CN101812632B - Preparation method of -40 to -60DEG C low-temperature impact toughness hot rolled H-shaped steel - Google Patents
Preparation method of -40 to -60DEG C low-temperature impact toughness hot rolled H-shaped steel Download PDFInfo
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Abstract
The invention relates to below -40 to -60DEG C low-temperature impact toughness hot rolled H-shaped steel and a preparation method thereof, which are characterized in that the steel components in percentage by weight (weight percentage) are as follows: C: less than or equal to 0.20, Mn: 0.80 to 1.70, Si: less than or equal to 0.55, P: less than or equal to 0.20, S: less than or equal to 0.020, Nb: 0.010 to 0.070, Ni: 0.30 to 0.90, B: 0.0003 to 0.0080, and the balance Fe and trace impurities. During the smelting process, the gas content in the steel is controlled to be as follows: (N): less than or equal to 40ppm, and (O) is less than or equal to 60ppm. A near-terminal abnormal continuous casting billet or a rectangular billet is adopted. The invention is applicable to the below -40 to -60DEG C low-temperature impact toughness hot rolled H-shaped steel and the preparation thereof, and the below -40 to -60DEG C impact performance stability of a V-shaped sample exceeds 27J. On the basis of stably providing performance, the invention is characterized by alloy use amount saving and low cost.
Description
Technical field
The present invention relates to have under the hot-rolled state H shaped steel of special purpose, particularly be higher than national standard and be lower than-40 ℃ of requirements and reach low-cost H shaped steel of-60 ℃ of temperature low-temperature impact toughness requirements and preparation method thereof.
Technical background
H shaped steel is a kind of novel economizer structural steel.The economical rationality of H shaped steel cross-sectional shape, mechanical property is good, and the each point extension is even on the cross section when rolling, internal stress is little, compares with common joist steel, has the advantage that modulus of section is big, in light weight, save metal, can make building structure alleviate 30～40%; Parallel because of the outside in its leg again, the leg end is the right angle, and assembling combination becomes member, can practice thrift welding, the riveting work amount reaches 25%.It is big to be usually used in the requirement bearing capacity, the heavy construction of cross section good stability (like factory building, Highrise buildings etc.), and bridge, boats and ships, handling machinery, Equipment Foundations, support, foundation pile etc.H shaped steel is labor and material saving significantly, reduces starting material, the energy and artificial consumption, and unrelieved stress is low, and outward appearance and surface quality are good; Engineering construction speed is fast, and floor space is little, and is suitable for all-weather construction, receives weather influence little.Be about 2～3 times of concrete structure construction speed with the speed of application of the steelwork of hot rolled H-shaped making, asset turnover significantly improves, and reduces financial expense, thereby reduces investment outlay.
Because the uniqueness of vast in territory, the geographical conditions of China, have north and south latitude difference, the thing height above sea level characteristics that differ greatly or the like, in high latitude, high altitude localities, the requirement of structural steel impact flexible need reach about-60 ℃; All there are hot rolled H-shaped satisfied-60 ℃ of impelling strength requirements of requirement oil platform construction at sea in addition, polar region exploitation, military use or the like special use aspect; The structure iron hot-rolled product of producing according to Europe superscript requires-50 ℃ of ballistic works, and for example according to pressing steel grade steel grade S275NL, the S355NL series that EN10027-1 and CR 10260 produce, S275ML, S355ML, S420ML, S460ML series require-50 ℃ of ballistic works; Grades of steel such as day mark SLA325, SLA365 require-55 ℃ of ballistic works.
