CALANDRE OBLIQUE DE LAMINOIR

SKEW ROLLING MILL ROLLER

Abrégé anglais

P/2982
IMPROVED SKEW ROLLING MILL ROLLER
Abstract of the Disclosure
The tapered working roller of a skew rolling mill is provided
with a deformation surface in the form of a paraboloid and a smoothing
surface at the end of smaller cross-section in the form having the approximate
shape of a hyperboloid.

Revendications

The embodiments of the invention in which an
exclusive property or privilege is claimed are defined
as follows:
1. In a skew rolling mill for cross section
reduction of an elongated stock as it moves along a
longitudinal axis without rotation about such axis, com-
prising:
a roller support means mounted for rotation
about said longitudinal axis;
a plurality of tapered working rollers mounted
within said roll support means and symmetrically about said
longitudinal axis, each of said rollers being mounted for
rotation about a secondary axis which intersects the
elongated stock;
primary means for rotating said roll support
means in a first direction; and
first intermediate means for rotating said
rollers about said secondary axis and into the surface of
said elongated stock for reducing the cross section of said
stock;
the improvement comprising said tapered working
rollers each including a first surface having the shape
of a paraboloid for substantially equal or decreasing
deformation in the cross section of the deformation taper
of said stock.
2. The skew rolling mill of Claim 1 wherein
each of said tapered working rollers has a second surface,
immediately adjacent said first surface and defining the
smaller end of said tapered working roller, having the
approximate shape of a hyperboloid for smoothing helically
shaped protrusions and grooves caused by said first surface
in the surface of the elongated stock during the cross section

reduction thereof.
3. The skew rolling mill of Claim 1 wherein each
first surface of said tapered working rollers satisfies
the formula:
<IMG>
wherein V1 is the feeding speed of the elongated
stock as it moves along the longitudinal axis at a location
prior to its engagement by said working rollers;
a = 3/T wherein T is the revolution time of said
roller support means;
.theta. 1 is the logarithmic reduction of the cross
section of the first pass of said working surface of said
roller about said stock;
.alpha. = strain hardening exponent of said stock;
R1 signifies the radius of said stock after
its cross section has been reduced; and
k = R1 exp (? x nk)
where n is the number of roller passes for a volume element
and
k = (1 +.alpha.)-1.

Description

6~
This invent~on relates to an improvement in a
skew rolling mill of the type described in U.S. Patent No.
3,735,617.
U.S. Patent No. 3,735,617 describes a skew
rolling mill which includes a driven roller carrier through
which longitudinally extending material is moved, with the
roller carrier being rotatably driven about the axis of
material which is to be rolled. Three spaced frustroconically
shaped working rollers are each rotatably driven in the
roller carrier about an axis which intersects with the
material to be rolled. The working rollexs reduce the
cross-section of the material, and as a result of the
angular displacement of the rollers with respect to the axis
of the material, the working rollers move such material.
It has ~een found that when this apparatus is
used for forming nonferrous metals in regions with small
dimensions, and in particular in the case of cold de-
formation, optimal rolling results are not achieved. For
example, undesirable elevations which are quite marked and
which have a helically shaped course, appear on the surface
of the roller stock. Furthermore, because the cross section
decreases too much in those regions that are formed last,
the roller slides quite severely on the rolled product,
thereby reducing the quality of the rolled product. -
In accordance with the present invention there
is provided an improved tapered working roller for a skew
rolling mill in which the working surface thereof is in
the form or shape of a paraboloid to thereby provide a
substantially equal or decreased de~ormation in the
cross-section of the deformation taper of the rolled stock.
In accordance with the invention~ a more extensive deformation
~ .
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6~3
can be achieved and undesirable elevations can be eliminated
or formed to an extent at ~hich they can be easily removed
by a drawing process.
Thus, there is provided an improvement in a skew
rolling mill for cross section reduction of an elongated
stock as it moves along a longitudinal axis ~ithout rotation
about the axis,: comprising a roller support means mounted
for rotation about the longitudinal axis, a plurality of
tapered working rollers moun-ted ~ithin said roll support
means and symmetrically about the longitudinal axis with
each of the rollers being mounted for rotation about a
secondary axis which intersects the elongated stock, pri-
mary means for rotating the roll support means in a first
direction and first intermediate means for rotating the
rollers about the secondary axis and into the surface of
the elongated stock for reducing the cross section of the
stock. The improvement which is provided comprises the
tapered working rollers each of which includes a first
surface which has the shape of a paraboloid for substantially
equal or decreasing deformation in the cross section of the
deformation taper of the stock.
The deformation in a skew rolling mill can be
regarded as a direct sequence of discrete individual de-
formations. For example, in the case of a three-roller
mill with fiv~e rotations for effecting the deformation,
the reduction by rolling occurs 15 times one a~ter the other~
With the linear tapered rollers of the prior art the re-
duction of thle diameter is proportional to the progress
of the material in the deformation zone, i.e., the relative
deformation blecomes larger and larger~ for example with
the lS rolling passes over the volume element. But this
feature is precisely the one which unfavorably influences
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~6~63
a formation process, particularly in cold deformation, but
also in warm deformation. Accord~n~ to the teaching of the
invention, working rollers of the skew rolling mill are
designed in such a way that the relative formation does not
increase, but remai`ns the same, or still better decreases
in correspondence with the strain hardening of the material.
Through the above-mentioned measures, the roll~ng force
remains the same, but a significantly higher degree of
formation is achieved. Furthermore, the undesirable
helical elevations do not occur to such a severe extent.
The hel;cal elevations can be inhibited still
~urther, as proposed according to another idea of the
invention, by designing the surface of the roller at
the end of smaller cross section to provide a smoothing
surface in the form having the approximate shape of a
hyperboloid.
Nearly optimal rolling results are achieved
if the working surface of the working rollers is designed
so that it approximately satisfies the formula
~r~ = Vl (1 +~) Rl ~Q~Rl~ ~ + (2 ~Rl) + ~
a . ~1 r2 ~Pl~ (~+1)(~+ 2)
In this formula, Vl signifies the feeding speed of the
stock; a is the frequency factor (a=3/T with T = revolution
time of the rotor); ~ 1 signifies the logarithmic re-
duction of cross-section of the first pass; ~ = strain
hardening exponent; Rl signifies the`radius of the rolled
bar; and r = running ordinate of the rolling contour. The
following holds for r;
3 r = Rl exp ( ~1 x nk)
where n is the number of rolling passes for a volume element
. - .
.

61~3
k ~
A skew rollin~ mill in which the working rollers were
designed according to the above formula yielded excellent
rolling results. The starting point here was that the slant
position of the rolling axles exerts no significant effect
on the result of rolling.
The invention is explained in more detail by
means of the embodiment shown schematically in Figure 1.
For the sake of clarity, the figure shows only
one working roller 1 of a skew rolling mill as disclosed
in U.S. Patent 3,735,617.
Referring to the drawin~, thare is shown a
tapered working roller 1 which is rotatably d~iven in a
roller carrier 2 about an axis which intersects with the
stock 3 to be rolled. The roller carrier is rotabably
driven about the axis of stock which is rolled~ The
working rollers reduce the cross-section of the stock, and
as a result of the angular displacement thereof with respect
to the axis of the stock, the working rollers move the
stock 3.
The working roller 1 essentially consists of a
deformation part 10 and a smoothing part 11 at the end of
roller 1 of smaller cross-section. While the smoothing
part 11 has the form which approximate the shape of a
hyperboloid, the surface of the deformation part 10 is
in the form o~ a paraboloid which satisfies the above
formula.
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