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Q Can alloy steel pipe be used in sour service?
A Yes, certain alloy steel grades are suitable for sour service (environments containing hydrogen sulfide, H₂S). Requirements include:
NACE MR0175 / ISO 15156 – Material requirements for H₂S environments in oil and gas production
Controlled hardness levels (typically ≤ 22 HRC for many grades)
Strict chemical composition control (low sulfur, controlled carbon)
Proper heat treatment (usually quenched and tempered)
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Q What is chrome-moly (Cr-Mo) steel pipe?
A Chrome-moly steel pipe (often abbreviated as Cr-Mo or chromoly) refers to alloy steel containing chromium and molybdenum as the primary alloying elements. The most common grades are covered under ASTM A335 (pipe) and ASTM A213 (tube).
Key characteristics: Chromium provides oxidation and corrosion resistance; Molybdenum adds strength at elevated temperatures and resists creep.
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Q What are the common applications of carbon steel pipe?
A Oil & Gas Industry: Crude oil and natural gas transmission pipelines, drilling platforms
Construction & Infrastructure: Structural frames, scaffolding, support columns
Power Generation: Boiler tubes, steam lines, heat exchangers
Automotive: Exhaust systems, structural components
Chemical Processing: Process piping, reactors, storage tanks
Water & Wastewater: Municipal water supply, sewage systems (requires coating)
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Q What are the main advantages of carbon steel pipe?
A High Strength: Excellent tensile and yield strength, suitable for high-pressure and heavy-load applications.
Cost-Effective: Abundant raw materials and lower production costs compared to stainless steel or alloy pipes.
Good Thermal Conductivity: Ideal for heat transfer applications such as heat exchangers and steam systems.
Weldability: Low-carbon grades are easy to weld, simplifying installation and repair.
Recyclability: 100% recyclable, supporting sustainability goals.
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Q What is the delivery condition of carbon steel pipes?
A Common delivery conditions include:
As rolled
Normalized
Quenched and tempered
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Q What surface treatments are available to carbon steel pipes?
A Common surface treatments include:
Black varnish coating, typically used for indoor storage and transport
Anti-corrosion coatings (FBE, 3LPE, 3LPP), typically used in underground pipelines and buried oil and gas pipelines
Galvanizing, typically used in outdoor, humid, or water service
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Q How is carbon steel pipe classified?
A There are two ways to classify carbon steel pipes:
By Carbon Content, Low Carbon (Mild), C< 0.25%, with High ductility, easy to weld and form characteristics, commonly used as structural tubing and general piping; Medium Carbon, C 0.25% – 0.60%, with Balanced strength and toughness characteristics, commonly used to Mechanical parts and heavy structures.
By Manufacturing Process, seamless pipe, with High strength, excellent pressure resistance characteristics, commonly applied in high-pressure, high-temperature systems; welded Pipe, with cost-effective, available in large diameters characteristics, commonly applied in Low-pressure fluid transport, structural use.
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Q What are the common standards for carbon steel pipes?
A Common international standards include:
ASTM A106 - Seamless carbon steel pipe for high-temperature service
ASTM A53 - Welded and seamless pipe for general use
API 5L - Line pipe for oil and gas transportation
ASTM A500 - Carbon steel structural tubing
EN 10219 / EN 10210 - European standards for structural hollow sections
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Q What's difference of the coating on casing tube and line pipe?
A The coating on casing tube is a thin “mill varnish” or “shop primer”, mainly used for a short-term rust prevention during storage and transport and identify the steel grade. The coatings on line pipe like FBE, 3LPP, 3LPE are mechanical protection, long-term corrosion resistance, a critical engineered component of the pipeline system.
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Q What's the different of joint, coupling of OCTG?
A Joint and Coupling refer to specific parts of the pipe assembly. A joint is a single, full-length piece of pipe, typically around 30 ft (Range 2 is most common), can be casing or tubing and usually threaded on both ends. Coupling is the short, thick-walled sleeve used to connect two pipe joints together, a separate piece of steel with threads on the inside of both ends.
