US1712972A - Method of forming blanks for making seamless tubes - Google Patents

Description

Ma 14, 1929- R. c. STIEFEL 1312372 METHOD OF FORMING BLANKS FOR MAKING SEAMLESS TUBES Filed Nov. 8, 1927 i l ll? WITNESS 4 F' 5 I INVENTOR j Gaba 46%# llatented May 14, 1929.

UNITED STATES BALPH C. STIEFEL, OJF ELLWOOD CITY, PENNSYLVANIA.

METHOD OF FOBMING BLANKS FOR MAKING SEAMLESS TUBES.

Application filed November 8, 1927.

The invention relates to the manufacture ot seamless tubng, and has particularly to do with the preparation of blanks for use in such manut'acture.

'l`he usual method of forming a blank for the manufacture of seamless tubing by plug rolling or other processes is to pierce and materially lengthen a solid billet by revolving it between obliquely-disposed barrelshaped rolls and force it over a mandrel held against longtudinal movement but mounted for rotaton with the billet. In some cases, particularly in the manufacture ot' larger sized tubing, .the thus pierced billet is passed through a second pair of obliquelydisposed barrel-shaped rolls and over a larger mandrel to` further lengthen the billet, enlarge its diameter, and reduce its ;wall thickness. i

'the barrel-shaped piercing rolls torm a converging enterng pass and a diverging enit pass, and accordingly have their highest peripheral speeds at the narrowest point ot the pass where the billet is reduced to its smallest diameter. Therefore, the billet is acted upon at diflerent transverse sections by peripheral roll speeds which are inversely in proportion p of the billet. This condition is very severe on the metal, producing severe distortions ot it and g'reatly aggravating or. developing defects in the billet which cause loss 'of material and increase the labor and other cost ot production.

'l`hese prej udicial consequences are'greatly magnified in the piercing operation, or operations, when a second piercing pass is used, hy reason of the fact that the billets while heing pierced have been materially elongated, particularly in the dverging portion ot the pass where the perced billet passes over' the enlarged tapered mandrel. The piercng action may be Compared to that of a continuous 'rolling mill in which each successivo pair of rolls forms a work pass. When a billet is being pierced each of its diametrical lines comes under compression a number of times similar to the successive compressions efl'ected by succeeding pairs of rolls in a continuous mill. However, in a continuous mill the successive roll passes are 'tormed to properly take care of the Volume or section of a work piece or blank in order to eliminate stresses on the blank between the passes; whereas in a piercing mill in to the angular surface speed Serial No. 231308.

which a billet is materially elongated in the entire pass, and also in which the diameter of 'the pierced portion of the billet is enlarged and its wall thiokness diminished, excessive stresses are imposed upon the metal, which stresses greatly magnity those necessarily inherent in a piercing operation by reason of the inversely varying roll speeds previously explained. Furthermore, these conditions of piercing result in an excessive Consumption of power, and in a correspondmg increase in Operating expense.

It is well known that billets used tor piercing must be of superior quality to withstand the punishment to which the metal is subjected by reason of the severe stresses imposed upon thom. When losses occur, that is to say, when detective tubing is produced, a chaotic condition arises, the operating management of the tube mill, believing that working conditions have been maintained constant and proper, attributes the losses to defective metal, and the steel manufacturer, believing that the metal is not defective, attributes the losses to improper conditions in the piercing procedure. Manifestly it is desirable to eliminate one of the causes of detective tubing so that the source ot trouble may be determined.

The object ot 'this invention is to provide a method of forming a blank for making a seamless tube whereby the stresses imposed on the metal are reduced to a minimuman as a result thereof the power consumptio lessened, the labor cost diminished, the scrap 'losses reduced, and the cause of scrap losses readily determmed.

