Why Is Enameling Steel Usually Cold Rolled? What Is Fish-Scaling Resistance?
Can ordinary cold-rolled steel simply replace enameling steel? Many buyers ask this — and the answer is usually no.
Enameling steel must not only meet forming requirements, but also withstand the subsequent enameling and firing process. Two problems are often overlooked in enamel production: surface quality and fish scaling.
This guide explains why cold rolling is commonly used for enameling steel, and how fish-scaling resistance affects the final enamelled product.
1. What Is Enameling Steel?
Enameling steel is a steel sheet designed to be coated with enamel (a glass-like coating) and fired at high temperature. The result is a surface that is corrosion-resistant, heat-resistant, and easy to clean.
- ✔ Water heaters
- ✔ Cookware
- ✔ Bathtubs
- ✔ Ovens
- ✔ Household appliances and sanitary products
💡 Key point: Enameling steel is not selected only for its mechanical strength. Its surface condition, formability, and behavior during firing are equally important.
2. Why Is Enameling Steel Usually Cold Rolled?
2.1 Better Surface Quality
- ✔ Smoother surface
- ✔ More uniform surface finish
- ✔ Better thickness consistency
Enamel coatings are sensitive to the substrate surface condition. A smoother, more uniform surface helps the enamel adhere properly and reduces surface defects.
2.2 Better Thickness Control
- ✔ Enameling steel is often used for thin-gauge products
- ✔ Cold rolling provides more precise thickness control
- ✔ Helps with stamping, forming, and final dimensions
2.3 Good Formability
- ✔ Water heater shells
- ✔ Oven panels
- ✔ Cookware and other pressed components
Many products require deep drawing or complex forming, so the steel must not only be strong — it must also form well.
2.4 More Consistent Mechanical Properties
- ✔ Rolling and annealing processes
- ✔ Grain structure control
- ✔ Yield strength and elongation
- ✔ Formability
3. Does Cold Rolling Alone Make Steel Suitable for Enameling?
No.
Ordinary cold-rolled steel is not the same as enameling steel. Even if two steel sheets have the same thickness, similar surface, and are both cold rolled, they may behave completely differently after enameling.
- ✔ Chemical composition
- ✔ Steelmaking process
- ✔ Annealing treatment
- ✔ Hydrogen absorption and diffusion behavior
- ✔ Substrate-enamel interaction
⚠️ Important: Cold rolling alone does not guarantee good enameling performance. The steel must also be designed and produced with the enameling process in mind.
4. What Is Fish Scaling in Enamelled Steel?
4.1 What Causes Fish Scaling?
The basic mechanism can be understood as follows:
Hydrogen enters steel → remains inside steel → enamel firing → gas pressure builds → blistering / cracking
During the enameling process, hydrogen can enter the steel. During the high-temperature firing process, if the hydrogen cannot be released in a controlled manner, pressure can build up between the steel substrate and the enamel layer, causing defects.
4.2 Why Is It Called "Fish Scaling"?
- ✔ Small blisters on the enamel surface
- ✔ Cracks and lifted enamel
- ✔ Scale-like appearance
The defect is called "fish scaling" or "fish-scale defect" because the surface pattern resembles fish scales. In Chinese, it is commonly referred to as 鳞爆 (lín bào).
5. What Is Fish-Scaling Resistance?
Fish-scaling resistance refers to the ability of enameling steel to resist enamel blistering or peeling caused by hydrogen-related pressure after firing.
This is not simply a matter of surface quality. It is related to what happens inside the steel:
- ✔ Hydrogen absorption
- ✔ Hydrogen diffusion
- ✔ Hydrogen trapping
💡 Key point: Fish-scaling resistance depends on the steel's chemistry, microstructure, and manufacturing process — not just its surface condition.
6. How Does Enameling Steel Resist Fish Scaling?
6.1 Steel Chemistry
- ✔ Certain alloying elements influence hydrogen behavior
- ✔ Chemical composition design affects microstructure and enamel adhesion
6.2 Steelmaking and Processing
- ✔ Clean steel production
- ✔ Inclusion control
- ✔ Rolling and annealing treatment
6.3 Hydrogen Trapping
Certain microstructural features or defects inside the steel can influence how hydrogen diffuses and is stored. This means the steel's microstructure can affect its fish-scaling performance. However, the exact mechanism varies between grades and standards.
