CN102482751A - Thick steel plate for ship hull and process for production thereof - Google Patents

Thick steel plate for ship hull and process for production thereof Download PDF

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Publication number
CN102482751A
CN102482751A CN2010800392474A CN201080039247A CN102482751A CN 102482751 A CN102482751 A CN 102482751A CN 2010800392474 A CN2010800392474 A CN 2010800392474A CN 201080039247 A CN201080039247 A CN 201080039247A CN 102482751 A CN102482751 A CN 102482751A
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steel
cooling
ferritic
amount
temperature
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CN102482751B (en
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中岛清孝
星野学
小田直树
益田晋宇
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Nippon Steel Corp
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Nippon Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Metal Rolling (AREA)

Abstract

Disclosed is a thick steel plate for a ship hull, which has a chemical composition comprising, in mass%, more than 0.03% and not more than 0.10% of C, 0.05% or less of P, 0.05% or less of S and 0.002 to 0.1% of Al, with the remainder being iron and unavoidable impurities. The thick steel plate contains ferrite and has a microstructure comprising at least one component selected from pearlite and bainite, wherein the area ratio of unprocessed ferrite in the microstructure is 85% or more, the average crystal particle diameter of the unprocessed ferrite is 5 to 40 [mu]m, and the density of cementite particles in the particles of the ferrite is 50000 particles/mm2 or less. The thick steel plate has yield strength of 235 MPa or more, tensile strength of 460 MPa or less, uniform elongation of 15% or more, and an average Charpy absorbed energy of 100 J or more at 0 DEG C.

Description

Hull is with Plate Steel and method of manufacture thereof
Technical field
The ship that the present invention relates to have the other side's one side that when collision, deforms and can prevent to be collided the buffering effect of damage takes place, makes the employed thickness of slab of fore part structure of the ship of crashworthiness raising is Plate Steel and method of manufacture thereof more than the 8mm.
The application based on November 20th, 2009 spy in japanese publication be willing to advocate right of priority for 2009-265118 number, and here cite its content.
Background technology
Present argosy has used thickness of slab to be the Plate Steel more than the 8mm in the fore part structure of ship, for even alleviate the power loss that resistance produced by wave on a small quantity, possesses tumble-home bow (bulbous bow on the bow under the water line; Bulbous bow).
In the past, be employed in the inner rigid structure (with reference to patent documentation 1 and 2) that disposes the crossbeam material that strengthens usefulness along direction in length and breadth at tumble-home bow.But the ship of tumble-home bow that possesses rigid structure is with his foul the time, for example; Shown in Figure 1A, the tumble-home bow 20a of colliding vessel 20 invades by the bilge 21a of colliding vessel 21, and then enlarges the destruction position; Damage is formed cut (hole) 21b sometimes by the shell of colliding vessel 21 (bilge 21a).
Therefore; In recent years; Proposed: when ship bumped each other, particularly the fore of colliding vessel was when being collided by the bilge of colliding vessel, not damage by the try one's best tumble-home bow (with reference to patent documentation 3～5) of structure of absorbing impact energy of the mode of the shell of colliding vessel.
In patent documentation 3, disclosing a kind of tumble-home bow, wherein, is the watertightness structure through making top ends, and making the circumference that is connected with top ends is non-watertightness structure (the inner structure that is communicated with external water of tumble-home bow), the absorbing impact energy.But therefore disclosed tumble-home bow in patent documentation 3 is difficult to reduce fully and makes wave resistance because the circumference that is connected with top ends is non-watertightness structure.
In addition, disclosed tumble-home bow in the patent documentation 3 therefore must carry out protection against corrosion processing to steel plate, thereby manufacturing cost increases owing to have non-watertightness structure.
Disclose a kind of tumble-home bow in the patent documentation 4, wherein, on the outside plate of the root of bulbous protrusion, the reduced thickness portion that has reduced horizontal flexural rigidity has been set.In addition, disclose a kind of tumble-home bow in the patent documentation 5, the low low strength portion of horizontal flexural strength (is the part that the low-yield steel below the 235MPa constitutes by lower yield point or 0.2% ys) has been set on the outside plate of the root of bulbous protrusion.
Disclosed tumble-home bow is through being provided with reduced thickness portion or low strength portion in the patent documentation 4 and 5 near the root of tumble-home bow, thereby when collision, makes the root bending of tumble-home bow easily.
That is, the disclosed tumble-home bow, when ship bumped with desired angle each other, for example, shown in Figure 1B, the tumble-home bow 30a of colliding vessel 30 bent at root 30b easily in patent documentation 4 and 5.Therefore, not top end face 30c but main surface 30d with the face of the tumble-home bow 30a that is contacted by the bilge 31a of colliding vessel 31, therefore reduced by the damage of the bilge 31a of colliding vessel 31.
But, in the patent documentation 4 and 5 in disclosed tumble-home bow and the patent documentation 3 disclosed tumble-home bow different, tumble-home bow self can not play a role as the vibroshock of absorbing impact energy.Therefore, infer: when bumping near 90 ° angle,, invade by the bilge of colliding vessel before root bends being collided reactive force each other by tumble-home bow for ship.
Need to prove the position of the tumble-home bow 30a before the dotted portion of Figure 1B is represented colliding vessel 30 and collided by colliding vessel 31.
As a result, disclosed tumble-home bow is restricted aspect the damage intensity of the bilge of colliding vessel in reduction in the patent documentation 4 and 5.
On the other hand,, also studied the good steel plate of energy absorption capability that uses when collision, disclose such steel plate in the patent documentation 6～10 as the means of the crashworthiness that improves ship.
Disclosed steel plate is through improving ferritic occupation rate and hardness, dwindle the size of second phase, increase work hardening, improving energy absorption capability thus in the patent documentation 6.
In addition, disclosed steel plate is through retained austenite being dispersed in the steel, utilizing phase change induction plasticity (TRIP) to increase work hardening in the patent documentation 7～9, and intensity and uniform elongation are improved, thereby improves energy absorption capability.
In addition, disclosed steel plate is to make it be organized as close grain ferritic subject organization in the patent documentation 10, utilizes precipitation strength to improve the intensity of ferritic phase, and anti-destruction characteristic is improved.
But the fore of colliding vessel is when collide by the bilge of colliding vessel, even be made up of the steel plate that energy absorption capability has improved by the bilge of colliding vessel, the tumble-home bow that needs only colliding vessel does not deform, and the danger that tumble-home bow runs through bilge is also high.In addition, according to the mode difference of collision, can't expect to obtain using the effect of the high steel plate of amount of energy.
Relative therewith, if can the absorbing impact energy, then can reduce by the damage of the bilge of colliding vessel at the tumble-home bow of colliding vessel as far as possible.
But the intensity of the steel plate that disclosed energy absorption capability is good in the patent documentation 6～10 is high, and work hardening is big, when therefore colliding the forces that is applied by colliding vessel is increased.Thereby before the abundant absorption energy, the possibility that tumble-home bow runs through bilge is high under the state that the distortion of tumble-home bow is not carried out fully.
In addition, in order to make the big bent plate of curvature that uses in the tumble-home bow, adopt through the wire heating carried out bending machining, is the wire heat processed more in its forming process.
This wire heat processed is to utilize following phenomenon: use gas furnace etc. that surface of steel plate is carried out the wire local heating, hot spots generation thermal expansion is restricted in around it and viscous deformation takes place.Usually, in order to improve operating efficiency, after heating, carry out water-cooled at once, according to the variation of the microstructure of mother metal, the material of the steel plate after the wire heat processed changes.
