CN108251756A - A kind of Nb-microalloying low temperature high-performance steel and preparation method thereof - Google Patents
A kind of Nb-microalloying low temperature high-performance steel and preparation method thereof Download PDFInfo
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- CN108251756A CN108251756A CN201711262021.0A CN201711262021A CN108251756A CN 108251756 A CN108251756 A CN 108251756A CN 201711262021 A CN201711262021 A CN 201711262021A CN 108251756 A CN108251756 A CN 108251756A
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 182
- 239000010959 steel Substances 0.000 title claims abstract description 182
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 239000010955 niobium Substances 0.000 claims abstract description 128
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 117
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims abstract description 117
- 229910000742 Microalloyed steel Inorganic materials 0.000 claims abstract description 115
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 46
- 238000000137 annealing Methods 0.000 claims abstract description 24
- 238000010791 quenching Methods 0.000 claims abstract description 21
- 230000000171 quenching effect Effects 0.000 claims abstract description 21
- 238000009792 diffusion process Methods 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 14
- 230000008569 process Effects 0.000 claims abstract description 11
- 238000005242 forging Methods 0.000 claims description 117
- 229910000734 martensite Inorganic materials 0.000 claims description 51
- 238000011533 pre-incubation Methods 0.000 claims description 16
- 238000004321 preservation Methods 0.000 claims description 16
- 239000002184 metal Substances 0.000 claims description 13
- 229910052751 metal Inorganic materials 0.000 claims description 13
- 229910001563 bainite Inorganic materials 0.000 claims description 11
- 239000012535 impurity Substances 0.000 claims description 7
- 238000005496 tempering Methods 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 abstract description 48
- 230000000694 effects Effects 0.000 abstract description 7
- 230000009466 transformation Effects 0.000 abstract description 7
- 239000004615 ingredient Substances 0.000 abstract description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 12
- 238000001816 cooling Methods 0.000 description 10
- 238000003723 Smelting Methods 0.000 description 9
- 230000006698 induction Effects 0.000 description 9
- 230000000717 retained effect Effects 0.000 description 9
- 229910001567 cementite Inorganic materials 0.000 description 8
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 8
- 239000000306 component Substances 0.000 description 7
- 239000013078 crystal Substances 0.000 description 7
- 230000036961 partial effect Effects 0.000 description 7
- 230000009467 reduction Effects 0.000 description 6
- 238000005728 strengthening Methods 0.000 description 6
- 239000006104 solid solution Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 238000003754 machining Methods 0.000 description 4
- 229910001562 pearlite Inorganic materials 0.000 description 4
- 239000003381 stabilizer Substances 0.000 description 4
- 230000002411 adverse Effects 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 229910000851 Alloy steel Inorganic materials 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 238000003763 carbonization Methods 0.000 description 2
- 239000008358 core component Substances 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000000265 homogenisation Methods 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 230000005764 inhibitory process Effects 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 239000000835 fiber Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 235000015170 shellfish Nutrition 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
Abstract
The invention discloses a kind of Nb-microalloying low temperature high-performance steels and preparation method thereof, include the following steps：Step A is heated to niobium micro-alloy steel billet 800~900 DEG C, and keeps the temperature 1.2~1.5h；Step B to carrying out quenching treatment by the niobium micro-alloy steel billet of isothermal holding, obtains the Nb-microalloying low temperature high-performance steel.High strength steel of the Nb-microalloying low temperature high-performance steel for 980MPa and more than rank, still maintains that intensity is high, elongation percentage is big, impact flexibility is high under low temperature environment (40 DEG C), will not generate brittleness；Make full use of the effect of Nb refinement austenite original grains, niobium micro-alloy steel billet first passes through 1100~1200 DEG C of diffusion annealing processing, carry out bainitic transformation heat treatment, improve the ingredient and its uniformity of steel billet, its tensile strength reaches more than 1000MPa, elongation after fracture is between 12~20%, AKV (40 DEG C) >=69J, meets and has heavy duty and the process components requirement of the product of impact flexibility.
Description
Technical field
The present invention relates to steel manufacturing field more particularly to a kind of Nb-microalloying low temperature high-performance steel and its preparation sides
Method.
Background technology
With global heavy duty equipment using area and the continuous improvement of security requirement, 980MPa and more than rank
Oneself is increasingly being applied in mechanical equipment core component high strength steel, extends equipment life and raising equipment safety to reach
Property reduces the effect of maintenance cost.And the high strength steel forged because its still maintained under low temperature environment (- 40 DEG C) intensity it is high,
Many advantages, such as elongation percentage is big, impact flexibility is high, and processing is easier to matching, by the favor of Heavy machinery industry circle.
Heavy duty equipment core component steel is needed by Surface hardening treatment more simultaneously, to improve the resistance to of equipment steel
Mill property, but the Surface hardening treatment complex process of 980MPa grade high-strengths steel and of high cost in heavy duty equipment, are unfavorable for
National Industrial energy-saving and emission-reduction.Under low temperature (- 40 DEG C) adverse circumstances, steel can generate brittleness, cause mechanical equipment fault frequent,
It cannot even use, bring security risk.Therefore it is badly in need of a kind of satisfaction heavy duty and low temperature resistant high performance steel alloy.
Invention content
It is an object of the invention to propose a kind of Nb-microalloying low temperature high-performance steel and preparation method thereof, avoid in low temperature
Steel generate brittle situation under (- 40 DEG C) adverse circumstances.
For this purpose, the present invention uses following technical scheme：
A kind of Nb-microalloying low temperature high-performance steel, according to mass percent, including following components：
C：0.32~0.38%,
Si：0.17~0.37%,
Mn：0.45~0.70%,
P：≤ 0.025%,
S：≤ 0.035%,
V：0.07~0.12%,
Cu：≤ 0.20%,
Cr：1.45~1.70%,
Mo：0.22~0.32%,
Ni：1.50~1.70%,
Nb：0.01~0.1%,
Surplus is Fe and inevitable impurity；
In its metal structure, ferritic volume fraction is 30~45%, and the volume fraction of bainite is 10~25%, is returned
The volume fraction of fiery martensite is 30~45%, and the volume fraction of austenite is 5~15% and the volume fraction of martensite is 5
~8%.
