Latest technologies and mill solutions for the production of long products ULRICH SVEJKOVSKY *

Transcription

1 Latest technologies and mill solutions for the production of long products BY ULRICH SVEJKOVSKY * SYNOPSIS: Steel products, especially long products like rebars, wire rod and sections are important construction materials for growing economies in the South East Asia region. These products should be produced locally to ensure its availability. This requires cost efficient solutions serving the local market demand. The ecological aspect of saving energy and protection of resources, paired with the demand of maximum flexibility and localization, are playing an increasingly important role. SMS group has developed and established new and proven plant solutions providing answers to these demands: Minimized CAPEX and OPEX and at the same time maximum energy efficiency and flexibility. For modernizations, we have developed so called performance modules, individual machines and components which will improve the performance of the mill in terms of quality, productivity, efficiency and Industry 4.0. These are low cost devices and equipment which can be installed in existing mills to make them more competitive. Keywords: Modernizations, Performance modules, Localization, CMT high efficient minimill, CEE technology, Small capacity rebar mills, HSD High Speed Delivery System, VCC Vertical Compact Coiler, MEERdrive * Vice President Sales Long Products, SMS group GmbH, Mönchengladbach, Germany 1

2 1. Introduction trends in a competitive market environment As everybody knows, the steel industry is volatile, facing problems with overcapacity and this is going along with a deterioration of steel prices. The focus of today should be to make existing mills more efficient by modernizations or by adding performance modules. Furthermore products such as rebars, wire rod and sections should be produced locally to ensure their availability and at the same time not rely on exports. This requires flexible, compact and cost efficient solutions serving the local market demand. The ecological aspect of saving energy and protection of resources, paired with the demand of maximum flexibility and localization, are playing an increasingly important role. Despite several factors like raw material source, price of labor and energy, the efficient production route also plays a major role. SMS group has developed and established new and proven plant solutions providing answers to these demands: Minimized CAPEX and OPEX and at the same time maximum energy efficiency and flexibility. In addition some of these technologies will increase the product quality or allow a steel producer to produce value added products. Performance Modules like process models and measuring gauges might help to make not only the production process transparent but improve the performance of the mill in terms of quality, productivity, efficiency and Industry CEE technology - low capex solutions for small capacity rebar mills We tried to investigate the influencing factors of the rebar costs. Some cost are more or less given and on some we have a mayor influence. - The most important factor is the scrap cost. Is local scrap available the price will be lower compared to remotely collected or imported scrap which is adding transportation costs. - Electric power cost are given by energy provider and we can influence only the power consumption of EAF, which in total has a minor influence. - Saving reheating energy, which means gas consumption, is a substantial saving by hot charging or direct charging. - The mill concept with consumables will record for only 3 USD/ton - The mayor influence is the yield and rolling light weight resp. minus tolerances, since most rebars are sold by theoretical weight or number of bars. - And the transportation cost of finished products is a substantial cost when serving the local market. - We came to the conclusion: - A market mill in the vicinity of customers with the availability of local scrap is the biggest influencing factor. - Is local scrap not available but a good local customer base, a re-rolling mill is a good choice. - The mill has to be efficient, allowing a high yield and able to roll tight tolerances for producing bars at minimum weight, is further important. 2

3 The right answer is our so called CEE mill. The economy of scale, which is the driving factor to install a large mill, has a minor impact on the operation costs but will help for the CAPEX ratio. To summarize, what is important for an competitive market: - Serving the local market, do not relay on Export - A decentralized plant allows to collect local scrap at reduced costs and will help to serve local customers - In order to ensure this, a small production unit might be required, which should be flexible, compact and efficient, resulting in an economical mill. - The minimill should be efficient with focus on conversion cost and reduced investment costs. SMS group s CEE technology stands for a Compact, Efficient and Economical plant design of small capacity rebar mills. The plant design has currently been developed to two different sizes: - CEE 150 Rolling Mill o Capacity 150,000 tpy o Billet size: 100 x 100 x 6,000 mm, 130 x 130 x 6,000 mm o Finished products: rebars dia. 8 to 40 mm quenched - CEE 300 Rolling Mill o Capacity 300,000 tpy o Billet size: 130 x 130 x 12,000 mm o Finished products: rebars dia. 8 to 40 mm quenched Fig. 1: Comparison of plant concepts - minimized requirements for land and balance of plant As the layout above shows, the mill is characterized by a compact mill arrangement and an efficient finishing end without traditional cooling bed and cold shear. Instead, only a cooling bank for finished length and tying facilities. In comparison with a 3

