... , 12.9 grade steel bolts. Steel bolts for the main power system, the machinery industry, the pharmaceutical industry, pharmaceutical ... steel boiler steel. System metallurgical plants, railway bridges, airport hangar, port machinery, high-rise buildings, civil span. Structural steel ... be from TB1/2-TB1.1/4 for English system, from TB12-TB30 for metric system.8-Our advantage: Good quality confirmed by ...