0Cr17Ni2 series low-P steel ingot and forge piece as well as preparation method and application thereof

Abstract

The invention provides a 0Cr17Ni2-series low-P steel ingot and forge piece as well as a preparation method and application thereof, and belongs to the technical field of metal materials. The preparation method of the 0Cr17Ni2-series low-P steel ingot, provided by the invention, comprises the following steps: smelting, refining, casting and performing first annealing on preparation raw materials of the 0Cr17Ni2-series low-P steel ingot in sequence to obtain the 0Cr17Ni2-series low-P steel ingot, the 0Cr17Ni2 series low-P steel ingot comprises the following elements in percentage by mass: 0.11 to 0.18 percent of C, less than or equal to 0.80 percent of Mn, less than or equal to 0.80 percent of Si, 16.00 to 18.00 percent of Cr, 1.50 to 2.50 percent of Ni, less than or equal to 0.012 percent of P, less than or equal to 0.010 percent of S and the balance of Fe. According to the method, the 0Cr17Ni2 series low-P steel ingot is obtained by controlling specific smelting and refining conditions, and the forged piece prepared from the 0Cr17Ni2 series low-P steel ingot has excellent high-temperature mechanical property.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and in particular to 0Cr17Ni2 series low-P steel ingots and forgings, and preparation methods and applications thereof. Background Art

[0002] 0Cr17Ni2 steel is an austenitic heat-resistant stainless steel containing ferrite. It has a good combination of strength and toughness and excellent corrosion resistance. It is widely used in the production of nitric acid, acetic acid and textile industries for shafts, piston rods, pumps and other parts that require both strength and toughness and corrosion resistance.

[0003] At present, the mechanical properties of 0Cr17Ni2 steel, especially its high-temperature mechanical properties, still need to be further improved in order to expand its application in high-end equipment such as aerospace, marine equipment, ship power equipment, and steam turbines, compressors, and air compressors for power generation. Summary of the invention

[0004] The object of the present invention is to provide 0Cr17Ni2 series low-P steel ingots and forgings, as well as preparation methods and applications. The forgings prepared using the 0Cr17Ni2 series low-P steel ingots provided by the present invention have excellent high-temperature mechanical properties.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for preparing a 0Cr17Ni2 series low-P steel ingot, comprising the following steps: The raw materials for preparing the 0Cr17Ni2 series low-P steel ingot are sequentially smelted, refined, cast and first annealed to obtain the 0Cr17Ni2 series low-P steel ingot; The element composition of the 0Cr17Ni2 series low-P steel ingot includes, by mass fraction, C 0.11-0.18%, Mn≤0.80%, Si≤0.80%, Cr 16.00-18.00%, Ni 1.50-2.50%, P≤0.012%, S≤0.010%, and the balance is Fe; The smelting includes a melting stage, an oxidation stage and a reduction stage in sequence; The conditions of the melting stage include: the molten pool temperature is 1550-1570°C; FeO is added, the mass of FeO is 2-3% of the mass of the molten steel; the basicity R is 2.0-2.5; the oxygen blowing pressure is 0.25-0.30MPa; The conditions of the oxidation stage include: oxygen blowing pressure ≥ 1.5 MPa; molten pool temperature 1660-1680°C; molten steel boiling time 6-10 min; adding Mn, the mass of Mn is 0.1-0.3% of the mass of molten steel; The conditions of the reduction stage include: adding thin slag material after slag discharge, adjusting the C mass content to 0.8-1.1%, adding ferrosilicon manganese alloy, ferromanganese alloy and ferrochrome alloy to make thin slag, and then adding reducing agent to make white slag; The refining includes sequentially performing a VOD stage, a VCD stage, a VOH stage and a VD stage; The conditions of the VOD stage include: vacuum degree of 90-110 mbar, vacuum pumping time of 1-1.5 h, oxygen blowing volume of 530-570 m 3 / h, Ar flow rate is 4~7m 3 / h; The conditions of the VCD stage include: vacuum degree of 15-20 mbar, vacuum pumping time of 13-18 min, Ar flow rate of 4-7 m 3 / h; The conditions of the VOH stage include: adding aluminum, CaO, CaF2 and FeSi, heating to 1650-1670°C, and Ar flow rate of 4-7m 3 / h; The conditions of the VD stage include: vacuum degree of 0.8~1.5mbar, vacuum pumping time ≥20min, Ar flow rate of 4~7m 3 / h.

[0006] Preferably, the casting conditions include: molten steel calming time of 6 to 10 minutes, argon blowing volume of 4 to 7 L / min, casting temperature of 1550 to 1570° C., and casting speed of 5 to 7 mm / s.

[0007] Preferably, the temperature of the first annealing is 840-860° C., and the holding time is 8-10 hours.

