CN101906591B - Ultra high strength ship plate steel and production method thereof - Google Patents

Abstract

The invention discloses ultra high strength ship plate steel and a production method thereof. A plate blank comprises the following components in percentage by weight: 0.02-0.09 percent of C, 0.1-0.4 percent of Si, 0.5-1.6 percent of Mn, 0.01-0.04 percent of Alt, 0.02-0.05 percent of Nb, 0.008-0.02 percent of Ti, 0.3-0.7 percent of Cr, 0.2-0.5 percent of Mo, 0.5-1 percent of Ni, 0.2-1 percent of Cu, less than 0.013 percent of P, less than 0.005 percent of S, less than 0.0012 percent of O, less than 0.0045 percent of N, less than 0.00015 percent of H and the balance of Fe and inevitable impurities. The production method comprises the following steps of heating the plate blank with the thickness of 220-300 mm before rolling at the temperature of 1250 DEG C; starting rough rolling at the starting temperature of not less than 1100 DEG C; starting finish rolling at the temperature of not more than 910 DEG C, and stopping finish rolling at the temperature of 870-890 DEG C; rolling a steel plate with the thickness of 10-60 mm; rapidly entering ACC to control cooling at the cooling speed of 8-12 DEG C/s after finish rolling; returning red at the temperature of 650-680 DEG C; and temperingfor 90-180min at the temperature of 500-680 DEG C. The product has good comprehensive mechanical property.

Description

A kind of ultra high strength ship plate steel and working method thereof

Technical field

The present invention relates to a kind of HSLA, specifically a kind of ultra high strength ship plate steel and working method thereof.

Background technology

Boats and ships to maximize, high speed direction Development Trend, make and make ship steel and must possess HS, H.T., thick specification, resistance to corrosion seawater, be prone to weld and characteristics such as good processability.Produce satisfied (spy) thick specification, simultaneously again can proof strength, index, good low-temperature flexibility and the weldableness of plasticity make ship steel, strong technical guarantee and power support will be provided for the develop rapidly of shipbuilding industry.

At present, in the production of the deck of boat steel widespread use controlled rolling and controlled cooling technology.Through appropriate design alloying element content and controlled rolling and controlled cooling parameter; Realize strengthening mechanisms such as phase transformation strengthening, refined crystalline strengthening and subgrain reinforcement like finishing temperature, final cooling temperature and rate of cooling etc.; Compensation is because the solution strengthening loss that carbon drop brings improves intensity and toughness.The controlled rolling and controlled cooling The Application of Technology reduces deck of boat steel production cost greatly, but for the thicker deck of boat, the product that adopts cooling controlling and rolling controlling process to obtain is organized usually inhomogeneous, influences the use of material.

Heat treating regime after rolling has remarkably influenced to the microstructure of low-carbon bainite steel and the behavior of separating out; And types of organization, various organize proportion, structure refinement degree with second mutually the behavior of separating out etc. of particle determined the final mechanical property of low-carbon bainite steel jointly; Thereby heat treating regime is one of key factor that further improves such steel comprehensive mechanical property; At present; For the high intensity levels deck of boat steel of ys, also explicitly call in some external classification society rules and adopt the delivery of QT state greater than 500MPa.Adopt the rational heat treatment system to have crucial meaning for the potentiality of giving full play to low-carbon bainite steel.Adopting controlled rolling and controlled cooling technology+subsequent heat treatment operation (TMCP+QT) can make ferrous materials obtain optimum properties, is effective way of the thick deck of boat of production HS (spy).

Summary of the invention

In order to overcome the not enough problem of the toughness and tenacity that adopts the thick specification ultra high strength ship plate steel of control control refrigeration technique production (spy) to exist; The purpose of this invention is to provide a kind of ultra high strength ship plate steel and working method thereof; The product that the present invention produces not only toughness and tenacity is good, and possesses good comprehensive performances.

