CN112647021B - High-strength 9% Ni steel for ultralow-temperature engineering fastener and preparation method thereof - Google Patents
High-strength 9% Ni steel for ultralow-temperature engineering fastener and preparation method thereof Download PDFInfo
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
- B21J5/002—Hybrid process, e.g. forging following casting
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/04—Refining by applying a vacuum
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- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/16—Remelting metals
- C22B9/18—Electroslag remelting
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- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C22C38/18—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
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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
- C22C38/18—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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y02P10/25—Process efficiency
Abstract
The invention provides high-strength 9% Ni steel for an ultralow-temperature engineering fastener and a preparation method thereof, and relates to the technical field of low-temperature metal materials. The invention adopts the vacuum induction and electroslag remelting smelting process, so that the high-strength 9% Ni steel for the ultralow-temperature engineering fastener has higher purity and lower gas content; the high-strength 9% Ni steel for the ultra-low temperature engineering fastener has extremely excellent room/low temperature mechanical properties by adopting forging and a matched heat treatment process with a high stable structure state, namely quenching and tempering. The data of the examples show that: the yield strength of the high-strength 9% Ni steel for the ultra-low temperature engineering fastener at room temperature is more than 800MPa, the elongation after fracture is more than 20%, the reduction of area is more than 65%, and the AKv impact absorption energy at minus 196 ℃ is more than 85J.
Description
Technical Field
The invention relates to the technical field of low-temperature metal materials, in particular to high-strength 9% Ni steel for ultralow-temperature engineering fasteners and a preparation method thereof.
Background
The 9% Ni steel is the only martensite type steel which can be used at the low temperature of-196 ℃ at present, and the 9% Ni steel has high yield strength and also has excellent low-temperature toughness and welding performance. In the prior art, in order to improve the low-temperature toughness of a 9% Ni steel forging, QLT (quenching and quenching at low temperature) is generally adopted during heat treatment, namely the toughness is improved by a method of 'complete quenching, sub-temperature quenching and tempering', the V-shaped impact energy of the forging treated by the method at the temperature of 196 ℃ below zero can reach more than 80J, but the yield strength is generally between 500 and 650MPa due to the sub-temperature quenching.
When 9% Ni steel is used as a fastener in large-scale low-temperature equipment under the working condition of-196 ℃, the yield strength is required to be more than 800 MPa; meanwhile, the low-temperature toughness index (-196 ℃ V-shaped impact energy is more than 80J) is ensured to be kept unchanged. However, the manufacturing methods disclosed in the prior art do not allow to obtain a 9% Ni steel that meets the performance requirements.
Disclosure of Invention
In view of the above, the invention aims to provide high-strength 9% Ni steel for ultralow-temperature engineering fasteners and a preparation method thereof. The high-strength 9% Ni steel for the ultralow-temperature engineering fastener obtained by the preparation method provided by the invention has the yield strength of more than 800MPa at room temperature, the elongation after fracture of more than 20%, the reduction of area of more than 65%, and the V-shaped impact energy at-196 ℃ of more than 85J. On the premise of ensuring the low-temperature toughness, the extremely excellent comprehensive mechanical property is obtained through the design of alloy components and a matched heat treatment process system, and particularly the yield strength is obviously improved.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of high-strength 9% Ni steel for an ultralow-temperature engineering fastener, which comprises the following steps:
smelting the raw materials according to a vacuum induction-electroslag remelting process, and casting the obtained smelting liquid to obtain a steel ingot; the raw materials are weighed according to the following weight percentage by element content: 0.02-0.06% of C, less than or equal to 0.15% of Si, 0.30-0.80% of Mn, less than or equal to 0.005% of S, less than or equal to 0.008% of P, less than or equal to 0.10% of Cr, 0.03-0.08% of V, 9.50-10.0% of Ni, 0.12-0.16% of Mo, less than or equal to 1.0ppm of H, less than or equal to 0.01% of O, less than or equal to 0.01% of N, and the balance of high-purity Fe;
forging the steel ingot to obtain a forging piece; the initial forging temperature of the forging is not more than 1200 ℃, and the final forging temperature of the forging is 850-900 ℃;
sequentially quenching and tempering the forging to obtain the high-strength 9% Ni steel for the ultralow-temperature engineering fastener;
the quenching process comprises the following steps:
carrying out first heat preservation on the forge piece after the forge piece is heated to T1 for the first time, carrying out second heat preservation after the forge piece is heated to T2 for the second time, and carrying out third heat preservation after the forge piece is heated to T3 for the third time;
the temperature T1 is 200-300 ℃, and the first heat preservation time is 1-2 h; the temperature T2 is 520-580 ℃, and the second heat preservation time is 1-2 h; the temperature T3 is 800-860 ℃, and the third heat preservation time is 1.5-2.0 h/100mm of the effective thickness of the forging piece;
the tempering comprises the following steps:
performing fourth heat preservation after fourth temperature rise to T4, and performing fifth heat preservation after fifth temperature rise to T5;
the temperature T4 is 250-350 ℃, and the fourth heat preservation time is 2-3 h; the temperature T5 is 520-580 ℃, and the fifth heat preservation time is 2.0-4.0 h/100mm of the effective thickness of the forge piece.
