Jin-Gyeong Kim

Evaluation of the Corrosion Property on the Welded Zone of Cast Steel Piston Crown with Types of Electrode

Wear and corrosion of the engine parts surrounded with combustion chamber is more serious compared to the other parts of the engine because temperature of the exhaust gas in a combustion chamber is getting higher and higher with increasing of using the heavy oil of low quality. Therefore, an optimum repair weldment as well as an available choice of the base metal for these parts are very important to prolong their lifetime in a economical point of view. It reported that there was an experimental result for repair weldment on the forged steel which would be generally used with piston crown material, however, it is considered that there is no study for the repair weldment on the cast steel of piston crown material. In this study, four types of electrodes such as 1.25Cr-0.5Mo, 0.5Mo Inconel 625 and 718 were welded with SMAW and GTAW methods on the cast steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected zone and base metal were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% H 2SO4 solution. In the cases of Inconel 625, 718, the weld metals and base metals exhibited the best and worst corrosion resistance respectively, however, 1.25Cr-0.5Mo and 0.5Mo indicated that corrosion resistance of the base metal was better than the weld metal. And the weld metal welded with electrodes of Inconel 625 revealed the best corrosion resistance among the electrodes, and Inconel 718 followed the Inconel 625. Hardness relatively also indicated higher value in the weld metal compared to heat affected zone and base metal. In particular, Inconel 718 indicated the highest value of hardness compared to other electrodes in the heat affected zone.

Electrochemical Evaluation of Corrosion Property of Welded Zone of Seawater Pipe by DC Shielded Metal Arc Welding with Types of Electrodes

The seawater pipes in the engine rooms of ships are surrounded by severely corrosive environments caused by fast flowing seawater contai- ning chloride ions, high conductivity, etc. Therefore, it has been reported that seawater leakage often occurs at a seawater pipe because of local corro- sion. In addition, the leakage area is usually welded using shielded metal arc welding with various electrodes. In this study, when seawater pipes were welded with four types of electrodes(E4311, E4301, E4313, and E4316), the difference between the corrosion resistance values in their welding zones was investigated using an electrochemical method. Although the corrosion potential of a weld metal zone welded with the E4316 electrode showed the lowest value compared to the other electrodes, its corrosion resistance exhibited the best value compared to the other electrodes. In addition, a heat affected zone welded with the E4316 electrode also appeared to have the best corrosion resistance among the electrodes. Furthermore, the corrosion resistance of the weld metal zone and heat affected zone exhibited relatively better properties than that of the base metal zone in all of the cases welded with the four types of electrodes. Furthermore, the hardness values of all the weld metal zones were higher than the base metal zone.

Evaluation of Corrosion Property of Welding Zone of Stainless Steel by Laser Welding

*Department of Marine Equipment Engineering, Korea Maritime Uni versity, Pusan, Korea**Department of Marine System Engineering, Korea Maritime Unive rsity, Pusan, Korea***Education and Research Division, Korea Institute of Maritime and Fisheries Technology. Pusan, KoreaKEY WORDS: Laser welding 레이저용접, Intergranular corrosion 입계부식, Weld metal 용접금속, Heat affected zone 열영향부, Corrosion current density 부식전류밀도, Chromium depletion 크롬결핍ABSTRACT: Laser welding was carried out on austenitic 304 (STS 304) and 2 2 APU stainless steels. In this case, the differences between t he corrosion characteristics of the welding zones of the two stain less steels were investigated using electrochemical methods. Th e Vickers hardness values of the weld metal (WM) zones in both cases, the STS 304 and 22 APU stainless steels, showed relatively higher values th an those of other welding zones. The corrosion current densities of the heat affe cted zone (HAZ) of the 22 APU and the base metal (BM) zone of t he STS 304 exhibited the highest values compared to the other welding zone s. It is generally accepted that when STS 304 stainless steel i s welded using a general welding method, intergranular corrosion is often observ ed at the grain boundary because of its chromium depletion area . However, when laser welding was performed on both the STS 304 and 22 APU stai nless steels, no intergranular corrosion was observed at any of the welding zones. Consequently, it is considered that the intergranular co rrosion of stainless steel can be controlled with the application of laser welding.교신저자 김진경: 부산광역시 영도구 동삼동 1125번지, 051-620-5791, jg21kim@naver.com