CN113481422B - Method for smelting steel ingot for ultralow-sulfur low-oxygen 55NiCrMoV7 module - Google Patents
Method for smelting steel ingot for ultralow-sulfur low-oxygen 55NiCrMoV7 module Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 147
- 239000010959 steel Substances 0.000 title claims abstract description 147
- 238000000034 method Methods 0.000 title claims abstract description 66
- 229910052717 sulfur Inorganic materials 0.000 title claims abstract description 40
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 38
- 239000001301 oxygen Substances 0.000 title claims abstract description 24
- 238000003723 Smelting Methods 0.000 title claims abstract description 22
- 239000011593 sulfur Substances 0.000 title claims abstract description 16
- 238000007670 refining Methods 0.000 claims abstract description 41
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims abstract description 34
- 238000007664 blowing Methods 0.000 claims abstract description 26
- 238000010079 rubber tapping Methods 0.000 claims abstract description 23
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 21
- 239000002893 slag Substances 0.000 claims abstract description 20
- 239000000463 material Substances 0.000 claims abstract description 19
- 229910052786 argon Inorganic materials 0.000 claims abstract description 17
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 10
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 8
- 230000003031 feeding effect Effects 0.000 claims abstract description 6
- 238000007667 floating Methods 0.000 claims abstract description 5
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 24
- 238000005266 casting Methods 0.000 claims description 21
- 239000000395 magnesium oxide Substances 0.000 claims description 12
- 239000000843 powder Substances 0.000 claims description 11
- 238000004886 process control Methods 0.000 claims description 11
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 10
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 10
- 239000004571 lime Substances 0.000 claims description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- BYFGZMCJNACEKR-UHFFFAOYSA-N aluminium(i) oxide Chemical compound [Al]O[Al] BYFGZMCJNACEKR-UHFFFAOYSA-N 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 7
- 238000009628 steelmaking Methods 0.000 claims description 7
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 6
- 229910001570 bauxite Inorganic materials 0.000 claims description 6
- 230000005540 biological transmission Effects 0.000 claims description 5
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 4
- 229910020413 SiO2—MgO Inorganic materials 0.000 claims description 4
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 239000010436 fluorite Substances 0.000 claims description 4
- 238000002844 melting Methods 0.000 claims description 4
- 230000008018 melting Effects 0.000 claims description 4
- 238000005086 pumping Methods 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 239000000956 alloy Substances 0.000 claims description 3
- 238000009529 body temperature measurement Methods 0.000 claims description 2
- 238000005261 decarburization Methods 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 claims description 2
- 230000001737 promoting effect Effects 0.000 claims description 2
- 238000006477 desulfuration reaction Methods 0.000 claims 1
- 230000023556 desulfurization Effects 0.000 claims 1
- 238000001514 detection method Methods 0.000 abstract description 12
- 239000002994 raw material Substances 0.000 abstract description 6
- 239000002245 particle Substances 0.000 abstract description 5
- 230000003749 cleanliness Effects 0.000 abstract description 4
- 238000007872 degassing Methods 0.000 abstract description 3
- 229910052748 manganese Inorganic materials 0.000 description 12
- 229910052750 molybdenum Inorganic materials 0.000 description 12
- 229910052759 nickel Inorganic materials 0.000 description 12
- 229910052804 chromium Inorganic materials 0.000 description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 10
- 238000005292 vacuum distillation Methods 0.000 description 8
- 229910052720 vanadium Inorganic materials 0.000 description 7
- 239000000126 substance Substances 0.000 description 6
- 229910000805 Pig iron Inorganic materials 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 229910000604 Ferrochrome Inorganic materials 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- 230000005611 electricity Effects 0.000 description 3
- 238000005242 forging Methods 0.000 description 3
- 238000009489 vacuum treatment Methods 0.000 description 3
- 229910004261 CaF 2 Inorganic materials 0.000 description 2
- 229910000616 Ferromanganese Inorganic materials 0.000 description 2
