CN101100728A - Nickel-saving type cobalt-free martensite aging ultrahigh strength steel - Google Patents
Nickel-saving type cobalt-free martensite aging ultrahigh strength steel Download PDFInfo
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- CN101100728A CN101100728A CNA2007101205121A CN200710120512A CN101100728A CN 101100728 A CN101100728 A CN 101100728A CN A2007101205121 A CNA2007101205121 A CN A2007101205121A CN 200710120512 A CN200710120512 A CN 200710120512A CN 101100728 A CN101100728 A CN 101100728A
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Abstract
Alloy steel with no Co and less Ni is available to be thin-wall cylinders or springs or gears, containing (wt%): Ni 11.5-14.5, Cr 3.75-5.25, Mo 2.25-3.75, Ti 1.2-1.6, and elements following below not more than the value behind: C 0.03, Si 0.1, Mn0.1, Al 0.30, Co 0.50, S 0.01, P 0.01, O 30ppm, N 30ppm, balanced with Fe. It has high yield strength, high plasticity, toughness, and excellent machining performance.
Description
Technical field
The invention belongs to field of alloy steel, particularly a kind of nickel-saving type cobalt-free martensite aging ultrahigh strength steel mainly is applicable to high-intensity spinning thin-wall barrel and spring, gear etc.
Background technology
In the prior art, make high strength spinning thin-wall barrel and spring, gears etc. the similarly material great majority of parts use are that 18Ni contains the Co maraging steel, be at first to develop by International nickel Co. Ltd. Inco. Ltd. (INCO) beginning of the sixties, its scheme is the cobalt that adds different content in iron nickel martensitic alloy, molybdenum, titanium, obtain yield strength by age hardening and reach 1400 respectively, 1700, the 18Ni of 1900Mpa (200), 18Ni (250) and 18Ni (300) steel, developed 18Ni (350) afterwards again, 13Ni (400), but owing to contain a large amount of Co element (7.5-15%) and a large amount of Ni, make and the very high restriction that is subject to shortage of resources of its raw materials cost therefore greatly limited the widespread use of 18Ni series maraging steel for a long time.
Entered since the eighties, because the cobalt valency rises steadily, the exploitation of cobalt-free maraging steel has obtained remarkable progress, all comes out in succession as the T-250 (18Ni-3Mo-1.4Ti-0.1Al) of the U.S., the W-250 (18Ni-4.5W-1.4Ti-0.1Al) of Korea S and the H16 Φ 6M6 (16Ni-6V-6Mo) of USSR (Union of Soviet Socialist Republics).These steel not only make production cost reduce by 20～30%, and performance also very contains the cobalt maraging steel near the respective strengths level.But still contain a large amount of Ni in these steel, performance does not reach the level that present 18Ni contains the Co steel again in the maraging steel of some low Ni, and it is suitable with the T250 steel that the maraging steel that therefore needs the no Co of exploitation to hang down Ni makes it performance.
Summary of the invention
The object of the present invention is to provide a kind of cost low, keep higher yield strength and plasticity and toughness, the nickel-saving type cobalt-free martensite aging ultrahigh strength steel that machinability is good.
According to above-mentioned purpose, the technical scheme of integral body of the present invention is:
It is alloy that the present invention is based on Fe-Ni-Cr, does not have the timeliness of utilizing Fe2Mo, Ni3Ti, Ni3Al on the Co martensitic matrix at ultralow-carbon and separates out and strengthen.When reducing Ni content, reduce cost for Ni with Cr and to save resource and to make over-all properties reach the level suitable with the T250 maraging steel.
In the alloy system, principal element is Fe, Ni, Cr, the three forms ultralow-carbon lath martensite matrix, contains strengthening element Mo, Ti etc. simultaneously, these elements main with matrix in strengthening phases such as Ni formation Fe2Mo, Ni3Ti, Ni3Al strengthen and reach high strength; Want the content of impurity elements such as strict control C, S, P, Si, Mn, O, N in addition in the steel, to improve the plasticity and the toughness of material.
According to above-mentioned purpose and whole technical scheme, the concrete technical scheme of the present invention is:
The chemical composition of this nickel-saving type cobalt-free martensite aging ultrahigh strength steel (weight %) is: C≤0.03%, Si≤0.1%, Mn≤0.1%, Ni 11.5-14.5%, Cr 3.75-5.25%, Mo2.25-3.75%, Ti 1.2-1.6%, Al≤0.30%, Co≤0.50%, S≤0.01%, P≤0.01%, O≤30PPm, N≤30PPm, surplus is Fe.
