[0001] The present invention relates to a method for cross rolling of products such as balls,
in particular the ones obtained from heads of scrap railway rails.
[0002] There are numerous methods for producing balls which are then used in ball mills
or rolling bearings. The most commonly employed methods include casting, die forging,
and rolling. In casting, balls are cast from cast steel into permanent moulds made
of metal, or so-called metal moulds. Die forging of balls is usually performed using
friction presses with billets in the form of rods made from steel which contains increased
amounts of carbon and manganese. Immediately after the process of die forging using
eccentric presses, flash trimming is performed. The process of producing balls is
most efficient if cross rolling is employed. During one roll turn, one ball is produced.
Within one minute it is possible to produce even up to 160 balls of approximately
30 mm in diameter or 40 balls of approximately 120 mm in diameter. Balls are rolled
in helical rolling mills equipped with two rolls, each roll having single grooves
cut over the screw line, their length being generally equal to 3.5 of the coil. The
axes of the rolls are inclined relative to the axis of the billet (rod), usually at
the angle ranging from 3° to 7°. In the course of rolling, the rolls turn in the same
direction, while the billet turns in the opposite direction. In order to obtain good
rolling results, the billet diameter should approximately equal 0.97 of the diameter
of finished balls. The diameter of the rolls is from 5 to 6 times bigger than the
diameter of balls. Information on helical rolling of balls is presented in the following
book:
W. Dobrucki, Zarys obróbki plastycznej metali, Wydawnictwo "Slask," Katowice 1975.
[0003] There is another method for cross-wedge rolling of four balls, described in:
Z. Pater, Walcowanie poprzeczno-klinowe, Wydawnictwo Politechniki Lubelskiej, Lublin
2009. This method consists in using two flat tools which move in the opposite directions,
thereby forming balls from the billet in the form of a rod whose diameter is equal
to the ball diameter. The tools used in rolling consist of two parts: a forming wedge
and a cutting pad. The forming wedge, which is of a typical shape, has longitudinal
wedge grooves of a transverse circular profile, and the distance between the grooves
is smaller than the diameter of the ball being formed. The effect of the forming wedge
is that balls connected by cylindrical connectors, whose diameter is approximately
half of the ball diameter, are produced. To separate the formed balls a cutting pad
needs to be used, the effect of which is that the connectors are transformed into
the missing parts of the balls. A characteristic of this is that during the cutting
process, the balls are drawn aside by the grooves, which are located in this part
of the tool at the angle towards the rolling direction, or the direction in which
the wedge tool moves.
[0004] The essence of the method for cross rolling of products such as balls, in particular
the ones obtained from heads of scrap railway rails, is that a billet in the form
of a head cut off a scrap railway rail is placed between two flat tools with initial
wedges, behind which there are wedges with longitudinal grooves of a semi-circular
profile, next the flat tools begin to move in the opposite directions with the same
velocity, and during this time the moving initial wedges cut into the billet and make
it rotate, thereby forming a semi-finished product in the form of a rod whose diameter
is bigger than or equal to the ball diameter, and then the wedges with the grooves
cut into the said semi-finished product, thereby forming balls which are in the final
stage of the rolling process separated from one another by cutters located at the
end of the flat tools. The process is done in a configuration wherein only one of
the flat tools moves in a sliding motion, while the other does not move.
[0005] The advantage of the invention is that it makes possible to simultaneously form many
balls, the quantity of which depends on the tool width. Thanks to the application
of this invention, it is possible to form balls using cheap material obtained from
scrap railway rails. The invention is environment-friendly as its application will
decrease the amount of scrap for metallurgical processing that reaches steel mills.
[0006] An exemplary embodiment of this invention is shown in the attached drawings, wherein
Fig. 1. shows the beginning of the cross rolling process as well as the type of the
billet used, Fig. 2 illustrates the moment of the rolling process when the semi-finished
product in the form of a rod is produced by the initial wedges, and Fig. 3 shows the
end of the rolling process and the produced balls.
[0007] The method for cross rolling of products such as balls, in particular the ones obtained
from heads of scrap railway rails, consists in that the billet 1 in the form of a
head cut off a scrap railway rail is placed between two flat tools 2 and 3 which have
the initial wedges 4 and 5, behind which there are the wedges 6 and 7 with the longitudinal
grooves 8 and 9 of a semicircular profile, next the flat tools 2 and 3 begin to move
in the opposite directions with the same velocity V, and during this time the moving
initial wedges 4 and 5 cut into the billet 1 and make it rotate, thereby forming the
semi-finished product 10 in the form of a rod whose diameter D1 is bigger than or
equal to the diameter D of the ball 11, and then the wedges 6 and 7 with the grooves
8 and 9 cut into the said semi-finished product, thereby forming the balls 11, which
are in the final stage of the rolling process separated from one another by the cutters
12 and 13 located at the end of the flat tools 2 and 3. The process is done in a configuration
wherein only one of the flat tools 2 or 3 moves in a sliding motion with the velocity
V, while the other tool 2 or 3 does not move.
1. A method for cross rolling of products such as balls, in particular the ones obtained
from heads of scrap railway rails, whereby a billet (1) in the form of a head cut off a scrap railway rail is placed between two flat tools
(2) and (3) which have the initial wedges (4) and (5), behind which there are wedges (6) and (7) with longitudinal grooves (8) and (9)
of a semicircular profile, next the flat tools (2) and (3) begin to move in the opposite directions with the same velocity (V), and during this time the moving initial wedges (4) and (5) cut into the billet (1) and make it rotate, thereby forming a semi-finished product (10) which has the form of a rod whose diameter (D1) is bigger than or equal to the diameter (D2) of a ball (11), next the wedges (6) and (7) with the grooves (8) and (9) cut into the semi-finished product (10) and form the balls (11), which are in the final stage of the rolling process separated from one another
by cutters (12) and (13) located at the end of the flat tools (2) and (3).
2. A method according to claim 1, whereby the process is done in a configuration wherein
only one of the flat tools (2) or (3) moves in a sliding motion with the velocity (V), while the other tool (2) or (3) does not move.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only.
It does not form part of the European patent document. Even though great care has
been taken in compiling the references, errors or omissions cannot be excluded and
the EPO disclaims all liability in this regard.
Non-patent literature cited in the description
- W. DOBRUCKIZarys obróbki plastycznej metali, WydawnictwoSlask,'' Katowice, 1975, [0002]
- Z. PATERWydawnictwo Politechniki Lubelskiej, LublinWalcowanie poprzeczno-klinowe, 2009, [0003]
