Common Problems in Smelting, Forging, and Rolling Stainless Steel Coils

Shrinkage Cavities

Shrinkage cavities are formed when molten steel shrinks in the steel mold.

Transverse Cracks

Transverse cracks appear on the surface of steel ingots. They are usually shallow and can be removed by fine grinding.

Longitudinal Cracks

Longitudinal cracks occur on the surface of the steel ingot, often at the upper part and corners. These cracks are deep and difficult to remove by grinding.

Scarring

Scarring refers to metal that splashes and adheres to the surface of the steel ingot, usually appearing in the lower part.

Double Skin

Double skin is identified by irregular dark color and looseness at the edge of the low-magnification test piece, with oxide inclusions (mainly ferrous oxide) around it.

Surface Inclusions

Surface inclusions are non-metallic materials embedded in the surface of the steel ingot, visible to the naked eye.

Surface Pores

Surface pores are tiny holes visible to the naked eye, mostly found in the middle and lower parts of the steel ingot. They are generally shallow and can be removed by finishing.

Bursting

Bursting occurs when the steel ingot's surface cracks due to extreme cold, often accompanied by a sound.

Rising

Rising refers to the irregular convex head of the steel ingot.

Reticulation

Reticulation is characterized by mesh-like protrusions on the surface of the steel ingot.

Pockets

Pockets are pits on the surface of the steel ingot.

Double Pouring

Double pouring shows as obvious reconnection marks around the surface of the steel ingot.

Flash

Flash refers to metal flakes at the head or tail of the steel ingot that are perpendicular to its surface.

Flying Fins

Flying fins are thin sheets formed on the surface of the steel ingot, perpendicular to its surface.

Bubbles

Bubbles are defects caused by degassing and deoxidation of molten steel or moisture in raw materials. They can be subcutaneous or internal.

• Prevention: Ensure proper oxidation, boiling, reduction, and deoxidation of molten steel. All refractory materials and the furnace chamber must be dry. Clean and evenly oil molds, prototypes, and other equipment.

White Spots

White spots are fine cracks visible on low-magnification samples.

• Transverse Samples: Appear as radioactive irregular jagged cracks.
• Longitudinal Samples: Appear as round or elliptical silver bright spots.
• Cause: Mainly influenced by hydrogen.