ALLLAND Steel Pipe Supply
Welcome to ALLLAND Steel Pipe Manufacturing. API 5CT C90 is a high-strength oil well pipe steel grade specifically designed for high-pressure, deep wells, and H₂S-corrosive environments, and is suitable for both production tubing and casing. ALLLAND’s 5CT C90 oil well tubing is widely used in oil and gas extraction, sour gas wells, offshore oilfields, and HPHT wells. It meets the standard requirement of a minimum yield strength of 90 ksi and undergoes a rigorous heat treatment process to ensure a balance between strength, hardness, toughness, and corrosion resistance.
Alllandsteel is a steel pipe manufacturer based in China with 25 years of experience.
The facility spans 22,000 square meters, represents a RMB 700 million investment, and operates four production lines (JCOE, ERW, SMLS, SSAW) alongside five coating lines.
With an annual production capacity of 250,000 tons, the factory covers specifications ranging from Ø406 to Ø1524 and holds multiple international certifications (API/ASTM/EN/ISO/JIS). Focused on steel pipes, creating value for you!
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API 5CT C90 is a high-strength OCTG (Oil Country Tubular Goods) steel grade used in oil and gas wells, primarily for casing and tubing. It is the Sour Service (hydrogen sulfide corrosion-resistant) steel grade specified in the API 5CT standard, designed specifically for deep wells, high-pressure wells, H₂S-containing acidic environments, and highly corrosive conditions.
W.T.:
Casing
5.21 mm – 16.13 mm (common)
Tubing
2.87 mm – 12.65 mm (common)
Length:
R1 (4.88 – 7.62 m)
R2 (7.62 – 10.36 m)
R3 (10.36 – 14.63 m)
Thread Types:
STC（Short Thread Casing）
LTC（Long Thread Casing）
BTC（Buttress Thread）
Premium Connection
Heat Treatment:
Quenched and Tempered（Q&T）
Standard:
API 5CT
Surface Treatment:
Black Painting/ Clear Varnish/ Anti-Rust Oil/ 3PE / FBE
Color Code:
Purple Band
OD Tolerance
Tubing Outer Diameter Tolerance: Typically: ±0.79 mm (±1/32″)
Casing Outer Diameter Tolerance:
OD ＜ 114.3 mm, ±0.79 mm
OD ≥ 114.3 mm, ±1% OD
Wall Thickness Tolerance: WT Tolerance = -12.5%
The API 5CT standard specifies a minimum wall thickness: not less than 87.5% of the nominal wall thickness.
Weight Tolerance: Permitted deviation in weight per piece: -3.5% to +6.5%
The average weight of the entire batch must not be lower than the theoretical weight.
Length Tolerance: R1 / R2 / R3
R1: 4.88 – 7.62 m
R2 (most common): 7.62 – 10.36 m
R3: 10.36 – 14.63 m
Thread Tolerance
API thread specifications require that STC, LTC, and BTC meet precision requirements for pitch, taper, thread height, and roundness. In deep well conditions, even the slightest deviation can lead to leaks or thread breakage.
| Property | Value |
|---|---|
| Yield Strength | 621–724 MPa |
| Tensile Strength | ≥ 689 MPa |
| Hardness | ≤ 25.4 HRC |
| Elongation | ≥ 15% (Reference) |
In the API 5CT standard, the strength grades are L80 → C90 → T95 → P110.
C90 offers higher strength than L80 while still providing a certain level of sulfur resistance, making it suitable for deeper well depths, higher well pressures, and greater axial loads.
API 5CT C90 also employs Quenched and Tempered (Q&T) treatment, a precise heat treatment process designed to achieve a balance between strength, toughness, and hardness.
| Element | Content |
|---|---|
| C | 0.30–0.37% |
| Mn | 1.00–1.35% |
| Cr | 0.80–1.10% |
| Mo | 0.20–0.30% |
| Ni | 0.25–0.65% |
| P | ≤ 0.020% |
| S | ≤ 0.01 |
Sour Service steels generally require extremely low sulfur (S) and phosphorus (P) content.
C90 offers higher strength than L80 and better resistance to SSC than P110, making it particularly suitable for deep-well acidic environments. Sulfide stress cracking is a sudden failure mode that poses a significant risk in oil wells. Although P110 has higher strength, it is more susceptible to hydrogen embrittlement.
Deep Wells: Higher strength, capable of withstanding greater suspension loads
High-Pressure Wells: Suitable for high formation pressure, high blowout pressure, and high collapse pressure.
Sour Gas Wells: H₂S corrosive environments and acidic natural gas wells.
Offshore Oilfields: Offshore platforms face complex operating conditions and severe corrosion; high-grade steel pipes such as C90 are generally the preferred choice.
| Item | L80 | C90 |
|---|---|---|
| Strength | 80 ksi | 90 ksi |
| Cost | Lower | Medium to High |
| Sour Service Resistance | Excellent | Excellent |
| Deep Well Capability | Standard | Stronger |
| Item | C90 | T95 |
|---|---|---|
| Yield Strength | 90 ksi | 95 ksi |
| SSC Risk | Lower | Higher |
| Cost | Lower | Higher |
| Applications | Deep Sour Wells | More Severe Sour Service Wells |
| Item | C90 | P110 |
|---|---|---|
| Sour Service Resistance | Strong | Weaker |
| Strength | Medium to High | Very High |
| H₂S Service Suitability | Suitable | Generally Not Recommended |
| Deep Well Capability | Strong | Extremely Strong |
Yes, C90 is specifically designed for H₂S sour service wells and must comply with the requirements of NACE MR0175 / ISO 15156.
Yes, seamless pipe is typically the preferred choice for deep wells, high-pressure wells, or sour service wells.
Common tests include:
