JP2852001B2 - Partial care for cracks in metal pieces - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for partially repairing cracks in metal slabs, for example, in a continuous casting line and in subsequent steps, for removing cracks existing along the edges of slabs and slabs.

[0002]

2. Description of the Related Art A typical prior art is a method of hot cutting with a hot scarf.
644 and JP-A-52-81048. Such a hot scarf operation involves high temperature and high dust, and not only has a problem that the working environment is remarkably deteriorated, but also it is difficult to determine the flaws remaining on the surface of the hot-cut steel slab after the hot scarf treatment. Further, in the hot scarf treatment, it is impossible to control the depth of the cutting, and uneven cutting occurs, and therefore, it is easy to leave a flaw, or to increase the amount of hot cutting by the hot scarf to prevent the remaining. It is necessary to increase the amount of ablation in such a manner, resulting in a decrease in yield.

[0003] In addition to such hot cutting with a hot scarf, there is a method of removing flaws by grinding with a grinder, which is disclosed in, for example, JP-A-1-242729. In this prior art, when a stainless steel slab or a stainless steel slab is ground by a grinder, the grinder is cared for in a specific temperature range to avoid the self-hardening of the stainless steel and to effectively remove the defective portion. When grinding such stainless steel slabs and stainless steel slabs with a grinder, the method of performing grinder care in a specific temperature range is also difficult depending on the type of steel slab, as in the case of the hot scarf method described above, in which high temperatures and high dust are generated Work below,
In addition, the determination of the flaws remaining on the surface after grinding has the same inconvenience as described above, and has drawbacks such as extremely high flaw removal cost. Increasing the grinder width increases the amount of unnecessary shaving, increases driving force, increases running costs, and reduces the yield.Thus, reducing the grinder width reduces efficiency and requires more grinders. , Care time is long, which is not preferable.

In such a grinding method using a grinder, as shown in FIG. 7A, when a workpiece 2 such as a slab or a steel slab has a flaw 2, the rotating grindstone 3 is rotated. When the grinding is performed by the depth d1, as shown in FIG. 7 (2), the flaw 4 which is a part of the flaw 2 remains in the workpiece 1, but is not visible from the surface 5. May have become. Such flaws 4 remaining inside the workpiece 1 are difficult to find visually after grinding, and it is difficult to reliably remove the flaws 2. Therefore, it is desired that the remaining portion 4 of the flaw 2 is visible from the surface of the workpiece 1 even after grinding.

[0005]

In each of the prior arts described above, any of the steel slabs having a rectangular cross section perpendicular to the axis is, for example, removed by removing cracks extending over a horizontal upper surface and a vertical side surface. It is difficult and time consuming.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of partially repairing a crack in a metal piece that removes a crack extending over a ridge of a metal piece such as a steel piece with good workability.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method for producing a metal piece, comprising the steps of forming cracks extending over a surface and a side surface of a metal piece at both end points on the surface and the side surface, or on both insides of the both end points. An abrasive water jet, which is a mixture of abrasive grains and a liquid, is sprayed from the nozzle hole of the nozzle onto the metal piece so as to connect points and form a grinding plane parallel to the ridge. The inclined water surface is formed by removing the portion near the ridge including, and connecting to both ends of the grinding plane along the longitudinal direction of the ridge and becoming shallower as going away from the grinding plane, by the abrasive water jet. On the surface and on the side surface, a depth D of the grinding plane and a length L along a ridge of the inclined plane are set to L / D ≧ 2, and an abrasive water for grinding the grinding plane is selected. Jet Angle between the axis of the line and a line perpendicular to the surface
Is a method of partially repairing cracks in a metal piece, characterized by selecting θ ≦ 60 degrees.

[0008]

According to the present invention, when removing a crack extending over, for example, one horizontal surface and one vertical surface forming a ridge of a steel slab having a rectangular cross section, for example, Grinding by an abrasive water jet so as to connect both end points on the surface and the side surface of the crack or both points inside the end points thereof and form a grinding plane parallel to the ridge. As a result, the working environment is better and cracks and flaws can be reliably removed as compared with the prior art method using the above-mentioned hot scarf and grinder.