[0008] The present invention provides a 0Cr17Ni2 series low-P steel ingot prepared by the preparation method described in the above technical solution.

[0009] Preferably, the average grain size of the 0Cr17Ni2 low-P steel ingot is ≤ grade 3.

[0010] The present invention provides a forging, which is prepared from the 0Cr17Ni2 low-P steel ingot described in the above technical solution.

[0011] The present invention provides a method for preparing the forging described in the above technical solution, comprising the following steps: The 0Cr17Ni2 low-P steel ingot is subjected to forging, second annealing, rough machining, third annealing and solution treatment in sequence to obtain the forging.

[0012] Preferably, the forging conditions include: initial forging temperature of 1150-1170°C, final forging temperature of 860-890°C, forging ratio ≥3.0, extension ratio ≥2.0, and total forging ratio ≥4.0.

[0013] Preferably, the second annealing temperature is 820-840°C, and the holding time is 8-10h; The temperature of the third annealing is 820-850° C., and the holding time is 8-10 hours; The solution treatment includes sequentially performing a first solution treatment and a second solution treatment; The temperature of the first solution treatment is 1180-1200°C, and the holding time is 1.5-2.5h; The temperature of the second solution treatment is 780-800° C., and the holding time is 8-10 hours.

[0014] The present invention provides the use of the 0Cr17Ni2 series low-P steel ingot described in the above technical solution, the forging described in the above technical solution, or the forging prepared by the preparation method described in the above technical solution in marine equipment, ship power equipment or power stations.

[0015] Beneficial effects: Compared with 0Cr17Ni2, by controlling specific smelting and refining conditions, the present invention optimizes the S content from ≤0.030wt% to ≤0.010wt%, which is beneficial to reducing sulfide inclusions and improving pitting corrosion resistance; the present invention optimizes the P content from ≤0.040wt% to ≤0.012wt%, which is beneficial to reducing P segregation brittleness and improving toughness and fatigue resistance. The 0Cr17Ni2 series low-P steel ingot provided by the present invention belongs to austenitic heat-resistant stainless steel. The forgings prepared using it have excellent high-temperature mechanical properties, overcome the disadvantage of 0Cr17Ni2 steel having high-temperature temper brittleness, and can be used in the manufacture of marine equipment, ship power equipment, and steam turbines, compressors, and air compressors for power generation, ensuring the reliability and safety of the operation of these high-end equipment. In addition, the 0Cr17Ni2 series low-P steel ingots and forgings provided by the present invention also have excellent corrosion resistance, stress resistance, fatigue resistance and good welding performance. DETAILED DESCRIPTION

[0016] The present invention provides a method for preparing a 0Cr17Ni2 series low-P steel ingot, comprising the following steps: The raw materials for preparing the 0Cr17Ni2 series low-P steel ingot are sequentially smelted, refined, cast and first annealed to obtain the 0Cr17Ni2 series low-P steel ingot; The element composition of the 0Cr17Ni2 series low-P steel ingot includes, by mass fraction, C 0.11-0.18%, Mn≤0.80%, Si≤0.80%, Cr 16.00-18.00%, Ni 1.50-2.50%, P≤0.012%, S≤0.010%, and the balance is Fe; The smelting includes a melting stage, an oxidation stage and a reduction stage in sequence; The conditions of the melting stage include: the molten pool temperature is 1550-1570°C; FeO is added, the mass of FeO is 2-3% of the mass of the molten steel; the basicity R is 2.0-2.5; the oxygen blowing pressure is 0.25-0.30MPa; The conditions of the oxidation stage include: oxygen blowing pressure ≥ 1.5 MPa; molten pool temperature 1660-1680°C; molten steel boiling time 6-10 min; adding Mn, the mass of Mn is 0.1-0.3% of the mass of molten steel; The conditions of the reduction stage include: adding thin slag material after slag discharge, adjusting the C mass content to 0.8-1.1%, adding ferrosilicon manganese alloy, ferromanganese alloy and ferrochrome alloy to make thin slag, and then adding reducing agent to make white slag; The refining includes sequentially performing a VOD stage, a VCD stage, a VOH stage and a VD stage; The conditions of the VOD stage include: vacuum degree of 90-110 mbar, vacuum pumping time of 1-1.5 h, oxygen blowing volume of 530-570 m 3 / h, Ar flow rate is 4~7m 3 / h; The conditions of the VCD stage include: vacuum degree of 15-20 mbar, vacuum pumping time of 13-18 min, Ar flow rate of 4-7 m 3 / h; The conditions of the VOH stage include: adding aluminum, CaO, CaF2 and FeSi, heating to 1650-1670°C, and Ar flow rate of 4-7m 3 / h; The conditions of the VD stage include: vacuum degree of 0.8~1.5mbar, vacuum pumping time ≥20min, Ar flow rate of 4~7m 3 / h.

