WO2004042093A1 - Iron structure product and metal structure product excelling in resistance to liquid metal embrittlement and process for producing the same - Google Patents

Iron structure product and metal structure product excelling in resistance to liquid metal embrittlement and process for producing the same Download PDF

Info

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
Authority
WO
WIPO (PCT)
Prior art keywords
liquid metal
metal embrittlement
steel
product
structure product
Prior art date
Application number
PCT/JP2003/014163
Other languages
French (fr)
Japanese (ja)
Inventor
Akihiro Miyasaka
Original Assignee
Nippon Steel Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nippon Steel Corporation filed Critical Nippon Steel Corporation
Priority to AU2003277584A priority Critical patent/AU2003277584A1/en
Publication of WO2004042093A1 publication Critical patent/WO2004042093A1/en

Links

Classifications

    • 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.

Abstract

An iron structure product and metal structure product excelling in resistance to cracking thereof as encountered when loaded with a stress and placed in an environment causing contact with a liquid metal, namely, resistance to liquid metal embrittlement; and a process for producing the same. In a metal structure product and iron structure product, a surface layer of 50 μm thickness from the surface thereof at a spot wherein a liquid metal embrittlement poses a problem is constituted of nanocrystal grains and is so structured that the major axis of these crystal grains or former austenitic grains is substantially parallel to the surface. Preferably, the ratio of length in the major axis direction to length in the minor axis direction with respect to these crystal grains or former austenitic grains is 5 or greater. This can be accomplished by subjecting to ultrasonic shock treatment the surface of metal structure product and iron structure product at a spot wherein a liquid metal embrittlement poses a problem. Preferably, a quality assurance inspection for investigating the plastic deformation of the region of 50 μm thickness from the surface thereof is carried out after the ultrasonic shock treatment.

