WO1997006286A1 - Aciers inoxydables particulierement utiles pour l'absorption de neutrons thermiques - Google Patents

Aciers inoxydables particulierement utiles pour l'absorption de neutrons thermiques Download PDF

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Publication number
WO1997006286A1
WO1997006286A1 PCT/JP1996/002258 JP9602258W WO9706286A1 WO 1997006286 A1 WO1997006286 A1 WO 1997006286A1 JP 9602258 W JP9602258 W JP 9602258W WO 9706286 A1 WO9706286 A1 WO 9706286A1
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Prior art keywords
stainless steel
less
content
neutron absorption
corrosion resistance
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PCT/JP1996/002258
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English (en)
Japanese (ja)
Inventor
Haruhiko Kajimura
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Sumitomo Metal Industries, Ltd.
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Priority claimed from JP7203230A external-priority patent/JPH0949066A/ja
Application filed by Sumitomo Metal Industries, Ltd. filed Critical Sumitomo Metal Industries, Ltd.
Priority to CA002229002A priority Critical patent/CA2229002C/fr
Priority to KR1019970709744A priority patent/KR100278058B1/ko
Priority to EP96926611A priority patent/EP0844312B1/fr
Priority to DE69608688T priority patent/DE69608688T2/de
Publication of WO1997006286A1 publication Critical patent/WO1997006286A1/fr
Priority to US08/984,689 priority patent/US5820818A/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F1/00—Shielding characterised by the composition of the materials
    • G21F1/02—Selection of uniform shielding materials
    • G21F1/08—Metals; Alloys; Cermets, i.e. sintered mixtures of ceramics and metals

