Patent Application
20250059628
This application claims priority to Chinese Patent Application No. 2023110275743, filed Aug. 16, 2023, which is herein incorporated by reference in its entirety.
The disclosure relates to the field of non-ferrous metal smelting and manufacturing technology, and more particularly to an aluminium (Al)-titanium (Ti)-niobium (Nb)-boron (B) intermediate alloy and preparation method and application thereof.
Aluminium-silicon (Si) alloys in the related art have good casting properties and advantages mainly including good casting fluidity, high strength, good mechanical processing performance, low shrinkage and low hot tearing tendency. The Al—Si alloys are widely used in automotive and aerospace fields. In the casting of the Al—Si alloys, acicular silicon structures are distributed on the matrix due to slow cooling during a casting process, which reduces a strength of castings and makes casting properties brittle, thereby seriously affecting mechanical properties. In applications of the Al—Si alloys in the automotive industry, when a wheel hub is loaded, stress concentration occurs at edges of a eutectic Si phase, which can easily cause microcracks and greatly reduce strength and plasticity, thus limiting applications of the Al—Si alloys in high specification and large-sized (no less than 19 inches) heavy-duty automotive wheel hubs. Developing a high-performance aluminum alloy refining agent (i.e., refiner) can greatly improve the Al—Si alloys mechanical properties and be put into practical applications.
A refining agent commonly used in industry at present is Al-5Ti—B alloy, but due to a Si poisoning effect, the Ti element in the refining agent easily reacts with Si to form titanium silicon compounds, greatly reducing its refining effect and failing to meet refining requirements in industry.
An Al—Nb—B refining agent can effectively refine the aluminum silicon alloys, but has obvious defects, particles of NbAl3 and NbB2 have a high density, making it prone to sedimentation in the melt, resulting in weakened refinement. Therefore, anti-fading ability of the Al Nb—B alloy is poor.
An Al—Ti—Nb—B alloy has nucleating particles of aluminum titanium/niobium compounds and titanium/niobium boride compounds that are miscible due to similar physical and chemical properties of Ti and Nb. By combining advantages and disadvantages of the Al—Ti—B alloy and the Al—Nb—B alloy, the Al—Ti—Nb—B alloy has a good refining effect on Al—Si alloys with high silicon content. A Chinese patent with publication No.: CN108251675A provides an Al—Ti—Nb—B refining agent and its preparation method and application for casting the aluminum silicon alloys. The preparation method of the Al—Ti—Nb—B refining agent is provided, which can refine a grain size of the Al—Si alloys to 150 micrometers. It can be seen that a refining performance of the Al—Ti—Nb—B refining agent is good. However, technical disadvantages are apparent, a required reaction temperature during preparation is high, B participates in the reaction in a form of powder, with a low absorption rate, and required environmental conditions for the preparation are harsh, complex operations are required in an inert gas environment. A Chinese patent with publication No.: CN112048629A provides a method for preparing an Al—Ti—Nb—B refining agent for casting the Al—Si alloys. Although the preparation method in this patent has a low preparation cost and a good refining effect, introduction of Nb oxide and various fluoride salts leads to more impurity elements, affecting quality and purity of the Al—Si alloys, and there are serious environmental pollution problems. At the same time, a preparation temperature of the Al—Ti—Nb—B refining agent in this patent is not low, melting time is long, and energy consumption is high.
To solve above technical problems, a first purpose of the disclosure is to provide a preparation method of an Al—Ti—Nb—B intermediate alloy, the preparation method provided by the disclosure has a simple process with a low smelting temperature, short time and low environmental pollution.
A second purpose of the disclosure is to provide the Al—Ti—Nb—B intermediate alloy prepared by the preparation method. The Al—Ti—Nb—B intermediate alloy has few internal defects, dispersion distribution of refined nucleating phases, and high purity.
A third purpose of the disclosure is to provide an application of the Al—Ti—Nb—B intermediate alloy.
