CN101481779B - High plasticity, high tenacity and ultra-high tensile steel, and manufacturing method thereof - Google Patents

Abstract

The invention discloses a steel with high plasticity, high toughness and high strength and a manufacturing method thereof. The components of the steel are as follows in terms of weigh percentage: 0.15 to 0.30 of C, 0.20 to 1.40 of Mn, 0.10 to 0.50 of Si, less than or equal to 0.015 of P, less than or equal to 0.012 of S, less than or equal to 0.20 of Ni, 0.40 to 1.50 of Cr, 0.50 to 1.00 of Mo, 0.05 to 0.10 of V, less than or equal to 0.2 of Cu, 0.01 to 0.05 of Al, 0.0005 to 0.0020 of B, and the balance of Fe and additional impurity elements. The manufacturing method comprises the following steps: smelting according to the formula, continuous casting into a blank, hot rolling into plates or tubes, quenching at the temperature of 875 to 930 DEG C for 25 to 40 minutes, tempering at the temperature of 625 to 675 DEG C for 30 to 90 minutes. The steel has yield strength of more than or equal to 1000MPa, tensile strength of more than or equal to 1100MPa, zero-degree-centigrade charpy impact work of more than or equal to 100J, specific elongation of 20 to 30 percent and is applicable to manufacture important structures of engineering machinery, high buildings and oil well pipes, and the like.

Description

High plasticity, high tenacity ultrahigh-strength steel and manufacture method thereof

Technical field

The present invention relates to a kind of manufacture method of ultrahigh-strength steel, particularly relate to a kind of super-refinement tempering lath martensite that in steel, forms with cleaning and be matrix, disperse distribution nano level precipitated phase and be feature heterogeneous structure, and therefore obtain the high-performance of multiple mechanical characteristics such as ultrahigh-strength steel, high-ductility and high tenacity, the manufacture method of low-cost ferrous materials.

Background technology

At present, ferrous materials remains the main body of structured material, it is the high-performance steel iron material and the key manufacture thereof of one that development has multifrequency natures such as collection superstrength, high-ductility and excellent low-temperature impact toughness etc., be satisfy modern important structure such as large-scale engineering machinery, Highrise buildings and harsh geology Service Environment oil well pipe to long-term safety, alleviate the important channel that deadweight and energy-saving and cost-reducing direction develop.It is generally acknowledged that in the world the structural steel of yield strength 〉=840MPa (120ksi) can be described as the superstrength structure iron, in the actual engineering sometimes in addition the yield strength of claimed structure steel reach more than the 1000MPa.How making this class steel reach other while of superstrength level, the low-temperature impact toughness with higher plasticity and excellence to satisfy structure to heavy duty, opposing impact and the adaptation requirement of displacement distortion greatly, is the research and development focus over past ten years.

In general, the intensity of steel and plasticity, toughness are usually expressed as the relation of growth and decline each other, and the high steel of intensity usually plasticity and toughness is just low, otherwise, for pursuing high plasticity and toughness, just must sacrifice the intensity of steel.Therefore, the development difficulty of high-ductility, high tenacity, ultrahigh-strength steel is very big, need carry out new exploration aspect the highly malleablized of ultrahigh-strength steel and the metallurgical means of strong plastifying.

Aspect the exploitation ultrahigh-strength steel, in order to improve intensity, utilize bainite or martensite as main tissue usually at present, utilize various refinement means simultaneously, expectation obtains higher intensity and toughness.This is carried out extensive exploration both at home and abroad, and formed multinomial achievement or patent.Analyzing this class achievement or the disclosed ultrahigh-strength steel of patent and relative manufacturing process thereof can find, they all exist a kind of of following many weak points or two kinds or two or more:

