JPH0682426A - Flaw detection method for wire rod surface cutting work line - Google Patents

Abstract

PURPOSE:To secure a user demand level about a flaw on a surface in on-line by detecting a flaw, which deeper than a cutting margin, by an eddy current flow detector before cutting, and after a sizing process. CONSTITUTION:A wire rod, which is produced by rolling, is sized and machined to meet such a size and size precision as to enable a flaw detection or cutting work as a following process to be carried out. After a sizing process, a flaw is detected by an eddy current flaw detector. Although there are some flaws, which are removable by cutting work in the following process, during this flow detection, the detection is carried out in the depth which is deeper than a cutting margin for the purpose of detecting a flaw which is not removable in cutting work. As the flaw remaining after cutting is large enough to be detected, the flaw can be detected surely even when the detection precision is reduced by vibration of the wire rod. In this way, the quality which meets the demand of a user can be secured by the inspection in the surface cutting work line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for flaw detection of a wire rod in a surface cutting line capable of simultaneously inspecting surface flaws when cutting the surface of the wire rod.

[0002]

2. Description of the Related Art Most of the wire rods manufactured by hot rolling are products having a desired shape by cold forging and cutting after secondary processing such as surface cutting (peeling etc.) and wire drawing. Is finished. In particular, when cold forging is performed after secondary working, if a flaw remains on the surface, the critical working rate is greatly reduced, cracking occurs after working, and it cannot be used as a product. In addition, even when the surface after secondary processing is used as it is as a product, if there are flaws on the surface, not only the commercial value will decrease, but also the strength as a product will decrease, which may cause a problem. is there.

Furthermore, the as-rolled wire has a decarburized layer on its surface, and it is not preferable in terms of quality if this decarburized layer is present in the final product. Therefore, in order to solve the above problems, the wire rod is hot-rolled, and then the surface is cut to remove surface defects such as scratches and decarburized layers, and surface flaws are inspected by a method such as eddy current flaw detection. However, it is necessary to ensure quality.

In the flaw inspection process such as the eddy current flaw detection,
It is necessary to inspect over the entire length, and when the surface is cut by peeling or the like, the accuracy of flaw detection due to flaw detection greatly decreases due to vibration of the wire and change in the surface skin due to cutting. Therefore, the defect inspection is conventionally performed at the time of drawing, which is the final step of the secondary processing.

[0005]

Problems to be solved by the invention have the following problems when a flaw inspection is performed in the drawing process. That is, depending on the user's request, the wire rod may be collectively pulled up by the steel material manufacturer up to the final step of secondary processing, or may be pulled out by the user. Further, even when the steel material manufacturer performs the drawing, there are cases where the material is drawn out by requesting the subcontractor and cases where it is not.

When performing a flaw inspection in such a situation,
It is necessary to install a flaw detection device for each of a large number of drawing machines installed in steel mills, subcontractors, and steel mill factories, resulting in large capital investment and maintenance costs. Also,
In the case of a wire rod product that is not drawn, it is difficult to guarantee flaws.

In order to solve the above problems, it is unavoidable to carry out a flaw inspection at the time of surface cutting such as peeling, which allows a full length flaw inspection other than at the time of drawing. In other words, the ratio of surface cutting processing performed by users and outsourcers is lower than that of drawing processing, so if flaw inspection is possible, it will be possible to perform flaw inspection with a small number of flaw detectors, and equipment cost will be reduced. It is possible to suppress the problem and it becomes easy for the steel material manufacturer to guarantee the quality.

However, as described above, if a flaw inspection is carried out during surface cutting such as peeling, a change in the surface skin due to the processing (a tool mark or the like is generated) and a vibration of the wire material during the cutting will cause flaw detection. Since the accuracy is greatly reduced, it is not possible to guarantee the flaw depth condition required by the user. Therefore, at present, the flaw inspection by the eddy current flaw detector is performed only at the time of drawing, which is the final step of the secondary processing, only for the wire material with which the quality is particularly required.

