Influence of the natural aluminium oxide layer on ... - ALU-WEB.DE

More documents

Recommendations

Info

ROLLING INDUSTRY ished rolled material but also for <strong>the</strong> slit strip, development <strong>of</strong> even more precise and rigid slitting machines is <strong>of</strong> highest importance. Shearing stresses have a big influence on subsequent workability <strong>of</strong> <strong>the</strong> strip. Single strips may curl or even jump out <strong>of</strong> <strong>the</strong> stamping die if stresses induced during slitting are too high. Width deviations could result in imperfect shapes due to <strong>the</strong> very narrow trim web at <strong>the</strong> edge <strong>of</strong> <strong>the</strong> strip before pressing. With highly accurate adjustment devices, modern slitting shears provide <strong>the</strong> best chance <strong>of</strong> an exact and repeatable knife shaft adjustment. It can be seen that <strong>the</strong> slitting shear must be able to be adjusted as closely as possible to certain parameters (immersion and cutting gap) according to <strong>the</strong> material conditions, this being essential for thinner strip gauges in particular Danieli Fröhling accommodates all <strong>of</strong> <strong>the</strong>se through a high standard <strong>of</strong> design and manufacturing: • Pre-tensioned elements giving backlash- free movement <strong>of</strong> machine parts. • High accuracy measuring systems to provide <strong>the</strong> adjustment system with necessary data. Rigid and solid design to prevent vibration. • Data bases store recipes for different slitting programmes • Tool clamping systems to ensure reliable clamping automatically actuated. Following <strong>the</strong>se demands, Danieli Fröhling developed a new generation <strong>of</strong> slitting heads. One <strong>of</strong> <strong>the</strong> main parameters for <strong>the</strong> strip edge quality is <strong>the</strong> knives’ immersion into <strong>the</strong> material to be cut. The optimal immersion depends on material grade, condition and strip thickness. The real immersion is a function <strong>of</strong> cutting force and machine rigidity. Part <strong>of</strong> <strong>the</strong> machine rigidity is <strong>the</strong> deflection <strong>of</strong> <strong>the</strong> knife shaft. By reducing <strong>the</strong> bearing distance and optimisation <strong>of</strong> <strong>the</strong> whole bearing system, a reduction <strong>of</strong> deflection by 44 percent is achieved. For subscribers www.alu-epaper.de Even faster – your added PLUS to <strong>the</strong> print medium The stiffness <strong>of</strong> a knife shaft could be increased by more than 130 percent. All <strong>of</strong> this results in even better, reproducible cutting edge quality and a lower transfer <strong>of</strong> cutting stress to <strong>the</strong> strip. In longitudinal slitting lines, a looping pit is applied for compensation <strong>of</strong> <strong>the</strong> different recoiler diameters <strong>of</strong> <strong>the</strong> single strips – caused by <strong>the</strong> differences <strong>of</strong> single strip cross section due to <strong>the</strong> rolling process. Due to <strong>the</strong> downgauging <strong>of</strong> finished products nowadays and <strong>the</strong> request <strong>of</strong> <strong>the</strong> finishing industry for larger recoiler diameters, tensioning <strong>of</strong> <strong>the</strong> strip with advanced braking units becomes ever more important. Danieli Fröhling has developed <strong>the</strong> vacuum braking roll in order to avoid or minimise <strong>the</strong> aforementioned disadvantages. Around 27 <strong>of</strong> <strong>the</strong>se units have been supplied to industry to date, and experiences have been ga<strong>the</strong>red over <strong>the</strong> past about 17 years. Advantage compared to <strong>the</strong> strip surface: • Very low surface pressure during braking • No damage <strong>of</strong> <strong>the</strong> strip surface • No friction between upper surface <strong>of</strong> <strong>the</strong> strip and braking means • Lowest possible friction at <strong>the</strong> lower side <strong>of</strong> <strong>the</strong> strip • Same specific strip tension at all strips, independent on <strong>the</strong> rolling pr<strong>of</strong>ile over <strong>the</strong> strip width. The international top level <strong>of</strong> trimming lines in <strong>the</strong> <strong>aluminium</strong> industry process coils with weight <strong>of</strong> around 30 tonnes at speeds <strong>of</strong> more that 1,200 m/min. Danieli Fröhling trimming lines, having proven <strong>the</strong>ir reliability at stable operation speeds <strong>of</strong> up to 1,500 m/min since years, are equipped with special features to provide precise products at maximum production, such as: • High-speed cropping • High precision electrostatic oiler • Edge trimming shear with automatic adjustment • Scrap suction devices for high-speed applications • Dedicated design <strong>of</strong> exit guide unit. Product services and support Vital to any organisation is <strong>the</strong> services pro- vided with both a new project and