1) disclosed ultrahigh-strength steel is when utilizing the martensite of refinement/bainite structure to strengthen, though also reached higher low-temperature impact toughness, but unit elongation is generally not high, usually can only reach 10%-20%, generally less demanding to the plasticity index of the ultrahigh-strength steel that proposed, even do not propose any requirement.As the disclosed superstrength steel pipe of international monopoly " the superstrength low-carbon alloy steel pipe and the manufacture method thereof of low-temperature flexibility excellence " (publication number WO2005035800A1), its YIELD STRENGTH and tensile strength can reach 930MPa and 1000MPa respectively, ductile-brittle transition temperature is below-60 ℃, but unit elongation Jin ≧ 9%; As the disclosed a kind of ultrahigh-strength steel of domestic patent " non-tempering easy-welding super strong steel and production method thereof " (publication number CN101086015), though the yield strength of this steel has reached more than the 980MPa, and-60 ℃ of low-temperature impact works reach more than the 100J, but the plasticity of steel is on the low side, and unit elongation can not be stablized and reaches more than 20%.Disclosed a kind of superstrength Plate Steel of and for example domestic patent " ultrahigh-strength steel and manufacture method thereof " (publication number CN1888120A) or hot-rolled steel sheet with good solidity to corrosion and fatigue resistance, though YIELD STRENGTH and tensile strength can reach 880MPa respectively and more than the 980MPa, and-20 ℃ of ballistic works reach more than the 100J, but the plasticity of steel is obviously not enough, and unit elongation one labour is all below 20%.As the disclosed ultrahigh-strength steel plates of international monopoly " weldable high-tensile steel of excellent in low temperature toughness " (publication number CN1146784A), through adopting microalloying in conjunction with controlled rolling, though the tensile strength of material has reached more than the 950MPa, ductile-brittle transition temperature is below-85 ℃, but related right claim and embodiment be the unit elongation data of not mentioned material all, illustrate that this patent does not propose the plasticity index requirement to disclosed ultrahigh-strength steel; The disclosed superstrength sleeve pipe of and for example domestic patent " oil and gas exploitation middle-deep well, ultra deep well petroleum casing pipe and production method thereof " (publication number CN1619005A), though material yield strength and tensile strength can reach 966-1103MPa respectively and more than the 1034MPa, horizontal full-scale ballistic work reaches more than the 40J, but related right claim and embodiment be the unit elongation data of not mentioned material all, illustrate that the ultrahigh-strength steel of this patent disclosure does not claim to plasticity index.

2) though disclosed ultrahigh-strength steel has also reached higher plasticity, low-temperature impact toughness is obviously not enough.As the disclosed a kind of ultrahigh-strength low-alloy steel of domestic patent " ultrahigh-strength low-alloy steel " (publication number CN1390972), its YIELD STRENGTH and tensile strength can reach 860-1200Mpa and 1000-1300MPa respectively, unit elongation is 15-25%, but 0 ℃ of full-scale low-temperature impact work Jin ≧ 33J.

3) disclosed ultrahigh-strength steel plasticity and low-temperature impact toughness are all not enough.As the disclosed a kind of ultrahigh-strength steel of domestic patent " ultrahigh-strength sleeved petroleum pipe with special jointer for resisting squeeze and production method thereof ", though its yield strength and tensile strength can reach 896-1150Mpa He ≧ 970MPa respectively, unit elongation Jin ≧ 9%, 0 ℃ full-scale low-temperature impact work Jin ≧ 33J.

4) though disclosed ultrahigh-strength steel has also reached higher low-temperature flexibility, also may reach higher plasticity, cost of alloy is higher.As international monopoly " ultrahigh-strength steel " (publication number CN1282381A) disclosed a kind of superstrength low-temperature steel with excellent low-temperature flexibility, although the tensile strength of material can reach more than the 830MPa, after chemical ingredients is preferred, the tensile strength of material even can reach more than the 1000MPa, owing to improve the main means of material plasticity and low-temperature flexibility is to comprise the nickel that adds more than 1.0%, the nickel add-on of optimizing even more than 1.5%, improve the distortion of materials ability by the friendship slippage that promotes dislocation, but increased the alloy raw material cost thus.

