CN115710674B - Pitting-resistant pipeline steel easy to weld and preparation method thereof - Google Patents
Pitting-resistant pipeline steel easy to weld and preparation method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 218
- 239000010959 steel Substances 0.000 title claims abstract description 218
- 238000002360 preparation method Methods 0.000 title abstract description 16
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- 230000007797 corrosion Effects 0.000 claims abstract description 48
- 238000003466 welding Methods 0.000 claims abstract description 40
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- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 23
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- 239000000126 substance Substances 0.000 claims abstract description 19
- 229910052796 boron Inorganic materials 0.000 claims abstract description 17
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 13
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 9
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 7
- 229910052802 copper Inorganic materials 0.000 claims abstract description 6
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 5
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 5
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 4
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 39
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- 239000011575 calcium Substances 0.000 claims description 34
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 7
- 239000010953 base metal Substances 0.000 claims description 7
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
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- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 2
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- 229910000676 Si alloy Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- ULGYAEQHFNJYML-UHFFFAOYSA-N [AlH3].[Ca] Chemical compound [AlH3].[Ca] ULGYAEQHFNJYML-UHFFFAOYSA-N 0.000 description 1
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- GSVIBLVMWGSPRZ-UHFFFAOYSA-N cerium iron Chemical compound [Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Fe].[Ce].[Ce] GSVIBLVMWGSPRZ-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention belongs to the technical field of pipeline steel preparation, and relates to pitting corrosion-resistant pipeline steel for easy welding and a preparation method thereof, and the pipeline steel is characterized by comprising the following chemical components in mass fraction: 0.03 to 0.08 percent of C, 0.05 to 0.35 percent of Si, 1.5 to 1.85 percent of Mn, 0.003 to 0.08 percent of Al, 0.2 to 0.35 percent of Cr, 0.08 to 0.15 percent of Cu, 0.01 to 0.08 percent of Nb, 0.001 to 0.005 percent of B, 0.005 to 0.015 percent of Ti, 0.0001 to 0.001 percent of RE, 0.001 to 0.006 percent of Ca, 0.001 to 0.02 percent of P, 0.001 to 0.004 percent of S, 0.002 to 0.007 percent of O and 0.004 to 0.01 percent of N, and satisfies the following relation: mn/C not less than 20% and not more than 40%, cr Cu+Nb B not less than 0.3% and not more than 0.6%, cr/Cu not less than 2.5, wherein [ ] represents element mass fraction and the balance is Fe. The invention realizes the pitting corrosion resistance of the pipeline steel and has the function of bearing high heat input welding conditions by optimizing the components, modifying and spheroidizing inclusions in the steel and fully utilizing the beneficial effects of the inclusions.
Description
Technical Field
The invention belongs to the technical field of pipeline steel preparation, and relates to pitting corrosion-resistant pipeline steel for easy welding and a preparation method thereof.
Background
Pipeline steel has been known as an important 'life line' of national economy because it is an important carrier for oil and gas resource transmission of petroleum, natural gas and the like. The energy demand is constantly promoting the development of oil and gas pipeline construction. In recent years, with the continuous development of steel smelting preparation technology, the quality of pipeline steel is also continuously improved. However, the inclusions such as oxygen, sulfur, nitrogen and the like in the steel still cannot be removed, and the steel is excessively required to be "clean", so that the smelting and manufacturing cost is very high. The conventional concept is that inclusions in steel damage the continuity of a steel matrix, and deteriorate the comprehensive mechanical properties of the steel. In view of the service conditions of the pipeline steel, the pipeline steel has good welding performance and corrosion resistance is also an important performance index. Among them, pitting corrosion is one of the main forms of corrosion of pipeline steel, and mainly occurs between precipitated phase particles such as inclusions in steel and a matrix. With the rapid development of steel preparation technology, the manufacturing industry also puts higher demands on the quality of pipeline steel, and the development of corrosion-resistant or weldable pipeline steel has become one of the hot spot directions in the pipeline steel field.
The invention patent CN 106011667A discloses a weather-proof corrosion-proof longitudinal submerged arc welded steel pipe, which is provided with high strength and excellent corrosion resistance by adding and utilizing the optimal proportion of Ni, cr, mo, cu and other elements, and is suitable for a longitudinal submerged arc welding process. Obviously, the invention adds noble alloys such as Ni, mo, cu and the like, which increases the metallurgical manufacturing cost undoubtedly, and meanwhile, the difficulty of accurately controlling the alloy proportion is higher.
The invention patent CN 112695246A discloses an acid corrosion resistant high strength pipeline steel and a manufacturing method thereof, the technology aims at H in the pipeline 2 S corrosion, unlike common low-C high-Mn component design, adopts an alloying component system with low C, low Mn and high Cr, eliminates the problem of manganese alloy element segregation caused by the high-Mn system from the component, avoids the formation of banded segregation tissue, and has excellent resistanceCorrosion performance, and has higher strength and toughness. The corrosion referred to in this patent falls into the category of uniform corrosion and does not relate to the pitting mechanism, and in particular, the weld performance is not evaluated.
The invention patent CN 111235465A discloses an 8-15mm thick corrosion-resistant high crack-stopping submarine pipeline steel X65MO and a production method thereof, adopts a design idea of adding a proper amount of relatively low-cost rare earth cerium-iron alloy to replace a part of Nb and Cr for low cost, fully plays a role in a controlled rolling and cooling process, and realizes high strength, high toughness and corrosion-resistant hot rolled coiled plates of materials through the mechanisms of fine grain strengthening and precipitation strengthening of alloy elements. The invention utilizes the beneficial characteristics of low-temperature toughness and corrosion resistance of the rare earth Ce and the corrosion resistance and toughness improvement performance of the pipeline steel base material by matching with the controlled rolling process, and has no description on welding performance.
