Design of the working tool of the screw rolling roughing mill for obtaining the wavy profile of the side surface of tube stock on the basis of computer simulation

Since the reserves of the direction of increasing partial pressing and reducing cycles are substantially exhausted, an example of a technical solution for improving the screw piercing based on minimizing partial pres-sing with the increase of cycles of partial pressing, i.e. piercing of profiling billets with a wavy profile is given. The advantages of this technology consist in the reduction of the deformation level in the axial zone of the billet and the decrease of the probability of occurrence of axial destruction. The most effective way of obtaining profiling billets is application of the profile on a three-roll roughing mill of the pipe-rolling plant. To obtain a wavy profile on the surface of the billet, a special roll pass design of three-roll roughing mill is required. Three rolls of the proposed calibration form a caliber, consisting of the input section which provides a secure grip on the billet, the work section with profiling ridges which provides application of the wave profile and the output section. The profiling process can proceed only in case of the equality of the length of the profile period and the billet’s step delivery at the exit of the roughing mill. It is also necessary to consider the ratio of the length profile period to the ridge height, since metal laps can be formed on the surface of the pipe liner after piercing with a low value of the ratio, and at high value of the ratio efficiency of profiling drastically decreases. The ridges on the work section of the rolls are shifted in the rolling direction by the value which is a multiple to the number of rolls, that is for a three-roll mill the shift is 1/3 of the period length of the profile. According to the results of the roll pass design, computer simulation of profiling billets on the roughing mill Q-FORM with positive results was conducted.