US2215933A - Method of making tubing - Google Patents

Description

P J. w. OFFUTT METHOD OF MAKING TUBING Filed April 23, 1938 Patented Sept. 24, 1940 7 ME'1HOD OF MAKING TUBING John W. Offutt, Ellwood City, Pa,

assignor to National Tube Company, a corporation of New Jersey Application April 23, 1938, Serial No. 203,945

3 Claims.

This invention relates to a method of making tubing, and particularly to an improved method of making smalldiameter tubing.

Heretofore, small diameter tubes, such as those of from one-eighth to one inch pipe sizes, when not made by the butt-weld process, have been sired diameter.

1 the pieces if they were As is well known, a sinking mill is a continuous universal mill having grooved rolls, with the grooves in each successive stand of rolls smaller than those in the preceding stand. The grooves in the first stand are slightly less in diameter than the reeled tube and the grooves in the last stand are of the diameter of the completed tube. The roll stands, of which from eight to twentyfour may be used, are arranged in tandem and are usually spaced as closely together as their construction will permit. The spacing will vary from twelve inches to as much as five feet, center to center.

The tube, while being passed through the sinking mill, does not have a supporting mandrel on its interior so that the reduction-in its diameter is'accompanied by thickening of the tube wall. In order to overcome this wall thickenin speed increments between rolls are increased to set up a stretching efiect between each set of rolls, thereby eliminating the wall thickening eflect as the wall thickness of the tube is actually reduced at the same time the diameter is reduced.

However, when the tubes are reduced in diameter in a sinking mill with the roll speeds adjusted for stretching, the tubes become materially heavier in wall thickness on their ends than in ,the middle. This thickening, which is of marked degree, extends for a distance from each end about equal to twice the distance between the roll' stands. This is because no pull can be exerted on a given section of its length unless the tube is pped simultaneously between two or more pairs of rolls, a condition that does not exist when the tube is entering or leaving the roll train forming the sinking mill.

That is to say, there can be no stretching until after the front end of the tube has'entered the second stand of the rolls and there will be none after the rear end stand.

As the thickened ends of the reduced tubes or pipe are constant regardless of the length of the finished piece, obviously-it would not benecessary to cut oil and scrap as great a percentage of long as if they were short and it is among the objects of We present inven' emerges from next to the last erably a nun welder 2 suitably tion to provide for manufacturing purposes as above described long lengths of tubing in place of short ones.

It is one of the objects of this invention to provide a method of manufacturing small diameter seamless tubing wherein the scrap is reduced to a minimum.

It is another object of the invention to provide an improved method of manufacturing tubing wherein tubing of a lighter gauge can be made than by any method heretofore known.

It is a further object of the present invention to provide an improved method of joining the ends of several lengths of tubing together as an aid in the manufacture thereof.

Various other objects and advantages of my invention will more fully appear during the course of the following specification, and will be particularly pointed out in the appended claims.

In the accompanying drawing, I have shown for the purpose of illustration one embodiment which myinvention may assume in practice.

In this drawing:

Figure 1 shows a plan of several pieces of apparatus used in connection with my improved method;

Figure 2 is a view showing three lengths of pipe welded together;

Figure 3 is an enlarged plan, partly in section, showing two ends being welded together;

Figure 4 is an enlarged plan, partly in section, showing the weld being compressed; and

Figure 5 is a view showing the pipes after being reduced in size with the weld and short crop removed.

In the manufacture of seamless tubing, after the lengths of tubing have been formed by piercing round billets or by casting, or in any-other known approved manner and suitably rolled, they are ready to be sized. In order to'produce a small diameter tubing, usually less than three inches in diameter, the tubing is passed through -a sinking and sizing machine, as has been described.

It will be understood that the maximum length at which rolled tubes can be commercially produced is limited (usually not over forty feet) and, in order'to produce tubes of greater lengths, it would be n to join several short tube lengths together.

According to the present invention, the adiacent ends of several lengths of tubing are joined together by welding after the rolling and reeling operations and prior to the sinking and sizing operation, as heretofore described.

Referring to the drawing, there is shown pref-, positioned on the entering side of a furnace 3. The furnace is adapted to reheat the tubing uniformly to a temperature approximately just below the scaleforming point as it passes therethrough. From the furnace the tubing passes directly into the first stand of the sinking rolls I and through the mill where it is elongated and reduced in size to the desired diameter.

A traveling flash welder is shown and preferably used for welding the ends of'the tubes together, but it will be understood that any suitable and practical welding device may be employed that will weld rapidly so as to keep up with the speed of the rolling mill.

