JPH07276083A - Low hydrogen type coated electrode - Google Patents

Abstract

PURPOSE:To produce a low hydrogen type coated electrode excellent in welding operability even in welding operation for narrow gaps in particular. CONSTITUTION:The outer circumference of a steel core wire is coated with a coating agent contg., as constituting ratio, by the wt.% of the coating agent, 2.5 to 9.0% Si and/or Si alloy (expressed in terms of Si), 0.5 to 5.0% Mn and/or Mn alloy (expressed in terms of Mn), 35.5 to 60.0% CaCO3, 7.5 to 24.0% CaFe2, 3.5 to 11.0% SiO2 and 1.5 to 9.0% TiO2, furthermore, in which, as for the grain size of Si and/or Si alloy, by the wt.% of Si and/or Si alloy, the ones of >=250mum are not substantially contained, the ratio of the ones of <250 to >=125mum is regulated to 7 to 25%, the ratio of the ones of <62 to >=22mum is regulated to 25 to 40% and the ratio of the ones of <22mum is regulated to 17 to 35% by a binder to form a low hydrogen type coated electrode. In particular, it is suitable for welding operation for the narrow gap welding part zones, particularly, of marine structures.

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 a low-hydrogen coated arc welding rod having excellent welding workability in a narrow groove welding portion such as an offshore structure. .

[0002]

2. Description of the Related Art In general structures, the groove angle is usually about 50 to 60 °, but in structures using thick steel plates of 50 mm or more, such as offshore structures, In consideration of welding efficiency, residual stress, and prevention of welding distortion, welding is often performed with a narrow groove with a groove angle of 30 to 40 °.

If the groove angle is 50 to 60 °, no problem occurs even if the conventionally used low hydrogen type covered arc welding rod is used, but the groove angle is 30 to 40.
If the angle becomes narrow, it is inevitable that the rod operation within the groove will be difficult to perform, and the familiarity between the base metal and the weld metal will decrease, resulting in a convex bead or defective penetration at that part, and X-ray There was a problem such as performance degradation.

Under these circumstances, the present invention is excellent in welding workability, especially in welding work with a narrow groove, and has a required performance as a welding rod (predetermined mechanical performance, It is an object of the present invention to provide a low-hydrogen-based coated arc welding rod, which is equipped with a stable welding metal).

[0005]

As a result of various studies to solve the above problems, the inventors of the present invention have made it possible to improve the familiarity between the base metal and the weld metal among various items of welding workability. In particular, focusing on the fact that it is necessary to increase the concentration of the arc, the coating materials CaCO ₃ , CaF ₂ ,
Various investigations were carried out on the particle size composition ratios of SiO ₂ , TiO ₂ , Si and Mn. As a result, it has been found that adjustment of the particle size composition ratio of Si is effective.

That is, in the present invention, the composition ratio of the coating material is
% Coating material (hereinafter the same), Si and / or Si alloy (Si conversion): 2.5-9.0% Mn and / or Mn alloy (Mn conversion): 0.5-5.0% CaCO _{3: 35.5~60.0% CaF 2: 7.5~24.0} % SiO 2: 3.5~11.0% TiO 2: containing 1.5 to 9.0%, and, Si And / or the grain size of the Si alloy is 250 μm or more: substantially free of less than 250 μm, 125 μm or more: 7-25% less than 62 μm, 22 μm or more: 25-40% less than 22 μm: 17-35% The gist is a low-hydrogen coated arc welding rod in which the coating material is coated on the outer circumference of the steel core wire with a fixing agent.

[0007]

The present invention will be described in more detail below.

The inventors of the present invention firstly concentrate the arc as a measure for effectively increasing the temperature of the base metal by the welding heat and melting it in order to improve the familiarity between the base metal and the weld metal in the narrow groove. It is effective to improve the property, and attention was paid to the grain size of the Si alloy as the means.

