초록 ▼

A superaustenitic stainless steel comprises in weight %, 0.15 to 0.9% C, 0.2 to 1.3% Si, 0 to 0.45% Mn, 32.5 to 37.5% Cr, 13.5 to 17.5% Ni, 3.2 to 5.5% Mo, 0 to 2% Nb, 0 to 0.5% B, 0 to 2% Zr and 30 to 51% Fe. In a preferred embodiment, the superaustenitic stainless steel consists essentially of, in

A superaustenitic stainless steel comprises in weight %, 0.15 to 0.9% C, 0.2 to 1.3% Si, 0 to 0.45% Mn, 32.5 to 37.5% Cr, 13.5 to 17.5% Ni, 3.2 to 5.5% Mo, 0 to 2% Nb, 0 to 0.5% B, 0 to 2% Zr and 30 to 51% Fe. In a preferred embodiment, the superaustenitic stainless steel consists essentially of, in weight %, 0.5 to 0.9% C, 0.2 to 0.5% Si, 0.2 to 0.4% Mn, 33.0 to 35.0% Cr, 15.5 to 17.5% Ni, 4.0 to 4.5% Mo, 0.7 to 0.9% Nb, 0.07 to 0.13% B, 0 to 0.05% Zr and 40 to 46% Fe. The superaustenitic stainless steel is useful for valve seat inserts for internal combustion engines such as diesel or natural gas engines.

대표청구항 ▼

1. A superaustenitic stainless steel comprising, in weight %: 0.15 to 0.9% C;0.2 to 1.3% Si;0 to 0.45% Mn;32.5 to 37.5% Cr;13.5 to 17.5% Ni;3.2 to 5.5% Mo;0 to 2% Nb;0 to 0.5% B;0 to 2% Zr; and30 to 51% Fe. 2. The superaustenitic stainless steel of claim 1, consisting essentially of 0.5 to 0.9% C, 0