The invention patent CN 102154587B discloses a pipeline steel for large heat input welding and a manufacturing method thereof, and the process simultaneously adds a large amount of Ti, ni, cu, nb and rare earth and other noble alloy elements, so that the smelting cost is high. And the patent strictly controls the ratio of titanium to nitrogen to be between 2 and 4, and the ratio of aluminum to nitrogen to be between 3 and 10. On the one hand, the difficulty in precisely controlling the composition of the composition is present, and on the other hand, a large amount of Nb is present in the steel, and the role of forming niobium nitride is not mentioned.
The invention patent CN 113046653A discloses a pipeline steel with excellent high heat input welding performance and a manufacturing method thereof, adopts a magnesium alloying technology, spheroidizes manganese sulfide inclusions of the steel, converts large inclusions into fine magnesium-containing oxides, becomes a solidification nucleation core of original austenite grains, effectively refines the structure of a steel plate, and can prevent the growth and deterioration of the grains in the welding process of a magnesium-containing matrix, thereby effectively reducing the adverse effect of welding. The process adds a large amount of Ni, cr, mo, cu, nb and other noble alloy elements, and increases the smelting and manufacturing cost. And the patent only shows the performance of the pipeline steel base material, and no report is made on the welding performance and pitting corrosion resistance of the product.
From the above prior art, in order to make the pipeline steel withstand the welding process with excellent corrosion resistance and high heat input, the existing pipeline steel is mostly manufactured by adding noble alloy elements such as Ni, mo, cu and Nb and by a controlled rolling and controlled cold rolling process. Obviously, the smelting cost of the pipeline steel is obviously increased, and in addition, the literature for improving the pitting corrosion resistance and the corrosion resistance of the pipeline steel is rarely reported.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the pitting corrosion resistant and easy-to-weld pipeline steel and the preparation method thereof, which are based on the components of low carbon, medium manganese, high chromium and low copper, and the smelting process is adjusted by self-made titanium-rare earth-calcium-nitrogen cored wires, so that the length-width ratio and shape of inclusions in the steel and the number of oxides and nitrides in the steel are reasonably controlled, the pitting corrosion resistant performance of the pipeline steel is realized, and the pipeline steel is simultaneously subjected to high heat input welding conditions.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
one of the technical proposal is as follows: the pitting corrosion resistant pipeline steel for easy welding is characterized by comprising the following chemical components in percentage by mass: 0.03 to 0.08 percent of C, 0.05 to 0.35 percent of Si, 1.5 to 1.85 percent of Mn, 0.003 to 0.08 percent of Al, 0.2 to 0.35 percent of Cr, 0.08 to 0.15 percent of Cu, 0.01 to 0.08 percent of Nb, 0.001 to 0.005 percent of B, 0.005 to 0.015 percent of Ti, 0.0001 to 0.001 percent of RE, 0.001 to 0.006 percent of Ca, 0.001 to 0.02 percent of P, 0.001 to 0.004 percent of S, 0.002 to 0.007 percent of O and 0.004 to 0.01 percent of N, and satisfies the following relation: mn of 20-20%]/[C]≤40,0.3％≤[Cr]+[Cu]+[Nb]+[B]≤0.6％,[Cr]/[Cu]Not less than 2.5, wherein%]Representing the mass fraction of elements, and the balance being Fe; the maximum value of the grain diameter of the inclusion in the steel is marked as Dmax, the minimum value of the grain diameter is defined as Dmin, and the length-width ratio of the inclusion is marked as Dmax/Dmin; the length-width ratio of the inclusions in the steel base material is more than or equal to 1 and less than or equal to Dmax/Dmin and less than or equal to 1.5, the total number of the inclusions is more than or equal to 85 percent, and the length-width ratio Dmax/Dmin and more than or equal to 3 of the inclusions is less than or equal to 6 percent; the number of oxide in the steel is 500-2000/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the The number of Ti-RE-Si-Ca series oxides with the grain size of 0.1-3 mu m accounts for more than or equal to 75 percent of the total inclusion, wherein the number of the oxides with the grain size of more than 5 mu m is less than or equal to 20/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the The nitrides in the steel comprise boron nitride and/or niobium nitride, and the number of the nitrides with the grain diameter of more than or equal to 300nm is less than or equal to 50/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the Separately precipitated from steelThe sulfide accounts for less than or equal to 4 percent of the total amount of the inclusions.
Further, the rare earth element RE in the steel is one or a combination of two of Ce, la and Y.
Further, the oxide comprises any one or more than two composite oxides of titanium oxide, rare earth oxide and calcium oxide.
Further, the sulfide comprises any one or more than two of manganese sulfide, calcium sulfide and rare earth sulfide.
Further, 60 to 90% of sulfides in the steel adhere to the oxide particles.
Further, 30 to 60% of the intragranular ferrite structure is nucleated at the edges of the Ti-RE-Si-Ca-based oxide + sulfide or nitride particles.
Furthermore, the impact toughness of the base metal welding heat affected zone is more than or equal to 80J at the temperature of minus 40 ℃ under the high heat input welding condition of less than or equal to 600 kJ.
