The aim of this work was to establish a temperature of finish rolling stage of Nb/Ti microalloyed steel containing 0.06 wt.% C, 0.77 wt.% Mn, 0.039 wt.% Nb and 0.015 wt.% Ti, using physical simulation. Samples were subjected to laboratory simulation at a twist plastometer at high temperatures, i.e. between 825 and 950 °C. Five pass deformation and interpass times were selected in accordance with a processing parameters at five stand finishing hot strip mill. Restoration (recovery and/or recrystallization) behavior was evaluated by calculation of Fraction Softening (FS) and Area Softening Parameter (ASP) values. At 950 °C all individual pass stress-strain curves, FS and ASP show full recrystallization in all interpass intervals. On the other hand, with a decrease in temperature to the interval of 875-825 °C, the extent of restoration is decreasing, leading to recovery as a sole softening mechanism at 825 °C, which was confirmed by the stress-strain curve shape, and values of FS and ASP. It is assumed that, due to high supersaturation, strain-induced precipitation promoted pinning of grain and subgrain boundaries and suppressed recrystallization. Therefore, the critical temperature for finish rolling was estimated to be 825 °C.

LPG cylinders are a type of pressure vessel that requires extreme care to store pressurized gas. This study addresses the determination and prediction of burst pressure (BP) and burst failure location in liquefied petroleum gas (LPG) fuel tanks using both experimental and finite element analysis (FEA) approaches. Experimental burst test studies were conducted hydrostatically and water was applied to the interior of the cylinder. A detailed finite element analysis of LPG cylinders is performed with the ABAQUS software and these analyses help to predict the burst pressure of the LPG cylinder when an internal load acts on it. Therefore, the burst pressure results were predicted and compared to experimental ones.

Liquefied Petroleum Gas (LPG) cylinder is a thin pressure vessel used to meet energy requirements in household applications. Bursting of a pressure vessel is disastrous and many fatal accidents are happened due to pressure vessel bursting. The main goal of the current paper is focused to determine experimentally the burst pressures (BP) and failure locations of LPG cylinders. To ensure that the cylinders are in conformance with International Standards. The experiments were carried out on two samples of LPG cylinders used in Libya (C1 and C2). The experimental burst test investigations done by hydrostatic test in which the cylinders were internally pressurized with water. The permanent volume expansions of the LPG cylinders due to internal pressure were also examined. All tests in this study were subject to standard specifications (ISO 4706), which is needed to be conducted on LPG cylinders before introducing them to the Libyan market. Among these tests, the hydro-tests are major tests to be conducted on LPG Cylinders to get approval and acceptance. Hydro-tests on LPG cylinders reveal permanent volumetric expansion of the cylinder, nominal hoop stresses at the time of destruction and the internal pressure at which a cylinder burst. These values are important to ensure that the design and construction of cylinders are safe and compiled to standards.

The main goal of the current paper is focused to investigate and reveal the importance critical

transition temperatures. Different techniques were used to reveal the critical transition temperatures.

The medium carbon vanadium titanium and titanium free micro alloyed steels tested in this work by

isothermal treatment. In order to reveal experimentally the critical forming temperatures and

compare it by predicted using equations and also describe the influence of alloying elements

on the transformation behavior, martensitic starting formation temperature. This study

has been carried out over a wide range of isothermal treatment temperature (270-350

The main goal of the current paper is focused to investigate the effect of isothermal heat treatment

temperature and time on microstructure and strength in a medium carbon vanadium titanium free micro

alloyed steel. Isothermal heat treatment was carried out in the temperature range 350 to 600 C° at

different holding times varying from 2s to 1200s followed by water quenching. Samples were

investigated using optical microscope (OM) and scanning electron microscopy (SEM) paired with

energy dispersive spectroscopy (EDS) and by compressive testing using a servo-hydraulic testing

machine. The results show that, the final microstructure of samples held at high temperatures (550 and

600°C) consists of polygonal intra-granularly nucleated ferrite idiomorphs, combined with grain

boundary ferrite and pearlite were produced and followed by retained austenite that transformed to

martensite upon quenching (incomplete transformation phenomenon). At intermediate temperatures

(450 and 500 °C) an interlocked acicular ferrite (AF) microstructure is produced, hence acicular ferrite

becomes prevalent in the microstructure at (450 °C). The microstructure after the heat treatment at

500°C consists coarse nonpolygonal ferrite grains separated by pearlite colonies. However, at low

temperatures (400 and 350°C), the final microstructure of the samples held at 350°C consists of

bainitic sheaves, where the sheave of parallel acicular ferrite plates, similar to bainitic sheaves but

intra-granularly nucleated were observed, which called in some references as sheaf type acicular ferrite

for samples isothermally treated at 400°C. Yield stress was determined by compression testing on samples

with final Microstructure, the results show that, the observed change in the microstructure is related by a

marked decrease of compressive yield strength, approximately from 1000 to 700 MPa.

