US2363476A - Method and apparatus for manufacturing seamless pipes and tubes - Google Patents

Description

Nov. 28, 1944'.

B. BANNISTER METHOD AND APPARATUS FOR MANUFACTURING SEAMLESS PIPES AAND TUBES Filed April 8, 1942 v 2 sheets-sneer 1 Nov. 28, 1944. B. BANNlsTER METHOD AND APPARATUS FOR MANUFACTURING SEAMLESS PIPES AND TUBES Filed April 8, 1942 2 vsh'eets-sheet 2 lill] Patented Nov. 1 944' l METHOD AND APPARATUS FOR MANUFAC- TUBING SEAMLESS PIPES AND TUBES Bryant Bannister, Mount Lebanon, Pa., assignor to National Tube Company, a corporation of New Jersey- Application April s, 1942, serial No. 438,190

(ol. so-is) 8 Claims.

This invention relates to the manufacture of seamless pipes .and tubes, and more particularly to the prevention ofthe formation of scale pits tion approaches the mandrel, by reason of lts `being forced into a slightly oval-shaped cross section. This scale may be blown from the inf terior of the workpiece by means of an air blast,"

but this alone will not prevent some scale from accumulating on the mandrel or plug and being rolled into the workpiece. Sincea loos'e scale is formed behind the plug, the air blast tends to draw the scale forward where it collects on the plug. .When this occurs, pits are formed in rthe wall of the pipe or tube, causing it or a large portion thereof to be rejected. In addition to the foregoing, `in the various operations and reheatings through which the seamless pipe and tube pass in the course of manufacture, a large amount of metal is lost due to scaling, amounting to as bar 5. The rear end of the mandrel bar 5 is pivotally disposed, as at 6, in a thrust block 1 which is rotatably carried in a housing 8 by means of suitable bearings Si. Interiorly disposed in the mandrel bar 5 is a pair of telescoped pipes I2 and I3. The interior pipe I2 is connected to a suitable high pressure air tank I4 and delivers compressed air through the bore I5 in the bar cap 4 to communicating nozzles I6 in the forward end of the said bar cap.

The outer pipe4 I3 is connected to a source of supply of water or other cooling uid and terminatesadjacent the forward end of the mandrel bar 5. At the rear end of the mandrel bar 5 there is provided a number of apertures for the withdrawal of the cooling uid. I

An annular chamber 2I is provided at the forward end of the mandrel bar 5; and it has a number of discharge orifices 2I' closely adjacent the much as 3 to 5 per cent of the original billet It is a further object of the present inventionl to produce tightly adhering scale on the interiors of seamless pipes an'dtubes.

The foregoing and furtherv objects and the method and means of accomplishing same will be apparent from the specification which follows and by reference to the accompanying drawings, in which:

Figure'l is adiagrammatic view, partly in'sec tion, of the rolls and mandrel or plug of a seamless pipe or tube mill.

Figure 2 is avsectional view of the forward end of the mandrel -or plug -showing the apparatus of the present invention in association therewith.

Referring more particularly to the drawings, the numeral 2 designates apair 'of suitably driven metalfworking rolls' which, in cooperation, are adapted to helically advance a tubular workpiece A over an interiorly disposed mandrel or plug 3 to thereby reduce the wall-thickness and increase the diameter of the said workpiece.

A The mandrel or plug 3 is disposed on a bar cap 4 which is carried on the forward vend of mandrel rear end of the mandrel or plug 3. The annular chamber 2| communicates with the interior of the mandrel bar 5 by means of a pipe 22 in which there is disposed a valve 23. The valve 23 is normally held in closed position by means of a spring 24; and is opened by pressure on a piston 25 which operates in a cylinder 26. Air under pressure is admitted to the cylinder 26 by a pipe 21 which is connected to the pipe I2.

In operation,'the workpiece A, heated to forging temperature, is introduced into the pass dened by the rolls 2 and the mandrel or plug 3, whereupon the mill operator opens y'a valve 28 to admit air under high pressure through the pipe I2, bore I5 and jets I6 to the interior of the said workpiece. This blows all loose and loosely adhering scale out of the workpiece, so that the surface thereof approaching the mandrel or plug 3 is substantially scale-free.

In order ,to produce the desired dense and closely adhering oxide nlm to protect the interior of the pipe or tube against scaling during this `and subsequent operations, such as reeling and sizing, and also to provide protection against corrosion inthe finished pipe,it is desired to expose the clean, heated interior surface of the workpiece to steam vaporimmediatel'y after it passes over the mandrel or plug and before the usual scale h as time to form thereon. This is accomplished by discharging water on the interiorof the heated workpiece as closely as possible to the rear end of the mandrel. A certain portionof this water evaporates to steam which becomes superheated andl partially` disassociates within a very short period of time. The generation of this steam, if sumcient water is admitted to the interior of the workpiece, produces an inor tube is cooling to below 1000 F. Care must be exercised, however, not to inject too much water into the pipe, as this will cause localized cooling and set up undesirable strains therein.

