KR102258423B1 - Welded structure having excellent brittle crack arrestability - Google Patents

Abstract

It is set as the welded structure provided with the reinforcing member 10 in the butt|matching part of the web 1 and the flange 2 . The cross section of the web is abutted to the surface of the reinforcing member, the web and the reinforcing member are joined by fillet welding, the flange surface and the reinforcing member surface are overlapped, and the reinforcing member is joined by fillet welding. At that time, the ratio Y (%) of the sum of the width of the unwelded portion of the overlapping surface in the joint cross-section of the fillet welded joint, the plate width of the reinforcing member and the leg length of the left and right fillet welds, and the shared temperature T (°C) It is adjusted so that the relationship of the brittle crack propagation stop toughness (Kca) _T (N/mm ^3/2 ) of the reinforcing member in this may satisfy|fill Y(%) >={6900-Kca}/85. Thereby, propagation of the brittle crack generated from the flange can be prevented or stopped by the reinforcing member.

Description

Welded structure with excellent brittle crack propagation stopping properties {WELDED STRUCTURE HAVING EXCELLENT BRITTLE CRACK ARRESTABILITY}

The present invention relates to a welded steel structure welded using, for example, a thick steel plate such as a large container ship or a bulk carrier, and in particular, the propagation of brittle cracks generated from the thick steel plate base material or welded joint, large-scale destruction of the structure It relates to a welded structure with excellent brittle crack propagation stopping properties that can be stopped before reaching

Container ships and bulk carriers have a structure in which, unlike a tanker, there are few partition walls in a hold and the opening part of a ship is large for the improvement of loading capacity, improvement of unloading efficiency, etc., for example. For this reason, in a container ship or a bulk carrier, it is necessary to especially strengthen or thicken a ship hull board.

In addition, container ships have been enlarged in recent years, and large ships such as 6,000-22,000TEU have been built. Here, TEU (Twenty feet Equivalent Unit) represents the number converted to a container of 20 feet in length, and represents an indicator of the loading capacity of a container ship. With the increase in size of such ships, the thickness of the outer plate of the hull is 50 mm or more, and the yield strength: 390 N/mm ^{or higher grade 2} thick steel plate tends to be used.

In recent years, from a viewpoint of shortening a construction period, the steel plate used as a hull outer plate is butt-welded by high heat input welding, such as electrogas arc welding, in many cases. In such high heat input welding, a significant decrease in toughness tends to occur in the weld heat affected zone, and it has become one cause of the occurrence of brittle cracks from the weld joint.

In ship body structure, from the viewpoint of safety, even if a brittle fracture occurs by any chance, it is necessary to stop the propagation of a brittle crack before it reaches a large-scale fracture, and to prevent hull separation.

In response to such a thought, the experimental examination result about the brittle crack propagation behavior of the weld part in the steel plate for shipbuilding less than 50 mm of plate|board thickness is reported in Nonpatent literature 1.

In this non-patent document 1, the propagation path and propagation behavior of brittle cracks forcibly generated in the weld are experimentally investigated, and if the fracture toughness of the weld is secured to a certain extent, the brittle crack in the base metal under the influence of the welding residual stress is Although the result that it deviates to the side in many cases is described, the example in which a brittle crack propagated along a welding part is also confirmed several examples. This suggests that it cannot be asserted that brittle fractures are unlikely to propagate straight along the weld.

However, in addition to the many achievements that a ship built by applying welding equivalent to the welding applied in Non-Patent Document 1 to a steel plate having a plate thickness of less than 50 mm, is operating without any problem, a steel plate base material with good toughness (shipbuilding E From the recognition that the ability to stop brittle cracks is sufficiently maintained, particularly, the properties of stopping propagation of brittle cracks in welded parts of steel for shipbuilding have not been required by the classification rules.

However, in recent large container ships exceeding 6,000 TEU, the plate thickness of the steel plate used exceeds 50 mm, and in addition to the decrease in fracture toughness due to the increase in plate thickness, high heat input welding has been adopted, which has a larger welding heat input. , the fracture toughness of the weld zone tends to further decrease. In such a thick large heat input welded joint, it has been shown that the brittle cracks generated from the weld may go straight to the base metal side without bending, and may not stop even in the base metal part of the steel plate such as aggregate (eg, non-patent document 2). For this reason, in the hull structure to which a thick high-strength steel plate having a plate thickness of 50 mm or more is applied, securing the safety is a major problem.

In addition, Non-Patent Document 2 also points out that a thick steel plate having special brittle crack propagation stopping properties is required for stopping the propagation of a particularly generated brittle crack.

In response to such a problem, for example, Patent Document 1 describes a welded structure in which aggregates are arranged so as to intersect butt welds and joined by fillet welding in a welded structure that is preferably a hull outer plate having a plate thickness of 50 mm or more. .

In the technique described in Patent Document 1, as an aggregate (reinforcing material), it has an average equivalent circle particle diameter of 0.5 to 5 µm over a thickness of 3 mm or more in the surface layer and the two-layer part, and a (100) crystal plane in a plane parallel to the plate thickness plane. It is assumed that a steel sheet having a microstructure having an X-ray surface intensity ratio of 1.5 or more is used. By using a steel sheet having such a microstructure as a reinforcing material to have a structure in which fillet welding is performed, even if a brittle crack occurs in the butt weld joint, brittle fracture can be stopped in the aggregate serving as the reinforcing material, which is fatal as the welded structure is destroyed. It is said that damage can be prevented.

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

In the welded structure described in Patent Document 2, an unwelded portion remains on the butt surface of the web at the cross section of the fillet welded joint, and the width of the unwelded portion, the left and right leg lengths of the fillet welded portion, and the web plate thickness The width of the unwelded portion is adjusted so that the sum ratio, X, satisfies the brittle crack propagation stop performance Kca of the member to be joined (flange) and a special relational expression. As a result, even when a thick material having a plate thickness of 50 mm or more is used as the member (flange) to be joined, the propagation of brittle cracks generated in the joining member (web) is stopped at the butt surface of the web and the flange of the fillet weld, It is said that propagation of the brittle crack to the member to be joined (flange) can be prevented.

