CN114107802A - High-strength anti-carburizing CNRE rare earth heat-resistant steel for cracking pipe joint and preparation method thereof - Google Patents
High-strength anti-carburizing CNRE rare earth heat-resistant steel for cracking pipe joint and preparation method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 141
- 239000010959 steel Substances 0.000 title claims abstract description 141
- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 115
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 106
- 238000005336 cracking Methods 0.000 title claims abstract description 72
- 238000005255 carburizing Methods 0.000 title claims abstract description 50
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 238000005275 alloying Methods 0.000 claims abstract description 46
- 238000005266 casting Methods 0.000 claims abstract description 40
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 35
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 35
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 30
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 18
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 16
- 238000005516 engineering process Methods 0.000 claims abstract description 15
- 238000005495 investment casting Methods 0.000 claims abstract description 13
- 239000000126 substance Substances 0.000 claims abstract description 5
- 239000000203 mixture Substances 0.000 claims abstract description 3
- 239000000956 alloy Substances 0.000 claims description 42
- 229910045601 alloy Inorganic materials 0.000 claims description 38
- 239000011572 manganese Substances 0.000 claims description 36
- 229910052748 manganese Inorganic materials 0.000 claims description 28
- 238000000034 method Methods 0.000 claims description 26
- 229910052751 metal Inorganic materials 0.000 claims description 21
- 239000002184 metal Substances 0.000 claims description 21
- 238000010079 rubber tapping Methods 0.000 claims description 21
- 230000008569 process Effects 0.000 claims description 19
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- 238000004939 coking Methods 0.000 claims description 18
- 229910052760 oxygen Inorganic materials 0.000 claims description 18
- 239000001301 oxygen Substances 0.000 claims description 18
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 17
- 229910052710 silicon Inorganic materials 0.000 claims description 17
- 229910000592 Ferroniobium Inorganic materials 0.000 claims description 12
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims description 12
- 229910000628 Ferrovanadium Inorganic materials 0.000 claims description 12
- OSMSIOKMMFKNIL-UHFFFAOYSA-N calcium;silicon Chemical compound [Ca]=[Si] OSMSIOKMMFKNIL-UHFFFAOYSA-N 0.000 claims description 12
- ZFGFKQDDQUAJQP-UHFFFAOYSA-N iron niobium Chemical compound [Fe].[Fe].[Nb] ZFGFKQDDQUAJQP-UHFFFAOYSA-N 0.000 claims description 12
- PNXOJQQRXBVKEX-UHFFFAOYSA-N iron vanadium Chemical compound [V].[Fe] PNXOJQQRXBVKEX-UHFFFAOYSA-N 0.000 claims description 12
- 238000002844 melting Methods 0.000 claims description 12
- 230000008018 melting Effects 0.000 claims description 12
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 11
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 10
- 239000005977 Ethylene Substances 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 10
- 238000003723 Smelting Methods 0.000 claims description 9
- 229910000882 Ca alloy Inorganic materials 0.000 claims description 8
- 229910052782 aluminium Inorganic materials 0.000 claims description 7
- 229910052684 Cerium Inorganic materials 0.000 claims description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 6
- 239000010703 silicon Substances 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 4
- WMOHXRDWCVHXGS-UHFFFAOYSA-N [La].[Ce] Chemical compound [La].[Ce] WMOHXRDWCVHXGS-UHFFFAOYSA-N 0.000 claims description 3
- 229910052746 lanthanum Inorganic materials 0.000 claims description 3
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical group [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 3
- 239000002994 raw material Substances 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 2
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- 125000004429 atom Chemical group 0.000 abstract description 9
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- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 32
- 229910000604 Ferrochrome Inorganic materials 0.000 description 24
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 15
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 10
- 229910001309 Ferromolybdenum Inorganic materials 0.000 description 9
- 239000011651 chromium Substances 0.000 description 9
- 229910052742 iron Inorganic materials 0.000 description 9
- 229910052759 nickel Inorganic materials 0.000 description 9
- 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 6
- 150000004767 nitrides Chemical class 0.000 description 6
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 5
- 239000011230 binding agent Substances 0.000 description 5
- 239000000395 magnesium oxide Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 235000019353 potassium silicate Nutrition 0.000 description 5
- 230000009467 reduction Effects 0.000 description 5
- 239000011819 refractory material Substances 0.000 description 5
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical group [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 5
- 230000007547 defect Effects 0.000 description 4
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- 229910000676 Si alloy Inorganic materials 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- UPHIPHFJVNKLMR-UHFFFAOYSA-N chromium iron Chemical compound [Cr].[Fe] UPHIPHFJVNKLMR-UHFFFAOYSA-N 0.000 description 3
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- 150000002430 hydrocarbons Chemical class 0.000 description 3
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- 238000012979 petrochemical cracking Methods 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
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- 229910052804 chromium Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910000599 Cr alloy Inorganic materials 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
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- 150000004706 metal oxides Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000003209 petroleum derivative Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
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- 239000000161 steel melt Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/22—Moulds for peculiarly-shaped castings
- B22C9/24—Moulds for peculiarly-shaped castings for hollow articles
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention relates to the field of petrochemical industry, in particular to high-strength anti-carburizing CNRE rare earth heat-resistant steel for a cracking pipe joint and a preparation method thereof. The chemical composition range is as follows according to weight percentage: 0.3-0.6% of C, 0.5-3.5% of Si, 6.0-13.0% of Mn, 16.0-26.0% of Cr, 1.0-5.0% of Ni, 0.3-3.0% of Mo, 0.05-0.50% of V, 0.05-0.50% of Nb, 0.2-0.6% of N, 0.005-0.5% of RE and the balance of Fe. According to the invention, strong solid solution strengthening and precipitation strengthening effects are generated by C, N co-alloying and V, Nb micro-alloying, so that the initial strength of the pipe joint is improved; the high-temperature structure is stabilized by means of rare earth microalloying, the decay rate of high-temperature strength is reduced, and the high-temperature strength is improved; the anti-carburizing capability is improved by utilizing the inhibition effect of high-concentration C, N interstitial atoms and rare earth elements on the diffusion of C atoms. And moreover, a pipe joint casting with uniform components, compact structure and excellent performance is obtained by adopting an intermediate frequency furnace high-nitrogen alloying technology, a high-purity rare earth treatment technology and a shell type precision casting technology.