Definitions

  • the present invention relates to ferritic and austenitic stainless steels having excellent thermal neutron absorption and used as nuclear fuel-related containers for transporting nuclear fuel, containers for storing used nuclear fuel or racks.
  • Thermal neutrons are generated from nuclear materials stored in nuclear fuel-related containers for transport of nuclear fuel, containers for storing spent nuclear fuel, or racks.
  • the materials used as these members are required to have excellent thermal neutron absorption capacity.
  • the base material of the material and the joints formed by welding these materials have excellent corrosion resistance. .
  • stainless steel containing about 1 wt% of B is generally used in the JIS SS 304 austenitic stainless steel having excellent corrosion resistance. This is because B has a large neutron absorption cross-sectional area, and the inclusion of B can improve the thermal neutron absorption capacity of stainless steel.
  • stainless steel containing B In addition to the hot workability, cold workability and toughness problems mentioned above, stainless steel containing B also has weldability problems. When stainless steel is used as a structural material, a joining method by welding is often adopted as a joining method. However, in conventional stainless steel containing B, since the B content is as high as about lwt%, cracks occur in the weld. In particular, solidification cracking of the melted portion is remarkable, and it may be difficult to manufacture containers.
  • Naturally occurring neutron absorption cross section is very large 1 57 G d. About 1 6 mixture of isotopes, including wt%, the absorption cross section 4 9 0 0 0 b der You. Natural B comprises from about 20 wt% of the large 1Q B neutron absorption cross section, the remaining portion consists of a small 11 B neutron absorption cross section, the neutron absorption cross section is 760 b.
  • Gd has about 4.4 times the neutron absorption capacity compared to B at the same weight. Therefore, when the same thermal neutron absorption capacity is added to stainless steel, it was expected that Gd would require a smaller amount of addition and would have a smaller effect on workability and corrosion resistance.
  • Japanese Unexamined Patent Publication (Kokai) No. 62-55757 discloses a stainless steel and austenitic stainless steel containing 0.1 to 3.0 wt% of Gd instead of B.
  • Japanese Patent Application Laid-Open No. 5-258581 discloses an austenitic stainless steel containing 0.2 to 1.0 *% of 8 and 0.1 to 2.0 wt% of Gd.
  • No. 1,92792 discloses an austenitic stainless steel containing up to 3.0 wt% B and 0.05-: L. 0 wt% Gd.
  • the stainless steel containing Gd disclosed in Japanese Patent Application Laid-Open No. 62-55757 does not contain B, so that deterioration in hot workability and cold workability can be avoided. I can do it.
  • the content of Gd is too high, there is still a problem that the hot workability is reduced.
  • Gd is an expensive alloying element, so there is a problem in economics if stainless steel has a high neutron absorption capacity.
  • the above-mentioned document shows a frit stainless steel containing 6 wt% or less of Ni, but when it contains several percent of Ni, the heat caused by the inclusion of Ni is included. A reduction in workability occurs.
  • the austenitic stainless steels disclosed in JP-A-5-255812 and JP-A-6-192792 have a high B content except for some of them, as shown in the examples.
  • the former is more than 0.7 wt% and the latter is more than 0.5 wt%. Interworkability and weldability are not sufficient. Therefore, when strong processing is performed, cracks may occur, and weld cracks may occur in the weld.
  • conventional stainless steel containing Gd alone or both B and Gd and having enhanced thermal neutron absorption capacity has a high workability, cold workability, toughness, weldability, and corrosion resistance including HAZ. I could not be satisfied with all the performances.
  • the present invention has been made in order to solve the above problems, and has excellent heat neutron absorption ability, as well as hot workability, cold workability, toughness, weldability, and corrosion resistance of a base material including HAZ.
  • An object of the present invention is to provide excellent ferritic and austenitic stainless steels suitable for use in containers for nuclear fuel. Disclosure of the invention
  • the present invention relates to a nuclear fuel container which is excellent in thermal neutron absorption capacity, has excellent hot workability, cold workability, toughness, weldability, and corrosion resistance of a base material including HAZ, and is inexpensive to produce.
  • the present invention relates to ferritic and austenitic stainless steels suitable for such applications.
  • the ferritic stainless steel of the present invention has the following chemical composition, and is preferably characterized in that the relationship between B and Gd satisfies the following formula (1). In weight percent, C 0.01% or less, S i 0.5% or less,
  • Nc ⁇ (1-0.015 XB%) x B% ⁇ + (4.4 x Gd%)
  • the content rates of C and N are respectively C: 0
  • N 0.008% or less
  • the toughness can be further improved.
  • the austenitic stainless steel of the present invention has the following chemical composition.
  • the relationship between B and Gd satisfies the above formula (1).
  • N 0.30% or less, Y 0.3% or less,
  • the B content was 0.2%. By setting the content to 0.5%, hot workability, cold workability, and weldability can be further improved.
  • the B content is kept low, the B content is selected as high as possible within the range, and the shortage of thermal neutron absorption capacity is compensated for by Gd.
  • the content of C and N is low for bright stainless steel, and the content of Mn is low for austenitic stainless steel. Therefore, in addition to the thermal neutron absorption capacity, it is excellent in workability such as hot workability and cold workability, and corrosion resistance, particularly HAZ. Furthermore, it has excellent toughness and weldability, and is inexpensive to manufacture, making it extremely suitable as a material for containers of nuclear fuel.
  • Gd has a larger neutron absorption cross-section than B, and is therefore an effective element for increasing the neutron absorption capacity of stainless steel.
  • Gd content increased, it was found that the cracks generated were remarkable.
