Electroslag welding method

Abstract

To provide an electroslag welding method capable of reducing the number of used members during a welding process and a manufacturing cost and shortening an unwelded part length.SOLUTION: In an electroslag welding method, a sectional shape of a bevel part formed by a skin plate, a diaphragm, and a patch having a pair of notches for sandwiching the diaphragm is a polygon formed by stacking the following shapes (1), (2), and (3) in this order from the diaphragm side toward the skin plate side: (1) a first rectangle in which a plate thickness WD of the diaphragm is a long side and a length (RG-b-c) obtained by subtracting a length b of each of the notches and a length c of a flat part from a root gap RG of the bevel part is a short side; (2) a trapezoid in which the plate thickness WD of the diaphragm is an upper bottom, a length (WD+2a=WS) obtained by adding a sum (2a) of depths a of the notches of the patch to WD is a lower bottom, and a length d of each of the notches is a height; and (3) a second rectangle in which the length WS of the lower bottom of the trapezoid is a long side and the length c of the flat part is a short side.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electroslag welding method, and more particularly to an electroslag welding method using an electroslag welding pad suitable for welding box columns for construction. [Background technology]

[0002] In architectural box columns, an internal diaphragm is sometimes built into the location where the beam is attached to make the structure resistant to horizontal loads. In this structure, a T-shaped structure is formed by the steel skin plate for the box column and the built-in diaphragm. The electroslag welding method, which is a vertical welding method, is often used as the welding method for forming this T-shaped structure from the viewpoint of welding efficiency.

[0003] This T-shaped structure is used in important infrastructure such as buildings, so it is necessary to reduce the risk of destruction. The heat-affected zone of welded joints welded with an ultra-high heat input of 40 kJ / mm or more is easily embrittled, and if seismic waves during a major earthquake apply loads from above, below, left and right to the welded joints between the box column and the beam, fracture will occur along the embrittled heat-affected zone, destroying the box column.

[0004] In order to reduce such damage, various techniques have been proposed. For example, Patent Document 1 discloses that abutment members each having a notch at an angle of less than 45° are disposed on both sides of a leg member of a T-shaped groove so that the notches face each other. It is described that this makes it possible to increase the penetration width of the molten metal in the skin plate without increasing the welding heat input, thereby improving the fracture toughness of the weld.

[0005] Patent Document 2 discloses that in electroslag welding, an opening cross section is provided that is composed of a curve with a radius of curvature without corners. This makes it possible to prevent the generation of unmelted parts (residual melt) at the corners of the groove, even if the welding heat input is reduced and the penetration of the molten part is reduced.

[0006] Patent Document 3 discloses a composite material abutment in which the part in contact with the molten metal is made of ceramic or flux and the outside is made of steel so that it can be tack-welded to a skin plate or an inner diaphragm, and the ceramic part has a notch in part. In addition, abutments in which the ceramic part has a two-stage notch in shape to smooth the flow of molten metal are disclosed. It is described that this makes it possible to prevent destruction due to the progression of a notch-shaped gap even if it occurs between the abutment and the skin plate.

[0007] Patent Document 4 also discloses that when electroslag welding is performed using a skin plate with a high C content, a thin steel plate with a low C content and a specified thickness is sandwiched between the diaphragm and the backing metal, and the two are brought into contact with each other to form a groove and perform welding. It is described that this makes it possible to suppress an increase in the C content of the weld metal, and achieves both high toughness of the weld metal and stabilization of that toughness (suppression of variation).

[0008] Furthermore, Patent Document 5 discloses a welding method in which the backing metal is made of ceramic or flux, and the width of the groove space expands as it approaches the skin plate. It also discloses that the ceramic backing metal is provided with a chamfer in a substantially arc shape at the corner between the end face that contacts the skin plate and the sealed space. It describes that this allows the molten metal to form a gentle base, so that no notches are generated at the joint, and therefore stress does not concentrate, preventing cracks from occurring.

[0009] All of the above-mentioned patent documents describe methods for improving the penetration of the weld metal and preventing the occurrence of weld cracks by changing the shape or material of the backing metal. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2007-61844 A [Patent Document 2] JP 2007-167928 A [Patent Document 3] JP 2006-192487 A [Patent Document 4] JP 2014-193483 A [Patent Document 5] JP 2003-112273 A Summary of the Invention [Problem to be solved by the invention]

[0011] However, in the above-mentioned prior art, even if the corners of the groove formed by the backing metal are welded so that the molten metal penetrates sufficiently, there are still cases where unwelded parts remain, which are not welded in parts. Therefore, there is a problem that defects (cracks) occur due to the existence of the unwelded parts.

