Common aluminum molds: 7075 aluminum alloy; Common titanium molds: TC4 titanium alloy; Steel molds: Heat-treated tool steel.

Aluminum Alloy Molds (7075)
Advantages:
1. Excellent acoustic conductivity, lightweight, easy to machine, fast turnaround, and lowest cost.
2. Suitable for large-sized welding horns; allows for complex tooth pattern engraving; good heat dissipation, preventing heat buildup.
3. Top choice for prototyping and new product testing; highly versatile.

Disadvantages:
Lower surface hardness and poor wear resistance; prone to rapid wear, flattened tooth profiles, and fatigue cracking when used with glass-fiber reinforced plastics or in high-volume continuous production; lifespan can be extended via hard anodizing, but it still falls short of titanium or steel.

Suitable Applications:
Standard ABS/PP/PC housings, chargers, toys, and small plastic parts; new product prototyping, small-to-medium batch production, large-surface welding horns; non-glass-fiber filled plastics.

Titanium Alloy Molds (TC4)
Advantages:
1. Superior acoustic performance, low internal energy loss, and stable amplitude; high fatigue strength, making them resistant to cracking during continuous mass production.
2. Combines lightweight properties with high wear and corrosion resistance; low heat generation and a lifespan far exceeding that of aluminum molds; compatible with surface coatings (tungsten carbide, nickel, Teflon).
3. Preferred choice for medical devices and precision electronics; meets cleanliness requirements.

Disadvantages:
Highest raw material and machining costs; difficult to machine; expensive.

Suitable Applications:

High-output continuous mass production, precision small parts, medical products, glass-fiber reinforced plastics, high-frequency machines (30kHz/40kHz); products requiring high welding consistency and cleanliness. 

Steel Horn (Heat-treated Tool Steel)

Advantages:
Offers the highest wear resistance and hardness among the three materials; excels in resisting abrasive wear; suitable for highly abrasive plastics containing glass fiber or mineral fillers.

Disadvantages:
1. High acoustic impedance and high acoustic energy loss; unsuitable for high-amplitude welding. Heavy weight leads to heat buildup during prolonged operation.
2. Prone to fatigue fracture under high-amplitude conditions; places greater load stress on the transducer. Difficult to tune; generally not recommended as a standard primary welding horn.

Applications:

Low-amplitude press-fitting, combined welding and cutting, webbing/non-woven fabric cutting, piercing/riveting; plastic parts with high glass fiber content; more commonly used for bottom fixture anvils rather than upper welding horns.