Description

液体金属脆化抵抗性の優れた金属構造製品、 鉄構製品およびそれら の製造方法 技術分野 Metal structure products with excellent liquid metal embrittlement resistance, iron products, and methods for producing them
本発明は、 金属材料、 たとえば、 鉄鋼材料を用いて、 橋梁や鉄塔 などの構造物を組み立てた後明にめっき処理して製造される金属構造 製品あるいは、 溶融めつき槽ゃ、 溶融めつき用ロールのよ うな溶接 部を含んで構成されめっき装置などに書用いられる金属装置部材など の金属構造製品において、 液体金属脆化抵抗性に優れた金属構造製 品、 鉄構製品 （鉄鋼材料によ り構成された金属構造製品） 、 および その製造方法に関するものであり、 特に、 溶接熱影響部を含む溶接 部の液体金属脆化抵抗性を向上させた金属構造製品、 鉄構製品、 お よびその製造方法に関する。 背景技術  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. In particular, 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
溶融金属と固体金属が直接接触する と、 金属の組み合わせによつ ては固体金属が高速で脆性的に破壊するこ とがあり 、 液体金属脆化 と して知られている。  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.
例えば、 高張力鋼やオーステナィ ト系ステンレス鋼などの鉄鋼材 料および N i 合金は、 溶融亜鉛や溶融鉛との接触で脆化し、 割れが 進展する。 この脆化割れには応力の存在が必要と されている。 そし てこの液体金属脆化割れは、 殆どが粒界割れであり、 その伝播速度 は秒速数メー トルに達する といわれている。  For example, 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.
橋梁や鉄塔などの金属構造製品の多く は、 鋼材を切断あるいは変 形加工した部材を溶接などによ り接合して鉄構製品と した後、 防鲭 のために、 亜鉛、 亜鉛—アルミニウム、 アルミニウムなどのメ ツキ が施される。 このメ ツキは、 これらのメ ツキ金属を溶融したメ ツキ 浴中に上記の鉄構製品を浸漬して行なうが、 そのとき、 鉄構製品の 溶接部、 主に溶接熱影響部 （H A Z ) などの残留応力が存在する箇 所が脆化し、 粒界割れが発生する。 また、 溶融めつき槽ゃ溶融めつ き ロールなどでは、 一部に溶接部を含んで構成されるこ とが多く こ れらのめつき装置用金属構造製品あるいは鉄構製品は、 その使用中 に溶融めつき金属と接触し、 上記と同様の現象が起こる。 Many metal structural products, such as bridges and steel towers, are made by cutting and deforming steel materials and joining them by welding, etc. to form steel products. For this purpose, zinc, zinc-aluminum, aluminum and other plating are applied. This plating is carried out by immersing the above steel product in a plating bath in which these plating metals are melted. At that time, the welded portion of the steel product, mainly the heat affected zone (HAZ), etc. The area where the residual stress exists is embrittled and grain boundary cracking occurs. In addition, the melting plating tank and the melting plating roll often include a welded part in some cases. In contact with the molten metal, the same phenomenon as above occurs.
従来、 この液体金属脆化割れを防止するために、 材料改善、 応力 の緩和などの観点から各種の対策が検討されてきた。 金属材料の面 から液体金属脆化抵抗性の優れた高強度の材料の開発がなされてい る （例えば、 特公平 2— 5 8 1 4号公報参照） 。  Conventionally, various countermeasures have been studied from the viewpoints of improving materials, relieving stress, etc., in order to prevent the liquid metal embrittlement cracking. High strength materials with excellent liquid metal embrittlement resistance have been developed from the viewpoint of metal materials (for example, see Japanese Patent Publication No. 2-5814).
しかしながら、 この材料においても液体金属脆化抵抗性、 強度の 面で必ずしも十分とはいえないものであった。 また、 残留応力の緩 和の面から、 例えば、 熱処理によ り溶接部などを応力除去焼鈍する こ となどが一般的であるが、 処理対象が大型の金属構造製品あるい は鉄構製品である場合は、 熱処理するための大型の熱処理炉が必要 となり 、 固定構造物などでは熱処理自体も不可能である。 このよ う に、 優れた液体金属脆化抵抗性を有する金属構造製品、 鉄構製品お よびそれらの製造方法は、 十分なものが得られていなかった。  However, this material was not necessarily sufficient in terms of liquid metal embrittlement resistance and strength. In addition, in order to reduce residual stress, for example, 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.
本発明は、 上述のよ うな問題点を解決し、 液体金属脆化に対する 抵抗性の優れた金属構造製品、 鉄構製品およびそれらの製造方法を 提供するこ とを課題とする。 発明の開示  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
本発明は、 上記の課題を解決するためになされたものであって、 例えば、 超音波で先端を振幅 2 0〜60 m、 周波数 1 9 k H z 〜 6 0 k Hz, 出力 0. 2〜 3kWで振動させる工具を用いて金属表面を打撃 する超音波衝撃処理を、 金属構造製品あるいは鉄構製品の液体金属 脆化が問題となる箇所に施すこ とによって、 その表層の組織を改善 し、 よって液体金属抵抗性の優れた構造製品を得るものであり、 ま た、 さ らには、 この処理を行なう際の適切な前処理、 ならびに処理 後の検査を行ない、 その効果を保証するものである。 その要旨と する と ころは、 以下のとおりである。 The present invention has been made in order to solve the above-mentioned problems. For example, the tip of the ultrasonic wave has an amplitude of 20 to 60 m and a frequency of 19 kHz to 60 kHz. By applying 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.
( 1 ) 金属構造製品の液体金属脆化が問題となる箇所の表面から 5 0 μπι以上の厚さの表層の結晶粒を超微細化する と と もに、 該表層 の結晶粒の長軸が表面に実質的に平行となるよ うにしたことを特徴 とする液体金属脆化抵抗性の優れた金属構造製品。  (1) From the surface of the metal structure product where liquid metal embrittlement is a problem, the surface crystal grains with a thickness of 50 μπι 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.
( 2 ) 鉄構製品の液体金属脆化が問題となる箇所の表面から 5 0 μ m以上の厚さの表層の結晶粒を超微細化する と ともに、 該表層の旧 オーステナイ ト粒の長軸が表面に実質的に平行となるよ うにしたこ とを特徴とする液体金属脆化抵抗性の優れた鉄構製品。  (2) From the surface of the steel structure product where liquid metal embrittlement is a problem, crystal grains of the surface layer with a thickness of 50 μm or more are ultra-fine, and the long axis of the former austenite grains of the surface layer A steel structure having excellent resistance to liquid metal embrittlement, characterized in that the steel is substantially parallel to the surface.
( 3 ) 前記鉄構製品の液体金属脆化が問題となる箇所が、 引張強度 4 9 0 NZmm2級以上の鋼であるこ とを特徴とする （ 2 ) に記載の 液体金属脆化抵抗性の優れた鉄構製品。 (3) The liquid metal embrittlement resistance according to (2), wherein the part where the liquid metal embrittlement of the steel product is problematic is steel having a tensile strength of 490 NZmm class 2 or higher. Excellent steel products.
( 4 ) 前記鉄構製品の液体金属脆化が問題となる箇所が、 溶接ボン ド部および/または溶接熱影響部を含むこ とを特徴とする （ 2 ) ま たは （ 3 ) に記載の液体金属脆化抵抗性の優れた鉄構製品。  (4) 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.
( 5 ) 前記表層の旧オーステナイ ト粒の長軸方向長さの短軸方向長 さに対する比が 5以上であるこ と を特徴とする （ 2 ) 〜 （ 4 ) のい ずれか 1つに記載の液体金属脆化抵抗性の優れた鉄構製品。  (5) The ratio according to any one of (2) to (4), wherein the ratio of the length of the former austenite grains in the major axis direction to the minor axis direction of the surface layer is 5 or more. Steel products with excellent resistance to liquid metal embrittlement.
( 6 ) 前記表層の旧オーステナイ ト粒の短軸方向長さが 5 μ ιη以下 であるこ とを特徴とする （ 2 ) 〜 （ 5 ) のいずれか 1 つに記載の液 体金属脆化抵抗性の優れた鉄構製品。 ( 7 ) 金属構造製品の液体金属脆化が問題となる箇所に超音波衝撃 処理を施し、 表面から 5 0 μπι以上の厚さの表層の結晶粒を超微細 化する と と もに、 該表層の結晶粒の長軸が表面に実質的に平行とな るよ うにするこ とを特徴とする液体金属脆化抵抗性の優れた金属構 造製品の製造方法。 (6) The liquid metal embrittlement resistance according to any one of (2) to (5), wherein the length of the prior austenite grains in the surface layer in the minor axis direction is 5 μιη or less. Excellent steel products. (7) Ultrasonic impact treatment is applied to the part of the metal structure product where liquid metal embrittlement is a problem, and the surface crystal grains with a thickness of 50 μπι or more are ultra-fine from the surface, and the surface layer A method for producing a metal structure product having excellent liquid metal embrittlement resistance, characterized in that the major axis of the crystal grains is substantially parallel to the surface.
( 8 ) 鉄構製品の液体金属脆化が問題となる箇所に超音波衝撃処理 を施し、 表面から 5 0 ； u m以上の厚さの表層の結晶粒を超微細化す る と と もに、 該表層の旧オーステナイ ト粒の長軸が表面に実質的に 平行となるよ う にするこ とを特徴とする液体金属脆化抵抗性の優れ た鉄構製品の製造方法。  (8) 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 μm 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.
( 9 ) 前記鉄構製品の液体金属脆化が問題となる箇所の金属が、 引 張強度 4 9 O N/ mm2級以上の鋼であるこ とを特徴とする （ 8 ) に 記載の液体金属脆化抵抗性の優れた鉄構製品の製造方法。 (9) 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. A method for manufacturing steel products with excellent resistance to oxidization.
( 1 0 ) 前記鉄構製品の液体金属脆化が問題となる箇所が、 溶接ボ ン ド部および Zまたは溶接熱影響部を含むこ とを特徴とする （ 8 ) または （ 9 ) に記載の液体金属脆化抵抗性の優れた鉄構製品の製造 方法。  (10) 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.
( 1 1 ) 前記表層の旧オーステナイ ト粒の長軸方向長さの短軸方、向 長さに対する比を 5以上とするこ とを特徴とする （ 8 ) 〜 （ 1 0 ) のいずれか 1 つに記載の液体金属脆化抵抗性の優れた鉄構製品の製 造方法。  (11) Any one of (8) to (10) characterized in that the ratio of the length of the old austenite grains in the major axis direction of the surface layer to the minor axis direction and the orientation length is 5 or more. 4. A method for producing a steel product having excellent resistance to liquid metal embrittlement according to (1).
