What is a wire rod
What is a wire rod?
Wire rod is the smallest section size in hot rolled section steel. In China, hot rolled round steel with a diameter of 5 ~ 9 mm and a total of eight specifications is called wire rod. Wire rod is also called wire rod because it is delivered in coils. The concept of wire rod in foreign countries is slightly different from that in China. In addition to circular section, it also has other shapes, and its diameter is inconsistent due to different demand and production technology level. According to different rolling mills, it can be divided into high-speed wire rod (high-speed wire rod) and ordinary wire rod (ordinary wire rod).
Wire rod is generally made of ordinary carbon steel and high-quality carbon steel. According to the steel distribution catalogue and different purposes, the wire rod includes ordinary low-carbon steel hot-rolled disc bar, high-quality carbon steel disc bar, carbon electrode disc bar, Quenched and tempered thread disc bar, steel wire rope disc bar, piano steel wire disc bar and stainless steel bar.
Classification of wire rod
According to the chemical composition of steel, wire rod can be divided into two categories: one is carbon steel, which can be divided into low carbon steel, medium carbon steel and high carbon steel according to the carbon content; Second, alloy steel. At present (1992), the steel types of wire rod are mainly ordinary low carbon steel, high-quality carbon steel, welding rod steel, steel wire rope steel, stainless acid resistant steel, heat-resistant steel, rolling bearing steel, etc.
According to the section shape, the wires are round, square, oval, trapezoid and special-shaped. There are few squares, less special shapes, and generally more circular sections.
Application of wire rod
There are two main uses of wire rod: one is for building materials; Second, it is used as raw material for wire drawing.
Wire rod for building materials, including ordinary low carbon steel, high-quality carbon steel and carbon spring steel. The varieties are round and threaded. The specifications with a diameter of 6 ~ 25 mm are most widely used, and those with a diameter of 28 ~ 32 mm are also often used. As a building material, the wire is required to ensure the chemical composition and weldability, and the physical properties are required to be uniform and stable, so as to facilitate cold bending, cold drawing and cold drawing. Wire rods of various specifications and diameters used in construction engineering are expected to be delivered in coils, so as to cut arbitrarily according to the length, so as to avoid waste.
Although there are many kinds of steel wires as wire drawing raw materials, there are only round ones. In order to reduce the drawing times, the diameter is generally 5 ~ 9 mm, and wire with diameter greater than 10 mm is also used for special purposes. As the wire drawing raw material, it is required to ensure the uniformity and stability of chemical composition and physical properties, the metallographic structure should be sorbitic as much as possible, the size should be accurate, the surface should be smooth, and the iron oxide scale should be thin, which is conducive to removal.
In general, wire rod has a wide range of uses and plays an important role in all sectors of the national economy. Some wires can be used directly after rolling, mainly for reinforcement of reinforced concrete and welding structural parts; Some are used as reprocessing raw materials after reprocessing. For example, it is drawn into various steel wires, twisted into steel wire rope, or woven into steel wire mesh; Rivets formed by hot forging or cold forging; After cold forging and rolling into bolts, and after various cutting and heat treatment into machine parts or tools; The spring is made by winding and heat treatment; Wait[ 2]
As a wire for construction, it must ensure chemical composition and weldability, have certain mechanical properties and be uniform and stable, so as to facilitate cold bending and bearing.
The wire used for wire drawing shall ensure uniform and stable chemical composition, metallographic structure and mechanical properties. The metallographic structure shall be sorbite as far as possible to reduce the annealing times during cold drawing. In addition, the specifications and dimensions shall be accurate, and the diameter is generally less than 12mm. The surface shall be smooth, the iron oxide scale shall be thin and easy to be washed off by acid, and the surface shall be free of defects such as ears and folding.
Application examples of wire rod
1. Ordinary low carbon steel hot rolled disc bar (GB701-65)
Ordinary low carbon steel hot-rolled disc bar is rolled from low-carbon ordinary carbon structural steel or carbon structural steel with low yield point. It is the most widely used coil bar in wire varieties, also known as flexible wire.
Main uses: the common line is mainly used for reinforcement of building reinforced concrete structures, and can also be cold drawn into steel wires for binding, etc.
2. Ordinary low carbon steel non torque controlled cold and hot rolled wire rod (ZBH4403-88)
The non torsion controlled cooling and hot-rolled wire rod is made of controlled cooling after rolling by the non torsion high-speed wire rod mill. The material is the same as that of the common wire, but the non torsion controlled cooling and hot-rolled wire rod has the advantages of high dimensional accuracy, good surface quality and high mechanical properties.
Main application: the dimensional accuracy of non torsion controlled cooling and hot rolling wire rod is divided into three levels: A, B and C. A. Class B and C precision are applicable to wire drawing, construction, packaging and welding rod, and class B and C precision are applicable to processing into bolts, screws and nuts.
