Method for prolonging service life of refractory furnace cover of LF (ladle furnace)

Abstract

The invention relates to a method for prolonging the service life of a refractory furnace cover of an LF (Ladle Furnace), which belongs to the technical field of steel smelting and comprises the following steps: the tapping temperature of a converter is not less than 1600 DEG C, and 400kg of lime and 1000kg of calcium aluminate slagging agent are added to form a slag layer with the thickness of 200-300mm; the electrifying interval from converter tapping to the LF refining furnace is smaller than or equal to 15 min; short electric arc slagging is adopted 10 min before LF electrification; in the heating process, about 300 kg of lime is supplemented in batches; sampling for 2-3 times every 10-15 minutes after early-stage slagging, and adjusting the components; and after the temperature reaches the standard, electrode voltage is reduced for heat preservation to avoid power-off cooling. The service life of the refractory furnace cover can be remarkably prolonged, practice verifies that the service life of the refractory furnace cover is prolonged by 4-5 times compared with that of traditional operation, the replacement frequency is reduced, and production continuity is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and in particular to a method for improving the service life of the refractory furnace cover of an LF refining furnace by optimizing production operations. Background Technology

[0002] The LF refining furnace is a key piece of equipment in steelmaking for refining molten steel. Its refractory furnace cover, as a core component, must withstand the high-temperature radiation of the electrode arc, the physical impact of splashing slag, the thermal stress of sudden temperature changes, and the chemical corrosion of the slag over extended periods. The lifespan of the refractory furnace cover directly affects the continuity and cost of refining production: an excessively short lifespan leads to frequent replacements, increasing the difficulty of production coordination; untimely replacement can also damage equipment such as the furnace top water-cooling pipes.

[0003] In existing technologies, improvements to the lifespan of refractory furnace covers mostly focus on material upgrades or structural design. For example, Chinese patent CN201621099632.9 improves lifespan by embedding anchors in the inner wall of the furnace cover and adding internal reinforcing ribs; Chinese patent CN201821114593.4 enhances strength by adding perforated rings to the electrode holes and reinforcing steel bars to the body; and Chinese patent CN201320663062.1 proposes a combined structural design to extend lifespan.

[0004] However, improper operation during the production process (such as excessive temperature drop in molten steel leading to slag crusting, high-temperature radiation from arc leakage, excessive slag splashing, and rapid heating and cooling of the furnace cover) is a significant cause of furnace cover peeling and cracking, yet this has long been overlooked. Therefore, there is an urgent need for a method to reduce furnace cover damage through systematic operational optimization to compensate for the shortcomings of existing technologies. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for improving the service life of refractory furnace covers of LF refining furnaces. The method aims to solve the problem of low service life and easy peeling and cracking of refractory furnace covers of LF refining furnaces caused by neglecting the optimization of production operations in the prior art. By standardizing the key operations in the converter tapping and LF refining process, the damage to the furnace cover caused by high temperature radiation, steel slag erosion and thermal stress is reduced, thereby significantly improving its service life.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for improving the service life of the refractory furnace cover of an LF refining furnace, which reduces damage to the refractory furnace cover by systematically standardizing the operation during the production process, thereby improving its service life, specifically including the following steps:

[0007] (1) The tapping temperature of the converter is required to be ≥1600℃, and the tapping slag material is 400kg lime and 1000kg slag-forming agent;

[0008] (2) The interval between the completion of steel tapping from the converter and the start of power supply to the LF refining furnace is ≤15min;

[0009] (3) Short electric arc slag making is used about 10 minutes before the LF refining furnace is powered on;

[0010] (4) During the heating process, add approximately 300 kg of lime in batches;

[0011] (5) After the initial slag formation in the LF refining furnace, samples are taken every 10 to 15 minutes to adjust the composition. The adjustment is carried out in 2 to 3 times to avoid adding too much at once.