( 1 2 ) 前記表層の旧オーステナイ ト粒の短軸方向長さを 5 / m以 下とするこ とを特徴とする （ 8 ) 〜 （ 1 1 ) のいずれか 1つに記載 の液体金属脆化抵抗性の優れた鉄構製品の製造方法。  (12) The liquid metal embrittlement according to any one of (8) to (11), wherein the length of the austenite grains in the surface layer in the minor axis direction is 5 / m or less. A method for manufacturing steel products with excellent resistance to oxidization.
( 1 3 ) 前記超音波衝撃処理を施す前に、 前記鉄構製品の液体金属 脆化が問題となる箇所及びその近傍箇所に、 前処理を施すこ と を特 徴とする （ 8 ) 〜 （ 1 2 ) のいずれか 1 つに記載の液体金属脆化抵 抗性の優れた鉄構製品の製造方法。 (13) Before performing the ultrasonic impact treatment, a pretreatment is performed on a portion where the liquid metal embrittlement of the steel structure product becomes problematic and a portion in the vicinity thereof, (8) to (8) 1 2) The liquid metal embrittlement resistor described in any one of Manufacturing method of steel products with excellent resistance.
( 1 4 ) 前記前処理が、 前記鉄構製品の液体金属脆化が問題となる 箇所及びその近傍箇所の内部応力および/または表面応力を変化さ せる処理であるこ とを特徴とする （ 1 3 ) に記載の液体金属脆化抵 抗性の優れた鉄構製品の製造方法。  (14) 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 method for producing a steel structure product having excellent liquid metal embrittlement resistance according to the above item.
( 1 5 ) 前記前処理が、 前記鉄構製品の液体金属脆化が問題となる 箇所の亀裂を検出する と共に、 検出された亀裂を除去する処理を含 むこ とを特徴とする （ 1 3 ) 又は （ 1 4 ) に記載の液体金属脆化抵 抗性の優れた鉄構製品の製造方法。  (15) 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).
( 1 6 ) 前記超音波衝撃処理が、 さ らに、 前記鉄構製品の液体金属 脆化が問題となる箇所の表面形状を応力集中の生じ難い形状と し、 かつ表面近傍に圧縮残留応力を付与するこ とを特徴とする （ 8 ) 〜 (16) 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. (8) ~
( 1 5 ) のいずれか 1つに記載の液体金属脆化抵抗性の優れた鉄構 製品の製造方法。 (15) The method for producing a steel structure product excellent in liquid metal embrittlement resistance according to any one of (15).
( 1 7 ) 前記鉄構製品の液体金属脆化が問題となる箇所に、 超音波 衝撃処理を施し、 その後さ らに、 品質保証検査をするこ とを特徴と する （ 8 ) 〜 （ 1 6 ) のいずれか 1つに記載の液体金属脆化抵抗性 の優れた鉄構製品の製造方法。  (17) An ultrasonic impact treatment is applied to the part where the liquid metal embrittlement of the steel structure product becomes a problem, and then a quality assurance inspection is performed (8) to (16). ). The method for producing a steel product excellent in liquid metal embrittlement resistance according to any one of the above.
( 1 8 ) 前記品質保証検査は、 超音波衝撃処理後の処理面が処理前 に比べて、 5 0 μ m以上の厚さが塑性変形しているこ と、 および処 理面が応力集中の生じ難い表面形状となっているこ とのいずれか一 方又は双方を確認するものであるこ とを特徴とする （ 1 7 ) に記載 の液体金属脆化抵抗性の優れた鉄構製品の製造方法。  (18) The quality assurance inspection stated that the treated surface after ultrasonic impact treatment was plastically deformed by a thickness of 50 μm or more compared to before treatment, and that the treated surface was subjected to stress concentration. (17) The method for producing a steel product excellent in liquid metal embrittlement resistance according to (17), characterized in that one or both of the surface shapes that hardly occur are confirmed. .
( 1 9 ) 前記品質保証検査の塑性変形しているこ との確認は、 超音 波衝撃処理後の処理面をス ンプ法によ り観察し、 処理していない部 分に比べてその 5 0 %以上の金属結晶粒が超微細粒であるかどう か を判断する こ とによるものであるこ とを特徴とする （ 1 8 ) に記載 の液体金属脆化抵抗性の優れた鉄構製品の製造方法。 (19) In the quality assurance inspection, the plastic deformation was confirmed by observing the treated surface after the ultrasonic shock treatment by the pump method and comparing it with the untreated portion. It is characterized by determining whether or not 0% or more of the metal crystal grains are ultra-fine grains. The feature is described in (18). For producing steel products having excellent resistance to liquid metal embrittlement.
( 2 0 ) 前記品質保証検査の塑性変形の確認は、 超音波衝撃処理後 の処理面の結晶粒度を超音波粒径測定装置によ り測定し、 処理して いない部分に比べてその 5 0 %以上の結晶粒が超微細粒であるかど うかを判断することによるものであるこ とを特徴とする （ 1 8 ) に 記載の液体金属脆化抵抗性の優れた鉄構製品の製造方法。  (20) In the quality assurance inspection, the plastic deformation was confirmed by measuring the crystal grain size of the treated surface after ultrasonic impact treatment with an ultrasonic particle size measuring device and comparing it with the untreated portion by 50%. (18) The method for producing an iron structure product having excellent liquid metal embrittlement resistance according to (18), wherein the determination is made by determining whether or not the crystal grains of not less than% are ultrafine grains.
( 2 1 ) 前記品質保証検査の応力集中の生じ難い表面形状の確認は 、 超音波衝撃処理後の処理面を型取材を用いて型取り し、 型取り し た面が応力集中の生じ難い表面形状であるかどうかを判断すること によるものであるこ とを特徴とする （ 1 8 ) に記載の液体金属脆化 抵抗性の優れた鉄構製品の製造方法。  (21) In the quality assurance inspection, the surface shape where stress concentration is unlikely to occur can be confirmed by molding the treated surface after ultrasonic impact treatment using a molding material, and the molded surface is the surface where stress concentration is unlikely to occur. (18) The method for producing a steel product excellent in liquid metal embrittlement resistance according to (18), wherein the method is based on determining whether the shape is a shape.
( 2 2 ) 前記品質保証検査の応力集中の生じ難い表面形状の確認は (22) The quality assurance inspection should confirm the surface shape where stress concentration hardly occurs.
、 超音波衝撃処理後の処理面を変位計を用いて測定し、 その変位が 応力集中の生じ難い面の変位の範囲内であるかどうかを判断するこ とによ り行なう ものであることを特徴とする （ 1 8 ) に記載の液体 金属脆化抵抗性の優れた鉄構製品の製造方法。 図面の簡単な説明 The measurement was performed using a displacement meter on the treated surface after ultrasonic impact treatment, and it was determined whether the displacement was within the range of displacement of the surface where stress concentration was unlikely to occur. (18) The method for producing a steel product having excellent liquid metal embrittlement resistance according to (18). BRIEF DESCRIPTION OF THE FIGURES
図 1 ( a ) は、 液体金属脆化による亀裂の進展状況を示す断面模 式図であり、 粒界が引張応力の方向に垂直な方向にある場合を示す 図 1 ( b ) は、 液体金属脆化による亀裂の進展状況を示す断面模 式図であり、 粒界のほとんどが引張応力の方向と平行な方向にある 場合を示す。  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.
図 2 ( a ) は、 鉄構製品の超音波衝撃処理前の断面組織を示す組 織写真である。  Figure 2 (a) is a tissue photograph showing the cross-sectional structure of a steel product before ultrasonic impact treatment.
図 2 ( b ) は、 鉄構製品の超音波衝撃処理前の断面組織の旧ォー ステナイ ト組織の状況を示す模式図である。 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.
図 3 ( a ) は、 鉄構製品の超音波衝撃処理後の断面組織を示す組 織写真である。  Figure 3 (a) is a tissue photograph showing the cross-sectional structure of a steel product after ultrasonic impact treatment.
図 3 ( b ) は、 鉄構製品の超音波衝撃処理後の断面組織の旧ォー ステナイ ト組織の状況を示す模式図である。  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.
図 4は、 液体金属脆化試験片の状況を示す図である。  FIG. 4 is a view showing the state of a liquid metal embrittlement test specimen.
発明を実施するための最良の形態 BEST MODE FOR CARRYING OUT THE INVENTION
本発明が対象とする金属構造製品は、 鉄鋼材料や N i 合金などの 金属材料によ り構成される鉄塔や橋梁などの構造物、 或いは機械部 品や配管、 容器槽などの構造部品を含むものである。 そしてこれら の構造製品は、 一般に、 金属材料に切削、 曲げなどの加工、 或いは さ らに、 溶接加工を施して組立てられ、 その後、 亜鉛、 亜鉛系合金 、 アルミニウム、 アルミニウム合金などの溶融金属メ ツキ浴に浸漬 して、 溶融めつきを施し、 製造される。 また、 溶融めつき容器や溶 融めっき槽などは、 加工によ り構造部品と した後それらが使用され る際に、 前述の溶融金属と接触することになる。 すなわち、 製造あ るいは使用の段階で、 金属構造製品、 鉄構製品は、 液体金属 （溶融 金属） と接触することになる。  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).
ところで、 液体金属脆化は、 金属構造製品 （固体金属） が引張応 力の存在下で液体金属と接触する環境にあると、 その表面に生じた 微小の亀裂が厚さ方向に進展し、 大きな割れとなって金属構造製品 の機能を低下させるものである。 図 1 ( a ) 、 図 1 ( b ) は、 金属 構造製品の液体金属脆化割れの亀裂の進展を説明するものであり、 金属材料の厚さ方向断面における結晶粒の粒界を示している。 なお By the way, 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
