CN104272084A

CN104272084A - Method for evaluating long brittle crack arresting ability in thick steel plate, and testing device and method for manufacturing thick steel plate using same

Info

Publication number: CN104272084A
Application number: CN201380022478.8A
Authority: CN
Inventors: 半田恒久; 伊木聪; 大井健次
Original assignee: NKK Corp
Current assignee: JFE Steel Corp; JFE Engineering Corp
Priority date: 2012-08-06
Filing date: 2013-08-02
Publication date: 2015-01-07
Also published as: CN107988471A; KR20140127363A; JP6165116B2; KR101728362B1; JP2015025205A; JPWO2014024445A1; WO2014024445A1

Abstract

Provided is a testing device and a method for evaluating long brittle crack arresting ability that is appropriate for an actual ship of thick steel plate (mainly thick steel plate having a thickness of at least 50 mm), the thick steel plate having excellent brittle crack arresting ability and being suitable for use in large container ships, bulk carriers, etc. When a tensile load is applied by a tensile tester in the direction perpendicular to the width of a large test sample having a width of at least 1.5 m, and long brittle crack arresting ability is evaluated for a long brittle crack of length 1 m or greater, a transmitting part for transmitting the tensile load from the tensile tester to the large test sample has thickened parts having a thickness at least 2.5 times that of the large test sample on either side of the center in the width of the large test sample spaced apart at least 2.8 times, preferably at least 4.1 times, the width of the large test sample, and the tensile load from the tensile tester is applied in positions on either side of the center of the large test sample in the direction perpendicular to the width by the thickened parts. A testing device having the transmitting part is provided.

Description

The evaluation method of the brittle-cracking propagation Stopping Ability of growing up of steel plate, for the test unit of this evaluation method and the manufacture method of steel plate

Technical field

The present invention relates to the steel plate (steel plate) (being mainly the steel plate that thickness of slab is more than 50mm) to being preferably used for manufacturing Large Container Ship (Mega-container carrier), bulk freighter (bulk carrier) etc., evaluating method and the test unit of the crack propagation Stopping Ability (long brittle crack arrestability) of the grow up brittle crack suitable with real ship.

Background technology

Container ship, bulk freighter, in order to improve load-bearing capacity (carrying capacity), improve cargo handling efficiency (cargo handling efficiency) etc., form the structure increasing upper opening portion (upper aperture) and so on.Therefore, in order to ensure rigidity (rigidity) and the longitudinal strength (longitudinal strength) of hull, for these ships, ship hull plate (outer plate of vessel ' s body) wall thickening must be made especially.

In recent years, Effects of Containers Growing Bigger, for the argosy of 6000 ~ 20000TEU (Twenty-foot Equivalent Unit: twenty-foot equivalent unit), the thickness of slab of ship hull plate is more than 50mm.If thickness of slab is more than 50mm, then cause destroying toughness (fracture toughness) to reduce due to thickness of slab effect (thickness effect), and thermal weld stress (welding heat input) also becomes greatly, the trend that the destruction toughness that therefore there is weld part (welded part) reduces further.Should illustrate, TEU represents and is converted into the number that length is the container of 20 feet, represents the index of the load-bearing capacity of container ship.

For the steel plate (being mainly the thinner steel that thickness of slab is less than 50mm) that boats and ships (ships), pipeline (linepipe) use; grain refined can be realized by TMCP (Thermo-Mechanical-Control-Process: thermomechanical Controlling Technology) method; improve low-temperature flexibility (low-temperature toughness), give excellent brittle-cracking propagation Stopping Ability (brittle crack arrestability).

Improving the method for brittle-cracking propagation Stopping Ability as not making cost of alloy (alloy cost) rise, proposing the technology of tissue (microstructure) micronization of the skin section of steel (surface part).Such as, Patent Document 1 discloses and be conceived to when brittle-cracking propagation, the shear lip (shear-lips) (plastic deformation area (plastic deformation area)) that steel skin section produces is to the effective situation of the raising of brittle-cracking propagation Stopping Ability, make the crystal grain miniaturization of shear lip part, the method that the Propagation of Energy (propagation energy) that the brittle crack of propagation is had absorbs.

In patent documentation 1, after hot-rolled steel plate, repeatedly carry out the following operation of more than 1 time, namely by controlled cooling model (controlled cooling), surface part is cooled to Ar ₃below transformation temperature, stop controlled cooling model thereafter, make surface part be heated to the operation of more than transformation temperature again, pressure is applied to steel therebetween.In patent documentation 1, by adopting such method, make it phase transformation repeatedly or processing recrystallization (recrystallization due to deformation), generate ultramicrofine ferritic structure (ferrite structure) or bainite structure (bainite structure) in surface part.

In patent documentation 2, with in the steel of ferrite-pearlite (pearlite) for main body micromechanism (microstructure), two surface elements are made up of the layer that equivalent circle mean grain size (average of equivalent circle diameter) is less than 5 μm, length breadth ratio (aspect ratio) is the ferritic structure of the ferrite crystal grain of more than 2 that has containing more than 50%.In addition, Patent Document 2 discloses following content: if by making the maximum depression rate of every 1 rolling in finish rolling (maximum rolling reduction) be less than 12% suppress partial re-crystallization phenomenon (recrystallization phenomenon), suppress the deviation (variation) of ferrite particle diameter, then can obtain brittle-cracking propagation Stopping Ability and improve such excellent effect.

