CN115181918B - High-strain-strengthening low-yield-ratio pipeline wide and thick plate and production method thereof - Google Patents
High-strain-strengthening low-yield-ratio pipeline wide and thick plate and production method thereof Download PDFInfo
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Abstract
The invention provides a high strain strengthening low yield ratio pipe line width thick plate and a production method thereof, wherein the wide thick plate comprises the following components in percentage by weight: c:0.050% -0.080%, si:0.26 to 0.45 percent of Mn:1.30 to 1.49 percent of Nb:0.010% -0.039%, V:0.041 to 0.079 percent, 0.005 to 0.008 percent of N, ti:0.008 to 0.020 percent, cr:0.15 to 0.25 percent, mo is less than 0.10 percent, ni is less than 0.12 percent, al:0.010 to 0.025 percent, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of S, less than or equal to 0.00015 percent of H and less than or equal to 0.0020 percent of O; wide and thick plate CE IIW Controlled at 0.35% -0.40% and CE Pcm Controlling the temperature to be 0.15-0.19%, and the production method comprises smelting, continuous casting, heating, rolling and cooling; the thickness of the wide and thick plate produced by the invention is more than or equal to 25mm, the width is more than 1600mm, the transverse yield strength is 420-520 MPa, the transverse tensile strength is 620-700 MPa, the transverse yield ratio is less than 0.75, the transverse impact energy average value at minus 60 ℃ is more than or equal to 250J, and the transverse DWTT shearing area at minus 20 ℃ is more than or equal to 85%; the longitudinal yield strength is 400-500 MPa, the longitudinal tensile strength is 600-680 MPa, and the longitudinal uniform elongation U is achieved EL More than or equal to 11 percent, the longitudinal yield ratio is less than 0.73, the longitudinal strain hardening index is more than or equal to 0.11, and the softening rate of the welded joint is less than or equal to 15 percent.
Description
Technical Field
The invention belongs to the field of metal materials, and particularly relates to a high-strain-strength-enhancement low-yield-ratio pipeline wide and thick plate and a production method thereof.
Background
Oil and gas are important components of world energy. With the development of society, the demand and consumption of oil and gas resources are increasing. In order to increase oil and gas resource supply, oil and gas projects are continuously extended to areas with complex geology and environment, such as oceans, high and cold, geology active areas, crossing areas and the like. Because the service conditions of the areas are harsh, stringent requirements are put on the corresponding steel for the oil and gas transmission pipelines; the product not only meets the high strength requirement, but also has the comprehensive properties of good crack-stopping toughness, strain strengthening property, low yield ratio and the like, and meanwhile, the high efficiency and large output are the main development direction and basic requirements of oil and gas pipeline construction, and the steel for the oil and gas pipeline is required to have the characteristics of thick walls, large plates, and the like in dimension specification. In addition, the product is easy to cause softening problem of a welding heat affected zone after welding, particularly when ring welding is carried out on steel pipes and steel pipe connection, so that strength and hardness are reduced, the service safety is directly affected, and therefore, good weldability and low welding softening rate are required.
At present, some researches are carried out on steel plates for pipelines with high strain, high plasticity and the like at home and abroad, and partial patents and documents are found through search, but the recorded contents of the steel plates are obviously different from the components, the production method, the performance, the product category, the dimension specification and the like in the technical scheme of the invention.
The patent literature (CN 106319390B) discloses X70 grade large deformation resistant pipeline steel, which adopts the design of high Ni (0.15-0.55%) and high Nb (0.04-0.10%) in the components, and has high alloy cost; the process adopts the processes of rolling control and cooling control, quenching and tempering in two-phase areas, and the like, and has complex production procedures and long manufacturing period.
