JPH11138267A - Flat fillet submerged arc welding method by two electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat fillet submerged arc welding method having an excellent slag peeling property and fitness in a bead toe part, without welding defects of undercuts and high temperature cracks or the like and used in the manufacture of an extremely thick wide flange shaped steel or the like. SOLUTION: Multi-layer welding by welding is executed by the use of bond flux containing, by weight, 20-40% iron powder, 5-10% SiO2 , 5-15% Al2 O3 , 5-20% MgO, TiO2 , 5-10% CaCO3 , 5-15% ZrO2 to a total weight of flux, and a flange steel plate side is welded in a final pass. Also, a preceding electrode wire diameter is preferably specified to 4.0-6.0 mm, a succeeding electrode wire diameter is preferably specified to 5.0-7.0 mm, and welding is executed with a distance between electrodes of 40-60 mm in initial layer welding and 10-30 mm from the second pass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a downward fillet submerged arc welding used for producing an extremely thick H-shaped steel used for steel structures such as steel frames and bridges, and more particularly to a large heat input multilayer. The present invention relates to a two-electrode downward fillet submerged arc welding method that has good slag removability and conformability of a bead toe in fill welding.

[0002]

2. Description of the Related Art In recent years, with the heightening of buildings using steel structures, steel box columns which have been used as columns have become increasingly thicker in steel plates, and two electrodes and one pass up to a plate thickness of about 60 mm. Welding, and at a plate thickness of about 70 mm, large heat input submerged arc welding with three electrodes and one pass was performed, and the work efficiency was rapidly improved. However, due to the increase in welding heat input, the steel plate to be welded is likely to deteriorate in the performance of the weld heat affected zone,
The welding technology itself, including welding materials and construction methods, has also reached the thickness limit. In addition, such large heat input submerged arc welding requires a leading electrode current of 2,000 A or more in order to melt the steel plate to be welded and obtain penetration into the backing metal, and some of the major welding equipments equipped with welding equipment are required. It was implemented only by steel bridge manufacturers, and its scope was limited.

On the other hand, construction costs have been reduced by using H-shaped steel, which has recently been used as a beam for buildings, as a pillar. For this reason, H-type steel sheets have a thickness of 60
It is extremely thick, up to 100 mm. Conventionally, high-efficiency downward fillet submerged arc welding has been applied to the manufacture of H-section steel. For example, in JP-A-59-76698,
It is disclosed that fillet welding is performed using a molten flux having a specified flux component, particle size, and bulk density to obtain good slag removability and bead appearance. However, since the above-mentioned technology is used with a relatively small heat input because the steel plate to be welded is as thin as approximately 13 mm in thickness, when applied to large heat input welding of an extremely thick H-section steel, the slag has poor fire resistance and has a good No bead appearance can be obtained.

Accordingly, the present inventors have previously disclosed a flux and a welding method applicable to large heat input as disclosed in Japanese Patent Application No. 8-102.
No. 914 proposed to apply nickel slag containing a large amount of MgO component having a high melting temperature. According to this, the melting temperature of nickel slag is about 1500 ° C,
It is higher than the melting temperature of the molten flux of 1200 to 1300 ° C. Therefore, the deep fillet submerged arc welding with large heat input has a deep penetration and a good bead shape can be obtained. However, only one-pass welding up to a plate thickness of about 25 mm has been studied. For example, when a K-groove shown in FIG. The slag is remarkably deteriorated due to biting.
In addition, in the single-layer welding on both sides, the amount of welding was insufficient, and the penetration was deep and the bead width was narrow, so that high-temperature cracking occurred. On the other hand, when the multi-pass welding was carried out using the flux, the number of welding passes was remarkably increased, but no crack was generated, but the bead did not conform to the toe end and undercut occurred, resulting in poor bead appearance. Was.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a submerged arc welding method for a down fillet of ultra-thick steel, in which excellent slag removability and conformability of a bead toe can be obtained and excellent welding workability can be obtained. An object of the present invention is to provide a two-electrode downward fillet submerged arc welding method capable of obtaining a welded joint portion having no welding defects such as cuts and hot cracks.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a plate having a thickness of 60 to 1 mm.
In the downward fillet submerged arc welding method for an extremely thick steel sheet of 00 mm, iron powder: 20 to
40 wt%, SiO ₂ : 5 to 10 wt%, Al ₂ O ₃ :
5 to 15 wt%, MgO: 5 to 20 wt%, TiO ₂ :
5-20 wt%, CaCO ₃ : 5-10 wt%, ZrO
₂ : It is characterized in that multi-pass welding is performed using a bond flux containing 5 to 15 wt%, and the final pass is to weld the flange steel plate side. Furthermore, the lead electrode wire diameter:
4.0-6.0 mm, trailing electrode wire diameter: 5.0-7.0.
0 mm, the distance between the electrodes is first layer welding: 40-60 mm,
Second pass and thereafter: This is a two-electrode downward fillet submerged arc welding method, which is also characterized by welding at 10 to 30 mm.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the two-electrode downward fillet submerged arc welding for manufacturing an ultra-thick H-section steel having a plate thickness of 60 mm or more, the following findings were obtained as a result of various studies on the flux and welding conditions. (1) In order to improve the efficiency of the fillet submerged arc welding work of the extremely thick H-section steel, it is sufficient to increase the wire melting rate by using a high current. However, if the current is simply increased, the amount of heat input to welding increases, and slag generated during welding cannot hold the weld metal, resulting in uneven bead width. Therefore, large heat input 2
In submerged arc welding of fillet facing down the electrode, it is important to provide the flux with fire resistance.

