JPH09253727A - Cold rolling method for metal strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely roll by predicating a rolling load based on a wedge indentation max sheet thickness reducing quantity, target elongating rate and sheet thickness at rolling mill input side by a prescribed equation and controlling the rolling with the rolling load in cold rolling of metal strip. SOLUTION: In cold rolling a metal strip, based on a wedge indentation max sheet thickness reducing quantity ΔTWEP, a target elongating rate (r) of rolled stock and a sheet thickness (hi ) of rolling mill input side of rolled stock, a rolling load P is predicted by the next equation, based on the resulting value, the rolling mill is controlled. P=PWED.α+Pb ,f (1-α), wherein Pb ,f is Bland and Ford's rolling load equation and PWED is the rolling load equation by a two dimensional wedge line plane indentation model. When a product of the inlet side sheet thickness and elongation rate is smaller than a wedge indentation max thickness reducing quantity ΔWED, the equation is governed by the two dimensional wedge plane wedge line indentation model, when exceeding the max thickness reducing quantity ΔTWED, the Bland and ford load equation is incorporated depending on its degree. By this method, the rolling load is precisely estimated and rolling is precisely executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rolling a metal strip in a cold rolling mill, and more particularly, it accurately predicts a rolling load value when a reduction ratio is low as in a temper rolling mill and achieves a target value. The present invention relates to a method of rolling.

[0002]

2. Description of the Related Art In the cold rolling process of steel strip, a cold rolled steel sheet finished to a target thickness is annealed and then temper-rolled to obtain a predetermined elongation to obtain a product. Target. The temper rolling mill is computer-controlled so that the target elongation rate can be obtained. In this computer control,
It is necessary to estimate the rolling load generated during rolling.

Conventionally, as an estimation model of rolling load, (2)
The well-known and conventional Bland & Ford rolling load equation shown in the equation has been used. _{P b & f = f (k} m, t 1, t 2) Q P L P ...... (3) k m: Mean deformation resistance, Q _P: rolling force function t _1, t _2: inlet side, outlet side unit tension

[0004]

However, in the case of rolling with a small reduction ratio such as pressure rolling, when rolling with a dull roll, the rolling load formula of Bland & Ford is used to determine the rolling load. Estimating, as shown in FIG. 3, the calculated rolling load tends to be larger than the actual rolling load.
That is, FIG. 3 shows a relational expression between the calculated rolling load calculated by using the Bland & Ford rolling load formula and the actual required value for the rolling load required to obtain a predetermined elongation. However, according to FIG. 3, about 19% of the calculated rolling load is larger than the actual rolling load. Also,
The standard deviation σ showing the accuracy of the relational expression between the actual rolling load and the calculated rolling load is also large at 13.8%.

This indicates that when the mathematical model using the rolling load formula of Bland & Ford is used, the elongation rate larger than the target value is obtained and the variation in the elongation rate is large.

The present invention has been made to solve the above problems, and an object thereof is to provide a method for performing cold rolling of a metal strip with high accuracy by using an accurate rolling load estimation formula. And

[0007]

[Means for Solving the Problems] The above-mentioned problem is to cool a metal strip.
During rolling, the maximum amount of reduction in wedge pressing (ΔT
_WED), The target elongation (r) of the rolled material, the pressure of the rolled material
Lathe entrance side plate thickness (h_i), The rolling load during rolling
Predict using the formula (1) below and apply pressure based on this predicted rolling load.
It is solved by controlling the rolling machine and rolling. P = P_WED・ Α + P_{b & f}・ (1-α) …… (1) where P_{b & f}Is the rolling load formula of Bland & Ford.
P_WEDIs the rolling load based on the two-dimensional wedge-plane indentation model
It is an expression. Also, α = 1 ... (r · h_i<Δ
T_WEDWhen) ΔT_WED/ (R · h_i) …… (r ・ h_i≧ ΔT_WEDNoto
It is. Here, the wedge press-in maximum plate thickness reduction amount ΔT
_WEDIs ΔT_WED= C ・ R ・ ΔT_B/ R_B...... Given in (2). Here, C is a roll wear correction coefficient. R is
Roll surface roughness, ΔT_BIs the reference plate thickness reduction amount, R_BIs the standard
Roll surface roughness.

(A) The plastic elongation in cold rolling occurs due to the combined action of the wedge-shaped projections distributed on the roll surface being pushed into the metal strip and the plastic deformation of the metal strip due to roll rolling. (b) There is an upper limit value for the plastic elongation generated when the wedge-shaped projection is pressed into the metal band, which is determined by the shape of the wedge and the like. Based on this idea, a new rolling load estimation formula was developed.