  • Austenitic stainless steel to which G d has been added tends to crack when heated at high temperatures, and when the content is high, cracks occur even at low heating temperatures. This tendency was also observed in the case of stainless steel containing a small amount of Ni.
  • (C) Corrosion resistance is to limit the Mn content in austenitic stainless steel to a low level, and to limit the C content and N content in a ferritic stainless steel to a low level. Improve by.
  • the B and Gd contents of the stainless steel of the present invention are determined in the following order.
  • Nc ⁇ (1-0.015x B%) x B% ⁇ + (4.4x Gd%) '... 2
  • Equation (3) expresses the thermal neutron absorption capacity Nc of stainless steel containing both B and Gd as B It is a formula shown in equivalent. This formula takes into account that when B is added, a B compound (boride) is generated and the density of the stainless steel decreases. If the B content is less than 0.3%, Equation (3) may be used.
  • Nc B% + (4.4xGd%) '... 3
  • the contents of B and Gd are determined based on the above-described concept. Therefore, it is possible to obtain a stainless steel having the required neutron absorption capacity and excellent hot workability, cold workability, toughness, weldability and corrosion resistance.
  • the thermal neutron absorption capacity Nc required for stainless steel is a value determined by conditions such as the use of stainless steel.
  • the stainless steel currently used for reactor control, nuclear fuel storage, etc. often needs to contain about 0.6% of natural B. Then, as a preferable condition, Nc ⁇ 0.8 was set as described above.
  • the ferrite stainless steel of the present invention limits the C content together with N as low as possible. By lowering the C content, the strength of the stainless steel is reduced to some extent. However, not only corrosion resistance is improved, but also hot workability and cold workability are improved, and weldability is also improved. In the case of the X-light stainless steel of the present invention, the C content is reduced. This is mandatory. Therefore, in the present invention, it is less than 0.01%. It is preferably 0.005% or less.
  • S i an element added for deoxidizing molten steel.
  • Si since A1 having a deoxidizing effect is added, Si may not be added.
  • the ferrite stainless steel of the present invention was used. In stainless steel, Si has little effect on the properties required for stainless steel. If Si is added, it must be 0.5% or less. If the Si content exceeds 0.5%, a eutectic having a low melting point is formed with Gd, which deteriorates hot workability.
  • Mn may not be added. It may be added to obtain effects such as deoxidation of molten steel and improvement of hot workability, but in such a case, the upper limit is preferably 1% or less. If it exceeds 1%, the corrosion resistance of the stainless steel decreases.
  • Cr An element essential for ensuring the corrosion resistance required for flylite stainless steel. If the Cr content is less than 13%, a stable corrosion-resistant film is not formed on the surface of stainless steel, so that a sufficient effect of improving corrosion resistance cannot be obtained. On the other hand, if the Cr content exceeds 26%, the hot workability deteriorates. Therefore, the Cr content was set to 13 to 26%.
  • B In the fluorite type stainless steel, B forms boride and has the property of deteriorating hot workability, cold workability, and weldability. However, in the case of the fluorine-based stainless steel of the present invention, in order to satisfy the required thermal neutron absorption capacity, it was positively added, and the upper limit was set to 1.1%. When the B content is 1.1% or less, the ferritic stainless steel of the present invention does not adversely affect properties such as hot workability, cold workability, and toughness.
  • the B content was set to 0.1 to 1.1%.
  • the neutron absorption capacity is satisfied by using B and Gd together.
  • B is inexpensive as an additive material
  • the stainless steel of the present invention is characterized by being used in preference to Gd.
  • Gd has about 4.4 times the neutron absorption enhancement effect of B at the same content.
  • the adverse effect on hot workability, etc. of mild stainless steel is less than that of B. Therefore, it was decided to contain at least 0.05%.
  • the upper limit was limited to 1.5%.
  • the Gd content of the fly-based stainless steel of the present invention is set to 0.05 to 1.5%, and a content as small as possible is selected within this range.
  • the ranges of the B and Gd contents are as described above, and the B and Gd contents are determined within this range. That is, when the neutron absorption capacity required for each of the fly-based stainless steels is determined, as described above, the B and Gd content in the order of (a)-(b) and (c) Should be requested. If the neutron absorption capacity Nc is 2, the lower limit of Gd for ferritic stainless steel is 0.05%, so substitute 2 for Nc and 0.05 for Gd in equation (2) to contain B. As a result, the B content is 1.83%, exceeding the upper limit of 1.1%. In this case, it is possible to determine the B and Gd content by setting the B content to a value that is 1.1 or less that is permissible in characteristics, and calculating the Gd content from equation (2). it can.
  • the B content does not necessarily need to be set to the upper limit, taking into account characteristics such as weldability and hot workability, the range permitted from the viewpoint of economic efficiency, and the like. An appropriate value may be appropriately selected.
  • A1 is an element added during steelmaking to deoxidize molten steel and obtain sound chips.
  • Gd is contained in a range of 0.05% to 1.5%, it is important to sufficiently deoxidize the molten steel so as not to generate oxides of Gd. . This is because when oxides of Gd are formed, the oxides remain in the steel as inclusions, and the inclusions may appear on the surface of the stainless steel. In that case, it is exposed on the surface It is necessary to sufficiently deoxidize the molten steel before adding Gd, since corrosion may proceed with the inclusions as starting points.
  • A1 acid-soluble Al
  • sol. A1 acid-soluble Al
  • Y is an element added as needed.
  • Y has the function of improving hot workability, and is an element that has an affinity for oxygen in molten steel that is stronger than that of A1, and thus is effective in preventing oxidation of Gd.
