JPH0457438B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a fired flux for submerged arc welding, which is particularly used for welding various low-alloy steels such as heat-resistant steel and low-temperature steel, and which has good welding workability and a low hydrogen content. The present invention relates to a sintered flux for submerged arc welding that provides a tough weld metal. (Prior art) As the safety requirements for welded structures of various low-alloy steels such as heat-resistant steel and low-temperature steel have recently become more sophisticated, the requirements for weld metals have increased, especially with regard to brittle fracture problems. Toughness levels are becoming extremely high. In order to meet these demands, a flux with a highly basic component is required, which can reduce the amount of oxygen in the weld metal and provide high toughness. Conventionally, highly basic molten fluxes or highly basic sintered fluxes with various component systems have been used, but in molten fluxes, high basic component systems tend to contain a large amount of hydrogen during melt production. This causes a problem in that the amount of diffusible hydrogen in the weld metal increases and cold cracking becomes more likely to occur. On the other hand, in calcined flakes, CaCO ₃ ,
It is possible to contain metal carbonates such as MgCO ₃ as a flux component, and the CO ₂ gas generated by the decomposition reaction of these metal carbonates during welding lowers the water vapor partial pressure in the arc atmosphere and diffuses the weld metal. This has many advantages in terms of construction, such as the fact that the preheating and inter-pass temperatures can be significantly lower than when using fused flux because the amount of hydrogen generated by the welding process can be significantly reduced, and the post-heat treatment for dehydrogenation after welding can be simplified. The benefits are great. By the way, as the content of metal carbonate in the fired flux increases, the amount of diffusible hydrogen in the weld metal gradually decreases, but the occurrence of pockmarks, which are bead surface defects that affect welding workability, becomes noticeable. A problem arises in that the amount of oxygen in the weld metal increases and the toughness decreases. This indicates that CO ₂ gas generated by the decomposition reaction of metal carbonates has the effect of lowering the water vapor partial pressure in the arc atmosphere, but on the other hand, CO ₂
This is because the gas acts as an oxidizing gas at high temperatures. In order to prevent such negative effects due to the oxidizing properties of CO ₂ gas, it is usually necessary to add or contain a deoxidizing element as a deoxidizing agent to calcined fluxes that contain a large amount of this type of metal carbonate. become.
For example, an ultra-low hydrogen sintered flux for narrow gap welding proposed in JP-A No. 58-135792 contains 5% or less of Si and Mn each.
The sintered flux for high-strength steel proposed in No. 77790 contains 3% or less of Si and/or Al. Similarly, commercially available calcined fluxes of various compositions containing large amounts of metal carbonates also contain deoxidizing elements;
In particular, Si is the most commonly used deoxidizing element. However, by using a fired flux to which a Si-based deoxidizing agent is added, there is no occurrence of spot marks, and the amount of oxygen in the weld metal can be reduced to the same level as when using a highly basic molten flux. If you try to reduce the metal carbonate content or the chemical composition of the wire used in combination (especially
Depending on the Si content), it may be necessary to add a large amount of these deoxidizers. New problems when using such sintered fluxes include, firstly, poor bead appearance and poor slag removability due to the occurrence of severe slag burning, as well as insufficient deoxidation reaction in low heat input welding. Welding workability is extremely poor, as the slag may not fully float up and remain in the weld metal (slag entrainment occurs). Second, adding a large amount of Si to the flux increases the amount of Si in the weld metal.
This increase in the amount of Si in the weld metal increases the strength and reduces the toughness. Furthermore, according to recent literature investigating the effect of Si content on the toughness of various weld metals, reducing the Si content of weld metal has a remarkable effect on reducing temper embrittlement of weld metal of Cr-Mo steel. has been known for a long time, but Al-killed low-temperature steel
It is becoming clear that reducing Si is effective in reducing SR embrittlement. According to experiments conducted by the present inventors using a highly basic molten flux,
If the Si content exceeds 0.2% in the weld metal of 21/4Cr-1Mo steel, the impact value (-40°C to -60°C) will decrease significantly both after SR and after embrittlement treatment (step cooling treatment), and preferably 0.10%. High toughness can be obtained when the Si content is reduced to about
Si is also present in the weld metal of 50HT and 60HT low-temperature steel.
