KR20190014068A - Welded structure excellent in brittle crack propagation stopping property - Google Patents

Abstract

The reinforcing members having a ratio of the plate thickness td to the plate width Wd of less than td / Wd of 2 are superimposed on the surface of the member to be joined having a plate thickness of 50 mm or more and joined together by fillet welding, Are welded together to form a welded structure. An unapplied portion of 95% or more of the plate thickness td of the reinforcing member at the joint end face is formed on the surface of the surface of the reinforcing member and the surface of the member to be joined. When the fillet weld condition is adjusted so that the fracture surface transition temperature vTrs (占 폚) of the fillet weld metal varies in accordance with the fillet leg length L and in relation to the plate thickness tf of the member to be welded, in the case of L? 20mm, vTrs? + 65-1.5 (tf-75) ... (1b), and when L < 20 mm, vTrs? 35-1.5 (tf-75) ... (1c), the toughness of the fillet weld metal is adjusted. As a result, it is possible to prevent the propagation of the brittle cracks generated from the member to be joined or the joining member by the fillet weld metal portion, and to provide a welded structure excellent in brittle crack propagation stopping properties preferable for the hull structure.

Description

Welded structure excellent in brittle crack propagation stopping property

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welded steel structure welded by using a steel plate such as a large container wire or a bulk carrier and more particularly to a welded steel structure in which a brittle crack propagation generated from a post- The present invention relates to a welded structure excellent in brittle crack propagation stopping properties that can be stopped before reaching a welded structure.

Unlike a tanker, for example, a container line or a bulk carrier has a structure in which a partition wall is small in the pod and an opening of the line-shaped portion is large in order to improve the loading capacity and the loading efficiency. Therefore, in the case of the container ship or the bulk carrier, it is particularly necessary to strengthen or thicken the hull outer plate.

In addition, container ships have recently become larger and larger ships such as 6,000 to 22,000 TEU have been constructed. Here, the 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 ship. With such a ship becoming larger, the hull outer plate tends to have a plate thickness of 50 mm or more and a steel sheet having a yield strength of 390 N / mm ² or more.

In recent years, the steel plate as the outer shell of the hull has been often butt welded by large heat welding such as, for example, electro-arc arc welding, from the viewpoint of shortening the construction period. In such large heat welding, a considerable reduction in toughness is likely to occur in the weld heat affected zone, and this is one cause of the occurrence of brittle cracks from the weld joint.

From the viewpoint of safety in the hull structure, from the viewpoint of safety in the past, it is necessary to stop the propagation of brittle cracks even before brittle fracture occurs before reaching a large scale fracture, and to prevent separation of the hull.

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

In this non-patent reference 1, if the propagation path and propagation behavior of the brittle crack forcedly generated in the weld portion are experimentally investigated and the fracture toughness of the weld portion is secured to some extent, However, a plurality of examples in which brittle cracks propagate along the welded portion have also been confirmed. This suggests that brittle fracture can not be assured that there is no possibility of propagating straight along the weld.

However, in the case where the same welding as in the non-patent reference 1 is applied to a steel plate having a plate thickness of less than 50 mm, and there is a great deal of evidence that the dried vessel is operating without any problem, a steel plate having good toughness Etc.) has a sufficient ability to stop the brittle crack, and in particular, the brittle crack propagation stopping property of the welded portion of the steel for shipbuilding has not been required in the rules of classification.

However, in recent large-sized container ships over 6,000 TEU, the plate thickness of steel plates used exceeds 50 mm, and in addition to lowering of fracture toughness due to an increase in plate thickness, large heat input welding with larger heat input is adopted , The fracture toughness of the welded portion tends to be lowered further. In such a welded joint of welded joints of the welded joints, there is a possibility that the brittle cracks generated from the welded joint do not bend toward the base material and go straight, and the welded joints may not stop at the base material part of the steel sheet. For this reason, in the hull structure to which the high strength steel plate having the plate thickness of 50 mm or more is applied, securing its safety is a serious problem.

