Abstract
The present generation Armoured Tracked Vehicles (ATVs) are constructed using Rolled homogenized armour (RHA) grade steels closely confirming with AISI 4340 specifications. However, in future Armoured Tracked Vehicles (ATVs), the overall weight of ATVs has to be reduced enormously and hence, the designers have prescribed to employ Ultra High Hard Armour (UHA) steels for the construction. Welding is considered to be one of the important fabrication methods in ATVs construction. However, welding of UHA steels is highly challenging due to higher hardness and higher carbon content. Shielded Metal Arc Welding (SMAW) is among the most widely employed welding process in the construction of ATVs since it is more versatile and cost-effective. Armour grade steels are welded conventionally using Austenitic Stainless Steel (ASS) consumables to eliminate the serious problems of hydrogen induced cracking. Hence, in this investigation, an attempt has been made to study the influence of ASS welding consumables on tensile properties and hardness of UHA steel joints made by SMAW process. UHA steel plates having 15 mm thickness were welded by SMAW process using five different ASS consumables (having different Creq/Nieq ratio). Tensile properties (unnotched and notched) of the welded joints were evaluated. From this investigation, it was observed that the joint welded using ASS consumable (having higher Creq/Nieq ratio) exhibited superior tensile properties as result of the evolution of ferrite phase with vermicular and globular morphology in the austenite matrix at weld metal region.
Highlights
Armour steel plates, closely confirming with AISI 4340 specifications, are principally used in construction of Armored Tracked Vehicles (ATVs)
The results indicated that the joints produced using LHF steel electrodes revealed superior tensile properties than Austenitic Stainless Steel (ASS) and HNS electrode joints
From the tensile properties of welded joints, the following inferences were derived: (i) All tensile specimens failed at weld metal region only, irrespective of welding consumables; (ii) The ASS1 joint exhibited lowest tensile strength of 575 MPa, which is only 27 % of base metal (BM) strength
Summary
Armour steel plates, closely confirming with AISI 4340 specifications, are principally used in construction of Armored Tracked Vehicles (ATVs). The problems normally encountered during welding of this steel are hydrogen induced cracking (HIC), heat affected zone (HAZ) softening [1] They are welded, nowadays, using gas metal arc welding (GMAW), shielded metal arc welding (SMAW) and flux cored arc welding (FCAW) processes using austenitic and ferrite consumables. Though these grade steels are meeting all the requirements (as per the military standards) satisfactorily, the mobility of the fighting vehicles in all terrains is of significant importance due to higher overall weight of the vehicles.
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