3. High quality carbon steel wire rod (GB4354-84). High quality carbon steel wire rod is rolled from high quality carbon structural steel. It is one of the wire rod varieties with large dosage.
Main uses: high quality carbon steel wire rod is mainly used for processing and manufacturing carbon spring steel wire, oil quenched and tempered carbon spring steel wire, prestressed steel wire, high-strength high-quality carbon structural steel wire, galvanized steel wire, galvanized stranded wire rope, etc.
4. High quality carbon steel wire rod without torsion controlled cooling and hot rolling (ZBH44002-88)
High quality carbon steel non torsion controlled cooling and hot rolling wire rod are rolled by non torsion high-speed wire rod mill, and controlled cooling treatment is adopted after rolling. Compared with high-quality carbon steel wire rod, it has high dimensional accuracy, good surface quality and high mechanical properties.
Main purpose: the main purpose is the same as that of high-quality carbon steel wire rod. It is commonly used to manufacture carbon spring steel wire, oil quenched and tempered carbon spring steel wire, prestressed steel wire, high-quality carbon structural steel wire, galvanized steel wire, etc.
5. Wire rod for rope making steel wire (YB349-64)
Wire rod for rope making steel wire is one of high-quality hot-rolled carbon structural steel.
Main application: wire rod for rope making steel wire can be made of high-quality carbon structural steel of 35, 40, 45, 55, 60, 65, 70, 75, 80 and 85 steel grades. The chemical composition complies with gb699 (technical conditions for high quality carbon structural steel).
6. Non torsion controlled cold and hot rolled wire rod for rope making steel wire (ZBH44004-88)
The rope making steel wire is made of non torsion controlled cold and hot rolling disc and high-quality carbon structural steel, which are rolled on non torsion wire rod mill and controlled cooling after rolling. The rolled wire rod has high dimensional accuracy, good surface quality and superior mechanical properties.
Main application: mainly used for drawing rope steel wire and steel strand steel wire.
7. Carbon electrode and steel wire rod (GB3429-82)
Carbon electrode steel wire rod is made of low-carbon high-quality carbon structural steel by hot rolling.
Main application: mainly used for manufacturing manual arc welding core.
8. Carbon electrode steel without torsion controlled cooling and hot rolling wire rod (ZBH44005-88)
Carbon electrode steel non torsion controlled cooling and hot rolling wire rod are made by rolling on closed torsion wire rod mill and controlled cooling after rolling. It has high dimensional accuracy, good surface quality and superior performance. It is a high-quality electrode steel wire rod.
Main application: it is mainly used to manufacture carbon steel hot-rolled disc bar with electric welding bar and steel core with coating.
9. Alloy structural steel hot rolled wire rod (GB3077-82)
Alloy structural steel hot rolled wire rod is made of alloy structural steel. Alloy structural steel has 26 steel groups and 78 steel grades. Each manufacturer selects each brand for production according to the requirements of the demander and different purposes.
Main application: hot rolled wire rod with alloy structure is mainly used for drawing steel wire, metal products and structural parts.
10. Hot rolled carbon tool steel wire rod (GB1298-86)
Carbon tool steel is rolled from high-quality or high-quality high-carbon steel. Good processability and wear resistance, low price.
Main uses: mainly used for drawing steel ratio and manufacturing tools.
11. Alloy tool steel hot rolled wire rod (GB1299-77)
Alloy tool steel is a kind of steel made by adding alloy elements such as chromium, tungsten, molybdenum, vanadium, silicon, manganese, nickel and cobalt to the matrix of carbon tool steel. Compared with carbon tool steel. It has the characteristics of good hardenability, small cracking tendency after heat treatment, and high wear resistance and heat resistance. Alloy tool steel hot rolled wire rod is made of alloy tool steel with 5 steel groups and 33 steel grades. It is produced by Dalian Steel Plant, Benxi Steel Plant and Shaanxi steel plant respectively.
Main uses: suitable for making measuring tools, cutting tools, cold and hot working molds, impact resistant tools, etc.
12. Spring steel hot rolled wire rod (GB1222-84)
Spring steel is a kind of steel used to make springs or other elastic elements. Springs and elastic elements mainly use their elasticity to absorb and store energy, so as to alleviate vibration, impact or make parts complete some actions. Because it works under the conditions of impact, vibration or long-term uniform periodic alternating stress, spring steel is required to have high yield strength, especially high yield ratio (the ratio of yield strength to tensile strength), high elastic fatigue strength, high temperature resistance and corrosion resistance. Spring steel shall also have good surface quality.
There are 17 grades of spring steel, including carbon spring steel and alloy spring steel.
Main application: spring steel hot-rolled wire rod is mainly used to produce coil springs for various purposes.
