JP2013184217A - Arc welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arc welding method by which welding is performed efficiently and a welded joint excellent in seismic performance and anti-fatigue characteristic can be formed even when a vertically inverted work is impossible.SOLUTION: A first steel plate A is arranged toward a butting direction or an orthogonal direction orthogonal to the butting direction with respect to a second steel plate B and has a plate thickness larger than that of the second steel plate B. The second steel plate B is arranged toward the butting direction with respect to the first steel plate A and has a groove D. When welding the first steel plate A and the second steel plate B, the back of the groove D is welded by overhead welding of two or more passes in the orthogonal direction of an end face on the side of the first steel plate A, and the back on the side of the second steel plate B is welded by overhead welding for bridging the groove D in the butting direction and also, after performing the overhead welding of one or more passes after bridging, filling welding and marginal welding of the groove D are performed by flat welding on the surface side on the side of the second steel plate B. Welding is performed in such a way that an angle θ of a base metal-weld metal boundary line between the weld metal formed by the overhead welding and the flat welding and the base metal of the second steel plate B is not larger than 135°.

Description

  The present invention relates to an arc welding method capable of efficiently performing welding even when a top-and-bottom reversal operation is impossible when a steel material used for a steel frame for construction is welded to construct a structure.

  The arc welding method in which steel materials are brought into contact with each other and integrated is applied to all steel structures including buildings. When performing butt welding, if the groove root gap (narrowest gap) is zero, residual penetration occurs, the entire cross section does not melt, and complete penetration may not be possible. For this reason, a groove is formed on one or both sides of the member to be welded so that the arc can easily hit the inclined surface in the groove so that proper penetration can be made, and then the weld metal is put into the groove. Filled.

  The root gap may also be caused by welding thermal distortion or unavoidable deterioration of member mounting accuracy. For this reason, in most butt welding, a root gap is provided and welding is performed. The route gap is required to have high skill because the molten iron melted at the time of welding is easily melted down. As a welding method to avoid melting, the groove is made into a V shape or a reshape, a steel backing metal is temporarily attached to the deepest root gap, and the backing metal is used as a mother during welding in the groove. A method of joining together with a steel plate is often used. This welding method has an advantage that one side of the steel plate can be welded all downward. However, the welding method for attaching the backing metal has a problem that the strength of the joint becomes weak as will be described later.

FIG. 9 is an enlarged view of a main part showing a state of a welded portion welded by a conventional arc welding method.
For example, as shown in FIG. 9, a second steel plate B100 having a small plate thickness is abutted against the first steel plate A100 having a large plate thickness, and a lathe groove D100 that is opened vertically above the second steel plate B100 is provided. When welding is performed by applying the backing metal S100 to the bottom of the groove D100, the first steel plate A100 and the second steel plate B100 are welded in all sections, so that static tensile strength as a joint is ensured. Can do.

  However, when the second steel plate B100 to which the first steel plate A100 is fixed is subjected to periodic fluctuations in the bending direction or the axial direction, such as earthquakes in high-rise buildings or stress P due to strong winds, the plate thickness is discontinuous. Stress concentration is applied to the part, which may cause fatigue failure. In this case, since the stress concentration increases as the angle of the discontinuous point becomes smaller, there is a problem that it is easily broken.

  In the case of the welded joint shown in FIG. 9, notches (also referred to as “notches”) are formed in the toe portions B101 and B102 to which the backing metal S100 is welded, and a very large stress is concentrated on the notches. become. Therefore, the welding method using the backing metal S100 has a problem that the earthquake resistance and fatigue resistance are liable to be inferior and the joint quality is low.

FIGS. 10A to 10E are enlarged views of main parts showing the states of the welded portions welded by the conventional arc welding method in the order of the welding work.
In order to obtain joint quality excellent in static tensile strength, earthquake resistance, and fatigue resistance, a welding method that does not use the backing metal S100 (see FIG. 9) is required. As shown in FIG. 10 (a), the most suitable welding method for this purpose is a double-sided welding method in which the groove D200 is divided into two K-types on the front side and the back side and no root gap is provided. In this welding method, as shown in FIG. 10B, after the front side of the groove D200 is welded, the steel plates A200 and B200 are turned upside down as shown in FIG. 10C. Then, as shown in FIG. 10 (d), the poorly welded portion and the weld cracked portion that are likely to occur with welding without a root gap are scraped off by gouging or the like, and then shown in FIG. 10 (e). Thus, the front side (upper side) of the groove D200 is welded and finished.

In the case of a joint shape by both-side welding in which both sides of the groove D200 are welded, there are no notches at the toe ends B101 and B102 (see FIG. 9) of the molten metal, and the steel plate B200 receives a periodic stress P. However, a large stress concentration does not occur at the toe ends B201 and F201 of the weld bead F200, and the stress P is transmitted to the steel plate A200. For this reason, in this case, high earthquake resistance and fatigue resistance can be obtained.
However, the double-sided welding method requires top-and-bottom reversal work, and there are many cases where reversal is physically impossible in assembly work at the steel frame site, and there is a problem that the place to be used is limited.

  When it is impossible to turn the top and bottom of the joint upside down and weld it upside down, a welding method for forming a joint without a metal backing metal and without a notch is available. There is a method using a glass fiber backing material S300 for welding (see FIG. 11A).

FIGS. 11A to 11C are main part enlarged views showing a state of a welded portion when welding is performed by the arc welding method described in Non-Patent Document 1. FIG.
For example, in the backing bead method described in Non-Patent Document 1, as shown in FIG. 11A, the backing material S300 is temporarily fixed to the back side (lower side) of the groove D300 with a force such as a spring. Welding is performed from the front side (upper side) to fill the groove D300 with molten metal. In this case, the backing material S300 is made of a material that is not welded to the metal, and can be easily removed from the weld bead F300 of the groove D300 after welding.

As shown in FIG.11 (b), the toe part B301 of the back side of the weld bead F300 is formed in a smooth shape, and a notch part is not formed.
However, as pointed out in Non-Patent Document 1, the backing material S300 is prone to crack E300 in the weld bead F300 due to the low heat conduction rate, as shown in FIG. 11 (c). . When the crack E300 occurs, it remains as it is unless it is repaired, and acts as a notch, so that there is a problem that the earthquake resistance and fatigue resistance are remarkably deteriorated.

  For this reason, the arc welding method does not use the backing metal S100 (see FIG. 9) and the backing material S300, and does not need to be turned upside down when welding. A method with excellent fatigue characteristics has been desired.

As a measure for such a demand, after welding the back side of the groove-shaped groove opened upward in the vertical direction to fill the root gap (hereinafter referred to as “bridge”), the front side of the groove ( There is a means for welding the upper side) in a downward posture that allows the work to be performed more efficiently than upward welding.
As another welding method, there is known a welding method for a beam-to-column joint of an architectural steel structure that is bridged by overlay welding on a non-groove side when a wide root gap exists (for example, a patent) Reference 1).

  12 (a) is an enlarged view of a main part showing a welded portion welded by the welding method described in Patent Document 1, and both FIG. 12 (b) and FIG. 12 (c) are described in Patent Documents 2 and 3. FIG. 12 (b) shows a state when stress is applied to the welded portion, and FIG. 12 (c) shows a state when a crack occurs in the welded portion. Indicates.

  However, since the welding method described in Patent Document 1 is easily melted down by the gravity of the weld bead when welded in an upward posture, the construction efficiency is remarkably high in the same welding material and welding equipment as in the conventional downward welding method. As shown in FIG. 12A, since the shape of the weld bead F410 on the back side after welding is convex, the stress concentration at the toe portions B401 and B402 is high, No improvement in fatigue resistance is observed.

  As another welding method, the welding material is a special flux-cored wire, and the current is changed to the positive polarity opposite to the normal, thereby improving the construction efficiency and the shape of the weld bead F400 during upward welding. And the welding method which does not use a backing metal and a backing material is known (for example, refer patent document 2, 3).

