EP0844312B1 - 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
EP0844312B1
EP0844312B1 EP96926611A EP96926611A EP0844312B1 EP 0844312 B1 EP0844312 B1 EP 0844312B1 EP 96926611 A EP96926611 A EP 96926611A EP 96926611 A EP96926611 A EP 96926611A EP 0844312 B1 EP0844312 B1 EP 0844312B1
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Prior art keywords
stainless steel
content
neutron absorption
corrosion resistance
absorption ability
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EP96926611A
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German (de)
English (en)
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EP0844312A1 (fr
EP0844312A4 (fr
Inventor
Haruhiko Kajimura
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Nippon Steel Corp
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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 claimed from PCT/JP1996/002258 external-priority patent/WO1997006286A1/fr
Priority claimed from US08/984,689 external-priority patent/US5820818A/en
Publication of EP0844312A1 publication Critical patent/EP0844312A1/fr
Publication of EP0844312A4 publication Critical patent/EP0844312A4/fr
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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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • 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 concerns ferritic and austenitic stainless steels of excellent thermal neutral absorption ability used as components for nuclear fuel transportation casks, spent nuclear fuel storage casks or racks in nuclear industries.
  • Thermal neutrons are generated from nuclear materials contained, for example, in nuclear fuel transportation casks, spent nuclear fuel storage casks or racks. For preventing thermal neutrons from leaking externally, it is demanded for the materials used for such components to have excellent thermal neutron absorption ability. Furthermore, for preventing such casks from undergoing damages by corrosion, it is demanded for base metals of the materials and weld zones of the materials by welding that they have excellent corrosion resistance.
  • stainless steel such as JIS SUS 304 series austenitic stainless steel of excellent corrosion resistance added with about 1 wt% of B (boron) have been usually used for the components described above. This is because B has a large absorption cross section of thermal neutrons and, therefore, thermal absorption ability of the stainless steel can be improved by the addition of B.
  • the thermal neutron absorption ability of a material is increased in proportion with the content of elements having large neutron absorption cross section. Accordingly, the thermal neutron absorption ability of the material is greater as the B content is higher.
  • B-containing austenitic stainless steel involve a drawback that hot workability, cold workability and toughness are deteriorated with the increase in the B content. For instance, since the hot workability is poor, cracking often occurs to rolled materials upon hot rolling for manufacturing hot rolled steel sheets. Such a problem also occurs similarly in a case of containing B in ferritic stainless steel .
  • the reason why the hot workability or cold workability of the B-containing stainless steel is poor may be considered as below.
  • a boride, (Cr,Fe) 2 B is generated. Since the boride has a melting point as low as 1200°C, it deteriorates the hot workability. Furthermore, since it is brittle at a normal temperature, this causes reduction of the cold workability and toughness. That is, upon hot working or cold working, cracks are generated from borides as initiation points.
  • the B-containing stainless steel also involves a problem of weldability.
  • a weld-joining method has often been employed as a joining method.
  • the B content in conventional B added stainless steel is as high as about 1 wt%, cracks are generated at the welded zones. Particularly, cracks at solidification are remarkable in molten portion, making it sometimes difficult to manufacture like as casks.
  • Naturally existent Gd is a mixture of isotopes containing about 16 wt% of 157 Gd having an extremely large neutron absorption cross section, and absorption cross section is 49,000b.
  • Natural B contains about 20 wt% of 10 B having a large neutron absorption cross section and the balance comprises 11 B of a small neutral absorption cross section, and the neutron absorption cross section of the natural B is 760b.
  • Gd has a neutron absorption ability about 4.4 times as great as that of B of an identical weight. Accordingly, for providing the same extent of the thermal neutron absorption ability upon addition to the stainless steel, it has been expected that the addition amount can be reduced and the effect on the workability and the corrosion resistance is also smaller in the case of Gd.
  • Japanese Patent Laid-Open 62-56557 discloses ferritic and austenitic stainless steel containing 0.1 to 3.0 wt% of Gd instead of B.
  • Japanese Patent Laid-Open 5-255812 discloses austenitic stainless steel incorporated with 0.2 to 1.0 wt% of B and 0.1 to 2.0 wt% of Gd
  • Japanese Patent Laid-Open 6-192792 discloses austenitic stainless steel incorporated with up to 3.0 wt% of B and from 0.05 to 1.0 wt% of Gd.
