US2025148A - Apparatus for the manufacture of pipes and tubes - Google Patents

Description

Dec. 24, 1935. B, BANNISTER APPARATUS FOR THE MANUFACTURE OF PIPES AND TUBES 2 Sheets-Sheet 1 Filed March 15, 1933 BEY/QNT 54/v/w67-5,

Dec. 24, 1935. B. BANNISTER 7 2,025,148

APPARATUS FOR THE MANUFACTURE OF PIPES AND TUBES Filed March 15, 1933 2 Sheets-Shet 2 V 34v PIEECING ELONGATING ZON E ZONEJ liweidow: BRYANT 5,4'N/v/s TEE,

v diameter oi the rolls increases.

Patented Dec. 24, 1935 UNITED STATES PATENT OFFICE APPARATUS FOR THE MANUFACTURE OF PIPES AND TUBES Bryant Bannister, Mount Lebanon, Pa.

Application March 15, 1933, Serial No. 660,967

3 Claims. (CI. 80-13) This invention relates to the manufacture of seamless pipes and tubes from cast or rolled rounds and more particularly to a novel form of piercing mill for forming a hollow and relatively thick-walled tube.

The usual piercing mill used for piercing a solid billet for subsequent rolling into seamless tubing of commercial dimensions operates to pierce and materially lengthen the solid billet without changing the diameter appreciably. This operation is performed by passing the sohd billet between a pair of power-rotated, obliquelydisposed barrel-shaped rolls which rotate and torce the billet longitudinally over a conical mandrel or plug which is free to rotate but restricted Irom moving longitudinally. The billet usually is maintained in proper position between the main or reducing rolls by stationary guiding members located above and below the billet.

These guiding members ofier considerable resistance to both rotational and longitudinal movement of the billet. In some cases the guiding members are of an improved type consisting of a pair of power-rotated guide rolls positioned intermediate the main rolls and with their mid planes substantially coincident with the longitudinal axis oi! the mill. These rolls have a peripheral speed in the direction of and greatly in excess of the axial travel of the billet.

In my invention I employ power-rotated guide rolls in combination with main rolls of the cone type to form a roll pass having a converging and a diverging section. The converging section is employed to grip the billet and rotate it while advancing it forward into the most constricted portion of the pass, commonly termed the.

gorge. This necking down" or the billet produces a slight elongation and tends to cause the central fibers of the billet to open permitting the entry of the piercing point or plug. The diverging portion of the pass increases in width between the main rolls at the same rate as the Thus as the billet is pierced and passesv the gorge its diameter increases substantially at the same rate as the rolls increase in diameter. This arrangement provides that the peripheral speed of the billet and the rolls is substantially the same for ceeding operations to be performed with a minimum number of subsequent steps and abuse to the material being formed into a tube. In producing tubes of small diameter it may be desirable to secure an expansion in diameter without 5 a reduction of cross-sectional area. in the expanding portion of the pass, but for tubes of large diameter and especially for those having relatively thin walls it is desirable to obtain both a substantial increase in diameter and at the 10 same time an increase in length in the piercing mill. The usual practice today in producing larger diameter pipe is to first pierce a billet of considerably smaller diameter than the finished pipe to be produced and then expand this pierced l5 billet to greater diameter in a second operation.

The billet is then reduced in wall thickness and elongated to the desired pipe size in subsequent operations. In my invention I obtain the required increase in billet diameter in the pierc- 20 ing mill and, as a consequence, I eliminate the usual second operation of expanding.

I take advantage of the natural tendency of the metal being pierced to flow most readily in a radial direction tending to produce a growth 25 in the perimeter of the .pierced portion of the billet and I so proportion and position the piercing plug with respect to the main rolls that the growth of perimeter or expansion of the billet proceeds without any material change in cross- 30 sectional area, and I also take advantage of the power-rotated guiding members by positioning them so that they locate the billet in its proper position and assist the billet through the pass without materially restraining the expansion in 35 diameter of the billet. It is obvious that so long as the cross-sectional area remains constant no elongation takes place. As previously stated, it is usually desirable to secure in addition to an increase in diameter a substantial increase in 40 length, and in my invention I secure such increase by proportioning the piercing plug at its large end so that the distance between the plug and the main rolls decreases at such a rate as to cause a reduction in cross-sectional area of the billet, 4 thereby producing elongation. V This increased metal displacement tends to produce a rapid increase in billet diameter. The guiding members are positioned so that their perimeters contact with the billet intermediate the 50 main rolls in this portion of the pass and prevent the rapid increase in diameter, and owing to the high rate of guide roll travel towards the outlet of the pass the potential increase in diameter is diverted into length.

It will be apparent to those skilled in the art that in order to cause metal of the billet to flow forwardly at a greater rate than the work rolls tend to impart in this direction, the metal must be free to flow or an upsetting action takes place. It is therefore desirable to locate the elongating section of the pass in the outlet portion only where the metal displaced forwardly by the guide rolls is free to move in this direction without being retarded by metal that is restrained from longitudinal movement by the work roll grip.

It is an object of the invention to provide for obtaining a substantial part of the increase in diameter of the work piece prior to obtaining elongation thereof. A further object of this invention is to provide a product which is free from sub-surface flaws sometimes present in tubes produced by prior art practices.

