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Патент USA US3075494

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Jan. 29, 1963
H. BENTELER
3,075,484
METHOD OF AND APPARATUS FOR CONTINUOUSLY PRODUCING
SMALL SECTION WELDED STEEL TUBES
Filed June 12. 1959
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4 Sheets-Sheet 1
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INVENTOR
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Jan. 29, 1963
H. BENTELER
3,075,484
METHOD OF AND APPARATUS FOR CONTINUOUSLY PRODUCING
SMALL SECTION WELDED STEEL TUBES
Filed June 12. 1959
4 Sheets-Sheet 2
‘ INVENTOR
Jan. 29, 1963
.
METHOD OF AND APP
. BENTELER
3,075,484
TUS FOR CONTINUOUSLY PRODUCING
SMALL SECTION WELDED STEEL TUBES
Filed June 12, 1959
I
4 Sheets-Sheet 3
, m/vewroR
W 8W4~
W
Jan- 29, 1953
H. BENTELER
3,075,484
METHOD OF AND APPARATUS FOR CONTINUOUSLY PRODUCING
SMALL SECTION WELDED STEEL TUBES
Filed June 12, 1959
‘
4 Sheets-Sheet 4
INVENTOR
WW
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3,@75,li3li
Patented Jan. 29, 1963
2
3 075,484
METHQD 6E‘ AND Al’PARATUS FOR CUNTINU
OUSLY PRQDUCING SMALL SECTION WELDED
STEEL TUBES
’ ameters, and to accept as unavoidable the drawbacks in
Helmut lienteler, Bielefelzi, Germany, assignor to Ben
teler-Werke Aktiengeseilschaft Wei-it Neuhaus, Schloss
placement of rolls in the bending and reducing mills and
in the Welding plant. Difficulties also arise in the proper
adjustment of the speed ratios for driving the independent
ly driven bending mill in relation to the following reducing
mill. Moreover, plants of this kind are naturally ex
tremely complicated and consequently costly to erect,
volved in giving effect to the periodical structural changes
that are thus required. These drawbacks are not con
?ned to the waste of time and labor involved in the re
Neuhaus, Kreis Paderborn, Germany
Fiied June 12, 1959, Ser. No. 819,854
Claims priority, appiication Germany June. 13, 1958
11 Claims. (Cl. 113-33)
This invention relates to a method of continuously pro
ducing small section welded steel tubes and an apparatus
for performing the same.
1
As known, small section welded tubes can be continu
ously produced by ?rst bending a strip into the shape
of a slotted tube in a bending mill comprising a plurality
of sets of bending rolls, and by welding together the ad
jacent longitudinal edges of the slotted tube to form a
longitudinal weld seam, the resultant continuous tube be-:
ing then passed through a cold rolling mill comprising
consecutive roll stands with approximately oval grooved
shaping rolls placed alternately at relative angles of 90°
and driven at progressively higher speeds for reducing the
tube to approximately its desired diameter, the ?nal shape
being imparted to the tube by a pass through at least one
set of circularly grooved shaping rolls. The advantage
of such combined roll bending and reducing mills is that
they permit tubes of di?erent diameter to be produced
170 _
apart from being more liable to suifer from functional and
operational troubles.
. These di?‘iculties will naturally be all the more evident
when it is desired to use such plants for producing small
and very small section welded steel precision made tubes,
for instance‘down to outside diameters of about 3 mm. and
wall thicknesses of as little as 0.25 mm. for which there
is an ever increasing demand more particularly in the
automobile, combustion engine, and machine tool in—
dustries to serve as fuel pipes, hydraulic pipes in brake
systems, and oil pipes in lubricating systems. In view of
the sensitivity of such small diameter tubes to any kind
of buckling stress one of the principal dii?culties is th
practical impossibility of ensuring that the speed ratios of
consecutive roll sets in the independently driven bending
mill and in the reducing mill, as well as the speed ratio
between bending and reducing mill are accurately matched
to avoid subjecting the tube to buckling stresses in any
from strips of the same width in one continuous opera
tion. It is not therefore necessary to use strips of different
stage of its passage through the production plant.
nor is it necessary, as would otherwise be the case, to
tions, tubes of a minimum outside diameter of 10 mm.
‘In view of these di?‘iculties recourse has again been
widths for producing tubes of diiferent ?nal diameters, 30 had to earlier methods of producing very small tube sec
replace the several rolls in the bending mill and the weld
being ?rst produced in a combined tube shaping and
welding machine and these tubes being then drawn down
cold in several passes on cold drawing benches, until the
desired ?nal diameters have been achieved. Although this
duced from a strip of the same width such a combined
method is less liable to introduce troubles, and waste is
plant permits the larger diameter tubes to be obtained
lower than in the aforedescribed methods, it is neverthe~
merely by inactivating or dismantling the ?nal roll sets
less unsatisfactory both from the technological as well as
comprised in the rolling mill.
from the economical angle in view of the known disad
Compared with earlier methods, wherein the diameter 40 vantages the cold drawing process possesses. Apart from
of the tube was reduced in a hot rolling reducing mill as it
the fact that the use of this method foregoes the advantages
emerged from a bending mill and welding machine, the
inherent in a method of continuously producing tubes in
aforedescribed method of cold rolling the tube to reduce
one operation in, very great lengths, the limitation imposed
its diameter affords the major advantage of not requiring
upon tube length by the length of the drawing benches
the tube to be intermediately heated to rolling tempera
necessitating a subdivision of the welded tube into drawing
ture and of therefore permitting the plant to be continuous
> bench lengths, the additional labor involved in the neces
in operation, a factor which substantially reduces the pro
sity of joining the drawing bench lengths together by weld
ing machine as well as the‘welding equipment itself to
adapt the plant to a strip of different width. Within the
range of diameters of ?nished tubes that can thus be pro
duction cost of weided steel precision made tubes.
Despite these advantages there is, however, a major
drawback. This drawback consists in that the reduction
in diameter that can be achieved by cold rolling is much
smaller than the reduction obtainable by hot rolling.
Whereas, in hot rolling, diameter reductions up to about
70 to 80% of the original cross section can be achieved,
the reduction obtainable by cold rolling a welded tube can
not, in order of magnitude, exceed about 15%. Another
drawback is that this limitation in the possible reduction
ratio renders the production of welded tubes of very
,
mg or forging and the loss of material due to the necessary
50 removal of the beaks from the ends of the tubes, as well
as the intermediate heat treatment required between con
’ secutive passes through the drawing plates of the drawing
bench combine to make this process very expensive.
The present invention is based on the thought that
the observance of certain conditions will in fact permit
Welded precision-made steel tubes to be produced in a
much more economical way by applying the basic prin
ciple ‘of production previously hereinabove described,
in a manner that overcomes the stated drawbacks.
small diameter, particularly below about 10 mm., an ex
It is, ‘therefore, the object of the present invention to
tremely di?icult matter, because the narrowness of the 60 provide an efficient method of continuously producing
strip that is then required introduces considerable di?i
culties into the processes of bending the strip into a slotted
tube and of welding the same in the welding machine.
‘Since a very wide range of sizes and diameters of pre
small section welded steel tubes, and apparatus for carry
ing out that method, which method comprises drawing a
steel strip through a bending mill, which comprises a
of freely rotating undriven bending roll sets,
cision-made steel tubes is usually required, the above 65 plurality
by the traction generated by a cold rolling reducing mill
described factors force producers either to equip them
~ which lacks intermediate circularly grooved roll pairs
selves with several plants for producing tubes within
and comprises only directly consecutive working roll
different diameter ranges and to operate these plants as
sets driven at relative speeds which exceed the speed
their order books may require, or alternatively to make use
actually corresponding with the elongation of the tube
of plants in which the roll sets can be exchanged for roll 70
due‘ to the rolling action between consecutive roll sets
ing down different strip widths to the‘ desired‘ ?nal di
and- impart a tensile stress to the rolled materialv in
3,075,484
excess of its yield point, and passing the tube between
a welding machine and said cold rolling reducing mill
through a plurality of guide rolls which prevent the
torsional forces engendered by the cold rolling reducing
mill from being transmitted to the section of tube passing
through said welding machine, and which at the same
time slightly deform the said‘ tube.