That is, the steel plate that disclosed energy absorption capability is good in patent documentation 6～10, the part that heats the back water-cooled is quenched, intensity rises partly, and the possibility that elongation reduces is high.
Therefore, use the intensity of tumble-home bow of such bent plate inhomogeneous, be difficult to distortion.Therefore, when possessing ship and his foul of this tumble-home bow, shown in Figure 1A; The fore 20a of colliding vessel 20 invades by the bilge 21a of colliding vessel 21; Destroy bilge 21a, and then destroy position expansion, thereby the danger that on hull, forms cut (hole) 21b is also big.
Relative with patent documentation 6～10, a kind of steel plate is disclosed in the patent documentation 11, it improves the bendability that is added thermogenesis by wire through the ys under reducing by 400 ℃.Concerning this steel plate, reduce in order to make the ys under 400 ℃, the ys of room temperature is also reduced.Therefore, this steel plate is being used under the situation of tumble-home bow, distortion is carried out easily when collision, can endergonic fully possibility thereby have tumble-home bow.But, according to the unified standard of international ship's classification federation (IACS), need the ys under the room temperature to satisfy more than the 235MPa, therefore use the dispersion-strengthened of fine cementite.But,, thereby satisfy the material of regulation because cementite to thermally labile, therefore is difficult to after the wire heating, keep the dispersion state of the cementite in the steel plate.In addition, there is following problem in the dispersion of fine cementite: can not get required work hardening characteristic, and be difficult to obtain being used for endergonic sufficient uniform elongation.
In addition, disclose a kind of tumble-home bow in the patent documentation 12 and 13 and used steel plate, it lowers yield-point through reducing the carbon amount, the toughness after raising processibility and the processing.But when making such ultra-low carbon steel plate, the melting load becomes greatly, and the cost increase, and is therefore not preferred economically.
Therefore; The Plate Steel that a kind of tumble-home bow of current needs is used; It significantly reduces in when navigation performance makes wave resistance and further reduces power loss, further improves the function of the puopulsion quality of ship, and performance reduces by the damage of the bilge of colliding vessel, the vibroshock function of absorbing impact energy effectively when collision.
The prior art document
Patent documentation
Patent documentation 1: TOHKEMY 2002-347690 communique
Patent documentation 2: TOHKEMY 2005-199736 communique
Patent documentation 3: japanese kokai publication hei 08-164887 communique
Patent documentation 4: TOHKEMY 2004-314824 communique
Patent documentation 5: TOHKEMY 2004-314825 communique
Patent documentation 6: japanese kokai publication hei 11-193438 communique
Patent documentation 7: japanese kokai publication hei 11-246934 communique
Patent documentation 8: TOHKEMY 2007-162101 communique
Patent documentation 9: TOHKEMY 2008-45196 communique
Patent documentation 10: TOHKEMY 2002-105534 communique
Patent documentation 11: TOHKEMY 2009-185380 communique
Patent documentation 12: japanese kokai publication hei 5-70885 communique
Patent documentation 13: japanese kokai publication hei 6-256891 communique
Summary of the invention
Invent problem to be solved
The present invention is in view of the above-mentioned requirements to tumble-home bow; Its problem is, provide can under the situation of the design that need not to change hull structure during in collision effectively the absorbing impact energy, can significantly reduce Plate Steel and the method for manufacture thereof used by the tumble-home bow of the damage of the bilge of colliding vessel.
The means that address the above problem
In depth study in order to solve above-mentioned problem, the result has accomplished the present invention, and its means are following.
(1) hull of a scheme of the present invention has following chemical ingredients with Plate Steel: in quality %; Contain C: surpass 0.03 and be below 0.10%, P: S≤0.05%: Al:0.002～0.1%≤0.05%; Remainder comprises iron and unavoidable impurities; And have following microstructure: comprise ferritic, and comprise in perlite, the bainite more than a kind, the unprocessed ferritic area occupation ratio in the above-mentioned microstructure is more than 85%; Above-mentioned unprocessed ferritic average crystallite particle diameter is 5～40 μ m, and above-mentioned ferritic intragranular cementite particle is counted 50000/mm with number density 2Below, ys is more than the 235MPa, and tensile strength is below the 460MPa, and uniform elongation is more than 15%, and the summer under 0 ℃ is more than the 100J than average absorption energy (average Charpy absorbed energy).
(2) above-mentioned (1) described hull is with in the Plate Steel; In quality %; Contain Si:0.03～1%, Mn:0.1～1.5%, Cu:0.02～0.5%, Ni:0.02～0.5%, Cr:0.02～0.5%, Mo:0.002 above and be lower than 0.2%, among Nb:0.002～0.02%, V:0.002～0.04%, Ti:0.002～0.04%, B:0.0002～0.002%, N:0.0005～0.008%, Ca:0.0003～0.005%, Mg:0.0003～0.005%, REM:0.0003～0.005% more than a kind as above-mentioned chemical ingredients; And carbon equivalent Ceq can be for below 0.30%.
Wherein, Ceq=[C]+[Si]/24+ [Mn]/6+ ([Cu]+[Ni])/15+ ([Cr]+[V])/10+ ([Mo]+[Nb])/5+ [Ti]/20+ [B]/3+ [N]/8.
Wherein, [C], [Si], [Mn], [Cu], [Ni], [Cr], [V], [Mo], [Nb], [Ti], [B], [N] are respectively the content in quality % of C, Si, Mn, Cu, Ni, Cr, V, Mo, Nb, Ti, B, N.
(3) above-mentioned (2) described hull is with in the Plate Steel, and in quality %, above-mentioned carbon equivalent Ceq can be for below 0.27%.
(4) above-mentioned (1) perhaps (2) described hull is with in the Plate Steel, and yield ratio can be for more than 0.70.
(5) hull of first scheme of the present invention with the method for manufacture of Plate Steel is: the steel billet that will have each described chemical ingredients in above-mentioned (1)～(3) is heated to 1000～1300 ℃; At A R3Accumulate draft in the above austenite one phase district of transformation temperature and be 30～98% rolling until reaching the goods thickness of slab; To quicken to cool off temperature, carry out air cooling since the cooling temperature more than 760 ℃ then until 400～650 ℃ by the speed of cooling of 1～50 ℃/second of thickness of slab average out to.
(6) hull of alternative plan of the present invention with the method for manufacture of Plate Steel is: the steel billet that will have each described chemical ingredients in above-mentioned (1)～(3) is heated to 1000～1300 ℃; At Ar 3Accumulate draft in the above austenite one phase district of transformation temperature and be 30～98% rolling until reaching the goods thickness of slab; To quicken to cool off temperature, under 400～650 ℃ temperature, carry out tempering since the cooling temperature more than 760 ℃ then until being lower than 400 ℃ by the speed of cooling of 1～50 ℃/second of thickness of slab average out to.
(7) hull of third party's case of the present invention with the method for manufacture of Plate Steel is: the steel billet that will have each described chemical ingredients in above-mentioned (1)～(3) is heated to 1000～1300 ℃; Accumulate draft in the austenite one phase district more than the Ar3 transformation temperature and be 30～98% rolling until reaching the goods thickness of slab; Carry out air cooling.
