Metal deforming – With use of control means energized in response to activator... – Metal deforming by use of roller or roller-like tool element
Reexamination Certificate
1999-11-23
2001-07-31
Tolan, Ed (Department: 3725)
Metal deforming
With use of control means energized in response to activator...
Metal deforming by use of roller or roller-like tool element
C072S008300, C072S038000, C073S600000, C073S620000, C073S624000
Reexamination Certificate
active
06266983
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a flaw detecting method and an apparatus therefor suitable for detecting flaws in a strip while being carried.
Further, this invention relates to the manufacture of a hot-rolled sheet or a cold-rolled sheet, and, in particular, an inspecting method and a manufacturing method of a sheet. This invention also relates to a manufacturing equipment for a sheet.
2. Description of Related Art
In the area of manufacture and working of metallic and nonmetallic strips such as steel strips, there is a demand for a technique of online detection of flaws contained in strips to achieve quality control and quality assurance. The need is particularly for an apparatus capable of detection of internal fine flaws, and such an apparatus is generally known as a testing apparatus.
There is an another technique comprising, analyzing a specimen sampled from rolled steel strip, estimating the quality level of whole steel strip on the basis of the results of analysis, as disclosed in Japanese Unexamined Patent Publication NO. 08-184537 and NO. 10-185902. However, these techniques have no reliability in their application to the evaluation of steel strip with few internal flaws such as steel strip for cans, because the probability of sampling of internal flaws is extremely low.
Testing apparatus capable of continuously testing over the entire volume of a strip (such as a steel strip) that is carried continuously mainly include testing apparatus based on the magnetic leakage flux testing technique and testing apparatus utilizing ultrasounds.
The magnetic leakage flux testing technique comprises magnetizing a strip (typically a ferromagnetic metallic strip) by a magnetizing device and detecting leakage of the magnetic flux caused by flaws using a magneto-sensitive element such as a Hall-effect element, coil, or magnetic diode.
It is, however, impossible to test a strip having a thickness of over approximately 0.5 mm by the magnetic leakage flux testing technique. For a strip having a thickness as large as that of a hot-rolled steel sheet, the ratio (flaw cross-sectional area/steel sheet cross-sectional area) becomes smaller, and this makes it difficult for the magnetic flux to leak to the surface.
The magnetic leakage flux is rapidly attenuated in inverse proportion to the distance from the strip surface. It is therefore necessary to control upward and downward fluctuations of the strip pass-line within ±0.1 mm, and limit the gap between the detecting head and the strip surface within 0.5 mm. Because of the necessity of such a strict gap control, it is difficult to continuously and stably test the strip in transfer. Particularly, at a high carrying speed of the strip, the gap control is more difficult.
Another problem of the magnetic leakage flux testing technique is that a false detection can easily occur because of many noise factors. The magnetic leakage flux testing technique has a further limitation that is impossible to obtain accurate information of the shape of a detected flaw.
The ultrasonic testing technique comprises applying ultrasounds into a strip, thereby detecting reflection or shadow caused by internal flaws. Because it is possible to provide a large gap between the strip surface and the detecting head as compared to the magnetic leakage flux testing method, and detect flaws even in a thick strip, the ultrasonic testing technique is considered more suitable for the continuous testing of general strips.
There is also known a contacting ultrasonic testing technique known as the lamb wave testing technique. This technique is based on the detection propagating the lamb wave in the width direction of the strip through rolling contact of a wheel search unit (detecting head) with the strip surface. A disadvantage of this technique is its low detectability and the presence of a dead zone in the strip thickness direction. Further, it is practically impossible to test a wide range of the strip continuously in high speed transfer.
Because the lamb wave testing technique is a contact type technique, the probe may sometimes become bound and further, the medium between wheel search unit and the strip cannot be stably supplied at high transfer speeds of the strip. Thus, the carrying speed of the strip is limited within a low range. The lamb wave testing technique has another risk of bursting of the wheel.
An immersion (or soak or dip) testing technique, such as water immersion testing, is a non-contact testing technique and is free from the problems as described above. That is, there is available an advantage of a slight effect of fluctuations of the pass-line upon transfer of the strip.
For immersion testing using ultrasounds for the propose of detecting flaws such as inclusions for the entire volume of a strip such as a rolled metallic sheet, the following two techniques are proposed, having different arrangements of the ultrasonic probe (detecting head):
(1) A technique comprising testing a rolled metallic sheet while carrying the same, by arranging a plurality of ultrasonic probes in the width direction of the rolled metallic sheet to be tested, as disclosed in Japanese Unexamined Patent Publication No. 60-78345; and
(2) A technique of testing a rolled metallic sheet while carrying the sheet by scanning the rolled metallic sheet in a direction substantially at right angles to the carrying direction of the sheet with ultrasonic probes, as described above, arranged in the width direction of the rolled metallic sheet.
Of these two types of immersion testing techniques, the technique (2) inevitably takes the form of a batch testing, and for the practical online application on a production line of a strip, the technique (1) is more suitable.
The immersion ultrasonic testing techniques are classified in terms of the kind of the ultrasonic probe into a pulse-who technique using a transmitting/receiving probe, a pulse-who technique using a double crystal ultrasonic probe, and a transmission technique based on arrangement of transmitting probe and receiving probe face to face with a strip to be tested between them.
In general, however, the ultrasonic beam is focused into a spot (“spot focused,” for example, with a diameter of 1 mm) in these techniques for increasing the detectability of the flaws to a sufficient level. Consequently, in these techniques, a large number of probes are required corresponding to the testing area. Thus, the number of the parts for the detecting instrument is large, which increases cost. The pulse-echo technique has a disadvantage of the presence of a dead zone directly below the surface of the strip.
In view of the disadvantages of the above-mentioned techniques, the present inventors proposed a testing method as disclosed in Japanese Unexamined Patent Publication Nos. 7-253414 and Japanese Unexamined Patent Publication No. 11-083815, that solves the problems involved in the test using above-described spot focused ultrasonic probe requiring many probes for testing the full volume.
The proposed method comprises conducting the pulse-echo testing by configuring the flaw detecting heads (hereinafter referred to as “detecting heads”) in an immersion and transmission-type arrangement. The term “transmission-type arrangement” means arranging a transmitting head and a receiving head face to face with the strip to be tested between them.
This method comprises transmitting a line-focused ultrasonic beam in the thickness direction of the strip, and receiving a echo from the flaw with a receiving head including a probe array of piezoelectric elements arranged in the width direction of the strip to be tested.
More specifically, the transmitting head comprises line-focused transmitting probe arrays arranged in the width direction of the strip to be tested, and the receiving head comprises line-focused receiving probe arrays arranged also in the width direction of the strip to be tested. The transmitting probe array and the receiving probe array are arranged face to face on the opposite side of the strip. Part of u
Aratani Makoto
Iri Masato
Kuguminato Hideo
Miyake Hidenori
Okada Susumu
Kawasaki Steel Corporation
Oliff & Berridg,e PLC
Tolan Ed
LandOfFree
Method and apparatus for detecting flaws in strip, method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for detecting flaws in strip, method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for detecting flaws in strip, method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2560778