CN118127419A - L415 grade pipeline steel hot rolled coil for ground gathering and conveying and production method thereof - Google Patents
L415 grade pipeline steel hot rolled coil for ground gathering and conveying and production method thereof Download PDFInfo
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- 230000007797 corrosion Effects 0.000 claims abstract description 59
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 14
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 13
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 12
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 11
- 229910052742 iron Inorganic materials 0.000 claims abstract description 9
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 9
- 239000000126 substance Substances 0.000 claims abstract description 7
- 239000012535 impurity Substances 0.000 claims abstract description 5
- 238000005096 rolling process Methods 0.000 claims description 59
- 230000009467 reduction Effects 0.000 claims description 27
- 238000001816 cooling Methods 0.000 claims description 23
- 238000009749 continuous casting Methods 0.000 claims description 17
- 238000010438 heat treatment Methods 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 11
- 238000007670 refining Methods 0.000 claims description 11
- 238000003723 Smelting Methods 0.000 claims description 9
- 238000007664 blowing Methods 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 8
- 239000011575 calcium Substances 0.000 claims description 6
- 229910052791 calcium Inorganic materials 0.000 claims description 5
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 4
- 238000006477 desulfuration reaction Methods 0.000 claims description 4
- 230000023556 desulfurization Effects 0.000 claims description 4
- 238000003825 pressing Methods 0.000 claims description 3
- 239000000047 product Substances 0.000 description 25
- 239000011572 manganese Substances 0.000 description 13
- 229910045601 alloy Inorganic materials 0.000 description 11
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- 238000013461 design Methods 0.000 description 7
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- 238000005728 strengthening Methods 0.000 description 6
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical class [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 3
- 229910001566 austenite Inorganic materials 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910000510 noble metal Inorganic materials 0.000 description 3
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- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
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- 238000001556 precipitation Methods 0.000 description 2
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- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 229910000677 High-carbon steel Inorganic materials 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
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- VREFGVBLTWBCJP-UHFFFAOYSA-N alprazolam Chemical compound C12=CC(Cl)=CC=C2N2C(C)=NN=C2CN=C1C1=CC=CC=C1 VREFGVBLTWBCJP-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000010779 crude oil Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
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- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical class Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 1
- 238000000840 electrochemical analysis Methods 0.000 description 1
- 238000006056 electrooxidation reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
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- 238000006467 substitution reaction Methods 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The invention relates to an L415 grade pipeline steel hot rolled coil for ground gathering and transportation and a production method thereof, wherein the chemical components in steel are C：0.061％～0.070％、Si：0.15％～0.25％、Mn：0.39％～0.48％、P≤0.012％、S：0.0028％～0.003％、Als：0.030％～0.045％、Nb：0.024％～0.030％、Ti：0.032％～0.038％、Cr：0.25％～0.31％、N≤0.004％, and the balance is iron and impurities. The yield strength of the hot rolled coil finished product is 426-477 MPa, the tensile strength is 557-570 MPa, and the elongation after fracture is more than or equal to 37%; the Charpy impact energy Akv at the temperature of minus 40 ℃ is more than or equal to 319J, the corrosion rate is 0.0240-0.0276 mm/a, the corrosion potential is more than or equal to minus 0.458V, and the corrosion current density is less than or equal to 1.08X10 ‑5A·cm‑2.
Description
Technical Field
The invention relates to the technical field of production of low-alloy hot-rolled coils, in particular to an L415-grade pipeline steel hot-rolled coil for ground gathering and transportation and a production method thereof.
