A large size 500n australian standard reinforcing bar and a method of producing the same

Abstract

The application provides a large-scale 500N Australian standard reinforcing steel bar and a production method thereof. The rolling specification of the 500N Australian standard reinforcing steel bar is phi 32-50mm, and single-line rolling is adopted. The production method of the large-scale 500N Australian standard reinforcing steel bar comprises the following steps: blast furnace molten iron smelting, molten iron desulfurization pretreatment, converter molten steel smelting, bloom continuous casting, heating furnace heating, rough rolling, medium rolling, water tank and recovery section, finishing rolling, K2 water tank and recovery section, finishing rolling, water tank and recovery section, shearing multiple times, cooling bed, shearing to a fixed size, collecting and warehousing. In the rough rolling, the opening rolling temperature is controlled at 950-1000 DEG C. The application greatly reduces the alloy cost of the reinforcing steel bar and improves the competitiveness of the exported steel and the enterprise benefits.

Description

Technical Field

[0001] This invention relates to the field of steel rolling technology, specifically to a 500N Australian and New Zealand standard steel bar and its production method, and more particularly to a large-diameter 500N Australian and New Zealand standard steel bar and its production method. Background Technology

[0002] 500N Australian and New Zealand standard steel bars possess high strength, good ductility and toughness, and weldability. These products are widely used in construction, bridges, highways, and other industries, serving as a crucial material for various infrastructure projects, primarily in Australia and other regions. Currently, China's domestic steel production capacity is severely oversupplied, leading to fierce competition. Steel exports are of significant importance in alleviating this overcapacity. However, the Australian and New Zealand standard 500N has very strict requirements for carbon equivalent. Larger gauge steel bars have lower compression ratios and coarser grains, resulting in lower performance for the same composition in larger gauges. Domestic manufacturers mostly improve strength by adding large amounts of V alloy, which keeps V alloy prices high, leading to higher production costs.

[0003] In summary, the existing technology has the following problems: When producing large-diameter 500N Australian and New Zealand standard steel bars, the existing process mainly improves the strength performance by adding a large amount of V alloy, which leads to higher production costs for enterprises. Summary of the Invention

[0004] This invention provides a large-diameter 500N Australian and New Zealand standard steel bar and its production method, in order to solve the problem in the prior art that the production of large-diameter 500N Australian and New Zealand standard steel bars mainly relies on adding a large amount of V alloy to improve strength performance, which leads to higher production costs for enterprises.

[0005] Therefore, this invention proposes a 500N Australian and New Zealand standard steel bar and its production method, particularly a large-diameter 500N Australian and New Zealand standard steel bar and its production method. 500 refers to a yield strength of 500 MPa, and N refers to a common grade. The method adopts the following technical solution:

[0006] A method for producing large-diameter 500N Australian and New Zealand standard (new standard is AS / NZS 4671:2019) steel bars, wherein the mass percentage of each chemical component in the large-diameter 500N Australian and New Zealand standard steel bars is: C: 0.18%~0.22%, Si: 0.20%~0.40%, Mn: 1.15%~1.25%, P≤0.045%, S≤0.045%, Nb: 0.020%~0.030%, with the remainder being Fe. The 500N Australian and New Zealand standard steel bars are rolled to a diameter of φ32~50mm using single-wire rolling. The method for producing the large-diameter 500N Australian and New Zealand standard steel bars includes the following steps:

[0007] Blast furnace iron smelting, iron desulfurization pretreatment, converter steelmaking, billet continuous casting, heating furnace heating, roughing rolling, intermediate rolling, water tank and recovery section, finishing rolling, K2 water tank and recovery section, finishing rolling, water tank and recovery section, shearing multiple lengths, cooling bed, shearing fixed lengths, collection, and warehousing; among which...

[0008] The roughing temperature is controlled at 950–1000℃.

[0009] The heating furnace has the following heating sections: a first heating section with a temperature of 1020–1080°C, a second heating section with a temperature of 1080–1140°C, and a soaking section with a temperature of 1060–1120°C.

[0010] Control the temperature of K2 inlet to 800-840℃.

[0011] Furthermore, the cooling bed temperature for the φ32mm specification is controlled at 570~610℃.

[0012] Furthermore, the cooling bed temperature for the φ36mm specification is controlled at 540~580℃.

[0013] Furthermore, the cooling bed temperature for the φ40mm specification is controlled at 520~560℃.

[0014] Furthermore, the cooling bed temperature for the φ50mm specification is controlled at 480~520℃.

