Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
  • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
  • C22C32/0026—Matrix based on Ni, Co, Cr or alloys thereof
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0207—Using a mixture of prealloyed powders or a master alloy
  • C22C33/0228—Using a mixture of prealloyed powders or a master alloy comprising other non-metallic compounds or more than 5% of graphite
• • 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
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• • 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
  • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
• • 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
  • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
• • 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
  • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/02—Making metallic powder or suspensions thereof using physical processes
  • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
  • B22F2009/041—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by mechanical alloying, e.g. blending, milling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/004—Dispersions; Precipitations
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/002—Heat treatment of ferrous alloys containing Cr

Definitions

• the present invention relates to a method for producing a ferritic oxide dispersion-strengthened steel having excellent high-temperature cleaving strength.
• the present invention relates to a method for producing a ferritic oxide dispersion strengthened steel capable of imparting cleave strength.
• the ferrite-based oxide dispersion strengthened steel of the present invention can be preferably used as a material for a fast breeder reactor fuel cladding tube, a first wall material for a fusion reactor, a material for thermal power generation, and the like, which require particularly high strength at high temperatures.
• Austenitic stainless steel has been used as a component of nuclear reactors, especially fast reactors, which require excellent high-temperature strength and neutron irradiation resistance.However, irradiation resistance such as swelling resistance is limited. . On the other hand, although ferritic stainless steel has excellent irradiation resistance, it has the disadvantage of low high-temperature strength.
• a ferrite-based oxide dispersion strengthened steel in which fine oxide particles are dispersed in a ferritic steel has been proposed as a material having excellent irradiation resistance and high-temperature strength characteristics. It is also known that in order to improve the strength of this ferritic oxide dispersion strengthened steel, it is effective to add Ti to the steel to further disperse the oxide dispersed particles. In particular, in order to improve the high-temperature creep strength of the ferritic oxide dispersion-strengthened steel, it is effective to increase the crystal grain size and make it equiaxed to suppress grain boundary sliding.
• austenitization is performed by securing a sufficient amount of ⁇ ⁇ ⁇ transformation by normalizing heat treatment with heating and holding at a temperature higher than the Ac 3 transformation point, and transforming the phase from a to a.
• a method has been proposed in which cooling is carried out at a sufficiently low rate so that a ferrite structure is obtained by performing a phase transformation from the ⁇ phase to the ⁇ phase, that is, at or below the critical ferrite formation rate (for example, Japanese Patent Application Laid-Open No. H11-134). See Japanese Patent Publication No.
• the heat treatment of the ferrite-based oxide dispersion-strengthened steel to obtain a coarse crystal grain structure is performed by performing a normalizing heat treatment of heating and holding at a temperature equal to or higher than the A c transformation point to obtain an ⁇ phase. Cooling is performed at a ferrite formation critical speed or lower.
• Ti has a strong affinity for C, which is an ⁇ -phase forming element in the matrix, so that Ti and C combine to form carbides.
• the C concentration in the matrix decreases, even if heat treatment is performed at a temperature higher than the Ac 3 transformation point, the matrix does not become a single phase and the untransformed single phase remains.
• the present invention suppresses the bond between Ti and C and maintains the C concentration in the matrix even when Ti is added to the ferritic oxide dispersion strengthened steel.
• the present invention performs a mechanical alloying process by mixing elemental powders or alloy powders and Upsilon 2 Omicron 3 powder, after solidification by hot extrusion, heat retention of the final heat treatment to Ac 3 transformation point or more And the subsequent cooling treatment at a critical speed of ferrite formation or lower, the C content is 0.05 to 0.25%, the C r is 8.0 to 12.0%, and the W is 0.2% by mass%. 1 to 4. 0% T i is 0. 1 to 1.
• T i 0 2 powder as the oxide in place of the metal T i powder as raw material powder, from T i to form carbides when combined with C in advance blocking It does not lower the C concentration in the matrix.