This shows, the above-mentioned existing ultrahigh-strength steel or the plasticity deficiency of material, the low-temperature flexibility deficiency of material, the plasticity of material and low-temperature flexibility are all not enough, the alloy raw material cost is higher, and all not belonging to multifrequency natures such as collection superstrength, high-ductility and excellent low-temperature flexibility is the economical ferrous materials of high-performance of one.

At present aspect the exploitation Hi-Stren steel, in order to improve the plasticity of steel, usually take in steel, to form ferrite/perlite, ferrite/martensite, ferrite/bainite, residual austenite/bainite, the bainite/combined heterogeneous structures of different soft and hard such as M-A island, and by thermal treatment or control the plasticity that ratio that means such as cold respectively form phase with regulation and control improves steel.As the disclosed a kind of ferrite/martensite dual phase steel of domestic patent " a kind of two-phase steel with fine crystal grain heat treating method of producing " (publication number CN1039621A), after control two-phase region hot rolling or thermal treatment, the two-phase ratio that obtains is respectively 80% and 20%, yield strength and tensile strength reach about 500MPa and 750MPa respectively, and unit elongation is a little more than 20%.As the disclosed a kind of ferrite of domestic patent " manufacture method of low yield strength ultrafine grain belt steel " (publication number CN1928130A)/perlite dual phase steel, reach about 85% by controlling cold ferrite refinement and the ratio of making, yield strength and tensile strength reach about 295-415MPa and 460-510MPa respectively, and unit elongation reaches 26-40%.Document (Shang Chengjia etc., University of Science ﹠ Technology, Beijing's journal, 2003, Vol.25 (3): the 288-290) ultra-fine bainite/ferrite dual phase steel of Ti Chuing, ferrite accounts for 20%, through 680 ℃ of tempering after 1 hour, unit elongation can be stablized and reaches more than 25%, but yield strength and tensile strength only reach 720MPa and 780MPa.Document (Wang Xuemin etc., calendar year 2001 China Steel nd Annual Meeting collection, 859-872) the ultra-fine bainite/martensite dual phase steel of Ti Chuing, after 3 hours, yield strength and tensile strength reach 747MPa and 772MPa respectively through 675 ℃ of tempering, unit elongation only about 16%.Document (Zhang Pijun etc., Northeastern University's journal (natural science edition), 2006, Vol.27 (4): the 414-417) acicular ferrite/martensite dual-phase steel of Ti Chuing, by controlling the acicular ferrite that cold back obtains 10-30%, unit elongation can reach 23-29%, but yield strength and tensile strength only reach 550-610MPa and 740-840MPa respectively.Document (Dong Yun etc., Hebei University of Technology's journal, 2000, Vol.29 (1): the 67-70) residual austenite/bainite dual-phase steel of Ti Chuing is the residual austenite of 11-15% by obtaining content after the 350-400 ℃ of isothermal processes, and yield strength and tensile strength reach 800-1000MPa and 1300-1600MPa respectively, unit elongation can reach 20-30%, the low-temperature impact toughness of not mentioned this steel of the document, but since wherein carbon content estimate that up to 0.60-0.75% its low-temperature impact toughness may be not enough.According to another document (I.Nobuyuki etc., JFE Technical Report 2006, No.7:20-26) report, the Chinese People's Anti-Japanese Military and Political College's distortion ferrite/bainite and the bainite/M-A island dual phase steel of Japan JFE exploitation, though the homogeneous deformation unit elongation can reach respectively more than 16% and 12%, yield strength only reaches 460MPa respectively and more than the 530MPa.

Above-mentioned existing dual phase steel this shows, although all can reach higher plasticity.But the problem that exists is: or undercapacity, or the low-temperature impact toughness deficiency, same, they do not belong to multifrequency natures such as collection superstrength, high-ductility and excellent low-temperature flexibility yet is the economical ferrous materials of high-performance of one.

