730 mpa-grade ultrahigh-strength steel plate for high-rise building and manufacturing method therefor

Abstract

The present invention belongs to the field of alloy steel manufacturing. Disclosed are a 730 MPa-grade ultrahigh-strength steel plate for a high-rise building and a manufacturing method therefor. The steel plate comprises the following chemical components: C, Si, Mn, P, S, Cr, Ni, Cu, Nb, V, Ti and Al, with the balance being Fe and inevitable impurity elements. By means of utilizing low-C microalloying and the design of adding a small amount of Cr, Ni and Cu components, Nb, V and other microalloy elements are precipitated in a two-stage rolling process, so as to play a role in pinning austenite grains, and inhibiting the growth of the austenite grains, thereby refining the grain size. By means of a rolling process of strictly controlling the temperature and the compression ratio in the two-stage rolling process assisted by the method of a subsequent rapid-water-entry controlled cooling, by means of accurately controlling the red returning temperature, a certain ratio of a bainite and ferrite structure is obtained. The steel plate has good comprehensive performance of a low yield ratio, high strength, a high level of extension and high low-temperature toughness, and has important significance for the development of steel structure buildings.

Description

A 730MPa grade ultra-high strength steel plate for high-rise buildings and its manufacturing method Technical Field

[0001] The present invention belongs to the field of alloy steel manufacturing, and relates to a steel plate for high-rise buildings and a manufacturing method thereof, and specifically to a steel plate for high-rise buildings with a tensile strength of 730 MPa and a manufacturing method thereof. Background Art

[0002] With the sustained and rapid development of my country's economy, urbanization has accelerated at an unprecedented pace. To conserve land and effectively utilize space, urban construction is naturally trending toward higher-rise and larger buildings. Steel structures are highly sought after in the market due to their high strength, light weight, excellent seismic performance, ease of building large spans and spaces, short construction cycles, reliable quality, environmental friendliness, and reusability. As China's building structures become taller, larger, and greener, ultra-high-strength steel with a tensile strength of 730 MPa or higher holds broad application prospects in high-rise buildings.

[0003] At present, there are few application results for ultra-high-strength medium-thick steel plates with a tensile strength of 730 MPa in the domestic construction industry, and there are few related patents. In addition, the production process is based on the quenching and tempering process. For example, the "A high-strength and high-toughness easily welded structural steel plate with a yield strength of 620 MPa and its preparation method" with publication number CN 112813344 B adopts a quenching + high-temperature tempering process to produce a yield strength of 620 MPa easily welded structural steel plate. Its disadvantages are: the process flow is relatively complicated, and the yield strength ratio of the final steel plate is not less than 0.88.

[0004] Publication number CN 115216681 A, "A method for producing Q620GJ with low yield ratio and high toughness," uses an online quenching + high-temperature tempering process to produce Q620GJ steel plates. Its disadvantages are: the process flow is relatively complex and the alloy element content is high. It is mainly used in the production of thick plates with a thickness of more than 80 mm.

[0005] Summary of the Invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a method for preparing 730MPa grade ultra-high strength steel plates for high-rise buildings.

[0007] Technical Solution: The present invention discloses a 730 MPa ultra-high-strength steel plate for high-rise buildings and a method for manufacturing the same. The steel plate comprises the following mass percentages: C: 0.11% to 0.13%, Si: 0.17% to 0.30%, Mn: 1.61% to 1.85%, P: ≤0.015%, S: ≤0.005%, Cr: 0.55% to 0.85%, Ni: 0.30% to 0.50%, Cu: 0.15% to 0.30%, Nb: 0.040% to 0.070%, V: 0.03% to 0.06%, Ti: 0.010% to 0.020%, and Al: 0.020% to 0.050%. The remainder is Fe and unavoidable impurities.

[0008] Furthermore, the composition of the 730 MPa ultra-high-strength steel plate for high-rise buildings is as follows by weight: C: 0.11%, Si: 0.17%, Mn: 1.61%, P: 0.011%, S: 0.005%, Cr: 0.55%, Ni: 0.31%, Cu: 0.15%, Nb: 0.040%, V: 0.031%, Ti: 0.015%, Al: 0.021%. The balance is Fe and unavoidable impurities.

