Rolling mills

A rolling mill is provided with at least one roll stand for rolling bar material having three adjustable driven roll disks arranged radially to the axis of the rolled material, the maximum working surface of at least one of said disks being at least 20% wider than the maximum working surface of the other two roll disks.

This invention relates to rolling mills and particularly to a rolling mill 
arrangement with at least one roll stand for rolling bar goods, with three 
adjustable driven roll disks arranged radially to the longitudinal axis of 
the rolled materials. 
A roll stand of the above type, in which the three roll disks are displaced 
by 120.degree. to each other, constitutes a part of the known body of 
technical knowledge through German Pat. No. 2,259,143. The advantages of 
the three-disk roll pass reside primarily in the fact that a better 
stretching of the rolled goods is achieved in the pass with a smaller 
broadening. Thus, a stretching of .lambda.(coefficient of elongation)=3.5 
can be achieved in the previously known three-disk roll pass. In addition, 
a more uniform deformation and consequently a more favorable stress 
distribution in the rolled material are obtained with a three-disk roll 
pass. As a result, materials with poor deformation characteristics, such 
as sintered tungsten or molybdenum, can also be flawlessly rolled in the 
three-disk roll pass. Furthermore, due to better deformation, the increase 
in temperature of the rolled goods during the rolling process is less in 
three-disk roll passes than in two-high roll passes of the same diameter 
and the same cross-section reductions, by means of which higher rolling 
velocities and thus a greater output and a better economy can also be 
achieved even at high mean tensile strength of the rolled materials. 
Structurally, it is advantageous for the forces to be absorbed in a 
three-disk roll stand that the forces are distributed on at least six 
bearings, while in two-high roll stands there are only 4 bearings. 
Consequently, a three-disk roll stand can absorb or exert higher rolling 
pressures. 
Three-disk rolls that have a profiled pass are proposed in German Pat. No. 
2,537,825 for use in a three-roll rolling mill, especially for the first 
roll passages of a strand coming from a casting machine. Thus, the roll 
disk should have a circular convex profile in the case of an original 
triangular cross section of the rolled goods. The underlying concept of 
this proposal is that the profiled disks exert a force in the rolled 
material that has a result essentially oriented toward the rolled material 
center. The idea of this construction is to avoid cracking during 
deformation. It is particularly designed for rolling aluminum and 
aluminum-magnesium alloys. 
Finally, an individual driving of the three roll disks in the case of a 
roll stand in the three-disk arrangement is known from the DE-Gm (German 
Utility model Pat. No.) 1,807,019. 
The present invention is based on the consideration that in the case of the 
familiar three-disk roll stands with adjustable roll disks the latter are 
brought together to a minimum roll gap after a few passages, and that the 
total stretching is thus limited. Based on this consideration, the present 
invention proposes to develop a rolling arrangement with a roll stand in 
the three-disk arrangement, with which a substantially greater total 
stretching is possible. 
This problem is solved in the generically similar rolling mill arrangement 
with at least one roll stand having three roll disks by the fact that the 
maximum working surface of one of the three roll disks is at least 20% 
wider than the maximum working surface of each of the other two roll 
disks. The working surface is preferably 30% wider than that of the other 
two roll disks. In the usual implementation the working surfaces of the 
other two roll disks have practically the same width, i.e., they have a 
maximum difference in width of only .+-.5%. 
Expediently, the roll disk whose axis is horizontal has a wider working 
surface. In this case, this roll disk with the wider working surface can 
form the upper or lower limitation of the pass. According to a 
particularly preferred construction, two roll disks exhibit a maximum 
working surface of width b, while the third, wider roll disk has a maximum 
working surface of width 1.4 b-2.0 b. 
In the case of the roll disk, it may be a solid disk or a facing fastened 
onto an inner-lying carrier body. This facing offers particular cost 
advantages because the expensive material has to be provided only in the 
form of the facing. 
The width of the maximum working surface is determined by the width of the 
maximum contact cross section of the rolled material. In the case of a 
rolled material with a multiangular contact cross section, the maximum 
working surface of the wider roll disk should preferably be at least 10% 
wider than the longest lateral surface of the contact cross section. 
