring in the metal blank during the swaging oper- 0 ations. If the cold-working of the blanks is to`o severe, the grain structure of the metal becomes extremely fine and thus its ductility decreases..

Likewise the hardness of the metal increases to such an extent that continued cold-working l5 causes it to crystallize or pulverize, whereupon the walls between the passages' -may form folds or fissures, or may tear, and little if any additional iiow occurs along the mandrels and the swaging dies. This is especially true when-a l0 large number of closely spaced passages are provided in the blank. Another disadvantage attending, lthe use' of severe swaging steps in these prior known methods is that the mandrels are seldom serviceable 5 for more than ten swaging, operations. This is probably due to thefact that the excessive coldworking of the blank hardens the metal to such an extent that continued cold-working causes it to rigidly grip the mandrels. Then, as this hard- 50 ened metal is forced along the mandrels, intensive tensile stresses are set up therein as well as an excessive concentrated frictional heat thus drawing the temper of the mandrels, and caus-i ing their premature failure. 55 An object of this invention is to provide a method o f swaging blowpipe nozzles and the like which will avoid the above and other difiiculties. K Other objects of the invention include: the pro- Vision of a method of swaging 'blowpipe nozzles in which the swaging operations are such that the mandrels are not materially affected and may be readily removed from the swaged blanks without resorting to heat and excessive tensile stress toseparate the sameythe provision of a method of swaging blowpipe nozzles in which the blanks are gradually elongated andthe oversize Ypassages graduallyreduced by employing a relatively large number ofA separate and successive swaging steps with successively smaller diameter mandrels; the provision of a method of swaging blowpipe nozzles in which a definite sequence of steps is maintained including the step of annealing' the metal blanks after certain swaging steps; vand the provision of a method of swaging metal blanks in which thecycleof steps may be `extended to produce blowpipe nozzles of any desired length, diameter, and bore for a given blank size.

The above and other objects of the invention will become apparent `from the following description.

In accordance with the present invention, a metal blank cut from copper bar-stock is provided with the desired number of rough oversize passages extendinglongitudinall'y through the 30 .I

same. Because certain defects. in prior swaged nozzles have been caused by inaccuracy in drilling, the passages are preferably drilled simul-I taneously from opposite ends of the blank by a pair of aligned drills so that they may be accurately-disposedwithin the blank. One suitable manner of drilling the blanks is disclosed in my copending application Serial No. 159,659, led.

August 18, 193'?.

For the purpose of removing any grease or oil 40 that may have collected on the blank during the' drilling operation, it is successively washed in cleansing media of carbon tetrachloride, a solution of water and potash, and extremely hot water. Then it may be dried by compressed air. i

After drying, the blank is annealed at a temperature of approximately 900 F., or to such a degree that the metal will give `a reading below zero on the B scale of the Rockwell hardness tester when a weight of one hundred kilograms is employed with a one-sixteenth inch penetrating ball. Such a degree of hardness-has been found sufficient to permit the first swaging vstep or steps without failurepf the blank yor gripping of the mandrels. After the annealing step, the

blank may be pickled in a solution of commercial sulphuric acid in order to remove the copper oxide that forms on it during the annealing operation; bright-dipped in a solution of nitric acid; and finally, washed in hot water and dried passages, but greater than the ultimate diameter of the finished passages. The wires of the mandrel are oiled, and they may be fed intothe oversize holes in the blank from either the flame end, or the entrance end thereof. ,Since the metal of the blank has a tendency to distort at the end which is led into the swaging dies, and this distortion is less objectionable at the entrance or seat end of the nozzle than at the iiame end, it is desirable in many instances to feed the mandrels into the blank from the flame end. This procedure may be followed except Where it is desired to nose the flame end of the nozzle, where it would be impracticable. The blank is preferably dusted with powdered mica and the assembly is fed into a rotary swaging machine, the die surfaces of which are at such angular relation that they automatically draw the assembly therebetween, thus elongating the blank and reducing its outside diameter, as well as making the oversize`bores approach the diameter ofthe wires of the first mandrel. The proper angle of the mouth of the swaging dies should be approximately 11 or less, and their crosssectional shape should be oval so as to insure drawing the blank and mandrel assembly there- 'between The blank and mandrelassembly is moved in and out of the swaging dies a considerable number of times in order to thoroughly hammer the blank. The procedure tends to loosen the mandrels within the passages, and makes it possible to withdraw the same from the blank without subjecting the blank to excessive heat, or applying extreme tensile stress tothe mandrels.

