Smelting method of low-carbon low-phosphorus high-alloy steel 08CrNi4MoVTi

Abstract

The invention discloses a smelting method of low-carbon low-phosphorus high-alloy steel 08CrNi4MoVTi. The smelting method comprises the working procedures of raw material preparation, converter smelting, LF refining, VD vacuum treatment and soft blowing. In the raw material preparation process, deslagging is carried out before VD is carried out, a middle-earlier-stage steel ladle which is continuously turned over for more than three times is selected, and double air bricks are opened on the steel ladle; in the converter smelting process, 22-24 tons of ferronickel and 1.5-2.5 tons of nickel shots are added into a trough, and 2-2.5 tons of nickel shots and 0.9-1.1 tons of ferro-molybdenum are added during tapping; high-quality lime with CaO larger than or equal to 92% is used in the blowing process, it is guaranteed that tapping C is smaller than or equal to 0.04%, and tapping P is smaller than 0.007%; in the LF refining process, the nickel content is 4.0% or above, the electrode state is confirmed before production, and turning-round recarburization in the smelting process is prevented; and adjusting the alloy when the molten steel temperature is not less than 1560 DEG C. The method can effectively shorten the smelting time and improve the purity of the molten steel.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgy, and particularly relates to a smelting method for a low-carbon, low-phosphorus, high-alloy steel 08CrNi4MoVTi. Background Art

[0002] Due to their excellent mechanical properties, corrosion resistance and weldability, low-carbon, low-phosphorus, high-alloy steels are widely used in key fields such as aero-engine components, high-end bearings, and nuclear power equipment. However, the smelting of such steel grades faces the contradiction between the ultra-low carbon requirement (C≤0.10%) and alloy carburization (such as alloy-borne C: 0.02 - 0.05%), which is prone to cause continuous casting billet cracks. The bottleneck in purity control is the phenomenon of phosphorus reversion (reversion P: 0.004 - 0.008%) and oxide inclusions (class B≤2.0 grade), which are difficult to meet the flaw detection standards (GB / T 4162 - 2008 class B) of high-end equipment; the dehydrogenation efficiency of existing processes is insufficient (H≥2ppm), resulting in an increased risk of white spot defects in large-section forgings. The traditional step-by-step alloying with low production efficiency makes the LF refining time up to 120 minutes. Therefore, there is an urgent need to develop a new smelting process that integrates precise carbon control, efficient dephosphorization, and dynamic thermal management to break through the technical barriers of high-alloy steel industrial production. Summary of the Invention

[0003] The purpose of the present invention is to provide a smelting method for a low-carbon, low-phosphorus, high-alloy steel 08CrNi4MoVTi, which can shorten the smelting time and improve the purity of molten steel.

[0004] To achieve the above purpose, the technical solution provided by the present invention is as follows: A smelting method for a low-carbon, low-phosphorus, high-alloy steel 08CrNi4MoVTi, including raw material preparation, converter smelting, LF refining, VD vacuum treatment, and soft blowing processes.

[0005] Preferably, in the raw material preparation process of the present invention, slag is poured before entering VD to ensure the vacuum degassing effect; a ladle that has been continuously recycled for more than three times in the middle and early stages is selected to ensure ladle heat storage, heat preservation, and the purity of molten steel; double tuyere bricks are opened in the ladle to ensure the uniformity of pouring temperature.

[0006] Preferably, in the converter smelting process of the present invention, 22 - 24 tons of ferronickel and 1.5 - 2 tons of nickel beans are added to the charging trough, 2 - 2.5 tons of nickel beans and 0.9 - 1.1 tons of ferromolybdenum are added during tapping; high-quality quicklime (CaO≥92%) is used during the blowing process to ensure that the tapped C≤0.04%, providing conditions for carbon addition during later alloy addition, and the tapped P<0.007% to ensure that the finished product meets the requirements.