、 鉄鋼材料の場合は、 旧オーステナイ ト粒界を示している。 この亀 裂の進展方向は、 図 1 ( a ) に示すよ うに、 引張応力 （残留応力、 外部応力） に垂直な方向で、 ほとんどの場合、 金属の結晶粒界、 あ るいは、 鉄鋼材料の場合は旧オーステナイ ト粒界、 に沿っている。 従って、 図 1 ( b ) に示すよ うに、 粒界の方向と引張応力の方向と が実質的に平行であれば、 この応力は亀裂の先端をさ らに開口させ るよ う には作用しないので、 進展を遅らせ、 すなわち亀裂の伝播抵 抗を向上させ、 液体金属脆化を抑制するこ とができる。 In the case of steel materials, the former austenite grain boundaries are shown. As shown in Fig. 1 (a), 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.
また、 結晶粒が超微細になれば、 粒界が著しく増えるこ と とな り 、 亀裂が金属材料の厚さ方向に進展するための経路が長く な り、 亀 裂の伝播抵抗を向上させるこ とになる。  Also, when the crystal grains become ultra-fine, the grain boundaries increase remarkably, the path for the crack to propagate in the thickness direction of the metal material becomes longer, and the crack propagation resistance is improved. And
発明者らはこの点に着目 し、 金属構造製品の液体金属脆化が問題 となる箇所の表層の結晶粒を超微細化し、 かつ、 この表層の結晶粒 の長軸方向が表面と実質的に平行になるよ う にする ものである。 表 層の結晶粒が超微細化され、 かっこの表層の結晶粒の長軸が、 引張 応力の方向と実質的に平行となるこ とによ り、 進展経路もさ らに長 く なるため、 上述のとおり、 亀裂の伝播抵抗性を高めることができ 、 液体金属脆化による割れを抑制するこ とができる。 また、 鉄鋼材 料の場合は、 上述のよ う に、 亀裂は旧オーステナイ ト粒界に沿って 進展する。 したがって、 鉄構製品の液体金属脆化が問題となる箇所 については、 当該箇所の表層の結晶粒を超微細化する と ともに、 こ の表層の旧オーステナイ ト粒の長軸が表面と実質的に平行となるよ うにする。 これによつて、 亀裂の伝播抵抗性を高めるこ とができ、 液体金属脆化による割れを抑制するこ とができる。  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. Therefore, in a place where liquid metal embrittlement of steel products becomes a problem, 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.
このよ うに、 液体金属脆化が問題となる箇所の表層の結晶粒を超 微細化し、 結晶粒の長軸方向が表面と実質的に平行になるよ うにす る、 或いは、 表層の結晶粒を超微細化し、 旧オーステナイ ト粒の長 軸方向が表面と実質的に平行となるよ う にする手段と して、 超音波 で先端のハンマー部を振幅 2 0〜 6 0 μ 周波数 1 9〜 6 0 k Hz 、 出力 0 . 2〜 3 kWで振動させる装置によ り金属表面を打撃してピ 一二ングを行なう超音波衝撃処理 （例えば米国特許第 6， 1 7 1， 4 1 5号明細書参照） が好適である。 この処理方法は、 基本的には ハンマーピーニングと同じであるが、 一回一回の打撃のエネルギー は小さいかわり に、 1秒間に 1万回を超える回数の打撃を与えるこ と によって、 金属に塑性変形を与えるものである。 このとき、 一回一 回の打撃力は小さいために、 打撃装置に生じる反動は殆どなく 、 ハ ンマ一ピーニング装置に比べて使用性、 施工性の面で優れている。 また、 1回の打撃エネルギーが小さいため、 先端部のハンマー形 状は、 小型にするこ とができ、 溶接部や接続部などの微小な部分や 狭隘な部分に対しても打撃処理を施すこ とができる。 この点におい て、 液体金属脆化が問題となる箇所が小さな部分でも処理が適用可 能となる。 この場合でも、 上述のよ う に打撃回数を極めて多く でき るこ とから、 十分な塑性変形を与えるこ とができる。 In this way, 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. As a means to make the old austenite grains super-fine, so that the long axis direction of the former austenite grains is substantially parallel to the surface, the hammer at the tip is ultrasonically amplified with an amplitude of 20 to 60 μ 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.
また、 この超音波衝撃処理は、 金属表面に対して非常に多く の回 数の打擊を与えているので、 金属表面に対して従来のハンマーピー ユングにはない効果があり、 また、 一回一回の打撃エネルギーショ ッ トは、 ショ ッ ト ピーニングよ り も大きいので、 従来のショ ッ ト ピ 一二ングにない効果もある。  In addition, since this ultrasonic impact treatment gives a very large number of hits to the metal surface, it has an effect on the metal surface that is not provided by the conventional hammer pie-jung. Each shot energy shot is larger than shot peening, so it has an effect that conventional shot pitting does not have.
すなわち、 先ず、 打撃の回数が多いこ とで、 処理の均一性が得ら れる。 ハンマーピーユングでも数パスを同一線上で実施すればある 程度の均一性が得られるが、 超音波衝撃処理の打撃周波数は、 1 9 〜 6 0 k Hzであり、 その得られる均一性はハンマーピーユングのそ れとは全く異なる レベルにあり、 処理ス ピー ドが 0 . δ πι Ζ分程度 であれば、 所要の金属表面のほとんどを均一にかつ欠陥を残すこ と なく仕上げるこ とができる。  That is, first, the number of hits increases the uniformity of the treatment. Although a certain degree of uniformity can be obtained by performing several passes on the same line in the hammer pie-jung, 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.δππιΖ, most of the required metal surface can be finished uniformly and without leaving any defects.
そして、 処理後の金属表面を平滑にする と と もに、 金属表層の金 属組織を微細化する作用があり、 極めて有利である。 Then, 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.
発明者らは、 鋼材の表面に 1 . 5 mmの曲率半径を有する先端ハ ンマーを有する超音波衝撃装置によ り、 振幅 5 0 μ πι、 周波数 2 5 k H z にて処理速度 0. 5 m/m i nで 1パスの超音波衝撃処理を 行ない、 処理前後の表層組織の状況を詳細に調査した。 その結果を 処理前後の鋼材の断面状況と して、 図 2 ( a ) 、 図 2 ( b ) 及び図 3 ( a ) 、 図 3 ( b ) に、 それぞれの組織写真及び模式図で示す。 なお、 図 2 ( a ) 、 図 3 ( a ) は、 全組織を表わしており、 図 2 ( b ) 、 図 3 ( b ) は、 旧オーステナイ ト粒の組織を模式的に示した ものである。 これらの図から判るよ うに、 処理面に垂直な断面は、 超音波衝撃処理によ り塑性変形し、 極めて微細化しているともに、 旧オーステナイ ト粒の長軸が表面にほぼ平行に伸展した組織となつ ている。 このよ うな表層組織では、 上述のとおり、 亀裂が進展する 経路がよ り長くなつており、 鋼材表面から伸展する亀裂の主たる進 展経路である結晶粒界の方向と引張応力の作用する方向とが近接す るため、 亀裂の進展が軽減されることが考えられた。  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 μππ 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, and Figures 2 (b) and 3 (b) schematically show the structure of the former austenite grains. . As can be seen from these figures, 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. In such a surface layer structure, as described above, 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.
そこで、 発明者らはこれを確認するために、 表 1に示す組成を有 する厚さ 1 6 mm鋼板に対して、 表 2に示すように処理条件を変え て超音波衝撃処理を実施し、 処理前後の表層部の組織を調査すると 共に、 図 4に示すビー ドオンプレー トで溶接部を形成する方法で、 液体金属脆化試験片を各水準ごとにそれぞれ 3個採取し、 液体金属 脆化割れ試験を実施した。  In order to confirm this, 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.
その結果を表 3に示す。  The results are shown in Table 3.
表 3から判るよ うに、 結晶粒径が 1 μ m以下の超微細粒となって いる表層が表面から 5 0 μ πι未満の厚さでは、 割れが発生しており 、 液体金属脆化感受性が高い。 一方、 超微細粒となっている表層の 厚さが 5 0 μ πι以上であって、 この表層の旧オーステナイ ト粒の長 軸が表面に実質的に平行である場合は、 割れの発生もなく、 優れた 液体金属脆化抵抗性を示すことがわかる。 As can be seen from Table 3, when the surface layer of ultrafine grains having a crystal grain size of 1 μm or less is less than 50 μππ from the surface, cracks occur and the susceptibility to liquid metal embrittlement is low. high. On the other hand, the thickness of the ultrafine grained surface layer is 50 μππ 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.
これは、 上述のとおり、 超音波衝撃処理によって表面から 5 0 /X m以上の厚さの表層が結晶粒径 1 μ m以下の超微細粒となり、 かつ、 この表層の旧オーステナイ ト粒の長軸が表面に実質的に平行となる ことによって、 表層の結晶粒界の殆どが応力の方向と実質的に平行 な方向に伸びるこ と となり 、 亀裂が発生し難く 、 また、 表面から粒 界に沿って進展する亀裂の進展経路が長く なるため、 亀裂が板厚方 向の深部に達して破断に到るまでの時間が長く なるためと考えられ る。 なお、 結晶粒径が 1 μ ιηを超える と、 結晶粒の大きなものが含 まれ、 均一な超微細化組織とならないためとはならないため、 安定 した液体金属抵抗性を確保できない。 表層の超微細組織とは粒径が 1 /z m以下の結晶粒であるものとする。 実質的に平行とは、 結晶粒 または旧オーステナイ ト粒の長軸の方向と表面とが、 ± 1 0° 以下 の角度であるこ と をいう。  This is because, as described above, 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 μm or less due to the ultrasonic impact treatment, and the length of the old austenite grains on this surface layer When 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. If the crystal grain size exceeds 1 μιη, stable liquid metal resistance cannot be ensured because a large crystal grain is included and a uniform ultrafine structure is not prevented. The superfine structure of the surface layer is a crystal grain having a particle size of 1 / zm or less. The term “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.
また、 長軸、 短軸は、 鋼材 （金属材料） の厚さ方向の断面、 すな わち、 鋼材 （金属材料） の処理表面に垂直な断面における結晶粒ま たは旧オーステナイ ト粒の長軸、 短軸をいう。  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.
この表層の結晶粒または旧オーステナイ ト粒の長軸方向長さ と短 軸方向長さ との比 （長軸方向長さ 短軸方向長さ） が 5以上である こ とが好ま しい。 これは、 上述と同様に、 結晶粒または旧オーステ ナイ ト粒が表面に平行な長軸方向に伸展したこ とによって、 応力の 方向に平行な結晶粒界がよ り長く な り、 亀裂の進展経路が長く なつ て破断に到るまでの時間が長く なるからと考えられる。 さ らに、 こ のよ う にするこ とによって、 結晶粒の超微細化も均一にできるため 液体金属脆化抵抗性に対して極めて有利である。  It is preferable that 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.
また、 この表層の結晶粒または旧オーステナイ ト粒の短軸方向長 さが 5 ju m以下であるこ とが好ましい。 短軸方向の長さが 5 μ πι以 上では、 表層の超微細化が不十分であり、 破断までの時間がやや短 く なる。 一方、 5 μ πι以下である と、 破断までの時間をよ り十分に 確保できる。 In addition, 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 μπι, 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 μπι, a sufficient time until fracture can be secured.
さ らに、 この超音波衝撃処理では、 塑性変形によ り表層を超微細 化組織とするこ とができる と共に、 表面形状をなめらかな面形状と し、 かつ表面近傍に圧縮残留応力を付与するこ ともできる。  In addition, in this ultrasonic impact treatment, 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.
