KR101185979B1 - Weld structure and welded joint having excellent brittle crack propagation resistance - Google Patents

Abstract

At least one of the steel plate welded joints 1, comprising: a steel plate welded joint formed by butt welding a steel sheet having at least a portion of the brittle crack propagation stopping property Kca of 4000 N / mm ^1.5 or more; The inclined bead 31 which extends from the welding line L phase of the said steel plate welding joint part 1 to the part, and inclines at the angle of the range of 15 degrees or more and 50 degrees or less with respect to the longitudinal direction of the steel plate welding joint part 1; The brittle crack propagation direction control part 3 provided with this is formed, and even if brittle crack generate | occur | produces in a weld joint, it can suppress that a brittle crack propagates along a weld joint or a base material.

Description

WELD STRUCTURE AND WELDED JOINT HAVING EXCELLENT BRITTLE CRACK PROPAGATION RESISTANCE}

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a welded joint having excellent brittle crack propagation properties for controlling and suppressing propagation of brittle cracks when a brittle crack occurs in the welded joint, and a welded structure having the welded joint.

In particular, the present invention relates to a welded structure having excellent brittle fracture propagation properties that can improve safety by controlling and suppressing propagation of cracks even when brittle cracks occur in a welded joint of a welded structure welded using a thick steel plate.

In recent years, the welding structure represented by ship welding structures, such as a large container ship and a bulk carrier, a building structure, and a civil steel structure, is required for the high safety against fractures, such as brittle cracks. In particular, the container ship is remarkably large in size, for example, as a large container ship of 6000 TEU or more is manufactured, the steel plate of the hull shell is thickened and strengthened so that a steel plate of 70 mm or more and a yield strength of 390 N / mm 2 or more is used. have.

Here, the Twenty feet Equivalent Unit (TEU) represents the number converted into a container having a length of 20 feet and represents an index of the loading capacity of the container ship.

Such large container ships have a structure in which a partition wall is removed and a large upper opening is secured in order to improve load capacity and loading efficiency. In particular, since it is necessary to secure the strength of the hull shell or inner plate, the above-described high strength steel sheet is used.

When drying the above-mentioned welding structure, high heat input welding (for example, electro gas arc welding) is widely applied for the purpose of reducing drying cost or improving drying efficiency. In multi-layered welding with a small amount of heat input, in particular, the number of welding steps increases significantly as the plate thickness of the steel sheet increases, so that welding with a high heat input to an extreme is required. However, when large heat input welding is applied to the welding of the steel sheet, the toughness of the heat affected zone (HAZ) decreases and the width of the weld heat affected zone also increases, so that fracture against brittle fracture is caused. Toughness tends to decrease.

For this reason, TMCP steel sheet (Thermo Mechanical Control Process: thermal processing) excellent in brittle fracture resistance for the purpose of suppressing the occurrence of brittle cracks in the welded joint and attaining propagation stop (rest) of brittle cracks. Control) is proposed. By using the TMCP steel sheet, the fracture toughness value, which is a resistance to brittle fracture generation, is improved, so that the probability of brittle fracture of the structure is extremely low in a normal use environment. However, if brittle fracture occurs during an earthquake or collision between structures and a disaster, brittle cracks propagate along the weld heat affected zone, and there is a possibility that large fracture occurs.

For example, in a welded structure represented by a container ship or the like, a TMCP steel plate having a sheet thickness of about 50 mm is used, and even if brittle cracks occur at the welded joint, the brittle cracks deviate from the welded portion to the base material by the welding residual stress. Therefore, it was thought that the brittle crack could be stopped in the base material by securing the arrestor performance of the base material. In addition, in larger welded structures such as large container ships exceeding 6000 TEU, a steel sheet with a larger plate thickness is required, and since thickening of the steel sheet is effective to simplify the structure, a thick steel sheet having high design stress is required. It was required to use. However, in the case of using such a thick steel sheet, there is a possibility that brittle cracks continue to propagate along the weld heat affected zone without causing a breakdown into the base material depending on the degree of fracture toughness of the weld heat affected zone, thereby causing a great breakage in the weld structure.

In order to solve the above problem, a part of the butt welded joint is subjected to repair welding (a groove is formed in a part of the joint and a groove filling is welded in that portion) to form brittle cracks that propagate along the weld heat affected zone. There is proposed a welded structure having a configuration to be pulled out to the side (for example, Patent Document 1).

However, in the weld structure of Patent Literature 1, it is effective when the fracture toughness of the base material is very excellent. However, when the fracture toughness of the base material is insufficient, brittle cracks that have escaped to the base material propagate long, and the strength as a structure may be significantly reduced. have. In addition, there is a problem that the volume of the groove filling weld increases, resulting in a long process time and an increase in manufacturing cost.

Further, in order to control the propagation of the brittle crack in the area where the brittle crack generated in the weld joint is to be stopped, the plate-shaped arrestor is welded through the welding line to intersect the weld line. A welded structure is proposed that uses an optimized structure in a surface layer region having a thickness of 2% or more of sheet thickness ratio (for example, Patent Document 2).

However, when the weld structure described in Patent Literature 2 is applied to a large-sized product, for example, brittle cracks propagated along the weld seam propagate along the weld seam for welding the arrestor to the steel plate, and enter into the arrestor. After propagating along the inside of the arrestor, it may propagate along the weld joint again. On the other hand, when the brittle crack propagated along the weld seam escapes to the base material side at the position of the arrestor and the weld seam for welding the arrestor to the steel sheet, if the fracture toughness of the base material is insufficient as described above, the brittle crack propagates long, The problem that the strength as a welded structure falls remarkably is also concerned.

Japanese Unexamined Patent Publication No. 2005-131708 Japanese Unexamined Patent Publication No. 2007-098441

The present invention has been made in view of the above problems, and for example, even when brittle cracks occur in welded joints, the brittle cracks can be prevented from propagating along the welded joints or the base metal, and fracture of the welded structure can be prevented. It is an object to provide a welded structure having excellent brittle fracture propagation resistance.

MEANS TO SOLVE THE PROBLEM The present inventors provide the joint structure which controls the propagation of the brittle crack like patent document 2 in the middle of a weld joint part, in order to prevent the brittle crack which generate | occur | produced in the weld joint part of a welded structure along a weld joint part or a base material. The case was intensively studied.

As a result, by optimizing the shape and steel properties of the joint structure that controls the propagation of brittle cracks, propagation of brittle cracks in the weld joint and the base material can be suppressed, and large-scale breakage can be prevented from occurring in the weld structure. It has been found that the present invention has been completed.

