Production method of rare earth microalloyed high-strength atmospheric corrosion-resistant low-temperature hot-rolled H-shaped steel for large-span structure

Abstract

The invention discloses a production method of rare earth microalloyed high-strength atmospheric corrosion-resistant low-temperature hot-rolled H-shaped steel for a large-span structure. The production method comprises a smelting process and a rolling process. The high-strength and high-toughness steel comprises the following chemical components in percentage by mass: 0.10%-0.15% of C, 0.40%-0.50% of S i, 1.25%-1.35% of Mn, less than or equal to 0.015% of P, less than or equal to 0.010% of S, 0.06%-0.08% of V, 0.30%-0.40% of Cr, 0.20%-0.25% of N i, 0.30%-0.40% of Cu, 0.0015%-0.0040% of Ce, 0.0070%-0.0110% of N and less than or equal to 0.0020% of O. The mechanical properties of the H-shaped steel meet the conditions that the lower yield strength ReL is larger than or equal to 440 MPa, the tensile strength Rm is larger than or equal to 580 MPa, and the impact toughness at the temperature of-50 DEG C is larger than or equal to 100 J.

Description

Technical Field

[0001] The invention belongs to the technical field of smelting, and in particular relates to a method for producing rare earth micro-alloyed high-strength atmospheric corrosion-resistant low-temperature hot-rolled H-shaped steel for large-span structures. Background Art

[0002] With the continuous development of construction engineering, bridge engineering and other fields, the performance requirements for steel used in large-span structures are getting higher and higher. Traditional hot-rolled H-shaped steel has certain deficiencies in strength, atmospheric corrosion resistance and low-temperature toughness, and it is difficult to meet the needs of modern engineering. Summary of the invention

[0003] The purpose of the present invention is to provide a method for producing rare earth microalloyed high-strength atmospheric corrosion-resistant low-temperature hot-rolled H-shaped steel for large-span structures, thereby improving its mechanical properties, especially low-temperature toughness.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for producing rare earth microalloyed high-strength atmospheric corrosion-resistant low-temperature hot-rolled H-shaped steel for large-span structures, comprising:

[0006] Smelting process: KR desulfurization, converter smelting, LF refining, continuous casting of profiled billets, slow cooling of cast billets; among them:

[0007] Carry out KR desulfurization treatment to effectively reduce the sulfur content in molten steel and improve the quality of molten steel. The sulfur content of molten steel entering the converter is ≤0.020%;

[0008] Combined blowing converter smelting, precise control of smelting temperature, time and composition. During the smelting process, oxygen blowing and slag making operations are carried out to remove impurities in the molten steel; low-high-low gun position control is adopted, and the gun position is 1.1m-1.5m; single slag operation is adopted, and the end point basicity is controlled according to 2.7-3.5, C≥0.06%, T≥1640℃; the final deoxidation adopts Al deoxidation, and the addition amount of 80% aluminum iron is 50kg-100kg / furnace, and the end point adopts a slide plate to block the slag;

[0009] Refining in-situ heating for more than 10 minutes, add slag-removing agent bauxite 100-150kg, fluorite balls 50-80kg, aluminum iron 500-80kg, aluminum particles 10-30kg, lime 500-600kg. Refining off-site temperature control ≥1630℃, use silicon manganese to add Mn element, if Si element is overloaded, use ferromanganese to add Mn element, V element is added by vanadium nitrogen alloy, Ce is added by 30% cerium iron alloy, soft blowing time ≥13min, after soft blowing, feed 150m-200m calcium wire, add 30% cerium iron alloy 30kg / furnace during wire feeding;

[0010] Argon blowing protection casting of large ladle with long nozzle, using Stolberg L7 protective slag, liquid slag layer controlled at 10mm-12mm. Superheat controlled at 20-35℃, using special-shaped billet single nozzle plug rod automatic control, according to different billet sections, the drawing speed is controlled at 0.7-1.1m / min to ensure constant drawing speed casting, the insertion depth of the immersion nozzle is 50-70mm, the secondary cooling uses a medium cooling water meter, the billet slow cooling time is more than 24 hours, the lower paving and the upper cover;