It has been found that when the amount exceeds 0.40 to 0.50%, the impact value (-60°C to -80°C) after SR decreases rapidly. At this time, the amount of oxygen in the weld metal must be kept below 300 ppm for weld metal of 21/4Cr-1Mo steel, and below 250 ppm for weld metal of 50HT and 60HT low-temperature steel, even if the above Si content is kept low. However, it is difficult to obtain high toughness.
In other words, in order to obtain a high-toughness weld metal, a reduction in the amount of oxygen and a reduction in Si are essential conditions. However, an increase in the amount of Si in the weld metal inevitably became a problem, and it was extremely difficult to obtain the same level of toughness as when using molten flux. Furthermore, in an attempt to reduce the increase in the amount of Si in the weld metal, even if the amount of Si added is reduced and deoxidizing elements such as Mn, Al, and Ti are added at the same time,
At the stage where the occurrence of pockmarks has been eliminated and the amount of oxygen in the weld metal has been reduced to almost the same level as when using fused flux, slag seizure occurs significantly, as in the case where Si is mainly added, and Excessive retention of Mn, Al, and Ti in the weld metal reduces toughness. Also,
Although the addition of Zr is effective in reducing the amount of oxygen in the weld metal, it promotes roughness on the bead surface and slag seizure, so the amount added is limited. In this way, in highly basic sintered fluxes that contain a large amount of metal carbonate in order to prevent low-temperature cracking, the occurrence of pockmarks due to the oxidizing properties of the generated _CO2 gas and an increase in the amount of oxygen in the weld metal can be avoided. It becomes a problem. On the other hand, conventional fired fluxes generally contain mainly Si as a deoxidizing agent, which deteriorates welding workability as typified by slag seizure and increases the amount of Si in the weld metal. Due to this increase, there has been a limit to the ability to obtain a high-toughness weld metal that can sufficiently satisfy recent demands for high toughness levels. (Problems to be Solved by the Invention) Therefore, the present invention can be used for welding various low-alloy steels such as heat-resistant steel and low-temperature steel, so that the amount of diffusible hydrogen in the weld metal is low and low-temperature cracking is less likely to occur. It also has good welding workability without the occurrence of spot marks or slag seizures, and even when used in combination with wires for various low alloy steels currently available on the market, the amount of Si, Mn, Al, and Ti in the weld metal is reduced. To provide a sintered flux for submerged arc welding that can obtain a weld metal with low temperature and high toughness by reducing the amount of oxygen to the same level or lower than that when using a highly basic molten flux while suppressing an increase in With the goal. (Means for Solving the Problems) The gist of the present invention is to convert metal carbonates into CO ₂
In a calcined flux that contains 3.5 to 12% in terms of amount and has a basicity B of 1.50 to 3.00 expressed by the following formula (1), the amount of CO ₂ that is C 0.05 to 0.50% and metal carbonate content. The ratio of the amount of C to the converted value (C%/CO ₂ %) is 0.010 to 0.050, one type or two of Ca or Mg
Contains a total of 0.5 to 5.0% of seeds and 2.0% or less of Si,
Mn2.0% or less, Al1.0% or less, Ti1.5% or less, Zr1.0
% or less in a total amount of 3.0% or less. Formula (1); Basicity B = CaO% + MgO% + CaF ₂ %/SiO ₂
%+0.5Al ₂ O ₃ % (wt%) The present inventors prototyped firing type fluxes having various component systems and varying the types and amounts of deoxidizing elements added and conducted detailed studies. As a result, the metal carbonate content was limited to prevent cold cracking and to improve welding workability, and the basicity of the weld metal was limited in order to maintain a low oxygen level in the weld metal and to improve welding workability. In mold flux, C as a deoxidizing agent is limited to an amount commensurate with the amount of CO ₂ gas generated due to the metal carbonate content, and even when added in large amounts, like Si, it has an adverse effect on welding workability and the performance of the weld metal. Ca or
It was discovered that the amount of oxygen in the weld metal could be significantly reduced by adding Mg and C at the same time.Furthermore, by limiting the amounts of Si, Mn, Al, Ti, and Zr added, Si This solution solves the above-mentioned problems when using this type of highly basic sintered flux containing mainly . (Actions of the Invention) The present invention will be described in detail below along with its effects. Metal carbonate: In order to reduce the amount of diffusible hydrogen in the weld metal and prevent the occurrence of cold cracking _,
Metal carbonates such as MgCO ₃ and BaCO ₃ must be contained in an amount of 3.5% or more in terms of CO ₂ amount (same as the amount of CO ₂ gas generated). In addition, in this case
The amount of diffusible hydrogen determined by WES1003 (gas chromatography method) is less than 4.5 cc per 100 g of weld metal even after being left in the atmosphere for about 4 hours, compared to when a highly basic melting type flux is used. Dehydrogenation treatment after welding can be greatly simplified and can be omitted in cases such as weld metal of 50HT steel. However, if the metal carbonate content exceeds 12% in terms of CO ₂ amount, the amount of CO ₂ gas generated will be excessive, resulting in poor welding workability such as arc instability, slag blow-up, and poor bead shape. Basicity B: Basicity B expressed by the following formula (1) is 1.50 ~
Must be 3.00. If the basicity B is less than 1.50, the oxygen content level of the weld metal becomes high, making it impossible to obtain a weld metal with high toughness. In addition, basicity B is
If it exceeds 3.00, welding workability will be poor, such as arc instability and poor bead shape. Formula (1); Basicity B = CaO% + MgO% + CaF ₂ %/SiO ₂
% + 0.5Al ₂ O ₃ % (weight %) In equation (1), CaO and MgO are replaced by CaCO ₃ and MgO contained as metal carbonates.