[0007] Preferably, in the LF refining process of the present invention, the in-place nickel is more than 4.0%. Before production, confirm the electrode status to prevent carbon increase due to electrode breakage during smelting. Adjust the alloy when the molten steel temperature ≥ 1560°C to ensure good double gas permeability of the ladle.

[0008] Preferably, in the VD process of the present invention, argon is blown throughout the process to ensure the stirring effect. The holding time is ≥ 25 minutes under a vacuum degree ≤ 67 Pa, and the strong argon stirring flow rate during the holding stage is 450 - 520 NL / min to ensure that the hydrogen, oxygen, and nitrogen contents meet the requirements.

[0009] Preferably, in the soft blowing process of the present invention, the soft blowing time is ≥ 25 min, and the argon flow rate is 15 - 20 NL / min.

[0010] Furthermore, for the 08CrNi4MoVTi produced by the method of the present invention, the chemical composition by weight percentage is as follows: C: 0.06 - 0.10%, Si: 0.17 - 0.37%, Mn: 0.45 - 0.70%, Ni: 4.35 - 4.75%, Mo: 0.30 - 0.57%, Cr: 0.35 - 0.65%, V: 0.04 - 0.08%, Ti: 0.005 - 0.020%, P ≤ 0.015%, S ≤ 0.008%, Al ≤ 0.030%, H < 1.5 ppm, O ≤ 20 ppm, N ≤ 60 ppm, and the rest are iron and inevitable impurity elements.

[0011] Furthermore, for the low-carbon, low-phosphorus, high-alloy steel 08CrNi4MoVTi produced by the method of the present invention, the inclusions are rated according to Method A in GB / T 10561—2005, and the results are: A fine ≤ 0.5 grade, A coarse ≤ 0.5 grade, B fine ≤ 1.0 grade, B coarse ≤ 1.0 grade, C fine ≤ 1.0 grade, C coarse ≤ 1.0 grade, D fine ≤ 1.0 grade, D coarse ≤ 1.0 grade, DS ≤ 1.5 grade; ultrasonic flaw detection meets Grade B of GB / T 4162 - 2008.

[0012] The inventive principle of the present invention lies in: Adopting the core principle of "precision composition control - efficient impurity removal coordination - process timing optimization", the high-efficiency and pure smelting of low-carbon, low-phosphorus, high-alloy steel is achieved through the following technical paths: (1) Raw material pretreatment and ladle management: By using the ladles in the middle and early stages that are continuously turned over three or more times (the best stage of ladle lining thermal stability), combined with the double tuyere brick design, ensure the uniform heat storage of the ladle, reduce the temperature drop of the molten steel (≤ 5°C / min), and at the same time avoid carbon increase caused by refractory material erosion (C increment ≤ 0.002%).

[0013] The slag-dumping operation before entering VD can remove the highly oxidizing slag (FeO + MnO ≥ 15%) remaining in the LF stage, create a low oxygen potential environment (α_O ≤ 5 ppm) for vacuum degassing, and improve the dehydrogenation and denitrification efficiency.

[0014] (2)Synergistic control of carbon and phosphorus in converter steelmaking Controlling the carbon content at the end of tapping (C ≤ 0.04%) reserves carbon addition space for subsequent alloying. Adding ferronickel (Ni ≥ 10%) and nickel beans (Ni ≥ 99.9%) in stages, and precisely matching the target composition through carbon equivalent balance (CE = [C] + [Ni] / 20) to avoid excessive carbon addition.

[0015] Using high-alkali lime (CaO ≥ 92%) to strengthen dephosphorization (dephosphorization rate ≥ 95%) and inhibit the re-dissolution of phosphorus ([P] at the end ≤ 0.007%).

[0016] (4)Optimization of alloy adjustment High-temperature alloying (molten steel ≥ 1560℃) combined with a dynamic thermodynamic model. During the tapping process of the converter, alloys with large specific gravity such as Ni and Mo are added first, and rapid melting is achieved through the convection of molten steel (melting time is shortened by 30%); confirm the electrode length before production to prevent carbon addition caused by electrode breakage (C increment ≤ 0.005%).

