CN105177455A

CN105177455A - 2400MPa-grade high-alloy ultrahigh-strength steel

Info

Publication number: CN105177455A
Application number: CN201510645184.1A
Authority: CN
Inventors: 金建军; 王晓震; 倪志铭; 胡春文; 江志华
Original assignee: BEIJING INSTITUTE OF AERONAUTICAL MATERIALS CHINA AVIATION INDUSTRY GROUP Corp
Current assignee: BEIJING INSTITUTE OF AERONAUTICAL MATERIALS CHINA AVIATION INDUSTRY GROUP Corp
Priority date: 2015-10-08
Filing date: 2015-10-08
Publication date: 2015-12-23
Anticipated expiration: 2035-10-08
Also published as: CN105177455B

Abstract

The invention belongs to the technical field of metal materials and relates to 2400MPa-grade high-alloy ultrahigh-strength steel. The 2400MPa-grade high-alloy ultrahigh-strength steel comprises, by weight, 0.20%-0.30% of C, 1.0%-3.0% of Cr, 9.5%-10.5% of Ni, 7.0%-9.0% of Co, 1.3%-2.0% of Mo, 1.3%-2.0% of Al, 0%-0.10% of Nb, 0%-0.10% of La, and the balance Fe. The tensile strength of the 2400MPa-grade high-alloy ultrahigh-strength steel is larger than or equal to 2400 MPa, and the yield strength of the 2400MPa-grade high-alloy ultrahigh-strength steel is larger than or equal to 2100 MPa; the 2400MPa-grade high-alloy ultrahigh-strength steel has good plasticity and toughness. The steel can be used as a high-strength structure part and is widely applied to airplanes and engines.

Description

A kind of 2400MPa level High-alloy Ultra-high Strength Steel

Technical field

The invention belongs to technical field of metal, relate to a kind of 2400MPa level High-alloy Ultra-high Strength Steel.

Background technology

Along with the development of aircraft industry, more and more higher to the lightweight requirements of structural part, thus ultrahigh-strength steel is had higher requirement, require higher intensity, good plasticity and toughness.At present High-alloy Ultra-high Strength Steel in, best with the AerMet100 steel over-all properties of Carpenter company of U.S. exploitation, this steel have about 2000MPa tensile strength and the excellent fracture toughness property of left and right.On the basis of AerMet100 steel, Carpenter company of the U.S. has developed again higher AerMet310 and the AerMet340 steel of intensity.The actual tensile strength of AerMet340 steel can reach 2379MPa, and a little more than 340KSi (2343MPa), but fracture toughness property is reduced to the ultrahigh-strength steel of AerMet series has a common shortcoming, is exactly the noble element Co containing more amount, and Co content is more than 14%, and thus price comparison is expensive.QuesTek company of the U.S. had developed M54 steel afterwards, although reduce Co content on the basis of AerMet100 steel, tensile strength is the same with AerMet100 steel, only has about 2000MPa.

Summary of the invention

The object of the invention is: research and develop a kind of tensile strength >=2400MPa, yield strength >=2100MPa, and there is the 2400MPa level High-alloy Ultra-high Strength Steel of good plasticity and toughness.

Technical scheme of the present invention is: 2400MPa level High-alloy Ultra-high Strength Steel chemical composition ranges is as follows by weight: C:0.20% ~ 0.30%, Cr:1.0% ~ 3.0%, Ni:9.5% ~ 10.5%, Co:7.0% ~ 9.0%, Mo:1.3% ~ 2.0%, Al:1.3% ~ 2.0%, Si≤0.10%, Mn≤0.10%, Nb≤0.10%, La≤0.10%, surplus is iron.

The heat treating regime that above-mentioned High-alloy Ultra-high Strength Steel obtains more than 2400MPa tensile strength is as follows:

Quenching: 900 DEG C ~ 1000 DEG C, insulation 0.5h ~ 2h, water-cooled, oil cooling or air cooling;

Deepfreeze :-50 DEG C ~-80 DEG C, insulation 1h ~ 3h, returns back to room temperature in air;

Timeliness: 520 DEG C ~ 560 DEG C, insulation 3h ~ 8h, air cooling.

Deepfreeze and timeliness can be carried out twice.

The advantage that the present invention has and beneficial effect are: the present invention is combined reinforced with Al, Mo, and strengthening effect is remarkable; Its tensile strength >=2400MPa of ultrahigh-strength steel of the present invention, yield strength >=2100MPa, specific tenacity is more than the high strength titanium alloy of 1300MPa level, there is good plasticity and toughness simultaneously, Co content is no more than 9%, have good economy concurrently, open the wide purposes of ultrahigh-strength steel at aviation field.It is the ultrahigh-strength steel that current intensity is the highest.

Embodiment

Below the present invention is described in further details.

1) chemical composition ranges

High-alloy Ultra-high Strength Steel of the present invention, its composition range is as follows by weight: C:0.20% ~ 0.30%, Cr:1.0% ~ 3.0%, Ni:9.5% ~ 10.5%, Co:7.0% ~ 9.0%, Mo:1.3% ~ 2.0%, Al:1.3% ~ 2.0%, Si≤0.10%, Mn≤0.10%, Nb≤0.10%, La≤0.10%, surplus is iron.

