JP2020041966A - Steel plate quality evaluation method - Google Patents

Abstract

To provide a method for evaluating the quality of steel plate simply with high accuracy.SOLUTION: Provided is a method for evaluating the quality of steel plate used in a welded structure 10, the welded structure 10 including a T joint part where, while the end face 11c of a joint member 11 is in contact with the face 12a to which to be jointed of a member 12 to which to be jointed, the joint member 11 is penetration welded for both ends into the member 12 to which to be jointed. The steel plate quality evaluation method includes: sampling, from a steel plate in thickness of 50 mm or more that constitutes the joint member 11 or the member 12 to which to be jointed, a tabular test piece the thickness direction of which matches the plate thickness direction of the steel plate and which includes a portion of region from the surface of the steel plate to a depth of 5 mm; measuring a nil-ductility transition temperature by an NRL drop test using the tabular test piece; and determining the brittle crack arrest characteristic of the steel plate that constitutes the joint member 11 or the member 12 to which to be jointed, on the basis of the nil-ductility transition temperature.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for evaluating the quality of a thick steel plate, and more particularly to a method for evaluating the quality of a thick steel plate for a welded structure used for a container ship or the like.

  In a large container ship carrying a large amount of cargo, a large opening (hatch) for loading and unloading cargo is formed in the upper deck (upper deck). A hatch side combing is provided on the upper deck so as to surround the hatch in order to prevent inflow of seawater and the like. Each of the upper deck and the hatch side combing is configured by welding a plurality of steel plates. The hatch side combing is welded on the upper deck.

  When a large container ship as described above sails on the sea, a load (longitudinal bending load) that bends the entire hull is applied to the hull by waves. In order to sufficiently secure the strength (longitudinal bending strength) of the hull against such a load, a high-strength thick steel plate is used for the upper deck and the hatch side combing.

  As described above, each of the hatch side combing and the upper deck has a configuration in which a plurality of steel plates are welded. In other words, a plurality of welds for welding steel plates are formed in the hatch side combing and the upper deck. Cracks generated at the weld are likely to propagate along the weld.

  For this reason, for example, when a crack occurs at the welded portion of the hatch side combing, the crack propagates along the welded portion toward the upper deck, and the propagated crack propagates to the welded portion of the upper deck. There are cases. Further, in addition to the above example, a crack may be generated from the upper deck and propagated toward the hatch side combing side.

  Therefore, in order to sufficiently improve the strength of the hull, it is necessary that the hatch side combing and the upper deck have a characteristic capable of stopping the growth of a crack as described above (brittle crack propagation stopping characteristic).

  Conventionally, when evaluating the brittle crack propagation arresting property of a thick steel plate used for hatch side combing and upper deck, an ESSO test (brittle fracture arresting test: a brittle crack is artificially generated in a test piece and the brittle A large-scale test such as a test for evaluating the ability to stop a crack was conducted.

  However, there is a problem that it is not easy to evaluate brittle crack propagation arresting characteristics because a large amount of time and cost are required to perform a large-scale test. Against this background, for example, Patent Literatures 1 and 2 propose a method for evaluating brittle crack propagation arrestability using a small test piece.

JP 2012-52873 A International Publication No. 2014/208072

  However, the method described in Patent Literature 1 is insufficient in terms of simplicity because it is necessary to collect a test piece from each position in the thickness direction of a thick steel plate and perform a Charpy impact test. Further, in the method described in Patent Document 2, since evaluation is performed using a test piece taken from the central part of the thickness of a thick steel plate, there is a problem that the brittle crack propagation stopping characteristics cannot be accurately evaluated.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a method for evaluating the quality of a thick steel plate with high accuracy and ease.

  The gist of the present invention is the following method for evaluating the quality of a thick steel plate.

(1) A quality evaluation method for a thick steel plate used for a welded structure,
The welding structure includes a T-joint portion in which the joining member is partially penetrated and welded to the joined member in a state where an end surface of the plate-shaped joining member is in contact with the joined surface of the plate-shaped joined member. Which has
From a thick steel plate having a thickness of 50 mm or more serving as the joining member or the member to be joined, a part of a region in which the thickness direction of the thick steel plate coincides with the thickness direction and a depth of 5 mm from the surface of the thick steel plate. Take a plate-like test piece containing
Using the plate-shaped test piece, measure the non-ductile transition temperature by the NRL drop weight test,
Based on the non-ductile transition temperature, determine the brittle crack propagation arresting property of the thick steel plate to be the joining member or the member to be joined,
Quality evaluation method for thick steel plates.

