CN114892072B - High-strength high-toughness hydrogen embrittlement-resistant steel plate and component optimization and preparation method thereof - Google Patents

Abstract

The invention discloses a high-strength high-toughness hydrogen embrittlement-resistant steel plate and a component optimization and preparation method thereof, wherein the steel plate comprises the following chemical components in percentage by mass: c:0.089-0.108%, si:0.067-0.080%, mn:0.84-1.05%, cr:0.37-0.57%, ni:2.10-2.42%, cu:0.87-1.09%, mo:0.52-0.60%, nb:0.043-0.056%, and the balance of Fe and unavoidable impurities. The quenching temperature of the steel plate is 850-870 ℃ and the tempering temperature is 500-580 ℃. The invention solves the problems of how to select proper target components under the precondition of controlling the cost and ensuring the weldability, and the problems of high strength with the yield strength not lower than 1000MPa, high low-temperature toughness with the impact energy not lower than 69J at minus 40 ℃ and hydrogen embrittlement sensibility being less than 20 percent are realized under the process conditions of quenching and high-temperature tempering. The invention can accelerate the development of novel steel materials with high strength, high-low temperature toughness and good hydrogen embrittlement resistance, and has great significance for engineering construction.

Description

A high-strength, high-toughness, hydrogen embrittlement-resistant steel plate and its component optimization and preparation method

Technical Field

The invention relates to a novel high-strength and high-toughness hydrogen embrittlement resistant steel plate and a component optimization and preparation method thereof, belonging to the technical field of high-strength steel plates.

Background Art

As engineering equipment gradually develops towards large-scale and lightweight, the strength level of the steel used is correspondingly improved. The use of ultra-high-strength steel with a yield strength of 1000MPa to manufacture beam structures of engineering machinery, automobile bodies, marine engineering and other equipment components can not only meet their strength requirements, but also reduce the weight of the equipment, reduce fuel consumption, and improve work efficiency. At the same time, the reduction in the wall thickness of the steel is not only conducive to reducing the difficulty of welding and improving welding efficiency, but also can move the center of gravity of the steel structure downward and improve safety. Toughness, as a comprehensive expression of strength and plasticity, reflects the ability of the material to absorb deformation during the deformation process. Among them, impact toughness reflects its resistance to external impact loads. High impact toughness can extend the service life of steel structures in low temperature environments.

At present, the number of domestic enterprises producing high-strength steel plates with a yield strength of 1000MPa is gradually increasing, and the ingredients and processes used are different. However, usually by adding a small amount of microalloying elements such as Nb, V and Ti on the basis of carbon steel, combined with optimized controlled rolling and controlled cooling process (TMCP technology) and quenching + tempering process, ultra-high strength steel plates that meet the needs can be produced. Patent documents with publication numbers CN104561827A and CN102560274A disclose a high-strength steel plate with a yield strength of 1000MPa and a method for manufacturing the same, which adopts a reheating quenching + tempering process, but the toughness of the steel plate is low and the strength and toughness match is poor. Patent documents with publication numbers CN106086657A and CN104532156A disclose ultra-high strength steels with a yield strength greater than 1300 MPa, whose carbon contents are 0.18-0.23% and 0.21-0.26% respectively. High carbon content increases the welding crack sensitivity of ultra-high strength steels, increases the tendency of welding cold cracks, and increases the difficulty of welding.

Due to the harsh use environment and stress conditions of ultra-high-strength steel, in addition to high strength and high toughness, good hydrogen embrittlement resistance is also an important factor affecting the widespread application of high-strength steel, especially high-strength steel with a yield strength of 1000MPa. Even at a lower hydrogen content, it is very easy to cause hydrogen-induced delayed fracture, posing a serious threat to the safety and reliability of engineering structures. From production to service, hydrogen atoms are everywhere, so it is crucial to conduct a strict hydrogen embrittlement sensitivity assessment on high-strength steel. Retrieving relevant technical literature on steel grades with similar strength levels found that the high-strength steels currently reported are limited to strong plasticity, and no corresponding hydrogen embrittlement sensitivity assessment has been conducted, and service safety cannot be accurately guaranteed. Therefore, accelerating the development of new steel materials with high strength, high and low temperature toughness and good hydrogen embrittlement resistance is of great significance to engineering construction and has become a technical problem that needs to be solved urgently.

Summary of the invention

In order to solve the problems of the prior art, the purpose of the present invention is to overcome the shortcomings of the existing technology, provide a high-strength and high-toughness hydrogen embrittlement resistant steel plate and its component optimization and preparation method, solve the problem of how to select appropriate target components under the premise of controlling costs and ensuring weldability, so that it can achieve high strength with a yield strength of not less than 1000MPa, high low-temperature toughness with an impact energy of not less than 69J at -40°C, and hydrogen embrittlement sensitivity of not more than 20% under quenching and high-temperature tempering process conditions. The present invention improves the comprehensive performance of high-strength and high-toughness hydrogen embrittlement resistant steel plates, and realizes the short-cycle research and development of new high-strength and high-toughness hydrogen embrittlement resistant steel plate materials.

