US2227313A - Method of making seamless tubes - Google Patents

Description

J. L. ,MAUTHE 2,227,313

METHOD OF MAKING SEAMLESS TUBES Filed Aug. 19, 1958 2 Sheets-Sheet 1 Fi 'JA.

INVENTOR James L. Mau 1'he R1351 M MIM Dec. 31,1940. J MAUTHE 4 2,227,313

METHOD OF MAKING SEAMLESS TUBES Filed Aug. 19, 1938 2 SheetsSheet 2 lNVENTOR Jam es LMau fh e Jamm MMJM Patented Dec. 31, 1940 UNITED STATES PATENT OFFICE James L. -Mauthe, Poland, Ohio, assignor to The Youngstown Sheet and Tube Company, Youngstown, Ohio, a corporation of Ohio Application August 19, 1938, Serial No. 225,749

4 Claims.

This invention relates to the manufacture of seamless pipe or tubes and, particularly, the making of such tubes having relatively large diameters, viz., 4 to 18", and relatively thin walls.

It has been the practice heretofore inmaking seamless tubes, to heat a billet of such size as to produce a single commercial length of tube, subjeot it to successive piercing operations and then plug rolling, followed by reeling, cross rolling if desired and sizing. In the practice of the method outlined, furthermore, it has been customary to effect a certain-amount of work in the piercing operations and a large amount of work in the plug mill. Numerous disadvantages characterize the method described but it has continued in-use. for lack of anything better. The heavy reductions effected in the plug mill prevent the production of a good surface inside the tubes. A further objection is that the inner and outer surfaces of pierced billets cool at different rates, the outside cooling more rapidly since it is exposed to the atmosphere and also because the work done on the billet in piercing is converted into heat which serves to maintain or elevate the temperature of the inner surface. This differential cooling, in some sizes and grades of steel, causes cracking and a rough surface condition. It has been attempted in the past to overcome these effects by cooling the inner surface with a steam spray. This, however, is expensive and not subject to accurate control.

A further disadvantage of the prior method lies in the fact that the billets employed for making tubes of many commercial lengths are too short to be handled in a walking beam furnace, for the reason that eiiicient heating in such furnaces requires a definite minimum spacin between the supporting beams.

I have invented a novel method and apparatus which overcomes the aforementioned objections and is characterized by further novel features and advantages over the existing practice. Accordingto the preferred procedure, I heat multiple length billets by passing them through a furnace of the walking beam type and then sever them into individual billets for further processing. The individual billets are subjected to an initial piercing and then reheated in a suitable furnace. They are then subjected to a second piercing operation during which a heavy reduction is effected. After the second piercing, the pierced shells are again reheated and plug rolled before reeling and sizing. If the individual bili5 lets ar long enough to be handled on a walking beam furnace, it is unnecessary to .pass them therethrough in multiple lengths. Any or all the operations after the second piercing operation, furthermore, may be omitted.

A detailed description of the method of my in- 5 vention and apparatus suitable for carrying it out will be given by referring to the accompanying drawings. In the drawings:

Figs. 1a and 1b when disposed side by side with the former on the left, constitute diagrammatic illustrations partly in plan and partly in section, of a seamless tube plant.

Referring now in detail to the drawings, billet heating furnaces ID of the walking beam type are disposed side by side and each is provided with a pusher ll adapted to eject billets therefrom onto a conveyor l2 disposed between the furnaces. The structural details of the furnaces themselves require no description since they are well known. They are preferably provided with 0 automatic control means whereby billets charged thereinto are progressively advanced toward the discharge end and thereby heated to the proper temperature. As already stated, if the billet for making a single commercial length of the char- 25 acter of tube to be manufactured is too short to be handled by the walking beams of the furnace, I charge multiple length billets intothe furnace, i. e., billets which are small integral multiples of (two or three times) the length of 30 the billet required for making a single tube of the desired commercial length.

