KR102001923B1 - Welded structure - Google Patents

Abstract

And a fillet welded joint in which the end face of the joining member 1 is in contact with the surface of the member to be joined 2 having a plate thickness of 50 mm or more and which joins the joining member 1 and the member to be joined 2 The welded length 3 and the weld width 13 of the fillet welded joint exceed 16 mm and the end face of the welded member 1 and the surface of the welded member 2 in the fillet welded joint (5) of the fillet welded joint (5) of 95% or more of the plate thickness (tw) of the welded member (1) on the cross section of the fillet welded joint, The Charpy impact test wave front transition temperature vTrs (占 폚) of the weld metal 5 and the plate thickness tf of the member to be welded 2 or the small And the value L of the other side.

Description

{WELDED STRUCTURE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welded steel structure (welded structure) welded using a steel plate, such as a large container wire or a bulk carrier. Particularly, the present invention relates to a welded structure excellent in brittle crack propagation stopping property capable of stopping the propagation of a brittle crack generated from a base metal of a post-steel plate or a welded joint before reaching a large-scale fracture of the structure.

Container ships and bulk carriers have a structure in which a large opening is provided in a ship-shaped portion, unlike, for example, a tanker or the like, for the purpose of improving the loading capacity and improving the unloading efficiency. Therefore, in a container ship or a bulk carrier, it is particularly necessary to strengthen or thicken the hull sheathing.

In addition, container ships have recently become large-sized, and large ships such as 6,000 to 20,000 TEU are being built. TEU (Twenty feet Equivalent Unit) represents the number converted into a container having a length of 20 feet, and indicates an index of the loading capacity of the container line. With such a ship becoming larger, the outer shell of the ship has a plate thickness of 50 mm or more, and a steel sheet having a yield strength of 390 N / mm < 2 >

In recent years, the steel sheet to be the outer shell of the ship is often butt-welded by large-volume heat welding such as, for example, electro-gas arc welding in view of shortening of the construction period. Such large heat welding is liable to be connected to a considerable reduction in toughness in the heat affected zone of the weld, which is one cause of the generation of brittle cracks from the weld joint part.

On the other hand, in the hull structure, from the viewpoint of safety in the past, it is thought that it is necessary to stop the propagation of the brittle cracks before reaching a large scale fracture to prevent the separation of the hull, even if brittle fracture occurs.

Based on this idea, Non-Patent Document 1 reports experimental results on brittle crack propagation behavior of a welded portion in a steel sheet for shipbuilding having a plate thickness of less than 50 mm.

In Non-Patent Document 1, the propagation path of the brittle crack forcedly generated in the welded portion and the propagation behavior are experimentally investigated. Here, if the fracture toughness of the welded portion is secured to some extent, there is a result that the brittle cracks often deviate from the welded portion to the base material side due to the influence of the welding residual stress. However, Has been confirmed. This suggests that brittle fracture can not be assured that there is no possibility of propagating straight along the weld.

However, there is a lot of evidence that a welded ship is applied to a steel plate having a plate thickness of less than 50 mm by welding equivalent to the welding applied in the non-patent document 1, ) Has a sufficient ability to stop the brittle crack, the brittle crack propagation stopping property of the welded portion of the steel for shipbuilding is not particularly required in the Rules for Classification.

However, in recent large-sized container ships exceeding 6,000 TEU, the plate thickness of the steel sheet used exceeds 50 mm, and in addition to the decrease of the fracture toughness due to the plate thickness increase, , The fracture toughness of the welded portion tends to be lowered further. This brittle heat transfer weld joint shows that the brittle cracks generated from the welded portion may go straight without bending to the base material side and may not stop at the base material portion of the steel sheet such as an aggregate (see Non-Patent Document 2, for example).

For this reason, securing the safety of the hull structure to which the high strength steel plate having the plate thickness of 50 mm or more is applied has become a big problem. Non-Patent Document 2 also points out that a post-steel plate having a specific brittle crack propagation stopping property is required for stopping the propagation of the brittle cracks generated in particular.

[0005] Regarding such a problem, for example, Patent Document 1 discloses a welded structure in which an aggregate is arranged so as to cross an abutting weld portion and is joined by fillet welding, preferably in a welded structure having a plate thickness of 50 mm or more .

In the technique described in Patent Document 1, the aggregate has an average circle equivalent particle size of 0.5 to 5 占 퐉 over a thickness of 3 mm or more in the surface layer portion and the two-layer (back layer) portion, And the X-ray surface intensity ratio of the crystal plane is 1.5 or more. By forming the steel plate having such a microstructure as fillet welded as a reinforcing material, brittle fracture can be stopped in the aggregate as a reinforcing material even if brittle cracks occur in the butt welded joint portion, It is possible to prevent it.