That is, the summary of this invention relates to the following content described in the Claim.

[1] A steel sheet welded joint, formed by butt welding steel sheets having a brittle crack propagation stop characteristic Kca of at least a partial region with 4000 N / mm ^1.5 or more,

At least one portion of the steel plate welded joint is provided with a brittle crack propagation direction control unit for controlling the propagation of brittle cracks generated in the steel plate welded joint,

This brittle crack propagation direction control part has the inclined bead formed by butt welding between the protrusion part formed in one steel plate, and the other steel plate which opposes this,

This inclined bead is continuously formed from the welding line of the steel plate welded joint, and is inclined and stretched at an angle in the range of 15 ° or more and 50 ° or less with respect to the length direction of the steel plate welded joint toward the inside of the other steel sheet. A rear end portion of the warp bead extending into the steel sheet is formed such that at least Kca of the steel sheet is directed toward a region of 4000 N / mm ^1.5 or more.

[2] The inclined bead provided in the brittle crack propagation direction control unit has a height H (mm) along the longitudinal direction of the steel plate welded joint and a horizontal width W (mm) in a direction crossing the longitudinal direction of the steel plate welded joint. Steel plate welded joint excellent in the brittle-resistant crack propagation property as described in said [1] characterized by satisfy | filling the relationship shown in the following formula (1) and (2).

2T ≤ H ????? (One)

d + 50 ≤ W ???? (2)

However, in said formula (1), (2), T represents the plate | board thickness (mm) of the said steel plate, and d represents the width (mm) of the weld metal part in the said steel plate welding joint part.

[3] A steel plate welded joint having excellent brittle crack propagation property according to the above [1] or [2], wherein the sheet thickness of the steel sheet is 25 mm or more and 150 mm or less.

[4] The steel sheet has a brittle crack propagation stop characteristic Kca of at least a portion of 6000 N / mm ^1.5 or more, and the rear end of the inclined bead is formed to face at least a region of Kca of 6000 N / mm ^1.5 or more. The steel plate welded joint excellent in the brittle-resistant crack propagation property as described in said [1] or [2] characterized by the above-mentioned.

[5] The steel sheet is made of at least two steel sheets arranged in the longitudinal direction of the steel plate welded joint, and a longitudinally arranged steel sheet welded joint is formed by butt welding the steel sheets arranged in the longitudinal direction of the steel sheet welded joint. And the longitudinally arranged steel plate welded joint comprises a transverse bead formed between the rear end of the inclined bead and the welded line of the steel plate welded joint of the fragile crack propagation direction controller extending from the weld line of the steel sheet welded joint. The steel plate welded joint excellent in the brittle-resistant crack propagation property as described in said [1] or [2] characterized by the above-mentioned.

[6] A weld structure in which steel sheet welded joints are formed by butt welding steel sheets having at least a portion of brittle crack propagation stop characteristics Kca of 4000 N / mm ^1.5 or more to the steel sheet welded joint, wherein [ The brittle crack propagation direction control part as described in 1] or [2] is provided, The weld structure excellent in the brittle crack propagation property characterized by the above-mentioned.

In addition, in this invention, the part containing a weld metal part and a welding heat influence part is defined as a weld joint part. In addition, the brittle crack propagation stop characteristic Kca is a numerical value in the temperature or design temperature at which this weld structure is used.

According to the welded structure of the present invention, an inner portion comprising inclined beads formed by butt welding between at least one portion of a welded joint formed by butt welding a steel sheet between a protrusion formed on one steel sheet and the other steel sheet opposed thereto. Since a brittle crack propagation direction control part is provided, even if brittle cracks generate | occur | produce in a weld joint, the brittle crack which propagates along a weld joint part is made to deviate to the site | part where the arresting crack propagation direction control part has a high performance of the steel plate base material, Alternatively, the brittle crack propagation direction control unit can prevent the brittle crack from propagating along the weld joint or the base metal.

Therefore, the welded structure which can prevent large-scale breakage beforehand can be obtained with high production efficiency and low cost.

As the welded structure according to the present invention is used for various welded structures such as building structures and civil steel structures, including large vessels, the welded structure can be enlarged, high safety against destruction, high efficiency of welding in drying, economical efficiency of steel, etc. Since this is satisfied at the same time, the industrial effect is quite large.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining this invention, It is a top view which shows the state in which the brittle-resistant crack propagation direction control part with the inclined bead was provided in a part of the steel plate welding joint part formed by welding steel plate.
FIG. 2: is a schematic diagram explaining the brittle crack propagation state in the case where the brittle crack propagation direction control part shown in FIG. 1 is provided in a part of steel plate weld joint.
It is a schematic diagram explaining the crack propagation characteristic of the steel plate welded joint and welded structure which concerns on this invention, and is an enlarged view of the principal part of the steel plate welded joint and welded structure shown in FIG.
It is a schematic diagram explaining the case where the steel plate welding joint and weld structure which concern on this invention are applied to the ship welding structure.
FIG. 5 is a view similar to FIG. 3 illustrating another example of the steel plate welded joint and the welded structure according to the present invention. FIG.
It is a figure similar to FIG. 3 explaining another example of the steel plate welded joint and welded structure which concerns on this invention.
FIG. 7 is a view similar to FIG. 3 illustrating another example of the steel plate welded joint and the welded structure according to the present invention. FIG.
It is a figure explaining the weld seam test body used by the Example of this invention.
It is a figure explaining the tensile test method for evaluating brittle crack propagation property in the Example of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the weld structure excellent in the brittle-resistant crack propagation property of this invention is described in detail, referring drawings. In addition, since this embodiment is described in detail in order to understand the meaning of invention better, it does not limit this invention unless there is particular notice.

Conventionally, brittle cracks generated in steel plate welded joints propagate along the longitudinal direction mainly along the steel plate welded joints. For this reason, the brittle crack which generate | occur | produced in the steel plate weld joint part originated, and there existed a problem that the big fracture might arise in the whole weld structure.

In order to effectively control the propagation direction of the brittle crack as described above, and to suppress the propagation of the crack in the welded structure, the present inventors further described the shape and steel characteristics of the member for controlling the propagation of the brittle crack. It was found that optimizing is important.

The basic principle of this invention is demonstrated using FIG.1 and FIG.2.

In the present invention, in the middle of the steel sheet welded joint 1 formed by butt welding the steel sheet 2 and the steel sheet 2, the brittle crack propagation direction control unit 3 for controlling the propagation of the brittle crack generated in the steel sheet welded joint Form.

