RU2542139C1 - Method of manufacturing of pipes "t=279(36" and "t=346(40" mm out of "08-18=10t-+" grade steel for nuclear power facilities - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: ingots of electroslag remelting process with size 620x100x1750±50 mm are heated in continuous furnaces to temperature 1260-1270°C, pierced in helical rolling mill to shells with size 620xID265x1985-2105 mm, that are heated from cold or hot fit to 1260-1270°C, pierced -rolled to shells 620xID390x2630-2800mm. At pipe rolling unit 8-16" the shells are rolled to tube stock 480x58x5500-5800 mm, straightened at 6-hi straightening unit, turned and bored to tube stock 470x47x5500-5800 mm. Defects are removed, heat treatment is performed and rerolling is performed at mill CPR 450 to commercial pipes of to tube stock.

EFFECT: improvement of pipe surface quality, decreasing of metal consumption.

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Description

The invention relates to pipe rolling production, and in particular to a method for the production of pipes with dimensions of ext. 279x36 and ext. 346x40 mm from steel grade 08X18H10T-Sh for nuclear power facilities, and can be used in rolling limiting hot-rolled pipes of size 480x58x5500-5800 mm in a tube rolling installation 8 -16 "with pilgrim mills from EShB ingots measuring 620x100x1750 ± 50 mm, followed by machining (turning and boring) into conversion pipes 470x47x5500-5800 mm and rolling them on the KhPT 450 mill into commodity or conversion pipes along routes 470x47x5500-5800 --- - n.346h40h6700-7300 ---- vn.279h36h92000-9500 mm and their acceptance on line 14 TU-LA-107-2001 with high demands on surface quality.

In pipe rolling production, a method is known for the production of commodity and conversion pipes from hardly deformed steel grades, including drilling a central hole with a diameter of 100 ± 5.0 mm in blanks and ingots of EAWs with a diameter of 380-500 mm, holding them on the grates of method furnaces at a temperature of 500-550 ° C for 70-95 minutes depending on the diameter, after which it is heated to a temperature of 1120-1140 ° C at a speed of 1.4-1.5 deg./min, flashing blanks and ingots of ESR into the sleeves size in size in diameter at rotation speed work rolls 25-40 rpm on the mandrel diameter, providing reduction on the pilgrim mill at least 25 mm (RF Patent No. 2175899, bull. No. 32, 11/20/2001).

The disadvantage of this method is that it is acceptable only for the production of hot-rolled commodity and conversion pipes of medium diameter, namely pipes with a diameter of 219-325 mm, because for rolling pipes with a diameter of more than 325 mm, a workpiece with a diameter of 540-620 mm is required, which, due to the low power of the drive of the cross-helical rolling mill, cannot be sewn, and most importantly, this method does not stipulate the allowance for machining of conversion pipes for the manufacture of commodity pipes high quality with dimensions of ext. 279x36 and ext. 346x40 mm from 08Kh18N10T-Sh corrosion-resistant steel for nuclear power facilities.

In pipe rolling production, there is a known method for the production of commodity and conversion hot-deformed pipes of large and medium diameters from corrosion-resistant hardly deformable steel and alloy grades in pipe-rolling plants with pilgrim mills, including drilling a central hole with a diameter of 100 ± 5.0 mm in ESR ingots and billets, heating them to the ductility temperature, the first flashing of ESR ingots or billets with a diameter of 460-600 mm in a cross-helical rolling mill with a hood of 1.2-1.4 at a speed of rotation of the work rolls 1 5-25 rpm, and the second and subsequent, if necessary, firmware rolls with a rise or landing in diameter of not more than 5.0% and a hood 1.4-1.75 at a roll speed of 20-50 rpm, using cold or hot insertion of sleeves into the furnace, the process of flashing from picking up the ESR ingots or blanks until they are completely on the mandrel is carried out with a decrease in the number of revolutions of the work rolls from 25 to 15, the established process of flashing at 15-20 rpm, and at the exit of the sleeve from the rolls the speed increases to 35-40 rpm, the firmware process - rolling (second firmware) from they capture the liner until it is completely on the mandrel with a decrease in the number of revolutions of the work rolls from 50 to 20, the steady rolling process at 20-25 rpm, the number of revolutions at the exit of the liner from the rolls is increased to 45-50, and the tubes are rolled on the pilgrim mill with extractor hood μ = 3.0-5.0 (RF Patent No. 2247612, bull. No. 7, March 10, 2005).