したがって、 好ま しく は、 超音波衝撃処理によって液体金属脆化 が問題となる箇所の表層を超微細化組織とする と共に、 この箇所の 表面を応力集中の生じ難い表面形状と し、 表面近傍に力を付与する こ とが好ま しい。 応力集中の生じ難い表面形状とは、 例えば、 溶接 止端部の場合、 応力集中係数が 2以下となるよ うな形状であって、 このよ うな表面形状とするこ とによって応力集中が生じ難く なり、 かつ表面近傍、 例えば表面から 5 0 μ m以内の範囲、 に圧縮残留応 力を付与するこ とによって、 液体金属脆化割れ起点となる微小な欠 陥が大きな亀裂に伸展するこ とを抑制するこ とができるので、 これ らの微小亀裂を無害化し、 さ らに、 液体金属脆化抵抗性を向上させ るこ とができる。  Therefore, preferably, 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. It is preferable to provide 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. By applying compressive residual stress to the vicinity of the surface, for example, within 50 μm from the surface, it is possible to prevent small defects, which are the starting point of liquid metal embrittlement cracks, from expanding into large cracks As a result, these microcracks can be rendered harmless, and the liquid metal embrittlement resistance can be improved.
以上のよ うに、 金属材料の表面に超音波衝撃処理を施すこ とによ つて、 その表層部を超微細化組織と し、 あるいは、 さ らに、 表面を 応力集中の生じ難い形状とする と共に圧縮残留応力を付与するこ と によって、 応力によって進展する液体金属脆化を抑制、 低減するこ とができ、 液体金属脆化抵抗性の優れた金属構造製品、 鉄構製品と するこ とができる。  As described above, by subjecting the surface of a metallic material to ultrasonic impact treatment, the surface layer has an ultra-fine structure, or the surface has a shape in which stress concentration is unlikely to occur. By applying 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. .
この超音波衝撃処理は、 金属構造製品を液体金属と接触させる前 、 例えば、 溶融めつきを施す前あるいは、 溶融めつき槽などと して 使用する前に施せば良く 、 前述の金属構造製品、 鉄構製品の少なく と も液体金属脆化が問題となる箇所に施せばよい。 その問題となる 箇所は金属構造製品、 鉄構製品の液体金属と接し、 かつ応力が負荷 ないし残留しう る個所である。 応力が集中ないし残留する具体的な 箇所と して、 溶接継手部 （溶接ボン ド部、 溶接熱影響部） が先ず挙 げられる。 金属構造製品、 鉄構製品の多く が溶接を伴って製作され 、 その溶接継手部には残留応力が発生する。 また、 溶接継手部の溶 接止端部は、 応力が集中しやすい。 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.
従って、 金属構造製品、 鉄構製品の溶接部、 すなわち、 溶接ボン ド部および または溶接熱影響部を含む部分を超音波衝撃処理する こ とが好ましく 、 さ らには、 溶接止端部を含めるこ と も好ま しい。 溶接部以外に、 応力が集中ないし負荷される箇所の例と しては、 金属構造製品、 鉄構製品を製造する段階で加えられるこ とのある、 鋸断、 せん断、 溶断などによる切断箇所がある。 これらの箇所は、 切断に伴って端面に大きな引張応力、 せん断応力が負荷される。 そ のほか、 金属構造製品、 鉄構製品には、 曲げや捻り を加えて構成さ れるこ とがあり 、 これらが集中する箇所には、 これらの曲げやねじ り に伴う引張応力が負荷されている。 これらの加工過程で生じる応 力のほか、 使用状態で外部から応力が負荷される箇所もあり 、 これ らも液体金属脆化が問題となり得る箇所であり、 本処理の対象とな る。 このよ うに引張応力が負荷されている箇所が、 液体金属と接触 する環境下にある と、 上述のとおり、 液体金属脆化を生じるこ と と なる。  Therefore, it is preferable that 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. In addition, 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. In addition to the 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.
上述のよ う に、 液体金属脆化の発生は、 環境、 応力及び材料の 3 つの条件が関与する。 本発明の超音波衝撃処理は、 このう ちの応力 条件を低減するこ と を主眼とするものであ り、 特に、 金属構造製品 の材料強度を限定するものではないが、 液体金属脆化は、 強度、 硬 度の高い場合に発生しやすいと言う観点から、 金属材料と して鋼材 を用いる鉄構製品の場合、 引張強度が 4 9 O N/mm2以上の鋼材か らなる構造製品の必要箇所には少なく と も施すこ とが好ましい。 引 張強度が 4 9 O N/mm2以上の鋼材では、 溶接部の残留応力がよ り 高く なるために、 液体金属脆化割れ感受性が一段と高く なる。 この ため、 引張強度が 4 9 0 N/mm2以上の鋼材の溶接部には、 超音波 衝撃処理を施すこ とが一段と有効である と と もに、 超音波衝撃処理 を施す効果もよ り大きい。 超音波衝撃処理を施す効果は、 材料の強 度が高く なる と ともによ り大き く なるので、 引張強度が 5 9 0 N/ mm2以上の鋼材の溶接部、 引張強度が 6 9 ON/mm2以上の鋼材 の溶接部、 引張強度が 7 8 0 N/mm2以上の鋼材の溶接部、 引張強 度が 9 8 O N/ mm2以上の鋼材の溶接部、 と強度が高く なるのにし たがって、 超音波衝撃処理を施す効果と必要性は大き く なる。 As mentioned 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. From the viewpoint that it is likely to occur when strength and hardness are high, steel is used as the metal material. In the case of steel products using steel, it is preferable to apply at least to necessary parts of structural products made of steel having a tensile strength of 49 ON / mm 2 or more. 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. Therefore, 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.
上述のよ うに超音波衝撃処理は、 先端部に所定の曲率半径を有す る先端ハンマーを有する超音波衝撃装置によ り、 振幅 2 0〜 6 0 μ m、 サイクル数 1 9〜 6 0 k H z にて必要の時間、 所要の金属表面 部分に対して行なうが、 この衝撃処理によ り表層部分を塑性変形さ せ、 超微細結晶組織と し、 かつ、 結晶粒あるいは旧オーステナイ ト 粒の長軸方向を表面に実質的に平行なものとする と と もに、 好ま し く は、 応力集中が発生し難い表面形状と し、 かつ残留圧縮応力付与 するこ とができ、 液体金属脆化抵抗性を高めるこ とができる。  As described above, 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 μm 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.
このためには、 超音波衝擊処理による表層の塑性変形の厚さは、 5 0 μΐη以上であるこ とが必要である。 5 0 /xm未満では、 表層の 5 0 μ ΐη以上を超微細な組織とするこ とが困難であり、 十分な液体金 属脆化抵抗性を得るこ とが困難となる。  For this purpose, the thickness of the plastic deformation of the surface layer by the ultrasonic impact treatment needs to be 50 μΐη or more. If it is less than 50 / xm, it is difficult to form a superfine structure of 50 μΐη or more in the surface layer, and it is difficult to obtain sufficient liquid metal embrittlement resistance.
また、 引張応力を解消し圧縮応力を付与する点からも、 表面から 5 Ο μ ιη以上の厚さを塑性変形させるこ とが必要である。 しかしな がら、 この表層の超微細組織或いは塑性変形の厚さを過度に大き く する と、 表層が過度に硬化したり、 変形が大き く な り過ぎたり して 製品と しての表面性状が悪く なる一方、 処理のためのコス トが増え るために好ま しく ない。 It is also necessary to plastically deform a thickness of 5 μμηη or more from the surface from the viewpoint of eliminating tensile stress and applying compressive stress. However, the thickness of this superficial microstructure or plastic deformation is excessively large. If this is done, the surface layer will be excessively hardened or deformed too much and the surface properties of the product will deteriorate, but this is not preferred because the cost for processing will increase.
所要の厚さの超微細組織或いは塑性変形を得るために必要な変形 のためのエネルギーはほぼ一定であるため、 1 サイ クルの衝撃エネ ルギーを大き く して短時間に処理しても良いが、 均一性を高めたい 場合や、 衝撃部位の位置をよ り精緻に制御し、 過度な塑性変形を防 止したい場合は、 1サイ クルの衝撃エネルギーを小さ く し、 二回以 上の処理を同一箇所に対して行なう こ とが好ましい。  Since the energy required for obtaining the ultra-fine structure or plastic deformation of the required thickness is almost constant, it is possible to increase the impact energy of one cycle and process it in a short time. If you want to improve the uniformity or control the location of the impact area more precisely and prevent excessive plastic deformation, reduce the impact energy per cycle and perform the process more than once. It is preferable to perform the same process.
また、 衝撃エネルギーによって生じる超微細組織或いは塑性変形 の厚さは、 衝撃装置の先端のハンマーの曲率半径 Rとも関係してお り 、 1サイ クルの衝撃エネルギーが同じでも、 Rが小さければ、 1 サ ィ クルの衝撃で生じる超微細組織或いは塑性変形の厚さは大き く な り 、 Rが大きければその厚さは小さ く なる。  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.
また、 表面を応力集中の生じ難い形状と し、 圧縮残留応力を付与 する場合は、 ハンマーの Rが小さければ、 1サイ クルで形成される 表面形状の範囲が狭いので繰り返し処理が必要とな り、 一方、 尺が 大きければ、 形状の制御が困難となるこ ともある。 従って、 超音波 打撃処理装置の先端のハンマーの形状は、 処理対象とする金属構造 製品の状況によって適宜選択する。  In addition, when the surface is formed in a shape that does not easily cause stress concentration and compressive residual stress is applied, if the radius of the hammer is small, the range of the surface shape formed in one cycle is narrow, so repeated treatment is necessary. On the other hand, if the length is large, it may be difficult to control the shape. Therefore, 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.
超音波衝撃処理を施すにあたっては、 金属構造製品、 鉄構製品の 処理対象箇所の表面から所要の厚さを超微細組織と し、 或いはさ ら に応力集中の生じ難い形状と し圧縮残留応力を付与するために必要 なハンマーの形状、 1 サイ クルの打撃エネルギー、 サイ クル数、 処 理回数などの処理条件を、 例えば、 金属材料ごとに、 また金属構造 製品の溶接部、 切断端面などの処理箇所ごとに予備試験などによ り 、 予め決めて置く こ とによって、 処理後に所要の超微細組織と し或 いは圧縮残留応力を付与するこ とができる。 When applying ultrasonic impact treatment, 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.
と ころで、 本発明の液体金属脆化抵抗性向上方法においては、 金 属構造製品、 鉄構製品の超音波衝撃処理を施す箇所に対して、 この 箇所の内部応力、 表面応力などの応力状態変化させるよ うな処理を 、 超音波衝撃処理を施した後には行なわないよ うにするこ とが必要 である。  However, in the method for improving liquid metal embrittlement resistance according to the present invention, 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.