In addition, non-patent document 2 points out that a post-steel sheet having a specific brittle crack propagation stopping property is required in order to stop the propagation of a brittle crack, which occurs in particular.

To solve this problem, for example, Patent Document 1 discloses a welded structure in which an aggregate is disposed so as to intersect a butt weld portion and is joined by fillet welding in a welded structure, preferably a plate having a plate thickness of 50 mm or more, .

In the technique described in Patent Document 1, as an aggregate (reinforcement), an average circle-equivalent particle diameter of 0.5 to 5 mu m over a thickness of 3 mm or more in the surface layer portion and a two-layer portion, A steel sheet having a microstructure having an X-ray surface strength ratio of 1.5 or more is used. By employing a structure in which the steel sheet having such a microstructure is formed by fillet welding using 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, Damage can be prevented.

Patent Document 2 discloses a welded structure having a fillet weld seam formed by fillet welding a joining member (web) to a member to be joined (flange) and having excellent brittle crack propagation stopping properties.

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

Patent Documents 3 to 5 also disclose a welded structure having a fillet weld seam formed by fillet welding a joining member (web) to a member to be joined (flange), and having excellent brittle crack propagation stopping properties.

In Patent Document 3, at least one of the welding leg length or welding width formed by fitting the end face of the welding member to the surface of the member to be welded having a plate thickness of 50 mm or more and joining the welding member and the welding member by fillet welding is 16 mm Or more of a plate thickness tw of the joining member at a cross section of the fillet weld seam is formed on the face of the joining member facing the end face of the joining member in the fillet weld seam at least 95% And the Charpy impact test fracture transition temperature vTrs of the fillet weld metal in the fillet welded joint is in the range of vTrs &amp;le; 1.5tf + 70 and / or in the relation of the plate thickness tf of the welded member and / test temperature for Charpy impact test: the absorption energy vE _-20 (J) in the -20 ℃ in relation to the thickness tf of the bonded member, and satisfies the vE _-20 ≥2.75tf-105 Key has a welded structure having a fillet weld metal is described.

And, it is said that, in such a welded structure, the brittle cracks generated in the member to be bonded can be prevented from propagating in the fillet welded metal before reaching a large scale fracture.

Patent Document 4 discloses that at least one of the welded leg length or welding width formed by fitting the end surface of the welding member to the surface of a member to be welded having a thickness of 50 mm or more and welding the welding member to the welding target by fillet welding A welded structure having a fillet weld seam of 16 mm or less in which the end face of the welded member in the fillet welded joint and the surface of the welded member have a thickness of tw % Or more unbaked portion and the Charpy impact test fracture transition temperature vTrs of the fillet weld metal in the fillet welded joint is in the range of vTrs (캜) ≤-1.5tf + 90 in relation to the plate thickness tf of the member to be welded and / examination of the Charpy impact test of the fillet weld metal temperature: the absorbed energy vE _-20 (J) in the -20 ℃ in relation to the thickness tf of the bonded member, 50≤tf (㎜) of ≤53 Yiwu is _{vE -20 ≥5.75, tf (㎜)} > In the case of 53, the vE _-20 (J) has a fillet weld metal satisfying the ≥2.75tf-140, In addition to the joining members, brittle crack propagation stopping toughness Kca is a welded structure composed of 2500N ^/ ㎜ ^2/3 or more steel in the common temperature is described.

By using such a welded structure, it is said that the brittle crack can be suspended in the base material of the fillet welded portion or the bonded member.