Preferably, the parameters of the vacuum induction-electroslag remelting process comprise vacuum induction parameters and electroslag remelting parameters; the vacuum induction parameters include: the chemical material power is 600-800 kW, and the power-rise rate is 200 kW/h; the refining temperature is 1550-1580 ℃, and the vacuum degree is less than 0.1 Pa; performing early-stage deoxidation by using Ca after refining is finished, performing final deoxidation by using Ni-Mg alloy after the components are adjusted to be qualified, wherein the final tapping temperature is 1590 +/-10 ℃; the electroslag remelting parameters comprise: the slag system for electroslag remelting is a ternary slag system; the ternary slag system comprises the following components: CaF 60%, Al2O325 percent of CaO, 15 percent of CaO; the melting speed is 10 &12 kg/min; the atmosphere of the electroslag remelting is dry air.
Preferably, the forging ratio of the forging is > 5.
Preferably, the forging further comprises embedding the obtained forging in sand and cooling to room temperature.
Preferably, the rates of the first temperature rise, the second temperature rise and the third temperature rise are independently less than or equal to 80 ℃/h.
Preferably, after quenching, the quenching method further comprises the step of soaking the obtained quenched forging in water for cooling, and then cooling the quenched forging to room temperature in air.
Preferably, after the tempering is finished, the obtained tempered forging is air-cooled to room temperature.
The invention also provides the high-strength 9% Ni steel for the ultralow-temperature engineering fastener, which is prepared by the preparation method in the technical scheme, the yield strength at room temperature is more than 800MPa, the elongation after fracture is more than 20%, the reduction of area is more than 65%, and the V-shaped impact energy at minus 196 ℃ is more than 85J.
The invention provides a preparation method of high-strength 9% Ni steel for an ultralow-temperature engineering fastener, which adopts a vacuum induction-electroslag remelting process to smelt, so that the high-strength 9% Ni steel for the ultralow-temperature engineering fastener has higher purity and lower gas content; the high-strength 9% Ni steel for the ultra-low temperature engineering fastener has extremely excellent room/low temperature mechanical properties by adopting forging and a matched heat treatment process with a high stable structure state, namely quenching and tempering. The data of the examples show that: the yield strength of the high-strength 9% Ni steel for the ultra-low temperature engineering fastener is more than 800MPa at room temperature, the elongation after fracture is more than 20%, the reduction of area is more than 65%, and the V-shaped impact energy at minus 196 ℃ is more than 85J.