The disadvantage of this method is that it also does not stipulate an allowance for machining conversion pipes for the manufacture of high-quality commodity pipes with dimensions of ext. 279x36 and ext. 346x40 mm from 08Kh18N10T-Sh corrosion-resistant steel for nuclear power facilities.

A known method for the production of seamless hot-deformed pipes with dimensions vn.279x36 and v.346x40 mm from ESR ingots of 08Kh18N10T-Sh corrosion-resistant steel with improved surface quality for nuclear power facilities with a bored inner and turned outer surface with a roughness R _{a of} no more than 10 μm according to GOST 2789 ( TU 14-158-131-2002 "Seamless hot-formed seamless pipes of high-quality stainless steel").

One of the main disadvantages of this method is that in the production of this technology more than 80% of the pipes after austenization have yield strengths at + 350 ° from 12 to 18 kgf / mm ² (with the norm according to TU 14-ЗР-55-2001 not less than 19 kgf / mm ² ). Another disadvantage is that the allowance for machining (boring and turning) of pipes with a length of 4000 mm should be at least 10 mm per side. Thus, during machining (turning and boring) with a RaHe roughness of more than 10 μm, 134.68 to 147.52 kg of expensive metal, i.e. from 26.2 to 34.5% (depending on the diameter and wall thickness of the pipes).

The closest technical solution is a method for producing high-quality pipes from corrosion-resistant steel grade 08X18H10T-Sh for nuclear power facilities, including rolling pipes in a pilgrim mill for technological rolling at HPT mills, machining - boring and turning of hot rolled pipes, on machines with a follow-up system into conversion billet pipes with metal removal, the value of which is determined from the expressions Δ _sb.n = KΔ _sb.s , Δ _sn.n = K ₁ Δ _sb.s , where Δ _sb.n is the value of the metal layer to be removed at races ochke under process roll, mm; Δ _sv.s - the value of the removed metal layer when boring to the finished size, mm; K = (0.5-0.6) is the coefficient of reduction in the size of the removed metal layer during boring, large values of which relate to pipes of large diameters; Δ _sn.n is the value of the metal layer to be removed during turning under a technological roll, mm; Δ _sn.s - the value of the removed metal layer during turning to the finished size, mm; To ₁ = (0.4-0.5) is the coefficient of reduction in the size of the removed metal layer during turning, large values of which relate to pipes of large diameters (RF Patent No. 2401169, 10/10/2010).

The disadvantage of this prototype is that it is aimed at the production of hot-rolled conversion tubes of 260-450x40-70 mm in size for subsequent machining - boring and turning into pipes of 245x19, 351x36, 415x50, 426x40, 426x50 and 436x45 mm in high quality from corrosion-resistant steel 08Kh18N10T-Sh for nuclear power facilities or rolling at a pilgrim mill of redistributed pipes 250-440x30-60 mm in size with subsequent machining for technological rolling at HPT mills into pipes of these sizes and does not solve technological issues production of commodity pipes with dimensions in. 279x36 and in. 346x40 mm for nuclear facilities from one diameter of ESR ingots instead of two.

The objective of the proposed method is the production of pipes of high quality for nuclear facilities with mechanical properties of metal that meet the requirements of TU 14-3 R-197-2001, reduction of allowance for machining (boring and turning) of hot-deformed tubes, using one of the pipe sizes for production diameter of ESR ingots instead of two, increasing the productivity of TPU 8-16 "with pilgrim mills, reducing the expenditure coefficient of the metal when redistributing the ingot ESR - commodity pipe increased quality according to TU 14-ЗР-197-2001, an increase in the length of commodity pipes, and consequently, a decrease in their cost.

