What are the commonly used materials of Chinese valves? I. Gray cast iron: Gray cast iron is suitable for water, steam, air, gas, oil and other media with nominal pressure PN≤ 1.0mpa and temperature ranging from -10℃ to 200℃.Common grades of gray cast iron are: HT200, HT250, HT300 and HT350.2. Malleable cast iron: suitable for water, steam, air and oil m