JPH09192827A - Strip cutting method for thick steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deformation of a strip plate by piercing a cutting hole beforehand near the end part of the steel plate cutting position of several lines to be cut. SOLUTION: The steel plate 1 is cut to pieces 1A-1D. Near the end part of steel plate cutting positions of pieces 1A-1D to be cut, cutting holes 2a-2e, 2aa-2ee are pierced beforehand. Strip plate are heated at both ends when cutting the steel plate 1. The pieces 1A, 1D outside in the width direction have a temp. deviation in the width direction larger than that of the pieces 1B, 1C due to cooling effect. Temp. deviation produces stress to be a cause for lateral bending of a strip plate. A cutting line position 3a between the cut holes 2a, 2aa is gas cut and the outside of the cut holes 2a, 2aa are left uncut. Both ends of piece 1A is fixed with the part left not to cause lateral bending due to stress. Cut off parts 4a, 4b are arranged outside the bar stock. 4a is cut at first and a temp. difference in the width direction of 1A, 1D is reduced. At the end, the outside of cut holes are cut and scraped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel sheet stripping method, and more particularly to a hot-rolled thick steel sheet, a thick steel sheet subjected to normalizing or tempering treatment, and accelerated cooling or direct quenching after hot rolling. The present invention relates to a method of cutting a thick steel plate for producing a narrow strip while suppressing lateral bending deformation from the thick steel plate and the like subjected to the above.

[0002]

2. Description of the Related Art Conventionally, a thick steel plate (hereinafter referred to as a steel plate) is cut at several places in the longitudinal direction of rolling to manufacture several narrow plate materials (hereinafter referred to as a strip plate). FIG. 3 schematically shows a conventional strip production state. For example, when a steel plate is cut into four strips to obtain four strips (FIG. 3 (a)),
In the case of such cutting work (hereinafter referred to as strip cutting), depending on the strip cutting method and the strip cutting conditions, the strip after stripping (particularly 1A strip and 1D strip that correspond to both sides of the steel strip) There was a large lateral bending deformation (Fig. 3 (b)). In particular, when a hot-rolled steel sheet (hereinafter referred to as a hot-rolled steel sheet) is divided into strips in the width direction while keeping the length as it is, strips corresponding to both end positions of the hot-rolled steel sheet are formed. The above-mentioned lateral bending deformation appears remarkably.

Further, in a steel plate obtained by accelerated cooling of a hot steel plate or by direct quenching of the steel plate, lateral bending deformation occurs in the strip due to uneven cooling in the plate width direction during cooling. Further, the strips often undergo a large lateral bending deformation due to different gas cutting conditions.

Such lateral bending of the strip becomes a serious problem at the time of strip cutting and welding at the time of manufacturing a structure using the strip. For this reason, in the past, generally, as a measure for laterally bending deformation when stripping in the width direction of a steel sheet, as a method of directly correcting the laterally bendingly deformed strip, the central portion of the convex deformation side end and the concave deformation side A method to correct by laterally bending and deforming in the opposite direction by applying external force from the end. Partially heat the convexly deformed side end that has undergone lateral bending deformation,
There is a method of correcting by utilizing the plastic shrinkage due to the generated thermal stress. Both of these require a large amount of equipment cost and a large amount of labor, so that the cost for processing is increased and the processing efficiency is significantly reduced.

As described above, as a fundamental measure, it is difficult to control the lateral bending deformation of the strip corresponding to the positions near both ends of the hot steel sheet, and the lateral bending of the strip due to uneven cooling of the steel sheet is difficult. Deformation was difficult to prevent.

[0006] However, Japanese Patent Publication No. 6-35054 has been proposed as an example of a solution to the problems that occur at the time of cutting. This outline predicts the form of lateral bending deformation of each strip after strip cutting from the plate surface temperature profile of the steel plate in the hot state immediately after the hot leveler process, and predicts the inside of the expected bending deformation of each strip. The cutting position located at (the concave deformation side) is controlled so that the cutting heat input to be cut is smaller than the cutting heat input at the cutting position located outside the curved deformation (convex deformation side). is there. Specifically, a cooling water spray nozzle for cooling the vicinity of the cut surface is provided at a predetermined position on the strip surface near the two cutting lines on both sides of the steel plate and behind the cutting torch (counter-cutting direction). By arranging and cooling the part near the cutting surface, the cutting heat input is made smaller than the cutting heat input of the cutting part along each of the other cutting lines (the central part side other than both sides of the steel plate). is there.

