Resumo:
The innovative methodology developed by the author allows the elaboration of an Angle Roll Pass Design based on the practical observations of the rolling process and applying mathematical criteria supported by Advanced Excel tools (Achieve goal, Procv-Proch, Macros) and AutoCad.
The development of the calculation had as initial basis the survey of the spread factors for angles previously studied by using Ekelund that is an empirical formula. The previously shown, the factors presents wide variation depending on the rolling conditions, the geometry of the grooves, the degree of free spread in the groove and the set-up of the guiding system among others.
There are enormous dimensional varieties of angles of the covered products, with linear mass from 0.6 up to 60 kg / m. Depending on the angle dimensions and technical characteristics of the rolling mill, angles they could be rolled from two to eleven passes.
There are at least four types of roll pass designs (currently used):
• Butterfly with one straight leg
• Butterfly with two straight legs
• Butterfly with Intermediate Edger pass
• Butterfly with opened pass
• Finally Special roll designs.
For the beginning of the project, it is necessary to define the initial draft, the number of passes and the reduction in each pass, the roll design method to be used, the spread factors, the finishing speed and the initial temperature.
As explained initially, these calculations are performed through Excel and for all passes are inputted the entering date in the spreadsheets. The whole calculation by the Ekelund formula is carried out as flat passes and at the end, these flat passes are transformed into shaped passes.
The height reduction of the passes are scheduled out and simultaneously, three heat transmissions types are calculated: (1) Heat loss by conduction from the bar to the rolls, (2) Heat gain by the deformation work and (3) Heat loss by radiance between exit time of the stand and the entering in the next pass. The temperature loss from contact with the cooling water is not taken in consideration once it is too low. The sum of these losses and gain generate the input temperature in the next pass.
Then each item is calculated for all the passes: Bite Angle, Spread, Section Reduction, Separating Force, Torque, Power, Temperature and others.
At the end of the calculation, it is checked if the desired size of the angle leg has been reached and otherwise it is necessary to adjust the initial stock or the spread factors. If this dimension is OK, we check the stand and if it is necessary, we adjust the initial draft, the reductions or the amount of passes.
The last step is to transform the flat passes into shaped passes. For all the components of the grooves are parameterized according to the number of passes and the type of roll design chosen. These parameters form the skeleton of the pass and the thickness of it is calculated so that this pass has the same section of the rectangular flat pass generated in the calculations. With these parameters, the grooves are drawn in AutoCad and the final dimensions are checked with the calculated values.
THE METHODOLOGY CAN BE USED IN THE OPPOSITE WAY: FROM AN EXISTING PASS DESIGN IT IS POSSIBLE TO CALCULATE ALL THE PARAMETERS OF THE STANDS AND PASSES AND CHECK IF ANY ITEM IS OUT OF ORDER AND CORRECT IT.
THIS METHODOLOGY WAS ALREADY USED FOR THE DEVELOPMENT OF NEW PROJECT AND ALSO TO EXISTING ONES, WITH COMPARISON OF THE RESULTS AND HAS SHOWN TO BE RELIABLe.
