JP2711060B2 - Low hydrogen coated arc welding rod - Google Patents

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 more particularly to an excellent effect applied to downward welding of a circumferential butt joint of a pipe.

[0002]

2. Description of the Related Art Conventionally, circumferential butt welding at the pipeline site has been performed in Japan by upward welding using a low hydrogen-based coated arc welding rod or an illuminite-based coated arc welding rod. In foreign countries, downward welding using a high cellulose-based coated arc welding rod is performed. But,
Since cracking due to hydrogen is a major problem in welding high-tensile steel pipes, especially in-field welding in cold regions, it is desirable to use low-hydrogen-based coated arc welding rods. Was very difficult to weld.

[0003]

In order to solve this problem, the present applicant has previously proposed Japanese Patent Application Laid-Open No. 4-369393. However, the low-hydrogen-based coated arc welding rod proposed above has much superior performance as compared with the previous one, but recently, higher efficiency and severe performance have been required, It was not always satisfactory, and improvement was required.

[0004] That is, in order to achieve high efficiency, one-layer, one-pass welding in which the number of passes is as small as possible is desired. In other words, in the case of one-layer two-pass welding, after welding the first bead, the first bead toe in the groove is ground with a grinder or the like before welding the second bead, and the groove is widened. Insufficient penetration was prevented. However, since the operation takes a long time, if the welding is performed in one layer and one pass, the above-described process is unnecessary. Therefore, a low hydrogen-based coated arc welding rod that can perform one layer and one pass has been desired.

[0005] However, in the conventional low hydrogen-based coated arc welding rod, when weaving is performed to perform one-layer one-pass welding, there is a disadvantage that slag is easily dripped, and dripping of the weld metal is apt to occur.

Further, in the conventional low-hydrogen-based coated arc welding rod, slag is liable to drip when a high current and a high welding speed are used in order to perform the uranami welding with high efficiency, so that the welding metal is concave. There was a disadvantage that it became a wave bead.

The present invention solves the above-mentioned disadvantages of the prior art, and can prevent sagging of slag even in one-layer one-pass welding by weaving. As a result, low-hydrogen coating that enables welding with a small number of passes is possible. An object of the present invention is to provide an arc welding rod.

[0008]

In the above situation, the present inventors first studied a method for preventing slag from dripping. It has been found that the conventional welding rod has a small arc spread and the droplet transfer lacks stability. As a result, when weaving is performed, the crater is insufficiently spread and the slag is liable to drop. Therefore, various investigations have been made on means for sufficiently securing the spread of the crater, spraying the arc, and stabilizing the droplet transfer. As a result, it was found that by adding ultrafine Ti oxide, the protective cylinder was stabilized, that is, the protective cylinder was uniformly melted, the directionality of the arc was stabilized, and the spread of the crater was easily controlled. .

With the conventional welding rod, since the construction is almost straight and the contact welding is used, the stability of the protective cylinder did not matter much. However, in the weaving construction, the welding rod was slightly separated from the base material. Therefore, a more uniform melting property of the protection tube was required, which was considered to be the reason that the conventional welding rod was not suitable for weaving.

[0010] However, although the ultrafine Ti oxide has the above-mentioned effects, on the other hand, the amount of spatter is not sufficiently reduced, and further improvement in spatter removal in the subsequent process and safety during welding is achieved. Turned out necessary.

The inventors of the present invention have studied various components, and as a result, by increasing the amount of carbon, which has been considered to be desirably low in the point of crack resistance in the conventional low hydrogen-based coating agent, The inventors have found that the arc can be stabilized and the amount of spatter generated can be reduced, and the present invention has been completed here.

That is, according to the present invention, the coating composition is
Metal carbonate: 30 to 50%, metal fluoride: 1.5 to 4
%, SiO ₂ : 5 to 12%, Ti oxide: 1 to 6% (however,
Ultrafine Ti oxide having a particle size of 0.3 μm or less should be contained by 40% or more. ), Si: 3-9%, Mn: 1-6%, F
e: a coating agent containing 25 to 50% is applied to the outer periphery of the steel core wire at a coverage of 20 to 35%, and the carbon content of the entire welding rod according to the following formula (1) is 0.08. The gist of the invention is a low-hydrogen coated arc welding rod characterized by being regulated to 0.25%. Carbon amount = (carbon amount in core wire) + {(carbon amount in coating agent) × (coverage / core ratio)} (1) where: coverage = (weight of coating agent / welding rod) Total weight) × 100% Core ratio = (weight of core wire / weight of entire welding rod) × 100%

In another aspect of the present invention, the coating composition further comprises N
i: 0.5 to 4.5%, Mo: 0.1 to 4.5%, Ti: 0.1
One or more of の う ち 3%, and / or B:
It is characterized by containing 0.05-0.2%.

