T95 occupies a precise and demanding position in the API 5CT casing grade ladder: it provides 95,000 psi minimum yield strength — higher than L80 but lower than P110 — while maintaining the sour service qualification that P110 cannot offer. It is the grade of choice when a well is deep enough that L80's strength is insufficient, but the presence of H₂S rules out the use of P110. Getting T95 right — specifying the correct sub-grade, verifying hardness certification, and confirming NACE compliance documentation — requires more diligence than any other common casing grade.
ZC Steel Pipe manufactures API 5CT T95 casing in Type 1 and Type 2 sub-grades, with full CVN impact testing, hardness certification, and NACE MR0175 documentation. We supply OCTG to oil and gas operators running sour service wells across the Middle East, Africa, and South America. This guide covers T95's specifications, its two sub-grade types, sour service qualification requirements, and how to position it correctly against L80 and P110 in a casing programme.
CONTENTS
What Is API 5CT T95?
T95 Type 1 vs Type 2
Chemical Composition
Mechanical Properties
Sour Service Qualification — NACE MR0175 / ISO 15156
T95 in the Sour Service Grade Ladder
T95 vs P110 — When Sour Service Rules Out High Strength
T95 vs L80 — When to Step Up
Standard Dimensions
Inspection and CVN Requirements
FAQ
1. What Is API 5CT T95?
STANDARD DEFINITION — API 5CT T95T95 is a Group 3 casing grade in API 5CT (Specification for Casing and Tubing). The "T" designates a sour-service-capable grade — one of four in API 5CT alongside L80, C110, and Q125. The "95" refers to the minimum yield strength of 95,000 psi (655 MPa). T95 is produced in two sub-grades — Type 1 and Type 2 — differentiated by maximum hardness. Both require quench-and-temper heat treatment. API 5CT also mandates Charpy V-Notch (CVN) impact testing for T95, reflecting its critical service application.
T95 was developed to address a gap that exists in deep sour wells: L80 (80 ksi) becomes uneconomic at depths where the collapse, burst, and tension loads exceed what L80 can handle at acceptable wall thickness, but P110 — the obvious next step in strength — cannot be used because of its lack of sour service qualification. T95 at 95 ksi closes that gap, providing a sour-qualified option 18% stronger than L80.
T95 is a speciality grade — it is not stocked like N80 or L80 and typically requires a minimum order quantity and longer mill lead time. It is used when the casing design genuinely demands it, not as a default upgrade.
2. T95 Type 1 vs Type 2
T95 Type 1
Min yield: 655 MPa (95,000 psi)
Max yield: 758 MPa (110,000 psi)
Min tensile: 724 MPa (105,000 psi)
Max hardness: 25.4 HRC (255 HV10)
Heat treatment: Quench and Temper (Q+T)
CVN: Required per API 5CT
Best for: Moderate sour service — verified H₂S partial pressure within NACE limits
T95 Type 2
Min yield: 655 MPa (95,000 psi)
Max yield: 758 MPa (110,000 psi)
Min tensile: 724 MPa (105,000 psi)
Max hardness: 23 HRC (241 HV10)
Heat treatment: Quench and Temper (Q+T)
CVN: Required per API 5CT
Best for: More aggressive sour service — tighter hardness margin to NACE 22 HRC limit
Engineering Insight — Why Type 2's 23 HRC Limit MattersNACE MR0175 / ISO 15156 limits carbon and low-alloy steel OCTG to 22 HRC maximum hardness in H₂S service. T95 Type 1's ceiling of 25.4 HRC gives less margin — if any individual hardness reading approaches that limit, there is limited buffer before the NACE threshold is breached. Type 2's 23 HRC ceiling sits only 1 HRC above the NACE limit, creating a tighter quality control envelope that reduces the risk of individual readings exceeding the NACE requirement. For critical sour service wells where the H₂S environment is aggressive or where the consequences of SSC failure are severe, Type 2 provides a meaningfully more conservative specification. The cost premium between Type 1 and Type 2 is generally modest — the tighter heat treatment control is the primary driver.