The apparatus for carrying out this methodv comprises‘
an undiiven freely rotating. roll bending mill for bend
ing a strip into a slotted tube, followed by a pair of 10
freely rotating horizontal rolls immediately preceding.
4
duce the ?nal diameter sincethe possible reduction per
pass is a limited ?gure and may vary, according to the
material, between about 5 and 8%, although in excep~
tional cases it may be higher.
A ?nal important feature of the invention is that the
powerful. torque applied to the tube by‘ the reducing rolls
shall. notv have any effect upon thetube as it passes
through the welding machine. The interposition of sets
of guide rolls between the welding machine and the
reducing mill ensures that. in tubes of the contemplated
small section the otherwise di?icult problem of welding
the very thin edges can be satisfactorily solved and
even a substantially headless ?ush seam produced if
a welding machine’ for closing the slot of the slotted
tube, means provided between the’ closing rolls. and‘
certain welding techniques are employed. The tensional
pressure rolls’ associated with the‘ welding‘. machine forv
guiding the edges of the slotted tube and, following said 15 stress‘m-aintained in the tube permits the closing of the
edges‘ of. the‘ slot-ted'tube to be delayed" until immediately
welding machine, pairs of guide rolls‘ for preventing the
welded tube from being axially twisted, said guide rolls
preceding a cold rolling reducing mill whieh' lacks‘ inter
before the tube runs into the welding machine, without
tensile stress to the rolled material in excess‘ of its yield
of the bead was an extremely dif?cult matter in the case
of tubes‘ having internal dimensions as’ small as those
any" risk of deformation or'other distort-ion- that might
adversely affect the quality‘ of‘the weld seam.
mediate circularly griooved shaping rolls and comprises
only directly‘ consecutive working r'oll sets with closed 20 ‘Moreover, separation‘ of the edges of the slot until
shortly‘ before the tube‘ enters the welding machine per
oval shaping grooves, placed in alternation in planes per
mits’ the bead, especially inside the‘ tube, to be satis
pendicular to they axial direction at relativev angles of 90°‘
factorily removed‘should' ‘the welding technique employed
and driven at relative speeds. which exceed the speeds‘
be‘ one‘ in which. the formation of a bead cannot be
corresponding with the elongation of. the tube due to
the rolling action of consecutive roll pairs and. impart a 25 avoided. In known methods of‘ operation the removal
point, the ?nal set of rolls being‘ a pair of circularly
grooved shaping rolls.
7
herein envisaged, because the thrust imparted to the
In view of the considerable velocity ratios which the
tube by the tube shaping rolls necessitated thatthe slot
uliarly from cold rolled strip material, and to roll them
down to their ?nal outside diameters between about 20
production‘ methods afford with regard to economy of
production in the case of precision made steel tubes of
to the initial section of the tube. To achieve this result
it is essential that a freely entrained bending mill should
be used, i.e. one that isnot powered, because this is
of a‘ particular width, to produce tubes of widely diifer
ing sections without the troublesome complication of ex
ly relieved of all axial thrust and subject only to adequate
fore‘ less liable to cause trouble in operation.
