Smelting method and application of low-carbon molten steel

Abstract

The invention belongs to the technical field of steel smelting, and particularly relates to a smelting method and application of low-carbon molten steel. The method comprises the following steps: carrying out LF refining, molten steel component adjustment and vacuum treatment on molten steel tapped from a converter to obtain molten steel for continuous casting; the LF refining comprises foaming slagging and decarburization treatment; in foaming slagging, a slagging agent comprises calcium carbonate. According to the smelting method of the low-carbon molten steel, calcium carbonate is added into the molten steel for slagging, electric arc heating enables calcium carbonate to be decomposed to generate carbon dioxide gas, slag foaming is promoted, the obtained foamed slag is large in surface area, uniform in thickness and high in stability, a stable foamed slag protection layer is formed, and then radiant heat loss of electric arcs to the furnace wall is reduced; the submerged arc effect is better, and molten steel recarburization caused by carbon escape loss in a graphite electrode and a molten steel tank refractory material is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel smelting, and particularly relates to a smelting method for low-carbon molten steel and its application. Background Art

[0002] For ultra-low-carbon steel grades with a required finished carbon content of less than 0.004%, steel enterprises with non-economic furnace ages cannot meet the process requirements solely by decarburizing with oxygen blowing in the converter. Therefore, it is necessary to carry out secondary refining outside the furnace to decarburize the molten steel tapped from the converter in order to reduce the carbon content in the molten steel.

[0003] When decarburizing is carried out during secondary refining outside the furnace, the un-deoxidized molten steel has intense slag surface reactions during the oxidation decarburization period in the LF furnace, poor submerged arc effect, and losses of graphite electrodes and refractories in the molten steel ladle, all of which can cause carbon pickup in the molten steel. To address this problem, the existing method is to use calcium oxide (quicklime) for submerged arc and slag formation on the un-deoxidized molten steel before decarburization, and use calcium carbide (CaC) to form a foamed slag by foaming slag on the un-deoxidized molten steel.

[0004] However, when using calcium oxide (quicklime) for power-on submerged arc and slag formation, the slag formation effect is not ideal, and carbon elements in the graphite electrodes and molten steel ladle will enter the molten steel (i.e., carbon pickup in the molten steel), resulting in the inability to smelt ultra-low-carbon steel; when using calcium carbide (CaC) to make a foamed slag, calcium carbide (CaC) will undergo a deoxidation reaction with the oxygen in the un-deoxidized molten steel, thereby reducing the oxygen content in the molten steel and further affecting the decarburization effect of the refining LF furnace. Summary of the Invention

[0005] To solve the above problems, the present invention provides a smelting method for low-carbon molten steel and its application to solve at least one aspect of the above technical problems.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a smelting method for low-carbon molten steel, including the following steps:

[0008] Performing LF refining, molten steel composition adjustment, and vacuum treatment on the molten steel tapped from the converter to obtain molten steel for continuous casting;

[0009] The LF refining includes foaming slag formation and decarburization treatment;

[0010] In the foaming slag formation, the slag former includes calcium carbonate;

[0011] The addition amount of the calcium carbonate is 4 kg / t to 6 kg / t.

[0012] The smelting method of low-carbon molten steel provided by the present invention adds calcium carbonate to the molten steel to form slag. The arc heating causes the calcium carbonate to decompose to generate carbon dioxide gas, which promotes the foaming of the slag. The obtained foamed slag has a large surface area, uniform thickness and high stability, forming a stable foamed slag protection layer. Furthermore, it reduces the radiant heat loss of the arc to the furnace wall, making the submerged arc effect better, and avoids the carbon escape loss in the graphite electrode and the refractory of the molten steel ladle, resulting in carbon increase in the molten steel. In the smelting method of low-carbon molten steel of the present invention, after foaming slag formation, a decarburization step is carried out, which can effectively reduce the carbon content in the molten steel while avoiding carbon increase in the molten steel during the refining process, and improve the decarburization effect during LF refining. It should be noted that the deoxidation, desulfurization, reduction slag formation, alloying and calcium treatment in the LF refining, the adjustment of molten steel composition and vacuum treatment (VD or RH vacuum treatment), etc. are all conventional operations in the art and are not particularly limited in the present invention. However, as an example, the conditions for deoxidation, desulfurization, reduction slag formation, alloying and calcium treatment in the LF refining include: the power transmission and temperature increase gear uses a voltage below 4 gears and a current below 5 gears for power transmission, and the flow rate of argon for bottom blowing stirring during the power transmission process is controlled according to 250 NL / min to 300 NL / min.

