JPH04305367A - Self-shielded arc welding method - Google Patents

Abstract

PURPOSE:To provide a self-shielded arc welding method. CONSTITUTION:This is the shielded arc welding method where a flux-cored wire having the fine diameter of 0.9-1.6mmphi and an engine welding machine with constant voltage characteristics are combined and arc welding is performed at a current value of 50-250A with DC straight polarity. Especially, external characteristics of a generator of the engine welding machine are made to the constant voltage characteristics having a dropping tendency of >=3V/100A which are made to the constant voltage characteristics of <1V/100A by AVR control and it is preferable to use the flux-cored wire containing 0.15-0.45% C based on the total weight of the wire. The high efficiency and high quality can by obtained by combination of a self-shielded arc welding wire with the engine welding machine in place of a coated electrode used in outdoor welding with a thin plate field (about 0.6-6.0mm thickness) of agricultural machinery and implements, electrical machinery and appliances, lightweight steel frames, etc., as substantial uses.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a self-shielded arc welding method, and more specifically, the present invention relates to a self-shielded arc welding method, and more specifically, the present invention relates to a self-shielded arc welding method. The present invention relates to an arc welding method that achieves high efficiency and quality by combining a self-shielded arc welding flux-cored wire and an engine welding machine instead of the coated arc welding rod used in welding.

0002

[Prior art and problems to be solved by the invention] In outdoor welding of thin plates, from the viewpoint of wind resistance and portability, coated arc welding rods (2.0 to 4.0 mmφ) and engine welding machines with drooping characteristics are mainly used. A combination of has been adopted, but
Due to recent labor shortages, increased workloads, etc., there is a demand for higher efficiency in welding.

On the other hand, self-shielded arc welding flux-cored wire has the following properties: (1) has a higher welding speed (approximately 1.5 to 2 times) compared to coated arc welding rods; (2) does not require attachment and detachment of the rod;
It has advantages such as being able to perform continuous welding, and ■ excellent wind resistance, and is effective in increasing the efficiency of outdoor welding.

However, conventional self-shielded arc welding flux-cored wire has problems in the low current range (50 to 25
The welding workability (arc stability, amount of spatter generation, etc.) at 0A) is poor, and the work efficiency is reduced. Furthermore, there are problems such as insufficient combination technology with an engine welding machine, which is often used for outdoor welding, and it has not yet been put into practical use. A combination technology of self-shielded arc welding flux-cored wire and engine welding machine especially for thin plate field, i.e. low current range (50~250A
), a technology that combines a small-diameter self-shielded arc welding flux-cored wire with excellent arc stability and an engine welding machine that is tailored to the characteristics of the wire and has portability (light weight) in mind has not previously existed.

[0005] As a prior art, there is an example of a combination of a large 300A class engine welding machine and a large diameter (2 to 3.2 mmφ) self-shielded arc welding flux-cored wire, but it is not possible to use a dedicated engine welding machine. However, there were no particular issues regarding dimensions or weight.

However, as a general-purpose machine for welding thin steel plates for general construction materials and for outdoor use, it is required to be smaller and lighter in terms of portability. Efficiency, arc stability, and spatter generation are important issues in product development, and in these respects, the current situation is that no engine welding machine for outdoor self-shielded arc welding has been put into practical use. .

[0007] The present invention was made in response to such a demand, and by combining a flux-cored wire and an engine welding machine, it is possible to reduce the size and weight of the welding machine.
Furthermore, it is an object of the present invention to provide a self-shielded arc welding method that has excellent arc stability in a low current range (50 to 250 A) and generates less spatter.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present inventors have completed various studies on the characteristics of engine welding machines, the composition of flux-cored wire, etc., and have hereby completed the present invention. It is.

That is, in the present invention, the wire diameter is from 0.9 to
Combining a 1.6mmφ thin flux-cored wire with an engine welding machine with constant voltage characteristics, the DC positive polarity
The gist is a self-shielded arc welding method characterized by performing arc welding at a current value of 250A.

[0010] In a particularly preferred embodiment, the generator external characteristic of the engine welding machine is a constant voltage characteristic with a drooping tendency of 3V/100A or more, and a constant voltage characteristic of less than 1V/100A by AVR control, or a flux-cored The wire should contain 0.2 to 0.5% of C based on the total weight of the wire.

The present invention will be explained in more detail below.

0012

[Effect]

First, the inventors of the present invention conducted various studies on the characteristics of engine welding machines and the composition of flux-cored wires, and as a result, they were able to obtain the following findings.

■Characteristics of the welding machine The engine welding machine is suitable for carrying out the self-shielded arc welding method outdoors for thin plates (approximately 0.6 to 6 mm thick) to be welded, which is the main object of the present invention. From the consideration of portability, the issue of making welding generators for engine welding machines smaller and lighter is discussed. The problem of making a welding generator smaller and lighter can be achieved by changing the external characteristics of the generator to constant voltage characteristics that are close to drooping.

