A method for smelting industrial pure iron

Abstract

The present invention discloses a method for smelting industrial pure iron, which reduces the non-ferrous elements in molten steel by adopting all-iron smelting, double-slag tapping, residual steel operation, dual-path LF+RH production to reduce the generation of Al2O3, a heating product in the RH treatment process, and protective pouring before continuous casting. Before converter blowing, padding is used, and slag is removed after treatment in the refining LF furnace to reduce the content of elements such as [Mn], [P], and [S] in the molten steel composition, thereby improving the purity of industrial pure iron. At the same time, fast feeding and strong oxidizing atmosphere are used during converter blowing, thereby eliminating the situation where spot blowing is required before smelting industrial pure iron. The method significantly improves the smelting process from the aspects of reducing the content of non-ferrous elements, avoiding rebound, improving converter conditions, smelting success rate, and simplicity of processing, operation, control, and use, and improves product quality and production efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for smelting industrial pure iron. Background Art

[0002] In the traditional process of smelting industrial pure iron, the contents of [Mn], [P], [S] and other elements are usually high. After the refining process is completed, the contents of [Mn], [P], [S] and other elements rebound during the continuous casting process. This rebound in composition not only causes an increase in non-ferrous elements in industrial pure iron, reducing the purity of industrial pure iron, but also increases the process cost. The added value of this type of steel is reduced, and the marginal benefit is greatly reduced.

[0003] In addition, the traditional industrial pure iron smelting method requires the converter to be blown before steel is produced. This operation has a great impact on the condition of the converter lining, especially the position of the furnace molten pool generally drops by 30 to 50 mm, which will cause irreversible damage to the converter lining. Summary of the invention

[0004] In order to overcome the defects of the above-mentioned prior art and solve the problem of increased rebound of elements such as [Mn], [P], [S] in the traditional industrial pure iron smelting composition and the impact on the converter lining, the present invention provides an innovative method for smelting industrial pure iron to achieve the goal of efficient, low-cost and sustainable smelting.

[0005] In order to achieve the above-mentioned invention object, the present invention provides a method for smelting industrial pure iron, which includes the following process flow: production preparation, molten iron pretreatment, converter smelting, ladle preparation, LF refining, RH refining, continuous casting and pouring, and the time from iron addition to pouring is controlled at 220 to 240 minutes; wherein, the molten iron pretreatment cycle is 50 to 70 minutes, the converter smelting cycle is 50 to 60 minutes, the LF refining cycle is 60 to 80 minutes, the RH refining cycle is 40 to 50 minutes, and 1 to 2 furnaces of RH tank washing are performed before production.

[0006] ① Production preparation: Optimize molten iron conditions, adopt full iron method for smelting, and add iron twice.

[0007] It is used as a tank for the ladle before the previous pouring or when other casting machines produce low carbon steel.

[0008] Stop the torpedo and scrap steel work one shift in advance before production to ensure high-quality molten iron conditions, ensure that the molten iron temperature is ≥1300℃, and the molten iron content is Mn≤0.12%, S≤0.030%, Ti≤0.040%, Cu≤0.010% by mass. The molten iron conditions select better grades of Ti, S, Cu, P and temperature. The converter is arranged to produce low-carbon steel for furnace washing. The scrap steel of the furnace washing furnace uses hanging rolling materials and must be discharged cleanly. The second furnace adopts the molten iron pretreatment method of silicon steel, and slag splashing is not allowed after steel is discharged.

[0009] By optimizing smelting raw materials, selecting high-quality molten iron conditions, limestone and sintered ore, selecting molten iron with low [Mn], [P], [S] and [Ti] contents before organizing converter production, and testing the impurity content of the same batch of limestone and sintered ore, the smelting success rate can be improved from the source of production and the external sources of non-ferrous elements can be reduced.

[0010] ②Pretreatment of molten iron:

[0011] The two furnaces of the furnace washing process were treated in the same way as silicon steel. After treatment, the molten iron [S] ≤ 0.0020% (pre-treatment sample), double slag removal, slag removal. Loading quantity control: The molten iron loading quantity is controlled according to the life of the ladle and is 193 ± 5 tons. Raw materials such as dolomite and sintering return ore are sent for inspection and testing the day before production to ensure that the quality of raw materials meets the process requirements.