[0013] In some possible implementation manners, the end-point oxygen content of the converter tapping is 550 ppm or more.

[0014] In some possible implementation manners, the carbon content in the molten steel is 0.005% or more.

[0015] In some possible implementation manners, in the foaming slag formation, the temperature of the molten steel < 1620 °C.

[0016] In some possible implementation manners, the thickness of the foamed slag obtained by the foaming slag formation is 5 mm to 10 mm.

[0017] In some possible implementation manners, the decarburization treatment includes the following steps:

[0018] Under the condition that the flow rate of argon ≥ 800 NL / min, the molten steel with a temperature above 1620 °C is stirred, and the stirring time is 10 min to 15 min.

[0019] In some possible implementation manners, the carbon content in the molten steel obtained after the decarburization treatment is 0.002% or less.

[0020] In some possible implementation manners, the LF refining further includes an arc stabilizing treatment;

[0021] The arc stabilizing treatment includes the steps of: after heating the molten steel after the decarburization treatment to above 1640 °C, adding quicklime for arc stabilization, and the addition amount is 0.65 kg / t to 1.12 kg / t.

[0022] In some possible implementation manners, the molten steel for continuous casting is composed of components with the following mass fractions:

[0023] 0.001% ≤ C ≤ 0.003%, 0.20% ≤ Si ≤ 0.30%, 0.90% ≤ Mn ≤ 1.00%, 0.020% ≤ Al ≤ 0.050%, 0.020% ≤ Nb ≤ 0.025%, 0.008% ≤ Ti ≤ 0.020%, and the balance is iron and inevitable impurities.

[0024] In a second aspect, the present invention provides an application of the method for smelting low-carbon molten steel provided by the present invention in the technical field of iron and steel smelting. Specific embodiments

[0025] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described and illustrated below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments provided by the present invention without creative efforts fall within the scope of protection of the present invention.

[0026] Obviously, the following description is only some examples or embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, the present invention can also be applied to other similar scenarios. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed by the present invention, some design, manufacturing or production changes based on the technical content disclosed by the present invention are only conventional technical means and should not be understood that the content disclosed by the present invention is insufficient.

[0027] However, there will be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present invention and is not intended to limit the subject matter recited in the claims.

[0028] If there is no special description, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0029] The term "content" refers to the mass fraction.

[0030] During the LF refining of molten steel, when calcium oxide (quicklime) is used for submerged arc with power supply and slag making, the slag-making effect is not ideal, the thickness and stability of the molten slag are poor, resulting in the carbon elements in the graphite electrode and the ladle entering the molten steel (i.e., the molten steel increases in carbon), thus making it impossible to smelt ultra-low carbon steel. In addition, the cost of the added calcium oxide is relatively high, increasing the production cost of steel. The principle of using calcium carbide (CaC) to make foamed slag is that CaC reacts with the oxygen in the molten steel to generate carbon dioxide gas, resulting in a decrease in the oxygen in the molten steel, that is, the oxygen reacting with the carbon in the molten steel decreases, thus making it impossible to achieve the smelting of ultra-low carbon molten steel. Therefore, when using calcium oxide (quicklime) and calcium carbide (CaC) for slag making of un-deoxidized molten steel during LF refining, the carbon content in the molten steel is required to be in a lower range (below 0.002%) in order to make the carbon content in the molten steel at the end of smelting relatively low.

[0031] To solve the above problems caused by calcium oxide (quicklime) and calcium carbide (CaC), the embodiment of the present invention proposes a method for smelting low-carbon molten steel, which uses the principle of calcium carbonate decomposition to make a foamed slag protective layer, increasing the surface area and thickness of the foamed slag and improving the stability of the foamed slag.

[0032] The following is a detailed description of a method for smelting low-carbon molten steel according to an embodiment of the present invention.