[0009] Furthermore, the composition of the 730 MPa-grade ultra-high-strength steel plate for high-rise buildings is as follows by weight: C: 0.12%, Si: 0.24%, Mn: 1.76%, P: 0.013%, S: 0.003%, Cr: 0.74%, Ni: 0.39%, Cu: 0.22%, Nb: 0.058%, V: 0.043%, Ti: 0.010%, Al: 0.040%. The balance is Fe and unavoidable impurities.

[0010] Furthermore, the composition of the 730 MPa ultra-high-strength steel plate for high-rise buildings is as follows by weight: C: 0.13%, Si: 0.30%, Mn: 1.85%, P: 0.010%, S: 0.004%, Cr: 0.85%, Ni: 0.50%, Cu: 0.29%, Nb: 0.070%, V: 0.06%, Ti: 0.020%, Al: 0.048%. The balance is Fe and unavoidable impurities.

[0011] Furthermore, a method for manufacturing 730MPa grade ultra-high strength steel plates for high-rise buildings comprises subjecting a steel billet having the same composition as the 730MPa grade steel to a converter smelting process, an off-furnace refining process, and a molten steel casting continuous billet process to produce a 730MPa grade steel continuous casting billet having a target composition; the continuous casting billet is then subjected to a slab heating furnace heating process, controlled rolling, controlled cooling, steel plate straightening, inspection, and warehousing processes. The specific steps are:

[0012] (1) Slab heating furnace heating system: heating temperature is 1180-1220℃, total furnace time is 10-14min / cm, uniform original austenite structure is obtained inside the steel;

[0013] (2) Rolling process: adopt controlled rolling and controlled cooling process, which is a two-stage controlled rolling, namely rolling in the austenite recrystallization zone and the austenite non-recrystallization zone, with a total reduction ratio of not less than 3 times: the starting temperature of rough rolling is ≥1080℃, and a large reduction method is adopted in this stage; the starting temperature of finishing rolling is 900-930℃, and the thickness of the warm billet is not less than 3.0 times the thickness of the finished product. In this stage, sufficient deformation is ensured to make the austenite grains stretched and deformed along the rolling direction. At the same time, by adding micro-alloying elements such as Nb and V, carbonitride particles are precipitated during the deformation process due to strain induction, which plays a role in pinning the austenite grains to prevent them from growing, thereby refining the structure after phase transformation and playing a certain role in precipitation strengthening; the final rolling temperature is 860-890℃;

[0014] (3) Cooling process: After rolling, the steel is quickly put into water for laminar cooling. The water temperature is 820-850℃, the final cooling temperature is 440-500℃, and then air-cooled to room temperature.

[0015] Furthermore, the 730MPa ultra-high-strength steel plate for high-rise buildings described in the present invention has a final microstructure of bainite + ferrite, with 85% to 90% bainite and 10% to 15% ferrite. This steel plate exhibits excellent comprehensive properties, including a low yield ratio, high strength, high elongation, and high and low-temperature toughness.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following characteristics: 1. The 730MPa grade ultra-high strength steel plate for high-rise buildings provided by the present invention adopts low C and micro-alloying, and is designed with a small amount of Cr, Ni, and Cu elements. Micro-alloying elements such as Nb and V are precipitated during the two-stage rolling process to pin austenite grains, inhibit the growth of austenite grains, and refine the grain size. At the same time, they play a certain precipitation strengthening role to ensure the high strength requirements of the steel plate; the addition of high solid solution strengthening element Cr significantly improves the solid solution strengthening effect of the steel plate, and the addition of an appropriate amount of Ni element ensures the strength of the steel plate while significantly improving the low temperature toughness of the steel plate. At the same time, the addition of an appropriate amount of Cu element provides a certain solid solution strengthening effect. Dissolution and precipitation strengthening, finally obtaining a steel plate with excellent performance; 2. The 730MPa grade ultra-high strength steel plate for high-rise buildings provided by the present invention adopts a production process of controlled rolling and controlled cooling, strictly controls the temperature of the two-stage rolling process and the rolling process of the compression ratio, supplemented by a subsequent rapid water immersion controlled cooling method, and obtains a certain ratio of bainite and ferrite structure through precise control of the red-return temperature, while obtaining stable and excellent mechanical properties, with a short production process and a simple preparation method; 3. The 730MPa grade ultra-high strength steel plate for high-rise buildings has excellent comprehensive performance of low yield ratio, high strength, high elongation, and high and low temperature toughness, which is of great significance to the development of high-rise, super-high-rise and large-scale steel structure buildings in my country. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is an OM diagram of the microstructure of a 730 MPa grade ultra-high strength steel plate for high-rise buildings according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0019] Example 1:

[0020] The 730 MPa ultra-high-strength steel plate for high-rise buildings disclosed herein has the following chemical composition by mass percentage: C: 0.11%, Si: 0.17%, Mn: 1.61%, P: 0.011%, S: 0.005%, Cr: 0.55%, Ni: 0.31%, Cu: 0.15%, Nb: 0.040%, V: 0.031%, Ti: 0.015%, and Al: 0.021%. The remainder is Fe and unavoidable impurities.

