CN111575582A - Thick-specification wide X65M pipeline steel hot-rolled coil and manufacturing method thereof - Google Patents
Thick-specification wide X65M pipeline steel hot-rolled coil and manufacturing method thereof Download PDFInfo
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
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- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C21D2211/00—Microstructure comprising significant phases
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Abstract
The invention discloses a thick and wide X65M pipeline steel hot-rolled coil and a manufacturing method thereof, wherein the hot-rolled coil comprises the following chemical components in percentage by mass: 0.06-0.08%, Si is less than or equal to 0.25%, Mn: 1.45% -1.60%, Nb: 0.045-0.055%, Ti: 0.020-0.030%, Cr: 0.25% -0.35%, Mo: 0.09% -0.12%, Alt: 0.020-0.050%, P less than or equal to 0.015%, S less than or equal to 0.008%, and the balance of Fe and inevitable impurities. The invention adopts the component design of C-Mn-Nb-Ti-Cr-Mo alloy and combines the pure steel smelting and TMCP controlled rolling and controlled cooling process to obtain the hot-rolled coil with low cost and excellent comprehensive performance.
Description
Technical Field
The invention belongs to the technical field of high-purity low-alloy high-strength steel products at an outlet, particularly relates to a thick and wide X65M pipeline steel hot-rolled coil and a manufacturing method thereof, and particularly relates to an L450M/X65M pipeline steel hot-rolled coil for a thick and wide (not less than 19mm) seawater desalination conveying welded pipe (such as high-frequency resistance welding or submerged arc spiral welding) and a manufacturing method thereof.
Background
The X65M extreme specification pipeline steel hot-rolled coil is used for engineering construction of the Saudi Arabic sea water desalination project. The project mainly adopts a spiral welded pipe with large pipe diameter and wall thickness, and the coiled plate has high required strength and good performance stability due to the influence of geographical environment.
Document CN 106282798A discloses thick gauge X65 pipeline steel and a production method thereof, wherein the pipeline steel comprises the chemical components of C: 0.03-0.06%, Si: 0.10-0.30%, Mn: 1.40-1.60%, P: less than or equal to 0.020%, S: less than or equal to 0.010 percent, Nb: 0.030-0.039%, V: 0.06-0.08%, Ti: 0.008-0.019%, Cr: 0.15-0.30%. Although the low content of C in the document is beneficial to the low-temperature toughness of the product, the cost of V noble element addition is high, the heating temperature is high, the energy consumption is high, and the production cost is overhigh.
Document CN 102851599B discloses a thick-walled low-cost X65 hot-rolled coil for spiral welded pipes and a manufacturing method thereof, which discloses chemical components of C: 0.05-0.10%, Si: 0.10-0.30%, Mn: 1.50-1.65%, P is less than or equal to 0.020%, S is less than or equal to 0.008%, Ti: 0.008% -0.020%, Als: 0.02% -0.06%, Nb: 0.04-0.07%, Cr: 0.10% -0.20%, V: 0.03 to 0.06 percent. The content range of C in the document is wide, the upper limit is close to a peritectic region, and the quality control of a casting blank is not facilitated; v is added with a large amount of noble elements, so that the cost is high and the environmental protection is poor; the heating temperature range in the production method is large, which is not beneficial to the stable control of the temperature in the rolling process, and the high upper limit of the temperature and the large energy consumption. And the adopted 170mm intermediate blank causes that the compression ratio is not high, which is not beneficial to ensuring the toughness of the product.
Document CN 106811699 a discloses an X65 hot-rolled coil for ERW and a manufacturing method thereof, which discloses the following components: c: 0.07 to 0.10 percent of Si: 0.10-0.30%, Mn: 1.10-1.25%, P is less than or equal to 0.018%, S is less than or equal to 0.005%, Ti: 0.008% -0.020%, Als: 0.02% -0.06%, Nb: 0.010% -0.019%, Cr: 0.30 to 0.50 percent. The content range of the document C is wide, the upper limit of the document C is close to a peritectic region, the quality control of a casting blank is not facilitated, and the content of Mn and Nb is not high so as to ensure the strength of thick-specification products. And the steel-making process has no RH vacuum treatment process, is not beneficial to removing harmful gas, and cannot be applied to the technical conditions of products requiring vacuum treatment. In addition, the heating temperature range is large, which is not beneficial to the stable control of the temperature in the rolling process, and the high upper limit of the temperature and the large energy consumption are realized.
