Wide and thick steel plate for high-performance marine oil and gas production riser and manufacturing method therefor

Abstract

Disclosed in the present invention are a wide and thick steel plate for a high-performance marine oil and gas production riser and a manufacturing method therefor. The steel plate comprises: C: 0.025-0.060%, Si: 0.20-0.50%, Mn: 0.80-1.40%, Nb: 0.010-0.035%, V: ≤0.080%, Ti: 0.005-0.020%, Ni: 0.01-0.10%, Mo: <0.15%, Cr: 0.10-0.40%, Cu: <0.15%, Zr: ≤0.025%, Al: 0.005-0.025%, N: 0.0040-0.010%, Ca: 0.0015-0.0040%, Ca / S: ≥1.6%, P: ≤0.010%, S: ≤0.002%, H: ≤0.00015%, O: ≤0.0018%, with the balance being iron and inevitable impurities.

Description

High-performance wide and thick steel plate for offshore oil and gas exploitation riser and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the field of materials and metallurgy, and more particularly to a high-performance wide and thick steel plate for offshore oil and gas exploitation riser and a preparation method thereof. BACKGROUND

[0002] With the growth of energy demand of human economic and social activities, the demand for oil and gas continues to increase, and only relying on land oil and gas resources cannot meet the corresponding demand, therefore, the development of offshore oil and gas resources is increasingly valued. According to the analysis of international authoritative agencies, offshore oil and gas resources account for about 63% of the global recoverable oil and gas reserves in the future, of which deep sea oil and gas resources account for 43%. The development of offshore oil and gas resources has become the main economic growth point of the oil and gas industry. Therefore, it is urgent to develop key equipment and materials for offshore oil and gas development, especially deep sea oil and gas development.

[0003] The riser system is a connecting channel between the offshore oil and gas platform and the underwater production system, and plays a crucial role in offshore oil and gas development. Steel catenary riser has gradually become the preferred riser form for offshore oil and gas development due to its simple structure, economy and other advantages. The riser serves in the marine environment for a long time, has low service temperature, is subjected to complex loads generated by sea current, surge, platform movement, seabed movement and fluid movement in the pipe, and is also subjected to corrosion of seawater and internal conveying medium for a long time; at the same time, the riser may face large deformation during laying, especially during deep sea laying, therefore, the offshore riser must have comprehensive properties such as high strength, low temperature toughness, high fatigue performance, corrosion resistance, strain resistance and good welding performance.

[0004] There are some related researches on steel for steel catenary riser at home and abroad. After searching, some patents and literatures are found, but the contents recorded in the patents and literatures are obviously different from the components, production method, performance, microstructure design and other aspects of the technical scheme of the present application. Patent EP17833981A discloses a high-strength seamless steel pipe and riser, which adopts high C (0.10% to 0.18%), high Ni, Mo and Cu alloy design, has high alloy cost, low weldability, and needs to be produced by using a quenching and tempering process, and has many manufacturing processes. Patent CN110106439A discloses an X65 grade steel plate for marine riser, which adopts high Nb and Ni in the composition, has high cost, and has ferrite structure, and has insufficient strain capacity and fracture strength. Patent CN116555670A discloses a marine riser steel, which also has high alloy content, and requires that the cumulative deformation of the last 2-3 passes of rough rolling is greater than 50%, which is difficult to realize industrialization for wide and thick steel plates, and requires high equipment capacity. Patent CN114763593A discloses a marine engineering steel, which adopts high Ni and Cr design and rolling + quenching and tempering process, has high cost, and has long manufacturing cycle.

[0005] In summary, the prior art has some deficiencies in the research on wide and thick steel plates for high-performance marine oil and gas exploitation riser, especially the wide and thick steel plates for marine oil and gas exploitation riser with comprehensive technical characteristics of high strength, low temperature toughness, high fatigue performance, corrosion resistance, strain resistance and good welding performance, and the production technology thereof.

[0006] SUMMARY

[0007] The present application aims to overcome the above-mentioned defects in the prior art, solve the problem of matching the comprehensive technical characteristics of high strength, high toughness, high fatigue performance, corrosion resistance, strain resistance and good welding performance of the wide and thick steel plate for high-performance marine oil and gas exploitation riser, break the traditional high Nb and high alloy design idea of the product, and provide a wide and thick steel plate for high-performance marine oil and gas exploitation riser with thickness ≥25 mm, high strength, high toughness, high fatigue performance, good corrosion resistance, strain resistance and welding performance, and a preparation method thereof, which is suitable for manufacturing high-performance marine oil and gas exploitation straight seam welded riser.

