JPH0999392A - Baked flux for submerged arc welding having excellent hygroscopic resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the diffusion of hydrogen into weld metal by an effective improvement in hygroscopic resistance. SOLUTION: This baked flux consists of a comps. which contains, by weight%, 3 to 70% total SiO2 , 5 to 30% Al2 O3 , 3 to 30% MgO, 5 to 40% MnO, <=10% CaO, 5 to 20% CaF2 , <=5% deoxidizing agent, <=5% additive alloy components, 4 to 8% sol. SiO2 and 1 to 3% sol.(Na2 +K2 O+Li2 O) and of which A value expressed by the following formula satisfies <=35: A=MgO+1.25CaO +0.37MnO+2.62Na2 O+2.31K2 O+3.09Li2 O, where within parenthesis is the contents of the flux components.

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, and particularly, it is intended to suppress the diffusion of hydrogen into the weld metal during welding by improving the moisture absorption resistance. .

[0002]

Fluxes for submerged arc welding (submerged arc welding) are roughly classified into baking type flux and melting type flux, but they are also excellent in workability and mechanical properties of the obtained weld metal. Due to its advantages, recently, the firing type flux has become the mainstream. This baking type flux is generally manufactured using water glass as a binder through the steps of kneading raw material powders such as oxides and fluorides → granulating → drying → baking.

The above-mentioned water glass is usually made by adding water to sodium silicate, potassium silicate or the like to form a solution, but alkali components such as sodium and potassium have high hygroscopicity. Further, water glass is foamed in the drying / firing process after granulation and increases the specific surface area of the flux, so that its hygroscopicity is further increased. When welding is performed using such a flux, the absorbed moisture is decomposed by arc heat into hydrogen, which diffuses into the weld metal and causes hydrogen cracking.

For this reason, in the burning type flux, various measures have been conventionally taken in order to prevent the diffusion of hydrogen into the weld metal. For example, Japanese Patent Publication No. 51-16172,
Japanese Patent Publication No. 52-25819, Japanese Patent Publication No. 56-8717, Japanese Patent Publication
56-53476 and JP-B-58-49356 disclose that diffusion of hydrogen is prevented by increasing the proportion of carbonate in the flux and reducing the H ₂ partial pressure by CO ₂ gas generated during welding. The method has been reported.

A method has also been proposed in which the binder itself is made to have a low moisture absorption to prevent the diffusion of hydrogen into the molten metal. For example, Japanese Patent Publication No. 51-26308 discloses a method of controlling the Na ₂ O / K ₂ O molar ratio of water glass and adjusting the firing temperature to reduce the moisture absorption. The official gazette proposes a method of reducing the hygroscopicity by using a low hygroscopic lithium silicate aqueous solution or by adding lithium silicate to water glass such as sodium silicate or potassium silicate.

Furthermore, Japanese Patent Publication No. 52-2700 discloses that hygroscopicity is obtained by adding a glass powder containing an alkali oxide, boron oxide, etc. to a flux and softening the glass powder during firing to cover the flux particles. Is disclosed.

In addition, JP-A-60-106695 proposes a method of lowering hygroscopicity by removing water in a vacuum after firing and then adsorbing carbon dioxide on the flux surface. .

[0008]

However, in the method of adding carbonate to the flux, in addition to the problem that the welding bead surface becomes rough due to the CO ₂ gas generated by the decomposition of carbonate during welding, particularly in high-speed welding. There was a problem with workability at the time. Further, by controlling the Na ₂ O / K ₂ O molar ratio of water glass or by adding lithium silicate, the specific surface area of the flux can be sufficiently reduced at the normal firing temperature (400 to 600 ° C). In the present situation, the hygroscopicity cannot be suppressed to a satisfactory degree. Furthermore, in the method of adding glass powder containing alkali oxide, boron oxide, etc. to the flux, since the glass powder is mixed in the flux and the particle size is limited, even if it is softened. It is not possible to sufficiently cover each flux particle, and it is also impossible to obtain sufficient moisture absorption resistance. Further, the method of adsorbing carbon dioxide gas on the flux surface has a problem that uniform carbonation over the entire surface is difficult, and even when carbonized, the hygroscopicity of the part rather increases.

The present invention advantageously solves the above-mentioned problems, and by improving the effective moisture absorption resistance, it is possible to advantageously reduce the diffusion of hydrogen into the weld metal, and a firing type flux for submerged arc welding. The purpose is to propose.

