A method of smelting a Fe-Cr-Ni based martensitic stainless steel

Abstract

The application discloses a smelting method of Fe-Cr-Ni-based martensitic stainless steel, which comprises two processes of vacuum smelting and electroslag remelting; the vacuum smelting process comprises six stages of batching, furnace charging, melting, refining, alloying and pouring, and the electroslag remelting process comprises four stages of consumable electrode preparation, pre-melted slag preparation, furnace charging and smelting; in the refining stage of the vacuum smelting process, the refining temperature is controlled to be 130-150 DEG C higher than the liquidus of the molten steel, and the relationship between the refining time T and the smelting furnace capacity M is T=(1.4-1.6)*M 1 / 2 , wherein the unit of the refining time is min, and the unit of the smelting furnace capacity is kg. The application is simple in operation, effectively inhibits the oxidation loss of Ti element in the electroslag process, guarantees that the Ti element yield is more than 95%, greatly guarantees the uniformity of the electroslag solidification structure and composition, and guarantees the cold and hot working performance of the material in the subsequent processing process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of special material preparation, and particularly relates to a smelting method of Fe-Cr-Ni-based martensitic stainless steel. BACKGROUND

[0002] The Fe-Cr-Ni-based martensitic stainless steel is different from the traditional concept of achieving high strength by taking alloy carbide or nitride as the main strengthening phase. The steel takes Cu, Mo, Ti and Al as the strengthening elements, takes intermetallic compound as the strengthening phase, and takes reversed austenite as the toughening phase, so that the steel obtains the best strength-toughness combination. C is an element that is harmful to the strength-toughness, and therefore the C is controlled at a low level. The development of the steel is regarded as a breakthrough in the development of super-high-strength steel, and has important significance.

[0003] The steel is usually prepared by a vacuum induction + electroslag remelting double smelting process. Since the alloy content is more than 20% by mass, the smelting process of the steel is extremely easy to cause serious segregation if not properly controlled, and the segregation cannot be reversed through subsequent processes. In order to effectively ensure the uniformity of the solidification structure and composition of the electroslag product and improve the cold and hot working performance of the material, the ingot quality needs to be effectively controlled from the beginning of the vacuum smelting. The Ti element can be accurately controlled during the vacuum smelting process, but during the electroslag smelting process, the Ti element is seriously lost due to the oxygen supply in the environment and the oxygen supply in the slag, and even falls below the control range. From the actual production process, it can be seen that a small change in the chemical composition of the material will cause a sharp change in the performance. Therefore, how to control the loss fluctuation of the Ti element in the electroslag process and ensure the uniformity of the chemical composition is also the core technology for preparing the material.

[0004] Formulating a reasonable smelting process is of great significance to improving the physical and chemical properties of the Fe-Cr-Ni-based martensitic stainless steel product, the product yield, and the stable industrial production of the product. SUMMARY

[0005] To solve the above technical problems, the application provides a smelting method of Fe-Cr-Ni-based martensitic stainless steel, which is simple in operation, effectively inhibits the oxidation loss of the Ti element in the electroslag process, ensures that the Ti element recovery rate is stably ensured to be more than 95%, greatly ensures the uniformity of the solidification structure and composition of the electroslag, ensures the cold and hot working performance of the material in the subsequent processing process, and has important significance for the stable industrial production of the product.

[0006] To solve the above problems, the technical scheme adopted by the present application is as follows: a smelting method of Fe-Cr-Ni-based martensitic stainless steel, the smelting method comprising two processes of vacuum smelting and electroslag remelting; the vacuum smelting process comprises six stages of batching, furnace charging, melting, refining, alloying and pouring, and the electroslag remelting process comprises four stages of consumable electrode preparation, pre-melted slag preparation, furnace charging and melting; in the refining stage of the vacuum smelting process, the refining temperature is controlled to be 130-150 DEG C above the liquidus of the molten steel, and the relationship between the refining time T and the smelting furnace capacity M is T=(1.4-1.6) x M 1 / 2 , wherein the unit of the refining time is min, and the unit of the smelting furnace capacity is kg.

