RU2311980C1 - Method for producing hot rolled commercial and conversion tubes with large and mean diameters from hard-to-form steels and alloys in tube rolling plants with pilger mills - Google Patents

Abstract

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

SUBSTANCE: method comprises steps of casting hollow ingots with height 2000 - 3200 mm in electroslag refining plants; turning and boring ingots for removing scale and micro-crackings till diameter 400 -620 mm at relation of diameter to wall thickness D/S = 4.5 - 7.0 whose larger values correspond to ingot-sleeves of less diameters; rolling hollow ingot-sleeves heated till yielding temperature with relation D/S = 5.0 -7.0 and height 2000-2750 mm in pilger mill to commercial and conversion tubes with wall thickness up to 30 mm; rolling ingot-sleeves with relation D/S = 4.5 - 5.5 and height 2750 - 3200 mm in pilger mill to conversion tubes with wall thickness more than 30 mm.

EFFECT: lowered metal consumption, elimination from manufacturing process one operation of heating and piercing drilled ingots to sleeve, enhanced efficiency, increased length of conversion and commercial tubes with larger thickness of walls.

2 cl, 1 tbl

Description

The invention relates to pipe rolling production, and in particular to a method for the production of hot-rolled commodity and conversion pipes of large and medium diameters from hardly deformable grades of steel and alloys, and can be used in pipe rolling installations with pilgrim mills in the production of pipes from steel and alloys of grades 08X18H10T, 12X18H12T, 08X17H15MZT , 10Х23Н18, 08Х20Н15С2, 10Х17Н13М2Т, 09Х14Н13Б2СР, 17Х18Н9, 08Х22Н6Т, 08Х10Н16Т2, 08Х10Н20Т2, ХН32, ХН78Т, 06ХН28МДТ, ХН60ВТ, ХН30МДБ, 15Х51, 15Х51, etc.

In pipe-rolling production, a method is known for producing hot-rolled commodity and conversion pipes of large and medium diameters in pipe-rolling plants with pilgrim mills from centrifugally cast hollow billets of stainless steel grades 08Х18Н12Т, 08Х18Н10Т, 08Х10Н20Т2, and 08Х10Н16Т2 (ТУ 14-3-5інкиніпні cast hollow from steel grades 08X18H12T, 08X18H10T, 08X10H20T2 and 08X10H16T2 with a diameter of 530-650 mm ", TU 14-3-1564-88" Seamless hot-deformed pipes from steel of the grades 08X10H20T2 and 08X10H16T2 for retractable systems ", TI 158-Tr. TB1 6-94 "Production of pipes from a hundred whether grades 08X10H20T2 and 08X10H16T2 according to TU 14-3-1564-88 ", TU 14-3-743-78" Seamless hot-rolled pipes from steel grade 08X18H12T ", TI 158-Tr. TB1-63-98" Production of seamless hot-rolled pipes from steel grade 08X18H12T for chemical engineering and for shirts of hydraulic cylinders of pilgerstan forgollers ", TU 14-3-765-78" Seamless hot-rolled stainless steel pipes ", TI 15 8-Tr. TB 1-69-98" Production of seamless hot-deformed steel pipes brand 08X18H12T for cylinders ").

The disadvantage of this method is that the pipes after rolling have a large number of defects on the outer and inner surfaces in the form of captivity and friability and require subsequent machining (turning and boring) with the removal of metal 10-12 mm per side or 20-25 mm the wall. Hot rolled pipes measuring 402 × 45 mm are machined and bored to a size of 377 × 20 mm, i.e. more than 50% of the metal goes into shavings. Since hot-rolled pipes roll with thick walls, i.e. with small hoods (μ = 2.0-3.5), then large grains occur in the microstructure of the pipe metal, and therefore, the pipe metal has low mechanical properties and does not withstand intergranular corrosion tests (Section 2.8 TU 14-3- 765-78 states that the macrostructure of the metal of the pipes should be dense, without traces of shrinkage friability, delamination, cracks, voids), and the results of the initial tests for micro- and macrocontrol are final.

In pipe-rolling production, a method is known for producing pipes from hardly deformable 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 heating to a temperature of 1120-1140 ° C at a speed of 1.4-1.5 deg./min, piercing the blanks and ingots of ESR into the sleeves size in size by diameter at a speed of rotation of the work rolls 25 -40 rpm on a mandrel with a diameter, I provide reducing them on a pilger mill of at least 25 mm (RF patent №2175899, Bul. №32, 20.11.2001).

