RU2288966C1 - Corrosion-resisting steel and article made of its - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the development of corrosion-resisting steel used as sheets or foil in soldered cellular panels, jacket articles and internal set articles working at temperature up to 450°C. Proposed corrosion-resisting steel comprises the following components, wt.-%: carbon, 0.005-0.03; chrome, 8.5-11; nickel, 10-16; molybdenum, 1.5-2.5; aluminum, 0.1-1.2; silicon, 0.2-1.3; calcium, 0.005-0.05; niobium, 0.1-0.3; cerium, 0.005-0.1; lanthanum, 0.003-0.05, and iron, the balance. Invention provides enhancing strength indices, impact tenacity and corrosion-resistance that allows decreasing weight of carrying cellular constructions and enhancing safety indices.

EFFECT: improved and valuable technical properties of steel.

4 cl, 2 tbl, 1 ex

Description

The invention relates to the field of metallurgy, in particular to the creation of corrosion-resistant steel, which, along with high strength, high toughness, high fatigue strength and high technological ductility, used as sheets or foils in soldered honeycomb panels, in the details of the lining, in the details of the inner set (stringers, corrugations, etc.) working up to 450 ° C.

Known corrosion-resistant steel for the manufacture of soldered honeycomb panels of the following chemical composition (wt.%):

Carbon 0.005-0.03 Chromium 12.6-14.1 Nickel 2.5-4.8 Molybdenum 1.2-2.0 Manganese 2.1-5.0 Aluminum 0.25-0.6 Silicon 0.75-1.2 Zirconium 0.01-0.08 Niobium 0.1-0.4

One or more elements from the group:

Cerium 0.005-0.1 Lanthanum 0.003-0.05 Yttrium 0.001-0.05 Iron rest

(A.S. USSR No. 1340213)

Steel has a sufficiently high strength σ _B = 1000-1200 MPa, but has a limited application temperature of up to 350 ° C, an increase in operating temperature to 450 ° C leads to a significant reduction in toughness and to a decrease in the reliability characteristics of a product made of this steel.

Known corrosion-resistant steel for the manufacture of power brazed-welded nodes of the following chemical composition (wt.%):

Carbon no more than 0,03 Chromium 10.0-13.0 Nickel 8.0-11.0 Molybdenum 0.4-0.9 Titanium 0.02-0.15 Cobalt 0.2-0.6 Boron 0.001-0.005 Lanthanum 0.01-0.1 Calcium 0.001-0.05 Iron rest

(RF patent No. 2175684)

Steel has the following mechanical properties: tensile strength 950-1020 MPa, elongation of 15-16%. The disadvantage of steel is the reduced toughness after heating at 450 ° C, 100 hours.

Also known are corrosion-resistant steels of martensitic class for a similar purpose of the following chemical compositions (wt.%):

Carbon 0.03-0.08 Chromium 12.8-14.5 Nickel 5.2-6.5 Molybdenum 0.7-1.2 Tungsten 0.7-1.2 Vanadium 0.15-0.3 Niobium 0.08-0.3 Nitrogen 0.01-0.03 Yttrium 0.001-0.01 Calcium 0.001-0.01 Zirconium 0.01-0.1 Lanthanum 0.01-0.1 Iron rest

(RF patent No. 2176283)

Carbon 0.08 Silicon 0.5-4.0 Manganese no more than 4.0 Nickel 5.0-9.0 Chromium 10.0-17.0 Molybdenum 0.3-2.5 Titanium 0.15-1.0 Aluminum no more than 0.1 Nitrogen no more than 0,03 Iron rest

(UK Patent No. 2145734)

Carbon 0.01 Silicon 1.5-2.95 Manganese no more than 5,0 Nickel 4.0 - 8.0 Chromium 12.0-18.0 Copper 0.5-3.5 Nitrogen no more than 0,15 Sulfur less than 0,004 Iron rest

(US Patent No. 4849166)

A disadvantage of the known corrosion-resistant steels of the martensitic class is their lack of manufacturability in the production of tape and foil, as well as a decrease in viscosity after the brazing process and operational heating at 450 ° C and, therefore, a decrease in the operational reliability of the product made of these steels.

