Summary of the invention
The invention provides a kind of steel, the technological deficiency such as Hi-Stren steel of the prior art is second-rate for solving, the Nomenclature Composition and Structure of Complexes of product is unreasonable.
The present invention also provides a kind of thermal treatment steel and manufacture method thereof being formed by these steel, for solving the technological deficiencies such as the impelling strength of thermal treatment steel of the prior art is lower.
The invention provides a kind of steel, contain by mass percentage following component raw material: C:0.16~0.21%; Si:0.6~1.2%; Mn:1.9~2.3%; Mo:0.3~0.4%; Nb:0.03~0.12%; Al:0.015~0.035%; Ti :≤0.13%; P :≤0.012%; S :≤0.01%; Surplus is Fe and inevitable element.
Further, described steel contain following feed composition by mass percentage: C:0.17~0.21%; Si:0.8~1.2%; Mn:1.9~2.3%; Mo:0.3~0.4%; Nb:0.03~0.06%; Al:0.015~0.035%; Ti :≤0.13%; P :≤0.012%; S :≤0.01%; Surplus is Fe and inevitable element.
Further, described steel contain following feed composition: C:0.19% by mass percentage; Si:1.0%; Mn:2.1%; Mo:0.35%; Nb:0.05%; Al:0.025%; Ti :≤0.08%; P :≤0.008%; S :≤0.005%; Surplus is Fe and inevitable element.
The present invention also provides a kind of manufacture method of thermal treatment steel, and above-mentioned arbitrary described steel are heat-treated.
Further, described thermal treatment comprises normalizing treatment, quench treatment and the temper of carrying out successively.
Further, described normalizing treatment specifically comprises: by above-mentioned arbitrary described steel be heated to 920~940 ℃ and be incubated 2~3 hours after cooling; Described quench treatment specifically comprises: the steel through described normalizing treatment are heated to 900~920 ℃ and to be incubated 2~3.5 hours for example, cooling after (2~3 hours); Described temper specifically comprises: the steel through described quench treatment are heated to 520~580 ℃ and to be incubated 3.5~7.5 hours for example, cooling after (3.5~4.5 hours).
Further, the heat-up rate of described normalizing treatment is 80~120 ℃/h, is further 90~110 ℃/h, for example 100 ℃/h; The heat-up rate of described quench treatment is 80~120 ℃/h, is further 90~110 ℃/h, for example 100 ℃/h; The heat-up rate of described temper is 40~60 ℃/h, is further 50 ℃/h.
Further, the heat-eliminating medium of described normalizing treatment and described temper is air, and the heat-eliminating medium of described quench treatment is water.And described normalizing treatment is cooled to room temperature, described quench treatment be cooled to about Ms (martensite start) point (Ms) or more than, described temper is cooled to room temperature.
The present invention also provides a kind of thermal treatment steel, according to above-mentioned arbitrary described manufacture method, makes.
Steel provided by the invention, product the Nomenclature Composition and Structure of Complexes is reasonable, and the precipitation strength of its dislocations strengthening by alloying element, close grain strengthening and microalloy has significantly improved intensity and the toughness of steel; In addition, the present invention, by optimizing the thermal treatment process to steel, has also significantly improved its impelling strength when guaranteeing steel strength, and formed thermal treatment steel have good over-all properties.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with embodiments of the invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is the present invention's part embodiment, rather than whole embodiment.Embodiment based in the present invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to the scope of protection of the invention.
Steel of the present invention, contain following component raw material: C:0.16~0.21% by mass percentage; Si:0.6~1.2%; Mn:1.9~2.3%; Mo:0.3~0.4%; Nb:0.03~0.12%; Al:0.015~0.035%; Ti :≤0.13%; P :≤0.012%; S :≤0.01%; Surplus is Fe and inevitable element.
Below, the component raw material to steel of the present invention is elaborated, if no special instructions, " % " represents mass percent.
C:0.16~0.21%
The content of carbon (C) is 0.21% when following, steel are in the process of cooling after influence of high austenizing temp and thermal distortion, no longer there is austenite to two phase decompositions of ferrite and cementite, crossing cold austenite will directly be transformed into the ferrite of various forms and leave the retained austenite of a small amount of rich carbon, thereby makes steel have good plasticity and toughness; And necessary carbon content (more than 0.16%) can for example, be separated out microalloy carbide with the trace alloying element adding (Nb, Ti) effect, it plays precipitation strength effect at hot stage inhibition recrystallize and low thermophase.C can be further 0.17~0.20%, for example 0.19%.
