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CN-122003513-A - Welded joint and pressure vessel

CN122003513ACN 122003513 ACN122003513 ACN 122003513ACN-122003513-A

Abstract

A welded joint having a specific chemical composition represented by the following formula (1) wherein Ceq is 0.350-0.490, the tensile strength is 490MPa-720 MPa, the equivalent circle diameter is 0.01-0.50 [ mu ] m at a position 1/4 and a position 1/2 of the thickness in the thickness direction from the surface, the number density of Ti-and N-containing inclusions is 1.0X10 5 /mm 2 or more, the average grain diameter of Ti-and N-containing inclusions is 150nm or less at the position 1/4 and the position 1/2, and the effective crystal grain diameter in the region between the weld line of the welded part and the position 1mm apart from the weld line of the weld heat affected part is 100.0 [ mu ] m or less. A pressure vessel comprising the welded joint described above. Ceq= [ C ] + [ Mn ]/6+ [ Ni ]/15+ [ Cu ]/15+ [ Cr ]/5+ [ Mo ]/5+ [ V ]/5 (1).

Inventors

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

Assignees

  • 日本制铁株式会社

Dates

Publication Date
20260508
Application Date
20241011
Priority Date
20231011

Claims (7)

  1. 1.A welded joint having a base material made of steel material and a welded portion, The steel has the following chemical composition in mass percent: C:0.03%~0.17%、 Si:0.10%~0.50%、 Mn:0.10%~1.70%、 P is below 0.025%, S is less than 0.0250%, Al:0.015%~0.100%、 Ti:0.005%~0.050%、 0.0100% Or less of O, N:0.0010%~0.0064%、 Ni:0~1.20%、 Cu:0~0.95%、 Cr:0~0.95%、 Mo:0~1.00%、 B:0~0.0050% Nb:0~0.034%、 V:0~0.10%、 Mg:0~0.020%、 Ca:0~0.020%、 REM:0~0.020%、 The rest part is Fe and impurities, And Ceq represented by the following formula (1) is 0.350 to 0.490, The tensile strength of the steel is 490 MPa-720 MPa, At a position 1/4 and a position 1/2 of the thickness in the thickness direction from the surface of the steel material, the equivalent circle diameter contained in the steel material is 0.01 μm to 0.50 μm and the number density of inclusions containing Ti and N is 1.0X10 5 /mm 2 or more, At the 1/4 and 1/2 portions, the average grain size of the Ti-and N-containing inclusions is 150nm or less, An effective crystal grain size in a region between a weld line of the weld portion and a position of the weld heat affected portion that is 1mm apart from the weld line is 100.0 μm or less, Ceq=[C]+[Mn]/6+[Ni]/15+[Cu]/15+[Cr]/5+[Mo]/5+[V]/5 (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 welded joint of claim 1, wherein the chemical composition comprises group A, [ Group A ] 1 Or more than 2 elements selected from the following elements: Ni:0.01%~1.20%、 Cu:0.01%~0.95%、 Cr:0.01%~0.95%、 0.01% -1.00% of Mo B:0.0003%~0.0050%。
  3. 3. The welded joint according to 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% -0.034% V:0.01%~0.10%。
  4. 4. The welded joint according to 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%~0.020%、 Ca 0.0003% -0.020% REM:0.0003%~0.020%。
  5. 5. The welded joint according to any one of claims 1 to 4, wherein the charpy impact absorption energy at-70 ℃ of the welding heat affected zone is 150J or more.
  6. 6. The welded joint according to any one of claims 1 to 5, wherein when the welded joint 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, a charpy impact absorption energy at-70 ℃ of the welding heat affected zone at the heat treated portion is 150J or higher.
  7. 7. A pressure vessel comprising the welded joint of any one of claims 1-6.

Description

Welded joint and pressure vessel Technical Field The present disclosure relates to welded joints 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. In many cases, welding is performed to join steel materials together when building a structure. A welding heat affected Zone (HEAT AFFECTED Zone: hereinafter referred to as "HAZ") is formed in the vicinity of a weld metal obtained by welding a steel material. In particular, the toughness of the HAZ (HAZ toughness) is deteriorated compared with the toughness of the base material due to coarsening of crystal grains or the like caused by weld line energy. For example, patent document 1 proposes a steel sheet having excellent toughness of a base material and a welded portion when multi-layer welding is performed. Patent document 2 proposes a welding steel excellent in HAZ toughness (particularly low temperature toughness) even when welding with a line energy in a wide range from a small line energy to a large line energy. Various steels and methods for producing steels have been proposed in which chemical compositions and inclusions are specified for the purpose of low-temperature toughness and high strength (for example, see patent documents 3 to 4). Patent document 1 Japanese patent application laid-open No. 2019-183205 Patent document 2 Japanese patent application laid-open No. 2004-218010 Patent document 3 Japanese patent application laid-open No. 2012-92422 Patent document 4 Japanese patent laid-open publication 2016-79461 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 demand for low-temperature toughness after PWHT of a welded joint has been further increased. The present disclosure addresses the problem of providing a welded joint and a pressure vessel suitable for low-temperature applications, which can obtain good low-temperature toughness both before and after post-weld heat treatment, using a steel material having high tensile strength as a base material. Means for solving the problems The gist of the present disclosure is as follows. <1> A welded joint comprising a base material made of steel material and a welded portion, The steel has the following chemical composition in mass percent: C:0.03%~0.17%、 Si:0.10%~0.50%、 Mn:0.10%~1.70%、 P is below 0.025%, S is less than 0.0250%, Al:0.015%~0.100%、 Ti:0.005%~0.050%、 0.0100% Or less of O, N:0.0010%~0.0064%、 Ni:0~1.20%、 Cu:0~0.95%、 Cr:0~0.95%、 Mo:0~1.00%、 B:0~0.0050% Nb:0~0.034%、 V:0~0.10%、 Mg:0~0.020%、 Ca:0~0.020%、 REM:0~0.020%、 The rest part is Fe and impurities, And Ceq represented by the following formula (1) is 0.350 to 0.490, The tensile strength of the steel is 490 MPa-720 MPa, At a position 1/4 and a position 1/2 of the thickness in the thickness direction from the surface of the steel material, the equivalent circle diameter contained in the steel material is 0.01 μm to 0.50 μm and the number density of inclusions containing Ti and N is 1.0X10 5/mm 2 or more, At the 1/4 and 1/2 portions, the average grain size of the Ti-and N-containing inclusions is 150nm or less, An effective crystal grain size in a region between a weld line of the weld portion and a position of the weld heat affected portion that is 1mm apart from the weld line is 100.0 μm or less. Ceq=[C]+[Mn]/6+[Ni]/15+[Cu]/15+[Cr]/5+[Mo]/5+[V]/5 (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 welded joint 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: Ni:0.01%~1.20%、 Cu:0.01%~0.95%、 Cr:0.1%~0.95%、 0.01% -1.00% of Mo B:0.0003%~0.0050%。 <3> The weld joint 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% -0.034% V:0.01%~0.10%。 The weld joint according to any one of <1> to <3>, wherein the chemical composition c