Known corrosion-resistant steel of the austenitic class of the following chemical composition (wt.%):

Carbon 0.02-0.08 Manganese 1.5-2.5 Silicon 0.5-1.0 Chromium 12.5-14.5 Nickel 14.5-16.5 Molybdenum 1.5-2.5 Titanium 0.1-0.4 Vanadium 0.02-0.05 Tantalum 0.005-0.2 Nitrogen no more than 0,01 Cobalt 0.02-0.05 Iron rest

(US Patent No. 4,530,719)

A disadvantage of the known corrosion-resistant steel of the austenitic class is the insufficient level of strength, limiting its use for the manufacture of power bearing structures.

The closest in chemical composition and purpose to the proposed steel is corrosion-resistant steel 03X6H16M2B, adopted as a prototype.

Steel has the following chemical composition (wt.%):

Carbon 0.005-0.03 Chromium 5.0-8.0 Nickel 14.0-18.5 Molybdenum 1.0-3.0 Aluminum 0.1-0.4 Niobium 0.1-0.3 Zirconium 0.05-0.2 Boron 0.001-0.003 Copper 0.3-0.8

At least one component from the group:

Cerium 0.005-0.1 Lanthanum 0.003-0.05 Yttrium 0.001-0.05 Iron rest

(RF patent No. 2221895)

Steel is designed for soldered honeycomb panels, which are sound-absorbing supporting structures, operable up to 450 ° С.

However, this steel has insufficient fatigue strength and corrosion resistance, as well as an insufficient level of strength characteristics, which limits its use in other parts of the new generation aircraft.

The technical task of the present invention is the creation of high-strength corrosion-resistant technological steel in the production of sheets and foils with high values of ductility and viscosity, which are stored in products after the brazing process, deep drawing and operational heating at temperatures up to 450 ° C and with high fatigue strength and corrosion resistance.

To achieve this, a corrosion-resistant steel containing iron, carbon, chromium, nickel, molybdenum, aluminum, niobium, cerium, lanthanum is proposed, characterized in that it additionally contains silicon and calcium in the following ratio of components (wt.%):

Carbon 0.005-0.03 Chromium 8.5-11.0 Nickel 10.0-16.0 Molybdenum 1.5-2.5 Aluminum 0.1-1.2 Silicon 0.2-1.3 Calcium 0.005-0.05 Niobium 0.1-0.3 Cerium 0.005-0.1 Lanthanum 0.003-0.05 Iron the basis

In this case, the ratio of components that determine the austenite content (%) in steel should satisfy the ratios:

For sheet: K _M = Cr + 0.6Mo + 1.5Ni + 0.7Si + 56С-0.1Al = 31 ÷ 32

For foil: K _M = Cr + 0.6Mo + 1.2Ni + 0.7Si + 56С-0.1Al = 29 ÷ 31.

The selected ratio of components for the sheet allows you to get a martensitic structure with a regulated content of residual austenite (18-20%), which allows you to get high strength, toughness and high fatigue strength, and for foil - austenitic-martensitic structure (~ 50% martensite + 50% austenite), which allows to obtain, along with high technological ductility, high strength.

The quantitative and qualitative content of elements in the proposed steel provides high strength, toughness, fatigue strength and corrosion resistance due to the introduction of silicon and calcium, as well as by increasing the chromium content.

Alloying with silicon provides high strength steel due to solid-solution hardening of the martensitic matrix. When the silicon content is less than 0.2%, the required level of strength is not achieved, and when the silicon content is more than 1.3%, embrittlement is observed during heating.

Doping with calcium by binding sulfur increases corrosion resistance.

The introduction of chromium in steel in an amount of 8.5-11% provides high corrosion resistance and does not lead to a decrease in viscosity during heating to 450 ° C due to the selected phase composition, characterized by a martensite formation coefficient (K _M ).

Thus, as a result of complex alloying with the specified ratio of alloying elements within the proposed composition, the necessary steel characteristics are achieved (high initial strength and toughness values, the absence of embrittlement during the thermal soldering cycle and after operational heating at 450 ° C), high fatigue strength and corrosion resistance, which allows you to create parts of the internal set (corrugation stringers), cladding details or soldered honeycomb panels and other parts that are supporting structures and.

An example implementation.

In laboratory conditions, the proposed composition of the steel smelted in a vacuum induction furnace was tested in comparison with the prototype.

The chemical and phase compositions and mechanical properties of the steels are shown in tables 1 and 2, where examples 1-4 of the proposed composition, and examples 5-6 of the composition of the prototype.

The mechanical and corrosion properties were determined after the following heat treatment modes with an imitation of the soldering heat cycle: soldering at 1160 ° С + hardening and tempering or soldering + hardening + cold working + tempering.