[0033] The embodiment of the present invention provides a method for smelting low-carbon molten steel, including the following steps:

[0034] S10. Subject the molten steel tapped from the converter to LF refining, molten steel composition adjustment and vacuum treatment to obtain molten steel for continuous casting;

[0035] The LF refining includes foaming slag making and decarburization treatment;

[0036] In the foaming slag making, the slag-making agent includes calcium carbonate;

[0037] The addition amount of calcium carbonate is 4 kg / t to 6 kg / t.

[0038] The smelting method of low-carbon molten steel provided by the embodiments of the present invention adds calcium carbonate to the molten steel to form slag. The electric arc raises the temperature to decompose calcium carbonate to generate carbon dioxide gas, which promotes the foaming of the slag. The obtained foamed slag has a large surface area, uniform thickness and high stability, forming a stable foamed slag protective layer, thereby reducing the radiant heat loss of the electric arc to the furnace wall, making the submerged arc effect better, and avoiding the carbon escape loss in the graphite electrode and the refractory of the molten steel ladle, which causes carbon increase in the molten steel. In the smelting method of low-carbon molten steel of the present invention, after foaming and slag formation, a decarburization step is carried out, which can effectively reduce the carbon content in the molten steel while avoiding carbon increase in the molten steel during the refining process, and improve the decarburization effect during LF refining. It should be noted that deoxidation, desulfurization, reduction slag formation, alloying and calcium treatment in LF refining, molten steel composition adjustment and vacuum treatment (i.e., VD / RH), etc. are all conventional operations in the art and are not particularly limited in the present invention. However, as an example, the conditions for deoxidation, desulfurization, reduction slag formation, alloying and calcium treatment in LF refining include: the power transmission and temperature increase gear uses a voltage below 4 gears and a current below 5 gears for power transmission, and the flow rate of argon gas for bottom blowing stirring during the power transmission process is controlled at 250 NL / min to 300 NL / min.

[0039] In some embodiments, in the above step S10, the oxygen content at the end point of the molten steel tapped from the converter is 550 ppm or more, preferably 550 ppm to 650 ppm. In this case, it is ensured that there is sufficient oxygen content for decarburization during the LF refining process of the molten steel, and the quality of the molten steel will not be reduced.

[0040] In some embodiments, in the above step S10, no alloys, refining slag and deoxidizer are added during the tapping process of the converter and after the furnace, and the recycling of casting residue slag is not carried out.

[0041] In some embodiments, in the above step S10, the carbon content in the molten steel tapped from the converter is 0.04% or more, preferably 0.04% to 0.06%.

[0042] In some embodiments, in the above step S10, during foaming and slag formation, the temperature of the molten steel < 1620 °C, preferably 1600 °C to 1610 °C.

[0043] In some embodiments, in the above step S10, the thickness of the foamed slag obtained by foaming and slag formation is 5 mm to 10 mm. In this case, the stability of the foamed slag is relatively high, and the formed foamed slag protective layer can effectively prevent the carbon escape loss in the graphite electrode and the refractory of the molten steel ladle during arc melting, which causes carbon increase in the molten steel.

[0044] In some embodiments, in the above step S10, the decarburization treatment includes the following steps:

[0045] Stir the molten steel at a temperature above 1620°C with an argon flow rate ≥ 800 NL / min for 10 min to 15 min at a stirring rate of 100 rpm to 120 rpm.

[0046] In the above decarburization treatment, decarburization products CO and CO2 are discharged from the molten steel with argon and enter the dust removal pipeline to deeply decarburize the molten steel; and a stable foam slag protection layer is generated due to foaming slag formation, so that only the carbon in the molten steel itself needs to be removed during the decarburization treatment, shortening the decarburization treatment time and thus improving production efficiency.

[0047] In some embodiments, in the above step S10, the carbon content in the molten steel obtained after decarburization treatment is 0.002% or less, preferably 0.001% to 0.002%. In this case, after the molten steel with a lower carbon content undergoes subsequent deoxidation, desulfurization, reduction slag formation, alloying, and calcium treatment, the carbon content in the obtained molten steel is 0.005% or less.

[0048] In some embodiments, in the above step S10, the LF refining further includes arc stabilization treatment;

[0049] The arc stabilization treatment includes: after heating the molten steel after decarburization treatment to above 1640°C, adding quicklime for arc stabilization, and the addition amount is 0.65 kg / t to 1.12 kg / t. In this case, those skilled in the art add quicklime according to the foaming situation of the slag. When the foaming effect and submerged arc effect of the slag are not good, quicklime is added to maintain the oxygen-rich condition of the molten steel, and the carbon eroded from the graphite electrode and the refractory of the molten steel ladle will be oxidized to avoid carbon increase in the molten steel.

