Aluminum-titanium-boron-carbon-niobium rare earth intermediate alloy refiner as well as preparation method and application thereof

Abstract

The invention discloses an aluminum-titanium-boron-carbon-niobium-rare earth intermediate alloy refiner and a preparation method and application thereof, and relates to the technical field of refiners, the refiner comprises the following components in percentage by mass: 4.5-5.5% of titanium, 0.8-1.2% of boron, 0.1-0.3% of carbon, 0.1-1.5% of niobium, 0.2-0.5% of rare earth and the balance of aluminum. The preparation method comprises the following steps: ball-milling and mixing a titanium source, a carbon source and aluminum powder, and hydraulically pressing into a precast block; heating an aluminum ingot until the aluminum ingot is completely molten, and then pressing the mixed powder precast blocks into an aluminum melt in batches to obtain a mixed melt; and sequentially adding an aluminum-boron alloy, an aluminum-niobium alloy and rare earth into the melt for melting, then adding carbon hexachloride for deslagging and refining, and then pouring into a mold for cooling. According to the refining agent, the grain structure of the aluminum-silicon alloy can be remarkably improved, the recession resistance and poison resistance of the high-silicon-content aluminum-silicon alloy are effectively improved through introduction of niobium and rare earth, and an effective refining effect on the aluminum-silicon alloy can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of refiners, and particularly relates to an aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner and its preparation method and application. Background Art

[0002] In order to cope with global warming caused by industrial fuels, new energy vehicles have emerged. First of all, lightweight design has become the key. Data shows that for every 10% reduction in the vehicle weight of new energy vehicles, the cruising range can be increased by 5%-6%. Among many automotive alloy materials, aluminum-silicon series cast aluminum alloys have the advantages of good casting fluidity, high strength, good machining performance, small shrinkage rate and low hot cracking tendency, and have become the most widely used hypoeutectic Al-Si materials for automotive and motorcycle wheels at present, and are widely used in the aerospace industry. With the development of automotive design towards light weight, energy saving and diversification, the application of cast aluminum alloys in the automotive industry is increasing day by day, and the application scope is constantly expanding.

[0003] However, during the casting process, due to the slow cooling rate, coarse α-Al phase, needle-shaped eutectic Si phases with different lengths and thicknesses, and pores will be formed. These coarse α-Al phases, needle-shaped eutectic Si phases and pores, similar to non-metallic inclusions in steel, will significantly reduce the performance of A356 aluminum alloy, resulting in a decrease in the strength of the casting and an increase in brittleness. In actual production, the use of refinement modification treatment can not only reduce the grain size of the alloy and obtain finer grains, but also reduce defects such as pores in the casting. In addition, the refinement modification treatment can also transform the needle-shaped eutectic Si phase into short rod-shaped or granular, changing its morphology, thereby fundamentally improving the performance of high-silicon-content aluminum-silicon alloys.

[0004] At present, although the Al-Ti-B and Al-Ti-C refiners widely used in industry have obvious grain refinement effects, they also have some disadvantages: the grain refinement performance of the refiner is affected by high content of Si in Al alloy (especially for Al-Si casting alloys with more than 6.5wt% Si) or the presence of a certain amount of Zr in Al alloy, which is called Si / Zr poisoning. The internal grain refinement phases TiB2 and TiC are prone to aggregation and precipitation in the aluminum melt, resulting in coarse local structure after solidification of the aluminum alloy, that is, the "anti-decay property" is poor. In addition, if elements such as Cr, Zr and Si exist in the alloy, "poisoning" will also occur. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide an aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner and its preparation method and application. The refiner can significantly improve the grain structure of aluminum-silicon alloys, and has excellent anti-poisoning and anti-decay properties, and can effectively refine aluminum-silicon alloys.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: Provide an aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner, which includes the following components by mass percentage: titanium (Ti) 4.5-5.5%, boron (B) 0.8-1.2%, carbon (C) 0.1-0.3%, niobium (Nb) 0.1-1.5%, and rare earth (Re) 0.2-0.5%, and the balance is aluminum (Al).

[0007] Further, it includes the following components by mass percentage: titanium 5%, boron 1%, carbon 0.2%, niobium 1%, and rare earth 0.3%, and the balance is aluminum.

[0008] Further, the rare earth is lanthanum (La).

[0009] Further, the mass percentage of the rare earth is one of 0.2%, 0.3%, 0.4%, and 0.5%.

