Wire rod, also known as wire rod, usually refers to small-diameter round steel in coils.
The diameter of the wire rod is in the range of 5-19 mm (usually 6-9 mm), and the lower limit is the minimum size of the hot-rolled steel section.
Chinese name wire rod
Foreign name steel wire rod
Alias wire
Diameter 5-19 mm
High-strength prestressed steel wire is an economical and efficient steel material with high tensile strength and yield strength, good plasticity, and low relaxation performance. It is widely used in the construction of cement products, bridges, nuclear power plants, high-rise long-span buildings, highways, etc. With the development of my country's prestressed industry, the production and use of 82B wire rods as raw materials for the production of high-strength prestressed steel wires have attracted more and more people's attention. Qinggang Iron and Steel Co., Ltd. has been producing 82B wire rods since December 2003. In order to further improve the quality of 82B wire rods, the central laboratory has specially set up a technical innovation project group "82B wire rod quality research" to comprehensively analyze the factors affecting 82B wire rods. analysis and research.
Organizational requirements editor broadcast
82B wire rod is a hot-rolled wire rod for prestressed steel wire and steel strand. Its domestic brand is 82MnA. Its chemical composition is shown in Table 1.
The metallographic structure of the wire rod should mainly be sorbite, and should not contain martensite, reticular cementite and structures harmful to performance.
Shape editing broadcast
Wire rod is round steel with a relatively small diameter. The product form is rolled into a coil and supplied. Common ones on construction sites are 6, 8, 10, and 12 mm in diameter. They are mostly made of low carbon steel and are generally not used for the main bars of reinforced concrete structures. , mostly used to make steel bar sleeves, and small-diameter ones are used for "brick reinforcement" in brick-concrete structures.
Category editing broadcast
There are many varieties of wire rod. Among carbon steel wire rods, low carbon steel wire rods are commonly known as soft wires, while medium and high carbon steel wire rods are commonly known as hard wires. Wire rod is mainly used as blank for drawing, and can also be directly used as building materials and processed into mechanical parts. Stainless steel wire rod is used to make stainless steel wire, stainless steel spring steel wire, stainless steel upset steel wire and stainless steel wire rope. With the advancement of production technology, square,
Hexagonal, sector-shaped and other special-shaped wire rods; the upper limit of diameter has been expanded to 38 mm; the plate weight has increased from the original 40-60 kg to 3,000 kg. Due to the development of a new post-rolling heat treatment process, the iron oxide scale on the surface of the wire rod has been significantly thinned, and the structural properties have also been greatly improved.
Use Edit Broadcast
Wire rods need to be straightened and cut using a steel bar straightening machine before use. At the same time, the oxidized scale is removed in the machine, and the strength is improved to a certain extent during repeated bending and stretching. For small construction sites that do not have a straightening machine, it is not advisable to use a winch to straighten the wire rod. Direct pulling is not advisable as it may easily cause too much plastic deformation. A pulley weight should be used at one end to control the pulling force.
Factor Analysis Editor Broadcast
1. Influence of segregation of components in continuous casting slabs
(1) Influence of central segregation
On the cross-section of the steel billet sample, use a Ø5.5mm drill bit to take 4 samples from the edges and the middle, and 1 sample from the center. Use an infrared carbon and sulfur meter to analyze the carbon and sulfur content, and use chemical methods to analyze Silicon, manganese and phosphorus content. The results show that the maximum mass fraction of carbon in the center is 1. 06%, and the segregation coefficient of each carbon in the center is 1. 33, which far exceeds the standard requirements (the center carbon segregation coefficient of billets for steel cords is ≤ 1. 05). The degree of elemental segregation is small. The wire rod rolled from this continuous casting billet is prone to brittle fracture when the user draws it, and the fracture is cup-cone shaped. A longitudinal section of the fracture sample revealed that there was a "V" shaped crack in the center, and the metallographic structure examination found that there was reticular or semi-reticular cementite in the center.