As the steel of the excellent performance of resistance to brittle-cracking propagation be subject to after plastic yield (plastic deformation) in patent documentation 3, disclosing by what adopt the condition manufacture described in following (a) ~ (d) is the steel of Main Tissues to be formed with the fine ferrite of subgrain (sub-grain) in crystal grain.In patent documentation 3, when the temperature of complexity such as not needing the cooling on steel plate top layer and heat controls (temperature control), improve the brittle-cracking propagation Stopping Ability after being subject to plastic yield.

A () guarantees the rolling condition of fine ferrite crystal grain, b () generates the rolling condition of fine ferrite structure in the part apart from the degree of depth on surface being more than 5% of steel thickness of slab, c () makes set tissue flourishing and the rolling condition utilizing heat energy (thermal energy) to configure the dislocation (dislocation) imported by processing (rolling) again and subgrain is formed in fine ferrite, (d) suppresses the cooling condition of the coarsening of fine ferrite crystal grain and the fine subgrain formed.

In addition, as the technological thought (technological thought) different from patent documentation 1 ~ 3, Patent Document 4 discloses to produce in the direction parallel with thickness of slab direction on the failure mechanics of steel by making set tissue (texture) flourishing and be separated (separation), relax the stress of brittle crack front end, improve the method for resistance to brittle-cracking propagation performance thus.In addition, describe in patent documentation 4 and made by controlled rolling (110) face X-ray intensity ratio (X-ray intensity ratio) be more than 2, and to make diameter of equivalent circle (equivalent circle diameter) be the thick grain of more than 20 μm be less than 10%.

Patent Document 5 discloses steel for welded structures, if use this steel for welded structures, then can improve the brittle-cracking propagation Stopping Ability of solder joint portion (welded joint).Specifically, in patent documentation 5, as above-mentioned steel for welded structures, disclose a kind of steel plate, it is characterized in that, the X ray face strength ratio in (100) face of the rolling surface in thickness of slab inside has more than 1.5.And, following content is described: if be this steel plate in patent documentation 5, then because set tissue is flourishing, crack propagation direction (crack propagation direction) is changed relative to the direction vertical with mechanical load direction (stress loading direction), guide brittle crack from solder joint portion to mother metal side, improve the brittle-cracking propagation Stopping Ability as seam.

In addition, Patent Document 6 discloses a kind of steel plate, it is characterized in that, be more than 1.3 at the X-ray intensity ratio in (211) face of the rolling surface of thickness of slab central portion, and be more than 1.5 at (100) face X-ray intensity ratio of the rolling surface of thickness of slab 1/4, be more than 1.5 at (100) face X-ray intensity ratio of the rolling surface of plate skin section.And, following content is described: if be this steel plate in patent documentation 6, then because set tissue is flourishing, make to produce crack (crack) near the brittle crack front end charged into from surface of steel plate via T seam (T-joint) etc., work as crack propagation resistance in this crack, the brittle-cracking propagation Stopping Ability for the brittle crack propagated in thickness of slab direction improves.

On the other hand, consider in Ship Structure (hull structure), even if just in case when producing brittle rupture (brittle fracture) from weld part, also need stop the propagation of brittle crack and prevent hull to be separated.Thickness of slab is less than to the brittle-cracking propagation behavior in the shipbuilding Plate Welding portion of 50mm, SRAJ (The Shipbuilding Research Association of Japan) the 147th council is studied by experiment.

147th council has investigated travel path, the dissemination of forcing the brittle crack produced at weld part by experiment, if results verification guarantees the destruction toughness (fracture toughness) of weld part to a certain extent, then make due to the impact of weld residual stress (welding residual stress) brittle crack be easy to from weld part to mother metal lateral deviation from.In addition, the 147th council also confirms the example that multiple brittle crack is propagated along weld part.

This fact suggests can not assert do not have brittle rupture along the possibility of weld part rectilinear propagation.But, have by with the 147th council apply weld equal welding be applied to thickness of slab be less than the steel plate of 50mm and the boats and ships built set sail without any problems a large amount of real results of (actual service).Except the real result that these are a large amount of, also recognize that the ability of the stopping brittle crack of the steel plate mother metal (shipbuilding E level steel etc.) that toughness is good is abundant, therefore shipbuilding with the brittle-cracking propagation Stopping Ability in welded steel portion always not required by ship's classification rule (Rules and Guidance for the survey and construction of steel ships) etc.

But, recently more than the thickness of slab of the Large Container Ship light plate of 6000TEU more than 50mm.If thickness of slab is more than 50mm, then due to thickness of slab effect, destruction toughness is reduced, and thermal weld stress also become large, the trend that the destruction toughness that therefore there is weld part reduces further.

Recently, in large heat input solder joint (large heat input welded joint of heavy gauge steel plate) of heavy wall that experiment display is such, the brittle crack produced from weld part not to the liftoff craspedodrome of mother metal lateral deviation and growing up (long), even if also do not stop (non-patent literature 1) in steel plate mother metal portions such as aggregate (stiffeners) (or also referred to as armatures).Thus, large problem is become at the secure context of Ship Structure of the steel plate guaranteeing the thickness of slab applying more than 50mm.

As evaluating the test guaranteeing the security of such hull, the ESSO that grows up (large-scale duplex ESSO) is had to test.This is grown up in ESSO test, because of the difference of evaluation method, the restriction of test unit etc., test findings is changed to some extent, has the problem may not evaluating the grow up brittle-cracking propagation Stopping Ability suitable with real ship.

As the test method(s) of the brittle-cracking propagation Stopping Ability (brittle-cracking propagation stopping toughness) of the evaluation steel plate of the technology recorded based on above-mentioned patent documentation 1 ~ 6, there is the test method(s) of the double tension test of the test specimen that uses width to be about 500mm and ESSO test etc., in order to correctly evaluate plate property, formulate detailed content (steel grade identification test method (steel grade qualified method) of Japanese welding association (The Japan Welding Engineering Society) of test method, the brittle crack of Nippon Kaiji Kyokai BJ Office (Nippon Kaiji Kyokai) stops the Kca test method (Kca test method) of design guidelines (guidelines on brittle crack arrest design)).