This brittle crack propagation direction control part 3 forms the protrusion part 4 in the butt-welded steel plate, and the other steel plate is provided with the notch 5 of the shape corresponding to the protrusion part 4, It is formed by butt welding.

The protruding portion 4 is inclined and protruded from the end of the steel sheet, and the welded portion between the protruding portion 4 and the cutout portion 5 is inclined toward the inside of the steel sheet and is inclined to extend. It is formed continuously from.

Even when the steel sheet weld joint is subjected to large breakdown energy and brittle cracking occurs in the steel sheet weld joint 1, the brittle crack propagation direction control section 3 is formed to control the propagation of the crack as follows.

The brittle crack CR generated in one side of the steel sheet welded joint 1 in the longitudinal direction (the upper part of Figs. 2A to 2E) has a boundary between the steel sheet 2 and the steel sheet welded joint 1. Thus propagates. When the crack CR reaches the inclined bead 31, the crack CR does not intrude into the protrusion 4, and as shown in FIG. 2A, along the boundary between the steel plate 2 and the inclined bead 31. It propagates and reaches the base material part of the steel plate 2. At this time, even when entering the base material portion, if the brittle crack propagation stop characteristic Kca of the steel sheet 2 is high, the growth of the crack CR can be stopped there.

In addition, depending on the degree of the breaking energy, the crack may enter the protrusion 4 from the inclined bead. Also in this case, when the height of the projection is sufficiently high or when the brittle crack propagation stop characteristic Kca of the base material forming the projection is sufficiently high, as shown in Fig. 2B, the inside of the region of the projection 4 Propagation of brittle cracks can be stopped.

Moreover, even when the brittle crack CR propagates from the other direction (lower side) of the steel plate welded joint 1 in the longitudinal direction, Kca of the brittle crack propagation direction control part 3 is made high, and a brittle crack propagation direction is carried out. If the height of the direction according to the weld joint of the control part 3 is sufficient, as shown in FIG.2 (f), progress of crack CR can be stopped inside the brittle crack propagation direction control part 3 inside. .

On the contrary, when Kca of the brittle crack propagation direction control part 3 is low, or when the shape of the brittle crack propagation direction control part 3 is not enough, like FIG.2 (c), brittle crack CR is carried out. It is supposed to penetrate this brittle crack propagation direction control part 3, or return to the steel plate welding joint from the inclined bead as shown in FIG.2 (d), and propagate again along the steel plate welding joint 1 again. In addition, when Kca of a steel plate is low, it is also assumed that the brittle crack which escaped from the inclined bead to the steel plate propagates along the steel plate as shown in FIG.

The present invention has been made by further studying the conditions of the base steel plate for preventing the development of brittle cracks, the conditions of the brittle crack propagation direction control unit for controlling the development of brittle cracks, and the like. Embodiment is described in detail.

[First Embodiment]

<Overall Configuration>

The first embodiment is that the brittle crack propagation stop characteristics of the base material Kca 4000 N / ㎜ ^1.5 or more plates (2) and the plate (2) by butt welding steel plate weld joint 1 is formed as shown in Fig. 3 It is an example of the case, and the form applied to this joint part is called the welded structure A, and is demonstrated below.

In the welded structure A, the brittle crack propagation direction control part 3 is formed in at least one part of the steel plate welding joint part 1 so that the propagation of the brittle crack which generate | occur | produced in the steel plate welding joint part may deviate to the steel plate base material side. The position at which the brittle-resistant crack propagation direction control section 3 is formed is preferably in the middle of the steel welded joint where the occurrence and propagation of cracks are predicted when exposed to large breaking energy due to collision or earthquake.

This brittle crack propagation direction control part 3 forms the protrusion part 4 in the butt-welded steel plate, and forms the notch 5 of the shape corresponding to the protrusion part 4 in the other steel plate, and buttes both. It forms between the steel plate joint part 11 and the steel plate joint part 12 by welding.

The protruding portion 4 is inclined and protruded from the end of the steel sheet, and the welded portion between the protruding portion 4 and the cutout portion 5 is inclined toward the inside of the steel sheet and is inclined to extend. It is formed continuously from.

The inclined bead 31 is formed to be inclined at an angle in the range of 15 ° or more and 50 ° or less with respect to the longitudinal direction of the steel plate welded joint 1, and is formed in the transverse bead at the rear end 31b of the inclined bead 31. One end 32a of the 32 is connected, and the other end 32b of the lateral bead 32 is connected to the steel plate joint 12.

<Steel plate>

The steel plate 2 consists of steel materials whose brittle crack propagation stop characteristic Kca becomes 4000 N / mm ^1.5 or more. 6000 N / mm ^1.5 or more is preferable at the point which further improves brittle crack propagation property.

As long as the steel sheet 2 satisfies the above Kca, the chemical composition, metal structure, and the like are not limited to specific ones. The steel sheet 2 has conventionally known steel sheet characteristics in fields such as marine welding structures, building structures, and civil steel structures. Can be used.

For example, the composition is based on the composition containing C: 0.01 to 0.18%, Si: 0.01 to 0.5%, Mn: 0.3 to 2.5%, P: 0.01% or less, and S: 0.001 to 0.02%. Depending on the composition, additionally N: 0.001 to 0.008%, B: 0.0001 to 0.005%, Mo: 0.01 to 1.0%, Al: 0.002 to 0.1%, Ti: 0.003 to 0.05%, Ca: 0.0001 to 0.003 %, Mg: 0.001 to 0.005%, V: 0.001 to 0.18%, Ni: 0.01 to 5.5%, Nb: 0.005 to 0.05%, Cu: 0.01 to 3.0%, Cr: 0.01 to 1.0%, REM: 0.0005 to 0.005% 1 type, or 2 or more types of, and remainder can mention the steel which consists of Fe and an unavoidable impurity.

In particular, as a steel sheet having a brittle crack propagation stop characteristic Kca of 6000 N / mm ^1.5 or more, a thick steel sheet having a composition disclosed in JP-A-2007-302993, JP-A-2008-248382 and the like can be suitably used.

The plate thickness of the steel plate 2 is good to be in the range of 25 mm or more and 150 mm or less. If the plate | board thickness of the steel plate 2 is this range, the steel plate strength as a weld structure can be ensured, and it becomes possible to obtain the outstanding brittle-resistant crack propagation property. In particular, in a welded structure using a steel sheet of 40 mm or more, there is no effective means for stopping the propagation of brittle cracks, and therefore, in a welded structure using a steel sheet of 40 mm or more, more preferably, 50 mm or more and 100 mm or less. The present invention is implemented more effectively.

