Low-fluorine high-calcium desulfurization slag system for electroslag remelting s-06 stainless steel and method of use thereof

Abstract

This invention relates to a low-fluorine, high-calcium desulfurization slag system for electroslag remelting S-06 stainless steel and its application method, belonging to the field of electroslag special metallurgical technology. It addresses the problems of high fluorine content and pollution in existing electroslag smelting slag systems, resulting in poor uniformity of the prepared steel ingots and uneven, thick slag skin. The mass percentage of each component in the low-fluorine, high-calcium desulfurization slag system of this invention is as follows: CaF2: 38.3%~42.1%, Al2O3: 23.2%~24.8%, CaO: 30.9%~32.8%, MgO: 1.0%~5.0%, SiO2: 0.8%~1.0%, C: 0.07%~0.1%, with the remainder being impurities. The slag system of this invention exhibits good metallurgical effects; when using this slag system for electroslag remelting S-06 stainless steel, the resulting steel ingots have a uniform elemental distribution and a uniform slag skin.

Description

Technical Field

[0001] This invention relates to the field of electroslag special metallurgy technology, and in particular to a low-fluorine, high-calcium desulfurization slag system for electroslag remelting S-06 stainless steel and its application method. Background Technology

[0002] S-06 stainless steel (07Cr15Ni5MoWVNb) possesses excellent strength and hardness, along with good toughness and wear resistance. It maintains stable mechanical properties at high temperatures, making it suitable for manufacturing bars, tubes, and plates for various mechanical applications. However, existing S-06 stainless steel smelting processes utilize slag systems with high fluoride content, poor component stability, susceptibility to fluctuations, and uneven, thick slag skin. Summary of the Invention

[0003] Based on the above analysis, the present invention aims to provide a low-fluorine, high-calcium desulfurization slag system for electroslag remelting S-06 stainless steel and its application method, in order to solve one of the following technical problems: the existing electroslag smelting slag system has a high fluoride content, resulting in poor uniformity of the prepared steel ingots and uneven and thick slag skin.

[0004] The objective of this invention is mainly achieved through the following technical solutions:

[0005] On the one hand, the present invention provides a low-fluorine, high-calcium desulfurization slag system for electroslag remelting S-06 stainless steel. The mass percentage of each component in the low-fluorine, high-calcium desulfurization slag system is as follows: CaF2: 38.3%~42.1%, Al2O3: 23.2%~24.8%, CaO: 30.9%~32.8%, MgO: 1.0%~5.0%, SiO2: 0.8%~1.0%, C: 0.07%~0.1%, and the remainder is impurities.

[0006] Furthermore, in the low-fluorine, high-calcium desulfurization slag system, the ratio of the C content to the minimum C content of 0.05% in S-06 stainless steel is ≤1.6.

[0007] Furthermore, in the low-fluorine, high-calcium desulfurization slag system, the ratio of Al2O3 content to the maximum Al content (0.1%) in S-06 stainless steel is 232~248.

[0008] Furthermore, in the low-fluorine, high-calcium desulfurization slag system, the ratio of SiO2 content to the maximum Si content of 0.6% in S-06 stainless steel is 1.33~1.67.

[0009] Furthermore, in the low-fluorine, high-calcium desulfurization slag system, the ratio of CaO content to the minimum residual Ca content (0.0015%) in S-06 stainless steel is 20600~21867.

[0010] Furthermore, in the low-fluorine, high-calcium desulfurization slag system, the ratio of CaO content to Al2O3 content is between 1.246 and 1.414.

[0011] Furthermore, the mass percentage of each component in the low-fluorine, high-calcium desulfurization slag system is as follows: CaF2: 38.3%~42%, Al2O3: 23.2%~24.8%, CaO: 30.9%~32.8%, MgO: 4.0%~5.0%, SiO2: 0.8%~1.0%, C: 0.06%~0.08%, with the remainder being impurities.

[0012] Furthermore, the melting point of the low-fluorine, high-calcium desulfurization slag system is 1290~1330℃; at 1600℃, its density is 2.64~2.66 g / cm³. 3 Its viscosity is 0.024~0.027 Pa·s, and its electrical conductivity is 1.96~2.68 S / cm.