The invention effect
According to the present invention; Have colliding under the situation of such accident generation of tumble-home bow from the fore of ship and the bilge of his ship; The globular part side of the tumble-home bow in the colliding vessel (from ship) occurs bending and deformation more equably, thus absorbing impact energy significantly.In addition, crushed through impingement area(s) in the absorbing impact energy, can reduce by the damage of colliding vessel (his ship) as far as possible, can help thus to prevent to be flowed out the pollution of the sea that is caused by the sinking of colliding vessel or oil.
Description of drawings
Figure 1A be ship that the expression fore part structure does not have the buffering effect colliding vessel when bumping with by the synoptic diagram of colliding vessel distortion separately.
Figure 1B be ship that the expression fore part structure has the buffering effect colliding vessel when bumping with by the synoptic diagram of colliding vessel distortion separately.
Fig. 1 C is that the expression fore part structure has the ship that has used the buffering effect that hull of the present invention obtains with Plate Steel colliding vessel and by the synoptic diagram of colliding vessel distortion separately when bumping.
Embodiment
Below, an embodiment of the invention are described.
Collide under the situation of such accident generation at the fore of boats and ships and the bilge of his ship with tumble-home bow; Shown in Fig. 1 C; If the head 10b of tumble-home bow 10a can carry out flexural deformation more equably; Then can absorb more collision energy, therefore the impact force of collision generation is able to relax.Its result can avoid by partial fracture and the breakage of the bilge 11a of colliding vessel 11, thereby can prevent the generation in cut (hole).
Need to prove the position of the tumble-home bow 10a before the dotted portion of Fig. 1 C is represented colliding vessel 10 and collided by colliding vessel 11.
Analyze the deformational behavior of studying such tumble-home bow through FEM; The result finds; About mechanical properties; In ys be more than the 235MPa, tensile strength is below the 460MPa, uniform elongation is under the situation more than 15%, when each other collision of ship, the forces that is applied by colliding vessel is diminished.And at this moment, tumble-home bow deforms easily, tumble-home bow with increased by the contact area of the bilge of colliding vessel, tumble-home bow is the absorbing impact energy effectively, thereby can significantly reduce by the damage in the bilge of colliding vessel.
Below, the qualification reason of the summer under the ys in this embodiment, tensile strength, uniform elongation, 0 ℃ than average absorption energy described.
Present argosy on the bow use in the structure thickness of slab as more than the 8mm, be the Plate Steel of 100mm to the maximum; For the fore of colliding vessel occurs bending and deformation; The ys of the steel plate that the yield strength ratio of the steel plate that basically, need in the fore of colliding vessel, use uses in by colliding vessel is little.But the ys of the steel plate that uses in the ship need satisfy the unified standard of international ship's classification federation (IACS), and the fore part structure with interior bone structure in the past needs to tolerate the intensity of fluctuation collision.In addition, when ys is excessively reduced, big energy absorption effect is arranged in the time of can't expecting to be out of shape.Consider above aspect, the ys of steel plate need be for more than the 235MPa.In addition, consider that from the ys of the employed steel plate of ship the upper limit of ys is preferably below the 400MPa usually.For fore when colliding more positively occurs bending and deformation, the ys of steel plate is more preferably below the 320MPa.
In order to improve energy absorption capability, need to improve tensile strength.But, when tensile strength becomes too high, when collision, the forces that is applied by colliding vessel is increased.At this moment, before the abundant absorption energy, the possibility that tumble-home bow runs through bilge is high under the state that the distortion of tumble-home bow is not carried out fully.Therefore, tensile strength on be limited to 460MPa.In order to obtain required energy absorption capability, the lower limit of tensile strength is preferably 300MPa.
In order to improve energy absorption capability, uniform elongation and tensile strength need to increase equally, and the following of uniform elongation is limited to 15%.For energy absorption capability is further improved, preferred uniform elongation is more than 20%.In addition, uniform elongation is high more good more, and the intensity in order to ensure essential is preferably below 50%.
In addition, the brittle rupture in order to prevent to collide, the summer under 0 ℃ is more than the 100J than average absorption energy requirement.That is,, then can't carry out the energy absorption implemented by flexural deformation, and then, the dangerous height of serious malicious event take place to other member propagating cracks if in when collision brittle destruction af-ter.Therefore, the above-mentioned summer is than the following 100J that is limited to of average absorption energy.In order to prevent brittle rupture, further improve security, the summer is preferably more than the 150J than average absorption energy.In addition, if consider the level that roughly can avoid the danger of brittle rupture, then the summer is preferably 500J than the endergonic upper limit.
In addition, yield ratio is preferably more than 0.70.When yield ratio reduced, work hardening increased, so the energy absorption capability of steel plate improves.But as stated, if work hardening increases, then the tumble-home bow of colliding vessel increases the forces that is applied by colliding vessel when collision.Therefore, before the abundant absorption energy, tumble-home bow might take place run through bilge under the state of the distortion of not carrying out tumble-home bow fully.Therefore, in order to guarantee the energy absorption capability as tumble-home bow fully, preferably the intensity according to steel plate limits yield ratio.In order more positively to guarantee the distortion of tumble-home bow, yield ratio more preferably more than 0.75, most preferably is more than 0.80.In addition, the processibility of the steel plate of using in order to ensure energy absorption capability and as tumble-home bow, yield ratio is preferably below 0.95.
Below, set forth the qualification reason of the microstructure in this embodiment.
The microstructure of steel plate is: contain ferritic as parent phase, except this ferritic, by constituting more than a kind of perlite, bainite.
At first, unprocessed ferritic is that the reason of parent phase is: utilize that the softest tissue comes inhibition strength in the tissue of steel plate, uniform elongation is improved, follow the diastrophic absorption energy of tumble-home bow to increase thereby make.In addition, the ferritic through processing such as two-phase region are rolling becomes uniform elongation and the summer reason than the reduction of average absorption energy, and therefore for fear of their reduction, the ferritic of parent phase is unprocessed ferritic.In addition, through processing ferritic generation, the anisotropy of steel plate increases, so the ferritic of parent phase is during for the processing ferritic, when collision, make tumble-home bow equably flexural deformation and making absorb in the steel plate can the quantitative change difficulty.Need to prove,, then judge not have the processing ferritic in the microstructure if the processing ferritic is below 1%.
With the reason that is set at perlite, bainite beyond the undressed ferritic be: only be difficult to guarantee intensity through unprocessed ferritic phase; The work hardening characteristic extremely reduces; Can't make uniform elongation is more than 15%, thus the energy absorption capability when being difficult to guarantee to collide.In addition, if there is martensite in the tissue, then being difficult to make tensile strength to be below the 460MPa, making the summer 0 ℃ under is more than the 100J than average absorption energy, so need carry out structure observation through opticmicroscope and confirm there is not martensite.
If unprocessed ferritic area occupation ratio is lower than 85%, then being difficult to make hard tissues such as processing ferritic beyond the undressed ferritic, perlite, bainite, martensite to surpass 15%, make tensile strength be below the 460MPa, make uniform elongation is more than 15%.Therefore, unprocessed ferritic area occupation ratio is more than 85%.Unprocessed ferritic area occupation ratio is preferably 90～95%.
When unprocessed ferritic particle diameter is lower than 5 μ m, be difficult to guarantee the uniform elongation more than 15%, when unprocessed ferritic particle diameter surpasses 40 μ m, be difficult to guarantee that summer under above 0 ℃ of ys that 235MPa is above and 100J is than average absorption energy.Therefore, making unprocessed ferritic particle diameter is 5～40 μ m.
