A control method for increasing the service life of tundish slag line

Abstract

The present invention relates to the field of metallurgy technology, and specifically discloses a control method for improving the service life of a tundish slag line. The method comprises the following steps: 1) improving the masonry quality of the tundish slag line, selecting corrosion-resistant refractory materials, making the tundish lining free of cracks, and increasing the masonry thickness of the tundish slag line by 10 mm; 2) strictly implementing the baking system curve during tundish baking, and adopting a heating-insulation-heating curve mode; 3) controlling the timing of adding a covering agent when the tundish is poured; 4) accelerating the ladle changing time and controlling it to between 1 minute 30 seconds and 1 minute 50 seconds, and controlling the height of the molten steel liquid level during the ladle changing; 5) controlling the height of the molten steel in the tundish during normal casting to between 1000 mm and 1150 mm; 6) optimizing the molten steel casting temperature; and 7) using argon gas protection throughout the casting process. The method improves the purity of the molten steel and significantly reduces the non-metallic inclusions, thereby improving product quality, reducing product costs, and significantly improving economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a control method for improving the service life of a tundish slag line. Background Art

[0002] Stainless steel products are increasingly popular among users. Stainless steel has a wide range of uses and features strong corrosion resistance and good formability. Improving production efficiency and reducing costs are key constraints in stainless steel production for stainless steel manufacturers. To produce high-quality stainless steel products, the corrosion resistance of stainless steel must be enhanced, which in turn requires improving production efficiency and molten steel purity. However, the number of continuous casting furnaces for stainless steel is limited by the rapid erosion of the tundish slag line, the low number of continuous casting furnaces, the increased foreign inclusions in the tundish refractory material, the increased grinding costs, and the low casting yield rate. Therefore, a method is needed to increase the service life of the tundish slag line, increase the number of continuous casting furnaces and the purity of molten steel. This method can increase the number of continuous casting furnaces for stainless steel, reduce production costs and slab grinding costs, significantly reduce the content of non-metallic inclusions in molten steel, ensure the casting yield rate, and meet the requirements of downstream users. Summary of the Invention

[0003] In view of the problems existing in the prior art, the object of the present invention is to provide a control method for improving the service life of the tundish slag line.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a control method for improving the service life of the tundish slag line, comprising the following steps:

[0005] 1) Improve the masonry quality of the tundish slag line, select corrosion-resistant refractory materials, make the tundish lining crack-free, and increase the masonry thickness of the tundish slag line by 10mm;

[0006] 2) The tundish baking strictly follows the baking system curve, adopting the curve mode of heating-keeping-heating;

[0007] 3) Before pouring the tundish, purge the tundish with argon for 2-3 minutes to drive out the gas in the tundish and control the timing of adding the covering agent when pouring the tundish;

[0008] 4) Speed ​​up the ladle change time and control it within 1 minute 30 seconds to 1 minute 50 seconds, and control the molten steel level during the ladle change;

[0009] 5) The height of the molten steel in the normal casting tundish is controlled at 1000mm-1150mm;

[0010] 6) Optimize molten steel casting temperature;

[0011] 7) Argon gas protection is used throughout the casting process.

[0012] Specifically, the corrosion-resistant refractory material in step 1) is a corrosion-resistant coating material applied to the inner wall of the tundish.

[0013] Specifically, the baking temperature in step 2) is 1100-1150° C., and the middle package can be put into use only after the quality of the inner wall is confirmed through on-line inspection.

[0014] Specifically, the timing for adding the covering agent when the tundish starts pouring in step 3) is to start adding 200 kg of high-alkalinity covering agent when the tundish liquid level reaches 600 mm, and to start adding 200 kg of high-magnesium covering agent when the tundish liquid level reaches 1000 mm. After the covering agent melts, a corrosion-resistant protective film is formed on the inner wall of the tundish.

[0015] Specifically, when the ladle is replaced in step 4), the molten steel level is controlled at 750mm-850mm, and 20-40kg of high-magnesium covering agent is added to the tundish when the ladle is replaced. The high-magnesium covering agent of the tundish melts when heated to form a corrosion-resistant protective film on the ladle wall, effectively reducing the corrosion of the molten steel and the ladle wall.

[0016] Specifically, the optimization of the molten steel casting temperature in step 6) requires strict control of the superheat of the molten steel in the tundish, which is controlled at 15°C-25°C, and the temperature deviation of the upper and lower furnaces is controlled at 3°C-5°C to avoid high-temperature erosion of the high-temperature steel on the slag line of the tundish.

[0017] Specifically, the entire casting process in step 7) is protected by argon and the tundish is fully sealed with a cover, and the tundish refractory material is used to block the space between the cover and the tundish to isolate the contact between the air and the refractory material, thereby effectively avoiding the secondary oxidation of the molten steel and the oxidation of the refractory material.

[0018] The present invention has the following beneficial effects:

[0019] Control method for improving service life of tundish slag line designed by the present invention

[0020] (1) The corrosion resistance of the tundish slag line is improved, and the number of stainless steel continuous casting furnaces has increased exponentially;

[0021] (2) The purity of molten steel is improved, the non-metallic inclusions are ≤0.5 level and below, and the non-metallic inclusions of steel strips are ≤0.5 level and above, which improves the deep drawing performance of steel strips;

[0022] (3) The output of castings increases, and the number of head and tail billets decreases accordingly, which reduces the cost of grinding and casting refractory materials, and at the same time, the yield rate of slabs increases accordingly. DETAILED DESCRIPTION

[0023] The following is a clear and complete further detailed description of the technical solutions in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] Example 1:

[0025] The refractory materials used in the embodiments of the present invention are all conventional tundish refractory materials in the metallurgical field and can be purchased through commercial channels.

