The hardness requirements of fire-poured air-cooled steel mainly depend on the specific application scenarios and requirements, which are introduced as follows:

1. First of all, air-cooled steel is a kind of material with good heat resistance and wear resistance, which is usually used to manufacture workpieces in high-temperature working environment, such as high-temperature furnaces and turbine blades. In these applications, air-cooled steel needs to withstand the test of high temperature and high pressure, so its hardness requirements are high.

2. Secondly, the hardness requirement of water air-cooled steel is also related to the specific process and manufacturing requirements. In the heat treatment process of steel, by controlling the parameters such as heating temperature and cooling rate, the steel can reach different hardness.