(2) A method for evaluating the quality of the steel plate serving as the joining member,
The plate-shaped test piece is collected so as to include a part of a region from one surface orthogonal to a thickness direction of the thick steel plate to be the joining member to a depth of 5 mm,
The non-ductility transition temperature measured by the NRL drop weight test is defined as NDTT (° C.), and the highest point of the heat-affected zone of the welded portion formed on the one surface side by the both-side partial penetration welding and the one surface. When the distance in the thickness direction of the joining member is h (mm),
When satisfying the following formulas (i) and (ii), it is determined that the thick steel plate serving as the joining member has excellent brittle crack propagation stopping characteristics.
The quality evaluation method of a thick steel plate according to the above (1).
NDTT ≦ −60 (i)
NDTT ≦ −30.5 × ln (h) −14.0 (ii)

(3) A quality evaluation method of the thick steel plate to be the member to be joined,
The plate-shaped test piece is collected so as to include a part of a region from one surface corresponding to the surface to be joined of the thick steel plate to be the member to be joined to a depth of 5 mm,
The non-ductility transition temperature measured by the NRL drop weight test is NDTT (° C.), the length of the joining member in a direction perpendicular to the end face is H (mm), and a predetermined allowable stress of the joining member is σ (N / mm ² ),
When satisfying the following formula (iii), it is determined that the thick steel plate as the member to be joined is excellent in brittle crack propagation arresting properties,
The quality evaluation method of a thick steel plate according to the above (1).
NDTT ≦ 360.4−46.8 × ln {σ (πH) ^0.5 } (iii)

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to evaluate the quality of the thick steel plate required for obtaining the welded structure excellent in brittle crack propagation stopping characteristics with high accuracy and simply.

It is a perspective view showing the welding structure constituted by the thick steel plate used as the object of quality evaluation concerning one embodiment of the present invention. It is a perspective view which shows the other welding structure comprised by the thick steel plate used as the object of quality evaluation which concerns on one Embodiment of this invention. It is a perspective view which shows the other welding structure comprised by the thick steel plate used as the object of quality evaluation which concerns on one Embodiment of this invention. It is sectional drawing of a welding structure. FIG. 3 is a view for explaining the shape of a structural model arrest specimen in Example 1. FIG. 9 is a view for explaining the shape of a structural model arrest specimen in Example 2.

  The present inventors have conducted studies to solve the above problems, and as a result, have obtained the following knowledge.

When a crack propagates from the hatch side combing toward the upper deck, the upper deck (member to be joined) is required to have brittle crack propagation stopping characteristics. In order to improve the brittle crack propagation arresting property over the entire thickness of the member to be joined, for example, a steel sheet having a Kca value at −10 ° C. which is an index of the brittle crack arresting property is 6000 N / mm ^1.5 or more. Must be used as a member to be joined. The Kca value is an index of the brittle crack propagation arresting property of the entire thickness of the thick steel plate evaluated by the ESSO test.

Furthermore, when a crack propagates from the upper deck toward the hatch side combing side, it is necessary to use a steel plate having a Kca value of 8000 N / mm ^1.5 or more for the hatch side combing (joining member). However, the manufacture of thick steel plate having a Kca value say 6000 N ^{/ mm 1.5} or more, or 8000 N ^{/ mm 1.5} or more is not easy, there is a problem that the manufacturing cost of the steel plate is increased.

  Therefore, as a result of repeated studies by the present inventors, by improving the brittle crack propagation arresting property in the surface layer region of the thick steel plate, which is the crack intrusion area, the brittle crack propagation arresting property of the entire contact structure is improved. It has been found that it can be improved at low cost.

  In other words, it is possible to evaluate the quality of the thick steel plate used for the welded structure with high precision and ease by performing only the evaluation of the brittle crack propagation arresting property in the surface layer, not the total thickness of the thick steel plate. Become.

  The present invention has been made based on the above findings. Hereinafter, a method for evaluating the quality of a thick steel plate according to an embodiment of the present invention will be described.