  • it is preferable to contain 0.0005% or more. However, if it exceeds 0.5%, the effect is saturated, so the upper limit was set to 0.5%.
  • Ni is an element to be added as necessary. It is added when it is necessary to further improve the toughness of ferritic stainless steel. If the Ni content is less than 0.05%, the effect of improving toughness cannot be obtained, and if it exceeds 0.7%, hot workability is impaired. Therefore, when Ni is included, the content is preferably set to 0.05 to 0.7%. When the Ni content exceeds 0.7%, the hot workability deteriorates because a eutectic having a low melting point is formed with Gd.
  • Mo is an element added as needed. It is added when it is necessary to further improve the pitting and crevice corrosion resistance of the fly stainless steel. To obtain the effect, 0.1% or more is necessary, and if it exceeds 3%, hot workability is reduced. Therefore, when Mo is added, the content is preferably set to 0.1 to 3%.
  • Ti and Nb Like Ti and Mo, Ti and Nb are elements to be added as necessary. These elements are added when it is necessary to improve the corrosion resistance and cold workability of the HAZ. To achieve this effect, 0.005% or more for both Ti and Nb When each content exceeds 1%, not only the effect of addition becomes saturated, but also the hot workability and the cold workability decrease. Therefore, when these elements are contained, the content is preferably set to 0.005 to 1%.
  • the N content is preferably as low as possible in order for the ferritic stainless steel of the present invention to have sufficient corrosion resistance. Therefore, the N content is set to 0.015% or less. More desirable is 0.008% or less.
  • P and S are both impurity elements that are inevitably mixed in from the raw materials used in the steelmaking process. These elements reduce the corrosion resistance and workability of ferritic stainless steel, so the smaller the better, the better.
  • P was set to 0.03% or less and S to 0.01% or less as far as there was no practical problem.
  • C is an austenite forming element, t but is an element effective for securing the stability and strength of the austenite phase of Osutenai preparative based stainless steel, C is an effect to reduce the HAZ corrosion resistance.
  • the austenitic stainless steel of the present invention emphasizes the corrosion resistance of HAZ, and the C content is
  • S i is an element added as a deoxidizer for molten steel.
  • Si since A 1 having a deoxidizing effect is added, Si may not be added.
  • the content must be 1% or less. If the S i content exceeds 1%, a eutectic with a low melting point is formed with Gd, which deteriorates hot workability. Preferably, it is 0.5% or less.
  • Mn Mn is an element that functions to stabilize the austenite phase, and is also an element that is effective in suppressing the adverse effects of inevitable impurity S. In order to obtain the effect, it is necessary to contain 0.1% or more. However, if the Mn content exceeds 0.9%, the corrosion resistance, particularly the corrosion resistance of HAZ, decreases. Therefore, the content of ⁇ 411 was set to 0.1 to 0.9%.
  • Ni and Cr Both Ni and Cr are essential elements for ensuring the metallographic structure and corrosion resistance required for austenitic stainless steel.
  • the content of Ni must be 7% or more and the content of Cr must be 18% or more.
  • the Ni content exceeds 22%, the production cost is increased, and a eutectic having a low melting point is formed with Gd, thereby deteriorating hot workability.
  • the Cr content exceeds 26%, the Ni content must be increased in order to austenitic stainless steel in accordance with the increase in the Cr content. As it increases, hot workability decreases.
  • the Ni content was 7-22% and the Cr content was 18-26%.
  • B In austenitic stainless steel, B forms borides and has the property of deteriorating hot workability, cold workability, and weldability.
  • 0.05% or more, preferably 0.2% or more of B is positively added to satisfy the thermal neutron absorption ability.
  • the upper limit of the B content was set to 0.75%.
  • the stainless steel of the present invention has a small effect on properties such as hot workability, cold workability, and weldability.
  • the preferable upper limit of the B content is 0.5%.
  • the present invention is characterized in that it is used in preference to Gd.
  • Gd has about 4.4 times the neutron absorption enhancement effect of B at the same content.
  • Gd has the function of preventing a decrease in weldability due to the inclusion of B. That is, in the case of austenitic stainless steel, the B content tends to peak around 0.3% and the weldability tends to decrease at around 0.1 to 0.8%, but when a small amount of Gd is included. In this case, this decrease in weldability can be suppressed.
  • Gd has the advantage that the adverse effects on the hot workability of austenitic stainless steel are less than those of B. Therefore, it was decided to contain at least 0.1%.
  • Gd is an expensive alloy element, it increases the production cost, and if its content is high, it impairs hot workability. Therefore, the upper limit of the Gd content was set to 1.5%.
  • the Gd content was set to 0.1 to 1.5%, and even within this range, the smallest possible Gd content was selected.
  • the ranges of the B and Gd contents are as described above, and the B and Gd contents are determined within this range. That is, if the neutron absorption capacity required for each austenitic stainless steel is determined, as described above, the contents of B and Gd are determined in the order of (a), (b), and (c). Just ask. If the thermal neutron absorption capacity Nc is 2, the lower limit of the Gd content of the austenitic stainless steel is 0.11%, so that in equation (2), Nc is 2 and Gd is 0.11. When the B content is calculated by substituting for, the B content is 1.55%, exceeding the upper limit of 0.75%. In this case, set the B content to 0.75% or less as permissible in characteristics, and determine the B and G d content by calculating the G d content from equation (2). Can O
  • the B content does not necessarily need to be set to the upper limit, taking into account characteristics such as weldability and hot workability, the range allowed from the viewpoint of economic efficiency, etc. An appropriate value may be appropriately selected.
  • the preferred range of the Gd content is 0.2 to 1.5%.
  • A1 is an element added during steelmaking to deoxidize molten steel and obtain sound chips.