In addition, exist with the number densometer above 50000/mm at ferritic intragranular 2Cementite particle the time, be easy to generate hole, so uniform elongation reduces, be difficult to guarantee the uniform elongation more than 15%.Thereby, ferritic intragranular cementite particle is defined as with number density counts 50000/mm 2Below.
Below, the reason of the amount that limits each element is described.Need to prove that following " % " is " quality % " under the situation that does not have special explanation.
C: surpass 0.03 and be below 0.10%
C is the element that makes the intensity increase of steel, in order to ensure the ys under the room temperature more than the 235MPa, the melting load is alleviated, and needs to surpass 0.03% C.But C amount surpasses at 0.10% o'clock, and for example the area occupation ratio of perlite grade in an imperial examination two-phase increases, and being difficult to make tensile strength to be below the 460MPa, making uniform elongation is more than 15%.Therefore, C amount on be limited to 0.10%.In order more positively to control ys, tensile strength, uniform elongation, the C amount is preferably 0.04～0.08%.
P：≤0.05％、S：≤0.05％
P is an impurity element, through solution strengthening the ys under the high temperature is increased, and makes the toughness deterioration, therefore need reduce P as far as possible.But P amount is 0.05% when following, and above-mentioned detrimentally affect can be allowed, thus P measure on be limited to 0.05%.S also is an impurity element, owing to make the toughness and the ductility deterioration of steel, therefore preferably reduces S as far as possible.But S amount is 0.05% when following, and above-mentioned detrimentally affect can be allowed, thus S measure on be limited to 0.05%.
Al：0.002～0.1％
Al is important element in the present invention, mainly adds for deoxidation.In order to carry out sufficient deoxidation, Al need be for more than 0.002%.But Al amount surpasses at 0.1% o'clock, generates the thick oxide compound and the Shu Qun thereof of alumina series, infringement toughness, so the Al amount on be limited to 0.1%.In order more positively to carry out deoxidation, further guarantee toughness, the Al amount is preferably 0.01～0.07%.
Above composition is the basal component of steel plate of the present invention.Can use the Plate Steel that the steel plate that contains these basal component at least uses as the good tumble-home bow of the crash energy absorption ability of target of the present invention (with the thickness of slab more than the 8mm as object.Need to prove that the upper limit of thickness of slab is not special to be limited, but that the reality use is about 100mm).In addition, in order to regulate intensity and toughness, can in steel, add Si, Mn, Cu, Ni, Cr, Mo, Nb, V, Ti, B, N as selecting element.Trace adds even these select element, also can improve the hardenability of steel, therefore except the intensity and flexible raising that are caused by the crystal grain miniaturization, also helps the intensity of solution strengthening, precipitation strength etc. to improve.In order to obtain this effect, the following of Si amount is limited to 0.03%, and the following of Mn amount is limited to 0.1%; The lower limit of Cu amount, Ni amount, Cr amount is respectively 0.02%; The lower limit of Mo amount, Nb amount, V amount, Ti amount is respectively 0.002%, and the following of B amount is limited to 0.0002%, and the following of N amount is limited to 0.0005%.But, when excessive interpolation is selected element arbitrarily, generate low temperature phase change tissues such as bainite easily, be more than 90% thereby be difficult to make ferritic area occupation ratio.At this moment, intensity increases, and uniform elongation reduces, and therefore being difficult to make tensile strength is below the 460MPa, and making uniform elongation is more than 15%.Therefore, need the upper limit be set to the amount of various selection elements.About this upper limit, the Si amount is 1%, and the Mn amount is 1.5%, and Cu amount, Ni amount, Cr amount are respectively 0.5%, and the Mo amount was 0.2% (not comprising 0.2%), and the Nb amount is 0.02%, and V amount, Ti amount are respectively 0.04%, and the B amount is 0.002%, and the N amount is 0.008%.In addition, about this upper limit, preferred Si amount is below 0.8%, and the Mn amount is below 1.2%; Cu amount, Ni amount, Cr amount are respectively below 0.3%, and the Mo amount is below 0.05%, and the Nb amount is below 0.01%; V amount, Ti amount are respectively below 0.02%, and the B amount is below 0.001%, and the N amount is below 0.006%.
In addition, when the interpolation of Mn, Cu, Ni, Cr, Mo, Nb, V, Ti, B, need make the carbon equivalent Ceq shown in following (1) formula is below the 0.30 quality %.When making carbon equivalent Ceq surpass 0.30 quality % when the excessive interpolation of above-mentioned element, as stated, generate low temperature phase change tissues such as bainite easily, being difficult to make ferritic area occupation ratio is more than 85%.At this moment, intensity increases, and uniform elongation reduces, and therefore being difficult to make tensile strength is below the 460MPa, and making uniform elongation is more than 15%.In addition, ys also increases, and the yield strength ratio that therefore has colliding vessel is by the big possibility of the ys of colliding vessel.At this moment, can't relax when collision to by the impact force of colliding vessel, its result is owing to by the partial fracture or the breakage of colliding vessel, produce the dangerous high of cut (hole).In addition, in order to make the big bent plate of curvature that uses in the tumble-home bow, under the situation of carrying out the wire heat processed, to heating the incomplete quench of back water-cooled, intensity rises partly, and uniform elongation reduces.In order to prevent these, carbon equivalent Ceq need be for below the 0.30 quality %.In order more positively to control tensile strength, ys, uniform elongation, preferred carbon equivalent Ceq is below the 0.27 quality %.Need to prove that carbon equivalent Ceq carries out the formula that coefficient is confirmed in multiple regression analysis through the dependency of the amount of studying above-mentioned element and intensity.
Ceq＝[C]+[Si]/24+[Mn]/6+([Cu]+[Ni])/15+([Cr]+[V])/10+([Mo]+[Nb])/5+[Ti]/20+[B]/3+[N]/8 (1)
Wherein, [C], [Si], [Mn], [Cu], [Ni], [Cr], [Mo], [Nb], [V], [Ti], [B], [N] are respectively the addition (quality %) of each element.
Therefore, the carbon equivalent Ceq (JIS) that stipulates among the carbon equivalent Ceq of (1) formula and the JIS or by the carbon equivalent after carbon equivalent Ceq (IIW) stdn of etc.ing of International Institude of Welding's regulation different (reference following (2) and (3) formulas).
Ceq(JIS)＝[C]+[Si]/24+[Mn]/6+[Ni]/40+[Cr]/5+[Mo]/4+[V]/14 (2)
Ceq(IIW)＝[C]+[Mn]/6+([Cu]+[Ni])/15+([Cr]+[Mo]+[V])/5 (3)
In addition, even above-mentioned selection element contains sometimes as unavoidable impurities, also requiring the carbon equivalent Ceq of (1) formula is below the 0.30 quality %.
In addition; Except above-mentioned selection element; Among the present invention, for the ductility that improves steel plate and improve HAZ toughness, in steel, can contain 0.0003～0.005% Ca, 0.0003～0.005% Mg, 0.0003～0.005% REM as selecting element.Through adding these, can guarantee ductility and HAZ toughness.Ca, Mg, REM amount separately is lower than at 0.003% o'clock, is difficult to obtain the effect that ductility improves and HAZ toughness improves of steel plate.On the other hand, when Ca, Mg, REM surpassed 0.005% interpolation respectively, these effects were saturated.Therefore, the amount of Ca, Mg, REM is set at 0.0003～0.005% respectively.
