Preparation method of Al-xTi intermediate alloy with high titanium content

Abstract

The invention discloses a preparation method of a high-titanium-content Al-xTi intermediate alloy, and relates to the technical field of non-ferrous metal alloy preparation. Titanium dioxide and potassium fluotitanate are used as a composite titanium source and an oxidizing agent, an industrial pure aluminum block is used as an intermediate alloy matrix material and a reducing agent, sodium chloride and potassium chloride are used as a composite solvent and a covering agent, calcium fluoride is used as a slag former and a deoxidizing agent, and a matched preparation process is adopted. The thermodynamic conditions in the reduction smelting process are optimized, inclusions in the intermediate alloy are reduced through the same casting mold, segregation of an alloy phase in the solidification process is reduced through rapid cooling, and finally the high-titanium-content intermediate alloy uniform in component is prepared. Through detection, the titanium concentration of the intermediate alloy is 10 wt% or above, the maximum value of titanium component deviation does not exceed 0.5%, the impurity concentration does not exceed 0.3 wt%, and the intermediate alloy has the advantages of being high in titanium content, high in purity, uniform in component and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal alloy preparation, and in particular to a method for preparing an Al-xTi master alloy with a high titanium content. Background Art

[0002] Aluminum-titanium master alloy is a commonly used aluminum alloy refiner. Adding a small amount of Ti element to aluminum alloy can significantly refine the grains of aluminum alloy, adjust the grain morphology, and thus improve the comprehensive mechanical properties of aluminum alloy. In order to meet the requirements of aluminum alloys with different structures and properties and improve the refinement or strengthening effect of the alloy, various multi-component aluminum master alloys have been gradually developed on the basis of Al-xTi binary master alloys. In addition to Al-xTi-yB and Al-xTi-yC master alloys, the common ones also include Al-xTi-zRE (RE is a rare earth element), Al-xTi-yB-zRE, Al-xTi-yC-zRE, Al-xTi-yB-zC, etc. Although these multi-component master alloys are superior to Al-xTi binary master alloys in many aspects, they also have various problems such as relatively complex preparation process, high cost, and narrow application range. The biggest problem of these multi-component alloys is that the ratio of different alloying elements contained in the master alloy is fixed, which is difficult to adjust, and the binary master alloy is still needed for adjustment. Therefore, Al-xTi binary master alloy is still regarded as one of the most commonly used aluminum alloy refiners and is widely used. It is particularly suitable for occasions where precise control of the aluminum alloy composition is required, and for occasions where boronizing agents are likely to cause "poisoning" of aluminum alloys (such as heat-resistant alloys containing Zr).

[0003] The grades of commercial Al-xTi master alloys are mainly Al-5Ti master alloys with low titanium content, and there are also some Al-10Ti and Al-15Ti master alloys with high titanium content. These aluminum alloys with high titanium content have higher refinement efficiency. Under the condition of achieving the same refinement effect, the addition amount of high titanium content aluminum-titanium master alloys is relatively small, which can not only improve the efficiency of placement and reduce energy consumption, but also inhibit the adverse effects of impurities contained in the master alloy itself on the base aluminum alloy, which is particularly important in the preparation of high-clean aluminum alloy materials. However, at present, except for the use of powder metallurgy, the preparation of Al-xTi master alloys with high Ti content is relatively difficult.

[0004] At present, the most commonly used preparation method for various aluminum master alloys is the melting method, that is, the aluminum ingot and the single substance of various alloy elements are melted and mixed at high temperature to generate a relatively uniform alloy melt, and various aluminum master alloys are obtained after casting. The advantage of this preparation method is that the alloy composition is relatively uniform. However, this method is not suitable for the preparation of Al-xTi master alloys. Since the melting point of Ti (1670℃) is very high, and the melting point of aluminum or aluminum alloy matrix (about 660℃) is very low, it is difficult for metal titanium to melt at the melting temperature that the matrix can withstand (generally 700-900℃). Other commonly used preparation methods for aluminum master alloys are powder metallurgy and reduction smelting. The raw materials of the powder metallurgy method are aluminum powder and alloy powder. After mixing evenly, they are pressed and formed and then sintered to prepare aluminum master alloys. The advantage of this method is that it has wide applicability, and can prepare aluminum master alloys containing high melting point and high density alloy elements, and it is also convenient to prepare aluminum master alloys with high alloy element content. However, it also has some obvious disadvantages, such as the high production cost of metal powder as raw material, low density of master alloy, uneven distribution of alloying elements and other problems. The raw materials for producing aluminum master alloy by thermal reduction method can be low-priced oxides, chlorides or salts, and the aluminum and aluminum alloy matrix are not required to be metal powder, and the alloying elements are not required to be metal single substances. In addition, the thermal reduction method has the advantages of the melting method, that is, the reduced alloying elements are usually evenly dispersed in the aluminum or aluminum alloy matrix as fine particles, making the distribution of alloying elements in the product more dispersed and more uniform. However, the thermal reduction method is restricted by various reduction thermodynamic and kinetic conditions, and is limited in the preparation of aluminum master alloys with high alloying element content. Summary of the invention