Obtain the technique means that hot rolling guarantees low-temperature impact toughness H shaped steel product, mainly contain two kinds of approach at present, a kind of is to realize refined crystalline strengthening through controlled rolling and controlled cooling in the rolling process, reaches the purpose that guarantees low-temperature impact toughness; Another kind is to reach the high purpose of low-temperature impact toughness through alloying constituents such as the nickel that adds the assurance low-temperature impact toughness, molybdenums.The tangible deficiency that these two kinds of approach all exist, controlled rolling and controlled cooling refined crystalline strengthening technology are very difficult to control aborning, to milling train require high, temperature control is difficult to realize and qualification rate is lower, and is big to the rhythm of production influence simultaneously, is not suitable for continuous batch production; Second kind of approach is that a large amount of nickel of interpolation, molybdenum alloy reduce low-temperature impact toughness significantly, but because nickel molybdenum cost is too high, economic production is difficult to realize.After taking boron niobium micro-alloy recombining process, low-temperature impact toughness has satisfied-40 ℃ of performance requriementss, but hot rolled H-shaped for the low-temperature impact toughness that is lower than-40 ℃ of low temperature requirements, can not satisfy performance requriements.Seek to produce that a kind of to be lower than-40 ℃ to-60 ℃ low-temperature impact toughness H shaped steel stable and low production cost extremely important; And have great economy and social benefit; Perfect to Chinese H shaped steel product changed to iron and steel power by big steel country China and to have great realistic meaning.
Require at present to be lower than-40 ℃ of hot rolled H-shaped low-alloy high-tensile structural steels that are generally to-60 ℃ of low-temperature impact toughness requirements, wherein wider with the Q345 level applications, being higher than other other low-alloy high-tensile structural steels of Q345 level also has application.With the Q345 rank is example explanation, and Q345 has that comprehensive mechanical property is good, and welding property, hot and cold processing characteristics and corrosion resisting property are all good, and C, D, E level steel require to have good low-temperature flexibility, and for example GB/T 1591-94 requires the Q345E steel vertically to be lower than-40 ℃ of A
KV>=27J.At present, mainly take niobium, vanadium, titanium micro-alloyedization and controlled rolling and controlled cooling process combined to improve steel over-all properties, particularly low-temperature impact toughness to Q345 rank low-alloy high-tensile structural steel.Its strengthening mechanism is precipitation strength and refined crystalline strengthening, and the latter also is useful to toughness.In the actual industrial production process of Q345 rank H shaped steel, through niobium, vanadium, titanium is single or combination microalloying and cooling controlling and rolling controlling process after, be lower than-40 ℃ of A
KVFluctuation is big and qualification rate is not high.H shaped steel is because the shape more complicated; Moulding process is definite basically, malleable pass deformation not, thereby adopt the controlled rolling temperature more and roll the back controlled chilling; Consider the restriction of mill load and the complicacy of controlled chilling, the operability that improves steel performance through cooling controlling and rolling controlling process is lower.
Summary of the invention
To the deficiency of prior art, the present invention provide a kind of and be lower than-40 ℃ hot rolled H-shaped and preparation method thereof until 60 ℃ of low-temperature impact toughness, the present invention is applicable to and is lower than-40 ℃ until-60 ℃ of hot rolled H-shaped and preparing methods of low-temperature impact toughness.
Summary of the invention
Through changing the hot rolled H-shaped chemical ingredients of the above rank of Q345, improve microstructure, thereby improve the mechanical property, particularly low temperature impact properties of the above rank H shaped steel of Q345.With the tough target that turns to of metal, on the basic ingredient of Q345 steel, add the low-temperature impact toughness that boron and nickel element improve the above steel grade of Q345 rank.
Detailed Description Of The Invention
The present invention is with hot rolled H-shaped as the basis more than the Q345 rank that does not need special thermal treatment; Consider in conjunction with actual steel-making controllability and quality product; Through on the steel grades basis, optimizing the steel composition, obtain a kind of H shaped steel with good low temperature impelling strength, technical scheme is following:
A kind of-40 ℃～-60 ℃ low-temperature impact toughness are hot rolled H-shaped, and the composition of steel weight percent is (%) as follows:
C:0.01～0.20, Mn 0.80～1.70, and Si 0.01～0.55, P≤0.020, S≤0.020, Nb 0.010～0.070, and Ni 0.30～0.90, and B 0.0003～0.0080, and surplus is Fe and trace impurity.
Preferably, composition of steel weight percent (%) as follows:
C 0.10～0.18, and Mn 1.00～1.40, and Si 0.10～0.40, P≤0.015, and S≤0.015, Nb 0.015～0.060, and Ni 0.30～0.70, and B 0.0005～0.0025, and surplus is Fe and trace impurity.
Preferably, composition of steel weight percent (%) as follows:
C 0.12～0.16, and Mn 1.20～1.35, and Si 0.15～0.30, P≤0.015, and S≤0.010, Nb 0.015～0.030, and B 0.0005～0.0020, and surplus is Fe and trace impurity.