[0013] The present invention also provides a method for using the above-mentioned low-fluorine, high-calcium desulfurization slag system for electroslag remelting of S-06 stainless steel, comprising the following steps: Step 1: Prepare a slag system using industrially pure CaF2, CaO, Al2O3, MgO, SiO2, and C in the specified mass percentages; Step 2: Pre-melt the prepared slag system, and after cooling, crush and seal the slag for storage; Step 3: Use the slag system obtained in Step 2 for the smelting of S-06 stainless steel.

[0014] Furthermore, in step 3, an electroslag furnace with an inert gas atmosphere protection function is used for smelting. The smelting process includes: Step 301: Load the melting electrode rods into the electroslag furnace crystallizer. The electrode composition should meet the composition requirements of S-06 stainless steel. Check and test the water, electricity, and gas systems of the electroslag furnace equipment and make them ready for use. Step 302: Before using electroslag smelting, pour the slag into the slag mixing hopper, stir and mix evenly, and set aside for later use; Step 303: After the electroslag furnace is ignited, the slag mixed with aluminum particles is added to the electroslag furnace crystallizer for electroslag smelting.

[0015] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. The slag system of this invention ensures good metallurgical performance stability by precisely controlling the content of each component, resulting in small fluctuations in the slag system composition. This guarantees that when using the slag system of this invention for electroslag remelting S-06 stainless steel, the resulting ingot has a uniform elemental distribution along its length, meets control standards, exhibits good surface quality, and a relatively uniform slag scale thickness distribution, with an average slag scale thickness of ≤1.7mm in the middle section of the ingot. For example, the C content difference between the ingot head and tail is less than 0.003% (e.g., 0.001%~0.003%); the Al content difference between the ingot head and tail is less than 0.004% (e.g., 0.001%~0.004%); the Si content difference between the ingot head and tail is less than 0.05% (e.g., 0.02%~0.04%); and the S content at both the ingot head and tail reaches less than 0.0013%, resulting in good desulfurization effect.

[0016] 2. The slag system of the present invention is pre-melted during use, which makes it easier to form relatively stable compounds between the slag system components, and thus less likely to cause large component fluctuations and performance differences during electroslag smelting.

[0017] 3. Compared with high-fluorine slag, the slag system of the present invention reduces environmental pollution and harm to the human body by significantly reducing CaF2 content, achieves excellent start-up effect by appropriately adjusting Al2O3 content, and improves desulfurization capacity by significantly increasing CaO content.

[0018] In this invention, the range of slag composition can be fine-tuned to achieve more preferred combinations, which is considered within the scope of protection of this invention. Some advantages of this invention will become apparent from the specification or may be learned by practicing the invention. Detailed Implementation

[0019] The embodiments of the present invention are described in detail below. These embodiments are used to illustrate the principles of the present invention and are not intended to limit the scope of the present invention.

[0020] This invention provides a low-fluorine, high-calcium desulfurization slag system for electroslag remelting S-06 stainless steel and its application method. The composition of the S-06 stainless steel, by mass percentage, is as follows: C: 0.05%~0.08%, Si≤0.6%, Mn≤0.6%, Cr: 13.5%~15.0%, Ni: 5.2%~5.7%, Cu≤0.25%, Mo: 0.8%~1.0%, W: 0.7%~1.0%, V: 0.15%~0.25%, Nb: 0.08%~0.15%, P<0.015%; S<0.01%, Al≤0.1%, residual Ca content 0.0015%~0.0045%, with the balance being iron and unavoidable impurity elements.

[0021] Existing slag systems for electroslag remelting S-06 stainless steel are mostly based on rough adjustments of slag composition according to production experience, lacking theoretical design rationality. The existing slag systems suffer from poor component stability, are prone to fluctuations, and have high fluoride content (≥65%). Therefore, after in-depth research, based on the alloying element system of S-06 stainless steel and the thermodynamic phase diagram of multi-element slag systems, and according to elemental balance and the matching of metal material / slag system properties, the inventors have provided a low-fluorine, high-calcium desulfurization slag system for electroslag remelting S-06 stainless steel. This slag system has a stable composition and structure, possesses advantages such as high-efficiency desulfurization and energy saving, and meets the requirements of electroslag melting of S-06 stainless steel.