3. Chemical Composition
| Element | T95 Type 1 Max (%) | T95 Type 2 Max (%) | Note |
| Carbon (C) | 0.35 | 0.35 | Lower than N80 — improves SSC resistance |
| Manganese (Mn) | 1.20 | 1.20 | Tighter limit vs N80 — controls hardenability |
| Molybdenum (Mo) | 0.85 | 0.85 | Supports high-temperature temper for hardness control |
| Chromium (Cr) | 1.50 | 1.50 | Improves hardenability and corrosion resistance |
| Nickel (Ni) | 0.99 | 0.99 | Improves low-temperature toughness |
| Silicon (Si) | 0.45 | 0.45 | Deoxidant — controlled for toughness |
| Phosphorus (P) | 0.020 | 0.020 | Tighter than N80 — critical for SSC resistance |
| Sulphur (S) | 0.010 | 0.010 | Tighter than N80 — MnS inclusions are SSC initiation sites |
Compared to N80, T95 has significantly tighter phosphorus (0.020 vs 0.030) and sulphur (0.010 vs 0.030) limits. This is deliberate — both elements are detrimental to SSC resistance. Sulphide inclusions (MnS) act as hydrogen trapping sites and crack initiation points in sour environments. The cleaner chemistry of T95 reflects its sour service application.
4. Mechanical Properties
| Property | T95 Type 1 | T95 Type 2 | Unit |
| Minimum yield strength | 655 | 655 | MPa (95,000 psi) |
| Maximum yield strength | 758 | 758 | MPa (110,000 psi) |
| Minimum tensile strength | 724 | 724 | MPa (105,000 psi) |
| Maximum hardness | 25.4 HRC / 255 HV10 | 23 HRC / 241 HV10 | HRC / HV |
| Heat treatment | Q+T | Q+T | — |
| CVN impact testing | Required | Required | Per API 5CT tables |
| API group | 3 | 3 | — |
5. Sour Service Qualification — NACE MR0175 / ISO 15156
T95 is one of four API 5CT grades explicitly designed for sour service. However, API 5CT certification alone does not guarantee NACE MR0175 / ISO 15156 compliance — that requires the purchaser to specify NACE compliance as a supplemental requirement on the purchase order, and the mill to certify that each heat meets the applicable NACE conditions.
The NACE MR0175 requirements for T95 casing include:
Maximum hardness: 22 HRC (HV 237) on any individual hardness measurement — note this is lower than both T95 Type 1 (25.4 HRC) and Type 2 (23 HRC) API 5CT limits. The NACE limit is the governing constraint for sour service.
Heat treatment: Q+T — mandatory for both types.
Chemistry: Low S and P as specified above — consistent with T95's API 5CT chemistry limits.
Documentation: A certified statement of NACE MR0175 / ISO 15156 compliance must accompany the MTC.
Critical Engineering Point — API 5CT T95 Type 1 Hardness Exceeds the NACE LimitThis is the most critical specification trap with T95: T95 Type 1 has a maximum hardness of 25.4 HRC per API 5CT, but NACE MR0175 limits carbon and low-alloy steel to 22 HRC for sour service. A pipe certified to API 5CT T95 Type 1 is NOT automatically NACE-compliant — individual readings between 22 and 25.4 HRC will pass API 5CT but fail NACE MR0175. For sour service wells, you must specify NACE compliance as a supplemental purchase requirement, and verify on the MTC that each tested pipe meets 22 HRC maximum, not just the API 5CT limit. T95 Type 2 (23 HRC API 5CT limit) provides better margin but still requires explicit NACE certification — the API 5CT certificate is not a substitute.