However, the aggregate, which is used as the reinforcing material in the technique described in Patent Document 1, requires a complicated process in order to form a steel sheet having a desired structure. As a result, productivity is lowered, It is difficult to secure a sufficient amount of water.

Patent Document 2 discloses a welded structure having a fillet welded joint formed by fillet welding a joining member (hereinafter, also referred to as a web) to a member to be joined (hereinafter, also referred to as a flange) with excellent brittle crack propagation stopping property. .

In the welded structure described in Patent Document 2, the unhardened portion of the web at the end face of the fillet welded joint is left on the face to be abutted against the flange, and the width of the unhardened portion and the leg lengths of the right and left sides of the fillet welded portion, The width of the unhardened portion is adjusted so that the sum ratio of the plate thicknesses, X, satisfies a specific relational expression with the brittle crack propagation stopping performance Kca of the member to be bonded (flange). As a result, even when the member to be joined (flange) is made of a post material having a plate thickness of 50 mm or more, the propagation of the brittle crack generated in the joining member (web) is stopped at the contact surface between the web of the fillet weld and the flange, It is possible to prevent the propagation of brittle cracks to the flange (flange).

However, in the technique described in Patent Document 2, since the brittle crack propagation stopping characteristics and the like of the joining member (web) are insufficient, the brittle crack generated in the member to be joined (flange) is a technique sufficient to stop propagating in the joining member Can not. In Patent Document 2, no consideration is given to the brittle crack propagation stopping property of the joining member (web).

With respect to such a problem, for example, in Patent Document 3,

&Quot; a fillet welded joint having a cross-section of a joint member against a surface of a member to be joined having a plate thickness of 50 mm or more and at least one of welded joint lengths or welding widths formed by joining the joint members and the jointed members by fillet welding, Wherein the welded structure has an untreated portion of 95% or more of the plate thickness tw of the welded member at the cross section of the fillet welded joint on the face of the welded member at the end face of the welded member and the surface of the welded member, Further, the Charpy impact test of the fillet weld metal in the fillet welded joint, vTrs =-1.5tf + 70 in relation to the plate thickness tf of the member to be welded, and / or the Charpy impact test test temperature: the absorbed energy vE _-20 (J) in the -20 ℃, in relation to the thickness tf of the bonded member, which satisfies the vE _-20 ≥2.75tf-105, Welded structure with fillet weld metal "

.

According to this welding structure, brittle cracks generated in the member to be bonded can be prevented from propagating to the fillet weld metal.

Further, in Patent Document 4,

&Quot; a fillet welded joint having a cross-section of a joint member against a surface of a member to be joined having a plate thickness of 50 mm or more and at least one of welded joint lengths or welding widths formed by joining the joint members and the jointed members by fillet welding, Wherein the welded structure has an untreated portion of 95% or more of the plate thickness tw of the welded member at the cross section of the fillet welded joint on the face of the welded member at the end face of the welded member and the surface of the welded member, Further, the Charpy impact test wave fracture transition temperature vTrs of the fillet weld metal in the fillet welded joint is preferably in the range of vTrs ≤ 1.5tf + 90 in relation to the plate thickness tf of the member to be welded, and / test temperature: in relation to the absorbed energy vE _-20 (J) is, the thickness tf of the bonded member in the -20 ℃ in the case of, 50≤tf≤53, vE _-20 5.75, tf> in the case of 53, vE _-20 ≥2.75tf-140 a, has a satisfactory fillet weld metal, in addition to the joining members, brittle crack propagation stopping toughness Kca is 2500N / ㎜ ^2/3 or more steel plate as a common temperature Welded structure "

.

By using such a welded structure, the brittle crack generated in the member to be bonded can be stopped in the base material of the fillet welded portion or the bonded member.

Further, in Patent Document 5,

&Quot; a fillet welded joint having a cross-section of a joint member against a surface of a member to be joined having a plate thickness of 50 mm or more and at least one of welded joint lengths or welding widths formed by joining the joint members and the jointed members by fillet welding, Wherein the weld metal of the butt welded joint portion has a toughness of not less than -65 占 폚 in terms of vTrs and / or not less than 140 占 in vE- ₂₀ , wherein the weld metal is a member having a welded joint portion together with the joint member and the member to be welded And the end face of the welded portion of the butt welded joint portion of the joint member in the fillet welded joint is brought into contact with the surface of the welded portion of the butt welded joint portion of the bonded member to be welded, And has an untreated portion of 95% or more of the thickness tw, and further has a charpy fill of the fillet weld metal in the fillet welded joint VTrs ≤ 1.5tf + 90 in relation to the thickness tf of the member to be welded and / or the absorption energy vE at -20 DEG C of the Charpy impact test of the fillet weld metal to _-20 (J) the blood in relation to the thickness tf of the joint member, if the 50≤tf≤53 include, vE _-20 ≥5.75, tf> in the case of 53, vE _-20 ≥2.75tf-140, Welded structure with satisfactory fillet weld metal "

.