After passing through the furnaces ll), billets are discharged (preferably alternately from the two furnaces) onto the conveyor l2. They are 35 then shifted to a conveyor 13 by means of pivoted transfer bars I and skids l5. The heated billet is advanced by means of the conveyor l3 to a billet cutter. indicated schematically at l6. If the billetis of multiple length, it is here severed 0 into individual lengths. I prefer to employ a hot billet cutter, i. e., one which severs the billet by means of a gas flame, although a hot saw or other billet severing means may also be employed. After the cutting of a multiple'length billet. the leading portion thereof is advanced to a position beside a centering device I! and transferred thereinto by rotatably mounted arms Hi. If the billets are long enough in single length to be handled by the walking beam furnaces, they are advanced directly to the centering device without stopping at the cutter IS. The centering device l1 preferably includes a torch for burning a hOle in the end of the billet to facilitate starting of the first piercing operation, A mechanical centering mechanism may be used, however, if desired. After centering, the billet is discharged across skids I9 onto a conveyor 20. It is then shifted by rotatable arms 2| onto skids 22 by which it is delivered onto the inlet table of the first piercing mill indicated diagrammatically at 23. After piercing of the billet, the resulting shell is moved from the outlet table 24 across skids 25 onto the conveyor 20.

A reheating furnace 28 overlies the portion of the conveyor 20 beyond the skids 25. The furnace may be of any desired structure and is adapted to prepare the pierced shell for the substantial reduction to be effected in the second piercing or expanding operation. The furnace temperature is preferably between 1900 and 2400" F. The reheating of the pierced shell after the first piercing operation has several important desirable results. In the first place, the cutting of multiple length billets allows the outer ends of the billets exposed to the atmosphere to be cooled to a temperature slightly below that of the severed ends of the billet which have been cut by the cutting torch. This temperature difference would hinder easy working of the steel to uniform dimensions if not corrected before too much work is completed. That is to say, the hotter end of the billet being more plastic than the cooler end, would be reduced more than the latter, thus producing a shell having a taperin wall thickness. This is substantially eliminated by the reheating after the initial piercing because the temperature throughout the shell is thereby made substantially uniform. A more important result is that reheating after the first piercing prevents the differential between the temperatures at the inner and outer surfaces of the shell mentioned above and thus precludes the cracking and rough surface condition previously encountered. Reheating after the first pierping, furthermore, permits a heavy reduction in the second piercing operation. The furnace 26 also serves to restore to the second portion of a multiple length billet the heat lost thereby while waiting for the first portion to be centered and advanced to the first piercer, before the second portion can be similarly treated. This furnace also equalizes the temperature throughout the material and overcomes the unequal cooling caused by the head end of the pierced shell passing over a water cooled mandrel while the rear end of the piece is being pierced.

The furnace 2B is preferably constructed for sidewise discharge of shells therefrom onto skids 21 by rotatable arms 28. From the skids 21, the reheated shell is delivered to the inlet table of a second piercing and expanding element 29. The piercing mill 29 is provided with inlet and outlet tables longer than those customarily employed, to facilitate handling the shell after a relatively heavy working effective to increase the diameter and reduce the wall thickness. Because the temperature of the shell is uniform throughout on leaving the furnace 26, the working of the metal in the mill 29 may be effected with greater accuracy and within the exacting tolerances re quired in this class of work. The wall thickness of the shell, for example, is substantially uniform along the entire length of the shell, as compared to the tapering wall section produced heretofore. The mill. 29 accomplishes much of the work which has previously been performed in the plug mill and may even be adjusted to reduce the pipe substantially to the finished size so that no rolling in the plug mill is required.

From the outlet table of the mill 29 indicated at .30, the shell is discharged across skids 3| to a conveyor 32. The latter charges the shell into a second reheating furnace 33, if reheating is necessary. From the furnace 33, the shell is delivered to a run out conveyor 34 and thence across skids 35 to the receiving table 36 of a plug mill indicated diagrammatically at 31. If reheating before plug rolling is not necessary, the shell is discharged from the conveyor 32 across skids 38 directly to the conveyor 34 and the skids 35.