future support. This can range from training, process studies right through to major FSTK projects. Danieli with its partner Innoval has <strong>the</strong> organisational structure to provide <strong>the</strong>se services to our clients. Summary It is evident that <strong>the</strong> end-users <strong>of</strong> high-end <strong>aluminium</strong> products in particular in <strong>the</strong> automotive, beverage and aerospace markets are continuously innovating to maintain <strong>the</strong>ir competitiveness, develop new products and increase <strong>the</strong>ir efficiency and added-value. Consequently, rolling and processing companies must respond to <strong>the</strong>se developments and also implement similar philosophies encompassing <strong>the</strong> efficient production <strong>of</strong> high quality end-products. The result <strong>of</strong> this market and product advancement requires companies such as Danieli to react and supply advanced high quality equipment and process solutions to meet <strong>the</strong>se evolving challenges by reacting to market requirements and providing a spectrum <strong>of</strong> enhanced solutions for <strong>the</strong> future. Danieli can do this! � 18 ALUMINIUM · EAC CONGRESS 2011
Longer campaigns with improved monolithics for lining <strong>aluminium</strong> melt-hold furnaces Andy Wynn, John Coppack and Tom Steele, Thermal Ceramics UK Ltd. To remain competitive, <strong>aluminium</strong> producers continue to increase productivity through <strong>the</strong>ir melt-hold furnaces. Increasing heat input to <strong>the</strong> furnace using more powerful burners is common practice. But faster melting leads to increased metal losses from surface oxidation and to segregation from large heat gradients. These effects are countered by increased use <strong>of</strong> fluxes and increased stirring. Given <strong>the</strong> increasingly challenging environment within which <strong>the</strong> refractory lining has to work, traditional lining solutions can no longer be relied upon to provide <strong>the</strong> service lives that were previously achieved. Therefore, a new generation <strong>of</strong> furnace lining materials is required to cope with today’s <strong>aluminium</strong> furnace. This work reports on a new monolithic material with improved performance, compared to existing materials, designed for use in <strong>the</strong> ramp/hearth area <strong>of</strong> <strong>aluminium</strong> furnaces. Improved behaviour against <strong>the</strong> critical performance criteria in this furnace region are demonstrated in <strong>the</strong> laboratory using industry standard test methods. The refractory lining <strong>of</strong> a typical furnace used for holding and melting <strong>aluminium</strong> has to withstand a wide variety <strong>of</strong> physical and chemical environments. Each <strong>of</strong> <strong>the</strong> different areas within <strong>the</strong> furnace (Fig. 1) presents a different set <strong>of</strong> operating conditions, in terms <strong>of</strong> peak temperature, metal contact, salt contact, etc. Therefore, in order for a monolithic material to perform in a particular area <strong>of</strong> <strong>the</strong> furnace, it needs to cope with <strong>the</strong> specific environmental conditions in that region. This is why furnace linings are complex arrangements, with different materials installed in different locations [1]. Background: In <strong>the</strong> last 30 years, a group <strong>of</strong> monolithic technologies has emerged, specifically designed to perform within <strong>the</strong> unique environment <strong>of</strong> <strong>aluminium</strong> melt-hold furnaces. These Al-resistant grades <strong>of</strong>ten contain ‘non-wetting’ additives, particularly in <strong>the</strong> metal contact areas, to minimize interaction between <strong>the</strong> refractory and <strong>the</strong> melt to suppress damage from ‘corundum growth’ [2]. As <strong>aluminium</strong> producers strive to increase productivity, <strong>the</strong> environment within <strong>the</strong> furnace is becoming more arduous. Chamber temperatures are increasing and more aggressive fluxes are being used, necessitating more frequent and severe cleaning operations <strong>of</strong> <strong>the</strong> furnace walls. To maintain high productivity, it is necessary to minimize <strong>the</strong> frequency <strong>of</strong> furnace downtime. The more aggressive conditions today mean that lining materials developed in <strong>the</strong> past are now being used be- yond <strong>the</strong>ir original intended design boundaries and <strong>the</strong>ir service performance is under threat, leading to more frequent lining repairs. Aluminium producers take a furnace <strong>of</strong>fline for repair once a critical lining area has degraded to <strong>the</strong> point <strong>of</strong> affecting <strong>the</strong> efficiency and/or safety <strong>of</strong> <strong>the</strong> operation. At this stage, not all <strong>the</strong> lining will have degraded to <strong>the</strong> point that it is in need <strong>of</strong> replacement or repair. Therefore, <strong>the</strong> frequency <strong>of</strong> furnace downtime is determined by <strong>the</strong> area <strong>of</strong> <strong>the</strong> furnace most quickly and frequently degraded during operation. In order to increase campaign times and decrease frequency <strong>of</strong> stoppages, we need to improve <strong>the</strong> service life <strong>of</strong> this weak link in <strong>the</strong> lining. To identify <strong>the</strong> region most frequently and quickly degraded, we worked with several <strong>aluminium</strong> producers. Their feedback suggested that <strong>the</strong> most common area that was <strong>the</strong> cause <strong>of</strong> repair downtime was <strong>the</strong> ramp / hearth area. The failure mechanisms within <strong>the</strong> furnace environment, that limit refractory service life, are listed in [1]. Since our target is to improve refractory performance in <strong>the</strong> ramp / hearth region, we need to understand which <strong>of</strong> <strong>the</strong>se failure modes are most critical to lining performance in this region. Performance targets: A study <strong>of</strong> working practices and furnace operating conditions at MEASURING & CONTROL a number <strong>of</strong> <strong>aluminium</strong> producers revealed that <strong>the</strong> ramp / hearth region <strong>of</strong> an <strong>aluminium</strong> melt-hold furnace is subjected to severe mechanical and <strong>the</strong>rmal stress during <strong>the</strong> loading <strong>of</strong> large ingot down <strong>the</strong> ramp. Frequent loading <strong>of</strong> heavy ingot to feed <strong>the</strong> furnace, <strong>of</strong>ten by fork lift truck, subjects <strong>the</strong> ramp to severe abrasive forces. As <strong>the</strong> ingot is usually at room temperature, <strong>the</strong>re is also considerable <strong>the</strong>r- mal shock on <strong>the</strong> ramp / hearth refractory, which is at furnace operating temperature. As <strong>the</strong> bottom <strong>of</strong> <strong>the</strong> ramp and <strong>the</strong> complete hearth are in contact with molten metal, <strong>the</strong> refractory is also subject to chemical attack from <strong>the</strong> alloy, alloying elements and flux additions. A study <strong>of</strong> ramp / hearth degradation <strong>of</strong> Al-resistant materials containing ‘non-wetting’ additives suggested that damage leading to furnace downtime is mostly due to <strong>the</strong> mechanical action <strong>of</strong> <strong>the</strong> erosion and <strong>the</strong>rmal shock from ingot loading. We <strong>the</strong>refore focused our work on developing a new Al-resistant material with improved abrasion and <strong>the</strong>rmal shock resistance. To achieve significant improvements in performance we set out to increase abrasion and <strong>the</strong>rmal shock resistance by 20% compared to existing materials. As metal and alkali resistance are secondary performance parameters in this furnace region, we also had to ensure that any changes we made to <strong>the</strong> materials did not degrade chemical resistance. EXPERIMENTAL Fig. 1: Furnace lining zones in a typical <strong>aluminium</strong> melt-hold furnace Two existing, industry leading Al-resistant monolithic materials used by many <strong>aluminium</strong> producers in <strong>the</strong> ramp / hearth area <strong>of</strong> ALUMINIUM · EAC CONGRESS 2011 19 Images: Thermal Ceramics
Page 1 and 2: Ebner Special Edition European Alum
Page 3: Christian Wellner Executive Directo
Page 6 and 7: ROLLING INDUSTRY Foil slitting tech
Page 8 and 9: ROLLING INDUSTRY Optifoil Heavyslit
Page 10 and 11: ROLLING INDUSTRY Focus on rolling m
Page 12 and 13: ROLLING INDUSTRY the</stron
Page 14: ROLLING INDUSTRY Gas-fired radiant
Page 17: Danieli Fröhling 6-high Diamond Mi
Page 21 and 22: Standard 1 Standard 2 New material
Page 23 and 24: Fig. 1: Selected AGC input variable
Page 25 and 26: �� The flexibility o
Page 27 and 28: Fig. 2: Optimized raw material calc
Page 29 and 30: necessary in the s
Page 31 and 32: Influence
Page 33 and 34: Principle of takin
Page 35 and 36: Counter platen with fixed tie rods
Page 37 and 38: option for the fut
Page 39 and 40: Photos: GIA In autumn 2009 Gerhardi
Page 41 and 42: Fig. 3: Experimental setup for extr
Page 43 and 44: initiation at the
Page 45 and 46: The medium-sized, family-run compan
Page 47 and 48: ��
Page 49 and 50: Surface modification and de-coating
Page 51 and 52: following pH values were prepared:
Page 53 and 54: AlMgSi(Cu) alloys”; Mat. Corr., 2
Page 55 and 56: Fig. 2: Al-base metal-alloys and Al
Page 57 and 58: APPLICATION-ORIENTED TECHNOLOGIES <
Page 59 and 60: level significantly, see Fig. 4. A
Page 61 and 62: q H2O = ε(46.52 - 94.9p H2Os)(p2 .
Page 63 and 64: Abbildungen: promeos Resource effic
Page 65 and 66: New: Hot air heating system for ind
Page 67 and 68: Fig. 2: Equilibrium phases for <str
Page 69 and 70:
Fig. 7: Net-remelting losses <stron
Page 71 and 72:
ant heat transfer between t
Page 73 and 74:
Fig. 1: Tool concept for th
Page 75 and 76:
EFFICIENT Yes, I/we would like to s
show all

Influence of the natural aluminium oxide layer on ... - ALU-WEB.DE

Create successful ePaper yourself

Delete template?

Save as template?