JPS59220202A - Cold rolling method of steel sheet - Google Patents

Abstract

PURPOSE:To prevent the generation of sizing flaws at an annealing stage by edge-stretch rolling, at a specific steepness, the edges of the innermost and outermost coiled parts of a cold-rolling steel sheet to be annealed in a box-type annealing furnace. CONSTITUTION:Only the lengths of a steel sheet to be rolled corresponding to the coiled sheet thickness of about 100mm. at the innermost coiled part and that of about 100mm. at the outermost coiled part of the cold rolling steel sheet, to be annealed in a box-type annealing furnace, are rolled into an edge-waving shape of about 0.7-1.0% steepness. The other part of the steel sheet to be rolled are cold rolled by regulating a shape target value of the whole sheet width of the sheet to the steepness of 0%. In this way, the generation percentage of seizing flaws at the parts concerned are reduced to approximately 0% by producing gaps between mutual steel sheets at said parts which are to be heated to the highest temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cold rolling a steel plate, and in particular to a method for cold rolling a steel plate to be rolled before a steel plate coil to be annealed in a box annealing furnace after cold rolling. be.

Conventionally, the surface shape of cold-rolled steel sheets has generally been that of steel sheets.

The goal has been to have a steepness of Oqb over the entire length.

The steepness is the wave height, which is a unit that represents the size of a steel plate when it is placed on a surface plate and waves occur on the steel plate as shown in Figure 1. It is determined by h/wavelength L and 100 (ch).

Conventionally, a steel plate coil that has been cold-rolled so that the target steepness is 0% over the entire length of the steel plate is annealed in a box-type annealing furnace, and the annealed coil is placed on the entry side of the skin pass rolling mill in the next process. During unwinding, a bending phenomenon occurs in the steel sheet, and only the bent portion exceeds the yield point, resulting in seizure defects due to stress strain, which can become a serious defect in the cold-rolled steel sheet.

The bending phenomenon of the steel plate that occurs when the annealed cold-rolled steel plate coil is unwound at the entrance side of the temper rolling mill in the next process is caused by seizure of the steel plates to each other during the annealing process.

In order to prevent seizure of the cold-rolled steel sheet coil during this annealing process, the present inventors conducted various research studies on the annealing condition of the cold-rolled steel sheet coil in a box-type annealing furnace.

FIG. 2 shows the temperature distribution in the thickness direction and width direction of the cold-rolled steel coil in the box-type annealing furnace when the can is opened during heating.

As is clear from FIG. 2, from the initial stage of heating, the innermost and outermost turns of the coil are heated faster in the thickness direction of the coil.
In the width direction, both edge portions are heated quickly.

Therefore, as shown in Figure 3, the temperature is highest at each corner of the inner and outer windings of the coil, and due to the thermal stress caused by the temperature distribution inside the coil, there is compressive stress at some corners. Each time it occurs.

As is well known, since the seizure phenomenon caused by thermal diffusion of metal depends on temperature and contact stress, the seizure phenomenon occurs most strongly at a portion of each corner shown in FIG.

Therefore, the incidence of the above-mentioned seizure defects is highest at the edges of the innermost and outermost turns of the coil.

The present invention has developed a method for cold rolling a steel sheet that prevents seizure of the ears of the innermost and outermost turns of the coil, which occurs during annealing of a cold rolled steel sheet coil.

An example of implementing the method of the present invention will be described below.

The wall thickness of the innermost winding part of the Suzuki cold rolled steel sheet coil annealed in a box-type annealing furnace is approximately 100 mm, and the wall thickness of the outermost winding part is approximately 10 mm.
Only the length of the rolled steel plate corresponding to 0 mm and 0.0 mm is made into an elongated shape with a steepness of about 0.7 to 1.0 inch, and for the rest, the shape target value of the entire width of the rolled steel plate is set to a steepness of 0%. It was then cold-rolled.

That is, in the present invention, the wall thickness of the innermost winding part of the steel plate coil after cold rolling of the rolled steel plate to be cold rolled is approximately 100 mm.
By elongating only the lengths corresponding to the outermost part and the wall thickness of the outermost part of approximately 100 mm, gaps are created between the steel plates in the relevant parts, and the incidence of seizure defects in the relevant parts is reduced. could be made into ff(l).

FIG. 4 shows the relationship between the steepness of the edge elongation in the above-mentioned portion, the wall thickness of the edge elongation at the inner and outer diameter portions of the coil, and the occurrence rate of seizure defects. By setting it to 0.71 or more, the occurrence rate of seizure defects is almost 0.
'%become.

Fig. 4 also shows the influence of the edge elongation wall thickness of the inner and outer diameter portions of the coil after edge elongation rolling on the occurrence rate of seizure defects. Elongation rolling of the corresponding length of rolled steel plate is highly effective in preventing seizure defects.

Note that the steepness is determined by 1. in order to prevent meandering within the line of the steel plate. The upper limit was set at Oq6.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram for determining the steepness, Figure 2 is an explanatory diagram showing an example of the temperature distribution of a cold rolled steel coil in a box-type annealing furnace, and Figure 3 is an explanatory diagram showing an example of the temperature distribution in a cold rolled steel coil. FIG. 4, which is an explanatory diagram showing the highest temperature part, is a graph showing the relationship between the steepness of the selvedge elongation, the wall thickness of the selvedge elongation of the inner and outer diameter portions of the coil, and the occurrence rate of seizure defects. Applicant Kawasaki Steel Co., Ltd. Agent Patent Attorney Yoshikai Ima Oka: 1. , ;-'
1 Figure 1 Figure 2 A-AIq distribution (y41 and v-1t direction (67) silently! Figure 3 Figure 4 Figure 1 Keyaki Sepashi Gorge (%)

Claims (1)

[Claims] The wall thickness of the innermost winding part of the cold rolled steel sheet coil to be annealed in a box-type annealing furnace is approximately 100 mm, and the wall thickness of the outermost winding part is approximately 1 mm.
Only the length of the rolled steel plate corresponding to 00 mm is made into an edge elongation shape with a steepness of about 0.7 to 1.0%, and the other shape target value of the entire plate width of the rolled steel plate is made into a steepness of 0. A cold rolling method for steel sheets characterized by cold rolling.