JPS6182906A - Method for reducing edge drop of cold rolled steel-sheet - Google Patents

Abstract

PURPOSE:To obtain a cold rolled steel-sheet having a practically rectangular cross-sectional shape and free from edge drop by forming the surface shapes of upper and lower work rolls under suspension used for the 1st pass rolling, into specific shapes, in case of cold rolling the sheet through plural passes by a mill of plural stands. CONSTITUTION:A flat lower roll 1 and an upper roll 2 having a specific shape are used for the 1st pass, for instance. That is, within in a range of 25-150mm distance (l), between a point 4 of the sheet end of a rolling stock 3 contacting the surface of roll 2, and a point 5 located close to the center of sheet width; the difference (delta) between respective gaps at the points 4 and 5 of the surfaces of the rolls 1, 2 under suspension, is regulated within a range of 0.05<delta<=0.5mm. Further, one side or both of the surfaces of rolls 1, 2 are formed so that the gap between the rolls 1, 2 increases gradually from the center of roll to its end. Thus, a cold rolled steel sheet free from edge drop is manufactured by using rolls 1, 2, having such surface shapes at the time of suspension for performing the 1st pass rolling.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to reducing edge drop of cold rolled steel sheets when the cold rolled steel sheets are produced by multiple passes of cold rolling using a rolling mill with two or more stands. It is about the method.

(Prior art) In the conventional cold rolling method, the work rolls have a sinusoidal diameter difference of 0 to 0.1 cage over the entire length of the roll barrel in order to maintain good flatness of the rolled material. is given to. For example, when rolling a steel plate with a maximum width of 1600 m using one rolling machine with a roll barrel length of 1730 m1, the point at the edge of the rolled material and the direction from the edge to the center of the width of the plate.
The gap difference between the upper and lower rolls at the point between 50 and 50 is O,02 when the initial crown is 0.1 m per roll.
It is 6m.

By the way, deviations in sheet thickness that occur in the sheet width direction in cold-rolled steel sheets include those caused by the curvature of the a-ru due to the rollability MK mentioned above, and those caused by metal 70-, which is noticeable only at both ends of the steel sheet.
Some cases are caused by edge drops caused by

An invention aimed at suppressing the occurrence of the edge drop phenomenon is disclosed in JP-A-59-113904. According to this disclosure, the gist of the invention is as follows.

"Each of the pair of drawing rolls is provided with a tapered part on at least one end that has been ground into a tapered part, and this taper part is located at both ends of the material to be rolled, and is used together with the reinforcing roll in the mill. A cold tandem rolling Sakaki train characterized by a stand arrangement in which an incorporated four-high rolling mill is arranged in at least the first stand, and a conventional work roll is incorporated in the final stand.'' Examples of this publication. In this example, the profile of the roll to which the trapezoidal roll method is applied is such that both the upper and lower work rolls are tapered and ground at the ends, EL = 50 mtpr, and EH = gloss μ. Here, EI (is the radius difference between the tapered part of the trapezoidal roll and the non-trapezoidal part at the plate end, and EL means the length of the trapezoidal part from the plate edge.And, conventional rolls are used for all stands. It is stated that the edge drop was improved by about 10 μm compared to the amount of edge drop when
It had not reached the level of Edge Drop Zero.

An object of the present invention is to provide a method for reducing edge drop of a cold rolled steel sheet that eliminates and improves the drawbacks of the conventional method of reducing edge drop of a cold rolled steel sheet, and the scope of the present invention is as set forth in the claims. The above object can be achieved by providing a method.

(Problems to be Solved by the Invention) Fig. 5 shows an example of the cross-sectional profile in the plate width direction of the rolled material before and after cold rolling, and the curve a in the figure shows the profile of the hot rolled material 2. .3 fl plate thickness and 1000 m plate width before cold rolling. Large edge drops are formed at both ends of the rolled material. The material is cold rolled to a thickness of 0.5 tpa
It is a profile of a cross section in the plate width direction of a cold-rolled material that has reached t. Yl points of 150 tz from the points xl and x2 at both ends of the board toward the center of the board width.

