AU670573B2 - Grinding method and grinding system for billet - Google Patents

Description

OP! DATE 09/05/94 AOJP DATE 21/07/94 APPLN. ID 35748/93 PCT NUMBER PCT/JP93/00218 S1111111 111111111111 AU9335748 (51) [E1fi9t9) 5 (11) [5 X11 5 WO 94/08754 B24C 5/02, B26F 3/00 Al Al (43) IWiB E 1994*4 28H (28.04.1994) (21 N FT, E ft-9 POT/JP93/00218 W O (MINAMI, Ken j i J P/JP) (22) d I 199342A23t(23. 02. 93) 7804 t@bt'jWP*1 8 iTifl1it 1- %ViE*WAR&t± A09lVbAiP Fukuoka, (JP) at-Mi- P (74) fttlA IMTV4/283319 1992$10 F218(21. 10. 92) JP 31a &f f 0-6, t(ASAMURA,Kiyoshi et al.) f100 ET{~mft ffrTo2$1# (71)W A( t( ATMtO4eLlJn c t flbcfTreA-331 Tokyo, (JP) (KAWASAKI JUKOOYO KABUSHIKI KAISHA)CJP/JPJ (81) F I T650-91 AHr0We *ZJIIIBiTETOl1 1 Hyogo, (JP) AT(0RIft'*), AU, BE(Riq4.T), BR, CH(W.si#R), VfrB31*tjk#t ?±(NIPPON STEEL CORPORATION)CJP/JP) DE( rHi43f), DK(RRi4@14, ES PFR(r ri1ff, 100-71 X3;QaftM)Zt#31T634q Tokyo, (JP) OB(R0flR GR(r 1FF), IE(R 1fti), IT( IWfAF)., (72) 5f a KR, LU( Wi"3'T MOC( R1W*),N N L Ri1.), R9: th IM4/ 0Ai Kno P:T(:Ii SE(R) I fW), US.

*9tt I MATS UMURA, Hi r o y u k i C J P/JP) T651-22 A -mf*i t 2E- -1 2-6-10 Hyogo,(JP) I EE$1f fA *U I IKEMOTOYoshikazu)CJP/JP) 651-15 A *SVet 8Tt1196 Hyogo, (JP) it0I3I(TSUJITA, Kei ji)(JP/JP) 674 AH8 i1AEt2ME5W25-10 Hyogo, (JP) 'f C3 TANAKA, Hide t aka) CJP/J P) 7 0 5 7 3 2670 AWfiEAfM-1%cP23-8-29 Hyogo, (JP) ±az (DA ITOKU, Ka z umi CJ P/J P) Tflt.(SHIMOKASA,Tomoharu)(JP/JP) AT±rZt (NOGAMI, Fuj i y a) C J P/J P) (54) Title GRINDING METHOD AND GRINDING SYSTEM FOR BILLET (54) 0O)f0 4r±U31 t YktJ, (57) Abstract A grinding method, in which an abrasive material (6) is ejected from a nozzle 6 108) onto a billet W) so as to grind the same, and which is applied to a continuous casting step or a step subsequent there- 8 4 to, which method is characterized in that abrasive material- 9 mixed high-pressure water is applied in the form of a jet to 1O 2 the surface of a billet so as to grind a flaw-carrying portion 3 (12, 12', 12", thereof; and a grinding system for practising this grinding method, having a supply source (19-20, 103) of a high-pressure liquid and an abrasive material, a nozzle 102) connected to the supply source, and a combination of an abrasive material recovering unit (104) for recovering as necessary the abrasive material, which has been used for a grinding operation, and returning the same to the supply source, and a flaw de tecting means (15-16, 101).

B91 07 1 23/8 GRINDING METHOD AND GRINDING SYSTEM FOR STEELS The present invention relates to material surface crinding and, in particular, to a grinding method and system for grinding defective surface portions of steel products such as slabs, blooms and billets in continuous casting lines or ingot casting lines or the like and after-processes following the same.

Steel products such as blooms, slabs and i0 billets, formed by continuous casting or ingot casting processes, may develop various defects during their casting. Such defects will lead to a reduction in product yield and a deterioration in product quality in after-processes following the casting.

To cope with this problem, such defects are removed by reconditioning during or after the production of steel products such as slabs, blooms or billets, so that only steel products from which all defects have been removed are fed to the after-processes, thereby preventing a reduction in product yield and a deterioration in product quality.