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 oblique rolling mill, cannot be sewn.

A method for producing hot-deformed pipes of large and medium diameters from corrosion-resistant hard-deformed steel and alloy grades on TPA with pilgrim mills is also known in pipe rolling production. It includes drilling a central hole with a diameter of 100 ± 5.0 mm in ESR ingots and billets, heating them to a ductility temperature , the first flashing of ESR ingots or blanks with a diameter of 460-600 mm in a piercing mill with a hood 1.2-1.4 at a speed of rotation of the work rolls of 15-25 rpm, and the second and subsequent, if necessary, flashing -rolls with a rise or run in diameter of not more than 5.0% and a hood of 1.4-1.75 at a roll rotation speed of 20-50 rpm, using cold or hot shell linings in the furnace, the process of flashing from picking ESR ingots or blanks until they are completely on the mandrel with a decrease in the number of revolutions of the work rolls from 25 to 15, the steady-state flashing process at 15-20 rpm, and at the exit of the sleeve from the rolls, the number of revolutions increase to 35-40 rpm, the flashing process rolling (second firmware) from the capture of the sleeve to the full location on the mandrel lead to by increasing the number of revolutions of the work rolls from 50 to 20, the steady-state rolling process at 20-25 rpm, and at the exit of the sleeve from the rolls, the number of revolutions is increased to 45-50, and the tubes are rolled on a pilgrim mill with an exhaust hood μ = 3.0- 5.0 (RF patent №2247612, bull. No. 7, 03/10/2005).

The disadvantage of this method is that when rolling pipes with a diameter of more than 325 mm, double piercing and double heating using cold or hot chuck are necessary, and this entails a decrease in the productivity of injection molding machines with pilgrim mills ≈ two or more times, an increase in the expenditure coefficient of metal from due to double burning and, as a result, an increase in the cost of finished products.

In pipe-rolling production, a method of rolling pipes on pilgrim mills is known, where the inner diameter of the sleeve blanks is determined by the degree of introduction of the mandrel into the sleeve blanks, i.e. so that the gap between the inner diameter of the blanks-sleeves and the diameter of the mandrel would be minimal and sufficient for its introduction. This gap is 10-25 mm. Larger values refer to large pipe diameters (F.A. Danilov et al. Hot rolling of pipes, Metallurgizdat, 1962, p. 294). The disadvantage of this method of rolling blanks-sleeves from hard-deformed grades of steel and alloys is the formation of defects in the form of flaws and landing blanks-sleeves on the mandrel (tightening the mandrels in the blanks-sleeves) due to the small gap between the inner diameter of the blanks-sleeves and mandrels. With a small gap, during deformation, a large contact surface forms at the metal – mandrel interface, metal flow along the mandrel is hindered by an increase in friction forces, as a result, more plastic surface metal layers break the metal layers on the inner surface of the pipe, which is also aggravated by natural heat removal Dornom. In addition, a small reduction in diameter creates a small ovalization, which leads to the fit of the sleeve tubes on the mandrels as they are rolled and cooled (tightening the mandrels), i.e. to the termination of the rolling process and, as a consequence, to increased marriage and metal consumption.

A well-known technical solution is a method for the production of hot-rolled conversion tubes from steel grade 20X25H25TY-Sh of size 325 × 0 mm for the manufacture of water-cooled furnace rollers of size 295 × 22 × 2750 mm, including drilling and boring of ESR ingots of size 480 × 1600 mm for a diameter of 285 + 5 / -0 mm, heating them to the temperature of plasticity, rolling on pilgrim mills into pipes of 325 × 40 mm in size on mandrels with an increased taper of 246/238 mm with a difference (gap) between the inner diameter of the drilled ingots-shells and the maximum diameter of the dorons equal to 40- 45 m, and the drawing coefficient μ = 3.4 (protocol No. 1031 for agreeing on the conditions for the supply of pipes made of steel 20Kh25N25TYu-Sh dated 12/14/2000 and a letter indicating pilot trial rolling of hot-rolled steel tubes of 325 × 40 mm in size from steel of the brand 20Х25Н25ТЮ-Ш).

