1. **Is duplex better than stainless steel?**
* **It depends on the application.** Duplex stainless steel (a *type* of stainless steel) offers higher strength and better resistance to stress corrosion cracking than standard austenitic stainless steels (like 304/316). However, standard stainless steels often have better formability and weldability. Duplex isn't universally "better" – the best choice depends on the specific requirements (strength, corrosion resistance, cost, fabricability).
2. **What is the code for duplex steel?**
* The most common standard grades and their codes are:
* **UNS S32205 / S31803:** The most widely used grade (2205 Duplex).
* **EN 1.4462:** The common European standard designation.
* **ASTM A182 F51 / F60:** For forged or rolled fittings.
* **ASTM A240/A240M:** For plate, sheet, and strip.
* **Other grades:** UNS S32750 (2507 Super Duplex), UNS S32760 (Zeron 100), UNS S32304 (2304 Lean Duplex).
3. **Which type of steel is stronger?**
* **Maraging steels** (e.g., 18Ni (250), 18Ni (300)) are among the strongest commercially available steels, achieving ultimate tensile strengths exceeding **2000 MPa (290 ksi)** after heat treatment. They are significantly stronger than common structural steels, tool steels, or stainless steels like duplex.
4. **What is the meaning of MPa in steel?**
* **MPa stands for Megapascal.** It's the unit used to measure **stress** or **strength** in steel (and most engineering materials).
* **1 Pascal (Pa) = 1 Newton of force per square meter (N/m²).**
* **1 Megapascal (MPa) = 1,000,000 Pascals = 1,000,000 N/m² = 1 N/mm².**
* It tells you how much force (in Newtons) a square millimeter of the steel can theoretically withstand before failing (Ultimate Tensile Strength - UTS) or before it starts to deform permanently (Yield Strength - YS).
5. **How to calculate the strength of steel?**
* You **cannot accurately calculate the intrinsic strength (like Yield or Tensile Strength) of a specific steel piece purely from theory or composition.** Strength is determined empirically through standardized **mechanical testing**.
* **The primary method is the Tensile Test (ASTM E8/E8M):**
1. A precisely machined sample (tensile coupon) is pulled apart in a controlled machine.
2. The machine measures the applied force and the elongation of the sample.
3. **Yield Strength (YS):** Calculated as the force at the point where the material *starts* to deform plastically (permanently) *divided by* the original cross-sectional area of the sample. `YS = Force_yield / Area_original`
4. **Ultimate Tensile Strength (UTS):** Calculated as the maximum force the sample withstands *divided by* the original cross-sectional area. `UTS = Force_max / Area_original`
