JPS61289902A - Cold rolling method with excellent suppression of edge drop - Google Patents

Abstract

PURPOSE:To improve the yield of a product by subjecting a material to be rolled to a cross reduction treatment on the inlet side of a cold rolling mill then rolling the thick-walled edge ends with the convergent parts at the ends of work rolls. CONSTITUTION:Edger rolls 3 are disposed on the inlet side of the cold rolling mill consisting of stands No.1-No.5 and the cross reduction rolling is executed. The work rolls 1, 1 formed with the convergent parts having a tapered shape, etc. on at least the end on one side are disposed to the stand No.1. The work rolls are constituted of ordinary flat rolls for the No.2 and subsequent stands. The ends of the material 2 to be rolled formed by the edger rolls 3 are thick- walled and the work rolls 1 of the stand No.1 act to decrease the increased thickness at the edges thereby suppressing the generation of an edge drop. An edge crack and edge wave are thereby prevented and therefore the yield of the product steel sheet is improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention belongs to the field of cold rolling technology for steel, and the content of the technology disclosed in this specification reduces edge drop, which is a concern during cold rolling. This paper proposes a rolling method suitable for producing cold-rolled steel sheets with fewer edge cracks.

(Prior Art) A material to be rolled after cold rolling exhibits a rapid decrease in thickness at both ends in the width direction, which is called "edge drop." This edge drop is the edge part of the rolled material.
This is caused by the metal flow in the width direction of the steel and the flattening of the surface of the work roll, and is largely controlled by the cold rolling conditions.

Conventionally, as a technique for reducing this edge drop, for example, Japanese Patent Application Laid-Open No. 59-113904 proposed by the present inventors
There is a method of disclosing the number. The technology disclosed herein is such that each of the pair of work rolls is provided with a tapered part that is tapered and ground at least at one end, the tapered parts are located on both sides of the material to be rolled, and the work rolls are incorporated into the mill housing together with the reinforcing roll. This method attempts to reduce edge drop by adopting a cold tandem rolling mill row in which a 4-high rolling mill is placed at least in the first stand and the final stand incorporates conventional work rolls. It is.

(Problems to be Solved by the Invention) FIG. 2 (al) shows a rolling method using a known trapezoidal work roll, which is also used in the present invention, in which both ends of the work roll 1 are tapered. 2 shows a rolling method in which a taper is formed only at one end of the work roll 1, and the work roll 1 is moved in the axial direction so that it can follow changes in the sheet width.

However, when rolling a normal rolled material using such work rolls, the elongation rate is smaller at the width edges than at the width center, so as shown in Figure 3, The tension on the exit side of the part becomes extremely high. For this reason, particularly in the case of brittle materials, occurrence of edge cracking or plate breakage as shown in FIG. 4 becomes a problem.

The aim of the present invention is to propose a cold rolling method that is effective in reducing edge drops during cold rolling and further preventing the occurrence of edge cracks and plate breaks in cold rolled sheets. .

(Means for Solving the Problems) In order to solve the above-mentioned problems that need to be solved, the present invention subjects a material to be rolled to a width reduction treatment on the entry side of a cold rolling mill, and the edge portions thickened by this treatment. A cold rolling method excellent in suppressing edge drop, characterized in that the edge end of the material to be rolled having the following properties is positioned on the tapered part of a pair of work rolls each having a tapered part formed on at least one end thereof. be adopted as a solution.

In this method, the width reduction process of the material to be rolled is performed in the first stand of the cold tandem rolling mill, and the tapered part of the work roll is ground into a tapered or curved shape. Use a crown-shaped one.

