Baixe o app para aproveitar ainda mais
Prévia do material em texto
EUROSTRIP® - THIN STRIP CASTING TECHNOLOGY LATEST STATUS; APPLICATIONS, FUTURE PERSPECTIVES 1) 1) 33 º Seminário de Fusão da ABM - Associação Brasileira de Metalurgia e Materiais- De 06 a 08 de maio de 2002 - Santos, SP. 2) Technical Director, VOEST-ALPINE Industria Ltda., Belo Horizonte / BRAZIL 3) General Manager EUROSTRIP, VOEST-ALPINE Industrieanlagenbau GmbH & Co, Linz / AUSTRIA 4) Managing Director, EUROSTRIP Int’l., Paris / FRANCE EBERHARD KARNITSCH 2) GERALD HOHENBICHLER 3) HUGUES LEGRAND 4) SYNOPSIS: Since the late 80's, strip casting developments in Europe were led by USINOR and Thyssen (the MYOSOTIS Project) and by AST and CSM (the Terni-Project), separately. In 1995 the Austrian Plant builder VOEST-ALPINE Industrieanlagenbau (VAI) joined Terni's development program. In 1999 it was decided to merge the individual efforts and to team-up in a joint venture. The EUROSTRIP�-Technology was born. Already in 1999, the first industrial EUROSTRIP� Plant was commissioned at KTN Krefeld by the EUROSTRIP� Team. Krefeld plant produces stainless steels today. In May 2001 an inline-rolling stand and inductive heating device were installed, which resulted in further improved strip quality level. Today, 1430 mm wide strip is produced there. Results from operation will be presented. The pilot plant at AST Terni was always the frontrunner in the group's R&D due to its flexibility. Since 1999 research was turned towards the production of Carbon and Silicon grades, and also installation of an inline-rolling stand, which allows the investigation of different process parameters of the EUROSTRIP� Technology. A summary about the potentials of Carbon Steel production via strip casting will be presented together with the impact to environment of this promising novel technology. Keywords: Strip casting, Vertical twin-roll casting process, EUROSTRIP®, KTN-Krefeld, AST-Terni, Reduction of emission; Implementation options Who is EUROSTRIP®? In the past, in Europe, strip casting developments have been led independently by USINOR and Thyssen (the MYOSOTIS Project) 1) and by AST and CSM (the Terni Project). In 1995 the Austrian plant builder VAI joined Terni’s development program and upgraded the plant. After ThyssenKrupp Steel acquired AST, it became obvious to concentrate the individual development work. September 17th, 1999 marks the day, when ThyssenKrupp Steel, USINOR and VAI decided to merge their efforts to further develop and market the strip casting technology for the production of carbon, stainless and silicon grades - The EUROSTRIP® technology was born. VAI is the exclusive plant builder in this cooperation. The EUROSTRIP® Team Besides two operating facilities in Krefeld and in Terni, there are laboratory facilities. Even hot tests on laboratory plants can not be directly extrapolated to full scale facilities, principal phenomena such as castability of special grades, influence of micro-alloys, process stability for different casting parameters and roll geometry deliver important insights. R&D work is further supported by an international team of specialists in plant operation, engineering, metallurgy, physics, fluid dynamics, hot- and cold forming and process automation, figure 1. Aachen Lab.- Caster Team IRSID Lab.- Caster Team CSM / Rome Research AST/CSM Pilot Plant Team VAI Engineeering/ Research USINOR Research TKSteel Research KTN Industrial Plant Team Figure 1: The EUROSTRIP® Network Principles of Strip Casting In the twin-roll strip casting process, liquid steel is poured between the counter-rotating rolls. Two ceramic side plates are pressed against the front faces of the casting rolls to contain the liquid-steel bath. Starting from the so-called meniscus, steel shells form on both roll surfaces. They quickly grow up to the narrowest point between the two rolls, the so-called “kissing point”, were the two shells join. It takes approx. 0.4 s until cast strip of a thickness of 2 mm has solidified. The casting speed ranges typically from 40 m/min to 130 m/min depending on the strip thickness, casting roll size and pool height. A principle sketch of the twin roll process is illustrated in figure 2, which indicates the main technical challenges for the successful implementation. Diameter of Rolls to control Capacity and Strip Thickness Lifetime of Side Dams for long casting time Fluid Dynamics of liquid Steel for homogenous solidification and stability of the process Surface structure of Rolls to control initial solidification and strip quality Protection of meniscus for strip quality Shape of rolls influence strip shape tolerances Position control influences strip thickness tolerances Figure 2: