JP3392347B2 - Sintered flux for submerged arc welding and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a firing type flux for submerged arc welding, which is used for welding steel structures such as ships, offshore structures, storage tanks, steel frames, bridges, etc., and particularly has moisture absorption resistance and pockmark resistance . An improved firing flux.

[0002]

2. Description of the Related Art Flux for submerged arc welding is
Manufactured by using silicon oxide (SiO ₂ ) as a main component and manganese oxide (MnO, Mn ₃ O ₄ ), calcium oxide (CaO), alumina (Al ₂ O ₃ ) and other oxides and fluorides as raw materials. ing. The flux for submerged arc welding is classified into a fusion type flux, a mixed type flux, and a firing type flux according to the manufacturing method.

Melt type flux is a flux obtained by melting raw materials in a melting furnace such as an electric furnace, cooling and pulverizing to a proper particle size. For this reason, there is a disadvantage that a large-scale facility is required, the manufacturing lot is increased, and the manufacturing cost is increased. The mixed flux is manufactured by directly mechanically mixing raw materials having different particle shapes and components. This mixed flux requires adjustment of particle size and bulk density of raw materials,
If this adjustment is not made, segregation of the flux raw material occurs when the flux is sprinkled at the welded spots, the slag generated during welding becomes uneven, and stable welding cannot be performed.

On the other hand, the firing type flux is generally a binder material for the flux raw material powder such as oxide or fluoride.
It is produced by the steps of kneading, granulating, drying, and firing by adding sodium silicate or the like. In rare cases, the binder may be omitted. Since this calcined flux can be manufactured with relatively simple equipment, it is inexpensive, and it is possible to add a deoxidizer and alloying elements, and it is possible to adjust the weld metal components. However, similar to the mixed type flux, the quality of the fired type flux, and thus the characteristics of the weld metal, greatly change depending on the raw materials. For example, the moisture content or hygroscopicity of the raw material such as crystal water greatly affects the amount of hydrogen (diffusible hydrogen) in the weld metal. The amount of diffusible hydrogen in these weld metals causes hydrogen cracking.

Therefore, various methods have heretofore been considered in order to reduce the amount of diffusible hydrogen in the weld metal welded by using the burning type flux. For example,
51-16172, Japanese Patent Publication No. 52-25819, Japanese Patent Publication 56
-8717, Japanese Patent Publication No. 56-53476 and Japanese Patent Publication 58
Japanese Patent Publication No. 49356 discloses a method of preventing hydrogen from diffusing into the weld metal by increasing the proportion of carbonate in the flux and lowering the H ₂ partial pressure by CO ₂ gas generated during welding. There is.

However, in the method of increasing the carbonate in the flux, the surface of the welding bead becomes rough due to the CO ₂ gas generated by the decomposition of the carbonate, and the workability deteriorates when high speed welding is performed. Was left with the problem.
Further, for example, in JP-B-51-25809, a low hygroscopic lithium silicate aqueous solution is used as a binder,
Alternatively, a method of lowering the moisture absorption of the binder by using water glass added with lithium silicate has been proposed. However, since lithium silicate is expensive and increases the cost of the flux, it is the current situation that it is not applied to ordinary flux.

The submerged arc welding is a welding method in which flux is previously sprayed on the surface of the welded portion and a bare wire is fed into the surface, and a large amount of flux is required due to its characteristic. Part of the flux is recovered and reused as it is, while the other part burns and disappears.
A part of it is used for chemical reaction with molten metal and is generated as slag.

Conventionally, welding slag generated after submerged arc welding (hereinafter referred to as submerged arc welding slag or simply welding slag) has been discarded as industrial waste, but a considerable amount of flux is also contained in the welding slag. The components remain, and recently, the reuse of welding slag has been studied from the viewpoint of effective utilization of resources. For example, Japanese Patent Laid-Open No. 57-181796 and Japanese Patent Laid-Open No. 7-227694 propose a method of reusing a welding slag by mixing an unused flux or the like. But these methods
The mixing ratio and particle size of the mixed type flux are specified, and no study has been made on the calcined type flux.