Preferably, the preparation method of the Nb-microalloying low temperature high-performance steel, includes the following steps：
Step A is heated to niobium micro-alloy steel billet 800~900 DEG C, and keeps the temperature 1.2~1.5h；
Step B to carrying out quenching treatment by the niobium micro-alloy steel billet of isothermal holding, obtains the Nb-microalloying low temperature
High-performance steel；
Wherein, according to mass percent, the niobium micro-alloy steel billet includes following components：
C：0.32~0.38%,
Si：0.17~0.37%,
Mn：0.45~0.70%,
P：≤ 0.025%,
S：≤ 0.035%,
V：0.07~0.12%,
Cu：≤ 0.20%,
Cr：1.45~1.70%,
Mo：0.22~0.32%,
Ni：1.50~1.70%,
Nb：0.01~0.1%,
Surplus is Fe and inevitable impurity.It is heated to 800~900 DEG C to niobium micro-alloy steel billet, preferably 840~
880 DEG C, and keep the temperature 1.2~1.5h, preferably 1.3~1.4h.After completing the isothermal holding, the niobium micro-alloy steel is carried out
Quenching treatment obtains partial saturation steel alloy.The quenching treatment is preferably oil quenching；To the specific behaviour of the quenching treatment
There is no particular/special requirement as mode, using quenching treatment mode well-known to those skilled in the art.
Preferably, the pretreatment to the niobium micro-alloy steel billet is further included before the step A：
Step C1 forges the niobium micro-alloy steel billet, obtains just forged steel base；
Step C2 is diffused annealing heat preservation to the just forged steel base, obtains hot forging state steel billet；
Step C3 forges the hot forging state steel billet, obtains finish-forging state steel billet.
Preferably, the step C1 first carries out pre-incubation to the niobium micro-alloy steel billet, then is forged；The pre-incubation
Temperature be 1200~1300 DEG C, preferably 1250~1280 DEG C；The time of pre-incubation is 1.5~3h, preferably 2~2.5h.
Pre-incubation is carried out to the niobium micro-alloy steel billet at 1200~1300 DEG C, ensures all alloying elements in the niobium micro-alloy steel billet
The abundant solid solution of especially Nb, and the limiting temperature kept the temperature and time be conducive to the abundant diffusion of alloying element, promote alloy
The homogenization of element ultimately facilitates the homogenization of tissue.
Preferably, in the step C1, the temperature forged is 900~1200 DEG C, and the deformation quantity forged is 85
~95%.Described forge is pulled out for multiple pier, and the number that forges is not particularly limited, can obtain forging for predetermined deformation quantity
Effect.
Preferably, the process that forges in the step C1 is：
Rough forge first is carried out to the niobium micro-alloy steel billet, then carries out finish forge；
The starting forging temperature of the rough forge is 1150~1200 DEG C, and the final forging temperature of the rough forge is 1100~1150 DEG C, institute
The deformation quantity for stating rough forge is 40~50%；
The starting forging temperature of the finish forge is 950~1000 DEG C, and the final forging temperature of the finish forge is 900~950 DEG C, the essence
The deformation quantity of forging is 75~80%.
The starting forging temperature of the rough forge is 1150~1200 DEG C, preferably 1175~1180 DEG C, is advantageously ensured that subsequent
The temperature requirement of finish forge, avoid causing due to temperature is too low after rough forge the niobium micro-alloy steel billet melts down heating again；
The final forging temperature of the rough forge is 1100~1150 DEG C, preferably 1120~1130 DEG C.The deformation quantity of the rough forge
It is 40~50%, preferably 42~45%：
The starting forging temperature of the finish forge is 950~1000 DEG C, preferably 970~980 DEG C；The final forging temperature of the finish forge is
900~950 DEG C, preferably 930~940 DEG C, pro-eutectoid ferrite caused by avoiding final forging temperature too low and austenite edge add
Work direction extends, and forms ferrite and the alternatively distributed banded structure pattern of pearlite after completing transformation, otherwise banded structure has
There is heredity, banded structure is serious, and austenite is preferentially in banded structure grain boundaries when forging rear continuous annealing heating if forging
It is formed, and quickly grown up to pearlite, band-like martensite is formed in subsequent cooling procedure, leads to the niobium micro-alloy steel billet
Elongation decline.The deformation quantity of the finish forge is 75~80%, preferably 76~78%；The deformation quantity of the finish forge is with described
Niobium micro-alloy steel billet after rough forge determines benchmark for deformation quantity.There is no special want to the concrete operations mode of the rough forge and finish forge
It asks, mode is forged using well-known to those skilled in the art.
Preferably, the temperature that diffusion annealing is kept the temperature in the step C2 is 1100~1200 DEG C, and preferably 1150~1180
℃；The time of the diffusion annealing heat preservation is 1.5~2h, preferably 1.6~1.8h.
Under the temperature condition of diffusion annealing heat preservation, the niobium micro-alloy steel billet generation martensitic traoformation, while
The uniformity for forging steel billet tissue is effectively improved in the diffusion annealing insulating process, makes the crystal grain for forging steel billet fine and smooth uniformly,
So as to improve forging banded structure, and then reduce the crystallite dimension for forging recrystallization so that it is more uniform to forge tissue.The expansion
Annealing insulating process is dissipated preferably to complete by way of heating；There is no particular/special requirement to the mode of the heating, using this field
Mode of heating known to technical staff.
Preferably, after diffusion annealing heat preservation, 20~30 DEG C are cooled to.
Preferably, the deformation quantity forged of the step C3 is 65~75%, preferably 70~72%.
Preferably, in the step A, the rate of heat addition is 1~10 DEG C/s；
In the step B, to after the niobium micro-alloy steel billet of isothermal holding carries out quenching treatment, being cooled to room temperature, institute
Cooldown rate is stated as 20~30 DEG C/s.
Preferably, in the step B, tempering isothermal holding is carried out to the niobium micro-alloy steel billet being cooled to room temperature, described time
The temperature of fire heat preservation is 560~650 DEG C, and after making niobium micro-alloy steel billet that martensitic traoformation occur, it is low to obtain the Nb-microalloying
Temperature high-performance steel；
In the metal structure of the Nb-microalloying low temperature high-performance steel, ferritic volume fraction is 30~45%, shellfish
The volume fraction of family name's body is 10~25%, and the volume fraction of tempered martensite is 30~45%, the volume fraction of austenite for 5~
15% and martensite volume fraction be 5~8%.
