JPH06238482A - Low hydrogen type coated electrode - Google Patents

Abstract

PURPOSE:To provide a coated electrode with which a large leg length is obtainable and equal leg characteristics are good even in gravity type single pass welding by using graphite limited in average grain size to a specific range. CONSTITUTION:This low hydrogen type coated electrode is formed by applying a coating material contg. 0.1 to 0.7% (wt.%, hereafter the same) graphite having 112 to 21mum average grain sizes, 3 to 14% magnesia clinker, 3 to 14% magnesite and 3 to 12% metal fluoride to a steel core wire by using water glass.

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, and in particular, in gravity one-pass welding in a horizontal fillet welding position, a coating capable of stably obtaining a large leg length and having good isosceles property. It relates to an arc welding rod.

[0002]

^2. Description of the Related Art A low hydrogen system coated arc welding rod (hereinafter simply referred to as a welding rod) for 490 N / mm ² high-strength steel containing magnesite-silica-fluorite as a main component is mainly composed of lime carbonate-fluorite. Compared with low hydrogen type welding rods, which have a smoother bead shape and extremely less undercut, they are often used for gravity type one-pass welding in horizontal fillet posture of steel for hull structure.

However, in recent years, as the size of ships has increased, the structural steel materials used have become thicker, and inevitably the welding bead in the welding rod is required to have a large leg length, and equality is important. It has become to. Here, the large leg length means that both the upper leg length and the lower leg length can be 8 mm or more (hereinafter referred to as the large leg length), and the isosceles property refers to the ratio of the upper leg length and the lower leg length, and generally, the upper leg length / It is desirable that the lower leg length is 0.9 or more. In the following description, it is expressed as isopod or upper leg length / lower leg length.

Under such a circumstance, when gravity type one-pass welding is performed on a thick steel plate having a plate thickness of about 30 mm using a conventional welding rod in a horizontal fillet posture, a bead with a large lower leg length and a small upper leg length, that is, a non-adherent bead. It has the big drawback that it becomes a uniform leg and the target leg length cannot be obtained. Also,
For horizontal fillet welding rods, as a method for obtaining good long leg length and isoscelesity, one pass is welded by gravity welding and then the shortage of the upper leg length is supplemented by the second pass manual welding. Although so-called two-pass welding is performed, it is a very inefficient method, and this is a serious problem in the industry aiming to improve efficiency.

Further, recently, even when a thick plate is welded using a flux-cored wire for carbon dioxide gas welding for the purpose of improving welding efficiency, the toe of the lower leg length is overlapped and a large leg length is obtained. Without being able to satisfy the isoscelesity. Further, as a conventional technique, Japanese Patent Laid-Open No. 49-
Japanese Patent Application Laid-Open No. 87544 and Japanese Patent Application Laid-Open No. 50-10741 disclose a method for achieving a good bead shape in a welding rod containing MgCO ₃ or SiO ₂ as a main component. 8mm rod diameter based on example
The welding rod of No. 3 was prototyped and the large leg length and the equipodality were investigated. However, none of them yielded the large leg length, and could not obtain the expected effect on the equipodality.

On the other hand, in order to ameliorate these problems, the present inventors have limited the average particle size of high carbon ferromanganese to a coating composition containing magnesite-silica sand-fluorite as a main component. Although it was found that the large leg length and the equipodality could be improved, intensive research was carried out, but after that the market requirements became more severe, and this technology could not adequately respond, and further stabilization of the large leg length and the isopodity is desired. Is starting to appear.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a welding rod which can be stably obtained with a large leg length and which has good isopodity, which cannot be achieved by the conventional large diameter welding rod. Is.

[0008]

In view of the above circumstances, the present inventors have found that a bead with a large leg length can be stably obtained in horizontal fillet welding of a large-diameter welding rod, and welding with good isoscelesity is achieved. We have been engaged in intensive research on the development of rods in terms of the coating composition and the average particle size of graphite. As a result, it was found that by limiting the average particle size of the graphite used, the fluidity of the molten slag was significantly improved and the target could be achieved.

A schematic view of this state is shown in FIGS. In FIG. 1, A is a state diagram of molten slag of a welding rod in which the average particle size of high carbon ferromanganese is limited, 1 is slag, and 2 is a diagram showing a molten pool. B is a state diagram of a molten slag of a welding rod in which the average particle size of graphite is limited, 1 is a slag, and 2 is a diagram showing a molten pool.