As a technique of utilizing welding slag as a raw material for a firing type flux, Japanese Patent Laid-Open No. 21537/1976 discloses that the welding slag is recovered in order to reduce the amount of CO gas generated during welding. However, it is described that de-ironing pulverization, particle size adjustment, and component adjustment are performed to obtain a firing type flux for submerged arc welding. However, in the technique described in the above-mentioned publication, CO which is a gas generated during welding is used.
Although the amount of gas generated is reduced, the specific conditions necessary for producing a fired flux from the submerged arc welding slag are not described, and the amount of diffusible hydrogen in the weld metal cannot always be reduced.

Further, the inventors of the present invention are likely to cause defects in the appearance of beads called pock marks when the reuse of the submerged arc welding slag is repeated, and the flux using the submerged arc welding slag has excellent pockmark resistance. We have found that it is necessary to use flux.

[0011]

DISCLOSURE OF THE INVENTION The present invention advantageously solves the above-mentioned problems and can reduce the diffusion of hydrogen in the weld metal and has excellent moisture absorption resistance. The purpose is to propose a manufacturing method of the slab. Another object of the present invention is to propose a firing type flux for submerged arc welding which is also excellent in pockmark resistance and a method for producing the same.

[0012]

Means for Solving the Problems The inventors of the present invention have diligently studied the water content or hygroscopicity of the flux raw material powder for the purpose of reducing the amount of diffusible hydrogen in the weld metal. I thought of adding. Welding slag has a vitreous and uniform composition, contains a component that can be used as a flux, and has an advantage that the content of crystal water is small. Furthermore, the present inventors have conducted various studies for adding welding slag to the flux raw material powder, and by adding an appropriate amount of welding slag powder having a specific particle size and specific surface area, it becomes a fired flux having excellent moisture absorption resistance. It was found that it is possible to obtain a weld metal with a small amount of diffusible hydrogen.

Further, the inventors of the present invention repeated the reuse of the submerged arc welding slag to obtain Li ₂ O, Na ₂ O and K ₂ O.
Since it is easy to remain, it was found that these were gradually accumulated, and pockmarks were likely to occur, and I came to think of regulating these accumulations. The present invention is configured based on such knowledge. That is, the present invention is
Flux is a firing type flux for submerged arc welding in which the raw material powder and the binder are mixed and granulated and fired.
Containing 90 wt%, Ri der specific surface area of 0.3 m ² / cm ³ or less, Li
_The total content of ₂ O, Na ₂ O and K ₂ O is 3 wt% or less
Excellent Ru fired Flux der for submerged arc welding in the resistance pockmarks resistance.

Further, the composition of the firing type flux for submerged arc welding according to the present invention is such that the weight percentage as a slag generator is
And, total SiO ₂ : 30-70%, manganese oxide: 5 in terms of MnO
~30%, MgO: 3~30%, Al 2 O 3: 2~20%, CaO: 10
% Or less, CaF ₂ : 15% or less, at least one kind or more, or a deoxidizing agent: 10% or less.

Further, the present invention provides a granulated production method of submerged arc welding sintering type flux calcined after mixing the binder with flux material powder, as a part of the flux raw material powder, preferably Li ₂ O, Na ₂ O and K ₂
A submerged arc welding slag having a total O content of 5 wt% or less is crushed, preferably mechanically crushed to obtain a welding slag powder having a particle diameter of 300 μm or less and a specific surface area of 0.1 to 0.5 m ² / g, Based on the total amount of flux raw material powder and binder
This is a method for producing a firing type flux for submerged arc welding, which is characterized by adding 10 to 90 wt%, and in the present invention, the firing is preferably performed at a temperature of 650 ° C or higher.