By using such a welded structure, the brittle crack generated in the member to be bonded can be stopped in the base material of the fillet welded portion or the bonded member. The brittle crack generated from the welded portion of the member to be welded or the brittle crack generated from the welded portion of the welded portion can be prevented from propagating at the welded portion of the fillet welded portion, the welded portion of the welded portion or the welded portion to be welded.

Japanese Patent Application Laid-Open No. 2004-232052 Japanese Patent Application Laid-Open No. 2007-326147 Japanese Patent Publication No. 5395985 Japanese Patent Publication No. 5365761 Japanese Patent Publication No. 5408396

 The 147th Research Meeting of the Japanese Society of Naval Architects of Japan: "A Study on the Evaluation of Brittle Fracture Strength of High Heat Strength Steel Plate for Hull", No. 87 (February 1978), p.35 ~  Yamaguchi Kinya et al., "Development of Ultra-Large Container Ship - Practical Application of New High Strength Sheets", Journal of the Japan Ship and Ocean Engineering Society, No. 3 (2005), pp.70-76, November 2005

However, in each of the techniques described in Patent Documents 3 to 5, it is necessary to limit the welding leg length (or welding width) to 16 mm or less. Therefore, from the viewpoint of securing the strength of the fillet welded portion, The plate thickness applicable to the joining member (flange) was 80 mm at the maximum.

Further, even when the plate thickness of the joining member (web) and the member to be welded (flange) is less than 80 mm, considering the deviation of the welding leg length in the executing step, the desired welding leg length And to limit the welding leg length to 16 mm or less in order to ensure brittle crack prevention performance requires a lot of effort in terms of construction management. In addition, there are cases where additional costs such as maintenance are required, and problems have been left in these points.

Further, in recent years, in the large-sized container line, the member is further made to become thinner, and a steel plate having a thickness of 100 mm or more is also used.

However, as described above, in each of the techniques described in Patent Documents 3 to 5, the plate thickness applicable to the joining member (web) and the member to be joined (flange) is 80 mm at the maximum, It can not be applied to welded structures with thickness.

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art, and it is an object of the present invention to solve the problems of the prior art, and to provide a method of preventing a brittle crack propagated in a member to be joined (flange) (Stopping) a brittle crack propagation stopping property of a welded structure.

The welded structure to which the present invention is applied is a welded structure including a fillet welded joint where the end face of the welded member (web) is brought into contact with the surface of the welded member (flange) and welded together by fillet welding.

In order to achieve the above object, the inventors of the present invention have extensively studied various factors affecting the brittle crack propagation stopping characteristics of a welded structure having a fillet welded joint exceeding 16 mm in welding leg length (and welding width).

As a result, in order to stop (stop) the propagation of the brittle cracks generated from the member to be welded (flange) when the welding leg length exceeds 16 mm, It is not sufficient to provide a discontinuous portion and to constitute a propagating portion of a brittle crack by a member having a brittle crack propagation stopping property having a brittle crack propagation stopping characteristic Kca or more that is a predetermined value or more.

Particularly, when the plate thickness tf (mm) of the member to be joined (flange) is large, the energy release rate (crack propagation driving force) of the brittle crack tip increases and the brittle crack is hardly stopped, ) Of the fillet welded portion, particularly the fillet welded metal, in accordance with the plate thickness tf (mm) of the fillet welded portion.

In addition, it is understood that it is necessary to improve the toughness of the fillet weld metal in accordance with the welding leg length and welding width because the spreading of the brittle crack becomes easier if the welding leg length and weld width of the fillet weld joint are longer than 20 mm I got it.

In addition, in the fillet welded joint, an unetched portion, that is, a discontinuous portion is secured on the surface of the member to be bonded and the surface of the welded portion facing the end face, and further, the toughness of the fillet welded metal is determined by the welding length (mm) It is possible to prevent the occurrence of the brittle cracks generated in the member to be bonded exceeding 80 mm in thickness, which is difficult in the conventional technique, by appropriately controlling the relationship between the welding width (mm) and the plate thickness tf (mm) It has been found that the radio wave to the joining member can be stopped (stopped) by the fillet weld metal.

