WO2021182525A1 - Clad steel sheet, method for manufacturing same, and welded structure - Google Patents

Clad steel sheet, method for manufacturing same, and welded structure Download PDF

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WO2021182525A1
WO2021182525A1 PCT/JP2021/009610 JP2021009610W WO2021182525A1 WO 2021182525 A1 WO2021182525 A1 WO 2021182525A1 JP 2021009610 W JP2021009610 W JP 2021009610W WO 2021182525 A1 WO2021182525 A1 WO 2021182525A1
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steel sheet
clad
clad steel
base material
less
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PCT/JP2021/009610
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French (fr)
Japanese (ja)
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真知 川
雄介 及川
柘植　信二
潤平 安藤
剛志 橋本
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日鉄ステンレス株式会社
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Priority to CN202180018681.2A priority Critical patent/CN115210399B/en
Priority to JP2022507251A priority patent/JP7357761B2/en
Publication of WO2021182525A1 publication Critical patent/WO2021182525A1/en

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present invention relates to a clad steel sheet having excellent hydrogen embrittlement resistance on the joint surface, a method for manufacturing the clad steel sheet, and a welded structure manufactured by a manufacturing process including welding or gouging using the clad steel sheet using a gas containing hydrogen.
  • Stainless steel and Ni-based alloys are suitable materials in severe corrosive environments because they have excellent corrosion resistance.
  • Examples of the above-mentioned corrosive environment include an oil well environment, a high chloride environment exposed to seawater and brackish water, plant equipment exposed to various acid solutions, a chemical tanker, and the like.
  • stainless steel and Ni-based alloys are used in seawater desalination plants, flue gas desalination equipment, chemical storage tanks, structural members such as oil pipes, pumps and valves, heat exchangers, etc. There is.
  • stainless steel and Ni-based alloys contain a large amount of alloying elements such as Cr, Ni, and Mo to ensure corrosion resistance, and compared to carbon steel and low alloy steel, not only material costs but also processing and welding costs. Is also expensive. It is also possible that the price will fluctuate significantly due to the soaring price of alloying elements. Therefore, its use may be restricted mainly in terms of cost.
  • a clad steel sheet is a material obtained by laminating two or more different types of metals. Further, a steel sheet that is not bonded is hereinafter referred to as a "solid steel sheet". Compared with solid steel sheets made only of high alloy steel, clad steel sheets can reduce the amount of high alloy steel used, reduce material costs, and reduce welding of dissimilar materials, so molten materials during welding can be reduced. Costs can also be reduced.
  • base material one metal is described as “base material” and the other metal (material) bonded to the base material is described as “laminated material”.
  • laminated material By laminating a material (laminated material) having excellent properties to the base material, both the excellent properties of the laminated material and the base material can be obtained.
  • a high alloy steel having the characteristics required in the usage environment is used for the laminated material, and a carbon steel or a low alloy steel having the toughness and strength required in the usage environment is used as the base material. ..
  • a carbon steel or a low alloy steel having the toughness and strength required in the usage environment is used as the base material. ..
  • the cost can be reduced as described above, but also the same characteristics as the solid steel sheet and the same strength and toughness as the carbon steel and the low alloy steel can be secured. Therefore, both economy and functionality can be achieved at the same time.
  • a diffusion layer of elements is formed at the interface of the laminated lumber (hereinafter simply referred to as "interface").
  • the concentration of each element gradually changes in the diffusion layer, but depending on the element concentration, the temperature at which martensitic transformation starts is high, and the critical cooling rate at which martensitic transformation occurs is slow. Transformation may occur.
  • Patent Document 1 discloses a technique for suppressing sensitization near the interface by controlling the thickness of the carbon diffusion layer at the interface of a duplex stainless clad steel sheet. However, there is no mention of the martensite phase at the interface.
  • Patent Document 2 discloses a technique for preventing delayed fracture of martensite at the interface by specifying the temperature and time of tempering after rolling for an austenitic stainless clad steel sheet. However, this technique is to prevent delayed fracture during manufacturing, and there is no disclosure of preventive techniques for welded structures.
  • Non-Patent Document 1 evaluates the hydrogen embrittlement susceptibility of martensite at the interface for the cladding of SUS316L and Inconel 625.
  • Patent Document 2 discloses a technique for preventing delayed fracture of martensite at an interface.
  • Patent Document 1 describes a method for evaluating the hydrogen embrittlement susceptibility of martensite at an interface.
  • the width of the diffusion layer differs depending on the heating temperature and the reduction ratio, but there is no description or suggestion about the relationship between the width of the diffusion layer and the hydrogen embrittlement sensitivity.
  • the present inventor controls the hardness and width of martensite at the interface, the hydrogen concentration in steel, and the stress applied to martensite in order to suppress the interfacial peeling of the clad due to hydrogen embrittlement during welding. was found to be a problem to be solved.
  • an object of the present invention is to provide a clad steel sheet having good hydrogen embrittlement resistance of the joint surface and excellent hydrogen embrittlement resistance, a method for producing the same, and a welded structure.
  • a clad steel sheet including a base material and a laminated material joined to the base material.
  • the base material is made of carbon steel or low alloy steel.
  • the laminated material is made of a corrosion-resistant alloy and is made of a corrosion-resistant alloy.
  • the chemical composition of the base material is C: 0.020 to 0.200%, Si: 1.00% or less, Mn: 0.10 to 3.00% in mass%. , P: 0.050% or less, S: 0.050%, Ceq is 0.20 to 0.40, and the balance has a component composition of Fe and impurities, according to [1].
  • Ceq is defined by the following equation (1).
  • Ceq C + Mn / 6 + (Cu + Ni) / 15+ (Cr + Mo + V) / 5 ...
  • C, Mn, Cu, Ni, Cr, Mo and V are elements of each element in the composition of the base steel sheet. The content (% by mass).
  • the component composition of the base material is, instead of a part of the Fe, in mass%, Ni: 0.01 to 1.00%, Cr: 0.01 to 1.00%, Mo: 0. 0.01 to 0.50%, Cu: 0.01 to 1.00%, Co: 0.01 to 0.50%, Se + Te: 0.01 to 0.10%, V: 0.001 to 0.100 %, Ti: 0.001 to 0.200%, Nb: 0.001 to 0.200%, Al: 0.005 to 0.300%, Ca: 0.0003 to 0.0050%, B: 0.
  • the base material and the laminated material are laminated so that the crimping surface becomes vacuum, and the four circumferences of the crimping surface are sealed by welding and clad.
  • T maximum heating temperature
  • T-20 ° C. in the heating furnace From the time when the maximum heating temperature T (° C.) in the heating furnace and the maximum heating temperature T-20 ° C. in the heating furnace are reached for the clad rolled material obtained by assembling one or more of the above clad materials as the material.
  • the time t (minutes) until extraction into the heating furnace, and the reduction ratio r calculated by the material thickness / product thickness, d calculated by the formula (2) is 1 or more and 9 or less. Heating and hot rolling are performed, and after rolling.
  • the average cooling rate in the TA3 (° C.) to 650 ° C. section calculated by the formula (3) is 2 ° C./s or more and the nanohardness at the interface between the base material and the laminated material is 7 GPa or more.
  • the present inventors conducted the following studies on the above problems. Specifically, in clad steel sheets made of various stainless steels and Ni-based alloys, the element diffusion and metallographic structure at the interface were investigated by changing the heating temperature, heating time, rolling ratio and cooling rate after rolling. , The relationship with the hydrogen embrittlement resistance of the interface was evaluated. As a result, the following findings (a) to (c) were obtained.
  • the carbon steel or low alloy steel as the base material is in contact with the stainless steel or Ni-based alloy as the laminated material.
  • the profile of the alloying elements at the interface could be organized by the temperature / time of material heating and the reduction ratio. Further, it was confirmed that the diffusion width of Cr and the width of the martensite phase correspond to each other when a laminated material containing 10% or more by mass% of Cr was used. Since Cr is the element that diffuses the fastest among the main alloy elements and further enhances hardenability, martensitic transformation occurs in the region where only the content of Cr is high and the content of austenite stabilizing elements such as Ni is low. Because.
  • the clad steel sheet according to the present invention includes a base material and a laminated material joined to the base material.
  • the base material consists of carbon steel or low alloy steel, which will be described later.
  • the laminated material is made of a corrosion-resistant alloy, and examples of the corrosion-resistant alloy include stainless steel and Ni-based alloys containing 10% or more of Cr. Further, the width of the region where the nanohardness is 7 GPa or more at the interface between the base material and the laminated material is 5 ⁇ m or less.
  • Nano-hardness of the clad interface The width of the region where the nano-hardness is 7 GPa or more at the clad interface shall be 5 ⁇ m or less. When the width of the region with nano-hardness of 7 GPa or more in the plate thickness direction exceeds 5 ⁇ m, the region of martensite, which is hard and highly sensitive to hydrogen embrittlement, is large, so the interface peels off when welding containing hydrogen in the welding gas is performed. In some cases. It is preferably 3 ⁇ m or less, and more preferably 1 ⁇ m or less. The smaller the region where the nanohardness is 7 GPa or more, the lower the hydrogen embrittlement sensitivity, so no lower limit is set.
  • the nano-hardness means the hardness of a material evaluated in accordance with an instrumentation indentation hardness test (also referred to as a nano-indentation test) specified in ISO 14577.
  • the base material consists of carbon steel or low alloy steel.
  • the preferable chemical composition of the base material is C: 0.020 to 0.200%, Si: 1.00% or less, Mn: 0.10 to 3.00%, P: 0.050% or less in mass%.
  • Ceq is defined by the following equation (1).
  • Ceq C + Mn / 6 + (Cu + Ni) / 15+ (Cr + Mo + V) / 5 ... Equation (1)
  • C, Mn, Cu, Ni, Cr, Mo and V are the contents (mass%) of each element in the component composition of the base material.
  • C is an element that improves the strength of steel, and when it is contained in an amount of 0.020% or more, sufficient strength is exhibited. However, if it exceeds 0.200%, the weldability and toughness are deteriorated. Therefore, the amount of C is set to 0.020 to 0.200%. It is preferably 0.040% or more, and more preferably 0.050% or more. On the other hand, the upper limit is preferably 0.100% or less, more preferably 0.080% or less. A more preferable range is 0.040% to 0.100%, and a more preferable range is 0.050% to 0.080%.
  • Si is an element that is effective in deoxidizing and improves the strength of steel. However, if it exceeds 1.00%, the surface properties and toughness of the steel deteriorate. Therefore, the amount of Si is set to 1.00% or less. It is preferably 0.50% or less. Si may not be contained. The preferable lower limit of the content of Si is 0.01%.
  • Mn is an element that increases the strength of steel, and its effect is exhibited when it is contained in an amount of 0.10% or more. However, if it exceeds 3.00%, the weldability is impaired and the alloy cost also increases. Therefore, the amount of Mn is set to 0.10 to 3.00%.
  • the lower limit is 0.50% and the upper limit is 2.00%. More preferably, the lower limit is 0.90% and the upper limit is 1.60%.
  • the amount of P is set to 0.050% or less. It is preferably 0.020% or less.
  • the amount of S is set to 0.050% or less. It is preferably 0.010% or less.
  • Ni 0.01 to 1.00%, Cr: 0.01 to 1.00%, Mo: 0.01 to 0 in mass% instead of a part of the Fe. .50%
  • Cu 0.01 to 1.00%
  • Co 0.01 to 0.50%
  • Se + Te 0.01 to 0.10%
  • V 0.001 to 0.100%
  • Ti 0.001 to 0.200%
  • Nb 0.001 to 0.200%
  • Al 0.005 to 0.300%
  • Ca 0.0003 to 0.0050%
  • B 0.0003 to 0. It can contain one or more selected from 0030% and REM: 0.0003-0.0100%.
  • Ni is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 1.00%, it causes deterioration of weldability and toughness. Therefore, when Ni is contained, the amount of Ni is set to 1.00% or less. It is preferably 0.50% or less, and more preferably 0.30% or less. The preferred lower limit of Ni content is 0.01%.
  • Cr is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 1.00%, it causes deterioration of weldability and toughness. Therefore, when Cr is contained, the amount of Cr is set to 1.00% or less. It is preferably 0.50% or less, and more preferably 0.30% or less. The preferred lower limit of Cr content is 0.01%.
  • Mo is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 0.50%, it causes deterioration of weldability and toughness. Therefore, when Mo is contained, the amount of Mo is 0.50% or less. It is preferably 0.30% or less, and more preferably 0.1% or less. The preferred lower limit of Mo content is 0.01%.
  • Cu is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 1.00%, it causes deterioration of weldability and toughness. Therefore, when Cu is contained, the amount of Cu is set to 1.00% or less. It is preferably 0.50% or less, and more preferably 0.30% or less. The preferred lower limit of Cu content is 0.01%.
  • Co is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 0.50%, the workability in hot water is impaired and the productivity is lowered. Therefore, when Co is contained, the amount of Co is set to 0.50% or less. It is preferably 0.30% or less, and more preferably 0.1% or less. The preferred lower limit of Co content is 0.01%.
  • Se and Te suppress the formation of oxides by diffusing easily oxidizable elements such as Mn, Si, and Al in the steel sheet onto the surface of the steel sheet, and improve the surface properties and plating properties of the steel sheet.
  • the total amount of Se and Te is 0.10% or less. More preferably, it is 0.05% or less.
  • the preferred Se + Te content lower limit is 0.01%.
  • Al is an element that is effective in deoxidizing steel. However, if it exceeds 0.300%, the toughness of the welded portion deteriorates. Therefore, when Al is contained, the amount of Al is set to 0.300% or less. It is preferably 0.100% or less. The preferable lower limit of Al content is 0.005%.
  • V increases the strength of steel by forming a carbonitride. However, if it exceeds 0.100%, it causes deterioration of weldability and toughness. Therefore, when V is contained, the amount of V is set to 0.100% or less. It is preferably 0.050% or less. The preferred lower limit of V content is 0.001%.
  • Ti is an element that refines crystal grains and increases strength, and its effect is exhibited by adding 0.001% or more. However, if it exceeds 0.200%, the weldability is impaired and the alloy cost also increases. Therefore, the amount of Ti is set to 0.001 to 0.200%.
  • the lower limit is 0.005% and the upper limit is 0.100%. More preferably, the lower limit is 0.010% and the upper limit is 0.050%.
  • Nb is an element that raises the recrystallization temperature, and its effect is exhibited by adding 0.001% or more. However, if it exceeds 0.200%, the weldability is impaired and the alloy cost also increases. Therefore, the amount of Nb is set to 0.001 to 0.200%.