Moreover, also in Patent Documents 3 to 5, a welded structure having a fillet weld joint formed by fillet welding a joining member (web) to a joined member (flange) and excellent in brittle crack propagation stopping properties is described.

In Patent Document 3, at least one of the welding leg length or welding width formed by abutting the end face of the joining member to the surface of the member to be joined with a plate thickness of 50 mm or more, and joining the joining member and the member to be joined by fillet welding is 16 mm A welded structure having the following fillet welded seams, wherein the end face of the joining member in the fillet welded joint and the surface of the joined member are abutted at 95% or more of the plate thickness tw of the joined member in the cross section of the fillet welded joint The Charpy impact test fracture transition temperature vTrs of the fillet weld metal in the fillet weld joint having an unwelded part is vTrs≤-1.5tf+70 in relation to the plate thickness tf of the member to be joined, and/or the fillet weld metal Test temperature of Charpy impact test: Welding with fillet weld metal in which _{absorbed energy vE -20 (J) at -20°C satisfies vE -20} ≥2.75tf-105 in relation to the plate thickness tf of the member to be joined The structure is described.

And if it is such a welded structure, it is said that the brittle crack which generate|occur|produced in a to-be-joined member can be prevented from propagating in a fillet weld metal before reaching a large-scale fracture.

Further, in Patent Document 4, at least one of the welding leg length or welding width formed by abutting the end face of the joining member to the surface of the member to be joined with a plate thickness of 50 mm or more, and joining the joining member and the member to be joined by fillet welding. A welded structure having a fillet welded joint of 16 mm or less, wherein the end face of the joining member in the fillet welded joint and the surface of the joined member are abutted, and the plate thickness tw of the joining member in the cross section of the fillet welded joint is 95 % or more, and the Charpy impact test fracture transition temperature vTrs of the fillet weld metal in the fillet welded joint has vTrs(°C)≤-1.5tf+90 in relation to the plate thickness tf of the member to be joined, and/or Test temperature of Charpy impact test of fillet weld metal: Absorbed energy vE _-20 (J) at -20°C with the plate thickness tf of the member to be joined, vE _{- when 50≤tf(mm)≤53 In the case of 20} ≥ 5.75, tf (mm) > 53, have _{a fillet weld metal satisfying vE -20} (J) ≥ 2.75 tf-140, and in addition to this, the joint member is subjected to brittle crack propagation stop toughness Kca at common temperature A welded structure composed of a steel plate of 2500 N/mm ^{2 / 3 or more is described.}

And by setting it as such a welded structure, it is said that a brittle crack can stop propagating in the base material of a fillet weld part or a joining member.

Further, in Patent Document 5, at least one of the welding leg length or welding width formed by butting the end face of the joining member against the surface of the member to be joined with a plate thickness of 50 mm or more, and joining the joining member and the member to be joined by fillet welding. A welded structure having a fillet weld seam of 16 mm or less, wherein both the joined member and the joined member are members having a butt weld joint, and the weld metal of the butt weld joint is -65° C. or less at vTrs, and/or vE _{- It} has a toughness of 20 to 140J or more, and the weld section of the butt weld joint of the joining member in the fillet welded joint is buttted to the weld surface of the butt welded joint of the joined member, and the butt welded joint cross section of the fillet welded joint In the Charpy impact test fracture front transition temperature vTrs of the fillet weld metal in a fillet welded joint having an unwelded portion of 95% or more of the plate thickness tw of the joined member, in the relation with the plate thickness tf of the joined member, vTrs( ℃)≤-1.5tf+90 and/or the test temperature of the Charpy impact test of the fillet weld metal: the absorbed energy vE _-20 (J) at -20°C in relation to the plate thickness tf of the member to be joined, A welded structure having a fillet weld metal that satisfies _{vE -20} ≥5.75 for 50≤tf(mm)≤53 and _vE-20 (J)≥2.75tf-140 for tf(mm)>53 is described. have.

And by setting it as such a welded structure, it is said that a brittle crack can stop by the base material of a fillet weld part or a joining member.

In addition, by using such a welded structure, brittle cracks generated from the welded part of the joined member or the brittle crack generated from the welded part of the joined member can be prevented from propagating in the fillet weld, the welded part of the joined member, or the welded part of the joined member. .

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

Non-Patent Document 1: Japanese Shipbuilding Research Association No. 147 Research Section: 「A Study on the Evaluation of Brittle Fracture Strength of High-Tensile Steel Plate High-Heat Input Joints for Hulls」 No. 87 (February 1978), p.35-53, Japanese Shipbuilding Research Association Non-Patent Document 2: Ginya Yamaguchi et al.: “Development of a super-large container ship—Practical use of new high-strength ultra-thick steel plates—”, Journal of Marine Engineering of Japan, No. 3 (2005), p.70-76, November 17, 2017 Non-Patent Document 3: Japanese Shipbuilding Research Association 169th Committee Report ("Research-Report- on the Design of Destruction Management and Control of Hull Structures-" (1979), p.118-136, 169th Committee of the Japan Shipbuilding Research Association)

However, the aggregate, which is a reinforcing material used in the technique described in Patent Document 1, requires a complicated process in order to obtain a steel sheet having a desired structure, reduces productivity, and it is difficult to stably secure a steel sheet having a desired structure. There was a problem.

In addition, the technique described in Patent Document 2 is to prevent brittle cracks generated in the joining member (hereinafter also referred to as a web) with a combination of structural discontinuity and the brittle crack propagation stopping performance of the joined member (hereinafter also referred to as a flange). is a technique to However, as shown in Non-Patent Document 3, in general, stopping the propagation of a brittle crack generated in the joined member (flange) of the fillet welded joint in the joining member (web) avoids the brittle crack generated in the joining member (web). It has been experimentally confirmed that it is more difficult than stopping the propagation with a joining member (flange).

