The invention relates to a metallic seal
ball valve, in particular to an expansion type metallic seal
ball valve which is used in high-temperature high-pressure medium occasions, and comprises an upper valve body, a lower valve body, a ball body arranged in a cavity of the lower valve body, a valve rod
assembly used for driving the ball body, a
valve seat and a seal structure, wherein the ball body is provided with a perforative through hole; the spherical surface of the ball body is provided with a penetrating deformation lance which is positioned in the same plane as the axis of the throughhole; and the valve body
assembly is matched with the ball body in a rotating way and matched with the lance in an opening and closing way when the
ball valve is closed. As the deformation lance is arranged on the ball body, when the ball valve is closed, the lance of the ball body is widened by the valve rod
assembly, and the ball body is enlarged, thus eliminating the gap between the ball body and the metallic
valve seat, realizing the seal, further improving the sealing effect, meeting the requirement of being used at high temperature and under
high pressure. In addition, when the valve isopened, the ball body is diminished and separated from the
valve seat seal surface; and
frictional resistance is not generated when in rotation, therefore, the operation is labor-saving.