CN1676656A

CN1676656A - Superhigh strength thick steel plate capable of large-line energy welding and its manufacturing method

Info

Publication number: CN1676656A
Application number: CN 200410017255
Authority: CN
Inventors: 刘自成; 丁建华
Original assignee: Baoshan Iron and Steel Co Ltd
Current assignee: Baoshan Iron and Steel Co Ltd
Priority date: 2004-03-29
Filing date: 2004-03-29
Publication date: 2005-10-05
Anticipated expiration: 2024-03-29
Also published as: CN1302144C

Abstract

This is a super intensive thick steel board which can be welded with jug line power. It contains 0.01-0.06%C, 0.10-0.50%Si, 1.00 -1.40%Mn, 0.010-0.050%Nb, 0.040-0.090%V, 0.60-1.00%Cu, 0.20-0.50%Cr, 0.20-0.50%Mo, 0.50-0.80%Ni, 5ppm-30ppmB, 0.005-0.020%Ti, 0.040-0.070%Als, and remained Fe and inevitable impurity: 0.065<=(%Cu*%V)<=0.085. The producing method includes: casting technique, slab heating, hot rolling, which is asynchronous rolling in austenite non-crystallized area, strain relaxation and direct cooling by quenching. This invention associates well the steel board's high intensity, high ductility and good weldability. It decreases the quantity of alloying agent and reduces the cost for steel board's production. It can as well improve the low-temperature flexibil ity and welability of the steel board, as it realizes welding with jug line power. As a result, it needs no pre-heating to weld steel board above 0 degree Centigrade.

Description

But the superstrength Plate Steel and the manufacture method thereof of large-line energy welding

Technical field

The present invention relates to a kind of tiny bainite/martensite lath of 5 μ m～10 μ m group crystal grain, yield strength of in containing Nb Ultra-low carbon low-alloy Plate Steel (ultra-low carbon lowalloyed steel heavy plate), obtaining greater than 800MPa, ULCB/martensite Plate Steel with good low-temperature flexibility and weldability.

Background technology

As everyone knows, low-carbon (LC) (high strength) low alloy steel is one of most important structural timber, is widely used among petroleum natural gas pipeline, ocean platform, shipbuilding, bridge, pressurized vessel, building structure, automotive industry, transportation by railroad and the machinofacture.Low-carbon (LC) (high strength) low alloy steel performance depends on the process system of its chemical ingredients, manufacturing processed, and wherein intensity, toughness and weldability are the most important performances of low-carbon (LC) (high strength) low alloy steel, and its final decision is in the microstructure state of finished steel.Along with science and technology constantly advances, people propose higher requirement to the obdurability and the weldability of steel, promptly improve performance significantly when steel plate is being kept lower manufacturing cost, save cost with the consumption that reduces steel, the own wt that alleviates steel construction is to improve security.Started development ferrous materials research of new generation climax at present in the world wide, required do not rolling up alloy content, obtained better tissue coupling by changing Technology, thereby obtain higher obdurability and weldability.Ultra-low-carbon bainite steel is exactly a big class high strength, high tenacity, the multi-usage steel grade that grows up in this period.Oneself has broken through the composition Design Mode of original high-strength low-alloy steel the design of alloy of this class steel, significantly reduced the content of carbon in the steel (the generally carbon content of this class steel≤0.05%), the intensity of steel no longer relies on the content of carbon, but with dislocations strengthening in the bainite matrix and phase transformation strengthening, V, Nb, Ti microalloy controlled rolling and controlled cooling strengthen and ε-Cu precipitation strength is main, thereby make such steel obdurability coupling splendid, especially the steel grades such as HY series that welding property is more traditional have had and have increased substantially, and need not carry out preheating and postweld heat treatment more than 0 ℃.The ULCB steel mainly can be divided into two big classes in the world at present: the first is the Cu-Nb-B series of representative with the U.S. and Canada; It two is to be the Mn-Nb-B series of representative with Japan.Because its excellent comprehensive performances and lower manufacturing cost, such steel extensively applies to oily steam pipe line, maritime facilities and the aspect, naval vessel, ocean of cold zone.The Physical Metallurgy of ULCB steel shows: the mechanical property of ULCB/martensite steel plate depends primarily on bainite/martensite lath group grain-size, microcosmic substructure configuration in bainite/martensite slat dimension and the bainite/martensite lath, refinement bainite/martensite lath group grain-size, the microcosmic substructure configuration of optimizing in bainite/martensite slat dimension and the bainite/martensite lath is to obtain high strength, high tenacity, than the most important condition of the ULCB/martensitic steel of low-alloy content, be to be the target that the metallurgical engineer pursues for many years always.