Converted value of each oxide amount of MgCO ₃ (CaCO ₃ % x 0.56,
The amount includes the amount equivalent to MgCO ₃ ×0.48).
In addition, in the flux of the present invention, main components other than metal carbonates are mainly CaO, MgO, CaF ₂ ,
Contains SiO ₂ , Al ₂ O ₃ but also TiO ₂ (6% or less),
MnO (5% or less), BaO (15% or less), _ZrO2 (10%
(below), metal oxides such as Na ₂ O + K ₂ O + Li ₂ O ₃ (total 6% or less), and MgF ₂ , BaF ₂ , other than CaF ₂ ,
Metal fluorides such as NaF and Na ₃ AlF ₆ may be contained. A calcined flux containing 3.5 to 12% of such metal carbonates and having a basicity B of 1.50 to 3.00 is added with the following deoxidizing elements in the form of metal powder or alloy powder as a deoxidizing agent. C: C requires an amount commensurate with the amount of CO ₂ gas generated based on the metal carbonate content, and in the flux of the present invention containing 3.5% to 12% of metal carbonate in terms of CO ₂ amount, generation of pockmarks and welding. In order to suppress the increase in the amount of oxygen in the metal, the ratio of the amount of C to the CO ₂ amount equivalent value of the metal carbonate content (C%/CO ₂ %) is 0.010 to 0.050 in the range of 0.05% to 0.50%. must be added accordingly. Furthermore, the addition of C and the limitation of the amount added depending on the amount of CO ₂ gas generated have the effect of effectively replenishing C into the weld metal and improving toughness. When using a calcined flux containing metal carbonates, the _CO2 gas generated is
By the reaction of CO ₂ → CO + O, it acts as an oxidizing gas, causing pockmarks and increasing the amount of oxygen. In addition, by reacting with C in the molten metal, the amount of C in the weld metal is high. This phenomenon shows a phenomenon in which the hardness decreases compared to the case where the hardenability is insufficient, and the decrease in toughness and strength due to insufficient hardenability becomes a problem. This tendency becomes more noticeable as the amount of CO ₂ gas generated increases, but by adding the limited amount of C mentioned above, it is possible to prevent a decrease in the amount of C in the weld metal, maintain hardenability, and adjust the strength. It becomes possible. However, if C is less than 0.05% or C%/CO ₂ % is less than 0.010, the effect of C addition is not obvious and pockmarks occur, the oxygen content of the weld metal increases, and the C content decreases. Toughness decreases. On the other hand, if the amount of C added exceeds 0.50% or the C%/CO ₂ % ratio exceeds 0.050, hot cracking is likely to occur, and the increase in the amount of C in the weld metal increases, resulting in an increase in strength. Toughness decreases. In addition to C powder, C alloys such as Si-C, Fe-Mn,
It may be C, carbide, etc. contained in Fe-Si, but is not particularly limited, but it is added as a deoxidizing agent and is contained in trace amounts in various raw materials blended as a slag forming agent. It does not contain C. Ca and Mg; one or two of Ca or Mg
Must be added in the range of 0.5-5.0% of total seeds. Ca and Mg suppress the occurrence of pockmarks and reduce the amount of oxygen in the weld metal. Moreover, even when these elements are added in large quantities, Si, Mn, Al,