The preparation method of the Al—Ti—Nb—B intermediate alloy includes following steps: potassium tetrafluoroborate (KBF4) powder, Nb powder, and Ti powder are ball milled to obtain mixed powder, the mixed powder is pressed to obtain a ball-milled block, an Al block is melted to obtain an Al melt, the ball-milled block is added to the Al melt followed by smelting to obtain alloy liquid, and the alloy liquid is cast to obtain the Al—Ti—Nb—B intermediate alloy.
In the preparation method of the disclosure, the KBF4 powder is used as a B source to reduce reaction difficulty of B with other elements in a melt, greatly improving an absorption rate of the B. The Nb powder is used as a Nb source, and the Ti powder is used as a Ti source. High-energy ball mill is used to ball mill the KBF4 powder, the Nb powder, and the Ti powder together to enhance reactivity of the KBF4 powder, the Nb powder, and the Ti powder, and to lower a reaction threshold. Then, the mixed powder is pressed into a compact form to obtain the ball-milled block, the ball-milled block is added to the Al melt followed by smelting. By adopting the above steps, elements can be evenly dispersed in the Al melt, react more fully, and distribution of refined particles is better, thereby obtaining the Al—Ti—Nb—B intermediate alloy with high purity.
In addition, in the preparation method of the disclosure, by pressing raw material powder (i.e., the KBF4 powder, the Nb powder, and the Ti powder) into the compact form (i.e., the ball-milled block) and then adding the ball-milled block to the Al melt, a reaction can be further promoted. Meanwhile, pressing the raw material powder into the compact form can prevent the raw material powder from adhering to crucible walls or floating on a surface of the Al melt during a feeding process, thus avoiding loss and consumption of raw materials and preventing a decrease in an absorption rate of the raw materials.
In an embodiment, a particle size of the Nb powder is in a range of 30-50 micrometers (m), and a particle size of the Ti powder is in a range of 1-50 μm. The inventor discovers that when the particle sizes of the Nb powder and the Ti powder are controlled to be in the ranges of the disclosure, the refined nucleating phases (refined particles) formed by the Al—Ti—Nb—B intermediate alloy has small sizes and large quantity, and the Al—Ti—Nb—B intermediate alloy has a good refining effect. If the particle sizes are too large, sizes and quantity of the refined particles are affected and a refining effect is reduced. If the particle sizes are too small, cost of the raw materials is increased and it is prone to oxidation and burning during a reaction process.
In an embodiment, a rotation speed in the ball milling (i.e., the step that the raw material powder is ball milled) is in a range of 200-300 revolutions per minute (r/min), and time of the ball milling is in a range of 4-6 hours (h). The rotation speed is controlled to be in the range to achieve the most uniform dispersion of materials and an optimal activation effect.
In an embodiment, the ball milling is wet milling, a milling medium is anhydrous ethanol, and a ball-to-material ratio is in a range of 5-15:1.
In an embodiment, the Al block is a commercially pure Al block.
In an embodiment, the Al block is melted at 750 degrees Celsius (° C.)-900° C. to obtain the Al melt. Furthermore, in an embodiment, the Al block is melted at 750° C.-850° C. to obtain the Al melt. Moreover, in an embodiment, the Al block is melted at 750° C.-800° C., to obtain the Al melt.
In an embodiment, the ball-milled block is wrapped in Al foil and added to the Al melt. The Al foil is used to wrap the ball-milled block to reduce the oxidation and burning of the raw material powder and improve alloy quality.
In an embodiment, a temperature of the smelting is in a range of 750° C.-900° C. Furthermore, in an embodiment, the temperature of the smelting is in a range of 750° C.-850° C. Moreover, in an embodiment, the temperature of the smelting is in a range of 750° C.-800° C. Time of the smelting is in a range of 20-60 minutes (min).
In the disclosure, since the ball milling activates the raw materials, there is no need to raise the temperature after obtaining the Al melt, and the temperature in the step that the Al block is melted can be maintained for the smelting. Moreover, melting time is short due to high reaction activity of the raw materials after activation.
