Performance stability improving method based on cooperative control of titanium content and heating temperature

Abstract

The invention discloses a performance stability improving method based on titanium content and heating temperature cooperative control, and belongs to the technical field of hot continuous rolling steel production. The invention provides a performance stability improving method based on titanium content and heating temperature cooperative control in order to improve the performance stability of high-titanium-content titanium microalloyed steel. According to the method, different slab tapping temperatures and intermediate slab thicknesses are designed according to different Ti contents and finished product thicknesses, the rough / finish rolling temperature and the laminar cooling final cooling temperature are controlled at the same time, through cooperative control over components and the process, the influence of the high titanium content on steel performance fluctuation is avoided, mechanical property fluctuation of finished product steel is reduced, and the quality of the finished product steel is improved. And the fluctuation range of the yield strength and the tensile strength is within + / -30MPa.

Description

Technical Field

[0001] The present invention belongs to the technical field of hot-rolled steel production, and in particular relates to a method for improving performance stability based on coordinated control of titanium content and heating temperature. Background Art

[0002] In recent years, the application of high-strength, lightweight automotive steels has become increasingly widespread, significantly driving the development of low-carbon, energy-saving, and emission-reduction strategies in the automotive manufacturing industry. In hot-rolled high-strength steels, microalloying elements such as Nb, V, and Ti have significant strengthening effects. Compared to Nb and V, Ti has a more pronounced advantage due to the following: 1) low ferrotitanium cost; 2) Ti has a smaller atomic weight, resulting in a slightly higher mass fraction of TiC for the same mass fraction of Ti; and TiC has a lower density. For the same mass fraction, TiC is approximately 14% higher than the volume fraction of VC and 56% higher than that of NbC; and 3) TiN inhibits austenite grain coarsening, thereby inhibiting grain growth during the slab heating and welding thermal cycles. However, since Ti precipitates Ti(CN) phases of varying sizes and quantities during the continuous casting-heating-rolling-cooling-coil-ing process, fluctuations in composition and processing can easily lead to variations in the size and quantity of Ti precipitates in the steel, resulting in performance fluctuations in hot-rolled titanium microalloyed high-strength steels. Therefore, it is crucial to improve the stability of the mechanical properties of various types of hot-rolled titanium microalloyed high-strength steels.

[0003] CN117340011A discloses a production method for reducing performance fluctuations of hot-rolled steel strips, wherein the composition of the steel is as follows: C: ≤ 0.10%, Mn: ≤ 1.25%, S: ≤ 0.005%, P: ≤ 0.012%, Si: ≤ 0.13%, Als: 0.02-0.08%, N ≤ 0.006%, Nb+Ti ≤ 0.040, and the remainder is Fe and unavoidable impurities; the method provides the following technical solutions for reducing performance fluctuations of hot-rolled steel strips caused by changes in cooling rate: When the preset cooling rate Vs and the target cooling rate Vo satisfy |Vs-Vo| / Vo≤13%, the cooling mode executes the front-stage normal cooling mode; when it satisfies 13%<|Vs-Vo| / Vo and Vs-Vo>0, the cooling mode executes the front-stage sparse cooling mode; when it satisfies 13%<|Vs-Vo| / Vo≤19% and Vs-Vo<0, the cooling mode executes the front-stage concentrated cooling mode; when it satisfies 19%<|Vs-Vo| / Vo and Vs-Vo<0, the cooling mode executes the front-stage encrypted cooling mode.

[0004] CN114309086B discloses a preparation method for improving the performance uniformity of Ti-reinforced cold-formed high-strength steel, comprising heating, rough rolling, finish rolling, laminar cooling, and coiling. This method utilizes a U-shaped cooling method to adjust the coiling temperature at the head and tail of the strip, making it higher than the set temperature at the normal position, thereby reducing performance fluctuations along the length. By regulating the rolling force of the first rough rolling pass and the rough rolling end temperature, the method can detect the heating effect of the ingot in the heating furnace. The furnace temperature is adjusted based on fluctuations in the rolling force and rough rolling end temperature to ensure uniformity during the heating process. Edge shielding is also employed to reduce performance fluctuations along the width of the strip, particularly at the edges. The amount of edge shielding is correlated with the strip thickness, thereby improving performance uniformity across the width of the strip.