In order to maintain as efficient and strong a weld as possible, it is desirable to allow both the outside and inside flash or overfill 4 and 5, re-

respectively, to remain on the tubing, as shown in Figure 3. The inside flash 5 does not interfere with the sinking and sizing operations but the outside flash 4 would tend to interfere with the tubing passing through the roll grooves. In order to eliminate this condition without grinding or shearing, it is proposed to reduce this outside flash diameter to at least the outside diameter of the tubing, preferably by compressing the flash inwardly (as is shown in Figure 4) in a suitable die or roll 6 positioned between the welder and the sinking and sizing mill or reheating furnace.

If it is not practical to weld the ends of the tubes together in a traveling flash welder, due to the speed with which the tubes are fed through the reducing or sinking mill, it is proposed to weld about three lengths of tubing about .thirty feet long together to make about a ninety foot length. A tube of such length could then be passed into a tunnel reheating furnace as it is welded and after the secondand last weld passed directly into the sinking and sizing mill located at the opposite end of the furnace.

With this arrangement the tube would not be in the welder and reducing mill at the same time, and could be stopped to make the welds in a stationary welder. The crops or scrap to dispose of the thickened ends would then be only onethird that necessary from a thirty foot length tube. For example, if the ninety foot tube is elongated to three times its original length in a stretching the total length will be two hundred seventy feet. Ii the roll centers were spaced twelve inches apart, which is entirely practical, and the thickened ends were two and one-hair" times the roll spacing or two and onehalf feet long, the total crop or scrap loss due to end thickening would be five feet; or less than two per cent. of the total tube length, which is a very reasonable figure in any tube making process.

As the tubes made by my improved method will be from fifty to one hundred or more feet in length instead of a mam'mum of from thirty to forty feet, and as the length necessary to cut ed the ends of the tubes to remove the thickened portions is comparatively short, say not over five percent, I am enabled to make seamless tubes of small diameter and thin wall with a scrap loss so small as to make the method practicable on a commercial scale. While I have shown and described an embodiment of my invention, it will be understood that this embodiment is merely for the purpose of illustration and description and that various other forms may be devised within the scope of my invention, as defined in the appended claims.

I claim:

1. In the manufacture or metal tubing of predetermined lengths, the method comprising the steps of continuously supplying lengths of tubular blanks of a predetermined size, successively welding the adjacent end of each of said lengths to the end of the foremost length so as to form a continuous length of tubing, successively compressing the flash of each of the welds between each of the successive joined lengths by forcing the welds together with the ends of the tubular blanks which they respectively join inwardly so that the outer diameter of the welded joints is no.greater than that of the tubular blanks, passing the continuous length of tubing into and through a reducing mill so as to elongate the same and reduce it to the desired predetermined diameter and size, and finally removing each of the welded joint portions therein together with the inwardly bent ends of the tubular blanks and scrapping the same so as to provide a plurality of lengths of tubing of a predetermined length having a uniform wall thickness throughout.

2. In the manufacture of metal tubing of predetermined lengths, the method comprising the steps of continuously supplying lengths of tubular blanks of a predetermined size, successiely welding the adjacent ends of each of said lengths to the end of the foremost length, successively compressing the flash of each of the welds" between each of the successive lengths by forcing the welds together with the ends of the tubular blanks which they respectively join inwardly so that the outer diameter of each of the welded joints is no greater than that of the tubular blanks, continuously and successively heating the joined lengths of tubular blanks to a predetermined temperature, passing the joined tubular blanks continuously into and through a reducing mill so as to elongate the same and reduce the blanks to a desired predetermined diameter and size, and finally removing each of the welded joint portions therebetween together with the inwardly bent ends of the tubular blanks and scrapping the same so as to provide a plurality of predetermined lengths of tubing having a uniform wall thickness throughout.

3. In the manufacture of metal tubing, the

'method comprising the steps of continuously supplying lengths of tubular blanks, rolling and reeling each of said blanks, successively welding the adjacent ends of each of said lengths to the end of the foremost length so as to provide a continuous length tubing, successively compressing the flash of each of the welds between each of the successive lengths by forcing the welds together with the ends of the tubular blanks which they respectively join inwardly so that the outer diameter of each of the welded joints is no greater than that of the tubular blanks, continuously passing the continuous length of tubinginto and through a furnace so as to heat the same to a predetermined temperature as it passes therethrough, then continuously passing the same into and through a reducing mill so as'to elongate the tubing and reduce it to the desired predetermined diameter, and finally cutting the continuous length tubing at each of the welded joint portions therein so as to remove the welds together with the bent ends of the tubular blanks and scrapp g the same so as to provide a plurality of lengths of tubing of a predetermined length having a uniform wall thickness throughout.

59ml W. OFFUTT.

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