Preferably, composition of steel weight percent (%) as follows:
| Impact temperature | C | Si | Mn | P | S | Ni | Nb | B |
| -50℃ | ≤0.20 | 0.01～ 0.55 | 0.80~1.70 | ≤ 0.020 | ≤ 0.020 | 0.30~0.85 | 0.010～0.060 | 0.0003～ 0.0050 |
| -55℃ | ≤0.20 | 0.01～ 0.55 | 0.80~1.70 | ≤ 0.015 | ≤ 0.015 | 0.30~0.85 | 0.010～0.070 | 0.0003～ 0.0080 |
[0019]?
| ?-60℃ | ≤0.20 | 0.01～ 0.55 | 0.80~1.70 | ≤ 0.015 | ≤ 0.015 | 0.40~0.90 | 0.010～0.070 | 0.0003～ 0.0080 |
Surplus is Fe and trace impurity.
A kind of-40 ℃～-60 ℃ hot rolled H-shaped preparing methods of low-temperature impact toughness is characterized in that the composition of steel weight percent is (%): C 0.01～0.20; Mn 0.80～1.70, and Si 0.01～0.55, P≤0.020; S≤0.020, Nb 0.010～0.070, and Ni 0.30～0.90; B 0.0003～0.0080, and surplus is Fe and trace impurity.In the smelting process, gas content in the control steel: (N)≤40ppm, (O)≤60ppm; Continuously cast bloom adopts special-shaped continuous casting steel billet in nearly terminal or rectangle steel billet; Protection of adjustment continuous casting and process for cooling use the big water-coating port thickened sealing ring after improving, and casting process is carried out total process protective casting; Bale slag-blanking detection alarm pattern adopts highest level, opens mouth of a river automatic closing function, closes the mouth of a river after the warning immediately, prevents down slag; Tundish adopts alkaline covering agent to combine carbonization rice husk to cover; Three streams all adopt the ST-SP/BM-HM covering slag; The secondary cooling water table is selected according to producing section, avoids surface crack to produce; The steel rolling heating and temperature control is at 1200～1260 ℃, and steel rolling breaking down temperature is controlled 1100～1150 ℃, and finishing temperature is controlled at the austenitic area between 850～920 ℃, rolls the back and adopts air cooling to room temperature.
Preferably, among said-40 ℃～-60 ℃ hot rolled H-shaped preparing methods of low-temperature impact toughness, above-mentioned composition of steel weight percent is (%): C 0.08～0.20; Mn 1.00～1.60, and Nb 0.015～0.070, and B 0.0005～0.0080; Si 0.10～0.55, P≤0.015, S≤0.015; Ni 0.30～0.90, and B 0.0003～0.0080, and surplus is Fe and trace impurity.
Preferably, in the smelting process, gas content in the control steel: (N) be controlled at≤0.0035%, and (O) be controlled at≤and 0.0050%.
In the smelting and the operation of rolling of this steel grade, other technology and parameter can use the method for prior art to carry out.
Indicate through experiment, through the boron of adding minute quantity, the performance of ability remarkably influenced material, there is advantageous effect in trace B to steel toughness.For the influence to rolling technology of the boron that reduces to add as far as possible, the present invention conservatively is limited to boron content in 0.0003%～0.0080% scope.
Trace B is to steel flexible advantageous effect:
(1) suppresses the brilliant fracture in phosphorus, sulphur segregation and edge
Along the boron of brilliant segregation can reduce phosphorus, sulphur the segregation of crystal boundary and cause along brilliant fracture, significantly improve low-temperature flexibility, this is because boron has suppressed the result that phosphorus, sulphur can improve the crystal boundary bonding force to the reduction and the boron self of crystal boundary.
(2) improve the form and the distribution of inclusion
After adding the boron processing,, be adsorbed on sulfide, oxide surface because boron is surface active element; Stop to be mingled with further and grow up, make to be mingled with tiny, the rounding that becomes, be uniformly distributed in crystal boundary; Basically eliminate the II type and be mixed in crystal boundary and gather partially, strengthened crystal boundary, reduced stress raisers; Suppressed crack initiation, reduced crack propagation velocity, toughness of material is improved.
