Coating capable of improving thickness of graphite layer on inner surface of precision casting and preparation process of coating

Abstract

The invention discloses a coating capable of improving the thickness of a graphite layer on the inner surface of a precision casting. The coating comprises an organic solvent and a solute, wherein the organic solvent is ethyl alcohol, and the solute comprises 60-65 parts of bauxite, 3-6 parts of electrolytic cerium, 1-3 parts of sodium bentonite, 3-7 parts of graphite and 1-1.5 parts of a dispersing agent. The baume degree of the coating is 62-68. According to the invention, 200-300-mesh bauxite, graphite, sodium bentonite and electrolytic cerium are adopted, and the active electrolytic cerium is added in a refractory material, so that a matrix can have good high-temperature strength and stability. The electrolytic cerium can promote the ductile progress of high-nickel austenitic nodular cast iron and reduces the formation of layered graphite layers. The coating is simple in formula, practical, simple and convenient in preparation process and full in effect and is worthy of application and promotion.

Description

technical field [0001] The invention belongs to the technical field of casting auxiliary materials, and in particular relates to a coating for improving the graphite layer thickness on the inner surface of precision castings and a preparation process thereof. Background technique [0002] High-nickel austenitic ductile iron has been used more and more in the manufacture of automobile exhaust pipes due to its good heat resistance and corrosion resistance, but due to its special solidification method, the cooling process of its inner surface is difficult The crystallization conditions are different from the outside, and it has a different structure and performance from the inside, which makes flake graphite defects appear on the inner surface, especially complex pipe castings; it seriously affects the quality of the castings, resulting in lower product qualification rates and performance declines, and This kind of defect often occurs at the intersection of pipe fittings or h...

AI Technical Summary

Problems solved by technology

The coating has a density of 1200-1400kg / m3 and is composed of a solute and an organic solvent; the organic solvent is selected from one or more mixtures of methanol, ethanol, and isopropanol; the solute includes the following components in weight percentage: aluminum Bauxite 60-75%, attapulgite 1-5%, sodium bentonite 0.5-1.5%, amorphous graphite 2-10%, flake graphite 3-15%, iron red 2-10%, polyvinyl alcohol shrinkage Butyraldehyde 1-5%, surfactant 0.1-0.5%, dispersant 0.1-0.5%, hydrochloric acid solution 1-5%; but it is not suitable for improving the graphite layer of high-nickel ductile iron castings, so a kind of high-nickel ductile iron casting is required. Nickel Ductile Iron Graphite Layer Maximized Treatment Coating