Microbial stress corrosion resistant pipeline steel and preparation method thereof

Abstract

The present invention provides a microbial stress corrosion resistant pipeline steel and a preparation method thereof, belonging to the technical field of pipeline steel. The microbial stress corrosion resistant pipeline steel provided by the present invention comprises, by mass percentage, 0.02-0.08% carbon, 0.2-0.3% silicon, 1.2-1.4% manganese, 0.2-0.3% chromium, 0.2-0.3% molybdenum, 0.2-0.4% nickel, 0.1-0.2% niobium, 0.3-1.0% copper, and the balance iron. The microbial stress corrosion resistant pipeline steel provided by the present invention has a yield strength greater than 600 MPa, an elongation loss of 14.44-16.43% at an open circuit potential, a cross-sectional reduction loss of 13.38-15.78%, an elongation loss of 28.21-36.40% at a potential of -0.9 V, and a cross-sectional reduction loss of 32.34-39.42%, and has good mechanical properties and resistance to microbial stress corrosion.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline steel, and in particular to a microbial stress corrosion resistant pipeline steel and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of my country's petroleum and energy industries, the requirements for the transportation of energy sources such as oil and natural gas have become increasingly stringent. Furthermore, the mileage of pipelines laid in recent years has increased, placing higher demands on the overall performance of pipeline steel. The corrosion effects of soil microorganisms on pipeline steel are hidden and latent, and the synergistic effects of stress can trigger stress corrosion cracking.

[0003] Under cathodic protection, the stress corrosion mechanism of pipeline steel in soil environments is a mixed mechanism of anodic dissolution and hydrogen embrittlement. Anodic dissolution is related to the formation of biofilms on the pipeline surface by microorganisms, while hydrogen embrittlement is related to the concentration, diffusion, and distribution of hydrogen atoms in the environment entering the steel. Both can lead to the initiation and propagation of microcracks and synergistically exacerbate stress corrosion cracking.

[0004] Based on the above stress corrosion mechanism, adding alloying elements that are both antibacterial and inhibit hydrogen embrittlement to steel is an effective means to improve the resistance of pipeline steel to microbial stress corrosion. According to research progress at home and abroad, most current research focuses on the single mechanism of microbial stress corrosion, and there are few reports on the design of microbial stress corrosion-resistant materials that couple the mechanisms of anodic dissolution and hydrogen embrittlement.

[0005] Therefore, providing a pipeline steel having good mechanical properties and resistance to microbial stress corrosion has become a technical problem to be solved urgently in this field. Summary of the Invention

[0006] The object of the present invention is to provide a microbial stress corrosion resistant pipeline steel and a preparation method thereof. The microbial stress corrosion resistant pipeline steel provided by the present invention has good mechanical properties and microbial stress corrosion resistance.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a microbial stress corrosion resistant pipeline steel, which comprises, by mass percentage, 0.02-0.08% of C, 0.2-0.3% of Si, 1.2-1.4% of Mn, 0.2-0.3% of Cr, 0.2-0.3% of Mo, 0.2-0.3% of Ni, 0.1-0.2% of Nb, 0.3-1.0% of Cu and the balance of Fe.

[0009] Preferably, the alloy comprises, by mass percentage: C: 0.04-0.07%, Si: 0.21-0.28%, Mn: 1.25-1.36%, Cr: 0.22-0.28%, Mo: 0.22-0.28%, Ni: 0.25-0.35%, Nb: 0.12-0.18%, Cu: 0.4-0.9% and the balance Fe.

[0010] Preferably, the alloy comprises, by mass percentage: C: 0.05-0.06%, Si: 0.22-0.25%, Mn: 1.28-1.30%, Cr: 0.24-0.26%, Mo: 0.24-0.26%, Ni: 0.28-0.30%, Nb: 0.14-0.16%, Cu: 0.6-0.8% and the balance Fe.

[0011] The present invention provides a method for preparing the microbial stress corrosion resistant pipeline steel described in the above technical solution, comprising the following steps:

[0012] (1) After melting the alloy raw materials, casting and homogenizing are performed to obtain a uniform steel billet;

[0013] (2) The uniform steel billet obtained in step (1) is rolled and aged to obtain microbial stress corrosion resistant pipeline steel.

