API 5CT C95 Oilfield Casing Pipe – Complete Technical Guide for B2B Buyers
If you're sourcing casing pipe for an oil or gas well project, chances are you've run into API 5CT C95. It's a grade that's been around the industry for decades and still gets specified in drilling programs across the globe. Whether you're a procurement manager, a drilling engineer, or a trading company, this guide walks you through everything that actually matters - specifications, chemistry, mechanical properties, sizing, testing, supplier evaluation, and the key standard update you need to know about.
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What Is API 5CT C95 Casing Pipe?
API 5CT C95 is a controlled yield‑strength steel grade classified under Group 2 of the API Spec 5CT specification. It was designed for oil and gas well casing applications where you need higher strength than standard grades like J55 or N80, combined with mandatory hardness control to guard against brittle failure modes.
Here's the thing - C95 sits in an interesting spot in the API grade hierarchy. It shares the same yield strength range as C90 (another Group 2 grade), but the two differ in chemical composition and intended service. C90 is a dedicated sour service grade (compliant with NACE MR0175/ISO 15156‑2), while C95 is not classified as a sour service grade. What C95 does offer is a hardness cap of 25.4 HRC, which provides better resistance to sulfide stress cracking (SSC) than uncontrolled grades like N80 or P110.
In practice, C95 casing pipe is placed downhole to provide structural integrity to the wellbore. It has to withstand external collapse pressure from surrounding rock formations, internal burst pressure from gases and fluids, and the deadweight of the casing string itself. That's why the mechanical properties are so tightly controlled.
API 5CT C95 Specifications
Here's a quick‑reference table of the key specification parameters. Save this for your procurement documents.
| Parameter | Specification |
|---|---|
| Governing Standard | API Spec 5CT / ISO 11960 |
| Grade | C95 (Type 1) |
| Group | Group 2 (restricted yield strength with mandatory hardness control) |
| Manufacturing Method | Seamless (SML) or Electric Resistance Welded (ERW) |
| Heat Treatment | Quenched and Tempered (Q&T) |
| Outer Diameter (Casing) | 4‑1/2" to 20" (114.3 mm – 508 mm) |
| Outer Diameter (Tubing) | 2‑3/8" to 4‑1/2" (60.3 mm – 114.3 mm) |
| Length Range | R1 (4.88–7.62 m), R2 (7.62–10.36 m), R3 (10.36–14.63 m) |
| Thread Types | STC (Short Round Thread), LTC (Long Round Thread), BTC (Buttress Thread) |
| Color Code | One brown band on pipe body; solid brown coupling |
| Sour Service (H₂S) | Not NACE MR0175 approved - see note below |
Chemical Composition of API 5CT C95 Grade
The chemical composition of C95 is what gives it the strength and toughness profile that drilling operations demand. The spec controls key elements tightly - especially phosphorus and sulfur, which are kept very low to reduce brittleness and cracking risk.
| Element | Min (%) | Max (%) | Role in C95 Steel |
|---|---|---|---|
| Carbon (C) | - | 0.35 | Provides strength and hardenability |
| Manganese (Mn) | - | 1.20 | Enhances strength and toughness |
| Molybdenum (Mo) | 0.25 | 0.85 | Improves hardenability and high‑temperature strength |
| Chromium (Cr) | - | 1.50 | Boosts corrosion resistance and hardenability |
| Nickel (Ni) | - | 0.99 | Enhances low‑temperature toughness |
| Phosphorus (P) | - | 0.020 | Kept low to prevent cold brittleness |
| Sulfur (S) | - | 0.010 | Minimized to reduce hot cracking risk |
A couple of things worth pointing out: Molybdenum has both a minimum (0.25%) and maximum (0.85%) limit - that's because Mo plays a critical role in achieving the right hardenability for Q&T processing. Too little and you won't get the strength; too much and you risk brittleness. The sulfur limit of 0.010% is quite tight, which is characteristic of Group 2 controlled grades.
Pro tip for buyers: Always request the Mill Test Certificate (MTC) per EN 10204 Type 3.1 for every heat. Verify that the actual chemistry falls within these limits - don't just take the supplier's word for it.