(3) effect of increase niobium, further crystal grain thinning
Boron adds in the niobium steel, has increased the resistance to austenite recrystallization, and this boron that mainly comes from strain inducing gathers partially.Because boron can reduce the crystal boundary spread coefficient of niobium, so boron has increased the effect of dragging of niobium to crystal boundary after adding the niobium steel.The compound obstruction to recrystallize of the microalloy of boron and niobium also derives from the formation of Nb, B mixture, and such mixture is present on the new crystal boundary, has increased the solute effect of dragging power of niobium atom, has reduced interfacial migration speed and recrystallize motivating force.This will help further crystal grain thinning.
(4) add chemical ununiformity, the refinement styloid that boron helps reducing continuously cast bloom, the final metallographic structure (like the thin perlite that looses) that forms the best alleviates the age hardening effect simultaneously.
(5) nickel: add nickel (Ni) steel is strengthened, improve the low-temperature performance, particularly toughness of steel, can also improve the hardening capacity of steel.
Description of drawings
Fig. 1 is embodiment 1 each steel grade A
Kv-t curve.X-coordinate is a temperature, unit ℃; Ordinate zou is the J of unit.
Embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is further specified, but be not limited thereto.
The Q345 chemical ingredients (heat analysis) of GB/T 1591-94 regulation: (%)
C≤0.18, Mn 1.00～1.60, Si≤0.55, P≤0.025, S≤0.025, V 0.02～0.15, Nb0.015～0.060, Ti 0.02～0.20, Al>=0.015, surplus is Fe and trace impurity.
Carbon: be most important composition in the steel, the carbon amount increases steel Medium pearlite amount and increases, and 50%FATT is risen.Therefore aborning for the toughness that improves material often is employed in the interior carbon content that reduces of composition range that this steel grade allows, then manganese content remedies consequent strength degradation in the composition by increasing.
Manganese: be very important alloy element.Manganese can enlarge the austenite phase region, makes A
4Point raises, A
3Point descends.Because A
3Temperature descends, and proeutectoid ferrite is separated out and refinement under lower temperature.Equally, because A
3Temperature descends, and has suppressed carbide and on the supercooled austenite crystal boundary, has separated out, and makes steel keep higher plasticity, and reduces the toughness-brittle transition temperature of steel, and therefore, manganese also is the main alloy element in the low-temperature steel.
Silicon: be main added elements in China's low alloy steel.Silicon in steel, do not form carbide and solid solution in ferritic, the solution strengthening effect is very strong, is only second to carbon, nitrogen, phosphorus and surpasses other elements, thereby improve the intensity and the hardness of steel significantly, reduces the toughness of steel simultaneously, improves fracture appearance transition tem.
Phosphorus: be the detrimental impurity in the steel.Because its segregation tendency is serious, just can work the mischief at fewer content state.Phosphorus is very harmful to the low-temperature performance of ferrous materials, generally believes that at present phosphorus is the main arch-criminal who causes the low temperature brittleness of steel.The segregation tendency of phosphorus in steel is more serious, causes banded structure, makes the mechanical property of steel inhomogeneous, and particularly those Cryogenic Steel, marine steel and anti-hydrogen induced cracking steel require phosphorus content less than 0.01% or 0.005%.
Sulphur: the detrimental impurity that is (except that free-cutting steel) in most steel grades.The segregation coefficient of sulphur in steel is maximum in all elements, if be segregated in crystal boundary, can cause that low temperature is along crystalline substance fracture and high-temperature embrittlement.Increase inclusion particle, be easy to cause inclusion crack, use characteristics and use properties are all suffered damage.For aviation with steel, oil and natural gas line of pipes steel, offshore production platform with steel etc., must strict control sulphur content, to guarantee necessary toughness.
Niobium, vanadium, titanium: a large amount of microalloy elements, particularly niobium that use have outstanding effect to the obdurability that improves material in controlled rolling at present.Make it in steel, to form carbon, nitrogen and carboritride, be utilized under the various conditions and produce dissolving and separate out mechanism and play and suppress grain growth and produce the precipitation strength effect, in controlled rolling, the former is particularly important.Its effect shows: hinder original austenite grains during (1) heating and grow up; (2) grain growth behind inhibition recrystallize and the recrystallize in the operation of rolling; (3) when low temperature, play the effect of precipitation strength.