According to another embodiment, at least the working surface of the wider 
roll disk is profiled. This profiling can be achieved by a convex curving 
of the working surfaces to the middle of the roll disk, in which case the 
curvature is expediently flattened in the center. 
However, an embodiment in which the working surface of the wider roll disk 
has a concave profiling is preferred. The profile is conveniently selected 
so that a pressure directed inward from the edges of the rolled material 
arises, such that dangerous tensile stresses that could easily lead to 
cracks are avoided. Thus, it has proved expedient in the case of a square 
contact cross section of the rolled material to provide the working 
surface of the wide roll disk with raised outer edges. Thus, the outer 
edge can be raised at an angle of preferably 15.degree.-45.degree. with 
respect to the horizontal working surface. The raised outer edges are 
provided so that they lie against two corners of the square billet in the 
contact cross section, while one of the other two roll disks with its 
non-profiled, essentially rectilinear working surface lies against the 
other two corners of the square billet. 
The roll disks are adjustable so that in reversing operation the pass 
opening can be brought together in accordance with the deformation. The 
adjustability is also advantageous in continuously operating rolling mill 
arrangements in facilitating a change in format or for compensating wear. 
It has proved advantageous if the three roll disks are jointly adjustable. 
In a particularly preferred rolling mill arrangement the roll stands with 
the three roll disks are driven in a reversing manner. Then either only 
one roll stand or two roll stands, one behind the other, can be provided, 
as desired. If two or more roll stands, one behind the other, are provided 
for the reversing drive, it is expedient if the disk with the wider 
working surface is displaced in the successive stands by 180.degree. with 
respect to the others. If only one roll stand is used, it is convenient to 
have a canting device in front of and beyond the stand so that the rolled 
material can be turned by the desired angle. 
In a rolling mill arrangement with a continuous roll stand setup, with at 
least three roll stands, one behind the other, at least the first two roll 
stands have three roll disks, one of which has the wider working surface 
and where in the second roll stand the roll disk with the wider working 
surface is displaced by 180.degree. with regard to the first stand. 
Care should be taken in both the reversing and continuously operating rolls 
so that in the successive roll passages the working surfaces of the roll 
disks make contact with the surface of the rolled material that was free 
of pressure in the previous roll passage. The surface on which the 
broadening occurs is involved here. This deformation concept is known in 
principle in order to achieve a definite final cross section. 
The rolling mill arrangement is suitable for various original cross 
sections, round or multiangular. However, particular advantages are 
evident in the rolling of rectangular and especially square rolled 
material. In the case of square rolled material original cross sections 
with a side length of 100-400 mm are preferred. The square original cross 
section permits utilizing practically the entire working surface of the 
wider roll disk with the one lateral length of the charge material, while 
the two other roll disks make contact at the edges of the square original 
cross section. The wide roll disk with the largest working surface 
determines the maximum original cross section, while the two narrow roll 
disks can exert the full rolling function. This results in a saving of 
material for the narrow roll disks. An even greater advantage resides in 
the fact that the pass opening can be brought together much more than with 
the roll disks of the previously known arrangement. This advantage is 
illustrated in the drawing by means of a square billet; it is particularly 
evident in the case of square original cross sections. The same is true to 
a somewhat lesser degree for the other original cross sections also. 
The rolling mill arrangement with the described roll stand is suitable for 
the hot or cold rolling of metals. The particular advantages are evident 
in the case of metals that are difficult to shape, especially in 
high-alloy steels. The particular advantages are thus evident in 
austenitic and ledeburitic steels, high-temperature steels, and tool 
steels. 
The three-disk arrangement offers the advantage that the final cross 
sections produced have a very good surface because each of the three roll 
disks acts uniformly on the rolled material without any relative movements 
between roll and rolled material, which are unavoidable in the case of the 
serrated pass openings. This also has an advantageous effect on the 
service life of the roll disks because the wear on the working surfaces is 
substantially reduced. 