Although the reason is not clearly elucidated, as one factor, the fracture driving force (stress magnification coefficient) when a crack rushes into the T-joint is higher in the joining member (web) than when it rushes into the member (flange) to be joined. It is thought that the side becomes larger when rushing in.

From these things, in the technique of patent document 2, since the brittle crack propagation stop characteristic of a web etc. are inadequate, it cannot be said that it is a sufficient technique which can stop the brittle crack generated in a flange from propagation in a web. That is, in the technique described in Patent Document 2, for example, brittle cracks generated in the strong deck (corresponding to the flange) of a large container ship assumed in the "British Crack Arrest Design Guidelines" (established in September 2009) of NK Classification of the Year are hatched. For cases such as propagating by hatch side coaming (equivalent to web), it cannot be said to have sufficient crack propagation stopping properties.

In addition, in the technique described in Patent Documents 3 to 5, since it is necessary to limit the fillet weld leg length (or welding width) to 16 mm or less, from the viewpoint of securing fillet weld strength, the maximum applicable plate thickness of the web and flange is 80 mm was the limit. However, in recent large-scale container ships, the thickness reduction of the member further progresses, and steel materials with a plate|board thickness of 100 mm are applied. In the case of such a thick member exceeding 80 mm, there existed a problem that it was almost impossible to apply the technique described in patent documents 3-5.

In addition, even when the plate thickness of the member is less than 80 mm, there is a large variation in the leg lengths of the fillet welds during on-site construction, so securing the strength of the fillet welds (Securing the fillet leg length) and ensuring the performance of preventing brittle cracks (Limited to the length of the fillet legs of 16 mm or less), there was a problem that it required a lot of effort in terms of construction management on site, and at the same time, additional costs such as maintenance were increased.

The present invention solves the problems of the prior art, and it is possible to stop or prevent the propagation of the brittle cracks generated in the flange to the web and the propagation of the brittle cracks generated in the web to the flange before reaching a large-scale fracture. An object of the present invention is to provide a welded structure excellent in brittle crack propagation stopping properties.

In order to achieve the above object, the present inventors intensively studied measures for reducing the variation in leg lengths of the fillet welds in the construction of the fillet welds for stopping brittle cracks. As a result, after changing the basic welding structure from the conventional fillet welding structure to a fillet welding structure having a reinforcing member in which a reinforcing member is disposed between the web and the flange, a joint in which the reinforcing member is attached to the flange surface by fillet welding is performed. I've been thinking about doing it in the factory. It was found that this made it easy to make the deviation of the leg length of a fillet welded part within a predetermined range, and led to the significant reduction of the implementation cost on site.

The joining of the reinforcing member to the flange surface by fillet welding is performed in the factory, so that the web and the reinforcing member are joined at a site where construction management is not easy, by butting the cross section of the web with the surface of the reinforcing member, It has been found that construction can be performed with fillet, partial penetration, or full penetration, etc., in which the conditions of bridge length management and heat input management are relaxed under welding conditions that are easy to construct and manage.

Moreover, the present inventors earnestly examined the various factors which affect the brittle crack propagation stop characteristic in the fillet weld structure which has a reinforcing member further.

As a result, in order to stop or stop the propagation of brittle cracks generated from the flange, it is essential to secure a structural discontinuity on the overlapping surface of the flange and the reinforcing member and to improve the brittle crack propagation stopping performance (arrest performance) of the reinforcing member. I prayed.

In addition, when the length of the structural discontinuity, that is, the undeposited width becomes shorter, the propagation of brittle cracks becomes easier, so it is necessary to make the arresting performance of the reinforcing member a performance according to the length (unwelded width) of the structural discontinuity. found out

In addition, the present inventors found that in order to prevent brittle cracks generated from the flange from propagating to the web and to block it in the reinforcing member, the ratio Y (%) of the unseated portion remaining on the overlapping surface of the flange and the reinforcing member and the arresting performance of the reinforcing member We have found that satisfying certain relationships is necessary. In addition, the ratio Y of the unadorned part is

Y (%): {(width of the unwelded portion of the overlapping surface of the reinforcing member and the flange in the joint cross-section of the fillet welded joint)/(the sum of the plate width of the reinforcing member and the leg length of the left and right fillet welds)}×100 was defined as

And, as a specific relationship, the following (2) formula

Y(%)≥{6900-(Kca) _T }/85 … (2)

(here, (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3/2} ) of the reinforcing member at common temperature T (°C)) was found.

On the other hand, in order to stop or stop the propagation of brittle cracks generated from the web, it is necessary to secure a structural discontinuity on the butt surface of the web and the reinforcing member, and at the same time, improve the brittle crack propagation stopping performance (arrest performance) of the reinforcing member. also contemplated.

In addition, when the length of the structural discontinuity (width of the unwelded portion) is shortened, the propagation of brittle cracks becomes easier. Therefore, it is necessary to set the arresting performance of the reinforcing member according to the length of the structural discontinuity, that is, the width of the unwelded portion. It was also found that Moreover, it was also discovered that, when the arresting performance of a reinforcement member is excellent, there may be no need also for the remainder of an unbonded part.

And, in order to prevent the brittle cracks generated from the web from propagating to the flange and to block the reinforcing member in the reinforcing member, the ratio X (%) of the unseated portion remaining on the butt surface of the web and the reinforcing member, and the arresting performance of the reinforcing member We have found that satisfying certain relationships is necessary. In addition, the ratio X (%) of the unadorned part is

X (%): {(width of the reinforcing member in the seam cross section of the fillet welded joint and the unwelded portion of the butt surface of the web)/((the sum of the plate thickness of the web and the leg length of the left and right fillet welds)}×100 In addition, it is assumed that X(%) includes 0%.

And, as a specific relationship, the following (1) formula

X(%)≥{5900-(Kca) _T }/85 ... (One)

(here, (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3/2} ) of the reinforcing member at common temperature T (°C)) was found.

