US1435306A - Butt-welded thin-walled tubing - Google Patents

Description

G. V. JOHNSTON.

BUTT WELDED THIN WALLED TUBING.

APPLICATION FILED AUG.22, I921.

Patented Nov. 14, 1922.

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BUTT WELDED THIN WALLED TUBING.

APPLICATION FILED AUG. 22 I921.

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BUTT WELDED mm WALLED TUBING.

APPLICATION FILED AUG.ZZ, 192l- Patented Nov. 14, 1922.

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G. V. JOHNSTON.

BUTT WELDED THIN WALLED TUBING.

APPLICATION FILED AUG.22,1921- 1,435,30 Patented Nov. 14,1922.

4 SHEETS-SHEET 4.

RA; QWEMQ Patented Nov. 14, 1922 GUSTAVE V. JOHNSTON, OF CHICAGO, ILLI TO THE EL YRIA IRON AND STEEL NOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, COMPANY, A CORPORATION OF OHIO.

BUTT-WELDED THIN-WALLED TUBING.

flriginal application filed June 9, 1919, Serial No. 302,392. Divided and this application filed August 22,

To all whom it may concern Be it known that I, GUSTAVE V. JonNsToN, a citizen of the United States, residing at Chicago, in the county of Cook and. State of Illinois, have invented certain new and useful Improvements in Butt-Welded Thin Walled Tubing, of which the following is a specification. v

My invention provides a novel and improved article of manufacture in thin-walled electrically butt-welded steel stock, and more particularly in tubing, that, after welding, exhibits advantageous characteristics and is adapted to be made at high speed (i. e., large footage per minute) and at low cost as (and preferably) by a method and apparatus substantially as set forth in my co-pending application, Serial No. 302,932, of which this application is a division.

According to my invention the thinwalled steel stock has its edges abutted and weld-united to form a seam that, preferably, has but a small, low burr along the seam-line in its raw state, (i. e., before deburring) and that presents along the seam or joint recurrent variations in metal texture and density or in character of the union, which variations correspond to rapid fluctuations of temperature to which the stock is subjected during the welding operation.

In tubing embodying my invention the recurrent variations along the joint may be textural difl'erences in a continuous weld, or they may be differences in extent of union that, if desired, may be characterized by complete-welding only at recurrent regular intervals and non-welded, close-butted con tact of the edges in the intervening short spaces.

Such a product is intended for manufacture by machine, and in the drawings I have shown apparatus suitable for the production of such tubing embodying my invention. In drawings Fig. l is a. side elevation of an electrical tube-welding machine; Fig. 2 is an elevation from the opposite side: Fig. 3 is'a section on line 38 of Fig.1: Fig. 4 is a detail of a part of the machine as seen from the plane 44 of Fig. 1; Fig, 5 is a section on line 5-5 of Fig. 1; and Fig. 6 is an enlargement of parts shown in Fig. 1,;with fragments broken away.

In making tubing that will embody my invention, in such a machine as shown, it

' 27 and appropria to engage in 1:

Serial N 0. 494,279.

is preferable, for high-speed and economical production, that the open-seamed tube-stock to be welded shall be made from flat strip 21 (Fig. 2) which by passage through a forming machine is formed into the cylin welding departments various departures may be made from the apparatus herein shown.

Power may be supplied to drive requisite parts of the machine by a variable-speed electric motor 26, through clutch 29, chain te gearing, so as. to turn the main shaft 62 from which are suitably driven all or" the positively rotated parts of the device. From this shaft are driven the pairs of rolls 40,- 40 thatin a suitable number of stages-form the flat strip into cylindrical stock. Structural details and advantageous adjustments in this depart ment are described in my co-pending application.

It is preferable that the open-seamed tube-stock be so formed in a position with its seam upward, and that it be so guided that it travels to the welding devices with ts seam exactly and pre-determinedly positioned, and for this reason I preferably employ a stock guiding at 89 in the drawing, a salient feature ,of which is a pair of grooved guide rolls 114 and 115, the former having an annular fin 120 projectin from the root of its groove e gap between the seam edges in the tube and prevent rotary movement of the tube in itsipassage through the machine. Specific structure and adjustments desirable in a means for effecting such guidance are more fully described in my aforesaid co-pending application.

.The tube-stock proceeds from the forming machine through a welding-throat which, in'the machine shown, is formed of rolls including two electrodes, conformed to the shape of the tube blank and a complemental' supporting roll. These collectively com,-

pletely, or substantially completely, enclose and support the blank throughout its circumference, thus providing against distortion of the thin tube under compression and device as indicated giving a pronounced compression effect.

The rolls, in the machine shown, all have their axes at the same, or approximately the same, cross-sectional plane sothat the confining of the blank is co-incident with closing pressure thereof, and inorder to provide intimate contact between the abutting edges of the tube-blank-and ood electrical contact between the tube-b ank surfaces and the electrodes, the size of the throat is preferably sufliciently less thanthe external size of the tube blank to insure a pronounced compression. As shown, this welding throat may be formed by a lower pressure roll 137 having a groove 157 of nearly 180 degrees extent and two roller electrodes 14:9 and 150 of twin construction, preferably as to 1 ing interposed between it and the main pow-c 5' regulable primary windings and a number' co-axially arranged and bolted together so revent relative movement either axially 01 radially, the two electrode rolls practically operating as a single wheel divided down the middle by a narrow insulator 160 so as to prevent short circuiting of the welding current. These electrodes jointly provide a' groove 155 of almost 180 degrees extent, complemental to the groove 157 in lower roll 137. It will be understood, of course, that there is a slight gap between the cylindrical exterior circumference of roll 137 and the electrode rolls 149 and 150, and that the insulation 160 does not come quite to the grooved surface. Also it will be understood that suitable adjustments of these parts may be provided, as more fully described in said co-pending application.-

The welding rolls in the present instance need not be driven, but revolve due to their being engaged by, the passing tube; while the supporting roll 137 may bepositively driven at the proper speed by suitable gearer shaft. Details in these regards, and as to straightening-rolls, eto., may be as described more in detail in my co-pending application.