FIG. 2A shows a bead shape of a welding rod in which the average particle size of high carbon ferromanganese is limited, 3 is a bead, and 4 is a bead.
Is a steel plate. B is a bead shape of a welding rod in which the average grain size of graphite is limited, 3 is a bead, and 4 is a steel plate.
In FIG. 1, in comparison with the welding rod A in which the average particle size of high carbon ferromanganese is limited, in the welding rod B in which the average particle size of graphite is limited, the molten slag 1 flows in the molten pool in an elongated shape, and the position of the molten pool 2 is increased. Is formed on the upper portion of the bead, it is presumed that, as shown in FIG. 2B, the large leg length and the equal leg property can be stably obtained as compared with the conventional welding rod A.

From the above results and the examination results of other coating compositions, the present inventors have found that the welding workability in horizontal fillet welding is good, the long leg length of the fillet bead is stably obtained, and the isosceles property is equal. A good welding rod was found. That is, the gist of the present invention is that 0.1 to 0.7% graphite having an average particle size of 112 to 212 μm, 3 to 14% magnesia clinker, 3 to 14% magnesite, and 3 to 3 metal fluorides.
A low hydrogen welding rod is characterized in that a coating material containing 12% is applied to a steel core wire using water glass.

[0012]

The present invention will be described in detail below. The constituent features of the welding rod of the present invention are based on the following test results.
The average particle size of graphite in the coating composition is 95-
The film was divided by changing variously within 230 μm. And, separately prepared, 12.9% of rutile, 11.5% of silica sand, 9.5% of fluorite, 3.5% of manganese dioxide, 10.4% of magnesia clinker, 10.8% of magnesite, 1.7 of ferrosilicon. %, Iron powder 35.1%, medium carbon ferromanganese 1.3%, mica 2.2%, lithium fluoride 0.45% and 0.65% of each graphite obtained by dividing the above average particle size. Dry mixing to remove sodium silicate (47
22% of water glass consisting of a combination of Baume 2) and potassium silicate (38 Baume) 1 was added and wet-mixed.
C: 0.07%, Si: 0.01%, Mn: 0.52
%, P; 0.012%, S; 0.005%, N; 0.0
13%, diameter 8 mm consisting of balance Fe, length 700 mm
The steel core wire was coated with an ordinary extrusion-type coating machine so that the coating outer diameter was 12.9 mm.

Further, in order to compare the present invention with a welding rod in which the average grain size of high carbon ferromanganese is limited, a welding rod in which the average grain size of high carbon ferromanganese is limited was manufactured. First, the high-carbon ferromanganese was divided into various particles with an average particle size of 50 to 90 μm and separately prepared, and manganese dioxide 2.9%, rutile 9.7%, silica sand 8.3%, and fluorite 8.3 were prepared separately. %, Magnesia clinker 10.2%, magnesite 7.9%, mica 1.3%, zircon oxide 0.4
%, Ferrosilicon 1.4%, iron powder 36.4%, potassium titanate 0.4%, lithium fluoride 0.4%, sodium alginate 0.6%, medium carbon ferromanganese 1.1%, Each of the divided high carbon ferromanganese of 10.7
% And dry-mixed, sodium silicate (47 Baume)
After 22% of water glass consisting of a combination of 2 + potassium silicate (38 Baume) 1 was added and wet-mixed, C: 0.0
6%, Si; 0.01%, Mn; 0.51%, P;
011%, S: 0.006%, N: 0.0012%, the balance of Fe 8 mm in diameter, 700 mm in length of steel core wire ordinary extrusion coating machine so that the coating outer diameter is about 12.8 mm Painted by.

Both welding rods were dried at a maximum temperature of 400.degree.
Using each of the prototype welding rods obtained, the size is 30
mm × width 100 mm × length 1000 mm, zinc-rich primer applied to approximately 20 μm 490N
/ Mm ² class high-strength steel material is assembled to enable T-type fillet welding, welding current 390A, rod ratio (welding bead divided by consumed rod length) is 1.2 times, horizontal fillet gravity Formula 1 pass welding was performed.

After that, the upper and lower leg lengths are measured using a leg length gauge and the isoscelesity is calculated, and for the graphite-added ones, an analytical sample is collected from the bead and the chemical analysis of [C] is performed. It was It has been separately confirmed that hot cracking does not occur if the [C] content of the weld metal is 0.13% or less.

The results are shown in Table 1 and Table 2 (continued from Table 1),
The results are shown in Table 3 and Table 4 (continued from Table 3). Tables 1 and 2 show examples of the present invention and comparative examples in which the average particle size of graphite is limited, and Tables 3 and 4 are application examples of welding rods in which the average particle size of high carbon ferromanganese is limited. When compared with the example of the present invention using graphite of No. 2, in the examples of the present invention of Tables 1 and 2, beads having a long leg length and stable is obtained, and the average particle diameter of graphite was It was found that the isodality of the beads and the stability of the large leg length are greatly affected.