Description
Technical Field
The invention relates to the field of petrochemical industry, in particular to high-strength anti-carburizing CNRE rare earth heat-resistant steel for a cracking pipe joint and a preparation method thereof.
Background
The cracking furnace is a main production device in the petrochemical industry, the cracking furnace tube is a core heat-resistant part of the cracking furnace, the pipe joint is an important part for connecting the cracking furnace tube, and once the cracking furnace tube fails, the long-period safe operation of the whole device is seriously influenced. The cracking furnace tube joint and the cracking furnace tube are in the same service environment, are subjected to hydrocarbon carburization under the condition of high temperature (800-1100 ℃), are also subjected to corrosion of oxygen-containing and sulfur-containing atmosphere, and are also subjected to stress action generated by internal pressure and self weight, and the action of temperature difference and complex stress such as fatigue, thermal shock and the like caused by starting and stopping. The common failure modes of the alloy material are carburization cracking, creep cracking, bulging, oxidation and the like, wherein the proportion of the oxidation of the inner wall and the carburization cracking is the largest. Therefore, the pipe joint material is required to have good high temperature carburization resistance, high temperature oxidation resistance, high creep rupture strength and other properties.
The common materials for pipe joints are generally high Cr, Ni austenitic heat resistant alloys, mainly HK40(Cr25Ni20) series and HP40(Cr25Ni35) series. In recent years, along with the gradual development of cracking furnaces with high parameters and large-scale, higher requirements are put on the performance of pipe joints, and the materials are selected to be optimized by micro-alloying or adding higher Cr and Ni elements, such as Cr35Ni45Nb, Cr28Ni48 heat-resistant alloy and the like. Chinese invention patents CN105039873A and CN105039827A respectively disclose microalloyed 25Cr35NiNb and 35Cr45NiNb alloy steels for ethylene cracking furnace tubes, and the high-temperature endurance strength of the ethylene cracking furnace tubes is effectively improved through microalloying Mo, W, Co, Zr, Ti, B and the like, so that the ethylene cracking furnace tubes meet the requirement that the high-temperature endurance fracture time is more than 100h under the conditions of 1100 ℃ and 17 MPa. The invention discloses a Chinese patent CN106498121A for solving the defects of high production cost of material selection of the prior cracking furnace tube, crack, large high-temperature thermal deformation, poor anti-carburizing capability, easy coking, bulging and the like in the using process, and discloses an ethylene cracking heat-resistant steel furnace tube and a preparation method thereof. The invention also discloses a nickel-based high-temperature alloy for the furnace tube of the cracking furnace, which solves the defects of cracks, deformation, poor anti-carburizing capability and the like in the use process of the existing HK40 or HP40 furnace tube. In addition, the invention is mainly directed at the coking problem of the furnace tube, Chinese invention patent CN102399571A discloses a cracking furnace tube for slowing down the coking and carburization of the ethylene cracking furnace tube and a preparation method thereof, the invention is based on the traditional high Cr and Ni alloy, at least one element of Al, Si or B is added to prepare the tube, then the tube is subjected to pre-oxidation heat treatment under the low oxygen partial pressure atmosphere, a layer of metal and/or non-metal oxide film is generated on the inner surface of the tube, when the cracking furnace tube is used for producing low carbon number olefin by the petroleum hydrocarbon cracking furnace, the deposition of coke on the inner wall of the furnace tube can be reduced by more than 70%.
Although the high-temperature endurance performance of the cracking furnace tube/tube joint can be obviously improved by optimizing the components of the alloy, the improvement is only based on the existing traditional material selection, the improvement of the anti-carburizing and anti-coking performance is not obvious, and the problems of carburizing and coking are not essentially solved. Moreover, the anti-coking capability improved by the pre-oxidation method is not stable, and the pre-oxidation process is complex and has high requirements on equipment capability. In addition, the above alloys contain a large amount of Ni element, and the alloy cost is high. Meanwhile, the Ni element has a remarkable catalytic action on hydrocarbon coking and is not beneficial to the improvement of the anti-coking performance. Therefore, on the premise of ensuring the high-temperature strength of the cracking pipe joint, the anti-carburizing and anti-coking performance is greatly improved through the optimization of an alloy system, and the cost is reduced, so that the cracking pipe joint is a problem to be solved urgently in the field of petrochemical industry.
Disclosure of Invention
The invention aims to provide high-strength anti-carburizing CNRE rare earth heat-resistant steel for a cracking tube joint and a preparation method thereof, wherein C, N co-alloying, V, Nb and RE microalloying is adopted to improve the high-temperature strength and anti-carburizing capability, solve the technical problems of insufficient strength and serious coking of the traditional high Cr-high Ni heat-resistant steel tube joint, and have lower alloy cost, thereby ensuring the long-term safe operation of a petrochemical cracking furnace and reducing the production cost.
The technical scheme of the invention is as follows:
a high-strength anti-carburizing CNRE rare earth heat-resistant steel for a cracking pipe joint comprises the following chemical components in percentage by weight: 0.3-0.6% of C, 0.5-3.5% of Si, 6.0-13.0% of Mn, 16.0-26.0% of Cr, 1.0-5.0% of Ni, 0.3-3.0% of Mo, 0.05-0.50% of V, 0.05-0.50% of Nb, 0.2-0.6% of N, 0.005-0.5% of RE and the balance of Fe.
