JP2603795B2 - Flaw grinding method according to flaw - 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 grinding and removing surface flaws on a metal plate by means of an abrasive water jet (AWJ).

[0002]

2. Description of the Related Art An abrasive is added to a high-pressure jet water stream.
In an abrasive water jet in which the abrasive is accelerated by a jet stream to collide with a workpiece and cut, it is disclosed that the abrasive is transported and added to the high-pressure jet stream in a pressurized state. -5014
No. 89 is disclosed.

[0003] If the abrasive is added and conveyed in a pressurized state, a large amount of the abrasive can be contained in the high-pressure jet water stream, so that there is an advantage that the cutting ability can be remarkably improved.

In recent years, attempts have been made to apply abrasive water jet processing, which is excellent in cutting performance and does not have a thermal effect on a workpiece, to remove flaws on a metal surface such as a steel plate for rolling. Became.

In application to the grinding of a metal surface, a high-pressure jet water jet nozzle is arranged at a predetermined interval from the surface to be ground and inclined, and the surface to which the high-pressure jet water flow is applied by the nozzle is widened. Various measures have been taken to increase the surface area and increase the grinding efficiency by moving the nozzle.

[0006] However, even though various devices have been devised for such surface grinding, a method for providing simple and optimal grinding conditions corresponding to the area and depth of surface flaws has not been established. In the automatic grinding, it takes a long time from the processing command to the end, adversely affects the yield of the slab, causes a residual flaw, and requires re-grinding.

[0007]

A problem to be solved in the present invention is a surface grinding method using an abrasive water jet which can efficiently grind surface flaws having different regions and depths, such as continuous cast slabs for rolling. Is to establish.

[0008]

According to the present invention, surface flaws are classified into cracks and pinholes in advance, and the surface flaws of the pinholes are classified into a dispersed type and a concentrated type. Then, grinding conditions by abrasive water jet necessary for grinding removal are determined in advance for each type of classification of these flaws, the surface flaws to be ground are determined and classified according to the above forms, and the classified surface The grinding process is performed under the preset grinding conditions according to the form of the flaw.

In the present invention, the pinholes are classified into the dispersed type and the aggregated type by a visual inspection or a flaw inspection device, in which a state of 2L or more with respect to one pinhole diameter L is defined as a dispersed type and a range smaller than 2L. Adjacent ones are centralized.

[0010] For the surface flaws of the dispersion type pinhole system, grinding is individually performed by setting a depth index corresponding to the diameter of the pinhole.

Further, for the surface flaw of the collective pinhole system, an inner region connecting the outer peripheral tangents of the pinhole generated on the outer peripheral portion of the collective area is determined, and the maximum diameter (pinhole) is determined. The depth is determined in the same manner as in the dispersion type.

For cracks, there is an unambiguous relationship between the length and depth of cracks from past experience, and the depth conversion index α is obtained from this relationship. Therefore, the depth H of the crack flaw predicted corresponding to the measured crack length L ₁ of the cracking defects in the surface of the object to be treated can be determined by the following equation.

Predicted depth H = measured crack length L ₁ × depth conversion index α Then, from the processing mode of the abrasive water jet, start grinding at a portion where L ₂ / H is 1 or more from the beginning of crack. Point.

[0014]

FIGS. 1 and 2 show the form of flaws on the surface of a continuous cast slab. FIG. 1 shows flaws of a pinhole type.

In the state immediately after casting shown in FIG.
Pinhole A is formed near the surface, but after casting,
As shown in (b), the pinhole is formed immediately below the surface scale B, and after being subjected to fusing or the like, the pinhole is in any of the states shown in (c), (d), and (e) of FIG. And adversely affects subsequent rolling. Therefore, it is necessary to perform the grinding according to the depth index with respect to the diameter of the pinhole appearing on the surface.

FIG. 2 shows a concentrated pinhole system. In the case of the concentrated pinhole system, the depth index is determined by the maximum diameter of the pinhole flaw, and the depth index is determined from the region of the tangent line of the collective pinhole. Grind at a predetermined distance.

FIG. 3 shows an embodiment for cracks. Respect FIG (a) and the predicted depth H of the crack flaw C shown in (b) showing the cross-section, the grinding start point S, the measured starting point L ₂ / H
, And the end point is set after L ₂ / H of the actual measurement end point, it is possible to perform grinding in a state as shown in FIG.

[0018]

EXAMPLE The present invention was applied to the removal of surface flaws of a slab having a thickness of 250 mm and a width of 980 mm.