The substantial stretching of .lambda.&gt;5, in particular .lambda.&gt;7, is 
advantageous in the described roll stand. A total stretching of .lambda.= 
about 9.0 can be achieved. It is thus possible to pass from a large 
original cross section to a very small final cross section with few or 
even only one reversing driven stand. This is a substantial advantage, 
especially with regard to extruded steel billets. It is advantageous here 
that a multiplicity of final cross sections of varying size can be 
produced from one original cross section (cross section predetermined by 
the extrusion mold).

Referring to the drawings and viewed in the direction of the rolled 
material, FIG. 1 shows a roll stand with three adjustable driven roll 
disks 1, 2, and 3 facing the longitudinal axis of the rolled material 
(three-disk arrangement). The roll disks 1, 2, and 3 respectively have a 
working surface 4, 5, and 6. The common adjusting arrangement 7, 
symbolically represented by arrows, is provided for all three roll disks 
1, 2, and 3 for adjusting the pass opening. Each of the three roll disks 
1, 2, and 3 has an independent drive 8. The axis of rotation of the lower 
roll disk 1 is horizontal, while those of the other two roll disks 2 and 3 
are at an angle of 45.degree. to the horizontal. The roll disks 2 and 3 
have working surfaces 5 and 6 of equal width. On the other hand, the 
working surface 4 of the lower roll disk 1 is considerably wider. The 
working surface 4 of the roll disk 1 is approximately 1.7 times wider than 
each of the working surfaces 5 and 6 of the roll disks 2 or 3. 
The enlarged segment (FIGS. 2 and 3) clearly shows the different widths of 
the working surfaces 4, 5, and 6. The enlarged segments (FIGS. 2 and 3) 
show with solid lines the position of the roll disks 1, 2, and 3 at the 
beginning of rolling and with dashed lines the position of the roll disks 
1, 2, and 3 after rolling is completed. The square original cross section 
20 at the beginning of rolling, e.g., of an extrusion billet, is reduced 
to a hexagonal cross section 24 after completion of rolling. In the 
alternative design according to FIG. 3 the wide working surface 4 of the 
roll disk 1 has outer edges 9 that are raised at an angle of about 
20.degree.. The raised outer edges 9 are located in the outer one-sixth of 
the working surface 4. The raised outer edge 9 passes to the edge into a 
shoulder-like horizontal flattening 10. 
FIG. 4 shows in plan view a first alternative of the overall rolling mill 
arrangement. In this alternative the three roll disks 1, 2, and 3 are 
arranged in a reversing stand 11. An edge and guide arrangement 12, 13 is 
provided in front of and behind the reversing stand 11. The roll tables 14 
and 15 are connected to these. The reversal of the direction of movement 
of the rolled material during passage through the reversing stand 11 is 
indicated by arrows. 
The rolling mill arrangement shown in FIG. 5 operates continuously with 
four roll stands 16, 17, 18, 19 arranged one behind the other. The 
direction of movement of the rolled material is indicated by an arrow. The 
rolled material comes from the roll table 14 through the guide arrangement 
25 to the first roll stand 16. The first roll stand 16 and the second roll 
stand 17 are designed as three-disk roll stands with the over-width roll 
disk 1. The subsequent roll stands 18 and 19 are three-disk roll stands in 
a previously known construction, i.e., with three roll disks of equal 
width. In the first two roll stands 16 and 17 the axis of rotation of the 
over-width roll disk 1 is horizontal in both cases. However, the roll 
disks 1 located in roll stands 16 and 17 are displaced by 180.degree. with 
regard to each other. In the first roll stand 16 the working surface 4 of 
the over-width roll disk 1 forms the lower limit of the pass opening and 
in the second roll stand 17 the working surface 4 of the over-width roll 
disk 1 forms, the upper limit of the pass opening. 
