CN-121983185-A - Method for controlling nitrogen content in steel, alloy steel and production method thereof

Abstract

The invention relates to the technical field of metal material preparation, and discloses a control method of nitrogen content in steel, alloy steel and a production method thereof. The method comprises the steps of firstly precisely determining the nitrogen solubility of each phase of steel in the cooling phase change process by utilizing Thermo-Calc software in an iterative calculation mode, and specifically, gradually increasing the nitrogen content of an initial system under the conditions of fixed steel components and pressure to perform multiple calculations until the nitrogen distribution of each phase output by two adjacent calculations is the same, and judging that the nitrogen is saturated in each phase at the moment, wherein the obtained nitrogen content is the actual solubility. Based on the method, the austenitic nitrogen solubility is used as a reference, the nitrogen content in the molten steel is accurately regulated and controlled according to the compression ratio range of the casting blank, the precipitation strengthening effect of nitrogen can be fully exerted, the defect of bubbles caused by supersaturation of nitrogen can be effectively avoided, and the technical problem that the strengthening effect and defect control are difficult to be compatible in alloy steel production is solved.

Inventors

• XU GUANG
• LIU PENG
• DAI ZHICAI
• JIN RENCHUN
• CHEN JIE
• LIU ZHAO
• LI GUOCANG
• LIU XUHUI
• QI JIANGHUA
• PENG XIALIN
• XU HAO
• DENG ZHIXUN
• LIANG WEN

Assignees

• 湖南华菱涟钢特种新材料有限公司
• 湖南华菱涟源钢铁有限公司

Dates

Publication Date

20260505

Application Date

20251127

Claims (10)

1. 1. A method for controlling nitrogen content in steel, comprising the steps of: S1, obtaining the nitrogen solubility of each phase in the steel cooling phase transformation process, namely calculating the nitrogen solubility of each phase in the steel cooling phase transformation process by adopting thermo-calc software, inputting steel components, pressure and initial system nitrogen content, and outputting first nitrogen distribution of each phase; S2, on the premise of keeping other calculation conditions such as steel components, pressure and the like unchanged, carrying out increasing treatment on the nitrogen content of the initial system, repeating the step S1, and outputting second nitrogen distribution of each phase; s3, under the condition that the nitrogen distribution of the second phases is identical to that of the first phases, judging that the nitrogen in each phase reaches a saturated state, wherein the corresponding nitrogen content in each phase is the actual solubility of the nitrogen in each phase; setting the number of input-output operations as N times (N is more than or equal to 2), and continuously performing iterative computation until the output N-th nitrogen distribution is the same as the N-1-th nitrogen distribution, wherein the obtained nitrogen content in each phase is the solubility of nitrogen in each phase; S4, obtaining the nitrogen solubility in the austenite according to the nitrogen solubility in each phase, regulating the nitrogen content in the molten steel to be in the range of the lower limit of the nitrogen solubility in the austenite of +0.004% to the lower limit of the nitrogen solubility in the austenite of +0.006% when the compression ratio of a casting blank is 60-120, and regulating the nitrogen content in the molten steel to be in the range of the lower limit of the nitrogen solubility in the austenite of +0.002% to the lower limit of the nitrogen solubility in the austenite of +0.003% when the compression ratio of the casting blank is > 7-60.
2. 2. The method of controlling nitrogen content in steel according to claim 1, wherein the initial system nitrogen content is set to a value substantially greater than the sum of empirically estimated nitrogen solubilities in the phases.
3. 3. The method for controlling nitrogen content in steel according to claim 2, wherein the initial system nitrogen content is not less than 0.1.
4. 4. The method for controlling nitrogen content in steel according to claim 1, wherein the steel composition comprises, in mass fraction, 0.22% -0.25% of C, 0.5% -0.6% of Si, 1.2% -1.4% of Mn, less than or equal to 0.03% of P, less than or equal to 0.03% of S, 0.06% -0.09% of V, 0.003% -0.006% of Nb when the casting blank compression ratio is >7 to <60, and 0.006% -0.01% of Nb when the casting blank compression ratio is 60 to 120.
5. 5. A method for producing an alloy steel by applying the method for controlling nitrogen content in steel according to any one of claims 1 to 4, characterized by comprising the steps of: proportioning according to a preset proportion, and smelting raw materials into molten steel; Refining the molten steel to obtain refined molten steel, wherein the refining comprises, but is not limited to, deoxidation and nitrogen microalloying, and the nitrogen microalloying process is used for adjusting the nitrogen content in the molten steel by using the control method for the nitrogen content in the steel according to any one of claims 1-4; and the refined molten steel is subjected to continuous casting and rolling and cooling treatment in sequence to obtain alloy steel.
6. 6. The method for producing an alloy steel according to claim 5, wherein the continuous casting and rolling includes a continuous casting treatment, a heating treatment, and a rolling treatment; The heating temperature in the heating treatment process is (Nb, V) (C, N) precipitation temperature +30 ℃, and the (Nb, V) (C, N) precipitation temperature is calculated by using thermo-calc software, and the heating time is 100-120 min.
7. 7. The method for producing an alloy steel according to claim 6, wherein the casting speed in the continuous casting treatment is controlled to be 3.1 to 3.5 m/min.
8. 8. The method for producing an alloy steel according to claim 5, wherein the cooling treatment includes air cooling.
9. 9. An alloy steel prepared by the alloy steel production method of any one of claims 5 to 8.
10. 10. The alloy steel according to claim 9, wherein the alloy steel has an average size of (Nb, V) (C, N) of 20 to 80 nm, a grain size level of 10 to 11, i.e., 2 9 ~2 10 grains per square inch, and has an improved yield strength of 50 to 120 MPa and an improved tensile strength of 60 to 150 MPa.

