A method of smelting an aluminium-free steel and a method of manufacturing thereof

Abstract

The application relates to the technical field of steelmaking, in particular to a smelting method and a preparation method of aluminum-free steel. The smelting method comprises the following steps: carrying out converter smelting on molten steel, adding first low-titanium-phosphorus iron into the molten steel according to the converter tapping amount, and obtaining first molten steel; carrying out RH decarburization on the first molten steel, and adding second low-titanium-phosphorus iron within a preset time of starting the decarburization, and obtaining second molten steel; and carrying out deoxidization on the second molten steel in stages, and obtaining aluminum-free molten steel. The method solves the technical problem of high titanium content in the aluminum-free molten steel.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steelmaking, and in particular to a smelting method of aluminum-free steel and a preparation method thereof. BACKGROUND

[0002] A certain kind of aluminum-free ultra-low-carbon phosphorus-containing steel has a very strict requirement on the impurity element titanium. The current production is to add all alloys in the RH refining, and the order of addition is generally silicon iron-manganese iron-phosphorus iron. The molten steel is preferentially subjected to decarburization treatment during RH treatment, and after the treatment is completed, the molten steel is deoxidized and alloyed. However, this method is easy to cause the titanium content of the molten steel to be too high and the vacuum treatment cycle to be too long. SUMMARY

[0003] The present application provides a smelting method of aluminum-free steel and a preparation method thereof to solve the technical problem of high titanium content in the molten aluminum-free steel.

[0004] In a first aspect, the present application provides a smelting method of aluminum-free steel, which comprises:

[0005] subjecting the molten steel to converter smelting, and adding first low-titanium phosphorus iron to the molten steel according to the converter tapping amount to obtain first molten steel;

[0006] subjecting the first molten steel to RH decarburization, and completing the addition of second low-titanium phosphorus iron within a preset time from the start of the decarburization to obtain second molten steel;

[0007] deoxidizing the second molten steel in stages to obtain aluminum-free molten steel.

[0008] Optionally, the converter smelting of the molten steel and the addition of the first low-titanium phosphorus iron to the molten steel according to the converter tapping amount to obtain the first molten steel comprise:

[0009] subjecting the molten steel to converter smelting, and adding first low-titanium phosphorus iron to the molten steel according to the converter tapping amount to obtain

[0010] the first molten steel, comprising:

[0011] subjecting the molten steel to converter smelting, and adding first low-titanium phosphorus iron to the molten steel when the converter tapping amount reaches 20% by weight to obtain the first molten steel; wherein the addition amount of the first low-titanium phosphorus iron is 4.8 kg to 5.0 kg with respect to 1 t of molten steel.

[0012] Optionally, the converter smelting of the molten steel and the addition of the first low-titanium phosphorus iron to the molten steel according to the converter tapping amount to obtain the first molten steel comprise:

[0013] The molten steel is subjected to converter smelting, and when the converter tapping amount reaches 20% by weight, first low-titanium phosphorus iron, lime and light-burned dolomite are added to the molten steel to obtain first molten steel; wherein, the addition amount of the first low-titanium phosphorus iron is 4.8kg-5.0kg, the addition amount of the lime is 1.5kg-2.0kg, and the addition amount of the light-burned dolomite is 0.5kg-1.5kg per 1t of molten steel.

[0014] Optionally, the preset time is ≤10min.

[0015] Optionally, the preset time is ≤5min.

[0016] Optionally, the first molten steel is subjected to RH decarburization, and the addition of second low-titanium phosphorus iron is completed in the early stage of the decarburization, comprising:

[0017] The first molten steel is subjected to RH decarburization, and the addition of second low-titanium phosphorus iron is completed within a preset time before the decarburization starts; wherein, the addition amount of the second low-titanium phosphorus iron is ≤0.4kg per 1t of molten steel.