- 238000013459 approach Methods 0.000 description 2
- 239000010882 bottom ash Substances 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000004512 die casting Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
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- 238000001192 hot extrusion Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D7/00—Casting ingots, e.g. from ferrous metals
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
- C21C7/0645—Agents used for dephosphorising or desulfurising
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
Abstract
The invention provides a method for smelting a steel ingot for an ultra-low-sulfur low-oxygen 55NiCrMoV7 module, which comprises the steps of reasonably selecting raw material components, raw material proportion and C, S, P content of initial smelting tapping in the initial smelting process; in the refining process, a high-alkalinity slag system is adopted, reasonable deoxidizers and the types and the use amounts of slagging materials are selected, and the contents of O and S in refined steel are controlled; the content of S and N, H, O in the molten steel is further reduced by controlling the effective vacuum degree and the degassing time in the vacuum process; the floating and the removal of the inclusion are fully promoted by controlling the argon flow and the soft blowing time in the process of returning to the ladle refining; the method has the advantages that the nozzle pressure is opened in the vacuum pouring process, so that the molten steel can be further dispersed, the N, H, O content in the molten steel can be further removed, the flow control in the pouring process can reduce the possibility that ladle slag is drawn into an ingot mold along with the molten steel in the later pouring period so as to ensure the good feeding effect of riser molten steel, the oxygen content and the S content of finished product molten steel can be controlled to be respectively below 15ppm and 0.001 percent, the cleanliness is high, and the forge piece has no large-particle inclusion with standard-exceeding flaw detection.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a method for smelting an ultra-low-sulfur low-oxygen 55NiCrMoV7 steel ingot for a module.
Background
The properties of the die steel are improved mainly by the following two ways in all countries of the world: one approach is to optimize the composition of the die steel and develop new steel grades, and the other approach is to improve the production flow and process control technology of the die steel. China has clearly proposed in planning: in the aspect of hot-work die steel, novel low-cost and long-service-life hot-work die steel with independent intellectual property rights is required to be developed; developing ultra-pure hot work die steel with uniform tissue; obtaining extremely low S, P content and ultra-fine structure; adding alloy elements with red hardness function to improve the hardness of the die at high temperature and prolong the service life of the hot-pressing die and the hot-extrusion die.
At present, the hot work die steel in China has the problem of coexistence of two polar differentiation: on one hand, the method is a rolled material which aims to pursue lower cost, has low performance, is suitable for dies with low requirements, or is forged into modules with various specifications to greatly improve the performance, but has low total cost compared with a forged material, so the rolled material occupies an important share of hot-work die steel market in a long period of time in the future; on the other hand, the forging material mainly with pursuit quality is mainly embodied in high-quality hot-working die steel, and is mainly applied to hot-working dies such as die-casting dies, forging dies, extrusion dies and the like, which is a necessary way for the die industry to move to the die forcing state in China. Although China does a lot of work in the aspect of developing and developing novel die steel, and carries out domestic research on part of foreign excellent hot-work die steel, the die steel with high quality and low price is provided for the market, but the die steel can be actually put to the market and is widely applied relatively rarely, H13 series universal hot-work die steel introduced from foreign is still the dominant position in the market at present, and special die-casting dies, hot-forging dies and hot extrusion dies aiming at different use requirements and working conditions are still few.
Disclosure of Invention
In view of the above, the invention aims to provide a method for smelting an ultra-low-sulfur low-oxygen 55NiCrMoV7 steel ingot for a module, which has higher cleanliness.
