Common Annealing Defects in Cold-Rolled Strip Steel: Causes and Analysis

Causes of Adhesion

1. Excessive tension during rolling or coiling

2. Poor strip shape (edge waves, center waves, multiple waves)

3. Irregular coil winding, especially in thinner gauges

4. Contaminated emulsion residue

5. Furnace over-temperature from thermocouple failure

6. Inadequate protective gas circulation

7. Deformed convection plates affecting gas flow

8. Excessive stacking pressure on thin materials

9. Incorrect annealing parameters for specific grades/specifications

Oxidation Causes

1. System leakage in furnace enclosure

2. Damaged protective covers or deformed flanges

3. Aged/deteriorated sealing rings

4. Cooler system failures

5. Premature high-temperature furnace discharge

6. Temperature control system malfunctions

7. Insufficient protective gas purging

8. Negative pressure during rapid cooling initiation

9. High dew point in protective gas

10. Equipment failures (valves, fans, utilities)

Carbon Black Edge Formation

Carbon deposits along strip edges result from residual rolling oil that isn’t completely removed during bell furnace annealing. Key contributing factors include:

• Rolling oil properties (viscosity, concentration, volatility)

• Contaminants introduced during rolling
  Solution: Selecting appropriate rolling oils proves more effective than modifying annealing processes.

Performance Deficiency Causes

1. Incorrect process parameters

2. Improper furnace loading affecting gas circulation

3. Insufficient temperature or inadequate soaking time

4. Measurement/control equipment malfunctions

Treatment Methods

• Optimize annealing parameters according to material specifications

• Ensure proper furnace loading alignment

• Maintain equipment calibration and functionality

• Implement adequate holding times at target temperatures

• Use suitable rolling oils to prevent carbon residues