Manufacturing method of weather-resistant bridge steel plate Q345qDNH with high impact toughness

Abstract

The present invention provides a weathering bridge steel plate Q345qDNH with high impact toughness and a manufacturing method. The chemical composition of the weathering bridge steel plate Q345qDNH with high impact toughness is as follows in weight percentage: C: 0.05 - 0.09 wt%, Si: 0.15 - 0.35 wt%, Mn: 1.10 - 1.30 wt%, P ≤ 0.020 wt%, S ≤ 0.008 wt%, Nb: 0.030 - 0.045 wt%, Ti: 0.010 - 0.020 wt%, Cr: 0.40 - 0.55 wt%, Ni: 0.30 - 0.40 wt%, Cu: 0.25 - 0.35 wt%, Alt: 0.020 - 0.040 wt%, N ≤ 0.005 wt%; the balance is Fe and inevitable trace elements. Through reasonable design of the composition and production process, the weathering bridge steel plate Q345qDNH product obtained by the present invention has a yield strength R eL ≥ 400 MPa, a tensile strength Rm ≥ 500 MPa, an elongation A ≥ 26%, and a low-temperature impact energy at -20 °C ≥ 270 J.

Description

Technical Field

[0001] The present invention relates to the field of steel production and manufacturing, and in particular to a weather-resistant bridge steel plate Q345qDNH and a manufacturing method thereof, in particular to a weather-resistant bridge steel plate Q345qDNH with high impact toughness and a manufacturing method thereof. Background Art

[0002] At present, with the development of my country's social economy and the gradual improvement of national infrastructure, the quality requirements for large-span, high-strength, lightweight bridge steel used in highway, railway and marine fields are getting higher and higher. Weather-resistant bridge steel plate Q345qDNH is a steel plate specially used for building highway or railway bridges. It is required to have high strength and toughness, and withstand the load and impact of locomotives and vehicles, and have good fatigue resistance, certain low-temperature toughness and atmospheric corrosion resistance.

[0003] In summary, the prior art has the following problems: the impact toughness of the existing weather-resistant bridge steel plate Q345qDNH can no longer meet the construction requirements of highway or railway bridges. Summary of the invention

[0004] The present invention provides a weather-resistant bridge steel plate Q345qDNH with high impact toughness and a manufacturing method, so as to solve the problem that the impact toughness of the existing weather-resistant bridge steel plate Q345qDNH cannot meet the construction requirements of building highway or railway bridges, thereby obtaining a weather-resistant bridge steel plate Q345qDNH with stable mechanical properties and high impact toughness.

[0005] To this end, the present invention proposes a weather-resistant bridge steel plate Q345qDNH and a manufacturing method, in particular, a weather-resistant bridge steel plate Q345qDNH with high impact toughness and a manufacturing method, wherein the chemical composition weight percentage of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is: C: 0.05-0.09wt%, Si: 0.15-0.35wt%, Mn: 1.10-1.30wt%, P≤0.020wt%, S≤0.008 wt%, Nb: 0.030-0.045wt%, Ti: 0.010-0.020wt%, Cr: 0.40-0.55wt%, Ni: 0.30-0.40wt%, Cu: 0.25-0.35wt%, Alt: 0.020-0.040wt%, N≤0.005wt%; the balance is Fe and inevitable trace elements; the yield strength R of the weather-resistant bridge steel plate Q345qDNH product with high impact toughness eL ≥400MPa, tensile strength Rm≥500MPa, elongation A≥26%, -20℃ low temperature impact energy≥270J.

[0006] The manufacturing method of the weather-resistant bridge steel plate Q345qDNH with high impact toughness comprises the following process steps performed in sequence:

[0007] Hot metal smelting in blast furnace → hot metal desulfurization pretreatment → molten steel smelting in converter → LF molten steel refining (ladle refining) → RH molten steel refining (molten steel vacuum cycle degassing) → slab continuous casting → hot slab heating → descaling → rough rolling → finishing rolling → straightening → sampling → steel plate level II flaw detection inspection → marking and storage;

[0008] Among them, the uniform heating temperature of the casting billet heating furnace is controlled to be 1160-1240°C.

[0009] Furthermore, it is ensured that the heating time of the ingot in the furnace is ≥210min and the soaking time is ≥35min.

[0010] Furthermore, the finishing rolling is set as 8 continuous passes.

[0011] Furthermore, the weather-resistant bridge steel plate Q345qDNH with high impact toughness does not use rolling mill cooling water and post-rolling controlled cooling water after rolling.

[0012] Furthermore, when the finished thickness of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is δ, 8≤δ≤10mm, the start temperature of finishing rolling is 1030±30℃, and the final temperature of finishing rolling is 850±30℃.