(2) Similarly, as the thickness of the extra-thick H-section steel increases, the groove cross-sectional area increases, so that the required amount of deposited metal also increases. Therefore, metal powder such as iron powder is added to the flux for the purpose of securing a high amount of deposited metal.However, it is necessary to mix a mineral raw material or an alloy component serving as a slag forming agent. It is necessary to apply the produced bond flux.

(3) Further, in the welding with high heat input, which is completed by single-layer welding, the penetration becomes deeper and the bead width becomes narrower, resulting in a pear-shaped penetration shape and high-temperature cracking. Furthermore, since the bead width is narrow, the bead does not fit well and the undercut occurs, resulting in poor bead appearance.
High-temperature cracking can be prevented by multi-pass welding, and the undercut of the bead toe does not occur by allocating the welding target position to each pass.

(4) On the other hand, in multi-pass welding, slag removability after each pass welding is particularly important in terms of welding work efficiency. In the multi-layer welding, the first layer welding is particularly aimed at the groove bottom, so that the welding slag is easily bitten. If welding is performed in the next pass while leaving the welding slag, work after welding is required to be reworked as a welding defect, resulting in a significant decrease in work efficiency.

Therefore, as a result of various studies on the flux composition, a component system which satisfies conditions such as fire resistance and which easily peels off slag after welding was found. Hereinafter, the reason for the limitation will be described in detail together with the operation of the present invention. [Iron powder: 20 to 40% by weight] It is necessary that the iron powder contains 20 to 40% by weight based on the total weight of the flux. The iron powder is melted by arc heat during welding, moves into the groove, and increases the amount of welding. In addition, the amount of slag generated during welding is reduced, and slag is easily removed. In order to obtain such an effect of iron powder, it is necessary to add 20% or more to the total weight of the flux. On the other hand, when the content exceeds 40%, melting of the iron powder becomes difficult, and some of the iron powder remains on the bead surface as projections, thereby significantly impairing the bead appearance.

[SiO ₂ : 5 to 10 wt%] It is necessary to contain 5 to 10 wt% of SiO _{2 based} on the total weight of the flux. SiO ₂ has the effect of increasing the viscosity of the slag and makes the weld slag a vitreous property. Therefore, if the slag bitten into the groove is vitrified, the slag is easily broken and the slag removal operation is facilitated. In order to obtain such an effect of SiO ₂ , it is necessary to add 5% or more to the total weight of the flux. On the other hand, 10%
If the temperature exceeds, the melting point of the slag decreases, and in the case of large heat input welding,
The molten metal cannot be held, the bead width is not uniform, and the bead appearance is poor.