Japanese Patent No. 4749067 JP 2001-71141 A Japanese Patent No. 3877843 "Steel Structure Technology" (Steel Structure Publishing) June 2000, pages 39-43 "Backing bead method applied to field welding of beam-column joints"

However, although the welding methods of Patent Documents 2 and 3 have improved workability, they still cannot satisfy the earthquake resistance and fatigue resistance characteristics or the welding efficiency.
There are three reasons for this.
The first reason is that, as compared with the conventional combination of reverse polarity and general-purpose welding wire, the shape surface has been improved, but as shown in FIG. In the case of welding, the vertical asymmetry of the joint shape is remarkable, and the entire weld bead F410 on the back side is a stress concentration location.
When viewed from the operating point of the amplitude stress P, the moment MB401 [force × distance] applied to the back side toe B401 is larger than the moment MF401 applied to the front side toe F401, and the transmission balance is increased. Because it is uneven in the vertical direction, it acts greatly on the back side.

  In addition, stress transmission is also gentle on the front side because the path widens from the toe part F401 to the toe part F402, whereas the back side is almost from the toe part B401 to the toe part B402. It reaches the steel plate A400 without being dispersed as a path. Due to these asymmetric top and bottom factors, the joint concentrates stress on the welded part on the back side, and is easy to break quickly and has poor earthquake resistance.

  The second reason is that although the weld bead F410 on the back side of the root gap welding in the upward posture is cross-linked, the thickness of the weld bead F410 on the back side is thin and easily melts down during the downward welding thereafter. The welding conditions such as the current of the lower welding lower layer must be lowered, and the efficiency of the welding operation is not increased.

  As shown in FIG. 12C, the third reason is that the most brittle when crack C occurs in the toe part F401 of the front-side weld bead F400 or the toe-end part B401 of the back-side weld bead F410. A base metal-weld metal boundary line W (a boundary line from the back end toe part B401 to the front end toe part F401 in FIG. 12B), a so-called bond part, A heat-affected zone (HAZ) may be transmitted all at once toward the opposite side and may break, resulting in a problem with earthquake resistance.

The problem with respect to the first and second reasons is due to the fact that the root purpose is to bridge the welding of the root gap as conventional common sense.
Therefore, there is a demand for an arc welding method capable of investigating and improving the above-mentioned problems, improving earthquake resistance against large earthquakes and improving fatigue resistance against periodic stresses, and enabling efficient welding. It was.

  The present invention has been made in view of such problems, and an arc that can be efficiently welded to form a welded joint having excellent earthquake resistance and fatigue resistance even when the upside down operation is impossible. It is an object to provide a welding method.

  In order to solve the above-described problem, an arc welding method according to the present invention is an arc welding method in which a first steel material and a second steel material are joint-welded by complete penetration, and the first steel material is the second steel material. The steel material is arranged in a butt direction or in an orthogonal direction orthogonal to the butt direction, and is formed to have a plate thickness larger than that of the second steel material, and the second steel material is formed with respect to the first steel material. When the first steel material and the second steel material are welded, the back side of the groove is arranged in two directions in the direction orthogonal to the end surface on the first steel material side. After performing the upward welding and performing the upward welding for bridging the groove in the abutting direction on the back surface on the second steel plate side, and performing the upward welding for one or more passes after the crosslinking, the second steel material side The front side is welded downward and welded in the groove by fill welding, The base material of the base material of the weld metal and the second steel formed by said downward welding direction welding - the angle of the weld metal boundary, wherein the welding to be less than 135 degrees.

According to such a configuration, when the first steel material and the second steel material are welded, the arc welding method according to the present invention has two or more passes in the direction orthogonal to the end surface on the first steel material side on the back side (lower side) of the groove. After performing upward welding and performing upward welding for bridging the groove in the butt direction on the back surface on the second steel plate side, and performing upward welding for one or more passes after crosslinking, the front side on the second steel material side ( Filling welding of the groove and extra welding are performed by downward welding on the upper side. That is, in this arc welding method, first, the back side of the groove is welded upward for two or more passes, so that the root gap can be reliably bridged and the lid can be covered. Since the thickness of the weld bead can be increased by laminating and superimposing the cross-linked part with a weld bead, the downward welding is performed under high current conditions when welding the front side of the groove. Even if it is performed, it can be prevented from being melted down, and the efficiency of welding work can be improved.
In addition, the arc welding method can improve the strength and stress transmission with respect to the external force applied to the weld bead by performing the filling welding of the groove and the extra welding by downward welding on the front side of the second steel material side. .
In addition, the arc welding method is such that the base metal-weld metal boundary line formed by upward welding and downward welding is welded so that the angle of the base metal-weld metal boundary line is 135 degrees or less, thereby forming the base metal-welded metal boundary line. It is possible to suppress the generation of cracks along the line, and to prevent the generated cracks from following the base metal-weld metal boundary line, thereby reducing the speed of the cracks.

  Moreover, it is preferable that a flux-cored wire is used for the upward welding, and a solid wire or a flux-cored wire is used for the downward welding.

  According to such a configuration, the flux-cored wire used for upward welding has a smaller amount of spatter than the solid wire, can make the shape of the weld bead flat, and has a relatively high current. However, the surface tension of the droplet is high, and slag is generated as a solid on the surface of the droplet, so that it is difficult for the droplet to fall off. For this reason, a flux cored wire can be used for upward welding.

  Moreover, it is preferable that the said flux cored wire used for the said upward welding makes a polarity positive polarity, and contains calcium fluoride or barium fluoride 0.5 to 10 mass% in total as a flux.

  According to such a configuration, by combining the polarity and fluoride, the molten pool becomes more difficult to sag even in the upward posture, the familiarity of the toe portion is improved, and the stress concentration can be reduced.

  Moreover, it is preferable that the said flux cored wire used for the said upward welding consists of a gas shield arc welding method combined with the carbon dioxide gas shield.

  According to such a configuration, the flux-cored wire can be welded using carbon dioxide gas as a shielding gas, thereby preventing nitrogen from being mixed in and obtaining a tough weld metal, thereby reducing the crack propagation speed.

  Further, the first steel material is made of a column member, and the second steel material is made of a beam member made of H-shaped steel, and is formed as a lower flange to be joined when joining to the pillar member. It is preferable.

  According to such a configuration, the second steel material is formed as a lower flange to be joined when joining to the column member, so even if it is a column member of H-shaped steel, without using the backing material, The groove can be welded upward, and the earthquake resistance and fatigue resistance can be improved as welding of the entire beam.

The present invention can provide an arc welding method capable of forming a welded joint excellent in earthquake resistance and fatigue resistance by efficiently welding even if the upside down operation is impossible.
Further, in the arc welding method, the root gap can be reliably closed by laminating so that the back side of the root gap is welded upward and cross-linked, and the weld bead is further stacked on the back side. For this reason, since welding does not occur when the front side of the groove is welded downward, it is possible to improve the work efficiency of the welding operation and to improve the stress transferability when an external force is applied to the welded portion. Thus, cracks are less likely to occur, and further propagation after cracks can be delayed.