That is, the setting of the unsealed part as described above and the toughness of the fillet weld metal are appropriately controlled in relation to the welding leg length (mm), the welding width (mm) and the plate thickness tf (mm) (Web) of the brittle crack generated in the member to be bonded (flange) to the joining member (web) without considering the brittle crack propagation stopping characteristic particularly for the steel sheet used for the joining member found.

Further, even in the case where the member to be bonded is a butt welded joint other than the base material, or when the joint member is a butt welded joint, the same effect can be obtained by using the above- Can be prevented from the fillet weld metal.

First, experimental results early to derive the present invention will be described.

(Unbonded portion width B of the non-welded portion in the cross section of the fillet welded joint) / (bonded portion) of the unfired welded portion Y (%) (= Plate thickness tw) x 100), and various fillet welded joints having various low-temperature toughness and welding leg lengths were produced. In addition, both the welding leg length and the welding width were adjusted to exceed 16 mm.

A steel plate having a butt welded joint portion and a plate thickness of 50 mm or more was used for the member to be welded (flange). Further, ordinary joining D-E class steels were used for bonding members (webs), which did not give any consideration to brittle crack propagation stop toughness Kca.

In addition, the butt welded joints were produced by one pass high-strength electro-arc arc welding (SEGARC or two-electrode SEGARC) or multi-layer carbonated gas arc welding (multilayer CO ₂ ).

Using the obtained large fillet welded joint, a very large structural model test body as shown in Fig. 4 (b) was produced, and a brittle crack propagation stop test was carried out. The very large structural model test body welded a steel plate having the same plate thickness as that of the flange 2 with an attach welding 8 below the member to be welded (flange) 2 of the large fillet welded joint 9.

In the very large structural model test body shown in Fig. 4 (b), the butt welded joint portion 11 of the member to be joined (flange) 2 is made to be perpendicular to the joint member (web) 1, 7 were processed so as to be the BOND part of the welded joint part 11.

Further, in the brittle crack propagation stop test, brittle cracks were generated by striking the mechanical notch, and it was examined whether or not the propagated brittle cracks stopped at the fillet welded portion. A test was conducted under the conditions of a stress of 243 to 257 N / mm 2 and a temperature of -10 캜. The stress of 243 to 257 N / mm 2 is a value corresponding to the maximum permissible stress of the steel sheet having a yield strength of 355 to 390 N / mm 2 applied to the hull. Temperature: -10 ° C is the ship's design temperature.

The obtained results are shown in Figs. 5 and 6. Fig.

5 is a graph showing the relationship between the Charpy impact test wavefront transition temperature vTrs (占 폚) of the fillet weld metal and the welded area And the plate thickness tf of the member affects the propagation stop of the brittle crack in the very large structural model test body. 6 is a graph showing the relationship between the Charpy impact test wavefront transition temperature vTrs (占 폚) of the fillet weld metal and the plate thickness tf of the member to be welded (flange) of 75% And L, which is the smaller value of the welding leg length and the welding width, on the propagation stop of the brittle crack in the super large structural model test body.

From the experimental results shown in Figs. 5 and 6, it can be seen that the unfused portion ratio Y is 95% or more and the toughness of the fillet welded portion, that is, the Charpy impact test wavefront transition temperature vTrs (占 폚) (Web), even if the plate thickness tf of the joining member (web) and the smaller value L of the welding leg length and the welding width satisfy the specific relationship, even if the load stress is 243 to 257 N / The brittle crack generated in the member to be bonded (flange) can be stopped at the fillet welded metal portion, and it is possible to prevent the brittle crack from propagating to the joint member (web).

The unfit welded portion ratio Y is a value defined by a ratio of the width B of the non-welded portion to the welded portion (web) plate thickness tw in the section of the fillet welded joint, (B / tw) x 100 (%).

From the above experimental results, it can be seen that the Charpy impact test wave front transition temperature vTrs (占 폚) of the fillet weld metal, the plate thickness tf of the member to be welded (flange) Relationship.

When L < 20, vTrs? -35-1.5 (tf-75) ... (1a)

L? 20, vTrs? -5L + 65-1.5 (tf-75) ... (1b)

(Mm)), L is the smaller value (mm) of the welding leg length and the welding width, vTrs is the Charpy impact test wave front transition temperature (캜) of the fillet weld metal, tf is the plate thickness (mm)

The present invention has been completed on the basis of this recognition by further studying. That is, the gist of the present invention is as follows.