On the other hand, in the case of a small diameter wire, the arc length self-control effect of the power supply is used to keep the arc length constant, but the effect of the self-control effect is greater as the slope of the constant voltage characteristic is smaller. It is. As the degree of inclination increases, the welding operator must constantly adjust the protruding length of the wire to keep the arc voltage constant, which requires skill. Therefore, it is difficult to simplify the welding work by adopting the self-shielded arc welding method as a semi-automatic welding method in place of a coated welding rod.

[0016] In order to solve the above problems, as a result of various studies on the external characteristics of the welding generator, 3V/100
By creating a constant voltage characteristic with a slope of A or more, and further changing the drooping constant voltage characteristic to a constant voltage characteristic of less than 1V/100A using AVR control, problems with engine speed fluctuations and a smaller, lighter generator can be solved. It was found that both the problems of oxidation and welding workability could be solved.

That is, as an engine welding machine, by making the external characteristics of the welding generator a constant voltage characteristic with a drooping tendency of 3V/100A or more,

[Table 1] shows the comparison of the dimensions and weight of the generator, it is significantly smaller and lighter, and has excellent portability outdoors.On the other hand, the constant voltage characteristic, which tends to droop, is reduced to less than 1V/100A by AVR control. By having constant voltage characteristics, it is possible to quickly respond to engine speed fluctuations, which not only stabilizes the arc but also simplifies outdoor welding work.

[0018] Even if the external characteristics of the welding generator can be solved, it may be insufficient in terms of arc stabilization and spatter generation, especially in the low current range (50 to 250 A). It has been found that a combination with the wire characteristics described below is necessary for this purpose.

■Wire characteristics First, the thin plate (thickness 0.
6 to 6.0 mm), the welding current is 50 to 250 A in consideration of burn-through, welding distortion, etc., and the wire diameter of the flux-cored wire is 0.9 to 1.6.
A small diameter of mmφ is desirable. When the diameter becomes thicker than 1.6 mm, the arc becomes unstable and the amount of spatter generated increases. Further, if the wire is thinner than 0.9 mm, there are problems such as deterioration of efficiency and deterioration of feeding performance (wire buckling). In addition, as for the power supply polarity, direct current positive polarity is appropriate from the viewpoint of welding workability.

Next, as a result of various studies on the composition of the flux-cored wire, we found that carbon in the wire is important for stabilizing the arc and reducing spatter in the low current range (50 to 250 A).
It was recognized that quantity is important. This point will be explained below based on experimental results.

The experimental conditions are as follows. <Sample wire> Wire diameter: 1.0 mmφ Flux: No. 1 in the examples described below. Mixed flux rate of No. 1: 12% <Engine welding machine> No. 1 in the examples described below. Characteristics of 1 (welding conditions) Welding current: 120A Polarity: DCEN Arc voltage: Voltage at which the arc length is approximately 1 mm Welding speed: 1
5cm/min Distance between tip and base metal: 15mm Welding method: Downward bead-on welding <Method for measuring amount of spatter> Same method as in Examples described below.

As shown in FIGS. 1 and 2, the experimental results show that the amount of spatter generated decreases as the output characteristics (V/100A) of the engine welding machine decreases and as the amount of C in the wire increases.

Based on the above results, it has been found that it is preferable to set the amount of C in the wire to 0.15 to 0.45% of the total weight of the wire, and to set the output characteristics of the engine welding machine to less than 1V/100A. . Here, the amount of C in the wire is 0.
The reason why the external characteristics were set to 15% or more and less than 1V/100A is that the low sputtering effect is effectively exhibited as shown in FIGS. 1 and 2. On the other hand, the upper limit of the amount of C in the wire is set to 0.
The reason why it is set at 45% is to prevent the arc blowing force from becoming too strong and increasing the amount of fume if this value is exceeded. The C source is not particularly limited, and graphite, C-containing alloys, and the like can be used.

The main components of the self-shielded arc welding method of the present invention have been explained above. In short, the present invention has the following advantages: The most distinctive features are controlling the external characteristics of the machine (V/100A), ■ using a small diameter flux-cored wire, and adjusting the amount of C in the wire to a high level. This significantly reduces the amount of spatter generated.

[0025] In order to fully achieve the purpose of the present invention, it is also necessary to meet the general requirements (composition, flux rate) for a self-shielded arc welding flux-cored wire, as shown below. . The content of each component is expressed as a percentage of the total weight of the wire.

Al: 2.0-4.0% Al acts as a deoxidizing and denitrifying agent.
If it is less than 0%, welding defects (pits, etc.) are likely to occur, wind resistance deteriorates, and outdoor welding becomes difficult. Moreover, if it exceeds 4.0%, the slag will burn onto the bead, impairing its appearance, and furthermore, the amount of fumes will increase. Therefore, A
It is desirable to add l in a range of 2.0 to 4.0%. In addition, as an Al source, in addition to Me-Al, Fe-Al,
Alloys such as Al-Li, Al-Mg, Ca-Al, etc. can be used.

