JP2006136904A - Apparatus and method of laser beam welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam welding apparatus which can carry out excellent welding work by taking into consideration the dispersion of joint clearances before the welding work. <P>SOLUTION: The shape of a bead B is measured just after welding by means of a bead shape measuring apparatus 11. Then, the underfill b of the bead B is calculated in real time by means of a control unit 1 based on the measured data. Then, a target value of the underfill is compared with the value of the measured underfill. When the value of the measured underfill is larger than the target value of the underfill, the speed for supplying a wire is increased stepwise, and also the welding speed is reduced stepwise. On the contrary, when the value of the measured underfill is smaller than the target value of the underfill, the speed for supplying the wire is reduced stepwise, and also the welding speed is increased stepwise. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser welding apparatus and a laser welding method in which a filler wire is used in combination as a filler material, and in particular, the shape of a bead immediately after welding is measured in parallel with the welding operation, and the amount of filler wire supplied according to the measurement result The present invention relates to a laser welding apparatus and a laser welding method in which welding conditions such as the above are variably controlled.

As is well known, laser welding is a welding method based on local heating, and therefore, heat input to the base metal and welding distortion are small, and it is frequently used for butt welding, lap welding, and the like. On the other hand, since laser welding melts and joins only the heat input part of the base metal, the amount of molten metal in the molten pool is small, and the gap tolerance between the base metals as a welded joint (gap margin) (Also, the gap tolerance) is small. For example, when a filler wire is not used at the time of lap welding of a thin steel plate having a thickness of about 1 mm, the clearance tolerance is said to be about 0.3 mm. Therefore, generally, as described in Patent Document 1, the gap tolerance is increased by using a filler wire as a filler material. In the above example, the gap is about 0.3 mm. It is said that the tolerance can be expanded to about 1.0 mm.
Japanese Patent Laying-Open No. 2003-71583 (FIG. 5)

  However, when trying to increase the clearance tolerance by using filler wire as described above, the welding speed is at most half that of the case where filler wire is not used at the maximum. In the case of lap welding or fillet welding, which is often used for welding steel plates, it is effective to increase the clearance tolerance unless appropriate welding conditions are set according to the degree of joint clearance, especially the wire supply rate and welding speed. Is not sufficiently obtained, and in some cases, the appearance of the bead may be extremely deteriorated.

  Further, in the technique described in Patent Document 1, even if it is assumed that the supply amount of filler wire, the welding speed, and the like are variably adjusted, the adjustment is performed according to the state of the groove before welding. Because it only adjusts the amount, etc., it cannot be applied to lap welding or fillet welding, which is often used for welding thin steel sheets, and there are still problems in improving and stabilizing the welding quality. .

  The present invention has been made paying attention to such problems, and measures the shape of the bead after welding to obtain an actual underfill, and variably controls the supply amount of the filler wire and the like according to the measurement. The present invention provides a laser welding apparatus and a laser welding method which are intended to increase the speed and improve and stabilize the welding quality. In particular, the present invention takes into account the variation in the size of the gap in advance even if there is a variation in the size of the gap (joint gap) between the base materials that is difficult to grasp quantitatively in lap welding or fillet welding. The present invention provides a laser welding apparatus and a laser welding method capable of performing satisfactory welding.

  According to the first aspect of the present invention, there is provided a laser optical system for irradiating a welding site with laser light, wire supply means for supplying a filler wire to the welding site, and the shape of the bead immediately after welding in parallel with the welding operation. For example, non-contact type bead shape measuring means, and the amount of filler wire supplied during the welding operation so that the actual underfill obtained from the measurement data of the bead shape measuring means is within a predetermined range, and And a control means for variably controlling the welding speed.

  That is, the invention according to claim 1 pays attention to the correlation between the joint gap and the underfill, which are difficult to grasp quantitatively anyway, and under certain conditions, even if the joint gap varies, the under-bead after welding Phil is based on the assumption that it is constant.

  The variable control of the supply amount of the filler wire includes a case where the supply of the filler wire is stopped. This is because, for example, when the gap between the base materials forming the lap joint is very small, proper welding may be performed under a good bead without supplying the filler wire. It is.

  Here, when the welding form is lap welding or fillet welding, as described in claim 3, it is possible to provide gap correction means for correcting a gap between the base materials at the welded portion. It is preferable for minimization.