  • austenitic stainless steel disclosed in Japanese Patent Laid-Open 5-255812 and Japanese Patent Laid-Open 6-192792 have high B-content as shown in examples except for several of them, that is, more than 0.7 wt% in the former and not less than 0.5 wt% in the latter, the hot workability, cold workability and weldability can not be considered sufficient. Accordingly, cracks may sometimes occur if intensive working is applied or weld-cracks may be caused to welded zone.
  • conventional stainless steel containing Gd alone or both of B and Gd for improving the thermal neutral absorption ability can not satisfy all the properties of the hot workability, cold workability, toughness and weldability, and the corrosion resistance including HAZ.
  • the present invention has been accomplished in order to solve the foregoing subject and it is an object to provide ferritic and austenitic stainless steel which are excellent in the thermal neutron absorption ability, as well as excellent in the hot workability, cold workability, toughness, weldability and corrosion resistance of a base metal including HAZ, and which are suitable to the use, for example, in nuclear fuel casks.
  • the present invention concerns ferritic and austenitic stainless steel which are excellent in the thermal neutron absorption ability, as well as excellent in the hot workability, cold workability, toughness, weldability and corrosion resistance of a base metal including HAZ, inexpensive in the manufacturing cost and suitable to the use, for example, in nuclear fuel casks.
  • the ferritic stainless steel comprises the following chemical composition, in which a relationship between B and Gd preferably satisfies the following equation (1) on the weight % basis: C: less than 0.01% Si: not more than 0.5% Mn: not more than 1% P: not more than 0.03% S: not more than 0.01% Ni: not more than 0.7% Cr: 13 - 26% B: 0.1 - 1.1% Gd: 0.05 - 1.5% Al: 0.002 - 0.1% N: not more than 0.015% Ti: not more than 1% Nb: not more than 1% Y: not more than 0.3% Mo: not more than 3% Balance: incidental impurities and Fe.
  • Nc ⁇ 0.8 in which Nc ⁇ (1 ⁇ 0.015 x B%) x B% ⁇ + (4.4 x Gd%)
  • the corrosion resistance particularly, the corrosion resistance for HAZ is further improved.
  • the Ni addition by from 0.05 to 0.7%, can further improve the toughness.
  • the austenitic stainless steel according to the present invention comprises the following chemical composition, in which a relationship between B and Gd preferably satisfies the following equation (1) on the weight % basis: C: not more than 0.02% Si: not more than 1% Mn: 0.1 - 0.9 % P: not more than 0.03% S: not more than 0.01% Ni: 7 - 22% Cr: 18 - 26% B: 0.05 - 0.75% Gd: 0.11 - 1.5% Al: 0.005 - 0.1% N: not more than 0.03% Y: not more than 0.3% Mo: not more than 3% Balance: incidental impurities and Fe.
  • the hot workability, cold workability and weldability can be further improved.
  • the B content is kept lower, but the B content should be selected as high as possible, within the restricted range, to supplement the insufficiency of the thermal neutron absorption ability with Gd.
  • the C content and the N content are kept lower in the ferritic stainless steel, while the Mn content is kept to be lower in the austenitic stainless steel. Accordingly, they are excellent in the workability such as hot workability and cold workability, and the corrosion resistance, particularly, the corrosion resistance for HAZ, in addition to the thermal neutron absorption ability. Furthermore, since they are satisfactory in the toughness and weldability and are inexpensive in manufacturing cost, they are highly suitable to materials for nuclear fuel casks.
  • Gd has a larger neutron absorption cross section compared with B, it is an element effective to enhance the neutron absorption ability of stainless steel.
  • Gd addition on the properties of Ni containing austenitic stainless steel, it has been found that cracks occur remarkably in forged materials along with increase in the Gd content upon hot working such as forging.
  • Gd-added austenitic stainless steel tend to be cracked when heated at high temperature and cause cracks even at a low heating temperature if the content is high. This trend is also observed in the ferritic stainless steel containing small amount of Ni.