(1) A welded structure comprising a fillet welded joint where an end face of the jointing member is in contact with a surface of a member to be welded having a plate thickness of 50 mm or more, and which joins the jointing member and the member to be welded,

Wherein the fillet weld joint has a welding leg length and a weld width of more than 16 mm,

Wherein the fillet welded joint has an unsealed portion of 95% or more of the plate thickness tw of the welded member on the cross-section of the fillet welded joint on the face of the end face of the welded member and the surface of the welded member ,

Further, with respect to the fillet weld metal of the fillet welded joint,

(L) is less than 20 mm, the Charpy impact test wave front transition temperature vTrs (占 폚) of the fillet weld metal and the plate thickness of the member to be welded tf satisfies the following expression (1a)

L is 20 mm or more, the Charpy impact test wave front transition temperature vTrs (占 폚) of the fillet weld metal, the plate thickness tf of the member to be welded and L satisfy the following relation (1b) .

group

vTrs? -35-1.5 (tf-75) ... (1a)

vTrs? -5L + 65-1.5 (tf-75) ... (1b)

Here, vTrs: Charpy impact test of fillet weld metal Wave front transition temperature (캜),

tf: thickness (mm) of the member to be bonded,

L: Small value (mm) of welding leg length and welding width

(2) The welded structure according to (1), wherein the member to be welded has a butt welded joint portion so as to intersect with the welded member.

(3) The welded structure according to (2), wherein the joining member has a butt welded joint portion, and the joining member is provided such that the butt welded joint portion of the joining member intersects the butt welded joint portion of the joined member .

According to the present invention, it is possible to provide a brittle crack joining member (web) formed on a member to be joined (flange) having a plate thickness of 50 mm or more, particularly 60 mm or more and a plate thickness of 80 mm or more, It becomes possible to stop (stop) the radio wave before reaching a large-scale destruction. Therefore, according to the present invention, it is possible to avoid the risk of large-scale brittle fracture such as separation of a hull such as a large container line or a bulk carrier, and it has a great effect in securing the safety of the hull structure, And has a remarkable effect.

Further, it is possible to manufacture a welded structure excellent in brittle crack propagation stopping property without harming safety without using a special steel plate by adjusting the dimensions of the non-welded portion and the toughness of the fillet welded metal at the time of construction It is effective.

1 is an explanatory view schematically illustrating an example of the cross-sectional configuration of a fillet welded joint. 1 (a) is a cross-sectional view of a joining member (web) 1 and a member to be joined (flange) 2 when the joining member (web) 1 and the member to be joined 1 (c) shows a case in which the gap 14 is present between the joining member (web) 1 and the member to be joined (flange) 2 in the case where the joining member d shows the case where the gap 14 is located between the bonding member (web) 1 and the member to be bonded (flange) 2 and the spacer 15 is inserted into the gap 14 .
2 is an explanatory diagram schematically showing another example of the configuration of a fillet welded joint. Fig. 2 (a) is an external view, and Fig. 2 (b) is a sectional view.
3 is an explanatory diagram schematically showing another example of the configuration of the fillet welded joint. Fig. 3 (a) is an external view, and Fig. 3 (b) is a sectional view.
4 is an explanatory diagram schematically showing the shape of a very large structural model test body. Fig. 4 (a) shows a case where the joining member (web) 1 is made of only the steel plate base material and the joining member (web) 1 is made of only the steel plate base material, 4 (c) shows the welding member (web) 1 having the butt welded joint portion 12 and the bonded member (flange) 2 having the welded joint portion 11, And the member (flange) 2 has the butt welded joint portion 11.
5 is a graph showing the influence of the toughness of the fillet weld metal and the flange plate thickness on the propagation stop of brittle cracks.
Fig. 6 is a graph showing the influence of the toughness of the fillet weld metal and the smaller value L of the welding leg length and weld width on the propagation stop of brittle cracks.

(Mode for carrying out the invention)

The welded structure of the present invention is characterized in that the end face of the welding member (web) 1 is in contact with the surface of the welded member (flange) 2 having a thickness of 50 mm or more, And a fillet welded joint joining the joint members (flanges) 2. Further, the fillet welded joint has the fillet weld metal 5, and the welding length 3 and the weld width 13 are set to exceed 16 mm. In addition, on the butting face of the joining member (web) 1 and the member to be joined (flange) 2 of the fillet welded joint, there is an unetched portion 4 which is a structural discontinuity portion.

This state is shown in Fig. 1 at the joint cross section. 1 (a) shows a case where the joining member (web) 1 is attached upright to the member to be joined (flange) 2, but the present invention is not limited to this. For example, as shown in Fig. 1 (b), the joining member (web) 1 may be attached to the member to be joined (flange) 2 at an angle? In this case, the thickness (tw) of the joint member (web) to be used in obtaining the ratio Y (%) of the unhardened portion is the length of the intersection of the joint member (web) (90 [deg.] - [theta]). 1 (c), the gap 14 may be formed between the joining member (web) 1 and the member to be joined (flange) 2. 1 (d), a gap 14 is formed between the joining member (web) 1 and the member to be joined (flange) 2, and furthermore, (15) may be inserted.