The second technical scheme is as follows: a preparation method of pitting corrosion-resistant pipeline steel for easy welding comprises the following steps:
step 1, wire manufacturing: nitriding the alloy of titanium, silicon, calcium, rare earth and boron, crushing the alloy into granular powder, wrapping the granular powder by an aluminum belt to form a cored wire, and enhancing the deep deoxidization effect; the cored wire comprises the following components in parts by mass: 15-35 wt.% of titanium, 5-22 wt.% of calcium, 1-25 wt.% of rare earth, 1-12 wt.% of boron, 1-10 wt.% of nitrogen, 5-30 wt.% of aluminum, 5-24 wt.% of silicon and the balance of unavoidable impurities, wherein the sum of the contents of rare earth, calcium and silicon is greater than the sum of the contents of titanium and aluminum, and the aim is to carry out deep desulfurization treatment and enhance inclusion modification and spheroidization;
the grain diameter of the core material of the cored wire is 0.5-5 mm, the weight of the core material is 150-500 g/m, and the wire diameter is 8-15 mm;
placing the cored wire on a wire feeder of a refining station for standby;
step 2, steelmaking:
1) In the molten steel smelting process, adopting a converter or an electric furnace to smelt, and tapping to a ladle, wherein argon is blown at the bottom in the smelting and tapping stage; 2) Transferring the ladle to a refining station, adjusting the components and the temperature of molten steel, and protecting the refining process by argon; 3) After the dissolved oxygen of molten steel is less than or equal to 20ppm and the dissolved nitrogen is less than or equal to 50ppm, feeding the cored wire, and stirring the molten steel for more than or equal to 4 minutes under the argon blowing amount of more than 300L/min; adjusting the molten steel components to meet the chemical component requirements of steel, and discharging; 4) In the casting blank process, carrying out full protection casting on molten steel to obtain a casting blank;
step 3, rolling:
the casting blank is sent into a rolling mill for rolling, and the final rolling temperature is more than or equal to 850 ℃; after rolling, water cooling to 450-700 ℃ and air cooling to room temperature.
Further, in the step 1), titanium, silicon, calcium, rare earth and boron alloy are crushed and then are uniformly mixed by a planetary ball mill, the ball milling speed is 200 r/min-400 r/min, and the ball milling time is 30-120 min.
Further, in the step 3), the rolling process adopts two-stage controlled rolling or high-temperature continuous rolling in a recrystallization zone.
The technical principle and design idea of the technical scheme of the invention are as follows: the prior pipeline steel with improved corrosion resistance or high heat input resistance is mainly prepared by alloying, rolling control and cooling control technologies, and the research on improving the pitting corrosion and welding performance of the pipeline steel is very little. The invention optimizes the alloy components and the smelting process to ensure the strength of the base material, and simultaneously ensures the uniform corrosion resistance of the base material through the design of the low-copper high-chromium corrosion-resistant element proportion. Titanium-rare earth-calcium oxide-based multi-phase particles are introduced into steel, the length-width ratio, the quantity and the like of each inclusion are reasonably controlled, and meanwhile, precipitation of sulfide phases which are easy to pitting effect is dispersed. Realizes the multiple functions of inducing ferrite nucleation and preventing austenite grain growth by nitride and dispersing easy pitting sulfide precipitation by the effective multiphase oxide particles. The modification and spheroidization of the inclusion particles in the steel significantly improves the pitting corrosion resistance of the pipeline steel.
The technical scheme of the invention adopts a low-cost component system of low carbon, medium manganese, high chromium, low copper and micro niobium, and the limit of Mn/C is less than or equal to 20 and less than or equal to 40, thereby ensuring the matrix strength of the steel, avoiding the formation of manganese segregation and banded segregation tissue caused by high manganese and reducing the tendency of pitting corrosion. The dependence of pipeline steel on expensive alloys such as nickel, vanadium, molybdenum and the like can be eliminated by reasonably controlling the relational expression of 0.3 less than or equal to [ Cr ] + [ Cu ] + [ Nb ] + [ B ] less than or equal to 0.6 and [ Cr ]/[ Cu ] more than or equal to 2.5; titanium-containing oxide formed by titanium in the cored wire is a strong effective element for forming fine needle-like ferrite in the crystal; rare earth, silicon and calcium alloy elements in the cored wire can be deeply desulfurized and effectively modify and spheroidize inclusions. The core material is coated by the aluminum belt instead of the steel belt, so that the calcium-aluminum composite deoxidization is formed, and the purpose of deep deoxidization is realized. A large number of tiny spheroidized titanium-rare earth-calcium oxide particles induce ferrite nucleation in coarse austenite crystals, so that sulfide (such as manganese sulfide) with strong pitting sensitivity is effectively dispersed and separated out, and the pitting tendency of pipeline steel is weakened. In addition, niobium nitride and boron nitride gather in the grain boundary, inhibit the growth of coarse austenite grains, and refine the structure of the welding heat affected zone of the pipeline steel base material. Through a great deal of experimental research, the length-width ratio, the number and the like of inclusions are defined and limited, and the pipeline steel can have the best target effect when the specific relation parameters are met.
Compared with the prior art, the invention has the beneficial effects that:
1) According to the invention, precious alloys such as Ni, mo, V and the like are not added, based on a component system of low-carbon-medium-manganese-high-chromium-low-copper-micro-niobium cheaper alloy, special treatment of inclusions is carried out through a specially-made Ti-RE-Si-Ca-N aluminum tape cored wire, deep deoxidization, deep desulfurization, inclusion denaturation and spheroidization effects are enhanced, the synergistic effect that titanium-rare earth-calcium-based oxide and niobium/boron nitride induce ferrite nucleation in a crystal and prevent grain growth is fully exerted, the yield is improved, and alloy resources are saved.
2) The invention effectively controls the quantity of inclusions and the length-width ratio in steel by a special smelting preparation method, simultaneously effectively disperses the precipitation of coarse strip sulfide phases, weakens the pitting tendency of the independent precipitation of the coarse strip sulfide, and gives consideration to the high heat input welding resistance and pitting corrosion resistance of the pipeline steel.
Drawings
FIG. 1 is an electron scan photograph of a typical Ti-Ce-Ca-based oxide inclusion in the steel of example 1 of the present invention, with an EDS spectrum of a complex oxide attached to the upper right corner.
Detailed Description
Embodiments of the present invention are further described below with reference to examples:
exemplary embodiments of the present disclosure will be described in more detail below, however, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
Example 1
In the embodiment, the pipeline steel plate with the pitting corrosion resistance and easy welding performance comprises the following chemical components in mass percent: 0.05% of C, 0.15% of Si, 1.7% of Mn, 0.03% of Al, 0.25% of Cr, 0.08% of Cu, 0.05% of Nb, 0.003% of B, 0.01% of Ti, 0.0008% of Ce, 0.003% of Ca, 0.004% of P, 0.003% of S, 0.005% of O and 0.008% of N, and satisfies the relation: mn/C of 20-40, cr Cu+Nb B of 0.3-0.6%, cr/Cu of 2.5 and Fe in balance.
