RU2550040C2 - Manufacturing method of three-layered hollow centrifugal cast sections from difficult-to-form steel grades and alloys, which are cladded with ductile carbon steel grades, and rolling from them on pipe rolling units with pilger mills of hot-rolled mechanically treated merchantable and process pipes of large and mean diameters - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: three-layered hollow centrifugal cast billets are cast from difficult-to-deform steel grades and alloys, which are cladded with ductile steels of carbon grades, with the size of 400-650×3200±100 mm with the ratio of thicknesses of ductile layers, which is restricted by mathematical relationship, their heating is performed to the temperature that is higher by 10-20°C than ductility temperature interval of difficult-to-form steel grades and alloys and rolling on the pilger mill with swaging as to the diameter, the value of which is decreased from 180 to 100 mm with increase of pipe diameter. Seeding on the pipe length equal to length of recoil of a supply unit is performed with supply of the billet to the deformation zone, which is equal to (0.5-0.7) of supply value m_unit at the steady-state rolling process, and rolling of the pilger head with supply equal to (1.1-1.25) m_unit.

EFFECT: reduction of consumption of expensive metal; increase of efficiency of a pipe rolling unit with pilger mills; reduction of pipe cost.

Description

The invention relates to metallurgical and pipe production, and in particular to a method for the production of three-layer hollow centrifugal cast billets from hardly deformable steel grades and alloys clad with plastic carbon steel grades, and rolling from them in pipe rolling plants with pilgrim mills of hot-rolled mechanically processed large commodity and conversion pipes and medium diameters, and can be used in the production of three-layer hollow tube billets in centrifugal casting plants forging and rolling from them hot-rolled three-layer pipes in tube-rolling plants with pilgrim mills for subsequent mechanical processing - turning and boring into commercial ones in accordance with GOST 9940 and mechanical converted tubes for rolling on HPT mills into pipes in accordance with GOST 9941.

In the practice of manufacturing billets by centrifugal casting, a method for manufacturing hollow bimetallic billets of various combinations is known, namely steel 10, 20 + 08X18H12T, steel 14X17H2 + 08X18H10T, steel 10G2B + 06XH28MDT, steel 08X18H12 + st.10, steel 10G2B + alloy XH65MB, steel 12X18H9 KhN65MV alloy, steel 30 + X12 (the steel indicated by the first forms the outer layer of the billet, and the second inner forms the cladding layer), where the thickness of the outer layer ranges from 0.4 to 0.65 of the total wall thickness of the centrifugally cast billet, and the thickness inner (cladding) layer, respectively, from 0.35 to 0.6 (M.I. Chepurko, N.P. Karpenko, A.V. Safyanov et al. "Technological basis for the production of bimetallic pipes", Chelyabinsk, "Metal", 1993, p.192-193).

In the practice of pipe production, there is a known method for the production of bimetallic wear-resistant pipes (st.30 + X12) on pipe rolling plants with pilgrim mills, including heating the initial centrifugal cast billets and rolling them on mandrels (M.I. Chepurko, N.P. Karpenko, A . V. Safyanov et al. “Technological basis for the production of bimetallic pipes”, Chelyabinsk, “Metal”, 1993, p. 39-47, p. 196-211).

The specified method for the production of bimetallic centrifugal cast billets is mainly used for the production of a billet for subsequent machining (turning and boring) and length cutting for the manufacture of individual parts. Centrifugally cast billets of the combination 30 + X12 are cast both for machining and for redistribution - rolling the billets at tube rolling plants with pilgrim mills into long bimetal wear-resistant pipes for transporting abrasive bulk materials and pulps (V.Ya. Osadchy, S.G. Chikalov, AV Safyanov et al. "Development and improvement of the technology for the production of bimetallic wear-resistant pipes of large and medium diameters for transporting abrasive materials and pulps on TPA 8-16" with pilgrim mills mi ". Proceedings of the Sixth Congress of Distributors, Lipetsk, October 18-21, 2005, Moscow, 2005, pp. 393-398. TU 14-158-10-75." Seamless hot-rolled bimetallic pipes from steel grades 30 + X12 ").

The disadvantage of this method of casting bimetallic centrifugally cast billets is that they are cast only in two layers, i.e. plastic carbonaceous or less alloyed layer only from the outer surface, during rolling of which into long wear-resistant pipes on pipe rolling plants with pilgrim mills on the inner surface, due to increased friction between the mandrel and X12 steel, flaws form, which in some cases lead to the formation of through transverse cracks (flaw). Another disadvantage of this method of casting bimetallic centrifugally cast tube billets is that the thickness of the plastic (outer) carbon layer is taken without taking into account the geometric dimensions of the billets and the amount of metal fume when heated to a ductility temperature for rolling on pilgrim mills.