In order to achieve the purpose, the invention adopts the technical scheme that: a method for smelting an ingot for an ultra-low-sulfur low-oxygen 55NiCrMoV7 module is characterized by comprising the following steps of:
s1, controlling the electric furnace steel-making process: sequentially completing material preparation, melting, slagging and dephosphorization, respectively controlling the content of C, P, S in molten steel to be 0.05-0.08% of C, less than or equal to 0.003% of P and less than or equal to 0.050% of S, and then carrying out tapping deoxidation operation;
s2, refining process control of the refining furnace: transferring the molten steel processed in the step S1 to a ladle refining station, adding lime, bauxite, fluorite and magnesia slagging materials, transmitting power for slagging, adding a deoxidizer in batches, and performing power transmission temperature raising, slagging, argon blowing, deoxidation and alloy adjustment operations to enable the components of the molten steel to meet the requirements of the 55NiCrMoV7 standard so as to further remove S and O in the molten steel;
s3, VD process control: transferring the molten steel processed in the step S2 into a vacuum chamber, and gradually pumping to improve the vacuum degree of the atmosphere so that the molten steel is subjected to C, O reaction and steel slag reaction under the vacuum condition, and further removing H, N, O and S in the molten steel;
s4, returning to LF ladle refining process control: transferring the molten steel treated in the step S3 to a ladle refining station again, transmitting power to raise the temperature to 1610 and 1620 ℃, enabling the argon flow to be less than or equal to 15NL/min, executing soft blowing operation, enabling the soft blowing time to be not less than 15min, promoting floating and removing of inclusions, and controlling the tapping temperature after the soft blowing treatment to 1585-1595 ℃;
s5, controlling the steel ingot casting process: and (3) after the chassis, the ingot mold and the riser are cleaned and ready to be matched, placing the ingot mold and the riser to a pouring station, draining the molten steel processed in the step S4, transferring the molten steel to the pouring station, performing vacuum pumping operation, starting temperature measurement when the vacuum degree is less than or equal to 0.5torr, controlling the pouring temperature at 1540-.
And in the step S1, the carbon blending amount is 1.0-1.3% during material blending. Further, if pig iron, scrap steel and C powder are selected for proportioning during proportioning, the following 2 furnace burden proportions can be specifically selected: firstly, when C blocks, pig iron and scrap steel are adopted for burdening, the burden mixture ratio is required to be as follows: the carbon blending amount is 1.0-1.3%, the pig iron amount accounts for 10-15% of the total material weight, and the coke block is generally blended according to 0.5-0.8% of the total material weight; the proportion of scrap steel is 85-90%; ② blending the whole scrap steel, wherein the carbon blending amount is 1.0-1.3%.
Further, in the step S1, after the batching is completed, the furnace burden in the electric furnace is sequentially melted down, oxygen-blown for decarburization, and then the active lime and the fluorite are added, wherein the tapping conditions of the electric furnace are as follows: 0.05 to 0.08 percent of C, less than or equal to 0.050 percent of S and less than or equal to 0.003 percent of P.
Further, in the step S1, when the electric furnace is tapped, 0.5-1.0kg/t molten steel amount of deoxidizer Al, 0.5-1.0/t molten steel amount of SiAlCaBa block and 0.5-2.0kg/t molten steel amount of SiAlCaBa powder are added in sequence along with the steel flow for deoxidation.
Further, after the molten steel processed in the step S1 is transferred to a ladle refining station, a CaO-Al2O3-SiO2-MgO slag system is adopted in the refining process to realize molten steel desulphurization and deoxidation, wherein the slag system comprises 48-56% of CaO, and Al2O 3: 19-25%, SiO 2: 9-15% of MgO and 4-9% of MgO.
Further, in the step S2, after the refining is finished, the S content in the molten steel is less than or equal to 0.003 percent, the O content is less than or equal to 30ppm, and the temperature of the refining station is controlled at 1670-.
Further, in the step S3, the vacuumizing time is 10-15min, the vacuum degree in the effective treatment process is 3.0torr-0.5torr, the argon flow is controlled at 60-80NL/min, and the effective vacuum treatment time is 15-25 min.
Further, in the step S4, the soft blowing time is not less than 15min, and the argon flow rate during soft blowing is controlled to be 15 to 20 NL/min.
Further, in the step S5, when pouring, the pouring speed of the ingot body is 3.2-3.8t/min, and the pouring speed of the riser is 1/3-1/2 of the pouring speed of the ingot body, so as to achieve a good feeding effect.
Compared with the prior art, the invention has the beneficial effects that: the invention reasonably selects the components of the raw materials and the proportion of the raw materials in the primary smelting process, controls the S, P content of the primary smelting steel tapping, adopts a high-alkalinity CaO-Al2O3-SiO2-MgO slag system in the refining process, selects the type and the dosage of a reasonable deoxidizer, controls the O and S content of the refined steel tapping, further reduces the S and N, H, O content in the molten steel in the vacuum process by controlling the effective vacuum degree and the degassing time, returns to the ladle refining process, fully promotes the floating and removal of inclusions by controlling the argon flow and the soft blowing time, ensures that the molten steel is more dispersedly removed with N, H and oxygen content in the molten steel in the vacuum casting process by opening the nozzle pressure, reduces the slag in the later casting period to enter the ingot mold by a flow control process means, ensures the good feeding effect of riser molten steel, ensures that the oxygen and S content control of the finished molten steel (before casting) respectively reaches below 15ppm and 0.001 percent, the high-cleanliness steel has high cleanliness, large-particle inclusions which exceed the flaw detection standard do not exist in a forged piece after a steel ingot is forged into a material, the ultra-detection meets the GB-T6402-20083 level requirement, and GB/T10561-2002 high-power inclusion rating A, B, C, D, Ds type inclusions are all 0.5 level.
