JPH11216569A - Fillet welding of ultra thick steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the manufacture and the like of an ultra thick H-shaped steel and the like, as well as to obtain a smooth appearance while the penetration of a bead toe part is good. SOLUTION: In this fillet welding method for an ultra thick steel plate, when a web plate thickness of 50-100 mm is designated as T, the groove depth is 2T<1/2> or more. After the first layer or the first and second layers are underlaid by gas shield arc welding using the wire of 1.0-2.0 mm wire diameter, the last layer is welded by 2 electrodes submerge arc welding while the steel grains of 0.6-1.4 mm diameter is sprayed. In this case, it is preferable to use the bounded flux containing 20-40 wt.% iron, 5-15 wt.% SiO2 , 5-15 wt.% Al2 O3 , 5-20 wt.% MgO, 5-20 wt.% TiO2 , 2-7 wt.% CO2 , and 3-13 wt.% ZrO2 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fillet weld used for producing an ultra-thick H-section steel used for steel structures such as steel frames and bridges, and more particularly, to a fillet weld formed by gas shielded arc welding. Thereafter, the present invention relates to a fillet welding method for an extra-thick steel plate capable of obtaining a smooth bead shape with a good fit at a toe portion by combining dispersal of steel grains in a groove and two-electrode submerged arc welding.

[0002]

2. Description of the Related Art In recent years, an extremely thick steel box column has been widely used as a column member of a high-rise building. In the production of this extremely thick box column, large heat input submerged arc welding of two electrodes and one pass is performed from the viewpoint of work efficiency up to a plate thickness of about 60 mm. However, due to the increase in welding heat input,
There is a concern that the performance of the heat affected zone of the welded steel sheet may deteriorate.

[0003] Therefore, recently, as an alternative to an extremely thick steel box column, a technique of applying an H-section steel having a plate thickness of 50 to 100 mm has been studied. In the manufacture of this H-section steel, it is a major issue to improve the efficiency of fillet welding. This is because, in the standard specification of construction work (hereinafter, referred to as JASS 6), when the web thickness T is required to set the groove depth to 2T ^1/2 or more, the groove cross-sectional area for extremely thick steel plate And the amount of welding work increases. FIG. 2 shows an example of a groove shape, where 1 is a web, 2 is a flange,
d ≧ 2T ^1/2 is required.

The present inventors have previously reported a flux and a welding method applicable to fillet welding with a large heat input, as disclosed in Japanese Patent Application No. Hei 8-1.
No. 02914 proposed to apply nickel slag containing a large amount of MgO component having a high melting temperature. According to this, deep penetration is achieved by the downward fillet submerged arc welding with a large heat input, 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, the K steel shown in FIG.
When a groove is formed and welded, slag bites into the groove and the slag removability is significantly deteriorated. In addition, when the large heat input submerged arc welding method used for steel frame columns is applied to the fillet welding of extra-thick H-section steel, the arc concentration is large, so undercuts occur on the web or flange, and the bead surface waveform is also reduced. Coarse and poor in bead smoothness.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a fillet welding of an extremely thick steel plate, which can obtain a smooth bead shape in which the toe has a good fit at the toe portion and has no welding defects such as undercuts and cracks. It is an object of the present invention to provide a method for welding a fillet of an extremely thick steel plate from which a joint can be obtained.

[0006]

According to the present invention, there is provided a method for producing a sheet having a thickness of 50 to 1 mm.
The groove depth is 2T when the web thickness of 00mm is T.
^{In the} fillet welding method for a steel plate having a thickness of ^1/2 or more, after the first or second layer is laid down by gas shielded arc welding using a wire having a wire diameter of 1.0 to 2.0 mm,
This is a method for welding a fillet of an extremely thick steel plate, wherein a steel grain having a particle size of 0.6 to 1.4 mm is scattered in a groove and two-electrode submerged arc welding is performed. Here, iron powder: 20 to 40 wt.
_{%, SiO 2: 5~15wt%,} Al 2 O 3: 5~15w
t%, MgO: 5 to 20 wt%, TiO2: 5 to ₂₀ w
_{t%, CO 2: 2~7wt%} , ZrO 2: 3~13wt
% Is also characterized in that a bond flux for submerged arc welding containing 0.1% is used.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the fillet welding method for producing an extremely thick H-section steel having a thickness of 50 mm or more, the following findings were obtained as a result of various examinations of welding conditions, flux composition, and the like. (1) In order to obtain deep penetration and to prevent hot cracking of the root portion and slag from being caught, it is necessary to lower the height by gas shield arc welding.