<Fragile Crack Propagation Direction Control Unit>

The brittle-resistant crack propagation direction control part 3 consists of a welding joint part formed in at least one part of the steel plate welding joint part 1, In the example shown in FIG. 3, the steel plate joint part of two parts which comprises the steel plate welding joint part 1 is shown. The brittle crack propagation direction control part 3 is formed between (11, 12).

The brittle fracture propagation direction control part 3 extends on the welding line L of the steel plate welded joint 1 (steel plate joint 11 in the illustrated example) and is 15 degrees or more with respect to the longitudinal direction of the steel sheet welded joint 1. And an inclined bead 31 inclined at an inclination angle θ in the range of 50 ° or less. Moreover, in the brittle crack propagation direction control part 3 of an illustration example, the one end 32a of the horizontal bead 32 is connected to the rear end 31b of the inclined bead 31, and the other end 32b of the horizontal bead 32 is ) Is connected to the steel plate joint 12.

The steel plate welded joint according to the present invention and the welded structure in which it is used are provided with the brittle crack propagation direction control section 3 as described above, even if a brittle crack occurs in the steel sheet welded joint 1. The propagation direction of the brittle crack is controlled to prevent the cracks from propagating so as to penetrate the steel plate weld joint 1 and the steel sheets 2 welded to each other are divided.

As described above, in the brittle crack propagation direction control section 3, the inclined bead 31 extending from the crown portion 31a disposed on the weld line L of the steel sheet welded joint 11 is a steel sheet welded joint 1. It is preferable to incline at angle (theta) of 15 degrees or more and 50 degrees or less with respect to the longitudinal direction of (11, 12).

By setting the inclination angle of the inclined bead 31 to the above range, even when brittle cracks propagating along the steel plate welded joint 11 are generated, the crack is guided from the steel plate welded joint along the inclined bead 31. In this way, it is possible to stably deviate to the base material side of the steel plate 2.

 If the angle θ of the inclined bead of the brittle crack propagation direction control part is less than 15 °, even if the crack propagates along the inclined bead, the position of the crack passing through the inclined bead is close to the position of the welded steel sheet which is the original crack propagation path. Because of the loss, there is a fear that the cracks rush into the steel plate weld joint again and propagate.

In addition, when the angle θ of the inclined bead exceeds 50 °, after the brittle crack propagated along the steel plate welded joint propagates along the inclined bead 31, it is possible to intrude into the protruding portion 4 without leaving the base metal side of the steel plate. Will grow. In this case, since brittle cracks intrude directly with respect to the brittle crack propagation direction control part, when the brittle crack propagation stop characteristic Kca of the projection part 4 is not enough, propagation of a crack does not stop and brittle crack propagation direction is performed. There is a risk of passing through the control unit and intruding into the steel plate welded joint again.

Moreover, if the angle θ of the inclined bead of the brittle crack propagation direction control part with respect to the longitudinal direction of the steel plate welding joint part exceeds 50 degrees, ensuring the height H of a brittle crack propagation direction control part in the range demonstrated below, brittle crack propagation will be carried out. The width W of the direction controller becomes too large and not realistic.

The better ranges of the inclination angles θ for guiding the brittle cracks to propagate along the inclined beads 31 are 20 degrees or more and 45 degrees or less, and the better ranges are 25 degrees or more and 40 degrees or less.

In addition, the horizontal beads 32 connecting the inclined beads 31 and the steel plate joint 12 have an angle θ2 (see FIG. 1B) between the horizontal beads 32 and the steel plate joint 12. What is necessary is just to form so that it may become 80 degree | times (preferably 90 degree | times) more than 110 degree | times. If it is out of this range, there is a risk that brittle cracks enter the projection 4 from the middle of the inclined bead or return to the steel plate joint as shown in FIG.

The protrusion part 4 formed in the brittle crack propagation direction control part 3 used for the steel plate welding joint 1 (welding structure A) of this embodiment has the height H (mm) along the longitudinal direction of the said steel plate welding joint. It is good that the horizontal width W (mm) projecting from the steel plate welded joint 1 satisfies the relationship represented by the following formulas (1) and (2).

2T ≤ H ????? (One)

d + 50 ≤ W ???? (2)

However, in said Formula (1), (2), T (mm) shows the plate | board thickness of the said steel plate, and d (mm) shows the width of the weld metal part in the said steel plate welding joint part.

By making each dimension value of the inclined bead 31 provided in the brittle-resistant crack propagation direction control part 3 into the said relationship, even if a brittle crack propagates along the steel plate weld joint 1, the propagation direction of a crack is inclined. By the bead, it becomes possible to effectively escape to the base material side of the steel sheet (2). In addition, even when the crack rushes into the protrusions 4, it is possible to stop the growth of the cracks inside the protrusions.

If the relationship between the dimensional values of the brittle crack propagation direction control part does not satisfy the relationship represented by the above formulas (1) and (2), depending on the crack state occurring in the welded joint of the steel sheet, the crack is the brittle crack propagation direction It is possible to enter the control unit and propagate at the steel plate weld joint without departing to the base metal side of the steel plate.

In order to stop the propagation of brittle cracking more reliably, the said height H is 200 mm or more, or 250 mm or more, 300 mm or more is more preferable, In said Formula (1), H / T is good at 2.0 or more, 3.0 or more This is better.

<Control of propagation direction of brittle cracks>

In the welded structure A having the above-described configuration, the control operation in the crack propagation direction when brittle cracking occurs in the steel plate welded joint 1 will be described below.

As shown in FIG. 3, the brittle crack which generate | occur | produced in the longitudinal direction of the steel plate welded joint 1 (the upper direction of the longitudinal direction in FIG. 3) is the other of the longitudinal direction in the steel plate welded joint 1; Propagation is started toward one side (downward in the longitudinal direction in FIG. 3) (see the dashed-dotted arrow in FIG. 3). At this time, in the steel plate welded joint 1 (welding structure A), the brittle crack which propagated the steel plate welded joint 1 in the longitudinal direction by the steel plate welded joint 1 in the illustrated example is the inclined bead 31. After propagating along, the propagation direction of the crack deviates to the base material side of the steel plate 2 near the rear end 31b of the inclined bead 31 as shown by the symbol F in FIG. 3. Then, the crack propagating toward the outside of the base plate (2) is suspended from the brittle crack propagation stop characteristics Kca 4000 N / ㎜ ^1.5 or more base region.

In addition, even when the brittle crack has advanced from the transverse bead 32 side in the opposite direction to the brittle crack shown in FIG. 3, propagation of the brittle crack is carried out in the middle of the protrusion part 4 as shown in FIG. You can stop it.

