CN111961976A

CN111961976A - Steel, preparation method and application thereof

Info

Publication number: CN111961976A
Application number: CN202010911376.3A
Authority: CN
Inventors: 邹喜洋; 史显波; 田研; 严伟; 周正平; 杨柯; 李端正; 单以银; 曾天翼
Original assignee: Institute of Metal Research of CAS; Hengyang Valin Steel Tube Co Ltd
Current assignee: Institute of Metal Research of CAS; Hengyang Valin Steel Tube Co Ltd
Priority date: 2020-09-02
Filing date: 2020-09-02
Publication date: 2020-11-20
Anticipated expiration: 2040-09-02
Also published as: CN111961976B

Abstract

The invention provides a steel, a preparation method and application thereof. The method comprises the following steps: the raw materials are prepared according to the following chemical components: the raw materials comprise, by weight, 0.08-0.30% of C, less than or equal to 0.5% of Si, less than or equal to 1.0% of Mn, 0.5-2.0% of Cu, less than or equal to 1.0% of Al, 0.01-0.2% of Ce, 0.5-1.5% of Cr, 0.5-1.5% of Mo, less than or equal to 0.3% of V, less than or equal to 0.005% of N, less than or equal to 0.005% of O, less than or equal to 0.005% of S, less than or equal to 0.005%; and (3) smelting, pouring and post-treating the raw materials in sequence to obtain steel, and adding Ce element into a reaction product system when the contents of O and S elements in the reaction product system are not more than 0.005 wt%. The prepared steel has the advantages of high strength, high toughness, sulfide stress corrosion resistance, microbial corrosion resistance and the like, and the structural function integration is realized.

Description

Steel, preparation method and application thereof

Technical Field

The invention relates to the field of alloy steel manufacturing, in particular to a steel, a preparation method and application thereof.

Background

Pipeline corrosion is a serious problem in the oil and gas exploitation, gathering and transportation process. Hydrogen sulfide (H)₂S) Sulfide Stress Corrosion (SSC) and microbial corrosion (MIC) are two important forms of pipeline corrosion. MIC is mainly caused by local corrosion (pitting corrosion), the occurrence and development of corrosion are unpredictable, and the corrosion parts are not regularly circulated. In recent years, pipeline leakage accidents caused by MIC frequently occur, and huge economic losses are caused to the oil and gas industry. Meanwhile, pitting corrosion caused by MIC is a crack source of SSC cracking, and the pitting corrosion and the SSC cracking promote each other, so that great challenge is brought to corrosion protection. In addition to corrosion resistance, there is a need to improve the strength and toughness of steel to solve the problem of increased cost of pipes due to thinning and elongation. However, as the strength of steel increases, the SSC sensitivity increasesIt is more difficult to develop SSC-resistant pipe steels with high strength, especially strength higher than 862MPa (125ksi grade). The strength, toughness and SSC resistance of steel are contradictory relations which cancel each other, and the key to balancing the contradictory relations is whether high strength, high toughness and SSC resistance can be obtained. Therefore, the development of the pipeline steel with high strength, high toughness, SSC resistance and MIC resistance is a technical problem to be solved urgently in the current metallurgical industry.

Disclosure of Invention

The invention mainly aims to provide a steel, a preparation method and application thereof, and aims to solve the problem that the existing steel cannot simultaneously meet the requirements of high strength, high toughness, sulfide stress corrosion resistance (SSC) and microbial corrosion resistance (MIC).

In order to achieve the above object, one aspect of the present invention provides a method for manufacturing a steel material, the method comprising: the raw materials are prepared according to the following chemical components: the raw materials comprise, by weight, 0.08-0.30% of C, less than or equal to 0.5% of Si, less than or equal to 1.0% of Mn, 0.5-2.0% of Cu, less than or equal to 1.0% of Al, 0.01-0.2% of Ce, 0.5-1.5% of Cr, 0.5-1.5% of Mo, less than or equal to 0.3% of V, less than or equal to 0.005% of N, less than or equal to 0.005% of O, less than or equal to 0.005% of S, less than or equal to 0.005%; and in the smelting process, when the contents of O element and S element in a reaction product system are not more than 0.005 wt%, Ce element is added into the reaction product system.