Drawings
FIG. 1 is a photograph of the invention at an early stage of casting;
FIG. 2 is a photograph of the invention at the middle of casting;
FIG. 3 is a photograph of the invention at the end of casting;
figure 4 is a drawing of a die steel product.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below with reference to the accompanying drawings in the present invention, it is obvious that the described embodiments are some, but not all embodiments of the present invention, and based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.
Example 1
Smelting a furnace of 55NiCrMoV7, wherein the molten steel amount of a single furnace is 55 tons, the steel ingot of a single furnace is 52.5 tons, and the finished product of the forged piece has the thickness of 600mm, the length of 3600mm and the width of 1600 mm. The steel ingot comprises the following chemical components in percentage by mass: c: 0.55%, Si: 0.21%, Mn: 0.85%, S0.0010%, P0.008%, Cr 1.16%, Ni 1.77%, Mo 0.51%, V: 0.09%; the balance being Fe and unavoidable impurities.
The steel ingot smelting method for the ultra-low sulfur and low oxygen 55CrNiMoV7 module comprises the following specific process steps of electric furnace steelmaking process control, refining furnace refining process control, VD process control and casting process control:
s1 electric furnace steelmaking process
(1) The electric furnace comprises the following ingredients: 42.3t of waste steel containing 0.60 percent of Ni0, 15.3t of common waste steel, 5t of pig iron (the carbon content is 4.3 percent), 62.6t of total material weight, 500kg of carbon block and 1.5t of bottom ash of the electric furnace;
(2) the oxygen flow control in the electric furnace steel making process is 1500-3The temperature of the molten steel is controlled at 1550 ℃ during the dissolution and the components of the molten steel during the dissolution are as follows: 0.19%, Si: 0.08%, Mn: 0.10%, S0.025, P0.025, Cr 0.10%, Ni 0.49%, Mo 0.12, Cu: 0.13 percent; removing initial slag, transmitting electricity to raise the temperature to 1580-.
(3) The molten steel during electric furnace tapping comprises the following components: 0.08%, Si: 0.02%, Mn: 0.04%, S0.021%, P0:003, Cr 0.06%, Ni 0.49%, Mo 0.12, Cu: 0.13 percent;
(4) 55kg of Al blocks and 55kg of SiAlCaBa blocks are added along with steel flow when the electric furnace is initially smelted and tapped, then 200kg of high-carbon ferromanganese and 300kg of high-carbon ferrochromium are added, and finally 55kg of composite deoxidizer SiAlCaBa powder is added.
