The powder manufacturer considers that it is used to cover the open riser of carbon steel, alloy steel, high manganese steel, cast steel and other castings and the common riser of sand mould. The powder manufacturer uses the riser cover, riser cover or riser heat preservation covering agent according to different risers. The powder manufacturer considers that the product covers the riser and immediately burns and heats, so that the solidification time of the riser is prolonged by 4-5 times and the heat preservation time is 30 minutes. About the same time, non-powder manufacturers believe that it affects the quality of the original metal. It obviously prolongs the time of top crust formation of riser. Molten steel in riser is under the action of atmospheric pressure for a long time, and improves the feeding efficiency of riser greatly, which is conducive to gas precipitation and inclusion floatation in castings.