[0010] Further, the content of inevitable impurities in the aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner is ≤0.15%.

[0011] The present invention also provides a preparation method of the above aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner, including the following steps: Step 1: Ball-mill and mix the titanium source, carbon source and aluminum powder, and then form by hydraulic pressure to obtain a preform; Step 2: Melt pure aluminum at a temperature of 750-800 °C, then add the preform obtained in Step 1 to melt and perform heat preservation and stirring treatment to obtain a mixed melt; Step 3: Heat up the mixed melt obtained in Step 2 to 800-1000 °C, add aluminum-boron alloy to melt, cool down to 750-850 °C and then add aluminum-niobium alloy to melt, then add rare earth to melt and perform heat preservation and stirring treatment, and then add carbon dichloride hexachloride for slag removal and refining, and finally pour it into a mold to cool to obtain the aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner.

[0012] In this solution, the mixed powder of the Ti source and C source after ball-milling with aluminum powder is added to the molten aluminum liquid prior to other elements, ensuring that the Ti and C elements are completely dissolved in the aluminum liquid. After the reaction is completed, C2Cl6 is added to the aluminum melt for degassing and refining. C2Cl6 will decompose itself to produce gas, and the generated Cl2 and C2Cl6 gases are immiscible with the aluminum melt.

[0013] Further, in Step 1, the titanium source is titanium powder; the carbon source is graphite.

[0014] Further, in Step 1, the rotation speed of the ball mill is 150-250 r / min, the ball-to-material ratio is 3:1, and the ball-milling time is 1-2 h.

[0015] The ball milling process can improve the reactivity of raw material powders, making them more likely to react in the melt. At the same time, high-energy ball milling can also improve the dispersibility of the powders, ensuring that the reaction is evenly distributed throughout the melt.

[0016] Furthermore, in step one, the hydraulic pressure is 15 - 20 kN, and the heat preservation time is 10 - 20 s.

[0017] Furthermore, in step one, a TYA - 600 type hydraulic testing machine is used for hydraulic pressure.

[0018] Furthermore, in step one, the preform is cylindrical with dimensions of Φ40 mm × 15 mm.

[0019] Furthermore, in step two, the preform is added to the melt in two batches.

[0020] The beneficial effect of adopting the further technical solution is that due to the poor wettability between C and aluminum alloy, adding in batches can enable the reaction to proceed fully.

[0021] Furthermore, in step two, the preform is added to the melt using a graphite bell.

[0022] Furthermore, in steps two and three, first heat preserve for 20 - 30 min, then stir at a rate of 2000 - 3000 r / min for 2 - 5 min. Heat preservation and stirring treatments are carried out every time after the alloy is melted and added.

[0023] The beneficial effect of adopting the further technical solution is that it eliminates the possible second-phase segregation phenomenon in the refining agent and promotes the uniform distribution of chemical components in the melt.

[0024] Furthermore, in step three, after stirring, remove the heat source and apply ultrasonic vibration at 20 kHz for 1 - 2 min.

[0025] Furthermore, in step three, the mold is a graphite mold; the mold is preheated to 100 - 200 °C before pouring.

[0026] Furthermore, in step three, the aluminum boron alloy is Al - 3B alloy; the aluminum niobium alloy is Al - 4Nb alloy.

[0027] The beneficial effect of adopting the further technical solution is that using aluminum boron alloy has higher boron utilization rate, better dispersibility (the aluminum matrix in Al - 3B is compatible with the Al - Ti - C system, avoiding the competitive reaction between carbon source and boron source, ensuring the synchronous generation of TiC and TiB2), less pollution, more stable process control, environmental protection, and better refining effect; a dense Al2O3 is formed on the surface of the Al - Nb alloy, blocking oxygen from contacting the internal Nb, and the Al - Nb carrier promotes the epitaxial growth of REB6 on the surface of NbC.

[0028] Furthermore, in step three, the rare earth can also be added in the form of aluminum alloy. For example, the rare earth lanthanum is added in the form of aluminum lanthanum alloy Al-10La.

[0029] The beneficial effect of adopting the further technical solution is that introducing La in the form of Al-10La pre-alloy can reduce the oxidation tendency of La, and at the same time, utilize the coating effect of Al to reduce burning loss.

[0030] Furthermore, it is rapidly cooled after pouring into the mold, aiming to inhibit the segregation of La and avoid the growth of Al-La phase and Al3Ti phase.