These and other objects will appear after referring to the drawings, in which:

Figure 1 is an end elevation of the apparatus of my invention. a

Figure 2 is a plan view of my novel piercingpass lationship of one work roll to one of the guide rolls which is shown, together with a portion of the billet, in a plane substantially 90 degrees from its true position in the mill.

Figure 4 is a view similar to Figure 3 in which I have disclosed a modified form of my invention.

Referring more particularly to the drawings, in Figure 1 there is disclosed an end elevation of the piercing mill of my invention. This mill comprises a pair of conical working rolls 2 and powerdriven guide rolls 3 forming a roll pass surrounding the billet 4.

In Figure 2 of the drawings the point of the piercing plug 5 is shown as positioned at the "gorge point of the working rolls 2. The positioning is nominal, as the plug may be given a lead or, in other words, extend into the converging portion 2 of the work pass. A conical piercing plug 5 is disposed in the interior of the billet 4 and is mounted on a bar 6 for rotation therewith but is prevented from longitudinal movement.

Figure 3 of the drawings discloses a composite view showing the relationship of the various work and guide rolls to the piercing plug and the billet. As before stated, in this view the section of the guide roll 3 and portion of the billet 4 are shown in a plane substantially degrees from their true positions in the mill. The contour of the tapered piercing plug 5 is such that its relationship to the diverging portion 2 of the work pass will provide that the decrease in wall thickness is compensated for by an increase in workpiece diameter, so that while the wall thickness is actually decreased the cross-sectional areaof the wall is not reduced with the result that the work-piece does not increase substantially in longitudinal length throughout this portion of the pass.

The work rolls are so proportioned that their surface speed bears a substantially constant ratio to the surface speed of a billet at all transverse sections of the expanding pass. In this form of the invention it will be seen that prior to the introduction of the point of the piercing plug the billet will be slightly elongated in the necking down which occurs in the converging portion 2 of the work pass but from'this point through to the outlet of the pass the pierced portion of Figure 3 is a composite view disclosing the rethe billet, while being expanded in a substantial degree, will acquire no elongation.

Referring to Figure 4, I have shown in the view similar to Figure 3 a modified form of the invention in which the forward end of the piercing plug 5 provides for piercing and expanding with constant cross-sectional area, and the rearward portion of the said plug is so proportioned that the crosssectional area tends to produce a rapid increase in billet diameter but the guide rolls 3 contact with the billet in this section of the pass and, because of their high rate of travel towards the outlet of the pass and contact with the metal of the billet, divert this potential increase in diameter into length. The work' rolls shown in 15 Figure 4 have the same speed relationship through the outlet portion of the pass heretofore mentioned.

It will, of course, be obvious to those skilled in the art that the reducing section of the piercing plug 5 may be extended towards the point of the plug any desired amount w th corresponding reduction in the zone wherein constant crosssectional area is maintained. In the extreme, the elongating zone might be extended from the point of the plug to the outlet of the pass, which will accomplish a constant elongation. In practicing this form of my invention it will readily follow that the guide rolls should contact the billet throughout the entire elongating zone.

From the foregoing description, it will be noted that there is no pushing or crowding of the metal of the work-piece into and through the gorge, or constricted portion of the pass, such as would tend to fold, crease, or buckle the metal so pushed or 35 crowded. Inasmuch as the guide rolls 3 contact, the work-piece at the outlet side of the gorge or constricted portion of the pass only, there is no straightening out of folded, creased, or buckled metal; and therefore the finished tube has no 40 fibers which are fractured or pulled-apart and consequently there are no sub-surface flaws, such as are present in the products of prior art practices where there is a pushing and crowding of the metal of the work-piece into and through 45 the gorge or constricted portion of the pass.

The term elongation in the claims is to be understood to mean that occurring in the diverging portion of the pass, and is not to be construed as defining the elongation which necessarily takes 50 place in the necking down of the billet.

While I have shown and described several speci'fic embodiments of my invention it willbe understood that I do not wish to be limited exactly thereto, since various modifications may be made 55 without departing from the scope of my invention, as defined in the following claims.

I claim:

1. Apparatus for piercing and expanding solid blanks comprising a plurality of metal working 0 rolls defining a pass including a gorge point adjacent its introductory end, in combination with at least one power-actuated guide roll disposed intermediate said metal working rolls, said guide roll being of a width substantially greater than 5 the diameter of the gorge of the pass and positioned to make initial contact with the work piece at a point between the gorge and the outlet end at least one power-actuated guide roll disposed intermediate said metal working rolls, said guide roll being 01 a width substantially greater than the diameter or the gorge of the pass and positioned to make initial contact with the work piece at a point between the gorge and the outlet end of the pass, whereby the contact or said guide roll is extended to the extreme outlet and of the wall reducing portion of said pass.

3. Apparatus for the manufacture of pipes and tubes comprising a plurality of helically-actin power-driven metal-working .rolls, said metalworking rolls defining a metal-pass which is constricted intermediate its ends, in combination metal-pass, said guide roll being so positioned that its eflfective contact area is disposed entirely between the constrictedfportion 0t said metalpass and the outlet end thereof and extends to the outlet end or the wall reducing portion or the pass.

BRYANT BANNISTER.

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