ISSN 0967-0912, Steel in Translation, 2009, Vol. 39, No. 8, pp. 669–676. © Allerton Press, Inc., 2009. Original Russian Text © V.M. Parshin, V.V. Busygin, A.D. Chertov, Yu.M. Aizin, A.V. Kuklev, A.V. Larin, L.V. Bulanov, 2009, published in “Stal,” 2009, No. 8, pp. 17–24.
Continuous Slab-Casting of Steel in Russia V. M. Parshina, V. V. Busyginb, A. D. Chertova, Yu. M. Aizinc, A. V. Kukleva, A. V. Larind, and L. V. Bulanovb aCentral
Scientific-Research Institute of Ferrous Metallurgy, Moscow, Russia bOOO Uralmash-Engineering, Yekaterinburg, Russia cZAO Korad, Moscow, Russia dOOO Modul-Engineering, Moscow, Russia
Abstract—The production of cast slabs in Russia is reviewed, and means of improving continuous casting are proposed. DOI: 10.3103/S0967091209080129
In the initial development of continuous casting in the Soviet Union, the construction of continuous slabcasting machines was a priority. The large-scale construction of such machines was preceded by experimental research at the Central Scientific-Research Institute of Ferrous Metallurgy (CSIFM). Somewhat later, some experimental units were built on the basis of designs by Stal’proekt Institute, as follows. In 1951, the world’s first semicontinuous vertical unit went into operation at the Krasnyi Oktyabr plant, for casting 150–180 × 600–800 mm corrosion-resistant steel slabs. In 1953, an experimental continuous-casting machine went into operation at Novo-Tul’sk metallurgical plant (NTMP), for casting 150–200 × 600 mm slabs and bars with square cross sections of side 150 and 200 mm. This unit became the experimental center not only of CSIFM but of numerous institutes in Russia and Ukraine. In 1955, an industrial unit for casting 175 × 420 mm blanks went into operation at the Krasnoe Sormovo plant. Two independent units were placed in a single pit of depth 13 m; they could cast steel from 50-t ladles. In 1958, two double-strand continuous slab-casting machines of tower type with a casting area at a height of 21 m went into operation in the open-hearth shop at Perm manufacturing plant. At first, the unit operated with periodic growth of 220 × 1000 mm slabs. In 1961 and 1962, the unit was reconstructed for the casting of 175 × 1020 mm slabs, with slipping of the crust. In 1964, this machine began to cast slab of width 1500 mm. This provided the basis for the design of equipment for broad-slab casting. On the basis of research findings and the successful startup of the electrosmelting shop at Novolipetsk Metallurgical Works (NMW) in 1959—with two 100-t furnaces and two vertical continuous-casting machines— it was decided to construct more continuous-casting
machines. Most of the plans were realized. The table presents the basic data regarding Russian slab machines. Note that most continuous-casting machines were built by the Ural Heavy-Manufacturing Plant (UHMP). Until recently, foreign firms had no access to the market. One exception was the construction of a slab machine at NMW in 1976 by Mannesmann (now part of SMS-Siemag). We now make some remarks regarding individual continuous-casting machines. PERM MANUFACTURING PLANT In 2000 and 2001, the open-hearth shop was radically reconstructed. Without shutting down production, the DSP-60/70 arc furnace and a ladle–furnace unit were built and put into operation. The open-hearth furnaces were then shut down. Today, the shop includes not only two continuous bloom-casting machines but two continuous slab-casting machines (producing 175 × 1020 and 165 × 720 mm slabs). Steep is cast directly from the casting ladle through a directional funnel and delivered below the melt level. The machine is constantly being upgraded, primarily by plant personnel. NOVOLIPETSK METALLURGICAL WORKS NMW has focused on slab production from its inception. Continuous-casting machines now operate in the first and second converter shops. Operation of the electrosmelting shop has been discontinued. The world’s first integrated combination of a converter and continuous-casting machine went into operation in converter shop 1. As well as killed carbon steel, rimmed steel was cast. In 1993, the outdated vertical continuous-casting machines in converter shop 1 were replaced by new high-speed curvilinear machines with vertical
