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WO2004042093A1 - Produit a structure de fer et produit a structure de metal ayant une excellente resistance a la fragilisation de metal liquide et procede de fabrication correspondant - Google Patents

Produit a structure de fer et produit a structure de metal ayant une excellente resistance a la fragilisation de metal liquide et procede de fabrication correspondant Download PDF

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Publication number
WO2004042093A1
WO2004042093A1 PCT/JP2003/014163 JP0314163W WO2004042093A1 WO 2004042093 A1 WO2004042093 A1 WO 2004042093A1 JP 0314163 W JP0314163 W JP 0314163W WO 2004042093 A1 WO2004042093 A1 WO 2004042093A1
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Prior art keywords
liquid metal
metal embrittlement
steel
product
structure product
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PCT/JP2003/014163
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English (en)
Japanese (ja)
Inventor
Akihiro Miyasaka
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Nippon Steel Corp
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Nippon Steel Corp
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Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Priority to AU2003277584A priority Critical patent/AU2003277584A1/en
Publication of WO2004042093A1 publication Critical patent/WO2004042093A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • 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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
    • C21D7/04—Modifying the physical properties of iron or steel by deformation by cold working of the surface
    • 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
    • C21D10/00—Modifying the physical properties by methods other than heat treatment or deformation
    • 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
    • C21D2201/00—Treatment for obtaining particular effects
    • C21D2201/03—Amorphous or microcrystalline structure

Definitions

  • the present invention relates to a metal structure product manufactured by assembling a structure such as a bridge or a steel tower using a metal material, for example, a steel material, and then plating it brightly.
  • Metal structure products such as metal equipment members, which include welds such as rolls and are used in plating equipment, etc., are used for metal structure products with excellent liquid metal embrittlement resistance, steel structure products (steel materials) Metal-structured product), and its manufacturing method.
  • metal-structured product with improved liquid metal embrittlement resistance of the welded part including the weld heat-affected zone, steel-structured product, and the like It relates to a manufacturing method. Background art
  • the solid metal When the molten metal and the solid metal come into direct contact, depending on the combination of the metals, the solid metal may break brittlely at high speed, which is known as liquid metal embrittlement.
  • iron and steel materials such as high-strength steel and austenitic stainless steel and Ni alloys become brittle when in contact with molten zinc or molten lead, and cracks develop.
  • This embrittlement crack requires the presence of stress.
  • Most of these liquid metal embrittlement cracks are grain boundary cracks, and their propagation speed is said to reach several meters per second.
  • this material was not necessarily sufficient in terms of liquid metal embrittlement resistance and strength.
  • it is common to perform stress relief annealing on welds and the like by heat treatment, but the processing target is large metal structural products or steel structure products. In some cases, a large heat treatment furnace for heat treatment is required, and heat treatment itself is impossible for fixed structures. As described above, sufficient metal structural products and iron structural products having excellent liquid metal embrittlement resistance and methods for producing them have not been obtained.
  • An object of the present invention is to solve the above-mentioned problems and to provide a metal structure product, an iron structure product, and a method for manufacturing the same, which have excellent resistance to liquid metal embrittlement. Disclosure of the invention
  • the tip of the ultrasonic wave has an amplitude of 20 to 60 m and a frequency of 19 kHz to 60 kHz.
  • ultrasonic impact treatment to strike the metal surface using a tool that vibrates at a frequency of 0.2 Hz to 3 kW at a frequency of 0.2 Hz to 3 kW, liquid metal embrittlement of metal structure products or steel structure products is applied to places where embrittlement is a problem. It improves the structure of the surface layer, thereby obtaining a structural product having excellent liquid metal resistance, and furthermore, performs appropriate pre-treatment and post-treatment inspection when performing this treatment. It guarantees its effect.
  • the summary is as follows.
  • the surface crystal grains with a thickness of 50 ⁇ or more are ultra-fine and the major axis of the crystal grains in the surface layer is A metal structure product having excellent resistance to liquid metal embrittlement characterized by being substantially parallel to the surface.