Background
The ground gathering and transporting pipeline is mainly used for transporting crude oil, sewage, natural gas and other substances, and pipeline corrosion failure events such as perforation, leakage, pipe explosion and the like are frequent due to the fact that a certain amount of chloride ions are contained in a transporting medium. At present, 20# steel, 16Mn, stainless steel or corrosion resistant alloy is used for the ground gathering pipeline adopted by each large oil-gas field, wherein the stainless steel and the corrosion resistant alloy cannot be popularized and used in a large area due to high cost, and the ground gathering pipeline adopting the 20# steel and the 16Mn materials is designed by high carbon steel, so that a large amount of Mo, cr, ni and Cu elements are required to be added to ensure the corrosion resistance of the ground gathering pipeline, and the alloy cost is high. Therefore, there is an urgent need to develop a steel for a ground gathering line, which is low in cost, strong in corrosion resistance and excellent in comprehensive mechanical properties.
The Chinese patent application No. CN201310368061.9 discloses a kind of steel for pipeline with resistance to corrosion of chloride ion and its preparation method, its composition is (weight percentage )：C 0.008％～0.02％,Si 0.05％～0.015％,Mn0.50％～0.85％,S≤0.010％,P≤0.01％,Mo 0.8％～2.0％,Al 0.001％～0.020％,Ni 0.50～1.2％,W 0.02～0.08wt％,Cr satisfies the inequality of 2.4-0.49[ Mo ] +11.8[ C ] +12.2[ W ]. Ltoreq.Cr.ltoreq.3.2-0.57 [ Mo ] +9.8[ C ] +7.2[ W ]. But its steel for pipeline is added with Mo, ni and W, resulting in higher alloy cost.
The Chinese patent application with the application number of CN201910420753.0 discloses a steel with yield strength of 500MPa grade and resistance to various medium corrosion and a preparation method thereof, wherein the steel comprises the components (the weight percentage of )：C 0.06％～0.10％,Si0.15％～0.40％,Mn 0.70％～1.20％,P≤0.025％,S≤0.01％,Cu 0.20％～0.40％,Ni 0.20～0.50％,Cr 0.50～1.0％,Sb 0.02～0.12％,Sn 0.005～0.030％,Nb 0.02～0.05％,Ti 0.015％～0.025％,Ca 0.001％0～0.003％,N≤0.006％. is that Sb, sn and Ni are added into the steel, so that the alloy cost is higher, the yield strength of the steel is more than or equal to 500MPa, but the impact energy at minus 40 ℃ is only 80J, and the product toughness is not well matched, so that the steel is not the preferred material of a ground gathering pipeline.
The patent No. CN201610801713.7 discloses thick X60 pipeline steel and a production method thereof, wherein the thick X60 pipeline steel comprises the following components ()：C 0.03％～0.05％,Si 0.10％～0.30％,Mn 1.30％～1.50％,P≤0.020％,S≤0.010％,Nb 0.025％～0.034％,V 0.05％～0.008％,Ti 0.010％～0.017％,Cr 0.20％～0.30％. is a traditional pipeline steel alloy design, the contents of Mn, P and S are higher, the corrosion resistance is relatively unfavorable, and in addition, the patent does not describe the corrosion resistance of ground gathering and transportation.
(4) The invention discloses a needle-shaped ferrite type X60 grade HIC resistant pipeline steel and a rolling method thereof, and application number CN202010215635.9, which comprises the following components (the weight percentage ),C 0.03％～0.06％,Si 0.15％～0.30％,Mn 0.600％～1.00％,S≤0.003％,P≤0.012％,Nb 0.020％～0.040％,Ti 0.010％～0.020％,Cr 0.20％～0.50％,Mo 0.10％～0.20％,Cu 0.15％～0.30％, product is added with Mo, ti and Cu, the use is obviously different from the invention, and the purpose of the invention is for HIC resistance and the ground gathering and transportation use is also different from the invention).
The Chinese patent application No. CN20131217916.8 discloses a CO2 corrosion resistant pipeline steel for ground gathering and transportation and a preparation method thereof, wherein the steel comprises the following components (weight percentage )：C 0.01％～0.08％,Si 0.10％～0.50％,Mn 0.50％～1.50％,P≤0.020％,S≤0.006％,Nb+V+Ti≤0.1％,Cr 1.0～3.0％,Mo0.10％～0.30％,Cu 0.10％～0.50％,Ni 0.10％～0.50％. but relates to the field of medium plate production, and noble metals such as Mo, ni and the like are added to obtain excellent corrosion resistance and low-temperature toughness, and the yield strength reaches more than 530 MPa.