In addition, when the reinforcing member is austenitic steel (high Mn steel, austenitic stainless steel, etc.) or a low-temperature nickel steel sheet (3.5% Ni steel, 5% Ni steel, 7% Ni steel, 9% Ni steel), It has been found that long brittle cracks propagating from the web or flange can be stopped in the reinforcing steel sheet without satisfying the formulas (1) and/or (2).

Moreover, the said welded structure WHEREIN: By making the height (gap) of the unwelded part of the overlapping surface of the said reinforcement member and the said flange 5 mm or more, it discovered that the said pole brittle crack became more easy to stop.

The present invention has been completed based on the above findings and further studies have been made.

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

(1) A welded structure comprising a reinforcing member at a butt portion of a web and a flange, wherein the reinforcing member is fillet welded to the web and the flange, and is excellent in brittle crack propagation stopping properties.

(2) the web is butt-welded to the reinforcing member, and an undeposited portion remains on the abutment surface, and/or the reinforcing member is overlapped and fillet welded to the flange, and an undeposited portion on the overlapping surface The welded structure as described in said 1 provided with the fillet weld seam which remain|survives.

(3) The welded structure according to 1 or 2, wherein the thickness of the web, the flange, and the reinforcing member are all 50 mm or more.

(4) The ratio X (%) (including 0%) of the unwelded portion defined below remaining on the butt surface of the reinforcing member and the web in the joint cross section of the fillet welded joint, and the common temperature T (°C) The welded structure according to 2 or 3, wherein the brittle crack propagation stop toughness (Kca) _T (N/mm ^{3/2 ) of the reinforcing member in ) satisfies the following formula (1).}

X (%): {(width of the unwelded portion remaining on the butt surface of the web and the reinforcing member in the joint cross-section of the fillet welded joint)/(sum of the sheet thickness of the web and the leg length of the left and right fillet welds)}× 100

X(%)≥{5900-(Kca) _T }/85 ... (One)

where (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3/2} ) of the reinforcing member at the common temperature T (°C)

(5) the ratio Y (%) of the unwelded portion defined below remaining on the overlapping surface of the reinforcing member and the flange in the joint cross-section of the fillet welded joint, and the above at the shared temperature T (°C) The welded structure according to any one of 2 to 4, wherein the brittle crack propagation stop toughness (Kca) _T (N/mm ^{3/2 ) of the reinforcing member satisfies the following formula (2).}

Y (%): {(width of the unwelded portion of the overlapping surface of the reinforcing member and the flange in the joint cross-section of the fillet welded joint)/(the sum of the plate width of the reinforcing member and the leg length of the left and right fillet welds)}×100

Y(%)≥{6900-(Kca) _T }/85 … (2)

where (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3 /2} ) of the reinforcing member at the common temperature T (°C)

(6) The welded structure according to any one of 1 to 5 above, wherein the flange or web has a butt weld joint in a shape intersecting the web or flange.

(7) The said web has a butt weld seam, The welded structure as described in said 6 which arrange|positions this web so that the butt weld seam of this web may intersect the butt weld seam of the said flange.

(8) The welded structure according to any one of 1 to 3, wherein the reinforcing member is an austenitic steel or a low-temperature nickel steel sheet.

(9) In the said welded structure, the height (gap) of the unwelded part of the overlapping surface of the said reinforcement member and the said flange is 5 mm or more, The said welded structure in any one of 2-8.

According to the present invention, the propagation of brittle cracks generated in a flange made of a thick steel plate having a plate thickness of 50 mm or more, and further, a plate thickness exceeding 80 mm, which has been difficult in the prior art, to the web, and to the flange of the brittle crack generated in the web It is possible to stop or stop the propagation of , or both, 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 hull separation in steel structures, particularly large container ships or bulk carriers, etc., resulting in a great effect in ensuring the safety of the hull structure, It has a special effect on the industry.

Further, according to the present invention, by adjusting the dimensions of the reinforcing member and the toughness of the fillet weld metal during construction, it is easy to stop the propagation of brittle cracks without using a special steel plate and without impairing safety. There is also an effect that this excellent welded structure can be manufactured.

In addition, according to the present invention, at the time of construction, the size of the unwelded portion remaining on the overlapping surface between the reinforcing member and the flange is adjusted, and at the same time, a reinforcing member having a brittle crack propagation stop characteristic according to the size of the unbonded portion is selected. Thereby, the welded structure excellent in the brittle crack propagation stop characteristic can be manufactured easily, without using a special steel plate in large quantities and without impairing safety|security. This effect is also the same for the unwelded part remaining on the abutting surface between the reinforcing member and the web.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing explaining typically the cross-sectional structure of a fillet welded joint. (a) is when the web 1, the reinforcing member 10, and the flange 2 are perpendicular to each other, (b) is when the web 1, the reinforcing member 10, and the flange 2 intersect at an angle , (c) shows a case where the height (gap) 14 of the unwelded portion of the overlapping surface of the reinforcing member 10 and the flange 2 is 5 mm or more.
It is explanatory drawing which shows typically another example of the structure of a fillet welded joint. (a) is an external view, (b) is a sectional view.
It is explanatory drawing which shows typically another example of the structure of a fillet welded joint. (a) is an external view, (b) is a sectional view.
It is explanatory drawing which shows typically the shape of the super-large structural model test body which targeted the brittle crack which generate|occur|produced and propagated from the flange used in the Example. (a) is when the flange (2) is made of only the steel plate base material, (b) is when the flange (2) has a butt welded seam, (c) is the web (1) and the flange (2) has a butt welded seam is the case
Fig. 5 is an explanatory diagram schematically showing the shape of a super-large structural model specimen for brittle cracks generated and propagated from the web used in Examples. (a) is when the web (1) is made of only a steel plate base material, (b) is when the web (1) has a butt welded seam, (c) is when the web (1) and the flange (2) have a butt welded seam is the case

Hereinafter, the present invention will be specifically described.

