EP3674426B1 - Method for production of ni-containing steel plate - Google Patents

Method for production of ni-containing steel plate Download PDF

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EP3674426B1
EP3674426B1 EP18848632.8A EP18848632A EP3674426B1 EP 3674426 B1 EP3674426 B1 EP 3674426B1 EP 18848632 A EP18848632 A EP 18848632A EP 3674426 B1 EP3674426 B1 EP 3674426B1
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steel
temperature
content
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German (de)
English (en)
French (fr)
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EP3674426A4 (en
EP3674426A1 (en
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Akito TABATA
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Kobe Steel Ltd
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Kobe Steel Ltd
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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
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/185—Hardening; Quenching with or without subsequent tempering from an intercritical temperature
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/001—Heat treatment of ferrous alloys containing Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Definitions

  • the present disclosure relates to a method for production of a Ni-containing steel plate.
  • the high-Ni steel plates are relatively inexpensive and are known to exhibit excellent low-temperature toughness by having the functions and effects, such as improvement of the toughness of a matrix of the steel by addition of Ni, the refinement of the microstructure of the steel by a heat treatment, and improvement of the toughness of the steel due to the presence of stable residual austenite (hereinafter sometimes referred to as "residual ⁇ ") even under an ultralow temperature.
  • residual ⁇ stable residual austenite
  • a steel plate (9% Ni steel) having a Ni content of about 9% by mass has been put into practical use in many cases as a material for tanks since it was used in a storage tank for LNG in 1963.
  • the amount of usage of the high-Ni steel plate is also expected to increase in the future.
  • Patent Document 1 discloses a method for production of a steel plate of a Ni-containing steel that has a sufficient low-temperature toughness even though the steel plate is an extremely thick member with a thickness exceeding 40 mm.
  • the Ni-containing steel as a raw material contains C, Ni and Mn in a predetermined content range, and each of the contents of P and S in the impurities is restricted to an extremely low level of 0.001% by weight (mass) or less. Then, this steel is subjected to hot-rolling, followed by quenching twice and tempering under specific conditions. Thus, the steel has improved low-temperature toughness.
  • FIG. 2 shows the results of examining the Charpy impact energy in a rolling direction (L direction) at -196°C and in a direction (C direction) orthogonal to the rolling direction for steel plates which have already been subjected to the above-mentioned heat treatment and then tensile pre-strain of 5%, followed by an aging treatment at 250°C for one hour.
  • Patent Document 1 describes that as shown in FIG. 2, the low-temperature toughnesses of the steel plate itself and a welding joint are drastically improved by setting the P content to 0.001% by weight (mass) or less.
  • Patent Document 1 JP 6-179909 A Further, JP H08 27517 A describes a heat treatment method for producing a 9%-Ni steel sheet.
  • the upper limit of P content needs to be restricted to 0.001% by mass as mentioned in Patent Document 1.
  • Patent Document 1 when the cleanliness of a steel plate is enhanced in order to restrict the upper limit of P content to 0.001% by mass, there occurs a problem of deterioration in the productivity of steel plates.
  • An embodiment of the present invention has been made in light of such circumstances and has an object to provide a method for production of a Ni-containing steel plate that has excellent low-temperature toughness after a plastic strain is applied thereto even when a P content exceeds 0.001% by mass.
  • Ni-containing steel plate that has excellent low-temperature toughness after the plastic strain is applied thereto even when the P content exceeds 0.001% by mass.
  • FIG. 1 is a diagram showing a relationship between the parameter H and the brittle fracture rate after the application of a plastic strain in an embodiment of the present invention.
  • a steel plate excellent in the low-temperature toughness after the application of the plastic strain (hereinafter sometimes referred to as a "strain aging property”) can be produced even when the P content exceeds 0.001% by mass, by controlling a parameter H specified by a heating temperature and a holding time during an intermediate heat treatment as well as a heating temperature and a holding time during a tempering treatment.
  • FIG. 1 is a diagram showing a relationship between the parameter H and the brittle fracture rate of a steel plate after the application of the plastic strain, as an index of the strain aging property.
  • the present inventors have found that by setting the parameter H to 1.73 ⁇ 10 -6 or more and 1.96 ⁇ 10 -6 or less, the brittle fracture rate of the steel plate after the application of the plastic strain can be set to 5% or less, thereby making it possible to produce the steel plate with excellent strain aging property.
  • the diffusion of C and Ni into the metallographic structure of the steel plate is controlled in the embodiment of the present invention by controlling the parameter H (that is, by controlling the heating temperature and the holding time during the intermediate heat treatment and the heating temperature and the holding time during the tempering treatment).