  • the C content is limited to a low value, 0 (oxygen) in the molten steel increases.
  • 0.1 to 1.5% of Gd is contained, it is important to sufficiently deoxidize the molten steel so that oxides of Gd are not formed. This is because when oxides of Gd are formed, these oxides remain as inclusions in the steel, and the inclusions may appear on the surface of the stainless steel. In such a case, corrosion may progress from inclusions exposed on the surface, so the molten steel must be sufficiently deoxidized to prevent the formation of Gd oxides. .
  • A1 acid-soluble A1
  • the content exceeds 0.1%, the effect is saturated and hot workability is further impaired. Therefore, the A1 content was set to 0.005 to 0.1%.
  • N is an element effective in stabilizing the austenitic phase in austenitic stainless steel. N may be added for that purpose. However, in the austenitic stainless steel of the steel of the present invention, since A1 is positively added, when the N content is high, fine A1N precipitates. Fine A 1 N deteriorates the cold workability of steel, so the smaller the N content, the better. N is easily mixed into molten steel in the steelmaking process, and its removal is not easy. Therefore, within a range that can be reached by commercial production and has no practical adverse effect, It was below.
  • Y is an element effective for improving the hot workability of austenitic stainless steel, and is an element added as necessary. To achieve this effect, 0.005% or more is required. On the other hand, if it exceeds 0.3%, the effect is saturated. Therefore, when ⁇ is added, the content is 0.
  • Mo is an element that is added as necessary, considering the working environment of austenitic stainless steel, because it has the function of improving pitting corrosion resistance and crevice corrosion resistance. In order to obtain the effect, it is necessary to contain 0.01% or more. On the other hand, when the content exceeds 3%, not only the effect is saturated, but also the hot workability is impaired. Therefore, when Mo is added, the content is preferably set to 0.01 to 3%.
  • P and S are both impurity elements that are inevitably mixed in from the raw materials used in the steelmaking process. These elements reduce the corrosion resistance and hot workability of austenitic stainless steel, so the smaller the better, the better. However, there is a limit to lowering P and S in commercial production, so that P is set to 0.0 as far as there is no practical problem.
  • Table 1 shows the chemical composition of the obtained steel ingot.
  • Steel Nos. 1 to 18 are of the stainless steel of the present invention, and Nos. 19 to 28 are of the comparative examples in which the content of some alloying elements is out of the range specified in the present invention.
  • Nc (B% + 4.4xGd%) when B ⁇ 0.3%
  • the high-temperature tensile test was performed under the test conditions of a rod-shaped test piece having a diameter of 10 mm and a length of 130 mm, a temperature of 1100 ° C, and a tensile speed of 1 / s, and the drawing ratio of the test piece was obtained.
  • the hot workability was evaluated based on this drawing ratio (high-temperature ductility).
  • the Charpy impact test was performed under the test conditions of a sub-size V notch test piece having a width of 1 to 4 specified in JIS Z2202 and a temperature of 80 ° C.
  • the corrosion resistance was investigated by using bead-on-blade welding by TIG welding and test specimens collected from HAZ. If the corrosion resistance of HAZ is good, it can be judged that the corrosion resistance of the base metal is good, so the corrosion resistance test of the base metal was omitted.
  • the HAZ surface of the test piece was polished with a piece of # 600 roughness paper.
  • the corrosion test was performed by immersing the test piece in an air-saturated solution containing 2500 ppm of B3 + and l OOOppm of C1—, at a temperature of 80 ° C and a potential sweep rate of 20 mV / min. It was carried out by a method of obtaining an electric potential when the density reached 100 A / cm 2 . Corrosion resistance was evaluated by a method of comparing pitting corrosion resistance according to the pitting potential required in this test.
  • each test material in Table 1 has a sufficient thermal neutron absorption capacity with a thermal neutron absorption capacity Nc of 1.1 or more.
  • 12 test materials of steels N 0.1, 5 to 14 and 18 of the present invention are examples in which the B content is close to the upper limit specified in the present invention, and by changing the Gd content, In this case, the neutron absorption capacity Nc of the ferritic stainless steel was set to a predetermined value.
  • the Nc values of these test materials are between 2.0 and 6.9.
  • the results for these twelve test materials indicate that the B content was kept at 1.1% or less, so the reduction in high temperature tensile test was as high as 67 to 83. It can be seen that the hot workability is good.
  • the pitting corrosion potential of HAZ was as high as 121 to 175 mV VsSCE, and it was confirmed that HAZ was also excellent in corrosion resistance.
  • Steel Nos. 2 to 4 of the present invention have a low Gd content, and steel Nos. 15 to 17 also contain a certain amount of Gd and have a low B content of 0.15 to 0.56%. is there.
  • These six test materials had a drawing value of 66 to 89% in the high temperature tensile test and a pitting corrosion potential of HAZ of 132 to 185 mV, confirming that both hot workability and HAZ corrosion resistance were excellent.
  • steel No. 15 and 16 containing 0.7% or less of N i is Shah ruby one impact value ll ⁇ 13 JZcm 2 and higher, and a high toughness.
  • the pitting potential of HAZ was 175 to 185 mVvs SCE, The latter was as high as 161 to 166 mVv s SCE, indicating that the corrosion resistance of HAZ including the base metal was particularly excellent.
  • the ferritic stainless steel of the present invention has a high neutron absorption.
  • the B content is limited to a low level, and the C content is less than 0.01% and ⁇ [ It supports the great effect of limiting the content to 0.015% or less.
  • the content of some of the alloying elements is out of the range specified in the present invention. Therefore, as is clear from Table 2, at least one of hot workability and corrosion resistance is inferior.
  • the steel No. 27 to B content exceeds the range defined in the present invention, 48% aperture in high-temperature tensile test, Charpy impact value of 3 JZcm 2 and both low, hot workability, toughness It is clear that both are bad. Since the B content is too high at 1.36%, the adverse effects are clearly apparent.