The considerable reduction in the tube section of up
to 85% that can be achieved as a result of the special
invention proposes to provide between directly consecu 30 edges should be closed a considerable distance ahead
of the welding point with the result that in the small
tive Working roll sets in the cold rolling mill and which
available diameters bead removing tools could not be
not only allow for the elongation of the tube due to the
located precisely owing to their considerable length.
rolling action but at the same time impart an amount
The advantages of the method proposed by the present
of tension to the tube which exceeds its yield point with
out reaching the ultimate stress, it is possible to produce 35 invention over methods hitherto practised are- not con
?ne dto the considerable‘ improvements which continuous
in one continuous operation welded tubes, more. partic~
small and very small gauge. They are also due to the
and about 3 mm., with a total reduction in section (both
in diameter and wall thickness) of about 80% related 40 fact that it is. possible in one installation, from a strip
changing the roll sets, as well as to the fact that much
less space is needed for accommodating the plant and
the only possible way of ensuring that the tube upon
entering the cold rolling reducing mill will be complete 45 that the latter is much simpler in construction and there
tension.
7
To achieve the effect envisaged by the invention it is,
construction and the particular speed ratios of the roll
furthermore, of importance that in the reducing mill
the grooves in cooperating rolls of the shaping, roll sets 50 sets in the proposed cold rolling reducing mill in con
junction With the tension imparted to the rolled material
should de?ne closed oval contours and that the rolls
by the drag transmitted to the freely entrained bending
of consecutive stands should work in rolling planes dis
placed through 90° angles, no intermediate circular shap
mill, provides not only the fundamental conditions neces
ing rolls being employed and the oval shaping roll sets
sary for producing tubes of ?nal cross sections that can
being closely consecutive because it is not otherwise pos 55 be varied within very wide limits (for instance from 20
sible to impart longitudinal tension in excess of its yield
down to about 3 mm.) from a strip of the same given
width, merely the last roll stands of the reducing mill
point to the material of the rolled tubes and to achieve
that measure of uniformity in the cold flowing deforma
being removed or replaced in conventional manner to de
tion which alone will permit the desired considerable re
termine the ?nal gauge of the tube, but the further advan
duction in section, amounting to as much as 80%' (both 60 tage also arises that the bending of the strip to form '
in relation to diameter and possibly also to wall‘ thick
a slotted tube as well as the welding operation are per
formed when the dimensions of the tube are still of an
mess) to be obtained.
For generating longitudinal tension above the yield
order in which these operations are much easier‘to con
point of the tube material, a feature which is primarily
trol with great precision even when tubes are produced
responsible for the considerable reduction in section 65 which have diameters as small as for instance, 3 mm.
achieved by the rolling mill, the peripheral speeds of the
It will be readily understood that-as is. alsov the case
rolls in consecutive working roll stands of the reducing
in the earlier method—~an exchange of the roll sets com
mill must be increased by about 1/2 to 3% beyond the
prised in the bending mill, or of the welding machine, or
speeds determined by the elongation of the tube as such,
of rolls associated with the welding machine, or of the
the speed ratios between consecutive roll sets depending 70
guide roll sets, is never required.
upon the number of stands required, in such a manner
In principle any of the hitherto conventionally em
that said ratio will be less in the case of a larger num
ployed welding techniques can also be used in the per
ber of passes than in the case of a smaller number of
formance of the method proposed by the present inven
passes. On the other hand, the number of roll stands
will depend upon the overall reduction requiredto pro 25 tion, However, ‘in order to avoid the formation espe
3,075,484
6
cially of a weld bead inside the tube, it is preferable if
use is made of an electric welding technique such as the
rgon arc welding process. A particularly useful welding
of example and with reference to the accompanying draw
ings, in which
FIG. 1 is a schematic representation of the entire plant
in elevational section;
technique is high frequency welding which produces a
weld head that is far less pronounced than that which
arises in resistance butt welding, and which at the same
time is capable of providing a good quality seam when
the speed of travel of the material is as high as the out
standing performance of the cold rolling reducing mill
will permit.