[0050] In some embodiments, in the above step S10, the carbon content in the molten steel obtained by LF refining is 0.05% or less.

[0051] In some embodiments, in the above step S10, the molten steel for continuous casting is composed of the following components by mass fraction:

[0052] 0.001% ≤ C ≤ 0.003%, 0.20% ≤ Si ≤ 0.30%, 0.90% ≤ Mn ≤ 1.00%, 0.020% ≤ Al ≤ 0.050%, 0.020% ≤ Nb ≤ 0.025%, 0.008% ≤ Ti ≤ 0.020%, and the rest is iron and inevitable impurities.

[0053] In some specific embodiments, a method for smelting low-carbon molten steel is proposed, and the steps are as follows:

[0054] S11. Convert hot metal into molten steel in a converter, control the end-point oxygen content to be above 550 ppm, and the carbon content in the molten steel to be above 0.04%.

[0055] S21. The molten steel is subjected to LF refining: foaming slag making, decarburization treatment, deoxidation, desulfurization, reduction slag making, alloying, and calcium treatment;

[0056] In the foaming slag making, calcium carbonate is used as the slag-making agent, and the addition amount is 4 kg / t to 6 kg / t;

[0057] In the decarburization treatment, under the condition that the flow rate of argon is ≥800 NL / min, the molten steel with a temperature above 1620 °C is stirred, the stirring time is 10 min to 15 min, and the stirring rate is 100 rpm to 120 rpm.

[0058] S31. The molten steel after LF refining is subjected to composition adjustment and vacuum treatment (VD or RH vacuum treatment) to obtain molten steel for continuous casting; the molten steel for continuous casting is composed of the following components by mass fraction:

[0059] 0.001% ≤ C ≤ 0.003%, 0.20% ≤ Si ≤ 0.30%, 0.90% ≤ Mn ≤ 1.00%, 0.020% ≤ Al ≤ 0.050%, 0.020% ≤ Nb ≤ 0.025%, 0.008% ≤ Ti ≤ 0.020%, and the rest is iron and inevitable impurities.

[0060] In some other specific embodiments, a smelting method for low-carbon molten steel is proposed, and the steps are as follows:

[0061] S12. The hot metal is subjected to converter steelmaking to obtain molten steel, and the end-point oxygen content is controlled to be above 550 ppm, and the carbon content in the molten steel is above 0.04%.

[0062] S22. The molten steel is subjected to LF refining: foaming slag making, decarburization treatment, arc stabilization treatment, deoxidation, desulfurization, reduction slag making, alloying, and calcium treatment;

[0063] In the foaming slag making, calcium carbonate is used as the slag-making agent, and the addition amount is 4 kg / t to 6 kg / t;

[0064] In the decarburization treatment, under the condition that the flow rate of argon is ≥800 NL / min, the molten steel with a temperature above 1620 °C is stirred, the stirring time is 10 min to 15 min, and the stirring rate is 100 rpm to 120 rpm;

[0065] The arc stabilization treatment includes the steps: after the molten steel after decarburization treatment is heated to above 1640 °C, quicklime is added for arc stabilization, and the addition amount is 0.65 kg / t to 1.12 kg / t.

[0066] S32. The molten steel after LF refining is subjected to composition adjustment and vacuum treatment (VD or RH vacuum treatment) to obtain molten steel for continuous casting; the molten steel for continuous casting is composed of the following components by mass fraction:

[0067] 0.001% ≤ C ≤ 0.003%, 0.20% ≤ Si ≤ 0.30%, 0.90% ≤ Mn ≤ 1.00%, 0.020% ≤ Al ≤ 0.050%, 0.020% ≤ Nb ≤ 0.025%, 0.008% ≤ Ti ≤ 0.020%, and the balance is iron and inevitable impurities.

[0068] The following further illustrates with specific embodiments.

[0069] Embodiment 1

[0070] Embodiment 1 provides a method for smelting low-carbon molten steel, and the steps are as follows:

[0071] (1) Molten iron is converted in a converter to obtain molten steel, and the final oxygen content is controlled to be 850 ppm, and the carbon content in the molten steel is 0.06%.