• a sufficient a-a transformation occurs during the heat treatment at or above the Ac 3 transformation point to form an r- single phase, and the subsequent heat treatment for cooling at or below the critical ferrite formation rate results in coarsening.
• An ⁇ phase having a crystal grain structure can be formed, and the high-temperature creep strength can be improved.
• the present invention performs a mechanical alloying process by mixing elemental powders or alloy powders and Upsilon 2 0 3 powder, after solidification by hot extrusion, heat retention of the Ac 3 transformation point or more as a final heat treatment and to it Subsequent criticality of ferrite formation
• C is 0.05 to 0.25%
• Cr is 8.0 to 12.0%
• W is 0.1 to 4.0%
• T i is 0. 1 ⁇ 1.
• Y 2 ⁇ 3 0.1 to 0.5%, ferrite-based oxide dispersion balance are dispersed F e and inevitable impurities or Ranaru Y 2 0 3 particles a method of manufacturing a strengthened steel, the excess oxygen content in steel (minus the amount of oxygen from the oxygen Upsilon 2 0 3 in the steel) is
• T i Ti content in steel, mass%
• This is a method for producing a ferritic oxide dispersion-strengthened steel having a coarse grain structure and excellent in high-temperature cleaving strength, characterized by additionally adding O 3 powder.
• the raw material powder is an unstable oxide
• the F e 2 03 powder additionally Rukoto to a predetermined range excess oxygen content in steel by adding, T i is without forming carbides by combining with C, and combined excess oxygen and formation
• T i is without forming carbides by combining with C
• combined excess oxygen and formation The formation of oxides does not lower the C concentration in the matrix.
• sufficient heat-induced transformation occurs during the heat treatment at or above the Ac 3 transformation point to form a single phase, and subsequent heat treatment for cooling at or below the critical ferrite formation critical rate results in coarsening.
• a phase having a crystal grain structure can be formed, and the high-temperature cleaving strength can be improved.
• Figure 1 shows optical micrographs of the experimental materials T14, MM13, T3, and ⁇ 4. It is.
• Fig. 2 is an optical microscope photograph of the experimental materials T5, ⁇ 6, and ⁇ 7.
• Figure 3 is a graph showing the relationship between the Ti content and the excess oxygen content (E x ..) of each trial material.
• FIG. 4 is a graph in which the region satisfying the condition for crystal coarsening in the graph of FIG. 3 is indicated by hatching.
• FIG. 5 is a graph showing a high temperature creep rupture test at 700 ° C. of the test materials T14, T3, and ⁇ 7.
• Cr is an important element for ensuring corrosion resistance, and if it is less than 8.0%, the deterioration of corrosion resistance becomes remarkable. If it exceeds 12.0%, the toughness and ductility may be reduced. For this reason, the Cr content is set to 8.0 to 12.0%.
• the content of C is determined for the following reasons.
• an equiaxed and coarse crystal grain structure is obtained by performing a heat treatment once at a temperature higher than the Ac 3 transformation point and a subsequent heat treatment for cooling. That is, in order to obtain an isotropic and coarse crystal grain structure, it is indispensable to cause a 0; ⁇ a transformation by heat treatment.
• the Cr content When the Cr content is 8.0-12.0%, it is necessary to contain C in an amount of 0.05% or more in order to cause the transformation.
• the ⁇ ⁇ ⁇ transformation is caused by a heat treatment at 100 to 1150 ° CX for 0.5 to 1 hour.
• the higher the C content the greater the amount of carbides (M 23 C 6 , M 6 C, etc.) deposited and the higher the high-temperature strength.
• the content exceeds 0.25%, the workability is poor. Become. For this reason, the C content is set to 0.05 to 0.25%.
