CN101481780B - Easy-to-weld superfine austenite crystal steel with superhigh intensity and high tenacity and manufacturing method thereof - Google Patents

Easy-to-weld superfine austenite crystal steel with superhigh intensity and high tenacity and manufacturing method thereof Download PDF

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CN101481780B
CN101481780B CN2008100800711A CN200810080071A CN101481780B CN 101481780 B CN101481780 B CN 101481780B CN 2008100800711 A CN2008100800711 A CN 2008100800711A CN 200810080071 A CN200810080071 A CN 200810080071A CN 101481780 B CN101481780 B CN 101481780B
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steel
temperature
austenite crystal
weld
intensity
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CN101481780A (en
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王青峰
淡婷
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燕山大学
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Abstract

The invention discloses an ultra-thin austenitic grained steel with ultrahigh strength, high toughness and easy welding and a manufacturing method thereof. The steel comprises the following components by weigh percentage: 0.04- 0.14% of C, 0.50- 1.42% of Mn, 0.10- 0.50% of Si, not more than 0.010% of S, not more than 0.015% of P, 0.10-0.15% of Ni, 0.03-0.29% of Cr, 0.08-0.34% of Mo, 0.030-0.060% of V, 0.10- 0.30% of Cu, 0.010- 0.050% of Al, 0.010- 0.050% of Ti, 0.020-0.046% of Nb, 0.0005- 0.0020% of B, and the balance of Fe and impurities, satisfying carbon equivalent CEQ<=0.60%, and crack sensitivity index PCM<=0.30%. The manufacturing method comprises the following steps: low-temperature short-time tempering pretreatment, short-time heat preservation after extremely fast and integral heating to more than Ac3, then holding the temperature, and extremely fast quenching to the room temperature. The austenitic grain of the steel has the average size of less than or equal to 6.5Mum, the yield strength of more than or equal to 840MPa, the tensile strength of more than or equal to 945MPa and tough-brittle transition temperature of less than or equal to minus 60 DEG C. The method is particularly suitable for heat treatment of working pieces with thin specification.

Description

Ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel and method of manufacture thereof

Technical field

The present invention relates to a kind of ultra-fine grain steel and method of manufacture thereof; Particularly relate to a kind of superfine austenite crystal steel and method of manufacture thereof with multifrequency natures such as superstrength, excellent low-temperature flexibility, good welds property, this method can be used for the manufacturing of thin specification high performance structural members such as latten, thin-wall seamless steel pipe, thin axial workpiece.

Background technology

At present, ferrous materials remains the main body of structured material, and welding remains main structure ME.To have multifrequency natures such as superstrength, excellent low-temperature flexibility and good welds property be the high-performance steel iron material and the key manufacture thereof of one in development, be satisfy modern important structure 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 ys >=840MPa (120ksi) can be described as the superstrength structure iron.How making this type steel reach other while of superstrength level, satisfied requirement to low-temperature flexibility and weldableness is the research and development focus over past ten years.

As everyone knows, in multiple intensifying technologys such as solution strengthening, precipitation strength, phase transformation strengthening and working hardening, have only crystal grain thinning, could improve the intensity and the toughness of steel simultaneously.Wherein, refine austenite crystal grain is especially remarkable to increasing substantially the effect of material at low temperature flexible.Because realizing the essential condition of grain refining is to improve the nucleus nucleation rate and suppress growth rate.Therefore; At present aspect exploitation high-performance superstrength structure iron, what extensively take is to be multimedia material toughening technologies such as core, integrated use are low-carbon alloyed, microalloying design, recrystallize controlled rolling (RCR), heat machinery control processing (TMCP), acceleration cooling with control deformation austenite recrystallization.This is carried out extensive exploration both at home and abroad, and formed multinomial patent.

