Steel plates are important to everything from construction and boilers to specialized industrial equipments. But when you’re choosing between alloy steel and carbon steel, it helps to understand their differences, key grades, and types of applications especially for industrial buyers, manufacturers or fabricators.
What is Carbon Steel Plate?
Carbon steel plates are made from iron alloyed with carbon. They’re straightforward, cost effective, and flexible for many industrial use.
In comparison to alloy steel, they are easier to weld and more affordable. As a result, carbon steel is widely used in construction, manufacturing, and shipbuilding. However, it offers less resistance to corrosion and heat, which may limit its use in high-stress environments.
Key grades of CS Plates include:
SA 537 Carbon Steel Class 1 & SA 537 Carbon Steel Class 2 in Plates
- Medium strength for pressure vessels
SA 516 Carbon Steel Grades 60, 65, 70
- Standard choices for boilers and power plants
SA‑516 Grades 60, 65, 70 with HIC tested
- Resistant to hydrogen induced cracking
SA‑516 Grades 60, 65, 70 with NACE compliance
- Fit for sour services oil & gas environments
Why you’d pick Carbon Plates:
- Solid Tensile Strengths
- Reliable Toughness
- Good Weldability
- Affordable and Available Globally
- Industry standards like ASTM / ASME specs
What Is Alloy Steel Plate?
Alloy steel plates are made by combining carbon steel with additional elements such as chromium, nickel, or molybdenum. As a result, these plates offer enhanced strength, durability, and resistance to heat and corrosion. Unlike carbon steel, alloy steel performs well in extreme environments. Therefore, it’s ideal for pressure vessels, pipelines, automotive parts, and heavy machinery.
Alloy steel plates mixture of iron and carbon with alloying elements like chromium, molybdenum, nickel for strength, temperature proofs or rust control.
ASTM A387 / ASME SA 387 chromium molybdenum alloy steel with lots of grades:
Alloy Steel Plate Grades We supply:
- A387 Grade 5, 11, 22 (each in Class 1 and 2)
Other common A387 grades:
- Gr 2, 9, 12 (Cl 1 & 2), Gr 21, 21L, 22L, Gr 91
Why you’d pick Alloy Plates:
- Manufactured for high temp services like boilers, pressure vessels.
- Better tensile yield strength and toughness.
- Improved rust preventions.
- Various alloys level for specific use cases like high Cr for rough and hard environment.
Alloy Steel vs Carbon Steel
| Features | Carbon Steel Plates | A387 Alloy Steel Plates |
|---|---|---|
| Main Alloying Elements | Iron + Carbon | Iron + C + Cr, Mo (sometimes Ni and V) |
| Strength & Toughness | Better especially SA 516, SA 537 grades | Higher: Class 2 and Class 1 within same grade |
| Temperature Proof | Useful up to 400°C | Excellent upto 600°C and above depending on grade |
| Corrosion Resistance | Low to moderate (HIC/NACE grade) | Moderate to high: especially higher alloy grades |
| Weldability | Generally good | Depends on alloy : weldability by grade |
| Cost Efficiency | Most cost-effective option | Costly, but performance often outweighs the cost |
| Common Uses of Plates | Boilers, tanks, structural parts | Pressure vessel, heat exchanger, powerplants |
Alloy Steel Plate Grades (ASTM A387)
Here are the standard grades of Alloy Steel Plates:
1) Grade 2 & 12 (Class 1 & 2)
-> Low Cr/Mo, for moderate-temp vessels
2) Grade 11 (1.0–1.5 % Cr, 0.45–0.65 % Mo)
-> Mildly higher temp use
3) Grade 22 / 22L (2.0–2.5 % Cr, 0.9–1.1 % Mo)
-> Common in power and boiler industries
4) Grade 21 / 21L (≈3 % Cr, =1 % Mo)
-> For slightly higher temp/rusty
5) Grade 5 (≈5 % Cr, 0.5 % Mo)
6) Grade 9 (≈9 % Cr, 1 % Mo)
7) Grade 91 (≈9 % Cr, 1 % Mo + V/Nb)
-> A shift in crack proof and heat temprature strength
All grades above are offered in Class 1 & Class 2 : except like 21L / 22L / 91, which have unique class availabilities
Carbon Steel Plates Grades (SA 537 & SA 516 with HIC & NACE Tested)
1) SA537 Class 1 & 2 Plates – medium strength, good for vessel shells
2) SA516 Grade 60 / 65 / 70 Plates – widely used in boilers, ships
3) HIC tested Plates – important for hydrogen exposure
4) NACE tested Plates – safe in oil & gas
These are well supported by standards, codes and widely stocked worldwide.
When to Use Alloy Steel and Carbon Steel
Carbon steel (SA 516, SA 537):
- Standard boilers, tanks, structured fabrication
- Cost driven applications where moderate tempraturestress are involved
Alloy steel (ASTM A387 series):
- High pressure or hot temperature environments (e.g. powerplants)
- Situations requiring corrosion control
- Projects where tensile strength improved to justify cost
When you compare alloy steel plates with carbon steel plates, you’ll notice clear differences in their composition and performance. Alloy steel contains additional elements like chromium, nickel, and molybdenum, which give it superior strength and corrosion resistance. Because of this, manufacturers use alloy steel plates in environments that demand durability, such as heavy machinery, pipelines, and pressure vessels.
Meanwhile, carbon steel plates consist mainly of iron and carbon. They offer excellent hardness and strength at a lower cost. Therefore, many industries choose carbon steel plates for construction, shipbuilding, and general fabrication. However, carbon steel does not resist corrosion or high temperatures as well as alloy steel.
In contrast, alloy steel plates handle extreme conditions more effectively. As a result, they last longer in harsh environments and require less maintenance. On the other hand, carbon steel plates provide a budget-friendly option when corrosion resistance is less critical.
To summarize, if your project demands high strength and resistance to wear, then alloy steel plates are the better choice. But, if cost is a priority and conditions are moderate, carbon steel plates will serve you well. Ultimately, your selection depends on your specific needs and environment.
Why Carbon Steel Plates Are Preferred for Cost-Effective Fabrication?
Besides strength and corrosion resistance, alloy steel plates also offer improved toughness and wear resistance. For example, industries like aerospace and automotive rely on alloy steel to meet strict safety and performance standards. Moreover, alloy steel’s ability to maintain its properties at high temperatures makes it suitable for power plants and chemical processing equipment. Consequently, investing in alloy steel plates can reduce downtime and maintenance costs over time.
Conversely, carbon steel plates excel in applications where cost efficiency and ease of fabrication matter most. Because carbon steel bends and welds easily, fabricators often prefer it for structural components and pipelines in non-corrosive environments. Still, to prevent rust and extend service life, carbon steel plates require protective coatings or treatments. Therefore, proper maintenance becomes crucial when using carbon steel in exposed or humid conditions.