The patent literature (CN 111304534B) discloses a high-strain steel plate for an L485 marine pipeline pipe and a manufacturing method thereof, wherein the high-strain steel plate for the L485 marine pipeline pipe and the manufacturing method thereof have the advantages that more elements such as Ni, cr, cu and the like are added into components to ensure the performance, and the cost is high; in the aspect of the production method, the processes of rolling control, cooling control, heat treatment and the like are adopted, so that the production procedures are more, and the energy consumption and the cost are high.
The patent literature (CN 111961957A) discloses an X80 grade pipeline steel plate with seawater corrosion resistance and large deformation resistance and a production method thereof, and the design of low C, low Mn, high Ni and high Cr and the high alloy and smelting cost are adopted.
Patent literature NbC nanoparticle reinforced steel plate for X80 plastic pipe and manufacturing method thereof (CN 109023069A) discloses a steel plate for X80 plastic pipe and a manufacturing method thereof, precious alloys Nb and Ni in the components are high in content, and the economy is not enough; in terms of the production method, after the controlled rolling and cooling of the steel plate is finished, a high-temperature solid solution and medium-temperature treatment process is needed to achieve the NbC strengthening effect, so that the energy consumption and the cost are high, and the manufacturing period is long.
Related literature: the organization and performance of thick-wall X70 pipeline steel (journal of Material Heat treatment, volume 37, 4, gu Shujun, liu Qingyou, li Ba) discloses a thick-wall X70 pipeline steel for marine pipelines, the literature has mainly studied the correlation of microstructure and performance, and the related products and production methods are few.
In view of the above, the prior art has not been able to study the wide and thick steel plate products with high strain-strengthening and low yield ratio, especially the wide and thick steel plate products with high crack-stopping toughness, high strain-strengthening, low yield ratio, low welding softening and thick specification.
Disclosure of Invention
The invention aims to overcome the problems and the shortcomings and provide a high-strain-strength low-yield-ratio pipeline wide-thick plate with high strength, high crack-arrest toughness, high strain-strength, low yield ratio and low welding softening property, wherein the thickness of the wide-thick plate is more than or equal to 25mm, and a production method thereof.
The invention aims at realizing the following steps:
the thickness of the high-strain-strength low-yield-ratio pipe line width thick plate is more than or equal to 25mm, and the width is more than 1600mm; the components are based on C, mn, cr, V, the yield strength and the yield ratio are properly reduced by adopting a low Mn design, the strain performance is promoted to be improved, the tensile strength is ensured by adding Cr and Si, a proper amount of V (CN) precipitation is obtained while the strengthening effect is exerted by V, C, N content control, the beneficial effects of V on phase change and welding softening are realized, and the comprehensive performance is improved; the adverse effect on toughness is reduced by reducing P, S, H, O content and controlling continuous casting billet quality and the like; the steel plate is matched with production processes such as smelting, heating, rolling, cooling and the like matched with alloy components to obtain comprehensive technical characteristics and ideal microstructure such as high strength, high crack-arrest toughness, high strain strengthening property, low yield ratio, low welding softening property, thick specification and the like.
The high-strain-strength low-yield-ratio thick plate with the line width comprises the following components in percentage by weight: c:0.050% -0.080%, si:0.26 to 0.45 percent of Mn:1.30 to 1.49 percent of Nb:0.010% -0.039%, V:0.041 to 0.079 percent, 0.005 to 0.008 percent of N, ti:0.008% -0.020%, cr:0.15 to 0.25 percent, mo is less than 0.10 percent, ni is less than 0.12 percent, al:0.010 to 0.025 percent, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of S, less than or equal to 0.00015 percent of H, less than or equal to 0.0020 percent of O, and the balance of iron and unavoidable impurities.
Further, nb+v in the wide thick plate: 0.06 to 0.10 percent and Ti/N is less than or equal to 3.