Some of the main challenges in strip-casting Main Challenges: • The first task is to distribute uniformly the liquid steel between the two rolls. This is a precondition for homogeneous solidification and stability of the process. EUROSTRIP® uses a relative simple SEN. • In contrary to the conventional casting process and due to the absence of relative movement between shell and mold, casting powders are not required, but special surface texture has to be foreseen to control the heat flux. • The atmospheric space above the mold level is filled with inert gas, which has to be distributed evenly. • A real key to twin-roll strip casting is the lateral containment. Ceramic side dams are pushed and positioned laterally against the rotating casting rolls. They have to assure the tightness of the mold against leakage of liquid steel and prevent solidification on these dams. Thermal shock resistance, low thermal conductivity and abrasion resistance is required to allow long casting duration. • The diameter of the rolls influences direct proportionally the plant’s capacity. EUROSTRIP® uses 1500mm rolls for high throughput rates. • The shape of the casting rolls influences the strip shape. This is a crucial element in providing exact strip tolerances and stability over a long casting duration. • Accurate roll position control is required to establish stabile strip tolerances. The EUROSTRIP® plant at KTN-Krefeld 2) In February 1999 the foundation stone was laid for the new strip caster. The Krefeld works are an ideal business case as there is no hot rolling mill and the conventionally cast slabs are transported to the Bochum hot strip mill by rail. The hot rolled coils are then returned to Krefeld for further cold processing (figure 3). The first successful cast was performed on the 10th of December 1999. Conventional route: slab/coil transportation app. 150 km to/from hot strip mill in Bochum 1 Melt shop 2 Cold rolling mill 3 New finishing shop New: Strip Casting route: direct link between melt shop and cold rolling mill 1 2 3 Figure 3: Production flow improvement at KTN Krefeld After some optimization steps fully stable and reliable casting conditions could be reached in the first half of 2000. In 2001 an in-line-rolling stand and an inductive heating furnace have been commissioned. The latest record was achieved on October 24, 2001, when producing first time a two ladle's sequence in grade AISI 304, 1430 mm wide, which is the maximum capacity of the current up-coiler. In figure 4 the process flow scheme of the Krefeld strip caster after installation of a double coiler in 2002 is shown. 90 t ladles are frequently cast. The tundish size is 18t. Upon exiting the casting rolls, the strip runs through the looping pit before it enters the inductive furnace. In-line rolling forces of up to 3800 t have been achieved so far, which enables KTN toproduce thinner austenitic grades, than possible by conventional hot rolling. Shear Ladle Turret 18 t Tundish Casting Rolls In-Line Hot Rolling Stand Inductive Heating 90 t Ladle 2-Coiler System Casting Speed : max. 150 m/min Strip Thickness : 1.4 / 4.5 m/min Strip Width: max. 1450 mm Cooling Figure 4: Process flow scheme of the KTN strip caster in 2002 Increased Capacity Productivity is clearly a major factor in achieving economic feasibility. The new process differs from conventional hot band production where the productivity is reduced when thinner gauges are rolled; this is because of limitations in maximum final rolling speed, which is restricted by strip transport speed and by coiler threading speed in the run-out area. In contrast, the productivity of strip casting increases with reduction in cast strip thickness, because the contact length from the meniscus to the ‘kissing point’ remains unchanged. To ensure that the strip solidifies in the same position (ie, the kissing point), the rotational speed of the roll must be increased when the strip thickness is reduced, see also figure 5. An additional feature of the new process is that by increasing roll diameter, the contact length between the meniscus and the ‘kissing point’ is enlarged and this results in a further improvement in productivity. Increased productivity is the key advantage of EUROSTRIP as a consequence of using the 1500 mm rolls. By comparison with 500 mm diameter rolls the productivity can be nearly doubled, under the same boundary conditions. Furthermore with 1500 mm diameter rolls a wider range of strip thickness can be produced, not only standard feedstock material for cold mills (> 2 mm) but also thinner gauges at large widths. As cast strip thickness in mm 500 mm Th eo re t ic al c ap ac ity in % (1 00 % a t 2 m m s tr ip th ic kn es s) (*) Literature and