The effect of each chemical element is as follows above:

C: main strengthening element, produces gap solution strengthening, forms alloy carbide Mo ₂c, increases secondary hardening peak value, obtains high strength.Along with the increase of C content, the intensity of alloy improves, but toughness reduces, and damages welding property.Therefore C content should control 0.20% ~ 0.30%.

Cr: improve solidity to corrosion, and have solution strengthening effect, can Mo be replaced ₂mo in C forms (Mo, Cr) ₂c, promotes secondary hardening reaction, reduces Mo ₂the Precipitation Temperature of C, improves overaging susceptibility, reduces tempering resistance.Cr content is more than 3%, and intensity will decline.18Ni type maraging steel is not because containing Cr, and solidity to corrosion is poor.Therefore Cr content should control 1.0% ~ 3.0%.

Mo: main strengthening element, alloy carbide Mo ₂the forming element of C is the reason forming secondary hardening peak.Along with the raising of Mo content, secondary hardening peak raises, and the intensity of alloy improves, but too high Mo content will reduce toughness.Therefore Mo content should control 1.3% ~ 2.0%.

Ni: improve toughness element, appropriate Ni are the guarantees that steel obtains high tenacity.But too high Ni content will increase the amount of residual austenite in steel, reduces intensity.Therefore Ni content should control 9.5% ~ 10.5%.

Co: although Co can not form compound with other elements, it promotes secondary hardening reaction strongly, promotes Mo ₂c small and dispersed is separated out.In addition, the acting in conjunction of Co, Mo can carry heavy alloyed obdurability.Consider cost-saving, Co content controls 7% ~ 9%.

Al: one of main strengthening element of this alloy, and Ni forms NiAl phase, with Mo ₂the common reinforced alloys of C.Improve with Al content, form more NiAl phase, alloy strength increases, but toughness reduces.Therefore Al content should control 1.3% ~ 2.0%.

Nb: crystal grain thinning element, should control below 0.10%.

La: inclusion conditioning element, should control below 0.10%.

Si: impurity element, reduces toughness, should control below 0.10%.

Mn: impurity element, reduces toughness, should control below 0.10%.

Other impurity elements in alloy, as S, P etc., reduce toughness, should control in lower level.

2) smelt

High-alloy Ultra-high Strength Steel of the present invention can adopt the methods such as vacuum induction, vacuum induction+esr or vacuum induction+vacuum arc remelting to smelt.

3) cogging forging

Its cogging of High-alloy Ultra-high Strength Steel of the present invention forging can adopt the conventional texturing machine such as forging hammer, pressing machine, milling train, and forging range is 1150 DEG C ~ 900 DEG C.

4) thermal treatment

High-alloy Ultra-high Strength Steel of the present invention, the heat treating regime obtaining more than 2400MPa tensile strength is as follows:

Timeliness: 520 DEG C ~ 560 DEG C, insulation 3h ~ 8h, air cooling.

Deepfreeze and timeliness can be carried out twice.

Embodiment 1:

First vacuum induction melting 25kg steel ingot is adopted.Ingot scalping also carries out cogging forging after excising dead head, and Forge Heating temperature is 1150 DEG C, is swaged into through two fire bar.Chemical analysis, stretching, impact specimen is got subsequently from bar.Stretching, impact specimen measure tensile property, impelling strength after quenching+deepfreeze+timeliness.

Sample heat treating regime is as follows:

Quenching: 900 DEG C, insulation 1h, oil cooling;

Deepfreeze :-70 DEG C, insulation 2h, returns back to room temperature in air;

Timeliness: 540 DEG C, insulation 5h, air cooling.

Test-results is in table 1 and table 2.

Table 1 chemical composition (wt%)

Composition	C	Cr	Ni	Mo	Co	Al	Nb	La	Si	Mn	S
												% by weight	0.25	2.07	10.16	1.64	8.07	1.54	0.05	0.003	0.04	0.05	0.002
Composition	P	Fe
												% by weight	0.005	Surplus

Table 2 mechanical property

Embodiment 2:

Sample heat treating regime is as follows:

Quenching: 950 DEG C, insulation 1h, oil cooling;

Deepfreeze :-70 DEG C, insulation 2h, returns back to room temperature in air;

Timeliness: 540 DEG C, insulation 5h, air cooling.

Test-results is in table 3 and table 4.

Table 3 chemical composition (wt%)

Composition	C	Cr	Ni	Mo	Co	Al	Nb	La	Si	Mn	S
												% by weight	0.30	2.03	10.10	1.70	8.10	1.80	0.06	0.004	0.03	0.02	0.001
Composition	P	Fe
												% by weight	0.003	Surplus

Table 4 mechanical property

Claims

1. a 2400MPa level High-alloy Ultra-high Strength Steel, is characterized in that, chemical composition ranges is as follows by weight: C:0.20% ~ 0.30%, Cr:1.0% ~ 3.0%, Ni:9.5% ~ 10.5%, Co:7.0% ~ 9.0%, Mo:1.3% ~ 2.0%, Al:1.3% ~ 2.0%, Si≤0.10%, Mn≤0.10%, Nb≤0.10%, La≤0.10%, surplus is iron.