JP2942142B2 - 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 having good welding workability, particularly excellent arc stability in a low current range and short-circuit resistance. Less than,
"Low hydrogen welding rod" for convenience
Called.

[0002]

2. Description of the Related Art Low hydrogen welding rods have excellent crack resistance and mechanical properties of the weld metal. It is applied to welding of large structures using thick plates, but in such important structures, welding heat input is often limited in order to secure the strength and low-temperature toughness of the weld metal,
Therefore, welding with stable arc even at a low current has been required.

[0003] However, unlike a non-low hydrogen welding rod containing an organic substance in a coating material, the low hydrogen welding rod is weak in arc spraying, so that the arc becomes unstable when welding in a low current range. In addition, there is a problem that welding is short-circuited easily during welding, and welding is difficult unless a skilled welder is used.

To cope with such a problem that the arc becomes unstable, for example, Japanese Patent Application Laid-Open No. 5-169296 discloses a method for limiting the particle size of silica sand and Japanese Patent Application Laid-Open No. 4-29489.
No. 2 proposes a method using silica lime. Both methods are inventions aimed at reducing the amount of spatter generated by increasing the stability of the arc, and cannot be a means for solving the arc stability and short-circuit resistance in a low current range.

On the other hand, in the industry using welding rods, the shortage of skilled welders has become a serious problem, and it has become difficult to rely on skilled workers forever. For this reason, at present, there is a strong demand for the development of a low-hydrogen welding rod with good welding workability that enables stable welding even for unskilled workers.

The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a low-hydrogen-based coated arc welding rod excellent in arc stability and short-circuit resistance particularly in a low current range.

[0007]

Means for Solving the Problems In order to solve the above problems, the present inventors examined the coating composition and found that the welding workability was better than that of conventional low hydrogen welding rods, We have found a low-hydrogen welding rod with remarkably excellent arc stability and short-circuit resistance in the basin.

That is, the present invention relates to a coating agent in weight%, carbonate lime: 25 to 55%, fluorite: 5 to 24%, rutile: 2 to 9%, Mn and / or Mn alloy (in terms of Mn): 1 to 5%, Si and / or Si alloy (Si conversion amount): 2 to 8%, and the particle size of the carbonated lime is the weight% of the carbonated lime.
Particles of less than 3 μm (A): 20% or less, particles of 3 μm or more and less than 16 μm (B): 15 to 40%, provided that A / B ≧ 1/3, particles of 125 μm or more: 10 to 45%. The gist of the present invention is a low-hydrogen-based coated arc welding rod obtained by applying a coating agent characterized in that it is applied to the outer periphery of a steel core wire.

Another feature of the present invention is that mica is suppressed to not more than 3% by weight of the coating agent.

[0010]

The present invention will be described below in more detail.

In order to maintain the arc at a low current, the arc length must be kept shorter than usual. At this time, the protection cylinder at the tip of the welding rod comes into contact with the steel plate. It was observed that the protective sheath was broken by only slight contact of the welding rod, resulting in a short circuit.

[0012] The cause was considered to be that the adhesive force between the coating materials was insufficient, so that tests were carried out by changing the type and amount of the adhesive, but no satisfactory results were obtained. . On the other hand, we tried to strengthen the bonding force between the coating material materials by using fine material and making the flux dense.
Certainly, the protection tube became harder, but the coating agent dropped off due to vibration during transportation due to a decrease in yield due to dry cracking of the coating material during welding rod manufacture and cracks inside the coating, and the protection tube during welding. In some cases, micro cracks were formed, and the short-circuit resistance was rather deteriorated.

Therefore, without causing dry cracking,
In addition, as a result of intensive studies on the optimal raw material particle size that also improves the bonding strength between the coating material raw materials, it can be solved particularly by regulating the particle size of carbonate lime, which is the main raw material of low hydrogen welding rods, to a specific range. Have been found, and have led to the present invention. First, the particle size composition of carbonated lime will be described.

Particle size composition of carbonated lime : Fine particles (B) having a size of 3 μm or more and less than 16 μm are necessary for filling large particles and improving the bonding force between coating materials, and 15% or more by weight of carbonated lime. Effective with However, in order to increase the fixing strength of the coating agent and obtain the strength of the predetermined protective cylinder, it is important that the ultrafine particles (A) having a size of less than 3 μm to fill the space between the fine particles are present. Less than particles
At least 1/3 of (B) is required.

On the other hand, when the amount of fine particles increases, dry cracking occurs, so the amount is limited. For ultrafine particles (A) having a particle size of less than 3 μm, 20% or less in terms of lime carbonate weight%,
For fine particles (B) having a size of 3 μm or more and less than 16 μm, lime carbonate weight%
At 40% or less.

