JPH0890226A - How to care for metal pieces - Google Patents

Abstract

(57) [Summary] [Purpose] To reliably remove the surface flaws of the steel slab after hot-scarfing with multiple torches and subjecting to melting and polishing, and to improve the grinding rate. [Structure] The surface of the steel slab is ground with a hot scarf using multiple torches, and the flaws on the surface after the ablation are detected, and the flaws are present on the surface peak after the ablation or in the vicinity of the peak. When spraying, an abrasive water jet of abrasive particles and liquid is jetted at an angle to the average virtual plane of the surface after fusing, and traverse movement is performed along the length direction of the peak to perform grinding. To do.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to maintenance of metal pieces for removing flaws on the surface of cast pieces such as slabs, blooms, billets and the like and metal pieces such as steel pieces in a continuous casting line and subsequent steps. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, the surface layer portion of a steel slab obtained in a continuous casting line is automatically subjected to hot scarfing to oxidize and remove it. Auxiliary fuel and oxygen gas are sprayed at a high speed from a plurality of torches arranged in a row, and the torch is moved in the longitudinal direction of the steel slab (JP-A-52-564).
4, JP-A-52-81048).

[0003]

The prior art for carrying out such a hot scarf treatment has the advantage that the fusing rate is extremely good, but there are peaks and troughs on the surface of the billet corresponding to each torch. Waves are alternately formed in the width direction of the steel slab to form undulations on the surface of the steel slab, and unmelted portions and burrs such as burrs are formed on the peaks of the surface of the steel slab.
As a result, the quality of the billet after rolling is adversely affected.

An object of the present invention is to provide a method for caring for a metal piece, which is capable of smoothing the surface of the metal piece after being abraded by a hot scarf and surely removing flaws.

[0005]

According to the present invention, the surface of a metal piece is ablated by a hot scarf, the flaws on the surface after the ablation are detected, and the ridges on the surface after the ablation and in the vicinity of the ridges are flawed. When there is, in the area where the flaw is present, an abrasive water jet that is a mixture of abrasive grains and a liquid, obliquely with respect to the average virtual plane of the surface after fusing, while jetting,
It is a method for caring for metal pieces, characterized by moving along the length direction of the ridges and grinding to remove flaws.

[0006]

According to the present invention, the surface of a metal piece such as a cast piece and a steel piece in a continuous casting line and the subsequent steps is hot scarf-treated with, for example, a plurality of torches, and is then abraded. Surface flaws, such as cracks,
When an unfused portion and flash are detected and the area where the flaw exists is present on the peak of the surface after fusing or an inclined surface near the crest, etc., an average virtual surface of the fusing The abrasive water jet is jetted obliquely to the plane while moving along the length direction of the crest to perform grinding, thus removing the flaw. Therefore, in addition to removing this flaw, the surface of the metal piece can be smoothed, and the grinding rate is improved by using the abrasive water jet. Furthermore, the accuracy of flaw detection after grinding by the abrasive water jet is improved. Will be able to improve. The grinding rate is a grinding weight per unit time, and its unit can be expressed in g / min.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view showing one step of one embodiment of the present invention. The slabs, slabs, billets, and other slabs or steel pieces 1 in the continuous casting line and subsequent steps have their surface layers oxidized and removed by hot scarf treatment, and as a result, peaks parallel to the longitudinal direction 2 of the steel pieces 1. 3 is formed.

The state in which this hot scarf process is performed is shown in the simplified plan view of FIG. A plurality of torches 4 are provided on the upper surface of the steel slab 1 at intervals in the width direction (left-right direction in FIG. 2) perpendicular to the longitudinal direction 2.
An auxiliary fuel such as propane gas and oxygen gas are injected from these torches 4 and sprayed onto the surface of the steel slab 1 at a high speed, and the surface layer portion of the steel slab 1 is removed by oxidation. The nozzle diameter of the torch 4 is, for example, 3 mmφ,
The distance between adjacent torches is, for example, 12 mm. These torches 4 are integrally moved in the longitudinal direction 2 of the steel slab 1.

FIG. 3 is an enlarged sectional view showing a state in which the surface layer portion of the steel slab 1 is melt-cut by a hot scarf. The thickness d1 of the surface layer portion 5 of the steel slab 1 is, for example, 1.5 to
Surface 2 with a thickness of 2 mm, after being ablated and removed
The surface from which the surface layer is removed is exposed.