The following was used as an abrasive water jet device.

The jet pressure was set to 3000 kgf / cm ² , and the abrasive was set to a mixture ratio of cast iron grit and grit of 0.7 (grit weight / water weight).

The depth index α was obtained from past data when this abrasive water jet apparatus was applied to the same steel slab.

[0022] The surface defects of the slab, by measuring the position and the diameter D of the dispersion-type pinhole system, and inputs to the control unit inputs the position of the crack flaw, crack flaw length L ₁ Then, the predicted depth H was obtained from the depth index α and input to the control device to operate the abrasive water jet device to perform surface grinding.

Table 1 shows the classification of flaws in the distributed pinhole system and the depth index α used. Table 1 for centralized type
The grinding was performed under the conditions described above and with the grinding area as a pinhole external tangent.

[0024]

[Table 1] Table 2 shows the crack length L ₁ and the applied depth index α.
Depth H obtained by the above, and the positions of the grinding start point and the grinding end point L ₂ / H are shown.

[0025]

[Table 2] As a result, the operation of the abrasive water jet was automatically operated to remove flaws, and good results were obtained.

[0026]

According to the present invention, the following effects can be obtained.

(1) Since discrimination of flaws and setting of grinding conditions can be quickly processed, the time from inspection to completion of grinding can be shortened.

(2) An appropriate depth and area corresponding to the form of the flaw can be reliably ground with high precision, and excessive grinding can be suppressed.

(3) A specific relationship between the depth and the area is found from the surface morphology of the flaw, and the grinding area is simply determined from the surface and the morphology, so that a highly reliable grinding state can be obtained.

(4) Since accurate grinding removal can be instructed from a simple flaw form, simplification of the system can be achieved. Further, it has become possible to supply a slab which guarantees extremely high quality without causing a residual flaw of a product.

[Brief description of the drawings]

FIG. 1 shows the form of surface flaws and the form of grinding of a distributed pinhole system.

FIG. 2 shows the form of surface flaws and the form of grinding of a concentrated pinhole system.

FIG. 3 shows a form of a surface flaw of a crack system and a mode of grinding.

[Explanation of symbols]

Grinding start from the end of the flaws found by A pinhole B surface scale C crack crack length H predicted depth S grinding start point L ₂ Kizufuka of H × predetermined constants L ₁ crack flaw, the distance at the end point

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazumi Daitoku 1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Yawata Works (72) Inventor Fujiya Nogami Kitakyushu, Fukuoka Nippon Steel Corporation Yawata Works, 1-1-1, Tobata-ku, Nippon Steel Corporation (72) Inventor Hiroyuki Matsumura 3-1-1, Higashikawasakicho, Chuo-ku, Kobe Kawasaki Heavy Industries, Ltd. Kobe Plant (72) Inventor Ikemoto Kiwa 3-1-1 Higashi-Kawasaki-cho, Chuo-ku, Kobe Kawasaki Heavy Industries, Ltd. Kobe Factory (72) Inventor Kyoji Tsujita 3-1-1, Higashi-Kawasaki-cho, Chuo-ku, Kobe Kawasaki Heavy Industries, Ltd. Inventor Hidetaka Tanaka 3-1-1 Higashi Kawasaki-cho, Chuo-ku, Kobe Kawasaki Heavy Industries, Ltd.

Claims (3)

(57) [Claims] 1. Surface flaws are classified in advance into crack-type flaws and pinhole-type flaws, and surface flaws of the pinhole-type flaws are classified into a dispersed type and a concentrated type. Grinding conditions by abrasive water jet necessary for grinding removal are determined in advance for each, and the surface flaws to be ground are determined and classified according to the above-described forms, and the above-mentioned pre-determined according to the form of each classified surface flaw. A flaw grinding method according to flaws that performs a grinding process under set grinding conditions. 2. The method according to claim 1, wherein the surface flaws to be ground are discriminated, and the classification for each of the forms is classified into a distributed pinhole, a concentrated pinhole, and a crack.
A flaw grinding method that predicts flaw depth based on a preset surface flaw form and sets a grinding start point and an end point based on the predicted flaw depth. 3. The method according to claim 2, wherein the depth of the flaw is predicted based on the form of the surface flaw using a depth conversion index obtained by experience, and the grinding start point and the end point are measured with the measured length and the depth conversion. A flaw grinding method according to the flaw obtained from the index.