ASTM A36 and ASTM A572 are two commonly used types of structural steel, ideal for applications including bridge and building construction, energy infrastructure, industrial manufacturing, road plates, and more.
Despite both being popular choices, A36 and A572 have notable differences in terms of strength, machinability, and composition. These differences can significantly impact a buyer’s decision on the most appropriate material for their project. This article will delve into the similarities and differences between these two grades.
A36 & A572 Material Specifications
Grades
The A572 steel plate specification includes five different grades: Grade 42, Grade 50, Grade 55, Grade 60, and Grade 65. Each grade has distinct chemical compositions and mechanical properties, offering a range of options for various applications. In contrast, the A36 steel plate specification does not include multiple grades and is standardized as a single grade.
Chemical Composition
A36 steel plate is classified as low carbon, or mild steel, with a carbon content ranging from 0.05% to 0.25%. This low carbon content makes A36 one of the most ductile types of carbon steel, meaning it can be easily formed and machined into various structural shapes.
A572 steel plate is also a type of mild carbon steel but with higher concentrations of specific chemical alloys like phosphorus, manganese, and silicon. These additions categorize A572 as a high-strength, low-alloy (HSLA) steel, providing higher strength and lower weight compared to standard mild steel. These characteristics make A572 steel plate ideal for structural applications that require high stress resistance, such as in the construction of bridges and transmission towers.
Chemical Composition of ASTM A36 Steel
| CHEMICALALLOY | UP TO ¾” THICK | OVER ¾” TO 1 ½” THICK | OVER 1 ½” TO 2 ½” THICK | OVER 2 ½” TO 4” THICK | OVER 4” THICK |
| CARBON MAX | 0.25% | 0.25% | 0.26% | 0.27% | 0.29% |
| MANGANESE | N/A | 0.80-1.20% | 0.80-1.20% | 0.85-1.20% | 0.85-1.20% |
| PHOSPHORUS MAX | 0.030% | 0.030% | 0.030% | 0.030% | 0.030% |
| SULFUR MAX | 0.030% | 0.030% | 0.030% | 0.030% | 0.030% |
| SILICON | 0.40% MAX | 0.40% MAX | 0.15-0.40% | 0.15-0.40% | 0.15-0.40% |
| COPPER MIN | 0.20% | 0.20 % | 0.20% | 0.20% | 0.20% |
Chemical Composition of ASTM A572 Steel
| CHEMICALALLOY | GRADE 42 | GRADE 50 | GRADE 55 | GRADE 60 | GRADE 65≥ ½” THICK | GRADE 65 OVER ½” TO 1 ¼” THICK |
| CARBON MAX | 0.21% | 0.23% | 0.25% | 0.26% | 0.26% | 0.23% |
| MANGANESE MAX | 1.35% | 1.35% | 1.35% | 1.35% | 1.35% | 1.65% |
| PHOSPHORUS MAX | 0.030% | 0.030% | 0.030% | 0.030% | 0.030% | 0.030% |
| SULFUR MAX | 0.030% | 0.030% | 0.030% | 0.030% | 0.030% | 0.030% |
| SILICON | 0.15-0.40% | 0.15-0.40% | 0.15-0.40% | 0.40% | 0.40% | 0.40% |
Mechanical Properties
The distinct chemical compositions of A36 and A572 steel result in different mechanical properties, notably in yield point and tensile strength. Yield point indicates the stress level at which a material deforms permanently, while tensile strength measures the force required to break or fail the material.
A572 steel contains higher levels of strengthening alloys, such as manganese and silicon, compared to A36 steel. These additional alloys impart greater strength to A572 steel, enabling it to support more weight and endure higher forces without breaking or failing. This enhanced strength is particularly important for structural applications.
Mechanical Properties of ASTM A36 & ASTM A572 Steel Plate
| GRADE | YIELD POINT | TENSILE STRENGTH |
| A36 | 36 KSI | 58-80 KSI |
| A572 GRADE 42 | 42 KSI | 60 KSI |
| A572 GRADE 50 | 50 KSI | 65 KSI |
| A572 GRADE 55 | 55 KSI | 70 KSI |
| A572 GRADE 60 | 60 KSI | 75 KSI |
| A572 GRADE 65 | 65 KSI | 80 KSI |
Material Testing for A36 & A572 Steel Plate
Charpy Impact Test for Cold Environments
In colder environments, structural engineers often require Charpy impact tests for A36 and A572 steel plates. These tests assess a material's ability to withstand significant forces at various temperatures, ensuring that structural materials remain durable and do not fail in harsh climates. A572 steel, with its additional strengthening alloys, is generally more suitable for cold environments compared to A36 steel.
Ultrasonic Testing for Thick Plates
For thick A36 and A572 steel plates—those exceeding three inches in thickness—ultrasonic testing (UT) might be requested. This testing method uses a probe to send sound waves into the material. When these waves encounter a flaw, they bounce back, allowing for the detection of internal defects that may be difficult to identify in thicker materials.
Are A36 & A572 Steel Plates Interchangeable?
While both A36 and A572 steel plates are commonly used in structural applications such as bridge and building construction, they are not interchangeable. A572 steel boasts higher strength and greater wear resistance than A36 steel, making it more appropriate for heavy load-bearing applications like transmission towers or structural components subjected to substantial forces.
A36 & A572 COST DIFFERENCE
As previously discussed, A36 steel has a minimum yield strength of 36,000 PSI, which it achieves through the inclusion of carbon and manganese. In contrast, A572-50 steel boasts a higher minimum yield strength of 50,000 PSI. While A572-50 also relies on carbon and manganese for its strength, it incorporates additional alloys such as columbium or vanadium. These extra elements enhance its overall strength, leading to A572-50 being generally priced approximately 2.5% to 5% higher than A36.
Sourcing A36 & A572 Steel Plate for Structural Applications
When selecting a supplier for A36 or A572 steel plate, consider the following factors to ensure you meet your structural application needs:
- Flexible Purchasing Options: Choose a supplier that offers multiple purchasing methods, such as online ordering or through a sales representative, allowing you to acquire A36 and A572 plates in the most convenient way for your business.
- Comprehensive Documentation: Ensure the supplier provides detailed paperwork confirming that the steel plate meets all required specifications and standards, guaranteeing the quality and compliance of the material.
- Sufficient Inventory: Opt for a supplier with a robust stock of A36 and A572 steel plates in various grades and sizes, ensuring availability and quick fulfillment of your orders.
CG Steel, with its 11 strategically located distribution centers across North America, maintains a well-stocked inventory of A36 and A572 steel plates in diverse grades and sizes. Additionally, existing customers can conveniently place orders for A36 and A572 plates via CG Steel’s ecommerce platform, Leeco Pro, offering enhanced flexibility and customization in the purchasing process.