(2) Considering the fatigue strength of the H-type steel, it is important to finish the final layer with one layer. For this reason, it is necessary to apply two-electrode large heat input submerged arc welding. However, in the large heat input submerged arc welding, arc concentration is high and an undercut occurs in the web or flange.
In order to prevent the undercut, it is necessary to reduce the arc concentration and make the arc wider, and it is important to disperse steel grains and perform the above-mentioned large heat input submerged arc welding.

(3) Further, in order to increase the amount of welding, it is necessary to combine iron powder-containing bond flux for submerged arc welding (hereinafter referred to as flux). FIG. 1 shows the welding procedure of the present invention, and the operation of the present invention and the reasons for limitation will be described in detail below.

[Prime by gas shielded arc welding]
In JASS 6, the groove depth d is specified, but the groove angle θ (FIG. 2) is not specified. Therefore, the groove cross-sectional shape changes greatly depending on the construction maker. In order to obtain a defect-free deep penetration at the root part, it is necessary to perform underlay welding by gas shielded arc welding. In FIG. 1, 3
Is a lower weld bead. In this case, it is necessary to select a wire diameter according to the groove shape. If it is less than 1.0 mm, the appropriate current is low and the work efficiency is poor, while if it exceeds 2.0 mm, the penetration of the groove bottom is insufficient. . Therefore,
The wire diameter was 1.0 to 2.0 mm. Further, in consideration of efficiency, gas shield arc welding was performed up to the first or second layer. The wire used is a solid wire, and a CO ₂ gas or an Ar—CO ₂ gas is used as a shielding gas.

[Two-electrode Submerged Arc Welding after Spraying of Steel Grains] If an attempt is made to increase the amount of welding by welding an extremely thick H-shaped steel sheet, the amount of welding is insufficient with one electrode. Need to apply. However, in the two-electrode welding, if the welding current is increased in order to increase the welding amount, the penetration becomes deep, the bead becomes narrow, and it becomes difficult to finish the final layer with one layer. The bead may be widened by increasing the arc generating point. Therefore, as shown in FIG. 1, steel grains 4 are scattered in the groove, and submerged arc welding is performed using the two electrodes 5 and 6. The steel grains are easy to melt, can be easily sprayed into the groove, and are excellent in workability. However, if the particle size is less than 0.6 mm, the above effect is not obtained, and the penetration of the submerged arc welding is deep and the bead is narrow. Also, 1.4
If it exceeds mm, an unmelted portion is generated, resulting in welding defects. Here, the steel grains of the present invention include not only granular ones but also cut wires obtained by cutting steel wires of various sizes.

[0012] The components of the steel grains are mainly composed of Fe,
From the viewpoint of cracking resistance, C is preferably 0.13% by weight or less, P and S are preferably 0.020% by weight or less, and other components include Si, Mn, Mo and other deoxidizing agents in consideration of the strength and toughness of the weld metal. An alloying agent can be included. Further, as shown in FIG. 1, the steel particles are scattered so that the distance h from the open front end surface of the web steel plate remains 0 to 5 mm.

FIG. 3 shows an example of the electrode arrangement viewed from the side surface of the submerged arc welding. The inclination of the electrodes 7 and 8, the distance between the electrodes 9, the wire protrusion lengths 10 and 11 and It is necessary to adjust the wire aiming position Q of the L pole 5 (leading electrode) or the T pole 6 (following) shown in FIG. The wire diameter is 4.0 to use a large current.
7.0 mm is appropriate.

