RU2293787C2 - Corrosion-resistant steel for in-vessel devices and heat-exchange equipment of nuclear power stations - Google Patents

Abstract

FIELD: ferrous metallurgy and nuclear engineering.

SUBSTANCE: invention relates to alloyed steels and alloys, which are designed for use in nuclear power mechanical engineering in manufacture of principal and auxiliary equipment of nuclear power stations meeting requirements for use and industrial safety of nuclear power engineering. Technical result of invention is provision of corrosion-resistant austenite steel with improved complex of principal mechanical, technological, and function properties, lower tendency for the grain growth during hot plastic and thermal treatment, as well as welding heatings, which ensures working reliability and required work resource of in-vessel devices and heat-exchange equipment of nuclear power stations. Proposed steel is composed of, wt %: carbon 0.05-0.08, silicon 0.20-0.45, manganese 0.50-0.75, chromium 17.00-19.00, nickel 9.50-10.50, titanium 0.30-0.60, vanadium 0.03-0.09, niobium 0.03-0.10, aluminum 0.05-0.15, sulfur 0.005-0.015, phosphorus 0.005-0.030, and iron - the rest, summary content of vanadium and niobium not having to exceed 0.15%, summary content of sulfur and phosphorus not having to exceed 0.04%, and summary content of silicon, manganese, and aluminum not having to exceed 1.25%.

EFFECT: improved performance characteristics of steel.

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Description

The invention relates to metallurgy of alloyed steels and alloys containing iron as a base with a predetermined ratio of alloying elements, and is intended for use in nuclear power engineering in the production of primary and auxiliary equipment of nuclear power plants that meet the requirements of operation and industrial safety of nuclear energy.

Known corrosion-resistant steels and alloys used in machine-building industries (for example, steel grades 12X18H9, 08X18H10T, 12X18H10T, as well as other analogues mentioned in the scientific, technical and patent literature [1-6]). However, the known materials do not provide the required level and stability of the basic mechanical and service characteristics, which reduces the operability and operational reliability of the used reactor equipment and does not meet modern nuclear safety requirements.

Closest to the claimed composition according to the purpose and composition of the components is austenitic chromium-nickel steel grade 08X18H10T according to GOST 5632-72, table 1, pages 17-18, pos.6-30 [2], containing alloying elements in the following ratio, in wt.%:

carbon ≤0.08 silicon ≤0.8 manganese ≤2.0 chromium 17.0-19.0 nickel 9.0-11.0 titanium 5C-0.7 sulfur ≤0.020 phosphorus ≤0.035 iron rest

This steel grade is characterized by a reduced level of mechanical properties, an increased tendency to grain growth during heat treatment and welding, and reduced technological ductility at the stage of metallurgical processing.

The technical result of the present invention is the creation of corrosion-resistant high-tech steel with an improved set of basic physical and mechanical properties, less prone to grain growth during heat treatment and welding heating, as well as increased technological ductility at the stage of metallurgical redistribution, which ensures operational reliability and the required resource work of internal reactor devices and heat exchange equipment of nuclear power plants.

The technical result is achieved due to the fact that the composition of the known steel containing carbon, silicon, manganese, chromium, nickel, titanium, sulfur, phosphorus and iron, additionally introduced vanadium, niobium and aluminum in the following ratio of components, in wt.%:

carbon 0.05-0.08 silicon 0.20-0.45 manganese 0.50-0.75 chromium 17.00-19.00 nickel 9.50-10.50 titanium 0.30-0.60 vanadium 0.03-0.09 niobium 0.03-0.10 aluminum 0.05-0.15 sulfur 0.005-0.015 phosphorus 0.005-0.030 iron rest

wherein:

- the total content of vanadium and niobium should not exceed 0.15%;

- the total content of sulfur and phosphorus should not exceed 0.04%;

- the total content of silicon, manganese and aluminum should not exceed 1.25%.

A restriction has been introduced on the total content of vanadium and niobium, since exceeding it negatively affects the formation of the most optimal structural state and significantly reduces the specified level of the basic physical and mechanical characteristics of the material.

The ratio of these alloying and modifying additives is chosen so that the claimed composition provides the required level and stability of the most important structurally sensitive characteristics of the material, which in many respects determine the high performance and operational reliability of the reactor internals and heat exchanging equipment of nuclear power plants.

The introduction into the inventive steel of microalloying and modifying additives of vanadium and niobium in the indicated ratio with other alloying elements, and first of all with carbon and titanium, improves its structural state and, as a result, the whole complex of basic mechanical and service properties that positively affect the technological plasticity and deformation ability of the metal at the stage of metallurgical redistribution, and also increases the work of nucleation and development of intergranular cracks in the conditions of static and dynamic loading eny. At the same time, studies have shown [4, 5] that grain is effectively crushed both during solidification of liquid metal, due to the creation of additional crystallization centers, and during various technological heating in the processes of hot deformation and heat treatment by inhibiting grain growth due to the optimal content of carbonitride phases. An increase in the content of vanadium and niobium outside the limits indicated in the claims reduces the effectiveness of their positive influence and does not lead to a noticeable improvement in the structurally sensitive characteristics of the working capacity of the material in the reactor equipment of power plants.

