**1. What is the difference between ERW and mild steel?**
- **ERW (Electric Resistance Welded)** refers to a manufacturing process where steel is formed into a pipe and the edges are welded using electrical resistance.
- **Mild steel** is a type of carbon steel with low carbon content (typically ≤0.25%), known for its ductility and weldability.
- **Key difference**: ERW is a method to produce pipes, while mild steel is a material. ERW pipes can be made from mild steel or other steel grades.
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**2. What are the 3 grades of steel pipe?**
Common grades of steel pipes include:
1. **ASTM A53** (general-purpose carbon steel pipe for structural/mechanical use).
2. **ASTM A106** (high-temperature service, seamless carbon steel pipes).
3. **ASTM A500** (cold-formed welded or seamless carbon steel tubing for structural applications).
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**3. What is the difference between seamless steel and carbon steel?**
- **Seamless steel** refers to pipes/tubes manufactured without welding, using processes like extrusion or rotary piercing.
- **Carbon steel** is a material category defined by its carbon content (typically 0.12–2.0% carbon).
- **Key difference**: "Seamless" describes the manufacturing method, while "carbon steel" defines the material composition. Seamless pipes can be made from carbon steel or other alloys.
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**4. What is the difference between ERW and DOM steel?**
- **ERW (Electric Resistance Welded)** pipes are formed by rolling steel coils and welding the seam electrically.
- **DOM (Drawn Over Mandrel)** pipes start as ERW or welded tubes, which are then cold-drawn over a mandrel to refine dimensions, improve surface finish, and enhance mechanical properties.
- **Key difference**: ERW is a welding process, while DOM involves post-weld cold-working to refine the pipe. DOM pipes have tighter tolerances and higher strength than standard ERW pipes.
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**5. Is DOM steel seamless?**
- **No**, DOM steel pipes are not seamless. They begin as welded tubes (often ERW), which are then processed through cold drawing and sizing. The original weld seam is retained but smoothed and strengthened during the DOM process.
