JPS5839032B2 - Consumable electrode gas shield arc welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a consumable electrode gas-shielded arc welding method that uses two or more types of inert gases or active gases having different potential gradients as shielding gases.

Generally speaking, in consumable electrode gas shielded arc welding, in which workpieces are welded with a gap with a constant cross-sectional area, such as an I groove or ■groove, facing each other, the weld penetration depth is It is affected more by the change in arc voltage value than by the change in arc voltage value.

For example, when performing electrogas vertical welding with workpieces 1 and 1 vertically opposed to each other with a gap width WO as shown in Fig. 1, even if the welding current value is increased, the penetration width Although W hardly increases, the penetration width increases significantly when the arc voltage is increased.

That is, the diameter is 1.611! ! The melt penetration ratio (WWo)/Wo is shown in the same figure when an aluminum material with a thickness of 25M is vertically welded by electrogas with a current value of 250A flowing through the consumable electrode of the aluminum material Il and an arc voltage of 25V. It is approximately 0.6.

Next, when a current of 500 A, which is twice the above current, is passed through an aluminum consumable electrode with a diameter of 2.4111111 and the arc voltage is maintained at 25 V as above, the penetration ratio is approximately 0.8.
It is.

On the other hand, when a current of 250 A is passed through an electrode with a diameter of 1.6 mm and the arc voltage is increased by 20 degrees to 30 V, the penetration ratio is about 1.15.

In this way, even if the arc voltage is kept at a constant value of 25 V and the welding current is doubled from 25 OA, the penetration ratio only increases slightly from 0.6 to 0.8. It can be seen that by simply increasing the arc voltage by 20% from 25V while keeping the welding current at a constant value of 25OA, the penetration ratio increases greatly from 0.6 to 1.15.

The reason why the penetration width does not increase even when the welding current is increased is that with a droop characteristic power supply, when the welding current is increased using the power supply's welding current regulator, the consumable electrode is used to maintain the arc length approximately constant. The welding current is increased by increasing the feeding speed of the consumable electrode, and in the case of a constant voltage characteristic power source, the feeding speed of the consumable electrode is increased by increasing the feeding speed of the consumable electrode using the feeding speed regulator of the control device, and in both cases, the amount of welding of the consumable electrode increases. However, since the groove width Wo, that is, the groove cross-sectional area is constant, the welding speed increases,
This is because the increase in the penetration width W becomes small.

For these reasons, variations in welding current have little effect on the penetration width, but slight variations in the arc voltage have a large effect on the penetration width.

Therefore, in order to maintain the melt penetration width at a substantially constant value, the arc voltage must be maintained at a substantially constant value.

Normally, if a power supply with drooping characteristics is used to feed a consumable electrode at a nearly constant speed with a nearly constant current, the apparent arc length expressed by the shortest distance between the tip of the consumable electrode and the workpiece when there is no disturbance is It becomes approximately constant, and the actual arc length also occurs between this shortest distance.

However, even if the apparent arc length is constant, the actual arc will not occur within the shortest distance due to disturbances such as the surface condition of the groove and fluctuations in the molten pool, so the actual arc length is the apparent arc length. increases and fluctuates.

As the actual arc length changes, the arc voltage also changes, and the penetration width cannot be kept constant.

In such cases, in the past, the feeding speed of the consumable electrode was changed to keep the arc voltage constant in order to keep the weld penetration width constant; If is set to a substantially constant value, the apparent arc length will change even if the arc voltage remains constant.

If this apparent arc length changes and the arc length becomes longer, flare-ups may occur or the arc directionality may deteriorate; conversely, if the arc length becomes shorter, spatter, protrusions, etc. may occur. This will cause inconvenience and prevent the best welding results from being obtained.

In other words, if you try to maintain the arc voltage at a constant value by changing the consumable electrode feeding speed in order to maintain the weld penetration width constant as in the past, the apparent arc length will inevitably deviate from the most appropriate value. Therefore, it is difficult to obtain stable welding results, and welding defects are likely to occur.

The present invention uses a drooping characteristic power source to keep the welding current at a substantially constant value, so that the apparent arc length, expressed as the shortest distance between the tip of the consumable electrode and the workpiece, becomes an optimal, substantially constant value. The consumable electrode feed speed is set, and even if the arc voltage changes due to disturbances during welding, the apparent arc length remains at an optimal approximately constant value, so the consumable electrode feed speed is not changed. By using two or more types of shielding gases with different potential gradients and changing the components of the shielding gas supplied to the welding area in accordance with the increase or decrease of the arc voltage, the arc voltage can be kept constant, and as a result, the penetration can be improved. This paper proposes a consumable electrode gas-shielded arc welding method that maintains a constant width.