[0007] Further, in the alloying stage of the vacuum smelting process, before adding alloying materials, the vacuum pump is closed, 20,000-30,000 Pa of argon is filled, the temperature is adjusted to be 30-50 DEG C above the liquidus of the molten steel, the alloying materials are added, and high-power stirring is performed for 5-15 min.

[0008] Further, in the pouring process of the vacuum smelting process, the tapping temperature is controlled to be 40-60 DEG C above the liquidus of the molten steel, and the pouring speed is controlled to be within the range of 150-180 kg / min.

[0009] Further, in the pre-melted slag preparation stage of the electroslag remelting process, the slag composition is as follows: CaF2: 50%-53%, CaO: 21%-24%, MgO: 3%-5%, and Al2O3: 17%-18%.

[0010] Further, in the pre-melted slag preparation stage of the electroslag remelting process, a certain proportion of Al powder and TiO2 is added to the slag system, the addition amount of the Al powder is (0.3-0.5)% of the mass of the pre-melted slag, and the addition amount of TiO2 is determined according to the Ti and Al contents in the ingot, and the specific relationship is as follows: [TiO2]%= [(2.45 x a 1 / 3 + 0.26 x a)]%, wherein Ti / Al=a, 0.15%≤[Al]≤0.5%, and 0.5%≤[Ti]≤1.2%.

[0011] Further, in the melting stage of the electroslag remelting process, the melting speed is controlled to be [(0.65-0.75) x D 结 ] kg / h, wherein D 结 is the diameter of the crystallizer, and the unit is mm.

[0012] Further, the whole process of the vacuum smelting and electroslag remelting processes is performed under the condition of argon protection, the purity of the argon is ≥99.99%, and the oxygen in the atmosphere during the whole smelting process is ≤50 ppm.

[0013] Further, the smelting method has a Ti element yield of ≥95%.

[0014] Further, the chemical composition and mass percentage of the Fe-Cr-Ni-based martensitic stainless steel are as follows: C: 0.005-0.02%, Si: 0.2-0.7%, Mn: 0.2-1%, P≤0.01%, S≤0.01%, Cr: 11-13%, Ni: 8-10%, Mo: 3.5-5%, Cu: 1.5-3.5%, Ti: 0.5-1.2%, Al: 0.15-0.5%, and the balance of Fe and inevitable impurities.

[0015] Further, in the batching stage of the vacuum smelting process, industrial pure materials are used as main raw materials, and high-purity alloy materials such as electrolytic nickel plate, metallic chromium, molybdenum bar, pure iron, graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum, and sponge titanium are selected.

[0016] Further, in the furnace charging stage of the vacuum smelting process, graphite is laid at the bottom of the crucible, and the amount is 1 / 2 of the added amount, and the pure iron is placed at the bottom of the crucible, the refractory metals such as metallic chromium, nickel plate, and molybdenum bar are placed in the middle, and part of the pure iron is charged in the upper part; the second material bin is charged with graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum particles, and sponge titanium.

[0017] The beneficial effects produced by the above technical solution are as follows: 1. The present application provides a smelting method of Fe-Cr-Ni-based martensitic stainless steel. In the vacuum smelting process, the alloy is uniformly dissolved in the molten steel through “high superheat refining”, the refining time is accurately controlled according to the furnace capacity, the content of O, N, and H gases in the molten steel and harmful elements in the steel are effectively reduced, the segregation generated in the solidification process of the molten steel is reduced through “low superheat and slow pouring speed pouring”, and the ingot quality of the vacuum ingot is ensured. 2. In the electroslag process, by adding a certain proportion of TiO2 and Al powder in the fixed slag system, the oxidation loss of Ti element in the electroslag process can be effectively inhibited, and the recovery rate of Ti element is stably ensured to be more than 95%, and then through “lower melting speed control”, the uniformity of the electroslag solidification structure and composition is greatly ensured, and the cold and hot working properties of the material in the subsequent processing process are ensured. The above smelting process is simple to operate, and it is of great significance for the stable industrial production of such products. DETAILED DESCRIPTION

[0018] The present application will be further described in detail below in combination with specific embodiments.

