Slag, preparation method of slag and refining method of titanium-containing stainless steel

Abstract

The invention provides molten slag, a preparation method of the molten slag and a refining method of titanium-containing stainless steel, and the molten slag comprises the following components in percentage by mass: 52%-58% of CaO, 0-8% of SiO2, 22%-27% of Al2O3, 2%-5% of TiO2, 0%-6% of CaF2 and 0-8% of MgO. The activity of SiO2 and Al2O3 in the slag is low, the reaction trend with the metal titanium element is weak, and the yield of the titanium alloy element can be increased. By improving the yield of titanium alloy elements, the consumption of titanium alloy can be reduced, the titanium alloying cost is reduced, and the energy consumption, the waste slag amount and the carbon emission in the steel manufacturing process are further reduced.

Description

Technical Field

[0001] The present application relates to the technical field of steelmaking, and in particular to a slag, a method for preparing the slag, and a method for refining titanium-containing stainless steel. Background Art

[0002] Titanium is an alloying element in steel. It is usually added in the hot molten steel in the form of titanium alloy. The main method of adding titanium is to feed titanium alloy wire or directly add ferro-titanium alloy. Since titanium is a strong reducing element, it is easily oxidized by air and slag on the surface of molten steel, resulting in a reduced yield of titanium alloy. Affected by different addition methods, slag deoxidation effect, and the required titanium content in molten steel, the yield of titanium alloy elements is low and fluctuates greatly. For example, the yield of titanium added to ferro-titanium alloy usually fluctuates between 40% and 90%, and the yield of titanium fed to titanium alloy wire is between 60% and 95%.

[0003] In the case where the titanium yield is relatively low and fluctuates greatly, how to increase the average value of the titanium yield and reduce the standard deviation (fluctuation) is a problem that needs to be further solved. Summary of the invention

[0004] Based on this, the present application provides a slag, a method for preparing the slag, and a method for refining titanium-containing stainless steel to improve the recovery rate of titanium alloy elements.

[0005] A first aspect of the present application provides a slag, which comprises, by mass percentage, 52%-58% CaO, 0-8% SiO2, 22%-27% Al2O3, 2%-5% TiO2, 0-6% CaF2 and 0-8% MgO.

[0006] In some embodiments, the slag further comprises impurities.

[0007] One or more embodiments of the present application provide a method for preparing slag, comprising the following steps:

[0008] The molten steel is mixed with deoxidized aluminum, ferrosilicon alloy and metallurgical flux containing slag preparation raw materials, and the mixed materials are heated to melt to prepare slag;

[0009] The slag contains, by mass percentage, 52%-58% CaO, 0-8% SiO2, 22%-27% Al2O3, 2%-5% TiO2, 0-6% CaF2 and 0-8% MgO.

[0010] In some embodiments, the slag further comprises impurities.

[0011] In some embodiments, the metallurgical flux comprises a calcium source, an aluminum source, and a titanium source, the calcium source comprising a calcium source for providing CaO and a calcium source for providing CaF2.

[0012] In some embodiments, the metallurgical flux includes at least one of the following features (1)-(5):

[0013] (1) The calcium source for providing CaO includes one or more of lime and a material containing CaO; alternatively, the material containing CaO includes refined slag containing CaO;

[0014] (2) The aluminum source includes one or more of aluminum oxide and a material containing Al2O3; optionally, the material containing Al2O3 includes refined slag containing Al2O3;

[0015] (3) The titanium source includes refined slag containing TiO2;

[0016] (4) The calcium source for providing CaF2 includes fluorite and a material containing fluorine; optionally, the material containing fluorine includes refined slag containing fluorine;

[0017] (5) The particle sizes of the calcium source, the aluminum source and the titanium source are independently ≤50 mm, and can be optionally 3 mm-50 mm.

[0018] In some embodiments, the preparation method comprises at least one of the following conditions (1)-(3):

[0019] (1) The loss on ignition (LOI) of each material in the metallurgical flux during the slag preparation process is independently ≤2%;

[0020] (2) The heating temperature is 1580° C.-1650° C.;

[0021] (3) The step of heating the mixed material to melt it comprises: while heating the mixed material, stirring the mixed material with air flow;

[0022] Optionally, the gas flow stirring atmosphere comprises nitrogen and / or argon.