  • steel Nos. 19, 22, and 24 in which the content of one or both of C and N is out of the range specified in the present invention have a pitting potential of 34 to 72 mV Vs SCE, All are lower than the examples of the present invention, and it is clear that they are inferior in corrosion resistance.
  • Steels Nos. 23 and 25 with too high Gd and Ni contents have extremely low draw values in high-temperature tensile tests, confirming that the hot workability is extremely poor.
  • Austenitic stainless steels having different chemical compositions were melted by a vacuum melting method and formed into a 30 kg ingot having a diameter of about 11 Omm.
  • Table 3 shows the chemical composition of the obtained steel ingot.
  • Steel Nos. 1 to 12 are austenitic stainless steels of the present invention, and steel Nos. 13 to 24 are comparative examples in which the content of some alloying elements is out of the range specified in the present invention.
  • Nc (B% + 4.4xGd%) when B ⁇ 0.3%
  • the high-temperature tensile test was performed under the following test conditions: a test piece having a diameter of 1 Omm and a length of 13 Omm, a temperature of 105 Ot: and a tensile speed of 1 / s, and the drawing ratio of the test piece was obtained.
  • the hot workability was evaluated based on this drawing ratio (high-temperature ductility).
  • a test piece with a width of 100 mm and a length of 100 mm was cut out from the above material, and TIG welding was performed on this test piece under the conditions of a voltage of 15 V, a current of 200 A, and a speed of 150 mm / min.
  • a ballast strain test with a strain of 2% is performed, a penetration test is performed, and the cracks are observed with a stereoscopic microscope to determine the length of the cracks that have occurred. Investigated.
  • the corrosion resistance was determined by subjecting the material after the solution heat treatment described above to a sensitization treatment at 650 ° C for 2 hours, followed by bead-on-blade welding by TIG welding, and a test taken from HAZ. The pieces were examined. If the corrosion resistance of HAZ is good, it can be judged that the corrosion resistance of the base metal is also good, so the corrosion resistance test of the base metal was omitted.
  • the HAZ surface of the test piece was polished with emery paper having a roughness of 600 incense.
  • the corrosion test was performed by immersing the test piece in an air-saturated solution containing 3000 ppm of B 3+ and 500 1 « ⁇ 1— at a temperature of 80 ° C and a potential sweep rate of 2 OmV / min. density was carried out by a method for determining the potential when it becomes 1 00 "AZc m 2.
  • the corrosion resistance, the pitting potential obtained in this study were evaluated by the method of comparing the pitting resistance.
  • cold workability 180 'bending of 6mm and 3mm bending radii on a 20mm wide, 3mm thick, 10mm long plate specimen. The bends were visually observed and evaluated by checking for cracks. Table 4 summarizes these results.
  • each test material of the present invention example has a sufficient thermal neutron absorbing ability when the thermal neutron absorbing ability Nc is 1.1 or more.
  • the three test materials of steel Nos. 10 to 12 of the present invention are examples in which the B content is close to the upper limit specified in the present invention, and by changing the Gd content, the austenitic stainless steel is changed. In this case, the neutron absorption capacity Nc was set to a predetermined value.
  • the Nc values of these test materials are as high as 1.5 to 6.0.
  • the results for these three test materials showed that the B content was suppressed to 0.75% or less, so the reduction in the high-temperature tensile test was as high as 72 to 75%. It can be seen that the hot workability is good. The weldability is relatively good with a crack length of 6.4 mm or less.
  • the pitting potential of the test specimens collected from the HAZ of the sensitized base metal was as high as 66 to 74 mVvs SCE, indicating that the base metal and HAZ were also excellent in corrosion resistance.
  • the B content of the other steels N 0.1 to 9 of the present invention is 0.5% or less and is lower than the above three test materials, so that hot workability, weldability, cold workability ( Properties such as bending workability).
  • test materials of steel Nos. 1 to 12 of the present invention each have a low Mn content of 0.9% or less. Therefore, the pitting potential of HAZ is as high as 71 mV Vs SCE or more, and the corrosion resistance of HAZ is particularly good. Of course, the corrosion resistance of the base material is also excellent.
  • the austenitic stainless steel of the present invention has high neutron absorbing ability, and is also excellent in hot workability, weldability, cold workability, and corrosion resistance. The reason is that, in addition to restricting the B content to a low 0.75%, the minimum required Gd is contained, and the Mn is further restricted to 0.9% or less.
  • test materials of steels N 0.23 and 24 whose Mn content exceeds the range specified in the present invention have extremely low pitting potential and are inferior in corrosion resistance of HAZ containing the base metal.
  • steels N 0.15 and 16 having too high a Gd content had a significantly low drawing value in a high-temperature tensile test and were inferior in hot workability.
  • the B content is limited to a low value in consideration of hot workability, weldability, etc.
  • the highest possible content is selected within the range, and the shortfall in thermal neutron absorption is compensated for by G d. Therefore, the stainless steel of the present invention has sufficient thermal neutron absorption capacity, is excellent in properties such as hot workability, weldability, and cold workability, and is inexpensive to manufacture.
  • the Mn is limited to a low value
  • the C and N contents are limited to a low value. Also has excellent corrosion resistance. Therefore, it is the most suitable material to be applied to nuclear fuel transport containers, spent nuclear fuel storage containers, racks, etc., which require high thermal neutron absorption capacity and excellent corrosion resistance.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Metallurgy (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Organic Chemistry (AREA)
  • Ceramic Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