S2 refining step
(1) After the refining bag is placed in a refining station, 800kg of lime, 250kg of bauxite and 100kg of magnesia are respectively added, the temperature is raised to 1580 ℃ by power transmission, 200kg of lime is added, and the addition of the lime, the bauxite and the magnesia slagging materials is finished within 40min of entering the station;
(2) in the LF electricity transmission slagging process, 135kg and 50kg of C powder and Al powder are added in batches, and high-carbon ferrochrome, a Ni plate, Mo iron, V iron and electrolytic Mn are added to adjust the chemical components of the molten steel;
(3) controlling the flow of argon of a steel ladle at 80-120NL/min in the refining process, and keeping the micro-positive pressure atmosphere of molten steel in the LF process;
(4) the refining time of the LF process is 129min, wherein the white slag is kept for 20min, and the LF tapping temperature is 1660 ℃;
(5) the molten LF tapping liquid comprises the following components: 0.54%, Si: 0.21%, Mn: 0.87%, S: 0.0022%, P: 0.008%, Cr 1.15%, Ni 1.75%, Mo 0.51, V: 0.09%, V: 0.09%; o16ppm, N112ppm, H4.0 ppm;
(6) the detection result of the final slag component of LF tapping is 53.2 percent of CaO, and the detection result of Al2O 3: 24.2%, SiO 2: 10.3%, MgO: 5.8%, CaF 2: 1.3 percent, TFe 0.32 percent, MnO 0.09 percent and S0.37 percent;
s3 VD procedure
(7) Controlling the vacuum degree in the vacuum treatment process to be between 1torr and 0.5torr, wherein the VD vacuumizing time is 15min, and the vacuum degree in the effective treatment process is between 2.0torr and 0.5 torr;
(8) controlling the flow of argon gas at 60-80NL/min, and effectively vacuum-treating for 20 min;
s4 returning to LF refining process
(9) After the ladle returns to the LF refining station, 10kg of C powder is added, after the yellow molten slag turns white, a deoxidizer is added within 15min, and the ladle is powered on and heated to 1610 ℃;
(10) returning to the heating process for sampling before soft blowing, wherein the molten steel comprises the following components: 0.55%, Si: 0.21%, Mn: 0.86%, S: 0.0012%, P: 0.008%, Cr 1.17%, Ni 1.76%, Mo 0.51, V: 0.09%; o: 10ppm, N: 40ppm, H: 2.2 ppm;
(11) adjusting Ar gas flow to 25L/min, executing soft blowing operation, observing that the steel liquid surface is not exposed, wherein the soft blowing time is 20min, and the tapping temperature after soft blowing is 1580 ℃.
S5 VC process
(12) The ladle returns to the LF and is transferred to a drainage station, the pressure of the ladle sliding plate is controlled between 0.2 and 0.3MPa after drainage, and the drainage quantity of molten steel is 0.5 t;
(13) preparing an auxiliary mould of the ingot mould, wherein the quality of the inner wall of a riser is good, the baking time of a steel ingot riser is not less than 6h, the inner wall of the riser before mould assembly is red, the ingot mould and a chassis are polished for light, and the mould assembly time is started when a steel ladle is vacuumized by VD (vacuum distillation) to ensure the good heat preservation and feeding effects of the riser;
(14) preparing a flow guide pipe: the honeycomb duct is baked well, and the honeycomb duct is assembled 5min before the ladle is drained;
(15) after the ladle is hoisted to the pouring station, vacuumizing is started, and the pouring vacuum degree of the tundish is less than or equal to 0.5 torr;
(16) opening a water gap argon 2min before casting, blowing argon pressure to 0.1-0.8Mpa, and adjusting the water gap pressure to 0.3Mpa after casting;
(17) preparing a steel finished product sample at a casting station, wherein the casting temperature is 1546 ℃, and the chemical components of the steel finished product sample are C: 0.55%, Si: 0.21%, Mn: 0.85%, S0.0010%, P0.008%, Cr 1.16%, Ni 1.77%, Mo 0.51%, V: 0.09%;
(18) controlling flow 2-3min before the pouring process, then performing full-flow pouring, controlling flow of the ladle again at the position about 150 away from the lower edge of the riser by the liquid level of the steel, wherein the total pouring time is 21min, and the photos of the early stage, the middle stage and the later stage of the pouring are respectively shown in figures 1-3.
The steel ingot metallurgical effect and the steel metallurgical quality are evaluated as follows: the content of the molten steel O before back heating and soft blowing is 10ppm, the content of the molten steel S before casting is 0.0010%, the nonmetallic inclusion is carried out according to the GB/T10561 specification, the grade of the nonmetallic inclusion of the forged steel is A, B, C, D, Ds, the grade is 0.5, the module carries out ultrasonic detection piece by piece according to GB/T6402/2008, the detection method and the judgment of the internal quality meet the specification, and no obvious defect or large-particle inclusion exists.
Example 2
The same process flow is adopted in this example as in example 1.
In the embodiment, a furnace of 55NiCrMoV7 is smelted, the single furnace has 48 tons of molten steel, a single steel ingot is 45.5 tons, and the finished product of the forged piece has the thickness of 650mm, the length of 3650mm and the width of 1400 mm. The steel ingot comprises the following chemical components in percentage by mass: c: 0.54%, Si: 0.15%, Mn: 0.85%, S0.0008%, P0.007%, Cr 1.12%, Ni 1.75%, Mo 0.51%, V: 0.08%, Cu: 0.08 percent; the balance being Fe and unavoidable impurities.
