AU8332582A

AU8332582A - Method of effecting bending

Info

Publication number: AU8332582A
Application number: AU83325/82A
Authority: AU
Inventors: J Stromberg
Original assignee: Plannja AB
Current assignee: Plannja AB
Priority date: 1981-04-13
Filing date: 1982-04-13
Publication date: 1982-11-04

Description

Method of effecting bending

This invention relates to a method of effecting the bending of a preferably hot rolled strip.

It is previously known to manufacture steel sections by hot rolling a workpiece to its ready shape. The workpiece passes through a series of roll pairs, which in steps impart to the workpiece a shape which increasingly resembles the final one. An obvious disadvantage of this method is, that a new set of rolls must be installed when a new section is to be manufactured. The exchange of rolls requires much time and thereby reduces the production. In addition, large investments are required for the procurement of new roll sets. As for the aforesaid reasons the number of roll sets must be restricted, also the assortment is restricted. It is also previously known to cold form a strip to the desired section, for example by means of an edging press. An almost optional form of the section can be brought about hereby, but very great forces are required for forming at the material thicknesses occurring in this connection. The equipment required for cold forming, thus, is very expensive, which of course is disadvantageous from an economic aspect.

The present invention has the object to propose a method of the aforesaid kind, at which the described disadvantages have been eliminated. This is achieved by a method which has been given the characterizing features defined in the attached claims.

Embodiments of the invention are described in the following, with reference to the accompanying drawings, in which Fig. 1 shows a preferably hot rolled strip provided with a longitudinal groove, Fig. 2 shows the corner portion of an agular iron, which has been brought about by bending the strip according to Fig. 1 inward to the groove, Fig. 3 shows the corner portion of an angular iron,which has been brought about by bending the strip according to Fig. 1 away from the groove, Fig. 4 shows a preferably hot rolled strip provided with two longitudinal grooves and having sections with different material thickness, Figs. 5a-5j shows different types of sections, which have been manufactured by the method according to the invention, and Fig. 6 shows a preferably hot rolled strip, which is provided with grooves located directly in front of each other on both sides of the strip.

The section of a preferably hot rolled strip shown in Fig. 1 is provided on one side with a groove 2, which extends along the entire length of the strip 1. The depth of the groove 2 in relation to the thickness of the strip 1, of course, can be varied, but a depth of the groove 2 being about Ho % of the thickness of the strip

1 seems preferable. The invention, of course, is in no way restricted to these dimensional relations between groove depth and strip thickness.

The groove 2 has a width which preferably is of the magnitude three times the strip thickness in the groove. These dimensional relations, of course, can as well be varied without thereby leaving the idea of the invention. The groove 2 formed in the strip 1, of course, can be brought about in different ways. It seems suitable, however, that the strip 1 is provided with one or more grooves

2 in connection with the rolling, which preferably is carried out in hot state.

An advantageous method of bringing about the groove 2 is to thread rings with suitably formed sections on the rolls shaping the strip 1. The rings are thereafter fixed in a suitable way in desired position on the rolls. This can be carried out, for example, by means of rings filling out the intermediate spaces between the profiled rings, or in some other way .

It is immediately understood that with the technique described above it is possible both to form several grooves in a strip and to change the distance of the grooves relative to each other, i.e. the positions of the grooves on the strip.

It should be pointed out in this connection that by attaching one or several cutting members on the rolls it is possible to obtain several workpieces at one and the same rolling.

When the strip 1 has been provided with one or several grooves 2, these grooves act as bending notches, when the portions of the strip 1 which are located on both sides of a groove 2 are to be caused to form an angle with each other which is smaller than 180 .

In Fig. 2 the corner of an angular iron 3 is shown, at which the flanges form an angle of 90 with each other. As appears from Fig. 2, the bending of the flanges has been carried out to the groove 2, which in Fig. 2 remains as an internal recess 2 in the corner of the angular iron

3.

The angular iron 5 shown in Fig. 3 has been formed in that the flanges 6 have been bent away from the groove 2, which in Fig. 3 remains as some kind of external bevel 2" in the corner of the angular iron 5 .

The bending proper of the portions on both sides of a groove can be carried out by an edging press or by means of rolls.

At present it seems to be most advantageous to use an edging press as the grooves 2 imply, that the forces to be applied to the bending decrease drastically. Assuming, that the depth of the groove 2 is HO % of the thickness of the strip, only about one tenth of the bending force is required compared with the bending force required at a strip without grooves. This is due to two reasons. One is that the bending resistance of the strip decreases bythe arrangement of a groove, and the other is that the bending forces need not be applied so closely to the line, about which the bending is to take place, because the groove acts as a bnding notch. When the force can be applied farther away from the bending line, of course a higher moment is obtained.

