Production method of FH40 hot-rolled H-shaped steel with excellent low-temperature impact toughness for ocean engineering structure

Abstract

The invention provides a production method of FH40 hot-rolled H-shaped steel with excellent low-temperature impact toughness for an ocean engineering structure, which comprises the following steps of: optimizing and adjusting the chemical components of the H-shaped steel: 0.12 to 0.15 percent of C, 0.40 to 0.50 percent of Si, 0.90 to 1.00 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, 0.20 to 0.30 percent of Cu, 0.020 to 0.030 percent of Nb, 0.20 to 0.30 percent of Ni, 0.065 to 0.080 percent of V and the balance of Fe and inevitable impurities, and optimizing and controlling the parameters of a steelmaking process, thereby obtaining the FH40 hot-rolled H-shaped steel with excellent low-temperature impact toughness for the ocean engineering structure. The FH40 hot-rolled H-shaped steel for the ocean engineering structure has more excellent low-temperature impact toughness and can be applied to a cold deep sea environment with severe conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical materials, and in particular relates to a production method of FH40 hot-rolled H-shaped steel for marine engineering structures with excellent low-temperature impact toughness. Background Art

[0002] As oil and gas are increasingly developed in the deep sea, the development prospects of offshore oil and gas are bright. In recent years, the country's public technology platform for oil and gas field development is also under construction. The prospects for my country's marine equipment manufacturing industry are very broad. It also drives the demand for steel structure materials including H-beams. In recent years, the replacement steel plate welded H-beam steel used in the construction of offshore floating production storage and offloading vessels is about 200,000 tons, providing a huge market for H-beams for marine engineering structures. Baosteel organized technical research based on its own technical equipment characteristics and successfully developed FH40 hot-rolled H-beams for marine engineering structures. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a FH40 hot-rolled H-shaped steel for marine engineering structures with excellent low-temperature impact toughness and a production method thereof. The technical solution of the present invention is as follows:

[0004] One aspect of the present invention provides a method for producing FH40 hot-rolled H-shaped steel for marine engineering structures with excellent low-temperature impact toughness, which comprises: a steelmaking process and a rolling process; wherein:

[0005] The steelmaking process includes: combined blowing converter smelting, LF refining, beam billet continuous casting and billet stacking slow cooling;

[0006] In the combined blowing converter smelting and LF refining, the composition of the molten steel for continuous casting is controlled to be calculated by mass percentage as follows: C 0.12%-0.15%, Si 0.40%-0.50%, Mn 0.90%-1.00%, P≤0.020%, S≤0.020%, Cu0.20-0.30%, Nb 0.020%-0.030%, Ni 0.20-0.30%, V 0.065-0.080%, and the rest is Fe and unavoidable impurities;

[0007] In the continuous casting of the profiled billet and the slow cooling of the billet stacking, protective pouring is adopted throughout the whole process, the superheat is ≤25°C, a weak cooling system is adopted, and before entering the drawing and straightening machine, the target temperature of the billet web is 920-940°C, the target temperature of the billet flange is 880-890°C, the R angle temperature of the billet is 980-1000°C, and the constant drawing speed operation is adopted, and the drawing speed is controlled at 0.8m / min-0.9m / min. After the continuous casting billet is cut, it is stacked and slowly cooled in time, and the slow cooling time is greater than 48 hours;

[0008] The rolling process includes: heating of the profiled blank, rough rolling, finish rolling and cooling.

[0009] In some embodiments, in the combined blowing converter smelting, the final slag basicity is controlled at 3.0, the endpoint control target C≥0.03%, T≥1610°C, SiMn and MnFe deoxidation and alloying are used, the final deoxidation uses Al deoxidation, lime is added during the steelmaking process, and slag is blocked during steelmaking.

[0010] In some embodiments, in the LF refining, the LF refining white slag operation is performed, and the slag sample is dipped after each lifting of the electrode, and silicon, calcium and barium are added according to the color of the slag, and white ash is added according to the viscosity of the slag, and the final slag requires white slag; Ar blowing operation is performed throughout the process, and desulfurization, composition fine-tuning and heating operations are performed according to the composition and temperature of the converter molten steel, and the temperature T after heating is ≥1560°C; ferroniobium, ferronickel and ferrovanadium are added in the later stage of refining to ensure that the soft blowing time is greater than 10 minutes.