Generally adopted means for reconditioning steel products are flame scarfing using a hot scarfer and 2 grinding using a grinder. An example of the flame scarfing method is shown in Japanese Patent Laid-Open No.

52-5644, according to which a gantry frame is arranged to have two supporting beams, on which two movable nozzle operation units for side and upper surface are mounted, respectively. Another example of the flame scarfing method is shown in Japanese Patent Laid-Open No. 52- 81048, according to which flame scarfing is performed by using a plurality of transversely arranged torches, making it possible to remove extensive defects without performing auxiliary flame scarfing in transverse direction at the beginning.

Regarding grinding using a grinder, an example thereof is shown in Japanese Patent Laid-Open No. 48- 46993, according to which billets, etc. are ground by using an abrasive wheel whose grinding performance is improved by employing a hydraulic or pneumatic cylinder.

Another example of the grinding method is shown in Jaanese Patent Laid-Open No. 1-242729, according to which cast stainless steels or other stainless steel products are reconditioned to effectively remove any defective portions therefrom in a specific temperature range, thereby avoiding the problem of the self-hardening property of stainless steels.

Apart from the above-described methods of removing defects through reconditioning by flame scarfing or grinding, various other reconditioning methods have been proposed which are mainly directed to descaling 3 during the production of steel products. For example, Japanese Patent Laid-Open No. 51-97894 discloses a method according to which a predetermined type of abrasive is sprayed through nozzles onto the surface of a stainless steel plate to effect wet grinding and descaling at the same time.

However, as will be discussed below, the abovedescribed steel product reconditioning methods have various problems.

Both the flame scarfing method disclosed in Japanese Patent Laid-Open No. 52-5644, in which a gantry frame is arranged to have two supporting beams, on which two movavle nozzle operation units for side and upper surface are mounted, respectively, and the method disclosed in Japanese Patent Laid-Open No. 52-81048, in which flame scarfing is performed by using a plurality of :ransversely arranged torches to make it possible to effect flame scarfing on extensive defects without performing auxiliary flame scarfing, have a problem in that the flame scarfing operation itself involves a high zemperature and a large amount of dust, causing a deterioration in working conditions. Moreover, with these methods, it is difficult to discriminate any defects remaining on the surface of the steel products after flame scarfing.

Further, in flame scarfing, it is impossible to control the scarfing depth, creating an unevenness.

4 Thus, some defects remain, but to prevent defects from remaining, the flame scarfing amount is increased, resulting in a reduction in yield.

Another problem with flame scarfing, compared with other types of methods, is that it requires equipment on a larger scale for automatizing the process to achieve an improvement in working conditions and operational efficiency, resulting in high costs.

Regarding grinding methods using a grinder, the above-described method disclosed in Japanese Patent Laid-Open No. 48-46993, in which billets, etc. are ground by using an abrasive wheel whose grinding performance is improved by employing a hydraulic or a pneumatic cylinder, and the method disclosed in Japanese Patent Laid-Open No. 1-24729, in which steel reconditioning by a grinder is performed on cast stainless steels or other other stainless steels in a specific temperature range; these methods involve, like the above-described flame scarfing methods, an operation under unfavorable conditions of high temperature and a large amount of dust depending upon the steel type.

Moreover, as in the above-described flame scarfing methods, it is difficult to discriminate any defects remaining on the steel surface after grinding, resulting in high defect-removal costs, etc.

Enlarging the grinder width results in a large amount of steel being unnecessarily ground and requires a 5 large driving power, which leads to an increase in running costs and a reduction in yield. On the other hand, reducing the grinder width results in a deterioration in efficiency because a large number of grinders are required, with the reconditioning time undesirably increased. The steel defect removal method such as disclosed in Japanese Patent Laid-Open No. 51- 97894, in which wet blasting are performed by spraying an abrasive through nozzles onto the surface of a stainless steel plate, is, at the present level of technology, mainly directed to descaling and, technically, still not sufficiently developed to be adopted in removing defects from steel products. Thus, it cannot be adopted, practically speaking.