The maximum value of the grain size of the inclusions in the steel is marked as Dmax, the minimum value of the grain size is defined as Dmin, and the aspect ratio of the inclusions is marked as Dmax/Dmin. The inclusion quantity with the inclusion length-width ratio of 1-Dmax/Dmin-1.5 in the steel base material accounts for 85% of the inclusion total quantity, and the inclusion length-width ratio Dmax/Dmin-3 accounts for 5% of the inclusion total quantity. The oxide in the steel contains one or more of titanium oxide, rare earth oxide and calcium oxide, and the number of the oxide is 800/mm 2 . The oxide with the particle size of 0.1-3 μm accounts for 85% of the total inclusions, wherein the oxide with the particle size of more than 5 μm accounts for 15 oxide/mm 2 . The nitrides in the steel comprise one or two of boron nitride and niobium nitride, and the number of the nitrides with the size of more than or equal to 300nm in the steel is 20/mm 2 . The amount of sulfide separately precipitated in the steel was 3% of the total amount of inclusions. In the steel, 60% of sulfides in the steel are attached to the periphery of the oxide particles, wherein the sulfides comprise one or more of manganese sulfide, calcium sulfide and rare earth sulfide. 40% of the intragranular ferrite structure in the steel sheet is nucleated at the edges of the Ti-Ce-Si-Ca-based oxide + sulfide or nitride particles.
The preparation method of the steel comprises the following process steps: nitriding the alloy of titanium, calcium, rare earth, silicon and boron, crushing the alloy into particle powder, fully mixing the particle powder in a planetary ball mill at the ball milling speed of 320r/min for 80min, and wrapping an aluminum belt to form a cored wire, wherein the titanium content is 20 wt%, the calcium content is 18 wt%, the rare earth cerium content is 5 wt%, the boron content is 5 wt%, the nitrogen content is 8 wt%, the aluminum content is 18 wt%, the silicon content is 22 wt%, and the balance is unavoidable impurities, and the sum of the contents of rare earth Ce, si and Ca is larger than the contents of Ti and Al; the grain diameter of the core material of the alloy cored wire is 2mm, the weight is 350g/m, and the wire diameter is 12mm; placing the alloy cored wire on a wire feeder of a refining station;
smelting molten steel by adopting an electric furnace, and tapping to a ladle, wherein argon is blown at the bottom in the smelting and tapping stage; transferring the ladle to a refining station, adjusting the components and the temperature of molten steel, and protecting the refining process by argon; after the oxygen content of molten steel reaches 15ppm and the nitrogen content reaches 50ppm, feeding the molten steel into the alloy cored wire, and stirring the molten steel for 5min under the condition of argon blowing amount of 380L/min; adjusting the alloy components of the molten steel to meet the chemical component requirements of the pipeline steel plate, and discharging; carrying out full-protection casting on molten steel to obtain a casting blank;
the casting blank is fed into a rolling mill, a two-stage control rolling process is adopted, the initial rolling temperature of the rolling mill is 1150 ℃, and the final rolling temperature is 1020 ℃; after rolling, water cooling to 500 ℃ and air cooling to room temperature.
According to the steps, the impact toughness of the base metal heat affected zone of the pipeline steel plate is 254J at the temperature of minus 40 ℃ under the high heat input welding condition of 150 kJ/cm.
Example 2
In the embodiment, the pipeline steel plate with the pitting corrosion resistance and easy welding performance comprises the following chemical components in mass percent: 0.06% of C, 0.08% of Si, 1.85% of Mn, 0.05% of Al, 0.28% of Cr, 0.11% of Cu, 0.04% of Nb, 0.002% of B, 0.015% of Ti, 0.0007% of La, 0.004% of Ca, 0.003% of P, 0.004% of S, 0.006% of O and 0.01% of N, and satisfies the relation: mn/C of 20-40, cr Cu+Nb B of 0.3-0.6%, cr/Cu of 2.5 and Fe in balance.
The maximum value of the grain diameter of the inclusion in the steel is marked as Dmax, the minimum value of the grain diameter is defined as Dmin, and the length of the inclusionThe width ratio is marked as Dmax/Dmin. The inclusion quantity with the inclusion length-width ratio of 1-Dmax/Dmin-1.5 in the steel base material accounts for 93% of the inclusion total quantity, and the inclusion length-width ratio Dmax/Dmin-3 accounts for 4% of the inclusion total quantity. The oxide in the steel contains one or more of titanium oxide, rare earth oxide and calcium oxide, and the quantity is 680 pieces/mm 2 . The oxide with the particle size of 0.1-3 μm accounts for 90% of the total inclusions, wherein the oxide with the particle size of more than 5 μm accounts for 10 oxide/mm 2 . The nitrides in the steel comprise one or two of boron nitride and niobium nitride, and the number of the nitrides with the size of more than or equal to 300nm in the steel is 15/mm 2 . The number of sulfide separated out from the steel is 2% of the total number of inclusions. In the steel, 50% of sulfides in the steel are attached to the periphery of the oxide particles, wherein the sulfides comprise one or more of manganese sulfide, calcium sulfide and rare earth sulfide. 35% of the intragranular ferrite structure in the steel sheet is nucleated at the edges of the Ti-La-Si-Ca-based oxide + sulfide or nitride particles.
