A method for controlling the TFe content in tundish slag during the continuous casting process of IF steel

Abstract

This invention belongs to the field of metallurgy, and particularly relates to a method for controlling the TFe content in tundish slag during the continuous casting of IF steel, comprising the following steps: a) recording the weight W1 of the tundish covering agent added to the impact zone during the initial casting of IF steel in the tundish; b) taking slag samples in the impact zone of the tundish during the middle of each ladle casting process; c) detecting the TFe mass percentage C of the slag samples. i ;d) If C i If the content is ≥3wt%, a modifier is added to the impact zone of the tundish during the (i+1)th heat of casting. The modifier consists of limestone and aluminum granules, with a mass ratio of limestone to aluminum granules of K:1. The modifier is packaged in bags, and the net weight of each bag is denoted as W0. The number of bags containing the modifier is denoted as N. i =0.32×W1×C i ×(K+1) / W0. The method provided by this invention can effectively reduce the TFe content in the ladle slag and reduce secondary oxidation pollution of molten steel without affecting the stability of the ladle steel casting process.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy, and particularly relates to a method for controlling the TFe content in the tundish slag during the continuous casting process of IF steel. Background Technology

[0002] In the continuous casting process, the tundish slag (formed by the tundish covering agent) plays an important metallurgical role, including heat preservation, inclusion adsorption, steel purification, and preventing secondary oxidation of the steel upon contact with air. However, in the continuous casting of IF steel, due to the high total iron (TFe) content in the ladle top slag, which corresponds to its strong oxidizing properties, a portion of the ladle top slag containing a high TFe content enters the tundish (bottom slag) with the molten steel towards the end of the ladle casting process, leading to a continuous accumulation and increase of TFe in the tundish slag.

[0003] When the TFe content in the tundish slag accumulates to a high level, the highly oxidizing tundish slag comes into contact with the molten steel, causing secondary oxidation and affecting the cleanliness of the steel. Particularly in the tundish impact zone, the high-TFe content ladle top slag flowing in at the end of the ladle casting process is blocked by the side walls and cannot flow into the casting areas on both sides of the tundish. This leads to a rapid accumulation of TFe content in the tundish slag within the impact zone, resulting in severe secondary oxidation pollution of the molten steel during contact. Furthermore, the high-speed inflow of molten steel through the long nozzle creates intense impact and agitation in the tundish impact zone, further exacerbating the secondary oxidation pollution of the molten steel by the ladle slag in this area.

[0004] Therefore, in order to suppress the secondary oxidation pollution of molten steel by tundish slag in the tundish impact zone, it is necessary to develop corresponding tundish slag modification technologies to effectively control the TFe content of tundish slag while maintaining stable tundish operating conditions. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for controlling the TFe content in the tundish slag during the continuous casting process of IF steel. This method can effectively reduce the TFe content in the tundish slag and reduce secondary oxidation pollution of molten steel without affecting the stability of the tundish steel casting process.

[0006] This invention provides a method for controlling the TFe content in the tundish slag during the continuous casting process of IF steel, comprising the following steps:

[0007] a) When the IF steel in the tundish is first poured, record the weight of the tundish covering agent added in the impact zone, denoted as W1;

[0008] b) During the middle stage of each ladle casting, slag samples are taken from the impact zone of the tundish;

[0009] c) Detect the TFe mass percentage content of the slag sample, denoted as C. i i refers to the i-th furnace in the middle package;

[0010] d) If Ci If the content is ≥3wt%, then the modifier is added to the impact zone of the intermediate ladle when the i+1th furnace of the intermediate ladle is poured.

[0011] The modifier consists of limestone and aluminum granules, with a mass ratio of limestone to aluminum granules of K:1, where K = 4 to 6; the modifier is packaged in bags, and the net weight of each bag is denoted as W0.

[0012] The number of bags containing the modifier is denoted as N. i The calculation method is as follows: N i =0.32×W1×C i ×(K+1) / W0, when the calculation result is not an integer, the calculated value is rounded up to the nearest integer as the final result.

[0013] Preferably, the limestone has a particle size of 3-7 mm; the aluminum particles have a particle size of 2-4 mm.

[0014] Preferably, W0 ≤ 10 kg.

[0015] Preferably, the modifier is prepared according to the following steps: mixing limestone and aluminum granules, packaging them, and obtaining the modifier.