(A), (b) is the principal part expansion longitudinal cross-sectional view which each shows the pattern of the groove | channel in the arc welding method which concerns on embodiment of this invention. It is a principal part expansion longitudinal cross-sectional view which shows the arc welding method which concerns on embodiment of this invention, (a) shows the state which performed the upward welding of the 1st pass, (b) shows the welded joint which welding was completed. . It is explanatory drawing which shows the example of a lamination | stacking when a root gap is welded and bridge | crosslinked with the arc welding method which concerns on this invention, (a)-(d) shows the 4th lamination example from the 1st lamination example. (A)-(c) shows each pattern when a crack generate | occur | produces in the welding part which joined the 1st steel plate and the 2nd steel plate with the arc welding method which concerns on embodiment of this invention. It is a figure which shows the comparative example and modification of the arc welding method which concern on embodiment of this invention, (a) is a perspective view which shows a comparative example and a modification, (b) is the X section (a comparative example) of (a). (C) is an expanded sectional view of the Y part (modification) of (a). It is a principal part expanded sectional view which shows Example 1 of the arc welding method which concerns on this invention. It is a figure which shows the comparative example of Example 2, (a) is a top view, (b) is a front view, (c) is a right view. It is a figure which shows Example 2 of the arc welding method which concerns on this invention, (a) is a front view, (b) is a right view. It is a principal part enlarged view which shows the state of the welding part welded with the conventional arc welding method. (A)-(e) is a principal part enlarged view which shows the state of the welding part welded with the conventional arc welding method in welding work order. (A)-(e) is a principal part enlarged view which shows the state of the welding part at the time of welding with the arc welding method described in the nonpatent literature 1. FIG. (A) is the principal part enlarged view which shows the weld part welded with the welding method of patent document 1, (b) and (c) are welding welded with the welding method of patent document 2, 3 together More specifically, (b) shows a state when stress is applied to the welded portion, and (c) shows a state when a crack occurs in the welded portion.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
In the description of the embodiment, the left and right directions of the first steel plate A and the second steel plate B change depending on the arrangement state of the members to be welded when welding. For this reason, in the embodiment of the present invention, for convenience, the upper side will be described as “front”, the lower side as “back”, the left side as “left”, and the right side as “right”.

  As shown in FIGS. 1A and 1B, the arc welding method according to the present invention uses a first steel plate A, A1 (first steel material) and a second steel plate B (second steel material) as backing materials. This is a method of welding a welded joint by complete penetration without using it. Before describing this arc welding method in detail, first, the first steel plates A and A1 and the second steel plate B joined by this arc welding method will be described.

<< Configuration of first steel plate and second steel plate >>
The first steel plates A, A1 (first steel material) and the second steel plate B (second steel material) are, for example, welded materials used when building a structure by welding steel materials used for steel frames for construction. It is a member.
1st steel plate A, A1 is arrange | positioned with respect to the 2nd steel plate B toward the horizontal direction (butting direction) like the 1st steel plate A shown to Fig.1 (a), or FIG. Like the 1st steel plate A1 shown to b), it consists of the member arrange | positioned toward the perpendicular direction (orthogonal direction orthogonal to a butt | matching direction), and joined to the 2nd steel plate B. As shown in FIG. The first steel plates A and A1 are formed to be thicker than the second steel plate B. That is, the first steel plates A and A1 are thicker than the second steel plate B (first steel plate A), as shown in FIG. 1A, or as shown in FIG. It consists of a flat plate or a columnar member (first steel plate A1) extending in a direction orthogonal to the second steel plate B.

  As shown in FIGS. 1 (a) and 1 (b), the second steel plate B is a steel plate that is disposed through the root gap G in the horizontal direction (butting direction) with respect to the first steel plates A and A1, and In order to form the groove D of the mold, for example, an inclined surface Bd inclined by about 45 degrees is formed with respect to the opposing surfaces of the first steel plates A and A1.

  As shown in FIGS. 1 (a) and 1 (b), the groove D is formed in a mold by two patterns and is welded by a mold groove. The shape of the groove D may be a shape close to this shape other than the shape of the shape, for example, a shape where the inclined surface Bd is a steep slope formed with an inclination angle of 45 degrees larger than 45 degrees, or an inclination It may be a gentle slope formed with an inclination angle of the surface Bd smaller than 45 degrees, or a J-type with the inclined surface Bd formed into a curved surface.

≪Configuration of welding wire≫
As shown in FIGS. 2A and 2B, the welding wire 2 (welding material) attached to the welding torch 1 has a flux-cored wire when the groove D is welded upward from the back side (lower side). It is desirable to be used. The flux-cored wire used for upward welding is a welding wire 2 having a positive polarity and containing calcium fluoride or barium fluoride as a flux in a total amount of 0.5 to 10% by mass, and a gas shield combined with a carbon dioxide shield It is desirable to be welded by an arc welding method.
Moreover, as shown in FIG.2 (b), when welding the welding wire 2 downward from the front side (upper side), a solid wire or a flux-cored wire is used.

It will be described that the welding material for upward welding is a flux-cored wire and the welding material for downward welding is a solid wire or a flux-cored wire.
Generally, it is not necessary to attach importance to the drooping prevention function of the weld bead Fb as in all-position welding in downward welding. For this reason, as the welding wire 2, both a solid wire and a flux-cored wire can be applied. These welding wires 2 occupying most of the area of the joint weld are made of CO ₂ , or CO ₂ and CO ₂ and Ar or O _{2 in} order to prevent nitrogen contamination from the atmosphere and to obtain a high-quality weld metal. It is desirable to apply a shielding gas such as a mixed gas.

  On the other hand, when welding upward, the weld bead Fa tends to sag, so a flux-cored wire is desirable as the welding material for upward welding. Since the amount of slag generated is very small, the solid wire cannot support the molten pool that tends to sag due to gravity during upward welding, and the weld bead Fa tends to be convex. If it becomes the convex-shaped weld bead Fa, the shape of the toe portion Ba approaches a notch shape, the stress concentration increases, and the earthquake resistance and fatigue resistance characteristics deteriorate. In the flux-cored wire, the slag generated by the contained oxide is solidified to prevent melting, the flat shape of the toe portion Ba is smooth despite the upward posture, and stress concentration occurs. A difficult weld bead Fa can be obtained. In this case, since the welding material does not easily drip even when the current is increased, the efficiency of the welding operation can be improved.

  Next, it will be described that the flux-cored wire is distributed with positive polarity (wire & base material +) and contains 0.5 to 10% by mass of calcium fluoride or barium fluoride as the contained flux. .

The flux-cored wire that is most popular as a welding material for the welding wire 2 is for reverse polarity and does not contain calcium fluoride or barium fluoride because the arc stability deteriorates.
On the other hand, it is desirable that the welding material used in the upward welding of the present invention is positively distributed and contains calcium fluoride or barium fluoride as the contained flux. When the positive polarity and the fluoride are combined, the molten pool becomes difficult to sag even in the upward posture, and the familiarity of the toe portion Ba can be improved and the stress concentration can be relaxed. Also, the arc stability can be improved. Further, the penetration becomes shallow, and the “penetration crossing angle θ135 degrees or less” controlled by the final pass of the upward welding can be easily obtained.

When the conventional welding method of reverse polarity is applied, the penetration becomes deeper in the final pass of “necessary cross-linking in the horizontal direction (butting direction) on the back side of the second steel plate B + one pass after cross-linking”. This is because the crossing angle with the welded portion becomes small.
The fluoride contained in the flux is most preferably calcium fluoride or barium fluoride. If calcium fluoride or barium fluoride is less than 0.5 mass% in terms of the total wire weight including the outer steel portion, the arc becomes unstable and welding becomes difficult. In addition, since the spatter will generate | occur | produce much when the content rate exceeds 10 mass%, welding becomes difficult.
Accordingly, the total amount of calcium fluoride or barium fluoride is 0.5 to 10% by mass.

Next, the point that the flux-cored wire is a gas shielded arc welding method combined with a carbon dioxide shield will be described.
When a proper amount of aluminum or the like is further added to the positive-polarity + fluoride flux-cored wire, no shielding gas is required and welding becomes possible. However, in no gas welding, nitrogen is mixed into the weld metal from the atmosphere, the toughness is lowered, and the crack propagation rate is increased. For this reason, by using carbon dioxide gas as a shielding gas, mixing of nitrogen is prevented, and a high toughness weld metal is obtained, so that the crack propagation speed can be reduced.
In addition to calcium fluoride or barium fluoride, the flux-cored wire can be used as a deoxidizer for weld metal refining, or as an arc stabilizer, such as C, Si, Mn, Mg, Ti, Al, Zr, P, S, K, Na, Ca, etc. can be further added and applied as a single element or compound.