The Nb-microalloying low temperature high-performance steel is 980MPa and the high strength steel of more than rank, in low temperature environment (- 40
DEG C) under still maintain that intensity is high, elongation percentage is big, impact flexibility is high, brittleness will not be generated.
Elements of the C as stable austenite at room temperature in the Nb-microalloying low temperature high-performance steel, is to ensure that Austria
The remaining essential elements of family name's body；The content of C has decisive role for the volume fraction of remaining martensite, therefore sets containing for C
Amount is 0.32~0.38% (according to mass percent), can improve stability of the retained austenite in processing, while ensure residual
The content of remaining martensite, and avoid the excessively high damage caused to machining of C content and the reduction of solderability.
Mn contributes to C in austenite equally as austenite stabilizer element, while cementite can be prevented to generate
Enrichment；Therefore the content (according to mass percent) of setting Mn is 0.45~0.70%, caused by Mn resultants can be avoided too low
The volume fraction of remaining martensite is less and Mn too high levels caused by hardening to ferrite or bainite, and then avoid pair
The reduction of machinability and the reduction of toughness.
P does not dissolve in cementite in 350~600 DEG C of isothermals, so as to which cementite is inhibited to be precipitated within this temperature range；
Extremely strong solution strengthening ability is played simultaneously, improves solution strengthening effect.Therefore the content of setting P is (according to mass percent)
≤ 0.025%, the solid solution strengthening effect for not only improving P plays, and does not also have a negative impact, and steel body is avoided to generate cold brittleness.
The content of S is arranged on (according to mass percent) in the range of≤0.035%, can improve the machining of steel body
Property, it does not also have a negative impact, steel body is avoided to generate red brittleness.
The content of Cu is arranged on (according to mass percent) in the range of≤0.20%, can improve the intensity of steel body and tough
Property, it does not also have a negative impact, steel body is avoided to generate red brittleness.
The content of V is arranged on (according to mass percent) in the range of 0.07~0.12%, can thinning microstructure crystal grain, improve
The intensity and toughness of steel body, V and C form carbide, improve the hydrogen attack resistance of steel body at high temperature under high pressure.
Si helps to increase ferritic volume fraction, improves the machinability of steel body as ferrite stabilizer.
In addition, Si can prevent the formation of cementite, so as to which C be made effectively to be enriched in austenite, therefore the addition of Si combination C elements, it is right
In by austenite stabilization in an appropriate volume fraction being at room temperature required.
The content of Cr is arranged on (according to mass percent) in the range of 1.45~1.70%, and Cr and C forms a variety of carbonizations
Object slows down the decomposition rate of austenite, the intensity and the quenching degree in heat treatment for significantly improving steel body.
Mo is solid-solution in ferrite, austenite and carbide, reduces the element of austenite phase field, therefore the content of Mo
(according to mass percent) is arranged in the range of 0.22~0.32%, is reduced when being coexisted with Cr, Mo or is inhibited other element institutes
Caused temper brittleness.
The content of Ni is arranged on (according to mass percent) in the range of 1.50~1.70%, and Ni significantly improves the strong of steel body
Degree, and steel body is made to keep good plasticity and toughness.
The content of Nb is arranged on (according to mass percent) in the range of 0.01~0.1%, in the partial saturation stage,
Nb elements give full play to the inhibition grown to austenite grain, and crystal grain thinning while avoids a large amount of precipitates to remaining horse
The influence of family name's body stability reduces the superheated susceptivity and temper brittleness of steel body.
The preparation method of the Nb-microalloying low temperature high-performance steel makes full use of the work of Nb refinement austenite original grains
With niobium micro-alloy steel billet first passes through 1100~1200 DEG C of diffusion annealing processing, carries out bainitic transformation heat treatment, improves steel billet
Ingredient and its uniformity；Ensure that retained austenite crystal grain is not thick when carrying out partial martensite between 800~900 DEG C
Change, realize part formation of martensite process, obtain martensite and retained austenite body tissue needed for niobium micro-alloy steel billet, help to carry
The intensity of high niobium micro-alloy steel billet.It is formerly diffused annealing and carries out bainitic transformation heat treatment, quenched to partial saturation
Stage, it is ensured that a certain amount of tempered martensite and remaining martensite are formed in tissue, using tempered martensite small structure, improves horse
Family name's body phase velocity so that martensitic traoformation occurs during tempering heat treatment, realizes partial martensite and tempered martensite
Change process generates a large amount of tempered martensites, finally obtains including ferrite, retained austenite, bainite, martensite and tempering horse
The niobium micro-alloy steel billet of family name's body, it is ensured that the raising of the tensile strength and elongation percentage performance of niobium micro-alloy steel billet, after tradition is overcome to forge
Normalizing heat treatment bainitic transformation is insufficient, and retained austenite is excessive at room temperature, and then the drawbacks of unstable mechanical property.
The preparation method of the Nb-microalloying low temperature high-performance steel, uniform formation is obtained in diffusion annealing；High intensity
Acquisition and elongation percentage guarantee, then realized by being quenched after isothermal holding in conjunction with subsequent temper so that
Martensite, retained austenite are distributed in tempered martensite body, improve steel body stability, real so as to ensure steel body elongation percentage
The niobium micro-alloy steel billet with high intensity and elongation percentage is now obtained, tensile strength reaches more than 1000MPa, and elongation after fracture is 12
Between~20%, AKV (- 40 DEG C) >=69J meets and has heavy duty and the process components requirement of the product of impact flexibility.
Description of the drawings
The present invention will be further described for attached drawing, but the content in attached drawing does not form any limitation of the invention.
The Nb-microalloying low temperature high-performance steel that Fig. 1 is embodiment A1 in the present invention carries out micro-organization chart；
The Nb-microalloying low temperature high-performance steel that Fig. 2 is embodiment A2 in the present invention carries out micro-organization chart；
The Nb-microalloying low temperature high-performance steel that Fig. 3 is embodiment A3 in the present invention carries out micro-organization chart；
The Nb-microalloying low temperature high-performance steel that Fig. 4 is embodiment A4 in the present invention carries out micro-organization chart.