It can, of course, also be imagined to carry out the bending of the portions on both sides of a groove 2 by means of roll pairs, the number of which depends on the form, to which the strip is to be bent.

In Fig. 4 a preferably hot rolled strip 7 is shown, which is provided with two grooves 8.

As appears from Fig. 4, the thickness of the strip 7 between the grooves 8 is smaller than outside the grooves 8. This variation in thickness of the strip 7 can be obtained in a relatively simple way, especially at hot rolling. It is thereby possible to obtain, for example, a U-section having different material thickness in the bottom and flanges. See below.

In Figs. 5a-5i different types of sections are shown which are manufactured of grooved, preferably hot rolled strips. In Fig. 5a an angular iron is shown with legs of equal length which form a right angle with each other. In Fig. 5b an angular iron is shown, the legs of which form an angle of about 60° with each other. Due to the fact that relatively small edging presses can be used for forming the sections, the angle between the legs of the section can be varied in a simple manner.

In Fig. 5c an angular iron is shown where the legs are not equally long and where the bending has been made inward to the groove. This variant is especially advantageous when it is desired to attach web reinforcing sheets. These sheets then need not be beveled at the corners, because a right-angled sheet corner can be received by the section according to Fig. 5c.

Pigs. 5d and 5e show Z-sections where the bending has been carted out to and, respectively, from the grooves, and where the grooves have been arranged on opposed sides of the strip. Fig. 5f shows a C-section, which as well can be provided with reinforcing sheets having right-angle corners. In Fig. 5g a U-section is shown which has different material thickness in the bottom and legs.

In Fig. 5h some kind of box section is shown where the portions form an angle with each other which is smaller than 90°. The free ends of the strip are joined, for example by welding.

Fig. 5 shows a box beam with rectangular cross-section, where one corner was formed, for example, by welding together the free ends of the strip. This box beam has different material thickness in walls adjacent to each other. In Fig. 5j a special section is shown, which is intended to illustrate that it is possible by applying the principle of the present invention to manufacture sections having different length of the flanges, walls or the like. Besides, the angle between these portions can be varied simply when using edging presses for the bending operation. In Fig. 6 is shown that it is, of course, also possible to imagines within the scope of the invention to provide a strip 9 with grooves 10a,10b located directly in front of each other on both sides of the strip 9. By forming grooves in a preferably hot rolled strip in the way described above, i.e. by attaching rings on the rolls, an absolutely straight groove is obtained, which in its turn implies that the bent edge will be absolutely straight.

In some of the accompanying Figures the lateral edges of the grooves have a certain inclination. This inclination, of course, can be varied, but the grooves must have a somewhat distinct definition in lateral direction. A further advantage with the method according to the present invention is that the holes and passages, with which the sections are to be provided, and the cross-cutting to desired lengths are carried out in flat state before the bending, which simplifies in a high degree the equipment necessary therefor.

Claims

1. A method of effecting the bending of a preferably hot rolled strip (1;7;9), c h a r a c t e r i z e d i n that bending notches are brought about in that longitudinal grooves (2 ;8 ; 10a, 10b) are formed in the strip (1;7;9) in connection with the rolling, and that bending thereafter is carried out in a suitable way, for example by edging pressing or by rolling whereby the material in the strip (1;7;9) directly in front of the grooves {2 ;8; 10a, 10b) is given curved shape.

2. A method as defined in claim 1, c h a r a c t e r ¬i z e d i n that the grooves (2;8;10a,10b) are brought about by rings, which are threaded on the rolls and fixed in lateral direction relative to the same.

3. A method as defined in claim 1 or 2, c h a r a c t e r i z e d i n that bending notches are brought about in that grooves (2;8) are applied to the strip (1;7) from one direction.

4. A method as defin-d in claim 3, c h a r a c t e r i z e d ά n that the grooves (2;8) are given a depth of the magnitude of 20-60% of the thickness of the strip (1;7).

5. A method as defined in claim 3 or 4, c h a r a c t e r i z e d i n that the grooves (2;8) are given a width of the magnitude of 1 to 4 times the thickness of the strip in the groove.

6. A method as defined in claim 1 or 2, c h a r a c t e r i z e d i n that bending notches are brought about in that grooves (10a,10b) located directly in front of each other are applied to the strip (9) on both sides of it.

7. A method as defined in any one or some of the preceding claims, c h a r a c t e r i z e d i n that the grooves (2;8;10a,10b) are given inclined edge portions.