绳素滑轮一般用来导向或支撑，以改变绳索及传递拉 力的方向或平衡绳索分支的拉力。承受负荷不大的小尺寸滑轮（Ｄ＜３５０ｍｍ）一般制成实体的滑轮，用Ｑ２３５－Ａ或铸铁（如ＨＴ１５０）；受大负荷的滑轮一般采用球铁（如ＱＴ４００－１５）或铸铁（如ＺＧ２５Ⅱ、ＺＧ３５ Rope pulley is generally used to guide or support, in order to change the direction of the rope and the transmission of tension or balance the tension of the rope branch. Small-sized pulleys (D <350mm) which are not subject to heavy loads are generally made of solid pulleys with Q235-A or cast iron (such as HT150); heavy-duty pulleys are usually made of ductile iron (such as QT400-15) or cast iron ZG25 Ⅱ, ZG35