Further, in the present invention, the set of the above-mentioned welding slag powder is used.
Depending on the composition, the flux composition is wt% and the slag forming agent
Then all SiO₂: 30 to 70%, manganese oxide: 5 in terms of MnO
~ 30%, MgO: 3-30%, Al₂O₃: 2-20%, CaO: 10
% Or less, CaF₂: 15% or less and at least one or more
Or further deoxidizer: 10% or less, preferably Li₂O, Na ₂O
And K₂The total O content should be 3wt% or less.
It is preferable to blend the flux raw material powder.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, welding slag powder is added as a part of the flux raw material powder. The amount of welding slag powder added is 10 with respect to the total amount of flux raw material powder and binder.
~ 90wt% If the amount of welding slag powder added is less than 10 wt%, the effect of reducing the amount of diffusible hydrogen in the weld metal cannot be expected. On the other hand, to add a deoxidizer for improving the bead appearance, or to add a binder at the time of granulation,
The upper limit of the amount of welding slag added was 90 wt%. From the viewpoint of adjusting the composition of the flux, the addition amount of the welding slag powder is preferably 50 wt% or less.

The welding slag to be added is Li in the welding slag.
A welding slag having a total content of ₂ O, Na ₂ O and K ₂ O of 5 wt% or less is preferable. If the total content of Li ₂ O, Na ₂ O and K ₂ O exceeds 5 wt%, Li in the product flux
The content of ₂ O, Na ₂ O and K ₂ O becomes large, and the gas escape from the slag of the gas generated during welding becomes very bad,
Pockmarks are more likely to occur.

The welding slag added to the flux of the present invention is obtained by mechanically crushing the welding slag generated after the submerged arc welding, and the particle diameter is 300 μm or less, in other words, 300 μm.
The following particles occupy almost 100% of the specific surface area: 0.1 to 0.5m ² /
It is preferable to use g of welding slag powder. If the particle size of the welding slag powder exceeds 300 μm, the granulation property deteriorates. Therefore, the particle size of the welding slag powder is preferably 300 μm or less.

Further, the specific surface area of the welding slag powder to be added is
If it is less than 0.1 m ² / g, the granulating property deteriorates, and the amount of the binder added during granulation increases. When the amount of the binder increases, it becomes difficult to remove the water content in the flux during firing, and the amount of diffusible hydrogen in the weld metal increases. On the other hand, when the specific surface area of the welding slag powder exceeds 0.5 m ² / g, the amount of moisture absorbed by the unmelted substance contained in the welding slag powder increases, and the amount of diffusible hydrogen in the weld metal increases. . Therefore, the specific surface area of the welding slag powder is preferably in the range of 0.1 to 0.5 m ² / g. As the specific surface area of the particles, a value measured by the BET method by nitrogen adsorption is used.

The unadjusted welding slag powder has a specific surface area of less than 0.1 m ² / g and a considerable amount of particles having a particle diameter of more than 300 μm. The welding slag powder is preferably generated from a flux having the same composition as the desired flux composition or a composition close to the desired flux composition. However, even in the case of welding slag generated from fluxes with different compositions, the flux composition can be adjusted by adding oxides or fluorides,
No particular problem.

In the present invention, depending on the composition of the welding slag powder added as a part of the flux raw material powder, the flux raw material powder contains at least one of the following slag-forming agents.
It is desirable to add so as to contain one or more species. The addition amount is represented by weight% (wt%) with respect to the total amount of the flux raw material powder and the binder. SiO ₂ : 30 to 70% SiO ₂ is added as a slag forming agent in order to maintain a good bead appearance. If it is less than 30%, the effect is small. Especially in the case of high-speed fillet welding, where conformability at the edge of the bead is important, good bead cannot be retained at less than 30%. On the other hand, 70
If it is contained in a large amount in excess of%, the viscosity becomes too high and the bead appearance is liable to be disturbed, and the slag releasability deteriorates. Therefore, the addition amount of SiO ₂ is
It is preferably in the range of 30 to 70%.