[0011] In some embodiments, the cross-sectional dimensions of the ingot are H555mm×440mm×105mm.

[0012] In some embodiments, in the heating process of the profiled blank, the profiled blank is heated in a heating furnace, the heating temperature of the profiled blank is 1200-1250° C., the total insulation time is 150-180 min, and the profiled blank is descaled by high-pressure water after being taken out of the furnace.

[0013] In some embodiments, in the rough rolling process, the rough rolling temperature is controlled to be 1140-1160° C., water cooling is used for controlled cooling, the rolling passes are 3-5 times, the total deformation is ≥40%, and then the rough rolled profile is sent to the finishing mill for finishing rolling.

[0014] In some embodiments, in the finishing rolling process, the starting temperature of the finishing rolling is controlled to be 950-980°C, the finishing rolling adopts warm rolling and water-cooled controlled rolling, the rolling passes are 5-7 times, the final rolling temperature is controlled to be 840-860°C, and the total reduction of the two-stage rolling is ≥70%.

[0015] In some embodiments, in the cooling process, a cooling bed is used for centralized cooling, and after the temperature drops below 150° C., straightening is performed in a straightening machine, and finally the steel wire is cut to size and bundled.

[0016] In some embodiments, the FH40 hot-rolled H-shaped steel for marine engineering structures with excellent low-temperature impact toughness has a transverse impact energy (KV2) of more than 169 J and a longitudinal impact energy (KV2) of more than 208 J at -20°C, and a transverse impact energy (KV2) of more than 104 J and a longitudinal impact energy (KV2) of more than 150 J at -60°C.

[0017] In some embodiments, the mechanical properties of the FH40 hot-rolled H-shaped steel for marine engineering structures with excellent low-temperature impact toughness also meet the following requirements: yield strength ≥ 466 MPa, and tensile strength ≥ 587 MPa.

[0018] Another aspect of the present invention provides a FH40 hot-rolled H-shaped steel for marine engineering structures having excellent low-temperature impact toughness, which is obtained by the above-mentioned production method.

[0019] Based on the above technical scheme, the present invention successfully develops a FH40 hot-rolled H-beam for marine engineering structure with better low-temperature impact toughness by optimizing and adjusting the chemical composition and content of the FH40 hot-rolled H-beam for marine engineering structure, and combining the optimization and control of steelmaking process parameters. The transverse impact energy (KV2) at -20°C reaches more than 169J, and the longitudinal impact energy (KV2) reaches more than 208J. The transverse impact energy (KV2) at -60°C reaches more than 104J, and the longitudinal impact energy (KV2) reaches more than 150J. In addition, the FH40 hot-rolled H-beam for marine engineering structure also has a relatively high strength, satisfying: yield strength ≥466MPa, tensile strength ≥587MPa. Therefore, the FH40 hot-rolled H-beam for marine engineering structure provided by the present invention has good mechanical properties, especially good low-temperature impact toughness. DETAILED DESCRIPTION

[0020] FH40 steel for marine engineering structures is required to have good low-temperature impact performance, good toughness and low ductile-brittle transition temperature. Its chemical composition and content should generally meet the following requirements in terms of mass percentage: C≤0.16%, Si≤0.50%, Mn0.90%~1.60%, P≤0.025%, S≤0.025%, Cu≤0.35%, Cr≤0.20%, Nb 0.020%~0.050%, Ni≤0.40%, V 0.05~0.10%, Ti≤0.0.2%, Mo≤0.08, Als≤0.015%, and the rest is Fe and unavoidable impurities. The impact temperature of the steel plate is required to be -60℃, especially in cold environments, it needs to have excellent low-temperature aging impact toughness. At present, the existing FH40 steel for marine engineering structures on the market has relatively good low-temperature impact toughness, but it still cannot meet the more severe deep-sea environment. Patent document CN118186293A provides a production method for hot-rolled H-beam AH40 for marine engineering structures having a similar chemical composition to FH40 steel for marine engineering structures. The AH40 hot-rolled H-beam for marine engineering structures developed by the patent document CN118186293A has a transverse impact energy (KV2) of about 150J and a longitudinal impact energy (KV2) of about 190J at -20°C through the control of steelmaking processes such as converter smelting, LF refining, continuous casting of special-shaped billets, and slow cooling of billet stacking. However, it is not yet known whether it meets the impact toughness requirements at -60°C. In view of this, the present invention successfully develops a FH40 steel for marine engineering structures with better low-temperature impact toughness by optimizing and adjusting the chemical composition and content of FH40 steel for marine engineering structures, combined with optimizing and controlling steelmaking process parameters. The transverse impact energy (KV2) of the steel at -20°C reaches more than 169J, and the longitudinal impact energy (KV2) reaches more than 208J. The transverse impact energy (KV2) of the steel at -60°C reaches more than 104J, and the longitudinal impact energy (KV2) reaches more than 150J. In addition, the FH40 steel for marine engineering structures also has relatively high strength, satisfying the following requirements: yield strength ≥466MPa, and tensile strength ≥587MPa.