In Patent Document 5, at least one of the welded leg length or welding width formed by fitting the end surface of the welding member to the surface of a member to be welded having a thickness of 50 mm or more and bonding the welding member and the welding target by fillet welding as a welded structure comprising a fillet weld joint below 16㎜, joining member and a member having a butt welded seam to be welded both absent, the weld metal portion butt weld seam is less than -65 ℃ in vTrs, and / or vE _{- 20} to 140 J or more and has a toughness of the welded joint of the butt welded joint of the fillet weld seam to be in contact with the welded surface of the butt welded joint of the welded joint and the butt welded joint of the fillet welded joint Of the plate thickness tw of the joining member in the fillet weld seam, The Charpy impact test fracture transition temperature vTrs of the welded metal is in the range of vTrs (캜) ≤-1.5tf + 90 in relation to the plate thickness tf of the member to be welded and / or the test temperature of the Charpy impact test of the fillet weld metal: absorption energy in the 20 ℃ vE _-20 (J) has, in relation to the thickness tf of the bonded member, 50≤tf (㎜) case of ≤53 has a _{vE -20 ≥5.75, tf (㎜)} > 53 A weld structure having a fillet weld metal satisfying vE- ₂₀ (J)? 2.75 tf-140 is disclosed.

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

It is also possible to prevent the brittle crack generated from the welded portion of the member to be bonded or the brittle crack generated from the welded portion of the welded portion from propagating in the welded portion of the fillet welded portion or the welded portion or the welded portion of the welded portion .

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-232052 Patent Document 2: Japanese Patent Application Laid-Open No. 2007-326147 Patent Document 3: Japanese Patent Publication No. 5395985 Patent Document 4: Japanese Patent No. 5365761 Patent Document 5: Japanese Patent Publication No. 5408396

Non-Patent Document 1: The 147th Research Meeting of Japan Shipbuilding Research Association: "Study on the Evaluation of Brittle Fracture Strength of High Heat Strength Steel Plate for Ship Hull" No. 87 (February 1978), p.35-53, Association Non-Patent Document 2: Yamaguchi Ginya et al., "Development of Very Large Container Ship - Practical Application of New High Strength Extreme Steel Plate," Japanese Society of Naval Architecture and Ocean Engineering, No. 3 (2005), p.70-76, November 2005 Non-Patent Document 3: Report of the 169th Committee of the Japanese Society of Naval Architects ("A Study on the Control Design of Destructive Management of Hull Structure - Report-" (1979), p.118-136,

However, since the aggregate as the reinforcing material used in the technique described in Patent Document 1 is a steel sheet formed with a desired structure, a complicated process is required, the productivity is lowered, and it is difficult to secure a steel sheet having a desired structure stably There was a problem.

The technique described in Patent Document 2 attempts to prevent brittle cracks generated in a bonding member (hereinafter also referred to as a web) with a combination of a discontinuity in structure and a brittle crack propagation stopping performance of a member to be bonded (hereinafter also referred to as a flange) Technology. However, as shown in Non-Patent Document 3, in general, propagating stopping of the brittle crack generated in the member to be joined (flange) of the fillet weld seam from the joint member (web) It is experimentally confirmed that it is difficult to stop the propagation in the joining member (flange).

The reason for this is not clarified, but as one factor, it is considered that the fracture driving force (stress intensity factor) at the time of cracking into the T joint portion is higher than that in the case where the fracture driving force It is conceivable that the side becomes larger when it goes in.

Accordingly, in the technique described in Patent Document 2, the brittle crack propagation stopping characteristics and the like of the joining member (web) are insufficient, so that the brittle crack generated in the member to be joined (flange) It is not enough technology. That is, the technique described in Patent Document 2 is, for example, a brittle crack generated in a strength deck (equivalent to a flange) of a large container ship proposed in NK Classification Guidelines for Brittle Crack Arrest Design (issued in September 2009) It can not be said that it has sufficient crack propagation stopping characteristics for cases such as those propagated to side coaming (equivalent to the web).

Further, in the technologies described in Patent Documents 3 to 5, since the fillet weld leg length (or welding width) needs to be limited to 16 mm or less, the joining member (web) and the member to be joined ) Was the maximum plate thickness of 80 mm. However, in recent large-sized container ships, the slope of members is further advanced, and a steel sheet having a thickness of 100 mm is applied. There has been a problem that it is almost impossible to apply the techniques described in Patent Documents 3 to 5 in the case of the lower member exceeding 80 mm.

