Cooling Intensity of Inverse Solubility Polyalkylene Glykol Polymers and Some Results of Investigations Focused on Minimizing Distortion of Metal Components

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In the paper some unusual processes are considered during quenching such as self-regulated thermal process when metallic probe is covered by insulating polymeric layer, oscillation of temperature in surface layers of probe, creation a “shoulder” when quenching in polymer solution, possibility to perform austempering process just in cold liquids. Above mentioned processes build a basis for the new intensive quenching technologies and can bring a great benefit for heat treating industry when further carefully investigated. It is shown that initial temperature gradients, which cannot be governed by classical law of Fourier, can be tested by Liscic/Petrofer probe, etc. The paper discusses how organize such international investigation to satisfy contemporary practical needs and solve unsolved problems of science in the field of quenching. Also, the results of investigations can be used for software designing and cooling recipes development during quenching steel parts in liquid media. It makes a great progress because at preset time only cooling curves and cooling rates are available that are used for comparable purpose and cannot be used for recipes development.

Section: Materials Sciencementioning

confidence: 99%

Section: Materials Sciencementioning

confidence: 99%

Liscic/Petrofer Probe to Investigate Real Industrial Hardening Processes and Some Fundamentals During Quenching of Steel Parts in Liquid Media

Kobasko¹,

Liščić

2017

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“…As a result, customizers face some problems connected with distortion issues because in many cases cooling should be interrupted at proper time to prevent non-uniformity of cooling during quenching as shown Fig. 6 [16,17]. A methodology is developed for testing liquid media as a quenchant and results of testing can be successfully used for recipes development.…”

Section: Discussionmentioning

confidence: 99%

Investigation of Transient Nucleate Boiling Processes and Their Practical Use in Heat Treating Industry

Kobasko¹

2017

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In the paper transient nucleate boiling process is widely discussed. It’s unknown previously and investigated by author characteristics create a basis for designing of new technologies which allow receiving super strengthened materials. Obtained results are also used for appropriate software development to be widely applied for control of technological processes and cooling recipes design. A possibility of transition from real heat transfer coefficients (HTCs) to effective HTCs is discussed in the paper too. It is shown that core temperature of steel parts at the end of transient nucleate boiling (self-regulated thermal process (SRTP)) is a linear function of a part dimension when convective heat transfer coefficient during quenching in liquid media is fixed. Also, it is shown that effective Kondrtajev number Kn is a function of part size and convection intensity and is almost linear function for large sizes of steel parts. Surface temperature at the beginning of self-regulated thermal process and at its end is calculated depending on size and intensity of cooling. Based on obtained new results, it is possible to design DATABASE for liquid quenchants using standard Inconel 600 probe combined with the Liscic/Petrofer probe. Obtained results can be useful for engineers and software designers.

“…According to author [1,15], an average effective Kondratjev number Kn can be find which allows calculating cooling time within the transient boiling nucleate boiling process using simple Eq. (8) Obtained data from Fig.…”

Section: Cooling Time Calculation During Quenching In Polymersmentioning

confidence: 99%

“…As a result, in heat treating industry sometimes a big distortion is observed after quenching machine components in water polymer solutions. Author [1] explained such behavior by non-uniform dissolving surface polymeric layer when quenching in water polymer solution of inverse solubility. Moreover, a long ago authors [2,3] came to conclusion that low water concentration of inverse solubility polymers (≈1 %) provides maximal cooling rate of standard probes and this important fact in not yet used in the practice to intensify quenching processes.…”

Section: Introductionmentioning

confidence: 99%

Research on Use of Low Concentration Inverse Solubility Polymers in Water for Hardening Machine Components and Tools

Kobasko¹,

Moskalenko

Dobryvechir³

2018

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There is an optimal water concentration of inverse solubility polymers ( 1 %) where in many cases film boiling is absent. Based on accurate experimental data of French and data of authors, it was shown that during quenching from 875 oC in cold water solutions of optimal concentration film boiling is completely absent for those steel parts initial heat flux densities of which are below critical value. It is established that initial heat flux density decreases with increase sizes of tested samples. Initial process of quenching (formation of boundary boiling layer), which makes further history of cooling, is not investigated deeply and widely yet enough. When film boiling is absent, mathematical model includes only transient nucleate boiling process and convection. In this case, cooling time within the transient nucleate boiling process can be calculated using average effective Kondratjev numbers Kn. They were evaluated for inverse solubility polymers depending on their concentration and sizes of tested samples. As a result, an improved technology of hardening large gears and bearing rings is proposed by authors. Its essence consists in interruption of accelerated cooling or turning off agitation of quenchant when dissolving of surface polymeric layer starts. Examples of performing improved technology are provided by authors. Developments can be used by engineers to switch from carburized large gears quenched in oil to gears made of optimal hardenability steel and quenched in water solutions of optimal concentration.