Analyzing disclosed superstrength structure iron of this type 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) requires to add valuable alloying elements such as a large amount of Cr, Mo, Ni, Cu in the steel,, increased the alloy resource cost though reached the corresponding strength rank.Like international monopoly " superstrength low-carbon alloy steel pipe and method of manufacture thereof that low-temperature flexibility is excellent " (publication number WO2005035800A1), require the actual content of chromium in the steel, molybdenum to reach 0.55~0.80% and 0.30~0.50% respectively; The patent JP60121219 of Sumitomo Metal Industries and JP89025371, requiring the nickel content in the steel is 1.00~3.00%, chromium content is 0.40~1.20%; Baosteel patent " but superstrength Plate Steel and method of manufacture thereof of large-line energy welding " (application number 200410017255.5), requiring nickel content is 0.50~0.80%, copper content is 0.50~0.80%; Wuhan Iron and Steel Plant patent " ultrahigh-strength steel and method of manufacture thereof " (publication number CN1888120A) with good solidity to corrosion and fatigue resistence, requiring to reach nickel content simultaneously is 0.30~0.80%, and copper content is 0.25~0.80%, and molybdenum content is 0.20~0.50%; The patent WO200039352 of Exxonmobil company, nickel content requirement >=1.0% in the steel; Another patent of the said firm " working method of the welding ultrahigh-strength steel plates that ultralow-temperature flexibility is excellent " (publication number CN1390960A), requiring Mo content is 0.30~0.70%.

2) require to adopt after the recrystallization zone controlled rolling low temperature rolling with roll back cooling fast, though reached the corresponding strength rank too, and reduced the alloy consumption, to metallurgical technology Equipment Requirement harshness, in fact increased equipment and process cost.Like above-mentioned patent WO200039352, require to roll the online speed of cooling in back 10 ℃/more than the s; Above-mentioned patent CN1390960A requires finishing temperature to be lower than 850 ℃; Above-mentioned patent CN1888120A, require finishing temperature be 780~850 ℃ and roll the back cooling rate be 15~35 ℃/s.

3) require the carbon content in the steel higher, though favourable to reaching the superstrength rank, diminish the welding property of steel.Like above-mentioned patent WO2005035800A1, requiring the carbon content scope is 0.06~0.18%; Disclosed Chinese patent " above ultrahigh-strength steel plates of ys 960MPa and method of manufacture thereof " (publication number CN184072A) and " above ultrahigh-strength steel plates of ys 1100MPa and method of manufacture thereof " (publication number CN1840723A), all requiring the carbon content scope is 0.08~0.20%.Because carbon content and carbon equivalent are higher, for avoiding producing the welding metallurgy defective, the measure that is absolutely necessary of processing parameters such as strict control preheating temperature and interlayer temperature, thus make the increase of structure manufacturing cost.

This shows; The alloy designs of above-mentioned existing superstrength structure iron and relative manufacturing process; Be unfavorable for all that with lower cost and resource consumption obtaining multifrequency natures such as collection superstrength, excellent low-temperature flexibility and good welds property is the high-performance steel iron material of one.

The another kind of method of refine austenite crystal grain is to utilize direct resistive heating or induction heating; Workpiece is heated to certain austenitizing temperature with speed faster; Behind isothermal treatment for short time, quench; To reach the purpose of refine austenite crystal grain, this also there is the report of relevant achievement and patent both at home and abroad.Developed a kind of manufacturing technology of superfine austenite crystal medium carbon alloy steel bar in 2006 like Japanese JFE company, after adopting extremely fast thermal cycling to quench, the austenite crystal mean sizes reaches 2~3 μ m.Chinese patent (publication number CN1045996A) is for shortening carburizing (or carbonitriding) time of steel; Proposed to utilize " chemical thermal treatment by several times and short cycle method " of resistance (or induction) heating; This method also can reach the purpose of refine austenite crystal grain when carrying out rapid carburization.Chinese patent " a kind of continuous induction heat treatment process for high-strength finish-rolled spiral steel bar " (publication number CN1453375A); Introduced in a kind of being applicable to carbon Cr-Mo-V Twisted Steel roll the back continuously induction quenching+tempering heat treatment, after replacing original rolling, wear water cooling+self-tempering technology, thereby solve the method for product performance fluctuation problem.This shows; Though above-mentioned achievement or patent have all adopted the quenching process of direct resistive heating or induction heating, all do not relate to have superstrength simultaneously, H.T., be prone to the high-performance steel iron material and the method for manufacture thereof of multifrequency natures such as welding and superfine austenite crystal.