[0005] In view of the above shortcomings, the present invention provides a method for preparing an Al-xTi master alloy with a high titanium content, which solves the problem that the preparation of a master alloy with a high titanium content by a thermal reduction method is easily restricted by reduction thermodynamics and kinetic conditions. The specific technical scheme is as follows:

[0006] A method for preparing an Al-xTi master alloy with a high titanium content comprises the following steps:

[0007] S1. Raw material pretreatment: taking the raw materials required for preparing the Al-xTi master alloy according to the ratio and vacuum drying them, the raw materials include titanium dioxide, potassium fluorotitanate, pure aluminum block, sodium chloride, potassium chloride and calcium fluoride; and mixing the sodium chloride and potassium chloride and dividing them into a bottom layer mixture of sodium chloride and potassium chloride, a middle layer mixture of sodium chloride and potassium chloride and an upper layer mixture of sodium chloride and potassium chloride according to the mass ratio;

[0008] Among them, titanium dioxide (TiO 2 ) and potassium fluorotitanate (K 2 TiF 6) as a composite titanium source and oxidant, industrial pure aluminum block (Al) as a master alloy matrix material and reducing agent, sodium chloride (NaCl) and potassium chloride (KCl) as a composite solvent and covering agent, calcium fluoride (CaF 2 ) as slag-forming agent and deoxidizer.

[0009] S2. Mixing and melting: the raw materials pretreated in step S1 are layered and placed into a crucible in the order of the bottom layer mixture of sodium chloride and potassium chloride, titanium dioxide, potassium fluorotitanate, the middle layer mixture of sodium chloride and potassium chloride, and calcium fluoride; the crucible is placed in a crucible furnace and heated to 700-750° C. to melt all the raw materials, and then kept warm for 20-40 minutes. During the warming period, the crucible is stirred with a graphite rod every 4-6 minutes until there is no solid adhesive on the bottom and inner wall of the crucible.

[0010] S3. Reduction smelting: continue to raise the temperature to 750-850°C, add the pure aluminum block into the crucible, stir and react, so that the aluminum block melts and reacts with the titanium ions in the molten salt for reduction. After 60-105 minutes, remove the scum on the surface of the melt, then add the upper layer mixture of sodium chloride and potassium chloride, stir while adding, keep warm for 30-60 minutes, and remove the scum.

[0011] S4. Cooling: Cool at a rate of 2-3°C / min. Stir continuously during the cooling process. Stop stirring when the furnace temperature drops to 700-710°C.

[0012] S5. Standing: Let the melt stand for 10 to 20 minutes after cooling.

[0013] S6. Rapid cooling: The crucible is taken out from the crucible furnace steadily and quickly, and is naturally cooled to room temperature to obtain an intermediate alloy casting.

[0014] Furthermore, in step S1, the mass ratio of the titanium dioxide to the pure aluminum block is 35-50%; the molar ratio of the potassium fluorotitanate to the titanium dioxide is 0.10-0.26; the total mass of the sodium chloride and potassium chloride after mixing is 28-32% of the mass of the pure aluminum block, and the molar ratio of the sodium chloride to the potassium chloride is 0.95-1.05; the mass of the calcium fluoride is 20-30% of the mass of the pure aluminum block.

[0015] Furthermore, in step S1, the bottom layer mixture of sodium chloride and potassium chloride accounts for 20-30% of the total mass of the sodium chloride and potassium chloride after mixing, the middle layer mixture of sodium chloride and potassium chloride accounts for 30-40% of the total mass of the sodium chloride and potassium chloride after mixing, and the rest is the upper layer mixture of sodium chloride and potassium chloride.