[0021] Specifically, the present invention provides a method for producing FH40 hot-rolled H-shaped steel for marine engineering structures with excellent low-temperature impact toughness, which includes: a steelmaking process and a rolling process; wherein the steelmaking process includes: combined blowing converter smelting, LF refining, special-shaped billet continuous casting and billet stacking slow cooling; the rolling process includes: special-shaped billet heating, rough rolling, finish rolling and cooling.

[0022] In some embodiments, in the combined blowing converter smelting, the final slag basicity is controlled at 3.0, the endpoint control target C≥0.03%, T≥1610℃, SiMn and MnFe deoxidation and alloying are used, and the final deoxidation uses Al deoxidation. Lime is added during the steelmaking process to block the slag during steelmaking.

[0023] In some embodiments, LF refining white slag operation, each time the electrode is lifted, dip the slag sample, add silicon calcium barium according to the slag color, add white ash according to the slag viscosity, and the final slag requires white slag. Ar blowing operation is carried out throughout the process, desulfurization, composition fine-tuning and heating operation are carried out according to the composition and temperature of the converter molten steel, and the temperature after heating is T≥1560℃. Niobium iron, nickel iron and vanadium iron are added in the later stage of refining to ensure that the soft blowing time is greater than 10min. The final controlled composition of the molten steel for continuous casting is calculated by mass percentage as follows: C 0.12%-0.15%, Si 0.40%-0.50%, Mn 0.90%-1.00%, P≤0.020%, S≤0.020%, Cu 0.20-0.30%, Nb 0.020%-0.030%, Ni 0.20-0.30%, V 0.065-0.080%, and the rest is Fe and unavoidable impurities.

[0024] In some embodiments, during the continuous casting of the special-shaped billets and the slow cooling of the billet stacking, protective pouring is adopted throughout the whole process, the superheat is ≤25°C, a weak cooling system is adopted, and before entering the straightening machine, the target temperature of the billet web is 920-940°C, the target temperature of the billet flange is 880-890°C, the R-angle temperature of the billet is 980-1000°C, and a constant pulling speed operation is adopted, and the pulling speed is controlled at 0.8m / min-0.9m / min. After the continuous casting billets are cut, they are promptly taken offline and stacked for slow cooling, and the slow cooling time is greater than 48 hours. The cross-sectional dimensions of the obtained continuous casting billets are H555mm×440mm×105mm.

[0025] In some embodiments, in the heating process of the profiled blank, the profiled blank is heated in a heating furnace, the heating temperature of the profiled blank is 1200-1250° C., the total insulation time is 150-180 min, and the profiled blank is descaled by high-pressure water after being taken out of the furnace.

[0026] In some embodiments, in the rough rolling process, the rough rolling temperature is controlled to be 1140-1160°C, water cooling is used for controlled cooling, the rolling passes are 3-5 times, the total deformation is ≥40%, and then the rough rolled special-shaped blank is sent to the finishing mill station for finishing rolling.

[0027] In some embodiments, in the finishing rolling process, the starting temperature of the finishing rolling is controlled to be 950-980°C, the finishing rolling adopts warm rolling and water-cooled controlled rolling, the rolling passes are 5-7 times, the final rolling temperature is controlled to be 840-860°C, and the total reduction of the two-stage rolling is ≥70%.

[0028] In some embodiments, in the cooling process, a cooling bed is used for centralized cooling, and after the temperature drops below 150° C., straightening is performed on a straightening machine, and finally the steel wire is cut to size and bundled.

