JP3223049B2 - Opening flaw removal method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abrasive water jet which can be suitably applied to, for example, a continuous casting line and a subsequent step for grinding and removing an opening flaw on the surface of a slab and a billet. The present invention relates to a method for removing an opening flaw using the method.

[0002]

2. Description of the Related Art As a prior art of a slab care operation for removing an opening flaw on the surface of a slab, there is known a cutting method using 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. 14A, when a flaw 2 is present on a workpiece 1 such as a slab or a steel slab, the rotating grindstone 3 is rotated. When grinding is performed by the depth d1, as shown in FIG. 14 (2), the flaw 4 which is a part of the flaw 2 remains in the workpiece 1, but cannot be seen 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] Still another prior art is disclosed in JP-A-51-97.
894. In this prior art, a predetermined abrasive is wet-sprayed from a nozzle onto the surface of a stainless steel plate to perform both grinding and descaling. At present, the method for removing and repairing the flaws of steel slabs, such as performing grinding and descaling by spraying an abrasive from a nozzle on the surface of a stainless steel sheet in a wet manner, is mainly performed by the latter descaling. It is technically still insufficient to grind and remove flaw defects on a piece, and cannot be practically adopted.

The inventor of the present invention sprays an abrasive water jet, which is a mixture of abrasive grains and water, from a nozzle hole of a nozzle on an opening flaw such as a crack or a hair crack formed on the surface of a cast piece such as a slab. Then, a method of removing the slab by grinding the surface of the slab was proposed. In this technique, as shown in FIG. 15 (1), when there is an opening flaw 7 which is a crack in the slab 6, when the flaw 7 is to be removed by grinding with an abrasive water jet 8,
A grinding depth d2 larger than the depth d1 of the flaw 7 is set (d1> d2), and a water jet 8 is jetted immediately above the flaw 7 to the slab 6 as shown in FIG. It has been found that when the recess 10 in the grinding area 9 is formed as described above, the opening flaw 11 having a depth d3 is further formed in the recess 14. Therefore, the slab 6 having the flaw 11
After the rolling, as shown in FIG. 15 (3), the recesses 12 are formed on the surface of the cast slab 6 after the rolling due to the remaining flaws 11.
Was formed. Depth d3 of remaining flaw 11
Is smaller than the depth d1 of the first flaw 7 and shallow.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to reliably remove opening flaws in a workpiece such as a metal piece such as a slab or a steel piece by using an abrasive water jet. An object of the present invention is to provide a method for removing an opening flaw.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a water jet, which is a mixture of abrasive grains and a liquid, is jetted from a nozzle hole of a nozzle to grind a surface of a workpiece to remove an opening flaw. In the removal method, an angle α formed between a direction in which the flaw extends and a straight line on which the axis of the nozzle is projected on the surface of the workpiece is selected to be 30 to 150 degrees. It is. The present invention also provides a method for removing an opening flaw in which a water jet, which is a mixture of abrasive grains and a liquid, is jetted from a nozzle hole of a nozzle to grind a surface of a workpiece to remove an opening flaw. And the angle α between the projected straight line of the axis of the nozzle on the surface of the workpiece is selected to be 30 to 150 degrees, and the abrasive grain is 0.2 to
An opening flaw removal method characterized by 2 mmφ. The present invention also provides a method for removing an opening flaw in which a water jet, which is a mixture of abrasive grains and a liquid, is jetted from a nozzle hole of a nozzle to grind a surface of a workpiece to remove an opening flaw. And the angle α between the projected straight line of the axis of the nozzle on the surface of the workpiece,
An opening flaw removal method characterized in that the angle θ between the surface of the workpiece and the nozzle axis is selected from 7 to 80 degrees. The present invention also provides a method for removing an opening flaw in which a water jet, which is a mixture of abrasive grains and a liquid, is jetted from a nozzle hole of a nozzle to grind a surface of a workpiece to remove an opening flaw. And the angle α formed by the projected straight line of the axis of the nozzle on the surface of the workpiece is selected to be 30 to 150 degrees, and the abrasive grains are 0.2 to 2 mmφ.
And the angle θ between the surface of the workpiece and the nozzle axis
Is selected at 7 to 80 degrees.