[0005] As can be seen from the above, existing patents mainly use technologies such as controlled laminar cooling mode, U-shaped cooling method, dynamic adjustment of heating furnace temperature, and edge shielding to reduce the performance fluctuation of steel in the plate length and width directions. There are no reports on the use of coordinated control of titanium content and heating temperature to achieve the reduction of performance fluctuations. Summary of the Invention

[0006] In order to reduce the performance fluctuation of titanium microalloyed steel with high titanium content, the present invention proposes a method for improving the stability of mechanical properties, which can be extended to various types of hot-rolled titanium microalloyed high-strength steels, thereby greatly improving product quality and enhancing product competitiveness.

[0007] The present invention provides a method for improving performance stability based on the coordinated control of titanium content and heating temperature, which adopts the process of converter smelting → LF refining → RH refining → continuous casting → hot rolling → laminar cooling → coiling to produce titanium microalloyed steel; The chemical composition of the titanium microalloyed steel is as follows by weight: C: 0.05-0.07%, Si: 0.05-0.10%, Mn: 1.70-1.80%, Nb: 0.035-0.045%, Ti: 0.080-0.105%, P≤0.015%, S≤0.004%, N≤0.0040%, and the remainder is Fe and unavoidable impurity elements; The hot rolling process includes heating of steel slab, rough rolling and finish rolling, specifically: Steel slab heating: After the steel slab obtained by continuous casting is air-cooled to room temperature, it is loaded into the slab heating furnace. When the titanium microalloyed steel has a content of 0.080% ≤ Ti < 0.090% and the finished steel plate has a thickness of 1.8mm ≤ < 4.0mm, the slab discharge temperature is controlled to be 1250±15℃; when the titanium microalloyed steel has a content of 0.080% ≤ Ti < 0.090% and the finished steel plate has a thickness of 4.0mm ≤ ≤ 10.0mm, the slab discharge temperature is controlled to be 1250±15℃. The furnace temperature is 1240±15℃; when the titanium content of the titanium microalloyed steel is 0.090%≤Ti content≤0.105% and the thickness of the finished steel plate is 1.8mm≤<4.0mm, the slab furnace discharge temperature is controlled to be 1240±15℃; when the titanium content of the titanium microalloyed steel is 0.090%≤Ti content≤0.105% and the thickness of the finished steel plate is 4.0mm≤≤10.0mm, the slab furnace discharge temperature is controlled to be 1230±15℃; Rough rolling: After the slab is unloaded from the furnace, it is subjected to rough rolling to obtain the intermediate bar. When the thickness of the finished steel plate is 1.8mm≤<4.0mm, the thickness of the intermediate bar is controlled to be 42±1mm; when the thickness of the finished steel plate is 4.0mm≤≤10.0mm, the thickness of the intermediate bar is controlled to be 55±1mm. The deformation of a single rough rolling pass is ≥18%, and the rough rolling outlet temperature is ≥1080℃. Finishing rolling: The intermediate billet is subjected to finishing rolling, and the finishing rolling inlet temperature is controlled to be ≤1050℃, and the finishing rolling outlet temperature is 870±15℃; In the laminar cooling, the intermediate billet is subjected to laminar cooling after finish rolling, and the final cooling temperature is controlled to be 600±15°C; The thickness of the finished steel plate is 1.8~10.0mm.

[0008] Wherein, in the above method, the thickness of the steel ingot obtained by continuous casting is 200~250mm.

[0009] In the above method, after the slab is taken out of the furnace, it is descaled and subjected to 6 passes of rough rolling to obtain an intermediate slab.

