Hot rolled steel strip for low-cost easily-formed low-temperature-resistant girder steel and production method of hot rolled steel strip

Abstract

The invention relates to a hot-rolled steel strip for low-cost easily-formed low-temperature-resistant girder steel and a production method thereof, and belongs to the technical field of hot-rolled steel strip production. According to the technical scheme, the steel strip comprises the following chemical components in percentage by mass: 0.06%-0.12% of C, 0.10%-0.20% of Si, 0.60%-0.80% of Mn, less than or equal to 0.025% of P, less than or equal to 0.020% of S, 0.01%-0.06% of AlS, 0.03%-0.05% of Ti, less than or equal to 0.0060% of N, less than or equal to 0.28% of Ceq and the balance of iron and inevitable impurities. The low-carbon-low-manganese-micro-titanium component design is adopted, and the converter argon blowing direct feeding and hot feeding and hot charging processes are combined, so that the cost can be reduced by about 70 yuan per ton of steel; according to the design, alloy solid solution strengthening and fine grain strengthening are comprehensively considered, so that good strength, plasticity and toughness can be guaranteed, the elongation percentage is 26% or above, 0a cold bending is normal, and the ballistic work at the temperature of-20 DEG C is 160 J or above.

Description

Technical Field

[0001] The invention relates to a low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel and a production method thereof, belonging to the technical field of hot-rolled steel strip production. Background Art

[0002] With the development of society and economy, the steel industry is facing increasing pressure to save resources, save energy and protect the environment. At present, the steel industry has serious overcapacity and product homogeneity competition is becoming increasingly fierce. Medium and wide bandwidth manufacturers have carried out technological improvements and management innovations, trying every means to reduce production costs, improve product quality and service levels, and increase the development of high value-added products, striving to seize the initiative in the fierce market competition.

[0003] Low alloy high strength structural steel is widely used in automobile beams, offshore platforms, ships, high-rise buildings, bridges, pressure vessels, engineering machinery and natural gas pipelines due to its high strength, light weight, good low temperature impact toughness and good welding performance. At present, most of the low temperature resistant low alloy high strength steel series adopt medium carbon-high manganese composition system or niobium vanadium titanium micro alloy strengthening, for example: Chinese patent CN202210155745X name "micro niobium alloyed Q355B low alloy high strength structural steel plate and its manufacturing method" and CN202211358040.4 name "micro niobium alloyed Q355B low alloy high strength structural steel plate". The problems of the existing technology are: low low temperature impact performance, poor forming performance and high alloy cost, which do not meet the conditions for industrial mass production. Summary of the invention

[0004] The purpose of the present invention is to provide a low-cost, easy-to-form, low-temperature resistant hot-rolled steel strip for beam steel and a production method thereof. A low-cost, easy-to-form, low-temperature resistant hot-rolled steel strip for beam steel is designed in accordance with the requirements of the national standard GB / T1591-2018 low-alloy high-strength structural steel. The product not only meets the low-temperature impact performance, but also takes into account the roll forming performance, reduces the industrial production cost, is suitable for industrial production, and solves the above-mentioned technical problems existing in the existing technology.

[0005] The technical solution of the present invention is: A low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel, wherein the chemical components of the steel strip are as follows: C: 0.06%-0.12%, Si: 0.10%-0.20%, Mn: 0.60%-0.80%, P≤0.025%, S≤0.020%, AlS: 0.01%-0.06%, Ti: 0.03%-0.05%, N≤0.0060%, Ceq≤0.28%, and the remainder is iron and unavoidable impurities.

[0006] The thickness of the steel strip is 2.0-12.0 mm.

[0007] The steel strip tensile test results show that the yield strength ReH is ≥390MPa, the tensile strength Rm is 490-550MPa, and the elongation after fracture A is ≥26%; the 180° cold bending test d=0a has no cracks or hairlines; the low-temperature impact test -20℃ impact energy KV2 is ≥160J.

[0008] The steel strip structure is F+P, the grain size rating is 10-11, the banded structure rating is 0, the inclusion rating of a single category is below 1.5, and the sum of the five categories of inclusion ratings is below 2.0.

