Sendzimir's 20-High mills are unique in that they have a small, chockless work roll and a cluster roll configuration supported by the Backing Assemblies. 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 or titanium.
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 other 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 bearing-saddle-bearing 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 mechanical 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 4-High/6-High 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 small size of Sendzimir’s work rolls, offers additional very important advantages: quality of surface, speed of replacement, and thin gauge capability. 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 have become 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, (Double) As-U-Roll crown control, or Flexible Segmented Backing Assemblies.
Sendzimir's 20-High cluster mills can roll any metal, especially very hard metals. They roll:
Our innovative staff of engineers and designers is available to design retrofit components or a 20-High mill designed to your specifications.