Cementite itself is not easily deformed and is distributed in a network or semi-network at the grain boundaries, which is very harmful to the quality of the wire rod. The wire rod is prone to cracks along the grain boundaries during drawing, and may break brittlely during further drawing. The reason is that there is central carbon segregation in the continuous casting billet itself. Although the wire rod structure is in an austenitized state during rolling and the rolling temperature is high, due to the limited holding time, the central carbon segregation is difficult to eliminate, thus destroying the wire rod. The uniform properties of the matrix structure cause the wire to form a cup-cone-shaped fracture during the drawing process and break. Central segregation is a representative defect of continuous cast billets. The solution is to use large-size rectangular billets for rolling. Because large-size billets can increase the rolling ratio during rolling and eliminate the above defects, so it is generally not suitable to use smaller than rectangular billets. 120mm × 120mm continuous cast billet, especially the rolled carbon mass fraction is greater than 0. 75% wire rod. In addition, the superheat of molten steel is strictly controlled, electromagnetic stirring and light reduction technology during continuous casting are adopted, and the cooling intensity of the secondary cooling section of continuous casting is strengthened to reduce central segregation.
(2) Effect of surface carburization
Part of the broken wire sample taken back from the user had a pen tip-shaped fracture, and there was a series of fish scale cracks on one side of the sample. According to past experience, it should be caused by uneven local tissue on the surface. Metallographic examination of the broken wire samples revealed that massive and reticular cementite appeared in the structure near the fish scale cracks.
This is due to improper operation during the continuous casting process. The graphite carbon in the mold powder enters the mold with the molten steel, causing local carbonization on the surface of the continuous casting billet.
2. Influence of non-metallic inclusions
Through the inspection of non-metallic inclusions in 82B wire rod, it was found that the non-metallic inclusions in 82B wire rod are generally C and D type inclusions, and there are more type C inclusions, up to C4.5e, and type D inclusions are generally 1 to 1 .Level 5. The maximum width of the observed inclusions is 30 μm, which far exceeds the standard requirements (the standard requires Class C ≤ 1, Class D ≤ 0. 5). Non-metallic inclusions exist in wire rods, which mainly cause the following hazards to subsequent processing of wire rods:
(1) When drawing and twisting deformation, the continuity of the steel wire matrix is destroyed, causing stress concentration. Once subjected to the action of tensile stress or shear stress, cracks will occur along the direction of the inclusions, making the steel wire easy to break during drawing and twisting. , and the fracture is irregular;
(2) Non-metallic inclusions reduce the mechanical properties of the steel wire, especially its transverse mechanical properties, which reduces the plasticity of the steel wire, makes it easy to break under high deformation, and reduces the bending and torsion values. Non-metallic inclusions become the source of fatigue fracture of the steel wire, causing The fatigue resistance limit of steel wire is reduced;
(3) During the heat treatment of the steel wire, due to the difference in the expansion coefficient of the non-metallic inclusions and the steel wire matrix, the continuity of the steel wire matrix is cut within the steel wire, acting as a local gap, causing micro cracks to form during the heat treatment of the steel wire. As the drawing continues, During twisting, microcracks expand and cause the wire to break.
3. Effect of gas content
Through oxygen and nitrogen analysis of 82B wire rod, it was found that the mass fraction of oxygen in the wire rod is (55 ~ 85) ×10-6, with an average of 68. 42 ×10-6, and the mass fraction of nitrogen is (50 ~ 60) ×10- 6 , with an average of 54. 09 ×10- 6 , far higher than the standard requirements (wO ≤25 ×10- 6 , wN ≤30 ×10-6 ). Excessive nitrogen content in steel will cause the deterioration of the steel. Nitrogen can increase the effective hardening of the steel, increase the strength and hardness of the steel, and significantly reduce the plasticity, impact resistance and toughness. Oxygen in steel can also have adverse effects on the mechanical properties of steel. The degree of influence is related to the concentration of oxygen and the type, distribution and amount of oxygen-containing inclusions. Hydrogen in steel is extremely harmful. As the hydrogen content in steel increases, the plasticity and toughness decrease significantly. Especially for high carbon steel such as 82B, this phenomenon is more serious during the processing and cooling process.