Disclosure of Invention
In view of one or more of the problems in the prior art, one aspect of the present invention provides a thick and wide X65M pipeline steel hot rolled coil, which comprises the following chemical components by mass percent: 0.06-0.08%, Si is less than or equal to 0.25%, Mn: 1.45% -1.60%, Nb: 0.045-0.055%, Ti: 0.020-0.030%, Cr: 0.25% -0.35%, Mo: 0.09% -0.12%, Alt: 0.020-0.050%, P less than or equal to 0.015%, S less than or equal to 0.008%, and the balance of Fe and inevitable impurities.
The mechanical properties of the hot-rolled coil meet the following requirements: yield strength Rt0.5Not less than 480MPa, tensile strength Rm not less than 600MPa, and elongation A50Not less than 40 percent, the Charpy impact power Akv at 0 ℃ is not less than 200J, and the Vickers hardness HV10 is not more than 235.
The thickness of the hot-rolled coil plate is more than or equal to 19mm, and the width of the hot-rolled coil plate is more than or equal to 1850 mm.
The invention also provides a manufacturing method of the thick-specification wide X65M pipeline steel hot-rolled coil, which comprises the following steps: KR molten iron desulfurization pretreatment, converter top and bottom blowing, LF furnace refining, RH vacuum treatment, slab continuous casting, reheating furnace, rough rolling high-pressure water descaling, fixed width press, E1R1 rough rolling mill, E2R2 rough rolling mill, flying shear, finish rolling high-pressure water descaling, F1-F7 finishing rolling mill, encrypted laminar cooling, coiling, tray transportation system, sampling and inspection; wherein:
after smelting raw materials are subjected to KR molten iron desulphurization pretreatment, converter top and bottom blowing, LF furnace refining, RH vacuum treatment and slab continuous casting processes in sequence, the formed continuous casting billet meets the conditions that P is less than or equal to 0.015 percent and S is less than or equal to 0.008 percent; wherein the vacuum degree of RH vacuum treatment is required to be less than or equal to 2.6mbar, and the vacuum maintaining time is more than or equal to 10 min; ensuring that the circulating pure degassing time is more than or equal to 7min during the RH vacuum treatment period; after RH vacuum treatment is finished, calcium wires are fed for calcium treatment, and soft blowing time is guaranteed to be more than 8min after wire feeding;
the method comprises the following steps of rolling by using a 2250mm hot continuous rolling unit in a rolling stage, wherein the thickness of the continuous casting is 230mm, heating the continuous casting to 1150-1175 ℃ by using a stepping heating furnace, discharging, performing two-stage controlled rolling by using a rough rolling unit and a finishing rolling unit, wherein the rolling pass is 3+5, the mode is 8 passes in total, the thickness of an intermediate billet is larger than or equal to 55mm, the starting temperature of finish rolling is smaller than or equal to 990 ℃, the finishing temperature of finish rolling is 815-855 ℃, uniformly cooling by using a front concentrated laminar cooling mode, namely, the speed of 20-30 ℃/s, and coiling at 500-540.
The manufacturing method of the thick-specification wide-width X65M pipeline steel hot-rolled coil provided based on the technical scheme is characterized in that C-Mn-Nb-Ti-Cr-Mo steel is taken as a main material, alloy component design of noble metals such as V, Ni and Cu is omitted, and pure steel smelting and TMCP controlled rolling and cooling processes are combined, so that the thick-specification wide-width X65M pipeline steel hot-rolled coil which is low in cost, suitable for seawater transportation and excellent in comprehensive performance is finally produced. Compared with the prior art, the invention has the following beneficial effects:
(1) in view of the rising price of V-iron alloy in recent two years and the cost increase of raw materials of a plurality of iron and steel enterprises, the invention reasonably utilizes proper amount of Si, Mn and Mo alloy to replace the V-iron alloy. The invention realizes the purposes of cost reduction, efficiency improvement and environmental protection of enterprises by adding trace Nb, Ti, Mo and Cr alloy elements and removing expensive and heavy pollution metals V, Ni and Cu, and is suitable for the production of thick and wide pipeline steel hot-rolled coils.