(Function) Next, the basis for using the above method as a means of solving the problem will be discussed below. FIG. 5 ia) shows the thickness deviation of a plate processed by a general cold rolling method, and a sharp edge drop occurs at the edge of the plate. FIG. 5(b) shows the plate thickness deviation after rolling this in a cold tandem mill. When rolling with normal work rolls (flank rolls), large edge drops occur, but when rolling with tapered work rolls (taper rolls) shown in Figure 2, edge drops are reduced. For being seen. However, if this method uses only tapered rolls, the elongation rate at the edge part of the plate is smaller than the elongation rate at the center of the width, so a large tension is generated at the edge part of the plate, making the material brittle. In this case, an ear crack as shown in Figure 4 occurred.

Therefore, the present inventors conducted further research taking the above-mentioned edge cracking into account. As a result, in order to increase the elongation rate of the edge portion in the width direction, width reduction was performed using an edge roll, for example, before cold rolling, and the edge portion We have found that it is effective to increase the thickness of the sheet and then roll it using a tapered work roll, a so-called taper roll.

That is, FIG. 6 ia) shows the plate thickness deviation after width reduction and before cold rolling, and the plate thickness increases at the edge portion due to width reduction. When a plate with thickened edges is rolled with a tapered work roll, the edge becomes shaped as shown in Figure 6 (bl) and the plate thickness deviation is reduced. Combined with the effect of increasing the thickness of the part, there are almost no cracks or nozzle drops.

Furthermore, the elongation rate of the edge portion and the elongation rate of the center portion became equal, and as shown in FIG. 6, the tension at the edge portion became approximately equal to the tension at the center portion, and the occurrence of edge cracking was also prevented.

On the other hand, when rolling with normal work rolls, the edge drop was larger and edge cracking occurred than in the case of implementing the method of the present invention. As described above, the present invention reduces edge drops and prevents edge cracking.

It is possible to prevent the occurrence of ear elongation.

When applying the method of the present invention to a cold tandem rolling mill, it is necessary to consider the effects of plate thickness and tension on the formation of edge drops. As can be seen from Fig. 8 (al, (bl), the thicker the board thickness on the entry side, the more the edge drop is formed from the inside, and the smaller the tension, the greater the amount of edge drop. This is an example of an area where edge dross is improved, and each curve in this figure shows the thickness distribution (curve α) caused by applying a tapered work roll, and the thickness distribution when using a normal work roll. In other words, the edge drop improvement amount (curve β) is shown.

The chain line r in the diagram is the profile of the tapered work roll, EH is the radius difference between the taper part and the flant part, and EL is the distance from the boundary point between the taper part and the flant part to the plate end. show.

As can be seen from Fig. 9, the amount of improvement in edge drop by the tapered work roll method does not follow the profile of the work roll, and the improved area remains within about 50a+m from the edge of the board toward the center. Edge position [! L =
In other words, the edge drop improvement area by the tapered work roll method is smaller than the value of 90 mm. In such an example, the edge drop improvement area is not equal to the length of EL, and is range)
This suggests that edge drops may not be improved. Considering that edge drops occur outward from around 50 mm from the sheet edge in normal work rolls, if the rolling conditions are constant in terms of the area where metal flow in the width direction is possible, the area where edge drops occur and the improved area are the same. This suggests that this is true. In other words, this means that the application of tapered work rolls to a cold tandem mill is effective only for stands where the rolling conditions are such that edge drop formation is significant. By the way, Table 1 shows typical examples of tension and plate thickness in a cold tandem rolling mill (5 stands).

Table 1 The table 1 above is shown in Figure 8 ial (As is clear from the comparison with BL, from the point of view of plate thickness, the upstream stand has a taper, while from the point of view of visual strength, the taper is applied to the first stand and the last stand. It can be seen that the effect of improving edge drop is large when a rolling work roll is applied.Also, when performing width reduction, the effect is more effective (closer to the center) when performed with a thicker upstream stand. This is suitable because it eliminates the occurrence of edge cracks because it improves the workability of the rolled material.