[0015] Furthermore, the large-diameter 500N Australian and New Zealand standard steel bar is rolled to a diameter of φ32mm, and the mass percentage of each chemical component is as follows: C: 0.20%, Si: 0.27%, Mn: 1.21%, P: 0.028%, S: 0.023%, Nb: 0.026%, CEV: 0.41%. The temperature of the first heating section is 1042℃, the temperature of the second heating section is 1103℃, the temperature of the soaking section is 1086℃, the heating time is 119min, the initial rolling temperature is 977℃, the K2 entry temperature is 826℃, and the upper cooling bed temperature is 594℃.

[0016] Furthermore, the large-diameter 500N Australian and New Zealand standard steel bar is rolled to a diameter of φ36mm, and the mass percentage of each chemical component is as follows: C: 0.20%, Si: 0.27%, Mn: 1.21%, P: 0.028%, S: 0.023%, Nb: 0.026%, CEV: 0.41%. The temperature of the first heating section is 1034℃, the temperature of the second heating section is 1095℃, the temperature of the soaking section is 1082℃, the heating time is 125min, the initial rolling temperature is 989℃, the K2 entry temperature is 817℃, and the upper cooling bed temperature is 562℃.

[0017] Furthermore, the large-diameter 500N Australian and New Zealand standard steel bar is rolled to a diameter of φ40mm, and the mass percentage of each chemical component is as follows: C: 0.20%, Si: 0.27%, Mn: 1.21%, P: 0.028%, S: 0.023%, Nb: 0.026%, CEV: 0.41%. The temperature of the first heating section is 1047℃, the temperature of the second heating section is 1083℃, the temperature of the soaking section is 1071℃, the heating time is 123min, the initial rolling temperature is 968℃, the K2 entry temperature is 822℃, and the upper cooling bed temperature is 536℃.

[0018] Furthermore, the large-diameter 500N Australian and New Zealand standard steel bar is rolled to a diameter of φ50mm, and the mass percentage of each chemical component is as follows: C: 0.20%, Si: 0.27%, Mn: 1.21%, P: 0.028%, S: 0.023%, Nb: 0.026%, CEV: 0.41%. The temperature of the first heating section is 1030℃, the temperature of the second heating section is 1109℃, the temperature of the soaking section is 1094℃, the heating time is 136min, the initial rolling temperature is 975℃, the K2 entry temperature is 834℃, and the upper cooling bed temperature is 501℃.

[0019] In addition, the present invention also provides a large-diameter 500N Australian and New Zealand standard steel bar, which is manufactured according to any of the methods described above. The mass percentage of each chemical component in the large-diameter 500N Australian and New Zealand standard steel bar is as follows: C: 0.18%~0.22%, Si: 0.20%~0.40%, Mn: 1.15%~1.25%, P≤0.045%, S≤0.045%, Nb: 0.020%~0.030%, and the remainder is Fe.

[0020] This invention provides large-size 500N ASX standard steel bars and their production method. The production method involves adding Nb microalloying to the product. Nb microalloying can improve the strength of the steel bars through solid solution strengthening, grain refinement strengthening, and precipitation strengthening, and also improves the hardenability of the steel bars. The Nb content is controlled at 0.020-0.030%. Tempered martensite is obtained through post-rolling quenching and self-tempering technology, which greatly improves the strength of the steel bars and reduces the amount of alloy used. This invention sets the initial rolling temperature to 950-1000℃, allowing the alloy to fully dissolve in austenite while preventing grain growth during heating and refining the austenite grains. During the rolling process, the temperature of the rolled piece increases significantly. To prevent grain growth caused by temperature rise during rolling, the K2 temperature of the ordinary bar is controlled at 800-840℃. Strong cooling is used after rolling to obtain tempered martensite and improve the strength of the steel bars. Using the preparation process of this invention, the strength of the finished steel bars is greatly improved, and the amount of alloy used is reduced. This reduces production costs for enterprises while also improving the competitiveness of exported steel and enterprise profits.

[0021] Attached Figure Description picture

[0022] Figure 1-a This is a macroscopic metallographic photograph of Embodiment 1 of the present invention;

[0023] Figure 1-b This is a photograph of the surface metallographic structure of Embodiment 1 of the present invention (magnified 500 times);

[0024] Figure 1-c A metallographic photograph (500x magnification) of 1 / 4 of the structure in Example 1 of the present invention;

[0025] Figure 1-d A photograph of the central metallographic structure of Embodiment 1 of the present invention (magnified 500 times);

[0026] Figure 2-a This is a macroscopic metallographic photograph of Example 3 of the present invention;

[0027] Figure 2-b This is a photograph of the surface metallographic structure of Example 3 of the present invention (magnified 500 times);

[0028] Figure 2-c A metallographic photograph (500x magnification) of 1 / 4 of the structure in Example 3 of the present invention;

[0029] Figure 2-d This is a photograph of the central metallographic structure of Embodiment 3 of the present invention (magnified 500 times). Detailed Implementation

[0030] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the invention is now described.

