CN101050508A

CN101050508A - Corrosion resistant structural steel with ultra high strength

Info

Publication number: CN101050508A
Application number: CN 200710099334
Authority: CN
Inventors: 杨卓越; 陈嘉砚; 苏杰; 丁雅莉
Original assignee: Central Iron and Steel Research Institute
Current assignee: Central Iron and Steel Research Institute
Priority date: 2007-05-17
Filing date: 2007-05-17
Publication date: 2007-10-10
Anticipated expiration: 2027-05-17
Also published as: CN100500922C

Abstract

This invention relates to an ultrahigh-strength and corrosion-resistant structural steel, whose chemical composition is: C less than or equal to 0.02 wt.%, Si less than or equal to 0.15 wt.%, Mn less than or equal to 0.15 wt.%, S less than or equal to 0.01 wt.%, P less than or equal to 0.01 wt.%, Cr 8.0-10.0 wt.%, Ni 11.5-14.5 wt.%, Mo 0.5-2.5 wt.%, Ti 1.0-2.0 wt.%, Al 0.02-0.5 wt.%, and Fe as balance. The strength of the structural steel is 1800-1900 MPa. The structural steel has such advantages as low cost, high strength, high fracture toughness, and high corrosion resistance.

Description

A kind of corrosion resistant structural steel with ultra high strength

Technical field

The invention belongs to field of alloy steel, particularly a kind of corrosion resistant structural steel with ultra high strength, its intensity reaches 1800-1900Mpa, has high toughness and solidity to corrosion simultaneously.

Background technology

In the prior art, along with scientific technological advance and human civilization progress, the corrosion resistant metal material that exploitation has superstrength has become inevitable trend and the scientific and technological target of pursuing.Because corrosion has not only been lost material, has been destroyed component surface, and makes material property degradation.According to the Direct Loss that cause because of material corrosion of the report U.S. in 2006 was 2,790 hundred million dollars/year, was equivalent to 3.2% of national GDP, if consider surface treatment cost such as cadmium plating, to environment damage etc., material corrosion causes damage then more surprising.

As everyone knows, intensity mainly adopts the steel grades such as maraging steel of low-alloy super-strength steel 300M and 18Ni above the steel of 1600MPa, though it is also fine that these steel have intensity, the toughness of superelevation, but do not contain the Cr element, corrosion stability is relatively poor, maraging steel with 18Ni (300) is an example, and fracture toughness property is at 70-80MPam ^1/2Between, but in 3.5% salt solution, drop to 30MPam ^1/2Below, thus these steel the use in corrosion-resistant environment more and more is restricted as structured material.Though and traditional PH Stainless Steel such as 13-8Mo and 17-4PH etc. have good solidity to corrosion, but intensity is on the low side, the Ti of U.S.'s development recently strengthens the Custom465 martensite aged stainless steel, corrosion stability is fine, but insufficient strength height, be lower than the maraging steel of 18Ni (250), use not ideal enough as structured material.Wherein table 1 is the chemical component table of above-mentioned existing several steel grades.

The chemical component table of the above-mentioned existing several steel grades of table 1

Summary of the invention

The object of the present invention is to provide the corrosion resistant structural steel with ultra high strength that a kind of cost is low, have high-fracture toughness.

According to above-mentioned purpose, the technical scheme of integral body of the present invention is: consider (showing 18Ni (300) and Custom 465 Chemical Composition tables the table 1) from present 18Ni (300) maraging steel and martensite aged stainless steel present situation, proportioning components by control Fe, Cr, Ni, forming Fe-Ni-Cr is alloy, and reduction Mo, raising Ti, make every effort to make intensity to be higher than martensite aged stainless steel, tensile strength level near 18Ni (300) maraging steel, contain higher Cr simultaneously, corrosion stability is far above 18Ni (300) maraging steel.And from improving the flexible angle, the Ni content of martensite aged stainless steel is no more than 11.25% usually, and the present invention brings up to 14.5% at most with Ni content, helps steel keeping the high-intensity while, has good toughness again.This invention steel does not contain expensive metal Elements C o, and Ni and Mo content are also lower simultaneously, so material cost is lower, has a extensive future.

According to above-mentioned purpose and technical scheme, the concrete technical scheme of the present invention is: it is (mass%): C≤0.02% that this tempering is learned moiety, Si≤0.15%, Mn≤.15%, S≤0.01%, P≤0.01%, Cr 8.0-10.0%, Ni 11.5-14.5%, Mo 0.5-2.5%, Ti 1.0-2.0%, Al 0.02-0.5%, surplus is Fe.

Above-mentioned chemical composition design is according to as follows:

C is considered as impurity element and controls, because C and Ti form brittle inclusion (Ti (C)) easily, therefore the toughness of infringement steel need C is controlled in 0.02%.

