Stainless steel surface color difference / customer complaints that the batch of stainless steel strips he purchased has color difference, which has a great impact on the use. It is understood that this batch of strips has a width of about 200mm and is 304. The color difference complained by the customer does exist and is more obvious. It is continuously dark in the longitudinal direction and is distributed on the upper surface of the steel coil. 4 of the 10 small coils There are chromatic aberrations on the surface, the width of the chromatic aberration varies from 3mm to 10mm, and the position of the chromatic aberration of each small roll is different. The customers of this batch of slitted rolls cut them into small plates of various sizes and make various shells after shearing and bending. Therefore, the surface requirements are high. Therefore, for the color difference on the material, the raw material is judged to be unqualified raw materials, and it is required to be returned. Check the sub-processing records, the record is that the surface of the raw material is checked for good quality and no defects, so it can basically be judged to be caused during processing. Such dark longitudinal defects cannot be erased. After inspection, it is not caused by oil contaminants. According to the traces, it can basically be judged that the processing equipment and the steel coil are caused by non-rolling direct contact. Considering that the indirect contact between the processing equipment and the upper surface of the steel coil is only on the side of the tension belt that establishes tension. Check the processing records of the day, and the wool felt was used when processing the batch of materials. After inspection, the wool felt has been used for a long time and has accumulated a large amount of stains. The surface is gray-black, and it is heated by friction with the steel plate and has a ball phenomenon. These nodules are hard and leave continuous dark friction marks on the surface of stainless steel under high pressure and high friction temperature. Identify the source of the problem and immediately request the use of wool felt to strengthen management. After use, use a brush to remove all kinds of attached dust and balls, and scrap the wool felt that cannot be used. It is required to strengthen the inspection of the rewinding position and punish the rewinding operator for the failure of inspection. The difference between stainless steel, especially cold-rolled stainless steel, and other materials is higher surface requirements. Many stainless steels are used for decorative materials or materials with high surface requirements. Therefore, the inspection and protection of stainless steel surfaces is one of the first points that the machining center should consider. In the process of processing, it is necessary to increase the inspection intensity, not let go of raw material defects, and do not create secondary defects, to ensure that the quality of materials can meet customer requirements.