[0023] The third aspect of the present application provides a method for refining titanium-containing stainless steel, comprising the following steps:

[0024] After opening the ladle for bottom blowing and stirring, take a sample of molten steel for analysis;

[0025] The molten steel is mixed with deoxidized aluminum, ferrosilicon alloy and metallurgical flux containing slag preparation raw materials in the LF furnace, and the temperature is raised by electricity to make slag;

[0026] After slag making is completed, the steel is removed and analyzed; after sampling, the molten steel is heated to a preset temperature in the LF furnace and the VD / VOD furnace, and the ladle bottom blowing flow rate is increased to perform strong stirring desulfurization;

[0027] After the desulfurization is completed and the molten steel sample is taken, titanium wire is fed or titanium-iron alloy is added to titanium alloy the molten steel;

[0028] Transport qualified molten steel to continuous casting or mold casting process;

[0029] The slag obtained by slag making contains, by mass percentage, 52%-58% CaO, 0-8% SiO2, 22%-27% Al2O3, 2%-5% TiO2, 0-6% CaF2 and 0-8% MgO.

[0030] In some embodiments, the refining method includes at least one of the following conditions (1)-(11):

[0031] (1) The molten steel is smelted by an AOD furnace, an EAF electric arc furnace, or a converter;

[0032] (2) The metallurgical flux comprises a calcium source, an aluminum source and a titanium source, wherein the calcium source comprises a calcium source for providing CaO and a calcium source for providing CaF2;

[0033] Optionally, the calcium source for providing CaO includes one or more of lime and a material containing CaO; further optionally, the material containing CaO includes refined slag containing CaO;

[0034] Optionally, the aluminum source includes one or more of aluminum oxide and a material containing Al2O3; further optionally, the material containing Al2O3 includes refined slag containing Al2O3;

[0035] Optionally, the titanium source comprises refined slag containing TiO2;

[0036] Optionally, the calcium source for providing CaF2 includes fluorite and a material containing fluorine element; further optionally, the material containing fluorine element includes refined slag containing fluorine element;

[0037] Optionally, the particle sizes of the calcium source, the aluminum source and the titanium source are independently ≤50 mm, and can be 3 mm-50 mm.

[0038] (3) The preset temperature is 1550°C-1660°C;

[0039] (4) The LF furnace is operated with a furnace cover and slight positive pressure;

[0040] (5) The working pressure of the VD / VOD furnace is 10Pa-12kPa;

[0041] (6) while the slag forming is being performed, adding ferrosilicon alloy and / or ferromanganese alloy to the molten steel for alloying;

[0042] (7) while carrying out the strong stirring desulfurization, adding ferrosilicon alloy and / or ferromanganese alloy to the molten steel for alloying;

[0043] (8) Before the step of feeding titanium wire or adding ferro-titanium alloy, the step further includes: after the desulfurization is completed, ferrosilicon alloy and / or ferromanganese alloy and / or temperature are replenished again;

[0044] (9) Before or after the step of feeding titanium wire or adding titanium-iron alloy, the method further includes: feeding calcium alloy wire and aluminum wire;

[0045] (10) The wire feeding speed of the wire feeder used in the titanium wire feeding is 2m / s-4m / s;

[0046] (11) The stirring time of strong stirring desulfurization is 3min-20min.

[0047] In some embodiments, the national standard grades of titanium-containing stainless steel include TP321 and TP409.

[0048] The slag provided above has low SiO2 and Al2O3 activities and weak reaction tendency with metallic titanium, which can improve the recovery rate of titanium alloy elements. Improving the recovery rate of titanium alloy elements can reduce the consumption of titanium alloy, reduce the cost of titanium alloying, and further reduce energy consumption, waste slag volume and carbon emissions in the steel manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0050] Figure 1 The figure is a histogram of the titanium element yield of Examples 1-23 and Comparative Examples 1-31.