Mechanical Properties of API 5CT C95
The mechanical properties are where C95 really defines itself. These values are non‑negotiable - if the pipe doesn't meet them, it doesn't meet the spec. Here's the full breakdown:
| Property | Metric | Imperial |
|---|---|---|
| Yield Strength (min) | 621 MPa | 90,000 psi |
| Yield Strength (max) | 724 MPa | 105,000 psi |
| Tensile Strength (min) | 689 MPa | 100,000 psi |
| Total Elongation Under Load | 0.5% | 0.5% |
| Hardness (max HRC) | 25.4 HRC | 25.4 HRC |
| Hardness (max HBW) | 255 HBW | 255 HBW |
Allowable Hardness Variation by Wall Thickness
API 5CT also specifies how much hardness can vary across the pipe wall, depending on wall thickness. This matters because thicker walls are harder to quench uniformly.
| Specified Wall Thickness (mm) | Allowable Hardness Variation (HRC) |
|---|---|
| ≤ 12.70 | 3.0 |
| 12.71 – 19.04 | 4.0 |
| 19.05 – 25.39 | 5.0 |
| ≥ 25.40 | 6.0 |
C95 Casing Pipe Dimensions and Size Chart
C95 casing pipe comes in a wide range of outer diameters and wall thicknesses to suit different well designs. The OD range for casing runs from 4‑1/2" all the way up to 20", covering everything from production casing to conductor pipe.
| Nominal Size (inch) | OD (mm) | Common Wall Thickness (mm) |
|---|---|---|
| 4‑1/2" | 114.3 | 5.21 – 12.70 |
| 5" | 127.0 | 5.59 – 12.70 |
| 5‑1/2" | 139.7 | 6.20 – 15.88 |
| 6‑5/8" | 168.3 | 7.32 – 12.06 |
| 7" | 177.8 | 6.91 – 13.72 |
| 7‑5/8" | 193.7 | 8.33 – 15.88 |
| 8‑5/8" | 219.1 | 6.71 – 14.15 |
| 9‑5/8" | 244.5 | 8.94 – 15.11 |
| 10‑3/4" | 273.1 | 8.89 – 15.11 |
| 11‑3/4" | 298.5 | 9.53 – 12.42 |
| 13‑3/8" | 339.7 | 8.38 – 14.27 |
| 16" | 406.4 | 16.51 – 44.45 |
| 20" | 508.0 | 16.13 – 26.19 |
Length Ranges
Casing pipe is supplied in three standard length ranges. Pick the one that matches your well design - longer pipe means fewer joints, but R3 can be harder to transport.
| Range | Casing Length (m) | Tubing Length (m) |
|---|---|---|
| R1 | 4.88 – 7.62 | 6.10 – 7.32 |
| R2 | 7.62 – 10.36 | 8.53 – 9.75 |
| R3 | 10.36 – 14.63 | 11.58 – 12.80 |
Thread Types and End Finishing
The thread connection you choose has a direct impact on well integrity. Get it wrong and you're looking at leaks, connection failures, or worse. Here are the main options for C95 casing:
- STC (Short Round Thread Casing): The most economical option. Best for shallow to medium‑depth wells with moderate loads. Shorter thread engagement means lower tensile capacity.
- LTC (Long Round Thread Casing): Longer thread engagement than STC, giving you better tensile and seal performance. A solid middle‑ground choice for most applications.
- BTC (Buttress Thread Casing): Designed for high‑tensile loads. The trapezoidal thread form resists axial loads better than round threads, making it ideal for deep wells and heavy casing strings.
For tubing applications, C95 can also be supplied with:
- EUE (External Upset End): Thicker at the threaded end for enhanced joint strength.
- NUE (Non‑Upset End): No upset, used in lower‑stress applications.
- IJ (Integral Joint): One end external upset, the other internal upset - no separate coupling needed.
Additional end‑finishing and processing options include drifting (full‑length or ends only), hydrostatic testing, couplings (EUE, AB Modified, turned down, special clearance), coating to customer specifications, and pup joints.