[0018] Optionally, the second molten steel is subjected to deoxidation in stages to obtain aluminum-free molten steel, comprising:

[0019] The second molten steel is subjected to first deoxidation by aluminum particles, so that the second molten steel has a target oxygen activity;

[0020] The second molten steel after the first deoxidation is subjected to second deoxidation by low-carbon ferrosilicon and manganese-based alloy to obtain aluminum-free molten steel.

[0021] Optionally, the second molten steel after the first deoxidation is subjected to second deoxidation by low-carbon ferrosilicon and manganese-based alloy,

[0022] to obtain aluminum-free molten steel, comprising:

[0023] The second molten steel after the first deoxidation is subjected to second deoxidation by controlling the addition sequence of low-carbon ferrosilicon and manganese-based alloy to obtain aluminum-free molten steel; wherein, the low-carbon ferrosilicon and the manganese-based alloy are added simultaneously.

[0024] Optionally, the target oxygen activity is 100ppm-150ppm.

[0025] In a second aspect, the present application provides a method for preparing aluminum-free steel, comprising the method of any one of the first aspect.

[0026] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0027] The smelting method of the aluminum-free steel provided by the embodiment of the present application adds low-titanium phosphorus iron in the early stage of converter smelting (before tapping, not in the early stage of smelting) to control the Ti content in the molten steel and make the top slag of the ladle quickly "solidify and form"; the low-titanium phosphorus iron is added in the early stage of RH decarburization to easily complete the oxidation of titanium and the floating of the generated titanium oxide when the oxygen activity of the molten steel is relatively high; and the deoxidation is carried out in stages to fully remove inclusions and ensure the cleanliness of the molten steel. In summary, the method realizes stable production of the extremely low-titanium phosphorus ultra-low-carbon aluminum-free steel. BRIEF DESCRIPTION OF DRAWINGS

[0028] The drawings incorporated in the specification and forming a part thereof illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, those drawings can also help the ordinary skilled in the art to obtain other drawings without any creative effort.

[0030] Figure 1 A flowchart of a smelting method of an aluminum-free steel provided by the embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the ordinary skilled in the art without any creative effort belong to the scope of protection of the present application.

[0032] 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 only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range description has specifically 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 specifically 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 this document, it refers to any cited number (fraction or integer) in the indicated range.

[0033] In the present application, the orientation words such as "upper" and "lower" are the directions of the drawing surface in the drawings unless otherwise stated. In addition, in the description of the present application, the terms "include", "contain" and the like mean "include but not limited to". In the present text, the relational terms such as "first" and "second" are only 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 kinds of relationships, for example, A and / or B can represent: A exists alone, A and B exist together, and B exists alone. Where A and B can be singular or plural. In the present text, "at least one" 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 single item or any combination of 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, and c can be single or multiple.

[0034] Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present application can be purchased on the market or prepared by existing methods.

[0035] In a first aspect, the present application provides a smelting method of aluminum-free steel, please refer to Figure 1 , the method comprises:

[0036] S1, converting smelting of molten steel, and adding first low-titanium phosphorus iron to the molten steel according to the converter tapping amount to obtain first molten steel;

[0037] S2, RH decarburization of the first molten steel, and adding second low-titanium phosphorus iron within a preset time of starting the decarburization to obtain second molten steel;

[0038] S3, deoxidizing the second molten steel in stages to obtain aluminum-free molten steel.

[0039] The control mechanism of each element of the aluminum-free steel is:

[0040] Titanium is a harmful element for this type of steel, which is easy to form TiN with N in the steel, which is more stable than AlN, and affects the amount of inhibitor in the steel. The production of TiN will also hinder the growth of grains during annealing, thereby affecting the performance of the steel. For this type of steel, the titanium content in the finished steel is required to be controlled below 0.0005%.

[0041] Phosphorus element in the production of non-oriented silicon steel, with silicon, aluminum and other alloy elements in the same role in improving the resistivity, and in a certain range of more significant, in improving the product punching performance is also more good, the corresponding design can be significantly reduced alloy cost.

