KR20200021548A - Welded structure - Google Patents

Abstract

The joining member 11 has a T-joint in which both joining parts are penetration-welded to the joined member 12 with the end surface 11c of the joining member 11 abutting the surface to be joined 12a of the joined member 12. When the length in the direction perpendicular to the end face 11c of the joining member 11 is H (mm), and the allowable stress of the joining member 11 set in advance is sigma (N / mm ² ). The lead-free transition temperature NDTT (° C) by the NRL drop test using the type P3 test piece taken from the 1 mm depth position of the surface to be joined 12a of the member to be joined is [NDTT ≦ 360.4-46.8 × ln The weld structure 10 which satisfies (σH) ^0.5 Pa].

Description

Welded structure

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

In large container ships carrying a large amount of cargo, a large opening (hatch) is formed in the upper deck (upper deck) for unloading the cargo. On the upper deck, hatch side coaming is provided to surround the hatch in order to prevent the inflow of seawater. The upper deck and the hatch side coaming are each constructed by welding a plurality of steel sheets. In addition, the hatch side coaming is welded on the upper deck.

When a large container ship as mentioned above sails at sea, the load (vertical bending load) which bends the whole hull is added to hull by blue. In order to sufficiently secure the hull strength (vertical bending strength) against such a load, a high strength thick steel sheet is used for the upper deck and the hatch side coaming.

As described above, the hatch side coaming and the upper deck each have a configuration in which a plurality of steel sheets are welded. In other words, the hatch side coaming and the upper deck are provided with a plurality of welds for welding steel sheets. Cracks generated in the weld portion are likely to propagate along the weld portion. For this reason, when a crack generate | occur | produces in the weld part of a hatch side coaming, for example, the crack propagates toward the upper deck side along a weld part, and the propagated crack may advance to the weld part of an upper deck. Therefore, in order to fully improve the strength of the hull, the hatch side coaming and the upper deck need to have a characteristic (brittle crack propagation stopping characteristic) that can stop the progress of the crack as described above.

For example, in patent documents 1 and 2, the welded structure regarding brittle crack propagation stop characteristic is disclosed.

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

By the way, in order to stop the propagation of the crack which generate | occur | produced in the hatch side coaming and propagated toward the upper deck side, as these members, the Kca value in -10 degreeC which is an index of brittle crack propagation stop characteristic, It is known that it is necessary to use a thick steel sheet of 6000 N / mm ^1.5 or more.

However, there is a problem in that it is difficult to stably manufacture a thick steel sheet having such a high brittle crack propagation stop characteristic, both in terms of technology and cost. Therefore, it is necessary to obtain a welded structure having excellent brittle crack propagation stop characteristics at low cost by a more rational method.

This invention is made | formed in order to solve such a problem, and an object of this invention is to provide the weld structure excellent in the brittle crack propagation stop characteristic.

This invention makes the following weld structure the summary.

(1) A welding structure in which the joining member has a T-joint welded to both sides of the joined member in the state where the cross section of the plate-shaped joining member abuts against the surface to be joined of the plate-shaped joined member,

When length in the direction perpendicular | vertical to the said cross section of the said joining member is set to H (mm), and the permissible stress of the said joining member set in advance is (sigma) (N / mm <^2> ),

Lead-free transition by NRL dropping test using a type P3 test piece specified in ASTM E208 where the member to be joined is taken from a 1 mm depth position of the surface to be joined and whose thickness direction coincides with the plate thickness direction of the member to be joined. The weld structure in which temperature NDTT (degreeC) satisfy | fills following formula (i).

NDTT≤360.4-46.8 x ln ｛σ (πH) ^0.5 ｝. (i)

(2) The weld structure according to the above (1), wherein the plate thickness t (mm) of the joined member satisfies the following (ii) formula.

t ≧ 50.0... (ii)

(3) The weld structure according to the above (1) or (2), wherein the plate thickness t (mm) of the joined member satisfies the following (iii) formula.

t> 80.0... (iii)

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

(5) The weld structure according to any of (1) to (4), wherein a Kca value of the total thickness at -10 ° C. of the joined member is less than 6000 N / mm ^1.5 .

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

1 is a perspective view illustrating a weld structure according to an embodiment of the present invention.
2 is a perspective view showing a welded structure according to another embodiment of the present invention.
3 is a perspective view illustrating a weld structure according to another embodiment of the present invention.
4 is a view for explaining the shape of the structural model arrest test body.