[0017] (4)Dynamic regulation of VD vacuum degassing The synergistic effect of argon stirring and vacuum degree (≤ 67 Pa) removes (H2, N2, CO) and inclusions through microbubble interface reactions, and stabilizes [H] < 1.0 ppm and [O] ≤ 20 ppm in the steel.

[0018] Prolong the soft blowing time (≥ 25 min) and control the argon flow rate (15 - 20 NL / min) to promote the coalescence and floating of micro-inclusions (≤ 5 μm), and reduce the number density of inclusions by 50%.

[0019] The beneficial technical effects of the present invention are as follows: (1)Significantly improved smelting efficiency Through the strategy of adding ferronickel / nickel beans in stages and high-temperature alloying in LF, the refining time is shortened to within 90 minutes (traditional process ≥ 120 minutes).

[0020] The design of double porous plugs in the ladle makes the argon distribution uniform (the proportion of dead zone volume ≤ 5%), the stirring efficiency is increased by 40%, and the compositional uniformity (C, Ni deviation ± 0.03%) reaches the international leading level.

[0021] (2)Breakthrough improvement in molten steel purity In the VD stage, the combined process of "strong stirring + deep vacuum" is adopted. The total oxygen content (T.O) in the steel is ≤15 ppm, the nitrogen content is ≤50 ppm, and the inclusion rating (class A ≤ 0.5 level, class B / C / D ≤ 1.0 level) is better than the ASTM E45 standard.

[0022] The aluminum content is controlled throughout the process (Al ≤ 0.030%). The proportion of inclusions is reduced from 70% in the traditional process to less than 20%, and the fatigue life is increased by 2 times. Detailed implementation mode

[0023] The present invention will be further described in detail below in conjunction with the embodiments. Embodiment 1

[0024] The smelting method of the low-carbon, low-phosphorus and high-alloy steel 08CrNi4MoVTi in this embodiment includes raw material preparation, converter smelting, LF refining, VD vacuum treatment and soft blowing, which are specifically as follows: 1) Raw material preparation: Pour 1.8 tons of slag before entering VD; Select ladle No. 14, with the slag line for 5 times and the furnace lining for 37 times, and open double porous plugs.

[0025] 2) Converter smelting: Add 22 tons of ferronickel and 1.5 tons of nickel beans to the charging trough. High-quality quicklime (CaO content 93.5%) is used during the blowing process. The tapping C: 0.03%, P: 0.005%, and the tapping temperature is 1650 °C. Add 2.5 tons of nickel beans and 1 ton of ferromolybdenum during the tapping process of the converter.

[0026] 3) LF refining: The in-place Ni: 4.05%. Confirm the electrode head before production, and it does not fall off during the smelting process. Adjust the alloy at the molten steel temperature of 1564 °C, and the refining time is 87 min.

[0027] 4) VD vacuum treatment: Argon gas is blown throughout the VD process. The vacuum degree ≤ 67 Pa is maintained for 30 minutes, and the lowest vacuum degree is 6 Pa. The strong argon gas stirring flow rate during the holding stage is 460 NL / min.

[0028] 5) Soft blowing: The soft blowing time is 25 minutes, and the argon gas flow rate is 18 NL / min.

[0029] The chemical composition of the high-alloy steel 08CrNi4MoVTi smelted in this embodiment is calculated by weight percentage as follows: C: 0.07%, Cr: 0.5%, Mo: 0.45%, Al: 0.015%, Ni: 4.58%, Si: 0.27%, Mn: 0.70%, V: 0.05%, Ti: 0.013%, P: 0.015%, S: 0.002%, H: 0.87 ppm, O: 14 ppm, N: 48 ppm, and the rest are iron and inevitable impurity elements.

