Vacuum metallurgy is a metallurgical operation under the condition of lower than standard atmospheric pressure. It can realize metallurgical processes that cannot be carried out in the atmosphere, prevent metal oxidation, separate substances with different boiling points, remove gases or impuriti...

In the era of traditional farmers, the easiest and cheapest way of transportation is manpower. Those from well-off families will use camels, cows and donkeys to assist in consignment. Due to limited energy, we cannot handle more cargo in a short time. Over time, various inventions came into being...