  According to a fourth aspect of the present invention, in addition to the bead shape measuring means, a penetration degree measuring means for measuring the degree of penetration of the bead on the back side of the bead is provided, and the control means includes an actual underfill amount. It is desirable that the welding wire supply amount and the welding speed be variably controlled in accordance with the degree of penetration of the beads.

  Further, the invention described in claim 5 is substantially the same as the invention described in claim 1 as a welding method, and irradiates the welded portion with laser light and supplies a filler wire to the same portion. During welding, the shape of the bead immediately after welding is measured in parallel with the welding operation, and the filler wire is measured so that the actual underfill obtained from the measurement data of the bead shape is within a predetermined range. The supply amount and the welding speed are variably controlled.

  Therefore, in at least the first and fifth aspects of the invention, the amount of filler wire supplied and the welding speed are set so that the measured underfill obtained as a result of measuring the shape of the bead immediately after welding is within a predetermined range. By actively performing variable control, for example, even if there are variations in the gaps between the base metals, which are joint gaps, the overall welding conditions are optimized, and the welding quality is improved throughout the entire weld line.

  According to the first and fifth aspects of the present invention, the filler wire supply rate and the welding speed are positively set so that the measured underfill obtained as a measurement result of the bead shape immediately after welding is within a predetermined range. Even if there are variations in the gaps between the base materials, the overall welding conditions are optimized, so that high-speed welding is possible while using filler wires together. As well as improving, welding quality can be improved and stabilized.

  FIG. 1 shows the case of lap welding as a more specific embodiment of the present invention.

  As shown in FIG. 1, a laser beam 3 output from a YAG laser oscillator 2 in accordance with an instruction (laser output command, depth of focus command, etc.) from a control device 1 as control means is guided to a laser optical system 5 through an optical fiber cable 4. The laser beam 3 is condensed by a condenser lens 6 that forms a part of the laser optical system, and then welded (welded) at the overlapping portion between the base materials (members to be welded) W1 and W2. The part) P is irradiated.

  An integrated laser head 7 is configured using the laser optical system 5 as a base body, and a filler wire 8 as a filler material is supplied to the laser head 7 through a wire guide 9 as a wire supply means. A bead shape measuring device 11 as a bead shape measuring means is attached to each of the wire feeding device 10 and the laser head 7 at a predetermined speed in the welding direction with respect to the base materials W1 and W2 according to an instruction from the control device 1. It will be welded by moving. In addition, an assist gas may be used in combination as necessary.

  The wire supply device 10 is controlled by a wire supply speed command from the control device 1, and as is well known, a laser beam is sent while feeding a filler wire 8 through a wire guide 9 at a predetermined speed by a motor-driven roller (not shown). The filler wires 8 are sequentially supplied into the molten pool 12 formed at the irradiation site (welding site) P.

  The bead shape measuring device 11 is directed to the position of the bead B immediately after welding, that is, the rear position of the molten pool 12 formed by the irradiation of the laser beam 3, and the shape of the bead B immediately after welding is changed in a light amount or image without contact. For example, a laser sensor or the like is used. The bead shape measuring device 11 receives reflected light from the surface of the bead B and acquires profile data of the bead B surface. Then, the measurement data of the bead shape measuring device 11 is taken into the control device 1, and the internal processing is performed with the depth of the depression formed on the surface of the bead B in addition to the width dimension a of the bead B as shown in FIG. A certain underfill b is calculated in real time, and the wire supply amount and the welding speed as the supply amount of the filler wire 8 are variably controlled according to the size of the measured underfill b, as will be described later. As shown in FIG. 2B, for example, underfill b can be calculated in the case of butt welding of base materials W3 and W4, which are differential thickness steel plates.

  Here, as shown in FIGS. 3 to 6, the wire supply amount, which is the supply amount of the filler wire 8 when the welding speed and the width a of the bead B formed as a result of the welding are changed in four stages, and welding. The relationship with the size of the possible joint gap G was examined. The laser output and the focal length of the condenser lens 6 were constant. Here, the wire supply amount is managed by the wire supply speed.

