JP2021094572A - Welding structure - Google Patents

Abstract

To provide a welded structure excellent in brittle crack propagation stop characteristics.SOLUTION: A welding structure 10 has a T joint part in which a joining member 11 is penetration welded to a member 12 to be joined at both side portions in a state in which an end surface 11c of the joining member 11 abuts on a surface 12a to be joined of the member 12 to be joined. The joining member 11 has a first surface 11a and a second surface 11b, a plate thickness of the joining member 11 is 50.0 mm or more, and shapes of first welding metal and second welding metal formed on each of the first surface 11a and the second surface 11b satisfy predetermined conditions. By using a test plate which is taken from a joining member 11 and having a first test plate surface and a second test plate surface which respectively correspond to the first surface 11a and the second surface 11b, when a test object having first test weld metal and second test weld metal whose shapes satisfy a predetermined condition is formed, and a quality evaluation test is subjected to the test object, a length of a crack to be developed on the test plate becomes a predetermined value or less.SELECTED DRAWING: Figure 4

Description

The present invention relates to a welded structure used in a container ship or the like.

In a large container ship carrying a large amount of cargo, a large opening (hatch) for loading and unloading cargo is formed on the upper deck (upper deck). In addition, hatch side combing is provided on the upper deck so as to surround the hatch in order to prevent the inflow of seawater. The upper deck and hatch side combing are each constructed by welding a plurality of steel plates. Also, the hatch side combing is welded onto the upper deck.

When a large container ship as described above sails over the sea, a load that bends the entire hull (vertical bending load) is applied to the hull due to waves. High-strength thick steel plates are used for the upper deck and hatch side combing in order to sufficiently secure the strength (longitudinal bending strength) of the hull against such a load.

Further, as described above, the hatch side combing and the upper deck each have a structure in which a plurality of steel plates are welded together. In other words, the hatch side combing and the upper deck are formed with a plurality of welds for welding the steel plates to each other. Cracks generated at the weld tend to propagate along the weld. Therefore, for example, when a crack occurs in the welded portion of the hatch side combing, the crack may propagate toward the upper deck side along the welded portion, and the propagated crack may propagate to the welded portion of the upper deck. .. Therefore, in order to sufficiently improve the strength of the hull, the hatch side combing and the upper deck need to have the property of stopping the growth of cracks as described above (the brittle crack propagation stopping property).

For example, Patent Documents 1 and 2 disclose a welded structure relating to brittle crack propagation stopping characteristics.

Japanese Unexamined Patent Publication No. 2007-326147 Japanese Patent No. 5365761

By the way, in order to stop the growth of cracks generated by hatchside combing and propagated toward the upper deck side, as these members, for example, the Kca value at −10 ° C., which is an index of brittle crack propagation stopping characteristics, is used. It is known that it is necessary to use a thick steel plate of 6000 N / mm ^{1.5 or more.}

In addition to the above example, cracks may occur from the upper deck and propagate toward the hatchside combing side. According to the results of the verification test conducted in the joint research between Nippon Kaiji Kyokai and The Japan Welding Engineering Society, when the plate thickness of the hatch side combing is more than 80 mm, it occurs on the upper deck and heads toward the hatch side combing side. It has been found that it is necessary to use a thick steel sheet having an extremely high Kca value of ^{8000 N / mm 1.5} or more in order to stop the growth of cracks propagating.

Conventionally, when evaluating the brittle rhagades propagation stop characteristic of a thick steel sheet used for hatchside combing, a structural model arrest test using a large specimen (brittle fracture propagation stop test: brittle cracks are artificially formed on a test piece. A test) was conducted to evaluate the ability to generate and stop brittle cracks.

However, since it takes a lot of time and cost to carry out a large-scale test, there is a problem that it is not easy to select a thick steel sheet having high brittle crack propagation stopping characteristics. Therefore, it is necessary to obtain a welded structure having excellent brittle crack propagation stopping characteristics at low cost by a simpler method.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a welded structure having excellent brittle crack propagation stopping characteristics.

The gist of the present invention is the following welded structure.