Furthermore, in the raw materials, the content of Cu element is 0.5-2.0 wt%, the content of Al element is 0.1-0.6 wt%, the content of Ce is 0.01-0.2 wt%, the content of Cr is 0.5-1.5 wt%, the content of Mo is 0.5-1.5 wt%, the content of V is 0.005-0.25 wt%, the content of N is less than or equal to 0.005 wt%, and the content of O and S is less than or equal to 0.005 wt%; preferably, the sum of the weight percentages of the Cu element, the Al element and the Ce element in the reaction product system is recorded as a, and a is more than or equal to 1.0 percent and less than or equal to 2.0 percent.

Further, in the step of batching, the raw material further comprises one or more of the group consisting of Nb, Ti, Ca and B, and the weight percentage of each element is not higher than 0.1%.

Further, the smelting process is a process of smelting the raw materials in a vacuum induction furnace, or a process of sequentially carrying out primary smelting and secondary refining on the raw materials in an electric furnace, or a process of sequentially carrying out primary smelting and secondary refining on the raw materials in a blast furnace.

Further, the post-processing step includes: heating and forging the steel ingot obtained in the pouring step in an austenite single-phase region, wherein the initial forging temperature in the heating and forging process is 1000-1100 ℃, the final forging temperature is not lower than 930 ℃, the first forging deformation of the steel ingot is less than 10%, and the total forging ratio is more than 6; and (3) cooling the heated and forged steel ingot to 550-650 ℃ by water, preserving the heat for 30-90 min, and finally cooling the steel ingot to room temperature by air to obtain the steel.

Further, the post-processing step includes: homogenizing the steel ingot obtained in the pouring step, wherein the temperature of the homogenizing treatment is 1130-1170 ℃, and the treatment time is 2-4 hours; hot rolling the steel ingot obtained by homogenization treatment, wherein the initial rolling temperature in the hot rolling step is 1000-1100 ℃, the final rolling temperature is not less than 930 ℃, the first rolling deformation is less than 10%, and the hot rolling accumulated reduction is more than 90%; and (3) cooling the steel ingot subjected to hot rolling to 550-650 ℃ by water, then preserving the heat at 550-650 ℃ for 30-90 min, and finally cooling the steel ingot to room temperature by air to obtain the steel.

In another aspect, the present application also provides a steel material, which is manufactured by the above manufacturing method provided in the present application.

Furthermore, the microstructure of the steel is a single martensite structure, the yield strength at room temperature is more than or equal to 700MPa, the tensile strength is more than or equal to 770MPa, and the impact energy of the full-size V-shaped notch is more than or equal to 120J at the temperature of 0 ℃.

The application further provides an application of the steel provided by the application in the field of petroleum and/or natural gas.

By applying the technical scheme of the invention, the chemical components are used as raw materials to be sequentially smelted, poured and post-treated to obtain the steel, and the Cu, Al, Ce, Mo, V and other alloy elements are compounded to play a synergistic effect, so that the prepared steel has the advantages of high strength, high toughness, sulfide stress corrosion resistance, microbial corrosion resistance and the like, and the structural function integration is realized.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a microstructure topography of the steel of example 2 after incubation at 570 ℃.

FIG. 2 is a graph showing the appearance of the oxide film on the surface of the steel of example 4 after the steel is subjected to heat preservation at 570 ℃.

FIG. 3 is a topographical map of nano-sized hydrogen traps precipitated from the structure of the steel of example 1 after incubation at 650 ℃.

FIG. 4 is a pit topography for the steel of example 4.

FIG. 5 is a topographical map of pits in the steel of comparative example 1.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.

As described in the background art, the existing steels cannot satisfy the problems of high strength, high toughness, sulfide stress corrosion resistance (SSC), and microbial corrosion resistance (MIC) at the same time. In order to solve the above-described problems, the present application provides a method for manufacturing a steel material, including: the raw materials are prepared according to the following chemical components: the raw materials comprise, by weight, 0.08-0.30% of C, less than or equal to 0.5% of Si, less than or equal to 1.0% of Mn, 0.5-2.0% of Cu, less than or equal to 1.0% of Al, 0.01-0.2% of Ce, 0.5-1.5% of Cr, 0.5-1.5% of Mo, less than or equal to 0.3% of V, less than or equal to 0.005% of N, less than or equal to 0.005% of O, less than or equal to 0.005% of S, less than or equal to 0.005% of P; and in the smelting process, when the contents of O element and S element in a reaction product system are not more than 0.005 wt%, Ce element is added into the reaction product system.