1 (c) and 1 (d), when the gap 14 is formed between the joint member (web) 1 and the member to be welded (flange) (Web) 1 side satisfies a predetermined condition. 1 (d), the fillet weld metal 5 may be melted into the spacer 15.

As described above, the welded structure of the present invention is a welded structure in which the structure is discontinuous at the abutting surface of the joint member (web) 1 and the member to be welded (flange) 2 in the fillet welded joint, 4). In the fillet welded joint, the abutting surface of the joining member (web) 1 and the member to be joined (flange) 2 becomes the propagating surface of the brittle crack, so that the unetched portion 4 is provided on the abutting surface. The existence of the non-applied portion 4 lowers the energy release rate (crack propagation driving force) of the brittle crack tip propagated on the member to be bonded (flange) 2, and the brittle crack becomes easy to stop on the abutting surface . Even if a brittle crack propagates from the member to be welded (flange) 2 to the fillet weld metal 5, the fillet weld metal 5 can be welded to the fillet weld metal 5 even if the plate thickness tf of the welded member (flange) The brittle crack does not propagate to the joining member (web) 1 but stops at the fillet weld metal 5 because it has an appropriate toughness according to the welding width.

In addition, brittle cracks are very rare when cracks are generated in the steel plate base material portion with few defects. Most of the brittle fracture incidents occurred in the welds in the past. Therefore, for example, in the fillet welded joint shown in Figs. 2A, 2B, 3A, and 3B, the brittle cracks generated from the butt welded joint portion 11 In order to prevent the propagation to the joining member (web) 1, first, the presence of the discontinuity of the structure, that is, the presence of the unetched portion 4 on the contact surface of the member to be joined and the joining member in the fillet welded joint It becomes important.

2 (a) shows a state in which the member to be welded (flange) 2 is a steel plate joined with the butt welded joint 11 and the welded member (web) 1 is welded to the welded portion of the welded joint FIG. 2 (b) is a sectional view of a fillet welded joint which is fillet welded so as to intersect with the welded joint portion 11.

3 (a) shows a state in which the joining member (web) 1 is a steel plate having the butt welded joint portion 12 and the member to be welded (flange) 2 is welded to the butt welded joint portion 11, Welded joint portion 11 of the member to be welded (flange) 2 and the butt welded joint portion 12 of the welded member (web) 1 are crossed by a fillet welded joint And Fig. 3 (b) is a sectional view.

2 (a), 2 (b), 3 (a) and 3 (b) show the case where the butt welded joint portion 11 and the web 1 are orthogonal to each other. But is not limited thereto. Needless to say, crossing at an angle is good. In addition, the method of manufacturing the fillet welded joint is not particularly limited, and any of the commercially available manufacturing methods can be applied. For example, the fillet welded joints may be manufactured by butt welding the flange steel plates and the web steel plates, and then performing the fillet welding on the obtained butt welded joints. In addition, a set of web steel plates before the butt welding is welded to the flanges, and then the web steel plates are welded together, and the resulting welded joint is welded (fillet welded) to the flange, May be manufactured.

In the welded structure of the present invention, the dimension 16 (the width B of the non-welded portion) of the non-welded portion 4 in the cross section of the fillet welded joint is preferably 95% or more of the web plate thickness tw to suppress the propagation of the brittle crack do. If the dimension (width B of the unfused portion) of the non-applied portion 4 is less than 95% of the bonding member (web) plate thickness tw, the plastic deformation in the fillet weld metal is suppressed and the brittle crack (Web) 1 can not be stopped (stopped) because the stress near the crack tip of the joint member (web) 1 becomes high. Therefore, the dimension 16 (the width B of the unfused portion) of the unfit portion 4 is set to 95% or more of the thickness (tw) of the joining member (web) for suppressing the propagation of brittle cracks. Further, it is preferably 96% or more and 100% or less.

Also, the fillet welded joint and weld width of the fillet welded joint shall be more than 16 mm. When the fillet welded joint has a welding leg length of 16 mm or less, it is advantageous to secure the propagation-blocking performance of the brittle crack. However, when the thickness of the member plate exceeds 80 mm, it becomes difficult to secure the strength of the fillet welded portion. Further, even when the thickness of the member plate is 80 mm or less, the risk of maintenance and the like in the practice is increased. For this reason, the fillet welded joint and the welding width of the fillet welded joint are to be more than 16 mm. The upper limit of the welding leg length and the welding width is not particularly limited, but is usually up to 40 mm from the viewpoints of the work efficiency and the assurance of the assortment performance.

