Method for rolling seamless hot rolled casing tubes with buttress thread

FIELD: processes for rolling seamless hot rolled casing tubes of given size having buttress thread.

SUBSTANCE: seamless hot rolled casing tubes with dimensions 426 x (10 - 12)mm having buttress thread are rolled in tube rolling plant 8 - 16" with pilger mills. Method comprises steps of casting ingots with hot top or without it; repairing ingots; heating ingots up to yielding temperature; piercing ingots to sleeves at mean diameter raising 10.2% and along length of ingot - 6.0 - 14.8%; rolling in pilger mill tubes with diameter 244,5, 273.1, 298.5, 323.9, 339.7, 406.4, and 473.1 at tilting sleeves-tubes by 90 ± 10° and saw cutting of them by measured lengths; heating sleeves-tubes in gas roller furnace; calibrating them in sizing mill at total reduction by diameter up to 1.0%; straightening them in skew-roll straightening machine and subjecting to electromagnetic control; marking; inspecting; trimming ends; realizing preliminary reception; subjecting tubes to ultrasound flaw detection; repairing their surface; subjecting repaired tubes to ultrasound flaw detection; cutting thread; screwing on couplings; hydraulically testing tubes; inspecting them; marking; weighing and painting. Steel ingots of given strength group without hot top are subjected to rolling for making tubes with size 585/540 x 1700 mm; ingots with hot top are subjected to rolling for making tubes with size 585/570 x 1900 mm. Cone shaped ingots having or having no hot tops are heated in heating furnaces till 1260 - 1280°C for 7.5 - 9/0 h at tilting in 20 - 25 min by angle 135°< α < 225° and they are soaked at such temperature for 25 - 30 min. Then ingots having no hot tops are rolled in skew rolling mill with diameter raising 5 - 10%; ingots with hot tops are rolled with diameter raising 2.5 - 5.5%. Tubes are rolled in pilger mill at feeding sleeve to deformation zone 15 - 20 mm while providing polishing coefficient 2.5 - 3.0 and tilting sleeve-tubes by angle 70 ± 5°. Then tubes are calibrated in sizing mill at total reduction along diameter 2.4 - 2.8 %, straightened in skew-roll straightening machine.

EFFECT: lowered metal consumption due to decreased quantity of flaws of metallurgical and rolling-process origin, reduced quantity of waste material caused by wall thickness difference and out-off-roundness due to more strict allowances for rolling, lowered number of thread-rejected tubes, less (by two times) loss of yield, reduced cost of commercial tubes of given assortment.

5 cl, 1 tbl

 

The invention relates to pipe production, in particular to a method of rolling hot rolled seamless casing pipes, and can be used in the production of seamless hot-rolled casing size 426×10-12 mm for pipe installation 8-16" with piligrimage countries with persistent threads "improvement on the buttress-"OTBT-426".

In pipe production in Russia known methods of production casing seamless steel pipes with a triangular thread diameters 114, 127, 140, 146, 168, 178, 194, 219, 245, 273, 299, 324, 340, 351, 377, 426, 473 and 508 mm with wall thickness from 5.2 to 16.7, with trapezoidal thread (OTM), which corresponds to the term "improvement on the buttress (buttress) in ISO and API 5CT, with a diameter of from 114 to 340 mm with wall thickness from 5.2 to 15.4 and gastight connections (OTG diameter from 114 to 273 mm with wall thickness from 5.2 to 16.5 mm groups strength from D to T, which are provided on a pipe units with automatic mills (114-245) mm and tube units with piligrimage mills (219-426) mm (GOST 632-80 "casing Pipes and couplings", THE 14-3-1575-88 "casing Pipe external diameter 351, 377 and 426 mm couplings".

The disadvantage of these methods is that GOST 632-80 and THE 14-3-1575-88 not provide for the production of pipes with a diameter of more than 340 mm with persistent thread type "BAT-tress". Pipe cannot withstand excessive pressure and can not work in North the regions of the Russian Federation. GOST 632-80 applies to seamless steel pipe with triangular and trapezoidal thread couplings, tubes with gastight connections and couplings, as well as collar without coupling female pipe used for casing of oil and gas wells. This standard provides for the production of pipes size 426×10-12, 473×11 and 508×11,1-16,1 mm only with a triangular thread groups strength D and E, and THE 14-3-1575-88 apply to seamless steel tubes with a triangular thread and couplings used to install oil and gas wells and pipe casing shortened length, used for manual drilling in geological exploration, construction of wells with mechanical and manual drilling on water "BURWOOD".

In the pipe industry known methods of production of seamless hot-rolled casing diameter 114,30, 127,00, 139,70, 168,68, 177,80, 193,68, 219,08, 244,48, 273,05, 298,45, 339,72, 406,40, 473,08 and 508,00 mm with wall thickness from 5.21 to 16,13 mm with persistent threads "improvement on the buttress steel grades EN, GOST types K55 (J55), M65, L80 (s), N80, Td, P110 and Q125dgroup strength, R, S, L, and E (Specification for casing and tubing. API specification 5CT, seventh edition, October, 2001. ISO11960:2001. Petroleum and natural gas industries - Steel pipes for execution as casing and tubing for wells) and standard on ezibuy connection casing, tubing and pipes for pipelines 114,3, 127,0, 139,7, 146,1, 177,8, 193,7, 219,1, 244,5, 273,0, 298,4, 323,9, 339,7, 406,4, 473,1 and 508,0 used in the oil and gas industry (GOST R 51906-2002 "Connection threaded casing, tubing and piping and threaded calibers for them. General technical requirements").

The disadvantage of these methods is that they lack casing size 426×10-12 mm all steel grades and groups of strength, which are necessary for fastening the gas and oil wells, including the Northern regions of the Russian Federation.

The closest technical solution is a method of rolling hot rolled seamless casing pipe size 426×10-12 mm TPA 8-16" with piligrimage mills "CHTPZ" with a triangular thread in the ordinary performance strength group D, including the casting of ingots size 585/540×1700 mm without profit, repair ingots, heating them to a temperature of plasticity 1270-1300°With the duration of heating is not less than 7.5 hours, firmware ingots in sleeves in the camp oblique rolling with the rise in the average diameter of 10.2%, and the length of the ingot from 6.0 to 14.2%, rolling tubes on piligrimages mill diameter in the hot condition 432-434 mm casting-off sleeves-pipe 90±10° and applying the liner in the deformation zone 18-22 mm (large values refer to the wall 12 mm, the smaller to the wall 10 mm) with a coefficient of polishing of 2.3-2.5, which depends on the feed and wall thickness of the pipe cutting saw to length, heated in a gas furnace roller to a temperature of 800-850°With calibration in the calibration mill with a total compression in diameter to 1.0%, the editing on konovalovas straightening machine, electromagnetic inspection, labeling, primary control, trimming ends, preliminary inspection, ultrasonic inspection, surface repair, ultrasonic inspection of the repaired pipe, cutting a triangular thread, sweeping-up, navendu couplings, hydraulic testing, inspection, labeling, weighing and painting of pipes (TI 158-Tr. TB - 23 - 2000 "instruction manual for site rental shop No. 1, Annex And table rolling casing pipes, casing pipes and tubes for pressure relief of the rings in THE 14-3-1575-87").