[0016] Furthermore, in step S1, an electrolyte may be added to the mixture of sodium chloride and potassium chloride to adjust the melt viscosity, and the amount of electrolyte added is 2-4% of the mass of the pure aluminum block. When the electrolyte is added, the electrolyte on the upper part of the intermediate alloy casting needs to be stripped before cutting the head when performing step S7.

[0017] Furthermore, the electrolyte is LiCl, CaCl 2 、BaCl 2 One or more of .

[0018] Furthermore, in step S1, the vacuum drying temperature is 95-110° C., and the time is 2-4 hours.

[0019] Furthermore, in step S4, the stirring rate is 60-120 rpm.

[0020] Furthermore, the concentration of Ti in the Al-xTi master alloy is ≥10wt%, that is, x≥10, and the impurity concentration is ≤0.3wt%.

[0021] The crucible used can be made of high-strength graphite, oxidation-resistant steel, nickel, tungsten, molybdenum and other high-temperature resistant materials.

[0022] Design principle of the present invention:

[0023] (1) By designing a reasonable raw material formula and molten salt system, more easily reducible particles are generated in the melt, such as TiF 6 2- , thus making up for the TiO 2 The defects of low solubility and difficulty in reduction cause titanium to be deeply reduced and eventually form a dispersed phase (mainly Al 3 Ti phase) is evenly distributed in the master alloy. Further, during the reduction process, potassium fluorotitanate dissolves to form TiF 6 2- ions, the Ti 4+ The TiO2 dissolved in the molten salt is continuously reduced by Al and decomposes. 2 With TiF 6 2- The free fluoride ions produced by decomposition react to form new TiF 6 2- groups, thus affecting the TiF 6 2- In the early stage of the reaction, when the concentration of potassium fluorotitanate is high, the TiO 2 Diluted TiF 6 2- concentration, slowing down the reduction reaction rate. In the middle and late stages of the reaction, when TiF 6 2-When the concentration is low and the free fluoride ion concentration is high, TiO 2 It reacts with free fluoride ions to form TiF 6 2- , for TiF in molten salt 6 2- This makes the reaction rate of the entire reduction process more uniform, which is conducive to the formation of an alloy phase with consistent particle size and distribution in the aluminum matrix.

[0024] (2) The purpose of adding the composite solvent in layers is to make it easier to mix the materials evenly during the heating process. The remaining composite solvent is added at the end of the reduction smelting process. The purpose is to avoid oxidation of the melt due to the loss of the covering agent, because the composite solvent will volatilize during the early heating process. Therefore, additional solvent is needed to avoid oxidation of the melt due to the lack of covering agent.

[0025] (3) The aluminum alloy melt has a low density and low viscosity at high temperatures, and the generated titanium-containing phase has a higher density than aluminum and has a tendency to settle. Therefore, at high temperatures, especially at the beginning of cooling, there are more titanium-containing phases in the melt, which are prone to aggregation and sedimentation, and more stirring is needed. When the melt temperature drops to a certain temperature range, the melt viscosity increases, the buoyancy increases, and the titanium-containing phase has difficulty settling, the stirring is stopped.

[0026] (4) The purpose of standing still at low temperature for a short time is to separate the metal melt from the solvent and the titanium dioxide dissolved in the solvent. The purpose of rapid cooling rather than cooling with the furnace is to prevent the precipitation of titanium-containing phases and segregation during the solidification process, so as to make the spatial distribution of alloy components more uniform. Solidification in a reduction smelting crucible instead of solidification by casting is to avoid the fluorine chloride electrolyte covering the surface of the melt from being mixed with the melt during the casting process, resulting in serious inclusions inside. At the same time, it is also to avoid the air being drawn into the melt during the casting process and generating a large number of pores in the solidified intermediate alloy.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention designs a new thermal reduction system (K 2 TiF 6 -TiO 2 As composite titanium source and oxidant, pure aluminum as aluminum matrix and reductant, NaCl-KCl as composite solvent, CaF 2 As a slag-forming agent), and a matching preparation process was adopted to optimize the thermodynamic conditions of the reduction smelting process, reduce the inclusions in the intermediate alloy by melting and casting in the same mold, and reduce the segregation of the alloy phase during the solidification process by rapid cooling, and finally prepare a uniform composition high titanium content Al-xTi (x≥10) intermediate alloy.

