A method for vacuum calcium treatment of an RH furnace

Abstract

The application relates to the technical field of steelmaking secondary refining process, in particular to a method for RH vacuum calcium treatment. The method comprises the following steps: according to the content of sulfur in molten steel, setting the adding amount of high-efficiency calcium-iron alloy; under the condition of setting the vacuum degree, adding the high-efficiency calcium-iron alloy with the set adding amount into the molten steel, and controlling the total argon flow of the vacuum chamber to carry out homogenization calcium treatment operation; under the condition of setting the time, carrying out soft blowing operation on the molten steel after calcium treatment, and controlling the argon flow of the ladle bottom blowing to promote the floating of inclusions. The application solves the technical problem of smoking in the existing RH vacuum calcium treatment process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steelmaking secondary refining process, and particularly relates to a method for RH vacuum calcium treatment. BACKGROUND

[0002] With the adjustment of the national environmental protection policy, enterprises increase environmental protection investment and research and development. As the first to be affected, all pollution points of steel enterprises need to be treated. The common calcium treatment method of RH furnace of steel enterprises is wire feeding method, that is, after the end of vacuum treatment of the RH furnace, wire feeding operation is performed on the molten steel in the ladle at the wire feeding position. After the wire feeding is completed, soft blowing, temperature measurement and sampling operations are performed. The dust removal effect of the wire feeding position of the RH furnace is generally poor, so there is a serious smoking problem in the wire feeding process. SUMMARY

[0003] The present application provides a method for RH vacuum calcium treatment to solve the technical problem of smoking in the existing RH vacuum calcium treatment process.

[0004] In a first aspect, the present application provides a method for RH vacuum calcium treatment, which comprises:

[0005] According to the content of sulfur in the molten steel, the addition amount of high-efficiency calcium-iron alloy is set;

[0006] Under the condition of setting the vacuum degree, the high-efficiency calcium-iron alloy with the set addition amount is added to the molten steel, and the total flow of argon in the vacuum chamber is controlled to perform homogenization calcium treatment operation;

[0007] Under the condition of setting the time, soft blowing operation is performed on the molten steel after calcium treatment, and the flow of ladle bottom argon is controlled to promote the floating of inclusions.

[0008] Optionally, according to the content of sulfur in the molten steel, the addition amount of high-efficiency calcium-iron alloy is set, which comprises:

[0009] 0.1 kg of high-efficiency calcium-iron is added to 1 ton of the molten steel for each 0.001 wt% of the sulfur content in the molten steel; wherein if the sulfur content in the molten steel is less than 0.001 wt%, 0.1 kg of high-efficiency calcium-iron is added to 1 ton of the molten steel.

[0010] Optionally, the content of sulfur in the molten steel is 0.0005 wt% to 0.0040 wt%.

[0011] Optionally, the set vacuum degree is 150 mbar to 200 mbar.

[0012] Optionally, the total flow of argon in the vacuum chamber is 1000 NL / min to 1400 NL / min.

[0013] Optionally, the argon bottom blowing flow rate of the ladle is 60-140 NL / min.

[0014] Optionally, the setting time is 5-10 min.

[0015] Optionally, the content of Ca in the chemical composition of the calcium-iron alloy is 33 wt%.

[0016] Optionally, under the condition of the setting vacuum degree, the high-efficiency calcium-iron alloy with the setting addition amount is added to the molten steel, the total argon flow rate is controlled, and the calcium treatment operation is performed, including:

[0017] Under the condition of the setting vacuum degree, the high-efficiency calcium-iron alloy with the setting addition amount is added to the molten steel, and the vacuum circulation is performed, and the total argon flow rate is controlled, and the calcium treatment operation is performed; the time of the vacuum circulation is 1 min.

[0018] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages:

