Basic knowledge and acceptance standard of steel wire rope

1、 Definition of steel wire rope

Steel wire rope is a spiral steel tow that twists the steel wires with mechanical properties and geometric dimensions meeting the requirements together according to certain rules. The steel wire rope is composed of steel wire, rope core and grease. Steel wire rope is a kind of rope which is first twisted into strands by multi-layer steel wires, and then twisted into a spiral shape by a certain number of strands with the rope core as the center. In material handling machinery, steel wire rope is used for lifting, traction, tensioning and bearing. The steel wire rope with light weight and high strength is not easy to break suddenly.

2、 Composition and function of steel wire rope

The steel wire rope is mainly composed of steel wire, rope core and grease.

1. Steel wire

The steel wire rope needs to bear the action of alternating load in the process of use, and its service performance is mainly determined by the mechanical properties of the steel wire, the surface state of the steel wire and the structure of the steel wire rope. The steel wire material includes carbon steel or alloy steel, which is made by cold drawing or cold rolling. The cross section of the steel wire is round or special-shaped (T-shaped, S-shaped, Z-shaped). The steel wire with special-shaped cross section is mainly used for the production of sealed steel wire rope, which has high tensile strength and toughness. The steel wire is properly treated to meet the needs of different service environmental conditions.

2. Rope core

The main function of the rope core is to support the steel wire rope to achieve a stable cross-sectional structure. The rope core includes steel core and fiber core. The fiber core includes natural fiber core and synthetic fiber core. The natural fiber core includes sisal, jute, cotton thread, etc., and the synthetic fiber core includes polyethylene and polypropylene filament, etc. The natural fiber core can store more lubricating grease, which can lubricate the steel wire rope and prolong the service life of the steel wire rope.

3. Grease

There are two main functions of spraying grease during the twisting process of steel wire rope. One is to lubricate the steel wire rope and slow down the wear of the steel wire surface. The other is that the grease can isolate the steel wire surface from the oxygen in the air and inhibit the oxidation and corrosion of the steel wire rope.

3、 Classification of steel wire rope

The steel wire rope can be classified according to the material, surface state, twisting method and purpose of the steel wire rope.

Basic knowledge and acceptance standard of steel wire rope

1. Classification by material

① Carbon steel wire rope is twisted with high-quality carbon structural steel wire as raw material.

② Stainless steel wire rope is made of stainless steel wire as raw material and twisted.

2. Classification by surface condition

① Phosphating coated steel wire rope (Chinese patent), referred to as phosphating steel wire rope for short. The phosphating film of rope making steel wire weighs 3-60g / m2. After phosphating, the steel wire is not cold drawn before twisting, and the strand rope, steel core and steel wire rope are directly twisted. The phosphating film can improve the wear resistance and corrosion resistance of the surface of rope making steel wire and effectively inhibit the occurrence of fretting fatigue.

② Galvanized steel wire rope includes two methods: hot galvanizing and electro galvanizing. The protection of steel wire by galvanized layer belongs to anodic protection. The thicker the galvanized layer, the stronger the anti-corrosion ability.

③ Plastic coated steel wire rope: the outer surface of the steel wire rope or the outer surface of the strand rope is coated with a certain thickness of plastic, including polyethylene, polypropylene, polyurethane, etc.

④ Smooth steel wire rope is a rope making steel wire obtained by cold drawing of raw materials after heat treatment and surface preparation. The steel wire will not undergo any surface treatment and will be directly twisted into strand rope, steel core and steel wire rope.

3. Classification according to twisting method

① Single strand rope, also known as single twist rope, is twisted by rope making steel wire around the central wire or hemp core. It can twist one or more layers of steel wire.

② Double stranded rope is made by twisting double stranded rope around rope core (steel core or fiber core). It can twist one or more layers of steel wire. It is the most widely used variety of steel wire rope.

③ The steel rope with the diameter of more than 60mm is mainly used as the steel rope with the diameter of more than 60mm.

4. Classification by status

① Point contact steel wire rope: the diameter of the steel wire in the strand is the same, the twist angle between each layer of steel wire is the same, and the twist distance is different, so the inner and outer layers of steel wire cross each other in a point contact state.

