Super 13Cr (S13Cr) is a quenched and tempered martensitic stainless steel oil country tubular goods (OCTG) grade engineered for wells where standard carbon steel corrodes — primarily high-CO₂ producing fields, deep gas condensate wells, and completions where reservoir temperature or chloride content exceeds what standard API 5CT L80 13Cr can handle. Its nominal chemistry of 13% chromium, 5% nickel, and 2% molybdenum (the 13-5-2 designation under API 5CRA / ISO 13680) delivers yield strengths from 95 ksi up to 125 ksi, a service temperature ceiling approaching 180°C, and markedly improved chloride pitting resistance over conventional 13Cr — at roughly half the material cost of duplex or super-duplex alloys.
ZC Steel Pipe manufactures and exports Super 13Cr tubing and casing in seamless form from our Hai'an City mill, compliant with API 5CRA / ISO 13680 Group 1 Category 13-5-2, with full MTC documentation, third-party inspection, and premium connection threading available on order. We supply corrosion-resistant OCTG to oil and gas operators across Africa, the Middle East, and South America.
CONTENTS
What Is Super 13Cr?
Chemical Composition & Metallurgy
Mechanical Properties by Grade Tier
Corrosion Service Envelope
Sizes, Weights & Connections
Standards & Compliance
Super 13Cr vs Standard 13Cr vs Modified 13Cr
Procurement Considerations
FAQ
1. What Is Super 13Cr?
Super 13Cr is a modified martensitic stainless steel developed to close the performance gap between standard API 5CT L80 13Cr and the fully austenitic corrosion-resistant alloys (duplex, super-duplex). The "super" designation is not a single standardised grade name — it refers to a family of 13% chromium alloys with additional nickel and molybdenum, classified under API 5CRA / ISO 13680 as Group 1, Material Category 13-5-2 (13% Cr, ~5% Ni, ~2% Mo).
STANDARD DEFINITION — SUPER 13CR / API 5CRA GROUP 1 CAT. 13-5-2
API 5CRA (Specification for Corrosion Resistant Alloy Seamless Tubes for Use as Casing, Tubing and Coupling Stock) / ISO 13680 governs Super 13Cr OCTG. Group 1 encompasses martensitic and precipitation-hardened stainless steels. Category 13-5-2 specifies the approximate composition range: 12–14% Cr, 4–6% Ni, 1.5–3% Mo, carbon ≤ 0.03%. UNS designation S41426. This is distinct from standard API 5CT L80 13Cr (UNS S42000, 12–14% Cr, negligible Ni/Mo, carbon ≤ 0.22%).
The addition of nickel stabilises the martensite microstructure and suppresses retained austenite that can reduce toughness, while molybdenum significantly improves resistance to localised pitting corrosion — the dominant failure mode for standard 13Cr in high-chloride formation waters. Together, these additions enable Super 13Cr to be used in wells where standard 13Cr fails prematurely, without stepping up to the cost and supply complexity of 22Cr or 25Cr duplex.
2. Chemical Composition & Metallurgy
Element | Standard 13Cr (L80 13Cr) | Modified 13Cr (13CrM) | Super 13Cr (S13Cr / 13-5-2) |
Chromium (Cr) | 12–14% | 12–14% | 12–14% |
Nickel (Ni) | ≤ 0.50% | ~3.5–4.5% | ~4.5–5.5% |
Molybdenum (Mo) | ≤ 0.25% | ~0.8–1.5% | ~1.5–3.0% |
Carbon (C) | ≤ 0.22% | ≤ 0.03% | ≤ 0.03% |
Manganese (Mn) | 0.25–1.0% | ≤ 1.0% | ≤ 1.0% |
UNS Designation | S42000 | — | S41426 |
Governing standard | API 5CT / ISO 11960 | API 5CRA / ISO 13680 | API 5CRA / ISO 13680 |
The low carbon content (≤ 0.03%) in Super 13Cr is the critical metallurgical distinction from standard L80 13Cr. High carbon in standard 13Cr promotes chromium carbide precipitation at grain boundaries during heat treatment, depleting chromium from the surrounding matrix and creating sensitized zones that are preferentially attacked in CO₂ and chloride environments. Super 13Cr's ultra-low carbon avoids this sensitisation mechanism while the added Ni and Mo provide the corrosion protection independently.