Summary of the invention

The object of the present invention is to provide a kind of ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel and method of manufacture thereof, said steel can be used for the manufacturing of thin specification high performance structural members such as latten, thin-wall seamless steel pipe and thin axial workpiece.Said method of manufacture have alloy resource consume less, heat treatment time is short, workpiece deformation is little, the oxidation and decarbonization layer thin and the lower advantage of production cost.

For realizing above-mentioned purpose, method of manufacture of the present invention may further comprise the steps: adopt smelting Technology for Clean Steel, process the blank of various cross-sectional shapes such as square billet, slab or circle base; With after the blank heating through after the distortion such as rolling, forging or drilling/rolling, obtain to have the profile and the size of tabular, bar-shaped or weldless steel tube; With the workpiece after being shaped at Ac 1Following temperature tempering 2~30 minutes; Adopt direct resistive heating or induction heating mode, workpiece is heated to actual Ac with the speed of 100~500 ℃/s 3More than 50~100 ℃, soaking time is no more than 60 seconds, quenches with the cooling rate of 50~500 ℃/s then; The workpiece that will pass through quench treatment is at Ac 1Below temperature tempering 2~30min or without temper; Make thin gauge sheet metal, bar and tubing with above-mentioned multifrequency nature.

For achieving the above object, need 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 carbon is a kind of cheap element that improves the intensity of steel.When carbon content is lower than 0.04%, inaccessible certain intensity; But when carbon content was higher than 0.14%, the toughness and the weldableness of steel significantly reduced.Therefore, carbon content should be controlled at 0.04~0.14%.

(2) manganese manganese is a kind of element of hardening capacity of effective increase steel, therefore also improves intensity and toughness.When manganese content is lower than 0.50%, inaccessible needed strength level; When manganese content is higher than 1.75%, can produce tangible segregation banded structure, toughness is descended.Therefore, manganese content should be controlled at 0.50~1.75%.

The most effective one of deoxidant element when (3) silicon silicon is a kind of steel-making, and can improve the intensity of steel.When silicone content was lower than 0.10%, steel was prone to oxidation; When silicone content was higher than 0.50%, the toughness and the weldableness of steel all reduced.Therefore, silicone content should be controlled at 0.10~0.50%.

(4) toughness of sulphur sulphur heavy damage steel.Therefore, sulphur content should be controlled at below 0.010%.

(5) toughness of phosphorus phosphorus heavy damage steel.Therefore, phosphorus content should be controlled at below 0.015%.

(6) boron adds the trace B of 5~20ppm in steel, can significantly increase the hardening capacity of low-carbon low-alloy steel, helps when quenching, obtaining martensite or the hard phase of bainite, and can save valuable iron alloy resources such as chromium, molybdenum, vanadium.In addition, because the electric steel nitrogen content is higher, when existing in steel with free nitrogen form, can cause the timeliness embrittlement of steel, boron can also be as nitrogen killer, to suppress the disadvantageous effect of nitrogen.

(7) nickel nickel is a kind of element that significantly improves the low-temperature flexibility of steel, and still, nickel is a kind of noble metal.Therefore, under the existing situation fully more than needed of low-temperature flexibility, nickel content is limited in below 0.50%.

(8) chromium chromium is a kind of intensity, toughness and corrosion proof element that significantly improves steel.But when chromium content was higher than 1.0%, the toughness of welded heat affecting zone obviously descended.Therefore, chromium content should be controlled at≤1.0%.

(9) the molybdenum molybdenum is a kind ofly to stop temper softening, effectively improve the element of the intensity of steel.But molybdenum-iron is a kind of valuable iron alloy, is necessary to limit its highest addition.Therefore, molybdenum content should be controlled at≤0.80%.

(10) the vanadium vanadium is a kind of element of intensity of effective raising steel, even add a spot of vanadium, also can stop the temper softening of steel.But vanadium iron also is a kind of valuable iron alloy, is necessary to limit its highest addition.Therefore, content of vanadium should be controlled at≤0.10%.

(11) copper copper is a kind of corrosion proof element that significantly improves steel, but because of its costliness, is difficult for adding, and therefore, copper content should be controlled at 0.10~0.30%.