[0019] The method of the RH furnace vacuum calcium treatment provided by the embodiments of the present application sets the addition amount of the high-efficiency calcium-iron alloy according to the content of sulfur in the molten steel, so as to sufficiently modify the sulfides; sets the vacuum degree and controls the total argon flow rate in the vacuum chamber, so as to make the molten steel circulation amount low, the high-efficiency calcium-iron alloy added is uniformly melted and reacted, and the absorption rate is optimal; sets the soft blowing time and controls the argon bottom blowing flow rate of the ladle, so as to ensure the micro-motion of the molten steel surface, avoid the exposure of the molten steel surface, ensure the sufficient reaction of the high-efficiency calcium-iron alloy, and promote the floating of the inclusions. In summary, the content of the present application solves the problem of smoking in the wire feeding calcium treatment process, avoids the problem of shell connection on the slag surface of the ladle, thereby eliminates the problem of secondary oxidation caused by the molten steel boiling and exposure in the wire feeding calcium treatment process, stabilizes the calcium treatment absorption rate, and in addition, the method also reduces the temperature loss, and eliminates the temperature sampling operation at the wire feeding position of the RH post. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0022] Figure 1 A flowchart of the method of the RH furnace vacuum calcium treatment provided by the embodiments of the present application. DETAILED DESCRIPTION

[0023] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, any other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0024] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers in the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in the present application, it refers to any cited number (fraction or integer) in the indicated range.

[0025] In the present application, the orientation words such as "upper" and "lower" are specific to the drawing direction in the drawings. In addition, in the description of the specification, the terms "include", "contain" and the like mean "include but not limited to". In the present text, the relationship terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. In the present text, "and / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent the cases of A alone, A and B together, and B alone. Wherein A, B can be singular or plural. In the present text, "one or more" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of the items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, c can be single or multiple.

[0026] Unless otherwise specifically indicated, all raw materials, reagents, instruments and equipment used in the present application can be purchased on the market or prepared by existing methods.

[0027] In a first aspect, the present application provides a method for RH furnace vacuum calcium treatment, please refer to Figure 1 , the method comprises:

[0028] S1, according to the content of sulfur in the molten steel, set the addition amount of high-efficiency calcium iron alloy;

[0029] S2, under the condition of setting the vacuum degree, adding the high-efficiency calcium iron alloy with the set addition amount to the molten steel, and controlling the total flow of argon in the vacuum chamber, the homogenization calcium treatment operation is carried out;

[0030] S3, under the condition of setting time, the molten steel after calcium treatment is carried out soft blowing operation, and the flow of argon in the ladle bottom blowing is controlled to promote the floating of inclusions.

[0031] In the embodiments of the present application, according to the content of sulfur in the molten steel, the addition amount of high-efficiency calcium iron alloy is set to fully modify the sulfide; the vacuum degree is set and the total flow of argon in the vacuum chamber is controlled, so that the circulating amount of molten steel is low, the added high-efficiency calcium iron is uniformly melted and reacted, and the absorption rate is best; the soft blowing time is set and the flow of argon in the ladle bottom blowing is controlled, which ensures the micro motion of molten steel surface, does not expose the molten steel surface, and ensures the full reaction of high-efficiency calcium iron, promotes the floating of inclusions.

[0032] In some embodiments, according to the content of sulfur in the molten steel, the addition amount of high-efficiency calcium iron alloy is set, comprising:

[0033] If the content of sulfur in the molten steel is 0.001% by weight, 0.1 kg of high-efficiency calcium iron is added to 1 ton of the molten steel; wherein, if the content of sulfur in the molten steel is less than 0.001% by weight, 0.1 kg of high-efficiency calcium iron is added to 1 ton of the molten steel.

[0034] In the embodiments of the present application, for the steel grade such as pipeline, the calcium treatment is mainly sulfide modification treatment, which first reacts with oxygen, and then, when the oxygen content is reduced to a certain range, calcium reacts with sulfur to form calcium sulfide. The sulfide modification is controlled according to Ca / S = 1, the sulfide modification is sufficient, the liquid steel cleanliness is higher, the efficient calcium-iron yield is about 30%, and the efficient calcium-iron-calcium content is 33%. According to the alloy addition amount formula G (kg) = (target value% - actual value%) * 1000 / alloy element content% / alloy element absorption rate%, according to Ca / S = 1, that is, the S content in the steel is 0.0010%, the required Ca is 0.0010%, the efficient calcium-iron addition amount G (kg) per ton of steel is 0.0010% * 1000 / 33% / 30% = 0.1 kg, the efficient calcium-iron addition amount is calculated according to the actual molten steel amount, and the efficient calcium-iron addition amount is set according to the above principle and calculation. If the addition amount is too small, the sulfide modification of the molten steel is not sufficient to a certain extent, which is not conducive to the quality of the steel; if the addition amount is too large, solid CaS is likely to be generated, and the water gap is likely to be blocked during pouring.

[0035] In some embodiments, the content of sulfur in the molten steel is 0.0005% to 0.0040% by weight.