In an embodiment, the smelting includes: stirring of the ball-milled block and the Al melt is performed for 0.5-1 min each time at time intervals of 10-20 min.
The inventor discovers that intermittent stirring results in a highest quality of the Al—Ti—Nb—B intermediate alloy, and it is easy to operate.
In an embodiment, the Al—Ti—Nb—B intermediate alloy includes the following compositions in percentage by weight: Al: 94.9%-96.7%, Ti: 0.5%-1.5%, Nb: 2.5%-4%, B: 0.3%-0.8%.
In an embodiment, the Al—Ti—Nb—B intermediate alloy includes refined nucleating phases, the refined nucleating phases are (Nb/Ti)Al3 and (Nb/Ti)B2, a weight percentage of the refined nucleating phases in the Al—Ti—Nb—B intermediate alloy is in a range of 1%-6%, a particle size of the refined nucleating phases is in a range from 1-80 μm, and a particle size of the (Nb/Ti)B2 is not greater than 5 μm.
It can be seen that the Al—Ti—Nb—B intermediate alloy provided by the disclosure has dispersion distribution of the refined nucleation phases and fine particles.
The disclosure further provides the Al—Ti—Nb—B intermediate alloy prepared by the preparation method.
The disclosure further provides an application method of the Al—Ti—Nb—B intermediate alloy prepared by the preparation method. The Al—Ti—Nb—B intermediate alloy is applied as a refining agent of an Al—Si alloy.
In an actual operation process, the application method specifically includes following steps. [0029](1) The Al—Si alloy to be refined is heated to a temperature of 730-750° C. to melt to obtain an Al—Si melt, after keeping the temperature unchanged for a period of time, the Al—Ti—Nb—B intermediate alloy is added to the Al—Si melt as the refining agent to obtain a mixture, and the mixture is stirred thoroughly followed by keeping the temperature unchanged for 5-15 min. [0030](2) After keeping the temperature unchanged, the mixture is stirred evenly and then cast into a round graphite mold to obtain a refined Al—Si alloy ingot.
In the application method of the Al—Ti—Nb—B intermediate alloy, an α-Al grain size of the refined Al—Si alloy can reach less than 90 μm.
Compared to the related art, the refining agent prepared by the preparation method of the disclosure uses a high-energy ball milling process to improve the reaction activity of the raw material powder, reduce the reaction threshold, and disperse all elements evenly in a melt. The distribution of the refined particles is more dispersed and the refining effect is excellent, far exceeding industrial production standards. The preparation process is simple, and a high-temperature box furnace is used as melting equipment. The operation is simple, and monofluoride salt is used. It not only ensures a full progress of the reaction, but also makes the quality and purity of the alloy high, reduces environmental pollution, and requires low preparation temperature and short melting time. The refining agent has high practical value for the application in refining the Al—Si alloy.
In order to make the purpose, technical solution, and effects of the disclosure clearer, detailed explanations of the disclosure are further provided below in conjunction with embodiments. The specific embodiments described here are only intended to explain the disclosure and are not intended to limit the disclosure.
Raw materials selected for the embodiments below are: a 356 alloy (a type of Al—Si alloy), KBF4 powder (99.95%), Ti powder (99.98%), Nb powder (99.98%) and commercially pure Al.
A preparation method of an Al—Ti—Nb—B refining agent of the embodiment 1
The Al—Ti—Nb—B refining agent includes the following compositions in percentage by weight: Ti: 1.0 weight percentage (wt. %), Nb: 3.0 wt. %, B: 0.5 wt. %, unavoidable impurity content less than 0.1 wt. %, and the rest is Al. The raw materials are weighed according to the compositions of the Al—Ti—Nb—B refining agent.
A preparation process of the Al—Ti—Nb—B refining agent includes following steps.
