4145
Data verified4145 is the high-carbon end of the standard Cr-Mo bar family, widely specified in oilfield practice (drill collars, subs) where 4140 hardness is not enough. The modified 4145H chemistry used by the oil industry is a related but distinct supply grade.
Chemical composition
| Element | Content (%) |
|---|---|
| C | 0.43–0.48 |
| Si | 0.15–0.35 |
| Mn | 0.75–1.00 |
| P | ≤0.035 |
| S | ≤0.040 |
| Cr | 0.80–1.10 |
| Mo | 0.15–0.25 |
Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.
Properties
| Hardness (Q&T) | 32–44 HRC typical |
| Tensile strength | 950–1200 MPa (Q&T, typ.) |
| Density | 7.85 g/cm³ |
Heat treatment
Normalize 870 °C; quench 845 °C oil; temper 480–620 °C. 4145H modified (higher Mo/Cr per API practice) is common for drill collars.
Equivalent grades
| Standard | Designation |
|---|---|
| aisi | 4145 |
Compare side by side: 4145 vs 4142 · 4145 vs 4150
Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.
Applications & Processing
Applications: Drill collars and subs, heavy shafts, high-strength bolts, downhole tool bodies.
Processing: Machines in annealed or Q&T condition; welding only with strict preheat and PWHT.
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Ask for a quotationVisit NasteelSource: SAE J404 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.