JPWO2020136777A1 - Welded structure - Google Patents

Abstract

The joint member 11 has a T-joint portion in which both side portions are welded to the joint member 12 in a state where the end surface 11c of the joint member 11 is in contact with the joint surface 12a of the joint member 12, and the joint member 11 is the first. It has one surface 11a and a second surface 11b, the plate thickness t (mm) of the joining member 11 satisfies [t ≧ 50.0], and the joining member 11 has 1 mm of the first surface 11a and the second surface 11b. The non-deferring transition temperature by the NRL weight drop test using the type P3 test pieces collected from the depth position is -60 ° C or less, and the highest point of the first heat-affected zone 15a of the first welded zone 13a. The relationship between the distance h1 (mm) from the first surface 11a and the distance h2 (mm) between the highest peak of the second heat-affected zone 15b of the second welded portion 13b and the second surface 11b [NDTT1 ≦ -30.5 × A welded structure 10 that satisfies ln (h1) -14.0] and [NDTT2 ≦ -30.5 × ln (h2) -14.0].

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 made 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. In order to secure sufficient strength (longitudinal bending strength) of the hull against such a load, a high-strength thick steel plate is used for the upper deck and the hatch side combing.

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 propagates toward the upper deck side along the welded portion, and the propagated crack propagates to the welded portion of the upper deck. In some cases. Therefore, in order to sufficiently improve the strength of the hull, the hatch side combing and the upper deck need to have the above-mentioned property of stopping the growth of cracks (brittle crack propagation stopping property).

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

JP-A-2007-326147 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, Kca at -10 ° C, which is an index of brittle crack propagation stopping characteristics. It is known that it is necessary to use a thick steel plate having a value 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 a demonstration test conducted in a joint research between the Nippon Kaiji Kyokai and the Japan Welding Engineering Society, in order to stop the growth of cracks that occur on the upper deck and propagate toward the hatchside combing side, , 8000 N / mm It has become clear that it is necessary to use a thick steel plate having an extremely high Kca value of ^1.5 or more.

However, there is a problem that it is difficult to stably produce a thick-walled steel sheet having such a high brittle crack propagation stopping property from both a technical aspect and a cost aspect. Therefore, it is necessary to obtain a welded structure having excellent brittle crack propagation stopping characteristics at low cost by a more rational 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.
The plate thickness t (mm) of the joining member satisfies the following equation (i).
The distance in the plate thickness direction of the joining member between the highest apex of the first heat-affected zone of the first welded portion formed on the first surface side and the first surface is defined as the distance h ₁ (mm), and the second When the distance in the plate thickness direction of the joining member between the highest apex of the second heat-affected zone of the second welded portion formed on the surface side and the second surface is a distance h ₂ (mm),
NRL drop using a type P3 test piece specified in ASTM E208, which is sampled from the 1 mm depth position of the first surface and the second surface of the joint member and whose thickness direction coincides with the plate thickness direction. The non-ductile transition temperature by the heavy test is -60 ° C or lower and satisfies the following equations (ii) and (iii).
Welded structure.
t ≧ 50.0 ・ ・ ・ (i)
NDTT ₁ ≤ -30.5 x ln (h ₁ ) -14.0 ... (ii)
NDTT ₂ ≤-30.5 x ln (h ₂ ) -14.0 ... (iii)
However, NDTT ₁ and NDTT ₂ have non-ductile transition temperatures (° C.) by NRL drop test using type P3 test pieces specified in ASTM E208, which are collected from 1 mm depth positions on the first surface and the second surface, respectively. ).

