CN100580124C - Tempered martensitic steel, method of producing a part from the steel and part obtained thereby - Google Patents

Tempered martensitic steel, method of producing a part from the steel and part obtained thereby Download PDF

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CN100580124C
CN100580124C CN200680013994A CN200680013994A CN100580124C CN 100580124 C CN100580124 C CN 100580124C CN 200680013994 A CN200680013994 A CN 200680013994A CN 200680013994 A CN200680013994 A CN 200680013994A CN 100580124 C CN100580124 C CN 100580124C
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steel
described steel
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CN101166844A (en
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雅克·蒙塔尼翁
菲利普·埃里捷
伊莎贝尔·佩斯莱尔布
克洛德·蒙斯
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Aubert and Duval SA
Safran Aircraft Engines SAS
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SNECMA SAS
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    • 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
    • C21D6/007—Heat treatment of ferrous alloys containing Co
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C21D1/32—Soft annealing, e.g. spheroidising
    • 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
    • C21D6/02—Hardening by precipitation
    • 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
    • C21D6/04—Hardening by cooling below 0 degrees Celsius
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/28—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for plain shafts
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • 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
    • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
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  • Metallurgy (AREA)
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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

The invention relates to steel which is characterised by the following composition as expressed in percentages by weight: - C = 0.18 0.30 %, - Co = 5 -7 %, - Cr = 2 - 5 %, - Al = 1 - 2 %, - Mo + W/2 = 1 - 4 %, - V = trace 0.3 %, - Nb = trace 0.1 %, - B = trace - 50 ppm, - Ni = 10.5 - 15 % with Ni = 7 + 3.5 Al, - Si = trace 0.4 %, - Mn = trace 0.4 %, - Ca = trace - 500 ppm, - Rare earths = trace - 500 ppm, - Ti = trace - 500 ppm, - O = trace - 200ppm if the steel is obtained by means of powder metallurgy or trace - 50 ppm if the steel is produced in air or under a vacuum from molten metal, - N = trace - 100 ppm, - S = trace - 50 ppm, - Cu = trace - 1 %, and - P = trace - 200 ppm, the remainder comprising iron and the inevitable impurities resulting from production. The invention also relates to a method of producing a part from said steel and to the part thus obtained.

Description

The sclerosis martensitic steel, use its method that prepare assembly and the assembly of method acquisition thus
Technical field
The present invention relates to martensitic steel, it hardens by duplex system (duplex system), promptly hardens by the suitable groups compound of use steel and the intermetallic compound and the separating out of carbide of thermal life operation gained.
Background technology
This steel must have:
-very high physical strength, but also need to have high tenacity and ductility simultaneously, promptly brittle fracture sensitivity is low; Must at high temperature (promptly reach) intensity that keeps very high to 400 ℃ temperature;
-good fatigue property, particularly it does not contain harmful inclusion, for example TiN and oxide compound; This feature must obtain by suitable composition and the working condition of controlling molten metal carefully.
And, its must be the surface can harden (case-hardened) but and nitrogenize so that can harden its surface, invest this surface high-wearing feature.
This steel is mainly used in the production of transmission shaft, in particular for aircraft engine.
In this application, the requirement of excellent high-temperature machinery intensity does not allow to use carbon steel, and its intensity is since 200 ℃ of degenerations.Conventional use be maraging steel, it has good strength under up to 350～400 ℃ temperature.Surpass under the situation of this scope in temperature, can carry out tempering process, to change its structure.
File US-A-5,393,388 have proposed a kind of steel compositions, and it is used to improve thermotolerance, and is particularly useful for improving fatigue property, ductility and toughness.The shortcoming of said composition is to have high Co content (8～16%), and this causes the steel price high.
Summary of the invention
The object of the present invention is to provide and can be used in the especially steel of production machinery assembly (for example being transmission shaft or structure unit), it has the physical strength at high temperature of further improvement, and has and make its fatigue property that still is suitable for these purposes and brittleness.Purpose is to make the production cost of this steel be lower than the existing steel that is used for the tool effect of these purposes.