[0029] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the description is considered to be exemplary and non-restrictive in nature.

[0030] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0031] Example:

[0032] The steelmaking process is: combined blowing converter smelting, LF refining, beam billet continuous casting, billet stacking slow cooling, and continuous casting billets with a cross-sectional size of H555mm×440mm×105mm are produced. Continuous casting billets with the chemical composition and content shown in Table 1 are produced as shown in Table 1 below, wherein in beam billet continuous casting and billet stacking slow cooling, the specific process parameters of each steel grade are controlled as shown in Tables 2 and 3 below, wherein Comparative Examples 1-3 all adopt the process parameters of Example 1 in beam billet continuous casting and billet stacking slow cooling.

[0033] Table 1: Chemical composition and content of continuous casting slabs in each example (mass percentage %)

[0034] Examples C Si Mn P S Cu Nb Ni V Example 1 0.12 0.40 0.94 0.011 0.005 0.21 0.020 0.25 0.065 Example 2 0.15 0.42 0.90 0.010 0.009 0.25 0.028 0.20 0.068 Example 3 0.14 0.43 0.97 0.014 0.006 0.20 0.029 0.24 0.080 Example 4 0.13 0.49 1.00 0.013 0.007 0.29 0.024 0.30 0.075 Comparative Example 1 0.12 0.40 0.94 0.011 0.005 0 0.020 0 0.065 Comparative Example 2 0.10 0.20 1.40 0.015 0.008 0 0.040 0 0.060 Comparative Example 3 0.10 0.20 1.40 0.015 0.008 0.21 0.040 0.25 0.060

[0035] Table 2: Superheat and casting speed control for each example

[0036] Examples Superheat(℃) Pulling speed(m / min) Example 1 21 0.83 Example 2 24 0.85 Example 3 22 0.87 Example 4 23 0.89

[0037] Table 3: Surface temperature of the billet entering the straightening machine for each example

[0038] Examples Flange plate end(℃) R angle(℃) Web(℃) Example 1 880 985 920 Example 2 882 990 935 Example 3 886 995 926 Example 4 888 998 932

[0039] The rolling process includes: heating of the profiled blank, rough rolling, finish rolling, and cooling to obtain FH40 hot-rolled H-shaped steel for marine engineering structures, the size of which can be H700mm×300mm×13mm×24mm. The process parameters of heating, rough rolling, finish rolling, and cooling of the profiled blank in each example are controlled as shown in Table 4 below, and comparative examples 1-3 adopt the process parameters of Example 1 in heating, rough rolling, finish rolling, and cooling of the profiled blank. The mechanical properties of the FH40 hot-rolled H-shaped steel for marine engineering structures produced by rolling in each example are tested, and the results are shown in Table 5 below.

[0040] Table 4: Process parameter control in heating, rough rolling, finishing rolling and cooling of profiled blanks in various examples

[0041]

[0042] Table 5: Mechanical properties of H-beams rolled in various examples

[0043]

[0044] It can be seen from Table 5 above that the FH40 hot-rolled H-beam for marine engineering structures of each embodiment not only has good yield and tensile strength, but also has good low-temperature impact toughness, satisfying: the transverse impact energy (KV2) at -20°C reaches 169J or more, the longitudinal impact energy (KV2) reaches 208J or more, the transverse impact energy (KV2) at -60°C reaches 104J or more, the longitudinal impact energy (KV2) reaches 150J or more, the yield strength is ≥466MPa, and the tensile strength is ≥587MPa. Although Comparative Examples 1-3 use the same steelmaking and rolling process parameters as Example 1 of the present application, since the chemical composition of the steel grades of these comparative examples is not within the range required by the present invention, the mechanical properties (especially the low-temperature impact toughness) of the hot-rolled H-beam produced by them are obviously not as good as the hot-rolled H-beam produced by the embodiment of the present application. Therefore, the present invention successfully develops an FH40 steel for marine engineering structures with better low-temperature impact toughness by optimizing and adjusting the chemical composition and content of the FH40 steel for marine engineering structures, combined with optimizing and controlling the steelmaking process parameters. The steel can be used in harsh deep-sea environments or colder marine environments.

