JP2000167670A - Fillet welding method of high strength thick plate steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fillet welding method of a high strength thick steel capable of obtaining a sufficient throat depth without generating a welding defect under a heat input of <=200 KJ/cm. SOLUTION: A T joint is formed of a web material subjected to groove preparation under tensile strength of >=590 MPa, a plate thickness of >=45 mm, and a flange material by two electrode flat position submerged arc welding. In the welding method, the sintered type flux containing iron powder of 20-40 wt.% and the welding wire satisfying the formula of 0.36×Cpl+0.34×Cw<=0.10 (Cpl is C quantity (wt.%) of steel, Cw is C quantity (wt.%) of wire) are used as welding materials. A preceding electrodes has a electric current of <=400 A and a voltage of (0.005 × preceding electrode electric current (A) +23) to (0.005 × preceding electrode electric current (A) +25) V, a succeeding electrodes has a voltage (0.005 ×preceding electrode electric current (A) +25) to (0.005 ×preceding electrode electric current (A) +40) V, particle joint penetration welding is done under a condition of a welding speed of >=21 cm/min and an input heat quantity of 200 KJ/cm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fillet welding method for a high-strength thick steel material for construction, and more particularly to a method for forming a T-joint with a small heat input and high efficiency up to a web thickness of about 100 mm. The present invention relates to a submerged arc fillet welding method for a high-strength thick steel material by partial penetration.

[0002]

2. Description of the Related Art In recent years, the thickness of members used as pillars has been increasing with the rise of buildings and the increase in buildings having large spaces without pillars. Also 80% yield ratio for construction
High-performance 590 (MPa) grade high-strength steel (HT), which achieves the following, has also been developed, and its application to buildings is gradually increasing. Further, in the construction of these high-rise buildings, in recent years, attempts have been made to use thick assembled H-section steel as the columns instead of box columns. The thickness of the steel sheet used for the web of these assembled H-section steels is generally in the range of 45 to 100 mm.
Further, as a welding method, generally, two-electrode submerged arc welding is adopted. In the case of fillet welding when assembling high-performance HT 590 grade steel into H-section steel, the Steel Materials Club has indicated welding construction guidelines. According to this, fillet welding requires welding heat input of 200 kJ / cm or less. It is prescribed to do. For this reason, assembly H made of HT590 grade steel
In order to manufacture a section steel, it is a major problem how to perform welding to obtain a necessary strength with a sound weld metal within a heat input limit of 200 kJ / cm or less.

[0003] As for a method of welding a thick-walled assembled H-section steel having a groove, for example, Japanese Patent Application Laid-Open No. 5-57448 discloses a partial penetration welding method for a web thickness of 60 to 120 mm. I have. However, this technique is not a method that can be used for welding with welding heat input of 200 kJ / cm or less. Further, Japanese Patent Application Laid-Open Nos. 7-68380 and 9-99371 both disclose methods for enabling full penetration welding up to a web thickness of 100 mm. However, these techniques also have applied welding heat inputs well in excess of 200 kJ / cm2.

[0004]

As described above, the conventional fillet welding method for a thick steel material has a welding heat input of 200 kJ / c.
m and cannot be applied to welding of assembled H-section steel using HT 590 grade steel, which is increasing recently.

In general, when an assembling H-section steel is used as a column, partial penetration welding is performed except in the vicinity of a joint portion where a beam is attached. Becomes Therefore, in the H-section steel used for construction, the ratio of partial penetration welding is much larger than that of full penetration welding. The strength of a fillet welded joint is calculated based on the throat thickness, and this throat thickness is originally evaluated (for joint strength calculation) by the actual throat thickness. In order to know the actual throat thickness, it is necessary to know the penetration depth of the fillet weld metal, which can be measured by using an ultrasonic flaw detection technique. However, employing this measurement for all welded H-section welds reduces productivity in producing steel frames.