In addition, even when the plate thickness of the member is less than 80 mm, since the deviation of the leg length of the fillet welded portion is large in the field of operation in the field, the strength of the fillet welded portion (securing the fillet leg length) (Limited to a fillet leg length of 16 mm or less) requires a lot of efforts in construction management in the field, and at the same time, there is a problem that additional costs such as maintenance are increased.

Disclosure of the Invention The present invention has been made to solve the above problems of the prior art and to provide a method of manufacturing a bonding member (web), in which propagation of a brittle crack generated in a member to be bonded (flange) Which is capable of stopping (stopping) all of the brittle crack propagation stopping characteristics before the welding is completed and before all of the welds are completely destroyed.

Means for Solving the Problems In order to achieve the above object, the inventors of the present invention have extensively studied a method for reducing the deviation of the leg length of the fillet welded portion in the construction of the fillet welded portion for stopping the brittle crack.

As a result, the basic welded structure is formed from a fillet welded structure of the related art, and a fillet welded structure having a reinforcing member having a reinforcing member disposed between the bonded member and the bonded member is used. Welded metal portion of the fillet welded metal portion. With this fillet welded structure, the construction of the fillet welded portion for stopping the brittle crack can be welded in the factory. It has also been found that this makes it easier to set the deviation of the leg length of the fillet weld within a predetermined range, leading to a drastic reduction in the borehole cost in the field.

In this way, the joining of the joining member and the reinforcing member performed at the site where strict construction management is strictly carried out is carried out by bringing the end face of the joining member into contact with the surface of the reinforcing member, and by the welding conditions (partial penetration, complete penetration, etc.) I knew that I could build it.

The present inventors have also studied various factors affecting brittle crack propagation stopping characteristics in a fillet welded structure having a reinforcing member.

As a result, in order to stop (stop) the propagation of the brittle cracks generated from the member to be bonded (flange), the discontinuous portion is ensured on the overlapping surface of the member to be joined (flange) and the reinforcing member, Considering that the energy release rate (crack propagation driving force) of the brittle crack tip increases and the brittle crack becomes difficult to stop when the tf (mm) becomes large, the fillet weld portion (flange) It is necessary to improve the toughness.

Further, it is also known that, if the leg length or the welding width of the fillet welded portion becomes long, the propagation of the brittle crack becomes easy, and therefore it is necessary to secure the toughness of the fillet welded metal according to the fillet welded leg length .

On the other hand, it is often easier to stop (stop) the propagation of the brittle cracks generated from the joining member (web) than to stop (stop) the propagation of brittle cracks generated from the member to be joined (flange) (Stop) of the propagation of the brittle crack generated from the joining member (web) is prevented from stopping (stopping) the propagation of the brittle crack generated from the member to be joined (flange) ).

The present invention has been completed on the basis of the above knowledge and by further review.

That is, the gist of the present invention is as follows.

(1) A fillet having a reinforcing member having a cross section welded to the surface of the reinforcing member by butt welding and the reinforcing member having a fillet weld seam welded to the surface of a member to be joined having a thickness of 50 mm or more, A welded structure comprising: a non-irradiated portion of 95% or more of a plate width Wd of a reinforcement member at an end face of the fillet weld seam on a surface of the fillet weld seam where the surface of the reinforcement member and the surface of the member to be welded are overlapped , And the reinforcing member satisfies the following expression (1a), wherein the ratio td / Wd of the plate thickness td to the plate width Wd satisfies the following expression (1a) and the fillet weld metal of the fillet weld seam is subjected to the Charpy impact test fracture transition (1b) or (2) in the relation between the plate thickness tf of the member to be bonded and the fillet leg length or the weld width L, corresponding to the fillet leg length or weld width L, (1c) &lt; tb &gt; &lt; tb &gt; &lt; TABLE &gt;

td / Wd < 2 ... (1a)

