Method of evaluating central segregation in steel

Patent metadata

Field	Value
Publication number	US-2024044822-A1
Application number	US-202118256096-A
Country	US
Kind code	A1
Filing date	Sep 6, 2021
Priority date	Dec 18, 2020
Publication date	Feb 8, 2024
Grant date	—

Abstract

A method of evaluating central segregation in steel with excellent correlation with HIC susceptibility is provided. A method of evaluating central segregation in steel includes: taking a sample from a steel, the sample having a cross section including a central segregation area; measuring an area ratio of an inclusion containing a segregation metal element in a region to be measured including the central segregation area in the cross section; and evaluating central segregation in the steel based on the area ratio measured.

First claim

1 . A method of evaluating central segregation in steel, the method comprising:
taking a sample from a steel, the sample having a cross section including a central segregation area; measuring an area ratio of an inclusion containing a segregation metal element in a region to be measured including the central segregation area in the cross section; and evaluating central segregation in the steel based on the area ratio measured.

2 . The method of evaluating central segregation in steel according to claim 1 , where letting M x1 A y1 be the inclusion and N x2 A y2 be a compound with a smaller solubility product than M x1 A y1 , the method further comprising:
treating the region to be measured in the sample with a solution containing ions of an element N to replace M located on a surface of the inclusion exposed in the region to be measured with N; then, measuring an area ratio of the element N in the region to be measured; and using the area ratio of the element N measured as the area ratio of the inclusion, where M denotes the segregation metal element contained in the inclusion, N denotes a metal element other than M, A denotes an element that combines with the element M to form the inclusion and combines with the element N to form the compound, x1 and y1 each denote a numerical value representing a composition ratio of the inclusion, and x2 and y2 each denote a numerical value representing a composition ratio of the compound.

3 . The method of evaluating central segregation in steel according to claim 2 , wherein M is Mn, A is S, and N is Ag.

4 . The method of evaluating central segregation in steel according to claim 2 , the method further comprising:
performing mapping analysis of the element N in the region to be measured using EPMA; determining an area ratio of a region where the element N is detected at or above a predetermined concentration in the region to be measured; and using the area ratio as the area ratio of the element N.

5 . The method of evaluating central segregation in steel according to claim 2 , the method further comprising:
acquiring an SEM image of the region to be measured; selecting a candidate region based on contrast in the SEM image, the candidate region being a candidate for the inclusion; performing SEM-EDS analysis on the candidate region to identify a region where the element N is detected at or above a predetermined concentration; determining an area ratio of the region in the region to be measured; and using the area ratio as the area ratio of the element N.

6 . The method of evaluating central segregation in steel according to claim 5 , wherein the SEM image is a reflected electron image.

7 . The method of evaluating central segregation in steel according to claim 1 , wherein the steel is a cast steel, a steel plate, or a steel sheet.

8 . The method of evaluating central segregation in steel according to claim 7 , wherein the cross section is a cross section perpendicular to a casting direction of the cast steel, a cross section perpendicular to a rolling direction of the steel plate, or a cross section perpendicular to a rolling direction of the steel sheet.

9 . The method of evaluating central segregation in steel according to claim 3 , the method further comprising:
performing mapping analysis of the element N in the region to be measured using EPMA; determining an area ratio of a region where the element N is detected at or above a predetermined concentration in the region to be measured; and using the area ratio as the area ratio of the element N.

10 . The method of evaluating central segregation in steel according to claim 3 , the method further comprising:
acquiring an SEM image of the region to be measured; selecting a candidate region based on contrast in the SEM image, the candidate region being a candidate for the inclusion; performing SEM-EDS analysis on the candidate region to identify a region where the element N is detected at or above a predetermined concentration; determining an area ratio of the region in the region to be measured; and using the area ratio as the area ratio of the element N.

11 . The method of evaluating central segregation in steel according to claim 10 , wherein the SEM image is a reflected electron image.

Assignees

• Jfe Steel Corp

Inventors

• Ishida Tomoharu
• Sugawara Seiya
• Tsuzumi Kenji

Classifications

• G01N33/20

  Metals · CPC title

• G01N2223/402

  mapping distribution of elements · CPC title

• G01N23/2251 Primary

  using incident electron beams, e.g. scanning electron microscopy [SEM] · CPC title

• G01N33/2028 Primary

  Metallic constituents · CPC title

• G01N23/2252

  Measuring emitted X-rays, e.g. electron probe microanalysis [EPMA] · CPC title