Method for regulating and controlling sulfide form by using pulse current

Abstract

The invention provides a method for regulating and controlling the form of sulfide by using pulse current. Compared with the prior art, the low-frequency effect of the pulse current is utilized, a current field which is evenly distributed is generated in the sulfur-containing molten steel, the spontaneous nucleation probability of sulfide is improved, precipitation of the sulfide in the solidification process is promoted, the sulfide is precipitated and grows in a blocky, spherical and fusiform mode, and formation of long-strip-shaped and chain-shaped sulfide is restrained; the method is simple in operation and easy to implement, avoids the generation of stress concentration and cracks in the service process of the sulfur-containing steel, realizes the control of the pulse current on the sulfide form in the solidification process, avoids many risks of regulating and controlling the sulfide through alloying means and additionally introducing external inclusions, has practical application value, and is convenient to popularize and apply.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for regulating the morphology of sulfides by using pulse current. Background Art

[0002] Due to the special service environment and harsh working conditions of wind power steel plates, higher fatigue life has always been the goal pursued by all high-end wind power steel plates, and non-metallic inclusions are the key problem that seriously restricts the improvement of fatigue life in steel. The fundamental reason is that the difference in characteristics between inclusions and the matrix destroys the continuity of the matrix. The presence of inclusions causes local stress around the inclusions in the processing and service environment of the steel plate, which can easily lead to cracks inside or on the surface of the steel body component. The stress concentration during the service process causes the cracks to further expand and worsen, and ultimately causes fatigue failure of wind power equipment.

[0003] Most of the existing technologies are to reduce the size of inclusions to make their distribution as uniform as possible to prevent small-sized inclusions from aggregating and growing into large-sized cluster polymers, thereby reducing the harm of large-sized inclusions to steel. However, although brittle non-metallic inclusions seriously damage fatigue strength, small and dispersed plastic non-metallic inclusions (sulfides) have a positive effect on improving the fatigue life of steel. At present, the morphology control of sulfide inclusions in fatigue-resistant wind power steel plates is particularly difficult, and there are unfavorable sulfide inclusions in chain, long strip, irregular and other shapes in the continuous casting billet. If the unfavorable shapes of sulfide inclusions can be transformed into favorable shapes such as spheres, blocks, and spindles, the fatigue life of wind power steel plates will be greatly improved. Summary of the invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a method for regulating the morphology of sulfides using pulse current, which can regulate the nucleation mechanism of sulfides in sulfur-containing steel and promote the formation of spherical, blocky and spindle-shaped sulfides.

[0005] The present invention provides a method for controlling the morphology of sulfides by using pulse current, comprising the following steps:

[0006] S1) providing molten steel; the molten steel contains sulfide;

[0007] S2) inserting two electrodes into the molten steel, and applying a pulse current until the molten steel is completely solidified; the voltage of the pulse current is 10-100V; the pulse current is 10-500A; the frequency of the pulse current is 1-5000Hz.

[0008] Preferably, in the step S1), the sulfur-containing steel is melted and then kept warm to obtain the molten steel; the keeping warm time is at least 20 minutes.

[0009] Preferably, the sulfide is selected from one or more of manganese sulfide, calcium sulfide, ferrous sulfide and sulfur oxides formed by polymerization thereof.

[0010] Preferably, the mass content of sulfur in the molten steel is 0.05% to 0.1%;

[0011] Calculated by mass percentage, the main components of the molten steel also include: Fe: 80% to 82%; Cr: 0.15% to 0.2%; V: 0.02% to 0.06%; Si: 0.2% to 0.3%; Mn: 0.5% to 0.8%; Ni: 0.05% to 0.08%.

[0012] Preferably, the mass content of sulfur in the molten steel is 0.07%;

[0013] Calculated by mass percentage, the main components of the molten steel also include: Fe: 81.31%; Cr: 0.18%; V: 0.04%; Si: 0.26%; Mn: 0.65%; and Ni: 0.06%.

[0014] Preferably, the electrode is selected from a graphite electrode or a pure iron electrode;

[0015] The ratio of the distance between the two electrodes to the surface diameter of the molten steel is 0.6 to 0.8;

[0016] The ratio of the depth of the electrode inserted into the molten steel to the depth of the molten steel is 0.9-1.

[0017] Preferably, the frequency of the pulse current is 1-500 Hz; the pulse current is 300-500A.