[0011] Rolling process: walking beam heating furnace, BD billeting, CCS universal rolling, walking beam cooling bed cooling; among them:

[0012] The preheating section temperature is ≤900℃, the heating section temperature is 1150℃-1330℃, the soaking section temperature is 1200℃-1260℃, the furnace discharge temperature is ≥1150℃, and the furnace time is 120min-180min;

[0013] BD1 billeting, rolling temperature 1150℃-1180℃, rolling passes are determined according to the final product specifications, and the total reduction is ≥40%;

[0014] CCS universal rolling, the temperature of the last pass of final rolling can be controlled at 900℃-930℃, which controls the final rolling temperature, refines the grain size, and ensures the strength and toughness of the finished H-beam;

[0015] The cooling bed is cooled naturally, and the finished product is straightened and sawed after the temperature is lower than 100℃.

[0016] Furthermore, the chemical composition of the H-beam in mass percentage is: C 0.10%-0.15%, Si0.40%-0.50%, Mn 1.25%-1.35%, P≤0.015%, S≤0.010%, V 0.06%-0.08%, Cr0.30%-0.40%, Ni 0.20%-0.25%, Cu 0.30%-0.40%, Ce 0.0015%-0.0040%, N0.0070%-0.0110%, O≤0.0020%, and the rest are Fe and impurities, with a total mass fraction of 100%.

[0017] Furthermore, it is suitable for profiled blanks of 350×290×100mm, 555×440×105mm, 730×370×905mm, and 1024×390×120mm.

[0018] Furthermore, the carbon equivalent CEV ≤ 0.48%, and the atmospheric corrosion resistance index I ≥ 6.3.

[0019] Furthermore, the mechanical properties of the H-shaped steel meet the following requirements: lower yield strength ReL≥440MPa, tensile strength Rm≥580MPa, -50°C impact toughness≥100J, and elongation after fracture≥28%.

[0020] Furthermore, the final rolling temperature is 900-930°C.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are:

[0022] The mechanical properties of the H-shaped steel meet the following requirements: lower yield strength ReL≥440MPa, tensile strength Rm≥580MPa, -50°C impact toughness≥100J, and elongation after fracture≥28%. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below

[0024] A method for producing rare earth microalloyed high-strength and tough atmospheric corrosion-resistant low-temperature hot-rolled H-shaped steel for large-span structures:

[0025] The smelting process is: KR desulfurization, converter smelting, LF refining, profiled billet continuous casting, and billet slow cooling.

[0026] Carry out KR desulfurization treatment to effectively reduce the sulfur content in molten steel and improve the quality of molten steel. The sulfur content of molten steel entering the converter is ≤0.020%.

[0027] Combined blowing converter smelting, precise control of smelting temperature, time and composition. During the smelting process, oxygen blowing, slag making and other operations are carried out to remove impurities in the molten steel. Low-high-low gun position control is adopted, and the gun position is 1.1m-1.5m. Single slag operation is adopted, and the end point basicity is controlled according to 2.7-3.5, C≥0.06%, T≥1640℃. Final deoxidation adopts Al deoxidation, and the addition amount of 80% aluminum iron is 50kg-100kg / furnace, and the end point adopts a slide plate to block the slag.

[0028] Refining in place heating for more than 10 minutes, add slag agent bauxite 100-150kg, fluorite ball 50-80kg, aluminum iron 500-80kg, aluminum particles 10-30kg, lime 500-600kg. Refining off-site temperature control ≥1630℃, use silicon manganese with Mn element, if Si element overload, use ferromanganese with Mn element, V element is added by vanadium nitrogen alloy, Ce is added by 30% ferrocerium alloy, soft blowing time ≥13min, feed calcium wire 150m-200m after soft blowing, add 30% ferrocerium alloy 30kg / furnace during wire feeding.