In order to achieve the above invention purpose, the present invention adopts the following technical solution:

A high-strength, high-toughness, hydrogen embrittlement-resistant steel plate, calculated by mass percentage, has the following main components and chemical compositions and proportions:

C: 0.089-0.110%, Si: 0.06-0.08%, Mn: 0.80-1.10%, Cr: 0.35-0.60%, Ni: 2.0-2.50%, Cu: 0.85-1.10%, Mo: 0.50-0.60%, Nb: 0.04-0.06%, the balance is Fe and inevitable impurities; the ingot is prepared by smelting process, and then hot rolled, quenched and High temperature tempering heat treatment; during hot rolling, it is rolled to a thickness of no more than 14 mm through multiple hot rolling, the initial rolling temperature is controlled to be 1150-1200°C, and the final rolling temperature is 950-1000°C; during heat treatment, the quenching temperature is controlled to be 850-870°C, and the temperature is lowered to room temperature after quenching, and then the tempering temperature is controlled to be 500-580°C, tempering heat treatment is performed, and then air-cooled to room temperature to obtain the high-strength, high-toughness, hydrogen embrittlement-resistant steel plate.

Preferably, the high-strength, high-toughness, hydrogen embrittlement-resistant steel plate has the following main chemical compositions, calculated by mass percentage:

C: 0.089-0.108%, Si: 0.067-0.080%, Mn: 0.84-1.05%, Cr: 0.37-0.57%, Ni: 2.10-2.42%, Cu: 0.87-1.09%, Mo: 0.52-0.60%, Nb: 0.043-0.056%, and the balance is Fe and inevitable impurities.

Preferably, the high-strength and high-toughness hydrogen embrittlement resistant steel plate has a yield strength of not less than 1000 MPa, a tensile strength of not less than 1000 MPa, an elongation of not less than 15%, an impact toughness of not less than 69 J at -40°C, and a hydrogen embrittlement sensitivity index HEI of not higher than 20%.

Further preferably, the high-strength and high-toughness hydrogen embrittlement resistant steel plate has a yield strength of not less than 1042 MPa, a tensile strength of not less than 1079 MPa, an elongation of not less than 15.8%, an impact toughness at -40°C of not less than 82 J, and a hydrogen embrittlement sensitivity index HEI of not higher than 15.4%.

A method for preparing the high-strength, high-toughness, hydrogen embrittlement-resistant steel plate of the present invention comprises the following steps: preparing an ingot by a smelting process, and then performing hot rolling, quenching and high-temperature tempering heat treatment; during hot rolling, rolling the ingot to a thickness of no more than 14 mm by multiple hot rolling steps, controlling the initial rolling temperature to be 1150-1200° C., and the final rolling temperature to be 950-1000° C.; during heat treatment, controlling the quenching temperature to be 850-870° C., cooling the temperature to room temperature after quenching, and then controlling the tempering temperature to be 500-580° C., performing tempering heat treatment, and then air cooling the ingot to room temperature to obtain the high-strength, high-toughness, hydrogen embrittlement-resistant steel plate;

The main chemical compositions and proportions of the components of the target high-strength, high-toughness, hydrogen embrittlement-resistant steel plate are as follows:

C: 0.089-0.110%, Si: 0.06-0.08%, Mn: 0.80-1.10%, Cr: 0.35-0.60%, Ni: 2.0-2.50%, Cu: 0.85-1.10%, Mo: 0.50-0.60%, Nb: 0.04-0.06%, and the balance is Fe and inevitable impurities.

Preferably, the smelting process adopts a vacuum induction melting furnace for smelting, and then prepares an ingot, and then cuts the ingot into steel blocks with a thickness of not less than 40 mm, and uses the steel blocks as hot-rolled steel.

Preferably, the heat treatment process is to heat the hot-rolled steel plate to a single-phase region of 850-870°C and keep it warm for at least 25 minutes, then water quench it and cool it to room temperature, then heat it to 500-580°C and keep it warm for at least 35 minutes, and then air cool it to room temperature.

A composition screening method for the high-strength, high-toughness, hydrogen embrittlement-resistant steel plate of the present invention selects target composition under the premise of controlling cost and ensuring weldability, comprising the following steps:

a. Target steel plate matrix chemical composition range:

According to the calculation of mass percentage, the chemical composition and proportion of the main components are tentatively formulated as follows:

C: 0.05-0.11%, Si: 0.05-0.09%, Mn: 0.50-1.10%, Cr: 0.30-0.60%, Ni: 1.0-2.50%, Cu: 0.70-1.10%, Mo: 0.50-0.60%, the balance is Fe and unavoidable impurities;

b. Determine the characteristic parameters and write the program file for integrated batch calculation:

Thermo-Calc calculation software package was used, and its TC-Python interface was adopted to use Python language to write a program file that can be used to calculate characteristic parameters under different composition and temperature conditions. Among them, characteristic parameter 1 is T ₀ temperature, representing the temperature when the Gibbs free energy of austenite and ferrite is equal, and characteristic parameter 2 is AC, representing the carbon content in austenite at T ₀ temperature; the key instructions in the program file include reading thermodynamic data, completing the thermodynamic calculation of characteristic parameters 1 and characteristic parameters 2 of different alloy systems; using loop statements to realize automatic assignment of alloy composition and temperature, and completing batch calculation; limiting the calculation error range to obtain valid data, and completing the output of calculation results;

c. Determine the calculation conditions and run the calculation program to screen the components:

Based on the composition range determined in step a, the calculation step length of each alloy element is set, and the program file I for calculating characteristic parameter 1 and characteristic parameter 2 in step b is used to obtain the calculation results of T ₀ and AC. On the basis of keeping the low T ₀ temperature, the point with a high AC value is selected as the target composition;

d. Use the first principles to calculate the segregation energy of hydrogen atoms and determine the microalloying elements:

The segregation energy ( _EMC ) of hydrogen atoms at the carbide/matrix interface is calculated by first principles, and the segregation energy of carbide NbC, TiC, VC/matrix interfaces corresponding to the selected Nb, V and Ti microalloying elements is calculated and compared, and the microalloying element in the carbide with the smallest segregation energy is selected as the alloying element to optimize the matrix chemical composition of the target steel plate proposed in step a.

e. Screen out the steel plate matrix and micro-alloy components:

According to step d, the microalloying elements are determined, added to the matrix chemical composition of the proposed target steel plate, and the matrix chemical components and component ratio range of the target steel plate are re-determined to prepare the target high-strength, high-toughness, hydrogen embrittlement-resistant steel plate.

Preferably, in the step d, the addition of Nb, V and Ti microalloying elements can produce precipitation strengthening and fine grain strengthening effects, however, Ti is easily combined with nitrogen to form square TiN or Ti(C,N) particles, which affects plastic toughness. In addition, since NbC, VC and TiC all have strong adsorption capacity for hydrogen atoms, they can be used as hydrogen traps to capture hydrogen atoms, inhibit the diffusion and segregation of hydrogen, and improve the hydrogen embrittlement resistance of steel. The present invention uses the first principle to calculate the segregation energy of hydrogen atoms at the carbide/matrix interface. From the segregation energy determined from the semi-coherent misfit dislocation interface, it can be found that: E _NbC (-0.99eV)＜E _TiC (-0.52eV)＜E _VC (-0.31eV), that is, the energy required for hydrogen absorption at the NbC/Fe interface is the smallest, that is, the hydrogen absorption capacity is the strongest, and the diffusion of hydrogen atoms in steel can be effectively inhibited. In addition, the present invention innovatively uses the first principle to calculate the change of segregation energy when Nb-V and Nb-Ti are added in combination, that is, the segregation energy of hydrogen atoms at the semi-coherent (Nb, V) C/Fe interface and the (Nb, Ti) C/Fe interface, and the calculated segregation energy is -0.42eV and -0.34eV. It can be seen that NbC has a stronger adsorption force on hydrogen atoms than (Nb, V) and (Nb, Ti) C, and is more conducive to improving the hydrogen embrittlement resistance of steel. Therefore, Nb microalloying is added to improve the comprehensive performance of steel.

After the composition of the high-strength and high-toughness hydrogen embrittlement resistant steel plate of the present invention is optimized, the target experimental steel is prepared according to the optimized matrix and microalloy components. After smelting, hot rolling, quenching + high-temperature tempering heat treatment, the quenching temperature is 850-870°C, the tempering temperature is 500-580°C, and the yield strength is above 1000MPa, the impact energy is above 69J at -40°C, and the hydrogen embrittlement sensitivity is less than 20%. A new type of high-strength and high-toughness hydrogen embrittlement resistant steel plate can be obtained.

Principle of the present invention:

A composition screening method for high-strength and high-toughness hydrogen embrittlement resistant steel plates, under the premise of ensuring weldability and reducing costs, screens matrix components and microalloy components through thermodynamic calculations and first-principles calculations of characteristic parameters, thereby obtaining a new type of high-strength and high-toughness hydrogen embrittlement resistant steel plate with a yield strength of more than 1000MPa, an impact energy of more than 69J at -40°C, and a hydrogen embrittlement sensitivity of less than 20%.

High-strength and high-toughness steel is developed from ordinary carbon steel, and alloy elements such as Ni, Cr, Mo, Si, Mn, and Cu are usually added to achieve the expected performance. Among them, the increase in carbon content can significantly improve the strength, but it will cause the service performance such as weldability to decrease. The increase in nickel content is beneficial to improve its strength and plasticity, but it will increase the cost. In addition, C, Ni, Mn, and Cu are austenite-forming elements, while Si, Cr, and Mo are ferrite-forming elements. The _T0 temperature marks the temperature when the free energy of ferrite and austenite is equal. Austenite-forming elements will cause this temperature to drop, which means that the strength of martensite is improved after quenching, while ferrite-forming elements will have the opposite effect; however, the carbon content (AC) in austenite at _T0 temperature will increase due to the presence of ferrite-forming elements. This effect will increase the stability of austenite and help ensure plasticity and toughness. It can be seen that the _T0 temperature and AC can be used as characteristic parameters to comprehensively evaluate the possible effects of different alloy components on the strength and toughness of experimental steel.