[0014]

First, the reasons for limiting each component and the coverage in the present invention are as follows.

Metal carbonate: 30 to 50% Metal carbonate is added as a gas generating agent, but if it is less than 30%, the amount of gas generated is small, shielding is insufficient, and the viscosity of the slag is reduced, so that pits are generated on the bead surface. I do. On the other hand, if it exceeds 50%, the viscosity of the slag is remarkably increased, and the adaptation of the bead is deteriorated, and the amount of generated gas is increased to increase the generation of spatter. Therefore, the amount of the metal carbonate is in the range of 30 to 50%. As the metal carbonate, for example, CaCO ₃ , BaCO ₃ , MgCO ₃ or the like is used.

Metal fluoride: 1.5 to 4% Metal fluoride has an effect of adjusting the viscosity and fluidity of slag. However, if the content is less than 1.5%, the effect is not obtained. If the content is more than 1.5%, a good bead is formed at the position of 2 to 4 o'clock. 4.5 to 6 o'clock and 7.5 to 7.5
At the position of 6 o'clock (see FIG. 1), the familiarity between the bead and the base material deteriorates. Therefore, the amount of metal fluoride is 1.5 to 4%
Range. As the metal fluoride, for example, Ca
F _2, etc. is used.

SiO ₂ : 5 to 12% SiO ₂ has the effect of strengthening the arc and ensuring penetration. However, if it is less than 5%, the arc is weak and the spread of the crater is small. In addition, the familiarity of the bead also deteriorates. on the other hand,
If it exceeds 12%, the slag disturbs and easily becomes entangled at the position of 2 to 4 o'clock, and a good bead cannot be obtained. Therefore, the amount of SiO ₂ is in the range of 5 to 12%.

Ti oxide: 1 to 6% (provided that the particle size is 0.3 μm)
The following ultra-fine Ti oxides contain 40% or more.) Ti oxides have an effect of uniformizing the melting of the protective cylinder, thereby making the directionality of the arc constant, and preventing the weld metal from sagging even during weaving. There is. For this purpose, it is necessary to contain 1 to 6% of a Ti oxide containing 40% or more of ultrafine Ti oxide having a particle size of 0.3 μm or less. If it is less than 1%, the effect cannot be obtained, and bead familiarity also deteriorates. On the other hand, if it exceeds 6%, the fluidity of the slag increases, and slag obstruction is likely to occur at 2 to 4 o'clock.

Si: 3 to 9%, Mn: 1 to 6% Si and Mn are added as deoxidizing agents. However, if each is less than the lower limit, the effect is not obtained. As a result, pits are generated on the bead surface.
Note that Si is a simple substance or Fe-Si, Si-Mn, and Ca-Si.
Mn is a metal Mn or Fe-Mn, Si
-Mn or the like.

Fe: 25 to 50% Fe is added to improve the welding efficiency.
If it is less than 50%, the effect is small, and if it exceeds 50%, the amount of the slag forming agent is relatively small, and the encapsulation of the slag is poor. Therefore, the Fe content is in the range of 25 to 50%. Fe is iron powder or Fe-Mn, Fe-S
It can be added as an Fe content such as i.

Coverage: 20-35% If the coverage is less than 20%, the amount of the slag forming agent decreases, and pits are generated due to insufficient shielding. On the other hand, if it exceeds 35%, the amount of the slag forming agent becomes too large, and the slag is disturbed, and a good bead cannot be obtained. Therefore, the coverage is in the range of 20 to 35%.

Carbon content (value of formula (1)): 0.08 to 0.25% If the carbon content defined by the following formula (1) is less than 0.08%, droplets become large and spattering occurs. 0.25%
It was found that the arc became too strong when exceeding the limit, the crater was dug down, the weld metal was easily dripped, and the amount of spatter was slightly increased. Therefore, in the present invention, the following
The carbon content defined by the equation (1) is restricted to a range of 0.08 to 0.25%. More preferably, it is 0.12 to 0.20%.

Carbon amount = (carbon amount in core wire) + {(carbon amount in coating agent) × (coverage / core ratio)} (1) where, coverage = (weight of coating agent / Weight of entire welding rod) × 100% Core ratio = (weight of core wire / weight of entire welding rod) × 100%

[0024] In addition to the above components, one or more of the following components can be added to the coating material in an appropriate amount, if necessary.

Ni: 0.5-4.5% Ni is effective in increasing the toughness of the ferrite structure, but if it is less than 0.5%, the effect cannot be obtained.
%, The arc is weakened, the droplet transferability is deteriorated, and poor penetration occurs. Therefore, the Ni amount is 0.5 to
The range is 4.5%.