Specific embodiment
Technical solution to further illustrate the present invention below with reference to the accompanying drawings and specific embodiments.
The each component and its mass percentage content of embodiment A1~A4 niobium micro-alloy steel billets, as shown in table 1, surplus Fe
With inevitable impurity；
Table 1
Embodiment A1
Nb-microalloying low temperature high-performance steel is prepared according to following steps：
Niobium micro-alloy steel billet as shown in Table 1 is put into 50kg vacuum induction furnace smeltings, and make small round steel by step 1
Base, by niobium micro-alloy steel billet with stove heat to 1200 DEG C of and pre-incubation 3h.
Step 2 then forges niobium micro-alloy steel billet on forging machine：
(2.1) rough forge is first carried out to the niobium micro-alloy steel billet, the starting forging temperature control of rough forge is at 1200 DEG C, the end of rough forge
Temperature control is forged at 1100 DEG C, niobium micro-alloy steel billet is forged into a diameter of 80mm from a diameter of 100mm, obtains just forged steel
Base.
(2.2) diffusion annealing that 1.5h is carried out at a temperature of 1100 DEG C to the just forged steel base is kept the temperature, and obtains hot forging state
Steel billet.
(2.3) finish forge is carried out to the hot forging state steel billet, the starting forging temperature control of finish forge is at 1100 DEG C, the finish-forging temperature of finish forge
Degree control forges into a diameter of 60mm at 950 DEG C, by niobium micro-alloy steel billet from a diameter of 80mm, obtains finish-forging state steel billet.
Step 3, the finish-forging state heating steel billet after forging to 880 DEG C and keep the temperature 1.5h, air-cooled after normalized treatment, Ran Hou
680 DEG C of heat preservation 2.5h, it is air-cooled spare after temper.
Step 4, with the heating speed of 10 DEG C/s by the finish-forging state heating steel billet to 860 DEG C, and isothermal keeps 1.5h, with
Quenching oil is as cold as room temperature afterwards；Quenched finish-forging state steel billet is heated to 590 DEG C, and isothermal is kept with the heating speed of 10 DEG C/s
2h, subsequent oil cooling to room temperature；Obtain Nb-microalloying low temperature high-performance steel.
Mechanics properties testing is carried out to Nb-microalloying low temperature high-performance steel obtained, the results are shown in Table 2；
Microstructure observation is carried out to Nb-microalloying low temperature high-performance steel obtained, micro-organization chart is as shown in Figure 1；
In the metal structure of Nb-microalloying low temperature high-performance steel obtained, ferritic volume fraction is 45%, bayesian
The volume fraction of body is 12%, and the volume fraction of tempered martensite is 30%, and the volume fraction of austenite is 7% and martensite
Volume fraction be 6%.
Embodiment A2
Nb-microalloying low temperature high-performance steel is prepared according to following steps：
Niobium micro-alloy steel billet as shown in Table 1 is put into 50kg vacuum induction furnace smeltings, and make small round steel by step 1
Base, by niobium micro-alloy steel billet with stove heat to 1250 DEG C of and pre-incubation 1.5h.
Step 2 then forges niobium micro-alloy steel billet on forging machine：
(2.1) rough forge is first carried out to the niobium micro-alloy steel billet, the starting forging temperature control of rough forge is at 1150 DEG C, the end of rough forge
Temperature control is forged at 1200 DEG C, niobium micro-alloy steel billet is forged into a diameter of 75mm from a diameter of 100mm, obtains just forged steel
Base.
(2.2) diffusion annealing that 1.5h is carried out at a temperature of 1160 DEG C to the just forged steel base is kept the temperature, and obtains hot forging state
Steel billet.
(2.3) finish forge is carried out to the hot forging state steel billet, the starting forging temperature control of finish forge is at 1000 DEG C, the finish-forging temperature of finish forge
Degree control forges into a diameter of 60mm at 940 DEG C, by niobium micro-alloy steel billet from a diameter of 75mm, obtains finish-forging state steel billet.
Step 3, the finish-forging state heating steel billet after forging to 890 DEG C and keep the temperature 1.5h, air-cooled after normalized treatment, Ran Hou
680 DEG C of heat preservation 2h, it is air-cooled spare after temper.
Step 4, with the heating speed of 10 DEG C/s by the finish-forging state heating steel billet to 850 DEG C, and isothermal keeps 1.2h, with
Quenching oil is as cold as room temperature afterwards；Quenched finish-forging state steel billet is heated to 580 DEG C, and isothermal is kept with the heating speed of 10 DEG C/s
2h, subsequent oil cooling to room temperature；Obtain Nb-microalloying low temperature high-performance steel.
Mechanics properties testing is carried out to Nb-microalloying low temperature high-performance steel obtained, the results are shown in Table 2；
Microstructure observation is carried out to Nb-microalloying low temperature high-performance steel obtained, micro-organization chart is as shown in Figure 2；
In the metal structure of Nb-microalloying low temperature high-performance steel obtained, ferritic volume fraction is 37%, bayesian
The volume fraction of body is 11%, and the volume fraction of tempered martensite is 34%, and the volume fraction of austenite is 10% and martensite
Volume fraction be 8%.
Embodiment A3
Nb-microalloying low temperature high-performance steel is prepared according to following steps：
Niobium micro-alloy steel billet as shown in Table 1 is put into 50kg vacuum induction furnace smeltings, and make small round steel by step 1
Base, by niobium micro-alloy steel billet with stove heat to 1260 DEG C of and pre-incubation 2h.
Step 2 then forges niobium micro-alloy steel billet on forging machine：
(2.1) rough forge is first carried out to the niobium micro-alloy steel billet, the starting forging temperature control of rough forge is at 1200 DEG C, the end of rough forge
Temperature control is forged at 1100 DEG C, niobium micro-alloy steel billet is forged into a diameter of 70mm from a diameter of 100mm, obtains just forged steel
Base.
(2.2) diffusion annealing that 2h is carried out at a temperature of 1150 DEG C to the just forged steel base is kept the temperature, and obtains hot forged steel
Base.
