A steelmaking production method for improving sulfide center segregation of medium carbon high sulfur steel

Abstract

The application discloses a steelmaking production method for improving sulfide central segregation of medium-carbon high-sulfur steel and belongs to the technical field of steelmaking in the metallurgical industry. The production method comprises the following steps: electric furnace smelting, LF refining, RH refining and continuous casting processes; silicon-calcium-barium is added to the molten steel in the electric furnace tapping for deoxidation, and pyrite is added in the LF for increasing sulfur; in the RH refining process, vacuum treatment time is 30-35 min, a Te wire is added after breaking the vacuum at a rate of 0.6-0.9 m / t steel, a sulfur wire is fed for fine adjustment of components, and soft blowing time is 15-20 min. The technical scheme can effectively improve the sulfide central segregation problem of the medium-carbon high-sulfur steel, the internal flaw detection qualified rate can be stably up to more than 97%, and the core quality is good.

Description

Technical Field

[0001] This invention belongs to the field of steelmaking technology in the metallurgical industry, specifically relating to a steelmaking production method that improves the segregation of sulfide centers in medium-carbon, high-sulfur steel. Background Technology

[0002] High-sulfur free-cutting steel is an alloy steel whose machinability is improved by adding a certain amount of sulfur, typically between 0.2% and 0.35%, through a specific smelting process. Sulfur in steel forms manganese sulfide inclusions with manganese and iron. These sulfides can disrupt the continuity of the base metal, reducing tool wear and surface roughness during machining. Free-cutting steel is commonly used in automotive, instrument, and engineering machinery parts. Generally, the machinability of steel increases with increasing sulfur content. However, high sulfur content can lead to the accumulation of sulfides in the core, severely affecting the core quality of the steel; therefore, it is necessary to control the morphology and distribution of sulfides in the steel.

[0003] Patent CN117363956A discloses a smelting process for low-carbon, high-sulfur steel, focusing on controlling the morphology of sulfides. Patent CN107828937B discloses a method for controlling sulfur during the smelting of high-sulfur steel, using blast furnace slag as a synthetic slag material to create low-basicity slag for sulfur control. Patent CN117604388A discloses a high-sulfur steel preparation process, focusing on the stable control of sulfur, with a very low sulfur content of 0.06%-0.07%.

[0004] Currently, there are very few patents that address and solve the problem of sulfide center segregation in high-sulfur steel. Summary of the Invention

[0005] The purpose of this invention is to provide a steelmaking method that improves the central aggregation of sulfides in medium-carbon high-sulfur steel. This method can significantly improve the aggregation of sulfides in the core of high-sulfur steel, improve the internal quality of the billet, and solve the problems existing in the background art.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is: a steelmaking method for improving the segregation of sulfide centers in medium-carbon high-sulfur steel, the method comprising: electric furnace smelting, LF refining, RH refining and continuous casting processes; in the RH refining process, the vacuum treatment time is 30-35 minutes, after breaking the vacuum, 0.6-0.9 m / t of Te wire is added, sulfur wire is fed in to finely adjust the composition, and the soft blowing time is 15-20 minutes.

[0007] The medium-carbon high-sulfur steel of this invention has the following composition and mass percentage: C: 0.4%-0.6%, Si: 0.2%-0.4%, Mn: 1.3%-1.7%, P<0.045%, S: 0.2%-0.35%, V: 0.05%-0.15%, N: 0.007%-0.009%, with the remainder being Fe and unavoidable impurities.

[0008] The electric furnace smelting process described in this invention uses an all-scrap electric furnace for smelting, with the steel output C controlled at 0.05-0.08% and the steel output temperature at 1590-1610℃. Silicon-calcium-barium alloy at 1.5-1.9 kg / t steel is added for deoxidation, and silicon-manganese alloy and high-carbon ferromanganese are used for alloying.

[0009] In the LF refining process described in this invention, the white slag time is 40-50 min, the bottom-blown argon flow rate is 500-600 NL / min, silicon carbide deoxidation is used, and the addition amount is 1.9-2.7 kg / t steel. Sulfurization is achieved by adding pyrite, with an addition amount of 6.2-6.9 kg / t steel.

[0010] The continuous casting process described in this invention focuses on adjusting the relevant processes that affect the quality of the core of the cast billet. The cross-section of the continuously cast billet is 200mm×200mm, the electromagnetic stirring current of the crystallizer is 300-350A, and the frequency is 2.5-3Hz.