[0012] (6) After the temperature meets the requirements, the electrode voltage level should be reduced to maintain the temperature, so as to avoid the operation of stopping the power supply to cool down after the temperature is too high in advance.

[0013] Furthermore, the present invention requires a converter tapping temperature of ≥1600℃, and the tapping slag material consists of 400kg lime and 1000kg slag-forming agent (the main component is calcium aluminate, and the slag layer thickness is 200-300mm), which can ensure sufficient refining slag thickness and good slag-forming effect.

[0014] Furthermore, the interval between the completion of steel tapping from the converter and the start of energizing the LF refining furnace is ≤15 minutes, thereby avoiding excessive temperature drop of molten steel due to excessive waiting time, which would lead to slag crust formation and affect the submerged arc effect and slag splashing during energization.

[0015] Furthermore, in the first 10 minutes or so after the LF refining furnace of this invention is powered on, a short electric arc is used for slag formation (reducing the electrode voltage). This is because continuous deoxidation of the slag surface is required during this period. A large amount of deoxidizing agents such as silicon carbide are added, and the slag formation is relatively poor. Therefore, a short electric arc is used to avoid damage to the refractory furnace cover caused by the high temperature radiation generated by the arc light leakage. After slag formation, the voltage can be appropriately increased for rapid heating.

[0016] Furthermore, during the heating process of this invention, approximately 300 kg of lime is added in batches. As the temperature of the LF refining process increases, the melting effect of the refining slag improves, and the slag layer thickness also becomes thinner. Therefore, by adding lime, the slag layer thickness is ensured, thereby avoiding affecting the electric arc submersion effect.

[0017] Furthermore, in the LF refining furnace of this invention, the composition is sampled and adjusted every 10 to 15 minutes after the initial slag formation, and the adjustment is carried out in 2 to 3 times to avoid adding too much at once. If too much is added at once, it will not only cause a large amount of steel slag to splash, but also cause the molten steel to be in continuous contact with air, resulting in secondary oxidation, which is not conducive to the submerged arc of the refining slag.

[0018] Furthermore, once the required temperature is met, the electrode voltage level needs to be reduced for heat preservation to avoid prematurely raising the temperature too high and then stopping the power supply to cool it down. This is because during this waiting period, the refractory furnace cover will be subjected to rapid heating and cooling, which is not conducive to the long-term use of the refractory.

[0019] The beneficial effect of this invention is that it solves the defects existing in the prior art.

[0020] 1. Reduce high-temperature radiation damage: Avoid initial arc leakage by using short-arc slag making (step 3), thereby reducing high-temperature radiation to the furnace cover;

[0021] 2. Reduce steel slag erosion: Control the thickness of the steel slag layer (step 1), add lime (step 4), and adjust the composition frequency (step 5) to ensure the effect of refining slag submerging arc and reduce the chemical erosion of the furnace cover by steel slag splashing.

[0022] 3. Mitigating thermal stress impact: Controlling the transfer time (step 2) avoids local high temperatures caused by slag crusting, and the heat preservation operation (step 6) avoids rapid cooling and heating of the furnace cover, reducing peeling and cracking.

[0023] 4. Significantly extended lifespan: Practical verification shows that the lifespan of refractory furnace covers can be increased by 4 to 5 times after adopting this method, reducing the replacement frequency and improving production continuity. Detailed Implementation

[0024] The effects of the present invention will be described in detail below with reference to specific embodiments and comparative examples. The tonnage and operating parameters of the LF refining furnace used in the embodiments are only examples and do not limit the scope of protection of the present invention.

[0025] Example 1 (120-ton LF refining furnace)

[0026] Operating steps:

[0027] 1. The tapping temperature of the converter is ≥1600℃ (100% compliance rate). When tapping, add 400kg lime + 1000kg slag-forming agent (calcium aluminate) and the slag layer thickness is 250mm.