Engineering Insight — Why Mo Controls Pitting Resistance
Pitting corrosion resistance in stainless steels is quantified by the PREN (Pitting Resistance Equivalent Number): PREN = %Cr + 3.3×%Mo + 16×%N. For standard L80 13Cr: PREN ≈ 13. For Super 13Cr with 2% Mo: PREN ≈ 13 + 6.6 = ~19.6. The molybdenum addition roughly doubles the pitting resistance index. This is why Super 13Cr holds its passive film in formation waters with 50,000+ mg/L chloride where standard 13Cr experiences rapid breakdown pitting.
3. Mechanical Properties by Grade Tier
Super 13Cr is commercially available at two principal yield strength tiers under API 5CRA / ISO 13680, typically designated 95 ksi and 110 ksi (occasionally 125 ksi for specialist deep-well applications). The 95 ksi tier is sour-service acceptable under NACE MR0175; the 110 ksi tier is used in sweet HPHT wells where CO₂ corrosion governs but H₂S is absent or negligible.
S13Cr — 95 ksi Tier
Min yield strength: 95 ksi (655 MPa)
Max yield strength: 110 ksi (758 MPa)
Min tensile strength: 110 ksi (758 MPa)
Hardness max: 30 HRC
Sour service (NACE): Acceptable (H₂S ≤ 1.5 psia)
Temperature ceiling: ~150°C (sweet); limited sour
Standard: API 5CRA / ISO 13680 Gr. 1
S13Cr — 110 ksi Tier
Min yield strength: 110 ksi (758 MPa)
Max yield strength: 125 ksi (862 MPa)
Min tensile strength: 125 ksi (862 MPa)
Hardness max: 32 HRC
Sour service (NACE): Sweet service only recommended
Temperature ceiling: ~180°C (sweet, CO₂ service)
Standard: API 5CRA / ISO 13680 Gr. 1
L80 13Cr (comparison baseline)
Min yield strength: 80 ksi (552 MPa)
Max yield strength: 95 ksi (655 MPa)
Min tensile strength: 95 ksi (655 MPa)
Hardness max: 23 HRC
Sour service (NACE): Acceptable (H₂S ≤ 1.5 psia)
Temperature ceiling: ~150°C (sweet)
Standard: API 5CT / ISO 11960
Procurement Note — 95 ksi vs 110 ksi Tier Selection
The 95 ksi tier is the default for any well where even trace H₂S is present in the reservoir. The 110 ksi tier is strictly for sweet (CO₂-only) wells where depth or temperature drives the need for higher mechanical ratings. Specifying 110 ksi in a well with H₂S — even at sub-NACE threshold partial pressures — creates an unmanaged sulfide stress cracking risk, as the higher strength condition sits above the NACE MR0175 hardness ceiling for Table A.19 sour-service acceptance.
4. Corrosion Service Envelope
Understanding where Super 13Cr works — and where it does not — is the central procurement decision. The material is designed for a specific window in the corrosion environment space, and operating outside that window leads to predictable failures.
Environment Parameter | L80 13Cr Limit | Super 13Cr (95 ksi) Limit | When to Upgrade to Duplex |
CO₂ partial pressure | Up to ~3.0 MPa (sweet) | Up to ~3.0 MPa (sweet) | When combined with high T or Cl⁻ |
H₂S partial pressure | ≤ 1.5 psia (NACE limit) | ≤ 1.5 psia (NACE limit) | > 1.5 psia H₂S |
Temperature (sweet) | Up to ~150°C | Up to ~180°C | > 180°C sweet or > 150°C with H₂S |
Chloride concentration | Low (< 20,000 mg/L typical) | Moderate (up to ~50,000 mg/L) | > 50,000 mg/L Cl⁻ or with H₂S |
pH range | pH ≥ 3.5 | pH ≥ 3.5 | Below pH 3.5 in any service |
HCl acid stimulation | Not compatible | Not compatible (inhibited only) | Not relevant to grade selection |
Elemental sulfur | Not compatible | Not compatible | Duplex or higher required |
Critical Engineering Point — The Chloride Threshold Is Not a Hard Boundary
The chloride limits above are indicative. In practice, pitting risk in Super 13Cr is a function of the combined interaction of Cl⁻ concentration, CO₂ partial pressure, temperature, and flow velocity. High-velocity flow helps maintain the passive film; stagnant conditions and crevice geometries (under deposits, under thread compound, inside couplings) dramatically reduce the tolerable chloride level. A well that appears within spec at static conditions can pit rapidly if flow is interrupted. For borderline cases, corrosion coupon testing under representative downhole conditions is the only reliable approach.