  • the lower limit is 0.005% and the upper limit is 0.100%. More preferably, the lower limit is 0.010% and the upper limit is 0.050%.
  • Ca refines the structure of the weld heat affected zone and improves toughness. However, if it exceeds 0.0050%, coarse inclusions are formed and the toughness is deteriorated. Therefore, when Ca is contained, the amount of Ca is set to 0.0050% or less. It is preferably 0.0030% or less. The preferable lower limit of Ca content is 0.0003%.
  • B is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 0.0030%, it causes deterioration of weldability and toughness. Therefore, when B is contained, the amount of B is set to 0.0030% or less. It is preferably 0.0020% or less. The preferable lower limit of the B content is 0.0003%.
  • REM refines the structure of the weld heat affected zone and improves toughness. However, if it exceeds 0.0100%, coarse inclusions are formed and the toughness is deteriorated. Therefore, when REM is contained, the amount of REM is 0.0100% or less. It is preferably 0.005% or less. The preferred lower limit of REM content is 0.0003%.
  • REM is a general term for 17 elements in which Y and Sc are combined with 15 elements of lanthanoids.
  • One or more of these 17 elements can be contained in the steel material, and the REM content means the total content of these elements.
  • the balance is Fe and impurities.
  • impurity is a component mixed by various factors of raw materials such as ore and scrap, and various factors in the manufacturing process when steel materials are industrially manufactured, and is allowed as long as it does not adversely affect the present invention. Means something.
  • the corrosion-resistant alloy is a stainless steel or nickel-based alloy containing 10% or more of Cr.
  • the laminated material of the present invention is made of a corrosion-resistant alloy. As described above, the corrosion-resistant alloy contains a large amount of Cr, and the diffusion of Cr increases the hardenability of the clad interface and facilitates the transformation to martensite, and the carbon on the base metal side diffuses to the mating material side to diffuse the base metal. A hard martensite phase is formed at the side interface, which causes a decrease in hydrogen embrittlement resistance of the joint surface. That is, the effect of the present invention is exhibited when a corrosion-resistant alloy containing a large amount of Cr is used. When the Cr content of the laminated material is 10% or more, the effect of applying the present invention is remarkable. If the Cr content is 15% or more, the effect can be more remarkable.
  • the present invention is a technique for a clad steel sheet having excellent hydrogen embrittlement resistance of a joint surface and a method for manufacturing the same by controlling the joint interface structure.
  • the steel type of the laminated material is not particularly specified, but stainless steel is an example of the laminated material.
  • a nickel-based alloy can be exemplified.
  • Stainless steels include austenite-based stainless steels, ferrite-based stainless steels, and two-phase stainless steels, and nickel-based alloys have various alloy components under trade names such as Inconel, Incoloy, and Hastelloy.
  • the maximum heating temperature T (° C.) in the heating furnace the time t (minutes) from the time when the heating temperature in the heating furnace reaches the maximum heating temperature T-20 ° C. to the extraction into the heating furnace, T A3 by the reduction ratio r which is calculated by the material thickness / product thickness d is calculated by the equation (2) performs a heating and hot rolling is 1 to 9, which is calculated by the equation (3) after rolling ( A clad steel plate is manufactured by cooling at an average cooling rate of 2 ° C./s or more in the section from (° C.) to 650 ° C.
  • the clad material is produced by the method described below. Specifically, after melting carbon steel and low alloy steel as a base material and corrosion resistant alloy as a binder by a known method such as a converter, an electric furnace, a vacuum melting furnace, etc., a continuous casting method or ingot formation- Create a slab by the slab method. The obtained slab is hot-rolled under commonly used conditions to obtain a laminated lumber and a base material which are hot-rolled plates. The obtained hot-rolled plate may be annealed, pickled, polished or the like, if necessary.
  • the above-mentioned laminated material and base material are laminated so that the crimping surface becomes a vacuum, and the four circumferences of the crimping surface are sealed by welding to assemble the clad material.
  • An insert material such as Ni foil may be inserted between the laminated material and the base material in order to improve the adhesion and the interfacial corrosion resistance.
  • the method of evacuating the crimping surface is not particularly specified, but a method of electron beam welding in vacuum or a vacuum pump after making holes for vacuuming in advance and welding 4 laps by arc welding or laser welding in the atmosphere. An example is a method of evacuating with.
  • the degree of vacuum (absolute pressure) is 0.1 Torr or less, a good bonding interface with less oxides at the interface can be obtained, more preferably 0.05 Torr or less, and the higher the degree of vacuum (the lower the absolute pressure). ) Since the bonding interface tends to be good, no lower limit is set.
  • the obtained clad material may be used as it is for hot rolling as a clad rolling material, or a material assembled by applying a release agent between two clad materials so as to be overlapped is used for hot rolling as a clad rolling material. You may. When two are stacked, it is desirable that the base materials and the laminated materials have the same thickness in order to reduce the plate warpage during cooling. Of course, it is not necessary to limit the assembly method described above.
  • the obtained clad-rolled material is subjected to the maximum heating temperature T (° C.) in the heating furnace and the maximum heating temperature T-20 ° C. in the heating furnace from the time when the heating furnace extraction occurs.
  • Heating and hot rolling are performed in which d calculated by the formula (3) is 1 or more and 9 or less based on the reduction ratio r calculated by the time t (minutes) and the material thickness / product thickness.
  • d exceeds 9, the element diffusion distance becomes long at the product interface, so that the width of the region where martensitic transformation can occur becomes large, and the hydrogen embrittlement resistance of the interface decreases.
  • d is 7 or less.
  • the maximum heating temperature T in the heating furnace is preferably 1050 to 1250 ° C. If the maximum heating temperature T is less than 1050 ° C., the hot workability deteriorates and the bonding strength also deteriorates. Therefore, the maximum heating temperature T is preferably 1050 ° C.
  • the maximum heating temperature T is more than 1250 ° C., the steel pieces are easily deformed in the heating furnace and flaws are likely to occur during hot rolling, and the diffusion at the interface becomes faster. Therefore, the maximum heating temperature T is preferably 1250 ° C. or lower, and more preferably 1220 ° C. or lower. The shorter the time t (minutes) from the time when the heating temperature in the heating furnace reaches the maximum heating temperature T-20 ° C. to the extraction in the heating furnace, the shorter the element diffusion distance at the interface, so no lower limit is set. Heating for 30 minutes or more is desirable to make the temperature uniform up to the center of the plate thickness.
  • the reduction ratio r calculated by the material thickness / product thickness is preferably 3 or more and 15 or less. If the reduction ratio r is less than 3, the interfacial bonding by rolling may be insufficient and the shear strength of the interface may be low. More preferably, it is 5 or more. If the rolling ratio is more than 15, the rolling time becomes long and the rolling cost increases. More preferably, it is 10 or less.
  • the size of the martensite phase region at the interface is mainly affected by the diffusion of Cr.
  • Cr diffusion occurs at a temperature of several hundred degrees Celsius or higher, the diffusion distance increases exponentially as the temperature rises, so that the actual diffusion is maintained near the maximum temperature during the material heating time. Occurs in.
  • the diffusion is negligibly small because the plate temperature drops rapidly during rolling and cooling. Therefore, it can be considered that the Cr diffusion distance of the product is such that the diffusion distance generated during heating is reduced by the ratio of the reduction ratio.
  • the authors measured the size of the martensite phase region by TEM observation of the thin film at the interface for clad products with various heating temperatures, times, and reduction ratios, and measured the maximum temperature T (° C.) in the heating furnace and the heating furnace.
  • the time t minutes (minutes) from the time when the heating temperature in the room reaches the maximum heating temperature T-20 ° C. to the extraction into the heating furnace and the value d calculated by the equation (2) from the reduction ratio r are the sizes of the martensite phase region. We have confirmed that it corresponds accurately with.
  • the average cooling rate in the TA3 (° C) to 650 ° C section calculated from equation (3) after rolling is 2 ° C / s or more.
  • the average cooling rate in the TA3 (° C) to 650 ° C section calculated from equation (3) after rolling is 2 ° C / s or more.
  • the width of the area is increased. It is preferably 4 ° C./s or higher.
  • T A3 (°C) 937.2-436.5C + 56Si-19.7Mn-26.6Ni + 136.3Ti-19.1Nb + 198.4Al ⁇ formula (3)
  • C, Si, Mn, Ni, Ti, Nb and Al are the contents (mass%) of each element in the component composition of the base steel sheet.
  • the present invention it is possible to obtain a clad steel sheet having excellent hydrogen embrittlement resistance on the joint surface.
  • the clad steel plate according to the present invention and the welded structure using the clad steel plate of the present invention do not require peeling measures at the time of welding or additional heat treatment.
  • the present invention frees us from controlling the hydrogen concentration in steel or the stress applied to martensite, if the hardness and width of the martensite at the interface are defined in the present invention.
  • the clad steel sheet has no limitation on the intended use, and can be applied to a structural member in which a solid steel sheet has been conventionally used. Therefore, the clad steel sheet greatly contributes to cost reduction.
  • the welded structure made of the clad steel sheet of the present invention can be a welded structure manufactured by a manufacturing process including welding using a gas containing hydrogen or gouging.
  • the clad steel sheet of the present invention has excellent hydrogen embrittlement resistance, hydrogen embrittlement does not occur even when it is used for welding using hydrogen as a welding gas.
  • the combined material with the chemical composition shown in Table 1 and the base material with the chemical composition shown in Table 2 are melted into steel pieces, and after undergoing the steps of hot rolling, annealing, and pickling, the combined material has a thickness of 30 mm, and the base material has a thickness of 30 mm.
  • a steel plate having a thickness of 130 mm was manufactured.
  • the base material and the combined material were laminated so that the crimping surface became a vacuum, and four circumferences of the crimping surface were sealed by welding to prepare a clad material.
  • the two clad materials were laminated by applying a release agent between the laminated materials so as to form a base material-laminated material-stripping agent-laminated material-base material, and assembled as a clad rolled material.
  • the obtained clad-rolled material was hot-rolled under the hot-rolling conditions shown in Table 3 and then peeled off at the release agent portion to obtain a clad steel sheet having a thickness of 53 mm (compression ratio 3) to 12 mm (compression ratio 13).
  • T indicates the maximum heating temperature (° C.) in the heating furnace before rolling
  • t is the time from the time when the heating temperature in the heating furnace reaches the maximum heating temperature T-20 ° C. to the extraction into the heating furnace.
  • (Minute) is shown.
  • r indicates the reduction ratio calculated by the material thickness / product thickness.
  • d represents a value calculated by the equation (2) from the above T
  • t represents the maximum heating temperature
  • CR indicates the average cooling rate (° C./s) from TA3 (° C.) to 650 ° C.
  • L indicates the width ( ⁇ m) of the region where the nanohardness is 7 GPa or more in the vicinity of the interface.
  • Hydrogen resistance is the result of the hydrogen embrittlement resistance evaluation test. A indicates good hydrogen embrittlement resistance, and X indicates poor hydrogen embrittlement resistance.
  • the measurement of nano-hardness is based on the instrumentation indentation hardness test specified in ISO 14577, and the nano-hardness is measured at a pitch of 0.5 ⁇ m in the range of 10 ⁇ m from the interface on the mating material side and the base material side in the plate thickness direction. bottom.
  • the conditions for nano-hardness measurement may be appropriately selected. For example, measurements with a load of 1000 ⁇ N, a push-in specified load of 5 sec, a hold of 0 sec, and a return of 5 sec are performed three times at each position, and the average value is taken as the nano-hardness. Can be exemplified. The range of the region where the nanohardness was 7 GPa or more was read and designated as L.
  • the cross section of the test piece was observed to confirm that the weld metal was separated from the interface by 2 mm or more.
  • the prepared test piece was charged with a cathode having a current density of 10 (A / m 2 ) ⁇ 72 (hr) in a 3 mass% NaCl + 3 g / L ⁇ NH 4 SCN aqueous solution before tensioning, and then 3% NaCl + 3 g / L ⁇ NH. 4 While charging the cathode at 10 (A / m 2 ) in the SCN aqueous solution, the strain was pulled to break at the strain rate of the parallel portion: 1 ⁇ 10 -3 (1 / s).
  • Sample numbers 1 to 41 are examples of the present invention, satisfying preferable production conditions, having a region length L of 5 ⁇ m or less having a nanohardness of 7 GPa or more, and having good hydrogen embrittlement resistance of the joint surface.
  • Sample numbers 42 to 47 are comparative examples, do not satisfy preferable production conditions, have a length L of a region having a nanohardness of 7 GPa or more of more than 5 ⁇ m, and have poor hydrogen embrittlement resistance of the joint surface. ..
  • the clad steel sheet of the present invention can be used in a high chloride environment such as that exposed to seawater, or in plant equipment exposed to an acid solution such as phosphoric acid or sulfuric acid as a corrosive environment. It may be applied to corrosive environments. Specific examples include seawater desalination plants, flue gas desulfurization equipment, chemical storage tanks, structural members such as oil country tubular goods, pumps and valves, and heat exchangers.

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Abstract

Provided is a stainless clad steel sheet having excellent hydrogen embrittlement resistance on a joint surface, wherein a stainless steel or Ni-based alloy is used as a cladding material, a carbon steel or low-alloy steel is used as a base material, and the width of a region having a nanohardness of at least 7 GPa is 5 μm or less at the interface between the base material and the cladding material. Since the joint surface of the clad steel sheet has a small area of martensite which is highly sensitive to hydrogen embrittlement, interfacial disbonding can be prevented even when welding is performed using a hydrogen-containing welding gas.

Description

クラッド鋼板およびその製造方法ならびに溶接構造物Clad steel sheet and its manufacturing method and welded structure
　本発明は、接合面の耐水素脆化性に優れたクラッド鋼板とその製造方法および、前記クラッド鋼板を用い水素を含むガスを使用する溶接またはガウジングを含む製造工程で製造した溶接構造物に関する。 The present invention relates to a clad steel sheet having excellent hydrogen embrittlement resistance on the joint surface, a method for manufacturing the clad steel sheet, and a welded structure manufactured by a manufacturing process including welding or gouging using the clad steel sheet using a gas containing hydrogen.
　ステンレス鋼やＮｉ基合金は耐食性に優れることから厳しい腐食環境において適した素材である。上述の腐食環境として、油井環境、海水や汽水に曝されるような高塩化物環境、各種酸溶液に曝されるプラント設備やケミカルタンカー等が例示される。そしてこのような腐食環境において、ステンレス鋼やＮｉ基合金は海水淡水化プラント、排煙脱硫装置、化学薬品の保存タンク、油井管等の構造部材ポンプ・バルブ類、熱交換器などに使用されている。 Stainless steel and Ni-based alloys are suitable materials in severe corrosive environments because they have excellent corrosion resistance. Examples of the above-mentioned corrosive environment include an oil well environment, a high chloride environment exposed to seawater and brackish water, plant equipment exposed to various acid solutions, a chemical tanker, and the like. In such a corrosive environment, stainless steel and Ni-based alloys are used in seawater desalination plants, flue gas desalination equipment, chemical storage tanks, structural members such as oil pipes, pumps and valves, heat exchangers, etc. There is.
