CN111032266B

CN111032266B - Welded structure

Info

Publication number: CN111032266B
Application number: CN201880054149.4A
Authority: CN
Inventors: 大川铁平; 岛田祐介; 小田直树
Original assignee: Nippon Steel and Sumitomo Metal Corp
Current assignee: Nippon Steel Corp
Priority date: 2018-05-18
Filing date: 2018-12-26
Publication date: 2020-11-24
Anticipated expiration: 2038-12-26
Also published as: KR102119175B1; WO2019220681A1; KR20200021548A; CN111032266A

Abstract

The welded structure (10) has a T-shaped joint part formed by fusion-welding both side portions of a joining member (11) to a member (12) to be joined in a state where an end surface (11c) of the joining member (11) is in contact with a surface (12a) to be joined of the member (12), wherein the length of the joining member (11) in a direction perpendicular to the end surface (11c) is set to H (mm), and the allowable stress of the joining member (11) set in advance is set to sigma (N/mm)²) In the case of (a), a non-ductile transition temperature NDTT (DEG C) obtained by an NRL drop weight test using a test piece of type P3 extracted from a 1mm depth position of a surface (12a) to be joined of a member (12) to be joined satisfies [ NDTT ≦ 360.4-46.8 × ln { σ (π H) ]^0.5}]。

Description

Welded structure

Technical Field

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

Background

In a large container ship on which a large amount of cargo is loaded, a large opening (hatch) for loading and unloading the cargo is formed in an upper deck (upper deck). Further, in order to prevent inflow of seawater and the like, a hatch side surrounding wall is provided on the upper deck so as to surround the hatch. The upper deck and the hatch side wall are both formed by welding a plurality of steel plates. Furthermore, the hatch side walls are welded to the upper deck.

When a large container ship such as that described above is sailed on the sea, a load (longitudinal bending load) that bends the entire ship body is applied to the ship body by waves. In order to sufficiently secure the strength (longitudinal bending strength) of the hull against such loads, high-strength thick steel plates are used for the upper deck and the hatch side walls.

Further, as described above, each of the trunk side surrounding wall and the upper deck has a structure in which a plurality of steel plates are welded. In other words, a plurality of welding portions for welding the steel plates to each other are formed on the trunk-side surrounding wall and the upper deck. Cracks generated in the welded portion are likely to propagate along the welded portion. Therefore, for example, when a crack is generated in the welded portion of the hatch side surrounding wall, the crack may propagate toward the upper deck side along the welded portion, and the crack propagating may propagate to the welded portion of the upper deck. Therefore, in order to sufficiently improve the strength of the hull, the trunk-side surrounding wall and the upper deck need to have a property (brittle crack propagation stopping property) capable of stopping the propagation of the crack.

For example, patent documents 1 and 2 disclose welded structures having brittle crack propagation stopping properties.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2007-326147

Patent document 2: japanese patent No. 5365761

Disclosure of Invention

Problems to be solved by the invention

However, in order to stop the propagation of a crack which is generated in the side surrounding wall of the hatch and propagates toward the upper deck side, it is known that it is necessary to use, for example, a Kca value of 6000N/mm at-10 ℃ as an index of brittle crack propagation stopping characteristics for these members^1.5The above thick steel plate.

However, there is a problem that it is difficult to stably manufacture such a thick steel plate having a high brittle crack propagation stop characteristic, both from a technical point of view and from a cost point of view. Therefore, it is necessary to obtain a welded structure having excellent brittle crack propagation stopping properties at low cost by a more rational method.

The present invention has been made to solve the above problems, and an object thereof is to provide a welded structure having excellent brittle crack propagation stopping properties.

Means for solving the problems

The present invention is mainly directed to the welded structure described below.

(1) A welded structure having a T-shaped joint portion formed by fusion-welding both side portions of a plate-shaped joining member to a surface to be joined of the plate-shaped joining member in a state where an end surface of the joining member is in contact with the surface to be joined of the plate-shaped joining member, wherein,

the length of the joint member in the direction perpendicular to the end faces is H (mm), and the allowable stress of the joint member set in advance is sigma (N/mm)²) In the case of (a) in (b),

the non-ductility transition temperature NDTT (c) obtained by an NRL drop weight test using a type P3 test piece specified by ASTM E208, which is extracted from a 1mm depth position of the surfaces to be joined of the joined members and whose thickness direction coincides with the plate thickness direction of the joined members, satisfies the following expression (i).

NDTT≤360.4－46.8×ln{σ(πH)^0.5}···(i)

(2) The welded structure according to the above (1), wherein the plate thickness t (mm) of the members to be joined satisfies the following expression (ii).

t≥50.0···(ii)

(3) The welded structure according to the above (1) or (2), wherein a plate thickness t (mm) of the members to be joined satisfies the following expression (iii).

t＞80.0···(iii)

(4) The welded structure according to any one of the above (1) to (3), wherein the yield stress of the members to be joined is 400 to 580MPa, and the tensile strength is 510 to 750 MPa.