The steel ingot smelting method for the ultra-low-sulfur low-oxygen 55CrNiMoV7 module comprises the working procedures of electric furnace steel-making process control, refining process control of a refining furnace, VOD process control and casting process control, and comprises the following specific process steps:
s1, and (1) the electric furnace comprises the following ingredients: 44.8t of waste steel containing 0.60 percent of Ni0, 7.7t of common waste steel, 4.5t of pig iron (the carbon content is 4.3 percent), 57t of total material weight, 450kg of carbon block and 1.3t of bottom ash of the electric furnace;
(2) the oxygen flow control in the electric furnace steelmaking process is 1500-1650m3/h, the molten steel temperature is 1560 ℃ during the melting and clearing, and the molten steel comprises the following components: 0.23%, Si: 0.09%, Mn: 0.12%, S0.024, P0.015%, Cr 0.15%, Ni 0.59%, Mo 0.12, Cu: 0.08 percent; removing initial slag, transmitting electricity to raise the temperature to 1580-.
(3) The molten steel during electric furnace tapping comprises the following components: 0.06%, Si: 0.03%, Mn: 0.04%, S0.021%, P0.003%, Cr 0.16%, Ni 0.60%, Mo 0.12%, Cu: 0.08 percent;
(4) when the steel is initially smelted and tapped from the electric furnace, 45kg of Al blocks and 45kg of SiAlCaBa blocks are added along with the steel flow, then 100kg of high-carbon ferromanganese and 100kg of high-carbon ferrochromium are added, and finally 50kg of composite deoxidizer SiAlCaBa powder is added.
S2, refining: (1) after the refining bag is placed at a refining station, 800kg of lime, 250kg of bauxite and 100kg of magnesia are respectively added, after the power is supplied and the temperature is raised to 1580 ℃, 150kg of lime is added, and the addition of lime, bauxite and magnesia slagging materials is finished within 40min after LF entering the station;
(2) adding 135kg and 50kg of C powder and Al powder in batches in the LF power transmission and slagging process, and adding high-carbon ferrochrome, Ni plates, Mo iron, V iron and electrolytic Mn to adjust chemical components of molten steel;
(3) controlling the flow of argon in a ladle in the refining process to be 80-120NL/min, and maintaining the micro-positive pressure atmosphere of molten steel in the LF process;
(4) refining for 121min in an LF process, wherein white slag is kept for 20min, and the LF tapping temperature is 1660 ℃;
(5) the LF tapping molten steel comprises the following components: 0.54%, Si: 0.14%, Mn: 0.87%, S0.0019%, P0.007%, Cr 1.13%, Ni 1.75%, Mo 0.51%, V: 0.09 percent and Cu0.08 percent; o16ppm, N106ppm, H5.1ppm;
(6) the detection result of the final slag component of LF tapping shows that CaO is 52.2%, Al2O 3: 23.2%, SiO 2: 11.1%, MgO: 6.2%, CaF 2: 2.0%, TFe 0.25%, MnO 0.08%, S0.42%;
s3, VD process:
(7) controlling the vacuum degree in the vacuum treatment process to be between 1torr and 0.5torr, wherein the VD vacuumizing time is 15min, and the vacuum degree in the effective treatment process is between 2.0torr and 0.5 torr;
(8) controlling the flow of argon gas at 60-80NL/min, and effectively vacuum-treating for 20 min;
s4 returns to the LF refining process:
(9) returning the ladle to LF refining and entering the station, adding 5-10kg of C powder, and after the yellowing slag turns white, transmitting power and heating to 1616 ℃;
(10) returning to the heating process for sampling before soft blowing, wherein the molten steel comprises the following components: 0.54%, Si: 0.15%, Mn: 0.86%, S: 0.0011%, P0.007%, Cr: 1.12%, Ni: 1.75%, Mo: 0.51%, V: 0.08%, Cu: 0.08 percent; o: 9.6ppm, N: 60ppm, H: 1.9 ppm;
(11) adjusting the Ar gas flow to be 20L/min, executing soft blowing operation, observing that the steel liquid surface is not exposed, wherein the soft blowing time is 20min, and the tapping temperature after soft blowing is 1586 ℃.