The specified method for the production of bimetallic pipes is used for the production of pipes whose layers have similar ductility or a similar coefficient of volume expansion at high temperatures. Therefore, heating in a wide temperature range with different rates of metal heating and different deformation values does not lead to pipe ruptures during their manufacture.

In the pipe industry, a method is known for the production of hollow bimetallic centrifugally cast billets for the manufacture of bimetallic wear-resistant pipes for transporting abrasive bulk materials and pulp combinations of steel 30 + X12 in size 400 × 80 (38 + 42) × 3500, 445 × 71 (35 + 36) × 3500, 540 × 70 (36 + 34) × 3200 and 650 × 65 (31 + 34) × 3200 mm, where the first numbers in brackets indicate the thickness of the plastic carbon layer, and the second - the thickness of the cladding wear-resistant layer (TU14-242-114- 75 "Bimetallic centrifugally cast billets (tubes-blanks) steel 10 + X12" and TI 158-Tr. TB1-22-95 "Manufacturing f seamless hot-rolled bimetallic pipes made of steel grades 30 + X12 ").

The disadvantage of this method for the production of hollow bimetallic centrifugally cast billets is the casting of only two-layer billets with approximately equal thicknesses of plastic and cladding layers of metal, during rolling of which into long-length wear-resistant pipes on tube-rolling plants with pilgrim mills on the inner surface of the pipes, due to increased friction between the mandrel and steel X12, flaws form, which in some cases lead to the formation of through transverse cracks (flaws). Another disadvantage of this method of casting hollow bimetallic centrifugally cast billets is also the fact that the thickness of the plastic (outer) carbon layer is taken without taking into account the geometric dimensions of the billets and the amount of metal fume when heated to a plasticity temperature for rolling in pipe rolling plants with pilgrim mills and this method It does not solve the technical and technological issues of the production of three-layer hollow centrifugal cast billets from hardly deformable grades of steel and alloys, plaques ductile carbon steel grades, and rolling from them in tube rolling units with pilgrim mills of hot-rolled mechanically processed commodity and conversion pipes of large and medium diameters.

In pipe-rolling production, a method is known for producing hot-rolled commodity and conversion pipes of large and medium diameters from hard-to-deform steel grades in pipe-rolling plants with pilgrim mills from EShP ingots of steel grade 10X9MFB-Sh (TU 14-134-398-2003 "Billet pipe - ingots for boiler pipes EShP ", TU 14-3R-55-2001" Seamless steel pipes for steam boilers and pipelines ", TI 158-Tr. TB1-56-2007" Production of seamless hot-rolled pipes for steam boilers and pipelines according to TU 14-3R-55- 2001 ").

The disadvantage of this method is that the pipes after rolling have a large number of defects on the inner surface in the form of captivity and friability, require subsequent machining (boring) with the removal of metal of 8-10 mm per side. This steel grade has a hot ductility range of 1160–900 ° C and an increased coefficient of linear expansion. If the ESR ingots-blanks are heated to a temperature of 1160 ° C, then when the ingots are pierced in a cross-helical rolling mill, the temperature of the metal in the deformation zone at the mandrel-inner surface of the sleeves increases by 50-70 ° C depending on the diameter of the ingot. When rolling sleeves on a pilgrim mill to tubes with an outer surface temperature of 1160 ° C or less, the end of rolling occurs at a temperature of 800-850 ° C, depending on the diameter and wall thickness, which leads to tightening of the mandrels even with a taper of 2.0 instead of 1 , 0 mm according to TI 158-Tr. TB1-56-2007. Heating of ESR ingots-blanks of this steel grade above 1160 ° C leads to overheating of the inner surface of the sleeves and the mass formation of internal captives. These pipes must be rejected or bored to a smaller wall thickness with metal removal from 8 to 10 mm per side, which, in turn, leads to increased metal consumption and an additional laborious operation - pipe boring.