On the other hand, in evaluating the throat thickness of a fillet weld, as one means for reducing the load of such ultrasonic flaw detection, a "theoretical throat thickness" for calculating the throat thickness starting from the groove bottom is used. There is a method to adopt. In this case,
If the groove search can be confirmed, the throat thickness can be calculated relatively easily by measuring the leg length after welding, and the strength of the welded joint can be assured. According to this idea, beveling is essential from the viewpoint of strength design. In the case of partial penetration welding, the groove depth is generally 2t ^1/2 or t / 3 when the web thickness is t.

Therefore, in order to obtain a reliable joint strength with a small heat input of 200 kJ / cm or less under such a groove shape, the inside of the groove is efficiently filled with the weld metal, and It is necessary to secure a welding amount such that a necessary throat thickness (leg length) can be obtained without welding defects.

In view of the above problems in the prior art, an object of the present invention is to provide a sheet having a tensile strength of at least 590 MPa and a sheet thickness of 45 mm.
In fillet welding between a web material that has been grooved to a thickness of at least 200 mm and a flange material, even with a welding heat input of 200 kJ / cm or less, welding defects such as cracks and undercuts do not occur.
An object of the present invention is to propose a fillet welding method for a high-strength thick steel material which can obtain a sufficient throat thickness.

[0009]

According to the present invention, a tensile strength of 59% is provided.
In the method of fillet welding of high-strength thick steel material, a T-joint is formed by two-electrode downward submerged arc welding of a web material that has been grooved with a thickness of 45 MPa or more and a flange material with a thickness of 0 MPa or more. As an example, a sintering flux containing iron powder: 20 to 40 wt% and a welding wire having a C content satisfying the following equation (1) are used. The leading electrode has a current of 1400 A or less and a voltage of (0.005 × leading electrode current ( A) +23) to (0.005 × leading electrode current (A) +32) V, and the voltage of the succeeding electrode is (0.005 × leading electrode current (A) +25) to (0.005 × leading electrode current (A) +40)
V, welding speed 21cm / min or more, heat input 200 kJ / c
This is a fillet welding method for a high-strength thick steel material, characterized in that partial penetration welding is performed under a condition of not more than m. 0.36 × C _pl + 0.34 × C _w ≦ 0.10 (1) where C _pl is the C content (wt%) of the steel material, and C _w is the C of the wire.
Amount (wt%)

Further, in the above invention, it is preferable that the welding is performed in a posture of the material to be welded in which the angle between the flange material and the horizontal plane is 50 to 70 °. Further, in each of the above inventions, welding is performed such that the target position of the leading electrode in the groove is within ± 3 mm of the groove center on the web surface, and the target position of the following electrode is 2 to 6 mm as the distance from the flange on the web surface. Is preferred. In the above inventions, the groove angle of the web is 35 to 60 ° when the thickness is 45 to 80 mm, and the thickness of the web is 80.
It is desirable to set the angle to 35 to 50 ° when the thickness is more than 100 mm.

[0011]

Embodiments of the present invention will be described below in detail. JP-A-5-57448 described above,
In the conventional welding of a thick assembled H-section steel disclosed in JP-A-7-68380 and JP-A-9-99371,
All of them are intended for low-strength steel of 490 MPa class, and are also fully penetration welded, with a heat input of 200 kJ / c
m is greatly exceeded. For this reason, these conventional techniques cannot be applied to welding of an assembling H-section steel of 590 MPa class or more, which requires strict heat input restriction. Therefore,
The inventors found that the welding strength of the thick wall was less than 200 kJ / cm.
The purpose of this study is to investigate the method of efficiently performing the partial penetration fillet welding of high-strength steel of 90 grade or more, and to perform two-electrode submerged arc welding using specific fluxes and wires and regulating welding conditions. The knowledge that it can be achieved was obtained.