[0028] 2. The average interval between steel tapping from the converter and LF energization is 13.6 minutes;

[0029] 3. For the first 10 minutes after energizing the LF, use a short arc to form slag with a voltage of 6 (310V) and a current of 3 (32.6A), and then adjust to a voltage of 4 (345V) for rapid heating.

[0030] 4. Lime was added in three batches during the heating process, with a total dosage of 316 kg;

[0031] 5. After slag formation, take samples every 12 minutes to adjust the composition, completing this process in two steps;

[0032] 6. After the temperature reaches the target, use 8 voltage levels (275V) and 3 current levels (32.6A) for heat preservation.

[0033] Results: After 1036 furnaces, the refractory furnace cover cracked and collapsed, requiring replacement.

[0034] Comparative Example 1 (120-ton LF refining furnace, without using the method of this invention)

[0035] Operating steps:

[0036] 1. Only 24% of the converters achieved a tapping temperature of ≥1600℃. When tapping, 600kg of lime and 300kg of slag-reducing agent were added, and the slag layer thickness was less than 150mm.

[0037] 2. The average interval between steel tapping from the converter and LF energization is 20.3 minutes;

[0038] 3. The LF is powered on using 4 voltage levels (345V) and 3 current levels (32.6A) throughout the entire process, without a short arc slag formation stage;

[0039] 4. Only 223 kg of lime is added at a time during the heating process;

[0040] 5. The ingredients are adjusted in one go;

[0041] 6. First, raise the temperature to 10-20°C above the required temperature, then turn off the power and wait for it to cool down.

[0042] Results: The refractory furnace cover developed severe cracks and collapsed after only 218 furnaces, with a lifespan of only 20% of that of Example 1.

[0043] Example 2 (100-ton LF refining furnace)

[0044] Operating steps:

[0045] 1. The tapping temperature of the converter is ≥1600℃ (compliance rate 98%). 380kg lime + 950kg slag-reducing agent (calcium aluminate) are added during tapping, and the slag layer thickness is 220mm.

[0046] 2. The average interval between steel tapping from the converter and LF energization is 12.8 minutes;

[0047] 3. For the first 10 minutes after energizing the LF, use a short arc to form slag with voltage level 5 (300V) and current level 2 (30.5A), and then adjust to voltage level 3 (330V) for rapid heating.

[0048] 4. Add lime twice during the heating process, for a total of 290 kg;

[0049] 5. After slag formation, take samples every 10 minutes to adjust the composition, completing this process in two steps;

[0050] 6. After the temperature reaches the target, use 7 levels of voltage (260V) and 2 levels of current (30.5A) for heat preservation.

[0051] Results: The refractory furnace cover developed slight cracks after 982 furnaces were produced and needs to be replaced.

[0052] Comparative Example 2 (100-ton LF refining furnace, without using the method of this invention)

[0053] Operating steps:

[0054] 1. The rate of achieving a converter tapping temperature ≥1600℃ is 35%. 500kg lime + 200kg slag-reducing agent are added during tapping, and the slag layer thickness is 120mm.

[0055] 2. The average interval between steel tapping from the converter and LF energization is 18.5 minutes;

[0056] 3. The LF is powered on using 3 voltage levels (330V) and 2 current levels (30.5A) throughout the entire process, without short arc slag formation;

[0057] 4. Add 200 kg of lime at once during the heating process;

[0058] 5. Ingredients adjusted in one go;

[0059] 6. If the temperature exceeds 10-15℃, then turn off the power to cool it down.

[0060] Results: The refractory furnace cover suffered severe collapse after only 195 furnaces, with a lifespan of only 20% of that of Example 2.

[0061] Example 3 (150-ton LF refining furnace)

[0062] Operating steps:

[0063] 1. The tapping temperature of the converter is ≥1600℃ (100% compliance rate). When tapping, add 420kg lime + 1050kg slag-forming agent (calcium aluminate) and the slag layer thickness is 280mm.