[0031] The present invention also provides an application of the above aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner in refining aluminum-silicon alloy with silicon content exceeding 6.5 wt%.

[0032] Furthermore, the dosage of the aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner is 0.2-1 wt% of the aluminum-silicon alloy.

[0033] Furthermore, the aluminum-silicon alloy is A356 alloy.

[0034] The present invention has the following beneficial effects: 1. The preparation method of the present invention not only provides new heterogeneous nucleation sites by reasonably controlling the addition amounts of niobium and lanthanum elements and the preparation conditions, but also solves the problems of poor wettability between Al and C and the aggregation of TiC. In addition, this method effectively reduces the aggregation of TiB2 phase particles, inhibits the generation of harmful Al4C3 phase, makes the size and distribution of Al3Ti phase particles more reasonable, and generates new effective refining phases Al 20 Ti2La, (Ti / Nb)C and (Nb / Ti)Al3, while reducing the gas content inside the alloy.

[0035] 2. This method does not require complex equipment or high-temperature and high-pressure conditions, nor the use of inert gas, thus greatly simplifying the preparation process. The refiner prepared by this method has the characteristics of simple process, low cost, remarkable refining effect, environmental friendliness, etc.

[0036] 3. Compared with the traditional fluoride reaction, the preparation method of the present invention reduces the emission of harmful gases, and adopts aluminum-boron, aluminum-niobium and aluminum-lanthanum master alloys to avoid the introduction of other impurities.

[0037] 4. The refiner of the present invention can significantly improve the grain structure of aluminum-silicon alloy, and has excellent anti-poisoning and anti-decay properties, and plays an effective refining role in refining aluminum-silicon alloy. Description of the Drawings

[0038] Figure 1 It is the XRD diagram of the refiner in Example 1 and Comparative Example 1; Figure 2Microstructure diagrams of the refiners in Example 1 and Comparative Example 1; Figure 3 Macrographs of the grains of A356 alloy before and after refinement; Figure 4 Macrograph of the grains of A356 alloy refined by the refiner in Example 1; Figure 5 Macrograph of the grains of A356 alloy refined by the refiner in Comparative Example 1; Figure 6 Macrograph of the grains of A356 alloy refined by the refiner in Comparative Example 2. Detailed implementation manners

[0039] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. For those not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained by purchasing in the market.

[0040] Example 1 An aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner (Al-5Ti-1B-0.2C-0.5Nb-0.2La) includes the following components by mass percentage: titanium 5%, boron 1%, carbon 0.2%, niobium 0.5%, and rare earth (lanthanum) 0.2%, the impurity content is ≤0.1%, and the balance is aluminum; Its preparation method includes the following steps: Step 1: Ball-mill and mix titanium powder, graphite powder and aluminum powder at 200 r / min for 1.5 h, with a ball-to-material ratio of 3:1, then perform hydraulic forming at a pressure of 18 kN and a holding time of 15 s to obtain a preform; the preform is cylindrical with dimensions of Φ40 mm×15 mm; Step 2: Melt pure aluminum at 760°C, and then add the preform obtained in Step 1 to melt in two portions using a graphite bell jar, with each portion held for 25 min and stirred at a rate of 2500 r / min for 3 min to obtain a mixed melt; Step 3: Heat the mixed melt obtained in Step 2 to 900°C, add aluminum-boron alloy Al-3B to melt, cool to 800°C and then add aluminum-niobium alloy to melt, then add aluminum-lanthanum alloy Al-10La to melt, hold for 25 min, stir at a rate of 2500 r / min for 3 min, remove the heat source and apply ultrasonic vibration at 20 kHz for 2 min, then add carbon dichloride hexachloride for slag removal and refining, and finally pour it into a graphite mold preheated to 150°C and rapidly cool to obtain the aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner.

[0041] Example 2 An Al-Ti-B-C-Nb-rare earth master alloy refiner (Al-5Ti-1B-0.2C-1Nb-0.2La), which is different from Example 1 in that the mass percentage of niobium is 1%.

[0042] Example 3 An Al-Ti-B-C-Nb-rare earth master alloy refiner (Al-5Ti-1B-0.2C-1.5Nb-0.2La), which is different from Example 1 in that the mass percentage of niobium is 1.5%.

[0043] Example 4 An Al-Ti-B-C-Nb-rare earth master alloy refiner (Al-5Ti-1B-0.2C-0.5Nb-0.3La), which is different from Example 1 in that the mass percentage of lanthanum is 0.3%.