Traditional yield strength mainly adds tempering (DQ+T or Q+T) by quenching greater than the Wide and Heavy Plates of 800MPa, and promptly so-called hardening and tempering method is produced, and this just requires steel plate necessity to have sufficiently high hardening capacity, i.e. hardenability index DI 〉=6.0mm " DI=0.311C ^1/2(1+0.64Si) * (1+4.10Mn) * (1+0.27Cu) * (1+0.52Ni) * (1+2.33Cr) * (1+3.14Mo) * 25.4 (mm) "; have sufficiently high intensity to guarantee steel plate; good low-temperature flexibility and along the microstructure of steel plate thickness direction and performance evenly; therefore in steel, add a large amount of Cr inevitably; Mo; Ni, alloying elements such as Cu, Mo and Cr content in this class steel plate generally will be controlled at 〉=and 0.50%, especially noble element Ni content will be controlled at 〉=(clear 59-129724 more than 1.00%, flat 1-219121), because the Ni element not only can improve the intensity and the hardening capacity of steel plate, reduce transformation temperature refinement bainite/martensite lath group grain-size; The more important thing is the unique element that can improve the low-temperature flexibility of bainite/martensite lath own of Ni.So, the alloy content of steel plate is higher, and carbon equivalent ce V and welding cold cracking Sensitivity Index Pcm are also higher, this brings bigger difficulty to site welding, need preheating before the weldering, postwelding needs thermal treatment, and welding cost raises, welding efficiency reduces, welding work on the spot environmental degradation.

Summary of the invention

But the superstrength Plate Steel and the manufacture method thereof that the purpose of this invention is to provide a kind of large-line energy welding, employing is than the alloy designs of low-carbon-equivalent, give full play to the potential of alloy designs itself and the effect of TMCP technology, realize the organic unity of high strength, high tenacity and the superior weldability of steel plate; Reduce the consumption of alloying element, as Cr, Mo, Ni etc., reduce the production cost of steel plate, improve the low-temperature flexibility and the weldability of steel plate, but realize the large-line energy welding, welding steel need not to carry out preheating more than 0 ℃.

Physical metallurgy analysis of the present invention:

As everyone knows, bainite/martensite is the phase transformation of shear type, it is the slippage by specific dislocation configuration in essence, realize that crystalline structure is transformed into the BCC (notes: the diffusion process of bainitic transformation process simultaneous interstitial atom C, N, B) of bainite/martensite by austenitic FCC, finish phase transition process, at one of the inner formation of original austenite grain or several bainite/martensite laths group crystal grain.Therefore any obstacle that can hinder the dislocation configuration slippage all can suppress growing up of bainite/martensite lath group, and refinement bainite/martensite lath is rolled into a ball grain-size, improves performance, the especially low-temperature flexibility of steel plate, because brittle-ductile transition temperature vTr. ∝ is d ^-1/2, wherein d is bainite/martensite lath group grain-size.The microalloy element that in steel, has added some amount, as Ti, Nb, V, B etc., in the deformation relaxation process after finish rolling, separating out of strain inducing microalloy carbonitride taken place, in the quenching process behind deformation relaxation, these tiny microalloy carbonitrides can become the nucleation site of lath of bainite/martensite lath; Secondly, at microalloy carbonitride particle as (Ti, Nb) (C N), the more important thing is at Fe ₂₃(CB) ₆Around the poor carbon of short period of time appears in the matrix, thereby these regional stabilization of austenites are reduced, granular bainite/the acicular ferrite of some amount preferentially forms in these zones, thereby the lath of bainite/martensite lath of follow-up generation is grown up and will be subjected to the restriction of granular bainite/acicular ferrite of forming earlier and obtain refinement; In addition, rolling formed high density dislocation also can be replied in the deformation relaxation process, and a large amount of dislocation relaxation generation polygonization processes form the Polygons substructure, promptly so-called subgrain structure.Have separating out of a large amount of microalloy carbonitrides on the border of these Polygons substructures simultaneously, further stablize the subgrain structure, the inhibition subgrain merges and grows up, and along with the time increase of deformation relaxation, the misorientation of subgrain both sides constantly increases, and subgrain boundary is constantly sharp.In the quenching process behind deformation relaxation, the lath of bainite/martensite lath that is deformed into is mutually grown up and is subjected to the inhibition of these Polygons subgrain boundaries, is confined in the tiny one by one subgrain, and lath of bainite/martensite lath group obtains further refinement.

Technical solution of the present invention is: but the superstrength Plate Steel of large-line energy welding, its composition (mass percent):

C?????????0.01％～0.06％

Si????????0.10％～0.50％

Mn????????1.00％～1.40％

Nb????????0.010％～0.050％

V?????????0.040％～0.090％

Cu????????0.60％～1.00％

Cr????????0.20％～0.50％

Mo????????0.20％～0.50％

Ni????????0.50％～0.80％

B????????5ppm～30ppm

Ti???????0.005％～0.020％

Al _s?????0.040％～0.070％

All the other are Fe and unavoidable impurities such as P, S;

Wherein, 0.065≤(%Cu * %V)≤0.085.