[0013] Furthermore, when the finished thickness of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is δ, and 10mm<δ≤16mm, the start temperature of finishing rolling is 960±30℃, and the final temperature of finishing rolling is 850±30℃.

[0014] Furthermore, when the finished thickness of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is δ, and 16mm<δ≤20mm, the start temperature of finishing rolling is 920±30℃, and the final temperature of finishing rolling is 840±30℃.

[0015] Furthermore, when the finished thickness of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is δ and 20mm<δ≤30mm, the start temperature of finishing rolling is 890±30℃ and the final temperature of finishing rolling is 820±30℃.

[0016] Furthermore, in the converter steelmaking, the molten iron entering the furnace is required to have S≤0.010wt%, argon is blown from the bottom throughout the smelting process, and the converter endpoint is controlled to have C: 0.04-0.06wt%, and P≤0.015wt%.

[0017] Furthermore, the finished product thickness δ of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is 10 mm, and the weight percentage of the chemical composition of the product is: C: 0.071wt%, Si: 0.25wt%, Mn: 1.22wt%, P: 0.014wt%, S: 0.003wt%, Nb: 0.040wt%, Ti: 0.019wt%, Cr: 0.45wt%, Ni: 0.33wt%, Cu: 0.28wt%, Alt: 0.026wt%, N: 0.0045wt%, the balance is Fe and inevitable trace elements, the slab heating furnace soaking temperature is 1218°C, the slab heating time in the furnace is 263min, the soaking time is 43min, the finishing rolling start temperature is 1023°C, the finishing rolling final rolling temperature is 834°C, and the product yield strength R eL It is 452MPa, the tensile strength Rm is 596MPa, the elongation A is 27.3%, and the low-temperature impact energy of -20℃ is 273J.

[0018] Furthermore, the finished product thickness δ of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is 16 mm, and the weight percentage of the chemical composition of the product is: C: 0.064wt%, Si: 0.25wt%, Mn: 1.18wt%, P: 0.013wt%, S: 0.004wt%, Nb: 0.037wt%, Ti: 0.017wt%, Cr: 0.45wt%, Ni: 0.32wt%, Cu: 0.27wt%, Alt: 0.029wt%, N: 0.0038wt%, the balance is Fe and inevitable trace elements, the slab heating furnace soaking temperature is 1211°C, the slab heating time in the furnace is 255min, the soaking time is 46min, the finishing rolling start temperature is 972°C, the finishing rolling final rolling temperature is 841°C, and the product yield strength R eL It is 451MPa, the tensile strength Rm is 548MPa, the elongation A is 29.8%, and the low-temperature impact energy of -20℃ is 327J.

[0019] Furthermore, the finished product thickness δ of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is 20 mm, and the weight percentage of the chemical composition of the product is: C: 0.080 wt%, Si: 0.23 wt%, Mn: 1.20 wt%, P: 0.013 wt%, S: 0.001 wt%, Nb: 0.034 wt%, Ti: 0.015 wt%, Cr: 0.46 wt%, Ni: 0.32 wt%, Cu: 0.27 wt%, Alt: 0.031 wt%, N: 0.0037 wt%, the balance is Fe and inevitable trace elements, the slab heating furnace soaking temperature is 1213 ° C, the slab heating time in the furnace is 260 min, the soaking time is 42 min, the finishing rolling start temperature is 912 ° C, the finishing rolling final rolling temperature is 839 ° C, and the product yield strength R eL It is 431MPa, the tensile strength Rm is 536MPa, the elongation A is 29.5%, and the low-temperature impact energy of -20℃ is 351J.

[0020] The present invention also provides a weather-resistant bridge steel plate Q345qDNH with high impact toughness, which is made according to any one of the methods in the aforementioned steps. The chemical composition weight percentage of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is: C: 0.05~0.09wt%, Si: 0.15~0.35wt%, Mn: 1.10~1.30wt%, P≤0.020wt%, S≤0.008wt%, Nb: 0.030~0.045wt%, Ti: 0.010~0.020wt%, Cr: 0.40~0.55wt%, Ni: 0.30~0.40wt%, Cu: 0.25~0.35wt%, Alt: 0.020~0.040wt%, N≤0.005wt%; the remainder is Fe and inevitable trace elements.

