Microstructural Evolution of Two Medium Carbon Microalloyed Steels during Hot Forging Process

2005 ◽  
Vol 500-501 ◽  
pp. 155-162 ◽  
Author(s):  
A. Al Omar ◽  
A. Chenaoui ◽  
Rachid Dkiouak ◽  
Jose María Cabrera ◽  
Jose Manuel Prado
Keyword(s):  
Microstructural Evolution ◽  
Hot Forging ◽  
Microalloyed Steels ◽  
Hollomon Parameter ◽  
Medium Carbon ◽  
Grain Sizes ◽  
Recrystallized Grain Size ◽  
Carbon Microalloyed ◽  
Hot Forging Process ◽  
Cyclic Dynamic

The main aim of the present investigation was to study the flow behaviour of two medium carbon microalloyed steels under hot forming conditions, and to analyse its microstructural evolution. The dependence of recrystallized grain size (Drec) on the Zener-Hollomon parameter Z shows a bimodal behaviour with transition from single to cyclic dynamic recrystallization. Also we observed that the variation of Drec normalized by Burgers vector (b) with sss normalized by shear modulus ( µ) shows the same bimodal behaviour cited above. The Derby’s universal equation cited in literature for recrystallized grain sizes was not followed; it seems that the presence of fine precipitated particles has a clear effect on this disagreement.

scholarly journals Effects of deformation on the microstructure of a Ti-V microalloyed steel in the phase transition region

2004 ◽  
Vol 57 (4) ◽  
pp. 303-311
Author(s):  
Wiliam Regone ◽  
Sérgio Tonini Button
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
Transition Region ◽  
Microstructural Evolution ◽  
Microalloyed Steel ◽  
Hot Forging ◽  
Microalloyed Steels ◽  
Air Cooling ◽  
Water Cooling ◽  
Phase Transition Region

Microalloyed steels are used in the forging of many automotive parts like crankshafts and connecting rods. They are hot worked in a sequence of stages that includes the heating to the soaking temperature, followed by forging steps, and finally the controlled cooling to define the microstructure and mechanical properties. In this work it was investigated the thermomechanical behavior and the microstructural evolution of a Ti-V microalloyed steel in the phase transition region. Torsion tests were done with multiple steps with true strain equal to 0.26 in each step. After each torsion step the samples were continuous cooled for 15 seconds to simulate hot forging conditions. These tests provided results for the temperature at the beginning of the phase transformation, and allowed to analyze the microstructural changes. Also, workability tests were held to analyze the microstructural evolution by optical and scanning electron microscopy. Results from the torsion tests showed that the temperature for the beginning of phase transformation is about 700 ºC. Workability tests held at 700 ºC followed by water-cooling presented microstructures with different regions: strain hardened, and static and dynamic recrystallized. Workability tests at 700 ºC followed by air-cooling showed a complex microstructure with ferrite, bainite and martensite, while tests at 650 and 600 ºC followed by water-cooling showed a microstructure with allotriomorphic ferrite present in the grain boundaries of the previous austenite.

New post forging treatment of medium carbon microalloyed steels

1997 ◽  
Vol 68 (6) ◽  
pp. 266-271 ◽  
Author(s):  
Radko Kaspar ◽  
Ignacio Gonzälez-Baquet ◽  
Johannes Richter ◽  
Georg Nußbaum ◽  
Alfred Köthe
Keyword(s):  
Microalloyed Steels ◽  
Medium Carbon ◽  
Carbon Microalloyed

scholarly journals Effect of High Ti Contents on Austenite Microstructural Evolution During Hot Deformation in Low Carbon Nb Microalloyed Steels

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 165 ◽  
Author(s):  
Leire García-Sesma ◽  
Beatriz López ◽  
Beatriz Pereda
Keyword(s):  
Microstructural Evolution ◽  
Hot Deformation ◽  
Solute Drag ◽  
Carbon Steels ◽  
Microalloyed Steels ◽  
Low Carbon ◽  
Grain Sizes ◽  
Austenite Recrystallization ◽  
Pancaked Austenite

This work has focused on the study of hot working behavior of Ti-Nb microalloyed steels with high Ti contents (> 0.05%). The role of Nb during the hot deformation of low carbon steels is well known: it mainly retards austenite recrystallization, leading to pancaked austenite microstructures before phase transformation and to refined room temperature microstructures. However, to design rolling schedules that result in properly conditioned austenite microstructures, it is necessary to develop models that take into account the effect of high Ti concentrations on the microstructural evolution of austenite. To that end, in this work torsion tests were performed to investigate the microstructural evolution during hot deformation of steels microalloyed with 0.03% Nb and different high Ti concentrations (0.05%, 0.1%, 0.15%). It was observed that the 0.1% and 0.15% Ti additions resulted in retarded softening kinetics at all the temperatures. This retardation can be mainly attributed to the solute drag effect exerted by Ti in solid solution. The precipitation state of the steels after reheating and after deformation was characterized and the applicability of existing microstructural evolution models was also evaluated. Determined recrystallization kinetics and recrystallized grain sizes reasonably agree with those predicted by equations previously developed for Nb-Ti microalloyed steels with lower Ti concentrations (<0.05%).

Application of thermomechanical treatment on medium-carbon microalloyed steels continuously cooled from forging temperature

1997 ◽  
Vol 68 (1) ◽  
pp. 27-31 ◽  
Author(s):  
Radko Kaspar ◽  
Ignacio González-Baquet ◽  
Nadja Schreiber ◽  
Johannes Richter ◽  
Georg Nußbaum ◽  
...  
Keyword(s):  
Thermomechanical Treatment ◽  
Microalloyed Steels ◽  
Medium Carbon ◽  
Carbon Microalloyed
Sign in / Sign up

Export Citation Format

Share Document