1. TECHNICAL FIELD The present invention relates to a method for evaluating the quality of a thick steel plate used for a welded structure. FIG. 1 is a perspective view showing a welded structure constituted by a thick steel plate to be subjected to quality evaluation according to one embodiment of the present invention. The welded structure 10 includes a joining member 11 and a joined member 12. The joining member 11 is plate-shaped, and has a pair of surfaces 11a and 11b orthogonal to the plate thickness direction. The member to be joined 12 has a plate shape, and has a surface to be joined 12a with which the end face 11c of the joining member 11 is brought into contact.

  Then, as shown in FIG. 1, the welded structure 10 has a T-joint portion in which the joining member 11 is partially penetrated and welded to the joined member 12 in a state where the end face 11c is in contact with the joined surface 12a. . In addition, in addition to the T-shaped structure as shown in FIG. 1, the welded structure having the T-joint includes, for example, a structure having a shape shown in FIGS.

  Further, the joining member 11 and the member to be joined 12 may be joined by fillet welding, or from the viewpoint of joining strength, a groove is provided in the joining member 11 and joined by groove welding. It may be something. As shown in FIGS. 1 to 3, the welded structure 10 has welds 13 a and 13 b formed on respective sides of the surfaces 11 a and 11 b.

  In the present invention, quality evaluation of a thick steel plate to be the joining member 11 or the member to be joined 12 is performed. Hereinafter, each step will be described in detail. In addition, in this invention, a thick steel plate means the steel plate whose board thickness is 50 mm or more.

2. Test Piece Sampling Step First, a plate-shaped test piece is sampled from a thick steel plate to be the joining member 11 or the member to be joined 12. The plate-shaped test piece is collected from the surface layer of a thick steel plate. Specifically, it is necessary to collect the thick steel plate so that the thickness direction of the thick steel plate coincides with the thickness direction and includes a part of a region from the surface of the thick steel plate to a depth of 5 mm.

  Further, as described later, in the method according to the present invention, the test is performed such that a crack is generated on a plane perpendicular to the longitudinal direction of the plate-shaped test piece. In the welded structure, cracks occur in a plane perpendicular to the direction of extension of the welds 13a and 13b (the Y direction shown in FIG. 1). Therefore, it is preferable that the plate-shaped test piece is collected so that its longitudinal direction coincides with the direction in which the Y direction of the welded structure is provided.

  There is no particular limitation on the shape and dimensions of the test piece, but it is preferable to use type P1 to P3 test pieces specified in ASTM E208. Among them, it is preferable to use the smallest type P3 test piece. The type P3 test piece is a test piece having a length of 130 mm, a width of 50 mm, and a thickness of 16 mm.

  For example, when collecting the above type P3 test piece, as described above, as long as the thickness direction of the thick steel plate coincides with the thickness direction and includes a part of the region from the surface of the thick steel plate to a depth of 5 mm. , From any location. For example, it may be collected in a region from the surface of the thick steel plate to a depth of 16 mm. Alternatively, after the surface of the thick steel plate is shaved by 1 mm, the steel plate may be sampled in a region from a depth of 1 mm to a depth of 17 mm.

  In the case where the quality evaluation of the thick steel plate to be the joining member 11 is performed, the plate-shaped test piece is included so as to include a part of a region from one surface orthogonal to the thickness direction of the thick steel plate to be the joining member 11 to a depth of 5 mm. Collect. The one surface orthogonal to the thickness direction of the thick steel plate serving as the joining member 11 is a surface corresponding to one of the surfaces 11a and 11b of the joining member 11 described above.

  On the other hand, in the case where the quality evaluation of the thick steel plate serving as the member to be joined 12 is performed, a part of a region from one surface corresponding to the surface 12a to be joined of the thick steel plate serving as the member to be joined 12 to a depth of 5 mm is included. Then, a plate-shaped test piece is collected.

3. Next, a non-ductile transition temperature NDTT (° C.) is measured using the above-described plate-shaped test piece. In the present invention, the non-ductile transition temperature NDTT (° C.) is measured by performing an NRL drop weight test based on ASTM E208. The NRL drop weight test will be described in detail.

  First, a weld bead extending in a direction parallel to the longitudinal direction of the plate-shaped test piece is formed on a surface perpendicular to the thickness direction of the plate-shaped test piece, which is a surface side of the thick steel plate. At that time, a welding material having low toughness specified in ASTM E208 is used. The length of the weld bead is adjusted to be in the range of 60 to 70 mm, and the width is adjusted to be in the range of 12 to 16 mm. Then, a notch parallel to the width direction of the plate-shaped test piece is formed on the weld bead. At this time, the width of the notch is 1.5 mm or less, and the distance between the groove bottom of the notch and the plate-shaped test piece is adjusted to be in a range of 1.8 to 2.0 mm.