Referring again to FIG. 1, when a plurality of torches 4 are moved to perform the hot scarf, peaks 3 are formed corresponding to the intervals between the torches 4, and the torches 4 form valleys. Is formed. In this way, after the hot scarf, the surface of the steel slab 1 becomes undulated,
On this surface, flaws such as cracks and flaws such as unwelded portions and burrs may be formed.

Therefore, according to the present invention, after the above-mentioned hot scarf fusing, the flaws on the surface of the steel slab 1 are detected automatically or manually by an operator. For the detection of this flaw, for example, eddy current flaw detection, an optical method using laser light or infrared rays, a configuration using ultrasonic waves, or another method may be used.

The flaw thus detected is present near the top of the mountain 3 or near its inclined surface, that is, near the mountain or its mountain, as indicated by reference numeral 6, as shown in the plan view of FIG. In this case, the region 7 where the one or more flaws 6 are present is ground by using an abrasive water jet to remove the flaws 6.

FIG. 5 is a perspective view showing in principle a state in which a region 7 having a flaw 6 is ground by an abrasive water jet. The nozzle 8 for jetting the water jet has an axis 9, which makes an angle θ with respect to an average virtual plane 10 of the surface of the steel slab 1 after fusing. The angle θ is selected to be, for example, 7 to 80 degrees, for example, 30 degrees, 45 degrees and 60 degrees. Figure 5
Then, this virtual plane 10 is represented by an xy plane.

The angle α in the virtual plane 10 formed by the lengthwise direction 11 of the crest 3 in the virtual plane 10 and the projection line 12 of the axis 9 of the nozzle 8 and thus the axis of the water jet to the virtual plane 10 is: For example, it may be selected from 30 to 150 degrees, preferably 60 to 120 degrees, and may be 90 degrees, for example. As a result, the flatness of the steel slab 1 after grinding can be improved, and the grinding rate can be improved.

The nozzle 8 forming the water jet is
As shown in FIG. 4, a robot having a plurality of axes traverses in a zigzag manner along a locus indicated by reference numeral 13 over a region 7 where the flaw 6 exists. The nozzle 8, and hence the water jet, traverses one path P1 along the length direction of the mountain 3, that is, in parallel, is displaced by a pitch P2 in the direction perpendicular to the mountain length direction 11, and again becomes 1 The traverse movement of the path P1 is performed, and such an operation is repeated. The pitch P2 is
For example, it may be 20 mm.

The abrasive water jet is a mixture of abrasive grains and a liquid such as water. The abrasive grains are fine particles such as garnet, cast iron brid, sand iron, alumina and silica sand, and the particle size is, for example. It is 0.2 to 2 mmφ and is jetted from a nozzle hole having an inner diameter of, for example, 4 mmφ in the nozzle 8 in a state where abrasive grains are mixed in high pressure water of 10 ³ to 10 ⁴ kg / cm ² . Abrasive grain size is 0.2mmφ
If it is less than the above range, the depth of the flaw becomes large during grinding, a perforation attack occurs, and the flatness becomes poor. Abrasive grain size is 2m
If it exceeds mφ, the inner peripheral surface of the nozzle hole of the nozzle for jetting the water jet will be worn by the abrasive grains.

FIG. 6 is a plan view showing a state in which the surface of the steel slab 1 is ground by an abrasive water jet, and FIG. 7 is a sectional view thereof. The abrasive water jet, indicated by reference numeral 14, grinds the ridges 3 of the billet 1 to reduce them, for example as indicated by the reference numeral 15, at which time the flaws 6 can be removed. it can. Thus, the abrasive water jet 14 is used to grind the adjacent ridges 3 simultaneously with the removal of the flaws 6 to smooth the surface of the steel slab 1, as shown in the cross section of the steel slab 1 in FIG. Is possible. Then, the billet 1 is moved in the longitudinal direction and rolled.

As described above, according to the present invention, the axis 9 of the nozzle 8, and thus the axis of the abrasive water jet, is oblique with respect to the imaginary plane 10, which makes it possible to improve the grinding rate. If, as shown in FIG. 9, the nozzle 8 and therefore the water jet 14 are jetted perpendicularly (θ = 90 degrees) to the virtual plane 10 of the steel piece 1 having the ridges 3, The discharge energy of the water jet 14 interferes with the reflected energy by the surface of the steel slab 1, and the grinding energy is significantly reduced.

Table 1 shows the experimental results of the present inventor.