Assuming Y2, for the profile between Y, , and Y2, the profile in the relevant area of the curve A is the same as the profile in the relevant area of the curve a multiplied by the rolling ratio before and after cold rolling. However, X at the edge of the drawing board with curve bK,
, X2 points each 100m towards the center of the board width
1. Zzz riX+, XzKToruZ+ -X+
, Z2 Although the amount of edge drop in the area of X2 is influenced by the amount of edge drop after hot rolling, it is thought that the amount of edge drop formed during cold rolling is the main factor. When cold-rolled steel sheets are press-formed or punched, the areas where edge drops occur can cause edge cracks during press-forming, and lamination defects occur when laminated by punching, which can be a major problem. Therefore, it is strongly desired to provide a cold-rolled steel sheet having a substantially rectangular cross-sectional shape in the sheet width direction that suppresses this edge drop.

The present inventors prepared five sheets of material and investigated the amount of edge drop formation after each pass when performing cold rolling by performing multiple passes of rolling using a rolling mill with two or more stands. 1
I got the diagram. The material to be subjected to the first pass has a rectangular cross-sectional shape in the sheet width direction, and for the rolled material obtained in the first pass, the sheet thickness at one point in the direction from the sheet edge to the center of the sheet width and the sheet thickness at the center of the sheet width. The difference between the thickness and the edge drop amount is plotted on the vertical axis.
The length of influence of the drop, that is, the distance from the edge of the board to the center of the board width, was taken as the (support) point on the horizontal axis. Next, the next material is the edge drop amount measured as described above for the rolled material obtained by removing both ends of the first pass rolled material and subjecting the rolled material whose cross section in the width direction is rectangular to the second pass. The vertical axis represents the influence length, and the horizontal axis represents the influence length, and the point (A) is defined as the point. Points (1), (2), and (4) were plotted as described above. FIG. 1 shows that the initial pass has a large influence on the occurrence of edge drops.

Therefore, Yumei Moto et al. were able to newly discover that it is effective to implement edge drop reduction measures at the initial stage of the bus.

(Means for Solving the Problem) The inventors of the present invention discovered that the fifth and final pass after the second pass.・For the 2-seat case, a normal flat work roll was used, and as shown in the Jl-Bas drawing, a furanotrol similar to Troll 1 was used, and a roll with a modified shape was used for the upper roll 2.

The distance l between point 4 where the edge of the rolled material 30 plate contacts the roll surface and point 5 on the roll surface located in the center direction of the sheet width from point 4,
The various upper rolls 2 and the lower roll 1 whose shapes are modified by the roll gear knob difference δ between the gap between the upper and lower work roll surfaces facing each other at the plate end and the gap between the upper and lower work roll surfaces facing each other at the point 5, 1
The relationship between l and δ in the path was investigated.

Figure 3 shows the results of the above survey.

In the above d pass (inspection), the edge
This is indicated as a drop (hereinafter, edge drop refers to the difference in plate thickness between the plate thickness at a position 5 mm from the plate end toward the plate width center and the plate thickness at the plate width center). [1, δ]
The edge drop is 0 to 5 μm in silk stitching.
A combination in which the cross-sectional shape of the cold-rolled product can be seen as a substantially rectangular cross-section in the range of is a combination that cannot be imaged x
Indicated in the figure by marks.

Regarding diagram 2g3, in the area where the ○ mark and the X mark are close to each other, if the boundary line between the ○ mark area and the The aC line is parallel to the line aC, and the ab line is parallel to the horizontal axis passing through point a at δ = Since poor flatness will occur, the boundary line will be the ab line parallel to the vertical axis passing through point d at l = 150 nL, and the area where the roll gap difference exceeds δ = 0.5 vwt will be chamfered on the work roll. The influence of remains until the end, resulting in an abnormally thick edge-up at the edge of the plate, so the dc line parallel to the horizontal axis passing through point d at δ=0°5 becomes the boundary line.The above line ab, ac, bd, cd were derived from points a and d determined by experiment. That is, C1, δ at point a] is [25, 0.05 trtrh
] C1, δ at point d] 'ri (150ram,
0-5 r+m':1. The range marked with O is ab,
Within the area surrounded by lines ac, db, and dc, the position of point a is l! = 25 mtn
δ = 0.05 The position of the trtrh point is l =
150-m δ = 0.05 ttnn The position of point C is 1 = 25 δ = 0.5 The position of point d is 1 = 15
0 fight δ = 0.5 look. By adjusting [1°δ] within the area surrounded by these four points, the edge drop Ed becomes 5μm≧Ed≧0, and the cross-sectional shape of the cold-rolled product can substantially realize a rectangular cross-sectional shape. can.

