USE OF STABILIZER ROLLS FOR STRIP FLATNESS WHILE
WIPING
春剑和春兰的区别DUBOIS MICHEL
Senior Rearch Engineer
Hot Dip Coatings
COCKERILL SAMBRE
企业员工手册10 Quai du Halage 4400 FLEMALLE
Email : Michel.
USE OF STABILIZER ROLLS FOR STRIP FLATNESS WHILE WIPING
DUBOIS Michel海子日记
Abstract
善举单数和双数Coating Weight uniformity is a major issue for cost reduction and Galvanized sheet quality improvement. Becau the final Zinc thickness is directly dependent on the nozzle to strip distance, any non parallelism between the wiper and the sheet will induce non uniform coating in the transver direction. This paper address the sheet gutter defect in the pot area and compares the efficiency of the 2 different designs to correct it : either a one or 2 stabilizer rolls. The approach is mainly theoretical bad on computer modeling of the internal stress during bending - unbending under tension (similar to what happens in a tension leveling machine). The Misaka flowchart (1) has been written in the Basic language and adapted to the pot hardware situation by Cockerill Sambre.
家谱范文The sheet gutter while wiping is evaluated by computing the residual stress through the sheet thickness after going through the turn down and submerged rolls. The plastic deformation depends directly on the true curvature radius of the sheet on the various rolls. Unfortunately, becau it is up to now impossible to determine the radius (becau not yet modeled) for the stabilizer rolls situation (the roll sheet contact is only on one line and the curvature radius much higher than the roll radius), veral defined values have been ud the model the gutter respon. The total strip elongation is also calculated.
The simulations have been conducted for 1 and 2 stabilizer rolls. In the first ca the wrapping angle,
and so the curvature radius, is modified thanks to up and down movements of the sink roll whereas it is the rolls intermesh which modifies the true sheet deflections in ca of 2 stabilizers. The material yield stress has been t from 80 to 120MPa according to specific tensile tests conducted at 450°C, thickness varied from 0.5 to 1.5mm, sink roll diameter tested from 600 to 900mm and sheet tension adjusted at 10 and 20MPa. For each ca the process window has been determined with the criteria of an absolute gutter below 2mm per meter wide.
The results show that the process window might be very narrow or even non existing in some cas with the 2 stabilizers system whereas it always exists with the other design. The strip tension has a low effect for a defined curvature radius, the sink roll diameter a big one (for memory it is not possible to model the true curvature radius with the strip tension). The stabilizer roll diameter has no effect provided it is lower than 80% of the sink roll one. This is due to the fact that the sheet curvature radius is always much higher than the roll radius.
As far as the total elongation (turn down to exit of the pot) is concerned, the 2 stabilizers design induces values from 0.02 to 0.06% (0.04 to 0.18%) on 1mm thick materials and 10MPa (20MPa) tension whereas it is clo to zero in ca of a single stabilizer. Conquently some shape improvement could be expected from the 2 stabilizers system and this is an advantage for horizontal
furnace in which it cannot be improved due to the abnce of multiple alternative flexion.寒暖流
建筑学基础To be sure that a process window exists for the 2 stabilizers design, a cond in line adjustment of the roll geometry (in addition to the classical intermesh) is needed in order to be able to modify independently the wrapping angle on each roll during annealing.
Reference : MISAKA & MASUI, Shape correction of the Steel Strip by Tension Leveler, Transaction ISIJ, Vol 18,1978