[0008] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0009] A wide and thick steel plate for high-performance marine oil and gas exploitation riser, characterized by comprising the following components in percentage by weight: C: 0.025%-0.060%, Si: 0.20%-0.50%, Mn: 0.80%-1.40%, Nb: 0.010%-0.035%, V≤0.080%, Ti: 0.005%-0.020%, Ni: 0.01%-0.10%, Mo<0.15%, Cr: 0.10%-0.40%, Cu<0.15%, Zr≤0.025%, Al: 0.005%-0.025%, N: 0.0040%-0.010%, Ca: 0.0015%-0.0040%, Ca / S≥1.6, P≤0.010%, S≤0.002%, H≤0.00015%, O≤0.0018%, and (Nb+V): 0.030%-0.105%, Ti / N≤2.5, ((Cr / 1.8)+Mo)≥0.15%, and the balance being iron and inevitable impurities.

[0010] The application further discloses a preparation method of the wide and thick steel plate for high-performance marine oil and gas exploitation riser, characterized by comprising: converter smelting, secondary refining, continuous casting process, heating process, rolling process and cooling process; in the rolling process, the heated continuous casting blank is sequentially subjected to rough rolling and finish rolling; the rough rolling comprises rough rolling section one, intermediate cooling and rough rolling section two; the rough rolling starting temperature is 1070-1130 DEG C, and the rough rolling final rolling temperature is 980-1030 DEG C; the last 2-3 passes of the rough rolling section one, the intermediate cooling and the rough rolling section two all adopt rapid spray water cooling; the rough rolling section two starting temperature is < 1050 DEG C, the total deformation rate is ≥ 30%, the deformation rate of each pass is ≥ 15% and increases from pass to pass, and the rough rolling speed is 1.0-1.8 m / s; after the rough rolling, the intermediate blank is rapidly cooled to 860-920 DEG C, and then is warmed to the finish rolling starting temperature 800-860 DEG C; the finish rolling final rolling temperature is 740-780 DEG C, the deformation rate in the finish rolling stage is 60-80%, and the total deformation rate below 800 DEG C is ≥ 15%.

[0011] The embodiment of the application has the following beneficial effects:

[0012] (1) The present invention uses low Nb, Mo, Mn design in the component to promote and accelerate the polygonal ferrite phase transformation before accelerated cooling, to ensure the proportion in the microstructure, and at the same time, to improve the alloy economy. Through the composite control of Mo and Cr, the strength is improved, and the yield ratio is controlled. Through the composite addition of Nb, V and N and the control of Al and Ti, good conditions are provided for the precipitation of Nb and V carbonitride, which promotes grain refinement and fine precipitation formation, plays a hydrogen trap effect, realizes the beneficial influence on strengthening, phase transformation, microstructure and steel plate performance and post-weld performance, and improves the strength, corrosion resistance and weldability. Through the addition of elements such as Zr and Ca to control inclusions, the adverse effects on fatigue performance are reduced. In addition, by reducing the contents of P, S, H and O and controlling the quality of continuous casting billets, the toughness, corrosion resistance and fatigue resistance are improved; matched with the smelting, heating, rolling and cooling production process matched with the alloy composition, the problem of matching the comprehensive technical characteristics of high strength, high toughness, high fatigue performance, corrosion resistance, strain resistance and good welding performance of the wide and thick steel plate for high-performance offshore oil and gas exploitation riser is solved.

[0013] (2) On the basis of the component design of the present invention, low-temperature heating, multi-stage thickness section high-temperature gradient deformation + low-temperature rolling, intermediate waiting temperature billet rapid cooling after rough rolling, low-temperature deformation and multi-stage water cooling are used to obtain the microstructure of polygonal ferrite + lath bainite, which can also include a small amount of granular bainite and dispersed distribution of fine precipitates, and the proportion, size and distribution control of each phase are ideal, which plays an important role in obtaining good comprehensive performance of the steel plate.