The preparation method of the steel comprises the following process steps: nitriding the alloy of titanium, rare earth lanthanum, silicon, calcium and boron, crushing the alloy into particle powder, fully mixing the particle powder in a planetary ball mill at the ball milling speed of 200r/min for 120min, and wrapping the particle powder by an aluminum belt to form a cored wire, wherein the titanium content is 34wt.%, the calcium content is 20wt.%, the rare earth content is 15wt.%, the boron content is 4wt.%, the nitrogen content is 5wt.%, the aluminum content is 10wt.%, the silicon content is 8wt.%, and the balance is unavoidable impurities, and the sum of the contents of rare earth La, si and Ca is greater than the sum of the contents of Ti and Al; the grain diameter of the core material of the alloy cored wire is 2mm, the weight of the core material is 230g/m, and the wire diameter is 8mm; placing the alloy cored wire on a wire feeder of a refining station;
smelting molten steel by adopting an electric furnace, and tapping to a ladle, wherein argon is blown at the bottom in the smelting and tapping stage; transferring the ladle to a refining station, adjusting the components and the temperature of molten steel, and protecting the refining process by argon; after the oxygen content of molten steel reaches 18ppm and the nitrogen content reaches 30ppm, feeding the molten steel into the alloy cored wire, and stirring the molten steel for 6min under the condition of argon blowing amount of 320L/min; adjusting the alloy components of the molten steel to meet the chemical component requirements of the pipeline steel plate, and discharging; carrying out full-protection casting on molten steel to obtain a casting blank;
the casting blank is fed into a rolling mill, the rolling process is controlled in two stages, the initial rolling temperature of the rolling mill is 1150 ℃, the final rolling temperature is 920 ℃, and the casting blank is cooled to 480 ℃ by water after rolling and then is cooled to room temperature by air.
According to the steps, the impact toughness of the base metal heat affected zone at-40 ℃ under the high heat input welding condition of 250kJ/cm is 217J.
Example 3
In the embodiment, the pipeline steel plate with the pitting corrosion resistance and easy welding performance comprises the following chemical components in mass percent: 0.07% of C, 0.25% of Si, 1.55% of Mn, 0.06% of Al, 0.3% of Cr, 0.12% of Cu, 0.05% of Nb, 0.001% of B, 0.01% of Ti, 0.0006% of Y, 0.005% of Ca, 0.002% of P, 0.003% of S, 0.005% of O and 0.007% of N, and the relational expression of 20-40% of Mn/C, 0.3-0% of Cr-Cu, 0.6% of Nb-B, 2.5-Cr/Cu and the balance of Fe is satisfied.
The maximum value of the grain size of the inclusions in the steel is marked as Dmax, the minimum value of the grain size is defined as Dmin, and the aspect ratio of the inclusions is marked as Dmax/Dmin. The inclusion quantity with the inclusion length-width ratio of 1-Dmax/Dmin-1.5 in the steel base material accounts for 88% of the inclusion total quantity, and the inclusion length-width ratio Dmax/Dmin-3 accounts for 3% of the inclusion total quantity. The oxide in the steel contains one or more of titanium oxide, rare earth yttrium oxide and calcium oxide, and the quantity is 950 pieces/mm 2 . The oxide with the particle size of 0.1-3 μm accounts for 78% of the total inclusions, wherein the oxide with the particle size of more than 5 μm accounts for 15 oxide/mm 2 . The nitrides in the steel comprise one or two of boron nitride and niobium nitride, and the number of the nitrides with the size of more than or equal to 300nm in the steel is 45/mm 2 . The number of sulfide separated out from the steel is 1% of the total number of inclusions. In the steel, 65% of sulfide in the steel is attached to the periphery of oxide particles, wherein the sulfide comprises one or two or more of manganese sulfide, calcium sulfide and rare earth sulfide. 50% of the intragranular ferrite structure in the steel sheet is nucleated at the edges of the Ti-Y-Si-Ca-based oxide + sulfide or nitride particles.
The preparation method of the steel comprises the following process steps: nitriding the alloy of titanium, rare earth yttrium, silicon, calcium and boron, crushing the alloy into particle powder, fully mixing the particle powder in a planetary ball mill at the speed of 250r/min for 100min. Wrapping an aluminum strip to form a cored wire, wherein the titanium content is 15 wt%, the calcium content is 5 wt%, the rare earth content is 18 wt%, the boron content is 10 wt%, the nitrogen content is 10 wt%, the aluminum content is 20 wt%, the silicon content is 15 wt%, and the balance is unavoidable impurities, and wherein the sum of the contents of rare earth Y, si and Ca is greater than the sum of the contents of Ti and Al; the grain diameter of the core material of the aluminum tape cored wire is 3mm, the weight of the core material is 350g/m, and the wire diameter is 10mm; placing the alloy cored wire on a wire feeder of a refining station;
smelting molten steel by adopting a converter, and tapping to a ladle, wherein argon is blown at the bottom in the smelting and tapping stage; transferring the ladle to a refining station, adjusting the components and the temperature of molten steel, and protecting the refining process by argon; after the oxygen content of molten steel reaches 15ppm and the nitrogen content reaches 45ppm, feeding the molten steel into the alloy cored wire, and stirring the molten steel for 4min under the condition of argon blowing amount of 480L/min; adjusting the alloy components of the molten steel to meet the chemical component requirements of the pipeline steel plate, and discharging; carrying out full-protection casting on molten steel to obtain a casting blank;
and (3) rolling the casting blank in a rolling mill, adopting a continuous high-temperature hot rolling process in a recrystallization zone, cooling the casting blank to 550 ℃ after rolling at a final rolling temperature of 1050 ℃, and cooling the casting blank to room temperature in an air.
According to the steps, the impact toughness of the base metal heat affected zone at-40 ℃ is 154J under the high heat input welding condition of 430 kJ/cm.
Example 4
In the embodiment, the pipeline steel plate with the pitting corrosion resistance and easy welding performance comprises the following chemical components in mass percent: 0.04% of C, 0.2% of Si, 1.6% of Mn, 0.32% of Cr, 0.1% of Cu, 0.002% of B, 0.05% of Al, 0.08% of Nb, 0.015% of Ti, 0.001% of Ce+La, 0.005% of Ca, 0.003% of P, 0.002% of S, 0.007% of O and 0.006% of N, and the relational expression of 20-40% of Mn/C, 0.3-0% of Cr-Cu, 0.6% of Nb-B, 2.5-Cr/Cu and the balance of Fe is satisfied.
