Steel plates used in building projects must always adhere to specific requirements, such as good mechanical properties, durability, temperature resistance, and machinability. To categorize their properties and characteristics, each steel type is assigned a unique grade designation based on its chemical composition. These grading systems were developed by the American Iron and Steel Institute (AISI) and the Society of Automotive Engineers (SAE).
This article will guide you through the differences between Grade 50 and 100 steel plates, including their features and characteristics, chemical composition, and applications.
Features and Characteristics
The Grade 50 steel plate, formally known as ASTM A572, is a standard structural steel plate for high-strength low alloy (HSLA). It is also known as a “workhorse” grade due to its high strength-to-weight ratio and corrosion resistance.
Because it contains more alloying elements than the usual carbon steel, Grade 50 is much more difficult to form; however, it has greater strength per unit weight. Due to their high capacity, these steel plates require fewer materials to meet strength benchmarks.
This steel plate type has the following characteristics:
- Density:80 g/cc
- Yield Strength: 345 mpa
- Tensile Strength: 450 mpa
- Elongation: 18%
- Bulk Modulus: 160 GPa
- Shear Modulus: 80 GPa
On the other hand, ASTM A709 or Grade 100 steel plates are also HSLA steel plates. Hot rolled black plates from the coil are brushed to achieve a quality-enhanced exterior for appearance and finishing, and Grade 100 steel is tempered past smoothed to ensure flatness during processing.
Manufacturers could also weld Grade 100 steel at room temperature without preheating. It is appropriate for all conventional welding methods that do not result in hardening or cold cracking.
The following characteristics also make up Grade 100 steel plates:
- Density:85 g/cc
- Yield Strength: 690 mpa
- Tensile Strength: 760-895 mpa
- Elongation: 18%
- Bulk Modulus: 160 GPa
- Shear Modulus: 80 GPa
As the percentages show, both Grade 50 and Grade 100 steel plates have the same bulk and shear modulus. Bulk modulus measures a substance’s ability to withstand volume changes when compressed on all sides, whereas shear modulus measures the material’s resistance to shear deformation.
Chemical Compositions
The chemical compositions of Grade 50 and Grade 100 steel plates are as follows:
| ASTM A572 (Grade 50) | Element | ASTM A709 (Grade 100) |
| 0.23% | Carbon, C | 0.10-0.21% |
| 98% | Iron, Fe | 98.215-99.5% |
| 1.35% | Manganese, Mn | 0.40-1.5% |
| 0.040% | Phosphorus, P | 0.035% |
| 0.40% | Silicon, Si | – |
| 0.050% | Sulfur, S | 0.040% |
Applications
A572 Grade 50 plates have high strength, formability, and excellent welding properties, making them suitable for various applications. They are generally used in applications where the plate has to be riveted, bolted, or welded.
Grade 50 steel plates are commonly used in the following structural applications:
- Truck frames
- Cranes
- Building structures
- Heavy construction equipment
- Transmission towers
- Bridges
- Freight cars
- Machinery
- Anchoring systems
Meanwhile, A709 Grade 100 plates provide high strength, tensile strength, and yield strength. These characteristics enable them to withstand harsher environments for a more extended period.
Grade 100 steel plates can be used in a variety of structural applications, including:
- School buses
- Truck frames
- Bridges
- Rail cars
- RV frames
- Fire trucks
- Vehicle chassis members
- Cranes
- Hauling vehicles
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