[0029] 2. The present invention uses titanium dioxide (TiO 2) and potassium fluorotitanate as raw materials for the alloy element titanium, the price is much lower than that of metallic titanium, the reduction smelting temperature is within the commonly used smelting temperature range of aluminum alloys, normal pressure non-vacuum smelting, no inert gas protection, low production energy consumption, thus having obvious cost advantages.

[0030] 3. The intermediate alloy prepared by the present invention has high purity, and except for Ti element, the content of other impurity elements is very low; since the reduction process is protected by electrolyte, the oxidation of the metal melt is suppressed, and the utilization rate of the alloy elements is improved; the titanium phase generated by the reaction is relatively dispersed in the aluminum matrix, and the quality of the intermediate alloy is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0032] Figure 1 This is a simplified process flow diagram of the preparation of the Al-xTi (x≥10) master alloy with high titanium content according to the present invention;

[0033] Figure 2 It is a comparison chart of average titanium concentration of the master alloy samples prepared in each embodiment and comparative example;

[0034] Figure 3 The figure is a comparison diagram of spatial composition uniformity of the master alloy samples prepared in each embodiment and the comparative example;

[0035] Figure 4 The figure is a comparison chart of the average impurity concentration of the intermediate alloy samples prepared in each embodiment and the comparative example. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0037] The raw material formulas of various embodiments and comparative examples are shown in Table 1.

[0038] Table 1 Raw material formula of Examples 1 to 6 and Comparative Examples 1 to 6 (in g)

[0039]

[0040] The process conditions of each embodiment and comparative example are shown in Table 2.

[0041] Table 2 Main process conditions of Examples 1 to 6 and Comparative Examples 1 to 6

[0042]

[0043] Table 2 Notes: The remaining operating steps and process conditions are exactly the same as those in Example 1.

[0044] Example 1

[0045] Raw material formula: weigh 1000.0g of industrial pure aluminum (Al) as the Al source for preparing the master alloy Al-xTi, weigh 350.0g of analytical pure titanium dioxide (TiO 2 ) and 262.9 g potassium fluorotitanate (K 2 TiF 6 ) as a Ti source for preparing the master alloy Al-xTi; weigh 300g of a composite solvent (a mixture of 131.8g of analytically pure sodium chloride (NaCl) and 168.2g of analytically pure potassium chloride (KCl)), weigh 20g of lithium chloride (LiCl) as an electrolyte, weigh 200g of analytically pure calcium fluoride (CaF 2 ) as slag-forming agent and deoxidizer.

[0046] According to this formula, Al-xTi master alloy is prepared according to the following specific steps (process flow is as follows Figure 1 shown).

[0047] S1. Raw material pretreatment: The above raw materials were vacuum dried at 105°C for 3 h.

[0048] S2. Mixed melting: Place the raw materials in a cylindrical crucible in the order of composite solvent (60 g), titanium dioxide, potassium fluorotitanate, composite solvent (120 g), lithium chloride and calcium fluoride, place the crucible in a crucible furnace and heat it to 700°C to melt all the raw materials, then keep warm for 30 minutes, stirring with a graphite rod every 5 minutes until there is no solid adhesive on the bottom and inner wall of the crucible.

[0049] S3. Reduction smelting: Raise the furnace temperature to 850°C, add pure aluminum blocks into the crucible, and stir at the same time, so that the aluminum blocks melt and react with the titanium ions in the molten salt to reduce them. After 60 minutes of reaction, remove the scum on the surface of the melt. Continue to maintain the furnace temperature, and add the remaining composite solvent (120g) into the crucible through the feeding pipe, stirring while adding, and continue to keep the temperature for 30 minutes, and then remove the scum again.

[0050] S4. Cooling: After the furnace temperature is lowered to 710°C at a cooling rate of 3°C / min, stirring is required before the furnace temperature drops to the upper temperature limit. Stop stirring when the temperature drops to within the temperature range.

[0051] S5. Standing: Let the melt stand for 10 minutes.

[0052] S6. Rapid cooling: Take the crucible out of the furnace steadily and quickly, and cool it naturally to near room temperature in the air.

[0053] S7. Cleaning and drying: The electrolyte on the upper part of the master alloy casting obtained in step S6 is stripped off, the upper and lower ends are cut off, and then the aluminum ingot is cleaned with warm water and air-dried to obtain the final aluminum-titanium master alloy product.

