By experimental research and analysis

it is clear that weak adhesion between columnar grains is the main reason for continuous cast bloom crack of 37Mn gas vessel steel. Factors that affect grain cohesion are analized by means of tensile test

SEM and dilatometer equipment

as well as optical microscopy. The results show that as increase in Al content from 0.007% yo0.033%%

hot ductility of the steel at 800 ℃ predominantly reduces while the volumn effect of A-F/P phase transformation increases. Micro cracks and voids tend to nucleate at grain boundry. Concentration of Al

P

S at grain boundry is also one reason of crack formation at the same time. Improvement measures are brought forward on that basis such as reducing N content from0.0080% to (0.0040%-0.0060%)

adding small amount of Cr (0.20%-0.25%) and Mo (0.05%-0.08%)

as well as soft cooling the cast bloom in the range of 750-600 ℃

the phase transformation stresses and thermal stresses are reduced effectively to avoid crack formation and spreading in the continuous cast bloom of 37Mn gas vessel steel.