Cu element is an element forming austenite in steel, has a small solubility in ferrite, and has a sharp decrease in solubility with a decrease in temperature, and Cu is hardly soluble in α -Fe at room temperature. Therefore, after the aging treatment, the Cu element can be precipitated in the form of a second phase, thereby strengthening the steel. The addition of Cu can promote the formation of a steel surface protective film and reduce the entering of H atoms into a steel matrix, and a nano-sized Cu-rich phase precipitated in the aging process can capture hydrogen to serve as a beneficial hydrogen trap effect. Both of these effects of Cu in steel can greatly reduce the deleterious effects of H on steel. The Cu in the steel also has the microbial corrosion resistance, when the Cu content is lower, the Cu-rich phase precipitated in the matrix is insufficient, and the microbial corrosion resistance is lower; when the Cu content is relatively excessively high, impact toughness and hot workability are adversely affected.

Al is an effective alloy element for deoxidation in steel, so that the Al has very strong bonding force with oxygen (O), and an alumina film layer is very stable and compact, so that the Al has good capability of hindering hydrogen (H) diffusion. The steel of the invention is added with not more than 1.0 wt% of Al, from H₂The source of S corrosion is considered, namely: the oxide film formed by Al in the steel is fully utilized to block the entering of H, the content of H in the steel is reduced, the possibility of SSC is effectively reduced, and the nano-sized Cu-rich phase and Ce in the steel have the effect of beneficial hydrogen trap, so that the excellent SSC resistance is achieved.

Rare earth elements in steel are called "industrial vitamins". The addition of a proper amount of rare earth to steel has multiple beneficial effects, such as: the molten steel can be purified, the grain boundary is optimized, and the corrosion source is reduced, so that the toughness and the uniform corrosion resistance of the steel are improved; in addition, the rare earth steel can also refine crystal grains and capture H atoms, so that the strength and toughness of the steel are improved and the hydrogen embrittlement sensitivity is reduced; moreover, the rare earth element Ce can interact with the outer surface of the bacterial cell membrane and replace metal elements which have important functions in the life process of bacteria, so that the life process of the bacteria is influenced, and the antibacterial effect is achieved. The rare earth Ce, Cu and Al are added to generate a synergistic effect, so that a more excellent effect can be exerted.

Cr and Mo in the steel are elements which effectively improve the hardenability of the steel, but the content of Cr and Mo cannot be too high, and too high can promote the generation of coarse carbides M₂₃C₆(M is Fe,Cr, Mo), and decrease the SSC resistance. The steel of the present invention also contains a proper amount of V, and by containing Mo and V together, formation of fine carbides MC (M is V and Mo) is promoted, thereby functioning as precipitation strengthening. The content of N in the steel is specified to be less than or equal to 0.005 wt%. Excess N readily combines with Al in the steel to produce large-sized AlN, thereby affecting SSC resistance and impact toughness.

The steel of the invention specifies that the contents of O and S are less than or equal to 0.005 wt%. Rare earth Ce has the characteristic of strong chemical activity, O, S inclusion is easy to form, if the contents of O and S are too high, the yield of Ce is influenced, large-size inclusion is formed, and not only can Ce not play a role, but also corrosion resistance and impact toughness are deteriorated.

In summary, the chemical components are used as raw materials to be sequentially smelted, poured and post-treated to obtain the steel, and the Cu, Al, Ce, Mo, V and other alloy elements are compounded to play a synergistic effect, so that the prepared steel has the advantages of high strength, high toughness, sulfide stress corrosion resistance, microbial corrosion resistance and the like, and structural and functional integration is realized.

In a preferred embodiment, the raw materials contain Cu 0.5-2.0 wt%, Al 0.1-0.6 wt%, Ce 0.01-0.2 wt%, Cr 0.5-1.5 wt%, Mo 0.5-1.5 wt%, V0.005-0.25 wt%, N0.005 wt% or less, and O and S0.005 wt% or less. On the basis of fully considering the influence of copper element, aluminum element, cerium element, chromium element, molybdenum element, vanadium element, nitrogen element, oxygen element and sulfur element on the performance of steel, the dosage of each element in the preparation raw materials is optimized to fully play the synergistic effect, thereby being beneficial to further improving the comprehensive performance of the steel in the aspects of strength, toughness, SSC resistance and MIC resistance.