Examples of the welding method of the present invention will be described below.

The present inventor conducted an experiment as shown in FIG. 2 in order to study the influence of shielding gas on arc voltage.

In this experiment, an aluminum consumable electrode with a diameter of 1.68 mm was used, the welding current was kept at a constant value of 20OA, the consumable electrode was fed at a nearly constant speed so that the apparent arc length was 611g1, and the shielding gas was Welding was performed by changing the components.

In this case, argon gas Ar is used as the shielding gas.
When only helium gas was used, the arc voltage was 20V, when a mixed gas of 50% argon gas Ar and 50% helium gas He was used, the arc voltage was 24V, and when only helium gas He was used, the arc voltage was It rose to 28V.

Therefore, it was confirmed that the arc voltage can be controlled by changing the mixing ratio of helium gas and argon gas.

The present invention utilizes this principle.

First, a description will be given of an apparatus for carrying out the arc welding method of the present invention in which two types of shielding gases having different potential gradients are used to change the gas components and keep the arc voltage substantially constant.

FIG. 3 is a configuration diagram of an apparatus for carrying out the welding method of the present invention, in which 1 is a workpiece, 2 is a consumable electrode fed at a substantially constant speed by a wire feeder (not shown), and 3 is a workpiece. Backing materials 4 are disposed on both sides of the gap between the objects to be welded, and a welding power source 4 has a substantially drooping characteristic, and its output terminal is connected to the object to be welded 1 and the consumable electrode 2 .

5 is an arc voltage detection circuit, 6 is a reference voltage setting circuit, 7A
8A is a servo amplifier that compares the output voltages of the arc voltage detection circuit 5 and the reference voltage setting circuit 6 and operates the servo valve 7B according to the output, and 8A is a cylinder that reciprocates by the fluid pressure supplied from the servo valve 7B. , 8B and 8C
These valves 8B and 8C are flow rate regulating valves that are linked to the operation of the cylinder 8A, and the flow rates of these valves 8B and 8C are increased and decreased in opposite directions, so that the sum of the two is approximately constant.

That is, when the cylinder 8A moves, for example, to the left, the gap of the flow rate adjustment valve 8B to which shielding gas A1 is supplied increases and the flow rate increases, and conversely, the gap of flow rate adjustment valve 8C to which shielding gas A2 is supplied decreases. Then, the flow rate decreases.

Next, the operation will be explained.

Welding is now started with the proper arc voltage and the piston 8A
It is assumed that the shield gas Al (for example, helium gas) and the shield gas A2 (for example, argon gas) are supplied at approximately the same flow rate.

After that, if the arc voltage increases, that voltage will be applied to terminal a.

The output voltage of the detection circuit 5 and the output voltage of the reference voltage setting circuit 6 are input to the servo amplifier 7A, and the output voltage of the servo amplifier 7A causes the servo valve 7B to control the cylinder 8A. Driven to move to the right.

Therefore, shielding gas A1 (helium gas) decreased and shielding gas boiling gas 2 (argon gas) increased, and as a result, the arc voltage decreased and returned to the appropriate arc voltage, and cylinder 8A also moved slightly from the center to the right position. Stop at a position.

Conversely, when the arc voltage decreases, the output voltage of the arc voltage detection circuit 5 and the output voltage of the reference voltage setting circuit 6 are input to the servo amplifier 7A, and the output voltage of the servo amplifier 7A causes the servo valve 7B to switch to the cylinder. 8A is driven to move leftward.

Therefore, as a result of shielding gas A1 (helium gas) increasing and shielding gas A2 (argon gas) decreasing, the arc voltage increases and returns to the appropriate arc voltage, and cylinder 8A moves to the left position from the above-mentioned position. It will stop at the specified position.

According to the device of this embodiment, while the consumable electrode is fed at a speed that makes the apparent arc length approximately constant,
By changing the mixing ratio of the shielding gas, the arc voltage can be maintained at a substantially constant value, and the melt penetration can be made substantially constant.

Next, FIG. 4 is a block diagram of another apparatus for carrying out the welding method of the present invention, and FIG. 5 is a diagram illustrating the operation of this apparatus.

In FIG. 4, the same parts as in FIG. 3 are given the same reference numerals.