[0012] That is, Patent Documents 1 and 2 aim to ensure a certain penetration width even when low heat input welding is performed on the welded portion of the corner of the groove, which is a measure to increase the toughness of the welded portion, but they do not take into consideration reducing the length of the unwelded portion described above. Therefore, the risk of fracture due to the unwelded portion is not eliminated.

[0013] Furthermore, in Patent Document 3, since the contact portion between the backing metal and the skin plate is made of ceramic, there is no indication of any intention to eliminate the risk of fracture by changing the length of the unwelded portion.

[0014] Furthermore, in Patent Documents 2 and 3, the metal is processed and manufactured using materials that require many steps, which increases the manufacturing cost.

[0015] In addition, Patent Document 4 is a method for increasing the toughness of the weld metal, but sandwiching a thin steel plate complicates the method of attaching the metal backing and increases the number of parts, which causes a problem of increased production costs, similar to Patent Documents 2 and 3.

[0016] Also, Patent Document 5 discloses a method for preventing notches from being formed at the contact portion between the backing and the skin plate in order to eliminate cracks caused by welding. However, since the backing is made of ceramic, it is not possible to expand the welded portion of the groove and reduce the unwelded portion, so there is a problem that the risk of fracture caused by the unwelded portion cannot be eliminated. This is thought to be due to the fact that the ceramic backing in Patent Document 5 has an arc shape, and the welded portion has a small degree of freedom in operation.

[0017] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide an electroslag welding method that can reduce the number of parts used during welding, reduce manufacturing costs, and shorten the length of the unwelded portion. [Means for solving the problem]

[0018] The present inventors have conducted extensive research to achieve the above object and have obtained the following findings. The contents will be explained below with reference to FIG. The central elliptical egg-shaped part is the welded part 8 formed by electroslag welding, and the part where the pair of abutting metals 1 (1a) and the skin plate 2 or the diaphragm 3 are not welded is the unwelded part. The tip (inner end) of the unwelded part between the abutting metals 1 (1a) and the skin plate 2 is a part that is considered to have a relatively high risk of brittle cracking due to the load acting on the building, and it is important to reduce this risk. In general, the shorter the length (Ln) of the unwelded part, the smaller the generated stress and stress intensity factor at the front edge of the unwelded part. In addition, the range over which the stress is transmitted is the length (Lm) of the welded part in Figure 3, and it is considered that the longer this length (Lm) is, the lower the risk of fracture occurrence.

[0019] Therefore, the target shape of the welded portion 8 is one that widens the egg-shaped welded portion 8, increases the length of the welded portion (Lm), and reduces the length of the unwelded portion (Ln). To achieve this, it was found that it is necessary to increase the degree of freedom in rod operation, which is the swing width of the welding torch during welding in electroslag welding (hereinafter also referred to as the "rod operation width"), and to make the shape of the groove portion 5 suitable for forming the welded portion 8 into a long egg shape.

[0020] The present invention was completed based on these findings and through further investigation, and the gist of the present invention is as follows. [1] A method for electroslag welding a skin plate and a diaphragm in a T-shaped structure, comprising using a backing having a pair of notches for clamping the diaphragm, the notches being configured from an inclined portion angled in the long side direction toward the skin plate, and a flat portion parallel to the long side. [2] The electroslag welding method according to [1], characterized in that the cross-sectional shape of the groove formed by the skin plate, the diaphragm, and a backing having a pair of notches for sandwiching the diaphragm is a polygon formed by stacking the following shapes (a), (b), and (c) in this order from the diaphragm side to the skin plate side. (a) The thickness of the diaphragm (W D A first rectangle having a long side and a short side of a length (RG-bc) obtained by subtracting the length (b) of the notch from the root gap (RG) of the groove and the length (c) of the flat portion which is a straight portion of the notch perpendicular to the skin plate, (b) The thickness of the diaphragm (W D ) is the upper base, and the thickness of the diaphragm (W D ) plus the sum (2a) of the depths (a) of the notches of the pair of abutments. D +2a=W S ) as a base and the length (b) of the cutout portion as a height, (c) The length of the lower base of the trapezoid (W S) as its long side and the length (c) of the flat portion as its short side. [3] In the above [2], the plate thickness of the diaphragm (W D ) is 30mm to 80mm, and the length of the lower base of the trapezoid (W S ) is 36 mm to 98 mm. [4] The electroslag welding method according to [2] or [3], characterized in that in the cross-sectional shape of the groove portion, a base angle (δ) of the trapezoid is 45° to 80°. [5] The electroslag welding method according to any one of [2] to [4], characterized in that the length (c) of the flat portion in the cross-sectional shape of the groove is 5 mm to 15 mm. [6] The electroslag welding method according to any one of [2] to [5], characterized in that the plate width (d) of the metal forming the groove is 45 mm to 80 mm, and the plate thickness (t) of the metal is 16 mm to 50 mm. [7] The electroslag welding method according to any one of the above [1] to [6], characterized in that the welding heat input is 40 kJ / mm to 100 kJ / mm. [8] The electroslag welding method according to any one of the above [1] to [7], characterized in that the oscillation travel time in the electroslag welding is 2.5 seconds to 5.0 seconds. Effect of the Invention