(1) Welding having a T-joint portion in which the joint member is partially welded to the joint member in a state where the end surface of the plate-shaped joint member is in contact with the joint surface of the plate-shaped joint member. It's a structure
The joining member has a first surface and a second surface perpendicular to the plate thickness direction of the joining member.
In the cross section perpendicular to the first surface and the surface to be joined,
The plate thickness t (mm) of the joining member,
_{In the first weld metal formed on the first surface side, the acute angle α 1} (°) formed by the line passing through the toe and the root on the joining member side and the surface to be joined, and the joint in the plate thickness direction. Partial penetration d ₁ (mm), as well as
_{In the second weld metal formed on the second surface side, the acute angle α 2} (°) formed by the line passing through the toe and the root on the joining member side and the surface to be joined, and the joint in the plate thickness direction. The partial penetration d ₂ (mm) of the above satisfies the following equations (i) to (v).
The joining member, in the quality evaluation test to carry out the following processes (a) ~ (d) in this order, but the following c ₁ and c ₂ are to satisfy the following (x) and (xi) equation,
Welded structure.
(A) A test plate having a first test plate surface and a second test plate surface corresponding to the first surface and the second surface, respectively, having a plate thickness of t (mm), a width of 240 mm, and a length of 500 mm. On the other hand, on one side surface in the width direction of the test plate, a step of forming a groove extending in the length direction on the first test plate surface side and the second test plate surface side, respectively.
(B) A run-up plate having a plate thickness of t (mm), a width of 260 mm, and a length of 500 mm and having a notch on one side in the width direction is prepared, and the one side surface of the test plate is formed. In a state of being in contact with the other side surface of the approach plate in the width direction, both side partial penetration welding is performed on the groove.
A toe and a root on the test plate side of the first test weld metal formed on the surface of the first test plate in a cross section perpendicular to the surface of the first test plate and the other surface of the run-up plate. _{The sharp angle β 1} (°) formed by the line passing through the runway plate and the other side surface of the run-up plate, _{the partial penetration b 1} (mm) of the joint in the plate thickness direction, and the second test plate surface side. _{In the formed second test weld metal, the sharp angle β 2} (°) formed by the line passing through the toe on the test plate side and the root and the other surface of the run-up plate, and the joint in the plate thickness direction. A step of forming a test piece having a plate thickness of t (mm), a width of 500 mm, and a length of 500 mm, in which the partial penetration b _{2 (mm) of the above satisfies the following equations (vi) to (ix).}
(C) Using the test piece, the approach plate is subjected to a test stress of ^{σ (N / mm 2} ), which is a preset allowable stress of the joining member, at a test temperature of −10 ° C. A step of applying an impact load to the notch to propagate a crack to the test plate via the first test weld metal and the second test weld metal.
_{(D) The distance c 1} (mm) in the width direction between the one side surface of the test plate and the tip of the crack extending through each of the first test weld metal and the second test weld metal. ) And c ₂ (mm).
t ≧ 50.0 ・ ・ ・ (i)
30.0 ≤ α ₁ ≤ 70.0 ... (ii)
30.0 ≤ α ₂ ≤ 70.0 ・ ・ ・ (iii)
3.0 ≤ d ₁ ≤ t / 3 ... (iv)
3.0 ≤ d ₂ ≤ t / 3 ... (v)
α ₁ −5.0 ≤ β ₁ ≤ α ₁ +5.0 ・ ・ ・ (vi)
α ₂ −5.0 ≦ β ₂ ≦ α ₂ +5.0 ・ ・ ・ (vii)
d ₁ ≤ b ₁ ≤ d ₁ +5.0 ... (viii)
d ₂ ≤ b ₂ ≤ d ₂ +5.0 ... (ix)
c ₁ ≤ b ₁ · tan (β ₁ ) + 10.0 ・ ・ ・ (x)
c ₂ ≤ b ₂・ tan (β ₂ ) + 10.0 ・ ・ ・ (xi)

(2) The plate thickness t (mm) of the joining member satisfies the following equation (xii).
The welded structure according to (1) above.
t> 80.0 ・ ・ ・ (xii)

(3) The yield stress of the joining member is 400 MPa or more and 580 MPa or less, and the tensile strength is 510 MPa or more and 750 MPa or less.
The welded structure according to (1) or (2) above.

(4) The Kca value of the total thickness of the joint member at −10 ° C. is less than ^{8000 N / mm 1.5.}
The welded structure according to any one of (1) to (3) above.

According to the present invention, a welded structure having excellent brittle crack propagation stopping characteristics can be obtained.

It is a perspective view which shows the welded structure which concerns on one Embodiment of this invention. It is a perspective view which shows the welded structure which concerns on other embodiment of this invention. It is a perspective view which shows the welded structure which concerns on other embodiment of this invention. It is sectional drawing of the welded structure. It is a figure for demonstrating the quality evaluation test in this invention. It is sectional drawing of the test body. It is a figure for demonstrating the brittle crack propagation test. It is a figure for demonstrating the shape of the structural model arrest test piece. It is a figure for demonstrating the quality evaluation method of a thick steel plate in an application example. It is sectional drawing of the test body.

As a result of studies by the present inventors to solve the above problems, the following findings have been obtained.

As described above, the structural model arrest test using a large test piece is generally used for the evaluation of the brittle crack propagation stop property of the thick steel sheet. However, if it is possible to evaluate the brittle crack propagation stop characteristics in a medium-sized test using a smaller test piece, it will be easier to select the thick steel sheet used for the welded structure, and excellent brittle crack propagation stop characteristics will be obtained at low cost. It becomes possible to manufacture a welded structure having a brittleness.

The present invention has been made based on the above findings. Hereinafter, the welded structure according to the embodiment of the present invention will be described.

1. 1. Structure of Welded Structure FIG. 1 is a perspective view showing a welded structure according to an embodiment of the present invention. The welded structure 10 according to the present embodiment includes a joining member 11 and a member to be joined 12. The joining member 11 is plate-shaped and has a first surface 11a and a second surface 11b perpendicular to the plate thickness direction. Further, the member to be joined 12 has a plate shape and has a surface to be joined 12a to which the end surface 11c of the member 11 is abutted.

Then, as shown in FIG. 1, the welded structure 10 has a T-joint portion in which the joint member 11 is partially welded to the joined member 12 in a state where the end surface 11c is in contact with the joined surface 12a. .. The welded structure having the T-joint portion includes, for example, a structure having a shape shown in FIGS. 2 and 3 in addition to the T-shaped structure as shown in FIG. Further, the joining member 11 is provided with a groove, and the joining member 11 is joined by groove welding.

In the present invention, a thick-walled joining member is targeted, and specifically, when the plate thickness of the joining member 11 is t (mm), the following equation (i) is satisfied. The plate thickness t (mm) of the joining member 11 preferably satisfies the following equation (xii). The upper limit of t is not particularly specified, but can be, for example, 200 mm, 150 mm, or 120 mm.
t ≧ 50.0 ・ ・ ・ (i)
t> 80.0 ・ ・ ・ (xii)

The plate thickness of the member to be joined is not particularly limited, but like the joint member, it is preferably 50.0 mm or more, and more preferably more than 80.0 mm.

Further, as shown in FIG. 1, the welded structure 10 has a first weld metal 13a formed on the first surface 11a side and a second weld metal 13b formed on the second surface 11b side.

The vicinity of the joint portion of the joint member 11 and the member to be joined 12 will be described in more detail with reference to FIG. FIG. 4 is a cross-sectional view of the welded structure 10 perpendicular to the first surface 11a and the surface to be joined 12a. In FIG. 4, hatching is not provided in order to avoid complicating the drawings.

