Since the early 1970s, heating insulation materials have been widely used in the casting industry to make riser sleeves to improve the feeding efficiency of risers. Good results have been achieved in the application of exothermic riser sleeve in steel castings and nodular iron castings.
After the exothermic riser sleeve is poured with molten metal, the heating material burns and releases a large amount of heat, so as to delay the solidification time of molten steel in the riser and improve the feeding efficiency.
Shanghai hoisting and transportation machinery factory and Xinjiang Karamay machinery factory adopt the blind exothermic sleeve process to give full play to the role of the riser, which reduces the design size of the riser sleeve and improves the process yield of castings, generally reaching 70 ~ 80%. The heating riser sleeve developed by relevant units is applied to nodular iron hydraulic parts, the feeding efficiency reaches 80%, and the heating material is saved by 25%.
The foundry riser sleeve is mainly composed of heating materials, heating insulation materials, oxygen supply materials, refractory backbone materials, and adhesives.
1. Heating material: aluminum powder, 12 mesh; Ferrosilicon powder, 5175 ferrosilicons, over 40 ~ 70 mesh; Iron oxide powder, over 40 ~ 70 mesh.
2. Heating and thermal insulation materials generally use wood carbon particles and sawdust. Its function is to prolong the combustion time of heating materials and ease the effect. After wood carbon particles and sawdust are burned, many pores appear in the heating sleeve, which has the function of heat preservation.
3. The oxygen supply material sodium nitrate is used to decompose and release oxygen atoms at high temperatures.
4. Refractory backbone materials slow down the reaction of heating materials and reduce costs. It is mainly composed of bauxite or quartz sand.
5. The adhesive is sodium silicate and clay.