(5) The welded structure according to any one of the above (1) to (4), wherein the Kca value of the joined members is less than 6000N/mm in thickness at-10 ℃^1.5。

ADVANTAGEOUS EFFECTS OF INVENTION

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

Drawings

Fig. 1 is a perspective view showing a welded structure according to an embodiment of the present invention.

Fig. 2 is a perspective view showing a welded structure according to another embodiment of the present invention.

Fig. 3 is a perspective view showing a welded structure according to another embodiment of the present invention.

Fig. 4 is a diagram for explaining the shape of the structure model crack arrest test body.

Detailed Description

The present inventors have made studies to solve the above problems, and as a result, have found the following findings.

As described above, in order to improve the brittle crack propagation stopping property over the entire thickness of the member used for the welded structure, it is necessary to use, for example, a Kca value of 6000N/mm^1.5The above thick-walled steel sheet.

However, for example, when a crack propagates from the hatch side surrounding wall toward the upper deck side, the crack can be stopped from propagating as long as the brittle crack propagation stopping property of the surface layer region of the upper deck into which the crack is to enter can be improved in accordance with the height and allowable stress of the hatch side surrounding wall. As a result, the brittle crack propagation stop characteristic of the entire welded structure can be improved at low cost.

The present invention has been completed based on the above findings. A welded structure according to an embodiment of the present invention will be described below.

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 of 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 1 st surface 11a and a 2 nd surface 11b perpendicular to the plate thickness direction. The joined member 12 is plate-shaped and has a joined surface 12a against which the end surface 11c of the joined member 11 abuts.

As shown in fig. 1, the welded structure 10 has a T-shaped joint portion formed by fusion-welding both side portions of the joining member 11 to the joined member 12 in a state where the end surface 11c is in contact with the joined surface 12 a. In the present embodiment, the welded structure 10 includes the 1 st welded portion 13a formed on the 1 st surface 11a side and the 2 nd welded portion 13b formed on the 2 nd surface 11b side. The welded structure having the T-shaped joint portion described above includes, for example, a structure having a shape shown in fig. 2 and 3 in addition to the T-shaped structure shown in fig. 1.

The joining member 11 and the member to be joined 12 may be joined by fillet welding, but from the viewpoint of the joining strength, it is preferable that the joining member 11 is provided with a groove and is joined by groove welding.

For example, when the welded structure 10 is applied to a container ship or the like, thick members to be joined are targeted. Specifically, when the plate thickness of the joined member 12 is t (mm), the following expression (ii) is preferably satisfied, and the following expression (iii) is more preferably satisfied.

t≥50.0···(ii)

t＞80.0···(iii)

The plate thickness of the joining member 11 is also not particularly limited, but is preferably 50.0mm or more, and more preferably greater than 80.0mm, as in the joined member 12.

2. Non-ductile transition temperature of joined members

As described above, in order to improve the brittle crack propagation stopping property over the entire thickness of the members to be joined, it is necessary to use, for example, a Kca value of 6000N/mm^1.5The above steel sheets have a problem that it is difficult to secure a steel sheet having such characteristics as a member to be joined. However, at least the height of the joint member and the expected allowable stress can be reducedThe brittle crack propagation stop property at the joining member side surface layer portion of the joined member is high, whereby the propagation of the crack is stopped.

That is, the non-ductile transition temperature of the surface layer portion of the joined member can be controlled in accordance with the height of the joining member and the allowable stress of the joining member set in advance, whereby the propagation of the crack can be stopped. Specifically, the higher the height of the joining member, the higher the allowable stress of the joining member, and the more easily the crack propagates, so it is necessary to lower the non-ductile transition temperature of the surface layer portion.

Therefore, the length of the joint member 11 in the direction perpendicular to the end face 11c is h (mm), and the allowable stress of the joint member 11 is σ (N/mm)²) In the case of (2), it is necessary that the non-ductile transition temperature NDTT (c) obtained by an NRL drop weight test using a test piece of type P3 defined by ASTM E208 extracted from a 1mm depth position of the surface to be bonded 12a satisfies the following expression (i).

NDTT≤360.4－46.8×ln{σ(πH)^0.5}···(i)

The NDTT measuring method is explained in detail. First, a test piece of type P3 defined by ASTM E208 was extracted from the surface to be bonded 12 a. The test piece of type P3 is a test piece having a length of 130mm, a width of 50mm and a thickness of 16 mm. At this time, after the surface to be bonded 12a was shaved by 1mm, the test piece was extracted so that the thickness direction thereof coincides with the plate thickness direction of the surface to be bonded 12 a. That is, the test piece is extracted from the region from the 1mm to 17mm depth position of the surface to be bonded 12 a.