  • the contents of B and Gd in the stainless steel of the present invention are determined by the following sequence.
  • B and Gd contents are determined based on the concept described above. Accordingly, it is possible to obtain stainless steel having required neutron absorption ability, as well as excellent in the hot workability, cold workability, toughness, weldability and corrosion resistance.
  • the B content is defined as from 0.1 to 1.1%.
  • the neutron absorption ability is satisfied by the combined use of B and Gd.
  • B since B is inexpensive in the cost as the alloying material, it is used preferentially to Gd in the stainless steel of the present invention.
  • Gd has an effect of improving the neutron absorption ability about 4.4 times as large as that of B of an identical content.
  • the ferritic stainless steel it gives less undesired effect, for example, on the hot workability compared with B. Accordingly, it is contained at least by 0.05%.
  • the upper limit is restricted to 1.5%.
  • the Gd content is defined as from 0.05 to 1.5% and a content as low as possible is selected within this range.
  • the range for the contents of B and Gd are as described above, and the contents of B and Gd are determined within the range. That is, if the neutron absorption ability required for each of the ferritic stainless steel is determined, the contents of B and Gd may be determined in the sequence of (a), (b) and (c) as described above. Assuming the neutron absorption ability Nc as 2, since the lower limit for Gd in the ferritic stainless steel is 0.05%, when the B content is determined by substituting 2 for Nc and 0.05 for Gd in the equation (2), the B content is 1.83% which exceeds upper limit of 1.1%. In this case, by setting the B content to 1.1% or less which is allowable in view of the property and determining the Gd content from the equation (2), the contents of B and Gd can be determined.
  • Al is an element added to steel making to obtain sound cast pieces by deoxidation of molten steel.
  • Gd is contained by from 0.05 to 1.5% in the ferritic stainless steel of the present invention, it is important to thoroughly deoxidize the molten steel so as not to form Gd oxides. If Gd oxides are formed, the oxides remain as non-metallic inclusions in the steel and the inclusions may appear on the surface of the stainless steel. In such a case, since corrosion may possibly proceed starting from the exposed non-metallic inclusions, it is necessary to thoroughly deoxidize the molten steel before addition of Gd.
  • the Al content is defined as from 0.002 to 0.1%.
  • the manufacturing cost is increased and eutectic having low melting temperature are formed by the reaction between Ni and Gd to deteriorate the hot workability.
  • the Cr content exceeds 26%, since the Ni content has to be increased in accordance with the increase of the Cr content for austenitizing the stainless steel in accordance with the increase in the Cr content, the manufacturing cost is increased and the hot workability is deteriorated.
  • the Ni content is defined as from 7 to 22%, while the Cr content is defined as from 18 to 26%.
  • B has a property of forming borides and deteriorating the hot workability, cold workability and weldability in the austenitic stainless steel.
  • B is positively added by not less than 0.05%, preferably, not less than 0.2% in the austenitic stainless steel of the present invention for satisfying the thermal neutron absorption ability.
  • the upper limit for the B content is defined as 0.75% with such view points. If the B content is not more than 0.75%, it gives less effect on the properties such as the hot workability, cold workability and weldability in the austenitic stainless steel of the present invention.
  • a preferred upper limit for the B content is 0.5%.
  • the neutron absorption ability is satisfied by the combined use of B and Gd in the austenitic stainless steel of the present invention.
  • B since B is inexpensive in the cost as the alloying material, it is used preferentially to Gd in the stainless steel of the present invention.
  • Gd has an effect of improving the neutron absorption ability about 4.4 times as large as that of B of an identical content. Furthermore, Gd has an effect of preventing the deterioration of the weldability caused by the addition of B.
  • the weldability tends to be lowered in a range about from 0.1 to 0.8% with a peak being at about 0.3%, but the deterioration of the weldability can be suppressed if a smaller amount of Gd is contained.
  • Gd has a feature of giving less undesired effect on the hot workability or the like of the austenitic stainless steel compared with B. Accordingly, it is contained at least by 0.1%.
  • Gd is an expensive alloying element, it increases the manufacturing cost and high content deteriorates the hot workability, so that the upper limit of the Gd content is defined as 1.5%.
  • the Gd content is defined as from 0.1 to 1.5% and the Gd content is selected as low as possible within these ranges.
