The choice depends entirely on the final application and manufacturing process.
| Aspect | Hot-Rolled (HR) 42CrMo | Cold-Drawn (CD) 42CrMo |
|---|---|---|
| Surface Finish | Poor (mill scale, decarb). Requires removal. | Excellent (bright, smooth). Often final finish. |
| Dimensional Tolerance | Wide (commercial). More stock to machine off. | Very tight (precision). Less waste, precise fits. |
| Straightness | Moderate. May require straightening. | Excellent. |
| Mechanical Properties (As-supplied) | Generally as per heat-treated state (if +QT) or soft (if +A). Properties are isotropic. | Anisotropic. Higher longitudinal strength due to cold work, but reduced ductility and much lower transverse impact toughness. |
| Cost | Generally lower. | Higher due to additional processing. |
| Primary Application | Components for heavy machining, forging, or custom heat treatment. | Precision components with minimal final machining, where finish and size are critical. |
| Key Disadvantage | Scale, decarb, poor tolerances. | Directional properties, residual stresses, not suitable for further heat treatment if hard-drawn (can distort). |