(2) The plate thickness t (mm) of the joining member, the distance h ₁ (mm) and the distance h ₂ (mm) satisfy the following equations (iv) and (v).
The welded structure according to (1) above.
h ₁ ≤ t / 4 ... (iv)
h ₂ ≤ t / 4 ... (v)

(3) In the cross section perpendicular to the first surface and the surface to be joined,
The sharp angle α ₁ (°) formed by the line passing through the toe and the root on the joint member side and the surface to be joined in the first welded portion, and the partial penetration d ₁ (mm) of the joint in the plate thickness direction. The distance s ₁ (mm) between the toe on the joint member side and the first surface, and the line passing through the toe and root on the joint member side in the second weld and the joint surface. The sharp angle α ₂ (°) formed by the joint, the partial penetration d ₂ (mm) of the joint in the plate thickness direction, and the distance s ₂ (mm) between the toe on the member to be welded and the second surface are as follows. Satisfy equations (vi) to (xi),
The welded structure according to (1) or (2) above.
45.0 ≤ α ₁ ≤ 70.0 ・ ・ ・ (vi)
45.0 ≤ α ₂ ≤ 70.0 ・ ・ ・ (vii)
d ₁ · sec (α ₁ ) · cos (α _1/2 ) ≧ 0.35t ・ ・ ・ (viii)
_{d 2 · sec (α 2)} · cos (α 2 /2)≧0.35t ··· (ix)
s ₁ ≧ d ₁ (sec (α ₁ ) -1) ・ ・ ・ (x)
s ₂ ≧ d ₂ (sec (α ₂ ) -1) ・ ・ ・ (xi)

(4) The plate thickness t (mm) of the joining member satisfies the following equation (xii).
The welded structure according to any one of (1) to (3) above.
t> 80.0 ・ ・ ・ (xii)

(5) The yield stress of the joining member is 400 to 580 MPa, and the tensile strength is 510 to 750 MPa.
The welded structure according to any one of (1) to (4) above.

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

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 shape of the structural model arrest specimen.

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

As described above, in order to improve the brittle crack propagation stopping characteristic over the entire thickness of the member used in the welded structure, for example, it is necessary to use a thick steel sheet having a Kca value of 8000 N / mm ^1.5 or more. ..

However, for example, when a crack propagates from the upper deck toward the hatch side combing side, the crack entry region is limited to the surface layer region of the thick steel plate used for the hatch side combing. If the brittle crack propagation stopping property of the surface layer region of the thick steel sheet can be improved, the crack growth can be stopped. As a result, the brittle crack propagation stopping property of the entire welded structure can be improved at low cost.

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 12 to be joined has a plate shape and has a surface 12a to be joined to which the end surface 11c of the member 11 is in contact.

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

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 welded portion 13a formed on the first surface 11a side and a second welded portion 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 FIGS. 1 and 4, a first weld metal 14a is formed on the first surface 11a side of the joining portion of the joining member 11 and the member to be joined 12. A first heat-affected zone 15a is formed at the boundary between the first weld metal 14a and the joining member 11 and the member to be joined 12. Similarly, the second weld metal 14b is formed on the second surface 11b side, and the second heat-affected zone 15b is formed at the boundary between the second weld metal 14b and the joining member 11 and the joined member 12. It is formed.

In the specification of the present application, the welded portion means a portion where the weld metal and the heat-affected zone are combined. That is, the region where the first weld metal 14a and the first heat-affected zone 15a are combined is the first welded zone 13a, and the region where the second weld metal 14b and the second heat-affected zone 15b are combined is the second welded zone. 13b.

Here, in order to limit the intrusion region of the crack generated from the joint member 12 and propagating to the joint member 11 only to the surface layer side of the joint member 11, the apex of the first surface 11a to the first welded portion 13a. It is necessary to control the depth up to and the depth from the second surface 11b to the highest apex of the second welded portion 13b.

Specifically, the distance h ₁ (mm) in the plate thickness direction of the joining member 11 between the apex of the first heat-affected zone 15a of the first welded portion 13a and the first surface 11a and the second of the second welded zone 13b. It is preferable that the distance h ₂ (mm) in the plate thickness direction between the maximum apex of the heat-affected zone 15b and the second surface 11b satisfies the following equations (iv) and (v).
h ₁ ≤ t / 4 ... (iv)
h ₂ ≤ t / 4 ... (v)

The lower limit of the distance h ₁ and the distance h ₂ is not particularly limited, but even when the joining member 11 and the member to be joined 12 are joined by fillet welding, the heat effect is up to a depth of about 1 mm. The part is formed. Therefore, 1 mm is a substantial lower limit of the distance h ₁ and the distance h ₂ .

