Dalam produksi pengecoran, although Slag Coagulants (or Slag Removers) make up a small percentage of material costs, their impact on casting quality and scrap rates is decisive. Many factories hesitate between using “Natural Perlite” Dan “High-Efficiency Composite Agents”: Should you save money with Perlite, or invest in the Composite version?
Below is a detailed “head-to-head” performance review.
Bulat 1: Core Performance Battle (Expansion, Isolasi, Binding)
We compare the two contenders across three critical dimensions:
| Review Dimension | Contender A: Natural Perlite | Contender B: Composite Slag Coagulant | Winner |
| 1. Expansion | Extreme (4-20x). Expands rapidly like popcorn when heated, creating large volume to cover the molten iron surface. Namun, due to its light weight, it generates dust and is easily sucked away by ventilation systems. | Moderate & Controlled. Formulas are adjusted to keep expansion within an optimal range. It covers well while maintaining density, reducing airborne dust and improving material utilization. | Draw (Perlite is bigger, Composite is more stable) |
| 2. Isolasi | Excellent. Utilizes the expanded honeycomb structure (trapping air) to block thermal radiation. | Superior. Composite types often contain fluxes or binders that form a dense “semi-molten shell” on the surface, sealing the molten iron like a heavy blanket to prevent heat loss through gaps. | Composite Agent 🏆 |
| 3. Binding | Miskin. Relies mainly on physical adsorption. The slag layer remains loose and granular. When skimming, the slag often “falls apart,” allowing small slag particles to slip through the rake back into the iron. | Strong. Undergoes micro-melting when heated, bonding scattered slag into a complete “skin” atau “cake.” It can be lifted off in one piece, ensuring very thorough cleaning. | Composite Agent 🏆 |
Catatan: The microscopic structure of Perlite after expansion is full of pores. This is the secret to its insulation, but also the reason for its low strength and fragility.
Bulat 1 Ringkasan
- Perlite: Wins on Initial Price. If your castings have low requirements for slag inclusion, or if used solely for simple ladle covering/insulation, it is a budget-friendly choice.
- Composite Agent: Wins on Efficiency and Cleanliness. Although the unit price is higher, its ability to “film and cake” reduces skimming time and metal loss. When factoring in the reduction of scrap rates, -nya actual ROI (Pengembalian Investasi) is often higher than Perlite.
Bulat 2: Deep Dive—The “Invisible Killer” Behavior of Inferior Agents
Why do some slag coagulants make slag harder to remove, or cause scrap rates to spike? This is usually due to the use of inferior products or improper formulations.
1. Why does slag become “hard to remove after cooling”?
This is typically a failure in controlling the Titik lebur Dan Viscosity of the agent.
- Over-burning & Wall Sticking: If the melting point of an inferior agent is too low, it turns into a liquid (rather than a viscous semi-solid) upon contact with high-temperature iron. This liquid slag acts like glue, sticking to the furnace or ladle walls. Upon cooling, it hardens like cement on the refractory lining, becoming nearly impossible to clean and potentially damaging the lining.
- Failure to Aggregate: Sebaliknya, if the melting point is too high or lacks binding components, the agent acts like loose sand. During skimming, the slag layer lacks cohesion. One pull of the rake scatters the slag, leading to unclean skimming and residual fines entering the mold.
Catatan: A high-quality composite agent should form a “Crust” atau “Cake” floating layer as shown above, possessing good integrity for one-step skimming.
2. Why does it cause “Slag Entrainment” (Inclusions in Iron)?
This is the most dangerous scenario, where inferior agents become accomplices to slag defects:
- ReaktifPorositas: Some low-quality products contain excessive moisture or impurities (MISALNYA., calcium carbonate that decomposes to release gas). When rolled into the molten iron, instead of adsorbing impurities, they react violently, generating bubbles that agitate the metal and pull floating slag back down into the melt.
- “Fake” Coagulation: Inferior agents may look like they are covering the surface, but they lack true adsorption capability (improper wetting angle). Tiny oxide inclusions are not “grabbed” by the agent but remain suspended in the sub-surface layer. When you pour—thinking the slag is gone—these invisible killers flow into the casting.
Catatan: Typical slag inclusion defect. Under a microscope, these inclusions are often found to be wrapped in oxides that were not effectively removed.
Final Verdict & Recommendations
Who is the King of Cost-Performance?
- For Ordinary Gray Iron (Manhole covers, Counterweights):Perlite is the King. The cost is low, and the performance is sufficient.
- For Ductile Iron, Auto Parts, & Presisi Castings:Composite Slag Coagulant is the absolute Value King. It significantly reduces scrap rates (slag is the enemy of ductile iron) and metal loss. The small price difference in the agent is negligible compared to the cost of a single scrapped casting.
