Stevens Point, OH, United States
Stevens Point, OH, United States

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Chavdar B.,EATON Inc | Goldstein R.,Fluxtrol Inc. | Ferguson L.,DANTE Solutions Inc.
23rd International Federation of Heat Treatment and Surface Engineering Congress 2016, IFHTSE 2016 | Year: 2016

Feasibility of making lightweight powertrain products with hot hydroforging of steel/low density material hybrid billets is explored. A bimaterial billet is designed such that a steel wall encloses a low density core 100%. Furthermore the low density core is selected among the materials that have lower melting or softening temperature than steel such as aluminum and glass. In hot hydroforging the bimaterial billet is heated to 1000-1200 C range similar to the conventional hot forging of steel. However, in hot hydroforging the core is in liquid or viscous state while steel shell is in solid state similar to the conventional hydroforming. During hot hydroforging the viscous/liquid core has negligible resistance to flow thereby providing a uniform hydrostatic pressure inside the steel and enabling a uniform deformation of the solid steel wall. Steel/aluminum bimetal billets were prepared. Then, the bimetal billets were hot hydroforged in closed dies in one blow. A uniform steel wall thickness was observed all around the forged part upon cross sectioning. However, there was also a large shrinkage void in the aluminum core. The large shrinkage void is formed due to the CTE mismatch between steel and aluminum and the volume increase of aluminum during phase change. The large shrinkage void can be eliminated if aluminum is replaced by glass that has a matching CTE to that of steel. Furthermore, glass doss not have to be fully melted at forging temperatures thereby mitigating the risks of phase change. On the other hand the molten aluminum core can be emptied out of steel shell after forging thereby giving rise to the novel concept of "investment forging". A hollow part with uniform steel shell can be formed for the ultimate weight and cost reductions. For example investment forging of hollow steel valves for engine applications is feasible by hot hydroforging. Copyright © 2016 ASM International® All rights reserved.

Goldstein R.,Fluxtrol Inc. | Chavdar B.,EATON Inc | Ferguson L.,DANTE Solutions Inc.
23rd International Federation of Heat Treatment and Surface Engineering Congress 2016, IFHTSE 2016 | Year: 2016

Recently, a concept to produce lightweight products by hot forging a steel shell that had a lightweight core was presented that could lead to component weight savings up to 50%. Some targeted products are gears, valves, and flanges. The steel shell is envisioned to carry most of the load in a target application while the lightweight core serves as a space holder during the forming process. After forming, the lightweight material may either remain in the component and contribute to the load carrying capacity, or be emptied out to achieve the ultimate weight reduction. In this paper, the concept studied is hot forged from a bimetal billet, which is a steel tube press fit with a solid aluminum core and welded shut with steel end caps. For the experimental part of the studies Al 7075 was selected as the core material due to its high strength to weight ratio and 1020 steel was selected because of its availability as a tube. Induction heating was selected as the heating method for bimetal forging. This is due to the ability of induction heating to rapidly heat the steel layer. Successful bimetal forging of a closed vessel requires the steel layer to be in the austenite phase prior to the aluminum reaching high temperatures to prevent compromising the weld seams. Modeling of the induction heating process is complex due to the dimensional movement of components during the process. A method was developed to accurately model the induction heating process and predict power requirements. The method will be described and the results of the models will be compared to experimental findings. The forming process will be discussed in another paper at the conference. The simulation presented is for solid state forging of a steel aluminum billet, but the method for modeling the process is the same for hot hydroforging or other material combinations. Copyright © 2016 ASM International® All rights reserved.

Li Z.C.,DANTE Solutions Inc. | Freborg A.,DANTE Solutions Inc. | Ferguson L.,DANTE Solutions Inc.
ASME 2016 11th International Manufacturing Science and Engineering Conference, MSEC 2016 | Year: 2016

Applications of the induction hardening process have been gradually increasing in the heat treatment industry due to its energy efficiency, process consistency, and clean environment. Compared to traditional furnace heating and liquid quenching processes, induction hardening is more flexible in terms of process control, and it can offer improved part quality. The commonly modified parameters for the process include the inductor power and frequency, heating time, spray quench delay and quench severity, etc. In this study, a single shot induction hardening process of a cylindrical component made of AISI 4340 is modeled using DANTE®. It is known that the residual stresses in a hardened steel component have a significant effect on high cycle fatigue performance, with higher magnitudes of surface residual compression leading to improved high cycle fatigue life. Induction hardening of steel components produces surface residual compression due to the martensitic transformation of the hardened surface layer, with a high magnitude of compression preferred for improved performance in general. In this paper, a preheat concept is proposed with the induction hardening process for enhanced surface residual compression in the hardened case. Preheating can be implemented using either furnace or low power induction heating, and both processes are modeled using DANTE to demonstrate its effectiveness. With the help of computer modeling, the reasons for the development of residual stresses in an induction hardened part are described, and how the preheat can be used to improve the magnitude of surface residual compression is explained. Copyright © 2016 by ASME.

