Method for rolling steel sections having flanges or flange-like portions

A method for rolling a steel section having flanges or flange-like portions from a steel bloom of rectangular cross section in a rolling mill having a train of roughing rolling stands for roughing, a universal rolling stand with a pair of opposing horizontal rolls and a pair of opposing vertical rolls, and a train of finishing rolling stands for finishing. The method includes rolling the bloom in the train of roughing rolling stands for roughing to a rough shape having a width greater than the shortest distance between the outer circumferences of the opposed vertical rolls in the universal rolling stand and having a reduced almost flat cross section including a portion to be shaped into flanges or flange-like portions in the final product, rolling the rough shape of flat cross section thus obtained in the universal rolling stand for causing the pair of vertical rolls and the pair of horizontal rolls to cooperatively give bending deformation mainly to the portions to be shaped into the flanges or flange-like portions, and finish rolling the rough shape produced from the bending deformation in the finishing rolling stands for finishing.

BACKGROUND OF THE INVENTION 
The present invention relates to a method for rolling steel sections, such 
as steel piles having flanges or flange-like portions using a train of 
shaping rolling stands and a universal rolling stand. 
In the past, such steel sections were usually produced by a shaping rolling 
method using rolling stands each fitted with upper and lower horizontal 
rolls, hereinafter generally called shaping rolling stands. They include 
breakdown stands, roughing stands, intermediate rolling stands and 
finishing rolling stands. More recently, however, as disclosed in Japanese 
Patent Publication No. 47-47784, there is a trend particularly in the 
rolling of H sections to employ a universal rolling stand fitted with a 
pair of horizontal rolls and a pair of vertical rolls in conjunction with 
the shaping rolling stands. This rolling method is herein called "the 
universal rolling method". 
The general differences between the shaping rolling method and the 
universal rolling method are illustrated schematically in FIG. 1 in 
connection with the rolling of steel sheet piles. The difference between 
the shaping rolling method shown in FIG. 1(a) and the universal rolling 
method shown in FIG. 1(b) lies in the manner in which the intermediate 
rolling passes (K-6, K-5 and K-4 in FIG. 1(a)) are changed. In the shaping 
rolling method these are shaping rolling passes whereas in the universal 
rolling method they are universal rolling passes. All other rolling passes 
of the universal rolling method are the same as those in the shaping 
rolling method. Adoption of the universal rolling method makes it possible 
to start with a steel bloom 2 of rectangular cross section as shown in 
FIG. 1(b) instead of the conventionally required roughly shaped beam blank 
1 shown in FIG. 1(a) and results in simplification of the breakdown 
rolling process, reduction of roll unit cost and easier adjustment of the 
contour and dimensions in the rolling of steel sections. These advantages 
contribute to the development of more economical rolling methods for 
producing steel sections having very precise contour and dimensions. 
The universal rolling method is, however, not completely free from defects 
and, in particular, involves the following two problems: 
(1) Because a bloom of rectangular cross section is used in place of the 
conventionally used beam blank, the starting material used in the 
universal rolling method has a greater cross sectional area than that used 
in the conventional method. Therefore, when the nature of the facilities 
makes it necessary to maintain a fixed magnitude of product elongation, it 
becomes necessary to use starting materials having a shorter length. This, 
in some cases, results in lowering of the rolling yield, the heating 
furnace productivity, etc. Therefore, in order to eliminate this 
disadvantage, it is necessary to provide a rolling method which can use a 
starting material of rectangular cross section which is as long and thin 
as possible. 
(2) It is generally more difficult to obtain a steel section of the desired 
final contour when a starting material with a rectangular cross section is 
used than it is when a roughly shaped beam blank is used and a 
considerable number of shaping rolling passes are nevertheless required 
before the universal rolling pass. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide a universal rolling 
method for steel sections which completely overcomes the above problems 
and, moreover, permits simplification of rolling mill layout, reduction of 
roll unit cost and the number of rolling passes, and improvement of 
rolling efficiency. 