[0014] (3) The wide and thick steel plate for high-performance offshore oil and gas exploitation riser of the present invention has a thickness of ≥25mm, a transverse yield strength of 430-530MPa, a transverse tensile strength of 570-660MPa, a transverse yield strength ratio of <0.79, a transverse impact energy at -60℃ of ≥250J, a transverse DWTT shear area at -40℃ of ≥85%, a transverse impact energy of the welding heat affected zone at -20℃ of ≥200J, a longitudinal yield strength of 400-500MPa, a longitudinal tensile strength of 550-640MPa, a longitudinal uniform elongation UEL of ≥12%, a longitudinal yield strength ratio of <0.78, a longitudinal strain hardening index of ≥0.12, a 10 7 cycle fatigue strength of ≥300MPa, an HIC corrosion resistance meeting CLR≤15%, CTR≤5%, CSR≤2% after 96 hours of NACE standard A solution corrosion, an SSCC corrosion resistance meeting no fracture and no visible cracks under 10 times magnification observation after 720 hours of saturated H2S solution immersion under 72% stress loading; the prepared offshore riser meets the requirements of X60, X65 grade and the like. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a microstructure morphology diagram of the steel plate of the embodiment 2 of the present application.

[0016] Figure 2 is a precipitated phase microstructure morphology diagram of the steel plate of the embodiment 4 of the present application. DETAILED DESCRIPTION

[0017] The present application is further described below in conjunction with specific embodiments, but the present application is not limited in any way by the embodiments.

[0018] I. Chemical composition and mechanical properties

[0019] The present application discloses a kind of wide and thick steel plate for high-performance marine oil and gas exploitation stand pipe, comprising the following weight percentage components: C: 0.025%~0.060%, Si: 0.20%~0.50%, Mn: 0.80%~1.40%, Nb: 0.010%~0.035%, V≤0.080%, Ti: 0.005%~0.020%, Ni: 0.01%~0.10%, Mo<0.15%, Cr: 0.10%~0.40%, Cu<0.15%, Zr≤0.025%, Al: 0.005%~0.025%, N: 0.0040%~0.010%, Ca: 0.0015%~0.0040%, Ca / S≥1.6, P≤0.010%, S≤0.002%, H≤0.00015%, O≤0.0018%, and (Nb+V): 0.030%~0.105%, Ti / N≤2.5, ((Cr / 1.8)+Mo)≥0.15%, and the rest is iron and inevitable impurities.

[0020] In a specific embodiment, the steel plate CE IIW =0.31%~0.38%, CEP cm =0.13%~0.16%, wherein, CE IIW =C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15;

[0021] CE Pcm =C+Si / 30+(Mn+Cu+Cr) / 20+Ni / 60+Mo / 15+V / 10+5B.

[0022] Specifically, the mechanism of action of each alloying element in the steel of the present application is as follows:

[0023] C is the basic element to improve strength, which plays a role in the form of alloy carbide precipitation and interstitial solid solution. In addition to using the solid solution strengthening of C, the application focuses on the characteristics of C in the warm rolling of the steel plate and the formation of fine precipitates with Nb and V at the waiting temperature, promoting the formation of fine precipitates, thereby increasing the nucleation site, refining the microstructure; increasing the hydrogen trap, reducing the hydrogen embrittlement tendency; at the same time, the effect of C on improving the hardenability and tensile strength is obvious, and it is also beneficial to the control of the yield ratio; however, too high carbon is not conducive to plasticity, toughness, weldability, corrosion resistance, etc., therefore, the content of C in the application is controlled to be 0.025% to 0.060%.

[0024] Si can improve the hardenability and strength, and increase the strain hardening rate, at the same time, in order to reduce the influence of Al on the formation of N compounds, the application uses Si to partially replace Al to play the role of deoxidizer; but too high Si content will increase M / A in the structure, reduce toughness and plasticity, therefore, the suitable range of Si in the application is 0.20% to 0.50%.

[0025] Mn can effectively improve the strength and hardenability, at the same time, Mn can also reduce the phase transition temperature, which is beneficial to the refinement of grains; and Mn is inexpensive, which can improve the economy of the product; but too high manganese content is easy to induce segregation, which leads to the reduction of corrosion resistance and fatigue resistance, therefore, the content of Mn in the application is controlled to be 0.80% to 1.40%.

[0026] Nb has a fine grain effect, which can improve the strength and toughness, and can also form fine Nb(CN) precipitates under appropriate process, which plays a role in precipitation strengthening and hydrogen trapping; however, too high Nb content, on the one hand, needs to increase the heating temperature of the continuous casting billet to ensure the solid solution effect, which increases the energy consumption, and on the other hand, inhibits the transformation of austenite to polygonal ferrite, which increases the difficulty of controlling the polygonal ferrite in the microstructure; at the same time, it also inhibits the formation of V precipitates when Nb+V is added in the application, therefore, the content of Nb is controlled to be 0.010% to 0.035%.