[0012] ③ Converter smelting: before adding iron, add 1.5-2t of active lime and 1.5-2t of dolomite as padding; the cooling material is preferably active lime and dolomite (the quality meets the process requirements); followed by limestone and sintered return ore. Specifically, the mass content of sulfur in the limestone is required to be ≤0.0050%; the mass content of sulfur in the sintered return ore is required to be ≤0.0050%; the mass content of copper, lead, antimony, arsenic, tin and bismuth elements is ≤0.0040%.

[0013] The converter combined blowing model adopts 300Nm 3 / h flow mode. The slag discharge operation is carried out after about 4 to 5 minutes of steelmaking, and slag and steel samples are taken at the same time.

[0014] Active lime is added according to the requirements of finished product P. Active lime is added in two batches according to 130% of the calculated amount, with about 1 / 2 added before slag discharge and another 1 / 2 of the total amount added after slag discharge.

[0015] The converter is over-blown, and the slag is discharged again after stopping the blowing. The steel is tapped out in the same way. The steel is blown out when the final point P is high to ensure that the final oxygen is greater than 700ppm; the final temperature is controlled at 1620-1630℃.

[0016] Double slag stopper (slide plate), residual steel tapping. The converter is not deoxidized, and slag samples are taken for analysis at the end point; 500kg of ladle ash and 50-100kg of fluorite are added during the tapping process; 500kg of ladle ash is quantitatively calculated, and 50-100kg of fluorite is added according to the fluidity and elasticity of the molten steel.

[0017] ④ Ladle preparation tank:

[0018] The ladle is put into the tank for the first time to produce RH low carbon steel, without cover, and the slag is turned over; or a re-baking tank is used to ensure the cleanliness of the ladle. Use low carbon drainage agent.

[0019] ⑤LF refining:

[0020] During the heating process of the LF furnace, a total of 800 to 1000 kg of lime is added in batches. After each power-on, argon is blown for 3 to 5 minutes. If the slagging process is poor, 20 to 50 kg of fluorite is added. No deoxidation is done during the whole process. Slag samples and steel samples are taken before and after LF.

[0021] After the refining LF treatment is completed, a slag scooping pan is used to scoop out the slag, and then 300 kg of top slag modifier is added and the temperature is adjusted again.

[0022] During the refining process outside the furnace, the first pouring: the temperature after LF argon is controlled at 1640±5℃, the temperature before RH argon reaches 1630±5℃, the temperature after RH argon is controlled at 1610±5℃, and the RH temperature can be slightly increased. Subsequent heats: the temperature after LF argon is controlled at 1610±5℃, the temperature before RH argon reaches 1600±5℃, the temperature after RH argon is controlled at 1590±5℃, and the RH temperature can be slightly increased.

[0023] ⑥RH refining:

[0024] RH furnace deep decarburization for 15 to 20 minutes, deoxidation after decarburization, Alt after argon pouring of the first continuous pouring is controlled at 0.030 to 0.040%; Alt after argon pouring of subsequent furnaces is controlled at 0.020 to 0.030%; re-pressurization after net circulation time ≥6 minutes.

[0025] ⑦Continuous casting: superheat target is 35℃, casting speed target is 1.2m / min.

[0026] Ultra-low carbon protective slag is used for mold slag, and carbon-free tundish slag is used for tundish slag. The tail billet optimization does not exceed 8100mm, and the number of optimized billets does not exceed 2. After the billet is off the line, the "surrounding cooling" method is used to slowly cool the billet. The tundish is purged with argon before pouring.

[0027] The above technical solution adopts a new smelting mode, and reduces non-ferrous elements in molten steel in a variety of ways, such as adopting full iron smelting, double slag tapping, leftover steel operation, dual-path LF+RH production to reduce the generation of Al2O3, a heating product in the RH treatment process, and protective pouring before continuous casting. This can effectively solve the problem of rebound increase in components [Mn], [P], [S], etc., and reduce the content of non-ferrous elements at the same time.

[0028] Secondly, advanced smelting process technologies have been introduced, such as the use of padding before converter blowing, double slag smelting, and slag removal after treatment in the refining LF furnace; this can reduce the content of components [Mn], [P], [S], etc. in the molten steel and improve the purity of industrial pure iron.