However, the known method has the following disadvantages. This method does not allow for rolling pipe size 426×10-12 mm with persistent threads "improvement on the buttress even strength group D. Technological parameters of rolling and geometric sizes of pipe 426×10-12 mm do not allow to cut quality persistent thread "improvement on the buttress due to ovality of the pipe ends and defects metallurgical and rolling origin (external, internal captive and rosslea metal). Heating of the ingots without limiting the heating time leads to peregrinate, and irrational casting-off on the furnace hearth furnaces in time and an arbitrary rotation angle leads to uneven heating of the ingot cross section, which in turn leads to the curvature of the liner and the varying wall thickness of the pipes on piligrimages the camp. Firmware bars open hearth furnace without a Central drilling in the piercing mill with the rise of the diameter of more than 10% leads to the formation of domestic captivity. When rolling pipe size 426×10-12 mm on piligrimages mill with elevated feed 18-22 mm, the ratio of the polishing 2,3-and 2,5 angle kantowski 90±10°when the third casting-off "condition" falls into "sprint", i.e. the gaps between the rollers and not fully rolled out, resulting in a cross-section varying wall thickness of the pipe. Calibration tubes of this size in pjatikletevoj mill with a total compression to 1.0% does not allow the tube to get with tighter tolerances diameter +1,0/-0,5%.

The objective of the proposed method is the production of seamless hot-rolled casing size 426×10-12 mm TPA 8-16" with piligrimage mills "CHTPZ" for cutting high-quality resistant thread "improvement on the buttress-"OTBT-426".

The technical result is achieved by the known method of production of seamless hot-rolled casing size 426×10-12 mm with persistent threads "improvement on the buttress-"OTBT-426", including the casting of ingots with profit or without p. the andwere, repair ingots, heating them to a temperature of plasticity, firmware ingots in sleeves in the camp oblique rolling with an average rise of a diameter of 10.2%, and the length of the ingot from 6.0 to 14.8%, rolling tubes on piligrimages mill diameter 244,5; 273,1; 298,5; 323,9; 339,7; 406,4 and 473,1 mm casting-off sleeves-pipe 90±10°, cutting saw to length, heated in a gas furnace roller, the calibration in the calibration mill with a total compression in diameter to 1.0%, the editing on konovalovas straightening machine, electromagnetic inspection, labeling, primary control, trimming ends, preliminary inspection, ultrasonic inspection, surface repair, ultrasonic inspection of the repaired pipe, threading, sweeping-up, navendu couplings, hydraulic testing, inspection, labeling, weighing and painting, with the rolling of pipes made from steel ingots strength group D without profit size 585/540×1700 and ingots with profit size 585/570×1900 mm, cone non-profit and profitable steel ingots strength group D is heated in the reheating furnaces to a temperature 1260-1280°With over 7,5-9,0 hours with the casting-off after 20-25 minutes at angle 135°≤α≤225° and maintained at this temperature for 25-30 minutes, non-profit bullion stitch in the camp oblique rolling with the rise in diameter from 5 to 10%, profit from podjimo the diameter from 2.5 to 5.5%, casing steel pipe strength group D rolled on piligrimages mill feed sleeve in the deformation zone of 15-20 mm with a coefficient of polishing from 2.5 to 3.0 and a casting-off sleeves-tube angle 70±5°, hot rolled seamless casing pipes are calibrated in the calibration mill with a total compression in diameter 2.4 to 2.8%.

The essence of the method lies in the fact that the proposed technological process of production of seamless hot-rolled casing size 426×10-12 mm TPA 8-16" with piligrimage countries with persistent threads "improvement on the buttress-"OTBT-426", missing the American standard API 5CT, Russian GOST R 51906-2002, GOST 632-80 and other standards of the world.

Heating of the ingots to a temperature of plasticity without limiting the duration of heating, the frequency of santovac, angle them at the casting-off and a fixed holding time at the temperature of plasticity leads to overheating or underheating, to uneven heating them by section and, as a consequence, defects (external and internal Plenum, Rosslau metal) and the curvature of the liner when flashing. A fixed feed rate when piligrimages rolling and angle kantowski angle of 70±5 at odds of polishing from 2.5 to 3.0 exclude hit part nerazgadannaja "riot" (thickening of the metal in the editions of caliber) during the third kantowski in the release of the caliber that drive the t to the lower transverse varying wall thickness, i.e. to improve the accuracy of pipe wall thickness. Firmware ingots in the oblique mill rolling with the rise of the diameter of more than 10% leads to the formation of internal captive and triangles when the firmware is rolling shrinkage of the part, therefore, the proposed non-profit ingots flash in the camp oblique rolling with the rise in diameter from 5 to 10%, and profitable with the rise in diameter from 2.5 to 5.5%. Rolling sleeves with increased curvature in the pipe on piligrimages mill leads to uneven deformation of the wall, i.e. to increased varying wall thickness. The increase in total reduction in diameter of pipe sizing mill to 2.4 to 2.8% instead of 1.0% significantly reduces their out-of-roundness and the difference of the diameters in length.

Comparative analysis of the prototype shows that the inventive method of manufacturing a hot rolled seamless casing pipe size 426×10-12 mm with persistent threads "improvement on the buttress-"OTBT-426" differs in that the rolling diameter 426×10-12 mm on piligrimages installation 8-16" produce ingots of steel strength group D without profit size 585/540×1700 and ingots with profit size 585/570×1900 mm, cone non-profit and profitable steel ingots strength group D is heated in the reheating furnaces to a temperature 1260-1280°for 7,5-9,0 hours with the casting-off after 20-25 minutes at angle 135°≤α≤225° and maintain PR is this temperature for 25-30 minutes, non-profit bullion stitch in the camp oblique rolling with the rise in diameter from 5 to 10%, profit from rising in diameter from 2.5 to 5.5%, casing steel pipe strength group D rolled on piligrimages mill feed sleeve in the deformation zone of 15-20 mm with a coefficient of polishing from 2.5 to 3.0 and a casting-off sleeves-tube angle 70±5°, hot rolled seamless casing pipes are calibrated in the calibration mill with a total compression in diameter 2.4 to 2.8%. These differences allow us to conclude that the criterion of "inventive step".

