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CN-122013049-A - Micro-niobium vanadium-substituted Q355 low-alloy angle steel and production process thereof

CN122013049ACN 122013049 ACN122013049 ACN 122013049ACN-122013049-A

Abstract

The invention discloses Q355 low alloy angle steel with micro niobium for replacing vanadium and a production process thereof. The chemical components of the angle iron are, by weight, 0.14% -0.22% of C, 0.25% -0.50% of Si, 1.10% -1.35% of Mn, 0.006% -0.012% of Nb, less than or equal to 0.020% of P, less than or equal to 0.015% of S, less than or equal to 0.0002% of H, less than or equal to 0.010% of N, and the balance of Fe and unavoidable impurities. The production process of the angle steel comprises the steps of smelting, continuous casting, rolling and controlled cooling after rolling, and the conventional alloy design with vanadium content is replaced by adding trace niobium, so that the finally obtained angle steel structure is a ferrite 75% -85% and pearlite 15% -25% complex phase structure, the ferrite grain size reaches 10-14.5 mu m, and the angle steel has excellent comprehensive properties of yield strength of more than or equal to 370 MPa, tensile strength of more than or equal to 550 MPa, elongation of more than or equal to 26%, and longitudinal impact energy of more than or equal to 56J at minus 20 ℃. Compared with the existing vanadium microalloyed angle steel product, the invention reduces the alloy cost, simultaneously combines the strength, toughness and welding performance, and is suitable for steel structure engineering with high requirements on mechanical properties and economy, such as power transmission towers.

Inventors

  • WANG HOUXIN
  • GUO AIMIN
  • WANG WENJUN
  • FENG YUNLI
  • GUO JIAN
  • LIU GUOLONG
  • LIU SHUAI
  • LIU WEIDONG
  • ZHANG LI

Assignees

  • 中信金属股份有限公司
  • 华北理工大学

Dates

Publication Date
20260512
Application Date
20260319

Claims (7)

  1. 1. The Q355 low alloy angle iron is characterized by comprising, by weight, 0.14% -0.22% of C, 0.25% -0.50% of Si, 1.10% -1.35% of Mn, 0.006% -0.012% of Nb, less than or equal to 0.020% of P, less than or equal to 0.015% of S, less than or equal to 0.0002% of H, less than or equal to 0.010% of N, and the balance of Fe and unavoidable impurities.
  2. 2. The Q355 low alloy angle steel for micro niobium vanadium replacement according to claim 1, wherein the mechanical property indexes of the angle steel are that the tensile strength is more than or equal to 550 MPa, the yield strength is more than or equal to 370 MPa, the elongation is more than or equal to 26%, and the longitudinal impact toughness at-20 ℃ is more than or equal to 56J.
  3. 3. The micro-niobium vanadium-substituted Q355 low alloy angle steel according to claim 1, wherein the microstructure of the angle steel is a complex phase structure of 75% -85% ferrite and 15% -25% pearlite, and the average grain size is 10-14.5 μm.
  4. 4. A process for producing Q355 low alloy angle steel with micro niobium for vanadium replacement as claimed in any one of the claims 1 to 3, comprising an electric furnace smelting, a continuous casting process, a rolling process and a cooling process, wherein, In the electric furnace smelting process, electric furnace smelting is adopted, the temperature of a molten pool is controlled to be 1620-1650 ℃, and LF refining is carried out to reduce the content of inclusions and stabilize the components of molten steel; In the continuous casting process, molten steel is injected into a tundish through a sliding nozzle at the bottom of a ladle, the temperature of the tundish is controlled to be 1530-1550 ℃, and the casting blank pulling speed is 0.8-2.2 m/min; In the rolling process, the blank is heated to 1190-1230 ℃ and kept at the initial rolling temperature of 1100-1150 ℃ and the final rolling temperature of 890-940 ℃ for 90-130 min, and the single-pass reduction rate is 15-25%; in the cooling process, the rolled piece is subjected to finish rolling, then is subjected to through-water cooling to 600-650 ℃, is subjected to air cooling to 250-350 ℃ in a cooling bed, is subjected to water cooling to 50 ℃, and is straightened by a straightener.
  5. 5. The process for producing Q355 low alloy angle steel with micro niobium for vanadium according to claim 4, wherein in the cooling procedure, the cooling rate is controlled to be 5-8 ℃ per second.
  6. 6. The process for producing Q355 low alloy angle steel with micro niobium for replacing vanadium according to claim 4, wherein the mechanical property index of the prepared angle steel is that the tensile strength is more than or equal to 550 MPa, the yield strength is more than or equal to 370 MPa, the elongation is more than or equal to 26%, and the longitudinal impact toughness at-20 ℃ is more than or equal to 56J.
  7. 7. The process for producing Q355 low alloy angle steel with micro niobium for vanadium according to claim 4, wherein the microstructure of the prepared angle steel is a complex phase structure of 75% -85% ferrite and 15% -25% pearlite, and the average grain size is 10-14.5 μm.

