JPH0798270B2 - One-sided back wave welding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a single-sided welding method in which a backing material is applied to the groove back surface and welding is performed from the front surface.

(Prior Art) Single-sided welding, in which welding is performed from the surface of a base material to form a back wave, is widely used for on-site welding in which the base material cannot be inverted or for plate welding of large steel plates.

With this one-sided welding, a good back bead can be formed relatively easily if the grooved gear is uniform over the entire length of the welding length, but if the grooved gear is not uniform, the welding operator can open it. A good backside bead cannot be formed unless welding is performed while adjusting the welding conditions (welding speed, welding voltage, welding current, etc.) according to the tip gear cup. In particular, it is extremely difficult to use a latent arc welding method in which the welded portion cannot be directly monitored or a gas shielded arc welding method using a thin wire having a small arc blowing force.

As a technique for solving this problem, Japanese Patent Application Laid-Open No. 61-
Japanese Patent Laid-Open No. 56775 proposes a method of controlling a back-bead by detecting a potential difference between a base metal and a copper strip by welding using a back strip with a flux dispersed on a copper strip. However, the above method is applicable only to welding using a backing material in which flux is spread on a copper plate, that is, a backing material in which an insulator having a high electric resistance is interposed between a base material and a conductor. And its usage range is narrow. To address the above problem, the applicant detects the welding current at the center position of the oscillating width and compares it with a threshold value set experimentally, and if the detected current value is greater than the threshold value, For example, Japanese Patent Application No. 61-224171 proposed a method of welding at a high welding speed and, if it is less than the threshold value, at a low welding speed. Here, the welding speed is set in advance in two stages of a speed higher than the expected speed and a speed lower than the expected speed, and is set from either of these. The reason why the welding speed is set in two stages is to simplify the apparatus, and the purpose can be economically achieved by controlling the welding steplessly. In this way, the welding current is detected every time in the center of the oscillating width, and the welding speed is switched every time the welding is performed by controlling the welding so that the wire protrusion length is kept constant. When the setting condition is changed due to the change, it is necessary to adjust the welding standard setting each time, and the vibration of the welding current value is different between when the EXT is long and when it is short, as shown in Fig. 2. , A method of removing only the vibration component by providing a fixed filter was proposed, but the response tends to be delayed due to the time constant of the fixed filter.

(Problems to be Solved by the Invention) As described above, it is difficult to automate single-sided welding in the conventional technology, and even if it is automated, its applicable range is limited, and the set value is changed according to the change of welding conditions. There was a problem that had to be readjusted.

(Means for Solving Problems) The present invention has been made to solve the above problems, and its gist is to apply a backing material to the groove back surface and supply a welding wire from the surface. In the one-sided welding method of the downward butt welding posture for performing welding, the welding current value at the groove width center is detected through a differentiating circuit, and the detection result from the differentiating circuit is compared with a preset proper reference value, and the comparison result The single-sided backside welding method is characterized in that the welding speed is controlled in accordance with the welding.

(Operation) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 is a view showing a wire oscillating type gas shield arc single-sided welding method.

A solid type backing material 3 having fire resistance is applied to the back surfaces of the base materials 1 and 2 which are butt-formed to form a V-shaped groove, and a guide rail 4 is fixed to the surface of the base material 2 with magnets 5 and 6. It has been placed. Reference numeral 7 denotes a welding carriage that is driven by a motor (not shown) along the guide rail 4 and travels.
Is equipped with an oscillating device 8. The oscillating device 8 oscillates the oscillating shaft 9 in the oscillating direction 10, that is, the groove width direction, and similarly oscillates or opens the welding torch 12 held by the welding torch holder 11 provided at the tip of the oscillating shaft 9 in the groove width direction. Fix it in the center of the tip width. The welding wire 13 is supplied into the groove through the welding torch 12, and a voltage is applied from the DC constant voltage welding power source 17 shown in FIG. 1 to perform welding. 14 is a gas shield nozzle.

The state of the back wave formation when welding is performed with the above configuration is schematically shown with respect to the positional relationship between the weld metal and the gas shield nozzle in FIG. First, in FIG. 1A, the welding speed, that is, the relationship between the speed of the welding carriage 7 and the weld metal 16 is proper, and the welding arc 15 does not precede the weld metal 16.
In addition, good backwater is formed without delay. In the figure (b), when the groove width is wider than in the case of the figure (a), the amount of the weld metal 16 is insufficient, the surplus speed becomes slower, and the speed of the welding carriage 7 is relatively lower than the appropriate speed. As soon as possible, the welding arc 15 leads the weld metal 16 and an excessive back wave is formed. In the worst case in FIG. 2B, there is a risk that the backing material 3 will be melted down and the weld metal 16 will hang down, making welding impossible. Further, in the same figure (c), when the groove width is narrower than in the case of the same figure (a), the amount of the weld metal 16 becomes excessive, the excess speed becomes faster, and the speed of the bogie is relatively lower than the appropriate speed. Therefore, the welding metal 16 precedes the welding arc 15 and a sufficient backside is not formed.

The welding current value is used when the welding wire is not oscillating because the welding torch 12 is at the groove width center position, so that value is used.However, when the welding wire is oscillating, the gas is placed at the center position. The position of the shield nozzle is detected by a potentiometer (not shown), and an electric circuit configuration (not shown) is input so that the welding current value signal is input only when the gas shield nozzle is located at the center. It has become.

Sensors may be used instead of the potentiometer.

