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Akron, United States

Kobasko N.I.,Intensive Technologies Ltd | Kobasko N.I.,IQ Technologies Inc.
Journal of ASTM International

A method for optimizing the chemical composition of steels to obtain optimal residual stress distribution throughout the section of a steel part is proposed, which is based on the analytical equation for the calculation of ideal critical diameter (DI). The advantage of this method consists of the opportunity to calculate the ideal critical size for a variety of geometries on the basis of their respective continuos-cooling transformation (CCT) diagrams. Detailed discussions are provided relating to the optimal depth of the hardened layer, which provides high surface compressive residual stresses and minimal tensile stresses in the core. It is also shown that the ratio of the DI to the diameter of the part with an optimal residual stress distribution should be the same, that is, DI/Dopt=const with steel parts of varying sizes. This relationship can be used for the development of new technologies for large-sized parts based on the results obtained for small parts. The service life of steel parts increases after intensive quenching due to the formation of high surface compressive residual stresses and improved mechanical properties. During intensive quenching, the effect of additional strengthening (super strengthening) of the material is observed, which is connected with the intensification of cooling process within the martensite range. Copyright © 2011 by ASTM International. Source

Kobasko N.I.,IQ Technologies Inc. | Batista A.A.,University of Sao Paulo | Canale L.C.F.,University of Sao Paulo | Totten G.E.,Portland State University | Dobryvechir V.V.,Intensive Technologies Ltd
Materials Performance and Characterization

The cooling capacity of coconut oil, palm oil, and petroleum oil were determined by solving the inverse problem (IP) using the newly developed commercial code, IQLab. It was shown that all of the oils exhibited shock-film-boiling, film-boiling, and convection-heat-transfer modes during the quenching process. The results of these investigations are necessary when developing a global database of the cooling capacity of different quenchants. The results obtained by solving the inverse problem are compared with simplified calculation results based on cooling time-temperature data obtained by using a multi-thermocouple Inconel 600 probe. The results obtained showed that the results from both methods agreed within ±10 %. These results suggest that the standard Inconel 600 probe can be used in many cases for determining average heat-transfer coefficients occurring when using vegetable oils, such as coconut oils, palm oils, and petroleum oils as quenchants. © 2013 by ASTM International. Source

In the paper the new explanation in manufacturing of Damascus steel, based on discovered the specific characteristics of transient nucleate boiling processes, is provided. Also, the future of continuous casting in the paper is discussed. According to discovered characteristics, duration of transient nucleate boiling process is directly proportional to squared size of a steel part and inversely proportional to thermal diffusivity of material, depends on configuration and initial temperature of component, thermal properties of liquid. The surface temperature of steel part during transient nucleate boiling process maintains at the level of boiling point of liquid and cannot be below it. Based on these characteristics, the new hypothesis regarding manufacturing of Damascus steel is proposed according to which the melted high carbon steel (containing 1- 2% carbon) was casted into copper forms cooled by cold water and then the steel was many times forged and quenched in special water salt solutions until finishing transient nucleate boiling process. Such simple technology provided extremely small spherical carbides distributed in steel which acted as a saw and made steel very strong. It is stated that high strength materials with fine microstructure can be achieved by applying intensive cooling to continuous casting. Source

Kobasko N.I.,IQ Technologies Inc.
ASTM Special Technical Publication

Low and limited hardenability (LH) steels are plain carbon steels characterized by a low content of alloying elements (Cr, Ni, Mo, W, V, etc.). The use of LH steels with an intensive quenching method allows full elimination of the carburization process for a variety of steel parts, such as, gear and bearing products, tools, low-wear parts for different applications. This is based on the steel super strengthening phenomenon and creation of high residual compressive stresses at the surface of intensively quenched steel parts. Both of these factors allow replacing expensive alloy steels with plain carbon steels. The unique characteristic of limited hardenability steels is that these alloys only harden to a shallow depth when heated and quenched. The main idea of this paper involves the creation of the optimal depth of a hardened shell which provides optimal stress distribution in quenched steel parts. Since the LH steel core does not harden significantly, a relatively high ductility of the core is maintained. The grain sizes of LH steels are greater than ASTM 8. Several patents on LH steels have been issued in Europe. A number of technical papers utilizing LH steels for gears and bearing products have been published in the Ukraine2 and Russia. Elimination of carburizing saves energy and prevents the emissions of thousands of tons of CO2 gases. Furthermore, the high level of compressive surface residual stresses and the steel super strengthening phenomenon eliminates the need for secondary shot peening or surface induction operations. Also, carburized alloy steels can be successfully replaced by LH steels to increase service life and decrease materials cost. Copyright © 2009 by ASTM International. Source

Kobasko N.I.,IQ Technologies Inc. | Kobasko N.I.,Intensive Technologies Ltd
ASTM Special Technical Publication

In this paper, a detailed discussion is provided regarding an effect of the accuracy of temperature measurements on the evaluation of heat transfer coefficients (HTCs) during quenching in liquid media. Some published results on the use of test probes for HTC determination are discussed. These results show that the values of HTCs obtained under the same quench conditions and using test probes of the same size differ by 5 to 8 times. This is a major reason for the writing of this paper. Understanding why there is such big difference in the experimental values for the HTC is very important in planning a study for the development of a global database for different kinds of quenchants. This understanding will help scientists and engineers to develop new, correct data on HTCs needed for computer simulations and for improving the quenching processes of steel parts. Copyright © 2012 by ASTM International 100 Barr Harbor Drive PO Box C700 West Conshohocken PA 19428-2959. Source

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