As can be seen from table 2, the proposed steel as for the option of sheet steel (for sheathing) - compositions 1 and 2, and for foil (for honeycomb filler) - compositions 3 and 4 compared with the prototype are increased:

tensile strength and yield strength:

for a sheet: σ _B at 190 ÷ 230 MPa and σ _0.2 at 100 ÷ 340 MPa;

for foil; σ _B at 280 ÷ 400 MPa and σ _0.2 at 200 ÷ 270 MPa;

the value of impact strength for the sheet after operational heating 450 ° C, 100 h higher compared with the prototype 1.7 ÷ 2.4 times, which is associated with the selected phase composition of steel,

resistance to low-cycle fatigue is 1.3 times higher, and resistance to corrosion cracking is ~ 2 times.

Thus, the use of the proposed steel will make it possible to create parts of the internal set (stringers, corrugations), sheathing parts or soldered honeycomb panels and other parts that are load-bearing structures and increase the reliability characteristics - resistance to low-cycle fatigue and corrosion cracking in new-generation aircraft.

Table 1
Chemical and phase composition of steels No. pl. Steel Semifinished The content of elements, mass% Phase composition FROM Cr Ni Mo Al Si Nb Ca Xie La Cu Zr I AT K _M * A **% one Proposed Sheet 0.005 10 10 2.0 0.1 1,0 0.2 0.01 0.005 0.003 - - - - 31 eighteen 2 - // - 0,03 eleven eleven 2,5 0.3 1.3 0.3 0.05 0.01 0.01 - - - - 32 twenty 3 Foil 0.005 8.5 fifteen 1,5 1,0 0.2 0.1 0.005 0.005 0.003 - - - - 29th 40 four - // - 0,03 9.0 16 2.0 1,2 0.3 0.3 0.05 0.1 0.05 - - - - 31 fifty 5 Prototype Sheet 0,03 8 fifteen 2.9 0.38 - 0.26 - 0.08 - 0.8 0.17 - 0.003 thirty 27 6 Foil 0,03 7.8 18.5 3.0 0.4 0.3 0.1 0.72 0.2 0.002 40 one hundred * K _M - coefficient of martensite formation;
** A% - the amount of austenite.

table 2
The mechanical properties of steels No. pl. Steel Semifinished σ _in σ _0.2 δ ₅ CCT * MCU ** CPN *** CCT * CPN *** MPa % J / cm ² N = 2 × 10 ⁶ c σ _max MPa marine environment τ = 3 months J / cm ² Marine environment τ = 3 months without heating after heating 450 ° C, 100 h one Proposed Sheet 1290 1000 16 58 500 σ = 900 MPa 48 σ = 800 MPa 2 - // - 1330 1240 fourteen fifty - // - 35 3 Foil 1060 900 24.5 67.5 400 σ = 700 MPa 45 σ = 600 MPa four - // - 1180 970 24 60.5 - // - 44 5 Prototype Sheet 1100 900 twenty 80 380 σ = 500 MPa twenty σ = 350 MPa 6 Foil 850 720 twenty one hundred 300 σ = 350 MPa 80 σ = 350 MPa * KST - impact strength of the sample with a fatigue crack,
** MTSU - low-cycle fatigue,
*** CPN - corrosion under stress.

Claims (4)

1. Corrosion-resistant steel containing iron, carbon, chromium, nickel, molybdenum, aluminum, niobium, cerium, lanthanum, characterized in that it additionally contains silicon and calcium in the following ratio, wt.%: Carbon 0.005-0.03 Chromium 8.5-11 Nickel 10-16 Molybdenum 1.5-2.5 Aluminum 0.1-1.2 Silicon 0.2-1.3 Calcium 0.005-0.05 Niobium 0.1-0.3 Cerium 0.005-0.1 Lanthanum 0.003-0.05 Iron Rest 2. Corrosion-resistant steel according to claim 1, characterized in that the ratio of the components determining the austenite content in the steel satisfies the following ratio: K _M = Cr + 0.6Mo + 1.5Ni + 0.75Si + 56С-0.1Al = 31 ÷ 32, where K _M is the coefficient of martensite formation. 3. Corrosion-resistant steel according to claim 1, characterized in that the ratio of the components determining the austenite content in the steel satisfies the following ratio: K _M = Cr + 0.6Mo + 1.2Ni + 0.75Si + 56С-0.1Al = 29 ÷ 31, where K _M is the coefficient of martensite formation. 4. A product of corrosion-resistant steel, characterized in that it is made of steel according to any one of claims 1 to 3.