S5 VC process:
wherein, the steps (12) to (16) are the same as in example 1.
(17) Preparing a steel finished product sample at a casting station, wherein the casting temperature is 1546 ℃, and the chemical components of the steel finished product sample are C: 0.54%, Si: 0.15%, Mn: 0.85%, S: 0.0008%, P0.007%, Cr: 1.12%, Ni: 1.75%, Mo: 0.51%, V: 0.09%, Cu: 0.08 percent;
(18) controlling flow 2-3min before the pouring process, then performing full-flow pouring, and controlling flow of the steel ladle again at the position which is about 150mm away from the lower edge of a riser on the liquid level of the steel ladle, wherein the total pouring time is 18 min.
The metallurgical effect and metallurgical quality of the steel ingot are evaluated as follows:
the steel ingot production of 4 ingots with 52.5t and 2 ingots with 45.5t is completed in the first batch, and the control levels of the O content and the S content of the metallurgical finished products are shown in a table 1. After the rough machining and flaw detection of the module forge pieces are finished, ultrasonic detection is carried out on the module forge pieces one by one according to GB/T6402/2008, obvious defects and large-particle inclusions do not exist, and a finished product object of the die steel is shown in figure 4.
TABLE 1 Module finished Steel liquid oxygen and Sulfur content
| Heat of furnace | G253 | G258 | G277 | G286 | G541 | G549 |
| Oxygen content of molten steel before casting is multiplied by 10-4％ | 13.7 | 11.8 | 10.2 | 9.3 | 9.6 | 14.7 |
| S content of molten steel% | 0.0010 | 0.0006 | 0.0007 | 0.0009 | 0.0008 | 0.0010 |
The non-metallic inclusion is carried out according to the GB/T10561, and the grades of the non-metallic inclusion of the forged steel are that A class is less than or equal to 0.5, B class is less than or equal to 0.5, C class is less than or equal to 0.5, D class is less than or equal to 0.5 and Ds class is less than or equal to 0.5.
In conclusion, the invention reasonably selects the components of the raw materials and the proportion of the raw materials in the primary smelting process, controls the S, P content of the primary smelting steel tapping, adopts a high-alkalinity CaO-Al2O3-SiO2-MgO slag system in the refining process, selects the type and the amount of a reasonable deoxidizer, controls the O and S content of the refined steel tapping, further reduces the S and N, H and the oxygen content in the molten steel in the vacuum process by controlling the effective vacuum degree and the degassing time, returns to the ladle refining process, fully promotes the floating and removal of inclusions by controlling the argon flow and the soft blowing time, ensures that the molten steel is further removed by opening the nozzle pressure in the vacuum casting process so as to more disperse the molten steel in N, H and oxygen content, reduces the slag tapping head in the later casting period to enter the ingot mould by a flow control process means, ensures the good feeding effect of the molten steel, and ensures that the O and S content control of the finished molten steel (before casting) respectively reaches below 15ppm and 0.001 percent, the high-purity high-power inclusion steel has high cleanliness, large-particle inclusions which exceed the standard of flaw detection are not generated in a forged piece after a steel ingot is forged into a material, the ultra-detection meets the requirement of GB-T6402-20083 level, the GB/T10561-2002 high-power inclusion rating A is less than or equal to 0.5, B is less than or equal to 0.5, C is less than or equal to 0.5, D is less than or equal to 0.5, and Ds is less than or equal to 0.5.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. A method for smelting an ingot for an ultra-low-sulfur low-oxygen 55NiCrMoV7 module is characterized by comprising the following steps of:
s1, controlling the electric furnace steel-making process: sequentially completing material preparation, melting, slagging and dephosphorization, respectively controlling the content of C, P, S in molten steel to be 0.05-0.08% of C, less than or equal to 0.003% of P and less than or equal to 0.050% of S, and then carrying out tapping deoxidation operation;