Super 13Cr's improved performance versus standard 13Cr in chloride-containing environments is directly attributable to the molybdenum addition, which raises the critical pitting temperature and slows the kinetics of passive film breakdown. Laboratory testing by major OCTG mills shows corrosion resistance maintenance at temperatures up to 180°C in 5% NaCl + 3.0 MPa CO₂ environments — conditions where standard L80 13Cr typically exceeds 0.1 mm/year corrosion rate at temperatures above 130–150°C.
5. Sizes, Weights & Connections
Standard Tubing Sizes
Super 13Cr is predominantly used in production tubing applications, where the corrosion environment is most severe (direct contact with produced fluids). Standard tubing sizes per API 5CRA / ISO 13680:
OD (inches) | Nominal Weight (lb/ft) | Wall Thickness (mm) | Typical Application |
2⅜" | 4.70 / 5.80 | 4.78 / 5.51 | Gas condensate, slim completion |
2⅞" | 6.50 / 8.70 | 5.51 / 7.01 | Production tubing, gas lift |
3½" | 9.30 / 12.70 | 6.35 / 8.38 | Main production tubing — most common |
4" | 9.50 / 11.00 | 5.74 / 6.65 | Higher-rate production |
4½" | 12.75 / 15.10 | 6.35 / 7.52 | Production tubing, horizontal wells |
5½" | 17.00 / 23.00 | 7.22 / 9.17 | Liner tubing, casing-as-tubing |
Casing Sizes
Super 13Cr casing is less common than tubing but is specified for liner strings and production casing sections in heavily corrosive wells. Availability above 9⅝" is limited due to manufacturing constraints on high-alloy seamless pipe at large diameters.
OD (inches) | Nominal Weight Range (lb/ft) | Common Connection |
4½" | 9.50 – 15.10 | Premium (gas-tight recommended) |
5½" | 15.50 – 26.80 | Premium |
7" | 20.00 – 38.00 | Premium or BTC (limited sour service) |
9⅝" | 36.00 – 58.40 | Premium (HPHT and CO₂ service) |
Connection Requirements
Super 13Cr has a significantly higher galling propensity than carbon steel OCTG, making connection selection and make-up procedure critical. The chromium oxide passive film that provides corrosion resistance is also harder and more brittle than the metallic surface of carbon steel — creating a situation where thread-to-thread contact during make-up can initiate galling almost instantly if the connection design, torque control, or thread compound is incorrect.
Field Note — Connection and Thread Compound Selection for Super 13Cr
Three rules for galling prevention with Super 13Cr: (1) Always use premium connections with a metal-to-metal seal and a defined shoulder — the controlled make-up geometry prevents thread contact before the seal engages. (2) Never use zinc-based API thread compound on 13Cr or Super 13Cr — zinc compounds can cause zinc embrittlement. Use PTFE-based, nickel-based, or copper-based specialty compounds. (3) Make-up speed must be controlled — the standard BTC rule of ≤ 15 RPM applies even more strictly to 13Cr series alloys. High RPM generates heat that breaks the protective film and triggers immediate galling.