[0010]

That is, the gist of the present invention is as follows. 1. In _{weight%, total SiO 2: 30~70%} , Al 2 O 3: 5~3
0%, MgO: 3-30%, MnO: 5-40%, CaO: 10% or less,
CaF ₂ : 5 to 20%, deoxidizer: 5% or less, additive alloy component: 5
% Or less, sol.SiO ₂ : 4 to 8%, sol. (Na ₂ O + K ₂ O + Li
₂ O): 1-3%, and the A value represented by the following formula is 35
A composition that satisfies the following conditions, which is characterized by having excellent moisture absorption resistance, and is a firing type flux for submerged arc welding (first
invention). Note A = MgO +1.25 CaO +0.37 MnO +2.62 Na ₂ O +2.
31 K ₂ O +3.09 Li ₂ O where the content of the flux component is

2. % By weight, total SiO ₂ : 30-70%,
_{Al 2 O 3: 5~30%,} MgO: 3~30%, MnO: 5~40%, Ca
O: 10% or less, CaF ₂ : 5 to 20%, deoxidizer: 5% or less, additive alloy component: 5% or less, sol.B ₂ O ₃ : 0.1 to 4%, sol.Si
O ₂ : 4 to 8%, sol. (Na ₂ O + K ₂ O + Li ₂ O): 1 to 3%, and the molar ratio is 4.0 ≧ (sol.SiO ₂ ) / (sol . (Na ₂ O + K ₂ O + Li ₂ O) ≧
Sintered flux for submerged arc welding (second invention) excellent in moisture absorption resistance, which satisfies 2.0.

3. % By weight, total SiO ₂ : 30-70%,
_{Al 2 O 3: 5~30%,} MgO: 3~30%, MnO: 5~40%, Ca
O: 10% or less, CaF ₂ : 5 to 20%, deoxidizer: 5% or less, additive alloy component: 5% or less, sol.B ₂ O ₃ : 0.1 to 4%, sol.Si
_{O 2: 4~8%, sol (} Na 2 O + K 2 O + Li 2 O):. Comprises 1-3%, and A value represented by the following formula is the composition that satisfies the 50 or less, Moreover, the molar ratio is 4.0 ≧ (sol.SiO ₂ ) / (sol. (Na ₂ O + K ₂ O + Li ₂ O)) ≧
Sintered flux for submerged arc welding excellent in moisture absorption resistance characterized by satisfying 2.0 (third invention). Note A = MgO +1.25 CaO +0.37 MnO +2.62 Na ₂ O +2.
31 K ₂ O +3.09 Li ₂ O where the content of the flux component is

In the above-mentioned firing type flux for submerged arc welding of the first, second and third inventions, it is desirable that the specific surface area of the flux is 0.2 m ² / cm ³ or less.

The present invention reduces the hygroscopicity derived from the flux component by limiting the amount of the component that readily reacts with H ₂ O to form a hydroxide in the flux component to a predetermined value or less, Furthermore, by lowering the softening temperature of the binder for granulating the flux, it is possible to facilitate the melting of the binder during firing and form a uniform film on the surface of each flux particle, thereby increasing the specific surface area of the flux after firing. By lowering it, it is possible to effectively prevent the absorption of moisture in the flux and, consequently, the diffusion of hydrogen into the weld metal. In particular, regarding the improvement of hygroscopicity by adjusting the binder, while improving the fluidity by dividing the network structure of SiO ₂ which is the main component of water glass used as a binder by Na ₂ O which is also the main component, By adding B ₂ O ₃ to water glass, the softening temperature of water glass is lowered.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The reason why the composition of the flux in the present invention is limited to the above range will be described below. totalSiO ₂ : 30 to 70 SiO ₂ is a component that adjusts the melting point of the flux and greatly affects the fluidity of the slag. If the amount of SiO ₂ is less than 30%, the fluidity of the slag becomes excessive, and not only the bead height becomes insufficient, but also the slag removability deteriorates, while if it exceeds 70%, the fluidity of the slag is impaired. As a result, the bead surface becomes rough, so the total SiO ₂ content was limited to the range of 30 to 70%.

Al ₂ O ₃ : 5 to 30% Al ₂ O ₃ is a component that affects the fluidity of slag. When the content is less than 5%, the fluidity becomes excessive, while when it exceeds 30%, the fluidity becomes excessive. Is significantly inhibited, so the range was limited to 5 to 30%.

MgO: 3 to 30% MgO is an effective component for improving the peelability of slag, but if the content is less than 3%, its effect of addition is poor, while 30%.
%, The melting point of the slag increases and the bead shape is deteriorated. Therefore, the content is limited to 3 to 30%.