The maximum value of the grain size of the inclusions in the steel is marked as Dmax, the minimum value of the grain size is defined as Dmin, and the aspect ratio of the inclusions is marked as Dmax/Dmin. The number of the inclusions with the aspect ratio of the inclusions being 1-1 Dmax/Dmin-1.5 in the steel base material accounts for 92% of the total number of the inclusions, and the aspect ratio of the inclusions Dmax/Dmin-3 accounts for the total number of the inclusionsThe amount was 2%. The oxide in the steel contains one or more of titanium oxide, rare earth oxide and calcium oxide, and the number of the oxide is 1500/mm 2 . The oxide with the particle size of 0.2-3 μm accounts for 84% of the total inclusions, wherein the oxide with the particle size of more than 5 μm accounts for 17 oxide/mm 2 . The nitrides in the steel comprise one or two of boron nitride and niobium nitride, and the number of the nitrides with the size of more than or equal to 300nm in the steel is 50/mm 2 . The number of individually precipitated sulfides in the steel was 3% of the total number of inclusions. In the steel, 45% of sulfides in the steel are attached to the periphery of the oxide particles, wherein the sulfides comprise one or more of manganese sulfide, calcium sulfide and rare earth sulfide. 60% of the intragranular ferrite structure in the steel plate is nucleated at the edges of Ti-Ce/La-Si-Ca-based oxide + sulfide or nitride particles.
The preparation method of the steel comprises the following process steps: nitriding the alloy of titanium, rare earth cerium, rare earth lanthanum, silicon, calcium and boron, crushing the alloy into particle powder, fully mixing the particle powder in a planetary ball mill at the ball milling speed of 350r/min for 50min. Wrapping an aluminum strip to form a cored wire, wherein the titanium content is 20 wt%, the calcium content is 20 wt%, the rare earth content is 10 wt%, the boron content is 5 wt%, the nitrogen content is 10 wt%, the aluminum content is 18 wt%, the silicon content is 15 wt%, and the balance is unavoidable impurities, and wherein the sum of the contents of rare earth Ce+La, si and Ca is greater than the sum of the contents of Ti and Al; the grain diameter of the core material of the aluminum tape cored wire is 4mm, the weight of the core material is 400g/m, and the wire diameter is 10mm; placing the cored wire on a wire feeder of a refining station;
smelting molten steel by adopting an electric furnace, and tapping to a ladle, wherein argon is blown at the bottom in the smelting and tapping stage; transferring the ladle to a refining station, adjusting the components and the temperature of molten steel, and protecting the refining process by argon; after the oxygen content of molten steel reaches 20ppm and the nitrogen content reaches 30ppm, feeding the molten steel into the alloy cored wire, and stirring the molten steel for 5min under the condition of argon blowing amount of 420L/min; adjusting the alloy components of the molten steel to meet the chemical component requirements of the pipeline steel plate, and discharging; carrying out full-protection casting on molten steel to obtain a casting blank;
the casting blank is fed into a rolling mill, the rolling process is controlled in two stages, the initial rolling temperature of the rolling mill is 1100 ℃, and the final rolling temperature is 900 ℃; after rolling, water cooling to 680 ℃ and air cooling to room temperature.
According to the steps, the impact toughness of the base metal heat affected zone at-40 ℃ is 120J under the high heat input welding condition of 530 kJ/cm.
Example 5
In the embodiment, the pipeline steel plate with the pitting corrosion resistance and easy welding performance comprises the following chemical components in mass percent: 0.05% of C, 0.06% of Si, 1.75% of Mn, 0.04% of Al, 0.35% of Cr, 0.1% of Cu, 0.02% of Nb, 0.001% of B, 0.015% of Ti, 0.0008% of Ce+Y, 0.006% of Ca, 0.002% of P, 0.001% of S, 0.006% of O and 0.005% of N, and the relational expression is satisfied, wherein the relational expression is 20-40% of Mn/C, 0.3-0% of Cr-Cu+0.6% of Nb-B, the ratio of Cr/Cu is more than or equal to 2.5, and the balance of Fe.
The maximum value of the grain size of the inclusions in the steel is marked as Dmax, the minimum value of the grain size is defined as Dmin, and the aspect ratio of the inclusions is marked as Dmax/Dmin. The inclusion quantity with the inclusion length-width ratio of 1-Dmax/Dmin-1.5 in the steel base material accounts for 85% of the inclusion total quantity, and the inclusion length-width ratio Dmax/Dmin-3 accounts for 6% of the inclusion total quantity. The oxide in the steel contains one or more than two of titanium oxide, rare earth oxide and calcium oxide, and the quantity is 1800 pieces/mm 2 . The oxide with the particle size of 0.1-3 μm accounts for 80% of the total inclusions, wherein the oxide with the particle size of more than 5 μm accounts for 50/mm 2 . The nitrides in the steel comprise one or two of boron nitride and niobium nitride, and the number of the nitrides with the size of more than or equal to 300nm in the steel is 18/mm 2 . The number of sulfide separated out from the steel is 2% of the total number of inclusions. In the steel, 55% of sulfides in the steel are attached to the periphery of the oxide particles, wherein the sulfides comprise one or more of manganese sulfide, calcium sulfide and rare earth sulfide. 55% of the intragranular ferrite structure in the steel plate is nucleated at the edges of the Ti-Ce/Y-Si-Ca-based oxide + sulfide or nitride particles.