[0027] V has solid solution and precipitation effect, and has a strong combination tendency with C and N, which can form fine precipitates with C and N during rolling and cooling, and play a role in refining grains, reducing aging sensitivity, increasing hydrogen traps, etc.; and V can promote the nucleation of ferrite during the transformation of austenite, which is beneficial to obtain polygonal ferrite, and can also improve the uniformity of the microstructure of the steel plate cross section; and it can also inhibit the formation of coarse structure during welding, and improve the toughness and hardness of the welded joint; but too high V content is not conducive to toughness and weldability, therefore, the content of V in the application is not more than 0.080%.

[0028] The application further sets the total content of Nb and V in the range of 0.030% to 0.105%, which is beneficial to guarantee fine and dispersed precipitates and prevent the precipitates from excessively growing; meanwhile, it is beneficial to the control of microstructure and alloy cost.

[0029] N: The application utilizes N to form fine precipitates with Nb, Ti and V, plays the roles of strengthening, fine-graining and hydrogen trap, improves the strength and toughness and corrosion resistance, but too high N content deteriorates the toughness and may cause defects of the steel plate, and the content is preferably controlled in the range of 0.0040% to 0.010%.

[0030] Ti easily forms Ti(CN) precipitates with high solid solution temperature, inhibits the grain growth of austenite under high temperature conditions; meanwhile, Ti can also refine the welding structure and improve the toughness of the heat-affected zone after welding; and Ti has the effect of fixing oxygen; but too high Ti and Ti / N will increase the size of precipitates and inhibit the formation of precipitates containing Nb and V, and in the application, the content of Ti is controlled in the range of 0.005% to 0.020% and Ti / N≤2.5.

[0031] Ni has the effect of solid solution strengthening, is beneficial to improve the toughness, can reduce the critical cooling speed, delay the pearlite transformation, reduce the Cu brittleness and improve the corrosion resistance; but too much Ni is not beneficial to the economy due to its high price; therefore, the content of Ni is controlled in the range of 0.01% to 0.10% in the application.

[0032] Mo can improve the hardenability, promote the transformation of low-temperature structure, has the effect of fine-graining and can effectively reduce the phase transition temperature; but Mo inhibits the formation of polygonal ferrite and increases the cost, therefore, the content of Mo is controlled below 0.15% in the application.

[0033] Cr can increase the hardenability and improve the tensile strength, has weak inhibition to the transformation of austenite to polygonal ferrite, is beneficial to increase the "hardness difference" of soft / hard phases in the microstructure and is beneficial to the control of strain and yield ratio; and Cr as a cheap element can replace Mo, Ni and Cu, effectively reduces the cost; but too high Cr content increases the sensitivity of welding cracks, therefore, the content of Cr is controlled in the range of 0.10% to 0.40% and ((Cr / 1.8)+Mo)≥0.15% in the application, which can guarantee the hardenability and strengthening effect, make up the strength loss caused by low Mn and Ni content, and is beneficial to the control of phase transition and microstructure and improves the strain performance.

[0034] Cu improves the hardenability, increases the proportion and hardness of hard phase structure and improves the tensile strength, and is beneficial to the corrosion resistance, but too high Cu content is not beneficial to the toughness, and the content of Cu is controlled below 0.15% in the application.

[0035] Zr is a strong deoxidizing element. This invention utilizes Zr oxides formed by the combination of Zr and oxygen. These oxides have a small density difference with molten steel, facilitating dispersed distribution. Simultaneously, the Zr oxides in molten steel carry an electric charge and possess a certain degree of conductivity, making them less prone to aggregation and growth. This promotes the fine and dispersed distribution of Zr oxides within the steel, fostering phase deformation nuclei, refining grains, and improving performance. Furthermore, Zr can refine the microstructure of the weld heat-affected zone, improving toughness. Moreover, the interaction between Zr and oxygen can reduce the interaction between V and oxygen, promoting the precipitation and formation of VN. However, excessively high Zr content leads to decreased toughness; therefore, in this invention, Zr ≤ 0.025%.

[0036] Al has a strong affinity for O and N and is a deoxygenating element. However, excessive Al content will promote the increase of Al-containing inclusions and the decrease of free N, affecting the formation of NbN and VN. In this invention, the Al content should be controlled between 0.005% and 0.025%.

[0037] Ca and Ca / S can promote the modification and spheroidization of inclusions, effectively improving corrosion resistance and toughness. Therefore, the Ca content of this invention is 0.0015% to 0.0040%, and the Ca / S ratio is ≥1.6.