Cu in the steel not only has a precipitation strengthening effect, but also has beneficial hydrogen traps and a microbial corrosion resistance effect. The composite addition of Cu, Al and Ce can play a synergistic role, can effectively prevent H from entering steel, can inhibit the formation of bacterial biofilms and plays a role in resisting microbial corrosion. In a preferred embodiment, the sum of the weight percentages of the Cu element, the Al element and the Ce element in the reaction product system is recorded as a, and a is more than or equal to 1.0 percent and less than or equal to 2.0 percent. The sum of the weight percentages of the Cu element, the Al element and the Ce element in the reaction product system is limited in the range, which is beneficial to further improving the SSC resistance and the MIC resistance of the steel.

In order to further improve the comprehensive performance of the steel, in a preferred embodiment, in the batching step, the raw material further comprises one or more of the group consisting of Nb element, Ti element, Ca element and B element, and the weight percentage of each element is not higher than 0.1%.

The Nb element can form carbide with the C element, which is beneficial to further improving the strength and toughness of the steel. Ti can refine grains, so that austenite grains of a steel billet are not grown too thick in a heating stage, the grains of the steel are further refined, and the strength and the toughness of the steel are improved. The addition of Ca element can perform deoxidation in smelting engineering; the addition of B element is favorable for improving the hardenability of the steel.

The steel material can be produced by a method commonly used in the art. For example, the smelting process is a process of smelting the raw material in a vacuum induction furnace, or a process of subjecting the raw material to primary electric furnace smelting and secondary external furnace refining in sequence, or a process of subjecting the raw material to primary blast furnace smelting and secondary external furnace refining in sequence.

Since the three manufacturing methods described above are different in principle, the process parameters in each process are also different.

In a preferred embodiment, the post-processing step comprises: heating and forging the steel ingot obtained in the pouring step in an austenite single-phase region, wherein the initial forging temperature in the heating and forging process is 1000-1100 ℃, the final forging temperature is not lower than 930 ℃, the first forging deformation of the steel ingot is less than 10%, and the total forging ratio is more than 6; and (3) cooling the heated and forged steel ingot to 550-650 ℃ by water, preserving the heat for 30-90 min, and finally cooling the steel ingot to room temperature by air to obtain the steel.

In a preferred embodiment, the post-processing step comprises: homogenizing the steel ingot obtained in the pouring step, wherein the temperature of the homogenizing treatment is 1130-1170 ℃, and the treatment time is 2-4 hours; hot rolling the steel ingot obtained by homogenization treatment, wherein the initial rolling temperature in the hot rolling step is 1000-1100 ℃, the final rolling temperature is not less than 930 ℃, the first rolling deformation is less than 10%, and the hot rolling accumulated reduction is more than 90%; and (3) cooling the steel ingot subjected to hot rolling to 550-650 ℃ by water, then preserving the heat at 550-650 ℃ for 30-90 min, and finally cooling the steel ingot to room temperature by air to obtain the steel.

The application also provides high-strength alloy steel which is prepared by the manufacturing method.

The chemical components are used as raw materials to be sequentially smelted, poured and post-treated to obtain steel, and the key alloy elements such as Cu, Al, Ce, Mo and V are compounded to play a synergistic effect, so that the prepared steel has the advantages of high strength, high toughness, sulfide stress corrosion resistance, microbial corrosion resistance and the like, and structural and functional integration is realized.

The steel with outstanding performances in all aspects can be prepared by optimizing various process parameters and ingredient compositions, and more preferably, the microstructure of the high-strength alloy steel is a single martensite structure, the yield strength at room temperature is more than or equal to 700MPa, the tensile strength is more than or equal to 770MPa, and the impact energy of a full-size V-shaped notch is more than or equal to 120J at the temperature of 0 ℃.

The steel has high strength, high toughness, sulfide stress corrosion resistance and microbial corrosion resistance, so that the pipeline corrosion caused by sulfide stress corrosion, microbial corrosion and the like can be well overcome by applying the steel in the field of petroleum and/or natural gas.

The present application also provides a method of manufacturing a steel pipe, the method comprising: preparing materials according to the chemical components of the steel to obtain the following raw materials: and then sequentially carrying out smelting, pouring, electroslag remelting, rolling and heat treatment on the raw materials to obtain the steel pipe, and adding Ce element into a reaction product system when the contents of O element and S element in the reaction product system are not more than 0.005 wt% in the smelting process.