[0042] Carbon element content more than 0.0025% will form fine inclusions with V, Ti and other molten steel, resulting in such steel performance significantly deteriorated, such steel generally requires finished carbon content <0.0025%, better carbon content ≤0.0015%.

[0043] Aluminum (Als) steel Als phosphorus is higher than 0.0010%, Al and N in the molten steel is easy to generate AlN and other harmful substances, deteriorating the performance of the steel.

[0044] By adding low titanium phosphorus iron in the early stage of converter smelting, to control the Ti content in the molten steel, and make the ladle top slag quickly "solidification forming"; adding low titanium phosphorus iron in the early stage of RH decarburization, to easily complete the oxidation of titanium and the floating of generated titanium oxide when the oxygen activity of the molten steel is relatively high; staged deoxidation to fully remove inclusions and ensure the cleanliness of the molten steel. The method can stably produce finished steel with titanium content ≤0.0005% (actual content generally ≤0.0003%), carbon content ≤0.0020% (actual content generally ≤0.0018%), phosphorus content of 0.12% ~ 0.14%, and Als content ≤0.0010% (actual content generally ≤0.0008%).

[0045] In some embodiments, the molten steel is subjected to converter smelting, and a first low-titanium phosphorus iron is added to the molten steel according to the converter tapping amount, to obtain a first molten steel, including:

[0046] The molten steel is subjected to converter smelting, and a first low-titanium phosphorus iron is added to the molten steel when the converter tapping amount reaches 20% by weight, to obtain a first molten steel.

[0047] The first molten steel includes:

[0048] The molten steel is subjected to converter smelting, and a first low-titanium phosphorus iron is added to the molten steel when the converter tapping amount reaches 20% by weight, to obtain a first molten steel.

[0049] In the embodiments of the present application, in the converter smelting, post-blowing is prohibited, nitrogen increase in the molten steel caused by converter post-blowing is reduced, and through the good reblowing effect of top and bottom combined blowing converter, the converter endpoint carbon is controlled at 0.035% ~ 0.055%, the oxygen activity is controlled at 350ppm ~ 650ppm, and the endpoint temperature is controlled at 1650 ~ 1670℃.

[0050] When the converter tapping amount reaches 20% by weight, the first low-titanium phosphorus iron is added, and the positive effect is: at this time, the titanium in the low-titanium phosphorus iron enters the molten steel almost "zero" due to the easy oxidation of titanium element, and the molten steel oxygen activity is 350ppm-650ppm.

[0051] In 1t of molten steel, the addition amount of the first low-titanium phosphorus iron is 4.8kg-5.0kg, and the positive effect is: under the condition of stable overall blowing in steelmaking and relatively stable converter tapping, the low-titanium phosphorus iron in this range is added, and generally the RH does not need to be adjusted again for the addition of low-titanium phosphorus iron, which is very beneficial to reducing the titanium content of the molten steel; if the addition amount of the low-titanium phosphorus iron is too high, it will cause the molten steel phosphorus content to exceed the standard to some extent, and the alloy is wasted; if the addition amount of the low-titanium phosphorus iron is too low, it will cause too much low-titanium phosphorus iron to be adjusted in the RH process to some extent, which is not conducive to controlling the titanium content of the molten steel. Specifically, in 1t of molten steel, the addition amount of low-titanium phosphorus iron can be 4.8kg, 4.9kg, 5.0kg, etc. The titanium content of the low-titanium phosphorus iron alloy is ≤0.60% by weight.

[0052] In some embodiments, the molten steel is subjected to converter smelting, and a first low-titanium phosphorus iron is added to the molten steel according to the converter tapping amount to obtain a first molten steel, comprising:

[0053] The molten steel is subjected to converter smelting, and when the converter tapping amount reaches 20% by weight, a first low-titanium phosphorus iron, white ash and light-burned dolomite are added to the molten steel to obtain a first molten steel; wherein, relative to 1t of molten steel, the addition amount of the first low-titanium phosphorus iron is 4.8kg-5.0kg, the addition amount of the white ash is 1.5kg-2.0kg, and the addition amount of the light-burned dolomite is 0.5kg-1.5kg.