[0051] Figure 2 The figure is a histogram of the titanium element yield of Examples 24-51 and Comparative Examples 32-120. DETAILED DESCRIPTION

[0052] For ease of understanding of the present invention, the application will be described more fully below with reference to relevant embodiments. The following provides preferred embodiments of the application. However, the application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the application more thorough and comprehensive.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0054] The terms "and / or", "or / and", and "and / or" used herein include any one of two or more related listed items, and also include any and all combinations of the related listed items, wherein the any and all combinations include any combination of two related listed items, any more related listed items, or all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in the present application, the technical solution undoubtedly includes technical solutions connected by "logical and", and also undoubtedly includes technical solutions connected by "logical or".

[0055] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0056] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0057] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0058] The temperature parameters in this application, unless otherwise specified, allow both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0059] In this application, unless otherwise specified, the size, particle size, and diameter generally refer to the average value. In this application, "particle size" and "particle size" have the same definition, both representing the average particle size of a sphere or a spheroid.

[0060] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0061] In the present application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0062] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0063] In the description of the application, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0064] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0065] If there is no special explanation, all the steps of the present application can be performed sequentially or randomly, preferably sequentially.

[0066] Affected by factors such as different addition methods, slag deoxidation effect and the required titanium content in molten steel, the recovery rate of titanium alloy elements during steelmaking is low. For example, the recovery rate of titanium element from titanium-ferroalloy input usually fluctuates within the range of 40-90%, and the recovery rate of titanium element from titanium alloy wire feed is between 60-95%. Therefore, it is urgent to provide a method for improving the recovery rate of titanium alloy elements.

[0067] The main components in the slag that undergo redox reactions with titanium are SiO2 and Al2O3. Metal Ti mainly undergoes the following two reactions with SiO2 and Al2O3:

[0068] SiO2 + Ti= TiO2 + Si ①

[0069] 2 / 3 Al2O3 + Ti= TiO2 + 4 / 3 Al ②

[0070] Define the oxidation tendency parameter lnQ of metal Ti:

[0071] QUR Si =K θ / (a-TiO2 / a-SiO2) and lnQ Al =K θ ·(a-Al2O3) 2 / 3 / a-TiO2 (metal Ti is in direct contact with slag)

[0072] QUR Si =K θ / (a-Si·a-TiO2 / a-SiO2) and lnQ Al =K θ ·(a-Al2O3) 2 / 3 / ((a-Al) 4 / 3 ·a-TiO2)

[0073] (Metal Ti is in contact with steel and slag)

[0074] When lnQ>0, the oxidation reaction proceeds forward, and the larger the value, the easier it is; vice versa.

[0075] Therefore, the present application starts from reducing the oxidation of titanium alloy elements, and reducing the activity or reaction trend of the two is the key to improving the yield of titanium elements.

[0076] One or more embodiments of the present application provide a slag, which contains, by mass percentage, 52%-58% CaO, 0-8% SiO2, 22%-27% Al2O3, 2%-5% TiO2, 0%-6% CaF2 and 0-8% MgO.

[0077] As a non-limiting example, the mass percentage of CaO contained in the slag can be but is not limited to 52%, 53%, 54%, 55%, 56%, 57%, 58% or a range between any two of the above mass percentages.

[0078] As a non-limiting example, the mass percentage of SiO2 contained in the slag can be but is not limited to 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or a range between any two of the above mass percentages, etc.

[0079] As a non-limiting example, the mass percentage of Al2O3 contained in the slag can be but is not limited to 22%, 23%, 24%, 25%, 26%, 27% or a range between any two of the above mass percentages.

[0080] As a non-limiting example, the mass percentage of TiO2 contained in the slag may be, but is not limited to, 2%, 3%, 4%, 5% or a range between any two of the above mass percentages.

[0081] As a non-limiting example, the mass percentage of CaF2 contained in the slag can be but is not limited to 0, 1%, 2%, 3%, 4%, 5%, 6% or a range between any two of the above mass percentages.

[0082] As a non-limiting example, the mass percentage of MgO contained in the slag can be but is not limited to 0, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or a range between any two of the above mass percentages.

