making dry cylinder and piston ring by hollow profile of cast iron ,the use of melted iron could increase a time (fromm 25％-50％)，and simplified process of technology ,improved the mechanical property ,prolonged the natural life.

the ball of the rate 1-2class,7-8class for the diameter,ball number 400-600mm2.

σb>=1350Mpa,δ>=2%,ak>=45Jmm2