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Sendzimir’s 20-high mills are unique in that they have a small, chockless work roll and a cluster configuration for the back-up rolls. The cluster configuration transmits the roll separating force from the work rolls to the mill housing. The small size of the work roll permits superior reductions on very hard materials, such as stainless steel.
Flex
Backing Assemblies and Segmented Idler Rolls
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Sendzimir mills are known worldwide for their ability to roll extremely hard materials to very thin gauges with few, if any, intermediate anneals. They consistently maintain quality aspects that are difficult, if not impossible, to duplicate on conventional mills. They are capable of consistently holding extremely close gauge tolerances on very wide strip as well as on metals ranging from soft aluminum alloys to stellite and molybdenum.
The pyramid configuration of the back-up rolls transmits the roll separating force along the length of the work rolls, through the intermediate rolls, to the back-up assemblies, and finally to the rigid monoblock housing. Since the work rolls are supported throughout their length, any uncontrolled deflection is minimal, and extremely close gauge tolerances can be maintained across the full width of the material being rolled.
By way of comparison, the rigidity of conventional mills is governed by the relatively large size of their work rolls and back-up rolls, which are supported by their necks in two separate housings connected by columns that elongate under load. Under rolling pressures, this design results in roll deflection and flattening, and therefore thickness variation, especially near the center of the strip. Gauge variation of incoming strip is difficult to correct.
The size of Sendzimir’s work rolls, being small, offers additional very important advantages: quality of surface, speed of replacement, and control of deflection. They can be manufactured of die steel, high-speed steel, or even tungsten carbide. The work roll material can therefore enable extremely high quality strip surface finishes. This is particularly important for bright stainless steels, for example. Additionally, tungsten carbide work rolls are much harder (85 Rc) and have a higher modulus of elasticity. This results in fewer passes, especially on the thinnest gauges.
The small, chockless work rolls are very easy to remove and install. Gauge-to-gauge times of under a minute are becoming standard on modern designs. The size of the work rolls also permits greater responsiveness to shape control mechanisms, whether they be tapered 1st intermediate rolls, As-U-Roll crown control, or Flexible Segmented Backing Assemblies.
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Sendzimir 20-high cluster mills commonly carry the prefix ZR, which stands for “Zimna,” the Polish word for “cold,” and “reversing.” This prefix was used the first time to describe Silesia's first reduction mill. The numbers, and sometimes letters, following this prefix describe the mill’s geometry, the relative size of its work roll, and the widest strip that the mill can roll. | |
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The number immediately following the “ZR” indicates the mill "section" size comprising a combination of of the backing bearings, the work rolls, and so on. For example, a ZR23 has backing bearings with a diameter of 8.858 inches (225 mm) and work rolls with a diameter of 1.578 inches (40 mm). A ZR32, on the other hand, has backing bearings of 1.875 inches in diameter and work rolls of 0.250 inches in diameter. The significance of the difference is that a ZR23 can roll ferrous and nonferrous materials down to a minimum gauge of 0.002 inches, while a ZR32 can roll ultrathin nonferrous foil down to 0.0001 inches, which is 20 times thinner!
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Sendzimir’s 20-high cluster mills can roll any metal, especially very hard metals. They roll:
autobody sheet
deep and extra-deep drawing, low-carbon steels
feed stock for the manufacture of tinplate
austenitic, martensitic, and ferritic stainless steels
non-oriented as well as grain-oriented silicon steels
high-carbon steels for items such as razor blades and saws
nonferrous metals such as brass and special alloys of brass, copper, bronze, berylium copper, and bimetals
metals such as aluminum, zirconium, molybdenum, silver, gold, tantalum, titanium, cobalt, and nickel, and their alloys, such as aluchrom
Sendzimir 20-high cluster mills: materials rolled & gauges attained (inches) |
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| mill section | ZR32 | ZR34 | ZR24 | ZR33 | ZR23 | ZR23M | ZR22 | ZR22B | ZR21B | |||||||||
| maximum strip width, narrowest mill | 4.25 | 7.50 | 7.50 | 13.00 | 19.00 | 19.00 | 26.00 | 26.00 | 33.00 | |||||||||
| maximum strip width, widest mill | 8.75 | 17.50 | 17.50 | 48.00 | 62.00 | 62.00 | 120.00 | 120.00 | 209.00 | |||||||||
| minimum strip gauge | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | |||||||||
| materials rolled | ultrathin nonferrous foil | electrical alloys, stainless steels, tantalum, zirconium, and super alloys | low carbon, high carbon, and stainless steels; nonferrous alloys | low and high carbon steel; nonferrous alloys | ferrous and nonferrous | heavy reductions on softer materials | ferrous | ferrous | low carbon, silicon, and stainless steels | |||||||||
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ZR32 | ZR34 | ZR24 | ZR33 | ZZR23 | ZR23M | ZR22 | ZR22B | ZR21B | |||||||||
| maximum strip width, narrowest mill | 108 | 191 | 191 | 330 | 483 | 483 | 660 | 660 | 838 | |||||||||
| maximum strip width, widest mill | 222 | 445 | 445 | 1219 | 1575 | 1575 | 3048 | 3048 | 5309 | |||||||||
| minimum strip gauge | 0.0025 | 0.0102 | 0.0203 | 0.0254 | 0.0508 | 0.0635 | 0.0762 | 0.0889 | 0.0889 | |||||||||
| materials rolled | ultrathin nonferrous foil | electrical alloys, stainless steels, tantalum, zirconium, and super alloys | low carbon, high carbon, and stainless steels; nonferrous alloys | low and high carbon steel; nonferrous alloys | ferrous and nonferrous | heavy reductions on softer materials | ferrous | ferrous | low carbon, silicon, and stainless steels | |||||||||
Above is a table of the various mill types, the materials for which they are best suited, and the gauges they can obtain.
More than 400 Sendzimir mill installations have been built in over 40 countries.
Chart to the left shows the popularity of the 20-high cluster mills that have been built since the 1940s: the ZR22 series is by far the most common. Of these particular mills, most are in the 50 to 52-inch maximum strip width range.
This country Chart shows the regions in which Sendzimir cluster mills are to be found: Europe and Asia are most heavily populated, with France and Japan being the preferred countries.
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