Detailed Description
The invention provides a preparation method of high-strength 9% Ni steel for an ultralow-temperature engineering fastener, which comprises the following steps:
smelting the raw materials according to a vacuum induction-electroslag remelting process, and casting the obtained smelting liquid to obtain a steel ingot; the raw materials are weighed according to the following weight percentage by element content: 0.02-0.06% of C, less than or equal to 0.15% of Si, 0.30-0.80% of Mn, less than or equal to 0.005% of S, less than or equal to 0.008% of P, less than or equal to 0.10% of Cr, 0.03-0.08% of V, 9.50-10.0% of Ni, 0.12-0.16% of Mo, less than or equal to 1.0ppm of H, less than or equal to 0.01% of O, less than or equal to 0.01% of N, and the balance of high-purity Fe;
forging the steel ingot to obtain a forging piece;
and sequentially quenching and tempering the forging to obtain the high-strength 9% Ni steel for the ultralow-temperature engineering fastener.
Smelting the raw materials according to a vacuum induction-electroslag remelting process, and casting the obtained smelting liquid to obtain a steel ingot; the raw materials are weighed according to the following weight percentage by element content: 0.02-0.06% of C, less than or equal to 0.15% of Si, 0.30-0.80% of Mn, less than or equal to 0.005% of S, less than or equal to 0.008% of P, less than or equal to 0.10% of Cr, 0.03-0.08% of V, 9.50-10.0% of Ni, 0.12-0.16% of Mo, less than or equal to 1.0ppm of H, less than or equal to 0.01% of O, less than or equal to 0.01% of N, and the balance of high-purity Fe.
In the invention, the raw material of the high-strength 9% Ni steel for the ultralow-temperature engineering fastener comprises 0.02-0.06% of C by mass, and preferably 0.029-0.043% by mass. In the present invention, C is interstitial solid solution atom, which can significantly improve the strength of 9% Ni% steel by solid solution strengthening, but also reduce toughness; in addition, C is also an austenite stabilizing element and can improve the stability of austenite, but in the invention patent, the improvement of the stability of austenite is mainly completed by Ni element, and the content range of C is controlled to be 0.02-0.06 percent in comprehensive consideration.
In the invention, the raw material of the high-strength 9% Ni steel for the ultralow-temperature engineering fastener comprises Si with the mass percentage content of less than or equal to 0.15%, and preferably 0.038-0.12%. In the present invention, Si has a strong solid solution strengthening effect, but an excessive amount of Si deteriorates the ductility and toughness of steel and increases the temper brittleness. Comprehensively, the Si content of the steel is controlled within 0.15 percent.
In the invention, the raw material of the high-strength 9% Ni steel for the ultralow-temperature engineering fastener comprises 0.30-0.80% of Mn by mass percentage, and preferably 0.61-0.71%. In the invention, the Mn has the same action with C and is an austenite stabilizing element, and the hardenability of the steel can be improved, and the Mn content of the steel is controlled to be 0.30-0.80% in comprehensive consideration.
In the invention, the raw material of the high-strength 9% Ni steel for the ultralow-temperature engineering fastener comprises Cr with the mass percentage content of less than or equal to 0.10%, and preferably 0.015-0.020%. In the present invention, Cr is bonded to N to form Cr, although the Cr can improve hardenability and atmospheric corrosion resistance of steel2N, thereby reducing the toughness of the steel and plastic, and therefore, the comprehensive consideration is controlled within 0.10 percent.
In the invention, the raw material of the high-strength 9% Ni steel for the ultralow-temperature engineering fastener comprises 0.03-0.08% of V by mass percentage, and preferably 0.037-0.044% by mass percentage. In the invention, the V can precipitate dispersed fine VC particles from a martensite matrix in the tempering process, has obvious precipitation strengthening effect, but can sacrifice part of ductility and toughness, and has higher cost. Comprehensively considered, the V content of the steel is controlled to be 0.03-0.08%.
In the invention, the raw material of the high-strength 9% Ni steel for the ultralow-temperature engineering fastener comprises 9.50-10.0% of Ni by mass, and preferably 9.61-9.97%. In the invention, the Ni is one of the most important alloy elements, can obviously improve the stability of austenite, and is beneficial to finally obtaining stable austenite; in addition, the hardenability and atmospheric corrosion resistance of the steel are improved by nickel, and the Ni content of the steel is controlled to be 9.50-10.0% in comprehensive consideration.