[0019] A smelting method of Fe-Cr-Ni-based martensitic stainless steel, the smelting method comprises two processes of vacuum smelting and electroslag remelting; the vacuum smelting process comprises six stages of batching, furnace charging, melting, refining, alloying, and pouring, and the electroslag remelting process comprises four stages of consumable electrode preparation, pre-melted slag preparation, furnace charging, and smelting; the specific control method is as follows:

[0020] Vacuum melting process:

[0021] (1)Batching: The vacuum smelting material is calculated according to the components of the Fe-Cr-Ni-based martensitic stainless steel in percentage by mass, taking industrial pure material as the main raw material, and selecting high-purity alloy materials such as electrolytic nickel plate, metallic chromium, molybdenum strip, pure iron, graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum, and sponge titanium. All elements in the metal material are considered for accurate calculation of the batching;

[0022] (2)Charging: The graphite is laid at the bottom of the crucible, with a usage of 1 / 2 of the supplement amount in the alloying process, and the pure iron is placed at the bottom of the crucible. The metallic chromium, nickel plate, and molybdenum strip are placed in the middle, and the upper part is filled with part of the pure iron. The second material bin is filled with graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum particles, and sponge titanium. After the ingot mold is dried, it is placed in the corresponding position;

[0023] (3)Melting: The vacuum degree in the chamber is extracted to ≤5 Pa, and the power is sent for heating until the steel material in the crucible is completely melted.

[0024] (4)Refining: After the metal material in the crucible is completely melted, the temperature is raised to 130-150℃ above the liquidus of the steel liquid, the vacuum is adjusted to ≤1 Pa, and the relationship between the refining time T(min) and the smelting furnace capacity M(kg) is T=(1.4-1.6)×M. 1 / 2 ;

[0025] (5)Alloying: Stop the vacuum, fill in 20000-30000 Pa of argon gas, adjust the temperature to 30-50℃ above the liquidus of the steel liquid, and sequentially add graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum particles, and sponge titanium. Stir for 5-15 min at high power, detect the composition, and fine-tune to pass the test;

[0026] (6)Pouring: Adjust the temperature to 40-60℃ above the liquidus of the steel liquid, control the pouring speed within the range of 150-180 kg / min, and perform electric casting. After the ingot is completely solidified, the mold can be removed.

[0027] Electroslag remelting smelting steps:

[0028] (1)Consumable electrode preparation: The vacuum smelting ingot is cut off from the cap portion to ensure that the end part has no shrinkage cavity, and the surface of the ingot is free of oxidation layer. If necessary, the surface is polished, and the pre-treated ingot is welded to the auxiliary electrode;

[0029] (2)Pre-melted slag preparation: A certain amount of TiO2 and Al powder is added to the pre-melted slag with the composition of CaF2: 50%-53%, CaO: 21%-24%, MgO: 3%-5%, and Al2O3: 17%-18%. The TiO2 addition amount is determined comprehensively according to the Al and Ti content in the ingot, and the specific relationship is [TiO2]%= [(2.45×a 1 / 3+0.26xa) %, wherein Ti / Al=a, 0.15 % ≤[Al]≤0.5 %, 0.5 % ≤[Ti]≤1.2 % ; the Al powder is added in an amount of (0.3-0.5) % of the mass of the pre-melted slag, and after stirring and mixing, is placed in a heating furnace for baking and standby;

[0030] (3) charging: placing an ingot plate of the same material on the ESR bottom water tank, placing an arc starter scrap of the same material at the center of the ingot plate, installing a crystallizer, a protective fume hood and a consumable electrode;

[0031] (4) melting: electrically starting an arc, slowly adding slag after the arc light is stable, controlling the melting speed [(0.65-0.75)xD 结 ] Kg / h (D 结 is the diameter of the crystallizer, mm) after the melting to a certain weight of the consumable electrode, closing the melting power after the top-up, and demolding after the complete solidification of the ESR ingot;

[0032] argon protection: continuously introducing argon as a protective gas during the whole melting process, the purity of the argon is ≥99.99 %, and the oxygen in the atmosphere during the whole melting process is ≤50 ppm;

[0033] Example 1

[0034] The smelting method of the Fe-Cr-Ni-based martensitic stainless steel according to the application is specifically as follows.