Summary of the invention

In order to solve the prior art above shortcomings, the invention provides a kind of high plasticity, high tenacity ultrahigh-strength steel and manufacture method thereof, satisfying modern important structure such as large-scale engineering machinery, Highrise buildings, harsh geology Service Environment oil well pipe to bearing heavy duty, opposing is impacted and adapt to the service requirements of big displacement distortion, and this method also must have noble metal nickel and consumes advantage less, that heat treatment time is short, production cost is lower.

For achieving the above object, manufacture method involved in the present invention may further comprise the steps: adopt smelting Technology for Clean Steel, by the alloying constituent that designs in advance, make the blank of various cross-sectional shapes such as slab or circle base; With after the blank heating through after the distortion such as rolling or drilling/rolling, obtain to have tabular or piped profile and size; Workpiece after being shaped is quenched after 25～40 minutes, carries out modified thermal treatment in the technology of 625 ℃～675 ℃ tempering air cooling after 30～90 minutes then by 875 ℃～930 ℃ insulations.By the above-mentioned relevant processing parameter of accurate control, the super-refinement tempering lath martensite that forms with cleaning in steel is that matrix, disperse distribution some amount nano level precipitated phase are the heterogeneous structure of feature, makes sheet material or tubing with above-mentioned multiple mechanical characteristic.

For achieving the above object, at first need to carry out well-designed and control to the chemical ingredients of the steel that the present invention relates to, wherein the mechanism of action of each alloying constituent is:

(1) carbon (C) carbon is a kind ofly can effectively improve intensity and alloying element with low cost.When carbon content was lower than 0.15%, for the sheet material or the tubing of above-mentioned requirements, hardening capacity was on the low side, was difficult to make the uniform tempered martensite of acquisition on the whole cross section of rolled piece by thermal treatment, thereby made intensity on the low side.When carbon content is higher than 0.30%, the toughness deficiency of steel, inaccessible obdurability coupling under superstrength.Therefore, carbon content should be controlled at 0.15～0.30%, and suitable carbon content scope should be 0.18～0.28%.

(2) manganese (Mn) manganese is a kind of element of hardening capacity of effective raising steel, can improve intensity and toughness simultaneously.But during the manganese too high levels, should in strand, form segregation, thereby in rolled piece, form banded structure, toughness is descended.Therefore, manganese content should be controlled at 0.20%～1.40%.Suitable manganese content range should be 0.40%～1.00%.

(3) silicon (Si) silicon is a kind of effective deoxidant element in steel-making, and can improve the intensity of steel.When silicone content is lower than 0.10%, the easy oxidation of steel, but its content surpasses at 0.50% o'clock, the toughness of infringement steel.Therefore, silicone content should be controlled at 0.10%～0.50%.Suitable silicone content scope should be 0.10%～0.40%.

(4) chromium (Cr) chromium is a kind of intensity, toughness and corrosion proof element that can improve steel in suitable interpolation scope simultaneously.When chromium content was lower than 0.40%, for the sheet material or the tubing of above-mentioned requirements, hardening capacity was on the low side, thereby makes intensity on the low side.When chromium content is higher than 1.50%, telescopic toughness deficiency, inaccessible obdurability coupling under superstrength.Therefore, chromium content should be controlled at 0.40～1.50%.Suitable chromium content range should be 0.40～1.10%.

(5) molybdenum (Mo) molybdenum be a kind of can effectively anti-temper softening, improve the element of the intensity of steel.Particularly in quenched and tempered steel during with the compound interpolation of chromium, strengthening effect is more obvious.When molybdenum content was lower than 0.50%, intensity was on the low side.When molybdenum content was higher than 1.00%, the cost of expensive alloys material significantly increased, and the toughness of steel obviously descends inaccessible obdurability coupling under superstrength.Therefore, molybdenum content should be controlled at 0.50%～1.00%, and suitable molybdenum content range should be 0.50%～0.80%.

