STRUKTUR MIKRO LAS BAJA C-Mn PADA PENGELASAN BUSUR TERENDAM DENGAN VARIASI MASUKAN PANAS (Microstructure of Submerged Arc C-Mn Steel Weld Metals with Variation of Heat Inputs)

ABSTRACT The present investigation aims to study the effect of heat input on the microstructure of submerged arc C-Mn steel weld metals. Specific attention was paid to the formation of acicular ferrite which improved weld mechanical properties. The welding process was carried out using four different heat inputs, namely 3.99 kJ/mm, 3.19 kJ/mm, 2.12 kJ/mm, and 1.77 kJ/mm. Microstructural examinations were performed using optical microscope in combination with scanning electron microscope (SEM) to study the mechanism in which acicular ferrite was performed. Results showed that weld metal with heat input of 2.12 kJ/mm produced weld metal with a large amount of acicular ferrite at the expense of grain boundary ferrite and Widmanstatten ferrite. It is evident that this acicular ferrite nucleates on the inclusions in the forms of Si02, TiO, and Al203. Key words : heat input, acicular ferrite, mechanical propertie

Development of a process envelope for friction stir welding of DH36 steel : a step change

Friction stir welding of steel presents an array of advantages across many industrial sectors compared to conventional fusion welding techniques. However, the fundamental knowledge of the friction stir welding process in relation to steel remains relatively limited. A microstructure and property evaluation of friction stir welded low alloy steel grade DH36 plate, commonly used in ship and marine applications has been undertaken. In this comprehensive study, plates of 2000 x 200 x 6 mm were butt welded together at varying rotational and traverse speeds. Samples were examined microscopically and by transverse tensile tests. In addition, the work was complemented by Charpy impact testing and micro-hardness testing in various regions of the weld. The study examined a wide range of process parameters; from this, a preliminary process parameter envelope has been developed and initial process parameter sets established that produce commercially attractive excellent quality welds through a substantial increase in the conventionally recognised weld traverse speed

A comprehensive study on the microstructure and mechanical properties of arc girth welded joints of spiral welded high strength API X70 steel pipe

In the paper, the effect of welding technology on the microstructure and mechanical properties of girth welded joints was presented. Metallographic examinations based on light microscopy and SEM were conducted on girth welded joints of API X70 steel pipe. Research has shown that microstructure of the heat-affected zone (HAZ) of MMA girth welded joints is not homogeneous and depends on the thermal history of each area during the welding process. Near the fusion line the zone is coarse, and further away there is a fine-grained zone. In the area of root passes the microstructure consists of recrystallized ferrite grains unlike to cap passes where the fine bainitic microstructure can be observed. In the case of MAG girth welded joints, the weld microstructure consists of primary austenite grains. The primary austenite boundaries serve as nucleation sites of ferrite. The microstructure of the HAZ varies continuously from a coarse—to fine-grained microstructure of the base material. The results of mechanical properties of girth welded joints are also presented. The hardness and strength of arc welded joints depend on welding filler materials as well as welding technology. The results of hardness distribution of MMA and MAG girth welded joints confirmed the results of microstructural evaluation

Advances in friction stir welding of steel : Project HILDA

A microstructure and property evaluation of friction stir welded DH36 6mm plate has been undertaken. The study examined a wide range of process parameters and, from this, a process parameter envelope has been developed and an initial process parameter set established that gives good welding properties. Thermo-mechanical deformation studies were developed to generate flow stress regimes over a range of stain rates and temperatures and these data will support the on-going local numerical modelling development. A preliminary thermo-fluid model has been developed to predict temperature and material flow during the FSW of steel grade DH36. In this model, materials are considered as highly viscous incompressible fluid. The welded material is flowing around the rotating tool thanks to the modelling of the friction at tool/workpiece interface. In parallel, a global numerical model is being developed to predict the inherent residual stresses and distortion of FSW butt welded assemblies often in excess of 6m long plate

Struktur Mikro Las Baja C-Mn Hasil Pengelasan Busur Terendam Dengan Variasi Masukan Panas

This research aims to study the effect of heat input of submerged arc welding on the microstructure of weld metal made from C-Mn steel. The study focused on the formation of acicular ferrite which could improve weld mechanical properties. The welding process was carried out using various heat inputs, i.e. 3.99 kJ/mm, 3.19 kJ/mm, 2.12 kJ/mm, and 1.77 kJ/mm. Microstructural examinations were performed using optical microscope and scanning electron microscope (SEM). Results show that the weld metal welded with heat input 2.12 kJ/mm produces more acicular ferrite than grain boundary and Widmanstatten ferrite. It is evident that this acicular ferrite nucleates on inclusions in the forms of SiO2, TiO, and Al2O3

A comparison between single sided friction stir welded and submerged arc welded DH36 steel thin plate

The adoption of the friction stir welding (FSW) process into the shipbuilding industry is being considered as a medium term issue. Currently the data on friction stir welded mild steels tends to be fragmented, with critical areas being short on specific data e.g. toughness. The work described has been put in place to directly compare friction stir welded and submerged arc welded thin plate. The plate thicknesses used were 4, 6 and 8mm thick DH36 grade steel, which are commonly used in the construction of vessels such and destroyers, frigates corvettes and offshore patrol vessels. Friction stir welding was carried out using the currently best established parameters for a single sided process and this was compared against Submerged Arc Welding (SAW) over the same thickness range. Distortion was found to be lower in friction stir welded steel, but the 4mm thick was still showing significant distortion. No issues were identified with weld metal strength, and toughness at -20OC was found to be comparable but more uniform across the weld area than with the submerged arc welded material. Microstructural observations have been linked to hardness, toughness and fatigue test data. The fatigue data includes the observation of preferential crack initiation relative to the trailing/leading side of the welding process. An assessment on the feasibility of the process in a shipbuilding environment will be included based on the data presented

Metallurgy of armour exhibited at the Palace Armoury, Valletta, Malta

The metallurgy of ten armour pieces from the Palace Armoury Collection in Malta was examined. Results showed that out of ten artefacts examined, six were produced in low carbon steel, one from a high carbon steel and three were made from wrought iron. One of the wrought iron armour pieces was fabricated from a phosphoric iron, an unusual material for these artefacts. All the steel artefacts exhibited a ferrite-pearlite microstructure. In their manufacture, no attempts had been made at producing martensite by full or slack quenching. All metal fragments contained slag inclusions. The elongated nature of the latter suggested that these artefacts were forged into shape.peer-reviewe

Deformation behavior of two continuously cooled vanadium microalloyed steels at liquid nitrogen temperature

The aim of this work was to establish deformation behaviour of two vanadium microalloyed medium carbon steels with different contents of carbon and titanium by tensile testing at 77 K. Samples were reheated at 1250°C/30 min and continuously cooled at still air. Beside acicular ferrite as dominant morphology in both microstructures, the steel with lower content of carbon and negligible amount of titanium contains considerable fraction of grain boundary ferrite and pearlite. It was found that Ti-free steel exhibits higher strain hardening rate and significantly lower elongation at 77 K than the fully acicular ferrite steel. The difference in tensile behavior at 77 K of the two steels has been associated with the influence of the pearlite, together with higher dislocation density of acicular ferrite. [Projekat Ministarstva nauke Republike Srbije, br. OI174004