The average particle size of graphite is 112 to 212.
As is clear from Tables 1 and 2, the value of μm is 112 to 2
Within the range of 12 μm, the welding workability is good and the upper leg length,
The target lower leg length of 8 mm or more is obtained and the isoscelesity is 0.9 or more, and the [C] amount of the weld metal is 0.13% or less, which is a limit amount that does not cause hot cracking. It is based on that.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

If the average grain size of graphite is less than 112 μm, the grain size is too small, so the [C] content of the weld metal is 0.1.
Although it is 3% or less, the fluidity of the slag is too small to obtain an unequal leg and a large leg length. When the average particle size exceeds 212 μm, a large leg length can be obtained and good isoscelesity is obtained, but the fluidity of the slag is excessive and the rod tip is liable to be slightly entangled.

Further, in order to investigate in detail the relationship between the average particle size of graphite and the amount added, a graphite having an average particle size of 112 to 212 μm is used, and a low hydrogen type coated arc which is usually used by changing the compounding ratio. The welding rods were combined so as to have a coating composition, coated with the steel core wire and water glass, dried at the maximum temperature of 400 ° C., and the same test as the above was conducted. ~ 212
It was confirmed that good results can be obtained by adding 0.1 to 0.7% of graphite limited to μm.

If the addition of graphite with the average particle size limited to 112 to 212 μm is less than 0.1%, the target flow form will not be obtained, so that the large leg length cannot be stably obtained and the isopia property is satisfied. I can't. On the other hand, if the amount of graphite added exceeds 0.7%, arc breakage is likely to occur, the yield of [C] content of the weld metal increases, and the hot crack resistance deteriorates.

The magnesia clinker is added to adjust the basicity of the slag and the viscosity of the slag, but if it is less than 3%, its effect cannot be obtained. On the other hand, 14%
If added in excess of 1.0, the viscosity of the slag becomes too high, deteriorating the bead shape and making the arc unstable. Magnesite has excellent arc stability, and CO ₂ It exerts the shielding effect of the weld metal as a source and smoothes the bead surface. If it is less than 3%, it is difficult to form a protective cylinder and pits are likely to occur. On the other hand, if it exceeds 14%, the slag tends to flow, and a normal bead shape cannot be obtained.

If the content of metal fluoride is less than 3%, the fluidity of the slag deteriorates and the bead shape becomes convex. On the other hand, 12
If it exceeds%, the sheath becomes shallow and short-circuits to the base material, making welding difficult. The average particle size of graphite in the above examination was calculated using the following equation after determining the weight ratio between the particle sizes according to JIS Z8801.

Average particle diameter D (μm) = (W1 × 297 + W
2 x 254 + W3 x 180 + W4 x 127 + W5 x 90
+ W6 × 68 + W7 × 53 + W8 × 22) / 100 However, each number indicates the average particle size between the measuring sieves, W1 to W
8 has the following meaning. W1: 297 μm or more wt% W2: 297 to 210 μm wt% W3: 210 to 149 μm wt% W4: 149 to 105 μm wt% W5: 105 to 74 μm wt% W6: 74 to 62 μm wt% W7: 62 to 44 μm wt% W8: less than 44 μm wt% Further, as the coating composition other than graphite, magnesia clinker, and magnesite, metal fluorides are fluorite, glaze, barium fluoride, Aluminum fluoride, lithium fluoride, etc. are shown. As another coating composition of the present invention, rutile as an arc stabilizer, potassium titanate, manganese dioxide, manganese carbonate, ferrosilicon as a deoxidizer and alloying agent, ferromanganese, ferro titanium, silica sand as a slag forming agent, Lime, dolomite, mica,
Iron powder is used as a welding efficiency improving agent such as talc, and sodium silicate or potassium silicate is used as water glass.

[0028]

[Example] JIS G 3523 having a steel core wire diameter of 8.0 mm
The outer diameter of the coating is about 12 depending on the combination of the coating agents shown in Table 5, Table 6 (continued from Table 5), Table 7, and Table 8 (continued-1 from Table 7) on the core wire corresponding to No. 1 of No. 1 The coating was performed so that the thickness would be 1.9 mm, and the maximum temperature was 400 ° C. × 60 minutes for drying. Welding was performed under the below-described welding conditions using each of the obtained welding rods, and general welding workability including leg length, isopodity, slag entanglement degree, and [C] amount of weld metal were investigated. The results are shown in Tables 6 and 9 (continued-2 in Table 7).