Comparison of the proposed method not only prototype, but also with other technical solutions in this field of technology is not allowed to reveal in them the features distinguishing the claimed method from the prototype that corresponds to the patentability of "inventive step".

The method was tested and implemented on pipe installation 8-16" with piligrimage mills "CHTPZ". In this way, were for the first time in 2004, industrial laminated trumpets size 426×11 mm of steel strength group D and pipe with persistent threads "improvement on the buttress-"OTBT-426".

In October 2004, TPA 8-16" with piligrimage mills "CHTPZ" was laminated industrial batch pipe size 426×11 mm of steel strength group D for the manufacture of casing with hard carving, "improvement on the buttress-"OTBT-426"), the existing and proposed technologies. Production was set to one the smelting of non-profit ingots steel strength group D size 585/540×1700 mm Weight melting ingots, rolled on existing technology, was 120,45 tons, and the weight is melting, laminated on the proposed technology, 122,5 tons. On existing technology ingots were renovated and accepted Rev. Heating of the ingots produced in furnaces No. 2. The heating temperature of the ingots was 1280-1300°and the duration of heating from 9.3 to 10,45 hours. The sleeves stitched into the piercing mill mandrel diameter of 425 mm, with a mean rise of the diameter of 10.2%, and the length of the ingot rise was from 6.0 to 14.8%, since the ingot has a cone shape. The liner had a 620×440×2800-2950 mm and greater curvature. 43 sleeves 13 there were external and internal destroyed. Sleeves were rolled on piligrimages mill in pipe size 426×11 mm in caliber 434 mm, the feed rate of the liner in the deformation zone ranged from 18 to 22 mm, and the angle of kantowski from 80 to 100°, the value of which depends on the path rollback of the feeding apparatus and professionalism of the roller. When the feed rate of 18 to 22 mm coefficient of polishing on the existing calibration of rolls for rolling tubes of this size ranged from 2.3 to 2.5. When the angle of kantowski sleeves-pipe equal to ≈90°during the third feed "rebellion" (wall thickening of the editions of the caliber), education is, which during the second filing, fell in release and not fully rolled out, which led to increased varying wall thickness (thickness variation) of the pipe. Pipe-whip was cutting the hot cutting saw two Krat length of 11.5 to 12.5 m Pipe before calibration is heated in a gas furnace roller and calibrated in pjatikletevoj sizing mill with a total compression on the diameter of 1.0%. After rolling tubes were preliminarily approved Rev. TCI made suitable pipe 72. The expenditure ratio of metal to rent amounted to $ 1,375. Pipe in quantity 72 pieces were aimed at sweeping-up. After the solid patch is printed conventionally fit was made 58 pipes. 14 pipes went into the marriage sabanyalanew due to ovality and bumpy (of varying wall thickness) on the body of the pipe. 58 pipes was aimed at cutting. After cutting, navartri couplings and hydraulic test fit made only 40 pipe. 18 pipes away in marriage in black (incomplete thread profile) and leakage during pressure testing. Fit that meets the requirements of GOST R 51906-2002 and API 5CT, made 40 pipe. The yield on the trumpets was 46.4%. Data on rolling, passing, threading and yield of casing size 426×11 mm with persistent threads "improvement on the buttress-"OTBT-426" steel strength group D on existing and proposed technologies listed in the table. The table shows that the proposed technology of Plav and steel strength group D, total weight of 122.5 tons of metal, laminated 88 pipe length 12,0-12,5 m Ingots was heated in furnaces No. 2 to the temperature 1260-1280°C. heating Time ranged from 8.0 to 8.5 hours. The ingots were kantonales furnace along with the interval from 20 to 25 minutes, the angle of kantowski ranged from 135 to 225°i.e. bullion regularly kantonales on average 180°. Before issuing from the furnace bullion in the first zone for uniform heating was maintained at a temperature 1260-1280° for 25-30 minutes. The ingots were stitched in the camp oblique rolling in sleeves size 600×440×3240 mm with the rise of diameter along the length of the ingots from 2.6%to 11%. Sleeves were smooth and had the least number of defects in the form of external and internal captive (two liners with small outer captivity and one sleeve with inner Planai), i.e. less than 4.3 times. The liner was applied to programowy mill and rolled in a tube with a feed rate of the liner in the deformation zone from 15 to 18 mm with a casting-off angle 70±5,0°. The ratio of the polishing in this case ranged from 2.6 to 2.8, and for the third time thickening from the "rebellion" was in caliber, bypassing the issue that gave the opportunity to significantly reduce the cross-raznesennost pipes. Pipe on piligrimages the camp rode in caliber 440 mm After piligrimage mill pipe is heated in a gas furnace roller and calibrated in pjatikletevoj calibration Stanes General compression by 2.4%. The expenditure ratio of metal to rent amounted to 1,275. Pipes in the amount of 88 pieces were aimed at sweeping-up. After the solid patch is printed fit was made 87 pipes. One tube went into marriage because of the tuberosity (of varying wall thickness) on the body of the pipe. 87 pipe was aimed at cutting. After cutting, navartri couplings and hydraulic test fit that meets the requirements of GOST R 51906-2002 and API 5CT, made 86 pipes. One pipe is rejected by the black screw cutting. The yield on the trumpets was 97,7%.

Thus, for the first time in world practice, the received pipe size 426×10-12 mm with persistent threads "improvement on the buttress, and the results of the experiment confirmed theoretical justification and legitimacy of the claims "a Method of production of seamless hot-rolled casing size 426×10-12 mm with persistent threads "improvement on the buttress-"OTBT-426" on TPA 8-16" with piligrimage mills due to the rational use of technological parameters of heating ingots and billets, firmware in their sleeves in the mills oblique rolling, rolling tubes on piligrimages mill, calibration tubes in pjatikletevoj calibration mill. The table shows that the pipes, laminated on the proposed technology (the way), have the least number of defects in the form of external and internal captivity, the smallest transverse and longitudinal krasnostein is here, the lowest out-of-roundness less expenditure ratio of metal-to-hire and highest yield (2.1-2.2 times) when threading because the best of the geometrical sizes of pipes.

Using the proposed method of production of hot rolled seamless casing pipe size 426×10-12 mm with persistent threads "improvement on the buttress-"OTBT-426" on TPA 8-16" with piligrimage mills will allow you to master the production of the necessary pipes for the oil and gas industry of Russia, to reduce the consumption of the metal by reducing defects metallurgical and rolling origin, pieces of varying wall thickness and ovality, by rolling tubes with tighter tolerances to reduce the number of rejected pipe carving, and therefore significantly reduce the cost of product pipes of this range.

