Mechanical Properties and Microstructure of Forged Steels

Forged steels represent a quite interesting material family, both from a scientific and commercial point of view, following many applications they can be devoted to [...

Effect of Q&P Process on 0.15C-MnSi Steels

The present study is focused on analyzing the effect of Mn amount on two experimental steel compositions, specially designed for Q&P (Quenching and Partitioning), 0.15C-2.5Mn-1.5Si and 0.15C-3Mn-1.5Si without significant contribution of Al. Two-Step Q&P thermal treatments were performed at laboratory scale in a quenching dilatometer Bähr DIL805A/D. The fractions of retained austenite were evaluated by X-ray diffraction techniques. The mechanical properties of the Q&P samples were evaluated, a strong dependence of strength, uniform elongation and strain hardening values on process parameters has been found. Higher uniform elongation were related to higher residual austenite contents. The 0.15C-3Mn-1.5Si steel showed systematically the largest mechanical values with respect to the 0.15C-2.5Mn-1.5Si steel.Peer ReviewedPostprint (published version

Effect of micro-alloying on quenching behaviour of steels for back-up rolls

The use of micro-alloyed steels for back-up rolls manufacturing gives the possibility to obtain advantages associated with the benefit of the application of micro-alloying elements and thermo-mechanical treatments. In this paper the effect of alloying elements has been evaluated aimed to improve steel hardenability and at the same time to reduce the fabrication cost. 3% Cr and 5% Cr steels are considered with a reduced Mo content. Analysis of alloying on hardenability is performed by means of metallurgical models and on laboratory scale. Results show a higher hardenability in the case of 5% Cr steels. Moreover, such family of steels also show a dependence on prior austenitic grain size. In both the steel families no warnings are detected in terms of residual austenite presence after quenching.</p

NIOBIUM EFFECT ON BASE METAL AND HEAT AFFECTED ZONE MICROSTRUCTURE OF GIRTH WELDED JOINTS

The development of steels for line pipes during the last decades has been driven by the need to obtain improved combinations of high strength, toughness, weldability on industrial scale at affordable prices. The effect of niobium content on the heat affected zone (HAZ) microstructure is reported in this paper. Niobium, for its specific thermodynamic and kinetic attitude to form carbide and nitride precipitates, played a key role in the development of modern HSLA steels Results show that niobium addition is able to refine both the bainitic packet and cells size in the heat affected zone during welding. This implies that niobium addition leads to an improvement of both toughness and hardness of welded joints manufactured by Nb micro-alloyed steels. </p

HEAT TREATMENT EFFECT ON INTERFACE MICROSTRUCTURE AND HARDNESS OF A MEDIUM CARBON STEEL CLADDED BY AISI 316 STAINLESS STEEL

This paper focuses on carbon steel/stainless steel clad plate properties. The cladding was performed by submerged arc welding (SAW) overlay process. Following chemical element diffusion a diffusion layer is formed between stainless steel and carbon steel interface of the cladded plate. Some hardness peaks were detected in the micro-alloyed steel close to the molten interface line in the coarse grained heat affected zone (CGHAZ). Results show that a stress relieving treatment is not sufficient to avoid hardness peaks. On the other hand, the hardness peaks in the CGHAZ of the micro-alloyed steel disappeared after quenching and tempering (Q&T)

ANALYSIS OF HEAT TREATMENT EFFECT ON MICROSTRUCTURAL FEATURES EVOLUTION IN A MICRO-ALLOYED MARTENSITIC STEEL

The microstructural evolution of a quenched and tempered medium-C micro-alloyed steel during tempering is analyzed The steel was heat treated in order to develop fully martensitic microstructures after quenching with different prior austenite grain sizes (AGS).Main results can be summarized as below:A very poor effect of AGS on packet size is found.High-angle boundary grains do not significantly grow after tempering; on the contrary, low-angle grain boundaries (cells) move, fully justifying the hardness evolution with tempering temperature. </ul

corrosion behaviour of aisi 460li super ferritic stainless steel

Following nickel and molybdenum significant price increase, nowadays the stainless steel market is moving toward an increasing use of ferritic stainless steel instead of austenitic stainless and therefore to the development of advanced ferritic stainless steels grades aimed to substitute the more expensive austenitic materials in all applications allowing it. Super-ferritic stainless steels are higher chromium (Cr) and molybdenum (Mo) steels with properties similar to those of standard ferritic alloys. Such elements increase high temperature and corrosion resistance in strong environment. This paper deal about the corrosion resistance of super-ferritic stainless steels with a Cr content ranging from 21% to 24%. </p

EFFECT OF AUSTENITIC GRAIN SIZE ON THE PHASE TRANSFORMATION OF A NOVEL 6.5% CR STEEL FOR FORGED COMPONENTS

In this paper the effect of quenching and tempering (Q&amp;T) thermal treatment on mechanical properties of a novel 6.5% Cr steel for forged components is studied. Main innovation of such steel is in the increased hardenability following the Cr content with respect to the more common 5% Cr steel allowing to add lower content of other elements aimed to achieve the target mechanical properties. Following to the high intrinsic hardenability of such steel based on the Cr content a poor effect of prior austenite grain size should be expected after quenching. Aim of this work is to evaluate such effect and to analyse the dependence of mechanical properties on it. </p

MODELLING PLASTIC DEFORMATION OF STAINLESS STEEL PIPES

Plastic deformation is the most common technique adopted to manufacture complex shape pieces in the most efficient way. Even higher requirements need to be faced in the different applications. In order to target such requirement quality and compliance tests are carried out aimed to guarantee that these standards are faced; this often means a waste of material and economic resources. A far as concerns welded stainless steel pipes many criticises affecting the general trend of subsequent machining need to be considered. In this paper the effects of different process parameters and geometrical constrains on austenitic stainless steel pipe forming are studied by Finite Elements Method (FEM) simulations. The model sensitivity to input parameters is reported. The feasibility of the simulated process is evaluated through the use of Forming Limit Diagrams (FLD). </p

effect of thermo mechanical processes on microstructure evolution in austenitic stainless steels

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