Especially when using the two last mentioned welding
techniques and when taking advantage of the considerable
reduction ratios of which the method according to the
invention is capable, the rate of production‘ of, welded
FIG. 2 is a welding machine, likewise in schematic
form, shown in a section taken on the line II—II in
FIG. 1;
E6. 3 is a plan view of the section of tube in course
16
of being welded;
FIG. 4 is a cross section of the tube in the plane indi
cated by IV—1V in FIG. 3, and
FIG. 5 is a cross section on the line V——V in FIG. 1
showing two pairs of rolls of the cold rolling reducing
mill working at a relative angle of 90°, likewise repre
and ?nished tubes can be raisedto an output which is 15 sented in schematic form.
at least 5 times that obtainable by, conventional methods.
It has been found that a useful arrangement is to pass
the slotted tube, with its edges separated until shortly
before it enters the welding machine, through a pair of
rolls disposed in a horizontal plane and embracing the
tube from either side for closing the slot, the edges of the
slot being guided by a special guide member from the
moment they leave the closing rolls to the moment they
For producing a welded precision-made steel tube with
a ?nal overall diameter of say 4.75 mm. and a wall thick
ness of 0.7 mm. a cold rolled steel strip 1a, 54 mm. wide
and 0.7 mm. thick, is fed into a plant schematically
shown in FIG. 1. Preferably the material of the strip
is a deep drawing steel of which a section of maximum
length is wound on a freely rotatable reel 2. It is with
drawn from this reel exclusively by the tensional pull
produced by a cold rolling reducing mill 3 which draws
25 the strip cold through the several forming devices in the
a special tool for the removal of the internal head, if the
direction indicated by arrow x.
nature of the welding process should make this desirable.
A bed 4 to which the several assemblies of the plant are
Although the assembly of freely rotating guide rolls
?rmly secured carries a circular shearing cutter 5 through
which follows the welding machine, and which consists
which the steel strip 1a is ?rst drawn as it unwinds from
of pairs of rolls having alternately oval and circular
the reel 2. The knives on the rollers of the shears trim
grooves, may be arranged so that consecutive roll pairs
the rolled raw edges of the cold rolled steel strip 1a to
work at relative angles of 90°, it is preferred not to
the exact width of say 51 mm. required for forming a
adopt this latter arrangement because it is then easier to
?nished tube of the above-mentioned dimensions.
prevent the tube from twisting within the operational
The trimmed strip then enters the rolls of a bending
range of the welding machine.
’
35 mill 6 with roll sets 6a, 6b, 60 which are not driven and
Moreover, it is preferred that the rolls of the cold
freely rotatable, each pair of rolls being located in a plane
rolling reducing mill which have oval grooves and which
which is substantially perpendicular to the direction of
it is proposed to arrange so that consecutive pairs of rolls
travel of the strip. The rolls are shaped to bend the strip
work at right angles, should be so disposed that said roll
into a slotted tube of approximately 16 mm. outside diam
pairs are alternately inclined in relation to a vertical
eter. Naturally, both the disposition and shape of the
plane at angles of 45°.‘ In the method according to the
rolls as well as the number of stands can be suitably
invention this latter arrangement aifords'the advantage
modified to adapt the arrangement to the given condi
that the weld seam of the tube which is especially sensi
tions of the bending operation they are required to per
form.
tive to deformational stress will always be in a zone where
the seam is exposed to minimum deformational stress, 45. Mounted on a more elevated platform 4a of the bed
whilst the tube passes through the relatively crossed con
4, following the bending roll sets in the direction of
secutive ‘roll stands in which the cross section is alter
travel of the strip, is a pair of closing rolls 7 operating
nately squeezed into ovality in two relatively perpendicu
in a plane at right angles to the rolls of the bending
lar directions. This is a matter of especial importance
mill 6. These rolls close the slot of the tube shortly be
because cold deformation imparts to the raw material 50 fore it enters the welding machine. The pair of rolls 7
is replaceable and rotates freely on vertical shafts which
of the tube considera le strength coupled with low elon
are relatively horizontally adjustable and placed as closely
gation‘so that ‘the weld seam and neighboring regions are
as possible to the following welding machine.
particularly liable to be affected by any bending stress.