MEANS TO SOLVE THE PROBLEM As a result of having examined in order to solve said subject, the present inventors acquired the following knowledge.

As mentioned above, in order to improve the brittle crack propagation stop characteristic over the whole thickness of the member used for a welded structure, it is necessary to use the thick steel plate whose Kca value is 6000 N / mm ^1.5 or more, for example.

However, for example, in the case where a crack propagates from the hatch side coaming to the upper deck side, the brittle crack propagation stop characteristic of the surface layer region of the upper deck into which the crack enters depends on the height and allowable stress of the hatch side coaming. If it can improve, it becomes possible to stop the progress of a crack. As a result, it becomes possible to improve the brittle crack propagation stop characteristic in the whole weld structure at low cost.

This invention is made | formed based on said knowledge. EMBODIMENT OF THE INVENTION Hereinafter, the welding structure which concerns on one Embodiment of this invention is demonstrated.

1. Composition of welding structure

1 is a perspective view illustrating a weld structure according to an embodiment of the present invention. The weld structure 10 which concerns on this embodiment is equipped with the joining member 11 and the to-be-joined member 12. As shown in FIG. The joining member 11 is plate-shaped and has a first surface 11a and a second surface 11b perpendicular to the plate thickness direction. Moreover, the to-be-joined member 12 is plate shape and has the to-be-joined surface 12a which the end surface 11c of the joining member 11 abuts.

As shown in FIG. 1, in the weld structure 10, the joining member 11 is welded to both sides of the joined member 12 by partial penetration welding while the end face 11c is in contact with the surface to be joined 12a. It has a T joint. In this embodiment, the welding structure 10 has the 1st welding part 13a formed in the 1st surface 11a side, and the 2nd welding part 13b formed in the 2nd surface 11b side. In addition, the weld structure which has said T joint part also includes the structure of the shape shown in FIGS. 2 and 3 in addition to a T-shaped structure, as shown in FIG.

In addition, although the joining member 11 and the to-be-joined member 12 may be joined by fillet welding, from a viewpoint of joining strength, the joining member 11 forms an improvement, and by the improvement welding It is preferable to join.

For example, when the welded structure 10 is used for a container ship etc., a thick joined member is used. Specifically, when the plate thickness of the joined member 12 is t (mm), it is preferable to satisfy the following formula (ii), and more preferably to satisfy the following formula (iii).

t ≧ 50.0... (ii)

t> 80.0... (iii)

Moreover, there is no restriction | limiting in particular also about the plate | board thickness of the joining member 11, It is preferable that it is 50.0 mm or more like the joined member 12, and it is more preferable that it is more than 80.0 mm.

2. Lead-free transition temperature of member to be joined

As described above, in order to improve the brittle crack propagation stop characteristic over the entire thickness of the member to be joined, for example, a steel sheet having a Kca value of 6000 N / mm ^1.5 or more needs to be used as the member to be joined, and has such characteristics. There is a problem that securing the steel sheet is difficult. However, at least the brittle crack propagation stop characteristic at the surface layer portion on the joining member side of the joined member can be improved according to the height of the joining member and the assumed allowable stress, thereby making it possible to stop the growth of the crack.

That is, it is possible to stop the progress of the crack by controlling the non-flammable transition temperature at the surface layer portion of the joined member in accordance with the height of the joined member and the allowable stress of the preset joined member. Specifically, the higher the height of the joining member and the higher the allowable stress of the joining member, the easier it is to crack. Therefore, it is necessary to lower the lead-free transition temperature in the surface layer portion.

Therefore, when the length in the direction perpendicular to the end face 11c of the joining member 11 is H (mm) and the allowable stress of the joining member 11 is sigma (N / mm ² ), It is necessary to satisfy the following formula (i) with the lead-free transition temperature NDTT (degreeC) by the NRL dropping test using the type P3 test piece prescribed | regulated to ASTM E208 taken from the 1 mm depth position of the to-be-joined surface 12a.

NDTT≤360.4-46.8 x ln ｛σ (πH) ^0.5 ｝. (i)

The measuring method of NDTT is demonstrated in detail. First, the type P3 test piece prescribed | regulated to ASTM E208 is extract | collected from the to-be-joined surface 12a side. A type P3 test piece is a test piece of 130 mm in length, 50 mm in width and 16 mm in thickness. At this time, after cutting the to-be-joined surface 12a 1 mm, it extracts so that the thickness direction of a test piece may correspond with the plate | board thickness direction of the to-be-joined member 12. FIG. That is, the test piece is taken out of the area | region from the 1 mm depth position to the 17 mm depth position of the to-be-joined surface 12a.

