Method for combining casting and selective laser melting formation to manufacture large-sized metal part

The invention discloses a method for combining casting and selective laser melting formation to manufacture a large-sized metal part. The method comprises the specific steps that the regular portion of a cast part structure is used as a matrix of selective laser melting, the matrix is installed on a platform of a selective laser melting device, and the matrix is guaranteed to be horizontal; by manually controlling a powder laying scraper of the selective laser melting device to horizontally lay metal powder used for forming a complicated part on the matrix on the cast matrix, powder is repeatedly laid until the powder completely fills in concave portions of the cast matrix, and after filling is completed, the powder on the surface of the matrix is thinned to a layer thickness; Ar gas is fed into a formation bin, independent sintering is manually conducted on the first layer of outline, and an automatic formation system is started to conduct part layered formation until the whole part is formed. By the adoptio