[0035] The equipment is used for 3 furnace tests by a 500 Kg vacuum induction furnace and a Φ300*1500 mm crystallizer protective atmosphere ESR furnace, the target values of the smelting components are shown in Table 1-1, and the smelting process parameters of the 1 # ~3 # furnace tests are shown in Table 1-2, the chemical component detection results of the ESR ingot and the Ti element yield are shown in Table 1-3, and the Ti 收得率 = ([Ti 真空 ] / [Ti 电渣 ]x100) %.

[0036] Table 1-1 Chemical component target (wt %) of Example 1

[0037] C Si Mn P S Cr Ni Mo Cu Ti Al 0.005 0.6 0.8 ≤0.01 ≤0.01 13 8.5 4 1.8 0.7 0.2

[0038] (1) vacuum smelting process:

[0039] batching: according to the components of the Fe-Cr-Ni-based martensitic stainless steel, the vacuum smelting materials are calculated in percentage by mass, taking industrial pure materials as main raw materials, and selecting high-purity alloy materials such as electrolytic nickel plate, metallic chromium, molybdenum strip, pure iron, graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum and sponge titanium, considering all elements in the metal materials, and accurately calculating the batching;

[0040] Charging: The graphite is placed at the bottom of the crucible, the amount is 1 / 2 of the amount of the alloying process, and the pure iron is placed at the bottom of the crucible, the metal chromium and nickel plate and molybdenum strip are placed in the middle, and the upper part is filled with part of the pure iron; the graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum particles and sponge titanium are placed in the second bin; one Φ210x1700mm ingot mold is dried and placed in the corresponding position;

[0041] Melting: vacuumize to a vacuum degree of ≤5Pa in the chamber, and send power to heat until the steel and iron materials in the crucible are completely melted.

[0042] Refining: after the metal materials in the crucible are completely melted, the temperature is raised to 130-150℃ above the liquidus of the steel liquid, the vacuum is adjusted to ≤1Pa, and the refining time is T=(1.45-1.6)xM 1 / 2 =(1.4-1.6)x500 1 / 2 =(31-36)min;

[0043] Alloying: stop vacuumizing, fill in 20000-30000Pa argon, adjust the temperature to 30-50℃ above the liquidus of the steel liquid, add graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum particles and sponge titanium in turn, high-power stirring for 5-15min, detect the composition, and fine-tune to qualified;

[0044] Pouring: adjust the temperature to 40-60℃ above the liquidus of the steel liquid, control the pouring speed in the range of 150-180kg / min, conduct electric pouring, and the ingot can be demolded after complete solidification.

[0045] (2) Electroslag remelting process:

[0046] Consumable electrode preparation: the vacuum smelting ingot is cut off the cap part to ensure that the end part has no shrinkage cavity, and the surface of the ingot is ensured to have no oxidation layer, if necessary, the surface is polished, and then welded to the auxiliary electrode after pretreatment;

[0047] Pre-melted slag preparation: the total mass of the pre-melted slag is 30kg, the components are CaF2: 50%-53%, CaO: 21%-24%, MgO: 3%-5%, and Al2O3: 17%-18%, a certain amount of TiO2 and Al powder is added in the pre-melted slag, the TiO2 addition amount is determined according to the Al and Ti content in the ingot: Ti / Al=3.5, [TiO2]%= [(2.45x a 1 / 3 +0.26x a)]%= [(2.45x 3.5 1 / 3 +0.26x 3.5)]%=4.6%, wherein the Al powder addition amount is 0.09-0.15kg, and after stirring and mixing, it is placed in a heating furnace for baking for standby;