As mentioned before, the addition of Nb, V and Ti microalloying elements can not only produce precipitation strengthening and fine grain strengthening effects, but also act as hydrogen traps to inhibit the diffusion of hydrogen and improve the hydrogen embrittlement resistance of steel. Therefore, the segregation energy of hydrogen atoms at the carbide/matrix interface is used as another characteristic parameter, and the calculation of Nb, V and Ti as well as composite carbides is carried out by first principles to evaluate the possible effects of different microalloying elements on the hydrogen embrittlement resistance of experimental steel.

Based on this, the present invention adopts the Thermo-Calc calculation software package to carry out batch calculation of _T0 temperature of alloys with different compositions and carbon content AC in austenite at _T0 temperature, and optimizes the matrix composition with the goal of lower _T0 temperature and higher AC. At the same time, the first principle calculation is adopted to determine the ideal microalloying element with the goal of minimizing the segregation energy.

The traditional research and development model of steel materials adheres to the idea of "trial and error" to carry out component optimization to obtain the desired performance. This method is time-consuming, costly, and inefficient, which seriously restricts the research and development progress of new steel grades. The present invention can use phase diagram thermodynamic calculations and first-principles calculations to achieve scientific design and verification of the target composition of new high-strength, high-toughness, hydrogen embrittlement-resistant steel plates, and complete short-cycle preparation, which is the original work of the present invention.

Compared with the prior art, the present invention has the following obvious outstanding substantial features and significant advantages:

1. The new high-strength and high-toughness hydrogen embrittlement-resistant steel plate designed by the present invention has reasonable composition, high strength, high toughness, and good hydrogen embrittlement resistance. It can be used in harsh use environments and stress conditions, accurately ensure service safety, and open up the application field of new high-strength and high-toughness hydrogen embrittlement-resistant steel plates;

2. The present invention can accelerate the development of new steel materials with high strength, high and low temperature toughness and good hydrogen embrittlement resistance, which is of great significance for engineering construction;

3. The method of the present invention is simple, easy to implement, low in cost, and suitable for popularization and use.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a calculation result of data points in the process of screening matrix components in the present invention.

Figure 2 Three highly symmetric typical atomic structures of the (001) _α-Fe /(001) _MC interface in DFT calculations.

DETAILED DESCRIPTION

The high-strength, high-toughness, hydrogen embrittlement-resistant steel plate of the present invention has the following chemical compositions and proportions of its main components in terms of mass percentage:

C: 0.089-0.110%, Si: 0.06-0.08%, Mn: 0.80-1.10%, Cr: 0.35-0.60%, Ni: 2.0-2.50%, Cu: 0.85-1.10%, Mo: 0.50-0.60%, Nb: 0.04-0.06%, the balance is Fe and unavoidable impurities;

The ingot is prepared by a smelting process, and then hot rolling, quenching and high-temperature tempering heat treatment are carried out; during hot rolling, the ingot is rolled to a thickness of no more than 14 mm through multiple hot rolling processes, the initial rolling temperature is controlled to be 1150-1200°C, and the final rolling temperature is controlled to be 950-1000°C; during heat treatment, the quenching temperature is controlled to be 850-870°C, the temperature is lowered to room temperature after quenching, and then the tempering temperature is controlled to be 500-580°C, tempering heat treatment is carried out, and then air cooling is carried out to room temperature to obtain the high-strength, high-toughness and hydrogen embrittlement resistant steel plate.

In the following embodiments, the high-strength, high-toughness, hydrogen embrittlement-resistant steel plate has the following main chemical compositions, calculated by mass percentage:

C: 0.089-0.108%, Si: 0.067-0.080%, Mn: 0.84-1.05%, Cr: 0.37-0.57%, Ni: 2.10-2.42%, Cu: 0.87-1.09%, Mo: 0.52-0.60%, Nb: 0.043-0.056%, and the balance is Fe and inevitable impurities.

The above scheme is further described below in conjunction with specific implementation examples. The preferred embodiments of the present invention are described in detail as follows:

In this embodiment, a composition optimization and preparation method of a high-strength, high-toughness, hydrogen embrittlement-resistant steel plate are as follows:

This embodiment carries out the research and development of a new type of high-strength, high-toughness, hydrogen embrittlement-resistant steel plate based on integrated computational material engineering technology. The _T0 temperature is innovatively selected as the characteristic parameter 1, and the carbon content AC in austenite at the _T0 temperature is innovatively selected as the characteristic parameter 2. The commercial computing software Thermo-Calc and the interface program are used to optimize the matrix alloy composition by using the phase diagram thermodynamic calculation, and the interaction between hydrogen atoms and microalloy carbides is calculated in combination with the first principle to determine the ideal microalloy element. Specifically, the following steps are included:

a. The range of chemical composition of the matrix of the proposed experimental steel plate is:

The chemical composition of the steel plate includes, by mass percentage, C: 0.05-0.11%, Si: 0.05-0.09%, Mn: 0.50-1.10%, Cr: 0.30-0.60%, Ni: 1.0-2.50%, Cu: 0.70-1.10%, Mo: 0.50-0.60%, and the balance is Fe and unavoidable impurities;

Among them, the Ni content is relatively low, which is beneficial to reducing production costs; the carbon content is less than 0.11%, which is the upper limit of the carbon content in the easy-to-weld zone in the Gravile diagram. The carbon equivalent of this composition range was calculated using formula (1), and it was found that the carbon equivalent in the composition range is between 0.18 and 0.33. This composition range is just in the easy-to-weld zone in the Gravile diagram, which is convenient for welding large structures;