≪Arc welding method≫
Next, the arc welding method will be described by taking the case where the first steel plate A and the second steel plate B are welded as an example.
The arc welding method is, for example, a welding method that is used when building a structure by welding the first steel plates A and A1 and the second steel plate B that are used for building steel frames. Even if the upside down operation is impossible, welding can be performed.

<First step>
When arc welding the first steel plate A and the second steel plate B, first, as shown in FIG. 2 (a), the welding torch 1 of the welding machine faces upward and below the first steel plate A and the second steel plate B. When a voltage from a welding power source (not shown) is applied between the welding wire 2 and the lower portion of the groove D, an arc current flows to generate an arc, and welding is performed. Then, the back side (lower side) of the groove D is welded upward in the vertical direction (orthogonal direction) of the end surface on the first steel plate A side to bridge the route gap G in the first pass. As a result, the lower end portion in the groove D is closed by the weld bead F.

<Second step>
Next, in the same manner as in the first pass, with the welding torch 1 facing upward, the back side (lower side) of the groove D is upward one or more passes in the vertical direction (orthogonal direction) of the end surface on the first steel plate A side. Welding is performed in the vertical direction (orthogonal direction) of the end face on the first steel plate A side for a total of two passes or more along with the first pass.
Further, the back cross-linked welded portion on the second steel plate B side is welded upward in the butt direction by one or more passes.
By doing so, “two or more passes in the vertical direction (orthogonal direction) of the end surface on the first steel plate A side” and “pass necessary for bridging in the horizontal direction (butting direction) on the back side of the second steel plate B side”. + 1 pass or more after crosslinking "is satisfied.

As shown in FIG. 2B, the moment MBb [force × distance] applied to the front side toe Bb from the operating point of the amplitude stress P and the moment MBa [force × distance] applied to the back side toe Ba are as follows. Since the moments MBa and MBb become closer to each other, the values become closer to each other, and the balance of stress transmission approaches the upper and lower parts equally, so that the action on the back side is substantially reduced. By this action, the stress concentration of the stress acting from the second steel plate B side is relaxed, the transmission efficiency on the first steel plate A side is improved, and the earthquake resistance and fatigue resistance characteristics are greatly improved.
In this case, the ideal upper limit of the distance between the moments MBa and MBb is such that the distance of the moment MBb applied to the front-side toe portion Bb and the distance of the moment MBa applied to the back-side toe portion Ba are the same. is there.

<Third step>
Next, as shown in FIG. 2 (b), the welding torch 1 is arranged on the front side (upper side) of the second steel plate B, and the front side of the second steel plate B is faced downward and the groove D is filled with the weld bead F. Filling welding and extra welding are performed like a lid. For this reason, since the bridge | crosslinking site | part of the root gap G can increase thickness, the intensity | strength with respect to the external force concerning the weld bead F and stress transmission property can be improved.
Further, when the back side is welded downward after the back side is welded upward and the root gap G is cross-linked by the weld bead Fa, the cross-linked portion is formed by the weld bead Fa of the upward welding, so that a high current condition is achieved. Even if welding is performed, it is difficult for the metal to melt, so that the efficiency of the welding operation can be improved.

  Thus, the angle θ of the base metal-weld metal boundary line W between the weld bead F (welded metal) formed by upward welding and downward welding and the base material of the second steel plate B is set to 135 degrees or less. It is formed by welding. If the angle θ at which the weld bead Fa of the upward welding and the weld bead Fb of the downward welding intersect is set to 135 degrees or less, the progress of the crack that follows follows the base metal-welded metal boundary line W. No longer.

≪Example of route gap cross-linking≫
FIG. 3 is an explanatory view showing a lamination example when the root gap G is welded and cross-linked by the arc welding method according to the present invention, and (a) to (d) are the first to fourth lamination examples. Indicates.
Next, it is bridged in the horizontal direction (butting direction) on the back side on the second steel plate B side by “two passes or more in the vertical direction (orthogonal direction) on the end surface on the first steel plate A side” by the specified upward welding. The lamination examples 1 to 4 of “required pass + one pass or more after crosslinking” will be described.

<First lamination example>
As shown in FIG. 3A, in the first stacking example, the root gap G is bridged by the first pass weld bead F1, and the first pass in the vertical direction of the end surface on the first steel plate A side by the weld bead F2. A one-pass weld bead F2 is laminated. Further, the third-pass weld bead F3 is laminated in the horizontal direction on the back side of the second steel plate B side.
In this way, in the first stacking example, “two or more passes in the vertical direction (orthogonal direction) of the end surface on the first steel plate A side” and the back side horizontal direction on the second steel plate B side (necessary cross-linking pass + 1 after cross-linking). More than pass) ”.

<Second lamination example>
As shown in FIG. 3B, in the second stacking example, the first gap welding bead F1 is used to bridge the root gap G, and the second pass welding bead F2 is used to perform wide weaving welding. Welding is performed using both “+1 pass in the vertical direction of the end face on the steel plate A side” and “+1 pass in the horizontal direction on the back side of the second steel plate B”.
In this way, in the second lamination example, two or more passes in the vertical direction of the end surface on the first steel plate A side ”and“ necessary cross-linking pass in the horizontal direction on the back side on the second steel plate B side + one or more passes after cross-linking ” And that is realized.

<Third lamination example>
The third stacking example shown in FIG. 3C is a stacking example when the root gap G is too wide to be cross-linked in one pass. In this case, the root gap G is first narrowed by overlay welding by upward welding as a first-pass weld bead F1 on the first steel plate A side of the root gap G.
Next, welding for bridging the root gap G is further performed between the build-up weld end face and the back side end face on the second steel plate B side as a second pass weld bead F2. Even if the root gap G is wide, the root gap G is bridged by the second pass weld bead F2.
Further, the third-pass weld bead F3 is stacked on the first-pass weld bead F1 in the vertical direction of the end surface on the first steel plate A side, and “+1 pass in the vertical direction of the end surface on the first steel plate A-side” is performed. .
Further, as the fourth pass, the weld bead F4 of the fourth pass is laminated in the horizontal direction on the back side of the second steel plate B side and completed.
In this way, in the third lamination example, “two or more passes in the vertical direction (orthogonal direction) of the end face on the first steel plate A side” and “the back side horizontal direction on the second steel plate B side (necessary cross-linking pass + after cross-linking) 1 pass or more) ”.

<Fourth lamination example>
As shown in FIG. 3D, in the fourth lamination example, first, build-up welding is performed by upward welding as the fourth pass on the first steel plate A side of the root gap G, and the first pass weld bead F1. To narrow the root gap G.
As the second pass, the second pass weld bead F2 is laminated by upward welding so as to connect the first steel plate A and the second steel plate B using the first pass weld bead F1 as a base. Thus, the bridging of the route gap G is completed, and “+1 pass in the vertical direction of the end surface on the first steel plate A side” is performed.
Further, as the third pass, the weld bead F3 of the third pass is stacked by welding upward in the horizontal direction on the back side of the first steel plate A side.
In this way, the third lamination example realizes “in the horizontal direction on the back side of the second steel plate B (required cross-linking pass + one or more passes after cross-linking)”. In addition, when the route gap G is wider and cannot be bridged in two passes, overlay welding is further performed in the horizontal direction (butting direction) by upward welding.

≪About crack≫
In the arc welding method of the present invention, in addition to the effect of improving the macro-shaped stress concentration by the improvement of the laminating method as described above and the effect of improving the efficiency of downward welding, an important rule is that the base material- This is an increase in propagation resistance after the occurrence of cracks by improving the shape of the weld metal boundary line W.
As a result, after the occurrence of a crack from the weld toe, the crack growth rate can be reduced and the time to break can be delayed.
Furthermore, with reference mainly to FIG. 12 (a) and FIGS. 4 (a) to (c), the occurrence of cracks and the point that the present invention can reduce the crack growth rate will be described in comparison with the prior art. To do.

