Innovations with rubber covered rolls improves bottom line at Tata Steel
February 20, 2006

Tata Steel has introduced rubber covered rolls with modified formulations in the continuous galvanising line (CGL) #1 in its cold rolling mill. This is yet another innovation at Tata Steel that has yielded extremely beneficial results to the company in terms of savings due to longer roll life and availability of the mill which in turn will help the mill to better its performance and contribute to the company’s turnover. There has been an increase of almost 300 per cent in straight life of these rolls and after removing the degraded skin of the rolls by minor surface grinding the life went up by another 375 per cent. There overall increase in service life of these rolls is 320 per cent. After encouraging results at CGL #1, the project team is now working on pickling line and tandem cold mill and CGL #2 lines of cold rolling mill. The company has applied for patenting the technology of rubber covering.

The technique for rubber covering has been developed in-house due to the efforts of a team of professionals from the Cold Rolling Mill, Metallography Lab and Scientific Services. Based on the enthusiasm shown by these departments, Dr T Mukherjee, deputy managing director, steel constituted a team form these departments to take up the challenge. The team took up the challenge to develop knowledge in this area to address the problem and CGL #1 line was identified as the first area to work on. They identified Rubber Technology Centre of IIT Kharagpur as the knowledge partner and signed a Memorandum of Understanding with them. Prof A K Bhowmik from IIT Kharagpur contributed immensely in the success of the project.

The Cold Rolling Mill of Tata Steel uses a number of rubber covered rolls in alkali degreasing sections, rinsing sections of hydrochloric acid, chromic acid, hot water and hot air. The function of these rolls is very critical to avoid liquid carry over to the next operation. The complete line has to undergo shut down for any problem in these squeeze rolls. Rubber covering on these rolls undergoes degradation during use because of the corrosive working atmosphere. Average life of these rolls is much below the world standard. Cold Rolling Mill has to incur on an average Rs 17 Lakhs / year as grinding and relining cost for these rolls and production loss in shut down due to problems in squeeze roll is Rs 1.6 Cr / year only in CGL # 1 line.

The team approached the problems in CGL1 line methodically. At first the team prepared the problem profile of the different rubber covered rolls being used in CGL1. Rolls in the alkali degreasing and chromate acid rinsing sections were identified as the most critical and in depth analysis was carried out for these rolls. Failure analyses were done on the rolls and based on this the root cause of the problem was identified. The root cause was further substantiated by some tests conducted in the laboratories by simulating the actual service conditions.

Based on the findings number of rubber formulations were developed in the laboratory by changing the blend composition to improve the properties of the rubber. Every new formulation was tested for rheometric properties, viscosity testing, swelling characteristics, abrasion resistance, tear strength etc and a few formulations were identified for production scale trial. Tata Steel signed MOU with two rubber manufacturers for manufacturing the rubber covered rolls under the supervision of the project team. The first set of rubber covered rolls with the modified formulations were put into service on October 6, 2005 in CGL #1. First trial results were very encouraging.