As a result, the cutting lines on both sides of the steel sheet are cooled in the vicinity by the cooling water and a part of the heat input at the time of cutting is taken away, and as a result, the cutting lines near the cutting lines on both sides are cut. The heat input is smaller than the heat input for cutting in the vicinity of other cutting. Therefore, the remaining heat input amount near the cutting lines on both sides is smaller than the remaining heat input amount near other cutting lines. Therefore, the thermal strain on both sides will be smaller than the thermal strain of other parts, and this thermal strain difference acts in the direction to correct the concave deformation, and the deformation of both side strips cut out from the steel plate should be minimized. You can

[0008]

According to the above-mentioned method, the temporary effect of deforming / preventing both sides of a strip is seen.
It is necessary to measure the surface temperature profile of the steel sheet in the hot state in advance, predict the deformation mode, and perform cutting cooling according to it, which complicates predictive control and equipment costs for spraying cooling water. There was a lot of room for improvement such as the increase of. In addition, the big problem is hot steel plate cutting,
At the time of cutting, the appearance of the strips on both sides seemed to be prevented from deforming in appearance, but the strips on both sides often re-formed (bent) when cooled to room temperature. . Therefore, it is an object of the present invention to provide a method for easily preventing deformation of both side portions of a steel plate during stripping by a simple method.

[0009]

The present invention has been made to solve the above problems, and the gist of the invention is to divide a thick steel plate in the width direction and at the same time into several strips in the rolling direction. In the cutting of, in the vicinity of the end of the steel plate cutting position of several strips that need to be cut in advance, a cutting hole is drilled, gas cutting is started from the cutting hole drilled in the steel plate end, After cooling to room temperature, start gas cutting, cut off parts other than strips on both sides of the steel plate, cut off the central part first, and adjust the heat input of the cutting line on both sides of the steel plate to a high level. To do.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have found that the deformation of both side strips at the time of cutting a steel sheet occurs as follows. That is, both ends of the steel strip are heated at the time of cutting, but the cooling effect due to heat conduction is greater than the cooling effect due to air cooling, so that as shown in FIG.
The piece or 1D piece has a larger width-direction temperature deviation than the piece 1B or 1C. If this temperature deviation is excessive, that is, if the temperature of the outer side portion of the 1A piece or 1D piece in the width direction becomes high, thermal expansion occurs in the width direction outer side portion of the steel sheet. However, thermal elongation occurs only near the widthwise outer side of the strip, and at the same time when elongation occurs, compressive stress due to restraint also occurs in the portion. When the generated compressive stress exceeds the yield stress of the steel sheet at that temperature, the portion undergoes yield / plastic deformation and remains as an extension when cooled at room temperature. This is a lateral bend in the strip.

In order to prevent this phenomenon, the present inventors have to physically suppress the difference in elongation in the lengthwise direction which occurs in the steel sheet 1 and which differs depending on the width direction. For example, as shown in FIG. At the time of (4 strips of 1A to 1D strips), at least one end or both ends (steel strips are stripped in the rolling direction) in the length direction of all positions (3a to 3e) to be stripped. (Corresponding to the front end and rear end) of
A small hole having a diameter of 10 mm or less is preliminarily drilled at a portion corresponding to at least a start point and / or an end point at the start of stripping 2a to 2
In addition, the perforation at this end is used as a reference position to simultaneously cut all the lines between the perforations.

Further, the heat input to the outermost sides of the steel sheet is adjusted so that the outer side 3a (or 3e) of the steel sheet in the width direction is immediately inside 3b.
The cutting gas burner heating power is adjusted and the heat input temperature is controlled so that the temperature is higher by 10 to 20 ° C. than the (or 3d) part. In addition, both sides of the steel sheet (both sides in the width direction of the steel sheet are not straight due to rolling, straightening, cooling, etc., but curved) are assumed to be discarded, and that portion is discarded. In the cut-off portions at both ends in the width direction of the steel plate in the middle of stripping, the center portion 4a is cut off, leaving 150 mm or more at both ends 4b in the length direction.

As is apparent from the above description, this is because the elongation in the width direction of the steel sheet that occurs in the steel sheet is physically left at the cut-off portions 4b so that the strips are restrained at the lengthwise ends. This is because it does not cause elongation, and thus does not cause plastic deformation elongation. Then, after cooling at room temperature, the remaining portions 4b and 2a from the holed portion to the end in the lengthwise direction.
2e and 2aa to 2ee are cut off.

For example, 2a, 2aa, 2e and 2e in FIG.
When the end cut-off portion of e is cut from the lengthwise end portion without punching and is cut as it is, the cut portion on the outer side in the width direction of the strip 1A or 1D can be thermally expanded freely,
On the other hand, the cutting part on the inner side in the width direction is constrained from expanding by not separating it by perforation, so during the heating for cutting, a larger amount of plastic shrinkage occurs than on the outer side, which causes the amount of deformation on the outer side and the inner side after cutting. A difference in residual stress occurs due to the difference between the two and becomes a camber.

