JPH0581323B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing hot strips, which involves rolling a plurality of hot strips having different widths from one slab.

[Prior art and problems]

Hot coils are produced by charging a slab of a certain size into a heating furnace, heating it to a predetermined temperature, rolling the heated slab in a group of rough rolling mills, and then rolling it in a group of finishing mills to achieve a predetermined plate thickness. It is manufactured by obtaining the board width and winding it up using a winding machine. Not all of the hot coils that are manufactured are made to order, and often some parts are not made to order. FIG. 2a is a diagram illustrating this, in which out of a hot coil having a total length l, a length _l1 portion is a ordered product, and the remaining _l2 portion is a non-ordered product. The size of the slab is selected so that only ordered products with width B and length l ₁ are rolled, which is preferable in order to eliminate the occurrence of non-ordered products.However, from the heating furnace efficiency, the slab occupancy rate It is desirable for the slab length to be high (the proportion of slabs occupied), and it is also desirable for the slab length to be long in terms of the production efficiency of the finishing rolling mill. Generating products.
Currently, there is a one-to-one correspondence between slabs and ordered products. In other words, it is extremely difficult to eliminate surpluses.

If it is possible to change the width and/or thickness of a non-customized product with a length l ₂ and use it as a different ordered product, it will be extremely effective in reducing surplus materials and can greatly contribute to improving yield.

From this point of view, the present invention changes the width within the coil to make one slab compatible with multiple ordered products, thereby increasing the proportion of ordered products without reducing the occupation of slabs in the heating furnace or reducing rolling efficiency. The aim is to improve production efficiency as a whole.

The production of multiple hot coils with different widths from one slab is disclosed in Japanese Patent Publication No. 59-10845, and this method involves rolling a slab into a stepped type in which the width dimension changes midway by adjusting the rigid roll opening of a roughing mill. The material is rolled into a rough rolled bar and cut at the stepped portion to form a plurality of bars with different widths, each of which is finished rolled independently. However, this method generates a lot of debris. In other words, the material thickness at the exit side of the rough rolling mill is 30 to 80 mm.
The material on the exit side of the finishing rolling machine is thin, such as 1.2 mm, and the stretching ratio is 25 to 70 times, so the stepped part formed in the rough rolling machine is also stretched 25 to 70 times. Everything will turn to trash. Furthermore, if the rough rolled bar is cut by a crop shear at the stepped part and separated into individual pieces, and then subjected to finish rolling, a reduction in rolling efficiency is caused, or is inevitable, and the material in the latter half of the separation is There are also problems such as a drop in temperature.

The present invention aims to provide a rolling method that can avoid such a reduction in rolling efficiency and the generation of scraps at stepped portions, and can suppress the occurrence of out-of-order products.

[Means for solving problems]

The present invention determines the dimensions of one slab by making it correspond to first and second ordered products having different widths,
When the slab, which has been roughly rolled to the same width, is rolled in a finishing mill, the width change point is tracked, and when the width change point enters between each stand of the finishing mill, the strip tension between the stands is changed, and the strip tension is changed between the stands. Then, the rolling adjustment is performed to cancel the change in plate thickness due to the change in tension, and the first and second ordered products are obtained in this way.

In the present invention, stepped hot coils are manufactured by tension control in a finishing mill. Japanese Patent Publication No. 55-13805 states that tension control is performed for the purpose of eliminating variations in the width of hot coils, that is, manufacturing hot coils of uniform width, but in the present invention, tension control is used to manufacture stepped hot coils that include multiple ordered products. do. For this purpose, a tension change is carried out when the width change point is engaged in the rolling stand, thereby changing the strip width from a previously existing first width to a different second width. By setting this second width to the width of the second ordered product, it is possible to prevent the occurrence of non-ordered products. The width of custom-made hot coils varies, for example, from 600 to 200 mm. Of course, the first and second slabs are made from one slab.
It is preferable that the ordered products have similar widths, so it is best to select an appropriate combination. To explain this with reference to Figure 2, the length l ₁ of a strip having a total length l is under tension T ₁ and the length l ₂ is under tension T ₂ (T ₁ < T ₂ ), and the length is as shown in Figure b. l ₁ part is custom made width B ₁ ,
The length l ₂ part is made to order with width B ₂ , and the entire length is also made to order. In this way, the shaded area between the first ordered item and the second ordered item becomes waste (this area can be used for over trimming)
However, the stepped portion during rough rolling is much smaller than the scrap portion generated during finish rolling.

If the width is changed by tension, the thickness will also change, so tension control and reduction control are performed at the same time. If the first ordered product and the second ordered product differ only in width but have the same plate thickness, the rolling reduction is adjusted to cancel out the change in thickness due to the change in tension.

