Abstract��The microstructure and inclusion microcomponent of the tensile fracture of Q345B H-beam with unqualified tensile strength were analyzed. It was found that the high level of inclusions was the main cause of the disagreement of the strength of the products. By increasing the soft blowing time�� adopting the casing type long water nozzle protection and pouring�� prolonging the casting time and so on�� in the mass-produced product�� the class A inclusion level was level 1.5�� the class B inclusion level was level 1�� and the total inclusion level was below 2.5 level. And the minimum yield strength of the product was 25 MPa higher than the standard grade�� the minimum tensile strength was 48 MPa higher than the standard. Thus�� the product can be stably produced in batches
2018, Vol. 36 