A well-known technical solution is also a method for the production of hot-rolled steel tubes from 20Kh25N25TYu-Sh steel with a size of 325 × 40 mm for the manufacture of water-cooled furnace rollers with a size of 295 × 22 × 2750 mm, including drilling and boring of ESR ingots with a size of 480 × 1600 mm and a diameter of 285 + 5 / -0 mm, heating them to the temperature of plasticity, rolling on pilgrim mills into 325 × 40 mm pipes on mandrels with an increased taper of 238/246 mm with a difference (gap) between the inner diameter of the bored shell ingots and the maximum diameter of the mandrels are equal m 40-45 mm, and a drawing coefficient µ = 3, 4 (protocol No. 1031 for agreeing on the conditions for the supply of steel pipes made of 20Kh25N25TYu-Sh steel dated 12/14/2000 and a letter of instruction for pilot industrial rolling of 325 × 40 hot rolled steel tubes mm from high alloy steel grade 20X25H25TYU-Sh).

The disadvantage of this method is the use of bored ingot shells with an inner diameter greater than the diameter of the mandrel by 40-45 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. Due to the presence of defects on the outer and inner surfaces, hot-rolled pipes from this high-alloy steel grade are subjected to mechanical processing - turning and boring with metal removal on the outer and inner sides of 8-10 mm. This method is aimed at the manufacture of water-cooled rollers from steel 20Kh25N25TYu-Sh and does not solve the technological issues of the production of commodity and flange hot-rolled pipes at TPU with pilgrim mills from corrosion-resistant hardly deformable steel grades and alloys with a low temperature range of hot ductility and a high coefficient of linear expansion.

и $${\Delta }_s^1=D/2(1-\sqrt{1-K^1}$$

, где D - наружный диаметр центробежно-литой биметаллической заготовки, мм; Δ_s - величина угара (утонения) толщины стенки пластичного (наружного) слоя центробежно-литой биметаллической заготовки при нагреве до температуры пластичности, мм; K - коэффициент угара металла по наружной поверхности центробежно-литой биметаллической заготовки при нагреве до температуры пластичности; $${\Delta }_s^1$$

- величина угара (утонения) толщины стенки пластичного (внутреннего) слоя центробежно-литой биметаллической заготовки при нагреве до температуры пластичности, мм; K¹ - коэффициент угара металла внутренней поверхности центробежно-литой биметаллической заготовки при нагреве до температуры пластичности. Полые 3-слойные центробежно-литые биметаллические заготовки нагревают в нагревательных печах перед пилигримовой прокаткой до температуры 1220-1240°C, а затем прокатывают на пилигримовом стане с обжатием по диаметру, величина которого уменьшается от 180 до 100 мм с увеличением диаметра биметаллических труб с 219 до 530 мм, отношение толщин пластичных слоев центробежно-литых биметаллических заготовок и труб принимают равным S_н/S_в=1,5-2,5, где S_н - толщина наружного пластичного слоя центробежно-литых биметаллических заготовок и труб, мм; S_в - толщина внутреннего пластичного слоя центробежно-литых биметаллических заготовок и труб, мм. Затравку (прокатку) центробежно-литых заготовок на длине трубы, равной длине отката подающего аппарата, ведут с подачей, равной (0,5-0,75)m_уст от величины подачи при установившемся процесс прокатки, а докатку (обкатку) пилигримовой головки - с подачей, равной (1,1-1,25)m_уст от величины подачи при установившемся процессе (Патент РФ №227849, Кл. В21В 21/00, от 20.07.1999, Бюл. №20 "Способ производства биметаллических труб центробежно-литых заготовок и биметаллических износостойких труб для транспортировки абразивных материалов и пульп на трубопрокатных установках с пилигримовыми станами").The closest technical solution is a method for the production of bimetallic centrifugal cast billets and bimetallic wear-resistant pipes for transporting abrasive bulk materials and pulps in tube-rolling plants with pilgrim mills, including casting of hollow centrifugally cast three-layer bimetallic billets taking into account the fume of the inner centrifugally plastic (outer) cast bimetallic billets in the process of heating them for rolling in heating furnaces to ductility temperature, etc. rolling of bimetallic pipes on pilgrim mills with crimps in diameter from 100 to 180 mm (100≤ΔD≤180), an increase in the thickness of the plastic layers of bimetallic centrifugally cast billets, taking into account fumes when heating billets for rolling to a plasticity temperature and with an increase in the outer diameter, values which are determined by the formulas $${\Delta }_s=D/2(\mathrm{one}-\sqrt{\mathrm{one}-K}$$

and $${\Delta }_s^{\mathrm{one}}=D/2(\mathrm{one}-\sqrt{\mathrm{one}-K^{\mathrm{one}}}$$

where D is the outer diameter of the centrifugal cast bimetallic billet, mm; Δ _s - quantity burn (necking) of the wall thickness of the plastic (outer) layer of centrifugally cast bimetallic blank when heated to plasticity temperature, mm; K is the coefficient of metal fumes along the outer surface of a centrifugally cast bimetallic billet when heated to ductility temperature; $${\Delta }_s^{\mathrm{one}}$$