  • the portion according to (2) or (3), wherein the portion where the liquid metal embrittlement of the steel structure product becomes a problem includes a weld bond portion and / or a weld heat affected zone. Steel products with excellent resistance to liquid metal embrittlement.
  • Ultrasonic impact treatment is applied to the parts of the steel product where liquid metal embrittlement is a problem, and the surface crystal grains with a thickness of 50 ⁇ m or more from the surface are ultra-fine, and A method for producing a steel product having excellent resistance to liquid metal embrittlement, characterized in that the major axis of the former austenite grains in the surface layer is substantially parallel to the surface.
  • the liquid metal embrittlement according to (8), wherein the metal of the steel structure product where the problem of liquid metal embrittlement is problematic is steel having a tensile strength of 49 ON / mm class 2 or higher.
  • the portion according to (8) or (9), wherein the portion where the liquid metal embrittlement of the steel structure product becomes a problem includes a welded bond portion and a Z or a heat affected zone.
  • a method for producing steel products with excellent liquid metal embrittlement resistance includes a welded bond portion and a Z or a heat affected zone.
  • the pretreatment is a treatment for changing the internal stress and / or the surface stress at a location where liquid metal embrittlement of the steel structure product is problematic and at a location near the location. ).
  • the pre-treatment is characterized in that the pre-treatment includes a process of detecting a crack at a location where liquid metal embrittlement of the steel structure product becomes a problem, and a process of removing the detected crack. Or the method for producing a steel product having excellent liquid metal embrittlement resistance according to (14).
  • the ultrasonic impact treatment further reduces the surface shape of the steel structure product where liquid metal embrittlement is problematic to a shape where stress concentration is unlikely to occur, and reduces compressive residual stress near the surface.
  • Fig. 1 (a) is a schematic cross-sectional view showing the progress of cracks due to liquid metal embrittlement.
  • Fig. 1 (b) shows the case where the grain boundaries are perpendicular to the direction of tensile stress.
  • FIG. 4 is a schematic cross-sectional view showing the state of crack propagation due to embrittlement, showing a case where most of the grain boundaries are in a direction parallel to the direction of tensile stress.
  • Figure 2 (a) is a tissue photograph showing the cross-sectional structure of a steel product before ultrasonic impact treatment.
  • Figure 2 (b) shows the old cross section of the steel structure product before ultrasonic impact treatment. It is a schematic diagram which shows the state of a stenite organization.
  • Figure 3 (a) is a tissue photograph showing the cross-sectional structure of a steel product after ultrasonic impact treatment.
  • Fig. 3 (b) is a schematic diagram showing the state of the former austenite structure of the cross-sectional structure of the steel structure product after the ultrasonic impact treatment.
  • FIG. 4 is a view showing the state of a liquid metal embrittlement test specimen.
  • the metal structural products targeted by the present invention include structures such as steel towers and bridges made of metal materials such as steel materials and Ni alloys, or structural components such as mechanical components, piping, and container vessels. It is a thing. In general, these structural products are assembled by cutting or bending metal materials, or by further welding, and then melting the molten metal, such as zinc, zinc-based alloys, aluminum, and aluminum alloys. It is immersed in a bath and subjected to melting and plating. In addition, hot-dip containers and hot-dip plating tanks come into contact with the above-mentioned molten metal when they are used as structural components after processing. In other words, at the stage of manufacturing or use, metal structure products and steel structure products come into contact with liquid metal (molten metal).
  • molten metal liquid metal
  • liquid metal embrittlement occurs when a metal structure product (solid metal) is in an environment in which it comes into contact with liquid metal in the presence of tensile stress. It is likely to crack and reduce the function of the metal structure product.
  • Fig. 1 (a) and Fig. 1 (b) explain the growth of liquid metal embrittlement cracks in metal structure products, and show the grain boundaries of crystal grains in the cross section in the thickness direction of the metal material. . Note that
  • the former austenite grain boundaries are shown.
