CS238687B1 - Thorn bar of rolling mill stands - Google Patents

Abstract

The mandrel rod consists of a mandrel extension of the clamping part of the end with coaxially placed and welded connecting tubes. At the welded ends of the individual parts are located guide extensions, the outer diameter of which corresponds to the inner diameter of the connecting tubes.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to mandrel rods for tube rolling stands, and more particularly to cold pillar rolling stands.

Pilot bars of pilger mill stands for cold rolling of tubes serve to secure the required position of the rolling mandrel during the rolling process. For straight-through mandrels, which are characterized by butt welding of individual parts, their straightness after welding is not guaranteed. During rolling with curved welded mandrel rods, the rod - workpiece is in contact on a very dull surface and the inner surface of the workpiece is damaged before rolling. The resulting scratches and shavings are rolled with dyeing and thus create inadmissible defects on the inner surface of the rolled tubes, unsuitable for use in, for example, nuclear power.

This disadvantage of the currently used mandrel bars is largely overcome by the mandrel of the rolling mill for rolling tubes, in particular of cold, formed by individual coaxially positioned parts, and by the adapter of the clamping part connected to each other by connecting pipes according to the invention. extensions, clamping parts and endings are provided with guide extensions whose outer diameter corresponds to the inner diameter of the connecting tubes.

The advantage of the inventive rod is that it is straight after welding the parts, it does not damage the inner surface of the rolled tubes and thus reduces the incidence of impermissible defects on the rolled tubes. The smoothness of the inner surface of the tubes ensures the reliability of the equipment, especially the nuclear power plant.

An exemplary embodiment of a mandrel bar according to the invention is shown schematically in the accompanying drawing, in which Figures 1 to 5 show the individual parts of the bar.

The mandrel rod of the pilger mill stands consists of the structural parts - mandrel extension 1, clamping part 2, end piece 2 and connecting tubes 4. The faces of the extension 1, clamping part 2, end pieces 2 and tube 4 are adapted to make a weld joint. The achievement of the corresponding diameter průměru was only to be realized in the region of the joint, in which case the inside diameter was turned. Great attention has been paid to the centering of the outer diameter and the inner diameter D of the pipe connecting pipes 4 on the lathe. The extension 2, the clamping part 2.1, the end 2 were provided at the joint end with a guide extension 2 whose outer diameter g corresponds to the inner diameter g of the connecting tube 4. Before welding, the ends of the connecting tubes 4 were heated.

In another case, the assembly of the mandrel rod from the adapter 1, the clamping portion 2, the end 2 of the tube 4 has been accomplished by molding or subcooling. Welding operations and grinding of the rod along its entire length were included as finishing.

The mandrel rod according to the invention is suitable for rolling tubes, in particular on cold rolling mill piles, where high demands are placed on the smooth surface of the tubes, especially the inner surface of tubes intended for nuclear power.

Claims (1)

Rolling mill mandrel rod for tube rolling; in particular made of a single piece of coaxially positioned parts, namely an extension piece, a clamping part and an end piece connected to one another by connecting pipes, characterized in that guide end pieces (3) are provided at the connecting ends of the end piece (2) and the end piece (3) 5) whose outer diameter (d) corresponds to the inner diameter (D) of the connecting tubes (4).