Si:0.6~1.2%
More than 0.6% element silicon (Si) be conducive to improve steel impact wear resistance, reinforced ferrite (every 1% Si can make ferrite yield strength improve 85MPa), promote the stabilization of residual austenite; Element silicon can also play solution strengthening effect to improve the anti-temper brittleness of low temperature the inhibition of having separated out to carbide of steel, and it can also reduce the transition temperature of bainite and the toughness that improves steel; Yet the toughness of steel can (> 1.2%) decrease when Si too high levels.Si can be further 0.85~1.15%, for example 1%.
Mn:1.9~2.3%
Manganese element (Mn) is the alloying element of strongly postponing perlitic transformation, the intensity that certain content (more than 1.9%) is conducive to improve the hardening capacity of steel and improves steel by solution strengthening effect, and it can Substitute For Partial metal M o; But Mn too high levels (> 2.3%) can make steel crystal grain have the tendency of alligatoring.Mn can be further 2.0~2.2%, for example 2.1%.
Mo:0.3~0.4%
More than 0.3% molybdenum element (Mo) can be postponed perlitic transformation, yet the retardation function to bainite transformation is less, adding of Mo can meet the requirement of steel in high strength and high tenacity, and its add-on is low with respect to traditional nickel element (Ni), and better effects if; Add-on can taken into account performance and cost below 0.4%.Mo can be further 0.32~0.38%, for example 0.35%.
Nb:0.03~0.12%
Niobium element (Nb) can be separated out the very carbide of small and dispersed in steel, play the effect of anchoring crystal boundary, thereby crystal grain thinning, raising toughness, particularly at the temperature transition microstructure ultra-fining treatment of new development, control in technological process, trace Nb is the prerequisite that forms and strengthen the Polygons born of the same parents shape substructure that has certain misorientation, and oarse-grained Nb precipitate is conducive to form intragranular acicular ferrite or granular bainite before bainitic transformation simultaneously.More than 0.03% Nb can improve the impelling strength of steel, the brittle transition temperature of reduction steel, and improves welding property, and while containing Nb and Mn, the effect of crystal grain thinning is more obvious simultaneously; The too high levels of Nb may cause the reduction of hardenability of steel.Nb can be further 0.04~0.06%, for example 0.05%.
Al:0.015~0.035%
Aluminium element (Al) determine nitrogen agent as the deoxidation in when steel-making, at content, is 0.015% crystal grain thinning of energy when above, improves the toughness of steel when low temperature and the brittle transition temperature of reduction steel; Yet too high Al content (> 0.035%) can reduce steel intensity and toughness at high temperature.Al can be further 0.02~0.03%, for example 0.025%.
Ti:≤0.13%
Titanium elements (Ti) is disperse phase forming element, and appropriate interpolation can improve the homogeneity of steel; Yet during add-on too much (> 0.13%), can cause the second-phase of disperse too much, thereby cause the elongation after fracture of steel to decline.
P:≤0.012%
Phosphoric (P) is inevitable impurity element, it can make the plasticity-of steel and toughness obviously decline, particularly even more serious at low temperatures (cold shortness), therefore should strictly control its content, to reaching extremely low content, admissible scope is≤0.012%, further≤0.01%, further≤0.008%.
S:≤0.01%
Element sulphur (S) is inevitable impurity element, and it can make steel produce red brittleness, thereby reduces ductility and the toughness of steel, its content should strictly be controlled, the content range of allowing is≤0.01%, further≤0.008%, further≤0.005%.
In steel of the present invention, also comprise other inevitable impurity element, for example N, O, H, its content should be controlled at ppm level, for example N≤60ppm, O≤10ppm, H≤1.3ppm.
Steel of the present invention can adopt ordinary method manufacture, for example: Electric furnace steel making (tapping temperature >=1580 ℃)+LF stove refining+VD stove vacuum outgas → pouring molten steel becomes steel ingot → ingot annealing → Heating Steel Ingots (1200~1220 ℃ are incubated about 6 hours, heat-up rate≤80 ℃/h) → Rolling from Ingot to make material → steel slow cooling → steel cleaning → steel inspection/check → packaging steel.Wherein, can adopt ordinary method in the refining procedure of steel, to adjust each chemical composition, thereby each element in the steel that make to make reach above-mentioned content range.
