JP3130768B2 - 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 system used for temporary welding for temporarily fixing an object to be welded before main welding in a manufacturing process of structures such as shipbuilding, bridges and buildings. The present invention relates to a coated arc welding rod, and more particularly, to a low hydrogen-based coated arc welding rod having excellent re-arc properties and insulation of a coated portion.

[0002]

2. Description of the Related Art Low-hydrogen coated arc welding rods have a lower diffusible hydrogen and oxygen content in the deposited metal than other non-low hydrogen coated arc welding rods such as illuminite and lime titania. It has the characteristics of being low in resistance to low-temperature cracking, ductility, toughness and X-ray performance. For this reason, the low hydrogen-based coated arc welding rod has a tensile strength of 100 kgf from mild steel.
Widely used, such as high-strength steel and low alloy steel of / mm ² class. Generally, the coating is CaCO ₃ and Ba
A metal carbonate such as CO ₃ as a main component, CaF ₂ , TiO _2
2 and slag forming agents such as SiO ₂ , Fe-Si, Fe-M
n and a deoxidizing agent such as a simple metal, an alloying agent, and the like. This coating agent is applied to the outer periphery of the steel core wire after adding an appropriate amount of water glass and sticking. Then, the coating agent coated steel core wire is subjected to a drying treatment at a temperature of 400 to 500 ° C. to produce a low hydrogen-based coated arc welding rod.

[0003] The object to be welded with a low hydrogen based coated arc welding rod,
That is, for important structures such as shipbuilding, bridges, buildings and various tanks, submerged arc welding (SAW), mag welding (MA)
Welding methods such as G) and MIG welding (MIG) are often used because of their high welding efficiency. However, in tack welding performed to fix an object to be welded before main welding, Covered arc welding, which has the advantages of simple and agile equipment such as a power supply and easy welding in all positions, is widely used.

[0004] Since the welded portion of the tack welding is rarely removed before the main welding, the coated arc welding rod for the tacking has excellent X-ray performance and the amount of diffusible hydrogen causing low-temperature cracking. Is required, and requirements such as excellent re-arcing property, insulation property, bead shape and appearance, and the like are required. In particular, in tack welding, in order to repeatedly generate an arc, it is necessary to have a re-arc property that it is easy to generate a re-arc when the arc is cut again after the arc is cut, and a welding rod is attached to the holder. In order to move to the welding position while holding it, it is necessary for the safety of the welder to have an insulating property for preventing re-ignition from a portion other than the tip of the coating material.

[0005] As a welding rod that can satisfy the above requirements, there is a low hydrogen-based coated arc welding rod. Unfortunately, the conventional low hydrogen-based coated arc welding rod is:
A major drawback is that the re-arcability, which is a requirement of the above, is inferior to other types of coated arc welding rods. In order to regenerate the arc, it is necessary that the electric resistance of the electrode (the tip of the welding rod) be low. However, in the low hydrogen-based coated arc welding rod, the electric resistance at the tip of the coating agent is high, and the electric conductivity is not good. When the object to be welded or the tip of the coating agent is at a high temperature for a few seconds after welding, re-arcing is easy due to the low electric resistance of the tip of the coating agent, but after 10 seconds or more, When the tip of the agent is cooled to some extent, re-arcing is difficult.

Conventionally, when re-arcing is performed, the covering portion at the tip is removed to expose the core, but in this method,
At the start of welding, insufficient shielding due to lack of a coating agent occurs, so that welding defects such as blow holes and pits occur in the deposited metal. For this reason, the backward starting rod method and the discarding method of generating an arc at a place different from the welded part are used, but these methods are complicated and require advanced transportation techniques. There is a disadvantage. For this reason, there is a demand for the development of a low-hydrogen-based coated arc welding rod having excellent re-arcing properties without having to rely on the backward starting rod operation method and the discarding method.

In order to solve this problem, a low-hydrogen coated arc welding rod for tacking with improved re-arc properties is disclosed in JP-A-54-159353 or JP-B-58-479.
No. 58 has been disclosed. The former regulates the average particle size and blending amount of iron powder in the coating material, and the latter regulates the apparent density and blending amount of iron powder in the coating material to increase the electrical conductivity at the tip of the coating material and re-arc. This is to improve the performance. With these low hydrogen based coated arc welding rods, the re-arcability was considerably improved.

[0008]

However, in the case of covered arc welding, the no-load voltage is reduced from 70 to 80 V to about 20 V by an electric shock prevention device for preventing electric shock of the welder.
, It is extremely difficult to re-arc. For this reason, it is required to further lower the electric resistance of the coating agent tip. In the case of such a low no-load voltage, it cannot be said that the conventional low-hydrogen-based coated arc welding rod for temporary attachment described above sufficiently satisfies the re-arc property.