The Chinese patent application with the application number of CN201410247308.6 discloses a 5Cr corrosion-resistant steel and a production method thereof, wherein the steel comprises the following components in percentage by weight: 0.05 to 0.07 percent of C, 0.10 to 0.30 percent of Si, 0.50 to 0.80 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.01 percent of S, 4.5 to 5.5 percent of Cr and 0.02 to 0.05 percent of N. The method relates to the field of steel for hot rolled steel bars, and has a large difference in mechanical property index requirement from a hot rolled coil product.
The paper "oil casing and gathering pipeline materials corrosion resistance screening evaluation test" (section Fang Wei et al, oil and gas field environmental protection, 2018.6, pages 24-28) mentions gathering pipeline steel, wherein the 20 steel, the 16Mn steel and the X65 steel are all designed by adopting high carbon alloy without Nb and compositely adding Cr, ni, mo and Cu, and the corrosion degree of the steel reaches moderate corrosion and even serious corrosion according to the uniform corrosion rate data provided by the steel, and the steel does not describe the production process and mechanical property of the steel.
The steel for the ground gathering and conveying pipeline related in the above publication is a medium-thickness plate product, noble metals Mo and Ni are basically added in alloy design, and Nb is not added except for the patent application of 'a steel with yield strength of 500MPa and resistance to various medium corrosion' and 'a preparation method of CO2 corrosion resistant pipeline steel for ground gathering and conveying'; the L415 grade pipeline steel hot rolled coil for ground collection and transportation breaks through the inherent thought that the ground collection and transportation steel adopts a high-carbon design, and opens a new way for obtaining enough strength and good corrosion resistance by adopting low-carbon steel.
Disclosure of Invention
The invention provides an L415 grade pipeline steel hot rolled plate coil for ground gathering and conveying and a production method thereof, which adopts C, mn and Si with lower content, and adds a proper amount of Ti to form nearly spherical Ti 4C2S2 which is not easy to deform, so that the product has excellent toughness; nb is added to improve the strengthening effect of fine crystals, and meanwhile, certain TiC is formed to improve the strength; the most economical Cr in the anti-corrosion element is added to obtain excellent corrosion performance, so that the corrosion rate is reduced, and the corrosion potential is improved; adopting low-temperature steel burning, two-stage controlled rolling and cooling to ensure that the final product obtains a fine and uniform microstructure; the small thickness intermediate billet rolling technology breaks through the limit that the thickness of the pipeline steel intermediate billet is more than 3.6 times of the thickness of a finished product, and can reduce the rolling reduction in the finish rolling stage, thereby reducing the dislocation density and further improving the corrosion resistance.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
A hot rolled coil of L415 grade pipeline steel for ground gathering and transportation comprises the chemical components of C：0.061％～0.070％、Si：0.15％～0.25％、Mn：0.39％～0.48％、P≤0.012％、S：0.0028％～0.003％、Als：0.030％～0.045％、Nb：0.024％～0.030％、Ti：0.032％～0.038％、Cr：0.25％～0.31％、N≤0.004％, weight percent of iron and unavoidable impurities.