Further, wide and thick plate CE IIW Controlled at 0.35% -0.40% and CE Pcm Controlled at 0.15% -0.19%, wherein CE IIW ＝C+Mn/6+(Cr+Mo)/5+(Ni+Cu)/15，
CE Pcm ＝C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/15+V/10+5B。
Further, the microstructure of the wide and thick plate is polygonal ferrite + bainite + carbonitride precipitation, the volume percentage of polygonal ferrite is 30% -80%, the ferrite quantity of 12 μm and below is more than 60% of the total ferrite quantity, the lath bainite in the bainite structure is more than or equal to 40%, the hardness difference between polygonal ferrite and bainite is more than or equal to 60HV, the steel plate matrix contains 0.02% -0.07% of carbonitride precipitation by mass, wherein the carbonitride precipitation below 10nm is more than or equal to 30% of the total carbonitride precipitation quantity.
Further, the thickness of the wide and thick plate is more than or equal to 25mm, the width is more than 1600mm, the transverse yield strength can reach 420-520 MPa, the transverse tensile strength reaches 620-700 MPa, the transverse yield ratio is less than 0.75, the transverse impact energy average value at minus 60 ℃ is more than or equal to 250J, and the transverse DWTT shearing area at minus 20 ℃ is more than or equal to 85%; the longitudinal yield strength can reach 400-500 MPa, the longitudinal tensile strength can reach 600-680 MPa, and the longitudinal uniform elongation U EL The longitudinal yield ratio is more than or equal to 11 percent and less than 0.73, the longitudinal strain hardening index is more than or equal to 0.11, the strength of the steel pipe manufactured by the steel plate can reach X70 grade, and the softening rate of the welded joint is less than or equal to 15 percent.
The reason for designing the components of the invention is as follows:
the strength can be obviously improved, and fine precipitation can be formed with V, nb and the like in the middle-temperature deformation, heat preservation and welding process of the steel plate, so that the beneficial effects of increasing the nucleation position, refining the microstructure, improving the strength, reducing the softening of a welding joint and the like are realized; meanwhile, the C in solid solution form can increase the strength and hardness of the hard phase in the multiphase structure, so that the mechanical property difference of the soft phase and the hard phase is increased, and the reduction of the yield ratio is facilitated; however, the increase in carbon is detrimental to plasticity and toughness; in the invention, C is controlled to be more suitable at 0.050% -0.080%.
Si can improve hardenability and strength, so that the strain hardening rate is increased; however, too high a content will increase M/A in the structure and decrease toughness and plasticity, which is suitably in the range of 0.26% to 0.45% in the present invention.
Mn can improve strength, but tends to cause an increase in yield ratio; meanwhile, mn can also improve the stability of austenite, reduce the transformation temperature, is beneficial to refining grains, but is unfavorable for forming soft-phase ferrite, so that the shadow response is denatured; in addition, the excessive manganese content is easy to induce segregation, promote the formation of inclusions such as MnS and the like, destroy the continuity and uniformity of a matrix and reduce the toughness, and the Mn content is controlled to be 1.30-1.49%.
Nb, V, nb+V: nb has stronger solid solution and fine crystallization effects, and can improve the strength and toughness; however, the content of Nb is too high, on the one hand, the heating temperature of the continuous casting billet needs to be raised to ensure the solid solution effect, and meanwhile, the formation of a V-containing precipitated phase is also inhibited. V has solid solution and precipitation effects, has stronger bonding tendency with C, N, and can form fine precipitation; wherein, the precipitation in the rolling process is easy to promote non-uniform nucleation and refine phase change tissue; the precipitation in the welding process can improve the hardness of the welded joint and reduce the softening rate, and compared with Nb and Ti, the precipitation temperature of V is relatively low, so that a tiny precipitated phase is easy to form; however, too high a V content affects toughness, so that the V content in the invention is 0.041% -0.079%. And Nb+V reaches 0.06-0.10%, so that good solid solution and precipitation effects can be realized, and the comprehensive performance is ensured.