[0018] Preferably, the time for applying the pulse current is 20 to 120 minutes.

[0019] Preferably, after the molten steel is completely solidified, the sulfide in the steel ingot is in the form of one or more of spherical, massive and spindle shapes.

[0020] Preferably, the diameter of the sphere is 5 to 50 μm; the length, width and height of the block are each independently 5 to 50 μm; the length of the spindle is 5 to 100 μm; and the diameter of the spindle is 1 to 30 μm.

[0021] The present invention provides a method for regulating the morphology of sulfides by using pulse current, comprising the following steps: S1) providing molten steel; the molten steel contains sulfides; S2) inserting two electrodes into the molten steel, applying pulse current until the molten steel is completely solidified; the voltage of the pulse current is 10-100V; the pulse current is 10-500A; the frequency of the pulse current is 1-5000Hz. Compared with the prior art, the present invention utilizes the low-frequency effect of the pulse current to generate a uniformly distributed current field in the sulfur-containing molten steel, improves the probability of spontaneous nucleation of sulfides, promotes the precipitation of sulfides during the solidification process, and makes the sulfides precipitate and grow in block, spherical, and spindle forms, inhibits the formation of long strips and chain sulfides, avoids stress concentration and cracks during the service process of the sulfur-containing steel, realizes the control of the morphology of sulfides by pulse current during the solidification process, and the operation method is simple and easy to implement, avoiding many risks of regulating sulfides by alloying means and introducing additional foreign inclusions, has practical application value, and is easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a sulfide morphology distribution diagram of the steel ingot obtained in Example 1 of the present invention;

[0023] Figure 2 This is a sulfide morphology distribution diagram of the steel ingot obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention provides a method for regulating the morphology of sulfides by using pulse current, comprising the following steps: S1) providing molten steel; the molten steel contains sulfides; S2) inserting two electrodes into the molten steel, and applying pulse current until the molten steel is completely solidified; the voltage of the pulse current is 10 to 100V; the pulse current is 10 to 500A; and the frequency of the pulse current is 1 to 5000Hz.

[0026] The present invention utilizes the low-frequency effect of pulse current to generate a uniformly distributed current field in the sulfur-containing molten steel, thereby increasing the probability of spontaneous nucleation of sulfides, promoting the precipitation of sulfides during the solidification process, and allowing sulfides to precipitate and grow in block, spherical, and spindle forms, thereby inhibiting the formation of long strip and chain sulfides, thereby avoiding stress concentration and cracks during the service of the sulfur-containing steel, and realizing the control of the sulfide form by pulse current during the solidification process. The operation method is simple and easy to implement, thereby avoiding many risks of regulating sulfides by alloying means and introducing additional foreign inclusions. The present invention has practical application value and is easy to promote and apply.

[0027] The present invention has no particular limitation on the sources of all raw materials, and any raw materials available on the market can be used.

[0028] In the present invention, molten steel is first provided; the molten steel is preferably obtained by melting sulfur-containing steel, and more specifically, by melting sulfur-containing steel and keeping it warm to obtain the molten steel; the melting temperature is preferably 1500°C to 1600°C, and more preferably 1550°C; the melting is preferably carried out in a smelting furnace; the heating rate of the melting is preferably 5 to 15°C / min, more preferably 8 to 12°C / min, and more preferably 10°C / min; the heating time of the melting is preferably 1 to 5h, more preferably 2 to 4h, and more preferably 3h; the keeping time is preferably at least 20m in, more preferably 20 to 60 min, more preferably 20 to 50 min, more preferably 20 to 40 min, and most preferably 30 min; the molten steel contains sulfides; the sulfides are preferably one or more of manganese sulfide, calcium sulfide, ferrous sulfide and sulfur oxides formed by their polymerization; the sulfides in the molten steel are in one or more of chain, long strip, irregular shapes, which are unfavorable forms that affect the performance; the mass content of sulfur element in the molten steel is preferably 0.05% to 0.1%, more preferably 0.06% to 0.08%, and more preferably 0.07%.

[0029] In a specific embodiment provided by the present invention, the main components of the molten steel, measured in mass percentage, also include: Fe: 80% to 82%; Cr: 0.15% to 0.2%; V: 0.02% to 0.06%; Si: 0.2% to 0.3%; Mn: 0.5% to 0.8%; Ni: 0.05% to 0.08%.

