JP2000141045A - Method for controlling bar steel welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a welding method having high welding quality capable of optimally controlling a position of a bar steel during the generation of an arc and a thrusting quantity after that according to individual welding states. SOLUTION: In a welding for a bar steel wherein a welding arc is generated between the bar steel and a steel plate, the bar steel and the steel plate are heated with the welding arc to partially melt them, and thereafter welding is executed by thrusting the bar steel into the steel plate, an arc voltage when the arc is generated is measured, a thrusting quantity of the bar steel is obtained from a linear expression of a measured value of the arc voltage showed as follows. d=a×V+b Here, the thrusting quantity is expressed by (d) and the arc voltage is expressed by V. Moreover, (a) and (b) are a proportional constant and preliminarily obtained prior to welding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stud welding of a steel bar such as a stud dowel or a reinforcing bar for a stud. More specifically, the height of the steel bar is controlled so that the arc voltage during the welding arc is constant, and the welding is controlled by the optimum value of the indentation of the steel bar based on this arc voltage to stabilize the welding quality. The present invention relates to a welding method for achieving In addition, a welding method by heating an arc generated at the tip of a steel bar, such as a SAP (submerged arc press) welding method using a particulate flux as an arc shielding material in place of a ceramic arc shielding material used for stud welding, is used. The invention can be applied.

[0002]

2. Description of the Related Art Stud welding is widely used in the fields of civil engineering and construction as a method for instantly welding a steel plate to a steel bar such as a stud dowel or a stud reinforcing bar. However, it is difficult to apply non-destructive inspection such as ultrasonic flaw detection to stud welds, and therefore, stabilization of welding quality is an essential issue.

As a conventional means for stabilizing the quality of a stud welded portion, for example, as disclosed in Japanese Patent Application Laid-Open No. 3-258462, there is a method of switching a pushing speed when pushing a steel bar from a high speed to a low speed. is there. Simultaneously with the arc start, the bar is pulled up to a predetermined height, and the bar and the steel plate are heated and melted. After holding the welding arc for a certain period of time, first, the steel bar is pushed in at a relatively high speed (about 200 mm / s) to prevent the cooling of the molten metal, and a relatively slow speed (about 30 mm / s) at the moment of contact with the molten metal. ) To prevent the molten metal from scattering. This method has succeeded in improving the stud welding quality. Further, by controlling the pushing operation at the time of pushing the steel bar with the servo motor, the reproducibility of the moving amount and the moving speed at the time of pushing the steel bar is improved, and the welding quality is stabilized.

[0004] However, in the welding of bar steel such as studs, even if the above-mentioned pushing speed is strictly controlled, the welding quality may vary.

For example, many welding defects such as undercuts are generated in a deck plate penetration type stud welding. In the deck plate penetration type stud welding, as shown in FIG. 3, the deck plate 23 is melted by the welding arc 25 in a state where the welded portion is surrounded by the arc shield 3, and the steel bar 1 and the base metal 2 are welded. However, the base material 2 and the deck plate 23
There is a gap 24 between them, and the gap amount L cannot be measured from the deck plate before welding.
If this gap becomes larger than expected, in the stud welding in which the indentation amount is set in advance as in the above-mentioned stud welding method, the stud tip does not reach the molten metal on the base material, and the undercut 27 shown in FIG. Will occur.

[0006] Also, in ordinary stud welding without inserting a deck plate, if the welding conditions of the steel bar change due to the length error of the steel bar or the mounting error at the time of setting, the pushing amount becomes insufficient or excessive, and the optimum value is obtained. , The welding quality varies.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a stud welding machine capable of controlling the position of a steel bar with a servomotor, and predicts the distance between the steel bar 1 and the base material 2 based on the arc voltage. However, it is an object of the present invention to provide a welding method that can optimally control the position of a steel bar during arc generation and the subsequent indentation amount according to each welding situation, and maintain high welding quality even in the above-described case. I do.

[0008]

According to the present invention, there is provided the following (1) to (3).

(1) A welding arc is generated between a steel bar and a steel sheet, and after the steel bar and the steel sheet are heated by the welding arc and locally melted, the steel bar is welded by pushing the steel bar into the steel sheet. 3. The method for controlling steel bar welding according to claim 1, wherein an arc voltage during the occurrence of the arc is measured, and from the measured value of the arc voltage, a pushing amount d of the steel bar is obtained by the following equation.