Mo: 0.1 to 4.5% Mo is effective for adjusting the strength, but if less than 0.1%, the effect cannot be obtained. On the other hand, if it exceeds 4.5%, the impact value is increased. Deteriorates. Therefore, the amount of Mo is set to 0.1 to 4.5%.

Ti: 0.1 to 3% The effect of Ti on the welding workability is that the arc concentration can be improved and the arc can be softened. However, if it is less than 0.1%, the arc concentration is inferior, causing poor fusion. On the other hand, if it exceeds 3%, the arc becomes too weak and poor penetration occurs. Therefore, the Ti amount is in the range of 0.1 to 3%. Ti is added in the form of, for example, Fe-Ti.

B: 0.05-0.2% B is effective for improving the conformity with the base material.
If the content is less than 0.05%, familiarity with the base material is inferior, so that skill is required for the operation of the rod. On the other hand, if it exceeds 0.2%, the arc becomes too weak, and poor penetration occurs. Therefore, the B content is in the range of 0.05 to 0.2%. B can be added in the form of a B alloy or a B oxide.

Incidentally, in order to adjust the mechanical properties of the deposited metal, one or more alloy components such as Cr, Cu and Nb may be added to the coating agent or the core wire. The other component compositions of the steel core wire are not particularly limited.

In the present invention, water glass is generally used as a viscous agent. However, since water glass contains a small amount of components such as Na ₂ O and K ₂ O, it is used as a slag forming agent and an arc stabilizer. Also works. In the case where a DC power supply is used, a water glass containing no K ₂ O is more preferable because the protective cylinder is more stable.

Next, an embodiment of the present invention will be described.

【Example】

A coating having a composition shown in Tables 1 and 3 was applied to a steel core wire at a coverage of 20 to 35% to prepare a test welding rod. Using these test welding rods, a butt joint (60 °) of a horizontal fixed pipe (10.3 mmt × 1016 mmφ)
V groove) by 1 layer 1 pass welding condition: current 80 ~ 2
20A, voltage 18-28V, welding speed 10-25cm / mi
Welding was performed in reverse at n, and workability at each welding position was investigated. The results are also shown in Table 2.

In the table, No. 1 to No. 10 are all examples of the present invention, and showed good results. There is no dripping of the weld metal and no dripping of the slag, and the amount of spatter is small.

On the other hand, No. 11 of the comparative example had too much metal carbonate, increased the amount of spatter generated, and lacked slag stability. Further, the amount of ultrafine Ti oxide in the Ti oxide was less than 40%, and the stability (dripping) of the weld metal was lacking.

In Comparative Example No. 12, the amount of Ti oxide was too large, and slag was obstructed. In addition, since the amount of carbon in the formula (1) was low, spattering occurred frequently. In addition, the amount of metal fluoride was large, the fluidity of the slag increased, and the compatibility with the base material was deteriorated.

In Comparative Example No. 13, the amount of SiO ₂ was large, and slag was obstructed. Further, the carbon content of the formula (1) was too high, and the stability of the weld metal was deteriorated.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

As described above in detail, according to the low hydrogen based coated arc welding rod of the present invention, it is possible to reduce
Even in layer 1 pass welding, dripping of slag can be prevented, and construction with a small number of passes can be achieved. Uranami construction is also possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a welding position in a downward welding of a circumferential butt joint of a pipe in a clockwise manner.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-367393 (JP, A) JP-A-61-229494 (JP, A) JP-A-62-161496 (JP, A)

Claims (3)

(57) [Claims] 1. Total weight% of coating agent (hereinafter the same), metal carbonate: 30 to 50%, metal fluoride: 1.5 to 4%, SiO ₂ : 5 to 12%, Ti oxide: 1 -6% (provided that 40% or more of ultrafine Ti oxide having a particle size of 0.3 μm or less), Si: 3-9%, Mn: 1-6%, Fe: 25-50%, Is coated on the outer periphery of the steel core wire at a coverage of 20 to 35%, and the carbon content of the entire welding rod according to the following formula (1) is 0.08 to 0.25%.
A low hydrogen coated arc welding rod characterized by being regulated as follows. Carbon amount = (carbon amount in core wire) + {(carbon amount in coating agent) × (coverage / core ratio)} (1) where: coverage = (weight of coating agent / welding rod) Total weight) × 100% Core ratio = (weight of core wire / weight of entire welding rod) × 100% 2. The coating composition further comprises: Ni: 0.5 to 4.5%,
2. The composition according to claim 1, wherein one or more of Mo: 0.1 to 4.5% and Ti: 0.1 to 3% are contained.
2. The low-hydrogen coated arc welding rod according to item 1. 3. The low hydrogen coated arc welding rod according to claim 1, wherein the coating agent further contains B: 0.05 to 0.2%.