N has stronger affinity with V, nb, ti and the like, is easy to form precipitates, plays an obvious role in inhibiting the growth of grains when a slab is heated, and can play a role in precipitation strengthening in the rolling, cooling and welding processes, so that certain N in steel is favorable for performance, but the content of N is too high to deteriorate toughness, and the content is preferably controlled to be 0.005-0.008 percent.
Ti, ti/N: ti can exert the effects of N fixation and C fixation, forms a Ti (CN) precipitated phase with higher solid solution temperature, and inhibits the growth of austenite grains under the high-temperature condition; meanwhile, ti can refine the welding structure and improve the toughness of a postweld heat affected zone; however, too high Ti and Ti/N content can inhibit the formation of V-containing precipitated phase, resulting in increased size of the precipitated phase, and the Ti content is controlled to be 0.008-0.020% and Ti/N is less than or equal to 3 in the invention.
Cr can improve hardenability, strengthen hard phase structure, and is beneficial to control of strain and yield ratio; moreover, the Cr element has high economy, can replace precious alloy elements, and reduces the cost; however, the excessive Cr content increases the sensitivity of welding cracks, so the Cr content is controlled to be 0.15-0.25 percent.
Mo can improve hardenability and strength of the steel plate; however, too high a content of molybdenum significantly increases the cost and suppresses ferrite transformation, and thus the present invention controls the Mo content to 0.10% or less.
Ni can improve the strength, delay pearlite transformation, facilitate microstructure control and grain refinement, and improve low-temperature toughness; however, ni has a higher price and is not suitable to be added excessively; therefore, the Ni content of the present invention is controlled to be 0.12% or less.
Al is deoxidizing element and has certain N fixing effect, and its content is too high to promote the increase of Al-containing inclusion and the decrease of free N, and the content of Al is controlled to be 0.010-0.025% as proper.
P, S is a harmful impurity element in the present invention; the toughness of P is reduced, and the invention controls the P to be less than or equal to 0.010 percent; the increase of the S content promotes the generation and growth of inclusions, and damages the continuity of a matrix, so that the performance is reduced, and therefore, the S content is less than or equal to 0.002 percent.
H. O is a harmful impurity element in the present invention; an increase in the content thereof results in a decrease in toughness, an increase in inclusions, therefore, the invention controls H to be less than or equal to 0.00015 percent and O to be less than or equal to 0.0020 percent.
CE according to the invention IIW Controlled at 0.35% -0.40% and CE Pcm The strength and toughness of the steel plate can be controlled to be 0.15-0.19%, so that the strength and toughness requirements of the steel plate can be met, the welding cracking tendency can be reduced, and the steel plate has good weldability.
The second technical scheme of the invention is to provide a production method of the high strain-strengthening low yield ratio pipe line width thick plate, which comprises smelting, continuous casting, heating, rolling and cooling;
the casting superheat degree of the continuous casting billet is 10-30 ℃, the continuous casting is performed under weak cooling and dynamic light reduction, the reduction is more than or equal to 4mm, the pulling speed of the continuous casting billet is 0.8-1.2 m/min, the center segregation of the continuous casting billet is less than or equal to C1.0 level, and the center porosity is less than or equal to 1.0 level. The control of the casting superheat degree, weak cooling, dynamic soft reduction and continuous casting billet drawing speed can effectively reduce the quality defect of the casting billet, and the control of center segregation and center porosity is the effective guarantee of the continuous casting billet quality.
The continuous casting blank is heated in multiple stages of a preheating section, a heating section 1, a heating section 2, a heating section 3 and a soaking section, the total heating time is 1.1 min/mm-2.0 min/mm, and the tapping temperature is 1100-1140 ℃. The multi-stage heating and the control of heating time of the continuous casting blank are beneficial to improving the heating efficiency and ensuring the uniformity; the low heating and tapping temperature is designed mainly for low Nb and V-containing components, so that the solid solution requirements of elements such as Nb and V are met, meanwhile, the austenite grains are effectively prevented from excessively growing and growing, the reduction of rolling time in the rough rolling stage is facilitated, and the low-temperature rolling is realized.