  • the direction of the crack growth is determined by the tensile stress (residual stress, Perpendicular to the external stresses) and in most cases along the metal grain boundaries or, in the case of steel materials, the former austenite grain boundaries. Therefore, as shown in Fig. 1 (b), if the direction of the grain boundary is substantially parallel to the direction of the tensile stress, this stress does not act to further open the tip of the crack. Therefore, the growth can be slowed down, that is, crack propagation resistance can be improved, and liquid metal embrittlement can be suppressed.
  • the inventors focused on this point and made the crystal grains of the surface layer of the metal structure product where liquid metal embrittlement was a problem ultra-fine, and the major axis direction of the crystal grains of this surface layer was substantially the same as the surface. It is intended to be parallel. Since the crystal grains in the surface layer are ultra-fine, and the major axis of the crystal grains in the parentheses is substantially parallel to the direction of the tensile stress, the propagation path becomes longer, so that As described above, crack propagation resistance can be increased, and cracking due to liquid metal embrittlement can be suppressed. In addition, in the case of steel materials, as described above, cracks propagate along the former austenite grain boundaries.
  • the crystal grains of the surface layer of the place are ultra-fine, and the long axis of the former austenite grains of this surface layer is substantially the same as the surface. Be parallel. As a result, crack propagation resistance can be increased, and cracking due to liquid metal embrittlement can be suppressed.
  • the crystal grains in the surface layer where liquid metal embrittlement is a problem are made ultra-fine so that the major axis direction of the crystal grains is substantially parallel to the surface, or the crystal grains in the surface layer are reduced.
  • the hammer at the tip is ultrasonically amplified with an amplitude of 20 to 60 ⁇ Frequency 19 to 6 0 kHz Ultrasonic impact treatment in which a metal surface is hit by a device vibrating at an output of 0.2 to 3 kW to perform pinning (see, for example, US Pat. No. 6,171,415). Is preferred.
  • This treatment method is basically the same as hammer peening, except that the energy of each impact is low, but instead of hitting more than 10,000 times per second, the metal is plastically deformed. It gives deformation. At this time, since the impact force of each impact is small, there is almost no recoil generated in the impact device, and the usability and workability are superior to the hammer peening device. In addition, since the energy of a single impact is small, the shape of the hammer at the tip can be made small, and it is possible to apply impact treatment to minute or narrow parts such as welds and connections. Can be. In this regard, the treatment can be applied to small portions where liquid metal embrittlement is a problem. Even in this case, since the number of impacts can be extremely increased as described above, sufficient plastic deformation can be given.
  • the number of hits increases the uniformity of the treatment.
  • the impact frequency of the ultrasonic impact treatment is 19 to 60 kHz, and the obtained uniformity is It is at a level completely different from that of Jung, and if the processing speed is about 0. ⁇ , most of the required metal surface can be finished uniformly and without leaving any defects.
  • the metal surface after the treatment is smoothed and the metal surface layer It has the effect of miniaturizing the genus tissue, which is extremely advantageous.
  • the inventors of the present invention used an ultrasonic impactor having a tip hammer having a radius of curvature of 1.5 mm on the surface of a steel material, with a processing speed of 0.5 at an amplitude of 50 ⁇ and a frequency of 25 kHz.
  • One-pass ultrasonic impact treatment was performed at m / min, and the state of the surface texture before and after the treatment was investigated in detail. The results are shown in Fig. 2 (a), Fig. 2 (b), Fig. 3 (a), and Fig. 3 (b) as the cross-sectional state of the steel material before and after the treatment, with the respective micrographs and schematic diagrams.
  • Figures 2 (a) and 3 (a) show the entire structure
  • Figures 2 (b) and 3 (b) schematically show the structure of the former austenite grains.
  • the cross section perpendicular to the treated surface is plastically deformed by the ultrasonic impact treatment and is extremely fine, and the long axis of the former austenite grains extends almost parallel to the surface. It has become.