EUROSTRIP® - lab. Plants 0 20 40 60 80 100 120 140 160 180 1 1,5 2 2,5 3 3,5 4 4,5 increased diameter of casting rolls Ø 1500 mm Ø 500 mm (*) Figure 5: Influence of casting roll diameter and strip thickness on capacity In-line rolling At the in-line rolling stand the cast thickness is reduced in size and the surface and internal structure is converted from an as-cast to an as-rolled condition. The situation for an in-line rolling stand is somewhat different from that of a conventional rolling mill. The conventional rolling mill utilizes the gap time between consecutive slabs to stabilize the thermal condition acting on the different components. In strip casting the rolling mill operates for several hours without interruption. For the above reason the ambient temperature inside the mill stand must be stabilized. 1,40 1,60 1,80 2,00 2,20 2,40 2,60 2,80 3,00 3,20 0 100 200 300 400 500 600 700 800 900 1000 1100 Width in mm Thickness in mm as-cast hot rolled reheated and hot rolled 28 % reduction 33 % reduction as cast tolerances acc. DIN EN 10051 Figure 6: Strip profile of 304 stainless grade from KTN’s strip caster In figure 6 typical strip profiles are shown. The figure compares the as-cast profile of a 2.9 mm strip with profiles after in-line hot rolling under different conditions. A strip of 2.1 mm is achieved with a reduction of 28% without the use of the inductive heating device. The relative profile remains unchanged, which was expected. The reduction can be further increased to 33% by higher rolling temperatures due to the heaters in operation. All profiles lie well within the relevant EN standards. Surface Quality and Mechanical Properties At Krefeld, an automated surface inspection system is installed at exit of the pickling line. The surface is another key subject in strip casting, as there are no options for surface treatment given until a hot band is produced. This is especially very critical with stainless grades, as they are used in exposed applications without coating. A typical graph of one coil (both surfaces) can be seen in figure 7. Exact preconditions have now been established by KTN for the production of coils and produces with satisfactory surface quality (see also figure 9 on the example of a steel sink unit). Coil inspection report Oct. 2001 Real defect “Scum on strip cast material Coil (97792) Figure 7: Chart of automated surface inspection system of 304 stainless grade from KTN’s strip caster Mechanical Properties Mechanical properties of the strips are at least equal to conventionally produced material. The as-cast hot band has slightly reduced elongation values, however utilizing the in-line rolling stand, the resulting properties, especially the elongation is excellent, see Table I. Strip Casting Material AISI 304 Stainless Steel Rp 02 [N/mm²] Rm [N/mm²] A80 [%] As cast strip * (example) thickness: 3 mm 230 530 48-50 In - line hot rolled strip 22 % hot reduction annealed (example) 280 610 54 conventional hot band annealed 255-330 590-690 47-54 * mechanical properties not affected by annealing Table I: Comparison of mechanical properties of 304 grade Also after cold rolling, the mechanical properties are very well suited. In addition, inclusions occur only in very small sizes very uniformly distributed. This results in increased corrosion resistance measured by the pitting potential (see figure 8). The roughness is also comparable with conventional material after cold rolling. Rp0.2 N/mm2 Rm N/mm2 A80 % Pitting potential mV/H Rz µm avg. strip casting material * 330 670 53 600 1.2 conventional material 240-350 590-690 50-60 400-550 0.9-1.5 * values for a cold rolled strip, 0.8 mm thickness, annealed and skin passed Figure 8: Comparison of mechanical properties of cold rolled 304 grade and product of strip cast material The EUROSTRIP® Plant at AST-Terni 3) In 1989 AST decided to build a pilot plant strip caster basing on the twin drum strip casting process. For the pilot plant a casting roll diameter of 1500 mm and a width of the rolls of 200 mm was chosen. In this phase first experiences were also made with carbon and silicon steel grades. The plant capacity was restricted to 15 t by the coiler system. In 1995 VAI has joined the cooperation with AST/CSM as the plant builder. After more than 200 casting trials of mainly stainless steel grades the coiler was upgraded to 60 t capacity. In 1998 it was decided to enlarge the casting width to 1350 mm. The new plant was commissioned mid 1999. The scheme can be depicted from figure 9. Ladle 60 t Drum coiler Tundish 15 t Low Carbon SteeI - galvanized Figure 9: Process flow scheme of the AST strip caster Terni achieved several milestones such as: • Stainless steel products (since 1996) • First 