High temperature steel for steam turbine and other applications

Patent metadata

Field	Value
Publication number	US-10316379-B2
Application number	US-201615296549-A
Country	US
Kind code	B2
Filing date	Oct 18, 2016
Priority date	Oct 30, 2015
Publication date	Jun 11, 2019
Grant date	Jun 11, 2019

Abstract

Steel compositions are provided. A steel composition may include iron; from 0.015 to 0.06 wt. % carbon; from 9 to 12 wt. % chromium; from 0.75 to 1.5 wt. % manganese; from 0.08 to 0.18 wt. % molybdenum; from 0.10 to 0.30 wt. % silicon; from 0.2 to 1.0 wt. % vanadium; from 0.05 to 1.2 wt. % niobium; and optionally, an amount of an additional precipitate forming alloying element. Methods of making the steel compositions are also provided.

First claim

What is claimed is:

1. A steel composition comprising
iron;
from 0.026 to 0.032 wt. % carbon;
from 9 to 12 wt. % chromium;
from 0.98 to 1.20 wt. % manganese;
from 0.11 to 0.13 wt. % molybdenum;
from 0.19 to 0.23 wt. % silicon;
from 0.2 to 1.0 wt. % vanadium;
from 0.05 to 0.07 wt. % niobium; and
optionally, an amount of an additional precipitate forming alloying element, wherein the steel composition is free of nitrogen, calcium and magnesium.

2. The steel composition of claim 1 , wherein the steel composition consists essentially of the iron, the carbon, the chromium, the manganese, the molybdenum, the silicon, the vanadium, and the niobium with the proviso that the steel composition is free of the nitrogen, the calcium, and the magnesium.

3. The steel composition of claim 1 , wherein the additional precipitate forming alloying element is present and is selected to provide core-shell precipitates in the steel composition comprising a core comprising a first monocarbide M a C and a shell comprising a second monocarbide M b C, wherein M a is the additional precipitate forming alloying element and M b is vanadium, niobium, or molybdenum.

4. The steel composition of claim 3 , wherein the additional precipitate forming alloying element is zirconium or hafnium.

5. The steel composition of claim 4 , wherein the additional precipitate forming alloying element is zirconium which is present in an amount of at least 0.06 wt. %.

6. The steel composition of claim 4 , wherein the additional precipitate forming alloying element is zirconium which is present in an amount of from 0.06 to 0.3 wt. %.

7. The steel composition of claim 4 , wherein the additional precipitate forming alloying element is hafnium which is present in an amount of from 0.12 to 0.40 wt. %.

8. The steel composition of claim 1 , wherein the steel composition consists essentially of the iron, the carbon, the chromium, the manganese, the molybdenum, the silicon, the vanadium, the niobium, and the additional precipitate forming alloying element with the proviso that the steel composition is free of the nitrogen, the calcium, and the magnesium.

9. The steel composition of claim 1 , wherein the additional precipitate forming alloying element is zirconium and the zirconium is present in an amount of at least 0.06 wt. %.

10. The steel composition of claim 1 , wherein the additional precipitate forming alloying element is zirconium and the zirconium is present in an amount of from 0.06 to 0.3 wt. %.

11. The steel composition of claim 1 , wherein
vanadium is present in an amount of from 0.2 to 0.4 wt. %;
and
zirconium is present in an amount of from 0.15 to 0.27 wt. %.

12. The steel composition of claim 1 , wherein
vanadium is present in an amount of from 0.2 to 0.4 wt. %;
zirconium is present in an amount of from 0.17 to 0.25 wt. %.

13. The steel composition of claim 1 , wherein
vanadium is present in an amount of from 0.2 to 0.4 wt. %;
and
zirconium is present in an amount of from 0.19 to 0.23 wt. %.

14. The steel composition of claim 1 , wherein the steel composition is characterized by a Vickers Hardness at about 700° C. of at least about 20 kg/mm 2 as measured after exposing the steel composition to a temperature of about 700° C. for about 1000 h.

15. A method of making a steel composition comprising
forming an ingot comprising
iron,
from 0.026 to 0.032 wt. % carbon,
from 9 to 12 wt. % chromium,
from 0.98 to 1.20 wt. % manganese,
from 0.11 to 0.13 wt. % molybdenum,
from 0.19 to 0.23 wt. % silicon,
from 0.2 to 1.0 wt. % vanadium,
from 0.05 to 0.07 wt. % niobium, and
optionally, an amount of an additional precipitate forming alloying element, wherein the ingot is free of nitrogen, calcium and magnesium;
normalizing the ingot; and
cooling the normalized ingot.

16. The method of claim 15 , wherein the method does not comprise subjecting the ingot to any additional thermomechanical processing steps.

17. The method of claim 15 , wherein the normalizing is conducted at a temperature in the range of from about 950° C. to about 1100° C.

Assignees

• Univ Northwestern

Inventors

• Gross Cameron T
• Du Yao
• Zhang Xu
• Isheim Dieter
• Vaynman Semyon
• Chung Yip-Wah
• Jiang Zilin
• Mathai Allan V

Classifications

• C22C38/24

  with vanadium · CPC title

• C21D1/28

  Normalising · CPC title

• C22C38/02

  containing silicon · CPC title

• C22C38/04

  containing manganese · CPC title

• C22C38/22

  with molybdenum or tungsten · CPC title