MnO: 5-40% MnO is a component that improves the familiarity of the toe of the bead, but if the content is less than 5%, its effect of addition is poor,
On the other hand, if it exceeds 40%, the fluidity of slag becomes excessive, so
The range was limited to 5-40%.

CaO: 10% or less CaO is a component that affects the fluidity of the slag. When the content exceeds 10%, the fluidity is impaired and the bead shape is deteriorated. I decided.

CaF ₂ : 5 to 20% CaF ₂ has a great influence on the fluidity of slag. When the content is less than 5%, the fluidity of slag is insufficient, while when it exceeds 20%, the fluidity is excessive. Therefore, the range is limited to 5 to 20%.

Deoxidizing agent: 5% or less Deoxidizing agents such as Fe-Si, Fe-Al and Fe-Mn contribute effectively to the improvement of the surface gloss of the beads, but even if added in excess of 5%. Since no further effect can be obtained, it is limited to 5% or less.

Additive alloy components: 5% or less In submerged arc welding, alloy components such as Ti, Ai, and Mo are usually added to the flux for the purpose of improving the impact value of the weld metal. If the content exceeds 5%, the alloy component becomes excessive and the impact value of the weld metal deteriorates, so the alloy component was made to be contained at 5% or less.

Sol.SiO ₂ : 4 to 8% Since sol.SiO ₂ represents water-soluble SiO ₂ , it is considered that it is caused only by water glass as a binder. Therefore, hygroscopicity of flux and flux particles It can be used as a parameter for evaluating the bond strength. If this content is less than 4%, sufficient adhesion strength cannot be obtained, so the flux is easily pulverized, while if it exceeds 8%, the softening temperature of the binder becomes high, the specific surface area of the flux becomes large, and the moisture absorption resistance increases. Sol.SiO ₂ is 4-8%
Limited to the range.

Sol. (Na ₂ O + K ₂ O + Li ₂ O): 1-3% sol. (Na ₂ O + K ₂ O + Li ₂ O) is each of water-soluble Na ₂ O, K ₂ O and Li ₂ O. The total content is shown, and these are considered to be only due to water glass as a binder like sol.SiO _2, and can be said to be an important parameter that regulates the hygroscopicity of the flux. These alkali metals act to reduce the specific surface area of the flux because they divide the SiO ₂ network structure in water glass and improve the flowability, but in the flux after firing, for example, Na ₂ O absorbs moisture. And becomes NaOH, and this NaOH is SiO ₂ derived from water glass.
It breaks the Si-O bond and affects the fluidity of the binder and the fixing strength of the flux. Also K ₂ O and Li ₂ O
Since it acts similarly to Na ₂ O, it is important to specify the total amount of these, and if the total amount of these is less than 1%, the effect of reducing the specific surface area is not sufficient. When the content exceeds%, not only the fixing strength is lowered but also the moisture absorption resistance is deteriorated, so the content of these is limited to the range of 1 to 3%.

The hygroscopicity of the flux A≤35 is that MgO, CaO, MnO, Na ₂ O, K ₂ O, which easily react with H ₂ O to form hydroxide, among the components.
It is considered that it mainly depends on the content of Li ₂ O. From this point of view, the enthalpy change per kg of each component when forming hydroxide from each component (oxide) is calculated, and the coefficient is calculated from the magnitude of the enthalpy change of each component, assuming 1 for MgO. A is the sum of the products of the quantities. Therefore,
This A is an index showing the hydratability of the flux component. Fig. 1 shows the composition of various types of calcined fluxes with different composition.
The results of investigating the relationship between the diffusible hydrogen content and the A value in the hydrogen test (JIS Z 3118) in which the sample is left to stand in an atmosphere of 30 ° C and 80% RH for 24 hours to absorb moisture are shown below. As shown in the figure, when A ≦ 35, the amount of diffusible hydrogen is 10 ml / 1
It was found to be as small as 00 g or less, that is, the hygroscopicity is small, but when A> 35, the amount of diffusible hydrogen sharply increases, that is, the hygroscopicity rapidly increases. Also, in the figure,
The results of the investigation in the case of adding B ₂ O ₃ as a binder are also shown, but in this case, if A ≦ 50, the hygroscopicity was not impaired. Therefore, in the first invention, the A value is limited to 35 or less, and in the third invention, the A value is limited to 50 or less.