The present invention has been made with a view toward solving the problems in the above-described conventional steel reconditioning techniques. It is accordinglys object of the present invention to provide an excellent steel grinding method which makes it possible not only to easily discriminate any defects remaining on the surfaces of steel products after grinding, such discrimination being important when improving working conditions and automating the steel production process, but also to selectively remove defective portions in accordance with the defect. Thus, a reduction in product costs is achieved, an improvement in yield is attained and, further, the product quality can be positively guaranteed, thereby contributing much NATIW\T\MNIYJ.A-9023.W.WI'D-4/6/96 -6to those fields of the iron industry.

According to a first aspect of the present invention there is provided a material surface grinding system for semiprocessed steel products such as slabs, billets and blooms produced in at least one of a continuous casting stage and stages subsequent to the continuous casting stage which system uses an abrasive water jet, comprising: a defect detection system including a first detector for detecting defects on a surface prior to grinding; an abrasive-water-jet-nozzle device adapted to make a relative movement with respect to a material surface; a supply system for supplying high-pressure-water and abrasive to the abrasive-waterjet-nozzle device; a recovery system for recovering used abrasive and recycling the used abrasive to the supply system; and a grinding controller for receiving information from the defect detection system and controlling operation of each of the abrasive-water-jet-nozzle device, the supply system and S: the recovery system.

According to a second aspect of the present invention there is provided a material surface grinding system for semiprocessed steel products such as slabs, billets and blooms produced in at least one of a continuous casting stage and stages subsequent to the continuous 20 casting stage which system uses an abrasive water jet, comprising: S(a) a defect detection system; an abrasivc-water-jet-nozzle device adapted to make a relative movement with respect to a material surface including: at least one nozzle; (ii) at least one nozzle driver for driving said at least one nozzle; and (iii) at least one nozzle driver controller, controlled by said grinding controller, and operating said at least one nozzle driver; a supply system for supplying high-pressure-water and abrasive to the abrasive-waterjet-nozzle device; a recovery system for recovering used abrasive and recycling the used abrasive to the supply system; and a grinding controller for receiving information from the defect detection system and C AN I Si 'IN'ATIVrRAN !ND\IA-9023.WiI) 41616 -7controlling operation of each of the abrasive-water-jet-nozzlc device, the supply system and the recovery system.

According to a third aspect of the present invention there is provided a method for removing surface defect portions on semiprocessed steel products such as slabs, billets and blooms produced in at least one of a continuous casting stage and stages subsequent to the continuous casting stage, comprising: detecting surface defect portions on said steel products produced in at least one of a continuous casting stage and stages subsequent to said continuous casting stage; ejecting at least one jet of fine abrasive particles mixed with high-pressure-water onto said surface defect portions in response to detection of said surface defect portions to remove said surface defect portions; and recovering and recirculating the abrasive for reuse in step The defect detection system for detecting defects on material surfaces employs a defect detecting device, which may consist of an image processing apparatus based on magnetic particle inspection or ultrasonic flaw detection, or an apparatus using a telecamera.

Grinding using an abrasive water jet employs a non-heating-type method. Therefore, the method does not involve surface-defect obscuration caused by the influence of heat or the melting of material surface portions, so that the detection of defects after machining is easy to perform. Further, since the turning ON/OFF of the machining operation is easy, no ignition 20 error as involved in flame scarfing occurs. In addition, due to the fact that the method adopts a non-contact-type machining means, the method is relatively free from service-life problems as compared with methods using grinding wheels, which makes it possible to easily construct an automated grinding system.

Moreover, when the sub-system for recovering the used abrasive is connected with the sub-system for supplying the abrasive to be mixed with a high-speed fluid jet, an abrasive circulation system is formed when the abrasive water jet is applied to the grinding of an extensive and continuous surface. A continuous operation is also possible when abrasive water jet nozzles, adapted to make a relative movement with respect to a plurality of steel products, are applied to the grinding of a wide material surface.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which: Fig. 1 is a schematic diagram showing how cutting is performed by using an abrasive water jet; Fig. 2 is a schematic diagram showing how partial cutting is performed by using the abrasive water jet; 5 Fig. 3 is a schematic diagram showing how surface grinding is performed by using the abrasive water jet; Fig. 4 is a sectional view of a part of a grinding Ssystem according to an embodiment of the present invention, showing how surface grinding is performed on the surface of a slab by the system; Fig. 5 is a partially sectional front view of the same; .oo a Fig. 6 is a plan view showing defects on the surface of a slab and how a nozzle is moved over them; Fig. 7 is a longitudinal sectional view of the same; Fig. 8 is a block diagram showing a slab grinding system according to an embodiment of the present invention; Fig. 9 is a plan view of a slab grinding system oe according to an embodiment of the present invention; Fig. 10 is a front view of part of the grinding system shown in Fig. 9; Fig. 11 is a side view of part of the grinding system shown in Fig. 9; Fig. 12 is a block diagram showing another embodiment of the present invention; Fig. 13 is a plan view of the embodiment shown in Fig.

