Study On Corrosion Resistance Of High Chromium Cast Iron

Excellent performances of high-chromium cast iron are dependent of (Cr, Fe)7C3type eutectic carbides with high hardness (1200-1800HV) and isolated distribution without forming a network in its microstructure, so it has good abrasion performance and malleability. At present, a lot of researches are done on structure and performance and abrasion performance of high-chromium cast iron, but few researches are done on corrosion and especially static corrosion of the high-chromium cast iron.By cooperating with Tengzhou Dongda Mining Co. Ltd., this paper mainly studies the corrosion situations of common16Cr3Mn and16Cr3MnCu high-chromium cast irons under the working conditions. Based on the analysis of heat treatment process of high-chromium cast iron, chemical composition and microstructure, this paper focuses on corrosion rule features and influences of Cu of corrosion performance under different PH value after subcritical heat treatment of16Cr3Mn and16Cr3MnCu.Based on successfully making subcritical heat treatment samples, this paper first compares the structure before and after going through subcritical heat treatment. Then the author adopts weight-loss method to study16Cr3Mn and16Cr3MnCu’s rule feature of static corrosion in acid or alkaline solution. By comparing the samples’weight differences and microstructure differences before and after corrosion, the paper records and analyzes the corrosion data, and makes a series of XY smooth scatter diagrams. According to the studies, high-chromium cast iron has the optimum corrosion resistance at subcritical treatment temperature of500℃and heat preservation of4hours. Besides, corrosion resistance performance of high-chromium cast iron’s will gradually weaken with the rise of temperature and acidity.In alkaline solution, the author adopts the same experimental method to analyze corrosion features. First of all, by means of microstructure analysis, when high-chromium cast iron goes through subcritical treatment and heat preservation, the author tests that its alkali corrosion resistance to is weaker than the casted. By comparing and analyzing a series of data diagrams, the treated high-chromium cast iron’s corrosion resistance performance becomes gradually decreased with the increased heat preservation time. Similarly, it becomes gradually decreased with the temperature rise of subcritical heat treatment. The author holds that high-chromium cast iron has the optimum corrosion resistance at subcritical treatment temperature of540℃and heat preservation of4hours. Besides, high-chromium cast iron’s alkali corrosion resistance decreases with the temperature rise of alkaline corrosive solution. At room temperature, high-chromium cast iron has a better corrosion resistance. When corrosion temperature rises to80℃, the weight increase of experimental sample is on the rise, and high-chromium cast iron’s corrosion is much stronger.At last, this paper bases on the two samples’composition differences in Cu and studies Cu’s influences towards the microstructure and corrosion performance of high-chromium cast iron. Through the analysis of experiment results, the function of Cu is to increase matrix corrosion potential, decrease the speed of corrosion, promote matrix inactivation, and make inactivation film more stable. Added Cu will improve the corrosion performance of high-chromium cast iron.