[0030] In a specific embodiment provided by the present invention, the main components of the molten steel, measured in mass percentage, also include: Fe: 81% to 81.5%; Cr: 0.16% to 0.2%; V: 0.03% to 0.05%; Si: 0.25% to 0.3%; Mn: 0.6% to 0.7%; Ni: 0.05% to 0.07%.

[0031] In a specific embodiment provided by the present invention, the main components of the molten steel, measured in mass percentage, include: Fe: 81.31%; Cr: 0.18%; V: 0.04%; Si: 0.26%; Mn: 0.65%; and Ni: 0.06%.

[0032] Insert two electrodes into the molten steel, and apply pulse current until the molten steel is completely solidified; the electrodes are preferably graphite electrodes or pure iron electrodes; the ratio of the diameter of the electrodes to the distance between the two electrodes is preferably 1:2 to 1:5, more preferably 1:2 to 1:4, and more preferably 1:3; the ratio of the distance between the two electrodes to the surface diameter of the molten steel is preferably 0.6 to 0.8, more preferably 0.6 to 0.7; the ratio of the depth of the electrode inserted into the molten steel to the depth of the molten steel is preferably 0.9 to 1, more preferably 0.9 to 0.98 , more preferably 0.9 to 0.96, more preferably 0.9 to 0.94, and most preferably 0.92; the voltage of the pulse current is preferably 10 to 100 V, more preferably 15 to 100 V, more preferably 20 to 100 V, more preferably 20 to 95 V, more preferably 30 to 95 V, more preferably 35 to 95 V, more preferably 40 to 95 V, and most preferably 42 to 95 V; in some embodiments provided by the present invention, the voltage of the pulse current is specifically 15 V, 42 V, 20 V, 66 V , 80V or 95V; the pulse current is preferably 10-500A, more preferably 50-500A, more preferably 80-500A, more preferably 100-500A, more preferably 150-500A, more preferably 250-500A, most preferably 300-500A; the pulse current is specifically 100A, 450A, 200A, 150A, 250A or 500A; the frequency of the pulse current is 1-5000Hz, preferably 10-5000Hz, more preferably It is 50-5000Hz, more preferably 80-5000Hz, and most preferably 100-5000Hz; the frequency of the pulse current is specifically 4000Hz, 100Hz, 800Hz, 5000Hz, 2000Hz or 200Hz; the time for applying the pulse current is preferably 20-120min, more preferably 30-120min; in some embodiments provided by the present invention, the time for applying the pulse current is specifically 30min, 120min or 60min.

[0033] In a specific embodiment provided by the present invention, the electrode is a graphite electrode, and when the frequency of the pulse current is 1 to 500 Hz and the pulse current is 300 to 500 A, the number of unfavorable sulfides accounts for less than 10%; when the frequency of the pulse current is 500 to 5000 Hz and the pulse current is 10 to 300 A, the number of unfavorable sulfides accounts for more than 10%.

[0034] In another specific embodiment provided by the present invention, the electrode is a pure iron electrode, and when the frequency of the pulse current is 1 to 500 Hz and the pulse current is 300 to 500 A, the number of unfavorable forms of sulfides accounts for less than 5%; when the frequency of the pulse current is 500 to 5000 Hz and the pulse current is 10 to 300 A, the number of unfavorable forms of sulfides accounts for more than 5%.

[0035] According to the present invention, the sulfide in the steel ingot after the molten steel is completely solidified is preferably in the form of one or more of spherical, blocky and spindle-shaped. More specifically, the diameter of the spherical shape is preferably 5-50 μm, more preferably 5-40 μm, more preferably 5-30 μm, and most preferably 10-30 μm; the length, width and height of the block shape are each independently preferably 5-50 μm, more preferably 5-40 μm, more preferably 5-30 μm, and most preferably 10-30 μm; the length of the spindle shape is preferably 5-100 μm, more preferably 10-100 μm, more preferably 30-100 μm, and most preferably 50-100 μm; the diameter of the spindle shape is preferably 1-30 μm, more preferably 5-30 μm, more preferably 5-20 μm, and most preferably 5-10 μm.