[0083] Understandably, the activities of SiO2 and Al2O3 in the slag are low, and the tendency to react with metallic titanium is weak, which can improve the recovery rate of titanium alloy elements. Improving the recovery rate of titanium alloy elements can reduce the consumption of titanium alloys, reduce the cost of titanium alloying, and further reduce energy consumption, waste slag and carbon emissions in the steel manufacturing process.

[0084] In some embodiments, the slag further comprises impurities.

[0085] One or more embodiments of the present application provide a method for preparing slag, comprising the following steps:

[0086] The molten steel is mixed with deoxidized aluminum, ferrosilicon alloy and metallurgical flux containing slag preparation raw materials, and the mixed materials are heated to melt to prepare slag;

[0087] The slag contains, in percentage by mass: 52%-58% CaO, 0-8% SiO2, 22%-27% Al2O3, 2%-5% TiO2, 0%-6% CaF2 and 0-8% MgO.

[0088] In some embodiments, the slag further comprises impurities.

[0089] In some embodiments, the metallurgical flux comprises a calcium source, an aluminum source, and a titanium source, the calcium source comprising a calcium source for providing CaO and a calcium source for providing CaF2.

[0090] As a possible implementation manner, the calcium source for providing CaO includes one or more of lime and a material containing CaO.

[0091] In some optional embodiments, the CaO-containing material includes refined slag containing CaO.

[0092] In some exemplary embodiments, the aluminum source includes one or more of alumina and an Al2O3-containing material.

[0093] In some optional embodiments, the Al2O3-containing material includes refined slag containing Al2O3.

[0094] As a possible embodiment, the titanium source includes refined slag containing TiO2.

[0095] In some optional embodiments, the calcium source for providing CaF2 includes fluorite and a material containing fluorine. Optionally, the material containing fluorine includes refined slag containing fluorine.

[0096] In some embodiments, the particle sizes of the calcium source, the aluminum source, and the titanium source are independently ≤50 mm, which is more conducive to storage, transportation, and rapid melting.

[0097] In some optional embodiments, the particle sizes of the calcium source, the aluminum source and the titanium source are independently 3 mm to 50 mm. For example, it can be, but is not limited to, 3 mm, 5 mm, 7 mm, 10 mm, 13 mm, 15 mm, 17 mm, 20 mm, 23 mm, 25 mm, 27 mm, 30 mm, 33 mm, 35 mm, 37 mm, 40 mm, 43 mm, 45 mm, 47 mm, 50 mm or a range between any two of the above particle sizes.

[0098] As a possible implementation manner, the particle sizes of the calcium source, the aluminum source and the titanium source are independently ≤3 mm.

[0099] In some embodiments, the LOI of each material in the metallurgical flux during the slag preparation process is independently ≤2%; thereby, the amount of dust generated is controlled, which is beneficial to the operating environment and human health.

[0100] It should be noted that the loss on ignition (LOI) refers to the weight reduction ratio of a specific sample after it is heated at a specific temperature of 110° C. or higher and kept warm for a certain period of time (for example, 10 min-15 min) in air or a protective atmosphere.

[0101] In some embodiments, the heating temperature is 1580°C-1650°C; for example, it can be but not limited to 1580°C, 1590°C, 1600°C, 1610°C, 1620°C, 1630°C, 1640°C, 1650°C or a range between any two of the above temperatures.

[0102] In some embodiments, the step of heating the mixed material to melt it includes: while heating the mixed material, stirring the mixed material with air flow to achieve desulfurization.

[0103] In some optional embodiments, the gas flow agitation atmosphere includes nitrogen and / or argon.

[0104] One or more embodiments of the present application provide a method for refining titanium-containing stainless steel, comprising the following steps:

[0105] After opening the ladle bottom blowing and stirring, take a sample of molten steel for analysis; mix the molten steel with deoxidized metal aluminum, ferrosilicon alloy and metallurgical flux containing slag preparation raw materials in the LF furnace, and turn on the power to heat up for slag making; after slag making, take a sample of molten steel for analysis; after sampling, heat the molten steel to the preset temperature in the LF furnace and VD / VOD furnace, increase the ladle bottom blowing flow rate for strong stirring desulfurization; after desulfurization, take a sample of molten steel, feed titanium wire or add ferrotitanium alloy to titanium alloy the molten steel; transport qualified molten steel to the continuous casting or mold casting process;

[0106] The slag obtained by slag making contains, by mass percentage, 52%-58% CaO, 0-8% SiO2, 22%-27% Al2O3, 2%-5% TiO2, 0%-6% CaF2 and 0-8% MgO.