[0021] The present invention provides a weather-resistant bridge steel plate Q345qDNH with high impact toughness and a manufacturing method by reasonably designing the composition and production process. The chemical composition weight percentage of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is: C: 0.05-0.09wt%, Si: 0.15-0.35wt%, Mn: 1.10-1.30wt%, P≤0.020wt%, S≤0.008wt%, Nb: 0.030-0.045wt%, Ti: 0.010-0.020wt%, Cr: 0.40-0.55wt%, Ni: 0.30-0.40wt%, Cu: 0.25-0.35wt%, Alt: 0.020-0.040wt%, N≤0.005wt%; the balance is Fe and inevitable trace elements;

[0022] The manufacturing method of the weather-resistant bridge steel plate Q345qDNH with high impact toughness comprises the following process steps performed in sequence:

[0023] Hot metal smelting in blast furnace → hot metal desulfurization pretreatment → molten steel smelting in converter → LF molten steel refining treatment → RH molten steel refining treatment → slab continuous casting → hot slab heating → descaling → rough rolling → finishing rolling → straightening → sampling → steel plate level II flaw detection inspection → marking and storage;

[0024] Among them, the uniform heating temperature of the casting billet heating furnace is controlled to be 1160-1240°C.

[0025] The present invention adds Cu, Ni, and Cr elements to the steel to ensure weather resistance, designs low carbon components in the steel, adds an appropriate amount of Nb+Ti microalloy, strictly controls the N content in the steel, and formulates a reasonable smelting-continuous casting-rolling process to achieve stable production of the product, thereby obtaining a weather-resistant bridge steel plate Q345qDNH with stable mechanical properties and high impact toughness. The yield strength R eL ≥400MPa, tensile strength Rm≥500MPa, elongation A≥26%, -20℃ low temperature impact energy≥270J. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a metallographic structure photograph of Example 1 of the present invention;

[0027] Figure 2 This is a metallographic structure photograph of Example 4 of the present invention. DETAILED DESCRIPTION

[0028] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the present invention is now described.

[0029] The present invention provides a weather-resistant bridge steel plate Q345qDNH with high impact toughness and a manufacturing method thereof. The yield strength R eL ≥400MPa, tensile strength Rm≥500MPa, elongation A≥26%, -20℃ low temperature impact energy≥270J.

[0030] 1. To achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0031] The invention discloses a method for manufacturing a weather-resistant bridge steel plate Q345qDNH with high impact toughness. The chemical composition weight percentage of the steel is C: 0.05-0.09wt%, Si: 0.15-0.35wt%, Mn: 1.10-1.30wt%, P≤0.020wt%, S≤0.008wt%, Nb: 0.030-0.045wt%, Ti: 0.010-0.020wt%, Cr: 0.40-0.55wt%, Ni: 0.30-0.40wt%, Cu: 0.25-0.35wt%, Alt: 0.020-0.040wt%, N≤0.005wt%; the balance is Fe and inevitable trace elements.

[0032] The manufacturing method of weather-resistant bridge steel plate Q345qDNH with high impact toughness has the following process route: blast furnace molten iron smelting → molten iron desulfurization pretreatment → converter molten steel smelting → LF molten steel refining treatment → RH molten steel refining treatment → slab continuous casting → hot slab heating → descaling → rough rolling → finishing rolling → straightening → sampling → steel plate level II flaw detection inspection → marking and storage.

[0033] Among them, specific technical measures include:

[0034] (1) The low carbon composition design is adopted to control the C range in the steel to 0.05-0.09wt%, which can effectively improve the impact toughness of the steel plate and make the steel plate have low welding crack sensitivity; the N in the steel is controlled to be ≤0.005wt%, which reduces the precipitation of Ti and N in the liquid steel during the slab continuous casting process, and can reduce the destructive effect of coarse TiN precipitates on the toughness of the steel plate for welded structures.

[0035] (2) The Nb content in the steel is designed to be 0.030-0.045wt%, so as to give full play to its role in refining grains, improving the impact toughness of the steel and reducing its brittle transition temperature; the Ti content in the steel is designed to be 0.010-0.020wt%, so as to reduce the N content in the steel that reacts with the Al element, inhibit the precipitation of AlN, and effectively reduce the surface cracks of the ingot.

[0036] (3) Converter steelmaking: The molten iron entering the furnace must be S≤0.010wt%; the smelting process uses argon gas at the bottom of the furnace throughout the process; the converter endpoint control C: 0.04-0.06wt%, P≤0.015wt%;

[0037] (4) LF molten steel refining treatment: The molten steel is treated in the LF furnace to remove inclusions, balance temperature and alloy;

[0038] (5) RH molten steel refining treatment: total vacuum cycle time 15 to 20 minutes, ultimate vacuum holding time more than 10 minutes; net cycle time more than 3 minutes; soft argon blowing time after calcium treatment 8 to 10 minutes; molten steel calming time: 15 to 30 minutes;

[0039] (6) Slab continuous casting: The ladle slag detection and control are adopted, the pouring temperature of the tundish is 1530-1560℃, the tundish uses an alkaline covering agent, low alloy steel protective slag is used, and the billet pulling speed is 0.85-1.16m / min.