  • the crack propagation path is longer, and the direction of the grain boundary, which is the main propagation path of the crack extending from the steel surface, and the direction in which the tensile stress acts are as follows. It was considered that the crack propagation was reduced because of the close proximity of the cracks.
  • the inventors carried out an ultrasonic impact treatment on a 16 mm thick steel sheet having the composition shown in Table 1 while changing the treatment conditions as shown in Table 2.
  • the structure of the surface layer before and after the treatment was investigated, and three liquid metal embrittlement specimens were collected for each level by the bead-on-plate method shown in Fig. 4 to form a liquid metal embrittlement crack. The test was performed.
  • the surface layer of ultrafine grains having a crystal grain size of 1 ⁇ m or less is less than 50 ⁇ from the surface, cracks occur and the susceptibility to liquid metal embrittlement is low. high.
  • the thickness of the ultrafine grained surface layer is 50 ⁇ or more, and the length of old austenite grains in this surface layer is When the axis is substantially parallel to the surface, no cracking occurs and excellent liquid metal embrittlement resistance is obtained.
  • the surface layer with a thickness of 50 / Xm or more from the surface becomes ultra-fine grains with a crystal grain size of 1 ⁇ m or less due to the ultrasonic impact treatment, and the length of the old austenite grains on this surface layer
  • the axis is substantially parallel to the surface, most of the surface grain boundaries extend in a direction substantially parallel to the direction of stress, so that cracks are unlikely to occur, and the surface is bound to the grain boundaries. This is probably because the propagation path of the crack that propagates along it becomes longer, and the time it takes for the crack to reach the depth in the plate thickness direction and reach the fracture becomes longer.
  • the superfine structure of the surface layer is a crystal grain having a particle size of 1 / zm or less.
  • substantially parallel means that the direction of the major axis of the crystal grains or the prior austenite grains and the surface are at an angle of ⁇ 10 ° or less.
  • the major axis and the minor axis are the cross-sections of the steel material (metal material) in the thickness direction, that is, the lengths of the crystal grains or the prior austenite grains in the cross section perpendicular to the processing surface of the steel material (metal material). Axis, short axis.
  • the ratio of the major axis length to the minor axis length (length in the minor axis direction) of the crystal grains or the prior austenite grains in the surface layer is 5 or more. This is because, as described above, the grain boundaries parallel to the stress direction become longer due to the extension of the grains or the prior austenite grains in the major axis direction parallel to the surface, and the crack propagation It is considered that the longer the route, the longer the time to break. In addition, this method is also extremely advantageous for liquid metal embrittlement resistance because ultrafine crystal grains can be made uniform.
  • the length in the minor axis direction of the crystal grains of this surface layer or the prior austenite grains it is preferable that the thickness be 5 jum or less. If the length in the minor axis direction is more than 5 ⁇ , the superfineness of the surface layer is insufficient, and the time until fracture is slightly shorter. On the other hand, if it is less than 5 ⁇ , a sufficient time until fracture can be secured.
  • the surface layer can be made into an ultrafine structure by plastic deformation, the surface shape can be made smooth, and a compressive residual stress is applied near the surface. You can do it.
  • the surface layer of the portion where liquid metal embrittlement is a problem by the ultrasonic impact treatment has an ultrafine structure, and the surface of this portion has a surface shape in which stress concentration is unlikely to occur, and a force is applied near the surface.
  • the surface shape in which stress concentration is unlikely to occur is, for example, in the case of a weld toe, a shape in which the stress concentration coefficient is 2 or less. With such a surface shape, stress concentration hardly occurs.
  • the surface layer has an ultra-fine structure, or the surface has a shape in which stress concentration is unlikely to occur.
  • compressive residual stress liquid metal embrittlement that develops due to stress can be suppressed and reduced, and metal structure products and steel structure products with excellent liquid metal embrittlement resistance can be obtained.