Current is supplied to the electrodes from transformer 24, that preferably comprises of single-turn secondary-coils that are all connected in multiple at their lower ends to bus-bars 178 from which the massive copper conductors 17 9 extend downwardly, these being secured to a pair of massive copper brush-holders 180 concentric to the axis of the welding rolls, each brush holder having brushes 182 making good electrical contact with the hub portion of the associated electrode.

The machine, according to best practice, should be run to feed the tube-stock smoothly. and evenly through the welding throat in continuous fashionv e., non-intermittently, at least a for runs ,of considerable length) and the electrodes should be supplied with impulsive current of high amperage and low voltage with the impulse frequency such that the tube-stock makes a substantial progression in the time interval between the effective peaks of current impulses' In practice I have found that for welding one-inch tubing of say .025, inch thickness, utilizing 60 cycle alternating current to supply the primary circuit of the transformer, the apparent welding current may be about 12000 amperesat an apparent voltage'of approximately 1.5 volts or a little more, as measured across the insulated gap of the roller electrodes at the nearest accessible point to their lines of contact with the tube being welded, and the speed of progression of the tube-stock may be over feet per minute to state a modest rate which, under proper current changes, can be considerably exceeded.

Under such conditions and with apparatus as described, the edges of the tube-stock are progressively raised to welding temperature rapidly, the current being so controlled and the speed so regulated that the extreme edges onlypractically the edge surfaces onlyof the thin stock are brought to a temperature approximating the fusing point (and possibly reaching that point) while the circumferentially contiguous portions are not heated high enough to render them soft and mushy. The feed rate being sufficiently fast to produce a substantial progression of the tube stock between the instants of optimum current flow, and the pressure on the stock and other resistance'affecting conditions being such that the current flow is confined, so to speak, chiefly to a narrow zone crossing the seam-line at about the plane of contact of the electrodes with the stock, a theretofore-unfused short length of the tube-stock is presented in contact with the electrodes at each recurrent instant of optimum current flow and therefore is subjected to the effect of a heat peak serving, in conjunction with the pressure, to affect a local weld; and the narrow zone of thusw'elded stock is removed from the heated area and out of the path of the heating current rapidly. Therefore the weld, although it may be continuous, is nevertheless non- I of metal texture due to different degrees of hardness and softness at the maximum temperature attained often exhibit themselves more or less plainly in the burr or upset of the weld, the more-heated softer portions upsetting and being forced out more than the intervening cooler or harder portions. Frequently on this account the burr of the weld exhibits a very clear stitch pattern, like a string of beads.

@ther conditions being similar the external manifestations of the recurrent weld may be reduced or minimized both by increasing the current and slowing down the feed rate; and on the other hand the recurrent effect may be made more pronounced by increase of speed or lessening of current How, and if desired the weld may in this way be made non-continuous; complete welding being effected only at the recurrent points of maximum heat, or heat peaks and tiny spaces in between being nonwelded.

According to the use to which it is to be ut the merchantable product may be varied 1n weld-characteristics from one completely welded throughout the seam length to one that is only welded at these regularly-recurrent closely-adjacent intervals. But in either such production the attainment of the recurrent variations in extent of heat-efl'ect is desirable and clearly betters the product. The less-heated, and consequently lesssoftened spaces along the seam-edges that I may term posts of metal, which intervene between the more-heated spots that receive the optimum current effect and are rendered much softer, may weld as completely as the intervening heat-peak spots, yet they tend to preserve the desired tube diameter and to reduce the burr and to promote uniformity in the welded product.

Of course it will be understood that as tube-stock thickness is increased, the speed at which production is had usually must be lowered somewhat, and it will further be understood that while I have herein specifically set forth approximate conditions for successful practice of my invention in making tubing of stock of one thickness, tubing of different thicknesses may be produced ac cordingly with my invention, and I have so produced it in thicknesses of about .050-inch as well as in much thinner stock.

ll claim:

1. As a new article of manufacture a length of electrically butt-welded thin steel stock wherein the seam presents regularly recurrent variations evidencing rapid fiuc tuations of the temperature applied during the welding operation.

2. As a new article of manufacture thinwalled electrically butt-welded steel tubing, wherein the abutting walls are united by recurrent weld presenting structural variations synchronizing with the alternations of the welding current.

3. As a new article of manufacture thinwalled' electrically butt-welded steel tubing,-

wherein the abutting walls are united by a substantially continuous weld presenting recurrent variations in metal texture in closely-adj acent narrow zones synchronizing with varying applications of welding current.

4. As a new article of manufacture, a'

alternate enlarged and reduced portions.

7. As a new article of manufacture, an article formed of thin steel, having a buttwelded continuous seam, the metal whereof embodies substantially regular recurrent Variations in metal texture, concomitant of re current inequalities of temperature.

8. As a new article of manufacture, an article formed of thin steel, having a buttwelded scam, the metal whereof presents regularly recurrent variations of metal density, due to progressive variations in extent of heating the metal. Q

9. As a new article of manufacture, a thin walled steel tube having a butt-welded seam incorporating successive closely spaced posts of less annealed metal and intervning completely welded spots of more-annealed metal.

GUSTAVE V. JOHNSTON.

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