[0031] I. To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0032] 1. The chemical composition, by weight percentage, is controlled as follows: C = 0.18%–0.22%, Si = 0.20%–0.40%, Mn = 1.15%–1.25%, P and S ≤ 0.045%, Nb = 0.020%–0.030%, with the remainder being Fe;

[0033] 2. The standard bar rolling specifications are φ32~50mm, using single-line rolling. The initial rolling temperature is 950~1000℃. The temperature of the rolled piece entering the 17th rolling mill (referred to as the K2 entry temperature) is controlled by the water tank after the 16th rolling mill, which is 800~840℃. The cooling bed temperature is controlled at 570~610℃ for φ32mm specifications; 540~580℃ for φ36mm specifications; 520~560℃ for φ40mm specifications; and 480~520℃ for φ50mm specifications.

[0034] The principle of this invention is as follows: C, Si, and Mn enhance the strength of reinforcing steel through solid solution strengthening, which can significantly improve the strength-to-yield ratio and improve building safety performance. However, the Australian and New Zealand standard for reinforcing steel has upper limits on C and Ceq (carbon equivalent symbol), so C is controlled at 0.18% to 0.22%, Mn at 1.15% to 1.25%, and excessive Si content will damage the plasticity of the reinforcing steel, so Si is controlled at 0.20% to 0.40%. Nb microalloying can improve the strength performance of reinforcing steel through solid solution strengthening, fine grain strengthening, precipitation strengthening, etc., and can also improve the hardenability of reinforcing steel, which is beneficial to the performance improvement of quenching and self-tempering process. However, excessive Nb will cause corner crack defects in the billet, affecting the surface quality of the finished reinforcing steel. Therefore, Nb is controlled at 0.020% to 0.030%. Tempered martensite is obtained through post-rolling quenching and self-tempering technology, which greatly improves the strength of reinforcing steel, reduces the amount of alloy used, and reduces production costs.

[0035] This invention sets the roughing rolling temperature to 950–1000℃ to allow the alloy to fully dissolve in austenite while preventing grain growth during heating and refining the austenite grains. During rolling, the workpiece temperature rises significantly. To prevent grain growth caused by this temperature rise, the temperature of the ordinary bar entering K2 is controlled at 800–840℃. After rolling, strong cooling is used, with the cooling bed temperature controlled at 570–610℃ for φ32mm bars; 540–580℃ for φ36mm bars; 520–560℃ for φ40mm bars; and 480–520℃ for φ50mm bars, obtaining tempered martensite to improve the strength of the reinforcing steel.

[0036] Based on the above principles, this invention provides a method for producing large-diameter 500N Australian and New Zealand standard steel bars, the specific technical measures of which include:

[0037] (1) The process of ordinary bar is as follows: blast furnace molten iron smelting → molten iron desulfurization pretreatment → converter molten steel smelting → billet continuous casting → heating furnace heating → rough rolling → intermediate rolling → water tank and recovery section → finish rolling → K2 water tank and recovery section → finish rolling → water tank and recovery section → cut multiple lengths → cooling bed → cut fixed lengths → collection, bundling, weighing, tagging, and warehousing.

[0038] (2) After BOF blowing, the molten iron is tapped using a sliding plate to block slag. Then, alloys and deoxidizers are added to make the C content 0.18% to 0.22%, the Si content 0.20% to 0.40%, the Mn content 1.15% to 1.25%, the P and S content ≤ 0.045%, the Nb content 0.020% to 0.030%, and the remainder Fe. Then, it is sent to the argon station for argon blowing. For continuous casting, appropriate secondary cooling parameters are selected, and the casting process is carried out using full-process protective casting.

[0039] (3) The square billets cast by continuous casting are heated in a heating furnace. The temperature of the first heating section is controlled at 1020-1080℃, the temperature of the second heating section is controlled at 1080-1140℃, the temperature of the soaking section is controlled at 1060-1120℃, the initial rolling temperature is controlled at 950-1000℃, and after roughing and intermediate rolling, the temperature of entering K2 is controlled at 800-840℃. The cooling bed temperature of φ32mm is controlled at 570-610℃; the cooling bed temperature of φ36mm is controlled at 540-580℃; the cooling bed temperature of φ40mm is controlled at 520-560℃; and the cooling bed temperature of φ50mm is controlled at 480-520℃.