[Al ₂ O ₃ : 5 to 15 wt%] Al ₂ O
₃ needs to be contained in an amount of 5 to 15% by weight based on the total weight of the flux. Al ₂ O ₃ has a melting temperature of about 2000
° C, which is relatively high, and has an excellent effect of increasing the fire resistance of the flux. Therefore, even in large heat input welding, the molten metal can be reliably held, and the spread of the bead is suppressed and the bead width is narrowed, so that the slag removability is improved. Such an A
The effect of l ₂ O ₃ requires addition of 5% or more based on the total weight of the flux. However, if it exceeds 15%, the bead width becomes too narrow, resulting in poor adaptation of the bead toe.

[MgO: 5 to 20 wt%] MgO needs to be contained in an amount of 5 to 20 wt% based on the total weight of the flux. MgO has a very high melting point of about 2700 ° C,
Provides fire resistance to the flux. In order to obtain the effect of forming a stable bead even in large heat input welding, addition of 5% or more is necessary. On the other hand, if it exceeds 20%, the welding slag becomes hard and bites into the groove, making it difficult to remove the slag.

[TiO ₂ : 5 to ₂₀ wt%] TiO ₂ needs to be contained in an amount of 5 to 20 wt% based on the total weight of the flux. TiO ₂ gives fluidity to molten slag,
This has the effect of improving the familiarity of the bead toe. To obtain such an effect of TiO ₂ , the addition of 5% or more is necessary. However, if it exceeds 20%, the fluidity of the slag becomes excessive, the wave on the bead surface becomes coarse, and the bead appearance becomes poor.

[CaCO ₃ : 5-10 wt%] CaCO _3
3 needs to contain 5 to 10% by weight based on the total weight of the flux. CaCO ₃ stabilizes the arc during welding. In multi-pass welding, diffusible hydrogen is accumulated in the weld metal as the number of welding passes increases, and low-temperature cracking due to diffusible hydrogen may occur near the final pass. CaCO ₃ is formed by CaO and C by arc heat during welding.
It has the effect of reducing the hydrogen partial pressure in the arc cavity which is decomposed into O ₂ , reducing the amount of hydrogen transferred to the weld metal, and reducing the amount of diffusible hydrogen. To obtain such an effect of CaCO ₃ , the addition of 5% or more is necessary. However, if it exceeds 10%, the amount of generated gas becomes excessive, the arc blows up sharply, the welding workability is deteriorated, and the bead is deteriorated. The appearance is poor.

[ZrO ₂ : 5 to 15 wt%] It is necessary to contain 5 to 15 wt% of ZrO ₂ with respect to the total weight of the flux. ZrO ₂ has a very high melting temperature of about 3000 ° C., similar to MgO, and provides fire resistance to the flux to form a stable bead even in welding with a large heat input. The addition of ZrO ₂ makes the welding slag fragile. In addition, the slag that has caught in the groove can be crushed even with a slight impact. To obtain such an effect, it is necessary to add 5% or more. However, if it exceeds 15%, the fire resistance becomes excessive, the fluidity of the slag is lost, and the bead appearance becomes poor. The effects of the flux component and the reasons for the limitation have been described above, but this is based on the assumption that the bond flux is obtained by granulating a mineral raw material as a slag agent or an alloy component that migrates into the groove as a molten metal using a binder such as water glass. It is assumed that.

[Final pass welding method] The H-shaped steel is manufactured by fillet welding a flange steel sheet and a web steel sheet. Normally, both sides are welded without a beveling process up to a plate thickness of about 25 mm. However, in welding of a very thick steel plate having a plate thickness of 60 mm or more, as shown in FIG. And perform multi-pass welding from both sides to obtain sufficient penetration.

As shown in FIG. 1, in the multi-layer welding for producing an extremely thick H-section steel, in order to obtain sufficient penetration of the first layer welding, the vertical line L and the surface of the flange steel plate 2 and the web steel plate 1 side are formed. each angle formed open crest as theta _1/2 which is half the included angle theta _1, the target position of the wire and the bottom of the groove. Subsequently, in the second and subsequent passes, multi-layer welding is performed by sorting the flange steel plate 2 or the web steel plate 1 in the groove.