[0016] Preferably, the mixing is carried out in a mixer; the ratio of the nominal volume of the mixer to the total volume of the limestone and aluminum particles is ≥5:1; the mixing speed is 60-90 r / min; and the mixing time is ≥20 min.

[0017] Preferably, the amount of the slag sample taken is ≥100g.

[0018] Preferably, the slag sample is cooled and ground before testing to obtain slag powder.

[0019] Preferably, the particle size of the slag powder is ≤200 mesh.

[0020] Preferably, the detection device is a handheld spectrometer.

[0021] Preferably, the modifier is added around the long nozzle of the intermediate package impact zone.

[0022] Compared with the prior art, the present invention provides a method for controlling the TFe content in tundish slag during the continuous casting of IF steel, comprising the following steps: a) recording the weight of the tundish covering agent added to the impact zone during the initial casting of IF steel in the tundish, denoted as W1; b) taking slag samples in the impact zone of the tundish during the middle of each ladle casting process; c) detecting the TFe mass percentage content of the slag sample, denoted as C. i d) If C iIf the content is ≥3wt%, a modifier is added to the impact zone of the tundish during the (i+1)th heat of casting. The modifier consists of limestone and aluminum granules, with a mass ratio of limestone to aluminum granules of K:1, where K = 4-6. The modifier is packaged in bags, and the net weight of each bag is denoted as W0. The number of bags containing the modifier is denoted as N. i The calculation method is as follows: N i =0.32×W1×C i ×(K+1) / W0, when the calculation result is not an integer, the calculated value is rounded up to the nearest integer as the final result. Based on the composition and production process characteristics of IF steel, this invention designs a special modifier for reducing TFe in tundish slag, which can ensure slag-forming performance while avoiding erosion of the tundish refractory material. Furthermore, based on production process data such as the TFe content of the tundish slag during steel casting, a method for controlling the TFe content of the tundish slag, including a method for calculating the theoretical amount of the modifier, is proposed. The method provided by this invention can effectively reduce the TFe content of the tundish slag and reduce secondary oxidation pollution of molten steel without affecting the stability of the tundish steel casting process. In addition, the modified tundish slag has strong Al2O3 inclusion adsorption performance, which helps to further improve the ability of the tundish slag to purify molten steel. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a method for controlling the TFe content in the tundish slag during the continuous casting process of IF steel, comprising the following steps:

[0025] a) When the IF steel in the tundish is first poured, record the weight of the tundish covering agent added in the impact zone, denoted as W1;

[0026] b) During the middle stage of each ladle casting, slag samples are taken from the impact zone of the tundish;

[0027] c) Detect the TFe mass percentage content of the slag sample, denoted as C. i i refers to the i-th furnace in the middle package;

[0028] d) If C i If the content is ≥3wt%, then the modifier is added to the impact zone of the intermediate ladle when the i+1th furnace of the intermediate ladle is poured.

[0029] The modifier consists of limestone and aluminum granules, with a mass ratio of limestone to aluminum granules of K:1, where K = 4 to 6; the modifier is packaged in bags, and the net weight of each bag is denoted as W0.

[0030] The number of bags containing the modifier is denoted as N. i The calculation method is as follows: N i =0.32×W1×C i ×(K+1) / W0, when the calculation result is not an integer, the calculated value is rounded up to the nearest integer as the final result.

[0031] In the method provided by this invention, the composition of the intermediate covering agent preferably includes Al2O3, CaO, MgO, and SiO2; wherein, the content of Al2O3 is preferably 30-40 wt%, specifically 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, or 40 wt%; the content of CaO is preferably 40-50 wt%, specifically 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, or 40 wt%. The content of MgO is preferably 10-20 wt%, specifically 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%; the content of SiO2 is preferably 2-10 wt%, specifically 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%.

[0032] In the method provided by the present invention, the amount of the intermediate covering agent added is preferably 200-800 kg, specifically 200 kg, 250 kg, 300 kg, 350 kg, 400 kg, 450 kg, 500 kg, 550 kg, 600 kg, 650 kg, 700 kg, 750 kg or 800 kg.

[0033] In the method provided by the present invention, the sampling amount of the slag sample is preferably ≥100g, more preferably 100-300g, and specifically can be 100g, 120g, 150g, 170g, 200g, 230g, 250g, 270g or 300g.

[0034] In the method provided by the present invention, the slag sample is preferably cooled and ground before testing to obtain slag powder; the particle size of the slag powder is preferably ≤200 mesh.

