The Hy-chrome liners are made up by two kinds of metal, outer metal and inner metal. Outer shell is made of high-quality carbon steel. Inner sleeve is made of wear-resistant high-chrome alloy iron. After heat treatment, hardness of inner sleeves can reach more than HRC62. Smoothness of inner surface is mirror-like. Tolerances of bore dimensions are strict. Normal service life can reach more than 800 hours.