Further, particles having a size of 125 μm or more are effective for preventing dry cracking, and exhibit an effect when added in an amount of 10% or more by weight of lime carbonate. However, if it is added in excess of 45%, the strength of the coating is degraded, and the protective cylinder is easily chipped. Therefore, particles in this range are 10 to 45% by weight of carbonated lime.
Is appropriate. The particle size was measured using a laser diffraction particle size analyzer.

According to the present invention, it is essential to add carbonated lime having the above-mentioned particle size composition as a coating agent. The reasons for limiting the carbonated lime and other raw material components are as follows.
In addition, the addition amount is a coating agent weight%.

Carbonated lime: 25% to 55% carbonated lime is a main component of the coating agent and has an action as a slag forming agent, a gas generating agent and the like. But 25
%, The amount of generated gas is insufficient, nitrogen and oxygen in the atmosphere cannot be shut off sufficiently, the pit resistance and blowhole resistance of the weld metal deteriorate, and the X-ray performance deteriorates remarkably. on the other hand,
If it exceeds 55%, the arc is too weak, spatters of large grains occur frequently, and moreover, it becomes a convex bead. Therefore, the content of carbonated lime in the coating agent is set in the range of 25 to 55%.

Rutile: 2 to 9% rutile has a function as a slag forming agent, a viscosity controlling agent, and a welding workability controlling agent such as arc stability. However, if it is less than 2%, the arc becomes unstable, undercuts occur, and spatter increases. On the other hand, if it exceeds 9%, the arc becomes too weak, and defects such as insufficient penetration occur. Therefore, the amount of rutile in the coating agent is in the range of 2 to 9%.

Fluorite: 5 to 24% fluorite acts as a viscosity modifier for slag. However, if it is less than 5%, the viscosity of the slag becomes too high, the slag does not uniformly cover the bead, the bead appearance deteriorates, and pits are generated. On the other hand, if it exceeds 24%, the viscosity of the slag is remarkably reduced, so that the slag is excessively covered and hinders the slag, causing defects such as slag entrainment and poor fusion. Therefore, the amount of fluorite in the coating agent is 5 ~
The range is 24%.

Mn and / or Mn alloy (Mn conversion amount): 1 to 1
If 5% Mn is less than 1%, the deoxidation becomes insufficient, and pits and blowholes are generated to lower the X-ray performance. 5%
Exceeding the range results in excessive deoxidation, and pits and blowholes are generated to lower the X-ray performance. Therefore, the Mn amount is 1 to 5
% Range. In addition, Mn can be added in the form of Mn alloy such as Fe-Mn and Fe-Si-Mn, in addition to metal Mn. In the case of Mn alloy, the Mn conversion amount is used.

Si and / or Si alloy (Si conversion amount): 2
When 8% Si is less than 2%, the conformity between the base metal and the weld metal is significantly deteriorated, the weld metal is easily dripped, the bead appearance is also deteriorated, and the deoxidation is insufficient, and pits and blow holes are generated. Decreases X-ray performance. On the other hand, if it exceeds 8%, deoxidation will be excessive, and pits and blow holes will be generated, lowering X-ray performance. Therefore, the Si amount is in the range of 2 to 8%. Note that Si can be added in the form of an alloy such as Fe-Si, Fe-Si-Mn or Ca-Si, and the Si alloy is added in an amount converted to a Si material.

Mica: 3% or less Mica is a raw material that improves paintability, improves productivity and yield, and also has a function as a slag forming agent.
However, if it exceeds 3%, the amount of slag and viscosity increase, defects such as poor slag entrainment and fusion occur, and the amount of diffusible hydrogen in the deposited metal increases due to the contained crystallization water (deterioration of the crack resistance of the welded joint). Therefore, in the present invention, it is desirable to suppress the content to 3% or less as necessary.

In order to adjust the welding workability such as arc strength, conformability, and spread of the crater, carbonates such as barium carbonate and magnesite, silicates such as talc and silica sand, Alternatively, alloy components such as Ni, Mo, Cr, Ti, and B can be added to the coating material in an appropriate amount in order to improve the mechanical properties of the weld metal.

Next, examples of the present invention will be described.

[0026]

EXAMPLES A coated arc welding rod having the coating agent shown in Table 1 was produced by the following method, and welding workability, X-ray performance, and productivity were investigated. Table 1 shows the results.

<Production of welding rod> 3.2 mmφ × 350 mmL
Of each coating agent around the mild steel core wire of 25 to 3
It was painted to 5% and dried at a maximum temperature of 450 ° C.

