Method for increasing the process stability, particularly the absolute thickness precision and the installation safety during the hot rolling of steel or nonferrous materials
View Patent ↗The invention relates to a method for increasing the process stability, particularly the absolute thickness precision and the installation safety during the hot rolling of steel of nonferrous materials, with small degrees of deformation (f) or no reductions while taking the high-temperature limit of elasticity (R e ) into account when calculating the set rolling force (F w ) and the respective setting position (s). The process stability can be increased with regard to the precision of the yield stress (k f,R ) and the set rolling force (F w ) at small degrees of deformation (f) or small reductions, during which the high temperature limit of elasticity (R e ) is determined according to the deformation temperature (T) and/or the deformation speed (phip) and is integrated into the function of the yield stress (k f ) for determining the set rolling force (F w ) via the relation (2) R e =a+e b1+b2·T .phip c , in which: R e represents the high temperature; phip represents the deformation speed, and; a, b, c represent coefficients.
1. Method for hot rolling of steel or nonferrous materials with small degrees of deformation (φ) or small reductions, comprising the steps of:
calculating a set rolling force (F w ) and a given adjustment position (s) by taking into account a yield point at elevated temperature (Re); and determining the yield point at elevated temperature (R e ) as a function of deformation temperature (T) and/or deformation rate (φp), which is then integrated in the function of flow stress (k f,R ) for determining the set rolling force (F w ), using the relation
R e= a+e b1+b2·T ·]p c (2)
by expanding a multiplicative flow curve relation by the yield point at elevated temperature (R e ) as a function of the deformation temperature (T) and deformation rate (φp) according to the formula
k f,R =a+e b1+b2·T ·]p c ·k f0 ·A 1 ·e m1·T ·A 2 ·] m2 ·A 3 .]p m3 (3)
in order to hot roll steel or nonferrous materials,
where
R e =yield point at elevated temperature
T =deformation temperature
φp=deformation rate
a,; b i ; c=coefficients
2. Method in accordance with claim 1 , wherein the flow stress (k f,R ) is integrated in conventional rolling force equation for determining the set rolling force (F w ) for automatic gage control as well as for computational models and automatic control processes according to the following equation
F w =Q p ·k f,R ·B ·( R w ·( h 0 −h 1 )) 1/2 (4)
where
F w =set rolling force
Q p =function for taking into account the roll gap geometry and friction conditions
k f,R =flow stress, taking into account the yield point
B=rolling stock width
R w =roll radius
h 0 =thickness before the pass
h 1 =thickness after the pass.
3. Method in accordance with claim 1 , wherein a material modulus (C M ) is calculated on the basis of the set rolling force (F w ), taking into account the yield point at elevated temperature (R e ) as a function of the deformation temperature (T) and deformation rate (φp) for degrees of deformation smaller than a material-specific smaller than a material-specific limiting degree of deformation (φ G ), according to the formula
C M =( F w −F m )/ dh 1 (5)
where
C M =material modulus
F w =set rolling force
F m =measured rolling force
dh 1 =change in the runout thickness.
4. Method in accordance with claim 3 , wherein a conventional gage meter equation is expanded into the form
ds AGC =(1 +C M /C G ) dh 1 =(1 +C M /C G )·(( F w −F m )/ C G +S−S soll ) (6)
where
ds AGC =change in the roll gap setting
C M =material modulus
C G =rolling stand modulus
dh 1 =change in the runout thickness
F w =set rolling force
F m =measured rolling force
S=adjustment of the roll gap
S soll =desired adjustment of the roll gap.