The present invention provides a method for rolling a steel section having 
flanges or flange-like portions from a steel bloom of rectangular cross 
section in a rolling mill comprising a train of roughing shaping rolling 
stands for roughing, a universal rolling stand comprising a pair of 
opposed horizontal rolls and a pair of opposed vertical rolls, and a train 
of finishing shaping rolling stands for finishing, which method comprises 
rolling the bloom in the train of roughing shaping rolling stands for 
roughing to a rough shape having a width greater than the shortest 
distance between the outer circumferences of the opposed vertical rolls in 
the universal rolling stand and having a reduced almost flat cross section 
including a portion to be shaped into flanges or flange-like portions in 
the final product, rolling the rough shape of flat cross section thus 
obtained in the universal rolling stand thereby causing the pair of 
vertical rolls and the pair of horizontal rolls to cooperatively subject 
the portions to be shaped into the flanges or flange-like portions to 
bending deformation, and finish rolling the rough shape produced for the 
bending deformation in finishing shaping rolling stands. 
Other objects of the present invention will be understood from the 
following descriptions.

DETAILED DESCRIPTION OF THE INVENTION 
Shaping rolling of ordinary steel sections has a long history and many 
shaping roll designs have been proposed and adopted in practice. Standard 
shaping roll designs can be found in large numbers in technical literature 
and reports. 
In the conventional methods as shown in FIGS. 1(a) and 1(b), the letter K 
designating a numbered pass represents a pass for shaping rolling by two 
horizontal rolls, and U designating a numbered pass represents universal 
rolling by two horizontal rolls and two vertical rolls. The numbers 
indicate the order of the passes with the final caliber roll pass being 
designated 1. The arrow indicates the sequence of the rolling steps and 
where two or more arrows traverse a pass, this indicates that reverse 
rolling is carried out to produce two or more passes through the shaping 
roll pass. 
One principle governing the design of shaping roll passes is that the width 
of the material entering the shaping rolling stand must generally be less 
than the width of the shaping rolls. That is to say, it is widely known 
that normal rolling of a material having a width larger than the width of 
the shaping roll is not generally possible since the material is either 
locally rolled by the side faces of the shaping rolls or a local metal 
flow is caused in the surface of the material being rolled by the side 
surfaces. 
This limitation on the width of the material being rolled is evident from 
FIG. 1(a) and (b) wherein it will be noted that the width of shaping rolls 
does not change substantially from passes K-11 to K-7. 
Nevertheless, as seen in FIG. 2, which shows one example of a series of 
shaping roll passes for rolling channel-shaped steel sections, it is 
possible to roll materials having a larger width than the width of the 
shaping rolls in the finishing passes (K-3 to K-1), since the flange 
portion of the material at this stage has already been subjected to 
bending deformation before the material enters the bite of the rolls in 
the rolling stand. Thus at the time the material is actually rolled, its 
width is substantially the same as the width of the shaping rolls. 
This phenomenon can be easily understood by considering a number of cross 
sections of the shaping rolls taken vertically in the advancing direction 
of the material at points between the inlet and outlet sides of the 
shaping rolls. FIGS. 3(a)-(e) are vertical cross sections taken at points 
(a)', (b)', (c)', (d)' and (e)' in FIG. 3A between the inlet of a 
finishing shaping roll pass for rolling a channel-shaped section and a 
point directly below the roll and also shows the relation between the 
shaping rolls and the material at these points. As can be noted from FIGS. 
3(a)-(e), when the angle of inclination of the side wall of the shaping 
rolls is large, the length l of the arm through which the bending moment 
is applied to the flange portion of the material by the shaping rolls 
increases in the direction from the point (e)' directly below the roll 
toward the inlet portion (a)'. Moreover, because the material being rolled 
is thin, the flange portion F can be easily bent. Thus, even a material 
having a width larger than the width of the shaping rolls can be 
satisfactorily rolled. 
Furthermore, as the material passes between the rolls of the rolling stand 
in the normal rolling operation, the portions thereof which are 
approaching but have not yet entered the maximum force of the shaping 
rolls are subjected to a force acting to reduce the width of the material 
so that a considerable reduction in width is effected at thin portions and 
portions of low cross sectional rigidity. The deformations occurring 
during such a roll pass can be regarded as one kind of roll forming. 
On the other hand, in the initial stages of rolling a steel sheet pile 
having a shape corresponding to the shaping roll pass K-1 shown in FIG. 1, 
the angle of inclination of the side wall is small and the material is 
thick and has a high cross sectional rigidity. As a consequence, it is 
difficult to effect bending deformation and, for this reason, the width of 
the material to be rolled must be slightly smaller than the width of the 
shaping rolls. 
