Method for producing h-shaped steel

Abstract

Plural calibers which perform a rough rolling step include: a grooving caliber configured to perform grooving vertically with respect to end parts in a width direction of a material to be rolled; one or plural split calibers formed with projections configured to create splits vertically with respect to the end parts in the width direction of the material to be rolled after being grooved to form divided parts on the end parts of the material to be rolled; and plural bending calibers formed with projections configured to abut against the splits and sequentially bend the formed divided parts, at least the split caliber of the last stage out of the one or plural split calibers is provided with caliber side surfaces configured to abut against right and left side surfaces of the material to be rolled and restrain the material to be rolled from right and left, and in the split caliber provided with the caliber side surfaces, rolling and shaping is performed under a condition where a caliber restraining rate B becomes 0.7 or more and less than 1.0.

1 . A method for producing H-shaped steel, the method comprising:
 a rough rolling step;   an intermediate rolling step; and   a finish rolling step, wherein:   a rolling mill that performs the rough rolling step is engraved with plural calibers configured to roll and shape a material to be rolled;   the plural calibers include:   a grooving caliber configured to perform grooving vertically with respect to end parts in a width direction of the material to be rolled;   one or plural split calibers formed with projections configured to create splits vertically with respect to the end parts in the width direction of the material to be rolled after being grooved to form divided parts on the end parts of the material to be rolled; and   plural bending calibers formed with projections configured to abut against the splits and sequentially bend the divided parts formed by the split caliber;   at least the split caliber of the last stage out of the one or plural split calibers is provided with caliber side surfaces configured to abut against right and left side surfaces of the material to be rolled and restrain the material to be rolled from right and left; and   in the split caliber provided with the caliber side surfaces, rolling and shaping is performed under a condition where a caliber restraining rate B represented by the following equation (1) becomes 0.7 or more and less than 1.0,
     B=t/t 0   (1)
 
   where t indicates a flange tip thickness when the split rolling and shaping, and the bending rolling and shaping are performed under the restraint in the caliber, and t 0  indicates a thickness of a slab end surface corresponding to a thickness of a flange tip formed by the grooving caliber.   
     
     
         2 . The method for producing the H-shaped steel according to  claim 1 , wherein
 the rolling and shaping is performed under a condition where a cumulative reduction rate until when the rolling and shaping in the split caliber provided with the caliber side surfaces is completed is 0.20 or more and 0.25 or less.   
     
     
         3 . The method for producing the H-shaped steel according to  claim 1 , wherein
 a tip angle of the projections formed on the one or plural split calibers is 25° or more and 40° or less.   
     
     
         4 . The method for producing the H-shaped steel according to  claim 1 , wherein
 in the one or plural split calibers and the plural bending calibers, light reduction is performed in a state where end surfaces of the material to be rolled are in contact with caliber surfaces facing the end surfaces in shaping of at least one pass or more.   
     
     
         5 . The method for producing the H-shaped steel according to  claim 1 , wherein:
 the plural calibers include a flat shaping caliber configured to perform flat shaping and rolling on the material to be rolled after passing through the plural split calibers and the plural bending calibers; and   the rolling and shaping in the flat shaping caliber is performed under a condition where a ratio I between a flange half-width and a flange thickness is 1.30 or more in a flange part of the material to be rolled corresponding to the divided part.   
     
     
         6 . The method for producing the H-shaped steel according to  claim 5 , wherein
 a raw material having a rectangular cross section and a thickness of 280 mm or more and 320 mm or less is used, and the flange half-width of the flange part of the material to be rolled before being subjected to the rolling and shaping in the flat shaping caliber is set to 200 mm or more.