The high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint is formed by co-alloying C, N in percentage by weight, wherein C + N is 0.60-1.00%; RE, V and Nb are microalloyed, wherein RE is 0.005-0.050%, V is 0.05-0.30% and Nb is 0.05-0.20%.
The high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint comprises the following chemical components in percentage by weight: 0.35-0.50% of C, 1.9-2.4% of Si, 7.0-10.0% of Mn, 18.0-24.0% of Cr, 2.0-4.0% of Ni, 0.8-2.0% of Mo, 0.05-0.25% of V, 0.05-0.15% of Nb, 0.25-0.50% of N, 0.020-0.035% of RE and the balance of Fe.
The high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint has the tensile strength of more than or equal to 100MPa at the high temperature of 1000 ℃, is used for the ethylene cracking pipe joint, and does not generate obvious coking phenomenon after being in service for more than three years.
The preparation method of the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint adopts intermediate frequency furnace smelting, and obtains a pipe joint casting with uniform components, compact structure and excellent performance through an intermediate frequency furnace high nitrogen alloying technology, a high-purity rare earth treatment technology and a shell type precision casting technology, and specifically comprises the following steps:
(1) smelting molten steel: smelting molten steel by adopting an intermediate frequency furnace, taking scrap steel, intermediate alloy and pure metal as raw materials, preferentially adding the scrap steel and the intermediate alloy or the pure metal, the elements of which are not easy to burn, and adding aluminum for pre-deoxidation after furnace burden is completely melted;
(2) alloying of Si and Mn: after pre-deoxidation, adding ferrosilicon or metallic silicon and electrolytic manganese in sequence to carry out Si and Mn alloying, and after melting down, fully deoxidizing by adopting a silicon-calcium alloy;
(3) nitrogen alloying: after manganese alloying, heating the molten steel to more than or equal to 1580 ℃, adding the nitrogen-containing alloy in batches, and adding the nitrogen-containing alloy for the next time after the molten steel does not tumble for more than or equal to 2 minutes, wherein the time interval of each time is more than or equal to 3 minutes;
(4) v, Nb microalloying: after the molten steel is finally deoxidized, adding ferrovanadium and ferroniobium for V, Nb microalloying before tapping for less than or equal to 10 minutes, and tapping when the components and the temperature of the molten steel meet the requirements;
(5) rare earth treatment: carrying out rare earth treatment by using high-purity rare earth metal in the tapping process, preparing the high-purity rare earth metal into small blocks of 0.1-1.5 kg, putting the small blocks into the bottom of a steel ladle, washing the small blocks with molten steel during tapping to melt the rare earth metal, and uniformly mixing the molten metal and the molten steel in the steel ladle;
(6) precision casting: and (3) pouring at the pouring temperature of 1480-1550 ℃, stably and quickly pouring, wherein the pouring time is less than or equal to 30min after pouring, and quickly cooling the pipe joint casting and the shell to room temperature in water.
In the steps (1) and (5), the intermediate frequency furnace and the steel ladle used for smelting and pouring molten steel are both made into a furnace lining and a ladle lining by adopting neutral or alkaline caking materials.
In the preparation method of the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint, in the step (3), the nitrogen-containing alloy adopted for nitrogen alloying is crushed to be less than 100mm, and is preheated at 400-800 ℃.
The preparation method of the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint is characterized in that after the step (3), components are detected on line according to molten steel, and finally the components are adjusted to target components.
In the step (5), the high-purity rare earth metal adopted for rare earth treatment is metal lanthanum, metal cerium or lanthanum-cerium mixed metal with the total oxygen content T.O less than or equal to 300ppm, the content of the rare earth element is more than 99 wt%, and the total oxygen content T.O in the molten steel before rare earth treatment is less than or equal to 60 ppm.
In the step (6), the precision casting shell mold is baked at 900-950 ℃ before pouring, and the temperature of the shell mold is not less than 850 ℃ during pouring.
The high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint and the preparation method have the design concept that:
1. design of material composition
C, N is adopted for alloying, so that a strong interstitial solid solution strengthening effect is generated, a high-temperature stable fine second phase is formed with alloy elements such as V, Nb and the like, a strong precipitation strengthening effect is generated, and the initial strength of the pipe joint is improved; the high-concentration C, N interstitial atoms are used for reducing the diffusion rate of C atoms and improving the anti-carburizing capability. Preferably, in the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint, the C + N is 0.50-1.20% (preferably 0.60-1.00%).
By V microalloying, fine VX (C, N) precipitated phase which is stable at high temperature is formed with C, N element, dislocation movement is hindered, and initial strength of the pipe joint is improved. Preferably, in the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint, V is 0.05-0.30%.
By microalloying Nb, a high-temperature stable fine NbX (C, N) precipitated phase is formed with C, N element, dislocation movement is hindered, and the initial strength of the pipe joint is improved. Preferably, in the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint, Nb is 0.05-0.20%.
By adopting rare earth microalloying, on the basis of exerting the functions of rare earth metamorphic inclusion and deep purification, the solid solution of rare earth is realized, the micro defects such as crystal boundary and phase boundary are stabilized, the coarsening of a second phase is delayed, the attenuation rate of the high-temperature strength of the pipe joint is reduced, and the high-temperature strength is improved; the anti-carburizing capability is improved by utilizing the inhibiting effect of the rare earth on the diffusion of C atoms. Preferably, in the high-strength and anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint, RE is 0.005-0.050%.
