If you cannot reduce strip crown in 304 stainless steel to under 40μm at 40mm from edge by using work roll shifting with CVC or smart crown, please contact me.

After the introduction of CVC or smart crown I thought my expertise about crown reduction is no longer necessary to new hot strip mills in the world. But I have found there are mills that cannot attain 40μm at 40mm from edge by using work roll shifting with CVC or smart crown in 304 stainless steel because of heavy center buckle at earlier finisher stands.

So I thought there might be some chance to use my expertise in the field of hard stainless steel production. Heavy center buckle in earlier stands clearly shows the weak point of CVC/smart crown or their limitation. Strip crown consists of bending curve portion and edge drop portion due to roll flattening and lateral direction material flow. CVC/smart crown can cope with bending curve and so OK for mild steel crown control, but not capable for very hard steel, which have big edge drop portion.

What is the difference between CVC/smart and taper roll? Taper roll changes the thickness deviation mainly from edge to about 1/4 – 1/3 inside portion from edge depending on strip width. CVC/smart crown changes the thickness deviation whole through width direction. Sensitivity to flatness is big at center and small at edge when changing the same amount of strip crown. Taper roll can change strip crown with small change of flatness. CVC/smart can change crown with big change of flatness. Crown consists of small thickness deviation at center area and big thickness deviation at edge to 1/4-1/3 area especially in hard steel, which means taper roll can effectively reduce strip crown compared to CVC/smart in hard steel.

In conclusion taper roll is much better to reduce strip crown in hard steel compared to CVC/smart. Actually taper roll produces 40μm at 25mm from edge in 304 stably, without early stands center buckle.
If you really want to reduce your big crown to 40μ, it is recommended to use taper roll.