Therefore, the present invention relates to a kind of steel, it is characterized in that containing following composition as expressed in weight percent:
-C＝0.18～0.30％
-Co＝5～7％
-Cr＝2～5％
-Al＝1～2％
-Mo+W/2＝1～4％
-V=trace～0.3%
-Nb=trace～0.1%
-B=trace～50ppm
-Ni=10.5～15% and Ni 〉=7+3.5Al
-Si=trace～0.4%
-Mn=trace～0.4%
-Ca=trace～500ppm
-rare earth element=trace～500ppm
-Ti=trace～500ppm
-O=trace～200ppm (if steel obtains by powder metallurgic method) or O=trace～50ppm (if steel prepares gained by molten metal in air or under the vacuum)
-N=trace～100ppm
-S=trace～50ppm
-Cu=trace～1%
-P=trace～200ppm
Remaining is a unavoidable impurities in iron and the production process.
Preferred its contains C=0.20～0.25%.
Preferred its contains Cr=2～4%.
Preferred its contains Al=1～1.6%, and more preferably 1.4～1.6%.
Preferred its contains Mo 〉=1%.
Preferred its contains Mo+W/2=1～2%.
Preferred its contains V=0.2～0.3%.
Preferred its contains Nb=trace～0.05%.
Preferred its contains Si=trace～0.25%, more preferably trace～0.10%.
Preferred its contains Mn=trace～0.25%, more preferably trace～0.10%.
Preferred its contains Ti=trace～100ppm.
Preferred its contains O=trace～10ppm.
Preferred its contains N=trace～50ppm, more preferably trace～10ppm.
Preferred its contains S=trace～10ppm, more preferably trace～5ppm.
Preferred its contains P=trace～100ppm.
Preferably, its martensite transformation temperature Ms is more than or equal to 140 ℃, and Ms=550-350xC%-40xMn%-17xCr%-10xMo%-17xNi%-8xW%-35xV%-10x Cu%-10xCo%+30xAl% ℃.
The invention still further relates to method, it is characterized in that comprising the following steps, be used for before the assembly completion, providing clear and definite shape for assembly by the steel slave component:
-preparation has the steel of above-mentioned composition;
This steel of-forging;
-carry out 4～20 hours soft temper operations at 600～675 ℃, in air, cool off thereafter;
-900～1000 ℃ of solution heat treated of carrying out at least 1 hour, in oil or air, cool off rapidly thereafter, to prevent separating out of intercrystalline carbide in the austenitic matrix;
-choose wantonly in-50 ℃ or following, preferred-80 ℃ or following, carry out the subzero treatment operation, make all austenitic transformations become martensite, temperature is lower 200 ℃ or more than Ms, and at least one treatment process continues at least 2 hours;
-choose wantonly in 150 ℃～250 ℃ martensites and carry out 4～16 hours softening treatment process gained, in the immobilized air, cool off then;
-in 475～600 ℃, preferred 490～525 ℃ are carried out age hardening in 5～20 hours.
Can also carry out nitrogenize operation or surface hardening operation to this assembly.
The invention still further relates to mechanical component or structure unit, it is characterized in that it is prepared according to aforesaid method.
Wherein, special, it can be transmission shaft, engine mounting device or the take-off and landing device element of engine.
As will be described, the present invention is at first based on is characterized in that a kind of steel compositions, thereby it particularly contains lower Co content and is different from prior art.Correspondingly adjust the content of other alloying element, especially the content of Al, Mo, W, Ni.In addition, the heat treatment step of optimizing has also been proposed.
The plastic region that these steel have (plastic domain) (tensile strength R mWith yield strength R P0.2Poor) in the middle of carbon steel and maraging steel.For maraging steel, described difference is very low, makes to cause high-yield strength but will break rapidly when it surpasses (exceeded).Steel of the present invention has in this respect can be by the characteristic of hardening mutually and/or the ratio of carbon is adjusted.
Steel of the present invention can use under as-quenched condition and be suitable for hardness and process as the instrument of 45HRC.It is in the middle of maraging steel (because it has the low soft martensite of carbon content, it can processed under the untreated as-quenched condition) and carbon steel (it must be processed under as-annealed condition).
The present invention is based on by uniting and use compound and M between β-NiAl shaped metal 2C type carbide makes to carry out hardening process, and based on the reversed austenite that forms in the age hardening operation (reversion austenite), it provides ductility (reversed austenite of a small amount of % between the lath martensite) by forming sandwich structure for martensite.
Must avoid the formation of nitride, especially have the Ti and the Al of embrittling effect; Therefore get rid of the addition (admissible maximum value is 500ppm, more preferably 100ppm) of any Ti, and the value of N is restricted to as far as possible minimum, by with its restriction to prevent the formation of AlN.
