Production method of niobium-vanadium composite reinforced Q460-grade hot-rolled steel plate

Abstract

The invention provides a production method of a niobium-vanadium composite reinforced Q460-grade hot-rolled steel plate, and relates to the technical field of steel rolling. Comprising the steps of converter smelting, LF furnace external refining, wide plate blank continuous casting, plate blank heating, plate blank rolling, steel plate stacking aging and high-temperature tempering, in the production process, the processes of steel plate stacking aging and high-temperature tempering are adopted, the situation that the plasticity of the steel plate is unqualified due to casting blank middle cracks, serious segregation and high hydrogen content can be effectively improved, and economic losses are reduced.

Description

Technical Field

[0001] This application relates to the field of steel rolling technology, and more specifically, to a method for producing niobium-vanadium composite reinforced Q460 grade hot-rolled steel plates. Background Technology

[0002] Niobium-vanadium composite reinforced Q460 grade hot-rolled steel plate belongs to the category of C and Mn low-alloy steel and is widely used in the field of steel strengthening. This type of steel plate usually adds 0.015%~0.040% niobium (Nb) and 0.040%~0.120% vanadium (V), and improves the strength of the steel plate through the precipitation strengthening effect of niobium and vanadium elements.

[0003] This type of steel plate has significant production advantages, with relatively simple production processes and short production cycles, thus enjoying broad application prospects in the market. However, from an economic perspective, to control costs, the C and Mn contents are generally set at relatively high levels during production, with C content typically above 0.16% and Mn content above 1.5%. However, the high C and Mn contents, coupled with the addition of relatively more microalloying elements, can lead to a series of problems. On the one hand, the addition of more alloying elements can easily cause severe segregation in the cast billet, thus affecting the uniform plasticity of the material and reducing the stability of the steel quality. On the other hand, the third brittle zone of this steel composition is wider than that of other low-alloy steels, significantly increasing the risk of cracks in the middle of the cast billet under normal continuous casting machine conditions. Moreover, when the hydrogen content is unstable, it can also lead to batch discrepancies in the plasticity indicators of the steel plate, resulting in product scrap and significant economic losses for the production enterprise.

[0004] In view of this, this application aims to provide a method for producing niobium-vanadium composite reinforced Q460 grade hot-rolled steel plate to better solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this application is to provide a method for producing Q460 grade hot-rolled steel plates reinforced with niobium-vanadium composite, which can solve the technical problem of unqualified plasticity of Q460 grade hot-rolled steel plates caused by intermediate cracks in the billet, severe segregation, and fluctuations in hydrogen content.

[0006] This application provides a method for producing niobium-vanadium composite reinforced Q460 grade hot-rolled steel plate, characterized by the following steps:

[0007] Converter smelting, LF ladle refining, wide slab continuous casting, slab heating, slab rolling, steel plate stacking aging, high-temperature tempering.

[0008] Furthermore, the weight percentage of the chemical composition of the steel plate is as follows:

[0009] C: 0.16%~0.20%, Si: 0.20~0.50%, Mn: 1.50~1.80%, P≤0.025%, S≤0.010%, Nb: 0.015%~0.040%, V: 0.040%~0.120%, N: 0.0070~0.0150%.

[0010] Furthermore, in the steel plate stacking aging step, the steel plates are stacked and naturally aged for more than 10 days after finishing.

[0011] Furthermore, in the high-temperature tempering step, the tempering temperature is 520~600℃, and the tempering coefficient is 2.5~3.5min / mm.

[0012] The beneficial effects of this invention are:

[0013] The present invention provides a method for producing Q460 grade hot-rolled steel plates with niobium-vanadium composite reinforcement, comprising the steps of converter smelting, LF ladle refining, wide slab continuous casting, slab heating, slab rolling, steel plate stacking aging, and high-temperature tempering. In the production process, from an economic perspective, the present invention adopts the processes of steel plate stacking aging and high-temperature tempering, which can effectively salvage the unqualified plasticity of steel plates caused by intermediate cracks in the slab, severe segregation, and fluctuations in hydrogen content, thereby reducing economic losses. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a production process flowchart in an embodiment of the present invention. Detailed Implementation

[0016] To facilitate understanding of the present invention, it will be described more fully below through embodiments, and preferred embodiments are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Any other implementation schemes obtained by modifying or equivalently substituting the technical solutions of the present invention without inventive step are all within the protection scope of the present invention.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0018] The numerical values ​​disclosed in the embodiments of this invention are approximate values, not definitive values. Where error or experimental conditions permit, all values ​​within the error range may be included, and the specific numerical values ​​disclosed in the embodiments of this invention are not limited to those specified in the embodiments.

[0019] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0020] Example 1

[0021] See Figure 1 As shown in the figure, this embodiment provides a method for producing a niobium-vanadium composite reinforced Q460 grade hot-rolled steel plate, including the following steps:

[0022] Converter smelting, LF ladle refining, wide slab continuous casting, slab heating, slab rolling, steel plate stacking aging, high-temperature tempering.

[0023] Specifically,

[0024] The converter smelting adopts a top-bottom combined blowing converter. During the smelting process, the slag basicity is between 2.8 and 3.5, the final carbon content of the molten steel is 0.06% to 0.10%, and the final temperature of the molten steel is 1620℃ to 1640℃.

[0025] During the LF ladle refining process, the refining time is 30-45 minutes, the soft stirring time is 8-15 minutes, and the white slag holding time is 20-25 minutes. Simultaneously, alloy materials are precisely added to adjust the composition, sequentially adding ferrosilicon, ferromanganese, ferroniobium, vanadium-nitrogen alloys, etc., to ensure that the content of each element reaches the specified range. At the end of the refining process, the molten steel temperature is adjusted to 1555℃-1575℃ to provide a suitable pouring temperature for the continuous casting process.