Data on rolling, passing, threading and the output of hot rolled seamless casing pipe size 426×11 mm with persistent threads "improvement on the buttress-"OTBT-426" steel strength group D on existing and proposed technologies are contained in the table.

Table
View technology.Steel gradeView the just.The size of the ingotsMode and heating technology FirmwareRolling on p/millThe total compression in CALIB. millThe flow rate. coeff. metal to use.The yield on the thread. thread
Temperature. heatingHeating timeThe period of kantowskiThe angle of the edges.Time as well.Size sleevesWalking in diameter.Velich. supplyAngle kantowskiCoeff. the polishing.
---mm°hourmindegminmm%mmdeg-%--
There.DIngots Martin. the outrage.585/540 ×17001280-1300not less than 7.5---620×440 ×2820from 6.0 to 14.818-2290±102,3-2,51,01,37546,4
Guestrooms.585/540 ×17001280-13008,0-8,520-25135≤α≤22525-30 600×440 ×3240from 2.6 to 11.015-2070±52,6-2,82,41,27597,7

1. Method for the production of seamless hot-rolled casing size 426×10-12 mm with persistent threads "improvement on the buttress-"OTBT-426", including the casting of ingots with profit or without profit, repair ingots, heating them to a temperature of plasticity, firmware ingots in sleeves in the camp oblique rolling with an average rise of a diameter of 10.2%, and the length of the ingot from 6.0 to 14.8%, rolling tubes on piligrimages mill diameter 244,5; 273,1; 298,5; 323,9; 339,7; 406,4 and 473,1 mm casting-off sleeves-tube angle (90±10)°, cutting saw to length, heated in a gas furnace roller, the calibration in the calibration mill with a total compression in diameter to 1.0%, the editing on konovalovas straightening machine, electromagnetic inspection, labeling, primary control, trimming ends, preliminary inspection, ultrasonic inspection, surface repair, ultrasonic inspection of the repaired pipe, threading, sweeping-up, navendu couplings, hydraulic testing, inspection, labeling, weighing and painting, with the rolling of pipes made from steel ingots strength group D without profit size 585/540×1700 and ingots with profit size 585/570×1900 mm

2. The method according to claim 1, characterized in that the cone of non-profit and profitable steel ingots strength group D is heated in the reheating furnaces to a temperature 1260-1280° With over 7,5-9,0 h with the casting-off after 20-25 min at angle 135°≤α≤225° and maintained at this temperature for 25-30 minutes

3. The method according to claim 1, characterized in that the non-profit bullion stitch in the camp oblique rolling with the rise in diameter from 5 to 10%, profit from rising in diameter from 2.5 to 5.5%.

4. The method according to claim 1, characterized in that the casing pipe steel strength group D rolled on piligrimages mill feed sleeve in the deformation zone of 15-20 mm, with a coefficient of polishing from 2.5 to 3.0 and a casting-off sleeves-tube angle (70±5)°.

5. The method according to claim 1, wherein a hot rolled seamless casing pipes are calibrated in the calibration mill with a total compression in diameter 2.4 to 2.8%.



 

Same patents:

FIELD: rolled tube production, namely rolling of large- and mean-diameter tubes of cold-resistant and corrosion-resistant steels, possibly in tube rolling plants with pilger mills including helical rolling mills.

SUBSTANCE: method comprises steps of casting ingots; drilling central opening with diameter 100±5.0 mm; heating ingots till yielding temperature; piercing ingots to sleeves in skew rolling mills; rolling tubes in pilger mills. Tubes of cold resistant and corrosion resistant steels are rolled from continuously cast billet with diameter 430 mm without central opening; tubes with diameter 273 and 299 mm are rolled in pilger mill from sleeves pierced in skew rolling mills at diameter raise 4.5 - 5.0% ; tubes with diameters 325 and 351 mm are rolled from sleeves pierced at diameter raise 15 - 20% and tubes with diameters 377 and 426 mm rolled of sleeves pierced at diameter raise 21 - 30%. Continuously cast billets are heated for piercing at rolling tubes with diameters 273 and 299 mm till temperature 1230 -1250°C; at rolling tubes with diameters 325 and 351 mm - till temperature 1250 -1270°C; at rolling tubes with diameters 377 and 426 mm - till temperature 1270 - 1290°C. Continuously cast billets are pierced in skew rolling mill at elongation factor 1.5 - 1.6; tubes are rolled in pilger mill at elongation in range 7.5 - 15.0 while rolling tubes with diameter 273 mm at large elongation values and tubes with diameter 426 are rolled with less elongation values. Tubes with diameters 273 and 299 mm are rolled with triple length and tubes with diameters 325, 351, 377 and 426 mm are rolled with double length. Continuously cast billets are pierced to sleeves with diameter raise 4.5 - 5.0% at revolution number of rolling rolls 44-40 rev/min; with diameter raise 15 - 20% at revolution number of rolling rolls 40 - 38 rev/min and with diameter raise 21 - 30% at revolution number of rolling rolls 38 - 36 rev/min.

EFFECT: lowered metal consumption for making tubes, simplified operations for restoring tubes by removing outer and inner flaws before and after ultrasound flaw detection, reduced cost of conversion continuously cast billet - cold resistant tube, improved effectiveness of producing tubes of given assortment.

5 cl, 1 tbl

FIELD: rolled tube production, namely rolling of large- and mean-diameter tubes of cold-resistant and corrosion-resistant steels, possibly in tube rolling plants with pilger mills including helical rolling mills.

SUBSTANCE: method comprises steps of casting ingots; drilling central opening with diameter 100±5.0 mm; heating ingots till yielding temperature; piercing ingots to sleeves in skew rolling mills; rolling tubes in pilger mills. Tubes of cold resistant and corrosion resistant steels are rolled from continuously cast billet with diameter 430 mm without central opening; tubes with diameter 273 and 299 mm are rolled in pilger mill from sleeves pierced in skew rolling mills at diameter raise 4.5 - 5.0% ; tubes with diameters 325 and 351 mm are rolled from sleeves pierced at diameter raise 15 - 20% and tubes with diameters 377 and 426 mm rolled of sleeves pierced at diameter raise 21 - 30%. Continuously cast billets are heated for piercing at rolling tubes with diameters 273 and 299 mm till temperature 1230 -1250°C; at rolling tubes with diameters 325 and 351 mm - till temperature 1250 -1270°C; at rolling tubes with diameters 377 and 426 mm - till temperature 1270 - 1290°C. Continuously cast billets are pierced in skew rolling mill at elongation factor 1.5 - 1.6; tubes are rolled in pilger mill at elongation in range 7.5 - 15.0 while rolling tubes with diameter 273 mm at large elongation values and tubes with diameter 426 are rolled with less elongation values. Tubes with diameters 273 and 299 mm are rolled with triple length and tubes with diameters 325, 351, 377 and 426 mm are rolled with double length. Continuously cast billets are pierced to sleeves with diameter raise 4.5 - 5.0% at revolution number of rolling rolls 44-40 rev/min; with diameter raise 15 - 20% at revolution number of rolling rolls 40 - 38 rev/min and with diameter raise 21 - 30% at revolution number of rolling rolls 38 - 36 rev/min.