VTrs &amp;le; -5L + 65-1.5 (tf-75) &amp;le; (1b)

In the case of L <20 mm, vTrs? 35-1.5 (tf-75) ... (1c)

here,

vTrs: Charpy impact test of fillet weld metal Fracture Transition Temperature (℃),

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

td: plate thickness (mm) of the reinforcing member,

Wd: plate width of reinforcing member (mm)

L: fillet leg length or weld width (mm).

(2) The welded structure according to (1), wherein the member to be bonded has a butt weld joint portion in a direction crossing the joint member.

(3) The welded structure according to (2), wherein the joining member has a butt weld joint portion and the butt weld joint portion of the joining member crosses the butt weld joint portion of the joining member.

According to the present invention, it is possible to prevent the propagation of brittle cracks to the joining member (web) caused by a member to be joined (flange) made of a post-steel sheet having a plate thickness of 50 mm or more, Both of the propagation of the brittle crack generated in the joining member (web) to the member to be joined (flange) can be stopped or prevented before reaching a large scale failure.

Therefore, according to the present invention, it is possible to avoid the risk of large-scale brittle fracture such as separation of the hull in a steel structure, particularly, in a large container ship or a bulk carrier, and a great effect is obtained in securing the safety of the hull structure, It has a remarkable effect in the industry.

Further, according to the present invention, by adjusting the dimensions of the reinforcing member and the toughness of the fillet weld metal at the time of construction, it is possible to easily perform the brittle crack propagation stopping property There is an effect that the excellent welded structure can be manufactured.

1 is an explanatory diagram schematically illustrating a cross-sectional configuration of a fillet weld seam. (a) shows a case where the joining member (web) 1 and the reinforcing member 10 and the member to be joined (flange) 2 are orthogonal to each other, (b) 10 and the member to be joined (flange) 2 cross each other at an oblique angle.
2 is an explanatory view schematically showing another example of the configuration of the fillet weld seam. (a) is an external view and (b) is a sectional view.
3 is an explanatory view schematically showing another example of the configuration of the fillet weld seam. (a) is an external view and (b) is a sectional view.
Fig. 4 is an explanatory view schematically showing the shape of a very large-scale structural model test object for brittle cracks generated and propagated from a member to be bonded (flange) used in the embodiment. Fig. (b) shows a case where the member to be welded (flange) 2 has a butt weld joint, (c) shows a case where the welded member (web) (Flange) 2 have a butt weld joint portion.
Fig. 5 is an explanatory diagram schematically showing the shape of a very large structural model test object for brittle cracks generated and propagated from a joint member (web) used in the embodiment. Fig. (b) shows a case where the joining member (web) 1 has a butt weld joint, (c) shows a case where the joining member (web) 1 And the member to be welded (flange) 2 have butt weld joints.

Hereinafter, the present invention will be described in detail.

The welded structure of the present invention is formed by joining the end face of the joining member 1 to the surface of the reinforcement member 10 and joining the joining member 1 and the reinforcement member 10, And a fillet weld seam superimposed on the surface of the member to be welded (2) of 50 mm or more and joined together by fillet welding. The welded structure has a fillet weld seam having a fillet weld metal 5 having a welded leg length 3 or a weld width 13 of L mm and the reinforcement member 10 and the bonded member (Not shown) which is a structural discontinuity is present on the superimposed surface of the flange (flange) 2. Further, in the welded structure of the present invention, the cross-section of the joining member 1 may include a structure discontinuity portion on the abutting surface that faces the surface of the reinforcing member 10.

This state is shown in Fig. 1 at a joint 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?