Aluminium: use as reductor.
Boron: the application of boron in steel mainly concentrates on the hardening capacity of trace B raising steel (ULCB steel and heat-treated steel), improves the toughness of steel through the tissue (lower bainite or tempered sorbite etc.) that obtains to have uniformly good comprehensive mechanical properties; Trace B improves the hot strength and the creep property of high temperature steel, improves the hot workability of stainless steel and high temperature steel; In soft steel, add boron, boron content is 3～5 times of traditional boron steel, and its steel rolling cooling control technology adopts slow cooling, and does not adopt the strong cold technology of traditional boron steel, its objective is the work hardening ability that reduces steel, rather than improves its obdurability; Then the wear resistance of utilizing the boride raising material of boron formation in high boron alloyed steel; Boron is also influential to the form and the distribution of as-cast structure, crystal boundary bonding force and inclusion.
Nickel: domestic and international research shows that nickel (Ni) can make steel strengthen, and improves the low-temperature performance, particularly toughness of steel, can also improve the hardening capacity of steel.
Table 1 is by the ys of different-alloy element raising and the mean ratio of tensile strength
Table 2 alloying element is to technically pure iron intensity and flexible influence
*Stove is cold to be 130, and air cooling is 300.
Consult document both domestic and external and obtain, be lower than-40 ℃ operating mode and adopt nickel series low-temperature steel more, and be lower than under-40 ~-60 ℃ the situation, Cryogenic Steel generally adopts the 0.5Ni steel.Its performance index all can reach, and ballistic work AKV is greater than the requirement of 27J in the time of-60 ℃.
Embodiment 1:
Nickel boron alloy Q345H shaped steel, the composition of steel weight percent is (%) as follows:
C≤0.18, Mn 1.00～1.60, Si≤0.25, P≤0.020, S≤0.010, Nb 0.010～0.070, and Ni 0.30～0.70, and B 0.0003～0.0060, and surplus is Fe and trace impurity.
Use steel by the smelting trial of above-mentioned Q345 steel optimized composition.Technical process: hot metal pretreatment → 120 ton combined blown converter → LF refining → casting for shaped blank continuous (whole process protection cast) → heating → de-scaling → rolling → cooling; Converter smelting notes controlling P content in the steel, and LF refining controlling inclusion content of steel reduces gas content (O)≤50ppm in the steel, (N)≤35ppm; Continuously cast bloom adopts special-shaped continuous casting steel billet in nearly terminal or rectangle steel billet, and continuous casting adopts the full guard casting; Use the big water-coating port thickened sealing ring after improving, casting process is carried out total process protective casting; Bag slag detection alarm pattern down adopts highest level, opens mouth of a river automatic closing function, closes the mouth of a river after the warning immediately, prevents down slag; Tundish adopts alkaline covering agent to combine carbonization rice husk to cover; Three streams all adopt the ST-SP/BM-HM covering slag; The secondary cooling water table is selected according to producing section, avoids surface crack to produce; Control strand cooling, steel rolling heating and temperature control be at 1200～1260 ℃, and 1100～1150 ℃ of steel rolling breaking down temperature controls between 850～920 ℃ of the control finishing temperatures, are rolled back cold bed air cooling to room temperature.
The actual chemical ingredients of test steel is as shown in the table.
Shock test adopts the summer than V-type impact specimen, and length direction is along rolling vertical, and the fluting direction is perpendicular to rolling surface.Use the observation by light microscope metallographic structure.Observe the impact fracture pattern with electronic probe.
As stated; It is good to test rolling Q345 steel low temperature impact properties; Be that normal temperature or low-temperature impact work all are significantly improved, add suitable nickel boron alloy, and control gas content well; Can further reduce the brittle transition temperature of Q345 steel, thereby solve the low excessively problem of H shaped steel low-temperature impact toughness effectively.From Figure of description 1, can see the nickel boron alloy H shaped steel that adopts the present invention to produce, the impelling strength transition curve tends towards stability, and does not have tangible brittle transition temperature, and low temperature impact properties is stable, especially-50 ℃ more than impact value stability high.