[0009] The insulation property is a characteristic particularly required when welding is performed in a narrow portion, but the conventional technique has a disadvantage that the insulation performance is inferior. In addition, recently, in order to increase productivity in the manufacturing process, a reduction in drying time, that is, a high-speed drying is required, so that when a compounding amount of iron powder is large, a drying crack of a coating portion is likely to occur. There are points.

The present invention has been made in view of such a problem, and has been developed as a low hydrogen coated arc welding rod for tacking.
Low hydrogen coated arc with excellent re-arc properties, excellent insulation of the coating, good weldability, bead shape / appearance and pit resistance, and excellent dry cracking resistance. It is intended to provide a welding rod.

[0011]

The low-hydrogen coated arc welding rod according to the present invention comprises a low-hydrogen coating agent containing iron powder,
In low hydrogen type covered electrode coated on the outer periphery of the steel core wire, wherein the iron powder is contained 20 to 60 mass% of the total coating agent in the coating agent, the average particle diameter 30 to 80μm
, And the said iron powder is characterized by containing C iron powder Mass per 0.005 to 0.10 mass%, oxygen 1.0 mass% or less.

In this case, metal fluoride is contained in the coating material in a total of 0.3 to 1.3 in terms of F with respect to the whole coating material.
It may contain mass%.

Further, the iron powder particle size can be more than 150μm is to be 8 to 20 mass% of the total iron.

[0014]

The present inventors have found that the re-arc properties are excellent, the insulation of the coating is excellent, the welding workability is good, the bead shape / appearance, the pit resistance and the resistance to dry cracking. As a result of conducting various experiments and researches to develop a low hydrogen-based coated arc welding rod having excellent characteristics, it has been found that the object of the present invention can be achieved particularly by appropriately setting the amount of iron powder and the average particle diameter.

When performing re-arcing, the covering portion is removed,
An arc can be generated by exposing the core portion and energizing it.However, in this method, insufficient shielding occurs due to lack of coating agent, and shortage of slag forming agent causes blowholes and pits in the deposited metal. Defects will occur. In addition, in order to perform re-arcing without removing the coating portion, it is necessary to impart electrical conductivity to the tip of the coating agent. Iron powder has a significant effect. The inventors of the present application have studied the components of iron powder, together with the particle size and amount of iron powder to be added to the coating agent, in order to enhance the electrical conductivity of the coating agent tip, and found the following facts. Was.
(1) The average particle size of the iron powder in the coating agent is 30 to 80 μm
That. (2) As a chemical component of iron powder in the coating agent, C: 0.00
5 to 0. l0 mass%, oxygen: 1.0 mass% it less. (3) the amount of iron powder in the coating is 20 to 60 mass% relative to the total coating agent.

If the requirements of (1), (2) and (3) are satisfied, basically the performance as a covered temporary welding arc welding rod can be sufficiently enhanced.

Furthermore, as a result of research on components in the coating agent other than iron powder, it was found that metal fluorides have an effect on the re-arcing property. From this viewpoint, the composition ranges of metal fluorides are shown below. It turned out that there was an appropriate range. (4) be restricted to the total 0.3 to 1.3 mass% of CaF _2, BaF ₂ and the like of the metal fluoride contained in the coating agent to the whole coating agent in terms of F.

In order to improve the re-arc property,
The particle size of the iron powder in the coating may be reduced, but when the particle size of the iron powder is reduced, the ratio of the iron powder in the coating is reduced to 20% in the present invention.
To 60 mass% and high for the drying step during production, drying cracks is likely to occur. Therefore, it is effective to add the iron powder having a coarse particle size to the coating agent to such an extent that the re-arc property is not impaired, in order to improve the dry cracking resistance. For this reason,
It is preferable to satisfy the following requirements. (5) the particle size contains 8 to 20 mass% or more of iron powder 150μm for the entire iron powder that. However, the average particle size of all iron powder in the coating agent is 30 to 80 μm as described above.

Hereinafter, the reasons for limiting the numerical values of the constituent elements defined as described above will be described. Average particle size of iron powder: 30 to 80 μm Iron powder is an essential raw material that is most frequently blended in a welding rod for tacking in order to maintain re-arcing properties. In addition, there is an effect that energization of the coating agent tip portion (protective tube) interposed between the welding object and the welding object is ensured, and re-arcing can be performed without exposing the steel core wire. When the average particle size of the iron powder is less than 30 μm, the welding workability and the bead shape are deteriorated, and the insulation is also poor. On the other hand, when the average particle size of the iron powder exceeds 80 μm, the re-arc property cannot be maintained.

