Method and apparatus for heat treatment of steel rail

Abstract

The present invention discloses a heat treatment method of steel rail, comprising the steps of: (1) keeping the rolled hot steel rail running continuously, and performing hot straightening process for it; (2) performing first heat treatment process for the rolled hot steel rail after the hot straightening process, i.e., forced cooling the rail head and the rail base of the steel rail in a jetting air cooling manner, and (3) performing second heat treatment process for the steel rail after the first heat treatment process, i.e., heating the rail head of the steel rail to a temperature of 850˜950° C., and then forced cooling the rail head of the steel rail in a jetting air cooling manner to a temperature that is close to the temperature of the rail base of the steel rail. Since the steel rail experiences second heat treatment process by reheating after it is heat treated using the residual heat of rolling, phase transition occurs in the steel rail in the two rapid cooling processes, and finer metallographic structure is obtained in the steel rail. When the steel rail experiences the second heat treatment process, the rail web and the middle part of the rail head have already been at high temperature, therefore the energy consumption in reheating is reduced. The present invention also discloses a heat treatment apparatus of steel rail using the above method.

1 . A heat treatment method of steel rail, comprising: 
 (1) keeping the rolled hot steel rail running continuously, and performing hot straightening process for it;    (2) performing first heat treatment process for the rolled hot steel rail after the hot straightening process, i.e., forced cooling the rail head and the rail base of the steel rail in a jetting air cooling manner; and    (3) performing second heat treatment process for the steel rail after the first heat treatment process, i.e., heating the rail head of the steel rail to a temperature of 850˜950° C., and then forced cooling the rail head of the steel rail in a jetting air cooling manner to a temperature that is close to the temperature of the rail base of the steel rail.    
     
     
         2 . The method of  claim 1 , wherein, in the first heat treatment process at step (2), the rail head and the rail base of the steel rail are cooled at a rate of 1˜5° C./s for 90˜130 s to a temperature of 500˜600° C.  
     
     
         3 . The method of  claim 1 , wherein, in the second heat treatment process at step (3), the rail head of the steel rail is cooled at a rate of 1˜5° C./s for 90˜130 s to a temperature of 450˜600° C.  
     
     
         4 . The method of  claim 1 , wherein, in the second heat treatment process at step (3), an intermediate frequency induction heater is used to heat the rail head of the steel rail.  
     
     
         5 . The method of  claim 1 , wherein, after the second heat treatment process at said step (3), subsequent finishing works are performed for the steel rail after the steel rail is cooled to the normal temperature.  
     
     
         6 . A heat treatment apparatus of steel rail, which is arranged following the steel rail rolling production line, comprising a front supporting unit ( 10 ), a hot straightening unit ( 20 ), a first air cooling unit ( 30 ), a heating unit ( 50 ), and a second air cooling unit ( 60 ) that are arranged in the order of the heat treatment processes of the steel rail.  
     
     
         7 . The apparatus of  claim 6 , wherein: 
 the front supporting unit ( 10 ), the hot straightening unit ( 20 ), the first air cooling unit ( 30 ), the heating unit ( 50 ), and the second air cooling unit ( 60 ) are arranged orderly and linearly in the direction of the steel rail rolling production line.    
     
     
         8 . The apparatus of  claim 6 , wherein: 
 the front supporting unit ( 10 ), the hot straightening unit ( 20 ) and the first air cooling unit ( 30 ) are arranged orderly and linearly in the direction of the steel rail rolling production line;    the heating unit ( 50 ) and the second air cooling unit ( 60 ) are arranged orderly and linearly opposite to the direction of the steel rail rolling production line; and    a translating unit ( 40 ) is provided between the outlet of the first air cooling unit ( 30 ) and the inlet of the heating unit ( 50 ).    
     
     
         9 . The apparatus of  claim 6 , wherein: 
 said front supporting unit ( 10 ) comprises a steel rail tilter ( 11 ) provided to turn the steel rail ( 1 ) to the state where the rail head of the steel rail faces upwards, a steel rail lifter ( 13 ) provided to lift the steel rail ( 1 ) onto the front roller track ( 12 ), and the front roller track ( 12 ) provided to convey the steel rail ( 1 ) to the hot straightening unit ( 20 );    said hot straightening unit ( 20 ) comprises at least three pairs of active straightening rollers ( 21 ) and passive straightening rollers ( 22 ) arranged spacing apart each other in the convey direction of the steel rail;    said first air cooling unit ( 30 ) and said second air cooling unit ( 60 ) each comprises an upper guide mechanism ( 34 ) and a lower guide mechanism ( 35 ) provided to constrain the movement tract of the steel rail ( 1 ), a first jetting air cooler ( 31 ) disposed above the rail head of the steel rail ( 1 ) to jet air towards and cool the top surface of the rail head, a second jetting air cooler ( 32 ) disposed at both sides of the rail head of the steel rail ( 1 ) to jet air towards and cool both sides of the rail head, and a third jetting air cooler ( 33 ) disposed below the rail base of the steel rail ( 1 ) to jet air towards and cool the rail base; and    said heating unit ( 50 ) comprises an upper guide mechanism ( 52 ) and a lower guide mechanism ( 53 ) provided to constrain the movement trace of the steel rail ( 1 ), and a heater ( 51 ) provided to heat the rail head of the steel rail ( 1 ).    
     
     
         10 . The apparatus of  claim 9 , wherein, said heater ( 51 ) is an intermediate frequency induction heater ( 51 ).  
     
     
         11 . The apparatus of  claim 8 , wherein, said translating unit ( 40 ) comprises a quick steel raising and shifting machine ( 41 ).  
     
     
         12 . The apparatus of  claim 6 , wherein, a collection rack ( 70 ) is provided after said second air cooling unit ( 60 ).