[0107] Understandably, the activities of SiO2 and Al2O3 in the slag are low, and the tendency to react with metallic titanium is weak, which can improve the recovery rate of titanium alloy elements. Improving the recovery rate of titanium alloy elements can reduce the consumption of titanium alloys, reduce the cost of titanium alloying, and further reduce energy consumption, waste slag and carbon emissions in the steel manufacturing process.

[0108] It should be noted that the recovery rate of titanium element by feeding titanium wire with a wire feeder and by adding titanium-iron alloy into molten steel for alloying can be increased by 3%-15%, and the recovery rate is more stable.

[0109] In some embodiments, the molten steel is molten steel smelted by an AOD furnace, an EAF electric arc furnace, or a converter.

[0110] In some embodiments, the metallurgical flux comprises a calcium source, an aluminum source, and a titanium source, the calcium source comprising a calcium source for providing CaO and a calcium source for providing CaF2.

[0111] As a possible implementation manner, the calcium source for providing CaO includes one or more of lime and a material containing CaO.

[0112] In some optional embodiments, the CaO-containing material includes refined slag containing CaO.

[0113] In some exemplary embodiments, the aluminum source includes one or more of alumina and an Al2O3-containing material.

[0114] In some optional embodiments, the Al2O3-containing material includes refined slag containing Al2O3.

[0115] As a possible embodiment, the titanium source includes refined slag containing TiO2.

[0116] In some optional embodiments, the calcium source for providing CaF2 includes fluorite and a material containing fluorine. Optionally, the material containing fluorine includes refined slag containing fluorine.

[0117] In some embodiments, the particle size of the calcium source, the aluminum source, and the titanium source are each independently ≤ 50 mm.

[0118] In some optional embodiments, the particle sizes of the calcium source, the aluminum source and the titanium source are independently 3 mm to 50 mm. For example, it can be, but is not limited to, 3 mm, 5 mm, 7 mm, 10 mm, 13 mm, 15 mm, 17 mm, 20 mm, 23 mm, 25 mm, 27 mm, 30 mm, 33 mm, 35 mm, 37 mm, 40 mm, 43 mm, 45 mm, 47 mm, 50 mm or a range between any two of the above particle sizes.

[0119] As a possible implementation manner, the particle sizes of the calcium source, the aluminum source and the titanium source are independently ≤3 mm.

[0120] In some embodiments, the preset temperature is 1550℃-1660℃; for example, it can be but not limited to 1550℃, 1560℃, 1570℃, 1580℃, 1590℃, 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, 1650℃, 1660℃ or a range between any two of the above temperatures.

[0121] As a possible implementation method, the LF furnace is operated with a furnace cover and slight positive pressure.

[0122] In some optional embodiments, the operating pressure of the VD / VOD furnace is 10Pa-12kPa.

[0123] In some embodiments, while the slag forming is being performed, ferrosilicon alloy and / or ferromanganese alloy is added to the molten steel for alloying.

[0124] In some embodiments, while the strong agitation desulfurization is being performed, ferrosilicon alloy and / or ferromanganese alloy is added to the molten steel for alloying.

[0125] As a possible implementation manner, before the step of feeding titanium wire or adding titanium-ferroalloy, the step further includes: replenishing ferrosilicon alloy and / or ferromanganese alloy and / or temperature again after desulfurization is completed.

[0126] In some embodiments, after or after the step of feeding titanium wire or adding titanium-iron alloy, the method further includes: feeding calcium alloy wire and aluminum wire.

[0127] In some embodiments, the wire feeding speed of the wire feeder used when feeding the titanium wire is 2m / s-4m / s; for example, it can be but not limited to 2m / s, 3m / s, 4m / s or a range between any two of the above wire feeding speeds.

