Stainless steel with good mirror polishability and method for producing same

Patent metadata

Field	Value
Publication number	US-12553115-B2
Application number	US-202117800971-A
Country	US
Kind code	B2
Filing date	Feb 24, 2021
Priority date	Feb 27, 2020
Publication date	Feb 17, 2026
Grant date	Feb 17, 2026

Abstract

The stainless steel contains 0.0001 mass % or more and 0.15 mass % or less of C, 0.30 mass % or more and 2.0 mass % or less of Si, 0.1 mass % or more and 15 mass % or less of Mn, 5 mass % or more and 30 mass % or less of Ni, 0.0001 mass % or more and 0.01 mass % or less of S, 16 mass % or more and 25 mass % or less of Cr, 0 mass % or more and 5 mass % or less of Mo, 0 mass % or more and 0.005 mass % or less of Al, 0 mass % or more and 0.0010 mass % or less of Mg, 0.0010 mass % or more and 0.0060 mass % or less of O, and 0.0001 mass % or more and 0.5 mass % or less of N, and at least includes an inclusion with an equivalent circle diameter of 5 μm or more, having the average composition of 5 mass % or more of MnO, 20 mass % or more of Cr 2 O 3 +Al 2 O 3 , 1 mass % or more of Al 2 O 3 , and 5 mass % or less of CaO. The number density of the inclusion having the composition is 0.5 inclusions/mm 2 or less.

First claim

The invention claimed is:

1 . A stainless steel, comprising:
C: 0.0001 mass % or more and 0.15 mass % or less, Si: 0.30 mass % or more and 2.0 mass % or less, Mn: 0.1 mass % or more and 15 mass % or less, Ni: 5 mass % or more and 30 mass % or less, S: 0.0001 mass % or more and 0.01 mass % or less, Cr: 16 mass % or more and 25 mass % or less, Mo: 0 mass % or more and 5 mass % or less, Al: 0 mass % or more and 0.005 mass % or less, Mg: 0 mass % or more and 0.0010 mass % or less, O: 0.0010 mass % or more and 0.0060 mass % or less, N: 0.0001 mass % or more and 0.5 mass % or less, and a remainder comprising Fe and inevitable impurities, and comprising at least one first inclusion with an equivalent circle diameter of 5 μm or more, having an average composition of MnO: 5 mass % or more, Cr 2 O 3 +Al 2 O 3 : 20 mass % or more, Al 2 O 3 : 1 mass % or more, and CaO: 5 mass % or less, wherein a number density of the at least one first inclusion is 0.5 inclusions/mm 2 or less.

2 . The stainless steel according to claim 1 ,
further comprising at least one second inclusion with an equivalent circle diameter of 5 μm or more, having an average composition of MgO: 10 mass % or more and Al 2 O 3 : 20 mass % or more, wherein the number density of the at least one second inclusion is 0.2 inclusions/mm 2 or less, and the number density of the sum of the at least one first inclusion and the at least one second inclusion is 0.5 inclusions/mm 2 or less.

3 . The stainless steel according to claim 1 ,
further containing at least any one of Cu: 0.1 mass % or more and 4.0 mass % or less, REM: 0.00001 mass % or more and 0.0030 mass % or less, Ca: 0.0001 mass % or more and 0.0050 mass % or less, B: 0.0001 mass % or more and 0.0050 mass % or less, Ti: 0.01 mass % or more and 0.50 mass % or less, Nb: 0.01 mass % or more and 0.50 mass % or less, V: 0.01 mass % or more and 1.00 mass % or less, W: 0.01 mass % or more and 1.00 mass % or less, Co: 0.01 mass % or more and 1.00 mass % or less, and Sn: 0.01 mass % or more and 1.00 mass % or less.

4 . The stainless steel according to claim 2 ,
further comprising at least any one of Cu: 0.1 mass % or more and 4.0 mass % or less, REM: 0.00001 mass % or more and 0.0030 mass % or less, Ca: 0.0001 mass % or more and 0.0050 mass % or less, B: 0.0001 mass % or more and 0.0050 mass % or less, Ti: 0.01 mass % or more and 0.50 mass % or less, Nb: 0.01 mass % or more and 0.50 mass % or less, V: 0.01 mass % or more and 1.00 mass % or less, W: 0.01 mass % or more and 1.00 mass % or less, Co: 0.01 mass % or more and 1.00 mass % or less, and Sn: 0.01 mass % or more and 1.00 mass % or less.

5 . A method for producing the stainless steel according to claim 1 ,
the method comprising a refining step of performing refining in VOD or AOD, wherein a slag composition is, in mass % ratio, CaO/SiO 2 : 1.1 or more and 1.7 or less, Al 2 O 3 : 4.0 mass % or less, and MgO: 10.0 mass % or less by, in the refining step, adjusting an amount of Al and an amount of Al 2 O 3 contained in a raw material or a ladle, performing deoxidation using a Fe—Si alloy or metal Si, and also adding CaO or SiO 2 , and moreover stirring molten steel at a stirring power of 50 W/ton or more for 5 minutes or more after adding a refining slag material and an alloy material.

6 . A method for producing the stainless steel according to claim 2 ,
the method comprising a refining step of performing refining in VOD or AOD, wherein a slag composition is, in mass % ratio, CaO/SiO 2 : 1.1 or more and 1.7 or less, Al 2 O 3 : 4.0 mass % or less, and MgO: 10.0 mass % or less by, in the refining step,
adjusting an amount of Al and an amount of Al 2 O 3 contained in a raw material or a ladle,
performing deoxidation using a Fe—Si alloy or metal Si, and
also adding CaO or SiO 2 , and
moreover stirring molten steel at a stirring power of 50 W/ton or more for 5 minutes or more after adding a refining slag material and an alloy material.

7 . A method for producing the stainless steel according to claim 3 ,
the method comprising a refining step of performing refining in VOD or AOD, wherein a slag composition is, in mass % ratio, CaO/SiO 2 : 1.1 or more and 1.7 or less, Al 2 O 3 : 4.0 mass % or less, and MgO: 10.0 mass % or less by, in the refining step, adjusting an amount of Al and an amount of Al 2 O 3 contained in a raw material or a ladle, performing deoxidation using a Fe—Si alloy or metal Si, and also adding CaO or SiO 2 , and moreover stirring molten steel at a stirring power of 50 W/ton or more for 5 minutes or more after adding a refining slag material and an alloy material.

8 . A method for producing the stainless steel with according to claim 4 ,
the method comprising a refining step of performing refining in VOD or AOD, wherein a slag composition is, in mass % ratio, CaO/SiO 2 : 1.1 or more and 1.7 or less, Al 2 O 3 : 4.0 mass % or less, and MgO: 10.0 mass % or less by, in the refining step,
adjusting an amount of Al and an amount of Al 2 O 3 contained in a raw material or a ladle,
performing deoxidation using a Fe—Si alloy or metal Si, and also adding CaO or SiO 2 , and moreover stirring molten steel at a stirring power of 50 W/ton or more for 5 minutes or more after adding a refining slag material and an alloy material.

Assignees

• Nippon Steel Stainless Steel Corp

Inventors

• Shibata Tooru
• Sakaizawa Yuto
• Fukumoto Shigeo
• Tanaka Akira
• Kikuchi Shin

Classifications

• C22C38/54

  with boron · CPC title

• C22C38/52

  with cobalt · CPC title

• C22C38/50

  with titanium or zirconium · CPC title

• C22C38/48

  with niobium or tantalum · CPC title

• C22C38/46

  with vanadium · CPC title