[0038] In this invention, P and S are considered harmful impurity elements. P can reduce toughness, and this invention sets P ≤ 0.010%. Increased S content promotes the formation and growth of inclusions, disrupts the continuity of the matrix, and leads to decreased fatigue and corrosion resistance. Therefore, S ≤ 0.002%.

[0039] Increased H and O content leads to decreased toughness, increased inclusions, and affects corrosion resistance and fatigue performance. Therefore, this invention controls H ≤ 0.00015% and O ≤ 0.0018%.

[0040] This invention CE IIW Controlled within 0.31% to 0.38%, CE Pcm By controlling the content at 0.13% to 0.16%, the strength and toughness requirements of the steel plate can be met, while also reducing the tendency for welding cracks, thus giving the steel plate good weldability.

[0041] In one specific embodiment, the microstructure of the steel plate is polygonal ferrite and bainite; the bainite includes lath bainite and granular bainite; the volume percentage of polygonal ferrite is 25% to 75%, and the average grain diameter is 5.0 μm to 10 μm; the steel plate contains fine carbonitrides with a particle size of 5 nm to 20 nm that are dispersedly distributed.

[0042] In a specific embodiment, the thickness of the steel plate is ≥25 mm; the transverse yield strength of the steel plate is 430-530 MPa, the transverse tensile strength is 570-660 MPa, the transverse yield strength ratio is <0.79, the transverse impact energy at -60℃ is ≥250 J, the transverse DWTT shear area at -40℃ is ≥85%, the average transverse impact energy at -20℃ in the welding heat affected zone is ≥200 J; the longitudinal yield strength is 400-500 MPa, the longitudinal tensile strength is 550-640 MPa, the longitudinal uniform elongation UEL is ≥12%, the longitudinal yield strength ratio is <0.78, the longitudinal strain hardening index is ≥0.12, the transverse fatigue strength is ≥300 MPa, the HIC corrosion resistance meets the CLR≤15%, CTR≤5%, CSR≤2% after corrosion in NACE standard A solution for 96 hours, and the SSCC corrosion resistance meets no fracture and no visible cracks under 10 times magnification observation after immersion in saturated H2S solution for 720 hours under a 72% stress loading condition. 7 The transverse fatigue strength is ≥300 MPa, the HIC corrosion resistance meets CLR≤15%, CTR≤5%, and CSR≤2% after corrosion in NACE standard A solution for 96 hours, and the SSCC corrosion resistance meets no fracture and no visible cracks under 10 times magnification observation after immersion in saturated H2S solution for 720 hours under a 72% stress loading condition.

[0043] II. Production process

[0044] The application also discloses a preparation method of the wide and thick steel plate for high-performance marine oil and gas exploitation risers according to any of the embodiments of the application, which comprises converter smelting, secondary refining, continuous casting process, heating process, rolling process and cooling process.

[0045] Further, the method specifically comprises the following steps:

[0046] In the converter smelting, the converter tapping temperature is ≤1640℃, C≤0.040%, the slag is blocked during tapping, and the thickness of the slag layer is ≤35 mm; lime and fluorite are added in a ratio of 4 / 1-5 / 1 to form top slag, and the weight percentage of FeO+MnO in the slag is controlled to be ≤1%.

[0047] In the secondary refining, after the molten steel obtained through the converter smelting is refined and deoxidized, Ti, Zr and V are added in sequence to adjust the composition of the molten steel.

[0048] In the continuous casting process, the static time after the molten steel is refined and before continuous casting is ≥10 min; the overheat degree of the continuously cast billet is 10-40℃, the holding time of the molten steel in the tundish during casting is ≥350 s, and the dynamic soft reduction amount of the cast billet is ≥4 mm; the continuous casting is performed at a constant pulling speed, the pulling speed is 0.6-1.5 m / min, the center segregation of the continuously cast billet is ≤C0.5 level, the center porosity is ≤0.5 level, and the A, B, C and D type inclusions are controlled to be within 1 level.

[0049] Specifically, the converter low-carbon, low-temperature, slag stopping can effectively control the carbon content of the final product, ensure the dephosphorization effect, reduce the phosphorus and sulfur; white slag making and controlling FeO+MnO in the slag can ensure the reducing capacity of the slag, fully remove the sulfur, reduce the inclusions, and improve the cleanliness; the adding sequence of Ti, Zr and V after the refining deoxidization can more effectively improve the yield and efficiency of the corresponding elements; the control of the static, pouring superheat and tundish residence time before the molten steel enters the machine can homogenize the molten steel temperature, effectively promote the inclusions to float and remove; the control of the dynamic soft reduction and the casting speed can effectively improve the quality of the casting blank, reduce the defects such as cracks and segregation, and the control of the center segregation, center porosity and inclusions is the effective guarantee for the quality of the continuous casting blank and the performance of the steel plate.