[0048] Melt: Put the same material starter plate on the ESR bottom water tank, put the same material arc starter scrap in the center of the starter plate, install the crystallizer, protective fume hood, consumable electrode;

[0049] Melt: Slowly add slag after arc is stable, control the melting rate to be 195-225 kg / h, supplement when the consumable electrode is left with a certain weight, turn off the melting power after supplement, and the ESR ingot can be demolded after complete solidification;

[0050] Argon protection: continuously input argon as protective gas during the whole melting process, the purity of argon is ≥99.99%, and the oxygen in the atmosphere during the whole melting process is ≤50 ppm;

[0051] After demolding, cut a slice at a position 200 mm away from the bottom of the ESR ingot, take two samples at the center, R / 2 and the edge of the cross section respectively for chemical composition detection and low magnification observation.

[0052] Table 1-2 in Example 1 # ~3 # Melt process parameter control of furnace

[0053]

[0054] In Table 1-2, TL is the liquidus temperature.

[0055] Table 1-3 in Example 1 # ~3 # Chemical composition (wt%) of ESR ingot of furnace and Ti element yield

[0056]

[0057]

[0058] Through the organization observation and chemical composition detection, the components of the ESR ingots of the 1#-3# furnaces are qualified, the solidification organization and composition are uniform, and the Ti yield is more than 95%.

[0059] Example 2

[0060] The smelting method of the Fe-Cr-Ni-based martensitic stainless steel is specifically as follows.

[0061] Three furnace tests are carried out by using a 3000 Kg vacuum induction furnace and a Φ550*2000 mm crystallizer protective atmosphere ESR furnace, the target values of smelting components are shown in Table 2-1, 1 # ~3 # The vacuum smelting process parameter control of the furnace is shown in Table 2-2, the chemical composition detection results of the ESR ingot and the Ti element yield are shown in Table 2-3, and the Ti 收得率 = ([Ti真空 ] / [Ti 电渣 ]×100)%.

[0062] Table 2-1 Chemical composition target (wt%)

[0063] C Si Mn P S Cr Ni Mo Cu Ti Al 0.015 0.5 0.5 ≤0.01 ≤0.01 12 10 5 3.5 1.2 0.15

[0064] (1) Vacuum melting process:

[0065] Batching: The vacuum smelting materials are calculated according to the components of the Fe-Cr-Ni-based martensitic stainless steel in mass percentage, and industrial pure materials are used as main raw materials. High-purity alloy materials such as electrolytic nickel plate, metallic chromium, molybdenum strip, pure iron, graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum, and sponge titanium are selected. All elements in the metal materials are considered for accurate calculation of batching;

[0066] Charging: The graphite is laid at the bottom of the crucible, with an amount of 1 / 2 of the supplement amount during alloying, and the pure iron is placed at the bottom of the crucible. The metallic chromium, nickel plate, and molybdenum strip are placed in the middle, and the upper part is filled with part of the pure iron. The second material bin is filled with graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum particles, and sponge titanium. A Φ420×2700mm ingot mold is dried and placed in the corresponding position.

[0067] Melting: The vacuum degree in the chamber is extracted to ≤5Pa, and power heating is performed until the steel materials in the crucible are completely melted.

[0068] Refining: After the metal materials in the crucible are completely melted, the temperature is raised to 130-150℃ above the liquidus of the steel liquid, the vacuum is adjusted to ≤1Pa, and the refining time is T=(1.45-1.6)×M 1 / 2 =(1.4-1.6)×3000 1 / 2 =(77-88)min;

[0069] Alloying: Stop vacuum, fill with 20000-30000Pa argon, adjust the temperature to 30-50℃ above the liquidus of the steel liquid, and add graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum particles, and sponge titanium in sequence. High-power stirring for 5-15min, detect the composition, and fine-tune to qualified.

[0070] Pouring: Adjust the temperature to 40-60℃ above the liquidus of the steel liquid, control the pouring speed within 150-180kg / min, and perform electric casting. After the ingot is completely solidified, demolding can be performed.