In the figure, 7C is a control circuit which receives the output voltage of the arc voltage detection circuit 5 and the output voltage of the reference voltage setting circuit 6 and supplies output voltages to the electromagnetic valves 8D and 8E depending on the magnitude and direction of the output voltages.

The operation will now be described with reference to FIG.

Assume that the shield gas A1 (for example, helium gas) supply electromagnetic valve 8D is operated to supply helium gas 100φ to the welding device.

As the helium gas is supplied, the arc voltage gradually increases, and when it reaches 24 (V) as shown in FIG. Open the supply solenoid valve 8D and
As shown in , the solenoid valve 8D is closed with a slight delay in time.

As a result, as shown in the figure, the shielding gas component gradually decreases from helium gas of 100 φ, and conversely, the argon gas gradually increases from 0%, and the arc voltage decreases as shown in A of the figure.

When the arc voltage drops to 20 [V], the solenoid valve 8D, which supplies helium gas again in the above-mentioned order, opens.
After a slight delay, the electromagnetic valve 8E that supplies argon gas closes, the shielding gas component decreases from 100% argon gas, the helium gas increases from 0%, and the arc voltage increases again.

Furthermore, the solenoid valve does not necessarily switch when the helium gas or argon gas reaches 100%, but may switch when the components are mixed, as shown at point P in the same diagram.

In the welding method using this device, the case where the arc voltage fluctuates by 24 ± 2 [■] was explained in the example, but the fluctuation is less than ±10 [■] of this degree, and moreover, the arc voltage fluctuates by ±2 [■].
Since the time for the maximum change in V] is extremely short, a uniform melt penetration width can be obtained.

According to the device of this embodiment, the consumable electrode is fed at a speed such that the apparent arc length is approximately constant.
Time for supplying two types of shielding gases A1 and A2;
That is, the supply time of shielding gas A1 is 11113, . . . as shown in FIG.
As shown in C in the figure, the supply time is t2. t4t...
By changing each of the times, the arc voltage can be kept constant and the melt penetration can be kept approximately constant.

In the above two embodiments, the shielding gas A1 is helium gas, and the shielding gas A2 is argon gas. Single gases or mixtures of gases can optionally be used.

Also, the present invention can be used with any welding material or welding position.

According to the welding method of the present invention, when the arc voltage changes, the consumable electrode feeding speed remains unchanged and the apparent arc length is maintained at an optimal approximately constant value, while two or more types with different potential gradients are welded. By changing the shielding gas component according to the increase/decrease of the arc voltage, the arc voltage can be kept constant, and as a result, the weld penetration width can be kept constant, which has great practical benefits.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between arc voltage or welding current and penetration ratio, Figure 2 is a diagram showing the relationship between welding current or shielding gas component and arc voltage, Figures 3 and 4 5 is a diagram showing the configuration of an apparatus for carrying out the welding method of the present invention, and FIGS. 5A to 5D are diagrams for explaining the operation of the apparatus shown in FIG. 4. DESCRIPTION OF SYMBOLS 1... Workpiece to be welded, 2... Consumable electrode, 4... Welding power source, 5... Arc voltage detection circuit, 6... Reference voltage setting circuit, 7A... Servo amplifier, 7B...・Servo valve, 7C...Discrimination circuit, 8A...Cylinder, 8B, 8
C...Flow rate adjustment valve, 8D, 8E...Solenoid valve, W...
・Welding width.

Claims (1)

[Scope of Claims] 1. In a gas-shielded arc welding method in which a consumable electrode and a workpiece are connected to a drooping characteristic power source and welded, the apparent distance between the tip of the consumable electrode and the workpiece is The consumable electrode is fed at a speed that maintains the arc length at an optimal approximately constant value, and two or more gases with different potential gradients are used as shielding gases, and the method responds to changes in arc voltage due to changes in the actual arc length. consumable electrode gas shielded arc welding, characterized in that by changing the components of the shielding gas supplied to the welding part, welding is performed while maintaining the arc voltage substantially constant without changing the substantially constant apparent arc length. Method. 2. The consumable electrode gas-shielded arc welding method according to claim 1, wherein two or more types of gases having different potential gradients are welded by changing their mixing ratio to maintain an approximately constant arc voltage. 3. The consumable electrode gas-shielded arc welding method according to claim 1, wherein two or more gases having different potential gradients are welded by changing the supply time ratio to maintain the arc voltage substantially constant.