The cooling water applied to the interior of the mandrel bar 5 ows into the front end thereof from the pipe I3 and exits through the apertures at the rear end of the mandrel bar. Since the mandrel bar is completely filled, water will flow into the annular chamber 2l when the valve23 is open and be sprayed onto the interior of the workpiece. The valve 23 is normally held closed by the action of spring 24 and is opened by air pressure operating on the piston 25. Since the air pressure is turned on bythe mill operator when the workpiece approaches the mandrel 3, and oii when it has passed thereover, it will be understood that the valve 23 controlling the entry of water to the chamber 2l is closed except when a workpiece is actually being rolled.

While I have shown and described one specific embodiment of the present invention, it will be seen that I do not wish to be limited exactly thereto, since various modiiications may be made lternal pressure which prevents air from entering and prevents undesirable oxidation while the pipe means arranged on the inner side` of said plug for delivering a fluid into the interior of the workpiece on that side of said plug so as to provide pressure within the workpiece immediately on the inner side o f said plug of anvamount suificient to prevent air from contacting the interior surface of the workpiece at this point thereby preventing oxidation by air of said surface while the workpiece cools immediately after working the same, the supply of said fluid to the interior of the workpiece being controlled by the air under pressure as it is delivered to the outer end of the mandrel bar.

4. In a tube rolling mill having a pair of opposed metal-working rolls which are adapted to helically advance a workpiece over an interiorly disposed mandrel, a mandrel bar, a mandrel plug livering a fluid into the interior of the workpiece without departing from the scope of the invention as dened in the appended claims.

r claim: B

1. In a tube rolling mill havi a pair of pposed metal-working rolls whi are adapted to helically advance a workpiece i interiorly disposed mandrel to reduce the wall thickness thereof, a mandrel bar, a mandrel plug arranged on the outer end of said mandrel bar, and means arranged on the inner side of said plug for delivering a fluid into the interior of the workpiece on that side of said plug so as to provide pressure within the workpiece immediately on the inner side of said plug of an amount suilicient to prevent air from contacting the interior surface of the workpiece at this point thereby preventing oxidation by air of said surface while the workpiece cools immediately after working the same. l

2. In a tube rolling mill having a pair of opposed metal-working rolls which are adapted to helically advance Ya workpiece over an interiorly disposed mandrel, a mandrel bar, a mandrel plug arranged on theouter end of said mandrel bar,

r, means arranged on the extreme outer end of said provide pressure within thevworkpiece immedi-A ately on the inner side of said plug of an amount suflicientto prevent air from contacting the interior surface -of -the workpiece at this point thereby preventing oxidation by air of said surface While the workpiece cools immediately after working the same.

3. In a tube rolling mill having a pair of opposed metal-working rolls which are adapted to helically advance a workpiece over an interiorly disposed mandrel, a mandrel bar, a mandrel plug arranged on the outer end of said mandrel barl means arranged on the extreme outer end of said mandrel bar Vbeyond said plug for delivering airv under pressure into the interior of the-workpiece, said plug having a bore arranged therethrough which communicates with said last mentioned means through which the air is conveyed thereto.

on that side of said plug so as to provide pressure within the workpiece immediately on the inner side of said plug of an amount sumcient to prevent air from contacting the interior surface of the workpiece at this point thereby preventing oxidation by air of said surface while the workpiece cools immediately after working the same, and means interconnecting said tubular member and said last mentioned means so that the iluid is forced into the workpiece by the air pressure when the air passes through the tubular member whereby the ow ci.' the fluid into the workpiece is controlled by the ilow of the air through th tubular member.

5. 'The combination as defined in claim 4, wherein the means connected to the tubular member for forcing the uid into the workpiece includes a valve the opening and closing of which is controlled by the air passing through the tubu- V lar member.

6. A' method of` reducing scale losses in the manufacture of seamless pipes and tubes, which includes helically advancing a heated workpiece over a mandrel plug to reduce the wall-thickness thereof, and subjecting the interior surface of the said workpiece toa steam atmosphere immediately after it over the mandrel plug so as to provide pressure within the workpiece at that point of an amount sumcient to prevent air from contacting the interior surface of the workpiece at this ypoint and thereby form a thin, tightly adhering oxide coating thereon which prevents oxidation by air of said interior surface while the workpiece cools after working the same.

y7. A method of/reducing scale losses in the manufacture of seamless pipes and tubes, which includes helically advancing a heated workpiece over a mandrel plug to reduce the wall-thickness thereof, and directing a stream of water onto the yinterior surface of the said workpiece immediately after it passes over the mandrel plug,

adhering oxide coating thereon which prevents oxidation by air of said interior surface while the workpiece cools after working the same. 8. A methodl of reducing scale losses in the manufacture of seamless pipes and tubes, which -includes helically `advancing a heated workpiece over a mandrel plug to reduce the wall-thickness thereof, and directing a stream of water onto the vwail of the tube immediately'after it passes 'over the mandrel plug, said stream being of sufficient volume to form asteam atmosphere within the 10 workpiece on contacting the highly heated walls thereof but insufficient to materially cool the same so asl to provide pressure within the workpiece at that. point of an amount sufilcient to prevent air from contacting the interior surface of the v workpiece at this point and thereby form a thin,

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