But the manufacture method of the superstrength Plate Steel of large-line energy welding of the present invention comprises the steps:

A) casting technique is cast as slab with the molten steel of mentioned component, pouring temperature≤1580 ℃;

B) slab heating, heating and temperature control is at 1150 ℃～1200 ℃;

C) hot rolling adopts big rolling pass draft to be rolled, and in austenite non-recrystallization district, at least one passage, more than preferred 2 passages adopts the asymmetrical rolling technology, control upper working rolls and lower working rolls velocity ratio 〉=1.05; Austenite non-recrystallization district accumulative total draft 〉=40%, percentage pass reduction 〉=10%;

D) deformation relaxation, the deformation relaxation temperature is at Ar ₃+ 60 ℃～Ar ₃+ 20 ℃ of some temperature ranges, deformation relaxation time t and austenite non-recrystallization accumulative total draft Ψ: lnt (s)=7.779-5.37 * 10 ^-2Ψ (%);

E) cooling, and direct quenching (direct quenching---be called for short DQ) cool to room temperature.

C content is preferably between 0.03%～0.05% between 0.01%～0.06%, to improve the low-temperature flexibility of bainite/martensite lath itself, greatly improves the weldability of steel plate.

Si promotes deoxidation of molten steel and can improve armor plate strength, but adopt the molten steel of Al deoxidation, the desoxydatoin of Si is little, though Si can improve the intensity of steel plate, and the low-temperature flexibility and the weldability of Si grievous injury steel plate, especially promote welded heat affecting zone M-A constituent element to form, the toughness of infringement welded H AZ, so the Si content in the steel should control lowly as far as possible, considers the economy and the operability of steelmaking process, Si content is controlled at≤and 0.50%, best≤0.30%.

For Ultra-low carbon content, the center segregation degree of Mn is reduced significantly, and the Mn content that suitably improves in the steel not only can improve mother metal armor plate strength and toughness, and can improve the hardening capacity of steel plate.But it is too much to add Mn, surpasses at 1.40% o'clock, the weldability of infringement steel plate and the toughness of HAZ.Therefore steel plate Mn content of the present invention is controlled between 1.00%～1.40%.

Nb content is preferably between 0.015%～0.030% between 0.010%～0.050%, to obtain best controlled rolling effect, does not damage the toughness of HAZ simultaneously.

V content is between 0.040%～0.090%, and along with the increase of steel plate thickness, V content is the capping value suitably.Adding the V purpose is that (C N) separates out in the bainite/martensite lath, improves the intensity of steel plate by V.V adds very few, is lower than 0.040%, and (C N) very little, can not effectively improve the intensity of steel plate to the V that separates out; The V addition is too much, is higher than 0.090%, infringement steel plate low-temperature flexibility and weldability.

Adding the Cu purpose is to separate out in the bainite/martensite lath by ε-Cu, improves armor plate strength; Simultaneously, add Cu and can also improve the hardening capacity of steel plate and the resistance to atmospheric corrosion of steel plate.But the Cu addition is too much, is higher than 1.00%, causes copper brittleness, cc billet surface quality and implosion problem easily; The Cu addition is very few, is lower than 0.60%, can not produce ε-Cu precipitation and separate out, and strengthens steel plate.Therefore Cu content is controlled between 0.60%～1.00%, and along with the increase of steel plate thickness, Cu content is the capping value suitably.

Add Cr and promote tiny bainite/martensite to form, improve the intensity and the toughness of steel plate, but the Cr addition surpasses at 0.50% o'clock, not only increase the manufacturing cost of steel plate, and promote the upper bainite among the HAZ to form, the weldability of infringement steel plate; Therefore Cr content is controlled between 0.20%～0.50%.

Add the hardening capacity of Mo raising steel plate, promote tiny bainite/martensite to form, improve the intensity and the toughness of steel plate; But the Mo addition surpasses at 0.50% o'clock, not only increases the manufacturing cost of steel plate, and the weldability of infringement steel plate, and increases the production cost of steel plate.Therefore Mo content is controlled between 0.20%～0.50%.

Ni is unique element that can improve the intensity and the low-temperature flexibility of steel plate, adds the copper brittleness phenomenon that Ni can also reduce Copper Bearing Steel in the steel, alleviates the intergranular cracking of course of hot rolling, improves the resistance to atmospheric corrosion of steel plate.Therefore theoretically, Ni content is high more within the specific limits good more in the steel, the welded heat affecting zone but too high Ni content can harden, weldability to steel plate is unfavorable, Ni is a kind of very noble element simultaneously, consider that from the ratio of performance to price Ni content is controlled between 0.50%～0.80%, do not damage the weldability of steel plate with the strength level of the hardening capacity of guaranteeing steel plate and steel plate.

The B atom gathers partially on austenite grain boundary, and the ferrite of strongly inhibited pro-eutectoid forms, and improves the hardening capacity of steel plate greatly, and the B atom can also form Fe in austenite crystal simultaneously ₂₃(CB) ₆Particle causes Fe ₂₃(CB) ₆Poor carbon district appears in matrix on every side, reduce austenitic stability, bring out granular bainite in the austenite crystal/acicular ferrite and form, this granular bainite/acicular ferrite both can suppress in the quenching process bainite/martensite lath and grow up refinement bainite/martensite lath group grain-size; Microstructure that again can refinement large-line energy welded H AZ is improved the low-temperature flexibility of HAZ.Therefore, B content is controlled between 5ppm～30ppm, preferably between 15ppm～20ppm, not only can guarantee steel plate hardening capacity, and can improve the low-temperature flexibility of large-line energy welded H AZ.

