Research On The Storage Stability Of The Magnesium-based Anti-oxidation Coatings For Steel Billet At High Temperature

At present,the high-temperature anti-oxidation technology for steel billet has been valued by scientific research institutions and Steel Corp at home and abroad,and some results have been achieved.However,there are still many problems in industrial application.Among them,the poor storage stability of such coatings is a ubiquitous problem.Generally,sedimentation and stratification occur from a few hours to a day,and even hard precipitation appears,resulting in failure to be used normally.Therefore,the temporary deployment is mostly used in Steel Corp.The poor storage stability will lead to a series of problems:The coating particles are coarse and the coating is uneven,which affects the oxidation resistance.Sedimentation occurs in a short time,so that pipes and spray guns are easily blocked.Hard precipitation causes the coatings to be scrapped,resulting in loss.Small batch allocation seriously affects the production efficiency.Therefore,a wide range of anti-oxidation technology has been obstructing.In view of the above problems,it is of great significance to improve the storage stability of coatings.In this thesis,in view of the poor storage stability technical problems of magnesium-based anti-oxidation coatings for steel billet at high temperature,the effects of the types,dosage of the suspension agent and storage condition on the storage stability of the coatings was discussed successively.The effect of storage time on the oxidation resistance and the mechanism of the high storage stability of the suspension agent were discussed.Specific work as follows:The influence factors of stability and stability mechanism of the anti-oxidation coatings was analyzed and discussed.The settlement rate was calculated by using the Stokes settlement model formula,and the measures to reduce the settlement were proposed,such as reducing particle size,reducing particle density and increasing viscosity.The effects of different kinds of modified etherification starch,such as Excelcon 100,ST 3000,301,FP6 and HPS,on the storage stability of the anti-oxidation coatings were investigated.The experimental results show that the starch thickener as a suspending agent cannot effectively improve the suspending properties of the coatings.One or two days,the coatings moisture and harden,leading to hardening and curing reaction.The effects of hydroxyethyl cellulose,modified hydroxyethyl cellulose and ethyl hydroxyethyl cellulose on the storage stability of the anti-oxidation coatings were studied.Through the study of the influence of suspending agent on the stability of the coatings,two kinds of cellulose ethers,250 HBR or BR 30000H,as suspending agent have a good effect.After 14 days of storage,they still maintain good water retention and flowability.The effects of the amount of 250 HBR and BR 30000H cellulose ethers,storage temperature and other factors on the storage stability were discussed.When the amount of cellulose is 0.26～0.33%and the storage temperature is 25 ℃,sealed and kept away from light,the shelf life of the coatings should be extended for at least 14 days from less than one day.At the same time,the anti-oxidation effect of the anti-oxidation coatings after using the suspending agent on the billet was studied.The oxidation burning rate is reduced by 70%and the oxidation burning loss is still reduced by 50%after the storage for 14 days.And then the protective effect has not changed much with storage time.The suspension stability mechanism of suspending agent was analyzed and discussed by means of scanning electron microscope(SEM),Zeta potentiometer and X-ray diffractometer(XRD).SEM test results show that the coating particles are adhered or embedded in the sol system,so as to play a role of suspension and anti sinking.The results of Zeta potential show that increasing the amount of cellulose ether can increase the absolute value of Zeta potential and make the system in stable state.The XRD test results of suspending agent-containing anti-oxidant coatings show that the suspending agent such as cellulose ether or starch ether will not cause the chemical reaction of the powder,thus ensuring the original function of the anti-oxidation coatings.