In addition, when these steel plates are applied to works, sometimes require to be that the ultra-large type such as ESSO test of growing up test (very large test) of more than 1.5m confirms that length is the performance of the brittle crack of growing up of more than 1m by width, but for test method, not yet formulate detailed content.

Patent documentation

Patent documentation 1: Japanese Unexamined Patent Publication 4-141517 publication

Patent documentation 2: Japanese Unexamined Patent Publication 2002-256375 publication

Patent documentation 3: Japanese Unexamined Patent Publication 11-256228 publication

Patent documentation 4: Japanese Unexamined Patent Publication 10-88280 publication

Patent documentation 5: Japanese Unexamined Patent Publication 6-207241 publication

Patent documentation 6: Japanese Unexamined Patent Publication 2008-214652 publication

Non-patent literature

Non-patent literature 1: mountain pass etc.: " practicality-of the exploitation-novel high-strength pole steel plate (new high strength heavy gauge steel plate) of super-container vessel (Mega-container carrier) ", Japan's boats and ships ocean engineering meeting will, 3, (2005), the 70th page.

Summary of the invention

In the technology that above-mentioned patent documentation 1 ~ 6 is recorded, for method, the test unit of evaluating the grow up brittle-cracking propagation Stopping Ability suitable with real ship, do not record.Therefore, use the technology recorded in patent documentation 1 ~ 6, the problem of the safety evaluatio suitable with real ship cannot be solved.In addition, the steel plate that above-mentioned patent documentation 1 ~ 6 is recorded does not relate to the brittle-cracking propagation Stopping Ability of growing up yet.Therefore, even if use the technology recorded in patent documentation 1 ~ 6, the problem illustrated in non-patent literature 1 cannot also be solved.

Therefore, the object of the present invention is to provide the manufacture method of method, test unit and the steel plate of evaluating the grow up brittle-cracking propagation Stopping Ability suitable with real ship.

The present inventor etc., to dynamic FEM parsing (dynamic finite element method analysis) at the thickness of thickened section (more thicker part) of the transfer part (transfer part) (being made up of the corbel back slab (tab plate) of testing machine and the pin chuck (pin-chuck) of testing machine) by changing cupping machine (tensile testing machine) and its interval, can simulate evaluation method, the test unit tested with the ESSO that grows up of the brittle-cracking propagation performance of growing up of real ship suitable (full-scale) and being studied.Its result, obtains following opinion: by the value making the thickness of thickened section and its be spaced apart regulation, can reproduce the situation suitable with not having the real ship of stress reflexion (stress wave reflection).

In the present invention, brittle crack of growing up is the length of charging into from other adjacent steel plate is the brittle crack of more than 1m.

In addition, use evaluation method, the test unit of the ESSO test of growing up obtained, the a large amount of steel plates obtain changing chemical composition and rolling condition, have investigated manufacturing condition and the relation of the brittle-cracking propagation Stopping Ability of brittle crack of growing up (being sometimes referred to as prevention performance (arrestability)) obtain opinion.

The present invention is studied further based on above-mentioned opinion and is made, and namely the present invention is as described below.

(1) a kind of evaluation method of brittle-cracking propagation Stopping Ability of growing up of steel plate, it is characterized in that, with cupping machine, there is the width right angle orientation load stretching loading of System for Large-scale Specimen of width of more than 1.5m, obtain for the crack length in above-mentioned System for Large-scale Specimen the propagation Stopping Ability of the brittle crack of growing up being more than 1m, wherein, to above-mentioned System for Large-scale Specimen transmission from the transfer part of the stretching loading of cupping machine to become the interval of more than 2.8 times of the width of above-mentioned System for Large-scale Specimen, there is in the mode at the center clamping the width right angle orientation of above-mentioned System for Large-scale Specimen the thickened section of more than 2.5 times of the thickness becoming above-mentioned System for Large-scale Specimen, from the stretching loading of above-mentioned cupping machine by load in the position at center of width right angle orientation clamping above-mentioned System for Large-scale Specimen with above-mentioned thickened section.

(2) evaluation method of the brittle-cracking propagation Stopping Ability of growing up of the steel plate recorded according to (1), is characterized in that having above-mentioned thickened section with the interval of more than 4.1 times that become the width of above-mentioned System for Large-scale Specimen.

(3) a kind of device evaluating the brittle-cracking propagation Stopping Ability of growing up of steel plate, it is characterized in that, there is the width right angle orientation load stretching loading of System for Large-scale Specimen of width of more than 1.5m, obtain for the crack length in above-mentioned System for Large-scale Specimen the propagation Stopping Ability of the brittle crack of growing up being more than 1m, wherein, to the transfer part of above-mentioned System for Large-scale Specimen transmission stretching loading to become the interval of more than 2.8 times of the width of above-mentioned System for Large-scale Specimen, there is in the mode at the center clamping the width right angle orientation of above-mentioned System for Large-scale Specimen the thickened section of more than 2.5 times of the thickness becoming above-mentioned System for Large-scale Specimen, by above-mentioned stretching loading load in the position at center of width right angle orientation clamping above-mentioned System for Large-scale Specimen with above-mentioned thickened section, loading capacity (load capacity) is more than 50MN (mega newton).

(4) (3) device of the brittle-cracking propagation Stopping Ability of growing up of evaluation steel plate of recording, is characterized in that having above-mentioned thickened section with the interval of more than 4.1 times that become the width of above-mentioned System for Large-scale Specimen.