6. Standards & Compliance
Super 13Cr sits outside the scope of API 5CT, which governs only standard carbon and low-alloy OCTG including L80 13Cr. The correct governing documents are:
Standard | Scope | Relevance to Super 13Cr |
API 5CRA / ISO 13680 | Corrosion Resistant Alloy seamless tubes for OCTG | Primary governing spec — Group 1, Cat. 13-5-2 |
NACE MR0175 / ISO 15156 | Materials for H₂S service | Table A.19: H₂S ≤ 1.5 psia, pH ≥ 3.5 (95 ksi only) |
API 5CT / ISO 11960 | Standard OCTG grades including L80 13Cr | Not applicable to Super 13Cr — governs standard 13Cr only |
API 5C5 | Connection performance testing (casing & tubing) | Premium connections for Super 13Cr should be qualified to API 5C5 CAL IV |
ASTM A276 / A484 | Stainless steel bar & general requirements | Reference for coupling/accessory material |
Engineering Insight — API 5CT vs API 5CRA: Why the Distinction Matters for Procurement
Many purchase orders for "13Cr tubing" are incorrectly written to API 5CT when Super 13Cr is actually intended — or worse, an API 5CT L80 13Cr product is substituted when a Super 13Cr (5CRA) grade was engineered into the well design. The two materials share a chromium percentage but are fundamentally different in terms of yield strength tier, corrosion performance, and sour service applicability. Always explicitly state the governing standard (API 5CRA / ISO 13680), the Group and Category (Group 1, 13-5-2), and the yield tier (95 ksi or 110 ksi) on the purchase order — never rely on the shorthand "Super 13Cr" alone.
7. Super 13Cr vs Standard 13Cr vs Modified 13Cr
The 13Cr family encompasses three distinct tiers that are frequently confused in procurement and engineering documentation. The table below summarises the practical decision boundaries.
Property | Standard 13Cr (L80 13Cr) | Modified 13Cr (13CrM, 13-4-1) | Super 13Cr (S13Cr, 13-5-2) |
Governing standard | API 5CT | API 5CRA | API 5CRA |
Yield strength | 80–95 ksi | 95–110 ksi | 95–125 ksi |
Temperature ceiling (sweet) | ~150°C | ~165°C | ~180°C |
Chloride tolerance | Low | Moderate | Moderate–High |
H₂S (NACE MR0175) | ≤ 1.5 psia (95 ksi only) | ≤ 1.5 psia (limited) | ≤ 1.5 psia (95 ksi only) |
Supply availability | Wide — commodity grade | Moderate | Good for standard sizes |
Relative cost vs L80 13Cr | Baseline | +15–25% | +25–40% |
CO₂ performance vs L80 13Cr | Baseline | Better above 150°C | Significantly better above 150°C |
Pitting resistance (PREN) | ~13 | ~16–17 | ~19–20 |
The Modified 13Cr tier (sometimes written 13CrM, 13-4-1, or by trade names such as Vallourec's 13CrM) occupies a midpoint — better than standard 13Cr but with slightly less Ni and Mo than full Super 13Cr. It is often the optimal choice when well temperature exceeds 150°C but the higher cost of Super 13Cr is difficult to justify without corrosion coupon data confirming the need. For comparison against the next tier up, see Super 13Cr vs Duplex 2205 →
8. Procurement Considerations
Lead Time and Mill Sourcing
Super 13Cr is manufactured by a smaller number of mills than standard OCTG grades, and most major producers (Vallourec, Nippon Steel, TMK, Tenaris) supply it under proprietary trade designations (Vallourec 13CrM/13CrS, Nippon Steel SM13CRS, Tenaris TenarisHydra). Chinese mills including ZC Steel Pipe produce Super 13Cr to API 5CRA specifications for projects requiring competitive pricing with full documentation. Lead times are typically 8–14 weeks versus 4–8 weeks for standard carbon OCTG — plan accordingly in well schedules.
Documentation Requirements
A complete Super 13Cr order package should include: governing standard and edition (API 5CRA / ISO 13680), grade designation (Group 1, Category 13-5-2), yield tier (95 or 110 ksi), dimensional specification (OD, nominal weight), connection type (premium — state qualified connection name and API 5C5 qualification level), end finish, PSL level, MTC requirements (heat chemical analysis, tensile, hardness, impact, hydrostatic test), and third-party inspection scope.
Procurement Note — Verify Heat Treatment Records
Super 13Cr's corrosion and mechanical performance are entirely dependent on correct quench-and-temper heat treatment. The typical cycle is solution annealing at 950–1050°C followed by quenching and tempering at 600–700°C. A pipe that has been under-tempered will show acceptable hardness on the MTC but will have reduced toughness and higher susceptibility to sulfide stress cracking. Always request the actual heat treatment records (furnace temperature logs, time-at-temperature, quench media) as a separate MTC deliverable — not just the hardness test result.