If the grain size of the Si alloy is made fine, even if the addition amount is the same as that of the conventional product, the Si alloy is uniformly distributed in the coating material, and the surface area to be coated becomes large. As a result, oxidation reaction occurs in a short time,
It was considered that the generation of thermal energy due to oxidation occurred in a shorter time, and as a result, the arc concentration was improved.

Therefore, a Si alloy having a smaller grain size than the conventional one and having the grain size shown below was experimentally produced and used. The particle size distribution was measured by a laser diffraction type particle size distribution measurement method using a Nikkiso Microtrac. 88 μm or more: 0 to 1% less than 88 μm, 62 μm or more: 2 to 5% less than 62 μm, 22 μm or more: 50 to 60% less than 22 μm: 35 to 45%

As a result, as expected, although the arc concentration was found to be satisfactory, in some cases the coating (protective cylinder) was missing during welding and the arc was not stable. This is because water glass and fine Si alloy react with each other and a large amount of hydrogen gas is generated. As a result, the gas is less likely to deviate from the inside of the coating and fine cracks are generated in the coating. It was thought to be connected.

Therefore, as a result of further studies on the composition of the particles, it was found that there is a particle size composition which can improve the concentration of the arc without causing dry cracking, and the present invention has been completed. .

That is, 250 μm or more: substantially free of less than 250 μm, 125 μm or more: 7 to 25%, less than 62 μm, 22 μm or more: 25 to 40%, less than 22 μm: 17 to 35%, and / or Si having a particle size constitution of Si alloy (converted to Si): contains 2.5 to 9.0%, and further contains Mn and / or M
n alloy (Mn conversion): 0.5-5.0%, CaCO ₃ : 35.5
_{~60.0%, CaF 2: 7.5~24.0%} , SiO 2: 3.
5 to 11.0% TiO _2: With coating agent containing 1.5 to 9.0%, chipping of the coating may be prevented, even stronger blown gatherable and arc arc, preform The familiarity with is also improved, and the X-ray performance can be further improved.

Next, the reasons for limiting the particle size constitution and the component composition in the present invention will be explained.

<Granularity composition ratio of Si and / or Si alloy>
(Total weight% of Si and / or Si alloy) 250 μm or more: substantially not contained Particles of 250 μm or more impede welding workability, particularly arc concentration, and therefore are not substantially included. The term "substantially free" as used herein means 4% or less.

125 μm or more and less than 250 μm: 7 to 25
% To prevent dry cracking, 125 μm or more and 250 μm
7% or more of particles are required, and if less than 7%, dry cracking is likely to occur. On the other hand, in order to obtain good welding workability and arc concentration, it is necessary to suppress it to 25% or less. Therefore, the range of particles of 125 μm or more and less than 250 μm is 7 to 25%. In addition, more desirably 7 to 15%
Is.

22 μm or more and less than 62 μm: 25-40% In order to obtain good welding workability and arc concentration, 2
25% or more of particles of 2 μm or more and less than 62 μm is required,
On the other hand, in order to prevent dry cracking, the amount should be 40% or less. Therefore, the range of particles of 22 μm or more and less than 62 μm is 25 to 40%. In addition, it is preferably 30 to 38%.

Less than 22 μm: 17 to 35% Fine particles of less than 22 μm are particles that are indispensable for improving welding workability and arc concentration, and also affect dry cracking. 17% or more is required for the concentration of the arc. However, in order to prevent dry cracking, it is necessary to suppress it to 35% or less. In addition, it is preferably 24 to 32%.

<Ingredient composition of coating agent> Si and / or Si alloy (Si conversion): 2.5-9.0% When Si accounts for less than 2.5% of the total weight of the coating agent, the base metal and the weld metal And the weld metal is liable to drop, the bead appearance is also poor, and deoxidation is insufficient at the same time, so that pits and blow holes are generated and X-ray performance is deteriorated. On the other hand, if it exceeds 9.0%, deoxidation becomes excessive and pits and blowholes are generated to deteriorate X-ray performance. Therefore, the amount of Si is made into the range of 2.5-9.0%. In addition, Si
The alloy can be added by Fe-Si, Fe-Si-Mn, Ca-Si or the like, and the Si alloy is added in an amount converted to the amount of Si.