[0022] Specifically, the mass percentage of each component in the low-fluorine, high-calcium desulfurization slag system used for electroslag remelting S-06 stainless steel is as follows: CaF2: 38.3%~42.1%, Al2O3: 23.2%~24.8%, CaO: 30.9%~32.8%, MgO: 1.0%~5.0%, SiO2: 0.8%~1.0%, C: 0.07%~0.1%, with the remainder being impurities.

[0023] Specifically, the low-fluorine, high-calcium desulfurization slag system used for electroslag remelting of S-06 stainless steel must meet at least one of the following relationships with the S-06 stainless steel material: 1) The ratio of the C content in the low-fluorine, high-calcium desulfurization slag system to the minimum C content of 0.05% in S-06 stainless steel is less than 1.6, for example, 1.2~1.6.

[0024] 2) The ratio of Al2O3 content in the low-fluorine, high-calcium desulfurization slag system to the maximum Al content of 0.1% in S-06 stainless steel is 232~248.

[0025] 3) The ratio of SiO2 content in the low-fluorine, high-calcium desulfurization slag system to the maximum Si content of 0.6% in S-06 stainless steel is 1.32~1.68.

[0026] 4) The ratio of the CaO content in the low-fluorine, high-calcium desulfurization slag system to the minimum residual Ca content (0.0015%) in S-06 stainless steel is 20600~21867.

[0027] 5) The ratio of CaO to Al2O3 in the low-fluorine, high-calcium desulfurization slag system is between 1.246 and 1.414.

[0028] Through in-depth research, the inventors discovered that when the C, Al2O3, and SiO2 in the aforementioned low-fluorine, high-calcium desulfurization slag system are correlated with the C, Al, and Si in S-06 stainless steel, the composition content in the steel ingot can be guaranteed to meet the requirements. Furthermore, elements such as V, Cr, Mn, Mo, W, Ni, Cu, and Nb in the stainless steel are difficult to oxidize, thus meeting desulfurization requirements. When only the C content in the slag is controlled without controlling Al2O3 and SiO2, it is easy for the Al content in the steel to be too high or the Si content to be too low. Conversely, when only Al2O3 and SiO2 in the slag are controlled while the C content is too high, it is easy for the C content in the steel to exceed the upper limit. Therefore, this invention employs a linked control of Al2O3 and SiO2.

[0029] It should be noted that the functions of each component in the above-mentioned low-fluorine, high-calcium desulfurization slag system are as follows: CaF2: CaF2 can lower the melting point and viscosity of slag in the slag system. Excessive CaF2 content can easily cause the volatilization of excess fluorides, while insufficient content will negatively impact the slag system's fluidity. Therefore, in this invention, the CaF2 content is controlled at 38.3%~42.1%.

[0030] Al2O3: Al2O3 can significantly reduce the electrical conductivity of slag, reduce power consumption, and improve productivity. Excessive Al2O3 content increases melting temperature and viscosity, making arc ignition difficult; excessively low content increases smelting power consumption. Therefore, in this invention, the Al2O3 content is controlled at 23.2%~24.8%.

[0031] CaO: The main function of CaO in the slag system is to increase the basicity of the slag and improve the desulfurization efficiency. Excessive CaO content can easily lead to the slag absorbing water and becoming damp, while insufficient CaO content will not achieve optimal desulfurization results. Therefore, in this invention, the CaO content is controlled at 30.9%~32.8%.

[0032] MgO: The role of MgO in the slag system of this invention is to prevent the slag system containing CaO from absorbing water and hydrogen during solid storage, and to reduce the permeability of H in the liquid slag state during the smelting process. MgO also reduces the oxygen and nitrogen content in the molten pool. Excessive MgO content can easily lead to increased slag viscosity, while insufficient MgO content is detrimental to slag system stability. Therefore, the MgO content is controlled at 1.0% to 5.0% in this invention.