The chemical components are used as raw materials to sequentially carry out smelting, pouring, electroslag remelting treatment, rolling and heat treatment to obtain the required steel pipe, the Cu, Al, Ce, Mo, V and other alloy elements are compounded to play a synergistic effect, and the electroslag remelting treatment process is combined, so that the prepared steel pipe has the advantages of high strength, high toughness, sulfide stress corrosion resistance, microbial corrosion resistance and the like, and the structural function integration is realized.

In another aspect of the application, a steel pipe is provided, and the steel pipe is manufactured by the manufacturing method. The steel pipe prepared by the preparation method has the advantages of high strength, high toughness, sulfide stress corrosion resistance, microbial corrosion resistance and the like, and the structural function integration is realized.

More preferably, the microstructure of the steel pipe is a single martensite structure, the yield strength at room temperature is more than or equal to 900MPa, the tensile strength is more than or equal to 1000MPa, and the impact energy of the full-size V-shaped notch is more than or equal to 150J at the temperature of 0 ℃.

The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.

Example 1

The steel comprises the following chemical components in percentage by weight: 0.091% of C, 0.24% of Si, 0.51% of Mn, 0.92% of Cu, 0.32% of Al, 0.12% of Ce, 1.0% of Cr, 0.82% of Mo, 0.004% of Nb, 0.20% of V, 0.001% of Ti, 0.003% of N, 0.001% of S, 0.002% of P, 0.002% of O, 0.005% of Ca and the balance of Fe. Wherein the sum of the contents of Cu element, Al element and Ce element is 1.36%.

Example 2

The steel comprises the following chemical components in percentage by weight: 0.14% of C, 0.21% of Si, 0.50% of Mn, 0.93% of Cu, 0.42% of Al, 0.15% of Ce, 1.0% of Cr, 0.85% of Mo, 0.003% of Nb, 0.005% of V, 0.002% of Ti, 0.005% of N, 0.001% of S, 0.002% of P, 0.004% of O, 0.001% of B and the balance of Fe. Wherein the sum of the contents of Cu element, Al element and Ce element is 1.50%.

Example 3

The steel comprises the following chemical components in percentage by weight: 0.097% of C, 0.22% of Si, 0.59% of Mn, 1.17% of Cu, 0.22% of Al, 0.13% of Ce, 1.02% of Cr, 0.80% of Mo, 0.10% of V, 0.004% of N, 0.001% of S, 0.002% of P, 0.003% of O, 0.001% of B and the balance of Fe. Wherein the sum of the contents of Cu element, Al element and Ce element is 1.52%.

Example 4

The steel comprises the following chemical components in percentage by weight: 0.099% of C, 0.23% of Si, 0.56% of Mn, 1.28% of Cu, 0.13% of Al, 0.15% of Ce, 0.96% of Cr, 0.82% of Mo, 0.01% of V, 0.001% of Ti, 0.002% of N, 0.001% of S, 0.004% of P, 0.005% of O and the balance of Fe. Wherein the sum of the contents of Cu element, Al element and Ce element is 1.56%.

Example 5

The differences from example 1 are: the holding temperature was 690 ℃, the first forging deformation was 5%, and the total forging ratio was 20.

Example 6

The differences from example 1 are: the heat preservation temperature is 690 ℃, the finish forging temperature in the heating forging process is 900 ℃, the first forging deformation is 12%, and the total forging ratio is 4.

Example 7

The differences from example 1 are: the holding temperature was 500 ℃.

Example 8

The differences from example 1 are: the heat preservation temperature is 690 ℃, and the steel comprises the following chemical components in percentage by weight: 0.091% of C, 0.24% of Si, 0.51% of Mn, 0.5% of Cu, 0.3% of Al, 0.2% of Ce, 1.0% of Cr, 0.82% of Mo, 0.004% of Nb, 0.20% of V, 0.001% of Ti, 0.003% of N, 0.001% of S, 0.002% of P, 0.002% of O, 0.005% of Ca and the balance of Fe. Wherein the sum of the contents of Cu element, Al element and Ce element is 1%.