When a crack C occurs from the toe end B401 or the toe end F401 of the weld bead F400 described as the third conventional problem shown in FIG. 12 (a), the direction in which the crack C advances depends on the base material. -It is often a weld metal boundary line W (stop end portion B401-stop end portion F401 in FIG. 12), a bond portion, and a heat affected zone (HAZ).
This is because this part has the property of undergoing a structure change to a hard and brittle nature when it undergoes the most rapid cooling during welding. Since the crack resistance is relatively smaller than that of the non-heat-affected zone of the steel plate and the weld metal, it propagates at a high speed. It becomes remarkable when the direction of the crack C is a straight line.

  However, if the direction of the crack is largely bypassed in the middle, the crack cannot follow it and travels inside the weld metal. This place is relatively tougher than the bond part and the heat-affected part, and has a high resistance to crack propagation. Therefore, the progress speed of the crack becomes slow, and the time to break can be lengthened. As means for realizing this mechanism, the present invention utilizes a mixed welding method of upward welding and downward welding.

  In order to prevent the crack progressing direction from following the base material-weld metal boundary line W, the base material-weld metal boundary line W may be bent sharply in the middle as shown in FIG. That is, by using the difference in penetration shape formed between the weld bead Fa (welded metal) of the upward welding and the weld bead Fb (welded metal) of the downward welding, the angle θ of each intersection is 135 degrees. If the control is performed as follows, the generated crack cannot follow the base metal-welded metal boundary line W.

4 (a) to 4 (c) show respective patterns when cracks occur in the welded portion where the first steel plate and the second steel plate are joined by the arc welding method according to the embodiment of the present invention.
For example, as shown to Fig.4 (a), when the crack C1 generate | occur | produced from the front side toe part Bb, after progressing along a base material-weld metal boundary line W, a weld metal is sent from the boundary part on the way. As it is, the speed of progress is slowed down and then penetrates.
As shown in FIG. 4B, on the contrary, when a crack C2 occurs from the back end toe portion Ba, the crack proceeds from the toe portion Ba along the boundary between the base metal and the weld metal. After passing through the weld metal and the base metal raw material part, the progress speed is reduced to a small speed, and then penetration occurs.
As shown in FIG. 4C, when the angle θ of the base metal-weld metal boundary W exceeds 135 degrees, the crack C4 follows the base metal-weld metal boundary W along that direction. , Leading to breakage early.

As means for realizing this, the above-described “in the horizontal direction on the back side of the second steel plate B side (necessary cross-linking pass + one or more passes after cross-linking)” is required. The penetration intersection angle θ cannot be controlled to 135 degrees only by the path that bridges the root gap G.
Further, if the heat input (current × voltage × 60 / welding speed, unit J / cm) calculated from the welding conditions of the final pass after crosslinking is too large, the crossing angle θ may exceed 135 degrees. It is necessary to satisfy the intersection angle θ of 135 degrees by suppressing heat input in consideration of the groove angle and the like.

Further, as for the progress of the crack C1 shown in FIG. 4A, “+1 pass in the vertical direction of the end surface on the first steel plate A side” is effective for extending the fracture crack time. If the welding is finished as it is after the bridge of the root gap G as in the prior art, the thickness of the weld bead F on the back side is thin, the distance in the direction from the toe portion Bb to the toe portion Bc is short, and it breaks quickly. To do.
However, if the thickness of the weld bead F is increased by “+1 pass in the vertical direction of the end surface on the first steel plate A side”, the distance to the fracture after progress of the weld metal is large. You can earn time.

As shown in FIG.4 (b), the crack C3 may generate | occur | produce toward the toe part Bb of the weld metal of the front side from the toe part Ba of the back side weld metal. In the case of this type, in the conventional construction method, as shown in FIG. 12 (c), the progress of the crack C coincides with the base metal-weld metal boundary line W, and the growth speed is very high because of the brittle metal characteristic region. Very fast.
However, as shown in FIG. 4B, by performing welding “in the horizontal direction on the back side of the second steel plate B side (necessary cross-linking pass + one pass after cross-linking)”, the crack C3 has a high toughness mother. Since the raw material portion is penetrated, the progress rate of the crack C3 can be slowed down.

As described above, the arc welding method of the present invention includes “+1 pass in the vertical direction of the end surface on the first steel plate A side” and “horizontal direction on the back side on the second steel plate B side (necessary for cross-linking + one pass or more after cross-linking). ) ”,“ Selected so that the crossing angle θ of the base metal-weld metal boundary W of the cross section of the second steel plate B formed by upward welding and subsequent downward welding intersects at an angle of 135 degrees or less. If it is satisfied under the condition of “heat input welding”, it is possible to obtain an effect of improving macro-form stress concentration and an effect of improving the efficiency of downward welding, and by increasing propagation resistance after the occurrence of cracks C1 to C4. The effect of prolonging the life can be obtained.
If the penetration intersection angle θ is 110 degrees or less, more preferably 90 degrees or less, the earthquake resistance and fatigue resistance can be improved.

[Modification]
The embodiment according to the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention. In addition, the already demonstrated structure attaches | subjects the same code | symbol and abbreviate | omits the description.
FIG. 5 is a view showing a comparative example and a modified example of the arc welding method according to the embodiment of the present invention, (a) is a perspective view showing the comparative example and the modified example, and (b) is an X part of (a). (C) is an enlarged sectional view of the Y portion (modified example) of (a).

  In the said embodiment, as shown to Fig.2 (a), (b), the case where the 1st steel plate A and the 2nd steel plate B were welded was demonstrated, However, The arc welding method of this invention is limited to a board | plate material. It is not something. For example, as shown in FIGS. 5A and 5C, the arc welding method according to the present invention includes a first steel material A2 made of a column member and a second steel material B2 made of a beam member made of H-shaped steel. It can also be applied when welding.

First, a comparative example will be described with reference to FIGS. 5 (a) and 5 (b).
The first steel material A500 of the comparative example is a steel building column that requires high earthquake resistance and fatigue resistance, a column part A510 made of a square steel pipe, and an upper diaphragm A520 inserted and coupled to the column part A510. , And a lower diaphragm A530 inserted and coupled below the upper diaphragm A520.
The second steel material B500 is a beam member made of an H-shaped steel welded to the first steel material A500, and a backing metal S500 is applied to the side web B510 that is fillet welded to the column portion A510 and the upper diaphragm A520. It has an upper flange B520 that is completely infused and joined by downward welding, and a lower flange B530 that is completely infused and joined by downward welding by applying the backing metal S500 to the lower diaphragm A530.

  Thus, in the field welding which joins an H section steel and a column, the work cannot be performed by inverting the first steel material A500 and the second steel material B500. For this reason, in the comparative example, when welding the first steel material A500 of the square steel pipe and the second steel material B500 of the H-shaped steel, the welding location of the upper diaphragm A520 and the upper flange B520, and the lower diaphragm A530 and the lower The backing metal S500 is used for both of the two welded portions with the flange B530.

In particular, in the comparative example, when a periodic fluctuation due to an earthquake or the like is applied in the bending direction or the axial direction from the second steel material B500 of the beam to the first steel material A500 of the column, the stress concentration is increased between the outer side and the lower side of the upper flange B520. It works most strongly on the outside of the flange B530. In the stress concentration portion, the upper flange B520 side is the toe end portion B501 of the bead, whereas the lower flange B530 side is a notch portion of the backing metal S500.
That is, although the stress concentration generated at the toe portion B501 in the portion having the upper flange B520 is small, the stress concentration generated in the toe portion B502 in the portion having the lower flange B530 is large, and the breaking speed is rate-limiting on the lower flange B530 side. It has become. For this reason, in the comparative example using backing metal S500, earthquake resistance and fatigue resistance are low.

  On the other hand, as shown in FIGS. 5A and 5C, the first steel material A2 and the second steel material B2 used in the modified example of the arc welding method of the present invention are both of the first comparative example. The steel material A500 and the second steel material B500 have the same shape, but the backing metal S is only at the joint portion between the upper diaphragm A22 and the upper flange B22, and at the joint portion between the lower diaphragm A23 and the lower flange B23. Is different in that it is not used.