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Parameters of Russian continuous slab-casting machines (as of September 2008) Supplier
Year of Number of Type of intro- machines machine duction × strands
Smelting process
Ladle capacity, t
Cross section mm
Note
Kamastal Perm manufacturing plant Lenin man- Vertical ufacturing plant
1958
14
Open hearth and electrosmelting
70
175 × 1020 165 × 720
Cast-slab output – 0.3 million t/yr
OAO Novolipetskii Metallurgicheskii Kombinat UHMP
Vertical
1959
2×2
Electrosmelting
110
UHMP
Vertical
1966
6×2
Converter shop 1
160
UHMP
Curvilinear
1974
4×2
Converter shop 2
300
SMS – Demag
Curvilinear
1975
1×2
Converter shop 2
300
150 × 170; 950 × 1020 Reconstructed in 1997– 1999 as two curvilinear 175–315 × 950–1850 machines (each with two 250–350 × 1150–2200 strands) with a vertical section (slab cross section 200–250 × 950–1850 mm): continuous-casting machine 6, VAI–UHMP; machine 4, VAI–NKMK 200–250 × 1000–2050
OAO Nizhnetagilísk Metallurgicheskii Kombinat UHMP
Curvilinear
1968
1×1
Open hearth
160
200–250 × 1500–1800 Withdrawn from operation
UHMP
CVS*
1996
1×2
Converter shop
160
UHMP – VAI
Radial
2000
1×2
Converter shop
160
Beam 530–1050 × 355, Hybrid machine (slab– 485 × 115–165, slab beam) 155–200 × 500–620
VAI
CVS
2004
1×1
Converter shop
160
200–300 × 1500–2700
240 × 1500 240 × 310–575
Hybrid machine: slab casting in two strands; beam casting in four strands
OAO Amurmetall UHMP
Vertical
1967
2×2
Open hearth
170
UHMP
Curvilinear
1974
1×1
Electrosmelting
100
UHMP
Curvilinear
1992
1×1
Open hearth
170
160 × 750–200 × 1550 Reconstructed in 1990 (slab cross section 180 × 180 × 1050 1200 mm) 200 × 1500 (max)
OAO Cherepovetskii Metallurgicheskii Kombinat Severstal UHMP
Vertical
1970
2×2
Electrosmelting
130
150–200 × 650–1550 Continuous-casting machine 1 reconstructed by ORMETO–YuUMZ, machine 2 replaced by a bar machine (by Rokop)
UHMP
Curvilinear
1980– 1981
3×2
Converter shop
350
200–250 × 1100–1900 Reconstructed in 2006 as a curvilinear machine with a vertical section (slab cross section 250–315 × 1020– 2200 mm)
UHMP
Curvilinear
1985
1×2
Converter shop
350
200–250 × 1400–1900
UHMP
Curvilinear
1989
1×2
Converter shop
350
200–250 × 1250–1900 Total slab output at OAO Severstal ~10 million t/yr
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Table. (Contd.) Supplier
Year of Number of Type of intro- machines machine duction × strands
UHMP
Curvilinear
1990
UHMP
Curvilinear
1994
UHMP
CVS
2006
UHMP
CVS
1992 1993
SMS – Demag
CVS
2004
VAI
CVS
2005
STB
CVS
2007
Smelting process
Ladle capacity, t
Cross section mm
OAO Magnitogorskii Metallurgicheskii Kombinat 3×2 Converter 350 250 × 750–2350 shop 250 × 1250–1350 250 × 1250–1350 1×2 Converter 350 250 × 750–2350 shop
Note
Hybrid (2–4)-strand continuous-casting machine 3 introduced in 2001, continuouscasting machine 2 in 2003. Reconstructed as a four-strand machine (slab cross section 250 × 1250–1350 mm)
1×2
Electros180 250 × 1250–2350 melting OAO Chelyabinskii Metallurgicheskii Kombinat Mechel 1×1 Electros130 150–170 × 1050–1550 melting 6 1×1 OAO UralStal 1×1 Electros160 170–190 × 1200 Output 0.8 million t/yr melting OAO Zapadno-Sibirskii Metallurgicheskii Kombinat 1×2 Converter 350 200–250 × 1050–1750 Output 2.4 million t/yr shop OAO Ashinskii Metallurgicheskii Zavod 1×1 Open 120 180–240 × 900–1600 Output 0.8 million t/yr hearth
* CVS, curvilinear machine with a vertical section.