For guaranteeing that free B atom exists in the steel, N content can not be too high in the steel, be combined into the BN particle to prevent N and B, so N content is controlled at below the 35ppm in the steel.

Add an amount of Ti in the steel and not only can eliminate the infringement of solid solution N steel plate toughness and weldability, guarantee that free B atom exists in the steel, and the TiN particle that forms can suppress in heating and the course of hot rolling austenite crystal and grows up, improve the low-temperature flexibility of steel plate, the more important thing is and suppress HAZ grain growth in the welding process, improve HAZ toughness.Therefore Ti content is 0.005%～0.020%, between best 0.007%～0.012%.

The molten aluminium Al of acid _sContent should be controlled to be: Al _s＞＞2 (N _Total-0.292Ti), eliminate the free N in the steel plate fully, stop the BN particle to form, guarantee the effect and the Fe of B element hardening capacity ₂₃(CB) ₆The formation of particle; Simultaneously, eliminate free N to mother metal steel plate and the infringement of HAZ flexible.Therefore actual Als content should be controlled between 0.040%～0.070%.

This invention steel can also contain Ca or rare earth REM and Fe and unavoidable impurities, as P, S etc.Ca or REM element are used for sulfide inclusion is carried out denaturing treatment, the nodularization sulfide inclusion, and its content should be controlled at Ca content≤0.01%, perhaps REM content≤0.01%.P, S content should be controlled lowly as far as possible, but consider the economy and the operability of steelmaking process, and P content is controlled at≤0.010%, and S content is controlled at≤and 0.005%.

0.065≤(%Cu * %V)≤0.085, with guarantee V in the drawing process (C, N) and ε-Cu separate out simultaneously, promptly (C, N) timeliness is separated out curve and is overlapped substantially fully for ε-Cu and V.

Casting technique of the present invention recommends to adopt continuous casting process, continuous casting process emphasis control pouring temperature and solidification of molten steel speed, and pouring temperature≤1580 ℃, best≤1570 ℃, continuous casting billet quality is better during the low temperature casting.

Slab heating temperature is controlled between 1150 ℃～1200 ℃, and when guaranteeing that original slab autstenitic grain size is relatively evenly tiny, V, the complete solid solution of Nb carbonitride are for follow-up controlled rolling and precipitation hardening provide condition.In the non-recrystallization temperature range, adopt big rolling pass draft to be rolled, austenite non-recrystallization district accumulative total draft 〉=40%, best 〉=45% as far as possible; Percentage pass reduction 〉=10%, with guarantee to have enough tiny strain inducing carbonitride separating out and dislocation is replied formation and is stablized tiny subgrain structure.

In austenite non-recrystallization district, have a passage at least, more than best 2 passages, adopt the asymmetrical rolling technology, control upper working rolls and lower working rolls velocity ratio 〉=1.05.

After the controlled rolling in austenite non-recrystallization district finishes, at Ar ₃+ 60 ℃～Ar ₃+ 20 ℃ of some temperature ranges, carry out the control of deformation relaxation process, deformation relaxation time t and austenite non-recrystallization accumulative total draft Ψ can obtain tiny bainite/martensite lath group crystal grain: lnt (s)=7.779-5.37 * 10 of 5 μ m～10 μ m by following relation control ^-2Ψ (%).Direct quenching subsequently (DQ) cool to room temperature (below 100 ℃).

In the timeliness peak temperature place of Cu timeliness, can separate out the ε-Cu particle of a large amount of small and disperseds and armor plate strength is improved significantly, but the low-temperature flexibility of steel plate also reduces simultaneously significantly, though the intensity decrease to some degree that causes steel plate is handled in overaging, but its low-temperature flexibility but improves significantly, for obtaining the coupling of intensity and low-temperature flexibility the best, the tempering temperature of steel plate is controlled between 550 ℃～600 ℃, causes the moderately overaging of ε-Cu precipitation hardening.

The present invention at first starts with from optimizing alloy designs, adopts ultralow C, low N, high Als, little Ti-B to handle and the Cu-Cr-Mo-Ni alloying process, and promptly adopting ultralow C purpose is malleableize bainite/martensite lath and the weldability of improving steel plate; Adopting Cu-Cr-Mo-Ni alloying purpose is that solution strengthening and phase transformation strengthening by alloying element itself remedies the loss of strength that ultralow C causes; Adopting little Ti-B processing intent is at the inner granular bainite/acicular ferrite nucleating point of implanting of austenite crystal, promote granular bainite in the austenite crystal/acicular ferrite to form, refinement bainite/martensite lath is rolled into a ball grain-size, improves the toughness of steel plate large-line energy welded H AZ.