Regarding the degree or severity of the swaging operation, it has been found that this is dependent upon the rcharacter of the metal being swaged. That is, the amount of cold-working to which a copper blank may be subjected without failure or gripping of the mandrels is de pendent upon the hardness imparted to the metal by such cold-working. Preferably the hardness produced by any particular swaging operation or series of operations should not exceed a reading of about 35 to 40 on the B scale of a' Rockwell hardness testerA when al weight of one hundred kilograms is employed with a one-sixteenth inch penetrating ball. Al- .dough the swaging increases the length of the blank, the reduction in external diameter as Well as the reduction of the cross-sectional area of the passages is of primary importance in order to avoid gripping of the mandrels and failure of the blank. Generally it is possible to control the rate of increased hardness and keep it within the above limits by restricting the reduction in cross-sectional area of the blank during each swaging operation or operations to approximately twenty-five percent of the previous crosssectional area.

It will be understood, however, that variations in the original diameter of the metal blanks, and the disposition of the passages therein will sages.

govern the rate at which the cross-sectional area can be reduced and still retain the hardness of the metal within the permissible limits. With a large number of closely related passages, less wall metal will Abe present and the degree of reduction of `the cross-sectional area1for any particular swaging step should obviously be less.

In some instances, for example, the reduction` may be as low as ten percent of the previous cross-sectional area, and exceeding this rate will cause defects to appear in the nozzle and/or gripping of the'mandrels. However, in any case, the permissible degree of area reduction can be readily determined by trial for any batch of copper, the desired size of blank, and finished construction of the nozzle. It is only necessary to determine the degree of swaging that may be accomplished Without rendering the metal so hard as to cause gripping of the mandrels or to produce defective nozzles.

Having determined in this manner the degree of reduction which is possible for the particular design of nozzle and gradeof copper employed, the least number of swaging steps and changes of mandrel size will be automatically xed. Thus, after the rst swaging step has been carried out as described above, the blank may be removed from the first mandrel, washed, annealed, pickled and bright-dipped before mounting it upon the wires of the second mandrel which may be constructed to permit a further reduction of the diameters of the passages. This procedure of inserting mandrels, swaging and extracting mandrels, is nowrepeated, using each time a smaller size mandrel wire and a smaller size swaging die. Thus a considerable number. of comparatively slight reductions in metal will take place during the swaging, and the resulting piece is not distorted as might otherwise be the case. The wire mandrels used in the finishing swages are of the same diameter as the desired holes in the finished piece.

During the swaging operation, the temperature of the blank may rise to approximately 200 to 300 F. due to the Working of the metal. Removal of the blank from any mandrel assembly should take place while it still retains this swaging -heat because it facilitates removal of the mandrels and eliminates excessive friction between the mandrels and the walls of the pas- This procedure greatly extends the life of the mandrels, since it, together with the thorougl'i hammering of the blanks, facilitates their` removal without subjecting the mandrels to excessive tensile stress and frictional heat, which latter would cause drawing of the mandrel temper.

