DE10332221B4 - Method for minimizing thickened ends during rolling of rolled products - Google Patents

Abstract

method to minimize thickened ends when rolling tubular or flat metallic rolled products in a multiple rolling stand Stretch reducing mill, in which a temporal change in the torque of individual driven rolling stands carried out is characterized in that in addition to the torque change the end portions of the rolled products before entering a rolling stand in comparison to the middle rolling temperature in the passage targeted towards the respective faces of the rolled products increasingly on a contrast higher temperature level heated become.

Description

The The invention relates to a method for minimizing thickened ends when rolling out of tubular or flat metallic rolled products in a plurality of rolling mills Stretch-reducing mill according to the features in the preamble of claim 1.

By the EP 1 109 634 B1 Such a method of minimizing thickened ends when rolling tubes in a prior art stretch reducing mill, wherein the torque of individual driven stands is timed as the end sections of a rolled product pass through the stretch reducing mill. In this way, the end portions are rolled at greater than the stationary ratios of roll speeds. However, the extent of the additionally applicable rolling torques is limited both on the plant side and rolling product side. Thus, it is conceivable that at high rolling torques the static friction on at least one roller can break off. Also, damage to the surface of the rolled product due to exceeding the Grenzumformvermögens occur. Furthermore, it is conceivable that damage to the engines, the gearbox or other rolling mill equipment can occur. In addition, high demands are placed on the dynamics of the machines and systems with high wear of the rollers and the machines.

Furthermore, the scope of DE 37 01 154 C2 It has been proposed to apply cooling fluid to the driven rollers of a rolling mill during operation, wherein the friction between the rollers and the rolling product increasing additives are admixed to at least one rolling mill arranged upstream and the friction reducing additives are added to the cooling liquid at at least one rolling mill arranged downstream.

From the DE 40 39 741 A1 For example, a method of minimizing thickened portions in rolling tubular metal rolling products in a multi-stand stretch-reducing mill is known. It is proposed to influence these sections in a targeted manner by local heating before the rolled product enters a rolling stand.

The GB 479,383 A deals with the use of material-technical phenomena when rolling flat metal workpieces. It is disclosed, to minimize thickened ends, to cool a rolled product along its length, except for its end portions, prior to entry into a mill stand.

Of the Invention is - starting from the above-mentioned prior art - the object of the, the Minimization of thickened ends through the use of material technology phenomena to reach.

These The object is achieved with the features specified in claim 1.

The targeted warming the end portions of a tubular or flat metallic rolled product prior to entry into a rolling stand lowers the higher temperature level compared to the mean rolling temperature before the rolling process, the yield stress compared to the lying between the end portions of the length of the rolled product from. Due to lower flow stress values at the end sections These are less slippage compared to those contacting them Rollers have. This will increase the stretch of the rolled product increased in the end sections and lowered the material spread. This reduced material spread ultimately leads to minimize the thickened end portions of the rolled product.

The Size of too heated End sections can be determined by the lengths of the Thickened ends are detected in the uninfluenced state and then by means of the achieved extension to the length of the to be heated End sections recalculated become.

The Invention assumes that usually rolled in a temperature range of 750 ° C to 1200 ° C.

From Meaning is that the end sections towards the respective End faces of the rolled product are increasingly raised in temperature. You can do this in the longitudinal pass electric auxiliary heating devices, such as. electromagnetic coils are used. The increase of Temperature levels occur in the passage of the rolled product.

Important It is also in the invention that the temperature increase together with a temporal change the torque of individual driven rolling stands is performed.

In the context of the invention, it is also conceivable, when acted upon with coolant Rollers to carry out the temperature increase according to claim 2, together with an admixture of the friction between the rollers and the rolled product changing additives to the cooling liquid. Whether the friction between the rolls and the rolled products is increased or decreased depends on the position of the rolling stands in the stretch reducing mill. It is also possible for this measure, which is known per se, to take place together with a temporal change in the torque of individual driven rolling stands.

Claims (2)

A method of minimizing thickened ends in rolling tubular or flat metallic rolled products in a multi-stand stretch reducing mill wherein a temporal change in torque of individual driven rolling stands is performed, characterized in that in addition to the torque change, the end portions of the rolled products prior to entry into a rolling stand in comparison to the mean rolling temperature in the course targeted towards the respective end faces of the rolled products are increasingly heated to a contrast higher temperature level. The method of claim 1, wherein the rolls the rolling stands with coolant be acted upon, characterized in that the temperature increase together with an admixture of the friction between the rollers and the Rolling product changing additives to the coolant carried out becomes.