The universal rolling method will now be described in comparison with the 
shaping rolling method. 
FIG. 4 is a plan view schematically showing the roll arrangement of a 
universal rolling stand for use in the universal rolling method. Because 
the axes of rotation of the pair of vertical rolls 4 and 4' perpendicular 
to the axis of the horizontal roll 3, the distance L' between the rolls 4 
and 4' at a point spaced toward the inlet side from the maximum space 
between these rolls is larger than the distance L between the vertical 
rolls 4 and 4' at the bite, i.e. along a line passing along the bottom of 
the horizontal roll 3 and the shortest distance between the rolls 4 and 
4'. This means that even a material having a width considerably larger 
than the width of the horizontal roll can easily be introduced between the 
rolls of the universal rolling stand and rolled. 
This geometrical relationship between the rolls in a universal stand is, of 
course, impossible to achieve in a two-roll rolling stand. 
FIGS. 5(z) and 5(b) schematically respectively show the angle of 
inclination .theta. of the flange portion F in the shaping rolling method 
and the universal rolling method. Because it is generally advantageous to 
effect bending deformation within a range wherein the direction of the 
rolling reduction coincides with the direction of the bending, the 
universal rolling method shown in FIG. 5(b) is more advantageous than the 
shaping rolling method shown in FIG. 5(a) in the rolling of steel sections 
having a relatively large flange angle .theta., such as steel sheet piles. 
The present invention has been made taking into consideration the 
advantages of the universal rolling method. 
The present invention is based on the technical idea of making the width of 
the material entering the universal rolling stand considerably larger than 
the distance between the opposing outer circumferential surfaces of the 
vertical rolls in the universal rolling stand and subjecting flanges or 
flange-like portions of the material to deformation by the bending action 
of the pair of vertical rolls in cooperation with the horizontal rolls. 
According to the present invention, the shaping rolling step prior to the 
universal rolling steps can be greatly simplified. 
The present invention will now be described in more detail. 
In FIGS. 6(a) and (b), two sections 8 and 8' obtained by somewhat different 
rolling processes are schematically compared. These sections are obtained 
by rolling blooms 5 and 5' of rectangular cross section by using shaping 
rolls of different flatness formed respectively by a pair of horizontal 
rolls 6 and 7 and another pair of horizontal rolls 6', 7', with the same 
web width W, web thickness tW and flange thickness tF, but with different 
heights h and h' of the upper rolls 6 and 6' and different angles of 
inclination .theta. and .theta.' of the portions f and f' corresponding to 
the flanges. Differences in the characteristics of the rolled material 
deformed by shaping rolls of different flatness have been described in 
many technical reports and, in short, it can be said that the elongation 
ratio (ratio of the height H of rectangular cross section of the bloom to 
the web thickness tW) of the web portion of the section being rolled is 
larger as the height of the shaping portion of the shaping roll and the 
angle of inclination .theta. of the portion of the rolled shaped 
corresponding to the flange because larger. Thus, in the section 8 shown 
in FIG. 6(a), since both h and .theta. are larger than h' and .theta.' in 
FIG. 6(b), the metal of the flange portion of the material being rolled 
tends to be drawn into the web portion, thus reducing the amount of 
material in the flange portion. As a result, the section 8 has the contour 
shown by the hatched portion in FIG. 6(a). This means that, if the rolled 
shaped formed by the pair of rolls is made flatter as in the case of rolls 
6' and 7' in FIG. 6(b), it becomes easier to produce steel sections of the 
desired contour and dimensions as shown by 8'. Thus, by flattening the 
shape formed by the shaping rolls, it becomes possible to reduce the 
required shapes to reach the finished shape and also to use a starting 
material of flatter and smaller rectangular cross section. 
One example of the present invention will be described in comparison with 
the conventional universal method shown in FIG. 1(b). 
FIG. 7(A) is a flow sheet showing an example of the present invention 
applied to the rolling of steel sheet piles having a contour corresponding 
to the shaping rolls of pass K-1. FIG. 7 (B) is an enlarged view of the 
profiles of the shaping rolls 11, 12, 14 and 15 of the shaping roll passes 
K-7 and K-6 in the shaping rolling step and the universal rolls of pass 
U-5 in the subsequent universal rolling step in the flow sheet of FIG. 
7(A). 