On manufacturing process, at first start with from the TMCP technology of optimizing, adopt the asymmetrical rolling technology, control upper working rolls and lower working rolls velocity ratio 〉=1.05, cause the steel plate serious asymmetry of double layer of metal rheology up and down, change the deformed state of steel plate central zone, make the steel plate central zone by plane strain state three the shear strain states that thicken, the rotation of lattice in the operation of rolling, degree of crook strengthens, the austenite strain stores can be increased, cause defect concentrations in crystals, as dislocation, stacking fault density increases considerably, the microalloy carbonitride that causes strain inducing to separate out increases considerably, regressive subgrain size reduces significantly, has greatly suppressed growing up of lath of bainite/martensite lath, refinement lath of bainite/martensite lath group grain-size.When upper working rolls and lower working rolls velocity ratio＜1.05, double layer of metal rheology asymmetry is very little up and down to cause steel plate, for changing steel plate center deformed state, increases austenitic deformation and stores and can act on not quite, so control upper working rolls and lower working rolls velocity ratio 〉=1.05.

Austenite non-recrystallization district accumulative total draft and percentage pass reduction also are one of important controlled variable of the present invention.When austenite non-recrystallization district adds up draft less than 40%, percentage pass reduction was less than 10% o'clock, the deformation storage can be lower in the austenite, deformed belt density and dislocation desity are all lower, dislocation polygonization process development imperfection, and the subgrain structure of formation is stable inadequately, the subgrain size is also bigger, simultaneously, strain inducing microalloy carbonitride is separated out also insufficient, and therefore refinement bainite/martensite lath is rolled into a ball crystal grain effectively.For obtaining effective thinning effect, austenite non-recrystallization district accumulative total draft should be controlled at greater than 40%, and percentage pass reduction should be controlled at greater than 10%.

Deformation relaxation time t and austenite non-recrystallization accumulative total draft Ψ must satisfy following relationship, as shown in Figure 1:

lnt(s)＝7.779-5.37×10 ^-2Ψ(％)……………………(1)

Could obtain the bainite/martensite lath group's grain-size of 5～10 μ m and the meticulous substructure configuration in the bainite/martensite lath.Deformation relaxation refinement bainite/martensite lath group grain-size is to be caused by separating out with the dislocation polygonization of the microalloy carbonitride in the deformation relaxation process, therefore anyly influence separating out of microalloy carbonitride and all influence thinning effect bainite/martensite lath group grain-size with dislocation polygonization process, the variation of these two processes simultaneously is with coordination degree is different mutually, also have a strong impact on the effect of refinement, have only two kinds of processes of working as to coordinate mutually, the common promotion, the best results of refinement, promptly requiring the microalloy carbonitride to separate out on the one hand not only can promote granular bainite/acicular ferrite to change, thereby the bainite/martensite lath group grain-size that refinement is follow-up, and can stable polygonal subgrain structure, strengthen the inhibition that the subgrain structure is grown up to the bainite/martensite lath; Require Polygons subgrain structure to become the preferential nucleation site of microalloy carbonitride on the other hand, promote separating out of microalloy carbonitride, strengthen and separate out the refining effect that causes.So the microalloy carbonitride is separated out kinetics and dislocation polygonization process kinetics must will mate mutually.When austenite non-recrystallization district accumulative total draft was low, dislocation desity was relatively low, and dislocation answer kinetics is relatively slow, and it is also relatively slow that the microalloy carbonitride is separated out kinetics, and this just requires deformation relaxation time lengthening, to obtain two process optimum matching.If the deformation relaxation time is too short, the subgrain structure is not completed into, and the microalloy carbonitride also fails fully to separate out, the restraining effect deficiency that the bainite/martensite lath is grown up, thereby refinement bainite/martensite lath group grain-size effectively.When austenite non-recrystallization district accumulative total draft was big, dislocation desity was higher relatively, and dislocation answer kinetics is very fast relatively, and it is also very fast relatively that the microalloy carbonitride is separated out kinetics, and this just requires the deformation relaxation time to shorten, to obtain two process optimum matching.If the deformation relaxation overlong time, alligatoring will take place in the microalloy carbonitride of separating out, and amounts of particles reduces, and the effect of refinement bainite/martensite lath group grain-size reduces; While deformation relaxation overlong time, the subgrain structure will take place to merge and grow up, the microalloy carbonitride is owing to the stabilization of alligatoring to the subgrain structure also greatly reduces, therefore, the restraining effect of the bainite/martensite lath being grown up with the subgrain structure of separating out of microalloy carbonitride all reduces significantly, thereby refinement bainite/martensite lath is rolled into a ball grain-size effectively.Therefore have only when austenite non-recrystallization district accumulative total draft and deformation relaxation time are satisfied formula (1), separate out and these two kinds of processes of dislocation polygonization of microalloy carbonitride can be coordinated mutually, promote jointly, obtain best thinning effect.

