RU2751407C1 - METHOD FOR PRODUCTION OF WELDED HEXAGON PIPES WITH THE SIZE “TURNKEY” 252+2x5+0.7x4300+20 mm OF BORON-CONTAINING ROLLED SHEETS FOR NPP EQUIPMENT - Google Patents

Abstract

FIELD: nuclear power engineering.

SUBSTANCE: invention relates to a method for the production of welded hexagonal pipes with a “turnkey size” 252±2×5+0,7×4300±20 mm of boron-containing sheet metal for NPP equipment. Sheet metal made of boron-containing steel is used, with wall thickness of 5+0.7 mm, length of 4300±20 mm and width of 847 mm, corresponding to the perimeter of the hexagonal pipe, with further bending in the matrix under the influence of a punch. A tight butt joint of the edges of the sheet for welding with a fiber laser in one pass in the through-melting mode at a radiation power of 8 kW and a welding speed of 3.5 m/min with the formation of a single longitudinal seam with width of at least 0.4 mm under conditions of protection of its top and root from oxidation in argon is provided.

EFFECT: labor intensity in pipe production is reduced.

2 cl, 2 dwg

Description

The invention relates to the field of nuclear engineering and can be used in metallurgical, petrochemical, food processing and a number of other industries.

Hexagonal tubes are used for storage pool racks, racks for fuel assemblies, transport and packaging kits for transporting nuclear fuel, sealed canisters and other equipment with nuclear fuel.

In conditions of compacted placement of hexagonal pipes with the smallest possible pitch, the requirements for their dimensional accuracy increase.

The traditional method of manufacturing such hexagonal pipes according to TU14-3-1630-89 [1] using an ESR ingot subjected to numerous forging operations differs, along with a high consumption coefficient of metal and a long production cycle, a significant difference in thickness and curvature beyond the required technical conditions.

So, for example, according to the well-known method for the production of hexagonal pipes [2], including the use of solid remelting ingots with a size of 480x1800x25 mm of electroslag remelting from boron-containing steel 04X14T3R1F-Sh, mechanical turning of the ingot is envisaged, then drilling of its central hole, and after heating to a temperature of 1030-1050 ° With its flashing into sleeves, followed by rolling on a Pilgerstan in a string tube with a size of 287x11x25600 mm.

After removal of technological waste, they are cut into pipes with a length of 10250-11000 mm, and then into pipes with a length of 5200 mm, followed by boring and turning into pipes with a size of 281x5x5250-5500 mm for profiling into hexagonal pipes 255x5x4300 mm.

The disadvantage of this method is, along with the excessively high labor intensity of their manufacture with numerous technological operations, violation of the geometry of the pipe, which is expressed in the appearance of a difference in thickness and its curvature.

A known method for the production of hexagonal pipes using conversion hollow ingots of electroslag remelting [3].

According to this method, hollow ingots are bored and turned to remove cavities and traces of flux into hollow billets with dimensions of 500x330x2750 mm. After heating to the plasticity temperature, they are rolled on a pilgrim mill in lash pipes measuring 325x12x22400-23300 mm with further cutting into crate pipes with a length of 7450-7750 mm, which are bored and turned into processing pipes with a size of 321x8x7450-7750 mm, and then they are rolled on the KhPT450 mill into pipes with a size of 284.8x6x10500-11000 mm, followed by cutting into billet pipes with a size of 284.8x6x5250-5500 mm for profiling into hexagonal pipes.

The disadvantage of this method for the production of hexagonal pipes using a hollow ingot is the high labor intensity of their manufacture associated with numerous forging operations, as well as mechanical cutting, turning and boring of pipes and additional rolling on the KhPT450 mill, which contribute to a decrease in productivity and an increase in the cost of pipe production.

Along with this, the appearance of shrinkage defects in hollow ingots made by the ESR method causes additional operations to eliminate them, which is also a disadvantage of this method of producing hexagonal pipes.

There is a known method for the production of hexagonal pipes from boron-containing sheet steel by laser welding each face of the pipe from a separate sheet, respectively with six longitudinal welds, which is mastered at enterprises in Germany and the Czech Republic, for example, JSC SKODA JS [4].

The specified method for the production of hexagonal pipes avoids the appearance of thickness variation and curvature characteristic of hexagonal pipes obtained by plastic deformation. The disadvantage of this method is the significant complication of the technological process for welding six separate edges of the pipe and the high cost of their manufacture.

The next disadvantage of this method of manufacturing hexagonal pipes is the use of sheet products with a low boron content of 0.8-1.15%, incompatible with the requirements for Russian-made hexagonal pipes, which, according to technical conditions, are 1.5-1.8% [1].

Known patent for a utility model describing a hexagonal pipe with a turnkey size of 257 ± 2.0 mm, made of boron-containing sheet steel with a welded seam obtained by laser welding, placed in the middle part in one of the pipe faces [5].

The disadvantage of this patent is the lack of a method for manufacturing a pipe, i.e. technological parameters characterizing the performance of sheet bending and laser welding operations, without which it is impossible to implement the proposed invention.

The closest to the claimed method for the production of welded hexagonal pipes from boron-containing sheet steel is the method of laser welding of two halves of a hexagonal pipe made of sheet metal of boron-containing steel 04X14T3R1F 1 meter long, used at a facility, the system of which focuses laser radiation into a spot with a diameter of 200-400 microns with a length waist of 10 mm with a welding speed of 1.5-3.3 m / min and a laser power of 5-7 kW (6).

The disadvantage of this method of manufacturing hexagonal pipes is the lack of evidence base for the extension of the specified welding mode to industrial-made hexagonal pipes with a length of 4300 mm used for NPP equipment.

