1. **Which steel grade is strongest?**
Ultra-high-strength steels like **maraging steels (e.g., 18Ni (250), 18Ni (300))** are among the strongest commercially available, with tensile strengths exceeding **2000 MPa (290 ksi)**. For structural applications, grades like **S1100QL, S960QL, or ASTM A514** offer very high strength.
2. **How thick is a S235 plate?**
S235 steel plate is available in a **wide range of thicknesses**. Commonly stocked standard thicknesses range from **3 mm up to 200 mm or more**. The specific thickness required depends entirely on the application and design specifications.
3. **Is S235JR mild steel?**
**Yes, S235JR is classified as mild steel.** It is a non-alloy, general-purpose structural steel with relatively low carbon content, good weldability, and formability, typical of mild steels.
4. **Which steel grade is the most expensive?**
**Specialized high-alloy steels** are typically the most expensive. This includes grades like **maraging steels (e.g., 18Ni maraging)**, **high-performance tool steels (e.g., powdered metallurgy HSS or tool steels)**, **super duplex stainless steels (e.g., S32750)**, and **high-temperature nickel alloys (e.g., Inconel 718)**. Cost depends heavily on alloying elements and manufacturing complexity.
5. **How do I choose the right steel grade?**
Choosing the right steel grade involves considering these key factors:
* **Mechanical Requirements:** Needed strength (yield, tensile), toughness (impact resistance), hardness, ductility, and fatigue resistance.
* **Service Environment:** Exposure to corrosion (atmosphere, chemicals, seawater), extreme temperatures (high or low), abrasion, or wear.
* **Fabrication Needs:** Required weldability, machinability, or formability.
* **Regulations & Standards:** Compliance with specific industry standards (e.g., EN, ASTM, ASME, API) or codes (e.g., for pressure vessels, construction).
* **Cost & Availability:** Balancing performance needs with budget constraints and material sourcing feasibility.
* **Weight:** Importance of minimizing weight may favor higher-strength grades.