molds, on the basis of designs developed by VAI and UHMP. In 1998, continuous-casting machine 6 went into operation, in place of vertical machines 5 and 6; in 2002, continuous-casting machine 4 went into operation, in place of machines 1 and 4. In 1975, converter shop 2 was inaugurated, with two 300-t converters and curvilinear continuous-casting machines 5–8 (designed by UHMP). In 1976, Demag radial continuous-casting machine 9 was introduced at the shop. It was later reconstructed by UHMP (with replacement of part of the radial section, by analogy with continuous-casting machines 5–8). Each machine is equipped with its own metal-supply unit. The casting of 08û steel with vacuum treatment in the flux was introduced at continuouscasting machine 5. The production equipment at the plant is constantly being upgraded. Continuous-casting machine 6 has been radically reconstructed; continuous-casting machine 7 is now being reconstructed; and there are plans for the reconstruction of continuouscasting machine 8 in converter shop 2, with conversion to vertical casting and the introduction of effective secondary cooling, a system for mild reduction, and an automatic control system. Provision is made for switching from 250 × 1850 mm to 310 × 2200 mm blanks. To ensure high slab quality, new ladle-treatment units (two-position circulatory vacuum units and ladle–furSTEEL IN TRANSLATION
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nace units) are being constructed. The total output of cast slabs is 10 million t/yr. OAO AMURMETALL Up to 97% of the metal produced is cast on the continuous-casting machines in the open-hearth shop. From the 1970s to the 1990s, 94–98% of the low-alloy steel produced and the steel for ship, bridge, and boiler construction was continuous-cast. Between 1996 and 2007, the vertical continuous slab-casting machines went out of operation, and the slab machine with ingot extrusion by a special mechanism (a stepping-beam mechanism) was mothballed and then restarted. OAO SEVERSTAL The development of continuous casting at Cherepovetsk Metallurgical Works began in the electrosmelting shop, where a vertical two-strand continuous slabcasting machine (capacity 600000 t/yr) went into operation in 1969. A second such machine went into operation in 1975. At the end of 1980, the introduction of the first stage of the converter shop began; this shop included two double-strand curvilinear continuouscasting machines (total capacity 2.5 million t/yr). This
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was followed by the introduction of continuous-casting machine 2 (1981), machine 4 (1985), and machine 5 (1989). The slab output of the shop was 7 million t/yr. After 30 years of operation, continuous-casting machine 1 in the electrosmelting shop underwent major reconstruction in 1999: the introduction of new molds with separate wall cooling; a spring-driven mold rocker, with a hydraulic drive; a water–air blank-cooling system; and a tractional and reduction cell with a distributed drive, permitting soft reduction. The machine’s slab output rose to 800000 t/yr. OAO ORMETO–YuUMZ and OOO Korad collaborated in the reconstruction. In 2002, continuous slabcasting machine 2 was replaced by a ROKOP bar machine. In the oxygen-converter shop, the continuouscasting machines are being equipped with automatic control systems, including a system for predicting slab quality. Modernization of the basic technological equipment is underway. The greatest modifications have been made to continuous-casting machine 2, reconstructed by UHMP in 2006. This is now a curvilinear machine, with a vertical section of height 2185 mm; it is equipped with a system for regulating the mold width during casting, a system for rupture prediction, a mildreduction system, and a system for dynamic control of secondary cooling. The increased length of the machine (38.2 m) permits casting of slabs with a thickness of 315 mm at a rate of 0.6–0.7 m/min. The capacity of the intermediate ladles is 4–27 t at continuous-casting machines 1 and 2 and 50 t at continuous-casting machine 5. Runs of 100 melts are possible, and repairs are only necessary after 1200 melts. The planned converter-steel output of 9.5 million t/yr is supported by two ladle–furnace units and a VD-OB vacuum unit. OAO NIZHNETAGIL’SKII METALLURGICHESKII KOMBINAT In 1968, Russia’s first single-strand curvilinear continuous slab-casting machine with a stepping-beam system for casting 150-t melts (designed by UHMP) went into operation in the open earth shop at Nizhnetagil’sk Metallurgical Works (NTMW). In the open-hearth shop, the output of continuous-cast steel was 300000 t/yr. After 25-year operation, the machine was dismantled, with the shutdown of the open-hearth shop. The reconstruction and development of NTMW between 1992 and 2000 called for complete transition to converter production and continuous casting of steel. To this end, the plant introduced four-strand continuous-casting machine 1 for the production of blooms and round blanks (diameter 430 mm) in 1995; and continuous-casting machine 2 for the production of 240 × 1500 mm slabs in two strands or, on installing a partition, 240 × 310–575 mm blanks in four strands. The length of the vertical mold is 1000 mm; the vertical section of the machine extends over 3.0 m. The metallurgical length of the unit is 29.5 m. The basic radius is 8.0 m. The working speed in slab casting is
