Special steel wire rope

Special steel wire rope

The high-strength compacted strand steel wire rope has good wear resistance, fatigue resistance and impact resistance, and its life span is 1.5 to 3 times that of ordinary steel wire ropes. Mainly used for imported cranes, truck cranes, crawler cranes, export lifting equipment, etc. The product quality reaches or exceeds the level of developed countries abroad, and has occupied a large domestic steel wire rope market for important purposes. The main products are compacted strand steel wire rope, swaged steel wire rope, plastic inset steel wire rope, plastic coated stand steel wire rope.

I. Basic concepts

1. Contact form: Generally speaking, steel wire ropes are divided into three types according to the contact form between the stranded steel wires, namely point contact, line contact and surface contact. In addition, there are point-line composite contact, line-surface composite contact and so on.

Point contact: The strand includes at least one layer of steel wires, and two adjacent layers of steel wires cross each other in point contact. When the wire rope is subjected to an external force, the steel wire is subjected to two forms of bending stress at the same time: the primary bending stress generated between the steel wire and the groove and the secondary bending stress generated by the mutual extrusion of the steel wires between the layers, so point contact The fatigue performance of steel wire rope is poor, and the breaking force is low. The advantage is that the steel wire rope is soft and simple to manufacture.

Line contact, also known as equal lay length or parallel lay, includes at least two layers of steel wires, all of which are strands twisted in one direction at a time, and adjacent layers of steel wires in the strand are in linear contact. Compared with point contact, when the number of steel wires in the strand is the same, the structure is compact, the breaking force of the wire rope is increased by 6~8%, there is only one bending stress in use, and the wear resistance and fatigue resistance are better. The disadvantage is that it is more flexible. difference.

Surface contact: At least one layer of steel wire is included in the strand. After the strand is deformed and processed by die drawing, rolling or forging, the shape of the steel wire and the size of the strand change, so that the contact form between each layer of the strand becomes Surface contact, while the metal area of the steel wire basically remains unchanged. The steel wire in the strand is similar to the special-shaped steel wire. The structure of the wire rope twisted by surface contact is particularly compact, the breaking force of the wire rope is increased, the contact stress between the wires in the strand is the smallest, and the wear resistance and fatigue resistance are better.

The surface contact is called compacted strand in today's wire rope terminology. The compacted strand wire rope mentioned later is the surface contact wire rope in the past.

2. Compacted steel wire rope: The steel wire rope that has undergone compaction is a compacted steel wire rope, and compaction is a technical term, which refers to the process. Its specialty is called metal pressure processing. There are many compaction processing methods, such as rolling and forging. Playing method, die drawing method, etc., actually all belong to pressure processing, and there are three basic forms as follows.

2.1 Compacted wire rope: After forming a rope, it is a multi-strand wire rope that is compacted (usually by forging) to reduce the diameter of the wire rope. For example, the wire rope K5×19S-FC for oil fishing operations, K6×31WS-IWRC for forest logging, etc. mentioned later (the identification method of compacted wire rope is in accordance with GB/T8706-2006)

2.2 Compacted stranded steel wire rope: Before forming a rope, a multi-strand steel wire rope that has undergone compaction processing such as die drawing, rolling or forging, that is, a multi-strand steel wire rope composed of compacted strands.

2.3 Swaged steel wire rope: a steel wire rope made of compacted strands that has undergone compaction processing to reduce the diameter of the steel wire rope.

3. Structural stability: the resistance of the wire rope to structural deformation during use. That is, the ability of the wire rope structure not to be damaged under the specified load. For example, after the steel wire rope is wound on the drum, the bottom steel wire rope often appears flattened, the lay length is elongated after the steel wire rope is impacted, and the inner wire jumps out.

4. Wear resistance: The steel wire rope exhibits resistance to wear when rotating and rubbing. It is manifested in the wear of the external steel wire and the reduction of the wire rope diameter. The wear performance depends on: the contact pressure stress between the surface steel wire and the wheel groove of the wire rope, the smaller the stress, the better the wear resistance; the thicker the outer wire diameter of the wire rope, the more wear resistant (so the Xilu type is used for the drilling wire rope, because Layer steel wire is thicker); line contact is poor, compacted strands are the next, and double compacted steel wire rope is better. The reason why the compacted steel wire rope has better abrasion resistance is because the outer steel wire of the compacted steel wire rope is flat and the contact surface with the bottom of the pulley groove is enlarged.

5. Fatigue life (also called fatigue resistance): The number of repeated bending fatigue of a steel wire rope before the wire breaks under certain alternating stress working conditions. Generally, a certain load is applied on the fatigue testing machine to reach the bending fatigue times of the specified number of broken wires. The number of fatigue depends on the size of the alternating load on the wire rope and various bending stresses on the wire. The number of bending fatigue of steel wire rope is generally more than 104, and the number of point contact fatigue is the least, followed by line contact, compacted strand steel wire rope and compacted steel wire rope are better. For example, when the steel wire rope of the same diameter and type, the outer steel wire is thin, the fatigue performance is better. Because the fatigue life is related to the contact form between the steel wires in the steel wire rope, the basic surface contact between the steel wire layers of the compacted steel wire rope group, the contact stress is small, and the fatigue resistance is increased.

6. Wire rope breaking force: refers to the minimum breaking force of wire rope specified by relevant standards. Generally, the actual tensile force of the wire rope to be broken on the tensile testing machine. Generally, the breaking force of compacted wire ropes is 10-20% higher than that of line contact wire ropes, or even more. Of course, the point contact wire rope has the lowest breaking force (these are compared under the same conditions).

Compacted steel wire rope has the advantages of compact structure, smooth surface, wear resistance, impact resistance, high metal density, high tensile strength, large carrying capacity, and long service life. It is used for important purposes such as oil, port, lifting and transportation. The product upgrade must choose the product, because the compacted stranded wire rope has more advantages than the twisted stranded wire rope, it has developed rapidly abroad.