JP2002126940A - Method for shearing steel bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress bending of steel bars in the vicinity of a sheared surface and crushing of the sheared surface without lowering productivity and needing complicated structure during shearing in a refining line and a machining line, in the cooling bed of a steel bars hot rolling line. SOLUTION: On the rear surface of the cooling bed of the rolling line, the steel bar is sheared after a sheared portion is locally heated to a blue brittleness temperature area. A shearing machine is provided with a mechanism to exert a force on a material to be sheared from two directions different from each other. First, a force from the first direction is applied, a shearing portion is brought into a yield state and a force is applied from the second direction for shearing. A notch having depth of 1.0 mm or more is formed in the portion to be sheared and the notch position is sheared. Shearing is effected with the steel bar on a fixed blade pressed by a press means with a press force being 1/3-1 as much as a yield stress. Thus, a need for a straightening work and a defective part cutting work after shearing is eliminated and further a load during shearing can be relieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of shearing a steel bar, such as a round bar or a square bar, to a predetermined length to suppress bending of the bar near the shear surface and crushing of the shear surface. is there.

[0002]

2. Description of the Related Art In a process of manufacturing a bar such as a round bar or a square bar, shearing is performed to cut a bar into a product having a predetermined length. In the steel bar hot rolling line, a shearing machine is installed on the rear surface of the cooling floor after rolling, and the steel bar rolled to a predetermined diameter and cooled is sheared to the product length. As a shearing machine, a blade having a caliber having a shape corresponding to the cross-sectional shape of a steel bar is arranged vertically, and an upper blade is usually used as a moving blade and a lower blade is used as a fixed blade. As shown in FIG. 5B, the movable blade 2 is lowered with respect to the steel bar 1 placed on the fixed blade 3 as shown in FIG.
Shear as shown in (c). Similar shearing is performed also in the bar refining process and the working process.

[0003] Generally, when shearing is performed, a ductile fracture surface generated at the initial stage of shearing and a brittle fracture surface generated thereafter appear on the shear surface. As an example of the problem of the shearing surface, as shown in FIG. 6A, the entire fracture surface is flattened, and the major axis a is longer than the diameter d of the steel bar indicated by the broken line, and the minor axis b is shorter than the diameter d. 7 is ductile fracture, 8
Is a brittle fracture surface. Then, as shown in FIG. 6B, defects such as “crush” 9, “ear” 10, and “dent” 11 may occur. The bending of the steel bar 1 due to the crushing 9 may hinder the passage of the post-processing line, and the ears 10 and the dents 11 may cause shape defects and defects after the processing.

As a countermeasure against these defects, it is important to suppress ductile deformation of the steel bar as much as possible. In a hot rolling line, high-temperature shearing of a steel material in a blue brittle temperature range is considered to be effective. For this purpose, the material feed rate in the cooling bed is adjusted so that the steel material temperature during shearing falls within the blue brittle temperature range. However, in the actual operation, it is necessary to shorten the staying time in the cooling floor, and continuity with the preceding and following processes is not maintained, thereby causing a problem that productivity is reduced. Regarding heating shearing, Japanese Utility Model Laid-Open No. 6-53020 proposes a device for injecting hot air into a shearing portion to heat it.
It increases the viscosity of the shearing portion, and no specific temperature is disclosed.

As another countermeasure, restraint shearing is also effective. This is to restrain the material to be sheared during shearing by a mechanism. Japanese Patent Application Laid-Open No. 6-79519 discloses that by restraining a bar, even if the bar has a variation in diameter or a bend in the longitudinal direction, the insertion of a cut-off portion of the bar is not hindered, and the squareness of the cut surface is reduced. However, there is disclosed a shearing device capable of obtaining an incision surface with a small height difference without generation of a tongue or a staying crack. However, it requires a complicated structure and is not suitable for normal shearing of steel bars.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a steel bar having a predetermined length in a cooling floor of a hot rolling line of a bar such as a round bar or a square bar, or in a refining line or a processing line. The purpose of the present invention is to suppress bending of a steel bar in the vicinity of a shear surface and crushing of the shear surface without lowering productivity and without requiring a complicated structure.

[0007]

According to a first method of the present invention for solving the above-mentioned problems, a method of shearing a cooled steel bar at a rear surface of a cooling floor of a steel bar hot rolling line is performed by guiding a steel bar to a front surface of a shearing machine. A method for shearing steel bars, comprising providing a heating device and locally heating a sheared portion of a material to be sheared to a blue-hot brittle temperature range and shearing.