[0064] 2. The average interval between steel tapping from the converter and LF energization is 14.2 minutes;

[0065] 3. For the first 10 minutes after energizing the LF, use a short arc slag formation with a voltage of 7 (320V) and a current of 4 (35.0A), and then adjust to a voltage of 5 (360V) for rapid heating.

[0066] 4. Lime was added in three batches during the heating process, with a total dosage of 325 kg;

[0067] 5. After slag formation, take samples every 15 minutes to adjust the composition, completing this process in 3 steps;

[0068] 6. After the temperature reaches the target, use 9 voltage levels (290V) and 4 current levels (35.0A) for heat preservation.

[0069] Results: After 1120 furnaces of this refractory furnace cover were produced, local cracks appeared, and it needs to be replaced.

[0070] Comparative Example 3 (150-ton LF refining furnace, without using the method of this invention)

[0071] Operating steps:

[0072] 1. The rate of achieving a converter tapping temperature ≥1600℃ is 28%. 650kg lime + 400kg slag-reducing agent are added during tapping, and the slag layer thickness is 180mm.

[0073] 2. The average interval between converter tapping and LF energization is 22.1 minutes;

[0074] 3. The LF is powered on using 5 voltage levels (360V) and 4 current levels (35.0A) throughout the entire process, without short arc slag formation;

[0075] 4. Add 250 kg of lime at once during the heating process;

[0076] 5. Ingredients adjusted in one go;

[0077] 6. If the temperature exceeds 20-30℃, then turn off the power to cool it down.

[0078] Results: The refractory furnace cover collapsed over a large area after only 230 furnaces, and its lifespan was 20.5% of that of Example 3.

[0079] The above embodiments and comparative examples show that the present invention can significantly reduce damage to refractory furnace covers and greatly improve their service life by systematically optimizing key operations of converter tapping and LF refining. It is applicable to LF refining furnaces of different tonnages and has strong practicality and promotion value.

[0080] The above description is only a specific embodiment of the present invention. Various examples and illustrations do not constitute a limitation on the substantive content of the present invention. Those skilled in the art can make modifications or variations to the above-described specific embodiments after reading the specification without departing from the substance and scope of the invention.

Claims

1. A method for improving the service life of refractory furnace covers in LF refining furnaces, characterized in that: Includes the following steps, (1) The tapping temperature of the converter is required to be ≥1600℃, and the tapping slag material is 400kg lime and 1000kg slag-forming agent; (2) The interval between the completion of steel tapping from the converter and the start of power supply to the LF refining furnace is ≤15min; (3) Short electric arc slag making is used 10 minutes before the LF refining furnace is powered on; (4) During the heating process, add a total of 300 kg of lime in batches; (5) After the initial slag formation in the LF refining furnace, samples are taken every 10 to 15 minutes to adjust the composition, and the adjustment is carried out in 2 to 3 times; (6) After the temperature meets the requirements, the electrode voltage level should be reduced to maintain the temperature, so as to avoid the operation of stopping the power supply to cool down after the temperature is too high in advance.

2. The method for improving the service life of the refractory furnace cover of an LF refining furnace as described in claim 1, characterized in that: In step (1), the main component of the slag-reducing agent is calcium aluminate, and the slag layer thickness is 200-300 mm.

3. The method for improving the service life of the refractory furnace cover of an LF refining furnace as described in claim 1, characterized in that: In step (3), short arc slag formation is achieved by reducing the electrode voltage.

4. The method for improving the service life of the refractory furnace cover of an LF refining furnace as described in claim 3, characterized in that: In step (3), the short electric arc slag forming uses a voltage of 6 levels with a voltage value of 310V. After slag formation, the voltage is adjusted to level 4 with a voltage value of 345V for heating.

5. The method for improving the service life of the refractory furnace cover of an LF refining furnace as described in claim 3, characterized in that: In step (3), the heat preservation stage uses 8 voltage levels with a voltage value of 275V.