阅读说明：本技术 一种真空感应冶炼制备超低氧轴承钢铸锭的方法 (Method for preparing ultralow-oxygen bearing steel ingot by vacuum induction smelting ) 是由 姜周华 王礼超 田家龙 任吉 蒋成钢 于 2021-07-21 设计创作，主要内容包括：一种真空感应冶炼制备超低氧轴承钢铸锭的方法,包括以下步骤：(1)按轴承钢成分准备原料以及金属铝、稀土镁脱氧剂；(2)将金属铝、稀土镁脱氧剂、原料中易挥发或易氧化的原料和第二部分碳源以分别放置在料仓；将其余原料和第一部分碳源置于坩埚内；(3)启动真空感应炉,抽真空并升温至物料始熔化,充入氩气；(4)物料全部熔化后,将第二部分碳源加入坩埚,再抽真空进行真空脱氧；(5)充入氩气加入金属铝进行铝脱氧；(6)稀土镁脱氧剂放入坩埚进行稀土镁脱氧；(7)进行浇注。本发明的三步脱氧使化学反应充分,降低钢中的氧、硫含量,降低钢中的夹杂物体积分数,改善铸锭的凝固组织。(A method for preparing an ultralow-oxygen bearing steel ingot by vacuum induction smelting comprises the following steps: (1) preparing raw materials and metallic aluminum and rare earth magnesium deoxidizers according to the components of the bearing steel; (2) respectively placing metal aluminum, a rare earth magnesium deoxidizer, a volatile or easily-oxidized raw material and a second part of carbon source in a bin; placing the rest raw materials and a first part of carbon source in a crucible; (3) starting a vacuum induction furnace, vacuumizing, heating until the materials are melted, and filling argon; (4) after the materials are completely melted, adding a second part of carbon source into the crucible, and vacuumizing for vacuum deoxidation; (5) argon is filled, and metal aluminum is added for aluminum deoxidation; (6) putting the rare earth magnesium deoxidizer into a crucible for rare earth magnesium deoxidation; (7) and (6) casting. The three-step deoxidation of the invention ensures that the chemical reaction is sufficient, reduces the oxygen and sulfur content in the steel, reduces the volume fraction of inclusions in the steel and improves the solidification structure of the cast ingot.)

1. A method for preparing an ultralow-oxygen bearing steel ingot by vacuum induction smelting is characterized by comprising the following steps:

(1) preparing raw materials and metallic aluminum and rare earth magnesium deoxidizers according to the components of the bearing steel; dividing a carbon source in a raw material into a first part of carbon source and a second part of carbon source; placing different volatile or easily-oxidized metals and/or alloys in the raw materials into different bins of a vacuum induction furnace, placing metallic aluminum into a single bin of the vacuum induction furnace, placing a rare earth magnesium deoxidizer into the single bin of the vacuum induction furnace, placing a second part of carbon source into the single bin of the vacuum induction furnace, and placing the rest raw materials and a first part of carbon source into a crucible of the vacuum induction furnace;

(2) starting the vacuum induction furnace, vacuumizing and heating until the materials in the crucible begin to melt, stopping vacuumizing, filling argon into the vacuum induction furnace, adding a second part of carbon source into the crucible after the materials in the crucible are completely melted, vacuumizing the vacuum induction furnace, and controlling the temperature to enable the materials in the crucible to be in a molten state for vacuum deoxidation;

(3) after the vacuum deoxidation is finished, argon is filled into the vacuum induction furnace; putting the raw materials which are easy to volatilize or oxidize into a crucible, and controlling the temperature to ensure that the materials in the crucible are in a molten state; after all the materials in the crucible are melted, putting the metallic aluminum into the crucible, and controlling the temperature to enable the materials in the crucible to be in a molten state; when the metal aluminum is completely melted, preserving heat for aluminum deoxidation;

(4) after the aluminum deoxidation is finished, putting a rare earth magnesium deoxidizer into the crucible, and controlling the temperature to enable the materials in the crucible to be in a molten state; when the rare earth magnesium deoxidizer is completely melted, the rare earth magnesium deoxidizer is subjected to heat preservation.

2. The method for preparing the ultra-low oxygen bearing steel ingot by vacuum induction smelting according to claim 1, wherein in the step (4), after the rare earth magnesium is deoxidized, the temperature of the materials in the crucible is adjusted to the pouring temperature, and then pouring is carried out, so as to obtain the ultra-low oxygen bearing steel ingot.