The disadvantage of this method is the use of bored ingot sleeves with an inner diameter greater than the diameter of the mandrel by 40-50 mm, because with smaller gaps on the inner surface of the pipes defects are formed in the form of flaws and frequent "tightening" of the mandrels, even with increased taper. The operation of boring ingots from a diameter of 100 mm to 285-290 mm is laborious and leads to increased consumption of metal, because when boring, 30 to 45% of the metal goes into shavings. The amount of chips increases with the diameter of the conversion pipe, i.e. the inner diameter of the ingot shells, and this ultimately leads to a significant increase in the cost of the finished product.

The closest technical solution is a method for the production of hot-rolled conversion pipes of large and medium diameters from hard-deformed steel and alloy grades in plants with pilgrim mills, including drilling a central hole with a diameter of 100 ± 5.0 mm in ESR ingots, heating to ductility temperature, expanding them into hollow workpieces with a hood μ = 1.2-1.8 without lifting in diameter, turning and boring them to remove forging defects, heating them to a ductility temperature and rolling on pilgrim mills with a hood μ≤5.0 or drilling ESR ingots with subsequent expansion into hollow billets with a hood μ = 0.9-1.5 with a diameter rise of 1.05 to 1.4 and rolling on pilgrim mills with a hood μ≤5 , 5 (RF patent No. 2242302, Bull. No. 35, 12.20.2004).

The disadvantage of this method is the additional operations of drilling ESR ingots, heating them to a temperature of plasticity and expansion into hollow blanks on radial forging machines or presses, followed by removal of forging or pressing defects by turning and boring, which ultimately leads to an increase expense ratio and a significant increase in the cost of the finished product.

The objective of the proposed method is the elimination of the expensive operation of expanding the ESR drilled ingots into hollow billet blanks, additional heating of the ESR drilled ingots before expansion, and most importantly, it reduces metal consumption during drilling of the ingots and converting them into hollow billet blanks, and, therefore, reduction the cost of hot-rolled commodity and conversion pipes of large and medium diameters from hardly deformable grades of steel and alloys.

The technical result is achieved by the fact that in the known method for the production of hot-rolled commodity and conversion pipes of large and medium diameters from hard-to-deform grades of steel and alloys on pipe rolling plants with pilgrim mills, including casting ingots on electroslag remelting plants, which are grind and bored, heated and rolled into pilgrims mills, electroslag remelting ingots are cast hollow with a height of 2000-3200 mm, grind and bore to remove scale and microcracks to a diameter 400-620 mm with a ratio of diameter to wall thickness D / S = 4.5-7.0, large values of which correspond to ingots - sleeves of smaller diameter, are heated to ductility temperature and rolled on pilgrim mills, hollow ingots - sleeves heated to ductility temperature with a ratio of D / S = 5.0 - 7.0 and a height of 2000-2750 mm are rolled on a pilgrim mill in commodity and conversion pipes with wall thicknesses up to 30 mm, and ingots - sleeves with a ratio of D / S = 4.5-5 , 5 and a height of 2750-3200 mm are rolled on a pilgrim mill in a conversion pipe with a wall thickness of more than 30 mm.

Hollow ingot sleeves cast on ESR installations are machined and bored to remove scale and microcracks with a diameter of 400-620 mm with ratios of diameter to wall thickness D / S = 4.5-7.0, large values of which relate to ingots-sleeves of smaller diameter , and a height of 2000-3200 mm, heated to a temperature of plasticity and rolled on pilgrim mills in commodity and conversion pipes. Sleeves with a ratio of D / S = 5.0-7.0, i.e. more thin-walled, 2000-2750 mm high, are rolled on a pilgrim mill into commodity and conversion pipes with wall thicknesses up to 30 mm, and ingot shells with a D / S ratio of 4.5-5.5 and a height of 2750-3200 mm are rolled on a pilgrim stand in the conversion pipe with a wall thickness of more than 30 mm, because when rolling pipes with a thicker wall, the feed rate on the pilgrim mill is higher and the temperature of the sleeve by the end of rolling does not drop below 750 ° C, which makes it possible to carry out the rolling process from longer sleeves, and therefore, reduce the expenditure coefficient of the metal due to the relative reduction in the share of technological waste (weight of pilger heads and seed ends).