For their sclerosis and non-embrittlement characteristic, the M of the preferred low-down Cr of Fe content, Mo, W and V 2The C carbide.They are stablized by Mo and W.The total content of Mo and the W content of half must be at least 1%.In order not damage forging property, and do not form Fe 7Mo 6The intermetallic compound of the μ phase of type (referring to Cr and V) necessarily can not surpass Mo+W/2=4%.Preferred Mo+W/2 is between 1～2%.
Cr and V are " metastable " carbide M 2The precursor of C stabilization.V-arrangement becomes the carbide that increases in " obstruction " crystal grain juncture and the restriction crystal grain heat treatment step at high temperature.Formation for the intermetallic compound that do not impel the non-required μ phase of wanting necessarily can not surpass V=0.3%.The preferred content of V between 0.2～0.3%.
The existence of Cr (being at least 2%) can reduce the content of V carbide, and improves M 2The content of C.In order not form the μ phase, and M 23C 6Carbide necessarily can not surpass 5%.Preferably can not surpass 4%.
With respect to the μ phase, the existence of C can impel M 2The generation of C.Yet excessive meeting causes the reduction of segregation and Ms.Its content must be between 0.18～0.30%, and preferred 0.20～0.25%.
Therefore Co can postpone the recovery of dislocation, and delays under the high temperature over-drastic timeliness mechanism in the martensite.Therefore it is maintained high thermotolerance.Yet, shadyly be, as mentioned above because Co can impel the generation of μ phase, the sclerosis that causes prior art to have the maraging steel of Fe-Ni-Co-Mo, its a large amount of existence causes can be used for forming M 2The minimizing of the Mo of C carbide and/or W quantity, described carbide is worth promoted mechanism to be hardened according to desirable.The Co content (5～7%) of suggestion and the content of other element are the compromise between these merits and demerits.
Ni is relevant with Al.If with respect to Ni, the content of Al is too high, cannot realize reversed austenite.If too much Ni is arranged, the level of NiAl type sclerosis phase can reduce significantly, and keeps a large amount of Al in solution.When quenching process finishes, must not have retained austenite and remaining must be martensitic structure.Therefore, if quenching process is used solid CO 2, Ms is necessary 〉=and 140 ℃.Formula according to routine calculates Ms:Ms=550-350xC%-40xMn%-17xCr%-10xMo%-17xNi%-8xW%-35xV%-10xCu%-10xCo%+30xAl% ℃.Must adjust the content of Ni according to other element for this reason.Need Al=1～2%, preferred 1～1.6%, more preferably 1.4～1.6%, and Ni=10.5-15%, and Ni 〉=7+3.5Al.Ideally, Al be 1.5% and Ni be 12～13%.Can help the existence of NiAl like this, it can improve tensile strength R m, and find that this tensile strength can be because of the lower variation of Co content.Yield strength Rp 0.2With with R mIdentical mode is influenced.
Compare with known steel among the US-A-5393388, wherein for high ductility and toughness are provided, very high reversed austenite content is an ideal, and in order to obtain the high mechanical strength under the high temperature, the present invention advocates and contains sclerosis B2 phase (especially NiAl).According to for Ni and Al fixed condition can guarantee to be enough to keep the ductility and the flexible reversed austenite content of the purposes that is suitable for expecting.
Can add B, but in order not make the forging property variation of steel, it can not be more than 50ppm.
A feature of the present invention also is and can substitutes at least a portion Mo by enough W.With regard to the monovalent atomic fraction, W compares less segregation in solidification process with Mo, and by forming the stable carbide of temperature performance, can at high temperature provide physical strength.Its shortcoming is the cost height, thereby and its can unite with Mo and use to optimize cost.According to the rules, Mo+W/2 is necessary between 1～4%, and preferred 1～2%.In order to limit the cost of steel, preferably keep Mo and be 1% minimum content.
If steel-making is to carry out in air, and N is a fixed in Nb and/or V carbonitride, in order to prevent the formation of embrittlement nitride AlN, N can be 100ppm at most.In order to make N≤50ppm, or≤10ppm, preferably under vacuum, make steel.
Cu can be at most 1%.It can use its ε to be included in the hardening process mutually, and the existence of Ni has limited its injurious effects.
Generally, must be with for example P and S etc. can and the element of crystal grain embrittlement be controlled in the following limit in the segregation of crystal grain juncture: S=trace～50ppm, preferred trace～10ppm, more preferably trace～5ppm, and P=trace～200ppm, preferred trace～100ppm.
