Roll mounting pressure is one of affecting parameters for the failure of WC rolls during hot rolling of steel wire rods.
Which company has supplied you the V mill or the whole wire rod mill? Did they specify any particular pressure? I think there must be a threshold Hydraulic pressure developed by hydraulic Jack for appropriate mounting but you must me checking roll alignment after mounting using optical technique. That can tell you exact roll mismatch otherwise product will not be good at all.
Thank you taking interest.
The supplier of wire rod mill is "Morgan Worcester".
The specified mounting hydraulic pressure range for Sizing Mill is 250 to 350 bar and there is no such provision for alignment checking using optical technique for this block. However, most of the roll/ring failure occurs for this block. Furthermore, we are grinding the rolls after a certain life/tonnage for reuse which is certainly a logistic procedure for all wire rod mills.
You may check the stock getting into these rolls. Sometimes more stock and higher temperature of strand may lead to such carbide roll failures. Do you observe pass burning prior to ending up the life of the rolls? Secondly, do you find roll cross after mounting? We were facing the same problem in our Morgan mill and we found that stock was more in our case. You may try to optimize side looper, interstand cooling and try to avoid drastic reduction. Try to control stock at Pre Finishing Mill and open interstand cooling at NTM. At which place you facing this problem NTM or RSM?
Thanks for your suggestion.
All the above mentioned affecting parameters were also taken into consideration.
We are facing this problem in the sizing block of RSM (29,30) and that to for smaller diameter rolls.
There must not be much issue related to higher stock if its 29 and 30th stand because those only control ovality. Do you check the profile after NTM exit or RSM Entry using rod gauge? Crack is on skin of the pass or at the radial direction? If its radial, mounting can be the problem.
Interstand cooling helps in reducing the excessive temperature of strand during rolling at NTM of Morgan mill which also helps in reducing the roll pass temperature. But you are facing the problem at RSM where the provision may not be given hence it won't be intended to affect much. The coil length is 13 km approx for RSM hence temperature exposure and friction on roll pass is higher in RSM.
The camera installed above the side loopers can help in this. However, no provision is given by Morgan to adjust sidelooper unlike uplooers where we can put the loop height in order to maintain the tension in the strand. For sidelooper, wide curve or spread curve of strand is not good it means higher stock is released from the previous stand.on the other hand, Very less spread shows higher tension hence pass separation should be such which can control the tension in optimised manner. Bigger opening may cause higher spread and more cross section area of strand and this material will pose more force to the rolls and in order to maintain the reduction, roll wear will increase due to high friction and roll failure would become prevalent.
Who is the supplier of WC rolls in your plant? The problem of failure is related to only particular manufacturer or irrespective of them?
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