Therefore, can contain in the scope of above-mentioned content in the steel among Si, Mn, Cu, Ni, Cr, Mo, Nb, V, Ti, B, N, Ca, Mg, the REM more than a kind as selecting element.
As stated, use the steel plate with following chemical constitution to use steel plate as hull: contain above-mentioned basal component and above-mentioned selection element as required, remainder comprises iron and unavoidable impurities.
As stated; Through adopting the steel plate of this embodiment; The globular part side of the tumble-home bow when the such accident of bilge collision from the fore of ship and his ship that has tumble-home bow under the situation of the design that need not to change hull structure takes place in the colliding vessel (from ship) occurs bending and deformation more equably, thus absorbing impact energy effectively.In addition, impingement area(s) is crushed in the absorbing impact energy, can significantly reduce thus by the damage of the bilge of colliding vessel (his ship).
Below, about limiting the reason of method of manufacture of the present invention, use an embodiment to describe.
At first, the molten steel that is adjusted to above-mentioned suitable chemical constitution is carried out melting through generally well-known melting method such as converters, make steel raw material (steel billet) through generally well-known castmethods such as continuous castings.
Then, this steel raw material is heated to 1000 ℃～1300 ℃ temperature with process furnace, what make steel raw material is organized as austenite one phase (γ is single-phase).When Heating temperature was lower than 1000 ℃, the tissue of steel raw material did not become austenite one phase fully mutually, and when Heating temperature surpassed 1300 ℃, heating γ particle diameter (the γ particle diameter that is caused by this heating) is thickization extremely.In these cases, be difficult to obtain fine tissue after rolling, so toughness reduces, perhaps hardenability increases, and hard second increases mutually, so elongation reduces.In order more positively to guarantee toughness and elongation, preferred Heating temperature surpasses 1050 ℃ and be below 1250 ℃.
Then carry out rolling be most important operation of the present invention.That is, need be at A R3Accumulate draft in the above austenite one phase district of transformation temperature and be 30～98% rolling until reaching goods thickness of slab (final thickness of slab).
At first, at A R3The reason that is rolled in the austenite one phase district more than the transformation temperature is: through being lower than A R3The two-phase region of transformation temperature is rolling and when in ferritic, introducing dislocation, uniform elongation significantly reduces, and being difficult to make uniform elongation is more than 15%.In addition, introduced the starting point that the ferritic of dislocation and the ferritic interface of not introducing dislocation become brittle rupture easily, toughness reduces, and therefore need avoid two-phase region rolling.In addition, carrying out under the rolling situation of two-phase region, the development through texture is easy to generate separation, therefore is difficult to guarantee that the summer under 0 ℃ is more than the 100J than average absorption energy.In addition, in this case, the anisotropy of steel plate increases, thus when therefore being difficult to make collision tumble-home bow equably flexural deformation make tumble-home bow absorb energy.Therefore, at A R3Be rolled in the austenite one phase district more than the transformation temperature.Need to prove that the upper limit of rolling temperature does not have special qualification, the Heating temperature in the above-mentioned process furnace is 1300 ℃, therefore can be set at 1300 ℃.But, make the miniaturization effectively of austenitic recrystal grain for the rolling temperature scope of guaranteeing the temperature higher fully than two-phase region, preferably temperature is high as far as possible.But, consider when temperature from process furnace to rolling beginning reduces, can be with making an appointment with (Heating temperature-50) ℃ to be set at the upper limit of rolling temperature.
Then, the reason that is rolled with 30～98% accumulation draft is described.When being lower than 30% accumulation draft, insufficient by the austenitic grain refined that recrystallize causes, the cooling that is difficult to through thereafter comes the crystallization control particle diameter.For crystallization control particle diameter more easily.Rolling accumulation draft is preferably more than 50%, more preferably more than 70%.In addition, to surpass under the situation that 98% accumulation draft is rolled, the crystal grain micronized effect is almost saturated, causes the reduction of Rolling Production rate.Therefore, the upper limit with the accumulation draft is set at 98%.In order further to guarantee the Rolling Production rate, the upper limit of accumulation draft is preferably 95%.
Behind the rolling, need under any condition among the following cooling conditions (first cooling conditions, second cooling conditions, the 3rd cooling conditions), cool off.First cooling conditions be since the cooling temperature more than 760 ℃ to quicken cooling off temperature (cooling stops temperature) by the speed of cooling of 1～50 ℃/second of thickness of slab average out to until 400～650 ℃, carry out air cooling then.In addition; Second cooling conditions be since the cooling temperature more than 760 ℃ to quicken to cool off until the temperature that is lower than 400 ℃ (cooling stops temperature) by the speed of cooling of 1～50 ℃/second of thickness of slab average out to, under 400～650 ℃ temperature (tempering temperature), carry out tempering then.In addition, the 3rd cooling conditions is the cooling of carrying out by air cooling enforcement.As a rule, air cooling has two kinds: naturally cooling in free air and the pressure cooling of carrying out through the artificial wind (air) that produces.At this, the naturally cooling (being also included within the situation of carrying out when steel plate passes through) in the selected free air.
About first cooling conditions, when cooling beginning temperature is lower than 760 ℃, before cooling,, therefore be difficult to come the crystallization control particle diameter through cooling because phase transformation generates ferritic and growth.In addition, at this moment, C enrichment in the austenite, hardenability improves, and therefore after cooling, generates the second hard phase, and elongation reduces.Therefore, cooling beginning temperature need be 760 ℃.For crystallization control particle diameter more easily and guarantee sufficient elongation, cooling beginning temperature is preferably more than 770 ℃.
In addition, about first cooling conditions, the speed of cooling when cooling off will speed up is set at the reason by 1～50 ℃/second of thickness of slab average out to and describes.When the speed of cooling when quickening cooling is lower than 1 ℃/second, be difficult to controlled chilling, therefore can't cool off uniformly, plate shape generation deterioration, or material produces deviation.The following of speed of cooling when therefore, quickening cooling is limited to 1 ℃/second.In addition, when the speed of cooling when quickening cooling surpassed 50 ℃/second, the crystallization particle diameter was lower than 5 μ m and becomes meticulous, therefore was difficult to guarantee the uniform elongation more than 15%.Be limited to 50 ℃/second on the speed of cooling when therefore, quickening cooling.In order more easily to carry out Cooling Control, to guarantee higher uniform elongation, the speed of cooling when quickening cooling is on average to be preferably 5～40 ℃/second by thickness of slab.
In addition, about first cooling conditions, the reason of quickening to cool off the temperature (quicken cooling and stop temperature) until 400～650 ℃ is described.Stop temperature and surpass under 650 ℃ the situation quickening cooling, because the grain growing of cooling after stopping, the crystal grain micronized effect that is caused by cooling disappears.Therefore, quicken cooling stop temperature on be limited to 650 ℃.In addition, when in being lower than 400 ℃ transition boiling scope, stopping to quicken cooling, can't cool off uniformly; Produce deviation on the material, be difficult to make tumble-home bow to be out of shape equably, make the remarkable deterioration of plate shape simultaneously; And; In this case, can't generate perlite or bainite, be difficult to guarantee the uniform elongation more than 15%.In addition, also generate with the number densometer above 50000/mm at ferritic intragranular sometimes 2Cementite particle, uniform elongation reduces.Therefore, quickening cooling stops the following of temperature and is limited to 400 ℃.In order to improve the crystal grain micronized effect, to guarantee higher uniform elongation, quicken to cool off the scope that stops temperature and be preferably 450～600 ℃.