The technical result is achieved by the fact that in the known method for the production of pipes with dimensions of ext. 279x36 and ext. 346x40 mm from steel grade 08Kh18N10T-Sh for nuclear power facilities, including heating ESR ingots to a plasticity temperature, piercing into sleeves, rolling the sleeves into hot rolled pipes, boring and turning of conversion pipes rolling of conversion pipes into commodity pipes, characterized in that electroslag remelting ingots of 620x100x1750 ± 50 mm in size are heated in methodological furnaces to a temperature of 1260-1270 ° C, stitched in a cross-screw mill rolling into billet sleeves of size 620хвн.265х1985-2105 mm, which are heated from cold or hot posad in methodological furnaces to a temperature of 1260-1270 ° С, stitched - rolled out in a cross-screw mill into sleeves of size 620хвн.390x2630-2800 mm , rolled on TPU 8-16 "with pilgrim mills into hot-rolled chimneys measuring 480x58x5500-5800 mm, hot-rolled chimneys are straightened on a six-roll straightening machine in several passes with a curvature of not more than 5.0 mm for the total length, hot-rolled chimney-pipes are turned and bored they are removed into mechanically processed pipes with a size of 470x47x5500-5800 mm, undetected defects are removed by grinding or gentle cleaning, heat treated - austenized, and then rolled at the KhPT 450 mill into commodity or conversion pipes along routes 470x47x5500-5800 ---- ext. 346x40x6700-7300 ---- ext. 279x36x9200-9500 mm, austenitization is carried out on commodity and conversion pipes, samples are taken from both ends of the commodity pipe after austenization for mechanical testing, pollution control with titanium nitrides and carbonitrides, grain, macrostructure, bend tests and tests for resistance to intergranular corrosion, commodity pipes are subjected to ultrasonic testing and pipe acceptance.

A comparative analysis of the proposed solution with the prototype shows that the claimed method differs from the known one in that electroslag remelting ingots of 620x100x1750 ± 50 mm in size are heated in methodological furnaces to a temperature of 1260-1270 ° C, stitched in a helical rolling mill into blanks of 620хвн size .265x1985-2105 mm, which is heated in a methodical furnace to a temperature of 1260-1270 ° C from cold or hot planting, flashed - rolled in a cross-helical mill into sleeves measuring 620хвн.390x2630-2800 mm, rolled on a 8-16 "TPUwith pilgrim mills into hot rolled pipe sizes of 480x58x 5500-5800 mm, hot rolled pipes are straightened on a six-roll straightening machine in several passes with a curvature of not more than 5.0 mm for the total length, hot rolled steel pipes are turned and bored into mechanical machined pipes of 470x47x5500- 5800 mm, not removed defects are removed by grinding or gentle cleaning, heat treatment is carried out - austenization, and then rolled on the KhPT 450 mill into commodity or conversion pipes along routes 470 x47x5500-5800 ---- ext. 346x40x6700-7300 ---- ext. 279x36x9200-9500 mm, austenitized commodity and conversion pipes, samples from each commodity pipe after austenitization are taken from both ends for mechanical testing, control on

contamination with titanium nitrides and carbonitrides, grain size, macrostructure, bend tests and tests for resistance to intergranular corrosion, commodity pipes are subjected to ultrasonic testing and pipe acceptance. Thus, these differences allow us to conclude that the criterion of "inventive step" is met.

Comparison of the proposed method not only with the prototype, but also with other technical solutions in this technical field, did not reveal the signs that distinguish the claimed method from the prototype, which corresponds to the patentability of "inventive step".

The method was tested on TPU 8-16 "with pilgrim mills of ChTPZ OJSC during rolling of conversion pipes of sizes 370x55x4550 and 445x58x5200 mm from ESR ingots of 470x100x1800 and 585x100x1650 mm in accordance with the existing technology and conversion tubes of size 480x58x5600 mm and 480x58x5600 mm from EShP ingots 6 we offer 616 mm x 20 mm ingots technologies Converting pipes 370x55x4550 mm in size were bored and turned in workshop No. 1 into commodity pipes of 279x36x4550 mm in size, and conversion tubes 445x58x5200 mm into commercial pipes of 346x40x5200 mm in size, with a roughness of the outer and inner surfaces Ra of no more than 10 microns , from which drums were selected, samples were made and mechanical tests were carried out. The pipes passed ultrasonic testing. Pipes ext. 279x36 mm in size were accepted as TU 14-ZR-197-2001 conditionally suitable, as they could not pass the yield strength tests at temperature + 350 ° C after austenization. The pipes were delivered for a different purpose. The consumption coefficient of the metal for pipes of this size was 1.946. Of the 3 pipes with a size of 344 x 40 mm, one pipe that passed was tested for yield strength at a temperature of + 350 ° C after austenization. for its intended purpose. The expenditure coefficient of metal for pipes of this size was 1.811. According to the proposed technology, the conversion pipes of size 480x58x5600 mm were turned and bored into conversion machined pipes of size 470x47x5600 mm. On one out of six pipe, the unreduced blackness was removed by grinding with abrasive wheels in accordance with the claims. Converted hot-rolled machined pipes with a size of 470x47x5600 mm were rolled at the KhPT 450 mill into pipes with a dimension of ext. 346x40x6900 mm with a roughness of the outer and inner surfaces Ra of no more than 2.5 μm. Drums were taken from three pipes, samples were made and mechanical tests were carried out. The pipes passed the ultrasonic inspection. Two pipes with a size of 346x40 mm were adopted in accordance with TU 14-ЗР-197-2001 for their intended purpose for nuclear facilities, and one as conditionally suitable, as did not pass the yield strength test at a temperature of + 350 ° C after austenization. The expenditure coefficient of the metal for pipes of this size was 1.538. Three pipes of 426x40 mm in size were rolled at the KhPT 450 mill into pipes of ext. 279x36x9250 mm. The average pipe length at delivery was 9000 mm. These pipes withstood all tests, were adopted according to TU 14-ЗР-197-2001 with increased requirements for surface quality and delivered for the intended purpose for nuclear power plants. The expenditure coefficient of metal for pipes of this size was 1.606. A pipe with a size of ext. 346x40 mm, which did not pass the yield strength test at a temperature of + 350 ° C after austenization, was rolled at the KhPT 450 mill into a pipe with a size of ext. 279x36x9000 mm, passed all tests and passed for its intended purpose for nuclear power plants.