[0010] In the above method, the intermediate billet is subjected to 7 passes of finish rolling.

[0011] In the above method, during laminar cooling, the cooling rate is controlled to be 25~35℃ / s.

[0012] In the above method, after the steel plate is coiled into a steel coil, it is placed in a slow cooling pit and slowly cooled to room temperature for 70 to 80 hours.

[0013] In the above method, the titanium microalloyed steel has a yield strength of 710-770 MPa, a tensile strength of 790-850 MPa, an elongation of ≥14%, and a yield strength fluctuation range of within ±30 MPa and a tensile strength fluctuation range of within ±30 MPa.

[0014] In the present invention, the steel slabs used in the hot rolling process can be produced using conventional processes in the art, such as converter smelting, LF refining, RH refining, and continuous casting, to obtain steel slabs having a thickness and composition meeting the aforementioned requirements, which are then subjected to the hot rolling process of the present invention. In addition to the hot rolling parameters described above, such as the furnace discharge temperature and intermediate slab thickness, other hot rolling parameters, such as the finishing reduction and the start temperature of the roughing roll, can be controlled according to conventional processes in the art.

[0015] The beneficial effects of the present invention are: The present invention designs different slab discharge temperatures and intermediate billet thicknesses for different Ti contents and finished product thicknesses. This avoids the problems of high-strength, high-Ti content steels, which are prone to the formation of inclusions such as Ti4C2S2 and TiN due to the high Ti content, easily forming TiC in the steel, causing large fluctuations in the Ti content that leads to precipitation strengthening, and significantly affecting the performance of the finished steel due to fluctuations in the hot rolling process. Simultaneously controlling the finishing rolling exit temperature and the laminar cooling final cooling temperature, the present invention successfully reduces the fluctuations in the mechanical properties of the finished steel through coordinated control of composition and process, keeping the fluctuation range of yield strength and tensile strength within ±30 MPa. This smaller performance fluctuation is conducive to the stable use of the product at the user end. Furthermore, the method for reducing the performance fluctuation of Ti microalloyed steel provided by the present invention can be extended to steels of other strength levels. DETAILED DESCRIPTION

[0016] Specifically, a method for improving performance stability based on coordinated control of titanium content and heating temperature, which produces titanium microalloyed steel using a process of converter smelting → LF refining → RH refining → continuous casting → hot rolling → laminar cooling → coiling; The chemical composition of the titanium microalloyed steel is as follows by weight: C: 0.05-0.07%, Si: 0.05-0.10%, Mn: 1.70-1.80%, Nb: 0.035-0.045%, Ti: 0.080-0.105%, P≤0.015%, S≤0.004%, N≤0.0040%, and the remainder is Fe and unavoidable impurity elements; The hot rolling process includes heating of steel slab, rough rolling and finish rolling, specifically: Steel slab heating: After the steel slab obtained by continuous casting is air-cooled to room temperature, it is loaded into the slab heating furnace. When the titanium microalloyed steel has a content of 0.080% ≤ Ti < 0.090% and the finished steel plate has a thickness of 1.8mm ≤ < 4.0mm, the slab discharge temperature is controlled to be 1250±15℃; when the titanium microalloyed steel has a content of 0.080% ≤ Ti < 0.090% and the finished steel plate has a thickness of 4.0mm ≤ ≤ 10.0mm, the slab discharge temperature is controlled to be 1250±15℃. The furnace temperature is 1240±15℃; when the titanium content of the titanium microalloyed steel is 0.090%≤Ti content≤0.105% and the thickness of the finished steel plate is 1.8mm≤<4.0mm, the slab furnace discharge temperature is controlled to be 1240±15℃; when the titanium content of the titanium microalloyed steel is 0.090%≤Ti content≤0.105% and the thickness of the finished steel plate is 4.0mm≤≤10.0mm, the slab furnace discharge temperature is controlled to be 1230±15℃; Rough rolling: After the slab is unloaded from the furnace, it is subjected to rough rolling to obtain the intermediate bar. When the thickness of the finished steel plate is 1.8mm≤<4.0mm, the thickness of the intermediate bar is controlled to be 42±1mm; when the thickness of the finished steel plate is 4.0mm≤≤10.0mm, the thickness of the intermediate bar is controlled to be 55±1mm. The deformation of a single rough rolling pass is ≥18%, and the rough rolling outlet temperature is ≥1080℃. Finishing rolling: The intermediate billet is subjected to finishing rolling, and the finishing rolling inlet temperature is controlled to be ≤1050℃, and the finishing rolling outlet temperature is 870±15℃; In the laminar cooling, the intermediate billet is subjected to laminar cooling after finish rolling, and the final cooling temperature is controlled to be 600±15°C; The thickness of the finished steel plate is 1.8~10.0mm.