Moreover, as mentioned later, a test is performed so that a crack may arise in the surface perpendicular | vertical to the longitudinal direction of a test piece. In the welded structure, cracks occur in the plane perpendicular to the stretching direction of the first welded portion 13a and the second welded portion 13b. Therefore, a test piece is extract | collected so that the longitudinal direction may match the extending | stretching direction of the weld part of a welded structure.

Then, the NRL dropping test based on ASTME208 is performed using the said test piece. Specifically, first, a weld bead extending in a direction parallel to the longitudinal direction of the test piece is formed on the surface on the surface side of the member to be joined perpendicular to the thickness direction of the test piece. In that case, the welding material uses the low toughness welding material prescribed | regulated to ASTME208. Adjust the length of the weld bead to 60 ~ 70mm and the width of 12 ~ 16mm. And a notch parallel to the width direction of a test piece is formed on a weld bead. At this time, the width of the notch shall be 1.5 mm or less, and adjust so that the distance between the groove bottom of the notch and the test piece may be in the range of 1.8 to 2.0 mm.

Then, the face on which the weld bead of the test piece is formed is directed downward, and both ends in the longitudinal direction are supported, and then the impact bending load due to dropping is added to the face on the opposite side to the weld bead. Subsequently, Break (with crack propagation) or No Break (without crack propagation) is determined by examining the state in which the brittle crack generated from the notch propagates to the test piece. If the brittle crack resulting from the notch propagates in the width direction of the test piece from the surface of the test piece to the end of the test piece, the test result is determined as Break (with crack propagation). If no crack is reached at the end in the width direction, the test result is determined as No Break.

The dropping test described above is started using, for example, two test pieces, at a temperature of -100 ° C, and changes the test temperature at intervals of 5 ° C (in the case of No Break, 5 ° C, and in the case of Break). 5 ° C. rise), the lower test temperature of 5 ° C. from the lowest test temperature at which No Break was obtained for both specimens.

In addition, as allowable stress of the above-mentioned predetermined joining member, for example, when a welded structure is for ships, the joining member becomes a hatch side coaming. Since the permissible stress of hatch side coaming is prescribed | regulated by the rules which the Society of Classifications decides, what is necessary is just to employ | adopt the value.

3. Mechanical properties of the member to be joined

There is no restriction | limiting in particular about the mechanical characteristic of the to-be-joined member used for the weld structure of this invention. However, when using a welded structure in container ships etc., it is preferable that the yield stress of the to-be-joined member used as an upper deck is 400-580 Mpa, and it is preferable that tensile strength is 510-750 Mpa. Moreover, it is more preferable that the yield stress of a to-be-joined member is 410-570 Mpa, and it is more preferable that tensile strength is 520-740 Mpa.

As described above, in the present invention, even if the brittle crack propagation stop characteristic is not excellent over the entire thickness of the member to be joined, it is possible to stop the growth of the crack. Therefore, in the technological and cost standpoint, it is preferred to use the Kca value of the total thickness of 6000N / mm ^1.5 is less than the bonded member in the -10 ℃. In addition, said Kca value can be calculated | required by the temperature gradient type ESSO test based on WES2815 standard.

Specifically, a full thickness large test piece having a dimension of about 500 mm x 500 mm x plate thickness is produced, and V notches are formed at the end of the test piece. A temperature gradient is given to the test piece, an impact load is loaded through the wedge to V notch, and brittle cracking is artificially generated. Kca value is computed based on the stress added to the test body, the temperature at the position where the propagation of brittle cracking stopped, and the length of a crack. The test is performed by changing the temperature gradient condition and the load load condition, and the Kca value at -10 ° C can be obtained by determining the relationship between the crack stop temperature and the Kca value.

4. Manufacturing method of welded structure

There is no restriction | limiting in particular about the manufacturing method of a welded structure, For example, the process of selecting the to-be-joined member in which the nonflammable transition temperature of a surface layer part satisfies the above-mentioned conditions, and joining a joining member to said to-be-joined member By performing the process of welding, it is possible to manufacture.