[0033] SiO2: The role of SiO2 in the slag system of this invention is to improve the solidification quality of the slag skin on the surface of the electroslag ingot, making the ingot less prone to slag skin breakage and surface pitting. Excessive SiO2 content is detrimental to the stability of the slag system, while insufficient content results in poor improvement of slag skin thickness uniformity and smoothness. Therefore, the SiO2 content is controlled at 0.8%~1.0% in this invention.

[0034] C: In the slag system of this invention, C plays a role in enhancing the initial protective atmosphere of the slag and strengthening slag lubrication. Excessive C content can easily lead to carbon increase in the molten pool, while insufficient C content results in inadequate protective atmosphere during the smelting process, especially in the initial stage of power-on startup, due to the high CaO content, easily leading to nitrogen increase. Therefore, in this invention, the C content is controlled at 0.07%~0.1%.

[0035] In the low-fluorine, high-calcium desulfurization slag system of the present invention, the addition amounts of CaF2 and MgO are precisely controlled to be 38.3%~42.1% and 1.0%~5.0%, respectively, to ensure that the viscosity of the slag system of the present invention is 0.024~0.027 Pa·s at 1600℃. When the slag system of the present invention is smelted at this viscosity, the slag skin of the electroslag ingot is uniform, the average thickness of the slag skin is ≤1.7mm, and the slag skin is easy to peel off from the ingot body when the electroslag ingot is cooled after smelting.

[0036] Specifically, the melting point of the aforementioned low-fluorine, high-calcium desulfurization slag system is 1290~1330℃; at 1600℃, its density is 2.64~2.66 g / cm³. 3 The viscosity is 0.024~0.027 Pa·s, and the electrical conductivity is 1.96~2.68 S / cm. Using this slag system, the average slag skin thickness of the electroslag ingot body can be ≤1.7mm.

[0037] In the production of S-06 stainless steel using electroslag remelting, the physicochemical properties of the slag system affect the quality of the steel ingots, as follows: (1) Melting point: The melting point of slag affects the conductivity, viscosity, and calorific value of the slag system. Excessively high or low melting points are detrimental to physicochemical reactions such as dephosphorization and desulfurization, and can easily cause internal and surface quality problems in steel ingots, resulting in metallurgical defects such as voids, pores, and inclusions. In this invention, the melting point range is designed to be 1290~1330℃ to ensure uniform surface quality of the steel ingots, prevent surface porosity, and achieve good energy-saving effects.

[0038] (2) Viscosity: The viscosity of slag affects its circulation velocity. Due to the electromagnetic stirring force, low-viscosity slag will have a strong stirring effect, which can enhance the slag's fluidity, facilitate heat transfer, and also enhance the diffusion at the reaction interface. In this invention, the viscosity at 1600℃ is 0.024~0.027 Pa·s, ensuring that the steel slag in the smelting process has good fluidity, improving the heat and mass transfer efficiency in the furnace, and reducing energy loss. This ensures that the average thickness of the slag skin of the electroslag ingot is less than 1.7 mm.

[0039] (3) Density: The density of the slag system mainly determines the amount of slag used in the electroslag remelting process, the melting point penetration rate through the slag layer, and the residence time, thus determining the purification effect during the electroslag remelting process, as well as the ease of slag-metal separation. Therefore, selecting a suitable slag system density has a certain impact on the metallurgical quality of the electroslag remelting process. In this invention, the density at 1600℃ is 2.64~2.66 g / cm³. 3 This ensures uniform steel ingot quality and low impurity content, while also guaranteeing better separation between the steel ingot and the electroslag surface.