[0021] Furthermore, a method for preparing a 730 MPa grade ultra-high strength steel plate for high-rise buildings comprises the following steps:

[0022] (1) The raw materials are subjected to converter smelting, off-furnace refining and casting to obtain a continuous casting billet with a thickness of 220 mm;

[0023] (2) The slab is placed in a heating furnace and heated at a temperature of 1180°C for a total time of 308 minutes;

[0024] (3) A two-stage rolling process is adopted: the starting temperature of the rough rolling is 1081℃, the thickness of the warm billet is 60mm, the starting temperature of the finishing rolling is 900℃, the final rolling temperature is 860℃, and the steel plate is rolled into a thickness of 20mm;

[0025] (4) After rolling, the steel is cooled by laminar cooling with the water inlet temperature at 820°C and the final cooling temperature at 500°C, followed by air cooling to room temperature.

[0026] Another preparation method thereof comprises the following steps:

[0027] (1) The raw materials are subjected to converter smelting, off-furnace refining and casting to obtain a continuous casting billet with a thickness of 220 mm;

[0028] (2) The slab is placed in a heating furnace and heated at a temperature of 1180°C for a total time of 308 minutes;

[0029] (3) A two-stage rolling process is adopted: the starting temperature of the rough rolling is 1090°C, the thickness of the warm billet is 120mm, the starting temperature of the finishing rolling is 905°C, the final rolling temperature is 880°C, and the steel plate is rolled into a thickness of 40mm;

[0030] (4) After rolling, the steel is cooled by laminar cooling with the water inlet temperature at 841°C and the final cooling temperature at 445°C, followed by air cooling to room temperature.

[0031] Example 2:

[0032] The 730 MPa ultra-high-strength steel plate for high-rise buildings disclosed herein has the following chemical composition by mass percentage: C: 0.12%, Si: 0.24%, Mn: 1.76%, P: 0.013%, S: 0.003%, Cr: 0.74%, Ni: 0.39%, Cu: 0.22%, Nb: 0.058%, V: 0.043%, Ti: 0.010%, and Al: 0.040%. The remainder is Fe and unavoidable impurity elements.

[0033] Furthermore, a method for preparing a 730 MPa grade ultra-high strength steel plate for high-rise buildings comprises the following steps:

[0034] (1) The raw materials are subjected to converter smelting, off-furnace refining and casting to obtain a continuous casting billet with a thickness of 220 mm;

[0035] (2) The slab is placed in a heating furnace and heated at a temperature of 1200°C for a total time of 220 minutes;

[0036] (3) A two-stage rolling process is adopted: the starting temperature of the rough rolling is 1085℃, the thickness of the warm billet is 70mm, the starting temperature of the finishing rolling is 930℃, the final rolling temperature is 880℃, and the steel plate is rolled into a thickness of 20mm;

[0037] (4) After rolling, the steel is cooled by laminar cooling with the water inlet temperature of 840℃ and the final cooling temperature of 492℃, and then air-cooled to room temperature.

[0038] Another preparation method thereof comprises the following steps:

[0039] (1) The raw materials are subjected to converter smelting, off-furnace refining and casting to obtain a continuous casting billet with a thickness of 220 mm;

[0040] (2) The slab is placed in a heating furnace and heated at a temperature of 1200°C for a total time of 228 minutes;

[0041] (3) A two-stage rolling process is adopted: the starting temperature of the rough rolling is 1091°C, the thickness of the warm billet is 150mm, the starting temperature of the finishing rolling is 930°C, the final rolling temperature is 890°C, and the steel plate is rolled into a thickness of 40mm;

[0042] (4) After rolling, the steel is cooled by laminar cooling with the water inlet temperature of 850℃ and the final cooling temperature of 440℃, and then air-cooled to room temperature.