1.0 m/min. The design output is 1100000 t/yr. In 2002, two-strand radial continuous-casting machine 3 (designed by VAI and UHMP) went into operation. This machine (basic radius 12 m) is intended to produce slabs and beams of various types. In 2004, single-strand continuous slab-casting machine 4 (designed by VAI) went into operation. This machine produces 200–300 × 1500– 2700 mm slabs, with the option of casting blanks of width 1150–1280 mm. Its annual output is 1500000 t/yr. This is one of the most up-to-date units in the metallurgical industry today. The radius of the radial section is 10 m; the casting rate is up to 1.3 m/min; the metallurgical length is 27.2 m. Note the small secondary-cooling chambers, the computerized slab-quality maintenance system, the system for protecting rupture, and the mildreduction system. The unit has now exceeded its design output. The output of continuous-casting machine 2 is 1530000 t/yr; that of continuous-casting machine 4 is 1390000 t/yr. OAO MAGNITGORSKII METALLURGICAL KOMBINAT Continuous casting was first introduced in November 1990, with the startup of the converter shop, which included converter 1 and continuous-casting machine 1. Subsequently, continuous-casting machines 2–4 went into operation. The UHMP two/four-strand design permitted the casting of two broad slabs (1100–2350 mm) or four narrow slabs (750–1080 mm) on these curvilinear machines. All the rollers of the supporting system were of split structure, with center bearings. Each machine had four single-blade gas-cutting units. Thanks to improvement in individual components and in the casting technology, increase in the number of melts in a series, reduction in downtime, and the introduction of automatic control systems, the total output in 2001 was more than 7.9 million t/yr. Since slabs of width 1250– 1350 mm were generally produced, it was decided to modernize the equipment so as to increase the productivity. At the end of 2001, continuous-casting machine 3 was modernized; in February 2003 continuous-casting machine 2 was reconstructed. Afterward, the machines were characterized by simultaneous casting in four strands through two double molds, with a common rocker mechanism for the pairs of strands. Collaborating with plant personnel, UHMP specialists developed a unique continuous-casting machine with an output of more than 3 million t/yr. Excellent organization permitted the dismantling of the old equipment and the installation of the new machine (weighing more than 3000 t) in record time (19 days). After reconstruction, the total output of the continuous-casting department rose to 10 million t/yr. After replacing the open-hearth furnaces by two upto-date 175-t electrofurnaces, the capacity of the electrosmelting shop rose to 4 million t/yr, whereas the productivity of the two existing continuous bar-casting machines in the shop was 2 million t/yr. In August 2006, STEEL IN TRANSLATION
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new two-strand curvilinear continuous-casting machine 5 went into operation in the shop. The productivity of this machine (characterized by multipoint billet flexure and a radial section of radius 8 m) is 2.2 million t/yr. Casting in 250 × 1250–2350 mm slabs is possible. The length of the machine is 31.7 mm; the length of the vertical section is 2.8 m; the height of the mold with slot channels is 900 mm; the maximum casting rate for 250 × 1250 mm slabs is 1.2 m/min. The total slab output at the plant is 12 million t/yr. In 2007, a contract was signed with SMS-Demag for the supply of new equipment for the production of slabs (thickness 190, 250, and 300 mm; width 1400–2700 mm) from a wide range of steel, including X-80–X-120 pipe steel for supply to a 5000 thin-sheet mill. The 5000 mill and the continuous-casting machine will in fact be delivered as a single unit. OAO CHELYABINSKII METALLURGICHESKII KOMBINAT In 1991 and 1992, single-strand continuous slab-casting machines (designed by UHMP) went into operation in the new electrosmelting shop. These machines were intended to produce 150–170 × 1050–1550 mm corrosion-resistant steel blanks. The length of the vertical section was 2.8 m; the basic radius was 6 m; and the metallurgical length was 16.9 m. Multipoint flexure of the blank was employed. Because of insufficient orders for corrosion-resistant steel, electrosmelting shop 6 began to produce carbon steel. The shop’s staff expends considerable effort on upgrading the casting technology