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Grades of steel is a method for classifying various types of steel based on their composition and mechanical properties. This system helps manufacturers and users understand which type of steel is most suitable for construction, automotive, and manufacturing purposes.
Factors such as cooling rates and the duration spent at critical temperatures greatly influence steel strength. Two sheets of steel with the same alloy composition can have different grades due to the heat treatment techniques used.
Grading systems like ASTM and SAE provide clear guidelines. ASTM uses letters and numbers to describe the unique properties of metals, while SAE employs a four-digit number that indicates the type of steel and its carbon concentration.
By understanding grades of steel, you can make better material selection choices. These standards help consumers, engineers, and architects ensure the quality and consistency of steel, making it an essential consideration in the construction process.
Grades of Steel System: Society of Automotive Engineers (SAE)
The grading system for steel (grades of steel) implemented by the Society of Automotive Engineers (SAE) categorizes steel based on the composition of its main elements.
For example, carbon steel is measured by the amount of carbon present, while alloy steel is grouped according to the type of alloying elements used, such as nickel, chromium, or molybdenum.
In the SAE system, a four-digit code is used to indicate the grade of steel. The first digit represents the main alloying element in the steel, with the following general categories:
- 1 for carbon steel
- 2 for nickel steel
- 3 for nickel-chromium steel
- 4 for molybdenum steel
- 5 for chromium steel
- 6 for chromium-vanadium steel
- 7 for tungsten-chromium steel
- 9 for silicon-manganese steel
- The last two digits typically represent the percentage of carbon content.
The SAE system provides standards that assist manufacturers and engineers in selecting the appropriate steel for specific applications, including the production of automotive components that require high strength and durability.
|
Type of Steel |
Series | Description |
Example |
| Carbon Steel | 10xx | Increasing numbers indicate higher carbon content. | 1020 (mild carbon steel), 1045 (high wear resistance) |
| Nickel Steel | 2xxx | Variations such as 23xx for high nickel content. | – |
| Nickel-Chromium Steel | 3xxx | Variations based on specific percentages of nickel and chromium. | 31xx (medium alloy content) |
| Molybdenum Steel | 4xxx | Often used for applications requiring high strength. | 4140 (high strength and toughness) |
| Chromium Steel | 5xxx | Varying levels of chromium depending on the grade. | 51xx (high carbon content) |
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Grades of Steel System: American Society for Testing and Materials (ASTM)
The American Society for Testing and Materials (ASTM) also has an internationally recognized steel grading system. This nonprofit organization develops voluntary standards for products, materials, systems, and services.
ASTM standards help ensure the safety and quality of products and services by providing standardized procedures and guidelines.
The ASTM system focuses more on testing standards and specifications that steel must meet to be accepted for specific uses. ASTM classifies steel based on its mechanical properties, such as resistance to stress, temperature, and extreme environments.
This classification helps ensure that the steel used meets the safety and performance requirements necessary for industrial applications.
ASTM has a variety of standards for steel, including grades, types, and specifications. Some commonly used ASTM standards include:
|
ASTM Code |
Description |
| ASTM A572-50 | A commonly used grade with a tensile strength of 65,300 psi and a yield strength of 50,000 psi. This material is used in structural applications, including bridges, buildings, and transmission towers. |
| ASTM A53 | A pipe steel suitable for high-pressure or mechanical applications. Also used in steam, water, gas, or air transportation systems. |
| ASTM A1003/A1003M | Standard specifications for coated carbon steel sheets for cold-formed framing members. |
| ASTM A1008/A1008M | Standard specifications for cold-rolled carbon steel sheets. |
| ASTM A1011/1011M | Standard specifications for hot-rolled carbon steel sheets and strips. |
| ASTM A1064/A1064M | Standard specifications for carbon steel wire and welded wire reinforcement for concrete. |
The ASTM code consists of letters followed by numbers, where the letters indicate the material category, such as “A” for ferrous metals and products, “B” for nonferrous metals, and so on.
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Tradecorp Uses LGS for Building Construction: How Is the Grade Determined?
At Tradecorp, we use light gauge steel (LGS) in our construction projects, particularly for building director’s offices and employee mess halls. LGS is known for its strength, durability, and lightweight properties, making it suitable for modern building needs.
We ensure that the materials used meet the Australian Standard AS 1397, which serves as a benchmark for material selection in construction. The LGS we choose is classified as grade G550, indicating strong performance for various construction applications.
The mechanical properties of steel are crucial in any building application. Yield strength, which is the steel’s ability to withstand loads without permanent deformation, is measured in megapascals (MPa). Common steel grades include:
- G250: Steel with a minimum yield strength of 250 MPa.
- G300: Steel with slightly higher strength, suitable for specific applications.
- G550: Ideal for roof sheets and structural components requiring high durability.
We also ensure that the chemical composition of the steel complies with AS 1397 standards, guaranteeing its reliability.
|
Grade |
Carbon (C) | Manganese (Mn) | Phosphorus (P) |
Sulfur (S) |
| G450, G500, G550 | 0.2% | 1.2% | 0.04% | 0.03% |
| G300, G350 (Note) | 0.3% | 1.6% | 0.1% | 0.035% |
| G250, G1 | 0.12% | 0.5% | 0.04% | 0.035% |
| G2 | 0.1% | 0.45% | 0.03% | 0.03% |
| G3 | 0.08% | 0.4% | 0.02% | 0.025% |
