JPH06331565A - Dignostic method of welded part of thin plate - Google Patents

Abstract

PURPOSE:To diagnose the soundness of a welded part in a noncontact manner and in a nondestructive manner by a simple mechanism during a welding operation by finding the ratio of the infrared reflected-light intensity difference of two specific wavelengths detected from the welded part of steel thin plates to the reflected-light intensity difference of two wavelengths detected from a steel-plate matrix part. CONSTITUTION:Steel plates 5 are irradiated with infrared rays from an infrared light source 11, reflected-light intensities Rn(lambda1), Rn(lambda2) near a specific wavelength lambda1=14mum and near a specific wavelength lambda2=18mum from a steel-plate matrix which is not affected thermally at all are detected 12, and their difference Sn is stored in a signal processing device as a reference value. Then, after a welding operation has been started, reflected-light intensities Rw(lambda1), Rw(lambda2) of the same wavelengths lambda1, lambda2 are detected 12 from a surface oxide-film region J in a steel-plate welded part K which has been discolored to be blackish as compared with the surface of the preform due to the thermal influence of a welding current, and the ratio of their difference Sw to the difference Sn is computed. Then, it is possible to judge whether a prescribed input heat quantity is supplied to the welded part K or not and whether the speed of electrode wheels 7A, 7B is normal or not. Consequently, the soundness of the welded part can be diagnosed quickly while the welding operation is being constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for diagnosing the soundness of a welded portion of a thin plate and a bonding state, and more specifically, a continuous annealing line, a continuous pickling line, a continuous hot dip galvanizing line, a continuous coating in a steel process. Non-destructive diagnosis of welding conditions and welding conditions near the weld line of thin plates after payoff reel in continuous processing processes such as lines, and welding conditions in spot welding during thin plate processing such as welding of automobile bodies. The present invention relates to a diagnostic method for nondestructive diagnosis.

[0002]

2. Description of the Related Art It is important from the viewpoint of product quality control to check the welding conditions and welding conditions of the welded portion in the welding process in the iron and steel industry, the non-ferrous metal industry such as aluminum, and the metal processing industry. As a checking means, a means for continuously inspecting a welded part online to diagnose the soundness of the welded part is widely adopted.

In a process such as a continuous annealing line in a steel rolling process or a continuous hot dip galvanizing line in which thin plates are continuously processed while running, in order to connect the thin plates (preceding plate and succeeding plate) to each other during the process. The welded joint is welded to and the integrity of the welded joint is diagnosed, but this weld joint diagnosis must be done promptly online.

For example, in the case of a continuous hot dip galvanizing line, as shown in FIG. 1, a steel plate 5 (subsequent plate) supplied from a payoff reel 1 is welded to a preceding plate being processed by a welding machine 2 and conveyed. However, the permissible time for this welding is restricted by the discharge of the material stored in the entry-side loop car 3 provided in front of the annealing furnace 4. Therefore, it is necessary to quickly perform weld diagnosis online.

In the welding in this case, as shown in FIG. 2, after cutting the tip of the thin plate 5 with a cutting machine (shear), the tip is slightly overlapped and fixed by a clamp 18, and the overlapped portion D is formed. It is performed by welding in the width direction while applying pressure with the upper and lower electrode wheels 7A.

At present, most of the welded parts diagnosis under online condition visually judge whether or not the alteration of the welded part K is caused by the operator hitting the welded part at a point A with a hammer or the like. Method (hereinafter referred to as hammering method)
The same applies to the continuous processing process of thin plates other than the above plating line.

On the other hand, as schematically shown in FIG. 3, there is a welded portion diagnostic method to which a so-called Erichsen test method is applied. This method cuts off a welded portion in order to set welding conditions, applies a jig to the welded portion to deform the welded portion, and determines whether or not a fracture E occurs. However, this method cannot be used online.