Manganese oxide (calculated as MnO amount): 5 to 30
% Manganese oxide is added in order to improve the familiarity of the bead end portion even if the welding speed becomes high. This is especially important when used for fillet welding flux. 5 in MnO conversion
If it is less than 30%, the effect is not observed, and if it exceeds 30%, the CO reaction in the molten pool becomes violent and the bead appearance deteriorates. Therefore, the amount of manganese oxide added is 5 to 30 in terms of MnO.
It is desirable to set it in the range of%.

MgO: 3 to 30% MgO is a useful component for controlling the melting point and viscosity of slag and ensuring excellent slag releasability. If it is less than 3%, a sufficient effect cannot be obtained. On the other hand, if it exceeds 30%, the viscosity tends to be too low, or the melting point is too high, so that the bead appearance tends to be deteriorated. Therefore, it is desirable that the MgO content be in the range of 3 to 30%.

Al ₂ O ₃ : 2 to 20% Al ₂ O ₃ is an important component for adjusting the viscosity and melting point of slag, but if it is less than 2%, these effects are poor.
On the other hand, if it exceeds 20%, the melting point rises too much and the bead shape is deteriorated. Therefore, it is preferable to set it in the range of 2 to 20%. CaO: 10% or less CaO is a component that affects the fluidity of slag, and 10%
If it exceeds, the fluidity is impaired and the bead shape is deteriorated, so CaO is preferably made 10% or less. In addition, it is preferably 0.1 to 5%.

CaF ₂ : 15% or less CaF ₂ is a component for improving the fluidity of slag, and if it exceeds 15%, the slag tends to flow. Therefore, CaF ₂ is 15
% Or less is desirable. The content is preferably 0.5% or more. In addition, Ti can be used as a slag generator if necessary.
O ₂ : 10% or less, BaO: 5% or less, ZrO: 5% or less, B
₂ O ₃ : 4% or less, CaCO ₃ : 5% or less may be added.

TiO ₂ is reduced during welding and Ti
To improve the toughness of the weld metal. However, if it exceeds 10%, the toughness deteriorates. BaO and ZrO are added to adjust the basicity and melting point of the slag. But 5
%, The bead appearance and the slag removability are deteriorated. B ₂ O ₃ migrates into the weld metal by a reduction reaction during welding and contributes to improving the toughness of the weld metal. However, when it exceeds 4%, solidification cracking of the weld metal is promoted.

CaCO ₃ decomposes during welding to generate CO ₂ ,
It is effective in reducing the amount of hydrogen in the weld metal because it lowers the hydrogen partial pressure. However, if it exceeds 5%, the bead appearance is deteriorated. Furthermore, it is preferable to add a deoxidizing agent other than the above. Deoxidizer: 10% or less It is preferable to add a deoxidizer in order to improve the surface gloss of the beads or to improve the toughness of the weld metal. As the deoxidizing agent, Ti, Al, Si, Mn or the like or an alloy of these elements and iron (Fe) can be considered. Among them, Si, Mn or ferrosilicon, ferromanganese are preferable. The deoxidizing agent may be added alone or in combination. However, even if added in excess of 10%, the effect is saturated, so it is desirable to add the deoxidizer at 10% or less. It is preferably 1% or more.

The flux raw material powders mixed in a predetermined amount are kneaded together with a binder, granulated and then fired. The granulation method is not particularly limited, but it is preferable to use a rolling granulator or an extrusion granulator. After being granulated,
It is preferable to carry out a sizing treatment such as dust removal or crushing of coarse particles to obtain particles having a particle size in the range of 0.075 to 1.4 mm.

The binder (binder) is preferably an aqueous solution of polyvinyl alcohol or the like, or water glass. Of these, sodium silicate (water glass) having a conventionally used molar ratio of SiO ₂ and Na ₂ O of 1 to 5 is sufficient.
Also, the amount used is 80 to 150cc per 1kg of flux raw material powder.
The degree is enough. The firing temperature is preferably 650 ° C or higher. If the firing temperature is lower than 650 ° C, the moisture brought in by the binder will be insufficiently dried, resulting in an increase of diffusible hydrogen in the weld metal. Further, by increasing the firing temperature, the specific surface area of the flux after firing can be reduced. The firing temperature is preferably 650 ° C. or higher so that the specific surface area of the flux is 0.3 m ² / cm ³ or lower.