(1) High energy ball milling of the raw materials: the Ti powder, the Nb powder, and the KBF4 powder are mixed in proportion to obtain mixed powder, the mixed powder is placed in a stainless-steel ball milling tank (which is washed and dried in advance), and added with stainless-steel beads with a ball-to-material ratio of 10:1, and then anhydrous ethanol as a ball milling medium is added to the stainless-steel ball milling tank to slightly submerge the mixed powder and balls (i.e., the stainless-steel beads). Then, the stainless-steel ball milling tank is vacuumed for 30 seconds to obtain a vacuumed tank, the vacuumed tank is filled with protective gas argon. Operations of vacuuming and filling with the protective gas argon are repeated three times to obtain a processed tank to ensure that air in the processed tank is completely discharged and avoid oxidation of metal raw material powder during a ball milling process. The processed tank is placed in a planetary ball mill with a rotation speed of 300 r/min for ball milling for 6 h.
After ball milling, the mixed powder in the processed tank is dried and compacted to obtain a ball-milled block for future use.
(2) Smelting of an Al—Ti—Nb—B alloy (the Al—Ti—Nb—B refining agent): the commercially pure Al is placed in a graphite clay crucible and heated to a temperature of 750° C. in a box-type high-temperature furnace followed by keeping the temperature unchanged for a period to obtain an Al melt, the ball-milled block is wrapped with Al foil and then is pressed into the Al melt to obtain a mixed melt, the mixed melt is stirred for half a minute and then is placed in the box-type high-temperature furnace for keeping the temperature unchanged for 40 min. During the 40 min, the mixed melt is thoroughly stirred by a graphite stirring rod for 0.5-1 min at intervals of 20 min. After the 40 min, floating slag on a surface of the mixed melt is removed, and then the mixed melt is stirred thoroughly to obtain alloy liquid, the alloy liquid is cast into a cast iron mold followed by solidification to obtain the Al—Ti—Nb—B alloy, denoted as an Al-3Nb-1Ti-0.5B-750° C. refining agent.
In order to characterize the compositions of the Al—Ti—Nb—B refining agent prepared in the embodiment 1, XRD analysis is performed on the Al-3Nb-1Ti-0.5B-750° C. refining agent prepared in the embodiment 1. As shown in
In order to observe a microstructure of the Al—Ti—Nb—B refining agent, the Al-3Nb-1Ti-0.5B-750° C. refining agent prepared in the embodiment 1 is characterized by scanning electron microscopy. As shown in
A method for refining the Al—Si alloy by the Al-3Nb-1Ti-0.5B-750° C. refining agent includes following steps.
The A356 alloy is placed in a graphite clay crucible and heated to a temperature of 730° C. in a well furnace to obtain an Al—Si melt, the Al—Si melt is added with the Al-3Nb-1Ti-0.5B-750° C. refining agent followed by keeping the temperature unchanged for 5 min to obtain a mixture, a refining agent amount is based on 0.09% Nb of a total weight of the mixture, the mixture is cast into a graphite disc mold to obtain a refined A356 alloy ingot (i.e., a refined A356 alloy).
The embodiment 2 is basically the same as the embodiment 1, with special features below.
Smelting of an Al—Ti—Nb—B alloy (the Al—Ti—Nb—B refining agent): the commercially pure Al is placed in a graphite clay crucible and heated to a temperature of 750° C. in a box-type high-temperature furnace followed by keeping the temperature unchanged for a period to obtain an Al melt, the ball-milled block is wrapped with Al foil and then is pressed into the Al melt to obtain a mixed melt, the mixed melt is stirred for half a minute and then is placed in the box-type high-temperature furnace for keeping the temperature unchanged for 60 min. During the 60 min, the mixed melt is thoroughly stirred by a graphite stirring rod for 0.5-1 min at intervals of 20 min. After the 60 min, floating slag on a surface of the mixed melt is removed, and then the mixed melt is stirred thoroughly to obtain alloy liquid, the alloy liquid is cast into a cast iron mold followed by solidification to obtain the Al—Ti—Nb—B alloy, denoted as an Al-3Nb-1Ti-0.5B-750° C.-60 min refining agent.
A method for refining the Al—Si alloy by the Al-3Nb-1Ti-0.5B-750° C.-60 min refining agent includes following steps.