[0030] The inclusions in the high-alloy steel 08CrNi4MoVTi of this example were rated according to Method A in GB / T 10561—2005. The results were as follows: A fine: 0.5 grade, A coarse: 0.5 grade, B fine: 1.0 grade, B coarse: 0.5 grade, C fine: 0 grade, C coarse: 0 grade, D fine: 1.0 grade, D coarse: 0.5 grade, DS: 1.0 grade. The ultrasonic flaw detection was Grade B in GB / T 4162-2008. Example 2

[0031] The smelting method of the low-carbon, low-phosphorus high-alloy steel 08CrNi4MoVTi in this example includes raw material preparation, converter smelting, LF refining, VD vacuum treatment, and soft blowing, which are specifically as follows: 1) Raw material preparation: Pour 2.0 tons of slag before entering VD; Select ladle No. 16, with 10 times for the slag line and 10 times for melting, and open double porous plugs.

[0032] 2) Converter smelting: Add 22.5 tons of ferronickel and 2 tons of nickel beans to the charging hopper. High-quality quicklime (CaO content 92.0%) is used during the blowing process. The tapping C: 0.04%, tapping P: 0.006%, tapping temperature 1658°C. Add 2 tons of nickel beans and 1.1 tons of ferromolybdenum during the tapping process of the converter.

[0033] 3) LF refining: The in-place Ni: 4.01%. Confirm the electrode tip before production, and it did not fall during the smelting process. Adjust the alloy at the molten steel temperature of 1570°C, and the refining time is 85 min.

[0034] 4) VD vacuum treatment: Argon gas is blown throughout the VD process. The vacuum degree ≤ 67 Pa is maintained for 28 minutes, and the lowest vacuum degree is 9 Pa. The strong argon gas stirring flow rate during the holding stage is 500 NL / min.

[0035] 5) Soft blowing: The soft blowing time is 33 minutes, and the argon gas flow rate is 16 NL / min.

[0036] The chemical composition of the high-alloy steel 08CrNi4MoVTi smelted in this example is as follows by weight percentage: C: 0.10%, Cr: 0.50%, Mo: 0.57%, Al: 0.030%, Ni: 4.61%, Si: 0.17%, Mn: 0.70%, V: 0.08%, Ti: 0.020%, P: 0.011%, S: 0.0015%, H: 0.93 ppm, O: 15 ppm, N: 50 ppm, and the rest are iron and inevitable impurity elements.

[0037] The inclusions of the high alloy steel 08CrNi4MoVTi in this example were rated according to Method A in GB / T 10561—2005. The results were as follows: A fine: 0.5 level, A coarse: 0.5 level, B fine: 1.0 level, B coarse: 0.5 level, C fine: 0 level, C coarse: 0 level, D fine: 1.0 level, D coarse: 1.0 level, DS: 0.5 level; ultrasonic flaw detection was Class B in GB / T 4162-2008. Example 3

[0038] The smelting method of the low-carbon, low-phosphorus high alloy steel 08CrNi4MoVTi in this example includes raw material preparation, converter smelting, LF refining, VD vacuum treatment, and soft blowing, which are specifically as follows: 1) Raw material preparation: Pour 1.7 tons of slag before entering VD; select ladle No. 8, with 15 times for the slag line and 33 times for melting, and open double porous plugs.

[0039] 2) Converter smelting: Add 23.5 tons of ferronickel and 1.75 tons of nickel beans to the charging trough. Use high-quality quicklime (CaO content 93.2%) during the blowing process. The tapping C: 0.03%, tapping P: 0.005%, tapping temperature 1661°C. Add 2.1 tons of nickel beans and 0.9 tons of ferromolybdenum during the converter tapping process.

[0040] 3) LF refining: The in-place Ni: 4.08%. Confirm the electrode head before production, and it did not fall during the smelting process. Adjust the alloy at a molten steel temperature of 1582°C, and the refining time is 82 min.

[0041] 4) VD vacuum treatment: Argon gas is blown throughout the VD process. The vacuum degree ≤ 67 Pa is maintained for 26 minutes, and the lowest vacuum degree is 8 Pa. The strong argon gas stirring flow rate during the holding stage is 520 NL / min.