[0026] The wide slab continuous casting employs a wide slab continuous casting machine, with a slab cross-section thickness of 150 mm and a width of 1800 mm to 3250 mm. During the continuous casting process, the steel grade of this invention is arranged in the middle of the casting cycle, the tundish temperature is 1528℃ to 1538℃, the slab casting speed is 1.20 m / min to 1.25 m / min, and end-effector electromagnetic stirring technology and a light reduction process are used to improve the internal quality of the slab. The slab aging time is over 600 minutes.

[0027] The slab heating adopts a walking beam furnace. The steel plate enters the furnace at a temperature below 540℃, the preheating section temperature is controlled at 800℃~900℃, the heating section temperature is 1200℃~1270℃, the soaking section temperature is 1220℃~1250℃, the furnace time is controlled at 110min~150min, and the slab exiting the furnace temperature uniformity is within ±10℃.

[0028] The slab rolling process employs a two-stage rolling process: roughing and finishing. In the roughing stage, a relatively large reduction is used, with 3-5 passes and a reduction of 15%-25% per pass, resulting in a roughing thickness of 2.2 times the finished product thickness. In the finishing stage, the initial rolling temperature is controlled between 850℃ and 950℃, depending on the finished steel plate thickness and the final rolling temperature, with a reduction of 8%-15% per pass, and a final finishing temperature of 780℃-840℃. Simultaneously, laminar flow cooling technology is used to cool the rolled steel plate at a rate of 5℃ / s-10℃ / s, with a final cooling and reddening temperature of 680℃-740℃.

[0029] The aforementioned steel plate stacking aging involves neatly stacking the finished steel plates in a dedicated stacking area and allowing them to age naturally for more than 10 days. The steel plates are typically removed from the production line at temperatures between 30℃ and 80℃ after finishing. This low-temperature, long-term stacking aging process allows abnormal internal structures to gradually stabilize under natural conditions, reducing structural stress and improving the plasticity issues caused by cracks in the middle of the cast billet, severe segregation, and fluctuations in hydrogen content.

[0030] In the high-temperature tempering step, the tempering temperature is 520~600℃, and the tempering coefficient is 2.5~3.5 min / mm. The steel plate that has undergone stacking aging is loaded into the tempering furnace, and the tempering time is calculated based on the steel plate thickness: Tempering time = Steel plate thickness × Tempering coefficient. For example, for producing a 25mm thick steel plate in this embodiment, the tempering time = 25 × (2.5~3.5) = 62.5~87.5 minutes.

[0031] During the tempering process, the temperature uniformity within the furnace is strictly controlled, with temperature fluctuations kept within ±10℃. High-temperature tempering treatment achieves hydrogen overflow and improves the abnormal microstructure at the segregation points of the steel plate, further eliminating internal stress, improving the plasticity and toughness of the steel plate, reducing the risk of unsatisfactory plasticity due to previous process issues, and enhancing product quality stability.

[0032] Examples 2-6 use the same production steps as Example 1.

[0033] Specifically, the composition of the niobium-vanadium composite reinforced Q460 grade hot-rolled steel plates in Examples 1-6 is as follows by weight percentage: the composition shown in Table 1 below, with the balance being Fe and unavoidable impurities.

[0034]

[0035] The stacking tempering process parameters and the performance test results of the final produced steel plates in Examples 1-6 above are shown in the table below:

[0036]

[0037] Comparing the performance data of steel plates without aging and high-temperature tempering with those with aging and high-temperature tempering, the elongation of steel plates treated with aging and high-temperature tempering increased by more than 7.5%, reaching an elongation of 23.5-25.5%, significantly improving the elongation index.

[0038] As can be seen from the performance test results of the above embodiments, the production method provided in this application, through the synergistic control of steel plate composition redesign and steel plate stacking aging and high-temperature tempering processes, effectively improves the unqualified plasticity of steel plates caused by intermediate cracks, severe segregation, and fluctuations in hydrogen content in the billet. This greatly enhances the comprehensive mechanical properties of niobium-vanadium composite reinforced Q460 grade hot-rolled steel plates, such as strength and toughness, while also improving the dimensional stability, structural stability, and performance uniformity of the steel plates, enabling the steel plates to better meet the needs of various engineering applications.

[0039] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for producing niobium-vanadium composite reinforced Q460 grade hot-rolled steel plate, characterized in that: Includes the following steps: Converter smelting, LF ladle refining, wide slab continuous casting, slab heating, slab rolling, steel plate stacking aging, high-temperature tempering.

2. The method for producing niobium-vanadium composite reinforced Q460 grade hot-rolled steel plate according to claim 1, characterized in that: The weight percentage of the chemical composition of the steel plate is as follows: C: 0.16%~0.20%, Si: 0.20~0.50%, Mn: 1.50~1.80%, P≤0.025%, S≤0.010%, Nb: 0.015%~0.040%, V: 0.040%~0.120%, N: 0.0070~0.0150%.

3. The method for producing niobium-vanadium composite reinforced Q460 grade hot-rolled steel plate according to claim 1, characterized in that: In the steel plate stacking aging step, the steel plates are stacked and allowed to age naturally for more than 10 days after finishing.

4. The method for producing niobium-vanadium composite reinforced Q460 grade hot-rolled steel plate according to claim 1, characterized in that: In the high-temperature tempering step, the tempering temperature is 520~600℃ and the tempering coefficient is 2.5~3.5min / mm.

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