[0029] Thirdly, by optimizing the charging and blowing process of the converter, the goal of rapid charging and strong oxidizing atmosphere in the blowing process is achieved, thereby eliminating the situation where spot blowing is required before steelmaking of industrial pure iron, and avoiding the impact of smelting industrial pure iron on the converter condition.

[0030] In addition, the present invention can improve the smelting success rate from the production source and reduce the external sources of non-ferrous elements by optimizing the smelting raw materials, selecting high-quality molten iron conditions, limestone and sintered ore, such as selecting molten iron with low contents of [Mn], [P], [S] and [Ti] before organizing converter production, and inspecting the impurity content of the same batch of limestone and sintered ore.

[0031] In summary, the method for smelting industrial pure iron of the present invention solves the problems of high content and rebound of components [Mn], [P], and [S] in traditional smelting methods, and the disadvantage of having to blow before steelmaking, through a new smelting mode, advanced smelting process technology, and optimization of smelting raw materials and other processing methods, and can be widely used in steelmaking plants.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] ① Reduction of non-ferrous element content: The novel smelting process technology and material selection system adopted by the present invention can effectively reduce the content of non-ferrous elements. By optimizing the smelting process, the non-ferrous element content of molten steel can be effectively controlled, thereby improving the quality and purity of pure iron.

[0034] ② Avoiding the rebound phenomenon of components: In the traditional smelting process, the rebound phenomenon often leads to an increase in the content of non-ferrous elements, reducing the smelting efficiency and product quality. However, the method of the present invention effectively avoids the occurrence of the rebound phenomenon by applying slag dredging technology and optimizing process parameters, thus ensuring the stability and continuity of the steelmaking process.

[0035] ③ Improve the converter condition: Since the present invention optimizes the converter smelting charging and blowing process, the purpose of rapid charging and strong oxidizing atmosphere in the blowing process is achieved, thereby eliminating the situation where spot blowing is required before steelmaking of industrial pure iron, and avoiding the influence of industrial pure iron smelting on the converter condition. By optimizing the converter operating parameters and smelting conditions, the temperature and gas composition in the converter are made more uniform and stable, effectively improving the controllability and operability of the steelmaking process.

[0036] ④ Improve the success rate of smelting: The process technology and the introduction of a consistent system adopted by the present invention significantly improve the success rate of smelting. Reducing the content of non-ferrous elements and avoiding rebound phenomena make the smelting process more stable and controllable, reduce the risk of smelting failure, and improve the success rate of smelting and the stability of product quality.

[0037] In summary, the method for smelting industrial pure iron of the present invention brings many beneficial effects in terms of reducing the content of non-ferrous elements, avoiding rebound, improving the condition of the converter, the smelting success rate, and the simplicity of processing, operation, control and use. It can significantly improve the smelting process of the steel plant and improve product quality and production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a trend chart of the reduction process of the non-ferrous element content in the molten steel by optimizing the full-process smelting method of industrial pure iron in the example. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with specific examples, but the present invention is not limited in any way. To avoid redundant description, the raw materials in the following examples are all commercially available products unless otherwise specified, and the methods used are all conventional methods unless otherwise specified.

[0040] A method for smelting industrial pure iron comprises the following process flow: production preparation, molten iron pretreatment, converter smelting, ladle preparation, LF refining, RH refining, continuous casting and pouring, and the time from iron addition to pouring is controlled within 220-240 minutes; wherein, the molten iron pretreatment cycle is 50-70 minutes, the converter cycle is 50-60 minutes, the LF refining cycle is 60-80 minutes, the RH refining cycle is 40-50 minutes, and the RH tank is washed once or twice before production.