C95 vs Other API 5CT Grades - How It Compares
One of the most common questions we get is: "Should I use C95 or [another grade]?" The answer depends on your well conditions - depth, pressure, temperature, and fluid composition. Here's a head‑to‑head comparison to help you decide:
| Grade | Yield (MPa) | Tensile (MPa) | Max Hardness | Sour Service | Typical Use |
|---|---|---|---|---|---|
| J55 | 379–552 | 517 | - | No | Shallow, low‑pressure wells |
| N80 | 552–758 | 689 | - | No | Medium‑depth, general service |
| L80 | 552–655 | 655 | 23 HRC | Yes | Sour service, moderate depth |
| C90 | 621–724 | 689 | 25.4 HRC | Yes | Sour service, deeper wells |
| C95 | 621–724 | 689 | 25.4 HRC | No | Higher strength, non‑sour |
| R95 | 655–758 | 724 | - | No | Replaced C95 in 9th Ed., non‑sour |
| T95 | 655–758 | 724 | 25.4 HRC | Yes | Sour service, deep wells |
| P110 | 758–965 | 862 | - | No | Deep, high‑pressure wells |
Key takeaway: C95 shares the same yield/tensile/hardness profile as C90, but without the sour service qualification. If you need the same strength and H₂S resistance, go with C90 or T95. If you need higher strength without sour service, R95 or P110 might be your pick.
Color Code Identification
API 5CT uses a color‑coding system to help identify pipe grades on the rig site. For C95, the identification is straightforward:
| Grade | Pipe Body | Coupling |
|---|---|---|
| C95 | One brown band | Solid brown (no band) |
Always verify the grade by checking both the color code and the stenciled markings on the pipe. The marking should include the manufacturer's name, standard, grade, OD, wall thickness, length, and heat number.
Important Standard Update: C95 and Recent API 5CT Editions
Here's something that catches a lot of buyers off guard: C95 was removed from API Spec 5CT starting with the 9th Edition (published in 2011). The grade was replaced by R95, which has a higher yield strength range (655–758 MPa vs. C95's 621–724 MPa) but without mandatory hardness testing requirements.
The current edition of API Spec 5CT is the 11th Edition, published in December 2023, with a Monogram Program effective date of January 1, 2025.
The grades listed in the 11th Edition are: H40, J55, K55, N80, R95, L80, C90, T95, C110, P110, Q125
C95 is not among them. However, this doesn't mean C95 pipe has disappeared from the market. Far from it. Many manufacturers still produce C95 to earlier edition specifications (typically the 8th Edition) because:
- Existing well designs and operator specifications still reference C95
- Some regional standards and company specs haven't been updated
- The mechanical properties and chemistry of C95 are well‑established and proven
- Replacement projects for existing C95 casing strings need matching material
What this means for you as a buyer: If you're specifying new casing for a project, consider whether R95 (the current standard replacement) meets your needs - it offers higher yield strength, though without hardness control. If you specifically need C95 with its hardness limits, make sure your purchase order references the correct edition of API 5CT and that your supplier can manufacture to those specs.
API 5CT C95 casing and tubing
Applications of API 5CT C95 Casing Pipe
C95 casing pipe is used across a range of oilfield applications, primarily where you need higher strength than standard grades but don't necessarily need the full sour service qualification of C90 or T95. Typical use cases include:
- Intermediate and production casing strings in medium to deep wells where formation pressures require yield strength above 80 ksi
- Surface casing in deeper well designs that need extra structural integrity
- Wells with mildly corrosive environments where the hardness control of C95 provides a safety margin, but full H₂S sour service qualification isn't required
- Oil and gas transportation from the producing zone to the surface pipeline after drilling is completed
- Wellbore wall support - preventing collapse of the borehole and protecting the tubing pipe
That said, if your well environment contains significant H₂S (hydrogen sulfide), you should not be using C95. In that case, specify C90, T95, or C110 - those are the NACE MR0175/ISO 15156‑2 approved sour service grades.