(6) vanadium (V) vanadium is a kind of element that can improve the intensity of steel, even add 0.01% vanadium, just can play anti-temper softening.The add-on of vanadium generally about 0.10%, still, because ferro-vanadium is on the high side, has limited the highest add-on of vanadium, and therefore, suitable content of vanadium scope is 0～0.10%.

(7) nickel (Ni) nickel is a kind of intensity and flexible element that can improve steel simultaneously, particularly improves low-temperature flexibility.But, should not add even not add as far as possible because nickel is on the high side.Therefore, Shi Yi nickel content range be≤0.20%.

(8) copper (Cu) copper is a kind of anti-corrosion element, simultaneously, also can play solution strengthening () or precipitation strength effect (separating out ε-Cu particle during tempering) at≤0.20% o'clock in steel.Too high copper content easily causes hot-short, need add nickel simultaneously and suppress, and should limit its highest add-on or does not add, therefore, copper content should be controlled at≤and 0.20%.

(9) aluminium (Al) aluminium is to need the deoxidant element that adds in the steel-making, and inclusion is had Denaturation, forms stable tiny AlN precipitation particles in addition in steel, and the effect of crystal grain thinning is arranged.Therefore, Shi Yi aluminium content range is 0.01～0.05%.

Boron (B) adds the trace B of 5～20ppm in steel, can significantly increase the hardening capacity of low-carbon low-alloy steel, help when quenching, obtaining martensite or the hard phase of bainite, and can save valuable iron alloy resources such as chromium, molybdenum, vanadium, B can combine with N simultaneously, fixing free N is to reduce the timeliness embrittlement effect that N causes.Therefore, the boron content range in the steel can be controlled in 5～20ppm, and suitable boron content range is 8～20ppm.

Therefore, according to above-mentioned manufacture method, the high plasticity, high tenacity ultrahigh-strength steel that the present invention relates to, its chemical ingredients is (wt%): C:0.15～0.30, Mn:0.20～1.40, Si:0.10～0.50, P :≤0.015, S :≤0.012, Ni :≤0.20, Cr:0.40～1.50, Mo:0.50～1.00, V:0.05～0.10, Cu :≤0.2, Al:0.01～0.05, B:0.0005～0.0020, surplus is Fe and incidental impurity element.

The high plasticity, high tenacity ultrahigh-strength steel that the invention described above relates to, because of adopting the tempering process of accurate control quenched martensite, can make full use of the reinforcement that super-refinement tempering lath martensite/nano level precipitated phase heterogeneous structure brings, plasticizing and malleableize effect, therefore, can reduce the wherein add-on of valuable alloying element, reduce carbon content, improve the comprehensive mechanical property of steel, the chemical ingredients of its optimization is (wt%): C:0.18～0.28, Mn:0.40～1.00, Si:0.10～0.40, P :≤0.012, S :≤0.010, Ni :≤0.20, Cr:0.40～1.10, Mo:0.50～0.80, V:0.05～0.10, Cu :≤0.2, Al:0.01～0.05, B:0.0008～0.0020, surplus is Fe and impurity element.

High plasticity, high tenacity ultrahigh-strength steel and manufacture method thereof that the invention described above is related must adopt the Clean Steel smelting technology when blank is produced, this is one of key measure that improves the ultrahigh-strength steel low-temperature flexibility.After measures such as the control of comprehensive employing raw material, hot metal pretreatment, converter top and bottom complex blowing, ladle argon-blown refining, vacuum-treat, the processing of Ca/Si silk inclusion modification, should make the metallurgical quality of blank reach following requirement:

(1) the total content Xian Zhi Zai ≦ 70ppm of the total content Xian Zhi Zai ≦ 30ppm of oxygen, nitrogen in the steel, or oxygen nitrogen total amount Xian Zhi Zai ≦ 100ppm.

