JPH11197881A - Low hydrogen type coated arc welding electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low hydrogen type coated arc welding electrode that enables superior re-arcing capability while satisfying various kinds of performance, even if no-load voltage is low on the secondary side of a welding machine, and that attains deep penetration so as to provide sturdy tack welding, in welding high-tensile steel of 490-720 M/mm<2> class. SOLUTION: The coating flux of the coated arc welding electrode contains 20-50 wt.% metallic carbonate, 0.5-3.5 wt.% metallic fluoride, 1.1-3.5 wt.% cellulose and 22-55 wt.% iron powder. In addition, the steel conductor is covered with the coating flux in which the weight ratio of cellulose based on iron powder is 0.04-0.10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-hydrogen coated arc welding rod used for important structures such as shipbuilding, construction, bridges, pressure vessels and the like.
mm ² class high-strength steel, low hydrogen coated arc welding rod (ex. , Low hydrogen rods).

[0002]

2. Description of the Related Art Low hydrogen rods have good resistance to fracture and toughness, so they are used for large structural steel, low temperature steel or heat resistant steel. Also used for previous tack welding. Intermittent tack welding is important for building a welded structure, but it is often required to accurately weld to a predetermined position, and if the tack weld is removed, it is extremely dangerous In order to do so, it is necessary to use a low hydrogen rod with sufficient penetration.

In order to facilitate tack welding, good re-arcing properties after arc interruption is required, and various proposals have been made for low hydrogen rods dedicated to tacking for the purpose of improvement. For example, Japanese Patent Publication No. 58-047956 discloses a coating in which fine iron powder is contained in a coating agent to provide conductivity between the distal end portion of the core wire and the distal end portion of the protective tube to improve re-arcing. An arc welding rod is disclosed. However,
With this coated arc welding rod, if the no-load voltage on the secondary side of the welding machine decreases due to the operation of large equipment, etc., or if the no-load voltage on the secondary side of the welding machine itself is low, it will be restarted due to insufficient starting voltage. Arcing becomes difficult. Further, since the arc voltage is reduced by containing iron powder, there is a problem that sufficient penetration cannot be obtained due to insufficient arc force.

[0004] Japanese Patent Application Laid-Open No. 9-70690 discloses that
In addition to limiting the content and particle size of the iron powder in the coating agent, by limiting the carbon and oxygen of the iron powder, a coated arc welding rod that ensures good re-arcability even with a low no-load voltage welding machine is disclosed. Have been. However, the coated arc welding rod also mainly contains iron powder, the arc force is weakened, and insufficient penetration occurs depending on welding conditions.

On the other hand, as a means for deepening the penetration of a low hydrogen rod, as disclosed in Japanese Patent Application Laid-Open No. Hei 7-241696, carbonated lime containing a clay mineral is used for the purpose of strengthening the arc force. To ensure deep penetration.
However, when this means is applied to a low-hydrogen bar containing iron powder exclusively for tacking for the purpose of improving the re-arc property, there is a problem that the arc becomes unstable and scattering of spatters increases.

[0006]

As described above, it has been found that there is no improvement in the conventional low hydrogen rods that satisfies other welding performances and ensures excellent re-arcability and deep penetration. Was. The present invention provides a low hydrogen system having a deep penetration so as to obtain excellent re-arc properties while satisfying various welding performances even when the no-load voltage on the secondary side of the welding machine is low, and to provide a strong tack. The purpose is to provide a stick.

[0007]

The inventors of the present invention have studied various coating components to solve the above-mentioned problems, and as a result, have found that low hydrogen having excellent re-arcing property and capable of ensuring deep penetration can be obtained. I found a stick. That is, the gist of the present invention is that metal carbonate is 20 to 50% by weight (hereinafter referred to as%), metal fluoride is 0.5 to 3.5%, cellulose is 1.1 to 3.5%, A low-hydrogen rod containing 22 to 55% iron powder and having a weight ratio of cellulose to iron powder of 0.04 to 0.10 applied to a steel core wire. .

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In improving the re-arc property, the protection cylinder formed during welding is basically made of iron powder in order to increase conductivity, but as described above, various performances can be satisfied only by adjusting the iron powder. In addition to this means, attention was paid to an organic substance that produces carbide having good conductivity in the protective cylinder, and it was found that this had a very great effect on the improvement of the re-arc property.

It has also been found that the application of an organic substance generates CO or CO ₂ gas having a high ionization voltage in the arc column, so that the arc force is increased and deep penetration into the workpiece can be ensured. Furthermore, in the case of using the organic substance and the iron powder in the coating agent in combination, the weight ratio of the organic substance to the iron powder greatly affects the penetration depth and the workability of welding, so it was important to determine the appropriate weight ratio.