As described above, the welded structure of the present invention has the non-applied portion 4 whose structure is discontinuous on the superposed surface of the reinforcing member 10 and the member to be joined (flange) 2. In the welded structure of the present invention, since the overlapping surface of the reinforcing member 10 and the member to be joined (flange) 2 is a propagation surface of brittle crack, the unapplied portion 4 is present on the overlapping surface. The existence of the non-applied portion 4 reduces the energy release rate (crack propagation driving force) of the brittle crack tip propagated through the joint member (web) 1 or the member to be welded (flange) On the surface, the brittle crack becomes easy to stop.

Thus, in the present invention, the fillet weld metal 5 that maintains a predetermined toughness is formed, and the brittle crack is stopped at the fillet weld metal 5.

In addition, it is extremely unlikely that brittle cracks occur in the base material portion of the steel sheet with few defects. Most of the brittle fracture incidents in the past have occurred in welds. Therefore, for example, when the member to be welded (flange) 2 is a steel plate joined at the butt joint 22 and the welding member (web) is welded to the welded portion (butt welded joint) (Filler) welded joints such as those shown in Fig. 2 which are fillet welded so as to intersect the welded joints (webs) 1 and 2 (welded joints) 3, the butt weld joint portion 22 of the member to be joined (flange) 2 and the butt weld joint portion 12 of the joint member (web) 1 intersect each other, In order to prevent the propagation of the brittle cracks generated from the butt weld joints 12 or 22 in all of the weld seams, it is important to first make the discontinuity of the structure exist.

Therefore, in the present invention, an unfit portion (structure discontinuity) 4 is formed on the overlapping surface of the member to be bonded and the reinforcing member in the fillet welded portion.

Fig. 2 (a) shows the appearance of the fillet weld seam, and Fig. 2 (b) shows the cross-sectional shape of the butt weld joint 22. Fig. 3 shows a state in which the joined member (web) 1 and the member to be welded (flange) 2 are steel plates having the butt weld joints 12 and 22, And the butt weld joints 12 of the joint members (webs) 1 intersect with each other. Fig. 3 (a) shows the appearance of the fillet weld seam, and Fig. 3 (b) shows the joint cross-sectional shape in the butt weld joints 12, 22.

2 and 3 show the case where the butt weld joint 22 and the web 1 are orthogonal to each other, the present invention is not limited to this. Of course it is good to cross at an angle.

The manufacturing method of the welded structure is not particularly limited, and any of the commercially available manufacturing methods can be applied. For example, the flange steel plates and the web steel plates may be butt welded together, and the obtained butt welding seam may be fillet welded through a reinforcing member to produce a welded structure. A pair of web steel plates before butt weld may be welded to a reinforcing member on the flange surface, then the web steel plates may be butt welded together, and the obtained butt weld seam may be welded to the flange to produce a welded structure.

In the present invention, the dimension of the unfit portion 4 on the section of the fillet welded joint is set to 95% or more of the width Wd of the reinforcing member in order to suppress the propagation of brittle cracks. If the dimension (width B) 16 of the non-application portion 4 is less than 95% of the width Wd of the reinforcing member, plastic deformation in the fillet weld metal is suppressed, and the vicinity of the crack tip of the brittle crack, It becomes difficult to stop or prevent the brittle cracks. Therefore, the dimension (width B) 16 of the non-applied portion 4 is limited to 95% or more of the width Wd of the reinforcing member due to the suppression of the brittle crack propagation. Further, it is preferably 96% or more and 100% or less.

In the present invention, the ratio of the plate thickness td of the reinforcing member to the plate width Wd of the reinforcing member, td / Wd,

td / Wd < 2 ... (1a)

The dimension of the reinforcing member is adjusted. When the plate thickness td of the reinforcing member and the plate width Wd of the reinforcing member do not satisfy the expression (1a), the stopping or stopping of the brittle crack generated from the joining member (web) And the propagation of the brittle cracks generated from the joining member (web) and the member to be bonded (flange) can not be stopped or stopped.

