Heat and corrosion resistant cast stainless steels with improved high temperature strength and ductility
Abstract
A cast stainless steel alloy and articles formed therefrom containing about 0.5 wt. % to about 10 wt. % manganese, 0.02 wt. % to 0.50 wt. % N, and less than 0.15 wt. % sulfur provides high temperature strength both in the matrix and at the grain boundaries without reducing ductility due to cracking along boundaries with continuous or nearly-continuous carbides. Alloys of the present invention also have increased nitrogen solubility thereby enhancing strength at all temperatures because nitride precipitates or nitrogen porosity during casting are not observed. The solubility of nitrogen is dramatically enhanced by the presence of manganese, which also retains or improves the solubility of carbon thereby providing additional solid solution strengthening due to the presence of manganese and nitrogen, and combined carbon. Such solution strengthening enhances the high temperature precipitation-strengthening benefits of fine dispersions of NbC. Such solid solution effects also enhance the stability of the austenite matrix from resistance to excess sigma phase or chrome carbide formation at higher service temperatures. The presence of sulfides is substantially eliminated.
Claims
exact text as granted — not AI-modified1 . A stainless steel alloy comprising:
from about 0.5 wt. % to about 10 wt. % manganese; and less than about 0.15 wt. % sulfur.
2 . The stainless steel alloy of claim 1 wherein the alloy is a CN-12 alloy or a CF8C alloy.
3 . The stainless steel alloy of claim 1 further comprising from about 0.2 wt. % to about 0.5 wt. % carbon and from about 1 wt. % to about 2.5 wt. % niobium.
4 . The stainless steel alloy of claim 3 wherein the alloy is a CN-12 alloy wherein niobium and carbon are present in a weight ratio of niobium to carbon ranging from about 3 to about 5.
5 . The stainless steel alloy of claim 1 wherein the alloy is a CF8C alloy wherein niobium and carbon are present in a weight ratio of niobium to carbon ranging from about 8 to about 11.
6 . The stainless steel alloy of claim 3 further comprising from about 0.10 wt. % to about 0.5 wt. % nitrogen.
7 . The stainless steel alloy of claim 3 further comprising less than about 0.04 wt. % phosphorous.
8 . The stainless steel alloy of claim 3 further comprising from about 0.2 wt. % to about 3.0 wt. % silicon.
9 . The stainless steel alloy of claim 3 further comprising from about 8 wt. % to about 25 wt. % nickel.
10 . The stainless steel alloy of claim 3 further comprising from about 18 wt. % to about 25 wt. % chromium.
11 . The stainless steel alloy of claim 3 further comprising about 0.5 wt. % molybdenum or less.
12 . The stainless steel alloy of claim 3 further comprising about 3.0 wt. % tungsten or less.
13 . The stainless steel alloy of claim 3 further comprising about 3.0 wt. % copper or less.
14 . The stainless steel alloy of claim 1 further comprising from about 0.02 wt. % to about 0.5 wt. % nitrogen.
15 . The stainless steel alloy of claim 1 further comprising from about 0.8 wt. % silicon or less.
16 . The stainless steel alloy of claim 1 further comprising from about 3.0 wt. % copper or less.
17 . The stainless steel alloy of claim 1 further comprising from about 0.3 wt. % to about 1 wt. % niobium.
18 . The stainless steel alloy of claim 1 further comprising from about 0.2 wt. % titanium or less.
19 . The stainless steel alloy of claim 1 further comprising from about 5.0 wt. % cobalt or less.
20 . The stainless steel alloy of claim 1 further comprising from about 3.0 wt. % aluminum or less.
21 . The stainless steel alloy of claim 1 further comprising from about 0.01 wt. % boron or less.
22 . The stainless steel alloy of claim 1 further comprising from about 3.0 wt. % tungsten or less.
23 . The stainless steel alloy of claim 3 further comprising about 3.0 wt. % vanadium or less.
24 . The stainless steel alloy of claim 1 wherein the alloy is a CN-12 alloy and wherein nitrogen and carbon are present in a cumulative amount ranging from 0.4 wt. % to 1.0 wt. %.
25 . The stainless steel alloy of claim 1 wherein the alloy is a CF8C alloy and wherein nitrogen and carbon are present in a cumulative amount ranging from 0.1 wt. % to 0.5 wt. %.
26 . A CN-12 stainless steel alloy comprising:
about 0.03% sulfur or less; from about 2 wt. % to about 5 wt. % manganese; niobium and carbon in a niobium:carbon wt. % ratio ranging from about 3.5 to 5.0.
27 . The CN-12 alloy of claim 26 wherein niobium is present in an amount ranging from about 1.5 wt. % to about 2.0 wt. %.
28 . The CN-12 alloy of claim 26 further comprising about 0.04 wt. % phosphorous or less.
29 . The CN-12 alloy of claim 26 further comprising from about 0.2 wt. % to about 1.4 wt. % silicon.
30 . The CN-12 alloy of claim 26 further comprising from about 12 wt. % to about 25 wt. % nickel.
31 . The CN-12 alloy of claim 26 further comprising from about 22 wt. % to about 25 wt. % chromium.
32 . The CN-12 alloy of claim 26 further comprising less than about 0.3 wt. % molybdenum or less.
33 . The CN-12 alloy of claim 26 further comprising about 3 wt. % copper or less.
34 . An article formed from the stainless steel alloy of claim 1 .
35 . An article formed from the stainless steel alloy of claim 26 .
36 . A stainless steel alloy comprising:
from about 2 wt. % to about 5 wt. % manganese; less than about 0.03 wt. % sulfur; and about 0.5 wt. % nitrogen or less.Join the waitlist — get patent alerts
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