The main points are listed below. (1) To obtain a large amount of deposition with limited welding heat input,
In order to contain a large amount of iron powder in the sintering flux and to effectively utilize the effect, it is necessary to adjust welding conditions, particularly welding voltage. (2) In order to efficiently secure the theoretical throat thickness with a small amount of welding, it is necessary to adjust the holding angle and groove angle of the work to obtain the leg length efficiently. (3) Since the steel plate is thick, partially penetrated, and is a high-strength steel, cracks easily occur in the weld metal. To avoid the occurrence of such cracks, the amount of C in the weld metal is sufficiently reduced. There is a need. (4) Under limited welding heat input, it is necessary to increase the welding speed by increasing the current.However, the leading electrode current and welding speed have a large effect on defects such as hot cracking and undercut. Is limited to a very narrow range. (5) In order to prevent the occurrence of defects such as undercut, poor fusion and slag entrapment, it is important to adjust the groove angle and the inclination angle of the work, and particularly to set the target position of the electrode. Based on the above findings, the inventors set the welding heat input 20
At 0 kJ / cm or less, a method for performing fillet welding by partial penetration in one pass without causing welding defects was completed.

Hereinafter, each component will be further described, including the reasons for limitation. -Iron powder in the flux: 20 to 40 wt% In order to effectively obtain the required amount of welding at a welding heat input of 200 kJ / cm or less, it is necessary to include 20 to 40 wt% iron powder in the flux. . If the amount of iron powder is less than 20wt%,
It is difficult to obtain the required welding amount with a small heat input of 200 kJ / cm or less. On the other hand, if it exceeds 40% by weight, the wetness of the bead, the flange and the web becomes poor, the bead shape becomes overlapped, the leg length on the flange side becomes unstable, and the bead surface becomes rough, resulting in poor appearance. The flux used in the present invention is desirably a fired flux having the following composition from the viewpoint of securing the appearance of the bead and the strength and toughness of the weld metal. SiO ₂ : 15 to 35 wt%, Al ₂ O ₃ : _{3 to} 20 wt%, TiO ₂ : 2
~10wt%, MgO: 15~35wt%, CaO: 3~8wt%, carbon dioxide component (CO ₂ terms): 4~15wt%, Si, Mn , Ti, A
l, total of Zr metal powder: 2-8 wt%

C content in the wire C content in the wire is 0.36 × C _pl + 0.34 × C _w ≦ 0.10
(Wherein, C _pl is C of the steel product (wt%), C _w represents the C content of the wire (wt%)) must satisfy the. Outside the range of the above formula, the C content in the weld metal exceeds 0.12 wt%,
This is because hot cracking occurs in the weld metal. C in the weld metal is supplied from the iron powder and the carbonate in the steel material, the wire, and the flux. As other components in the wire,
In order to improve the strength and toughness of the weld metal, it is desirable to include Si: 0.35 wt% or less and Mn: 1.0 to 2.2 wt%. Further, it may further contain Mo, Ni, or the like. About wire diameter
A range from 4.8 to 6.4 mm is preferred. Next, the welding conditions will be described.

Groove angle: 35 to 60 ° (50 °) If the groove angle is smaller than 35 °, the cross-sectional shape of the weld bead becomes an elongated shape with a large penetration into the width, and the hot cracking susceptibility increases, Cracks are likely to occur. On the other hand, if it is larger than 60 °, the groove cross-section becomes too large,
It becomes difficult to secure the required amount of welding within the limit of welding heat input of 200 kJ / cm or less, and it becomes easy to generate defects of poor fusion, in which the groove inside the bead becomes unmelted. If the thickness of the groove exceeds 80 mm, it is difficult to secure a necessary welding amount and a sufficient throat thickness unless the thickness is more narrowed. Therefore, at such a plate thickness, the upper limit of the groove angle needs to be 50 °.