Further, if td / Wd becomes too small, there arises a problem that the longitudinal stiffness of the reinforcing member is lowered, so that the lower limit value of td / Wd is preferably 0.2.

Further, in the present invention, the relationship between the plate thickness tf of the member to be bonded and the fillet leg length or the weld width L corresponding to the fillet leg length or weld width L is expressed by the following formula (1b)

In the case of L? 20 mm, vTrs? -5L + 65-1.5 (tf-75) ... (1b)

In the case of L < 20 mm, vTrs? 35-1.5 (tf-75) ... (1c)

(T) is the plate thickness (mm) of the member to be welded, L is the fillet leg length or weld width (mm)),

The toughness of the fillet weld metal is adjusted. L is the smaller of the fillet leg length and the welding width.

(1b) or (1c) is satisfied in relation to the plate thickness tf of the member to be welded (flange) and the fillet leg length L, the toughness of the fillet welded metal satisfies the above- It is possible to obtain a welded structure in which desired brittle crack propagation blocking performance is secured for a welded structure having a plate thickness of 50 mm or more of the member (web). When the toughness of the fillet weld metal does not satisfy the above-mentioned formula (1b) or formula (1c), the toughness of the fillet weld metal is insufficient and the toughness of the welded metal The brittle crack can not be prevented by the fillet weld metal part.

(1b) or (2b) in the relationship between the fillet weld metal and the plate thickness tf of the member to be joined (flange) and the fillet leg length (weld width) (1c), the brittle crack generated in the member to be welded (flange) and the propagation of the brittle crack generated in the joint member (web) can all be blocked by the fillet weld metal.

In addition, the welded structure of the present invention includes the fillet weld seam described above. For example, the welded structure may include a hull structure in which the outer plate of the hull of the ship is a flange and the partition is a web, And the like.

Example

Hereinafter, the present invention will be described in detail based on examples.

4 (a), 4 (b), and 4 (c), using the post-steel plate having the plate thicknesses shown in Table 1-1 and Table 1-2 as the joining member (web), the reinforcing member, And 5 (a), 5 (b) and 5 (c) were fabricated. 4 (a), 4 (b) and 4 (c) show a case in which brittle cracks are generated and propagated from a member to be bonded (flange) And a brittle crack is generated and propagated from the brittle crack. In the fillet weld seam thus manufactured, the unfolded portion 4 as shown in Fig. 1 (a) is placed on the abutting surface of the reinforcing member 10 and the member to be joined 2, and the unfolded portion ratio Y (= The width B of the uncoated portion, and the plate width Wd of the reinforcing member). In addition, the untreated portion was not left on the abutting surface of the joining member (web) and the reinforcing member.

4 (a)) or a post-welded steel plate having a butt weld joint (Fig. 4 (b)), and the joining member (flange) 4 (a) and 4 (b)) or a post-welded steel plate having a butt weld joint (Fig. 4 (c)). The joining member (web) of the case of Fig. 5 is also a post-welded steel plate (Fig. 5 (b)) having a rear steel plate (base material only) 5 (a) and 5 (b)) or a post-welded steel plate having a butt weld joint (Fig. 5 (c)). The butt weld seams were fabricated by one pass electrothermal arc welding (one electrode EGW, two electrodes EGW, SEGARC, two electrodes SEGARC) or multilayer CO ₂ welding.

The fillet weld seam is a fillet weld seam having fillet weld metal of various toughness, various fillet leg lengths, or welding widths by changing welding conditions such as welding material, welding heat input and shielding gas. Fillet leg length, and weld width are both average values. In addition, the toughness of the fillet weld metal was determined by taking a Charpy impact test piece (10 mm thick) 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 ) Were obtained.