The initial rolling temperature of rough rolling is 1080-1120 ℃, and the final rolling temperature of rough rolling is 970-1030 ℃, wherein the rough rolling adopts transverse and longitudinal rolling, and the continuous casting billet is rapidly cooled after the transverse rolling is finished, and the average cooling speed is more than or equal to 2 ℃/s; the longitudinal rolling starting temperature is below 1050 ℃, the total deformation rate of longitudinal rolling is more than or equal to 30%, the deformation rate of each pass is more than or equal to 15%, the deformation rate is gradually increased each pass, and the rough rolling speed is 1.0 m/s-1.8 m/s. The rolling temperature and the deformation process in the rough rolling stage enable austenite grains to be recrystallized, and through accelerated cooling after transverse rolling, low-temperature longitudinal rolling and lower rolling speed, the rolling deformation is promoted to permeate into the thickness center of a casting blank, the structure near the thickness center is refined, the uniformity of the structure performance of the steel plate is improved, and meanwhile, the growth of the grains is restrained; the use of progressively increasing deformation rates from pass to pass during the longitudinal rolling stage promotes sufficient recrystallization of the austenite.
The thickness of the intermediate blank to be warmed is 2.8-4.5 t, wherein t is the thickness of the finished steel plate, and the proper thickness of the intermediate blank to be warmed can meet the accumulation of austenite deformation and deformation energy in an unrecrystallized area.
The initial rolling temperature of the finish rolling is 800-850 ℃, the final rolling temperature of the finish rolling is 700-760 ℃, wherein the total deformation rate below 780 ℃ is more than or equal to 15%, water cooling is carried out after air cooling for 20-80 s after rolling, the final cooling temperature is 50-140 ℃, preferably, the temperature of the steel plate in the length direction after final cooling is gradually reduced, and the final cooling temperature difference between the head part and the tail part of the steel plate length is 30-70 ℃; preferably, the cooling process adopts sectional water cooling, wherein when the temperature of the steel plate is more than or equal to 400 ℃, the water quantity of the upper header pipe is controlled to be 400-600 (L/mm) 2 Min); when the temperature of the steel plate is less than 400 ℃, the water quantity of the upper header pipe is controlled to be 150-300 (L/mm) 2 Min), the water quantity ratio of the upper header and the lower header is less than or equal to 0.5. The finish rolling stage mainly promotes austenite deformation, increases nucleation positions, and simultaneously promotes formation of deformation-induced ferrite through control of temperature and deformation rate in the low-temperature rolling process; air cooling for a short time after rolling promotes precipitation of fine carbonitrides and forms part of ferrite; can be obtained by adopting low final coolingSupersaturated microstructure is adopted to form a high-hardness microstructure mainly comprising bainite, so that hardness difference of soft and hard phases in the microstructure is increased; the problem of difference between microstructure and performance in the length direction caused by heat dissipation and the like before water cooling is started is solved by controlling the difference of the final cooling temperature in the length direction of the steel plate, and the uniformity of the performance of the steel plate is improved; the adoption of the front-fast and rear-slow sectional water cooling process can accelerate the cooling of the high-temperature section, inhibit the high-temperature phase change, reduce the internal stress by the smaller cooling water quantity of the low-temperature section and improve the shape of the cooled plate.
The microstructure of the high-strain-strength low-yield-ratio pipe line width thick plate is polygonal ferrite, bainite and carbonitride precipitation, the volume percentage of the polygonal ferrite is 30% -80%, the ferrite quantity of 12 μm and below is more than 60% of the total ferrite quantity, the lath bainite in the bainite structure is more than or equal to 40%, the hardness difference between the polygonal ferrite and the bainite is more than or equal to 60HV, the matrix contains 0.02% -0.07% of carbonitride precipitation by mass percentage, and the carbonitride precipitation below 10nm is more than or equal to 30% of the total carbonitride precipitation quantity. The steel plate has the comprehensive technical characteristics of high strength, high crack-arresting toughness, high strain strengthening property, low yield ratio, low welding softening property, thick specification and the like, and meets the requirements of manufacturing pipelines in areas with complex geology and environment such as ocean, high and cold, geology active areas, crossing areas and the like.