However, if the final pass is on the web steel sheet 1 side as shown in FIG. 2B, as shown in FIG.
Final pass before the wire 4 aiming position becomes flange steel plate 2 side, flange steel plate 2 surface as shown in FIG. 1 has a small inclination is large angle between the vertical line L and theta _1/2. As shown in FIG. 2A, since there is no bead in the pass before damping the flow of the molten slag on the web steel plate 1 side, the molten slag flows toward the web steel plate 1 by gravity in the welding before the final pass. . Therefore, an undercut 3 occurs at the bead toe on the flange steel plate 2 side.

Conversely, as shown in FIG. 3B, when the target position of the wire 4 in the final pass is on the side of the flange steel plate 2, FIG.
As shown in, the angle between the vertical line L and the web steel plate 1 side surface of the steel sheet is large and θ _1/2 + θ 2, the inclination becomes loose. Therefore, as shown in FIG. 3A, no molten slag flows during welding before the final pass, and no undercut occurs at the bead toe. In the subsequent final pass, as shown in FIG. 3B, the molten slag is stopped by the bead 5 of the previous pass and does not flow, so that no undercut occurs.

[Reason for Limiting Wire Diameter and Distance between Poles] In two-electrode welding according to the present invention, the leading electrode has a role of controlling the penetration depth, and the trailing electrode has a role of controlling the bead width. Therefore, the leading electrode is preferably small in diameter to increase the current density, and the wire diameter is suitably 4.0 to 6.0 mm. 4.0mm
If it is less than 1, a high current cannot be used, and high-temperature cracking also occurs. On the other hand, if it exceeds 6.0 mm, the amount of penetration decreases. Also, the wire diameter of the subsequent electrode is suitably 5.0 to 7.0 mm in order to increase the bead width. If it is less than 5.0 mm, the effect of widening the bead width cannot be obtained. If it exceeds 7.0 mm, a high current is required to melt the wire, the current balance with the preceding electrode is poor, the arc becomes unstable, and the bead width is uneven. Becomes

Further, the distance between the electrodes greatly affects the penetration depth, and the distance between the electrodes is set to 40 to 60 mm in the first layer welding which requires deep penetration. If the distance between the electrodes is less than 40 mm, the arc of the leading electrode is interfered by the trailing electrode and is drawn backward, so that deep penetration cannot be obtained. On the other hand, if it exceeds 60 mm, the interference of the arc does not occur, but the molten pool becomes two pools, the wave on the bead surface is coarse, and the bead appearance is poor. In the second pass and thereafter, the weld pool is a semi-one pool, and the distance between the electrodes is 10 to 30 mm to make the bead width uniform without welding defects such as undercuts at the bead toe.
When the thickness is less than 10 mm, the arc blows up violently, resulting in poor bead appearance. If it exceeds 30 mm, the bead width becomes too wide, and the slag removability in the groove deteriorates.

[0024]

EXAMPLES A bond flux having a composition shown in Table 1 was trial-produced, a steel sheet having a chemical composition shown in Table 2 was processed into a groove shown in FIG. 1, and a wire having a chemical composition shown in Table 3 was used. Under the welding conditions, the second pass and thereafter were distributed to both sides of the groove, and the target position of the wire in the final pass and the distance between the electrodes were changed to perform submerged arc welding with two electrodes. Welding workability such as slag peeling property and bead familiarity during welding, and the presence of hot cracks and penetration of the first layer were examined by ultrasonic testing after welding. The results are summarized in Tables 5 and 6.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

[Table 6]

In Table 5, Test No. 1 to 6 are examples of the present invention and test Nos. 7 to 22 are comparative examples. Test N which is an example of the present invention
o. In the case of Nos. 1 to 6, the flux composition, the target wire position of the final pass, the wire diameter, and the distance between the electrodes are appropriate, so the penetration of the first layer, the slag removability, the familiarity of the beads are good, and there is no high-temperature cracking. Met.

Test No. 7, the projection is generated in the high bead surface of iron powder in the flux code F-7, also, Al ₂ O
_{3, the} slag peeling property was deteriorated. Test No. 8
In Example 1, the flux code F-8 was high in SiO _2, resulting in irregular bead width, and ZrO ₂ was low, so that slag peeling was poor. Test No. 9 is the flux symbol F-9
Of MgO is high, the welding slag becomes hard, and the peelability deteriorates.
In addition, since CaCO ₃ was high, the blow-up of the arc was severe and welding workability was deteriorated.