[0036] According to the present invention, when no electrode is inserted into the molten steel and no pulse current is applied, the amount of sulfides in unfavorable forms accounts for 30% to 50% of the total amount of sulfides; when a graphite electrode is inserted and no pulse current is applied, the amount of sulfides in unfavorable forms accounts for 70% to 90% of the total amount of sulfides; when a graphite electrode is inserted and a pulse current is applied, the amount of sulfides in unfavorable forms accounts for 10% to 20% of the total amount of sulfides, and the amount of sulfides in one or more improved forms of spherical, massive, and spindle shapes accounts for 80% to 90% of the total amount of sulfides; when a non-graphite electrode (such as a pure iron electrode) is inserted and no pulse current is applied, the situation is consistent with the situation of not inserting an electrode; when a non-graphite electrode (such as a pure iron electrode) is inserted and a pulse current is applied, the amount of sulfides in unfavorable forms accounts for 5% to 10% of the total amount of sulfides; the amount of sulfides in one or more improved forms of spherical, massive, and spindle shapes accounts for 90% to 95% of the total amount of sulfides.

[0037] In order to further illustrate the present invention, a method for controlling the morphology of sulfides using pulse current provided by the present invention is described in detail below in conjunction with embodiments.

[0038] The reagents used in the following examples are all commercially available.

[0039] Example 1

[0040] A method for controlling the morphology of sulfides using pulse current comprises the following steps:

[0041] S1. A smelting furnace is used to melt sulfur-containing steel to obtain sulfur-containing molten steel, whose main components are Fe: 81.31%; Cr: 0.18%; V: 0.04%; Si: 0.26%; Mn: 0.65%; Ni: 0.06%; S: 0.07%; the heating rate is 10°C / min; the heating time is 3h; the melting temperature is 1550°C; the holding time is 30min;

[0042] S2. Insert two preheated graphite electrodes into the sulfur-containing molten steel and stop heating the sulfur-containing molten steel. The electrode diameter is 10 mm; the electrode spacing is 30 mm; the electrode insertion depth is 35 mm; the molten steel depth is about 38 mm; and the bottom area is about 2000 mm. 2 ; Then, a pulse current is applied to the sulfur-containing molten steel through electrodes for 30 minutes until the molten steel is completely solidified. The pulse voltage is 15V, the pulse frequency is 4000Hz, and the pulse current is 100A to obtain a steel ingot.

[0043] The sulfide morphology distribution of the steel ingot prepared in Example 1 is as follows: Figure 1 As shown by Figure 1 It can be seen that the sulfide forms are mainly spherical, massive and spindle-shaped. According to statistics, the number of sulfides in unfavorable forms accounts for 19% of the total sulfides.

[0044] Example 2

[0045] A method for controlling the morphology of sulfides using pulse current comprises the following steps:

[0046] S1. A smelting furnace is used to melt sulfur-containing steel to obtain sulfur-containing molten steel, the main components of which are Fe: 81.31%; Cr: 0.18%; V: 0.04%; Si: 0.26%; Mn: 0.65%; Ni: 0.06%; S: 0.07%; the heating rate is 10°C / min; the heating time is 3h; the melting temperature is 1550°C; the holding time is 30min;

[0047] S2. Insert two preheated graphite electrodes into the sulfur-containing molten steel and stop heating the sulfur-containing molten steel. The electrode diameter is 10 mm; the electrode spacing is 30 mm; the electrode insertion depth is 35 mm; the molten steel depth is about 38 mm; and the bottom area is about 2000 mm. 2 ; Then, a pulse current is applied to the sulfur-containing molten steel through electrodes for 2 hours until the molten steel is completely solidified. The pulse voltage is 42V, the pulse frequency is 100Hz, and the pulse current is 450A to obtain a steel ingot.

[0048] The sulfide forms of the steel ingot prepared in Example 2 are mainly spherical, massive and spindle-shaped. According to statistics, the number of sulfides in unfavorable forms accounts for 10% of the total sulfides.

[0049] Example 3

[0050] A method for controlling the morphology of sulfides using pulse current comprises the following steps:

[0051] S1. A smelting furnace is used to melt sulfur-containing steel to obtain sulfur-containing molten steel, the main components of which are Fe: 81.31%; Cr: 0.18%; V: 0.04%; Si: 0.26%; Mn: 0.65%; Ni: 0.06%; S: 0.07%; the heating rate is 10°C / min; the heating time is 3h; the melting temperature is 1550°C; the holding time is 30min;

[0052] S2. Insert two preheated graphite electrodes into the sulfur-containing molten steel and stop heating the sulfur-containing molten steel. The electrode diameter is 10 mm; the electrode spacing is 30 mm; the electrode insertion depth is 35 mm; the molten steel depth is about 38 mm; and the bottom area is about 2000 mm. 2 ; Then, a pulse current is applied to the sulfur-containing molten steel through electrodes for 1 hour until the molten steel is completely solidified. The pulse voltage is 20V, the pulse frequency is 800Hz, and the pulse current is 200A to obtain a steel ingot.