- the value of fumes (thinning) of the wall thickness of the plastic (inner) layer of a centrifugally cast bimetallic billet when heated to a plasticity temperature, mm; K ¹ - the coefficient of carbon loss of the metal of the inner surface of a centrifugal cast bimetallic billet when heated to ductility temperature. Hollow 3-layer centrifugal cast bimetallic billets are heated in heating furnaces before the pilgrim rolling to a temperature of 1220-1240 ° C, and then rolled on a pilgrim mill with compression in diameter, the value of which decreases from 180 to 100 mm with an increase in the diameter of bimetallic pipes from 219 to 530 mm, the thickness ratio of plastic layers centrifugally cast bimetallic billets and tubes shall be equal to S _n / S _a = 1.5-2.5, where S _n - thickness of the outer plastic layer of centrifugally cast bimetallic billets and tubes, mm; S _in - the thickness of the inner plastic layer of centrifugal cast bimetallic billets and pipes, mm The seed (rolling) of centrifugally cast billets along the pipe length equal to the length of the rollback of the feeding apparatus is carried out with a feed equal to (0.5-0.75) m _mouth from the feed value at the steady rolling process, and the rolling (rolling) of the pilgrim head - with a feed equal to (1.1-1.25) m _mouth of the feed rate during the steady-state process (RF Patent No. 227849, Cl. B21B 21/00, 07/20/1999, Bull. No. 20 "Method for the production of bimetallic centrifugal pipes cast billets and bimetallic wear-resistant pipes for transporting abrasive materials and slurries to pipe rolling plants ah with pilgrim camps ").

The disadvantage of this prototype, as well as the above analogues, is that it is aimed at the production of bimetallic wear-resistant pipes of 219 × 14, 273 × 14, 325 × 16, 426 × 20 and 530 × 25 mm for transportation of abrasive materials and slurries with wear-resistant layer, which is not more than 50% of the total wall thickness, and does not solve the technical and technological issues of the production of three-layer centrifugal cast billets from hard-deformed steel grades and alloys clad with plastic carbon steel grades, and rolling from them onto ruboprokatnyh plants with hot pilger machined commodity and metal recycling pipes of large and medium diameter of hard steels and alloys.

The objective of the proposed method is the development of the production of commodity and conversion machined pipes from hard-deformed grades of steel and alloys (not stitched on transverse helical rolling mills), elimination of the formation of defects on the outer and inner surfaces of commodity and conversion machined pipes, exclusion from the technological process of flashing technology ingot blanks and firmware-rolling of sleeve blanks in cross-helical rolling mills, reduction of metal consumption, with redistribution of three a hollow centrifugally cast billet made of hard-deformed grades of steel and alloys is a commodity or conversion machined hot-rolled pipe, an increase in the productivity of TPU with pilgrim mills, and therefore, a decrease in the cost of pipes made of corrosion-resistant hard-deformed grades of steel and alloys.

The technical result is achieved by the fact that in the known method for the production of three-layer hollow centrifugal cast billets from hardly deformable steel grades and alloys clad with plastic carbon steel grades, and rolling from them in tube rolling plants with pilgrim mills of hot-rolled mechanically processed commodity and conversion pipes of large and medium diameters , including the casting of three-layer hollow centrifugally cast billets, taking into account the fumes of plastic layers during heating for rolling into a heater GOVERNMENTAL furnaces to plasticity temperature, with a ratio of plastic layer thicknesses equal to S _n / S _a = 1.5-2.5, the values of which increase with increasing outer diameter workpieces and product pipes, three-layered wear-resistant rolling pipes on a pilger rolling mills with a reduction in diameter , the value of which decreases from 180 to 100 mm with an increase in the diameter of the commodity pipes from 219 to 550 mm, the seed on the pipe length equal to the length of the rollback of the feeding apparatus, with the filing of a three-layer hollow centrifugally cast billet in the deformation zone equal to (0.5-0 , 7) m _mouth from the value of feeds and during the steady rolling process, while the pilgrim head is run-in with a feed equal to (1.1-1.25) m _mouth , three-layer hollow centrifugally cast mechanically machined - turned and bored blanks of hard-deformed steel grades and alloys plated with plastic carbon grades steel, produce a diameter of 400 to 650 mm and a length of 3200 ± 100 mm with a ratio of D / S = 4.5-7.0, large values of which relate to billets of larger diameter, the ratio of the thicknesses of the plastic layers of hollow centrifugally cast three-layer billets and labor taken to be S _i.n.p. / S _i.v.p. = 1.3-3.0, where S _i.n.p. - the thickness of the outer layer of ductile carbon steel grades of centrifugally cast mechanically machined three-layer pipe billets and hot rolled pipe of the i-th size, mm; S _i.v.p. - the thickness of the inner layer of plastic carbon steel grades of centrifugally cast mechanically machined three-layer pipe billets and hot-rolled conversion tubes of i-size, mm, the thickness of the outer and inner cladding layers of plastic carbon steel grades and central layers of hard-deformed steel grades and three-layer hollow alloys centrifugally cast billets with a size of 400-650 × 3200 ± 100 mm are determined from the expressions