and equipment and improving the organization of production. Liquid steel is supplied from the converter shop to the electrosmelting shop. Since the pumping and storage section was not designed for the simultaneous operation of hydraulic cutters at both machines, a Gega gas cutter was introduced at continuous-casting machine 2. As a result, both machines may operate at once, with a total productivity of 700000 t/yr. However, some problems remain unresolved—for example, the life of the supporting rollers in the radial zone. Management has decided to reconstruct electrosmelting shop 6, with the replacement of the two existing slab machines by a Danieli machine, for a design output of 1200000 t/yr. OAO ZAPADNO-SIBIRSKII METALLURGICHESKII KOMBINAT In 2005, a continuous slab-casting machine went into operation in converter shop 2, which contains two 350-t converters. Construction of the machine, on the basis of a VAI design, took 18 months. Its output (slab of dimensions 200, 250 × 1050–1750 and 6000–12000 mm) is 2.4 million t/yr. This radial (R = 10 mm) two-strand machine with a linear section (length 2.4 m) is characterized by multipoint billet flexure; its metallurgical length is 27.4 m. Equipped with a 60-t intermediate ladle, the machine permits casting at 1.8 m/min. The design incorSTEEL IN TRANSLATION
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porates up-to-date Scada systems. Presently, 70% of the steel produced in converter shop 2 is cast on this machine; the remainder is still chill-cast. According to design data, there is sufficient scope for increasing the production of continuous-cast slab and bar. Because there is no capacity for processing cast slab at the plant, most of the slab is exported. OAO URAL’SKAYA STAL In October 2004, a single-strand continuous slabcasting machine (output 800000 t/yr) went into operation at the plant as part of its modernization and expansion program (undertaken in collaboration with SMSDemag). The arc-furnace capacity is 160 t. The curvilinear continuous-casting machine with a vertical section (basic radius 10.5 m) has six points of billet flexure (R1 = 60 m and R6 = 11 m) and four straightening points (R7 = 10.5 and R10 = 33 m). The metallurgical length of the machine is 30.3 mm. The cast billet is of thickness 190 and 270 mm and width 1200 mm. A straight mold is employed (length 900 mm). The maximum casting speed is 1.6 m/min for 190-mm slab and 1.2 m/min for 270-mm slab. At present, 30 melts are cast each day, in runs of 60 melts (16 melts per intermediate ladle). Hot slabs are transported on trolleys with insulated lids to the continuous furnaces of the 2800 thick-sheet mill. OAO ASHINSKII METALLURGICHESKII ZAVOD In 2006, in accordance with the reconstruction plan for steel smelting in the open-hearth shop, a ladle–furnace unit was installed. In July 2007, a single-strand curvilinear continuous-casting machine with a vertical section (length 2620 mm) went into operation. This state-of-the-art machine (designed by STB, Italy) permits the installation of a mild-reduction system. The slab dimensions are 180, 240 × 900–1600 mm; the basic radius of the machine is 8 m; there are nine points of billet flexure and ten straightening points; the metallurgical length of the machine is 25.87 m. The linear mold (length 900 mm) is characterized by slot cooling; the hydraulic rocker system includes servo valves. The casting-ladle capacity is 120 t, while the intermediate ladle holds 27 t, when the working level of metal is 1000 mm. The casting nucleus is introduced from below. The casting speed is 1.4–1.5 m/min for 180-mm slab and 1.0–1.2 m/min for 240-mm slab. The output is 800000 t/yr. DISCUSSION On the basis of the data here presented, we see that vertical continuous-casting machines were only favored in the initial stages. Beginning in the 1970s, curvilinear machines rose to prominence, with the active advocacy of UHMP specialists. In this period, UHMP was essentially the only supplier of continuous slab-casting
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machines. Productivity and slab quality were greatly impeded by vertical machines, the casting of single melts, and the lack of ladle-treatment equipment. Recently, a greater variety of continuous-casting machines appeared: moderate-slab machines (billet thickness 90–120 mm); thin-slab machines (billet thickness 50–80 mm); and roller machines (strip thickness 2.5–3 mm). However, most continuous-casting machines are still traditional slab machines, producing billet of thickness 150–400 mm and width 750–3250 mm. In many cases, given the demand for a wide range of slab, combined systems are built. Analysis of the data in the table indicates that most continuous-casting machines are now outdated. Accordingly, an active reconstruction program is underway in Russia and elsewhere. The new machines incorporate recent achievements in manufacturing and metallurgy: effective and flexible ladle treatment