[0009]

According to the present invention, an abrasive water jet, which is a mixture of abrasive grains and a liquid, for example, water, is sprayed from a nozzle hole of a nozzle onto a workpiece such as a metal piece such as a slab or a steel slab. Grinding can be performed to remove the opening flaws. According to the method using such a water jet, the working environment is better than the method described in relation to the prior art using the above-described hot scarf and grinder. Therefore, it is easy to control the shape of the grinding area.

In particular, according to the present invention, the angle α between the direction in which the opening flaws such as cracks and hair cracks extend and the straight line on which the axis of the nozzle is projected on the surface of the workpiece is defined as 3
By selecting from 0 to 150 degrees, particularly preferably from 60 to 120 degrees, the flatness of the workpiece after grinding can be improved and the grinding rate can be improved. The grinding rate is the grinding weight per unit time, and the unit can be expressed in g / min. If the angle α is selected to be less than 30 degrees, it will be difficult to completely remove the flaw even after grinding, as described with reference to FIG. Therefore, by selecting the angle α to be equal to or more than the above-mentioned range of 30 degrees, it is possible to prevent the abrasive grains from entering the opening flaws, thereby preventing the advance grinding from occurring and preventing the grinding from being enlarged, The energy that the abrasive grains flow along the opening flaws can be reduced, and the flatness can be improved. Further, by selecting the angle α in the above range, the jet energy of the water jet can be effectively utilized for grinding by utilizing the groove of the opening flaw, and the grinding rate can be improved as described above. .

When the angle α is set to a value exceeding 150 degrees, as in the above-mentioned case, the grinding is performed in an enlarged manner, and the flatness is reduced and the grinding rate is reduced.

Further, according to the present invention, by selecting the abrasive grains of the abrasive water jet to have a diameter of 0.2 to 2 mmφ, it is possible to improve the grinding rate and suppress the expansion grinding. If the abrasive grains are less than 0.2 mmφ, the grooves become deeper during the grinding of the opening flaws, causing a perforation attack and poor flatness. If the diameter of the abrasive grains exceeds 2 mmφ, the inner peripheral surface of the nozzle hole of the nozzle for jetting the water jet will be worn by the abrasive grains.

Further, according to the present invention, the angle θ between the surface of the workpiece and the nozzle axis is selected to be 7 to 80 degrees, thereby improving the grinding rate and performing the grinding for removing the opening flaw. It can be carried out. If the angle θ is less than 7 degrees, the jet energy of the water jet is close to being parallel to the surface of the workpiece to be ground and collides with it. Poor rate.

If the angle .theta. Is selected to a value exceeding 80 degrees, the discharge energy of the water jet from the nozzle interferes with the reflection energy due to the reflection of the water jet on the workpiece surface, and the grinding energy is greatly reduced. .

According to the present invention, a combination of the angle α and the diameter of the abrasive grains may be implemented.
A combination of the diameter of the abrasive grains and the angle θ may be implemented. Further, according to the present invention, a combination of the angles α and θ may be implemented, and a combination of the diameter of the abrasive grains and the angle θ and other combinations may be implemented.

[0016]

FIG. 1 is a perspective view schematically showing the principle of an embodiment of the present invention. An elongated opening flaw 16 such as a crack or a crack is present on a workpiece 15 such as a slab, a bloom or a billet of a continuous casting line or a metal piece such as a steel slab in a subsequent process.
Is sprayed along the nozzle axis 17 from a nozzle hole 38 of the nozzle 17 shown in FIG. 2 along the nozzle axis 17 by spraying an abrasive water jet, which is a mixture of abrasive grains and liquid water.
6 is removed by grinding. In FIG. 1, for convenience of understanding, an axis 18 on the surface of the workpiece 15 of the opening flaw 16 is defined as a y-axis, and a direction perpendicular to the axis 18 and within the surface of the workpiece 15 is defined as an x-axis. The direction perpendicular to the surface of the workpiece 15 is defined as the z-axis. According to the concept of the present invention, the angle α between the direction in which the axis 18 of the opening flaw 16 extends and the straight line 20 on which the axis 19 of the nozzle 17 is projected on the surface of the workpiece 15 is 30 to 150 degrees. , Preferably 60 to
Choose at 120 degrees. Thereby, the flatness can be improved and the grinding rate can be improved.

Further, the angle θ between the surface of the workpiece 15 and the axis 19 of the nozzle 17 is selected to be 7 to 80 degrees. This can also improve the grinding rate.