[0040] (4) Conductivity: In the entire electroslag remelting process, the slag pool can be regarded as a resistor, providing the necessary resistance heat for remelting. When the current, voltage, and effective area of ​​the slag pool are constant, the distance between the consumable electrode and the molten metal pool is proportional to the conductivity of the slag. If the conductivity is too low, the electrode spacing (distance between the consumable electrode and the molten metal pool) will be shortened. If the electrode spacing is too short, the electroslag remelting process will be unstable, and it will also affect the reaction time of the steel slag during the falling of small molten metal droplets, which is not conducive to the removal of inclusions. In this invention, the conductivity at 1600℃ is 1.96~2.68 S / cm, which provides sufficient heat transfer for the electroslag smelting process and ensures the smooth progress of the electroslag smelting process.

[0041] Preferably, the mass percentage of each component in the low-fluorine, high-calcium desulfurization slag system used for electroslag remelting S-06 stainless steel is as follows: CaF2: 38.3%~42%, Al2O3: 23.2%~24.8%, CaO: 30.9%~32.8%, MgO: 4.0%~5.0%, SiO2: 0.8%~1.0%, C: 0.06%~0.08%, with the remainder being impurities.

[0042] Through hot-state experiments and production research, this invention has found that the composition of the above-mentioned electroslag remains stable during long-term smelting.

[0043] On the other hand, the present invention also provides a method for using the above-mentioned low-fluorine, high-calcium desulfurization slag system for electroslag remelting of S-06 stainless steel, comprising the following steps: Step 1: Prepare a slag system using industrially pure CaF2, CaO, Al2O3, MgO, SiO2, and C in the specified mass percentages; Step 2: Pre-melt the prepared slag system. After pre-melting, the target composition of the slag is controlled within the specified composition range of the slag system of this invention. After cooling to 25~50°C, crush and seal for storage. Step 3: Use the slag system obtained in Step 2 for the smelting of S-06 stainless steel.

[0044] Specifically, in step 2 above, the prepared slag system is pre-melted using a heating furnace. The furnace temperature is raised to 1400~1450℃ and maintained for 40~45 minutes. After pre-melting, the target composition of the slag is controlled within the specified composition range of this invention. After cooling to 25~100℃, it is crushed using a crusher to crush it to a particle size ≤0.3cm and then sealed and stored in 10Kg / bag.

[0045] It should be noted that excessively high pre-melting holding temperatures can lead to severe furnace erosion and high carbon content in the slag, while excessively low temperatures can result in poor slag flowability at the furnace edges. Excessively long holding times increase smelting costs, while insufficient holding times lead to poor slag formation. Therefore, the holding temperature should be controlled at 1400~1450℃, for example, 1400℃, 1410℃, 1420℃, 1430℃, 1440℃, and 1450℃; the holding time should be 40~45min, for example, 40min, 41min, 42min, 43min, 44min, and 45min.

[0046] Specifically, in step 3 above, an electroslag furnace with an inert gas atmosphere protection function can be used for smelting. The smelting process includes: Step 301: Load the melting electrode rod into the electroslag furnace crystallizer. The electrode composition meets the composition requirements of S-06 stainless steel (where Si is controlled at the upper limit of S-06, and P and S are controlled at the lower limit). Grind the surface of the electrode rod to remove the peel, and make the surface glossy without oxide layer. Then it is ready for use. Check and test the water, electricity and gas systems of the electroslag furnace equipment. It is ready for use. Step 302: Before using the electroslag smelting, unseal the sealed slag material and pour it into the slag mixing hopper. Add 30-50g of aluminum granules, stir and mix evenly, and set aside for use. Step 303: After the electroslag furnace is ignited, the slag mixed with aluminum particles is added to the electroslag furnace crystallizer for electroslag smelting.

[0047] Specifically, in step 303 above, approximately 5-10 minutes after the arc is ignited, slag mixed with aluminum particles is slowly added to the electroslag furnace crystallizer. The amount of slag added within 10 minutes should not exceed 90 kg. After the molten metal pool and slag pool are initially established, the remaining slag is added within one hour. The purpose of this operation is to avoid excessive slag inclusions in a short period, which could cause difficulties in melting the slag, after the molten metal pool and slag pool have formed in the electroslag crystallizer. Simultaneously, choosing a low slag addition rate and appropriately extending the slag addition time can, to some extent, delay the short-term oxidation and consumption of aluminum particles in the slag.