[0014] Preferably, the temperature of the homogenization treatment in step (1) is 1180-1200° C., and the time of the homogenization treatment is 1-2 hours.

[0015] Preferably, the initial rolling temperature in step (2) is 950-1100°C, and the final rolling temperature is 800-820°C.

[0016] Preferably, the reduction of the final rolling is 8-12%.

[0017] Preferably, the step (2) further includes a cooling treatment after the rolling is completed.

[0018] Preferably, the cooling rate of the cooling treatment is 25-35°C / s.

[0019] Preferably, the temperature of the aging treatment in step (2) is 450-550° C., and the time of the aging treatment is 1-2 hours.

[0020] The present invention provides a microbial stress corrosion resistant pipeline steel, which comprises, by mass percentage, 0.02-0.08% of C, 0.2-0.3% of Si, 1.2-1.4% of Mn, 0.2-0.3% of Cr, 0.2-0.3% of Mo, 0.2-0.3% of Ni, 0.1-0.2% of Nb, 0.3-1.0% of Cu and the balance of Fe. The present invention improves weldability by adding C element, and contributes to the formation of ferrite and bainite, and improves the mechanical properties of steel by adding Si element as a reducing agent and deoxidizer. The addition of Mn element causes solid solution strengthening, thereby improving the strength and toughness of steel. The Cr element can increase the hardenability of steel and has a secondary hardening effect, thereby improving the hardness and wear resistance of carbon steel, while also refining the grains of the rust layer and preventing the penetration of corrosive ions. Mo, Ni and Nb have the effect of refining grains, Mo can promote the formation of acicular ferrite and reduce the ductile-brittle transition temperature, Ni can improve the corrosion resistance of steel and also improve the strength of steel while maintaining good plasticity and toughness, and Nb can produce precipitation strengthening effect, thereby improving the strength and toughness of steel. Cu has a low solid solubility in ferrite and can precipitate a nano-ε-Cu phase in the ferrite, thereby improving the strength of steel, forming beneficial hydrogen traps to improve the resistance to hydrogen-induced cracking, and also having the effect of poisoning bacteria. Experimental results show that the microbial stress corrosion resistant pipeline steel provided by the present invention has a yield strength of 621.4-681.0 MPa, a tensile strength of 713.9-769.4 MPa, an impact toughness of 135.7-192.6 J, an resistance to Bacillus cereus rate of 12-65%, an elongation loss at open circuit potential of 14.44-16.43%, a cross-sectional shrinkage loss of 13.38-15.78%, and a maximum reduction of nearly 20% in microbial stress corrosion sensitivity compared with pipeline steel without Cu addition; the elongation loss at a potential of -0.9 V (vs. SCE) is 28.21-36.40%, and the cross-sectional shrinkage loss is 32.34-39.42%. The microbial stress corrosion sensitivity is reduced by nearly 30% compared with pipeline steel without Cu addition, and has good mechanical properties and microbial stress corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an SEM image of the microbial stress corrosion resistant pipeline steel in Example 4 of the present invention;

[0022] Figure 2 This is the SEM image of the microbial stress corrosion resistant pipeline steel in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The present invention provides a microbial stress corrosion resistant pipeline steel, which comprises, by mass percentage, 0.02-0.08% of C, 0.2-0.3% of Si, 1.2-1.4% of Mn, 0.2-0.3% of Cr, 0.2-0.3% of Mo, 0.2-0.3% of Ni, 0.1-0.2% of Nb, 0.3-1.0% of Cu and the balance of Fe.

[0024] The microbial stress corrosion-resistant pipeline steel provided herein comprises 0.02-0.08% C by mass, preferably 0.04-0.07%, and more preferably 0.05-0.06%. In the present invention, C improves weldability and contributes to the formation of ferrite and bainite. Limiting the C content to this range improves the mechanical properties of the pipeline steel.

[0025] The microbial stress corrosion-resistant pipeline steel provided herein comprises 0.2-0.3% Si by mass, preferably 0.21-0.28%, and more preferably 0.22-0.25%. In the present invention, Si acts as a reducing agent and deoxidizer, improving the mechanical properties of the steel. Limiting the Si content to the aforementioned range avoids the adverse effects of excessive Si content on toughness while simultaneously improving the mechanical properties of the steel.