Significant slag seizure does not occur when deoxidizing elements such as Ti are added, and the yield of Ca and Mg in the weld metal is extremely small or almost non-existent, resulting in increased strength of the weld metal. There will be no adverse effects such as a decrease in toughness, or temper embrittlement or SR embrittlement due to post-weld heat treatment. Furthermore, the flux of the present invention simultaneously adds the above-mentioned C and Ca or Mg (or both Ca and Mg) as essential deoxidizing elements. This makes it possible to easily reduce the amount to the same level as, or even less than, the same level. The effect of significantly reducing the amount of oxygen in the weld metal due to the simultaneous addition of C and Ca or Mg prevents excessive oxidation of the droplet surface during the transition stage of the droplet from the tip of the wire in the arc atmosphere to falling into the molten pool. This is also thought to be due to the synergistic effect of promoting sufficient deoxidation reaction in the deoxidation reaction stage of the molten pool. In other words, when a fired flux containing a large amount of metal carbonate is used, the droplets melted and separated from the wire tip are oxidized by CO ₂ gas generated by the decomposition reaction of the metal carbonate while moving through the arc atmosphere. This excessively oxidizes the surface of the weld metal, enriching the amount of oxygen in the molten metal and increasing the amount of oxygen in the weld metal. On the other hand, C first dissolves in the weld metal,
A deoxidizing reaction takes place in the molten pool, and the reducing gas CO gas generated at this time lowers the oxygen partial pressure in the arc atmosphere and suppresses oxidation of the droplet surface. In addition, Ca and Mg have a low gaseous temperature and a high vapor thickness at their melting point, which lowers the oxygen partial pressure in the arc atmosphere and, like C, works to suppress oxidation on the droplet surface. . Next, in the deoxidation reaction stage of the molten pool, C can perform a sufficient deoxidation reaction even in the high temperature range during the process of solidification of the molten metal, and Ca and Mg added at the same time have an affinity for oxygen. It is an extremely large element and can carry out a powerful deoxidation reaction even in the low temperature range just before solidification of molten metal. Furthermore, the violent boiling stirring caused by the reaction at this time may be caused by a small amount added as a chemical component or deoxidizer in the wire or steel plate.
It promotes the deoxidation reaction of Si, Mn, Al, Ti, etc. and the floating of the generated oxides. By adding C and Ca and/or Mg simultaneously in this way, oxidation of the droplet surface in the arc atmosphere is suppressed, and the deoxidation reaction in the molten pool is promoted, making it easier to reduce the amount of oxygen in the weld metal. This made it possible to significantly reduce the Note that if the amount of Ca or Mg added is less than 0.5% in total of one or both of Ca or Mg, it will not work effectively to prevent the occurrence of pockmarks and reduce the amount of oxygen in the weld metal. On the other hand, Ca
Alternatively, if the total amount of one or two types of Mg exceeds 5.0%, welding workability will be poor, such as arc instability and bead disturbance. Furthermore, when the flux of the present invention is added with deoxidizing elements other than C and Ca or Mg, Si2.0%
Below, the total of one or more of Mn 2.0% or less, Al 1.0% or less, Ti 1.5% or less, and Zr 1.0% or less must be 3.0% or less. These elements suppress the occurrence of pockmarks and increase in the amount of oxygen in the weld metal, but
If added in large amounts exceeding the above limited range, slag seizure will occur and Si, Mn, and
As the amount of Al and Ti increases, toughness decreases due to increased strength, and tempering embrittlement and SR occur due to heat treatment after welding.