The objective of the invention is to realize through following technical scheme:

A kind of ultra high strength ship plate steel is characterized in that: the chemical ingredients mass percent is in this ultra high strength ship plate steel: C 0.02-0.09%, Si 0.1-0.4%, Mn 0.5-1.6%, Al 0.01-0.04%; Nb 0.02-0.05%, Ti 0.008-0.02%, Cr 0.3-0.7%, Mo 0.2-0.5%; Ni 0.5-1%, Cu 0.2-1%, P＜0.013%, S＜0.005%; O＜0.0012%, N＜0.0045%, H＜0.00015%, all the other are Fe and inevitable impurity.The upper content limit of tramp element is controlled at S＜0.002% and is advisable in the steel.

Steel grade of the present invention mainly be organized as granular bainite.In the granular bainite forming process, the ferritic of separating out from supercooled austenite is lath-shaped at first and has higher dislocation desity, removes in the tissue outside the ferritic structure, also exists a large amount of tiny M-A island.Because the M-A island is the hard phase, when these M-A islands be when separating out with the mode of small and dispersed they can with dislocation generation interaction, hinder the motion of dislocation, promptly improve the intensity of steel through the mode of dispersion-strengthened.Therefore, steel grade of the present invention is the intensity that improves steel through refined crystalline strengthening, dislocations strengthening, 3 kinds of modes of dispersion-strengthened jointly.The M-A island is distributed in ferrite lath inside in low-carbon (LC) granular bainite tissue, and tiny ferrite lath has littler effective grain-size, can stop the expansion of crackle effectively.The M-A island that these disperses distribute is tiny and approximately be spherical, and with second comparing of having sheet, angular shape, spherical second more can reduce stress concentration mutually, becomes the germinating source of crackle and the low-yield diffusion admittance of crackle in the time of can avoiding rupturing.In addition; When the M-A island is to distribute with discontinuous mode in matrix, have between island and the island certain apart from the time because the centre is the lath ferritic with excellent toughness; Crackle more is difficult for expansion, so the formation of the continuous extended channel of crackle has been avoided on discontinuously arranged M-A island.Therefore, the existence on M-A island can guarantee certain toughness and plasticity when increasing hardness of steel.

Consider from three aspects during the composition design: low carbon content is adopted for guaranteeing the good welds performance in (1); (2) come proof strength through adding alloying element cu, Cr, Mo; (3) add the low-temperature performance that alloying element Ni guarantees steel.

Based on above tissue design, in the selection of composition, the present invention adopts the Mo-Cu-Nb-B compound action, can realize HS, H.T., weldability and resistance to corrosion seawater a small amount of the interpolation under other alloying element conditions.

The combined action of Mo, Nb, Cu and B is following: ferritic transformation is significantly postponed in Mo and B combined action; Nb and B mutually promote, the compound transition temperature that adds fashionable reduction bainite, and further thinning microstructure improves dislocation desity in the matrix; The proeutectoid ferrite that Cu and B federation further suppress before the bainite transformation generates; Cu can make the carbide high-temp strain of Nb induce and separate out acceleration, and recrystallize stops temperature and raises, and helps carrying out controlled rolling of non-recrystallization zone and further refinement phase transmutation product.

A kind of working method of ultra high strength ship plate steel is characterized in that this working method comprises desulfurizing iron, converter top and bottom blowing, vacuum-treat, continuous casting, controlled rolling and controlled cooling, and temper, concrete process step is:

(1) will satisfy the molten steel casting that chemical ingredients requires and become the 220-300mm heavy slab; Roll the luggage stove heating of advancing, heating zone and soaking zone temperature are 1220-1260 ℃, rate of heating 8-10min/cm, heat-up time 200-400min;

(2) in the roughing operation, start rolling temperature>=1100 ℃, roughing finishing temperature>=1000 ℃; Intermediate blank treats that temperature thickness is 96-150mm; Finish rolling start rolling temperature≤910 ℃, 870-890 ℃ of finish rolling finishing temperature;

(3) entering ACC control is cold fast after the finish rolling, cooling rate 8-12 ℃/s;

(4) return red temperature: 650-680 ℃; Tempering temperature: 500-680 ℃, time 90-180min obtains ultra high strength ship plate steel.