(2) hazardous elements S+P in the steel ≦ 0.025%, Pb+Sn+As+Sb+Bi ≦ 0.15%;

(3) content of steel inclusion is measured by ASTM E45 standard " dislike most slightly visual field method (method A) ".The high-content of inclusion is: carefully be inclusion Shui Ping ≦ 2; It slightly is inclusion Shui Ping ≦ 1.

High plasticity, high tenacity ultrahigh-strength steel and manufacture method thereof that the invention described above is related, its profile comprises the high performance structural member of different cross section shapes such as hot rolled plate and tubing, with blank through overheating deforming when obtaining needed shape and size, in the scope that the metallurgical technology equipment condition allows, should adopt controlled rolling as far as possible, promptly main suitably control blank heating temperature, distribute texturing temperature and deflection and roll the back water spray and cool off by pass sequence (or forging table).Its purpose mainly is a refinement deformation austenite crystal as far as possible, and obtains to roll uniformly the attitude tissue.Thermal distortion technology can adopt following canonical parameter: when producing sheet material, slab heating temperature is 1200 ℃～1250 ℃, and the roughing temperature is 1200 ℃～1250 ℃, and total draft is 60～70%; Final rolling temperature is 950 ℃～850 ℃, and deflection is 30～40%; Roll the back air cooling.When producing tubing, circle base Heating temperature is 1200 ℃～1250 ℃, after heat centering, is carrying out hot-puncturing process more than 1200 ℃, and deflection is 60～70%; Carry out hot continuous rolling at 1050 ℃～1150 ℃, deflection is 20～30%; Through 850 ℃～950 ℃ sizings, deflection is 10～20% again, and deflection can distribute between different passages according to the ability of milling train, but should make the deformation austenite in the steel that abundant recrystallize takes place as far as possible when rolling, avoids forming or residual shear zone.

High plasticity, high tenacity ultrahigh-strength steel and manufacture method thereof that the invention described above is related for obtaining super-refinement tempering lath martensite/nano level precipitated phase heterogeneous structure, must accurately be controlled the tempering process of quenched martensite.Specifically, need by control tempering temperature and tempering time, with regulation and control tempering lath martensitic width between 0.20～0.40 μ m, the percent by volume of precipitated phase between the 8-12%, the equivalent yardstick between 30-50nm, form is needle-like or the suitable parameter of organizing such as bar-shaped, be convenient to bring into play the hard phase of precipitated phase conduct, tempering lath martensite as soft synergy when being out of shape, thereby satisfy the requirement that steel of the present invention need possess comprehensive mechanical properties such as superstrength, high-ductility and excellent low-temperature impact toughness simultaneously.For steel of the present invention, when carrying out modified thermal treatment, suitable processing parameter is: 875 ℃～930 ℃ insulations were quenched after 25～40 minutes, then at 625 ℃～675 ℃ tempering air cooling after 30～90 minutes.

Description of drawings

Fig. 1 is the metallographic structure of high plasticity, high tenacity ultrahigh-strength steel.

Embodiment

The present invention is described in further detail below in conjunction with specific embodiment.

The high plasticity, high tenacity ultrahigh-strength steel that the present invention relates to, its chemical ingredients (wt%) is listed in table 1.

Table 1: the chemical ingredients of steel of the present invention (wt%)

Annotate: the unit of element chemistry compositions such as B, 0, N is ppm in the table.Residual element total amount Pb+Sn+As+Sb+Bi: ≦ 0.15.

