JP2001318004A - Device and method for measuring molten droplet temperature distribution in arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely measure a temperature or a temperature distribution of a molten droplet. SOLUTION: A beam emitted from the molten droplet D in the arc welding is separated into two spectral beams by triangular prisms 14, 15 as beam splitters. The first filter 19 and the second filter 20 are arranged in spectral beam emitting sides of the beam splitters to transmit separately the spectral beams of two wavelengths λ1, λ2 neighoring each other. Brightness of the beam of the wavelength λ1 transmitted through the first filter is detected by a camera unit 3, and brightness of the beam of the wavewlength λ2 transmitted through the second filter is detected by another camera unit. The temperature distribution of the droplet is computed and output by a personal computor 5 based on brightness signals of the beams of the wavelengths λ1, λ2 provided by the two camera units 3, 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for measuring a droplet temperature distribution in arc welding using two-color radiation temperature measurement.

[0002]

2. Description of the Related Art Gas metal arc (GMA) welding such as mag welding is a welding method that can be used for mechanization and robotization, and is highly efficient.
It is widely used for welding mild steel and high-tensile steel in the field of manufacturing shipbuilding and industrial machinery. In GMA welding, a welding wire serves as an electrode for arc discharge. The welding wire as an electrode is melted by the arc heat to form droplets. The molten metal separates from the wire end and moves to the base metal, filling the groove or forming a surplus portion to become a weld metal. At the same time, since the droplet is heated to a temperature equal to or higher than the melting point, it also contributes to the melting of the base material and greatly affects quality such as penetration. In addition, it has been pointed out that metal vapor is generated from the surface of a high-temperature droplet, which becomes fumes harmful to the human body and deteriorates the working environment. Reduce fumes,
In order to ensure stable welding quality, it is necessary to suppress excessive heat input. For that purpose, it is necessary to clarify the correlation between parameters such as welding current and the droplet temperature.

[0003]

Heretofore, a GMA arc has been generated using a welding wire on the anode and a dig torch on the cathode side, and the droplet has been collected on a calorimeter to estimate the temperature. According to this method, it is possible to grasp the tendency that the average retained heat of the droplet increases as the current value is increased. However, in order to estimate the droplet temperature from the retained heat, values such as specific heat and emissivity are required. These values vary significantly depending on the temperature, and thus it is difficult to ensure accuracy and reliability. In addition, in order to control the welding current waveform according to the workpiece thickness, shape, welding posture, etc., and to ensure welding quality in a clean working environment, the relationship between parameters such as current value and droplet temperature is important. Need to be revealed. For that purpose, it is difficult with the conventional method, and it is necessary to measure the droplet temperature during welding on the spot.

An object of the present invention is to provide an apparatus and a method for measuring a droplet temperature distribution of arc welding based on a non-contact optical method.

[0005]

The inventors of the present invention focused on the fact that the energy of thermal radiation radiated from an object depends on the surface temperature of the object, and described this relationship as Planck's radiation law and two-color radiation temperature measurement. By elucidation by the method, the droplet temperature distribution measuring apparatus and droplet temperature distribution measuring method of the present invention were established.

That is, the apparatus for measuring the temperature distribution of droplets of arc welding according to the present invention comprises a beam splitter for dispersing light emitted from droplets of arc welding into two light beams, and two wavelengths λ1 which are close to each other. a first filter and a second filter arranged on the spectral beam exit side of the beam splitter for separately transmitting the light beams of λ2;
First light detecting means disposed on the output side of the first filter transmitting the first light beam and detecting the luminance of the light beam of wavelength λ1, and the output side of the second filter transmitting the light beam of wavelength λ2 A second light detecting means disposed for detecting the luminance of the light beam having the wavelength λ2, and a luminance signal of the light having the wavelengths λ1 and λ2 obtained by the first and second light detecting means as an input signal. Calculating means for calculating and outputting the temperature of the droplet based on the formula.

[0007]

(Equation 5)

Here,

[0009]

(Equation 6)

E (λ, T): Spectral emission divergence of the droplet (W
/ M3) ε (λ, T): Spectral emissivity (0 to 1) 1 for black body Eb: Spectral emissivity of black body (W / m3)

[0011]

[Formula 7]

The Planck constant h = 6.6256 × 10−3
4 [J · s] Boltzmann's constant k = 1.38054 × 10−17 [J
· K-1] c1 = c2 h = 5.9548 c2 = ch / k = 0.014388 [m · K] In an actual measurement system, a relationship in which an optical system such as a beam splitter or first and second filters is used. Thus, the heat radiation light emitted from the droplet by these optical systems is attenuated. Therefore,
In order to measure the droplet temperature distribution in consideration of the light attenuation characteristics of all optical systems, a function representing the light attenuation characteristics of the all optical systems including the beam splitters through which the light of the droplets passes with respect to the light of the wavelengths λ1 and λ2 Is F (λ), and the irradiance ratio R
The above-mentioned droplet temperature is calculated based on the following equation representing (T).

