Castings are metal moulded objects obtained by various casting methods, i.e. the smelted liquid metal is injected into the pre-prepared mould by pouring, pressure injection, inhalation or other casting methods, and after cooling down and subsequent processing such as grinding, the object is obtained with a certain shape, size and performance. The use of castings is very wide, has been used to hardware and the entire mechanical and electronic industry, and its use is into the trend of continuous expansion. Specifically used in construction, hardware, equipment, construction machinery and other large machinery, machine tools, ships, aerospace, automotive, locomotive, electronics, computers, electrical appliances, lamps and other industries, many of them are ordinary people all day contact, but do not understand the metal objects.

Where HT250 is the grade of grey cast iron, HT stands for grey cast iron, HT is the abbreviation of grey cast iron in Hanyu Pinyin, grey cast iron HT250 means the minimum tensile strength of 250MPa for ø30 specimens.