(5) (3) or (4) device of the brittle-cracking propagation Stopping Ability of growing up of evaluation steel plate of recording, it is characterized in that, above-mentioned loading capacity is more than 80MN.

(6) a kind of manufacture method of steel plate of brittle-cracking propagation Stopping Ability excellence of growing up, it is characterized in that, comprise the device recorded any one of use (3) ~ (5), evaluate the operation of the brittle-cracking propagation Stopping Ability of growing up of steel plate.

(7) a kind of manufacture method of steel plate of brittle-cracking propagation Stopping Ability excellence of growing up, it is characterized in that, (6) in the manufacture method of the steel plate recorded, by the heating temperatures of Steel material at 900 ~ 1350 DEG C, then be that the temperature province of 1000 ~ 850 DEG C is with after accumulation reduction ratio (cumulative rolling reduction) more than 10% rolling in surface of steel plate temperature, be that the temperature province of 900 ~ 600 DEG C is with accumulation reduction ratio more than 50% in surface of steel plate temperature, surface of steel plate temperature at the end of rolling is 800 ~ 550 DEG C and carries out hot rolling and manufacture, the steel composition of above-mentioned Steel material in mass %, containing below C:0.15%, below Si:0.6%, Mn:0.8 ~ 2.4%, S:0.001 ~ 0.05%, containing at least a kind that is selected from Ti:0.005 ~ 0.05% or Nb:0.001 ~ 0.1%, further containing being selected from below Cu:2%, below V:0.2%, below Ni:2%, below Cr:0.6%, below Mo:0.6%, below W:0.5%, below B:0.005%, at least a kind in below Zr:0.5%, remainder is made up of Fe and inevitable impurity.

(8) manufacture method of the steel plate of the brittle-cracking propagation Stopping Ability excellence of growing up recorded according to (7), wherein, further after end hot rolling, be cooled to 400 DEG C with the cooling velocity of more than 5 DEG C/sec (cooling rate).

(9) steel plate for brittle-cracking propagation Stopping Ability excellence of growing up, is characterized in that, is to utilize the manufacture method recorded any one of (6) ~ (8) to manufacture.

According to the present invention, the evaluation being difficult to up to now carry out the brittle crack Stopping Ability of growing up correctly evaluated can be implemented under the condition suitable with not having the real ship of stress reflexion (reflection of stress wave).In addition, the imparting of the brittle-cracking propagation Stopping Ability of the excellence that the main steel plate that is more than 50mm to thickness of slab (t) that can realize difficulty up to now carries out, can stop growing up brittle crack under the condition suitable with not having the real ship of stress reflexion, industrially exceedingly useful.

Accompanying drawing explanation

Fig. 1 represents that specimen width is the figure of the size shape of the ESSO test specimen of growing up of 2400mm.

Fig. 2 represents that specimen width is the figure of the size shape of the ESSO test specimen of growing up of 1500mm.

Fig. 3 represents for investigating the figure of stress reflexion on the dynamic FEM analytic model (model 1) of the impact of the evaluation of brittle-cracking propagation Stopping Ability of growing up.

Fig. 4 represents for investigating the figure of stress reflexion on the dynamic FEM analytic model (model 2) of the impact of the evaluation of brittle-cracking propagation Stopping Ability of growing up.

Fig. 5 represents for investigating the figure of stress reflexion on the dynamic FEM analytic model (model 3) of the impact of the evaluation of brittle-cracking propagation Stopping Ability of growing up.

Fig. 6 is the analysis result of the model for dynamic analysis as Fig. 3 ~ 5, represents the figure of the impact at (the some C's of Fig. 3 ~ 5) dynamic stress amplification coefficient (thickness of thickened section and its interval) when test condition charges into breadboard to brittle crack of growing up.Here, Kd is dynamic stress amplification coefficient (dynamic stress intensity factor) (the dynamic stress amplification coefficient of the some C of Fig. 3 ~ 5) of brittle crack when charging into breadboard of growing up, Kd _aeff/W=8.3for A _effcondition (the A of/W=8.3 _effduring for specimen width W 8.3 times) under, brittle crack of growing up charges into dynamic stress amplification coefficient during breadboard.A _effthe condition of/W=8.3 is until brittle crack of growing up charges into breadboard the condition of loading reduction (reduction of the reacting force (reaction force) of pole (pin)) does not occur (namely, until grow up, brittle crack charges into breadboard, is not arrived the condition of pole hole position by the crackle unloading stress elastic wave (unloading stress elastic wave) produced caused by (crack initiation) and opening (crack opening)).

Fig. 7 is the figure of shape of the test specimen of the enforcement representing the ESSO test that is applicable to grow up, the corbel back slab of testing machine, the pin chuck of testing machine.

Embodiment

The present invention is used under the condition suitable with not having the real ship of stress reflexion, evaluates brittle-cracking propagation Stopping Ability of growing up.The invention is characterized in, the transfer part from the stretching loading of cupping machine is being transmitted to ESSO test specimen (also referred to as System for Large-scale Specimen) of growing up, to become the interval of more than 2.8 times of the width W of System for Large-scale Specimen, to clamp the mode of the widthwise central of System for Large-scale Specimen, to be set to the thickened section of more than 2.5 times of the thickness of slab t of System for Large-scale Specimen.Should illustrate, System for Large-scale Specimen refers to the System for Large-scale Specimen recorded in Nippon Kaiji Kyokai BJ Office's " brittlement crevasse crack prevention design guidelines " Appendix B (2009).