[0040] In addition, the present invention also provides a large-diameter 500N Australian and New Zealand standard steel bar, which is manufactured according to any of the methods described above. The mass percentage of each chemical component in the large-diameter 500N Australian and New Zealand standard steel bar is as follows: C: 0.18%~0.22%, Si: 0.20%~0.40%, Mn: 1.15%~1.25%, P≤0.045%, S≤0.045%, Nb: 0.020%~0.030%, and the remainder is Fe. II. Specific Implementation Methods

[0042] 1. The rolling specifications of the ordinary bar (ordinary speed bar stock) are φ32~50mm, and single-line rolling is adopted. Table 1 is a comparison table of chemical composition (by mass percentage) of various embodiments of the present invention.

[0043] Table 1: Composition (%) of steel in each embodiment

[0044]

[0045] 2. The specific heating process parameters for each rolled steel bar specification of the present invention are shown in Table 2. Table 2 is the heating process parameter corresponding to each example described in Table 1.

[0046] Table 2: Heating process of steel in each embodiment

[0047]

[0048] 3. In this invention, the initial rolling temperature is set to 950–1000℃ to ensure the alloy is fully dissolved in the austenite, while simultaneously preventing grain growth during heating and refining the austenite grains. During rolling, the workpiece temperature rises significantly. To prevent grain growth caused by this temperature rise, the temperature of the ordinary bar entering K2 is controlled at 800–840℃. Strong cooling is used after rolling. Specific upper cooling bed temperatures for each specification are shown in Table 3.

[0049] Table 3: Rolling process of steel in various bar examples

[0050] Example 1 Φ32 977 826 594 Example 2 Φ36 989 817 562 Example 3 Φ40 968 822 536 Example 4 Φ50 975 834 501

[0051] 4. The mechanical properties of each embodiment are shown in Table 4. Combined with Tables 1-3 above, it can be seen that through reasonable control of chemical composition and the adoption of appropriate rolling processes, the finished steel bars in Embodiments 1-4 meet the various performance requirements of the Australian and New Zealand Standard 500N, which can significantly reduce the alloy cost of steel bars and significantly improve the competitiveness of exported steel and corporate profits.

[0052] Table 4: Mechanical properties of steel in each embodiment

[0053]

[0054] 5. Examples 1 and 3 are representative metallographic structures, as shown in Table 5. In the metallographic structure, F represents ferrite, P represents pearlite, S represents sorbite, and GB represents granular bainite. The metallographic structure of Example 1 is shown in Figure 1. Figure 1-a , Figure 1-b , Figure 1-c , Figure 1-d The images shown are photographs of the macroscopic metallographic structure, surface metallographic structure, 1 / 4 section metallographic structure, and central metallographic structure of Example 1, respectively; the metallographic structure of Example 3 is shown in Figure 2. Figure 2-a , Figure 2-b , Figure 2-c , Figure 2-d The images show the macroscopic metallographic structure, surface metallographic structure, 1 / 4 metallographic structure, and central metallographic structure of Example 3, respectively.

[0055] Table 5: Metallographic structures of Examples 1 and 3

[0056]

[0057] This invention provides a large-size 500N Australian and New Zealand standard steel bar and its production method. In the production method: C is controlled at 0.18% to 0.22%, Mn is controlled at 1.15% to 1.25%, and Si content is controlled at 0.20% to 0.40% because excessive Si content will damage the plasticity of the steel bar. Nb microalloying can improve the strength performance of the steel bar through solid solution strengthening, fine grain strengthening, precipitation strengthening, etc., and can also improve the hardenability of the steel bar. Nb is controlled at 0.020% to 0.030%. Tempered martensite is obtained by post-rolling quenching and self-tempering technology, which greatly improves the strength of the steel bar, reduces the amount of alloy used, and reduces production costs. Furthermore, this invention significantly increases the temperature of the rolled piece during the rolling process. To prevent grain growth caused by the temperature rise during rolling, the temperature of the ordinary bar entering K2 is controlled at 800–840℃. After rolling, strong cooling is employed, with the cooling bed temperature controlled at 570–610℃ for φ32mm bars; 540–580℃ for φ36mm bars; 520–560℃ for φ40mm bars; and 480–520℃ for φ50mm bars. This obtains tempered martensite, improving the strength of the reinforcing steel. This invention can meet the various performance requirements of the Australian and New Zealand Standard 500N, significantly reducing the alloy cost of reinforcing steel and improving the competitiveness of exported steel and enterprise profits.