Can use Ca as antioxidant, it is final finds that residual quantity is arranged (≤500ppm).Similarly, according to the operation that is used for refining molten metal finally can keep remaining rare earth element (≤500ppm).
Acceptable oxygen content depends on that steel is to obtain or change by producing gained by molten metal in air or under the vacuum by powder metallurgic method.Under first situation, tolerable mostly is the content of 200ppm most.Under second situation, maximum level is 50ppm, preferred 10ppm.
As an example, tested the sample of steel, its composition (weight percent) is presented in the table 1:
A (object of reference) B (object of reference) C (the present invention) D (the present invention) E (the present invention)
C％ 0.233 0.247 0.239 0.244 0.247
Si％ 0.082 0.031 0.031 0.037 0.030
Mn％ 0.026 0.030 0.033 0.033 0.030
S ppm 1.0 7.3 3.8 6.1 6.7
P ppm 54 ＜30 ＜30 ＜30 ＜30
Ni％ 13.43 13.31 12.67 12.71 13.08
Cr％ 2.76 3.08 3.38 3.38 3.29
Mo％ 1.44 1.53 1.52 1.53 1.53
Al％ 0.962 1.01 1.50 1.50 1.49
Co％ 10.25 10.35 6.18 6.24 6.33
Cu％ 0.014 ＜0.010 0.011 0.012 0.011
Ti％ ＜0.020 ＜0.020 ＜0.020 ＜0.020 ＜0.020
Nb％ ＜0.0050 ＜0.0050 ＜0.0050 ＜0.0050 0.054
B ppm ＜10 ＜5 ＜5 29 ＜5
Ca ppm ＜50 ＜50 ＜50 ＜50 ＜50
N ppm ＜3 13 13 12 14
O ppm ＜3 4.8 3.4 4.4 7.7
V％ ＜0.010 0.252 0.245 0.254 0.253
Table 1: the composition of specimen
Object of reference steel A corresponds to the steel of US-A-5393388, therefore has high Co content.
Object of reference steel B corresponds to the steel suitable with steel A, wherein adds V under the situation that does not change Co content.
Steel C corresponds to the present invention, especially compares with B with steel A, has improved the content of its Al, has reduced the content of Co.
Steel D of the present invention further adds B.
Steel E of the present invention further adds Nb.
These samples forge the Flat Steel Bar that (forged) becomes 75x35mm by following condition by the 200kg ingot iron.Under 1250 ℃, carry out at least 16 hours homogenizing treatment process, be used to cut apart first forging process of the coarse texture of ingot iron then; Reaching once more after 1180 ℃ cross section in temperature is that the crude product of 75x75mm carries out forging; At last, each crude product is placed in 950 ℃ the baking oven, then, under this temperature, it is forged into the Flat Steel Bar of 75x35mm, make its granular texture by refining by these successive operations.
After the forging, sample is carried out following processing:
-900 ℃ of solution heat treated of carrying out 1 hour, in air, cool off thereafter;
-in-80 ℃ of subzero treatment operations of carrying out 8 hours;
-carry out age hardening in 5 hours in 495 ℃, in air, cool off thereafter.
Characteristic (the tensile strength R of sample m, elastic limit Rp0.2, elongation A5d, shrinking percentage Z, rebound resilience KV, HRC hardness, ASTM granularity) and table 2 illustrate.In the case, they are to measure under the envrionment temperature of standard.
R m(Mpa) Rp0.2 (Mpa) A5d(％) Z(％) KV(J) HRC Granularity ASTM
A 2176 1956 11.2 58 25/27 55.3 8
B 2218 2002 9.9 56 26/30 56.3 8/9
C 2316 2135 9.5 49 20/24 57.6 8
D 2328 1997 8.9 43 21/22 57.9 8
E 2303 1959 10 47 16/19 57.6 9
Table 2: the characteristic of specimen
As seen sample C of the present invention, D and E have much larger than the tensile strength of object of reference sample A and B.Elastic limit is at least the identical order of magnitude.Opposite with the measurement of tensile strength, if carried out described heat treatment step, then reduce ductility (area reduces and elongation at break (reduction of areaand elongation at break)) and rebound resilience.
Object of reference sample B only demonstrates and adds V to steel A, only improve some characteristic, and its improvement ratio great majority is lower than example of the present invention.