As shown in FIG. 4, a first weld metal 13a is formed on the first surface 11a side of the joining portion of the joining member 11 and the member to be joined 12. Similarly, the second weld metal 13b is formed on the second surface 11b side.

Here, the crack generated from the member 12 to be joined propagates to the joint member 11 via the first weld metal 13a and the second weld metal 13b. Therefore, it is important to control the shape of the weld metal from the viewpoint of limiting the intrusion region of the crack propagating from the member to be joined 12 to the joint member 11 and ensuring the joint strength.

Specifically, in the first weld metal 13a, in a line L ₁ passing through the toe and the root of the joint member 11 side acute angle alpha ₁ formed by the joining surface 12a _(°) and the second weld metal 13b, joining _{The sharp angle α 2 (°) formed by the line L 2} passing through the toe on the member 11 side and the root and the surface to be welded 12a satisfies the following equations (ii) and (iii), respectively.
30.0 ≤ α ₁ ≤ 70.0 ... (ii)
30.0 ≤ α ₂ ≤ 70.0 ・ ・ ・ (iii)

The joining member 11 side of the toe in the first weld metal 13a, means an intersection _{A 1} between the outer edge and the first surface 11a of the first weld metal 13a. Also, the joining member 11 side of the root of the first weld metal 13a, means an intersection _{B 1} between the outer edge and the end face 11c of the first weld metal 13a. Similarly, the bonding member 11 side of the toe at the second weld metal 13b, means an intersection _{A 2} between the outer edge and the second surface 11b of the second weld metal 13b, the bonding member 11 side in the second weld metal 13b the root mean an intersection _{B 2} between the outer edge and the end face 11c of the second weld metal 13b.

_{Further, the partial penetration d 1} (mm) of the joint in the plate thickness direction of the first weld metal 13a _{and the partial penetration d 2} (mm) of the joint in the plate thickness direction of the second weld metal 13b are the plates of the joining member 11. In relation to the thickness t (mm), the following equations (iv) and (v) are satisfied, respectively.
3.0 ≤ d ₁ ≤ t / 3 ... (iv)
3.0 ≤ d ₂ ≤ t / 3 ... (v)

The boundaries between the first weld metal 13a and the second weld metal 13b and the joining member 11 can be easily visually identified.

2. Quality Evaluation Test According to the research conducted by the present inventors, welding with excellent brittle crack propagation stopping characteristics at low cost by using a thick steel plate that satisfies the predetermined criteria by the medium-sized quality evaluation test described later as a joining member. We have found that a structure can be obtained.

The test method will be described in detail. FIG. 5 is a diagram for explaining the quality evaluation test in the present invention. In the quality evaluation test in the present invention, the following steps (a) to (d) are carried out in order. Each process will be described.

(A) Groove forming step From the thick steel plate used for the joining member 11, it has a first test plate surface 21a and a second test plate surface 21b corresponding to the first surface 11a and the second surface 11b, respectively, and the plate thickness is high. A test plate 21 having t (mm), a width of 240 mm, and a length of 500 mm is collected. That is, the first surface 11a of the joining member 11 is the first test plate surface 21a of the test plate 21, and the second surface 11b of the joining member 11 is the second test plate surface 21b of the test plate 21.

On the surface 21c on one side (upper side in FIG. 5) of the test plate 21 in the width direction, a groove extending in the length direction is formed on the first test plate surface 21a side and the second test plate surface 21b side, respectively. The shape and dimensions of the groove may be appropriately selected so that the shape and dimensions of the weld metal portion formed in the welding step described later satisfy the specified specifications.

(B) Welding Step A run-up plate 22 having a plate thickness of t (mm), a width of 260 mm, and a length of 500 mm is prepared. The material of the approach plate 22 is not particularly limited, and for example, a steel plate embrittled by heat treatment can be used. Further, a notch 22a is formed on one side (upper side in FIG. 5) of the approach plate 22 in the width direction. The shape of the notch 22a is not particularly limited, but the shape shown in FIG. 5 can be used.

Then, in a state where the surface 21c on one side in the width direction of the test plate 21 is in contact with the surface 22b on the other side (lower side in FIG. 5) in the width direction of the approach plate 22, both sides are partially welded to the groove. To form the test body 20. After that, it is preferable to delete the surplus generated by welding. As a result, the test body 20 has a rectangular parallelepiped shape with a plate thickness of t (mm), a width of 500 mm, and a length of 500 mm.

It is important to control the shape of the weld metal formed on the test body 20 in order to evaluate the brittle crack propagation stopping characteristic of the welded structure 10 by the test plate 21 collected from the thick steel plate used for the joint member 11. It becomes. The shape of the weld metal formed on the test body 20 will be described in more detail with reference to FIG. FIG. 6 is a cross-sectional view of the test body 20 perpendicular to the first test plate surface 21a and the other side surface 22b of the approach plate 22. In FIG. 6, hatching is not provided in order to avoid complicating the drawings.

As shown in FIG. 6, the first test weld metal 23a is formed on the first test plate surface 21a side of the joint portion between the test plate 21 and the approach plate 22, and the second test weld is formed on the second test plate surface 21b side. The metal 23b is formed.