[0009] A production method of the above-mentioned low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel, comprising converter smelting, argon blowing station, continuous casting, heating, rough rolling, finish rolling, cooling and coiling steps; The continuous casting process is as follows: the billet width is ≤620 mm, the pulling speed is 1.30-1.60 m / min, the billet width is >620 mm, the pulling speed is 0.90-1.30 m / min, and the billet thickness is 180-230 mm. The heating process is heating in a walking beam heating furnace, the total residence time in the heating furnace is 160 to 210 minutes, the temperature of the heating furnace soaking section is 1220 to 1310° C., and the soaking time is 35 to 48 minutes; The rough rolling process is to perform 8 rough rolling passes (5 flat and 3 vertical) to roll the intermediate billet into a thickness of 30-35 mm, the dephosphorization water pressure is 18-23 MPa, and the rough rolling outlet temperature is 1030-1090°C; The finishing rolling process is to roll the steel strip into a thickness of 2.0-12.0 mm through 7 passes of finishing rolling, the finishing rolling inlet temperature is 1020-1080° C., and the final rolling temperature is 870-910° C.; The cooling process is that the steel strip is first rapidly cooled to 680-720°C at 20-40°C / s in the front rough adjustment section of the laminar flow, then air-cooled for 2-4s in the middle, and then rapidly cooled to the coiling temperature of 580-610°C at 20-40°C / s in the rear fine adjustment section of the laminar flow.

[0010] The converter smelting and argon blowing station processes are existing technologies, and the mass percentages of the chemical components of the steel strip are controlled to be: C: 0.06%~0.12%, Si: 0.10%~0.20%, Mn: 0.60%~0.80%, P≤0.025%, S≤0.020%, AlS: 0.01%~0.06%, Ti: 0.03%~0.05%, N≤0.0060%, Ceq≤0.28%, and the remainder is iron and unavoidable impurities.

[0011] The design of the composition and process parameters of the present invention is mainly based on the following principles: the present invention adopts a low-carbon-low-manganese-micro-titanium composition design. Compared with the medium-carbon composition system, the low-carbon composition system avoids the peritectic zone, which is conducive to the stability of continuous casting steel, improves the quality of the ingot, and has a high elongation of the finished product, and improves the forming performance; by replacing 0.60% manganese with 0.04% titanium, the alloy cost can be significantly reduced by about 30 yuan / ton. Through the titanium microalloy and the controlled rolling air cooling system, based on adjusting the carbon distribution, the grains are refined, the toughness and plasticity of the product are improved, and the elongation is guaranteed to be more than 26%, the 0a cold bending is normal, and the impact energy of -20℃ is more than 160J; the steelmaking area adopts the converter argon blowing directly upward, saving about 30 yuan / ton in refining costs; the hot delivery and hot loading in the steel rolling area shortens the furnace time, improves the rolling rhythm, and reduces the cost by about 10 yuan / ton, further reducing the cost. Through the effective implementation of the above measures, low-cost, easy-to-form, low-temperature resistant beam steel hot-rolled steel strips can be produced to meet the requirements of the national standard GB / T1591-2018 and the processing requirements of customers.

[0012] The beneficial effects of adopting the above technical scheme are: the present invention adopts a low-carbon-low-manganese-micro-titanium component design, combined with the converter argon blowing straight-up process and the hot delivery and hot loading process, which can reduce the cost by about 70 yuan / ton of steel; the low-carbon, low-manganese and micro-titanium design comprehensively considers the alloy solid solution strengthening and fine grain strengthening to ensure good strength, plasticity and toughness, and meets the elongation of more than 26%, normal 0a cold bending, and -20℃ impact energy of more than 160J. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the metallographic structure diagram of the hot-rolled steel strip for low-cost, easy-to-form, low-temperature-resistant beam steel according to Example 1 of the present invention; Figure 2 This is the metallographic structure diagram of the hot-rolled steel strip for low-cost, easy-to-form, low-temperature-resistant beam steel according to Example 2 of the present invention; Figure 3 This is the metallographic structure diagram of the hot-rolled steel strip for low-cost, easy-to-form, low-temperature-resistant beam steel according to Example 3 of the present invention. DETAILED DESCRIPTION

[0014] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings. Example

[0015] The finished product thickness of the hot-rolled steel strip for low-cost, easy-to-form, low-temperature-resistant beam steel in this embodiment is 2.0 mm, and its chemical composition and mass percentage are shown in Table 1.