The highest apex of the first heat-affected zone 15a means the tip of the first heat-affected zone 15a in the plate thickness direction, and similarly, the highest apex of the second heat-affected zone 15b is the second heat-affected zone 15b. Means the tip in the plate thickness direction of. Further, as shown in FIG. 4, the distance h ₁ is the distance between the first surface 11a and the virtual surface 11d parallel to the first surface 11a and passing through the tip of the first heat-affected zone 15a in the plate thickness direction. The distance h ₂ is the distance between the second surface 11b and the virtual surface 11e that is parallel to the second surface 11b and passes through the tip of the second heat-affected zone 15b in the plate thickness direction.

Further, in the first weld portion 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 welding portion 13b, the bonding member 11 side The acute angle α ₂ (°) formed by the line L ₂ passing through the toe and the root of the above and the surface to be welded 12a preferably satisfies the following equations (vi) and (vii), respectively.
45.0 ≤ α ₁ ≤ 70.0 ・ ・ ・ (vi)
45.0 ≤ α ₂ ≤ 70.0 ・ ・ ・ (vii)

The joining member 11 side of the toe in the first weld portion 13a, means an intersection _{A 1} between the outer edge and the first surface 11a of the first weld metal 14a. Also, the joining member 11 side of the root of the first welding part 13a, meaning intersection _{B 1} between the outer edge and the end face 11c of the first weld metal 14a. Similarly, the bonding member 11 side of the toe at the second weld portion 13b, means an intersection _{A 2} between the outer edge and the second surface 11b of the second weld metal 14b, the bonding member 11 side in the second welding portion 13b the root mean an intersection _{B 2} between the outer edge and the end face 11c of the second weld metal 14b.

Further, the partial penetration d ₁ (mm) of the joint in the plate thickness direction of the first weld 13a and the partial penetration d ₂ (mm) of the joint in the plate thickness direction of the second weld 13b are as follows (viii). It is preferable to satisfy the equation and the equation (ix). Here, the values calculated on the left side of the following equations (viii) and (ix) represent effective throat thicknesses Td ₁ (mm) and Td ₂ (mm), respectively.
d ₁ · sec (α ₁ ) · cos (α _1/2 ) ≧ 0.35t ・ ・ ・ (viii)
_{d 2 · sec (α 2)} · cos (α 2 /2)≧0.35t ··· (ix)

The partial penetration d ₁ of the joint is a virtual surface parallel to the first surface 11a and passing through the end portion of the first weld metal 14a on the plate thickness center side in the plate thickness direction of the joining member 11. It is a distance from 11f. Further, the partial penetration d ₂ of the joint is virtually parallel to the second surface 11b and passes through the end portion of the second weld metal 14b on the plate thickness center side in the plate thickness direction of the joining member 11. It is the distance from the surface 11g.

Further, the distance s ₁ (mm) between the toe on the side of the member to be joined 12 and the first surface 11a in the plate thickness direction of the first welded portion 13a and the toe on the side to be joined 12 in the second welded portion 13b. It is preferable that the distance s ₂ (mm) between the second surface 11b and the second surface 11b satisfies the following equations (x) and (xi), respectively.
s ₁ ≧ d ₁ (sec (α ₁ ) -1) ・ ・ ・ (x)
s ₂ ≧ d ₂ (sec (α ₂ ) -1) ・ ・ ・ (xi)

The distance s ₁ and the distance s ₂ are the weld leg lengths of the first welded portion 13a and the second welded portion 13b in the plate thickness direction, respectively. Specifically, the distance s ₁ is virtual passing through the first surface 11a and the end portion parallel to the first surface 11a and opposite to the plate thickness center of the first weld metal 14a in the plate thickness direction of the joining member 11. It is a distance from the target surface 11h. Further, the distance s ₂ is a virtual surface parallel to the second surface 11b and passing through an end portion of the second weld metal 14b in the plate thickness direction of the joining member 11 opposite to the plate thickness center. This is the distance from 11i.

