DE1135401B - Process for the production of seamless steel tubes - Google Patents

Description

Method for the manufacture of seamless steel pipes The manufacture Seamless steel tubes can be done in a known manner by doing the following Performing procedural steps one after the other: 1. Casting the blocks, 2. Reshaping the Blocks, e.g. B. Rolling out the blocks into billets, 3. Subdividing the billets into blanks from a weight corresponding to the pipe to be produced, 4. reshaping of the blanks to thick-walled hollow bodies by punching, 5. further forming, z. B. Stretch out the perforated blanks or z. B. oblique rolling to form blanks, 6. stretching the Pellets on a ready-made pipe stretching system, e.g. B. Pushing the rounds on the push bench, or rolling on the pilger mill or boot mill into tubes.

There are now methods known in which these work sequences, if necessary with the interposition of heating furnaces to warm up the rolling stock best processing temperature, utilizing the manufacturing heat up to finished pipe to be carried out.

In general, however, these operations are carried out after the casting of the Steel into blocks or, after the blocks have been rolled out, into billets made of different materials Reasons, including z. B. because the steel and / or rolling mill is separate from the pipe mill is interrupted. The further processing of the blocks or rolled billets takes place after reheating the same in successive steps to the finished pipe.

In order to process unsuitable blanks in the production process, e.g. B. as a result of cracks, malfunctions and excessive rejects of finished pipes To avoid surface or material defects as a result of surface or material defects, it is now common practice to the cooled blocks or billets before further processing or reheating from the surface for cracks, slag inclusions and other externally visible Surface defects by visual inspection or known methods, e.g. B. Magnetoflux, or, if the core of the blank is included in the examination, by ultrasound or to examine x-ray procedures. However, it is known that the investigations on full block or billet cross-sections no guarantee for the behavior of the blank during further processing, especially when punching and stretching. By Investigations on the full cross-section, the reject will be less than if at all no under-booking would occur. However, any possible errors that the due to poor behavior of the material during further processing, e.g. B. cracks, and by dimensional deviations, e.g. B. unequal pipe and bottom wall thicknesses, especially arise when punching blanks that are not heated uniformly, not recorded. All of the material side and the processing resulting errors on the blanks with the arrangement of the ready-made pipe stretching system directly behind the Luppenfortigung Pipe or bottom tears in the hole or lobe stretching system to a standstill entire pipe production plant with the downstream, which are used for further processing extensive systems.

In addition, the finished pipes rejected as defective are located at the bottom numerous pipes that were already present or occurred during punching and stretching Errors are due.

In order to avoid that the finished pipe stretching system either through Pipe or floor cracks shut down or due to material, surface or other Flawed blanks from which no perfect finished pipes can be produced, is charged, based on a known method for producing seamless pipes by casting blocks, forming, e.g. B. Rolling out the blocks to billets, dividing the billets into blanks from a pipe to be produced corresponding weight, forming the blanks into thick-walled hollow bodies Punching, further forming, e.g. B. skew rolling, from hollow bodies to bulges and stretching, z. B. Pushing, the blows to pipes, the workflow for pushing one Testing of the workpiece is interrupted when it is cold and after it has been withdrawn unusable or continued after the usable workpieces have been reheated, proposed according to the invention, the material testing on the blanks, d. H. before the Stretching out the lobes to make pipes.

Proceeding in this way has the advantage that all existing in the blocks Defects or poor material properties in the workpiece as a result of the large at Punching and stretching occurring stresses increase or only become after this sequence of work.

The inspection of the cooled blanks is carried out by visual inspection and lor by means of known crack or material defect testing devices both from the Surface as well as from the wall of the hole, so that, there are also the material cross-sections are lower, a more precise and flawless examination is possible than with a massive blank. In addition, the wall and floor thicknesses of the hollow blocks can be measured so that bulbs with impermissible dimensional deviations are eliminated or but also the causes for the deviations can be eliminated.

There is a risk that bulbs of unequal wall thickness will be produced when punching especially in the process in which the processing of the refrigerated Billet or blank runs out and there is a risk that the massive blank is not heated evenly over the cross-section when heated, so that the material flows unevenly in the hole. This uneven flow of the material is often also the cause of cracks. As in this case with the previous If the procedure is no longer checked, blanks with undersized dimensions are eliminated not possible.

The reheating of the long hole pieces before the last process step can be more advantageous and expedient inductive in a device that is immediate is arranged in front of the finish pipe stretching system, happen. In the case of a system that working according to this procedure, it is possible to change the work cycle of the forming process up to the examination to be controlled in such a way that even in the event of failure of faulty blanks the downstream finished pipe stretching system regardless of the forming up to Luppe operated continuously with few disruptions and a high overall degree of utilization can be.

Claim 2 is a real sub-claim with no independent meaning.

Claims (2)

PATENT CLAIM: 1. Method of manufacturing seamless steel tubes by casting blocks, reshaping, e.g. B. Rolling out the blocks into billets, subdivisions the billet in blanks of a weight corresponding to the pipe to be produced, Forming the blanks into thick-walled hollow bodies by punching, further forming, z. B. inclined rolling, the hollow body to hollow and stretching, z. B. Push, the Rods to pipes, the workflow for inserting a test of the workpiece interrupted when cold and unusable after leaving or after Reheating of the usable workpieces is continued, characterized in that that the workpiece test on the blanks, d. H. before stretching out the lobes Pipes. 2. A method for producing seamless steel pipes according to claim 1, characterized in that the heating of the long hole pieces before the last Process step is done inductively, in a device those immediately before the plant to carry out the last deformation process is arranged. Considered publications: German Patent Specifications No. 916 823, 843 834; German patent applications St 3029 I b / 7 b (published on December 31, 1952); E 4126 VI / l.8 c (published on June 11, 1952).