[0053] The sulfide forms of the steel ingot prepared in Example 3 are mainly spherical, massive and spindle-shaped. According to statistics, the number of sulfides in unfavorable forms accounts for 16% of the total sulfides.

[0054] Example 4

[0055] A method for controlling the morphology of sulfides using pulse current comprises the following steps:

[0056] S1. A smelting furnace is used to melt sulfur-containing steel to obtain sulfur-containing molten steel, the main components of which are Fe: 81.31%; Cr: 0.18%; V: 0.04%; Si: 0.26%; Mn: 0.65%; Ni: 0.06%; S: 0.07%; the heating rate is 10°C / min; the heating time is 3h; the melting temperature is 1550°C; the holding time is 30min;

[0057] S2. Insert two preheated pure iron electrodes into the sulfur-containing molten steel and stop heating the sulfur-containing molten steel. The electrode diameter is 10 mm; the electrode spacing is 30 mm; the electrode insertion depth is 35 mm; the molten steel depth is about 38 mm; and the bottom area is about 2000 mm. 2 ; Then, a pulse current is applied to the sulfur-containing molten steel through electrodes for 30 minutes until the molten steel is completely solidified. The pulse voltage is 66V, the pulse frequency is 5000Hz, and the pulse current is 150A to obtain a steel ingot.

[0058] The sulfide forms of the steel ingot prepared in Example 4 are mainly spherical, massive and spindle-shaped. According to statistics, the number of sulfides in unfavorable forms accounts for 10% of the total sulfides.

[0059] Example 5

[0060] A method for controlling the morphology of sulfides using pulse current comprises the following steps:

[0061] S1. A smelting furnace is used to melt sulfur-containing steel to obtain sulfur-containing molten steel, the main components of which are Fe: 81.31%; Cr: 0.18%; V: 0.04%; Si: 0.26%; Mn: 0.65%; Ni: 0.06%; S: 0.07%; the heating rate is 10°C / min; the heating time is 3h; the melting temperature is 1550°C; the holding time is 30min;

[0062] S2. Insert two preheated pure iron electrodes into the sulfur-containing molten steel and stop heating the sulfur-containing molten steel. The electrode diameter is 10 mm; the electrode spacing is 30 mm; the electrode insertion depth is 35 mm; the molten steel depth is about 38 mm; and the bottom area is about 2000 mm. 2 ; Then, a pulse current is applied to the sulfur-containing molten steel through electrodes for 1 hour until the molten steel is completely solidified. The pulse voltage is 80V, the pulse frequency is 2000Hz, and the pulse current is 250A to obtain a steel ingot.

[0063] The sulfide forms of the steel ingot prepared in Example 5 are mainly spherical, massive and spindle-shaped. According to statistics, the number of sulfides in unfavorable forms accounts for 7% of the total sulfides.

[0064] Example 6

[0065] A method for controlling the morphology of sulfides using pulse current comprises the following steps:

[0066] S1. A smelting furnace is used to melt sulfur-containing steel to obtain sulfur-containing molten steel, the main components of which are Fe: 81.31%; Cr: 0.18%; V: 0.04%; Si: 0.26%; Mn: 0.65%; Ni: 0.06%; S: 0.07%; the heating rate is 10°C / min; the heating time is 3h; the melting temperature is 1550°C; the holding time is 30min;

[0067] S2. Insert two preheated pure iron electrodes into the sulfur-containing molten steel and stop heating the sulfur-containing molten steel. The electrode diameter is 10 mm; the electrode spacing is 30 mm; the electrode insertion depth is 35 mm; the molten steel depth is about 38 mm; and the bottom area is about 2000 mm. 2 ; Then, a pulse current is applied to the sulfur-containing molten steel through electrodes for 2 hours until the molten steel is completely solidified. The pulse voltage is 95V, the pulse frequency is 200Hz, and the pulse current is 500A to obtain a steel ingot.

[0068] The sulfide forms of the steel ingot prepared in Example 6 are mainly spherical, massive and spindle-shaped. According to statistics, the number of sulfides in unfavorable forms accounts for 5% of the total sulfides.