[0011] In the continuous casting process described in this invention, the electromagnetic stirring current frequencies at the solidification end are 350-400A and 10-15Hz, respectively.

[0012] In the continuous casting process described in this invention, the reduction amount of the light reduction process is 8.5-11.5 mm, and the reduction range is selected between 0.3-0.9 solid fraction at the center of the billet and 11.5-14 m from the liquid surface.

[0013] The ultrasonic internal flaw detection pass rate of the medium carbon high sulfur steel described in this invention can be stably reached over 97%, achieving high core quality.

[0014] The beneficial effects of adopting the above technical solution are as follows: By employing reasonable steelmaking refining and continuous casting processes, the present invention improves the morphology of sulfide inclusions and enhances the purity of molten steel by using tellurium treatment to spheroidize and refine sulfides and optimize the process of electric arc refining and light reduction to achieve solute reflux and supplement solidification shrinkage. This effectively controls the morphology and distribution of inclusions in steel, resulting in a more uniform distribution of manganese sulfide in the cross-section of medium-carbon high-sulfur steel. The technical solution of the present invention can effectively improve the problem of sulfide center agglomeration in medium-carbon high-sulfur steel and has good core quality. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments.

[0016] Example 1

[0017] (1) According to an embodiment of the present invention, a medium carbon high sulfur steel has a continuous casting billet cross section of 200mm×200mm and its main components are shown in Table 1.

[0018] Table 1. Main components and content (wt%) of medium-carbon high-sulfur steel

[0019] element C Si Mn P S V N content 0.40 0.20 1.70 0.019 0.350 0.050 0.007

[0020] (2) All scrap steel electric furnace smelting is adopted, the steel output C is 0.08%, the steel output temperature is 1590℃, 1.5 kg / t of silicon-calcium-barium is added, and silicon-manganese alloy and high-carbon ferromanganese are used for alloying.

[0021] (3) In the LF process, the white slag time is 40 min, the bottom blowing argon flow rate is 500 NL / min, silicon carbide deoxidation is used, and the addition amount is 1.9 kg / t steel. Sulfurization is increased by adding pyrite, and the addition amount is 6.2 kg / t steel.

[0022] (4) In the RH process, the vacuum treatment time is 30 minutes. After breaking the vacuum, 0.9 m / t Te wire is added, and the composition is finely adjusted by feeding in sulfur wire. The soft blowing time is 20 minutes. The above process can improve the purity of molten steel and improve the morphology of sulfide inclusions.

[0023] (5) In the continuous casting process, the electromagnetic stirring current of the crystallizer is 350A and the frequency is 3Hz. The electromagnetic stirring current frequencies at the solidification end are 400A and 15Hz, respectively. The reduction amount of the light reduction process is 11.5mm. The reduction range is selected between 0.3-0.6 solids at the center of the billet and 12m from the liquid surface.

[0024] In this embodiment, a total of 1,334 rolled products were produced, and the internal flaw detection pass rate was 97.6%.

[0025] Example 2

[0026] (1) The cross-section of the continuous casting billet in this embodiment is 200mm×200mm, and the main components are shown in Table 2;

[0027] Table 2 shows the main components and content (wt%) of medium-carbon high-sulfur steel.

[0028] element C Si Mn P S V N content 0.51 0.28 1.30 0.015 0.317 0.098 0.008

[0029] (2) All scrap steel electric furnace smelting is adopted, the steel output C is 0.07%, the steel output temperature is 1595℃, 1.6 kg / t of silicon-calcium-barium is added, and silicon-manganese alloy and high-carbon ferromanganese are used for alloying.

[0030] (3) In the LF process, the white slag time is 47 min, the bottom blowing argon flow rate is 550 NL / min, silicon carbide deoxidation is used, and the addition amount is 2.1 kg / t steel. Sulfurization is increased by adding pyrite, and the addition amount is 6.3 kg / t steel.

[0031] (4) In the RH process, the vacuum treatment time is 32 minutes. After breaking the vacuum, 0.8 m / t of Te wire is added, and the composition is finely adjusted by feeding in sulfur wire. The soft blowing time is 20 minutes. The above process can improve the purity of molten steel and improve the morphology of sulfide inclusions.