4. Influence of rolling process
Since the rolling of high-wire wire rods is completed in a prescribed pass system, the deformation conditions are basically fixed, and the deformation parameters of each pass have been determined. In actual production, it is mainly through the control of the rolling temperature, that is, temperature-controlled rolling. To achieve this. The main purpose of temperature-controlled rolling is to refine grains: through low-temperature opening rolling, the size of the original austenite grains can be controlled; by lowering the final rolling temperature, the formation of austenite grains can be prevented from growing; by finishing rolling The rapid water cooling of the wire after reaching the set spinning temperature not only quickly transforms the deformed austenite into supercooled austenite, fully preparing for the structural transformation, but also controls the supercooled austenite grains. size. However, it should be noted that due to the load limitation of the rolling mill equipment, the rolling temperature cannot be too low, otherwise the equipment is prone to accidents. In addition, if the opening rolling temperature is controlled too low, it will easily lead to uneven heating of the billet, uneven austenitization, insufficient dissolution of carbides, and defects such as looseness in the billet that cannot be completely eliminated, resulting in poor wire rod passing performance and final structure. abnormal. Through the austenite grain size inspection of 82B wire rod, it was found that the grain size of 82B wire rod produced by Qinggang is grade 6 to 7. Compared with those of Wuhan Iron and Steel, Baosteel, and Shagang (grade 8), the grain size is coarser. .
When the opening rolling temperature is controlled at 990 ~ 1 010 ºC, the austenite grain size is level 7; when the opening rolling temperature is controlled at 1 000 ~ 1 050 ºC, the austenite grain size is level 6. This shows that the opening rolling temperature has a significant impact on the The austenite grain size has a greater influence. Under the premise of normal production, the opening rolling temperature should be controlled as low as possible.
5. Influence of controlled cooling process after rolling
The main purpose of controlling cooling is to control the degree of subcooling and cooling rate to obtain the sorbite structure required for strengthening and toughening. According to the principle of metal heat treatment, speeding up the cooling rate can move the continuous cooling curve to the lower right, the faster the cooling rate. For Stelmer's standard cooling mode - forced air cooling, the cooling rate cannot reach the critical transformation temperature for the formation of martensite. The faster the air cooling speed, the easier it is for austenite to transform into troostite. Therefore, a large air volume is used during actual cooling to achieve rapid cooling. On the one hand, the amount of ferrite precipitation can be controlled, and on the other hand, undercooling can be increased. Spend. 82B wire rod has special requirements for strength. Setting a higher spinning temperature and increasing the cooling rate can achieve the effect of improving strength.
As the spinning temperature increases, the tensile strength of the wire rod increases significantly, which seems to contradict the theory that the higher the spinning temperature, the coarser the grains, and the lower the spinning temperature, the finer the grains. In fact, this type of steel has been micro-alloyed, coupled with temperature-controlled rolling during rolling. After recovery and recrystallization, the deformed austenite grains are already quite fine. Even if the spinning temperature is increased, the coarseness of the grains will not be affected. The degree of oxidation is relatively small, so the impact on strength is negligible. It should be noted that the spinning temperature cannot be too high, otherwise due to the limitations of the air cooling equipment, the structural transformation of the high carbon steel wire rod cannot be completely completed on the controlled cooling line. Not only will the expected structure not be obtained, but also thicker irregularities will easily form on the surface of the wire rod. The iron oxide scale that is conducive to drawing reduces the overall performance of the wire rod. It is necessary to reasonably control the spinning temperature and the cooling rate after rolling to obtain a fine sorbite structure so that the finished product has high strength and good plasticity.
The structural inspection of 82B wire rod found that the structure is S + P and there is no F structure, which meets the standard requirements. However, the sorbitization rate is generally around 85%, which is still far behind the standard requirement of ≥95%. Compared with Shagang and Baosteel, the local trostitization rate is lower, only about 65% (Shagang 75%, Baosteel 85%). Its pearlite groups are larger and the grains are coarser. Therefore, after rolling, the 82B wire rod The controlled cooling process needs further optimization.