Above-mentioned acceleration cooling can proceed to and be lower than 400 ℃ temperature, but need carry out tempering (second cooling conditions) this moment under 400～650 ℃ temperature after quickening cooling.Its reason is: the deviation of the material that stops to produce owing to the cooling when being lower than 400 ℃ and the deterioration of plate shape, the deterioration of uniform elongation are recovered through tempering.Therefore, in order to obtain this effect, need make tempering temperature is more than 400 ℃.In addition, surpassing under 650 ℃ the tempering temperature, carrying out, be difficult to guarantee ys and toughness sometimes with softening being able to that thickization of crystal grain accompanies.In addition, generate with the number densometer above 50000/mm at ferritic intragranular 2The situation of cementite particle under, through this tempering, cementite particle is reduced, improve uniform elongation.Therefore, tempering temperature on be limited to 650 ℃.In order more positively to guarantee uniform elongation, ys, toughness, preferably making tempering temperature is 450～600 ℃.Need to prove that the cooling after the tempering is preferably air cooling.
In addition, as stated, guarantee the uniform elongation more than 15%, can under the condition of not carrying out water-cooled, carry out air cooling (the 3rd cooling conditions) for the crystallization particle diameter is controlled to be 5～40 μ m.Under this air cooled situation, can easily evenly cool off, the material deviation is little, and the plate shape is also good.In addition, consider from the aspect that can guarantee ferritic structure fully, preferably carry out air cooling, but prolong cooling time, productivity reduces.Therefore, under the situation that has sufficient affluence aspect the productivity, preferably select air cooling.
But, in order to realize productivity and hardenability to a certain degree simultaneously, and guarantee the intensity of the collision characteristic and the mother metal of mother metal, preferably cool off through first method of cooling or second method of cooling.
As stated, according to this embodiment, thereby can be manufactured under the situation of the design of not changing hull structure, the absorbing impact energy can significantly reduce the Plate Steel of being used by the tumble-home bow of the damage of the bilge of colliding vessel effectively.Promptly; Through utilizing the Plate Steel of making by this embodiment; Have colliding under the situation of such accident generation of tumble-home bow from the fore of ship and the bilge of his ship; The globular part side of the tumble-home bow in the colliding vessel (from ship) occurs bending and deformation more equably, thus absorbing impact energy effectively.In addition, through utilizing the Plate Steel of being made by this embodiment, impingement area(s) is crushed in the absorbing impact energy, thereby can significantly reduce by the damage of the bilge of colliding vessel (his ship).
Embodiment
After in steel making working procedure, carrying out the chemical ingredients adjusting of molten steel, make strand through continuous casting.The chemical ingredients of these strands is shown in table 1 and table 2.At this, A R3Transformation temperature is tried to achieve from the thermal expansion curve, and this thermal expansion curve is to use the Formaster test film of gathering from these strands, carries out obtaining by having applied with 0.5 ℃ of/second hot resume of refrigerative (historical process) after 1200 ℃ austenitizing handles.The strand of use table 1 and table 2 is made the Plate Steel that thickness of slab is 8～30mm (steel plate).Each Plate Steel of expression creates conditions in the table 3.Need to prove that the acceleration cooling in the table 3 is through the water-cool control speed of cooling.
Figure BDA0000140207960000161
Table 3
The individual number density of the area occupation ratio of the microstructure of each steel plate of expression in the table 4 (undressed ferritic, processing ferritic, second phase), the average crystallite particle diameter of ferritic phase, ferritic intragranular cementite particle.The average crystallite particle diameter of the area occupation ratio of the microstructure of each steel plate and ferritic phase is the measured value that comprises that never the thickness of slab central position of center segregation obtains, with the typical value of these measured values as each steel plate.The area occupation ratio of microstructure uses the optical microscope photograph of 100 times or 500 times to measure through image analysis.At this moment, in order to distinguish processing ferritic and the undressed ferritic that extends along rolling direction, measure size and the size of thickness of slab direction of the rolling direction of ferritic crystal grain grain.The value (aspect ratio) that the length of the rolling direction of ferrite crystal grain is obtained divided by the length of the thickness of slab direction of ferrite crystal grain is that the ferritic more than 1.5 is defined as the processing ferritic, aspect ratio is lower than 1.5 ferritic and is defined as undressed ferritic.The average crystallite particle diameter of ferritic phase is to use the optical microscope photograph of the area occupation ratio of measuring microstructure, measures based on JIS G 0551 (2005) " the micrographic test method of steel-grain size number ".The individual number density of ferritic intragranular cementite particle is to try to achieve through following method: use scanning electron microscope; 20000 times, the photograph taking in 5 visuals field are carried out in the zone that ferritic intragranular comprised; Number to cementite particle is counted; Divided by total photo area, try to achieve therefrom.
Table 4
* P: perlite, B: bainite, M: martensite
The mechanical properties and the amount of energy of each Plate Steel have been shown in the table 5.Tensile properties (ys, tensile strength, uniform elongation) uses the total thickness test film to measure, and the summer is used the test film mensuration of gathering from the thickness of slab central part than collision characteristic, with the typical value of these measured values as each steel plate.Ys, tensile strength, uniform elongation are used JIS1B tension test sheet (with reference to JIS Z 2201 (1998)), measure through the tension test based on JIS Z 2241 (1998) " metal material stretching test method ".This tension test is that each 2 above-mentioned tension test sheets are made an experiment, with on average being recorded in the table 5 of these measured values.Summer under 0 ℃ uses the 2mmV groove summer than bump test sheet than average absorption energy, measures than bump test through the summer based on JIS Z 2242 (2005) " summer of metallic substance is than collision test method ".This summer is under 0 ℃, each 3 above-mentioned summer to be made an experiment than bump test sheet than bump test, with on average being recorded in the table 5 of these measured values.Amount of energy is tried to achieve by the area of stress-deformation curve usually.But, wherein, use by above-mentioned tensile properties of trying to achieve, obtain amount of energy approx through following (4) formula, energy absorption capability is estimated.
EA＝(YS+TS)/2×uEL (4)
At this, EA is amount of energy (MPa), and YS is ys (MPa), and TS is tensile strength (MPa), and uEL is a uniform elongation (-).
Table 5
Figure BDA0000140207960000221
Annotate 1) EA=(YS+TS)/2 * uEL
Steel numbering system 1～20 is the embodiment of Plate Steel of the present invention.Because chemical ingredients and the method for manufacture shown in the table 3 shown in the table 1 satisfy condition of the present invention, so the microstructure shown in the table 4 satisfies condition of the present invention.Therefore, with regard to steel numbering system 1～20, the mechanical properties shown in the table 5 satisfies condition of the present invention.Its result; The energy absorption capability of the comparative example of stating behind the energy absorption capability ratio of steel numbering system 1～20 is good, and the characteristic of the Plate Steel of these steel numbering systems 1～20 is sufficient for conduct has the Plate Steel that when colliding, can prevent effectively to be used by the tumble-home bow of the buffering effect of the damage of colliding vessel.In addition; Among these embodiment; The method of manufacture of the Plate Steel of steel numbering system 1～8,11～15,17,18,20 is owing to quicken cooling after rolling, therefore compares with the method for manufacture of the Plate Steel of steel numbering system 9,10,16,19, can significantly shorten manufacturing time.Need to prove that under the situation of the Plate Steel that uses steel plate to use as tumble-home bow, amount of energy need be for more than the 60MPa in table 5.