D = a × V + b [d: pushing amount,
V: arc voltage, a, b: constant] (2) The height of the bar during welding is controlled so that the measured value of the arc voltage at the time of the arc generation becomes a constant value. The method for controlling steel bar welding according to 1).

(3) The method for controlling steel bar welding according to (2), wherein the constant value is a predetermined value set in advance.

[0012]

FIG. 1 shows an example of the construction of a welding apparatus for performing bar welding according to the present invention. In FIG. 1, a steel bar 1 cast on a base material 2 is clamped by a holder 5,
The tip is surrounded by the arc shield 3 and pressed against the base material 2. The holder 5 is fixed on a moving table 6 that moves along a guide 9 passed between the side plates 11 and 12 of the base 10. Further, the moving table 6 is fixed to the screw rod 8 via a nut body 7, and controls the pushing and pulling operation of the holder 5 and the bar 1 on the moving table 6 by rotating the screw rod 8 by the servo motor 13. be able to.

The present inventor has investigated the occurrence of welding defects under various welding conditions using the apparatus shown in FIG. 1, and has found that there is a correlation between the arc voltage and welding defects as follows.

First, an investigation was conducted assuming a deck penetration welding as shown in FIG. The deck plate 23 was made of a galvanized steel plate, and the gap L between the deck plate 23 and the base material 2 was variously changed by inserting spacers having different thicknesses.

FIG. 5 shows the occurrence of welding defects when the indentation amount d is changed for various clearance amounts L. When the gap amount L is small, the indentation amount d is small, and when the gap amount L is large, the indentation amount d is increased to prevent the occurrence of welding defects.

In order to estimate the optimum pushing amount obtained from the arc voltage, the arc voltage was measured. FIG.
Shows the relationship between the gap amount L and the arc voltage V. In deck plate welding, the deck plate melts at the same time as the arc is generated, and an arc is generated between the tip of the steel bar and the base metal. For this reason, when L is small, the arc length is short and the arc voltage is also small, and as L increases, the arc length is long and the arc voltage is also increased.

From these results, it can be seen that the welding quality can be stabilized by obtaining in advance the relationship between the arc voltage V and the optimum pushing amount d when the gap L is changed in the preliminary test. This relationship can be expressed by a simple linear equation shown below.

D = a × V + b (a and b are constants) By way of example, by setting a = 0.25 and b = −1, the optimum pushing amount d can be obtained from the arc voltage V. . Within the range tested by the inventors, d can always be determined by a linear expression for V, but the proportional constants a and b
Since the value varies depending on the thickness of the stud, the specific resistance of the steel material, and the like, it is strictly necessary to obtain the value for each welding condition. However, once the constants are determined, high-quality welding can be performed with exactly the same control for a series of weldings performed under the same conditions for the steel type and stud thickness. Generally, in stud welding, thousands to hundreds of thousands of stud materials having the same steel type and the same diameter are often welded, and constants a and b may be prepared according to welding conditions to be actually performed. It is enough.

Since the arc voltage V usually fluctuates during the arc generation, it is sufficient to use an arc voltage V which can obtain a constant reproducibility such as an average value of the fluctuation width or an instantaneous value at a specific time after the arc is generated. It is preferable to control the position of the steel bar so that the specific arc voltage V is maintained without fluctuation. By doing so, the accuracy of the above-mentioned relational expression is increased because the measurement accuracy of V is improved, and the control effect of the present method is enhanced.

Since the value of the arc voltage V does not take a completely different value for each welding but rather takes a substantially equal value in a range of welding conditions where the same constants a and b can be used in the above relational expression, It is most preferable as an embodiment that a constant value of the arc voltage V is set from the beginning and the position of the steel bar is controlled so that the arc voltage V becomes the set value. This is because, if controlled in this way, the pressing is performed with the constant pressing amount obtained from the above-mentioned relational expression. Therefore, the arc voltage V is kept constant, and the pressing is performed with the constant pressing amount based on the voltage V. This is because the welding control of the present invention can be realized by only the above, and high welding quality can be maintained.

[0021]

[Embodiment 1] 19 m in diameter using the apparatus of FIG.
m stud dowels were welded through a 1.2 mm deck plate. The welding power source 14 (DC power source for stud welding) is formed by power cables 15 and 16, with the minus side (cable 15) turned into a steel bar and the plus side (cable 16).
Is connected to the base material. The arc voltage is taken out from the holder 5 and the base material 2 via voltage measuring cables 17 and 18,
It is taken into the pushing amount calculating device 20. Pushing amount calculation device 19
Calculates the pushing amount d according to the linear expression of V, and outputs the pushing amount to the servo motor control device 20. The other welding conditions were fixed, the welding current was 1800 A, the arc time was 1.0 s, the pushing amount was d, and then a further low-speed pushing of 2 mm for reliable welding was performed. Further, since the gap type arc shield was used, the steel bar was not pulled up prior to the indentation.