　一方でステンレス鋼やＮｉ基合金は耐食性を確保するためＣｒ、Ｎｉ、Ｍｏなどの合金元素が多く含有されており、炭素鋼や低合金鋼と比較すると材料コストはもちろん、加工や溶接などのコストも高い。また合金元素の高騰などによって価格が大きく変動することも考えられる。そのため、主にコストの面からその使用が制限される場合がある。 On the other hand, stainless steel and Ni-based alloys contain a large amount of alloying elements such as Cr, Ni, and Mo to ensure corrosion resistance, and compared to carbon steel and low alloy steel, not only material costs but also processing and welding costs. Is also expensive. It is also possible that the price will fluctuate significantly due to the soaring price of alloying elements. Therefore, its use may be restricted mainly in terms of cost.
　上述のようにコストの面を考慮した場合、加工や溶接などの観点からはクラッド鋼板を材料として使用することが有効である。クラッド鋼板とは、異なる二種類以上の金属を貼り合せた材料をいう。また、貼り合わせを行わない鋼板を以下、「ソリッド鋼板」と称する。クラッド鋼板は、高合金鋼のみからなるソリッド鋼板と比較し、高合金鋼を使用する量を低減することができ、材料コストを低減することができるとともに、異材溶接が少なくできるため溶接時の溶材コストなども低下することができる。 In consideration of cost as described above, it is effective to use clad steel sheet as a material from the viewpoint of processing and welding. A clad steel sheet is a material obtained by laminating two or more different types of metals. Further, a steel sheet that is not bonded is hereinafter referred to as a "solid steel sheet". Compared with solid steel sheets made only of high alloy steel, clad steel sheets can reduce the amount of high alloy steel used, reduce material costs, and reduce welding of dissimilar materials, so molten materials during welding can be reduced. Costs can also be reduced.
　また、二種類の金属を貼り合わせたクラッド鋼板において、一方の金属を「母材」と記載し、母材に貼り合せた他方の金属（素材）を「合せ材」と記載する。優れた特性を有する材料（合せ材）を母材に貼り合せることで、合せ材と母材とがそれぞれ有する優れた特性を双方とも得ることができる。 Further, in a clad steel sheet in which two types of metals are bonded together, one metal is described as "base material" and the other metal (material) bonded to the base material is described as "laminated material". By laminating a material (laminated material) having excellent properties to the base material, both the excellent properties of the laminated material and the base material can be obtained.
　例えば、合せ材に、その使用環境で要求される特性を有する高合金鋼を用い、母材にその使用環境で要求される靭性および強度を有する炭素鋼または低合金鋼を用いた場合が考えられる。このような場合、上述のようにコストを低減することができるだけでなく、ソリッド鋼板と同等の特性と、炭素鋼および低合金鋼と同等の強度および靭性とを確保できる。このため、経済性と機能性とが両立できる。 For example, it is conceivable that a high alloy steel having the characteristics required in the usage environment is used for the laminated material, and a carbon steel or a low alloy steel having the toughness and strength required in the usage environment is used as the base material. .. In such a case, not only the cost can be reduced as described above, but also the same characteristics as the solid steel sheet and the same strength and toughness as the carbon steel and the low alloy steel can be secured. Therefore, both economy and functionality can be achieved at the same time.
　以上のような経緯から、ステンレス鋼やＮｉ基合金を用いたクラッド鋼板のニーズは、近年各種産業分野で益々高まっている。しかしながら、クラッド鋼板を利用する際には、合せ材と母材との接合部での剥離を防止することが重要である。使用中に合せ材と母材とが剥離すると、所望する耐食性等の特性、および強度が得られない場合がある。また、例えば、構造物の穴あき、倒壊などの危険が生じることも考えられる。 From the above background, the needs for clad steel sheets using stainless steel and Ni-based alloys have been increasing more and more in various industrial fields in recent years. However, when using a clad steel sheet, it is important to prevent peeling at the joint between the laminated material and the base material. If the laminated material and the base material are peeled off during use, the desired properties such as corrosion resistance and strength may not be obtained. In addition, for example, there may be a risk of perforation or collapse of the structure.
　ステンレス鋼やＮｉ基合金を合せ材とするクラッド鋼板では圧延時の加熱中に、ＣｒやＮｉが合せ材から母材側へ、Ｃが母材から合せ材側へ拡散することによって、母材と合せ材の界面（以下単に「界面」という。）に元素の拡散層が生じる。拡散層中は各元素の濃度が徐々に変化するが、元素濃度によってはマルテンサイト変態が開始する温度が高く、マルテンサイト変態が生じる臨界冷却速度が遅い領域で、圧延後の冷却中にマルテンサイト変態が生じる場合がある。 In a clad steel sheet made of stainless steel or Ni-based alloy, during heating during rolling, Cr and Ni diffuse from the laminated material to the base material side, and C diffuses from the base material to the laminated material side, thereby forming a base material. A diffusion layer of elements is formed at the interface of the laminated lumber (hereinafter simply referred to as "interface"). The concentration of each element gradually changes in the diffusion layer, but depending on the element concentration, the temperature at which martensitic transformation starts is high, and the critical cooling rate at which martensitic transformation occurs is slow. Transformation may occur.
　クラッド鋼板の通常の使用形態では界面のマルテンサイトは界面剥離に影響を与えないが、例えば溶接ガスに水素を用いて溶接した場合にはマルテンサイトに水素が入るとともに、構造上の応力や溶接時の変形、溶接部近傍での母材の変態などによって界面に応力が生じ、その複合作用によって水素脆化が生じる可能性が想定される。 In the normal usage of clad steel plate, martensite at the interface does not affect the interface embrittlement, but for example, when welding is performed using hydrogen as the welding gas, hydrogen enters the martensite, and structural stress and during welding It is assumed that there is a possibility that hydrogen embrittlement will occur due to the combined action of stress generated at the interface due to the deformation of the base metal and the deformation of the base metal in the vicinity of the weld.
　特許文献１には二相ステンレスクラッド鋼板について界面の炭素拡散層の厚みを制御することで界面近傍の鋭敏化を抑制する技術が開示されている。しかしながら、界面でのマルテンサイト相に関する記載はない。 Patent Document 1 discloses a technique for suppressing sensitization near the interface by controlling the thickness of the carbon diffusion layer at the interface of a duplex stainless clad steel sheet. However, there is no mention of the martensite phase at the interface.
　特許文献２にはオーステナイト系ステンレスクラッド鋼板について、圧延後の焼戻しの温度・時間を規定することで界面のマルテンサイトの遅れ破壊を防止する技術が開示されている。しかしながら、この技術は製造時の遅れ破壊の防止であり、溶接構造物についての防止技術の開示はない。 Patent Document 2 discloses a technique for preventing delayed fracture of martensite at the interface by specifying the temperature and time of tempering after rolling for an austenitic stainless clad steel sheet. However, this technique is to prevent delayed fracture during manufacturing, and there is no disclosure of preventive techniques for welded structures.
　また、非特許文献１ではＳＵＳ３１６Ｌおよびインコネル６２５のクラッドについて、界面のマルテンサイトの水素脆化感受性を評価している。 In addition, Non-Patent Document 1 evaluates the hydrogen embrittlement susceptibility of martensite at the interface for the cladding of SUS316L and Inconel 625.
特開２０１３－２０９６８８号公報Japanese Unexamined Patent Publication No. 2013-209688 特開平６－７８０３号公報Japanese Unexamined Patent Publication No. 6-7803
　本発明者は、鋭意検討の結果、解決すべき以下の課題を知見した。
　特許文献２には、界面のマルテンサイトの遅れ破壊を防止する技術の開示がある。しかし焼戻し工程が増えることはコスト増加につながるため、実用上焼戻しなしでの界面のマルテンサイトの耐水素脆化性を向上させる技術が求められるが、その解決手段については開示も示唆もない。
　非特許文献１には、界面のマルテンサイトの水素脆化感受性の評価方法についての記載はある。しかし、実際のクラッド鋼においては、加熱温度と圧下比に応じて拡散層の幅が異なると推定されるが、拡散層の幅と水素脆化感受性の関係についての記載も示唆もない。
　本発明者は、マルテンサイトはその硬度が高いほど水素脆化感受性が高くなること、さらに、拡散層中のマルテンサイト幅が大きいほど微小な水素脆化が大きな界面剥離につながる危険性が高くなることを認識した。さらに本発明者は、溶接時の水素脆化によるクラッドの界面剥離を抑制するためには、界面のマルテンサイトの硬度と幅、鋼中の水素濃度およびマルテンサイトに付加される応力を制御することが解決すべき課題であると知見した。 As a result of diligent studies, the present inventor has found the following problems to be solved.
Patent Document 2 discloses a technique for preventing delayed fracture of martensite at an interface. However, since increasing the number of tempering steps leads to an increase in cost, a technique for improving the hydrogen embrittlement resistance of martensite at the interface without tempering is required in practice, but there is no disclosure or suggestion of a solution.
Non-Patent Document 1 describes a method for evaluating the hydrogen embrittlement susceptibility of martensite at an interface. However, in an actual clad steel, it is estimated that the width of the diffusion layer differs depending on the heating temperature and the reduction ratio, but there is no description or suggestion about the relationship between the width of the diffusion layer and the hydrogen embrittlement sensitivity.
According to the present inventor, the higher the hardness of martensite, the higher the sensitivity to hydrogen embrittlement, and the larger the width of martensite in the diffusion layer, the higher the risk that minute hydrogen embrittlement will lead to large interfacial exfoliation. I realized that. Furthermore, the present inventor controls the hardness and width of martensite at the interface, the hydrogen concentration in steel, and the stress applied to martensite in order to suppress the interfacial peeling of the clad due to hydrogen embrittlement during welding. Was found to be a problem to be solved.
　上記記載の課題認識に鑑み、本発明は、接合面の耐水素脆化性が良好な耐水素脆化性に優れたクラッド鋼板およびその製造方法ならびに溶接構造物を提供することを目的とする。 In view of the above-mentioned recognition of the problems, an object of the present invention is to provide a clad steel sheet having good hydrogen embrittlement resistance of the joint surface and excellent hydrogen embrittlement resistance, a method for producing the same, and a welded structure.
　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り、下記のクラッド鋼板およびその製造方法ならびに溶接構造物を要旨とする。
［１］母材と、前記母材に接合された合せ材とを備えるクラッド鋼板であって、
　前記母材は、炭素鋼または低合金鋼からなり、
　前記合せ材は、耐食性合金からなり、
　クラッド鋼板の母材と合せ材の界面において、ナノ硬さが７ＧＰａ以上である領域の板厚方向の幅が５μｍ以下であることを特徴とするクラッド鋼板。
［２］請求項１に記載のクラッド鋼板において母材の化学組成が質量％でＣ：０．０２０～０．２００％、Ｓｉ：１．００％以下、Ｍｎ：０．１０～３．００％、Ｐ：０．０５０％以下、Ｓ：０．０５０％を含有し、かつＣｅｑが０．２０～０．４０であり、残部がＦｅ及び不純物からなる成分組成を有する［１］に記載のクラッド鋼板。ここで、Ｃｅｑは次式（１）により定義される。
Ｃｅｑ＝Ｃ＋Ｍｎ／６＋（Ｃｕ＋Ｎｉ）／１５＋（Ｃｒ＋Ｍｏ＋Ｖ）／５・・・式（１）式中、Ｃ、Ｍｎ、Ｃｕ、Ｎｉ、Ｃｒ、ＭｏおよびＶは、母材鋼板の成分組成における各元素の含有量（質量％）である。
［３］前記母材の成分組成が、さらに前記Ｆｅの一部に替えて、質量％で、Ｎｉ：０．０１～１．００％、Ｃｒ：０．０１～１．００％、Ｍｏ：０．０１～０．５０％、Ｃｕ：０．０１～１．００％、Ｃｏ：０．０１～０．５０％，Ｓｅ＋Ｔｅ：０．０１～０．１０％、Ｖ：０．００１～０．１００％、Ｔｉ：０．００１～０．２００％、Ｎｂ：０．００１～０．２００％、Ａｌ：０．００５～０．３００％、Ｃａ：０．０００３～０．００５０％、Ｂ：０．０００３～０．００３０％およびＲＥＭ：０．０００３～０．０１００％から選ばれる１種または２種以上を含有する、［２］に記載のクラッド鋼板。
［４］前記クラッド鋼板の合せ材が、質量％でＣｒ：１０％以上を含有するステンレス鋼またはニッケル基合金であることを特徴とする、［１］～［３］のいずれか１つに記載のクラッド鋼板。 The present invention has been made to solve the above problems, and the gist of the present invention is the following clad steel sheet, its manufacturing method, and a welded structure.
[1] A clad steel sheet including a base material and a laminated material joined to the base material.
The base material is made of carbon steel or low alloy steel.
The laminated material is made of a corrosion-resistant alloy and is made of a corrosion-resistant alloy.
A clad steel sheet having a width in the plate thickness direction of 5 μm or less in a region where the nanohardness is 7 GPa or more at the interface between the base material and the laminated material of the clad steel sheet.
[2] In the clad steel sheet according to claim 1, the chemical composition of the base material is C: 0.020 to 0.200%, Si: 1.00% or less, Mn: 0.10 to 3.00% in mass%. , P: 0.050% or less, S: 0.050%, Ceq is 0.20 to 0.40, and the balance has a component composition of Fe and impurities, according to [1]. Steel plate. Here, Ceq is defined by the following equation (1).
Ceq = C + Mn / 6 + (Cu + Ni) / 15+ (Cr + Mo + V) / 5 ... In formula (1), C, Mn, Cu, Ni, Cr, Mo and V are elements of each element in the composition of the base steel sheet. The content (% by mass).
[3] The component composition of the base material is, instead of a part of the Fe, in mass%, Ni: 0.01 to 1.00%, Cr: 0.01 to 1.00%, Mo: 0. 0.01 to 0.50%, Cu: 0.01 to 1.00%, Co: 0.01 to 0.50%, Se + Te: 0.01 to 0.10%, V: 0.001 to 0.100 %, Ti: 0.001 to 0.200%, Nb: 0.001 to 0.200%, Al: 0.005 to 0.300%, Ca: 0.0003 to 0.0050%, B: 0. The clad steel plate according to [2], which contains one or more selected from 0003 to 0.0030% and REM: 0.0003 to 0.0100%.