As described later, the test was performed so that cracks were generated on the surface of the test piece perpendicular to the longitudinal direction. In the welded structure, cracks occur in the surfaces perpendicular to the extending direction of the 1 st welded part 13a and the 2 nd welded part 13 b. Therefore, the test piece is extracted so that the longitudinal direction of the test piece coincides with the extending direction of the welded portion of the welded structure.

Thereafter, the above test piece was used to carry out an NRL drop weight test according to ASTM E208. Specifically, first, a weld bead extending in a direction parallel to the longitudinal direction of the test piece is formed on the surface of the test piece on the front side of the joined member perpendicular to the thickness direction. In this case, a welding material having a low toughness as defined in ASTM E208 was used as the welding material. The length of the weld bead is adjusted to be in the range of 60mm to 70mm, and the width is adjusted to be in the range of 12mm to 16 mm. Then, a notch parallel to the width direction of the test piece was formed in the weld bead. In this case, the width of the notch is 1.5mm or less, and the distance between the bottom of the notch and the test piece is adjusted to a range of 1.8mm to 2.0 mm.

Then, the surface of the test piece on which the weld bead was formed was faced downward and both ends in the longitudinal direction of the test piece were supported, and then an impact bending load by a drop weight was applied to the surface on the side opposite to the surface on which the weld bead was formed. Then, the propagation state of the brittle crack generated from the notch to the test piece was examined to determine Break (crack propagation) or No Break (crack propagation free). When a brittle crack generated from the notch propagates on the surface of the test piece in the width direction of the test piece and reaches the end, the test result is judged as "Break" (crack propagation is present). When the crack did not reach the end in the width direction, the test result was judged to be No Break (No crack propagation).

In the drop weight test described above, the test temperature was changed at 5 ℃ intervals from the condition of, for example, -100 ℃ using each of the two test pieces (decrease by 5 ℃ in the case of No Break, and increase by 5 ℃ in the case of Break), and the temperature 5 ℃ lower than the lowest test temperature at which No Break was obtained was set as the non-ductile transition temperature for both test pieces.

In addition, as the allowable stress of the above-described joint member set in advance, for example, in the case where the welded structure is used for a ship, the joint member becomes a hatch side surrounding wall. Since the allowable stress of the trunk side surrounding wall is determined according to the standard determined by the classification society, this value may be adopted.

3. Mechanical properties of joined members

The mechanical properties of the members to be joined used in the welded structure of the present invention are not particularly limited. However, when a welded structure is used in a container ship or the like, the yield stress of the joined member to be the upper deck is preferably 400 to 580MPa, and the tensile strength is preferably 510 to 750 MPa. The yield stress of the members to be joined is more preferably 410MPa to 570MPa, and the tensile strength is more preferably 520MPa to 740 MPa.

As described above, in the present invention, even if the members to be joined are not excellent in brittle crack propagation stop characteristics over the entire thickness, crack propagation can be stopped. Therefore, from the viewpoint of technique and cost, it is preferable to use a Kca value of less than 6000N/mm at-10 ℃ through the thickness^1.5The joined member of (1). The Kca value can be obtained by a temperature gradient-type ESSO test conforming to WES2815 standard.

Specifically, a large test piece having a size of about 500mm × 500mm × plate thickness and a relatively large overall thickness is produced, and a V-shaped notch is formed at an end of the test piece. A temperature gradient is applied to the test piece, and the V-shaped notch is loaded with an impact load by means of a wedge, thereby artificially generating brittle cracks. The Kca value is calculated from the stress applied to the test body, the temperature at the position where propagation of the brittle crack stops, and the length of the crack. The test was conducted by changing the temperature gradient condition and the load condition, and the relationship between the crack stop temperature and the Kca value was obtained, thereby obtaining the Kca value at-10 ℃.

4. Method for manufacturing welded structure

The method for producing the welded structure is not particularly limited, and for example, the welded structure can be produced by performing a step of sorting the members to be joined whose surface layer portion has a non-ductile transition temperature satisfying the above-described conditions, and a step of welding the joining member to the above-described members to be joined.

In the welding step, the end face of the joining member can be welded along the end face in a state where the end face is butted against the surface to be joined of the members to be joined. In this case, it is desirable to perform groove processing on the joined member side of the joining member in advance. The entire end surface of the joining member may be beveled, but only the joint portion to be joined to the member to be joined may be beveled.

Further, the welding method is not particularly limited eitherBy using CO₂A known method such as welding or arc welding (SMAW) may be used. The heat input amount is preferably set to, for example, 0.5kJ/mm to 3.0 kJ/mm.