[0040] (7) Medium and thick plate rolling: Control the soaking temperature of the billet heating furnace to 1160-1240℃, ensure that the billet is heated in the furnace for ≥210min and soaked for ≥35min, so that the micro-alloying elements Nb and Ti are dissolved and the austenite grain size is controlled; the final rough rolling pass is manually rolled with a large reduction to uniformly form the hot-rolled structure and improve the steel plate shape and stamping performance after rolling; the finishing rolling is continuously rolled for 8 passes. The billet thickness of different thicknesses, the target temperature of the finishing rolling, and the target temperature of the final rolling are shown in Table 1. No mill cooling water or post-rolling controlled cooling water is used after the steel plate is rolled.

[0041] Table 1 Billeting and controlled rolling schemes for different thicknesses

[0042]

[0043] 2. Embodiment

[0044] (1) The present invention provides a weather-resistant bridge steel plate Q345qDNH with high impact toughness and a manufacturing method, wherein the weather-resistant bridge steel plate Q345qDNH with high impact toughness adopts the following composition ratio and specific process. Table 2 shows the composition (by weight percentage) of each embodiment steel as follows:

[0045] The chemical composition of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is: C: 0.071wt%, Si: 0.25wt%, Mn: 1.22wt%, P: 0.014wt%, S: 0.003wt%, Nb: 0.040wt%, Ti: 0.019wt%, Cr: 0.45wt%, Ni: 0.33wt%, Cu: 0.28wt%, Alt: 0.026wt%, N: 0.0045wt%; the remainder is Fe and inevitable trace elements;

[0046] The chemical composition of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is: C: 0.064wt%, Si: 0.25wt%, Mn: 1.18wt%, P: 0.013wt%, S: 0.004wt%, Nb: 0.037wt%, Ti: 0.017wt%, Cr: 0.45wt%, Ni: 0.32wt%, Cu: 0.27wt%, Alt: 0.029wt%, N: 0.0038wt%; the balance is Fe and inevitable trace elements;

[0047] The chemical composition of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is: C: 0.080wt%, Si: 0.23wt%, Mn: 1.20wt%, P: 0.013wt%, S: 0.001wt%, Nb: 0.034wt%, Ti: 0.015wt%, Cr: 0.46wt%, Ni: 0.32wt%, Cu: 0.27wt%, Alt: 0.031wt%, N: 0.0037wt%; the balance is Fe and inevitable trace elements;

[0048] The chemical composition of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is: C: 0.067wt%, Si: 0.24wt%, Mn: 1.18wt%, P: 0.012wt%, S: 0.003wt%, Nb: 0.034wt%, Ti: 0.018wt%, Cr: 0.44wt%, Ni: 0.33wt%, Cu: 0.27wt%, Alt: 0.033wt%, N: 0.0042wt%; the balance is Fe and inevitable trace elements;

[0049] Table 2: Product chemical composition (wt%)

[0050] Examples C Si Mn P S Alt Nb Ti Cr Ni Cu N Example 1 0.071 0.25 1.22 0.014 0.003 0.026 0.040 0.019 0.45 0.33 0.28 0.0045 Example 2 0.064 0.25 1.18 0.013 0.004 0.029 0.037 0.017 0.45 0.32 0.27 0.0038 Example 3 0.080 0.23 1.20 0.013 0.001 0.031 0.034 0.015 0.46 0.32 0.27 0.0037 Example 4 0.067 0.24 1.18 0.012 0.003 0.033 0.034 0.018 0.44 0.33 0.27 0.0042

[0051] (2) The specific process parameters for rolling the weather-resistant bridge steel plate Q345qDNH with high impact toughness and a thickness of 8-30 mm are shown in Table 3. The thicknesses of the weather-resistant bridge steel plate Q345qDNH with high impact toughness are 10 mm, 16 mm, 20 mm, and 25 mm, respectively. Table 3 is the process parameters corresponding to the example steel described in Table 2.

[0052] Table 3: Specific process parameters of each embodiment

[0053]

[0054]

[0055] (3) The product of the present invention is a weather-resistant bridge steel plate Q345qDNH with high impact toughness. The detailed mechanical properties are shown in Table 4. The weather-resistant bridge steel plate Q345qDNH obtained by the present invention has the following mechanical properties: ReL≥400MPa, tensile strength Rm≥500MPa, elongation A≥26%, and low-temperature impact energy of -20°C≥270J. Table 4 shows the mechanical properties corresponding to the component steels described in the embodiments of Table 2.