[0021] By making the width of the groove larger on the skin plate side than on the diaphragm side, the present invention increases the freedom of rod operation, expands the welded area, and stably reduces the unwelded area, thereby improving fracture safety even under low welding heat input. [Brief description of the drawings]

[0022] [Figure 1] 1 is a schematic cross-sectional view showing a groove portion of an electroslag welding method according to the present invention. FIG. [Diagram 2]1 is a schematic cross-sectional view showing an electroslag welding metal according to the present invention. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing a deposition range of a weld metal. [Figure 4] FIG. 2 is a schematic cross-sectional view showing a groove portion and a backing metal in the experimental results of electroslag welding. [Diagram 5] FIG. 2 is a schematic cross-sectional view showing a welded joint as a result of an electroslag welding experiment. [Figure 6] FIG. 1 is a schematic diagram showing the stress distribution results in the vicinity of a weld in electroslag welding. [Figure 7] 4A to 4C are schematic cross-sectional views showing a method for processing a notch portion of a metal plate according to the present invention. [Figure 8] FIG. 1 is a perspective view showing a schematic overview of a conventional electroslag welding method. [Figure 9] 1 is a perspective view showing an outline of an electroslag welding method according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Representative embodiments of the electroslag welding method according to the present invention will be described in detail below with reference to the drawings, but the present invention is not limited to these. Also, since the drawings are intended to conceptually explain the present invention, the dimensions and ratios of each member shown may differ from the actual ones.

[0024] [Background to the Invention] The present invention focuses on the cross-sectional shape of the groove portion of electroslag welding, particularly the unwelded portion between the backing metal and the skin plate. First, the background to the invention will be described.

[0025] In electroslag welding, it is difficult to change the shapes of the skin plate and diaphragm, which are the structures to be welded, but the metal plate 1 is a welding material and has a high degree of freedom in changing its shape. On the other hand, if the processing cost of the metal plate shape is high, it will be difficult to adopt it, so we considered reducing the processing man-hours for the metal plate.

[0026] In electroslag welding, as shown in FIG. 8, a welding torch 11, for example, Φ12 mm, is moved left and right and moves horizontally (oscillates), building up the weld metal as it rises, and a T-shaped structure (also called a "T-joint") is welded along its entire longitudinal length.

[0027] The inventors reasoned that a smaller horizontal movement distance would result in less penetration. That is, in the case of the notch shape of the backing metal shown in the above-mentioned Patent Document 1, if the corner is acute and the angle is large (45° or more), it is thought that the molten metal will flow in and the length of the unwelded part can be reduced by that amount, but the possibility of welding defects tends to increase. Also, from the viewpoint of the freedom of rod operation, the welding torch must be kept at a distance from the workpiece as much as possible without coming into contact with it, but there is also the problem that this becomes difficult.

[0028] Therefore, the inventors considered widening the width of the skin plate side of the groove to increase the degree of freedom in rod operation, and furthermore, designing the cross-sectional shape of the groove to have a flat section of about 12 mm on the side closer to the skin plate. They found that such a shape can increase the degree of freedom in horizontal movement of the welding torch (degree of freedom in rod operation) and reduce the length of the unwelded portion, and thus completed the present invention.

[0029] [Bevel] First, a groove formed by the electroslag welding method according to the present invention will be described with reference to FIG.