4 conventional mill for a capacity of tpy, the expected overall savings in steel buildings and foundation is 40%, with a total length of the plant which is only half. The advantage of the CEE concept can be summarized as follows: Compact layout of the rolling mill area RMS finishing end, without cold shear and traditional finishing end Automated process with reproducible quality and high yield Reduced manpower due to less equipment installed in the bar finishing facilities, that results in reduced conversion costs Limited civil works Reduced investment and installation costs 3. High efficient minimill concept - CMT endless rolling technology While in a conventional minimill it is established practice to cool down, store and subsequently re-heat cast billets for independent rolling operations, the SMS CMT (Continuous Mill Technology) process has taken the basic minimill concept one step forward: It links the meltshop, caster and rolling mill together with an uninterrupted process of 23h operation per day and size/ roll change once a day within 1 hour. Fig. 2: CMT plant concept The key of this process is the endless billet production without cutting and directly feeding of the billet to the rolling mill. This direct linking of the rolling mill with the steelworks enables short distances. The billet temperature cycle is completely eliminated by the direct link between the continuous casting machine and the rolling mill. Billets are delivered by the CCM at a high temperature, already in the range required for rolling. Instead of an oil- or gas-fired furnace, an inductive heating system is employed. This system does not reheat the billets but only equalizes the billet temperature profile, both in cross section and lengthwise, thus ensuring ideal rolling conditions with minimum energy input. The induction heater gives you perfect control of the starting 4

5 temperature for the rolling mill - according to the billet speed. This solution requires much lower investment costs compared to a traditional reheating furnace. By eliminating the complete reheating stage, energy costs and the impact on the environment are markedly reduced. Fig. 3: Reheating energy required for different casting-rolling concepts Furthermore SMS group supply covers also the complete electrical and automation package that includes Level-1 and Level-2 process control. In addition to seamlessly integrating the process functional units, implement the state-of-the-art process solutions already highlighted, the automation system will allow customers to meet all possible market demands with built-in capabilities for plant-wide production planning, scheduling, tracking and reporting. CMT minimill concept is designed for producing rebars for a capacity as small as of tpy and 500,000 tpy of rebar with diameters from 8 to 40 mm. Examples of market mills of smaller size are the mill Rabigh Steel in Saudi Arabia with a capacity of tpy and El Marakby in Egypt for a capacity of tpy producing rebars and wire rod. Higher capacities are also possible, but this mill should serve a more global market and is not meat as local mill. Also a CEE 150 could be equipped with a meltshop of same size and laid out as CMT minimill. A typical CMT 300 is rated for a production of tpy. At the base of this concept there is a melt shop with a productivity of 50t/h, and a single-strand continuous caster producing casting a 130x130 mm billet. The cast product is fed endless into the rolling mill at a speed of 6 m/min. Higher productivities can be covered by increasing the casting speed up to 7m/min or by increasing the cast section to 150x150mm. The CMT500 is rated, for t/y, with a hourly productivity of 75t/h while casting a 165x165mm endless billet. The main advantages of the CMT technology are: Compact design and thus less required land, building areas and cranes Maximum energy efficiency because of the minimized heat losses. Maximum flexibility because the system automatically adjusts temperature input for each single billet 5

6 Power on-demand because Inductive Heating coils are energized only when needed. Consequently IH is powered off during inter-billet time as well as during maintenance and emergency shut-downs Increased metallic yield, as almost no additional scale is formed due to the missing reheating cycle of a classical reheating furnace as well as no crop losses Ease of operation thanks to the integrated process control and automation system of the CMT functional units Reduction of CO2 and NOx emissions 4. Modernization concepts low investment, high efficiency Standstill is a step back. Especially in a market with overcapacities it is important to consider not only the increase in production, but also product and process optimizations. Particularly at the present time, new plants often do not suit the budget of a company. Most plant operators have therefore been increasingly concentrating on modernizing their facilities and asking questions like: Which is the best modernization strategy for me to remain competitive? What kind of modifications are needed to maximize the efficiency and sustainability of existing plants? Performance modules could be an answer to those questions: they can be applied into new or existing plants and result in an immediate increase of efficiency and flexibility, lower the production costs and improve environmental sustainability. SMS group provides technology and product solutions which have evolved in close cooperation with customers. In the course of modernization measures, existing facilities may be provided with state of-the-art technology. But even smaller investments can be highly effective and make an existing plant more efficient. Carrying out modernization work does not automatically mean to stop production for a longer period. Here, individual solutions help to optimize the production process. High Speed Delivery system HSD The HSD system is also part of CEE and CMT concept, but also very well suited for modernizations, to make existing mills more efficient. This technology has been developed by SMS group many years ago and since then has constantly been improved. The system allows for rolling a single strand at high speed of up to 50 m/s onto the cooling bed. The High Speed Delivery system HSD (Fig.4) comprises of a finishing block with tungsten carbide roll rings, dividing shear, pinch rolls, bar braking rolls and a drum- type discharging system to charge the bars into the cooling bed notch. 6