<Welding test method (welding workability and X-ray performance)> Groove shape: shown in FIG. Steel type: SM490 Shape dimensions: 9mmt × 150mmw × 500mmL Welding posture: Upward Welding power supply: AC (AC) Welding method: After front welding, the back is suspended and back welding Welding current: 80 to 90 Amp (3.2mmφ rod low current Judgment criteria for welding workability: ○ (good), △ (slightly poor), ×
(Defective) (Evaluation with particular emphasis on arc stability and short-circuit resistance) Judgment criteria for X-ray performance: Grade based on JIS Z 3104: Class 1 (Good) (○), Class 2 (Slightly poor) (△), Class 3 or lower (bad)
(X) three stages.

<Productivity> In the coating / drying process, the ratio of defective products having dry cracks in the coating to all welding rods is 1%.
The following are good (○), more than 1% and slightly less than 3% (％),
Those exceeding 3% were evaluated in three stages of bad (x). At that time, the selected good welding rods were packed in a 5 kg paper box for packing the product, dropped on a steel plate from a height of 1 m, and if the weight of the dropped coating exceeded 5.0 g, cracks were present inside the coating. Considering that it may have been done, the judgment was changed to a grade one rank lower.

In Table 1, No. 1 to No. 14 are examples of the present invention, all of which show excellent arc stability and short-circuit resistance when welded in a low current range, and have good X-ray performance. Also, there was no drying crack, the yield was good, and the coating did not fall off in the dropping test.

On the other hand, of Comparative Examples No. 15 to No. 26, No. 15 and No. 16 have few ultrafine particles of less than 3 μm per lime carbonate, and No. 15 has many particles of 125 μm or more. In addition, there is no bonding force between the coating material materials, and both the welding workability and the X-ray performance are poor.

Comparative Example No. 17 was 3 μm / carbonate lime.
Although fine particles having a particle size of less than 16 μm exist, ultrafine particles having a particle size of less than 3 μm are insufficient, and the bonding force between the coating material materials is not sufficient.

Comparative Example No. 18 is 16 μm
Although the fine particles having a particle size of less than m were sufficient, the yield was within the range of “good” because the coarseness of 125 μm or more was insufficient. However, in the drop test, 5.0 g or more of the coating material was found to have fallen, so the rank was slightly poor. is there. In addition, the protective tube sometimes cracks during welding, making it difficult to weld, and the welding workability and X-ray performance are somewhat poor.

In Comparative Examples No. 19 and No. 20, the yield itself was in the range of “poor” because the amount of fine particles of less than 16 μm per carbonate lime was too large and the coarseness of 125 μm or more was too small. Of course, the protection tube during welding is severely chipped, and welding workability, X-ray performance, and productivity are poor.

Comparative Example No. 21 has a low X-ray performance due to a small amount of carbonated lime and a large amount of fluorite, and entrainment of slag.
Poor fusion occurred. In Comparative Example No. 22, since the amount of rutile was large, the arc was weak and poor penetration occurred.

Comparative Example No. 23 contained many Si and Mn, and had poor X-ray performance due to generation of pits and blowholes.
The welding workability was good. In Comparative Example No. 24, the content of Si and fluorite was small, the bead appearance was deteriorated, and pits and blowholes were generated due to insufficient deoxidation. In Comparative Example No. 25, Mn was small, and X-ray performance was poor due to generation of pits and blowholes, but welding workability was good.

In Comparative Example No. 26, since the amount of lime carbonate was large and the amount of rutile was small, the arc was weak, unstable, and spatter increased.

[0038]

[Table 1]

[0039]

As described in detail above, according to the present invention,
It is possible to provide a low hydrogen coated arc welding rod having excellent welding workability, particularly excellent arc stability and short-circuit resistance in a low current range, and stable welding can be performed even by an unskilled welder. .

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a groove shape in a welding test.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-179292 (JP, A) JP-A-54-102254 (JP, A) JP-B-63-58077 (JP, B2) JP-B-60 5397 (JP, B2)

Claims (2)

(57) [Claims] 1. Coating agent weight%, carbonate lime: 25-55%, fluorite: 5-24%, rutile: 2-9%, Mn and / or Mn alloy (Mn equivalent): 1-5% , Si and / or Si alloy (in terms of Si): 2 to 8%, and the particle size of the carbonated lime is less than 3 μm by weight% of carbonated lime (A): 20% or less, Particles (B) having a size of 3 μm or more and less than 16 μm: 15 to 40%, provided that A / B ≧ 1/3 and particles having a size of 125 μm or more: 10 to 45%. Low hydrogen coated arc welding rod applied to 2. The low hydrogen coated arc welding rod according to claim 1, wherein mica is suppressed to 3% or less in terms of coating weight%.