[0030] The groove portion 5 refers to a space formed by arranging the skin plate 2 and the diaphragm 3 in a T-shaped structure and arranging a pair of metal plates 1c having cutout portions 4 (shown in Figure 2) described later so that the cutout portions 4 face each other. The cross-sectional shape of the space formed by using the above-mentioned metal piece 1c is configured as follows.

[0031] The skin plate 2 and diaphragm 3 are combined into a T-shaped structure, and the cross-sectional shape formed by the skin plate 2, the diaphragm 3, and abutment 1c having a pair of notches 4 for sandwiching the diaphragm 3 is groove portion 5. The shape of groove portion 5 is a polygon formed by overlapping the following shapes (A), (B), and (C) in this order from the diaphragm 3 side to the skin plate 2 side.

[0032] (a) Thickness of diaphragm 3 (W D A first rectangle having a long side of the notch portion 4 and a short side of the notch portion 4, the length (RG-bc) of which is obtained by subtracting from the root gap (RG) of the groove portion 5 the length (b) of the notch portion 4 and the length (c) of the flat portion 7 which is a straight portion of the notch portion 4 perpendicular to the skin plate 2; (b) Thickness of diaphragm 3 (W D ) is the upper base, and the thickness of diaphragm 3 (W D ) plus the sum (2a) of the depths (a) of the notches of the pair of contacts 1 (W D +2a=W S ) is the base and the length of the cutout (b) is the height of the trapezoid. (c) The length of the bottom base of the trapezoid (b) (W S ) as its long side and the length of the flat part (c) as its short side.

[0033] Here, the thickness of the diaphragm 3 (W D ) is preferably in the range of 30 mm to 80 mm. S ) is preferably 36 mm to 98 mm, and more preferably 36 mm to 60 mm.

[0034] Furthermore, the base angle (δ) of the trapezoid is preferably 45° to 80°. If the base angle (δ) is less than 45°, the flow of the molten metal becomes unstable, causing defects in the formation of the welded part and large unwelded parts. On the other hand, if it exceeds 80°, the shape of the notch 4 becomes small, the degree of freedom of rod operation described below decreases, and the formation of the welded part becomes insufficient. The angle is preferably 50° to 75°.

[0035] The length (c) of the flat portion 7, which is the straight portion of the cutout portion 4 perpendicular to the skin plate 2, is preferably 5 mm to 15 mm. If it is less than 5 mm, the trapezoid shape of the cutout portion 4 becomes small, and if it exceeds 15 mm, the trapezoid shape of the cutout portion 4 becomes large, and in either case, sufficient effect cannot be obtained. The preferred length is 7 mm to 12 mm.

[0036] The root gap (RG) of the groove portion 5 is the distance from the short side of the diaphragm 3 on the skin plate 2 side to the skin plate 2, and is preferably 15 mm to 50 mm, and more preferably 18 mm to 25 mm.

[0037] Next, as for the shape of the cutout portion 4, the depth (a) of the cutout portion is preferably 3 mm to 10 mm as shown in Fig. 2. If it is less than 3 mm, the trapezoid shape of the cutout portion 4 becomes small, and if it exceeds 10 mm, the trapezoid shape of the cutout portion 4 becomes large, and in either case, sufficient effect cannot be obtained. The depth is preferably 5 mm to 8 mm.

[0038] The length (b) of the cutout is preferably 5 mm to 12 mm. If it is less than 5 mm, the depth (a) of the cutout cannot be made large, so the trapezoid shape of the cutout 4 becomes small, and if it exceeds 12 mm, the trapezoid shape of the cutout 4 becomes large, so that sufficient effect cannot be obtained. The length is preferably 7 mm to 10 mm.

[0039] Furthermore, the angle (θ) of the cutout portion has a relationship with the base angle (δ) of the trapezoid described above of [θ+δ=90°]. Therefore, the angle (θ) of the cutout portion is preferably 10° to 45°, and more preferably 15° to 40°.

[0040] [Reserves] Next, the cross-sectional shape of the backing 1c suitable for forming the above-mentioned groove portion 5 has a notch portion 4 formed by a notch processing method described later, as shown in FIG.

[0041] The cross-sectional shape of the abutment 1c before notching is a rectangle with the plate width (d) as the long side and the plate thickness (t) as the short side. Of the four sides of the rectangle, the long side on the side that abuts against the diaphragm 3 is shorter than the plate width (d), and the short side on the side that abuts against the skin plate 2 is shorter than the plate thickness (t).