The temperature range of deformation relaxation is controlled at Ar ₃+ 60 ℃～Ar ₃+ 20 ℃, to obtain the matching effect with the dislocation polygonization of separating out of best carbonitride.When the deformation relaxation temperature surpasses Ar ₃In the time of+60 ℃, because relaxation temperature is higher, the dislocation Recovery Process is carried out comparatively fast, the polygonization process is carried out comparatively fast, and dislocation desity reduces rapidly, the corresponding postponement that causes the microalloy carbonitride to separate out, separate out quantity and reduce dislocation polygonized structure less stable; When the deformation relaxation temperature is lower than Ar ₃During+20 ℃ of some temperature, the ferrite transformation of pro-eutectoid takes place, reason is in the district's controlled rolling of austenite non-recrystallization, causes Ar ₃Move on the point, cause strain-induced transformation to take place, cause ferrite content and microstructure ununiformity significantly to increase, armor plate strength and toughness descend significantly, so the temperature range of deformation relaxation must be controlled at Ar ₃+ 60 ℃～Ar ₃Between+20 ℃.

Beneficial effect of the present invention

The present invention has realized yield strength of 800 MPa Plate Steel low-carbon-equivalent alloy designs; be that carbon equivalent " C+Mn/6+ (V+Cr+Mo)/5+ (Cu+Ni)/15 " is than common other hardened and tempered steel plate of equality strength level low 0.10%～0.15%; this not only reduces the production cost of steel plate; improved the low-temperature flexibility of mother metal steel plate; and the weldability of steel plate and the low-temperature flexibility of HAZ have greatly been improved; but realize the large-line energy welding; when welding more than 0 ℃; steel plate need not to carry out preheating; improved site welding efficient; improved the work situation of site welding; reduced welding cost, made the Product Green environmental protectionization.

Embodiment

But the superstrength Plate Steel embodiment and the comparative example of the welding of the present invention's large-line energy see Table 1, and its manufacture method embodiment and comparative example see Table 2.

Table 3 is the physicals of the embodiment of the invention and comparative example.

Table 1

The steel sample	?C(％)	?Si(％)	?Mn(％)	?P(％)	?S(％)	?Als(％)	?Nb(％)	?V(％)	??N(ppm)	?Ti(％)	?Cr(％)	?Cu(％)	???Ni(％)	?Mo(％)	??B(ppm)	??REM(ppm)
The steel sample	?C(％)	?Si(％)	?Mn(％)	?P(％)	?S(％)	?Als(％)	?Nb(％)	?V(％)	??N(ppm)	?Ti(％)	?Cr(％)	?Cu(％)	???Ni(％)	?Mo(％)	??B(ppm)	??REM(ppm)	Embodiment 1	?0.036	?0.21	?1.35	?0.009	?0.004	?0.052	?0.021	?0.073	????31	?0.009	?0.32	?0.94	????0.76	??0.35	????16	????40
Embodiment 2	?0.046	?0.18	?1.23	?0.008	?0.003	?0.050	?0.018	?0.085	????33	?0.010	?0.39	?0.86	????0.67	??0.29	????18	????37	Embodiment 1	?0.036	?0.21	?1.35	?0.009	?0.004	?0.052	?0.021	?0.073	????31	?0.009	?0.32	?0.94	????0.76	??0.35	????16	????40
Embodiment 2	?0.046	?0.18	?1.23	?0.008	?0.003	?0.050	?0.018	?0.085	????33	?0.010	?0.39	?0.86	????0.67	??0.29	????18	????37	Embodiment 3	?0.042	?0.24	?1.31	?0.009	?0.003	?0.048	?0.023	?0.070	????29	?0.010	?0.36	?0.99	????0.77	??0.33	????17	????39
Embodiment 4	?0.035	?0.29	?1.39	?0.008	?0.004	?0.057	?0.026	?0.086	????35	?0.011	?0.32	?0.86	????0.73	??0.33	????19	????34	Embodiment 3	?0.042	?0.24	?1.31	?0.009	?0.003	?0.048	?0.023	?0.070	????29	?0.010	?0.36	?0.99	????0.77	??0.33	????17	????39
Embodiment 4	?0.035	?0.29	?1.39	?0.008	?0.004	?0.057	?0.026	?0.086	????35	?0.011	?0.32	?0.86	????0.73	??0.33	????19	????34	Embodiment 5	?0.048	?0.26	?1.16	?0.010	?0.002	?0.066	?0.026	?0.087	????35	?0.012	?0.34	?0.82	????0.69	??0.36	????17	????41
Embodiment 6	?0.018	?0.46	?1.38	?0.009	?0.001	?0.0055	?0.036	?0.078	????37	?0.011	?0.41	?0.93	????0.76	??0.44	????21	????42	Embodiment 5	?0.048	?0.26	?1.16	?0.010	?0.002	?0.066	?0.026	?0.087	????35	?0.012	?0.34	?0.82	????0.69	??0.36	????17	????41
Embodiment 6	?0.018	?0.46	?1.38	?0.009	?0.001	?0.0055	?0.036	?0.078	????37	?0.011	?0.41	?0.93	????0.76	??0.44	????21	????42	Embodiment 7	?0.030	?0.19	?1.26	?0.008	?0.003	?0.0063	?0.031	?0.081	????34	?0.010	?0.39	?0.89	????0.78	??0.40	????23	????38
Comparative example 1	?0.046	?0.18	?1.23	?0.008	?0.003	?0.050	?0.018	?0.085	????33	?0.010	?0.39	?0.86	????0.67	??0.29	????18	????37	Embodiment 7	?0.030	?0.19	?1.26	?0.008	?0.003	?0.0063	?0.031	?0.081	????34	?0.010	?0.39	?0.89	????0.78	??0.40	????23	????38
Comparative example 1	?0.046	?0.18	?1.23	?0.008	?0.003	?0.050	?0.018	?0.085	????33	?0.010	?0.39	?0.86	????0.67	??0.29	????18	????37	Comparative example 2	?0.035	?0.29	?1.39	?0.008	?0.004	?0.057	?0.026	?0.086	????35	?0.011	?0.32	?0.86	????0.73	??0.33	????19	????34
Comparative example 3	?0.11	?0.30	?1.03	?0.006	?0.003	?0.057	?0.012	?0.04	????/	?/	?0.54	?0.28	????1.41	??0.48	????15	????/	Comparative example 2	?0.035	?0.29	?1.39	?0.008	?0.004	?0.057	?0.026	?0.086	????35	?0.011	?0.32	?0.86	????0.73	??0.33	????19	????34