[0017] The present invention provides a method for producing the titanium microalloyed steel. The reasons for limiting the main alloying elements in the steel of the present invention are explained below.

[0018] Carbon is a key element in steel, forming structures such as bainite, pearlite, and cementite. Appropriately reducing the carbon content helps reduce pearlite and cementite content, thereby improving the steel's elongation. Furthermore, carbon is a component of the TiC second phase, so reducing the fluctuation range of the carbon content helps stabilize and control the TiC precipitation phase. Therefore, the present invention controls the carbon content to 0.05-0.07%.

[0019] Mn plays a role in solid solution strengthening, improving toughness, and improving hardenability in steel. Using a higher content of Mn is beneficial to promoting the formation of fine-grained ferrite structure in the steel described in the present invention. At the same time, reducing the composition fluctuation range of the Mn content is beneficial to reducing the fluctuation of the solid solution strengthening effect. Therefore, the present invention controls the Mn content to 1.70~1.80%.

[0020] Nb in steel mainly plays the role of inhibiting austenite coarsening and refining grains, reducing the composition fluctuation range of Nb content, and helping to reduce the fluctuation of grain refinement strengthening effect. Therefore, the present invention controls the Nb content to 0.035~0.045%.

[0021] Ti forms a TiC precipitate phase in steel to achieve the effect of precipitation strengthening, reducing the composition fluctuation range of the Ti content, which is beneficial to reducing the fluctuation of the precipitation strengthening effect. Therefore, the present invention controls the Ti content to 0.080~0.105%.

[0022] S and N are inherent impurity elements in steel and easily combine with Ti to form Ti4C2S2 and TiN inclusions, respectively. This not only reduces the toughness and plasticity of the steel, but also reduces the content of TiC precipitation phase, thereby causing fluctuations in the precipitation strengthening effect. Therefore, the present invention limits the S and N contents to ≤0.004% and ≤0.0040%, respectively.

[0023] The reasons for the production process limitations are explained below in conjunction with the control requirements for the stability of the mechanical properties of steel described in the present invention.

[0024] As can be seen from the foregoing, the steel of the present invention has a high steel strength level and a high Ti content of 0.080-0.105%, which is prone to forming inclusions such as Ti4C2S2 and TiN, resulting in the actual formation of TiC in the steel. The Ti content that provides the precipitation strengthening effect fluctuates greatly, and when the Ti content is high, the performance of the finished steel is greatly affected by the fluctuation of the hot rolling process. At the same time, the fluctuation range of the Ti content of the present invention is 0.025%. Since Ti is chemically active in the molten steel, the content fluctuation range is large. Therefore, in order to reduce the impact of the large fluctuation range of the Ti content, different heating temperatures are designed for the control targets of different Ti contents to reduce the performance fluctuation of the finished steel, as follows: (1) Slab out-of-furnace temperature When the Ti content is between 0.080% and less than 0.090%, a higher slab tapping temperature is adopted. Different slab tapping temperatures are designed for thin steel gauges (1.8 to less than 4.0 mm) and thick steel gauges (4.0 to 10.0 mm). This is because steel with a thickness of 1.8 to less than 4.0 mm experiences a more rapid temperature drop during rolling. To compensate for this temperature drop, a higher slab tapping temperature of 1250 ± 15°C is adopted. Steel with a thickness of 4.0 to 10.0 mm experiences a slower temperature drop during rolling, so a lower slab tapping temperature of 1240 ± 15°C is adopted. It is worth noting that the slab tapping temperature fluctuation range of ±15°C is also controlled to stabilize the solid solution content of elements such as Mn, Nb, and Ti, thereby stabilizing the mechanical properties of the finished steel.