  • the range for the B and Gd contents are as described above, and the B and Gd contents are determined within these ranges. That is, if the neutron absorption ability required for each of the austenitic stainless steel is determined, the B and Gd contents may be determined in the sequence of (a), (b) and (c) as described above. Assuming the neutron absorption ability Nc as 2, since the lower limit for Gd content in the austenitic stainless steel is 0.11%, when the B content is determined by substituting 2 into Nc and 0.11 into Gd in the equation (2), the B content is 1.55% which exceeds the upper limit of 0.75%. In this case, by setting the B content to 0.75 or less allowable in view of the properties and determining the Gd content from the equation (2), the contents of B and Gd can be determined.
  • the Gd is added by more than the lower limit value, it is not always required to determine the Gd content to the upper limit value and an appropriate value may be selected while taking allowable range into consideration with a view point of properties such as the weldability and the hot workability and the economical reason.
  • a preferred range for the Gd content is from 0.2 to 1.5%.
  • Al is an element added in steel making to obtain sound cast pieces by deoxidation of molten steel. Particularly, since the C content is restricted low in the austenitic stainless steel of the present invention, 0 (oxygen) in the molten steel is increased. Furthermore, since 0.1 to 1.5% of Gd is contained, it is important to thoroughly deoxidize the molten steel so as not to form Gd oxides.
  • the oxides remain as non-metallic inclusions in the steel and the inclusions may appear on the surface of the stainless steel. In such a case, since corrosion may possibly proceed starting from the exposed non-metallic inclusions, it is necessary to thoroughly deoxidize the molten steel so as not to form Gd oxides.
  • the Al content is defined as from 0.005 to 0.1%.
  • ferritic stainless steel For ferritic stainless steel, a relationship between chemical compositions and the properties of the steel was examined. Ferritic stainless steels of different chemical compositions were melted by a vacuum melting furnace and they were cast into steel ingots each of 30 kg and about 110 mm diameter.
  • Table 1 shows chemical compositions of the resultant steel ingots.
  • Steel numbers No. 1 - 18 are ferritic stainless steel for the examples of the present invention and No. 19 - 28 are ferritic stainless steel of comparative examples in which the content for some of several alloying elements is out of the range specified by the present invention.
  • the high temperature test was conducted by using rod-shaped test pieces each of 10 mm diameter and 130 mm length, under the test conditions at a temperature of 1100°C and a tensile speed of 1/s, to determine a reduction of area for each test specimen.
  • the hot workability was evaluated by the reduction of area (high temperature elongation).
  • the Charpy impact test was conducted by using subsized V-notched Charpy test piece of 1/4 size (width) as specified in JIS Z2202, under a test condition at a temperature of 80°C.
  • the corrosion resistance was investigated for the test specimens prepared by applying bead on blade welding by TIG arc welding and sampling from HAZ. If the corrosion resistance for HAZ is satisfactory, it can be judged the corrosion resistance for the base metal is also satisfactory, so that the corrosion resistance for the base metal was omitted.
  • the surface of the HAZ of the test piece was polished by emery paper of 600# coarseness.
  • the corrosion test was conducted by a method of immersing the test pieces in an air saturated solution containing 2500 ppm of B 3+ and 1000 ppm of Cl- and determining a potential when a current density reached 100 ⁇ A/cm 2 under the conditions at a temperature of 80°C and at a potential sweep rate of 20 mV/min. The corrosion resistance was evaluated by the test of comparing the corrosion resistance based on a pitting potential obtained by the test.
  • each of test materials in Table 1 has a sufficient thermal neutral absorption ability, having a thermal neutron absorption ability Nc of not less than 1.1.
  • twelve test materials of steels No. 1, 5 - 14 and 18 for examples of the present invention are examples having the B content approximate to the upper limit defined in the present invention in which the neutron absorption ability Nc in the ferritic stainless steel is defined to a predetermined value by varying the Gd content.
  • the Nc values for the test materials are from 2.0 to 6.9.
  • the reduction of area in the high temperature tensile test is as high as 67 - 83% and it can be seen that the hot workability is satisfactory.