It will be apparent that the character of the metal and the permissible degree of reduction may be such that in certain instances a blank may be given more than one swaging operation while employing the same mandrel, thus further elongating the blank and reducing its external diameter without further reducing the diameters of the passages. Also, certain of the swaging steps are often carried out on only a portion of the blank, suchas the tip or name end thereof. However, no matter what the deta. s of the particular swaging step or steps are before the mandrelis changed and the blank annealed, the

hardness of the metal is preferably maintained determined, the blank may be subjected to as many swaging steps as are necessary to produce a nozzle of predetermined shape and passage arrangement, and the mandrels may at all times be easily removed without the application of extreme heat or excessive tensile stress. It will be understood that between each successive reduction of bore or passage diameter, or before mounting the blanks upon a mandrel, the diameter of the wires o which are less than thosepreviously employed, the blank is properly washed in order to remove any oil or grease that may collect thereon during swaging. -Whenever necessary, which is usually prior to each change of mandrels, the blank may be annealed or otherwise treated to increase the grain growth and restore the ductility to a point where it will effect a reading of below zero on the Rockwell tester. Pickling and bright-dipping are also utilized after each annealing step, as previy ously explained.

In practicing the above-described process on a commercial basis blanks' 1% inches in diameter and 2 inches in length, having a central passage 0.295 inch in diameter surrounded by eight passages 0.111 inch in diameter, have been swaged into substantially completel nozzle blanks 6% inches long with diameters of 1 inch at the. entrance end and 1% inch at the iiame end. Such blanks are then ready for final machining and finishing to produce complete Oxy-acetylene cutting nozzles. The preparation and swaging of an original blank has been-effectively carried out in the following steps without failure of the blank or gripping of any mandrel: (l) the blank is mounted on a mandrel assembly and swaged to increase the length and reduce both the external diameter and the diameters of the passages; (2) before removing the mandrel, the blank is swaged again to reduce the external diameter and in-Y crease the length; (3) the mandrel is then removed, the blank washed, annealed, pickled, bright-dipped, mounted on a second mandrel and swaged a third time toincrease length and decrease both the external diameter and the diameters of the passages; (4) before removing the second mandrel, the blank is again swaged to increase the length and decrease the external diameter; (5,) the second mandrel is removed,

the blank washed, annealed, pickled, brightdipped, mounted on a third mandrel and swaged to increase the length, reduce the external diameter and the diameters of the passages over a major portion of the length of the blank; and (6) before removing the third mandrel the blank is again swaged adjacent the flame end thereof to reduce the external diameter and increase the length still further.

These operations -produce the substantially complete nozzle blank which is 6% inches inlength, the degree of cross-sectional area reduction averaging about 20 percent through each successive swaging operation. The third mandrel is thenremoved and the blank is cut to approximate length by removing a portion of the nally reduced exit end. It is then machined, all burrs and chips removed from the passages, washed again, annealed, pickled, bright-dipped and finally inspected and ready for use. It will be under- -stood that with certain grades of copper, it may be desirable to anneal and/or change mandrels after each of the swinging steps.

The principles of this invention may be applied so as to produce nozzles of any desired length and having any desired bore, the only hunting factors being the volume of metal in the blank and the neness of wire mandrels available. In some instances, nozzles have been formed as long as 23 inches with bores of extremely minute cross-section.

In the accompanying drawing, illustrating one form of nozzle blank of the invention inA various A stages of its production,

Fig. 1 is a longitudinal section through an unswaged blank having oversize passagestherein;

Fig. 4 is a longitudinal section through a metal i blank and associated parts, following a subsequent swaging operation; and

Fig. 5 is a longitudinal section through a blowpipe nozzle, following the nal swaging operation and the machining of certain parts.

Referring to the Idrawing, a metal blank II, preferably made of copper bar stock, may have formedtherein an axial passage I3, and a plurality of spaced longitudinal passages I5 disposed parallel to passage I3, and respectively, equidistant from the latter. Eachof the passages I3, I5 is of larger diameterthan the corresponding passage desired in the nished nozzle. The passages preferably arefo-rmed in the manner herevinbefore described.

. Fig. 3 illustrates the metal blank I Iafter it has been subjected to one or more swaging operations, the mandrels II, I9 used in the last of these swaging steps being shown in place, together with spacing members 2 I, 23,-employed for maintaining the mandrels properly spaced from each other.

