Grey iron casting is done in a foundry. Grey iron castings are made by pouring molten iron alloys into molds. The finished iron casting may be machined, but grey iron cannot be forged or extruded at any temperature, so it must be cast. Grey iron castings have a lower tensile strength than other cast iron products. A grey iron casting absorbs vibrational energy and converts it to heat, providing excellent damping capability. Because of its high thermal conductivity, strength, durability, machinability, and relatively low cost, grey iron is widely used for valves, engine blocks, brake drums, pump housings, and cast-iron cookware.