Embodiment 1

Embodiments of the invention 1 are chosen sulphur, raw material that phosphorus content is low, adopt the 50Kg vacuum oven to smelt, and make chemical ingredients in the steel satisfy the requirement of table 1, and surplus is Fe and unavoidable impurities element.Adopt protection of inert gas to cast then, every stove waters two ingots, is the ingot casting mean diameter? 120mm.After the excision of ingot casting rising head, being made into thickness of slab on the 250mm milling train is that 12mm, width are the hot-rolled sheet of 200mm.Wherein, main hot rolling technology is: slab heating temperature is 1200～1250 ℃, and it is 1150～1180 ℃ that breaking down begins temperature, and the total draft of roughing is 60～70%, and the roughing end temp is 1020～1070 ℃.It is 930～980 ℃ that finish rolling begins temperature, and the total draft of finish rolling is 30～40%, and the finish rolling end temp is 850～870 ℃.Roll the back air cooling.Subsequently, take a sample on hot-rolled sheet, be processed into the test specimen that is of a size of 12mm * 12mm * 80mm, adopt two chamber type electric resistance furnaces to quench respectively and tempering by technology shown in the table 2, quenchant adopts saturated aqueous common salt.After the modifier treatment, the room temperature tensile performance in wale-wise of testing experiment steel and 0 ℃ of horizontal low-temperature impact work of full sample.The results are shown in Table 2.

Table 2: the quenching-and-tempering process of steel of the present invention and Mechanics Performance Testing result

As can be seen from Table 2, according to the steel plate of the inventive method preparation, as technology steel 6-12, the comprehensive mechanical property that all has superstrength, high-ductility and excellent low-temperature flexibility.And technology steel 1-5, although composition is identical with heat forming technology, because the tempering process difference, the intensity of steel and flexible coupling are then not as technology steel 6-12.

Embodiment 2

Embodiments of the invention 2 are chosen preprocessed molten iron+P, the low high-quality steel scrap of S content is as raw material, adopt 150 tons of electric furnaces to smelt, and Clean Steel smelting technologyes such as employing external refining, vacuum outgas (VD), inclusion modification and Argon stirring, make chemical ingredients in the steel satisfy the requirement of table 1, level of inclusions reaches above-mentioned requirements.Invention steel continuous casting being become outside dimension then is the round base of 310mm.During pipe perforation tandem rolling, the temperature of strict each technology of control.Strand is heated to 1250 ℃, and after heat centering, 1200～1250 ℃ of cross piercings, deflection is 60～70%; The tube rolling temperature range is controlled at 1100～1150 ℃, and deflection is 20～30%; The sizing temperature is controlled at more than the Ar3, and deflection is 10～20%, air cooling, sawing, once hot strong then, and straightening temperature is 500～600 ℃.Roll the attitude pipe behind 880～900 ℃ of heating, insulation 35min, in water-based hardening liquid, quench, then at 645～675 ℃ of air coolings after 45～75min insulation tempering.After the modified thermal treatment, carry out secondary heat and rectify, straightening temperature is 500～600 ℃.Body after the shaping is of a size of Φ 244.48mm * 15.11mm.The comprehensive mechanical property of sampling and testing steel pipe on production tube.The tensile performance in wale-wise of steel pipe is: yield strength 1030～1170MPa, tensile strength are that 1120～1260MPa, unit elongation are 20～30%, and 0 ℃ of horizontal full-scale charpy impact merit of steel pipe is 105～130J.

Claims (4)

1. high plasticity, high tenacity ultrahigh-strength steel, it is characterized in that: the chemical ingredients of described steel is (wt%): C:0.15～0.30, Mn:0.20～1.40, Si:0.10～0.50, P :≤0.015, S :≤0.012, Ni :≤0.20, Cr:0.40～1.50, Mo:0.25～1.35, V:0～0.10, Cu :≤0.2, Al:0.01～0.05, B:0.0005～0.0020, surplus is Fe and incidental impurity element, and wherein the high-content of inclusion is: carefully be level of inclusions≤2, slightly be level of inclusions≤1, the content of steel inclusion " is disliked slightly visual field method-A most " by ASTM E45 standard and is measured; The total content of oxygen is limited in≤total content≤70ppm of 30ppm, nitrogen, perhaps oxygen, nitrogen total amount≤100ppm; The residual element total amount is (wt%) Pb+Sn+As+Sb+Bi :≤0.15; Form lath martensite with 0.20～0.40 μ m submicron order width in the described steel and be matrix, disperse volume of distribution mark between the 8-12%, the heterogeneous structure of the nano level precipitated phase of equivalent yardstick between 30-50nm, yield strength 〉=1000MPa, tensile strength 〉=1100MPa, unit elongation are 20～30%, 0 ℃ of horizontal full-scale charpy impact merit 〉=100J.