[0042] The cutout portion 4 formed by the cutout processing is composed of an inclined portion 6 and a flat portion 7. The inclined portion 6 is a plane inclined at an angle to the long side direction, and its cross-sectional shape has an inclination angle (θ) of the cutout portion with respect to the long side direction of the backing metal 1c. In other words, it is inclined from the inclination start point 12 on the long side to the inclination end point 13, which is the intersection of the depth (a) of the cutout portion and the length (b) of the cutout portion. The flat portion 7 is a plane in the long side direction, and its cross-sectional shape is a straight portion of the cutout portion 4 perpendicular to the skin plate 2, and has the length (c) of the flat portion from the inclination end point 13 parallel to the long side.

[0043] In other words, the notch portion 4 is a portion where a corner of the cross-sectional shape of the metal 1c before notching is partially removed, and is a trapezoid with the length (c) of the flat portion as its upper base, the sum (b+c) of the length (b) of the notch portion and the length (c) of the flat portion as its lower base, and the depth (a) of the notch portion as its height.

[0044] Here, the cross-sectional shape of the metal abutment 1c has a plate width (d) of preferably 45 mm to 80 mm, more preferably 48 mm to 60 mm, and a plate thickness (t) of preferably 16 mm to 50 mm, more preferably 21 mm to 33 mm.

[0045] The material of the abutment 1c is steel. The composition of the steel is preferably, for example, SS400. More preferably, the composition is similar to that used for skin plates and diaphragms.

[0046] [Electroslag welding method] Next, the electroslag welding method will be described. A general method is shown in Figure 3 and Figure 8, and the method of the present invention is shown in Figure 9. Figures 8 and 9 show an example of the external appearance and internal structure during welding.

[0047] In order to assemble the skin plate 2 and the diaphragm 3 into a T-shaped structure and perform electroslag welding, a pair of backing metals 1 (also called "backing metals") are placed to sandwich the diaphragm 3. As described above, the distance between the skin plate 2 and the diaphragm 3 is called the root gap (RG), and the distance between the opposing pairs of backing metals 1 is called the groove width (W D This groove width (W D ) is the same as the plate thickness of the diaphragm 3. The root gap (RG) and groove width (W D ) is called the groove portion 5. A welding torch 11 is inserted into the groove portion 5 to perform electroslag welding, and as a result, the skin plate 2, the diaphragm 3, and a portion of the pair of abutments 1 are melted to form a welded portion 8.

[0048] Generally, the cross-sectional shape of the abutment 1 (1a) that has been conventionally used is rectangular, and the material thereof includes metal materials such as copper plate and steel plate (for example, flat steel), as well as ceramic materials.

[0049] [Notch processing method for the notched part] Next, an example of a cutting method for forming the notch portion 4 of the electroslag welding pad 1c according to the present invention will be described with reference to FIG.

[0050] One corner of the metal 1c is cut from two directions. In one direction, the metal 1c is cut from diagonally above the long side of the cross-sectional shape at an angle (the angle of the notch) θ, and in the other direction, the metal 1c is cut parallel to the long side of the cross-sectional shape.

[0051] As described above, the angle θ of the cutout portion is preferably 10° to 45°, and more preferably 15° to 40°.

[0052] Regarding ease of processing, although the present invention requires rough processing (cutting) of two surfaces, there is no significant difference in the work involved compared to the one-surface processing of Patent Document 1, and it is easier than the processing and manufacturing methods of Patent Documents 2 to 5.

[0053] As a specific processing method, for example, mechanical cutting may be performed in the direction of each dotted arrow as shown in Fig. 7. At the tip of the arrow, if the cutting is performed in a rough processed state without any processing, excessive cutting marks may remain, but this portion is melted by the flow of molten metal in electroslag welding even if it penetrates deep into the material by about 2 to 3 mm, so there is no need to perform finish processing. Therefore, the electroslag welding backing according to the present invention can be manufactured by simple cutting alone.

[0054] As a processing method, for example, in addition to cutting by saw cutting, mechanical processing methods or processing methods by gas cutting can be used.

[0055] [Electroslag welding conditions] Regarding the welding conditions of the electroslag welding method according to the present invention, the target welding heat input is 40 kJ / mm to 100 kJ / mm. EXAMPLES

[0056] The present invention will be described below with reference to examples. However, the following examples are merely intended to illustrate and explain the present invention in more detail, and are not intended to limit the scope of the present invention.