The A356 alloy is placed in a graphite clay crucible and heated to a temperature of 730° C. in a well furnace to obtain an Al—Si melt, the Al—Si melt is added with the Al-3Nb-1Ti-0.5B-750° C.-60 min refining agent followed by keeping the temperature unchanged for 5 min to obtain a mixture, a refining agent amount is based on 0.09% Nb of a total weight of the mixture, the mixture is cast into a graphite disc mold to obtain a refined A356 alloy ingot (i.e., a refined A356 alloy).
In order to characterize the compositions of the Al—Ti—Nb—B refining agent prepared in the embodiment 2, XRD analysis is performed on the Al-3Nb-1Ti-0.5B-750° C.-60 min refining agent prepared in the embodiment 2. As shown in
In order to observe a microstructure of the Al—Ti—Nb—B refining agent, the Al-3Nb-1Ti-0.5B-750° C.-60 min refining agent prepared in the embodiment 2 is characterized by scanning electron microscopy. As shown in
The embodiment 3 is basically the same as the embodiment 1, with special features below.
Smelting of an Al—Ti—Nb—B alloy (the Al—Ti—Nb—B refining agent): the commercially pure Al is placed in a graphite clay crucible and heated to a temperature of 850° C. in a box-type high-temperature furnace followed by keeping the temperature unchanged for a period to obtain an Al melt, the ball-milled block is wrapped with Al foil and then is pressed into the Al melt to obtain a mixed melt, the mixed melt is stirred for half a minute and then is placed in the box-type high-temperature furnace for keeping the temperature unchanged for 40 min. During the 40 min, the mixed melt is thoroughly stirred by a graphite stirring rod for 0.5-1 min at intervals of 20 min. After the 40 min, floating slag on a surface of the mixed melt is removed, and then the mixed melt is stirred thoroughly to obtain alloy liquid, the alloy liquid is cast into a cast iron mold followed by solidification to obtain the Al—Ti—Nb—B alloy, denoted as an Al-3Nb-1Ti-0.5B-850° C. refining agent.
A method for refining the Al—Si alloy by the Al-3Nb-1Ti-0.5B-850° C. refining agent includes following steps.
The A356 alloy is placed in a graphite clay crucible and heated to a temperature of 730° C. in a well furnace to obtain an Al—Si melt, the Al—Si melt is added with the Al-3Nb-1Ti-0.5B-850° C. refining agent followed by keeping the temperature unchanged for 5 min to obtain a mixture, a refining agent amount is based on 0.09% Nb of a total weight of the mixture, the mixture is cast into a graphite disc mold to obtain a refined A356 alloy ingot (i.e., a refined A356 alloy).
In order to characterize the compositions of the Al—Ti—Nb—B refining agent prepared in the embodiment 3, XRD analysis is performed on the Al-3Nb-1Ti-0.5B-850° C. refining agent prepared in the embodiment 3. As shown in
In order to observe a microstructure of the Al—Ti—Nb—B refining agent, the Al-3Nb-1Ti-0.5B-850° C. refining agent prepared in the embodiment 3 is characterized by scanning electron microscopy. As shown in
The comparative embodiment 1 is basically the same as the embodiment 1, with special features below: the raw material powder (i.e., the mixed powder) is not ball milled by the planetary ball mill, while other operations are same. A raw material absorption rate of an Al—Ti—Nb—B alloy prepared in the comparative embodiment 1 significantly decreases, and there are residues on an inner wall and a bottom of the graphite clay crucible that do not react. The number of refined nucleating phases generated decreases, and a grain size of a refined A356 alloy is greater than 300 μm, which is far inferior to a refining effect of the embodiment 1.
The embodiments described in the disclosure only describe preferred embodiments of the disclosure, and do not limit the concept and scope of the disclosure. Without departing from the design concept of the disclosure, all variations and modifications made by those skilled in the art to the technical solution of the disclosure should fall within the scope of protection of the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023110275743 | Aug 2023 | CN | national |