[0048] Specifically, in step 3 above, the design range of the main key process parameters is as follows: electrode diameter approximately 490~510mm, crystallizer diameter approximately 650~670mm, slag layer design approximately 140~160kg, the thickness of the arc-initiating bottom plate of the electroslag furnace crystallizer should reach more than 2.0cm, the power input during the arc-initiating stage is approximately 60~70 kW, the power input during the steady-state stage is 45~50 kW, and the average melting rate is approximately 7.5 kg / min.

[0049] Specifically, the smelting effect of step 3 above is as follows: the element distribution along the length of the steel ingot is uniform and meets the control standard, the surface quality is good, the slag thickness distribution is relatively uniform, and the average slag thickness in the middle section of the steel ingot is ≤1.7mm.

[0050] Examples 1-3 Examples 1-3 provide a low-fluorine, high-calcium desulfurization slag system for electroslag remelting S-06 stainless steel. The specific composition of the slag system is shown in Table 1 below.

[0051] The basic physical properties of the slag systems in Examples 1-3 are as follows: melting point of 1290~1330 ℃; density of 2.64~2.66 g / cm³ at 1600 ℃. 3 The viscosity is 0.024~0.027 Pa·s, and the electrical conductivity is 1.96~2.68 S / cm, as shown in Table 2 below.

[0052] The method of using the slag system in Example 1 includes the following steps: Step 1: Prepare a slag system using industrially pure CaF2, CaO, Al2O3, MgO, SiO2, and C in the specified mass percentages; Step 2: Pre-melt the prepared slag system using a heating furnace. Raise the furnace temperature to 1450℃ and maintain it for 40 minutes. After pre-melting, control the target composition of the slag within the specified composition range of this invention. After cooling to 30~50℃, crush it with a crusher until the particle size is ≤0.3cm. Seal and store it in 10Kg / bag. Step 3: Use the slag system obtained in Step 2 for the smelting of S-06 stainless steel.

[0053] Specifically, in step 3 above, a 5t argon atmosphere-protected electroslag furnace can be used for smelting. The smelting process includes: Step 301: Load approximately 4.8t of melting electrode rods into the electroslag furnace crystallizer. The electrode composition should meet the requirements of S-06 stainless steel (where Al is controlled within the upper limit of S-06, and P and S are controlled within the lower limit). Grind and remove the peel from the surface of the electrode rods until they are glossy and free of oxide layer. Then, check and test the water, electricity, and gas systems of the electroslag furnace equipment. Once they are ready for use, proceed with the process. Step 302: Before using the electroslag smelting, unseal the sealed slag material and pour it into the slag mixing hopper. Add 30-40g of aluminum granules, stir and mix evenly, and set aside for use. Step 303: After the electroslag furnace is ignited, the slag mixed with aluminum particles is added to the electroslag furnace crystallizer for electroslag smelting.

[0054] Specifically, in step 303 above, about 10 minutes after the arc is started, slag mixed with aluminum particles is slowly added to the electroslag furnace crystallizer. The amount of slag added within 10 minutes shall not exceed 70 kg. After the molten metal pool and slag pool are initially established, the remaining slag material shall be added within 1 hour.

[0055] Specifically, in step 3 above, the design range of the main key process parameters is as follows: electrode diameter approximately 500 mm, crystallizer diameter approximately 660 mm, slag layer design approximately 150 kg, electroslag furnace crystallizer arc-initiating bottom plate thickness reaching more than 2.1 cm, arc-initiating stage power input approximately 65 kW, steady-state stage power input 45~50 kW, and average melting rate approximately 7.5 kg / min.

[0056] The method of using the slag system in Example 2 is generally the same as that in Example 1, except that: Step 1: Prepare a slag system using industrially pure CaF2, CaO, Al2O3, MgO, SiO2, and C in the specified mass percentages; Step 2: Pre-melt the prepared slag system using a heating furnace. Raise the furnace temperature to 1440℃ and maintain it for 42 minutes. After pre-melting, control the target composition of the slag within the specified composition range of this invention. After cooling to 30~50℃, crush it with a crusher until the particle size is ≤0.3cm. Seal and store it in 10Kg / bag.