すなわち、 超音波打撃処理を施して、 当該箇所の表層を超微細組 織と し、 或いは塑性変形させて表面形状を応力集中の生じ難い形状 と し、 かつ残留圧縮応力を付与した後で、 当該箇所及びその近傍箇 所の表層の組織、 塑性変形状況、 応力状態などを変化させるよ うな 処理、 例えば、 塑性加工、 矯正、 熱処理、 溶接などを施すと、 超音 波衝撃処理によ り形成された液体金属脆化を抑制するための上記の 表層の性状がこれによつて減殺され、 抑制効果が低下する。  That is, after applying an ultrasonic impact treatment to make the surface layer of the relevant portion into an ultra-fine structure, or by plastically deforming the surface to a shape in which stress concentration is unlikely to occur and applying a residual compressive stress, When processing such as plastic working, straightening, heat treatment, welding, etc., is performed to change the surface structure, plastic deformation state, stress state, etc. of the surface layer at or near the point, it is formed by ultrasonic impact processing. As a result, the properties of the surface layer for suppressing liquid metal embrittlement are reduced by this, and the suppression effect is reduced.
従って、 本発明の超音波衝撃処理方法においては、 金属構造製品 、 鉄構製品の少なく とも当該処理を施す箇所に対しては、 例えば、 塑性加工、 矯正、 熱処理、 溶接など、 当該箇所の表層の組織、 塑性 変形状況、 応力状態などを変化させるよ う な処理は、 超音波衝撃処 理を施す前に、 前処理と して施しておく こ とが好ましく 、 超音波衝 撃処理後は、 このよ う な処理を行なわないよ うにするこ とが好ま し い。  Therefore, in 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.
また、 上記の前処理においては、 上述の各処理のほか、 液体金属 脆化が問題となる箇所に対する亀裂の有無を検査し、 検出された亀 裂を除去する処理を含むこ とが好ま しい。 すなわち、 目視検査、 浸 透探傷検査、 磁粉探傷検査、 渦流探傷検査など金属構造製品、 鉄構 製品の亀裂を検査する適切な手段によ り、 液体金属脆化が問題とな る箇所、 すなわち、 超音波衝撃処理を施そう とする箇所に対して亀 裂の有無を検査し、 そして、 検出された亀裂に対して、 事前にこれ を除去する処理を施すものである。 除去する方法は、 亀裂部分をグ ライ ンダー、 切削工具等によ り研削 · 切削して除去する方法、 或い は溶接によ り亀裂部を溶融接着する方法な適宜など方法を採用しう る。 In addition, 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. In other words, 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. As for 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. .
また、 特に、 除去した亀裂の深さが 3mm以上である場合は、 亀裂 部分を研削除去し、 肉盛溶接を行った後、 この箇所の表面をグライ ンダ一、 切削工具等の機械的手段によ り平滑な形状に仕上げ、 さ ら に上述の亀裂の検査処理によつて亀裂が検出されないこ とを確認す る処理を含むこ とが好ましい。  In particular, if the depth of the removed crack is 3 mm or more, 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.
本発明においては、 必要に応じて上述の前処理を施した後、 上記 の超音波衝撃処理を施し、 その後、 必要に応じて、 品質保証検査を 行なう。  In the present invention, 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.
超音波衝撃処理後の品質保証検查は、 処理面が処理前と比較して 5 0 μ m以上の厚さまで塑性変形しているこ と、 すなわち、 表面か ら 5 0 m以上の厚さの表層が超微細組織となっているこ と、 およ び処理面が応力集中の生じ難い表面形状となっているかどうかのい ずれか一方又は双方を確認するものである。  Quality assurance inspection after ultrasonic impact treatment indicates that the treated surface is plastically deformed to a thickness of 50 μm 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.
処理面が処理前と比較して 5 0 /z m以上の厚さまで塑性変形して いるこ とを確認するには、 ス ンプ法によ り処理面の複製を制作し、 その結晶組織を観察するか、 あるいは処理面の結晶粒度を超音波粒 径測定装置によるかのいずれかによ り結晶粒度を測定し、 結晶粒の 5 0 %以上が粒径 1 μ m以下の超微細粒であるかどうかを判断する こ とによって行なう こ とができる。 超微細結晶粒が 5 0 %未満では 、 表層の超微細化が不十分である。  To confirm that 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. Or 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 μm 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.
また、 処理面が応力集中の生じ難い表面形状となっているかどう かを確認するには、 例えば歯科用形象材のよ うな型取り材を用いて 型取り し、 型取り した複製の表面形状を検査するか、 或いは、 レ一 ザ一変位計などの高精度な変位測定装置を用いて表面の変位を測定 するこ とによって、 処理面が応力集中のし難い表面の曲率ないしは 変位を有するかどうかを判断するこ とによって行なう こ とができる 以上のよ う な方法によ り、 超音波衝撃処理後の表層組織或いは、 表面形状を確認する品質保証検査を行なう こ とによって、 金属構造 製品、 鉄構製品の液体金属脆化が問題となる箇所の液体金属脆化抵 抗性の向上を確認するこ とができる。 Also, to check whether the treated surface has a surface shape that does not easily cause stress concentration, for example, mold using a molding material such as a dental shape material, and examine the surface shape of the replicated mold. Inspect or review By measuring the surface displacement using a high-precision displacement measuring device such as a displacement meter, it is possible to determine whether the treated surface has a curvature or displacement on the surface where stress concentration is difficult. By the quality assurance inspection that confirms the surface structure or surface shape after ultrasonic impact treatment by the above-mentioned method, liquid metal embrittlement of metal structure products and steel structure products can be reduced. It can be confirmed that the liquid metal embrittlement resistance at the problematic point is improved.
なお、 この品質保証検査によ り、 所要の表面形状或いは表層組織 が得られていない場合は、 超音波衝撃処理を繰り返し、 所要の表層 組織或いはさ らに表面性状となるよ う にするこ とはいう までもない  If the required surface shape or surface texture is not obtained by the quality assurance inspection, the ultrasonic impact treatment is repeated to obtain the required surface texture or further surface texture. Needless to say
実施例 Example
以下に実施例によ り、 本発明を説明する。  Hereinafter, the present invention will be described with reference to examples.
表 1 に示す組成の鋼 （板厚 1 6 m m ) を母材 1 と し、 共金系の溶 接材料を用いてアーク溶接した溶接部 2試験体と し、 超音波衝撃処 理を付与して表層の金属組織を、 超微細結晶粒と し、 旧オーステナ ィ ト粒の長軸が表面に実質的に平行な結晶粒からなる層状組織と し た。 比較材と して溶接ままおよび小さい振幅の超音波衝撃処理を行 なった試験体を用いた。 図 4に概略を示す要領で、 幅 1 0 O m m、 長さ 2 0 0 m m、 板厚は元厚まま、 の試験片の中央に、 ビー ドオン プレー トで溶接部を形成し、 そのまま液体金属脆化試験片と した。 言う までもなく 、 溶接ままの試験片の溶接部には溶接残留応力が存 在している。 表 1 供試鋼材の組成 （ma s s % )
Figure imgf000021_0001
これらの試験片を、 4 5 0 °Cの溶融亜鉛めつき浴中に 3分間浸漬 した。 試験後の試験片は、 浸透試験および断面観察によって液体金 属脆化の発生の有無を確認した。 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. Thus, 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. As comparative materials, as-welded specimens and specimens subjected to ultrasonic impact treatment with small amplitude were used. As shown schematically in Fig. 4, the width is 100 Omm, the length is 200 mm, and 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%)
Figure imgf000021_0001
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.
表 2に超音波衝撃処理条件を示し、 表 3には表層の金属組織状況 および液体金属脆化割れ試験結果を示す。 表 2 超音波衝撃処理条件  Table 2 shows the conditions of the ultrasonic impact treatment, and Table 3 shows the metallographic condition of the surface layer and the results of the liquid metal embrittlement cracking test. Table 2 Ultrasonic shock treatment conditions
Figure imgf000021_0002
Figure imgf000021_0002
- ： 超音波衝撃処理を施していないこ とを示す 表 3 超音波衝撃処理試験片の組織状況と液体金属脆化割れ試験結果 -: Indicates that no ultrasonic impact treatment has been applied. Table 3 Structural conditions of ultrasonic impact treated test pieces and results of liquid metal embrittlement cracking test
Figure imgf000022_0001
Figure imgf000022_0001
一 ： 超音波衝撃処理を施していないこ と を示す。 表 3から明らかな通り、 表層の金属組織を、 超微細結晶粒と し、 旧オーステナイ ト粒の長軸が表面に実質的に平行な結晶粒からなる 層状組織と した本発明例 1 〜 8では液体金属脆化がまったく発生し ていないのに対して、 溶接ままあるいは処理が不充分な比較例 9 〜 1 2では液体金属脆化が発生しており、 本発明の効果が明らかであ る。 産業上の利用可能性  1: Indicates that no ultrasonic impact treatment has been performed. As is clear from Table 3, in Examples 1 to 8 of the present invention in which the metal structure of the surface layer was ultrafine crystal grains and the long axis of the former austenite grains was a layered structure composed of crystal grains substantially parallel to the surface. Although liquid metal embrittlement did not occur at all, in Comparative Examples 9 to 12 where welding was performed or processing was insufficient, liquid metal embrittlement occurred, and the effect of the present invention is clear. Industrial applicability
本発明の液体金属脆化抵抗性の優れた金属構造製品、 鉄構製品は 、 液体金属脆化の問題となる箇所に超音波衝撃処理が施され、 表層 の結晶粒が超微細細化されかつ、 その結晶粒または、 旧オーステナ イ ト粒の長軸が、 表面と実質的に平行となっており、 さ らに好適に は、 表面が応力集中が生じ難い表面形状で、 かつ残留圧縮応力が付 与されているため、 液体金属と接触しても微小亀裂が生じ難く また 、 微小亀裂が存在しても亀裂の厚さ方向への進展が抑制され、 破断 時間が大幅に伸び、 液体金属脆化に対して優れた抵抗性を有する。 また、 本発明の方法によれば、 超音波衝撃処理後の品質保証検査を 組み合わせるこ とによって、 処理を施した箇所の表層が所定の層状 組織となり 、 さ らには表面形状となっているこ とを確認できるため 、 金属構造製品、 鉄構製品の所要箇所の液体金属脆化抵抗性を確実 に向上させるこ とができる。 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. Has excellent resistance to Further, according to the method of the present invention, by combining the quality assurance inspection after the ultrasonic impact treatment, 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.