The acute angle beta ₁ formed in the first test weld metal 23a, a line M ₁ that passes through the toe and the root of the test plate 21 side and the surface 22b of the other side of the run-up plate 22 _(°) and the second test weld metal _{In 23b, the acute angle β 2 (°) formed by the line M 2} passing through the toe on the test plate 21 side and the root and the surface 22b on the other side of the approach plate 22 is the following equations (vi) and (vii), respectively. I am satisfied.
α ₁ −5.0 ≤ β ₁ ≤ α ₁ +5.0 ・ ・ ・ (vi)
α ₂ −5.0 ≦ β ₂ ≦ α ₂ +5.0 ・ ・ ・ (vii)

The toe of the test plate 21 side in the first test weld metal 23a, means an intersection C ₁ between the outer edge and the first test plate surface 21a of the first test weld metal 23a. Further, the test plate 21 side route in the first test weld metal 23a, means an intersection D ₁ of the and the one side surface 21c of the outer edge and the test plate 21 of the first test weld metal 23a. Similarly, the toe of the test plate 21 side in the second test weld metal 23b, means an intersection C ₂ of the outer edge and the second test plate surface 21b of the second test weld metal 23b, the second test weld metal 23b the test plate 21 side route in means intersection D ₂ between one side surface 21c of the outer edge and the test plate 21 of the second test weld metal 23b.

_{Further, the partial penetration b 1} (mm) of the joint in the plate thickness direction of the first test weld metal 23a _{and the partial penetration b 2} (mm) of the joint in the plate thickness direction of the second test weld metal 23b are as follows (viii). ) And (ix) are satisfied.
d ₁ ≤ b ₁ ≤ d ₁ +5.0 ... (viii)
d ₂ ≤ b ₂ ≤ d ₂ +5.0 ... (ix)

Partial penetration b ₁ of the joint, a first test plate surface 21a, the end portion of the thickness center of the first test weld metal 23a in the thickness direction of the first test plate surface 21a and parallel to and test plate 21 It is the distance from the virtual surface 21f through which it passes. Further, the partial penetration b ₂ of the joint is parallel to the second test plate surface 21b and the second test plate surface 21b, and is the end of the second test weld metal 23b on the plate thickness center side in the plate thickness direction of the test plate 21. It is the distance from the virtual surface 21g passing through the portion.

(C) Brittle crack propagation test process Using the test piece 20, at a test temperature of −10 ° C., a preset allowable stress of the joining member 11 of σ (N / mm ² ) is applied as a test stress. An impact load is applied to the notch 22a provided on the approach plate 22, and a crack is propagated to the test plate 21 via the first test weld metal 23a and the second test weld metal 23b.

As the allowable stress of the preset joining member, for example, when the welded structure is for a ship, the joining member is hatch side combing. Since the allowable stress of hatchside combing is determined by the rules established by the ship classification association, that value may be adopted. The temperature of the test body 20 is uniform at −10 ° C., and the temperature of the approach plate 22 is not particularly specified. Other conditions are not limited as long as the crack extends to the test plate 21, but WES2815 may be compliant.

FIG. 7 is a diagram for explaining a brittle crack propagation test. As shown in FIG. 7, jigs 24a and 24b are joined to both ends of the test body 20 in the length direction by welding, and tensile stress is applied from both sides in the length direction to apply the test stress described above to the test body 20. Can be given.

Further, in this step, since it is necessary to propagate the crack to at least the test plate, it is necessary to select a material so that the crack does not stop at the approach plate or the weld metal when an impact load is applied. ..

(D) Brittle crack measurement step The crack progress state of the test plate 21 after the above steps (a) to (c) are sequentially performed is investigated. _{Specifically, the distance c 1} (mm) in the width direction between the one side surface 21c of the test plate 21 and the tip of the crack that has propagated through each of the first test weld metal 23a and the second test weld metal 23b. ) And c ₂ (mm). Since the position of the crack tip cannot be confirmed as it is after the test, the fracture surface is exposed by forcibly breaking the test piece by applying a load.

_{In the joining member 11 used in the welded structure 10 according to the present invention, c 1} and c ₂ are the following (x) and (xi) in the quality evaluation test in which the steps (a) to (d) described above are sequentially carried out. ) The equation needs to be satisfied. As a result, the welded structure 10 having excellent brittle crack propagation stopping characteristics can be obtained.
c ₁ ≤ b ₁ · tan (β ₁ ) + 10.0 ・ ・ ・ (x)
c ₂ ≤ b ₂・ tan (β ₂ ) + 10.0 ・ ・ ・ (xi)

3. 3. Mechanical Properties of Joining Members There are no particular restrictions on the mechanical properties of the joining members used in the welded structure of the present invention. However, when the welded structure is used in a container ship or the like, the yield stress of the joint member is preferably 400 MPa or more and 580 MPa or less, and the tensile strength is preferably 510 MPa or more and 750 MPa or less. The yield stress of the joining member is more preferably 410 MPa or more and 570 MPa or less, and the tensile strength is more preferably 520 MPa or more and 740 MPa or less.

From the viewpoint of cost, it is preferable to use a joining member having a Kca value of the total thickness at −10 ° C. of ^{less than 8000 N / mm 1.5.} The Kca value can be obtained by a temperature gradient type ESSO test based on the WES2815 standard.

4. Manufacturing method of welded structure The manufacturing method of the welded structure is not particularly limited. For example, a step of selecting a joining member whose evaluation result by a quality evaluation test satisfies the above-mentioned conditions and a step of selecting the joining member to be joined. It can be manufactured by performing a process of welding to a member.

In the welding step, it can be manufactured by welding along the end face of the above-mentioned joint member with the end face of the joint member abutting against the surface to be joined. At this time, the side to be joined of the joining member is grooved. The groove processing may be performed over the entire end face of the joint member, or may be performed only at the joint portion with the member to be joined.

Further, the welding method is not particularly limited, and _{a known method such as CO 2} welding or shielded metal arc welding (SMAW) may be adopted. The amount of heat input is preferably, for example, 0.5 kJ / mm or more and 3.0 kJ / mm or less.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Various steel sheets having a plate thickness t (mm) shown in Table 1 and having a first surface and a second surface orthogonal to the plate thickness direction were prepared. After that, each steel plate has a first test plate surface and a second test plate surface corresponding to the first surface and the second surface, respectively, and the plate thickness is t so that the rolling direction of the steel plate is the length direction. A test plate having a width of (mm), a width of 240 mm, and a length of 500 mm was collected. Then, on one surface in the width direction of the test plate, grooves extending in the length direction were formed on the first test plate surface side and the second test plate surface side, respectively.