Using the obtained large fillet weld seam, a very large structural model test body as shown in Figs. 4 and 5 was prepared and a brittle crack propagation stop test was carried out. The large-scale structural model test body of FIG. 4 also has a structure in which a member to be joined (flange) 2 and a member to be joined (flange) 2 are welded to the lower side of the member to be welded (flange) 2 of the large fillet weld seam 9 having a reinforcing member A steel plate having the same plate thickness was welded. The super large structural model test body of Fig. 5 is formed of the same material as that of the joint member (web) 1 with the use of the welded joint 8 below the joint member (web) 1 of the large fillet weld joint 9 having a reinforcing material. Thick steel plates were welded.

The tip of the machine notch 7 is set so that the base material of the joint member (web) 1 or the member to be welded (flange) 2, the BOND portion of the butt weld joints 12 and 22, .

In the brittle crack propagation stop test, a mechanical notch was hit to generate a brittle crack, and whether or not the propagated brittle crack stopped at the fillet weld was examined.

All the tests were conducted under the conditions of a test stress of 100 to 283 N / mm ² and a temperature of -10 캜. The test stress of 100N / ㎟ is the average value of the normal stress acting on the hull. The test stress of 257N / ㎟ is equivalent to the maximum permissible stress of the steel sheet with a yield strength of 390N / ㎟ and the test stress of 283N / 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.

The obtained results are shown in Tables 2-1 and 2-2.

[Table 1-1]

[Table 1-2]

[Table 2-1]

[Table 2-2]

As shown in Table 2-1 and Table 2-2, in the case of the present invention, even when the brittle crack is propagated from the member to be bonded (flange) or when the brittle crack is propagated from the bonding member (flange) All cracks entered the fillet weld metal of the fillet weld and stopped.

On the other hand, in the comparative example deviating from the scope of the present invention, when the brittle crack is propagated from the member to be bonded (flange) or when the brittle crack is propagated from the bonding member (flange) The brittle crack propagated without stopping at the fillet weld, and it was impossible to prevent the propagation of the brittle crack from the fillet weld metal.

One; A joining member (web) 2; The member to be bonded (flange)
3; Leg length 4; Hairdressing
5; Fillet weld metal 7; Mechanical notch
8; Soluble contact
9; Large fillet weld seam with reinforcement member
10; A reinforcing member 12; Web butt weld joint
13; Welding width 16; Bonding width (B)
22; Flange butt weld joint
θ; Cross angle

Claims (3)

A fillet welded structure having a reinforcing member welded to the surface of the reinforcing member and welded to the surface of the member to be welded with a plate having a thickness of 50 mm or more, And a non-decorated portion having 95% or more of the plate width Wd of the reinforcing member at the end face of the fillet weld seam on the surface of the fillet weld seam overlapping the surface of the reinforcing member and the surface of the member to be bonded, Wherein the reinforcing member satisfies the following expression (1a), and the fillet weld metal of the fillet weld seam is made of the fillet welded metal with the ratio td / Wd of the plate thickness td to the plate width Wd satisfying the Charpy impact test fracture transition temperature vTrs (1b) or (1c) in the relationship between the plate thickness tf of the member to be bonded and the fillet leg length or the weld width L corresponds to the fillet leg length or weld width L, Welded structure with excellent brittle crack propagation stopping property using fillet weld metal satisfying the formula:
td / Wd < 2 ... (1a)
In the case of L? 20 mm, vTrs? -5L + 65-1.5 (tf-75) ... (1b)
In the case of L < 20 mm, vTrs? 35-1.5 (tf-75) ... (1c)
here,
vTrs: Charpy impact test of fillet weld metal Fracture Transition Temperature (℃),
tf: thickness (mm) of the member to be bonded,
td: plate thickness (mm) of the reinforcing member,
Wd: plate width of reinforcing member (mm)
L: fillet leg length or weld width (mm). The method according to claim 1,
Wherein the member to be welded has a butt weld joint in a direction crossing the welded member. 3. The method of claim 2,
Wherein the joining member has a butt weld joint portion and the joining member is arranged so that the butt weld joint portion of the joining member crosses the butt weld joint portion of the joining member.

Images