In the invention, the raw material of the high-strength 9% Ni steel for the ultralow-temperature engineering fastener comprises 0.12-0.16% of Mo by mass, and preferably 0.15% by mass. In the invention, Mo is the most important alloy element which obviously improves the yield strength of the invention, on one hand, Mo can obviously improve the hardenability of steel, reduce the temper brittleness and obviously improve the room temperature strength and the delayed fracture resistance of the steel; however, as the Mo content in the steel increases, the ductility and toughness of the steel, particularly the low-temperature ductility and toughness, may be reduced. Comprehensively, the Mo content of the invention is controlled to be 0.12-0.16%.
In the invention, the raw material of the high-strength 9% Ni steel for the ultralow-temperature engineering fastener comprises P and S, and the P and S are impurity elements in the steel, so that the ductility, toughness and welding performance are obviously reduced, and therefore, the content of the P and the content of the S in the raw material for preparing the high-strength 9% Ni steel for the ultralow-temperature engineering fastener are respectively controlled within 0.008% and 0.005%.
In the invention, the raw materials of the high-strength 9% Ni steel for the ultra-low temperature engineering fastener comprise H, O and N; H. o and N are gas elements in steel, which obviously reduces the ductility and toughness, particularly the low-temperature ductility and toughness, so the gas content in the high-strength 9 percent Ni steel for preparing the ultralow-temperature engineering fastener is strictly controlled to be less than or equal to 1.0ppm of H, less than or equal to 0.01 percent of O and less than or equal to 0.01 percent of N.
In the present invention, the raw material of the high-strength 9% Ni steel for the ultra-low temperature engineering fastener includes the balance of high-purity iron.
The addition form of each component in the raw materials is not particularly limited as long as the mass percentage content of the elements can be met.
In the invention, the parameters of the vacuum induction-electroslag remelting process comprise vacuum induction parameters and electroslag remelting parameters; the vacuum sensing parameters preferably include: the chemical material power is 600-800 kW, and the power-rise rate is 200 kW/h; the refining temperature is 1550-1580 ℃, and the vacuum degree is less than 0.1 Pa; performing early-stage deoxidation by using Ca after refining is finished, performing final deoxidation by using Ni-Mg alloy after the components are adjusted to be qualified, wherein the final tapping temperature is 1590 +/-10 ℃; the electroslag remelting parameters preferably comprise: the slag system for electroslag remelting is a ternary slag system; the ternary slag system comprises the following components: CaF 60%, Al2O325 percent of CaO, 15 percent of CaO; the melting speed is 10-12 kg/min; the atmosphere of the electroslag remelting is dry air.
In the invention, the steel ingot is prepared by adopting a vacuum melting and electroslag remelting method, so that the purity, the uniform components and the lower gas content of the steel ingot can be ensured, and the toughness of the final 9% Ni steel for the ultralow-temperature engineering fastener is improved.
After the steel ingot is obtained, the steel ingot is forged to obtain a forging.
In the invention, the initial forging temperature of the forging is not more than 1200 ℃, preferably 1160-1200 ℃; the final forging temperature of the forging is 850-900 ℃. In the invention, the forging ratio is preferably > 5, and more preferably 6 to 7; in the present invention, the forging is preferably performed on a press. After forging, the invention preferably comprises embedding the obtained forged piece into sand and cooling to room temperature to obtain the forged piece.
In the invention, the forging process can ensure that the structure of the 9% Ni% steel is uniformly distributed and austenite grains are refined, and lays a foundation for improving the comprehensive mechanical property of the 9% Ni% steel after subsequent heat treatment.
After the forging piece is obtained, sequentially quenching and tempering the forging piece to obtain the high-strength 9% Ni steel for the ultralow-temperature engineering fastener.
In the present invention, the quenching process comprises the following steps: and carrying out first heat preservation on the forge piece after the first temperature rise to T1, carrying out second heat preservation after the second temperature rise to T2, and carrying out third heat preservation after the third temperature rise to T3.