(12) even titanium adds a spot of titanium in steel, the also effective tissue of refinement steel improves the toughness and the welding property of steel.Suitable titanium content should be controlled at 0.010~0.050%.

(13) aluminium adds aluminium in steelmaking process, can reduce the inclusion content in the steel, and crystal grain thinning.Suitable aluminium content is 0.010~0.050%.

(14) niobium adds≤0.050% Nb in steel, and its effect is the austenitic grain-size of remarkable refinement deformation, improves the hardening capacity of steel during modifier treatment, and through Nb separating out or secondary hardening when the tempering, improves the temper resistance and the intensity of steel.

(15) other elements and span of control thereof are in other residual element steel: tin (Sn)≤0.05%; Antimony (Sb)≤0.05%; Plumbous (Pb)≤0.05%; Arsenic (As)≤0.05%; The total amount of residual element is controlled by following requirement in the steel: Sn+Sb+Pb+As≤0.15%

Therefore, according to above-mentioned method of manufacture, the ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel that the present invention relates to, its chemical ingredients is (wt%): C:0.04~0.14; Mn:0.50~1.75, Si:0.10~0.50, S :≤0.010, P :≤0.015; Ni :≤0.50, Cr :≤1.00, Mo :≤0.80, V :≤0.10; Cu:0.10~0.30, Al:0.010~0.050, Ti:0.010~0.050; Nb :≤0.050, B:0.0005~0.0020, surplus is Fe and incidental impurity element.

According to the chemical ingredients of above-mentioned ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel, the carbon equivalent C of this steel EQ(%)≤0.60, welding crack Sensitivity Index P CM(%)≤0.30.C EQWith press P CMCalculate like following formula respectively:

C EQ(%)=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15;

P CM(%)=C+(Mn+Cr+Cu)/20+Si/30+Mo/15+Ni/60+V/10+5B;

The ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel that the invention described above relates to because of adopting extremely fast thermal cycling quenching technology, can make full use of reinforcement and malleableize effect that the austenite crystal super-refinement brings, therefore; Can reduce the wherein add-on of valuable alloying element, reduce carbon content and carbon equivalent, improve the welding property of steel, the chemical ingredients of its optimization is (wt%): C:0.04~0.12; Mn:0.70~1.60, Si:0.10~0.45, S :≤0.008, P :≤0.012; Ni :≤0.35, Cr :≤0.75, Mo :≤0.60, V:0.01~0.08; Cu:0.10~0.30, Al:0.010~0.050, Ti:0.010~0.040; Nb :≤0.050, B:0.0008~0.0020, surplus is Fe and incidental impurity element.According to the chemical ingredients of the ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel of above-mentioned optimization, the carbon equivalent C of this steel EQ(%)≤0.50, welding crack Sensitivity Index P CM(%)≤0.28.

Ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel and method of manufacture 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, make the metallurgical quality of blank reach following requirement:

(1) in the steel total content of oxygen be limited in≤total content of 30ppm, nitrogen is limited in≤60ppm, or oxygen nitrogen total amount is limited in≤90ppm.

(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 level of inclusions≤2; It slightly is level of inclusions≤1.

Ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel and method of manufacture thereof that the invention described above is related; Its profile comprises the structural part of various high-performance such as latten, thin-wall seamless steel pipe, axle class formation spare, thin specification; 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 or control to forge as far as possible, promptly main suitably control blank heating temperature, distribute texturing temperature and deflection and roll the back and spray water and cool off by pass sequence (or forging table).Its purpose mainly is a refinement deformation austenite crystal and roll (forging) attitude tissue uniformly as far as possible.Thermal distortion technology can adopt following canonical parameter: with blank heating to 1200~1250 ℃, carry out the thermal distortion of multi-pass then.Roughing or rough forge temperature are 1150~1200 ℃, and deflection is 60~70%; Finish rolling or finish forge temperature are 850~950 ℃, and deflection is 30~40%.The back acquisition that is shaped has tabular, bar-shaped or piped profile and size.

Ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel and method of manufacture thereof that the invention described above is related, its rolled piece or forging generally also need carry out one temper before carrying out extremely fast the thermal cycling induction quenching.Reason is: rolling attitude or forging in the attitude tissue, often form the bainite and/or the martensitic stucture that are distributed with the residual austenite film between lath, in quenching heat-processed because of organizing genetic phenomenon to be difficult for the tiny austenite crystal of acquisition.The tempered purpose is that the residual austenite film is decomposed, thereby avoids when quenching heating, forming thick austenite crystal.For guaranteeing the effect of temper, tempering temperature is chosen in 500~650 ℃, and tempering time is 5~30 minutes.

Ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel and method of manufacture thereof that the invention described above is related; For obtaining the austenite crystal of super-refinement; Must be to the rolled piece or the forging that will pass through above-mentioned temper; Adopt direct resistive heating or induction heating to carry out fast austenitizing in short-term, rapid quenching cooling then.The key parameter of extremely fast thermal cycling quench treatment comprises rate of heating, austenitizing temperature, soaking time and the quench cooling rate that is described below.

(1) the general requirement rate of heating is 100~500 ℃/s.With the raising of rate of heating, the superheating temperature of austenitic transformation increases, and nucleation rate improves, and the degree of austenite crystal refinement increases thereupon.When rate of heating increase to 100 ℃/when s is above, can obtain the austenite crystal of super-refinement.

(2) the general requirement austenitizing temperature finishes about 50 ℃~100 ℃ temperature of transition point for surpassing actual austenite.With the raising of rate of heating, the superheating temperature of austenitic transformation increases, and austenite actual beginning transition point and end transition point all are higher than the equilibrium phase height of steel.Answer strictness to choose and control austenitizing temperature, cross when low, will be unfavorable for organizing homogenizing with composition like this temperature; When too high, will be unfavorable for the refinement of austenite crystal like this temperature.

(3) general requirement austenitizing soaking time is no more than 60 seconds.Soaking time is too short, will be unfavorable for the homogenizing of composition; Soaking time is long, will be unfavorable for the control of refinement, oxidation and decarbonization and the workpiece deformation degree of austenite crystal.

(4) the general requirement quench cooling rate is 50~500 ℃/s.Cooling rate to be exceedingly fast is quenched; Its purpose has two: one, limits growing up of austenite crystal in good time, and the 2nd, improve the condensate depression of austenite continuous cooling transformation strongly, suppress pro-eutectoid and change; Promote thin ferrite bainite or martensitic transformation, make steel of the present invention obtain the uniform tissue state.

Ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel and method of manufacture thereof that the invention described above is related, after quenching through thermal cycling extremely fast, generally can be according to request for utilization, whether select tempering as final thermal process status.As need tempering, generally can adjust its obdurability matching status when making steel reach the superstrength rank through choosing and control tempering temperature and tempering time.

Description of drawings

The metallographic structure of Fig. 1 ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel.

Embodiment

Below in conjunction with specific embodiment ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel and the method for manufacture thereof that the present invention relates to are done further to describe in detail.

The ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel, its chemical ingredients 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, O, N is ppm in the table.Pb+Sn+As+Sb+Bi≤0.15%。

The method of manufacture and the implementation result thereof of these several kinds invention steel are following:

Embodiment 1

Invention steel 1 adopts dark desulfurization of molten iron and preparatory dephosphorizing technology; Make S≤0.005, P≤0.015 in the molten iron; In 150 tons of converters, carry out top bottom blowing, molten steel passes through vacuum-treat again after Argon is handled; Make chemical ingredients in the steel satisfy the requirement of table 1, surplus is Fe and unavoidable impurities element.Molten steel further is cast into the slab of 240mm * 1450mm section, on the 2150mm milling train, is made into the hot-rolled sheet that thickness of slab is 3-12mm then.Wherein, main hot continuous rolling production technique is: slab heating temperature is 1150~1200 ℃, and it is 1120~1180 ℃ that roughing begins temperature, and the total draft of roughing is 60~70%, and the roughing end temp is 1000~1050 ℃.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 850~920 ℃.Roll the back and adopt the laminar flow cooling, and batch at 530~650 ℃.Get the hot-rolled sheet that thickness of slab is 12mm, be processed into the workpiece that cross dimensions is 10mm * 60mm after, adopt induction heating to carry out extremely fast thermal cycling and quench.