of liquid steel before casting, so as to ensure the required steel parameters: —intermediate ladles of increased capacity (40–60 t), using partitions, filters, and injection elements so as to ensure final refining of the metal; —molds with intermediate slot cooling and usually with anticorrosion and antiwear coatings; the molds can process 140000–150000 t of steel before replacement and are equipped with an automatic system for hydraulic control of the slab width; —a spring-based rocker mechanism for the mold, with a hydraulic or electromechanical drive, permitting a wide range of rocking options (including inverse rocking); —equipment for monitoring and maintaining the metal level in the mold and systems for monitoring the thermal state of the mold and for preventing rupture of the solidifying billet; —multipoint billet flexure (in the vertical mold and in the initial supporting Bender section) and straightening for uniform stress distribution at the solidification front; —dynamic secondary cooling of the billet, automatically maintaining a specified temperature field (a twocomponent cooling system is widely used); —rollers in the guide system that include a onepiece barrel, internal cooling, and intermediate bearings; the roller diameter is minimized, depending on the position in the continuous-casting line; —dynamic control of the roller inclination and the taper of the roller unit (including control in transient casting conditions); together with the system for calculating the final point of hardening, this ensures soft reduction of the billet so as to reduce axial liquation and ensure the required slab thickness; —durable refractory materials; —automated supply of slag-forming mixtures to the mold;
—electromagnetic mixing for optimization of the liquid-steel fluxes and the thermal state of the metal meniscus in the mold; —systems for the fast replacement of worn elements (molds, segments, rollers, etc.); —accessibility and ease of monitoring of the mechanisms. Thus, modern continuous-casting machines, including Russian machines, are flexible, dynamic, and highly evolved. They are capable of high productivity and accommodate a range of billet sizes and materials. Whereas billet reduction in casting was once impossible, it is now feasible, with some care. It is often said that the casting speed in Russian machines is two thirds or even half of that in foreign machines. This was true of the first Russian continuouscasting machines, with little automatic monitoring, and may be attributed to deficiencies of the machines and of the casting technologies, as well as the accident-prevention systems. Today, Russian machines are practically as fast as their foreign counterparts. For comparison, we now consider continuous casting at some foreign enterprises. Dillinger Hüttenwerke Plant This full-cycle enterprise produces thick sheet [1, 2]. In 1968, an oxygen-converter shop with 190-t converters went into operation. In the shop, continuous-casting machines 3–5 went on line in 1968, 1974, and 1998, respectively. About 97% of the shop’s steel is cast on these machines; the rest is chill-cast. All three machines are two-strand vertical units, with slab flexure after complete solidification. Continuous-casting machine 3 was characterized by metallurgical length 10.5 m; radius of curvilinear section 8 m; casting speed 0.5–0.8 m/min; slab thickness 200 and 260 mm; and slab width 1000– 1600 mm. Reconstruction in 2001 and 2002 increased the metallurgical length to 12 m, with 15% increase in casting speed (to 0.9 m/min). The maximum possible slab thickness was increased from 260 to 300 mm. The parameters of continuous-casting machine 4 are identical to those of machine 3 after reconstruction; the casting rate is 0.4–0.8 m/min for slab of thickness 200–300 mm and width 2200 mm. Continuous-casting machine 5 produces 400-mm slab at the typical casting speed of 0.3 m/min, with a mold length of 700 mm. Note that this speed corresponds to vertical machines with limited metallurgical length (12 m in the present case). Nippon Kokan Plant, Fukuyama, Japan Single-strand continuous slab-casting machine 6 at this plant is intended to produce slab of high quality at high speed and low cost [3]. The length of the vertical section (3.0 m) in this curvilinear machine is sufficient for elimination of large inclusions that might lead to surface defects of the slabs. There are ten points of slab STEEL IN TRANSLATION