Claims

1 . 金属構造製品の液体金属脆化が問題となる箇所の表面から 5 0 m以上の厚さの表層の結晶粒を超微細化する と ともに、 該表層 の結晶粒の長軸が表面に実質的に平行となるよ う にしたこ とを特徴 とする液体金属脆化抵抗性の優れた金属構造製品。 1. Ultra-fine crystal grains with a thickness of 50 m or more from the surface of the metal structure product where liquid metal embrittlement is a problem, and the major axis of the crystal grains of the surface layer is substantially on the surface. A metal structure product with excellent liquid metal embrittlement resistance, characterized by being parallel to each other.
一一  Eleven
2 . 鉄構製品の液体金属脆化が問題となる箇所の表面から 5 0 μ m以上の厚さの表層の結晶粒を超微細化する と ともに、 該表層の旧 オーステナイ ト粒の長軸が表面に実質的に平行となるよ うにしたこ とを特徴とする液体金属脆化抵抗性の範優れた鉄構製品。  2. From the surface of the steel product where liquid metal embrittlement is a problem, the surface grains with a thickness of 50 μm or more are ultra-fine from the surface, and the long axis of the old austenite grains on the surface layer is reduced. A steel product excellent in liquid metal embrittlement resistance, characterized by being substantially parallel to the surface.
3 . 前記鉄構製品の液体金属脆化が問題 0. となる箇所が、 引張強度 4 9 O NZ m m 2級以上の鋼であるこ とを特徴とする請求項 2に記載 の液体金属脆化抵抗性の優れた鉄構製品。 3. The liquid metal embrittlement resistance according to claim 2, wherein the portion where the problem of liquid metal embrittlement of the steel structure product is 0 is steel having a tensile strength of 49 O NZ mm class 2 or higher. Steel products with excellent properties.
4 . 前記鉄構製品の液体金属脆化が問題となる箇所が、 溶接ボン ド部および または溶接熱影響部を含むこ とを特徴とする請求項 2 または 3に記載の液体金属脆化抵抗性の優れた鉄構製品。  4. The liquid metal embrittlement resistance according to claim 2 or 3, wherein the portion where the liquid metal embrittlement of the steel structure product becomes a problem includes a weld bond part and / or a weld heat affected zone. Excellent steel products.
5 . 前記表層の旧オーステナイ ト粒の長軸方向長さの短軸方向長 さに対する比が 5以上であるこ とを特徴とする請求項 2 〜 4のいず れか 1項に記載の液体金属脆化抵抗性の優れた鉄構製品。  5. The liquid metal according to any one of claims 2 to 4, wherein a ratio of a length in a long axis direction of the austenite grains of the surface layer to a length in a short axis direction is 5 or more. Steel products with excellent embrittlement resistance.
6 . 前記表層の旧オーステナイ ト粒の短軸方向長さが 5 m以下 であるこ とを特徴とする請求項 2 〜 5のいずれか 1項に記載の液体 金属脆化抵抗性の優れた鉄構製品。  6. The iron structure excellent in liquid metal embrittlement resistance according to any one of claims 2 to 5, wherein the minor axis length of the former austenite grains in the surface layer is 5 m or less. Product.
7 . 金属構造製品の液体金属脆化が問題となる箇所に超音波衝撃 処理を施し、 表面から 5 0 m以上の厚さの表層の結晶粒を超微細 化する と と もに、 該表層の結晶粒の長軸が表面に実質的に平行とな るよ う にするこ とを特徴とする液体金属脆化抵抗性の優れた金属構 造製品の製造方法。 7. Ultrasonic impact treatment is applied to the parts of the metal structure product where liquid metal embrittlement is a problem, so that the surface crystal grains with a thickness of 50 m or more from the surface are ultra-fine and the surface layer A method for producing a metal structure product having excellent resistance to liquid metal embrittlement, characterized in that the major axis of the crystal grain is substantially parallel to the surface.
8 . 鉄構製品の液体金属脆化が問題となる箇所に超音波衝撃処理 を施し、 表面から 5 0 μ πι以上の厚さの表層の結晶粒を超微細化す ると ともに、 該表層の旧オーステナイ ト粒の長軸が表面に実質的に 平行となるよ う にするこ とを特徴とする液体金属脆化抵抗性の優れ た鉄構製品の製造方法。 8. Ultrasonic impact treatment is applied to parts of steel products where liquid metal embrittlement is a problem, to make the surface crystal grains with a thickness of 50 μπι or more ultra-fine from the surface, A method for producing a steel product having excellent resistance to liquid metal embrittlement, characterized in that the major axis of the austenite grains is substantially parallel to the surface.
9 . 前記鉄構製品の液体金属脆化が問題となる箇所の金属が、 引 張強度 4 9 O NZ m m 2級以上の鋼であるこ とを特徴とする請求項 8 に記載の液体金属脆化抵抗性の優れた鉄構製品の製造方法。 9. The liquid metal embrittlement according to claim 8, wherein the metal in the portion of the steel structure product where liquid metal embrittlement is problematic is steel having a tensile strength of 49 O NZ mm class 2 or higher. Manufacturing method of steel products with excellent resistance.
10. 前記鉄構製品の液体金属脆化が問題となる箇所が、 溶接ボン ド部および/または溶接熱影響部を含むこ とを特徴とする請求項 8 または 9に記載の液体金属脆化抵抗性の優れた鉄構製品の製造方法  10. The liquid metal embrittlement resistance according to claim 8 or 9, wherein the portion where the liquid metal embrittlement of the steel structure product becomes a problem includes a weld bond portion and / or a heat affected zone. Of manufacturing steel products with excellent durability
11. 前記表層の旧オーステナイ ト粒の長軸方向長さの短軸方向長 さに対する比を 5以上とすることを特徴とする請求項 8 〜 1 0のい ずれか 1項に記載の液体金属脆化抵抗性の優れた鉄構製品の製造方 法。 11. The liquid metal according to any one of claims 8 to 10, wherein a ratio of a major axis length of the former austenite grains to a minor axis length of the surface layer is 5 or more. A method of manufacturing steel products with excellent embrittlement resistance.
12. 前記表層の旧オーステナイ ト粒の短軸方向長さを 5 μ ιη以下 とするこ とを特徴とする請求項 8 〜 1 1 のいずれか 1 項に記載の液 体金属脆化抵抗性の優れた鉄構製品の製造方法。  12. The liquid metal embrittlement resistance according to any one of claims 8 to 11, wherein the length of the austenite grains in the surface layer in the minor axis direction is 5 μιη or less. Manufacturing method of excellent steel products.
13. 前記超音波衝撃処理を施す前に、 前記鉄構製品の液体金属脆 化が問題となる箇所及びその近傍箇所に、 前処理を施すこ と を特徴 とする請求項 8 〜 1 2のいずれか 1項に記載の液体金属脆化抵抗性 の優れた鉄構製品の製造方法。  13. A pre-treatment is performed on a part where liquid metal embrittlement of the steel structure product becomes a problem and a part in the vicinity thereof before the ultrasonic impact treatment is performed. 4. The method for producing an iron product having excellent liquid metal embrittlement resistance according to item 1.
14. 前記前処理が、 前記鉄構製品の液体金属脆化が問題となる箇 所及びその近傍箇所の内部応力および/または表面応力を変化させ る処理であるこ とを特徴とする請求項 1 3に記載の液体金属脆化抵 抗性の優れた鉄構製品の製造方法。 14. The pretreatment is a treatment for changing internal stress and / or surface stress at a location where liquid metal embrittlement of the steel product becomes a problem and at a location in the vicinity thereof. 3. The method for producing a steel structure product having excellent liquid metal embrittlement resistance according to item 1.
15. 前記前処理が、 前記鉄構製品の液体金属脆化が問題となる箇 所の亀裂を検出する と共に、 検出された亀裂を除去する処理を含む こ とを特徴とする請求項 1 3又は 1 4に記載の液体金属脆化抵抗性 の優れた鉄構製品の製造方法。 15. The method according to claim 13, wherein the pretreatment includes a process of detecting a crack at a location where liquid metal embrittlement of the steel structure product is a problem, and removing the detected crack. 15. The method for producing a steel product having excellent liquid metal embrittlement resistance according to 14.
16. 前記超音波衝撃処理が、 さ らに、 前記鉄構製品の液体金属脆 化が問題となる箇所の表面形状を応力集中の生じ難い形状と し、 か つ表面近傍に圧縮残留応力を付与するこ とを特徴とする請求項 8〜 1 5のいずれか 1項に記載の液体金属脆化抵抗性の優れた鉄構製品 の製造方法。  16. 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 applies compressive residual stress near the surface. The method for producing a steel product excellent in liquid metal embrittlement resistance according to any one of claims 8 to 15, characterized by the above-mentioned.
17. 前記鉄構製品の液体金属脆化が問題となる箇所に、 超音波衝 撃処理を施し、 その後さ らに、 品質保証検査をするこ とを特徴とす る請求項 8〜 1 6のいずれか 1項に記載の液体金属脆化抵抗性の優 れた鉄構製品の製造方法。  17. The method according to claim 8, wherein an ultrasonic impact treatment is applied to a portion of the steel product where liquid metal embrittlement is a problem, and then a quality assurance inspection is performed. The method for producing a steel product having excellent liquid metal embrittlement resistance according to any one of the preceding claims.
18. 前記品質保証検査は、 超音波衝撃処理後の処理面が処理前に 比べて、 5 0 μ m以上の厚さが塑性変形しているこ と、 および処理 面が応力集中の生じ難い表面形状となっているこ とのいずれか一方 又は双方を確認するものであるこ と を特徴とする請求項 1 7 に記載 の液体金属脆化抵抗性の優れた鉄構製品の製造方法。  18. The quality assurance inspection stated above indicates that the treated surface after ultrasonic impact treatment is plastically deformed by a thickness of 50 μm or more compared to before treatment, and that the treated surface is less likely to generate stress concentration. The method for producing a steel product having excellent liquid metal embrittlement resistance according to claim 17, wherein one or both of the shapes are confirmed.
19. 前記品質保証検査の塑性変形しているこ との確認は、 超音波 衝撃処理後の処理面をスンプ法によ り観察し、 処理していない部分 に比べてその 5 0 %以上の金属結晶粒が超微細粒であるかどうかを 判断するこ とによるものであること を特徴とする請求項 1 8 に記載 の液体金属脆化抵抗性の優れた鉄構製品の製造方法。  19. In the above quality assurance inspection, plastic deformation was confirmed by observing the treated surface after ultrasonic impact treatment by the sump method and comparing the untreated portion with 50% or more of the metal. The method for producing a steel product excellent in liquid metal embrittlement resistance according to claim 18, characterized in that it is determined whether or not the crystal grains are ultrafine grains.
20. 前記品質保証検査の塑性変形の確認は、 超音波衝撃処理後の 処理面の結晶粒度を超音波粒径測定装置によ り測定し、 処理してい ない部分に比べてその 5 0 %以上の結晶粒が超微細粒であるかどう かを判断するこ とによるものであるこ とを特徴とする請求項 1 8に 記載の液体金属脆化抵抗性の優れた鉄構製品の製造方法。 20. In the quality assurance inspection, plastic deformation is confirmed by measuring the crystal grain size of the treated surface after ultrasonic impact treatment with an ultrasonic particle size measuring device, and comparing it with the untreated portion by 50% or more. Claim 18 characterized by determining whether or not the crystal grains are ultrafine grains. A method for producing a steel product having excellent resistance to liquid metal embrittlement as described above.
21. 前記品質保証検査の応力集中の生じ難い表面形状の確認は、 超音波衝撃処理後の処理面を型取材を用いて型取り し、 型取り した 面が応力集中の生じ難い表面形状であるかどうかを判断するこ とに よるものであるこ とを特徴とする請求項 1 8に記載の液体金属脆化 抵抗性の優れた鉄構製品の製造方法。  21. In the quality assurance inspection, the surface shape where stress concentration is unlikely to occur is confirmed by molding the treated surface after ultrasonic impact treatment using a molding material, and the molded surface is a surface shape where stress concentration is unlikely to occur. 19. The method for producing a steel product having excellent liquid metal embrittlement resistance according to claim 18, wherein the method is to judge whether or not the steel product has liquid metal embrittlement resistance.
22. 前記品質保証検査の応力集中の生じ難い表面形状の確認は、 超音波衝撃処理後の処理面を変位計を用いて測定し、 その変位が応 力集中の生じ難い面の変位の範囲内であるかどうかを判断するこ と によ り行なう ものであるこ とを特徴とする請求項 1 8に記載の液体 金属脆化抵抗性の優れた鉄構製品の製造方法。  22. In the quality assurance inspection, the surface shape where stress concentration is unlikely to occur can be confirmed by measuring the treated surface after ultrasonic impact treatment using a displacement meter, and the displacement is within the range of displacement of the surface where stress concentration is unlikely to occur. 19. The method for producing a steel product having excellent liquid metal embrittlement resistance according to claim 18, wherein the method is performed by judging whether or not the product is liquid metal embrittlement resistance.
PCT/JP2003/014163 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 WO2004042093A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2002-322850 2002-11-06
JP2002322850A JP4351433B2 (en) 2002-11-06 2002-11-06 Iron structure products having excellent resistance to liquid metal embrittlement and methods for producing the same