Relative therewith, steel numbering system 21～37 is the comparative example of Plate Steel.Wherein, as shown in table 2, the chemical ingredients of steel numbering system 21～27 satisfies condition of the present invention, but the condition of the discontented unabridged version invention of the method for manufacture of table 3, so the condition of the discontented unabridged version invention of microstructure.In addition, the method for manufacture of steel numbering system 28～32 satisfies condition of the present invention, but the condition of the discontented unabridged version invention of chemical ingredients.In addition, the condition of all discontented unabridged version invention of the chemical ingredients of steel numbering system 33～37, method of manufacture.
Below, the comparative example of the Plate Steel reason than Plate Steel difference of the present invention is described.
About steel numbering system 21, in method of manufacture, be rolled up to being lower than A R3The temperature of transformation temperature.That is to say that it is rolling that this steel numbering system 21 has carried out two-phase region.What accompany therewith is that cooling beginning temperature is lower than 760 ℃.Therefore, undressed ferritic area occupation ratio is lower than 85%, and uniform elongation is lower than 15%.Therefore, the amount of energy of steel numbering system 21 is poorer than the amount of energy of steel numbering system 1～20.In addition, the summer separates than average absorption energy, therefore is lower than 100J.Thereby, in tumble-home bow, under the situation of the steel plate of application steel numbering system 21, in tumble-home bow, produce brittle rupture during collision, might carry out the energy absorption that causes by flexural deformation.Therefore, be difficult to the steel plate of steel numbering system 21 is used as the good steel plate of crash energy absorption ability.
About steel numbering system 22, in method of manufacture, speed of cooling is greater than 50 ℃/second.Therefore, ferritic crystallization particle diameter is lower than 5 μ m, and uniform elongation is lower than 15%.In addition, cooling stops temperature and is lower than 400 ℃, does not carry out tempering.Therefore, the individual number density of cementite particle is greater than 50000/mm 2This also is that uniform elongation is lower than 15% reason.Can know that by above result the amount of energy of steel numbering system 22 is poorer than the amount of energy of steel numbering system 1～20.
About steel numbering system 23, in method of manufacture, cooling beginning temperature is lower than 760 ℃.Therefore, carbon enrichment in the austenite, hardenability extremely improves.Therefore, in cooling, being difficult to generate ferritic, as second phase, is not perlite or bainite, surpasses 10% hard martensite but generate.Therefore, tensile strength surpasses 460MPa, and uniform elongation is lower than 15%.In addition, the summer also is lower than 100J than average absorption energy.Therefore, the amount of energy of steel numbering system 23 is poorer than the amount of energy of steel numbering system 1～20, and the steel plate of steel numbering system 23 is not suitable for as the good steel plate of crash energy absorption ability.
About steel numbering system 24, in method of manufacture, Heating temperature is above 1300 ℃.Therefore, the chap of heating austenite crystal is big, and cooled ferritic crystallization particle diameter is greater than 40 μ m.Its result, ys is lower than 235MPa, and the summer is lower than 100J than absorbing energy.The amount of energy of the amount of energy of steel numbering system 24 and steel numbering system 1～20 is equal, but poorer than the characteristic of steel numbering system 1～20 as the characteristic of the steel numbering system 24 of structural steel.Therefore, the steel plate of the steel numbering system 24 good steel plate of crash energy absorption ability that is difficult to use as tumble-home bow uses.
About steel numbering system 25, in method of manufacture, under 700 ℃, carry out tempering.Therefore, ferritic crystallization particle diameter is greater than 40 μ m, and ys is lower than 235MPa, and the summer is lower than 100J than absorbing energy.Same with steel numbering system 24, the amount of energy of the amount of energy of steel numbering system 25 and steel numbering system 1～20 is equal, but poorer than the characteristic of steel numbering system 1～20 as the characteristic of the steel numbering system 25 of structural steel.Therefore, the steel plate of the steel numbering system 25 good steel plate of crash energy absorption ability that is difficult to use as tumble-home bow uses.
About steel numbering system 26 and 27, in method of manufacture, cooling stops temperature and is lower than 400 ℃.At this moment, need suitably carry out tempering, but steel numbering system 26 does not carry out tempering, steel numbering system 27 tempering temperatures are lower than 400 ℃.Therefore, the individual number density of ferritic intragranular cementite particle is greater than 50000/mm 2Its result, uniform elongation is reduced to less than 15%, so the amount of energy of steel numbering system 26 and 27 is poorer than the amount of energy of steel numbering system 1～20.
About steel numbering system 28, in chemical ingredients, the C amount surpasses 0.10%.Thus, undressed ferritic area occupation ratio is lower than 85%, and the area occupation ratio of second phase increases on the contrary.Therefore, tensile strength is greater than 460MPa, and uniform elongation is lower than 15%.Thereby the amount of energy of steel numbering system 28 is poorer than the amount of energy of steel numbering system 1～20.
About steel numbering system 29, in chemical ingredients, the C amount is below 0.03%.The hardenability of this steel numbering system 29 extremely reduces, and therefore the chap of ferritic crystallization particle diameter is greatly until surpassing 40 μ m.Its result, ys is lower than 235MPa, and the summer is lower than 100J than absorbing energy.The amount of energy of the amount of energy of steel numbering system 29 and steel numbering system 1～20 is equal, and steel numbering system 29 does not satisfy as the needed characteristic of structural steel.
About steel numbering system 30, in chemical ingredients, the Mn amount surpasses 1.5%, and the Nb amount surpasses 0.02%, and the V amount surpasses 0.04%, and carbon equivalent surpasses 0.30%.In addition, about steel numbering system 31, in chemical ingredients, the Ni amount surpasses 0.5%, and the Mo amount is more than 0.2%, and carbon equivalent surpasses 0.30%.Therefore, these steel numbering systems 30 and 31 the undressed ferritic area occupation ratio area occupation ratio that is lower than 85%, the second phase increases.Its result, tensile strength are greater than 460MPa, and uniform elongation is lower than 15%.Therefore, steel numbering system 30 and 31 amount of energy are poorer than the amount of energy of steel numbering system 1～20.
About steel numbering system 32, in chemical ingredients, the Si amount surpasses 1%, and the Cr amount surpasses 0.5%.Its result, undressed ferritic area occupation ratio is lower than 85%, the second phase area rate to be increased.Therefore, the uniform elongation of this steel numbering system 32 is lower than 15%, and the amount of energy of steel numbering system 32 is poorer than the amount of energy of steel numbering system 1～20.In addition because the excessive alloy that added, so the summer be reduced to and be lower than 100J than absorbing energy, also do not satisfy characteristic as structural steel.
About steel numbering system 33, in chemical ingredients, C amount surpasses 0.1%, and Cu amount and Ni amount surpass 0.5%, and carbon equivalent surpasses 0.30%, and in method of manufacture, it is rolling to carry out two-phase region.Therefore, undressed ferritic area occupation ratio is lower than 85%, and tensile strength is greater than 460MPa, and uniform elongation is lower than 15%.Its result, the amount of energy of steel numbering system 33 is than the remarkable variation of amount of energy of steel numbering system 1～20.In addition, increased the processing ferritic, so the summer also is lower than 100J than absorbing energy through two-phase region is rolling.Thereby brittle rupture dangerous high is so the steel plate of steel numbering system 33 is not suitable for the Plate Steel used as tumble-home bow.