, $$S_{i.n.P.}=\frac{D_{i.c.s.}\pm \sqrt{D_{i.c.s.}^2-\mathrm{four}{\mu }_{i.}(D_{i.g.P.t.}-S_{i.\mathrm{at}.g.P.t.})S_{i.\mathrm{at}.g.P.t.n.}}}{2}$$

,

, $$S_{i.leg.}=\frac{(D_{i.c.s.}-2S_{i.n.P})\pm \sqrt{{(D_{i.c.s.}^{}-2S_{i.n.P.})}^2-\mathrm{four}{\mu }_{i.}(D_{i.g.P.l.t.}-S_{i.g.P.l.t.})S_{i.g.P.l.t.}}}{2}$$

,

, $$S_{i.\mathrm{at}.P}=\frac{(D_{i.c.s.}-2S_{i.n.n.}-2S_{i.leg.})\pm \sqrt{{(D_{i.s.}-2S_{i.n.n.}-2S_{i.leg.})}^2-\mathrm{four}{\mu }_i(D_{i.g.P.l.t.}-S_{i.\mathrm{at}.g.P.m.t.}-S_{i.g.P.l.t.}-S_{i.g.\mathrm{at}.P.t.\mathrm{at}n.})S_{i.g.\mathrm{at}.P.t.\mathrm{at}n.}}}{2}$$

,

where S _i.n.p. - the thickness of the outer cladding layer of plastic carbon steel grades of a three-layer centrifugal cast tubular billet i-size, mm; D _i.c.z. - the outer diameter of a three-layer centrifugal cast tubular billet i-size, mm; D _i.h.p. - the outer diameter of the hot-rolled three-layer conversion pipe of the i-th size, mm; S _i.y. - the thickness of the outer cladding layer of plastic carbon steel grades of hot-rolled conversion three-layer pipe of the i-th size, mm; µ _i. - drawing coefficient when rolling three-layer centrifugal cast billets of i-size on a pilgrim mill to hot-rolled three-layer pipes of i-size; S _i.leg. - wall thickness of hard-deformed steel grades and alloys of a three-layer centrifugally cast tubular billet of the i-th size, mm; D _i.h.p. - the diameter of the hot-rolled conversion pipe from hard-deformed steel grades and alloys of the i-th size, mm; S _i.h.p. - wall thickness of the hot-rolled conversion pipe from hard-deformed steel grades and alloys of the i-th size, mm; S _i.v.p. - the thickness of the inner cladding layer of plastic carbon steel grades of a three-layer centrifugal cast tubular billet i-size, mm; S _i.G.P.H. - the thickness of the inner cladding plastic layer of carbon steel of the hot-rolled conversion three-layer pipe of the i-th size, mm, the outer diameter of the conversion three-layer hot rolled pipes is determined from the expression D _i.p. = D _i.t.m. + 2Δ _i1 + 2Δ _i2, where D _i.t.m. - the outer diameter of the commodity or conversion machined pipe, mm; Δ _i1 is the thickness of the outer cladding layer of plastic carbon steel grades when rolling hot-rolled pipe of the i-th size, mm; Δ _i2 is the thickness of the outer layer of hard-deformed grades of steel and alloys, removed when turning the conversion of 3-layer hot-rolled pipes into commodity and conversion machined pipes of the i-th size, mm, the wall thickness of the conversion of three-layer hot-rolled pipes is determined from the expression S _i.p. = S _i.h.p. + S _i.leg. + S _i.G.P.H. , the supply of liquid metal during casting of pipe billets is carried out according to the mass necessary for the formation of the specified geometric dimensions of the three-layer hollow centrifugal cast billets, which is determined from the expressions P _i. = 0,00314 (D _i.ts.z. -S _i.n.z.) S _i.n.z. ρ _at L _s , P _i. = 0,00314 (D _{i.ts.z. i.n.z.} -S -S _i.leg.) S _i.leg. ρ _lay. L _s , P _i. = 0,00314 (D _{i.ts.z. i.n.z.} -S -S _i.leg. -S _i.u.vn.) S _i.u.vn. ρ _y L _s where ρ _у is the specific gravity of liquid carbon metal, g / cm ³ , ρ is _light. - the specific gravity of the liquid alloyed metal, g / cm ³ ; L _s - length of a three-layer centrifugal cast tube billet of the i-th size, m, three-layer centrifugal cast tube billets for rolling on a piligim mill are heated according to the regime of hardly deformable grades of steel and alloys to a temperature of 10-20 ° C above the temperature range of hot plasticity of data grades of steel and alloys are dispensed from the furnace and rolled in a pipe mill on a pilgrim mill.