Description

Method for controlling nitrogen content in steel, alloy steel and production method thereof Technical Field The invention belongs to the technical field of alloy steel production, and particularly relates to a control method of nitrogen content in steel, alloy steel and a production method thereof. Background In the course of continuous and vigorous development of the steel industry, the production technology is continuously innovated and advanced, and the requirements on the steel performance are also increasingly severe and diversified. In order to meet the urgent demands of the fields such as aerospace, automobile manufacturing, high-end construction and the like for the comprehensive properties of high strength, high toughness, good weldability, corrosion resistance and the like of steel, steel enterprises continuously search for and apply new alloying technologies. Among them, the nitrogen microalloying technology, by virtue of its remarkable advantages, gradually becomes one of the key methods of improving the steel properties and saving the valuable alloy resources. Nitrogen is an effective alloying element and can play a unique role in precipitation strengthening in steel. The alloy can form fine dispersed nitride precipitated phases with micro-alloy elements such as titanium, niobium, vanadium and the like in steel, and the precipitated phases can effectively block dislocation movement in the deformation process of the steel, so that the yield strength and the tensile strength of the steel are improved. Meanwhile, the nitrogen microalloying can refine the grain structure of the steel to a certain extent, and further improve the toughness and welding performance of the steel. Compared with the traditional alloying elements, the nitrogen source is rich and the cost is low, and the nitrogen microalloying technology can obviously improve the performance of the steel without obviously increasing the production cost, so the nitrogen microalloying method is widely focused and intensively studied in the steel industry. However, with the widespread use of nitrogen microalloying technology in steel production, a series of new problems emerge. When the nitrogen content in the steel is continuously increased, various defects are very easy to occur in the production process of the steel, and the quality and performance of the steel are seriously affected. Among them, defects such as cracks, rotten steel, pores, etc. are particularly prominent. The strength and toughness of the steel can be reduced due to the generation of cracks, so that the steel is easy to break in the use process, the safety of the structure is seriously affected, the surface quality of the steel can be deteriorated due to the rotten steel phenomenon, the subsequent processing difficulty and cost are increased, the compactness of the steel can be reduced due to the existence of pores, and the corrosion resistance and mechanical property of the steel are affected. Based on this, it is necessary to provide a method for controlling nitrogen content in steel, alloy steel and a method for producing the same, so as to alleviate or solve the above-mentioned problems. Disclosure of Invention The invention aims to solve the technical problem that the precipitation strengthening capability and the defect avoiding capability are difficult to be compatible in the preparation process of alloy steel in the common technology, and provides a control method for the nitrogen content in steel, which comprises the following steps: S1, obtaining the nitrogen solubility of each phase in the steel cooling phase transformation process, namely calculating the nitrogen solubility of each phase in the steel cooling phase transformation process by adopting thermo-calc software, inputting steel components, pressure and initial system nitrogen content, and outputting first nitrogen distribution of each phase; S2, on the premise of keeping other calculation conditions such as steel components, pressure and the like unchanged, carrying out increasing treatment on the nitrogen content of the initial system, repeating the step S1, and outputting second nitrogen distribution of each phase; s3, under the condition that the nitrogen distribution of the second phases is identical to that of the first phases, judging that the nitrogen in each phase reaches a saturated state, wherein the corresponding nitrogen content in each phase is the actual solubility of the nitrogen in each phase; setting the number of input-output operations as N times (N is more than or equal to 2), and continuously performing iterative computation until the output N-th nitrogen distribution is the same as the N-1-th nitrogen distribution, wherein the obtained nitrogen content in each phase is the solubility of nitrogen in each phase; S4, obtaining the nitrogen solubility in the austenite according to the nitrogen solubility in each phase, regulating the nitrogen content in the molten steel to be in the ra