The alloy elements with lower cost such as C, N, Mn, RE and the like are adopted to greatly replace noble alloy elements such as Ni and the like, and the alloy cost is obviously reduced while the austenite structure is stabilized. Preferably, in the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint, Ni is 2.0-4.0, and Mn is 6.0-10.0.
2. Preparation method
The high-nitrogen alloying of the intermediate frequency furnace adopts baked nitrogen-containing alloy, the baked nitrogen-containing alloy is crushed to the diameter of less than 100mm, the temperature of molten steel is strictly controlled in the high-nitrogen alloying process, and the nitrogen-containing alloy is added in batches, so that the yield of N element is improved; and in the nitrogen alloying process, after the manganese alloying process, the solubility of N in molten steel is improved by utilizing the solid solution effect of manganese on N, so that the high-nitrogen alloying of the intermediate frequency furnace is realized.
The rare earth treatment adopts high-purity rare earth metal with the total oxygen content of less than or equal to 300ppm and the rare earth element content of more than or equal to 99 wt%, and controls the O content in molten steel before the rare earth treatment to be less than or equal to 60ppm, so that on the basis of playing the roles of metamorphic inclusion and deep purification, partial rare earth exists in a solid solution form, the high-temperature structure is stabilized, the attenuation rate of the high-temperature strength of the pipe joint is reduced, the high-temperature strength is improved, the diffusion of C atoms is inhibited, and the anti-carburizing capability is improved.
The precise casting shell mold refractory material is magnesia, the binder is water glass, the shell mold is baked at 900-950 ℃ before casting, the shell mold temperature is not lower than 850 ℃ during casting, and the internal and surface quality of a pipe joint casting is guaranteed.
The invention has the advantages and beneficial effects that:
1. according to the invention, through the combination of alloy design and preparation process control of the cracking pipe joint, C, N co-alloying and V, Nb and RE micro-alloying are adopted to generate strong solid solution strengthening and precipitation strengthening effects, so that the initial strength of the pipe joint is improved. The high-temperature structure is stabilized by means of rare earth microalloying, the decay rate of high-temperature strength is reduced, and the high-temperature strength is improved. The anti-carburizing capability is improved by utilizing the inhibition effect of high-concentration C, N interstitial atoms and rare earth elements on the diffusion of C atoms.
2. The invention adopts the medium frequency furnace high nitrogen alloying technology, the high purity rare earth treatment technology and the shell mold precision casting technology to obtain the pipe joint casting with uniform components, compact structure and excellent performance, replaces the traditional high Cr-high Ni heat-resistant steel pipe joint to be used in the cracking furnace, can effectively solve the technical problems of creep cracking, serious coking and the like of the petrochemical cracking pipe joint, prolongs the service life and reduces the production cost.
3. Compared with the traditional high Cr-high Ni heat-resistant steel pipe joint, the CNRE rare earth heat-resistant steel for the cracking pipe joint disclosed by the invention has the advantages that on the basis of ensuring the high-temperature mechanical property and the carburization resistance, the Ni content is rapidly reduced, the service life of a cracking furnace is greatly prolonged, the production cost is reduced, and the CNRE rare earth heat-resistant steel has obvious technical advantages and cost advantages.
Drawings
FIG. 1 is a diagram of a high-strength anti-carburizing CNRE rare earth refractory steel cracking pipe joint.
FIG. 2 is a carburized layer morphology of a rare earth heat-resistant steel pipe joint of example 1.
FIG. 3 is a carburized layer morphology of a rare earth heat-resistant steel pipe joint of example 2.
FIG. 4 is a carburized layer morphology of a rare earth heat-resistant steel pipe joint of example 3.
FIG. 5 shows the appearance of a carburized layer of a conventional Cr25Ni20 heat-resistant steel for comparative example.
Detailed Description
In the specific implementation process, the high-strength and anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint disclosed by the invention is subjected to co-alloying and V, Nb and RE microalloying by C, N, wherein the alloy component ranges are as follows in percentage by weight: 0.3 to 0.6% (preferably 0.35 to 0.46%) of C, 0.5 to 3.5% (preferably 1.95 to 2.4%) of Si, 6.0 to 13.0% (preferably 7.3 to 9.95%) of Mn, 16.0 to 26.0% (preferably 18.6 to 23.7%) of Cr, 1.0 to 5.0% (preferably 2.20 to 3.75%) of Ni, 0.3 to 3.0% (preferably 0.8 to 1.9%) of Mo, 0.05 to 0.50% (preferably 0.07 to 0.25%) of V, 0.05 to 0.50% (preferably 0.08 to 0.13%) of Nb, 0.2 to 0.6% (preferably 0.26 to 0.48%) of N, 0.005 to 0.5% (preferably 0.020 to 0.035%) of RE, and the balance Fe.
The high-strength and anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint is smelted by adopting an intermediate frequency furnace, and a pipe joint casting with uniform components, compact structure and excellent performance is obtained by adopting an intermediate frequency furnace high nitrogen alloying technology, a high-purity rare earth treatment technology and a shell type precision casting technology. The method specifically comprises the following steps:
(1) smelting molten steel: molten steel is melted by adopting an intermediate frequency furnace, the furnace lining adopts alkaline refractory, high-quality scrap steel, intermediate alloy and pure metal are taken as raw materials, the scrap steel and the intermediate alloy or the pure metal, elements of which are not easy to burn, are preferentially added, and aluminum is added for pre-deoxidation after furnace burden is completely melted.
(2) Alloying of Si and Mn: after pre-deoxidation, ferrosilicon or metallic silicon and electrolytic manganese are added in sequence to carry out Si and Mn alloying, and after melting down, calcium silicon is adopted to carry out full deoxidation.