[0072] (2) The molten steel is subjected to LF refining: foaming slag making, decarburization treatment, deoxidation, desulfurization, reduction slag making, alloying, and calcium treatment;

[0073] In the foaming slag making, calcium carbonate is used as the slag-making agent, and the addition amount is 6 kg / t;

[0074] In the decarburization treatment, the molten steel at a temperature of 1650 °C is stirred at an argon flow rate of 900 NL / min for 10 min, and the stirring rate is 120 rpm.

[0075] (3) The molten steel after LF refining is subjected to composition adjustment and vacuum treatment to obtain molten steel for continuous casting; the molten steel for continuous casting is composed of the following components by mass fraction:

[0076] C: 0.003%, Si: 0.20%, Mn: 0.90%, Al: 0.020%, Nb: 0.020%, Ti: 0.008%, and the balance is iron and inevitable impurities.

[0077] Embodiment 2

[0078] Embodiment 2 provides a method for smelting low-carbon molten steel, and the steps are basically the same as those in Embodiment 1, except that:

[0079] (1) In it, the final oxygen content is 550 ppm, and the carbon content in the molten steel is 0.05%.

[0080] (2) In it, in the foaming slag making, calcium carbonate is used as the slag-making agent, and the addition amount is 4.5 kg / t;

[0081] In the decarburization treatment, the molten steel at a temperature of 1620 °C or above is stirred at an argon flow rate of ≥ 800 NL / min for 10 min, and the stirring rate is 100 rpm.

[0082] (3) In this case, the molten steel for continuous casting consists of the following components by mass fraction:

[0083] C: 0.002%, Si: 0.25%, Mn: 1.00%, Al: 0.042%, Nb: 0.023%, Ti: 0.015%, and the balance is iron and inevitable impurities.

[0084] Example 3

[0085] Example 3 provides a method for smelting low-carbon molten steel. The steps are basically the same as those in Example 1, except that:

[0086] (1) In this case, the final oxygen content is 600 ppm, and the carbon content in the molten steel is 0.04%.

[0087] (2) In the foaming slag making process, calcium carbonate is used as the slag-making agent, and the addition amount is 5 kg / t;

[0088] In the decarbonization treatment, the molten steel at a temperature above 1620 °C is stirred under an argon flow rate ≥ 800 NL / min for 10 min, and the stirring rate is 110 rpm.

[0089] (3) In this case, the molten steel for continuous casting consists of the following components by mass fraction:

[0090] C: 0.0025%, Si: 0.30%, Mn: 0.9%, Al: 0.028%, Nb: 0.025%, Ti: 0.020%, and the balance is iron and inevitable impurities.

[0091] Example 4

[0092] Example 4 provides a method for smelting low-carbon molten steel. The steps are basically the same as those in Example 1, except that:

[0093] (2) In the LF refining process, in the foaming slag making process, calcium carbonate is used as the slag-making agent, and the addition amount is 4 kg / t;

[0094] 1.12 kg / t of calcium oxide is added after the decarbonization treatment to stabilize the arc.

[0095] Example 5

[0096] Example 5 provides a method for smelting low-carbon molten steel. The steps are basically the same as those in Example 1, except that:

[0097] (2) In the LF refining process, in the foaming slag making process, calcium carbonate is used as the slag-making agent, and the addition amount is 5 kg / t;

[0098] 1.0 kg / t of calcium oxide is added after the decarbonization treatment to stabilize the arc.

[0099] Example 6

[0100] Example 6 provides a method for smelting low-carbon molten steel, and the steps are basically the same as those in Example 1, except that:

[0101] (2) In LF refining, during foaming slag formation, calcium carbonate is used as the slag-making agent, and the addition amount is 6 kg / t;

[0102] After decarbonization treatment, 0.65 kg / t of calcium oxide is added to stabilize the arc.

[0103] Comparative Example 1

[0104] Comparative Example 1 provides a method for smelting low-carbon molten steel, and the steps are basically the same as those in Example 1, except that:

[0105] (1) In this step, the controlled final oxygen content is 500 ppm, and the carbon content in the molten steel is 0.06%.

[0106] (2) In this step, calcium oxide is used as the slag-making agent, and the addition amount is 6 kg / t.