FIG. 1 shows the average particle size of iron powder on the tack weldability by taking the average particle size of iron powder on the horizontal axis and the amount of iron powder in the coating agent on the vertical axis. FIG. 6 is a graph showing the relationship between In the figure, ○ and ● indicate that the C content in the iron powder was 0.0
For 05 to 0.04 mass%, □ and ■ the C in the iron powder
The amount is the case of 0.05 to 0.10 mass%. Both oxygen content of iron powder in is 0.5 mass%. Then, those in which the re-arc property ratio (the ratio of those in which re-arcing occurred) of 90% or more were obtained were represented by ○ and □, and those having less than 90% were represented by ● and Δ. As is clear from FIG. 1, when the average particle size of the iron powder is less than 30 μm, the insulating property becomes poor. On the other hand, if the average particle size of the iron powder exceeds 80 μm, the re-arc property deteriorates. For this reason, the average particle size of the iron powder is set to 30 to 80 μm.

The average particle size was measured by a commercially available particle size distribution analyzer using a laser diffraction / scattering method (for example, Nikkiso Co., Ltd. Microtrac).

C content in iron powder: 0.005 to 0.1
C in the 0% by mass iron powder has an effect of maintaining the electrical conductivity of the coating agent. For this reason, in the case of the welding rod for tacking, the amount of iron powder is increased, the energization resistance at the tip of the coating agent (protective cylinder) is reduced, and energization is performed. However, in the case of iron powder having a low content of conductive C, even if the power supply is low in no-load, the current-carrying resistance does not decrease enough to have a sufficient re-arcing property, and it is difficult to conduct current. On the other hand, when an iron powder containing excessive C is added to the coating agent, the current is supplied to the portion other than the protection tube at the tip of the coating agent, that is, the coating portion not exposed to the high temperature, and the insulating property is reduced. Therefore, the C content in the iron powder is regulated so that the iron powders that come into contact with each other in the coating material other than the protective cylinder do not conduct electricity and have an insulating property, and the protective cylinder has sufficient electrical conductivity. There is a need to. And Thus, C is re-arc resistance, sufficient electric conductivity can not be obtained is degraded is less than 0.005 quality <br/> mass% in the iron powder, 0. l0 exceeds mass% and the insulating resistance is lowered.

FIG. 2 is a graph showing the relationship between the amount of C in the iron powder and the re-arcing rate by taking the C content in the iron powder on the horizontal axis and the re-arcing rate on the vertical axis. In the figure, ○ indicates that the average particle size of the iron powder is 30 to 40 μm, and the compounding amount of the iron powder is 30 to 40.
A case of mass%, △ average particle size of 50 to 60μ
m, the amount is 40 to 50 mass%, □ the average particle size of 70
To 80 [mu] m, the amount is the case of 40 to 50 mass%. Both oxygen content of iron powder in is 0.5 mass%.

As is apparent from FIG. 2, C in iron powder
When the content exceeds 0.1 mass%, the insulating property becomes poor. Further, when the C content is less than 0.005 mass%,
The re-arcing rate drops sharply. For this reason, C in iron powder
Content is 0.005 to 0.10 mass%.

Oxygen in iron powder: not more than 1.0% by mass Oxygen in iron powder forms an insulating layer on the surface of the iron powder that comes into contact with the coating agent, and gives good insulation to the coating. However, in the case of iron powder containing excessive oxygen, an insulating layer is formed so thick that it does not disappear even in a protection tube heated to a high temperature, so that the protection tube does not conduct electricity at the time of re-arcing.

FIG. 3 is a graph showing the relationship between the amount of oxygen in the iron powder on the horizontal axis and the re-arcing rate on the vertical axis. In the figure, ○ indicates that the average particle size of the iron powder is 30 to 45 μm,
Amount of iron powder is 25 to 40 mass%, □ is the average particle diameter of 60 to 75 [mu] m, the amount of iron powder 45 to 60 mass% of iron powder. In each case, the carbon content in the iron powder was 0.0
6 is a mass%. As shown in FIG. 3, when the oxygen content in the iron powder is more than 1.0 mass%, re-arc resistance rate is remarkably lowered. Therefore, the oxygen content in the iron powder and 1.0 quality <br/> weight% or less.

It should be noted that the lower the oxygen, the better the electrical conductivity, but the effect of inhibiting the insulating property is extremely small as compared with C described above.