[0020]

[Table 1]

A circle mark in Table 1 indicates that the traverse movement direction corresponds to a right angle or a parallel direction. The defect detection accuracy is based on Example 1, and the larger the numerical value is, the easier the defect is to be found. In the comparative example of Table 1, the traverse movement direction of each pass of the nozzle 8 forming the abrasive water jet is perpendicular to the longitudinal direction of the crest 3 (left and right direction in FIG. 4 and FIG. 9). Each of the degrees θ is an experimental result when θ = 90 degrees as shown in FIG. 9. It is understood that Examples 1 to 3 of the present invention are superior in smoothness, grinding rate and flaw grinding accuracy as compared with the comparative example.

[0022]

As described above, according to the present invention, after the surface of a metal piece such as a cast piece and a steel piece in a continuous casting line and subsequent steps is ablated by a hot scarf, a flaw is detected and the flaw is detected. When the existing area exists at or near the mountain, the abrasive water jet
While jetting diagonally to the average virtual plane, it moves along the length direction of the mountain to perform grinding, thereby removing flaws and smoothing the surface of the metal piece, Further, the grinding rate can be improved, and the accuracy of detecting flaws after the grinding can be improved. Moreover, after that, for example, when rolling or the like, the quality of the product after rolling can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a state in which the surface of the steel slab 1 is melt-cut by a hot scarf.

FIG. 3 is a cross-sectional view showing a state in which the hot scarf shown in FIG.

FIG. 4 is a plan view showing a state in which a region 7 having a flaw on the surface of the steel slab 1 after the ablation is ground by an abrasive water jet.

FIG. 5 is a perspective view showing the principle of grinding by an abrasive water jet.

FIG. 6 is a plan view showing a state in which grinding is performed using an abrasive water jet 14.

FIG. 7 is a cross-sectional view showing a state where grinding is performed by the abrasive water jet 14.

FIG. 8 is a cross-sectional view showing a state in which the ridges 3 of the steel slab 1 are ground by the abrasive water jet 14.

FIG. 9 is a sectional view for explaining a comparative example of the present invention.

[Explanation of symbols]

 1 Steel piece 2 Longitudinal direction of steel piece 1 3 Mountain 4 Torch 6 Defect 7 Region where defect 6 exists 8 Nozzle 9 Axis 10 Virtual plane 14 Abrasive water jet θ Angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Kazumaro Inaoka 1-1 Tobahata-cho, Tobata-ku, Kitakyushu City, Fukuoka Prefecture, Nippon Steel Co., Ltd., Yawata Works (72) Inventor, Kazumi Totoku, Kitakyushu, Fukuoka Prefecture No. 1-1, Hibata-cho, Shin-Nippon Steel Co., Ltd. (72) Inventor, Takuya Kubota 1-1, No. 1-1, Hibata-cho, Tobata-ku, Kitakyushu, Kitakyushu, Fukuoka (72) Invention Fujiya Nogami 1-1 Hibahata-cho, Tobata-ku, Kitakyushu, Fukuoka Prefecture Inside the New Hachiman Works (72) Inventor Tomohiro Furuta 1-1, Hibata-cho, Tobata-ku, Kitakyushu, Fukuoka Prefecture New Nippon Steel Inside Yawata Works (72) Inventor Hiroyoshi Nagai 3-1-1 Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo Inside Kawasaki Heavy Industries, Ltd.'s Kobe factory (72) Inventor Yoshikazu Ikemoto Hyogo 3-1-1 Higashikawasaki-cho, Chuo-ku, Kobe City Kawasaki Heavy Industries, Ltd. Kobe factory (72) Inventor Hirotsuna Kuchiki 3-1-1, Higashikawasaki-cho, Chuo-ku, Kobe City, Hyogo Prefecture Kawasaki Heavy Industries Ltd. (72) ) Inventor Tsuyoshi Kimura 3-1, 1-1 Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo Prefecture Kawasaki Heavy Industries Ltd. Kobe factory

Claims (1)

[Claims] 1. A surface of a metal piece is ablated by a hot scarf, a flaw on the surface after ablation is detected, and when a flaw is present on the surface of the abraded surface or near the peak,
In the area where the flaw exists, an abrasive water jet that is a mixture of abrasive grains and a liquid, obliquely with respect to the average virtual plane of the surface after fusing, while jetting, the length of the mountain A method for caring for a metal piece, which comprises moving along a direction and grinding to remove a flaw.