Furthermore, according to the present invention, when the metal piece is rolled by rolling after grinding and removing the crack, the so-called falling flaw called a barb due to a fold on the surface of the metal piece occurs after the rolling, and the defect is formed. In order to prevent this, an inclined surface that becomes shallower away from the grinding plane is further formed by an abrasive water jet, and the length L along the ridge of the inclined surface is formed on the surface and the side surface. And the depth D of the grinding plane (D1, D2 in the embodiments described later) is selected to be twice or more.

Further, according to the present invention, the angle θ between the axis of the abrasive water jet and a line perpendicular to the surface is selected to be 60 degrees or less, whereby the abrasive water necessary for removing cracks is selected. The jet grinding energy is reduced. If the angle θ is 6
Above 0 degrees, the jetting energy of the abrasive water jet interferes with the reflected energy of the surface, greatly reducing the grinding energy, and, as another problem, the water jet grinds the metal pieces deep from the surface. Need arises,
Therefore, the energy required for grinding the water jet is increased, and the removal efficiency is greatly reduced.

[0011]

FIG. 1 is a perspective view showing an embodiment of a steel slab 6 according to one embodiment of the present invention after partial care for cracks. Billet 6
For example, slabs, blooms, billets, etc. obtained from continuous casting lines and subsequent processes,
In a continuous casting line, it is performed by vertical-curved or curved continuous casting equipment. FIG. 2A shows the steel slab 6.
It is a perspective view of a part of. In a vertical-curved or curved continuous casting plant, the slab guided from the tundish through the mold is bent at the bend of the continuous casting plant,
It is bent back again, straightened straight, cut by a cutting machine, and carried out as a billet. Therefore, a portion 7a of the crack 7 is opened on the horizontal upper surface 8 of the billet 6, and a portion 7b of the crack 7 is opened on one vertical side surface 9. On this side surface 9, cooling water is injected in a continuous casting facility, and therefore, a crack 7 b is easily formed on this side surface 9. Thus, the crack 7 is
Extending over the surface 8 and the side surface 9 forming the ridge 10 of FIG. Cracks also occur on the horizontal lower surface 11 of the billet 6 as in the case of the cracks 7. The drawing direction at the time of casting the billet 6 is indicated by an arrow 12.

FIG. 2B also shows cracks 13 formed over the ridges 14 of the steel slab 6, cracks 13 a open on the surface 11, and cracks 13 a on the side surface 9.
b opens. According to the invention, such surfaces 8,1
Cracks extending between 1 and the side surface 9 are removed by grinding using an abrasive water jet.

FIG. 3 is a plan view of the billet 6 of FIG. 2A, and FIG. 4 is a side view of the billet 6 of FIG. 2A. The procedure for removing the crack 7 will be described with reference to these drawings. Assuming a straight line 17 connecting an end point 15 on the surface 8 of the crack 7 and an end point 16 on the side surface 9,
So as to form a grinding plane 18 parallel to the ridge 10,
As shown in FIG. 5, an abrasive water jet 20 is jetted from the nozzle hole of the nozzle 19. The axis of this water jet 20 and thus the axis 21 of the nozzle 19
Is the aforementioned grinding plane 18 parallel to the ridge 10 containing the straight line 17
Is on an extension of

The abrasive water jet 20 is a mixture of abrasive grains and a liquid, for example, water.
³ to 10 ⁴ kgf / cm ² , for example, 3000 kgf / c
It is ejected from the nozzle hole of the nozzle 19 at m ² . The abrasive grains are
Garnet, cast iron grid, iron sand, alumina, silica sand and other fine particles, the particle size of which is 0.2 to 2 mmφ,
The inner diameter of the nozzle hole is, for example, 4 mmφ. Thus, the portion 22 from the ridge 10 including the crack 7 can be removed. If the grain size of the abrasive grains is less than 0.2 mmφ, the depth of the flaw becomes large at the time of grinding, and a piercing attack occurs,
The flatness deteriorates. When the particle size of the abrasive exceeds 2 mmφ,
The inner peripheral surface of the nozzle hole of the nozzle that jets the water jet is worn by the abrasive grains.