Mn or Mn alloy (Mn conversion): 0.5 to 5.0
% If the Mn in the total weight of the coating agent is less than 0.5%, deoxidization becomes insufficient, and pits and blowholes are generated to deteriorate the X-ray performance. On the other hand, if it exceeds 5.0%, deoxidation becomes excessive, and pits and blow holes are generated to deteriorate X-ray performance. Therefore, the amount of Mn is set in the range of 0.5 to 5.0%.
Note that Fe-Mn, Fe-Si-Mn, or the like, or metal Mn can be applied to the Mn alloy, and the Mn alloy is added in an amount converted into the amount of Mn.

CaCO ₃ : 35.5 to 60.0% CaCO ₃ is the main component of the coating agent, and acts as a slag forming agent and a gas generating agent. But 3
If it is less than 5.5%, the amount of gas generated is insufficient, nitrogen and oxygen in the air cannot be sufficiently blocked, the pit resistance and blowhole resistance of the weld metal deteriorate, and the X-ray performance deteriorates significantly.
On the other hand, if it exceeds 60.0%, the arc becomes too weak, large-sized spatters frequently occur, and convex beads are formed. Therefore, the amount of CaCO ₃ is set in the range of 35.5 to 60.0%.

CaF ₂ : 7.5 to 24.0% CaF ₂ acts as a viscosity adjusting agent for slag. However, if it is less than 7.5%, the viscosity of the slag becomes too high, the bead is not uniformly covered with the slag, the bead appearance deteriorates, and pits occur. On the other hand, if it exceeds 24.0%, the viscosity of the slag is remarkably reduced, so that the slag is excessively covered and the slag interferes with the slag, causing defects such as slag entrapment and fusion failure. Therefore, the amount of CaF ₂ is 7.5 to 24.
The range is 0%.

SiO ₂ : 3.5 to 11.0% SiO ₂ has a function as a slag forming agent, a viscosity adjusting agent and a welding workability adjusting agent such as arc strength. However, if it is less than 3.5%, the viscosity of the slag decreases and
The amount of slag is insufficient, the slag does not cover the beads uniformly, and the arc is too weak and the crater spreads too small, resulting in defects such as markedly poor bead appearance, lack of familiarity, and insufficient penetration, which makes welding difficult. On the other hand, if it exceeds 11.0%, the slag amount and the viscosity increase, so that the slag does not escape with the arc force, and defects such as slag entrainment and fusion failure occur. Therefore, the amount of SiO ₂ is 3.5-11.0%
The range is.

TiO ₂ : 1.5-9.0% TiO ₂ has a function as a slag forming agent, a viscosity adjusting agent, and a welding workability adjusting agent such as arc stability. However, if it is less than 1.5%, the arc becomes unstable, undercutting occurs, and spatter increases. On the other hand, if it exceeds 9.0%, the arc becomes too weak and defects such as insufficient melting occur. Therefore, the amount of TiO ₂ is set in the range of 1.5 to 9.0%.

If necessary, an appropriate amount of a carbonate such as BaCO ₃ or MgCO _{3 is} added to the coating material in order to adjust the welding workability such as the strength of the arc, the conformability and the spread of the crater. It can be added. Similarly, the strength of the arc,
In order to adjust welding workability such as arc stability, K
_An appropriate amount of silicate containing ₂ O or Na ₂ O can be added to the coating agent. Further, in order to improve the mechanical properties of the weld metal, alloy components such as Ni, Mo, Ti and B can be added to the coating agent in appropriate amounts, and iron powder is added to improve the efficiency. It can also be added to the coating agent in an appropriate amount.

Next, examples of the present invention will be described.