Publications (1)

Publication Number Publication Date
WO2004042093A1 true WO2004042093A1 (en) 2004-05-21

Family

ID=32310400

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2003/014163 WO2004042093A1 (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

Country Status (3)

Country Link
JP (1) JP4351433B2 (en)
AU (1) AU2003277584A1 (en)
WO (1) WO2004042093A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100595292C (en) * 2007-06-15 2010-03-24 中国科学院金属研究所 High speed processing method for realizing superfine crystal grain structure on metallic material surface
EP4074847A4 (en) * 2020-02-13 2023-06-21 JFE Steel Corporation High-strength steel sheet and method for producing same

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006030800A1 (en) * 2004-09-17 2006-03-23 Nippon Steel Corporation High strength machine parts and shaft excellent in fatigue characteristics, and method for improving fatigue characteristics thereof
JP2009291918A (en) * 2008-06-09 2009-12-17 Jfe Steel Corp Method of extending fatigue life of metal material subjected to repeated load history
JP6123461B2 (en) * 2013-04-30 2017-05-10 新日鐵住金株式会社 Ultrasonic shock treatment method
CN104531979A (en) * 2014-12-23 2015-04-22 清华大学深圳研究生院 Technology for refining metal surface crystal grains by electric pulse and ultrasonic coupling
CN106967867A (en) * 2017-03-10 2017-07-21 安徽省伟业净化设备有限公司 A kind of plasticity for being used to prepare the carbon steel plate of medicine equipment recovers processing technology

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6479320A (en) * 1987-09-19 1989-03-24 Nippon Steel Corp Improvement of material quality of metal for welding austenitic stainless steel
JPH081514A (en) * 1994-06-16 1996-01-09 Toshiba Corp Surface treatment method for structure in reactor
JPH09234585A (en) * 1996-02-29 1997-09-09 Mitsubishi Heavy Ind Ltd Welding equipment with welding residual stress reducing equipment
US6171415B1 (en) * 1998-09-03 2001-01-09 Uit, Llc Ultrasonic impact methods for treatment of welded structures
JP2003113418A (en) * 2001-10-04 2003-04-18 Nippon Steel Corp Method for improving fatigue life and long-life metal material

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6479320A (en) * 1987-09-19 1989-03-24 Nippon Steel Corp Improvement of material quality of metal for welding austenitic stainless steel
JPH081514A (en) * 1994-06-16 1996-01-09 Toshiba Corp Surface treatment method for structure in reactor
JPH09234585A (en) * 1996-02-29 1997-09-09 Mitsubishi Heavy Ind Ltd Welding equipment with welding residual stress reducing equipment
US6171415B1 (en) * 1998-09-03 2001-01-09 Uit, Llc Ultrasonic impact methods for treatment of welded structures
JP2003113418A (en) * 2001-10-04 2003-04-18 Nippon Steel Corp Method for improving fatigue life and long-life metal material

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100595292C (en) * 2007-06-15 2010-03-24 中国科学院金属研究所 High speed processing method for realizing superfine crystal grain structure on metallic material surface
EP4074847A4 (en) * 2020-02-13 2023-06-21 JFE Steel Corporation High-strength steel sheet and method for producing same

Also Published As

Publication number Publication date
JP4351433B2 (en) 2009-10-28
AU2003277584A1 (en) 2004-06-07
JP2004156100A (en) 2004-06-03

Similar Documents

Publication Publication Date Title
Guo et al. Microstructure and mechanical properties of laser welded S960 high strength steel
JP4719297B2 (en) Welded joint with excellent fatigue resistance and method for producing the same
JP2003113418A (en) Method for improving fatigue life and long-life metal material
Shi et al. Effect of laser shock peening on microstructure and fatigue properties of thin-wall welded Ti-6A1-4V alloy
Tomków et al. Temper bead welding of S460N steel in wet welding conditions
US20040244882A1 (en) Method for processing welded metal work joints by high-frequency hummering
JP4441166B2 (en) Method for improving environmentally-assisted cracking resistance of steel structure products
Fowler et al. Fatigue and bending behaviour of friction stir welded DH36 steel
Ramakrishnan et al. Studies on fracture toughness of cold wire addition in narrow groove submerged arc welding process
JP5052918B2 (en) Welded joint, welded structure excellent in crack initiation propagation characteristics, and method for improving crack initiation propagation characteristics
WO2004042093A1 (en) Iron structure product and metal structure product excelling in resistance to liquid metal embrittlement and process for producing the same
Okane et al. Fatigue properties of butt welded aluminum alloy and carbon steel joints by friction stirring
JP4837428B2 (en) Ultrasonic impact treatment method for weld toe
JP3793501B2 (en) Rail reinforcement and repair method
Chennaiah et al. Influence of heat input and PWHT on the microstructure and mechanical properties in dissimilar (IS2062-EN8) welded joints
JP3914856B2 (en) Welding method for galvanized steel sheet to prevent plating cracking during welding
JP4767885B2 (en) Welded joint, welded structure excellent in brittle crack propagation stopping characteristics, and method for improving brittle crack propagation stopping characteristics
Türkan et al. The influence of corrosion on the mechanical behavior of AISI 316L stainless steel welds
Kazasidis et al. Comparative study of toughness between the AH 40 fatigue crack arrester steel and its weld metal in the case of robotic metal-cored arc welding
Wang et al. Achieving a high-strength dissimilar joint of T91 heat-resistant steel to 316L stainless steel via friction stir welding
Knysh et al. Influence of corrosion damage on cyclic fatigue life of tee welded joints treated by high-frequency mechanical peening
Baskutis et al. Experimental study of welded joints of aluminium alloy AW6082
Pandey et al. Experimental analysis on microstructure, mechanical properties, and corrosion behavior of TIG welded AISI 444 ferritic stainless steels
Pandey et al. Experimental analysis on microstructure, mechanical properties, and corrosion behavior of TIG welded AISI 444 ferritic stainless steels
Goo Effect of Post-Weld Heat Treatment on the Fatigue Behavior of Medium-Strength Carbon Steel Weldments. Metals 2021, 11, 1700

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BW BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE EG ES FI GB GD GE GH GM HR HU ID IL IN IS KE KG KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NI NO NZ OM PG PH PL PT RO RU SC SD SE SG SK SL SY TJ TM TN TR TT TZ UA UG US UZ VC VN YU ZA ZM ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): BW GH GM KE LS MW MZ SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LU MC NL PT RO SE SI SK TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct application non-entry in european phase