7. Cold Rolling and Fish-Scaling Resistance: What Is the Connection?
It is important not to oversimplify the relationship:
⚠️ Important: Cold rolling itself does not automatically give steel fish-scaling resistance.
The final performance of enameling steel is the result of a complete process chain:
Steel chemistry → Steelmaking → Hot rolling → Cold rolling → Annealing → Final properties
Cold rolling primarily addresses:
- ✔ Surface quality
- ✔ Thickness accuracy
- ✔ Formability
Fish-scaling resistance involves:
- ✔ Steel composition
- ✔ Microstructure
- ✔ Hydrogen behavior
- ✔ Manufacturing process
💡 Key point: Cold rolling and fish-scaling resistance are related but different performance requirements. Both must be considered when selecting enameling steel.
8. Ordinary Cold Rolled Steel vs Enameling Steel
9. Common Applications of Cold Rolled Enameling Steel
🔥 Water Heaters
- ✔ Deep forming
- ✔ Enamel coating
- ✔ Corrosion resistance
- ✔ Fish-scaling resistance
🍳 Cookware
- ✔ Pots, pans, baking products
🏠 Ovens and Household Appliances
- ✔ Oven panels, appliance components
🛁 Sanitary Products
- ✔ Bathtubs, sanitary equipment
10. How to Choose Enameling Steel for Your Application
Consider these factors:
- ✓ Required thickness
- ✓ Forming method
- ✓ Drawing depth
- ✓ Surface requirements
- ✓ Enameling process
- ✓ Firing temperature
- ✓ Fish-scaling resistance
- ✓ Required mechanical properties
- ✓ Steel grade and applicable standard
- ✓ MTC and quality documentation
💡 Key point: The right grade depends on the forming process and enameling method — not simply on the required thickness.
11. Frequently Asked Questions
❓ Why is cold rolled steel used for enameling?
Cold rolling provides better surface finish, more precise thickness control, and good formability — all important for the enameling process.
❓ What is fish scaling in enameling steel?
Fish scaling is a defect where small blisters or cracks appear on the enamel surface after firing. It is caused by hydrogen-related pressure between the steel and the enamel layer.
❓ What causes fish scaling?
Hydrogen enters the steel during processing or enameling. During high-temperature firing, the hydrogen can create internal pressure, leading to blistering or peeling of the enamel.
❓ Is all cold rolled steel suitable for enameling?
No. Ordinary cold-rolled steel is not specifically designed for enameling. Enameling steel has specific chemical composition, processing, and hydrogen behavior requirements.
❓ How does enameling steel prevent fish scaling?
Through steel chemistry, clean steel production, controlled microstructure, and hydrogen behavior management. The exact mechanism varies between grades and standards.
❓ Is DC01EK an enameling steel?
DC01EK is a European standard grade commonly used for enameling applications. It is specifically designed with properties suitable for the enameling process.
❓ What is the difference between DC01EK and DC04ED?
Both are enameling steel grades, but they differ in formability and intended application. DC04ED typically offers better deep-drawing properties. The right choice depends on the forming process and product requirements.
12. Final Thoughts
Cold rolling gives enameling steel the surface, dimensional accuracy, and forming characteristics needed for manufacturing. But good enameling performance requires more than a smooth cold-rolled surface.
Fish-scaling resistance, steel chemistry, and hydrogen behavior also need to be considered.
💡 Our view: For buyers of enameling steel, the key question is not simply "Is it cold rolled?" but "Is it designed and produced for the enameling process I use?" If you are sourcing DC01EK, DC04ED, or other enameling steel, confirm the grade, standard, and fish-scaling requirements before ordering.
📚 Further Reading & Related Content
- 🔗 What Is DC01EK Enameling Steel?
- 🔗 DC04ED Enameling Steel: Properties and Applications
- 🔗 How to Read a Steel Plate Mill Test Certificate (MTC)
- 📄 EN 10209, EN 10130, ASTM A424
Need Cold Rolled Enameling Steel?
CEHE STEEL supplies cold rolled enameling steel including DC01EK, DC04ED, and other grades. Send us your required grade, thickness, and application — we'll confirm availability and provide a quotation with full MTC documentation.