[0032] (5) In the continuous casting process, the electromagnetic stirring current of the crystallizer is 350A and the frequency is 3Hz. The electromagnetic stirring current frequencies at the solidification end are 400A and 15Hz, respectively. The reduction amount of the light reduction process is 11.5mm. The reduction range is selected between 0.5-0.9 solid fraction at the center of the billet and 13.5-14m from the liquid surface.

[0033] In this embodiment, a total of 1258 rolled products were produced, and the internal flaw detection pass rate was 98.9%.

[0034] Example 3

[0035] (1) The cross-section of the continuous casting billet in this embodiment is 200mm×200mm, and the main components are shown in Table 2;

[0036] Table 3 shows the main components and content (wt%) of medium-carbon high-sulfur steel.

[0037] element C Si Mn P S V N content 0.44 0.29 1.58 0.017 0.289 0.088 0.008

[0038] (2) All scrap steel electric furnace smelting is adopted, the steel output C is 0.06%, the steel output temperature is 1596℃, 1.65 kg / t of silicon-calcium-barium is added, and silicon-manganese alloy and high-carbon ferromanganese are used for alloying.

[0039] (3) In the LF process, the white slag time is 45 min, the bottom blowing argon flow rate is 550 NL / min, silicon carbide deoxidation is used, and the addition amount is 2.5 kg / t steel. Sulfurization is increased by adding pyrite, and the addition amount is 6.5 kg / t steel.

[0040] (4) In the RH process, the vacuum treatment time is 33 minutes. After breaking the vacuum, 0.7 m / t of Te wire is added, and the composition is finely adjusted by feeding in sulfur wire. The soft blowing time is 20 minutes. The above process can improve the purity of molten steel and improve the morphology of sulfide inclusions.

[0041] (5) In the continuous casting process, the electromagnetic stirring current of the crystallizer is 330A and the frequency is 3Hz. The electromagnetic stirring current frequencies at the solidification end are 350A and 15Hz, respectively. The reduction amount of the light reduction process is 10.5mm. The reduction range is selected between 0.45-0.8 solid fraction at the center of the billet and 11.5-13m from the liquid surface.

[0042] In this embodiment, a total of 1258 rolled products were produced, and the internal flaw detection pass rate was 98.9%.

[0043] Example 4

[0044] (1) The cross-section of the continuous casting billet in this embodiment is 200mm×200mm, and the main components are shown in Table 2;

[0045] Table 4. Main components and content (wt%) of medium-carbon high-sulfur steel

[0046] element C Si Mn P S V N content 0.45 0.40 1.57 0.019 0.226 0.125 0.008

[0047] (2) All scrap steel electric furnace smelting is adopted, the steel output C is 0.06%, the steel output temperature is 1599℃, 1.7 kg / t of silicon-calcium-barium steel is added, and silicon-manganese alloy and high-carbon ferromanganese are used for alloying.

[0048] (3) In the LF process, the white slag time is 45 min, the bottom blowing argon flow rate is 550 NL / min, silicon carbide deoxidation is used, and the addition amount is 2.6 kg / t steel. Sulfurization is increased by adding pyrite, and the addition amount is 6.7 kg / t steel.

[0049] (4) In the RH process, the vacuum treatment time is 33 min, after which 0.7 m / t of Te wire is added, sulfur wire is fed in to fine-tune the composition, and the soft blowing time is 17 min. The above process can improve the purity of molten steel and improve the morphology of sulfide inclusions.

[0050] (5) In the continuous casting process, the electromagnetic stirring current of the crystallizer is 310A and the frequency is 2.8Hz. The electromagnetic stirring current frequencies at the solidification end are 360A and 12Hz, respectively. The reduction amount of the light reduction process is 9.5mm. The reduction range is selected between 0.3-0.8 solid fraction at the center of the billet and 11.5-13m from the liquid surface.

[0051] In this embodiment, a total of 1258 rolled products were produced, and the internal flaw detection pass rate was 98.9%.