C _eq ＝C+Si/30+(Cu+Mn+Cr)/20+Ni/60+Mo/15+V/10+5B (1)

b. Determine the characteristic parameters and write the program file for integrated batch calculation:

Thermo-Calc calculation software package was used, and its TC-Python interface was adopted to use Python language to write a program file that can calculate characteristic parameters under different composition and temperature conditions. Among them, characteristic parameter 1 is T ₀ , which represents the temperature when the Gibbs free energy of austenite and ferrite is equal, and characteristic parameter 2 is AC, which represents the carbon content in austenite at T ₀ temperature. The written program file can read the thermodynamic data in TC software, that is, TCFE10 database, complete the thermodynamic calculation of characteristic parameters 1 and characteristic parameters 2 of different alloy systems, and obtain the variation law of T ₀ and AC with composition.

The loop statement in the Python program is used to realize the automatic assignment of alloy composition and temperature, that is, the alloy element content and temperature are assigned one by one according to the calculation step size in Table 1 below, batch calculation is completed, the calculation error range is limited to obtain valid data, and the calculation results are output;

c. Determine the calculation conditions and run the calculation program to screen the components:

Based on the composition range determined in step a, the range of each alloy element is divided with a certain step length, as shown in Table 1. A total of 4×3×4×3×4×2×3=3456 composition points are calculated. The program file for integrating the calculation of characteristic parameters 1 and 2 in step b is used, and the composition range and step length are input. Finally, 3456 groups of calculation results of T ₀ and AC are obtained, and a set of calculated values of characteristic parameters is obtained. The calculation results are shown in Figure 1.

On the basis of keeping the T ₀ temperature low, the point with high AC value is selected as the target component, as shown in the circle in Figure 1;

Table 1. Calculation step length table for each alloy element

C Si Mn Cu Ni Cr Mo 0.05 0.05 0.5 0.7 1 0.4 0.5 0.07 0.07 0.7 0.9 1.5 0.6 0.55 0.09 0.09 0.9 1.1 2 0.6 0.11 1.1 2.5

d. Use the first principles to calculate the segregation energy of hydrogen atoms and determine the microalloying elements:

Based on density functional theory (DFT), the first-principles calculations on the interaction between (001) _α-Fe /(001) _MC interface and hydrogen were performed to gain insight into the hydrogen trapping behavior, where M represents Nb, V, and Ti microalloying elements;

This example calculates the trapping effect of hydrogen atoms on the coherent and semi-coherent interfaces between α-Fe and MC carbides by focusing on the Baker-Nutting (NB) orientation relationship ((001) _Fe || (001) _MC and [100] _Fe || [110] _MC );

Figure 2 shows three highly symmetric typical atomic structures about the (001) _α-Fe /(001) _MC interface in DFT calculations:

(I) Fe-on-C configuration, where the Fe atom is located on top of the C atom;

(II) Fe-on-M configuration, where Fe atoms are located on top of Nb atoms;

(III) bridged configuration, in which the Fe atom has two C atoms and two Nb atoms as nearest neighbors;

The segregation energy of hydrogen at the interface of α-Fe and VC, TiC, and NbC in three configurations was determined by DFT calculation. The results are shown in Table 2. It can be seen that the segregation energy of hydrogen is the lowest in the bridging configuration of the (001) _α-Fe /(001) _NbC interface, that is, the effect of NbC in capturing hydrogen atoms is the most obvious.

In addition, the present invention selects the bridging configuration with the lowest segregation energy, and calculates the interaction between Nb-V composite carbide (Nb, V) C and Nb-Ti composite carbide (Nb, Ti) C and hydrogen. The calculation results are shown in Table 2. It can be seen that the segregation energy of hydrogen atoms at the (001) _α-Fe / (001) _NbC interface is the lowest, indicating that NbC has the strongest capture effect on hydrogen atoms. For this reason, it is proposed to add 0.04-0.06% Nb to improve the hydrogen embrittlement resistance of steel;

Table 2. Segregation energy of hydrogen atoms at the (001)α-Fe/(001)MC interface

Hydrogen capture interface Configuration Hydrogen atom segregation energy (eV) (001)Fe/(001)TiC Fe-on-C -0.29 Fe-on-Ti -0.48 Bridge -0.52 (001)Fe/(001)VC Fe-on-C -0.12 Fe-on-V -0.39 Bridge -0.31 (001)Fe/(001)NbC Fe-on-C -0.18 Fe-on-Nb -0.58 Bridge -0.99 (001)Fe/(001)(Nb,V)C Bridge -0.42 (001)Fe/(001)(Nb,Ti)C Bridge -0.34

In this embodiment, the segregation energy (E _MC ) of hydrogen atoms at the carbide/matrix interface is calculated by first principles. The results show that E _NbC (-0.99 eV)＜E _TiC (-0.52 eV)＜E _VC (-0.31 eV), that is, the energy required for hydrogen absorption at the NbC/Fe interface is the smallest, that is, the hydrogen absorption capacity is the strongest, which can effectively inhibit the segregation of hydrogen atoms in the steel to the grain boundaries;