By the above-described action, even when a brittle crack occurs in the steel plate welded joint 1 and the welded structure A of the present embodiment, the brittle crack propagates extensively in the welded joint or the base metal, for example. Since it is possible to suppress the occurrence of large-scale breakdown, it is possible to prevent large-scale destruction from occurring in advance.

The welding structure A in which the steel plate welding joint 1 of this embodiment is used is applied to various welding structures, such as a large ship, a building structure, and a civil steel structure, for example, to enlarge and destroy a welding structure. It is possible to simultaneously satisfy high safety, high efficiency of welding in drying, and economical efficiency of steel.

<Method of manufacturing a crack propagation direction control part>

Below, an example of the method of manufacturing the brittle-resistant crack propagation direction control part 3 in the above-mentioned welding structure A is demonstrated.

In a welded structure having a steel plate welded joint formed by butt welding steel sheets to each other, the rust-resistant crack propagation direction control unit is welded to the steel plate where the occurrence or propagation of cracks is expected when exposed to large breaking energy due to collision or earthquake. and, during the brittle crack propagation stop characteristics Kca is 4000 N / ㎜ ^1.5 or more steel plate is formed by a steel sheet welded joint portion is provided with at least one.

This brittle fracture propagation direction control part 3 forms the projection part 4 in the butt-welded steel plate, and forms the notch 5 of the shape corresponding to the projection part 4 in the other steel plate, It is formed by butt welding. At this time, the welding order is not particularly limited, but the steel sheet weld joint 11 and the steel sheet weld joint 12 are first formed by welding, and then the brittle crack propagation direction control unit 3 is formed by welding. to be.

As a welding method used when forming the weld joint, the welding of the steel plate weld joints 11 and 12 is performed in terms of welding efficiency, such as an electro gas arc welding method (EG welding method or two-electrode VEGA welding method (2 VEGA)). ), A high heat input welding such as the submerged arc welding method (SAW) is applied, and semi-automatic carbon gas welding or hand welding is preferably applied to the welding forming the brittle crack propagation direction control section 3. In addition, by appropriately applying the welding jig, the effect of the present invention can be exerted even when a welding method such as two-electrode VEGA welding is used when forming the brittle crack propagation direction controller 3.

In this embodiment, as mentioned above, the welding method and the welding material at the time of forming the steel plate weld joint 1 by butt-welding the steel plates 2 are not specifically limited. In addition, the starting point of new fatigue cracks or brittle cracks is suppressed in the steel plate joints 11 and 12 and the brittle crack propagation direction control section 3 which suppress the brittle crack propagation as much as possible and form the steel plate weld joint 1. In order to prevent occurrence, it is advisable to completely fill each weld seam with weld metal without welding defects.

According to the said procedure, the steel plate welding joint part 1 and the welding structure A which were excellent in the brittle-resistant crack propagation property of this embodiment shown in FIG. 3 can be manufactured.

<Example of Ship Structure Applying Welding Structure>

An example of the ship structure to which the above-mentioned welding structure A was applied is shown in the schematic diagram of FIG.

As shown in FIG. 4, the ship structure 70 includes an aggregate (reinforcement material) 71, a deck plate (horizontal member) 72, a hull inner plate (vertical member) 73, and a hull shell plate 74. It is composed. In addition, the ship structure 70 of an example of illustration is a part of the longitudinal direction of the steel plate welding joint part 1 (not shown in FIG. 4) formed by butt-welding the several steel plate 2 which comprises the hull inner board 73. As shown in FIG. By providing the brittle-resistant crack propagation direction control part 3 in the structure, it becomes a structure provided with the welding structure A of this embodiment.

According to the ship structure 70 of the said structure, by applying the structure of the welding structure A of this embodiment, even if the brittle crack propagating along a steel plate welding joint part generate | occur | produces, for example, in the brittle crack propagation direction control part 3 As a result, the propagation direction of the crack can be effectively controlled. Thereby, the brittle crack which arose in the welded steel plate part can be stably stopped, and large-scale breakage can be prevented from occurring in the hull inner plate 73 and the ship structure 70.

[Second Embodiment]

Hereinafter, the welding structure B which is 2nd Embodiment of this invention is demonstrated in detail, mainly referring FIG. In addition, in the following description, in the structure common to the welding structure A of 1st Embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

In the welded structure B of this embodiment, as shown in FIG. 5, the brittle crack propagation stop characteristic Kca of the area | region 20a, 20a of one part of a base material has the brittle crack propagation direction control part 3 4000 N / mm ^1.5 or more. This is an example of the case where the steel plate weld joint 10 is formed by butt welding the steel sheets 20 and 20, and in this respect, the entire base metal of the steel sheet 2 has a brittle crack propagation stop characteristic Kca of 4000 N / mm ^1.5. It is different from the welded structure A of 1st Embodiment mentioned above.

In the welded structure B needs to be installed adjacent the inside brittle crack propagation direction, at least the area (20a) (3) the brittle crack propagation stop characteristics Kca is 4000 N / ㎜ ^1.5. In FIG. 5, the horizontal bead 32 of the brittle crack propagation direction control part has shown the example which contact | connects the area | region 20a.

According to the welding structure B, when the brittle crack generate | occur | produces in the steel plate welding joint part 10, the inclination bead which the crack propagated along the steel plate welding joint part 10 was equipped in the brittle crack propagation direction control part 3 was equipped with. It is possible to deviate to the base material side of the steel plate 20 at the position of the vertex 31a or the rear end 31b of (31) (refer the dashed-dotted line arrow in FIG. 5). In addition, like the steel plate welded joint 1 and the welded structure A of the first embodiment, the crack deviating to the base metal side of the steel sheet 20 immediately stops in the region 20a of the steel sheet 20, and therefore, the steel sheet welded joint It is possible to prevent (10) from breaking and to prevent large-scale breakage of the weld structure B. In addition, this embodiment of the steel plate welded seam 10 and the welded structure, B is more preferably in the brittle crack propagation stop characteristics Kca of the area (20a) is a 6000 N / ㎜ ^1.5 or more.

[Third embodiment]

Hereinafter, the welding structure C which is 3rd Embodiment of this invention is abbreviate | omitted, and abbreviate | omits common part with previous embodiment, referring FIG. 6 mainly.

The welded structure C is an example in the case where the butt welded steel sheet is formed by butt welding a plurality of longitudinally arranged steel sheets.