[0128] In some embodiments, the stirring time of the strong stirring desulfurization is 3 min-20 min; for example, it can be but not limited to 3 min, 5 min, 7 min, 10 min, 13 min, 15 min, 18 min, 20 min or a range between any two of the above times.

[0129] In some optional embodiments, the total time of the refining process is 30 min-70 min; for example, it can be but not limited to 30 min, 40 min, 50 min, 60 min, 70 min or a range between any two of the above times.

[0130] In some embodiments, the national standard grades of titanium-containing stainless steel include TP321 and TP409.

[0131] The technical scheme of the present invention is described in detail below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods for which specific conditions are not specified in the following embodiments are preferably referred to the guidance given in the present invention, and can also be carried out according to the experimental manual or conventional conditions in the art, or according to the conditions recommended by the manufacturer, or with reference to experimental methods known in the art.

[0132] In the following specific embodiments, the measured parameters of raw material components may have slight deviations within the range of weighing accuracy unless otherwise specified. For temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed.

[0133] It should be noted that the metallurgical flux used in the following embodiments includes refined slag containing TiO2 and lime, wherein the lime meets the quality requirements of "ordinary metallurgical lime grade 2" in the metallurgical standard YBT042-2014 "Metallurgical Lime" and has a particle size of 3mm-30mm; the particle size of the refined slag is 3mm-30mm, and its chemical composition meets the requirements of Table 1.

[0134] Table 1

[0135] <![CDATA[Al2O3(%)]]> CaO(%) <![CDATA[SiO2(%)]]> <![CDATA[TiO2(%)]]> MgO(%) <![CDATA[Fe2O3(%)]]> Typical Value 72 8.5 0.5 16.5 1.2 1.1 Specifications 63-78 5-12 <3.0 15-18 <4.0 <1.5

[0136] The metallurgical fluxes used in the following comparative examples include fluorite and lime, wherein the lime meets the quality requirements of "Ordinary Metallurgical Lime Grade 2" in the metallurgical standard YBT042-2014 "Metallurgical Lime", and has a particle size of 3mm-30mm; the fluorite meets the 3mm-30mm particles processed from FL-85 fluorite lump ore in accordance with the YB / T5217-2019 standard.

[0137] The steel type used in the following embodiments and comparative examples is TP321, and the mass percentage of titanium element in molten steel is required to be 0.28%-0.36%.

[0138] 1. Refining of titanium-containing stainless steel

[0139] The preparation processes of Examples 1-23 and Comparative Examples 1-31 are as follows:

[0140] Step S1, transporting the molten steel smelted by the AOD furnace, EAF electric arc furnace and converter to the LF furnace;

[0141] Step S2, open the ladle bottom blowing, stir for 3 minutes and then take the molten steel sample for analysis;

[0142] Step S3, adding deoxidized metal aluminum and / or ferrosilicon alloy, and adding metallurgical flux to perform heating and slag-making operations, and obtaining slag components as shown in Table 2; at the same time, adding ferrosilicon alloy and / or manganese silicon alloy to the molten steel for alloying;

[0143] Step S4, after heating the molten steel to 1630° C. in the LF furnace and the VD / VOD furnace, stop heating and take a sample of the molten steel for analysis; perform a strong stirring desulfurization operation with a stirring time of 8 min; the pressure of the VD / VOD furnace is 1 Pa-500 Pa; during the strong stirring desulfurization operation, ferrosilicon alloy and / or ferromanganese alloy is added to the molten steel for alloying;

[0144] Step S5, after the desulfurization operation is completed, a molten steel sample is taken for analysis, and then a titanium-iron alloy is added to the molten steel to perform titanium alloying on the molten steel;

[0145] Step S6: transport the qualified molten steel to the continuous casting or mold casting process.

[0146] The amount of molten steel added, the amount of metallurgical flux added, the composition of the slag obtained by slag making, and the titanium yield of Examples 1-23 and Comparative Examples 1-31 are shown in Table 2, respectively.

[0147] Table 2

[0148]

[0149]

[0150] The preparation process of Examples 24-51 and Comparative Examples 32-120 is similar to that of Examples 1-23 and Comparative Examples 1-31, with the difference being that in Examples 24-51 and Comparative Examples 32-120, titanium feeding method is adopted to add titanium-iron alloy to molten steel to titanium alloy the molten steel; wherein the wire feeding speed of the wire feeding machine is 2m / s-4m / s.