[4] Described in any one of [1] to [3], wherein the laminated material of the clad steel sheet is a stainless steel or a nickel-based alloy containing Cr: 10% or more in mass%. Clad steel sheet.
［５］［１］～［４］のいずれか１つに記載のクラッド鋼板において、母材と合せ材を圧着面が真空になるよう積層して圧着面の４周を溶接により密封してクラッド素材とし、１又は２以上の前記クラッド素材を組み立てたクラッド圧延素材について加熱炉内の最高加熱温度Ｔ（℃）、加熱炉内での加熱温度が最高加熱温度Ｔ－２０℃となった時点から加熱炉抽出までの時間ｔ（分）、素材厚／製品厚で計算される圧下比ｒによって式（２）で計算されるｄが１以上９以下である加熱と熱間圧延を行い、圧延後に式（３）で計算されるＴＡ３（℃）～６５０℃区間の平均冷却速度が２℃／ｓ以上の冷却を行い、母材と合せ材の界面のナノ硬さが７ＧＰａ以上である領域の板厚方向の幅を５μｍ以下とすることを特徴とする、［１］～［４］のいずれか１つに記載のクラッド鋼板の製造方法。
　ｄ＝２．２×１０５×√（ｅｘｐ（－３．２×１０４／（Ｔ＋２７３））×ｔ）／ｒ　・・・式（２）
　ＴＡ３（℃）＝９３７．２－４３６．５Ｃ＋５６Ｓｉ－１９．７Ｍｎ－２６．６Ｎｉ＋１３６．３Ｔｉ－１９．１Ｎｂ＋１９８．４Ａｌ　・・・式（３）
式中、Ｃ、Ｓｉ、Ｍｎ、Ｎｉ、Ｔｉ、ＮｂおよびＡｌは、母材鋼板の成分組成における各元素の含有量（質量％）である。 [5] In the clad steel plate according to any one of [1] to [4], the base material and the laminated material are laminated so that the crimping surface becomes vacuum, and the four circumferences of the crimping surface are sealed by welding and clad. From the time when the maximum heating temperature T (° C.) in the heating furnace and the maximum heating temperature T-20 ° C. in the heating furnace are reached for the clad rolled material obtained by assembling one or more of the above clad materials as the material. The time t (minutes) until extraction into the heating furnace, and the reduction ratio r calculated by the material thickness / product thickness, d calculated by the formula (2) is 1 or more and 9 or less. Heating and hot rolling are performed, and after rolling. In the region where the average cooling rate in the TA3 (° C.) to 650 ° C. section calculated by the formula (3) is 2 ° C./s or more and the nanohardness at the interface between the base material and the laminated material is 7 GPa or more. The method for producing a clad steel sheet according to any one of [1] to [4], wherein the width in the plate thickness direction is 5 μm or less.
d = 2.2 × 10 5 × √ (exp (-3.2 × 10 4 / (T + 273)) × t) / r ・ ・ ・ Equation (2)
T A3 (℃) = 937.2-436.5C + 56Si-19.7Mn-26.6Ni + 136.3Ti-19.1Nb + 198.4Al ··· formula (3)
In the formula, C, Si, Mn, Ni, Ti, Nb and Al are the contents (mass%) of each element in the component composition of the base steel sheet.
［６］［１］～［４］のいずれか１つに記載のクラッド鋼板を用いてなる溶接構造物。
［７］前記クラッド鋼板が、溶接ガスに水素を用いた溶接に使用されることを特徴とする、［１］～［４］のいずれか１つに記載のクラッド鋼板。 [6] A welded structure using the clad steel sheet according to any one of [1] to [4].
[7] The clad steel sheet according to any one of [1] to [4], wherein the clad steel sheet is used for welding using hydrogen as a welding gas.
　本発明によれば、接合面の耐水素脆化性に優れたクラッド鋼板を得ることができる。 According to the present invention, it is possible to obtain a clad steel sheet having excellent hydrogen embrittlement resistance on the joint surface.
式（２）の値ｄと熱間圧延後の冷却速度ＣＲが、耐水素脆化特性に及ぼす影響を示す図である。It is a figure which shows the influence which the value d of the formula (2) and the cooling rate CR after hot rolling have on the hydrogen embrittlement resistance property.
　本発明者らは上記の課題に対し、以下の検討を行なった。具体的には、種々のステンレス鋼およびＮｉ基合金を合せ材とするクラッド鋼板において、加熱温度、加熱時間、圧下比および圧延後の冷却速度を変化させて界面の元素拡散と金属組織について調査し、界面の耐水素脆化性との関係を評価した。その結果、以下（ａ）～（ｃ）の知見を得た。 The present inventors conducted the following studies on the above problems. Specifically, in clad steel sheets made of various stainless steels and Ni-based alloys, the element diffusion and metallographic structure at the interface were investigated by changing the heating temperature, heating time, rolling ratio and cooling rate after rolling. , The relationship with the hydrogen embrittlement resistance of the interface was evaluated. As a result, the following findings (a) to (c) were obtained.
　（ａ）クラッド鋼板の界面のナノ硬さが７ＧＰａ以上の領域が薄いほどマルテンサイトの水素脆化感受性が低くなる傾向にある。このため、７ＧＰａ以上の領域を５μｍ以下にすることが有効である。 (A) The thinner the region where the nanohardness at the interface of the clad steel sheet is 7 GPa or more, the lower the hydrogen embrittlement sensitivity of martensite tends to be. Therefore, it is effective to set the region of 7 GPa or more to 5 μm or less.
　（ｂ）クラッド鋼板の圧延素材においては、母材となる炭素鋼または低合金鋼と、合せ材となるステンレス鋼またはＮｉ基合金とが接している。界面の合金元素のプロファイルは素材加熱の温度・時間および圧下比によって整理できた。またＣｒが質量％で１０％以上含まれている合せ材を用いた際に、Ｃｒの拡散幅とマルテンサイト相の幅が対応していることを確認した。これは主要合金元素のうちＣｒが最も拡散が速く、さらに焼入れ性を高める元素であるため、Ｃｒの含有量のみが高くＮｉなどのオーステナイト安定化元素の含有量が低い領域でマルテンサイト変態が生じるためである。 (B) In the rolled material of the clad steel sheet, the carbon steel or low alloy steel as the base material is in contact with the stainless steel or Ni-based alloy as the laminated material. The profile of the alloying elements at the interface could be organized by the temperature / time of material heating and the reduction ratio. Further, it was confirmed that the diffusion width of Cr and the width of the martensite phase correspond to each other when a laminated material containing 10% or more by mass% of Cr was used. Since Cr is the element that diffuses the fastest among the main alloy elements and further enhances hardenability, martensitic transformation occurs in the region where only the content of Cr is high and the content of austenite stabilizing elements such as Ni is low. Because.
　（ｃ）界面のマルテンサイトの硬さは圧延後の冷却速度に影響される。この機構は下記のように考えられる。圧延後の冷却中に冷却速度が遅く、オーステナイト→フェライト変態やオーステナイト→フェライト＋パーライト変態に伴う炭素の吐き出しおよび拡散が生じる場合には、オーステナイト相に固溶していた炭素は、Ｃｒを多く含有しており炭素の活量係数の低い合せ材側に濃化する。このとき、合せ材側がオーステナイト相であれば濃化程度はより大きくなる。この機構により、圧延後の冷却速度が遅い場合には界面近傍で炭素濃度が高くなる領域が生じ、その領域とマルテンサイト相が生成しうる領域が重なるとクラッド鋼板の界面に硬質なマルテンサイト相が生成し、界面の耐水素脆化性が低下する。 (C) The hardness of martensite at the interface is affected by the cooling rate after rolling. This mechanism is considered as follows. When the cooling rate is slow during cooling after rolling and carbon discharge and diffusion due to austenite → ferrite transformation or austenite → ferrite + pearlite transformation occur, the carbon dissolved in the austenite phase contains a large amount of Cr. It concentrates on the austenite side, which has a low carbon activity coefficient. At this time, if the laminated material side is an austenite phase, the degree of concentration becomes larger. Due to this mechanism, when the cooling rate after rolling is slow, a region where the carbon concentration becomes high is generated near the interface, and when that region and the region where the martensite phase can be formed overlap, the hard martensite phase is formed at the interface of the clad steel plate. Is generated, and the hydrogen embrittlement resistance of the interface is reduced.
　したがって、接合面の耐水素脆化性に優れたクラッド鋼板を得るためには、加熱時のＣｒ拡散と圧延後の冷却時のＣ拡散を制御する必要がある。本発明は、上記の知見に基づいてなされたものである。以下、本発明の各要件について詳しく説明する。 Therefore, in order to obtain a clad steel sheet having excellent hydrogen embrittlement resistance on the joint surface, it is necessary to control Cr diffusion during heating and C diffusion during cooling after rolling. The present invention has been made based on the above findings. Hereinafter, each requirement of the present invention will be described in detail.
　１．本発明の構成
　本発明に係るクラッド鋼板は、母材と、母材に接合された合せ材とを備える。母材は後述の炭素鋼または低合金鋼からなる。また合せ材は耐食性合金からなり、耐食性合金としてＣｒを１０％以上含有するステンレス鋼やＮｉ基合金などを例示できる。さらに、前記母材と前記合せ材の界面においてナノ硬さが７ＧＰａ以上である領域の幅が５μｍ以下である。 1. 1. Configuration of the Present Invention The clad steel sheet according to the present invention includes a base material and a laminated material joined to the base material. The base material consists of carbon steel or low alloy steel, which will be described later. Further, the laminated material is made of a corrosion-resistant alloy, and examples of the corrosion-resistant alloy include stainless steel and Ni-based alloys containing 10% or more of Cr. Further, the width of the region where the nanohardness is 7 GPa or more at the interface between the base material and the laminated material is 5 μm or less.
　２．クラッド界面の特性
　本発明に関わるクラッド鋼板の界面特性について説明する。良好な接合面の耐水素脆化性を有するクラッド鋼板を得るためにはクラッド界面での硬質なマルテンサイト相の生成を抑制する必要がある。 2. Characteristics of clad interface The interface characteristics of the clad steel sheet according to the present invention will be described. In order to obtain a clad steel sheet having good hydrogen embrittlement resistance on the joint surface, it is necessary to suppress the formation of a hard martensite phase at the clad interface.
　２－１．クラッド界面のナノ硬さ
　クラッド界面においてナノ硬さが７ＧＰａ以上の領域の幅は５μｍ以下とする。ナノ硬さが７ＧＰａ以上の領域の板厚方向の幅が５μｍ超では硬質で水素脆化感受性の高いマルテンサイトの領域が大きいため溶接ガスに水素を含有する溶接を実施した際に界面が剥離する場合がある。好ましくは３μｍ以下であり、更に好ましくは１μｍ以下である。ナノ硬さが７ＧＰａ以上の領域が小さいほど水素脆化感受性は低くなるため下限は設けない。
　ここでナノ硬さとは、ＩＳＯ　１４５７７に規定する計装化押し込み硬さ試験（ナノインデンテーション試験ともいう。）に準拠して評価した材料の硬さを意味する。 2-1. Nano-hardness of the clad interface The width of the region where the nano-hardness is 7 GPa or more at the clad interface shall be 5 μm or less. When the width of the region with nano-hardness of 7 GPa or more in the plate thickness direction exceeds 5 μm, the region of martensite, which is hard and highly sensitive to hydrogen embrittlement, is large, so the interface peels off when welding containing hydrogen in the welding gas is performed. In some cases. It is preferably 3 μm or less, and more preferably 1 μm or less. The smaller the region where the nanohardness is 7 GPa or more, the lower the hydrogen embrittlement sensitivity, so no lower limit is set.
Here, the nano-hardness means the hardness of a material evaluated in accordance with an instrumentation indentation hardness test (also referred to as a nano-indentation test) specified in ISO 14577.
　３．母材の化学組成
　母材は炭素鋼または低合金鋼からなる。また母材の好ましい化学組成は、質量％でＣ：０．０２０～０．２００％、Ｓｉ：１．００％以下、Ｍｎ：０．１０～３．００％、Ｐ：０．０５０％以下、Ｓ：０．０５０％を含有し、かつＣｅｑが０．２０～０．４０であり、残部がＦｅ及び不純物からなる成分組成を有する鋼板である。ここで、Ｃｅｑは次式（１）により定義される。
　Ｃｅｑ＝Ｃ＋Ｍｎ／６＋（Ｃｕ＋Ｎｉ）／１５＋（Ｃｒ＋Ｍｏ＋Ｖ）／５・・・式（１）
　式中、Ｃ、Ｍｎ、Ｃｕ、Ｎｉ、Ｃｒ、ＭｏおよびＶは、母材の成分組成における各元素の含有量（質量％）である。 3. 3. Chemical composition of base material The base material consists of carbon steel or low alloy steel. The preferable chemical composition of the base material is C: 0.020 to 0.200%, Si: 1.00% or less, Mn: 0.10 to 3.00%, P: 0.050% or less in mass%. S: A steel sheet containing 0.050%, having a Ceq of 0.20 to 0.40, and having a component composition in which the balance is Fe and impurities. Here, Ceq is defined by the following equation (1).
Ceq = C + Mn / 6 + (Cu + Ni) / 15+ (Cr + Mo + V) / 5 ... Equation (1)
In the formula, C, Mn, Cu, Ni, Cr, Mo and V are the contents (mass%) of each element in the component composition of the base material.
　Ｃは鋼の強度を向上させる元素であり、０．０２０％以上含有させることで十分な強度を発現する。しかし、０．２００％を超えると溶接性および靭性の劣化を招く。したがって、Ｃ量は０．０２０～０．２００％とする。好ましくは０．０４０％以上であり、さらに好ましくは０．０５０％以上である。一方上限値は０．１００％以下が好ましく、０．０８０％以下がさらに好ましい。より好ましい範囲は０．０４０％～０．１００％であり、更に好ましい範囲は０．０５０％～０．０８０％である。 C is an element that improves the strength of steel, and when it is contained in an amount of 0.020% or more, sufficient strength is exhibited. However, if it exceeds 0.200%, the weldability and toughness are deteriorated. Therefore, the amount of C is set to 0.020 to 0.200%. It is preferably 0.040% or more, and more preferably 0.050% or more. On the other hand, the upper limit is preferably 0.100% or less, more preferably 0.080% or less. A more preferable range is 0.040% to 0.100%, and a more preferable range is 0.050% to 0.080%.