[0054] After ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 12.3wt%, the impurity element concentration is 0.27wt% (all refer to the total impurity concentration, the same as the case below), and the rest is aluminum, corresponding to Figure 2 The alloying element concentration of Example 1; the uniformity deviation of titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, and the Ti concentration deviation is only 0.41%; the impurity element concentration is as follows Figure 4 shown.

[0055] Example 2

[0056] The difference between this embodiment and embodiment 1 is only that the ratio of the molten salt components in the raw material formula for preparing the Al-xTi master alloy is different. The amount of each raw material is shown in Table 1.

[0057] The preparation process steps and conditions are exactly the same as those in Example 1.

[0058] After ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 11.1wt%, the total impurity elements are 0.30wt%, and the rest is aluminum, corresponding to Figure 2 The alloying element concentration of Example 2; the uniformity deviation of titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, and the Ti concentration deviation is only 0.34%; the impurity element concentration is as follows Figure 4 shown.

[0059] Example 3

[0060] The difference between this embodiment and embodiment 1 is only that the ratio of the molten salt components in the raw material formula for preparing the Al-xTi master alloy is different. The amount of each raw material is shown in Table 1.

[0061] The preparation process steps and conditions are exactly the same as those in Example 1.

[0062] After ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 10.5wt%, the total impurity elements are 0.29wt%, and the rest is aluminum, corresponding to Figure 2 The alloy element concentration of Example 3; the uniformity deviation of titanium element in the alloy is as follows Figure 3As shown in the figure, the 5-point test results show that the uniformity is very good, and the Ti concentration deviation is only 0.25%; the impurity element concentration is Figure 4 shown.

[0063] Example 4

[0064] The difference between this embodiment and embodiment 1 is only that the ratio of the molten salt components in the raw material formula for preparing the Al-xTi master alloy is different. The amount of each raw material is shown in Table 1.

[0065] The preparation process steps and conditions are exactly the same as those in Example 1.

[0066] After ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 10.6wt%, the total impurity elements are 0.28wt%, and the rest is aluminum, corresponding to Figure 2 The alloying element concentration of Example 4; the uniformity deviation of titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, and the Ti concentration deviation is only 0.22%; the impurity element concentration is as follows Figure 4 shown.

[0067] Example 5

[0068] The difference between this embodiment and embodiment 1 is only that the preparation process conditions are different, and the raw material formula is exactly the same as that of embodiment 1. The specific amounts are shown in Table 1.

[0069] Except that steps S3, S4 and S5 are different from those in Example 1, the remaining preparation process conditions are exactly the same as those in Example 1, as follows:

[0070] S3. Reduction smelting: Raise the furnace temperature to 750°C, add pure aluminum blocks into the crucible, and stir at the same time, so that the aluminum blocks melt and react with the titanium ions in the molten salt to reduce them. After 60 minutes of reaction, remove the scum on the surface of the melt. Continue to maintain the furnace temperature, and add the remaining composite solvent (120g) into the crucible through the feeding pipe, stirring while adding, and continue to keep the temperature for 30 minutes, and then remove the scum again.

[0071] S4. Cooling: After the furnace temperature is lowered to 700°C at a cooling rate of 2°C / min, stirring is required before the furnace temperature drops to the upper temperature limit. Stop stirring when the temperature drops to within the temperature range.

[0072] S5. Standing: Let the melt stand for 20 minutes.

[0073] After ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 10.0wt%, the total impurity elements are 0.24wt%, and the rest is aluminum, corresponding to Figure 2 The alloying element concentration of Example 5; the uniformity deviation of the titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, and the Ti concentration deviation is only 0.18%; the impurity element concentration is as follows Figure 4 shown.

[0074] Example 6

[0075] The difference between this embodiment and embodiment 1 is only that the preparation process conditions are different, the raw material formula is the same, and the specific amounts are shown in Table 1.

[0076] Except that steps S2, S3, S4 and S5 are different from those in Example 1, the remaining preparation process conditions are exactly the same as those in Example 1, as follows:

[0077] S2. Mixed melting: Place the raw materials in a cylindrical crucible in the order of composite solvent (90 g), titanium dioxide, potassium fluorotitanate, composite solvent (90 g), and calcium fluoride, and place the crucible in a crucible furnace and heat it to 700°C to melt all the raw materials. Then keep the temperature for 30 minutes, stirring with a graphite rod every 5 minutes until there is no solid adhesive on the bottom and inner wall of the crucible.

