**1. Is HSS hot rolled or cold rolled?**
Hollow Structural Sections (HSS) are primarily **cold rolled**. They are manufactured by taking a hot-rolled steel coil and cold-forming it into a circular, square, or rectangular shape. The final forming and welding of the seam is done at room temperature, which gives the steel a smooth, finished surface and increased strength. However, the starting material is hot-rolled steel, so it's a hybrid process that relies on cold-forming.
**2. What are the three types of hot rolled steel?**
There are many ways to categorize hot-rolled steel, but three common types based on their primary form and application are:
* **Hot-Rolled Structural Steel:** Used in construction for frames, beams (like I-beams), and channels. A36 steel is a classic example.
* **Hot-Rolled Steel Bars:** These come in various shapes (round, square, flat) and are used for fabrication, machining, and as raw material for further processing.
* **Hot-Rolled Steel Sheet/Plate:** Wide, flat products used in manufacturing for automotive frames, railroad cars, agricultural equipment, and as the starting material for cold-rolled sheets.
**3. Is HSS Grade B or C?**
This is a common point of confusion. "Grade B" and "Grade C" typically refer to grades of **High-Strength Low-Alloy (HSLA) steel** under the ASTM A572 standard. **HSS (Hollow Structural Sections)** are governed by a different standard, **ASTM A500**. The most common grades for HSS are **A500 Grade B** and **A500 Grade C**. So, an HSS member can be *A500 Grade B* or *A500 Grade C*, but it is not the same as the "Grade B/C" from the A572 standard for plates and bars.
**4. Is 1018 steel hot rolled or cold rolled?**
**1018 steel is available in both hot-rolled and cold-rolled forms.** The number "1018" refers to the chemical composition (a carbon steel with approximately 0.18% carbon). The term "hot-rolled" or "cold-rolled" describes the manufacturing process.
* **Hot-Rolled 1018** has a rough, scaly surface and is used where precise shapes and tolerances are not critical.
* **Cold-Rolled 1018 (CRS)** has a smooth, finished surface, tighter dimensional tolerances, and higher strength. It is often used for machining and precision parts.
**5. Is 1018 the same as A36?**
No, **1018 and A36 are not the same.** They are two different grades of steel with key differences:
* **Classification:** A36 is a **mild structural steel** classified by its mechanical properties (primarily its minimum yield strength of 36 ksi). 1018 is a **carbon steel** classified by its specific chemical composition.
* **Strength:** A36 has a minimum yield strength of 36,000 psi. 1018 typically has a higher yield strength, around 53,700 psi for cold-rolled and 45,000 psi for hot-rolled.
* **Chemistry:** The chemical composition of A36 can vary as long as the mechanical properties are met. 1018 has a strict and consistent chemical composition, making it more predictable for heat treatment and machining.
* **Use:** A36 is best for structural applications like buildings and bridges. 1018 is better for parts that require machining, carburizing, or need a good balance of strength and ductility.