The flux of the present invention is preferably a firing type flux produced by the above-mentioned steps, in which the flux raw material and the binder are mixed and fired. As a part of the flux raw material powder, the flux is generated after submerged arc welding. Contains 10 to 90wt% of welding slag powder and has a specific surface area of 0.3m ²
The flux is less than / cm ³ . By the process described above, the specific surface area of the flux is 0.3 m ² / cm ³ or less,
When the specific surface area of the flux exceeds 0.3 m ² / cm ³ , the amount of diffusible hydrogen in the weld metal increases. Therefore, the upper limit of the specific surface area of the calcined flux of the present invention is set to 0.3 m ² / cm ³ . For the specific surface area, a value measured by the BET method is used as in the case of the welding slag powder.

The welding slag powder is based on the total amount of flux.
10 to 90 wt% is contained. If the amount of welding slag powder is less than 10 wt%, the effect of reducing the amount of diffusible hydrogen in the weld metal cannot be expected. On the other hand, the content of the welding slag powder was set to 90 wt% as an upper limit in order to add a deoxidizer for improving the bead appearance or to add a binder at the time of granulation. The content is preferably 50 wt% or less.

Further, in the flux of the present invention, it is preferable to limit the total content of Li ₂ O, Na ₂ O and K ₂ O among the flux components to 3 wt% or less. When the total amount of Li ₂ O, Na ₂ O, and K ₂ O exceeds 3 wt%, the gas escape from the slag of the gas generated during welding becomes very bad, and a pock mark easily occurs. To reduce the total amount of Li ₂ O, Na ₂ O and K ₂ O to 3 wt% or less, the addition amount of welding slag should be 50%.
It is preferable to limit it to wt% or less.

The flux of the present invention comprises welding slag powder and
It is a composition obtained by mixing and firing a flux raw material powder other than the welding slag powder added according to the composition of the welding slag powder and a binder. As the flux raw material powder, it is preferable to contain at least one or more of the following slag-forming agents, or at least one or more deoxidizing agents. As a slag generator, weight% (wt%) based on the total amount of flux
In, SiO _2: 30~70%, manganese oxide (in amount of MnO terms): 5~30%, MgO: 3~30 %, Al 2 O 3: 2~20
%, CaO: 10% or less, CaF ₂ : 15% or less, Ti if necessary
O ₂ : 10% or less, BaO: 5% or less, ZrO: 5% or less, B
₂ O ₃ : 4% or less, CaCO ₃ : 5% or less, and deoxidizing agents include Ti, Al, Si, Mn, etc. or alloys of these elements and iron (Fe), and the content is 10%. The following is preferable. The reason for limiting the content of the flux raw material powder is the same as the reason described in the section of the flux raw material powder.

[0035]

Example 1 Welding slag generated by submerged arc welding having the composition shown in Table 1 was mechanically pulverized to obtain a welding slag powder having a particle size of 300 μm or less and a specific surface area of 0.21 m ² / g. Then, the welding slag powder, the other flux raw material powder and the binder were mixed in the proportions shown in Table 2 and granulated into particles of 12 to 100 mesh. Then, it was baked at 650 ° C. for 1 hour. Water glass was used as the binder.