  • the pitting potential for HAZ is as high as 121 - 175 mV vs SCE, and it was recognized that they were also excellent in the corrosion resistance for HAZ.
  • steel No. 2 - 4 are examples having lower Gd content
  • steels No. 15-17 are examples of containing the Gd amount to some extent and the lower B content of from 0.15 to 0.56%. It has been confirmed that such six test materials have the reduction of area in high temperature tensile test of from 66 to 89%, the pitting potential for HAZ of from 132 to 185 mV and are excellent both in the hot workability and the corrosion resistance for HAZ.
  • steels No. 15 and 16 containing not more than 0.7% of Ni have high toughness with the Charpy impact value being as high as from 11 to 13 J/cm 2 .
  • steels No. 4 - 5 containing Mo and steels No. 11 - 14 containing either one or both of Ti and Nb it has been found that the pitting potential for HAZ is high for both of them, that is from 175 to 185 mV vs SCE for the former and from 161 to 166 mV vs SCE for the latter, and the corrosion resistance for HAZ including the base metal is particularly excellent.
  • the ferritic stainless steel of the present invention have high neutron absorption ability, as well as are excellent in the hot workability, corrosion resistance and toughness and this supports the large effect of restricting the B content lower, and restricting the C content to less than 0.01% and restricting the N content to not more than 0.015%.
  • steels No. 19 - 28 of comparative examples as shown in Table 1, contents of several elements among the alloying elements are out of the range as specified in the present invention. Accordingly, as apparent from Table 2, at least one of the properties of the hot workability and the corrosion resistance is poor. Particularly, steel No. 27 having the B content exceeding the range defined by the present invention have lower reduction of area of 48% in high temperature tensile test of 48% and lower Charpy impact value of 3 J/cm 2 , and it is apparent that both of the hot workability and the toughness are poor. Since the B content is excessively high as 1.36%, the undesired effect thereof appears distinctly.
  • steels No. 19, 22 and 24 with one or both of the contents for C and N being outside of the range specified by the present invention have the pitting potential of from 34 to 72 mV vs SCE, each of which is lower compared with the examples of the present invention and it is apparent that they are poor in the corrosion resistance.
  • Steels No. 23 and 25 having excessively high Gd and Ni contents have extremely low reduction of area in high temperature tensile test, which supports that the hot workability is extremely poor.
  • Austenitic stainless steel For austenitic stainless steel, a relationship between chemical compositions and the properties of steel was examined. Austenitic stainless steel of different chemical compositions were melted by a vacuum melting furnace and they were cast into steel ingots each of 30 kg and about 110 mm diameter.
  • Table 3 shows chemical compositions of the resultant steel ingots.
  • Steels No. 1 - 12 are austenitic stainless steel for examples of the present invention and steels No. 13 - 24 are austenitic stainless steel of comparative examples having contents for several alloying elements outside of the range specified by the present invention.
  • the high temperature tensile test was conducted by using a rod-shaped test pieces each of 10 mm diameter and 130 mm length, under the test conditions at a temperature of 1050°C and a tensile speed of 1/s, to determine a reduction of area for each test specimen.
  • the hot workability was evaluated by the reduction of area (high temperature elongation).
  • the weldability was evaluated by cutting out test specimens each of 100 width and 100 length from the materials, applying TIG arc welding to the test pieces under the condition at a voltage of 15 V, a current of 200 A and a velocity of 150 m/min and measuring cracks in the welded zones.
  • the cracks in the welded zones were investigated by a method of applying a Varestrain test at 2% distortion, conducting a penetration flaw detection test, observing cracked portion with a stereo-microscope and determining the length of cracks developed.
  • the corrosion resistance was investigated for the test specimens prepared by subjecting the material after the solution heat treatment to a sensitizing treatment of further keeping at 650°C for 2 hours, applying bead on blade welding by TIG arc welding and sampling test specimens from HAZ. If the corrosion resistance for HAZ is satisfactory, it can be judged that the corrosion resistance for the base metal is also satisfactory, so that the corrosion resistance for the base metal was omitted.
  • the surface of the HAZ of the test piece was polished by emery paper of 600# coarseness.