1130 mm wide strip produced within EUROSTRIP® (May 1999) • Training facility to support the KTN strip caster start-up (1999) • Stable inline rolling of the cast product (2000) • Sellable C-steel hot band (since 2001) The main technical data and some views of the strip caster and the in-line rolling stand in operation can be seen in figure 10. Overview EUROSTRIP® Plant In-line Rolling • Heat size: 60 t • Tundish contents: 15 t • Casting Roll Diameter: 1500 mm • Steel Grades: Carbon Grades Strip CasterStrip Caster Hot rolling standHot rolling stand Drum coilerDrum coiler Hot rolling standHot rolling stand • Max. Width: 1130 mm • In-line rolling: since 2000 • Strip thickness: 1.4 - 4.0 mm Figure 10: Main technical data and views on the AST stripcaster Crown AST optimized the casting roll shape in order to achieve satisfactory strip crown. In the next figure 11 strip profiles with different reductions are compared. On low carbon steel it is possible to achieve a reduction of about 41%, which results in a strip thickness of about 1.5 mm, when an as-cast thickness of 2.5 mm is adjusted. The crown remains constant at different reduction ratios with about 30-60 µm and can be further improved by careful selection of the casting roll profile. 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10 2.20 2.30 2.40 2.50 2.60 0 100 200 300 400 500 600 700 800 900 1000 1100 Strip width in mm st rip th ic kn es s in m m 27 % Hot red. Ratio 34 % Hot red. Ratio 41 % Hot red. Ratio As cast Figure 11: Crown of a low carbon steel grade cast at AST Terni’s strip caster Roughness Hot band roughness is slightly higher than conventional processes. The roughness is created by the surface texture of the casting rolls, which is required to control the heat removal rate in the absence of casting powders. In-line rolling is supportive and smoothens the surface during the rolling operation. Today, Ra values are achieved, which already reach the vicinity of those produced in conventional and thin slab routes, as illustrated in figure 12. The roughness of cold rolled material is adjusted upon customer’s requirements. 0 5 10 15 as cast strip 27 % in-line rolled strip typical conventional HSM typical thin slab conventional cold rolled* R a [µ m ] *Cold rolled roughness - EN 10130 Surface appearance Ra [µm] best bright ≤≤≤≤ 0.4 bright ≤ ≤ ≤ ≤ 0.9 dull 0.9 - 1.6 Thickness = 1.5 - 3 mm / Width = 1130 mm Figure 12: Comparison of hot band roughness of low carbon grades of different production routes Scale Scale formation is another critical subject during the production of hot rolled bands. As the solidified steel exits the casting machine, oxides will start to form on the surface of the product. The rate and structure of these oxides is dependent on the temperature, the material being produced and the contact time. In conventional and thin slab routes, high-pressure water descalers remove the scale before rolling. In strip casting, similar descalers cannot be installed before the mill stand, due to slow process speed and small as-cast thickness, which would result in a large temperature drop. In figure 13 a comparison is made. 0 5 10 15 as cast strip no-inertisation as cast strip inertisation future development goal strip typical conventional HSM typical thin slab conventional cold rolled Sc al e th ic kn es s [µ m ] Thickness = 1.5 - 3 mm / Width = 1130 mm Figure 13: Comparison of scale thickness of low carbon grades of different production routes In strip casting, to produce a good rolled surface certain amounts of scale are used to lubricate the roll bite during the deformation phase. If, however, too much scale is present during this phase the result is a defect. It is for this reason that the area after the casting machine, is partially enclosed in a protective atmosphere to slow down the growth of scale, leading to an optimum layer of scale being presented to the Rolling mill. The protective atmosphere reduces the scale layer thickness to a large amount. A similar layer to conventional and thin slab processes can be achieved, however future development will focus on further reduction. Economics and Benefits Strip casting requires fewer steps than any other hot band production process, which results in clear potential investment savings. The process offers a significant conversion-cost advantage when compared with other casting/rolling processes. Production at higher capacities is particularly advantageous in terms of economic benefits and this is a distinct feature of the EUROSTRIP process as a result of the use of large diameter casting rolls. Figure 14 compares conversion cost estimates for EUROSTRIP with those of some other processes, where conversion costs are defined as