🔎 Common Mild Steel: SS400 vs. S45C—What Do the Codes Mean? 2024/12/13

SS400 vs. S45C: How to Choose? Understanding Steel Naming Rules and Uses
Did you know? For common mild steels like SS400 and S45C, every letter and number has a specific meaning—they aren't just named randomly! These codes represent crucial information like material type, composition, strength, and more, allowing engineers and procurement staff to quickly identify the right steel.
Today, we'll break this down into two main categories: Structural Steel and Mechanical Structural Steel, to help you make more informed material choices.

 ➤ Structural Steel Series (SS490, SS400, SS350, SM490)
Structural Steel is primarily used for buildings, bridges, machine bases, and steel structures. It is characterized by moderate strength, high weldability, and good workability. Here are a few common types:

💡 點此查看／Click to view: Structural Steel Series (SS/SM)

材質 Material	抗拉強度 (MPa) Tensile Strength (MPa)	主要用途 Main Applications
SS490 SS490	≥490 MPa	大型鋼結構、橋樑、重型設備 Large-scale steel structures, bridges, heavy equipment
SS400 SS400	≥400 MPa	建築鋼構、機械基座、鋼樑 Building structures, machine bases, steel beams
SS350 SS350	≥350 MPa	輕型建築結構、一般機械零件 Lightweight building structures, general machine parts
SM490 SM490	≥490 MPa	重型建築結構、船舶工程 Heavy building structures, shipbuilding engineering

 ➤ Mechanical Structural Steel Series (S45C, S50C)
Mechanical Structural Steel is mainly used for machine parts, shafts, gears, and molds. Its key feature is that its strength and hardness can be increased through heat treatment, offering good wear resistance.

💡 點此查看／Click to view: Mechanical Structural Steel (S45C/S50C)

材質 Material	含碳量 Carbon Content	主要用途 Main Applications
S45C S45C	約 0.45% Approx. 0.45%	軸承、齒輪、模具、機械零件 Bearings, gears, molds, machine parts
S50C S50C	約 0.50% Approx. 0.50%	高強度零件、耐磨部件 High-strength parts, wear-resistant components

 ➤ Detailed Analysis: SS400 vs. S45C 
These are two of the most common mild steels. Let's dive into their properties and applications.
 
● SS400 (General Structural Steel)
Naming: "SS" stands for "Structural Steel"; "400" indicates a tensile strength ≥400 MPa
Properties: Moderate strength, good workability, high weldability
Applications: Steel structures, machine brackets, steel beams, steel plates, etc.

 ● S45C (Mechanical Structural Steel)
Naming: "S" stands for "Steel"; "45" indicates a carbon content of 0.45%; "C" stands for "Carbon."
Properties: Hardness and wear resistance are increased after heat treatment; ideal for machine parts
Applications: Bearings, gears, molds, high-load machine components  ➤ Q&A: Common Questions Answered
❓ Why can't S45C replace SS400?
S45C has a higher carbon content, which results in poor weldability. If used in building structures, it can lead to weld cracks or brittleness issues. Therefore: use SS400 for building structures, and S45C for machine parts.
Rec. 709
❓ I need high-strength steel. Should I choose SS400 or S45C?
If it's for a building structure (like beams or brackets), you should choose SS400 or the stronger SS490.
If it's for machine parts (like bearings or gears), you should choose S45C or the harder S50C, and use heat treatment to enhance hardness.

❓ Can SS400 be heat-treated to increase its strength?
SS400 is a low-carbon steel and is not suitable for quenching. However, its surface hardness can be increased through cold working or surface hardening (like induction heating). In contrast, S45C is much more suitable for quenching and tempering.

❓ Does S45C rust easily?
S45C has no anti-rust properties. If exposed to the air, it will rust easily. It typically requires surface treatment (like galvanizing, painting, or phosphating) or protection with lubricating oil when used in machine parts.  💡 Conclusion
There's a lot of science behind steel naming conventions!
By analyzing SS400, S45C, SS350, SS490, SM490, and S50C, we can clearly see the different properties, strengths, and applications of each.

 ✔ When selecting steel, you must decide based on strength requirements, processing methods, and the operating environment:
Two  ● Structural Steel (SS400, SS490, SM490) is suitable for buildings and steel structures
 ● Mechanical Structural Steel (S45C, S50C) is suitable for machine parts and precision components

📞 Contact Us
If you have steel purchasing, processing, or cutting needs, feel free to contact Guokai Steel!
📧 Email: sales@guokaisteel.com.tw
📩 Official Line Account: @guokai

【 Copyright Notice 】
All article content on this website, including text, layout, and images, is originally written by Guokai Steel and is protected by copyright. Unauthorized reprinting, excerpting, rewriting, or use for commercial purposes is strictly prohibited. If you wish to collaborate or share, please contact us.