A production method of an L415 grade pipeline steel hot rolled coil for ground gathering and transportation comprises the following technical processes: molten iron pretreatment, converter smelting, external refining, continuous casting, slab heating, rolling, laminar cooling and coiling; wherein the following processes are controlled:
1) Smelting in a converter; top blowing or top-bottom combined blowing is adopted;
2) Refining outside the furnace; adopting LF furnace light desulfurization treatment and calcium treatment;
3) Continuous casting; adopting a dynamic soft pressing mode;
4) Heating the plate blank; heating the continuous casting slab to 1159-1171 ℃;
5) Rolling; adopting a two-stage rolling control and cooling control mode; the finishing temperature of rough rolling is 984-995 ℃, rough rolling is carried out for at least 5 times, the rolling reduction rate of the first pass is 18.3-19.7%, the rolling reduction rate of each pass is gradually increased, and the rolling reduction rate of the last pass is 20.9-22.9%; after rolling, finishing rolling at 785-792 deg.c and at least 7 times, with the first rolling reduction rate being 18.2-19.4%, the last rolling reduction rate being 5.7-8.5%;
6) Laminar cooling and coiling; and finally cooling to 522-540 ℃ at a speed of 13.8-15.2 ℃/s, coiling, and finally cooling to room temperature.
Further, the yield strength of the hot rolled coil finished product is 426-477 MPa, the tensile strength is 557-570 MPa, and the elongation after fracture is more than or equal to 37%; the Charpy impact energy Akv at the temperature of minus 40 ℃ is more than or equal to 319J; the corrosion rate is 0.0240-0.0276 mm/a, the corrosion potential is more than or equal to-0.458V, and the corrosion current density is less than or equal to 1.08X10 -5A·cm-2.
Further, in the step 5), the ratio of the thickness of the rolled intermediate billet to the thickness of the finished steel plate is less than or equal to 3.0.
Further, the thickness of the continuous casting slab is 172-175 mm, the thickness of the rolled intermediate billet is 54-56 mm, and the thickness of the finished steel plate is 18-20 mm.
Compared with the prior art, the invention has the beneficial effects that:
1) The inherent thought of the high-carbon design of the existing ground gathering and conveying steel is broken through, and the low-carbon, low-manganese and low-sulfur phosphorus design is adopted, so that the product is ensured to have excellent corrosion resistance and weldability;
2) The high-content Ti is adopted, so that on one hand, the long-strip MnS is completely modified into nearly spherical Ti 4C2S2, the toughness and the corrosion resistance of the product are improved, and on the other hand, the rest Ti forms TiC to improve the strength;
3) Noble metals Ni and Mo are not added, and Cr is independently added to ensure corrosion resistance and strength, so that the product has great advantages in the aspect of economy;
4) The two-stage controlled rolling and cooling are adopted, so that the product is ensured to have good toughness matching;
5) The precisely distributed pass reduction rate is combined with the small-thickness intermediate billet rolling technology, so that the limit that the thickness of the pipeline steel intermediate billet is more than 3.6 times of the thickness of a finished product is broken, the reduction of the finish rolling stage is reduced, the dislocation density is reduced, and the corrosion resistance of the steel is further improved.
Detailed Description
The invention relates to an L415 grade pipeline steel hot rolled coil for ground gathering and transportation, which comprises the following chemical components by weight percent C：0.061％～0.070％、Si：0.15％～0.25％、Mn：0.39％～0.48％、P≤0.012％、S：0.0028％～0.003％、Als：0.030％～0.045％、Nb：0.024％～0.030％、Ti：0.032％～0.038％、Cr：0.25％～0.31％、N≤0.004％, and the balance of iron and unavoidable impurities.
The invention relates to a production method of a L415 grade pipeline steel hot rolled coil for ground gathering and transportation, which comprises the following technical processes: molten iron pretreatment, converter smelting, external refining, continuous casting, slab heating, rolling, laminar cooling and coiling; wherein the following processes are controlled:
1) Smelting in a converter; top blowing or top-bottom combined blowing is adopted;
2) Refining outside the furnace; adopting LF furnace light desulfurization treatment and calcium treatment;
3) Continuous casting; adopting a dynamic soft pressing mode;
4) Heating the plate blank; heating the continuous casting slab to 1159-1171 ℃;
5) Rolling; adopting a two-stage rolling control and cooling control mode; the finishing temperature of rough rolling is 984-995 ℃, rough rolling is carried out for at least 5 times, the rolling reduction rate of the first pass is 18.3-19.7%, the rolling reduction rate of each pass is gradually increased, and the rolling reduction rate of the last pass is 20.9-22.9%; after rolling, finishing rolling at 785-792 deg.c and at least 7 times, with the first rolling reduction rate being 18.2-19.4%, the last rolling reduction rate being 5.7-8.5%;
6) Laminar cooling and coiling; and finally cooling to 522-540 ℃ at a speed of 13.8-15.2 ℃/s, coiling, and finally cooling to room temperature.