  As shown in FIG. 2, the underfill b is the depth of the depression formed on the surface of the bead B, and there is a correlation as shown in FIG. 7 between the underfill b and the strength of the welded joint. In order to ensure stable welding quality, it is necessary to manage the underfill b to be within a predetermined range. As is apparent from FIGS. 3 to 6, in order to achieve a good welded state (indicated as “OK” in FIGS. 3 to 6), the underfill b is set to 0. 0 regardless of the welding speed and the bead width a. It must be 1 to 0.2 mm. On the other hand, as shown in FIG. 8A, when the surface of the bead B is raised (excessive) without becoming a depression, the bead B is not formed and is not welded because the joint gap is excessive. The probability of being in a state is high. This tendency can be said not only in the case of lap welding in FIG. 10A but also in the case of butt welding and fillet welding in FIGS.

  Further, as apparent from FIG. 2, the fact that the bead B penetrates to the back surface of the base material W2 (base materials W3 and W4 in the case of butt welding shown in FIG. 2B) is also a strength of the welded joint. 2 and 9, when the penetration width c penetrates the entire width of the bead b (the width dimension a in FIG. 2A) is assumed to be 100%, It has been found that the strength as a welded joint is sufficient when the back surface penetration rate is in the range of 10 to 100% (for example, about 0 to 0.5 mm). On the contrary, even if the back surface penetration rate of the bead B exceeds 100%, only the filler wire 8 is consumed only by increasing the bead width b together with the penetration width c, which is disadvantageous in terms of cost.

  Therefore, in FIG. 3 to FIG. 6, the condition indicated by “☆ (star)” is “underfill b is in the range of 0.1 to 0.2 mm” and “bead B has a back surface penetration rate of 10 to 100%. It is an optimum condition that satisfies “within the range of”. Here, Table 1 is an excerpt of only the conditions indicated by stars in FIGS. 3 to 6, and the supply amount of the filler wire 8 is minimized according to the size of the joint gap G, and The conditions when the welding speed is maximized and the shape of the bead B under the conditions are shown. That is, from Table 1, although the joint gap G and the width a of the bead B are proportional, the underfill b is constant regardless of the size of the joint gap G and the width a of the bead B. Understandable.

  In this embodiment, the range is set as a target value so as to satisfy the condition of “underfill b is in the range of 0.1 to 0.2 mm”, and the supply speed and welding speed of the filler wire 8 as the wire supply amount. Are variably controlled. In other words, as is apparent from FIGS. 3 to 6, when the joint gap G is different even at the same welding speed, there are a plurality of regions where “underfill b is in the range of 0.1 to 0.2 mm”, and FIG. Since it is possible to further increase the welding speed in the region other than the asterisks of ˜6, the welding speed corresponding to the supply amount of the filler wire 8 is set in advance as shown in Table 1.

  More specifically, in the state of FIG. 1, a molten pool 12 is formed in the vicinity of the irradiated portion of the laser beam 3, and the molten metal resolidifies on the rear side of the molten pool 12 with the movement of the laser beam 3, and the bead B is formed. Since the shape of the bead B is measured, the bead shape measuring device 11 measures the shape of the bead B, and based on the measurement data, the control device 1 measures the undersize of the corresponding part of the bead B (see FIG. 2) and the measured under. Fill b is calculated in real time. Further, the control device 1 compares the preset target value of the underfill b with the actually measured underfill b. If the actually measured underfill b is larger than the set target value, the filler wire as shown in Table 1 is used. The wire supply speed, which is the supply amount of 8, is increased stepwise (the wire supply amount is increased), and the welding speed is decreased stepwise accordingly.

  On the contrary, when the measured underfill b is smaller than the set target value, the wire supply speed is decreased stepwise (increase the wire supply amount) as shown in Table 1, and the welding speed is increased stepwise accordingly. Increase to.

  Further, as shown in Table 1, when the wire supply speed (wire supply amount) is “0”, the underfill b also becomes “0”, and when the filler wire 8 is supplied, the underfill b is changed. Instead, if the bulge as shown in FIG. 8A exceeds the allowable limit of 0.2 mm, for example, it is judged that unwelding as shown in FIG. Processes such as signal generation and alarm stop. It should be noted that the above-described allowable limit value for swell is set in advance.

  Similarly, in parallel with the processing as described above, the set target value of the width dimension of the bead B set in advance for each welding speed in Table 1 is compared with the measured bead width a, and the measured bead width a is determined. If it is out of the set target value range, there is a possibility that the laser output is reduced, the focus is abnormal, etc., so that processing such as generation of an abnormal signal and alarm stop is performed as described above.

  Thus, even if the shape of the bead B after welding changes due to the change in the joint gap G, welding can always be performed under almost ideal welding conditions according to the size of the joint gap G, and the filler wire 8 Therefore, it is possible to optimize the supply amount and to weld at the maximum allowable welding speed.