Zhengde Steel wire rod(s) is also called wire rod, which usually refers to small-diameter round steel in a coil. The diameter of the wire rod is in the range of 5-19mm (usually 6-9mm), and the lower limit is the minimum size of the hot-rolled steel section. There are many varieties of wire rods. Low carbon steel wire rods in carbon steel wire rod(s) are commonly called soft wires, and medium and high carbon steel wire rods are commonly called hard wires. Wire rods are mainly used as blanks for wire drawing, and can also be directly used as building materials and processed into mechanical parts. Stainless steel wire rod(s) are used in the manufacture of stainless steel wire, stainless steel spring steel wire, stainless upset forging steel wire and steel wire for stainless steel wire rope. With the advancement of production technology, wire rods with square, hexagonal, fan-shaped and other special-shaped sections have appeared; the upper limit of diameter has been expanded to 38 mm; the weight of the coil has increased from the original 40-60 kg to 3000 kg. Due to the development of a new post-rolling heat treatment process, the iron oxide scale on the surface of the wire rod has been significantly thinned, and the structure and performance have also been greatly improved.
| OD(mm) |
Area(mm²) |
Weight(kg/m) |
L(m) |
Weight(kg/s) |
| Φ5.5 |
23.8 |
0.187 |
1000 |
187 |
| Φ6 |
28.3 |
0.222 |
1000 |
222 |
| Φ6.5 |
33.2 |
0.26 |
1000 |
260 |
| Φ7 |
38.5 |
0.302 |
1000 |
302 |
| Φ7.5 |
44.2 |
0.347 |
1000 |
347 |
| Φ8 |
50.3 |
0.395 |
1000 |
395 |
| Φ8.5 |
56.7 |
0.445 |
1000 |
445 |
| Φ9 |
63.6 |
0.499 |
1000 |
499 |
| Φ9.5 |
70.9 |
0.556 |
1000 |
556 |
| Φ10 |
78.5 |
0.617 |
1000 |
617 |
| Φ10.5 |
86.6 |
0.69 |
1000 |
690 |
| Φ11 |
95 |
0.746 |
1000 |
746 |
| Φ11.5 |
104 |
0.815 |
1000 |
815 |
| Φ12 |
113 |
0.888 |
1000 |
888 |
| Φ12.5 |
123 |
0.963 |
1000 |
963 |
| Φ13 |
133 |
1.04 |
1000 |
1040 |
| Φ13.5 |
143 |
1.12 |
1000 |
1120 |
| Φ14 |
154 |
1.21 |
1000 |
1210 |
| Φ14.5 |
165 |
1.3 |
1000 |
1300 |
| Φ15 |
177 |
1.39 |
1000 |
1390 |
| Φ15.5 |
189 |
1.48 |
1000 |
1480 |
| Φ16 |
201 |
1.58 |
1000 |
1580 |
| Φ17 |
227 |
1.78 |
1000 |
1780 |
| Φ18 |
254 |
2 |
1000 |
2000 |
| Φ19 |
284 |
2.23 |
1000 |
2230 |
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Shandong Zhengde Metal Manufacturing Co., Ltd. is a production and sales company integrating hot-rolled steel coils, cold-rolled steel coils, galvanized steel coils, color-coated steel coils, section steel, steel pipes, steel wires, metal mesh, stainless steel, aluminum, copper and other metal products integrated large enterprises. Five production and sales bases have been formed in Binzhou, Liaocheng, Wuxi, Tianjin, Jinan and Tai'an, with more than 100 production lines, 4 nationally recognized laboratories, 2 technical engineering centers, and 5 enterprise technology centers. Products are exported to more than 50 countries and regions such as North America, South America, Europe, Middle East region, Russia, Africa, North America, and other parts of the world.
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Price advantage: discounts based on real market prices;
Transaction security: There will be no loss of customer funds;
After-sales guarantee: the customer's problem is our problem;
Long-term cooperation: quality assurance, price advantage, sincere service can last for a long time.
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