US2042552A - Process for producing seamless tubes - Google Patents

Description

Jlme 1936- M. ROECKNER El AL 2,042,552

June 2, 1936. M. ROECKNER gr m. 2y042,552

PROCESS FOR PRODUCING SEAMLESS TUBES:

Filed Nov. 9, 1934 3 Sheets-Sheet 2 June 2,1936. M, R CKNER H 2,042,552

PROCESS FOR. PRODUCING SEAMLESS TUBES part of the billet which is reduced by the cutting Patented June 2, 1936 z,o42,5s2 rnocsss son PRODUNG smmss TUBES Martin Roeckner and Joue Seirin, Mulheim- Ruhr, Gernmany, assignors to Deutsche Rohrehwerke Aktiengeseflschafla Dugseldort, Germany Application November 9, 1934, Serial No. 752,282

' In Germany November 27, 1933 M (01. 80-62) part reduced by the first pair of rolls is hih and? 5 Claims.

It is known to produce tubes irom a hollow billet by means of several pairs of rolls arranged around-the billet a certain distance irom its axis, one roll of each pair acting on the wall from the inside and the other on the wall from the outside. In this known construction the rolls have dififerent widths or profiles; thus, the flrst pair of rolls cuts a groove into the billet, the groove being widened by the successive pairs of rollers, so that a=part 0! the billet reduced by the first pair of rolls is graduafly stretched in the direction of one end of the hollow billet. The inside and outside rolls 01 the pairs of rollers are in the known construction so provlded that they roll on the outer and inner faces of the billet on single track helical lines. The greater the pitch of the helical lines selected, the larger is that of the shoulders on the first pair of rolls and which must be stretched towards the end in a single rotation 01' the hollow billet, by the next pair of rollers. The pitch must be such that the pairs of rolls can, according to their width, stretch the reduced part of the billet in asingle rotation. The greater the pitch of the helical limes, the greater becomes the force which is required in efiecting the change 01. shape. Furthermore, the depth of the impression made by the sho1flders of the pairs 01 rolls must be such that the part of the billet reduced by the flrst' that the width of a roll, which has been designed for use with a particular number of pairs of rolls for a particular thiclmess of wall of the hollow billet and a particular depth of groove,must be used with one particular pitch only. -If one of these dimensions should be chai1ged, it would theoreticafly be necessary for some other form of roll to be selectedotherwise there is the posis shaped to produce the finished tube is dependent upon the pitch of the helicaHine track made upon the working rolls and also by the depth of the groove. As the pitch is possible 01 variation only wlthin relatively small limits, considerable depths of groove are frequently selected in order to efiect the necessary shaping more rapidly.

This means that, With a given source of power, the pitch of the tracks made by the workingrolls must be small and the consequence is thatthe' narrow. The great disadvantage of this is that the metal 01 the billet at the reduced part does not move in the way that was intended towards. the neutral-plane of the wall of the tube that is. to be rolled, but tilts over sideways. The result is that the metal et the billet moves, under the pressure of the succeeding pairs of rolls, less and les in the manner intended and that at the position 0! change into the portions of the billet already rolled out a orease is formedat the base of the reduced part; this crease formed in the 4 passage of the billet between the several pairs of rollers, gives' rise to excessive .rolling, which is damaging to the finished article and affects its 15 In these figures A is the wall of the hollow billet that is to be rolled, and B1, B2, B3 0 and B4 are the peflpheral portions of the working rolls.

these disadvantages. According to the invention The purpose of the present invention is to avoid the'shoulders of the first pair of rolls make a 25 groove, which is not, however, as deep as is required but is quite shallow; 'it is then deepened by the succeeding pairs of rolls until the desired depth is reached.

Figures 5 to 8-illustrate how, with the same final depth of groove and the same pitch, the

' metal at the reduced position moves smoothly, as

desired, towards the neutral plane of the Wall of the tube. According to the invention the first pair of rolls B1 (Figure 5) makes a groove, but 1ess 35 deep than required; the second pair of rolls then bath widens and deepens the groove towards the end. The third pair of rolls continues both operations, and finally the fourth pair 01 rolls (Figure'8) ,stretches the metal to the final thick ness required for the wall.

The process of the invention not only affords protection aainst the tilting of a high narrow -ridge of metal that has been'produced by the flrst pair of rolls, but it also ensures uniform treatment right through the m'aterial by reason of the absolutely uniform movement of the metal during the Whole working operation. For this reason the process Of' the invention admits of the better utilization of the possibilities provided by an available source of power having a limited output. Thus, for example, the pitch ofthe helical line styleof track for the working rolls may be increasedwhile retaining the final depth of groove produced according to the prier proeess, or the depth of the groove niay be increased pitch 01. the helica1 lines and. ro-

ducing the same depth of groove the rolling mil] is V means when the rolls are disposed in, for example, two helical limes the pitch may be doubled, so that the rolls penetrate only to hait the depth with the same effort for each operation; By reason of the uniform change of form due to the lesser depth of impression the speed of the rolling miil can be increased, so that netwithstanding the lesser depth 01 impression and the consequent increase in the requisite length et passage through the rolling mil] for the material'being rolled. the total working time is reduced. Particularly advantageous is the disposition of the pairs of rolls in a plurality of helical iines, if the shallow grooves pressed by the flrst pair of rolls of the same heiical lines are increased to the desired depth by the subsequent pairs ci rolls.

