RU2515716C1 - Low-activated fire-resistant radiation-resistant steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: steel contains, wt %: carbon 0.16-0.25, silicon 0.30-1.30, manganese 0.50-2.00, chrome 10.00-13.50, tungsten 0.50-2.50 and/or molybdenum 0.60-0.90, vanadium 0.20-0.40, nickel 0.50-0.80, niobium 0.20-0.40 and/or tantalum 0.01-0.30, boron 0.001-0.008, cerium 0.001-0.02 and/or zirconium nitride, aluminium 0.005-0.02, iron and admixtures - balance.

EFFECT: steel has high fire resistance with preservation of low level of induced radioactivity and its quick collapse.

4 cl, 3 tbl

Description

The invention relates to metallurgy of heat-resistant steels used in nuclear energy, in particular, for the manufacture of parts of active zones of fast-neutron nuclear reactors and equipment of thermonuclear reactors.

Known low-activated radiation-resistant steel containing carbon, silicon, manganese, chromium, nickel, vanadium, copper, molybdenum, cobalt, tungsten, yttrium, niobium, aluminum and iron in the following ratio, wt.%: Carbon - 0.13-0 ,eighteen; silicon - 0.20-0.35; Manganese - 0.30-0.60; chrome - 2.0-3.5; nickel - 0.01-0.05; vanadium - 0.10-0.35; copper - 0.01-0.10; molybdenum - 0.01-0.05; cobalt - 0.01-0.05; tungsten -1.0-2.0; yttrium - 0.05-0.15; niobium - 0.01-0.05; aluminum - 0.01-0.10; iron is the rest.

Moreover, the total content of nickel, cobalt, molybdenum, niobium and copper in the known steel is not more than 0.2 wt.%, And the ratio (V + 0.3W) / C varies from 3 to 6. Steel has a low level of induced activity, but is not heat resistant at temperatures exceeding 500 ° C.

(RU No. 2135623, MKI 6 C22C 38/52, published 08/27/1999]

Known low-activated heat-resistant radiation-resistant steel containing carbon, silicon, manganese, chromium, tungsten, vanadium, titanium, boron, cerium and / or yttrium, zirconium, tantalum, nitrogen and iron in the following ratio, wt.%: Carbon - 0.10 -0.21; silicon - 0.10-0.80; Manganese - 0.50-2.00; chrome - 10.00-13.50; tungsten - 0.80-2.50; vanadium - 0.05-0.40; titanium - 0.03-0.30; boron - 0.001-0.008; cerium and / or yttrium in the amount of 0.001-0.10; zirconium - 0.05-0.20; tantalum - 0.05-0.20; nitrogen - 0.02-0.15; iron is the rest.

The ratio of the total content of vanadium, titanium, zirconium and tantalum to the total content of carbon and nitrogen is from 2 to 9.

However, the heat resistance of this steel of 650 ° C is insufficient at temperatures in the core of the new generation of reactors of 650-710 ° C.

(RU No. 2211878, C22C 38/32, published September 10, 2003)

The objective of the invention and the technical result is the creation of steel with heat resistance to a temperature of 710 ° C while maintaining a low level of induced radioactivity and its rapid decline.

The technical result is achieved by the fact that low-activated heat-resistant radiation-resistant steel contains carbon, silicon, manganese, chromium, tungsten and / or molybdenum, vanadium, nickel, niobium and / or tantalum, boron, cerium and / or zirconium nitride, aluminum, iron and inevitable impurities in the following ratio of components, wt.%:

Carbon 0.16-0.25 Silicon 0.30-1.30 Manganese 0.50-2.00 Chromium 10.0-13.50 Tungsten and / or 0.50-2.50 Molybdenum 0.60-0.90 Vanadium 0.20-0.40 Nickel 0.50-0.80 Niobium and (or) 0.20-0.40 Tantalum 0.01-0.30 Boron 0.001-0.008 Cerium and (or) 0.001-0.020 Zirconium nitride 0.05-0.20 Aluminum 0.005-0.02 Iron and impurities rest

The technical result is also achieved if the steel also contains at least one element selected from the group, wt.%: Titanium 0.03-0.30, nitrogen 0.08-0.17, calcium 0.005-0.02, zirconium 0.05-0.20; the total content of impurities of fusible metals - lead, bismuth, tin, antimony and arsenic does not exceed 0.05 wt.%, and the content of inevitable impurities of sulfur, phosphorus and oxygen does not exceed, wt.%: sulfur≤0.008; phosphorus≤0.008 and oxygen≤0.005.