The angle formed by the flange of the workpiece and the horizontal plane:
50 to 70 ° Angle of inclination of flange material during welding (work angle, Fig. 1
Θ) is a large downward heat input when performing fillet welding.
It is a very important factor in determining the flange leg length and the web leg length. When the inclination angle is smaller than 50 °, the web-side leg length can be reduced and the flange-side leg length can be obtained efficiently, but on the other hand, the bead width is reduced, the hot cracking susceptibility is increased, and cracks are easily generated. . In addition, depending on the groove angle, the electrode is difficult to enter the groove, so that it is necessary to take measures such as tilting the electrode, and poor fusion or undercut is likely to occur. On the other hand, when the inclination angle exceeds 70 °, the leg length on the web side is long, the leg length on the flange side is short, and the throat thickness is small.

· Current of the leading electrode: 1400 A or less If the current of the leading electrode exceeds 1400 A, the penetration deepens,
Hot cracking sensitivity increases. In addition, welding heat input is 200 kJ / c
If it is less than m, the width of the weld bead hardly changes, so that the penetration becomes deeper with respect to the bead width, and cracks are extremely likely to occur. Therefore, the current of the leading electrode is 1400
It is necessary to limit to A or less. If it is less than 600 A, it is difficult to secure the required amount of welding because it satisfies the requirements of welding heat input, welding speed, and welding voltage. The ratio I _L / I _T of the current I _{L of the} leading electrode and the current I _T of the following electrode is preferably in the range of 0.8 to 1.1 from the viewpoint of preventing welding defects.

Welding speed: 21 cm / min or more When the welding speed is lower than 21 cm / min, undercutting defects are likely to occur mainly on the flange side. However, if it exceeds 50 cm / min, it is difficult to satisfy the required welding amount while satisfying the current requirement. Therefore, it is desirable to limit the welding amount to 50 cm / min or less.

Lead electrode voltage: (0.005 × lead electrode current)
(A) +23) to (0.005 x leading electrode current (A) +32) V If the voltage of the leading electrode is smaller than the lower limit of the above equation, the consumption of flux is reduced, the amount of iron powder to be deposited is reduced, and welding is performed. It is easy to run out of quantity. In addition, a short-circuit phenomenon frequently occurs, and the arc becomes unstable, the tip of the penetration portion becomes thin, and cracks and slag entrapment are likely to occur. On the other hand, when the voltage is larger than the upper limit of the above equation, the welding heat input calculated by current × voltage ÷ welding speed is increased, but the protruding length of the wire is shortened, and the amount of the wire melted by the resistance heating is reduced. . For this reason, the amount of welding does not increase in spite of the increase in heat input, and the amount of welding is insufficient at 200 kJ / cm or less, making it impossible to secure an appropriate throat thickness or increasing the arc length. The bottom of the tip remains melting,
Undercuts are likely to occur. Furthermore, since the amount of gas generated by decomposition of the carbonate increases, the blow-up of the gas becomes intense, and welding workability and bead appearance are impaired.

-Trailing electrode voltage: (0.005 x trailing electrode current)
(A) +25)-(0.005 x leading electrode current (A) + 40) V The voltage of the trailing electrode is (0.005 x trailing electrode current (A) + 25)-
(0.005 × leading electrode current (A) +40) V. When the value is lower than the lower limit of this formula, the amount of the consumed flux decreases, the amount of the iron powder transferred from the flux to the deposited metal decreases, and the deposited amount becomes insufficient. In addition, the bead becomes convex, and the bead toe tends to overlap. If the voltage is extremely reduced, the short circuit phenomenon becomes frequent, the arc becomes unstable, and poor fusion and poor bead appearance tend to occur. On the other hand, if the voltage is higher than the upper limit of the above equation, current × voltage ÷
Although the welding heat input calculated by the welding speed is higher, the protruding length of the wire is shorter, and the amount of the wire that is melted by the resistance heating is reduced. For this reason, the amount of welding does not increase in spite of the increase in heat input, and the amount of welding is insufficient under 200 kJ / cm, and an appropriate throat thickness cannot be secured. In addition, undercuts are likely to occur and gas blow-up becomes severe, which impairs welding workability and bead appearance.