12; Fig. 14 is a side view of Fig. 13; 950629,poper\kay,35748-93. 179,8 9- Fig. 15 is a front view of part of the eL'Lbodiment shown in Fig. 13; and Fig. 16 is a side view of part of Fig. Figs. 1 through 3 are schematic diagrams o 0**0 o 0 .00 0* 0 I 000 .0 00 0 0 0 .00 0 0* 0 0* 950629, pftoper~kay,3 574 8-93. 179,9 showing how a cast slab is ground by means of a highpressure water jet mixed with abrasive (an abrasive water jet). Numeral 1 indicates a nozzle of a so-called abrasive water jet apparatus. High-pressure water jet at a fixed pressure is supplied to a mixing chamber (not shown) and mixed with an abrasive in the form of fine particles, such as garnet sand, silica sand, alumina, iron san", or cast-iron grit to form a jet 2 having a fixed small diameter, which is expelled at ultra-high speed onto a steel slab 3 to be ground. Figs. 1 through 3 show how cutting (grinding) is performed when the relative traversing speed of the nozzle 1 with respect to the slab 3 (the nozzle feeding speed or the speed at which the slab 3 is fed) is varied.

Fig. 1 shows normal cutting, in which grinding is performed over the entire thickness t of the slab 3.

-n this case, the relative traversing speed of the nozzle is in a low-speed range which is low enough to enable the slab 3 to be cut in a satisfactory manner. Drag lines 4o are formed over the thickness t of the slab 3.

Fig. 2 shows a case in which the relative movement of the nozzle 1 and the slab 3 is made at a higher speed than in the case of Fig. 1. Here, the cutting is not effected over the entire thickness t of the siab 3, the cutting depth hl showing a fluctuation by a difference Ahl at the bottom portion formed by the cutting.

In the example of Fig. 3, the relative 11 traversing speed between the nozzle 1 and the slab 3 is even nigher than in the example of Fig. 2. The cutting depth h2 in this case is smaller than that in Fig. 2, At the same time, the fluctuation in depth Ah2 is also smaller thai that in Fig. 2, with the result that the bottom surface formed by the cut grooves are practically smooth, thus making it possible to perform the so-called groove grinding.

In the presen. v the above grinding principle and grinding-speed ranges of the abrasive water jet are applied to the grinding of the surface of a steel slab 3.

Further, i th rn invention, by adopting the above-described principle, the surface of the steel slab 3 is subjected, though microscopically, to a positive grinding action due to the the eroding effect of the abrasive grains in the ultra-high-speed water jet, thereby making it possible to remove defects under ideal conditions involving no generation of heat.

By the relative feeding of the nozzle 1 forming the above jet spout, it is possible to smooth the entire surface of the steel slab 3 by grinding it uniformly, or partially by selecting defective portions existing on or near the surface.

Further, due to the provision of the sub-system for detecting defects, etc. before and/or after the above-described grinding, it is possible to detect defects, etc. existing on or near the surface of the 12 steel slab 3, and the positions and sizes such defects. Information on these defects is .nput and fed back to be utilized in the grinding operation, whereby it is possible to stabilize the process for removing defects on the surface, etc. of steel. products and to positively guarantee the quality thereof and, further, to realize a completely automated working process.

Further, since the steel surfaces after grinding are not covered with oxide scales or the like, defect detection after grinding is relatively easy to perform.

Next, an embodiment of the present invention will be describe] with reference to the drawings from Fig. 4 onwards.

In the following description, the components which are the same as those of Figs. 1 through 3 will be referred to by the same reference numerals.