The amount of iron powder in the coating agent: 20 to 60
The amount of the iron powder in the amount% affects the contact ratio of the iron powder in the coating agent. Even if the average particle diameter, C content, and oxygen content are in the above ranges, if the amount of iron powder is too small, the iron powder does not come into contact with each other. And the re-arcing rate is reduced. Conversely, if the amount of the iron powder is too large, the insulation property deteriorates and arc instability is caused, causing defects such as pits and blowholes in the weld bead. Therefore, it is necessary to regulate the iron powder amount in the coating in 20 to 60 mass%.

[0029] That is, as shown in FIG. 1, the iron powder amount in the coating is less than 20 mass%, re-arc resistance is inferior, the iron powder amount conversely exceeds 60 mass%, the insulation Property becomes poor. Therefore, iron powder amount in the coating is from 20 to 60 quality <br/> mass%.

The total amount of metal fluorides in the coating agent in terms of F is:
0.3 to 1.3% by mass Basically, there is no problem in the performance as a temporary welding rod only by the regulation on the iron powder as defined in claim 1, but in order to further improve the re-arcing property, It is desirable to regulate the amount of metal fluoride (F) in the coating agent. The metal fluoride (F) has a function of adjusting the strength of the arc and adjusting the melting point of the produced slag to adjust the bead shape, and adjusts the forming temperature of the protective cylinder heated to a high temperature. Therefore, it affects the re-arc property. Further, metal fluoride has an effect of preventing generation of pits.

[0031] The metal fluoride by adding 0.3% to 1.3 mass% in terms of F, the re-arc resistance further can be further improved, the inhibition and adjusting the bead shape of the pit The effect is obtained. The amount of metal fluoride is F
If more than 0.3 less than mass% or 1.3 mass% in terms of, these effects can not be obtained. The metal fluoride is C
It can be added with aF ₂ , BaF ₂ , AlF ₃ or the like.

Iron having a particle size of 150 μm or more based on the total iron powder
The amount of powder: 8 to 20% Basically, as defined in claim 1 or 2, there is no problem in the performance as a tack welding rod, but the yield at the time of production is further increased and the productivity is improved. Therefore, it is effective to add a small amount of iron powder having a coarse particle size. By adding coarse iron powder to the coating agent, the bonding strength between the particles is maintained at an appropriate level and the escape of moisture is improved as compared with the case of only fine particles, so that even during high-speed drying, drying cracks are more likely. It is even less likely to occur, and high productivity can be obtained. Iron powder having a particle size of less than 150 μm does not have the above effects. Also, when the particle size is 150 μm.
The content in total iron powder in m or more iron powder, 8 mass%
The effect is not exhibited less than, more than 20 mass%, bonding strength is reduced in the reverse, anti-drying cracking resistance deteriorates fast drying.

Other components constituting the flux in the present invention include, in addition to the above components, oxides such as carbonates, TiO ₂ and SiO ₂ which are added to ordinary low hydrogen-based coating agents. Fe-Si, Fe-Mn, Ni-M as acid agent and alloying agent
g or the like may be added, and these additions do not impair the effects of the present invention at all.

[0034]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Table 1 below shows the average particle size, C content, oxygen content, and iron powder content of the blended iron powder, the composition of metal fluoride, and the composition of other coating components. The coating having the properties and component compositions shown in Table 1 was applied to a carbon steel core wire (diameter 4.0).
(mm, length 400 mm) to produce a low hydrogen-based coated arc welding rod. Thereafter, tests of re-arc property and insulation property were performed. The core is JIS G3523.
(Coated arc welding rod core wire) was used. The test results are shown in Table 2 below.

[0035]

[Table 1] In addition, in addition to these components, Na ₂ O, K ₂
O, Li ₂ O and the like are contained.

[0036]

[Table 2]

The re-arc test was performed at 200 A to 24 V using an AC power supply (no-load voltage: 20 V) equipped with an electric shock prevention device.
The welding position was horizontal fillet welding such that the contact of the test rod with the test plate was constant. The test method is
First, after welding with a welding rod length of 50 mm, the arc
After holding for a second, the tip of the test rod (protective tube) was again lightly brought into contact with the test plate to cause re-arcing. At that time, whether or not re-arcing was performed was repeatedly tested with 30 or more rods. The evaluation of the re-arc is good when the re-arc is performed 90% or more (95%).
% Or more: 、, 90 to less than 95%:）), and less than 90% were poor (×).

