Burn-up

In the context of the foundry industry, burn-up refers to the process where materials, typically sand, core materials, or molding compounds, degrade or burn away during the metal casting process. This occurs due to the extreme temperatures involved when molten metal is poured into the mold or core, causing certain materials to burn, decompose, or vaporize. Burn-up can affect the quality of the casting and the performance of the mold or core.

There are a few key meanings and implications of "burn-up" in the foundry:

1. Burn-Up of Core Sand or Molding Sand:

• Core sand or molding sand is used to form molds and cores for casting metals. When the molten metal comes into contact with the sand, especially in high-temperature castings, some of the sand or binder materials may burn or decompose. This is referred to as burn-up.
• The extent of burn-up depends on the temperature of the molten metal, the composition of the sand and binders, and the specific casting process used.
• Excessive burn-up can lead to defects such as rough surfaces, porosity, or insufficient strength in the mold/core, which can negatively affect the quality of the final metal part.

2. Burn-Up in Sand Cores:

• When creating sand cores (which are used to form internal cavities in castings), burn-up refers to the degradation of the sand and binder material due to the heat from the molten metal.
• This can weaken the core structure, causing it to collapse or not maintain the intended shape during casting, leading to defects in the final part.

3. Burn-Up of Binder Materials:

• Binders are substances used to hold the sand particles together in molds and cores. In some cases, certain binders (such as resins or organic compounds) can burn away or degrade when exposed to the high heat of molten metal. This can affect the mold’s integrity and lead to defects in the cast part.

4. Impact on Casting Quality:

• Burn-up can lead to various problems such as:
  • Surface imperfections: Excessive burn-up can cause roughness or defects on the surface of the cast part.
  • Porosity: The burning or degradation of sand and binders can leave voids or holes in the casting.
  • Core collapse: If the sand core weakens too much due to burn-up, it may collapse during the casting process, leading to internal defects.

5. Burn-Up in Furnace Operations:

• In some foundries, "burn-up" might also be used to describe the burning of scrap materials in the furnace as part of the melting process. This includes the process of consuming metals, alloys, or scrap materials in the furnace as they are melted down to be poured into molds.

Conclusion:

In the foundry industry, burn-up refers to the degradation or consumption of materials, particularly sands, cores, or binder systems, due to the high temperatures associated with molten metal casting. It is important to manage burn-up properly to maintain the integrity of molds, cores, and castings, ensuring high-quality metal parts and efficient production.