[0016] The production method of the low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel of this embodiment includes converter smelting, argon blowing station, continuous casting, heating, rough rolling, finish rolling, cooling and coiling processes, and the specific process steps are as follows: (1) Continuous casting process: The composition segregation was controlled by stabilizing the casting speed. The casting speed was 0.90 m / min, and the steel billet with a thickness of 180 mm and a width of 840 mm was obtained by continuous casting. The chemical composition and mass percentage of the continuous casting steel billet are shown in Table 1. (2) Heating process: Heating in a walking beam heating furnace, the total residence time in the heating furnace is 160 min, the heating temperature in the soaking section of the heating furnace is 1310 ° C, and the soaking time is 35 min; (3) Rough rolling process: 8 passes of rough rolling, the intermediate billet thickness is 30 mm, the dephosphorization water pressure is 18 MPa, and the rough rolling outlet temperature is 1090 °C; (4) Finishing rolling process: 7 passes of finishing rolling to form a steel strip with a thickness of 2.0 mm, the finishing rolling inlet temperature is 1080°C, and the final rolling temperature is 910°C; (5) Cooling process: The steel strip is first rapidly cooled to 720°C at 20°C / s in the front rough adjustment section of the laminar flow, then air-cooled for 2.0s in the middle, and then rapidly cooled to the coiling temperature of 610°C at 40°C / s in the rear fine adjustment section of the laminar flow.

[0017] The properties of the hot-rolled steel strip for the low-cost, easy-to-form, low-temperature-resistant beam steel of this embodiment are shown in Table 2; Figure 1 . Example

[0018] The finished product thickness of the hot-rolled steel strip for low-cost, easy-to-form, low-temperature-resistant beam steel in this embodiment is 6.5 mm, and its chemical composition and mass percentage are shown in Table 1.

[0019] The production method of the low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel of this embodiment includes converter smelting, argon blowing station, continuous casting, heating, rough rolling, finish rolling, cooling and coiling processes, and the specific process steps are as follows: (1) Continuous casting process: The component segregation was controlled by stabilizing the casting speed. The casting speed was 1.30 m / min. The steel billet with a thickness of 200 mm and a width of 620 mm was obtained by continuous casting. The chemical composition and mass percentage of the continuous casting steel billet are shown in Table 1. (2) Heating process: Heating in a walking beam heating furnace, the total residence time in the heating furnace is 194 min, the heating temperature in the soaking section of the heating furnace is 1280 ° C, and the soaking time is 41 min; (3) Rough rolling process: 8 passes of rough rolling, the intermediate billet thickness is 33 mm, the dephosphorization water pressure is 23 MPa, and the rough rolling outlet temperature is 1068 °C; (4) Finishing rolling process: After 7 passes of finishing rolling, the steel strip is rolled into a thickness of 6.5 mm. The finishing rolling inlet temperature is 1074°C and the final rolling temperature is 885°C. (5) Cooling process: The steel strip is first rapidly cooled to 708°C at 35°C / s in the front rough adjustment section of the laminar flow, then air-cooled for 3.5s in the middle, and then rapidly cooled to the coiling temperature of 597°C at 31°C / s in the rear fine adjustment section of the laminar flow.

[0020] The properties of the hot-rolled steel strip for the low-cost, easy-to-form, low-temperature-resistant beam steel of this embodiment are shown in Table 2; Figure 2 . Example

[0021] The finished product thickness of the hot-rolled steel strip for low-cost, easy-to-form, low-temperature-resistant beam steel in this embodiment is 12.0 mm, and its chemical composition and mass percentage are shown in Table 1.