  Then, after the surface on which the weld bead is formed of the plate-shaped test piece is directed downward and both ends in the longitudinal direction are supported, the impact due to the falling load is applied to the surface on the opposite side of the plate where the weld bead is formed. Apply bending load. Thereafter, Break (no crack propagation) or No Break (no crack propagation) is determined by examining the state in which the brittle crack generated from the notch has propagated through the test piece. If the brittle crack generated from the notch propagates on the surface of the test piece in the width direction of the test piece and proceeds to the end, the test result is determined to be Break (crack propagation). If no crack reaches the end in the width direction, the test result is determined to be No Break (no crack propagation).

  There is no need to particularly limit the method of specifying the non-ductile transition temperature from the results of the above-mentioned drop test. For example, using two plate-shaped test pieces, starting from the condition of −100 ° C., changing the test temperature at 5 ° C. intervals (5 ° C. decrease for No Break, 5 ° C. for Break) Ascending) For both of the two plate-shaped test pieces, a temperature lower by 5 ° C. than the lowest test temperature at which No Break was obtained can be set as the non-ductile transition temperature.

4. Brittle Crack Propagation Stopping Characteristic Determination Step Based on the non-ductile transition temperature obtained by the above steps, it is determined whether or not a thick steel plate has excellent brittle crack propagation stopping properties. Although there is no particular limitation on the specific determination method, for example, in the case of performing quality evaluation of a thick steel plate serving as a joining member, or in the case of performing quality evaluation of a thick steel plate serving as a member to be joined, respectively, as follows: Can be determined.

4-1. Regarding quality evaluation of thick steel plate as a joining member When a crack propagates from a member to be joined toward the joining member, the depth of the area where the crack enters is determined by the joining of the joining member and the joining member. It largely depends on the structure of the part.

  The structure of the surface portion of the joining member will be described in detail with reference to FIG. FIG. 4 is a cross-sectional view of the welded structure 10 perpendicular to the surface 11a and the surface 12a to be joined. In FIG. 4, hatching is not used to avoid complicating the drawing.

  As shown in FIGS. 1 and 4, a weld metal 14 a is formed on the surface 11 a side of the joint between the joining member 11 and the member to be joined 12. A heat affected zone 15a is formed at the boundary between the weld metal 14a and the joining member 11 and the joined member 12. In the specification of the present application, a region where the weld metal 14a and the heat-affected zone 15a are combined is a welded zone 13a.

  Here, the intrusion region of the crack generated from the member to be joined 12 and propagated to the joint member 11 depends on the depth from the surface 11a to the highest point of the heat affected zone 15a of the welded portion 13a. That is, the crack propagation can be stopped by controlling the non-ductile transition temperature in the surface layer portion of the joining member according to the depth from the surface 11a to the highest point of the heat-affected zone 15a of the welded portion 13a. become. Specifically, as the depth from the surface 11a to the highest point of the heat-affected zone 15a of the welded portion 13a is larger, the crack is more likely to propagate, so a thick steel plate having a low non-ductile transition temperature in the surface layer is required. You.

Therefore, when quality evaluation of a thick steel plate as a joining member is performed, the non-ductile transition temperature measured by the NRL drop weight test is set to NDTT (° C.), and the top of the heat-affected zone 15a of the welded portion 13a from the surface 11a. When the distance (h) in the thickness direction of the joining member 11 is defined as h (mm) and the following formulas (i) and (ii) are satisfied, the thick steel plate serving as the joining member has a brittle crack propagation stopping property. Can be determined to be excellent.
NDTT ≦ −60 (i)
NDTT ≦ −30.5 × ln (h) −14.0 (ii)

  The highest point of the heat-affected zone 15a means the tip of the heat-affected zone 15a in the thickness direction. Further, as shown in FIG. 4, the distance h is a distance between the surface 11a and a virtual surface 11d that is parallel to the surface 11a and passes through the front end of the heat-affected zone 15a in the thickness direction. The position of the tip of the heat-affected zone 15a can be easily determined by exposing it by nital corrosion.