In the second invention method, when shearing a steel bar,
A mechanism for applying a force to the sheared material from two different directions is provided in the shearing machine. First, a force is applied from the first direction to bring the sheared portion into a yielding state, and then a force is applied from the second direction. This is a method for shearing steel bars, wherein the steel bars are sheared.

In the third invention method, when shearing a steel bar,
A method for shearing steel bars, wherein a notch having a depth of 1.0 mm or more is formed at least at one location in a shearing direction of a shearing portion of a material to be sheared, and the notched position is sheared. A fourth invention method is characterized in that, when shearing a steel bar with a fixed blade and a moving blade, the steel bar on the fixed blade is pressed by a pressing means with a pressing force of 1/3 to 1 times the yield stress of the steel bar. Is a shearing method.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The first invention method is a method of shearing a steel bar in a cooling floor of a steel bar hot rolling line, wherein a steel bar 1 fed in the direction of an arrow as shown in FIG. The steel bar 1 is locally heated to the blue brittle temperature range by the induction heating device 4 and sheared in the temperature range. The shearing device has a moving blade 2 and a fixed blade 3, which are simplified in FIG.
Both blades 2 and 3 have a caliber shape according to the cross-sectional shape and size of the steel bar 1. The round bar 1 may be sent one by one, or may be a multi-line which is sent a plurality of times at the same time.

According to the first invention method, the sheared portion of the steel bar is embrittled, ductile deformation at the time of shearing is remarkably suppressed, and a trouble in the process of processing the product steel bar due to occurrence of bending near the sheared surface and crushing of the sheared surface. The occurrence is eliminated. In addition, since the steel bar cooled to a temperature lower than the blue brittle temperature range in the cooling floor is heated to the blue brittle temperature range in a short time by the induction heating device 4, it is necessary to adjust the line speed for shearing. Therefore, the flow of the material including the preceding and following processes is not disturbed, and high productivity is maintained.

In the first invention method, the temperature of the shearing portion is reduced to a temperature not higher than the blue brittleness temperature range -200 ° C., that is, a temperature not lower than 200 degrees lower than the blue hot brittleness temperature range, and then heated to the blue hot brittle temperature range. By doing so, bending near the shear surface and crushing of the shear surface are further suppressed, and the shape of the shear surface is further improved. This is considered to be because free C and free N in the steel bar are reduced in the temperature range of -200 ° C. or less in the blue brittleness temperature range, the yield elongation of the steel bar is reduced, and the ductile deformation is further suppressed.

According to a second aspect of the present invention, a mechanism for applying a force to a steel bar to be sheared from two different directions is provided in a shearing machine. First, a force is applied from a first direction to bring a sheared portion into a yielding state. Then, shearing is performed by applying a force from the second direction. This method is not limited to the hot rolling line, and can also be applied to shearing in a bar refining step, a processing step, and the like. Also, the present invention can be applied to a multi-line as well as a line sent one by one.

FIG. 2 shows an example in which three steel bars 1 are simultaneously sheared. The bar 1 is conveyed and placed on the fixed blade 3 as shown in FIG. 4A, and the upper movable blade 2 shown by the broken line is lowered,
Next, the fixed blade 3 is moved to the right as shown in FIG. 2B, and a force is applied to the steel bar 1 in the first direction indicated by the dashed line A to bring the sheared portion into a yielding state. Next, as shown in (c), the fixed blade 3 is returned to the original position, the movable blade 2 is lowered, and a force is applied to the steel bar 1 in the second direction indicated by the dashed line B to shear it. In FIG. 2A, the movable blade 2 after descending may come into contact with the steel bar 1, and a force is applied obliquely when the fixed blade 3 is moved rightward as shown in FIG. 2B. Should be fine.

According to the second invention method, the steel bar 1 is first made as shown in FIG.
In FIG. 2B, a force is applied in a first direction such as A and a yield state is established, and then a force is applied in a second direction as shown in B in FIG. Therefore, the deformation of the steel bar 1 is dispersed in the first direction and the second direction, the amount of deformation in each direction is reduced, and the ductile deformation that occurs in the initial stage of shearing is suppressed, and collapse and dents are generated. Is suppressed.

As a mechanism for applying forces in two different directions in the second invention method, in addition to a mechanism for moving the movable blade 2 in the shearing direction, in the example of FIG. 2, the fixed blade 3 is moved in a direction perpendicular to the shearing direction. Although a mechanism is provided for causing the force, a force can also be applied by a member other than the blade. It is effective that the angle between the two different directions for applying the force is 45 ° to 135 °.