Ferguson B.L.,DANTE Solutions Inc. | Li Z.,DANTE Solutions Inc. | Freborg A.M.,DANTE Solutions Inc.
Journal of Materials Engineering and Performance | Year: 2014

Quench probes have been used effectively to characterize the quality of quenchants for many years. For this purpose, a variety of commercial probes, as well as the necessary data acquisition system for determining the time-temperature data for a set of standardized test conditions, are available for purchase. The type of information obtained from such probes provides a good basis for comparing media, characterizing general cooling capabilities, and checking media condition over time. However, these data do not adequately characterize the actual production quenching process in terms of heat transfer behavior in many cases, especially when high temperature gradients are present. Faced with the need to characterize water quenching practices, including conventional and intensive practices, a quench probe was developed. This paper describes that probe, the data collection system, the data gathered for both intensive quenching and conventional water quenching, and the heat transfer coefficients determined for these processes. Process sensitivities are investigated and highlight some intricacies of quenching. © 2014, ASM International.

Ferguson B.L.,DANTE Solutions Inc. | Freborg A.M.,DANTE Solutions Inc. | Li Z.,DANTE Solutions Inc.
23rd International Federation of Heat Treatment and Surface Engineering Congress 2016, IFHTSE 2016 | Year: 2016

Carburization of alloy steels promotes the formation of compressive residual surface stress upon quenching, and that compressive surface stress enhances fatigue life. To further investigate the role of residual stress on fatigue strength, a project was undertaken to assess the role of residual stress magnitude on bending fatigue life of a spur gear through innovative quenching and the achievement of deeper compressive surface stress. DANTE Solutions demonstrated the feasibility of improving the bending fatigue life of Pyrowear 53 steel gears by achieving deeper compressive residual stress in carburized and quench hardened parts. At the same time, concepts of integrated computational engineering (ICME) were employed for simulation of the steel heat treatment and then of the gear service stresses. Computer simulations of two different quenching processes, conventional oil quenching and intensive quenching, were conducted using the DANTE heat treatment simulation software to predict differences in final residual stress state. Although similar hardness profiles were predicted for both processes, the predicted surface stresses at the center of the gear root were -600 MPa and -300 MPa, with the intensive quenching producing higher compression. These predictions agreed with XRD measurements. The stresses predicted at the tooth fillet were even more compressive and maintained similar separation between the two quenching methods. The simulations showed that timing and sequence of martensite formation that occurred during the quenching process was related directly to the magnitude of compressive residual surface stress. Tooth bending fatigue tests, conducted by Gear Research Institute, showed an endurance limit difference of 15% between the two quenching methods, with higher surface compression yielding higher fatigue life. Scatter in the data was significant, even with surface conditions within product specification. Isotropic surface finishing increased the endurance limit, and the difference between quenching methods was maintained. Copyright © 2016 ASM International® All rights reserved.

Freborg A.M.,DANTE Solutions Inc. | Li Z.,DANTE Solutions Inc. | Ferguson B.L.,DANTE Solutions Inc.
23rd International Federation of Heat Treatment and Surface Engineering Congress 2016, IFHTSE 2016 | Year: 2016

Quench hardening of work rolls for steel rolling is used to impart both residual compression and hardness to the roll surface to promote durability, wear resistance and life. Minimizing required roll re-dressing and mill down time are important cost drivers for improved work roll surface life. Developing the necessary metallurgical and mechanical response of these rolls in heat treatment is complex, often involving a heating and quenching sequence in which thermal gradients are controlled at both the outer surface and by application of internal cooling through the roll's hollow center. Depth of hardness, along with surface and internal residual stresses, are challenging to control. Typically, methods for developing such heat treating practices are based heavily on in-plant experimental trials, as well as "experience." The advent of accurate heat treatment simulation allows for analytically based process engineering to be used to examine roll heat treatments to improve depth of hardening and overall metallurgical response. In this paper, virtual experiments are conducted to characterize practical heating, cooling and quenching regimes to study how varied practices may be used to control residual stress, hardness and metallurgical structure. Because of heat treatment's highly non-linear nature, simulation is a valuable tool for examining part response sensitivities. The heat treatment response of a typical steel mill work roll is examined under a variety of heating and quenching conditions. The relationship between residual stress and hardness is not straightforward, as will be shown. Therefore, the use of heat treatment modeling, which allows examination of the in-process thermal and transformation stresses in conjunction with microstructural changes, is an important tool for understanding the heat treatment of these rolls. Copyright © 2016 ASM International® All rights reserved.