Figs. 4 and 5 show how the steel slab 3 is ground in accordance with an embodiment of the present invention, along with the construction of a nozzle head 4 of a side untrainment type. Abrasive 6 consisting of garnet sand or the like is supplied to a mixing chamber by a negative pressure due to the venturi effect of an ultra-high-speed water jet 9 generated at a water nozzle 8 connected to a high-pressure water piping 7. The water jet 9 and the abrasive 6 are mixed with each other in the interior of the abrasive nozzle i, which extends from the mixing chamber 10, accelerated and ejected from the 13 abrasive nozzle 1 onto a predetermined portion of the slab 3 as a jet 2 having a predetermined small diameter to grind the surface of the slab 3 in relative movement, based on the grinding principle described above.

In the above process, the axis of the abrasive nozzle 1 is held at the proper angle with respect to the slab 3 in accordance with the kind of the slab and the type of defect, and the abrasive nozzle is caused to make a relative movement with respect to the slab 3 while swinging or rotating at an appropriate speed and pitch so as to sufficiently cover the defects, etc. on the surface, thereby effecting a desired grinding, etc.

In an experiment, the abrasive was supplied at a speed of 0.5 kg/min or more, and the high-pressure water was supplied at a pressure of 1000 kgf/cm 2 or more and a flow rate of 2 lit./min., the working distance between the nozzle and the steel being not more than 200 mm. In this case, the inpinging angle with respect to the slab 3 ranged, for example, from 10 to 1700, and the relative speed between the slab 3 and the abrasive nozzle 1 when the abrasive nozzle was swung or rotated was approximately 1 to 10 m/min. Under these conditions, very satisfactory results were obtained. Such conditions, however, somewhat differ depending upon the kind of slab, the type of defect and the kind of abrasive 6, etc.

Figs. 6 and 7 show in more detail an example of the way the abrasive nozzle 1 is operated. As shown in 14 the drawings, to cope with defects 12, 12', 12" and 12"', various kinds of swinging mo-es for the abrasive nozzle 1 can be combined in terms of grinding range, direction and pitch.

In the embodiment shown in Fig. 7, an appropriate rounding is effected in the boundaries between the surface portions 3' where grinding is performed on the defects 12, 12', 12" and 12"' and the surface portions and 3" where no grinding is performed, in order that extremely large differences in thickness may not be generated between these portions.

The abrasive nozzle 1 can also perform grinding as in the above case by a rotation within an appropriate radius, instead of swinging, and pitch feed.

Next, Fig. 8 is a block diagram showing the entire system including an inspection process. In the system shown, an articulated robot is used as a driving device 13 for the abrasive nozzle 1. Searching results obtained at an inspection stage 14 prior to grinding by a defect detecting mechanism 15 consisting of a CCD camera or the like are input to a defect detection system 16 as information on the defects 12, etc. on the slab 3 (in terms of location, size, depth, etc.), grinding being automatically performed in a grinding (scarfing) stage 17 in accordance with the information.

The entire surface of a continuous casting steel product is scanned with a telecamera by a camera driving device which operates in accordance with signals 15 from a camera drive controller in a defect detection system, thereby obtaining defect information in terms of size, configuration, area, depth, etc. The image processing apparatus in defect detection system performs coordinate transformation on the location of any defect and, on the basis of the coordinates thereby obtained, he location is settled as an address on the steel surface. The information from the image processing apparatus in terms of configuration, depth, grinding range, procedures and location, is input to a collectivecontrol computer in grinding controller. The input information is supplied to the grinding system to be used as driving instructions for controlling a nozzle drive controller, an abrasive supply system and high-pressurewater generator, etc. to cause the high-pressure fluid nozzle for abrasive water jetting to traverse the steel surface by means of a guide mechanism working on an address basis to perform grinding.

It is possible, as needed, to perform inspection by an optical inspection means during and after the grinding by using the defect detection mechanisms 15' and 15" and the defect detection system 16, utilizing the detection results for feedback during grinding or for re-grinding.

Further, this embodiment adopts a system in which the used abrasive 6 is recovered and supplied to an abrasive feeding device 19 for re-utilization, the 16 fragmental abrasive being separated and removed by a recovery/re-feeding device 18.

Numeral 20 indicates a high-pressure water generator; numeral 7' indicates a high-pressure water piping; numeral 21 indicates a nozzle drive controller; numeral 22 indicates a grinding controller for overall grinding control; numeral 23 indicates waste abrasive; numeral 24 indicates new abrasive; and numeral indicates an inspection stage. Figs. 9, 10 and 11 show external views of the entire system of the embodiment shown in Fig. 8, in which three articulated robots cooperate to continuously grind the surface of a steel slab 3 or the like in an average tact time of 7 minutes.