The rolling load due to the former action is given by the rolling load equation based on the two-dimensional wedge-row plane indentation model,
The rolling load due to the latter action is given by the rolling load equation of Bland & Ford.

Equation (1) shows that when the product of the strip thickness and the elongation rate is smaller than the wedge depression maximum strip thickness reduction amount ΔT _WED , the rolling load equation is governed by the two-dimensional wedge array plane indentation model, When the product of elongation and elongation exceeds the maximum wedge thickness reduction ΔT _WED , Bl depending on the degree
It shows that the rolling load formula of and & Ford is added.

The roll surface roughness R in the equation (2) is the surface roughness of the roll before rolling, and the unit may be the same as the reference roll surface roughness R _B.

Further, the reference plate thickness reduction amount ΔT _B is obtained by tuning the actual rolling load so that the predicted rolling load and the actual rolling load match. That is, in the actual machine, r ・ in the range where the rolling load calculated by only the two-dimensional wedge-row plane indentation model matches the actual load well.
Finding h _i and _letting this maximum value be ΔT _WED ,
The reference plate thickness reduction amount ΔT _B is calculated by back-calculating the formula and used as a constant thereafter.

Further, as shown in FIG. 2, the roll wear correction coefficient C is a coefficient determined by the total length (WR rolling length) of the metal strip rolled by the roll.

[0014]

EXAMPLE The present invention was applied to an actual temper rolling mill to confirm the accuracy of the rolling load estimation formula.

As a two-dimensional wedge-row plane indentation model,
The one expressed by the following equation (4) was used.

[0016]

[Equation 1]

In the equation (4), p is the pushing pressure of the steel plate of one wedge, R _MAX is the wedge height, θ is the wedge apex angle, K ₁ is the number of longitudinal wedges, K ₂ is the number of wedges in the width direction, and h is Average plate thickness, L _P is the contact arc length, and r is the elongation rate.

Actually, in equation (4), it is determined by the steel plate pushing pressure p of _one wedge, the number of wedges in the longitudinal direction K ₁ , the number of wedges in the width direction K ₂ , the wedge height R _MAX , and the wedge apex angle θ.

[0019]

[Equation 2] Are treated as one constant (Dull constant),
The dull constant was determined by tuning so that the predicted rolling load matches the actual rolling load in the actual machine.

The contact arc length L _P is L _P = (R ′ · Δh)
^1/2 , (R 'is the flat roll diameter of Hitchcock, and Δh is the amount of reduction in plate thickness). The well-known rolling load formula of Bland & Ford was used.

Further, as the reference roll surface roughness R _B ,
2 μm, and the reference plate thickness reduction amount ΔT _B was 8 μm.

As the roll wear correction coefficient C, the one shown in FIG. 2 was used. The results are shown in FIG. According to Fig. 1, the difference between the actual rolling load and the calculated rolling load is 2% on average.
The standard deviation is close to 8%. FIG.
Compared with the conventional method, both values are smaller than the conventional method,
It can be seen that the estimation accuracy has improved.

In temper rolling using the method of the present invention, the length of the portion having a poor elongation is about 10 m as compared with the conventional case.
To less than 5 m.

[0024]

In the present invention, since the rolling load is estimated by the combination of the rolling load formula by the two-dimensional wedge-row plane indentation model and the rolling load formula of Bland & Ford, the rolling load can be accurately estimated. , Accurate rolling can be done.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of correspondence between a calculated rolling load and an actual rolling load according to the present invention.

FIG. 2 is a diagram showing an example of changes in roll wear correction coefficient in the present invention.

FIG. 3 is a diagram showing an example of correspondence between calculated rolling load and actual rolling load in a conventional example.

Claims (1)

[Claims] 1. A method for cold rolling a metal strip, comprising a wedge
Maximum indentation thickness reduction (ΔT_WED) And the rolled material eye
Standard elongation rate (r), rolling mill entry side plate thickness (h)_i)
Based on this, predict the rolling load during rolling with the following formula (1),
Rolling is controlled by controlling the rolling mill based on this predicted rolling load.
A method for cold rolling a metal strip, which comprises: P = P_WED・ Α + P_{b & f}・ (1-α) ・ ・ ・ (1) where α = 1 …… (r ・ h_i<
ΔT_WEDWhen) ΔT_WED/ (R · h_i) …… (r ・ h_i≧ ΔT_WEDNoto
KI) ΔT_WED= C ・ R ・ ΔT_B/ R_B…… (2) Here, P_WEDIs the two-dimensional wedge-plane indentation model
Rolling load obtained by P _{b & f}Is the rolling load of Bland & Ford
Rolling load calculated by the formula, C is roll wear correction coefficient,
R is roll surface roughness, ΔT_BIs the reference plate thickness reduction amount, R_BIs
It is a standard roll surface roughness.