[Stainless steel NO.1 surface roll print] quality objection analysis
A food equipment manufacturing company purchased a batch of 304 hot-rolled coils from a steel plant to make beer cans. Before the steel coil was used, the company arranged to process, directly trimming and flattening the length, but during the manufacturing process, it was found that the stainless steel surface was uneven, which had affected the product quality, so it raised a quality objection to the steel mill.
After receiving the complaint from the user, the steel mill immediately arranged technical personnel to the site to understand the situation. From the surface of the fixed-length steel plate, the defects are periodic, and they bulge along the width of the strip, giving a more obvious feel.
In order to further understand the use of this batch of steel plates, the technical staff also specifically learned from the user the process flow of making beer wine cans (as shown below).
The wine cans produced by the user are made according to the order placed by the beer manufacturer. The size and diameter of the wine can have been determined. The user uses the hot-rolled and cold-rolled stainless steel plates that have been flattened to weld the medium and thin stainless steel plates. Processed into wine filling.
As we all know, in the can-making process of stainless steel 304 strip steel, honeycomb welding, and channel fusion welding methods can be used (as shown in the figure below). Due to the periodic roll mark defects of stainless industrial plates, hot-rolled steel, and cold-rolled steel False fusion welding is formed in the hybrid welding process, and after re-welding is required, a 30 kg water test is used at the same time, and then liquid ammonia cooling test is performed.
The defects of this batch of steel plates have periodic spacing, and the symmetry in the width direction of the upper and lower surfaces appears at the same time. The surface of the plate is convex and has a more obvious hand feeling. It is not produced during the pickling process of cold rolling (as shown below).
We know that such periodic roll printing defects are caused by the roll pressing against or being impacted by the head of the hot strip at a low temperature, and the roll surface hardness decreases. As the strength of the stainless steel strip is higher than that of the roller surface, the stripe defect left on the roller surface due to the huge impact at the moment of biting steel cannot be eliminated due to the small relative reduction of the finished frame.
Generally speaking, in order to ensure the surface of the steel, in the process of rolling stainless steel strip, a mathematical model is used to control the water output of the roll cooling water to increase the biting temperature of the finishing strip head and reduce the impact on the roll. After grinding the replaced finishing work roll, the hardness of the roll surface should be measured to ensure the surface hardness of the roll.
At the same time, it also shows that in the production process, even a little mistake will cause greater losses. To enhance the competitiveness of products in the market, enterprises must master the actual needs and procurement standards of users, and understand the key control points and technical requirements of users’ production processes. Customer satisfaction, only a starting point without an end!