The welded structure of this invention is a welded structure which equips the butt|matching part of the web 1 and the flange 2 with the reinforcement member 10. In the welded structure of the present invention, the surface of the reinforcing member 10 is superimposed on the surface of the flange 2, the reinforcing member 10 and the flange 2 are joined by fillet welding, and the surface of the reinforcing member 10 is attached to the surface of the reinforcing member 10. It is a welded structure formed by butt|matching the cross section of the web 1, and joining the reinforcing member 10 and the web 1 by fillet welding. In the welded structure of the present invention, the web 1, the flange 2, and the reinforcing member 10 are all made of thick steel with a plate thickness of 50 mm or more.

In the welded structure of the present invention, the flange 2 and the reinforcing member 10 are joined by fillet welding, and the reinforcing member 10 and the web 1 are joined by fillet welding, respectively, and fillet weld metals 5 and 51, respectively. It has a fillet seam having Then, the unbonded portion 4 as a structural discontinuity is provided on the overlapping surface of the flange 2 and the reinforcing member 10 and/or on the abutting surface of the reinforcing member 10 and the web 1 .

This state is shown in FIG. 1 by a joint cross section. In addition, although Fig.1 (a) shows the case where the web 1 is erected with respect to the flange 2, and is attached, in this invention, it is not limited to this. For example, as shown in FIG.1(b), you may attach the web 1 at an angle θ with respect to the flange 2 inclined. Moreover, as shown in FIG.1(c), it is good also considering the unwelded part height (gap) 14 of the overlapping surface of the reinforcing member 10 and the flange 2 being 5 mm or more.

In the welded structure of the present invention, the overlapping surface of the flange 2 and the reinforcing member 10 and the abutting surface of the reinforcing member 10 and the web 1 serve as the propagation surface of the brittle crack. Therefore, in the present invention, the unbonded portion 4 is provided on the overlapping surface of the flange 2 and the reinforcing member 10 and/or the abutting surface of the reinforcing member 10 and the web 1 . By the presence of the unbonded portion 4, the energy release rate (crack propagation driving force) at the tip of the brittle crack that has propagated through the web 1 or the flange 2 decreases, and the brittle crack on the overlapping surface or the facing surface. becomes easier to stop. In addition, in the present invention, there are cases where it is sufficient to leave the unwelded portion 4 on the butt surface when the entry direction of the brittle crack is from the web and on the overlapping surface in the case of from the flange, either side.

In addition, in the present invention, after the reinforcing member 10 is disposed between the flange 2 and the web 1 and the un-attached portion 4 remains as described above, the reinforcing member 10 is restrained by a predetermined or more. It is a member that maintains performance. Thereby, the brittle crack stops in the reinforcing member 10 .

In addition, it is extremely rare that brittle cracks occur in the base metal part of the steel sheet with few defects. Most of the past brittle fracture accidents have occurred in welds. Therefore, for example, the flange 2 as shown in Fig. 2 is made into a steel sheet joined by the butt-welded joint 11, and the web 1 is used as a welded portion of the butt-welded joint (butt-welded joint) ( 11) In the fillet welded joint fillet welded so as to intersect, in order to prevent the propagation of brittle cracks generated from the butt weld joint 11, it is important to first make a structural discontinuity. Therefore, in this invention, the unwelded part 4 is made to exist in the overlapping surface of the flange 2 and the reinforcement member 10 in a fillet welding part.

In addition, (a) of FIG. 2 shows the external appearance of a fillet welded joint, and FIG.2(b) shows the joint cross-sectional shape in the butt-welded joint part 11. As shown in FIG.

Moreover, as shown in FIG. 3, the web 1 is set as the steel plate which has the butt weld joint part 12, and the flange 2 is set as the steel plate which has the butt weld joint part 11, and the flange 2 In a fillet welded joint that is fillet welded so that the butt welded joint 11 and the butt welded joint 12 of the web 1 intersect, brittle cracks generated from the butt welded joint 11 or the butt welded joint 12 Similarly, in order to prevent the propagation of , it becomes important to have a discontinuity in the structure. Therefore, in the present invention, the unwelded portion 4 is provided on the overlapping surface of the flange 2 and the reinforcing member 10 in the fillet welded portion, and the abutting surface of the web 1 and the reinforcing member 10, respectively. . Cosmetic chakbu between the stage, the web (1) and the reinforcing member 10 (4) is not if the brittle crack propagation stopping toughness of the reinforcing member 10 more than 5900N ^/ ㎜ ^3/2 is required.

In addition, (a) of FIG. 3 shows the external appearance of a fillet welded joint, and FIG.3(b) shows the joint cross-sectional shape in the butt-welded joint parts 11 and 12. In addition, FIG.

In addition, although the case where the butt weld joint part 11 and the web 1 orthogonally crossed was shown in FIG. 2, FIG. 3, in this invention, it is not limited to this. Of course, it is good to cross them at an angle.

Moreover, it is not necessary to specifically limit the manufacturing method of a welded structure, All the normal manufacturing methods are applicable. For example, the butt weld joint obtained by butt-welding the steel plates for flanges and the steel plates for webs may be fillet welded through a reinforcement member, and a welded structure may be manufactured. In addition, a set of steel sheets for a web before butt welding is temporarily welded to a reinforcing member on the flange surface, and then the steel sheets for a web are butt welded to each other, and the obtained butt weld joint may be welded to the flange to produce a welded structure.

In the present invention, in order to block the brittle cracks generated from the flange in the web without propagating to the web, the ratio Y (%) of the unseated portion remaining on the overlapping surface of the flange and the reinforcing member and the arresting performance of the reinforcing member are (2) Formula

Y(%)≥{6900-(Kca) _T }/85 … (2)

(here, (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3/2} ) of the reinforcing member at common temperature T (°C)) is adjusted to be satisfied. In addition, preferably, the following (2)'

Y(%)≥{7900-(Kca) _T }/85 ... (2)'

(here, (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3 /2} ) of the reinforcing member at the common temperature T (°C)).