Further, the yield strength of the hot rolled coil finished product is 426-477 MPa, the tensile strength is 557-570 MPa, and the elongation after fracture is more than or equal to 37%; the Charpy impact energy Akv at the temperature of minus 40 ℃ is more than or equal to 319J; the corrosion rate is 0.0240-0.0276 mm/a, the corrosion potential is more than or equal to-0.458V, and the corrosion current density is less than or equal to 1.08X10 -5A·cm-2.
Further, in the step 5), the ratio of the thickness of the rolled intermediate billet to the thickness of the finished steel plate is less than or equal to 3.0.
Further, the thickness of the continuous casting slab is 172-175 mm, the thickness of the rolled intermediate billet is 54-56 mm, and the thickness of the finished steel plate is 18-20 mm.
The components of the L415 grade pipeline steel for ground gathering and conveying adopt C-Mn-Nb-Ti-Cr series alloy design, and a two-stage controlled rolling and cooling technology is adopted to obtain a uniform and fine ferrite-pearlite (F-P) structure so as to ensure that a product has excellent toughness, and Cr is independently added so as to ensure that the product has excellent corrosion resistance; the main elements in the steel are used and selected for the following reasons:
C: the low-carbon-content design is the basic guarantee for ensuring that the pipeline steel for ground gathering and transportation has excellent toughness, good welding performance and corrosion resistance. Therefore, the invention controls the content of C to be 0.061-0.070 percent.
Si: is an important reducing agent and deoxidizing agent in the steelmaking process, and most of carbon steel contains less than 0.5 percent of Si, so that the strength of ferrite-pearlite structure types can be obviously improved, but the high Si content can lose the plasticity and toughness of the material, so that the Si content is controlled at a lower level, namely, the Si content is controlled at 0.15 to 0.25 percent.
Mn: manganese has solid solution strengthening effect, and can reduce gamma-alpha transformation temperature, thereby refining ferrite grains; however, manganese is liable to segregate, and too high a content thereof can cause serious segregation, and the toughness and corrosion resistance of the material are lost. Therefore, the manganese content is controlled to be 0.39-0.48 percent.
P: the steel is extremely easy to highly segregate during molten steel solidification, a banded F-P structure can be formed, P can greatly reduce the benefits brought by C reduction in the steel, and the toughness and corrosion resistance of the steel are lost; therefore, P should be as little as possible as a harmful element in the steel, and the P content of the present invention is controlled to be 0.012% or less.
S: the alloy is an unavoidable impurity element in steel, the toughness and corrosion resistance of the steel are reduced, the lower the alloy is generally hoped to be, the better the alloy is, and the invention utilizes the action of Ti element modified MnS to ensure that a certain amount of S in Ti and molten steel forms Ti 4C2S2 with the stability larger than that of MnS, and the corrosion resistance and toughness index of the product can be improved; therefore, the S content is controlled to be 0.0028-0.003%.
Als: is an unavoidable deoxidizing element in steel, and can form fine and dispersed AlN particles by adding proper amount of aluminum, thereby being beneficial to refining grains and improving the toughness of the steel. Therefore, the Als content is controlled to be 0.030% -0.045%.
Nb: is the most main element for realizing controlled rolling in modern microalloyed pipeline steel, can reduce proper gamma-alpha transformation temperature, improve austenite recrystallization temperature, promote austenite and ferrite refinement, play a role in fine grain strengthening, and improve strength and toughness. In addition, the NbC formed after hot rolling can play a role in precipitation strengthening; but Nb is a noble element and the strengthening effect is no longer obvious after adding to a certain amount. Therefore, the Nb content is controlled to be 0.024% -0.030%.