The embrittlement becomes significant, and the object of the present invention cannot be achieved. It should be noted that addition of a large amount of Zr is not preferable since it has an adverse effect on welding workability. Si: Depending on the amount of Si in the wire, it may be added within a range of 2.0% or less, but if it is added in excess of 2.0%,
Slag seizure occurs and the amount of Si in the weld metal increases, reducing toughness. Mn, Al, Ti: Each may be added within the above limited range, but if added in excess, these elements will cause slag seizure and reduce toughness, just like Si, so the amount added should be kept as small as possible. is preferred. Incidentally, addition of a small amount of Ti acts as a deoxidizing agent and also works effectively to improve toughness as an alloying element for Ti or Ti-B in the weld metal of Al-killed low-temperature steel. Zr: Adding 1.0% or less is effective in reducing the amount of oxygen in the weld metal, but adding more than 1.0% causes problems such as roughness on the bead surface and slag seizure. As described above, the present invention uses Si as a deoxidizing agent to be added to a highly basic calcined flux containing a large amount of metal carbonate, which is commonly used in conventional calcined fluxes of this type. C and Ca and/or
Alternatively, by adding a new deoxidizer system that simultaneously adds Mg, welding workability is good, and the amount of oxygen can be reduced to a high base while keeping the amount of Si, Mn, Al, and Ti in the weld metal low. This significantly reduces the flux to the same or lower level than when using a molten flux, making it possible to obtain a weld metal with extremely high toughness that has never been seen before. (Example) The following is a concrete example. Example 1 The flux of the present invention (B1,
B4, B7, B9) and comparative flux (B10).
Redry at 300℃ x 1hr, then immediately after drying and in the atmosphere (temperature 32℃~33℃, humidity 80~82%)
After leaving for 4 hours, WES1003 (gas chromatography method)
The amount of diffusible hydrogen in the weld metal was measured according to . Table 4 shows the results. When the flux of the present invention was used in Test Nos. 1 to 4, the amount of diffusible hydrogen per 100 g of weld metal showed a low value of 4.2 cc or less even after being left in the atmosphere for 4 hours, whereas in No. 5, the flux showed a low value of 4.2 cc or less per 100 g of weld metal. Since the metal carbonate content of B10 was low and the CO ₂ equivalent value was less than 3.5%, it showed a significantly higher value than when the above-mentioned flux of the present invention was used. Example 2 Plate thickness t ₁ = 25 mm with chemical components shown in Table 2
A387Gr.22 steel in the shape shown in Figure 1 a, α = 20°, t _R
Wire W1 (wire diameter: 4.0 mm) with the chemical composition shown in Table 3 was prepared with a bevel with a backing metal of =16 mm, and the flux of the present invention (B3~B5, B7~
B9) and comparative fluxes (B11 to B21), a multilayer welding test was conducted by the layered method shown in FIG. 1b. Welding conditions are AC power supply 550Amp ^-26 ~
27Volt-30cm/min, preheating temperature 200℃, and interpass temperature 200℃. Note that as a dehydrogenation treatment after welding, a heat treatment (300° C. or less) was performed for about 3 minutes using a preheating gas burner. In addition to observing welding workability during welding, holding at 690℃ x 10 hours (furnace cooling)
After SR treatment and embrittlement treatment (GEStep
Figure 1b shows the weld metal after cooling treatment.
JIS No. 4 2 mm V-notch impact test specimen A and JISA No. 1 tensile test specimen C, in which a notch B was placed in the center of the weld metal with the plate thickness direction t ₂ = 10 mm as the center, as shown in , and analysis samples taken from the same tensile test specimens. Each was subjected to a test. These results are shown in Table 5. Test Nos. 1 to 6 were conducted using the fluxes of the present invention (B3 to B5,
B7 to B9) showed good welding workability and high impact values both after SR and after embrittlement treatment. In addition, the amount of Si in the weld metal at this time is 0.18% or less, or the amount of oxygen is
It was below 260ppm. No. 7 to No. 17 are cases where comparison flux was used. No.7 is flux
Arc instability due to excessive metal carbonate content in B11, poor bead shape, No. 8 flux
Because the basicity of B12 is too low, the amount of oxygen in the weld metal increases and the impact value decreases significantly, and No. 9 is a flux.
Arc instability and poor bead shape due to too high basicity of B13; No. 10 has frequent pockmarks due to the small amount of deoxidizing agent added to flux B14; No. 11
Because the amount of Si added to flux B15 was too large, significant slag seizure occurred and the impact value decreased.
No. 12 suppresses the amount of Si added in flux B16, allowing for Mn, Al,
Although the amount of Ti added was increased, slag seizure occurred as well.For No. 13, the amount of C added in flux B17 was small, so the amount of C in the weld metal decreased and the amount of oxygen increased, resulting in a decrease in impact value. In No. 14, high-temperature cracking occurred in the crater area due to the addition of too much C in flux B18, and in No. 15, spot marks occurred due to the addition of too little Mg in flux B19, and the amount of oxygen in the weld metal increased. In No. 16, the total amount of Ca and Mg added in flux B20 was too high, resulting in unstable arc and poor appearance due to bead disturbance. In No. 17, the addition amount of Ca and Mg in flux B21 was too high, resulting in poor appearance.