[0045] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for producing FH40 hot-rolled H-shaped steel for marine engineering structures with excellent low-temperature impact toughness, characterized in that: The production method comprises: a steelmaking process and a rolling process; wherein: The steelmaking process includes: combined blowing converter smelting, LF refining, beam billet continuous casting and billet stacking slow cooling; In the combined blowing converter smelting and LF refining, the composition of the molten steel for continuous casting is controlled to be calculated by mass percentage as follows: C 0.12%-0.15%, Si 0.40%-0.50%, Mn 0.90%-1.00%, P≤0.020%, S≤0.020%, Cu 0.20-0.30%, Nb 0.020%-0.030%, Ni 0.20-0.30%, V 0.065-0.080%, and the rest is Fe and unavoidable impurities; In the continuous casting of the profiled billet and the slow cooling of the billet stacking, protective pouring is adopted throughout the whole process, the superheat is ≤25°C, a weak cooling system is adopted, and before entering the drawing and straightening machine, the target temperature of the billet web is 920-940°C, the target temperature of the billet flange is 880-890°C, the R angle temperature of the billet is 980-1000°C, and the constant drawing speed operation is adopted, and the drawing speed is controlled at 0.8m / min-0.9m / min. After the continuous casting billet is cut, it is stacked and slowly cooled in time, and the slow cooling time is greater than 48 hours; The rolling process includes: heating of the profiled blank, rough rolling, finish rolling and cooling.

2. The production method according to claim 1, wherein in the combined blowing converter smelting, the final slag basicity is controlled at 3.0, the endpoint control target C≥0.03%, T≥1610°C, SiMn and MnFe deoxidation and alloying are adopted, the final deoxidation adopts Al deoxidation, lime is added during the steelmaking process, and slag is blocked during steelmaking.

3. The production method according to claim 1 or 2, wherein in the LF refining, the LF refining white slag operation, each time the electrode is lifted up, the slag sample is dipped, silicon, calcium and barium are added according to the color of the slag, and white ash is added according to the viscosity of the slag, and the final slag requires white slag; Ar blowing operation is carried out throughout the process, desulfurization, composition fine-tuning and heating operations are carried out according to the composition and temperature of the converter molten steel, and the temperature T after heating is ≥1560°C; ferroniobium, ferronickel and ferrovanadium are added in the later stage of refining to ensure that the soft blowing time is greater than 10 minutes.

4. According to the production method according to any one of claims 1 to 3, the cross-sectional dimensions of the ingot are H555mm×440mm×105mm.

5. The production method according to any one of claims 1 to 4, wherein in the profiled blank heating process, the profiled blank is heated in a heating furnace, the heating temperature of the profiled blank is 1200-1250° C., the total insulation time is 150-180 min, and high-pressure water is used to descale the profiled blank after it is taken out of the furnace; In the rough rolling process, the rough rolling temperature is controlled to be 1140-1160° C., water cooling is used for controlled cooling, the rolling passes are 3-5 times, the total deformation is ≥40%, and then the rough rolled profile is sent to the finishing mill station for finishing rolling; In the finishing rolling process, the starting temperature of the finishing rolling is controlled to be 950-980°C, the finishing rolling adopts warm rolling and water-cooled controlled rolling, the rolling passes are 5-7 times, the final rolling temperature is controlled to be 840-860°C, and the total reduction of the two-stage rolling is ≥70%; In the cooling process, a cooling bed is used for centralized cooling, and after the temperature drops below 150° C., the straightening is performed in a straightening machine, and finally the steel wire is cut to size and bundled.

6. According to the production method described in any one of claims 1 to 5, the FH40 hot-rolled H-shaped steel for marine engineering structures with excellent low-temperature impact toughness has a transverse impact energy (KV2) of more than 169 J and a longitudinal impact energy (KV2) of more than 208 J at -20°C, and a transverse impact energy (KV2) of more than 104 J and a longitudinal impact energy (KV2) of more than 150 J at -60°C.

7. According to the production method described in any one of claims 1 to 6, the mechanical properties of the FH40 hot-rolled H-shaped steel for marine engineering structures with excellent low-temperature impact toughness also meet the following requirements: yield strength ≥ 466 MPa, tensile strength ≥ 587 MPa.

8. A FH40 hot-rolled H-shaped steel for marine engineering structures having excellent low-temperature impact toughness, obtained by the production method according to any one of claims 1 to 7.

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