The boundary between the first weld metal 14a and the second weld metal 14b and the joining member 11 can be easily visually identified. Further, the tip positions of the first heat-affected zone 15a and the second heat-affected zone 15b can also be easily determined by making them appear by nital corrosion.

Even if the above equations (vi) to (xi) are not satisfied, it is possible to improve the brittle crack propagation stopping characteristic, but from the viewpoint of ensuring higher joint strength, the above (vi) to (xi) xi) It is preferable to satisfy the equation.

2. 2. Non-ductile transition temperature of the joining member As described above, in order to improve the brittle crack propagation stopping characteristic over the entire thickness of the joining member, for example, a steel plate having a Kca value of 8000 N / mm ^1.5 or more is used as the joining member. There is a problem that it is necessary to secure a steel sheet having such characteristics. However, it is possible to stop the growth of cracks by improving the brittle crack propagation stopping property at least in the surface layer portion of the joining member according to the depth of the region where the cracks enter.

That is, by controlling the non-ductile transition temperature in the surface layer portion of the joining member according to the depth from the surface to the apex of the welded portion, it is possible to stop the growth of cracks. Specifically, the greater the depth from the surface to the top of the weld, the easier it is for cracks to grow, so it is necessary to lower the non-ductile transition temperature in the surface layer.

Therefore, the non-ductile transition temperature by the NRL drop test using the type P3 test piece specified in ASTM E208, which is collected from the 1 mm depth position of the first surface 11a and the second surface 11b, is set to -60 ° C or lower. , And it is necessary to satisfy the following equations (ii) and (iii).
NDTT ₁ ≤ -30.5 x ln (h ₁ ) -14.0 ... (ii)
NDTT ₂ ≤-30.5 x ln (h ₂ ) -14.0 ... (iii)
However, NDTT ₁ and NDTT ₂ are non-ductile transition temperatures (° C.) by NRL weight drop test using type P3 test pieces collected from 1 mm depth positions of the first surface 11a and the second surface 11b, respectively.

The measuring method of NDTT ₁ and NDTT ₂ will be described in detail. First, a type P3 test piece defined in ASTM E208 is collected from each of the first surface 11a side and the second surface 11b side. The type P3 test piece is a test piece having a length of 130 mm, a width of 50 mm, and a thickness of 16 mm. At this time, after scraping each of the first surface 11a and the second surface 11b by 1 mm, the test piece is collected so that the thickness direction of the test piece coincides with the plate thickness direction of the joining member 11. That is, the test piece is collected from the region from the 1 mm depth position to the 17 mm depth position of the first surface 11a and the second surface 11b.

Further, as will be described later, the test is performed so that cracks occur on the surface perpendicular to the longitudinal direction of the 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, the test piece is collected so that its longitudinal direction coincides with the stretching direction of the welded portion of the welded structure.

Then, using the above test piece, an NRL weight drop test conforming to ASTM E208 is carried out. Specifically, first, a weld bead extending in a direction parallel to the longitudinal direction of the test piece is formed on the surface side surface of the joining member perpendicular to the thickness direction of the test piece. At that time, the welding material having low toughness specified in ASTM E208 is used. The length of the weld bead is adjusted to be in the range of 60 to 70 mm and the width is adjusted to be in the range of 12 to 16 mm. Then, a notch parallel to the width direction of the test piece is formed on the weld bead. At this time, the width of the notch is 1.5 mm or less, and the distance between the groove bottom of the notch and the test piece is adjusted to be in the range of 1.8 to 2.0 mm.

