1 3-1-E-通过不断的现代化改造取得成功：萨尔茨吉特扁钢厂的热带钢轧机 YP_OK_

512Success through Continuous Modernization— The Hot Strip Mill of Salzgitter FlachstahlKarsten Matthies, Ralf Luttmann (Salzgitter Flachstahl GmbH)Stefan Berger, Karl Hoen (SMS Siemag AG)Abstract: The hot strip mill of Salzgitter Flachstahl (Germany) went in operation in 1963 and is a textbookexample of how continuous modernization can maintain a hot strip mill state-of-the-art even after almost five decades. In the last ten years, virtually all mechanical equipment and the complete automation system were modernized by SMS Siemag. With creative concepts, the individual revamp steps were realized with minimum downtimes and without significant restrictions in production.Keywords: Modernization, hot strip mill, Salzgitter Flachstahl, CVC ® plus, UNI plus coilerSalzgitter Flachstahl GmbH (SZFG) is the largest steel subsidiary in the German Salzgitter group, andconcentrates on manufacturing strip steel. In 2010, more than 4,300 employees produced some 4.8 million t of raw steel and generated sales of EUR 2.5 billion.The integrated steel plant at the Salzgitter location covers all process stages from the coking plant to surfacetreatment. The core plant in the production process is the hot wide strip mill. As the only hot strip mill in the company, it is decisive for the quality of the finished products and the product range. As all upstream and downstream process stages depend on it, the hot wide strip mill must comply with top levels of availability.The hot strip mill went into production in 1963, and today it is designed for a capacity of 4.3 million t/year of hot strip in widths from 800 to 2,000 mm and thicknesses of 1.5 to 25.4 mm. This output mainly goes to thecompany’s own cold rolling mill, the tube works of Salzgitter, and the automotive industry.22%21%31%Wheel6%suppliers10%Gas bottle,Fig. 1: Product mix of Salzgitter Flachstahl’s hot strip mill1 Continuous modernizationTo secure its market position as one of Europe’s leading manufacturers of quality flat steel, SZFG pursues a philosophy of continuous modernization and improvement of its production plants. That is why all the sections in the hot strip mill have been upgraded in three modernization phases since 1999.SMS Siemag AG has been Salzgitter’s partner for continuous modernization of the hot wide strip mill for many years. Together, suitable strategies and solutions were developed that ensured that revamps could be carried out with513minimum shutdowns and without significant interruption of production.2 Modernization in 1999 and 2001/2003In the first modernization phase in 1999, coilers 1 and 2 were revamped and equipped with new automation. The goal here was to expand the product range and improve coiling quality.The focus of the second stage, from 2001 to 2003, was increasing production, improving product quality, and expanding the product range. The following measures were carried out to achieve this:Installation of a slab sizing pressInstallation of a new roughing millInstallation of CVC ® systems in stands F2 to F5 in the finishing lineNew automation in the roughing and finishing mills.Innovative modernization strategies reduced the necessary shutdowns to a minimum and achieved a higher plant availability. The roughing stand was replaced in just 18 days. To achieve this, SMS Siemag completely assembled the roughing stand next to the rolling line, tested it with the new electrics and automation, then shifted it into the rollingmill using special lifting gear.Fig. 2: Shifting of the completely pre-assembled roughing mill standTo ensure plant availability during installation of the new automation, SMS Siemag implemented a switchover mode. That means the old system remained in place as a backup system during a transition period. The functions and controls in the new automation were implemented, tested, and optimized step by step.3 Modernization 2008 – 2011The latest modernization phase started in 2008 and was completed in 2011. The main improvements were:Wider opening dimensions in the entire plantInstallation of CVC ® in stand F1Replacement of the entire drive technology in the finishing millReplacement of the entire intermediate stand equipment from F1 to F7Installation of a 3rd down coilerNew coil transport systemNew electrics and automation for the down coiler and coil transportExpansion of the water treatment systemThe goals of this modernization were wider finished strip widths, increased production, and an extended product514range, above all of higher-strength steels.3.1 Modernization of the finishing millTo increase finished strip width from 1,880 to 2,000 mm, the