Austenitic stainless steel excellent in high temperature strength and corrosion resistance, heat resistant pressurized parts, and the manufacturing method thereof
View Patent ↗An austenitic stainless steel suited for ultra supercritical boilers, which consists of C: 0.03-0.12%, Si: 0.1-1%, Mn: 0.1-2%, Cr: not less than 20% but less than 28%, Ni: more than 35% but not more than 50%, W: 4-10%, Ti: 0.01-0.3%, Nb: 0.01-1%, sol. Al: 0.0005-0.04%, B: 0.0005-0.01%, and the balance Fe and impurities; and also characterized by the impurities whose contents are restricted to P: not more than 0.04%, S: not more than 0.010%, Mo: less than 0.5%, N: less than 0.02%, and O (oxygen): not more than 0.005%. Heat resistant pressurized parts excellent in thermal fatigue properties and structural stability at high temperatures, which have a coarse grain whose grain size number is 6 or less, and whose mixed grain ratio is 10% or less.
1. An austenitic stainless steel characterized by consisting of, by mass %, C: 0.03-0.12%, Si: 0.1-1%, Mn: 0.1-2%, Cr: not less than 20% but less than 28%, Ni: more than 35% but not more than 50%, W: 4-10%, Ti: 0.01-0.3%, Nb: 0.01-1%, sol. Al: 0.0005-0.04%, B: 0.0005-0.01%, and the balance Fe and impurities; and also characterized by the impurities whose contents are restricted to P: not more than 0.04%, S: not more than 0.010%, Mo: less than 0.5%, N: less than 0.02%, and O (oxygen): not more than 0.005%, and further characterized by having a coarse grain whose grain size number is 6 or less and whose mixed grain ratio is 10% or less.
2. Heat resistant pressurized parts excellent in thermal fatigue property and structural stability at high temperatures, which are made of an austenitic stainless steel according to claim 1 .
3. Heat resistant pressurized parts according to claim 2 , characterized by having a creep strength of 80 MPa or more and a reduction of area of 55% or more for a creep rupture time of 10,000 hours at 750° C.
4. An austenitic stainless steel characterized by consisting of, by mass %, C: 0.03-0.12%, Si: 0.1-1%, Mn: 0.1-2%, Cr: not less than 20% but less than 28%, Ni: more than 35% but not more than 50%, W: 4-10%, Ti: 0.01-0.3%, Nb: 0.01-1%, sol. Al: 0.0005-0.04%, B: 0.0005-0.01%, and at least one alloying element selected from at least one group mentioned below, and the balance Fe and impurities; and also characterized by the impurities whose contents are restricted to P: not more than 0.04%, S: not more than 0.010%, Mo: less than 0.5%, N: less than 0.02%, and O (oxygen): not more than 0.005%, and further characterized by having a coarse grain whose grain size number is 6 or less and whose mixed grain ratio is 10% or less,
the first group: Zr of 0.0005-0.1 mass %,
the second group: Ca of 0.0005-0.05 mass % and,
the third group: REM, Hf and Pd of 0.0005-0.2 mass %, respectively.
5. Heat resistant pressurized parts excellent in thermal fatigue property and structural stability at high temperatures, which are made of an austenitic stainless steel according to claim 4 .
6. Heat resistant pressurized parts according to claim 5 , characterized by having a creep strength of 80 MPa or more and a reduction of area of 55% or more for a creep rupture time of 10,000 hours at 750° C.
7. An austenitic stainless steel characterized by consisting of, by mass %, C: 0.03-0.12%, Si: 0.1-1%, Mn: 0.1-2%, Cr: not less than 20% but less than 28%, Ni: more than 35% but not more than 50%, W: 6-10%, Ti: 0.01-0.3%, Nb: 0.01-1%, sol. Al: 0.0005-0.04%, B: 0.0005-0.01%, and the balance Fe and impurities; and also characterized by the impurities whose contents are restricted to P: not more than 0.04%, S: not more than 0.010%, Mo: less than 0.5%, N: less than 0.02%, and O (oxygen): not more than 0.005%, and further characterized by having a coarse grain whose grain size number is 6 or less and whose mixed grain ratio is 10% or less.
8. Heat resistant pressurized parts excellent in thermal fatigue property and structural stability at high temperatures, which are made of an austenitic stainless steel according to claim 7 .
9. Heat resistant pressurized parts according to claim 8 , characterized by having a creep strength of 80 MPa or more and a reduction of area of 55% or more for a creep rupture time of 10,000 hours at 750° C.
10. An austenitic stainless steel characterized by consisting of, by mass %, C: 0.03-0.12%, Si: 0.1-1%, Mn: 0.1-2%, Cr: not less than 20% but less than 28%, Ni: more than 35% but not more than 50%, W: 6-10%, Ti: 0.01-0.3%, Nb: 0.01-1%, sol. Al: 0.0005-0.04%, B: 0.0005-0.01%, and at least one alloying element selected from at least one group mentioned below, and the balance Fe and impurities; and also characterized by the impurities whose contents are restricted to P: not more than 0.04%, S: not more than 0.010%, Mo: less than 0.5%, N: less than 0.02%, and O (oxygen): not more than 0.005%, and further characterized by having a coarse grain whose grain size number is 6 or less and whose mixed grain ratio is 10% or less,
the first group: Zr of 0.0005-0.1 mass %,
the second group: Ca of 0.0005-0.05 mass, and
the third group: REM, Hf and Pd of 0.0005-0.2 mass %, respectively.
11. Heat resistant pressurized parts excellent in thermal fatigue properties and a structural stability at high temperatures, which is made of an austenitic stainless steel according to claim 10 .
12. Heat resistant pressurized parts according to claim 11 , characterized by having a creep strength of 80 MPa or more and a reduction of area of 55% or more for a creep rupture time of 10,000 hours at 750° C.