　Ｓｉは脱酸に有効であり、また鋼の強度を向上させる元素である。しかしながら、１．００％を超えると鋼の表面性状及び靭性の劣化を招く。したがって、Ｓｉ量は１．００％以下とする。好ましくは０．５０％以下である。Ｓｉは含有しなくても良い。Ｓｉの好ましい含有量下限は０．０１％である。 Si is an element that is effective in deoxidizing and improves the strength of steel. However, if it exceeds 1.00%, the surface properties and toughness of the steel deteriorate. Therefore, the amount of Si is set to 1.00% or less. It is preferably 0.50% or less. Si may not be contained. The preferable lower limit of the content of Si is 0.01%.
　Ｍｎは鋼の強度を上昇させる元素であり、０．１０％以上含有させることでその効果が発現する。しかしながら、３．００％を超えると溶接性が損なわれるとともに合金コストも増大する。したがって、Ｍｎ量は０．１０～３．００％とする。好ましくは下限は０．５０％であり、上限は２．００％である。更に好ましくは下限は０．９０％％であり、上限は１．６０％である。 Mn is an element that increases the strength of steel, and its effect is exhibited when it is contained in an amount of 0.10% or more. However, if it exceeds 3.00%, the weldability is impaired and the alloy cost also increases. Therefore, the amount of Mn is set to 0.10 to 3.00%. Preferably, the lower limit is 0.50% and the upper limit is 2.00%. More preferably, the lower limit is 0.90% and the upper limit is 1.60%.
　Ｐは鋼中の不純物であり、含有量が０．０５０％を超えると靭性が劣化する。したがって、Ｐ量は０．０５０％以下とする。好ましくは０．０２０％以下である。 P is an impurity in steel, and if the content exceeds 0.050%, the toughness deteriorates. Therefore, the amount of P is set to 0.050% or less. It is preferably 0.020% or less.
　Ｓは鋼中の不純物であり、含有量が０．０５０％を超えると靭性が劣化する。したがって、Ｓ量は０．０５０％以下とする。好ましくは０．０１０％以下である。 S is an impurity in steel, and if the content exceeds 0.050%, the toughness deteriorates. Therefore, the amount of S is set to 0.050% or less. It is preferably 0.010% or less.
　Ｃｅｑ（炭素当量）は、鋼の化学組成から硬度と溶接性を見積もるために用いられる値であり、式（１）で計算される。Ｃｅｑが高いほど硬さは向上し、溶接性は劣化する。Ｃｅｑが０．２０未満では構造物として十分な強度が得られない。したがって、Ｃｅｑは０．２０以上とする。好ましくは０．２３以上である。Ｃｅｑが０．４０超では溶接性が劣化し、パス間温度管理や後熱処理が必要になるなど溶接コストが増加する。したがって、Ｃｅｑは０．４０以下とする。好ましくは０．３５以下である。
　Ｃｅｑ＝Ｃ＋Ｍｎ／６＋（Ｃｕ＋Ｎｉ）／１５＋（Ｃｒ＋Ｍｏ＋Ｖ）／５・・・式（１）
　式中、Ｃ、Ｍｎ、Ｃｕ、Ｎｉ、Ｃｒ、ＭｏおよびＶは、母材の成分組成における各元素の含有量（質量％）である。 Ceq (carbon equivalent) is a value used to estimate hardness and weldability from the chemical composition of steel, and is calculated by the formula (1). The higher the Ceq, the higher the hardness and the worse the weldability. If Ceq is less than 0.20, sufficient strength as a structure cannot be obtained. Therefore, Ceq is set to 0.20 or more. It is preferably 0.23 or more. If Ceq exceeds 0.40, the weldability deteriorates, and the welding cost increases due to the need for inter-pass temperature control and post-heat treatment. Therefore, Ceq is set to 0.40 or less. It is preferably 0.35 or less.
Ceq = C + Mn / 6 + (Cu + Ni) / 15+ (Cr + Mo + V) / 5 ... Equation (1)
In the formula, C, Mn, Cu, Ni, Cr, Mo and V are the contents (mass%) of each element in the component composition of the base material.
　前記母材の成分組成にさらに、前記Ｆｅの一部に替えて質量％で、Ｎｉ：０．０１～１．００％、Ｃｒ：０．０１～１．００％、Ｍｏ：０．０１～０．５０％、Ｃｕ：０．０１～１．００％、Ｃｏ：０．０１～０．５０％、Ｓｅ＋Ｔｅ：０．０１～０．１０％、Ｖ：０．００１～０．１００％、Ｔｉ：０．００１～０．２００％、Ｎｂ：０．００１～０．２００％、Ａｌ：０．００５～０．３００％、Ｃａ：０．０００３～０．００５０％、Ｂ：０．０００３～０．００３０％およびＲＥＭ：０．０００３～０．０１００％から選ばれる１種または２種以上を含有することができる。 In addition to the component composition of the base material, Ni: 0.01 to 1.00%, Cr: 0.01 to 1.00%, Mo: 0.01 to 0 in mass% instead of a part of the Fe. .50%, Cu: 0.01 to 1.00%, Co: 0.01 to 0.50%, Se + Te: 0.01 to 0.10%, V: 0.001 to 0.100%, Ti: 0.001 to 0.200%, Nb: 0.001 to 0.200%, Al: 0.005 to 0.300%, Ca: 0.0003 to 0.0050%, B: 0.0003 to 0. It can contain one or more selected from 0030% and REM: 0.0003-0.0100%.
　Ｎｉは鋼の焼入れ性を向上させる元素であり、圧延後の鋼の強度及び靭性を向上させる。しかしながら、１．００％を超えると溶接性および靭性の劣化を引き起こす。したがってＮｉを含有する場合、Ｎｉ量は１．００％以下とする。好ましくは０．５０％以下であり、より好ましくは０．３０％以下である。好ましいＮｉ含有量下限値は０．０１％である。 Ni is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 1.00%, it causes deterioration of weldability and toughness. Therefore, when Ni is contained, the amount of Ni is set to 1.00% or less. It is preferably 0.50% or less, and more preferably 0.30% or less. The preferred lower limit of Ni content is 0.01%.
　Ｃｒは鋼の焼入れ性を向上させる元素であり、圧延後の鋼の強度及び靭性を向上させる。しかしながら、１．００％を超えると溶接性および靭性の劣化を引き起こす。したがってＣｒを含有する場合、Ｃｒ量は１．００％以下とする。好ましくは０．５０％以下であり、より好ましくは０．３０％以下である。好ましいＣｒ含有量下限値は０．０１％である。 Cr is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 1.00%, it causes deterioration of weldability and toughness. Therefore, when Cr is contained, the amount of Cr is set to 1.00% or less. It is preferably 0.50% or less, and more preferably 0.30% or less. The preferred lower limit of Cr content is 0.01%.
　Ｍｏは鋼の焼入れ性を向上させる元素であり、圧延後の鋼の強度及び靭性を向上させる。しかしながら、０．５０％を超えると溶接性および靭性の劣化を引き起こす。したがってＭｏを含有する場合、Ｍｏ量は０．５０％以下とする。好ましくは０．３０％以下であり、より好ましくは０．１％以下である。好ましいＭｏ含有量下限値は０．０１％である。 Mo is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 0.50%, it causes deterioration of weldability and toughness. Therefore, when Mo is contained, the amount of Mo is 0.50% or less. It is preferably 0.30% or less, and more preferably 0.1% or less. The preferred lower limit of Mo content is 0.01%.
　Ｃｕは鋼の焼入れ性を向上させる元素であり、圧延後の鋼の強度及び靭性を向上させる。しかしながら、１．００％を超えると溶接性および靭性の劣化を引き起こす。したがってＣｕを含有する場合、Ｃｕ量は１．００％以下とする。好ましくは０．５０％以下であり、より好ましくは０．３０％以下である。好ましいＣｕ含有量下限値は０．０１％である。 Cu is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 1.00%, it causes deterioration of weldability and toughness. Therefore, when Cu is contained, the amount of Cu is set to 1.00% or less. It is preferably 0.50% or less, and more preferably 0.30% or less. The preferred lower limit of Cu content is 0.01%.
　Ｃｏは鋼の焼入れ性を向上させる元素であり、圧延後の鋼の強度及び靭性を向上させる。しかしながら、０．５０％を超えると熱間での加工性が損なわれて生産性が低下する。したがってＣｏを含有する場合、Ｃｏ量は０．５０％以下とする。好ましくは０．３０％以下であり、より好ましくは０．１％以下である。好ましいＣｏ含有量下限値は０．０１％である。 Co is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 0.50%, the workability in hot water is impaired and the productivity is lowered. Therefore, when Co is contained, the amount of Co is set to 0.50% or less. It is preferably 0.30% or less, and more preferably 0.1% or less. The preferred lower limit of Co content is 0.01%.
　ＳｅおよびＴｅは鋼板中のＭｎ、Ｓｉ、Ａｌ等の酸化しやすい元素が鋼板表面に拡散されて酸化物を形成することを抑制し、鋼板の表面性状やめっき性を高める。しかしながら、合計で０．１０％を超えるとこの効果が飽和する。したがって、ＳｅおよびＴｅを添加する場合はＳｅとＴｅの合計量は０．１０％以下とする。より好ましくは０．０５％以下である。好ましいＳｅ＋Ｔｅ含有量下限値は０．０１％である。 Se and Te suppress the formation of oxides by diffusing easily oxidizable elements such as Mn, Si, and Al in the steel sheet onto the surface of the steel sheet, and improve the surface properties and plating properties of the steel sheet. However, if the total exceeds 0.10%, this effect is saturated. Therefore, when Se and Te are added, the total amount of Se and Te is 0.10% or less. More preferably, it is 0.05% or less. The preferred Se + Te content lower limit is 0.01%.
　Ａｌは鋼の脱酸に効果がある元素である。しかしながら、０．３００％を超えると溶接部の靭性の劣化を引き起こす。したがってＡｌを含有する場合、Ａｌ量は０．３００％以下とする。好ましくは０．１００％以下である。好ましいＡｌ含有量下限値は０．００５％である。 Al is an element that is effective in deoxidizing steel. However, if it exceeds 0.300%, the toughness of the welded portion deteriorates. Therefore, when Al is contained, the amount of Al is set to 0.300% or less. It is preferably 0.100% or less. The preferable lower limit of Al content is 0.005%.
　Ｖは炭窒化物を形成することで鋼の強度を上昇させる。しかしながら、０．１００％を超えると溶接性および靭性の劣化を引き起こす。したがってＶを含有する場合、Ｖ量は０．１００％以下とする。好ましくは０．０５０％以下である。好ましいＶ含有量下限値は０．００１％である。 V increases the strength of steel by forming a carbonitride. However, if it exceeds 0.100%, it causes deterioration of weldability and toughness. Therefore, when V is contained, the amount of V is set to 0.100% or less. It is preferably 0.050% or less. The preferred lower limit of V content is 0.001%.
　Ｔｉは結晶粒を微細化させて強度を増加させる元素であり、０．００１％以上の添加でその効果が発現する。しかし、０．２００％を超えると溶接性が損なわれるとともに合金コストも増大する。したがって、Ｔｉ量は０．００１～０．２００％とする。好ましくは下限は０．００５％であり、上限は０．１００％である。更に好ましくは下限は０．０１０％であり、上限は０．０５０％である。 Ti is an element that refines crystal grains and increases strength, and its effect is exhibited by adding 0.001% or more. However, if it exceeds 0.200%, the weldability is impaired and the alloy cost also increases. Therefore, the amount of Ti is set to 0.001 to 0.200%. Preferably, the lower limit is 0.005% and the upper limit is 0.100%. More preferably, the lower limit is 0.010% and the upper limit is 0.050%.
　Ｎｂは再結晶温度を上げる元素であり、０．００１％以上の添加でその効果が発現する。しかし、０．２００％を超えると溶接性が損なわれるとともに合金コストも増大する。したがって、Ｎｂ量は０．００１～０．２００％とする。好ましくは下限は０．００５％であり、上限は０．１００％である。更に好ましくは下限は０．０１０％であり、上限は０．０５０％である。 Nb is an element that raises the recrystallization temperature, and its effect is exhibited by adding 0.001% or more. However, if it exceeds 0.200%, the weldability is impaired and the alloy cost also increases. Therefore, the amount of Nb is set to 0.001 to 0.200%. Preferably, the lower limit is 0.005% and the upper limit is 0.100%. More preferably, the lower limit is 0.010% and the upper limit is 0.050%.
　Ｃａは溶接熱影響部の組織を微細化し、靭性を向上させる。しかしながら、０．００５０％を超えると粗大な介在物を形成して靭性を劣化させる。したがってＣａを含有する場合、Ｃａ量は０．００５０％以下とする。好ましくは０．００３０％以下である。好ましいＣａ含有量下限値は０．０００３％である。 Ca refines the structure of the weld heat affected zone and improves toughness. However, if it exceeds 0.0050%, coarse inclusions are formed and the toughness is deteriorated. Therefore, when Ca is contained, the amount of Ca is set to 0.0050% or less. It is preferably 0.0030% or less. The preferable lower limit of Ca content is 0.0003%.
　Ｂは鋼の焼入れ性を向上させる元素であり、圧延後の鋼の強度及び靭性を向上させる。しかしながら、０．００３０％を超えると溶接性および靭性の劣化を引き起こす。したがってＢを含有する場合、Ｂ量は０．００３０％以下とする。好ましくは０．００２０％以下である。好ましいＢ含有量下限値は０．０００３％である。 B is an element that improves the hardenability of steel and improves the strength and toughness of rolled steel. However, if it exceeds 0.0030%, it causes deterioration of weldability and toughness. Therefore, when B is contained, the amount of B is set to 0.0030% or less. It is preferably 0.0020% or less. The preferable lower limit of the B content is 0.0003%.
　ＲＥＭは溶接熱影響部の組織を微細化し、靭性を向上させる。しかしながら、０．０１００％を超えると粗大な介在物を形成して靭性を劣化させる。したがってＲＥＭを含有する場合、ＲＥＭ量は０．０１００％以下とする。好ましくは０．００５％以下である。好ましいＲＥＭ含有量下限値は０．０００３％である。 REM refines the structure of the weld heat affected zone and improves toughness. However, if it exceeds 0.0100%, coarse inclusions are formed and the toughness is deteriorated. Therefore, when REM is contained, the amount of REM is 0.0100% or less. It is preferably 0.005% or less. The preferred lower limit of REM content is 0.0003%.
　ここで、ＲＥＭとは、ランタノイドの１５元素にＹおよびＳｃを合せた１７元素の総称である。これらの１７元素のうちの１種以上を鋼材に含有することができ、ＲＥＭ含有量は、これらの元素の合計含有量を意味する。 Here, REM is a general term for 17 elements in which Y and Sc are combined with 15 elements of lanthanoids. One or more of these 17 elements can be contained in the steel material, and the REM content means the total content of these elements.
