DE2351316A1 - Cold drawing thin walled weldless tubes - produces accurately concentric bore involves internal mandrel and external die - Google Patents

Abstract

The tube is firstly not formed from an ingot. The outside surface at one extremity of the tube is turned exactly concentric with the bore. The tube is placed over a fixed mandrel, and an external guide or die fitted with a shaving knife is placed over the tube and is held concentric and axially level with the mandrel. The tube is then drawn between the mandrel and the die and shaving knife assembly. The dimensions and concentricity of the resulting tube are accurately predictable, as the knife cuts the exterior of the tube to leave a surface which is accurately concentric with the interior surface.

Description

225131

Cable and metal works

Gutehoffnungshütte Aktiengesellschaft 1-1282

Oct 10, 1973

Process for the production of seamless metallic pipes

The invention relates to a method for producing seamless metallic pipes, in which a pipe is first pressed or hot-rolled from a block, which is produced by cold rolling and / or pulling is reduced in its cross-section.

Seamless metallic tubes are for the most part in the way manufactured by first pressing or rolling a block over a mandrel and optionally the tube thus obtained in a known manner brings to the desired cross-section.

It has been shown that the pipes produced in this way have an eccentrically mounted bore. The eccentricities occur particularly in the extruded tube and can no longer be substantially eliminated by the subsequent cold rolling or drawing processes. The pipe presses commonly used today work in such a way that a heated press block is first inserted into the transducer and punched by means of the dome. The perforated press block is then pressed over the mandrel through a die. The thorn "swims" in the process. The degree of displacement of the mandrel to the die is not constant, but is on average approx. 10 %. The reasons for this relocation are essentially to be found in the type of press or due to the process. In the case of hot-rolled tubes, the degree of displacement is approx. 5 % »

These eccentricities cannot be substantially eliminated in cold rolling and / or drawing.

509 8 17/0105 ORIGINAL INSPECTED

The invention is based on the object of specifying a method with which it is possible to manufacture seamless metallic tubes with considerably more precise dimensions. This task is achieved in a method of the type mentioned in that, according to the invention, the pressed or hot-rolled The pipe is turned off at one end on the jacket surface in such a way that the hole is centered on the jacket surface, that the tube is arranged from the twisted end over a fixed mandrel and a concentric to the mandrel Guide for the jacket surface is drawn and at least part of the jacket surface of the pipe is peeled continuously. With the help of the method according to the invention, it is now possible to produce pipes that have an exactly centrally mounted Have bore. The peeled material can be saved and melted down again. As particularly beneficial it has been found to widen the bore of the pipe slightly during the peeling process. That way is ensures that oval shaped or indented pipes can be peeled exactly.

The invention is explained in more detail using an example.

First of all, the extruded or hot-rolled tube, which has an eccentrically mounted bore, is inserted into a tube suitable device turned off at its end in such a way that the bore of the tube is concentric to the outer circumferential surface of the pipe is located. A mandrel bar is then inserted into the pipe or the pipe is inserted over a mandrel bar and a mandrel attached to the mandrel bar. Then the turned end of the tube is placed in a guide and pulled over the mandrel. During the drawing process, the mandrel and guide are always mounted concentrically to one another.

^ SP _{£ QT5D} 5 0 9 8 17/0105

It is essential that the mandrel counter to the direction of pull seen protruding from the guide and the peeling is carried out in the area of the dome, since only the mandrel has the material in pushes the cutting area of the peeling device.

With the help of the method according to the invention, it has also been possible to produce curved or oval-shaped tubes that have an eccentrically mounted Have bore to be peeled so that the bore is centered on the outer surface of the pipe. The essential one The advantage of the method according to the invention is to be seen in that the tubes now have a smaller one with the same outer diameter Weight, more precise dimensions and the peeled materi al used again in the melting process can be.

ORIGINAL! NSPECTED

5098 17/0 105

Claims (2)

Kabel- und Metallwerke Gutehoffnungshütte Aktiengesellschaft i-1282 Oct. 10, 1973 Patent claims 1. A process for the production of seamless metallic pipes, in which a pipe is first pressed from a block or hot-rolled by cold rolling and / or drawing is reduced in its cross-section, characterized in that the pressed or hot-rolled tube one end is turned off on the lateral surface in such a way that the bore is centered on the lateral surface that the tube from the twisted end over a fixed mandrel and one arranged concentrically to the mandrel Guide for the lateral surface drawn and thereby continuously at least part of the lateral surface of the Pipe is peeled. 2. The method according to claim 1, characterized in that the bore of the pipe is slightly during the peeling process is widened. 509817/0105