JPH0456681B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a cold continuous rolling mill.

Reducing the rolling load generated when rolling a metal plate has many advantages, such as downsizing the rolling mill, reducing roll wear, facilitating rolling of high-strength materials, and improving the shape of the plate.

In order to achieve the above objective, conventionally, a continuous rolling mill with multiple four-high rolling mills in which the upper and lower work rolls have the same diameter and speed has been used to reduce the rolling load per machine. Although the continuous rolling mill has high productivity, the equipment cost is high, and when working with hard materials such as high-tensile steel or thin work-hardened materials such as low carbon steel, the rolling load increases due to the flatness of the work rolls. However, the rolling of the material does not progress, and the so-called rolling limit is easily reached, making rolling difficult.

Furthermore, multi-roll mills with small-diameter work rolls are used to roll hard materials such as high-strength steel, but the rolling speed is low, resulting in low productivity, and the large number of rolls increases roll costs.

On the other hand, in recent years, rolling methods have been developed to reduce the rolling load.
The RD rolling method (Rolling Drawing method) was developed.
In this RD rolling method, as shown in Fig. 1, the rotational speeds of adjacent rolls a and b are different speeds v ₀ and v ₁ ,
When the thickness of the entrance side of the metal plate s is h ₀ and the thickness of the exit side is h ₁ , the relationship h ₀ /h ₁ = v ₁ /v ₀ is maintained, and the front tension t _f of the roll gap and the rear This is a different speed rolling method that utilizes the difference between the tension and the tension _tb , and can achieve a large reduction with a small rolling load.

This variable speed rolling method was applied to a continuous rolling mill, and in order to eliminate the drawbacks of a continuous rolling mill using a multi-roll rolling mill having work rolls of equal diameter and constant speed, continuous rolling as shown in Figures 2 and 3 was carried out. Although a continuous rolling mill has recently been developed, the continuous rolling mill has the following drawbacks.

() The threading process for winding the plate is troublesome, it is difficult to cool the rolls, and it is not suitable for high-speed rolling, resulting in poor productivity.

() Because it is rolling at different speeds, it is necessary to make the front tension t _f of the roll gap larger than the rear tension t _b , but the tension value increases as it approaches the exit side of the rolling mill, and rolling becomes impossible due to plate breakage. There is a risk that this may occur.

() When rolling high-strength materials, it is preferable to use small-diameter rolls, but if small-diameter rolls are used in the rolling mills shown in Figures 2 and 3, the deflection deformation of the rolls will increase, resulting in the shape of the rolled plate. becomes worse.

Note that a, b, c, d, in Figures 2 and 3
e, a', b', c', d', and e' are rolls, and s is a metal plate.

The present invention was made for the purpose of eliminating the above-mentioned drawbacks of conventional continuous rolling mills. The final stand is equipped with a different speed rolling mill that performs rolling so that the ratio of the thickness to the exit side plate thickness is approximately equal to the circumferential speed ratio of the upper and lower work rolls, and the front tension is greater than the rear tension. .

Next, the basic basis on which the present invention was made will be explained.

If all the stands of a plurality of rolling mills can be made into different speed rolling mills, the effects of different speed rolling can be utilized to the fullest compared to normal rolling. However, when considering one different speed rolling mill, the rear tension t _b and the front tension
t _f is the deformation resistance of the material, k is the plate thickness on the entry side, h ₀ is the plate thickness on the exit side, and h ₁ is the plate thickness on the exit side. In order to achieve different speed rolling, t _f −t _b = _klo ( h ₀ /h ₁ ) ...() must be maintained. Therefore, the tension between the rolling mills in which straight path type different speed rolling mills are successively arranged becomes higher as the stage progresses. If the position of each variable in the i-th stand is expressed by the precision i, then t _f , _i −t _b , _i = k _i ln(h ₀ , _i / h ₁ , _i ) t _f , _i+1 − t _b , _i
+1 = k _i+1 ln (h ₀ , _i+1 /h ₁ , _i+1 ) However, since t _f , _i = t _b , _j+1 , t _f , _i+1 −t _b , _i = k _i ln (h ₀ , _j / h ₁ , _i ) + k _i
+1 (h ₀ , _i+1 / h ₁ , _i+1 ).

After all, if stands 1 to n are all different speed rolling mills, t _f , _o −t _b , ₁ = _o Σ ⁱ⁼¹ k _i ln (h ₀ , _i /h ₁ , _i ), and if k If _i is constant and k, then t _l

Claims (1)

[Claims] 1. In a continuous rolling mill in which multiple rolling mills are arranged continuously for rolling, the ratio of the inlet side plate thickness to the outlet side plate thickness of the rolling mill is approximately equal to the circumferential speed ratio of the upper and lower work rolls, and the front tension is A continuous rolling mill characterized in that a final stand is equipped with a different speed rolling mill that rolls at a rate greater than the tension.