A comparative analysis of the proposed solution with the prototype shows that the claimed method differs from the known one in that the electroslag ingots are re-melted by hollow 2000-3200 mm high, grind and bore to remove scale and microcracks by a diameter of 400-620 mm with a ratio of diameter to wall thickness D / S = 4.5-7.0, large values of which correspond to ingots - sleeves of smaller diameter, are heated to plasticity temperature and rolled on pilgrim mills, and hollow ingots heated to plasticity temperature are sleeves with a ratio D / S = 5.0-7.0 and a height of 2000-2750 mm are rolled on a pilgrim mill in commodity and conversion pipes with wall thicknesses up to 30 mm, and ingots are sleeves with a ratio of D / S = 4.5-5, 5 and a height of 2750-3200 mm are rolled on a pilgrim mill in a conversion pipe with a wall thickness of more than 30 mm. 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 a pipe-rolling installation with pilgrim mills 8-16 of "ChTPZ" OJSC when rolling commodity pipes 377 × 25 mm in size and 377 × 45 mm in size with solid and hollow ingots EShP steel grade 10X17H13M2T, cast on a pilot plant EShP OJSC "ZMZ ". In production were set 10 solid ESR ingots of 540 × 1650 mm in size, 5 hollow ESR ingots of 540 × 90 × 2750 mm in size with a D / S ratio of 6.0 and 5 hollow ESR ingots of 540 × 110 × 3200 mm in size with a ratio D / S = 4.9, which is consistent with claim 2. The center was drilled in solid-state ESP ingots under the conditions of OAO ChTPZ an open hole with a diameter of 100 ± 5.0 mm. Rolling of commodity pipes 377 × 25 mm in size from solid ESR ingots was carried out in two firmwares, since firmware ESHG ingots from steel grade 10X17H13M2T could not be flashed for one firmware due to excess load on the firmware drive The first firmware was made on a mandrel with a diameter of 250 mm in sleeves measuring 540 × 138 × 2100 mm, the length of the sleeve is limited by the input side of the piercing mill, because with the second rolling firmware, it is impossible to set a sleeve longer than 2100 mm into the mill. Before the first flashing, the ESR ingots were heated in the furnace for 9.0 hours to a plasticity temperature of (1250-1260) ° С. Posad liners for the second firmware were made using hot posad, i.e. at a temperature of 600-700 ° C. The heating time for the second firmware was 6.5 hours. The second firmware for rolling commodity pipes was made on a mandrel with a diameter of 350 mm. The size of the sleeves was 540 × 88 × 2950 mm. The liners were rolled on a pilgrim mill in commodity pipes measuring 377 × 25 mm. The average length of pipes at delivery was 9.95 m, total 49.75 m. 10.796 tons of pipes were commissioned in accordance with the technical documentation. The expenditure coefficient of the metal for this batch amounted to 1.374.

Rolling of conversion tubes of 377 × 45 mm in size from solid ESR ingots using the existing technology was also carried out in two firmwares. The first firmware was produced on a mandrel with a diameter of 250 mm in sleeves measuring 540 × 138 × 2100 mm. Before the first flashing, the ESR ingots were heated in the furnace for 9.0 hours to a plasticity temperature of (1250-1260) ° С. Posad liners for the second firmware were made using hot posad, i.e. at a temperature of 600-700 ° C. The heating time for the second firmware was 6.5 hours. The second firmware for rolling pig tubes was made on a mandrel with a diameter of 325 mm. The size of the sleeves was 540 × 100 × 2650 mm. The liners were rolled on a pilgrim mill in a conversion pipe size of 377 × 45 mm. The average length of pipes at delivery was 5.85 m, and the total length was 29.25 m. 10.794 tons of pipes were commissioned in accordance with the technical documentation. The expenditure coefficient of the metal for this batch amounted to 1.374.

According to the proposed technology, rolling of commodity pipes 377 × 25 mm in size was made from hollow ESR ingots of 540 × 90 × 2750 mm in size, which were heated in a methodical furnace to a ductility temperature (1240-1250) ° С. The average heating time of hollow ingots was 7.0 hours. Hollow ingots heated to plasticity temperature were fed by a crane to a pilgrim mill and rolled into pipes 377 × 25 mm in size. The average pipe length at the rental was 9.65 m, and the total length was 48.25 m. 10.471 tons of pipes were commissioned in accordance with the standard technical documentation. The expenditure coefficient of the metal was 1.311.

Converting pipes 377 × 45 mm in size according to the proposed technology were produced from hollow ESR ingots of 540 × 110 × 3200 mm in size, which were heated in a methodical furnace to a ductility temperature (1240-1260) ° С. The average heating time of hollow ingots was 7.5 hours. Hollow ingots heated to plasticity temperature were fed by a crane to the pilgrim mill and rolled into pipes 377 × 45 mm in size. The average pipe length at the rental was 8.55 m, and the total length was 41.75 m. It was commissioned in accordance with NTD 15.406 tons of pipes. The expenditure coefficient of the metal for this batch was 1.211. The data on rolling and delivery of commodity pipes 377 × 25 mm in size and conversion tubes 377x45 mm in size made of 10X17H13M2T steel according to the existing and proposed technologies are given in the table.