6. T95 in the Sour Service Grade Ladder
API 5CT defines four grades specifically intended for sour service applications. T95 sits between L80 and C110 in the strength ladder:
| Grade | Min Yield (MPa / ksi) | Max Yield (MPa / ksi) | Max Hardness (HRC) | NACE HRC Limit | CVN Required |
| L80 | 552 / 80 | 655 / 95 | 23 HRC | 22 HRC | No |
| T95 Type 1 | 655 / 95 | 758 / 110 | 25.4 HRC | 22 HRC | Yes |
| T95 Type 2 | 655 / 95 | 758 / 110 | 23 HRC | 22 HRC | Yes |
| C110 | 758 / 110 | 828 / 120 | 30 HRC (Type 1) / 27 HRC (Type 2) | Per NACE annex | Yes |
| Q125 | 862 / 125 | 1034 / 150 | No limit specified | Not standard sour | Yes |
Related: API 5CT L80 Casing — Sour Service Specs → | API 5CT P110 Casing — High Strength Specs → | API 5CT N80 Casing — Sweet Service →
7. T95 vs P110 — When Sour Service Rules Out High Strength
| Property | T95 (Type 1 / Type 2) | P110 |
| Min yield (MPa) | 655 | 758 |
| Max yield (MPa) | 758 | 965 |
| Hardness limit | 25.4 / 23 HRC | None |
| Sour service qualified | Yes — with NACE supplement | No |
| CVN testing | Required | Not required |
| H₂S environment | Suitable | Not suitable |
| Deep sweet wells | Yes — but P110 more efficient | Preferred |
| Typical depth | 2,500–5,000 m sour | 3,000–6,000+ m sweet |
The decision between T95 and P110 is not usually a difficult one — it is driven by the well's H₂S content. If confirmed H₂S is present above the NACE threshold (0.0003 MPa partial pressure), P110 is ruled out entirely. If the well is sweet, P110 gives better collapse and burst performance per unit weight. The engineering error to avoid is specifying P110 in a well with uncertain or marginal H₂S content, assuming the risk is low — NACE MR0175 compliance is a binary requirement, not a risk tolerance question.
8. T95 vs L80 — When to Step Up
L80 and T95 are both sour service grades — the question is whether the casing design requires the additional 18% yield strength that T95 provides. The answer comes from the casing design calculation, not from a rule of thumb. The practical triggers for stepping from L80 to T95 are:
Collapse requirement: L80 wall thickness needed to resist collapse is too heavy for the drilled hole size or the weight budget
Burst requirement: Kick scenarios produce burst loads exceeding L80's capacity at acceptable wall thickness
Tension requirement: Long casing strings in deep wells generate tensile loads approaching L80's pipe body yield strength at the top joint
Well depth: Typically above 3,500–4,000 metres in sour service environments where L80's strength-to-weight economics deteriorate
Procurement Note — T95 Is Not a Stock GradeUnlike L80 and N80, T95 is not routinely stocked by Chinese OCTG mills or pipe distributors. It is an order-to-make grade requiring specific chemistry heats, controlled Q+T heat treatment, CVN testing, and hardness certification. Lead times for T95 from Chinese mills are typically 10–16 weeks from order confirmation, depending on mill schedule and the CVN testing and documentation requirements. Budget procurement lead time accordingly — T95 should not be a last-minute upgrade from L80 when the well has already been spud. Source it on the basis of the pre-spud casing design.
9. Standard Dimensions
T95 is available in the same standard casing sizes as L80 — from 4½" through 20" OD. The most commonly ordered sizes for intermediate and production casing in deep sour wells are 5½", 7", 9⅝", and 13⅜".
| OD (inches) | Common Weights (lb/ft) | Typical Use in Sour Wells |
| 5" | 11.5 – 18.0 | Production casing / liner |
| 5½" | 14.0 – 26.8 | Production casing |
| 7" | 17.0 – 38.0 | Intermediate / production casing |
| 7⅝" | 24.0 – 45.3 | Intermediate casing |
| 9⅝" | 32.3 – 61.1 | Intermediate casing |
| 13⅜" | 48.0 – 85.0 | Surface / intermediate casing |
| 16" | 65.0 – 109.0 | Surface casing |
10. Inspection and CVN Requirements
| Test / Inspection | T95 Type 1 | T95 Type 2 | Frequency |
| Tensile test | Required | Required | Per heat and lot |
| Hardness test | Required — max 25.4 HRC | Required — max 23 HRC | Per pipe |
| CVN impact test | Required | Required | Per lot (3 specimens) |
| Hydrostatic test | Required | Required | Per pipe |
| Drift test | Required | Required | Per pipe |
| NDE (UT/EM) | Supplemental — specify on order | Supplemental — specify on order | Per pipe if specified |
| NACE compliance cert | Required for sour service | Required for sour service | Per heat |
| MTC (EN 10204 3.1) | Standard | Standard | Per heat |
| Third-party inspection | Strongly recommended | Strongly recommended | Per order |
11. Frequently Asked Questions
What is API 5CT T95 casing pipe?
