*BK1系列材质为***氮化钢38CrMoAl、SACM645*氮化保温：505℃38小时、550℃34小时*氮化层深：单边0.48mm以上*氮化层硬度：HV960 以上*直线度每米小于0.06*料管生产范围：内孔（?14-?250）长度5000mmBK1 series(nitride barrel)*BK1 series is made of high quality nitride steel 38CrMoAl、SACM645*nitride insulation:38 hours of 505℃,34 hours of 550℃*nitride layer deep:unilateral more than 0.48 mm*the hardness:HV960 above*straighthess is less than 0.06 per meter*feed barrel production within the scope of hole (?14-?250)length is 5000mm