RU2198751C2 - Method for helical piercing of ingots of electroslag and vacuum refining from low-ductile boron- containing steels - Google Patents

Abstract

FIELD: rolled tube production, namely ingot piercing method, possibly manufacture of mean- and large-diameter tubes from ingots of low-ductile steels in tube rolling plant with pilger mills. SUBSTANCE: method comprises steps of heating ingots, piercing them with use of mandrel; deforming ingot after approaching it to nose portion of mandrel at drawing rolling rolls together before time moment of metal contact with mandrel; realizing piercing to size on mandrel at providing elongation value no more than 1.3. EFFECT: possibility for making sleeves of ingots of low-ductile boron-containing steels without flaws due to elimination of metal cracking at main deformation process on mandrel. 1 cl

Description

 The invention relates to pipe rolling production, and in particular to a method of flashing ingots, and can be used in the production of pipes of medium and large diameter from ESR and VDP low-plastic steel ingots in pipe rolling plants with pilgrim mills.

 A known method of rolling ingots in an oblique rolling mill is that a heated ingot is deformed in a deformation zone consisting of three successive zones: in the first zone, a solid or hollow body without a mandrel is rolled, and in the second, a hollow body with intense wall deformation is rolled on the mandrel and in the third zone, the run-in of the body without an internal rigid mandrel (see F.A. Danilov et al. "Hot rolling of pipes", Metallurgizdat, 1962, pp. 40-41).

 The disadvantage of this method is that when flashing low-plastic steels in the first zone, cracking of the inner part of the ingot occurs due to stresses that exceed the tensile strength. As metal passes through subsequent zones, cracks develop into through flaws on the liner.

 A known method of cross-screw firmware, including information and breeding rolls (AS 532410 "Method of cross-screw firmware").

 The disadvantage of this method is that when flashing hard-deformed and low-plastic steels with maximum roll reduction, maximum stresses arise. The stress state diagram does not change, i.e. there are no additional forces that would reduce stresses in the inner part of the ingot arising from the action of work rolls.

 The purpose of the invention is the elimination of the formation of cracks on sleeves when piercing ingots from low-plastic boron-containing steels.

 This goal is achieved by the fact that in the known method of cross-screw firmware, which consists in deformation of a heated ingot on the mandrel, the deformation of the ingot is performed after the ingot is brought to the nose of the mandrel by reducing the work rolls until the metal is on the mandrel, while the firmware must be sized the size on the mandrel, providing a hood no more than 1.3.

 The essence of the method lies in the fact that by bringing the ingot to the nose of the mandrel and gradually increasing the friction forces, due to the rolls being reduced to the moment when the metal is on the mandrel, minimal deformation is created for this steel grade. In this process, the firmware from the very beginning comes with backwater from the mandrel, i.e. the stress-strain state diagram changes, leading to a decrease in the internal stresses in the ingot, causing cracking.

 At the same time, the size-in-size firmware on the mandrel, providing an exhaust hood of no more than 1.30, creates a minimum load on the work rolls, and, accordingly, less stress, which eliminates the formation of cracks in the metal during the main deformation on the mandrel.

 Using the proposed method of cross-screw firmware will allow to obtain sleeves from ingots of ESR and VDP low-plastic boron-containing steels without defects.

 Comparative analysis with the prototype shows that the inventive method of cross-screw flashing of ESR and VDP ingots from low-plastic boron-containing steels is characterized in that the deformation of the ingot is carried out after the ingot is brought to the mandrel nose by reducing the work rolls until the metal is on the mandrel, and the firmware should be made according to the outer diameter, size to size on the mandrel, providing a hood no more than 1.3.

 Thus, the claimed method meets the criteria of the invention of "Novelty."

 Comparison of the proposed method not only with the prototype, but also with other technical solutions in the art did not allow them to identify signs that distinguish the claimed method from the prototype, which allows us to conclude that the criterion of "Significant differences".

 The method was tested and implemented on a pipe-rolling installation with pilgrim mills 8-16 "OAO" ChTPZ ".

 According to this method, ingots of low-plastic boron-containing steel of the ChS-82 grade were first stitched (Cr = 14.9%, B = 1.5%, Ti = 2.9%, etc.).

 410x100x1350 mm ingots were set for hire. The firmware was carried out size in size on a mandrel with a diameter of 200 mm, i.e. the diameter of the sleeve was 410 mm, and the hood was 1.28.

 There were no defects in the form of cracks on the obtained liners with a size of 410 × 210 in.x1720 mm, i.e. the proposed method of cross-screw firmware made it possible to relieve some of the stresses during deformation and to exclude cracking along brittle borides in steel.

Claims (1)

 The method of cross-screw flashing of ESR and VDP ingots from low-plastic boron-containing steels, including heating the ingots, flashing them on the mandrel, characterized in that the ingot is deformed after the ingot is fed to the mandrel nose by reducing the work rolls until the metal is on the mandrel, while the firmware should be made size to size on the mandrel, providing a hood no more than 1.3.