In the invention, the temperature of T1 is 200-300 ℃, preferably 230-250 ℃; the first heat preservation time is 1-2 h; the temperature rise rate of the first temperature rise is preferably less than or equal to 80 ℃/h, and more preferably 80 ℃/h.
In the invention, the temperature of T2 is 520-580 ℃, preferably 550-560 ℃; the second heat preservation time is 1-2 h; the temperature rise rate of the second temperature rise is preferably less than or equal to 80 ℃/h, and more preferably 80 ℃/h.
In the invention, the temperature of T3 is 800-860 ℃, preferably 820-840 ℃; the third heat preservation time is 1.5-2.0 h/100mm of the effective thickness of the forged piece, namely when the effective thickness of the forged piece is 100mm, the third heat preservation time is 1.5-2.0 h; and when the effective thickness of the forging is 200mm, the third heat preservation time is 3.0-4.0 h. In the present invention, the temperature increase rate from T2 to T3 is preferably 80 ℃ C/h or less, and more preferably 80 ℃ C/h.
After quenching is finished, soaking and cooling the obtained quenched forged piece to room temperature preferably; the time for cooling the inlet water is preferably 1 h.
In the present invention, the tempering comprises the steps of: and carrying out fourth heat preservation after fourth temperature rise to T4, and carrying out fifth heat preservation after fifth temperature rise to T5.
In the invention, the temperature of T4 is 250-350 ℃, preferably 250-260 ℃; the fourth heat preservation time is 2-3 h; the temperature rise rate of the fourth temperature rise is preferably less than or equal to 80 ℃/h, and more preferably 80 ℃/h.
In the invention, the temperature of T5 is 520-580 ℃, preferably 550-560 ℃; the fifth heat preservation time is 2.5-4.0 h/100mm of the effective thickness of the forged piece, namely when the effective thickness of the forged piece is 100mm, the fifth heat preservation time is 2.0-4.0 h; and when the effective thickness of the forging is 200mm, the fifth heat preservation time is 4.0-8.0 h. In the present invention, the temperature increase rate of the fifth temperature increase is not more than 80 ℃/h, and more preferably 80 ℃/h.
After the tempering is finished, the invention preferably cools the obtained tempered forging to room temperature in air.
In the invention, the quenching and tempering process can convert the matrix structure of the 9% Ni% steel into a stable residual austenite structure mainly comprising tempered martensite with extremely fine lath width and a film, thereby ensuring the strength and low-temperature toughness of the 9% Ni% steel.
The invention also provides the high-strength 9% Ni steel for the ultralow-temperature engineering fastener, which is prepared by the preparation method in the technical scheme, the yield strength at room temperature is more than 800MPa, the elongation after fracture is more than 20%, the reduction of area is more than 65%, and the V-shaped impact energy at minus 196 ℃ is more than 85J.
The high-strength 9% Ni steel for ultra-low temperature engineering fasteners and the method for manufacturing the same according to the present invention will be described in detail with reference to the following examples, which should not be construed as limiting the scope of the present invention.
Example 1
According to the following steps: c: 0.029%, Si: 0.038%, Mn: 0.61%, Cr: 0.020%, Ni: 9.61%, V: 0.037%, Mo: 0.15%, S: 0.004%, P: 0.0068%, H: 0.8ppm, O: 0.0086%, N: 0.0064 percent of Fe with high purity as the rest.
Smelting by a process of vacuum smelting and electroslag remelting, and casting the obtained smelting liquid to obtain a steel ingot required by forging; the technological parameters of vacuum melting and electroslag remelting are as follows: the parameters of vacuum induction melting comprise: the chemical material power is 700kW, and the power-rise rate is 200 kW/h; the refining temperature is 1560 DEG CThe hollowness is less than 0.1 Pa; performing early-stage deoxidation by using Ca after refining is finished, performing final deoxidation by using Ni-Mg alloy after the components are adjusted to be qualified, and controlling the final tapping temperature to 1580 ℃; the electroslag remelting process comprises the following steps: the slag system is a ternary slag system which comprises the following components in percentage by weight: CaF 60%, Al2O325 percent of CaO, 15 percent of CaO; the melting speed is 11 kg/min; the atmosphere was dry air.
