Hot-Rolled Steel Grades

According to the World Steel Association, there are more than 3,500 different steel grades, each of which has unique physical and chemical properties. This broad variety makes steel suitable for a wide range of applications.

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Hot-rolled steel is one of the most frequently used types of steel; its excellent formability enables it to be manufactured into bars, sheets, tubes, and various other components. It is available in numerous grades, which find use in various applications.

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Overview of Hot-Rolled Steel

Hot-rolled steel is carbon steel that has been heated to above its recrystallization point (typically at or above 1,700° F), flattened to the desired size and thickness by high-speed rollers, and worked into the necessary form (e.g., bar, plate, sheet). It can be low-carbon (containing up to 0.3% carbon), medium-carbon (containing 0.3&#;0.6% carbon), or high-carbon (containing more than 0.6% carbon). The processed material exhibits excellent mechanical properties at a lower cost than cold-rolled steel, which makes it an appropriate choice for many applications, including construction, railroad tracks, and sheet metal. However, since the process can cause scaled surface textures and/or material shrinkage, the material is best suited for applications that do not have tight tolerances or strict surface finishing requirements.

What Is the Steel Hot Rolling Process?

The process of making hot-rolled steel is as follows:

1. Heating the steel to above its optimal rolling temperature
2. Forming and rolling the steel into a large rectangular piece
3. Feeding the piece through a series of roll mills to form and stretch it into a thin strip
4. Water cooling the strip at the rate needed to achieve the desired metallurgical properties
5. Winding it into a coil (if needed)

Common Hot-Rolled Steel Grades

Hot-rolled steel is available in many grades or standards set by the Society of Automotive Engineers (SAE) or the American Society for Testing and Materials (ASTM). Some of the most widely used are:

• A36: This is one of the most popular hot-rolled steel grades as it is weldable and machine washable and has excellent mechanical properties.
• C and C: These hot-rolled steel grades are more formable, machinable, and weldable than alloy and high-carbon steels. The main difference between them is carbon content; C has between 0.08% to 0.13% carbon content by weight, while C has between 0.14% to 0.20% carbon content by weight.
• A: This versatile hot-rolled steel grade is widely used in automobile bodies, metal fabrication, and sheet metal structural applications.
• C: This hot-rolled steel grade is AISI-designated. It has highly similar mechanical and chemical properties to A36 but a slightly lower carbon content. It is used for furniture, automotive components, structures, and more.
• A500: This hot-rolled steel grade is also a low-carbon alloy. It is solely used for tubing.
• C: Like C, this hot-rolled steel grade is AISI designated. However, it is medium-carbon steel, which means it offers greater strength.
• C: This medium-carbon hot-rolled steel grade contains manganese and sulfur, which make it easier to machine.

Learn More About Hot-Rolled Steel From McDonald Steel

Want to learn more about hot-rolled steel? Ask the experts at McDonald Steel. We are tooled to roll over 500 symmetrical and asymmetrical hot-rolled steel shapes. Our products find application in a diverse range of markets, where they serve as ideal alternatives to forged, cast, extruded, cold drawn, and machined steel components. For additional information on hot-rolled steel and the various grades available, contact us today.

It&#;s easy to talk about how important steel is to our world. It&#;s used to build bridges and skyscrapers, cutlery and cookware, furniture, auto parts, and so much more. If we want to get especially self-aware, steel is used to make the very machines that process steel. Steel&#;s versatility is clear, but there is still much to be understood about how it is processed. Specifically, what is the difference between hot rolled steel and cold rolled steel, and why would one process be more suited than the other for certain applications?

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Hot Rolled Steel Process

Developing hot rolled (HR) steel begins with heating steel slabs to an extremely high temperature, above their recrystallization point, to soften the steel. From there, the softened steel is passed between powerful rollers to thin and shape the steel into its desired thickness. The HR steel process is fast and efficient, which makes HR steel a cost-effective option.

Hot Rolled Steel Properties

Once the hot rolled steel process is complete, you&#;ll find HR steel to have:

• Strength & Ductility: HR steel retains good strength and ductility, making it ideal for applications requiring bending or shaping.
• Formability: Not only can HR steel be formed to the desired thickness and shape during HR steel processing, but it can also be heated and re-formed as needed.
• A Rough Surface: Due to the high processing temperatures, HR steel has a mill scale (oxide layer) on its surface and a rougher finish. It may require additional treatment for aesthetics if desired or needed.
• Dimensional Variation: As a result of cooling following the rolling process, individual HR steel final products can vary in shape and dimension from batch to batch.

Cold Rolled Steel Process

The cold rolled (CR) steel process begins as HR steel and then goes through further processing. Once cooled to room temperature, the steel is again passed through rollers, this time with significant pressure. This helps achieve tighter tolerances and a smoother finish.

Cold Rolled Steel Properties

With the extra processing CR steel goes through, you&#;ll find cold rolled steel to have:

• High Strength & Hardness: Cold working strengthens the steel&#;s crystal structure, making it harder and stronger than HR steel.
• Superior Surface Finish: CR steel boasts a smooth, shiny surface, ideal for applications requiring paint or a polished look.
• Tight Tolerances: Cold rolling delivers more precise dimensions compared to HR steel.
• Work Hardening: The cold working process can introduce internal stresses in the steel. To improve its formability, CR steel may undergo annealing, a heat treatment that softens the material.

Hot Rolled vs. Cold Rolled Steel: Choosing Between HR and CR Steel

Certain applications are better suited for hot rolled steel and others for cold rolled steel. There are some general guidelines to follow, but it&#;s also helpful to discuss with a steel manufacturing expert like Capital Steel & Wire to determine exactly what type of steel is best for your application. This expertise is particularly important when considering hot rolled steel grades and cold rolled steel grades, which can look confusing and intimidating at first.

In general, HR steel is ideal for applications that prioritize affordability and formability, as well as hidden structural elements (supports, fasteners, agricultural implements, etc.). When used as hidden structural elements, HR steel typically doesn&#;t need to be treated for aesthetics as its rough edges won&#;t be seen, all the while its strength and ductility give you the support you need in your application.

For projects requiring high strength, smooth finishes and tight tolerances, CR steel is the way to go. Automotive parts, appliances, oil, gas and energy parts, and more benefit from the precise dimensions and aesthetically pleasing smooth finish of CR steel.

Choose HR or CR Steel from Capital Steel

By understanding HR vs. CR steel, you can make informed decisions when selecting the best material for your next project. Capital Steel & Wire is here to answer your questions and help you figure out exactly what is the best material for your next project. Contact us today to find the perfect steel solution.

If you want to learn more, please visit our website Hot Rolled Steel Slab.