  • This ultrasonic impact treatment may be performed before the metal structure product is brought into contact with the liquid metal, for example, before applying a melting plating or before using as a melting plating tank. Fewer steel products In particular, it may be applied to a place where liquid metal embrittlement becomes a problem. The problematic points are those that come into contact with the liquid metal of metal structure products and iron structure products, and where stress is applied or remains. Weld joints (weld bond, heat affected zone) are first mentioned as specific places where stress is concentrated or remains. Many metal structure products and iron structure products are manufactured with welding, and residual stress is generated in the welded joints. Also, stress tends to concentrate at the weld toe of the weld joint.
  • the welded portion of the metal structure product or the steel structure product that is, the portion including the weld bond portion and / or the weld heat affected zone is subjected to the ultrasonic impact treatment, and further includes the weld toe portion.
  • This is also good. Examples of places where stress is concentrated or loaded other than welds are cuts due to sawing, shearing, fusing, etc., which may be added at the stage of manufacturing metal structure products and steel structure products. is there. At these locations, large tensile and shear stresses are applied to the end faces as they are cut.
  • metal structure products and steel structure products are sometimes constructed by adding bending or twisting, and where these are concentrated, tensile stress accompanying these bending or twisting is applied. I have.
  • stresses generated during these processing steps there are also places where external stress is applied during use, and these are also places where liquid metal embrittlement can be a problem and are subject to this treatment. If the place where the tensile stress is applied is in an environment where it comes into contact with the liquid metal, liquid metal embrittlement occurs as described above.
  • the occurrence of liquid metal embrittlement involves three conditions: environment, stress and material.
  • the ultrasonic impact treatment of the present invention is aimed at reducing the stress conditions among them, and in particular, does not limit the material strength of a metal structure product.
  • steel is used as the metal material.
  • the tensile strength is 4 9 ON / mm 2 or more steel for higher Ri good residual stress of the weld, further increases the liquid metal embrittlement cracking sensitivity.
  • the welded portion of the tensile strength 4 9 0 N / mm 2 or more steel, monitor and a and this subjected to ultrasonic impact treatment is more effective, ultrasonic impact treatment to apply effects Ri good large.
  • Effect applying ultrasonic impact treatment since the strength of the material becomes becomes rather large Ri good both high, weld tensile strength 5 9 0 N / mm 2 or more steel, tensile strength 6 9 ON / mm weld two or more steel weld tensile strength 7 8 0 N / mm 2 or more steel, therefore the tensile-strength is to weld 9 8 oN / mm 2 or more steel, a strength is increased Thus, the effect and necessity of applying the ultrasonic impact treatment is increased.
  • the ultrasonic impact treatment is performed by an ultrasonic impact device having a tip hammer having a predetermined radius of curvature at the tip, with an amplitude of 20 to 60 ⁇ m and a cycle number of 19 to 60 k. Hz is applied to the required metal surface for the required time, but this impact treatment causes the surface layer to be plastically deformed to have an ultra-fine crystal structure, and the crystal grains or former austenite grains
  • the major axis direction is substantially parallel to the surface, and preferably, the surface shape is such that stress concentration is unlikely to occur, and residual compressive stress can be applied, so that liquid metal embrittlement occurs. Resistance can be increased.
  • the thickness of the plastic deformation of the surface layer by the ultrasonic impact treatment needs to be 50 ⁇ or more. If it is less than 50 / xm, it is difficult to form a superfine structure of 50 ⁇ or more in the surface layer, and it is difficult to obtain sufficient liquid metal embrittlement resistance.
  • the thickness of the microstructure or plastic deformation caused by the impact energy is also related to the radius of curvature R of the hammer at the tip of the impactor. If the impact energy of one cycle is the same, but R is small, 1 The thickness of the microstructure or plastic deformation caused by the impact of the cycle increases, and the larger the R, the smaller the thickness.
  • the shape of the hammer at the tip of the ultrasonic impact treatment device is appropriately selected according to the condition of the metal structure product to be treated.
  • the required thickness from the surface of the part to be treated of a metal structure product or iron structure product is made into an ultra-fine structure, or a shape in which stress concentration is less likely to occur, and the compressive residual stress is reduced.