[0078] S3. Reduction smelting: Raise the furnace temperature to 800°C, add pure aluminum blocks into the crucible, and stir at the same time, so that the aluminum blocks melt and react with the titanium ions in the molten salt to reduce them. After 90 minutes of reaction, remove the scum on the surface of the melt. Continue to maintain the furnace temperature, and add the remaining composite solvent (120g) into the crucible through the feeding pipe, stirring while adding, and continue to keep the temperature for 45 minutes, and then remove the scum again.

[0079] S4. Cooling: After the furnace temperature is lowered to 705°C at a cooling rate of 2°C / min, stirring is required before the furnace temperature drops to the upper temperature limit. Stop stirring when the temperature drops to within the temperature range.

[0080] S5. Standing: Let the melt stand for 20 minutes.

[0081] According to ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 10.1wt%, the total impurity elements are 0.27wt%, and the rest is aluminum, corresponding to Figure 2 The alloying element concentration of Example 6; the uniformity deviation of titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, and the Ti concentration deviation is only 0.2%; the impurity element concentration is as follows Figure 4 shown.

[0082] Comparative Example 1

[0083] K of this embodiment2 TiF 6 With TiO 2 The molar ratio is 0.07, which is beyond the scope of the claims and has an impact on product performance.

[0084] Except for the different formula from Example 1, the other operation steps and process conditions of this example are exactly the same as those of Example 1. The specific formula of raw materials is shown in Table 1.

[0085] According to ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 6.2wt%, the total impurity elements are 0.25wt%, and the rest is aluminum, corresponding to Figure 2 The alloy element concentration of Comparative Example 1; the uniformity deviation of titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, the Ti concentration deviation is 0.55%; the impurity element concentration is as follows Figure 4 shown.

[0086] Comparative Example 2

[0087] The TiO 2 The addition amount accounts for 60% of the mass of pure aluminum, which has an impact on product performance when it exceeds the scope of the claims.

[0088] Except for the formula that is different from that of Example 1, the remaining operating steps and process conditions of this example are exactly the same as those of Example 2. The specific formula is shown in Table 1.

[0089] According to ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 5.9wt%, the total impurity elements are 0.35wt%, and the rest is aluminum, corresponding to Figure 2 The alloy element concentration of Comparative Example 2; The uniformity deviation of titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, the Ti concentration deviation is 0.69%; the impurity element concentration is as follows Figure 4 shown.

[0090] Comparative Example 3

[0091] The influence on product performance when the addition amount of CaF, a slag-forming agent in this comparative example, exceeds the scope of the claims.

[0092] Except for the formula being different from that of Example 1, the other operation steps and process conditions of this comparative example are exactly the same as those of Example 1. The specific formula is shown in Table 1.

[0093] According to ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 7.8wt%, the total impurity elements are 0.31wt%, and the rest is aluminum, corresponding to Figure 2 The alloy element concentration of Comparative Example 3; the uniformity deviation of titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, the Ti concentration deviation is 0.42%; the impurity element concentration is as follows Figure 4 shown.

[0094] Comparative Example 4

[0095] This comparative example illustrates the influence on product performance when the preparation process conditions exceed the scope of protection of the rights.

[0096] Except that the process conditions of operation step S3 are different from those of Example 1, the formulation and other operation and process conditions of this comparative example are exactly the same as those of Example 1. The specific formulation of raw materials is shown in Table 1.

[0097] The preparation process conditions S3 are as follows:

[0098] S3. Reduction smelting: Raise the furnace temperature to 720°C, add pure aluminum blocks into the crucible, and stir at the same time, so that the aluminum blocks melt and react with the titanium ions in the molten salt to undergo a reduction reaction. After the reaction lasts for 105 minutes, remove the scum on the surface of the melt. Continue to maintain the furnace temperature, and add the remaining composite solvent (120g) into the crucible through the feeding pipe, stirring while adding, and continue to keep the temperature for 60 minutes, and then remove the scum again.