Aiming position of leading electrode: within ± 3 mm of groove center on web surface Aiming position of leading electrode is ± 3 mm at groove center on web surface
mm (The position where the seam of the web and flange coincides with the center of the wire is defined as 0, and the deviation of the center of the wire from 0 on the web surface (a in FIG. 2 (a)) is ± 3.
mm or less). The case where it is shifted to the flange side is minus, and the case where it is shifted to the web side is plus. When the target position is out of the above range, the groove bottom is likely to remain without being dissolved. It also causes undercut and poor fusion. The inclination of the leading electrode is preferably within a range between the bisector of the included angle (dotted line in FIG. 2) and the perpendicular.

The target position of the trailing electrode The target position of the trailing electrode has a very large effect on welding defects and bead appearance. Moreover, if the flange side is not aimed at than the center of the bead width after welding, an appropriate weld bead cannot be obtained. If the distance b in FIG. 2B is smaller than 2 mm, undercuts are likely to occur on the flange side, while if it is larger than 6 mm, the beaded toe portion on the web side has an overlapping shape, which impairs the bead appearance. Therefore, the target position of the succeeding electrode is set to 2 mm ≦ b ≦ 6 mm.
Like the preceding electrode, the inclination of the following electrode is preferably within a range between the bisector of the included angle and the perpendicular.

[0023]

The present invention will be specifically described below with reference to examples. Table 1
The composition of the flux used for welding is shown below. They are,
All are firing type fluxes. Table 2 shows the chemical composition of the welding wire used. The diameters of these wires were 4.5, 4.8, 6.4, and 6.8 mm, respectively. Table 3
Table 1 shows the thickness and chemical composition of the steel sheet used. These are all high-performance, high-strength steels with a tensile strength of 590 MPa or more and a yield ratio of 80% or less. The steel plate has a groove depth of 2 ／ t to t / 3
mm (t: web thickness) K-groove (see Fig. 2)
Using the above welding material, a downward fillet two-electrode submerged arc welding was performed in one pass on both sides.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

Example 1 The welding conditions were a leading electrode current-voltage: 1200 A-32 V, a trailing electrode current-voltage: 1000 A-36 V, welding speed: 23 cm / min.
(Welding heat input: 194 kJ / cm 2), welding was performed with the target position a of the leading electrode being 0 mm and the target position b of the succeeding electrode being 5 mm. The distance between the leading electrode and the trailing electrode is 40 mm on the web surface, the protrusion length is 40 mm for the leading electrode from the web surface, and 60 mm for the trailing electrode from the web surface. The electrode had a receding angle of 5 °, and the trailing electrode had an advancing angle of 5 °. Table 4 shows the results of welding under the above conditions.

In Table 4, in all of the inventive examples Nos. 1 to 8, good weld beads having a sufficient throat thickness and leg length were obtained. On the other hand, in No. 9, the C amount of the wire was 0.13.
Since the content was as high as wt%, the C content in the weld metal was increased, and hot cracking occurred. In No. 10, the amount of iron powder in the flux was 15wt%
Low, the amount of welding is insufficient and the target theoretical throat thickness
It was 26 mm, 1 mm smaller than 27 mm. In No. 11, the bead appearance was poor because the amount of iron powder in the flux was as large as 45%.