　本発明の母材の化学組成において、残部はＦｅおよび不純物である。ここで「不純物」とは、鋼材を工業的に製造する際に、鉱石、スクラップ等の原料、製造工程の種々の要因によって混入する成分であって、本発明に悪影響を与えない範囲で許容されるものを意味する。 In the chemical composition of the base material of the present invention, the balance is Fe and impurities. Here, the "impurity" is a component mixed by various factors of raw materials such as ore and scrap, and various factors in the manufacturing process when steel materials are industrially manufactured, and is allowed as long as it does not adversely affect the present invention. Means something.
　４．耐食性合金が、Ｃｒを１０％以上含有するステンレス鋼またはニッケル基合金
　本発明の合せ材は、耐食性合金からなる。前述のように、耐食性合金はＣｒを多く含有し、そのＣｒの拡散によってクラッド界面の焼入れ性が上がりマルテンサイトに変態しやすくなるとともに、母材側の炭素が合せ材側に拡散し、母材側界面に硬質なマルテンサイト相が形成され、接合面の耐水素脆化性を低下させる原因となる。即ち、Ｃｒを多く含有する耐食性合金を用いる場合に、本発明の効果が発揮される。合せ材のＣｒ含有量が１０％以上であれば、本発明を適用することによる効果が顕著に表れる。Ｃｒ含有量が１５％以上であればより顕著に効果が発揮できる。 4. The corrosion-resistant alloy is a stainless steel or nickel-based alloy containing 10% or more of Cr. The laminated material of the present invention is made of a corrosion-resistant alloy. As described above, the corrosion-resistant alloy contains a large amount of Cr, and the diffusion of Cr increases the hardenability of the clad interface and facilitates the transformation to martensite, and the carbon on the base metal side diffuses to the mating material side to diffuse the base metal. A hard martensite phase is formed at the side interface, which causes a decrease in hydrogen embrittlement resistance of the joint surface. That is, the effect of the present invention is exhibited when a corrosion-resistant alloy containing a large amount of Cr is used. When the Cr content of the laminated material is 10% or more, the effect of applying the present invention is remarkable. If the Cr content is 15% or more, the effect can be more remarkable.
　本発明は接合界面組織の制御による、接合面の耐水素脆化性に優れたクラッド鋼板およびその製造方法についての技術であり、合せ材の鋼種は特に規定されないが、合せ材の例としてステンレス鋼またはニッケル基合金を例示できる。ステンレス鋼にはオーステナイト系ステンレス鋼、フェライト系ステンレス鋼、二相系ステンレス鋼があり、ニッケル基合金にはインコネル、インコロイ、ハステロイなどの商品名で種々の合金成分がある。 The present invention is a technique for a clad steel sheet having excellent hydrogen embrittlement resistance of a joint surface and a method for manufacturing the same by controlling the joint interface structure. The steel type of the laminated material is not particularly specified, but stainless steel is an example of the laminated material. Alternatively, a nickel-based alloy can be exemplified. Stainless steels include austenite-based stainless steels, ferrite-based stainless steels, and two-phase stainless steels, and nickel-based alloys have various alloy components under trade names such as Inconel, Incoloy, and Hastelloy.
　５．製造方法　
　本発明に係るクラッド鋼板の製造方法について説明する。前述のように良好な接合面の耐水素脆化性を得るためには金属組織を制御する必要があるが、そのような金属組織は鋼の化学組成と適切な製造条件を組み合わせることで実現できる。
　上記のクラッド鋼板において、母材と合せ材を圧着面が真空になるよう積層して圧着面の４周を溶接により密封してクラッド素材とする。１又は２以上のクラッド素材を組み立ててクラッド圧延素材とする。組み立てたクラッド圧延素材について、加熱炉内の最高加熱温度Ｔ（℃）、加熱炉内での加熱温度が最高加熱温度Ｔ－２０℃となった時点から加熱炉抽出までの時間ｔ（分）、素材厚／製品厚で計算される圧下比ｒによって式（２）で計算されるｄが１以上９以下である加熱と熱間圧延を行い、圧延後に式（３）で計算されるＴＡ３（℃）～６５０℃区間の平均冷却速度が２℃／ｓ以上の冷却を実施し、クラッド鋼板を製造する。
　ｄ＝２．２×１０５×√（ｅｘｐ（－３．２×１０４／（Ｔ＋２７３））×ｔ）／ｒ　・・・式（２）
　ＴＡ３（℃）＝９３７．２－４３６．５Ｃ＋５６Ｓｉ－１９．７Ｍｎ－２６．６Ｎｉ＋１３６．３Ｔｉ－１９．１Ｎｂ＋１９８．４Ａｌ　・・・式（３）
式中、Ｃ、Ｓｉ、Ｍｎ、Ｎｉ、Ｔｉ、ＮｂおよびＡｌは、母材鋼板の成分組成における各元素の含有量（質量％）である。 5. Production method
A method for manufacturing a clad steel sheet according to the present invention will be described. As mentioned above, it is necessary to control the metallographic structure in order to obtain good hydrogen embrittlement resistance of the joint surface, and such a metallographic structure can be realized by combining the chemical composition of steel and appropriate manufacturing conditions. ..
In the above-mentioned clad steel sheet, the base material and the laminated material are laminated so that the crimping surface becomes a vacuum, and the four circumferences of the crimping surface are sealed by welding to form a clad material. Assemble one or more clad materials into a clad rolled material. For the assembled clad-rolled material, the maximum heating temperature T (° C.) in the heating furnace, the time t (minutes) from the time when the heating temperature in the heating furnace reaches the maximum heating temperature T-20 ° C. to the extraction into the heating furnace, T A3 by the reduction ratio r which is calculated by the material thickness / product thickness d is calculated by the equation (2) performs a heating and hot rolling is 1 to 9, which is calculated by the equation (3) after rolling ( A clad steel plate is manufactured by cooling at an average cooling rate of 2 ° C./s or more in the section from (° C.) to 650 ° C.
d = 2.2 × 10 5 × √ (exp (-3.2 × 10 4 / (T + 273)) × t) / r ・ ・ ・ Equation (2)
T A3 (℃) = 937.2-436.5C + 56Si-19.7Mn-26.6Ni + 136.3Ti-19.1Nb + 198.4Al ··· formula (3)
In the formula, C, Si, Mn, Ni, Ti, Nb and Al are the contents (mass%) of each element in the component composition of the base steel sheet.
　５－１クラッド素材
　クラッド素材は、以下に記載の方法により製造される。具体的には、転炉、電気炉、真空溶解炉等の公知の方法で母材となる炭素鋼および低合金鋼ならびに合せ材となる耐食性合金を溶製した後、連続鋳造法または造塊－分塊法によりスラブを作成する。得られたスラブを通常用いられる条件で熱間圧延し、熱延板である合せ材及び母材とする。得られた熱延板に対し、必要に応じて、焼鈍、酸洗、研磨などを施してもよい。
　上記の合せ材および母材を圧着面が真空になるよう積層して圧着面の４周を溶接により密封してクラッド素材を組み立てる。密着性や界面耐食性を改善するために合せ材と母材の間にＮｉ箔などインサート材を挿入しても良い。圧着面を真空にする方法は特に規定されないが、真空中で電子ビーム溶接する方法や、予め真空引き用の穴を開けておき大気中でアーク溶接やレーザー溶接で４周を溶接した後に真空ポンプで真空引きする方法などが例示できる。真空度（絶対圧）は０．１Ｔｏｒｒ以下であれば界面の酸化物などが少ない良好な接合界面が得られ、より好ましくは０．０５Ｔｏｒｒ以下であり、真空度は高いほど（絶対圧が低いほど）接合界面が良好になる傾向が有るため特に下限は設けない。
　得られたクラッド素材はそのままクラッド圧延素材として熱間圧延に供してもよいし、２つのクラッド素材の間に剥離剤を塗布して重ねるように組み立てたものをクラッド圧延素材として熱間圧延に供してもよい。２つを重ねる場合は冷却時の板反りを少なくするために母材同士、合せ材同士はそれぞれ等厚であることが望ましい。もちろん、上記で記述した組立方式に限定する必要はない。 5-1 Clad material The clad material is produced by the method described below. Specifically, after melting carbon steel and low alloy steel as a base material and corrosion resistant alloy as a binder by a known method such as a converter, an electric furnace, a vacuum melting furnace, etc., a continuous casting method or ingot formation- Create a slab by the slab method. The obtained slab is hot-rolled under commonly used conditions to obtain a laminated lumber and a base material which are hot-rolled plates. The obtained hot-rolled plate may be annealed, pickled, polished or the like, if necessary.
The above-mentioned laminated material and base material are laminated so that the crimping surface becomes a vacuum, and the four circumferences of the crimping surface are sealed by welding to assemble the clad material. An insert material such as Ni foil may be inserted between the laminated material and the base material in order to improve the adhesion and the interfacial corrosion resistance. The method of evacuating the crimping surface is not particularly specified, but a method of electron beam welding in vacuum or a vacuum pump after making holes for vacuuming in advance and welding 4 laps by arc welding or laser welding in the atmosphere. An example is a method of evacuating with. If the degree of vacuum (absolute pressure) is 0.1 Torr or less, a good bonding interface with less oxides at the interface can be obtained, more preferably 0.05 Torr or less, and the higher the degree of vacuum (the lower the absolute pressure). ) Since the bonding interface tends to be good, no lower limit is set.
The obtained clad material may be used as it is for hot rolling as a clad rolling material, or a material assembled by applying a release agent between two clad materials so as to be overlapped is used for hot rolling as a clad rolling material. You may. When two are stacked, it is desirable that the base materials and the laminated materials have the same thickness in order to reduce the plate warpage during cooling. Of course, it is not necessary to limit the assembly method described above.
　５－２．熱間圧延
　続いて、得られたクラッド圧延素材を加熱炉内の最高加熱温度Ｔ（℃）、加熱炉内での加熱温度が最高加熱温度Ｔ－２０℃となった時点から加熱炉抽出までの時間ｔ（分）、素材厚／製品厚で計算される圧下比ｒによって式（３）で計算されるｄが１以上９以下である加熱と熱間圧延を行う。ｄが９超の場合は製品界面で元素拡散距離が長くなるため、マルテンサイト変態が生じ得る領域の幅が大きくなり、界面の耐水素脆化性が低下する。好ましくはｄが７以下である。ｄが１未満では界面での元素拡散が少なすぎ、十分な接合強度が得られない。好ましくはｄが３以上である。
　ｄ＝２．２×１０５×√（ｅｘｐ（－３．２×１０４／（Ｔ＋２７３））×ｔ）／ｒ　・・・式（２） 5-2. Hot Rolling Subsequently, the obtained clad-rolled material is subjected to the maximum heating temperature T (° C.) in the heating furnace and the maximum heating temperature T-20 ° C. in the heating furnace from the time when the heating furnace extraction occurs. Heating and hot rolling are performed in which d calculated by the formula (3) is 1 or more and 9 or less based on the reduction ratio r calculated by the time t (minutes) and the material thickness / product thickness. When d exceeds 9, the element diffusion distance becomes long at the product interface, so that the width of the region where martensitic transformation can occur becomes large, and the hydrogen embrittlement resistance of the interface decreases. Preferably d is 7 or less. If d is less than 1, the element diffusion at the interface is too small and sufficient bonding strength cannot be obtained. Preferably d is 3 or more.
d = 2.2 × 10 5 × √ (exp (-3.2 × 10 4 / (T + 273)) × t) / r ・ ・ ・ Equation (2)
　加熱炉内の最高加熱温度Ｔ（℃）、加熱炉内での加熱温度が最高加熱温度Ｔ－２０℃となった時点から加熱炉抽出までの時間ｔ（分）、素材厚／製品厚で計算される圧下比ｒはｄが上記範囲内となるように適宜定めれば良いが、界面の耐水素脆化性以外の特性や製造性の観点から以下に好ましい範囲を例示する。
　加熱炉内の最高加熱温度Ｔは１０５０～１２５０℃とするのが好ましい。最高加熱温度Ｔが１０５０℃未満であると熱間加工性が悪化し、接合強度も劣化する。このため、最高加熱温度Ｔは１０５０℃以上であるのが好ましく、１１００℃以上であるのがより好ましい。一方、最高加熱温度Ｔが１２５０℃超であると、加熱炉内で鋼片が変形したり熱延時に疵が生じやすくなったりするとともに、界面での拡散が速くなる。このため、最高加熱温度Ｔは１２５０℃以下であるのが好ましく、１２２０℃以下であるのがより好ましい。
　加熱炉内での加熱温度が最高加熱温度Ｔ－２０℃となった時点から加熱炉抽出までの時間ｔ（分）は短いほど界面での元素拡散距離が短くなるため下限は特に設けないが、板厚中央まで温度を均一にさせるには３０分以上の加熱が望ましい。
　素材厚／製品厚で計算される圧下比ｒは３以上１５以下とすることが好ましい。圧下比ｒが３未満である場合は圧延による界面接合が不十分で界面のせん断強度が低くなる可能性がある。より好ましくは５以上である。また圧下比が１５超である場合は圧延時間が長くなり圧延コストが増加する。より好ましくは１０以下である。 Calculated by the maximum heating temperature T (° C) in the heating furnace, the time t (minutes) from the time when the heating temperature in the heating furnace reaches the maximum heating temperature T-20 ° C to the extraction in the heating furnace, and the material thickness / product thickness. The reduced reduction ratio r may be appropriately determined so that d is within the above range, but a preferable range is exemplified below from the viewpoint of properties other than the hydrogen brittle resistance of the interface and manufacturability.
The maximum heating temperature T in the heating furnace is preferably 1050 to 1250 ° C. If the maximum heating temperature T is less than 1050 ° C., the hot workability deteriorates and the bonding strength also deteriorates. Therefore, the maximum heating temperature T is preferably 1050 ° C. or higher, and more preferably 1100 ° C. or higher. On the other hand, when the maximum heating temperature T is more than 1250 ° C., the steel pieces are easily deformed in the heating furnace and flaws are likely to occur during hot rolling, and the diffusion at the interface becomes faster. Therefore, the maximum heating temperature T is preferably 1250 ° C. or lower, and more preferably 1220 ° C. or lower.
The shorter the time t (minutes) from the time when the heating temperature in the heating furnace reaches the maximum heating temperature T-20 ° C. to the extraction in the heating furnace, the shorter the element diffusion distance at the interface, so no lower limit is set. Heating for 30 minutes or more is desirable to make the temperature uniform up to the center of the plate thickness.