  • the corrosion test was conducted by a method of immersing test pieces in an air saturated solution containing 3000 ppm of B 3+ and 500 ppm of Cl- and determining a potential when a current density reached 100 ⁇ A/cm 2 under the conditions at a temperature of 80°C and at a potential sweep rate of 20 mV/min.
  • the corrosion resistance was evaluated by a method of comparing the corrosion resistance based on the pitting potential obtained by the test.
  • the cold workability was evaluated by the method of subjecting a plate-like test pieces each of 20 mm width, 3 mm thickness and 100 mm length to 180° bending at a radius of 6 mm and 3 mm in a cold state, observing bent portions with naked eyes and investigating the absence or presence of cracks.
  • each of test materials for examples of the present invention has a sufficient thermal neutral absorption ability, having a thermal neutron absorption ability Nc of not more than 1.1.
  • three test materials of steels No. 10 - 12 for examples of the present invention are examples having the B content approximate to the upper limit defined in the present invention in which the neutron absorption ability Nc in the austenitic stainless steel is defined to a predetermined value by varying the Gd content.
  • the Nc values for the test materials are as high as 1.5 to 6.0.
  • the Mn content is lower as not more than 0.9%. Accordingly, the pit potential for HAZ is as high as not less than 71 mV vs SCE and the corrosion resistance for HAZ is particularly satisfactory. They are of course excellent in the corrosion resistance of the base metal.
  • the austenitic stainless steel of the present invention have high neutron absorption ability, as well as are excellent in the hot workability, weldability, cold workability and corrosion resistance. This is because the B content is restricted lower as 0.75% and, in addition, Gd is contained by a required minimum amount and, furthermore, Mn is restricted to not more than 0.9%.
  • steels No. 13 - 24 of comparative examples contents for several elements among the alloying elements are out of the range specified in the present invention as shown in Table 3. Accordingly, as apparent from Table 4, at least one of the properties of the hot workability, the weldability, the cold workability and the corrosion resistance is poor. Particularly, four test materials of steels No. 13 - 15 and 19 having the B content exceeding the range specified by the present invention have a reduction of area in a high temperature tensile test of not more than 67% and they are poor in the hot workability, weldability and extremely deteriorated in bending, that is, the cold workability.
  • test materials of steels No. 23 and 24 in which the Mn content exceeds the range specified by the present invention have extremely low pitting potential and it is apparent that they are poor in the corrosion resistance for HAZ as well as the base metal. Furthermore, steels No. 15 and 16 having excessively high Gd content have extremely low reduction of area in the high temperature tensile test and were poor in the hot workability.
  • the steels No. 17 and 18 are examples in which other elements than Gd are within the range specified by the present invention and in which Gd is not contained. In this case, cracking is remarkable and the weldability was poor as apparent from the results for the weldability in Table 4. It has been confirmed that the combined use of B and a small amount of Gd is effective also in view of the weldability.
  • the B content is restricted low in view of the hot workability, the weldability and the like, the content is selected as high as possible within the specified range and insufficiency of the thermal neutron absorption ability is compensated with Gd. Accordingly, the stainless steel of the present invention have sufficient thermal neutron absorption ability, are excellent in the properties such as hot workability, weldability and cold workability and also inexpensive for the manufacturing cost.
  • Mn is restricted low in the ferritic stainless steel while C and N contents are restricted low in the austenitic stainless steel, they are also excellent in the corrosion resistance for the base metal and the weld heat affected zone (HAZ).

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Claims (9)

  1. Acier inoxydable ferritique ayant une excellente capacité d'absorption des neutrons thermiques, comprenant la composition chimique suivante en % en masse : C : moins de 0,01 % Si : pas plus de 0,5 % Mn : pas plus de 1 % P : pas plus de 0,03 % S : pas plus de 0,01 % Ni : pas plus de 0,7 % Cr: 13-26 % B : 0,1-1,1 % Gd : 0,05-1,5 % Al : 0,002-0,1 % N : pas plus de 0,015 % Ti : pas plus de 1 % Nb : pas plus de 1 % Y : pas plus de 0,3 % Mo : pas plus de 3 % complément : impuretés accidentelles et Fe.