[0035] In the method provided by the present invention, the detection device is preferably a handheld spectrometer.

[0036] In the method provided by this invention, if C i≥3wt% indicates that due to the slag discharge from the ladle and the high TFe content in the slag in the impact zone of the tundish, the slag has strong oxidizing properties and is prone to secondary oxidation pollution of the molten steel. It is necessary to add a modifier to reduce the TFe content.

[0037] In the method provided by the present invention, the CaO content of the limestone in the modifier is preferably ≥50wt%, more preferably 50-55wt%, specifically 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, or 55wt%; the SiO2 content of the limestone is preferably ≤5wt%, more preferably 0.5-5wt%, specifically 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, or 5wt%; and the particle size of the limestone is preferably 3-7mm.

[0038] In the method provided by the present invention, the Al content of the aluminum particles in the modifier is preferably ≥95wt%, more preferably 95-99wt%, specifically 95wt%, 96wt%, 97wt%, 98wt%, or 99wt%; the particle size of the aluminum particles is preferably 2-4mm.

[0039] In the method provided by the present invention, the mass ratio of limestone to aluminum particles in the modifier is (4-6):1, specifically 4:1, 4.2:1, 4.5:1, 4.7:1, 5:1, 5.2:1, 5.5:1, 5.7:1 or 6:1.

[0040] In the method provided by the present invention, the net weight W0 of each bag of the modifier is preferably ≤10kg, more preferably 0.5-10kg, and specifically can be 0.5kg, 1kg, 2kg, 3kg, 4kg, 5kg, 6kg, 7kg, 8kg, 9kg or 10kg.

[0041] In the method provided by the present invention, the modifier is preferably prepared according to the following steps: mixing limestone and aluminum granules, packaging them, and obtaining the modifier. The mixing is preferably carried out in a mixer; the ratio of the nominal volume of the mixer to the total volume of the limestone and aluminum granules is preferably ≥5:1, more preferably (5-15):1, specifically 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1; the mixing speed is preferably 60-90 r / min, specifically 60 r / min, 65 r / min, 70 r / min, 75 r / min, 80 r / min, 85 r / min or 90 r / min; the mixing time is preferably ≥20 min, more preferably 20-90 min, specifically 20 min, 30 min, 40 min, 50 min, 60 min, 65 min, 70 min, 80 min or 90 min.

[0042] In the method provided by the present invention, the modifier is preferably added around the long nozzle of the intermediate impact zone to avoid the added modifier from stacking up, which would affect the modification effect and the slag formation in the impact zone.

[0043] The technical solution provided by this invention, based on the composition and production process characteristics of IF steel, designs a special modifier for reducing TFe in tundish slag, which can ensure slag-forming performance while avoiding erosion of the tundish refractory material. Furthermore, based on production process data such as the TFe content of the tundish slag during steel casting, a method for controlling the TFe content of the tundish slag, including a method for calculating the theoretical amount of modifier, is proposed. The technical solution provided by this invention can effectively reduce the TFe content of the tundish slag and reduce secondary oxidation pollution of molten steel without affecting the stability of the tundish steel casting process. In addition, the modified tundish slag has strong Al2O3 inclusion adsorption properties, which helps to further improve the tundish slag's ability to purify molten steel.

[0044] For clarity, the following examples will be used to provide a detailed description.

[0045] Example 1

[0046] Under the converter LD→vacuum RH→continuous casting CC process, slag modification of 10 heats of IF steel in a single tundish:

[0047] (I) Preparation of the modifier:

[0048] (1) The raw materials for preparing the modifier are limestone and aluminum granules. The weight ratio of limestone to aluminum granules is K:1, K=5. The properties of the two raw materials are shown in Table 1:

[0049] Table 1 Raw material composition and properties

[0050]

[0051] (2) Add the above raw materials to the mixer in proportion and mix well. The ratio of the nominal volume of the mixer to the volume of the raw materials is 12:1. The mixing time is 25 minutes and the mixer speed is 65 r / min. Fluorite, sodium salt and other co-solvents are prohibited during the process.

[0052] (3) The mixed modifier is packaged into small bags, each weighing W0 = 5 kg.

[0053] (II) Modifier addition process:

[0054] (1) When the IF steel is poured into the tundish, record the weight of the tundish covering agent added to the impact zone: W1 = 400 kg; the composition of the tundish covering agent used is shown in Table 2:

[0055] Table 2 shows the composition of the coating agent (unit: wt%).