[0027]

EXAMPLE An Si alloy having a grain size composition ratio shown in Table 1 was used for a steel core wire of 4.0 mmφ × 450 mmL, and a coating material having a compounding composition shown in Table 2 was used together with a fixing agent to provide a coverage of 25 to 35% The coated arc welding rod applied in the range of was prepared. Under the welding conditions shown in Table 3, the marine structure shown in FIG. 1 was welded to a test plate having a groove angle, and the workability and X-ray performance of the welding rod were evaluated. The results are shown in Table 2.

In Table 2, No. 1 to No. 14 are examples of the present invention, and productivity, welding workability, and X-ray performance were all good.

On the other hand, Comparative Example No. 15 is a conventional product Fe-
Since Si was used, the arc concentration was poor, the weld metal became a convex bead, and penetration failure occurred on both sides of the bead, resulting in a marked deterioration in X-ray performance.

Comparative Example No. 16 uses the finely produced Si alloy shown in paragraph 0010, which had a good arc concentration, but the protective tube was missing during welding. However, the arc becomes unstable and welding is difficult. In addition, the yield decreased due to dry cracking during the production of the welding rod.

In Comparative Example No. 17 also, the grain size of the Si alloy used was fine, and there were some cracks in the coating during drying, and the yield decreased. Further, since Si in the coating agent is too low and CaCO ₃ is too high, the base material and the weld metal are not well compatible with each other, resulting in a convex bead, resulting in pits and blowholes due to poor penetration and insufficient deoxidation, resulting in X-rays. Performance has deteriorated significantly.

The yield of Comparative Example No. 18 also decreased, similar to No. 17. Si in the coating is too high, and moreover, SiO ₂
Is too low, the arc is weak, the bead appearance is poor due to lack of viscosity and amount of slag, pits and poor penetration due to excessive deoxidation occur, and X-ray performance is significantly deteriorated.

In Comparative Example No. 19, the Mn in the coating material was too high and the CaCO ₃ was too low, so that pits and blowholes frequently occurred due to excessive deoxidation and insufficient shield, and the X-ray performance was significantly deteriorated.

In Comparative Example No. 20, the CaF ₂ content in the coating material was too low and the TiO ₂ content was too high, so the X-ray performance was significantly deteriorated due to defective pitting and poor penetration due to the arc being too weak.

In Comparative Example No. 21, the Mn in the coating material was too low and the CaF ₂ was too high, so slag entrainment, pits and blowholes due to poor fusion and insufficient deoxidation were generated, and the X-ray performance was remarkable. It got worse.

In Comparative Example No. 22, since the amount of SiO ₂ was too high, the X-ray performance was remarkably deteriorated due to the inclusion of slag and the poor fusion due to the slag obstruction.

In Comparative Example No. 23, since the TiO ₂ was too low, the arc was unstable, and undercutting caused insufficient penetration, resulting in a marked deterioration in X-ray performance.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

As described above in detail, according to the low hydrogen type covered arc welding rod of the present invention, excellent welding workability can be obtained even in the welding construction of narrow groove welding such as offshore structures. At the same time, the required performance such as mechanical performance as a welding rod and securing of weld metal without defects can be obtained.

[Brief description of drawings]

FIG. 1 is a view showing a groove shape, where (a) shows a groove angle of a general structure and (b) shows a groove angle of an offshore structure.

Claims (1)

[Claims] 1. The composition ratio of the coating material is the coating material weight% (hereinafter the same), and Si and / or Si alloy (Si conversion): 2.5-9.0% Mn and / or Mn alloy (Mn) _{Convert): 0.5~5.0% CaCO 3: 35.5~60.0} % CaF 2: 7.5~24.0% SiO 2: 3.5~11.0% TiO 2: 1.5 ~ 9.0%, and the grain size of Si and / or Si alloy is 250μm or more: substantially does not include less than 250μm, 125μm or more: 7-25% less than 62μm, 22μm or more: 25-40% 22μm Less than: 17-35%, a low-hydrogen-based coated arc welding rod in which a coating agent is coated on the outer periphery of a steel core wire with a fixing agent.