In the welded structure of the present invention, when the smaller value of the welding leg length and the welding width of the fillet weld metal in the fillet welded joint is L and L is less than 20 mm, the Charpy of the fillet welded metal The impact test wave front transition temperature vTrs (占 폚) and the plate thickness tf of the member to be bonded satisfy the following formula (1a) and L is 20 mm or more, the Charpy impact test wave front transition temperature vTrs ° C), the thickness tf of the member to be bonded, and L satisfy the following expression (1b).

group

vTrs? -35-1.5 (tf-75) ... (1a)

vTrs? -5L + 65-1.5 (tf-75) ... (1b)

Here, vTrs: Charpy impact test of fillet weld metal Wave front transition temperature (캜),

tf: thickness (mm) of the member to be bonded,

L: Small value (mm) of welding leg length and welding width

The fillet weld metal satisfies the above-mentioned formula (1a) or (1b) with respect to L, which is the smaller one of the plate thickness tf of the member to be welded (flange) 2, 5 and 6, the welded structure having a plate thickness of 50 mm or more of the member to be welded (flange) 2 can be used as a welded structure having desired brittle crack propagation blocking performance have. In addition, since the welding leg length and weld width are larger than 16 mm, the present invention is also applicable to a welded structure having a plate thickness of the member to be welded (flange) 2 of not less than 50 mm but also not less than 60 mm and not more than 80 mm. The upper limit of the welding leg length and the welding width is not particularly limited, but is usually up to 40 mm. The upper limit of the plate thickness of the member to be joined (flange) 2 is not particularly limited, but is usually up to 120 mm. When the low-temperature toughness of the fillet weld metal does not satisfy the above-mentioned formula (1a) or (1b), the low-temperature toughness of the fillet weld metal is insufficient and the brittle crack Can not be prevented from propagating in the fillet welded metal part. Further, when the length of the welded arc exceeds 40 mm and the plate thickness of the member to be welded (flange) 2 exceeds 120 mm, it becomes difficult to achieve both the work efficiency and the assurance of the arc performance.

As described above, in the relationship between the fillet weld metal and the plate thickness tf of the member to be welded (flange), and further, L, which is the smaller value of the welding leg length and weld width, , The brittle crack generated in the member to be welded (flange) can be prevented from propagating in the fillet weld metal.

The lower limit of vTrs is not particularly limited, but is generally -130 캜 when a general purpose welding material for marine applications is applied. Further, in order to lower the vTrs to -130 ° C, it is necessary to apply a special (expensive) welding material such as a low temperature tank welding material.

Further, L is a value smaller than the welding leg length and the welding width, and therefore is not limited, but is usually more than 16 mm but not more than 40 mm.

The thickness of the joining member (web) 1 is not particularly limited, but is usually 50 to 120 mm. When the thickness of the joining member is less than 50 mm, application of the present invention to conventional joining members (webs) and members to be joined (flanges) can prevent propagation of brittle cracks. On the other hand, since the plate thickness of the main steel hull structural steel sheet specified in IACS UR (International Rules of the Society) is 100 mm at most, it is hard to imagine that the plate thickness of the joining member exceeds 120 mm.

The welded structure includes the fillet welded joint described above. For example, the welded structure may have a hull structure in which the outer shell of the ship is a flange and the partition wall is a web, or a deck is a flange, a hull structure having a hatch as a web, and the like.

Hereinafter, an embodiment will be described.

Example

4 (a), the post-steel plate having the plate thickness tw shown in Table 1 is used as a joining member (web), and the post-steel plate having the plate thickness tf shown in Table 1 is used as a member to be joined (flange) ), A large fillet welded joint 9 of an actual structure size having a shape shown in Figs. 4 (b) and 4 (c) was produced. 1 (a), 1 (c), or 1 (d)) on the abutting surface of the joining member 1 and the member to be joined 2 in the manufactured large-sized fillet welded joint 9, The same unhardened portion 4 was present in a state in which the unfolded portion ratio Y (= (width B of the uncoated portion / plate thickness tw of the joint member (web)) was varied. (The base material only) (Fig. 4 (a)) or the post-welded steel plate having the butt welded joint (Fig. 4 (b) 4 (a) and 4 (b)), or a post-welded steel plate with an abutting welded joint (Fig. 4 (c)).