Here, the percentage Y (%) is

_{Y(%):{(width B F of the} unwelded portion of the overlapping surface of the reinforcing member and the flange in the joint cross-section of the fillet welded joint)/(the plate width D _{W of the reinforcing member and the leg length l F} of the left and right fillet welds sum)}×100. In addition, the reinforcing member and the width _F B of the overlapping surface beauty chakbu 4 of the flange of the joint cross-section of the fillet weld joint in Figure 1, the leg length of fillet weld is represented by _F l.

When the ratio Y (%) of the undeposited portion remaining on the overlapping surface and the brittle crack propagation stop toughness (Kca) _T of the reinforcing member at the common temperature T (°C) do not satisfy Equation (2), the brittleness generated from the flange The crack cannot be stopped in the reinforcing member.

In addition, here, the brittle crack propagation stop toughness Kca of the reinforcing member to be used is obtained by performing a temperature gradient type brittle crack propagation stop test (ESSO test) on the reinforcing member (steel sheet) in advance, and is obtained at the common temperature T (°C). It is assumed that the brittle crack propagation stop toughness Kca is used.

In addition, as "common temperature T", "-10 degreeC" which is the design temperature of a ship shall be used normally.

In addition, in the present invention, in order to block the brittle cracks generated from the web in the reinforcing member, the ratio X (%) of the unseated portion remaining on the abutting surface of the web and the reinforcing member and the arresting performance of the reinforcing member are determined by the following formula (1)

X(%)≥{5900-(Kca) _T }/85 ... (One)

(here, (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3 /2} ) of the reinforcing member at common temperature T (°C)) is adjusted to be satisfied.

Here, the ratio X (%) is

_{X(%):{(width B W of the} unwelded portion of the butt surface of the web and the reinforcing member in the joint cross-section of the fillet welded joint)/((the thickness of the web t _W and the length of the left and right fillet welds l _W sum)}×100.

When the ratio X (%) of the unbonded portion remaining on the butt surface and the brittle crack propagation stop toughness (Kca) _T of the reinforcing member at the common temperature T (°C) do not satisfy Equation (1), brittleness generated from the web The crack cannot be stopped in the reinforcing member.

In addition, in the case of brittle cracking from the web, when the (Kca) _T of the reinforcing member used is high, even when the ratio X (%) of the undeposited part is 0%, the formula (1) can be satisfied, and the brittle crack It can also be stopped by a reinforcing member. However, in order to stop the propagation of brittle cracks generated from the flange in the reinforcing member, there is a limit to _{(Kca) T of the reinforcing member that can be used.} There is a need.

In this way, when a brittle crack occurs and propagates in the web, the ratio X (%) of the unbonded portion and the brittle crack propagation stop toughness (Kca) _T of the reinforcing member are expressed in equation (1), and the brittle crack occurs in the flange. and propagation, if the ratio Y (%) of the undeposited portion and the toughness (Kca) _T of the reinforcing member to stop propagation of brittle cracks are adjusted to satisfy Equation (2), the generated and propagated brittle cracks are prevented or stopped in the reinforcing member can do it

In addition, in an actual steel structure, it is necessary to adjust the _{ratios X and Y of the un-bonded portion and the brittle crack propagation stop toughness (Kca) T} of the reinforcing member to be used so that the equations (1) and (2) can be simultaneously satisfied. desirable.

In addition, in the present invention, the reinforcing member is austenitic steel (high Mn steel, austenitic stainless steel, etc.) or a low-temperature nickel steel sheet (3.5% Ni steel, 5% Ni steel, 7% Ni steel, 9% Ni steel) , and in this case, the above formulas (1) and/or (2) may not be satisfied. Since austenitic steel (high Mn steel, austenitic stainless steel, etc.) has a crystalline structure that does not undergo brittle fracture, propagation of long brittle cracks can be prevented. Although it is not necessary to specifically limit the detail of a chemical component, The crystal structure in common use temperature (-10 degreeC) needs to be austenite. For example, C: 0.2 to 0.6%, Si: 0.1 to 1.0%, Mn: 22 to 26%, P: 0.03% or less, S: 0.01% or less, B: 0.01% or less, N: 0.15% or less, Nb It is good to have a chemical composition or the like in which +Ti+V is 0.3% or less. On the other hand, low-temperature nickel steel sheet (3.5% Ni steel, 5% Ni steel, 7% Ni steel, 9% Ni steel) has a crystal structure that is brittle and fractures, but has extremely high toughness at -10℃, the design temperature of the hull, Propagation of long brittle cracks can be prevented. As the nickel steel sheet for low temperature, for example, a nickel steel sheet for a low temperature pressure vessel prescribed in JIS G 3127 may be used. These steels are very expensive and have problems such as cutability and handling, so they are not usually used in large quantities for the main hull structure, but if limited to a small amount locally like the reinforcing member of the present invention, it is also economically There is no problem with construction.

In this invention, in the said welded structure, it is good also considering the height (gap) of the unwelded part of the overlapping surface of the said reinforcement member and the said flange as 5 mm or more. By ensuring the height (gap) of an unwelded part 5 mm or more, the local stress concentration of a fillet weld metal becomes small, and the said pole brittle crack becomes more easy to stop.

In addition, the welded structure of the present invention having the above-described fillet welded seam is, for example, a hull structure in which the outer plate of a ship is a flange and a bulkhead is a web, or a deck is a flange, and the hatch is a web Applicable to hull structure, etc.

Example

Hereinafter, based on an Example, this invention is demonstrated in detail.

Using the thick steel plate of the plate thickness shown in Tables 1-1 and 1-2 as the web and the flange, the reinforcing member shown in Table 1-1 and Table 1-2 is provided at the butt portion of the web and the flange, as shown in FIG. (a), (b), (c) and the large-scale welded structure joint 9 of the actual structure size of the shape shown to Fig.5 (a), (b), (c) was produced. 4 (a), (b), (c) shows a case in which brittle cracks are generated and propagated from the flange, and (a), (b), (c) of FIG. 5 (a), (b), (c) are brittle cracks generated and propagated from the web. A case is assumed.