The data on the rolling of high-quality pipes with dimensions of ext. 279x36 and ext. 346x40 mm from 08Kh18N10T-Sh corrosion-resistant steel according to TU 14-ZR-197-2001 for nuclear facilities according to the existing and proposed technologies are shown in Table 1. It can be seen from the table that the yield for its intended purpose when rolling pipes for nuclear power plants using the existing technology amounted to 17.7%, and according to the proposed technology, from the first presentation, 83.3%. After rolling the pipe with the size extra 346x40 mm into the pipe with the size extra 279x36 mm, the yield was 100%. The expenditure coefficient of metal when rolling pipes ext. 279x36 mm in size according to the proposed technology is reduced by 340 kg, and when rolling pipes in ext. 349x40 mm in size by 273 kg. According to the proposed technology, when rolling pipes with a size of ext. 279x36 mm, the average increase in length of pipes was 2.09 times, while rolling pipes with a size of ext. 346x40 mm was 1.41 times, and the roughness of the outer and inner surfaces was reduced by more than 4.0 times .

Using the proposed method for the production of pipes with dimensions of extra 279x36 and extra 346x40 mm of high quality from corrosion-resistant steel 08Kh18N10T-Sh for nuclear power facilities will significantly reduce the consumption of expensive metal, increase the yield of pipes for nuclear power plants from the first presentation, reduce the roughness of the outer and inner surfaces and significantly increase their length, and therefore, reduce the cost of pipes and reduce the number of welding joints when installing pipelines at nuclear power plants.

Claims (1)

Method for the production of pipes with dimensions of 279x36 and 346x40 mm from 08Kh18N10T-Sh steel for nuclear power facilities, including heating ESR ingots to a plastic temperature, piercing sleeves, rolling sleeves into hot rolled pipes, boring and turning of conversion pipes, rolling of conversion pipes into commodity pipes, characterized in that electroslag remelting ingots of 620x100x1750 ± 50 mm in size are heated in methodological furnaces to a temperature of 1260-1270 ° C, stitched in a helical rolling mill into blanks 620x in size 265x1985-2105 mm which are heated from cold or hot posad to 1260-1270 ° C in method furnaces, flashed - rolled in a cross-helical mill into sleeves measuring 620хвн. 390x2630-2800 mm, rolled on 8-16 "TPU with pilgrim mills to conversion hot-rolled pipes with dimensions of 480x58x5500-5800 mm, hot rolled pipes are straightened on a six-roll straightening machine in several passes with a curvature of not more than 5.0 mm for the total length, hot rolled steel pipes are turned and bored into mechanically processed pipe rum 470x47x5500-5800 mm, non-removed defects are removed by grinding or gentle cleaning, heat treated - austenized, and then rolled on the KhPT 450 mill into commodity or conversion pipes along routes 470x47x5500-5800 ---- ext. 346x40x6700-7300 --- - ext. 279x36x9200-9500 mm, commodity and conversion pipes are subjected to austenization, samples are taken from each commodity pipe after austenization from two ends for mechanical testing, pollution control of titanium nitrides and carbonitrides, grain size, macrostructure, bending and contamination tests the role of resistance to intergranular corrosion, commodity pipes are subjected to ultrasonic testing and acceptance of pipes.