[0054] The addition of low-titanium phosphorus iron, white ash and light-burned dolomite has the positive effect of promoting the floating of oxidized titanium and improving the melting of the slag material, ensuring the subsequent melting effect of the slag material, uniformly spreading on the top of the molten steel, and quickly "solidifying and forming". After tapping, the ladle is bottom blown for 2min, and the steel sample is taken after the furnace is taken out, which is used as the RH refining station composition sample.

[0055] In some embodiments, the preset time is ≤10min.

[0056] In the embodiments of the present application, the RH inlet molten steel is rapidly decarburized by pre-vacuum + RH forced oxygen decarburization mode, and the carbon content of the molten steel is reduced to 10-13 ppm after 12-15 min. The decarburization is ended according to the RH carbon control model, and the temperature and oxygen are measured. During this period, the low-titanium phosphorus iron is adjusted according to the phosphorus content of the post-furnace steel sample, the adjustment amount is controlled to be ≤0.4 kg / t of molten steel, and the adjustment is completed within 10 min after the start of RH decarburization. At this time, the oxygen activity of the molten steel is relatively high, and the oxidation of titanium and the floating of the generated titanium oxide can be easily completed. If the titanium oxide is not floated at the late stage or the end of the decarburization, it will be reduced into the molten steel by the added deoxidizing alloy, causing the titanium content of the product to be high. Specifically, the time can be 10 min, 8 min, 6 min, 4 min, etc.

[0057] In some embodiments, the preset time is ≤5 min.

[0058] Preferably, the low-titanium phosphorus iron is completed within 5 min after the start of RH decarburization.

[0059] In some embodiments, the first molten steel is subjected to RH decarburization, and the second low-titanium phosphorus iron is added within a preset time before the decarburization, comprising:

[0060] The first molten steel is subjected to RH decarburization, and the second low-titanium phosphorus iron is added within a preset time before the decarburization. The addition amount of the second low-titanium phosphorus iron is ≤0.4 kg relative to 1 t of molten steel.

[0061] The addition amount of the second low-titanium phosphorus iron is ≤0.4 kg relative to 1 t of molten steel, which has the positive effect of effectively reducing the titanium content of the molten steel. If the addition amount is too high, it will increase the titanium content of the molten steel to a certain extent. Specifically, the addition amount can be 0.4 kg, 0.3 kg, 0.35 kg, etc.

[0062] In some embodiments, the second molten steel is subjected to deoxidation in stages to obtain an aluminum-free molten steel, comprising:

[0063] The second molten steel is subjected to first deoxidation by aluminum particles to have a target oxygen activity.

[0064] The second molten steel after the first deoxidation is subjected to second deoxidation by low-carbon silicon iron and manganese alloy to obtain an aluminum-free molten steel.

[0065] According to the above oxygen determination results and the state of the vacuum chamber and the ladle, aluminum particles are added for pre-deoxidation operation, and 0.11-0.125 kg / t of molten steel is used to remove 100 ppm of oxygen.

[0066] The positive effects of the first deoxidation with aluminum particles: the steel grade is aluminum-free, and the aluminum deoxidation forms aluminum oxide inclusions that are easy to cluster and float up, and the alloy yield is increased by 5%; the inclusions formed by low-carbon ferrosilicon + metal manganese / electrolytic manganese deoxidation are relatively complex and not easy to float up, which affects the quality and purity of the molten steel. The molten steel is circulated for 4-6 minutes after the first deoxidation is completed to ensure that the Al2O3 inclusions generated are fully floated up. If the time is too short, the Al2O3 inclusions have not fully floated up, and if the time is too long, it is a waste of efficiency, and increases the RH vacuum steam consumption and refractory consumption.

