**1. What is the difference between ASTM A775 and ASTM A934?**
ASTM A775 and ASTM A934 are both standards for epoxy-coated reinforcing steel bars (rebar). The primary difference lies in their application method and the point of coating.
* **ASTM A775** covers epoxy-coated rebar that is coated *after* it has been cut and bent to its final shape. This is the traditional method used for most construction projects.
* **ASTM A934** covers epoxy-coated rebar that is coated *before* it is bent. The rebar is then bent at the factory using specialized techniques that do not damage the coating. This standard is typically used for prefabricated rebar assemblies, where precise, factory-controlled bending is required.
**2. What is an ASTM A312 pipe?**
ASTM A312 is a standard specification for *seamless and welded austenitic stainless steel pipes*. These pipes are widely used for their excellent corrosion resistance and high-temperature strength. Common applications include chemical processing, petrochemical plants, food and beverage processing, pharmaceutical systems, and power generation. The most common grades under this standard are TP304/304L and TP316/316L.
**3. What is the difference between ASTM A790 and A789?**
ASTM A790 and A789 are both standards for *seamless and welded ferritic/austenitic duplex stainless steel tubes*. The key difference is their intended use:
* **ASTM A790** covers pipes intended for *pressure and mechanical applications*. It is the standard for *Duplex Stainless Steel Pipe*.
* **ASTM A789** covers tubes intended for *heat exchanger and condenser tubes, and general service*. It is the standard for *Duplex Stainless Steel Tubing*.
The main distinction is that "pipe" is typically designated by Nominal Pipe Size (NPS) and schedule, and is used for transporting fluids. "Tubing" is typically designated by its outside diameter and wall thickness, and is often used in structural applications or heat exchangers.
**4. What is A790 pipe made of?**
ASTM A790 pipe is made from *Duplex (ferritic/austenitic) Stainless Steel*. This is a family of stainless steels with a mixed microstructure of about 50% ferrite and 50% austenite, which provides high strength and excellent resistance to stress corrosion cracking. Common material grades under the A790 standard include:
* **S31803:** The standard duplex grade.
* **S32205:** A more common, modern duplex grade with tighter composition controls, often considered the standard for 2205 Duplex.
* **S32750:** Super Duplex (e.g., 2507), offering higher strength and corrosion resistance.
* **S32760:** Another super duplex grade (e.g., Zeron 100).
**5. What is ASTM A995 GR 4A equivalent to?**
ASTM A995 Grade 4A is a cast duplex stainless steel material used for valves, fittings, and other pressure-containing castings. Its closest and most widely recognized wrought (forged or rolled) equivalent is **UNS S31803 / UNS S32205**, commonly known as **2205 Duplex Stainless Steel**. This means that a casting made of A995 Gr 4A has similar corrosion resistance and mechanical properties to a pipe or fitting made from wrought 2205 duplex stainless steel (such as those per ASTM A790).