The invention has the beneficial effects that:
(1) The components of the invention are based on C, mn, cr, V, a low Mn design is adopted, the yield strength and the yield ratio are properly reduced, the tensile strength is ensured by adding Cr and Si, and the content control of V, C, N is adopted, so that the beneficial effect of V is utilized to obtain a proper amount of V (CN) precipitation while the strengthening effect is exerted, thereby realizing the beneficial effects on phase change and welding softening and improving the comprehensive performance; the adverse effect on toughness is reduced by reducing P, S, H, O content and controlling continuous casting billet quality and the like; the production processes of smelting, heating, rolling, cooling and the like matched with alloy components are matched, so that the difficult problem of matching comprehensive technical characteristics of high strength, high crack-stopping toughness, high strain strengthening property, low yield ratio, low welding softening property, thick specification and the like of the high-strain-strengthened pipe line width thick plate is solved.
(2) The composition design and the production method of the invention obtain the microstructure of polygonal ferrite and bainite, the proportion of each phase, the grain size, the hardness difference of the soft phase and the hard phase and the like are controlled ideally, and simultaneously, a large number of tiny precipitation in dispersion distribution is obtained, thereby playing an important role in improving the performance of the steel plate.
(3) The thickness of the high-strain-strength low-yield-ratio pipe line width thick plate is more than or equal to 25mm, the width is more than 1600mm, the transverse yield strength can reach 420-520 MPa, the transverse tensile strength reaches 620-700 MPa, the transverse yield ratio is less than 0.75, the transverse impact power average value at minus 60 ℃ is more than or equal to 250J, and the transverse DWTT shearing area at minus 20 ℃ is more than or equal to 85%; the longitudinal yield strength can reach 400-500 MPa, the longitudinal tensile strength can reach 600-680 MPa, and the longitudinal uniform elongation U EL The longitudinal yield ratio is more than or equal to 11 percent and less than 0.73, the longitudinal strain hardening index is more than or equal to 0.11, the strength of the steel pipe manufactured by the steel plate can reach X70 grade, and the softening rate of the welded joint is less than or equal to 15 percent.
Drawings
FIG. 1 is a typical microstructure of example 1 of the present invention.
FIG. 2 is a typical precipitated phase diagram of example 1 of the present invention.
Detailed Description
The invention is further illustrated by the following examples.
According to the technical scheme, the embodiment of the invention carries out smelting, continuous casting, heating, rolling and cooling.
In the continuous casting process, the casting superheat degree of the continuous casting blank is 10-30 ℃, the continuous casting is performed under weak cooling and dynamic light pressure, the reduction is more than or equal to 4mm, the continuous casting blank pulling speed is 0.8-1.2 m/min, the central segregation of the continuous casting blank is less than or equal to C1.0 level, and the central looseness is less than or equal to 1.0 level.
The continuous casting blank is heated in multiple stages of a preheating section, a heating section 1, a heating section 2, a heating section 3 and a soaking section, the total heating time is 1.1 min/mm-2.0 min/mm, and the tapping temperature is 1100-1140 ℃.