FIG. 2 is a longitudinal sectional view of the nozzle 17, and FIG.
Indicates the bottom surface of the nozzle 17. The nozzle 17 is formed in a right cylindrical shape, the length L1 is, for example, 200 mm, and the inner diameter D1 of the nozzle hole 38 is, for example, 4 mmφ. Above the nozzle 17, a mixing container 21 is provided,
High pressure water of 10 ³ to 10 ⁴ kgf / cm ² , for example, 3000 kgf / cm ² is supplied through a pipe 22, abrasive grains are supplied from a pipe 23, and both are mixed in a mixing vessel 21.
These are mixed in the mixing chamber 24 inside, and are jetted from the tip of the nozzle hole 38 to form an abrasive water jet and jetted onto the surface of the workpiece 15. The abrasive grains are in the form of fine particles such as garnet, cast iron grid, cast steel grid, iron sand, alumina, silica sand and the like.
The mixture is introduced into the nozzle 17 from the mixing chamber 24 in a state where the diameter is set to 2 mm to 2 mm and mixed with high-pressure water. This nozzle 17
It is mounted on the wrist of a robot having a plurality of axes and is traversed.

FIG. 4 is a plan view showing a traverse movement locus of the nozzle 17. This movement trajectory is indicated by reference numeral 25. The robot moves the nozzle 17 in the longitudinal direction of the workpiece 15 by one pass P1 and moves the nozzle 17 by one pitch P2 in the width direction of the workpiece 15 for the same grinding operation for each pass P1. Make a move. The pitch P2 may be, for example, about 2 mm.

FIG. 5 is a simplified plan view of the workpiece 15 for explaining the angle α. As described above, the angle formed by the axis 18 which is the direction in which the opening flaw 16 extends and the axis 19 of the nozzle 17 and thus the axis of the water jet projected on the surface of the workpiece 15 is α.

FIG. 6 shows a state in which the water jet 26 is jetted from the nozzle 17 and the flaw 16 and its vicinity are ground. The angle between the surface of the workpiece 15 and the nozzle axis 19 is defined as θ as described above.

FIG. 7 shows a cross section of the workpiece 15 after grinding with a water jet, as viewed from the section line VII-VII in FIG. 5, and FIG. 8 shows the flaw 16 as viewed from the section line VIII-VIII in FIG. 2 shows a cross section of the workpiece 15 after grinding. In order to remove the flaw 16 by grinding, a grinding area 27 including the flaw 16 is determined, and the robot 17 controls the traverse movement of the nozzle 17 so that the grinding area 27 is formed. The conditions,
For example, the traverse relative speed of the nozzle 17 with respect to the workpiece 15, the distance and the angle α or the angle θ, which are the standoff amounts between the nozzle hole 38 and the workpiece 15, are changed.
Furthermore, at least one of the flow rates of the abrasive particles supplied from the conduit 23 shown in FIG. 2 is changed.

In FIG. 7, in the grinding area 27, a grinding depth D1 is determined in the vicinity of the flaw 16, and the inclined surface 2 of the peripheral area 28 of the grinding area 27 becomes shallower toward the outside.
Grind so that 9 is formed. The width L1 of the peripheral portion 28 where the inclined surface 29 is formed is at least twice the depth D1 of the portion 42 inside the peripheral portion 28 of the grinding area 27, that is, L1 / D1 ≧ 2 (1) Choose. The flaw 16 is present on the inner part 42.

In FIG. 8, similarly, the grinding area 27
An inclined surface 31 is formed in the peripheral portion 30 of the above, and the width L2 of the peripheral portion 30 is selected to be at least twice the depth D1 of the inner portion 42, that is, L2 / D1 ≧ 2 (2). Thus, the peripheral portions 28, 30 of the grinding area 27 are
The reason why the inclined surfaces 29 and 31 are formed is that when the water jet of the present invention is used to perform rolling after grinding and removing flaws on the workpiece 15, the surface of the workpiece 15 after the rolling is removed.
This is in order to prevent the occurrence of a flaw defect caused by folding called a scab.