[0107] Comparative Example 2

[0108] Comparative Example 2 provides a method for smelting low-carbon molten steel, and the steps are basically the same as those in Example 1, except that:

[0109] (1) In this step, the controlled final oxygen content is 600 ppm, and the carbon content in the molten steel is 0.06%.

[0110] (2) In this step, calcium oxide is used as the slag-making agent, and the addition amount is 4 kg / t.

[0111] To verify the progressiveness of the method for smelting low-carbon molten steel in the embodiments of the present invention, the carbon content in the molten steel after decarbonization treatment in the examples and comparative examples was detected. The results of calcium carbonate / calcium oxide and the carbon content in the molten steel are shown in Table 1 below.

[0112] Table 1

[0113]

[0114] From the data in Table 1 above, at least the following conclusions can be obtained:

[0115] (1) For the method for smelting low-carbon molten steel provided in the embodiments of the present invention, calcium carbonate is added to the molten steel, and the arc heating causes calcium carbonate to decompose to generate carbon dioxide gas, which promotes the foaming of the slag. The obtained foamed slag has a large surface area, uniform thickness and high stability, forming a stable foamed slag protection layer, thereby reducing the radiant heat loss of the arc to the furnace wall, making the submerged arc effect better, and avoiding the loss of carbon in the graphite electrode and the refractory of the molten steel ladle due to carbon escape, resulting in an increase in the carbon content of the molten steel.

[0116] (2) The smelting method of low-carbon molten steel provided by the embodiments of the present invention can carry out the decarburization step after foaming slag-making, which can avoid the carburization of molten steel during the refining process, effectively reduce the carbon content in the molten steel, and improve the decarburization effect during LF refining.

[0117] It should be noted that the present invention is not limited to the above embodiments. The above embodiments are only examples, and the embodiments with the same composition and the same effect as the technical idea within the technical solution scope of the present invention are included in the technical scope of the present invention. In addition, within the scope not departing from the gist of the present invention, various modifications that can be conceived by those skilled in the art to the embodiments and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of the present invention.

Claims

1. A method for smelting low-carbon molten steel, characterized in that: The steps include: The molten steel tapped from the converter is subjected to LF refining, molten steel composition adjustment and vacuum treatment to obtain molten steel for continuous casting; The LF refining includes foaming slag making and decarburization treatment; In the foaming slag making, the slag making agent includes calcium carbonate; The added amount of calcium carbonate is 4kg / t to 6kg / t.

2. The method for smelting low-carbon molten steel according to claim 1, characterized in that: The LF refining also includes arc stabilization treatment; The arc stabilization treatment comprises the following steps: heating the molten steel after the decarburization treatment to above 1640° C., adding quicklime for arc stabilization, the added amount of which is 0.65 kg / t to 1.12 kg / t.

3. The method for smelting low-carbon molten steel according to claim 1, characterized in that: The final oxygen content of the converter steel is above 550 ppm.

4. The method for smelting low-carbon molten steel according to claim 1, characterized in that: The carbon content in the molten steel is above 0.005%.

5. The method for smelting low-carbon molten steel according to claim 1, characterized in that: During the foaming slag making, the temperature of the molten steel is less than 1620°C.

6. The method for smelting low-carbon molten steel according to claim 1, characterized in that: The thickness of the foamed slag obtained by the foaming slag making is 5mm to 10mm.

7. The method for smelting low-carbon molten steel according to claim 1, characterized in that: The decarburization process comprises the following steps: The molten steel at a temperature above 1620° C. is stirred at an argon flow rate of ≥800NL / min for 10 min to 15 min.

8. The method for smelting low-carbon molten steel according to claim 1, characterized in that: The carbon content in the molten steel obtained after the decarburization treatment is less than 0.002%.

9. The method for smelting low-carbon molten steel according to claim 1, characterized in that: The molten steel for continuous casting is composed of the following components by mass fraction: 0.001%≤C≤0.003%, 0.20%≤Si≤0.30%, 0.90%≤Mn≤1.00%, 0.020%≤Al≤0.050%, 0.020%≤Nb≤0.025%, 0.008%≤Ti≤0.020%, and the rest are iron and unavoidable impurities.

10. Application of the method for smelting low-carbon molten steel as claimed in any one of claims 1 to 9 in the field of steel smelting technology.

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