[0026] Step 1) Select corrosion-resistant coating material to improve the quality of the slag line of the tundish. The thickness of the slag line is increased by 10 mm. There are no defects such as cracks and peeling on the slag line and the inner wall.

[0027] Step 2) The tundish is baked in strict accordance with the baking system curve, adopting the curve mode of heating-keeping-heating-heating; to prevent the tundish from heating too fast during baking, which may cause cracks on the inner wall of the tundish. The tundish is inspected online to confirm the quality of the inner wall. The baking temperature is 1100-1150℃. It can be put into use only after meeting the above requirements.

[0028] Step 3): Before pouring, purge the tundish with argon for 2-3 minutes to drive out the gas in the tundish and reduce the oxidative corrosion of oxygen on the refractory material of the tundish.

[0029] Step 4): When the height of the molten steel in the tundish reaches 600mm, 200kg of high-alkalinity covering agent is added. When the liquid level in the tundish reaches 1000mm, 200kg of high-magnesium covering agent is added to form a corrosion-resistant protective film on the inner wall of the tundish.

[0030] Step 5): Accelerate ladle replacement time to 1 minute 30 seconds to 1 minute 50 seconds. The molten steel height should be no less than 750mm when changing ladles. Add 20kg-40kg of high-magnesium coating agent to the tundish during ladle replacement. The high-magnesium coating agent melts upon heating, forming a corrosion-resistant protective film on the ladle wall, effectively reducing erosion between the molten steel and the ladle wall. The molten steel height in the normal casting tundish is 1000mm-1150mm to prevent erosion at the slag line within the tundish.

[0031] Step 6): Strictly control the superheat of molten steel. The superheat of molten steel in the tundish should be between 15℃ and 25℃. The temperature deviation between the upper and lower furnaces should be controlled between 3℃ and 5℃ to avoid high temperature erosion of the slag line of the tundish by high temperature steel.

[0032] Step 7): Argon gas is used throughout the casting process to effectively isolate the contact between air and refractory materials and avoid secondary oxidation of molten steel.

[0033] After the implementation of this method, the number of continuous casting furnaces for stainless steel increased, the output of castings increased, non-metallic inclusions were ≤0.5 level, and the detection rate of non-metallic inclusions in steel strips was ≤0.5 level, reaching more than 95%, which improved the deep drawing performance of the steel strips. The number of head and tail billets was reduced accordingly, reducing the cost of grinding and the cost of refractory materials for castings, and at the same time, the yield rate of slabs was increased accordingly.

[0034] The present invention is not limited to the above-mentioned embodiments. Anyone should be aware that any structural changes made under the guidance of the present invention, and any technical solutions that are the same or similar to those of the present invention, fall within the scope of protection of the present invention.

[0035] The technology, shape, and structure not described in detail in the present invention are all well-known technologies.

Claims

1. A control method for improving the service life of the tundish slag line, characterized in that: The following steps are involved: 1) Improve the masonry quality of the tundish slag line, select corrosion-resistant refractory materials, make the tundish lining crack-free, and increase the masonry thickness of the tundish slag line by 10mm; 2) The tundish baking strictly follows the baking system curve, adopting the curve mode of heating-keeping-heating; 3) Before pouring, purge the tundish with argon for 2-3 minutes to drive out the gas inside the tundish. Control the timing of adding the covering agent when pouring. When the tundish liquid level reaches 600mm, start adding 200kg of high-alkalinity covering agent. When the tundish liquid level reaches 1000mm, start adding 200kg of high-magnesium covering agent. After the covering agent melts, it forms a corrosion-resistant protective film on the inner wall of the tundish. 4) Speed ​​up the ladle change time and control it within 1 minute 30 seconds to 1 minute 50 seconds, and control the molten steel level during the ladle change. The molten steel level is controlled at 750mm-850mm during the ladle change. When changing the ladle, add 20-40kg of high-magnesium covering agent to the tundish. The high-magnesium covering agent of the tundish melts under heat and forms a corrosion-resistant protective film on the ladle wall. 5) The height of the molten steel in the normal casting tundish is controlled at 1000mm-1150mm; 6) Optimize molten steel casting temperature; 7) Argon gas protection is used throughout the casting process.

2. The control method for improving the service life of the tundish slag line according to claim 1, characterized in that: The corrosion-resistant refractory material in step 1) is a corrosion-resistant coating material applied to the inner wall of the tundish.

3. The control method for improving the service life of the tundish slag line according to claim 1, characterized in that: The baking temperature in step 2) is 1100-1150° C. The middle package can be put into use only after the quality of the inner wall is confirmed after the package is inspected online.

4. The control method for improving the service life of the tundish slag line according to claim 1, characterized in that: The optimization of the molten steel casting temperature in step 6) requires strict control of the superheat of the molten steel in the tundish, the superheat is controlled at 15°C-25°C, and the temperature deviation of the upper and lower furnaces is controlled at 3°C-5°C.

5. The control method for improving the service life of the tundish slag line according to claim 1, characterized in that: The entire casting process in step 7) is protected by argon and the tundish is fully sealed with a cover, and the space between the cover and the tundish is blocked by refractory material to isolate the contact between air and the refractory material.