In addition to the above conditions, there is comfort in increasing the roll gap practically by increasing it gradually from the center of the roll barrel towards 11.1 parts.

Taking the above and M), in a 71% l bath roll, (a) δ exceeds 0.05γ1') and is within the range of 5 mN or less at any point within the range from 150 to 150. None.

(b) Make the roll gap gradually larger from the center of the roll surface toward the ends.

If the above conditions (a) and (b) are met, edge drop I
It has been demonstrated that it is possible to produce a cold-rolled steel sheet in which Ed satisfies 5 μm≧Ed≧O and has a substantially rectangular cross-sectional shape.

By the way, the example EL=50ha shown in the embodiment disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 59-113904.

EH = 50 brocade, according to the symbols used in the description of the present invention, gL + = /, E) ( is equivalent to δ, but since EH is applied to the upper and lower rolls, δ = 2 E [(next) , 1=50 h, 620.1 .mu.m.It is stated that the edge drop could be improved by about 10 .mu.m in this example, which shows that the method of the present invention is superior.

Next, the present invention will be explained with reference to examples.

Example: Using the Genmei method, a work roll consisting of 5 stands with a diameter of
A hot-rolled material having a thickness of 2.3 mm was cold-rolled to a finished size of 0.5 fl thick and 10001 mm wide using a 100 to 600 m/m mill. l = 50 tax + a = 0.1 at the end of the roll on the first stand
The shape of mu was modified, and the lower roll of the first stand and the second
The upper and lower rolls of ~5 stands were straight rolls with δ=0. As shown in Figure 4, the profile in the width direction of the cold-rolled sheet obtained by this rolling is the thickness at a point 5 mm from the edge of the sheet toward the center of the sheet width, and at a point at the center of the sheet width. The difference in edge drop was less than 5 μm, and the cross-sectional shape of the cold-rolled product was substantially rectangular.

Instead of the roll on the first stand, by making the upper and lower roll surfaces the same shape and setting δ to 0.05+a, the gap between the opposing roll surfaces at the plate end can be set to (1,
Even with 1tnx, the same effect as above could be obtained.

(Effects) As described above, according to the method of the present invention, it is possible to produce a cold-rolled steel sheet having a substantially rectangular cross-sectional shape and having no edge drop, which could not be achieved conventionally.

[Brief explanation of the drawing]

Figure 1 shows that the initial pass has a large effect on the occurrence of edge drops, Figure 2 shows the shape of the work roll in the first pass, and Figure 3 shows that mid-edge drops occur in the first bus. Figure 4 is a profile diagram of the cross section in the width direction of the cold rolled plate obtained in the example, and Figure 5 is the profile diagram of the cross section in the width direction of the cold rolled plate obtained in the example before and after conventional cold rolling. It is a profile diagram of the cross section of the later steel plate in the plate width direction. 1...lower roll, 2...upper roll, 3...rolled material,
4...The point where the edge of the plate contacts the roll, 5...The point where the point a distance l from the edge of the plate towards the center of the plate width comes into contact with the roll.

Claims (1)

[Claims] 1. When manufacturing cold rolled steel sheets by cold rolling in two or more passes using a rolling mill with two or more stands, the non-rolling surfaces of the upper and lower work rolls used in the first pass rolling A method for reducing the edge drop of a cold-rolled steel sheet characterized by making the shape as shown in (a) and (b) below: (a) The roll gap between the longitudinal surfaces of the upper and lower work rolls during non-rolling is reduced. , the gap between the upper and lower work roll surfaces facing each other at any point within a range of 25 to 150 mm from the edge of the plate of the rolled material to the center of the width of the plate, and the edge of the plate facing each other. The difference between the gap between the upper and lower work roll surfaces is not more than 0.05 mm and no more than 0.5 mm; and (b) the gap between the upper and lower roll surfaces gradually increases from the center of the roll to the end. The roll surface of one or both of the upper and lower work rolls is formed in the shape.