3. The method for preparing the ultra-low oxygen bearing steel ingot by vacuum induction smelting according to claim 1, wherein in the step (1), the rare earth magnesium deoxidizer is a rare earth magnesium alloy; when the bearing steel contains nickel, the rare earth magnesium deoxidizer is a rare earth magnesium alloy or a metal rare earth and magnesium-nickel alloy.

4. The method for preparing the ultra-low oxygen bearing steel ingot by vacuum induction smelting according to claim 1, wherein in the step (1), the easily volatile or oxidizable raw materials comprise a silicon source, a manganese source, a vanadium source and a niobium source; wherein the silicon source is industrial silicon or ferrosilicon alloy, the manganese source is electrolytic manganese or ferromanganese, the vanadium source is metal vanadium or ferrovanadium alloy, and the niobium source is metal niobium or ferroniobium alloy.

5. The method for preparing the ultra-low oxygen bearing steel ingot by vacuum induction smelting according to claim 1, wherein in the step (2), the first vacuum pumping is performed until the air pressure in the vacuum induction furnace is less than or equal to 3Pa, and the second vacuum pumping is performed until the air pressure in the vacuum induction furnace is less than or equal to 20 Pa.

6. The method for preparing the ultra-low oxygen bearing steel ingot by vacuum induction smelting according to claim 1, wherein in the steps (2) and (3), argon is filled into the vacuum induction furnace until the pressure is 20000-40000 Pa.

7. The method for preparing the ultra-low oxygen bearing steel ingot by vacuum induction smelting according to claim 1, wherein in the step (2), the vacuum deoxidation time is 10-60 min.

8. The method for preparing the ultra-low oxygen bearing steel ingot by vacuum induction smelting according to claim 1, wherein in the step (3), the aluminum deoxidation time is 5-30 min.

9. The method for preparing the ultra-low oxygen bearing steel ingot by vacuum induction smelting according to claim 1, wherein in the step (4), the rare earth magnesium deoxidation time is 2-10 min.

10. The method for preparing the ultra-low oxygen bearing steel ingot by vacuum induction smelting according to claim 3, wherein the magnesium-nickel alloy contains 20-25% of Mg and the balance of Ni by mass percent; the metal rare earth is metal cerium or metal lanthanum.

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to a method for preparing an ultralow-oxygen bearing steel ingot by vacuum induction smelting.

Background

The bearing is a key basic component of many important high-end equipment, the service environment of the bearing is very complex, and the bearing is often required to bear high contact stress, alternating load and sliding wear, which puts extremely high requirements on various performances of bearing steel, especially rolling fatigue contact life and stability.

In order to improve the service life and stability of bearing steel, a great deal of research finds that the fatigue life and stability of the bearing steel have a direct relation with the content of harmful impurity elements in the steel, particularly the oxygen content, so that the oxygen content in the bearing steel is controlled to be less than 5ppm in Japanese Shanyang special steel and Swedish OVAKA (ISIJ, 1985, 71(14), 1631-; when the oxygen content in the steel is low enough, titanium nitride inclusions, large-size brittle inclusions, segregation and liquated carbides in the steel become more important influencing factors, so that in order to meet the higher quality requirement of the aviation bearing steel, vacuum induction melting and vacuum arc remelting (double vacuum melting process) become a general smelting process of the aviation bearing steel.

Although the double vacuum melting process is beneficial to degassing and segregation improvement, the refining slag is not adsorbed to remove impurities in the process, and the final oxygen content of the finished steel is mainly determined by the oxygen content in the raw materials, for example, "a smelting production method of ultra-pure high-carbon chromium bearing steel" (CN2005100273940/2006) considers that the oxygen content in the smelted finished steel is lower than 3ppm only when the oxygen content in the vacuum induction smelting raw materials does not exceed 7ppm, and the requirement of excessively high raw material cleanliness inevitably increases the smelting cost of the bearing steel; in addition, the size and distribution characteristics of inclusions in the steel cannot be effectively controlled.

Disclosure of Invention

The invention aims to provide a method for preparing an ultra-low oxygen bearing steel cast ingot by vacuum induction smelting, which adopts a three-step combined deoxidation method of vacuum deoxidation, aluminum deoxidation and rare earth magnesium treatment to effectively reduce the end-point oxygen content of steel, improve the cleanliness level of molten steel, reduce the size and quantity density of inclusions in the steel, reduce the requirement of vacuum induction smelting on the purity of raw materials, and adopt the raw materials with the total oxygen content of more than 80ppm to smelt the ultra-pure bearing steel with the oxygen content of not more than 4 ppm.