[0026] The microbial stress corrosion-resistant pipeline steel provided by the present invention includes 1.2-1.4% Mn by mass, preferably 1.25-1.36%, and more preferably 1.28-1.30%. In the present invention, the addition of Mn causes solid solution strengthening, improving the strength and toughness of the steel. Limiting the Mn content to the aforementioned range improves the mechanical properties of the steel while preventing excessive Mn content from forming inclusions that could adversely affect weldability.

[0027] The microbial stress corrosion-resistant pipeline steel provided by the present invention includes 0.2-0.3% Cr by mass, preferably 0.22-0.28%, and more preferably 0.24-0.26%. In the present invention, Cr can increase the hardenability of the steel and have a secondary hardening effect, improving the hardness and wear resistance of carbon steel. It can also refine the rust layer grains and prevent the penetration of corrosive ions. Limiting the Cr content to the above range can improve the mechanical properties of the alloy and enhance the corrosion resistance of the steel.

[0028] The microbial stress corrosion-resistant pipeline steel provided herein includes, by mass percentage, 0.2-0.3% Mo, preferably 0.22-0.28%, and more preferably 0.24-0.26%. In the present invention, Mo refines grains, promotes the formation of acicular ferrite, and reduces the ductile-brittle transition temperature. Limiting the Mo content to the aforementioned range improves the mechanical properties of the steel.

[0029] The microbial stress corrosion-resistant pipeline steel provided by the present invention includes 0.2-0.4% Ni by mass, preferably 0.25-0.35%, and more preferably 0.28-0.30%. In the present invention, Ni refines grain size and improves the corrosion resistance of the steel, while also increasing the steel's strength while maintaining good plasticity and toughness. Limiting the Ni content to the aforementioned range improves the steel's mechanical properties and corrosion resistance.

[0030] The microbial stress corrosion-resistant pipeline steel provided herein includes 0.1 to 0.2% Nb by mass, preferably 0.12 to 0.18%, and more preferably 0.14 to 0.16%. In the present invention, Nb can significantly refine grains and provide moderate precipitation strengthening, thereby improving the strength and toughness of the steel. Limiting the Nb content to the aforementioned range improves the mechanical properties of the steel.

[0031] The microbial stress corrosion-resistant pipeline steel provided by the present invention includes 0.3-1.0% Cu by mass, preferably 0.4-0.9%, and more preferably 0.6-0.8%. In the present invention, Cu has a low solid solubility in ferrite, which can precipitate a nano-ε-Cu phase in the ferrite. The ε-Cu phase can increase the strength of the steel, form beneficial hydrogen traps to enhance resistance to hydrogen-induced cracking, and also has a toxic effect on bacteria. Limiting the Cu content to the above range can improve the mechanical properties and microbial stress corrosion resistance of the steel while avoiding excessive Cu causing deterioration of the steel's processing properties and grain boundary embrittlement.

[0032] The microbial stress corrosion resistant pipeline steel provided by the present invention improves the mechanical properties and corrosion resistance of the pipeline steel by adding C, Si, Mn, Cr, Mo, Ni and Nb elements. By adding the Cu element, a nano-ε-Cu phase is precipitated in the ferrite, thereby improving the strength of the steel, forming beneficial hydrogen traps to enhance the resistance to hydrogen-induced cracking, and at the same time having the effect of poisoning bacteria, thereby improving the microbial stress corrosion resistance of the pipeline steel.

[0033] The present invention also provides a method for preparing the microbial stress corrosion resistant pipeline steel described in the above technical solution, comprising the following steps:

[0034] (1) After melting the alloy raw materials, casting and homogenizing are performed to obtain a uniform steel billet;

[0035] (2) The uniform steel billet obtained in step (1) is rolled and aged to obtain microbial stress corrosion resistant pipeline steel.

[0036] The present invention performs casting and homogenization treatment after melting alloy raw materials to obtain a uniform steel billet.

[0037] The present invention has no special limitation on the alloy raw materials. Commonly used alloy raw materials on the market can be used as long as the composition of the pipeline steel is within the above-defined range.

[0038] The present invention has no special limitation on the casting, and any casting method commonly used by those skilled in the art may be used.

[0039] In the present invention, the homogenization temperature is preferably 1180-1200°C, more preferably 1190-1200°C; and the homogenization time is preferably 1-2 hours, more preferably 1-1.5 hours. Setting the homogenization temperature and time within these ranges allows the steel to reach the austenitizing temperature and achieve a more uniform composition.