  In the lap welding of galvanized steel sheets, if the joint gap G is not always ensured, porosity (group of small blow holes in the weld metal) is generated, resulting in poor welding. In such a case, for example, the filler wire 8 is supplied in a very small amount (very low speed) even under conditions where welding is possible without supplying the filler wire 8 as shown in the uppermost table of Table 1. Welding shall be performed.

  Furthermore, by adopting a non-contact type bead shape measuring device 11, it is not necessary to install the bead shape measuring device 11 near the welded portion, and functional deterioration due to thermal influence immediately after spattering or bead B generation is achieved. In addition to being able to prevent this, it is possible to ensure a large degree of design freedom near the welded part.

  FIG. 10 shows a second embodiment of the present invention, and the same reference numerals are given to the portions common to FIG.

  In this second embodiment, a penetration measuring device (penetration measuring means) 13 that measures the penetration rate (penetration) of the back surface of the bead B in a non-contact manner is used in addition to the bead shape measuring device 11. It is a thing.

  As the penetration measuring device 13, a non-contact type device similar to the bead shape measuring device 11 is used, and a bead penetrating to the back surfaces of the base materials W1 and W2 on the opposite side of the measurement site by the bead shape measuring device 11. The penetration width c (see FIG. 2) of B is measured as optical or image information. Then, the measurement data obtained by the penetration measuring device 13 is also taken into the control device 1, and the back surface penetration rate of the bead B is calculated in real time as a percentage when the width dimension a of the bead B is 100%. Above, it collates with the preset target value set beforehand.

  The penetration measuring device 13 is integrally attached to the laser head 7 via a bracket 14 as shown in FIG. However, it is not always necessary for the penetration measuring device 13 to be integrated with the laser head 7, and the point is that the penetration width c of the bead B can be measured at a position opposite to the measurement site by the bead shape measuring device 11. For example, as shown in FIG. 12, the penetration measuring device 13 may be arranged independently on the back side of the base materials W1 and W2, and the penetration measuring device 13 may be moved in synchronization with the laser head 7.

  In the present embodiment, without setting the relationship between the wire supply amount and the welding speed as shown in Table 1, only the set target value for the underfill b and the set target value for the back surface penetration rate are set in advance. It is assumed that the wire supply amount (wire supply speed) of the filler wire 8 is variably controlled according to the measured underfill b and the welding speed is variably controlled according to the measured back surface penetration rate. More specifically, when the measured underfill b is larger than the set target value, the wire supply speed is increased (the wire supply amount is increased), while when the measured underfill b is smaller than the set target value. Reduces the wire feed rate (increases the wire feed rate). Further, when the actually measured back surface penetration rate is larger than the set target value, the welding speed is increased. On the other hand, when the actually measured back surface penetration rate is smaller than the set target value, the welding speed is decreased.

  In this case, the relationship between the wire supply amount and the welding speed as shown in Table 1 is set in advance, and the wire supply amount and the welding speed are variably controlled stepwise as in the first embodiment. Of course, it is also possible.

  13 and 14 show the third and fourth embodiments of the present invention. The same reference numerals are given to the parts common to FIG. 1, and the configuration other than the main parts is not shown.

  In the third and fourth embodiments shown in FIGS. 13 and 14, the vicinity of the welded portion is forcibly made to minimize the gap G formed between the base materials W1 and W2 that form the weld joint. A pressure pin 15 or a pressure roller 16 is attached to the laser head 7 via a bracket 17 as a gap correction means for restraining the pressure.

  According to this embodiment, the joint gap G can be reduced, so that the welding speed can be improved and the wire supply amount can be reduced, the productivity can be further improved, and the joint gap G before correction can increase the gap tolerance. Even if it exceeds, welding becomes possible by straightening. In addition, the welding quality is stabilized by keeping the distance between the base material and the laser optical system constant. In particular, since the change in the shape of the bead B due to the deviation of the focal length can be prevented in advance, there is an advantage that the change in the joint gap G due to the change in the shape of the bead B can be detected with high accuracy.

  Here, when it is necessary to more strictly manage the welding quality in each of the above-described embodiments, it is desirable to use a monitoring system as disclosed in, for example, JP-A-2003-320467.