The design considerations of above-mentioned chemical composition is as follows:
Nickel: Ni there is no strengthening effect to the matrix of maraging steel, and why to contain the Ni of sufficient amount in the maraging steel, be in order to guarantee in the cooling after solid solution or the austenitizing that (no matter speed of cooling how) can both generate martensite, and do not generate ferrite or other phase.
Ni has active effect to the toughness that improves steel.After the ageing treatment in the matrix ni content be lower than at 10% o'clock and can cause toughness and reduce.Ti is fully with Ni
3There is consumption Ni in Ti intermetallic compound form, improves intensity in the precipitation strength mode; Some generates Ni Mo
3Mo also consumes Ni in the precipitation strength mode.
Ni in the maraging steel can promote Ni
3The aging precipitation of Mo.But reducing Ni content is enough to make thick Laves to separate out mutually.
Containing Ni in the maraging steel is can both generate martensite in order to guarantee in solid solution and the austenitizing ag(e)ing process afterwards.To the 18Ni martensitic aging composition of steel system of practicality, at first separate out Ni
3Ti and Fe
2Mo separates out Ni then
3Mo.Ni content after a little while, Ni
3Ti only limits on crystal boundary and lath circle.
Chromium: Cr is a ferrite former, and the increase of Cr content will reduce the complete martensitic ability that obtains.In maraging steel, Cr is the same with Ni to be solid-solubilized in the matrix, has the solution strengthening effect; Cr also significantly improves the hardening capacity of steel.
Do not form strengthening phase as Ti, Mo etc. between Cr and the strengthening element, but Cr influences the power of separating out of these strengthening phases,, reduced Ni because Cr has replaced Ni that the Ni content in the matrix is reduced
3Ti and Ni
3Mo etc. separate out power, and therefore too much Cr content will reduce the intensity of steel, and the Cr content of the best should be controlled at a suitable level.
For no Co maraging steel, suitable strength and the tough sexual needs strict control of the content range of Ni and Cr to obtaining.For guaranteeing toughness, need about 17% (nickel+chromium), for guaranteeing that austenite is transformed into martensite fully, (nickel+chromium) should be greater than 21%.
Molybdenum: Mo generates Fe
2Mo and Ni
3These two kinds of precipitates of Mo can improve intensity not reducing under the tough implementations.Mo can generate Ni with Ni
3The Mo intermetallic compound is strengthened matrix, and can be suppressed P and S separating out at crystal boundary.But as it is too much to add Mo, then separates out Fe in matrix
2Mo reduces matrix toughness, and at this class precipitate rich easily long-pending H when crystal boundary is separated out
2, delayed fracture susceptibility is improved.So getting Mo content is controlled at about 3%.
Titanium: Ti can be by forming Ni
3Ti improves the intensity of steel.When Ti content surpasses 1.6%, acicular Ni
3Ti will separate out in crystal boundary, and toughness is sharply descended.But when Ti content did not reach 1.2%, not only intensity did not reach requirement, suppresses austenite and separate out effect and reduce in ag(e)ing process, thereby promote softening (overaging) in the timeliness.So Ti content is remained on 1.2～1.6%.
Ti has tangible influence to intensity and toughness.Ti forms Ni in ag(e)ing process
3Ti strengthens steel, but loss in toughness is bigger, adds the influence of the segregation of Ti, and the steel fracture toughness is obviously descended.
In steel, exist impurity element C, N to capture part Ti and form Ti (C, N), cause embrittlement, reduce the toughness and the plasticity of steel steel.Ti fixedly steel inclusion S generates TiS, reduces grain boundary segregation.The following of Ti is limited to 0.8%.As it is too much to add Ti, then causes Ni
3The Ti precipitate increases, and causes matrix toughness to descend, so the upper limit is no more than 1.60%.
The control of impurity element
Carbon: carbon is very huge to the influence of martensitic intensity, even under the low-down situation of the content of carbon, martensitic intensity is significantly improved.C and Ti generate the TiC non-metallic inclusion, not only reduce the toughness of steel, and consume the element that Ti:C is obstruction Ti precipitation strength more, are controlled at below 0.005% and can eliminate above-mentioned disadvantageous effect.So the C amount is limited in below 0.01%.