(2) As the thick-specification wide-width high-strength coil plate is examined for rolling load, when rolling wide-width X65M pipeline steel in many prior arts, the short-pass rolling is difficult to simultaneously consider the rough rolling load and the pass reduction rate more than or equal to 20%. Therefore, in order to ensure that the lower finish rolling inlet temperature avoids the damage of recrystallization to the toughness, and simultaneously, the rolling rhythm is not influenced, the lower tapping temperature is very important, so that the toughness of the product can be ensured to a certain extent, the overload of a rolling mill is avoided, the production efficiency is high, the operability is strong, and the performance is stable.
In conclusion, the L450M/X65M hot-rolled coil which has excellent mechanical properties and low cost is obtained, the coil can be used for oil and gas transmission pipeline construction engineering, various indexes of the product not only meet the technical requirements of users, but also have outstanding economic benefits and good social benefits, and the manufacturing method has simple process control and high production efficiency.
Drawings
FIG. 1 is a metallographic structure photograph of a hot-rolled coil obtained in example 1 of the present invention.
Detailed Description
The invention aims to provide a thick and wide X65M pipeline steel hot-rolled coil with stable product performance and low cost, and provides a manufacturing method of the thick and wide X65M pipeline steel hot-rolled coil with low cost, high production efficiency, simple process control and strong operability, which mainly adopts C-Mn-Nb-Ti-Cr-Mo steel as a main starting point, cancels alloy design of V, Ni and Cu noble metals, and combines pure steel smelting and TMCP controlled rolling and controlled cooling processes to finally produce a product with low cost, suitability for seawater transportation and excellent comprehensive performance.
The thick and wide X65M pipeline steel hot-rolled coil comprises the following chemical components in percentage by mass: 0.06-0.08%, Si is less than or equal to 0.25%, Mn: 1.45% -1.60%, Nb: 0.045-0.055%, Ti: 0.020-0.030%, Cr: 0.25% -0.35%, Mo: 0.09% -0.12%, Alt: 0.020-0.050%, P less than or equal to 0.015%, S less than or equal to 0.008%, and the balance of Fe and inevitable impurities.
The main elements in the chemical composition are selected based on the following principle:
c: the C content in the steel increases, the yield strength and the tensile strength increase, but the ductility and the toughness decrease. For pipeline steel, if the carbon content is too high, the toughness of the steel is rapidly reduced, and the weldability is deteriorated, so that the design idea of adopting low-carbon components is a precondition for designing high-toughness pipeline products. Therefore, the carbon content is controlled to be less than or equal to 0.08 percent.
Si: the deoxidizing element is dissolved in the ferrite to improve the strength of the steel, but the plasticity and the toughness are lost, the Si content is not too high, and the general control range is 0.15-0.25%.
Mn: manganese can be infinitely replaced and dissolved with iron, is a good solid solution strengthening element, is mainly used for compensating strength loss caused by reduced content of C in pipeline steel, and is the most important and most economic strengthening element. Mn is also an element for expanding a gamma phase region, can reduce the gamma-alpha phase transition temperature of steel, is beneficial to obtaining a fine phase transition product, and can improve the toughness of the steel and reduce the ductile-brittle transition temperature. Therefore, the manganese content of the invention is 1.45-1.60%.
Nb: niobium has the effect of increasing the strength and toughness of steel and is the most typical and most widely used microalloying element. Niobium carbonitrides may precipitate from austenite during heating and rolling, or at phase boundaries during transformation, or from supersaturated ferrite during final cooling to refine the grains. Niobium is most obvious in improving austenite recrystallization temperature and reducing brittle transition temperature, but Nb is a precious element, so that the niobium content is controlled to be 0.045% -0.055%.
Ti: titanium has strong affinity with carbon and nitrogen in the heating and solidification processes, forms very stable TiC and TiN particles which are enriched at a crystal boundary, forms insoluble second phase particles to block the migration and dislocation motion of the crystal boundary, has the function of strongly preventing the growth of the crystal particles, and has obvious effect of improving the fracture toughness of a heat affected zone during steel welding. Therefore, the Ti content is controlled to be 0.020-0.030 percent.