Subsequently, a run-up plate having a plate thickness of t (mm), a width of 260 mm, and a length of 500 mm was prepared. As the approach plate, a steel plate embrittled by heating at 1200 ° C. and then air-cooling was used. A notch having the shape shown in FIG. 5 was provided on one side of the approach plate in the width direction. Then, in a state where one surface of the test plate on which the groove was formed was in contact with the other surface in the width direction of the approach plate, both side partial penetration welding was performed on the groove. Welding conditions are as shown in Table 2. In Table 2, "CO ₂ " means CO ₂ welding, and "SMAW" means shielded metal arc welding. After that, the surplus generated by welding was deleted. As a result, a rectangular parallelepiped test piece having a plate thickness of t (mm), a length of 500 mm, and a width of 500 mm was produced.

In the test body, the first test weld metal was formed on the first test plate surface side of the joint portion between the test plate and the approach plate, and the second test weld metal was formed on the second test plate surface side. ^{Then, using each test piece, in a state where σ (N / mm 2} ), which is a preset allowable stress of the joining member, is applied as a test stress at a test temperature of −10 ° C., in the length direction of the approach plate. An impact load was applied to the notch provided at one end of the above, and a crack was propagated to the test plate.

After the test was completed, a load was applied to the test piece and forced fracture was performed to expose the fracture surface, and the progress of cracks that rushed into the test plate was investigated. Then, a cross section of the weld metal (first test weld metal and second test weld metal) of the test plate and the approach plate was cut out at a position 200 mm to the left and right from the center position in the load direction of the test piece. Photographs of the cross sections of the welded joints at these two locations were taken with a digital camera, the shape of the weld metal was measured from the photographic images, and the average value of the measurement results at the two locations was calculated. The results are also shown in Table 2.

Subsequently, the No. 4 tensile test piece described in JIS Z 2241: 2011 is collected from a position 1/4 of the thickness of each steel plate in a direction perpendicular to the rolling direction, and a tensile test is performed in accordance with JIS Z 2241: 2011. Yield stress (YS), tensile strength (TS) and total elongation (EL) were measured.

Further, the Kca value of the total thickness of each steel sheet at −10 ° C. was determined by a temperature gradient type ESSO test based on the WES2815 standard. The results are also shown in Table 1.

Then, the above-mentioned various steel plates were used as a test plate (joining member 41), and the structural model arrest test piece shown in FIG. 8 was prepared and tested. A welded joint in which a steel plate having a plate thickness of 100 mm _{was joined by CO 2} welding was used as a run-up welded joint (member to be joined 42), and a _{welded structure 40 was manufactured by CO 2} welding or shielded metal arc welding (SMAW) under the conditions shown in Table 3. ..

After that, the notch 46b was introduced into the fusion line portion 46a of the welded structure 40. Then, the welded structure 40 is cooled to the ship design temperature of −10 ° C., the allowable stress of the joining member 41, σ (N / mm ² ), is loaded as a test stress, and only the vicinity of the notch portion is about −50 ° C. The notch was rapidly cooled and a blow was applied to the notch through a wedge to generate and propagate brittle cracks.

Structural model after the test Using the arrest test piece, one side (first surface side) and the other side (first surface side) and the other side (first surface side) of the joining member and the member to be joined are located 250 mm to the left and right from the center position in the load direction of the test piece. A cross section of the weld metal (first weld metal and second weld metal) on the two surface sides) was cut out. Photographs of the cross sections of these two welded joints were taken with a digital camera, the shape of the weld metal was measured from the photographic images, and the average value of the measurement results at the two locations was used.

Table 3 also shows the measured shape of the weld metal and the results of the test using the above-mentioned structural model arrest test piece. When the brittle crack stopped at the test plate, it was judged as "stop", and when the test plate was broken, it was judged as "propagation".

As is clear from Table 3, when a joining member satisfying the provisions of the present invention was used, excellent brittle crack propagation stopping characteristics were obtained, whereas in a comparative example not satisfying the provisions of the present invention. When the joining member was used, the brittle crack propagated to the joining member.

5. Quality Evaluation Method for Thick Steel Sheets As described above, in the welded structure 10 according to the present invention, the joint member 11 is evaluated by a quality evaluation test under the above-mentioned conditions. The quality evaluation test can be applied as a quality evaluation method for thick steel sheets. The quality evaluation method of the thick steel sheet as an application example can be expressed by the following (Appendix 1) and (Appendix 2).