The present invention can significantly improve the low-temperature impact toughness of the above rank H shaped steel of Q345, is lower than-40 ℃～-60 ℃ impelling strength A
KVGreater than 27J, quality product is easier to guarantee.Considered the controllability of actual industrial production in the optimizing components process as far as possible; And under the situation that more current valuable alloying element prices rise steadily; Replace valuable alloying element with cheap relatively boron, improving low-temperature impact toughness with boron nickel compound action has bigger meaning and magnetism.
Claims (2)
1. the preparation method of one kind-40 ℃～-60 ℃ impelling strength nickel boron alloy H shaped steel is characterized in that, the composition of steel weight percent is (%): C 0.10～0.18; Mn 1.00～1.40, and Si 0.10～0.40, P≤0.015; S≤0.015; Nb 0.015～0.060, and Ni 0.30～0.70, and B 0.0005～0.0025; In the smelting process, gas content in the control steel: (N)≤0.004%, (O)≤0.0060%; Continuously cast bloom adopts special-shaped continuous casting steel billet in nearly terminal or rectangle steel billet; Protection of adjustment continuous casting and process for cooling use big water-coating port thickened sealing ring, and casting process is carried out total process protective casting; Bale slag-blanking detection alarm pattern adopts highest level, opens mouth of a river automatic closing function, prevents down slag; Tundish adopts alkaline covering agent to combine carbonization rice husk to cover; Three streams all adopt the ST-SP/BM-HM covering slag; The secondary cooling water table is selected according to producing section, avoids surface crack to produce; The steel rolling heating and temperature control is at 1200～1260 ℃, and steel rolling breaking down temperature is controlled 1100～1150 ℃, and finishing temperature is controlled at the austenitic area between 850～920 ℃, rolls the back and adopts air cooling to room temperature.
2. the preparation method of-40 ℃～-60 ℃ impelling strength nickel boron alloy H shaped steel as claimed in claim 1 is characterized in that, in the smelting process, gas content in the control steel: (N) be controlled at≤0.0035%, (O) be controlled at≤and 0.0050%.
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| CN102554167A (en) * | 2012-02-14 | 2012-07-11 | 首钢总公司 | Method for controlling defects of H-shaped steel |
| CN102676921B (en) * | 2012-05-04 | 2014-04-09 | 武汉钢铁(集团)公司 | Cold-resistant high-strength hot-rolled angle steel and production method thereof |
| CN103042028A (en) * | 2012-12-21 | 2013-04-17 | 山西新泰钢铁有限公司 | Method for rolling H-shaped steel with stable impact energy |
| CN103820706A (en) * | 2013-12-12 | 2014-05-28 | 山西新泰钢铁有限公司 | Hot-rolling H-shaped steel containing and vanadium boride and having excellent low-temperature impacttoughness and preparation method of hot-rolling H-shaped steel |
| CN103820718B (en) * | 2014-03-10 | 2015-10-28 | 武钢集团昆明钢铁股份有限公司 | A kind of toughness hot rolled i shaped steel of high strength high/low-temperature impact and working method thereof |
| CN104805354A (en) * | 2015-04-30 | 2015-07-29 | 内蒙古包钢钢联股份有限公司 | Boracic deep low temperature hot rolling H-section steel and preparation method thereof |
| CN105063472A (en) * | 2015-08-07 | 2015-11-18 | 舞阳钢铁有限责任公司 | Low-cost 345 Mpa level low-alloy steel sheet and production method thereof |
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| CN105586534B (en) * | 2016-02-22 | 2017-08-25 | 山东钢铁股份有限公司 | A kind of hot rolled H-shaped and its production method of the thick low ductile-brittle transition temperature of spy |
| CN108396228B (en) * | 2018-05-15 | 2020-05-19 | 马钢(集团)控股有限公司 | High-weather-resistant hot-rolled H-shaped steel with yield strength of 450MPa and heat treatment process thereof |
| CN109093099A (en) * | 2018-09-30 | 2018-12-28 | 宁波市镇海甬鼎紧固件制造有限公司 | A kind of low temperature resistant high-strength nut and its production method |
| CN111945064A (en) * | 2020-07-31 | 2020-11-17 | 山东钢铁股份有限公司 | 355 MPa-level low-temperature-resistant hot-rolled H-shaped steel for ocean engineering and preparation method thereof |
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