Research And Application Of Sulfur Resistance Coatings Used In Ductile Iron Casting

When the furan resin-bonded molds hardened by para-toluenes-ulfonic Acidis usedin pouring ductile iron, a layer of flake graphite layers will appear on the casting surface，that will decline the mechanical properties of the castings significantly.The problem canbe effectively reduce through using an alcohol based sulfur resistance coating on thesurface of the furan resin-bonded molds. This paper aim to develop a casting coatingswith good comprehensive performance to solve this problem.Through researched in thechoice of coating refractory powder, coating preparation process,coating performancetesting, the actual effect of resistance sulfur and so on,the following results wereachieved.Through a comprehensive analysis of common fire-resistant cast iron powder,andaccording to the increases of the sulfur content within the coating after thepouring,finally, dolomite powder, graphite powder, silica powder, talc, and iron pinkwere choosed as refractory powder.In order to analyze the suspension performance of several suspending agent, therate of gel and soft level of coating were compared.finally,F-80suspending agent wasselected. Preparation process was analyzed and the coating preparation process andadditives pretreatment were determined.Several experimental design such as sngle-factor method, orthogonal method weremade to analyze the coating performance of each components, and optimize the coatingformulation. the best ratio of coating (total mass fraction of refractory powder),15%dolomite powder, earthy graphite powder5%,15%flake graphite powder, talcumpowder6%,4%iron pink, quartz powder55%, F-80suspending agent5%,1.5%phenolic resin, rosin0.5%,0.1%polyvinyl butyral,industrial alcohol amount (dosagebased on density and Baume degree to ensure that the density of1.17~1.20g/cm~3,Baume degree in the25~30Be`). Proved by the actual casting,the sulfur resistance coatings prepared in this paper hasgood use process performance, high strength, resistance to rub off, good suspensionperformance, good leveling, and no flow marks, no bubbles,no other obvious defectsafter pouring, achieve the commodity standards. While metallographic observation wasmade to the casting, we found that compared with other coatings the thickness of flakegraphite in the cast`s surface was reduced nearly50%,besides it has low cost.Experiment were made to compare with several other types of coating, andaccording to the results,we analyze the mechanism of coating resistance sulfur. Thechange in sulfur content of coating after pouring was selected to expressed thecoatings`absorption of sulfur. ESEM experiment picture and permeabilitymeasurements of sintered coating was selected to expressed the ability of coating toshield gas. These indicators have a more accurate to Measure the sulfur resistance ofthe coating, and hava a strong reference value.