opening dimensions in the entire plant wereincreased. In the finishing mill, this stage was also used to replace the intermediate stand equipment.New equipment for stands F1 to F7 consists of:New intermediate stand cooling systems with higher cooling performanceNew hydraulic side guides on new entry and exit guidesDifferential-tension loopers to improve rolling stabilityRoll gap lubrication and anti-peeling equipment to extend work roll service lifeFurthermore, stand F1 was equipped with CVC ® technology so that now the entire finishing mill works with CVC ®. Thanks to CVC ®, SZFG can produce strip to the narrow geometrical tolerances demanded by the market.To meet current market demands and keep pace with future developments in the range of products anddimensions, it was necessary to replace the main drives of the finishing mill. The old DC drives were replaced by new, powerful synchronous machines (F1 – F7) and new main gears (F1 – F4).3.2 New downcoiler and expansion of the coil transport systemTo expand the product range to include wider strip and above all higher-strength steels, a UNI plus coiler was installed as an additional coiler. It can coil tube steels up to strength class X80 and is designed for strip up to 2,000mm wide and 1.2 to 25.4 mm thick. The new UNI-plus coiler was installed behind the two existing coilers.Fig. 3: Installation of pre-assembled coiler in coiler pitThis increase in production capacity made it necessary to also expand the coil transport system. Starting with the new coiler No. 3, SMS Logistiksysteme GmbH installed a new coil transport system parallel to the old system. Here, the coils are transported with a horizontal axis. The old coil transport system was largely dismounted, and in its place a new coil inspection line was installed.3.3 Revamp strategyBecause the upstream and downstream process stages depend on the hot strip mill, it was essential to implement the revamp with minimal shutdown times. In close cooperation, SZFG and SMS Siemag drew up a strategy that involved five shutdowns, each for a duration of eight to ten days.The greatest challenge of this modernization phase was replacing the motors and installing the main gears. To achieve minimum shutdown times, the existing foundations of the old motors were re-used. SMS Siemag installed the new gears before the shutdown in the motor hall and adjusted the tooth contact pattern. During the shutdown, after the old motors were dismantled and the foundations prepared, the overhead crane moved the up to 150-t gears as complete units into position. Then the motors were installed, and the plant resumed production.515Fig. 4: Insertion of finsh-assembled F1 main gear unitFor the changeover of the automation on the already existing coilers 1 and 2, a switchover mode was used to ensure availability and full productivity over the entire period. The coiling strategies that have proved so efficient inrecent years for Salzgitter Flachstahl’s specific product range were adopted in the new automation system.Fig. 5: Principle of switchover mode3.4 Results of the modernizationWith this continuous modernization of its hot strip mill over the years, Salzgitter Flachstahl has achieved the following goals:Production increases from 2.8 (1999) to 3.3 (2006) to 4.3 million t/year (from 2012)Increased finished strip width from 1,880 to 2,000 mmExpansion of the product range. In the field of higher-strength steels, SZFG has successfullyproduced strip from tube grades of strength class X80 with a thickness of 19 mm and a width of 2000 mm.Furthermore, because the entire finishing mill is equipped with CVC ® systems, a more flexible rolling program is possible. This also improves strip quality and the availability of the plant.4 SummaryContinuous modernization of the production plants is a key factor in the sustained success of SalzgitterFlachstahl. After completion of the latest modernization phase, SZFG has a hot strip mill completely equipped with state-of-the-art technology. The entire plant is designed so that it not only meets today’s demands, but also has thepotential to manage and influence new market developments.SMS Siemag was Salzgitter’s partner for the continuous modernization of the rolling mill technology. They teamed up to jointly develop the individual measures, the modernization strategies and the detailed planning. In this way, the optimum solution for the plant was achieved. Even when there were changes to the plan at short notice, creative solutions were found. Apart from a few exceptions, the deadlines were met, modernization times complied with, and commissioning projects were on schedule.516。