Below, with Fig. 1 ~ 7, the present invention is described.These figure in addition to fig. 6 represent large-scale tensile test fixture (jig).In these figure in addition to fig. 6; 1 refers to ESSO test specimen of growing up; 11 breadboards referring to ESSO test specimen 1 of growing up; the 12 run-up plates (crack-running plate) referring to ESSO test specimen 1 of growing up; 13 refer to machining otch (machined notch); 14 refer to gas protective arc welding portion (welded part of electrogas arc welding), and 15 refer to CO ₂shielded arc welding meets portion (welded part of CO ₂arc welding), 2 corbel back slabs referring to testing machine, 3 pin chucks referring to testing machine, 31 pole holes referring to testing machine, 32 refer to nut shape portion (strengthening the thickened section around pole hole), and W refers to the width of ESSO test specimen of growing up.The present invention is to have the System for Large-scale Specimen of the width W of more than 1.5m for object.In addition, usually, the width W of System for Large-scale Specimen is below 3m.

First, by the impact of dynamic FEM analyzing and evaluating stress reflexion, obtain the insignificant test condition of impact of stress reflexion.

The grow up shape of ESSO test specimen 1 and the size of each several part that use in resolving shown in Fig. 1,2.ESSO test specimen 1 of growing up, breadboard 11 and run-up plate 12 shown in Fig. 1 carries out CO by the rolling direction (rolling direction) (R.D.) along breadboard 11 ₂the weld part 15 that shielded arc welding connects is (hereinafter referred to as CO ₂shielded arc welding meets portion 15) engage.

In order to produce brittle crack, the connecting portion (bond) along the weld part midway in the gas protective arc welding portion 14 of run-up plate 12 is processed with machining otch 13.Grow up in ESSO test specimen 1 shown in Fig. 2, be processed with machining otch 13 at the connecting portion of the end in the gas protective arc welding portion 14 of run-up plate 12, other is formed in the same manner as Fig. 1.

Dynamic FEM analytic model shown in Fig. 3 ~ 5.Fig. 3,5 is the use of the analytic model (analysis model) of the ESSO test specimen of growing up of Fig. 1, and Fig. 4 is the use of the analytic model of the ESSO test specimen of growing up of Fig. 2.Illustrated dynamic FEM analytic model is the parameterized model (parametrical model) for finding out the condition not having stress reflexion, is the model of the impact of the shape and size for resolving transfer part.

Transfer part is the part that the stretching loading of in the future self stretch testing machine is delivered to System for Large-scale Specimen 1.Specifically, transfer part refers to the end of load stretching loading in System for Large-scale Specimen 1, relative to the part that the center (position of the otch leading section of machining otch 13) of the width right angle orientation of System for Large-scale Specimen 1 is symmetrically made up of the corbel back slab 2 of testing machine and the pin chuck 3 of testing machine.The thickness in test specimen thickness of slab t direction in transfer part is become the part of more than 2.5 times of specimen thickness t (thickness of slab) as thickened section.Should illustrate, when Width is from thickness of slab direction viewing test plate, the direction vertical relative to rolling direction (R.D.), width right angle orientation is rolling direction (R.D.).

The thickened section of transfer part is the pin chuck 3 of the testing machine of 3 times becoming specimen thickness t (thickness of slab) when the analytic model of Fig. 3, being the corbel back slab 2 of the testing machine of more than 2.5 times and the pin chuck 3 of testing machine that become specimen thickness t (thickness of slab) when the analytic model of Fig. 4, is the nut shape portion (strengthening the thickened section around pole hole) 32 of the pin chuck 3 of testing machine when the analytic model of Fig. 5.In addition, the upper limit of the thickness of thickened section is not particularly limited, and usually, the thickness of thickened section is less than 20 times of specimen thickness t (thickness of slab).

Stretching loading from cupping machine (not shown) utilizes the pole (not shown) that is loaded into the cupping machine of the pole hole 31 of thickened section and in the width right angle orientation of System for Large-scale Specimen 1 by symmetrically load.

In the present invention, the interval of thickened section (is sometimes referred to as A _eff) be interval the shortest in the interval of thickened section.When being interposed between the analytic model of Fig. 3 between thickened section be left and right the pin chuck 3 becoming the testing machine of 3 times of specimen thickness t (thickness of slab) between interval (A in figure _eff), when the analytic model of Fig. 4 be left and right the corbel back slab 2 becoming the testing machine of 2.5 times of specimen thickness t (thickness of slab) between interval (A in figure _eff), be the interval (A in figure in opposed face, the nut shape portion 32 of the pin chuck 3 of the testing machine in left and right when the analytic model of Fig. 5 _eff).

In Fig. 6, as analysis result, test condition (thickness of thickened section and its interval (A are shown _eff)) the dynamic stress amplification coefficient of (the some C of Fig. 3 ~ 5) causes when charging into breadboard 11 to crackle of growing up impact.

As shown in Figure 6, if A _effshorten, then dynamic stress amplification coefficient be not put to the test machine pole hole 31 around shape (shape in the corbel back slab 2 of testing machine, the pin chuck 3 of testing machine or nut shape portion 32) the restriction ground of thickened section reduce.And, if A _effshorter than 2.8 times of test specimen width W (if A _eff/ W is less than 2.8), then reduce and further become remarkable.

As shown in Figure 6, when the propagation rate of crack (crack propagation speed) is scope (the general crack velocity of rectilinear propagation weld part) of 500 ~ 800m/s, if A _efffor more than 2.8 times of specimen width W, then can obtain and the A not producing loading and reduce _effthe test condition of/W=8.3 is equal (not producing more than 95% of the test condition that loading reduces) dynamic stress amplification coefficient almost.That is, during the ESSO that grows up tests, if make the interval A of the thickened section of transfer part _efffor more than 2.8 of specimen width W, then can realize the test condition suitable with real ship that the impact of the reflection unloading stress wave (wave of unloading characteristics) is little.