[0057] For comparison with the electroslag welding pad according to the present invention, a conventional pad having a rectangular cross section and a pad having a triangular cutout as described in Patent Document 1 were prepared. Using these pads, electroslag welding experiments were carried out, and the cross-sectional shapes of the welded metal parts were observed, while the length of the unwelded parts and the stress distribution were measured. The experimental results are shown below.

[0058] FIG. 4 is a schematic diagram showing a cross section of the groove of a T-joint and a cross section of the used metal in an experiment in which electroslag welding was performed using the following three types of metal.

[0059] Experiment No. A: Conventional rectangular cross-section abutment 1a (Fig. 4(a)) The cross-sectional shape of the metal plate 1a in (A) is plate width d = 50 mm, plate thickness t = 28 mm, and the material used is flat steel.

[0060] Experiment No. B: Abutment 1b having a triangular cutout portion in cross section described in Patent Document 1 (FIG. 4(b)) The cross-sectional shape of the metal plate 1b in (B) was d = 50 mm in width, t = 28 mm in thickness, a = 5.7 mm in depth of the notch, and θ = 30° in angle. The material used was flat steel.

[0061] Experiment No. C: Electroslag welding abutment 1c according to the present invention (cross-sectional trapezoidal notch) (FIG. 4(c)) The cross-sectional shape of the metal abutment 1c of the present invention (C) was as follows: plate width d = 50 mm, plate thickness t = 28 mm, notch depth a = 5.7 mm, notch length b = 10 mm, flat length c = 12 mm, and notch angle θ = 30°. The material was SS400, and readily available flat steel was used.

[0062] The welding conditions for the electroslag welding in the experiment are as follows: Welding current: 380A, welding voltage: 48V, wire feed speed: 8.5m / min. The oscillation movement time (one way) was 3 seconds for (A) and (B) and 4.6 seconds for (C). The distance between the welding torch and the back metal when oscillation was stopped was 2 mm, and the distance between the skin plate and the welding torch was 2 mm.

[0063] The results of the experiment are shown in Figure 4. The T-joint has a structure in which a skin plate 2, a diaphragm 3, and a pair of metal fittings 1 face each other, and a welded portion 8 is formed by welding in the space (groove portion 5) surrounded by them. The welded portion 8 has an elliptical (egg-shaped) shape in the center. The size of the welded portion 8 is such that in the metal fitting 1a of (A), the width of the ellipse is small and the shape is close to a perfect circle (Figure 4(a)), in the metal fitting 1b of (B), the width of the ellipse is slightly larger (Figure 4(b)), and in the metal fitting 1c of (C) of the present invention, the width of the ellipse is the largest (Figure 4(c)).

[0064] Inside the ellipse are two circles, one above the other, and an arrow pointing up and down between the two circles. These arrows indicate the horizontal movement distance of the welding torch, i.e., the degree of freedom of the rod operation width, with (C) having the largest movement width (degree of freedom). This result shows that the backing 1c having the notch shape of the present invention has the largest movement width of the molten metal and is the most effective in reducing unwelded areas.

[0065] Furthermore, the results of observing the actual cross-sectional shape are shown in a schematic diagram in Figure 5. The cross-sectional shape shown in Figure 5 was observed by polishing the specimen and then using an etching solution to clarify the image of the welded part, which was then photographed.

[0066] Fig. 5(a) shows the case of the metal fitting 1a(A), and the solid circle shows the welded part without the notch. Fig. 5(b) shows the case of the metal fitting 1b(B) with the notch part having a triangular cross section, where the welded part spreads out into a slightly elliptical shape. Fig. 5(c) shows the case of the metal fitting 1c(C) of the present invention with the notch part having a trapezoidal cross section, where the elliptical shape of the welded part is the widest, and it was found that the unwelded part was reduced.

[0067] If a tensile force acts on the diaphragm member in the longitudinal direction of the diaphragm member, the stress generated at the front edge of the unwelded portion was evaluated by FEM analysis. A model was created in which a beam is connected to the back of the diaphragm by sandwiching the skin plate of a box column, and the stress contour of the maximum principal stress when the diaphragm is pulled until the displacement in the tensile direction reaches 20 mm is shown in Figure 6. According to this, in the top row, Figure 6(a), the stress area exceeding 700 MPa is widely distributed from the weld metal to the heat-affected zone. However, when the shape of the metal plate is changed from that of the metal plate 1b(B) in Figure 6(b) to that of the metal plate 1c(C) of the present invention in Figure 6(c), it was found that the stress area gradually becomes smaller.