Modification of steel with aluminum in the indicated ratio with silicon and manganese contributes to a deeper deoxidation of the metal during the smelting process and reduces its contamination by non-metallic inclusions and gases. It also provides a significant slowdown in grain growth during high-temperature heating and reduces the tendency of steel to structural anisotropy. The introduction of aluminum in the specified ratio with silicon and manganese outside the limits specified in the claims reduces the effectiveness of its positive effect on the structural state of the resulting metal.

The choice of the complex alloying system of the claimed composition also includes limiting the total content of sulfur and phosphorus, which largely determine the dynamics of the formation of grain boundary segregations at operating temperatures and reduce the cohesive strength between grains, which negatively affects the deformation ability of the metal during long-term operation of reactor equipment.

The obtained higher level of mechanical, welding-technological and service characteristics of steel is ensured by complex alloying of the claimed composition in the indicated ratio with other elements, balanced chemical and phase composition, normalized content of introduced microalloying and modifying additives, as well as control of metal purity in sulfur and phosphorus.

In TsNII KM "Prometey", together with other industry enterprises, in accordance with the plan of ongoing research and development, the necessary set of laboratory, design and experimental-industrial work was carried out on the smelting, plastic and heat treatment of the created steel grade. The metal was smelted in electric arc metallurgical furnaces with processing at an out-of-furnace refining and evacuation unit (UVRV) followed by pressure treatment at industrial forging and pressing equipment to obtain semi-finished products of the required assortment. The metal was tested to determine the complex of basic mechanical and technological properties.

The chemical composition of the investigated materials, as well as the results of determining the whole complex of the most important properties and characteristics, are presented in tables 1 and 2.

The expected technical and economic effect of using the developed steel grade in the national economy will be expressed in increasing the operational reliability and service life of the created reactor equipment.

LITERATURE

1. F.F. Himushin. "Heat-resistant steels and alloys." - M.: Metallurgy, 1969.

2. GOST 5632-72. “High-alloy steels and corrosion-resistant, heat-resistant and heat-resistant alloys” (grades and technical requirements). - M .: Standard, 1977 - prototype.

3. F.B. Pickering. "Physical metallurgy and steel development." - M.: Metallurgy, 1982.

4. V.G. Azbukin, Yu.F. Balandin, V.N. Pavlov et al. "Corrosion-resistant steels and alloys for equipment and pipelines of nuclear power plants". - Kiev: Naukova Dumka, 1983.

5. V.G. Azbukin, V.I. Gorynin, V.N. Pavlov. "Promising corrosion-resistant materials for equipment and pipelines of nuclear power plants." - St. Petersburg, 1998.

6. I.V. Gorynin, A.D. Amaev, V.A. Nikolaev and others. "Radiation damage to steel for pressurized water reactors." - M .: Energoizdat, 1981.

7. M.V. Dobrynina. "The effect of the chemical composition and thermomechanical processing regimes on the grain size in large-size forgings from 08Kh18N10T steel." - Materials of the 4th industry scientific and technical conference on the problems of materials science, St. Petersburg, Central Research Institute of CM "Prometheus", 2004.

8. V.N. Pavlov, V.P. Loginov and others. Materials of the 5th international scientific and technical conference "Problems of materials science in the design, manufacture and operation of nuclear power plants." - St. Petersburg, 1998.

Table 1
The chemical composition of the investigated materials Structure Conventional composition number The content of elements, wt.% FROM Si Mn Cr Ni Ti V Nb Al S R V + nb S + P Al + Si + Mn Fe The claimed one 0.05 0.20 0.50 17.00 9.50 0.30 0,03 0.10 0.15 0.005 0,030 0.13 0,035 0.85 rest 2 0,07 0.30 0.60 18.50 10.00 0.50 0.09 0.06 0.10 0.010 0.005 0.15 0.015 1.00 - // - 3 0.08 0.45 0.75 19.00 10.50 0.60 0.06 0,03 0.05 0.015 0,025 0.09 0,040 1.25 - // - Famous four 0.08 0.70 1,50 18.00 10.00 0.60 - - - 0,020 0,035 - - - - //

Claims (1)

Corrosion-resistant steel for internals and heat exchanging equipment of nuclear power plants containing carbon, silicon, manganese, chromium, nickel, titanium, sulfur, phosphorus, iron, characterized in that it additionally contains vanadium, niobium and aluminum in the following ratio of components, wt. %: Carbon 0.05-0.08 Silicon 0.20-0.45 Manganese 0.50-0.75 Chromium 17.00-19.00 Nickel 9.50-10.50 Titanium 0.30-0.60 Vanadium 0.03-0.09 Niobium 0.03-0.10 Aluminum 0.05-0.15 Sulfur 0.005-0.015 Phosphorus 0.005-0.030 Iron Rest while the total content of vanadium and niobium should not exceed 0.15%; the total content of sulfur and phosphorus should not exceed 0.04%; the total content of silicon, manganese and aluminum should not exceed 1.25%.