[0029] The composition of the molten steel for continuous casting is C 0.10%-0.15%, Si 0.40%-0.50%, Mn 1.25%-1.35%, P≤0.015%, S≤0.010%, V 0.06%-0.08%, Cr 0.30%-0.40%, Ni 0.20%-0.25%, Cu0.30%-0.40%, Ce 0.0015%-0.0040%, N 0.0070%-0.0110%, O≤0.0020%, and the rest is Fe and impurities, with a total mass fraction of 100%; carbon equivalent CEV≤0.48%, and atmospheric corrosion resistance index I≥6.3.

[0030] The carbon equivalent calculation formula is:

[0031] CEV=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15

[0032] The calculation formula of atmospheric corrosion resistance index I is:

[0033] I=26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.49(%Si)+17.28(%P)-7.29

[0034] (%Cu)(%N i)-9.10(%N i)(%P)-33.39(%Cu) 2

[0035] Argon blowing protection casting is used for long nozzles of large ladle, and Stolberg L7 protective slag is used, and the liquid slag layer is controlled at 10mm-12mm. The superheat is controlled at 20-35℃, and the single nozzle plug rod of special-shaped billet is used for automatic control. According to different billet sections, the drawing speed is controlled at 0.7-1.1m / min to ensure constant drawing speed casting, and the insertion depth of the immersion nozzle is 50-70mm. The secondary cooling adopts the intermediate cooling water meter, and the slow cooling time of the billet is more than 24 hours, and the lower layer is covered.

[0036] Suitable for profiled blanks of 350×290×100mm(BB1), 555×440×105mm(BB2), 730×370×905mm(BB3), and 1024×390×120mm(BB4).

[0037] The rolling process is: walking beam heating furnace, BD billet opening, CCS universal rolling, and walking beam cooling bed cooling.

[0038] The preheating section temperature is ≤900℃, the heating section temperature is 1150℃-1330℃, the soaking section temperature is 1200℃-1260℃, and the furnace exit temperature is ≥1150℃. The furnace time is 120min-180min.

[0039] BD1 blanking, rolling temperature 1150℃-1180℃, rolling passes are determined according to the final product specifications, and the total reduction is ≥40%.

[0040] CCS universal rolling, the temperature of the last pass of final rolling can be controlled at 900℃-930℃, which controls the final rolling temperature, refines the grain size, and ensures the strength and toughness of the finished H-beam.

[0041] The cooling bed is cooled naturally, and the finished product is straightened and sawed after the temperature is lower than 100℃.

[0042] Table 1 Chemical composition of each example

[0043]

[0044] Table 2 Carbon equivalent of each example

[0045] Examples Carbon equivalent CEV / % Atmospheric corrosion resistance index I Example 1 0.476 6.69 Example 2 0.449 6.58 Example 3 0.473 6.56 Example 4 0.424 6.34

[0046] Table 3 Starting and final rolling temperatures of each example

[0047] Examples Rolling temperature (℃) Finishing rolling temperature(℃) Example 1 1158 906 Example 2 1173 923 Example 3 1180 930 Example 4 1150 900

[0048] Table 4 Mechanical properties of each example

[0049]

[0050] Table 5 Atmospheric corrosion resistance of each example

[0051] Examples Relative corrosion rate relative to Q355B Example 1 49％ Example 2 51％ Example 3 53％ Example 4 55％