[0058] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for producing large-diameter 500N Australian and New Zealand standard steel bars, characterized in that, The mass percentage of each chemical component in the large-diameter 500N Australian and New Zealand standard steel bar is as follows: C: 0.18%~0.22%, Si: 0.20%~0.40%, Mn: 1.15%~1.25%, P≤0.045%, S≤0.045%, Nb: 0.020%~0.030%, with the remainder being Fe. The 500N Australian and New Zealand standard steel bar is rolled to a diameter of φ32~50mm using single-wire rolling. The production method of the large-diameter 500N Australian and New Zealand standard steel bar includes the following steps: Blast furnace iron smelting, iron desulfurization pretreatment, converter steelmaking, billet continuous casting, heating furnace heating, roughing rolling, intermediate rolling, water tank and recovery section, finishing rolling, K2 water tank and recovery section, finishing rolling, water tank and recovery section, shearing multiple lengths, cooling bed, shearing fixed lengths, collection, and warehousing; among which... The roughing temperature is controlled at 950–1000℃. The heating furnace has the following heating sections: a first heating section with a temperature of 1020–1080°C, a second heating section with a temperature of 1080–1140°C, and a soaking section with a temperature of 1060–1120°C. During the rolling process, the temperature of the workpiece increases significantly. To prevent grain growth caused by the temperature rise during rolling, the temperature at the K2 inlet is controlled at 800-840℃; strong cooling is used after rolling. For the φ32mm specification, the cooling bed temperature is controlled at 570~610℃; For the φ36mm specification, the cooling bed temperature is controlled at 540~580℃; For φ40mm specifications, the cooling bed temperature is controlled at 520~560℃; For φ50mm specifications, the cooling bed temperature is controlled at 480~520℃.

2. The method for producing large-diameter 500N Australian and New Zealand standard steel bars as described in claim 1, characterized in that, The large-diameter 500N Australian and New Zealand standard steel bar is rolled to a diameter of φ32mm. The mass percentage of each chemical component is as follows: C: 0.20%, Si: 0.27%, Mn: 1.21%, P: 0.028%, S: 0.023%, Nb: 0.026%, CEV: 0.41%. The temperature of the first heating section is 1042℃, the temperature of the second heating section is 1103℃, the temperature of the soaking section is 1086℃, the heating time is 119min, the initial rolling temperature is 977℃, the K2 entry temperature is 826℃, and the upper cooling bed temperature is 594℃.

3. The method for producing large-diameter 500N Australian and New Zealand standard steel bars as described in claim 1, characterized in that, The large-diameter 500N Australian and New Zealand standard steel bar is rolled to a diameter of φ36mm. The mass percentage of each chemical component is as follows: C: 0.20%, Si: 0.27%, Mn: 1.21%, P: 0.028%, S: 0.023%, Nb: 0.026%, CEV: 0.41%. The temperature of the first heating section is 1034℃, the temperature of the second heating section is 1095℃, the temperature of the soaking section is 1082℃, the heating time is 125min, the initial rolling temperature is 989℃, the K2 entry temperature is 817℃, and the upper cooling bed temperature is 562℃.

4. The method for producing large-diameter 500N Australian and New Zealand standard steel bars as described in claim 1, characterized in that, The large-diameter 500N Australian and New Zealand standard steel bar is rolled to a diameter of φ40mm. The mass percentage of each chemical component is as follows: C: 0.20%, Si: 0.27%, Mn: 1.21%, P: 0.028%, S: 0.023%, Nb: 0.026%, CEV: 0.41%. The temperature of the first heating section is 1047℃, the temperature of the second heating section is 1083℃, the temperature of the soaking section is 1071℃, the heating time is 123min, the initial rolling temperature is 968℃, the K2 entry temperature is 822℃, and the upper cooling bed temperature is 536℃.

5. The method for producing large-diameter 500N Australian and New Zealand standard steel bars as described in claim 1, characterized in that, The large-diameter 500N Australian and New Zealand standard steel bar is rolled to a diameter of φ50mm. The mass percentage of each chemical component is as follows: C: 0.20%, Si: 0.27%, Mn: 1.21%, P: 0.028%, S: 0.023%, Nb: 0.026%, CEV: 0.41%. The temperature of the first heating section is 1030℃, the temperature of the second heating section is 1109℃, the temperature of the soaking section is 1094℃, the heating time is 136min, the initial rolling temperature is 975℃, the K2 entry temperature is 834℃, and the upper cooling bed temperature is 501℃.

Images