Analysis of Typical Defects of Stainless Steel Medium and Heavy Plate
What is a Stainless Steel Medium and Heavy Plate?
Generally speaking, the stainless steel plate we refer to every day often refers to a 1219*2438 plate, which is often referred to as four or eight feet. But many people don’t know
what kind of plate is a plate?
In fact, not all stainless steel plates can be called medium-thickness plates, only steel plates that meet a certain thickness requirement can be called this way.
So what is the specific thickness of the plate?
Stainless steel medium-thick plates refer to steel plates with a thickness of 4-25.0mm, those with a thickness of 25.0-100.0mm are called thick plates, and those with a thickness of more than 100.0mm are extra-thick plates. Widely used to make various containers, furnace shells, furnace plates, bridges and automotive static steel plates, low alloy steel plates, bridge steel plates, general steel plates, boiler steel plates, pressure vessel steel plates, pattern steel plates, automobile beam steel plates, tractors Some parts and welding components.
Defects of stainless steel plate
In the use of stainless steel medium and thick plates, attention should be paid to the occurrence of defects. Small longitudinal cracks, peak cracks, edge cracks, inclusions, and scars on the surface of the steel plate will affect the surface quality, cause revisions, and reduce product quality.
The performance of stainless steel plate defects
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 plate, and the macroscopic direction is perpendicular to the rolling direction, showing a “mountain peak” shape.
3. Sideline cracks. The cracks mainly occur at the distance of 20-80mm from the edge of the steel plate. A 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.
Causes of defects
Small longitudinal cracks are formed when small impurities are mixed into the crystallizer;
Peak cracks are mainly caused by transverse cracks in the sub-skin corner of the outer arc of the cast slab;
Edge cracks are caused by the rollover of the billet’s corners to the surface during the rolling process;
Inclusions and scars are caused by the surface oxidation residue not being cleaned up during finishing.
Measures to prevent defects
1. Regularly check the crystallizer, especially the water sample, to see if there are any small impurities mixed in, causing the water quality to change.
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 slabs 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 casting, reduce the difference in deformation resistance between the upper and lower surfaces of the rolling, thereby reducing the uneven deformation of the edges of the rolling.
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.