[0067] The positive effects of the second deoxidation with low-carbon ferrosilicon + manganese alloy: it is beneficial to control the area ratio of inclusions, and the area ratio of inclusions is within 25 ppm. The manganese alloy can be metal manganese or electrolytic manganese.

[0068] In some embodiments, the second deoxidation of the second molten steel after the first deoxidation by low-carbon ferrosilicon and manganese alloy to obtain aluminum-free molten steel, comprises:

[0069] The second deoxidation of the second molten steel after the first deoxidation by controlling the addition sequence of low-carbon ferrosilicon and manganese alloy to obtain aluminum-free molten steel; wherein the low-carbon ferrosilicon and the manganese alloy are added at the same time.

[0070] The molten steel is circulated for 4-6 minutes after the first deoxidation to measure the temperature and oxygen, and according to the actual oxygen value, the low-carbon ferrosilicon deoxidizes 100 ppm of oxygen at 0.23 kg / t of molten steel. The positive effects of the addition of alloyed low-carbon ferrosilicon and manganese alloy:

[0071] First, the time interval of alloy addition is shortened by 2-3 minutes, improving the efficiency; second, the simultaneous addition of the two types of alloys is equivalent to silicon-manganese composite deoxidation, which is significantly better than silicon deoxidation or manganese deoxidation in terms of oxygen control, with a difference of 20-30% in the end oxygen control of the molten steel, and the inclusions formed by this composite deoxidation are relatively large and easy to float up and be removed from the molten steel, thereby achieving high cleanliness control of the molten steel. This step is equivalent to composite deoxidation alloying of the molten steel, which can effectively reduce the total oxygen and free oxygen of the molten steel, and can also reduce the RH vacuum period by 2-3 minutes; the molten steel is pure circulated for ≥4 minutes after the addition of low-carbon ferrosilicon and manganese alloy is completed.

[0072] In some embodiments, the target oxygen activity is 100-150 ppm.

[0073] The positive effect of controlling the first deoxidization end molten steel oxygen target to be 100 ppm to 150 ppm is: controlling the cleanliness of the molten steel. If the oxygen activity is too low, the Als content of the molten steel is likely to exceed the standard; if the oxygen activity is too high, the effect of pre-deoxidization is not obvious, and the improvement of the molten steel cleanliness control is not obvious. Specifically, the oxygen activity can be 100 ppm, 110 ppm, 120 ppm, 130 ppm, 140 ppm, 150 ppm, etc.

[0074] In a second aspect, the present application provides a preparation method of the aluminum-free steel, which comprises the method of any one of the embodiments of the first aspect.

[0075] The preparation method of the aluminum-free steel is based on the above-mentioned smelting method of the aluminum-free steel. The specific steps of the smelting method of the aluminum-free steel can be referred to the above-mentioned embodiments. Since the preparation method of the aluminum-free steel adopts part or all of the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0076] The present application will be further described in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods not specified in the following embodiments are generally determined according to the national standards. If there is no corresponding national standard, the international standard, the conventional condition, or the condition suggested by the manufacturer is used.

[0077] Example 1:

[0078] The converter tapping temperature is 1661℃, the carbon content of the molten steel is 0.052%, and the end point oxygen activity measurement value is 475ppm. The converter is normally tapped, and when the tapping amount reaches 1 / 5 of the average daily tapping amount, 4.87kg / t of low-titanium phosphorus iron, 1.65kg / t of lime and 0.73kg / t of light-burned dolomite slag are added. The ladle bottom blowing flow rate is dynamically adjusted according to 170-190L / min. After the tapping is completed, the ladle bottom blowing continues for 2min, and the furnace sample is taken, which is used as the RH refining station composition sample. The actual tapping amount of this furnace is 225t.

