6吋钢管芯152.4×4, 152.4×5, 152.4×6, 152.4×8, 151.5×5, 151.5×6, 150. 5×6等规格,内径公差稳定在0.2以内,不圆度稳定在0.2以内,直线度稳定在0.2以内