(2.3) finish forge is carried out to the hot forging state steel billet, the starting forging temperature control of finish forge is at 1000 DEG C, the finish-forging temperature of finish forge
Degree control forges into a diameter of 60mm at 940 DEG C, by niobium micro-alloy steel billet from a diameter of 70mm, obtains finish-forging state steel billet.
Step 3, the finish-forging state heating steel billet after forging to 865 DEG C and keep the temperature 1.5h, air-cooled after normalized treatment, Ran Hou
680 DEG C of heat preservation 2h, it is air-cooled spare after temper.
Step 4, with the heating speed of 10 DEG C/s by the finish-forging state heating steel billet to 860 DEG C, and isothermal keeps 1.4h, with
Quenching oil is as cold as room temperature afterwards；Quenched finish-forging state steel billet is heated to 590 DEG C, and isothermal is kept with the heating speed of 10 DEG C/s
2h, subsequent oil cooling to room temperature；Obtain Nb-microalloying low temperature high-performance steel.
Mechanics properties testing is carried out to Nb-microalloying low temperature high-performance steel obtained, the results are shown in Table 2；
Microstructure observation is carried out to Nb-microalloying low temperature high-performance steel obtained, micro-organization chart is as shown in Figure 3；
In the metal structure of Nb-microalloying low temperature high-performance steel obtained, ferritic volume fraction is 42%, bayesian
The volume fraction of body is 10%, and the volume fraction of tempered martensite is 34%, and the volume fraction of austenite is 6% and martensite
Volume fraction be 8%.
Embodiment A4
Nb-microalloying low temperature high-performance steel is prepared according to following steps：
Niobium micro-alloy steel billet as shown in Table 1 is put into 50kg vacuum induction furnace smeltings, and make small round steel by step 1
Base, by niobium micro-alloy steel billet with stove heat to 1300 DEG C of and pre-incubation 1.5h.
Step 2 then forges niobium micro-alloy steel billet on forging machine：
(2.1) rough forge is first carried out to the niobium micro-alloy steel billet, the starting forging temperature control of rough forge is at 1200 DEG C, the end of rough forge
Temperature control is forged at 1150 DEG C, niobium micro-alloy steel billet is forged into a diameter of 70mm from a diameter of 100mm, obtains just forged steel
Base.
(2.2) diffusion annealing that 2h is carried out at a temperature of 1180 DEG C to the just forged steel base is kept the temperature, and obtains hot forged steel
Base.
(2.3) finish forge is carried out to the hot forging state steel billet, the starting forging temperature control of finish forge is at 980 DEG C, the finish-forging temperature of finish forge
Degree control forges into a diameter of 60mm at 930 DEG C, by niobium micro-alloy steel billet from a diameter of 70mm, obtains finish-forging state steel billet.
Step 3, the finish-forging state heating steel billet after forging to 880 DEG C and keep the temperature 1.2h, air-cooled after normalized treatment, Ran Hou
680 DEG C of heat preservation 1.5h, it is air-cooled spare after temper.
Step 4, with the heating speed of 10 DEG C/s by the finish-forging state heating steel billet to 860 DEG C, and isothermal keeps 1.5h, with
Quenching oil is as cold as room temperature afterwards；Quenched finish-forging state steel billet is heated to 590 DEG C, and isothermal is kept with the heating speed of 10 DEG C/s
2h, subsequent oil cooling to room temperature；Obtain Nb-microalloying low temperature high-performance steel.
Mechanics properties testing is carried out to Nb-microalloying low temperature high-performance steel obtained, the results are shown in Table 2；
Microstructure observation is carried out to Nb-microalloying low temperature high-performance steel obtained, micro-organization chart is as shown in Figure 4；
In the metal structure of Nb-microalloying low temperature high-performance steel obtained, ferritic volume fraction is 42%, bayesian
The volume fraction of body is 10%, and the volume fraction of tempered martensite is 35%, and the volume fraction of austenite is 7% and martensite
Volume fraction be 6%.
Table 2
As shown in Table 2, the preparation method of the Nb-microalloying low temperature high-performance steel is reliable and stable, the micro- conjunction of niobium produced
Aurification low temperature high-performance steel intensity is high, and be hit good toughness, and excellent properties are still maintained in storm, severe cold adverse circumstances,
The advantages that intensity is high, elongation percentage is big and impact flexibility is high is still maintained under low temperature environment (- 40 DEG C), tensile strength reaches
More than 1000MPa, elongation after fracture is between 12~20%, AKV (- 40 DEG C) >=69J, meets and has heavy duty and impact flexibility
The process components requirement of product.
The each component and its mass percentage content of embodiment B1~B12 alloy billets, as shown in table 3, surplus for Fe and
Inevitable impurity.
Table 3
Embodiment B1~B12 prepares niobium micro-alloy steel according to following steps：
Niobium micro-alloy steel billet as shown in table 3 is put into 50kg vacuum induction furnace smeltings, and make small round steel by step 1
Base, by niobium micro-alloy steel billet with stove heat to 1300 DEG C of and pre-incubation 1.5h.
Step 2 then forges niobium micro-alloy steel billet on forging machine：
(2.1) rough forge is first carried out to the niobium micro-alloy steel billet, the starting forging temperature control of rough forge is at 1200 DEG C, the end of rough forge
Temperature control is forged at 1150 DEG C, niobium micro-alloy steel billet is forged into a diameter of 70mm from a diameter of 100mm, obtains just forged steel
Base.
(2.2) diffusion annealing that 2h is carried out at a temperature of 1180 DEG C to the just forged steel base is kept the temperature, and obtains hot forged steel
Base.
(2.3) finish forge is carried out to the hot forging state steel billet, the starting forging temperature control of finish forge is at 980 DEG C, the finish-forging temperature of finish forge
Degree control forges into a diameter of 60mm at 930 DEG C, by niobium micro-alloy steel billet from a diameter of 70mm, obtains finish-forging state steel billet.