[0099] According to ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 7.3wt%, the total impurity elements are 0.27wt%, and the rest is aluminum, corresponding to Figure 2 The alloy element concentration of Comparative Example 4; the uniformity deviation of titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, the Ti concentration deviation is 0.28%; the impurity element concentration is as follows Figure 4 shown.

[0100] Comparative Example 5

[0101] This comparative example illustrates the influence on product performance when the preparation process conditions exceed the scope of protection of the rights.

[0102] Except that the process conditions of operation step S3 are different from those of Example 1, the formulation and other operation steps and process conditions of this comparative example are exactly the same as those of Example 1. The specific formulation of raw materials is shown in Table 1.

[0103] The preparation process conditions S3 are as follows:

[0104] S3. Reduction smelting: Raise the furnace temperature to 800°C, add pure aluminum blocks into the crucible, and stir at the same time, so that the aluminum blocks melt and react with the titanium ions in the molten salt to reduce them. After the reaction lasts for 30 minutes, remove the scum on the surface of the melt. Continue to maintain the furnace temperature, and add the remaining composite solvent (120g) into the crucible through the feeding pipe, stirring while adding, and keep the temperature for 30 minutes, and then remove the scum again.

[0105] According to ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 7.5wt%, the total impurity elements are 0.24wt%, and the rest is aluminum, corresponding to Figure 2 The alloy element concentration of Comparative Example 5; the uniformity deviation of titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, and the deviation of Ti content is only 0.31%; the concentration of impurity elements is as follows Figure 4 shown.

[0106] Comparative Example 6

[0107] This comparative example illustrates the influence of the slow cooling process conditions on the product performance.

[0108] This comparative example has the same formulation as that of Example 1 except that the process conditions of operation step S6 are different from those of Example 1. The specific formulation of raw materials is shown in Table 1.

[0109] The preparation process conditions S6 are as follows:

[0110] S6. Slow cooling: Cool the crucible in the furnace until it slowly drops to near room temperature.

[0111] According to ICP test analysis, the average Ti content in the three samples of Al-xTi master alloy prepared by the above raw material formula and process steps is 8.5wt%, the total impurity elements are 0.28wt%, and the rest is aluminum, corresponding to Figure 2 The alloy element concentration of Comparative Example 6; the uniformity deviation of titanium element in the alloy is as follows Figure 3 As shown in the figure, the 5-point test results show that the uniformity is very good, and the deviation of Ti content is only 1.34%; the concentration of impurity elements is as follows Figure 4 shown.

[0112] The average titanium concentration of the intermediate alloy samples prepared in the above-mentioned embodiments and comparative examples is: 3 samples are prepared for each embodiment and comparative example, and the titanium content of the 3 samples is measured respectively and the average value is taken as the average titanium concentration of the intermediate alloy sample in the embodiment. Figure 2The data show that the titanium concentration of all the samples in the examples is above 10wt%, and the titanium concentration of the sample prepared in Example 5 is very close to 10wt%. However, the titanium concentration of the samples prepared in all the comparative examples is lower, and none of them reaches 10wt%. It can be seen that different composition formulas and process conditions have a great influence on the titanium concentration of the intermediate alloy.

[0113] The spatial composition uniformity of the master alloy samples prepared in the above-mentioned embodiments and comparative examples is as follows: samples are taken from at least 5 different locations on the master alloy samples prepared in each embodiment and comparative example, and after the Ti concentration of these samples is measured, the difference between the maximum Ti concentration and the minimum Ti concentration is taken as the spatial composition deviation of the master alloy. Figure 3 The data show that the composition deviation of the alloying element Ti in all the example samples is very small, with the maximum value not exceeding 0.5%, while in the comparative examples, the composition deviation of the alloying element Ti is generally larger, with the maximum value reaching 1.34%.

[0114] Depend on Figure 4 The data show that the purity of the master alloy samples is relatively high, and the impurity concentration in each embodiment does not exceed 0.3wt%, and the impurities in the comparative examples are generally slightly higher than those in the embodiments, but also do not exceed 0.4wt%. The impurities in the aluminum master alloy prepared by thermal reduction method mainly come from the raw materials. Since the present invention uses industrial pure aluminum and analytical pure titanium dioxide as raw materials, the master alloy has a relatively high purity.