It will be seen more particularly by reference to FIGS.
Although the main field of application of the method
3 and 4 that a sword 16, adjustably a?‘ixed to a support
and apparatus proposed by the present invention is, and
9 is located between the pair of closing rolls 7 and pres
its major economic advantages arise in, the production of
sure rolls 8 associated with the welding machine. The
welded high precision steel tubes having a ?nal outside
object of this sword 1b is to align the edges of the slot of
diameter between 20 and 3 mm., advantages will also
the tube in known manner with the position of the elec
be gained in the production of tubes of greater size. For
enter the first pressure roll associated with the welding
machine, said guide member being possibly associated with
instance, a welded tube of 90 mm. outside diameter and 60 trode immediately before the tube passes the welding
a wall thickness of 1.2 mm. could be reduced to a ?n
ished tube of 20v mm. diameter and a w‘ 11 thickness of 1.2
and less, or a welded tube of say 40 mm. outside di
point.
In the illustrated example a welding machine ill is em
ployed which is one equ'pped for performing a gas-elec
trical welding operation, more particularly the argon arc
ameter and 1 mm. wall thickness might be reduced to a
tube of any desired ?nal cross section, down to say an 65 process of welding, and to this end it comprises a tungsten
electrode 12 supported on a bracket 13 which permits the
outer diameter of 9 mm. and a wall thickness of 1 mm.
electrode to be adjusted in the vertical plane. Whereas
and less.
current is supplied to the electrode through a cable 14
Preferably the cold rolling reducing mill will be
from a welding transformer not specially shown in the
equipped, with two-high roll stands with grooved rolls en
70 drawings, the inert argon gas is admitted through a duct
closing an oval contour. However, in certain cases three
15 inside the bracket 13 and a nozzle jacket 13a which
high or even four-high roll stands could be used with
surrounds the tungsten electrode 12.
roughly oval grooved shaping rolls.
The pressure rolls 8, associated with the Welding ma
A preferred embodiment of a bending and rolling mill
according to the invention will now be described by way 75 chine and likewise freely ,rotatably mounted in substan
tially horizontal planes, support and guide the welded tube
3,075,484.
7
Behind the cold rolling reducing. mill 3 is a longitudi
in. such a way that the cross section of the slotted tube
nally
traversible saw 18 which reciprocates at a speed
cannot vary. As will be seen more particularly by refer-.
determined by the lengths of tube it is desired to out. A
ence to FIG. 2 the peripheries of each of the pressure
circular blade ‘18a of the saw 18 cuts the required lengths
rolls 3 are formed with a groove 8a shaped to conform
as it moves in the direction of and at the speed of travel
5
with the outside diameter of the tube and to surround‘
of
the issuing tube, the cut lengths being discharged on
something over 3A of the periphery of the tube as it passes
to a conveyor frame 19 or into. a basket whence they are
under the electrode.
removed for use as required.
The weld seam produced by the argon arcv welding
According to the purpose for which the tubes are in
process is extremely even and ?at, and scarcely builds
up a head, so that tools for removing the bead and ?at 10 tended, the cut lengths maybe annealed in known manner
before further processing.
'
tening the weld seam are not required either on the out
While the method herein described, and the form of
side or on the inside of the seam. Moreover,v it has been
apparatus for carrying this method into effect, constitute
found that the considerable reduction in diameter during
preferred embodiments of the invention, it is to 'be un
the subsequent cold rolling process levels out minor eleva
derstood that the invention is not limited to this precise
tions in the formation of the seam to such an extent that
in the?nished tube the presence of the weld'seam is hard
ly detectable. Nevertheless there would be no: objecj
tion,, for instance in. the eventv of the tube being welded
by a resistance. butt welding process, to af?xing a suitable
bead removing. tool to the sword 1.0 or to, the‘ bracket 9
which carries the sword.