[0042] 5) Soft blowing: The soft blowing time is 35 minutes, and the argon gas flow rate is 15 NL / min.

[0043] The chemical composition of the high alloy steel 08CrNi4MoVTi smelted in this example is by weight percentage: C: 0.06%, Cr: 0.35%, Mo: 0.43%, Al: 0.018%, Ni: 4.58%, Si: 0.23%, Mn: 0.45%, V: 0.06%, Ti: 0.020%, P: 0.012%, S: 0.0023%, H: 0.9 ppm, O: 14 ppm, N: 46 ppm, and the rest are iron and inevitable impurity elements.

[0044] The inclusions in the high-alloy steel 08CrNi4MoVTi of this example were rated according to Method A in GB / T 10561—2005, and the results were as follows: A fine: 0.5 level, A coarse: 0.5 level, B fine: 0.5 level, B coarse: 0 level, C fine: 0 level, C coarse: 0 level, D fine: 1.0 level, D coarse: 0.5 level, DS: 0.5 level; ultrasonic flaw detection was Class B in GB / T 4162-2008. Example 4

[0045] The smelting method of the low-carbon, low-phosphorus high-alloy steel 08CrNi4MoVTi in this example includes raw material preparation, converter smelting, LF refining, VD vacuum treatment, and soft blowing, which are specifically as follows: 1) Raw material preparation: Pour 2.1 tons of slag before entering VD; Select ladle No. 5, with the slag line used 13 times and melted 25 times, and double porous plugs are opened.

[0046] 2) Converter smelting: Add 23.5 tons of ferronickel and 1.9 tons of nickel beans to the charging hopper. High-quality quicklime (CaO content 93.5%) is used during the blowing process. The tapping C is 0.04%, the tapping P is 0.006%, the tapping temperature is 1652°C. During the tapping process of the converter, 2.2 tons of nickel beans and 0.9 tons of ferromolybdenum are added.

[0047] 3) LF refining: The in-place Ni is 4.11%. Confirm the electrode tip before production, and it did not fall off during the smelting process. Adjust the alloy at the molten steel temperature of 1579°C, and the refining time is 90 min.

[0048] 4) VD vacuum treatment: Argon gas is blown throughout the VD process. The vacuum degree ≤ 67 Pa is maintained for 29 minutes, and the lowest vacuum degree is 7 Pa. The strong argon gas stirring flow rate during the holding stage is 450 NL / min.

[0049] 5) Soft blowing: The soft blowing time is 32 minutes, and the argon gas flow rate is 20 NL / min.

[0050] The chemical composition of the high-alloy steel 08CrNi4MoVTi smelted in this example is calculated by weight percentage as follows: C: 0.08%, Cr: 0.53%, Mo: 0.30%, Al: 0.014%, Ni: 4.35%, Si: 0.28%, Mn: 0.62%, V: 0.06%, Ti: 0.017%, P: 0.013%, S: 0.008%, H: 0.8 ppm, O: 10 ppm, N: 43 ppm, and the rest are iron and inevitable impurity elements.

[0051] The inclusions of the high alloy steel 08CrNi4MoVTi in this example were rated according to Method A in GB / T 10561—2005. The results were: A fine: 0.5 level, A coarse: 0.5 level, B fine: 1.0 level, B coarse: 1.0 level, C fine: 0 level, C coarse: 0 level, D fine: 1.0 level, D coarse: 1.0 level, DS: 1.0 level; ultrasonic flaw detection was Grade B in GB / T 4162-2008. Example 5

[0052] The smelting method of the low-carbon, low-phosphorus high alloy steel 08CrNi4MoVTi in this example includes raw material preparation, converter smelting, LF refining, VD vacuum treatment and soft blowing, which are as follows: 1) Raw material preparation: Pour 1.9 tons of slag before entering VD; Select ladle No. 2, with 15 times of slag line and 21 times of melting, and open double porous plugs.