[0043] Example 3:

[0044] The present invention discloses a method for manufacturing a 730 MPa ultra-high-strength steel plate for high-rise buildings, wherein the chemical composition of the steel plate is as follows: C: 0.13%, Si: 0.30%, Mn: 1.85%, P: 0.010%, S: 0.004%, Cr: 0.85%, Ni: 0.50%, Cu: 0.29%, Nb: 0.070%, V: 0.06%, Ti: 0.020%, and Al: 0.048%. The remainder is Fe and unavoidable impurity elements.

[0045] Furthermore, a method for preparing a 730 MPa grade ultra-high strength steel plate for high-rise buildings comprises the following steps:

[0046] (1) The raw materials are subjected to converter smelting, off-furnace refining and casting to obtain a continuous casting billet with a thickness of 220 mm;

[0047] (2) The slab is placed in a heating furnace and heated at a temperature of 1220°C for a total time of 280 minutes;

[0048] (3) A two-stage rolling process is adopted: the starting temperature of the rough rolling is 1100℃, the thickness of the warm billet is 65mm, the starting temperature of the finishing rolling is 920℃, the final rolling temperature is 876℃, and the steel plate is rolled into a thickness of 20mm;

[0049] (4) After rolling, the steel is cooled by laminar cooling with the water inlet temperature of 834°C and the final cooling temperature of 487°C, and then air-cooled to room temperature.

[0050] Another preparation method thereof comprises the following steps:

[0051] (1) The raw materials are subjected to converter smelting, off-furnace refining and casting to obtain a continuous casting billet with a thickness of 220 mm;

[0052] (2) The slab is placed in a heating furnace and heated at a temperature of 1218°C for a total time of 286 minutes.

[0053] (3) A two-stage rolling process is adopted: the starting temperature of the rough rolling is 1090℃, the thickness of the warm billet is 124mm, the starting temperature of the finishing rolling is 900℃, the final rolling temperature is 862℃, and the steel plate is rolled into a thickness of 40mm;

[0054] (4) After rolling, the steel is cooled by laminar cooling with the water inlet temperature of 825℃ and the final cooling temperature of 471℃, and then air-cooled to room temperature.

[0055] Table 1 Chemical composition of 730MPa grade ultra-high strength construction steel (wt.%)

[0056] Table 2 Mechanical properties of 730MPa grade ultra-high strength construction steel

[0057] As can be seen from Table 2, the mechanical properties of Examples 1 to 3 are as follows: yield strength ≥624 MPa, tensile strength ≥750 MPa, elongation ≥19%, yield strength ratio ≤0.85, -40°C low-temperature impact value ≥166 J, and Z-direction section shrinkage ≥65%, all of which are higher than the requirements specified in the standard GB / T 19879-2015. The performance stability is good and can meet the structural design requirements of high-rise buildings in my country.

[0058] The present invention adopts a low-C, low-microalloying design, and simultaneously adds a small amount of Cr, Ni, and Cu elemental composition design. Microalloying elements such as Nb and V are precipitated during the two-stage rolling process to pin austenite grains, inhibit the growth of austenite grains, and refine the grain size. At the same time, they play a certain precipitation strengthening role to ensure the high strength requirement of the steel plate. The addition of Cr, a high solid solution strengthening element, significantly improves the solid solution strengthening effect of the steel plate. By adding an appropriate amount of Ni, the strength of the steel plate is ensured while the low-temperature toughness of the steel plate is significantly improved. At the same time, the addition of an appropriate amount of Cu provides a certain solid solution and precipitation strengthening again, and finally a steel plate with excellent performance is obtained.

[0059] The 730MPa-grade ultra-high-strength steel plate for high-rise buildings provided by the present invention adopts a controlled rolling and controlled cooling production process, a rolling process that strictly controls the temperature and compression ratio of the two-stage rolling process, and a subsequent rapid water immersion controlled cooling method. By accurately controlling the red-return temperature, a certain ratio of bainite and ferrite structure is obtained, and stable and excellent mechanical properties are obtained at the same time. The production process is short and the preparation method is simple.

[0060] The 730MPa grade ultra-high strength steel plate for high-rise buildings provided by the present invention has excellent comprehensive properties of low yield ratio, high strength, high elongation, and high and low temperature toughness, which is of great significance to the development of high-rise, ultra-high-rise and large-scale steel structure buildings in my country.

[0061] The present invention develops a 730MPa grade construction steel plate with excellent performance through relatively economical composition design and controlled rolling and cooling production process, which can meet the needs of high-rise, super high-rise and large-scale building design in my country.

