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CN-122029300-A - Steel material and pressure vessel

CN122029300ACN 122029300 ACN122029300 ACN 122029300ACN-122029300-A

Abstract

A steel material having a specific chemical composition represented by the following formula, wherein alpha is 4.0-16.0, the steel material has a tensile strength of 1500-930 MPa, a microstructure of a portion having a thickness of 1/4 from the surface comprises lower bainite and martensite, the sum of the area ratios of the lower bainite and the martensite is 15.0% or more, the sum of the area ratios of the upper bainite, the lower bainite and the martensite is 90.0% or more, and the Mn concentration of a center segregation portion at a portion having a thickness of 1/2 is 2.00% or less. α=0.50× [ C ] × (1+0.64 [ si ])× (1+4.10 [ mn ])× (1+0.27 [ cu ])× (1+0.52 [ ni ])× (1+2.33 [ cr ])× (1+3.14 [ mo ])

Inventors

  • Uchiyama Koya
  • NAKANISHI DAISUKE
  • USUKI HIROKAZU
  • SHIRAHATA HIROYUKI

Assignees

  • 日本制铁株式会社

Dates

Publication Date
20260512
Application Date
20241011
Priority Date
20231011

Claims (9)

  1. 1. A steel material having the following chemical composition in mass%: C:0.03%~0.20%、 Si:0.01%~0.50%、 Mn:0.10%~1.50%、 p is below 0.025%, S is less than 0.0250%, Ni:2.65%~4.45%、 Al:0.001%~0.100%、 0.0100% Or less of O, N is less than 0.0100%, Cu:0~1.50%、 Cr:0~3.00%、 Mo:0~2.00%、 B:0~0.0050%、 Nb:0~0.050%、 Ti:0~0.050%、 V:0~0.10%、 Mg:0~0.0200%、 Ca:0~0.0200%、 REM:0~0.0200%、 The rest part is Fe and impurities, And alpha represented by the following formula (1) is 4.0 to 16.0, The tensile strength of the steel is between 4000 and 930MPa, The microstructure of a portion 1/4 of the thickness in the thickness direction from the surface of the steel material comprises lower bainite and martensite, the sum of the area ratios of the lower bainite and the martensite is 15.0% or more, and the sum of the area ratios of the upper bainite, the lower bainite and the martensite is 90.0% or more, The Mn concentration of the center segregation portion at a portion 1/2 of the thickness in the thickness direction from the surface of the steel material is 2.00% or less, α=0.50×√[C]×(1+0.64[Si])×(1+4.10[Mn])×(1+0.27[Cu])×(1+0.52[Ni])×(1+2.33[Cr])×(1+3.14[Mo]) (1), Wherein the symbol of element in the formula (1) represents the content in mass% of each corresponding element contained in the steel material, and zero is substituted when the corresponding element is not contained.
  2. 2. The steel product as claimed in claim 1 wherein the chemical composition comprises group A, [ Group A ] 1 Or more than 2 elements selected from the following elements: Cu:0.01%~1.50%、 Cr:0.01%~3.00%、 0.01% -2.00% of Mo B:0.0003%~0.0050%。
  3. 3. The steel product as claimed in claim 1 or claim 2 wherein the chemical composition comprises group B, [ Group B ] 1 Or more than 2 elements selected from the following elements: Nb:0.001%~0.050%、 0.001% -0.050% Ti V:0.01%~0.10%。
  4. 4. A steel product as claimed in any one of claims 1 to 3 wherein the chemical composition comprises group C, [ Group C ] 1 Or more than 2 elements selected from the following elements: Mg:0.0003%~0.0200%、 Ca 0.0003% -0.0200% REM:0.0003%~0.0200%。
  5. 5. The steel product as set forth in any one of claims 1 to 4 wherein the average crystal grain size of the microstructure of the portion 1/2 of the thickness in the thickness direction from the surface of the steel product is 20.0 μm or less.
  6. 6. The steel product as claimed in any one of claims 1 to 5 wherein the aspect ratio of prior austenite grains at a position 1/2 of the thickness in the thickness direction from the surface of the steel product is 1.5 or more.
  7. 7. The steel product as claimed in any one of claims 1 to 6 wherein the charpy impact absorption energy at-100 ℃ of a portion of 1/2 of the thickness is 150J or more.
  8. 8. The steel product as set forth in any one of claims 1 to 7 wherein, when the steel product is subjected to heat treatment at a temperature range of 425 ℃ or higher at a temperature rise rate and a temperature fall rate of 55 ℃/h and held at 600 ℃ for 2 hours, the charpy impact absorption energy at-100 ℃ of a portion 1/2 of the thickness of the heat treated portion is 150J or higher.
  9. 9. A pressure vessel comprising the steel product as claimed in any one of claims 1 to 8.