A comparative analysis of the proposed solution with the prototype shows that the claimed method differs from the known one in that three-layer centrifugally cast machined - turned and bored workpieces from hard-deformed steel grades and alloys clad with plastic carbon steel grades are produced with a diameter of 400 to 650 mm and a length 3200 ± 100 mm with a ratio D / S = 4.5-7.0, large values of which relate to a workpiece with a larger diameter, the ratio of the thicknesses of the plastic layers of hollow centrifugally cast three-layer workpieces and conversion pipes are taken equal to S _i.n.p. / S _i.v.p. = 1.5-3.0, where S _i.n.p. - the thickness of the outer layer of ductile carbon steel grades of centrifugally cast mechanically machined three-layer pipe billets and hot rolled pipe of the i-th size, mm; S _i.v.p. - the thickness of the inner layer of plastic carbon steel grades of centrifugally cast mechanically machined three-layer pipe billets and hot-rolled conversion tubes of i-size, mm, the thickness of the outer and inner cladding layers of plastic carbon steel grades and central layers of hard-deformed steel grades and three-layer hollow alloys centrifugally cast billets with a size of 400-650 × 3200 ± 100 mm are determined from the expressions

, $$S_{i.n.P.}=\frac{D_{i.c.s.}\pm \sqrt{D_{i.c.s.}^2-\mathrm{four}{\mu }_{i.}(D_{i.g.P.t.}-S_{i.\mathrm{at}.g.P.t.})S_{i.\mathrm{at}.g.P.t.n.}}}{2}$$

,

, $$S_{i.leg.}=\frac{(D_{i.c.s.}-2S_{i.n.P})\pm \sqrt{{(D_{i.c.s.}^{}-2S_{i.n.P.})}^2-\mathrm{four}{\mu }_{i.}(D_{i.g.P.l.t.}-S_{i.g.P.l.t.})S_{i.g.P.l.t.}}}{2}$$

,

, $$S_{i.\mathrm{at}.P}=\frac{(D_{i.c.s.}-2S_{i.n.n.}-2S_{i.leg.})\pm \sqrt{{(D_{i.s.}-2S_{i.n.n.}-2S_{i.leg.})}^2-\mathrm{four}{\mu }_i(D_{i.g.P.l.t.}-S_{i.\mathrm{at}.g.P.t.n.}-S_{i.g.P.l.t.}-S_{i.g.\mathrm{at}.P.t.\mathrm{at}n.})S_{i.g.\mathrm{at}.P.t.\mathrm{at}n.}}}{2}$$