Ti: is an extremely strong nitride forming element, one of the functions of Ti is nitrogen fixation, and the second function is to completely modify long MnS into nearly spherical Ti 4C2S2 according to the contents of S and N in the product, so that the toughness and corrosion resistance of the product are improved; the third function is to form part TiC along with the further improvement of Ti, and play a role of precipitation strengthening so as to improve the strength; however, too high a Ti content would result in a loss of toughness of the steel. Therefore, the Ti content is controlled to be 0.032-0.038 percent.
Cr: the hardenability can be effectively improved, and the strength, especially the tensile strength, of the product can be improved; in addition, cr can also effectively improve the oxidation resistance of the steel, and form a compact passivation film, so that the corrosion resistance of the steel is improved; however, if the amount of the additive is too large, the plasticity and toughness are lost. Therefore, the Cr content is controlled to be 0.25-0.31%.
N: the increase of the nitrogen content can obviously improve the strength of the steel, but the plasticity, particularly the toughness, is obviously reduced, and meanwhile, the weldability is poor, the cold brittleness is aggravated, so that the lower the content is, the better the content is; because the content is too low, the steelmaking cost is increased, and therefore, the invention controls the N to be less than or equal to 0.004 percent.
The invention relates to a production method of a L415 grade pipeline steel hot rolled coil for ground gathering and transportation, which comprises the following production process flows: molten iron pretreatment, converter smelting, external refining (LF+Ca treatment), continuous casting, slab heating, rolling, laminar cooling and coiling. Unlike the prior art, the following process is controlled:
1) Smelting to continuous casting process: after molten iron pretreatment, top blowing or top-bottom combined blowing is adopted in converter smelting; the external refining adopts LF refining, and the quantity and the morphology of inclusions are controlled through light desulfurization treatment and calcium treatment so as to improve the plasticity and the toughness of steel; the continuous casting adopts a dynamic soft reduction mode, so that center porosity is reduced, and the quality of a continuous casting blank is improved.
2) Heating, rolling and laminar cooling: the continuous casting slab is heated to 1159-1171 ℃ by a step heating furnace, and austenite grains coarsen obviously under the heating temperature due to the action of Nb in steel, and the solid solution of Nb and Ti is ensured. Then adopting a two-stage rolling control and cooling technology, wherein the rough rolling finishing temperature is 984-995 ℃, the rough rolling is carried out for at least 5 times, the reduction rate of the first pass is 18.3-19.7%, the reduction rate of each pass is gradually increased, and the reduction rate of the last pass is 20.9-22.9%; after rolling, finishing rolling at 785-792 deg.c and at least 7 times, with the first rolling reduction rate being 18.2-19.4%, the last rolling reduction rate being 5.7-8.5%; the dislocation generated by deformation in the finish rolling stage is less (defects such as dislocation and the like are microstructure with weak corrosion), the dislocation density is reduced, the corrosion resistance of the finished product can be improved, then the finished product is cooled to 522-540 ℃ by adopting a laminar cooling mode at the speed of 13.8-15.2 ℃/s for coiling, and finally the finished product is cooled to room temperature by air cooling.
The L415 grade pipeline steel hot rolled coil for ground gathering and transportation has excellent toughness and corrosion resistance: the yield strength is 426-477 MPa, the tensile strength is 557-570 MPa, and the elongation after fracture is more than or equal to 37%; the Charpy impact energy (average value of 3 samples) at the temperature of minus 40 ℃ is Akv more than or equal to 319J, the corrosion rate is 0.0240-0.0276 mm/a, the corrosion potential is more than or equal to minus 0.458V, and the corrosion current density is less than or equal to 1.08X10 -5A·cm-2.