It is an object of the present invention to solve the above-mentioned problems and to provide a flaw detection method for a wire rod in a surface cutting processing line, which can surely guarantee a user-required level regarding surface defects.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on a method for enabling flaw detection within a surface cutting processing line. And the fact that a flaw remains after cutting means
It was considered to be limited to the case where a flaw having a depth equal to or greater than the cutting allowance was present before cutting. Therefore, after the sizing step and before the cutting, the flaw was confirmed again with respect to the wire rod which was subjected to flaw detection with a eddy current flaw detector to a depth equal to or more than the cutting allowance, and then subjected to the cutting process. As a result, it was confirmed by inspection before cutting that defects after cutting could be guaranteed, and the present invention was completed.

The reason why flaws can be guaranteed after cutting by the inspection before cutting is as follows. The wire rod vibrates irrespective of before and after the cutting work, and this vibration has a bad influence on the flaw detection accuracy as described above. However, in the case of flaw detection after cutting, while the flaw detection accuracy of the quality required by the user (for example, a flaw depth of 0.05 mm or less) is required,
Before cutting, it is sufficient if flaws deeper than the cutting allowance can be detected (for example, if the cutting allowance is 0.20 mm, if a flaw of 0.25 mm or more can be detected, a flaw depth of 0.05 mm or less can be guaranteed). Therefore, the flaw inspection can be accurately performed even if the accuracy of flaw detection is lowered due to vibration.

The wire rod flaw detection method of the present invention obtained by the above-described study is a method of cutting the surface of a wire rod while detecting the presence or absence of microscopic flaws on the surface of the wire rod. It is characterized in that after the sizing step of finishing the wire rod to an intermediate size for improving the dimensional accuracy, the presence or absence of surface flaws is inspected by an eddy current flaw detector, and then cutting is performed.

The present invention is intended for all processing methods for cutting the surface of a wire, such as a peeling process for cutting the cutting tool while rotating it around the wire and a method for cutting with a peeling die.

In the present invention, it is essential that flaw detection be performed after the sizing step. Since flaw detection is difficult with dimensional accuracy as rolled, the sizing step is an essential step for enabling flaw detection. As the sizing method in the present invention, a method using a roller, a drawing die or the like can be used.

In the flaw detection process of the present invention, it is necessary to detect a flaw from the surface to a depth equal to or more than the cutting allowance. Therefore, it is necessary to appropriately adjust the frequency of the alternating current flowing in the flaw detection coil according to the cross-sectional dimension of the wire and the cutting allowance.

[0016]

In the method of the present invention, first, the wire rod manufactured by rolling is subjected to the sizing process, and then the wire rod is processed to a dimension and a dimensional accuracy that allow flaw detection and cutting in the subsequent steps. And
After the sizing process, a flaw inspection is performed with an eddy current flaw detector. At the time of this flaw inspection, there are also flaws that can be removed by cutting in the post-process, but especially for the purpose of detecting flaws that cannot be removed by cutting, a flaw inspection is performed on the depth above the cutting allowance from the surface. I do. Since the flaws remaining after cutting are sufficiently large before cutting, even if the inspection accuracy deteriorates due to the vibration of the wire rod, it can be reliably detected.
Therefore, it is possible to guarantee the quality that satisfies the user's request by the inspection in the surface cutting processing line.

[0017]

【Example】

The features of the present invention will be described below with reference to examples. In order to perform the experiments described below, high carbon chromium bearing steel S produced by melting in an electric furnace and hot rolling was performed.
A UJ2 wire rod was prepared. The wire diameter of the wire is 13.0 mm.
Next, the wire rod was subjected to spheroidizing annealing so as to have a property capable of being subjected to subsequent secondary processing, and used as a test material for the test shown below.

