Steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas and method of producing the same

Abstract

By having a steel composition containing, by mass %, C: 0.02% to 0.50%, Si: 0.05% to 0.50%, Mn: 0.5% to 2.0%, P: 0.05% or less, S: 0.01% or less, Al: 0.01% to 0.10%, N: 0.0005% to 0.008%, O: 0.01% or less, and V: 0.05% to 0.30% and Mo: 0.05% to 1.13% where a ratio of number of V atoms to number of Mo atoms is in a range of 0.6 to 2.0, the balance being Fe and inevitable impurities, and controlling the average particle size of fine complex carbides of V and Mo in a range of 1 nm to 20 nm, a steel structure for hydrogen gas such as a hydrogen storage vessel or a hydrogen line pipe that has excellent hydrogen embrittlement resistance in high pressure hydrogen environment can be obtained.

1 . A steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas, comprising
 a steel composition containing, by mass %:
 C: 0.02% to 0.50%, 
 Si: 0.05% to 0.50%, 
 Mn: 0.5% to 2.0%, 
 P: 0.05% or less, 
 S: 0.01% or less, 
 Al: 0.01% to 0.10%, 
 N: 0.0005% to 0.008%, 
 O: 0.01% or less, and 
 V: 0.05% to 0.30% and Mo: 0.05% to 1.13% where a ratio of number of V atoms to number of Mo atoms is in a range of 0.6 to 2.0, 
 the balance consisting of Fe and inevitable impurities, wherein 
   fine complex carbides of V and Mo have an average particle size of 1 nm to 20 nm.   
     
     
         2 . A steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas, comprising
 a steel composition containing, by mass %:
 C: 0.02% to 0.50%, 
 Si: 0.05% to 0.50%, 
 Mn: 0.5% to 2.0%, 
 P: 0.05% or less, 
 S: 0.01% or less, 
 Al: 0.01% to 0.10%, 
 N: 0.0005% to 0.008%, 
 O: 0.01% or less, and 
 Ti: 0.02% to 0.12% and Mo: 0.02% to 0.48% where a ratio of number of Ti atoms to number of Mo atoms is in a range of 0.5 to 2.0, 
 the balance consisting of Fe and inevitable impurities, wherein 
   fine complex carbides of Ti and Mo have an average particle size of 1 nm to 20 nm.   
     
     
         3 - 7 . (canceled) 
     
     
         8 . The steel structure for hydrogen gas according to  claim 1 , wherein
 the steel composition further contains at least one selected from groups (a) and (b):   (a) at least one selected from, by mass %:
 Cu: 0.05% to 1.0%, 
 Ni: 0.05% to 12.0%, 
 Cr: 0.1% to 2.5%, 
 Nb: 0.005% to 0.1%, 
 W: 0.05% to 2.0%, and 
 B: 0.0005% to 0.005%; and 
   (b) at least one selected from, by mass %:
 Nd: 0.005% to 1.0%, 
 Ca: 0.0005% to 0.005%, 
 Mg: 0.0005% to 0.005%, and 
 REM: 0.0005% to 0.005%. 
   
     
     
         9 . The steel structure for hydrogen gas according to  claim 2 , wherein
 the steel composition further contains at least one selected from groups (a) and (b):   (a) at least one selected from, by mass %:
 Cu: 0.05% to 1.0%, 
 Ni: 0.05% to 12.0%, 
 Cr: 0.1% to 2.5%, 
 Nb: 0.005% to 0.1%, 
 W: 0.05% to 2.0%, and 
 B: 0.0005% to 0.005%; and 
   (b) at least one selected from, by mass %:
 Nd: 0.005% to 1.0%, 
 Ca: 0.0005% to 0.005%, 
 Mg: 0.0005% to 0.005%, and 
 REM: 0.0005% to 0.005%. 
   
     
     
         10 . The steel structure for hydrogen gas according to  claim 1 , wherein
 the steel structure for hydrogen gas is a hydrogen storage vessel or a hydrogen line pipe.   
     
     
         11 . The steel structure for hydrogen gas according to  claim 2 , wherein
 the steel structure for hydrogen gas is a hydrogen storage vessel or a hydrogen line pipe.   
     
     
         12 . The steel structure for hydrogen gas according to  claim 8 , wherein
 the steel structure for hydrogen gas is a hydrogen storage vessel or a hydrogen line pipe.   
     
     
         13 . The steel structure for hydrogen gas according to  claim 9 , wherein
 the steel structure for hydrogen gas is a hydrogen storage vessel or a hydrogen line pipe.   
     
     
         14 . A method of producing the steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas according to  claim 1 , comprising
 heating a steel raw material having the steel composition according to  claim 1  to Ac 3  transformation temperature or higher;   then hot rolling the steel raw material to obtain a hot rolled material;   then quenching the hot rolled material from Ar 3  transformation temperature or higher to 250° C. or lower at a cooling rate of 1° C./s to 200° C./s; and   then tempering the hot rolled material at a temperature of 600° C. or higher and Ac 1  transformation temperature or lower to obtain a steel structure for hydrogen gas.   
     