Example 9

The differences from example 1 are: the heat preservation temperature is 690 ℃, and the steel comprises the following chemical components in percentage by weight: 0.091% of C, 0.24% of Si, 0.51% of Mn, 0.5% of Cu, 0.2% of Al, 0.01% of Ce, 1.0% of Cr, 0.82% of Mo, 0.004% of Nb, 0.20% of V, 0.001% of Ti, 0.003% of N, 0.001% of S, 0.002% of P, 0.002% of O, 0.005% of Ca and the balance of Fe. Wherein the sum of the contents of Cu element, Al element and Ce element is 0.71%.

Comparative example 1

The steel comprises the following chemical components in percentage by weight: 0.24% of C, 0.31% of Si, 0.49% of Mn, 0.001% of Cu, 0.04% of Al, 1.0% of Cr, 0.80% of Mo, 0.02% of Nb, 0.006% of N, 0.002% of S, 0.003% of P, 0.005% of O, 0.003% of Ca and the balance of Fe. Wherein the sum of the contents of the Cu element, the Al element and the Ce element is 0.041 percent.

Comparative example 2

The steel comprises the following chemical components in percentage by weight: 0.25% of C, 0.28% of Si, 0.55% of Mn, 0.001% of Cu, 0.03% of Al, 1.03% of Cr, 0.88% of Mo, 0.02% of Nb, 0.10% of V, 0.005% of N, 0.001% of S, 0.002% of P, 0.005% of O and the balance of Fe. Wherein the sum of the contents of Cu element, Al element and Ce element is 0.031%.

Comparative example 3

The steel comprises the following chemical components in percentage by weight: 0.16% of C, 0.24% of Si, 0.54% of Mn, 0.001% of Cu, 0.05% of Al, 1.3% of Cr, 0.79% of Mo, 0.004% of Nb, 0.11% of V, 0.005% of N, 0.001% of S, 0.002% of P, 0.004% of O and the balance of Fe. Wherein the sum of the contents of Cu element, Al element and Ce element is 0.051%.

Comparative example 4

The steel comprises the following chemical components in percentage by weight: 0.27% of C, 0.20% of Si, 0.51% of Mn, 0.001% of Cu, 0.04% of Al, 1.02% of Cr, 0.80% of Mo, 0.006% of Nb, 0.10% of V, 0.005% of N, 0.002% of S, 0.003% of P, 0.004% of O and the balance of Fe. Wherein the sum of the contents of the Cu element, the Al element and the Ce element is 0.041 percent.

Comparative example 5

The differences from example 1 are: the heat preservation temperature is 690 ℃, and the steel comprises the following chemical components in percentage by weight: 0.091% of C, 0.24% of Si, 0.51% of Mn, 0.92% of Cu, 0.32% of Al, 0.005% of Ce, 1.0% of Cr, 0.82% of Mo, 0.004% of Nb, 0.20% of V, 0.001% of Ti, 0.003% of N, 0.001% of S, 0.002% of P, 0.002% of O, 0.005% of Ca and the balance of Fe. Wherein the sum of the contents of Cu element, Al element and Ce element is 1.36%.

The steel materials in the examples and comparative examples were prepared as follows:

(1) mixing raw materials according to preset chemical components, and obtaining a steel ingot through vacuum induction smelting and pouring.

(2) Forging a steel ingot in an austenite single-phase region: the initial forging temperature is 1080 ℃, the final forging temperature is 950 ℃, the 1 st forging deformation of the steel ingot is 8%, the forging ratio is 7, the steel ingot is cooled to 550-650 ℃ by water after forging, the heat preservation time is 1h, the steel ingot is cooled to room temperature by air after heat preservation, and the specific heat preservation temperature and the corresponding related performance are shown in table 1.

Cutting a mechanical property sample from the prepared steel ingot, wherein the specification of a tensile sample is 5mm in diameter, the gauge length is 25mm, and the testing temperature is room temperature; the impact specimen size was 10mm × 10mm × 55mm, V-notch, test temperature was 0 ℃.

The pitting caused by MIC is considered as the greatest damage to the material, and the pitting depth is considered as an important index for quantitatively evaluating the MIC resistance of the material. The method evaluates the quality of MIC resistance by the maximum pit depth of the surface of the material.

The prepared sample blocks of each example and comparative example are soaked in oil gas produced water containing SRB for 21 days, and the maximum pitting depth of the surface of the sample after corrosion due to SRB corrosion is detected by a laser confocal microscope, and the result is shown in Table 1.