That is, the first steel material A2 and the second steel material B2 are columnar materials and beam materials for steel buildings that require high earthquake resistance and fatigue resistance.
The first steel material A2 is a square steel pipe having a column part A21 made of a square steel pipe, an upper diaphragm A22 provided on the column part A21, and a lower diaphragm A23 provided on the lower side of the upper diaphragm A22. Become.
The second steel material B2 includes a side web B21 that is fillet welded to the column portion A21, an upper flange B22 that is completely welded and joined by downward welding with a backing metal S applied to the upper diaphragm A22, and a lower diaphragm. It is made of H-section steel having a lower flange B23 which is welded upward without using the backing metal S to A23, cross-linked with the weld bead Fa, and then completely welded and joined with the weld bead Fb of the downward weld. .
In the upper flange B22 and the lower flange B23, joint surfaces facing the upper diaphragm A22 and the lower diaphragm A23 are formed on inclined surfaces, respectively, thereby forming a lave groove.

In the field welding, since the top-and-bottom reversing work cannot be performed, when joining the upper flange B22, the backing metal S is attached to the inside of the beam. Therefore, when welding the lower diaphragm A23 and the lower flange B23, first, the back side of the groove is welded upward two or more passes in the direction orthogonal to the end surface on the lower diaphragm A23 side, and the rear surface on the lower flange B23 side. In this case, upward welding is performed to bridge the groove in the butt direction, and upward welding is performed for one or more passes after bridging, and then the front side on the lower flange B23 side is welded downward and overfilled by downward welding. By performing the above, it is possible to improve earthquake resistance and fatigue resistance as welding of the entire beam.
Thus, the arc welding method of the present invention can be applied not only to welding of flat steel plates but also to welding of a column member and a beam member.
Note that this arc welding method may be applied to the upper flange B22 in the same manner as appropriate.

Next, Embodiment 1 of the arc welding method according to the present invention will be described with reference to FIG.
FIG. 6 is an enlarged cross-sectional view of a main part showing Embodiment 1 of the arc welding method according to the present invention.
As shown in FIG. 6, the steel plate A (first steel material) is made of a plate material whose material is SN490B (rolled steel for building structure), whose plate thickness is 32 mm, and whose end face on the welding side is vertical. The steel plate B (second steel material) is made of a plate material having a material of SN490B, a plate thickness of 22 mm, and an end face on the welding side forming a lave groove D1 with an inclination angle θ1 of 35 degrees. Steel plate A and steel plate B were subjected to complete penetration welding by aligning the respective center lines and having a root gap G of 1 to 10 mm.

Then, while the steel plate A was fixed after welding, a fatigue test was performed by applying a double-bending amplitude stress to the steel plate B at a position 200 mm away from the toe portion Ba on the groove D1 side. The results are shown in Table 1. The load stress was 500 MPa, and the number of breaks was evaluated. The case of 1 × 10 ⁵ or less was regarded as unacceptable (x), and the case of exceeding 1 × 10 ⁵ was regarded as acceptable. And ◎ most excellent to 10 × 10 ⁵ or more. Among them, a case of less than 5 × 10 ⁵ or more 10 × 10 ⁵ ○ next to it, as 1 × 10 ⁵ Super 5 × 10 in the case of less than ⁵ further lower adequate range △ expressed. In Table 1, Example No. 1-18 and Comparative Example No. The kind of welding wire at the time of performing upward welding and downward welding in 1-9, a component, welding conditions, and a test result are shown.

The composition of the welding wire used in the experiment shown in Table 1 is that the wire WF1 is 0.05% by mass C + 0.5% by mass Si + 2.0% by mass Mn + 1% by mass CaF + 1% by mass Al + 0.5% by mass Mg. Is a flux cored wire.
The wire WF2 is 0.06% by mass C + 0.7% by mass Si + 2.0% by mass Mn + 2% by mass Ti, and the type is a flux-cored wire (no addition of fluoride).
The wire WF3 is 0.10% by mass C + 0.2% by mass Si + 1.2% by mass Mn + 1% by mass CaF + 5% by mass Al + 0.5% by mass Mg + 0.5% by mass CaCO 3, and the type is a flux-cored wire.
The wire WF4 is 0.05% by mass C + 1.0% by mass Si + 1.6% by mass Mn + 5% by mass BaF + 0.2% by mass Mg, and the type is a flux-cored wire.
The wire WF5 is 0.03% by mass C + 0.1% by mass Si + 2.6% by mass Mn + 0.5% by mass CaF + 0.4% by mass Mg + 0.5% by mass Al + 0.2% by mass CaCO 3 and the type is a flux-cored wire. .
The wire WF6 is 0.05% by mass C + 0.5% by mass Si + 2.0% by mass Mn + 10.0% by mass CaF + 1% by mass Al + 0.5% by mass Mg, and the type is a flux-cored wire.
The wire WF7 is 0.05% by mass C + 0.5% by mass Si + 2.0% by mass Mn + 11.0% by mass CaF + 1% by mass Al + 0.5% by mass Mg, and the type is a flux-cored wire (over fluoride).
The wire WS1 is 0.05 mass% C + 0.8 mass% Si + 1.7 mass% Mn + 0.18 mass% Ti, and the type is a solid wire.
The wire WS2 is 0.05% by mass C + 0.5% by mass Si + 1.5% by mass Mn + 0.09% by mass Ti, and the type is a solid wire.

As shown in Table 1, Example No. In Nos. 1 to 18, good welding properties and fatigue resistance characteristics of the joints were obtained as a result of performing welding work under the conditions satisfying the problems of the present invention.
That is, Example No. 1, as a result of welding using a slid wire in the upward welding, the crossing angle θ of the base metal-welded metal boundary line is 136 degrees, and the number of fractures by the fatigue test is 2 × 10 ⁵ times. Experimental results satisfying the problems of the present invention were obtained.
Example No. 2, as a result of welding with a reverse pole using a welding wire outside the composition of the flux cored wire (FCW) during upward welding, the crossing angle θ of the base metal-welded metal boundary is 100 degrees. The number of breaks in the fatigue test was 4 × 10 ⁵ times, and experimental results satisfying the problems of the present invention were obtained.
Example No. In No. 3, welding was performed using a welding wire having a composition other than the flux cored wire (FCW) during upward welding. As a result, the crossing angle θ of the base metal-welded metal boundary line was 94 degrees, and the fatigue test was performed. The number of times of breakage was 3 × 10 ⁵ times, and experimental results satisfying the problems of the present invention were obtained.

Example No. 4, as a result of welding with a reverse pole in the upward welding, the crossing angle θ of the base metal-welded metal boundary line was 88 degrees, and the number of breaks in the fatigue test was 4 × 10 ⁵ times. The experimental results satisfying the above problems were obtained.
Example No. In No. 5, welding was performed using the wire WF3 without a shielding gas during upward welding. As a result, the crossing angle θ between the base metal and the weld metal boundary line was 100 degrees, and the number of fractures in the fatigue test was 5 × 10. ^{It was 5} times, and experimental results satisfying the problems of the present invention were obtained.
Example No. 6, as a result of welding with a total number of passes of 2 using the wire WF1 in the upward welding, the crossing angle θ of the base metal-welded metal boundary line is 76 degrees, and the number of fractures in the fatigue test is 12 × 10 ⁵ times, an experimental result satisfying the problems of the present invention was obtained.

Example No. 7, as a result of welding with a total number of passes of 3 using the wire WF1 in the upward welding, the crossing angle θ of the base metal-welded metal boundary line is 65 degrees, and the number of fractures by the fatigue test is 15 × 10 ⁵ times, an experimental result satisfying the problems of the present invention was obtained.
Example No. In No. 8, as a result of welding with a total number of passes of 3 using the wire WF4 in the upward welding, the crossing angle θ of the base metal-welded metal boundary line is 60 degrees, and the number of fractures by the fatigue test is The number of times was 16 × 10 ⁵ times, and experimental results satisfying the problems of the present invention were obtained.
Example No. 9, as a result of welding with a total number of passes of 4 using the wire WF5 in the upward welding, the crossing angle θ of the base metal-welded metal boundary line is 95 degrees, and the number of fractures by the fatigue test is It was 7 × 10 ⁵ times, and an experimental result satisfying the problems of the present invention was obtained.