[0056] <![CDATA[Al2O3]]> High MgO <![CDATA[SiO2]]> 34.1 44.4 15.2 6.3

[0057] (2) During the middle stage of each ladle casting, take about 150g of slag sample from the impact zone of the ladle, cool it, and then quickly grind it into powder using an automatic grinder. The powder particle size is ≤200 mesh.

[0058] (3) The TFe content of the slag sampled in step (2) was determined by handheld spectrometer; the results showed that the content of the slag in the 3rd, 6th and 9th furnaces of the slag was higher than 3%, reaching C3=3.7%, C6=3.1% and C9=4.2% respectively.

[0059] (4) Since C3, C6, and C9 all exceed 3%, it indicates that a modifier needs to be added for modification. The amount of modifier added is as follows:

[0060] N3 = 0.32 × W1 × C3 × (K+1) / W0 = 0.32 × 400 × 3.7% × (5+1) / 5 = 6 bags;

[0061] N6 = 0.32 × W1 × C3 × (K+1) / W0 = 0.32 × 400 × 3.1% × (5+1) / 5 = 5 bags;

[0062] N9 = 0.32 × W1 × C3 × (K+1) / W0 = 0.32 × 400 × 4.2% × (5+1) / 5 = 7 bags;

[0063] In the above formula, when the calculation result is not an integer, the calculated value is rounded up to the nearest integer as the final result;

[0064] (5) Based on the results of step (4), it can be determined that in order to reduce the TFe in the slag of the tundish in the impact zone, 6 bags, 5 bags and 7 bags of modifier should be taken respectively and quickly added to the impact zone of the tundish at the time of casting of the 4th, 7th and 10th heats of the tundish. When adding, the modifier should be evenly distributed around the long nozzle to avoid the added modifier from stacking up, which would affect the modification effect and the slag formation in the impact zone.

[0065] After applying the technology of this embodiment, the refractory erosion in the impact zone of the tundish slag modification process is normal, the slag-forming performance of the tundish slag is good, no crusting occurs, the TFe in the slag in the impact zone of the tundish is stably controlled within 3%, and the average [Al]s (acid-soluble aluminum, representing the aluminum content in the molten steel) burn-off from the RH outlet to the continuous casting tundish is reduced from 73ppm before application to 57ppm.

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of controlling the TFe content of the tundish slag in an IF steel continuous casting process, characterized in that, It comprises the following steps: a) recording the weight of the covering agent added in the tundish impact area at the beginning of pouring, denoted as W1; b) taking a slag sample in the tundish impact area at the middle stage of pouring each ladle; c) detecting the TFe mass percentage of the slag sample, denoted C i , i denotes the i-th ladle d) if C i ≥ 3 wt%, adding a modifying agent to the tundish impact zone at the start of the tundish of the i+1th ladle The components of the modifier are limestone and aluminum particles, the mass ratio of the limestone and aluminum particles is K:1, K=4-6; the modifier is bagged, and the net weight of each bag is denoted as W0; The number of bags of the modifier added is denoted as N i The calculation method is: N i = 0.32 x W1 x C i x (K+1) / W0, and when the calculation result is not an integer, then the calculation value is rounded up as the final result.

2. The method of claim 1, wherein, The particle size of the limestone is 3-7 mm; the particle size of the aluminum particles is 2-4 mm.

3. The method of claim 1, wherein, W0≤10 kg.

4. The method of claim 1, wherein, The modifier is prepared according to the following steps: Mixing the limestone and aluminum particles, bagging, and obtaining the modifier.

5. The method of claim 4, wherein, The mixing is carried out in a mixer; the ratio of the nominal volume of the mixer to the total volume of the limestone and aluminum particles is ≥5:1; the stirring speed of the mixing is 60-90 r / min; and the stirring time of the mixing is ≥20 min.

6. The method of claim 1, wherein, The sampling amount of the slag sample is ≥100 g.

7. The method of claim 1, wherein, The slag sample is cooled and ground to obtain a slag sample powder before detection.

8. The method of claim 7, wherein, The particle size of the slag sample powder is ≤200 mesh.

9. The method of claim 1, wherein, The equipment used for the detection is a handheld spectrometer.

10. The method of claim 1, wherein, The modifier is added around the long nozzle of the tundish impact area.

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