Forging the steel ingot at the initial forging temperature of 1200 ℃ and the final forging temperature of 900 ℃ according to a forging ratio of 7, embedding the forged piece obtained after forging into sand, and cooling to room temperature to obtain a forged piece with the effective thickness of 80 mm;
heating to 230 ℃ at a speed of 80 ℃/h, preserving heat for 2 hours, then heating to 560 ℃ at a speed of 80 ℃/h, and preserving heat for 2 hours; then raising the temperature to 840 ℃ at a speed of 80 ℃/h, and preserving the temperature for 1.5 hours; and soaking in water for cooling for 1 hour to room temperature after the heat preservation is finished.
Heating to 260 ℃ at a speed of 80 ℃/h, preserving heat for 2 hours, then heating to 580 ℃ at a speed of 80 ℃/h, and preserving heat for 3 hours; and after the heat preservation is finished, discharging from the furnace, and air-cooling to room temperature to obtain the high-strength 9% Ni steel for the ultralow-temperature engineering fastener.
Example 2
According to the following steps: c: 0.043%, Si: 0.12%, Mn: 0.71%, Cr: 0.015%, Ni: 9.97%, V: 0.044%, Mo: 0.15%, S: 0.003%, P: 0.003%, H: 0.5ppm, O: 0.009%, N: 0.0053% and the balance of high-purity Fe.
Smelting by a process of vacuum smelting and electroslag remelting, and casting the obtained smelting liquid to obtain a steel ingot required by forging; the technological parameters of vacuum melting and electroslag remelting are as follows:
the parameters of vacuum induction melting comprise: the chemical material power is 750kW, and the power-rise rate is 200 kW/h; the refining temperature is 1570 ℃, and the vacuum degree is less than 0.1 Pa; performing early-stage deoxidation by using Ca after refining is finished, performing final deoxidation by using Ni-Mg alloy after the components are adjusted to be qualified, and controlling the final tapping temperature to 1590 ℃; the electroslag remelting process comprises the following steps: the slag system is a ternary slag system which comprises the following components in percentage by weight: CaF 60%, Al2O325 percent of CaO, 15 percent of CaO; the melting speed is 12 kg/min; the atmosphere is dry air, and the H element in the remelting process is controlledThe content of (a).
Forging the steel ingot at the initial forging temperature of 1160 ℃ and the final forging temperature of 850 ℃ according to the forging ratio of 6, embedding the forged piece obtained after forging into sand, and cooling to room temperature to obtain a forged piece with the effective thickness of 150 mm;
heating to 200 ℃ at a speed of 80 ℃/h, preserving heat for 2 hours, then heating to 560 ℃ at a speed of 80 ℃/h, and preserving heat for 2 hours; then raising the temperature to 820 ℃ at a speed of 80 ℃/h, and preserving the heat for 2.5 hours; and soaking in water for cooling for 1 hour to room temperature after the heat preservation is finished.
Heating to 250 ℃ at a speed of 80 ℃/h, preserving heat for 2 hours, then heating to 550 ℃ at a speed of 80 ℃/h, and preserving heat for 5 hours; and after the heat preservation is finished, discharging from the furnace, and air-cooling to room temperature to obtain the high-strength 9% Ni steel for the ultralow-temperature engineering fastener.
Comparative example 1
Referring to national standards of 9% Ni steel plates (GB/T2451) for low-temperature pressure vessels, 9% Ni590B steel with the highest strength grade and the best toughness in the standards is selected for comprehensive comparison, and the performance comparison results are shown in Table 1.