The slab 3 is fed in the direction indicated by the arrows.

Next, another embodiment of the present invention will be described with reference to Figs. 12 through 16.

The system shown in the drawings comprises a defect detection system 101, an abrasive-water-jet-nozzle device 102, a supply system 103 for supplying highpressure water and abrasive to the nozzles, and a recovery system 104 for recovering the used abrasive and re-feeding the same to the supply system 103.

Information from these systems are input to a grinding controller 105, and the input information is used for controlling the systems by a judgment function of the grinding controller 105.

17 The slab W to be ground is processed through three stages: inspection stage SI, grinding stage S2 and inspection stage S3. One of the inspection stages S1 and S3 may be omitted.

The defect detection system 101 comprises a defect detection system 111 for detecting defects on the slab surface prior to grinding, a defect detection system 112 for detecting surface defects during grinding, and a defect detection system 113 for detecting defects on the slab surface after grinding for the next process. The surface defect conditions in each of these stages are detected, and information thereon is input to the grinding controller 105, the abrasive nozzle device 102 and the supply system 103 being controlled in accordance with variations in the information.

The abrasive water jet nozzle device 102 comprises a nozzle drive controller 106 controlled by the grinding controller 105, and nozzles 108 driven by a nozzle driver 107.

Figs. 13 through 16 show a specific system arrangement for Lhe system shown in Fig. 12.

The system shown comprises: a supply system 103 consisting of a high-pressure water generator 31 and an abrasive supply device 32 shown in Fig. 12; and front and rear nozzle devices 121 and 122 for respectively grinding the upper and lower surfaces of slabs, which are reversed by a reversing device 42. Each of the nozzle devices 121 and 122 has three nozzles 108 arranged along 18 the longitudinal dimension of the slabs W produced by a continuous casting machine 41. Each nozzle 108 is attached to the tip of a 6-axis articulated robot 125 provided on a nozzle guide 124 arranged on a base 123 astride a slab moving bed 109. Each nozzle 108 is driven and controlled by the nozzle drive controller 106 and the nozzle driver 107 shown in Fig. 12.

A robot and an NC device can be used as the driving devices for the nozzles 108. One or a plurality of articulated robots may be installed on the floor, ceiling or walls, or in a combination of these installation locations. The driving devices may be stationary or, as in the example shown in the drawings, capable of travelling along one axis or more. The abrasive nozzle head may be of a direct injection type, in which the abrasive and water are mixed at high pressure beforehand and expelled at high pressure through the nozzle in a slurry-like state. Further, the nozzles may be operated so as to move in a variety of rotating and swinging movements.

As described above, in accordance with the present invention, a high-pressure water jet is mixed with abrasive and expelled against steel products, thereby making it possible to perform automatic grinding by devie useF.

without contactA Thus, conventional defect removal means, such as flame scarfing and wheel grinding, which have been manually performed under severe working conditions involving noise and heat, can be dispensed 19 w-hn, thus leading to a marked improvement in working conditions (by realizing an unmanned working process, etc.) In addition, the method of the present invention provides the excellent effect of making it possible to positively remove any defects existing on or near the surface of a steel product, the removal being effected in a stable manner and to a desired depth without involving any fusion or deterioration of the material caused by heat. Further, by utilizing the abrasive circulation

C.

system as needed, an excellent system can be provided in which it is possible to perform a continuous operation without deteriorating the function of the abrasive water jet itself, which leads to saving of resources and a reduction in cost.

Thus, the present invention provides an excellent machining means for the removal of steel surface detects, which removal has tended to become more and more necessary due to the recent increase in demand for higher quality materials.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such S• as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.

950629,p:\opcr\kay, 3 5748-93. 179,19

Claims (13)

1. A material surface grinding system for semiprocessed steel products such as slabs, billets and blooms produced in at least one of a continuous casting stage and stages subsequent to the continuous casting stage which system uses an abrasive water jet, comprising: a defect detection system including a first detector for detecting defects on a surface prior to grinding; an abrasive-water-jet-nozzle device adapted to make a relative movement with respect to a material surface; a supply system for supplying high-pressure-water and abrasive to the abrasive-water- jet-nozzle device; a recovery system for recovering used abrasive and recycling the used abrasive to the supply system; and a grinding controller for receiving information from the defect detection system and controlling cperation of each of the abrasive-water-jet-nozzle device, the supply system and the recovery system. I A material surface grinding system according to claim 1 wherein said supply system S. comprises a high pressure water generator and an abrasive supply device.