Step 3, the finish-forging state heating steel billet after forging to 880 DEG C and keep the temperature 1.2h, air-cooled after normalized treatment, Ran Hou
680 DEG C of heat preservation 1.5h, it is air-cooled spare after temper.
Step 4, with the heating speed of 10 DEG C/s by the finish-forging state heating steel billet to 860 DEG C, and isothermal keeps 1.5h, with
Quenching oil is as cold as room temperature afterwards；Quenched finish-forging state steel billet is heated to 590 DEG C, and isothermal is kept with the heating speed of 10 DEG C/s
2h, subsequent oil cooling to room temperature；Obtain niobium micro-alloy steel.
Mechanics properties testing is carried out to niobium micro-alloy steel obtained, the results are shown in Table 4；
The metal structure of niobium micro-alloy steel obtained is as shown in table 5.
Table 4
Table 5
By table 4 and table 5 and by the comparison of embodiment B1~B12 and embodiment A1~A4 it is found that the niobium micro-alloy
Change elements of the C in low temperature high-performance steel as stable austenite at room temperature, be to ensure that the remaining essential elements of austenite；C
Content have a decisive role for the volume fraction of remaining martensite, therefore set the content of C to be (according to mass percent)
0.32~0.38%, stability of the retained austenite in processing can be improved, while ensure the content of remaining martensite, and keep away
The excessively high damage caused to machining of C content and the reduction of solderability are exempted from.
Mn contributes to C in austenite equally as austenite stabilizer element, while cementite can be prevented to generate
Enrichment；Therefore the content (according to mass percent) of setting Mn is 0.45~0.70%, caused by Mn resultants can be avoided too low
The volume fraction of remaining martensite is less and Mn too high levels caused by hardening to ferrite or bainite, and then avoid pair
The reduction of machinability and the reduction of toughness.
P does not dissolve in cementite in 350~600 DEG C of isothermals, so as to which cementite is inhibited to be precipitated within this temperature range；
Extremely strong solution strengthening ability is played simultaneously, improves solution strengthening effect.Therefore the content of setting P is (according to mass percent)
≤ 0.025%, the solid solution strengthening effect for not only improving P plays, and does not also have a negative impact, and steel body is avoided to generate cold brittleness.
The content of S is arranged on (according to mass percent) in the range of≤0.035%, can improve the machining of steel body
Property, it does not also have a negative impact, steel body is avoided to generate red brittleness.
The content of Cu is arranged on (according to mass percent) in the range of≤0.20%, can improve the intensity of steel body and tough
Property, it does not also have a negative impact, steel body is avoided to generate red brittleness.
The content of V is arranged on (according to mass percent) in the range of 0.07~0.12%, can thinning microstructure crystal grain, improve
The intensity and toughness of steel body, V and C form carbide, improve the hydrogen attack resistance of steel body at high temperature under high pressure.
Si helps to increase ferritic volume fraction, improves the machinability of steel body as ferrite stabilizer.
In addition, Si can prevent the formation of cementite, so as to which C be made effectively to be enriched in austenite, therefore the addition of Si combination C elements, it is right
In by austenite stabilization in an appropriate volume fraction being at room temperature required.
The content of Cr is arranged on (according to mass percent) in the range of 1.45~1.70%, and Cr and C forms a variety of carbonizations
Object slows down the decomposition rate of austenite, the intensity and the quenching degree in heat treatment for significantly improving steel body.
Mo is solid-solution in ferrite, austenite and carbide, reduces the element of austenite phase field, therefore the content of Mo
(according to mass percent) is arranged in the range of 0.22~0.32%, is reduced when being coexisted with Cr, Mo or is inhibited other element institutes
Caused temper brittleness.
The content of Ni is arranged on (according to mass percent) in the range of 1.50~1.70%, and Ni significantly improves the strong of steel body
Degree, and steel body is made to keep good plasticity and toughness.
The content of Nb is arranged on (according to mass percent) in the range of 0.01~0.1%, in the partial saturation stage,
Nb elements give full play to the inhibition grown to austenite grain, and crystal grain thinning while avoids a large amount of precipitates to remaining horse
The influence of family name's body stability reduces the superheated susceptivity and temper brittleness of steel body.
The each component and its mass percentage content of embodiment C1~C4 niobium micro-alloy steel billets, as shown in table 6, surplus Fe
With inevitable impurity；
Table 6
Embodiment C1
Niobium micro-alloy steel is prepared according to following steps：
Niobium micro-alloy steel billet as shown in table 6 is put into 50kg vacuum induction furnace smeltings, and make small round steel by step 1
Base, by niobium micro-alloy steel billet with stove heat to 1200 DEG C of and pre-incubation 3h.
The niobium micro-alloy steel billet is heated to 860 DEG C, and isothermal keeps 1.5h by step 2 with the heating speed of 10 DEG C/s,
Subsequent quenching oil is as cold as room temperature；Quenched niobium micro-alloy steel billet is heated to 590 DEG C, and isothermal with the heating speed of 10 DEG C/s
Keep 2h, subsequent oil cooling to room temperature；Obtain niobium micro-alloy steel.
Mechanics properties testing is carried out to niobium micro-alloy steel obtained, the results are shown in Table 7.
In the metal structure of niobium micro-alloy steel obtained, ferritic volume fraction is 45%, the volume fraction of bainite
It is 11%, the volume fraction of tempered martensite is 35%, and the volume fraction of austenite is for the volume fraction of 3% and martensite
6%.
Embodiment C2
Niobium micro-alloy steel is prepared according to following steps：
Niobium micro-alloy steel billet as shown in table 6 is put into 50kg vacuum induction furnace smeltings, and make small round steel by step 1
Base, by niobium micro-alloy steel billet with stove heat to 1250 DEG C of and pre-incubation 1.5h.
Step 2 then forges niobium micro-alloy steel billet on forging machine：
(2.1) rough forge is first carried out to the niobium micro-alloy steel billet, the starting forging temperature control of rough forge is at 1150 DEG C, the end of rough forge
Temperature control is forged at 1200 DEG C, niobium micro-alloy steel billet is forged into a diameter of 75mm from a diameter of 100mm, obtains just forged steel
Base.
(2.2) diffusion annealing that 1.5h is carried out at a temperature of 1160 DEG C to the just forged steel base is kept the temperature, and obtains hot forging state
Steel billet.
(2.3) finish forge is carried out to the hot forging state steel billet, the starting forging temperature control of finish forge is at 1000 DEG C, the finish-forging temperature of finish forge
Degree control forges into a diameter of 60mm at 940 DEG C, by niobium micro-alloy steel billet from a diameter of 75mm, obtains finish-forging state steel billet.