[0017] The present invention firstly describes the element composition of the 0Cr17Ni2 series low-P steel ingot.

[0018] In the present invention, the element composition of the 0Cr17Ni2 series low-P steel ingot includes C 0.11-0.18%, specifically 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17% or 0.18%, by mass fraction.

[0019] In the present invention, the element composition of the 0Cr17Ni2 series low-P steel ingot includes Mn≤0.80%, calculated by mass fraction, and specifically can be 0.50%, 0.55%, 0.60%, 0.61%, 0.62%, 0.63%, 0.64%, 0.65%, 0.66%, 0.68%, 0.70%, 0.75% or 0.80%.

[0020] In the present invention, the element composition of the 0Cr17Ni2 series low-P steel ingot includes Si≤0.80%, by mass fraction, and specifically can be 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75% or 0.80%.

[0021] In the present invention, the element composition of the 0Cr17Ni2 series low-P steel ingot includes Cr 16.00-18.00%, specifically 16.00%, 16.20%, 16.40%, 16.60%, 16.80%, 16.91%, 17.05%, 17.12%, 17.20%, 17.40%, 17.60%, 17.80% or 18.00%, by mass fraction.

[0022] In the present invention, the element composition of the 0Cr17Ni2 series low-P steel ingot includes Ni 1.50-2.50%, specifically 1.50%, 1.70%, 1.90%, 2.10%, 2.30%, 2.38%, 2.39%, 2.41% or 2.50%, by mass fraction.

[0023] In the present invention, the element composition of the 0Cr17Ni2 series low-P steel ingot includes P≤0.012% by mass, and specifically can be 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.010%, 0.011% or 0.012%.

[0024] In the present invention, the element composition of the 0Cr17Ni2 series low-P steel ingot includes S≤0.010%, specifically 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009% or 0.010%, by mass fraction.

[0025] In the present invention, the element composition of the 0Cr17Ni2 low-P steel ingot includes the balance Fe by mass fraction.

[0026] The preparation method of the 0Cr17Ni2 low-P steel ingot of the present invention is described in detail below. In the present invention, unless otherwise specified, the raw materials and reagents used are commercially available products well known to those skilled in the art.

[0027] The present invention smelts the raw materials for preparing the 0Cr17Ni2 series low-P steel ingot. In the present invention, the raw materials for preparing preferably include scrap steel and alloy raw materials; in the present invention, the scrap steel is preferably pure scrap steel with an S mass fraction of ≤0.020% and a P mass fraction of ≤0.020%. The present invention preferably controls and detects harmful elements in the scrap steel, which is conducive to obtaining the 0Cr17Ni2 series low-P steel ingot through subsequent smelting, refining, casting and first annealing; the types of the alloy raw materials preferably include Cr alloy and Ni alloy, and the Cr alloy and Ni alloy are preferably high-grade alloys, that is, low-S and low-P alloys; in an embodiment of the present invention, specifically, pure scrap steel and alloy raw materials with an S content of ≤0.020wt% and a P content of ≤0.020wt% are placed in an electric arc furnace (EAF) for smelting. In the present invention, the smelting includes a melting stage, an oxidation stage and a reduction stage in sequence. In an embodiment of the present invention, the raw materials for preparing and slag-making auxiliary materials used for smelting are pre-baked to ensure sufficient drying. The present invention preferably adopts the "three high methods" to remove phosphorus in the smelting process, which specifically includes high basicity, high oxygen potential and high slag amount.

[0028] In the present invention, the conditions of the melting stage include: the molten pool temperature is 1550~1570℃, preferably 1560℃; FeO is added, the mass of FeO is 2~3% of the mass of molten steel, preferably 2.2~2.5%; the basicity R is 2.0~2.5, preferably 2.2~2.3; the oxygen blowing pressure is 0.25~0.30MPa, preferably 0.28MPa. The present invention preferably carries out the melting stage under the above conditions, which is conducive to ensuring high basicity and high oxygen potential. The present invention reduces the P content to ≤0.008wt% in the melting stage and enters the oxidation stage.

[0029] In the present invention, the conditions of the oxidation stage include: oxygen blowing pressure ≥1.5MPa, preferably 1.6-2.5MPa; molten pool temperature is 1660-1680°C, preferably 1670°C; C removal amount ≥40%, sampling analysis satisfies C content of 0.8wt%, P content ≤0.010wt%, S content ≤0.020wt%; Mn is added after the molten steel is boiled for 6-10min (more preferably 7-8min), and the mass of Mn is 0.1-0.3% of the mass of the molten steel, preferably 0.15-0.25%, more preferably 0.2%; when the C content is 0.80-1.0wt%, the P content is ≤0.010wt%, the S content is ≤0.020wt% and the molten steel temperature is 1670-1720°C (preferably 1700°C), the reduction stage is entered. The present invention preferably carries out the oxidation stage under the above conditions, which is conducive to ensuring high oxygen potential and high slag amount. The slag making amount in the oxidation stage is high, and the P content is reduced to ≤0.010wt% by continuous slag making and continuous slag discharge. Specifically, the P content can be 0.008~0.010wt%.