Description

Micro-niobium vanadium-substituted Q355 low-alloy angle steel and production process thereof Technical Field The invention relates to the technical field of metallurgical materials and steel production processes, in particular to low-alloy high-strength structural steel, and especially relates to micro-niobium vanadium-substituted Q355 low-alloy angle steel and a production process thereof. Background The angle steel is used as a main component of engineering such as an electric iron tower, a bridge, a steel structure factory building and the like, and has high requirements on mechanical properties and economy. With the rapid development of electric power infrastructure construction, the angle steel for the iron tower is required to have higher strength and toughness, and also required to have good welding performance and low-temperature impact resistance. At the same time, alloying costs are also a key issue of industry concern. At present, a vanadium micro-alloying process is generally adopted for the low-alloy angle steel of the grade Q355, and the strengthening mechanism mainly depends on precipitation strengthening of V (C, N). For example, in Chinese patent No. CN120443055A, a Q355E grade low temperature resistant angle steel and a production method thereof are disclosed, wherein the V addition amount is 0.025-0.045%, and the mechanical property meets the requirement, but in order to prevent the performance fluctuation caused by massive precipitation of the cubic VN, the N content in the steel is controlled to be 0.0060-0.0080 wt%, so that the technical requirements of steelmaking and steel rolling are increased, and the production cost is increased. In addition, the price fluctuation of vanadium resources is large, the alloy cost is high, and the large-scale popularization of the technology is not facilitated. The use of niobium element to replace vanadium element is one of the main technical directions in the research and development of the current angle steel material. For example, chinese patent No. 110699598A discloses a niobium microalloyed high-strength high-weather-resistance angle steel and a preparation process thereof, and 0.015% -0.060% of Nb is added to replace V, so that the structure is effectively refined, the element segregation is improved, and the toughness of the material is improved. However, the carbon content of the angle steel is low (0.05% -0.12%), so as to meet the requirements of mechanical properties and weather resistance, and meanwhile, various alloying elements such as Ni, cr, cu and the like are added, so that the alloy cost is obviously improved, and the angle steel is difficult to popularize and use in non-weather-resistant occasions. In addition, other technical means, such as introducing TiC precipitation strengthening or adopting a low-temperature finish rolling process, can improve the strength and toughness, but also generally faces the problems of rising production cost, higher requirement on rolling equipment and the like, and restricts the wide application of the rolling equipment in actual production. Therefore, how to further reduce the alloy cost and improve the structure uniformity and the performance stability on the basis of ensuring the mechanical properties becomes a technical problem to be broken through in the field. Disclosure of Invention In order to solve the technical problems, the invention provides the micro-niobium vanadium-substituted Q355 low-alloy angle steel and the production process thereof, wherein 0.006% -0.012% of niobium element is introduced into the steel to replace the traditional 0.015% -0.025% of vanadium content, and the optimized controlled rolling and cooling process is combined, so that the uniformity of the structure is improved, the growth of crystal grains is inhibited, the yield strength and the low-temperature impact toughness of the angle steel are obviously improved under the combined action of fine grain strengthening and second phase dispersion precipitation strengthening, and the Q355 low-alloy angle steel with stable performance and meeting the engineering application requirements of power transmission towers and the like is obtained. In order to achieve the technical purpose, the invention adopts the following scheme: in the first aspect, the invention provides Q355 low alloy angle iron with micro niobium for replacing vanadium, which comprises, by weight, 0.14% -0.22% of C, 0.25% -0.50% of Si, 1.10% -1.35% of Mn, 0.006% -0.012% of Nb, less than or equal to 0.020% of P, less than or equal to 0.015% of S, less than or equal to 0.0002% of H, less than or equal to 0.010% of N, and the balance of Fe and unavoidable impurities. Further, the specification range of the angle steel is 16-25 # and the thickness is less than or equal to 25 mm. Further, the mechanical property index of the angle steel is that the tensile strength is more than or equal to 550 MPa, the yield strength is more than or equal to 370 MPa, the elon