In the test, artificial flaws are attached to the surface of the test material in advance, the wire with the artificial flaw is subjected to eddy current flaw detection, and the flaw remaining after the surface cutting by peeling can be detected by flaw detection. I went by the method of confirming whether or not. Further, in order to accurately confirm the effect of the present invention, tests were carried out on both the conventional flaw detection method of flaw detection on a wire after cutting and the method according to the present invention.

The eddy current flaw detector used is a probe rotation type device, which uses a probe coil as a coil, and has a detection effective width of 2.5 mm. This probe is 9000r.p.
While rotating at a speed of m., the test material was moved straight to the center position of the rotation at a speed of 50 m / min to perform flaw detection on the portion having the artificial flaw. The frequency of the alternating current supplied to the probe was 300 kHz.

At the time of surface cutting and flaw detection, a wire rod as a test material was used for 12.6 mm by sizing from a wire diameter of 13.0 mm.
Then, the final dimension was 12.2 mm (cutting allowance 0.20 mm) by processing to mm and then peeling. Therefore, assuming that the flaw depth does not change due to sizing, flaws having a depth of more than 0.20 mm before cutting will remain after cutting. Further, the type of artificial flaw was an axial square groove (slit), and the depth was set to three levels of 0.25 mm, 0.30 mm, and 0.35 mm, and the depth that remained after cutting was set. Then, the flaws of the respective depths were set at predetermined positions on the surface of the test material, and the test was carried out according to the procedure described above. Table 1 shows the test results.

[0022]

[Table 1]

In Table 1, ◯ indicates that detection was possible, and x indicates that detection was not possible. The depths of the flaws shown in Table 1 are values before cutting by peeling.

As is apparent from Table 1, the conventional method can detect only flaws having a depth of 0.35 mm or more before cutting (corresponding to flaws having a depth of 0.15 mm or more after cutting) and 0.25 mm before cutting. , 0.30mm flaw (after cutting, depth is 0.05m
m, equivalent to a 0.10 mm flaw) could not be detected. It is considered that this is because, as described above, the peeling process detects a flaw in a state where the wire material vibrates greatly, so that the detection sensitivity is lowered and the flaw which is shallow due to cutting cannot be detected. In addition, as for the wire rod after the test, as a result of visually confirming the places where the artificial flaws were initially attached, it was confirmed that the flaws remained at all the places. Therefore, in the conventional method, the flaws remaining after cutting are also overlooked.
On the other hand, when the flaw detection was performed by the method of the present invention, it was confirmed that all the artificial flaws described above could be detected.

In the method of the present invention, flaw detection is performed immediately after sizing and before cutting, and the wire rod after cutting is not inspected. Therefore, it is not confirmed whether there is any final flaw. Therefore, in order to confirm the reliability of the inspection method according to the present invention,
Wires having different artificial flaws (depth, position, number, etc.) were manufactured, and the flaw detection method of the present invention was repeated in the same manner as in the above-mentioned Examples. Then, the flaw detection results were analyzed in detail in order to check whether there were any flaws that could not be detected by the flaw detection. As a result, it was confirmed that all defects existing after cutting could be detected without overlooking.

[0026]

As described above, according to the flaw detection method of the present invention, after sizing, the presence or absence of surface flaws before cutting is inspected by an eddy current flaw detector to remove surface flaws in a cutting line such as peeling. It became possible to carry out the inspection of. With the development of the present invention, since it is not necessary to perform a flaw inspection in the conventional drawing process, it is possible to perform a flaw inspection without installing a flaw detection device for each pulling machine owned by a user or an outsourcer. This makes it easier to guarantee defects.

Claims (1)

[Claims] 1. A method of cutting a surface while detecting the presence or absence of microscopic flaws existing on the surface of the wire, the method comprising: a sizing step of finishing the wire before cutting into an intermediate dimension to improve dimensional accuracy. A method for flaw detection of a wire rod in a surface cutting processing line, which comprises inspecting for the presence of surface flaws with an eddy current flaw detector and then performing cutting processing.