L'invention concerne un acier inoxydable ferritique, contenant en pour-cent poids les ingrédients chimiques principaux suivants, tout en satisfaisant de préférence à la relation (1) entre B et Gd: C moins de 0,01 %, Mn 1 % ou moins, Ni 0,7 % ou moins, Cr 13-26 %, B 0,1-1,1 %, Gd 0,05-1,5 %, Al 0,002-0,1 %, N 0,0015 % ou moins. L'invention concerne également un acier inoxydable austénitique, contenant en pour-cent poids les ingrédients chimiques principaux suivants, tout en satisfaisant de préférence à la relation (1) entre B et Gd: C 0,02 % ou moins, Mn 0,1-0,9 %, Ni 7-22 %, Cr 18-26 %, B 0,05-0,75 %, Gd 0,11-1,5 %, Al 0,005-0,1 %, N 0,030 % ou moins. Ces aciers ont d'excellentes propriétés d'absorption des neutrons thermiques. Egalement, ils sont faciles à transformer, à chaud ou à froid, ils présentent une bonne résistance à la corrosion, en particulier à la corrosion HAZ, et ils sont peu coûteux à fabriquer. En plus, ils ont une grande dureté et sont faciles à souder. Ces matériaux conviennent tout particulièrement bien à la réalisation de récipients destinés à recevoir des combustibles nucléaires, etc. Nc ≥ 0,8 (1), où Nc = {(1-0,015 x B %) x B %} + (4,4 x Gd %).
PCT/JP1996/002258 1995-08-09 1996-08-08 Aciers inoxydables particulierement utiles pour l'absorption de neutrons thermiques WO1997006286A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
CA002229002A CA2229002C (fr) 1995-08-09 1996-08-08 Aciers inoxydables particulierement utiles pour l'absorption de neutrons thermiques
KR1019970709744A KR100278058B1 (ko) 1995-08-09 1996-08-08 열중성자 흡수능이 우수한 페라이트계 스테인레스강
EP96926611A EP0844312B1 (fr) 1995-08-09 1996-08-08 Aciers inoxydables particulierement utiles pour l'absorption de neutrons thermiques
DE69608688T DE69608688T2 (de) 1995-08-09 1996-08-08 Rostfreier stahl mit hervorragenden thermisch-neutronen-adsorbtionseigenschaften
US08/984,689 US5820818A (en) 1996-08-08 1997-12-03 Stainless steel having excellent thermal neutron absorption ability