Table 2

The steel sample	Steel plate thickness mm	Heating temperature ℃	Finishing temperature ℃	The velocity ratio of upper working rolls and lower working rolls (%)	The asymmetrical rolling passage	Finish rolling accumulative total draft (%)	The deformation relaxation time (s)	Tempering temperature ℃
The steel sample	Steel plate thickness mm	Heating temperature ℃	Finishing temperature ℃		The asymmetrical rolling passage	Finish rolling accumulative total draft (%)	The deformation relaxation time (s)	Tempering temperature ℃	Embodiment 1	?50～100	????1100	????780	????1.08	????2	????65	????70	????580
Embodiment 2	?50～100	????1100	????780	????1.07	????2	????50	????165	????580	Embodiment 1	?50～100	????1100	????780	????1.08	????2	????65	????70	????580
Embodiment 2	?50～100	????1100	????780	????1.07	????2	????50	????165	????580	Embodiment 3	?50～100	????1100	????780	????1.15	????1	????55	????120	????580
Embodiment 4	?50～100	????1100	????780	????1.08	????2	????60	????95	????580	Embodiment 3	?50～100	????1100	????780	????1.15	????1	????55	????120	????580
Embodiment 4	?50～100	????1100	????780	????1.08	????2	????60	????95	????580	Embodiment 5	?50～100	????1100	????780	????1.10	????2	????70	????55	????580
Embodiment 6	?50～100	????1100	????780	????1.20	????1	????48	????173	????580	Embodiment 5	?50～100	????1100	????780	????1.10	????2	????70	????55	????580
Embodiment 6	?50～100	????1100	????780	????1.20	????1	????48	????173	????580	Embodiment 7	?50～100	????1100	????780	????1.05	????3	????62	????90	????580
Comparative example 1	?50～100	????1100	????780	????1.00	????0	????55	????0	????580	Embodiment 7	?50～100	????1100	????780	????1.05	????3	????62	????90	????580
Comparative example 1	?50～100	????1100	????780	????1.00	????0	????55	????0	????580	Comparative example 2	?50～100	????1100	????780	????1.00	????0	????55	????0	????580
Comparative example 3	?50～100	????1100	????700～800	????1.00	????0	????≥45	????0	????600	Comparative example 2	?50～100	????1100	????780	????1.00	????0	????55	????0	????580

Table 3

The steel sample	??YP ??MPa	??TS ??MPa	??δ ??％	?Akv(-20℃) ?????J	?Akv(-40℃) ????J	Welding flawless preheating temperature ℃	Welding heat analog parameter: T _max＝1350℃、t _8/5＝100s
							Welding heat analog parameter: T _max＝1350℃、t _8/5＝100s	????Akv(-40℃)/J
							Embodiment 1	????Akv(-40℃)/J	??852	??938	??25	????302	???233	????0	????93
Embodiment 2	??861	??950	??26	????289	???221	????0	Embodiment 1	????101	??852	??938	??25	????302	???233	????0	????93
Embodiment 2	??861	??950	??26	????289	???221	????0	Embodiment 3	????101	??867	??942	??25	????297	???245	????0	????85
Embodiment 4	??855	??952	??24	????311	???268	????0	Embodiment 3	????95	??867	??942	??25	????297	???245	????0	????85
Embodiment 4	??855	??952	??24	????311	???268	????0	Embodiment 5	????95	??868	??957	??26	????315	???229	????0	????88
Embodiment 6	??845	??928	??27	????298	???231	????0	Embodiment 5	????82	??868	??957	??26	????315	???229	????0	????88
Embodiment 6	??845	??928	??27	????298	???231	????0	Embodiment 7	????82	??857	??946	??26	????288	???243	????0	????91
Comparative example 1	??611	??736	??26	????251	???146	????0	Embodiment 7	????67	??857	??946	??26	????288	???243	????0	????91
Comparative example 1	??611	??736	??26	????251	???146	????0	Comparative example 2	????67	??598	??743	??25	????258	???168	????0	????73
Comparative example 3	??659	??810	??25	????192(0℃)	???190(20℃)	????50	Comparative example 2	21 (actual welding)	??598	??743	??25	????258	???168	????0	????73

