US3552170A - Method of treating hollow blooms in rolling mills - Google Patents

Method of treating hollow blooms in rolling mills Download PDF

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Publication number
US3552170A
US3552170A US799147A US3552170DA US3552170A US 3552170 A US3552170 A US 3552170A US 799147 A US799147 A US 799147A US 3552170D A US3552170D A US 3552170DA US 3552170 A US3552170 A US 3552170A
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United States
Prior art keywords
rolls
bloom
speed
stand
stands
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US799147A
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English (en)
Inventor
Gerd Pfeiffer
Horst Biller
Claus Schrey
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Vodafone GmbH
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Mannesmannroehren Werke AG
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Publication date
Priority claimed from DE19681652564 external-priority patent/DE1652564C/de
Application filed by Mannesmannroehren Werke AG filed Critical Mannesmannroehren Werke AG
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Publication of US3552170A publication Critical patent/US3552170A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/78—Control of tube rolling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B17/00—Tube-rolling by rollers of which the axes are arranged essentially perpendicular to the axis of the work, e.g. "axial" tube-rolling
    • B21B17/02—Tube-rolling by rollers of which the axes are arranged essentially perpendicular to the axis of the work, e.g. "axial" tube-rolling with mandrel, i.e. the mandrel rod contacts the rolled tube over the rod length
    • B21B17/04—Tube-rolling by rollers of which the axes are arranged essentially perpendicular to the axis of the work, e.g. "axial" tube-rolling with mandrel, i.e. the mandrel rod contacts the rolled tube over the rod length in a continuous process