Alloying with titanium, zirconium, nitrogen and calcium in the composition of the steel provides a decrease in activability under the influence of neutron irradiation and increases the rate of decline of the induced activity of the steel.

Limiting the content of lead, bismuth, tin, antimony and arsenic increases the resistance of steel to low-temperature radiation embrittlement (NTRO) under neutron irradiation.

A high level of heat resistance is ensured by the formation of a stable martensitic-ferrite structure with the presence of solid solution strengthening elements (C, N, B) and substitution elements (W and (or) Mo, V, Nb and / or Ta, Cr, Ni), hardening carbide (MeC, Me ₂ C, Me ₂₃ C ₆ , etc.), nitride (MeN, Me ₂ N) and carbonitride (MeCN) phases, as well as particles of the Laves type Fe ₂ (W, Mo).

High resistance to low-temperature radiation embrittlement (NTRO) is ensured by the limited δ-ferrite content in the steel structure, the preferred precipitation of V, Ti, Nb and / or Ta and Zr carbides, nitrides and carbonitrides in the steel structure compared to similar chromium compounds, an additional limitation the content in the steel of low-melting elements (copper, lead, bismuth, tin, antimony and arsenic), as well as sulfur, phosphorus and oxygen, to an even greater degree contributes to an increase in the resistance of NTRO steel.

The creation of a low-activation heat-resistant radiation-resistant steel is carried out by introducing finely dispersed particles of zirconium nitride uniformly distributed in the volume of steel into the steel structure. At the same time, complex alloying of steel with elements with a rapid decrease in the induced radiation activity is preserved and a certain relationship is created between γ ° stabilizing elements (C, N, Mn, Ni) and α stabilizing elements (Cr, Mo, W, Nb, V, Ta, Ti, Zr, Mo, Nb, etc.).

The introduction of finely dispersed zirconium nitrides into the steel allows the formation of a large number of crystallization centers uniformly distributed in the metal volume.

In the process of solidification, chemically stable particles of zirconium nitride, being in the melt, have increased resistance to dissociation and will be centers of crystallization of austenitic grains, which significantly crushes the primary austenitic grain, increases the border area of austenitic grains, which significantly reduces the amount of vanadium and niobium carbides and nitrides falling over the boundaries of austenitic grains, and increases their dispersion. This provides an increase in strength properties and at the same time indicators of ductility and viscosity, and also forms precipitates that increase strength at elevated temperatures. Zirconium nitride also plays the role of an additional nucleus of phases released during creep, due to which a finer dispersed phase distribution is formed and the heat resistance of steel increases.

The aluminum content in an amount of 0.005-0.02 wt.% Favorably changes the shape of non-metallic inclusions, cleans and strengthens grain boundaries, increases their ductility, toughness and heat resistance, which leads to an increase in the service and technological properties of steel.

The steel according to the invention was smelted in a 150 kg induction furnace, with metal casting on ingots (5 heats), from which samples were forged after forging to determine mechanical properties and heat resistance.

As the known steel, metal (EP823 steel - heat 6) of the industrial production method was selected, heat-treated according to the standard regime: normalization from 1050 ° C, tempering at 720 ° C for 3 hours (Table 1).

Tensile tests were carried out on cylindrical samples of five times the length with a diameter of the calculated part of 6 mm in accordance with GOST 1497-84 at room temperature and GOST 9651-84 at elevated temperatures (Table 2). As a criterion of heat resistance, tests for long-term strength were used, which were carried out according to GOST 10145-62 (Table 3).

Table 2 shows the mechanical properties of steels depending on the test temperature obtained after heat treatment: normalization from 1050 ° C, tempering at a temperature of 730 ° C, air cooling.

The results of tests for long-term strength (table 3) showed that the proposed steel is more heat resistant at 650 and 710 ° C than the prototype steel.

Since the foundations of the inventive steel and steel of the prototype are close, the previously obtained data on the calculation of the kinetics of the decrease in induced activity (dose rate - radiation) in steels after the alleged exposure in a DEMO thermonuclear reactor for 10 years and subsequent exposure to 500 years indicate the preservation of the claimed steel low induced activity of the prototype steel (especially for steel compositions, where tungsten is introduced instead of molybdenum and tantalum is introduced instead of niobium, as well as zirconium and titanium, these elements, being inactive, are not magnify the induced activity of the inventive steel), especially noticeable after aging over 10 years. After aging for 50 years with the inventive steel, you can work without special protection and send it to remelting for reuse.