[0071] (2) Electroslag remelting process:

[0072] Consumable electrode preparation: The cap portion of the ingot from the vacuum smelting is cut off to ensure that the end part has no shrinkage cavity, and the surface of the ingot is free of oxidation layer. If necessary, the surface is polished, and the pre-treated ingot is welded to the auxiliary electrode.

[0073] Pre-melted slag preparation: the total mass of the pre-melted slag is 150 kg, and the components are CaF2: 50% to 53%, CaO 21% to 24%, MgO 3% to 5%, Al2O3 17% to 18%, a certain amount of TiO2 and Al powder is added into the pre-melted slag, the TiO2 addition amount is determined according to the Al and Ti content in the ingot: Ti / Al = 8, [TiO2] % = [(2.45 x a 1 / 3 + 0.26 x a)] % = [(2.45 x 8 1 / 3 + 0.26 x 8)] % = 7%, wherein the Al powder addition amount is 0.45 kg to 0.75 kg, and after stirring and mixing, it is placed in a heating furnace for baking for standby;

[0074] Furnace charging: placing a same-material starter plate on the ESR bottom water tank, placing a same-material arc starter scrap in the center of the starter plate, installing a crystallizer, a protective hood, and a consumable electrode;

[0075] Melting: arc striking, after the arc light is stable, slowly adding slag, after slagging is finished, controlling the melting speed to be 357.5 to 412.5 kg / h, when the melting is to a certain weight of the consumable electrode, performing top-up, after the top-up is finished, turning off the melting power, and after the ESR ingot is completely solidified, demolding can be performed;

[0076] Argon protection: continuously inputting argon as a protective gas during the entire melting period, the argon purity is ≥99.99%, and the oxygen in the atmosphere during the entire melting process is ensured to be ≤50 ppm;

[0077] After demolding, slicing at a distance of 200 mm from the bottom of the ESR ingot, taking two samples at each of the three positions of the center, R / 2, and the edge of the cross section for chemical composition detection and low-magnification structure observation.

[0078] Table 2-2, Example 2 1 # to 3 # Furnace smelting process parameter control

[0079]

[0080]

[0081] In Table 2-2, TL is the liquidus temperature.

[0082] Table 2-3, Example 2 1 # to 3 # Furnace ESR ingot chemical composition (wt%) and Ti element yield

[0083]

[0084] Through the organization observation and chemical composition detection, the components of the ESR ingots of 1#-3# furnace times are qualified, the solidification organization and the component are uniform, and the Ti yield is more than 95%.

[0085] Example 3

[0086] The smelting method of the Fe-Cr-Ni-based martensitic stainless steel is specifically as follows.

[0087] The equipment adopts a 5000 Kg vacuum induction furnace and a Φ600*2500 mm crystallizer protective atmosphere ESR furnace to perform three furnace times tests, the smelting component target values are shown in Table 3-1, the 1 # -3 # The vacuum smelting process parameter control of the furnace times is shown in Table 3-2, the ESR ingot chemical composition detection results and the Ti element yield are shown in Table 3-3, the Ti 收得率 = ([Ti 真空 ] / [Ti 电渣 ] * 100) %.

[0088] Table 3-1 Chemical composition target of Example 3 (wt%)

[0089] C Si Mn P S Cr Ni Mo Cu Ti Al 0.02 0.7 0.8 ≤0.01 ≤0.01 13 9 4 3.0 0.5 0.5

[0090] (1) Vacuum smelting process:

[0091] Batching: according to the components of the Fe-Cr-Ni-based martensitic stainless steel, the vacuum smelting materials are calculated in percentage by mass, taking industrial pure materials as main raw materials, and selecting high-purity alloy materials such as electrolytic nickel plate, metal chromium, molybdenum strip, pure iron, graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum and sponge titanium, considering all elements in the metal materials, and accurately calculating the batching;

[0092] Furnace charging: the graphite is laid at the bottom of the crucible, the amount is 1 / 2 of the supplement amount in the alloying process, and the pure iron is placed at the bottom of the crucible, the metal chromium, nickel plate and molybdenum strip are placed in the middle, and the pure iron is further charged in the upper part; the graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum particles and sponge titanium are charged in the second material bin; and one Φ500*3300 mm size ingot mold is dried and placed in the corresponding position;

[0093] Melting: vacuumizing to the vacuum degree in the chamber ≤ 5 Pa, and sending power to heat until the steel and iron materials in the crucible are completely melted.