(Appendix 1)
In a welded structure having a T-joint portion in which the end face of the plate-shaped joint member is in contact with the joint surface of the plate-shaped joint member and the joint member is partially welded to the joint member on both sides. It is a quality evaluation method for a thick steel plate used and used as a joining member.
The joining member has a first surface and a second surface perpendicular to the plate thickness direction of the joining member.
In the cross section perpendicular to the first surface and the surface to be joined,
The plate thickness t (mm) of the joining member,
_{In the first weld metal formed on the first surface side, the acute angle α 1} (°) formed by the line passing through the toe and the root on the joining member side and the surface to be joined, and the joint in the plate thickness direction. Partial penetration d ₁ (mm), as well as
_{In the second weld metal formed on the second surface side, the acute angle α 2} (°) formed by the line passing through the toe and the root on the joining member side and the surface to be joined, and the joint in the plate thickness direction. The partial penetration d ₂ (mm) of the above satisfies the following equations (i) to (v).
The following steps (a) to (d) are provided.
Quality evaluation method for thick steel sheets.
(A) With respect to a test plate having a first test plate surface and a second test plate surface corresponding to the first surface and the second surface, respectively, and having a plate thickness of t (mm), the test plate has a thickness of t (mm). A step of forming a groove extending in the length direction on one side surface in the width direction on the first test plate surface side and the second test plate surface side, respectively.
(B) A run-up plate having a plate thickness of t (mm) and provided with a notch on one side in the width direction is prepared, and the one-sided surface of the test plate is formed on the one-side surface of the run-up plate in the width direction. In a state of being in contact with the other side surface, both sides of the groove are subjected to partial penetration welding.
A toe and a root on the test plate side of the first test weld metal formed on the surface of the first test plate in a cross section perpendicular to the surface of the first test plate and the other surface of the run-up plate. _{The sharp angle β 1} (°) formed by the line passing through the runway plate and the other side surface of the run-up plate, _{the partial penetration b 1} (mm) of the joint in the plate thickness direction, and the second test plate surface side. _{In the formed second test weld metal, the sharp angle β 2} (°) formed by the line passing through the toe on the test plate side and the root and the other surface of the run-up plate, and the joint in the plate thickness direction. A step of forming a test piece in which the partial penetration b ₂ (mm) of the above satisfies the following formulas (vi) to (ix) and the plate thickness is t (mm).
(C) A step of applying an impact load to the notch of the approach plate using the test body to propagate a crack to the test plate via the first test weld metal and the second test weld metal.
(D) A step of determining whether or not the thick steel sheet has excellent brittle crack propagation stopping characteristics based on the crack progress.
t ≧ 50.0 ・ ・ ・ (i)
30.0 ≤ α ₁ ≤ 70.0 ... (ii)
30.0 ≤ α ₂ ≤ 70.0 ・ ・ ・ (iii)
3.0 ≤ d ₁ ≤ t / 3 ... (iv)
3.0 ≤ d ₂ ≤ t / 3 ... (v)
α ₁ −5.0 ≤ β ₁ ≤ α ₁ +5.0 ・ ・ ・ (vi)
α ₂ −5.0 ≦ β ₂ ≦ α ₂ +5.0 ・ ・ ・ (vii)
d ₁ ≤ b ₁ ≤ d ₁ +5.0 ... (viii)
d ₂ ≤ b ₂ ≤ d ₂ +5.0 ... (ix)

(Appendix 2)
In the step (d), in the width direction, the one side surface of the test plate and the tip of the crack that has propagated through each of the first test weld metal and the second test weld metal. When the distances are c ₁ (mm) and c ₂ (mm), and c ₁ and c ₂ satisfy the following equations (x) and (xi), the thick steel sheet is excellent in brittle crack propagation stopping property. To judge,
The quality evaluation method for thick steel sheets according to Appendix 1.
c ₁ ≤ b ₁ · tan (β ₁ ) + 10.0 ・ ・ ・ (x)
c ₂ ≤ b ₂・ tan (β ₂ ) + 10.0 ・ ・ ・ (xi)

The quality evaluation method of the thick steel sheet in the application example will be described. The above quality evaluation method is a method for evaluating the quality of a thick steel plate used for a welded structure and serving as a joining member. Since the configuration of the welded structure to be evaluated for quality is as described above, the description thereof will be omitted.

FIG. 9 is a diagram for explaining a quality evaluation method for a thick steel plate in an application example. The above quality evaluation method includes the following steps (a) to (d). Each process will be described.

(A) Groove forming step A test plate 31 is collected from a thick steel plate. The test plate 31 has a first test plate surface 31a and a second test plate surface 31b corresponding to the first surface 11a and the second surface 11b of the joining member 11, respectively. That is, the first surface 11a of the joining member 11 is the first test plate surface 31a of the test plate 31, and the second surface 11b of the joining member 11 is the second test plate surface 31b of the test plate 31.

The plate thickness of the test plate 31 is the same as the plate thickness of the thick steel plate serving as the joining member 11, that is, t (mm). The width and length of the test plate 31 are not particularly limited, but the width is preferably 150 mm or more and 1000 mm or less, and the length is preferably 300 mm or more and 2000 mm or less. If all of them are too small, it will be difficult to evaluate the quality accurately, and if they are too large, it may not be possible to evaluate the quality at low cost.

On the surface 31c on one side (upper side in FIG. 9) of the test plate 31 in the width direction, a groove extending in the length direction is formed on the first test plate surface 31a side and the second test plate surface 31b side, respectively. The shape and dimensions of the groove may be appropriately selected so that the shape and dimensions of the weld metal portion formed in the welding step described later satisfy the specified specifications.

(B) Welding process A run-up plate 32 having the same thickness and length as the test plate 31 is prepared. That is, the thickness of the approach plate 32 is t (mm). Since the length of the approach plate 32 is the same as the length of the test plate 31, it is preferably 300 mm or more and 2000 mm or less. Further, the width of the approach plate 32 is preferably 150 mm or more and 1600 mm or less. If the width of the approach plate 32 is too small, there is a risk that sufficient driving force will not be obtained when a crack enters the test plate 31 from the approach plate 32, and if it is too large, quality evaluation at low cost will not be possible. Because there is.

The material of the approach plate 32 is not particularly limited. For example, a steel plate embrittled by heat treatment, a butt weld joint in which a crack growth region is a welded portion, or a crack growth region is embrittled by electron beam welding. A steel plate or the like can be used. Further, a notch 32a is formed on one side (upper side in FIG. 9) of the approach plate 32 in the width direction. The shape of the notch 32a is not particularly limited, but the shape shown in FIG. 9 can be used.

Further, side grooves as shown in FIG. 9 may be formed on one or both of the pair of surfaces orthogonal to the thickness direction of the approach plate 32. By having the side groove, the crack grows along the side groove and easily enters the test plate 31. In the configuration shown in FIG. 9, the side grooves are formed in all lengths from one side to the other side in the width direction of the approach plate 32, but may be formed only in a part thereof.