Manufacturing Process
C95 casing pipe is manufactured using two primary methods:
Seamless Pipe (SML)
The go‑to method for high‑grade casing. Seamless pipe is produced by rotary piercing or continuous mandrel rolling, where a solid steel billet is heated and pierced to form a hollow tube without any weld seam. This eliminates the weld as a potential failure point - which is exactly what you want in high‑pressure downhole environments. Most C95 casing on the market is seamless.
Electric Resistance Welded (ERW)
ERW pipe is formed by rolling steel plate into a cylinder and welding the seam using electrical resistance. While ERW has improved significantly over the years and can meet API 5CT requirements, it's generally used for less critical applications or when cost is a primary driver. For C95 specifically, seamless is the preferred and more common choice.
Heat Treatment
As a Group 2 grade, C95 requires Quenched and Tempered (Q&T) heat treatment. The pipe is heated to austenitizing temperature, rapidly quenched (typically in water or polymer), and then tempered at a lower temperature to achieve the right balance of strength, toughness, and hardness. This process is what gives C95 its controlled mechanical properties - without proper Q&T, the pipe won't meet spec.
Looking for cut‑to‑length C95 casing pipe? We offer custom cutting, threading, and coupling services to match your exact well specifications. Get a Custom Quote →
Testing and Inspection Requirements
Quality assurance is non‑negotiable in the oilfield. C95 casing pipe goes through a rigorous testing protocol before it ships. Here's what you should expect from any reputable manufacturer:
Destructive Testing
- Tensile Test: Verifies yield strength, tensile strength, and elongation meet API requirements.
- Hardness Test: Rockwell C (HRC) and Brinell (HBW) hardness measurements to confirm compliance with the 25.4 HRC / 255 HBW maximum.
- Impact Test (Charpy V‑notch): When specified (e.g., per API 5CT SR16), confirms toughness at low temperatures.
- Flattening Test: Checks ductility and weld integrity (for ERW pipe).
Non‑Destructive Examination (NDE)
- Hydrostatic Testing: Each length is pressure‑tested, typically to 3,000 psi in the plain‑end (unthreaded) condition.
- Electromagnetic Inspection (EMI): Detects surface and sub‑surface defects using electromagnetic flux leakage.
- Ultrasonic Testing (UT): Uses high‑frequency sound waves to detect internal flaws and wall thickness variations.
- Magnetic Particle Inspection (MPI): Finds surface and near‑surface cracks and discontinuities.
- Drift Test: Confirms the internal diameter meets spec by passing a drift mandrel through the full pipe length (or just the ends).
Dimensional and Visual Inspection
- Straightness, OD, wall thickness, weight, and length verification
- Surface finish inspection - no cracks, folds, laps, scabs, or other defects permitted
- Any defects found must be completely removed, with removal depth not exceeding 12.5% of nominal wall thickness
For critical applications, buyers should also consider third‑party inspection by recognized agencies such as SGS, Bureau Veritas (BV), or TÜV. This adds an independent layer of verification on top of the manufacturer's own quality control.
FAQ
Is API 5CT C95 a sour service grade?
No. C95 is not classified as a sour service grade and is not listed in NACE MR0175/ISO 15156‑2 as an approved grade for H₂S‑containing environments. While C95 does have a maximum hardness limit of 25.4 HRC (which provides some resistance to sulfide stress cracking), it does not carry the full sour service qualification that C90, T95, or C110 have. If your well contains H₂S, use one of those grades instead.
Was C95 removed from the API 5CT standard?
Yes. C95 was removed from API Spec 5CT starting with the 9th Edition (2011). It was replaced by R95, which has a higher yield strength range (655–758 MPa) but without mandatory hardness testing. The current 11th Edition (2023) does not include C95. However, many manufacturers still produce C95 pipe to earlier edition specifications, and it remains widely available in the market.
What is the difference between C95 and R95?
The main differences are: (1) R95 has a higher yield strength range (655–758 MPa vs. 621–724 MPa for C95); (2) R95 does not have mandatory hardness requirements, while C95 has a maximum hardness of 25.4 HRC / 255 HBW; (3) R95 is in the current API 5CT standard, while C95 is not. If you need hardness control, C95 is the better choice. If you need higher yield strength without hardness testing, R95 is the way to go.