(3) Nitrogen alloying: after manganese alloying, heating the molten steel to 1580-1650 ℃, adding the nitrogen-containing alloy with the diameter less than or equal to 100mm and baked at 400-800 ℃ in batches, and adding the nitrogen-containing alloy for the next time after the molten steel does not tumble for 2-8 minutes, wherein the interval time of each time is 3-10 minutes.
(4) Component adjustment: according to the online detection of components of the molten steel, C, Si and Mn are adjusted to target components, and then the molten steel is finally deoxidized.
(5) V, Nb microalloying: and after the molten steel is subjected to final deoxidation, adding ferrovanadium and ferroniobium for V, Nb microalloying 5-10 minutes before tapping, and tapping when the components and the temperature of the molten steel meet the requirements.
(6) Rare earth treatment: before rare earth treatment, the total oxygen content T.O in molten steel is less than or equal to 60ppm, rare earth treatment is carried out by adopting high-purity rare earth metal in the tapping process, the high-purity rare earth metal is metal lanthanum, metal cerium or lanthanum-cerium mixed metal with the total oxygen content T.O less than or equal to 300ppm, the content of rare earth elements is more than 99 wt%, the high-purity rare earth metal is made into small blocks of 0.1-1.5 kg and is put at the bottom of a steel ladle, the adding amount of the rare earth metal is 0.01-0.08% of the weight of the molten steel, and the molten steel melts the rare earth during tapping and is uniformly mixed in the steel ladle.
(7) Shell mold casting: the method is characterized in that magnesia is selected as a refractory material of the precision casting shell mold, water glass is selected as a binder, the shell mold is baked at 900-950 ℃ before casting, the temperature of the shell mold is more than or equal to 850 ℃ during casting, the casting temperature is 1480-1550 ℃, stable and rapid casting is carried out, the time is less than or equal to 30min after casting is finished, and the pipe joint casting and the shell mold are rapidly cooled to room temperature in water.
Sampling at the pipe joint body, detecting the tensile property of the pipe joint at room temperature and high temperature, and the technical indexes are as follows:
at room temperature, the yield strength is 490-595 MPa, the tensile strength is 915-990 MPa, the elongation is 45-60%, and the reduction of area is 45-55%. At the high temperature of 1000 ℃, the yield strength is 50-80 MPa, the tensile strength is 115-135 MPa, the elongation is 55-65%, and the reduction of area is 50-60%.
In order to make the technical solution and advantages of the present invention more clear, the following detailed description is made with reference to the specific embodiments and the accompanying drawings.
Example 1
In the embodiment, the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint comprises the following specific components in percentage by weight:
| element(s) | Content (mass fraction, wt.%) |
| C+N | 0.61(C0.35，N0.26) |
| Si | 1.95 |
| Mn | 7.34 |
| Cr | 18.6 |
| Ni | 3.72 |
| Mo | 0.82 |
| V | 0.07 |
| Nb | 0.10 |
| RE | 0.020 |
| Fe | Balance of |
In this example, the preparation process of the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint is as follows:
molten steel is smelted by adopting an intermediate frequency furnace, and the furnace lining of the intermediate frequency furnace adopts an alkaline refractory and an alkaline casting ladle. The alloy ingredients are scrap steel, ferrochromium nitride, low-carbon ferrochromium, high-iron ferrochromium, electrolytic manganese, nickel plate, ferrosilicon, ferromolybdenum, ferroniobium, ferrovanadium, high-purity rare earth metal and the like. Wherein, the chromium iron nitride is crushed to be less than 85mm, and is preheated for more than 4 hours at 600 ℃ together with ferrosilicon, ferromolybdenum, low-carbon ferrochrome, high-iron ferrochrome, scrap steel and the like, and the electrolytic manganese, ferrovanadium and ferroniobium are preheated for more than 2 hours at 200 ℃. Firstly, charging scrap steel, nickel plates, ferromolybdenum, low-carbon ferrochromium and high-carbon ferrochromium into a furnace, and realizing tightness at the bottom and looseness at the top in the charging process to prevent bridging. And after the alloy materials are completely melted, adding an aluminum wire for pre-deoxidation. After pre-deoxidation, adding ferrosilicon for silicon alloying, and after melting down, adding calcium-silicon alloy for full deoxidation; and then, adding electrolytic manganese for manganese alloying, and adding a silicon-calcium alloy for full deoxidation after melting down. After manganese alloying, the temperature of the molten steel is increased to 1590 ℃, the ferrochrome nitride is added in 3 batches, and the molten steel is added for the next time after not turning over for 2 minutes, with the interval of 5 minutes each time. After nitrogen alloying, sampling and analyzing components, and adjusting C, Si and Mn in the molten steel to target values according to the component analysis result. After the components are qualified, adding the silicon-calcium alloy for final deoxidation treatment, and controlling the total oxygen content in the molten steel. And after final deoxidation, adding ferrovanadium and ferroniobium for V, Nb microalloying 5 minutes before tapping, and preparing to tap when the components and the temperature of the molten steel meet the requirements. Before rare earth treatment, the total oxygen content T.O in the molten steel is 30ppm, and during the tapping process, high-purity rare earth metal is adopted for rare earth treatment, wherein the high-purity rare earth metal is pure cerium metal with the total oxygen content T.O of 190ppm, and the content of rare earth elements is 99.5 wt%. Making high-purity rare earth metal into small blocks of about 0.8kg, placing the small blocks into the bottom of a steel ladle close to the side of a furnace mouth, wherein the addition amount of the rare earth metal is 0.04 percent of the weight of molten steel, covering the small blocks with a small amount of clean and dry scrap iron or steel scrap, and melting the rare earth metal by the molten steel in the tapping process. The pipe joint casting is cast by shell mold precision casting, magnesia is selected as a shell mold refractory material, water glass is selected as a binder, the shell mold is baked at 950 ℃ before casting, the temperature of the shell mold is 900 ℃ and the casting temperature is 1540 ℃ during casting, stable and rapid casting is carried out, and the pipe joint casting and the shell mold are rapidly cooled to room temperature by entering water 20min after casting is completed.