[0030] In the present invention, the conditions of the reduction stage include: adding thin slag material after removing the slag produced in the oxidation stage, adjusting the C content to 0.8-1.1wt% (preferably 1.0wt%), then adding ferrosilicon manganese alloy, ferromanganese alloy, ferrochrome alloy and ferronickel alloy, adding reducing agent to make white slag after the thin slag is made, the white slag retention time is preferably 18-23min (more preferably 20min), the molten steel temperature is preferably 1670-1720℃ (more preferably 1700℃) when it is transferred into the ladle, the slag in the ladle is preferably ≤1kg / t, and the molten steel temperature is preferably 1630-1680℃ (more preferably 1650℃) when it is discharged for subsequent processes. In the present invention, the thin slag material is preferably lime and fluorite; the amount of lime added is preferably 180-220kg / t, more preferably 200kg / t; the amount of fluorite added is preferably 60-80kg / t, more preferably 70kg / t. In the present invention, the addition amount of the ferrosilicon manganese alloy is preferably 4~5kg / t, more preferably 4.5~5kg / t; the addition amount of the ferromanganese alloy is preferably 4~7kg / t, more preferably 5kg / t; the addition amount of the ferrochromium alloy is preferably 160~170kg / t, more preferably 165kg / t; the addition amount of the ferronickel alloy is preferably 18~20kg / t, more preferably 19.5kg / t. In the present invention, the reducing agent preferably includes a first reducing agent and a second reducing agent. In the present invention, the first reducing agent preferably includes ferrosilicon powder or calcium carbide; the amount of the ferrosilicon powder is preferably 4~7kg / t, more preferably 5kg / t; the amount of the calcium carbide is preferably 2~3kg / t, more preferably 2.3kg / t. In the present invention, the second reducing agent preferably includes carbon powder or AD powder; the amount of the carbon powder is preferably 0.8-1.5 kg / t, more preferably 1 kg / t; the amount of the AD powder is preferably 5-8 kg / t, more preferably 6.6 kg / t.

[0031] After the smelting is completed, the present invention refines the obtained molten steel. In the embodiment of the present invention, the molten steel obtained after the smelting is transferred to a vacuum refining furnace (VODC) for refining. In the present invention, the refining includes sequentially performing a VOD stage, a VCD stage, a VOH stage and a VD stage.

[0032] In the present invention, the conditions of the VOD stage include: vacuum degree of 90-110 mbar, preferably 100 mbar; oxygen blowing volume of 530-570 mbar; 3 / h, preferably 550m 3 / h; Ar flow rate is 4~7m 3 / h, preferably 5m 3 / h; C content is 0.70~0.90wt%, preferably 0.80wt%; vacuum time is 1~1.5h, preferably 1.25h.

[0033] In the present invention, the conditions of the VCD stage include: vacuum degree of 15-20 mbar, preferably 18 mbar; vacuum pumping time of 13-18 min, preferably 15 min; Ar flow rate of 4-7 m 3 / h, preferably 5m 3 / h.

[0034] In the present invention, the conditions of the VOH stage include: adding aluminum, CaO, CaF2 and FeSi, then heating to 1650-1670°C (preferably 1660°C), and Ar flow rate of 4-7m 3 / h, preferably 5m 3 / h. In the present invention, the addition amount of aluminum is preferably 1-2kg / t, more preferably 1.5kg / t; the addition amount of CaO is preferably 1-4kg / t, more preferably 2kg / t; the addition amount of CaF2 is preferably 6-10kg / t, more preferably 8kg / t; the addition amount of FeSi is preferably 4-7kg / t, more preferably 5kg / t.

[0035] In the present invention, the conditions of the VD stage include: vacuum degree of 0.8-1.5 mbar, preferably 1.0 mbar; vacuum time ≥ 20 min, preferably 25 min; Ar flow rate of 4-7 m 3 / h, preferably 5m 3 / h.

[0036] After the VD stage is completed, the present invention preferably adds CaSi powder to the bottom of the intermediate ladle in advance, passes Ar through the bottom of the ladle, exhausts the air in the ladle, and discharges the material in the Ar protective atmosphere for subsequent processes. The present invention discharges the material in the Ar protective atmosphere to prevent secondary oxidation. In the present invention, the addition amount of the CaSi powder is preferably 0.8-1.5 kg / t, more preferably 1 kg / t.