Steel of the present invention have been broken through the Composition Design thinking of traditional high-strength low alloy steel, rely on no longer merely intensity and the performance of the total amount raising steel of C and alloying element, but by the Nomenclature Composition and Structure of Complexes (bainite structure) of optimizing product, making steel have good mechanical property and physicochemical property, may be intensity and toughness that dislocations strengthening, the close grain strengthening of alloying element and the precipitation strength of microalloy have improved steel.
Further, can heat-treat above-mentioned steel, thereby form thermal treatment steel.Described thermal treatment is selected from normalizing, annealing, quenching, tempering, solid solution, timeliness, one or more in modified, and its technique generally comprises heating and cooling, also comprises alternatively insulation, and those skilled in the art can carry out according to actual needs routine and select.This thermal treatment can change the microstructure of steel inside, thereby gives the use properties that steel are good.
Particularly, the present invention proposes a kind of manufacture method of thermal treatment steel, and it is heat-treated above-mentioned steel.Further, described thermal treatment comprises normalizing treatment, quench treatment and the temper of carrying out successively.
Described normalizing treatment specifically comprises: by above-mentioned arbitrary described steel be heated to 920~940 ℃ and be incubated 2~3 hours after cooling, specifically can after 2 hours, be cooled to room temperature 930 ℃ of insulations; Described quench treatment specifically comprises: by the steel through described normalizing treatment be heated to 900~920 ℃ and be incubated 2~3.5 hours after cooling, specifically can 910 ℃ of insulations be cooled to after 2 hours Ms (martensite start) point (Ms) left and right or more than; Described temper specifically comprises: by the steel through described quench treatment be heated to 520~580 ℃ and be incubated 3.5~7.5 hours after cooling, specifically can be cooled to room temperature after 3.5 hours 550 ℃ of insulations.
Further, the heat-up rate of controlling described normalizing treatment is 80~120 ℃/h, and the heat-up rate of described quench treatment is 80~120 ℃/h, and the heat-up rate of described temper is 40~60 ℃/h.
Through above-mentioned heat treated thermal treatment steel, in microscopic examination tissue, there is bainite structure, it has excellent over-all properties, and particularly its tensile strength, impact of collision toughness, low-temperature impact toughness all increase.
Embodiment 1
The steel (by mass percentage) that contain following feed composition according to above-mentioned conventional manufacture method preparation: C:0.19%; Si:1.0%; Mn:2.1%; Mo:0.35%; Nb:0.05%; Al:0.025%; Ti:0.07%; P:0.006%; S:0.005%; Surplus is Fe and inevitable element.
Adopt dilatometry to detect the transformation temperature of these steel, wherein Ac1 is 737 ℃, and Ac3 is 877 ℃, and Ms is 388 ℃, measures transformation temperature and is conducive to the parameter of thermal treatment process to carry out choice and optimization.
Above-mentioned steel are heat-treated, specifically comprise as follows step in sequence:
Normalizing treatment: the heat-up rate of take is heated to approximately 930 ℃ as 100 ℃/h of left and right by above-mentioned steel, at this temperature, about 2 hours rear air coolings of (approximately 930 ℃) insulation are to room temperature;
Quench treatment: the heat-up rate of take is heated to approximately 910 ℃ as 100 ℃/h of left and right by the steel through above-mentioned normalizing treatment, at this temperature, after about 2 hours water-cooled to 500 ℃ left and right in (approximately 910 ℃) insulation;
Temper: the heat-up rate of take is heated to approximately 550 ℃ as 50 ℃/h of left and right by the steel through above-mentioned quench treatment, at this temperature, about 3.5 hours rear air coolings of (approximately 550 ℃) insulation, to room temperature, form thermal treatment steel.
Through microscopic examination, in the tissue of these thermal treatment steel, there is bainite structure; In addition, adopt this area ordinary method to detect the over-all properties of above-mentioned thermal treatment steel and 20SiMn2MoV, the results are shown in Table 1.
Embodiment 2
The steel (by mass percentage) that contain following feed composition according to above-mentioned conventional manufacture method preparation: C:0.21%; Si:0.8%; Mn:1.9%; Mo:0.4%; Nb:0.06%; Al:0.015%; Ti:0.08%; P:0.008%; S:0.005%; Surplus is Fe and inevitable element.