1. A superaustenitic stainless steel comprising, in weight %: 0.15 to 0.9% C;0.2 to 1.3% Si;0 to 0.45% Mn;32.5 to 37.5% Cr;13.5 to 17.5% Ni;3.2 to 5.5% Mo;0 to 2% Nb;0 to 0.5% B;0 to 2% Zr; and30 to 51% Fe. 2. The superaustenitic stainless steel of claim 1, consisting essentially of 0.5 to 0.9% C, 0.2 to 0.5% Si, 0.2 to 0.4% Mn, 33.0 to 35.0% Cr, 15.5 to 17.5% Ni, 4.0 to 4.5% Mo, 0.7 to 0.9% Nb, 0.07 to 0.13% B, 0 to 0.05% Zr and 40 to 46% Fe. 3. The superaustenitic stainless steel of claim 1, further comprising incidental impurities of one or more of Al, As, Bi, Cu, Ca, Ce, Co, Hf, Mg, N, P, Pb, S, Sn, Ta, Ti, V, W, Y and Zn with a total content of incidental impurities of 1.5 weight % or less. 4. The superaustenitic stainless steel of claim 1, having a microstructure with an austenitic matrix free of primary carbides, ferrite and/or martensite, the microstructure having strengthening phases distributed along interdendritic regions or intergranular regions. 5. The superaustenitic stainless steel of claim 1, having a microstructure with intergranular or dendritic regions comprising an austenitic matrix; and interdendritic regions comprising eutectic reaction phases. 6. The superaustenitic stainless steel of claim 5, wherein the austenitic matrix is rich in Cr; the eutectic reaction phases are rich in Ni; and/or the austenitic matrix contains precipitates of niobium carbide and/or niobium carbonitride. 7. The superaustenitic stainless steel of claim 1, wherein C is 0.5 to 0.9%. 8. A valve seat insert comprising in weight %: 0.15 to 0.9% C;0.2 to 1.3% Si;0 to 0.45% Mn;32.5 to 37.5% Cr;13.5 to 17.5% Ni;3.2 to 5.5% Mo;0 to 2% Nb;0 to 0.5% B;0 to 2% Zr; and30 to 51% Fe. 9. The valve seat insert of claim 8, consisting essentially of 0.5 to 0.9% C, 0.2 to 0.5% Si, 0.2 to 0.4% Mn, 33.0 to 35.0% Cr, 15.5 to 17.5% Ni, 4.0 to 4.5% Mo, 0.7 to 0.9% Nb, 0.07 to 0.13% B, 0 to 0.05% Zr and 40 to 46% Fe. 10. The valve seat insert of claim 8, wherein the insert is a casting. 11. The valve seat insert of claim 8, wherein the insert has a hardness from about 35 to about 45 Rockwell C, a compressive yield strength from about 80 ksi to about 100 ksi at about room temperature; and/or a compressive yield strength from about 60 ksi to about 80 ksi at 1000° F. 12. The valve seat insert of claim 8, wherein the insert has an ultimate tensile rupture strength from about 50 ksi to about 70 ksi at about room temperature; and/or an ultimate tensile rupture strength from about 40 ksi to about 60 ksi at about 1000° F. 13. The valve seat insert of claim 8, wherein the insert exhibits a dimensional stability of less than about 0.3×10−3 inches per inch of insert outside diameter (O.D.) after heating for about 20 hours at about 1200° F.; and wherein the weight % Mn is present in an amount effective to produce a microstructure free of σ-iron-chromium tetragonal precipitates, martensite phases and/or ferrite phases after heating the insert to about 20 hours at about 1200° F. 14. The valve seat insert of claim 8, wherein: (a) the insert exhibits an HV10 Vickers hardness from about 420 HV10 at about room temperature to about 335 HV10 at about 1000° F.; or(b) the insert exhibits a decrease in hardness of 25% or less when heated from about room temperature to about 1000° F. 15. A method of manufacturing an internal combustion engine comprising inserting the valve seat insert of claim 8 in a cylinder head of the internal combustion engine. 16. The method of claim 15, wherein the engine is a diesel or natural gas engine. 17. A method of operating an internal combustion engine comprising closing a valve against the valve seat insert of claim 8 to close a cylinder of the internal combustion engine and igniting fuel in the cylinder to operate the internal combustion engine. 18. The method of claim 17, wherein the valve: (i) is a high-chromium iron-based alloy or a high-temperature, nickel-based superalloy;(ii) the valve is hard-faced with a high temperature, wear-resistant alloy strengthened by carbides. 19. The valve seat of claim 8, wherein C is 0.5 to 0.9%. 20. A method of making a superaustenitic stainless steel, comprising in weight %: 0.15 to 0.9% C;0.2 to 1.3% Si;0 to 0.45% Mn;32.5 to 37.5% Cr;13.5 to 17.5% Ni;3.2 to 5.5% Mo;0 to 2% Nb;0 to 0.5% B;0 to 2% Zr; and30 to 51% Fe; wherein:(a) the superaustenitic stainless steel is cast into a shaped component from a melt at a temperature from about 2800° F. to about 3000° F.; or(b) a powder of the superaustenitic stainless steel is pressed into a shaped component and sintered at a temperature from about 1950° F. to about 2300° F. in a reducing atmosphere, wherein the reducing atmosphere is hydrogen or a mixture of dissociated ammonia and nitrogen. 21. The method of claim 20, wherein the shaped component is a valve seat insert and the superaustenitic stainless steel consists essentially of 0.5 to 0.9% C, 0.2 to 0.5% Si, 0.2 to 0.4% Mn, 33.0 to 35.0% Cr, 15.5 to 17.5% Ni, 4.0 to 4.5% Mo, 0.7 to 0.9% Nb, 0.07 to 0.13% B, 0 to 0.05% Zr and 40 to 46% Fe. 22. The method of claim 20, further comprising precipitation hardening by heat treating the shaped component at a temperature from about 900° F. to about 1700° F. for about 2 hours to about 15 hours; and the heat treating is performed in an inert, oxidizing, or reducing atmosphere, or in a vacuum such that a hardness of the shaped component after heat treating is greater than a hardness of the shaped component before heat treating.