The reduction ratio r calculated by the material thickness / product thickness is preferably 3 or more and 15 or less. If the reduction ratio r is less than 3, the interfacial bonding by rolling may be insufficient and the shear strength of the interface may be low. More preferably, it is 5 or more. If the rolling ratio is more than 15, the rolling time becomes long and the rolling cost increases. More preferably, it is 10 or less.
　上述のように、界面のマルテンサイト相の領域の大きさは、Ｃｒの拡散が主に影響する。Ｃｒ拡散は数百℃以上の温度で生じるものの、温度が高くなるに連れて拡散距離は指数関数的に大きくなるため、実質的な拡散は素材加熱時間のうち最高温度近傍で保持されている間で生じる。また圧延時および冷却時は板温度が速やかに低下するため拡散は無視できるほど小さい。したがって、製品のＣｒ拡散距離は加熱時に生じた拡散距離が圧下比の割合だけ小さくなると考えてよい。なお筆者らは種々の加熱温度・時間・圧下比のクラッド製品について界面の薄膜ＴＥＭ観察によるマルテンサイト相の領域の大きさの測定を実施し、加熱炉内の最高温度Ｔ（℃）、加熱炉内での加熱温度が最高加熱温度Ｔ－２０℃となった時点から加熱炉抽出までの時間ｔ（分）と圧下比ｒから式（２）で計算した値ｄがマルテンサイト相の領域の大きさと精度良く対応していることを確認している。 As mentioned above, the size of the martensite phase region at the interface is mainly affected by the diffusion of Cr. Although Cr diffusion occurs at a temperature of several hundred degrees Celsius or higher, the diffusion distance increases exponentially as the temperature rises, so that the actual diffusion is maintained near the maximum temperature during the material heating time. Occurs in. In addition, the diffusion is negligibly small because the plate temperature drops rapidly during rolling and cooling. Therefore, it can be considered that the Cr diffusion distance of the product is such that the diffusion distance generated during heating is reduced by the ratio of the reduction ratio. The authors measured the size of the martensite phase region by TEM observation of the thin film at the interface for clad products with various heating temperatures, times, and reduction ratios, and measured the maximum temperature T (° C.) in the heating furnace and the heating furnace. The time t (minutes) from the time when the heating temperature in the room reaches the maximum heating temperature T-20 ° C. to the extraction into the heating furnace and the value d calculated by the equation (2) from the reduction ratio r are the sizes of the martensite phase region. We have confirmed that it corresponds accurately with.
　５－３．圧延後の冷却
　圧延後に式（３）から計算されるＴＡ３（℃）～６５０℃区間の平均冷却速度は２℃／ｓ以上とすることが望ましい。２℃／ｓ未満の冷却速度ではオーステナイト→フェライト変態やオーステナイト→フェライト＋パーライト変態に伴い、界面のマルテンサイトになり得るオーステナイト領域に炭素が拡散して濃化するため、ナノ硬さが７ＧＰａ以上となる領域の幅が増加する。好ましくは４℃／ｓ以上である。上限は特に設けないが、冷却速度が速い場合マルテンサイト組織が主となり母材が高強度となりすぎたり靭性が劣化したりするため、望ましくは１０℃／ｓ以下である。
　ＴＡ３（℃）＝９３７．２－４３６．５Ｃ＋５６Ｓｉ－１９．７Ｍｎ－２６．６Ｎｉ＋１３６．３Ｔｉ－１９．１Ｎｂ＋１９８．４Ａｌ　・・・式（３）
式中、Ｃ、Ｓｉ、Ｍｎ、Ｎｉ、Ｔｉ、ＮｂおよびＡｌは、母材鋼板の成分組成における各元素の含有量（質量％）である。 5-3. Cooling after rolling It is desirable that the average cooling rate in the TA3 (° C) to 650 ° C section calculated from equation (3) after rolling is 2 ° C / s or more. At a cooling rate of less than 2 ° C / s, carbon diffuses and concentrates in the austenite region, which can become martensite at the interface, due to austenite → ferrite transformation or austenite → ferrite + pearlite transformation, so the nanohardness is 7 GPa or more. The width of the area is increased. It is preferably 4 ° C./s or higher. Although no upper limit is set, it is preferably 10 ° C./s or less because the martensite structure becomes the main component and the base metal becomes too high in strength or the toughness deteriorates when the cooling rate is high.
T A3 (℃) = 937.2-436.5C + 56Si-19.7Mn-26.6Ni + 136.3Ti-19.1Nb + 198.4Al ··· formula (3)
In the formula, C, Si, Mn, Ni, Ti, Nb and Al are the contents (mass%) of each element in the component composition of the base steel sheet.
　本発明によれば、接合面の耐水素脆化性に優れたクラッド鋼板を得ることができる。本発明に係るクラッド鋼板、及び本発明のクラッド鋼板を用いてなる溶接構造物は、溶接時の剥離対策や付加的な熱処理などを必要としない。界面のマルテンサイトの硬度と幅を本発明とすれば、鋼中の水素濃度またはマルテンサイトに付加される応力を制御することから解放される。また、上記クラッド鋼板は、使用用途の制限がなく、従来、ソリッド鋼板が用いられていた構造部材に適用できる。このため、上記クラッド鋼板は、低コスト化に大きく貢献するものである。本発明のクラッド鋼板を用いてなる溶接構造物は、水素を含むガスを使用する溶接またはガウジングを含む製造工程で製造した溶接構造物とすることができる。 According to the present invention, it is possible to obtain a clad steel sheet having excellent hydrogen embrittlement resistance on the joint surface. The clad steel plate according to the present invention and the welded structure using the clad steel plate of the present invention do not require peeling measures at the time of welding or additional heat treatment. The present invention frees us from controlling the hydrogen concentration in steel or the stress applied to martensite, if the hardness and width of the martensite at the interface are defined in the present invention. Further, the clad steel sheet has no limitation on the intended use, and can be applied to a structural member in which a solid steel sheet has been conventionally used. Therefore, the clad steel sheet greatly contributes to cost reduction. The welded structure made of the clad steel sheet of the present invention can be a welded structure manufactured by a manufacturing process including welding using a gas containing hydrogen or gouging.
　本発明のクラッド鋼板は、耐水素脆化性に優れるので、溶接ガスに水素を用いた溶接に使用しても水素脆化が生じることがない。 Since the clad steel sheet of the present invention has excellent hydrogen embrittlement resistance, hydrogen embrittlement does not occur even when it is used for welding using hydrogen as a welding gas.
　以下、実施例によって本発明をより具体的に説明するが、本発明はこれらの実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
　表１に示す化学組成の合せ材および表２に示す化学組成の母材を溶製して鋼片とし、熱間圧延、焼鈍、酸洗の工程を経て合せ材は厚さ３０ｍｍ、母材は厚さ１３０ｍｍの鋼板を製造した。得られた合せ材と母材を素材として、母材と合せ材を圧着面が真空になるよう積層して圧着面の４周を溶接により密封してクラッド素材を作成した。２つのクラッド素材を母材－合せ材－剥離剤－合せ材－母材となるように合せ材と合せ材の間に剥離剤を塗布して重ね、クラッド圧延素材として組み立てた。得られたクラッド圧延素材について、表３に示す熱間圧延条件で熱間圧延を行った後に剥離剤部分で剥離させ、厚さ５３ｍｍ（圧下比３）～１２ｍｍ（圧下比１３）のクラッド鋼板を製造した。 The combined material with the chemical composition shown in Table 1 and the base material with the chemical composition shown in Table 2 are melted into steel pieces, and after undergoing the steps of hot rolling, annealing, and pickling, the combined material has a thickness of 30 mm, and the base material has a thickness of 30 mm. A steel plate having a thickness of 130 mm was manufactured. Using the obtained laminated lumber and base material as materials, the base material and the combined material were laminated so that the crimping surface became a vacuum, and four circumferences of the crimping surface were sealed by welding to prepare a clad material. The two clad materials were laminated by applying a release agent between the laminated materials so as to form a base material-laminated material-stripping agent-laminated material-base material, and assembled as a clad rolled material. The obtained clad-rolled material was hot-rolled under the hot-rolling conditions shown in Table 3 and then peeled off at the release agent portion to obtain a clad steel sheet having a thickness of 53 mm (compression ratio 3) to 12 mm (compression ratio 13). Manufactured.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　クラッド鋼板の圧延において表３に記載の条件を変化させ、各特性値を調べた。以下、表３における製造条件の項目について説明する。表３において、Ｔは圧延前の加熱炉内の最高加熱温度（℃）を示し、ｔは加熱炉内での加熱温度が最高加熱温度Ｔ－２０℃となった時点から加熱炉抽出までの時間（分）を示す。ｒは素材厚／製品厚で計算される圧下比を示す。ｄは上記Ｔ、ｔ、ｒから式（２）で計算される値を示す。ＴＡ３は母材の化学組成から式（３）で計算される値（℃）を示す。ＣＲはＴＡ３（℃）～６５０℃までの平均冷却速度（℃／ｓ）を示す。Ｌは界面近傍でナノ硬さが７ＧＰａ以上である領域の幅（μｍ）を示す。耐水素は耐水素脆化性評価試験の結果であり、Ａは耐水素脆化性が良好、Ｘは不良を示す。
　ｄ＝２．２×１０５×√（ｅｘｐ（－３．２×１０４／（Ｔ＋２７３））×ｔ）／ｒ　・・・式（２）
　ＴＡ３（℃）＝９３７．２－４３６．５Ｃ＋５６Ｓｉ－１９．７Ｍｎ－２６．６Ｎｉ＋１３６．３Ｔｉ－１９．１Ｎｂ＋１９８．４Ａｌ　・・・式（３）
式中、Ｃ、Ｓｉ、Ｍｎ、Ｎｉ、Ｔｉ、ＮｂおよびＡｌは、母材鋼板の成分組成における各元素の含有量（質量％）である。 In the rolling of the clad steel sheet, the conditions shown in Table 3 were changed, and each characteristic value was examined. Hereinafter, the items of the manufacturing conditions in Table 3 will be described. In Table 3, T indicates the maximum heating temperature (° C.) in the heating furnace before rolling, and t is the time from the time when the heating temperature in the heating furnace reaches the maximum heating temperature T-20 ° C. to the extraction into the heating furnace. (Minute) is shown. r indicates the reduction ratio calculated by the material thickness / product thickness. d represents a value calculated by the equation (2) from the above T, t, and r. TA3 represents a value (° C.) calculated by the formula (3) from the chemical composition of the base material. CR indicates the average cooling rate (° C./s) from TA3 (° C.) to 650 ° C. L indicates the width (μm) of the region where the nanohardness is 7 GPa or more in the vicinity of the interface. Hydrogen resistance is the result of the hydrogen embrittlement resistance evaluation test. A indicates good hydrogen embrittlement resistance, and X indicates poor hydrogen embrittlement resistance.
d = 2.2 × 10 5 × √ (exp (-3.2 × 10 4 / (T + 273)) × t) / r ・ ・ ・ Equation (2)
T A3 (℃) = 937.2-436.5C + 56Si-19.7Mn-26.6Ni + 136.3Ti-19.1Nb + 198.4Al ··· formula (3)
In the formula, C, Si, Mn, Ni, Ti, Nb and Al are the contents (mass%) of each element in the component composition of the base steel sheet.
　ナノ硬さの測定はＩＳＯ　１４５７７に規定する計装化押し込み硬さ試験に準拠し、合せ材側、母材側に界面から板厚方向に各１０μｍ範囲を０．５μｍピッチでナノ硬さを測定した。ナノ硬さ測定の条件は適宜選択すればよいが、例えば荷重１０００μＮ、押し込み指定荷重まで５ｓｅｃ、保持０ｓｅｃ、戻り５ｓｅｃとする測定を各位置で３回実施し、その平均値をナノ硬さとする測定を例示できる。ナノ硬さが７ＧＰａ以上ある領域の範囲を読み取り、Ｌとした。なお、合せ材と母材の間にＮｉ箔などインサート材を挿入した場合は、合せ材とインサート材の界面、インサート材と母材の界面について、それぞれ測定すれば良い。 The measurement of nano-hardness is based on the instrumentation indentation hardness test specified in ISO 14577, and the nano-hardness is measured at a pitch of 0.5 μm in the range of 10 μm from the interface on the mating material side and the base material side in the plate thickness direction. bottom. The conditions for nano-hardness measurement may be appropriately selected. For example, measurements with a load of 1000 μN, a push-in specified load of 5 sec, a hold of 0 sec, and a return of 5 sec are performed three times at each position, and the average value is taken as the nano-hardness. Can be exemplified. The range of the region where the nanohardness was 7 GPa or more was read and designated as L. When an insert material such as Ni foil is inserted between the laminated material and the base material, the interface between the laminated material and the insert material and the interface between the insert material and the base material may be measured respectively.
　耐水素脆化性の評価として下記の試験を実施した。試験片は板厚方向の長さを確保するため、クラッド鋼板の合せ材側に合せ材と同じ鋼種を溶接し、母材側に母材と同じ鋼種を溶接し、クラッド界面を含む平行部が４φ×２０ｍｍでクラッド界面に６０°、ρ＝０．１ｍｍ、のノッチを入れて３φとした丸棒試験片を作成した。溶接による熱影響を抑制するため、溶接方法として入熱が小さく溶接金属の幅を小さくできる電子ビーム溶接を選択し、溶接後に研削を実施した。なお、試験片の断面観察を実施し、溶接金属が界面から２ｍｍ以上離れていることを確認している。
　作成した試験片を引張前に３質量％ＮａＣｌ＋３ｇ／Ｌ・ＮＨ４ＳＣＮ水溶液中で電流密度１０（Ａ／ｍ２）×７２（ｈｒ）の陰極チャージを行った後、３％ＮａＣｌ＋３ｇ／Ｌ・ＮＨ４ＳＣＮ水溶液中で１０（Ａ／ｍ２）陰極チャージしながら平行部の歪速度：１×１０－３（１／ｓ）で破断まで引っ張った。引張前および引張中の陰極チャージをせずに引っ張る試験を別途実施し、破断までのストロークを比較し、チャージ有り材のストローク／チャージ無し材のストロークが０．２５以上であれば良好と評価して表３の「耐水素」欄に「Ａ」と表記し、０．２５未満であれば不良と評価して表３の「耐水素」欄に「Ｘ」と表記した。 The following tests were carried out to evaluate the hydrogen embrittlement resistance. In order to secure the length of the test piece in the plate thickness direction, the same steel type as the mating material is welded to the mating material side of the clad steel plate, and the same steel type as the base material is welded to the base material side, and the parallel part including the clad interface is formed. A round bar test piece having a size of 4φ × 20 mm and having a notch of 60 ° and ρ = 0.1 mm was formed at the clad interface to make 3φ. In order to suppress the heat effect of welding, electron beam welding, which has a small heat input and can reduce the width of the weld metal, was selected as the welding method, and grinding was performed after welding. The cross section of the test piece was observed to confirm that the weld metal was separated from the interface by 2 mm or more.