In this example, the pipe joint body was sampled, and the room temperature and high temperature tensile properties of the pipe joint and the morphology of the carburized layer after 30 hours of accelerated carburization at 1000 ℃ were examined to evaluate the strength and carburization resistance of the pipe joint. The test results were as follows:
| temperature/. degree.C | Yield strength/MPa | Tensile strength/MPa | Elongation/percent | Reduction of area/%) |
| At room temperature | 494 | 917 | 58.5 | 50 |
| 1000 | 53 | 118 | 61.5 | 55 |
As shown in fig. 1 and 2, the morphology of the carburized layer after 30 hours of accelerated carburization at 1000 ℃ shows that no significant carburization occurs. The tensile strength at room temperature reaches 917MPa, the tensile strength at high temperature of 1000 ℃ reaches 118MPa, and the high-strength steel has high room temperature and high temperature strength. The C, N interstitial atoms and RE atoms with high concentration inhibit the diffusion of C atoms, have good anti-carburizing capability, are used for the joint of the ethylene cracking pipe, and do not generate obvious coking phenomenon within three years.
Example 2
In the embodiment, the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint comprises the following specific components in percentage by weight:
in this example, the preparation process of the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint is as follows:
molten steel is smelted by adopting an intermediate frequency furnace, and the furnace lining of the intermediate frequency furnace adopts an alkaline refractory and an alkaline casting ladle. The alloy ingredients are scrap steel, ferrochromium nitride, low-carbon ferrochromium, high-iron ferrochromium, electrolytic manganese, nickel plate, ferrosilicon, ferromolybdenum, ferroniobium, ferrovanadium, high-purity rare earth metal and the like. Wherein, the chromium iron nitride is crushed to be less than 40mm, and is preheated for more than 4 hours at 600 ℃ together with ferrosilicon, ferromolybdenum, low-carbon ferrochrome, high-iron ferrochrome, scrap steel and the like, and the electrolytic manganese, ferrovanadium and ferroniobium are preheated for more than 2 hours at 200 ℃. Firstly, charging scrap steel, nickel plates, ferromolybdenum, low-carbon ferrochromium and high-carbon ferrochromium into a furnace, and realizing tightness at the bottom and looseness at the top in the charging process to prevent bridging. And after the alloy materials are completely melted, adding an aluminum wire for pre-deoxidation. After pre-deoxidation, adding ferrosilicon for silicon alloying, and after melting down, adding calcium-silicon alloy for full deoxidation; and then, adding electrolytic manganese for manganese alloying, and adding a silicon-calcium alloy for full deoxidation after melting down. After manganese alloying, the temperature of the molten steel is raised to 1650 ℃, the ferrochromium nitride is added in 3 batches, and the molten steel is added for the next time after not boiling for 4 minutes, with the interval of 8 minutes each time. After nitrogen alloying, sampling and analyzing components, and adjusting C, Si and Mn in the molten steel to target values according to the component analysis result. After the components are qualified, adding the silicon-calcium alloy for final deoxidation treatment, and controlling the total oxygen content in the molten steel. And after final deoxidation, adding ferrovanadium and ferroniobium for V, Nb microalloying 7 minutes before tapping, and preparing to tap when the components and the temperature of the molten steel meet the requirements. Before rare earth treatment, the total oxygen content T.O in molten steel is 40ppm, and in the tapping process, rare earth treatment is carried out by adopting high-purity rare earth metal, wherein the high-purity rare earth metal is pure cerium metal with the total oxygen content T.O of 250ppm, and the content of rare earth elements is 99.8 wt%. Making high-purity rare earth metal into small blocks of about 1.2kg, placing the small blocks into the bottom of a steel ladle close to the side of a furnace mouth, wherein the addition amount of the rare earth metal is 0.06 percent of the weight of molten steel, covering the small blocks with a small amount of clean and dry scrap iron or steel scrap, and melting the rare earth metal by the molten steel in the tapping process. The pipe joint casting is cast by shell mold precision casting, magnesia is selected as a shell mold refractory material, water glass is selected as a binder, the shell mold is baked at 900 ℃ before casting, the temperature of the shell mold is 860 ℃ and 1500 ℃ during casting, stable and rapid casting is carried out, and the pipe joint casting and the shell mold are rapidly cooled to room temperature by entering water 30min after casting is completed.
In this example, the pipe joint body was sampled, and the room temperature and high temperature tensile properties of the pipe joint and the morphology of the carburized layer after 30 hours of accelerated carburization at 1000 ℃ were examined to evaluate the strength and carburization resistance of the pipe joint. The test results were as follows:
| temperature/. degree.C | Yield strength/MPa | Tensile strength/MPa | Elongation/percent | Reduction of area/%) |
| At room temperature | 592 | 989 | 55.5 | 45 |
| 1000 | 76 | 131 | 56.0 | 57 |
As shown in FIG. 3, the morphology of the carburized layer after 30h of accelerated carburization at 1000 ℃ is shown, and as can be seen from the figure, no significant carburization occurs. The room temperature tensile strength reaches 989MPa, the high temperature tensile strength reaches 131MPa at 1000 ℃, and the high room temperature and high temperature strength is realized. The C, N interstitial atoms and RE atoms with high concentration inhibit the diffusion of C atoms, have good anti-carburizing capability, are used for the joint of the ethylene cracking pipe, and do not generate obvious coking phenomenon within three years.
