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Typical Defect Forms And Solutions For Stainless Steel Medium And Heavy Plates

Mar 30, 2021

Typical forms of several defects in stainless steel medium and heavy plates:

1. Small longitudinal cracks, the shape of the small longitudinal cracks on the surface of the steel plate is less than 200mm in length, less than 3mm in width, and less than 0.3mm in depth.

2. Peak-shaped cracks, all of which occur at 5-60mm from the edge of the lower surface of the steel sheet, and the macroscopic direction is perpendicular to the rolling direction, showing a "mountain peak" shape.

3. Sideline cracks, which mainly occur at a distance of 20-80mm from the edge of the steel plate. The shape is a number of parallel longitudinal cracks of different sizes. The rule is that the thicker and wider the steel plate, the more serious the defects.

4. Inclusions, scars, inclusions and scars are distributed regularly, and the phenomenon is obvious after finishing operations such as edge flame peeling crack inspection or casting slab scratch flame cleaning.

The reasons may be analyzed:

Small longitudinal cracks are formed when small impurities are mixed into the mold; peak cracks are mainly caused by transverse cracks in the outer corner of the cast slab; edge cracks are caused by the rollover of the slab's edges and corners to the surface during the rolling process; Inclusions and scars are caused by the surface oxidation residue not being cleaned up during finishing.

In order to reduce the occurrence of the above situation of stainless steel materials, the following measures should be actively taken:
1. Regularly check the crystallizer, especially the water sample, to see if there are small impurities mixed in, which may cause water quality changes.

2. Strictly control the overage service of the equipment to ensure the timely maintenance of the sector section, and avoid deep scratches on the casting billet due to the occurrence of partial rollers in the sector section not rotating.

3. Implement the water distribution zone control of the bending section, dynamically control the corner temperature of the end face cast slab with different widths, and prevent the corner temperature of the cast slab from entering the brittle zone during the bending process.

4. Use wide-end cast billets to produce large-width steel plates as much as possible to reduce the amount of expansion during rolling of the steel plate, thereby reducing the uneven deformation of the edges during rolling of the wide steel plate, and weakening the width of the sideline cracks of the steel plate.

5. Improve the uniformity of the casting temperature in the heating furnace, optimize the slab heating process, reduce the temperature difference between the upper and lower surfaces of the cast, reduce the difference in deformation resistance between the upper and lower sides of the rolling piece, thereby reducing the uneven deformation of the edge of the rolling piece.

6. Improve the slab finishing ability to avoid secondary defects such as incomplete cleaning of the oxide slag and local deep burn marks after the slab finishing.