About these baking type fluxes,
Using a flux that has absorbed moisture for 24 hours and a flux that does not absorb moisture in an atmosphere with relative humidity of 80%, JIS Z
According to 3118, the amount of diffusible hydrogen in the weld metal was measured.
The diffusible hydrogen amount was repeatedly tested three times, and the average value was used. The results are shown in Table 3.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

From Table 3, the blending amount of the welding slag powder is 10% by weight.
In the examples of the present invention (flux No. 3 to No. 7) described above,
The amount of diffusible hydrogen in the deposited metal is reduced. Meanwhile, welding slag powder
Comparative example in which the compounding amount of is out of the range of the present invention (Flux N
In No.1 and No.2), the amount of diffusible hydrogen is high.
It The Li in the welding slag used₂O, Na₂O and K₂
The total content of O was 5% or less, and the obtained flack
Li in Su₂O, Na₂O and K₂The total content of O is flack
No. 1 to No. 4 and No. 8 are 3% or less, and the pock mark resistance is
It was good. On the other hand, flux No.5, No.6, No.7
Li in the flux ₂O, Na₂O and K₂Total O content
Are 3.7%, 3.3% and 3.7%, respectively.
Weld beads using flux generate pockmarks
did. In addition, the welding bead using flux No. 7
Pockmarks occurred frequently. (Example 2) Shown in Table 4 as a part of the flux raw material powder.
Welding sludge generated by submerged arc welding of soot composition
Was added. The welding slag is shown in Table 5 by mechanical grinding.
Welding slag powder with soot particle size and specific surface area was used. Welding slag
The amount of powder added is the total amount of flux raw material powder and binder.
To 30 wt%. Flux source containing welding slag powder
Knead the powder and the binder (water glass), and
Granulated into shish particles. Then, burn at 850 ℃ × 15min
And the composition and specific surface area shown in Table 5
It was a cousin.

These fluxes were treated at 30 ° C. and 80% relative humidity.
% Treatment in an atmosphere of moisture absorption, no moisture absorption,
The amount of diffusible hydrogen in the weld metal was measured according to JIS Z 3118 using these fluxes. The test was repeated 3 times, and the amount of diffusible hydrogen was shown as the average value thereof. The results are shown in Table 5.

[0042]

[Table 4]

[0043]

[Table 5]

From Table 5, the present invention example (flux No. 8 to N
o.10) has low diffusible hydrogen content and good bead appearance. However, in the example of the present invention (flux No. 11) in which the specific surface area of the welding slag powder is large, the bead appearance is good, but the amount of diffusible hydrogen generated increases and the moisture absorption resistance deteriorates slightly. Flux No. 11 had pits in the weld beads when the flux after moisture absorption was used.

In the comparative example (flux No. 12) in which the particle shape of the welding slag powder is large and the flux specific surface area is out of the range of the present invention, the granulating property is poor and the bead appearance is poor and the diffusible hydrogen The quantity could not be measured. Incidentally, the total content of Li ₂ O, Na ₂ O and K ₂ O in the weld slag used was 5% or less, the total of Li ₂ O, Na ₂ O and K ₂ O in the resulting flux The content of flux No. 8 to No. 11 was 3% or less, and the pock mark resistance was good. (Example 3) Welding slag powder adjusted to the particle shape shown in Table 6 by mechanical pulverization was added as a part of the flux raw material powder, and was kneaded and granulated together with other flux raw material powder and a binder, and then at 550 to 850 ° C. It was fired at the temperature of. The addition amount of the welding slag powder was 30 wt% with respect to the total amount of the flux raw material powder and the binder. The firing time was fixed at 5 min.

Table 6 shows the flux composition and the specific surface area of the flux after firing. For these fluxes, diffusible hydrogen in the weld metal was measured in the same manner as in Example 1 and Example 2, and the results are shown in Table 6.

[0047]

[Table 6]

From Table 6, the flux specific surface area is 0.3 m ² / c.
In the examples of the present invention (flux No. 14 to No. 16) of m ³ or less, the diffusible hydrogen content was suppressed to a low level. The specific surface area of the calcination type flux becomes smaller and the amount of diffusible hydrogen decreases as the calcination temperature rises. It is considered that the absorption of water decreased due to the decrease in the specific surface area of the flux.