〔Example〕

FIG. 1 shows an embodiment of the present invention. 11 to 17 are the first to seventh stands of the finishing mill, which sequentially roll the strip 20 supplied from a rough rolling mill (not shown) to a desired thickness and width. 21, 22,...
...27 is a lowering device for each stand, 31, 31,...
. . 37 is the same roll cell, and 41, 42, . . . 47 are speed detectors. 51, 52, . . . 56 are loopers provided between each stand. Reference numeral 61 denotes an online process computer that takes in data from the rolling down device, load cell, speed detector, and host computer (not shown) of each stand, and calculates the speed control device 62, looper control device 63, and rolling position control device 64 of each stand. control. The host computer is for production control, and when making the product shown in Figure 2b, it corresponds the first ordered product and the second ordered product to one slab, and calculates the respective sizes L ₁ and B ₁ , l ₂ and B ₂ on calculator 6
Transmit to 1. The calculator 61 calculates the strip width change point at the entry side of the finishing rolling mill from the size, and controls the looper to change the tension while the change point passes between the stands.

FIG. 3 shows how the strip width changing point P passes through each stand one after another and the strip width _B2 is expanded one after another. In order to suppress as much as possible the expansion of the point at which the strip width changes while passing through the finishing mill, the computer 61 tracks the changing portion and changes in tension are determined for each stand. Since there is a relationship between the tension τ and the plate width change rate ΔB/B as shown in Figure 4, the required tension τ is calculated from the necessary ΔB/B, and the tension between each stand is added to this value. Change when the width change point is entered.
The required inter-stand tension τ is generally expressed by the following formula.

τ=f (ΔB, B, G, T, h) ...(1) Here, ΔB is the change in the strip width, B is the strip width, G is a constant determined by the steel type, T is the strip temperature, and h is the strip thickness. It is. When the tension changes, the plate thickness also changes, and this relationship is as shown in FIG. 5, and the plate thickness change Δh is expressed by the following equation.

Δh=g(τ, B, ΔB, h, T) ...(2) Changing the tension τ changes the plate thickness change rate Δh/h, so if there is no difference in thickness between the first and second ordered products, Find the roll gap change ΔS to make Δh=0,
As a result, the reduction of the exit side stands 12, 13, . . . 17 in the section is predictively controlled at the same time as the tension is changed. In order to prevent the strip from meandering, it is better to place the side guide close to the strip width, but in this case, the opening degree of the side guide should also be changed at the point where the width changes. For this purpose, a side guide opening/closing device (not shown) as shown in FIG. 1 may be provided, and this may be controlled by the computer 61.

Furthermore, since there is a delay in changing the tension by changing the looper tension reference value and there is a limit to the tension changing range, it is better to change the stand roll speed at the same time. The speed control device 62 of FIG. 1 is for this purpose. That is, in the present invention, the looper reference tension,
The mill speed and reduction value are simultaneously changed to a new settling position after changing the width (non-interference control), and if necessary, side guide control is also performed at the same time.

FIG. 6 shows the outlet side plate thickness, rolling position, and outlet side plate width of each stand, and F1 to F7 indicate finishing stands 1 to 7, which correspond to 11 to 17 in FIG. 1.
The solid line indicates when the plate width is changed by tension control.
The dotted line is when this is not done. Therefore, regarding the plate width, the dotted line is also the plate width of the portion running from the stepped portion. In this example, the plate thickness is not changed, and the part after the stepped part is made wider. Therefore, the plate thickness becomes large, so the reduction position is lowered (the opening degree is made smaller) to prevent the plate thickness from decreasing. .

In this example, we have given an example of manufacturing a series of hot coils having two widths B ₁ and B ₂ corresponding to the first and second ordered products, but of course this is not limited to two types of ordered products, but can be applied to a wide variety of other products. Therefore, it may include a variety of widths. Further, the different ordered products may have different widths and thicknesses, and in this case, the rolling adjustment for the change in thickness will be made at the change point.

〔Effect of the invention〕

As explained above, in the present invention, the inner plate width of the coil is changed at the finish rolling stage by changing the tension.
It becomes possible to allocate parts that should be out-of-order items to other ordered items, which can contribute to improving yield.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of main parts of the invention, Fig. 3 is an explanatory diagram of the rolling process, and Figs. 4 and 5 are illustrations of tension, plate width, etc. The graph and FIG. 6 are charts explaining the plate thickness, plate width, etc. of each stand. In the drawing, 20 is a strip, and P is a width change point.

Claims (1)

[Claims] 1. Determine the dimensions of one slab to correspond to the first and second ordered products with different widths, and track the width changes when rolling the slab, which has been roughly rolled to the same width, in a finishing mill. However, when the width change point enters between each stand of the finishing rolling mill, the strip tension between the stands is changed, and a rolling adjustment is performed to cancel the change in plate thickness due to the change in tension. 2. A method for producing hot strips, which is characterized by obtaining the ordered product.