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples.

Examples

After various steel sheets having thicknesses shown in table 1 were prepared, the non-ductile transition temperature at the surface layer portion of one side surface (bonded surface) was examined for each steel sheet. Specifically, after the joint surface was cut to 1mm, a type P3 test piece defined by ASTM E208 was extracted so that the thickness direction of the test piece coincides with the plate thickness direction of the steel plate. Then, the test piece was subjected to an NRL drop weight test in accordance with ASTM E208 to determine the non-ductile transition temperature NDTT (. degree.C.).

Next, a No. 4 tensile test piece described in JISZ 2241 was extracted from the 1/4 position of the thickness of each steel sheet in the direction perpendicular to the rolling direction, and a tensile test was performed in accordance with JIS Z2241 to measure the Yield Stress (YS), the Tensile Strength (TS), and the total Elongation (EL).

Then, the Kca value of the entire thickness at-10 ℃ of each steel sheet was determined by the temperature gradient ESSO test conforming to WES2815 standard. These results are shown in table 1.

[ Table 1]

TABLE 1

Thereafter, the various steel sheets described above were used as test sheets (joined members 12), and a structural model crack arrest test body shown in fig. 4 was produced and tested. Will have the height H (mm) shown in Table 2 and pass through CO₂A welded joint obtained by welding steel plates 100mm thick was treated as a flow-through welded joint (Japanese: flux-assisted fusion hand) (joint member 11) by CO under the conditions shown in Table 2₂The welded structure 10 is manufactured by welding or arc welding (SMAW). At this time, the joint member 11 is provided with two pieces having a depth of 1/3 of the plate thicknessThe side bevel is used to join the joining member 11 and the member to be joined 12 by bevel welding.

[ Table 2]

TABLE 2

NDTT≤360.4-46.8×ln(σ(TTH)^0.5)...(i)

Then, the notch 16b is provided in the weld line portion 16a of the welded structure 10. Then, the welded structure 10 was cooled to-10 ℃ which is the ship design temperature, and loaded with a test stress corresponding to the allowable stress σ of the joining member 11 shown in table 2, and only the vicinity of the notch portion was rapidly cooled to about-50 ℃, and a shock was applied to the notch portion via a wedge to generate and propagate a brittle crack.

The measured shape of the welded portion and the results of the test using the structural model crack arrest test body are shown in table 2. The test piece was determined to be stopped when the brittle crack stopped at the test piece, and was determined to be broken when the test piece was broken.

As is clear from table 2, excellent brittle crack propagation stopping characteristics were obtained when the members to be joined that satisfy the definition of the present invention were used, whereas brittle cracks were propagated to the members to be joined when the members to be joined that do not satisfy the definition of the present invention were used in the comparative examples.

Industrial applicability

As described above, according to the present invention, a welded structure having excellent brittle crack propagation stopping characteristics can be obtained.

Description of the reference numerals

10. Welding the structure; 11. an engaging member; 11a, surface 1; 11b, surface 2; 11c, end faces; 12. an engaged member; 12a, a surface to be bonded; 13a, 1 st welded part; 13b, 2 nd welding part; 16a, a melting wire portion; 16b, notches.

Claims

1. A welded structure having a T-shaped joint portion formed by fusion-welding both side portions of a plate-shaped joining member to a surface to be joined of the plate-shaped joining member in a state where an end surface of the joining member is in contact with the surface to be joined of the plate-shaped joining member, wherein,

when the length of the joint member in the direction perpendicular to the end faces is H and the allowable stress of the joint member set in advance is σ,

the non-ductility transition temperature NDTT obtained by an NRL drop weight test using a type P3 test piece specified by ASTM E208, extracted from a 1mm depth position of the joined surface of the joined member, and having a thickness direction matching a plate thickness direction of the joined member satisfies the following expression (i), wherein H is in mm, and σ is in N/mm²The temperature of the NDTT is,

NDTT≤360.4－46.8×ln{σ(πH)^0.5}···(i)。

2. the welding construct of claim 1,

the plate thickness t of the joined member satisfies the following expression (ii), and the unit of t is mm,

t≥50.0···(ii)。

3. the welding construct of claim 1,

the plate thickness t of the joined members satisfies the following expression (iii), and t is expressed in mm,

t＞80.0···(iii)。

4. the welding construct of claim 2,

t＞80.0···(iii)。

5. the welded structure according to any one of claims 1 to 4,

the joined member has a yield stress of 400 to 580MPa and a tensile strength of 510 to 750 MPa.

6. The welded structure according to any one of claims 1 to 4,

the Kca value of the whole thickness of the joined member at-10 ℃ is less than 6000N/mm^1.5。

7. The welding construct of claim 5,