Test No. 10 is the flux symbol F-1
Since the iron powder of No. 0 was low and the amount of welding was insufficient, and the Al ₂ O ₃ was high, the bead width was narrow and the conformity of the bead toe was poor. Test No. 11 is the flux symbol F
Since TiO _{2 of} -11 was high and the fluidity of the slag was excessive, the ripples on the bead surface became coarse, and because CaCO ₃ was low, the arc was not stable, the bead width was not uniform, and the bead adaptation was poor.

Test No. 12 is the flux symbol F-1
2 had low SiO _{2 and} high ZrO ₂ , the fluidity of the slag was lost, and the slag removability and bead appearance deteriorated. Test No. In No. 13, MgO and TiO ₂ having a flux code of F-13 were low, so that the slag was poor in fire resistance and fluidity, and the slag peeling property and the penetration of beads were deteriorated.

Test No. In No. 14, the target position of the final pass was the web steel plate side, and undercut occurred on the flange side before the final pass. Test No. 15 is the symbol W for welding conditions
Since the diameter of the leading electrode wire of No. 3 was small, the penetration of the first layer was deep and hot cracking occurred. Test No. In No. 16, the leading electrode wire diameter of the welding condition W4 was large, so that the penetration of the first layer was insufficient.

Test No. In No. 17, since the diameter of the trailing electrode wire of the welding condition symbol W5 was small, the bead width was not widened and the conformity of the bead toe was deteriorated. Test No. In No. 18, the wire diameter of the trailing electrode of welding condition symbol W6 was large, the current balance between the leading electrode and the trailing electrode was poor, the arc was unstable, and the adaptability of the bead toe was deteriorated.

Test No. In No. 19, since the distance between the electrodes of the first layer was short, the penetration was shallow. Test No. In No. 20, since the distance between the electrodes after the second pass was short, the arc blow-up was severe and welding workability was deteriorated. Test No. In No. 21, since the distance between the electrodes after the second pass was long, the molten pool became two pools, and the waves on the bead surface became coarse. Test No. 22
Since the distance between the electrodes of the first layer was long, the bead width was widened and the slag removability was deteriorated.

[0038]

As described above in detail, according to the two-electrode downward fillet submerged arc welding method of the present invention, the slag peeling property and the bead in the fillet welding used when manufacturing an extremely thick H-section steel or the like. The weldability of the toe is good and excellent welding workability can be obtained, and there is no welding defect such as undercut or hot crack, so that an extremely thick H-section steel can be provided with high efficiency.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a groove shape when manufacturing an extremely thick H-section steel.

FIG. 2 is a cross-sectional view showing a welding lamination procedure of a comparative example, and FIG.
Shows the state before the final pass, and (b) shows the state after the final pass.

FIG. 3 is a cross-sectional view showing a welding lamination procedure according to the present invention;
Shows the state before the final pass, and (b) shows the state after the final pass.

[Explanation of symbols]

1 web steel plate 2 a flange steel plate 3 undercut 4 wire 5 beads t _w the thickness t _f thickness d groove depth of the flange steel L vertical theta ₁ flange steel and the web steel plate side GMA surface of the web steel plate before path angle angle theta ₂ web steel sheet surface and the groove surface Nasu forms

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Katsutoshi Sueda 3-5-4 Tsukiji, Chuo-ku, Tokyo Nippon Steel Welding Industry Co., Ltd.

Claims (2)

[Claims] In a downward fillet submerged arc welding method for an extremely thick steel plate having a thickness of 60 to 100 mm, iron powder: 20 to 40 wt% and SiO ₂ : 5 to the total weight of the flux.
_{~10wt%, Al 2 O 3:} 5~15wt%, MgO:
_{5~20wt%, TiO 2: 5~20wt%} , CaCO
₃ : Multi-pass welding using a bond flux containing 5 to 10 wt% and ZrO ₂ : 5 to 15 wt%, and the final pass is welding on the flange steel plate side. Method. 2. Lead electrode wire diameter: 4.0 to 6.0 m
m, trailing electrode wire diameter: 5.0-7.0 mm, distance between electrodes: first layer welding: 40-60 mm, second pass and thereafter: 1
2. The method for welding a two-electrode downward fillet submerged arc according to claim 1, wherein the welding is performed at 0 to 30 mm.