• W is an important element that forms a solid solution in the alloy and improves the high-temperature strength, and is added in an amount of 0.1% or more. If the W content is increased, the creep rupture strength is improved by the solid solution strengthening action, carbide (M 23 C 6 , M 6 C, etc.) precipitation strengthening action, and intermetallic compound precipitation strengthening action. If it exceeds, the amount of ⁇ ferrite increases and the strength also decreases. For this reason, the W content is 0.1 to 4.0%.
• T i plays an important role in the dispersion strengthening of Y 2 0 3, to form a composite oxide of Upsilon 2 ⁇ 3 reacts with Y 2 T i 2 ⁇ 7 or Y 2 T i 0 5, acid Has the function of refining the oxide particles. This effect tends to be saturated when the Ti content exceeds 1.0%, and when the Ti content is less than 0.1%, the miniaturization effect is small. For this reason, the Ti content is 0.1-1.0%.
• Y 2 ⁇ 3 is an important additive that improves high-temperature strength by dispersion strengthening.
• the content is less than 0.1%, the effect of dispersion strengthening is small and the strength is low.
• the content exceeds 0.5%, curing is remarkable and a problem occurs in workability. For this reason, the content of ⁇ 2 ⁇ 3 is set to 0.1 to 0.5%.
• the method for producing a ferrite-based oxide dispersion strengthened steel according to the present invention comprises mixing a raw material powder such as a metal element powder, an alloy powder, and an oxide powder so as to have a target composition, and performing a so-called mechanical alloying treatment (mechanical alloying). G) to alloy. After filling this alloyed powder into an extrusion capsule, it is degassed, sealed, and hot-extruded to be solidified, for example, into an extruded rod. The obtained hot-extruded rod is subjected to a heat treatment at a temperature higher than the transformation point of Ac 3 and a subsequent cooling heat treatment at a speed lower than the critical ferrite formation rate as the final heat treatment.
• a raw material powder such as a metal element powder, an alloy powder, and an oxide powder so as to have a target composition
• mechanical alloying treatment mechanical alloying
• the cooling heat treatment can be a furnace cooling heat treatment in which the furnace is gradually cooled in a furnace, and the cooling rate below the ferrite formation critical rate is generally 100 ° C.
• the time can be set to Z time or less, preferably 50 ° C.Z time or less.
• the A c 3 transformation point is about 900 to 1200 ° C., and when the C content is 0.13%, A c 3 The transformation point is about 950 ° C.
• metal T is used as a raw material powder to be mixed in the mechanical alloying treatment.
• how to use the T i ⁇ 2 powder instead of the i powders can be employed.
• Ding 1 0 2 is not able to bind to C to Ding 1 You, as a result, it is possible to suppress the reduction of the C concentration in the matrix.
• Mixing amount of T I_ ⁇ 2 powder may be such that in the range of 0.1 to 1.0% as T i content.
• a means for preventing Ti in steel from bonding with C to form carbides and lowering the C concentration in the matrix it is not suitable as a raw material powder to be mixed during mechanical alloying treatment.
• method of increasing by mixing F e 2 ⁇ 3 powder is stable oxide additionally excess oxygen content in steel can be employed.
• Ti combines with the excess oxygen in the steel derived from Fe 2 ⁇ 3 to form oxides and does not combine with C to form carbides, thus reducing the C concentration in the matrix. Can be suppressed.
• the mixing amount of the Fe 2 ⁇ 3 powder depends on the amount of excess oxygen in the steel.
• Table 1 shows the target composition and composition of the ferrite-based oxide dispersion strengthened steel prototype. Features are shown together
• test materials MM 1 3 and T 14 are basic composition
• T 3 is increased excess oxygen amount by adding the F e 2 0 3 on the composition of the T 14 samples
• T 4 is T i the addition amount increased sample
• T 5 increased the excess oxygen content by adding together F e 2 ⁇ 3 increasing the T i added sample volume
• T in the composition of Ding 6 and Ding 7 T 14 This is a sample in which the amount of excess oxygen was increased by adding 0.125 Ti 0. 25 Ti in the form of i in the form of chemically stable oxides (Ti 2 ).