In addition, if make A _eff/ W is more than 4.1 times, then become and do not produce more than 97% of the test condition that loading reduces, can more preferably test (more perfect test).If make A _eff/ W is more than 6 times, then become and the identical condition of test condition not producing loading and reduce, can more preferably test.

According to more than, if make A _efffor more than 2.8 times of specimen width W, then can carry out the evaluation of the condition suitable with real ship.Such as use the interval (A between the nut shape portion as thickened section (screw nut like part) 32 (relative to the thickness of slab 60 ~ 100mm of System for Large-scale Specimen 1, thickness is 400mm) shown in Fig. 7 _eff) be the transfer part of 8800mm, evaluate when growing up brittle-cracking propagation Stopping Ability, fully can carry out the evaluation of the condition suitable with real ship.

Resolved by above FEM, make the interval A of loading load/be delivered to thickened section (corbel back slab of testing machine or the pin chuck etc. of testing machine) _efffor more than 2.8 times, more preferably more than 4.1 times of specimen width.And then, be more preferably preferably more than 6 times.

In order at the test specimen using more than specimen width 1.5m with above-mentioned condition, by the grade (242 ~ 300N/mm of the maximum allowable stress (maximum allowable stress) of boats and ships ²degree), when not giving excessively additional to testing machine during test specimen fracture, evaluate brittle crack Stopping Ability of growing up, the loading capacity that must make testing machine is more than 50MN.

Thus, the test unit can evaluating the brittle-cracking propagation Stopping Ability of growing up under the condition suitable with real ship not having stress reflexion be the thickness of loading load/be delivered to thickened section (corbel back slab of testing machine or the pin chuck etc. of testing machine) is more than 2.5 times relative to specimen thickness and more than 2.8 times that are positioned at that the interval (bee-line (shortest distance)) of this thickened section at test specimen two ends is specimen width, loading capacity is the device of more than 50MN.

When carrying out the evaluation of middle more than the specimen width 2m recorded such as the design guidelines (Guidelines on Brittle Crack Arrest Design) of the brittle crack prevention of Nippon Kaiji Kyokai BJ Office, the loading capacity that must make testing machine is more than 80MN.Therefore, more preferably loading capacity is the test unit of more than 80MN.The higher limit of loading capacity is not particularly limited, but usually, the loading capacity of test unit is below 100MN.

According to the evaluation method of the brittle-cracking propagation Stopping Ability of growing up of the above-mentioned condition suitable with real ship, even if when producing brittle rupture in steel plate and weld part thereof, also at the brittle crack reaching front the growing up of stopping of large-scale damage (havoc), the steel plate of the thickness of slab of more than 50mm can mainly be selected.The preferred one-tenth of this steel plate is grouped into, and preferred manufacturing condition is as described below.Should illustrate, in explanation, % is quality %.By the way, the steel plate that thickness is less than 50mm can stop growing up brittle crack with existing steel plate (such as shipbuilding E level steel (E crass shipbuilding steel) etc.).

[one-tenth is grouped into]

Below C:0.15%

C is required in order to ensure intensity.From the view point of guaranteeing intensity, the lower limit of preferred C amount is 0.02%.But if C amount is more than 0.15%, then welding heat affected zone (welded heat-affected zone) (HAZ) toughness reduces, and therefore the upper limit that C measures is defined as less than 0.15%.Should illustrate, further flourishing in order to make the set in (211) face and (100) face organize, preferred C amount is less than 0.03%.

Below Si:0.6%

Si is to the effective element of raising intensity.In order to obtain this effect, the content of preferred Si is more than 0.01%.If Si amount more than 0.6%, then makes welding heat affected zone (HAZ) toughness significantly deteriorated.Therefore, Si amount is defined as less than 0.6%.

Mn：0.8～2.4％

Mn is to the effective element of high strength.From the view point of guaranteeing intensity, Mn amount is more than 0.8%.But if Mn amount is more than 2.4%, then base metal tenacity (toughness of base material) may deterioration.Therefore, Mn amount is the scope of 0.8 ~ 2.4%.Should illustrate, the preferable range of Mn amount is 1.0 ~ 1.7%.

Below S:0.001 ~ 0.05%

Due to crack (parallel with surface of steel plate breaks) must be produced in brittle crack leading edge, so S amount is more than 0.001%.But S forms non-metallic inclusion (non-metal inclusion) and makes ductility (ductility) and toughness deterioration.Therefore, S amount is less than 0.05%.

1 kind in Ti:0.005 ~ 0.050%, Nb:0.001 ~ 0.1% or 2 kinds

Ti has the precipitate (precipitate) by forming carbonide (carbide), nitride (nitride); suppress the growth of the austenite crystal (austenite grain) of heating period when steel plate manufactures and contribute to grain refined, and the coarse grains of suppression welding heat affected zone (HAZ) and improve the effect of HAZ toughness.In order to obtain these effects, Ti amount is more than 0.005%.On the other hand, if Ti amount too much, then toughness deterioration.Therefore, Ti amount is less than 0.050%.

The raising of Nb to precipitation strength (precipitation strengthening) and toughness is also effective.In addition, Nb suppresses austenitic recrystallization (recrystallization), promotes by the effect produced based on rolling condition described later.In order to obtain these effects, Nb amount is more than 0.001%.If Nb amount is more than 0.1%, then there are quenching structure (hardened microstructure) spiculation (needle-like) and the trend of toughness deterioration.Therefore, Nb amount is less than 0.1%.