[0008]

The above-mentioned conventional hammering method is a kind of destructive test, and it causes deformation of a normal welded portion, and of course impedes labor saving. Various problems still remain, such as the difficulty of making a precise diagnosis, the inability to perform a quantitative evaluation, and the long line down time. Furthermore, since the structure of the welding machine is inherently complicated and it is difficult to secure the space for installing the necessary sensors around it, it is a simple structure and is a non-destructive, non-contact type diagnostic technology. The reality is that the development of

By the way, conventionally, as a nondestructive inspection method for material defects, (A) ultrasonic flaw detection test, (B) radiation transmission test (X-ray transmission imaging), (C) magnetic flaw detection test (leakage magnetic flux / magnetic powder flaw detection test) ), (D) There are eddy current flaw detection tests, but (A) requires a contact medium between the ultrasonic probe and the material to be inspected, and applying it immediately after welding causes the joint to cool rapidly. ,
Inappropriate because it is hardened and deteriorates, (B),
(C) is difficult to apply due to problems such as long inspection time and low sensitivity, while (D) has high detectability of defects near the surface, but keeps lift-off from the steel plate surface constant. When applied online, it is very difficult because of problems such as being caught at the edge of the steel sheet and roughening the surface quality of the joint. Therefore, these conventional inspection methods have various problems in practical use.

The present invention has been made by paying attention to such an actual situation, and its purpose is to solve the above-mentioned problems and to immediately perform non-destructive, non-contact immediately on-line while continuing welding. It enables the soundness diagnosis of the welded part by using the method, does not require the contact medium, does not cause the problem of deterioration due to the rapid cooling of the welded part, and has a simple structure that is excellent in practicality and suitable for general purposes. Another object of the present invention is to provide a method for diagnosing a welded portion of a thin plate.

[0011]

The present invention has the following constitution in order to achieve the above object. That is, the present invention is a method for diagnosing a welded portion that is performed online in a welding step in a continuous processing process of a steel thin plate, irradiating the welded portion of the thin plate with infrared light, and from the reflected light, a wavelength Around λ ₁ = 14 μm, wavelength λ ₂ = 18 μ
The reflected light intensities Rw (λ ₁ ) and Rw (λ ₂ ) of two wavelengths around m are detected and the difference Sw = Rw (λ ₁ ) −Rw (λ ₂ ) is calculated. The reflected light intensities Rn (λ ₁ ) and Rn (λ ₂ ) are similarly detected by irradiating the part with infrared light, and the difference S
By calculating n = Rn (λ ₁ ) −Rn (λ ₂ ), and calculating the ratio of the difference Sw and the difference Sn, the heat input amount on the steel plate surface caused by the factor of the heat input amount variation to the joint due to welding is calculated. It is a method for diagnosing a welded part of a thin plate, which is characterized by obtaining a change and estimating the soundness of welding and a bonding state of a welded part from the value of the heat input amount under the online welding.

[0012]

The welded part to which the method of the present invention is applied is illustrated in FIG. On the left and right sides of the welded portion K, there are a weld heat affected zone F (hatched portion) and a surface discolored portion G. The welding heat-affected zone is a quench-hardened portion (hereinafter referred to as heat-affected zone). Incompletely joined states when welding conditions are inaccurate include joint cracks I and base metal cracks H. The causes of this incompletely joined state are (1) that a predetermined welding current value cannot be obtained and a sufficient width of the heat-affected zone F cannot be maintained.
(2) Oxide film existing on the joint, insufficient heat generation, insufficient joint reduction, etc. on the surface / inner part of the joint crack I. (3) From the cross-sectional states of A, B and C in FIG. As can be seen, the superposed portion is crushed and greatly deformed, and there is a base material crack H or the like that occurs at that time.

On the other hand, the surface of the joint portion (nugget portion) formed by welding is discolored in an apparent blackish color as compared with the surface of the peripheral base material portion due to the heat effect of the welding current, and an area having an oxide film as shown in FIG. It is known that J is formed.
When the infrared light is irradiated to the portion of the oxide film region J and the intensity of the reflected light is detected, depending on the state of formation of the oxide film,
The reflected light intensity changes in a specific wavelength range. Further, the absorption amount of infrared light in the oxide film region J also changes, and as shown in the wavenumber-reflectance diagram of FIG. 6, the reflectance near a certain wavenumber W ₁ , In other words, it is clear that the absorption rate fluctuates greatly. From the above, by detecting the intensity of the reflected light, it is possible to know the mode of the region of the heat-affected zone in the nugget portion. In addition, the reflected light intensity of the infrared light in the specific wavelength region in the oxide film region J largely depends on the welding conditions. For example, when a normal welding current value cannot be obtained, even if the current value is normal. This will change depending on the case where the speed of the electrode wheel becomes high and insufficient heat input to the joint occurs.