Ni is one of important alloying element of steel of the present invention, and Ni strengthens precipitated phase Ni ₃Ti and Ni ₃(Mo, Ti) element, can strengthen martensitic matrix cross slip ability again, reduce Cold Brittleness Transition Temperature, but too high Ni increases residual austenite content, cause intensity to reduce, also increase material cost simultaneously, therefore considering precipitation strength phase Ni chemical equivalent, and consider remaining a certain amount of Ni in martensitic matrix, Ni is controlled between the 11.5-14.5% is advisable.

Cr also is one of important alloying element of steel of the present invention, and Cr guarantees that steel has certain corrosion stability, also can improve hardening capacity simultaneously, and control transformation temperature As, Ms etc.But too high Cr can cause forming ferrite, the toughness of steel is descended, so Cr should be controlled between the 8.0-10.0%.

Mo, Ti are the main strengthening elements of steel of the present invention, Mo has the effect that purifies crystal boundary, suppresses embrittlement, especially suppresses thermal embrittlement, and Mo has the age hardening effect simultaneously, but do not contain under the situation of Co a little less than the age hardening effect, so Mo content is lower than traditional maraging steel; The ageing strengthening effect of Ti is still very remarkable under the condition that does not contain Co, and strengthening precipitated phase mainly is Ni ₃Ti.In addition, the market value of Mo is higher, and the market value of Ti is lower, and therefore low Mo content, high Ti content improve the cost performance of steel.But too high Mo, Ti all lose toughness, especially Ti.Therefore after taking all factors into consideration, Mo and Ti are controlled at respectively: Mo 0.5-2.5%; Ti 1.0-2.0%.

Al also is the main strengthening element of steel of the present invention, and Al makes the martensitic matrix ordering of steel, promptly forms NiAl, Ni ₂(Al Ti) waits ordered phase, and this all has tangible strengthening effect, and Al has the effect of protection Ti simultaneously, but too high Al has bigger infringement to the toughness of steel, therefore is controlled at 0.02-0.5%.

Meanwhile, need S, P, Si and Mn etc. are controlled at following level: Si≤0.15%, Mn≤0.15%, S≤0.01%, P≤0.01% in order to guarantee the obdurability of steel.Gas content is not higher than 30ppm simultaneously.

The present invention has compared with prior art that cost is low, superstrength, high-fracture toughness, high anti-corrosion advantage.Above-mentioned advantage is specially: alloying element contents such as this steel Ni, Mo reduce, and do not contain expensive metal elements such as Co, and material cost is lower; Its intensity reaches 1800-1900Mpa (290ksi level); Fracture toughness property still can reach 80MPam ^1/2, and have higher corrosion stability, can use under the worse environment than 18Ni maraging steel; Processing performance is suitable with the 18Ni maraging steel; Be suitable for using under the medium atmosphere.

The preparation method that employing of the present invention and prior art are intended mutually:

Steel of the present invention adopts vacuum induction melting, smelts base and should carry out hot-work subsequently between 1150-800 ℃ the 1150-1200 ℃ of processing that homogenizes.Forging blank intensity after water-cooled behind 900 ℃ of austenitizings ,-73 ℃ of deepfreezes is lower, and cold deformation ability and cutting ability are good, can carry out near the clean processing that is shaped, reach following performance: Rp0.2 〉=1800MPa after 480-510 ℃ of timeliness subsequently, Rm 〉=1900MPa, A 〉=8%, Z 〉=45%.The timeliness after strain is very little, the member precision is guaranteed, and do not have oxidation, the decarburization problem.

Embodiment

The employing vacuum induction melting has added the vacuum consumable refusion and smelting steel of the present invention and compared steel, chemical ingredients sees Table in 2.Table 3 is steel of the present invention and the mechanical property of compared steel and the contrast table of corrosion rate.In the above-mentioned tabulation, sequence number 1-4# is the embodiment of the invention, and the 5# compared steel is PH13-8Mo, and the 6# compared steel is 17-4PH, and the 7# compared steel is Custom465, and the 8# compared steel is 18Ni maraging steel (300 grades), and the 9# compared steel is 300M.Steel ingot is forged into the rod iron that diameter is 60mm, after the solution heat treatment of steel of the present invention through 900 ℃ * 1h, carry out the ageing treatment of 510 ℃ * 4h again, and comparative steel is carried out normal thermal treatment respectively under the condition that is fit to.Carried out level and smooth tension test respectively, U type notch shock and fracture toughness test.Solidity to corrosion adopts salt-fog test, and test conditions: concentration is 50 ± 5g/L sodium chloride solution; PH value is 6.5-7.2; Salt fog the temperature inside the box is 35 ± 2 ℃; Spray pattern is spraying continuously; Time is 480 hours.