[0037] After the refining is completed, the present invention casts the obtained molten steel. The casting of the present invention is preferably carried out in an argon protective atmosphere. Before the casting, the present invention preferably pre-checks the casting system and the steel mold to ensure that they are dry, moisture-free, clean and pollution-free. In the present invention, the casting conditions include: the molten steel calming time is preferably 5~10min, more preferably 7min; the argon blowing amount is preferably 4~7L / min, more preferably 5L / min; the casting temperature is preferably 1550~1570℃, more preferably 1560℃; the casting speed is preferably 5~8mm / s, more preferably 6mm / s. The present invention casts in an Ar protective atmosphere to prevent secondary oxidation and ensure the purity of the vacuum molten steel. In the present invention, after the casting is completed, it is preferably cooled in the mold, and the cooling time in the mold is preferably according to the formula T (h) = 35R 2(m) × 1.2, where R is the mold radius, and demolding is performed after the mold is cooled.

[0038] After the casting is completed, the present invention performs a first annealing on the obtained steel ingot to obtain the 0Cr17Ni2 series low-P steel ingot. In the present invention, the temperature of the first annealing is preferably 840-860°C, more preferably 850°C; the holding time is preferably 8-10h, more preferably 9h; after the holding is completed, the furnace is preferably cooled to ≤200°C before being taken out of the furnace. The present invention preferably performs a first annealing quickly on the steel ingot obtained after demolding to prevent the temperature of the steel ingot from dropping excessively.

[0039] After the first annealing, the present invention preferably performs surface inspection and composition inspection on the obtained steel ingot to obtain a qualified product.

[0040] The present invention provides a 0Cr17Ni2 low-P steel ingot prepared by the preparation method described in the above technical solution. In the present invention, the average grain size of the 0Cr17Ni2 low-P steel ingot is preferably ≤ grade 3, specifically grade 1 or grade 2.

[0041] The present invention provides a forging, which is prepared from the 0Cr17Ni2 low-P steel ingot described in the above technical solution.

[0042] The present invention provides a method for preparing the forging described in the above technical solution, comprising the following steps: The 0Cr17Ni2 low-P steel ingot is subjected to forging, second annealing, rough machining, third annealing and solution treatment in sequence to obtain the forging.

[0043] In the present invention, the 0Cr17Ni2 low-P steel ingot is preferably subjected to blanking and heat treatment in sequence before forging; in the embodiment of the present invention, the 0Cr17Ni2 low-P steel ingot is blanked, then subjected to heat treatment, and forged after the heat treatment is completed. In the present invention, the temperature of the heat treatment is preferably 1170-1190°C, more preferably 1180°C; the holding time is preferably 8-10h, more preferably 9h.

[0044] In the present invention, the forging conditions include: the initial forging temperature is preferably 1150~1170℃, more preferably 1160℃, the final forging temperature is preferably 860~890℃, more preferably 870℃; the cooling method is preferably furnace cooling to ≤200℃ and air cooling out of the furnace; the forging ratio is preferably ≥3.0, specifically 3.0; the extension ratio is preferably ≥2.0, more preferably 2.2~2.5; the total forging ratio is preferably ≥4.0, specifically 4.0.

[0045] After forging, the present invention performs a second annealing on the obtained workpiece. In the present invention, the temperature of the second annealing is preferably 820-850°C, more preferably 830°C; the holding time is preferably 8-10h, more preferably 9h; the heating rate to the temperature of the second annealing is preferably 70-90°C / h, more preferably 80°C / h; after the holding is completed, the furnace is preferably cooled to ≤200°C and then air-cooled.

[0046] After annealing, the present invention performs rough machining on the workpiece, and preferably uses ultrasonic flaw detection, and then performs a third annealing. In the present invention, the temperature of the third annealing is preferably 820-850°C, more preferably 830°C; the holding time is preferably 8-10h, more preferably 9h; after the holding is completed, strong wind rapid cooling is preferred.

[0047] After annealing, the present invention performs a solution treatment on the workpiece. In the present invention, the solution treatment preferably includes a first solution treatment and a second solution treatment in sequence. In the present invention, the temperature of the first solution treatment is preferably 1180~1200°C, more preferably 1190°C; the holding time is preferably 1.5~2.5h, more preferably 2h; and water cooling is preferably performed after the holding is completed. In the present invention, the temperature of the second solution treatment is preferably 780~800°C, more preferably 790°C; the holding time is preferably 8~10h, more preferably 9h; and strong wind rapid cooling is preferably performed after the holding is completed.

[0048] After the solution treatment, the present invention preferably performs physical and chemical property testing, dimensional testing, and non-destructive testing (NDT testing) on ​​the obtained workpiece to obtain a qualified product.