operational costs plus capital charges. The equipment considered in this comparison are casters, reheating facilities (if required) and hot rolling mills supplied on a turnkey basis. The capacity range is covered by one or more casters with additional investments for the reheating and mill equipment. In all cases, the casting and rolling steps are hot or directly connected. The reference grade for the comparison is low carbon steel, 1250 mm x 2 mm. With a EUROSTRIP facility such as in figure 15 producing 0.5 Mt/year of strip, it is possible to achieve the same low conversion costs as that of a thin-slab casting/rolling mill plant producing about 2 Mt/year, or a modern conventional plant producing about 3 Mt/year. The main benefits of the new strip casting process are summarised below. • Lower specific investment costs - about 45% less than a conventional plant and about 35% less than a thin-slab casting/rolling facility • Less space requirements - only 15% of the space required for a conventional facility and about 40% of a thin-slab casting/rolling plant including infrastructure; the actual requirement for a EUROSTRIP plant is 110 x 150 m (incl. infrastructure) with the length from ladle turret to down-coiler only 60-80 m (see Figure 12) • Just-in-time production - only a few minutes are needed to produce a hot band thus substantially reducing inventories and improving customer service • Lower energy consumption - roughly 1400 MJ/t less than the energy required by a conventional production route, and less than 50% of a thin-slab casting/rolling plant • Lower atmospheric emissions - SO2, CO2 and NOx are reduced by about 70-90% compared with a conventional production route. 0 20 40 60 80 100 120 0,0 0,5 1,0 1,5 2,0 2,5 3,0 Capacity [million t/a] C on ve rs io n C os ts [E UR \t] Conventional, Hot Connected Depending on Location and Boundary Condition of Capital Charges Direct Rolling, CSP-Type Direct Rolling, Steckel Mill 1/2 Stand Figure 14 Comparison of conversion costs from liquid steel to hot band of different process Figure 15: EUROSTRIP® facility Environment and Energy Due to the nature of the strip casting process, the EUROSTRIP® technology consumes less energy when compared to any other hot band production process. The liquid steel is converted immediately to a solid strip between the casting rolls and is rolled in-line, fully utilizing the latent heat of the strip. Optionally, the strip temperature can slightly be increased before hot rolling in case of specific requirements posed by plant the lay-out or process route. The energy savings are roughly 1400 MJ/t when compared to conventional routes with cold charging of slabs (fig. 16). The final savings will depend on the production flow of the plant investigated, however in comparison to a thin slab casting/direct rolling process, the savings are remarkably higher than 60%. This is not only true for the heating energy, but also for the electrical energy of the transformation and rolling steps in the true near-net-shape-casting process. Casting thickness [mm] Casting speed [m/min] Charging temperature [°C] 2-3 70 210 210 210 210 40-90 4 3 2 1.5 1.5 - 1100 1000 750 500 20 Strip caster Thin slab caster HDR HCR Warm charging Cold charging Energy consumption [MJ/t] 0 500 1000 1500 2000Ref.: K. Emoto et al; Proceeding RestructuringSteel Plants in the Ninetees ; London, 1986 electricity fuel *) *) adjusted by EUROSTRIP ® Fig. 16: Reductions of energy consumptions by strip casting. Since less energy is required for the EUROSTRIP® process, the emissions are reduced substantially. At the KTN Krefeld facility, for example, natural gas is used to fire the reheating furnaces, resulting in considerable savings due to fewer emissions reduced by 70%– 90% for SO2, CO2 and NOx when compared to the conventional route. This greatly preserves resources and facilitates official authorization for new EUROSTRIP® plants (fig. 17). The wastes created by mold casting fluxes are eliminated and lubricants such as oil and grease from the continuous casting and hot rolling process are reduced to about 40% per ton of hot band, which simplifies the treatment of the cooling water and deposits of solid wastes. Strip Casting Continuous Casting +Hot Rolling CO2 NOX SO2 25 k g/ t 20 g /t 15 g /t CO2 NOX SO2 18 5 kg /t 29 0 g/ t 50 g /t Source KTN Fig. 17: Reductions of emissions by strip casting Implementtion Options Considering the vast potential and the advantages of the strip casting technology, there are numerous options for the implementation into existing steel production plants as well as for establishing a “Greenfield” market mill. The optimum business case will strongly vary from case to case. The production of steel is still a