The preparation method of the steel comprises the following process steps: nitriding titanium, rare earth cerium, rare earth yttrium, silicon, calcium and boron, crushing into particle powder, fully mixing in a planetary ball mill at the ball milling speed of 400r/min for 30min. Wrapping an aluminum strip to form a cored wire, wherein the titanium content is 10 wt%, the calcium content is 15 wt%, the rare earth content is 7 wt%, the boron content is 8 wt%, the nitrogen content is 5 wt%, the aluminum content is 30 wt%, the silicon content is 20 wt%, and the rest is unavoidable impurities, and wherein the sum of the contents of rare earth Ce+ Y, si and Ca is greater than the sum of the contents of Ti and Al; the grain diameter of the core material of the aluminum tape cored wire is 3mm, the weight of the core material is 500g/m, and the wire diameter is 15mm; placing the cored wire on a wire feeder of a refining station;
smelting molten steel by adopting an electric furnace, and tapping to a ladle, wherein argon is blown at the bottom in the smelting and tapping stage; transferring the ladle to a refining station, adjusting the components and the temperature of molten steel, and protecting the refining process by argon; after the oxygen content of molten steel reaches 12ppm and the nitrogen content reaches 30ppm, feeding the molten steel into the alloy cored wire, and stirring the molten steel for 8min under the condition of argon blowing amount of 320L/min; adjusting the alloy components of the molten steel to meet the chemical component requirements of the pipeline steel plate, and discharging; carrying out full-protection casting on molten steel to obtain a casting blank;
and (3) rolling the casting blank in a rolling mill, adopting a continuous high-temperature hot rolling process in a recrystallization zone, cooling the casting blank to 640 ℃ after rolling at a finishing temperature of 1000 ℃, and cooling the casting blank to room temperature in an air.
According to the steps, the impact toughness of the base metal heat affected zone at-40 ℃ is 88J under the high heat input welding condition of 600 kJ/cm.
Comparative example 1
In the comparative example, the chemical components of the pipeline steel plate are, by mass, 0.08% of C, 0.2% of Si, 1.5% of Mn, 0.1% of Cr, 0.15% of Cu, 0.15% of Mo, 0.08% of Al, 0.01% of Nb, 0.001% of B, 0.002% of Ca, 0.005% of P, 0.006% of S, 0.007% of O, 0.009% of N, and the balance of Fe and residual elements, wherein the weight percentage is not more than 20% and less than 40% of Mn/C, not more than 0.3% and less than or equal to [ Cr ] + [ Cu ] + [ Nb ] + [ B ] and not more than 0.6% of [ Cr ]/[ Cu ]: is not less than 2.5.
Smelting molten steel by adopting an electric furnace, tapping to a ladle, and blowing argon at the bottom during tapping; conveying the steel ladle to a refining station for refining, and adjusting the components and the temperature of molten steel; the refining process adopts argon for protection; after the dissolved oxygen of the molten steel reaches 20ppm and the dissolved nitrogen reaches 35ppm, feeding aluminum-calcium deoxidized alloy blocks, and stirring the molten steel for 7min by bottom blowing argon; adjusting the alloy composition of molten steel to meet the chemical composition requirement of pipeline steel, and discharging; carrying out full-protection casting on molten steel to obtain a casting blank; heating a casting blank by adopting a hot charging heating furnace, wherein the heating temperature of the casting blank is 1200 ℃, the heating time is 120min, the initial rolling temperature of a rolling mill is 1150 ℃, and the final rolling temperature is 980 ℃; after rolling, water cooling to 500 ℃ and air cooling to room temperature. The number of the inclusions with the grain size of 0.2-3 mu m in the steel plate accounts for 35% of the total number of the inclusions, wherein the number of the inclusions with the grain size of more than 5 mu m is 80. According to the above steps, the microstructure of the heat affected zone of the steel plate is coarse side lath ferrite and Wittig structure under the high heat input welding condition of 400 kJ/cm; the impact toughness of the welding heat affected zone at-40 ℃ is measured twice and is respectively 18J and 44J. The comparative example does not add a special Ti-RE-Si-Ca-N aluminum tape cored wire, can not obtain dispersed beneficial inclusion particles in steel, and has no reasonable control on the number and the length-width ratio of the inclusion, so that the welding performance of the steel base material is poor. In addition, the large-size inclusions are increased, and the pitting corrosion resistance of the base material is reduced.
Comparative example 2
In the comparative example, a pipeline steel plate comprises the following chemical components in percentage by mass: 0.08% of C, 0.25% of Si, 1.65% of Mn, 0.15% of Cr, 0.1% of Mo, 0.1% of Ni, 0.1% of Cu, 0.006% of Al, 0.003% of Ca, 0.007% of P, 0.008% of S, 0.006% of O, 0.006% of N, and the balance of Fe and residual elements.
Smelting molten steel by adopting an electric furnace, tapping to a ladle, and blowing argon at the bottom during tapping; conveying the steel ladle to a refining station for refining, and adjusting the components and the temperature of molten steel; the refining process adopts argon for protection; after the dissolved oxygen of the molten steel reaches 30ppm and the dissolved nitrogen reaches 45ppm, feeding aluminum-calcium deoxidized alloy blocks, and stirring the molten steel for 8min by bottom blowing argon; adjusting the alloy composition of molten steel to meet the chemical composition requirement of pipeline steel, and discharging; carrying out full-protection casting on molten steel to obtain a casting blank; heating a casting blank by adopting a hot charging heating furnace, wherein the heating temperature of the casting blank is 1250 ℃, the heating time is 80min, and carrying out high-temperature continuous rolling in a recrystallization zone, wherein the final rolling temperature is 1100 ℃; after rolling, water cooling to 460 ℃ and air cooling to room temperature. According to the above steps, the microstructure of the heat affected zone of the steel sheet is coarse bainitic ferrite and polygonal ferrite under the high heat input welding condition of 600 kJ/cm; the impact toughness of the welding heat affected zone at-40 ℃ is detected twice as 37J and 12J respectively. The comparative example pipeline steel is added with corrosion-resistant alloy elements such as Mo, ni, cu and the like, but the manufacturing cost of the steel is increased undoubtedly; the aluminum-calcium deoxidization has insufficient regulation and control capability on the tendency of beneficial inclusion; the increase of micro-alloy elements increases the hardenability of the base material; finally, under the high heat input welding, the impact toughness of a heat affected zone is difficult to meet the service requirement.