[0040] After obtaining the uniform steel billet, the present invention performs rolling and aging treatment on the uniform steel billet to obtain microbial stress corrosion resistant pipeline steel.

[0041] In the present invention, the initial rolling temperature is preferably 950-1100° C., more preferably 1000-1050° C.; the final rolling temperature is preferably 800-820° C., more preferably 800-810° C. In the present invention, setting the initial and final rolling temperatures within the above ranges can form a steel having a predominantly bainite structure.

[0042] In the present invention, the reduction of the final rolling is preferably 8-12%, more preferably 10%. In the present invention, limiting the reduction of the final rolling to the above range can improve the mechanical properties of the steel.

[0043] In one embodiment of the present invention, the reduction during the rolling process is preferably 37.1% at 1100°C, 32.7% at 1000°C, 32.4% at 850°C, and 10% at 800°C. Limiting the reduction at different temperatures to the above ranges can provide the alloy with good mechanical properties.

[0044] The present invention preferably further includes a cooling process after the rolling is completed.

[0045] In the present invention, the cooling rate of the cooling treatment is preferably 25-35°C / s, more preferably 25-30°C / s. The present invention limits the cooling rate to the above range to ensure that the steel structure is acicular ferrite and bainite, which is beneficial to improving the mechanical properties of the alloy.

[0046] In the present invention, the cooling treatment is preferably water cooling, and more preferably cooling the rolled steel in a water laminar flow region. The present invention can improve the mechanical properties of the steel by water cooling.

[0047] In the present invention, the aging treatment temperature is preferably 450-550°C, more preferably 500°C; and the aging treatment time is preferably 1-2 hours, more preferably 1-1.5 hours. Limiting the aging treatment temperature and time to the above ranges ensures that the pipeline steel has better mechanical properties and resistance to microbial stress corrosion.

[0048] In the present invention, cooling treatment is preferably performed after the aging treatment is completed.

[0049] In the present invention, the cooling treatment after the aging treatment is preferably air cooling. The present invention has no special limitation on the operation of the air cooling, and the air cooling operation commonly used by those skilled in the art can be used to cool to room temperature.

[0050] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0051] Example 1

[0052] The present invention provides a microbial stress corrosion resistant pipeline steel, which comprises, by mass percentage, 0.05% C, 0.23% Si, 1.21% Mn, 0.28% Cr, 0.27% Mo, 0.25% Ni, 0.15% Nb, 0.33% Cu and the balance Fe.

[0053] The preparation method of the microbial stress corrosion resistant pipeline steel comprises the following steps:

[0054] (1) The alloy raw materials are melted, cast, and then homogenized at 1200°C for 1 hour to obtain a uniform steel billet;

[0055] (2) The uniform steel billet obtained in step (1) is initially rolled at 1100° C. with a reduction of 37.1%, a reduction of 32.7% at 1000° C., a reduction of 32.4% at 850° C., and a final rolling temperature of 800° C. with a reduction of 10%. After rolling, the billet enters a water laminar flow area for cooling at a cooling rate of 25° C. / s, and finally cooled to room temperature. After aging treatment at 500° C. for 1 h, the billet is air-cooled to room temperature to obtain a microbial stress corrosion resistant pipeline steel.

[0056] Example 2

[0057] The present invention provides a microbial stress corrosion resistant pipeline steel, which comprises, by mass percentage, 0.07% C, 0.22% Si, 1.20% Mn, 0.25% Cr, 0.28% Mo, 0.32% Ni, 0.17% Nb, 0.58% Cu and the balance Fe.

[0058] The preparation method of the microbial stress corrosion resistant pipeline steel is the same as that in Example 1.

[0059] Example 3

[0060] The present invention provides a microbial stress corrosion resistant pipeline steel, which comprises, by mass percentage, 0.05% C, 0.21% Si, 1.36% Mn, 0.24% Cr, 0.22% Mo, 0.30% Ni, 0.19% Nb, 0.72% Cu and the balance Fe.

[0061] The preparation method of the microbial stress corrosion resistant pipeline steel is the same as that in Example 1.

