Nodular iron pipe was manufactured by means of suspension liquid as coating which was prepared by diatomite as refractory in inner-wall of pipe mold.Raw material for coating

coating preparation and its performance as well as proper coating ways were described.The experimental results show that bentonite slurry should be stirred for 2 hours continuously and then held for 10 hours to prepare coating.Diatomite is the desirable refractory for thermal mold coating.For pipe-mold with small aperture

bentonite content should be higher to some extent

where the weight ratio of diatomite content to bentonite is approximately（8～15）to 1

while for pipe mold with large aperture

bentonite content should be lower

where the weight ratio of diatomite content to bentonite is approximately（12～20）to 1.Spraying with gas was a acceptable access.