[0053] 2) Converter smelting: Add 22.3 tons of ferronickel and 2 tons of nickel beans to the charging trough. High-quality quicklime (CaO content 94.8%) is used during the blowing process. The tapping C: 0.03%, tapping P: 0.004%, tapping temperature 1668 °C. Add 2 tons of nickel beans and 1 ton of ferromolybdenum during the tapping process of the converter.

[0054] 3) LF refining: The in-place Ni: 4.06%. Confirm the electrode head before production, and it did not fall off during the smelting process. Adjust the alloy at the molten steel temperature of 1575 °C, and the refining time is 85 min.

[0055] 4) VD vacuum treatment: Argon gas is blown throughout the VD process. The vacuum degree ≤ 67 Pa is maintained for 30 minutes, and the lowest vacuum degree is 8 Pa. The strong argon gas stirring flow rate during the holding stage is 460 NL / min.

[0056] 5) Soft blowing: The soft blowing time is 28 minutes, and the argon gas flow rate is 20 NL / min.

[0057] The chemical composition of the high alloy steel 08CrNi4MoVTi smelted in this example is by weight percentage: C: 0.07%, Cr: 0.51%, Mo: 0.44%, Al: 0.015%, Ni: 4.75%, Si: 0.37%, Mn: 0.57%, V: 0.04%, Ti: 0.005%, P: 0.011%, S: 0.0018%, H: 0.7 ppm, O: 13 ppm, N: 48 ppm, and the rest are iron and inevitable impurity elements.

[0058] The inclusions in the high alloy steel 08CrNi4MoVTi of this embodiment were rated according to Method A in GB / T 10561—2005. The results were as follows: fine A: 0.5 level, coarse A: 0.5 level, fine B: 1.0 level, coarse B: 0.5 level, fine C: 0 level, coarse C: 0 level, fine D: 1.0 level, coarse D: 1.0 level, DS: 1.5 level; ultrasonic flaw detection was Class B in GB / T 4162-2008. Example 6

[0059] The smelting method of the low-carbon, low-phosphorus high alloy steel 08CrNi4MoVTi in this embodiment includes raw material preparation, converter smelting, LF refining, VD vacuum treatment, and soft blowing, which are specifically as follows: 1) Raw material preparation: Pour 2.3 tons of slag before entering VD; select ladle No. 6, with 16 times of slag line and 21 times of melting, and open double porous plugs.

[0060] 2) Converter smelting: Charge 23.1 tons of ferronickel and 1.6 tons of nickel beans into the trough. High-quality quicklime (CaO content 93.9%) is used during the blowing process. The tapping C is 0.04%, the tapping P is 0.006%, the tapping temperature is 1649°C. During the tapping process of the converter, 2.25 tons of nickel beans and 1 ton of ferromolybdenum are added.

[0061] 3) LF refining: The in-place Ni is 4.10%. Confirm the electrode tip before production, and it does not fall off during the smelting process. Adjust the alloy at the molten steel temperature of 1580°C, and the refining time is 89 min.

[0062] 4) VD vacuum treatment: Argon gas is blown throughout the VD process. The vacuum degree ≤ 67 Pa is maintained for 30 minutes, and the lowest vacuum degree is 10 Pa. The strong argon gas stirring flow rate during the holding stage is 500 NL / min.

[0063] 5) Soft blowing: The soft blowing time is 38 minutes, and the argon gas flow rate is 18 NL / min.

[0064] The chemical composition of the high alloy steel 08CrNi4MoVTi smelted in this embodiment is as follows by weight percentage: C: 0.09%, Cr: 0.65%, Mo: 0.52%, Al: 0.030%, Ni: 4.62%, Si: 0.33%, Mn: 0.57%, V: 0.07%, Ti: 0.013%, P: 0.012%, S: 0.002%, H: 0.8 ppm, O: 12 ppm, N: 46 ppm, and the rest are iron and inevitable impurity elements.