First, the kind of organic substance for obtaining excellent re-arc properties was selected by the following investigation. That is, Table 1
In the iron powder-containing low-hydrogen coating agent shown in (1), the organic substances such as cellulose, corn starch, wheat starch, and dextrin were changed to 0.3 to 5.0%, and this was changed to a diameter of 3.
JIS G3523 SWY11 of 0mm, length 400mm
Was coated and dried at a maximum temperature of 350 ° C. to produce a welding rod as a trial, and the re-arc property was investigated using an AC welding machine having a no-load voltage of 60 V on the secondary side.

[0011]

[Table 1]

The inspection method is as follows. A JIS G3106 SM490B steel plate having a thickness of 9 mm, a width of 100 mm and a length of 300 mm is assembled in a T-shape, and a horizontal fillet bead is placed at a current of 200 A until the molten bar length becomes 200 mm. The body and the remaining welding rod were cooled to room temperature. Thereafter, the protective cylinder of the welding rod was lightly brought into contact with the fillet portion of the test piece, and immediately the one in which an arc was generated was determined to be a pass, and the result was repeatedly expressed as a total of 10 passes. The results obtained from this experiment are shown in FIG.

These organic substances have a higher heat resistance in the coating agent during welding than the simple substance and play the role of an insulator. However, in the protective cylinder exposed to a high temperature (600 to 800 ° C.) or in the vicinity thereof, it burns. In order to produce carbide having good conductivity, it was effective in improving the re-arc property, and in particular, cellulose exhibited the most excellent re-arc property.

The major reason is that cellulose is fibrous, unlike other organic substances, and the cellulose in the protective cylinder exhibits fibrous carbides, which are in a state of complex connection. Since the conductivity between the tip portions is improved, an extremely excellent re-arc property can be obtained.

Further, cellulose has a high carbonization temperature as a simple substance (cellulose: 310 to 350 ° C., other organic substances:
230-270 ° C.), in the protective case, the ash content of the insulator, which is the thermal final substance of the carbide, is also one of the factors that can improve the re-arc property.

Next, with respect to cellulose and iron powder which have a great effect on the improvement of re-arc properties, it was investigated how the content and the weight ratio of cellulose to iron powder affect re-arc properties and welding performance. . The procedure is as follows:
Cellulose was added to the coatings in Table 1 at 0.3 to 5.0.
%, The iron powder was changed from 10 to 65%, and the weight ratio of cellulose to the iron powder became 0.01 to 0.32, and a welding rod having a diameter of 4.0 mm and a length of 400 mm was obtained as described above. Were prototyped, and various welding performances were investigated using an AC welding machine having a secondary-side no-load voltage of 60 V.

First, in the re-arc test, a test was conducted based on the above-mentioned test pieces, welding conditions, and judgment. ×
Marked. In the penetration depth survey, the plate thickness was 20 mm and the width was 10
JIS G3106, SM490 with 0 mm and 300 mm length
B steel plate in a downward position, current 200A, welding speed 18cm /
Perform straight rod movement at min and weld so as to obtain a bead length of 220 mm.
Macro sections were taken at positions of 60 mm, 100 mm, 140 mm, and 180 mm so that the penetration depth 2 shown in FIG. 2 could be measured. The values are average values obtained from the five cross sections, and the penetration depth was determined to be good when the penetration depth was 2.0 mm or more, slightly poor when 1.0 mm or more and less than 2.0 mm, and poor when less than 1.0 mm.

In the investigation of the welding workability, it was found that
mm, width 100mm, length 450mm steel plate assembled into T type, horizontal fillet and upright down posture using current 200A,
The arc state, the slag state, the degree of spatter, the sticking resistance and the appearance of the beads were examined. The judgment was a comprehensive judgment of each posture, and was determined to be good, slightly inferior, or inferior.

FIG. 3 shows the results obtained from the above test. The re-arc properties are improved as the contents of iron powder and cellulose are increased. However, when the content of cellulose is less than 1.1%, the effect is not seen, and when the content exceeds 3.5%, the coating material is deteriorated during welding. And the burning resistance of the stick deteriorated. If the content of iron powder is less than 22%, the re-arc property is poor, and if it exceeds 55%, the melting rate becomes slow, so that the bar burning resistance is deteriorated. If the content of cellulose is small, the penetration depth becomes extremely shallow. When the weight ratio of cellulose to iron powder was less than 0.04, the arc force was weak and the penetration was shallow, and when it was more than 0.10, the arc was too strong and unstable, resulting in increased scattering of spatter.