[0036] The positive effect of controlling the content of sulfur in the molten steel to be 0.0005% to 0.0040% by weight is to ensure the smooth progress of the calcium treatment process. If the content is too high, the desulfurization effect is not good due to abnormal factors, and the calcium treatment cost is increased. Specifically, the content of sulfur can be 0.0005% by weight, 0.0010% by weight, 0.0015% by weight, 0.0020% by weight, 0.0025% by weight, 0.0030% by weight, 0.0035% by weight, 0.0040% by weight, etc.

[0037] In some embodiments, the set vacuum degree is 150 mbar to 200 mbar.

[0038] The positive effect of setting the vacuum degree to be 150 mbar to 200 mbar is that the surface of the efficient calcium-iron is steel material, which needs a certain time to melt. Under this vacuum degree, the molten steel circulation amount is low, the added efficient calcium-iron is uniformly melted and reacted, and the absorption rate is best. If the vacuum degree is too high, the molten steel circulation amount is too fast, the efficient calcium-iron reacts violently, and slag absorption accidents are likely to occur. If the vacuum degree is too low, the molten steel circulation amount is lower, the efficient calcium-iron melting and reaction are slow, and the time needs to be prolonged, which affects the efficiency. Specifically, the vacuum degree can be 150 mbar, 160 mbar, 170 mbar, 180 mbar, 190 mbar, 200 mbar, etc.

[0039] In some embodiments, the total argon flow of the vacuum chamber is 1000 NL / min to 1400 NL / min.

[0040] The total argon flow rate of the vacuum chamber is controlled to be 1000 NL / min to 1400 NL / min to complement the setting of the above-mentioned vacuum degree. Specifically, the total argon flow rate of the vacuum chamber can be 1000 NL / min, 1100 NL / min, 1200 NL / min, 1300 NL / min, 1400 NL / min, etc.

[0041] In some embodiments, the ladle bottom argon blowing flow rate is 60 NL / min to 140 NL / min.

[0042] The positive effect of controlling the ladle bottom argon blowing flow rate to be 60 NL / min to 140 NL / min is that the flow rate can ensure the micro-motion of the liquid steel surface, not expose the liquid steel surface, ensure the full reaction of the high-efficiency calcium iron, and promote the floating of inclusions. If the flow rate is too high, it can cause the liquid steel surface to be exposed, causing secondary oxidation of the liquid steel. If the flow rate is too low, it can not ensure the full reaction of the high-efficiency calcium iron, and the floating of inclusions is insufficient. Specifically, the bottom argon blowing flow rate can be 60 NL / min, 80 NL / min, 100 NL / min, 120 NL / min, 140 NL / min, etc.

[0043] In some embodiments, the setting time is 5 min to 10 min.

[0044] The "setting time" refers to the soft blowing time, and the soft blowing time is controlled to be 5 min to 10 min to complement the above-mentioned soft blowing flow rate. Specifically, the soft blowing time can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc.

[0045] In some embodiments, in the chemical composition of the calcium-iron alloy, the content of Ca is 33% by weight.

[0046] The positive effect of controlling the content of Ca in the chemical composition of the calcium-iron alloy to be 33% by weight is that the particle size suitable for the feeding system is 20 to 50 mm, and the high-efficiency calcium iron is designed to have an appearance size of 40 to 50 mm, which ensures the maximum calcium content within the applicable range. If the content of Ca is too high, the high-efficiency calcium iron has a larger size, and the discharging process is easy to be blocked. If the content of Ca is too low, the high-efficiency calcium iron has a smaller size, and more high-efficiency calcium iron needs to be added under the premise of the same amount of calcium, which causes greater temperature loss.

[0047] In some embodiments, under the condition of setting the vacuum degree, the high-efficiency calcium-iron alloy with a set addition amount is added to the liquid steel, and the total argon flow rate is controlled to perform calcium treatment operation, which includes:

[0048] Under the condition of setting the vacuum degree, the high-efficiency calcium-iron alloy with a set adding amount is added into the molten steel, vacuum circulation is carried out, and argon total flow is controlled to carry out calcium treatment operation; the time of the vacuum circulation is 1 min.

[0049] The positive effect of controlling the time of vacuum circulation to be 1 min: this time just ensures uniform melting and reaction of the high-efficiency calcium-iron; if the time is too long, the cycle is prolonged, and temperature loss is increased; if the time is too short, uniform melting and reaction cannot be ensured, and the absorption rate is reduced.