In a welding process, it can manufacture by welding along the cross section in the state which made the end surface of a joining member abut on the to-be-joined surface of the to-be-joined member mentioned above. At this time, it is preferable to improve-process the to-be-joined member side of a joining member. Although improvement process may be performed over the whole cross section of a joining member, you may perform only to the joining place with a to-be-joined member.

In addition, the welding method is not particularly limited also, and by employing a known method, such as CO ₂ welding or coated arc welding (SMAW). It is preferable that heat input amount shall be 0.5-3.0 kJ / mm, for example.

EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these Examples.

EXAMPLE

After preparing the various steel plates which have the plate | board thickness shown in Table 1, the lead-free transition temperature in the surface layer part of the surface (surface to be joined) of one side was investigated about each steel plate. Specifically, after cutting the surface to be bonded 1 mm, the type P3 test piece specified in ASTM E208 was taken so that the thickness direction of the test piece coincided with the plate thickness direction of the steel sheet. And using the said test piece, the NRL dropping test based on ASTME208 was implemented, and the lead-free transition temperature NDTT (degreeC) was calculated | required.

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

In addition, the Kca value of the total thickness in -10 degreeC of each steel plate was calculated | required by the temperature gradient type ESSO test based on WES2815 standard. The results are shown in Table 1 together.

TABLE 1

Thereafter, the above various steel sheets were used as test plates (joint members 12), and the structural model arrest test bodies shown in Fig. 4 were produced and tested. Has a height H (mm) shown in Table 2, the steel sheet having a thickness of 100mm under the conditions shown for joining the weld joint to one trillion weeks (助走) welded joint (joint member 11), and in Table 2 by the CO ₂ welding CO ₂ to prepare a welding structure 10 by welding or the shield metal arc welding (SMAW). At that time, both sides improvement of the depth of 1/3 of the plate | board thickness was formed in the joining member 11, and the joining member 11 and the to-be-joined member 12 were joined by improvement welding.

TABLE 2

Thereafter, the notch 16b was introduced into the fusion line portion 16a of the weld structure 10. Then, the weld structure 10 is cooled to −10 ° C., which is a ship design temperature, and a test stress corresponding to the allowable stress σ of the joining member 11 shown in Table 2 is loaded, and only the vicinity of the notched part is quenched at about −50 ° C. Then, a blow was applied to the notch through a wedge to generate and propagate brittle cracks.

The shape of the measured weld part and the result of the test using the structural model arrest test body are shown in Table 2 together. When the brittle crack stopped in the test plate, it was stopped, and when the test plate was broken, it was determined to be broken.

As apparent from Table 2, in the case of using a member to be satisfied that satisfies the provisions of the present invention, an excellent brittle crack propagation stop characteristic was obtained, whereas the member to be joined of the comparative example which did not satisfy the provisions of the present invention was used. In this case, brittle cracks were propagated to the joined member.

[Industry availability]

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

10: welded structure
11: joining member
11a: first surface
11b: second surface
11c: cross section
12: member to be joined
12a: surface to be joined
13a: first welded portion
13b: second weld
16a: fusion line section
16b: notch

Claims (5)

A welding structure in which the joining member has a T-joint welded to both sides of the joined member in the state in which a cross section of the plate-shaped joining member abuts against the joined surface of the joined member in the form of a plate,
When length in the direction perpendicular | vertical to the said cross section of the said joining member is set to H (mm), and the permissible stress of the said joining member set in advance is (sigma) (N / mm <^2> ),
Lead-free transition by NRL dropping test using a type P3 test piece specified in ASTM E208, wherein the member to be joined is taken from a 1 mm depth position of the surface to be joined, and the thickness direction coincides with the plate thickness direction of the member to be joined. The weld structure in which temperature NDTT (degreeC) satisfy | fills following formula (i).
NDTT≤360.4-46.8 x ln ｛σ (πH) ^0.5 ｝. (i) The method according to claim 1,
The plate | board thickness t (mm) of the said to-be-joined member satisfy | fills following (ii) Formula.
t ≧ 50.0... (ii) The method according to claim 1 or 2,
The plate | board thickness t (mm) of the said to-be-joined member satisfy | fills following (iii) Formula.
t> 80.0... (iii) The method according to any one of claims 1 to 3,
The weld structure whose yield stress of the said joined member is 400-580 Mpa, and tensile strength is 510-750 Mpa. The method according to any one of claims 1 to 4,
The members to be joined the Kca value of the total thickness of the -10 ℃ member of 6000N / mm ^1.5 is less than the welding structure.

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