[0025] Similarly, when the Ti content is 0.090~0.105%, a lower slab furnace temperature is used. This is because when the Ti content is higher, the Ti content in the solid solution in the steel is higher, and more Ti eventually forms TiC precipitation phase. Therefore, appropriately lowering the slab furnace temperature can stabilize the performance fluctuations of the finished steel. The specific requirements are: if the finished steel plate thickness is 1.8~<4.0mm, the slab furnace temperature is 1240±15℃; if the finished steel plate thickness is 4.0~10.0mm, the slab furnace temperature is 1230±15℃.

[0026] (2) Rolling process The rough rolling process mainly causes dynamic recrystallization of austenite to promote the refinement of austenite grains. The present invention requires that the deformation of the rough rolling pass is ≥18%, otherwise the rolling deformation cannot penetrate into the core of the intermediate billet, which in turn causes the failure of austenite recrystallization in the core, thereby forming an uneven mixed crystal structure. At the same time, the dynamic recrystallization of austenite also has requirements for the rolling temperature. The critical recrystallization temperature is generally in the range of 930-970℃, so the rough rolling outlet temperature must be higher than this temperature. The present invention requires the rough rolling outlet temperature to be ≥1080℃. At the same time, the use of a lower finishing rolling inlet temperature is beneficial to increase the deformation resistance of the material, promote the flattening of the austenite structure during the finishing rolling process, and provide more nucleation points for subsequent phase transformations. The present invention requires the finishing rolling inlet temperature to be ≤1050℃.

[0027] (3) Intermediate billet thickness Cumulative deformation during the finishing rolling process promotes flattening of austenite, thereby providing more nucleation cores for subsequent phase transformation and promoting grain refinement. The thickness of the intermediate bar significantly influences the cumulative deformation during finishing. Therefore, thinner steels use smaller intermediate bar thicknesses, while thicker steels use larger intermediate bar thicknesses to achieve similar cumulative deformation. Therefore, the present invention limits the intermediate bar thickness to: when the finished steel plate thickness is 1.8 to <4.0 mm, the intermediate bar thickness is 42 ± 1 mm at the slab furnace temperature; when the finished steel plate thickness is 4.0 to 10.0 mm, the slab furnace temperature is 55 ± 1 mm.

[0028] (4) Laminar cooling process The present invention limits the fluctuation range of the finishing rolling exit temperature and the final cooling temperature to ±15°C to reduce the fluctuation range of the finished steel properties. The finishing rolling exit temperature is limited to 870±15°C. Large fluctuations in the finishing rolling exit temperature can affect the amount of deformation-induced TiC precipitation during the rolling process. The final cooling temperature is limited to 600±15°C. Large fluctuations in the final cooling temperature can affect the amount of TiC precipitation caused by ferrite supersaturation.

[0029] In the method of the present invention, the thickness of the steel slab obtained by continuous casting is 200-250 mm.

[0030] In the method of the present invention, after the slab is taken out of the furnace, it is descaled and subjected to six passes of rough rolling to obtain an intermediate slab.

[0031] In the method of the present invention, the intermediate billet is subjected to 7 passes of finish rolling.

[0032] In the method of the present invention, during laminar cooling, the cooling rate is controlled to be 25-35°C / s.