quite individualized task. The thousands of steel producers worldwide have adopted plant lay-outs, processes and production routes as required by the market and strategy or as driven by political or socio-economical reasons. The optimum business plan must be developed individually and will result in a custom-tailored facility. However, in order to provide a more focused approach, the individual implementation cases and business options can be clustered into the following two groups (Fig. 18) ! For existing Integrated Mills as add-on product line ! For New products ! For existing Mini-Mills for flat products with new applications ! For existing Mini-Mills for long products - substitution of product lines ! For “Close-the-gap” scenarios in existing mills 2. Stand-alone Greenfield EUROSTRIP® Mill with new melt-shop ! “Forward” integration possibility for Pig-Iron, HBI/DRI producers ! “Backward” integration possibility for Tube Mills, Steel Service Centers 1. Brownfield EUROSTRIP® Mill Fig. 18: Application options of EUROSTRIP® Summary EUROSTRIP® is a strip casting technology based on the vertical twin-roll casting process as patented by Henry Bessemer 1856. Today, strip casting is reality. This was possible on the basis of the in-depth understanding of the metallurgy of rapid solidification. Advancement in process models, sensor technique and automation hardware allows precise control of the fast process. Improvements of refractory under the harsh environment of a strip caster allow stable casting conditions today. EUROSTRIP® is a cooperation of ThyssenKrupp Steel, Usinor and VAI with the goal to further develop and jointly market the strip casting technology. The two operating plants are located at KTN, Krefeld, Germany for the production of austenitic stainless grades and at AST, Terni, Italy for the refinement of C-grades and electrical steels. In 2002 KTN Krefeld will start commercial operation and EUROSTRIP® will be licensed to interested customers, to whom strip casting provides an economical solution. For updates and further information please visit our website www.eurostrip.info . Acknowledgements We would like to thank the numerous individuals in France, Germany, Italy and Austria, who made the strip casting success for EUROSTRIP® possible. We also gratefully thank the European Commission for funding of the Thermie project (IN/124-96). References 1. H.-U. Lindenberg, “Entwicklung des Bandgießens nichtrostender Edelstähle - EUROSTRIP® “Aachener Stahl Kolloquium, March 22-23, 2001 2. M. Walter, G. Stebner, J.M. Damasse, P. Tolve, G. Hohenbichler, “EUROSTRIP® - initial operational results of the plant at Krefeld Works” CCC2000, Linz / Austria, June 5-7, 2000 3. A. Mascanzoni, J. M. Damasse, G. Hohenbichler, “EUROSTRIP® - development of carbon steel strip casting” CCC2000, Linz / Austria, June 5-7, 2000 4. G. Hohenbichler, U. Albrecht-Früh, J. M. Damasse, R. Capatosti, “EUROSTRIP® - future perspectives of the strip casting process for flat steel production” CCC2000, Linz / Austria, June 5-7, 2000 EBERHARD KARNITSCH 2) GERALD HOHENBICHLER 3) HUGUES LEGRAND 4) SYNOPSIS: Who is EUROSTRIP®? The EUROSTRIP® Team Principles of Strip Casting The EUROSTRIP® plant at KTN-Krefeld 2) After some optimization steps fully stable and reliable casting conditions could be reached in the first half of 2000. In 2001 an in-line-rolling stand and an inductive heating furnace have been commissioned. The latest record was achieved on October 24, Mechanical properties of the strips are at least equal to conventionally produced material. The as-cast hot band has slightly reduced elongation values, however utilizing the in-line rolling stand, the resulting properties, especially the elongation is e Also after cold rolling, the mechanical properties are very well suited. In addition, inclusions occur only in very small sizes very uniformly distributed. This results in increased corrosion resistance measured by the pitting potential (see figure 8). T The EUROSTRIP® Plant at AST-Terni 3) The main technical data and some views of the strip caster and the in-line rolling stand in operation can be seen in figure 10. AST optimized the casting roll shape in order to achieve satisfactory strip crown. In the next figure 11 strip profiles with different reductions are compared. On low carbon steel it is possible to achieve a reduction of about 41%, which results in a str Hot band roughness is slightly higher than conventional processes. The roughness is created by the surface texture of the casting rolls, which is required to control the heat removal rate in the absence of casting powders. In-line rolling is supportive a Economics and Benefits Summary Acknowledgements References
Compartilhar