The preparation, welding, and post-processing steps for deck plate penetration welding will be described below.

First, the welding preparation step will be described. 1) Cover the tip of the steel bar 1 with the arc shield 3. 2) The steel bar 1 is fixed to the holder 5. 3) Fix the welding machine so that the tip of the steel bar 1 matches the predetermined welding position.

Next, the welding process will be described. 4) Start supplying the welding current. 5) Start measuring the arc voltage. 6) The arc voltage V is measured until immediately before the steel bar is pressed, and the average value of the arc voltage V is determined. 7) According to the primary equation d = 0.25V-1, arc voltage V
Is calculated from the average value of. 8) The steel bar is pushed in by the pushing amount d obtained in 7). 9) Stop supplying the welding current.

Next, the post-processing step will be described. 10) Remove the welding machine. 11) The arc shield 3 is pulverized and removed. 12) Visually inspect the appearance of the weld.

By repeating the above series of steps, good weld quality can be obtained.

Table 1 shows a comparison between the welding method of the present invention and the conventional welding method with respect to the quality of the welded portion when the gap L between the deck plate 23 and the base material 2 changes. In the conventional method, all welding was performed using the welding conditions when the gap L between the deck plate 23 and the base material 2 was 2 mm.

In the conventional method using a servomotor, since the pushing amount d is always constant, when the gap amount L is 0 mm,
In the case where the reinforcing bar is pushed into the unwelded portion of the base material at the time of pushing, and the gap amount L is 3 mm, the pushing is insufficient and many welding defects occur. On the other hand, in the welding method of the present invention, the gap amount L
Therefore, good welding quality could be obtained in all welding tests because the indentation amount was controlled to an appropriate value according to.

As described above, by applying the welding method of the present invention, good welding quality can be ensured even in deck plate penetration welding in which the gap amount L varies.

[0030]

[Table 1] Next, as an application example of the present invention, an embodiment in welding a large-diameter reinforcing bar will be described. In the above-mentioned deck plate penetration welding, the indentation amount of the steel bar was obtained by detecting the arc voltage, but here, the arc voltage is measured and the height of the steel bar is controlled so that the value is always constant. We tried to stabilize the welding quality by using this method.

As shown in FIG. 2, the welding method used here is called an SAP (submerged arc press) welding method, and instead of an arc shield used in ordinary stud welding, welding is performed using a powder flux. This is a welding method characterized by enabling welding of a large-diameter steel bar having a diameter of about 30 mm by surrounding a portion. A general AC power source for submerged welding was used as the welding power source. Deformed rebars having diameters of 25 mm, 32 mm, and 38 mm were used for the steel bars.

Hereinafter, the welding preparation step, the welding step, and the post-processing step will be described.

First, the procedure for preparing for welding will be described. 1) The welding apparatus of the present invention shown in FIG. 1 is set on a steel plate. 2) The gap holding metal fitting 4 for holding the gap at the time of arc start is inserted between the reinforcing steel and the steel plate. The distance between the tip of the steel bar 1 and the base material 2 was 5 mm. 3) Surround the weld with a powder flux 21. The components of the flux are as shown in Table 2.

Next, the welding process will be described. 4) Energization of the welding power source is started, and a welding current (1000 A) flows between the steel bar and the steel plate. 5) Simultaneously with the occurrence of the arc, the steel bar 1 is pulled up to a predetermined height. The lifting amount was 5 mm. 6) The measurement of the arc voltage is started, and an average value for a predetermined time is obtained. Here, the average value for one second was obtained. 7) The height of the steel bar 1 is corrected so that the average value of the obtained arc voltages becomes equal to a preset reference value (45 V in this case). 8) The above operations 3) and 4) are repeated for a certain period of time (here, about 20 seconds) to maintain a stable arc state. 9) Primary equation d = 0.2 × V + 1 previously obtained
The steel bar 1 is pushed in at a predetermined speed by a pushing amount d = 21 mm according to No. 2, and the tip of the rebar and the base metal are welded. 10) Stop the welding current.

