Why are there black lines and spots on the bottom of the thermos?

Hello everyone, "Dong Dong Talk Cup" is here. I have shared in many articles about the black lines, black spots or black spots on the bottom of the newly purchased thermos cups. I thought this kind of content would not receive much attention, but it turned out to be the most replied to, and it has been going on. http://www.zhanyict.com/en/ProductsDetail-VB-10439.htmlAmong the many reply pictures, I found that there are many well-known brands of cups with this kind of problem, both traditional and new generation, which surprised me. In so many years of work experience, both I and the cup factory where I work agree that products with this kind of problem are absolutely prohibited from being put on the market.

The black lines, black spots and black spots inside the thermos are mostly formed during the manufacturing process, and some are caused by improper use (there are various reasons for improper use, so I won’t go into details). http://www.zhanyict.com/en/ProductsDetail-VB-10439.htmlNext, I will mainly talk about how this phenomenon is caused during the production process.

1. Material impurities: During the production process of the thermos cup, the stainless steel material may contain some tiny impurities. http://www.zhanyict.com/en/ProductsDetail-VB-10439.htmlWhen these impurities are melted and re-solidified at high temperatures, black spots or black spots may form.

2. Wear of production equipment. During long-term use, production equipment may wear out, http://www.zhanyict.com/en/ProductsDetail-VB-10439.htmland the released tiny metal particles may adhere to the inside of the thermos cup, forming black lines or spots.

3. During the welding process, insufficient shielding gas or impure welding materials may cause black oxidation or residue in the weld area.

4. Although some people say that this phenomenon at the bottom of the cup does not affect its use, to me this is an unqualified product. http://www.zhanyict.com/en/ProductsDetail-VB-10439.htmlFriends, does the thermos cup you purchased have this phenomenon?

In some replies, the editor found that the bottom welding of some thermos bottles actually had obvious jagged edges. This effect is usually caused by poor welding technology or improper equipment adjustment. http://www.zhanyict.com/en/ProductsDetail-VB-10439.htmlUnder the same strict quality standards, the editor also believes that it is an unqualified product. The reasons are as follows:

Improper control of welding speed and power. If the moving speed during welding is too fast or the welding power is set improperly, it may cause uneven welds and form jagged edges. http://www.zhanyict.com/en/ProductsDetail-VB-10439.htmlIt can also be understood that the production factory is just blindly pursuing production efficiency in order to reduce costs.

Equipment accuracy problem: If the welding equipment used is not accurate, it may also cause uneven weld edges.

Regarding the phenomenon of black lines, black dots and black spots, many friends said that the customer service said that they will disappear after cleaning and will not affect the use. http://www.zhanyict.com/en/ProductsDetail-VB-10439.htmlYou can try it. If it is indeed as the customer service said, then most of them are probably just dirty and will not affect continued use. Regarding the sawtooth phenomenon, since this is only caused by production technology and quality management, it does not affect continued use. You can only decide based on your own living habits and quality requirements.