Fig. 4 illustrates a swaged blank Il at a subsequent intermediate stage of nozzle production, immediately following a swaging operation applied at and adjacent the tip end 28 of the blank, showing a set of mandrels 25, 21 in place in the longitudinal passages. The respective ends of these mandrels are secured in the mandrel-spacing members 29, 3I.

Fig. 5 illustrates the blowpipe nozzle I I of Fig. 4, subsequent to the machining of the outersurface of the nozzle for sizing the same, and for tapering and undercutting certain portions thereof; and after reaming certain portions 33, 35 of the inner surface of the central passage 31 to enlarge its internal diameter to adapt it for use for the intended purpose.

Although the various features of the improved swaging method have been described in detail to fully disclose one embodiment of this invention, it will be apparent that a number of changes may be made in such details, and certain features may be used without others, without departing from the principles of the invention.

What is claimed is:

1. A method of making Oxy-acetylene blowpipe nozzles and the like which comprises forming a plurality of oversize passages within a solid metal blank; and gradually elongatingand reducing the cross-section of such blank by subjecting it to a series of separate and successive swaging operations while each passage contains a mandrel, and employing successively smaller mandrels within said passages during certain of the sepawhich said blank is annealed prior to each change to successively smaller mandrels, thereby preventing the hardness of the metal from exceeding about 40 Rockwell Bh y 3. A method of making Oxy-acetylene blowpipe no-zzles and the like as claimed in claim l, in which the average percentageof reduction of cross-sectional area effected by each swaging operation is about 20 percent.

4. A method of making Oxy-acetylene blowpipe nozzles and thelike as claimed .in claim l, in which said passages are formed by drilling portions of each of said passages` simultaneously from each end of the blank.

5. A method of making Oxy-acetylene blowpipe nozzles which comprises inserting a plurality of mandrels within a like number of rough oversize passages within a metal blank; feeding the blank and mandrel assembly between a. pair of swaging dies with the entrance end ofsaid blank leading; repeating said operation with smaller mandrels and swaging dies; and nosing the flame end of said blank by feeding the blank between another set of dies with the ame end of said blank leading.

6. A method of making oxy-acetylene blowpipe nozzles whichcomprises inserting a plurality of mandrels within a like number of rough oversize passages within a metal blank; feeding said blank and mandrels into a swaging machine; and moving said mandrel assembly into and out of the swaging machine a considerable number of timesl whereby said blank is thoroughly hammered and said mandrels are somewhat loosened within said passages.

7. A method of making a blowpipe nozzle which comprises drilling a plurality of substantially parallel oversize passages through a blank ofductile metal such as copper; gradually elongating and reducing the cross-section of such blank and said passages by subjecting said blank to a series of separate and successive swaging operations while each of said passages contains a mandrel; successively substituting sets of man-y drelsof smaller diameter after .certain of said separate swaging operations; annealing said blank prior to each substitution of a set of smaller mandrels; and so correlating the successiv swaging operations that the average reduction of crosssectional area effected by each swaging operation is. about 20 percent and the 'hardness effected by any ofthe swaging operations before the blank is `annealed is not greater thanabout 40 Rockwell B.

8. A method of making'ablowpipe nozzle, which comprises forming a plurality of oversize passages extending longitudinally through a blank of ductile metal such as copper; graduallyelongating andreducing the cross-section o f such blank and said passages by subjecting said blank to a series of` separate and successive swaging operations while eachofsaid passages contains a mandrel; successively substituting sets of mandrels of smaller diameter after certain of said separate swaging operations; annealing said-blank prior to each substitution o'f a set of smaller mandrels; and so correlating the successive swaging operations that the average reduction of cross-sectional area effected by each swaging operation ,is about 20 percent and the hardness effected by any of the swaging operationsbefore the blank is annealed is not greater than about 40 Rockwell B,

9. A method of making a blowpipe nozzle, which comprises forming a plurality of Aoversize passages within and extending longitudinally through a blank of metal having a hardness below 0 Rockwell B, gradually elongating said blank and reducing the cross-section of said blank and said passagesby subjecting said blank to a

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