Step 3, the finish-forging state heating steel billet after forging to 890 DEG C and keep the temperature 1.5h, air-cooled after normalized treatment, Ran Hou
680 DEG C of heat preservation 2h, it is air-cooled spare after temper.
Step 4, with the heating speed of 10 DEG C/s by the finish-forging state heating steel billet to 850 DEG C, and isothermal keeps 1.2h, with
Quenching oil is as cold as room temperature afterwards, obtains niobium micro-alloy steel.
Mechanics properties testing is carried out to niobium micro-alloy steel obtained, the results are shown in Table 7；
In the metal structure of niobium micro-alloy steel obtained, ferritic volume fraction is 47%, the volume fraction of bainite
It is 15%, the volume fraction of tempered martensite is 25%, and the volume fraction of austenite is for the volume fraction of 10% and martensite
3%.
Embodiment C3
Niobium micro-alloy steel is prepared according to following steps：
Niobium micro-alloy steel billet as shown in table 6 is put into 50kg vacuum induction furnace smeltings, and make small round steel by step 1
Base, by niobium micro-alloy steel billet with stove heat to 1260 DEG C of and pre-incubation 2h.
Step 2 then forges niobium micro-alloy steel billet on forging machine：
(2.1) rough forge is first carried out to the niobium micro-alloy steel billet, the starting forging temperature control of rough forge is at 1200 DEG C, the end of rough forge
Temperature control is forged at 1100 DEG C, niobium micro-alloy steel billet is forged into a diameter of 70mm from a diameter of 100mm, obtains just forged steel
Base.
(2.2) finish forge is carried out to the hot forging state steel billet, the starting forging temperature control of finish forge is at 1000 DEG C, the finish-forging temperature of finish forge
Degree control forges into a diameter of 60mm at 940 DEG C, by niobium micro-alloy steel billet from a diameter of 70mm, obtains finish-forging state steel billet.
Step 3, the finish-forging state heating steel billet after forging to 865 DEG C and keep the temperature 1.5h, air-cooled after normalized treatment, Ran Hou
680 DEG C of heat preservation 2h, it is air-cooled spare after temper.
Step 4, with the heating speed of 10 DEG C/s by the finish-forging state heating steel billet to 860 DEG C, and isothermal keeps 1.4h, with
Quenching oil is as cold as room temperature afterwards；Quenched finish-forging state steel billet is heated to 590 DEG C, and isothermal is kept with the heating speed of 10 DEG C/s
2h, subsequent oil cooling to room temperature；Obtain niobium micro-alloy steel.
Mechanics properties testing is carried out to niobium micro-alloy steel obtained, the results are shown in Table 7；
In the metal structure of niobium micro-alloy steel obtained, ferritic volume fraction is 35%, the volume fraction of bainite
It is 34%, the volume fraction of tempered martensite is 25%, and the volume fraction of austenite is for the volume fraction of 5% and martensite
1%.
Embodiment C4
Niobium micro-alloy steel is prepared according to following steps：
Niobium micro-alloy steel billet as shown in table 6 is put into 50kg vacuum induction furnace smeltings, and make small round steel by step 1
Base, by niobium micro-alloy steel billet with stove heat to 1300 DEG C of and pre-incubation 1.5h.
Step 2 then forges niobium micro-alloy steel billet on forging machine：
(2.1) rough forge is first carried out to the niobium micro-alloy steel billet, the starting forging temperature control of rough forge is at 1200 DEG C, the end of rough forge
Temperature control is forged at 1150 DEG C, niobium micro-alloy steel billet is forged into a diameter of 70mm from a diameter of 100mm, obtains just forged steel
Base.
(2.2) diffusion annealing that 2h is carried out at a temperature of 1180 DEG C to the just forged steel base is kept the temperature, and obtains hot forged steel
Base.
(2.3) finish forge is carried out to the hot forging state steel billet, the starting forging temperature control of finish forge is at 900 DEG C, the finish-forging temperature of finish forge
Degree control forges into a diameter of 60mm at 850 DEG C, by niobium micro-alloy steel billet from a diameter of 70mm, obtains finish-forging state steel billet.
Step 3, the finish-forging state heating steel billet after forging to 880 DEG C and keep the temperature 1.2h, air-cooled after normalized treatment, Ran Hou
680 DEG C of heat preservation 1.5h, it is air-cooled spare after temper.
Step 4, with the heating speed of 10 DEG C/s by the finish-forging state heating steel billet to 860 DEG C, and isothermal keeps 1.5h, with
Quenching oil is as cold as room temperature afterwards；Quenched finish-forging state steel billet is heated to 590 DEG C, and isothermal is kept with the heating speed of 10 DEG C/s
2h, subsequent oil cooling to room temperature；Obtain niobium micro-alloy steel.
Mechanics properties testing is carried out to niobium micro-alloy steel obtained, the results are shown in Table 7；
In the metal structure of niobium micro-alloy steel obtained, ferritic volume fraction is 45%, the volume fraction of bainite
It is 15%, the volume fraction of tempered martensite is 34%, and the volume fraction of austenite is for the volume fraction of 1% and martensite
5%.