4-2. About quality evaluation of thick steel plate as a member to be joined When a crack propagates from the joint member to the member to be joined, the brittle crack propagation arresting property at the surface layer on the joint member side of the member to be joined Is improved according to the height of the joining member and the assumed allowable stress, thereby making it possible to stop the growth of the crack.

  That is, by controlling the non-ductile transition temperature in the surface layer portion of the member to be joined in accordance with the height of the joining member and a preset allowable stress of the joining member, it becomes possible to stop the growth of the crack. . Specifically, the higher the height of the joining member and the higher the allowable stress of the joining member, the more easily the crack is likely to propagate. Therefore, it is necessary to lower the non-ductile transition temperature in the surface layer.

Therefore, when performing quality evaluation of a thick steel plate as a member to be joined, the non-ductile transition temperature measured by the NRL drop weight test is set to NDTT (° C.), and the length in a direction perpendicular to the end face of the joint member is set to H. (Mm), when the predetermined allowable stress of the joining member is σ (N / mm ² ), and when the following formula (iii) is satisfied, the thick steel plate as the member to be joined stops brittle crack propagation. It can be determined that the characteristics are excellent.
NDTT ≦ 360.4−46.8 × ln {σ (πH) ^0.5 } (iii)

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

  After preparing various steel plates having the plate thicknesses shown in Table 1, for each steel plate, the non-ductile transition temperature in the surface layer on one side was investigated. Specifically, after shaving the surface by 1 mm, a type P3 test piece specified by ASTM E208 was sampled so that the thickness direction of the test piece coincided with the thickness direction of the steel sheet. Then, an NRL drop weight test based on ASTM E208 was performed using the test piece to determine a non-ductile transition temperature NDTT (° C.).

After that, the above various steel plates were used as test plates (joining members 11), and a structural model arrest test body shown in FIG. 5 was prepared and tested. A welded joint obtained by joining a steel plate having a thickness of 100 mm by CO ₂ welding was used as an approaching welded joint (member 12 to be joined), and a welded structure 10 was produced by CO ₂ welding or covered arc welding (SMAW) under the conditions shown in Table 1. .

  Thereafter, a notch 16b was introduced into the fusion line portion 16a of the welded structure 10. Then, the welded structure 10 is cooled to the ship design temperature of −10 ° C., a test stress of 257 MPa corresponding to the design stress of EH40 is applied, and only the vicinity of the notch is rapidly cooled to about −50 ° C. An impact was applied through a wedge to generate and propagate a brittle crack.

Using the structural model arrest specimen after the test, a cross section of one welded portion between the joining member and the member to be joined was cut out at a position 250 mm left and right from the center in the longitudinal direction of the specimen. Thereafter, the resultant was polished and subjected to nital corrosion to reveal a weld metal portion and a weld heat affected zone (a region heated to an Ac ₁ transformation point or higher during welding). The photographs of the cross sections of these two welded joints were respectively taken with a digital camera, the shape of the welded portion was measured from the photographic images, and the average value of the measurement results at the two places was used.

  Then, based on the obtained non-ductile transition temperature NDTT (° C.) and the distance h (mm) in the thickness direction of the joining member between the uppermost point of the heat-affected zone of the welded portion and the above-mentioned surface, it is used as a joining member. It was determined whether or not the thick steel plate had excellent brittle crack arrestability.

  In addition, regarding the results of the test using the structural model arrest specimen, it was determined that when the brittle crack stopped at the test plate, the test was stopped, and when the test plate was broken, the propagation was determined. The results are summarized in Table 1.

  As is clear from Table 1, when the thick steel sheet determined to be good by the evaluation method of the present invention was used as a joining member, the brittle crack stopped at the test plate, but was determined to be poor. When a thick steel plate was used, the result was that the brittle crack propagated to the joining member.

  After preparing various steel plates having the plate thicknesses shown in Table 2, with respect to each steel plate, the non-ductile transition temperature in the surface layer of one surface (the surface to be joined) was examined. Specifically, after the surface to be joined was shaved off by 1 mm, a type P3 test piece specified by ASTM E208 was sampled so that the thickness direction of the test piece matched the thickness direction of the steel sheet. Then, an NRL drop weight test based on ASTM E208 was performed using the test piece to determine a non-ductile transition temperature NDTT (° C.).