The present invention adopts controlled rolling and controlled cooling technology+subsequent heat treatment operation to produce ultra high strength ship plate steel, and the ultra high strength ship plate steel that obtains possesses good comprehensive performances, because of carbon equivalent is low, can weld.Mechanical property R _EH＞550MPa, R _m＞670MPa, cross direction elongation A＞20% ,-60 ℃ of summers, Z was to stretching relative reduction in area＞35% than the horizontal value＞200J of impact absorbing energy, and cold-bending property is good.

Description of drawings

Fig. 1 is the top layer metallographic structure figure of ultra high strength ship plate steel according to the invention.

Fig. 2 is the metallographic structure figure of heart portion of ultra high strength ship plate steel according to the invention.

Embodiment

Embodiment

A kind of F550 ultra high strength ship plate steel, composition is by weight percentage: C 0.067, and Si 0.16, and Mn 1.51, and P 0.01; S 0.002, and Al 0.01, and Nb 0.026, and Ti 0.012, and Cr 0.3; Mo 0.3, and Ni 0.7, and Cu 0.7, and all the other are Fe and inevitable impurity.

A kind of working method of above-mentioned F550 ultra high strength ship plate steel, the smelting technology aspect adopts converter steelmaking, and the dark decarburization of top bottom blowing is adopted the further decarburization of RH vacuum-treat, and is carried out alloying.

Smelt and be cast into the 220mm heavy slab by above composition; Slab is sent into process furnace, 1250 ± 10 ℃ of Heating temperatures, heat-up time 300min; Tapping temperature >=1180 ℃, the roughing start rolling temperature is 1160 ℃, roughing finishing temperature >=1000 ℃; Intermediate blank is treated temperature thickness 96mm; 910 ℃ of finish rolling start rolling temperatures, 890 ℃ of finish rolling finishing temperatures; It is cold to get into the ACC control after the finish rolling fast, cooling rate 8-12 ℃/s; Return 680 ℃ of red temperature, product thickness 60mm.This slab is sent into process furnace carry out tempering, 550 ℃ of tempering temperatures, tempering time 100min obtains the F550 ultra high strength ship plate steel.

Fig. 1 is the top layer metallographic structure figure of ultra high strength ship plate steel according to the invention, and Fig. 2 is the metallographic structure figure of heart portion of ultra high strength ship plate steel according to the invention.Can know that by figure surface of steel plate and the metallographic structure of heart portion are the granular bainite tissue.The toughness and tenacity of ultra high strength ship plate steel is good, high comprehensive performance, R _EH=610MPa, R _m=705MPa, cross direction elongation A=20.5% ,-60 ℃ of summers reach more than the 200J than the horizontal value of impact absorbing energy, and all more than 35%, cold-bending property is good to the stretching relative reduction in area for Z.

Claims (1)

1. the working method of a ultra high strength ship plate steel is characterized in that this working method comprises desulfurizing iron, converter top and bottom blowing, vacuum-treat, continuous casting, controlled rolling and controlled cooling, and temper, concrete process step is:

(1) will satisfy the molten steel casting that chemical ingredients requires and become the 220-300mm heavy slab; Roll the luggage stove heating of advancing, heating zone and soaking zone temperature are 1220-1260 ℃, rate of heating 8-10min/cm, heat-up time 200-400min; The chemical ingredients mass percent is in this molten steel: C 0.02-0.09%, Si 0.1-0.4%, Mn 0.5-1.6%, Al0.01-0.04%; Nb 0.02-0.05%, Ti 0.008-0.02%, Cr 0.3-0.7%, Mo 0.2-0.5%; Ni 0.5-1%, Cu 0.2-1%, P＜0.013%, S＜0.002%; O＜0.0012%, N＜0.0045%, H＜0.00015%, all the other are Fe and inevitable impurity;

(2) in the roughing operation, start rolling temperature>=1100 ℃, roughing finishing temperature>=1000 ℃; Intermediate blank treats that temperature thickness is 96-150mm; Finish rolling start rolling temperature≤910 ℃, 870-890 ℃ of finish rolling finishing temperature;

(3) entering ACC control is cold fast after the finish rolling, cooling rate 8-12 ℃/s;

(4) return red temperature: 650-680 ℃; Tempering temperature: 500-680 ℃, time 90-180min obtains ultra high strength ship plate steel.

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