API Q125 Casing
Data verifiedQ125 is the top standard strength grade in API 5CT: a 125 ksi yield casing for ultra-deep and high-pressure wells where even P110 cannot carry the string weight or burst load. It is a mill-produced Q&T product, bought to performance rather than chemistry.
Chemical composition
| Element | Content (%) |
|---|---|
| P | ≤0.030 |
| S | ≤0.030 |
| Note | API 5CT sets no C/Mn limits for Q125 — chemistry is mill practice, delivery is quenched & tempered |
Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.
Properties
| Yield strength | 862–1034 MPa (125–150 ksi) |
| Tensile strength | ≥931 MPa (135 ksi) |
| Density | 7.85 g/cm³ |
Heat treatment
Quenched and tempered by the mill; high-collapse and special-clearance variants are common order options.
Equivalent grades
| Standard | Designation |
|---|---|
| aisi | API 5CT Q125 |
| gb | Q125 (GB/T 19830) |
Compare side by side: API Q125 Casing vs API P110 Casing
Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.
Applications & Processing
Applications: Ultra-deep wells, high-pressure gas wells, heavy casing strings, high-collapse service.
Processing: Premium connections are the norm at this strength; not for sour service unless a specific sour-qualified variant is ordered and tested.
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Ask for a quotationVisit NasteelSource: API 5CT published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.