Example 3
In the embodiment, the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint comprises the following specific components in percentage by weight:
| element(s) | Content (mass fraction, wt.%) |
| C+N | 0.94(C0.46，N0.48) |
| Si | 2.12 |
| Mn | 8.8 |
| Cr | 20.92 |
| Ni | 3.35 |
| Mo | 1.4 |
| V | 0.25 |
| Nb | 0.08 |
| RE | 0.035 |
| Fe | Balance of |
In this example, the preparation process of the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint is as follows:
molten steel is smelted by adopting an intermediate frequency furnace, and the furnace lining of the intermediate frequency furnace adopts an alkaline refractory and an alkaline casting ladle. The alloy ingredients are scrap steel, ferrochromium nitride, low-carbon ferrochromium, high-iron ferrochromium, electrolytic manganese, nickel plate, ferrosilicon, ferromolybdenum, ferroniobium, ferrovanadium, high-purity rare earth metal and the like. Wherein, the chromium iron nitride is crushed to be less than 50mm, and is preheated for more than 4 hours at 600 ℃ together with ferrosilicon, ferromolybdenum, low-carbon ferrochrome, high-iron ferrochrome, scrap steel and the like, and the electrolytic manganese, ferrovanadium and ferroniobium are preheated for more than 2 hours at 200 ℃. Firstly, charging scrap steel, nickel plates, ferromolybdenum, low-carbon ferrochromium and high-carbon ferrochromium into a furnace, and realizing tightness at the bottom and looseness at the top in the charging process to prevent bridging. And after the alloy materials are completely melted, adding an aluminum wire for pre-deoxidation. After pre-deoxidation, adding ferrosilicon for silicon alloying, and after melting down, adding calcium-silicon alloy for full deoxidation; and then, adding electrolytic manganese for manganese alloying, and adding a silicon-calcium alloy for full deoxidation after melting down. After manganese alloying, the temperature of the molten steel is raised to 1620 ℃, ferrochromium nitride is added in 3 batches, and the molten steel is added for the next time after not turning over for 3 minutes, wherein the interval of each time is 9 minutes. After nitrogen alloying, sampling and analyzing components, and adjusting C, Si and Mn in the molten steel to target values according to the component analysis result. After the components are qualified, adding the silicon-calcium alloy for final deoxidation treatment, and controlling the total oxygen content in the molten steel. And after final deoxidation, adding ferrovanadium and ferroniobium for V, Nb microalloying 6 minutes before tapping, and preparing to tap when the components and the temperature of the molten steel meet the requirements. Before rare earth treatment, the total oxygen content T.O in molten steel is 50ppm, and in the tapping process, high-purity rare earth metal is adopted for rare earth treatment, wherein the high-purity rare earth metal is pure cerium metal with the total oxygen content T.O of 140ppm, and the content of rare earth elements is 99.9 wt%. Making high-purity rare earth metal into small blocks of about 0.5kg, placing the small blocks into the bottom of a steel ladle close to the side of a furnace mouth, wherein the addition amount of the rare earth metal is 0.06 percent of the weight of molten steel, covering the small blocks with a small amount of clean and dry scrap iron or steel scrap, and melting the rare earth metal by the molten steel in the tapping process. The pipe joint casting is cast by adopting shell mold precision casting, magnesia is selected as a shell mold refractory material, water glass is selected as a binder, the shell mold is baked at 930 ℃ before casting, the temperature of the shell mold is 890 ℃ and the casting temperature is 1530 ℃ during casting, stable and rapid casting is carried out, and the pipe joint casting and the shell mold are rapidly cooled to room temperature in water after 20 min.
In this example, the pipe joint body was sampled, and the room temperature and high temperature tensile properties of the pipe joint and the morphology of the carburized layer after 30 hours of accelerated carburization at 1000 ℃ were examined to evaluate the strength and carburization resistance of the pipe joint. The test results were as follows:
| temperature/. degree.C | Yield strength/MPa | Tensile strength/MPa | Elongation/percent | Reduction of area/%) |
| At room temperature | 581 | 974 | 45.0 | 51 |
| 1000 | 66 | 126 | 57.5 | 52 |
As shown in FIG. 4, the morphology of the carburized layer after 30h of accelerated carburization at 1000 ℃ is shown, and as can be seen from the figure, no significant carburization occurs. The room temperature tensile strength reaches 974MPa, the high temperature tensile strength reaches 126MPa at 1000 ℃, and the high room temperature and high temperature strength is realized. The C, N interstitial atoms and RE atoms with high concentration inhibit the diffusion of C atoms, have good anti-carburizing capability, are used for the joint of the ethylene cracking pipe, and do not generate obvious coking phenomenon within three years.
Comparative example
The traditional material for casting the petrochemical cracking tube is high Cr and high Ni type austenitic heat-resistant alloy, and the most basic materials are HK40(Cr25Ni20), HP40(Cr25Ni35) and Cr35Ni45, Cr28Ni48 and the like developed on the basis. The Ni content of the heat-resistant alloy is very high, and the Ni element has a remarkable catalytic action on hydrocarbon carburization and coking, so that the carburization and coking rates of the pipe joint are accelerated, even the defects of carburization cracking and the like are caused, and the service life is reduced. As shown in FIG. 5, in the case of Cr25Ni20 heat-resistant alloy, after accelerated carburization at 1000 ℃ for 30 hours, the carburized layer depth was about 0.8mm, which is much larger than that of CNRE rare earth heat-resistant steel.
Claims (10)
1. The high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint is characterized by comprising the following chemical components in percentage by weight: 0.3-0.6% of C, 0.5-3.5% of Si, 6.0-13.0% of Mn, 16.0-26.0% of Cr, 1.0-5.0% of Ni, 0.3-3.0% of Mo, 0.05-0.50% of V, 0.05-0.50% of Nb, 0.2-0.6% of N, 0.005-0.5% of RE and the balance of Fe.