[0033] In the method of the present invention, after the steel plate is coiled into a steel coil, it is placed in a slow cooling pit and slowly cooled to room temperature for 70 to 80 hours.

[0034] In the method of the present invention, the titanium microalloyed steel has a yield strength of 710-770 MPa, a tensile strength of 790-850 MPa, an elongation of ≥14%, and a yield strength fluctuation range of within ±30 MPa and a tensile strength fluctuation range of within ±30 MPa.

[0035] The present invention is further described in detail below through examples, but the protection scope of the present invention is not limited to the scope of the examples.

[0036] The titanium microalloyed steels described in Examples 1 to 4 of the present invention and Comparative Examples 1 to 4 were first subjected to converter smelting, LF refining, RH refining, and continuous casting to obtain steel ingots with a thickness of 230 mm. The steel ingots were then subjected to hot rolling, laminar cooling, and coiling to obtain finished steel plates. The specific composition and process are shown in Tables 1 and 2.

[0037] Table 1 Chemical composition of steels of the present invention and comparative examples (wt%) Table 2 Process parameters of the embodiments of the present invention and the comparative examples Table 3 Mechanical properties of steels of the present invention and comparative examples Table 1 shows the composition of the steel of the embodiment of the present invention and the comparative example, Table 2 shows the production process parameters of the steel of the embodiment of the present invention and the comparative example, and Table 3 shows the mechanical properties of the steel of the embodiment of the present invention and the comparative example.

[0038] As shown in Table 3, the mechanical properties of the steels of Examples 1 to 4 all meet the requirements, namely, the yield strength is 710-770 MPa, the tensile strength is 790-850 MPa, the elongation is ≥14%, and the yield strength and tensile strength fluctuation range are within the range of ±30 MPa (upper and lower limits 60 MPa), which are 31 MPa and 35 MPa, respectively.

[0039] The chemical composition of the steels in Comparative Examples 1 and 2 exceeds the requirements of ≤0.0040% and ≤0.004%, respectively, at 0.0060% and 0.008%. Since N and S will combine with Ti to produce TiN and Ti4C2S2 inclusions, respectively, the Ti content actually used to form the TiC second phase precipitation and play a precipitation strengthening role is reduced, which in turn causes the yield strength and tensile strength to be lower than the required values. At the same time, the minimum roughing pass reduction of the steel in Comparative Example 2 during the rolling process is 16%, which is lower than the required value of ≥18%. The finishing rolling start temperature is 1069°C, which is higher than the required value of ≤1050°C, resulting in coarsening of the structure and a reduction in strength.

[0040] The chemical composition of the steels in Comparative Examples 3 and 4 both meet the requirements, but the slab tapping temperature in Comparative Example 3 is relatively high, at 1259°C, exceeding the required value of 1225-1255°C. Due to the high tapping temperature, the solid-solution Ti content in the steel is relatively high, ultimately leading to a higher TiC content precipitated, which in turn results in higher yield strength and tensile strength than the required values. The slab tapping temperature in Comparative Example 4 is relatively low, at 1206°C, lower than the required value of 1215-1245°C. The solid-solution Ti content in the steel is relatively low, and the cooling rate is relatively low, at 22°C, lower than the required value of 25-35°C / s. The final cooling temperature is relatively high, at 633°C, higher than the required value of 585-615°C. The final cooling temperature deviates from the nose point temperature of TiC precipitation (600°C), resulting in a lower TiC content in the final precipitation, which in turn results in lower yield strength and tensile strength of the finished steel.

[0041] At the same time, the yield strength and tensile strength fluctuation ranges of the steels in Examples 1 to 4 are relatively high, namely 98 MPa and 90 MPa, respectively, which are much higher than the required value of ±30 MPa.