In the steel plate welded joint 10A and the welded structure C of the present embodiment, as shown in FIG. 6, at least two or more lengths in which the steel sheets 20A and 20A to be butt-welded are arranged in the longitudinal direction of the steel plate welded joint 10A. It consists of a longitudinally arranged steel plate (joints 21 and 22 in FIG. 6 and a pair of 23 and 24, simply referred to as a steel sheet), and a longitudinally-arranged steel plate welding joint by butt-welding these longitudinally-oriented steel sheets ( 25, 26) are formed. Moreover, the horizontal bead formed in the rear end 31b side of the inclined bead 31 of the brittle crack propagation direction control part 30 is comprised including the longitudinal direction steel plate welding joint parts 25 and 26, The steel plate welded joint 10A and the welded structure C differ in this respect from the steel plate welded joints 1 and 10 and the welded structures A and B of the first and second embodiments described above.

In addition, in the example shown in FIG. 6, four steel sheets 21-24 are shown as a longitudinal direction steel plate for the convenience of illustration, and the steel plate 21 and the steel plate 22 are the longitudinal direction steel plate welding joint part 25. In FIG. The steel plate 23 and the steel plate 24 are joined by the longitudinal direction steel plate welding joint 26. As shown in FIG. In the welded structure C of the illustrated example, the longitudinally arranged steel plate welded joints 25 and 26 are formed in a straight line.

In addition, in the steel plate welded joint 10A and the welded structure C of the present embodiment, the brittle crack propagation stop characteristic Kca of the base metal constituting the steel sheet 22 and the steel sheet 24 is 4000 N / mm ^1.5 or more, The brittle crack propagation stop characteristic Kca of (21) and the steel plate 23 is a structure not specifically defined.

According to the steel plate welded joint 10A and the welded structure C of the present embodiment, similarly to the welded structures A and B described above, even when brittle cracks occur in the steel plate welded joint 10A, the brittle cracks are formed by the inclined beads ( By propagating along 31, it can escape to the base material side of the steel plate 20A at the position of the rear end 31b of the inclined bead 31 (refer to the dashed-dotted arrow in FIG. 6). In the example shown in FIG. 6, the brittle crack which generate | occur | produced in 10 A of steel plate weld joints deviates to the longitudinal direction steel plate 22 side which comprises 20 A of steel plates.

In addition, since the crack which escaped to the base material side of the steel plate 20A stops immediately in the longitudinally aligned steel plate 22 with the brittle crack propagation stop characteristic Kca, the steel plate weld joint 10A does not break, and the weld structure C Large-scale destruction can be prevented.

In addition, in the steel plate welded joint 10A and the welded structure C of the present embodiment, the base metal of the longitudinally arranged steel sheets 22 and 24 forming the steel sheet 20A has a brittle crack propagation stop characteristic Kca = 6000 N / mm ^1.5 or more. much better.

Fourth Embodiment

Hereinafter, the steel plate weld joint 10B and the weld structure D which are 4th Embodiment of this invention are demonstrated, referring mainly FIG.

As shown in FIG. 7, the steel plate welded joint 10B and the welded structure D of the present embodiment have at least two or more longitudinally arranged steel sheets in which the steel sheet 20B is arranged in the longitudinal direction of the steel plate welded joint 10B. 7 and 43, 44), and the longitudinally arranged steel plate weld joints 35 and 36 are formed by butt welding the longitudinally arranged steel sheets together. The structure is partially common with the steel plate welding joint 10A and the welding structure C of 3rd Embodiment.

Further, the steel plate welded joint 10B and the welded structure D of the present embodiment have brittle crack propagation stop characteristics Kca of the base metals of all the longitudinally arranged steel sheets 41 to 44 constituting the steel sheet 20B of 4000 N / mm ^1.5 or more. It is.

According to the welded structure D, even when brittle cracks generate | occur | produce in the steel plate welded joint 10B like the above-mentioned steel plate welded joint 1, 10, 10A and welded structures A-C, this brittle crack is inclined bead. At the position of the vertex 31a of (31), it can be made to move to the base material side of the steel plate 20B (refer to the dashed-dotted line arrow in FIG. 7). In addition, since the Kca of the longitudinally arranged steel sheets 41 and 43 is also high, even when the propagation direction of the brittle crack does not change in the direction along the inclined beads 31, the base material or the projections 4 of the longitudinally arranged steel sheets 41 are not changed. The crack which penetrated in can be stopped by the arrester performance of the longitudinally arranged steel sheets 41 and 43. In addition, even when brittle cracks have advanced from the steel plate joint 12 side, propagation of the brittle cracks can be stopped in the middle of the protrusion part 4 as shown in FIG.

As a result, large-scale breakage can be prevented from occurring in the steel plate welded joint 10B and the welded structure D. FIG. In addition, in the steel plate welded joint 10B and the welded structure D of the present embodiment, the base materials of all the longitudinally arranged steel sheets 41 to 44 constituting the steel sheet 20B have brittle crack propagation stop characteristics Kca = 6000 N / mm ^1.5 or more. Is better.

Hereinafter, the present invention will be described in more detail with reference to examples of a welded structure having excellent brittle fracture propagation properties according to the present invention. However, the present invention is not limited to the following examples, and may be suitable for the purpose of the present invention. It is also possible to carry out a change suitably in the range which exists, and all are included in the technical scope of this invention.

Example

[Manufacture of Welding Structure]

First, in the steelmaking process, deoxidation and desulfurization and chemical composition of molten steel were controlled, and the ingot of the chemical component shown in Table 1 was produced by continuous casting as follows. Further, the steel plate having a plate thickness of about 52 mm was produced by reheating and hot rolling the ingot under the production conditions according to the technical standards of the Japanese Maritime Association (NK) standard hull rolled steels KA32, KA36, and KA40. In addition, various heat treatments were performed on the steel sheet, and the heat treatment conditions were controlled to appropriately adjust the brittle crack propagation stop characteristic Kca (N / mm ^1.5 ) of the base material to various values.

From the produced steel plate, the size of a test piece collects ESSO test (brittle crack propagation stop test) piece of 500 mm x 500 mm x plate | board thickness suitably, and evaluates and confirms Kca characteristic in -10 degreeC, and is brittle- The soft wavefront transition temperature vTrS1 (° C.) was measured. Table 1 also shows the Kca characteristics and vTrS1.

Next, as shown in FIG. 3, the projection part 4 and the notch which can be mutually engaged are formed in the weld end 2a, 2b of the steel plate 2 so that the inclined bead of the dimension shown in Table 2, Table 4 may be formed. (5) was formed and further refined according to the welding method to be applied.