3. A material surface grinding system according to claim 1 wherein said defect detection system includes an image processing apparatus based on ultrasonic flaw detection.

4. A material surface grinding system according to claim 1 wherein said defect detection system uses a telecamera. A material surface grinding system according to any one of claims 1 to 4 wherein said defect detection system further comprises a second detector for detecting defects on a surface during grinding.

6. A material surface grinding system according to any one of claims 1 to 5 wherein said defect detection system further comprises a third detector for detecting defects on a surface after \-5/6196 -21 grinding.

7. A material surface grinding system for semiprocessed steel products such as slabs, billets and blooms produced in at least one of a continuous casting stage and stages subsequent to the continuous casting stage which system uses an abrasive water jet, comprising: a defect detection system; an abrasive-water-jet-nozzle device adapted to make a relative movement with respect to a material surface including: at least one nozzle; (ii) at least one nozzle driver for driving said at least one nozzle; and (iii) at least one nozzle driver controller, controlled by said grinding controller, and operating said at least one nozzle driver; a supply system for supplying high-pressure-water and abrasive to the abrasive-water- jet-nozzle device; a recovery system for recovering used abrasive and recycling the used abrasive to the supply system; and a grinding controller for receiving information from the defect detection system and controlling operation of each of the abrasive-water-jet-nozzle device, the supply system and *the recovery system.

8. A material surface grinding system according to claim 7 wherein said supply system comprises a high pressure water generator and an abrasive supply device.

9. A material surface grinding system according to claim 7 wherein said defect detection system includes an image processing apparatus based on ultrasonic flaw detection. A material surface grinding system according to claim 7 wherein said defect detection system uses a telecamera.

11. A material surface grinding system according to claim 7 wherein said at least one nozzle driver comprises at least one robot. .ST l'l NI'l\AMIINIIA-1021.WI') -,IIR/, -22-

12. A material surface grinding system according to claim 7 wherein said at least one nozzle driver is stationary.

13. A material surface grinding system according to claim 7 wherein said at least one nozzle driver is capable of driving along one or more axes.

14. A method for removing surface defect portions on semiprocessed steel products such as slabs, billets and blooms produced in at least one of a continuous casting stage and stages subsequent to the continuous casting stage, comprising: detecting surface defect portions on said steel products produced in at least one of a continuous casting stage and stages subsequent to said continuous casting stage; ejecting at least one jet of fine abrasive particles mixed with high-pressure-water onto said surface defect portions in response to detection of said surface defect portions to remove said surface defect portions; and recovering and recirculating the abrasive for reuse in step A method as claimed in claim 14 further comprising the step of inspecting surfaces of said steel products produced in at least one of a continuous casting stage and stages subsequent to the continuous casting stage during or after the step

16. A method according to claim 14 or 15 wherein said at least one jet is ejected through at least one nozzle.

17. A method according to any one of claims 14, 15 or 16 wherein defects detected in step are subjected to coordinate transformation by a defect detection system and at least one high-pressure liquid ejecting nozzle is driven and moved in response to information obtained through the coordinate transformation by said defect detection system. DATED this fourth day of June 1996 NIPPON STEEL CORPORATION KAWASAKI JUKOGYO KABUSHIKI KAISHA %:By DAVIES COLLISON CAVE SRegistered Patent Attorneys for the Applicant(s) v<" p ABSTRACT Disclosed are a grinding method in which abrasive is projected onto a steel product W) through a nozzle 108) to perform grinding thereon such as in a continuous casting process or in a subsequent process, wherein high-pressure water jet mixed with the abrasive is projected onto the surface of the steel product to grind defects (12, 12', 12", 12"' on the surface, etc. thereof, and a grinding system for executing this grinding method, the system including supply souirces of high-pressure liquid and abrasive (19- 103), a nozzle device 102) connected with these supply sources, an abrasive recovery device (104) for recovering the used abrasive as needed and restoring the same to the supply sources, and cumbined detection systems (15-16, 101)