In the third invention method, a notch 5 is formed in a shearing portion of a steel bar 1 to be sheared as shown in FIG. 3, and the position of the notch 5 is sheared. The notch 5 is formed at right angles in the length direction on the surface of the steel bar. Although FIG. 3 shows an example in which the notch 5 is formed at one location in the shearing direction, the notch 5 may be formed at two opposing locations or the entire circumference. The notch 5 is formed to have a depth of 1.0 mm or more. This method is applicable not only to a hot rolling line but also to shearing in a bar refining process and a working process, and is also applicable to a multi-line.

The shape of the notch 5 is preferably V-shaped as shown in FIG. 3, but may be U-shaped or U-shaped. Such notches 5 cause stress concentration at the time of shearing, thereby suppressing ductile deformation occurring at the initial stage of shearing, thereby suppressing collapse and dents. The effect is remarkable when the depth of the notch 5 is 1.0 mm or more, and may be any depth as long as it can be obtained by the notch forming means such as a cutting tool or a saw.

In the fourth invention method, as in the example shown in FIG. 4, the steel bar 1 on the fixed blade 3 is pressed by the pressing device 6 with a pressing force of 1/3 to 1 times the yield stress of the steel bar 1. And moving blade 2
Let go down and shear. This method is applicable not only to a hot rolling line but also to shearing in a bar refining process and a working process, and is also applicable to a multi-line.

The portion of the steel bar to be pressed is preferably on the fixed blade 3 and as close as possible to the movable blade 2. According to the fourth invention method, the ductile deformation at the initial stage of shearing is suppressed, and the occurrence of collapse and dents is suppressed. The effect appears when the holding force is 1/3 or more of the yield stress of the steel bar. If the holding force exceeds the yield stress of the steel bar, crushing occurs due to holding. In the above-described embodiments of the present invention, the down-cut method has been described as an example, but an up-cut method or a running shear method may be used, and the shear method is not limited.

The above-described invention methods of the present invention can be more effective when implemented in combination. There are the following six combinations as two combinations. That is, the first
After heating according to the invention method, a method of shearing by applying force in two directions according to the second invention method, a method of forming notches and shearing according to the third invention method, and a method of pressing and shearing according to the fourth invention method It is. Also, a method of forming a notch by the third invention method and then applying a force in two directions by the second invention method to shear, and a method of pressing and shearing by the fourth invention method. Further, it is a method of pressing down by the fourth invention method and applying a force in two directions by the second invention method to shear.

There are the following four combinations as the three combinations. That is, a notch is formed by the third invention method after heating by the first invention method, and a shear is then applied by applying force in two directions by the second invention method. The third invention is obtained by heating by the first invention method. Notch is formed by the method
A method of pressing and shearing according to the invention method, a method of heating by the first invention method, pressing by the fourth invention method, applying a force in two directions by the second invention method, and a notch by the third invention method. Is formed and then pressed by the fourth invention method, and sheared by applying force in two directions by the second invention method.

Further, as a combination of four, after heating by the first invention method, a notch is formed by the third invention method, then pressed by the fourth invention method, and a force is applied in two directions by the second invention method. There is a method of applying and shearing. In each combination described above, the order of the first invention method and the third invention method can be changed.

[0024]

[Examples] (1) Low carbon round steel with a diameter of 65 mmφ (JIS G405
For 1 S25C), the temperature at the time of shearing was changed by induction heating, and the result of observation and determination of the shear surface is shown in Table 1. The clearance between the fixed blade and the moving blade is 1.0 mm, and the shear rate is 2.0
m / s. In the judgment results, ◎ indicates that the appearance is good and there is almost no crushing (crushing rate: 0 to 1%) ○ indicates good appearance but slight crushing (crushing rate: 2 to 4%) × indicates that the appearance is not heated It is equal to or less than and there is a crush (crush amount ratio: 5% or more). The crush amount ratio indicates the ratio of the width of the crush 9 to the diameter d in FIG. 400 in the blue brittle temperature range
When heated and sheared at ℃, almost no crushing or bending was observed, there were no ears, and the squareness was good. The one heated to 400 ° C. at a temperature of 200 ° C. or less before heating was particularly good.

[0025]

[Table 1]

(2) Bearing steel with a diameter of 65 mmφ (JIS G4805
SUJ2), the temperature during shearing was changed by induction heating,
Table 2 shows the results of observation and determination of the shear surface. The clearance between the fixed blade and the movable blade is 1.0 mm, and the shearing speed is 2.0 m / s
It is. The symbols ◎, 、, and × in the judgment result are the same as in Table 1. Also in this example, the sample heated to 500 ° C. in the blue brittle temperature range and sheared showed almost no crushing or bending, no ears, and a good squareness. A steel bar heated to 500 ° C. at a temperature of 300 ° C. or lower before heating was particularly good.

