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Gas carburized and quenched low alloy steels typically produce surface microstructures which contain martensite, retained austenite and often NMTP's (non-martensitic transformation products). The NMTP's are caused by a reduction of surface hardenability in the carburizing process from loss of alloying elements to oxidation. Gas carburized low alloy steels such as SAE 8620 with NMTP's on the surface have been shown to have inferior bending fatigue properties when compared to more highly alloyed steels which do not form NMTP's, such as SAE 4615M. One method of minimizing the formation of oxides and eliminating NMTP formation during carburizing and quenching is to use plasma carburizing instead of conventional gas carburizing. In this study the microstructures and bending fatigue performance of plasma carburized SAE 8620 and SAE 4615M is compared to the same alloys conventionally gas carburized and quenched.

Over the last ten years fatigue tests or wear tests, with and without debris present, have been performed on at least 11 different bearings including five sizes of ball bearings, five sizes of tapered roller bearings and one cylindrical bearing. After evaluating these tests, which include two series that were conducted in the author's laboratory, six factors have been identified that influence bearing performance when debris is present. These factors are debris (size and distribution), lubricant system, lubricant film thickness, levels of filtering, bearing materials and contact size. The results are summarized in table form.

An experimental study of two warm and hot forged 0.30% carbon ferrite/pearlite microalloyed steels demonstrates that the optimal combination of strength and toughness is achieved in a warm forged, fan cooled condition. The properties of the warm forged microalloyed steel approached the combination of strength and toughness achieved in a heat treated 1037 steel, tested at an equivalent hardness level of 20 to 28 HRC. These warm forged microalloyed steels were successfully substituted for heat treated 1037/1040 steels in two automotive transmission hub applications. The benefits of implementing the warm forged microalloyed steel hubs include the elimination of the heat treatment, and the associated costs and problems.

Increased size, payload and horsepower requirements are the trend in today's off-highway industry. This paper discusses the role of new anti-friction roller bearing technology in avoiding problems created by changing design considerations and the performance/cost/EPA triad currently squeezing designers and manufacturers of rubber tired earthmoving machinery. A comparison is made of bearing fatigue life determined by several methods including those derived from vehicle instrumentation and purely empirical criteria. Some common problems relating to the mounting and set up of large wheel bearings are also reviewed together with corresponding remedies.

Incorporating tapered roller bearings in finite element and other structural analyses requires special considerations. Tapered roller bearing properties such as induced thrust, induced moment, load zone, and bearing stiffness can substantially affect the results of such analyses. This paper will discuss pertinent tapered roller bearing structural properties, two potential modeling techniques, and several examples on how bearing models were incorporated into structural analyses.

Improved fuel economy translates into significant savings over the life of a fleet vehicle. Aside from fuel cost savings, tighter emissions regulations require truck Original Equipment Manufacturers (OEMs) to improve the fuel economy of the products they bring to market. OEMs are dependent on Tier 1 suppliers for many systems which have a direct impact on vehicle fuel efficiency. Tier 1 suppliers are then dependent on sub-suppliers for components which affect the fuel efficiency of the system. Improvements in tapered roller bearing design and technology can significantly improve the fuel efficiency of driveline systems. This paper summarizes the improvement in bearing efficiency by applying advanced design and technology solutions. Analysis was used to predict the affect of design changes, leading to an optimized solution. Testing was performed to verify the improvement in bearing efficiency.

Building quality into products requires the dedication of a total team that includes the product designer, process engineer, production personnel, process maintenance personnel, and a total process control system. Operating a process to a known state of capability and sustaining it must be recognized as a multiple functional task as technological changes occur. The understanding of how to manage with changed capability requires a team to understand the characteristics of both the process and the product which need to be monitored to assure that quality is built in. With the increased usage of computers into a manufacturing environment, the task of real time, preemptive management of a process can be achieved. Competitive advantage is a result of the improved capability of the total process that provides maximum yield, process up-time, and sustainability of results.

This paper describes how one American steel producer has been able to provide value which has benefitted the automotive industry in the past and how it is striving to provide value now and intends to do so for many decades into the future. As an alloy steel bar and tube manufacturer serving the automotive industry since its infancy, the Company has had to conquer many serious problems and challenges over the years. The current challenge is doing business as an American company in today's growing global society. In addition to overcoming the obstacles created by today's business environment, it will take continued innovativeness to provide value to the customer. THE THOUGHT OF MAKING STEEL probably never entered the mind of Henry Timken, the Company's founder, who spent most of his career producing carriages, buggies, and wagons. He was more concerned with friction in the axle bearings and what he could do to reduce it.

Debris resistant bearings are being promoted by various bearing manufacturers as a solution for many contaminated lubrication environments. The baseline for such claims is often unclear for the bearing user and leaves questions as to how the information relates to specific field applications. In order to determine the benefits, if any, of these new product offerings and to assess their effectiveness, a standard method of evaluation is needed. An approach to satisfying this need is described and typical results are provided for several commercially available bearing products.

Predicting fatigue performance in concentrated contacts under thin film (or mixed) lubrication conditions has historically involved various empirical approaches. Typically a lubrication parameter is used in an experimentally derived equation to predict the expected rolling contact performance. However, this model doesn't explain the performance improvements. Enhanced finish bearings have exhibited longer life than standard finish bearings, especially when bearings are operated with thin EHL film. In this paper, the contact surfaces of test bearings were analyzed by using a micro-macro contact model in which the macro-contact was elastic contact, and the micro-contact was elastic-plastic contact. The interior subsurface stress maps were calculated from the real contact surfaces, which included the effects of roughnesses, waviness, and profiles.