[0094] Refining: after the metal materials in the crucible are completely melted, the temperature is raised to 130-150 ℃ above the liquidus of the steel liquid, the vacuum is adjusted to ≤ 1 Pa, and the refining time is T = (1.45-1.6) * M 1 / 2 = (1.4-1.6) * 5000 1 / 2 = (99-113) min;

[0095] Alloying: stop vacuum, fill in 20000-30000 Pa argon, adjust the temperature to 30-50℃ above the liquidus of the steel liquid, add graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum particles, and sponge titanium in sequence, high-power stirring for 5-15 min, detect the composition, and fine-tune to qualified;

[0096] Pouring: adjust the temperature to 40-60℃ above the liquidus of the steel liquid, control the pouring speed in the range of 150-180 kg / min, conduct electric pouring, and after the ingot is completely solidified, demolding can be performed.

[0097] (2) Electroslag remelting process:

[0098] Consumable electrode preparation: cut off the cap portion of the ingot prepared by vacuum smelting to ensure that the end portion is free of shrinkage holes, and ensure that the surface of the ingot is free of oxide layers. If necessary, the surface is polished, and after pretreatment, it is welded to an auxiliary electrode;

[0099] Pre-melted slag preparation: the total mass of the pre-melted slag is 250 kg, and the components are CaF2: 50%-53%, CaO: 21%-24%, MgO: 3%-5%, and Al2O3: 17%-18%. A certain amount of TiO2 and Al powder is added to the pre-melted slag. The TiO2 addition amount is determined comprehensively according to the Al and Ti content in the ingot: Ti / Al = 1, [TiO2] % = [(2.45 × a 1 / 3 + 0.26 × a)] % = [(2.45 × 1 1 / 3 + 0.26 × 1)] % = 2.7%, wherein the Al powder addition amount is 0.75-1.25 kg. After stirring and mixing, it is placed in a heating furnace for baking and standby;

[0100] Furnace charging: place a dummy block of the same material on the electroslag bottom water tank, place a same material arc starter scrap in the center of the dummy block, install the crystallizer, protective hood, and consumable electrode;

[0101] Melting: arc striking, after the arc light is stable, slowly add slag, after slag melting is completed, control the melting rate to be 390-450 kg / h, perform top-up when the consumable electrode is melted to a certain weight, after top-up is completed, turn off the melting power, and after the electroslag ingot is completely solidified, demolding can be performed;

[0102] Argon protection: continuously introduce argon as a protective gas during the entire melting process, the argon purity is ≥99.99%, and the oxygen in the atmosphere during the entire melting process is ≤50 ppm;

[0103] After demolding, cut a slice at a distance of 200 mm from the bottom of the electroslag ingot, take two samples at the center, R / 2, and the edge of the cross section for chemical composition detection and low magnification structure observation.

[0104] Table 3-2 1 # -3 #Control of process parameters in a furnace campaign

[0105]

[0106] In Table 3-2, TL is the liquidus temperature.

[0107] Table 3-3 Chemical composition of ESR ingot in Example 3 # ~3 # Chemical composition of ESR ingot (wt%) and Ti yield in a furnace campaign

[0108]

[0109]

[0110] Through the observation of the structure and the detection of the chemical composition, the components of the ESR ingot in the 1st to 3rd furnace campaign are qualified, the solidification structure and the components are uniform, and the Ti yield is more than 95%.