[Iron powder in flux: 20 to 40 wt.
%] Iron powder is 20 to 40 wt% based on the total weight of the flux
It is necessary to contain. The iron powder is melted by the arc heat during welding, moves into the groove, and increases the amount of welding. 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 15 wt%] It is necessary to contain 5 to 15 wt% of SiO ₂ with respect to the total weight of the flux. SiO ₂ has the effect of increasing the viscosity of the slag. 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, if it exceeds 15%, the melting point of the slag decreases, and in the case of large heat input welding, the molten metal cannot be retained, and the bead width becomes uneven, resulting in poor bead appearance.

[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, and can reliably hold the molten metal even in large heat input welding. Such an effect of Al ₂ O ₃ requires addition of 5% or more with respect to the total weight of the flux, but if it exceeds 15%, the bead width becomes narrow, and the conformity of the bead toe becomes poor.

[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. To obtain the effect of forming a stable bead in large heat input welding, addition of 5% or more is necessary. On the other hand, if it exceeds 20%, the weld slag becomes hard, and the slag removability deteriorates.

[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 , it is necessary to add 5% or more. However, if it exceeds 20%, the fluidity of the slag becomes excessive, the wave of the bead surface becomes coarse, and the bead appearance becomes poor.

[CO ₂ : _{2 to} 7 wt%] The amount of CO ₂ in the flux in the present invention refers to CaCO ₃ or BaCO _3.
Refers to the equivalent of CO _{2 in} the components added as carbonates. It is necessary that CO ₂ be contained in an amount of 2 to 7% by weight based on the total weight of the flux. CO ₂ stabilizes the arc during welding. Also, CO ₂ has the effect of lowering the hydrogen partial pressure in the arc cavity during welding, reducing the amount of hydrogen transferred to the weld metal, and reducing the amount of diffusible hydrogen. Such CO ₂
To obtain the effect of (2), it is necessary to add 2% or more.
%, The amount of generated gas becomes excessive, the arc blows up sharply, the welding workability deteriorates, and the bead appearance becomes poor.

[ZrO ₂ : 3 to 13 wt%] ZrO ₂ needs to be contained in an amount of 3 to 13 wt% based on the total weight of the flux. ZrO ₂ has a very high melting temperature, similar to MgO, of about 3000 ° C., and provides fire resistance to the flux,
Stable bead formation is possible in welding with a large heat input. Addition of 3% or more is necessary to obtain such effects, but if it exceeds 13%, the fire resistance becomes excessive, the fluidity of the slag is lost, and the bead appearance becomes poor. Although the essential components of the flux have been described above, the effects of the present invention are not impaired even if other compositions, alloy components, and the like are added in accordance with the type and groove shape of the steel sheet.

[0021]

EXAMPLE A flux having the composition shown in Table 1 was trial-produced.
A steel sheet having the chemical composition shown in Table 3 was processed into a groove shown in FIG.
Using a gas shielded arc welding wire having the chemical composition shown in Table 1, a steel grain shown in Table 4, and a submerged arc welding wire shown in Table 5, a combination of Tables 6 and 7 and an extremely thick steel as shown in FIG. Fillet welding was performed. In either case,
The thickness T of the web steel plate was the same as the thickness t of the flange steel plate. The groove angle θ was 50 °.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

[Table 6]

[0028]

[Table 7]

The gas shielded arc welding has a current of 30.
0-450A, voltage 35-45V, speed 20-30cm
/ Min range, and underlay welding was performed. In the two-electrode submerged arc welding, the electrodes are arranged as shown in FIG.
Was performed under the conditions described in the figure. The wire target position Q in FIG. 1 is L pole 5 (leading electrode) 11 mm, T pole 6 (following electrode) 13 mm, the L pole has a current of 900 to 1100 A, the voltage 32 to 40 V, the T pole has a current of 800 to 1000 A, Voltage 3
The test was performed in the range of 5 to 45 V and the speed of 20 to 50 cm / min.