Then, after the surface on which the weld bead is formed of the test piece is directed downward and both ends in the length direction are supported, the impact bending load due to the drop weight is applied to the surface on the opposite side of the weld bead. Add. Then, by examining the state in which the brittle crack generated from the notch propagates to the test piece, Break (with crack propagation) or No Break (without crack propagation) is determined. If the brittle crack generated from the notch propagates on the surface of the test piece in the width direction of the test piece and progresses to the end thereof, the test result is determined to be Break (with crack propagation). If the crack does not reach the end in the width direction, the test result is determined to be No Break (no crack propagation).

The above drop test is carried out using two test pieces each, for example, starting from the condition of -100 ° C and changing the test temperature at 5 ° C intervals (in the case of No Break, the temperature is lowered by 5 ° C. In the case of an increase of 5 ° C.), the temperature 5 ° C. lower than the lowest test temperature at which No Break was obtained for both of the two test pieces is defined as the non-ductile transition temperature.

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 to 580 MPa, and the tensile strength is preferably 510 to 750 MPa. The yield stress of the joining member is more preferably 410 to 570 MPa, and the tensile strength is more preferably 520 to 740 MPa.

4. Method of manufacturing a welded structure The method of manufacturing a welded structure is not particularly limited, but for example, a step of selecting a joint member whose surface layer portion has a non-distracting transition temperature satisfying the above-mentioned conditions and a step of selecting the joint member to be covered. It can be manufactured by performing a process of welding to a joint 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, it is desirable to groove the side of the joint member to be joined. 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. At this time, in order to reduce the width of the heat-affected zone (the length represented by (h ₁ − d ₁ ) and (h ₂ − d ₂ ) in FIG. 4), the amount of heat input should be 0.5 to 3. It is preferably 0 kJ / mm.

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

After preparing various steel sheets having the plate thickness shown in Table 1, the non-ductile transition temperature in the surface layer portion of one side surface (first surface) and the other side surface (second surface) was investigated for each steel sheet. .. Specifically, after the first surface and the second surface are each scraped by 1 mm, the thickness direction of the test piece coincides with the plate thickness direction of the steel plate from each surface, and the longitudinal direction of the test piece is welded. A type P3 test piece specified in ASTM E208 was collected so as to coincide with the stretching direction of the portion. Then, using the test piece, an NRL weight drop test based on ASTM E208 was carried out to determine non-ductile transition temperatures NDTT ₁ (° C.) and NDTT ₂ (° C.).

Subsequently, the No. 4 tensile test piece described in JIS Z 2241 was 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 was performed in accordance with JIS Z 2241 to perform a tensile stress. (YS), tensile strength (TS) and total elongation (EL) were measured. The results are also shown in Table 1.

Then, the above-mentioned various steel plates were used as a test plate (joining member 11), and the structural model arrest test piece shown in FIG. 5 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 (joined member 12), and a welded structure 10 was produced by CO ₂ welding or shielded metal arc welding (SMAW) under the conditions shown in Table 2. ..

After that, the notch 16b was introduced into the fusion line portion 16a of the welded structure 10. Then, the welded structure 10 is cooled to the ship design temperature of −10 ° C., a test stress of 257 MPa corresponding to the design stress of EH40 is applied, and only the vicinity of the notch portion is rapidly cooled to about −50 ° C. to the notch portion. A blow was applied through the 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 (second 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 longitudinal direction of the test piece. A cross section of the welded portion (first welded portion and second welded portion) on the surface side) was cut out. After that, it was polished and subjected to nital corrosion to reveal the weld metal part and the weld heat-affected zone (the region heated above the Ac ₁ transformation point during welding). Photographs of the cross sections of the welded joints at these two locations were taken with a digital camera, the shape of the welded portion was measured from the photographic images, and the average value of the measurement results at the two locations was used.