Mg: 0.3 to 1.5% Mg acts as a deoxidizing agent and a shielding agent (generates metal vapor during welding to shield the arc column and molten pool), and also acts as a slag forming agent in beads. It also has the role of adjusting the shape. However, if it is less than 0.3%, the arc becomes unstable and
Moreover, the bead shape also deteriorates. Moreover, if it exceeds 1.5%, the arc blowing force becomes too strong and spatter and fumes increase. Therefore, it is desirable to add Mg in a range of 0.3 to 1.5%. In addition, as a Mg source, Me
-In addition to Mg, alloys such as Al-Mg, Ni-Mg, and Si-Mg can be used.

Mn: 0.3 to 3.0% Mn acts as a deoxidizing agent and has the effect of adjusting the strength of the weld metal. However, if it is less than 0.3%, the strength will be insufficient,
Moreover, when it exceeds 3.0%, the strength becomes excessive and bending ductility is impaired. Therefore, it is desirable to add Mn in a range of 0.3 to 3.0%. In addition, as a Mn source, Me-M
In addition to n, Fe-Mn, Fe-Si-Mn, etc. can be used.

Metal fluoride (in terms of fluorine): 0.1 to 2.0
% metal fluoride is both a shielding agent and a major slag former. However, if it is less than 0.1%, shielding deteriorates and welding defects (pits, etc.) occur. Furthermore, the bead shape also deteriorates. On the other hand, if it exceeds 2.0%, the melting point of the slag will drop too much, the bead shape will deteriorate, and fumes and spatter will increase. Therefore, it is desirable to add the metal fluoride in an amount of 0.1 to 2.0% in terms of fluorine. Note that metal fluorides include CaF2, BaF2, LiF
2. Although SrF2, NaF, Na2SiF6, etc. can be used, it is preferable to use BaF2 and SrF2, especially considering welding workability in a low current range (spatter generation amount, bead shape, etc.).

Flux rate: 8 to 20% If the flux rate is less than 8%, the arc becomes unstable and spatter increases. Moreover, if it exceeds 20%, the outer metal of the wire becomes too thin, resulting in poor feeding performance. Therefore, the flux rate is preferably in the range of 8 to 20%.

It goes without saying that the cross-sectional shape of the flux-cored wire used in the present invention is not limited at all.

Next, examples of the present invention will be shown.

[0033]

【Example】

[Table 2] A flux-cored wire with the composition shown in the table was prepared using a conventional method (flux rate = 12%), arc welding was performed in combination with an engine welding machine with the output characteristics shown in Table 2, and the amount of spatter generated was measured. Welding workability was also investigated. The results are also listed in Table 2. The welding conditions and the method for measuring the amount of spatter are as follows.

Welding conditions: Polarity: DCEN Arc voltage: Voltage for arc length of approximately 1 mm Welding speed: 2
0cm/min Distance between tip and base metal: 15mm Welding method: Downward bead-on welding

Method for measuring spatter amount: Under the above welding conditions, welding was performed by the downward bead-on-plate method using the apparatus shown in FIGS. 3 and 4 (in the figure, 3 is a spatter collection plate, 4 is a wire feeding device, 5 is the torch, 6 is the base material,
7 indicates a trolley) was used. That is, the amount of spatter generated was determined by collecting spatter scattered around the arc point using a collecting plate and measuring the weight. The measurement time was 1 minute, and the value per unit time (g/min) was calculated.

In Table 2, Experiment No. 1~No. 5 are examples of preferred embodiments of the present invention, and all of them are in the low current range (
50 to 250 A), the arc stability was excellent and the occurrence of spatter was extremely low.

[0037]

[Effects of the Invention] As detailed above, the combination of self-shielded arc welding flux-cored wire and engine welding machine is useful for improving the efficiency of outdoor welding mainly for thin plate fields such as agricultural machinery, electrical machinery, and lightweight steel frames. Technology is extremely important, but according to the present invention, in particular: (1) controlling the external characteristics of an engine welding machine, (2) using a small diameter wire and adjusting the amount of carbon in the wire to a high level, It is possible to significantly improve arc stability and spatter generation in the low current range, which are problems with self-shielded arc welding flux-cored wires. Furthermore, the fact that we were able to establish this technology in combination with an engine welding machine will greatly contribute to increasing the efficiency of outdoor welding in the future.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the output characteristics of an engine welding machine and the amount of spatter generated.

FIG. 2 is a diagram showing the relationship between the amount of C in a flux-cored wire and the amount of spatter generated.

FIG. 3 is a side view showing a spatter generation amount measuring device.

FIG. 4 is a plan view showing a spatter generation amount measuring device.

Claims (3)

[Claims] [Claim 1] Perform arc welding at a current value of 50 to 250 A with positive DC polarity by combining a small diameter flux-cored wire with a wire diameter of 0.9 to 1.6 mmφ and an engine welding machine with constant voltage characteristics. A self-shielded arc welding method featuring: [Claim 2] The generator external characteristics of the engine welding machine are
Constant voltage characteristics with a tendency to droop over 3V/100A, AV
2. The method according to claim 1, wherein the R control has a constant voltage characteristic of less than 1 V/100 A. 3. The method according to claim 1, wherein the flux-cored wire contains 0.15 to 0.45% of C based on the total weight of the wire.