Optimization of Hot Rolling Parameters in SSLNA Grade Rolling

Lean Optimization of SSLNA Rolling(Jan - April 2015) 

The optimization of the entire process is very difficult, that the effort has been taken only to stabilize the parameters of Rolling in Roughing mill. According to the suggestions made by SAIL- R&D, 7pass rolling is now adopted and steps have been taken to optimize the 7 pass rolling, but it is also accompanied by a lot of difficulties that make the rolling hard. The effects, analysis, and suggestions are made for parameters by increasing the number of passes to 9 thereby decreasing the Wastages, enhancing the Utilization of Re-Heating Furnace. 

Results of Lean Management:  

As per the trial run carried out by the suggested input parameters such as discharge temperature, pace rate, retention time and slab size the output data are recorded in the EDAS system. The data that are taken for consideration from the EDAS are roll force, spike, the percentage of reduction and change of length in every pass. After analyzing the following data the following conclusions have been made.

Analyzing the roll force recorded for both 9 passes and 7 passes SSLNA rolling, it is seen that the roll

force for 7 pass rolling starts with a low value and creates a sudden hike in the consecutive passes.

At the same time in case of 9 passes rolling the roll force starts and proceeds in a gradual scale. This

shows that the mill is utilized in a smooth loading condition both in terms of mechanical and

electrical. Thus the mill remains unsaturated. This is mainly due to the reduction in a number of

passes. As we reduce the number of passes the percentage of reduction for a pass turns in a gradual

scale so all other parameters that depend on the no. of passes such as roll force, current utilization

in rolling and peak current utilization time follows a gradual scale. 

At the same time productivity increases. This can be justified by the pacing rate. As the pacing rate is reduced from 26 min to 24 min, the number of slabs passing in an instance of time increases. It is seen that the amount of slab in case of 7 passes is 37 tons per hour but for 9 passes it is 40 tons per hour. For the data, it is clear that the productivity increases from 67% to 73% on comparing the quantity rate with 55 tons per hour which are as per the norms.

Thus by increasing the number of passes, it is clear that the equipment is working under controlled

operating parameters. This prevents the loss due to machine failure. At the same time, the quality of

the rolling and productivity of the whole HRM increases. This shows that the rolling remains

optimized in roughing mill. Hence 9 pass rolling is better than 7 pass rolling, under the suggested

parameters in roughing mill