The butt weld joints were fabricated by 1-pass substitution heat electrogas arc welding (SEGARC and 2-electrode SEGARC) or multi-layer carbon dioxide welding (multilayer CO ₂ ). In the fillet welded joint, the welding conditions such as the welding material, the heat input for welding and the shielding gas were changed, and a fillet welded joint having various low temperature toughness and various welding leg lengths or welding widths was formed. The low-temperature toughness of the fillet weld metal was determined by taking a Charpy impact test piece (10 mm in thickness) from a butt weld joint manufactured under the same conditions as the fillet weld metal or fillet weld, and measuring the fracture transition temperature vTrs (° C). Further, in some fillet welded joints, the gap 14 was left between the joint member (web) 1 and the member to be welded (flange) 2. In the fillet welded joint, a fillet welded joint was produced by inserting the spacer 15 into the gap 14 between the joint member (web) 1 and the member to be welded (flange) 2.

Using the obtained large fillet welded joint 9, a large-scale structural model test body as shown in Fig. 4 was produced and subjected to a brittle crack propagation stop test.

The super large structural model test specimen is a welded weld 8 on the underside of the member to be welded (flange) 2 of the large fillet welded joint 9 and a steel plate having the same plate thickness as the welded member (flange) Welded.

In the very large structural model test body shown in Fig. 4 (b), the butt welded joint portion 11 of the member to be joined (flange) 2 is made to be perpendicular to the joint member (web) 1, 4 (c), the butt weld joint portion 11 of the member to be joined (flange) 2 and the butt weld joint portion 12 of the joint member (web) 1 were intersected. Then, the tip of the machine notch 7 was machined to be the BOND portion of the welded joint portion 11 or the weld metal WM.

Further, in the brittle crack propagation stop test, brittle cracks were generated by striking the mechanical notch, and it was examined whether or not the propagated brittle cracks stopped at the fillet welded portion. A test was conducted under the conditions of a stress of 100 to 283 N / mm 2 and a temperature of -10 캜. The stress of 100N / ㎟ is the average value of the normal stress acting on the hull and the stress of 257N / ㎟ is the value of the maximum allowable stress of the yield strength of 390N / The yield strength applied to the hull is equivalent to the maximum permissible stress of 460N / ㎟ grade steel. The temperature -10 ° C is the ship's design temperature. Further, in the calculation of the right side values of the equations (1a) and (1b), the fractional part is rounded off and displayed.

The obtained results are shown in Table 1.

In the inventive example, all the brittle cracks propagated in the member to be welded (flange), then entered into the fillet weld metal and stopped. On the other hand, in all of the comparative examples, the brittle crack propagated to the joining member (flange) without stopping in the fillet weld metal, and it was impossible to prevent the propagation of the brittle crack from the fillet weld metal.

1: joining member (web)
2: Member to be bonded (flange)
3:
4: Cosmetic application
5: Fillet welded metal
7: Machine notch
8: Welding welding
9: Large fillet welded joint
11: The butt welded joint portion of the member to be joined (flange)
12: The butt welded joint portion of the joint member (web)
13: Welding width
14: Gap
15: Spacer
16: Dimensions of the non-wearing area (width B of the non-wearing area)
θ: cross angle

Claims (3)

A welded structure comprising an end face of a joining member which is in contact with a surface of a member to be welded having a plate thickness of 60 mm or more and a fillet welded joint joining the joining member and the welded member,
The weld leg length and weld width of the fillet welded joint are greater than 16 mm,
A non-decorated portion of 95% or more of the plate thickness tw of the bonding member at the cross section of the fillet welded joint is provided on the face of the face of the bonding member in the fillet welded joint and the surface of the member to be bonded ,
Further, with respect to the fillet weld metal of the fillet welded joint,
(L) is less than 20 mm, the Charpy impact test wave front transition temperature vTrs (占 폚) of the fillet weld metal and the plate thickness of the member to be welded tf satisfies the following expression (1a)
L is 20 mm or more, the Charpy impact test wave front transition temperature vTrs (占 폚) of the fillet weld metal, the plate thickness tf of the member to be welded and L satisfy the following relation (1b) .
group
vTrs? -35-1.5 (tf-75) ... (1a)
vTrs? -5L + 65-1.5 (tf-75) ... (1b)
Here, vTrs: Charpy impact test of fillet weld metal Wave front transition temperature (캜),
tf: thickness (mm) of the member to be bonded,
L: Small value (mm) of welding leg length and welding width The method according to claim 1,
And the member to be welded has an abutting welded joint portion so as to intersect with the welding member. 3. The method of claim 2,
Wherein the welding member has an abutting welded joint portion and the abutting member is provided such that an abutting welded joint portion of the abutting member and an abutting welded joint portion of the bonded member intersect each other.

Images