Definitions

  • R1- R8 I at 00000000 1 GOQQQDOQXF F1 4 CDQOOOOOC) QQUUUGLKJ 61 G2 G3 64 G5 G7 6 /n ven furs Gerd Pf e/ f fer H Bil/er a? Schrey hlt/t'l l (I f Q L S he/r Attorney United States Patent US. Cl.
  • the reduction in the speed rolls is a fraction of the 'dilference between the 7 speed of the mandrel prior and subsequent to entry of the leading end of the bloom into a particular stand or a fraction of the difference between the speed of the mandrel prior and subsequent to issue of the trailing end of the bloom out of a particular stand.
  • the present invention relates to a method of treating hollow blooms in continuous rolling mills. More particularly, the invention relates to improvements in a method of treating hollow blooms which are mounted on mandrels during travel between the driven rolls of successive roll stands in a rolling mill. Still more particularly, the invention relates to improvements in a method of converting thick-walled hollow blooms, especially those which are produced in roll piercing mills, into elongated tubular intermediate products or tubes of reduced wall thickness and increased length. Such intermediate products can be treated in a further rolling mill to yield tubes of desired wall thickness.
  • a continuous rolling mill normally comprises a row of 2-high stands whose rolls are driven independently of rolls in the other stands and wherein the blooms are treated during a single pass.
  • the distance between the stands is such that the bloom is treated simultaneously by the rolls of two or more stands during a certain stage of the pass.
  • An object of the present invention is to provide a method of treating hollow blooms in continuous rolling mills in such a way that the formation of bulges is prevented or that the bulges are much less pronounced than in rolling mills which are operated in accordance with presently known methods.
  • Another object of the invention is to provide a method of treating hollow blooms in rolling mills in such a way that the percentage of waste is reduced and that the time required for secondary treatment is reduced to a minimum.
  • a further object of the invention is to provide a method of treating hollow blooms in rolling mills in such a way that the likelihood of damage to parts of the rolling mills is much less pronounced than in rolling mills which are operated in accordance with presently known methods.
  • Still another object of the invention is to provide a rolling mill for treatment of hollow blooms in accordance with the above-outlined method.
  • the method of our invention is employed to regulate the treatment of hollow blooms in continuous rolling mills wherein the bloom is mounted on a mandrel and is conveyed through a row of several (preferably five or more) roll stands.
  • the rolls of each stand are driven independently from the rolls of the other stands and the peripheral speed of rolls in successive stands exceeds the speed of rolls in preceding stands by a ratio which is always dependent on elongation of the bloom.
  • the method comprises the steps of conveying a bloom lengthwise so that its leading and trailing ends move through and beyond successive stands whereby the speed of the mandrel increases whenever the leading end reaches the rolls of a stand and whenever the trailing end moves beyond the rolls of a stand, and reducing the rotational speed of those rolls which engage the bloom by a fraction of the increase in speed of the mandrel when the leading end reaches the region of the rolls of the second stand, and when the trailing end leaves the rolls of the first stand. If necessary, the speed of those rolls which engage the bloom is reduced again when the leading end of the bloom reaches the region of rolls of the third, fourth, etc. stand and when the trailing end leaves the rolls of the second, third, etc. stand.
  • Rotational speed of those rolls which engage the bloom is preferably reduced by the factor a a-l-b Ad wherein a is the coefiicient of friction between the mandrel and the bloom, b is the coefiicient of friction between the rolls and the bloom, and A d is the difference (a) between the speeds of the mandrel prior and subsequent to the entry of the leading end of the bloom into the second stand and, if necessary, into the third etc. stand or between the speeds of the mandrel prior and subsequent to the issue of the trailing end of the bloom out of the first stand and if necessary, the second, third etc. stands.
  • the value a can be replaced by a factor which is proportional to the difference between the interval required by the leading end of the bloom to advance from the foremost stand to the second stand and the interval required by the trailing end to cover the same distance, i.e., to move from the foremost stand to the second stand.
  • Such replacement is made aft-er the leading end or the trailing end advances from the second stand into the region of rolls of the third stand.
  • the length of aforementioned intervals is preferably measured by electrical or electronic timer means, and the speed or rolls which engage the bloom is changed automatically by electronic means in accordance with the result of such measurement, i.e., as a function of the difference between the two intervals.
  • the bloom normally consists of steel or other metallic material, and the speed of rolls which engage the bloom is in our method reduced by a certain amount.
  • the reduction in speed can be repeated when the leading end of the bloom reaches the rolls in the third, fourth, etc. stand and/or when the trailing end of the bloom leaves the rolls in the second, third, fourth, etc. stand.
  • it suffices if the speed of those rolls which engage the hollow bloom is reduced when the leading end moves into engagement with the rolls of the second, third and eventually fourth stand and/or when the trailing end moves beyond the rolls in the first, second, third and eventually fourth stand.
  • FIG. 1 is a schematic side elevational view of a continuous rolling mill with six stretching stands and two non-stretching stands, a bloom being shown prior to entry of its leading end into the foremost stand;
  • FIG. 2 illustrates the rolls of the rolling mills and the bloom in a position when its leading end reaches the rolls of the second stand;
  • FIG. 3 is a similar view but showing the bloom in engagement with all of the rolls
  • FIG. 4 shows the bloom in a position when its trailing end leaves the foremost stand
  • FIG. 5 shows the trailing end of the bloom when it leaves the rolls of the second stand.
  • FIG. 1 there is shown a rolling mill with six stretching roll stands G1-G6 and two nonstretching roll stands G7, G8 each of which comprises a set of driven rolls flanking the path for a tubular metallic bloom 10 which surrounds a mandrel 11.
  • the rolls R1 of the first stand G1 are driven by a motor or analogous prime mover M1.
  • This motor is of the variablespeed type or it drives the rolls R1 by way of a variablespeed transmission T1.
  • the motor M2 drives the rolls R2 of the second stand G2 by way of a variable-speed transmission T2.
  • Similar motors are transmissions are employed to drive the rolls R3-R8 of the stands G3- G8.
  • Each set of rolls of a stand can be driven independently of the sets of the rolls in the other stand or stasds.
  • FIG. 1 illustrates that stage of operation when the leading end of the hollow blooms 10 approaches the rolls R1 in the first stand G1.
  • the leading end of the bloom 10 is about to be engaged by the rolls R2.
  • the bloom 10 is engaged by each pair of rolls (R1R8).
  • the trailing end of the bloom 10 is about to leave the rolls R1.
  • FIG. 5 illustrates that stage of treatment in which the trailing end of the bloom 10 is about to leave the rolls R2.
  • the formation of one or more bulges on the bloom 10 is prevented by regulating the speed of rolls R1-R8 during travel of the leading end of the bloom 10- from the rolls R1 toward the rolls R8 and/or by regulating the speed of the rolls R2-R8 during travel of the trailing end of the bloom from the rolls R1 toward the rolls R8.
  • the peripheral speed of rolls R2 exceeds the peripheral speed of rolls R1
  • the peripheral speed of rolls R3 exceeds the peripheral speed of rolls R2, and so forth, in order to account for elongation of the bloom during travel through the gaps between successive pairs of rolls.