  • the parameter H that is, by controlling the heating temperature and the holding time during the intermediate heat treatment and the heating temperature and the holding time during the tempering treatment.
  • the parameter H increases, the diffusion of C and Ni is promoted during the intermediate heat treatment and the tempering treatment, whereas when the parameter H decreases, the diffusion of C and Ni is suppressed during the intermediate heat treatment and the tempering treatment.
  • the parameter H by controlling the parameter H within a predetermined range, the diffusion of C and Ni is controlled during the intermediate heat treatment and the tempering treatment, thereby consequently controlling the enrichment of C and Ni into the residual ⁇ .
  • the enrichment of C and Ni into the residual ⁇ significantly contributes to the stability of the residual ⁇ , in which the residual ⁇ remains in the steel plate without experiencing the process-induced transformation even when the plastic strain is applied to the steel plate.
  • the steel plate with excellent strain aging property can be produced by compensating for the deterioration of the strain aging property due to an increase in the P content.
  • Basic elements i.e., C, Si, Mn, P, S, Ni, Al, and N will be first described, and further elements which may be selectively added will be then described.
  • Carbon (C) is an element that increases the strength of a steel plate.
  • the C content needs to be 0.040% by mass or more.
  • the C content exceeding 0.060% by mass leads to reduction in the low-temperature toughness.
  • the C content is set at 0.040% by mass or more and 0.060% by mass or less.
  • the lower limit of C content is preferably 0.045% by mass in order to more contribute to an increase in the strength of the steel plate.
  • Silicon (Si) is an element that acts as a deoxidizer and improves the strength of steel. To obtain these effects, the Si content needs to be 0.10% by mass or more. If the Si content is extremely large, exceeds 0.30% by mass, the temper embrittlement susceptibility of the steel will be enhanced. Thus, the Si content is set at 0.10% by mass or more and 0.30% by mass or less. The lower limit of Si content is preferably 0.15% by mass in order to more contribute to an increase in the strength of steel.
  • Manganese (Mn) needs to be added in an amount of 0.50% by mass or more in order to contribute to an increase in the strength of steel.
  • the addition of Mn in an amount exceeding 0.70% by mass leads to enhanced temper embrittlement susceptibility, thus reducing the toughness of steel.
  • the Mn content is set at 0.50% by mass or more and 0.70% by mass or less.
  • the lower limit of Mn content is preferably 0.60% by mass in order to more contribute to an increase in the strength of steel.
  • Phosphorus (P) and sulfur (S) both are elements that reduce the toughness of steel, and thus the contents of P and S are desirably lowered as much as possible.
  • the P content is allowed to be 0.0025% by mass or less (not including 0% by mass), and the S content is allowed to be 0.0010% by mass or less (not including 0% by mass).
  • P is added in an amount of 0.0010% by mass or more and 0.0025% by mass or less.
  • the P content is more preferably 0.0015% by mass or more and 0.0025% by mass or less.
  • Nickel (Ni) is an essential element in the embodiment of the present invention and has the effect of imparting high toughness to a steel plate at low temperature. If the Ni content is less than 9.10% by mass, its effect becomes lower. If Ni is added in a large amount exceeding 9.40% by mass, its effect is saturated and also uneconomical. Thus, the Ni content is set at 9.10% by mass or more and 9.40% by mass or less.
  • Aluminum (Al) needs to be added in an amount of 0.0020% by mass or more as a deoxidizer. However, if Al is added in an amount exceeding 0.050% by mass, the cleanliness of the steel is degraded. Thus, the Al content is set at 0.020% by mass or more and 0.050% by mass or less. To further enhance the cleanliness, the upper limit of Al content is preferably 0.045% by mass.
  • N Nitrogen
  • the N content is set at 0.0050% by mass or less (not including 0% by mass).
  • the balance being iron and inevitable impurities.
  • Inevitable impurities are trace elements (for example, As, Sb, Sn, and the like) brought into situations, including raw materials, source materials, manufacturing facilities, and the like, which are allowed to be mixed in the steel plate.
  • elements such as P and S, whose content ranges are separately specified as mentioned above, despite being inevitable impurities which are preferably contained in a smaller amount in general.
  • the term "inevitable impurities" constituting the balance is based on the concept that excludes the elements whose content ranges are specified separately.
  • Cu, Cr, Mo, V, Nb, Ti, and B are elements contributing to the improvement of the strength of steel.
  • One or more of these elements may be selected as necessary to be contained in the steel.
