Multi-phase steel especially for production of standard-gauge rails

Abstract

Object of the invention is multi-phase steel, used for production of standard-gauge rails, characterized by the fact that the content of basic elements in the steel is no less than: C—0.15% wt, Si—0.60% wt, Mn—1.20% wt, Cr—1.20% wt, Ni—0.20% wt, Mo—0.10% wt, and additionally contains: Ti—0.01-0.25% wt, satisfying the relationship (% wt Mo)/(% mas. Ti)>1; Al—0.01-0.80% wt; B—0.001-0.003% wt., H2≤2 ppm, N≤80 ppm, volume of individual constituents is in relation to the total weigh of multiphase steel.

1 . Multi-phase steel, preferably used for the production of standard gauge rail wherein the content of basic elements in the steel is not less than:
 C: 0.15 wt. %;   Si: 0.60 wt. %;   Mn:1.20 wt. %;   Cr: 1.20 wt. %;   Ni: 0.20 wt. %;   Mo: 0.10 wt. %;   
       and, additionally, multi-phase steel contains:
 Ti: 0.01-0.25wt. % satisfying the relationship (% wt Mo)/(% mas. Ti) >1; 
 Al: 0.01-0.80 wt. %; 
 B: 0.001-0.003 wt. %; 
 H 2 ≤2 ppm; 
 N≤80 ppm, 
 
       the contents of alloy elements and carbon satisfy the following relationship:
   0. 15≤C≤0.77*CE  (1)
 
 
       where CE is a carbon concentration at an eutectoid point, calculated using the following equation:
   CE=0.768-0.0522(% Mn)-0.037(% Cr)-0.113(% Si)-0.012(% Mo)-0.068(% Ni)-0.006(% Cu);  (2)
 
 
       and contents of Al, Si, Ti, C and N satisfy the following limitations:
   [(Al)+(Si)]/C≤2.5  (3)
 
 
       and 
       
         
           
             
               
                 
                   
                     
                       
                         ( 
                         
                           % 
                            
                           
                               
                           
                            
                           Ti 
                         
                         ) 
                       
                       
                         [ 
                         
                           
                             ( 
                             
                               % 
                                
                               
                                   
                               
                                
                               C 
                             
                             ) 
                           
                           + 
                           
                             
                               12 
                               14 
                             
                              
                             
                               ( 
                               
                                 % 
                                  
                                 
                                     
                                 
                                  
                                 N 
                               
                               ) 
                             
                           
                         
                         ] 
                       
                     
                     ≥ 
                     0.03 
                   
                 
                 
                   
                     ( 
                     4 
                     ) 
                   
                 
               
             
           
         
       
       the amount of the individual constituents is in relation to the total weigh of multi-phase steel 
     
     
         2 . Multi-phase steel according to  claim 1  wherein the temperature of bainitic transformation B s  initiation is no higher than 460° C., and temperature of martensitic transformation M s  initiation is no less than 300° C. 
     
     
         3 . Multi-phase steel according to  claim 1  wherein after the rail cooling in still air, the content of bainitic ferrite is above 70% vol. of steel, allotrimorphic ferrite below 10% vol. of steel, self-tempered martensite below 10% vol of steel, retained austenite connected with bainitic ferrite-of carbon content min. 1.25% wt-above 10% vol. of steel, bainitic ferrite is hardened with nano-particles of TiC carbide.