  • the speed of the rolls R1 (namely, those rolls which already engage the bloom 10 prior to the entry into the following rolls), is reduced to a predetermined extent. Also, when the leading end of the bloom 10 advances toward and is engaged by the rolls R3, the speed of rolls R1, R2 is reduced again. This reduces the likelihood of bulge formation.
  • the reduction in the speed of those rolls which engage the bloom 10 is a fraction of the difference between the speeds prior and subsequent to the entry of the leading end of the bloom 10 into the second, third, etc. stretching stands G2-G6.
  • the reduction in the speed of those rolls which engage the bloom whenever the leading end of the bloom 10 reaches the rolls R2, R3, etc. is preferably selected in the following way: It equals the difference between the speed of the mandrel 11 prior and subsequent to entry of the leading end into a particular stand G multiplied by the coefficient of friction between the mandrel 1'1 and bloom 10 and divided by the sum of coefficient of friction between the mandrel and bloom on the one hand and the bloom and the respective rolls on the other hand.
  • the reduction (Av) in the speed of rolls is a function of the difference (Ad) in speeds of the mandrel 11 and a function of the factor wherein a is the coefiicient of friction between the bloom 10 and mandrel 11, and b is the coefficient of friction between the bloom 10 and a particular roll R.
  • the factor Ad equals the difference between the speed of mandrel prior and subsequent to the issue of the trailing end of the bloom 10 out of the rolls R1, R2, etc.
  • the rolling mill comprises six stretching stands G1-G6) and two non-stretching stands (G7, G8) and that the speed of r0llsR1-R8 is regulated only during that phase of a pass during which the trailing end of the bloom 10 moves from the rolls R1 toward the rolls R6.
  • the distance between the gap defined by the rolls R1 and the gap defined by rolls R6 is 7 meters, the initial length of the bloom 10 is 5 meters, and the length of the intermediate product is 20 meters.
  • the initial peripheral speeds of rolls R1 to R6 are as follows:
  • the aforementioned speeds of the rolls R1-R8 remain unchanged while the leading end or the trailing end of the bloom advances from the rolls -R1 toward and beyond the rolls R6.
  • the speed of rolls R2R8 is regulated in the following way while the trailing end of the bloom 10 moves from the rolls R1 toward and beyond the rolls R2, R3 R8:
  • coefficient a (friction between the mandrel and the blooms) varies considerably in response to wear on the mandrel as well as in dependency on the condition and type of the material of the bloom.
  • the method of constantly determining the value of a or an equivalent factor constitutes another feature of our invention. This involves measuring the length of the interval required by the leading end of the bloom to move from the rolls R1 to the rolls R2, measuring the length of the interval required by the trailing end of the bloom to cover the distance between the rolls R1 and R2, and determining the difference between the lengths of these intervals. It was found that such difference is a good indicator of the coefficient of friction between the mandrel and the bloom.
  • the difference in speeds of leading and trailing ends of a bloom between the first and second roll stands can be used as a parameter for calculation of the coefficient of friction between the bloom and the mandrel.
  • the speed of rolls in the stands of the rolling mills can be varied in accordance with a program which is established by consideration of the fact that the coefiicient a varies in response to repeated utilization of the mandrel.
  • the speed of rolls can be varied automatically by electronic means in the course of a rolling operation. For example, an electronic timer mechanism (not shown) is started automatically by the rolls R1 when the leading end of the bloom enters the first or foremost roll stand, and the mechanism is automatically arrested when the leading end enters the second stand.
  • the mechanism is started again by rolls R1 when the trailing end of the bloom moves beyond the foremost stand and is arrested when the trailing end leaves the second stand.
  • Thestarting and stoppage of the mechanism can be caused by change of stresses upon the rolls of the stands G1, G2 when the leading or trailing end of the bloom enters or leaves such stands.
  • the electronically determined difference between the two measured intervals is utilized for automatic regulation of speeds of rolls in the remaining stands by effecting appropriate changes in speeds which are listed in the preceding table. It is normally sufficient to carry out corrections only when the difference between the two measurements exceeds a predetermined minimum value.
  • the minimum value is 70 milliseconds if the bloom with dimensions 116 x 3.25 mm.
  • the speed of the mandrel 11 increases as a function of the peripheal speed of rolls in successive stands.
  • the speed of the mandrel 11 assumes a value corresponding to an average speed of rolls which engage the bloom provided that the pressure which the rolls of successive stands transmit to the bloom is the same. If the pressure transmitted by a particular pair of rolls is higher, the speed of the mandrel closely approximates the speed of such particular rolls.
  • the mandrel 11 is accelerated whenever the trailing end of the bloom 10 moves beyond a pair of rolls.
  • the speed of the mandrel approximates the average speed of rolls which remain in engagement with the bloom.
  • the speed of the mandrel 11 changes stepwise (abruptly) whenever the leading end of the bloom enters or the trailing end of the bloom leaves a set of rolls.
  • These sudden changes in speed of the mandrel influence the speed of the bloom in such a way that each increase in speed of the mandrel causes an increase in speed of the bloom and attendant formation of a bulge which is due to an discontinuity in flow of material of the bloom.
  • the aforementioned regulation of the speed of rolls during the first and/or last stage of a pass insures that the above mentioned discontinuity is prevented and that the intermediate product is free of bulges or at least nearly free of bulges with respect to intermediate products produced by conventional rolling methods.
  • a method of regulating the treatment of hollow blooms in continuous rolling mills wherein a bloom is mounted on a mandrel and is conveyed through a row of at least three roll stands, the rolls of each stand are driven independently of the rolls of the other stands and wherein the peripheral speed of rolls in successive stands exceeds the speed of rolls in preceding stands by a ratio which is always dependent on elongation of the bloom, comprising the steps of conveying a bloom lengthwise so that its leading and trailing ends move through and beyond successive stands, the speed of the mandrel increasing whenever the leading end reaches the rolls of a stand and whenever the trailing end moves beyond the rolls of a stand; and reducing the rotational speed of those rolls which still engage the bloom by a fraction of the increase in speed of the mandrel when the trailing end leaves the rolls in the first stand.
  • a method of regulating the treatment of hollow blooms in continuous rolling mills wherein a bloom is mounted on a mandrel and is conveyed through a row of at least three roll stands, the rolls of each stand are driven independently of the rolls of the other stands and wherein the peripheral speed of rolls in successive stands exceeds the speed of rolls in preceding stands by a ratio which is always dependent on elongation of the bloom, comprising the steps of conveying a bloom lengthwise so that its leading and trailing ends move through and beyond successive stands, the speed of the mandrel increasing whenever the leading end reaches the rolls of a stand and whenever the trailing end moves beyond the rolls of a stand; and reducing the rotational speed of those rolls which already engage the bloom by a fraction of the increase in speed of the mandrel when the leading end enters the rolls in the second stand.