,

where S _i.n.p. - the thickness of the outer cladding layer of plastic carbon steel grades of a three-layer centrifugal cast tubular billet i-size, mm; D _i.c.z. - the outer diameter of a three-layer centrifugal cast tubular billet i-size, mm; D _i.h.p. - the outer diameter of the hot-rolled three-layer conversion pipe of the i-th size, mm; S _i.y. - the thickness of the outer cladding layer of plastic carbon steel grades of hot-rolled conversion three-layer pipe of the i-th size, mm; µ _i is the drawing coefficient when rolling three-layer centrifugal cast billets of the i-th size on a pilgrim mill to the hot-rolled three-layer pipes of the i-th size; S _i.leg. - wall thickness of hard-deformed steel grades and alloys of a three-layer centrifugally cast tubular billet of the i-th size, mm; D _i.h.p. - the diameter of the hot-rolled conversion pipe from hard-deformed steel grades and alloys of the i-th size, mm; S _i.h.p. - wall thickness of the hot-rolled conversion pipe from hard-deformed steel grades and alloys of the i-th size, mm; S _i.v.p. - the thickness of the inner cladding layer of plastic carbon steel grades of a three-layer centrifugal cast tubular billet i-size, mm; S _i.G.P.H. - thickness of the inner plastic layer of the cladding of the hot rolled carbon steel pipe pig sandwich i-th size, mm, an outside diameter of three-layer hot-rolled metal recycling pipe is determined from expressions D _i.p. = D _i.t.m. + 2Δ _i1 + 2Δ _i2 , where D _i.t.m. - the outer diameter of the commodity or conversion machined pipe, mm; Δ _i1 is the thickness of the outer cladding layer of plastic carbon steel grades when rolling hot-rolled pipe of the i-th size, mm; Δ _i2 is the thickness of the outer layer of hard-deformed grades of steel and alloys, removed when turning the conversion 3-layer hot rolled pipes into commodity and conversion machined pipes of the i-th size, mm, the wall thickness of the conversion three-layer hot rolled pipes is determined from the expression S _i.п = S _i.h.p. + S _i.leg. + S _i.G.P.H. , the supply of liquid metal during casting of pipe billets is carried out according to the mass necessary for the formation of the specified geometric dimensions of the three-layer hollow centrifugal cast billets, which is determined from the expressions P _i. = 0.00314 (D _{i.s.- s-} S _i.z.z ) S _i.z.z. ρ _y L _s , P _i. = 0,00314 (D _{i.ts.z. i.n.z} -S -S _i.leg.) S _i.leg. ρ _lay. L _s , P _i. = 0,00314 (D _{i.ts.z i.n.z.} -S -S _i.leg. -S _i.u.vn.) S _i.u.vn. ρ _y L _s Where ρ _y. - the specific gravity of the liquid carbon metal, g / cm ³ ; ρ _lay. - the specific gravity of the liquid alloyed metal, g / cm ³ ; L _s - the length of a three-layer centrifugal cast tube billet of the i-th size, m, three-layer hollow centrifugal cast tube billets for rolling on a piligim mill are heated according to the regime of hard-to-deform grades of steel and alloys to a temperature of 10-20 ° C above the temperature range of hot ductility of these grades steel and alloys are discharged from the furnace and rolled on a pilgrim mill in the conversion pipes. Thus, the claimed method meets the criterion of "inventive step".

Comparison of the proposed method not only with the prototype, but also with other technical solutions in the art did not allow them to identify signs that distinguish the claimed solution from the prototype, which allows us to conclude that the patentability condition is "inventive step".

The method has been tested and implemented at Cherepovets Foundry and Mechanical Plant OJSC and at a pipe rolling plant with 8-16 pilgrim mills at ChTPZ OJSC. Three three-layer hollow centrifugal castings were cast at the Cherepovets Foundry and Mechanical Plant OJSC in accordance with the claims. cast bimetallic pipe billets with a size of 460 × ext. 240 × 3200 mm, the Thickness of the plastic layers of centrifugally cast pipe billets was determined by the formulas given in the claims, defined by the size of the hot rolled pipes (285 × 32 × 13000 mm, where the outer plastic layer is made of steel of 20-4 mm grade, the inner is 3.0 mm, and the main wall is made of 06KHN28MDT steel - 25 mm). The wall of 25 mm is accepted at the rate of 100% guarantee of receiving commodity pipes after machining - turning and boring of 273 × 20 mm Casting CLP produced in accordance with the claims.

