Hot rolled steel is one of the most widely used materials in manufacturing, construction, automotive, and heavy machinery. Known for its versatility, cost-effectiveness, and ease of fabrication, hot rolled steel comes in multiple grades, each designed for specific mechanical properties and performance requirements.
Understanding the grades of hot rolled steel helps engineers, fabricators, and procurement specialists select the right material for their projects. Different grades vary in strength, ductility, toughness, weldability, and corrosion resistance. In this article, we will explore the main categories and grades of hot rolled steel, their properties, and common applications.
Hot rolled steel is produced by heating steel slabs above their recrystallization temperature, typically around 900°C to 1100°C, and then rolling them into desired shapes. Because the steel is rolled at high temperatures, it is easier to shape and form, making it ideal for large structural components and applications where exact tolerances are not critical.
After rolling, the steel is cooled in air, which may result in slight variations in dimensions but gives the material its characteristic rough surface texture.
Good Formability – Easy to shape and bend during manufacturing.
High Toughness – Can withstand heavy loads and impacts.
Cost-Effective Production – Less processing compared to cold rolled steel.
Versatility – Suitable for a wide range of industries.
Dimensional Variations – Tolerances are not as tight as cold rolled steel, but acceptable for many applications.
Hot rolled steel grades can generally be grouped into four major categories:
Carbon Steel Grades
Alloy Steel Grades
High-Strength Low-Alloy (HSLA) Steel Grades
Specialty Grades for Specific Applications
Carbon steels are the most common hot rolled steels, defined by their carbon content.
Carbon Content – Up to 0.25%
Examples – ASTM A36, S235JR
Properties – Excellent weldability, good ductility, low cost.
Applications – Structural beams, general fabrication, sheet metal work.
Carbon Content – 0.25% to 0.60%
Examples – C45, SAE 1045
Properties – Higher strength and hardness than mild steel, moderate ductility.
Applications – Shafts, gears, axles, machine parts.
Carbon Content – 0.60% to 1.00%
Examples – SAE 1095
Properties – Very high hardness, lower ductility, wear-resistant.
Applications – Springs, cutting tools, high-strength wires.
Alloy steels contain additional elements such as chromium, molybdenum, nickel, or vanadium to enhance properties.
4140 Steel – Chromium-molybdenum alloy steel with high strength, toughness, and wear resistance. Common in automotive, oil, and gas industries.
4340 Steel – Nickel-chromium-molybdenum alloy steel known for high strength and fatigue resistance.
8620 Steel – Nickel-chromium-molybdenum alloy used for carburized parts requiring a tough core and hard surface.
HSLA steels are designed to provide better mechanical properties and greater resistance to corrosion than carbon steel, without significantly increasing weight.
A572 Steel – High-strength structural steel used in bridges, buildings, and construction equipment.
A588 Steel (Weathering Steel) – Contains copper and other alloying elements for enhanced corrosion resistance; used in outdoor structures without painting.
S355MC – High-strength steel used in automotive frames and chassis.
Certain hot rolled steel grades are tailored for niche requirements:
AR400 / AR500 – Abrasion-resistant steel used in mining equipment and heavy-duty machinery.
Shipbuilding Steels (AH36, DH36) – High-strength steels for marine and offshore applications.
Pressure Vessel Steels (A516 Grade 70) – Designed for boilers and pressure vessels.
Rail Steels – Special grades for high wear resistance and toughness in railway tracks.
Different countries use their own classification systems and standards for hot rolled steel:
ASTM (American Society for Testing and Materials) – Common in the United States, e.g., ASTM A36, ASTM A572.
EN (European Norm) – European standards such as EN 10025-2 (S235, S355).
JIS (Japanese Industrial Standards) – Examples include SS400 and SM490.
GB (Chinese National Standards) – Q235, Q345.
ISO Standards – International harmonized guidelines.
When selecting a hot rolled steel grade, consider:
Mechanical Strength Requirements – Choose a grade with appropriate tensile and yield strength.
Weldability – Low carbon grades offer better weldability.
Corrosion Resistance – Weathering steels or alloy steels for harsh environments.
Formability – Mild steels are easier to bend and shape.
Cost and Availability – Some grades are more readily available in certain markets.
| Feature | Hot Rolled Steel | Cold Rolled Steel |
|---|---|---|
| Processing Temperature | Above recrystallization temperature | Below recrystallization temperature |
| Surface Finish | Rough with scale | Smooth and polished |
| Tolerances | Less precise | More precise |
| Cost | Lower | Higher |
| Strength | Generally lower | Higher after work hardening |
Hot rolled steel is the preferred choice for applications where cost and ease of production are more important than precision surface finish.
ASTM A36 – Structural beams, channels, plates.
4140 Alloy Steel – Shafts, bolts, gears.
A588 Weathering Steel – Bridges, outdoor sculptures, building facades.
AR400 – Mining and construction equipment.
S355MC – Automotive chassis, heavy-duty frames.
To ensure consistent performance, reputable suppliers such as sakysteel provide hot rolled steel with verified mechanical properties, dimensional accuracy, and certified test reports. This helps industries avoid costly rework and ensures compliance with engineering standards.
The steel industry is evolving toward more sustainable production, improved alloy compositions, and enhanced surface protection methods. Developments include:
Advanced HSLA Steels – Offering higher strength-to-weight ratios.
Corrosion-Resistant Alloy Steels – Reducing the need for coatings.
Environmentally Friendly Production – Lower carbon emissions in manufacturing.
These advancements will give engineers more choices and better performance for specific applications.
Hot rolled steel is a foundational material in many industries, with grades ranging from low carbon mild steel to high-strength alloy and weathering steels. Each grade offers unique mechanical and chemical properties suited to specific applications.
Understanding the different grades of hot rolled steel, their properties, and standards ensures that you can select the right material for your project, whether it’s for structural beams, automotive parts, pressure vessels, or abrasion-resistant components. Working with trusted suppliers like sakysteel guarantees that you receive high-quality, certified materials tailored to your requirements, ensuring safety, performance, and long-term durability.