Thus, the table shows that according to the proposed method for the production of hot-rolled commodity pipes (GOST 9940) with a size of 377 × 25 mm, a decrease in the expenditure coefficient of the metal by 63 kg per ton of pipes was obtained (from 1.374 to 1.311), the total heating time of the ESR ingots was reduced from 15 , 5 hours to 7.0 hours, i.e. more than 2.0 times, the process of flashing ESR ingots and rolling of sleeves in an oblique rolling mill is excluded, and therefore, an increase in the productivity of the pilgrim installation is correspondingly more than 2.0 times. When rolling conversion pipes of 377x45 mm in size according to the proposed technology, a decrease in the metal consumption coefficient by 163 kg per ton of pipes was obtained (from 1.374 to 1.211), the total heating time of the ESR ingots was reduced from 15.5 hours to 7.5 hours, i.e. more than 2.0 times, the process of flashing ESR ingots and rolling of sleeves in an oblique rolling mill is excluded, and therefore, an increase in the productivity of the pilgrim installation by more than 2.0 times is obtained. According to the proposed technology, through the use of hollow ESR ingots of a larger mass, an increase in the average pipe length from 5.85 to 8.35 m is obtained, i.e. 1.43 times.

Using the proposed method for the production of hot-rolled commodity and conversion pipes of large and medium diameters from hard-to-deform grades of steel and alloys in tube-rolling plants with pilgrim mills will significantly reduce metal consumption, reduce the likelihood of formation of defects in the form of captures and flaws during flashing and rolling of sleeves in oblique rolling mills to exclude from the process double heating and double firmware (firmware and rolling), thereby increasing the performance of the pilgrim installation more than two times during rolling of pipes of this assortment and significantly increase the length of conversion and commodity pipes with a ratio of D / S = 4.4-5.5, i.e. pipes with thicker walls.

Table
Data on rolling and delivery of commodity pipes 377 × 25 mm in size and 377 × 45 mm conversion tubes from 10Kh17N13M2T steel according to the existing and proposed technologies Type technologist. Pipe size Type and size of workpieces set. metal in production Will continue. heating Sleeve Dimensions Pilgrim mill pipe rolling Consumption. coefficient metal ESR ingot ESW hollow ingot First past The second past. First past The second past. Wednesday length Total length Weight of pipes mm mm mm PC. tons hour hour mm mm m m tons - Creatures. 377 × 25 540 × 1650 - 5 14,825 9.0 7.5 540 × 138 × 2100 540 × 88 × 2950 9.95 49.75 10,796 1,374 377 × 45 540 × 1650 - 5 14,825 9.0 7.5 540 × 138 × 2100 540 × 100 × 2650 5.85 29.25 10,794 1,374 Suggestion 377 × 25 - 540 × 90 × 2750 5 13,723 - 7.0 - - 9.65 48.25 10,471 1,311 377 × 45 - 540 × 110 × 3200 5 18,656 - 7.5 - - 8.35 41.75 15,406 1,211

Claims (2)

1. Method for the production of hot-rolled commodity and conversion pipes of large and medium diameters from hard-to-deform grades of steel and alloys on pipe rolling plants with pilgrim mills, including casting ingots on electroslag remelting plants, which are grind and bored, heated and rolled on pilgrim mills, characterized in that electroslag remelting ingots are cast hollow 2000-3200 mm high, grind and bore to remove scale and microcracks to a diameter of 400-620 mm with a diameter to The thickness of the wall is D / S = 4.5-7.0, large values of which correspond to ingots - sleeves of smaller diameter, are heated to the ductility temperature, and rolled on pilgrim mills. 2. The method according to claim 1, characterized in that the hollow ingots heated to a temperature of plasticity are sleeves with a ratio D / S = 5.0-7.0 and a height of 2000-2750 mm and are rolled on a pilgrim mill in commodity and conversion pipes with a thickness walls up to 30 mm, and ingots - sleeves with a ratio D / S = 4.5-5.5 and a height of 2750-3200 mm are rolled on a pilgrim mill in conversion tubes with a wall thickness of more than 30 mm.