[0049] The present invention provides the use of the 0Cr17Ni2 low-P steel ingot described in the above technical solution, the forging described in the above technical solution, or the forging prepared by the preparation method described in the above technical solution in marine equipment, ship power equipment or power stations. In the present invention, the 0Cr17Ni2 low-P steel ingot or forging can be used to prepare parts of steam turbines, compressors or compressors, for example, it can be used to prepare steam turbine stators, compressor rotors or compressor blades. In the present invention, the working temperature of the forging is preferably not more than 550°C, more preferably 538~550°C.

[0050] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] The detection methods in the following experimental process include: the allowable deviation of the chemical composition of the finished steel product adopts GB / 222, the chemical composition analysis method of steel and alloy adopts GB / T223, the macrostructure and defect acid etching test method of steel adopts GB / T226, the sampling location and sample preparation of mechanical properties of steel and steel products adopt GB / T2975, the metal average grain size test method adopts GB / 16394, the standard rating chart microscopic inspection method for the determination of non-metallic inclusion content in steel adopts GB / T10561, the spark atomic emission spectrometry (conventional method) for the measurement of multi-element content of stainless steel adopts GB / T11170; the metallographic determination method of delta ferrite content in martensitic stainless steel adopts GB / T4402.

[0052] The mechanical properties test methods in the following experimental process include: room temperature tensile test method adopts GB / T228.1, specifically using Φ5mm standard specimens, using WE-300 tensile testing machine, the test temperature is 25℃, and the tensile strength Rm and yield strength R P0.2 , elongation after fracture A and cross-sectional shrinkage Z; the impact performance adopts the Charpy pendulum impact test method for metal materials in accordance with GB / T 229-2020; the hardness requirement test HBW adopts the GB5310-2008 standard; the hardness test method adopts GB / T231.1; the high-temperature mechanical properties, compressive resistance and endurance strength MPa of the forgings are tested in accordance with GB / T8732-2014 standard, the grading method for strength grades QT1 and QT2 adopts EN10269-2006, and the high-temperature performance data are cited from EN10269-2006 and DIN17240-1976.

[0053] Comparative Example 1 The chemical composition of the steel ingot of grade 0Cr17Ni2 is shown in Table 1.

[0054] Example 1 The chemical composition of the steel ingot in this embodiment is shown in Table 1, and the specific preparation method is as follows: (1) Selecting pure scrap steel and high-grade Cr alloy and Ni alloy with S content ≤ 0.020wt% and P content ≤ 0.020wt% as raw materials; placing the raw materials in an electric arc furnace (EAF) for smelting, wherein the smelting includes a melting stage, an oxidation stage and a reduction stage in sequence; The conditions of the melting stage include: the molten pool temperature is 1560°C; FeO is added, the mass of FeO is 2.5% of the mass of the molten steel; the molten pool basicity R is 2.2; the oxygen blowing pressure is 0.28MPa, so that the P content is reduced to ≤0.008wt%; The conditions of the oxidation stage include: oxygen blowing pressure of 2.5MPa, molten pool temperature of 1670°C, high oxygen potential, C removal of ≥40%, sampling analysis to meet the C content of 0.8wt%, P content ≤0.010wt%, S content ≤0.020wt%; Mn is added after the molten steel is boiled for 7min, the mass of Mn is 0.2% of the mass of the molten steel, the slag making amount is high, and slag making and slag discharge are continuously carried out, and the reduction stage is entered when the C content is 0.80-1.0wt%, the P content is ≤0.010wt%, the S content is ≤0.020wt% and the molten steel temperature is 1700°C; The conditions of the reduction stage include: after removing the slag produced in the oxidation stage, adding thin slag material (specifically 200kg / t of lime and 70kg / t of fluorite), adjusting the C content to 1.0wt%, then adding 5kg / t of ferrosilicon manganese alloy, 5kg / t of ferromanganese alloy, 165kg / t of ferrochrome alloy and 19.5kg / t of ferronickel alloy, adding a reducing agent (specifically 5kg / t of ferrosilicon powder and 1kg / t of carbon powder) to make white slag after the thin slag is made, keeping the white slag for 20 minutes, transferring the molten steel into a ladle when the temperature of the molten steel is 1700°C, skimming the slag in the ladle until the residual amount is ≤1kg / t, and discharging the material when the temperature of the molten steel is 1650°C; (2) transferring the molten steel having a temperature of 1650° C. obtained after smelting into a vacuum refining furnace (VODC) for refining, wherein the refining includes sequentially performing a VOD stage, a VCD stage, a VOH stage and a VD stage; The conditions of the VOD stage include: vacuum degree of 100 mbar, vacuum pumping time of 1.5 h, oxygen blowing volume of 550 m 3 / h, Ar flow rate is 5m 3 / h, C content is 0.80wt%; The conditions of the VCD stage include: vacuum degree of 18 mbar, vacuum pumping time of 15 min, Ar flow rate of 5 m 3 / h; The conditions of the VOH stage include: adding 1kg / t of aluminum, 2kg / t of CaO, 8kg / t of CaF2 and 5kg / t of FeSi, then heating to 1660°C, with an Ar flow rate of 5m 3 / h; The conditions of the VD stage include: vacuum degree of 1.0 mbar, vacuum pumping time of 25 min, Ar flow rate of 5 m 3 / h; After the VD stage is completed, 1kg / t of CaSi powder is pre-added to the bottom of the tundish, and then Ar is passed through the bottom of the tundish to exhaust the air in the tundish. The vacuum molten steel at a temperature of 1620℃ is poured into the tundish, and the final deoxidation is completed under the protection of Ar to complete the discharge; (3) Pre-check the casting system and steel mold to ensure that they are dry, free of moisture, clean and free of pollution, and cast the molten steel obtained after refining. The casting conditions include: molten steel quenching time of 7 minutes, casting in Ar protective atmosphere, argon blowing volume of 5L / min, casting temperature of 1560℃, and casting speed of 6mm / s; after casting, the mold is cooled, and the cooling time in the mold is calculated according to the formula T (h) = 35R 2 (m) × 1.2, where R is the mold radius, and the mold is demoulded after the cooling in the mold is completed; (4) annealing the steel ingot obtained after demolding, wherein the annealing conditions include: heating from room temperature to 850°C at a heating rate of 80°C / h, and keeping the temperature for 9 hours; after the end of the heat preservation, cooling the furnace to ≤200°C and air cooling the steel ingot out of the furnace to obtain the steel ingot.