[0056] Table 4: Mechanical properties of various examples

[0057] Examples Finished product thickness / mm <![CDATA[R eL / MPa]]> <![CDATA[R m / MPa]]> A / ％ <![CDATA[-20 °C low-temperature impact energy A kv / J]]> Example 1 10 452 596 27.3 273 Example 2 16 451 548 29.8 327 Example 3 20 431 536 29.5 351 Example 4 25 424 518 28.2 307

[0058] (4) The finished product thickness of the weather-resistant bridge steel plate Q345qDNH with high impact toughness involved in Examples 1-4 ranges from 10 to 25 mm, and the metallographic structure is F+P, with F grain size level of 10.5 to 10.0. The metallographic structure data of each example is shown in Table 5, and the metallographic structure photo of Example 1 is shown in Figure 1 The metallographic structure photo of Example 4 is shown in Figure 2 .

[0059] Table 5: Metallographic structure data of each embodiment

[0060] Examples Finished product thickness / mm organize F Grain size / grade Example 1 10 F+P 10.5 Example 2 16 F+P 10.5 Example 3 20 F+P 10.0 Example 4 25 F+P 10.0

[0061] The present invention provides a weather-resistant bridge steel plate Q345qDNH with high impact toughness and a manufacturing method by rationally designing the composition and production process. According to the composition requirements of the national standard GB / T 714, Cu, Ni, and Cr elements are added to the steel to ensure weather resistance, and through the design of low-carbon components in the steel, an appropriate amount of Nb+Ti microalloy is added, the N content in the steel is strictly controlled, and a reasonable smelting-continuous casting-rolling process is formulated to achieve stable production of the product and obtain a weather-resistant bridge steel plate Q345qDNH with stable mechanical properties and high impact toughness. The mechanical properties of the weather-resistant bridge steel plate Q345qDNH obtained by the present invention are R eL ≥400MPa, tensile strength Rm≥500MPa, elongation A≥26%, -20℃ low temperature impact energy≥270J.

[0062] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. The components of the present invention can be combined with each other without conflict, and any equivalent changes and modifications made by any technician in the field without departing from the concept and principle of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for manufacturing a weather-resistant bridge steel plate Q345qDNH with high impact toughness, characterized in that: The chemical composition weight percentage of the weather-resistant bridge steel plate Q345qDNH with high impact toughness is: C: 0.064wt%, Si: 0.25wt%, Mn: 1.18wt%, P: 0.013wt%, S: 0.004wt%, Nb: 0.037wt%, Ti: 0.017wt%, Cr: 0.45wt%, Ni: 0.32wt%, Cu: 0.27wt%, Alt: 0.029wt%, N: 0.0038wt%; the balance is Fe and inevitable trace elements; the manufacturing method of the weather-resistant bridge steel plate Q345qDNH with high impact toughness includes the following process steps performed in sequence: Hot metal smelting in blast furnace → hot metal desulfurization pretreatment → molten steel smelting in converter → LF molten steel refining treatment → RH molten steel refining treatment → slab continuous casting → hot slab heating → descaling → rough rolling → finishing rolling → straightening → sampling → steel plate level II flaw detection inspection → marking and storage; The metallographic structure is F+P, and the F grain size grade is 10.5; The weather-resistant bridge steel plate Q345qDNH with high impact toughness does not use mill cooling water and post-rolling controlled cooling water after rolling; The finished weather-resistant bridge steel plate Q345qDNH with high impact toughness has a thickness of 16 mm, a heating furnace soaking temperature of 1211° C., a heating time of 255 min, a soaking time of 46 min, a finishing rolling start temperature of 972° C., a finishing rolling final rolling temperature of 841° C., and a product yield strength R eL It is 451MPa, the tensile strength Rm is 548MPa, the yield strength ratio is 0.82, the elongation A is 29.8%, and the low-temperature impact energy of -20℃ is 327J.

2. The method for manufacturing the weather-resistant bridge steel plate Q345qDNH with high impact toughness according to claim 1, characterized in that: The finishing rolling is set as 8 continuous passes.

3. The method for manufacturing the weather-resistant bridge steel plate Q345qDNH with high impact toughness according to claim 1, characterized in that: The converter steelmaking process: the molten iron entering the furnace is required to be S≤0.010wt%, the smelting process adopts bottom blowing of argon throughout the process, and the converter endpoint is controlled to be C: 0.04-0.06wt%, and P≤0.015wt%.

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