Be selected from least a kind in below Cu:2.0%, below V:0.2%, below Ni:2.0%, below Cr:0.6%, below Mo:0.6%, below W:0.5%, below B:0.0050%, below Zr:0.5%

Below Cu:2.0%

Cu can mainly separate out in order to strengthening.In order to obtain this effect, preferred Cu amount is more than 0.05%.If Cu amount is more than 2.0%, then precipitation strength too much and toughness is deteriorated.Therefore, preferred Cu amount is 2.0%.

Below V:0.2%

V is solution strengthening (solute strengthening) and the available composition of precipitation strength.In order to obtain this effect, preferred V amount is more than 0.001%.If V amount more than 0.2%, then significantly damages toughness and the weldability (weldability) of mother metal.Therefore, preferred V amount is less than 0.2%.

Below Ni:2.0%

Ni makes intensity and toughness improve.In addition, Ni breaks effectively to Cu when preventing rolling when adding Cu.In order to obtain this effect, preferred Ni amount is more than 0.05%.But Ni is expensive, even and if excessively add Ni, this effect is also saturated.Therefore, preferred Ni amount is less than 2.0%.

Below Cr:0.6%

Cr has the effect improving intensity.In order to obtain this effect, preferred Cr amount is more than 0.01%.But, if Cr amount is more than 0.6%, then the toughness deterioration of weld part.Therefore, preferred Cr amount is less than 0.6%.

Below Mo:0.6%

Mo has the effect of intensity when improving normal temperature and high temperature.In order to obtain this effect, preferred Mo amount is more than 0.01%.But if Mo amount is more than 0.6%, then weldability deterioration, therefore, preferred Mo amount is less than 0.6%.

Below W:0.5%

W has the effect improving elevated temperature strength.In order to obtain this effect, preferred W amount is more than 0.05%.But, if W amount is more than 0.5%, then not only make toughness deterioration, and price is high.Therefore, preferred W amount is less than 0.5%.

Below B:0.005%

B separates out with the form of BN in rolling, and the ferrite crystal grain after rolling (ferrite grain) is attenuated.In order to obtain this effect, preferred B amount is more than 0.001%.But, if B amount is more than 0.005%, then toughness deterioration.Therefore, B amount is defined as less than 0.005%.

Below Zr:0.5%

Zr is except improving intensity, also improves the element of the resistance to plating disruptiveness (plating cracking resistance) of zinc-plated material (galvanized material).In order to obtain this effect, preferred Zr amount is more than 0.03%.But, if Zr amount is more than 0.5%, then the toughness deterioration of weld part.Therefore, preferred Zr amount is less than 0.5%.

Steel of the present invention is except mentioned component composition, and remainder is Fe and inevitable impurity.Should illustrate, as inevitable impurity, below tolerable P:0.035%, below Al:0.08%, below N:0.012%, below O:0.05%, Mg:0.01% are such as the following.

In manufacturing condition, preferably specify heating-up temperature (heating temperature), hot-rolled condition (hot rolling condition), cooling condition (cooling condition).When not specifying in explanation, temperature, cooling velocity get the mean value of thickness of slab direction (thickness direction).

[heating-up temperature]

Steel material is at the heating temperatures of 900 ~ 1350 DEG C.Heating-up temperature is more than 900 DEG C is necessary with controlled rolling described later (controlled rolling) in order to carry out homogenizing of material.In addition, making heating-up temperature be less than 1350 DEG C is become significantly because of surface oxidation (surface oxidization) during excessive high temperature, and can not avoid the coarsening (coarsening) of crystal grain (crystal grain).Should illustrate, in order to improve toughness, the upper limit of preferred heating-up temperature is 1150 DEG C.

[hot-rolled condition]

In the temperature province that surface of steel plate temperature is 1000 ~ 850 DEG C, be rolled under the condition of more than 10% at accumulation reduction ratio.By this rolling, austenite crystal partial recrystallisation, so tissue becomes fine and evenly.

Should illustrate, the rolling when the temperature more than 1000 DEG C, because encourage the growth of austenite crystal, so not preferred in order to grain refined.On the other hand, be less than the rolling during temperature of 850 DEG C, because enter austenite not re-crystallization territory (no-recrystallization temperature range in austenite) when being less than 850 DEG C completely, so not preferred in order to the homogenising of crystal grain.In addition, when accumulation reduction ratio is less than 10%, not preferred because of the insufficient fine reason of austenite crystal.

In the temperature province that surface of steel plate temperature is 900 ~ 600 DEG C, accumulation reduction ratio be more than 50%, surface of steel plate temperature at the end of rolling carries out hot rolling under being the condition of 800 ~ 550 DEG C.Utilizing this operation, importing the deformation for making the crystal grain miniaturization after phase transformation.

By being rolled the temperature province of 900 ~ 600 DEG C, thus have crystal grain miniaturization and effect to the favourable set tissue prosperity of prevention property.

In addition, by making accumulation reduction ratio be more than 50%, thus there is the effect of the prosperity promoting crystal grain miniaturization and set tissue further.

Thereafter, by being that the temperature province of 850 ~ 550 DEG C is rolled in surface of steel plate temperature, crystal grain miniaturization, obtains good prevention performance (brittle-cracking propagation Stopping Ability of growing up).

[cooling condition]

After terminating hot rolling, be preferably cooled to 400 DEG C with the cooling velocity of more than 5 DEG C/sec.The temperature province till 400 DEG C is cooled to the cooling velocity of more than 5 DEG C/sec, lath of bainite (bainiteluth) is flourishing, become the propagation resistance (crack propagation resistance) of crackle, good prevention performance (brittle-cracking propagation Stopping Ability of growing up) can be obtained.