• Table 2 summarizes the results of component analysis of each prototype material (hot extruded bar) obtained above.
• the excess oxygen content is a value obtained by subtracting the amount of oxygen in the dispersion oxides from acid elementary charge in test material (Y 2 0 3) in the analysis of chemical components.
• Optical micrographs of the gold phase structure of each prototype after heat treatment are shown in Fig. 1 (T14, 1413, ⁇ 3, ⁇ 4) and Fig. 2 ( ⁇ 5, ⁇ 6, ⁇ 7).
• T grain growth occurs, T 6, T 7, the basic sample was added F e 2 03 the composition (T 3), and T i to cash forte T i 0 2 samples with the addition of (T 6 , ⁇ 7).
• MM 13 and T 14 are both basic compositions and have the same composition, but MM 13 (excess oxygen content: 0.137%) has crystal grains growing. At T14 (excess oxygen content: 0.110%), the grain growth was small. The reason for this is that mechanical alloying and It is probable that the amount of oxygen mixed into the steel was slightly different during the subsequent heat treatment and other processes, and that MM13 had an excess amount of oxygen sufficient to chemically bond with Ti in the steel.
• the graph in Fig. 3 shows the relationship between the Ti content of each trial material and the excess oxygen content. From this graph, a prototype that satisfies the relationship of E x. ⁇ > 0.6 1 T i [E x. :: excess oxygen content (), T i: Ti content in steel (%)] It can be seen that for the materials MM13, T3, ⁇ 6, and ⁇ 7, the crystal grains became coarse due to the furnace cold heat treatment.
• the ⁇ the excess oxygen content of only every T i in the steel to form a T i 0 2 is present (if the residual C content in the matrix is more than 1 3% 0.1), the crystal grain coarsening Is considered to occur.
• the residual C content in the matrix in consideration of the formation of ⁇ i 0 2 and T i C is 0.13% (1.08 X 10 0 (-4 mol / g) or more, it is considered that sufficient heat-transformation occurs during the heat treatment and the crystal grains become coarse due to the furnace cooling heat treatment.
• the amount of residual C in the matrix (C ′ rmol / g) in consideration of the formation of T i O 2 and T i C is expressed by the following equation.
• conditional expression for grain coarsening is as follows.
• the range of the upper and lower limits of the above-described conditional expression for grain coarsening is indicated by hatched portions, and the measured values of each trial material are plotted.
• the formula is calculated with the C content being 0.13%, but the test materials MM13, T3, ⁇ 6, and ⁇ 7 on which the crystal grains have grown are all located within the shaded area, and the crystal grains are formed. Prototypes ⁇ 14, ⁇ 5, ⁇ 4, which did not lengthen, are all located outside the shaded area, indicating that this condition is valid.
• the trial material number where the trial material number is not shown, the sample material located within the shaded area has coarsened crystal grains, and the one located outside the shaded area has a larger grain size. It has been confirmed that no coarsening has occurred.
• the heat treatment according to the present invention that is, the normalization heat treatment (heating and holding above the transformation point of Ac 3: 150: xihr), followed by the furnace cooling heat treatment ( Heat-removal heat treatment at a ferrite formation critical speed or lower: A sample (T 3 (cooled from 105 O to 600 ° C at a rate of 37 ° C / hr) that has been coarsened FC material) and T7 (FC material) were prepared.
• test materials T14, T3, and T7 normalizing heat treatment (1500 ° CX 1 r ⁇ air cooling (AC)) and subsequent tempering heat treatment (780 ° CX1 r ⁇ Air cooling (AC)) to prepare samples with fine crystal grains (T14 (NT material), T3 (NT material), T7 (NT material)).

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• 2002
  • 2002-08-08 JP JP2002231781A patent/JP3792624B2/ja not_active Expired - Fee Related
• 2003
  • 2003-08-07 CN CNB038055813A patent/CN100385030C/zh not_active Expired - Fee Related
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