[0115] from Figure 2 and Figure 4 It can be seen that all embodiments can simultaneously meet the requirements of high titanium content, purity and uniformity of alloy component distribution, while all comparative examples cannot simultaneously meet these requirements. It can be seen that the present invention can produce high-quality Al-xTi (x≥10) master alloys under the premise of strictly controlling the raw material formula and preparation process conditions.

[0116] In summary, the present invention prepares an Al-xTi (x≥10) intermediate alloy with a high titanium content by a thermal reduction + smelting method, which has both the low cost of raw materials of the thermal reduction method and the high product quality of the smelting method.

[0117] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for preparing an Al-xTi master alloy with a high titanium content, characterized in that: The following steps are involved: S1. Raw material pretreatment: taking the raw materials required for preparing the Al-xTi master alloy according to the ratio and vacuum drying them, the raw materials include titanium dioxide, potassium fluorotitanate, pure aluminum block, sodium chloride, potassium chloride and calcium fluoride; and mixing the sodium chloride and potassium chloride and dividing them into a bottom layer mixture of sodium chloride and potassium chloride, a middle layer mixture of sodium chloride and potassium chloride and an upper layer mixture of sodium chloride and potassium chloride according to the mass ratio; S2. Mixing and melting: the raw materials pretreated in step S1 are layered into a crucible in the order of the bottom layer mixture of sodium chloride and potassium chloride, titanium dioxide, potassium fluorotitanate, the middle layer mixture of sodium chloride and potassium chloride, and calcium fluoride, and the crucible is placed in a crucible furnace and heated to 700-750°C, and then kept warm for 20-40 minutes, with interval stirring during the insulation period; S3. Reduction smelting: Continue to raise the temperature to 750-850°C, add the pure aluminum block to the crucible, stir the reaction, after 60-105min, remove the scum on the surface of the melt, then add the sodium chloride and potassium chloride upper mixture, add while stirring, keep warm for 30-60min, remove the scum; S4. Cooling: Cooling at a rate of 2 to 3 ° C / min, stirring continuously during the cooling process, and stopping stirring when the furnace temperature drops to 700 to 710 ° C; S5. Standing: Let the melt stand for 10 to 20 minutes after cooling; S6 rapid cooling: the crucible is smoothly and quickly removed from the crucible furnace, and naturally cooled to room temperature to obtain an intermediate alloy casting; S7. Cleaning and drying: The master alloy casting is cut, cleaned and air-dried to obtain the final aluminum-titanium master alloy product.

2. The method for preparing a high titanium content Al-xTi master alloy according to claim 1, characterized in that: In step S1, the mass ratio of the titanium dioxide to the pure aluminum block is 35-50%; the molar ratio of the potassium fluorotitanate to the titanium dioxide is 0.10-0.26; the total mass of the sodium chloride and potassium chloride after mixing is 28-32% of the mass of the pure aluminum block, and the molar ratio of the sodium chloride to the potassium chloride is 0.95-1.05; the mass of the calcium fluoride is 20-30% of the mass of the pure aluminum block.

3. The method for preparing a high titanium content Al-xTi master alloy according to claim 1, characterized in that: In step S1, the bottom layer mixture of sodium chloride and potassium chloride accounts for 20-30% of the total mass of the sodium chloride and potassium chloride after mixing, the middle layer mixture of sodium chloride and potassium chloride accounts for 30-40% of the total mass of the sodium chloride and potassium chloride after mixing, and the rest is the upper layer mixture of sodium chloride and potassium chloride.

4. The method for preparing a high titanium content Al-xTi master alloy according to claim 1, characterized in that: In step S1, electrolyte may be added to the mixture of sodium chloride and potassium chloride, and the added amount is 2-4% of the mass of the pure aluminum block.

5. The method for preparing a high titanium content Al-xTi master alloy according to claim 4, characterized in that: The electrolyte is one or more of LiCl, MgCl2, CaCl2, and BaCl2.

6. The method for preparing a high titanium content Al-xTi master alloy according to claim 1, characterized in that: In step S1, the vacuum drying temperature is 95-110° C. and the time is 2-4 hours.

7. The method for preparing a high titanium content Al-xTi master alloy according to claim 1, characterized in that: In step S4, the stirring rate is 60-120 rpm.

8. The method for preparing a high titanium content Al-xTi master alloy according to claim 1, characterized in that: The concentration of Ti in the Al-xTi master alloy is ≥10wt%, that is, x≥10, and the impurity concentration is ≤0.3wt%.

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