(Welding conditions) Test plate: 490 N / mm ² grade steel tensile steel plate (36 t × 10)
0mmw × 1000mml) Inorganic zinc rich primer 20μm coating Gravity welding machine; commercial product Welding position: 1-pass horizontal fillet welding Welding current: 380-400A Lover ratio; 1.2 In addition, the evaluation standard is upper leg length , Both lower leg length 8
Those with a diameter of more than mm were marked with a good ◯, and those with a diameter of less than mm were marked with a bad X.

Regarding the isosceles property, those in which the value obtained by dividing the upper leg length by the lower leg length was 0.95 or more were evaluated as good ◯, and those less than 0.95 were evaluated as bad x. Regarding the fluidity of slag and the general workability of welding, those that are comparable to conventional rods are marked with a good mark, and those that are inferior are marked with a bad mark. Regarding the amount of [C] of the weld metal, those of 0.13% or less are good,
Those exceeding 13% were regarded as defective.

M1 and M2, which are application examples of the welding rods in which the average particle size of high carbon ferromanganese is limited in Tables 5 and 6 (continued from Table 5), have an average particle size of high carbon ferromanganese and an addition amount thereof. This is an example in which the equipodality is not stable even if it is appropriate. Table 7, Table 8 (continued from Table 7-1), Table 9 (continued from Table 7-
In the welding rods L1 to L12 of the present invention shown in 2), since the average particle diameter and the addition amount of graphite are appropriate, the large leg length can be stably obtained, and the isosceles property and the welding workability are good and the welding is performed. The metal [C] showed very good results.

In the welding rod of the comparative example, L13 was interrupted because the amount of metal fluoride added was too large and the coating cylinder became shallow and the welding rod short-circuited to the base material, making welding difficult. Since the amount of metal fluoride added to L14 was too small, the flowability of the slag was poor and the welding workability was deteriorated. In L15, since the amount of added magnesite was too large, the fluidity of the slag was excessive and the bead shape was deteriorated.

With respect to L16, since the amount of magnesite added was too small, the protective cylinder became brittle and the welding workability deteriorated.
Regarding L17 to L18, since the average particle size of graphite is too small, the [C] content of the weld metal is low and good, but the fluidity of the slag is too small and the isosceles property deteriorates and a large leg length is not obtained. .

In L19 to L20, since the amount of graphite added is too large, a large leg length can be obtained and the isosceles property is good.
The fluidity of the slag is excessive and the slag entangles at the tip of the welding rod,
Welding workability deteriorated. In L21, since the amount of graphite added was too small, the flow morphology of the slag was inferior and the isosceles property deteriorated.

Since the amount of magnesia clinker added to L22 was too large, the viscosity of the slag became too high, the bead shape deteriorated, and the arc became unstable. L23 ~ L24
In addition, since the addition amount of magnesia clinker was too small, the viscosity of the slag was not adjusted, and the welding workability and the isopodity deteriorated. In L25 to L26, since the average particle size of graphite is too large, a large leg length can be obtained, and the isosceles property is good,
The fluidity of the slag is excessive and the slag entangles at the tip of the welding rod,
Welding workability deteriorated.

L27 is an example in which graphite is not added at all, but the fluidity of the slag is deteriorated and the isosceles property is deteriorated, and a large leg length cannot be obtained.

[0037]

[Table 5]

[0038]

[Table 6]

[0039]

[Table 7]

[0040]

[Table 8]

[0041]

[Table 9]

[0042]

As described above, according to the welding rod of the present invention, even in the gravity type one-pass welding in the horizontal fillet posture, it is not necessary to compensate for the shortage of the upper leg length unlike the conventional low hydrogen type welding rod. Since the large leg length is stably obtained and the isosceles property is good, the welding efficiency can be improved and the working man-hour can be greatly reduced, which is a great contribution to the industry.

[Brief description of drawings]

FIG. 1A is a flow diagram of molten slag of a welding rod in which the average particle size of high carbon ferromanganese is limited, and B is a flow diagram of molten slag of the welding rod of the present invention.

FIG. 2A is a cross-sectional view of a fillet bead shape welded with a welding rod in which the average particle size of high carbon ferromanganese is limited, and B is a cross-sectional view of a fillet bead shape welded with the welding rod of the present invention.

[Explanation of symbols]

 1 Molten slag 2 Molten pool 3 Fillet beads 4 Steel plate

Claims (1)

[Claims] 1. Graphite having an average particle size of 112 to 212 μm 0.1 to 0.7% (weight%: the same hereinafter), magnesia clinker 3 to 14%, magnesite 3 to 14%,
A low hydrogen-based coated arc welding rod, characterized in that a coating material containing 3 to 12% of metal fluoride is applied to a steel core wire using water glass.