[0052] Example 5

[0053] (1) The cross-section of the continuous casting billet in this embodiment is 200mm×200mm, and the main components are shown in Table 3;

[0054] Table 5. Main components and content (wt%) of medium-carbon high-sulfur steel

[0055] element C Si Mn P S V N content 0.60 0.30 1.65 0.014 0.20 0.150 0.009

[0056] (2) All scrap steel electric furnace smelting is adopted, the steel output C is 0.05%, the steel output temperature is 1610℃, 1.9 kg / t of silicon-calcium-barium steel is added, and silicon-manganese alloy and high-carbon ferromanganese are used for alloying.

[0057] (3) In the LF process, the white slag time is 50 min, the bottom blowing argon flow rate is 600 NL / min, silicon carbide deoxidation is used, and the addition amount is 2.7 kg / t steel. Sulfurization is increased by adding pyrite, and the addition amount is 6.9 kg / t steel.

[0058] (4) In the RH process, the vacuum treatment time is 35 minutes. After breaking the vacuum, 0.6 m / t of Te wire is added, and the composition is finely adjusted by feeding in sulfur wire. The soft blowing time is 15 minutes. The above process can improve the purity of molten steel and improve the morphology of sulfide inclusions.

[0059] (5) In the continuous casting process, the electromagnetic stirring current of the crystallizer is 300A and the frequency is 2.5Hz. The electromagnetic stirring current frequencies at the solidification end are 350A and 10Hz, respectively. The reduction amount of the light reduction process is 8.5mm. The reduction range is selected between 0.3-0.8 solid fraction at the center of the billet and 11.5-13m from the liquid surface.

[0060] In this embodiment, a total of 1,670 rolled products were produced, and the internal flaw detection pass rate was 98.6%.

[0061] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A steelmaking method for improving the segregation of sulfide centers in medium-carbon, high-sulfur steel, characterized in that, The production method includes: electric furnace smelting, LF refining, RH refining and continuous casting processes; in the RH refining process, the vacuum treatment time is 30-35 minutes, after breaking the vacuum, 0.6-0.9 m / t of Te wire is added, sulfur wire is fed in to fine-tune the composition, and the soft blowing time is 15-20 minutes. In the continuous casting process, the reduction amount of the light reduction process is 8.5-11.5 mm, and the reduction range is selected between 0.3-0.9 solid fraction at the center of the billet and 11.5-14 m from the liquid surface.

2. The steelmaking method for improving sulfide center segregation in medium-carbon high-sulfur steel according to claim 1, characterized in that, The composition and mass percentage of the medium-carbon high-sulfur steel are as follows: C: 0.4%-0.6%, Si: 0.2%-0.4%, Mn: 1.3%-1.7%, P<0.045%, S: 0.2%-0.35%, V: 0.05%-0.15%, N: 0.007%-0.009%, with the remainder being Fe and unavoidable impurities.

3. The steelmaking method for improving sulfide center segregation in medium-carbon high-sulfur steel according to claim 1, characterized in that, The electric furnace smelting process uses an all-scrap electric furnace for smelting, with the steel's carbon content controlled at 0.05-0.08% and the tapping temperature at 1590-1610℃. Silicon-calcium-barium alloy (1.5-1.9 kg / t) is added for deoxidation, and silicon-manganese alloy and high-carbon ferromanganese are used for alloying.

4. A steelmaking method for improving sulfide center segregation in medium-carbon high-sulfur steel according to claim 1, characterized in that, In the LF refining process, the white slag time is 40-50 min, the bottom-blown argon flow rate is 500-600 NL / min, silicon carbide deoxidation is used, and the addition amount is 1.9-2.7 kg / t steel. Sulfurization is achieved by adding pyrite, with an addition amount of 6.2-6.9 kg / t steel.

5. A steelmaking method for improving sulfide center segregation in medium-carbon high-sulfur steel according to any one of claims 1-4, characterized in that, In the continuous casting process, the cross-section of the continuously cast billet is 200mm×200mm, the electromagnetic stirring current of the crystallizer is 300-350A, and the frequency is 2.5-3Hz.

6. A steelmaking method for improving sulfide center segregation in medium-carbon high-sulfur steel according to any one of claims 1-4, characterized in that, In the continuous casting process, the electromagnetic stirring current frequencies at the solidification end are 350-400A and 10-15Hz, respectively.

7. A steelmaking method for improving sulfide center segregation in medium-carbon high-sulfur steel according to any one of claims 1-4, characterized in that, The ultrasonic internal flaw detection pass rate of the medium carbon high sulfur steel can be stably maintained at over 97%.