The method of the invention comprises the following steps:

(1) preparing raw materials and metallic aluminum and rare earth magnesium deoxidizers according to the components of the bearing steel; dividing a carbon source in a raw material into a first part of carbon source and a second part of carbon source; placing different volatile or easily-oxidized metals and/or alloys in the raw materials into different bins of a vacuum induction furnace, placing metallic aluminum into a single bin of the vacuum induction furnace, placing a rare earth magnesium deoxidizer into the single bin of the vacuum induction furnace, placing a second part of carbon source into the single bin of the vacuum induction furnace, and placing the rest raw materials and a first part of carbon source into a crucible of the vacuum induction furnace;

(2) starting the vacuum induction furnace, vacuumizing and heating until the materials in the crucible begin to melt, stopping vacuumizing, filling argon into the vacuum induction furnace, adding a second part of carbon source into the crucible after the materials in the crucible are completely melted, vacuumizing the vacuum induction furnace, and controlling the temperature to enable the materials in the crucible to be in a molten state for vacuum deoxidation;

(3) after the vacuum deoxidation is finished, argon is filled into the vacuum induction furnace; putting the raw materials which are easy to volatilize or oxidize into a crucible, and controlling the temperature to ensure that the materials in the crucible are in a molten state; after all the materials in the crucible are melted, putting the metallic aluminum into the crucible, and controlling the temperature to enable the materials in the crucible to be in a molten state; when the metal aluminum is completely melted, preserving heat for aluminum deoxidation;

(4) after the aluminum deoxidation is finished, putting a rare earth magnesium deoxidizer into the crucible, and controlling the temperature to enable the materials in the crucible to be in a molten state; when the rare earth magnesium deoxidizer is completely melted, the rare earth magnesium deoxidizer is subjected to heat preservation.

In the method, after the rare earth magnesium deoxidation is finished, the temperature of the materials in the crucible is adjusted to the pouring temperature, and then pouring is carried out, so as to obtain the ultra-low oxygen bearing steel ingot.

In the method, the rare earth magnesium deoxidizer is a rare earth magnesium alloy; when the bearing steel contains nickel, the rare earth magnesium deoxidizer is a rare earth magnesium alloy or a metal rare earth and magnesium-nickel alloy.

In the method, the volatile or easily-oxidized raw materials comprise a silicon source, a manganese source, a vanadium source and a niobium source; wherein the silicon source is industrial silicon or ferrosilicon alloy, the manganese source is electrolytic manganese or ferromanganese, the vanadium source is metal vanadium or ferrovanadium alloy, and the niobium source is metal niobium or ferroniobium alloy.

In the step (2), the first vacuum-pumping is performed until the air pressure in the vacuum induction furnace is less than or equal to 3Pa, and the second vacuum-pumping is performed until the air pressure in the vacuum induction furnace is less than or equal to 20 Pa.

In the steps (2) and (3), argon is filled into the vacuum induction furnace until the pressure is 20000-40000 Pa.

The carbon source is graphite.

The easily volatile or oxidizable raw materials comprise a silicon source, a manganese source, a vanadium source and a niobium source; wherein the silicon source is industrial silicon or ferrosilicon alloy, the manganese source is electrolytic manganese or ferromanganese, the vanadium source is metal vanadium or ferrovanadium alloy, and the niobium source is metal niobium or ferroniobium alloy.

In the step (2), the vacuum deoxidation time is 10-60 min.

In the step (3), the aluminum deoxidation time is 5-30 min.

In the step (4), the rare earth magnesium deoxidation time is 2-10 min.

The metal rare earth is metal cerium or metal lanthanum.

The magnesium-nickel alloy contains 20-25% of Mg and the balance of Ni by mass percent.

In the step (1), the total oxygen content of all the raw materials is 80 to 280 ppm.

The oxygen content of the ultra-low oxygen bearing steel ingot is 0.1-4.0 ppm.

The first part of carbon sources accounts for 40-60% of the total mass of the carbon sources.

In the step (3), the calculation formula of the addition amount of the metal aluminum is as follows:

M1＝(0.1～0.5)A/b (1)；

in the formula, A is the total mass of all raw materials, the unit is t, b is the yield of Al, and M1 is the addition of metallic aluminum, the unit is kg; wherein the b selection value of the yield of the aluminum is 95-100%.