Handling and Storage
Super 13Cr tubing requires more careful handling than carbon steel OCTG. Thread protectors must be kept clean and in place. The chromium oxide passive film re-forms after mechanical damage, but storage in environments with standing water, soil contact, or dissimilar-metal contact (e.g., carbon steel racks without protective coating) can initiate crevice corrosion under protectors during long storage periods. For long laydown periods (> 3 months), inspect and re-dress thread protectors with fresh compound on receipt.
For complete handling and failure prevention guidance, see Field Operations: Preventing Galling and Oxygen Pitting in 13Cr Tubing →
9. Frequently Asked Questions
What is Super 13Cr OCTG?
Super 13Cr (S13Cr) is a quenched and tempered martensitic stainless steel OCTG grade with a nominal composition of 13% chromium, 5% nickel, and 2% molybdenum. Governed by API 5CRA / ISO 13680 as Group 1, Category 13-5-2, it offers yield strengths from 95 to 125 ksi, CO₂ corrosion resistance up to approximately 180°C, and improved chloride pitting resistance compared to standard API 5CT L80 13Cr — at lower cost than duplex or super-duplex alloys.
What is the difference between 13Cr and Super 13Cr?
Standard 13Cr (L80 13Cr under API 5CT) has a simple 13% Cr chemistry, yield 80–95 ksi, and a service temperature ceiling around 150°C. Super 13Cr adds ~5% Ni and ~2% Mo (the 13-5-2 composition), raising yield to 95–125 ksi, improving CO₂ corrosion resistance to ~180°C, and significantly increasing resistance to chloride pitting. The governing standard also differs — API 5CRA / ISO 13680 applies to Super 13Cr rather than API 5CT.
What H₂S limit applies to Super 13Cr?
NACE MR0175 / ISO 15156 Table A.19 specifies H₂S partial pressure ≤ 1.5 psia with pH ≥ 3.5 for Super 13Cr (UNS S41426) in the 95 ksi yield condition. The 110 ksi tier is not considered sour-service acceptable under current NACE guidance. Super 13Cr is not suitable for wells with H₂S above the NACE threshold — 22Cr or 25Cr duplex, or higher CRA grades, are required instead.
What sizes is Super 13Cr tubing available in?
Most commonly 2⅜", 2⅞", 3½", 4", 4½", and 5½" OD, with 3½" and 4½" the dominant production tubing sizes. Super 13Cr casing runs from 4½" to 9⅝" OD, though availability above 7" is more restricted. All standard tubing weights (nominal lb/ft) per API 5CRA are available from ZC Steel Pipe on an order-to-make basis.
Can Super 13Cr be used in acidizing operations?
No — not without full corrosion inhibitor qualification. Both standard 13Cr and Super 13Cr corrode rapidly in hydrochloric acid stimulation environments. Running neat HCl through a Super 13Cr string will cause catastrophic material loss at the pipe bore. If acid stimulation is required, a proprietary corrosion inhibitor must be qualified at the specific acid concentration, temperature, and contact time planned, with inhibitor injection confirmed before acid enters the string.
What connections are used with Super 13Cr tubing?
Premium metal-to-metal seal connections are the industry standard for Super 13Cr in most applications. The galling propensity of martensitic stainless steel on API thread forms makes standard EUE/NUE connections risky for gas wells and HPHT service. Premium connections with a defined make-up shoulder, controlled thread geometry, and compatibility with PTFE-based or nickel-based thread compound are required. ZC Steel Pipe's ZC-2 gas-tight premium connection is qualified for use with Super 13Cr tubing under API 5C5 CAL IV.
Supply Super 13Cr OCTG for Your Next Project
ZC Steel Pipe manufactures Super 13Cr tubing and casing to API 5CRA / ISO 13680 Group 1 Category 13-5-2 at our Hai'an City mill. We supply 95 ksi and 110 ksi yield tiers in all standard sizes from 2⅜" through 9⅝", with premium connections including our patented ZC-2 gas-tight connection. Full MTC documentation, third-party inspection, dimensional inspection reports, and heat treatment records available on every order.
Active supply to oil and gas projects in Africa, the Middle East, and South America. Competitive lead times and pricing against Western mill grades.
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Contact Mandy: mandy.w@zcsteelpipe.com | WhatsApp: +86-139-1579-1813
Related: Casing & Tubing Product Page · Premium Connections · L80 13Cr Metallurgy Deep-Dive → · API 5CT L80 Casing Guide →