By the way, since there is a difference in the reflected light intensity of the irradiated infrared light between the surface of the steel sheet base material which is not affected by heat at all and the surface of the oxide film region, there is a difference between the two surfaces due to the difference. Although it is possible to recognize the difference, in order to accurately recognize the oxide film area based on the difference in hue without being affected by other factors such as the rough surface of the surface, reflection of two wavelengths is required. It is desirable to obtain the difference in light intensity and compare by the difference. As shown in FIG. 7, the difference in reflected light intensity between two types of wavelengths specified as the heat input to the welded joint using the welded sample. As is clear from the test result of examining the relationship with, a linear function relationship is established between the reflected light intensity difference and the relative heat input.

Focusing on the fact that a resistance welding machine such as a narrow lap seam welding machine conducts welding by applying a high current to its electrode, the size of the heat affected zone F and the surface discolored zone G as shown in FIG. It is known from the test results on the weld sample that the width of the is proportional to the welding current value. However, the electrode wheel speed is constant. On the other hand, regarding the problem of the strength of the joint portion due to the size of the heat affected zone F and the width of the surface discolored zone G, FIG.
Judging from the results of the Erichsen test as shown in
It is clear that welding at a current value lower than the predetermined welding current value by about 5% has a large effect on the welding current because cracks are formed at the joint interface.
In addition, in the case of a good bonded state, when an Erichsen test is performed, cracks are formed perpendicularly to the bonded interface.

By performing the method of the present invention on the joining state in the welded portion described above, the soundness of the welded portion is immediately diagnosed in a non-destructive, non-contact manner immediately after that while continuing the welding while continuing the welding. You can also
At this time, the contact medium is not required, the deterioration of the welded portion is not caused, and the soundness can be diagnosed with a simple structure. Therefore, it is excellent in practicality and suitable for general use.

That is, according to the method of the present invention, the difference in the two-wavelength reflected light intensity or the difference in the absorption amount of the infrared light radiated to each of the oxide film area formed on the surface of the joint and the steel sheet base material is detected,
By calculating the ratio, it is possible to judge whether a predetermined heat input is supplied to the joint, and also whether the speed of the electrode wheel is normal. Can be quickly diagnosed below. Such a diagnostic method is a non-destructive method and a non-contact method,
Further, since the contact medium is not required, the deterioration of the welded portion or the like is not caused, and the structure is simple.
It is not only practical but also suitable for general purposes.

[0018]

EXAMPLES Examples of the present invention will be described below. FIG. 8 schematically shows the structure of the welding portion diagnostic device mounting portion in the welding machine according to the embodiment of the present invention. Further, FIG. 9 shows a configuration of the welded part diagnostic device 9 in FIG.
The welder in this example is a narrow lap seam welder,
With respect to the housing 6 of the main body, a pair of upper and lower electrode wheels 7A and 7B are provided in front and back with reference to the welding direction (the direction of the outline arrow).
The welding electrode and the reduction rolls 8A and 8B, which are realized in, are attached respectively. The welder diagnostic device 9 is provided in the welder at a position 50 to 200 mm on the welding line behind the reduction rolls 8A and 8B. The welded part diagnosis device 9 is formed to include an infrared light source 11, a detector 12, and a control part 13, and is fixed to the tip of a welded part copying mechanism 10 attached to the housing 6.

The detector 12 includes a light receiving portion 14 and a chopper 1.
5. A motor 16 for rotating the chopper 15 is provided. The chopper 15 has three windows as shown in FIG. 9B, two of which are filters (filtering filters). 19) and 20 are attached respectively, and the other one
A dark filter 21 is attached to one of them, and when it is rotated by the motor 16, three windows alternately move in front of the lens of the light receiving unit 14 to move. on the other hand,
The control unit 13 includes a signal processing device 17 that introduces an optical signal from the light receiving unit 14 and electrically processes the signal, and a controller 18 that controls the start and stop of the light receiving unit 14 and the motor 16.

