Rolling of Beam
Fig. 10.1 Beam Profile.
Beams are the most typical flanged sections, if judged by the methods of rolling and roll pass designing. The rolling of beam design comprise two distinct stages of deformation;
- (a) Obtaining the initial rough beam profile.
- (b) Rolling the rough profile in to beam of the specified size.
The first stage is characterized by a sharp transformation fr om a rectangular cross section to rough beam form. The second stage consists in a gradual transformation from rough to the finished section.
Methods of Beam Design
The First Method
The first method Fig. 10.2 (i) is generally used for rolling of smaller beam sizes from 100 nun to 300 nun. It comprises only close beam passes. Non uniform deformation is given in the first forming passes i.e., in a web cutting pass with V cutting element. The input material is generally rectangular in shape. In subsequent passes, under the influence of more or less uniform deformation of the separate elements of the profile, the strip gr adually gets the size of the final profile. The open and close elements of flanges are changed alternatively between top and bottom rolls thus equalizing tensions. To ease the delivery of the strips from the rolls and for easy redressing, the wall of the groove is given a taper of 2-3% in the dead part and sometimes 5-6% is also recommended for the live side of the beam.
Fig. 10.2 Different Method of Beam Design
Widening or spread of profile is considerable in the roughing passes and it gradually decreases towards the end of the rolling, hi the last pass, it is generally kept to 0.01 of the width of the whole profile.
Medium and heavy beams, sizes from 300 mm to 700 nun are rolled by sequence shown in Fig. 10.2 (if), The input i.e., rectangular billet is first rolled in open beam passes of blooming mill and in rolls of two high reversing roughing stand of structural mill. Several passes are performed in each groove by changing the gap between rolls. Overfills, on sides are eliminated by turning the bar 90°and passing it through in barrel pass. Deformation in open pass will continue till web thickness is reduced to a value from three to five times the final thickness. Further rolling will be performed in close beam passes.
Third Method Fig. 10.2 (ш) is used in rolling of wide flanged beam, including parallel flange beam. The same procedure and rolling schedule explained earlier, is used here also to get the rough section. The difference is that the rough beam section is further rolled in universal stands.
Fig. 10 .3 Universal Beam Section.
Advantages of Universal Rolling;
- • Ability to produce tailor sizes to suit application:
- • Web and flange thicknesses can be adjusted independently.
- • Capacity to increase/decrease flange length.
- • Reduced roll costs.
- • Reduced setup times and costs.
- • Quicker section change
- • Better surface quality.
- • Better mechanical properties
Fourth method Fig. 10.2 (tv), Diagonal method of rolling, uses close beam passes, inclined to the horizontal (diagonal) has found wide application in beam rolling due to following reasons:
- • Due to the inclination of the open flange, the reduction in profile can be given high and it will lead to decrease in total number of passing.
- • Off requires for the redressing of roll become reduced and due to this, life of roll get increased.
- • It is also possible to reduce the profile without spread and even to give some reduction along width.
- • With shallow cut in rolls, roll become more stronger and chances of roll breakage will be less and it also facilitates more reduction over work piece.
Disadvantages of using diagonal method of rolling are as follows:
- • It makes the necessity of using both rolls with increased initial diameter, because close flanges are simultaneously in the top and bottom part of the groove.
- • Appearance of the considerable axial forces on the rolls due to high inclination of roll.
Diagonal method is popular in those designs of wider flange beam, where height of flange does not permit to use the straight beam method. The coefficient of reduction in the diagonal rolling will be always greater than the close flange beam rolling design.
Conventional Rail & Structural Mill
Universal Rail and Structural Mill
Fig. 10.5 Layout of Universal Rail and Structural Mill.
Continuous Combined Bar and Structural Mill
Fig. 10.6 Continuous combined Bar and Structural Mill.