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flexure. The metallurgical length of the machine is 49 m; the basic radius is 10 m; the length of the mildreduction zone is 17 m. The slab thickness is 220, 250, and 300 mm; the slab width is 675–2100 mm; the maximum casting speed is 3 m/min. Secondary water–air cooling is employed; the solidification nucleus is introduced at the top. The 80-t intermediate ladle, without partitions or barriers, is used in hot-rotation mode. The monthly output of the machine is 177000 t. The high casting rate is entirely consistent with the metallurgical length of the machine. Salzgitter Flachstahl Continuous-Casting Machine Salzgitter Flachstahl continuous-casting machine 3 (output 600000 t/yr) went into operation in 2004 in Salzgitter. This curvilinear machine has a vertical section with a length of 2.6 m. The basic radius is 9 m; the metallurgical length is 30.95 m. The casting rate for 250 × 850–2100 mm slabs is 1.35 m/min. At the same time, the installation of three additional segments permits increase in the casting rate to 1.6 m/min. The mass of the cast melt is 210 t; the capacity of the intermediate ladle is 34 t. Secondary water–air cooling is employed; the solidification nucleus is introduced at the top [4]. Mittal Steel Lazaro Cardenas The casting rate at this Spanish plant is 1.3 m/min for 200-mm slab, 1.15 m/min for 225-mm slab, and 1.00 m/min for 250-mm slab, according to [5]. Nippon Steel Plant, Nagoya Two-strand vertical continuous-casting machine 2 with subsequent billet flexure permits a monthly output of 260000 t, with a casting rate of 2.2 m/min for 245 × 900–1630 mm slabs [6]. ThyssenKrupp CSA Companhia Siderurgica This company, based in Rio de Janeiro (Brazil), is constructing a new metallurgical plant in the vicinity of Santa Cruz, for cast-slab production at a rate of 5 million t/yr [7]. The steel-smelting shop will be equipped with two 300-t converters and two vertical doublestrand continuous-casting machines with billet flexure. The mold length in the casting machine is 900 mm; the length of the vertical section is 2800 mm; the basic radius is 9000 mm; the metallurgical length is 30 m. (Two additional segments may be installed.) The slab thickness is 255 mm, the width is 800–2000 mm, and the length is 6–12 m. The maximum casting speed is 1.6 m/min; the capacity of the intermediate ladle is 80 t. Secondary water–air cooling is employed; the monthly output is 208500 t. The machine will be equipped with devices ensuring high slab quality and the best economic indices. STEEL IN TRANSLATION
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Reviewing this brief account of foreign machines, we conclude that the design casting speeds of Russian machines are entirely comparable with those of their competitors. Casting speeds are basically determined by the design features of the machine, the preparation of the steel for casting, the grade of steel, and the requirements on the cast and forged products. In Russia today, no imported machine can be regarded as preferable to domestic equipment. A survey of recent construction and reconstruction projects suggests approximate parity between domestic and foreign suppliers in the Russian market: six VAI machines (11 strands), at OAO NLMK (continuous-casting machines 4 and 6 in converter shop 1 and machine 6 in converter shop 2), OAO NTMK (continuous-casting machines 3 and 4 in the converter shop), and at OAO ZSMK; two SMSDemag machines (two strands) at OAO Amurmetall and OAO Ural’skaya Stal; one STB machine (one strand) at OAO Ashinskii Metallurgicheskii Zavod; four UHMP machines (12 strands) at OAO MMK (continuous-casting machines 2, 3, and 5) and OAO Severstal (continuous-casting machine 2 in the converter shop); one ORMETO–YuUMZ machine in the electrosmelting shop at OAO Severstal. These data indicate that the trend in construction and reconstruction is to introduce curvilinear machines with a vertical section and subsequent billet flexure. The use of a vertical section (length 2.5–3.0 m) in the continuous-casting machine improves the purity of the steel, with particular reduction in inclusions larger than 100 μm. Note, however, that the slab then undergoes deformation twice in casting: bending beyond the vertical section and subsequent straightening. Accordingly, the expediency of using machines with a vertical mold must be given special consideration in each specific design. Note the growth in slab casting recently. About 35– 36 million t of steel is continuous-cast to slab. However, the main source of further improvement in continuous-casting machines is the broader use of smart control systems. The theoretical principles of continuous casting have now been adequately developed; subsequent theoretical refinements are mainly of secondary order. Such adjustments cannot radically improve the economics of continuous casting. A promising approach is to develop virtual models on the basis of theoretical description of the process. Virtual models are widely used in industry. They permit adjustment of the process parameters and rapid problem solving. A common feature of such systems is their determinate logic, which imposes certain constraints. These systems are incapable of spontaneous adaptation, learning, or self-improvement. In the optimization of continuous casting, the best results are obtained using smart technology. In the near future, significant growth of smart technology is expected, with improvement in the speed and efficiency of simulation of complex production processes [8]. The