Thereafter, the above various steel plates were used as test plates (members to be joined 12), and a structural model arrest test body shown in FIG. 6 was prepared and tested. A welding joint having a height H (mm) shown in Table 2 and a steel plate having a thickness of 100 mm joined by CO ₂ welding is referred to as a run-up welding joint (joining member 11), and is subjected to CO ₂ welding or coating under the conditions shown in Table 2. The welded structure 10 was produced by arc welding (SMAW). At this time, both sides of the groove having a depth of 1/3 of the plate thickness were provided on the joining member 11, and the joining member 11 and the member to be joined 12 were joined by groove welding.

  Thereafter, a notch 16b was introduced into the fusion line portion 16a of the welded structure 10. Then, the welded structure 10 is cooled to a ship design temperature of −10 ° C., and a test stress corresponding to the allowable stress σ of the joining member 11 shown in Table 2 is applied, and only the vicinity of the notch portion is rapidly cooled to about −50 ° C. Then, the notch was hit through a wedge to generate and propagate a brittle crack.

  Then, based on the obtained non-ductile transition temperature NDTT (° C.), the height H (mm) of the joining member and the allowable stress σ, whether the thick steel plate used as the member to be joined has excellent brittle crack propagation stopping characteristics It was determined whether or not.

  In addition, regarding the results of the test using the structural model arrest specimen, it was determined that when the brittle crack stopped at the test plate, the test was stopped, and when the test plate was broken, the propagation was determined. Table 2 summarizes the results.

  As is clear from Table 2, when a thick steel plate determined to be good according to the evaluation method of the present invention was used as a member to be joined, the brittle crack stopped at the test plate, but was determined to be defective. When a thick steel plate was used, the result was that the brittle crack propagated to the member to be joined.

  As described above, according to the present invention, it is possible to easily and accurately evaluate the quality of a thick steel plate required to obtain a welded structure having excellent brittle crack arrestability.

DESCRIPTION OF SYMBOLS 10 Welded structure 11 Joining member 11a, 11b Surface 11c End face 11d Virtual surface 12 Member to be joined 12a Joined surface 13a, 13b Welded part 14a, 14b Weld metal 15a, 15b Heat affected part 16a Fusion line part 16b Notch

Claims (3)

A quality evaluation method for a thick steel plate used for a welded structure,
The welding structure includes a T-joint portion in which the joining member is partially penetrated and welded to the joined member in a state where an end surface of the plate-shaped joining member is in contact with the joined surface of the plate-shaped joined member. Which has
From a thick steel plate having a thickness of 50 mm or more serving as the joining member or the member to be joined, a part of a region in which the thickness direction of the thick steel plate coincides with the thickness direction and a depth of 5 mm from the surface of the thick steel plate. Take a plate-like test piece containing
Using the plate-shaped test piece, measure the non-ductile transition temperature by the NRL drop weight test,
Based on the non-ductile transition temperature, determine the brittle crack propagation arresting property of the thick steel plate to be the joining member or the member to be joined,
Quality evaluation method for thick steel plates. A method for evaluating the quality of the thick steel plate serving as the joining member,
The plate-shaped test piece is collected so as to include a part of a region from one surface orthogonal to a thickness direction of the thick steel plate to be the joining member to a depth of 5 mm,
The non-ductile transition temperature measured by the NRL drop weight test is defined as NDTT (° C.), and the highest point of the heat-affected zone of the welded portion formed on the one surface side by the both-side partial penetration welding and the one surface When the distance in the thickness direction of the joining member is h (mm),
When the following formulas (i) and (ii) are satisfied, it is determined that the thick steel plate serving as the joining member has excellent brittle crack propagation stopping characteristics.
The quality evaluation method for a thick steel plate according to claim 1.
NDTT ≦ −60 (i)
NDTT ≦ −30.5 × ln (h) −14.0 (ii) A quality evaluation method of the thick steel plate to be the member to be joined,
The plate-shaped test piece is collected so as to include a part of a region from one surface corresponding to the surface to be joined of the thick steel plate to be the member to be joined to a depth of 5 mm,
The non-ductile transition temperature measured by the NRL drop test is NDTT (° C.), the length in the direction perpendicular to the end face of the bonding member is H (mm), and the allowable stress of the bonding member set in advance is H σ (N / mm ² ),
When satisfying the following formula (iii), it is determined that the thick steel plate as the member to be joined is excellent in brittle crack propagation arresting properties,
The quality evaluation method for a thick steel plate according to claim 1.
NDTT ≦ 360.4−46.8 × ln {σ (πH) ^0.5 } (iii)

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