API 5CT T95 is a sour-service-qualified OCTG casing grade with a minimum yield strength of 655 MPa (95,000 psi). It is one of four API 5CT grades designed for H₂S-containing wells, produced in two types: Type 1 (max 25.4 HRC) and Type 2 (max 23 HRC). T95 fills the gap in the sour service grade ladder between L80 (80 ksi) and C110 (110 ksi), used in deep sour wells where L80's strength is insufficient but P110's lack of sour service qualification rules it out.
What is the difference between T95 Type 1 and Type 2?
Both types have identical yield strength requirements (655–758 MPa) and require quench-and-temper heat treatment. The difference is maximum hardness: Type 1 allows up to 25.4 HRC and Type 2 allows up to 23 HRC. Type 2's tighter hardness ceiling provides a smaller margin to the NACE MR0175 limit of 22 HRC, offering better assurance of NACE compliance in aggressive sour environments. Type 2 requires more precise heat treatment control and carries a modest cost premium over Type 1.
Is T95 suitable for sour service?
Yes — T95 is specifically designed for sour service. However, API 5CT certification alone is not sufficient for NACE MR0175 compliance. The purchaser must specify NACE compliance as a supplemental purchase requirement, and critically, T95 Type 1's API 5CT hardness limit of 25.4 HRC exceeds the NACE limit of 22 HRC — meaning individual pipes that pass API 5CT testing may still fail the NACE requirement. Always specify NACE compliance explicitly and verify the hardness data on the MTC, not just the grade designation.
What is the difference between T95 and P110?
T95 is a sour-service grade with a controlled maximum hardness and NACE MR0175 qualification. P110 is a high-strength sweet service grade with no hardness limit and no sour service qualification. T95 minimum yield (655 MPa) is lower than P110 (758 MPa), but T95 can be used in H₂S-containing wells while P110 cannot. For wells with confirmed H₂S above the NACE threshold, T95 is mandatory; P110 is ruled out regardless of its strength advantage.
What is the difference between T95 and L80?
T95 and L80 are both sour service grades but at different strength levels. L80 has a minimum yield of 552 MPa (80 ksi) and T95 has 655 MPa (95 ksi) — approximately 18% stronger. T95 is used when L80's strength is insufficient for the well's collapse, burst, or tension requirements, typically in deeper wells exceeding 3,500–4,000 metres. T95 also requires CVN impact testing (which L80 does not) and is a non-stock order-to-make grade with longer lead times than L80.
What CVN toughness is required for T95?
API 5CT mandates Charpy V-Notch (CVN) impact testing for T95 — one of the requirements that distinguishes it from N80 and P110. The minimum CVN values are specified in the API 5CT tables as a function of pipe OD and wall thickness, with separate minimums for individual specimens and the average of three. Testing is performed at 0°C unless a lower temperature is specified by the purchaser. The CVN requirement reflects T95's critical sour service application, where toughness is essential to resist brittle fracture in hydrogen-charged environments.
Source API 5CT T95 Casing from ZC Steel Pipe
ZC Steel Pipe manufactures API 5CT T95 casing in Type 1 and Type 2, with full CVN impact testing, per-pipe hardness certification, NACE MR0175 compliance documentation, and EN 10204 3.1 or 3.2 MTC. Third-party inspection (SGS, Bureau Veritas, TÜV) and supplemental NDE available. We hold independent patents in premium connection technology for T95 casing for gas well and critical service applications.
T95 is an order-to-make grade — lead times are typically 10–16 weeks. Contact us early in your casing design process for mill availability, pricing, and technical support.
mandy.w@zcsteelpipe.com
WhatsApp: +86-139-1579-1813
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