[0062] Example 4

[0063] The present invention provides a microbial stress corrosion resistant pipeline steel, which comprises, by mass percentage, 0.06% C, 0.20% Si, 1.35% Mn, 0.26% Cr, 0.29% Mo, 0.29% Ni, 0.13% Nb, 0.98% Cu and the balance Fe.

[0064] The preparation method of the microbial stress corrosion resistant pipeline steel is the same as that in Example 1.

[0065] The morphology of the microbial stress corrosion resistant pipeline steel in Example 4 is shown in FIG. Figure 1 As shown, from Figure 1 It can be seen that the microstructure of the steel is polygonal ferrite and bainite, and the grain size ranges from 5 to 10 μm.

[0066] Comparative Example 1

[0067] The present invention provides a microbial stress corrosion resistant pipeline steel, which comprises, by mass percentage, 0.06% C, 0.25% Si, 1.29% Mn, 0.29% Cr, 0.29% Mo, 0.33% Ni, 0.13% Nb, 0.02% Cu and the balance Fe.

[0068] The preparation method of the microbial stress corrosion resistant pipeline steel is the same as that in Example 1.

[0069] The morphology of the microbial stress corrosion resistant pipeline steel in Comparative Example 1 is as follows: Figure 2 As shown, from Figure 2 It can be seen that the microstructure of the steel is polygonal ferrite and bainite, and the grain size ranges from 10 to 20 μm, which is larger than that of Example 4.

[0070] Comparative Example 2

[0071] The present invention provides a microbial stress corrosion resistant pipeline steel, which comprises, by mass percentage, 0.06% C, 0.26% Si, 1.25% Mn, 0.28% Cr, 0.28% Mo, 0.22% Ni, 0.14% Nb, 1.35% Cu and the balance Fe.

[0072] The preparation method of the microbial stress corrosion resistant pipeline steel is the same as that in Example 1.

[0073] The present invention adopts a dilution culture counting method to count the number of bacteria attached to the surface of pipeline steel to conduct an antibacterial test on the microbial stress corrosion resistant pipeline steel.

[0074] The present invention conducts a slow strain rate tensile test on microbial stress corrosion resistant pipeline steel, the test environment is a bacteria-containing environment, the test temperature is room temperature, the strain tensile rate is 1×10 -6 s -1 The open circuit potential is without any external potential, the cathode potential is at -0.9 V (vs. SCE), the stretching process is always in a bacteria-containing environment, and the stress corrosion sensitivity of the microbial stress corrosion-resistant pipeline steel in a microbial environment is evaluated by calculating the elongation loss and cross-sectional shrinkage loss of the pipeline steel.

[0075] Table 1 shows the chemical composition by mass percentage of the microbial stress corrosion resistant pipeline steels of Examples 1 to 4 of the present invention and Comparative Examples 1 to 2.

[0076] Table 1 Chemical composition mass percentage of microbial stress corrosion resistant pipeline steels of Examples 1 to 4 of the present invention and Comparative Examples 1 to 2

[0077] Element C Si Mn Cr Mo Ni Nb Cu Example 1 0.05 0.23 1.21 0.28 0.27 0.25 0.15 0.33 Example 2 0.07 0.22 1.20 0.25 0.28 0.32 0.17 0.58 Example 3 0.05 0.21 1.36 0.24 0.22 0.30 0.19 0.72 Example 4 0.06 0.20 1.35 0.26 0.29 0.29 0.13 0.98 Comparative Example 1 0.06 0.25 1.29 0.29 0.29 0.33 0.13 0.02 Comparative Example 2 0.06 0.26 1.25 0.28 0.28 0.22 0.14 1.35

[0078] In the present invention, the antibacterial rate of the microbial stress corrosion-resistant pipeline steels of Examples 1 to 4 and Comparative Examples 1 to 2 is calculated by the antibacterial rate formula, which is: antibacterial rate (%) = (number of viable bacteria in Comparative Example 1 - number of viable bacteria in the embodiment) / number of viable bacteria in Comparative Example 1 × 100%.

[0079] Table 2 shows the antibacterial rate and mechanical property data of the microbial stress corrosion resistant pipeline steels of Examples 1 to 4 and Comparative Examples 1 to 2 in the present invention.