In addition, in the fillet welded joint in the manufactured large-scale welded joint 9, an unwelded portion 4 as shown in Fig. 1(a) is formed on the overlapping surface of the reinforcing member 10 and the flange 2, The unwelded width B _{F , the plate width D W} of the reinforcing member 10 , and the leg length l _F of the left and right fillet welds were changed, and the ratio Y of the unwelded portion was changed and made to exist. In addition, in the fillet welded joint in the produced large-scale welded joint 9, an unwelded portion 4 as shown in Fig. 1(a) is provided on the butt surface of the reinforcing member 10 and the web 1, The unwelded width B _W , the sheet thickness t _W of the web 1 , and the leg length l _W of the left and right fillet welds were changed, and the ratio X of the unbonded portion was changed and made to exist. Moreover, the case where the ratio X of the unadhered part is 0% is also included.

In addition, in the fillet welded joint in the manufactured large-scale welded joint 9, a thick steel plate having a _{(Kca) -10} °C of 2500 to 11000 (N/mm ^{3 / 2 ) was used as the reinforcing member 10 .} . In addition, in some welded structures, as shown in FIG.1(c), the unwelded part height (gap) 14 of the overlapping surface of the reinforcement member 10 and the flange 2 was 5 mm or more.

In addition, in Fig. 4, the flange is a thick steel plate (base material only) (Fig. 4 (a)), a thick steel plate having a butt welded seam (Fig. 4 (b), (c)), and the web is a thick steel plate (base material) Only) (FIG. 4(a),(b)), it was set as the thick steel plate (FIG. 4(c)) which has a butt weld seam. In Figure 5, the web is a thick steel plate (base material only) (Fig. 5 (a)), a thick steel plate having a butt welded seam (Fig. 5 (b), (c)), and the flange is a thick steel plate (base material only) (FIG. 5(a), (b)), it was set as the thick steel plate (FIG. 5(c)) which has a butt weld seam.

In addition, a butt weld joint 11 was prepared by substituting 1-pass heat electro gas arc welding (first electrode and second electrode EGW) or a multi-layer carbon dioxide gas arc welding (multilayer CO _2). In addition, a butt weld joint 12 was produced by the segmental arc welding (first electrode and second electrode SEGARC) or a multi-layer carbon dioxide gas arc welding (multilayer CO _2).

In addition, fillet welding of the reinforcing member 10 and the flange 2 is mainly performed by carbon dioxide arc welding to change the groove shape and welding conditions, and as shown in Tables 2-1 and 2-2, fillet weld metal ( The leg length l _F of 5) and welding width W _F were variously changed. In the fillet welding of the reinforcing member 10 and the web 1, the groove shape and welding conditions are changed mainly by partial penetration carbon dioxide arc welding, and as shown in Tables 2-1 and 2-2, fillet welding is performed. The leg length l _W of the metal 51 and the welding width W _W were variously changed. In addition, here, the leg length and welding width are the average values of the left and right sides.

Moreover, using the obtained large size welded structure joint 9, the super large structure model test body shown in FIG. 4 and FIG. 5 was produced, and the brittle crack propagation stop test was implemented. In addition, in the super-large structural model test body of FIG. 4 , a steel sheet of the same thickness as the flange 2 was welded by tack welding 8 under the flange 2 of the large fillet welded joint 9 . And the front-end|tip of the machine notch 7 was processed so that it might become the BOND part of the butt weld joint part 11, or the weld metal WM. In addition, in the super-large structural model test body of FIG. 5 , a steel plate having the same plate thickness as that of the web 1 was welded under the web 1 of the large-scale welded structure joint 9 by tack welding 8 . And the front-end|tip of the machine notch 7 was processed so that it might become the BOND part of the butt weld joint part 12, or the weld metal WM.

In the brittle crack propagation stop test, a brittle crack was generated by hitting the mechanical notch, and it was investigated whether the propagated brittle crack stopped at the fillet weld.

All tests were also performed on the conditions of stress 100-283 N/mm<2>, and temperature:-10 degreeC. Stress 100N/mm2 is the average value of the stress normally acting on the hull, and the stress 257N/mm2 is the value equivalent to the maximum allowable stress of the 390N/mm2 grade steel sheet with yield strength applied to the hull, and the stress 283N/mm2 is applied to the hull. It is a value corresponding to the maximum allowable stress of the 460N/mm2 grade steel sheet with yield strength being used. Temperature -10°C is the design temperature of the vessel.

The obtained results are shown in Tables 3 and 4. Table 3 shows the brittle crack propagation stop test results when the web is used as the crack introduction part and Table 4 is the case when the flange is used as the crack introduction part.

[Table 1-1]

[Table 1-2]

[Table 2-1]

[Table 2-2]

[Table 3]

[Table 4]

As shown in Tables 3 and 4, in the examples of the present invention, in either case where the brittle crack propagated from the flange or propagated from the web, the crack rushed into the reinforcing member of the fillet weld and stopped.

On the other hand, in the comparative example outside the scope of the present invention, the brittle crack propagated without stopping in the reinforcing member, and the propagation of the brittle crack could not be prevented.