Furthermore, this embodiment calculates the segregation energy of hydrogen atoms at the semi-coherent (Nb, V) C/Fe interface and (Nb, Ti) C/Fe interface to be -0.42 eV and -0.34 eV, respectively. It can be seen that NbC has a stronger adsorption force on hydrogen atoms than (Nb, V) C and (Nb, Ti) C, and is more conducive to improving the hydrogen embrittlement resistance of steel. Therefore, Nb microalloy is added to improve the comprehensive performance of steel.

e. Prepare experimental steel based on the selected matrix and microalloy components:

A 20kg vacuum induction melting furnace was used to prepare the ingots and then cut out steel blocks with a thickness of 40 mm for hot rolling; they were rolled to 14 mm through multiple hot rolling passes, with an initial rolling temperature of 1150-1200°C and a final rolling temperature of 950-1000°C; the target composition and the measured composition are shown in Table 3;

Table 3. Composition (wt.%) and carbon equivalent of the experimental steel plate of this embodiment

The hot-rolled experimental steel plate was heated to 850-870℃ single-phase region and kept for 25min, then water quenched to room temperature, then heated to 500-580℃ and kept for 35min, then air-cooled to room temperature. The final experimental steel plate can obtain excellent performances of yield strength above 1000MPa, -40℃ impact toughness above 69J, and hydrogen embrittlement sensitivity less than 20%. The heat treatment process and performance of the experimental steel plate are shown in Table 4:

Table 4. Heat treatment process and mechanical properties of the experimental steel plate in this embodiment

It can be seen from the data in Table 4 that the yield strength of the experimental steel prepared by using the preferred composition in this embodiment reaches more than 1000 MPa, and the impact toughness at -40°C is more than 69 J.

Combined with cathode hydrogen charging, electrolyte: 0.2mol/LH ₂ SO ₄ +0.5g/L thiourea; hydrogen charging time: 24h; current density: 2mA/cm ² . And slow tensile (strain rate: 1×10 ^-5 /s) experiments, the hydrogen embrittlement sensitivity of the experimental steel after 860℃ quenching + 500℃ tempering was evaluated. The performance comparison before and after hydrogen charging is shown in Table 5:

It can be seen from the data in Table 5 that the hydrogen embrittlement sensitivity index of the experimental steels is less than 20%.

Table 5. Comparison of slow tensile properties of the steel plate of this embodiment before and after hydrogen filling after tempering at 500℃

Steels with similar chemical compositions are selected as comparative examples, and their chemical compositions and carbon equivalents are shown in Table 6. Compared with the comparative examples, the carbon equivalent of the steels designed by the present invention is comparable to or even lower.

Table 6. Comparative Example Composition and Carbon Equivalent Table

Table 7 is a comparison of the mechanical properties of the embodiments of the present invention and comparative examples 1 to 5. It can be seen that the carbon content of comparative example 1 is relatively low, so the yield strength is not ideal. Comparative example 2 improves its yield strength by adding Nb-Ti composite on the basis of comparative example 1, but the toughness is significantly reduced. Comparative examples 3 and 4 also have low-carbon components, but 6-7% of Ni is added to make up for the strength loss, which increases the production cost. Among them, comparative example 3 adopts Nb-V composite addition, which increases the yield strength of the steel, but the toughness is extremely low. The yield strength of comparative example 4 is not ideal, but the toughness is good. Comparative example 5 increases the carbon content and adopts V-Ti composite addition. Its yield strength and toughness are better, but the higher carbon content may lead to reduced weldability. The steel with lower carbon and nickel content designed by the present invention is used to obtain ideal strength and low-temperature toughness.

Table 7. Mechanical properties comparison table

In addition, the hydrogen embrittlement resistance of the embodiment was compared with that of high-strength steel comparative examples 5 to 8 of the same strength level, as shown in Table 8.

Table 8. Comparison of hydrogen embrittlement resistance

It can be seen from the above results that the hydrogen embrittlement sensitivity of this embodiment is less than 20%, and it has good hydrogen embrittlement resistance. However, the four comparative examples with the same strength level, after electrochemical pre-charging of hydrogen, showed a plastic loss of up to 35-60% when slowly stretched at a low strain rate, and showed a low hydrogen embrittlement resistance. Comparative Example 8 uses Nb-V composite addition, and the content of microalloying elements is greater than the content of Nb microalloying elements in the embodiment of the present invention, but its hydrogen embrittlement sensitivity index is 37.0%, and its hydrogen embrittlement resistance is lower than that of the patented steel. The above embodiments solve the problem of how to select appropriate target components under the premise of controlling costs and ensuring weldability, so that it can achieve high strength with yield strength > 1000MPa, high low-temperature toughness with impact energy > 69J at -40°C, and excellent performance with hydrogen embrittlement sensitivity less than 20% under quenching and high-temperature tempering process conditions. The steel composition designed in the above embodiment is reasonable. The new high-strength and high-toughness hydrogen embrittlement resistant steel plate of the present invention has high strength, high toughness, and good hydrogen embrittlement resistance. It can be applied to harsh use environments and stress conditions, accurately ensures service safety, and opens up the application field of new high-strength and high-toughness hydrogen embrittlement resistant steel plates; the method of the above embodiment of the present invention accelerates the development of new steel materials with high strength, high and low temperature toughness and good hydrogen embrittlement resistance, which is of great significance for engineering construction.