Slag seizure occurs and the impact value decreases because the total amount of Si, Al, Ti, and Zr added is too large. Example 3 SM- with chemical components shown in Table 2 and plate thickness t ₁ = 20 mm
50B steel in the shape shown in Figure 2 a, α = 20°, t _R = 16mm
The wire W2 (wire diameter 4.0 mm) with the chemical composition shown in Table 3 was treated with the flux of the present invention (B1, B2, B5, B6,
B7) and comparative fluxes (B12, B14, B15,
B17, B18, B19, B21) in combination with Figure 2b
Multilayer welding tests were conducted using the layered method shown in Figure 1. Welding conditions are AC power supply 650Amp-28Volt-30cm/
min, the interpass temperature is 150℃ without preheating. In addition to observing welding workability during welding, weld metal as welded (AW) and after SR treatment at 600°C x 6 hours (furnace cooling) was examined in the plate thickness direction t ₂ = 10 mm as shown in Figure 2b. A JIS No. 4 2 mm V-notch impact test piece A, in which a notch B was placed in the center of the weld metal with a notch B in the center, and a NK 10 mm round bar tensile test piece C, and analytical samples taken from the same tensile test pieces were used for testing.
These results are shown in Table 6. Test Nos. 1 to 5 were conducted using the fluxes of the present invention (B1, B2,
B5, B6, B7), all showed good welding workability, low Si content and low oxygen content in the weld metal, and high impact values after AW and SR. On the other hand, in No. 6, the basicity of flux B12 is too low, so the amount of oxygen in the weld metal increases and the impact value decreases, and in No. 7, the basicity of flux B12 is too low.
Pockmarks occur due to the small amount of deoxidizing agent added in No. 8, and the impact value decreases due to an increase in the amount of oxygen in the weld metal. In No. 8, slag seizure occurs due to the addition of too much Si in flux B15. In addition, although the amount of oxygen in the weld metal decreased, the amount of Si increased, resulting in a decrease in impact value and significant SR embrittlement due to the increase in strength. The increase in the amount of oxygen and the decrease in the amount of C in the metal lead to insufficient hardenability and a decrease in the impact value.For No. 10, the strength increased due to the addition of too much C in flux B18, resulting in a decrease in the impact value. Flux B19 Mg
No. 12 has flux B21 Si, Al, Ti, and
Slag seizure occurs because the total amount of Zr added is too large, and the impact value decreases and significant SR embrittlement occurs due to the increased strength of the weld metal.

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[Table] (Effects of the Invention) The present invention provides a method for dispersion of weld metal when manufacturing welded structures of heat-resistant steel and low-temperature steel as well as various low-alloy steels that require high low-temperature toughness by submerged arc welding. For submerged arc welding, it has good welding workability and makes it possible to obtain a weld metal with unprecedented high toughness without losing the characteristics of the fired flux, which has a low hydrogen content and is resistant to cold cracking. It is a sintered flux and has extremely high industrial practicality.

[Brief explanation of the drawing]

Figures 1 and 2 are Example 2 and Example 3, respectively.
In the figure, a shows the groove shape, and b shows the stacked layer method and the sampling positions of the impact test piece and the tensile test piece.

Claims (1)

[Claims] At 1% by weight, the amount of metal carbonate is 3.5 in terms of CO ₂ amount.
~12%, and the basicity B expressed by the following formula (1) is
In the firing type flux which is 1.50 to 3.00,
C0.05 to 0.50%, and the ratio of C amount to the CO ₂ amount conversion value of metal carbonate content (C%/CO ₂ %) is 0.010 to 0.050, the sum of one or two of Ca or Mg.
Contains 0.5 to 5.0%, and Si2.0% or less, Mn2.0%
The following is a sintered flux for submerged arc welding characterized by containing at least 3.0% in total of one or more of Al 1.0% or less, Ti 1.5% or less, and Zr 1.0 or less. Formula (1); Basicity B = CaO% + MgO% + CaF ₂ %/SiO ₂
+0.5Al ₂ O ₃ % (weight%)