As shown in FIG. 9A, a grinding area for removing a flaw on the workpiece 15 by a water jet is formed by a recess 33 having a vertical peripheral portion 32.
As shown in FIG. 9 after rolling,
As shown in (2), a part 34 of the surface of the workpiece 15 is folded to cause a falling flaw indicated by reference numeral 35. In the present invention, the inclined surfaces 29 and 31 are formed and
By performing the grinding so as to satisfy the expression (2), it is possible to prevent such a flaw defect as shown in FIG. 9 from occurring after rolling.

FIG. 10 is a graph showing the experimental results of the present inventor, showing the angle α and the flatness of the surface of the workpiece 15. FIG. 11 is a graph showing the relationship between the angle α and the grinding rate according to an experiment performed by the present inventor. Angle α is 30 to 15
It is understood that the flatness is good and the grinding rate is good in the range of 0 degrees. The angle α is preferably 60
Choose between degrees and 120 degrees. In the experiments of FIGS. 10 and 11, the angle θ is 45 degrees.

FIG. 12 is a graph showing the experimental results of the present inventor, and shows the relationship between the average particle size of the abrasive grains forming the water jet 26 and the flatness. FIG. 13 shows the experimental results of the present inventor, and shows the relationship between the average particle size of the abrasive grains and the grinding rate. It can be seen that when the grain size of the abrasive grains is 0.2 mmφ or more, the flatness and the grinding rate are good. In FIGS. 12 and 13, the angle θ is 45 degrees.

If the grain size of the abrasive grains exceeds 2 mmφ, the inner peripheral surface of the nozzle hole 38 of the nozzle 17 will be worn by the abrasive grains, making it difficult to use for a long time. Therefore, in the present invention, the abrasive particles are selected to have a particle size of 0.2 to 2 mmφ.

Further, in the present invention, the angle θ is selected in the range of 7 to 80 degrees. When the angle θ is less than 7 degrees, the water jet 26 collides close to parallel to the ground surface on the surface of the workpiece 15, so that the collision energy is not transmitted to the workpiece 15 and the grinding rate is reduced. descend. If the angle θ exceeds 80 degrees, the discharge energy of the water jet 26 interferes with the energy reflected by the surface of the workpiece 15 and the grinding energy is greatly reduced.

According to the present invention, not only slabs and steel slabs, but also other metal slabs, and the surface of or near the surface of a workpiece made of other materials are ground using an abrasive water jet. It can be implemented extensively to remove it.

[0031]

As described above, according to the present invention, cracks or hair cracks present on a workpiece such as a metal piece such as a slab and a steel slab are removed from the nozzle hole of the nozzle by the abrasive grains and the liquid. When the abrasive water jet, which is a mixture of the two, is sprayed and removed by grinding, the angle α between the direction in which the opening flaw extends and the projected straight line of the nozzle axis on the surface of the workpiece is 30 to 30 °. By selecting 150 degrees, it is possible to prevent the occurrence of enlarged grinding and improve the flatness, and it is possible to effectively utilize the water jet injection energy for grinding, thereby improving the grinding rate.

Further, according to the present invention, by selecting the abrasive grains of the abrasive water jet to have a diameter of 0.2 to 2 mmφ, the expansion grinding is suppressed, the flatness is improved, and the grinding rate is improved. In addition, the nozzle holes can be prevented from being worn by abrasive grains.

Further, according to the present invention, by selecting the angle θ between the surface to be processed and the nozzle axis to be 7 to 80 degrees, the grinding rate can be improved and the energy of the water jet can be efficiently reduced for grinding. It can be used.

[Brief description of the drawings]

FIG. 1 is a simplified perspective view for explaining the principle of the present invention.

FIG. 2 is a longitudinal sectional view of a nozzle 17;

FIG. 3 is a bottom view of the nozzle 17;

FIG. 4 is a plan view of the workpiece 15 showing a traverse movement trajectory of the nozzle 18;

FIG. 5 is a plan view of a workpiece 15 having a flaw 16 for explaining an angle α.

FIG. 6 shows a water jet 2 injected from a nozzle 17
FIG. 6 is a cross-sectional view showing a state in which an opening flaw 16 is ground and removed by 6.

7 is a view showing a flaw 16 viewed from the section line VII-VII in FIG.
FIG. 4 is a cross-sectional view showing a state after grinding removal.

8 is a diagram showing a workpiece 1 after grinding and removing a flaw 16 by a water jet as viewed from a cutting plane line VIII-VIII in FIG.
5 is a sectional view of FIG.