Next, the welding method and conditions shown in Table 2 and Table 4 were applied, and the steel plate joint part 11 was formed by first welding a part between welding stages 2a and 2b of the steel plate 2. Further, by applying the welding methods and conditions shown in Tables 2 to 5 to weld between the welding ends 2a and 2b of the steel sheet 2, the brittle crack propagation direction control section 3 and the steel plate joint 12 are welded. By forming, the steel plate weld joint 1 was formed and the steel plates 2 and 2 were bonded together. At this time, as shown in FIG. 8, it adjusted so that the position of the rear end 31b of the brittle crack propagation direction control part 3 may be set to 1500 mm from the lower end of the steel plate 2. As shown in FIG.

In addition, as a welding method, EG: general electrogas arc welding method, VEGA: single electrode electrogas arc welding method with a rocking mechanism of an electrode, 2VEGA: 2 electrode electrogas arc welding method with rocking mechanism of an electrode, SEG: electrode one electrode electro gas arc welding, with a rocking mechanism SAW: submerged arc welding, CO _2: was used as a shield metal arc welding process: carbon dioxide gas arc welding, SMAW.

In addition, in the formation parts of the steel plate joints 11 and 12 and the brittle crack propagation direction control part 3, in order to prevent the origin of a new crack, a welding process is performed so that each weld joint may be completely filled with a weld metal. It was. Thereafter, each joint was cooled to prepare a steel plate welded joint and a welded structure (examples of the present invention and a comparative example) shown in FIG. 3. In addition, by joining the steel sheets under the conditions shown in Tables 2 to 5 as described above, steel plate welded joints and welded structures (examples of the present invention and comparative examples) shown in FIGS. 5 to 7 were manufactured.

[Evaluation test]

The following evaluation tests were done about the steel plate welded joint and welded structure manufactured by the said procedure.

First, the test apparatus 90 shown in FIG. 9 was prepared, and each sample of the welded structure produced by the said procedure was adjusted suitably, and it attached to the test apparatus 90. FIG. At this time, the window frame 81 which is a crack generating part provided in the steel plate welding joint part 1 shown in FIG. 8 is for forcibly generating a brittle crack by applying a predetermined stress to a wedge, and the notch-shaped tip part is 0.2 mm. Slit processing of the width.

Next, brittle cracks were generated in the steel plate welded joint 1 by applying tensile stresses of 262 N / mm ² and 300 N / mm ^{2 in} the direction perpendicular to the weld line L of the steel plate welded joint 1. Moreover, the brittle crack propagation property of the weld structure was evaluated by propagating this brittle crack on the welding line L of the steel plate welding joint part 1 (steel plate joint part 11). At this time, the brittle crack generating part was cooled to -60 ° C. or lower, but the temperature of the steel plate welded joint 1 as the brittle crack propagation part was -10 ° C. which is a general design temperature of the ship.

Moreover, the test frame 81 was formed in the steel plate joint part 12, and the brittle crack was made to intrude into the brittle crack propagation direction control part 3 from the bottom.

Furthermore, after the brittle crack propagated along the steel plate welded joint 1 reaches the brittle crack propagation direction control part 3, the direction and stop position where the brittle crack propagates are confirmed, and the crack propagates and stops. The form was evaluated in the following 5 steps ([a]-[f]) corresponding to (a)-(f) of FIG. 2, and is shown in Table 2 below.

(a) After the brittle crack reached the brittle crack propagation direction control part, the crack propagated along this control part, and after that, it penetrated to the base material side of the steel plate, and stopped immediately in the steel plate (FIG. 2). in the form of (a)).

[b] After the brittle crack reached the brittle crack propagation direction control part, it entered the projection part of the steel plate without following this control part, and stopped immediately at this projection part (a form of FIG. 2 (b)).

(c) After the brittle crack reaches the brittle crack propagation direction control part, it enters and propagates the projection of the steel sheet without following the control part, returns to the steel sheet weld joint as it is, and propagates again along the steel sheet weld joint (Fig. 2). in the form of (c)).

[d] After the brittle crack reaches the brittle crack propagation direction control part, the crack propagates along this control part, and returns along the steel sheet weld joint as it is, and then propagates again along the steel sheet weld joint (see FIG. 2 (d)). shape).

[e] After the brittle crack propagated in or along the brittle crack propagation direction control part, it protruded into the base material side of the steel plate at the subsequent stage and propagated along the steel plate (a form of FIG. 2 (e)).

[f] After the brittle crack advanced from the lower side reached the brittle crack propagation direction control part, it stopped immediately at this protrusion (form of FIG. 2 (f)).

Table 1 shows the chemical composition of the steel sheet used in the present embodiment, the steel sheet manufacturing conditions, and the brittle crack propagation stop characteristic Kca (N / mm ^1.5 ) of the base metal, and when the steel sheet welded joint 1 was formed. Table 2 lists the welding conditions, the shape of the brittle crack propagation direction controller 3 and the evaluation results of the weld conditions and brittle crack propagation when forming the longitudinally arranged steel plate weld joints adjacent to the brittle crack propagation direction controller 3. To Table 5.

[Evaluation results]

Inventive Examples 1 to 19 shown in Tables 2 to 5 are examples of the steel plate welded joint 1 and the welded structure A of the first embodiment shown in FIG. 3, and Inventive Examples 20 to 25 are the third shown in FIG. 6. Embodiments 26-30 to the steel plate welding joint part 10A and welding structure C of embodiment, Inventive examples 31-33 to steel plate welding joint part 10B and welding structure D of 4th embodiment shown in FIG. Is an example regarding the steel plate welded joint 10 and the welded structure B of 2nd Embodiment shown in FIG. In addition, the invention examples 14, 22, 28 are the examples which a crack penetrated into the brittle crack propagation direction control part 3 from below.

In addition, the comparative examples 1 and 2 shown in Table 2 are the examples which have the same structure as the weld structure A, the comparative examples 3 and 4 have the same structure as the weld structure B, and the comparative examples 5 and 6 have the same structure as the weld structure C. , Comparative Examples 7 to 9 are examples each having the same structure as the welded structure D. FIG. In addition, the comparative example 6 is an example in which the crack penetrated from the bottom.

As shown in Tables 2 to 5, in the steel sheet welded joint and the welded structure according to the present invention (Examples 1 to 33), all forms of propagation of brittle cracks are [a], [b] or [f]. The progress of the crack could be stopped. As a result, even when brittle cracks occur in the welded joint of the welded structure of the present invention, it is possible to suppress the propagation of the cracks along the welded joint or the base material, to prevent the fracture of the welded structure, and to prevent brittle crack propagation. This excellent thing was confirmed.

