Before answering, we must first understand the primary purpose of normalizing 4140 steel: to prepare a good microstructure for the final heat treatment. In most cases, normalizing is a pretreatment process.
Secondly, after normalizing, 4140 steel ultimately obtains fine pearlite with a small amount of ferrite (uniform microstructure and refined grains), resulting in improved performance. Normalizing, as the final heat treatment, is sufficient to meet the requirements for non-critical, medium-load parts.
| 4140+N Mechanical Properties | ||||
| Tensile Strength | Yield Strength | Elongation | Reduction of Area | Hardness |
| ≥685MPa | ≥415MPa | ≥20% | ≥50% | 200-250HB |