2. according to the described high plasticity, high tenacity ultrahigh-strength steel of claim 1, it is characterized in that: the chemical ingredients of described steel is (wt%): C:0.18～0.28, Mn:0.40～1.00, Si:0.10～0.40, P :≤0.012, S :≤0.010, Ni :≤0.20, Cr:0.40～1.10, Mo:0.25～0.95, V:0～0.10, Cu :≤0.2, Al:0.01～0.05, B:0.0008～0.0020, [O+N] :≤0.010; Residual element total amount Pb+Sn+As+Sb+Bi :≤0.15, surplus is Fe and incidental impurity element; Yield strength 〉=1020MPa, tensile strength 〉=1120MPa, unit elongation are 24～30%, 0 ℃ of horizontal full-scale charpy impact merit 〉=100J.

3. method of making the described high plasticity, high tenacity ultrahigh-strength steel of claim 1 is characterized in that:

(1) molten steel of employing converter or electrosmelting low-sulfur, phosphorus content further after external refining, vacuum outgas and inclusion modification are handled, adopts continuous cast method to cast slab or circle base;

When (2) producing sheet material, slab heating temperature is 1200 ℃～1250 ℃, and the roughing temperature is 1200 ℃～1250 ℃, and total draft is 60～70%; Final rolling temperature is 950 ℃～850 ℃, and deflection is 30～40%; Roll the back air cooling; When producing tubing, circle base Heating temperature is 1200 ℃～1250 ℃, after heat centering, is carrying out hot-puncturing process more than 1200 ℃, and deflection is 60～70%; Carry out hot continuous rolling at 1050 ℃～1150 ℃, deflection is 20～30%; Through 850 ℃～950 ℃ sizings, deflection is 10～20% again, air cooling, sawing, once hot strong then, and straightening temperature is 500～600 ℃;

(3) carry out modified thermal treatment after being shaped, its technology is: 875 ℃～930 ℃ insulations were quenched after 25～35 minutes, and then 625 ℃～675 ℃ tempering after 30～90 minutes, air cooling, secondary heat are rectified, and straightening temperature is 500～600 ℃.

4. method of making the described high plasticity, high tenacity ultrahigh-strength steel of claim 2 is characterized in that:

(1) molten steel of employing converter or electrosmelting low-sulfur, phosphorus content further after external refining, vacuum outgas and inclusion modification are handled, adopts continuous cast method to cast slab or circle base;

When (2) producing sheet material, slab heating temperature is 1200 ℃～1250 ℃, and the roughing temperature is 1200 ℃～1250 ℃, and total draft is 60～70%; Final rolling temperature is 950 ℃～850 ℃, and deflection is 30～40%; Roll the back air cooling; When producing tubing, circle base Heating temperature is 1200 ℃～1250 ℃, after heat centering, is carrying out hot-puncturing process more than 1200 ℃, and deflection is 60～70%; Carry out hot continuous rolling at 1050 ℃～1150 ℃, deflection is 20～30%; Through 850 ℃～950 ℃ sizings, deflection is 10～20% again, air cooling, sawing, once hot strong then, and straightening temperature is 500～600 ℃;

(3) carry out modified thermal treatment after being shaped, its technology is: 875 ℃～930 ℃ insulations were quenched after 25～35 minutes, and then 625 ℃～675 ℃ tempering after 30～90 minutes, air cooling, secondary heat are rectified, and straightening temperature is 500～600 ℃.

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