The samples evaluated for SSC resistance were loaded at constant load with 80% yield strength according to NACE TM0177 standard, Methoda, solution A.

FIG. 4 is a pit topography for the steel of example 4.

FIG. 5 is a topographical map of pits in the steel of comparative example 1.

TABLE 1

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: the chemical components are used as raw materials to be sequentially smelted, poured and post-treated to obtain steel, and Cu, Al, Ce, Mo, V and other alloy elements are compounded to play a synergistic effect, so that the prepared steel has the advantages of high strength, high toughness, sulfide stress corrosion resistance, microbial corrosion resistance and the like, and structural and functional integration is realized.

It is noted that the terms first, second and the like in the description and in the claims of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those described or illustrated herein.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for producing a steel material, characterized by comprising:

the raw materials are prepared according to the following chemical components:

the raw materials comprise, by weight, 0.08-0.30% of C, less than or equal to 0.5% of Si, less than or equal to 1.0% of Mn, 0.5-2.0% of Cu, less than or equal to 1.0% of Al, 0.01-0.2% of Ce, 0.5-1.5% of Cr, 0.5-1.5% of Mo, less than or equal to 0.3% of V, less than or equal to 0.005% of N, less than or equal to 0.005% of O, less than or equal to 0.005% of S, less than or equal to 0.005% of;

and in the smelting process, when the contents of O element and S element in a reaction product system are not more than 0.005 wt%, adding Ce element into the reaction product system.

2. The production method according to claim 1, wherein the raw material contains 0.5 to 2.0 wt% of Cu, 0.1 to 0.6 wt% of Al, 0.01 to 0.2 wt% of Ce, 0.5 to 1.5 wt% of Cr, 0.5 to 1.5 wt% of Mo, 0.005 to 0.25 wt% of V, 0.005 wt% or less of N, and 0.005 wt% or less of O and S.

3. The production method according to claim 1 or 2, wherein the sum of the weight percentages of the Cu element, the Al element and the Ce element in the reaction product system is represented as a, and a is 1.0% to 2.0%.

4. The manufacturing method according to claim 2 or 3, wherein in the batching step, the raw material further comprises one or more of the group consisting of Nb, Ti, Ca and B, and the weight percentage of each element is not higher than 0.1%.

5. The production method according to any one of claims 1 to 4, wherein the melting process is a process of subjecting the raw material to vacuum induction furnace melting, or a step of subjecting the raw material to electric furnace primary refining and external refining in this order, or a step of subjecting the raw material to blast furnace primary refining and external refining in this order.

6. The manufacturing method according to claim 5, wherein the post-processing step includes:

heating and forging the steel ingot obtained in the pouring step in an austenite single-phase region, wherein the initial forging temperature in the heating and forging process is 1000-1100 ℃, the final forging temperature is not lower than 930 ℃, the first forging deformation of the steel ingot is less than 10%, and the total forging ratio is more than 6;

and cooling the heated and forged steel ingot to 550-650 ℃ by water, preserving the heat for 30-90 min, and finally cooling the steel ingot to room temperature by air to obtain the steel.

7. The manufacturing method according to claim 5, wherein the post-processing step includes:

homogenizing the steel ingot obtained in the pouring step, wherein the temperature of the homogenizing treatment is 1130-1170 ℃, and the treatment time is 2-4 hours;

hot rolling the steel ingot obtained by the homogenization treatment, wherein the initial rolling temperature in the hot rolling step is 1000-1100 ℃, the final rolling temperature is not less than 930 ℃, the first rolling deformation is less than 10%, and the hot rolling accumulated reduction is more than 90%;

and cooling the steel ingot subjected to hot rolling to 550-650 ℃ by water, then preserving the heat at 550-650 ℃ for 30-90 min, and finally cooling the steel ingot to room temperature by air to obtain the steel.

8. A steel product produced by the production method according to any one of claims 1 to 7.

9. The steel product as claimed in claim 8, wherein the microstructure of the steel product is a single martensite structure, the yield strength at room temperature is not less than 700MPa, the tensile strength is not less than 770MPa, and the full-size V-notch impact energy is not less than 120J at 0 ℃.

10. Use of the steel according to claim 8 or 9 in the field of oil and/or gas.