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  • Mechanical Engineering (AREA)
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US799147A 1968-02-01 1969-02-03 Method of treating hollow blooms in rolling mills Expired - Lifetime US3552170A (en)

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Application Number Priority Date Filing Date Title
DE19681652564 DE1652564C (de) 1968-02-01 1968-02-01 Verfahren zum Auswalzen einer Hülse zu einer Rohrluppe über eine Dornstange in einem Walzwerk

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3722244A (en) * 1970-03-07 1973-03-27 Nippon Kokan Kk Method of controlling continuous rolling of metal strips
US3919872A (en) * 1973-09-24 1975-11-18 Kocks Gmbh Friedrich Methods and apparatus for tube rolling
DE2750637A1 (de) * 1977-11-09 1979-05-10 Mannesmann Ag Verfahren zum herstellen nahtloser rohre
FR2441438A1 (fr) * 1978-11-17 1980-06-13 Nippon Steel Corp Procede de laminage d'un tube en continu
US4318294A (en) * 1978-12-29 1982-03-09 Nippon Steel Corporation Method of manufacturing seamless metal pipes and tubes
US4404832A (en) * 1981-02-20 1983-09-20 Mannesmann Aktiengesellschaft Operating a rolling mill working on seamless tubing
US20120137745A1 (en) * 2009-06-19 2012-06-07 Sms Innse Spa Tube rolling plant

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4394822A (en) 1980-06-06 1983-07-26 Morgan Construction Company High reduction method and apparatus for continuously hot rolling products

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3722244A (en) * 1970-03-07 1973-03-27 Nippon Kokan Kk Method of controlling continuous rolling of metal strips
US3919872A (en) * 1973-09-24 1975-11-18 Kocks Gmbh Friedrich Methods and apparatus for tube rolling
DE2750637A1 (de) * 1977-11-09 1979-05-10 Mannesmann Ag Verfahren zum herstellen nahtloser rohre
FR2441438A1 (fr) * 1978-11-17 1980-06-13 Nippon Steel Corp Procede de laminage d'un tube en continu
US4318294A (en) * 1978-12-29 1982-03-09 Nippon Steel Corporation Method of manufacturing seamless metal pipes and tubes
US4404832A (en) * 1981-02-20 1983-09-20 Mannesmann Aktiengesellschaft Operating a rolling mill working on seamless tubing
US20120137745A1 (en) * 2009-06-19 2012-06-07 Sms Innse Spa Tube rolling plant
US8387430B2 (en) * 2009-06-19 2013-03-05 Sms Innse Spa Tube rolling plant

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GB1226504A (it) 1971-03-31

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