  • the inventors of the present application have found that a steel plate with excellent strain aging property can be produced even when the P content exceeds 0.001% by mass, by quenching a rolled material having a predetermined chemical composition from a predetermined quenching temperature, and performing an intermediate heat treatment and tempering on the quenched material by strictly controlling the heating time and the holding time such that the parameter H to be mentioned later in detail falls within a predetermined range.
  • a raw material for production of steel that satisfies the requirements for the above-mentioned chemical composition is molten by a conventional method in a usual blasting furnace such as a converter and is cast into a slab (raw material steel) by a continuous casting method.
  • the obtained raw material steel is heated to a temperature that enables hot-rolling by a conventional method, and then subjected to the hot-rolling (AR: As-Roll) to obtain a steel plate having a desired thickness (for example, 32 mm).
  • the steel plate is subjected to a quenching treatment by reheating to a quenching temperature of 800°C or higher and 820°C or lower and then quenching.
  • the quenching is performed at an average cooling rate of 5°C/sec or more to a cooling end temperature of 200°C or lower.
  • the quenching is performed by, for example, water cooling or the like. For example, in the case of water cooling, the average cooling rate sufficiently becomes 5°C/sec or more until the cooling end temperature of 200°C or lower.
  • the quenching temperature exceeds 820°C, austenite grains are coarsened by recrystallization, and as a result, the low-temperature toughness of the steel plate may be deteriorated. In contrast, when the quenching temperature is lower than 800°C, the quenching becomes insufficient, which could deteriorate the strain aging property and make the strength of the steel plate insufficient.
  • the steel plate is reheated to a heating temperature (intermediate heat treatment temperature) to 690°C or higher and 710°C or lower which corresponds to a two-phase region where ferrite and austenite coexist.
  • a heating temperature intermediate heat treatment temperature
  • 710°C or lower which corresponds to a two-phase region where ferrite and austenite coexist.
  • the cooling is performed at an average cooling rate of 5°C/sec or more to a cooling end temperature of 200°C or lower.
  • the cooling is performed by, for example, water cooling or the like. For example, in the case of water cooling, the average cooling rate sufficiently becomes 5°C/sec or more until the cooling end temperature of 200°C or lower.
  • the uniform martensite microstructure obtained in the above-mentioned quenching step is transformed into a ferrite microstructure and an austenite microstructure when being heated to the heating temperature of the two-phase region.
  • C and Ni are diffused into the austenite microstructure, resulting in the enrichment of C and Ni into the austenite microstructure.
  • the austenite microstructure is transformed into the martensite microstructure to form a mixed microstructure of a clean ferrite microstructure and a martensite microstructure containing the enrichment of C and Ni.
  • the intermediate heat treatment temperature is lower than 690°C, the amount of austenite formed in the subsequent tempering step becomes insufficient, which leads to the deterioration of the strain aging property.
  • the intermediate heat treatment temperature exceeding 710°C falls within a temperature range of a single-phase region, whereby no ferrite microstructure is formed there.
  • an austenite microstructure containing the enrichment of C and Ni cannot be obtained.
  • austenite is not formed in the sequent tempering step, leading to the deterioration of the strain aging property.
  • the steel plate is subjected to the tempering treatment by being reheated to a tempering temperature of 570°C or higher and 600°C or lower and held for a predetermined period of time after the tempering temperature is reached.
  • a cooling method is not particularly limited and is preferably, for example, water cooling or the like.
  • the martensite microstructure obtained in the intermediate heat treatment step also includes a portion where C and Ni are densely enriched and a portion where C and Ni are not densely enriched.
  • the portion thereof where C and Ni are densely enriched is reversely transformed into the austenite microstructure even at a temperature around the tempering temperature because A s point (reverse transformation start temperature) is lowered.
  • C and Ni are densely enriched.
  • the portion where C and Ni are not densely enriched does not experience the reverse transformation because the A s point thereof is not lowered so much, and thus is subjected to a usual tempering treatment for adjusting the hardness of steel or the like.
  • the final metallographic structure obtained after the tempering step includes a ferrite microstructure, a martensite microstructure, and a residual ⁇ microstructure. It is considered that in the reverse transformed austenite microstructure obtained by heating to the tempering temperature, C and Ni are further enriched through the heating and holding processes. In the residual ⁇ obtained in this way according to the embodiment of the present invention, C and Ni are densely enriched. Thus, the steel plate obtained by the production method according to the embodiment of the present invention has improved strain aging property.
  • the tempering temperature is lower than 570°C, the amount of residual ⁇ in the obtained steel plate is small, leading to the deterioration of the strain aging property.
  • the tempering temperature exceeds 600°C, both the size and quantity of the residue ⁇ increases, leading to the deterioration of the strain aging property.