[0065] The inclusions of the high alloy steel 08CrNi4MoVTi in this embodiment were rated according to Method A in GB / T 10561—2005, and the results were as follows: A fine: 0.5 level, A coarse: 0.5 level, B fine: 1.0 level, B coarse: 0.5 level, C fine: 0 level, C coarse: 0 level, D fine: 1.0 level, D coarse: 1.0 level, DS: 1.0 level; ultrasonic flaw detection was Class B in GB / T 4162-2008.

[0066] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be modified or equivalently replaced, and any modification or partial replacement without departing from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims

1. A smelting method of a low-carbon, low-phosphorus and high-alloy steel 08CrNi4MoVTi, characterized in that, It includes raw material preparation, converter smelting, LF refining, VD vacuum treatment and soft blowing processes.

2. The smelting method of a low-carbon, low-phosphorus, high-alloy steel 08CrNi4MoVTi according to claim 1, characterized in that, In the raw material preparation process, slag is poured before entering VD. Medium and early-stage ladles that are continuously recycled more than three times are selected, and the ladles are equipped with double porous plugs.

3. The smelting method of a low-carbon, low-phosphorus, high-alloy steel 08CrNi4MoVTi according to claim 1, characterized in that, In the converter smelting process, 22 - 24 tons of ferronickel and 1.5 - 2.5 tons of nickel beans are added to the charging hopper, and 2 - 2.5 tons of nickel beans and 0.9 - 1.1 tons of ferromolybdenum are added during tapping.

4. The smelting method of a low-carbon, low-phosphorus and high-alloy steel 08CrNi4MoVTi according to claim 1, characterized in that, In the converter smelting process, high-quality quicklime with CaO≥92% is used during the blowing process to ensure that the C content in the tapped steel is ≤0.04% and the P content is <0.007%.

5. The smelting method of a low-carbon, low-phosphorus, high-alloy steel 08CrNi4MoVTi according to claim 1, characterized in that, In the LF refining process, the nickel content in place is above 4.0%. Before production, the electrode status is confirmed to prevent carbon increase due to electrode breakage during smelting; alloy is adjusted when the molten steel temperature ≥1560°C.

6. The smelting method of a low-carbon, low-phosphorus and high-alloy steel 08CrNi4MoVTi according to claim 1, characterized in that, In the VD process, argon gas is blown throughout the process. The holding time is ≥25 minutes under a vacuum degree ≤67 Pa, and the strong argon gas stirring flow rate during the holding stage is 450 - 520 NL / min.

7. The smelting method of a low-carbon, low-phosphorus and high-alloy steel 08CrNi4MoVTi according to claim 1, characterized in that, In the soft blowing process, the soft blowing time is ≥25 min, and the argon gas flow rate is 15 - 20 NL / min.

8. The smelting method of a low-carbon, low-phosphorus and high-alloy steel 08CrNi4MoVTi according to claim 1, characterized in that, The chemical composition of 08CrNi4MoVTi produced by the said method is by weight percentage: C: 0.06 - 0.10%, Si: 0.17 - 0.37%, Mn: 0.45 - 0.70%, Ni: 4.35 - 4.75%, Mo: 0.30 - 0.57%, Cr: 0.35 - 0.65%, V: 0.04 - 0.08%, Ti: 0.005 - 0.020%, P≤0.015%, S≤0.008%, Al≤0.030%, H≤1.5 ppm, O≤20 ppm, N≤60 ppm, and the rest are iron and inevitable impurity elements.

9. The smelting method of a low-carbon, low-phosphorus and high-alloy steel 08CrNi4MoVTi according to claim 1, characterized in that, For the low-carbon, low-phosphorus high-alloy steel 08CrNi4MoVTi produced by the said method, the inclusions are rated according to Method A in GB / T10561—2005, and the results are: A fine ≤0.5 grade, A coarse ≤0.5 grade, B fine ≤1.0 grade, B coarse ≤1.0 grade, C fine ≤1.0 grade, C coarse ≤1.0 grade, D fine ≤1.0 grade, D coarse ≤1.0 grade, DS ≤1.5 grade; ultrasonic flaw detection meets Grade B of GB / T 4162 - 2008.