Nitrogen: maraging steel adopts vacuum melting usually, so N content is very low, only is 25～35ppm.People seldom note the effect of micro-N in the past.But nearest studies show that, even micro-N also has very big negative impact to the toughness of steel, is one of reason of changing of ultrahigh-strength steel toughness.N existence form in steel almost completely belongs to TiN:N not only descends toughness with the non-metallic inclusion form of TiN, and TiN is the point sequence shape and arranges, and the crack defect that exists in steel, makes steel toughness variation.Therefore N content is controlled at below the 30ppm.
Oxygen: O is the forming element of nonmetal oxide in the steel, and the O in the steel mainly exists with the form of various oxide compounds.Oxide compound causes damage to the plasticity and toughness of steel, particularly oxide compound oxide compound especially surperficial, subsurface is remarkable to the fatigue property influence of steel, therefore this type of ultrahigh-strength steel adopts vacuum metling technology to produce more at present, the O that removes as far as possible in the steel reduces the content of oxide compound, so O content is controlled at below the 30ppm.
Aluminium: Al when steel-making as reductor, be to improve the recovery rate that adds Ti, earlier with addition element Ti again after the Al deoxidation.Al content is 0.03% when following, and oxygen content in steel will increase oxide particle above 15ppm, reduce the toughness of steel.Greater than 0.15% o'clock, then generate the Ni that toughness is degenerated as Al content easily
3Al is measured less than 0.30% so Al contains.
Silicon, manganese: concerning maraging steel, these elements all are the reasons that increases oxide inclusion, and this element adds up to as surpasses 0.06%, then tensile strength is surpassed 250kgf/mm
2The toughness of the material of level is brought harmful effect.So determine Si, Mn, content below 0.10%, reduce the influence of inclusion to mechanical property.
Sulphur: Ti (C, N) content is big to the influence of Kic more than the influence of S content.Therefore, S content often will be considered with other element combined influence in the steel is unified the influence of steel flexible.Certainly S content influences and can not ignore the maraging steel flexible.It is reported that S content impacts maraging steel Xia Shi considerable influence.But when S less than 0.01% the time, the impelling strength of steel is not subjected to the influence of S content, and some raising.S content should be less than 0.01% in the maraging steel, and thinks that containing S in the steel mainly exists with Ti2S (Y phase) inclusion form.Be strip, be distributed in fracture, can cause impelling strength to have directivity ground to descend.
Phosphorus: P seldom forms compound with other elements in steel; but P accumulates in crystal boundary or lath boundary usually, weakens the bonding strength on crystal boundary or lath border, thereby the toughness of steel is worked the mischief; though the existence of Mo can partly suppress P the gathering of crystal boundary or border, for 250kgf/mm
2The material of level is answered the content of the P in the strict control steel, and it is limited to below 0.01%.
The preparation method that employing of the present invention is similar to prior art:
Steel of the present invention adopts the smelting technology of the disconnected remelting of vacuum induction furnace smelting, vacuum induction+electroslag furnace remelting or vacuum induction+vacuum consumable.The steel ingot processing that should homogenize under 1200 ℃ is carried out hot-work subsequently after the melting in 1180-850 ℃ of scope, 830-940 ℃ of solution treatment, carries out ageing treatment at last in 480-530 ℃ of scope after the hot-work.
The present invention compared with prior art have cost low, keep higher yield strength and plasticity and toughness, the advantage that machinability is good is the ultrahigh-strength steel that belongs to a kind of high comprehensive performance.Above-mentioned concrete advantage is: compared with prior art, the present invention does not only contain short metal Co element, and replaces Ni to reduce the use of Ni with Cr, provides cost savings and has saved resource, it is suitable with C250, T250 steel that over-all properties reaches, and is the ultrahigh-strength steel that belongs to a kind of high comprehensive performance.Room temperature strength R
m〉=1760Mpa, R
P0.2〉=1660MPa, A% 〉=8.0%, Z 〉=45%.
The specific embodiment mode
Embodiment
The chemical ingredients scope of not having cobalt nickel-saving type maraging steel according to the present invention is smelted 3 stoves steel of the present invention on 20 kilograms of vacuum induction furnaces, its concrete chemical ingredients is as shown in table 1.
After 3 stove smelting steels are cast into ingot, the thermal treatment that homogenizes, forge into the mechanical property sample, carry out solid solution and ageing treatment subsequently.Its concrete processing parameter is as follows:
Homogenize 1200 ℃ of thermal treatment temps of steel ingot, 6 hours time.
1150-1180 ℃ of hot-work Heating temperature, 1 hour heat-up time.