From the above, it can be seen that, in order to obtain a good re-arcing property and a deep penetration even when the no-load voltage on the secondary side of the welding machine is low while maintaining good other performances, it is necessary to use cellulose in an amount of 1: 1. It was found that the weight ratio of cellulose to iron powder should be 0.04 to 0.10. Hereinafter, the action of each coating component in the present invention and the reason for limiting the component range will be described.

[Metal carbonate: 20 to 50%] Metal carbonates are lime carbonate, magnesium carbonate, barium carbonate, and the like. Decomposes and generates CO ₂ gas, which shields the weld metal and molten slag from the atmosphere, prevents the intrusion of nitrogen and oxygen, and lowers the partial pressure of water vapor. The purpose is to adjust the fluidity and viscosity of the slag. If the content is less than 20%, the amount of diffusible hydrogen increases and the slag removability deteriorates. On the other hand, if it exceeds 50%, the arc force becomes excessively strong, the arc stability is deteriorated, and the spatter increases.

[Metal fluoride: 0.5 to 3.5%] Metal fluorides are fluorite, cryolite, sodium fluoride, etc., which lower the melting point of slag and produce slag with good fluidity. To be included. If it is less than 0.5%, appropriate fluidity cannot be obtained, so that the bead appearance is poor, and if it exceeds 3.5%, the slag encapsulating property is deteriorated, so that the bead appearance deteriorates, and it becomes difficult to perform downward welding. Arc stability deteriorates.

[Cellulose: 1.1-3.5%] Cellulose is the most important part in the present invention. In the protective cylinder, it becomes a fibrous carbonized material and the conductive property between the tip of the core wire and the protective cylinder. When used together with iron powder, excellent re-arc properties can be obtained even when the no-load voltage on the secondary side of the welding machine is low. Further, since the arc force is increased in order to increase the arc voltage, deep penetration is obtained and it is extremely effective to secure a strong tack weld. If it is less than 1.1%, no effect is obtained in improving the re-arc property, and sufficient penetration cannot be obtained.
If it exceeds 3.5%, the welding rod will burn during welding, and the function of the low hydrogen rod cannot be exhibited.

[Iron powder: 22 to 55%] Iron powder is a basic component of the present invention, and is an essential component for improving the re-arc property because it improves the conductivity of the protective tube. Further, since the amount of slag is reduced, the downward welding can be facilitated. If it is less than 22%, the effect of improving the re-arc property is not exhibited, and if it exceeds 55%, the arc power is weak and the melting rate is slow, so that the Joule heat increases and the bar burning resistance deteriorates.

[Weight ratio of cellulose to iron powder: 0.1.
04-0.10] The weight ratio of cellulose to iron powder is
It is extremely important to obtain deep penetration and good welding performance while securing excellent re-arc properties in the present invention. If the ratio is less than 0.04, the arc voltage is reduced and the arc force is weakened, so that sufficient penetration cannot be obtained. If it exceeds 0.10, on the contrary, the arc force becomes excessively strong and scattering of spatters increases. Further, in the tack welding of downward or horizontal fillet, a bead shape of the main welding is deteriorated because a convex bead is exhibited due to the deterioration of the encapsulating property of the slag.

In the present invention, it is preferable that a deoxidizing agent other than the above-mentioned coating agent, an arc stabilizer, a slag forming agent, and a fixing agent are contained in the following ranges. Examples of the deoxidizing agent include ferrosilicon, metal manganese, and ferro-titanium, which can provide a defect-free and healthy weld metal and ensure good toughness and strength. One or two of these can be used in combination, and the appropriate content thereof is 6.5 to 17.5.
%.

The arc stabilizer includes rutile, wollastonite, etc., which can be used alone or in combination of two.
The proper content is preferably 0.5 to 4.5%. The slag forming agent includes silica sand, feldspar, magnesium oxide and the like, and can be used in one kind or in combination of two or more kinds, and the appropriate range of the content is preferably 0.2 to 2.5%. The fixing agent of potassium silicate and sodium silicate is used alone or in a total of two solid masses of 3.5 to 8.5 in the coating agent.
% Is preferably used.

In the steel core wire used in the present invention, the steel core wire contains 0.01 to 0.08% of C, 0.05% or less of Si, 0.2 to 1.0% of Mn, P is 0.03% or less, S
Is preferably contained in the range of 0.03% or less.