Regarding the infrared optical system of the welded part diagnostic device 9, infrared light is emitted from the infrared light source 11 to irradiate the steel plate 5, and the reflected light generated by this is rotated by three filters 19, 20. , 21 through which light is received by the light receiving section 14 periodically. At this time, as shown in the graph of FIG. 10, the light receiving unit 14 receives light in synchronization with the synchronization signal P _S. Here, the signal processing device 17 has two wavelengths in the steel sheet base metal portion as reference values which are detected and calculated in advance by the weld portion diagnosis device 9, that is, λ ₁ (near 14 μm) and wavelength λ ₂ ( Difference in reflected light intensity around 18 μm) Sn = Rn (λ
₁ ) -Rn (λ ₂ ) is stored. Then, after the start of welding, the difference in the reflected light intensities of the same two wavelengths in the surface oxide film area J of the steel plate welded portion, Sw = Rw (λ ₁ ) −Rw (λ ₂ ) is calculated as the signal processing device 1.
After the calculation in step 7, the ratio Sw / difference Sw / Sn of the difference Sw /
Calculate Sn.

Further, n points are measured in the width direction of the steel sheet, and the moving average (1 / n) Σ (Sw / Sn) is calculated by the signal processor 17. Welded part diagnostic device 9 thus obtained
The difference in the state of formation of the oxide film area J on the surface of the joint due to welding based on the output signal from the infrared optical system of By comparison, it is possible to diagnose the soundness of the weld. The standard at this time is to confirm the joint strength by an Erichsen test and a tensile test.

[0022]

The method for diagnosing a welded portion of a thin plate according to the present invention comprises:
While continuing welding, immediately after that, the soundness of the welded part can be immediately diagnosed by the non-destructive and non-contact method. Furthermore, the contact medium is not required, the deterioration of the welded part is not caused, and the soundness of the welded part can be diagnosed with a simple structure, which is excellent in practicality and suitable for general use. It is a thing.

Therefore, a continuous annealing line in the steel rolling process,
In a continuous treatment process such as a continuous hot-dip galvanizing line, it is possible to prevent plate breakage during sheet passing, which is caused by insufficient welding current and defective welding, accompanying the welding process of thin plates.
Further, the time required for the inspection can be shortened as compared with the conventional hammering method. Furthermore, the automation of the inspection makes it possible to promote the automation of the production process, significantly reduce the work load, and contribute to the rationalization of production. The effect of improving quality without scratches is achieved.

[Brief description of drawings]

FIG. 1 is a process schematic diagram of a continuous hot-dip galvanizing line.

FIG. 2 is a perspective view for explaining the welding situation in the welding process in the line shown in FIG. 1 together with cross sections of a steel plate overlapping portion and a joint portion.

FIG. 3 is a sequential explanatory view of an Erichsen test method for evaluating fracture resistance of a welded portion.

FIG. 4 is an enlarged sectional view of a joint portion of a welded portion.

FIG. 5 is a perspective view showing an oxide film region of a joint portion of a welded portion.

FIG. 6 is a diagram showing the relationship between the wave number of infrared light applied to a steel sheet and the reflectance.

FIG. 7 is a diagram showing the relationship between the relative heat input and the reflected light intensity difference in the oxide film region of the welded portion.

FIG. 8 is a schematic structural diagram of a welding portion diagnostic device attachment portion in the welding machine according to the embodiment of the present invention.

9 is a schematic structural diagram of a welded part diagnosis device 9 in FIG.

10 is a graph showing an optical signal output state of the light receiving section 14 in FIG.

[Explanation of symbols]

5--steel plate, 9 ... weld diagnostic device,
11 ... Infrared light source, 12 ... Detector, 13 ... Control unit,
14 ... Light receiving part,

Claims (1)

[Claims] 1. A method for diagnosing a welded portion which is carried out online in a welding process in a continuous processing process of a thin steel plate, wherein the welded portion of the thin plate is irradiated with infrared light, and a wavelength λ is obtained from the reflected light. ₁ = around 14 μm, wavelength λ ₂ = 18 μ
The reflected light intensities Rw (λ ₁ ) and Rw (λ ₂ ) of two wavelengths around m are detected and the difference Sw = Rw (λ ₁ ) −Rw (λ ₂ ) is calculated. The reflected light intensities Rn (λ ₁ ) and Rn (λ ₂ ) are similarly detected by irradiating the part with infrared light, and the difference S
By calculating n = Rn (λ ₁ ) −Rn (λ ₂ ), and calculating the ratio of the difference Sw and the difference Sn, the heat input amount on the steel plate surface caused by the factor of the heat input amount variation to the joint due to welding is calculated. A method for diagnosing a welded part of a thin plate, which comprises determining a change and estimating the soundness of welding and a bonding state of a welded part from the value of the heat input amount under online welding.