PPGI Steel Sheet quality analysis
1)Poor bendability (T-bend)
Features:
When the steel is bent by 180 degrees, the PPGI steel sheet coating of the processed part is cracked and the coating is peeled off.
Cause:
1. The amount of pre-processing is too much.
2. The coating thickness is too thick.
3. Over-baking.
4. The manufacturer of the bottom coating is different from the manufacturer of the top coating, or the dilute A material is misused.
2)Poor hardness (pencil hardness)
Use a drafting pencil to make a strong stroke on the surface of the PPGI steel sheet coating, wiping away and leaving a scratch on the surface.
Cause:
1. The furnace temperature is low and the coating is not fully cured.
2. Inappropriate heating conditions.
3. The coating thickness is thicker than specified.
3)Bump Features
Due to the steel strip’s external impact, the plate’s surface appears protruding or concave, some with a certain spacing and some without.
Cause:
1. Foreign matter is mixed on the roller during coating.
2. The thin plate products’ tie marks when bundled.
3. It is subject to external impact when rewinding.
4)Edge Bubble
Features:
There is paint on both sides, and after drying, air bubbles appear.
Cause:
The raw material has burrs and is stained with paint, with gaps on both sides.
5)Pockmark
Features:
After painting, foreign matter or dust from the outside will have rice grain-like protrusions on part or all of the surface.
Cause:
1. Other types or companies’ coatings are mixed into the coating.
2. It is caused by foreign matter in the paint.
3. Poor washing in the pretreatment process.