When the rare earth magnesium deoxidizer is a rare earth magnesium alloy, the calculation formula of the addition amount of the rare earth magnesium deoxidizer in the step (4) is as follows:

M2＝(0.05～0.5)A/(c*D) (2)；

in the formula, A is the total mass of all raw materials, the unit is t, c is the yield of rare earth, D is the mass percent of Re in the rare earth magnesium alloy, and M2 is the addition of the rare earth magnesium deoxidizer, the unit is kg; wherein the yield c of the rare earth is 5-60%.

When the rare earth magnesium deoxidizer is metal rare earth and magnesium-nickel alloy, the calculation formula of the addition amount of the metal rare earth in the step (4) is as follows:

M3＝(0.05～0.5)A/(c*E) (3)；

in the formula, A is the total mass of all raw materials, the unit is t, c is the yield of the rare earth, E is the mass percentage of Re in the metal rare earth, and M3 is the addition of the metal rare earth, and the unit is kg; wherein the yield c of the rare earth is 5-60%;

the calculation formula of the addition of the magnesium-nickel alloy is as follows:

M4＝(0.01～0.05)A/(f*G) (4)；

in the formula, A is the total mass of all raw materials, the unit is t, f is the yield of magnesium, G is the mass percent of Mg in the magnesium-nickel alloy, and M4 is the addition of the magnesium-nickel alloy, and the unit is kg; wherein the yield selection value of magnesium is 1-20%.

Compared with the prior art, the invention has the following beneficial effects:

(1) three-step deoxidation is carried out, the chemical reaction is sufficient, and the oxygen in the raw material can be reduced from more than 80ppm to less than 4 ppm;

(2) the added rare earth can further reduce the oxygen and sulfur contents in the steel and the volume fraction of inclusions in the steel, and can modify aluminum-containing inclusions to make the inclusions harmless;

(3) the added magnesium can also react with the rare earth inclusions to form magnesium-containing inclusions with lower density, so that the inclusions can be promoted to float upwards and stay in the crucible in the casting process; in addition, the inclusions generated by magnesium treatment are fine and dispersed, so that dendrites can be refined, and the solidification structure of the cast ingot can be obviously improved.

Drawings

FIG. 1 is a photographic view of the appearance of an ultra low oxygen bearing steel ingot in an embodiment of the present invention;

FIG. 2 is a plot of the area fraction of inclusions in an ultra low oxygen bearing steel ingot and a comparative test according to an embodiment of the present invention;

FIG. 3 is a graph of the number density of inclusions versus the average diameter of ultra low oxygen bearing steel castings according to embodiments of the present invention and comparative tests.

Detailed Description

The composition of the ultralow-oxygen bearing steel ingot in the embodiment of the invention is M50 aviation bearing steel.

In the embodiment of the invention, the raw material is prepared into industrial pure iron according to the components of the bearing steel.

In the embodiment of the invention, the mass content of oxygen in the industrial pure iron is 0.0032 percent.

In the embodiment of the invention, the mass content of oxygen in the metal chromium is 0.131%.

The crucible adopted in the embodiment of the invention is made of magnesium aluminate spinel.

The metal aluminum in the embodiment of the invention is aluminum beans.

When the rare earth magnesium deoxidizer is added in the embodiment of the invention, the rare earth magnesium deoxidizer is respectively placed in different bins, the addition is averagely divided into 3-5 batches, and after the current batch of rare earth magnesium deoxidizer is completely melted, the next batch of rare earth magnesium deoxidizer is added.

In the embodiment of the invention, the rare earth magnesium alloy contains 15-45% of Re, 5-25% of Mg and the balance of Ni according to mass percent, wherein Re is La or Ce.

In the embodiment of the invention, the prepared raw materials are calculated according to the total amount of all the raw materials and the rare earth magnesium deoxidizer, and the yield is calculated.

In the embodiment of the invention, the total oxygen content of all the raw materials is 80-280 ppm.

In the embodiment of the invention, because the same reaction furnace is adopted, the yield and the coefficient are calculated according to the same value.

The following are preferred embodiments of the present invention.