The chemical component table of table 2 steel of the present invention and compared steel

Steel grade and numbering		C	Si	Mn	P	S	Ni	Cr	Co	Mo	Ti	Al	Fe
Steel grade and numbering		C	Si	Mn	P	S	Ni	Cr	Co	Mo	Ti	Al	Fe	Steel of the present invention	1	0.007	0.04	0.02	0.003	0.002	11.5	9.9	-	2.5	1.4	0.08	Surplus
2	0.004	0.06	0.13	0.003	0.0012	12.4	9.0	-	2.0	1.5	0.02	Surplus			1	0.007	0.04	0.02	0.003	0.002	11.5	9.9	-	2.5	1.4	0.08	Surplus
2	0.004	0.06	0.13	0.003	0.0012	12.4	9.0	-	2.0	1.5	0.02	Surplus	3		0.003	0.12	0.07	0.005	0.002	13.8	8.5	-	1.3	1.8	0.3	Surplus
4	0.005	0.05	0.06	0.002	0.004	14.3	8.2	-	0.6	1.7	0.05	Surplus	3		0.003	0.12	0.07	0.005	0.002	13.8	8.5	-	1.3	1.8	0.3	Surplus
4	0.005	0.05	0.06	0.002	0.004	14.3	8.2	-	0.6	1.7	0.05	Surplus	Compared steel		5	0.03	0.06	0.04	0.005	0.002	8.2	12.5	-	2.3	-	1.2	Surplus
6	0.05	0.6	0.7	0.01	0.008	4.3	16.8	-	0.30	Cu 3.8	-	Surplus			5	0.03	0.06	0.04	0.005	0.002	8.2	12.5	-	2.3	-	1.2	Surplus
6	0.05	0.6	0.7	0.01	0.008	4.3	16.8	-	0.30	Cu 3.8	-	Surplus		7	0.005	0.08	0.07	0.005	0.004	11.0	11.7	-	1.0	1.6	-	Surplus
8	0.003	0.01	0.01	0.003	0.002	18.5	-	8.5	4.98	0.65	0.080	Surplus		7	0.005	0.08	0.07	0.005	0.004	11.0	11.7	-	1.0	1.6	-	Surplus
8	0.003	0.01	0.01	0.003	0.002	18.5	-	8.5	4.98	0.65	0.080	Surplus		9	0.41	1.72	0.75	0.004	0.003	1.81	0.76	-	0.42	-	V0.07	Surplus

The mechanical property of table 3 steel of the present invention and compared steel and the contrast table of corrosion rate

Sample		Rm MPa	R _P0.2 MPa	A ％	Z ％	A _KU2 J	K _IC MPa·m ^1/2	Corrosion rate (g/m ²·h)
Sample		Rm MPa	R _P0.2 MPa	A ％	Z ％	A _KU2 J	K _IC MPa·m ^1/2	Corrosion rate (g/m ²·h)	The invention steel	1	1820	1730	10.0	60	55	105	0.006
2	1840	1740	9.5	58	53	98	0.008			1	1820	1730	10.0	60	55	105	0.006
2	1840	1740	9.5	58	53	98	0.008	3		1900	1810	8.0	48	33	80	0.010
4	1870	1780	8.5	50	41	85	0.011	3		1900	1810	8.0	48	33	80	0.010
4	1870	1780	8.5	50	41	85	0.011	Compared steel		5	1620	1482	12	45	50	82	0.003
6	1365	1262	15	52	60	80	0.004			5	1620	1482	12	45	50	82	0.003
6	1365	1262	15	52	60	80	0.004		7	1700	1610	9.0	55	45	82	0.002
8	1920	1870	8.0	56	42	80	Not anti-corrosion		7	1700	1610	9.0	55	45	82	0.002
8	1920	1870	8.0	56	42	80	Not anti-corrosion		9	1960	1580	10	50	46	71	Not anti-corrosion

Can see that from table 3 steel of the present invention is when tensile strength reaches 1900MPa, fracture toughness property still can reach 80MPam ^1/2, compares with Custom465 with PH13-8Mo, 17-4PH and to have higher intensity and toughness, but solidity to corrosion is lower slightly, the obdurability level of this steel is near 300 grades of maraging steel, but have solidity to corrosion preferably, with 300M mutually specific tenacity but have high toughness and solidity to corrosion with lower slightly.

Claims

1, a kind of corrosion resistant structural steel with ultra high strength, it is characterized in that it is (mass%): C≤0.02% that this tempering is learned moiety, Si≤0.15%, Mn≤0.15%, S≤0.01%, P≤0.01%, Cr 8.0-10.0%, Ni 11.5-14.5%, Mo 0.5-2.5%, Ti 1.0-2.0%, Al 0.02-0.5%, surplus is Fe.