[0055] Example 2 The chemical composition of the steel ingot in this example is shown in Table 1. The specific preparation method is shown in Example 1.

[0056] Example 3 The chemical composition of the steel ingot in this example is shown in Table 1. The specific preparation method is shown in Example 1.

[0057] Table 1 Chemical composition of steel ingots in Examples 1 to 3 and Comparative Example 1

[0058] Example 4 The steel ingot in Example 1 was used to prepare the forgings, and the specific preparation method was as follows: (1) blanking the steel ingot, heating it to 1180° C., keeping it at that temperature for 9 hours, and then forging it. The forging conditions include: the initial forging temperature is 1160° C., the final forging temperature is 870° C., the cooling method is furnace cooling to ≤200° C. and air cooling after exiting the furnace, the forging ratio is 3.0, the elongation ratio is 2.5, and the total forging ratio is 4.0; (2) annealing the workpiece obtained after forging, wherein the annealing conditions include: heating from room temperature to 830°C at a heating rate of 80°C / h, and keeping the temperature for 9 hours; cooling the furnace to ≤200°C after the end of the heat preservation, and then cooling in air out of the furnace; (3) Rough machining the workpiece obtained after annealing and inspecting it using ultrasonic flaw detection; (4) The workpieces that have passed the ultrasonic flaw detection are subjected to annealing and solution treatment in sequence; The annealing temperature is 830°C, the holding time is 9h, and strong wind cooling is performed after the holding time is completed; The solution treatment includes a first solution treatment and a second solution treatment in sequence; the temperature of the first solution treatment is 1190°C, the holding time is 2 hours, and water cooling is performed after the holding period; the temperature of the second solution treatment is 790°C, the holding time is 9 hours, and strong wind rapid cooling is performed after the holding period to obtain the forging.

[0059] Example 5 The steel ingot in Example 2 was used to prepare forgings, and the specific preparation method was as shown in Example 4.

[0060] Example 6 The steel ingot in Example 3 was used to prepare forgings, and the specific preparation method was as shown in Example 4.

[0061] Test Example 1 The average grain sizes of the steel ingots in Comparative Example 1 and Examples 1 to 3 were tested, and the specific results are shown in Table 2.

[0062] Table 2 Average grain size metallographic grade of the steel ingots in Comparative Example 1 and Examples 1 to 3

[0063] The room temperature mechanical properties of the steel ingots in Comparative Example 1 and Examples 1 to 3 were tested, and the specific results are shown in Table 3.

[0064] Table 3 Room temperature mechanical properties test results of the steel ingots in Comparative Example 1 and Examples 1 to 3

[0065] Test Example 2 The forgings in Examples 4 to 6 were subjected to high temperature mechanical property tests, and the specific results are shown in Table 4.