[0041] ① Production preparation: optimize the molten iron conditions, adopt the full iron method for smelting, and add iron twice;

[0042] ② Hot metal pretreatment: Hot metal [S] after treatment ≤ 0.0020%;

[0043] ③ Converter smelting: before adding iron, add 1.5-2t of active lime and 1.5-2t of dolomite as padding;

[0044] ④ Ladle preparation tank: The ladle is put into the tank for the first time to produce RH low-carbon steel, and low-carbon drainage agent is used;

[0045] ⑤LF refining: After the treatment, use the slag tray to remove the slag, then add 300kg of top slag modifier and adjust the temperature again;

[0046] ⑥RH refining: RH furnace deep decarburization for 15-20min, deoxidation after decarburization, the Alt after the first pouring of argon is controlled at 0.030-0.040%; the Alt after the subsequent pouring of argon is controlled at 0.020-0.030%; re-pressurization after the net circulation time ≥6min;

[0047] ⑦Continuous casting: superheat target is 35℃, casting speed target is 1.2m / min.

[0048] Example

[0049] A method for smelting industrial pure iron, the specific process flow is:

[0050] ① Production preparation: The casting or other casting machines before production are scheduled to produce low-carbon steel, and the ladle is used as a tank. Stop the torpedo and scrap steel work one shift in advance before production to ensure high-quality molten iron conditions. The molten iron temperature is 1320℃, and the mass percentage of Mn in the molten iron is 0.11%, S: 0.028%, Ti: 0.034%, Cu: 0.003%. The full iron method is used for smelting, and iron is added twice. The converter is arranged to produce low-carbon steel for furnace washing. The scrap steel of the furnace washing furnace uses hanging rolling materials and must be discharged cleanly. The second furnace uses the molten iron pretreatment method of silicon steel, and slag splashing is not allowed after steel is discharged.

[0051] ② Pretreatment of hot metal: Both furnaces of the washing furnace are treated in the same way as silicon steel. After treatment, hot metal [S] ≤ 0.0020% (pretreatment sample), double slag removal is adopted, and the slag is removed cleanly. The amount of hot metal charged is controlled at 193 tons. The raw materials such as active lime, limestone, dolomite and sintering return ore are sent for inspection and testing the day before production to ensure that the quality of the raw materials meets the process requirements.

[0052] ③ Converter smelting: before adding iron, add 1.8t of active lime and 1.6t of dolomite as padding; limestone is selected as cooling material, and the mass content of sulfur in the limestone is 0.0050%. The converter double blowing model is selected as 300Nm 3 / h flow mode. The slag discharge operation is carried out after 5 minutes of steelmaking and smelting, and slag and steel samples are taken at the same time. Active lime is added according to the finished product P requirements. Active lime is added in two batches according to 130% of the calculated amount. About 1 / 2 is added before slag discharge, and 1 / 2 of the total amount is added after slag discharge. The converter is over-blown, and the slag is discharged again after stopping the blowing. The steel is discharged with equal samples. The steel is blown out when the end point P is high to ensure that the end point oxygen is greater than 700ppm; the end point temperature is controlled at 1625℃. Double slag tapping (slide plate) and residual steel tapping. The converter is not deoxidized, and slag samples are taken for analysis at the end point; 500kg of ladle ash and 50kg of fluorite are added during the steel tapping process.

[0053] ④ Ladle preparation tank: The ladle is put into the tank for the first production of RH low-carbon steel, without a cover and with the slag removed; or a re-baking tank is used to ensure the cleanliness of the ladle. Use a low-carbon drainage agent.

[0054] ⑤LF refining: During the heating process of the LF furnace, 1000kg of lime is added in batches. After each power-on, argon is blown for 5 minutes. If the slag formation is poor, 50kg of fluorite is added. No deoxidation is performed during the whole process. Slag samples and steel samples are taken before and after LF. After the LF refining treatment is completed, a slag scooping pan is used to scoop the slag, and then 300kg of top slag modifier is added, and the temperature is adjusted again.

[0055] During the refining process outside the furnace, the first pouring: LF argon after temperature 1640 ℃, RH argon before temperature 1630 ℃, RH argon after temperature 1610 ℃, RH can be slightly heated. Subsequent heats: LF argon after temperature 1610 ℃, RH argon before temperature 1600 ℃, RH argon after temperature 1590 ℃, RH can be slightly heated.

[0056] ⑥RH refining: RH furnace deep decarburization for 20 minutes, deoxidation after decarburization, Alt after argon in L1 furnace is controlled at 0.030%; Alt after argon in subsequent furnaces is controlled at 0.020%; re-pressurization after net cycle time of 8 minutes.