[0050] S4, in the heating process, the continuous casting blank adopts multi-stage heating of preheating, heating and soaking, the total heating time is 1.0 min / mm-1.8 min / mm, and the discharge temperature is 1100℃-1170℃. Specifically, the multi-stage heating of the continuous casting blank and the control of the total heating time are beneficial to improve the heating efficiency and uniformity; since the Nb content is low in the present application, the low-temperature heating discharge can meet the element solid solution needs, at the same time, can effectively reduce the austenite grain size, and more beneficial to reduce the rough rolling temperature, reduce the rolling time in the rough rolling stage, realize high efficiency and low temperature rolling.

[0051] S5, in the rolling process, the heated continuous casting blank is sequentially subjected to rough rolling and finish rolling; the rough rolling includes rough rolling section one, intermediate cooling and rough rolling section two; the rough rolling starting temperature is 1070℃-1130℃, and the rough rolling final rolling temperature is 980℃-1030℃; the last 2-3 passes of the rough rolling section one, the intermediate cooling and the rough rolling section two all adopt rapid spray water cooling; the rough rolling section two starting temperature is <1050℃, the total deformation rate is ≥30%, the deformation rate of each pass is ≥15% and increases pass by pass, and the rough rolling speed is 1.0 m / s-1.8 m / s; after the rough rolling, the intermediate blank is rapidly cooled to 860℃-920℃, and then is warmed to the finish rolling starting temperature 800℃-860℃, the finish rolling final rolling temperature is 740℃-780℃, the deformation rate in the finish rolling stage is 60%-80%, and the total deformation rate below 800℃ is ≥15%.

[0052] S6, in the cooling process, the rolled steel plate is pre-straightened and then subjected to two-stage cooling, the starting water cooling temperature is 690℃-740℃, the water cooling end temperature is 100℃-250℃, there are 15 groups of water cooling headers, and the water amount of the upper headers of the first 5-7 groups during water cooling is 350L / m 2 *min-550L / m 2 *min, the water amount of the upper headers of the rest is 150L / m 2 *min-330L / m 2 *min.

[0053] Specifically, the rough rolling focuses on the process of low-temperature rolling + thickness section high temperature gradient deformation. Due to the low Nb and V-containing design of the present application, the austenite recrystallization temperature is reduced, so that the austenite grain recrystallization is realized by low-temperature rolling and the grain growth is effectively inhibited in the rough rolling stage; the thickness section temperature gradient is significantly increased through multi-stage rapid cooling, and the rolling deformation is promoted to penetrate into the center of the slab thickness by the low-temperature and low-speed rolling in the second stage of rough rolling, so as to refine the structure near the center of the thickness and improve the uniformity of the structure and performance of the steel plate; the deformation rate is increased in each pass in the second stage of rough rolling, which can promote the austenite to fully recrystallize. The deformation rate in the finishing rolling stage can ensure the deformation and flattening degree of the unrecrystallized austenite; the rapid cooling of the intermediate warm slab after rough rolling can rapidly reduce the temperature and effectively inhibit the austenite growth; the low-temperature rolling and low-temperature deformation rate control in the finishing rolling stage, on the one hand, is beneficial to the formation of substructure in the microstructure and the accumulation of deformation energy; on the other hand, it can promote the formation of a small amount of deformation-induced ferrite, improve the plasticity and toughness, and provide good thermodynamic and kinetic conditions for the precipitation of Nb(CN) and V(CN), thereby playing the roles of fine-grain, pinning, promoting phase transformation nucleation, etc.; the pre-straightening of the rolled steel plate is beneficial to improving the uniformity of water cooling and ensuring the shape of the steel plate; the starting water cooling temperature control can ensure the formation of part of the polygonal ferrite soft phase structure before accelerating water cooling; the low final cooling temperature can form a high-hardness structure mainly composed of bainite; the segmented water cooling process of fast cooling at the beginning and slow cooling at the end can increase the cooling speed at high temperature and inhibit high-temperature phase transformation, and at the same time, the small amount of cooling water at low temperature can reduce the internal stress and improve the shape after cooling.