Further in the direction of‘ travel, indicated by the
method and form of apparatus, and that changes may be
made in either without departing from the scope of the
invention which is de?ned in thevqappended claims.
I, claim:
1. Apparatus for‘ continuously producing small section
welded tubing comprising, in combination, a cold rolling
reducing mill for reducing the diameter of a welded tube
‘with circular and oval grooves. The vertical roll. sets are
likewise arranged to be freely rotatable. The‘ purpose of
which advances continuously, through the reducing mill,
the latter tensioning and stretching the tubing while‘ lon
gitudinally‘ advancing the same; welding means» located
along the path of movement of the tubing in advance of
said reducing mill for welding together the edges of a
slotted tube, said welding means including rolls which
ing the section of tube passing through the welding ma
pulling the slotted tube through and beyond said welding
arrow x, of a welded tube 1', immediately behind the weld
iing‘machine, there is provided an assembly‘ of guide rolls
16 which in the illustrated embodiment consists‘ of, four
sets of rolls 16a, 16b, 16c and 16d provided alternately
advance the edges of the slotted tube toward each other
these rolls is to suppress the transmission of torque from
the subsequent cold rolling reducing mill 3 to the welded 30 to form a tube of substantially circular cross section and‘
said latter rolls being freely rotatable, said reducing mill
tube 1 and to prevent any such torsional forces from affect
means; and deforming guide means located along the
chine.
path of movement of the tubing between said welding
From the guide roll assembly or deforming means 16
the tube 1 passes into the cold rolling reducing mill 3. 35 means and said reducing mill for slightly deformingthe
cross sectional con?guration of the tubing to a non-circu
This is the only assembly of the plant which is positively
lar con?guration to prevent torsional forces created in the
driven. A drive shaft not shown in the drawings is con~
tubing in said cold rolling reducing mill from backing up
nected through appropriate transmission means, for in
beyond said deforming guide means to said welding
stance through V-belt transmissions 17, with in?nitely
variable gearings, likewise not specially shown, which are 40 means, said reducing mill pulling the tubing through said
deforming guide means.
associated with several roll stands 3a, 3b, 3c and 3d.
2. Apparatus as recited in claim -1 and wherein said
These permit the speed ratios from roll stand to roll
reducing mill includes successive roll sets all except the
stand to be adjusted in such a way thatthe resultant
last of which include a pair of cooperating rolls each
tensional stress in the welded tube 1 exceeds the yield
formed with a groove of substantially semi-elliptical con‘
point of the material and maintanns cold deformational
?guration, the groove surfaces of the cooperating rolls
flow across the entire tube section and around its en
forming together a substantially closed elliptical passage
tire periphery.
and engaging the tubing passing therethrough substantial
The tube 1. which is only slightly deformed in the guide
ly along the whole outer surface thereof.
roll assembly 16 is rolled down in the cold rolling reduc
3. Apparatus as recited in claim 1 wherein said de
ing mill 3 in twenty one passes in the, for instance, 21
roll stands provided for the purposes of the illustrated 50 forming guide means are constituted by guide roll means
example, and its diameter is reduced from 16, mm. to
4.75 mm, the weight per meter of the tube being thus
reduced from about 0.264 kg. to about 0.07 kg. Con
sequently the tube emerges from the cold rolling reducing
‘mill at approximately 3.8 times the optimum welding
speed which in the argon arc Welding process in its present
state of development is about 8 meters per minute, but
‘which can be increased by employing the high frequency
‘welding technique to 40 meters per minute and in the
further development of this process to even more.
The working roll sets of the cold rolling reducing mill
3, which are placed in alternation at right angles to one
another, and which are provided with oval shaping
consisting of freely rotatable guide rolls.
4. Apparatus as recited in claim 3 and wherein said
guide roll means includes successive roll sets which al
ternately deform the tithing into oval and circular cross
sections.