s2, refining process control of the refining furnace: transferring the molten steel processed in the step S1 to a ladle refining station, adding lime, bauxite, fluorite and magnesia slagging materials, transmitting power for slagging, adding a deoxidizer in batches, and performing power transmission temperature raising, slagging, argon blowing, deoxidation and alloy adjustment operations to enable the components of the molten steel to meet the requirements of the 55NiCrMoV7 standard so as to further remove S and O in the molten steel; after refining is finished, the S content in the molten steel is less than or equal to 0.003 percent, the O content is less than or equal to 30ppm, and the temperature of the refining outlet is controlled at 1670-;
in the refining process, a CaO-Al2O3-SiO2-MgO slag system is adopted to realize molten steel desulfurization and deoxidation, and the slag system comprises 48-56% of CaO and Al2O 3: 19-25%, SiO 2: 9-15 percent of MgO, 4-9 percent of MgO;
s3, VD process control: transferring the molten steel processed in the step S2 into a vacuum chamber, and gradually pumping to improve the vacuum degree of the atmosphere so that the molten steel is subjected to C, O reaction and steel slag reaction under the vacuum condition, and further removing H, N, O and S in the molten steel;
s4, returning to LF ladle refining process control: transferring the molten steel processed in the step S3 to a ladle refining station again, transmitting power to raise the temperature to 1610 and 1620 ℃, enabling the argon flow to be less than or equal to 15NL/min, executing soft blowing operation, enabling the soft blowing time to be not less than 15min, promoting floating and removing of inclusions, controlling the tapping temperature after the soft blowing treatment to 1585-1595 ℃, controlling the content of O, S of the processed molten steel to be less than or equal to 15ppm and less than or equal to 0.001 percent respectively;
s5, controlling the steel ingot casting process: and (3) after the chassis, the ingot mold and the riser are cleaned and ready to be matched, placing the ingot mold and the riser to a pouring station, draining the molten steel processed in the step S4, transferring the molten steel to the pouring station, performing vacuum pumping operation, starting temperature measurement when the vacuum degree is less than or equal to 0.5torr, controlling the flow of the molten steel at a pouring temperature of 1540-.
2. The method for smelting an ultra-low sulfur and low oxygen 55NiCrMoV7 steel ingot for module according to claim 1, wherein the method comprises the following steps: and in the step S1, the carbon blending amount is 1.0-1.3% during material blending.
3. The method for smelting the steel ingot for the ultra-low-sulfur low-oxygen 55NiCrMoV7 module according to claim 1, wherein the method comprises the following steps: and S1, after the burdening is finished, melting down furnace burden in the electric furnace, blowing oxygen for decarburization, and then adding active lime and fluorite, wherein the tapping condition of the electric furnace is as follows: 0.05 to 0.08 percent of C, less than or equal to 0.050 percent of S and less than or equal to 0.003 percent of P.
4. The method for smelting an ultra-low sulfur and low oxygen 55NiCrMoV7 steel ingot for module according to claim 1, wherein in step S1, when tapping from an electric furnace, a deoxidizer Al is added in an amount of 0.5-1.0kg/t molten steel, an amount of SiAlCaBa lumps is added in an amount of 0.5-1.0kg/t molten steel, and an amount of SiAlCaBa powder is added in an amount of 0.5-2.0kg/t molten steel in this order.
5. The method for smelting an ultra-low sulfur and low oxygen 55NiCrMoV7 steel ingot for module according to claim 1, wherein the method comprises the following steps: in the step S3, the vacuumizing time is 10-15min, the vacuum degree in the effective processing process is 3.0-0.5 torr, the argon flow is controlled at 60-80NL/min, and the effective vacuum processing time is 15-25 min.
6. The method for smelting an ultra-low sulfur and low oxygen 55NiCrMoV7 steel ingot for module according to claim 1, wherein the method comprises the following steps: in the step S4, the soft blowing time is not less than 15min, and the argon flow during soft blowing is controlled at 15-20 NL/min.
7. The method for smelting the steel ingot for the ultra-low-sulfur low-oxygen 55NiCrMoV7 module according to claim 1, wherein the method comprises the following steps: in the step S5, when in pouring, the pouring speed of the ingot body is 3.2-3.8t/min, and the pouring speed of the riser is 1/3-1/2 of the pouring speed of the ingot body, so that a good feeding effect is achieved.
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