[0066] Table 4 High temperature mechanical properties test results of forgings in Examples 4 to 6

[0067] It can be seen from the above test results that the 0Cr17Ni2 low-P steel ingot provided by the present invention has an S content optimized from ≤0.030wt% to ≤0.010wt% compared with the original 0Cr17Ni2 steel ingot, which is beneficial to reducing sulfide inclusions and eliminating sulfide band segregation; the P content is optimized from ≤0.040wt% to ≤0.012wt%, which is beneficial to reducing phosphorus segregation, and further beneficial to improving mechanical properties, such as elongation after fracture and cross-sectional shrinkage. At the same time, the present invention adopts EAF (electric arc furnace) + VODC (vacuum refining furnace) + argon protection casting process, which can minimize non-metallic inclusions, improve the purity of molten steel and the quality of steel, and significantly improve the average grain size metallographic grade of the steel ingot, from the original ≤4 level to ≤3 level, and the forgings prepared by using the steel ingot have stable high temperature resistance, which can fully meet the working conditions and use requirements of high-end equipment parts forgings such as turbine stators, compressor rotors, and compressor blades for aerospace, ship power, and power generation.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a 0Cr17Ni2 low-P steel ingot, characterized in that: The following steps are involved: The raw materials for preparing the 0Cr17Ni2 series low-P steel ingot are sequentially smelted, refined, cast and first annealed to obtain the 0Cr17Ni2 series low-P steel ingot; The element composition of the 0Cr17Ni2 series low-P steel ingot includes, by mass fraction, C 0.11-0.18%, Mn≤0.80%, Si≤0.80%, Cr 16.00-18.00%, Ni 1.50-2.50%, P≤0.012%, S≤0.010%, and the balance is Fe; The smelting includes a melting stage, an oxidation stage and a reduction stage in sequence; The conditions of the melting stage include: the molten pool temperature is 1550-1570°C; FeO is added, the mass of FeO is 2-3% of the mass of the molten steel; the basicity R is 2.0-2.5; the oxygen blowing pressure is 0.25-0.30MPa; The conditions of the oxidation stage include: oxygen blowing pressure ≥ 1.5 MPa; molten pool temperature 1660-1680°C; molten steel boiling time 6-10 min; adding Mn, the mass of Mn is 0.1-0.3% of the mass of molten steel; The conditions of the reduction stage include: adding thin slag material after slag discharge, adjusting the C mass content to 0.8-1.1%, adding ferrosilicon manganese alloy, ferromanganese alloy and ferrochrome alloy to make thin slag, and then adding reducing agent to make white slag; The refining includes sequentially performing a VOD stage, a VCD stage, a VOH stage and a VD stage; The conditions of the VOD stage include: vacuum degree of 90-110 mbar, vacuum pumping time of 1-1.5 h, oxygen blowing volume of 530-570 m 3 / h, Ar flow rate is 4~7m 3 / h; The conditions of the VCD stage include: vacuum degree of 15-20 mbar, vacuum pumping time of 13-18 min, Ar flow rate of 4-7 m 3 / h; The conditions of the VOH stage include: adding aluminum, CaO, CaF2 and FeSi, heating to 1650-1670°C, and Ar flow rate of 4-7m 3 / h; The conditions of the VD stage include: vacuum degree of 0.8~1.5mbar, vacuum pumping time ≥20min, Ar flow rate of 4~7m 3 / h.

2. The preparation method according to claim 1, characterized in that: The casting conditions include: molten steel calming time of 6 to 10 minutes, argon blowing volume of 4 to 7 L / min, casting temperature of 1550 to 1570° C., and casting speed of 5 to 7 mm / s.

3. The preparation method according to claim 1 or 2, characterized in that: The first annealing temperature is 840-860° C., and the holding time is 8-10 hours.

4. The 0Cr17Ni2 low-P steel ingot prepared by the preparation method according to any one of claims 1 to 3.

5. The 0Cr17Ni2 low-P steel ingot according to claim 4, characterized in that: The average grain size of the 0Cr17Ni2 low-P steel ingot is ≤ grade 3.

6. A forging, characterized in that: It is prepared from the 0Cr17Ni2 low-P steel ingot as described in claim 4 or 5.

7. The method for preparing a forging according to claim 6, characterized in that: The following steps are involved: The 0Cr17Ni2 low-P steel ingot is subjected to forging, second annealing, rough machining, third annealing and solution treatment in sequence to obtain the forging.

8. The preparation method according to claim 7, characterized in that: The forging conditions include: initial forging temperature of 1150-1170° C., final forging temperature of 860-890° C., forging ratio ≥3.0, extension ratio ≥2.0, and total forging ratio ≥4.

0.

9. The preparation method according to claim 8, characterized in that: The second annealing temperature is 820-840°C, and the holding time is 8-10h; The temperature of the third annealing is 820-850° C., and the holding time is 8-10 hours; The solution treatment includes sequentially performing a first solution treatment and a second solution treatment; The temperature of the first solution treatment is 1180-1200°C, and the holding time is 1.5-2.5h; The temperature of the second solution treatment is 780-800° C., and the holding time is 8-10 hours.

10. Use of the 0Cr17Ni2 low-P steel ingot according to claim 4 or 5, the forging according to claim 6, or the forging prepared by the preparation method according to any one of claims 7 to 9 in marine equipment, ship power equipment or power stations.

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