According to the existing technology, three 440 × 1700 mm ESB ingots of steel grade 06KHN28MDT, which were supplied by ZMZ, were set into production. Through ingots-blanks at JSC "ChTPZ" through central holes were drilled with a diameter of 100 ± 5 mm, and then they were bored to a diameter of 250 mm, which is more than the diameter of the mandrel from 24 to 30 mm. Hollow ingots were heated to a temperature of 1180 ° C, because the interval of hot plastic deformation of the alloy 06KHN28MDT during rolling 1170-900 ° C. After delivery from the furnace, ingot billets were fed by a crane to the inlet side of the pilgrim mill. Hollow ingots-blanks were rolled on heated cone mandrels with a diameter of 220/226 mm in a caliber of 295 mm with lining carbon rings for partial removal of pilgrim heads to carbon metal. When rolling pipes were tightening the mandrels in the pipes. The temperature of the end of rolling is 860-870 ° C. The first pipe was removed from the mandrel by additional rolling of the stuck pipe with increased feeds and a 0.8% diameter reduction due to roll reduction and removal of the mandrel from the pipe by the feeding apparatus during rollback of the mandrel with the pipe (RF Patent No. 2220794). From two pipes, the mandrels were removed by the feeding apparatus after heating the pipes with mandrels in the first zone of the furnace to a temperature of 1070–1180 ° C. The time to extract the mandrels was more than an hour. After rolling, three redistribution tubes 290 × 35 × 5000 mm in size were obtained. On the outer and inner surfaces of the pipes there were flaws up to 5.0 mm deep. Conveyor pipes were turned and bored into commodity pipes measuring 273 × 20 × 5000 mm. Pipes adopted in accordance with GOST 9940. The mass of pipes delivered amounted to 1871 kg The expenditure coefficient of the alloy from the workpiece to the finished pipe was 3.254.

According to the proposed technology, three DLCs measuring 460 × ext. 240 × 3200 mm with a total weight of 9110 kg were heated in a methodical furnace to a temperature of 1180-1200 ° C. The heating of the three-layer CLZ was made in accordance with the claims. Three-layer TsLZ after delivery from the furnace by a crane were fed to the entrance side of the pilgrim mill. Hollow CLPs were rolled on heated mandrels with a diameter of 222/224 mm in a caliber of 295 mm with lining carbon rings for partial removal of the pilgrim heads on carbon metal into twin three-layer pipes measuring 285 × 32 × 13000 mm. When rolling pipes, tightening mandrels in the pipes were absent. The temperature of the end of the rolling was 910-900 ° C. After rolling, they were straightened and cut into equal lengths. There were no defects on the outer and inner surfaces of the pipes. Conversion pipes were turned and bored into commodity pipes measuring 273 × 20 × 7500 mm. Pipes adopted in accordance with GOST 9940. The mass of delivered pipes amounted to 4864 kg. The expenditure coefficient of 06KHN28MDT alloy from the workpiece to the finished pipes was 1.430, and the total - 1.873.

Data on the production of conversion and commodity machined pipes 273 × 20 mm in size from 06XH28MDT alloy according to GOST 9940 according to the existing and proposed technologies show that in the production of commodity machined pipes 273 × 20 mm in size from 06KHN28MDT alloy according to the proposed technology, a decrease in the consumption coefficient by 1824 kg alloy for each ton of pipes, tightening of mandrels in conversion pipes and heating of stuck pipes together with mandrels in the first zone of method furnaces to remove them on pilgrim st anah.

Using the proposed method for the production of hot-rolled chimneys at TPU with pilgrim mills from three-layer hollow centrifugally cast billets from hard-to-deform steel grades and alloys clad with plastic carbon steel grades, and rolling them from tube-rolling plants with hot-rolled mechanically machined large pilgrim pipe-mill machines and and medium diameters will reduce the cost of expensive metal, eliminate the time-consuming operation of heating stuck pipes together with the mandrel to retrieve them for pilger mills, to increase productivity TPU pilger and hence reduce the cost of the pipes.

Claims (1)

A method for the production of three-layer hot rolled machined pipes with a diameter of 219 to 550 mm, comprising casting three-layer hollow centrifugally cast billets from hard-deformed steel grades and alloys clad with plastic steels of carbon grades, 400-650 × 3200 ± 100 mm in size, with a ratio of thicknesses of plastic layers, equal
_I.n.p S / S _i.v.p = 1.3-3.0,
where S _i.np - the thickness of the outer plastic layer of pipe blanks of the i-th size, mm;
S _i.v.p - the thickness of the inner plastic layer of pipe blanks of the i-th size, mm,
heating to a temperature of 10–20 ° C above the temperature range of ductility of hard-deformed grades of steel and alloys and rolling on a pilgrim mill with compression in diameter, the value of which decreases from 180 to 100 mm with an increase in the diameter of the pipes, while the seed on the pipe length equal to the length rollback of the feeding apparatus is carried out with the supply of the workpiece to the deformation zone equal to (0.5-0.7) of the feed rate m _mouth at the steady rolling process, and the pilgrim head is run-in with the feed equal to (1.1-1.25) m _mouth