Table 7
As shown in Table 7, by the comparison of embodiment C1 and embodiment A1 it is found that fine and close by the niobium micro-alloy steel billet forged
Degree is high, good toughness and steel fibre composition centainly uniformly flow to form, moment overload impact is avoided to be broken, -10~-30
DEG C low temperature environment under also have preferable mechanical property, not cracky improves the intensity of Nb-microalloying low temperature high-performance steel；
By the comparison of embodiment C2 and embodiment A2 it is found that by quenched finish-forging state steel billet progress temper, make
It obtains the finish-forging state steel billet during tempering heat treatment and martensitic traoformation occurs, realize partial martensite and tempered martensite mistake
Journey generates a large amount of tempered martensites, finally obtains including ferrite, retained austenite, bainite, martensite and tempered martensite
Niobium micro-alloy steel billet, it is ensured that the raising of the tensile strength and elongation percentage performance of niobium micro-alloy steel billet, overcome tradition forge after normalizing
Heat treatment bainitic transformation is insufficient, and retained austenite is excessive at room temperature, and then the drawbacks of unstable mechanical property；
Steel billet group is forged it is found that being effectively improved in diffusion annealing insulating process by the comparison of embodiment C3 and embodiment A3
The uniformity knitted makes the crystal grain for forging steel billet fine and smooth uniformly, so as to improve banded structure is forged, and then reduce and forge recrystallization
Crystallite dimension so that it is more uniform to forge tissue；
By the comparison of embodiment C4 and embodiment A4 it is found that the final forging temperature of finish forge is 900~950 DEG C, preferably 930
~940 DEG C, pro-eutectoid ferrite and austenite are extended along machine direction caused by avoiding final forging temperature too low, after completing transformation
Ferrite and the alternatively distributed banded structure pattern of pearlite are formed, otherwise banded structure has heredity, if forging band-like
Tissue is serious, and austenite is preferentially formed, and quickly long to pearlite in banded structure grain boundaries when forging rear continuous annealing heating
Greatly, band-like martensite is formed in subsequent cooling procedure, the elongation of the niobium micro-alloy steel billet is caused to decline.
The technical principle of the present invention is described above in association with specific embodiment.These descriptions are intended merely to explain the present invention's
Principle, and it cannot be construed to limiting the scope of the invention in any way.Based on explanation herein, the technology of this field
Personnel would not require any inventive effort the other specific embodiments that can associate the present invention, these modes are fallen within
Within protection scope of the present invention.
Claims (10)
1. a kind of Nb-microalloying low temperature high-performance steel, which is characterized in that according to mass percent, including following components：
C：0.32~0.38%,
Si：0.17~0.37%,
Mn：0.45~0.70%,
P：≤ 0.025%,
S：≤ 0.035%,
V：0.07~0.12%,
Cu：≤ 0.20%,
Cr：1.45~1.70%,
Mo：0.22~0.32%,
Ni：1.50~1.70%,
Nb：0.01~0.1%,
Surplus is Fe and inevitable impurity；
In its metal structure, ferritic volume fraction is 30~45%, and the volume fraction of bainite is 10~25%, is tempered horse
The volume fraction of family name's body is 30~45%, the volume fraction of austenite be 5~15% and the volume fraction of martensite be 5~
8%.
2. a kind of preparation method of Nb-microalloying low temperature high-performance steel as described in claim 1, which is characterized in that including with
Lower step：
Step A is heated to niobium micro-alloy steel billet 800~900 DEG C, and keeps the temperature 1.2~1.5h；
Step B to carrying out quenching treatment by the niobium micro-alloy steel billet of isothermal holding, obtains the high property of the Nb-microalloying low temperature
It can steel；
Wherein, according to mass percent, the niobium micro-alloy steel billet includes following components：
C：0.32~0.38%,
Si：0.17~0.37%,
Mn：0.45~0.70%,
P：≤ 0.025%,
S：≤ 0.035%,
V：0.07~0.12%,
Cu：≤ 0.20%,
Cr：1.45~1.70%,
Mo：0.22~0.32%,
Ni：1.50~1.70%,
Nb：0.01~0.1%,
Surplus is Fe and inevitable impurity.
3. the preparation method of Nb-microalloying low temperature high-performance steel according to claim 2, which is characterized in that in the step
The pretreatment to the niobium micro-alloy steel billet is further included before rapid A：
Step C1 forges the niobium micro-alloy steel billet, obtains just forged steel base；
Step C2 is diffused annealing heat preservation to the just forged steel base, obtains hot forging state steel billet；
Step C3 forges the hot forging state steel billet, obtains finish-forging state steel billet.
4. the preparation method of Nb-microalloying low temperature high-performance steel according to claim 3, it is characterised in that：The step
C1 first carries out pre-incubation to the niobium micro-alloy steel billet, then is forged；
The temperature of the pre-incubation is 1200~1300 DEG C, and the time of pre-incubation is 1.5~3h.
5. the preparation method of Nb-microalloying low temperature high-performance steel according to claim 3, it is characterised in that：The step
In C1, the temperature forged is 900~1200 DEG C, and the deformation quantity forged is 85~95%.
6. the preparation method of Nb-microalloying low temperature high-performance steel according to claim 3, which is characterized in that the step
The process that forges in C1 is：
Rough forge first is carried out to the niobium micro-alloy steel billet, then carries out finish forge；
The starting forging temperature of the rough forge is 1150~1200 DEG C, and the final forging temperature of the rough forge is 1100~1150 DEG C, described thick
The deformation quantity of forging is 40~50%；
The starting forging temperature of the finish forge is 950~1000 DEG C, and the final forging temperature of the finish forge is 900~950 DEG C, the finish forge
Deformation quantity is 75~80%.
7. the preparation method of Nb-microalloying low temperature high-performance steel according to claim 3, it is characterised in that：The step
The temperature that diffusion annealing is kept the temperature in C2 is 1100~1200 DEG C, and the time of the diffusion annealing heat preservation is 1.5~2h.
8. the preparation method of Nb-microalloying low temperature high-performance steel according to claim 3, it is characterised in that：The step
The deformation quantity forged of C3 is 65~75%.
9. the preparation method of Nb-microalloying low temperature high-performance steel according to claim 2, it is characterised in that：The step
In A, the rate of heat addition is 1~10 DEG C/s；
It is described cold to after the niobium micro-alloy steel billet of isothermal holding carries out quenching treatment, being cooled to room temperature in the step B
But rate is 20~30 DEG C/s.
10. the preparation method of Nb-microalloying low temperature high-performance steel according to claim 9, it is characterised in that：The step
In rapid B, tempering isothermal holding is carried out to the niobium micro-alloy steel billet being cooled to room temperature, the temperature of the tempering heat preservation is 560~650
DEG C, after making niobium micro-alloy steel billet that martensitic traoformation occur, obtain the Nb-microalloying low temperature high-performance steel；
In the metal structure of the Nb-microalloying low temperature high-performance steel, ferritic volume fraction is 30~45%, bainite
Volume fraction for 10~25%, the volume fraction of tempered martensite is 30~45%, the volume fraction of austenite for 5~
15% and martensite volume fraction be 5~8%.
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