Example 1

Preparing raw materials of industrial pure iron, metal chromium, molybdenum strips, metal vanadium, electrolytic manganese, graphite, aluminum beans (metal aluminum), rare earth metal and magnesium alloy according to the components of M50 aviation bearing steel; the rare earth metal adopts metal cerium, and the purity is more than 99 percent; the magnesium alloy is magnesium-nickel alloy, and the magnesium content is 20.62%;

dividing graphite into a first part of graphite and a second part of graphite; the first part of graphite accounts for 60 percent of the total graphite by mass;

placing industrial pure iron, metal chromium, molybdenum strips and a first part of graphite in a crucible of a vacuum induction furnace;

sequentially putting a second part of graphite, electrolytic manganese, metal vanadium, aluminum beans, magnesium-nickel alloy and metal cerium into different bins of a vacuum induction furnace;

starting the vacuum induction furnace, vacuumizing until the air pressure is less than or equal to 3Pa, heating until the materials in the crucible begin to melt, stopping vacuumizing, and filling argon into the vacuum induction furnace until the air pressure is 40000 Pa; a 30kg vacuum induction furnace is adopted, the power is 10kW at the beginning, and the melting is started when the power reaches 40 kW;

after the materials in the crucible are completely melted, adding a second part of graphite into the crucible, vacuumizing the vacuum induction furnace until the pressure is less than or equal to 20Pa, controlling the temperature to enable the materials in the crucible to be in a molten state, and preserving the heat for 30min for vacuum deoxidation;

after the vacuum deoxidation is finished, argon is filled into the vacuum induction furnace until the air pressure is 40000 Pa; putting electrolytic manganese and metal vanadium into a crucible, and controlling the temperature to enable materials in the crucible to be in a molten state; after all the materials in the crucible are melted, putting the aluminum beans into the crucible, and controlling the temperature to enable the materials in the crucible to be in a molten state; when the aluminum beans are completely melted, preserving the heat for 5min for aluminum deoxidation;

after the aluminum deoxidation is finished, putting the magnesium-nickel alloy and the metal cerium into a crucible, and controlling the temperature to enable the materials in the crucible to be in a molten state; when the rare earth magnesium deoxidizer is completely melted, preserving the heat for 3min to perform rare earth magnesium deoxidation;

after the rare earth magnesium deoxidation is finished, adjusting the temperature of the materials in the crucible to the pouring temperature, and then pouring to obtain an ultra-low oxygen bearing steel ingot;

the adding amount of the aluminum beans M1 is 0.15A/99 percent and 0.15 kg/t;

the addition amount of the metal cerium M3 is 0.25A/(50% 99%) and 0.51 kg/t;

the addition amount of the magnesium-nickel alloy M4 is 0.04A/(5% 20.62%) -3.88 kg/t;

the O content of the ultra-low oxygen bearing steel ingot is 0.00013 percent, and the S content is 0.0010 percent;

the appearance photograph of the ultra-low oxygen bearing steel ingot is shown in figure 1, the area fraction curve of the inclusions is shown in figure 2, and the number density-average diameter curve of the inclusions is shown in figure 3;

the same raw materials are adopted, the same materials are prepared according to the traditional vacuum deoxidation method, a comparison test is carried out, the obtained ingot has the O content of 0.0020 percent and the S content of 0.0021 percent, the appearance photo of the ingot is shown in figure 1, the area fraction curve of the inclusions is shown in figure 2, and the number density-average diameter curve of the inclusions is shown in figure 3.

Example 2

The method is the same as example 1, except that:

(1) the first part of graphite accounts for 50% of the total graphite mass;

(2) when the materials in the crucible begin to melt, stopping vacuumizing, and filling argon until the air pressure is 30000 Pa;

(3) preserving the temperature for 40min to perform vacuum deoxidation;

(4) preserving the temperature for 10min to perform aluminum deoxidation;

(5) keeping the temperature for 6min to perform rare earth magnesium deoxidation;

(6) the addition amount of the metal cerium M3 is 0.15A/(50% 99%) -0.3 kg/t; the addition amount of the magnesium-nickel alloy M4 is 0.02A/(5% 20.62%) -1.94 kg/t; the O content of the ultra-low oxygen bearing steel ingot is 0.00027%, and the S content is 0.0015%.

Example 3

The method is the same as example 1, except that:

(1) the metal rare earth adopts metal lanthanum, and the purity is more than 99 percent; the first part of graphite accounts for 40% of the total graphite by mass;

(2) when the materials in the crucible begin to melt, stopping vacuumizing, and filling argon until the air pressure is 20000 Pa;

(3) preserving the temperature for 30min to perform vacuum deoxidation;

(4) keeping the temperature for 3min to perform rare earth magnesium deoxidation;

(5) the addition amount of metal lanthanum M3 is 0.25A/(50% 99%) -0.51 kg/t; the addition amount of the magnesium-nickel alloy M4 is 0.02A/(5% 20.62%) -1.94 kg/t; the O content of the ultra-low oxygen bearing steel ingot is 0.00016%, and the S content is 0.0010%.

