Grain refinement of ultrasonic metal melts

Device Overview

Ultrasonic metal melt equipment is primarily used to remove impurities, eliminate bubbles, refine grain structure, and enhance casting quality. This is a clean and relatively efficient technique. Porosity remains one of the major defects in aluminum alloy castings, as it compromises both mechanical properties and pressure sealing integrity. Porosity occurs either when gases precipitate from the molten metal during solidification or when liquid metal fails to compensate for inter-dendritic space and volume shrinkage. Therefore, effective bubble removal is crucial for improving casting quality.

20k Ultrasonic Metal Melting Equipment (Ceramic Tool Head)

15k Ultrasonic Metal Melting Equipment (Titanium Alloy Tool Head)

Operational principle

1. Thermal Effects: The thermal action of ultrasound can produce two forms of thermal effects: one is the thermal effect generated by continuous waves, and the other is the instantaneous thermal effect. The combination of these effects intensifies internal friction, leading to partial absorption of acoustic energy which is converted into medium energy, thereby raising the temperature of the liquid medium and altering its viscosity and fluidity.

2. Acoustic flow effect: When sound waves reach a certain intensity, the jet stream induced by the acoustic flow effect circulates throughout the entire molten metal, forming a circulation pattern. Acoustic flow represents a combination of circulation and turbulence, exerting intense vibration and agitation effects on the molten metal.

3. Cavitation Effect Cavitation is a physical phenomenon induced by ultrasonic waves and serves as the primary mechanism by which ultrasound refines metallic melts. When liquids are subjected to high-intensity ultrasound, the sound waves propagating through the liquid medium generate alternating cycles of high pressure (compression) and low pressure (depression). During low-pressure cycles, intense ultrasound generates vacuum bubbles or voids within the liquid. Upon reaching a volume where they can no longer absorb energy, these bubbles collapse violently during high-pressure cycles; the instantaneous collapse of small bubbles generates pressures up to tens of thousands of atmospheres, exerting significant impact forces on the surrounding liquid to achieve stirring effects.

Cavitation schematic diagram

Device Advantages

1. The welding process is simple and easy to master, significantly reducing tin consumption while cutting production time and markedly improving efficiency under identical operating conditions;

2. It substantially enhances product conductivity, lowers circuit resistance, increases contact area, and improves the durability of immersion welding tools;

3. Requiring no flux or cleaning agents, it minimizes corrosion and prevents water or air pollution, completely eliminating false welding and short circuits.

Plant parameter

20k ultrasonic metal melting equipment (ceramic tool head)

15k ultrasonic metal melting equipment (with titanium alloy tool head)

Experimental Demonstration

Comparison of tool heads made from different materials

The ultrasonic melt processing equipment is equipped with high-strength titanium alloy tool heads that exhibit superior corrosion resistance and high-temperature tolerance, with a maximum operating temperature of 1300°C. These tools facilitate more direct and pronounced intermolecular interactions within the molten material. Additionally, they feature simple installation requirements without necessitating modifications to the customer's existing production equipment or process workflows.

Ceramic Tool Head

During ultrasonic casting of metal melts, the tool holder directly contacts the high-temperature molten metal, transmitting ultrasonic waves to perform ultrasonic treatment. Under such conditions, combined effects of high-temperature erosion and thermal stress can rapidly damage tool holders made of conventional materials. Ceramic materials, renowned for their resistance to high-temperature erosion and wear, have become the preferred material for ultrasonic tool heads.

Titanium alloy tool head

Effect of metal melt

1. Removal of impurities: The flotation of minute inclusions in molten steel is highly challenging; only when they aggregate does the process become more feasible. By applying ultrasonic waves to the solution using ultrasonic metal melting equipment, the standing wave generated by ultrasound can effectively promote the separation and aggregation of inclusion particles within the solution.

2. Gas removal: When elastic vibrations of ultrasound are introduced into the molten metal, cavitation occurs; gases dissolved in the liquid metal move toward the cavities, promoting the formation and continuous growth of bubble cores until they reach a size sufficient for expulsion from the molten metal.

3. During the continuous casting of grain-refined aluminum-silicon alloys, ultrasonic treatment can refine the grains of the cast and improve the plasticity and ductility of the alloy, making it more suitable for applications in building materials and automotive engine pistons. Applying ultrasound to molten aluminum alloys prevents the formation of oxide inclusions and refines their microstructure.

4. Enhances the quality of cast billets by acting on the mold, improving the surface quality of the castings. Suitable for small square billets, large square billets, and slab billets; ultrasonic vibration does not require negative sliding. Applying ultrasonic vibration to the mold during casting of small square billets and large square billets yields smooth casting surfaces.

Grain refinement experiment

Step 1: Heat the aluminum block until it melts	Step 2: Ultrasonic treatment
Step 3: Final aluminum ingot quality	Step 4: Silicon nitride ceramic tip surface

Experimental results observed under electron microscopy

Experiment Site