Then, in a state where the surface 31c on one side in the width direction of the test plate 31 is in contact with the surface 32b on the other side (lower side in FIG. 9) in the width direction of the approach plate 32, both side partial penetration welding is performed on the groove. To form the test body 30. After that, it is preferable to delete the surplus generated by welding. As a result, the test body 30 becomes a rectangular parallelepiped having a plate thickness of t (mm).

The length and width of the test body 30 are not particularly limited, and are determined by the respective dimensions of the test plate 31 and the approach plate 32. Since the width of the test body 30 is the total width of the test plate 31 and the approach plate 32, it is preferably 300 mm or more and 2600 mm or less. Further, since the length of the test body 30 is the same as the length of the test plate 31 and the approach plate 32, it is preferably 300 mm or more and 2000 mm or less.

Further, the width of the test plate 31 and the width of the approach plate 32 are preferably about the same, the width of the approach plate 32 is L (mm), and the width of the test body 30, that is, the test plate 31 and the approach plate 32. When the total width is W (mm), it is preferable that 0.4 ≦ L / W ≦ 0.7 is satisfied.

It is important to control the shape of the weld metal formed on the test body 30 in order to evaluate the brittle crack propagation stopping characteristic of the welded structure 10 by the test plate 31 collected from the thick steel plate used for the joint member 11. It becomes. The shape of the weld metal formed on the test body 30 will be described in more detail with reference to FIG. FIG. 10 is a cross-sectional view of the test body 30 perpendicular to the first test plate surface 31a and the other side surface 32b of the approach plate 32. In FIG. 10, hatching is not provided in order to avoid complicating the drawings.

As shown in FIG. 10, the first test weld metal 33a is formed on the first test plate surface 31a side of the joint portion between the test plate 31 and the approach plate 32, and the second test welding is performed on the second test plate surface 31b side. The metal 33b is formed.

The acute angle beta ₁ formed in the first test weld metal 33a, a line M ₁ that passes through the toe and the root of the test plate 31 side and the surface 32b of the other side of the run-up plate 32 _(°) and the second test weld metal _{In 33b, the acute angle β 2 (°) formed by the line M 2} passing through the toe on the test plate 31 side and the root and the surface 32b on the other side of the approach plate 32 is the following equations (vi) and (vii), respectively. I am satisfied.
α ₁ −5.0 ≤ β ₁ ≤ α ₁ +5.0 ・ ・ ・ (vi)
α ₂ −5.0 ≦ β ₂ ≦ α ₂ +5.0 ・ ・ ・ (vii)

The toe of the test plate 31 side in the first test weld metal 33a, means an intersection C ₁ between the outer edge and the first test plate surface 31a of the first test weld metal 33a. Further, the test plate 31 side route in the first test weld metal 33a, means an intersection D ₁ of the and the one side surface 31c of the outer edge and the test plate 31 of the first test weld metal 33a. Similarly, the toe of the test plate 31 side in the second test weld metal 33b, means an intersection C ₂ of the outer edge and the second test plate surface 31b of the second test weld metal 33b, the second test weld metal 33b the test plate 31 side route in means intersection D ₂ between one side surface 31c of the outer edge and the test plate 31 of the second test weld metal 33b.

_{Further, the partial penetration b 1} (mm) of the joint in the plate thickness direction of the first test weld metal 33a _{and the partial penetration b 2} (mm) of the joint in the plate thickness direction of the second test weld metal 33b are as follows (viii). ) And (ix) are satisfied.
d ₁ ≤ b ₁ ≤ d ₁ +5.0 ... (viii)
d ₂ ≤ b ₂ ≤ d ₂ +5.0 ... (ix)

Partial penetration b ₁ of the joint, a first test plate surface 31a, the end portion of the thickness center of the first test weld metal 33a in the thickness direction of a and the test plate 31 parallel to the first test plate surface 31a It is the distance from the virtual surface 31f through which it passes. Further, the partial penetration b ₂ of the joint is parallel to the second test plate surface 31b and the second test plate surface 31b, and is the end of the second test weld metal 33b on the plate thickness center side in the plate thickness direction of the test plate 31. It is a distance from a virtual surface 31g passing through the portion.

(C) Brittle crack propagation test process Using the test piece 30, an impact load is applied to the notch 32a of the approach plate 32 at a predetermined test temperature in a state where a predetermined test stress is applied, and the crack propagates to the test plate 31. Let me. The test temperature is not particularly limited and is preferably set to the operating temperature or lower of the welded structure 10, for example, −10 ° C. or lower. Further, the test stress applied to the test body 30 is not particularly limited, and for example, σ (N / mm ² ), which is a preset allowable stress of the joining member 11, may be set as the test stress.

As the allowable stress of the preset joining member, for example, when the welded structure is for a ship, the joining member is hatch side combing. Since the allowable stress of hatchside combing is determined by the rules established by the ship classification association, that value may be adopted. The temperature of the test piece is made uniform at a predetermined test temperature, and the temperature of the approach plate is not particularly specified. For other conditions, it is preferable to comply with WES2815.

Further, in this step, since it is necessary to propagate the crack to at least the test plate, it is necessary to select a material so that the crack does not stop at the approach plate or the weld metal when an impact load is applied. ..

(D) Judgment step The state of crack growth is investigated for the test plate 31 after the above steps (a) to (c) are sequentially performed. Then, based on the investigation result, it is determined whether or not the thick steel sheet has excellent brittle crack propagation stopping characteristics.