The decrease in the specific surface area of the calcination type flux due to the increase in the calcination temperature is considered to be because the uniform film was easily formed on the surface of the flux particles due to the increase in the melting amount of the binder (binder) or the decrease in the viscosity. To be The total content of Li ₂ O, Na ₂ O and K ₂ O in the welding slag used was 5% or less, and
The total content of Li ₂ O, Na ₂ O and K ₂ O was 3% or less, and the pockmark resistance was good. (Example 4) After adjusting the particle size to 300 µm or less and the specific surface area to 0.13 m ² / g by mechanical pulverization, the magnetically selected welding slag powder having the composition shown in Table 7 was used as a part of the flux material powder. The total amount of powder and binder is 50% by weight, kneaded with other flux raw material powder and binder, and granulated to 12 to 60 mesh particles, then 75
The composition was baked at 0 ° C. for 30 minutes to obtain a baked flux having the composition and specific surface area shown in Table 8. As the binder, water glasses having different Na ₂ O and K ₂ O contents were used.

Regarding these fluxes, Examples 1 and 2 were used.
The diffusible hydrogen in the weld metal was measured in the same manner as in, and the results are shown in Table 8.

[0051]

[Table 7]

[0052]

[Table 8]

From Table 8, the invention example (flux No. 17) in which the total content of Na ₂ O and K ₂ O in the flux is 3 wt% or less has a low diffusible hydrogen content and a good bead appearance is obtained. I understand. On the other hand, in the comparative example (flux No. 18) in which the total content of Na ₂ O and K ₂ O exceeded 3 wt% using the binder in which the content of Na ₂ O and K ₂ O was intentionally increased, Although the amount of hydrogen is low, a pock mark is generated on the surface of the weld bead and the bead appearance is poor.

[0054]

EFFECTS OF THE INVENTION According to the present invention, a calcined flux having excellent moisture absorption resistance can be obtained. By welding using the calcined flux of the present invention, a weld metal with less diffusible hydrogen can be obtained. A remarkable effect is that the risk of hydrogen cracking of the welded portion is significantly reduced.

Further, according to the present invention, even if the welding slag is repeatedly reused, the generation of the pock mark can be prevented.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Nobuo Tezuka, No. 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Kawasaki Steel Works, Ltd. Chiba Works (72) Kaname Nishio, No. 1 Kawasaki-cho, Chuo-ku, Chiba, Japan Kawasaki Steel Chiba Works Co., Ltd. (56) Reference JP-A-9-99392 (JP, A) JP-A-4-313490 (JP, A) JP-A 51-21537 (JP, A) JP-A 50-47837 ( JP, A) JP 49-93237 (JP, A) JP 52-40892 (JP, B1) JP 60-36875 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 35/362 B23K 35/40

Claims (4)

(57) [Claims] 1. A submerged arc welding slag is contained in an amount of 10 to 90 wt% with respect to the total amount of flux and has a specific surface area of 0.3 m ² / cm.
³ Ri der hereinafter, Li ₂ O, the content of Na ₂ O and K ₂ O in total
Pock mark resistance characterized by less than 3 wt%
Excellent firing flux for submerged arc welding. 2. A method for producing a firing type flux for submerged arc welding, which comprises mixing a flux raw material powder and a binder, and then granulating and firing the mixture, in which a submerged arc welding slag is crushed as a part of the flux raw material powder. Particle size: 300 μm or less, specific surface area: 0.1 to 0.5 m ² / g Welding slag powder, based on the total amount of flux raw material powder and binder
A method for producing a sintered flux for submerged arc welding, which is characterized by adding 10 to 90 wt%. 3. The submerged arc welding slag is Li
_The method for producing a calcined flux for submerged arc welding according to claim 2 , which is a submerged arc welding slag having a total content of ₂ O, Na ₂ O and K ₂ O of 5 wt% or less. 4. A submerged arc method for manufacturing a welding firing type flux according to claim 2 or 3, characterized in that the firing at a temperature of at least 650 ° C. The.