When only the strip is cut without cutting 4a and 4b in FIG. 1, 1A or 1B is used.
Since the plastic shrinkage occurs only on the inner side in the width direction of the strip, even larger camber occurs when the strip is cut. In the present invention, as described above, the cutting end portion perforation may not be perforated, and the cutting may be terminated at the position corresponding to the perforation of the cutting portion at the end of gas cutting.

FIG. 2 shows 1A and 1D in FIG. 1C.
In the strips, the horizontal axis indicates the difference between the temperature in the widthwise outer end and the temperature in the inner edge of each strip 20 minutes after cutting, and the chamber amount of each strip immediately after cutting and after cooling at room temperature is set to the vertical axis. It is the figure which showed the relationship for an axis. In either case,
The widthwise outer end of the strip is 0 to 30 ° C higher than the inner end
If it is raised, the camber of the strip after cutting and separating is ± 1 mm
It can be suppressed to /9.4 mm. The target temperature difference is 10
It is sufficient to raise the temperature of the outer end portion of 20 ° C.

[0017]

EXAMPLES C: 0.14 to 0.16%, Si: 0.20
As shown in Table 1, a room temperature thick steel plate having ˜0.45% and Mn: 1.10 to 1.50% is cut off each width 50 mm without making the width direction both ends into a product. 1A,
1D has a strip width of 530 mm, 1B and 1C have a strip width of 60
5 gas torches are used at the same time so as to be cut off at 0 mm, a cutting hole 2a having a diameter of 10 mm is formed, and a width direction outer side portion of the gas torch that cuts the strips 1A and 1D at a cutting speed of 0.3 m / min. Adjust the amount of gas in the torch and measure the temperature 10 mm inside from the gas cutting part of the strip, and strip 1
The temperature of the outer end portions in the width direction of A and 1D is higher than the inner temperature by about 12 ° C. 20 minutes after cutting, and the cutting hole 2 is maintained.
Cut to b. The strips were cut off after cooling to room temperature in a state where the holes were not separated from the strip lengthwise ends. As a result, the strip bending was 0 mm.

[0018]

[Table 1]

The strip according to the present invention has almost no bending amount even when strips are cut from both sides of the steel plate.
All good strips without deformation were obtained. On the other hand, in the comparative example, since the present invention was not adopted, the strips cut out from both sides were bent and deformed, and the correction work in the next step was required, and the work cost was increased.

[0020]

EFFECTS OF THE INVENTION According to the method for cutting thick steel plate of the present invention, it can be carried out by a simple method, and although the cutting time of the side parts of the steel plate is slightly increased, the deformation of the bar plates on both sides can be suppressed. Since the cost and time required for the straightening work can be shortened, the total cost can be reduced, which is a useful invention in the production of strips.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a stripping method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a camber amount after stripping and a temperature difference in a steel plate.

FIG. 3 is a schematic view illustrating bending of a strip when cutting by a conventional method.

[Explanation of symbols]

1 Thick Steel Plates 1A, 1B, 1C, 1D Strips 2a, 2b, 2c, 2d, 2e Cutting Start Perforations 2aa, 2bb, 2cc, 2dd, 2ee Cutting End Perforations 3 Cutting Line Position 4a Sides 4b that are cut off first 4b Side cut-off part 11 Cutting line

Claims (7)

[Claims] 1. A method of cutting a steel sheet which is divided into a plurality of strips in the rolling direction at the same time, characterized in that a cutting hole is formed in the vicinity of an end of a cutting position of several strips requiring cutting in advance. Method for cutting thick steel plate. 2. The method for cutting a thick steel plate according to claim 1, wherein the cutting holes at the ends of the steel plate are formed at least on the side where the cutting is to be started according to the number of cutting lines. 3. The method of cutting a thick steel plate according to claim 1, wherein gas cutting is started from a cutting hole formed at an end of the steel plate. 4. The method for cutting a thick steel plate according to claim 1, wherein the gas cutting is started after the steel plate is cooled to room temperature. 5. A cut-off portion other than the strips is provided on both sides of the steel sheet, both side portions of the steel sheet are left when cutting both side portions of the steel sheet, only the central portion is cut to the side portion first, and the portion is cut off. The method for cutting a thick steel plate according to any one of claims 1 to 4. 6. The method for cutting a thick steel plate according to claim 1, wherein the heat input of the cutting lines on both sides of the steel plate is adjusted to be high. 7. The amount of heat input to be increased by the cutting lines on both sides of the steel plate,
The method for cutting thick steel plates according to claim 6, wherein the temperature is set to 10 to 20 ° C.