The invention combines the conventional corrosion test and the electrochemical corrosion test to evaluate the corrosion performance of the product; the corrosion test conditions were as follows:
1) Placing the sample in saturated sodium chloride solution for full immersion test, wherein the immersion period is 6 months, and calculating the corrosion rate in mm/a after the test is finished;
2) 2) performing electrochemical test in NaCl solution with 3.5% of corrosive medium, adopting a three-electrode system, wherein a working electrode is a sample to be tested, an auxiliary electrode is a Pt screen mesh, a saturated calomel electrode is a reference electrode, and calculating corrosion potential and corrosion current through a Tafil curve.
The following examples are given by way of illustration of detailed embodiments and specific procedures based on the technical scheme of the present invention, but the scope of the present invention is not limited to the following examples.
[ Example ]
The chemical composition of the steel of each example is shown in Table 1, the rolling process parameters of the steel of each example are shown in Table 2, the main pass reduction of each example is shown in Table 3, and the main performance parameters of the product of each example are shown in Table 4.
TABLE 1 chemical composition of the steel (wt.%)
Table 2 main production process parameters of steel
TABLE 3 Primary pass reduction for each example
TABLE 4 Main Performance parameters of the products
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (5)
1. A hot rolled coil of L415 grade pipeline steel for ground surface gathering is characterized in that the steel comprises the chemical components of C：0.061％～0.070％、Si：0.15％～0.25％、Mn：0.39％～0.48％、P≤0.012％、S：0.0028％～0.003％、Als：0.030％～0.045％、Nb：0.024％～0.030％、Ti：0.032％～0.038％、Cr：0.25％～0.31％、N≤0.004％, weight percent of iron and unavoidable impurities.
2. The production method of the L415 grade pipeline steel hot rolled coil for ground surface gathering and transportation according to claim 1, which is characterized by comprising the following technical processes: molten iron pretreatment, converter smelting, external refining, continuous casting, slab heating, rolling, laminar cooling and coiling; wherein the following processes are controlled:
1) Smelting in a converter; top blowing or top-bottom combined blowing is adopted;
2) Refining outside the furnace; adopting LF furnace light desulfurization treatment and calcium treatment;
3) Continuous casting; adopting a dynamic soft pressing mode;
4) Heating the plate blank; heating the continuous casting slab to 1159-1171 ℃;
5) Rolling; adopting a two-stage rolling control and cooling control mode; the final rough rolling temperature is 1040-1055 ℃, rough rolling is carried out for at least 5 times, the first pass rolling reduction is 18.4-19.7%, then the rolling reduction of each pass is gradually increased, and the rolling reduction of the last pass is 21.3-22.9%; after rolling, finishing rolling at 770-781 deg.c to finish rolling with the first rolling reduction of 17.6-19.1% and the last rolling reduction of 6.1-8.7%;
6) Laminar cooling and coiling; and finally cooling to 522-540 ℃ at a speed of 13.8-15.2 ℃/s, coiling, and finally cooling to room temperature.
3. The production method of the L415 grade pipeline steel hot rolled coil for ground surface gathering and transportation according to claim 1, wherein the yield strength of the finished hot rolled coil is 426-477 MPa, the tensile strength is 557-570 MPa, and the elongation after break is more than or equal to 37%; the Charpy impact energy Akv at the temperature of minus 40 ℃ is more than or equal to 319J; the corrosion rate is 0.0240-0.0276 mm/a, the corrosion potential is more than or equal to-0.458V, and the corrosion current density is less than or equal to 1.08X10 -5A·cm-2.
4. The method for producing a hot rolled coil of L415 grade pipeline steel for surface transportation as claimed in claim 1, wherein in said step 5), the ratio of the thickness of the rolled intermediate billet to the thickness of the finished steel plate is not more than 3.0.
5. The method for producing a hot rolled coil of L415 grade pipeline steel for ground surface collection and transportation according to claim 1, wherein the thickness of the continuous casting slab is 172-175 mm, the thickness of the rolling intermediate slab is 54-56 mm, and the thickness of the finished steel plate is 18-20 mm.
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