[0027]

[Table 2]

(3) Carbon steel round steel with a diameter of 65 mmφ (JIS G4
051 S45C), as shown in FIG. 2, a force was applied in two directions and sheared. The clearance is 1.0 mm and the shear rate is 2.0 m / s. The angle between the two directions of application of the force was 45 °. In Table 3, the fixed blade horizontal stroke (1
When (the second time) is 4 to 12 mm, it is in the yielded state.

In the judgment results, ◎ indicates that the appearance is good and there is almost no crushing (crushing rate: 0 to 1%) ○ indicates good appearance but slight crushing (crushing rate: 2 to 4%) × indicates the first time (Crush rate: 5% or more). As shown in Table 3, the first and second shears with a stroke of 8 mm or more and the second with a stroke of 8 mm or more showed almost no crushing or bending, no ears, and a good squareness.

[0030]

[Table 3]

(4) Carbon steel round bar (JIS G4
No. 051 S45C), a notch was formed at the sheared portion of the steel bar, and the position of the notch was sheared to observe the sheared surface. The clearance is 0.2 mm and the shear rate is 2.0 m / s. The notch faces in the shearing direction 2
The bottom of the notch was formed at right angles to the shear direction. The symbols ◎, 、, and × in the judgment result are the same as in Table 1. As shown in Table 4, as shown in Table 4, a notch having a width of 0.1 mm and a depth of 1.0 mm or more was formed.
There were no ears and the squareness was good.

[0032]

[Table 4]

(5) Carbon steel round bar (JIS G4
051 S45C) The steel bar on the fixed blade was pressed and sheared by the presser device, and the sheared surface was observed and judged.
Shown in Clearance 1.0mm, shear rate 2.0m /
s. The symbols ◎, 、, and × in the judgment result are the same as in Table 1. The yield stress of this round bar is 350 N / mm ² . The results are shown in Table 5. In particular, those obtained by shearing with a holding force of a yield stress (350 N / mm ² ) showed almost no crushing or bending, no ears, and a good squareness.

[0034]

[Table 5]

[0035]

According to the method of the present invention, bar steel such as round bar and square bar is sheared in a cooling floor of a hot rolling line, and in a refinement line or a processing line without reducing productivity. In addition, the ductile deformation at the initial stage of shearing is suppressed without requiring a complicated structure, and the occurrence of crushing, bending and dents is suppressed. Therefore, the straightening work after the shearing and the cutting work of the defective part are not required, and the equipment cost and the manufacturing cost can be reduced. Further, the load at the time of shearing can be reduced, and the equipment cost of the shearing machine can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of the method of the present invention.

FIGS. 2 (a), (b) and (c) are explanatory views showing another example of the method of the present invention.

FIG. 3 is an explanatory view showing another example of the method of the present invention.

FIG. 4 is an explanatory view showing another example of the method of the present invention.

FIGS. 5A, 5B, and 5C are explanatory diagrams showing examples of a conventional method.

FIGS. 6A and 6B are explanatory diagrams showing examples of defects in a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Steel bar 2 ... Moving blade 3 ... Fixed blade 4 ... Induction heating device 5 ... Notch 6 ... Holding device 7 ... Ductile fracture surface 8 ... Brittle fracture surface 9 ... Collapse 10 ... Ear 11 ... Denting

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Tatsuya Sato 12 Nakamachi, Muroran-shi, Hokkaido F-term in Nippon Steel Corporation Muroran Works 3C039 AA13 AA22 3C051 FF28

Claims (4)

[Claims] 1. An induction heating device is provided in front of a shearing machine for shearing a cooled steel bar on the rear surface of a cooling floor of a steel bar hot rolling line, and a shearing portion of a material to be sheared is locally heated to a blue brittle temperature range. A method for shearing steel bars, wherein the steel bars are heated and sheared. 2. In shearing a steel bar, a mechanism for applying a force to a material to be sheared from two different directions is provided in a shearing machine. First, a force is applied from a first direction to bring a sheared portion into a yielded state. A method for shearing steel bars, wherein shearing is performed by applying a force from a second direction. 3. The shearing of a steel bar is characterized in that a notch having a depth of 1.0 mm or more is formed in at least one portion of a shearing portion of a material to be sheared in a shearing direction, and the notched position is sheared. How to shear steel bars. 4. A steel bar characterized in that, when the steel bar is sheared by the fixed blade and the moving blade, the steel bar on the fixed blade is pressed by the pressing means with a pressing force of 1/3 to 1 times the yield stress of the steel bar. Shearing method.