Claims

1. A 730MPa grade ultra-high strength steel plate for high-rise buildings, characterized in that: Its chemical composition is calculated by weight percentage: C: 0.11% to 0.13%, Si: 0.17% to 0.30%, Mn: 1.61% to 1.85%, P: ≤0.015%, S: ≤0.005%, Cr: 0.55% to 0.85%, Ni: 0.30% to 0.50%, Cu: 0.15% to 0.30%, Nb: 0.040% to 0.070%, V: 0.03% to 0.06%, Ti: 0.010% to 0.020%, Al: 0.020% to 0.050%. The balance is Fe and unavoidable impurity elements.

2. The 730MPa grade ultra-high strength steel plate for high-rise buildings according to claim 1, characterized in that: Its chemical composition by weight percentage is: C: 0.11%, Si: 0.17%, Mn: 1.61%, P: 0.011%, S: 0.005%, Cr: 0.55%, Ni: 0.30%, Cu: 0.15%, Nb: 0.040%, V: 0.03%, Ti: 0.010%, Al: 0.020%; the remainder is Fe and unavoidable impurity elements.

3. The 730MPa grade ultra-high strength steel plate for high-rise buildings according to claim 1, characterized in that: Its chemical composition by weight percentage is: C: 0.12%, Si: 0.24%, Mn: 1.76%, P: 0.013%, S: 0.003%, Cr: 0.74%, Ni: 0.39%, Cu: 0.22%, Nb: 0.058%, V: 0.043%, Ti: 0.010%, Al: 0.040%; the remainder is Fe and unavoidable impurity elements.

4. The 730MPa ultra-high strength steel plate for high-rise buildings according to claim 1, characterized in that: Its chemical composition by weight percentage is: C: 0.13%, Si: 0.30%, Mn: 1.85%, P: 0.010%, S: 0.004%, Cr: 0.85%, Ni: 0.50%, Cu: 0.29%, Nb: 0.070%, V: 0.06%, Ti: 0.020%, Al: 0.048%; the remainder is Fe and unavoidable impurity elements.

5. A method for preparing a 730MPa grade ultra-high strength steel plate for high-rise buildings as claimed in any one of claims 1 to 4, characterized in that: The steel billet having the same composition as the 730MPa grade steel is sequentially subjected to a converter smelting process, an off-furnace refining process and a molten steel pouring continuous casting billet process to produce a 730MPa grade steel continuous casting billet having a target composition; The continuous casting billet is then subjected to various processes in sequence to finally produce 730MPa grade ultra-high strength steel plates for high-rise buildings.

6. The method for preparing a 730MPa grade ultra-high strength steel plate for high-rise buildings according to claim 5, characterized in that: The preparation steps of subjecting the continuous casting billet to various processes in sequence to obtain a 730MPa grade ultra-high strength steel plate for high-rise buildings are as follows: (1): Heating system of slab heating furnace; (2): Rolling process; (3): Cooling process.

7. The method for preparing a 730MPa grade ultra-high strength steel plate for high-rise buildings according to claim 6, characterized in that: In step (1), the heating temperature is 1180-1220° C., and the total time in the furnace is 10-14 min / cm.

8. The method for preparing a 730MPa grade ultra-high strength steel plate for high-rise buildings according to claim 6, characterized in that: In step (2), the rolling process is a two-stage controlled rolling process, i.e., rolling in the austenite recrystallization zone and the austenite non-recrystallization zone, with a total compression ratio of not less than 3 times: Among them, the starting temperature of rough rolling is ≥1080℃, and a large reduction method is adopted in this stage; The starting temperature of finishing rolling is 900-930℃, the thickness of the warm billet is not less than 3.0 times the thickness of the finished product, and the final rolling temperature is 860-890℃.

9. The method for preparing a 730MPa grade ultra-high strength steel plate for high-rise buildings according to claim 6, characterized in that: In step (3), the steel is quickly put into water after rolling and subjected to laminar cooling, the water inlet temperature is 820-850°C, the final cooling temperature is 440-500°C, and then air-cooled to room temperature.

10. The method for preparing a 730MPa grade ultra-high strength steel plate for high-rise buildings according to claim 6, characterized in that: The final structure type of the prepared steel plate is bainite + ferrite structure, wherein the amount of bainite is 85% to 90% and the amount of ferrite is 10 to 15%.

Images