The objective of the claimed method for the manufacture of hexagonal pipes is to exclude from the process of their production numerous and labor-intensive forging operations that reduce labor productivity and contribute to the appearance of different thickness and curvature of pipes, which are inherent in the traditional method of their manufacture with plastic deformation of a solid or hollow ingot, as well as reducing to a minimum the number of welded longitudinal seams connecting the edges.

The technical solution according to the claimed method of manufacturing a hexagonal pipe is achieved by using sheet products made of steel grade 04H14T3R1F (ChS82) according to TU 14-1-5655-2016 [7] with a boron content of 1.5-1.8% in a heat-treated state with a fixed thickness wall of 5 + 0.7 mm, and a sheet width of 847 mm, corresponding to the total width of six sides of a pipe with a length of 4300 ± 20 mm, subjected to bending in a matrix, with a bottom surface located at an angle of 120 (Fig. 1), under the influence of a punch, forming successively each of the six corners between the edges of the pipe, followed by clamping on the stand of each edge of the pipe (Fig. 2), providing a tight butt joint of the edges of the sheet for fiber laser welding in one pass in the through-penetration mode at a radiation power of 8 kW and a welding speed 3.5 m / min with the focusing of the laser beam into a spot with a diameter of at least 420 μm and a waist length of 12 mm with a width of the heat-affected zone of no more than 3 mm with the formation of one p Rodolny welded seam with a width of not less than 0.4 mm in conditions of protection of its top and root from oxidation in argon atmosphere.

The practical implementation of the claimed method for the production of welded hexagonal pipes from boron-containing sheet steel with a turnkey size of 252 ± 2x5 + 0.7x4300 ± 20 mm was carried out in the department of the metallurgical complex of the OJSC Tyazhpressmash.

The initial blank for the manufacture of a hexagonal pipe was a hot-rolled sheet 5 + 0.7 mm thick made of steel grade 04X14T3R1F (ChS82) with a boron content of 1.5-1.8 in accordance with the requirements of TU 14-1-5655-2016 [7].

Cutting the sheet made it possible to obtain a workpiece with a width of 847 mm and a length of 4300 mm.

The bending of the obtained hot-rolled sheet blank was carried out in a matrix with the bottom surface located at an angle of 120 ° (Fig. 1), using a punch, which bends the hot-rolled sheet to form six angles between the pipe faces in the sequence shown in Fig. 1 from 1 to 6 room.

The next technological operation was carried out at the stand, in which the edges of the hexagonal pipe workpiece are clamped, after bending it (Fig. 2) to ensure a tight butting fit of the sheet edges, a necessary condition for obtaining a high-quality welded seam.

Welding of the butt joint of the edges of the sheet was carried out using an LS-10 fiber laser with a maximum radiation power of 10 kW, the parameters of the optical system of which allow focusing the laser beam into a spot with a diameter of 420 μm and a waist length of 12 mm.

Welding of the butt joint of the edges of the sheet was carried out in one pass in the through penetration mode at a radiation power of 8 kWh and a speed of 3.5 m / min, ensuring the formation of a longitudinal seam with a width of at least 0.4 mm.

In this case, the protection of the top and root of the weld from oxidation was carried out using an inert gas argon.

As a result of the work performed at the OJSC "Tyazhpressmash", a turnkey hexagonal pipe of 252 ± 2x5 + 0.7x4300 ± 20 mm was obtained from boron-containing sheet steel grade 04X14T3R1F (ChS82) with one longitudinal welded seam that fully meets the requirements of the technical conditions for this products, including in terms of such indicators as thickness variation and curvature.

At the same time, the labor intensity of manufacturing pipes according to the claimed method decreased by 45-50% compared to the traditional method of their production by plastic deformation of the ingot, and labor productivity increased by 3-5 times.

Sources of information:

1. TU 14-3R-1630-2009 "Seamless hexagonal steel pipes".

2. RF patent 2547613 C2 dated 10.12.2013.

3. RF patent 2536023 C2 dated 20.12.2014.

4. Minutes of the meeting on FCS dated 20.04.2018.

5 RF patent 121760 U1 dated 11.10.2017.

6. Report of the Research Institute of Nuclear Research "MEPhI" "Laser welding of pipes from steel ChS82" Moscow 2019.

7. TU 14-1-5655-2016 "Hot-rolled plate from corrosion-resistant steel grade 04H14T3R1F (ChS82)".

Claims (2)

1. Method for the production of welded hexagonal pipes from boron-containing sheet metal with a turnkey size of 252 ± 2 × 5 + 0.7 × 4300 ± 20 mm for NPP equipment, including the use of sheet metal with a wall thickness of 5 + 0.7 mm for longitudinal seam welding each individual pipe face or two of its halves, characterized in that the heat-treated sheet metal used with a boron content of 1.5-1.8% with a wall thickness of 5 + 0.7 mm, a length of 4300 ± 20 mm and a width of 847 mm, corresponding to the entire perimeter of a hexagonal pipe, is bent in a matrix with a bottom surface located at an angle of 120 °, under the influence of a punch, which forms each of the six corners between the edges of the pipe, followed by clamping on the stand of each of its edges, providing a tight butt joint of the edges of the sheet for fiber welding laser in one pass in the through-penetration mode at a radiation power of 8 kW, a welding speed of 3.5 m / min with a laser beam focusing into a spot with a diameter of at least 420 microns and a sweep length pots 12 mm with a width of the heat-affected zone of not more than 3 mm with the formation of one longitudinal weld with a width of at least 0.4 mm in conditions of protection of its top and root from oxidation in an argon atmosphere. 2. The method according to claim 1, characterized in that the heat treatment of sheet metal made of boron steel with a wall thickness of 5 + 0.7 mm is carried out according to the mode: tempering at a temperature of 750-800 ° C with a holding time of at least 20 minutes and further air cooling.

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