### **1. What is A671 pipe made of?**
**ASTM A671 pipe** is fabricated from **pressure vessel-quality steel plates** using **electric-fusion welding with filler metal**. Key characteristics include:
- **Material Grades**: Designated by codes like "CC60", where "CC" indicates the strength class (based on ASTM A516 Gr.60 steel plate), and "60" denotes minimum yield strength (60 ksi or ~415 MPa).
- **Chemistry**: Low-carbon steel with controlled alloys (e.g., C ≤0.23%, Mn 0.79–1.3%, Si 0.13–0.45%, and limits on P, S ≤0.035%) to enhance weldability and toughness.
- **Manufacturing**: Pipes are **double-sided, full-penetration welded** and may undergo **stress-relieving (CL22)** or **normalizing (CL32)** heat treatments to optimize mechanical properties.
- **Applications**: Designed for **low-temperature/high-pressure services** (e.g., -46°C to ambient), commonly in diameters ≥405 mm and thicknesses ≥6.4 mm.
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### **2. What is the difference between ASTM and ASME pipe?**
**ASTM** and **ASME** standards differ in scope and application:
- **ASTM (American Society for Testing and Materials)**: Defines **material properties** (chemistry, tensile strength) and test methods. Pipes under ASTM standards (e.g., ASTM A671) are generic material specifications.
- **ASME (American Society of Mechanical Engineers)**: Focuses on **fitness for service**, especially pressure equipment. ASME standards (e.g., ASME BPV Code Section II) adopt ASTM materials but add **rigorous fabrication rules**, weld procedure qualifications, and additional testing (e.g., enhanced NDE) for safety-critical applications.
- **Key Distinction**: ASTM sets material "ingredients," while ASME certifies how materials are **processed, fabricated, and inspected** for pressurized systems. ASME-stamped pipes (e.g., SA671) are mandatory for boilers/pressure vessels.
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### **3. What is the difference between WCC and LCC carbon steel?**
**WCC** and **LCC** are both carbon steel castings but differ in temperature suitability:
- **WCC (Standard Grade)**: Used for **ambient to high temperatures** (-29°C to 425°C). Prioritizes tensile strength (≥485 MPa) but **lacks mandatory low-temperature impact testing**.
- **LCC (Low-Temperature Grade)**: Qualified for **cryogenic service down to -46°C**. Requires **Charpy V-notch impact testing** at -46°C (minimum 20 J average energy) to ensure fracture resistance. Achieved via refined microstructure from normalizing and controlled Mn/Ni content.
- **Applications**: WCC suits valves/pumps for water/steam; LCC is essential for LNG, cryogenic storage, or cold process piping.
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### **4. What is the difference between EFW and HFW pipe?**
Both are electric-welded processes but leverage distinct principles:
- **EFW (Electric Fusion Welding)**: A broad category where **filler metal is added** to join plates/coils. Heat comes from electric arcs (e.g., submerged arc welding). Produces thicker welds suited for large-diameter pipes.
- **HFW (High-Frequency Welding)**: A subtype of ERW (Electric Resistance Welding). Uses **high-frequency current** exploiting:
- **Skin Effect**: Current concentrates on the steel surface.
- **Proximity Effect**: Current flows precisely along the edge joint.
This allows **filler-free**, rapid fusion of edges via localized resistance heating. Common for smaller diameters (e.g., oil/gas line pipe).
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### **5. What is A671 CC60 22 material?**
This designates a **specific grade/class under ASTM A671**:
- **CC60**: Indicates the base steel plate is **ASTM A516 Gr.60** (yield strength ≥220 MPa, tensile 415–555 MPa).
- **CL22**: Specifies **stress-relieved heat treatment** (post-weld heating to ~600°C to reduce residual stresses without altering microstructure).
- **Applications**: Used in **low-temperature, high-pressure systems** (e.g., petrochemical chillers). Welding requires **low-hydrogen practices** (e.g., TIG-80Ni1/W506Ni electrodes) to prevent cracking and maintain -46°C toughness.
For deeper exploration, consult ASTM A671/A671M-16 or ASME Section VIII for fabrication rules.
