People's Daily Online once said that "304 steel is recommended for the purchase of stainless steel products." 304 steel refers to stainless steel with a chromium content of 18% and a nickel content of 8%. The "18-8" we see on 304 stainless steel products is the content of chromium and nickel. The codes of other stainless steel products such as "13-0" (420 steel) and "18-0" (430 steel) also refer to the content of these two metals.
304 steel is corrosion-resistant and high-temperature resistant (800°C). It is a nationally recognized food-grade stainless steel and is widely used in corrosion-resistant containers, tableware, furniture, and medical equipment. Therefore, 304 stainless steel products purchased through formal channels are already very safe, and you can choose with confidence.
316 stainless steel can be said to be an upgraded version based on 304 (control the proportion of impurities, add 2% molybdenum). Therefore, the high temperature strength has jumped to 1200 degrees, and the toughness, hardness and corrosion resistance are stronger than 304 steel. But strength also has a price, that is, the cost is higher and the price is more expensive.
But as far as it is used as a vacuum flask, 304 is enough to meet the needs, and the better performance of 316 is somewhat overkill in this regard. Therefore, 316 is more used in medical equipment.