As can be seen from Table 3: steel of the present invention not only yield strength and tensile strength than existing steel (comparative example 3-" Nippon Steel's skill newspaper " the 75th phase P43～50 in 1997) more than high 150MPa～200MPa; The low-temperature flexibility of main is steel of the present invention and weldability than existing steel excellence many, show as steel of the present invention and need not preheating, welded H AZ toughness height in welding more than 0 ℃; It can also be seen that the composition that adopts steel of the present invention simultaneously and the steel plate (comparative example 1 and comparative example 2) that does not adopt technology of the present invention to produce, though welding property does not change substantially, but the yield strength of steel plate and tensile strength reduce significantly and reach about 150MPa～200MPa, and the low-temperature flexibility of steel plate also decreases.

In sum, according to the present invention, adopt more a spot of alloy content, the carbon equivalent design of the carbon equivalent of promptly more common yield strength of 800 MPa Plate Steel low 0.10%～0.15% just can arrive the performance index that yield strength is 800MPa.Not only saved alloy content greatly, the content of noble element Ni, Mo, Cr especially, the content of Ni element has especially greatly improved the weldability (steel plate need not weld preheating, postweld heat treatment) of steel plate; And production cost and customer using cost have been reduced.Because the present invention does not need to add any equipment, production technique is simple, and process control is easy, can have the Heavy Plate Production producer that quickens cooling equipment to all and promote, and has very strong adaptability, the feature of environmental protection and high economy.

Claims

But 1. the superstrength Plate Steel of large-line energy welding, its composition (mass percent):

C????????0.01％～0.06％

Si???????0.10％～0.50％

Mn???????1.00％～1.40％

Nb???????0.010％～0.050％

V????????0.040％～0.090％

Cu???????0.60％～1.00％

Cr???????0.20％～0.50％

Mo???????0.20％～0.50％

Ni???????0.50％～0.80％

B????????5ppm～30ppm

Ti???????0.005％～0.020％

Al _s??????0.040％～0.070％

All the other are Fe and unavoidable impurities such as P, S;

Wherein, 0.065≤(%Cu * %V)≤0.085.
2. but the superstrength Plate Steel of large-line energy welding as claimed in claim 1 is characterized in that described C is preferably 0.03%～0.05%.
3. but the superstrength Plate Steel of large-line energy welding as claimed in claim 1 is characterized in that described Si is preferably 0.10%～0.30%.
4. but the superstrength Plate Steel of large-line energy welding as claimed in claim 1 is characterized in that described Nb is preferably 0.015%～0.030%.
5. but the superstrength Plate Steel of large-line energy welding as claimed in claim 1 is characterized in that described B is preferably 15ppm～20ppm.
6. but the superstrength Plate Steel of large-line energy welding as claimed in claim 1 is characterized in that described Ti is preferably 0.007%～0.012%
7. but the superstrength Plate Steel of large-line energy welding as claimed in claim 1 is characterized in that, can also contain Ca or rare earth REM; Ca≤0.01%, REM≤0.01%.
8. but the superstrength Plate Steel of large-line energy welding as claimed in claim 1 is characterized in that described P≤0.010%, S≤0.005%.
9. but the manufacture method of the superstrength Plate Steel of large-line energy welding comprises the steps:

A) casting technique is cast as slab with the molten steel of mentioned component, pouring temperature≤1580 ℃;

B) slab heating, heating and temperature control is at 1150 ℃～1200 ℃;

C) hot rolling adopts big rolling pass draft to be rolled, and in austenite non-recrystallization district, at least one passage adopts the asymmetrical rolling technology, control upper working rolls and lower working rolls velocity ratio 〉=1.05; Austenite non-recrystallization district accumulative total draft 〉=40%, percentage pass reduction 〉=10%;

D) deformation relaxation, the deformation relaxation temperature is at Ar ₃+ 60 ℃～Ar ₃+ 20 ℃ of some temperature ranges, deformation relaxation time t and austenite non-recrystallization accumulative total draft Ψ: lnt (s)=7.779-5.37 * 10 ^-2Ψ (%);

E) cooling, direct quenching, cool to room temperature.
10. but the manufacture method of the superstrength Plate Steel of large-line energy welding as claimed in claim 9 is characterized in that described step a casting technique is a continuous casting process.
11. but the manufacture method of the superstrength Plate Steel of large-line energy as claimed in claim 9 welding is characterized in that described step a pouring temperature≤1570 ℃.
12. but the manufacture method of the superstrength Plate Steel of large-line energy as claimed in claim 9 welding is characterized in that described step c hot rolling is more than rolling preferred 2 passages in austenite non-recrystallization district.