EFFECT: lowered metal consumption for making tubes, simplified operations for restoring tubes by removing outer and inner flaws before and after ultrasound flaw detection, reduced cost of conversion continuously cast billet - cold resistant tube, improved effectiveness of producing tubes of given assortment.

5 cl, 1 tbl

FIELD: rolled tube production, namely processes for producing hot rolled commercial and conversion tubes of large and mean diameters of hard-to-form steels and alloys, possibly in tube rolling plants with pilger mills.

SUBSTANCE: method comprises steps of casting ingots by electroslag refining; drilling central opening with diameter 100 ± 5.0 mm; heating them till yielding temperature; piercing ingots to sleeves; rolling mean-diameter tubes in pilger mills to commercial or conversion tubes; secondary heating sleeves till yielding temperature; rolling them out in skew rolling mill to sleeves at thinning their walls; rolling commercial or conversion tubes of large and mean diameters in pilger mills depending upon kind of steel; or drilling and boring electroslag refining ingots to hollow ingots whose inner diameter exceeds by 40 - 50 mm diameter of mandrel; heating them till yielding temperature and rolling in pilger mills to hot rolled commercial or conversion tubes. Tubes rolled in pilger mills from hollow ingots of electroslag refining at elongation factor more than 5 are used as commercial tubes. Tubes rolled at elongation factor less than 5 are used as conversion tubes. Rolling of tubes from hollow billets in pilger mill is realized at bottom end of tubes turned forward and pilger head is formed from contracted portion. Invention provides lowered metal consumption, reduced quantity of flaws such as slivers and scabs, lowered load of drive unit of pilger mills due to optimal deformation parameters, eliminate breakage of spindles and rolls.

EFFECT: lowered cost of producing tubes of high-cost hard-to-form steels and alloys in tube rolling aggregates with pilger mill.

3 cl, 1 tbl

FIELD: rolled tube production, namely processes for producing hot rolled commercial and conversion tubes of large and mean diameters of hard-to-form steels and alloys, possibly in tube rolling plants with pilger mills.

SUBSTANCE: method comprises steps of casting ingots by electroslag refining; drilling central opening with diameter 100 ± 5.0 mm; heating them till yielding temperature; piercing ingots to sleeves; rolling mean-diameter tubes in pilger mills to commercial or conversion tubes; secondary heating sleeves till yielding temperature; rolling them out in skew rolling mill to sleeves at thinning their walls; rolling commercial or conversion tubes of large and mean diameters in pilger mills depending upon kind of steel; or drilling and boring electroslag refining ingots to hollow ingots whose inner diameter exceeds by 40 - 50 mm diameter of mandrel; heating them till yielding temperature and rolling in pilger mills to hot rolled commercial or conversion tubes. Tubes rolled in pilger mills from hollow ingots of electroslag refining at elongation factor more than 5 are used as commercial tubes. Tubes rolled at elongation factor less than 5 are used as conversion tubes. Rolling of tubes from hollow billets in pilger mill is realized at bottom end of tubes turned forward and pilger head is formed from contracted portion. Invention provides lowered metal consumption, reduced quantity of flaws such as slivers and scabs, lowered load of drive unit of pilger mills due to optimal deformation parameters, eliminate breakage of spindles and rolls.

EFFECT: lowered cost of producing tubes of high-cost hard-to-form steels and alloys in tube rolling aggregates with pilger mill.

3 cl, 1 tbl

FIELD: rolled tube production, namely process for rolling seamless hot rolled casing tubes for cutting buttress thread in standard and in cold resistant variant, possibly in tube rolling plant with pilger mills.

SUBSTANCE: method comprises steps of casting ingots with head, without it or continuously cast billets; heating them till yielding temperature; piercing in skew rolling mill to sleeves; rolling tubes in pilger mill; sizing them in sizing mill and in presses for calibrating end portions to nominal outer diameter in cold state 426 mm with limit fluctuation from nominal size (+1.0) - (-0.5)%. Such calibration is performed for minimum outer diameter in cold state whose value exceeds nominal diameter by 0.4 mm. Invention allows produce tubes with size 426 x 10 - 12 mm with buttress thread in tube rolling plant 8 -16".

EFFECT: lowered metal consumption, enhanced efficiency of threading, cutting off equipment and of hydraulic press, decreased cost of tube conversion of given assortment.

1 tbl

FIELD: rolled tube production, namely tube rolling process, possibly in tube rolling plants with pilger mills.

SUBSTANCE: method for producing tubes of cast ingots of austenite class steels comprises steps of piercing ingots to sleeves; rolling sleeves to tubes of target size; subjecting them to heat treatment; straightening tubes in skew-roll straightening machine. Tubes with relation of diameter to their wall thickness equal to or less than 7.3 in cold state are subjected to multiple deformation in straightening machine where rolls are mounted in horizontal plane without tube camber. Before each pass rolls are drawn together by value Δ ≤ 0.005 Dr where Dr -real diameter of tube, mm. Deformation of tube in desired number of passes is interrupted after burrs appear on back end of tube.

EFFECT: improved stable mechanical properties of thick wall rolled tubes.

3 cl

FIELD: manufacture of rolled products, namely gages for calibrating working tool for tube cold rolling.

SUBSTANCE: in calibrating gage for working tool development of profile of outer working tool and profile of inner working tool are in the form of curves having portions for reducing, crimping and calibrating. Curves of profiles of crimping portions of outer and inner working tools depend upon factor Q of tube working. Said factor changes according to law of monotonic descending function and it is equal to relation of logarithmic reduction value of tube wall to logarithmic reduction value of tube mean diameter. Range of Q factor change is set according to yielding resource of rolled material. Factor Q = Q init x e-q * x/l where q = ln Q init/Q fin - boundary factor; l - length of crimping portion of outer and inner working tools; x - current length of portion of outer and inner working tools in designed range; Qinit , Qfin - boundaries of range of changing of Q factor. Curves of profiles are determined by means of next equation Dmean i-1 / Dmean i= (ti-1 /t i)1/Qi where Dmean i - mean diameter of tube in i-section equal to sum of diameter of inner working tool and tube wall thickness or to difference of diameter of outer working tool and tube wall thickness; ti - thickness of tube wall for i-section; Qi -factor of tube working for i-section.