[0151] The amount of molten steel added, the amount of metallurgical flux added, the composition of the slag obtained by slag making, and the titanium yield of Examples 24-51 and Comparative Examples 32-120 are shown in Table 3, respectively.

[0152] Table 3

[0153]

[0154]

[0155]

[0156]

[0157] Comparing the average composition of the slag obtained by slag making in Example 1-23 and the average composition of the slag obtained by slag making in Comparative Example 1-31, the titanium element mainly undergoes the following two reactions with SiO2 and Al2O3 in the slag:

[0158] SiO2 + Ti= TiO2 + Si ①

[0159] 2 / 3 Al2O3 + Ti= TiO2 + 4 / 3 Al ②

[0160] Define the oxidation tendency parameter lnQ of metal Ti:

[0161] QUR Si =K θ / (a-TiO2 / a-SiO2) and lnQ Al =K θ ·(a-Al2O3) 2 / 3 / a-TiO2 (metal Ti is in direct contact with slag)

[0162] QUR Si =K θ / (a-Si·a-TiO2 / a-SiO2) and lnQ Al =K θ ·(a-Al2O3) 2 / 3 / ((a-Al) 4 / 3 ·a-TiO2)

[0163] (Metal Ti is in contact with steel and slag)

[0164] When lnQ>0, the oxidation reaction proceeds forward, and the larger the value, the easier it is; vice versa.

[0165] When metal Ti is in direct contact with slag, it can be considered that a-Ti=1, a-Si=1, and a-Al=1. The oxidation tendency parameters lnQ of the embodiment and the comparative example are shown in Table 4. As can be seen from Table 4, the tendency of metal Ti to react with Al2O3 in the slag is very weak or it can be considered that there is no reaction, but the reaction with SiO2 is relatively strong; and compared with the embodiment, the reaction tendency of SiO2 in the slag of the comparative example is stronger.

[0166] Table 4

[0167]

[0168] The titanium element yield histogram of Examples 1-23 and Comparative Examples 1-31 using the injection method is shown in FIG. Figure 1 As shown, the titanium element yield histogram of Examples 24-51 and Comparative Examples 32-120 using the wire feeding method is as follows Figure 2 As shown. Figure 1 and Figure 2 It can be seen that the mean titanium element yield in the embodiment is 74% and 81% for the input method and the wire feeding method, respectively, and the standard deviations are 3.8% and 4.0%, respectively. The mean titanium element yield in the comparative example is 68% and 77%, respectively, and the standard deviations are 7.2% and 5.2%, respectively. The mean titanium element yield in the embodiment is 6% and 4% higher than that in the comparative example, and the standard deviation is low. This shows that the titanium element yield in the embodiment is improved and more stable.

[0169] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0170] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A slag, characterized in that: The slag contains, by mass percentage, 52%-58% CaO, 0-8% SiO2, 22%-27% Al2O3, 2%-5% TiO2, 0-6% CaF2 and 0-8% MgO.

2. The slag according to claim 1, characterized in that The slag also contains impurities.

3. A method for preparing slag, characterized in that: The steps include: The molten steel is mixed with deoxidized aluminum, ferrosilicon alloy and metallurgical flux containing slag preparation raw materials, and the mixed materials are heated to melt to prepare slag; The slag contains, by mass percentage, 52%-58% CaO, 0-8% SiO2, 22%-27% Al2O3, 2%-5% TiO2, 0-6% CaF2 and 0-8% MgO.

4. The preparation method according to claim 3, characterized in that: The slag also contains impurities.

5. The preparation method according to claim 3, characterized in that: The metallurgical flux comprises a calcium source, an aluminum source and a titanium source, wherein the calcium source comprises a calcium source for providing CaO and a calcium source for providing CaF2.