[0080] Table 2 Antibacterial rate and mechanical properties data of microbial stress corrosion resistant pipeline steel in Examples 1 to 4 and Comparative Examples 1 to 2 of the present invention

[0081]

[0082]

[0083] Table 3 shows the microbial stress corrosion resistance of the microbial stress corrosion resistant pipeline steels of Examples 1 to 4 and Comparative Examples 1 to 2 in the present invention.

[0084] Table 3 Microbial stress corrosion resistance of the pipeline steels resistant to microbial stress corrosion in Examples 1 to 4 and Comparative Examples 1 to 2 of the present invention

[0085]

[0086] It can be seen from the data in Tables 2 and 3 that the microbial stress corrosion resistant pipeline steel provided by Examples 1 to 4 of the present invention has a yield strength of 621.4 to 681.0 MPa, a tensile strength of 713.9 to 769.4 MPa, an impact toughness of 135.7 to 192.6 J, and an resistance to Bacillus cereus of 12 to 65%; the elongation loss at the open circuit potential is 14.44 to 16.43%, the section reduction loss is 13.38 to 15.78%, and the microbial stress corrosion sensitivity is reduced by nearly 20% compared with the pipeline steel without Cu addition; the elongation loss at the potential of -0.9 V (vs. SCE) is 28.21 to 36.40%, and the section reduction loss is 32.34 to 39.42%. The microbial stress corrosion sensitivity is reduced by nearly 30% compared with the pipeline steel without Cu addition. While having good mechanical properties, it also has antibacterial ability and good microbial corrosion resistance.

[0087] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A microbial stress corrosion resistant pipeline steel, comprising, by mass percentage, 0.02-0.08% C, 0.2-0.3% Si, 1.2-1.4% Mn, 0.2-0.3% Cr, 0.2-0.3% Mo, 0.2-0.3% Ni, 0.12-0.2% Nb, 0.6-1.0% Cu, and the balance Fe; The microbial stress corrosion-resistant pipeline steel has a yield strength of 621.4-681.0 MPa, a tensile strength of 713.9-769.4 MPa, an impact toughness of 135.7-192.6 J, an resistance to Bacillus cereus of 12-65%, an elongation loss of 14.44-16.43% at an open circuit potential, and a cross-sectional shrinkage loss of 13.38-15.78%. The elongation loss at a potential of -0.9 V (vs. SCE) is 28.21-36.40%, and the cross-sectional shrinkage loss is 32.34-39.42%.

2. The microbial stress corrosion resistant pipeline steel according to claim 1, characterized in that: In terms of mass percentage, its composition is: C: 0.04~0.07%, Si: 0.21~0.28%, Mn: 1.25~1.36%, Cr: 0.22~0.28%, Mo: 0.22~0.28%, Ni: 0.25~0.35%, Nb: 0.12~0.18%, Cu: 0.6~0.9% and the balance Fe.

3. The microbial stress corrosion resistant pipeline steel according to claim 2, characterized in that: In terms of mass percentage, its composition is: C: 0.05~0.06%, Si: 0.22~0.25%, Mn: 1.28~1.30%, Cr: 0.24~0.26%, Mo: 0.24~0.26%, Ni: 0.28~0.30%, Nb: 0.14~0.16%, Cu: 0.6~0.8% and the balance Fe.

4. The method for preparing the microbial stress corrosion resistant pipeline steel according to any one of claims 1 to 3, comprising the following steps: (1) After melting the alloy raw materials, casting and homogenizing are performed to obtain a uniform steel billet; (2) The uniform steel billet obtained in step (1) is rolled and aged to obtain microbial stress corrosion resistant pipeline steel.

5. The preparation method according to claim 4, characterized in that The temperature of the homogenization treatment in step (1) is 1180-1200° C., and the time of the homogenization treatment is 1-2 hours.

6. The preparation method according to claim 4, characterized in that In the step (2), the initial rolling temperature is 950-1100° C., and the final rolling temperature is 800-820° C.

7. The preparation method according to claim 6, characterized in that The final rolling reduction is 8-12%.

8. The preparation method according to claim 4, characterized in that The step (2) further includes a cooling process after the rolling is completed.

9. The preparation method according to claim 8, characterized in that The cooling rate of the cooling process is 25-35°C / s.

10. The preparation method according to claim 4, characterized in that The temperature of the aging treatment in step (2) is 450-550° C., and the time of the aging treatment is 1-2 hours.

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