In the insulation test, welding was performed under the condition of 200 A to 24 V using an AC power supply (no load voltage: 80 V) without an electric shock prevention device, and the welding posture was horizontal fillet as in the re-arc test. The test method was such that after first welding for 20 seconds, the arc was turned off, the coating of the test rod was immediately brought into contact with the test plate from the holder side, and moved while contacting the test plate toward the tip of the rod until ignition occurred. The distance between the arc ignition point and the tip was measured, and the average length of 30 or more repetitions was 1
A case of less than 0 mm was evaluated as good (○), and a case of 10 mm or more was evaluated as poor (×).

Regarding the bead shape and the pit resistance, the beads were observed in the above two tests, and the bead shape and the pit resistance were judged. Regarding the bead shape, three cross-sections of a cross-sectional macro test specimen were taken out of a bead length of 100 mm, the upper and lower leg lengths were measured, and the upper leg length / lower leg length = 0.90 to 1.0 was favorable for all cross sections (0.95 to 1.0 1.0: 、, 0.90 to 0.95:）), and others were poor (×). Pit resistance is 100mm bead length
One or less of them were good (0: 、 １, one: ○), and two or more were bad (x).

Further, the resistance to drying cracking was determined at a coating speed of 500 m.
/ Min, a coated arc welding rod was manufactured at a baking temperature of 450 ° C., and the presence or absence of dry cracks was visually determined. Good dry cracking rate of 5% or less (less than 2%: ２, 2 to 5%:
）) A case exceeding 5% was regarded as defective. In the overall evaluation, each item having at least one x was evaluated as x, and as for each item having no x, the larger number of ◎ and で in each item was adopted in the overall evaluation.

The test offer No. 1 to No. 7 is an example of the present invention, all of which are good in re-arcing property, insulation resistance and bead shape, with little occurrence of pits and dry cracks,
It was in a good range. On the other hand, the comparative examples (No. 8 to N
o. In the case of 14), no satisfactory re-arcing property, insulation resistance, bead shape or the like was obtained.

That is, in Comparative Example No. In Comparative Example No. 8, since the average particle size of the iron powder was as small as 28 μm, the insulation resistance and the bead shape were deteriorated. 9 was as large as 84 μm, so that the re-arc property was deteriorated. Comparative Example No. 10 has a C content of iron powder of 0.
Re arc resistance is deteriorated because 003 mass% and less, Comparative Example No. 11 resistance to dielectric edge property is deteriorated because C is large and 0.18 mass% in the iron powder. Comparative Example No. 12 re arc resistance is deteriorated because the oxygen in the iron powder is large and 1.3 mass%. Comparative Example No. 13 re arc resistance is deteriorated because the content of iron powder is small and 18 mass% of the coating agent, Comparative Example No. 14 To 62 mass% and a high content of iron powder, resistance to dielectric edge property is degraded pitting resistance was also degraded.

[0043]

As described above, according to the present invention,
By appropriately setting the average particle size, component, and amount of iron powder in the coating agent for low hydrogen coated arc welding rods, and further regulating metal fluoride in the coating agent, it can be used as a temporary welding rod. Excellent re-arcing, insulation, welding workability, bead shape / appearance and pit resistance are obtained. Therefore, the present invention greatly contributes to the efficiency of tack welding and the safety of steel structures.

[Brief description of the drawings]

FIG. 1 is a graph showing the influence of the average particle size and the amount of iron powder on the performance of a tack welding rod.

FIG. 2 is a diagram showing the relationship between the C content in iron powder and the re-arcing rate.

FIG. 3 is a diagram showing the relationship between the amount of oxygen in iron powder and the re-arcing rate.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-171294 (JP, A) JP-A-54-159353 (JP, A) JP-B-59-1516 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) B23K 35/365 B23K 35/30 330

Claims (3)

(57) [Claims] 1. A low hydrogen-based coated arc welding rod in which a low hydrogen-based coating agent containing iron powder is applied to the outer periphery of a steel core wire, wherein the iron powder contains 20 to 6 parts of the entire coating agent in the coating agent.
0 mass% is contained, the content and the average particle size of 30 to 80 [mu] m, wherein the iron powder iron powder Mass per 0.005 to 0.10 mass% of C, oxygen 1.0 mass% or less A low-hydrogen coated arc welding rod characterized in that: Wherein the metal fluoride in the coating agent, a low hydrogen system according to claim 1, characterized in that it contains a total of 0.3 to 1.3 mass% relative to the total coating agent in terms of F Covered arc welding rod. 3. A low hydrogen type covered electrode as claimed in claim 1 or 2, wherein the iron powder is what particle size of more than 150μm is 8 to 20 mass% of the total iron.