The specific determination method is not particularly limited, but for example, the surface 31c on one side of the test plate 31 and the tip of the crack that has propagated through each of the first test weld metal 33a and the second test weld metal 33b. When the distances c ₁ (mm) and c ₂ (mm) in the length direction are measured and the distances c ₁ and c ₂ satisfy the following equations (x) and (xi), the thickness of the joining member is obtained. It can be determined that the steel plate has excellent brittle crack propagation stopping characteristics.
c ₁ ≤ b ₁ · tan (β ₁ ) + 10.0 ・ ・ ・ (x)
c ₂ ≤ b ₂・ tan (β ₂ ) + 10.0 ・ ・ ・ (xi)

As described above, according to the present invention, it is possible to obtain a welded structure having excellent brittle crack propagation stopping characteristics.

10 Welded structure 11 Joint member 11a First surface 11b Second surface 11c End surface 11f to 11i Virtual surface 12 Joint member 12a Joint surface 13 Weld metal 13a First weld metal 13b Second weld metal 20 Specimen 21 Test Plate 21a 1st test plate surface 21b 2nd test plate surface 21c One side surface 21f, g Virtual surface 22 Run-up plate 22a Notch 22b Other side surface 23 Test weld metal 23a 1st test weld metal 23b 2nd test weld Metal 24a, b Jig 30 Specimen 31 Test plate 31a 1st test plate surface 31b 2nd test plate surface 31c One side surface 31f, g Virtual surface 32 Run-up plate 32a Notch 32b Other side surface 33 Test weld metal 33a 1st test weld metal 33b 2nd test weld metal 40 Welded structure 41 Joining member 42 Joined member 43 Welding metal 46a Fusion line part 46b Notch

Claims (4)

A welded structure having a T-joint portion in which the joint member is partially welded to the joint member on both sides in a state where the end surface of the plate-shaped joint member is in contact with the joint surface of the plate-shaped joint member. There,
The joining member has a first surface and a second surface perpendicular to the plate thickness direction of the joining member.
In the cross section perpendicular to the first surface and the surface to be joined,
The plate thickness t (mm) of the joining member,
_{In the first weld metal formed on the first surface side, the acute angle α 1} (°) formed by the line passing through the toe and the root on the joining member side and the surface to be joined, and the joint in the plate thickness direction. Partial penetration d ₁ (mm), as well as
_{In the second weld metal formed on the second surface side, the acute angle α 2} (°) formed by the line passing through the toe and the root on the joining member side and the surface to be joined, and the joint in the plate thickness direction. The partial penetration d ₂ (mm) of the above satisfies the following equations (i) to (v).
The joining member, in the quality evaluation test to carry out the following processes (a) ~ (d) in this order, but the following c ₁ and c ₂ are to satisfy the following (x) and (xi) equation,
Welded structure.
(A) A test plate having a first test plate surface and a second test plate surface corresponding to the first surface and the second surface, respectively, having a plate thickness of t (mm), a width of 240 mm, and a length of 500 mm. On the other hand, on one side surface in the width direction of the test plate, a step of forming a groove extending in the length direction on the first test plate surface side and the second test plate surface side, respectively.
(B) A run-up plate having a plate thickness of t (mm), a width of 260 mm, and a length of 500 mm and having a notch on one side in the width direction is prepared, and the one side surface of the test plate is formed. In a state of being in contact with the other side surface of the approach plate in the width direction, both side partial penetration welding is performed on the groove.
A toe and a root on the test plate side of the first test weld metal formed on the surface of the first test plate in a cross section perpendicular to the surface of the first test plate and the other surface of the run-up plate. _{The sharp angle β 1} (°) formed by the line passing through the runway plate and the other side surface of the run-up plate, _{the partial penetration b 1} (mm) of the joint in the plate thickness direction, and the second test plate surface side. _{In the formed second test weld metal, the sharp angle β 2} (°) formed by the line passing through the toe on the test plate side and the root and the other surface of the run-up plate, and the joint in the plate thickness direction. A step of forming a test piece having a plate thickness of t (mm), a width of 500 mm, and a length of 500 mm, in which the partial penetration b _{2 (mm) of the above satisfies the following equations (vi) to (ix).}
(C) Using the test piece, the approach plate is subjected to a test stress of ^{σ (N / mm 2} ), which is a preset allowable stress of the joining member, at a test temperature of −10 ° C. A step of applying an impact load to the notch to propagate a crack to the test plate via the first test weld metal and the second test weld metal.
_{(D) The distance c 1} (mm) in the width direction between the one side surface of the test plate and the tip of the crack extending through each of the first test weld metal and the second test weld metal. ) And c ₂ (mm).
t ≧ 50.0 ・ ・ ・ (i)
30.0 ≤ α ₁ ≤ 70.0 ... (ii)
30.0 ≤ α ₂ ≤ 70.0 ・ ・ ・ (iii)
3.0 ≤ d ₁ ≤ t / 3 ... (iv)
3.0 ≤ d ₂ ≤ t / 3 ... (v)
α ₁ −5.0 ≤ β ₁ ≤ α ₁ +5.0 ・ ・ ・ (vi)
α ₂ −5.0 ≦ β ₂ ≦ α ₂ +5.0 ・ ・ ・ (vii)
d ₁ ≤ b ₁ ≤ d ₁ +5.0 ... (viii)
d ₂ ≤ b ₂ ≤ d ₂ +5.0 ... (ix)
c ₁ ≤ b ₁ · tan (β ₁ ) + 10.0 ・ ・ ・ (x)
c ₂ ≤ b ₂・ tan (β ₂ ) + 10.0 ・ ・ ・ (xi) The plate thickness t (mm) of the joining member satisfies the following equation (xii).
The welded structure according to claim 1.
t> 80.0 ・ ・ ・ (xii) The yield stress of the joining member is 400 MPa or more and 580 MPa or less, and the tensile strength is 510 MPa or more and 750 MPa or less.
The welded structure according to claim 1 or 2. The Kca value of the total thickness of the joining member at −10 ° C. is less than ^{8000 N / mm 1.5.}
The welded structure according to any one of claims 1 to 3.

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