What is the difference between C95 and C90?
C95 and C90 have identical mechanical properties (yield strength, tensile strength, and hardness limits). The key difference is that C90 is a dedicated sour service grade with stricter chemical composition controls and NACE MR0175/ISO 15156‑2 compliance, available in two types (Type 1 and Type 2 with different chemistries). C95 has less restrictive chemistry and is not sour service qualified.
What is the difference between C95 and T95?
T95 has a higher yield strength range (655–758 MPa vs. 621–724 MPa for C95) and higher minimum tensile strength (724 MPa vs. 689 MPa). T95 is also a NACE‑approved sour service grade, while C95 is not. Both share the same maximum hardness limit of 25.4 HRC / 255 HBW. For deep wells with H₂S, T95 is the correct choice.
What sizes are available for C95 casing pipe?
C95 casing pipe is available in outer diameters from 4‑1/2" (114.3 mm) to 20" (508 mm), with various wall thicknesses depending on the size. Common sizes include 5‑1/2", 7", 9‑5/8", and 13‑3/8". Length ranges follow API standards: R1 (4.88–7.62 m), R2 (7.62–10.36 m), and R3 (10.36–14.63 m).
What thread types are available for C95 casing?
C95 casing is available with STC (Short Round Thread Casing), LTC (Long Round Thread Casing), and BTC (Buttress Thread Casing) connections. For tubing sizes, EUE (External Upset End), NUE (Non‑Upset End), and IJ (Integral Joint) connections are available. Premium connections with metal‑to‑metal seals can also be supplied for critical applications.
What is the color code for C95?
C95 is identified by one brown band on the pipe body and a solid brown coupling with no additional band color.
Can C95 casing pipe be welded?
C95 is primarily manufactured as seamless pipe, but ERW (Electric Resistance Welded) versions are also available. Field welding of casing is generally not recommended for high‑strength grades - threaded connections (STC, LTC, BTC) are the standard joining method. If welding is absolutely necessary, it must be performed by qualified personnel using approved procedures with proper pre‑heat and post‑weld heat treatment.
What heat treatment does C95 receive?
C95 is Quenched and Tempered (Q&T). The pipe is austenitized, rapidly quenched, and then tempered to achieve the specified combination of strength, toughness, and hardness. This is consistent with all Group 2 grades in API 5CT, which require controlled heat treatment to meet their mechanical property requirements.
What documentation should I request with my C95 order?
At minimum, request: (1) Mill Test Certificate per EN 10204 Type 3.1 (or 3.2 for third‑party witnessed); (2) Material Test Report with full chemistry and mechanical test results for each heat; (3) NDE/inspection reports; (4) Dimensional inspection records; (5) Heat number traceability. For sour or critical service applications, also request NACE compliance documentation if applicable.
What is the typical delivery time for C95 casing pipe?
For ex‑stock material, delivery is typically 7–25 days after receiving the deposit. For new production orders, expect 30–60 days depending on quantity, size, and threading requirements. Always confirm lead times with your supplier before placing the order, especially for large quantities or non‑standard sizes.
Get Your C95 Casing Pipe Quote Today
Whether you need a single truckload or a full well program's worth of C95 casing pipe, we've got you covered. Here's what we offer:
- Full size range: 4‑1/2" to 20" OD, seamless and ERW
- All thread types: STC, LTC, BTC, EUE, NUE, IJ, and premium connections
- Custom processing: Cut‑to‑length, threading, coupling, coating, drifting
- Complete documentation: EN 10204 3.1/3.2 MTC, full traceability
- Third‑party inspection: SGS, BV, TÜV welcome
- Global shipping: Bundle packaging with thread protectors
Send us your requirements - OD, wall thickness, thread type, length range, and quantity. Get a detailed quotation within 24 hours.
Disclaimer: This article is for informational purposes only. Always consult the current edition of API Spec 5CT and applicable standards (NACE MR0175/ISO 15156‑2) for your specific application. C95 has been removed from API Spec 5CT since the 9th Edition; verify grade availability and specification compliance with your supplier before ordering.
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