By operating in this manner with rolls disposed in multi-track helical lines a further disadvantage is avoided, which has made itseli objectionable in connection with the known rolling method with rolls disposed on a single track helical line. rolls, for example with four pairs of rolls on a single trac]; -helical line, as shown in Figures 1 to 8 of the accompanying drawings, the stretchmg 01 the work after its passage through the pairs of rolls results in a wavy formation 01 the end face of the oncdming tube. If the plant be, for example, so selected that when there are; four pairs of rolls each pair affects one-quarter of. the total stretching, and if the billet be able to move ireely towards the end then, il. the rolling operation is interrupted at any particule: mome nt, the distances betWeen the working portion o! each roll and the rear end face 01. the

work measured on fines parallel to the axis of the tube, would necessarfly difler,that is to say, the distance would, in the case of the fourth pair oi rolls be of necessity greater than in the case of the first pair 01! rolls by three-quarters of the total stretching. As, however, in the known processes the distance between the flrst and the fourth pair of rolls is only one-quarter of the periphery oif the tube, considerable forces must operate within this quarter of the periphery of the tube, striving to adjust themselves to the difl'erences in length referred to. This is actuaily eflected in practice and involves the upsetting of the rolled-out part of the hollow billet, so

that the thickness of- Wall 01. the rolled tube when flnished is aiwayS greater by several tenths than that which is calculated from the setting of the rolls.

This very important disadvaritage of the known mrocess as wellas the danger et the over-tuming of the reduced part of the billet are avoided or reduced to a practically negligible extent by the seiection ci. multi-track helicai lineS for the When working with several pairs of' working rolls. The considerable difference cf stretch before referred to, which exists, for example, in the case of four pairs of rolls within one-quarter of the periphery of the tube, can be halved by selecting twohelicai lines for the .5

- rolls instead of the one, without, however, there being any reduction in the total stretching, which stretching is .obtained by traversing the two-track helix the axial distance previosly covered in the On''track heiix. The advantages of 10 having multi-track helical.lines for the setting of the working rolls are made morefully evident as the number 01 pairs of rolls increases. Figure 9 illustrates the diflerences ci. length which are theoretically produced at the advanc- 15 ing end face of the work by four pairs of rolls disposed'on a single helical line. The letter A represents a development of the outside of the tube being rolled. Figure 10 indicates the formation oithe advancing end face 01 the work A where the pitch is the same for twotrack helical limes as for the single helioal line, and the same stretch is obtained as in the exampie according to Figure 9.

Figures 11 to 14 show the meansaccording to 25 the invention ior obtaining the desired grooving or impression in a rolling mil] built for six pairs of rolls, for increasing of the depth to which the single pairs of rolls penetrates and further, the multi-track helical limes. tien there are provided two helical-lines each having three pairs of rolls operating one behind the other. The disposition 01- the two helical lines with respect to each other is shown in Figure 14, again in the development of the work A, 35 and the influence of this disposition upon the reduction in the diflerences or stretching in the advancing end face can be recognized.

The separate pairs'of rolls are so disposed on; their respective helicai paths that the pairs 01. 40 rolls B1, B2, B3 and 31, B2, B3 are spaced at intervals o: V;th of the periphery of the work and each set of rolls is in close sequence. They may, however, be arranged in staggered reiationship in such manner that the pair of rolls B1 is separated by of the periphery et the work being rolled irom the pair ci. rolls B1, naturally, however, only in such a way that the pair of rolls B1 remains on one line 01. the two helical lines selected and the pair 01 rolls Bi' remains on the otheriine. Similariy the pair B2 would be disposed behind the pair B2, and B3 behind the pair 13:.

- We claim: r

1. A process for produczing tubes from hollow billets by stretching principally in the axiai direction by means of a plurality of pairs of rolls,

eonsistinginsubieeting the holiowbillet intended to form the tube to rolling by pairs of rolls, the

inside and on the outside of the hollow billet, the axis of the said rolls being out of alignment with the axis of the hollow billet and the said rolls being set to roll upon the outer and inner faces of the hollow billet in a helical direction, the rolls of the respective pairs of rolls being in succession et diierent and increasing width and of different and increasing depth et engagement, whereby a groove is formed in the metal of the hollow billet by the first pair of rolls and is widened and deepened-succeasively by a, succeSsive flo'w of the metal produced by each of the succeeding pairs of rolls so that the part of the billet reduced by the first pair of rolls is graduaily stretched towards one end et the hol- In this connec- 60 low billet without the formation of fissures or overtumings until the desired thickness of the work is attalned.

2. A process for produclng tubes from hollow billets according to qlaim 1, wherein the groovlng of the hollowbflleb nd the widenlng and deepening ofthe said roovlng are prod1xced by a plurality of pairs oi rolls arranged one behind the other. v

3. A process for producing tubes from ho llow billets accordlng to lalm 1, wheteln the groom lng of the hollow billet and the widening and deepenlng of the said groovihg are produced b a plurality of pairsof rolls disposed upon a plurality of helieal fines.

4. A process for pmducing tubes frolm hollow billets accordlng to claim 1, whereln the groovmg of the hollow billet and the widening and deepenlng 01 the said groovlng are produced by a plurahty of pairs of rolls arranged one behind the other and On a, plurality cf he1ica1 limes.

5. A process for producing tubes from hollow billets accordlng to clalm 1, wherein the groovlng of the hollow billet and the widening and deepenlng of the sald grooving are produced by pairs of rolls arranged On a plurality of hlical llnes which deepen as far as required the groove formedin the surfaces of the billet by the first pair of rolls on the same helical fine.

MARTIN ROECKNER. JOSE smvmm.

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