In the paper,the structure and properties of ESC27Si2Mn2Ni2CrMo for largedia column teeth drilling body are studied.

In view of the present conditions about large post serrate drillers made in our China, an improvement of the existing drill steel material in use is carried out, thereupon, a large post serrate driller of  160 mm is developed by applying a technique of electroslag melting casting.

Because of the lower rock fragmentation efficiency and defective geometrical shape of chisel bit, Sweden has replaced chisel bit with taper connecting cross chisel bit and button bit since the mid seventies.

Now, we propose that chisel bit is renewed with more advantageous composite cutter bit gradually.

The technology and design of one-step molding bore bit;

The results show that the microstructure of new type bainite steel bore bit is bainite ferrite (BF) and retained austenite and has good strength-toughness, wear resistance and has higher tempering resistance.

The warm extrusion forming process and the die for bore bit were analyzed,It is fornd that the main reactor of die & in-die were fractured is forming pressure,structure & manufacture of the die and forming machine etc,and some related measures was tabed to improve using age of die.