Above-mentioned steel are heat-treated, specifically comprise as follows step in sequence:
Normalizing treatment: the heat-up rate of take is heated to approximately 920 ℃ as 90 ℃/h of left and right by above-mentioned steel, after being incubated at this temperature about 3 hours, air cooling is to room temperature;
Quench treatment: the heat-up rate of take is heated to approximately 900 ℃ as 90 ℃/h of left and right by the steel through above-mentioned normalizing treatment is incubated rear water-cooled to 450 ℃ left and right about 3 hours at this temperature;
Temper: the heat-up rate of take is heated to approximately 580 ℃ as 60 ℃/h of left and right by the steel through above-mentioned quench treatment, after being incubated about 5 hours at this temperature, air cooling is to room temperature, form thermal treatment steel, in its tissue, have bainite structure, mechanical property detected result is in Table 1.
Embodiment 3
The steel (by mass percentage) that contain following feed composition according to above-mentioned conventional manufacture method preparation: C:0.17%; Si:1.2%; Mn:2.3%; Mo:0.3%; Nb:0.03%; Al:0.035%; Ti:0.1%; P:0.01%; S:0.006%; Surplus is Fe and inevitable element.
Above-mentioned steel are heat-treated, specifically comprise as follows step in sequence:
Normalizing treatment: the heat-up rate of take is heated to approximately 940 ℃ as 110 ℃/h of left and right by above-mentioned steel, after being incubated at this temperature about 2.5 hours, air cooling is to room temperature;
Quench treatment: the heat-up rate of take is heated to approximately 920 ℃ as 100 ℃/h of left and right by the steel through above-mentioned normalizing treatment is incubated rear water-cooled to 400 ℃ left and right about 2.5 hours at this temperature;
Temper: the heat-up rate of take is heated to approximately 520 ℃ as 40 ℃/h of left and right by the steel through above-mentioned quench treatment, after being incubated about 4.5 hours at this temperature, air cooling is to room temperature, form thermal treatment steel, in its tissue, have bainite structure, mechanical property detected result is in Table 1.
Embodiment 4
The steel (by mass percentage) that contain following feed composition according to above-mentioned conventional manufacture method preparation: C:0.21%; Si:1.0%; Mn:2.1%; Mo:0.35%; Nb:0.12%; Al:0.025%; Ti:0.13%; P:0.012%; S:0.01%; Surplus is Fe and inevitable element.
Above-mentioned steel are heat-treated, specifically comprise as follows step in sequence:
Normalizing treatment: the heat-up rate of take is heated to approximately 930 ℃ as 80 ℃/h of left and right by above-mentioned steel, after being incubated at this temperature about 2.5 hours, air cooling is to room temperature;
Quench treatment: the heat-up rate of take is heated to approximately 910 ℃ as 110 ℃/h of left and right by the steel through above-mentioned normalizing treatment is incubated rear water-cooled to 500 ℃ left and right about 2 hours at this temperature;
Temper: the heat-up rate of take is heated to approximately 550 ℃ as 50 ℃/h of left and right by the steel through above-mentioned quench treatment, after being incubated about 7.5 hours at this temperature, air cooling is to room temperature, form thermal treatment steel, in its tissue, have bainite structure, mechanical property detected result is in Table 1.
The mechanical property detected result of table 1 thermal treatment steel
As seen from the results in Table 1:
Tensile strength >=the 1450Mpa of the thermal treatment steel that the present invention manufactures, impact of collision toughness >=62J, low-temperature impact toughness >=40J; With respect to traditional 20SiMn2MoV, more than its tensile strength has improved 64Mpa, more than impact of collision toughness has improved 7J, more than low-temperature impact toughness has improved 13J, the excellent combination property of these thermal treatment steel, can be widely used in the fields such as marine oil, traffic.
Finally it should be noted that: each embodiment, only in order to technical scheme of the present invention to be described, is not intended to limit above; Although the present invention is had been described in detail with reference to aforementioned each embodiment, those of ordinary skill in the art is to be understood that: its technical scheme that still can record aforementioned each embodiment is modified, or some or all of technical characterictic is wherein equal to replacement; And these modifications or replacement do not make the essence of appropriate technical solution depart from the scope of various embodiments of the present invention technical scheme.