830～900 ℃ of solid solubility temperatures, 1 hour heat-up time, air cooling
500 ℃ of aging temps, 5 hours time.
The mechanical property test of may well ask after the processing the results are shown in Table 2.
In order to contrast, in table 1 and table 2, added the composition and the performance data of C250, T250 steel.
As can be seen from Table 1, compare with the C250 steel, the present invention does not contain Co, has saved strategic resource.Compare with the T250 steel, the present invention has reduced Ni content with Cr for Ni and has reduced cost.
As seen from Table 2, the present invention compares with compared steel C250, T250, and tensile strength and yield strength and C250 are suitable with the T250 steel, and unit elongation is also suitable, but the relative reduction in area of invention steel will be higher than C250 and T250 steel, may to take from small size sample relevant with the performance of invention steel.See that comprehensively the performance of the performance of invention steel and compared steel C250, T250 is suitable, but does not contain Co, has reduced Ni content, therefore having saved resource has reduced cost.
The chemical component table of table 1 embodiment of the invention and Comparative Examples steel (weight %)
| C | Ni | Cr | Co | Mo | Ti | Al | Si | Mn | S | P | Fe | ||
| Steel of the present invention | 1 | 0.01 | 12.0 | 3.75 | / | 2.98 | 1.50 | 0.05 | 0.10 | 0.10 | 0.002 | 0.005 | Surplus |
| 2 | 0.01 | 11.7 | 4.5 | / | 2.83 | 1.34 | 0.03 | 0.10 | 0.10 | 0.002 | 0.005 | Surplus | |
| 3 | 0.01 | 11.5 | 4.5 | / | 3.05 | 1.38 | 0.05 | 0.10 | 0.10 | 0.003 | 0.003 | Surplus | |
| 4 | 0.01 | 13.75 | 5.18 | / | 3.35 | 1.55 | 0.10 | 0.10 | 0.10 | 0.002 | 0.005 | Surplus | |
| 5 | 0.01 | 13.92 | 4.98 | / | 3.53 | 1.28 | 0.08 | 0.10 | 0.10 | 0.002 | 0.005 | Surplus | |
| Comparative Examples | C250 | 0.004 | 17.88 | / | 8.23 | 4.82 | 0.49 | 0.09 | 0.02 | 0.10 | 0.002 | 0.004 | Surplus |
| T250 | 0.007 | 18.65 | / | 0.02 | 3.14 | 1.54 | 0.10 | 0.04 | 0.02 | 0.002 | 0.006 | Surplus | |
The mechanical property contrast table of table 2 embodiment of the invention and Comparative Examples steel
Claims (1)
1. a nickel-saving type cobalt-free martensite aging ultrahigh strength steel is characterized in that the chemical composition (weight %) of this steel is C≤0.03%, Si≤0.1%, Mn≤0.1%, Ni 11.5-14.5%, Cr 3.75-5.25%, Mo 2.25-3.75%, Ti 1.2-1.6%, Al≤0.30%, Co≤0.50%, S≤0.01%, P≤0.01%, O≤30PPm, N≤30PPm, surplus is Fe.
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| CN200710120512A CN100588735C (en) | 2007-08-21 | 2007-08-21 | The nickel-saving type cobalt-free martensite aging ultrahigh strength steel |
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| CN200710120512A CN100588735C (en) | 2007-08-21 | 2007-08-21 | The nickel-saving type cobalt-free martensite aging ultrahigh strength steel |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103255336A (en) * | 2012-02-15 | 2013-08-21 | 宝山钢铁股份有限公司 | Manufacturing method of high purity cobalt-free maraging steel |
| CN114214572A (en) * | 2021-12-06 | 2022-03-22 | 北京科技大学 | High-strength and high-toughness corrosion-resistant steel suitable for marine environment and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| SU870482A1 (en) * | 1979-08-24 | 1981-10-07 | Предприятие П/Я Р-6762 | Martensite-aged steel |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103255336A (en) * | 2012-02-15 | 2013-08-21 | 宝山钢铁股份有限公司 | Manufacturing method of high purity cobalt-free maraging steel |
| CN103255336B (en) * | 2012-02-15 | 2015-07-08 | 宝钢特钢有限公司 | Manufacturing method of high purity cobalt-free maraging steel |
| CN114214572A (en) * | 2021-12-06 | 2022-03-22 | 北京科技大学 | High-strength and high-toughness corrosion-resistant steel suitable for marine environment and preparation method thereof |
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