In the practice of the invention, a blank tor making a seamless tube is formed by progressively piercing a solid billet in such a manner as to effect a minimum elongation of it. Rather than commencing with a relatively short and thick billet, as is the prevalling practice, I use a billet of relatively increased length and diminished diameter," and elongate it only in the converging portion of a pass between piercing rolls, and there only to the extent necessary to cause suflicient grip upon thebillet by the rolls to force the billet over the point of a piercing mandrel. In the diverging portion of the roll pass the cross sectional area of the then pierced portion of the billet is maintained constant, so that the diameter of the billet is increased and its wall thickness diminished' without imposing upon the metal the excessive ing portion of the pass. Also, consider-ing stresses heretofore existing incident to the the pierced portion of the billet in the pass elongaton of the billet in this portion of as extending froni the transverse plane 'the`pass. When the pierced billet is again through the point of the mandrel to the passed through a piercing nill' to further transverse plane through the points 7, the enlarge its diameter and dininish its wall cross sectional area of the major part of the thickness, this i done with little, if any, pierced portion of the billet is maintained elongation of the billet in any portion of the uniforn during the expanding and reducing pass, and with consequent elimination of operation. Thus the billet is pierced with a severe stressing of the metal. nininun attending elongation, and with The invention will be further explained little, if any, elongation in the divcrging with reference to the accompanying drawportion of the piercing pass where elongation ings, of which Fig. 1 is a View of a pair of stresses are severest on the metal. barrel-shaped piercing rolls, showing a solid When, in the practice of this invention, billet in the process of being pierced; Fig. 2 the pierced billet 4 of Fig. 4 is acted upon a View of a air of mushroom-shaped rolls to enlarge its diameter and dininish its wall showing a pierced billet in the process of thickness, it is preferably passed through having its diameter increased and its wall a piercing nill of the type indicated in thickness diminished; Fig. 3 a side View of Fig. 2 as comprising a pair of mushrooma solid billet of such relative proportions as type rolls 10 and a mandrel ll arranged bemay advantageously be used in the practice tween them, although if desired' ba'relof the invention; Fig. 4 a longitudinal censhaped piercing rolls may be used. By usiw tral sectional view of the billet of Fig. 3 after mushroon-type rather than barrel-shape having been pierced 'by the nill of Fig. 1; rolls, the peripheral speeds of the rolls at and Fig. 5 a longitudinal central sectional their various points in the diverging porview of the billet of Fig. 4 after having tion of the piercing pass corresponds in passed through the mill of Fig. 2. general to the angular speed of 'otation ot' The piercngnill of Fig. 1 conprises a the pierced billet at the various points that pair of barrel-shaped obliquely-disposed work is applied to it to enlarge its diameter rolls 1 which, with a mandrel 2 arranged and reduce its wall thickness. As in the between them, form a piercing pass. A case of the nill of Fig. 1, the pass forned solid billet 3, such as shown in Fig. 3, enters by the rolls 10 also has a converging and a the left end of the roll ass and leaves its diverging portion, but in neither of these right end in the form oi a pierced billet 4, portions is the pierced billet elongated. In such as illustrated in Fig. 4:. The piercing the converging portion of the pass, extendpasshas two portions, a converging portion 'ing from'the plane of the points 12 to the extending from the plane of points 5 where plane of the points 13, the billet is gripped the solid billet is engaged by the rolls to the and pressed inwardly upon the head of manplane of points 6 where the rolls are of drel 11, but its wall thickness is not there greatest diameter, and a diverging portion reduced and the metal is only slightly extending from the plane of points 6 to the worked. When in the diverging portion of plane of points 7 where the pierced billet the pass, extending from the plane of the passes beyond the nandrel'. In practice the points 13 to that of the points 14, the diamtaper of the rolls to form the converging pass eter of the billet is enlarged and its wall is only of such angularity as is necessary to thickness diminished with effecting little, f produce enough grip between therolls and any, elongation. Accordingly, throughout the billet to force the billet forwardly onto the entire pass the cross sectional area ot the point of the mandrel which custonarily the pierced billet remains unifo'rm. extends into the converging portion of the The solid billet 3 shown in Fig. 3, the pass. This conver `nce necessarily produces i -ced billet, of Fig. 4, and the expanded soneelongation o the billet, butthoroughgill t 15 of Fig 5 typically represent a out the major porti-on of the convcrging secblank-f -ming procedur capable of being tion of the pass the billet is solid and therea--i d out in th practice of this invention. fore elongation stresses do not so severely The ratio of the length to the diameter of Stress or unish the metal. solid billet 3 is greater than that used in the In the iverging pass, the piercing rolls 1 customary practice, and the percentage 1nand the mandrel 2 are so forned or tapered crease in length of this billet to produce and adjusted that there is little, if any, elonthe pierced billet 4 is less than in the cusgation of the pierced billet. Such'being the tomary practice. Furthermore, the excase, the cross sectional area of the pierced panded billet 15 of Fig. 5 is of the same, or portion of the billet remainsuniforn' in all substantially `the same, length as the pierced transverse planes from that passing through bill t 4 These views therefore show how, the points 6 to that passing through the in the preparation of a blank according to points 7 at the end of the pass, or in other this invention, the blank s gven a n1n mu n words, in all transverse planes in the divergelongation with an attendant dmnuton n working stresses placed upon the blank. By thus diminishing the stresses, much less power is required, scrap losses are materially reduced,' one of the causes of defective tubing is greatly reduced if not entirely eliminated, and the labor and other cost of manufacture of tubing is materially reduced.

According to the provisions of the patent statutes, I have explained the principle and mode of operation of my invention, and' have illustrated and described a specific mannerin which it may be practiced. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim as my invention:

1. The method of forming a blank for making a seamless tube, comprising progressively piercing a solid billet, and simultaneously expanding the diameter and reducing the Wall thickness of the pierced portion of the billet while maintaining the cross sectional area of the major part of the pierced portion of the billet substantially uniform during the expandng and reducing operation;

2. The method of forming a blank for making a seamless tube, comprising progressively piercing a solid billet, simultaneously expanding the diameter and reducing the wall thickness of the pierced portion ot' the billet, then expanding the diameter and reducing the wall thickness of the pierced billet, and during both of the expanding and reducing ,Operations maintaining the cross sectional area of the billet substantially uniform. r

3. The method of forinng a blank for making a seamless tube, comprising piercing a solid billet, and subsequently expanding the diameter and reducing the Wall thiokness of the pierced billet While maintaining the cross sectional area of the pierced billet substantially uniform.

In testimony whereof, I sign my name.

RALPH o. STIEFEL.

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