6. The preparation method according to claim 5, characterized in that: The metallurgical flux comprises at least one of the following features (1)-(5): (1) The calcium source for providing CaO includes one or more of lime and a material containing CaO; alternatively, the material containing CaO includes refined slag containing CaO; (2) The aluminum source includes one or more of aluminum oxide and a material containing Al2O3; optionally, the material containing Al2O3 includes refined slag containing Al2O3; (3) The titanium source includes refined slag containing TiO2; (4) The calcium source for providing CaF2 includes fluorite and a material containing fluorine element; optionally, the material containing fluorine element includes refined slag containing fluorine element; (5) The particle sizes of the calcium source, the aluminum source and the titanium source are independently ≤50 mm, and can be selected to be 3 mm-50 mm.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The preparation method comprises at least one of the following conditions (1)-(3): (1) The loss on ignition (LOI) of each material in the metallurgical flux during the slag preparation process is independently ≤2%; (2) The heating temperature is 1580° C.-1650° C.; (3) The step of heating the mixed material to melt it includes: while heating the mixed material, stirring the mixed material with air flow; Optionally, the gas flow stirring atmosphere comprises nitrogen and / or argon.

8. A method for refining titanium-containing stainless steel, characterized in that: The steps include: Open the ladle for bottom blowing, stir and take molten steel samples for analysis; The molten steel is mixed with deoxidized aluminum, ferrosilicon alloy and metallurgical flux containing slag preparation raw materials in the LF furnace, and the temperature is raised by electricity to make slag; After slag making is completed, the molten steel is sampled for analysis; after sampling, the molten steel is heated to a preset temperature in the LF furnace and the VD / VOD furnace, and the ladle bottom blowing flow rate is increased to perform strong stirring desulfurization; After the desulfurization is completed and the molten steel sample is taken, titanium wire is fed or titanium-iron alloy is added to titanium alloy the molten steel; Transport qualified molten steel to continuous casting or mold casting process; The slag obtained by slag making contains, by mass percentage, 52%-58% CaO, 0-8% SiO2, 22%-27% Al2O3, 2%-5% TiO2, 0-6% CaF2 and 0-8% MgO.

9. The refining method according to claim 8, characterized in that The refining method comprises at least one of the following conditions (1) to (11): (1) The molten steel is smelted by an AOD furnace, an EAF electric arc furnace, or a converter; (2) The metallurgical flux comprises a calcium source, an aluminum source and a titanium source, wherein the calcium source comprises a calcium source for providing CaO and a calcium source for providing CaF2; Optionally, the calcium source for providing CaO includes one or more of lime and a material containing CaO; further optionally, the material containing CaO includes refined slag containing CaO; Optionally, the aluminum source includes one or more of aluminum oxide and a material containing Al2O3; further optionally, the material containing Al2O3 includes refined slag containing Al2O3; Optionally, the titanium source comprises refined slag containing TiO2; Optionally, the calcium source for providing CaF2 includes fluorite and a material containing fluorine element; further optionally, the material containing fluorine element includes refined slag containing fluorine element; Optionally, the particle sizes of the calcium source, the aluminum source and the titanium source are independently ≤50 mm, and may be 3 mm to 50 mm; (3) The preset temperature is 1550°C-1660°C; (4) The LF furnace is operated with a furnace cover and slight positive pressure; (5) The working pressure of the VD / VOD furnace is 10Pa-12kPa; (6) while the slag forming is being performed, adding ferrosilicon alloy and / or ferromanganese alloy to the molten steel for alloying; (7) while carrying out the strong stirring desulfurization, adding ferrosilicon alloy and / or ferromanganese alloy to the molten steel for alloying; (8) Before the step of feeding titanium wire or adding ferro-titanium alloy, the step further includes: after the desulfurization is completed, ferrosilicon alloy and / or ferromanganese alloy and / or temperature are replenished again; (9) Before or after the step of feeding titanium wire or adding titanium-iron alloy, the method further includes: feeding calcium alloy wire and aluminum wire; (10) The wire feeding speed of the wire feeder used in the titanium wire feeding is 2m / s-4m / s; (11) The stirring time of strong stirring desulfurization is 3min-20min.

10. The refining method according to any one of claims 8 to 9, characterized in that: The national standard grades of titanium-containing stainless steel include TP321 and TP409.

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