[0054] The following are specific embodiments

[0055] Examples 1-8

[0056] The chemical composition of the steel in examples 1-8 of the present application is shown in Table 1. The smelting and refining process of examples 1-8 of the present application is shown in Table 2. The continuous casting process of examples 1-8 of the present application is shown in Table 3. The heating and rough rolling process of examples 1-8 of the present application is shown in Table 4. The finishing rolling and cooling process of examples 1-8 of the present application is shown in Table 5. The microstructure of examples 1-8 of the present application is shown in Table 6. The mechanical properties of the steel plate of examples 1-8 of the present application are shown in Table 7. The corrosion resistance of examples 1-8 of the present application is shown in Table 8. The microstructure morphology of the steel plate of example 2 of the present application is shown in Figure 1. The precipitated phase microstructure morphology of the steel plate of example 4 of the present application is shown in Figure 2.

[0057] Table 1 Chemical composition of steel in examples 1-8 of the present application (%)

[0058] Table 2 Smelting and refining process of examples 1-8 of the present application

[0059] Table 3 Continuous casting process of examples 1-8 of the present application

[0060] Table 4 Heating and rough rolling process of the inventive examples 1-8

[0061] Table 5 Finishing rolling and cooling process of the inventive examples 1-8

[0062] Table 6 Microstructure of the inventive examples 1-8

[0063] Table 7 Mechanical properties of the steel plates of the inventive examples 1-8

[0064] Note: The tensile sample is a full-thickness rectangular sample with a parallel test section plate width of 38.1 mm; the impact sample size is 10*55*55 mm

[0065] Table 8 Corrosion resistance of the inventive examples 1-8

[0066] According to the above results, the thickness of the wide-thick steel plate for high-performance marine oil and gas exploitation riser of the present application is ≥25 mm; the low Nb, Mo and Mn design is adopted in the composition to promote and accelerate the polygonal ferrite phase transition before accelerated cooling, to ensure the proportion thereof in the microstructure, and meanwhile, to improve the alloy economy. The strength is improved and the yield ratio is controlled through the composite control of Mo and Cr. The grain refinement and fine precipitation formation are promoted through the composite addition of Nb, V and N and the control of Al and Ti, the hydrogen trap effect is exerted, the beneficial effects on strengthening, phase transition, microstructure and post-weld performance of the steel plate are realized, and the strength, corrosion resistance and weldability are improved. The inclusions are controlled through the addition of elements such as Zr and Ca, and the adverse effects on fatigue performance are reduced. In addition, the toughness, corrosion resistance and fatigue resistance are improved by reducing the contents of P, S, H and O and controlling the quality of continuous casting billets; the steel plate is matched with the smelting, heating, rolling and cooling production processes matched with the alloy composition to obtain the comprehensive technical characteristics of high strength, high toughness, high fatigue performance, good corrosion resistance, strain resistance and weldability and ideal microstructure, to meet the requirements of manufacturing high-performance marine oil and gas exploitation riser.

[0067] The above-described examples only express several embodiments of the present application, and the description is relatively specific and detailed, but it should not be understood as limiting the scope of the patent application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A wide and thick steel plate for high performance offshore oil and gas production riser, characterized by, The steel plate comprises the following components by weight percentage: C: 0.025%-0.060%, Si: 0.20%-0.50%, Mn: 0.80%-1.40%, Nb: 0.010%-0.035%, V≤0.080%, Ti: 0.005%-0.020%, Ni: 0.01%-0.10%, Mo<0.15%, Cr: 0.10%-0.40%, Cu<0.15%, Zr≤0.025%, Al: 0.005%-0.025%, N: 0.0040%-0.010%, Ca: 0.0015%-0.0040%, Ca / S≥1.6, P≤0.010%, S≤0.002%, H≤0.00015%, O≤0.0018%, and (Nb+V): 0.030%-0.105%, Ti / N≤2.5, ((Cr / 1.8)+Mo)≥0.15%, and the balance being iron and inevitable impurities.

2. The wide and thick steel plate for high-performance offshore oil and gas production risers according to claim 1, characterized by, The steel sheet CE IIW is 0.31% to 0.38%, CE Pcm is 0.13% to 0.16%, wherein, CE IIW = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15; CE Pcm = C + Si / 30 + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 15 + V / 10 + 5B.