[0029]

EXAMPLE A coating composition having the composition shown in Table 2 was applied to a coating having a diameter of 4.0 mm.
After coating and coating a 400 mm long JIS G3523 SWY11 steel core wire, it was dried at a maximum temperature of 350 ° C.
Various kinds of welding rods were prototyped. Using an AC welding machine with a no-load voltage of 60 V on the secondary side of the welding machine, the re-arc property, penetration depth, and welding workability were examined by the above-described test specimen, welding conditions, and judgment, respectively. In the evaluation of the welding workability and the overall evaluation, a good mark was indicated by a circle, a slightly poor mark was indicated by a mark, and a poor mark was indicated by a cross mark. Table 2 shows the results of these investigations and the overall judgment.

[0030]

[Table 2]

In Table 2, welding rods No. 1 to No. 14 are examples of the present invention, and welding rods No. 15 to No. 28 are comparative examples.
The welding rods No. 1 to No. 14, which are examples of the present invention, have individual components satisfying the requirements of the present invention, and having a low no-load voltage on the secondary side of the welding machine while satisfying various welding performances. However, excellent re-arc properties were obtained, and good penetration was also ensured.

The welding rods No. 15, No. 23, N
No. 26 is an example in which the content of cellulose in the coating agent was small, and therefore, sufficient carbides could not be formed in the protective cylinder, and the re-arc property was poor. In addition, No. 23 contained a large amount of iron powder and did not use cellulose, so that the arc force was weak, the welding workability was deteriorated, and the penetration was shallow. No.26
Because of the large amount of metal carbonate and metal fluoride, the arc became unstable and welding workability deteriorated, and the penetration ratio became shallow because the weight ratio of cellulose to iron powder was small.

The welding rods No. 18 and No. 24 were excellent in re-arc properties due to the large amount of cellulose, but were poor in stick burning resistance. Further, in No. 24, the spatter was large because the weight ratio of cellulose to iron powder was large, and the slag peeling was also deteriorated because the amount of metal carbonate was small, resulting in poor welding workability.

The welding rods No. 20 and No. 28 have a low re-arc property because of a low content of iron powder, and No. 20 has a high arc strength because the weight ratio of cellulose to iron powder is large, resulting in a bead appearance. Deteriorated, and the spatter was scattered much and the amount of metal carbonate was large, so that the arc became unstable and the welding workability became poor.

The welding rod No. 21 has a good re-arc property and a sufficient penetration because the cellulose content and the weight ratio of the cellulose to the iron powder are appropriate. The bar burnability was poor, and the welding workability was slightly inferior.

The welding rods No. 22 and No. 25 are examples in which the weight ratio of cellulose to iron powder is not appropriate. No.22
Since the ratio was large, the amount of spatter was large and welding workability was slightly deteriorated. In contrast, in No. 25, the ratio was small, and the penetration depth was shallow.

The welding rods No. 16, No. 17, No. 19 and No. 27 have excellent re-arc properties because the content of cellulose and iron powder and the weight ratio of cellulose to iron powder are moderate. Although deep penetration can be obtained, welding workability deteriorates because the content of metal carbonate or metal fluoride is not proper. The breakdown was that No. 16 had too much metal fluoride, so the slag encapsulation was poor and the bead appearance deteriorated, and No. 17 was poor in metal slag, and the slag peeling property was poor. In addition, No. 19 was poor in fluidity of the slag and inferior in bead appearance because of a small amount of metal fluoride, and No. 27 was unstable due to a large amount of metal carbonate.

[0038]

As described above, the low-hydrogen rod of the present invention satisfies good welding performances and has excellent re-arc characteristics even in a welding machine having a low no-load voltage on the secondary side. Obtained
In addition, since a weld metal having a deep penetration can be secured, the work efficiency of tack welding can be remarkably improved, and the safety of the welded structure during construction can be greatly contributed.

[Brief description of the drawings]

FIG. 1 is a diagram showing the effect of the type of organic substance in a coating agent on re-arc properties.

FIG. 2 is a diagram showing a penetration depth of a weld metal;

FIG. 3 shows the content of cellulose and iron powder in the coating agent, and
It is a figure which shows the influence which the weight ratio of the cellulose with respect to iron powder has on re-arc property and various welding performances.

[Explanation of symbols]

 1: weld metal 2: penetration depth 3: test steel plate

Claims (1)

[Claims] 1. A metal carbonate of 20 to 50% by weight, a metal fluoride of 0.5 to 3.5% by weight and a cellulose of 1.1 to 1.1% by weight.
It is characterized by being applied to a steel core wire using a coating agent containing 3.5% by weight, 22 to 55% by weight of iron powder, and having a weight ratio of cellulose to iron powder of 0.04 to 0.10. Low hydrogen coated arc welding rod.