Description

Steel material and pressure vessel Technical Field The present disclosure relates to steel and pressure vessels. Background The steel material can be used for welded structures such as buildings, bridges, ships, line pipes, marine structures, pressure vessels (tanks), and the like. Steels excellent in strength and low-temperature toughness and stress are effective for use at low temperatures. Low-temperature steel is used for a pressure vessel for low temperature such as a liquefied gas storage tank. Among the low-temperature steels, there are Al killed steels, nickel steels, high Mn steels, austenitic stainless steels, and the like, depending on the use temperature. For example, nickel steel such as 3.5% ni steel is used as a material for loading cans of liquefied ethane and liquefied ethylene at temperatures around-100 ℃. As in the 3.5% Ni steel, ni is often contained in steel materials that require securing low-temperature toughness typified by pressure vessels for low temperatures. For example, patent document 1 proposes a nickel-containing steel sheet for low temperature, which has a specific chemical composition containing 3.0% or more and less than 5.0% of Ni, an alumina cluster index of 0.030 or less, an effective crystal grain size of 12.0 μm or less, an average value of tensile strength of 540mpa to 610mpa, and a charpy impact absorption energy of 150J or more at-140 ℃. Patent document 2 proposes a nickel-containing steel for low temperature having excellent toughness, which has a specific chemical composition containing 2.7% -5.0% Ni, and has a prior austenite grain diameter of 20 μm or less at the time of quenching and heating, an effective crystal grain diameter of 12 μm or less after heat treatment, and a tensile strength of 450mpa to 690mpa. Patent document 3 proposes a high-tensile steel for high heat input welding containing 1.0 to 10.0% ni. Patent document 4 proposes a method for producing high-tensile steel containing 0.5 to 4.0% ni and having excellent weldability and low-temperature toughness. Patent document 1 Japanese patent No. 6610352 Patent document 2 Japanese patent No. 6984319 Patent document 3 Japanese patent laid-open No. 2-163342 Patent document 4 Japanese patent laid-open No. 2-254120 Disclosure of Invention Problems to be solved by the invention For low-temperature steel used in a pressure vessel for low temperature, both high strength and securing of low-temperature toughness are desired. In addition, the low-temperature pressure vessel is manufactured by welding steel materials, and in order to remove residual stress generated by welding, post WELD HEAT TREATMENT (sometimes referred to as PWHT) is sometimes performed. Recently, the low-temperature toughness after PWHT of steel has been further improved. The subject of the present disclosure is to provide a steel material and a pressure vessel which have high tensile strength and can obtain good low-temperature toughness both before and after heat treatment after welding and are suitable for low-temperature applications. Means for solving the problems The gist of the present disclosure is as follows. <1> A steel material having the following chemical composition in mass%: C:0.03%~0.20%、 Si:0.01%~0.50%、 Mn:0.10%~1.50%、 p is below 0.025%, S is less than 0.0250%, Ni:2.65%~4.45%、 Al:0.001%~0.100%、 0.0100% Or less of O, N is less than 0.0100%, Cu:0~1.50%、 Cr:0~3.00%、 Mo:0~2.00%、 B:0~0.0050%、 Nb:0~0.050%、 Ti:0~0.050%、 V:0~0.10%、 Mg:0~0.0200%、 Ca:0~0.0200%、 REM:0~0.0200%、 The rest part is Fe and impurities, And alpha represented by the following formula (1) is 4.0 to 16.0, The tensile strength of the steel is between 4000 and 930MPa, The microstructure of a portion 1/4 of the thickness in the thickness direction from the surface of the steel material comprises lower bainite and martensite, the sum of the area ratios of the lower bainite and the martensite is 15.0% or more, and the sum of the area ratios of the upper bainite, the lower bainite and the martensite is 90.0% or more, The Mn concentration of the center segregation portion at a portion 1/2 of the thickness in the thickness direction from the surface of the steel material is 2.00% or less. α=0.50×√[C]×(1+0.64[Si])×(1+4.10[Mn])×(1+0.27[Cu])×(1+0.52[Ni])×(1+2.33[Cr])×(1+3.14[Mo]) (1) Wherein the symbol of element in the formula (1) represents the content (mass%) of each corresponding element contained in the steel material. Substituting zero without the inclusion of the corresponding element. <2> The steel material according to <1>, wherein the chemical composition comprises the following group A. [ Group A ] 1 Or more than 2 elements selected from the following elements: Cu:0.01%~1.50%、 Cr:0.01%~3.00%、 0.01% -2.00% of Mo B:0.0003%~0.0050%。 <3> The steel material according to <1> or <2>, wherein the chemical composition comprises the following group B. [ Group B ] 1 Or more than 2 elements selected from the following elements: Nb:0.001%~0.050%、 0.001% -0.050% Ti V:0.01%~0.1