Particularly, in example of the present invention, increase Al, and keep high-content Ni, cause occurring the phase NiAl that more hardens, and it is an important factor improving tensile strength.
In order to obtain the preferential high mechanical strength of the present invention to sample D with E adds B respectively and Nb is unnecessary.
Other experiment of being carried out, the especially experiment that sample C is carried out make to be determined except carrying out treatment process, is necessary in carrying out the soft temper operation under at least 600 ℃ the temperature for the complete recrystallization of steel in the solution heat-treatment process before dissolving.For example, the soft temper operation can be carried out 8 hours under 650 ℃, cooled off in air then.Therefore, the product by the direct gained of heat machinery conversion (thermomechanical transformation) is easy to finish at last operation (finishing, peeling, processing ...), and it gives assembly clear and definite shape.
650 ℃ carry out 8 hours soft temper operations and in air, cool off after, under 935 ℃, carry out 1 hour solution heat treated, in oil cool off thereafter, then, in-80 ℃ of subzero treatment operations of carrying out 8 hours, carry out the operation that 8 hours (for the tension test test piece) or 16 hours (for the resiliency test test piece) eliminates stress in 200 ℃ then, then, carry out 12 hours timeliness (ageing) operations in 500 ℃, thereafter cool off in air, making and obtaining the ASTM granularity is 8 and following mechanical characteristics:
-under 20 ℃, vertically: R m=2271MPa; R P0.2=1983MPa; A5d=11.8%; Z=57%; KV=27J;
-under 20 ℃, laterally: R m=2273MPa; R P0.2=2023MPa; A5d=8.8%; Z=41%; KV=22～24J;
-under 400 ℃, vertically: R m=1833MPa; R P0.2=1643MPa; A5d=11.1%; Z=58%.
Therefore under vertical 20 ℃, obtain excellent trading off between tensile strength, ductility and the rebound resilience.Under laterally, rebound resilience is keeping acceptable value.And, at 400 ℃, keeping very high tensile strength, therefore steel of the present invention has overcome above-mentioned problem effectively.
Generally, for the final assembly that obtains has Ideal Characteristics, the method for best heat-treated steel of the present invention is after forging the assembly base, and finishes in the end that operation (finishing operation) is preceding to give this assembly clear and definite shape:
-carry out 4～20 hours soft temper operations at 600～675 ℃, in air, cool off then;
-900～1000 ℃ of solution heat treated of carrying out at least 1 hour, in oil or air, cool off rapidly then, to prevent separating out of intergranular carbide in the austenitic matrix;
-choose wantonly in-50 ℃ or following, preferred-80 ℃ or following, carry out the subzero treatment operation, make all austenitic transformations become martensite, temperature is lower 200 ℃ or more than Ms, continues at least 2 hours at least one treatment process; Especially for the lower composition of Ni content, this subzero treatment operation is not too favourable;
-choose wantonly in 150 ℃～250 ℃ martensites and carry out 4～16 hours softening treatment process the back gained that quenches, in the immobilized air, cool off then;
-in 475～600 ℃, preferred 490～525 ℃ are carried out age hardening in 5～20 hours.
The preferable use of steel of the present invention is the durable assembly as mechanical engineering and structure unit, it need have the tensile strength of 2200MPa～2350MPa at low temperatures, in conjunction with ductility and rebound resilience, it equals the characteristic of the high-strength steel of the best at least, and at high temperature (400 ℃) have tensile strength and the best fatigue characteristic of 1800MPa.
But but steel of the present invention also has the advantage of surface hardening and nitrogenize.Therefore, it can give the assembly high-wearing feature of using this steel.Its application for described expection is especially favourable.

Claims (30)

1. steel is characterized in that being made up of following material as expressed in weight percent:
-C＝0.18～0.30％
-Co＝5～7％
-Cr＝2～5％
-Al＝1～2％
-Mo+W/2＝1～4％
-V=trace～0.3%
-Nb=trace～0.1%
-B=trace～50ppm
-Ni=10.5～15% and Ni 〉=7+3.5Al
-Si=trace～0.4%
-Mn=trace～0.4%
-Ca=trace～500ppm
-rare earth element=trace～500ppm
-Ti=trace～500ppm
When steel is when obtaining by powder metallurgic method, O=trace～200ppm; Or when steel prepares gained by molten metal in air or under the vacuum, O=trace～50ppm
-N=trace～100ppm
-S=trace～50ppm
-Cu=trace～1%
-P=trace～200ppm
Remaining is a unavoidable impurities in iron and the production process.