Example No. 10, as a result of welding with a total number of passes of 2 using the wire WF6 in the upward welding, the crossing angle θ of the base metal-welded metal boundary line is 83 degrees, and the number of fractures by the fatigue test is 10 × 10 ⁵ times, an experimental result satisfying the problems of the present invention was obtained.
Example No. 11, as a result of welding with a total number of passes of 2 using the wire WF1 during the upward welding, the crossing angle θ of the base metal-welded metal boundary line is 100 degrees, and the number of fractures by the fatigue test is It was 7 × 10 ⁵ times, and an experimental result satisfying the problems of the present invention was obtained.
Example No. 12, the total number of passes was 2 using the wire WF1 in the upward welding, and the heat input of the final pass in the direction of the steel plate B was increased to 18 [kJ / cm]. The crossing angle θ between the base metal and the weld metal boundary line was 100 degrees, and the number of breaks in the fatigue test was 9 × 10 ⁵ times, and experimental results satisfying the problems of the present invention were obtained.

Example No. 13, as a result of welding with a total number of passes of 5 using the wire WF1 during the upward welding, the crossing angle θ of the base metal-welded metal boundary line is 80 degrees, and the number of fractures by the fatigue test is 12 × 10 ⁵ times, an experimental result satisfying the problems of the present invention was obtained.
Example No. 14, as a result of welding with a total number of passes of 6 using the wire WF1 in the upward welding, the crossing angle θ of the base metal-welded metal boundary is 72 degrees, and the number of fractures in the fatigue test is 14 × 10 ⁵ times, an experimental result satisfying the problems of the present invention was obtained.
Example No. 15, as a result of welding with a total number of passes of 2 using the wire WF5 in the upward welding, the crossing angle θ of the base metal-welded metal boundary line was 87 degrees, and the number of fractures by the fatigue test was 11 × 10 ⁵ times, an experimental result satisfying the problems of the present invention was obtained.

Example No. 16, the total number of passes was welded with 2 passes using the wire WF1 during the upward welding, and welding was performed using a shield gas of Ar 80% + CO ₂ 20% during the downward welding. The crossing angle θ between the base metal and the weld metal boundary line was 79 degrees, and the number of breaks in the fatigue test was 13 × 10 ⁵ times, and experimental results satisfying the problems of the present invention were obtained.
Example No. 17, the total number of passes was welded using the wire WF1 during the upward welding, and as a result, the crossing angle θ of the base metal-welded metal boundary line was 85 degrees, and the number of fractures in the fatigue test was 10 × 10 ⁵ times, an experimental result satisfying the problems of the present invention was obtained.
Example No. In No. 18, the total number of passes was 3 using the wire WF1 during the upward welding, and the heat input of the final pass in the direction of the steel plate B was reduced to 5 [kJ / cm]. The crossing angle θ between the base metal and the weld metal boundary line was 61 degrees, and the number of fractures in the fatigue test was 17 × 10 ⁵ times, and experimental results satisfying the problems of the present invention were obtained.

  As described above, Example No. 1 to 18, the penetration intersection angle θ of the base metal-welded metal boundary formed by the upward welding and the downward welding of the steel sheet B is 135 degrees or less, and the weldability and fatigue resistance of the joint are improved. I was able to confirm that it improved.

Next, experimental results of Comparative Examples 1 to 9 will be described.
In Comparative Example 1, it was a downward welding method with a backing metal, and the fatigue resistance of the joint was poor due to the notch shape inevitably generated between the backing metal and the base metal.
In Comparative Example 2, a ceramic backing material was attached and welded and then removed, but a hot crack occurred in the center of the weld metal. For this reason, the fatigue resistance of the joint was poor.
In Comparative Example 3, there was no backing metal, and a combination of upward welding and downward welding, but the number of passes of upward welding, which is the purpose of crosslinking, was small in one pass, and the bridge was not sufficiently formed. Smelting occurred during downward welding. Moreover, the fatigue resistance of the joint was poor.

In Comparative Example 4, there is no backing metal and a combination of upward welding and downward welding, but by laminating the end surface on the steel plate A side of upward welding into two layers, it melts down during downward welding. There wasn't. However, since the lamination by the pass after bridge | crosslinking was not performed on the back surface at the side of the steel plate B, since the thickness of the weld bead by upward welding was thin, the joint fatigue strength was bad.
In Comparative Example 5, there is no backing metal, and the upward welding and the downward welding are combined, but the crossing after the cross-linking is appropriately performed on the back surface on the steel plate B side, so the penetration intersection angle θ is also good. The joint fatigue strength was improved. However, since two layers of the end surface on the steel plate A side were not laminated, it melted down during the downward welding.
In the comparative example 6, without backing metal, it is a combination of upward welding and downward welding, after a plurality of passes to build up the vertical end surface on the steel plate A side, and then to the back surface on the steel plate B side. One-pass lamination after crosslinking was performed. However, since the heat input was high in the final pass after cross-linking to the back surface on the steel plate B side, the crossing angle θ of the base metal-welded metal boundary W exceeded 135 degrees, and the fatigue resistance of the joint was poor.

In the comparative example 7, without backing metal, it is a combination of upward welding and downward welding, and after a plurality of passes to build up the vertical end surface on the steel plate A side, to the back surface on the steel plate B side. Two-pass lamination after crosslinking was performed. However, in Comparative Example 7, since the heat input in the final pass after crosslinking to the back surface on the steel plate B side was high, the crossing angle θ of the base metal-welded metal boundary W exceeded 135 degrees, and the fatigue resistance characteristics of the joint Was bad.
In Comparative Example 8, without backing metal, it is a combination of upward welding and downward welding, and since the root gap G is wide, after multiple passes to build up the vertical end face on the steel sheet A side The welding which bridge | crosslinks the root gap G of the steel plate B was performed. However, in Comparative Example 8, since the lamination after crosslinking was not performed, the fatigue resistance characteristics of the joint were poor.
In Comparative Example 9, upward welding and downward welding were combined without backing metal, and a solid wire was used for upward welding. Since the route gap G is wide, welding for bridging the route gap G of the steel plate B was performed after a plurality of passes for overlaying the vertical end surface on the steel plate A side. However, in Comparative Example 9, since the lamination after crosslinking was not performed, the fatigue resistance characteristics of the joint were poor.
In Comparative Example 10, there is no backing metal, and the upward welding and the downward welding are combined, and the end surface on the steel plate A side of the upward welding is laminated in two layers, so that it melts down during the downward welding. I didn't. In the first heat input adjustment, the crossing angle θ of the base metal-welded metal boundary line W became 135 degrees or less, but because the lamination after crosslinking was not performed, the balance of the vertical moment was poor and the stress concentration was on the back side. The fatigue resistance of the joint was poor because it was not concentrated and improved.

Thus, in Comparative Examples 1 to 4 and 6 to 9, the crossing angle θ of the base metal-welded metal boundary line W exceeded 135 degrees, and the fatigue resistance characteristics of the joints due to the number of fractures in the fatigue test were poor. In Comparative Example 5, the fatigue angle of the joint was good due to the number of fractures in the fatigue test when the crossing angle θ of the base metal-weld metal boundary line W was 135 degrees or less, and the fatigue test fracture resistance was good. As a result, meltdown occurred.
On the other hand, Example 1 is Example No. In all of Nos. 1 to 18, the penetration intersection angle θ of the base metal-welded metal boundary line was 135 degrees or less, the weldability and the fatigue resistance characteristics of the joint were good, and there was no melting.