The shape of the measured welded portion is also shown in Table 2, and the results of the test using the above-mentioned structural model arrest test piece are shown in Table 3. When the brittle crack stopped at the test plate, it was judged to be stopped, and when the test plate was broken, it was judged to be broken.

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 a comparative example not satisfying the provisions of the present invention. When the joining member of No. 1 was used, the brittle crack propagated to the joining member.

In addition, the test No. In 1, 2, 4 and 5, since the equations (vi) to (xi) were further satisfied, the joint strength was high and the results were even better.

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 11d to i Virtual surface 12 Joint member 12a Joint surface 13a First weld 13b Second weld 14a First weld metal 14b Second Welded metal 15a 1st heat affected zone 15b 2nd heat affected zone 16a Fusion line part 16b Notch

Claims (5)

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.
The plate thickness t (mm) of the joining member satisfies the following equation (i).
The distance in the plate thickness direction of the joining member between the highest apex of the first heat-affected zone of the first welded portion formed on the first surface side and the first surface is defined as the distance h ₁ (mm), and the second When the distance in the plate thickness direction of the joining member between the highest apex of the second heat-affected zone of the second welded portion formed on the surface side and the second surface is a distance h ₂ (mm),
NRL drop using a type P3 test piece specified in ASTM E208, which is sampled from the 1 mm depth position of the first surface and the second surface of the joint member and whose thickness direction coincides with the plate thickness direction. The non-ductile transition temperature by the heavy test is -60 ° C or lower and satisfies the following equations (ii) and (iii).
Welded structure.
t ≧ 50.0 ・ ・ ・ (i)
NDTT ₁ ≤ -30.5 x ln (h ₁ ) -14.0 ... (ii)
NDTT ₂ ≤-30.5 x ln (h ₂ ) -14.0 ... (iii)
However, NDTT ₁ and NDTT ₂ have non-ductile transition temperatures (° C.) by NRL drop test using type P3 test pieces specified in ASTM E208, which are collected from 1 mm depth positions on the first surface and the second surface, respectively. ). The plate thickness t (mm), the distance h ₁ (mm), and the distance h ₂ (mm) of the joining member satisfy the following equations (iv) and (v).
The welded structure according to claim 1.
h ₁ ≤ t / 4 ... (iv)
h ₂ ≤ t / 4 ... (v) In the cross section perpendicular to the first surface and the surface to be joined,
The sharp angle α ₁ (°) formed by the line passing through the toe and the root on the joint member side and the surface to be joined in the first welded portion, and the partial penetration d ₁ (mm) of the joint in the plate thickness direction. The distance s ₁ (mm) between the toe on the joint member side and the first surface, and the line passing through the toe and root on the joint member side in the second weld and the joint surface. The sharp angle α ₂ (°) formed by the joint, the partial penetration d ₂ (mm) of the joint in the plate thickness direction, and the distance s ₂ (mm) between the toe on the member to be welded and the second surface are as follows. Satisfy equations (vi) to (xi),
The welded structure according to claim 1 or 2.
45.0 ≤ α ₁ ≤ 70.0 ・ ・ ・ (vi)
45.0 ≤ α ₂ ≤ 70.0 ・ ・ ・ (vii)
d ₁ · sec (α ₁ ) · cos (α _1/2 ) ≧ 0.35t ・ ・ ・ (viii)
_{d 2 · sec (α 2)} · cos (α 2 /2)≧0.35t ··· (ix)
s ₁ ≧ d ₁ (sec (α ₁ ) -1) ・ ・ ・ (x)
s ₂ ≧ d ₂ (sec (α ₂ ) -1) ・ ・ ・ (xi) The plate thickness t (mm) of the joining member satisfies the following equation (xii).
The welded structure according to any one of claims 1 to 3.
t> 80.0 ・ ・ ・ (xii) The yield stress of the joining member is 400 to 580 MPa, and the tensile strength is 510 to 750 MPa.
The welded structure according to any one of claims 1 to 4.

Images