Sol.B ₂ O ₃ : 0.1-4% B ₂ O ₃ lowers the softening temperature of water glass as a binder for fixing flux particles to each other, promotes melting of the binder on the flux surface, and It is added for the purpose of reducing the specific surface area. However, if the content is less than 0.5%, the effect is not sufficient, while if it exceeds 4%, the adhesion strength of the flux is reduced.
The range is limited to 0.1 to 4%.

The molar ratio is 4.0 ≧ (sol.SiO ₂ ) / (sol. (Na ₂
O + K ₂ O + Li ₂ O)) ≧ 2.0 (sol.SiO ₂ ) / (sol. (Na ₂ O + K ₂ O + Li ₂ O)) is a measure of the adhesion between flux particles. Yes, this ratio
If it is less than 2.0, sufficient adhesion cannot be obtained and the flux is easily pulverized, while if it exceeds 4.0, uniform flux particles cannot be obtained, so the above range is limited.

Although the composition of the flux according to the present invention has been described above, it is preferable that the specific surface area of the flux is 0.2 m ² / cm ³ or less from the viewpoint of moisture absorption resistance. This is because the larger the specific surface area of the flux is, the higher the moisture absorption is, and the more the amount of diffusible hydrogen in the weld metal is increased, as shown in FIG. In this respect, if the specific surface area of the flux is 0.2 m ² / cm ³ or less, it was intentionally allowed to absorb moisture (30
Even with a flux of 80 ° C, 80% RH for 24 hours, the amount of diffusible hydrogen in the weld metal can be suppressed to 10 ml or less (per 100 g).

[0029]

【Example】

Example 1 Commercially available water glass was prepared to prepare various binders shown in Table 1. 1 kg of flux material with the composition shown in Table 2
120g of B4 (excluding water) in Table 1 was added, and kneading, granulation, drying, firing and particle size adjustment were carried out in accordance with a conventional method, and firing flux No. 1 for submerged arc welding shown in Table 3 Got 4. The firing conditions were 600 ° C. and 1 hour. Hydrogen test (30 ℃, 80
Table 4 shows the results of an investigation on the amount of diffusible hydrogen in the case of carrying out (% RH, 24 hr). The hydrogen test is JIS Z 3118.
Was repeated 3 times according to

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

In Table 4, all the conforming examples of Nos. 1 and 2 were able to suppress the amount of diffusible hydrogen to a low level even after absorbing moisture. On the other hand, No. 3 to 4 with A value exceeding 35
The hydrogen content increased after moisture absorption.

Example 2 For each of the binders shown in Table 1 above, 120 g of binder (excluding water) was added to 1 kg of the flux raw material having the component composition shown in Table 5, and kneading, granulation, drying and firing were carried out according to a conventional method.
The particle size was adjusted to obtain the firing flux for submerged arc welding shown in Table 6. The firing conditions are 600 ° C and 1 hr.
And Hydrogen test (30 ℃,
Table 7 shows the results of an investigation on the amount of diffusible hydrogen when 80% RH, 24 hr).

[0036]

[Table 5]

[0037]

[Table 6]

[0038]

[Table 7]

In Table 7, all the conforming examples of Nos. 1 to 3 were able to suppress the amount of diffusible hydrogen to a low level even after absorbing moisture. On the other hand, No. 4, which uses water glass without addition of B ₂ O ₃ , does not satisfy the requirement that the A value is 35 or less, and therefore the amount of hydrogen increased after moisture absorption. Further, in Nos. 5 and 6, since the SiO ₂ concentration was low and the B ₂ O ₃ concentration was too high, the gelation of water glass was promoted and the granulation property deteriorated, resulting in pulverization. In No. 7, the softening temperature of the water glass was high because the SiO ₂ concentration was too high, and as a result, the fluidity during firing was poor and the specific surface area of the flux was large, leading to an increase in the amount of hydrogen. No. 8 is an alkaline component (Li
_{Since the} concentration of ₂ O + Na ₂ O + K ₂ O) was low, the fluidity was deteriorated, and as a result, the wettability with respect to the flux particles was deteriorated, and the adhesion between particles became insufficient, resulting in pulverization. In No. 9, the amount of hydrogen is high because the concentration of the alkaline component (Li ₂ O + Na ₂ O + K ₂ O) is too high. In No. 10, since the SiO ₂ / (Li ₂ O + Na ₂ O + K ₂ O) ratio was small, the fixing strength was lowered, and as a result, it was pulverized.