By the way, focusing on the protruding length EXT of the wire regarding the difference between when the backside wave is formed favorably and when it is not formed, when the backside wave is excessively large, the protrusion length EXT is the longest, It can be seen that the protrusion length EXT is the shortest when a sufficient backside is not formed, and the case where a good backside is formed is an intermediate wire protrusion length between the two. When using a DC constant voltage welding power source as the welding power source to feed the wire at a constant speed and perform welding, if the wire protrusion length is long, the welding current value will be low, and if the wire protrusion length is short, the welding current value will be high. That is clear by Ohm's law. Ie , I = welding current value, E = welding voltage value (constant pressure), R =
The welding voltage value is the preset constant pressure value E by the resistance value of (EKT) + (arc length), and the welding current value I is inversely proportional according to the change of (EXT) in R. Changes to.

In the present invention, the above welding current value is detected, and the welding speed is controlled according to the result, so that the welding metal 15 does not precede the welding metal 16 and vice versa. First I found out that I should do it.

However, when the welding current value is detected as described above, as shown in the welding current value (I) of FIG. 2, as EXT becomes longer, the self-control characteristics of the DC constant voltage welding power source and the joule of the welding wire 13 are increased. Due to the heat generation, the change and fluctuation range of the welding current value become large, and the fluctuation range of the appropriate current value in the figure becomes more than that, and if it is input to the control circuit that controls the welding speed as it is, the welding speed will cause hunting. invention was welded by controlling the speed of the welding vehicle as a detection value the proper voltage value of the differential output voltage value of the converted magnitude to those at and differential output voltage using the figures in this variation range (E _D) Good results have been obtained. This will be described below.

FIG. 1 is a control block diagram for carrying out the present invention.

The detection power from the DC constant voltage welding power source 17 is passed through the shunt 23 and connected to the gas shield nozzle 14 so that the welding current value I
The output voltage Ei is generated from the shuttle 23 by flowing the current. The waveform of the output voltage Ei at this time is equivalent to the welding current value (I) in FIG. The output voltage Ei is converted by the differentiating circuit 24 into the differential output voltage value E _D shown in FIG. The converted differential output voltage value E _D and the reference voltage value E _S from the appropriate reference circuit 19 are compared with the comparison circuit 18 to obtain a comparison difference voltage ± ΔE. Further, the comparison difference voltage ± ΔE is amplified by the amplifier 20, and the electric power output circuit 21 controls the speed of the welding carriage motor 22 to continuously target the proper voltage value of FIG. The positional relationship between the metal and the gas shield nozzle is properly controlled, and welding is performed as intended.

(Example) An example of welding by the method of the present invention will be described below.

Welding method is CO ₂ gas shield welding method, base material is mild steel, plate thickness 1
A V groove was formed with a groove angle of 40 ° using a 6 mm groove groove 3-8 mm, and a refractory solid backing material was applied to the back surface of the groove for welding. Other welding conditions are as follows.

Welding wire: 1.6 mm diameter solid wire Appropriate welding current value: 400 A, Welding voltage: 34 V Distance between gas shield nozzle and base material: 30 mm Wire oscillating width: 6 mm, oscillating frequency: 50 times / min Welding results under welding conditions , A very good backwater was formed.

In the above examples, the CO ₂ gas shield welding method showed an example of welding using a refractory solid type backing material for the backing material, but even in the submerged welding method using a DC constant voltage welding power source,
The method of the present invention can be applied to the welding as long as the welding is performed by feeding the wire at a constant speed, and the backing material may be a steel plate. The same applies to the MAG welding method and the MIG welding method.

(Effects of the Invention) As described above, according to the present invention, one-sided welding of a member having a poor groove precision can be easily performed, and a welder can save time and effort such as readjustment of conditions during welding. The effect of can be further enhanced.

[Brief description of drawings]

FIG. 1 is a control block diagram of the present invention, FIG. 2 is a schematic diagram of the relationship between welding current value, differential output voltage value and back bead at weld metal and gas shield nozzle position, and FIG. 3 is wire oscillating type gas shield single-sided welding. It is explanatory drawing of a method. 1, 2 ... Base material, 3 ... Backing material, 4 ... Guide rail, 5, 6 ... Magnet, 7 ... Welding carriage, 8 ... Oscillating device, 9 ... Oscillating shaft, 10 ... Oscillating direction, 11 ... Welding torch holder, 12 … Welding torch, 13… Welding wire, 14… Gas shield nozzle, 15… Welding arc, 16… Welding metal, 17… DC constant voltage welding power supply, 18… Comparison circuit, 19… Proper reference circuit, 20…
Amplifier, 21 ... Power output circuit, 22 ... Welding carriage motor, 23 ...
Cyanto, 24 ... Differentiating circuit, 25 ... Wire reel.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Aoki 5-10-1, Fuchinobe, Sagamihara-shi, Kanagawa Inside Nihon Nippon Steel Co., Ltd. Technical Research Institute (56) Reference JP-A-53-33949 (JP, 53-33949) A)

Claims (1)

[Claims] 1. A single-sided welding method in which a backing material is applied to the rear surface of the groove and a welding wire is supplied from the front surface to perform welding in a downward butt welding posture, in which the welding current value at the center of the groove width is passed through a differential circuit. A single-sided backside welding method, which comprises detecting, comparing the detection result from the differentiating circuit with a preset proper reference value, and controlling the welding speed according to the comparison result to perform welding.