In summary: The above embodiments innovatively propose a novel composition optimization and preparation method for high-strength and high-toughness hydrogen embrittlement-resistant steel plate, which has the comprehensive properties of high strength, high toughness and excellent hydrogen embrittlement resistance while controlling cost and ensuring weldability, and has obvious application reference value in material design research and engineering construction fields.

The above describes the embodiments of the present invention in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be equivalent replacement methods. As long as they meet the purpose of the invention and do not deviate from the technical principles and inventive concepts of the present invention, they belong to the protection scope of the present invention.

Claims (8)

1. The high-strength high-toughness hydrogen embrittlement resistant steel plate is characterized by comprising the following main components in percentage by mass:

c:0.089-0.110%, si:0.06-0.08%, mn:0.80-1.10%, cr:0.35-0.60%, ni:2.0-2.50%, cu:0.85-1.10%, mo:0.50-0.60%, nb:0.04-0.06%, and the balance of Fe and unavoidable impurities; preparing an ingot by adopting a smelting process, and then carrying out hot rolling, quenching and high-temperature tempering heat treatment; when hot rolling is carried out, the thickness of the hot rolled steel is not more than 14mm through multiple hot rolling, the initial rolling temperature is controlled to be 1150-1200 ℃, and the final rolling temperature is controlled to be 950-1000 ℃; when heat treatment is carried out, the quenching temperature is controlled to be 850-870 ℃, the temperature is reduced to room temperature after quenching, then the tempering temperature is controlled to be 500-580 ℃, tempering heat treatment is carried out, and then air cooling is carried out to room temperature, so that the high-strength high-toughness hydrogen embrittlement-resistant steel plate is obtained;

the high-strength high-toughness hydrogen embrittlement resistant steel plate is prepared by adopting a component optimization method of the following high-strength high-toughness hydrogen embrittlement resistant steel plate, and a target component is selected on the premise of controlling cost and ensuring weldability, and the method comprises the following steps:

a. and (3) drawing up the chemical composition range of the matrix of the target steel plate:

the main chemical components and the proportions thereof are preliminarily calculated according to the mass percentage:

c:0.05-0.11%, si:0.05-0.09%, mn:0.50-1.10%, cr:0.30-0.60%, ni:1.0-2.50%, cu:0.70-1.10%, mo:0.50-0.60%, and the balance of Fe and unavoidable impurities;

b. determining characteristic parameters and writing a program file for developing integrated batch calculation:

program files for calculating characteristic parameters under different components and temperature conditions can be developed by utilizing a Thermo-Calc calculation software package and adopting a TC-Python interface to write through Python language, wherein the characteristic parameters 1 are T ₀ Temperature, representing the temperature at which the free energies of austenite and ferrite are equal, characteristic parameter 2 being AC, representing T ₀ Carbon content in austenite at temperature; the key instructions in the program file comprise the steps of reading thermodynamic data and finishing thermodynamic calculation of characteristic parameters 1 and 2 of different alloy systems; realizing alloy by adopting cyclic statementAutomatic assignment of components and temperature, and batch calculation is completed; defining a calculation error range to obtain effective data, and completing the output of a calculation result;

c. determining calculation conditions, and running a calculation program to perform component screening:

setting calculation step length of each alloy element based on the component range determined in the step a, and adopting the program file I for calculating the characteristic parameter 1 and the characteristic parameter 2 in the step b to obtain T ₀ And AC, while keeping T low ₀ On the basis of temperature, selecting a point with a high AC value as a target component;

d. calculating the partial energy of the hydrogen atoms by using a first sexual principle, and determining the microalloy elements:

computing the partial energy E of hydrogen atoms at the interface of carbide/matrix by adopting the first sexual principle _MC Calculating and comparing partial energy aggregation of carbides NbC, tiC, VC/matrix interfaces corresponding to Nb, V and Ti microalloy elements to be selected, and selecting microalloy elements in carbides with minimum partial energy aggregation as alloy addition elements to optimize the matrix chemical components of the target steel plate formulated in the step a;

e. screening steel plate matrixes and microalloy components:

determining micro-alloy elements according to the step d, adding the determined micro-alloy elements to the chemical components of the matrix of the planned target steel plate, and redefining the chemical components and the component proportion range of the matrix of the target steel plate to prepare the target high-strength high-toughness hydrogen embrittlement-resistant steel plate.

2. The high-strength high-toughness hydrogen embrittlement resistant steel plate according to claim 1, wherein the main chemical components of the steel plate are as follows in mass percent:

c:0.089-0.108%, si:0.067-0.080%, mn:0.84-1.05%, cr:0.37-0.57%, ni:2.10-2.42%, cu:0.87-1.09%, mo:0.52-0.60%, nb:0.043-0.056%, and the balance of Fe and unavoidable impurities.