  That is, the reflected light of the YAG laser beam 3 irradiated to the welded part for laser welding and the plasma light generated at the welded part are detected by an optical sensor, converted into an electric signal, and the electric signal This is stored as a change with time, and the FFT waveform of the signal is calculated. Then, a total signal strength sum f (α) in the calculated FFT waveform frequency band (α) and a total signal strength f (β) in the frequency band (β) are calculated, and the total sum f (α of each signal strength is calculated. ) And f (β) are respectively plotted on the X axis and the Y axis constituting the two-dimensional coordinate system, and the intersection of the straight lines X = f (α) and Y = f (β) is obtained. Furthermore, based on the inspection result of the quality of the welded part of the workpiece welded by the YAG laser beam, the type of quality of the obtained intersection point is specified, and the type of quality (good product, porositating, It is desirable to create a region of underfill and non-welding in a two-dimensional coordinate system.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows more concrete 1st Embodiment of the laser welding apparatus which concerns on this invention. (A) is sectional explanatory drawing of a lap welding joint, (B) is sectional explanatory drawing of a butt-welding joint. The characteristic view which shows the relationship between the wire supply speed when welding speed and bead width are made constant, and the joint clearance gap which can be welded. The characteristic view which shows the relationship between the wire supply speed when welding speed and bead width are made constant, and the joint clearance gap which can be welded. The characteristic view which shows the relationship between the wire supply speed when welding speed and bead width are made constant, and the joint clearance gap which can be welded. The characteristic view which shows the relationship between the wire supply speed when welding speed and bead width are made constant, and the joint clearance gap which can be welded. The characteristic view which shows the relationship between underfill and the intensity | strength as a welded joint. (A) is sectional explanatory drawing of a lap welding joint, (B) is sectional explanatory drawing of a butt-welding joint. (C) Cross-sectional explanatory drawing of a fillet weld joint. The characteristic view which shows the relationship between the back surface penetration degree of a bead, and the intensity | strength as a welded joint. The structure explanatory view showing the 2nd embodiment of the present invention. Detailed explanatory drawing of the principal part of FIG. Explanatory drawing which shows the modification of FIG. The principal part structure explanatory drawing which shows the 3rd Embodiment of this invention. The principal part structure explanatory drawing which shows the 4th Embodiment of this invention.

Explanation of symbols

1 ... Control device (control means)
2 ... YAG laser oscillator 3 ... Laser light 5 ... Laser optical system 6 ... Condensing lens (laser optical system)
7 ... Laser head 8 ... Filler wire 10 ... Wire supply device (wire supply means)
11 ... Bead shape measuring device 13 ... Penetration measuring device (penetration measuring means)
15 ... Pressure pin (clearance correction means)
16 ... Pressure roller (clearance correction means)
a ... bead width B ... bead b ... underfill c ... back surface penetration width G ... joint gap P ... welding site W1, W2 ... base material

Claims (6)

A laser optical system for irradiating the welding site with laser light;
Wire supply means for supplying a filler wire to the weld site;
Bead shape measuring means for measuring the shape of the bead immediately after welding in parallel with the welding operation;
Control means for variably controlling the supply amount and welding speed of the filler wire during the welding operation so that the measured underfill obtained from the measurement data of the bead shape measuring means is within a predetermined range;
A laser welding apparatus comprising:   2. The laser welding apparatus according to claim 1, wherein the bead shape measuring means is a non-contact type.   3. The laser welding apparatus according to claim 1, wherein the welding mode is lap welding or fillet welding, and includes a gap correction unit that corrects a gap between the base materials at a welding site. In addition to the bead shape measuring means, a penetration degree measuring means for measuring the degree of penetration of the bead on the back side of the bead is provided,
The said control means variably controls the supply rate of the filler wire according to the measured underfill, and the welding speed according to the penetration degree of the bead, respectively. Laser welding equipment. A method of performing welding while irradiating a laser beam to a welding part and supplying a filler wire to the same part,
In parallel with the welding operation, measure the shape of the bead immediately after welding,
A laser welding method characterized by variably controlling the amount of filler wire supplied and the welding speed so that the measured underfill obtained from the measurement data of the bead shape falls within a predetermined range. In addition to measuring the bead shape, measure the degree of penetration of the bead on the back side of the bead,
6. The laser welding method according to claim 5, wherein the supply amount of the filler wire is variably controlled according to the measured underfill based on the bead shape measurement, and the welding speed is variably controlled according to the penetration degree of the bead.

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