Mo: can effectively improve the hardenability of steel, enlarge a gamma phase region, reduce the gamma-alpha phase transformation temperature, inhibit the formation of Polygonal Ferrite (PF), promote the transformation of Acicular Ferrite (AF), improve the precipitation strengthening effect of Nb (C, N), and improve the strength and fracture toughness of steel. Due to the rapid increase in the price of V iron in the last two years, more and more steel mills are looking for other elements to replace it. The content of the added small amount of Mo is controlled to be 0.09-0.12%.
Cr: cr can improve hardenability, so that the steel has better comprehensive mechanical properties after quenching. However, the cost of Cr alloy is also high, so the content of Cr is generally controlled to be 0.25-0.40%.
And (3) Alt: the deoxidizing element is added with a proper amount of aluminum to form fine and dispersed AlN particles, which is beneficial to refining crystal grains and improving the toughness of steel, and the content of Alt is controlled to be 0.020-0.050%.
P, S: is an inevitable impurity element in steel, the lower the content of the impurity element is, the better the content of the impurity element is, but the lower the content of the impurity element is, the production cost is increased, and the P is less than or equal to 0.015 percent and the S is less than or equal to 0.008 percent.
In summary, in the alloy composition design adopted by the invention, the elements are coordinated to play a role, and the coordination relationship between any element or the content change of the element and other elements is changed, so that the comprehensive mechanical property of the product is influenced, and therefore, the overall design of the alloy composition is closely related to the comprehensive mechanical property of the final product.
The manufacturing method provided by the invention comprises the following processes: KR desulfurization, converter, LF furnace, RH, slab continuous casting, reheating furnace, rough rolling high-pressure water descaling, fixed width press, E1R1 rough rolling machine, E2R2 rough rolling machine, heat preservation cover, flying shear, finish rolling high-pressure water descaling, F1-F7 finishing rolling machine, encrypted laminar cooling, coiling, tray transportation system, sampling and inspection, wherein:
smelting raw materials are sequentially subjected to KR molten iron desulphurization pretreatment, converter top and bottom blowing, LF refining, RH refining and continuous casting process treatment to form a high-purity continuous casting billet, wherein P is less than or equal to 0.015%; s is less than or equal to 0.008 percent; the vacuum degree requirement of the RH procedure is less than or equal to 2.6mbar, and the vacuum maintaining time is more than or equal to 10 min. The pure degassing time of circulation is ensured to be more than or equal to 7min during the RH vacuum treatment period. And after the RH vacuum treatment is finished, feeding a calcium wire for calcium treatment, and ensuring that the soft blowing time is more than 8min after wire feeding. And adopting a continuous casting billet soft reduction technology to control center segregation.
The method comprises the steps of rolling by a 2250mm hot continuous rolling unit, wherein the thickness of the continuous casting is 230mm, heating the continuous casting to 1150-1175 ℃ by a stepping heating furnace, discharging, performing two-stage controlled rolling by a rough rolling unit and a finish rolling unit, wherein the rolling pass is 3+5 in a mode of 8 passes, the thickness of an intermediate billet is not less than 55mm, the start rolling temperature of finish rolling is not more than 990 ℃, the finish rolling temperature is 815-855 ℃, uniformly cooling by adopting a front concentrated laminar cooling mode, namely, the speed of 20-30 ℃/s, and coiling at 500-540 ℃.
The present invention will be described in detail below with reference to specific examples.
Examples
The chemical compositions of examples 1 to 4 are shown in table 1 below, the specific process system adopted in each example is shown in table 2 below, and the mechanical properties of the hot-rolled coils obtained in each example are shown in table 3 below.