EFFECT: improved quality of rolled tubes due to uniform distribution of residual stresses along tube length.

3 cl, 1 dwg, 2 tbl, 2 ex

FIELD: rolled tube production, namely process for straightening end curvature of cold rolled large- and mean-diameter tubes.

SUBSTANCE: method comprises steps of rolling tubes on cone mandrel in cold rolling mill while front end of cone mandrel is spaced from outer guide by distance 850 - 900 mm and inner diameter of guide exceeds outer diameter of tube by 30 - 40 mm. Then tube is straightened in six-roll straightening machine. End curvature of tube is straightened by means of detachable cylindrical inserts mounted onto mandrel stem with possibility of rotation and translation motion relative to stem. Said inserts are fixed at end side of stem by means of washer and fastening screw. Length of cylindrical inserts is determined according to expression Lin = K x Dt, where Dt - outer diameter of tubes, mm; K = (1.5 - 3.0), coefficient having large values for rolling tubes with smaller diameters. Diameter of cylindrical inserts is determined according to expression Din = Din. t - Δ, where Din.t - inner diameter of tubes, mm; Δ = (0.5 - 1.0) - gap between inner diameter of tube and outer diameter of insert whose large values correspond to tubes with larger wall thickness, mm. Front end of insert is rounded by radius whose value is determined according to expression R = Ro - R fr , where Ro - radius of cylindrical insert, mm; R fr - radius of front end of mandrel, mm. Detachable cylindrical inserts are made of cast iron with spherical graphite; lubricant layer is applied onto said inserts before rolling each tube.

EFFECT: lowered factor of metal consumption, lowered (or completely eliminated) quantity of curvature scrap of tube end.

7 cl, 1 dwg, 1 tbl, 1 ex

FIELD: rolled tube production, namely production of casing tubes for thread cutting, possibly in well known tube rolling aggregates with pilger mills and also in tube rolling aggregates with new generation of pilger mills controlled by means of computers.

SUBSTANCE: method comprises steps of heating ingots and continuously cast billets till yielding temperature; piercing them to sleeves in skew rolling mills; rolling tubes on long mandrel in pilger mills and sizing them in calibration mill. Deformation value along rolled tube lengths in pilger mill is cyclically decreased by (n+1) times where n - number of multiple tubes, pieces. Said deformation is decreased due to opening rolls by value determined according to expression Δ = (1.0 - 2.0)H where H - height of initial thread profile, mm. Deformation is decreased in portions of tubes whose lengths are determined according to expression L = Lc + K where Lc - length of coupling, mm; K = 50 - 150 mm, factor taking into account waste value and allowance along length of multiple tubes at working their ends with thickened wall, mm. Tube lengths are cut by multiple tubes along center of thickened portions. Nominal inner diameter of tube end portions is lowered at calibration by value determined with use of expression Din = Dnom - K1, where Dnom - nominal inner diameter of tube, mm; K1 - coefficient taking into account lowered inner diameter of end portions of casing tubes at calibration, mm; K1 ≤ 3 for tubes with diameter 245 - 340 mm and K1 ≤ 4 for tubes with diameter 351 - 508 mm. Casing tubes are rolled in such a way that to provide their wall thickness less by 1.0 - 1.5 mm than respective nominal thickness of wall according to standard given in specification. All operations and calculations are performed with use of computer. Invention allows produce for oil and gas industry branches of Russia tubes having high reliability of their threaded joints, lower nominal wall thickness of tubes by 1.0 -1.5 mm.

EFFECT: lowered metal consumption due to reduced number of flaws of threaded joints and reduced wall thickness of tubes, improved efficiency of threading, of cut-off equipment and of hydraulic press, decreased cost of conversion of tubes of given size.

13 cl, 1 tbl

FIELD: tube production, namely production of tubes of low ductile steel with given boron content in tube rolling plants with pilger mills for further conversion of such tubes to hexahedral tubes for compacted storage of waste nuclear fuel.

SUBSTANCE: method for producing tubes of steel with boron content 1.3 -1.8% comprises steps of casting by means of electroslag refining hollow ingots with size 480 -490 x 270 in. x 2300 -2500 mm; boring them and turning for removing air holes and flux traces and producing hollow blanks with size 470 - 480 x 280 in. x 2300 - 2500 mm with surface roughness Rz ≤ 40 micrometers; forming on ends of hollow blanks (corresponding to bottom ends) at outer side - blunted cone along length L = (1.5 - 2)Sbl with blunting value h = (5.0 - 6.0) St, where Sbl - wall thickness of hollow blanks of electroslag refining, mm; St - wall thickness of conversion tubes, mm; h - blunting value of wall of hollow blanks of electroslag refining, mm. Blanks are heated till plasticity temperature 1040 -1060°C, rolled on mandrels with diameter 264/265 mm in pilger mill to conversion tube-bundles with size 290 x 12 x 22000 - 23000 mm at elongation factor μ = 10.7 - 11.4. Technological wastes such as pilger heads and others are cut-off by means of hot cutting saw. Tube-bundles are divided by two tubes of the same length or length multiple to that of conversion blank and then they are subjected to warm straightening in six-roll straightening machine at using heating temperature of rolling process. Invention allows reduce temperature of heating hollow blanks by 20 - 30°C.

EFFECT: elimination of operation for piercing ingots in skew rolling mills, shortened time period for heating hollow blanks, lowered metal consumption, reduced cost of commercial hexahedral tube-blanks.

3 cl, 1 dwg, 1 tbl, 1 ex

FIELD: rolled tube production, namely processes for piercing ingots and billets for making seamless hot-deformed large-diameter tubes.

SUBSTANCE: method comprises steps of heating ingots and billets until yielding temperature; piercing them to hollow thick-wall sleeves in first skew rolling mill for further expanding to thin-wall sleeves in second skew rolling mill and rolling to large-diameter tubes in plants provided with automatic or pilger mills; piercing ingots and billets to thick-wall sleeves in first piercing mill with working rolls driven to rotation in one side and expanding billets to thin-wall sleeves in second piercing mill with working rolls driven to rotation in opposite side.

EFFECT: enhanced geometry of tubes, lowered metal consumption, improved efficiency of tube rolling plants.

1 tbl

FIELD: tube production processes and equipment, namely preparation of rolls of pilger mills for hot rolling of tubes.