[0111] The above examples are only used to illustrate but not to limit the technical solutions of the present application. Although the present application is described in detail with reference to the above examples, those skilled in the art should understand that the present application can still be modified or equivalently replaced without departing from the spirit and scope of the present application, and any modification or partial replacement should be covered in the scope of the claims of the present application.

Claims

1. A method for smelting Fe-Cr-Ni based martensitic stainless steel, characterized in that: The smelting method includes two processes: vacuum smelting and electroslag remelting. The vacuum smelting process includes six stages: batching, charging, melting, refining, alloying, and casting. The electroslag remelting process includes four stages: preparation of consumable electrodes, preparation of pre-melted slag, charging, and melting. In the refining stage of the vacuum smelting process, the refining temperature is controlled at 130~150℃ above the liquidus line of the molten steel. The relationship between the refining time T and the furnace volume M is: T = (1.4~1.6) × M 1 / 2 The refining time is in minutes, and the furnace volume is in kilograms. During the alloying stage of the vacuum smelting process, before adding alloying materials, turn off the vacuum pump, introduce 20,000 to 30,000 Pa of argon gas, adjust the temperature to 30 to 50°C above the liquidus line of the molten steel, add the alloying materials, and stir at high power for 5 to 15 minutes. During the vacuum smelting and casting process, the tapping temperature is controlled at 40-60°C above the liquidus line of the molten steel, and the casting speed is controlled within the range of 150-180 kg / min. In the pre-melted slag preparation stage of the electroslag remelting process, the slag composition is: CaF2: 50%–53%, CaO: 21%–24%, MgO: 3%–5%, Al2O3: 17%–18%. A certain proportion of Al powder and TiO2 are added to the slag system. The amount of Al powder added is (0.3–0.5)% of the mass of the pre-melted slag, and the amount of TiO2 added is determined based on the Ti and Al content in the ingot. The specific relationship is: [TiO2]% = [(2.45 × a 1 / 3 +0.26×a)]%, where Ti / Al=a, 0.15%≤[Al]≤0.5%, 0.5%≤[Ti]≤1.2%; During the smelting stage of the electroslag remelting process, the melting rate is controlled at [(0.65~0.75)×D]. 结 ]kg / h, the D 结 The diameter of the crystallizer is in mm.

2. The smelting method for Fe-Cr-Ni based martensitic stainless steel according to claim 1, characterized in that: The entire process of vacuum smelting and electroslag remelting is carried out under argon protection, with argon purity ≥99.99%, ensuring that the oxygen content in the atmosphere during the entire smelting process is ≤50ppm.

3. The smelting method for Fe-Cr-Ni based martensitic stainless steel according to claim 1, characterized in that: The smelting method yields a Ti element recovery rate of ≥95%.

4. The smelting method for Fe-Cr-Ni based martensitic stainless steel according to claim 1, characterized in that: The chemical composition and mass percentage of the Fe-Cr-Ni based martensitic stainless steel are as follows: C: 0.005-0.02%, Si: 0.2-0.7%, Mn: 0.2-1%, P≤0.01%, S≤0.01%, Cr: 11-13%, Ni: 8-10%, Mo: 3.5-5%, Cu: 1.5-3.5%, Ti: 0.5-1.2%, Al: 0.15-0.5%, with the balance being Fe and unavoidable impurities.

5. The smelting method for Fe-Cr-Ni based martensitic stainless steel according to claim 1, characterized in that: The vacuum smelting process, in the batching stage, uses industrial pure materials as the main raw materials, and selects high-purity alloy materials such as electrolytic nickel plates, metallic chromium, molybdenum bars, pure iron, graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum, and sponge titanium. The vacuum smelting process is carried out in the furnace loading stage as follows: graphite is laid at the bottom of the crucible, with the amount being 1 / 2 of the total amount added, and pure iron is placed at the bottom of the crucible. Metallic chromium, nickel plates, and molybdenum strips are placed in the middle, and some pure iron is loaded at the top. Graphite, industrial silicon, electrolytic manganese, electrolytic copper, aluminum granules, and sponge titanium are loaded into the secondary hopper.

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