2. The high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint according to claim 1, characterized in that C, N is adopted for co-alloying in percentage by weight, and C + N is 0.60-1.00%; RE, V and Nb are microalloyed, wherein RE is 0.005-0.050%, V is 0.05-0.30% and Nb is 0.05-0.20%.
3. The high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint according to claim 1, characterized in that the chemical composition range is as follows by weight percent: 0.35-0.50% of C, 1.9-2.4% of Si, 7.0-10.0% of Mn, 18.0-24.0% of Cr, 2.0-4.0% of Ni, 0.8-2.0% of Mo, 0.05-0.25% of V, 0.05-0.15% of Nb, 0.25-0.50% of N, 0.020-0.035% of RE and the balance of Fe.
4. The high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint as claimed in claim 1, wherein the tensile strength at the high temperature of 1000 ℃ is not less than 100MPa, and the steel is used for the ethylene cracking pipe joint and does not generate obvious coking phenomenon after being used for more than three years.
5. A preparation method of the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint, which is characterized by comprising the following steps of smelting in an intermediate frequency furnace, and obtaining a pipe joint casting with uniform components, compact structure and excellent performance by using an intermediate frequency furnace high nitrogen alloying technology, a high-purity rare earth treatment technology and a shell type precision casting technology, wherein the preparation method comprises the following steps of:
(1) smelting molten steel: smelting molten steel by adopting an intermediate frequency furnace, taking scrap steel, intermediate alloy and pure metal as raw materials, preferentially adding the scrap steel and the intermediate alloy or the pure metal, the elements of which are not easy to burn, and adding aluminum for pre-deoxidation after furnace burden is completely melted;
(2) alloying of Si and Mn: after pre-deoxidation, adding ferrosilicon or metallic silicon and electrolytic manganese in sequence to carry out Si and Mn alloying, and after melting down, fully deoxidizing by adopting a silicon-calcium alloy;
(3) nitrogen alloying: after manganese alloying, heating the molten steel to more than or equal to 1580 ℃, adding the nitrogen-containing alloy in batches, and adding the nitrogen-containing alloy for the next time after the molten steel does not tumble for more than or equal to 2 minutes, wherein the time interval of each time is more than or equal to 3 minutes;
(4) v, Nb microalloying: after the molten steel is finally deoxidized, adding ferrovanadium and ferroniobium for V, Nb microalloying before tapping for less than or equal to 10 minutes, and tapping when the components and the temperature of the molten steel meet the requirements;
(5) rare earth treatment: carrying out rare earth treatment by using high-purity rare earth metal in the tapping process, preparing the high-purity rare earth metal into small blocks of 0.1-1.5 kg, putting the small blocks into the bottom of a steel ladle, washing the small blocks with molten steel during tapping to melt the rare earth metal, and uniformly mixing the molten metal and the molten steel in the steel ladle;
(6) precision casting: and (3) pouring at the pouring temperature of 1480-1550 ℃, stably and quickly pouring, wherein the pouring time is less than or equal to 30min after pouring, and quickly cooling the pipe joint casting and the shell to room temperature in water.
6. The method for preparing the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint according to claim 5, wherein in the steps (1) and (5), the furnace lining and the ladle lining are both made of neutral or alkaline caking materials in intermediate frequency furnaces and ladles used for molten steel smelting and pouring.
7. The method for preparing the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint according to claim 5, wherein in the step (3), the nitrogen-containing alloy adopted in nitrogen alloying is crushed to be less than 100mm and is preheated at 400-800 ℃.
8. The method for preparing a high-strength, anti-carburizing CNRE rare earth heat-resistant steel for cracking pipe joints according to claim 5, wherein after the step (3), the components are detected on line according to molten steel, and finally adjusted to target components.
9. The method for preparing a high-strength anti-carburization CNRE rare earth heat-resistant steel for cracking pipe joints according to claim 5, wherein in step (5), the high-purity rare earth metal used for the rare earth treatment is lanthanum metal, cerium metal or lanthanum-cerium mixed metal with a total oxygen content T.O of less than or equal to 300ppm, the rare earth element content is more than 99 wt%, and the total oxygen content T.O in the molten steel before the rare earth treatment is less than or equal to 60 ppm.
10. The preparation method of the high-strength anti-carburizing CNRE rare earth heat-resistant steel for the cracking pipe joint according to claim 5, wherein in the step (6), the precision casting shell mold is baked at 900-950 ℃ before pouring, and the temperature of the shell mold is not less than 850 ℃ during pouring.
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| CN115896609A (en) * | 2022-07-06 | 2023-04-04 | 钢铁研究总院有限公司 | High-strength high-plasticity air valve steel and preparation method thereof |
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| CN112410664A (en) * | 2020-11-09 | 2021-02-26 | 中国科学院金属研究所 | High-strength and anti-nodule CNRE rare earth heat-resistant steel for hearth roll and preparation method thereof |
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| CN112410664A (en) * | 2020-11-09 | 2021-02-26 | 中国科学院金属研究所 | High-strength and anti-nodule CNRE rare earth heat-resistant steel for hearth roll and preparation method thereof |
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| 中国科学院信息咨询中心编: "《中国科学院新技术新产品汇编 第4分册 仪器设备、机械、金属》", 31 December 1990, 中国科学院信息咨询中心 * |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115896609A (en) * | 2022-07-06 | 2023-04-04 | 钢铁研究总院有限公司 | High-strength high-plasticity air valve steel and preparation method thereof |
| CN115896609B (en) * | 2022-07-06 | 2024-04-05 | 钢铁研究总院有限公司 | High-strength high-plasticity air valve steel and preparation method thereof |
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