At this time, the present invention Examples 1, 2, 12 to 14, 16, 26, the angle θ of the inclined bead 31 of the brittle crack propagation direction control unit 3 is 30 degrees or less with respect to the longitudinal direction of the steel plate welded joint 1 Or 45 degrees or more, it is an example in which a crack penetrated into the base material (projection part 4) of the steel plate 2 from the brittle crack propagation direction control part 3, and stopped in the steel plate 2. As shown in FIG.

In addition, in this invention other than that, the brittle crack which reached the brittle crack propagation direction control part 3 propagates along the said control part, and intrudes into the base material of a steel plate, and stops immediately.

Thus, it was confirmed that the steel plate welded joints and the welded structures of the present invention examples 1 to 33 all had predetermined brittle crack propagation properties.

On the other hand, in the welded structures of Comparative Examples 1 to 9, the propagation of the brittle crack is not [c] because any of the base material properties of the steel sheet and the shape of the brittle crack propagation direction control part do not satisfy the requirements of the present invention. It is an example which became the form of [e] and was unable to stop propagation of brittle cracks.

In the welded structures of Comparative Examples 1 and 7 to 9, the brittle cracks which entered the steel plate base material side near the brittle crack propagation direction control part did not stop at the base material part, but again entered the weld joint part and propagated, and the evaluation was slightly lower [ c]. In Comparative Example 1, since the angle θ of the inclined bead 31 exceeded 50 °, in Comparative Example 7, the height H of the brittle crack propagation direction control unit was insufficient, and the horizontal width W was Since the above formula (2) is not satisfied, Comparative Examples 8 and 9 show that the angle θ2 formed by the weld metal parts of the longitudinally arranged steel plate welded joints with the steel plate welded joints is less than 80 ° or 110 °. Came out.

In Comparative Example 2, since the angle of the inclined bead was insufficient, and the horizontal width W did not satisfy the above formula (2), and in Comparative Example 6, the restoring performance of the base metal of the steel sheet was insufficient. The brittle crack which changed the propagation direction along the propagation direction control part propagates again along the steel plate weld joint part, and became [d].

In Comparative Examples 3 to 5, the restoring performance of the base metal of the steel sheet was insufficient, and although the brittle crack propagation direction could be controlled by the brittle crack propagation direction control unit, the brittle cracks intruding into the base metal of the steel sheet remained intact. This is an example of propagation and [e].

As a result, even when brittle cracks occur in the welded joint and the welded structure of the steel sheet welded joint of the present invention, it is possible to suppress the propagation of the crack along the welded joint or the base material and to prevent the fracture of the welded structure. It is clear that the brittle crack propagation is excellent.

1, 10, 10A, 10B welded steel plate
A, B, C, D welded structure
2, 20, 20A, 20B steel plate
20a area (site outside of the rear end side of the inclined bead of the brittle crack propagation direction controller extending from the weld line of the steel plate welded joint with respect to the longitudinal direction of the steel sheet welded joint)
3, 30 brittle crack propagation direction control
31 inclined bead
32 Landscape Bead
31b trailing (bevel bead)
4 projection of steel plate
5 cutout of steel plate
25, 26, 35, 36 longitudinally arranged steel plate welded joints
21, 22, 23, 24, 41, 42, 43, 44 longitudinally arranged steel sheet
70 ship structure
L welding line
Height along the longitudinal direction of the welded seam of the H bead
Intersecting with the longitudinal direction of the steel plate welded joint of W bevel
The width in the direction

Claims (6)

In a welded structure in which steel sheet welded joints are formed by butt welding steel sheets having a brittle crack propagation stop characteristic Kca of at least some region to 4000 N / mm ^1.5 or more,
At least one portion of the steel plate welded joint is provided with a brittle crack propagation direction control unit for controlling the propagation of brittle cracks generated in the steel plate welded joint,
The brittle crack propagation direction control unit includes an inclined bead formed by butt welding between a protrusion formed on one steel plate and the other steel plate opposite thereto,
The inclined bead is continuously formed from the welding line of the steel plate welded joint, and is inclined and stretched at an angle in the range of 15 ° or more and 50 ° or less with respect to the length direction of the steel plate welded joint toward the inside of the other steel sheet. And a rear end portion of the inclined bead extending into the steel sheet is formed such that at least Kca of the steel sheet is directed toward a region of 4000 N / mm ^1.5 or more. The said beveled bead which is provided in the said brittle-resistant crack propagation direction control part is a horizontal width in the direction which crosses the height H (mm) along the longitudinal direction of the said steel plate welding joint part, and the longitudinal direction of a steel plate welding joint part. Each dimension of W (mm) satisfy | fills the relationship shown by following formula (1), (2), The steel plate weld joint excellent in the brittle resistance crack propagation property characterized by the above-mentioned.
2T ≤ H ????? (One)
d + 50 ≤ W ???? (2)
In the above formulas (1) and (2), T represents the plate thickness (mm) of the steel sheet, and d represents the width (mm) of the weld metal portion in the steel plate weld joint. The plate | board thickness of the said steel plate is 25 mm or more and 150 mm or less, The steel plate welded joint excellent in the brittle resistance crack propagation property of Claim 1 or 2 characterized by the above-mentioned. The steel sheet has a brittle crack propagation stop characteristic Kca of at least a partial region of 6000 N / mm ^1.5 or more, and the rear end of the inclined bead has at least Kca of 6000 N / mm ^1.5 of the steel sheet. Steel plate welded joint having excellent brittle fracture propagation, characterized in that it is formed so as to face an area. 3. The steel sheet according to claim 1 or 2, wherein the steel sheet comprises at least two steel sheets arranged in the longitudinal direction of the steel plate welded joint, and at the same time, the steel sheets arranged in the longitudinal direction of the steel plate welded joint are butt welded together. A steel plate welded joint is formed, and the longitudinally arranged steel plate welded joint is formed between the rear end of the inclined bead propagation direction control part extending from the weld line of the steel sheet welded joint and the welded line of the steel sheet welded joint. A welded steel sheet having excellent brittle crack propagation, characterized by including a transverse bead. A weld structure in which a steel plate welded joint is formed by butt welding steel sheets having at least a part of brittle crack propagation stop characteristic Kca of 4000 N / mm ^1.5 or more to the at least one portion of the steel plate welded joint. The brittle crack propagation direction control part of Claim 2 is provided, The weld structure excellent in the brittle crack propagation property characterized by the above-mentioned.

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