After plug rolling, if required, the usual finishing operations such as reeling and sizing may be performed on the shell by apparatus well known in the art.

A typical example of the practice of the invention described herein is the manufacture of 10% outside diameter pipe having a wall thickness of .218". In this example, the double length billet is 8 /4" in diameter by 13' 1.39" long and is cut in two after heating. After the first piercing, the outside diameter is 9 /2 with a wall thickness of .750" and the length 1 After the second piercing the shell is 11%;" in diameter with a wall thickness of .297" and the length is 34 8%" long. The plug rolling produces a pipe 10%" in diameter with a .233" wall, 47' long.

The wall thickness is reduced to .218" by conventional reeling and sizing operations. From the foregoing it will be seen that the plug rolling effects a reduction in the wall thickness of only .064". This reduction may be as high as .180" for certain grades of steel on certain dimensions of pipe and, as stated above, may be entirely eliminated for other grades of steel on certain dimensions of pipeand, as stated above, may be entirely eliminated for other grades and sizes.

It will be apparent from the foregoing description that the invention is characterized by numerous advantages over the method previously used in the manufacture of seamless tubes. Most of these advantages have already been mentioned. They include the avoidance of cracking and rough surface conditions produced by a difference in the rate of cooling between the inner and outer surfaces of the shell, the ability to meet exacting tolerances as to wall thickness, the possibility of effecting most of the reduction in the second piercing mill, and the possibility of utilizing a walking beam furnace which is readily subject to automatic control. Secondary advantages are the possibility of eliminating plug rolling and economy and efficiency in the manufacture. of thin walled, large diameter pipe having a high uniformity of wall thickness. It will be understood that although I have disclosed conventiona1 finishing procedure, viz., reeling, sizing, etc., variations may be introduced therein. By effecting the heavy reduction in the second piercing mill instead of the plug mill, I avoid the adverse effect of the latter upon the condition of the inner surface of the shell.

I have illustrated and described but a preferred embodiment and practice of the invention, but 6 changes therein may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In a method of making seamless tubes the steps including heating a billet to a temperature suitable for piercing, subjecting the heated billet to a piercing operation, thereby creating a temperature differential between the leading and trailing ends of the resulting shell, subjecting the shell to a second piercing to reduce its wall thickness, and substantially preventing a progressive decrease in the wall thickness from the leading end toward the trailing end of the shell by supplying heat to the shell before the second piercing.

2. In a method of making seamless tubes the steps including heating a billet to a temperature suitable for piercing, subjecting the heated billet to a piercing operation, thereby creating a temperature differential between the leading and trailing ends of the resulting shell, subjecting the shell to a second piercing to reduce its wall thickness, and substantially preventing a progressive decrease in the wall thickness from the leading end toward the trailing end of the shell by substantially equalizing the temperature of the oncepierced shell along the entire length thereof before the second piercing.

3. In a method of making seamless tubes the steps including heating a billet to a temperature suitable for piercing, subjecting the heated billet to a piercing operation, thereby creating a temperature differential between the leading and trailing ends of the resulting shell, subjecting the shell to a second piercing to reduce its wall thickness, and substantially preventing a progressive decrease in the wall thickness from the leading end toward the trailing end of the shell by so reheating the once-pierced shell as substantially to eliminate said differential.

4. In a method of making seamless tubes the steps including heating multiple-length billet to a temperature suitable for piercing, severing the billet into portions, subjecting one of the severed portions to a piercing operation, thereby creating a temperature differential between the leading and trailing ends of the resulting shell, subjecting the shell to a second piercing to reduce its wall thickness, and substantially preventing a progressive decrease in the wall thickness from the leading end toward the trailing end of the shell by supplying heat to the shell before the 20 second piercing.

- JAMES L. MAUTHE.

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