[0013]

(Equation 8)

U: Upper limit of the wavelength to be measured L: Lower limit of the wavelength to be measured In analyzing the formation process of the thermal spray coating, the droplet speed is an important particle property as well as the droplet temperature. The speed can be easily measured by combining the first or second light detecting means with a trigger means for a camera shutter.

Further, the method for measuring the temperature distribution of droplets of arc welding according to the present invention is characterized in that the light radiated from the droplets of arc welding is reduced to two.
Splitting the light into two beams, separately filtering light of two wavelengths λ1 and λ2 close to each other from the two beams, and detecting the luminance of the light of the wavelength λ1 and the luminance of the light of the wavelength λ2. Process and the wavelengths λ1 and λ
Calculating the temperature distribution of the droplet based on the relationship of the above formulas 1 to 3 using the luminance signal of the light of No. 2 as an input signal. When calculating the temperature distribution of the droplet, the temperature distribution is calculated on the basis of the relationship of Equation 4 in consideration of the optical attenuation characteristics of the optical system.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an apparatus for measuring a droplet temperature distribution in arc welding according to the present invention. In the figure, 1 is a condenser lens unit, 2 is a spectral unit, 3 and 4 are camera units, and 5 is a computer as arithmetic means.

The condensing lens unit 1 is a combination of a plurality of lenses in the optical axis direction. The condensing lens unit 1 condenses radiated light radiated from a droplet of arc welding and introduces the radiated light into the spectroscopic unit 2. The spectral unit 2 includes an L-shaped housing 6, a plurality of lenses 7 to 13 housed inside the housing 6, and a prism 1.
4 to 18 and filters 19 and 20. More specifically, a first lens 7 is provided to face the condenser lens unit 1, and a pair of triangular prisms 14 and 15 constituting a beam splitter are provided on the secondary side of the first lens 7. One of the light beams that have been split by the triangular prisms 14 and 15 and reflected at right angles is the second lens 8, the third lens 9,
The light is introduced into the camera unit 3 as first light detection means through the triangular prism 16, the first filter 19, and the fourth lens. In addition, the triangular prisms 14 and 1
The other light beam split by 5 goes straight as it is and passes through the fifth lens 11, the triangular prisms 17 and 18, the sixth lens 12, the second filter 20, and the seventh lens 13 to another light beam as second light detecting means. It is designed to be introduced into the camera unit 4.

Each of the camera units 3 and 4 has a high-speed and high-sensitivity black-and-white imaging type CCD device, and has
Any pixel (for example, 1 pixel out of 68 pixels × 493 pixels)
The luminance data of (00 pixels × 100 pixels) can be taken in and output to a personal computer.

In the droplet temperature distribution measuring apparatus configured as described above, the condenser lens unit 1 is set to face the tip of the wire of the welding torch T as shown in FIG. Since a droplet is formed at the wire tip of the electrode E of the welding torch T, the droplet is imaged by the CCD elements of the camera units 3 and 4.

There is a specific correlation between the wavelength of light emitted from the droplet and its divergence (luminance) for each temperature of the droplet surface. Figure 2 shows an example of this correlation for the heat radiation emitted from a black body in accordance with Planck's radiation law. Even at the same wavelength, the divergence differs for each temperature, and the divergence increases as the temperature increases. I understand. A normal object is not a black body, and the wavelength dependence of radiant energy is smaller than the energy emitted by a black body at the same temperature, unlike FIG. 2, and is given by the following equation.

[0021]

(Equation 9)

E (λ, T): Spectral radiant emittance of the droplet (W
/ M3) ε (λ, T): Spectral emissivity (0 to 1) 1 for black body Eb: Spectral emission divergence of black body (W / m3) where Eb (λ, T) on the right side is It is expressed by the following equation.

[0023]

[Formula 10]

Planck constant h = 6.6256 × 10−3
4 [J · s] Boltzmann's constant k = 1.38054 × 10−17 [J
· K-1] c1 = c2 h = 5.9548 c2 = ch / k = 0.014388 [m · K] Since the emissivity varies depending on the temperature, wavelength, atmosphere, surface condition, etc. even for the same material, it is general. Must be obtained in advance. However, the two-color radiation thermometry described below
If the emissivity of an object whose unknown emissivity can be regarded as constant in a narrow wavelength band, light of two wavelengths can be selected, and the temperature can be determined from the ratio of the respective radiant emittance. That is, the spectral emissivity of the object at the temperature T differs depending on the wavelength, but if the two wavelengths λ1 and λ2 are close to each other,
Since it can be assumed that ε (λ1, T) = ε (λ2, T), the droplet temperature (distribution) can be obtained from the ratio of the radiation divergence by the following expression using Expressions 2 and 3. .