Thus, the proposed steel can be used in nuclear energy for the manufacture of elements of the active zones of atomic reactors, for example, cladding of fast-neutron fuel rods of the BN type. The use of steel will provide a high national economic effect by improving the properties of heat resistance and resistance to low-temperature radiation embrittlement.

The proposed steel has undergone extensive laboratory testing at OAO NPO TsNIITMASH and is recommended for industrial testing.

Table 1 The chemical composition of the proposed and known steel The content of components, wt.% Swimming trunks number one 2 3 four 5 6 Carbon 0.16 0.20 0.25 0.18 0.20 0.16 Silicon 0.30 1.10 1.00 1.20 0.40 1.18 Manganese 0.50 1.20 2.00 2.00 0.80 0.60 Chromium 10.00 12.50 13.50 13.00 12.00 10.90 Nickel 0.50 0.70 0.50 0.50 0.80 0.80 Molybdenum 0.60 0.90 - 0.85 0.90 0.76 Tungsten 0.50 1.80 2.00 1,50 - 0.69 Niobium 0.20 0.25 - 0.40 0.30 0.33 Tantalum - 0.01 0.15 0.10 0.25 - Vanadium 0.20 0.25 0.10 0.35 0.25 0.30 Boron 0.001 0.003 0.007 0.006 0.008 0.006 Calcium 0.005 0.005 0.01 0,020 0.02 - Cerium 0.001 0.015 0.005 0,020 0.02 0.10 Aluminum 0.005 0.015 0.008 0.008 0.02 0.02 Zirconium nitride - 0.20 0.10 0.015 0.40 - Titanium - 0,035 0,03 - - - Nitrogen - 0.08 0.15 - 0.17 0.04 Sulfur 0.008 0.006 0.008 0.008 0.008 0.008 Phosphorus 0.008 0.015 0.009 0.008 0.009 0.01 oxygen 0.006 0.004 0.005 0.003 0.005 0.006 ∑Pb, Bi, Sb, As, Sn 0.004 0.003 0.004 0.005 0.006 0.006 Iron Rest Rest Rest Rest Rest Rest

table 2 Mechanical properties of the proposed and known steels Steel composition T isp., ° C σ _{0.2, N / mm} ² σ b, N / mm ² δ,% one twenty 850 950 fifteen 650 500 550 twenty 710 360 380 25 2 twenty 870 970 fourteen 650 510 560 twenty 710 365 395 24 3 twenty 865 1150 fifteen 650 520 570 twenty 710 350 375 25 four twenty 850 950 fifteen 650 500 550 twenty 710 360 380 25 5 twenty 870 970 fourteen 650 510 560 twenty 710 365 395 24 Famous twenty 700 820 16 650 320 420 eighteen 710 280 295 25

Table 3 The limits of long-term strength of steel depending on the test temperature Steel composition T isp., ° C Long-term strength, N / mm ² , during 10 ⁵ hours one 650 120 710 105 2 650 123 710 104 3 650 135 710 110 four 650 130 710 123 5 650 125 710 105 6 650 108 710 85

Claims (4)

1. Low activated heat-resistant radiation-resistant steel containing carbon, silicon, manganese, chromium, tungsten and / or molybdenum, vanadium, nickel, niobium and / or tantalum, boron, cerium and / or zirconium nitride, aluminum, iron and inevitable impurities, characterized the fact that it contains components in the following ratio, wt.%:
carbon 0.16-0.25 silicon 0.30-1.30 manganese 0.50-2.00 chromium 10.0-13.50 tungsten and / or 0.50-2.50 molybdenum 0.60-0.90 vanadium 0.20-0.40 nickel 0.50-0.80 niobium and / or 0.20-0.40 tantalum 0.01-0.30 boron 0.001-0.008 cerium and / or 0.001-0.020 zirconium nitride 0.05-0.20 aluminum 0.005-0.02 iron and impurities rest 2. Steel according to claim 1, characterized in that it contains at least one element selected from the group, wt.%: Titanium 0.03-0.30, nitrogen 0.08-0.17, calcium 0.005-0 02 and zirconium 0.05-0.20. 3. Steel according to claim 1, characterized in that the total content of impurities of fusible metals - lead, bismuth, tin, antimony and arsenic - does not exceed 0.05 wt.%. 4. Steel according to claim 1, characterized in that the content of impurities — sulfur, phosphorus and oxygen — does not exceed, wt.%: Sulfur ≤0.008, phosphorus ≤0.008 and oxygen ≤0.005.