[0022] The production method of the low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel of this embodiment includes converter smelting, argon blowing station, continuous casting, heating, rough rolling, finish rolling, cooling and coiling processes, and the specific process steps are as follows: (1) Continuous casting process: The component segregation was controlled by stabilizing the casting speed. The casting speed was 1.60 m / min. The steel billet with a thickness of 230 mm and a width of 550 mm was obtained by continuous casting. The chemical composition and mass percentage of the continuous casting steel billet are shown in Table 1. (2) Heating process: Heating in a walking beam heating furnace, the total residence time in the heating furnace is 210 min, the heating temperature in the soaking section of the heating furnace is 1220 ° C, and the soaking time is 48 min; (3) Rough rolling process: 8 passes of rough rolling, the intermediate billet thickness is 35 mm, the dephosphorization water pressure is 21 MPa, and the rough rolling outlet temperature is 1030 °C; (4) Finishing rolling process: After 7 passes of finishing rolling, the steel strip is rolled into a thickness of 12.0 mm. The finishing rolling inlet temperature is 1020°C and the final rolling temperature is 870°C. (5) Cooling process: The steel strip is first rapidly cooled to 680°C at 40°C / s in the front rough adjustment section of the laminar flow, then air-cooled for 4.0s in the middle, and then rapidly cooled to the coiling temperature of 580°C at 20°C / s in the rear fine adjustment section of the laminar flow.

[0023] The properties of the hot-rolled steel strip for the low-cost, easy-to-form, low-temperature-resistant beam steel of this embodiment are shown in Table 2; Figure 3 .

[0024] Table 1 Chemical composition and mass percentage of hot-rolled steel strip for low-cost, easy-to-form, low-temperature-resistant beam steel of Example 1-3 (%)

[0025] The balance of the components in Table 1 is iron and unavoidable impurities.

[0026] Table 2 Mechanical properties of hot-rolled steel strip for low-cost, easy-to-form, low-temperature-resistant beam steel of Example 1-3

[0027] The present invention designs a low-cost, easy-to-form, low-temperature resistant hot-rolled steel strip for beam steel in accordance with the requirements of the national standard GB / T1591-2018 low-alloy high-strength structural steel. The product not only meets the low-temperature impact performance, but also takes into account the roll forming performance and reduces the industrial production cost, thus being suitable for industrial production.

Claims

1. A low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel, characterized in that: The chemical components of the steel strip are as follows: C: 0.06%-0.12%, Si: 0.10%-0.20%, Mn: 0.60%-0.80%, P≤0.025%, S≤0.020%, AlS: 0.01%-0.06%, Ti: 0.03%-0.05%, N≤0.0060%, Ceq≤0.28%, and the remainder is iron and unavoidable impurities.

2. The low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel according to claim 1, characterized in that: The thickness of the steel strip is 2.0-12.0 mm.

3. A low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel according to claim 1 or 2, characterized in that: The steel strip tensile test results show that the yield strength ReH is ≥390MPa, the tensile strength Rm is 490-550MPa, and the elongation after fracture A is ≥26%; the 180° cold bending test d=0a has no cracks or hairlines; the low-temperature impact test -20℃ impact energy KV2 is ≥160J.

4. A low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel according to claim 1 or 2, characterized in that: The steel strip structure is F+P, the grain size rating is 10-11, the banded structure rating is 0, the inclusion rating of a single category is below 1.5, and the sum of the five categories of inclusion ratings is below 2.

0.

5. A method for producing a low-cost, easy-to-form, low-temperature-resistant hot-rolled steel strip for beam steel according to any one of claims 1 to 4, characterized in that: It includes converter smelting, argon blowing station, continuous casting, heating, rough rolling, finishing rolling, cooling and coiling processes; The continuous casting process is as follows: the billet width is ≤620 mm, the pulling speed is 1.30-1.60 m / min, the billet width is >620 mm, the pulling speed is 0.90-1.30 m / min, and the billet thickness is 180-230 mm. The heating process is heating in a walking beam heating furnace, the total residence time in the heating furnace is 160 to 210 minutes, the temperature of the heating furnace soaking section is 1220 to 1310° C., and the soaking time is 35 to 48 minutes; The rough rolling process is to roll the intermediate billet into a thickness of 30-35 mm through 8 rough rolling passes, the dephosphorization water pressure is 18-23 MPa, and the rough rolling outlet temperature is 1030-1090°C; The finishing rolling process is to roll the steel strip into a thickness of 2.0-12.0 mm through 7 passes of finishing rolling, the finishing rolling inlet temperature is 1020-1080° C., and the final rolling temperature is 870-910° C.; The cooling process is that the steel strip is first rapidly cooled to 680-720°C at 20-40°C / s in the front rough adjustment section of the laminar flow, then air-cooled for 2-4s in the middle, and then rapidly cooled to the coiling temperature of 580-610°C at 20-40°C / s in the rear fine adjustment section of the laminar flow.

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