A Batch Number or Lot Number refers to a specific quantity of material that has been processed together under uniform conditions after the initial melting. A single Heat can be divided into multiple Batches/Lots.
Key Differences and Significance:
| Feature | Heat Number | Batch / Lot Number |
|---|---|---|
| Scope | Tracks the molten steel from the furnace. | Tracks a subset through subsequent processing. |
| Creation | Assigned at melting. | Assigned at a later processing stage. |
| What it tracks | Chemical composition homogeneity. | Processing history uniformity. |
Example: Heat #A1234 (100 tons of 4140) might be split:
Batch B1: 40 tons hot-rolled into 50mm rounds on Mill #1 on a specific date.
Batch B2: 60 tons hot-rolled into 100mm rounds on Mill #2 the next day.
These batches may then undergo different heat treatments (e.g., Batch B1 is annealed, Batch B2 is normalized). The Batch Number allows tracking this specific thermo-mechanical history, which directly influences the final microstructure and mechanical properties. Both numbers are essential for complete traceability.