FIG. 9 is a cross-sectional view for explaining that a folding defect occurs due to the folding of the workpiece 15 after rolling when a vertical peripheral portion 32 is formed on the workpiece 15;

FIG. 10 is a graph showing an experimental result of the present inventor and showing a relationship between an angle α and flatness.

FIG. 11 is a graph showing experimental results of the present inventor,
5 is a graph showing a relationship between an angle α and a grinding rate.

FIG. 12 is a graph showing the experimental results of the present inventor and showing the relationship between the particle size of the abrasive grains and the flatness.

FIG. 13 is a graph showing the experimental results of the present inventor and showing the relationship between the particle size of abrasive grains and the grinding rate.

FIG. 14 is a cross-sectional view for explaining a method of grinding a workpiece 1 by a prior art grinder.

FIG. 15 is a cross-sectional view for explaining a problem when the opening flaw 7 present in the workpiece 6 is ground by the previously proposed abrasive water jet.

[Explanation of symbols]

15 Workpiece 16 Opening flaw 17 Nozzle 18 Axis 16 of flaw 16 19 Nozzle axis 20 Straight line where nozzle axis 19 of nozzle 17 is projected on the surface of workpiece 15 25 Traverse movement locus of nozzle 17 26 Abrasive water Jet 27 Grinding area 28, 30 Peripheral part 29, 31 Inclined surface 38 Nozzle hole 42 Inner part

Continuing from the front page (72) Inventor, Kazumaro Inaoka 1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Yawata Works (72) Inventor Tomoji Shimogasa 1 Tobihata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka No. 1 Inside Nippon Steel Corporation Yawata Works (72) Inventor Yuzen Nagai 3-1-1 Higashi Kawasaki-cho, Chuo-ku, Kobe City, Hyogo Prefecture Kawasaki Heavy Industries, Ltd.Kobe Plant (72) Inventor Yoshikazu Ikemoto Kawasaki Heavy Industries, Ltd.Kobe Plant, 3-1-1 Higashi-Kawasaki-cho, Chuo-ku, Kobe-shi, Hyogo (72) Inventor Hirotatsu Kuchi 3-1-1, Higashi-Kawasaki-cho, Chuo-ku, Kobe, Hyogo, Japan (72) Inventor Tsuyoshi Kimura 3-1-1 Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo Kawasaki Heavy Industries, Ltd. Kobe Factory (56) References JP-A-5-33820 (JP, A) JP-A-49-46533 (JP, A) JP-A-62-119729 (JP, A) JP-A-5-228839 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B24C 1/00 B24C 5/02

Claims (4)

(57) [Claims] 1. A method for removing an opening flaw, in which a water jet, which is a mixture of abrasive grains and a liquid, is jetted from a nozzle hole of a nozzle to grind a surface of a workpiece to remove an opening flaw. And the angle α between the projected straight line of the axis of the nozzle on the surface of the workpiece and 30 to 150
A method for removing opening flaws, which is always selected. 2. A method for removing an opening flaw in which a water jet, which is a mixture of abrasive grains and a liquid, is jetted from a nozzle hole of a nozzle to grind a surface of a workpiece to remove an opening flaw. And the angle α between the projected straight line of the axis of the nozzle on the surface of the workpiece and 30 to 150
A method for removing opening flaws, wherein the abrasive grains are 0.2 to 2 mm in diameter. 3. A method for removing an opening flaw in which a water jet, which is a mixture of abrasive grains and a liquid, is jetted from a nozzle hole of a nozzle to grind a surface of a workpiece to remove an opening flaw. And the angle α between the projected straight line of the axis of the nozzle on the surface of the workpiece and 30 to 150
The angle θ between the surface of the workpiece and the nozzle axis is 7 to 8
A method for removing opening flaws, wherein the method is selected at 0 degrees. 4. A method of removing an opening flaw, in which a water jet, which is a mixture of abrasive grains and a liquid, is jetted from a nozzle hole of a nozzle to grind a surface of a workpiece to remove an opening flaw. And the angle α between the projected straight line of the axis of the nozzle on the surface of the workpiece and 30 to 150
The abrasive grain is 0.2 to 2 mmφ, and the angle θ between the surface of the workpiece and the nozzle axis is 7 to 8
A method for removing opening flaws, wherein the method is selected at 0 degrees.