About steel numbering system 34, the Mo amount is more than 0.2%, and carbon equivalent surpasses 0.30%.In addition, in method of manufacture, Heating temperature is higher than 1300 ℃.Except the high chemical ingredients of hardenability, under the big state of heating austenite crystal chap, carry out excessive quenching, therefore undressed ferritic area occupation ratio is lower than the area occupation ratio increase of 85%, second phase.Its result, the uniform elongation of steel numbering system 34 is lower than 15%, and the amount of energy of steel numbering system 34 is poorer than the amount of energy of steel numbering system 1～20.
About steel numbering system 35, in chemical ingredients, the C amount is below 0.03%, and in method of manufacture, cooling beginning temperature is lower than 760 ℃.Except the extremely insufficient chemical ingredients of hardenability, do not carry out suitable cooling, therefore the chap of ferritic crystallization particle diameter is greatly until surpassing 40 μ m.What accompany therewith is, ys is lower than 235MPa, and the summer is lower than 100J than absorbing energy.The amount of energy of the amount of energy of this steel numbering system 35 and steel numbering system 1～20 is equal, but the steel plate of steel numbering system 35 does not have the characteristic of the Plate Steel of using as tumble-home bow concurrently.
About steel numbering system 36, in chemical ingredients, the Ti amount surpasses 0.04%, and in method of manufacture, tempering temperature is above 650 ℃.Its result, the chap of ferritic crystallization particle diameter is greatly until surpassing 40 μ m, and in addition, through the embrittlement of separating out of TiC, the summer significantly reduces than absorbing energy, is lower than 100J.At this moment, even the amount of energy that is calculated by intensity and elongation is high, the danger that produces brittle rupture during the distortion of the tumble-home bow when collision is also high, therefore can't expect the sufficient energy absorption that accompanies with flexural deformation eventually.
About steel numbering system 37, in chemical ingredients, the C amount surpasses 0.10%, and the Si amount surpasses 1%, and the Mn amount surpasses 1.5%, and the Mo amount is more than 0.2%, and the B amount surpasses 0.002%, and carbon equivalent is 0.30%.In addition, about this steel numbering system 37, in method of manufacture, speed of cooling is greater than 50 ℃/second.Therefore, carry out excessive quenching, undressed ferritic area occupation ratio is lower than 85%, and ferritic crystallization particle diameter is lower than 5 μ m.Its result, tensile strength significantly surpass 460MPa, and uniform elongation also significantly is lower than 15%.Its result, the amount of energy of steel numbering system 37 is poorer than the amount of energy of steel numbering system 1～20.In addition, the summer also is lower than 100J than absorbing energy, and the Plate Steel that the steel plate of steel numbering system 37 is difficult to use as tumble-home bow is used.
Can know by above embodiment,, crash energy absorption ability Plate Steel that good tumble-home bow is used and method of manufacture thereof can be provided through adopting the present invention.When this Plate Steel is used for tumble-home bow; Under the situation of the design that need not to change hull structure; When the such accident of the bilge of fore with boats and ships of tumble-home bow (colliding vessel) and his ship (by colliding vessel) collision took place, the globular part side of the tumble-home bow in the colliding vessel occured bending and deformation more equably, thus absorbing impact energy effectively; Impingement area(s) is crushed in the absorbing impact energy, thereby can significantly reduce by the damage of the bilge of colliding vessel.
Need to prove that the present invention is not limited to above-mentioned embodiment, can in the scope that does not break away from purport of the present invention, carry out various changes and implement.
Utilizability on the industry
Can be provided to need not to change to have under the hull structural design situation and when each other collision of ship, can prevent Plate Steel and the method for manufacture thereof used by the fore part structure of the buffering effect of the damage of colliding vessel effectively.
Nomenclature
10 colliding vessels
The 10a tumble-home bow
The 10b head
11 by colliding vessel
11a is by the bilge of colliding vessel

Claims (7)

1. a hull is used Plate Steel; It is characterized in that having following chemical ingredients:, contain C in quality %: surpass 0.03 and be below 0.10%, P: S≤0.05%: Al:0.002～0.1%≤0.05%; Remainder comprises iron and unavoidable impurities
And has following microstructure: comprise ferritic; And comprise in perlite, the bainite more than a kind; Unprocessed ferritic area occupation ratio in the said microstructure is more than 85%; Said unprocessed ferritic average crystallite particle diameter is 5～40 μ m, and said ferritic intragranular cementite particle is counted 50000/mm with number density 2Below, ys is more than the 235MPa, and tensile strength is below the 460MPa, and uniform elongation is more than 15%, and the summer under 0 ℃ is more than the 100J than average absorption energy.
2. hull according to claim 1 is used Plate Steel; It is characterized in that; In quality %; Contain Si:0.03～1%, Mn:0.1～1.5%, Cu:0.02～0.5%, Ni:0.02～0.5%, Cr:0.02～0.5%, Mo:0.002 above and be lower than 0.2%, among Nb:0.002～0.02%, V:0.002～0.04%, Ti:0.002～0.04%, B:0.0002～0.002%, N:0.0005～0.008%, Ca:0.0003～0.005%, Mg:0.0003～0.005%, REM:0.0003～0.005% more than a kind as said chemical ingredients; And carbon equivalent Ceq is below 0.30%, wherein
Ceq＝[C]+[Si]/24+[Mn]/6+([Cu]+[Ni])/15+([Cr]+[V])/10+([Mo]+[Nb])/5+[Ti]/20+[B]/3+[N]/8，
Wherein, [C], [Si], [Mn], [Cu], [Ni], [Cr], [V], [Mo], [Nb], [Ti], [B], [N] are respectively the content in quality % of C, Si, Mn, Cu, Ni, Cr, V, Mo, Nb, Ti, B, N.
3. hull according to claim 2 is used Plate Steel, it is characterized in that, in quality %, said carbon equivalent Ceq is below 0.27%.
4. hull according to claim 1 and 2 is used Plate Steel, it is characterized in that, yield ratio is more than 0.70.
5. a hull is characterized in that with the method for manufacture of Plate Steel,
To have that the steel billet of each described chemical ingredients is heated to 1000～1300 ℃ in the claim 1～3;
At A R3Accumulate draft in the above austenite one phase district of transformation temperature and be 30～98% rolling until reaching the goods thickness of slab;
To quicken to cool off temperature, carry out air cooling since the cooling temperature more than 760 ℃ then until 400～650 ℃ by the speed of cooling of 1～50 ℃/second of thickness of slab average out to.
6. a hull is characterized in that with the method for manufacture of Plate Steel,
To have that the steel billet of each described chemical ingredients is heated to 1000～1300 ℃ in the claim 1～3;
At Ar 3Accumulate draft in the above austenite one phase district of transformation temperature and be 30～98% rolling until reaching the goods thickness of slab;
To quicken to cool off temperature, under 400～650 ℃ temperature, carry out tempering since the cooling temperature more than 760 ℃ then until being lower than 400 ℃ by the speed of cooling of 1～50 ℃/second of thickness of slab average out to.
7. a hull is characterized in that with the method for manufacture of Plate Steel,
To have that the steel billet of each described chemical ingredients is heated to 1000～1300 ℃ in the claim 1～3;
At Ar 3Accumulate draft in the above austenite one phase district of transformation temperature and be 30～98% rolling until reaching the goods thickness of slab;
Carry out air cooling.
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