[0057] Step 302: Before using the electroslag smelting, unseal the sealed slag material and pour it into the slag mixing hopper. Add 40-50g of aluminum granules, stir and mix evenly, and set aside for later use. The method of using the slag system in Example 3 is generally the same as that in Example 1, except that: Step 1: Prepare a slag system using industrially pure CaF2, CaO, Al2O3, MgO, SiO2, and C in the specified mass percentages; Step 2: Pre-melt the prepared slag system using a heating furnace. Raise the furnace temperature to 1400℃ and maintain it for 45 minutes. After pre-melting, control the target composition of the slag within the specified composition range of this invention. After cooling to 30~50℃, crush it with a crusher until the particle size is ≤0.3cm. Seal and store it in 10Kg / bag.

[0058] Specifically, the smelting effect of the above embodiments 1-3 is as follows: the element distribution along the length of the ingot is uniform and meets the control standard, the surface quality is good, the slag thickness distribution is relatively uniform, and the average slag thickness in the middle section of the steel ingot is ≤1.7mm.

[0059] Table 1. Partial Components of the Slag System

[0060] Table 2 Basic physical properties of slag systems

[0061] In this embodiment, samples were taken from both the ingot head and tail after smelting for chemical analysis of elemental content, as shown in Table 3 below. Table 3 shows that the steel ingots prepared in this embodiment have uniform composition. For example, the C content difference between the ingot head and tail is less than 0.003% (e.g., 0.001%~0.003%); the Al content difference is less than 0.004% (e.g., 0.001%~0.004%); the Si content difference is less than 0.05% (e.g., 0.02%~0.04%); and the S content at both the ingot head and tail is less than 0.0013%, indicating good desulfurization effect.

[0062] Table 3. Sampling and testing results from the beginning and end of the spindles / %

[0063] The inventors conducted extensive research during the research process, and some poorly performing solutions are now presented as comparative examples.

[0064] Comparative Example 1 This comparative example provides a slag system for electroslag remelting S-06 stainless steel. The specific composition of the slag system is approximately: CaF2: 68%~72%, Al2O3: 28%~32%, with the remainder being impurities.

[0065] The method of using the slag in this comparative example is the same as that in Example 1, and will not be repeated here.

[0066] After smelting in this comparative example, samples were taken from both the ingot head and tail for chemical analysis of elemental content, as shown in Table 4 below. The C content difference between the ingot head and tail in this comparative example reached 0.005%, the Al content difference reached 0.01%, and the Si content difference was 0.05%. The S content was relatively high. The compositional uniformity of this comparative example was worse than that of the example, resulting in poorer desulfurization performance.

[0067] Table 4. Sampling and testing results from the beginning and end of the spindle / %

[0068] Comparative Example 2 This comparative example provides a slag system for electroslag remelting S-06 stainless steel. The specific composition of the slag system is: CaF2: 65%, Al2O3: 18%, CaO: 8%, MgO: 8%, SiO2: 0.3%, C: 0.65%, with the remainder being impurities.

[0069] The method of using the slag system in this comparative example is the same as that in Example 1.

[0070] After smelting in this comparative example, samples were taken from both the ingot head and tail for chemical analysis of elemental content, as shown in Table 5 below. The compositional uniformity of this comparative example is worse than that of the example, resulting in poorer desulfurization performance.

[0071] Table 5. Sampling and testing results from the beginning and end of the spindles / %

[0072] Comparative Example 3 This comparative example provides a slag system for electroslag remelting S-06 stainless steel. The specific composition of the slag system is the same as that in Example 1, and will not be repeated here.

[0073] The method of using the slag system in this comparative example is the same as the overall steps in Example 1, except that: Step 3: Use the slag system obtained in Step 2 for the smelting of S-06 stainless steel.

