Dual grain refinement method for automobile aluminum alloy hub

Abstract

The invention discloses a dual grain refinement method for an automobile aluminum alloy hub. The dual grain refinement method includes the following steps that a, aluminum alloy melt is taken out of a smelting furnace through a preheated casting ladle; b, when the temperature of the aluminum alloy melt is higher than liquidus temperature by 20 DEG C-60 DEG C, an ultrasonic vibration head is immersed below the liquid level of the aluminum alloy melt by 1-10 mm to be treated ultrasonically, the frequency of ultrasonic treatment is 5-30 kHz, the volume power is 1-50 W / cm<3>, and treatment time is 3-40 seconds; c, the aluminum alloy melt is poured into a preheated mold after being treated ultrasonically for hub forming manufacturing. The direct-contact ultrasonic treatment is carried out on the aluminum alloy melt, by means of acoustic cavitation and acoustic streaming effects of ultrasonic waves, forced nucleation in quantity in the aluminum alloy melt is achieved, and the melt convection effect is generated; without additionally adding a refiner or a modificator, primary crystal a-Al and eutectic crystal Si can be refined at the same time, the tissue and performance requirements for the hub can be met, and the dual grain refinement effect is achieved.

Description

technical field [0001] The invention relates to the technical field of wheel hub manufacturing, in particular to a double grain refinement method for an automobile aluminum alloy wheel hub. Background technique [0002] The automobile industry is developing rapidly. In 2013, China's automobile production has exceeded 20 million, making it the veritable largest country in automobile production. The wheel hub is an important part of the car. The aluminum alloy wheel hub has gradually replaced the status of the steel wheel hub with the advantages of light weight, good heat dissipation and beautiful appearance; however, the mechanical properties of aluminum alloy hubs are worse than those of steel, so it is an important method to improve the mechanical properties of aluminum alloy hub hubs. It is grain refinement. [0003] The traditional grain refinement method of aluminum alloy is to add refiner or modifying agent; the aluminum alloy wheel is usually made of hypoeutectic Al-S...

AI Technical Summary

Problems solved by technology

That is to say, there are two kinds of grains in the aluminum alloy of the wheel hub that need to be refined, and different refiners need to be added respectively. There is no method or substance that can refine the primary a-Al phase and the eutectic Si phase at the same time; and There is a certain mutual offset effect between Ti refiner and Sr and other modifiers, so that the effect of grain refinement is affected to a certain extent

[0004] In addition, iron is the most common and harmful element in aluminum alloys. Under conventional casting conditions, the Fe-rich phases in aluminum alloys, especially aluminum-silicon alloys, such as β-Al5FeSi and δ-Al4FeSi2, tend to grow into thick needle flakes. Deteriorating the mechanical properties of the alloy; the source of Fe in aluminum alloys is mainly the erosion of raw materials and iron tools used, even in the aluminum alloys with high purity for automobile wheels, there are 0.15%~0.2% Fe, so the wheel hub castings There may still be a small amount of needle-like β-Al5FeSi phase

At present, the method to reduce the harm of Fe-rich phase in aluminum alloy is mainly to add neutralizing elements, followed by rapid solidification and overheating of the melt. Among them, the most commonly used neutralizing element is Mn, which can effectively improve the morphology of Fe-rich phase and make the needle piece The β-Al5FeSi phase transforms into the Chinese character-shaped Al15(Fe,Mn)3Si2 which has little influence on the performance. It is generally believed that adding Mn to the alloy at the ratio of Mn / Fe=1 / 2 can obtain better neutralization of Fe. Effect, continue to increase the addition of Mn, although it can further reduce the harmful effect of β phase, but at the same time it will generate polygonal primary α-Al15(Fe,Mn)3Si2 with high hardness, which will reduce the machinability of the alloy, and even according to Adding Mn at a higher Mn / Fe ratio cannot completely eliminate the harmful effects of β-Fe, and adding a large amount of Mn will also increase the cost; while rapid solidification and melt overheating have the defects of expensive process equipment, high cost, and difficult control of the process , greatly restricting its industrial application

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