[0044] Example 5 An Al-Ti-B-C-Nb-rare earth master alloy refiner (Al-5Ti-1B-0.2C-0.5Nb-0.5La), which is different from Example 1 in that the mass percentage of lanthanum is 0.5%.

[0045] Example 6 An Al-Ti-B-C-Nb-rare earth master alloy refiner, including the following components by mass percentage: titanium 4.5%, carbon 0.1%, niobium 0.5% and rare earth 0.2%, the impurity content ≤ 0.15%, and the balance is aluminum; Its preparation method includes the following steps: (1) Ball-mill and mix titanium powder, graphite powder and aluminum powder, ball-mill at 250 r / min for 1 h, the ball-to-material ratio is 3:1, then perform hydraulic forming, the pressure is 15 kN, and the heat preservation time is 20 s to obtain a preform; (2) Melt pure aluminum at 750 °C, then add the preform obtained in step one to melt in two times using a graphite bell, keep warm for 20 min each time and stir at a rate of 2000 r / min for 2 min to obtain a mixed melt; (3) Heat the mixed melt obtained in step two to 800 °C, add Al-3B aluminum-boron alloy to melt, cool down to 750 °C and then add aluminum-niobium alloy to melt, then add aluminum-lanthanum alloy Al-10La to melt, keep warm for 20 min, stir at a rate of 2000 r / min for 2 min, then add carbon dichloride hexachloride for slag removal and refining, and finally pour it into a graphite mold preheated to 100 °C and quickly cool to obtain the Al-Ti-B-C-Nb-rare earth master alloy refiner.

[0046] Example 7 An aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner, comprising the following components by mass percentage: titanium 5.5%, boron 1.2%, carbon 0.3%, niobium 1.5% and rare earth 0.5%, the impurity content ≤ 0.15%, and the balance is aluminum; Its preparation method includes the following steps: (1) Ball-mill and mix titanium powder, graphite powder and aluminum powder, ball-mill at 150 r / min for 2 h, the ball-to-material ratio is 3:1, then perform hydraulic forming, the pressure is 20 kN, and the heat preservation time is 10 s to obtain a preform; (2) Melt pure aluminum at 800 °C, and then add the preform obtained in step one to melt in two times using a graphite bell jar, keep warm for 30 min each time and stir at a rate of 3000 r / min for 5 min to obtain a mixed melt; (3) Heat the mixed melt obtained in step two to 1000 °C, add aluminum-boron alloy Al-3B to melt, cool down to 850 °C and then add aluminum-niobium alloy to melt, then add aluminum-lanthanum alloy Al-10La to melt, keep warm for 20 min, stir at a rate of 3000 r / min for 5 min, then add carbon dichloride hexachloride for slag removal and refining, and finally pour it into a graphite mold preheated to 200 °C and quickly cool to obtain the aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner.

[0047] Comparative Example 1 An Al-Ti-B-C master alloy refiner, comprising the following components by mass percentage: titanium 5%, boron 1% and carbon 0.2%, the impurity content ≤ 0.15%, and the balance is aluminum.

[0048] Comparative Example 2 An aluminum-titanium-boron-carbon-rare earth master alloy refiner (Al-5Ti-1B-0.2C-0.2La), different from Example 1 in that niobium is not added in step three.

[0049] Test Example 1 (1) In order to characterize the composition of the refiner, X-ray diffraction analysis was performed on the refiners of Example 1 and Comparative Example 1 respectively, and the results are as Figure 1 shown. The phase composition of the refiner in Example 1 is α-Al, TiB2, TiC, Al3Ti, Al 20 Ti2La, (Ti,Nb)C and (Ti,Nb)Al3 phases.

[0050] (2) In order to observe the microstructure of the refiner, scanning electron microscopy characterization was performed on the refiners of Example 1 and Comparative Example 1 respectively, and the results are as Figure 2 shown.

[0051] From Figure 2It can be seen that the refiners in Example 1 and Comparative Example 1 have uniform structures. The sizes of the refined nucleation particles Al3Ti are 10 μm and 20 μm respectively, and the sizes of TiC and TiB2 particles are less than 1 μm.