SUBSTANCE: method comprises steps of mechanically working portion of roll in roll-turning machine tool with use of contour follower for surfacing it with overlap 5 - 10° to side of cold portion from zero point and from angle of lengthwise outlet; under-flux surfacing working portion with wear-resistant refractory steel layer having allowance for mechanical working; mechanically working rolls with use of contour follower until their ready size and grinding working surface. Mechanical working of rolling portion of roll after surfacing is performed along portion from 0.25 - 0.30 of striker length until end of angle of lengthwise outlet adjoined to polishing portion. Grinding of polishing portion and of 0.25 - 0.30 of angle of lengthwise outlet adjoined to polishing portion is realized. Mechanical working of rolling portion of roll for surfacing from zero point until 0.25 -0.30 of striker portion is performed while taking into account allowance of surfaced layer for finish working.

EFFECT: enhanced strength of rolls of pilger mills, improved accuracy of their geometry size and quality of tube surface, lowered consumption of high-cost steel wire rod.

2 cl, 1 dwg, 1 tbl

FIELD: rolled tube production processes and equipment, namely manufacture of hot deformed mean- and large-diameter tubes of corrosion resistant hard-to-form steels and alloys, possibly making tubes in tube rolling aggregates with pilger mills.

SUBSTANCE: method comprises steps of drilling electroslag-refining ingots or billets with diameter 380-500 mm; holding them on grates of furnace at temperature 500-550°C for 70-95 min depending upon diameter of blank; heating up to temperature 1120 - 1140°C at rate 1.4 - 1.5 °C/min; piercing billets for forming sleeves at revolution number of rolling rolls 25 - 40 rev/min on mandrel with diameter providing reduction degree in pilger mill no less than 25 mm; realizing first piercing of electroslag-refining ingots or billets with diameter 460-600 mm in piercing mill at elongation degree 1.2 -1.4 and at revolution number of rolling rolls 15 -25 rev/min; realizing second and next (if necessary) piercing or expanding processes at diameter fit no more than 5.0%, elongation degree 1.4 -1,75 and revolution number of rolls 25 - 50 rev/min; seasoning cold sleeves after their first piercing with diameter 460-600 mm at relation D/S = 3.0 -4.5 on grates at temperature 400-500°C for 50 - 70 min depending upon sleeve diameter and wall thickness; heating sleeves until yielding temperature 1100 - 1260°C at rate 1.6 - 1.8°C/min depending upon kind of steel; uniformly heating sleeves with temperature 600 - 800 C after piercing mill until yielding temperature 1100 - 1260°C at rate 1.7 - 2.0°C/min; before discharging sleeves out of furnace keeping them for 45 -60 min at plasticity temperature while tilting sleeves in 10-15 min by angle 180є. Process of piercing sleeves that begins from gripping ingots or billets until their complete fitting onto mandrel is realized at decreased revolution number of rolling rolls from 25 until 15 rev/min. Stable piercing process is performed is realized at 15 -20 rev/min. At outlet of sleeve revolution number of rolls is increased up to 35 -40 rev/min. Piercing (expanding) process beginning from gripping sleeve until complete fitting of it onto mandrel is realized at decreased revolution number of rolling rolls from 50 until 20 rev/min. Stable expanding process is realized 20-25 rev/min. At outlet of sleeve revolution number of rolls is increased up to 45 - 50. Tubes are rolled in pilger mill at elongation degree μ = 3.0 - 5.0. Invention provides possibility for making high quality hot deformed tubes of large and mean diameters from corrosion resistant hard-to-form steels and alloys in tube rolling aggregates with pilger mills.

EFFECT: reduced metal consumption factor at conversion of electroslag-refining ingot to hot rolled tube, lowered cost of tubes.

5 cl, 1 tbl

FIELD: drive systems of cold rolling pilger mills.

SUBSTANCE: drive system includes rolling stand that may perform reciprocation motion; at least one crank and connecting rod mechanism operated by means of drive unit and having crank arm with balancing weight at least for partially balancing inertia forces created by rolling stand; connecting rod jointly connecting rolling stand and crank arm; at least one arranged eccentrically and driven to rotation counter-balance for balancing inertia forces and (or) moments of inertia. Motion of crank and connecting rod mechanism and counter-balance is synchronized by means of gearing. At least one crank and connecting rod mechanism is provided with single counter-balance. Motion plane of balancing weight of crank and connecting rod mechanism driven to rotation coincides with motion plane of counter-balance driven to rotation. Crank and connecting rod mechanism, counter-balance and drive unit are mutually joined through gearing. Drive unit through said gearing drives shaft joined with counter-balance. Mounted on shaft pinion of said gearing through other gearing drives shaft joined with crank and connecting rod mechanism. Balancing weight or counter-balance is in the form of eccentrically arranged mass of one gear wheel of gearing.

EFFECT: lowered cost for maintaining simplified -design rolling mill, reduced investment cost.

11 cl, 10 dwg

FIELD: drive systems of rolling mills, namely of pilger cold rolling mill.

SUBSTANCE: drive system includes at least one rolling stand mounted with possibility of reciprocation motion; at least one crank and connecting rod mechanism having crank arm with balancing weight at least for partially compensating inertia forces of rolling stand; drive unit and connecting rod jointly connecting rolling stand and crank arm; at least one counter-balance mounted with possibility of eccentric rotation in order to compensate inertia forces and (or) moments of inertia. In order to provide effective compensation of inertia forces in simplified drive system, at least one counter-balance is mounted with possibility of driving it to rotation by means of autonomous drive unit isolated from drive unit of crank and connecting rod mechanism. Said autonomous drive unit of counter-balance acts in rotation direction opposite to rotation direction of crank arm. Mass values of mass of rolling stand, balancing weight, counter-balance are selected in such a way that to compensate as possible first-order components of inertia forces of rolling stand at operation of drive system. System is provided with unit for controlling or regulating autonomous drive unit depending upon angle ϕ6 and (or) revolution number of crank arm. Rotation center of counter-balance is selected in such a way that including inertia forces of rolling stand and (or) balancing weight moments of inertia of all masses of drive system are at least significantly compensated.

EFFECT: enhanced efficiency, simplified design of rolling mill.

13 cl, 1 dwg

FIELD: production of conversion tubes of low-ductility steel with boron content 1.3 - 1.8%.

SUBSTANCE: method comprises steps of drilling ingots of electroslag refining, heating them till ductility temperature, piercing in piercing mill for making sleeves; rolling sleeves in pilger mill to tube-blanks, cooling, repairing, cutting tube-blanks by two blanks, heating them up to ductility temperature, piercing-rolling in piercing mill and rolling conversion tubes in pilger mill. Ingots of electroslag refining with diameter 460 - 480 mm are drilled from their bottom end along length L = H - B, where H - height of ingot, mm; B - under-drilled part of ingot equal to 100 - 120 mm. Then ingots are soaked at temperature 450 - 500°C on grates of heating furnace without tilting for 90 - 120 min; heated till 800 - 850° C at rate 1.8 - 2.0°C/min; then heated up to ductility temperature 1050 - 1090°C at rate 2.1 - 2.2°C/min at tilting in 15 - 20 min and soaked at such temperature for 70 - 80 min at tilting by angle about 180° in 10 -15 min.