The first four passes, as they can be effected with a roll stand described 
in FIGS. 1 and 2, are shown in FIGS. 6-9. The original cross section is 
depicted by dashed lines and the final cross section by solid lines. The 
reference number of the original cross section is written outside of the 
cross section and the reference number of the final cross section was 
written on the cross section surface. During the first pass (FIG. 6) the 
original square cross section 20, e.g., an extrusion billet, is deformed 
with about 10% reduction to a final cross section 21. It should be noted 
that the rolled material coming from the roll table 14 lies with its full 
lateral length on the working surface 4 of the wide roll disk 1 and is 
deformed by the latter. The two upper-lying edges of the rolled material 
are deformed by the upper two roll disks 2 and 3. During the second pass 
(FIG. 7) the rolled material and the pass opening have an attitude 
displaced by 180.degree. with regard to each other. As described in 
connection with FIG. 5, this displaced arrangement can be achieved in a 
continuously operating rolling mill arrangement by another arrangement of 
the roll disk 1 in the second stand 17. In the case of a rolling mill 
arrangement with reversing drive (FIG. 4) the rolled material is turned by 
180.degree. after the first pass by means of a canting arrangement and fed 
into the second pass as shown in FIG. 7 after reversing the direction of 
movement. The roll disks 1, 2, and 3, are newly adjusted during the 
turning of the rolled material. During the second pass the roll disks 2 
and 3 then act on the edges of the rolled material, which were located in 
the region of the working surface 4 of the over-width roll disk 1 during 
the first pass. The rolled material leaves the second pass with the final 
cross section 22. The pass reduction is about 17% during the second pass. 
After the second passage the rolled material is again turned by 180.degree. 
and after another adjustment of the three roll disks 1, 2, and 3 fed into 
the third pass shown in FIG. 8. The reduction in the third pass is ca. 
18%. The rolled material leaves the third pass with the final cross 
section 23. This final cross section 23 already exhibits a somewhat 
hexagonal shape. A turning of the rolled material by 60.degree. is thus 
sufficient for further rolling reduction. This is shown in the fourth pass 
(FIG. 9). The fourth pass is rolled with a cross section reduction of 
about 20% until the desired hexagonal final cross section 24 is reached. 
Of course, additional passes can follow the fourth pass until the desired 
final cross section is achieved, in which case the material is turned in 
the same manner by 60.degree. and the roll disks are further moved 
together. The amount of adjustment and the degree of reduction are 
dependent on the quality of the material to be rolled. They can be 
selected according to need. The roll disks 1, 2, and 3 can be brought 
together to a minimum spacing that still avoids a mutual touching of the 
roll disks 1, 2, and 3. The minimal cross section to be achieved is thus 
determined. A numerical example for an alloy steel is given below. Alloy 
steel was rolled from an extrusion with a square cross section of 150 mm 
of lateral length and 10 mm edge radius to a 54 mm hexagon. 
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Cross Section 
Stretching 
Turning after 
Pass No. mm.sup.2 .lambda. the pass by 
______________________________________ 
STARTING 22414 -- -- 
MATERIAL 
CROSS SECTION 
150 mm 
1 20150 1.11 180.degree. 
2 16800 1.20 180.degree. 
3 13780 1.22 180.degree. 
4 11020 1.25 60.degree. 
5 8410 1.31 60.degree. 
6 6420 1.31 60.degree. 
7 4900 1.31 60.degree. 
8 3740 1.31 60.degree. 
9 2860 1.31 60.degree. 
10 = 54 mm hexagon 
2525 1.13 -- 
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With regard to the square cross section of the starting material of 150 mm 
of side length, a total stretching of .lambda.=8 is calculated down to a 
final hexagonal cross section with a width over the flats of 54 mm. 
If such a roll stand with an over-width roll disk is used for a lesser 
total stretching, e.g., as a roughing stand component in front of a 
subsequent fine train or wire train, the width difference between the roll 
disk 1 and the disks 2 and 3 can be maintained smaller than in the case of 
a high total stretching. In the case of a lower total stretching, a 
turning of the rolled material by only 60.degree. can be begun earlier 
during the course of rolling. 
The alternative design of the over-width roll disk 1, shown in FIG. 3, 
offers the advantage that a pressure directed inward develops at all edges 
of the rolled material even during the first pass. This is particularly 
advantageous in the case of materials that are difficult to shape. 
In the foregoing specification, we have set out certain preferred practices 
and embodiments of our invention, however, it will be understood that this 
invention may be otherwise embodied within the scope of the following 
claims.