In this article we will discuss about: 1. Meaning of Ausforming 2. Ausforming Process 3. Structural Changes 4. Strengthening Factors 5. Important Applications . Request PDF on ResearchGate | Ausforming of medium carbon steel | The prospect of rather than the refinement of microstructure by the ausforming process. PDF | In recent years, the high tensile steels have got much attention in of brittle fracture initiation in bainite steel manufactured by ausforming.
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rather than the refinement of microstructure by the ausforming process. Clear evi- dence is reported for the mechanical stabilisation of the. the mechanical properties of substitute high strength steels, in relation to their potential applications. The ausforming process. It is well known that the isothermal. Ausforming also known as Low and High temperature thermomechanical treatments is a This treatment is an important part in the processing of steel. Its origin originates from early uses of steel management. Discovered by Benjamin, it is currently a.
Primary emphasis was on the improvements possible in rolling contact fatigue. In support of this, heat-treat, corrosion, hardness, and microstructural studies have been performed. It has been shown that a certain process for working steel in the metastable austenitic condition as applied to the rolling contact fatigue life of M bearing steel will substantially improve life, thereby increasing bearing reliability. The remarkable improvements in life exceeding percent will be a significant factor in meeting the long-life-bearing requirements for advanced air-breathing propulsion systems. A metallurgical analysis has been conducted and a mechanism is proposed which is thought to be the primary factor in providing the significant improvements in rolling contact fatigue life. It is shown that these improvements in life are possible without any significant increase in hardness of the subject materials. Evidence is presented which indicates that the life improvement is primarily due to more uniform carbide dispersion, reduction of massive carbide particles, and reduction in martensite platelet size.
Coagulation of carbides and growth of martensitic laths takes place at these temperatures. The creep tests were carried out at and K up to rupture, which occurred after about 4. Zmienko, A. Gudenko, P. Kozlov, A.
For each sample the following research procedure was applied: i identification of all second phases precipitations using differential X-ray analysis method; ii study of spatial distribution of second phases using scanning electron microscope and transmission electron microscope; iii numerical investigation of mass fraction and average size of AB2 particles using developed algorithm of statistical processing of images from electron microscope.
It was found that for all melts mass fraction-time curve has global maximum and the rate of subsequent reduction of mass fraction depends on content of alloying elements. Zheng, F. Zhang, and T.
Wang, Effects of ausforming on isothermal bainite transformation behaviour and microstructural refinement in medium-carbon Si—Al-rich alloy steel, Mater.
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He, A. Zhao, C. Zhi, and H. Fan, Acceleration of nanobainite transformation by multi-step ausforming process, Scripta Mater. CrossRef Google Scholar  W. Li, H. Gao, Z. Nakashima, S. Hata, and W.
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Bhadeshia, Bainite orientation in plastically deformed austenite, Int. CrossRef Google Scholar  J. Zhao, Y. Huang, C. Zhi, and F. Zhao, Acceleration of bainite transformation at low temperature by warm rolling process, Mater.
Today Proc. CrossRef Google Scholar  S. Singh and H. Bhadeshia, Quantitative evidence for mechanical stabilisation of bainite, Mater. A process that both of the two steps were above, Ms Q-B-B , has been demonstrated to increase transformation rate and improve the amount of bainitic ferrite, which probably results from the additional hysteresis free energy provided by the first quenching process. Keywords: nanostructured bainite, bearing steel, two-step austempering process, phase transformation 1.
Introduction The bearing is a basic and key component in many mechanical parts, and bearings with the required properties are necessary for steady operation of the machinery. Therefore, improving the properties of bearing steel has been the goal of material researchers.
Nanostructured bainitic microstructure not only possesses excellent strength and toughness [ 1 , 2 , 3 , 4 , 5 ], but exhibits a high wear resistance and has a better rolling contact fatigue performance compared to the martensitic microstructure [ 6 , 7 , 8 , 9 , 10 , 11 ].
This material is therefore suitable for the bearing application [ 12 , 13 , 14 ]. To obtain the nanostructured bainitic microstructure and a hardness of at least 58 HRC, the steel should be austempered at a lower temperature [ 15 ]. This inevitably results in a long austempering time, which is not acceptable to the bearing industry.
To accelerate kinetics of the bainitic phase transformation, researchers have developed methods such as adding Co and Al [ 16 , 17 ], or reducing Mn [ 18 ] in the steel to enlarge the free energy difference, thus obtaining a higher driving force for phase transformation.
Other approaches include introducing extra stress that is lower than the yield stress, or introducing a magnetic field to induce phase transformation [ 19 , 20 ]. Carrying out the ausforming process before the bainitic phase transformation can also notably influence the kinetics, which are determined by the ausforming temperature and extent of deformation [ 21 , 22 ].