Both ends 23, 24 along the longitudinal direction of the ridge 10
Are similarly formed by the abrasive water jet 20. The inclined surfaces 25 and 26 are inclined so as to become shallower as the distance from the grinding plane 18 increases. Regarding the inclined surface 25,
The distance from the side surface 10 of the grinding plane 18 on the surface 8;
Therefore, when the depth of the ground plane 18 is D1 and the length of the inclined surface 25 along the ridge 10 is L, L / D1 ≧ 2 (1) is selected.

Similarly, as shown in FIG. 4, when the distance from the surface 8 of the grinding plane 18, that is, the depth of the grinding plane 18 is D2 on the side surface 9, with respect to the inclined surface 25, L / D2 ≧ 2 Select in (2). The same applies to the other inclined surface 26.

As a result, after the flaw 7 is removed by grinding,
When the side surface 9 and the other side surface are sandwiched between width reduction rolls having a vertical rotation axis, and then the steel slab 6 is sandwiched between work rolls having upper and lower horizontal rotation axes, the surface of the product after the rolling is rolled. In addition, it is possible to prevent the occurrence of a flaw defect due to folding called a scab.

If the flaws existing across the ridge 10 of the billet 6 were to be removed by a water jet as shown in FIG. If a surface 27 perpendicular to the ridge 10 is formed, a portion 29 of the surface of the billet 6 is folded after rolling, as shown in FIG.
In this case, the falling flaw shown by the above is generated. In the present invention, the inclined surface 25 is ground so as to be formed so as to satisfy Expressions 1 and 2 described above, and the inclined surface 26 is also ground in the same manner, whereby the inclined surface shown in FIG. Defects can be prevented from occurring after rolling.

The angle θ between the straight line 17 and thus the line 31 perpendicular to the surface 8 formed by the grinding plane 18 is chosen such that θ ≦ 60 degrees (3), whereby the abrasive water jet 2
This prevents the energy for grinding 0 from increasing. If the angle θ exceeds 60 degrees, the discharge energy of the water jet 20 interferes with the energy reflected by the surface 8 of the steel slab 6, and the grinding energy is greatly reduced.
When the angle θ exceeds 60 degrees, the grinding energy of the abrasive water jet 20 is greatly increased, and the removal efficiency is reduced. Angle θ is selected to be, for example, 7 degrees or more. When the angle θ is less than 7 degrees, the water jet 20 collides closer to being parallel to the surface 8, so that the collision energy is not transmitted to the billet 6, and the grinding rate is reduced.

In the above-described embodiment, the grinding plane 18 is determined based on the straight line 17 connecting both end points 15 and 16 of the crack 7 on the surfaces 8 and 9, but as another embodiment of the present invention, FIG. As shown in FIG. 5, a point 32 inside (leftward in FIG. 5) the end point 15 and an end point 1 on the side surface 9
A point 33 inside (downward in FIG. 5) than point 6 is selected, and ridge 1 including a straight line connecting point 15 or 32 and point 16 or 33 is selected.
A grinding plane parallel to 0 may be formed. For example, a grinding plane including points 32 and 33 may be formed, and for example, point 1 may be set so that the angle θ satisfies the above formula.
The grinding plane may be formed so as to include a straight line connecting 5, 33 or a straight line connecting points 32, 16. Point 32 is side 9
And the point 33 may be defined at a distance of 1.1 × D2 from the surface 8, thus detecting the end points 15 and 16 of the flaw 7. Thus, even if a detection error occurs due to the above, the crack 7 can be reliably removed.

The invention can be practiced not only with steel slabs but also with aluminum and copper and other metal slabs.

The experimental results of the present inventor will be described.

[0023]

[Table 1]

In Table 1, a circle in the column of scratch generation after rolling indicates that no scratch occurs after the rolling, and a cross indicates that scratch occurs after the rolling. The working time in Table 1 indicates the time required for the grinding operation using the abrasive water jet 20, the mark "O" indicates that the working time is relatively short, and the mark "X" indicates that the working time is relatively short. Represents a long time.

Comparative Examples 1 to 3 not satisfying the above-mentioned formulas 1 to 3
In No. 3, it can be seen that flaws occur after rolling, and that the working time by the abrasive water jet becomes longer.

[0026]

As described above, according to the present invention, cracks extending over the surface and side surface forming the ridge of a metal piece such as a steel piece are removed by grinding with an abrasive water jet. Therefore, compared to the method using a hot scarf and a grinder described in relation to the above-mentioned prior art, it is possible to maintain a good working environment and to reliably remove cracks and flaws in a desired shape. In addition, the metal pieces are not excessively removed to remove the cracks, and the yield is improved.

