We recommended ZGCr5Mo double medium quenched steel or high Cr alloy steel which develop and promote to country by our company which has the characteristics of high quenching hardness, high toughness values and ideal cost effectiveness.The service life can be guaranteed in over 6 years (42000 hours), generally about 8 years, and the maintenance is almost zero. Since 1995,the application of hundreds of less than φ3800 mm mill liners recreived a satisfactory effect in electric power industry nationwide.For example,the service life of composite liners of huaibei power plant is 14 years, basic maintenance free. Through the unique heat treatment process（ double medium ), the hardness is very uniform whose hardness difference is less than HRc1.