[0068] Table 1 shows an overview of the comparative experiments using the above three types of metal, as well as the welding conditions and experimental results.

[0069] [Table 1]

[0070] Looking at the results of the stress intensity factor, compared to the conventional metal plate 1a (A), the metal plate 1b (B) had a 70.1% reduction, while the metal plate 1c (C) of the present invention had a 60.6% reduction.

[0071] The results of the measurement of the length of the unwelded portion showed that compared to the conventional metal plate 1a (A), the unwelded portion length of metal plate 1b (B) was reduced by 80.6%, while the unwelded portion length of metal plate 1c (C), an example of the present invention, was the shortest, being reduced by 70.3% compared to metal plate 1a (A).

[0072] That is, in the case of the metal 1c(C) of the present invention, the length of the unwelded portion is reduced and the width of the weld metal itself is expanded, so that the generated stress is reduced and the stress intensity factor is also reduced.

[0073] As described above, the abutment of the present invention having a flat portion that can improve the degree of freedom of rod operation can be manufactured relatively easily, and by using this abutment, the shape of the welded portion can be changed and the length of the unwelded portion can be reduced. As a result, the stress intensity factor of the tip of the unwelded portion can be reduced, and the fracture safety can be further improved. [Explanation of symbols]

[0074] 1. Reserve 1a Rectangular cross section brace 1b. Abutment with a triangular cutout 1c Abutment having a trapezoidal cross-section 2 Skin Plate 3 Diaphragm 4 Notch 5 Bevel section 6 Slope 7 Flat section 8 Welded area 9 Molten slag 10 Welding wire 11 Welding torch 12 Starting point of slope 13 Slope End Point a Depth of the notch b Length of the notch c Length of flat section d Plate width t Plate thickness RG Root Gap W D Width of diaphragm side of groove W S Width of the skin plate side of the groove Lm Length of welded part Ln Length of unwelded part θ Angle of the notch δ Base angle of a trapezoid

Claims

1. A method for electroslag welding a skin plate and a diaphragm in a T-shaped structure, comprising using a metal plate having a pair of notches for sandwiching the diaphragm, the notches being configured from an inclined portion having an angle in the long side direction toward the skin plate side, and a flat portion parallel to the long side.

2. 2. The electroslag welding method according to claim 1, characterized in that a cross-sectional shape of a groove portion formed by the skin plate, the diaphragm, and a backing having a pair of notches for sandwiching the diaphragm is a polygon formed by stacking the following shapes (a), (b), and (c) in this order from the diaphragm side to the skin plate side. (A) The thickness of the diaphragm (W D A first rectangle having a long side and a short side of a length (RG-bc) obtained by subtracting the length (b) of the notch portion from the root gap (RG) of the groove portion and the length (c) of the flat portion which is a straight portion of the notch portion perpendicular to the skin plate, (b) The thickness of the diaphragm (W D ) is the upper base, and the plate thickness of the diaphragm (W D ) plus the sum (2a) of the depths (a) of the notches of the pair of abutments. D +2a=W S ) as a base and the length (b) of the cutout portion as a height; (c) The length of the lower base of the trapezoid (W S ) as its long side and the length (c) of the flat portion as its short side.

3. The thickness of the diaphragm (W D ) is 30 mm to 80 mm, the length of the lower base of the trapezoid (W S 3. The electroslag welding method according to claim 2, wherein the distance between the contact hole and the gap is 36 mm to 98 mm.

4. 3. The electroslag welding method according to claim 2, wherein in the cross-sectional shape of the groove portion, a base angle (δ) of the trapezoid is 45° to 80°.

5. 3. The electroslag welding method according to claim 2, wherein in a cross-sectional shape of the groove, the length (c) of the flat portion is 5 mm to 15 mm.

6. 3. The electroslag welding method according to claim 2, wherein the plate width (d) of the metal forming the groove is 45 mm to 80 mm, and the plate thickness (t) of the metal is 16 mm to 50 mm.

7. 7. The electroslag welding method according to claim 1, wherein the welding heat input is 40 kJ / mm to 100 kJ / mm.

8. 7. The electroslag welding method according to claim 1, wherein an oscillation travel time in the electroslag welding is 2.5 seconds to 5.0 seconds.

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