Stainless steel for hot forging and hot forging method using said steel

Abstract

A micro-alloyed austenitic stainless steel for hot forging is provided. The micro-alloyed austenitic stainless steel has the following composition in weight %: 16.0%≦Cr≦25.0%; 8.0%≦Ni≦25.0%; traces≦Mo≦6.0%; traces≦C≦0.08%; traces≦Si≦1.0%; traces≦Mn≦3.0%; traces≦P 21 0.045%; traces≦S≦0.035%; traces≦Cu≦2.0%; traces≦N≦0.2%; traces≦V≦0.3%; traces≦Ti≦0.3%; traces≦B≦0.005%; traces≦W≦3.0%; 0.015%≦Nb≦0.100%, the remainder being iron and inevitable manufacturing impurities.

1 - 16 . (canceled) 
     
     
         17 . A micro-alloyed austenitic stainless steel for hot forging having the following composition in weight %:
 16.0%≦Cr≦25.0%;   8.0%≦Ni≦25.0%;   traces≦Mo≦6.0%;   traces≦C≦0.08%;   traces≦Si≦1.0 %;   traces≦Mn≦3.0%;   traces  23  P≦0.045%;   traces≦S≦0.035%;   traces≦Cu≦2.0%;   traces≦N≦0.2%;   traces≦V≦0.3%;   traces≦Ti≦0.3%;   traces≦B≦0.005%;   traces≦W≦3.0 %;   0.015%≦Nb≦0.100%,   the remainder being iron and inevitable manufacturing impurities.   
     
     
         18 . The stainless steel as recited in  claim 17  having the following composition in weight %:
 17.0%≦Cr≦19.0%; 
 8.0%≦Ni≦10.0%; 
 traces≦Mo≦6.0%; 
 traces≦C≦0.08%; 
 traces≦Si≦1.0 %; 
 traces≦Mn≦2.0%; 
 traces≦P≦0.045%; 
 traces≦S≦0.035%; 
 traces≦Cu≦2.0%; 
 traces≦N≦0.2%; 
 traces≦V≦0.3%; 
 traces≦Ti≦0.3%; 
 traces≦B≦0.005%; 
 traces≦W≦3.0 %; 
 0.015%≦Nb≦0.100%; 
 the remainder being iron and inevitable manufacturing impurities. 
 
     
     
         19 . The stainless steel as recited in  claim 17  having the following composition in weight %:
 18.0%≦Cr≦20.0 %; 
 8.0%≦Ni≦12.0%; 
 traces≦Mo≦6.0%; 
 traces≦C≦0.03%; 
 traces≦Si≦1.0 %; 
 traces≦Mn≦2.0%; 
 traces≦P≦0.045%; 
 traces≦S≦0.035%; 
 traces≦Cu≦2.0%; 
 traces≦N≦0.2%; 
 traces≦V≦0.3%; 
 traces≦Ti≦0.3%; 
 traces≦B≦0.005%; 
 traces≦W≦3.0 %; 
 0.015%≦Nb≦0.100%, 
 the remainder being iron and inevitable manufacturing impurities. 
 
     
     
         20 . The stainless steel as recited in  claim 17  having the following composition in weight %:
 16.0%≦Cr≦18.0%; 
 10.0%≦Ni≦12.5%; 
 2.0%≦Mo≦2.5%; 
 traces≦C≦0.08%; 
 traces≦Si≦1.0 %; 
 traces≦Mn≦2.0%; 
 traces≦P≦0.045%; 
 traces≦S≦0.035%; 
 traces≦Cu≦2.0%; 
 traces≦N≦0.2%; 
 traces≦V≦0.3%; 
 traces≦Ti≦0.3%; 
 traces≦B≦0.005%; 
 traces≦W≦3.0 %; 
 0.015%≦Nb≦0.100%, 
 the remainder being iron and inevitable manufacturing impurities. 
 
     
     
         21 . The stainless steel as recited in  claim 17  having the following composition in weight %:
 16.0%≦Cr≦18.0%; 
 10.0%≦Ni≦14.0%; 
 2.0%≦Mo≦3.0%; 
 traces≦C≦0.02%; 
 traces≦Si≦1.0 %; 
 traces≦Mn≦2.0%; 
 traces≦P≦0.045%; 
 traces≦S≦0.035%; 
 traces≦Cu≦2.0%; 
 traces≦N≦0.2%; 
 traces≦V≦0.3%; 
 traces≦Ti≦0.3%; 
 traces≦B≦0.005%; 
 traces≦W≦3.0 %; 
 0.015%≦Nb≦0.100%, 
 the remainder being iron and inevitable manufacturing impurities. 
 
     
     
         22 . The stainless steel as recited in  claim 17  having the following composition in weight %:
 19.0%≦Cr≦23.0 %; 
 23.0%≦Ni≦25.0%; 
 4.0%≦Mo≦5.0%; 
 traces≦C≦0.02%; 
 traces≦Si≦1.0 %; 
 traces≦Mn≦2.0%; 
 traces≦P≦0.045%; 
 traces≦S≦0.035%; 
 1.0%≦Cu≦2.0 %; 
 traces≦N≦0.2%; 
 traces≦V≦0.3%; 
 traces≦Ti≦0.3%; 
 traces  23  B≦0.005%; 
 traces≦W≦3.0 %; 
 0.015%≦Nb≦0.100%, 
 the remainder being iron and inevitable manufacturing impurities. 
 
     
     
         23 . The stainless steel as recited in  claim 17  wherein the niobium content (Nb) is 0.030% by weight or higher. 
     
     
         24 . The stainless steel as recited in  claim 17  wherein the niobium content (Nb) is 0.035% by weight or higher. 
     
     
         25 . The stainless steel as recited in  claim 17  wherein the niobium content (Nb) is lower than 0.050% by weight. 
     
     
         26 . The stainless steel as recited in  claim 17  wherein the niobium content (Nb) is 0.045% by weight or lower. 
     
     
         27 . The stainless steel as recited in  claim 17  wherein the carbon content (C) is lower than 0.05% by weight. 
     
     
         28 . The stainless steel as recited in  claim 17  wherein the carbon content (C) is 0.02% by weight or lower. 
     
     
         29 . The stainless steel as recited in  claim 17  wherein the chromium content (Cr) is lower than 23% by weight. 
     
     
         30 . The stainless steel as recited in  claim 17  wherein the phosphorus content (P) is 0.04% by weight or lower, and/or the sulfur content (S) is 0.03% by weight or lower. 
     
     
         31 . The stainless steel as recited in  claim 17  wherein the nitrogen content (N) is 0.1% by weight or lower. 
     
     
         32 . A hot forging method to forge a part from an ingot of the stainless steel as recited in  claim 17 . 
     
     
         33 . The hot forging method as recited in  claim 32  wherein the ingot has an initial weight of 50 tonnes or higher. 
     
     
         34 . The hot forging method as recited in  claim 32  wherein the ingot has an initial weight of 100 tonnes or higher. 
     
     
         35 . The hot forging method as recited in  claim 32  wherein the ingot is hot forged at a temperature of between 1300° C. and 1050° C. 
     
     
         36 . The hot forging method as recited in  claim 32  wherein the ingot is hot forged at a temperature of between 1250° C. and 1150° C. 
     
     
         37 . The hot forging method as recited in  claim 32  wherein the hot forging is conducted for a period of time longer than 24 hours. 
     
     
         38 . The hot forging method as recited in  claim 32  wherein the hot forging is conducted for a period of time longer than 36 hours.