13. Hot rolled ball bearing steel wire rod (YB9-68)
Ball bearing steel, abbreviated as bearing steel, is a kind of steel used to manufacture rings (shaft sleeves) and rolling elements (balls) of various rolling bearings. Due to the particularity of its application, bearing steel is required to have high and uniform hardness, wear resistance, high elasticity and fatigue strength. Sufficient toughness and hardenability, and certain corrosion resistance in atmospheric environment or lubricant. Some special-purpose rolling bearings also require high temperature resistance, corrosion resistance, non-magnetic, ultra-low temperature, high precision, long service life and other properties. Therefore, the selection and quality requirements of bearing steel are stricter than those of general steel.
Bearing steel usually refers to high carbon chromium steel, in addition to carburized bearing steel and high carbon chromium stainless bearing steel. There are 5 steel grades commonly used for rolling ball bearing steel hot-rolled wire rods.
Main application: hot rolled wire rod of ball bearing steel is mainly used to manufacture steel balls (steel balls) of bearings.
14. Stainless steel wire rod (GB4356-84)
Stainless steel wire rod is hot rolled from stainless steel of various grades and different structures.
Main uses: stainless steel wire rod is mainly used to manufacture stainless steel wire, stainless spring steel wire, stainless top forging steel wire and steel wire for stainless steel wire rope. According to the main industrial uses, stainless steel wire rods can also be divided into stainless steel and stainless acid resistant steel wire rods.
15. Stainless steel wire rod for welding (GB4241-84)
The chemical composition of stainless steel wire rod for welding is different from that of general stainless steel wire rod. In order to ensure its excellent welding performance and improve weld quality, the remarkable characteristics of stainless steel wire rod for welding are low carbon content, less toxic impurities such as phosphorus and sulfur, and high nickel and chromium content.
Main application: mainly used for manufacturing welding rod, steel core and welding wire.
Quality requirements of wire rod
The quality of wire rod has a great influence on the next process. The new wire rod mill plays an important role in improving wire rod quality, so the new wire rod mill has great vitality and has developed rapidly in recent years. The quality requirements for wire rod are summarized in six aspects:
- Dimensional tolerance;
- Surface quality;
- Chemical composition;
- Metallographic structure;
- Mechanical properties and disc weight.
With the development of production technology, users put forward higher and higher requirements in these aspects. It is these growing requirements that promote the new development of wire rod rolling technology and equipment. Among them, especially the coil weight has played a great role in promoting the development of wire rod mill. High speed wire rod mill (such as rolling mill) is produced to meet the above quality and output requirements.
Production process of wire rod
Wire rod is generally produced by high-speed wire, and its production process can be divided into the following steps:
- The billet is heated to more than 1100 ℃ by a stepping heating furnace;
- The heated billet is discharged from the furnace for high-pressure water descaling;
- Enter the roughing mill for rolling, and the roughing mill is a hot continuous rolling unit;
- The rolled piece after rough rolling enters the water cooling section for cooling to control its internal metallographic structure;
- After leaving the water cooling section, it enters the medium mill and finishing mill for further rolling;
- The finished rolled piece is ejected by the wire spinner to form a coil shape;
- The coiled wire is cooled in the air cooling section;
- At the end of the air cooling section, the wire is rolled into a drum shape by the winder;
- The rolled wire is sent to the baler for bundling;
- Enter the finished product warehouse.
Cooling mode of wire rod
The cooling methods after wire rolling can be divided into two categories: one is called natural cooling method; The other is called controlled cooling method.
Natural cooling method
Natural cooling method, that is, after the wire is rolled out of the finished product frame of the finishing mill, it is wound into a disc by the winding machine, and then hung on the hook conveyor for natural cooling during operation or transferred to the wire product stacking yard for natural cooling through roller table, chain conveyor and other equipment. The basic characteristic of natural cooling method is that the wire rod is naturally cooled at high temperature.
However, if the cooling time is long, the generated iron oxide scale is serious, and the cooling rates of the inner and outer layers of the wire coil are different, resulting in uneven microstructure and properties of the whole length of the wire, with a fluctuation range of about 20%.
Controlled cooling method
Controlled cooling method means that the cooling after wire rolling is carried out under controlled conditions. Its basic feature is that the rolled wire rod is immediately supercooled from high temperature to the phase transformation temperature required for the formation of sorbite phase transformation (generally 650 ~ 800 ° C), and then it is cooled in loose coils at different cooling rates. This avoids the disadvantages of natural cooling method and significantly improves the quality of wire rod.
There are many kinds of controlled cooling methods, mainly including STELMORE method, schrmann method, intermittent water cooling method, ed method, EDC method, flow cooling bed method, etc. These methods have their own advantages and disadvantages. Among them, the more common application is the STELMORE method. It is reported that there are more than 150 STELMORE cooling lines in the world.
Source: Network Arrangement – China Wire Rod Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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