Table 1: examples chemical composition (wt%)
Table 2: example Process regime
Table 3: mechanical Properties of example steels
Note that tensile test and impact test
As can be seen from the embodiment, the steel of the embodiment of the invention has the advantages that the chemical components and the mechanical properties meet the requirements of the API5L standard, the surplus is moderate, and the yield strength R ist0.5Greater than or equal to 480MPa (even greater than or equal to 500MPa), tensile strength Rm greater than or equal to 600MPa (even greater than or equal to 635MPa), and elongation A50Not less than 40 percent, the Charpy impact power Akv at 0 ℃ is not less than 200J, and the Vickers hardness HV10 is not more than 235. Other technical indexes completely meet the technical requirements of X65M hot-rolled coils for seawater desalination projects. FIG. 1 is a photograph showing the metallographic structure of the hot rolled coil obtained in example 1, and it can be seen that the metallographic structure is acicular ferrite + bainite, the grains are fine and uniform, the strip structure is absent, and the grain size is 11.5 grade or more. Therefore, the thick-specification wide-width X65M pipeline steel hot-rolled coil provided by the invention has excellent mechanical properties, stable product performance, low manufacturing method cost, high production efficiency, simple process control and strong operability, and is suitable for large-scale popularization and use.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A thick-specification wide X65M pipeline steel hot-rolled coil is characterized in that the hot-rolled coil comprises the following chemical components in percentage by mass: 0.06-0.08%, Si is less than or equal to 0.25%, Mn: 1.45% -1.60%, Nb: 0.045-0.055%, Ti: 0.020-0.030%, Cr: 0.25% -0.35%, Mo: 0.09% -0.12%, Alt: 0.020-0.050%, P less than or equal to 0.015%, S less than or equal to 0.008%, and the balance of Fe and inevitable impurities.
2. The hot rolled steel sheet as claimed in claim 1, wherein the hot rolled steel sheet has mechanical propertiesCan satisfy the following conditions: yield strength Rt0.5Not less than 480MPa, tensile strength Rm not less than 600MPa, and elongation A50Not less than 40 percent, the Charpy impact power Akv at 0 ℃ is not less than 200J, and the Vickers hardness HV10 is not more than 235.
3. The hot rolled coil as claimed in claim 1 or claim 2, wherein the hot rolled coil has a thickness of 19mm or more and a width of 1850mm or more.
4. The method of manufacturing a thick gauge wide X65M pipeline steel hot rolled coil as claimed in any one of claims 1 to 3, comprising the process of: KR molten iron desulfurization pretreatment, converter top and bottom blowing, LF furnace refining, RH vacuum treatment, slab continuous casting, reheating furnace, rough rolling high-pressure water descaling, fixed width press, E1R1 rough rolling mill, E2R2 rough rolling mill, flying shear, finish rolling high-pressure water descaling, F1-F7 finishing rolling mill, encrypted laminar cooling, coiling, tray transportation system, sampling and inspection; wherein:
after smelting raw materials are subjected to KR molten iron desulphurization pretreatment, converter top and bottom blowing, LF furnace refining, RH vacuum treatment and slab continuous casting processes in sequence, the formed continuous casting billet meets the conditions that P is less than or equal to 0.015 percent and S is less than or equal to 0.008 percent; wherein the vacuum degree of RH vacuum treatment is required to be less than or equal to 2.6mbar, and the vacuum maintaining time is more than or equal to 10 min; ensuring that the circulating pure degassing time is more than or equal to 7min during the RH vacuum treatment period; after RH vacuum treatment is finished, calcium wires are fed for calcium treatment, and soft blowing time is guaranteed to be more than 8min after wire feeding;
the method comprises the following steps of rolling by using a 2250mm hot continuous rolling unit in a rolling stage, wherein the thickness of the continuous casting is 230mm, heating the continuous casting to 1150-1175 ℃ by using a stepping heating furnace, discharging, performing two-stage controlled rolling by using a rough rolling unit and a finishing rolling unit, wherein the rolling pass is 3+5, the mode is 8 passes in total, the thickness of an intermediate billet is larger than or equal to 55mm, the starting temperature of finish rolling is smaller than or equal to 990 ℃, the finishing temperature of finish rolling is 815-855 ℃, uniformly cooling by using a front concentrated laminar cooling mode, namely, the speed of 20-30 ℃/s, and coiling at 500-540.
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| CN112981258B (en) * | 2021-02-09 | 2022-03-22 | 鞍钢股份有限公司 | X70M hot-rolled steel plate for thin-specification gas transmission straight welded pipe and manufacturing method |
| CN112981254B (en) * | 2021-02-09 | 2022-03-22 | 鞍钢股份有限公司 | Wide high-strength high-toughness thick-wall X80M pipeline steel plate and manufacturing method thereof |
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