The present example illustrates the present invention as applied to the 
rolling of a steel sheet pile having a contour corresponding to the 
shaping rolls of pass K-1 in FIG. 1(b) and is described in respect of the 
shape in the universal pass and the shaping rolls in the preceding passes 
for shaping rolling. 
The starting bloom used in the conventional universal method is 180 mm high 
and 480 mm wide in cross section. In the present invention, a bloom having 
a cross section 110 mm in height and 510 mm in width is used. The 
following rolling pass schedules are used. 
______________________________________ 
Conventional Method 
Present Invention 
Shaping Number of Shaping Number of 
Roll Pass 
Passes Roll Pass Passes 
______________________________________ 
K-12 2 
K-11 2 
K-10 2 
K-9 1 
K-8 1 
K-7 1 K-7 3 
K-6 1 K-6 2 
______________________________________ 
The average elongations prior to the universal pass are as follows: 
______________________________________ 
Cross Sectional 
Cross Sectional 
Area of Start- Area before Number Average 
ing Material Universal Pass 
of Elonga- 
mm.sup.2 mm.sup.2 Passes tion 
______________________________________ 
Conven- 
tional 
Method 86,400 17,454 10 1.17 
Present 
Invention 
56,100 17,454 5 1.27 
______________________________________ 
The state of contact of the material being rolled with the pair of 
horizontal rolls and the pair of vertical rolls and the stages of 
deformation of the material in the universal pass between the inlet side 
and a position directly below the horizontal roll will now be described 
with reference to FIGS. 8(a)-8(d) in connection with the rolling of a 
steel sheet pile. 
FIGS. 8(a) (d) show slightly cut away vertical cross sections taken at the 
points (a)', (b)', (c)' and (d)' shown in FIG. 8(A) on the inlet side of 
the universal pass U-5 shown in FIGS. 7(A) and (B). (The numeral 17 
represents the upper horizontal roll of the universal rolling stand and 
the numeral 18 represents the lower horizontal roll.) The deformation of 
the material into the rolled section 16 as well as the contact of the 
material 13 with the upper and lower horizontal rolls 17 and 18, and the 
vertical rolls 19 and 19' can be understood from these figures. Thus, in 
FIG. 8(a) the material 13 begins to contact the upper and lower horizontal 
rolls and the vertical rolls 19 and 19'. In FIG. 8(b), the bending 
deformation of the material 13 proceeds and the portions corresponding to 
the flanges of the material are particularly subjected to the bending 
force exerted by the vertical rolls 19 and 19' in cooperation with the 
upper and lower horizontal rolls 17 and 18. In FIG. 8(c), the bending of 
the material 13 is completed and the material closely fits the shape 
defined by the rolls. In FIG. 8(d), the material has been rolled into the 
final rolled section 16 of a predetermined thickness corresponding to that 
of the final pass in the universal pass. 
According to the present invention, the starting material 9 of rectangular 
cross section and the shapes of the two roll-shaping roll passes K-7 and 
K-6 formed by the rolls preceding the universal roll-pass U-5 can be made 
substantially flatter than those used in the conventional shaping rolling 
method. Moreover, only two shaping roll passes are required for the 
shaping rolling steps prior to the universal rolling step in the present 
invention. This is four shaping roll passes fewer than the six required 
for shaping rolling prior to the universal rolling step in the 
conventional method. 
The advantages of the present invention will be described using numerical 
data. 
In the universal rolling method as shown in FIG. 1(b), the widths of the 
central portions of the materials in the shaping roll pass K-6 and the 
universal pass U-5 are compared. The reduction by the vertical rolls in 
the first pass at U-5 is 36 mm and the width of the shaping rolls to pass 
K-6, namely the width of the material, increases proportionally. On the 
other hand, in the example of the present invention as shown in FIGS. 7(A) 
and (B), it is possible to increase the width of the shaping rolls in pass 
K-6 by 120 mm as compared the width of the shaping rolls in pass K-6 shown 
in FIG. 1(b). Further, the cross sectional area of the starting material 
in FIG. 1(b) is 86,400 mm.sup.2 while the cross sectional area of the 
material 9 in the example shown in FIGS. 7(A) and (B) is 56,100 mm.sup.2, 
which is about the same as the cross sectional area of 54,150 mm.sup.2 of 
the starting beam blank used in the caliber rolling method shown in FIG. 
