The Mechanical Properties & Microstructural Analysis Of Welded DPS In Compliance To A Selected International Standard

Noorazmi, Muhammad Naquib (2019) The Mechanical Properties & Microstructural Analysis Of Welded DPS In Compliance To A Selected International Standard. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

This researches is to characterize the effect of annealing temperature to the mechanical properties and microstructure of Dual Phase Steel (DPS) produced through heat treatment of mild steel and also to determine the suitable Dual Phase Steel (DPS) that is in compliance to a selected international standard for welding. High ductility, affordability, weld ability and good machinability characteristics of mild steel has put mild steel into the popular choice of steel for consumers. However, due to lack of alloying elements compared to those found in stainless steel means that mild steel is more prone to corrosion. On the top of that, mild steel also being in the low hit when it comes to strength capability and it restrict the usage of mild steel in applications where load bearing and strength is essential. Even though, mild steel has found its own territory in various industries, some other application needs the material used to be harder, without reducing the formability and stronger while keeping the price affordable and competitive. Dual phase steel (DPS) has been introduced to fill in the gap left by mild steel and provide better strength steel by heat treatment process. The selected for this particular project occurs in the inter critical temperature which is 740°C, 760°C, 780°C and 800°C within the α-ferrite and γ-austenite phase region from Fe-Fe₃C phase diagram. Quenching was done right after austenitizing in order to produced martensite through diffusionless transformation. The volume fraction of martensite (%) was then analyze for each temperature. Characterization of the samples were done by Rockwell Hardness Test (ASTM A370-14) , morphological observation using light microscope and tensile testing is carried out using universal testing machine (UTM) of 500 KN capacity as 5 per ASTM code E8-09 after shielded metal arc welding SMAW process of mild steel and Dual Phase Steel. In the observation the higher intercritical temperature of annealing, the higher the percentage of the martensite volume fraction. For the hardness more volume fraction of martensite, more hardening occur in specimen. Eventhough hardness increase with the higher annealing temperature due to formation of martensite. However, at certain point it already reduces the weldability of Dual Phase Steel. The overall objective of this project has been achieved. Dual phase steel mechanical properties and microstructure analysis had been analyzed and studied, and also shielded metal arc welding. The hardness of the steel was determined from the experiment result.

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