Embodiment 2

Invention steel 2 is chosen sulphur, raw material that phosphorus content is low, adopts the 50Kg vacuum oven to smelt, and makes 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; The ingot casting mean diameter is with after the excision of ingot casting rising head, forges the bar that becomes again.Main forging process is: blank is through 1150~1200 ℃ of heating, and it is 1120~1180 ℃ that rough forge begins temperature, and the total draft of rough forge is 60~80%, and the rough forge end temp is 1000~1050 ℃.It is 930~980 ℃ that finish forge begins temperature, and the total draft of finish forge is 20~40%, and the finish forge end temp is 850~950 ℃.The forging air cooling carries out the tempering of 520 ℃ * 10min again after room temperature.The long bar that makes of intercepting 1000mm adopts induction heating to carry out extremely fast thermal cycling and quenches.

Embodiment 3

Invention steel 3 adopts the 500Kg electric furnaces to smelt, and steelmaking feed is chosen sulphur, fine fodder that phosphorus content is low.The chemical ingredients of molten steel is after the fast branch in stokehold satisfies the requirement of table 1; Adopt protection of inert gas to cast; Every stove waters an ingot; Ingot casting is of a size of with after the excision of ingot casting rising head, forges the bar that becomes .After operations such as cross piercing, tandem rolling and sizing, bar is processed into the weldless steel tube of diameter 52mm * wall thickness 4.2mm.Main tube-rolling technique parameter is: blank carries out cross piercing after 1200~1250 ℃ of heating, and deflection is 60~70%; Carry out tube rolling at 1150~1100 ℃ then, carry out tension force at 850~900 ℃ and decide tube reducing, deflection is 30~40%.The steel pipe air cooling carries out the tempering of 550 ℃ * 10min again after room temperature.The long weldless steel tube that makes of intercepting 1000mm adopts induction heating to carry out extremely fast thermal cycling and quenches.

Extremely fast thermal cycling quenching that invention steel 1~3 adopts and tempering process parameters, austenite average grain size statistics and Mechanics Performance Testing result see table 2.Wherein welded heat affecting zone (HAZ) flexible evaluation method is: adopt earlier Gleeble3500 trier simulation welding coarse grain zone tissue, the Thermal Cycle parameter comprises 1350 ℃ of maximum heating temperatures, 800~500 ℃ t cooling time accordingly 8/5It is 25 seconds; Charpy impact merit during then according to " the GB/T229-1994 metal summer is than test with notched test piece method " test simulation welding coarse grain zone-20 ℃.In addition, limited because of the thin-wall seamless steel pipe size, therefrom the intercepting standard carries out the test of ballistic work.In the present invention, adopt the hydraulic bursting test method that the normal temperature and the serial low temperature fracture behaviour of steel pipe are estimated, and combine the scanning electron microscopic observation of fracture, confirmed its corresponding ductile-brittle transition temperature.

Table 2: extremely fast thermal cycling quenching technology, microstructure and the Mechanics Performance Testing result of steel of the present invention

Can find out,, all to have the austenite crystal, superstrength of super-refinement, excellent low-temperature flexibility like invention steel 1-1~1-4,2-1,2-2,3-1 and 3-2 etc. according to the steel plate of the inventive method preparation from table 2; Invention steel 1-1~1-4,2-1 and 2-2 also have good HAZ toughness; And comparative steel 1-1,2-1 and 3-1 etc.; Although composition is identical with the foregoing invention steel respectively with heat forming technology, different because of quenching technology, corresponding microstructure and mechanical property all are inferior to the foregoing invention steel.