[0025]

[Equation 11]

However, in an actual measurement system, various lenses, filters, prisms, and the like are used to select a specific wavelength, so that the heat radiation emitted from the droplet is attenuated through these, and the camera unit 3, 4 is introduced.
Optical elements such as lenses have wavelength dependence as shown in FIGS. 3A to 3C. For example, the camera units 3 and 4 have characteristic curves of wavelength versus sensitivity as shown in FIG. , Second
The filter 20 has a wavelength dependence as shown in FIG. 3B, and the first filter 19 has a wavelength dependence as shown in FIG. Therefore, the ratio of irradiance R (T) observed throughout the measurement system is expressed by the following equation.

[0027]

(Equation 12)

Here, U is the upper limit of the wavelength to be measured, and L
Is the lower limit of the wavelength to be measured.

[0029]

As described above, according to the present invention, light beams of two adjacent wavelengths are extracted from the heat radiation emitted from the droplets of arc welding, and the emissivity is determined from the ratio of the spectral radiation emittance (brightness) of these light beams. The droplet temperature (distribution) can be measured without having to calculate the fog, which can provide useful data for analyzing the fume generation process and help to ensure welding quality in a clean work environment. .

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a droplet temperature distribution measuring device showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between wavelength and spectral radiation divergence (luminance).

3A is a characteristic curve of wavelength versus sensitivity of a camera unit, FIG. 3B is a curve showing a wavelength dependence of light transmittance of a first filter, and FIG. 3C is a wavelength dependence of a second filter; Is a relationship curve of wavelength versus light transmittance, which indicates

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Condensing lens unit 2 Spectrum unit 3, 4 Camera unit (1st and 2nd light detection means) 5 Personal computer 6 Housing 7-13 Lens 14-18 Triangular prism T Welding torch E Electrode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B23K 31/00 B23K 31/00 K (72) Inventor Atsushi Muramoto 2-1-1 Taoyuan, Ikeda-shi, Osaka No. 1 Daihatsu Industry Co., Ltd. (72) Inventor Naoyoshi Koji 2-1 Yamadaoka, Suita-shi, Osaka Prefecture F-term (Reference) 2G066 AA04 AC20 BA14 BA23 BC15 CA02

Claims (5)

[Claims] 1. The light emitted from a droplet of arc welding is applied to
A beam splitter that splits the light into two light beams, a first filter and a second filter that are disposed on a spectral beam output side of the beam splitter to separately transmit light beams of two wavelengths λ1 and λ2 that are close to each other; First light detection means disposed on the emission side of the first filter that transmits the light beam of wavelength λ1 to detect the brightness of the light beam of wavelength λ1, and emission of the second filter that transmits the light beam of wavelength λ2 A second light detecting means disposed on the side for detecting the luminance of the light beam having the wavelength λ2; and a luminance signal of the light having the wavelengths λ1 and λ2 obtained by the first and second light detecting means as an input signal. And a calculating means for calculating and outputting the temperature distribution of the droplet based on the following equation. [Formula 1] Where: E (λ, T): Spectral radiant emittance of droplet (W / m3) ε (λ, T): Spectral emissivity (0 to 1) 1 for black body Eb: Spectral radiant emittance of black body ( W / m3) [Formula 3] Planck constant h = 6.6256 × 10−34 [J ·
s] Boltzmann's constant k = 1.38054 × 10−17 [J
· K-1] c1 = c2 h = 5.9548 c2 = ch / k = 0.014388 [m · K] 2. When the function representing the light attenuation characteristic of the entire optical system including the beam splitter through which the light of the droplet passes with respect to the light of the wavelengths λ1 and λ2 is F (λ), the irradiance ratio R 2. A droplet temperature distribution measuring apparatus for arc welding according to claim 1, wherein the droplet temperature is calculated based on the following equation representing (T). (Equation 4) U: Upper limit of wavelength to be measured L: Lower limit of wavelength to be measured 3. The droplet temperature distribution and droplet velocity are measured by combining said first or second light detecting means and a trigger means of a camera shutter.
The droplet temperature distribution measuring device for arc welding according to the above. 4. The light radiated from the droplets of the arc welding is set to 2
Splitting the light into two beams, separately filtering light of two wavelengths λ1 and λ2 close to each other from the two beams, detecting the luminance of the light of the wavelength λ1 and the luminance of the light of the wavelength λ2 A luminance signal of the light having the wavelengths λ1 and λ2 as an input signal;
Calculating a temperature distribution of the droplets based on the relations of Expressions 1 to 3 of claim 1. 5. The method for measuring a droplet temperature distribution of arc welding according to claim 4, further comprising a step of calculating a droplet temperature distribution based on the relationship of the mathematical expression 4 of claim 2.