The initial rolling temperature of rough rolling is 1080-1120 ℃, and the final rolling temperature of rough rolling is 970-1030 ℃, wherein the rough rolling adopts transverse and longitudinal rolling, and the continuous casting billet is rapidly cooled after the transverse rolling is finished, and the average cooling speed is more than or equal to 2 ℃/s; the longitudinal rolling starting temperature is below 1050 ℃, the total deformation rate of longitudinal rolling is more than or equal to 30%, the deformation rate of each pass is more than or equal to 15%, the deformation rate is gradually increased one by one, and the rough rolling speed is 1.0 m/s-1.8 m/s;
the thickness of the intermediate blank to be warmed is 2.8 to 4.5t, wherein t is the thickness of the finished steel plate;
the initial rolling temperature of the finish rolling is 800-850 ℃, the final rolling temperature of the finish rolling is 700-760 ℃, wherein the total deformation rate below 780 ℃ is more than or equal to 15%, the finish cooling temperature is 50-140 ℃ after air cooling for 20-80 s after rolling.
Preferably, the temperature of the steel plate in the length direction after final cooling is gradually reduced, and the difference of the final cooling temperature of the head part and the tail part of the steel plate in length is 30-70 ℃.
Preferably, the cooling process adopts sectional water cooling, and when the temperature of the steel plate is more than or equal to 400 ℃, the water quantity of the upper header pipe is controlled to be 400-600 (L/mm) 2 Min); when the temperature of the steel plate is less than 400 ℃, the water quantity of the upper header pipe is controlled to be 150-300 (L/mm) 2 Min), the water quantity ratio of the upper header and the lower header is less than or equal to 0.5.
The composition of the steel of the example of the invention is shown in Table 1. The main technological parameters of continuous casting and heating of the steel of the embodiment of the invention are shown in Table 2. The main process parameters of rough rolling of the steel of the embodiment of the invention are shown in Table 3. The main process parameters of the finish rolling and cooling of the steel of the embodiment of the invention are shown in table 4. The properties of the inventive example steels are shown in Table 5. The microstructure of the steel of the example of the invention is shown in Table 6.
TABLE 1 composition (wt%) of the inventive example steel
TABLE 2 main process parameters for continuous casting and heating of the inventive example steel
TABLE 3 main process parameters for roughing the inventive example steels
TABLE 4 essential process parameters for finishing and cooling of the inventive example steel
Note that: the tensile sample is a full-thickness rectangular sample, and the width of a parallel test section plate is 38.1mm; the impact specimen had a size of 10.55.55 mm.
TABLE 5 Properties of the inventive example Steel
TABLE 6 microstructure of example steels according to the invention
The present invention has been properly and fully described in the above examples, which are intended to be illustrative only and not limiting, various changes and modifications can be made by one skilled in the art without departing from the spirit and scope of the present invention, and any modifications, equivalent substitutions, improvements, etc. should be included in the scope of the present invention, which is defined by the appended claims.
Claims (5)
1. The high-strain-strength low-yield-ratio thick plate with the line width is characterized by comprising the following components in percentage by weight: c:0.050% -0.080%, si:0.26% -0.45%, mn:1.30% -1.49%, nb:0.010% -0.039%, V:0.051% -0.079%, 0.005% -0.008% of N, ti:0.008% -0.020%, cr:0.15% -0.25%, mo < 0.10%, ni < 0.12%, al:0.010% -0.025%, P is less than or equal to 0.010%, S is less than or equal to 0.002%, H is less than or equal to 0.00015%, and O is less than or equal to 0.0020%; wide and thick plate CE IIW Controlled to be 0.35% -0.40%, CE Pcm Controlled to be 0.15% -0.19%, wherein CE IIW =C+Mn/6+(Cr+Mo)/5+(Ni+Cu)/15 ，CE Pcm =c+si/30+ (mn+cu+cr)/20+ni/60+mo/15+v/10+5b, the balance being iron and unavoidable impurities; nb+v in wide and thick plate: 0.06% -0.10% and Ti/N is less than or equal to 3; the microstructure of the wide-thickness plate is polygonal ferrite, bainite and carbonitride precipitation, the volume percentage of polygonal ferrite is 30% -80%, the ferrite quantity of 12 mu m and below is more than 60% of the total ferrite quantity, the lath bainite in the bainitic structure is more than or equal to 40%, the hardness difference between polygonal ferrite and bainite is more than or equal to 60HV, the steel plate matrix contains 0.02% -0.07% of carbonitride precipitation by mass, wherein the carbonitride precipitation below 10nm is more than or equal to 30% of the total carbonitride precipitation quantity;