② Wire rope in line contact: the twist distance of each layer of steel wire in the strand is the same, and the twist angle is different. The inner and outer layers of steel wires are in contact with each other on a spiral line in a line contact state. Under the same service conditions, the service life of wire contact wire rope is longer than that of point contact wire rope.

③ Compacted steel wire rope, formerly known as surface contact steel wire rope, forms a contact surface between steel wires after forging and drawing in the process of steel wire rope twisting, including strand rope compaction, steel wire rope compaction and rope strand double compaction.

④ Sealed steel wire rope: the outer layer is made of special-shaped steel wire, including the steel wire with T-shaped, S-shaped and Z-shaped section structure. It has smooth surface and good wear resistance. Compared with other types of steel wire ropes with the same diameter, it has high tensile strength and can withstand transverse pressure, but it has poor flexibility, complex process and high manufacturing cost. It is often used as bearing rope, such as cable crane and cable on overhead ropeway.

4、 Application and inspection of steel wire rope

Due to the unique performance of steel wire rope, so far, no more ideal product has been found at home and abroad to comprehensively or replace steel wire rope in one field. Therefore, steel wire rope has become an indispensable component or material in metallurgy, mining, oil and gas drilling and production, machinery, chemical industry, Aerospace and other fields. Its quality has also been concerned by many domestic industries and invested a lot of manpower Material resources for the use of steel wire rope research and product development.

Application of steel wire rope

Before putting into production, the steel wire rope products must be accepted and tested. The significance of this step is to accurately and truly reflect the quality state of the steel wire rope, so as to predict the service life of the steel wire rope, avoid potential safety hazards and ensure safe production. Here is a brief introduction to the acceptance criteria of steel wire rope:

1. Inspection items

The acceptance inspection items of steel wire rope mainly include the following six items: ① shape and position dimension ② structure inspection ③ surface quality ④ supplier inspection report ⑤ strength test ⑥ fatigue test.

2. Inspection equipment

Micrometer, Wancai etm504c microcomputer controlled electronic universal testing machine, Wancai steel wire rope bending fatigue testing machine.

3. Acceptance criteria

① Dimensional and structural requirements

The diameter of the steel wire rope can be measured with a micrometer, and the structure can be observed with the naked eye. However, due to the different application industries and uses of the steel wire rope, the requirements for size and structure are also different. Therefore, the specific inspection is based on the actual situation, and there is no unified description here.

② Surface quality of steel wire rope

The surface quality of steel wire rope can be observed by naked eyes. The specific requirements are as follows:

1. The steel wire rope is made of galvanized steel wire, and the galvanized layer of the steel wire shall be uniform, continuous and free of crack and peeling;

2. Each strand in the steel wire rope and each steel wire in each share shall be tightly twisted, and there shall be no overlapping marks, protrusions, broken, crushed and disorderly crossed steel wires;

3. The steel wire surface in the steel wire rope shall be free of defects such as scratch, flattening or hard bending.

③ The supplier is required to provide inspection report for each batch of products and carefully check whether the relevant performance of the products is qualified.

④ Breaking force and tensile strength of steel wire rope.

The breaking tensile force and tensile strength of steel wire rope can be measured by the universal electronic testing machine controlled by etm504c microcomputer. The specific test methods and parameter indexes can refer to GB / t8358-2006 breaking tensile test method of steel wire rope, which specifies the terms and definitions, test principles, sample preparation, test procedures and test reports of breaking tensile test method of steel wire rope.

⑤ Bending fatigue test

In some applications, fatigue is the main cause of steel wire rope damage. The performance of steel wire rope bearing bending fatigue can be evaluated by using Wantan steel wire rope bending fatigue testing machine. The terms and definitions, test principles, test devices, test parameters, sample requirements, test procedures and test reports of steel wire rope bending fatigue test for elevator are specified in Yb / t4288-2012 steel wire rope bending fatigue test method for elevator.

4. Inspection record

The inspection results shall be recorded in the incoming inspection records. Those judged to be qualified shall be directly put into storage. If judged to be unqualified, the supplier shall be notified to return the goods. The supplier shall provide the corrective and preventive measures report, deliver the goods again, and then report to the inspector for inspection. Only those qualified can be put into storage and use.