It is clear that the process of the invention is only a preferred embodiment and is not intended to limit the scope of the invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (10)
1. The pitting corrosion resistant pipeline steel for easy welding is characterized by comprising the following chemical components in percentage by mass: 0.03 to 0.08 percent of C, 0.05 to 0.35 percent of Si, 1.5 to 1.85 percent of Mn, 0.003 to 0.08 percent of Al, 0.2 to 0.35 percent of Cr, 0.08 to 0.15 percent of Cu, 0.01 to 0.08 percent of Nb, 0.001 to 0.005 percent of B, 0.005 to 0.015 percent of Ti, 0.0001 to 0.001 percent of RE, 0.001 to 0.006 percent of Ca, 0.001 to 0.02 percent of P, 0.001 to 0.004 percent of S, 0.002 to 0.007 percent of O and 0.004 to 0.01 percent of N, and satisfies the following relation: mn/C is less than or equal to 20 and less than or equal to 40, cr+Cu is less than or equal to 0.3% and Nb+B is less than or equal to 0.6%, wherein [ ] represents element mass fraction and the balance is Fe;
the maximum value of the grain diameter of the inclusion in the steel is marked as Dmax, the minimum value of the grain diameter is defined as Dmin, and the length-width ratio of the inclusion is marked as Dmax/Dmin; the length-width ratio of the inclusions in the steel base material is more than or equal to 1 and less than or equal to Dmax/Dmin and less than or equal to 1.5, the total number of the inclusions is more than or equal to 85 percent, and the length-width ratio Dmax/Dmin and more than or equal to 3 of the inclusions is less than or equal to 6 percent; the number of oxide in the steel is 500-2000/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the The number of Ti-RE-Si-Ca series oxides with the grain size of 0.1-3 mu m accounts for more than or equal to 75 percent of the total inclusion, wherein the number of the oxides with the grain size of more than 5 mu m is less than or equal to 20/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the The nitrides in the steel comprise boron nitride and/or niobium nitride, and the number of the nitrides with the grain diameter of more than or equal to 300nm is less than or equal to 50/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the The quantity of sulfide separated out from steel is less than or equal to 4% of the total quantity of inclusions.
2. The pitting corrosion resistant easy-to-weld pipeline steel according to claim 1, wherein the rare earth element RE in the steel is any one or a combination of any two or more of Ce, la and Y.
3. The pitting corrosion resistant easy-to-weld line steel according to claim 1, wherein the oxide comprises any one or two or more of titanium oxide, rare earth oxide, and calcium oxide.
4. The pitting corrosion resistant easy welding line steel according to claim 1, wherein the sulfide comprises any one or two or more of manganese sulfide, calcium sulfide and rare earth sulfide.
5. The pitting corrosion resistant easy welding line steel according to claim 1, wherein 60 to 90% of sulfides in the steel are attached around the oxide particles.
6. The pitting corrosion resistant easy-to-weld line steel according to claim 1, wherein 30 to 60% of the intragranular ferrite structure is nucleated at the edges of Ti-RE-Si-Ca-based oxide + sulfide or/and nitride particles.
7. The pitting corrosion resistant pipeline steel for easy welding according to claim 1, wherein the impact toughness of a base metal welding heat affected zone is more than or equal to 80J at-40 ℃ under the high heat input welding condition of less than or equal to 600 kJ.
8. The method for preparing the pitting corrosion resistant easy-to-weld pipeline steel according to claim 1, which is characterized by comprising the following steps:
step 1, wire manufacturing:
nitriding the alloy of titanium, silicon, calcium, rare earth and boron, crushing the alloy into granular powder, wrapping the granular powder by an aluminum belt to form a cored wire, and enhancing the deep deoxidization effect;
the cored wire comprises the following components in parts by mass: 15-35 wt.% of titanium, 5-22 wt.% of calcium, 1-25 wt.% of rare earth, 1-12 wt.% of boron, 1-10 wt.% of nitrogen, 5-30 wt.% of aluminum, 5-24 wt.% of silicon and the balance of unavoidable impurities, wherein the sum of the contents of rare earth, calcium and silicon is greater than the sum of the contents of titanium and aluminum, and the aim is to carry out deep desulfurization treatment and enhance inclusion modification and spheroidization;
the grain diameter of the core material of the cored wire is 0.5-5 mm, the weight of the core material is 150-500 g/m, and the wire diameter is 8-15 mm;
placing the cored wire on a wire feeder of a refining station for standby;
step 2, steelmaking:
1) In the process of smelting molten steel, adopting a converter or an electric furnace to smelt, and tapping to a ladle, wherein argon is blown at the bottom in the smelting and tapping stage;
2) Transferring the ladle to a refining station, adjusting the components and the temperature of molten steel, and protecting the refining process by argon;
3) After the dissolved oxygen of molten steel is less than or equal to 20ppm and the dissolved nitrogen is less than or equal to 50ppm, feeding the cored wire, and stirring the molten steel for more than or equal to 4 minutes under the argon blowing amount of more than 300L/min; adjusting the molten steel components to meet the chemical component requirements of steel, and discharging;
4) In the casting blank process, carrying out full protection casting on molten steel to obtain a casting blank;
step 3, rolling:
the casting blank is sent into a rolling mill for rolling, and the final rolling temperature is more than or equal to 850 ℃; after rolling, water cooling to 450-700 ℃ and air cooling to room temperature.
9. The method for preparing the pitting corrosion resistant and easy-to-weld pipeline steel, according to claim 8, wherein in the step 1, titanium, silicon, calcium, rare earth and boron alloy are crushed and then are uniformly mixed by a planetary ball mill, the ball milling speed is 200 r/min-400 r/min, and the ball milling time is 30-120 min.
10. The method for producing a pitting corrosion resistant and easy-to-weld line steel according to claim 8, wherein in the step 3, the rolling process is a two-stage controlled rolling or a high-temperature continuous rolling in a recrystallization zone.
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