Further, according to the present invention, an inclined water jet is formed by connecting an inclined surface to both end points of a surface and a side surface of a crack, or to both end portions of a grinding plane connecting both points inside the both end points. On the surface and the side surface, along the ridge of the inclined surface.
Is selected to be at least twice the depth D of the grinding plane, whereby it is possible to prevent a broken flaw called a heddle caused by being folded after rolling.

Furthermore, according to the present invention, the angle θ between the axis of the abrasive water jet and a line perpendicular to the surface is selected to a value of not more than 60 degrees, whereby the abrasive water jet can be ground. The required energy is small, and the cracks can be reliably removed.

[Brief description of the drawings]

FIG. 1 is a perspective view of a steel piece 6 showing a state after partial care according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a state in which cracks 7, 13 are formed on a steel slab 6. FIG.

FIG. 3 is a plan view of the steel slab 6 of FIG. 2A after partial care.

FIG. 4 is a side view of the billet 6 shown in FIG. 2A after partial care.

FIG. 5 is a cross-sectional view showing a state in which an abrasive water jet 20 is sprayed on a steel slab 6 to partially repair a crack.

FIG. 6 is a view for explaining that a flaw defect occurs after the surfaces 27 and 28 perpendicular to the ridge 10 are formed on both ends of the grinding plane 18 on the steel slab 6;

FIG. 7 is a cross-sectional view for explaining a problem of the prior art caused by the grinder.

[Explanation of symbols]

 6 Billet 7 Crack 8,11 Surface 9 Side 10 Ridge 15,16 End point 18 Grinding plane 19 Nozzle 20 Abrasive water jet 25,26 Inclined surface 32,33 point

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazumi Daitoku 1-1, Tobata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Yawata Works (72) Inventor Takuya Kubota Tobata-ku, Kitakyushu-shi, Fukuoka No. 1-1 Hibata-cho, Nippon Steel Corporation Yawata Works (72) Inventor Fujiya Nogami 1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Yawata Works (72) Inventor Tomohiro Furuta 1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Yawata Works (72) Inventor Yuzen Nagai 3-1-1 Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo Kawasaki Heavy Industries Inside Kobe Plant (72) Inventor Kiwa Ikemoto 3-1-1 Higashi Kawasaki-cho, Chuo-ku, Kobe City, Hyogo Prefecture Kawasaki Heavy Industries, Ltd. Inside Kobe Plant (72) Inventor Hirozuna Kuchiki Kawasaki Heavy Industries, Ltd., Kobe Factory, Kobe, Kobe, Kobe, Japan (72) Inventor Tsuyoshi Kimura 3-1-1, Higashikawasaki-cho, Chuo-ku, Kobe, Hyogo, Japan Kawasaki Heavy Industries, Ltd. 56) References JP-A-5-50202 (JP, A) JP-A-6-126621 (JP, A) JP-A-51-81684 (JP, A) JP-A-51-137191 (JP, A) Showa 51-145432 (JP, A) Actually open Showa 63-56904 (JP, U) Japanese Patent Publication No. 56-51069 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B24C 1 / 00 B22D 11/12 B24C 1/04 B24C 3/00

Claims (1)

(57) [Claims] 1. A crack extending over a surface and a side surface forming a ridge of a metal piece, connecting both end points on the surface and the side surface, or both points inside the both ends, and being parallel to the ridge. An abrasive water jet, which is a mixture of abrasive grains and a liquid, is sprayed from the nozzle hole of the nozzle onto the metal piece so as to form a smooth grinding surface, and the metal piece is ground to remove the ridge-side portion including cracks. Forming an inclined surface, which is continuous with both ends of the grinding plane along the longitudinal direction of the ridge and becomes shallower as it goes away from the grinding plane, by the abrasive water jet, on the surface and on the side surface; And the depth D of the grinding plane
And the length L along the ridge of the inclined surface is selected as L / D ≧ 2, and the angle θ between the axis of the abrasive water jet for grinding the grinding surface and a line perpendicular to the surface is , Θ ≦ 60 degrees, a method for partially repairing cracks in metal pieces.