After welding, penetration into the groove root, penetration and smoothness of the bead in the final layer, and the presence or absence of defects in the weld were examined. Table 8 shows the test results. Test symbols T1 to T
11 satisfies the conditions of the present invention, and the components of the flux are also in the preferred range of the present invention, so that in the fillet welding of an extremely thick steel, a good bead shape at the toe and a smooth bead shape can be obtained, A weld joint having no welding defects such as undercut and crack was obtained. However, the test symbols T12 to T20 had troubles for the following reasons.

[0031]

[Table 8]

T12 has a small wire diameter for gas shielded arc welding and is formed of three layers, so that the work efficiency is poor. In addition, iron powder and SiO ₂ in the flux are low, and CO
_Since there were many ₂ , undercuts occurred and the surface smoothness was poor. In T13, since the diameter of the steel grain was small, the concentration of the submerged arc was not alleviated, and an undercut occurred. In T14, since the diameter of the steel grain was large, an unmelted defect occurred in the welded portion.

T15 has a large amount of MgO in the flux, resulting in poor slag removability, and has a small amount of CO _2, causing hydrogen cracking. At T16, gas shielded arc welding was not performed, so that the root portion was insufficiently penetrated, and no undercut occurred because no steel particles were sprayed. T1
No. 7 has a large wire diameter for gas shielded arc welding, so that penetration at the root portion is insufficient, and TiO _{2 in the} flux
And the surface smoothness was poor due to large amounts of ZrO ₂ .

In T18, since the flux contained a small amount of SiO _{2 and a} large amount of Al ₂ O _{3, the} bead width was not uniform, an undercut occurred, and the surface smoothness was poor. T19 had poor adaptation because the flux contained a large amount of Al ₂ O _{3 and a} small amount of TiO ₂ . T20 is 1 for submerged arc welding
Since the electrode was used and the amount of iron powder in the flux was small, the amount of welding was insufficient. In addition, since the amount of MgO was small and the amount of ZrO ₂ was small, undercutting occurred and the surface smoothness was poor.

[0035]

As described above in detail, according to the fillet welding method of the present invention, when manufacturing an extremely thick H-section steel, etc., the bead toe portion can be adjusted well and a smooth appearance can be obtained. Highly efficient production without welding defects is possible.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a welding procedure according to the present invention.

FIG. 2 is a cross-sectional view showing a groove shape when manufacturing an extremely thick H-section steel.

FIG. 3 is a side view showing an example of an electrode arrangement in two-electrode submerged arc welding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Web steel plate 2 Flange steel plate 3 Underfill welding bead 4 Steel grain 5 L pole 6 T pole 7 L pole inclination angle 8 T pole inclination angle 9 Distance between poles 10 L pole protrusion length 11 T pole protrusion Length T Web plate thickness t Flange steel plate thickness d Groove depth θ Groove angle h Remaining depth of groove after spraying steel grains Q Target position of wire

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B23K 9/173 B23K 9/173 A 33/00 33/00 Z 35/362 310 35/362 310B (72) Inventor Katsutoshi Sueda Tokyo 3-5-4 Tsukiji, Chuo-ku, Tokyo Nippon Steel Welding Industry Co., Ltd.

Claims (2)

[Claims] 1. A web thickness of 50 to 100 mm is defined as T
In the fillet welding method for an extremely thick steel plate having a groove depth of 2T ^1/2 or more, the first or second layer is gas-shielded using a wire having a wire diameter of 1.0 to 2.0 mm. After being prepared by arc welding, the final layer has a particle size of 0.6 to
A fillet welding method for an extremely thick steel plate, which comprises spraying 1.4 mm steel grains and performing two-electrode submerged arc welding. 2. Iron powder: 20 to the total weight of the flux
40 wt%, SiO ₂ : 5 to 15 wt%, Al ₂ O ₃ : 5
１５15 wt%, MgO: 5-20 wt%, TiO ₂ : 5
_{~20wt%, CO 2: 2~7wt%} , ZrO 2: 3~
2. The method according to claim 1, wherein a bond flux for submerged arc welding containing 13 wt% is used.