1(a). Therefore, according to the present invention, the elongation of the 
material due to rolling is not excessive, and nearly the same product as 
obtained in the conventional shaping rolling method can be obtained 
without creating problems such as the lowering of the efficiency of the 
heating furnace and lowering of the production yield. 
The only problem that can be envisioned here is the possibility that, since 
the vertical rolls 19 and 19' of the universal rolling stand are not 
driven, the material 13 might not be normally bitten when it first 
contacts the vertical rolls 19 and 19'. However, in the actual rolling 
operation, as shown by the hatched portion in FIG. 9, the material being 
rolled has a tongue-like portion 20 formed during the shaping rolling 
prior to the universal pass and this portion contacts the horizontal rolls 
17 and 18 before it contacts the vertical rolls 19 and 19' so that there 
is no problem in the gripping of the material, a fact confirmed by actual 
rolling operations. Even if the tongue-like portion is not formed, the 
material 13 is bitten by the horizontal rolls 17 and 18 before it is 
bitten by the vertical rolls 19 and 19', if, for example, the material 13 
is maintained as flat as possible in the shaping roll pass (K-6) prior to 
the universal roll-pass (U-5) and is supplied to the horizontal rolls 17 
and 18 having a wavy web groove as shown by U-5 in FIG. 7(A). 
On the other hand, when the material 13 is maintained in its wavy form in 
the shaping roll pass K-6 shown in FIG. 7(A) and the wave height in the 
pass shape formed by the pair of horizontal rolls 17 and 18 in the 
universal pass shown in FIG. 7(A) is made higher than that in shaping roll 
pass K-6, the horizontal rolls bite the material 13 earlier than the 
vertical rolls 19 and 19'. Normally, the tongue-like portion 20 is almost 
always formed on the material 21 as shown in FIG. 9 so that satisfactory 
biting is assured thereby. 
With the above rolling procedures, the following advantages are obtained in 
addition to the advantages of the conventional universal rolling method 
described earlier. 
(1) By adoption of the conventional universal rolling method for steel 
sheet piles in the manner according to the present invention, the shapes 
of the shaping rolls used in the rough shaping step can be markedly 
simplified, and thus the number of shaping roll passes required is 
considerably reduced. 
(2) Reduction of the required number of shaping roll passes makes it 
possible to lay out new mills more compactly and in existing mills to 
reduce the number of rolls kept in stock. 
(3) The use of flat starting materials of rectangular cross section permits 
use of a shallower rolled shape than in conventional shaping rolling or 
universal rolling so that the difference in the circumferential speed of 
the roll at various portions of the rolled shape profile is reduced with a 
corresponding reduction in roll wear and lowering of unit roll cost. 
(4) Mill layout can be made compact because a bloom of rectangular cross 
section as small as the beam blank used in the conventional shaping 
rolling method can be used. 
(5) Because of the shallow rolled shape mentioned in (3) above, the rolling 
condition is similar to that of steel plate so that it is possible to 
increase the reduction rate per pass over that in the conventional method 
and to reduce the number of passes, thus improving rolling efficiency. 
The foregoing descriptions of embodiments of the present invention have 
been made in connection with the rolling of steel sheet piles but steel 
sections include various forms and sizes of rolled materials and the 
present invention should not be limited to the specific sections described 
above. The present invention can be applied to rolling of all forms of 
sections and such rolling is within the scope of the present invention 
insofar as a material having a large width is used as the starting 
material and bending deformation of the flange portion of the material 
being rolled is effected by vertical rolls. 
As described hereinbefore, in the present invention the width of the 
material to be rolled in the universal rolling step is made larger than 
the width of the pass formed by the pair of horizontal rolls of the 
universal rolling stand and the flanges or flange-like portions of the 
material being rolled are subjected to bending deformation by the vertical 
rolls of the universal stand, whereby it is possible to use a flat bloom 
of rectangular cross section in place of a roughly shaped beam blank and 
thus it is possible to employ flat roughing passes in the rough rolling 
step as compared with the conventional roughing passes; so that the 
breakdown step and the rough shaping by shaping rolling prior to universal 
rolling are markedly simplified, namely the number of shaping rolls 
required and the number of rolls required to be kept in stock are reduced. 
The unit roll cost is lowered because of less wear on the rolls, the 
heating furnace efficiency is increased and the mill layout is made 
compact. In this way, the present invention provides various advantages 
for rolling of steel sections.