[0079] The post-furnace sample phosphorus content is 0.127%, the station temperature is 1612℃, the RH oxygen blowing temperature is raised by 90m 3 , 0.2kg / t of phosphorus iron is added when the vacuum decarburization is 6min, the oxygen is set to 325ppm, then 0.23kg / t of aluminum particles are added, and after 4.5min of circulation, the oxygen is set again, the molten steel oxygen activity is 135ppm, then low-titanium silicon iron and metal manganese / electrolytic manganese are added, and after 4min of circulation, the temperature is measured and the sample is taken to end the RH treatment. The RH vacuum period is 23min.

[0080] Example 2:

[0081] Converter tapping temperature 1667°C, the assay of molten steel carbon content 0.045%, the endpoint oxygen activity measurement value 585ppm. Converter normal tapping, tapping amount reaches the average amount of daily tapping 1 / 5, add low titanium phosphorus iron 4.95kg / t molten steel, while adding 1.87kg / t lime and 1.15kg / t light-burned dolomite slag. The ladle bottom blowing flow rate is dynamically adjusted according to 200-230L / min. After tapping, the ladle bottom blowing continues for 2min, and the furnace sample is taken, which is used as the RH refining station composition sample. The actual tapping amount of this furnace is 227t.

[0082] The furnace sample phosphorus content is 0.130%, the station temperature is 1619°C, the RH is not blown oxygen heating, the phosphorus iron is adjusted 0.1kg / t at the time of vacuum decarburization for 4min, the oxygen is fixed at 355ppm at the end of decarburization, then 0.253kg / t aluminum particles are added, and the oxygen is fixed again after 5.2min of circulation. The molten steel oxygen activity is 105ppm, then low titanium silicon iron and metal manganese / electrolytic manganese are added, and the RH treatment is ended after 4min of temperature measurement and sampling. The RH vacuum period is 22.5min.

[0083] Example 3

[0084] Converter tapping temperature 1657°C, the assay of molten steel carbon content 0.037%, the endpoint oxygen activity measurement value 717ppm. Converter normal tapping, tapping amount reaches the average amount of daily tapping 1 / 5, add low titanium phosphorus iron 5.0kg / t molten steel, while adding 2.0kg / t lime and 1.35kg / t light-burned dolomite slag. The ladle bottom blowing flow rate is dynamically adjusted according to 230-250L / min. After tapping, the ladle bottom blowing continues for 2min, and the furnace sample is taken, which is used as the RH refining station composition sample. The actual tapping amount of this furnace is 224t.

[0085] The furnace sample phosphorus content is 0.133%, the station temperature is 1610°C, the RH is blown oxygen heating 77m 3 , the phosphorus iron is adjusted 0.27kg / t at the time of vacuum decarburization for 5min, the oxygen is fixed at 417ppm at the end of decarburization, then 0.35kg / t aluminum particles are added, and the oxygen is fixed again after 4.0min of circulation. The molten steel oxygen activity is 123ppm, then low titanium silicon iron and metal manganese / electrolytic manganese are added, and the RH treatment is ended after 4min of temperature measurement and sampling. The RH vacuum period is 21.8min.

[0086] Example 4

[0087] The converter tapping temperature is 1662 ℃, the carbon content of the molten steel is 0.036%, and the final oxygen activity measurement value is 797 ppm. The converter is normally tapped, 5.0 kg / t of low-titanium phosphorus iron is added when the tapping amount reaches 1 / 5 of the average daily tapping amount, 1.90 kg / t of lime and 1.4 kg / t of light-burned dolomite slag are added at the same time. The bottom blowing flow rate of the ladle is dynamically adjusted according to 230-250 L / min. The bottom blowing of the ladle continues for 2 min after the tapping is completed, and the steel sample is taken after the furnace is tapped. This steel sample is used as the RH refining station composition sample. The actual tapping amount of this furnace is 225.5 t.