[0074] Specifically, in step 3 above, a 5t argon atmosphere-protected electroslag furnace can be used for smelting. The smelting process includes: Step 301: Load approximately 4.8t of smelting electrode rods into the electroslag furnace crystallizer. The electrode composition meets the composition requirements of S-06 stainless steel (where Al is controlled at the upper limit of S-06, and P and S are controlled at the lower limit). The surface of the electrode rods is not polished or peeled, and the surface has an oxide layer. It is ready for use. Step 302: Before using the electroslag smelting, unseal the sealed slag material and pour it into the slag mixing hopper. Add 300-500g of aluminum granules, stir and mix evenly, and set aside for use. Step 303: After the electroslag furnace is ignited, the slag mixed with aluminum particles is added to the electroslag furnace crystallizer for electroslag smelting.

[0075] After smelting in this comparative example, samples were taken from both the ingot head and tail for chemical analysis of elemental content, as shown in Table 6 below. The compositional uniformity of this comparative example is worse than that of the example, resulting in poorer desulfurization performance.

[0076] Table 6. Sampling and testing results from the beginning and end of the spindles / %

[0077] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-fluorine, high-calcium desulfurization slag system for electroslag remelting S-06 stainless steel, characterized in that, The mass percentage of each component in the low-fluorine, high-calcium desulfurization slag system is as follows: CaF2: 38.3%~42.1%, Al2O3: 23.2%~24.8%, CaO: 30.9%~32.8%, MgO: 1.0%~5.0%, SiO2: 0.8%~1.0%, C: 0.07%~0.1%, with the remainder being impurities.

2. The low-fluorine, high-calcium desulfurization slag system according to claim 1, characterized in that, In the aforementioned low-fluorine, high-calcium desulfurization slag system, the ratio of the C content to the minimum C content of 0.05% in S-06 stainless steel is ≤1.

6.

3. The low-fluorine, high-calcium desulfurization slag system according to claim 1, characterized in that, In the low-fluorine, high-calcium desulfurization slag system, the ratio of Al2O3 content to the maximum Al content (0.1%) in S-06 stainless steel is 232~248.

4. The low-fluorine, high-calcium desulfurization slag system according to claim 1, characterized in that, In the aforementioned low-fluorine, high-calcium desulfurization slag system, the ratio of SiO2 content to the maximum Si content (0.6%) in S-06 stainless steel is 1.33 to 1.

67.

5. The low-fluorine, high-calcium desulfurization slag system according to claim 1, characterized in that, In the low-fluorine, high-calcium desulfurization slag system, the ratio of CaO content to the minimum residual Ca content (0.0015%) in S-06 stainless steel is 20600~21867.

6. The low-fluorine, high-calcium desulfurization slag system according to claim 1, characterized in that, In the low-fluorine, high-calcium desulfurization slag system, the ratio of CaO content to Al2O3 content is between 1.246 and 1.

414.

7. The low-fluorine, high-calcium desulfurization slag system according to claim 1, characterized in that, The mass percentage of each component in the low-fluorine, high-calcium desulfurization slag system is as follows: CaF2: 38.3%~42%, Al2O3: 23.2%~24.8%, CaO: 30.9%~32.8%, MgO: 4.0%~5.0%, SiO2: 0.8%~1.0%, C: 0.06%~0.08%, with the remainder being impurities.

8. The low-fluorine, high-calcium desulfurization slag system according to any one of claims 1 to 7, characterized in that, The melting point of the low-fluorine, high-calcium desulfurization slag system is 1290~1330℃; at 1600℃, its density is 2.64~2.66 g / cm³. 3 Its viscosity is 0.024~0.027 Pa·s, and its electrical conductivity is 1.96~2.68 S / cm.

9. A method of using the low-fluorine, high-calcium desulfurization slag system according to any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: Prepare the slag-based raw materials according to the mass percentage; Step 2: Pre-melt the prepared slag raw materials, and after cooling, crush and seal the slag for storage; Step 3: Use the slag system obtained in Step 2 for the smelting of S-06 stainless steel.

10. The method of use according to claim 9, characterized in that, The pre-melting holding temperature is 1400~1450℃.

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