Claims (5)

1. ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel, it is characterized in that: the chemical ingredients of said steel is by weight percentage: C:0.04~0.14%, Mn:0.50~1.42%; Si:0.10~0.50%, S :≤0.010%, P :≤0.015%; Ni:0.10~0.15%, Cr:0.03~0.29%, Mo:0.08~0.34%; V:0.030~0.060%, Cu:0.10~0.30%, Al:0.010~0.050%; Ti:0.010~0.050%, Nb:0.020~0.046%, B:0.0005~0.0020%; Surplus is Fe and incidental impurity element, and wherein the content of inclusion is: carefully being level of inclusions≤2, slightly is 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 the total content of oxygen≤0.0030%, nitrogen≤0.0060%, the perhaps total content of oxygen and nitrogen≤0.0090%; Residual element total amount Pb+Sn+As+Sb+Bi :≤0.15%.
2. a kind of ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel according to claim 1; It is characterized in that: the original austenite average grain size of said steel≤6.5 μ m; Ys>=840MPa; Tensile strength>=945MPa, ductile-brittle transition temperature≤-60 ℃, carbon equivalent is C by weight percentage EQ≤0.60%, the welding crack Sensitivity Index is P by weight percentage CM≤0.30%, C EQAnd P CMCalculate by following formula respectively:
C EQ(%)=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15;
P CM(%)=C+(Mn+Cr+Cu)/20+Si/30+Mo/15+Ni/60+V/10+5B。
3. ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel according to claim 1 and 2 is characterized in that: the chemical ingredients of said steel is by weight percentage: C:0.04~0.12%, Mn:1.26~1.42%; Si:0.10~0.45%, S :≤0.008%, P :≤0.012%; Ni:0.10~015%, Cr:0.03~0.29%, Mo:0.08~0.34%; V:0.050~0.060%, Cu:0.12~0.24%, Al:0.010~0.050%; Ti:0.010~0.040%, Nb:0.020~0.046%, B:0.0008~0.0020%, the total content of oxygen and nitrogen≤0.0090%; Pb+Sn+As+Sb+Bi :≤0.10%, surplus is Fe and incidental impurity element; The original austenite average grain size of said steel≤5.2 μ m, ys>=980MPa, tensile strength>=1050MPa, tough-crisp transition temperature≤-60 ℃, carbon equivalent C EQ≤0.50%, welding crack Sensitivity Index P CM≤0.28%.
4. method of making claim 1 or 2 described ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steels is characterized in that: said method comprising the steps of:
(1) adopts smelting Technology for Clean Steel, process the blank of square billet, slab or circle base cross-sectional shape;
(2) with after the above-mentioned blank heating through rolling, forge or the cross piercing distortion after, obtain required tabular, bar-shaped or piped profile and size;
(3) tabular, the bar-shaped or tubular workpiece after will being shaped is at Ac 1Following temperature is carried out temper;
(4) adopt direct resistive heating or induction heating mode, tabular, bar-shaped or tubular workpiece is heated to actual Ac with the speed of 100~500 ℃/s 3More than 50~100 ℃, soaking time is no more than 60 seconds, 50~500 ℃/s of quench cooling rate is reduced near room temperature the temperature of steel rapidly; Tabular, bar-shaped or not tempering of tubular workpiece after the quenching is perhaps at Ac 1Following temperature tempering is in short-term processed and is satisfied the finished product that use properties requires.
5. method of making the described ultrahigh-intensity high-toughness easy-to-weld superfine austenite crystal steel of claim 3 is characterized in that: said method comprising the steps of:
(1) adopts smelting Technology for Clean Steel, process the blank of square billet, slab or circle base cross-sectional shape;
(2) with blank heating to 1200~1250 ℃, carry out the thermal distortion of multi-pass then; Roughing or rough forge temperature are 1150~1200 ℃, and deflection is 60~70%; Finish rolling or finish forge temperature are 850~950 ℃, and deflection is 30~40%; The back acquisition that is shaped has tabular, bar-shaped or piped profile and size;
(3) workpiece after will being shaped was 500~650 ℃ of tempering 2~30 minutes;
(4) adopt direct resistive heating or induction heating mode, the workpiece that will pass through temper is heated to 1000 ℃ with the speed of 200 ℃/s, and the residence time under this temperature is no more than 30 seconds; Then it is immersed in the water-based hardening liquid and quench, drop near room temperature 100~500 ℃/s of quench cooling rate, the not tempering of workpiece after quench treatment up to temperature.
CN2008100800711A 2008-12-06 2008-12-06 Easy-to-weld superfine austenite crystal steel with superhigh intensity and high tenacity and manufacturing method thereof CN101481780B (en)

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