  • the processing conditions such as the shape of the hammer, the impact energy of one cycle, the number of cycles, and the number of times of processing required to apply, for example, the processing of each metal material, and the processing of welded parts and cut end faces of metal structure products By pre-determining each part by preliminary tests, etc., the required ultra-fine structure can be obtained after processing. Or compressive residual stress.
  • a stress state such as an internal stress and a surface stress of a metal structure product or a steel structure product is subjected to an ultrasonic impact treatment. It is necessary not to perform such a treatment after the ultrasonic shock treatment.
  • the ultrasonic impact treatment method of the present invention at least a portion of the metal structure product or the iron structure product to be subjected to the treatment is subjected to, for example, plastic working, straightening, heat treatment, welding, etc.
  • the treatment for changing the structure, the state of plastic deformation, the state of stress, and the like is preferably performed as a pre-treatment before performing the ultrasonic impact treatment. It is preferable not to perform such processing.
  • the above pretreatment preferably includes, in addition to the above-described treatments, a treatment for inspecting a portion where liquid metal embrittlement is problematic for a crack and removing the detected crack.
  • a treatment for inspecting a portion where liquid metal embrittlement is problematic for a crack and removing the detected crack e.g., by means of visual inspection, penetrant inspection, magnetic particle inspection, eddy current inspection, etc., appropriate means for inspecting cracks in metal structure products and iron structure products, where liquid metal embrittlement becomes a problem, Inspect the area to be subjected to the ultrasonic impact treatment for cracks, and check the detected cracks in advance. Is performed.
  • the method of removal a method of removing the cracked part by grinding and cutting with a grinder, a cutting tool, etc., or a method of melting and bonding the cracked part by welding, etc., as appropriate, may be adopted. .
  • the cracked portion is ground and removed, and after overlay welding, the surface of this portion is used for mechanical means such as grinding and cutting tools. It is preferable to include a process for finishing to a smoother shape and further confirming that no crack is detected by the crack inspection process described above.
  • the above-mentioned pre-processing is performed as necessary, and then the above-described ultrasonic impact processing is performed. Thereafter, the quality assurance inspection is performed as necessary.
  • Quality assurance inspection after ultrasonic impact treatment indicates that the treated surface is plastically deformed to a thickness of 50 ⁇ m or more compared to before the treatment, that is, that the treated surface has a thickness of 50 m or more from the surface. It is to check whether the surface layer has an ultrafine structure and / or whether the treated surface has a surface shape in which stress concentration is unlikely to occur.
  • the treated surface is plastically deformed to a thickness of 50 / zm or more compared to the untreated surface, make a replica of the treated surface by the pump method and observe the crystal structure.
  • the grain size of the treated surface is measured with an ultrasonic grain size measuring device, and it is determined that 50% or more of the grains are ultrafine grains with a grain size of 1 ⁇ m or less. You can do this by judging whether or not. If the ultrafine crystal grains are less than 50%, the superfineness of the surface layer is insufficient.
  • the ultrasonic impact treatment is repeated to obtain the required surface texture or further surface texture.
  • a steel (sheet thickness 16 mm) having the composition shown in Table 1 was used as the base metal 1, a welded part 2 was arc-welded using a common metal welding material, and an ultrasonic impact treatment was applied.
  • the metal structure of the surface layer was determined to be ultrafine crystal grains, and a layered structure composed of crystal grains in which the long axis of the prior austenite grains was substantially parallel to the surface.
  • comparative materials as-welded specimens and specimens subjected to ultrasonic impact treatment with small amplitude were used. As shown schematically in Fig.
  • the width is 100 Omm
  • the length is 200 mm
  • the plate thickness is the original thickness.
  • a welded part is formed at the center of the test piece with a bead-on plate, and the liquid metal is used as it is.
  • An embrittlement specimen was used. Needless to say, welding residual stress exists in the weld portion of the as-welded test specimen.
