CHARACTERIZATION OF ADHESIVENESS AND BENDING ENDURANCE OF Zn COATING IN GALVANIZED STEEL

• Main Author: YUDAPRAWIRA (NIM : 12506002), PRASASTI
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/23691
• Institution: Institut Teknologi Bandung

Coating of steel using Zn as the coat is a way to increase the resistance of steel against corrosion thus increasing the life time of the steel. In hot-dip galvanizing process, one of the coating techniques process is done by using a non-oxidizing furnace (NOF), so it is no longer required pre-cleaning and fluxing before the galvanizing process. In NOF, the steel is heated to avoid thermal shock to the steel when it dipped into bath of molten zinc. NOF that is being used by PT. Fumira injects H2 with a volume of 40%. The company try to reduce this volume until 20%. There is a concenr that the change of this parameter can cause negatif effect to the mechanical properties of steel, especially the adhesiveness and bending endurance of Zn coat in deep drawing application. Specimen that is being used in this research is a specimen from a coil that has been coated by Zn from PT. Fumira as as received specimen. It is then prepared to for bending test. The test is conducted by bending the specimen to 180°. If there are no cracks on the surface of the bent steel, then the galvanized steel is labelled as 0T quality. However, if the surface of the bent steel has a crack, it is necessary to test the spesimen again by inserting a single specimen with the same thickness between the specimen when the bending is conducted. If there is crack on the surface of the bent steel, then it is labelled 1T quality. The test is done until the galvanized steel is not cracking on the n-test with n-T quality. After that, the bent steel observed using an optical microscope to see whether there are cracks. Further observation is made by using SEM and the chemical composition were analized by using EDX. <br /> <br /> <br /> <br /> In this bending test, the specimens tested did not experience cracking based on visual observation without any magnifying visual aids. The quality of all specimens tested were 0T. However, in the observation using an optical microscope, crack was discovered on the surface of bent specimen. Crack found in the specimens have various sizes, up to 60 &#956;m. After further investigation by using SEM and EDX, the observed crack on the specimen has 99,65% FeO. This is showing the absence of Zn layer covering the steel. Based on this research, the best condition of the study were the specimen that have the smallest crack is the H20-BL specimen. However, further research needs to be done to find out the existence of the oxide and the characteristic of the oxide thickness of each intermetalic layer, due to reduction of % volume of H2 to 20% the specimens have a higher value of thickness and higher value of hardness.