[0050] The application will be further described below in combination with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. The experimental methods not specified in the following examples are generally determined according to national standards. If there is no corresponding national standard, the general international standard, conventional conditions, or the conditions suggested by the manufacturer are used.

[0051] Specific process flow:

[0052] First: set the base table

[0053] The mass percentage of sulfur content in the molten steel is graded, the adding amount of the high-efficiency calcium-iron is set according to different mass percentages of sulfur content, which is defined as the high-efficiency calcium-iron adding amount base table.

[0054] The new high-efficiency calcium-iron alloy is used, which is wrapped with pure calcium particles in a steel shell, and the shape is similar to a cylinder with a diameter of about 40-50 mm, and the mass percentage is: [Ca]=33%, and the rest is iron.

[0055] According to the sulfur content in the molten steel before calcium treatment, the percentage is 0.0005%-0.0040%, 0.1 kg / t steel of high-efficiency calcium-iron is added for every 0.001% of sulfur content in the molten steel (not less than 0.001%), and a grading adding table is set, that is, the high-efficiency calcium-iron adding amount base table.

[0056] Second: calcium treatment operation

[0057] During the RH furnace vacuum treatment process, the molten steel composition sample is taken, after the temperature and alloying adjustment is completed under vacuum, the vacuum degree is adjusted to 150-200 mbar, the total gas flow is increased to 1000-1400 NL / min, the high-efficiency calcium-iron is added according to the high-efficiency calcium-iron adding amount base table, and the vacuum is broken after 1 min of vacuum circulation; after breaking the vacuum, the temperature is measured and the sample is taken.

[0058] Finally: soft blowing operation

[0059] The double bottom blowing flow of the ladle is set to 60-140 NL / min to ensure that the center slag surface of the ladle is slightly moved and the molten steel is not exposed, the soft blowing time is set to 5-10 min, the treatment is ended, and the ladle is hoisted for casting. For specific process parameters, please refer to Table 1, Table 1

[0060]

[0061] Table 2 Results of RH furnace vacuum calcium treatment

[0062] Serial number Temperature loss °C Absorption % Example 1 Example 2 3 20 Example 3 6 22 Comparative Example 1 4 21 ​ 10 17

[0063] Compared with the comparative example 1, the method of RH furnace vacuum calcium treatment according to the embodiments of the present application reduces the temperature loss and stabilizes the absorption rate.

[0064] The above description is merely a specific implementation of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for vacuum calcium treatment in an RH furnace, characterized in that, The method includes: The amount of high-efficiency calcium-iron alloy added is determined according to the sulfur content in the molten steel. For every 0.001% by weight of sulfur in the molten steel, 0.1 kg of high-efficiency calcium-iron alloy is added to 1 ton of molten steel; if the sulfur content in the molten steel is less than 0.001% by weight, 0.1 kg of high-efficiency calcium-iron alloy is added to 1 ton of molten steel. Under a set vacuum level, the high-efficiency calcium-iron alloy with a set addition amount is added to the molten steel, and the total flow rate of argon gas in the vacuum chamber is controlled to perform a homogenization calcium treatment operation. Under set time conditions, the calcium-treated molten steel is subjected to a soft blowing operation, and the flow rate of bottom blowing argon gas in the ladle is controlled to promote the floating of inclusions. The set vacuum level is 150 mbar to 200 mbar, the total argon flow rate in the vacuum chamber is 1000 NL / min to 1400 NL / min, the bottom blowing argon flow rate in the ladle is 60 NL / min to 140 NL / min, and the set time is 5 min to 10 min; The high-efficiency calcium-iron alloy has a steel shell encasing pure calcium granules, and its shape is similar to a cylinder with a diameter of 40-50 mm. The mass percentage is [Ca] = 33%, and the rest is iron. The sulfur content in the molten steel is 0.0005% to 0.0040% by weight.

2. The method according to claim 1, characterized in that, The process of adding a predetermined amount of the high-efficiency calcium-iron alloy to the molten steel under a set vacuum condition, and controlling the total argon flow rate, to perform calcium treatment includes: Under a set vacuum condition, the high-efficiency calcium-iron alloy with a set addition amount is added to the molten steel and vacuum circulation is performed, while controlling the total flow rate of argon gas to perform calcium treatment; the vacuum circulation time is 1 minute.

Images