The prepared test piece was charged with a cathode having a current density of 10 (A / m 2 ) × 72 (hr) in a 3 mass% NaCl + 3 g / L · NH 4 SCN aqueous solution before tensioning, and then 3% NaCl + 3 g / L · NH. 4 While charging the cathode at 10 (A / m 2 ) in the SCN aqueous solution, the strain was pulled to break at the strain rate of the parallel portion: 1 × 10 -3 (1 / s). A separate test was conducted to pull the material before and during tensioning without charging the cathode, and the strokes until fracture were compared. If the stroke of the charged material / the stroke of the uncharged material was 0.25 or more, it was evaluated as good. In the "hydrogen resistance" column of Table 3, "A" was written, and if it was less than 0.25, it was evaluated as defective and "X" was written in the "hydrogen resistance" column of Table 3.
　製造条件および上記の結果をまとめて表３および図１に示す。図１は、式（２）の値ｄを横軸、熱間圧延後のＴＡ３（℃）～６５０℃までの平均冷却速度ＣＲを縦軸とし、白丸は耐水素脆化性が良好、Ｘ印は不良を示す図である。 The production conditions and the above results are summarized in Table 3 and FIG. In FIG. 1, the value d of the formula (2) is on the horizontal axis, the average cooling rate CR from TA3 (° C.) to 650 ° C. after hot rolling is on the vertical axis, and the white circles have good hydrogen embrittlement resistance, X. The mark is a diagram showing a defect.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　試料番号１～４１は本発明例であり、好ましい製造条件を満足し、ナノ硬さが７ＧＰａ以上である領域の長さＬが５μｍ以下であり、良好な接合面の耐水素脆化性を有する。試料番号４２～４７は比較例であり、好ましい製造条件を満足せず、ナノ硬さが７ＧＰａ以上である領域の長さＬが５μｍ超であり、接合面の耐水素脆化性が不良である。 Sample numbers 1 to 41 are examples of the present invention, satisfying preferable production conditions, having a region length L of 5 μm or less having a nanohardness of 7 GPa or more, and having good hydrogen embrittlement resistance of the joint surface. .. Sample numbers 42 to 47 are comparative examples, do not satisfy preferable production conditions, have a length L of a region having a nanohardness of 7 GPa or more of more than 5 μm, and have poor hydrogen embrittlement resistance of the joint surface. ..
　上述したように、本発明例では良好な接合面の耐水素脆化性が得られた。一方、比較例では好ましい製造条件を満足せず、ナノ硬さが７ＧＰａ以上である領域の長さが本発明の規定から外れたため、接合面の耐水素脆化性が不良であった。 As described above, in the example of the present invention, good hydrogen embrittlement resistance of the joint surface was obtained. On the other hand, in the comparative example, the preferable production conditions were not satisfied, and the length of the region where the nanohardness was 7 GPa or more was out of the specification of the present invention, so that the hydrogen embrittlement resistance of the joint surface was poor.
　本発明によれば、接合面の耐水素脆化性が良好なクラッド鋼板を得ることができ、産業上極めて有用である。合せ材として耐食性合金を適用すれば、本発明のクラッド鋼板は、腐食環境として、海水に曝されるような高塩化物環境、リン酸または硫酸などの酸溶液に曝されるプラント設備等での腐食環境等に適用可能性がある。具体的には、海水淡水化プラント、排煙脱硫装置、化学薬品の保存タンク、油井管等の構造部材、ポンプ・バルブ類、熱交換器などである。 According to the present invention, a clad steel sheet having good hydrogen embrittlement resistance on the joint surface can be obtained, which is extremely useful in industry. If a corrosion-resistant alloy is applied as the laminate, the clad steel sheet of the present invention can be used in a high chloride environment such as that exposed to seawater, or in plant equipment exposed to an acid solution such as phosphoric acid or sulfuric acid as a corrosive environment. It may be applied to corrosive environments. Specific examples include seawater desalination plants, flue gas desulfurization equipment, chemical storage tanks, structural members such as oil country tubular goods, pumps and valves, and heat exchangers.

Claims (7)

  1. 　母材と、前記母材に接合された合せ材とを備えるクラッド鋼板であって、
    　前記母材は、炭素鋼または低合金鋼からなり、
    　前記合せ材は、耐食性合金からなり、
    　クラッド鋼板の母材と合せ材の界面において、ナノ硬さが７ＧＰａ以上である領域の板厚方向の幅が５μｍ以下であることを特徴とするクラッド鋼板。     A clad steel sheet including a base material and a laminated material joined to the base material.
    The base material is made of carbon steel or low alloy steel.
    The laminated material is made of a corrosion-resistant alloy and is made of a corrosion-resistant alloy.
    A clad steel sheet having a width in the plate thickness direction of 5 μm or less in a region where the nanohardness is 7 GPa or more at the interface between the base material and the laminated material of the clad steel sheet.
  2. 　請求項１に記載のクラッド鋼板において母材の化学組成が質量％でＣ：０．０２０～０．２００％、Ｓｉ：１．００％以下、Ｍｎ：０．１０～３．００％、Ｐ：０．０５０％以下、Ｓ：０．０５０％を含有し、かつＣｅｑが０．２０～０．４０であり、残部がＦｅ及び不純物からなる成分組成を有する請求項１に記載のクラッド鋼板。ここで、Ｃｅｑは次式（１）により定義される。
    Ｃｅｑ＝Ｃ＋Ｍｎ／６＋（Ｃｕ＋Ｎｉ）／１５＋（Ｃｒ＋Ｍｏ＋Ｖ）／５・・・式（１）式中、Ｃ、Ｍｎ、Ｃｕ、Ｎｉ、Ｃｒ、ＭｏおよびＶは、母材鋼板の成分組成における各元素の含有量（質量％）である。     In the clad steel sheet according to claim 1, the chemical composition of the base material is mass%, C: 0.020 to 0.200%, Si: 1.00% or less, Mn: 0.10 to 3.00%, P: The clad steel sheet according to claim 1, which contains 0.050% or less, S: 0.050%, has a Ceq of 0.20 to 0.40, and has a component composition in which the balance is composed of Fe and impurities. Here, Ceq is defined by the following equation (1).
    Ceq = C + Mn / 6 + (Cu + Ni) / 15+ (Cr + Mo + V) / 5 ... In formula (1), C, Mn, Cu, Ni, Cr, Mo and V are elements of each element in the composition of the base steel sheet. The content (% by mass).
  3. 　前記母材の成分組成が、さらに前記Ｆｅの一部に替えて、質量％で、Ｎｉ：０．０１～１．００％、Ｃｒ：０．０１～１．００％、Ｍｏ：０．０１～０．５０％、Ｃｕ：０．０１～１．００％、Ｃｏ：０．０１～０．５０％，Ｓｅ＋Ｔｅ：０．０１～０．１０％、Ｖ：０．００１～０．１００％、Ｔｉ：０．００１～０．２００％、Ｎｂ：０．００１～０．２００％、Ａｌ：０．００５～０．３００％、Ｃａ：０．０００３～０．００５０％、Ｂ：０．０００３～０．００３０％およびＲＥＭ：０．０００３～０．０１００％から選ばれる１種または２種以上を含有する、請求項２に記載のクラッド鋼板。 The component composition of the base material is further replaced with a part of the Fe, and in mass%, Ni: 0.01 to 1.00%, Cr: 0.01 to 1.00%, Mo: 0.01 to 0.50%, Cu: 0.01 to 1.00%, Co: 0.01 to 0.50%, Se + Te: 0.01 to 0.10%, V: 0.001 to 0.100%, Ti : 0.001 to 0.200%, Nb: 0.001 to 0.200%, Al: 0.005 to 0.300%, Ca: 0.0003 to 0.0050%, B: 0.0003 to 0 The clad steel plate according to claim 2, which contains one or more selected from 0.0003% and REM: 0.0003 to 0.0100%.
  4. 　前記クラッド鋼板の合せ材が、質量％でＣｒ：１０％以上を含有するステンレス鋼またはニッケル基合金であることを特徴とする、請求項１～請求項３のいずれか１項に記載のクラッド鋼板。 The clad steel sheet according to any one of claims 1 to 3, wherein the laminated material of the clad steel sheet is a stainless steel or a nickel-based alloy containing Cr: 10% or more in mass%. ..
  5. 　請求項１～請求項４のいずれか１項に記載のクラッド鋼板において、母材と合せ材を圧着面が真空になるよう積層して圧着面の４周を溶接により密封してクラッド素材とし、１又は２以上の前記クラッド素材を組み立てたクラッド圧延素材について加熱炉内の最高加熱温度Ｔ（℃）、加熱炉内での加熱温度が最高加熱温度Ｔ－２０℃となった時点から加熱炉抽出までの時間ｔ（分）、素材厚／製品厚で計算される圧下比ｒによって式（２）で計算されるｄが１以上９以下である加熱と熱間圧延を行い、圧延後に式（３）で計算されるＴＡ３（℃）～６５０℃区間の平均冷却速度が２℃／ｓ以上の冷却を行い、母材と合せ材の界面のナノ硬さが７ＧＰａ以上である領域の板厚方向の幅を５μｍ以下とすることを特徴とする、請求項１～請求項４のいずれか１項に記載のクラッド鋼板の製造方法。
    　ｄ＝２．２×１０５×√（ｅｘｐ（－３．２×１０４／（Ｔ＋２７３））×ｔ）／ｒ　・・・式（２）
    　ＴＡ３（℃）＝９３７．２－４３６．５Ｃ＋５６Ｓｉ－１９．７Ｍｎ－２６．６Ｎｉ＋１３６．３Ｔｉ－１９．１Ｎｂ＋１９８．４Ａｌ　・・・式（３）
    式中、Ｃ、Ｓｉ、Ｍｎ、Ｎｉ、Ｔｉ、ＮｂおよびＡｌは、母材鋼板の成分組成における各元素の含有量（質量％）である。     In the clad steel plate according to any one of claims 1 to 4, the base material and the laminated material are laminated so that the crimping surface becomes vacuum, and the four circumferences of the crimping surface are sealed by welding to form a clad material. Extraction from the heating furnace from the time when the maximum heating temperature T (° C.) in the heating furnace and the heating temperature in the heating furnace reach the maximum heating temperature T-20 ° C. for the clad rolled material obtained by assembling one or more of the clad materials. The time to time t (minutes), the rolling ratio r calculated by the material thickness / product thickness, and the d calculated by the formula (2) is 1 or more and 9 or less. ), The average cooling rate in the section from TA3 (° C) to 650 ° C is 2 ° C / s or more, and the nano-hardness of the interface between the base material and the laminated material is 7 GPa or more in the plate thickness direction. The method for producing a clad steel sheet according to any one of claims 1 to 4, wherein the width of the clad steel sheet is 5 μm or less.
    d = 2.2 × 10 5 × √ (exp (-3.2 × 10 4 / (T + 273)) × t) / r ・ ・ ・ Equation (2)
    T A3 (℃) = 937.2-436.5C + 56Si-19.7Mn-26.6Ni + 136.3Ti-19.1Nb + 198.4Al ··· formula (3)
    In the formula, C, Si, Mn, Ni, Ti, Nb and Al are the contents (mass%) of each element in the component composition of the base steel sheet.
  6. 　請求項１～請求項４のいずれか１項に記載のクラッド鋼板を用いてなる溶接構造物。 A welded structure using the clad steel sheet according to any one of claims 1 to 4.
  7. 　前記クラッド鋼板が、溶接ガスに水素を用いた溶接に使用されることを特徴とする、請求項１～請求項４のいずれか１項に記載のクラッド鋼板。 The clad steel sheet according to any one of claims 1 to 4, wherein the clad steel sheet is used for welding using hydrogen as a welding gas.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS52102848A (en) * 1976-02-26 1977-08-29 Nippon Steel Corp Method of gas shield arc welding
JPH0657377A (en) * 1992-08-12 1994-03-01 Nippon Steel Corp High corrosion resistant clad steel plate remarkably excellent in interface fracture resistance at working
WO2019189871A1 (en) * 2018-03-30 2019-10-03 日鉄ステンレス株式会社 Two-phase stainless-clad steel sheet and production method thereof
WO2020071343A1 (en) * 2018-10-01 2020-04-09 日鉄ステンレス株式会社 Clad austenitic stainless steel sheet, base steel sheet and method for producing clad steel sheet

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5223360B2 (en) * 2007-03-22 2013-06-26 Ｊｆｅスチール株式会社 High-strength hot-dip galvanized steel sheet with excellent formability and method for producing the same
PL2474639T3 (en) * 2009-08-31 2019-09-30 Nippon Steel & Sumitomo Metal Corporation High-strength galvannealed steel sheet
US10099311B2 (en) * 2013-04-17 2018-10-16 Nippon Steel & Sumitomo Metal Corporation Spot welding method
MY176531A (en) * 2013-10-21 2020-08-13 Jfe Steel Corp Austenitic stainless clad steel plate and method for producing thereof
CN107075645B (en) * 2014-11-11 2020-06-16 杰富意钢铁株式会社 Ni alloy clad steel sheet and method for producing same
US10704132B2 (en) * 2016-02-25 2020-07-07 Nippon Steel Corporation High-strength hot-dip galvanized steel sheet excellent in impact peeling resistance and worked portion corrosion resistance
KR20190084092A (en) * 2017-03-29 2019-07-15 닛폰세이테츠 가부시키가이샤 As-rolled steel pipe for line pipe
CN110303045B (en) * 2019-06-14 2020-07-10 北京科技大学 Preparation method of high-interface bonding strength stainless steel composite plate for knife and scissors

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS52102848A (en) * 1976-02-26 1977-08-29 Nippon Steel Corp Method of gas shield arc welding
JPH0657377A (en) * 1992-08-12 1994-03-01 Nippon Steel Corp High corrosion resistant clad steel plate remarkably excellent in interface fracture resistance at working
WO2019189871A1 (en) * 2018-03-30 2019-10-03 日鉄ステンレス株式会社 Two-phase stainless-clad steel sheet and production method thereof
WO2020071343A1 (en) * 2018-10-01 2020-04-09 日鉄ステンレス株式会社 Clad austenitic stainless steel sheet, base steel sheet and method for producing clad steel sheet

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