[0088] The post-furnace sample has a phosphorus content of 0.123%, the station temperature is 1614 ℃, and the RH oxygen blowing temperature is raised by 53 m 3 , 0.4 kg / t of phosphorus iron is added when the vacuum decarburization time is 10 min, the oxygen is fixed at 472 ppm at the end of decarburization, then 0.423 kg / t of aluminum particles are added, and the cycle is 4.0 min. After the oxygen is fixed again, the molten steel oxygen activity is 137 ppm, then low-titanium silicon iron and metal manganese / electrolytic manganese are added, and the cycle is 4 min. The RH treatment is completed after the temperature is measured and the sample is taken. The RH vacuum cycle is 23.2 min.

[0089] Comparative Example 1

[0090] The converter tapping temperature is 1663 ℃, the carbon content of the molten steel is 0.041%, and the final oxygen activity measurement value is 523 ppm. The converter is normally tapped, 1.65 kg / t of lime slag is added at the same time when the tapping amount reaches 1 / 5 of the average daily tapping amount. The bottom blowing flow rate of the ladle is dynamically adjusted according to 150-170 L / min. The bottom blowing of the ladle is turned off after the tapping is completed. The actual tapping amount of this furnace is 225 t.

[0091] The station temperature is 1614 ℃, and the RH oxygen blowing temperature is raised by 55 m 3 , 4.93 kg / t of phosphorus iron is added when the vacuum decarburization time is 14 min, the oxygen is fixed and the temperature is measured 1 min after the addition of phosphorus iron is completed, the oxygen is fixed at 387 ppm at the end of decarburization, then low-carbon silicon iron is used for deoxidization and alloying, the molten steel is circulated for 2.6 min after the addition of low-carbon silicon iron is completed, the manganese alloy is added, the manganese alloy is added to the molten steel for pure circulation for 4.7 min, and the treatment is completed. The RH vacuum cycle is 24.6 min.

[0092] Table 1 shows the smelting results of the aluminum-free steel

[0093]

[0094] As shown in Table 1, the molten steel prepared by the smelting method of the aluminum-free steel of the present application has a Ti content of less than 0.0005% by weight, and the inclusions are controlled at 25.5 ppm. The method realizes stable production of low-titanium phosphorus ultra-low-carbon aluminum-free steel.

[0095] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.

Claims

1. A method for smelting aluminum-free steel, characterized in that: The method comprises: The molten steel is subjected to converter smelting, and when the converter tapping rate reaches 20 weight percent, a first low-titanium ferrophosphorus, lime, and light-burned dolomite are added to the molten steel to obtain a first molten steel; wherein, relative to 1 ton of the molten steel, the amount of the first low-titanium ferrophosphorus added is 4.8 kg to 5.0 kg, the amount of the lime added is 1.5 kg to 2.0 kg, and the amount of the light-burned dolomite added is 0.5 kg to 1.5 kg, and the oxygen activity at the converter endpoint is controlled to be 350 ppm to 650 ppm; Performing RH decarburization on the first molten steel, and completing adding a second low-titanium ferrophosphorus within a preset time from the start of the decarburization to obtain a second molten steel, wherein the amount of the second low-titanium ferrophosphorus added is ≤0.4 kg relative to 1 ton of the molten steel, and the preset time is ≤10 minutes; performing a first deoxidation on the second molten steel using aluminum particles so that the second molten steel has a target oxygen activity of 100 ppm to 150 ppm; Controlling the order of adding low-carbon ferrosilicon and manganese alloy, performing a second deoxidation on the second molten steel after the first deoxidation to obtain aluminum-free molten steel; the low-carbon ferrosilicon and the manganese alloy are added simultaneously; The titanium content of the low-titanium ferrophosphorus alloy is ≤0.60 wt%; The Ti content of the molten steel prepared by the smelting method is below 0.0005 wt%.

2. The method according to claim 1, characterized in that The preset time is ≤5min.

3. A method for preparing aluminum-free steel, characterized in that: The method includes the smelting method according to any one of claims 1 to 2.

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