3. The wide and thick steel plate for high-performance marine oil and gas production risers according to claim 1, characterized by, The microstructure of the steel plate is polygonal ferrite and bainite; The bainite comprises lath bainite and granular bainite; The volume percentage of the polygonal ferrite is 25%-75%, and the average grain diameter is 5.0-10 μm; The steel plate contains fine carbonitride with a particle size of 5-20 nm dispersedly distributed therein.

4. The wide and thick steel plate for high-performance marine oil and gas production risers according to claim 1, characterized by, The thickness of the steel plate is ≥25 mm; the transverse yield strength of the steel plate is 430-530 MPa, the transverse tensile strength is 570-660 MPa, the transverse yield strength ratio is <0.79, the average transverse impact energy at -60 ℃ is ≥250 J, the transverse DWTT shearing area at -40 ℃ is ≥85%, the average transverse impact energy at -20 ℃ in the welding heat affected zone is ≥200 J; the longitudinal yield strength is 400-500 MPa, the longitudinal tensile strength is 550-640 MPa, the longitudinal uniform elongation U EL ≥12%, the longitudinal yield strength ratio is <0.78, the longitudinal strain hardening index is ≥0.12, the 10 7 The cyclic fatigue strength is ≥300 MPa, the HIC corrosion resistance satisfies CLR≤15%, CTR≤5%, and CSR≤2% after corrosion in NACE standard A solution for 96 hours, the SSCC corrosion resistance satisfies no fracture and no visible cracks under 10 times magnification after immersion in saturated H2S solution for 720 hours under 72% stress loading.

5. A method of manufacturing a wide and thick steel plate for a high performance offshore oil and gas production riser as claimed in any one of claims 1 to 4, characterized in that, The steel plate comprises: converter smelting, secondary refining, continuous casting process, heating process, rolling process and cooling process; In the rolling process, the heated continuous casting billet is sequentially subjected to rough rolling and finish rolling; the rough rolling comprises rough rolling stage one, intermediate cooling and rough rolling stage two; the rough rolling starting temperature is 1070-1130 °C, and the rough rolling final temperature is 980-1030 °C; the last 2-3 passes of the rough rolling stage one, the intermediate cooling and the rough rolling stage two all adopt rapid spray water cooling; the rough rolling stage two starting temperature is <1050 °C, the total deformation rate is ≥30%, the deformation rate of each pass is ≥15% and increases from pass to pass, and the rough rolling speed is 1.0-1.8 m / s; after the rough rolling, the intermediate warm-up billet is rapidly cooled to 860-920 °C, and then is warmed up to the finish rolling starting temperature of 800-860 °C, the finish rolling final temperature is 740-780 °C, the deformation rate in the finish rolling stage is 60%-80%, and the total deformation rate below 800 °C is ≥15%.

6. The preparation method according to claim 5, characterized in that, In the converter smelting, the converter tapping temperature is ≤1640 °C, C≤0.040%, the slag is blocked during tapping, and the slag layer thickness is ≤35 mm; lime and fluorite are added in a ratio of 4 / 1-5 / 1 to form top slag, and the weight percentage of FeO+MnO in the slag is controlled to ≤1%.

7. The preparation method according to claim 5, characterized in that, In the secondary refining, after the molten steel obtained by the converter smelting is refined and deoxidized, Ti, Zr and V are sequentially added to adjust the composition of the molten steel.

8. The preparation method according to claim 5, characterized in that, In the continuous casting process, the static time of molten steel after refining and before continuous casting is greater than or equal to 10 min; the overheat of the continuous casting billet is 10-40 DEG C, the residence time of molten steel in the tundish during casting is greater than or equal to 350 s, and the dynamic soft reduction amount of the continuous casting billet is greater than or equal to 4 mm; the continuous casting adopts constant speed, the speed is 0.6-1.5 m / min, the center segregation of the continuous casting billet is less than or equal to C0.5 level, the center porosity is less than or equal to 0.5 level, and the A, B, C and D type inclusions are controlled to be less than or equal to 1 level.

9. The preparation method according to claim 5, characterized in that, In the heating process, the total heating time is 1.0-1.8 min / mm, and the discharge temperature is 1100-1170 DEG C.

10. The method of claim 5, wherein, In the cooling process, the rolled steel plate is pre-straightened and then cooled in two stages, the initial water cooling temperature is 690-740 DEG C, the final water cooling temperature is 100-250 DEG C, there are 15 groups of water cooling headers, the water flow of the first 5-7 groups of upper headers is 350 L / m 2 *min-550 L / m 2 *min, the water flow of the rest of the upper headers is 150 L / m 2 *min-330 L / m 2 *min.

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