Charlie Li Z.,DANTE Solutions Inc.
ASME 2015 International Manufacturing Science and Engineering Conference, MSEC 2015 | Year: 2015

A hollow R.R. Moore rotation fatigue sample made of AISI 9310 is processed using vacuum carburization and high pressure gas quenching. The vacuum carburization schedule is designed to through carburize the thin wall section of the fatigue sample to 0.7% wt.% carbon, followed by 10 bar nitrogen quench. Some samples showed significant bow distortion after quench hardening, and further investigations indicated that the unbalanced wall thickness from machining is the main cause of the bow distortion. In this paper, DANTE, a commercial heat treatment software is used to study the cooling, phase transformation, and stress evolution during quenching. The effect of unbalance wall thickness on distortion is also investigated. Residual stress state in the quench hardened sample is critical to the fatigue performance during rotational bending fatigue tests. In this study, the unbalanced geometry has insignificant effect on the residual stresses after quench hardening. However, the unbalanced geometry will affect the applied stress significantly during a rotation fatigue test. Copyright © 2015 by ASME.

Li Z.,DANTE Solutions Inc. | Ferguson B.L.,DANTE Solutions Inc.
ASME 2014 International Manufacturing Science and Engineering Conference, MSEC 2014 Collocated with the JSME 2014 International Conference on Materials and Processing and the 42nd North American Manufacturing Research Conference | Year: 2014

Residual stresses are critical to the fatigue performance of parts. In general, compressive residual stress in the surface is beneficial, and residual tension is detrimental because of the effect of stress on crack initiation and propagation. Carburization and quench hardening create compressive residual stresses in the surface of steel parts. The laser peening process has been successfully used to introduce residual compression to the surface of nonferrous alloy parts. However, the application on carburized steel parts has not been successful so far. The application of laser peening on carburized steel parts is limited due to two main reasons: 1) the high strength and low ductility of carburized case, and 2) the compressive residual stresses in the surface of the part prior to laser peening. In this paper, the carburization, quench hardening, and laser peening processes are integrated using finite element modeling. The predicted residual stresses from quench hardening and laser peening are validated against residual stresses determined from X-ray diffraction measurements. An innovative concept of laser peening with preload has been invented to enhance the residual compression in a specific region of laser peened parts. This concept is proved by FEA models using DANTE-LP. Copyright © 2014 by ASME.

Li Z.,DANTE Solutions Inc. | Lynn Ferguson B.,DANTE Solutions Inc. | Freborg A.,DANTE Solutions Inc.
Thermal Process Modeling - Proceedings from the 5th International Conference on Thermal Process Modeling and Computer Simulation, ICTPMCS 2014 | Year: 2014

Gears are the most important components for transmissions. In many situations, the size of a transmission design needs to be reduced without decreasing power density. One of the most effective methods is to reduce the gear size while keeping the same output torque capacity. In general, gears used in heavy load conditions are made of steel, and gear tooth residual surface stresses are critical to the fatigue performance. Compressive residual stresses in the critical region of a gear improve its fatigue performance. However, many steel gears are not processed to obtain residual surface compression, or the benefit of residual compression is not considered in the gear and transmission design. In this paper, virtual computer models using DANTE® software are used to assist with achieving gear size reduction by including steel grade hardenability and heat treatment in the design process. In this study, the original gear is made of AISI4340 and oil quenched and tempered. The gear with reduced size is made of AISI 8620. Carburization and oil quenching are used to introduce residual compression to the root fillet of the gear tooth; this is the most critical region concerning high cycle bending fatigue performance. By taking advantage of the residual compression at the root fillet, the gear with reduced size can deliver the same torque load while having better bending fatigue performance relative to the original gear. Copyright © 2014 ASM International ® All rights reserved.

Freborg A.,DANTE Solutions Inc. | Ferguson B.,DANTE Solutions Inc. | Li Z.,DANTE Solutions Inc.
Thermal Process Modeling - Proceedings from the 5th International Conference on Thermal Process Modeling and Computer Simulation, ICTPMCS 2014 | Year: 2014

Understanding development and response of residual stresses in steel parts during processing and subsequent loading applications is a critical engineering requirement. Carburization introduces an additional factor in terms of hardening and a varied residual stress gradient from case to the core. Aerospace transmission components are typically manufactured from high strength, case carburized alloy steels such as AMS 6308 (Pyrowear®53). The combination of carburization and quench hardening of these steels produces residual compressive surface stresses and high surface hardness, for the specific purpose of enhancing fatigue resistance and surface durability. Using an internal state variable (ISV) material model, the DANTE heat treatment simulation software code has been successfully applied for carburized and heat treated gear steel applications. The model provides critical engineering data for understanding microstructural, residual stress and distortion response. This paper describes the use of heat treatment simulation to engineer residual stress and distortion response in a complex shaped AMS 6308 alloy steel coupon, for subsequent cyclic load testing and evaluation of stress relaxation. The criticality for accurate use of process-descriptive boundary conditions is presented in the context of vacuum carburizing and gas quenching. Model predicted residual stress and distortion response for a tapered, notched coupon are validated against x-ray diffraction and dimensional physical testing. A loading model is presented indicating stress concentration and effective loading stress exceeding UTS in the tapered notch. The model is validated against a static loading test, showing fracture initiating in the predicted location of stress concentration. Copyright © 2014 ASM International ® All rights reserved. Copyright © 2014 ASM International ® All rights reserved.

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