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successful use of smart technology in continuous casting is illustrated by the following examples [9–12]: monitoring of the metal level in the intermediate ladle; simulation of billet solidification; dynamic control of secondary cooling; detection of latent defects in the billet; and optimization of the extrusion rate and mild reduction of the cast slab. Smart systems are being rapidly introduced in industry. In current conditions, a promising approach is the development and introduction of standardized program modules. This permits modification of the formulation of a multifactorial optimization problems and its solution by universal methods, including remote diagnostics and improvement of the production conditions from a remote server by the developer of the continuous-casting technology or equipment [11, 12]. Software based on smart technologies and remote testing of continuous-casting equipment and conditions must be universal and satisfy the following conditions: generality of the solution and universality of the mathematical model; applicability to any optimization and control problems; adaptability to change in the conditions and goals; simple variation of the target function; visual monitoring of system operation at any stage; automatic identification of unknown factors influencing the process; ranking of the relevant factors by genetic algorithms; monitoring of interference and prediction of drift of the process parameters; compatibility with any control system; and ease of introduction on the basis of existing equipment, without capital expenditures. We may draw on the latest developments in information science, artificial-intelligence systems, multifactorial analysis, fuzzy-set theory, fuzzy logic, and singular matrices. Possible techniques include multifactorial analysis and verification of digital dynamic video images of information fluxes, and emulation and adaptation of neural structures and simulations of continuous-casting processes. In practice, the greatest difficulty is posed by the preparation of information sets to ensure effective operation of the smart optimization system. Therefore, automated preprocessing of the information fluxes is required, as well as monitoring and automated analysis of the quality of the initial information. Where databases of technological and economic characteristics of continuous casting are available, the software permits a global maximum of efficiency within the specified production constraints. For the nonspecialist, a user-friendly interface must be created, on the basis of standard Microsoft
Office software. Industrial tests of the smart modules demonstrate highly efficient multifactorial optimization of production. There is significant scope for reducing material, energy, and financial outlays at metallurgical plants [12]. Thus, Russian specialists have access to a large set of patented techniques for creating technologically and economically optimal continuous-casting machines on the basis of the latest technical accomplishments. REFERENCES 1. Munich, B., Stiga, A., and Wagner, P., Modernization of Continuous-Casting Machines 3 and 4 at Dillinger, Chern. Met., 2005, no. 5, pp. 34–38. 2. Hecht, M., Zhu, Zh., Lachmund, H., and Tacke, K.-H., Molds of Continuous-Casting Machines for Thick Slabs, Chern. Met., 2006, no. 4, pp. 41–47. 3. Kuribayashi, A., Mori, T., and Ozawa, K., Construction and Operation of Fukuyama 6 CCM, NKK Techn. Rev., 1995, no. 73, pp. 7–14. 4. Grethe, W., Muller, T., Muller, P., et al., Increasing Steel Productivity and Expanding the Grade Range: New Continuous-Casting Machines, Chern. Met., 2005, no. 11, pp. 35–39. 5. Tsai, H., Yin, H., Lowry, M., et al., Analysis of Transverse Corner Cracks on Slabs and Countermeasures, Iron Steel Technol., 2006, vol. 3, no. 7, pp. 23–31. 6. Nippon Steel Corporation NSC, Steel Times Intern., 1993, no. 3, pp. 51, 52, 54. 7. Lindenberger, H.-W., Sheffer, F.-W., and Igelbusher, A., Construction of New Steelworks in Brazil by ThyssenKrupp CSA, Chern. Met., 2009, no. 2, pp. 45–52. 8. Kruglov, V.V. and Borisov, V.V., Iskusstvennye neironnye seti. Teoriya i praktika (Artificial Neural Networks: Theory and Practice), Moscow: Goryachaya Liniya–Telekom, 2002. 9. Slab Casting Control by Neural Network and Fuzzy Logic, Metallurg. Plant. Technol. Intern., 2001, no. 6, pp. 76–77. 10. Fan, X., Zhang, L., Cai, X., Wang, G., and Liu, X., Hot Strip Coiling Temperature Control Based on Fuzzy SelfAdjustable PID Parameter Controller, J. Iron Steel Res. (China), 2001, no. 2, pp. 59–61. 11. Parshin, V.M. and Chertov, A.D., Smart Quality-Control Systems for Continuous-Cast Billet, Stal, 2005, no. 2, pp. 37–43. 12. Parshin, V.M. and Chertov, A.D., Quality Control of Continuous-Cast Billet, Stal, 2005, no. 1, pp. 20–29.
STEEL IN TRANSLATION
Vol. 39
No. 8
2009