Example 3 120 g (excluding water) of the B1 to B3 binders shown in Table 1 above was added to 1 kg of a flux raw material having the composition No. F1, F2, and F4 shown in Table 2 above, and a conventional method was used. Kneading, granulation, drying,
Firing and particle size adjustment were performed to obtain firing flux Nos. 1 to 3 for submerged arc welding shown in Table 8. Table 9 shows the results of investigating the amount of diffusible hydrogen when a hydrogen test (30 ° C., 80% RH, 24 hr) was performed on each of the above fluxes.

[0041]

[Table 8]

[0042]

[Table 9]

In Table 9, Nos. 1 to 3 are all sol. B ₂ O ₃
Included in the range of 0.1 to 4%, A ≤ 50, and 4.0 ≥ (sol.
Since SiO ₂ ) / (sol. (Na ₂ O + K ₂ O + Li ₂ O)) ≧ 2.0 is satisfied, the amount of diffusible hydrogen could be significantly reduced.

Example 4 Fluxes having the same composition as Test Nos. 1 to 3 in Table 6 but different only in the firing temperature were prepared, and the specific surface area of these fluxes and the amount of diffusible hydrogen in the weld metal during welding were compared. Table 10 shows the results of examining the relationship. The specific surface area was measured by the BET method.

[0045]

[Table 10]

As is clear from Table 10, by setting the specific surface area of the flux to 0.2 m ² / cm ³ or less, the hygroscopicity of the flux is suppressed more effectively and the amount of diffusible hydrogen in the weld metal is further improved. It can be seen that it can be reduced.

[0047]

As described above, according to the present invention, by reducing the hydration property of the flux component and further lowering the softening temperature of the binder, there has been a problem in the past when welding or waiting for firing type flux. It is possible to effectively reduce the moisture absorption in, and it is possible to significantly reduce the diffusion of hydrogen into the weld metal.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the A value and the amount of diffusible hydrogen.

FIG. 2 is a graph showing the relationship between the specific surface area of flux and the amount of diffusible hydrogen before and after moisture absorption.

Claims (4)

[Claims] 1. A _{weight%, total SiO 2: 30~70%} , Al 2 O 3: 5~30%, MgO: 3~30%, MnO: 5~40%, CaO: 10% or less, CaF ₂ : 5-20%, deoxidizing: 5% or less, additional alloy component: 5% or _{less, sol.SiO 2: 4~8%, sol} (Na 2 O + K 2 O + Li 2 O):. 1~ A firing flux for submerged arc welding, which is excellent in moisture absorption resistance and has a composition containing 3% and having an A value represented by the following formula of 35 or less. Note A = MgO +1.25 CaO +0.37 MnO +2.62 Na ₂ O +2.
31 K ₂ O +3.09 Li ₂ O where the content of the flux component is 2. A _{weight%, total SiO 2: 30~70%} , Al 2 O 3: 5~30%, MgO: 3~30%, MnO: 5~40%, CaO: 10% or less, CaF ₂ : 5-20%, deoxidizing: 5% or less, additional alloy component: 5% or _{less, sol.B 2 O 3: 0.1 ~4} %, sol.SiO 2:. 4~8%, sol (Na 2 O + K ₂ O + Li ₂ O): 1-3% in composition, and molar ratio 4.0 ≧ (sol.SiO ₂ ) / (sol. (Na ₂ O + K ₂ O + Li ₂ O) ) ≧
Sintered flux for submerged arc welding with excellent moisture absorption resistance, which satisfies 2.0. Wherein the _{weight%, total SiO 2: 30~70%} , Al 2 O 3: 5~30%, MgO: 3~30%, MnO: 5~40%, CaO: 10% or less, CaF ₂ : 5-20%, deoxidizing: 5% or less, additional alloy component: 5% or _{less, sol.B 2 O 3: 0.1 ~4} %, sol.SiO 2:. 4~8%, sol (Na 2 O + K ₂ O + Li ₂ O): 1-3%, and the composition represented by the following formula has an A value of 50 or less, and the molar ratio is 4.0 ≧ (sol.SiO ₂ ) / (Sol. (Na ₂ O + K ₂ O + Li ₂ O)) ≧
Sintered flux for submerged arc welding with excellent moisture absorption resistance, which satisfies 2.0. Note A = MgO +1.25 CaO +0.37 MnO +2.62 Na ₂ O +2.
31 K ₂ O +3.09 Li ₂ O where the content of the flux component is 4. The firing type flux for submerged arc welding according to claim 1, 2 or 3, which has a specific surface area of 0.2 m ² / cm ³ or less and is excellent in moisture absorption resistance.