the production method of the high-strain-strengthening low-yield-ratio pipe line width thick plate comprises smelting, continuous casting, heating, rolling and cooling;
the initial rolling temperature of rough rolling is 1080-1120 ℃, and the final rolling temperature of rough rolling is 970-1030 ℃; wherein, the rough rolling adopts transverse and longitudinal rolling, and after the transverse rolling is finished, the continuous casting billet is rapidly cooled, and the average cooling speed is more than or equal to 2 ℃/s; the longitudinal rolling starting temperature is below 1050 ℃, the total deformation rate of longitudinal rolling is more than or equal to 30%, the deformation rate of each pass is more than or equal to 15%, the deformation rate is gradually increased each pass, and the rough rolling speed is 1.0 m/s-1.8 m/s;
the thickness of the intermediate blank to be warmed is 2.8-4.5 t, wherein t is the thickness of a finished steel plate;
the initial rolling temperature of the finish rolling is 800-850 ℃, the final rolling temperature of the finish rolling is 700-760 ℃, the total deformation rate below 780 ℃ is more than or equal to 15%, water cooling is carried out after air cooling for 20-36 s after rolling, and the final cooling temperature is 50-140 ℃;
the cooling process adopts sectional water cooling, when the temperature of the steel plate is more than or equal to 400 ℃, the water quantity of the upper header pipe is controlled to be 400-600L/m 2 * min; when the temperature of the steel plate is less than 400 ℃, controlling the water quantity of the cooling upper header to be 150-300L/m 2 * min, the water quantity ratio of the upper header and the lower header is less than or equal to 0.5.
2. The high strain strengthened low yield ratio pipe linewidth thick plate according to claim 1, wherein the thickness of the thick plate is more than or equal to 25mm, the width is more than 1600mm, the transverse yield strength is 420-520 MPa, and the transverse tensile strength is 620-700MPa, transverse yield ratio is less than 0.75, transverse impact energy average value at minus 60 ℃ is more than or equal to 250J, transverse DWTT shearing area at minus 20 ℃ is more than or equal to 85%; the longitudinal yield strength is 400-500 MPa, the longitudinal tensile strength is 600-680 MPa, and the longitudinal uniform elongation U is achieved EL More than or equal to 11 percent, the longitudinal yield ratio is less than 0.73, the longitudinal strain hardening index is more than or equal to 0.11, and the softening rate of the welded joint is less than or equal to 15 percent.
3. The high strain strengthened low yield ratio thick plate with line width according to claim 1, wherein the temperature of the steel plate in the length direction after final cooling is gradually reduced, and the temperature difference of the head and the tail of the steel plate is 30-70 ℃.
4. The high-strain-strengthening low-yield-ratio pipe linewidth thick plate according to claim 1, wherein in the continuous casting process, the casting superheat of a continuous casting billet is 10-30 ℃, the continuous casting is performed by weak cooling and dynamic soft reduction, the reduction is more than or equal to 4mm, the continuous casting billet pulling speed is 0.8-1.2 m/min, the center segregation of the continuous casting billet is less than or equal to C1.0 level, and the center porosity is less than or equal to 1.0 level.
5. The high-strain-strengthening low-yield-ratio thick plate with the line width of the pipe according to claim 1, wherein the continuous casting blank is heated in multiple stages of a preheating section, a heating section 1, a heating section 2, a heating section 3 and a soaking section, the total heating time is 1.1-2.0 min/mm, and the tapping temperature is 1121-1140 ℃.
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