[0069] Comparative Example 1

[0070] The difference from Example 1 is that a graphite electrode was inserted but no pulse current was applied.

[0071] The sulfide morphology distribution of the steel ingot prepared in Comparative Example 1 is as follows: Figure 2 As shown by Figure 2 It can be seen that the sulfide forms are mainly unfavorable forms such as chain, long strip and irregular. According to statistics, the number of sulfides in unfavorable forms accounts for 81% of the total sulfides.

[0072] Comparative Example 2

[0073] The difference from Example 2 is that a pure iron electrode is inserted but no pulse current is applied.

[0074] The sulfide morphology of the steel ingot prepared in Comparative Example 2 still has a large number of unfavorable chain-like, long-strip-like, and irregular-shaped sulfides, and the number of unfavorable sulfides accounts for 38% of the total sulfides.

[0075] Table 1 Ingot preparation conditions and sulfide content results

[0076]

[0077] It can be seen from the above embodiments and comparative examples that the sulfide morphology in the steel ingot prepared by comparative example 1 is mainly in the unfavorable form of chain, long strip, and irregular shape. This is because the electrode inserted into the molten steel is a graphite electrode, which increases the carbon content in the molten steel. The increase in carbon content will cause the sulfide morphology to change to the unfavorable form of chain, long strip, and irregular shape. However, the graphite electrode is also used. The sulfide morphology in the steel ingots prepared in Examples 1 to 3 of the present invention is mainly in the favorable form of sphere, block and spindle. To avoid the influence of carbon element on the sulfide morphology, there are still a large number of unfavorable sulfides in comparative example 2. However, pure iron electrodes are used to avoid the introduction of carbon elements into the molten steel. The sulfide morphology in the steel ingots prepared in Examples 4 to 6 of the present invention is mainly spherical, block and spindle, and the proportion of unfavorable sulfides is significantly reduced. The pulse current acts on the solidification stage of sulfur-containing steel, which can regulate the morphology of sulfides from unfavorable forms such as chain, long strip, and irregular shape to favorable forms such as sphere, block and spindle.

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for controlling the morphology of sulfides using pulse current, characterized in that: The following steps are involved: S1) providing molten steel; the molten steel contains sulfide; S2) inserting two electrodes into the molten steel, and applying a pulse current until the molten steel is completely solidified; the voltage of the pulse current is 10-100V; the pulse current is 10-500A; the frequency of the pulse current is 1-5000Hz.

2. The method according to claim 1, characterized in that In the step S1), molten steel is obtained by melting sulfur-containing steel and keeping it warm; the insulation time is at least 20 minutes.

3. The method according to claim 1, characterized in that The sulfide is selected from one or more of manganese sulfide, calcium sulfide, ferrous sulfide and sulfur oxides formed by polymerization thereof.

4. The method according to claim 1, characterized in that: The mass content of sulfur in the molten steel is 0.05% to 0.1%; Calculated by mass percentage, the main components of the molten steel also include: Fe: 80% to 82%; Cr: 0.15% to 0.2%; V: 0.02% to 0.06%; Si: 0.2% to 0.3%; Mn: 0.5% to 0.8%; Ni: 0.05% to 0.08%.

5. The method according to claim 1, characterized in that The mass content of sulfur in the molten steel is 0.07%; Calculated by mass percentage, the main components of the molten steel also include: Fe: 81.31%; Cr: 0.18%; V: 0.04%; Si: 0.26%; Mn: 0.65%; and Ni: 0.06%.

6. The method according to claim 1, characterized in that The electrode is selected from a graphite electrode or a pure iron electrode; The ratio of the distance between the two electrodes to the surface diameter of the molten steel is 0.6 to 0.8; The ratio of the depth of the electrode inserted into the molten steel to the depth of the molten steel is 0.9-1.

7. The method according to claim 1, characterized in that The frequency of the pulse current is 1-500 Hz; the pulse current is 300-500A.

8. The method according to claim 1, characterized in that The time for applying the pulse current is 20 to 120 minutes.

9. The method according to claim 1, characterized in that: After the molten steel is completely solidified, the sulfide in the ingot is in the form of one or more of spherical, massive and spindle shapes.

10. The method according to claim 9, characterized in that The diameter of the sphere is 5 to 50 μm; the length, width and height of the block are independently 5 to 50 μm; the length of the spindle is 5 to 100 μm; and the diameter of the spindle is 1 to 30 μm.

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