2. steel according to claim 1 is characterized in that it contains C=0.20～0.25%.
3. steel according to claim 1 is characterized in that it contains Cr=2～4%.
4. according to each described steel in the claim 1～3, it is characterized in that it contains Al=1～1.6%.
5. according to each described steel in the claim 1～3, it is characterized in that it contains Al=1.4～1.6%.
6. according to each described steel in the claim 1～3, it is characterized in that it contains Mo 〉=1%.
7. according to each described steel in the claim 1～3, it is characterized in that it contains Mo+W/2=1～2%.
8. according to each described steel in the claim 1～3, it is characterized in that it contains V=0.2～0.3%.
9. according to each described steel in the claim 1～3, it is characterized in that it contains Nb=trace～0.05%.
10. according to each described steel in the claim 1～3, it is characterized in that it contains Si=trace～0.25%.
11., it is characterized in that it contains Si=trace～0.10% according to each described steel in the claim 1～3.
12., it is characterized in that it contains Mn=trace～0.25% according to each described steel in the claim 1～3.
13., it is characterized in that it contains Mn=trace～0.10% according to each described steel in the claim 1～3.
14., it is characterized in that it contains Ti=trace～100ppm according to each described steel in the claim 1～3.
15., it is characterized in that it contains O=trace～10ppm according to each described steel in the claim 1～3.
16., it is characterized in that it contains N=trace～50ppm according to each described steel in the claim 1～3.
17., it is characterized in that it contains N=trace～10ppm according to each described steel in the claim 1～3.
18., it is characterized in that it contains S=trace～10ppm according to each described steel in the claim 1～3.
19., it is characterized in that it contains S=trace～5ppm according to each described steel in the claim 1～3.
20., it is characterized in that it contains P=trace～100ppm according to each described steel in the claim 1～3.
21. according to each described steel in the claim 1～3, it is characterized in that its martensite transformation temperature Ms more than or equal to 140 ℃, and Co%+30xA1% ℃ of Ms=550-350x C%-40x Mn%-17x Cr%-10x Mo%-17x Ni%-8x W%-35x V%-10x Cu%-10x.
22. by the method for steel slave component, it is characterized in that it comprises the following steps, be used for before the assembly completion, providing clear and definite shape for assembly:
-preparation has the steel of each described composition in the claim 1～21;
-forge described steel;
-carry out 4～20 hours soft temper operations at 600～675 ℃, in air, cool off then;
-900～1000 ℃ of solution heat treated of carrying out at least 1 hour, in oil or air, cool off rapidly thereafter, to prevent separating out of intercrystalline carbide in the austenitic matrix;
-in 475～600 ℃, carry out age hardening in 5～20 hours.
23., it is characterized in that carrying out age hardening in 5～20 hours at 490～525 ℃ according to the described method of claim 22 by the steel slave component.
24. according to the described method of claim 22 by the steel slave component, it is characterized in that it further is included in-50 ℃ or following, carry out the subzero treatment operation, make all austenitic transformations become martensite, temperature is lower 200 ℃ or more than Ms, and at least one treatment process continues at least 2 hours.
25. according to the described method of claim 22 by the steel slave component, it is characterized in that it further is included in-80 ℃ or the following subzero treatment operation of carrying out, make all austenitic transformations become martensite, temperature is lower 200 ℃ or more than Ms, and at least one treatment process continues at least 2 hours.
26., it is characterized in that it further is included in the softening treatment process that 150 ℃～250 ℃ martensites to gained carry out 4～16 hours, cools off then in the immobilized air according to each described method in the claim 22～25 by the steel slave component.
27., it is characterized in that described assembly also carries out surface hardening or nitrogenize operation according to each described method in the claim 22～25 by the steel slave component.
28. the structure unit assembly is characterized in that it is to prepare gained according to each described method in the claim 22～27.
29. mechanical component is characterized in that it is to prepare gained according to each described method in the claim 22～27.
30. mechanical component according to claim 29 is characterized in that it is an engine driveshaft.
CN200680013994A 2005-04-27 2006-04-20 Tempered martensitic steel, method of producing a part from the steel and part obtained thereby Active CN100580124C (en)

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FR0504254A FR2885141A1 (en) 2005-04-27 2005-04-27 Hardened martensitic steel contains amounts of carbon, cobalt, chrome and aluminum with traces of other minerals
FR0507482 2005-07-12

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