  • Table 1 Composition of test steel (mass%) These specimens were immersed in a bath of molten zinc at 450 ° C. for 3 minutes. After the test, the presence or absence of liquid metal embrittlement was confirmed by a penetration test and cross-sectional observation.
  • Table 2 shows the conditions of the ultrasonic impact treatment
  • Table 3 shows the metallographic condition of the surface layer and the results of the liquid metal embrittlement cracking test.
  • the metal structure product having excellent liquid metal embrittlement resistance and the iron structure product of the present invention are subjected to ultrasonic impact treatment at a location where liquid metal embrittlement is problematic, and the crystal grains of the surface layer are ultra-fine and fine.
  • the major axis of the crystal grains or the prior austenite grains is substantially parallel to the surface, and more preferably, the surface has a surface shape in which stress concentration is unlikely to occur, and the residual compressive stress is small. Attached As a result, microcracks are less likely to occur even when in contact with liquid metal.Also, even if microcracks are present, the growth of the cracks in the thickness direction is suppressed, and the rupture time is significantly increased, resulting in liquid metal embrittlement.
  • the surface layer of the treated portion has a predetermined layered structure and further has a surface shape. Therefore, the liquid metal embrittlement resistance at required portions of the metal structure product and the iron structure product can be surely improved.

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Abstract

Produit à structure de fer et produit à structure de métal ayant une excellente résistance au craquèlement auquel il peut être confronté lorsqu'il subit une contrainte et qu'il est placé dans un environnement provoquant un contact avec un métal liquide, et notamment, une résistance à la fragilisation par le métal liquide, ainsi que procédé de fabrication correspondant. Dans ce produit à structure de métal et ce produit à structure de fer, une couche de surface ayant une épaisseur de 50 νm à partir de la surface dans un point où la fragilisation par le métal liquide peut poser problème est constituée de grains de nanocristaux et est structurée de manière à ce que l'axe principal de ces grains de structure soit sensiblement parallèle à la surface. De préférence, l'allongement dans la direction principale par rapport à la direction secondaire, vis-à-vis de ces grains de cristaux ou des anciens grains austénitiques est de 5 ou plus. On peut arriver à ce résultat en soumettant à un traitement de choc par ultrasons la surface du produit de structure de métal et le produit de structure de fer dans un point dans lequel la fragilisation du métal liquide pose problème. De préférence, une inspection de l'assurance de qualité destinée à analyser la déformation plastique de la région de 50 νm d'épaisseur à partir de la surface est effectuée après le traitement de choc par ultrasons.
PCT/JP2003/014163 2002-11-06 2003-11-06 Produit a structure de fer et produit a structure de metal ayant une excellente resistance a la fragilisation de metal liquide et procede de fabrication correspondant Ceased WO2004042093A1 (fr)

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AU2003277584A AU2003277584A1 (en) 2002-11-06 2003-11-06 Iron structure product and metal structure product excelling in resistance to liquid metal embrittlement and process for producing the same

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JP2002-322850 2002-11-06
JP2002322850A JP4351433B2 (ja) 2002-11-06 2002-11-06 液体金属脆化抵抗性の優れた鉄構製品およびそれらの製造方法

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CN100595292C (zh) * 2007-06-15 2010-03-24 中国科学院金属研究所 在金属材料表层实现超细晶粒组织结构的高速加工方法
EP4074847A4 (fr) * 2020-02-13 2023-06-21 JFE Steel Corporation Feuille d'acier à haute résistance mécanique et son procédé de production

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JP6123461B2 (ja) * 2013-04-30 2017-05-10 新日鐵住金株式会社 超音波衝撃処理方法
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EP4074847A4 (fr) * 2020-02-13 2023-06-21 JFE Steel Corporation Feuille d'acier à haute résistance mécanique et son procédé de production
US12378626B2 (en) 2020-02-13 2025-08-05 Jfe Steel Corporation High-strength steel sheet and method for manufacturing the same

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