Analysis of phase transformation in high strength low alloyed steels

The effect of low-alloy additions on phase transformation of high strength low alloyed steels is reported. Various as-quenched materials with microstructures consisting of low carbon (granular) bainitic, mixed bainitic/martensitic and fully martensitic microstructures were reproduced in laboratory. Results show that for a given cooling rate, an increase of austenite grain size (AGS) and of Mo and Cr contents decreases the transformation temperatures and promotes martensite formation

Thermo-mechanical process parameters effect on a 9 % Cr-2 % W steel

In this paper the effect of thermo-mechanical parameters on the mechanical behavior of a 9 % Cr-2 % W steel is investigated by hot rolling and heat treatment on pilot scale. Results show a strong effect of reheating temperature before rolling on the material hardness, due to an increase of hardenability following the austenite grain growth. A poor effect of the hot reduction and of the following tempering temperature is detected in the total investigated deformation range. A loss of impact energy is found coupled with the hardness increase. The tensile properties values are strongly depending upon the tempering temperature and an increase of tensile yield stress (Rp0,2) and ultimate stress (Rm) have been recorded in tensile test carried on at T = 550°C and T = 650°C

RETRACTION of the paper: About some issues concerning shape memory alloys application s in neuro-rehabilitation, METABK 59(1) (2020), 137-140.

RETRACTION NOTICE for the paper: About some issues concerning shape memory alloys application s in neuro-rehabilitation, METABK 59(1) (2020), 137-140

Analysis of anisotropic hardening in high strength steel (HSS) in line pipes for strain-based applications

In this paper are reported the results of an extensive and innovative mechanical characterization carried out on three large diameter line pipes for gas transportation useful to calibrate a new plasticity finite element numerical simulation (FEM) model developed at Rina Consulting – Centro Sviluppo Materiali. In particular, the anisotropic hardening for the materials has been characterized by tensile tests carried out in the base material of the pipe with tensile specimen extracted along different orientations, considering also the pipe through thickness direction

Pipe diameter and pipe thickness effect on the plastic deformation behaviour of austenitic stainless steels

The high quality standards required for metal forming call for compliance tests aimed to guarantee that such standards are faced. Such tests often implies a waste of time and of economic resources. In particular, if stainless steel pipe forming is considered, many factors need to be taken into account. Scope of the work presented in this paper is to analyse the effect of different process parameters and geometrical constrains on the cold forming of austenitic stainless steel pipes by Finite Element Method (FEM). Results of such analysis will allow to map the effect of different parameters

DILATOMETRIC STUDY OF HIGH STRENGTH STEELS HARDENABILITY

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Vanadium micro-alloyed high strength steels for forgings

To fulfill the industrial demand of forged steels with high tensile properties and microstructural requirements coupled with reduced cost, the possibility to increase the properties of C-Mn steels by means of precipitation strengthening as achieved by micro-alloying (and without the addition of expensive elements such as Mo and Cr) has been evaluated. In order to do that, the effect of V addition has been exploited by means of metallurgical modelling followed by a laboratory ingot manufacturing. Heat treatment has been designed aimed to achieve the desired target tensile properties. Results show that ASTM A694 F70 grade requirements can bel fulfilled by 0,15% V addition and a proper heat treatment in a ferrite-pearlite microstructure, representative of a forged component

Analysis of the micro-voids fraction in structural steels and its evolution during plastic deformation until failure

In this work the results of an experimental analysis performed on different steels of commercial use having different microstructure and yield value are reported. The materials were characterized by performing tensile and torsion tests, bringing the material up to rupture. The specimens were extracted according to different orientations to verify the influence of anisotropy on the size and distribution of micro-voids present in the broken material. After the mechanical tests, an analysis was made of the amount of micro-voids present in the original, not deformed material and in the deformed material until failure. The results obtained show that for all the analyzed steels the initial fraction of micro-voids is negligible, and no growth or formation of further voids is observed as the applied plastic deformation increases, even for strain values close to rupture