3. The high-strength high-toughness hydrogen embrittlement resistant steel sheet according to claim 1, wherein: the yield strength is not lower than 1000MPa, the tensile strength is not lower than 1000MPa, the elongation is not lower than 15%, the impact toughness at-40 ℃ is not lower than 69J, and the hydrogen embrittlement sensitivity index HEI is not higher than 20%.

4. A high strength, high toughness, hydrogen embrittlement resistant steel sheet according to claim 3, characterized in that: the yield strength is not lower than 1042MPa, the tensile strength is not lower than 1079MPa, the elongation is not lower than 15.8%, the impact toughness at-40 ℃ is not lower than 82J, and the hydrogen embrittlement sensitivity index HEI is not higher than 15.4%.

5. A method for preparing the high-strength high-toughness hydrogen embrittlement resistant steel sheet according to claim 1, characterized in that an ingot is prepared by a smelting process, and then hot-rolled, quenched and tempered at high temperature; when hot rolling is carried out, the thickness of the hot rolled steel is not more than 14mm through multiple hot rolling, the initial rolling temperature is controlled to be 1150-1200 ℃, and the final rolling temperature is controlled to be 950-1000 ℃; when heat treatment is carried out, the quenching temperature is controlled to be 850-870 ℃, the temperature is reduced to room temperature after quenching, then the tempering temperature is controlled to be 500-580 ℃, tempering heat treatment is carried out, and then air cooling is carried out to room temperature, so that the high-strength high-toughness hydrogen embrittlement-resistant steel plate is obtained;

the main components of the prepared target high-strength high-toughness hydrogen embrittlement resistant steel plate are as follows:

c:0.089-0.110%, si:0.06-0.08%, mn:0.80-1.10%, cr:0.35-0.60%, ni:2.0-2.50%, cu:0.85-1.10%, mo:0.50-0.60%, nb:0.04-0.06%, and the balance of Fe and unavoidable impurities.

6. The method for producing a high-strength and high-toughness hydrogen embrittlement resistant steel sheet according to claim 5, characterized in that: the smelting process adopts a vacuum induction smelting furnace to smelt, then an ingot is prepared, the ingot is cut into steel blocks with the thickness not less than 40mm, and the steel blocks are used as hot rolled steel.

7. The method for producing a high-strength and high-toughness hydrogen embrittlement resistant steel sheet according to claim 6, characterized in that: the heat treatment process comprises the steps of heating a hot rolled steel plate to a single-phase region with the temperature of 850-870 ℃ for heat preservation for at least 25min, then performing water quenching, cooling to room temperature, heating to the temperature of 500-580 ℃ for heat preservation for at least 35min, and then performing air cooling to the room temperature.

8. A component optimization method of a high-strength high-toughness hydrogen embrittlement resistant steel sheet according to claim 1, characterized by selecting a target component on the premise of controlling cost and ensuring weldability, comprising the steps of:

a. and (3) drawing up the chemical composition range of the matrix of the target steel plate:

the main chemical components and the proportions thereof are preliminarily calculated according to the mass percentage:

c:0.05-0.11%, si:0.05-0.09%, mn:0.50-1.10%, cr:0.30-0.60%, ni:1.0-2.50%, cu:0.70-1.10%, mo:0.50-0.60%, and the balance of Fe and unavoidable impurities;

b. determining characteristic parameters and writing a program file for developing integrated batch calculation:

program files for calculating characteristic parameters under different components and temperature conditions can be developed by utilizing a Thermo-Calc calculation software package and adopting a TC-Python interface to write through Python language, wherein the characteristic parameters 1 are T ₀ Temperature, representing the temperature at which the free energies of austenite and ferrite are equal, characteristic parameter 2 being AC, representing T ₀ Carbon content in austenite at temperature; the key instructions in the program file comprise the steps of reading thermodynamic data and finishing thermodynamic calculation of characteristic parameters 1 and 2 of different alloy systems; realizing automatic assignment of alloy components and temperature by adopting a circulation statement, and completing batch calculation; defining a calculation error range to obtain effective data, and completing the output of a calculation result;

c. determining calculation conditions, and running a calculation program to perform component screening:

setting calculation step length of each alloy element based on the component range determined in the step a, and adopting the program file I for calculating the characteristic parameter 1 and the characteristic parameter 2 in the step b to obtain T ₀ And AC, while keeping T low ₀ On the basis of temperature, selecting a point with a high AC value as a target component;

d. calculating the partial energy of the hydrogen atoms by using a first sexual principle, and determining the microalloy elements:

computing the partial energy E of hydrogen atoms at the interface of carbide/matrix by adopting the first sexual principle _MC Calculating and comparing partial energy aggregation of carbides NbC, tiC, VC/matrix interfaces corresponding to Nb, V and Ti microalloy elements to be selected, and selecting microalloy elements in carbides with minimum partial energy aggregation as alloy addition elements to optimize the matrix chemical components of the target steel plate formulated in the step a;

e. screening steel plate matrixes and microalloy components:

determining micro-alloy elements according to the step d, adding the determined micro-alloy elements to the chemical components of the matrix of the planned target steel plate, and redefining the chemical components and the component proportion range of the matrix of the target steel plate to prepare the target high-strength high-toughness hydrogen embrittlement-resistant steel plate.

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