Example 4

The method is the same as example 1, except that:

(1) the rare earth magnesium deoxidizer is a rare earth magnesium alloy, and comprises 30% of Ce, 15% of Mg and the balance of Ni by mass percent;

(2) the first part of graphite accounts for 55 percent of the total graphite by mass; placing the rare earth magnesium alloy in a bin;

(3) when the materials in the crucible begin to melt, stopping vacuumizing, and filling argon until the air pressure is 35000 Pa;

(4) preserving the temperature for 60min to perform vacuum deoxidation;

(5) after the vacuum deoxidation is finished, argon is filled to the air pressure of 30000 Pa;

(6) preserving the temperature for 10min to perform aluminum deoxidation;

(7) after the aluminum deoxidation is finished, the rare earth magnesium alloy is placed into a crucible; keeping the temperature for 5min to perform rare earth magnesium deoxidation;

(8) the addition amount of the rare earth magnesium alloy M2 is 0.2A/(30%. 30%) -2.22 kg/t; the O content of the ultra-low oxygen bearing steel cast ingot is 0.00040%, and the S content is 0.0010%.

Example 5

The method is the same as example 1, except that:

(1) the rare earth magnesium deoxidizer is a rare earth magnesium alloy, and comprises 45% of La, 5% of Mg and the balance of Ni by mass percent;

(2) the first part of graphite accounts for 55 percent of the total graphite by mass; placing the rare earth magnesium alloy in a bin;

(3) when the materials in the crucible begin to melt, stopping vacuumizing, and filling argon until the air pressure is 30000 Pa; a 10kg vacuum induction furnace is adopted, the power of the vacuum induction furnace is 5kW at the beginning, and the melting is started when the power reaches 15 kW;

(4) preserving the temperature for 10min to perform vacuum deoxidation;

(5) after the vacuum deoxidation is finished, argon is filled to the pressure of 20000 Pa;

(6) after the aluminum deoxidation is finished, the rare earth magnesium alloy is placed into a crucible; keeping the temperature for 2min to perform rare earth magnesium deoxidation;

(7) the addition amount of the rare earth magnesium alloy M2 is 0.2A/(30% 45%) -1.48 kg/t; the O content of the ultra-low oxygen bearing steel ingot is 0.00038%, and the S content is 0.0012%.

Example 6

The method is the same as example 1, except that:

(1) the rare earth magnesium deoxidizer is a rare earth magnesium alloy, and comprises 15% of La, 25% of Mg and the balance of Ni by mass percent;

(2) the first part of graphite accounts for 45 percent of the total graphite by mass; placing the rare earth magnesium alloy in a bin;

(3) when the materials in the crucible begin to melt, stopping vacuumizing, and filling argon until the air pressure is 25000 Pa; a 100kg vacuum induction furnace is adopted, the power of the vacuum induction furnace is 20kW at the beginning, and melting is started when the power reaches 100 kW;

(4) preserving the temperature for 30min to perform aluminum deoxidation;

(5) after the aluminum deoxidation is finished, the rare earth magnesium alloy is placed into a crucible; keeping the temperature for 10min to perform rare earth magnesium deoxidation;

(6) the addition amount of the rare earth magnesium alloy M2 is 0.1A/(30% 15%), 2.22 kg/t; the O content of the ultra-low oxygen bearing steel ingot is 0.00033%, and the S content is 0.0011%.

Example 7

The method is the same as example 1, except that:

(1) the first part of graphite accounts for 50% of the total graphite mass;

(2) when the materials in the crucible begin to melt, stopping vacuumizing, and filling argon until the air pressure is 30000 Pa; a 1t vacuum induction furnace is adopted, the power of the vacuum induction furnace is 120kW at the beginning, and the melting is started when the power reaches 380 kW;

(3) preserving the temperature for 60min to perform vacuum deoxidation;

(4) keeping the temperature for 20min to perform aluminum deoxidation;

(5) keeping the temperature for 8min to perform rare earth magnesium deoxidation;

(6) the addition of cerium metal M3-0.2A/(50%. 99%) -0.4 kg/t; the addition amount of the magnesium-nickel alloy M4 is 0.02A/(5% 20.62%) -1.94 kg/t; the O content of the ultra-low oxygen bearing steel ingot is 0.00029 percent, and the S content is 0.0014 percent.