Next, a post-processing step after welding will be described. 11) Remove the powder flux 21 remaining undissolved. 12) Remove the solid slag covering the weld. Removal of the slag can be easily carried out by crushing with a pitching hammer or the like. 13) Perform a predetermined visual inspection.

By repeating the above steps, it is possible to perform stable welding of steel bars at all times.

Table 3 summarizes the welding qualities of the conventional SAP welding method without controlling the pulling height and the welding method of the present invention. In the conventional method, since the tip of the reinforcing bar easily comes into contact with the molten pool as the reinforcing bar diameter increases, the incidence of welding defects such as undercut and slag-in increases, and the range of appropriate welding conditions narrows. On the other hand, in the welding method of the present invention, no defects were generated, and very good welding quality was able to be secured.

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

As described above, according to the present invention, by optimally controlling the pulling position and the pushing amount of the bar, the reproduction can be performed independently of the gap amount between the deck plate and the base material in the deck plate penetration stud welding. Provided is a concrete control method capable of obtaining good and good welding quality. Further, in welding of a large diameter steel bar, which has been difficult to ensure the quality, welding defects such as slag-in and undercut can be reduced, and the welding quality can be improved. For this reason, repair of welding defects is extremely reduced,
The efficiency of the welding process can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a welding device for welding bar steel according to the present invention.

FIG. 2 is a diagram illustrating an example of application of the present invention to a SAP welding method. Only welds are displayed. Others are the same as FIG.

FIG. 3 is a diagram showing a state of stud welding through a deck plate.

FIG. 4 is a diagram showing an example of a welding defect generated in deck plate penetration stud welding.

FIG. 5 is a diagram illustrating a relationship between a pushing amount and a welding quality when a gap amount of a deck plate is changed.

FIG. 6 is a diagram illustrating an arc voltage when a gap amount of a deck plate is changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Steel bar 2 ... Base material 3 ... Arc shield 4 ... Gap holding bracket 5 ... Holder 6 ... Moving table 7 ... Nut body 8 ... Screw rod 9 ... Guide 10 ... Base 11, 12 ... Side plate 13 ... Servo motor 14 ... Welding power supply 15 ... Power cable (minus) 16 ... Power cable (plus) 17 ... Arc voltage measurement cable (minus) 18 ... Arc voltage measurement cable (plus) 19 ... Push amount calculation device 20 ... Servo motor control device 21 ... Body flux 22 ... Flux fixing cylinder 23 ... Deck plate 24 ... Gap 25 ... Arc 26 ... Weld metal 27 ... Undercut L ... Gap amount between deck plate 23 and base material 2

Continued on the front page (72) Inventor Yasutomo Ichiyama 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Hiroshi Tachikawa 2-6-3 Otemachi, Chiyoda-ku, Tokyo New Inside Nippon Steel Corporation (72) Inventor Masakuni Wakabayashi 20-1 Shintomi, Futtsu City, Chiba Prefecture Inside Nippon Steel Corporation Technology Development Division (72) Inventor Shigeki Terasaki 2-6-3 Otemachi, Chiyoda-ku, Tokyo New Nippon Steel Corporation (72) Inventor Yoshiyuki Era 3-1-47-407 Yatsu, Narashino-shi, Chiba (72) Inventor Masayuki Ogaki 1-39-6, Kushita, Kazo-shi, Saitama (72) Inventor Endo Year Makoto 609-1 Matsudo Nitta, Matsudo City, Chiba Prefecture (72) Inventor Norio Noda 1660-4 Masuo, Kashiwa City, Chiba Prefecture (72) Inventor Makoto Suzuki 3-4-404 Hanamigawa, Hanamigawa-ku, Chiba City, Chiba (72) Invention Person Toru Furukawa 134-4 Hihide, Abiko City, Chiba Prefecture

Claims (3)

[Claims] In a welding of a steel bar, a welding arc is generated between a steel bar and a steel plate, the steel bar and the steel plate are heated by the welding arc to locally melt the steel bar, and then the steel bar is welded by pushing the steel bar into the steel plate. A method for controlling the welding of a steel bar, comprising: measuring an arc voltage during the occurrence of an arc; and calculating an indentation d of the steel bar from the measured value of the arc voltage by the following equation. d = a × V + b [d: pushing amount, V: arc voltage, a, b: constant] 2. The method for controlling steel bar welding according to claim 1, wherein the height of the steel bar during welding is controlled so that the measured value of the arc voltage when the arc is generated becomes a constant value. . 3. The method according to claim 2, wherein the constant value is a predetermined value set in advance.