Embodiment

Use Adjustment becomes the steel billet (steel slab) of the various chemical compositions shown in table 1, manufactures steel plate according to the condition shown in table 2.To each steel plate obtained like this, the ESSO test specimen of growing up of the size shape shown in construction drawing 1, uses above-mentioned method of the present invention and for test.Test is at stress 257N/mm ², test temperature-10 DEG C condition under implement.Here, stress 257N/mm ²be yield strength (yield strength) multiplex in hull be 40kgf/mm ²the maximum allowable stress of level steel plate, temperature-10 DEG C is the design temperature of boats and ships.The large-scale tensile test fixture shown in ESSO test Fig. 7 of growing up carries out.

The result that the ESSO that enforcement grown up tests is shown in table 2.No2,3,5,6,8,9,12,14 is examples of manufacture method of the present invention, and brittle crack stops at breadboard.Therefore, they can be evaluated as " well " according to evaluation method of the present invention.No.1,4,7,10,11,13,15,16 is comparative examples of manufacture method of the present invention, and brittle crack does not stop.Therefore, they can be evaluated as " poor " according to evaluation method of the present invention.

[table 1]

[table 2]

Symbol description

1 grows up ESSO test specimen

11 breadboards

12 run-up plates

13 machining otch

14 gas protective arc welding portions

15 CO ₂shielded arc welding meets portion

The corbel back slab of 2 testing machines

The pin chuck of 3 testing machines

The pole hole of 31 testing machines

32 nut shape portions

Claims

1. the evaluation method of the brittle-cracking propagation Stopping Ability of growing up of a steel plate, it is characterized in that, there is the width right angle orientation load stretching loading of System for Large-scale Specimen of width of more than 1.5m, evaluate for the crack length in described System for Large-scale Specimen the propagation Stopping Ability of the brittle crack of growing up being more than 1m

To described System for Large-scale Specimen transmission from the transfer part of the stretching loading of cupping machine to become the interval of more than 2.8 times of the width of described System for Large-scale Specimen, there is in the mode at the center clamping the width right angle orientation of described System for Large-scale Specimen the thickened section of more than 2.5 times of the thickness becoming described System for Large-scale Specimen

From the stretching loading of described cupping machine by load in the position at center of width right angle orientation clamping described System for Large-scale Specimen with described thickened section.

2. the evaluation method of the brittle-cracking propagation Stopping Ability of growing up of steel plate according to claim 1, is characterized in that, has described thickened section with the interval of more than 4.1 times that become the width of described System for Large-scale Specimen.

3. evaluate the test unit of the brittle-cracking propagation Stopping Ability of growing up of steel plate for one kind, it is characterized in that, there is the width right angle orientation load stretching loading of System for Large-scale Specimen of width of more than 1.5m, evaluate for the crack length in described System for Large-scale Specimen the propagation Stopping Ability of the brittle crack of growing up being more than 1m

To the transfer part of described System for Large-scale Specimen transmission stretching loading with the interval of more than 2.8 of the width of described System for Large-scale Specimen times, the thickened section of more than 2.5 times in the mode at the center clamping the width right angle orientation of described System for Large-scale Specimen with the thickness becoming described System for Large-scale Specimen

By described stretching loading load in the position at center of width right angle orientation clamping described System for Large-scale Specimen with described thickened section, loading capacity is more than 50MN.

4. the test unit of the brittle-cracking propagation Stopping Ability of growing up of evaluation steel plate according to claim 3, is characterized in that, has described thickened section with the interval of more than 4.1 times that become the width of described System for Large-scale Specimen.

5. the test unit of the brittle-cracking propagation Stopping Ability of growing up of the evaluation steel plate according to claim 3 or 4, is characterized in that, described loading capacity is more than 80MN.

6. a manufacture method for the steel plate of brittle-cracking propagation Stopping Ability excellence of growing up, is characterized in that, comprises the operation using the device according to any one of claim 3 ~ 5 to evaluate the brittle-cracking propagation Stopping Ability of growing up of steel plate.

7. the manufacture method of the steel plate of brittle-cracking propagation Stopping Ability excellence of growing up according to claim 6, it is characterized in that, by the heating temperatures of Steel material at 900 ~ 1350 DEG C, then be that the temperature province of 1000 ~ 850 DEG C is with after accumulation reduction ratio more than 10% rolling in surface of steel plate temperature, be that the temperature province of 900 ~ 600 DEG C is 800 ~ 550 DEG C with the surface of steel plate temperature at the end of accumulation reduction ratio more than 50%, rolling and carries out hot rolling and manufacture in surface of steel plate temperature

The steel composition of described Steel material in mass %, containing below C:0.15%, below Si:0.6%, Mn:0.8 ~ 2.4%, S:0.001 ~ 0.05%, containing at least a kind that is selected from Ti:0.005 ~ 0.05% or Nb:0.001 ~ 0.1%, further containing at least a kind that is selected from below Cu:2%, below V:0.2%, below Ni:2%, below Cr:0.6%, below Mo:0.6%, below W:0.5%, below B:0.005%, below Zr:0.5%, remainder is made up of Fe and inevitable impurity.

8. the manufacture method of the steel plate of brittle-cracking propagation Stopping Ability excellence of growing up according to claim 7, wherein, further after end hot rolling, is cooled to 400 DEG C with the cooling velocity of more than 5 DEG C/sec.

9. a steel plate for brittle-cracking propagation Stopping Ability excellence of growing up, is characterized in that, is to utilize the manufacture method according to any one of claim 6 ~ 8 to manufacture.