5. Apparatus as recited in claim 4 and wherein all of
the rolls of said guide roll means have parallel axes,
respectively.
6. Apparatus as recited in claim 3 and wherein said
60 reducing mill includes successive roll sets all except the
last of which provide the tubing ‘with an oval cross sec
tion, the last roll set of said reducing mill providing the
tubing with a circular cross section.
grooves, roll down the welded tube 1 in consecutive passes
7. Apparatus as recited in claim 6 and wherein the suc
to the desired ?nal cross section of the ?nished tube, 65 cessive roll sets of the reducing mill are respectively lo
precision of the ?nal section being ensured by the provi
cated in planes inclined by 90° one with respect to the
sion of a ?nal pair of circular shaping rolls 30! (see FIG.
next, all of said planes being inclined at an angle of 45°
5). According to the ?nal diameter that is required, a
with respect to a vertical plane, and said welding means
suitable number of roll pairs at the end of the mill can be
providing a weld located in said vertical plane so that the
removed or replaced, the ?nal. circular roll pair 3d always 70 deformation resulting from the roll sets of said reducing
forming the ?nal‘stand in the mill. As will be seen by
mill does not act directly on the weld.
reference to FIG. 5 the working roll stands of the cold
8. A method of continuously producing welded tubing
rolling reducing mill 3 are placed at an angle of 45° to
of small inner diameter, comprising the steps of welding
the vertical and incline in alternation to the right and the
75 the edges of a slotted tube to each other while continu
left;
3,075,484
9
10
ously advancing the tube by pulling forces; passing the
edges of the tubing are welded to each other so that the
thus welded tube continuously through consecutive roll
deformation of the tubing by the rolls of the reducing
sets of a cold rolling reducing mill while driving the rolls
of the consecutive sets at respectively increasing speeds
which tension the tubing in excess of its yield point while
decreasing the diameter of the tubing from roll set to roll
mill never is applied directly to the weld.
11. A method as recited in claim 8 and wherein all
except the last of the roll sets of the reducing mill give the
tubing an oval cross section while the last roll set gives
the tubing a circular cross section.
set and providing by thus driving the rolls the pulling
forces advancing the slotted tube during welding; and
slightly deforming the cross~sectional con?guration of the
Welded tubing to a cross section of non-circular con?gura 10
‘tion during the continuous movement of said tubing sub
sequent to the welding thereof but in advance of the re
ducing mill While advancing the tubing solely by the ten
sion derived from the reducing mill for preventing tor
sional forces created in the tubing in the reducing mill 15
from backing up to the tube portion being welded.
9. A method as recited in claim 8 and wherein the rolls
of the consecutive sets of the reducing mill are driven
at peripheral speeds increased by about 1/2 to 3% beyond
the speeds required for the elongation of the tubing in
the reducing mill.
10. A method as recited in claim 8 and wherein the
successive roll sets of the reducing mill act in planes which
are alternately inclined with respect to each other by 90°
and which are all spaced from the line along Which the
20
References Cited in the file of this patent
UNITED STATES PATENTS
446,498
617,363
Williams _____________ __ Feb. 17, 1891
Skogse _______________ __ Ian. 10, 1899
v1,352,493
Wolffgram ___________ __ Sept. 14, 1920
1,812,409
1,888,607
1,944,096
1,984,083
2,017,360
2,156,934
2,400,889
2,693,632
Leckie ______________ __ June 30,
Offutt _______________ _._ Nov. 22,
Mayweg _____________ __ Jan. 16,
Riemenschneider _______ __ Dec. 11,
Waterman ___________ __ Oct. 15,
Barrett ______________ __ May 2,
Ridder ______________ __ May 28,
Heussner ____________ __ Nov. 9,
1931
1932
1934
1934
1935
1939
1946
1954
FOREIGN PATENTS
759,819
Great Britain __________ _.. Oct. 24, 1956
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