One; web 2; flange
4; uncoated part 5; fillet weld metal
51; fillet weld metal 7; machine notch
8; tack welding
9; Large welded structural seam with reinforcing member (large welded seam)
10; Reinforcing member 11 Flange butt weld seam
12; web butt weld seam θ; intersection angle

Claims (20)

A welded structure comprising a reinforcing member in a butt portion of a web and a flange,
the reinforcing member is formed by fillet welding to the web and the flange, and a fillet welded portion of the reinforcing member and the web and a fillet welded portion of the reinforcing member and the flange are each independent;
The web is butt-welded to the reinforcing member, and an undeposited portion remains on the abutment surface, and/or a fillet wherein the reinforcing member is overlapped and fillet welded to the flange, and an un-seamed portion remains on the overlapping surface. provided with a welded seam,
The ratio X (%) (including 0%) of the un-bonded portion remaining on the butt surface of the reinforcing member and the web in the seam cross section of the fillet welded joint, X (%) (including 0%), and the common temperature T (°C), A welded structure excellent in brittle crack propagation stopping properties in which the brittle crack propagation stop toughness (Kca) _T (N/mm ^{3/2 ) of the reinforcing member satisfies the following formula (1):}
X (%): {(width of the unwelded portion remaining on the butt surface of the web and the reinforcing member in the joint cross-section of the fillet welded joint)/(sum of the sheet thickness of the web and the leg length of the left and right fillet welds)}× 100
X(%)≥{5900-(Kca) _T }/85 ... (One)
Here, (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3/2} ) of the reinforcing member at the common temperature T (°C). The method of claim 1,
All of the thickness of the web, the flange and the reinforcing member is 50 mm or more of a welded structure. The method of claim 1,
The ratio Y (%) of the unwelded portion defined below remaining on the overlapping surface of the reinforcing member and the flange in the joint cross section of the fillet welded joint, and the reinforcing member at the shared temperature T (°C) A welded structure in which the brittle crack propagation stop toughness (Kca) _T (N/mm ^3/2 ) satisfies the following formula (2):
Y (%): {(width of the unwelded portion of the overlapping surface of the reinforcing member and the flange in the joint cross-section of the fillet welded joint)/(the sum of the plate width of the reinforcing member and the leg length of the left and right fillet welds)}×100
Y(%)≥{6900-(Kca) _T }/85 … (2)
Here, (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3/2} ) of the reinforcing member at the common temperature T (°C). 3. The method of claim 2,
The ratio Y (%) of the unwelded portion defined below remaining on the overlapping surface of the reinforcing member and the flange in the joint cross section of the fillet welded joint, and the reinforcing member at the shared temperature T (°C) A welded structure in which the brittle crack propagation stop toughness (Kca) _T (N/mm ^3/2 ) satisfies the following formula (2):
Y (%): {(width of the unwelded portion of the overlapping surface of the reinforcing member and the flange in the joint cross-section of the fillet welded joint)/(the sum of the plate width of the reinforcing member and the leg length of the left and right fillet welds)}×100
Y(%)≥{6900-(Kca) _T }/85 … (2)
Here, (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3/2} ) of the reinforcing member at the common temperature T (°C). 5. The method according to any one of claims 1 to 4,
The flange or web is a welded structure having a butt weld seam in a form that intersects the web or flange. 6. The method of claim 5,
The said web has a butt weld seam, The welded structure formed by arrange|positioning this web so that the butt weld seam of the said web may intersect the butt weld seam of the said flange. 3. The method according to claim 1 or 2,
The reinforcing member is a welded structure made of austenitic steel or nickel steel for low temperature. 5. The method according to any one of claims 1 to 4,
In the welded structure, the height (gap) of the unwelded portion of the overlapping surface of the reinforcing member and the flange is 5 mm or more. 6. The method of claim 5,
In the welded structure, the height (gap) of the unwelded portion of the overlapping surface of the reinforcing member and the flange is 5 mm or more. 7. The method of claim 6,
In the welded structure, the height (gap) of the unwelded portion of the overlapping surface of the reinforcing member and the flange is 5 mm or more. 8. The method of claim 7,
In the welded structure, the height (gap) of the unwelded portion of the overlapping surface of the reinforcing member and the flange is 5 mm or more. A welded structure comprising a reinforcing member in a butt portion of a web and a flange,
the reinforcing member is formed by fillet welding to the web and the flange, and a fillet welded portion of the reinforcing member and the web and a fillet welded portion of the reinforcing member and the flange are each independent;
The web is butt-welded to the reinforcing member, and an undeposited portion remains on the abutment surface, and/or a fillet wherein the reinforcing member is overlapped and fillet welded to the flange, and an un-seamed portion remains on the overlapping surface. provided with a welded seam,
The ratio Y (%) of the unwelded portion defined below remaining on the overlapping surface of the reinforcing member and the flange in the joint cross section of the fillet welded joint, and the reinforcing member at the shared temperature T (°C) Welded structure with excellent brittle crack propagation stop properties, in which the brittle crack propagation stop toughness (Kca) _T (N/mm ^{3/2 ) satisfies the following formula (2):}
Y (%): {(width of the unwelded portion of the overlapping surface of the reinforcing member and the flange in the joint cross-section of the fillet welded joint)/(the sum of the plate width of the reinforcing member and the leg length of the left and right fillet welds)}×100
Y(%)≥{6900-(Kca) _T }/85 … (2)
Here, (Kca) _T ^{: brittle crack propagation stop toughness (N/mm 3/2} ) of the reinforcing member at the common temperature T (°C). 13. The method of claim 12,
All of the thickness of the web, the flange and the reinforcing member is 50 mm or more of a welded structure. 13. The method of claim 12,
The flange or web is a welded structure having a butt weld seam in a form that intersects the web or flange. 14. The method of claim 13,
The flange or web is a welded structure having a butt weld seam in a form that intersects the web or flange. 15. The method of claim 14,
The said web has a butt weld seam, The welded structure formed by arrange|positioning this web so that the butt weld seam of the said web may intersect the butt weld seam of the said flange. 16. The method of claim 15,
The said web has a butt weld seam, The welded structure formed by arrange|positioning this web so that the butt weld seam of the said web may intersect the butt weld seam of the said flange. 14. The method according to claim 12 or 13,
The reinforcing member is a welded structure made of austenitic steel or nickel steel for low temperature. 18. The method according to any one of claims 12 to 17,
In the welded structure, the height (gap) of the unwelded portion of the overlapping surface of the reinforcing member and the flange is 5 mm or more. 19. The method of claim 18,
In the welded structure, the height (gap) of the unwelded portion of the overlapping surface of the reinforcing member and the flange is 5 mm or more.

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