[0052] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing rare earth microalloyed high-strength atmospheric corrosion-resistant low-temperature hot-rolled H-beam for large-span structures, characterized in that: include: Smelting process: KR desulfurization, converter smelting, LF refining, continuous casting of special-shaped billets, slow cooling of billets; among which: Carry out KR desulfurization treatment to effectively reduce the sulfur content in molten steel and improve the quality of molten steel. The sulfur content of molten steel entering the converter is ≤0.020%; Combined blowing converter smelting, precise control of smelting temperature, time and composition, during the smelting process, oxygen blowing and slag making operations are carried out to remove impurities in molten steel; low-high-low gun position control is adopted, and the gun position is 1.1m-1.5m; single slag operation is adopted, and the end point basicity is controlled according to 2.7-3.5, C≥0.06%, T≥1640℃; final deoxidation adopts Al deoxidation, and the addition amount of 80% aluminum iron is 50kg-100kg / furnace, and the end point adopts a slide plate to block the slag; Refining in situ heating for more than 10 minutes, adding slagging agent bauxite 100-150kg, fluorite ball 50-80kg, aluminum iron 500-80kg, aluminum particles 10-30kg, lime 500-600kg, refining off-site temperature control ≥1630℃, silicon manganese is used to add Mn element, if Si element is overloaded, ferromanganese is used to add Mn element, V element is added by vanadium nitrogen alloy, Ce is added by 30% cerium iron alloy, soft blowing time ≥13min, after soft blowing, feed calcium wire 150m-200m, add 30% cerium iron alloy 30kg / furnace during wire feeding; Argon blowing protection casting of large ladle with long nozzle, using Stolberg L7 protection slag, liquid slag layer controlled at 10mm-12mm, superheat controlled at 20-35℃, using special-shaped billet single nozzle plug automatic control, according to different billet sections, the drawing speed is controlled at 0.7-1.1m / min to ensure constant drawing speed casting, the insertion depth of the immersion nozzle is 50-70mm, the secondary cooling uses a medium cooling water meter, the billet slow cooling time is more than 24 hours, the lower paving and the upper cover; Rolling process: walking beam heating furnace, BD billeting, CCS universal rolling, walking beam cooling bed cooling; among them: The preheating section temperature is ≤900℃, the heating section temperature is 1150℃-1330℃, the soaking section temperature is 1200℃-1260℃, the furnace discharge temperature is ≥1150℃, and the furnace time is 120min-180min; BD1 billeting, rolling temperature 1150℃-1180℃, rolling passes are determined according to the final product specifications, and the total reduction is ≥40%; CCS universal rolling, the temperature of the last pass of final rolling can be controlled at 900℃-930℃, which controls the final rolling temperature, refines the grain size, and ensures the strength and toughness of the finished H-beam; The cooling bed is cooled naturally, and the finished product temperature is lower than 100℃ before straightening and sawing; The chemical composition of the H-beam in mass percentage is: C 0.10%-0.15%, Si 0.40%-0.50%, Mn1.25%-1.35%, P≤0.015%, S≤0.010%, V 0.06%-0.08%, Cr 0.30%-0.40%, Ni0.20%-0.25%, Cu 0.30%-0.40%, Ce 0.0015%-0.0040%, N 0.0070%-0.0110%, O≤0.0020%, and the rest are Fe and impurities, with a total mass fraction of 100%.

2. The method for producing rare earth microalloyed high-strength atmospheric corrosion-resistant low-temperature hot-rolled H-beam for long-span structures according to claim 1, characterized in that: Suitable for special-shaped blanks of 350×290×100mm, 555×440×105mm, 730×370×905mm, and 1024×390×120mm.

3. The method for producing rare earth microalloyed high-strength atmospheric corrosion-resistant low-temperature hot-rolled H-beam for long-span structures according to claim 1, characterized in that: Carbon equivalent CEV≤0.48%, atmospheric corrosion resistance index I≥6.

3.

4. The method for producing rare earth microalloyed high-strength atmospheric corrosion-resistant low-temperature hot-rolled H-beam for long-span structures according to claim 1, characterized in that: Final rolling temperature is 900-930℃.

5. The method for producing rare earth microalloyed high-strength atmospheric corrosion-resistant low-temperature hot-rolled H-beam for long-span structures according to claim 1, characterized in that: The mechanical properties of the H-shaped steel meet the following requirements: lower yield strength ReL≥440MPa, tensile strength Rm≥580MPa, -50°C impact toughness≥100J, and elongation after fracture≥28%.

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