EFFECT: lowered content of waste material, improved quality of conversion tubes, reduced cost of ready product.

5 cl, 1 tbl

FIELD: production of conversion tubes of low-ductility steel with boron content 1.3 - 1.8%.

SUBSTANCE: method comprises steps of drilling ingots of electroslag refining, heating them till ductility temperature, piercing in piercing mill for making sleeves; rolling sleeves in pilger mill to tube-blanks, cooling, repairing, cutting tube-blanks by two blanks, heating them up to ductility temperature, piercing-rolling in piercing mill and rolling conversion tubes in pilger mill. Ingots of electroslag refining with diameter 460 - 480 mm are drilled from their bottom end along length L = H - B, where H - height of ingot, mm; B - under-drilled part of ingot equal to 100 - 120 mm. Then ingots are soaked at temperature 450 - 500°C on grates of heating furnace without tilting for 90 - 120 min; heated till 800 - 850° C at rate 1.8 - 2.0°C/min; then heated up to ductility temperature 1050 - 1090°C at rate 2.1 - 2.2°C/min at tilting in 15 - 20 min and soaked at such temperature for 70 - 80 min at tilting by angle about 180° in 10 -15 min.

EFFECT: lowered content of waste material, improved quality of conversion tubes, reduced cost of ready product.

5 cl, 1 tbl

FIELD: tools for die rolling of cone elongated hollow metallic articles by hot rolling of cylindrical tubes in pilger mills at lowered diameter and wall thickness from one end of tube to other.

SUBSTANCE: roll for die rolling includes along circle of its barrel round cross section groove with outlets. Length of said groove includes successively arranged striker formed by radius of roll ridge of increased length, having constant angles of cross outlet in one third of striker length and smoothly lowered in its remaining part till outlets of polishing portion ( radius of roll ridge in end of portion with constant value of cross outlet consists 1.3 of radius of roll ridge in the beginning of said portion), polishing portion with constant radius of roll ridge, transition portion and idle portion. Round variable groove pass with cross outlets is arranged along helical line on cylindrical surface of roll with ideal diameter. Number of pitches of helical line is determined as n = (L sin α)/(2πRr) + B + B1 , where L - length of cone article, mm; Rr - rolling radius of roll, mm; α -inclination angle of axis of roll grooved pass relative to axis of roll, °; B - length of idle portion at inlet equal to (0.20 - 0.25)n; B1 -length of idle portion at outlet equal to (0.10 -0.15)n. Semipass of upper roll has left-hand and semipass of lower roll has right-hand direction of helical line or vice versa. Groove of roll is half round one with cross tangential or oval outlets with angles 30 - 32°. Values of said angles are constant ones, they are equal to 30 -35° for central angle and they are smoothly decreased to outlet cross section to 20 - 18°.

EFFECT: possibility for making by hot rolling cone elongated hollow metallic articles having improved strength at significantly lowered mass, reduced cost of articles.

4 cl, 1 dwg

FIELD: rolled stock production, namely manufacture of elongated conversion large- and mean-diameter tubes of centrifugally cast hollow billets and ingots of electroslag refining of steels 08X10H20T2 and 08X10H16T2 for telescopic systems of periscopes of submarines while providing values of impact viscosity KCU more than 100 J/cm2.

SUBSTANCE: method comprises steps of producing centrifugally cast billets, heating them till ductile temperature, rolling in pilger mill to thick-wall tubes with allowance for mechanical working, subjecting tubes to heat treatment. In pilger mill conversion hot rolled tubes are rolled while taking into account 1 - 3 rerolling procedures in cold rolling mills depending upon type of billet and dimension of ready product (length, diameter, wall thickness). Conversion hot rolled tubes are rolled to intermediate and final sizes in cold rolling mills at elongation value μ = 1.2 - 1.55. Centrifugally cast hollow billets and drilled ingots of electroslag refining are soaked on grates of furnace without tilting them at 950 -1000°C for 180 - 300 min of homogenization depending upon diameter and wall thickness. Then centrifugally cast billets are uniformly heated up to 1150 -1200°C at heating rate 2.3 - 2.5° C/min at tilting in periods of 15 - 20 min at total period of heating 8 - 11 hours. Ingots of electroslag refining are heated up to 1200 -1250°C at heating rate 1.8 - 2.0°C/min while tilting them in 20 - 25 min for total heating period 9.5 - 12.5 hours. Large-size billets and ingots are heated for more long periods. Centrifugally cast hollow billets are rolled in pilger mill to hot rolled conversion tubes while taking into account 2 - 3 next rerolling of them in cold rolling mills. Sleeves pierced of ingots are rolled in pilger mill to conversion hot rolled conversion tubes while taking into account 1 - 2 rerolling processes in cold rolling mills. Ingots with diameter up to 500 mm are pierced in skew rolling mill to sleeve at one piercing operation with elongation value μ = 1.2 - 1.4. Ingots with diameter 540 mm and more are pierced at two piercing operations with elongation value μ1 = 1.2 -1.4 and μ2 = 1.1 - 1.3 respectively. Conversion elongated cold rolled tubes after rolling them to intermediate size are subjected to austenitization in mode providing temperature of furnace space at time moment of charging in range 1000 - 1100°C, heating according to power of furnace up to 1050 ± 15°C, soaking at such temperature for 1 min per 1 mm of tube wall thickness and cooling in air. Conversion elongated cold rolled tubes of ready size after rolling and austenitization are subjected to heat treatment - tempering in mode providing charging at 700 - 730°C; heating according to power of furnace; soaking at temperature 685 ± 15°C for 5 - 5.5 h; cooling in air.

EFFECT: strict geometry size of diameter and thickness of walls of elongated conversion tubes, lowered metal consumption, enhanced operational reliability of ready products.

8 cl, 2 tbl

FIELD: electrical engineering.

SUBSTANCE: proposed method that can be used to control systems incorporating frequency converter with off-line voltage inverter and induction motor operating into mechanisms handling alternating cyclic load (deep-well pimps, crank gear drive mechanisms, and the like) involves automatic correction of motor speed as function of voltage deviation in dc current section from maximal permissible value which makes it possible to dispense with energy dissipating and rectifying devices affording recuperation mode.

EFFECT: reduced cost and maintenance charges, enhanced operating reliability.

1 cl, 1 dwg

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