[0029]

[Table 4]

Example 2 The welding wire used had the chemical composition shown in B-1. The wire diameter of the leading electrode was 4.8 mm, and the wire diameter of the trailing electrode was 6.4 m.
m. Table 5 shows the results. Nos. 1 to 13 are invention examples, in which no weld defects were found, and good weld beads having a sufficient throat thickness and leg length were obtained. In contrast, N
In o. 14, since the leading electrode current exceeded 1400 A, the penetration became too deep with respect to the bead width, and hot cracking occurred. In No. 15, the leading electrode voltage was too low, the tip of the penetration became thin, and slag was involved. In No. 16, conversely, the lead electrode voltage was too high, and the welding input was high, but a sufficient amount of welding was not obtained.
Shortage. In No. 17, the trailing electrode voltage was too low, resulting in poor bead appearance. In No. 18, the voltage of the trailing electrode was too high, resulting in an insufficient amount of welding and undercut. N
In o. 19, an undercut occurred because the welding speed was lower than 21 cm / min.

In No. 20, the trailing electrode voltage was too high, undercut occurred, the amount of welding was insufficient, and the target theoretical throat thickness of 29 mm was 1 mm short. In No. 21, the leading electrode voltage was too high, the amount of welding was insufficient, and the theoretical throat thickness was 1 m from 29 mm.
m was insufficient, and a defect occurred in which the bottom of the groove was still melted. No. 22
In this case, the trailing electrode voltage was too high, resulting in undercut and insufficient throat thickness.

[0032]

[Table 5]

[0033]

As described above, according to the present invention,
Partial penetration welding of high-strength H-section steel with high tensile strength of 590 MPa class or higher can be performed in one pass (one pass on both sides) with welding heat input of 200 kJ / cm or less. Since the manufacturing cost can be reduced and the delivery time can be shortened, it greatly contributes industrially.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state of fillet welding of an assembled H-section steel.

FIG. 2 is an explanatory diagram showing target positions of respective electrodes in fillet welding in a groove.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B23K 35/30 320 B23K 35/30 320F 35/362 310 35/362 310B // C22C 38/00 301 C22C 38 / 00 301Y (72) Inventor Tadamasa Yamaguchi 2-3-2 Uchisaiwai-cho, Chiyoda-ku, Tokyo F-term in Kawasaki Steel Corporation (reference) 4E001 AA03 BB05 CA02 CA07 CC04 DA01 DA05 DB01 DC01 DC05 DC07 DF05 EA01 EA02 EA03 EA05 EA05 EA06 EA07 EA09 QA04 4E081 AA12 BA05 BA34 BA37 BA40 BB03 BB07 BB13 BB15 CA05 DA01 DA10 DA11 DA12 DA18 DA35 DA48 DA55 DA57 EA05 YR03 4E084 BA02 DA18 DA28 FA09 FA11 FA15 HA04

Claims (3)

[Claims] 1. The tensile strength is 590 MPa class or more, and the thickness is 45 mm
A T-joint is formed by two-electrode downward submerged arc welding of the grooved web material and the flange material,
In the fillet welding method for high-strength thick steel, the welding electrode uses a sintering flux containing iron powder: 20 to 40 wt% and a welding wire whose C content satisfies the following formula (1). When the current is 1400A or less and the voltage is (0.005 ×
Lead electrode current (A) +23)-(0.005 x Lead electrode current (A) +
32) V, the voltage of the trailing electrode is (0.005 x trailing electrode current (A) +
25) to (0.005 × leading electrode current (A) +40) V, high strength characterized by partial penetration welding under conditions that the welding speed is 21 cm / min or more and the heat input is 200 kJ / cm or less Fillet welding method for thick steel. 0.36 × C _pl + 0.34 × C _w ≦ 0.10 (1) where C _pl is the C content of steel (wt%) and C _w is the C of the wire.
Amount (wt%) 2. The angle between the flange material and the horizontal plane is 50 to 70.
2. The method for welding a fillet of a high-strength thick-walled steel material according to claim 1, wherein the welding is performed in a position of the material to be welded at an angle of °. 3. The target position of the leading electrode within the groove is within ± 3 mm of the center of the groove on the web surface, and the target position of the following electrode is 2-6 mm from the flange on the web surface.
The fillet welding method for a high-strength thick steel material according to claim 1 or 2, wherein the welding is performed with a thickness of mm.