  • the tempering temperature exceeding 600°C is not preferable also from the viewpoint of ensuring the strength of the steel plate.
  • the parameter H represented by the following formula (1) is set at 1.73 ⁇ 10 -6 or more and 1.96 ⁇ 10 -6 or less in the above-mentioned intermediate heat treatment step and tempering step.
  • H D Ni ,L ⁇ t L 0.5 + D Ni ,T ⁇ t T 0.5 ⁇ Ni + ⁇ D C ,L ⁇ t L 0.5 + D C ,T ⁇ t T 0.5 ⁇ C
  • the embodiment of the present invention is configured by focusing on the diffusion of C and Ni.
  • the diffusion of an element is basically substantially proportional to the square root of the product of the diffusion coefficient and the time.
  • the square root of this product is determined for each element of C and Ni, and then the formula for adding these square roots together is defined as the parameter H.
  • the parameter H is defined by considering each heat treatment of the intermediate heat treatment and the tempering treatment.
  • the parameter H defined in this way becomes an index indicative of the extent of diffusion of C and Ni during the intermediate heat treatment and the tempering treatment.
  • the parameter H is less than 1.73 ⁇ 10 -6 , the diffusion of C and Ni into the austenite microstructure becomes insufficient during the intermediate heat treatment, and the amount of residual ⁇ also becomes insufficient in the steel plate, thus deteriorating the strain aging property. If the parameter H exceeds 1.96 ⁇ 10 -6 , C and Ni are excessively diffused into the austenite microstructure, and the amount of residual ⁇ is decreased, thus deteriorating the strain aging property. Examples
  • a test steel plate was produced by smelting a steel containing a chemical composition shown in Table 1, hot-rolling a cast steel, and then applying a heat treatment shown in Table 2 to the rolled steel piece obtained. All the produced steel plates had a thickness of 32 mm. Samples were taken out of these steel plates. During both the quenching treatment and the intermediate heat treatment, the cooling was performed by water cooling.
  • Table 2 Numeral values underlined in Table 2 means that they deviated from the range specified by the present invention.
  • Table 1 Raw material steel Chemical composition (% by mass, Balance: Fe and inevitable impurities) C Si Mn P S Ni Al N A 0.051 0.21 0.65 0.0021 0.0006 9.17 0.025 0.0036 B 0.052 0.22 0.65 0.0018 0.0009 9.20 0.030 0.0031 C 0.049 0.22 0.64 0.0023 0.0005 9.23 0.027 0.0027 [Table 2] Sample No.
  • Samples Nos. 1 to 5 and 15 were samples produced by the production method that satisfied the requirements of the embodiment of the present invention. All three test pieces of each of these samples had a brittle fracture rate of 5% or less and exhibited excellent strain aging property.
  • Samples Nos. 6 to 14 were samples produced by a production method that did not satisfy the requirements of the embodiment of the present invention. At least one of three test pieces of each of these samples had a brittle fracture rate exceeding 5% and was inferior in strain aging property.
  • Sample No. 6 was inferior in the strain aging property because of a low tempering temperature and a low parameter H.
  • Samples Nos. 7 to 9 was inferior in the strain aging property because of a high parameter H.
  • Sample No. 10 was inferior in the strain aging property because of a low intermediate heat treatment temperature and a low parameter H.
  • Sample No. 11 was inferior in the strain aging property because of a high parameter H.
  • Sample No. 12 was inferior in the strain aging property because of a high intermediate heat treatment temperature and a high parameter H.
  • Sample No. 13 was inferior in the strain aging property because of a high tempering temperature and a high parameter H.
  • Sample No. 14 was inferior in the strain aging property because of a low quenching temperature.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
EP18848632.8A 2017-08-25 2018-08-13 Method for production of ni-containing steel plate Active EP3674426B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2017162740 2017-08-25
JP2018131749A JP7076311B2 (ja) 2017-08-25 2018-07-11 Ｎｉ含有鋼板の製造方法
PCT/JP2018/030209 WO2019039339A1 (ja) 2017-08-25 2018-08-13 Ｎｉ含有鋼板の製造方法

Publications (3)

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JPH06179909A (ja) 1992-12-14 1994-06-28 Sumitomo Metal Ind Ltd 極低温用鋼材の製造方法
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JP5594329B2 (ja) * 2012-07-23 2014-09-24 Ｊｆｅスチール株式会社 低温靱性に優れたＮｉ含有厚鋼板
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CN106191661B (zh) * 2016-08-23 2017-10-27 南京钢铁股份有限公司 一种低成本高强韧薄规格9Ni钢板的制造方法
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