Next, Example 2 of the arc welding method according to the present invention will be described with reference to FIGS.
FIG. 7 is a diagram showing a comparative example of Example 2, in which (a) is a plan view, (b) is a front view, and (c) is a right side view. FIGS. 8A and 8B are diagrams showing Example 2 of the arc welding method according to the present invention, in which FIG. 8A is a front view and FIG. 8B is a right side view.

  In Example 2, the arc welding method of the present invention is applied to a column-beam structure called a beam penetration type or a through-diaphragm type, which is the most frequently used type in an actual steel structure construction.

<< Regarding Comparative Example of Example 2 >>
First, a comparative example will be described with reference to FIGS.
As shown in FIGS. 7A to 7C, the first steel material A600 is formed of a square steel pipe that forms a column of a steel building, and is inserted and coupled to a column part A610 extending in the vertical direction and the column part A610. The upper diaphragm A620 is formed, and the lower diaphragm A630 inserted and coupled to the lower part of the upper diaphragm A620.

  The second steel material B600 is a beam welded to the first steel material A600 and is made of H-section steel. The second steel material B600 includes a side web B610 that is fillet welded to the column part A610, an upper flange B620 that is completely welded and joined by downward welding with the backing metal S610 applied to the upper diaphragm A620, and a lower diaphragm. And a lower flange B630 that is completely welded and joined by downward welding with the backing metal S620 applied to A630.

  Using the backing metal S610 and S620 at the welding location between the upper diaphragm A620 and the upper flange B620 and the welding location between the lower diaphragm A630 and the lower flange B630, It was welded in a downward posture in all passes with a combination of carbon dioxide shields. Then, after welding, as in Example 1, an earthquake resistance evaluation test was performed using this test work.

  Specifically, the column portion A610 is fixed, and a load 1.2 times the proof stress of the second steel material B600 is periodically applied in the vertical amplitude direction from above and below the stiffener positions of both beams, and the upper flange B620 and the lower flange It was 21 times when the frequency | count until the fracture | rupture of either B630 was measured. The broken position is a welded portion between the lower flange B630 and the lower diaphragm A630, and a crack progressed upward from the notch portion inevitably generated by the backing metal S620 to the lower flange B630.

  That is, with respect to the load stress on the entire H-shaped steel of the beam, which is the second steel material B600, the outer side of the lower flange B630 (beside the welded bead shape formed on the outer side (upper side) of the upper flange B620 ( This shows that stress is more likely to be concentrated in the bead shape where the backing metal S620 formed on the lower side is located. On the contrary, the lower backing metal S610 on the upper flange B620 and the welding surplus on the upper side of the lower flange B630 are relatively undominated with respect to earthquake resistance.

<< About Example 2 >>
As shown in FIGS. 8A and 8B, the basic structure of the second embodiment of the present invention is compared with the comparative example of the second embodiment shown in FIGS. 7A to 7C. The first steel material A3 and the second steel material B3 are similar in that the first steel material A600 and the second steel material B600 are the same. The second embodiment of the present invention and the comparative example are that the second embodiment is not provided with a backing metal at the groove of the welded portion between the lower flange B33 and the lower diaphragm A33, and the lower flange B33 and the lower flange. The difference is that after the back side of the groove of the welded portion with the diaphragm A33 is welded upward and bridged, the front side of the groove is subjected to filling welding and extra welding by downward welding.

The first steel material A3 is a square steel pipe having a column portion (not shown), an upper diaphragm A32, and a lower diaphragm A33.
The second steel material B3 is a side web B31 that is fillet welded to the column portion (not shown), an upper flange B32 that is completely intruded and joined by downward welding with the backing metal S applied to the upper diaphragm A32, and It consists of an H-section steel beam having a lower flange B33 joined to the lower diaphragm A33 by upward welding and downward welding.

  When welding the lower flange B33 of the backingless and the lower diaphragm A33, first, the wire WF1 and a carbon dioxide shield were welded in an upward posture to be crosslinked. One pass was required for welding to bridge the route gap G. After that, “+1 pass in the vertical direction of the end face of the bottom diaphragm A33 (first steel plate A side)” and “in the horizontal direction on the back side of the lower flange B33 (second steel plate B side) + one pass or more after cross-linking The back side of the groove was welded in a total of 2 passes (same laminating method as in FIG. 2B) while weaving wide.

  Thereafter, in the same manner as the welding method of the upper flange B32, filling welding and extra welding of the groove D were performed by combining the SW1 solid wire and the carbon dioxide shield with the welding wire 2 facing downward. It was confirmed that the angle θ of the base metal-weld metal boundary W in the cross section of the welded portion of the lower flange B33 formed by upward welding and subsequent downward welding was 101 degrees.

  Then, the same earthquake resistance evaluation test as the above-mentioned comparative example was implemented using the test work. As a result, the first steel material A3 and the second steel material B3 welded and connected to the first steel material A3 broke 45 times. The fracture position is a welded portion between the lower flange B33 and the lower diaphragm A33, which has progressed from the toe portion of the final bead on the back side toward the front side, but is different from the base metal-welded metal boundary line W. I did not do it. Therefore, it was confirmed that the penetration intersection angle θ was 135 degrees or less and the weldability and the fatigue resistance characteristics of the joint were advanced.

As described above, the arc welding method of the present invention uses the arc welding method of the present invention to weld the lower flange B33 to the conventional welding method, thereby improving the stress concentration and causing the fracture to break in the fatigue test. It has been confirmed that the number of times can be more than doubled, and it can be improved to a joint structure mode having earthquake resistance and fatigue resistance.
It is obvious that the earthquake resistance and fatigue resistance can be further improved by using the arc welding method of the present invention for the upper flange B32 together with the lower flange B33.

DESCRIPTION OF SYMBOLS 1 Welding torch 2 Welding wire A Steel plate (1st steel material)
A1 1st steel plate (1st steel material)
A2, A3 1st steel material A22, A32 Over-diaphragm A23, A33 Under-diaphragm B Steel plate (1st steel material)
B1 2nd steel plate (2nd steel material)
B2, B3 Second steel material B22, B32 Upper flange B23, B33 Lower flange D, D1 Groove F Weld bead (welded metal)
Fa Weld bead for upward welding Fb Weld bead for downward welding F1 Weld bead for the first pass F2 Weld bead for the second pass F3 Weld bead for the third pass F4 Weld bead for the fourth pass W Base metal-weld metal boundary line θ, θ2 Base metal-weld metal boundary angle

Claims (5)

An arc welding method in which a first steel material and a second steel material are joint-welded with complete penetration,
The first steel material is arranged in a butting direction with respect to the second steel material or in an orthogonal direction perpendicular to the butting direction, and is formed to have a plate thickness larger than that of the second steel material,
The second steel material is disposed toward the butt direction with respect to the first steel material, and has a groove,
When welding the first steel material and the second steel material, the back side of the groove is welded upward two or more passes in the direction orthogonal to the end surface on the first steel material side, and the back surface on the second steel plate side is After performing the upward welding that bridges the groove in the butt direction, and performing the upward welding for one or more passes after the crosslinking, the filling side welding and extra welding of the groove by downward welding on the front side on the second steel material side And
Welding is performed so that an angle of a base metal-weld metal boundary line between a weld metal formed by the upward welding and the downward welding and a base material of the second steel material is 135 degrees or less. Arc welding method. For the upward welding, a flux-cored wire is used,
The arc welding method according to claim 1, wherein a solid wire or a flux-cored wire is used for the downward welding.   The flux-cored wire used for the upward welding has a positive polarity and contains a total of 0.5 to 10% by mass of calcium fluoride or barium fluoride as a flux. The described arc welding method.   The arc welding method according to claim 2 or 3, wherein the flux-cored wire used for the upward welding is formed by a gas shielded arc welding method combined with a carbon dioxide gas shield. The first steel material is a column member,
The said 2nd steel material consists of the beam member formed from H-section steel, and the lower flange joined when joining to the said column member is formed. The arc welding method according to any one of the above.

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