Therefore, in a cold tandem rolling mill, width reduction is performed at least at the position of the first stand (inlet side), and then rolling is performed with the tapered part of the tapered part of the tapered work roll positioned inside the rolled material. is effective, and the present invention can be applied appropriately to the second stand and beyond.

In short, the present invention performs width reduction by arranging an edger roll on the entrance side of a cold rolling mill, and then rolls the tapered part of a pair of work rolls which have a tapered part or a tapered curve on at least one end of the material to be rolled. By rolling the plate at the inner side of the plate, edge drop is reduced and edge cracking and plate breakage are prevented.

(Example) A mother plate with a plate width of 1100 m+ and a plate thickness of 2.6 n+m was
An example of the present invention when cold rolling was carried out in a five-stand cold tandem rolling mill as shown in the figure is shown below. Note that the reference numeral 3 in the drawing represents a material to be rolled, and the reference numeral 4 represents an edger roll.

The width reduction amount is 3 mm on one side. Other stands do not perform width reduction. The profile of the tapered work roll is as shown in Figure 2 (al).
+m, El =50mm, [! H=25 μm. This tapered work roll is used as the first stand, and the other stands are normal rolls. For comparison, a case was conducted in which normal rolls were used for all stands and a case in which a tapered work roll of the above shape was used in the first stand, without any width reduction.

The amount of extrusion knob on the exit side of each stand is 10th.
Shown in the figure. According to the present invention, the first stand suddenly
7 edge drop has been improved, and although edge drops are formed in subsequent stands, the first one until the final stand
The suppressing effect of the stand continued, and the edge drop was improved by about 20 μm.

Moreover, defects such as ear cracking and ear elongation did not occur.

(Effects of the Invention) As explained above, according to the present invention, edge drop can be significantly reduced, and the occurrence of edge cracking and edge elongation can be prevented.
As a result, it becomes possible to manufacture cold-rolled steel sheets at a high yield without impeding surface quality or causing shape defects.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of equipment for implementing the present invention, and FIG. 2 is a tapered work roll used in the present invention [(a) is a work roll with tapers at both ends, (bl is a work roll) Figure 3 is a diagram explaining the relationship between a roll with a taper on only one side and a rolled material, and Figure 3 generally shows the position in the width direction and exit side of a rolled material when rolled with a tapered work roll. A graph showing the relationship between tension; Figure 4 is a diagram showing the state of edge cracks in the rolled material; Figure 5 +a) is a graph showing the thickness deviation of the mother plate before general cold rolling; Figure 5 1bl is a graph showing the sheet thickness deviation after cold rolling tal, Figure 6 fat is a graph showing the sheet thickness deviation before cold rolling after width reduction, Figure 5 1bl is ( FIG. 7 is a graph showing the thickness deviation according to the present invention after cold-rolling al. 9 is a graph showing the influence of plate thickness and tension on edge drop during cold rolling. FIG. 9 is a graph showing areas where edge drop is improved. FIG. 10 is a graph showing the effects of implementing the present invention during tandem rolling. It is a transition diagram of the edge drop in 1... Work roll with tapered on both sides l'... Work roll with tapered on one side 2... Material to be rolled 3... Esosure roll Fig. 3 During recursion Two swords (Question 2 Figure 4 Figure 5 (a) Ogisara fan sword ° Unode huge* (mmn (b) O-tei wo woman'In1j et al/) l Hina-k (bi) Figure 6 (a) (b) *mrmm of lf1miI7) Figure 7 Figure 8 (a) (b)

Claims (1)

[Claims] 1. The material to be rolled is subjected to a width reduction treatment on the entry side of a cold rolling mill, and the edge end of the material to be rolled, which has an edge portion thickened by this treatment, is applied to at least one end thereof. A cold rolling method excellent in suppressing edge drop, characterized in that rolling is carried out by positioning a pair of work rolls on which a tapered part is formed. 2. The cold rolling method according to claim 1, characterized in that the above rolling is performed in at least the first stand of a cold tandem rolling mill.