TABLE 1 comparison of comprehensive mechanical properties at room temperature and low temperature of examples 1-2 and comparative example 1
As can be seen from table 1: after quenching and tempering heat treatment, the high-strength 9% Ni steel for the ultralow-temperature engineering fastener can obtain excellent toughness matching, and compared with the national standard (comparative example 1), the yield strength at room temperature is remarkably improved to over 800MPa, the elongation after fracture is over 20%, the reduction of area is over 65%, and the V-shaped impact energy at-196 ℃ is over 85J. It can thus be seen from the above embodiments: the preparation method provided by the invention is reliable, and can meet the requirements of strength and plastic toughness of high-strength 9% Ni steel for ultralow-temperature engineering fasteners.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. The preparation method of the high-strength 9% Ni steel for the ultralow-temperature engineering fastener is characterized by comprising the following steps of:
smelting the raw materials according to a vacuum induction-electroslag remelting process, and casting the obtained smelting liquid to obtain a steel ingot; the raw materials are weighed according to the following weight percentage by element content: 0.02-0.06% of C, 0.038-0.12% of Si, 0.30-0.80% of Mn, less than or equal to 0.005% of S, less than or equal to 0.008% of P, less than or equal to 0.10% of Cr, 0.03-0.08% of V, 9.50-10.0% of Ni, 0.12-0.16% of Mo, less than or equal to 1.0ppm of H, less than or equal to 0.01% of O, less than or equal to 0.01% of N, and the balance of high-purity Fe;
forging the steel ingot to obtain a forging piece; the initial forging temperature of the forging is not more than 1200 ℃, and the final forging temperature of the forging is 850-900 ℃;
sequentially quenching and tempering the forging to obtain the high-strength 9% Ni steel for the ultralow-temperature engineering fastener;
the quenching process comprises the following steps:
carrying out first heat preservation on the forge piece after the forge piece is heated to T1 for the first time, carrying out second heat preservation after the forge piece is heated to T2 for the second time, and carrying out third heat preservation after the forge piece is heated to T3 for the third time;
the temperature T1 is 200-300 ℃, and the first heat preservation time is 1-2 h; the temperature T2 is 520-580 ℃, and the second heat preservation time is 1-2 h; the temperature T3 is 800-860 ℃, and the third heat preservation time is 1.5-2.0 h/100mm of the effective thickness of the forging piece;
the tempering comprises the following steps:
performing fourth heat preservation after fourth temperature rise to T4, and performing fifth heat preservation after fifth temperature rise to T5;
the temperature T4 is 250-350 ℃, and the fourth heat preservation time is 2-3 h; the temperature T5 is 520-580 ℃, and the fifth heat preservation time is 2.0-4.0 h/100mm of the effective thickness of the forge piece.
2. The production method according to claim 1,the parameters of the vacuum induction-electroslag remelting process comprise vacuum induction parameters and electroslag remelting parameters; the vacuum induction parameters include: the chemical material power is 600-800 kW, and the power-rise rate is 200 kW/h; the refining temperature is 1550-1580 ℃, and the vacuum degree is less than 0.1 Pa; performing early-stage deoxidation by using Ca after refining is finished, performing final deoxidation by using Ni-Mg alloy after the components are adjusted to be qualified, wherein the final tapping temperature is 1590 +/-10 ℃; the electroslag remelting parameters comprise: the slag system for electroslag remelting is a ternary slag system; the ternary slag system comprises the following components: CaF 60%, Al2O325 percent of CaO, 15 percent of CaO; the melting speed is 10-12 kg/min; the atmosphere of the electroslag remelting is dry air.
3. The method of claim 1, wherein the forging has a forging ratio of > 5.
4. The method of claim 1, further comprising cooling the resulting forging to room temperature after forging by embedding it in sand.
5. The method of claim 1, wherein the first, second, and third ramp rates are independently ≦ 80 ℃/h.
6. The method of claim 1, further comprising, after quenching, soaking the resulting quenched forging in water to cool and then air cooling to room temperature.
7. The method of claim 1, wherein after the tempering is complete, the resulting tempered forging is air cooled to room temperature.
8. The high-strength 9% Ni steel for the ultra-low temperature engineering fastener obtained by the preparation method of any one of claims 1 to 7 is characterized in that the yield strength at room temperature is more than 800MPa, the elongation after fracture is more than 20%, the reduction of area is more than 65%, and the V-shaped impact energy at-196 ℃ is more than 85J.
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