  2. Acier inoxydable ferritique ayant une excellente capacité d'absorption des neutrons thermiques, comprenant la composition chimique selon la revendication 1 qui répond à l'équation (1) suivante : Nc ≥ 0,8    où Nc = {(1-0,015 x B%) x B%} + (4,4 x Gd%).
  3. Acier inoxydable ferritique ayant une excellente capacité d'absorption des neutrons thermiques selon la revendication 1 ou 2, où les teneurs en C et N sont : C : pas plus de 0,005 % N : pas plus de 0,008 %.
  4. Acier inoxydable ferritique ayant une excellente capacité d'absorption des neutrons thermiques selon la revendication 1, 2 ou 3, où la teneur en Ni est de 0,05 à 0,7 %.
  5. Acier inoxydable austénitique ayant une excellente capacité d'absorption des neutrons thermiques, comprenant la composition chimique suivante en % en masse : C : pas plus de 0,02 % Si : pas plus de 1 % Mn : 0,1-0,9 % P : pas plus de 0,03 % S : pas plus de 0,01 % Ni : 7-22 % Cr : 18-26 % B : 0,05-0,75 % Gd : 0,11-1,5 % Al : 0,005-0,1 % N : pas plus de 0,030 % Y : pas plus de 0,3 % Mo : pas plus de 3 % complément : impuretés accidentelles et Fe.
  6. Acier inoxydable austénitique ayant une excellente capacité d'absorption des neutrons thermiques, comprenant la composition chimique selon la revendication 5 qui répond à l'équation (1) suivante : Nc ≥ 0,8 où Nc = {(1-0,015 x B%) x B%} +(4,4xGd%).
  7. Acier inoxydable austénitique ayant une excellente capacité d'absorption des neutrons thermiques selon la revendication 5 ou 6, où la teneur en B est de 0,2 à 0,75 %.
  8. Acier inoxydable austénitique ayant une excellente capacité d'absorption des neutrons thermiques selon la revendication 5 ou 6, où la teneur en B est de0,2 à 0,5 %.
  9. Acier inoxydable austénitique ayant une excellente capacité d'absorption des neutrons thermiques selon la revendication 5, 6, 7 ou 8, où les teneurs en Mo et Y sont : Mo : 0,01-3 % Y : 0,001-0,3 %.
EP96926611A 1995-08-09 1996-08-08 Aciers inoxydables particulierement utiles pour l'absorption de neutrons thermiques Expired - Lifetime EP0844312B1 (fr)

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
JP20323095 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
JP203230/95 1995-08-09
JP272164/95 1995-10-20
JP27216495 1995-10-20
JP27216495 1995-10-20
PCT/JP1996/002258 WO1997006286A1 (fr) 1995-08-09 1996-08-08 Aciers inoxydables particulierement utiles pour l'absorption de neutrons thermiques
US08/984,689 US5820818A (en) 1996-08-08 1997-12-03 Stainless steel having excellent thermal neutron absorption ability

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EP0844312A1 EP0844312A1 (fr) 1998-05-27
EP0844312A4 EP0844312A4 (fr) 1998-12-23
EP0844312B1 true EP0844312B1 (fr) 2000-05-31

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JP5259515B2 (ja) 2009-07-28 2013-08-07 株式会社東芝 中性子遮蔽材、その製造方法および使用済み燃料用キャスク
CN103748249B (zh) * 2011-08-22 2016-06-08 日本冶金工业株式会社 热加工性和表面性状优异的含硼不锈钢
CN113913680A (zh) * 2021-07-26 2022-01-11 中国科学院金属研究所 一种具有优良中子吸收性能的含Gd双相不锈钢及其制备方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2007010A (en) * 1977-10-03 1979-05-10 British Nuclear Fuels Ltd Solvent extraction columns
JPS5589459A (en) * 1978-12-27 1980-07-07 Daido Steel Co Ltd Boron-containing stainless steel having good corrosion resistance and workability
GB2086429A (en) * 1980-10-23 1982-05-12 British Steel Corp Steel alloys having enhanced thermal neutron absorption properties
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
JP2827798B2 (ja) * 1992-10-30 1998-11-25 住友金属工業株式会社 高耐食ほう素含有ステンレス鋼

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EP0844312A4 (fr) 1998-12-23

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