     
         15 . A method of producing the steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas according to  claim 2 , comprising
 heating a steel raw material having the steel composition according to  claim 2  to Ac 3  transformation temperature or higher;   then hot rolling the steel raw material to obtain a hot rolled material;   then quenching the hot rolled material from Ar 3  transformation temperature or higher to 250° C. or lower at a cooling rate of 1° C./s to 200° C./s; and   then tempering the hot rolled material at a temperature of 600° C. or higher and Ac 1  transformation temperature or lower to obtain a steel structure for hydrogen gas.   
     
     
         16 . A method of producing the steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas according to  claim 8 , comprising
 heating a steel raw material having the steel composition according to  claim 8  to Ac 3  transformation temperature or higher;   then hot rolling the steel raw material to obtain a hot rolled material;   then quenching the hot rolled material from Ar 3  transformation temperature or higher to 250° C. or lower at a cooling rate of 1° C./s to 200° C./s; and   then tempering the hot rolled material at a temperature of 600° C. or higher and Ac 1  transformation temperature or lower to obtain a steel structure for hydrogen gas.   
     
     
         17 . A method of producing the steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas according to  claim 9 , comprising
 heating a steel raw material having the steel composition according to  claim 9  to Ac 3  transformation temperature or higher;   then hot rolling the steel raw material to obtain a hot rolled material;   then quenching the hot rolled material from Ar 3  transformation temperature or higher to 250° C. or lower at a cooling rate of 1° C./s to 200° C./s; and   then tempering the hot rolled material at a temperature of 600° C. or higher and Ac 1  transformation temperature or lower to obtain a steel structure for hydrogen gas.   
     
     
         18 . A method of producing the steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas according to  claim 1 , comprising
 forming a steel material having the steel composition according to  claim 1  into a formed body with a predetermined shape;   then heating the formed body up to Ac 3  transformation temperature or higher;   then quenching the formed body from Ar 3  transformation temperature or higher to 250° C. or lower at a cooling rate of 0.5° C./s to 100° C./s; and   then tempering the formed body at a temperature of 600° C. or higher and Ac 1  transformation temperature or lower to obtain a steel structure for hydrogen gas.   
     
     
         19 . A method of producing the steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas according to  claim 2 , comprising
 forming a steel material having the steel composition according to  claim 2  into a formed body with a predetermined shape;   then heating the formed body up to Ac 3  transformation temperature or higher;   then quenching the formed body from Ar 3  transformation temperature or higher to 250° C. or lower at a cooling rate of 0.5° C./s to 100° C./s; and   then tempering the formed body at a temperature of 600° C. or higher and Ac 1  transformation temperature or lower to obtain a steel structure for hydrogen gas.   
     
     
         20 . A method of producing the steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas according to  claim 8 , comprising
 forming a steel material having the steel composition according to  claim 8  into a formed body with a predetermined shape;   then heating the formed body up to Ac 3  transformation temperature or higher;   then quenching the formed body from Ar 3  transformation temperature or higher to 250° C. or lower at a cooling rate of 0.5° C./s to 100° C./s; and   then tempering the formed body at a temperature of 600° C. or higher and Ac 1  transformation temperature or lower to obtain a steel structure for hydrogen gas.   
     
     
         21 . A method of producing the steel structure for hydrogen gas with excellent hydrogen embrittlement resistance in high pressure hydrogen gas according to  claim 9 , comprising
 forming a steel material having the steel composition according to  claim 9  into a formed body with a predetermined shape;   then heating the formed body up to Ac 3  transformation temperature or higher;   then quenching the formed body from Ar 3  transformation temperature or higher to 250° C. or lower at a cooling rate of 0.5° C./s to 100° C./s; and   then tempering the formed body at a temperature of 600° C. or higher and Ac 1  transformation temperature or lower to obtain a steel structure for hydrogen gas.   
     
     
         22 . The method of producing the steel structure for hydrogen gas according to  claim 14 , wherein
 the steel structure for hydrogen gas is a hydrogen storage vessel or a hydrogen line pipe.   
     
     
         23 . The method of producing the steel structure for hydrogen gas according to  claim 15 , wherein
 the steel structure for hydrogen gas is a hydrogen storage vessel or a hydrogen line pipe.   
     
     
         24 . The method of producing the steel structure for hydrogen gas according to  claim 16 , wherein
 the steel structure for hydrogen gas is a hydrogen storage vessel or a hydrogen line pipe.   
     
     
         25 . The method of producing the steel structure for hydrogen gas according to  claim 17 , wherein
 the steel structure for hydrogen gas is a hydrogen storage vessel or a hydrogen line pipe.