7 Fig. 4: High Speed Delivery System HSD With the HSD system the production costs can be minimized due to: Better control of the bar tolerance, since only one strand will be rolled in each stand and the size can be precisely adjusted in the finishing block. Since rebars are generally sold by number of bar or theoretical weight, rolling minus tolerances are possible, which will considerably increase the material yield. Lower guide costs as HSD eliminates the need of slitting boxes and twister guides. Less cobbles and crop end losses and less trial bars thanks to easy operation of HSD, while multi- slitting of small sizes requires demanding and delicate set-up operation. Considerably higher yield as there is only one bar per cooling bed notch. Multiple bars per notch generate overlapping or misalignment which affects the downstream cold cutting, counting and bundling operation. In addition, the HSD allows producing even small sizes in straight lengths like starting form 6mm, which are normally rolled on a wire rod mill in coils and then restraightened. Figure 6 shows the comparison of the different systems in terms of production costs savings depending on the size, savings up to 13 Euro/ton is possible which can reach several million Euro savings per year. Fig. 5: Production cost comparison HSD versus Slitting 7

8 Vertical Compact Coiler VCC The Vertical Compact Coiler VCC is today s state-of-the art solution for producing compact and torsion-free coils - exactly what more and more rebar processors are requiring for automatic handling in cat and bent machines (Fig. 6). It can be installed behind existing mills and produces a perfect coil shape as you can find in Figure 8. Fig. 6: VCC System Fig.7: Coil at the exit of a VCC line One of the most important features is coiling in the vertical position. Plant operators eliminate the need for turning manipulators and at the same time reduce the process cycle time, as all coils are formed in the final position. The VCC is able to process coils of up to 5,000 kg. The high weight contributes to the efficiency of the downstream process. The VCC allows to procure very dense coils with high coil weight, all layers are in order and spooled torsion free. At the same time the compact coil dimension is ideal for storage, transport and handling. The VCC can be added to any rebar mill either to have coils as an additional product or to replace conventional pouring reels. These VCC lines can operate at a rolling speed of up to 40 m/s and spool dimensions form plain round 8 to 25mm, rebars 6-25mm or even larger sizes or small flats, hexagons and squares. By adding this installation to existing mills, the productivity of the mill will be increase substantially as well as the coil shape will be improved remarkably compared to ware rod coils or Garett coils. 8

9 MEERdrive wire rod finishing block Highest efficiency and maximum flexibility within the production process - these are the key factors for success in the wire rod market. Conventional group driven wire rod blocks set up limitations. Those blocks are only able to roll with fixed reduction ratios which require fix roll ring diameters within the individual block. Complex gear box configurations are necessary which are subject to wear and maintenance. Furthermore, conventional blocks require huge motors with capacity up to 7000kW on the medium voltage supply. With the MEERdrive (Fig. 9) SMS group introduced a drive concept that overcomes the limitations of conventional solutions. The clue: the concept is based on individual drives for each stand position. Fig. 9: MEERdrive wire rod block The MEERdrive offers a number of advantages over the conventional block: Reduced maintenance and spare parts A large distribution gear box as well as line shaft and bevel gears for driving the individual stands are not required anymore. Further all motors are small low voltage stand motors and in case of motor failure only a small spare motor is required. This all reduces the cost for spare parts and regular maintenance. Increased flexibility The individual drive concept allows total flexibility in the roll pass design: customers can individual select reductions that fit their needs like different reduction for different sizes or steel grades. Also free roll adjustment is possible to compensate for wear or different material spread behavior. Reduced roll costs Also a free selection of roll diameter is possible, so that only the worn out roll set has to be replaced or re-dressed. In the conventional mill all rolls have to be redressed to the same dimension, which increase the roll wear drastically. This reduces the work in the roll shop and its redressing work. Also the roll inventory is only one third compared to a conventional block arrangement. Reduced energy consumption Since less mechanical parts are required the idle power is reduced. This drive concept results in lower energy consumption and reduced CO2 emissions. Better product quality The free adjustment of roll because of wear and spread as well the optimized pass design results in better tolerance and ovality. Further small motors will recognize the tension between two block in case of an arrangement with two 9

10 blocks. This allows the recognition of tension so that the rolling speed for low tension rolling can be optimized. By this the tolerance along the rod length can be optimized. This all sumps up to a total cost saving in the block arrangement of up to 31% compared to the conventional block arrangement (Fig. 9). The MEERdrive allows the highest flexibility and best product quality and allows the reduction of operation cost. Further on, thanks to the individual design, the stands can be arranged in any concept like 6 stands plus 4 stands, 4 plus 4 stands or any other combination. Thermo-mechanical rolling is possible in this split bock arrangement. Also in a 4 stand MEERdrive Plus all sizes can be finished applying the single family rolling concept. The MEERdrive concept is well suited for modernizations to replace existing blocks to increase rolling speed, product quality and flexibility at reduced operation costs. Fig.9: Comparison of operation costs MEERdrive block versus conventional wire rod block 5. Conclusion As a leading partner in the world of metals, SMS group always strives to serve customers with the right concept for their needs. SMS group has therefore developed and established new and proven plant solutions providing answers to these demands: Minimized CAPEX and OPEX and at the same time maximum energy efficiency and flexibility. Furthermore plant operators can receive new and well-founded suggestions how the efficiency of their production lines can be improved by intelligent expansions, adaptations and modernizations. Thanks to technology modules ready for use, they will be able to considerably improve their product quality and output and reduce operating, energy and material costs at the same time. So, no need for always a new construction to remain at the cutting edge of technological development. 10