Claims

1. A method for improving performance stability based on coordinated control of titanium content and heating temperature, characterized in that: Titanium microalloyed steel is produced by adopting the process of converter smelting → LF refining → RH refining → continuous casting → hot rolling → laminar cooling → coiling; The chemical composition of the titanium microalloyed steel is as follows by weight: C: 0.05-0.07%, Si: 0.05-0.10%, Mn: 1.70-1.80%, Nb: 0.035-0.045%, Ti: 0.080-0.105%, P≤0.015%, S≤0.004%, N≤0.0040%, and the remainder is Fe and unavoidable impurity elements; The hot rolling process includes heating of steel slab, rough rolling and finish rolling, specifically: Steel slab heating: After the steel slab obtained by continuous casting is air-cooled to room temperature, it is loaded into the slab heating furnace. When the titanium microalloyed steel has a content of 0.080% ≤ Ti < 0.090% and the finished steel plate has a thickness of 1.8mm ≤ < 4.0mm, the slab discharge temperature is controlled to be 1250±15℃; when the titanium microalloyed steel has a content of 0.080% ≤ Ti < 0.090% and the finished steel plate has a thickness of 4.0mm ≤ ≤ 10.0mm, the slab discharge temperature is controlled to be 1250±15℃. The furnace temperature is 1240±15℃; when the titanium content of the titanium microalloyed steel is 0.090%≤Ti content≤0.105% and the thickness of the finished steel plate is 1.8mm≤<4.0mm, the slab furnace discharge temperature is controlled to be 1240±15℃; when the titanium content of the titanium microalloyed steel is 0.090%≤Ti content≤0.105% and the thickness of the finished steel plate is 4.0mm≤≤10.0mm, the slab furnace discharge temperature is controlled to be 1230±15℃; Rough rolling: After the slab is unloaded from the furnace, it is subjected to rough rolling to obtain the intermediate bar. When the thickness of the finished steel plate is 1.8mm≤<4.0mm, the thickness of the intermediate bar is controlled to be 42±1mm; when the thickness of the finished steel plate is 4.0mm≤≤10.0mm, the thickness of the intermediate bar is controlled to be 55±1mm. The deformation of a single rough rolling pass is ≥18%, and the rough rolling outlet temperature is ≥1080℃. Finishing rolling: The intermediate billet is subjected to finishing rolling, and the finishing rolling inlet temperature is controlled to be ≤1050℃, and the finishing rolling outlet temperature is 870±15℃; In the laminar cooling, the intermediate billet is subjected to laminar cooling after finish rolling, and the final cooling temperature is controlled to be 600±15°C; The thickness of the finished steel plate is 1.8~10.0mm.

2. The method for improving performance stability based on coordinated control of titanium content and heating temperature according to claim 1, characterized in that: The thickness of the steel ingot obtained by continuous casting is 200~250mm.

3. The method for improving performance stability based on coordinated control of titanium content and heating temperature according to claim 1, characterized in that: After the slab comes out of the furnace, it is descaled and subjected to 6 passes of rough rolling to obtain the intermediate slab.

4. The method for improving performance stability based on coordinated control of titanium content and heating temperature according to claim 1, characterized in that: The intermediate billet is subjected to 7 passes of finishing rolling.

5. The method for improving performance stability based on coordinated control of titanium content and heating temperature according to claim 1, characterized in that: During laminar cooling, the cooling rate is controlled at 25~35℃ / s.

6. The method for improving performance stability based on coordinated control of titanium content and heating temperature according to claim 1, characterized in that: After the steel plate is coiled into a coil, it is placed in a slow cooling pit and slowly cooled to room temperature for 70 to 80 hours.

7. The method for improving performance stability based on coordinated control of titanium content and heating temperature according to any one of claims 1 to 6, characterized in that: The titanium microalloyed steel has a yield strength of 710-770 MPa, a tensile strength of 790-850 MPa, an elongation of ≥14%, and a yield strength fluctuation range of within ±30 MPa and a tensile strength fluctuation range of within ±30 MPa.

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