[0057] ⑦ Continuous casting: superheat target is 35℃, casting speed target is 1.2m / min. Ultra-low carbon protective slag is used for protective slag, and carbon-free tundish slag is used for tundish slag. The tail billet optimization does not exceed 8100mm, and the number of optimized billets does not exceed 2. After the billet is off the line, the "surrounding cooling" method is used to slowly cool the billet. The tundish is purged with argon before pouring.

[0058] In the embodiment, the process of reducing the content of non-ferrous elements in the molten steel is as follows: Figure 1 As shown, through the attached Figure 1 It can be seen that the non-ferrous element content in the molten steel can be reduced to 783ppm, which improves the smelting success rate of industrial pure iron and the purity of the product. The erosion of the converter lining has been significantly improved, the erosion depth has been shortened by about 30mm, and the number of continuous treatment furnaces of a single converter has been increased to more than 4 furnaces.

[0059] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for smelting industrial pure iron, characterized in that: The method comprises the following process flow: production preparation, molten iron pretreatment, converter smelting, ladle preparation, LF refining, RH refining, continuous casting, and the time from iron addition to pouring is controlled within 220-240 minutes; wherein, the molten iron pretreatment cycle is 50-70 minutes, the converter smelting cycle is 50-60 minutes, the LF refining cycle is 60-80 minutes, the RH refining cycle is 40-50 minutes, and the RH tank is washed 1-2 times before production; ① Production preparation: optimize the molten iron conditions, adopt the full iron method for smelting, and add iron twice; the molten iron conditions are as follows: the molten iron temperature is ≥1300℃, Mn≤0.12%, S≤0.030%, Ti≤0.040%, Cu≤0.010% in the molten iron; ② Hot metal pretreatment: Hot metal [S] after treatment ≤ 0.0020%; ③ Converter smelting: before adding iron, add 1.5~2 t of active lime and 1.5~2 t of dolomite as padding; The cooling materials used for converter smelting are active lime, dolomite, limestone, and sintered return ore; among them, the sulfur content of limestone is required to be ≤0.0050%; the sulfur content of sintered return ore is required to be ≤0.0050%, and the contents of copper, lead, antimony, arsenic, tin, and bismuth are all ≤0.0040%; The converter smelting adopts double slag tapping and residual steel tapping; 500 kg of ladle ash and 50-100 kg of fluorite are added during the tapping process; ④ Ladle preparation tank: The ladle is put into the tank for the first time to produce RH low-carbon steel, and low-carbon drainage agent is used; ⑤LF refining: During the heating process of the LF furnace, 800-1000 kg of lime is added in batches. After each power-on, argon is blown for 3-5 minutes without deoxidation. After the treatment, the slag is removed using a slag tray, and then 300 kg of top slag modifier is added, and the temperature is adjusted again. ⑥RH refining: RH furnace deep decarburization for 15~20 min, deoxidation after decarburization, the Alt after the first pour of argon is controlled at 0.030%~0.040%; the Alt after the subsequent pour of argon is controlled at 0.020%~0.030%; re-pressurization after the net circulation time ≥6 min; During the refining process outside the furnace, the first pouring: the temperature after LF argon is controlled at 1640±5℃, the temperature before RH argon reaches 1630±5℃, and the temperature after RH argon is controlled at 1610±5℃; the subsequent heats: the temperature after LF argon is controlled at 1610±5℃, the temperature before RH argon reaches 1600±5℃, and the temperature after RH argon is controlled at 1590±5℃; ⑦Continuous casting: superheat target is 35℃, casting speed target is 1.2 m / min; By adopting the above method for smelting industrial pure iron, the content of non-ferrous elements in molten steel is reduced to 783 ppm.

2. The method according to claim 1, characterized in that The amount of molten iron charged in step ② is controlled at 193±5 t according to the life of the ladle.

3. The method according to claim 1, characterized in that Step ③: blow out steel at the high point of converter smelting end point P to ensure that the end point oxygen is greater than 700 ppm; the end point temperature is controlled at 1620℃~1630℃.

4. The method according to claim 1, characterized in that In step ⑦, ultra-low carbon protective slag is used for continuous casting, and carbon-free tundish slag is used for tundish slag; the tundish is purged with argon before pouring.

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