Isothermal transformation characteristics of a medium carbon Ti-V microalloyed steel were

investigated using light microscopy, scanning electron microscopy (SEM) equipped with energy

dispersive spectroscopy (EDS), and by uniaxial compressive testing. Samples austenitized on 1100 C

were isothermally treated in the range from 350 to 600 C and subsequently water quenched. The

final microstructure of the samples held at 350 C consisted of bainitic sheaves and had compressive

yield strength, approximately from 1000 MPa, which is attributed to high dislocation density of

low bainite. At 400 and 450 C, acicular ferrite became prevalent in the microstructure. It was also

formed by a displacive mechanism, but the dislocation density was lower, leading to a decrease of

compressive yield strength to approximately 700 MPa. The microstructure after the heat treatment at

500 C consisted of coarse non-polygonal ferrite grains separated by pearlite colonies, principally

dislocation free grains, so that the compressive YS reached a minimum value of about 700 MPa. The

microstructure of the samples heat-treated at 550 and 600 C consisted of pearlite and both grain

boundary and intragranular ferrite, alongside with some martensite. After 600 s, austenite became

stable and transformed to martensite after water quenching. Therefore, the presence of martensite

increased the compressive YS to approx. 800 MPa.

This work is focused on nucleation stages during isothermal austenite decomposition in two medium carbon Vanadium Ti / Ti free micro alloyed steels. Isothermal treatment was carried out in the temperature range 350 to 600οC. Metallographic evaluation using optical and scanning electron microscopy (SEM) enabled determination of the nucleation onset phases of isothermally decomposed austenite. Mainly three phases are found to be relevant to this initiation stage of transformation: first is related to grain boundary nucleated ferrite (GBF), second is related to intra-granularly nucleated ferrite (IGF) and the third to pearlite (P). GBF and IGF are divided into the high temperature and the low temperature segments as consequence of either displacive or diffusion nature of transformation. Addition of titanium to V – micro alloyed steel in this work seems to be balanced by a slightly higher C and Mn content, leading to limited effect on nucleation stage of austenite decomposition. The results show that during continuous cooling, onset of pearlite phase can take place. It occurs at temperatures ≥ 500 C°, followed by an incomplete reaction phenomenon. The main characteristics of pearlite is always nucleated on the surface between proeutectoid ferrite and austenite. Incubation time for onset of pearlite decrease with decrease of temperature.

The aim of the present paper is focused on nucleation onset and development morphologies of acicular ferrite and to evaluate microstructure and mechanical properties during isothermal austenite transformation in titanium free micro-alloyed steel. Isothermal treatment was carried out in the temperature range 350 to 450 C. These treatments were interrupted at different times between 2 and 1800 s in order to analyze the evolution of the microstructure. Yield stress was determined by compression testing on samples with final Microstructure. The metallographic evaluation was done by using optical and scanning electron microscopy (SEM) enabled determination of the nucleation onset at all treatments and subsequent on the development of acicular ferrite of isothermally treated titanium free micro-alloyed steel. The results show that during continuous cooling, dominantly acicular ferrite microstructure is formed. Main characteristics of acicular ferrite are intragranular nucleation and strongly disorganized microstructure with a larger ability to deflect cracks. Acicular ferrite is, therefore, widely recognized to be a desirable microstructure due to good mechanical properties.

. The aim of the present paper is focused on post weld heat treatment qualification by

describes the results of an investigation to understand the micro structural changes that taken place in type 304L stainless steel weld deposits as function of temperature / time by showing any presence of re-crystallization and / or strain induced grain boundary migration and the dissolution of any carbide formed at grain boundaries in welding monitored by metallographic examination.

Data required for calculation the static re-crystallization kinetics have been evaluated from laboratory simulations. Series of two hit isothermal tests were conducted on high temperature torsion machine. These tests were conducted on four different temperatures and using inter-pass times between 0.5 and 5s with aim to investigate the influence of thermal activation on static re-crystallization. All tests were conducted on temperatures over TNR temperature, i.e. in temperature range in which all niobium is present only in solid solution. Method of evaluation of re-crystallization fraction was mechanical metallography, i.e. evaluation based on shape of each stress- strain curve. The fraction softening was calculated for all temperatures, together with avrami exponent, nA, and activation energy for re-crystallization, QSRX. Activation energy for static re-crystallization QSRX  281 KJ/mol and avrami exponent nA  1 determined in this work are in excellent agreement with previously reported data.