[0052] Test Example 2 The refined intermediate alloy ingots of Example 1, Comparative Example 1 and Comparative Example 2 prepared were crushed and then ball-milled using a planetary ball mill with a ball-to-material ratio of 10:1, a rotation speed of 300 - 400 rpm for 30 hours, and 0.5% ethanol was added simultaneously to prevent cold welding.

[0053] Weigh the Al-Si-based A356 alloy into a clay crucible and place it in a crucible resistance furnace at a temperature of 770 °C to make it in a molten state; then weigh 0.5% of the ball-milled refiner based on the mass of the molten Al-Si alloy, add the refiner to the molten Al-Si alloy and keep it warm for a certain time. Subsequently, take the crucible out of the furnace, stir the melt thoroughly, and then pour it into a cast iron mold, cool and demold to obtain the refined A356 alloy ingot. The macroscopic grain diagrams of the original A356 alloy ingot, the A356 alloy refined by the refiner of Example 1, the A356 alloy refined by the refiner of Comparative Example 1, and the A356 alloy refined by the refiner of Comparative Example 2 are respectively as Figure 3 、 Figure 4 、 Figure 5 and Figure 6 shown.

[0054] From Figure 3 、 Figure 4 、 Figure 5 and Figure 6 it can be seen that the average grain size of the original A356 alloy reaches more than 1500 μm. The average grain sizes of the A356 alloy ingots refined by the refiners of Example 1, Comparative Example 1 and Comparative Example 2 are reduced to below 90 μm, 150 μm and 112 μm respectively, which are 6%, 10% and 7.5% of the original A356 alloy. It can be seen from Comparative Example 2 that niobium can significantly improve the anti-decay ability of the refiner. The grains start to coarsen significantly only 60 minutes after adding the rare earth element, which also indicates that the refiner of Example 1 can effectively improve the grain structure of the Al-Si alloy.

[0055] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner, characterized in that Comprising the following components by mass percentage: titanium 4.5 - 5.5%, boron 0.8 - 1.2%, carbon 0.1 - 0.3%, niobium 0.1 - 1.5% and rare earth 0.2 - 0.5%, the balance being aluminum.

2. The aluminum-titanium-boron-carbon-niobium-rare earth master alloy grain refiner according to claim 1, characterized in that, Comprising the following components by mass percentage: titanium 5%, boron 1%, carbon 0.2%, niobium 1% and rare earth 0.3%, the balance being aluminum.

3. The aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner according to claim 1 or 2, characterized in that, The rare earth is lanthanum.

4. The preparation method of the aluminum-titanium-boron-carbon-niobium-rare earth master alloy fining agent according to any one of claims 1-3, characterized in that, Including the following steps: Step 1: Ball-mill and mix titanium source, carbon source and aluminum powder, and then perform hydraulic forming to obtain a preform; Step 2: Melt pure aluminum at a temperature of 750 - 800 °C, then add the preform obtained in Step 1 to melt and perform heat preservation and stirring treatment to obtain a mixed melt; Step 3: Heat up the mixed melt obtained in Step 2 to 800 - 1000 °C, add aluminum-boron alloy to melt, cool down to 750 - 850 °C and then add aluminum-niobium alloy to melt, then add rare earth to melt and perform heat preservation and stirring treatment, and then add carbon dichloride hexachloride for slag removal and refining, and finally pour it into a mold to cool to obtain an aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner.

5. The preparation method of the aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner according to claim 4, characterized in that, In Step 1, the titanium source is titanium powder; the carbon source is graphite.

6. The preparation method of the aluminum-titanium-boron-carbon-niobium-rare earth master alloy modifier according to claim 4, characterized in that In Step 1, the pressure of the hydraulic forming is 15 - 20 kN, and the heat preservation time is 10 - 20 s.

7. The preparation method of the aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner according to claim 4, characterized in that, In Step 2 and Step 3, first heat preserve for 20 - 30 min, and then stir at a rate of 2000 - 3000 r / min for 2 - 5 min.

8. The preparation method of the aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner according to claim 4, characterized in that, In Step 3, the aluminum-boron alloy is Al-3B alloy; the aluminum-niobium alloy is Al-4Nb alloy.

9. Application of the aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner according to any one of claims 1 - 3 in refining an aluminum-silicon alloy with a silicon content exceeding 6.5 wt%.

10. The application according to claim 9, characterized in that, The dosage of the aluminum-titanium-boron-carbon-niobium-rare earth master alloy refiner is 0.2 - 1 wt% of the aluminum-silicon alloy.

Images