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP7/203230 1995-08-09
JP7203230A JPH0949066A (ja) 1995-08-09 1995-08-09 熱中性子吸収用フェライト系ステンレス鋼
JP27216495 1995-10-20
JP7/272164 1995-10-20

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WO1997006286A1 true WO1997006286A1 (fr) 1997-02-20

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CA (1) CA2229002C (fr)
DE (1) DE69608688T2 (fr)
WO (1) WO1997006286A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8481986B2 (en) 2009-07-28 2013-07-09 Kabushiki Kaisha Toshiba Neutron shielding material, method of manufacturing the same, and cask for spent fuel
CN113798487A (zh) * 2021-08-27 2021-12-17 四川大学 一种新型Fe基球形屏蔽合金粉末及其制备方法

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100774097B1 (ko) * 2006-02-16 2007-11-06 학교법인 포항공과대학교 이트륨을 함유하는 페라이트계 스테인레스 강
KR102061839B1 (ko) * 2012-07-30 2020-01-02 단국대학교 천안캠퍼스 산학협력단 중성자 흡수소재 및 그의 제조방법
DE102018130945A1 (de) 2017-12-12 2019-06-13 Vdm Metals International Gmbh Eisen-chrom-nickel-bor-legierung
WO2022103243A1 (fr) * 2020-11-16 2022-05-19 울산과학기술원 Acier inoxydable austénitique sur lequel est formé un film d'oxyde d'alumine résistant à la corrosion dans un eutectique plomb ou plomb-bismuth, et procédé de fabrication associé

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JPS5589459A (en) * 1978-12-27 1980-07-07 Daido Steel Co Ltd Boron-containing stainless steel having good corrosion resistance and workability
JPH05255812A (ja) * 1992-03-12 1993-10-05 Nisshin Steel Co Ltd 熱中性子遮蔽用オーステナイト系ステンレス鋼

Patent Citations (2)

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JPS5589459A (en) * 1978-12-27 1980-07-07 Daido Steel Co Ltd Boron-containing stainless steel having good corrosion resistance and workability
JPH05255812A (ja) * 1992-03-12 1993-10-05 Nisshin Steel Co Ltd 熱中性子遮蔽用オーステナイト系ステンレス鋼

Non-Patent Citations (1)

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Title
See also references of EP0844312A4 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8481986B2 (en) 2009-07-28 2013-07-09 Kabushiki Kaisha Toshiba Neutron shielding material, method of manufacturing the same, and cask for spent fuel
US8624211B2 (en) 2009-07-28 2014-01-07 Kabushiki Kaisha Toshiba Neutron shielding material, method of manufacturing the same, and cask for spent fuel
CN113798487A (zh) * 2021-08-27 2021-12-17 四川大学 一种新型Fe基球形屏蔽合金粉末及其制备方法
CN113798487B (zh) * 2021-08-27 2022-07-08 四川大学 一种Fe基球形屏蔽合金粉末及其制备方法

Also Published As

Publication number Publication date
KR19990028428A (ko) 1999-04-15
DE69608688D1 (de) 2000-07-06
CA2229002A1 (fr) 1997-02-20
KR100278058B1 (ko) 2001-01-15
DE69608688T2 (de) 2001-02-01
CA2229002C (fr) 2001-06-19
KR100294354B1 (ko) 2001-07-12

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