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For evaluation of quenchants under real industrial conditions, the new Liščić/Petrofer probe is designed. Liščić/Petrofer is special upon design, because it is instrumented with 3 thermo-couples on the same radius of the cross- section at the middle of the probe length. The outer thermocouple measures the temperature at 1 mm below surface, the second one at 4.5 mm below surface, and the third one at the center of the probe. The working principle of the probe is the measurement of the dynamics of heat extraction which is best represented by the change of temperature gradients. Second type of probe developed to evaluate the cooling properties of relatively small samples of a quenchant used in this paper is standard ASTM D6200 probe, which consists from cylindrical test specimen having one thermocouple at its geometrical center. Comparative testing was recently performed with the Liščić/Petrofer probe and standard probe with one vegetable oil (Palm Oil) and a commercially available conventional mineral oil (Kalenol 32). The work was performed at the Quenching Research Centre (QRC) of the Faculty for Mechanical Engineering, University of Zagreb, Croatia. The results of this paper showed distinctive differences in the quenching behavior of these two quenchant media. The results of this comparative study are reported herein.

The quenching oils contain base oil and different types of additives according to application requirements and also safety impact to the workers or environment. High-performance quenching oils must have very high oxidation and thermal resistance, high flash point, low sludge formation and acceptable heat-transfer characteristics. That can be achieve by proper components selection, both base oils and additives. Adequate selection of quenching media decreases the risk of tensile stresses, cracking and workpiece distortion, and imparts cleanliness to metal parts. There are numerous compounds available for formulate quenching oils: as base oil are mineral, synthetic and natural oils, used separately or in combination, as additives are used different rust and oxidation preventives, accelerators, busters and others. Mineral base oils are widely used because of their advantages with respect to stability in comparison to natural oils, or lower prices in comparison to synthetic oils. In this work are presented the results of laboratory investigation of physical and chemical properties of new quenching oils based on several types of mineral oils and proper additives at different treat levels. Cooling characteristics of oils are determined at three temperatures according to ISO 9950 standard.

By metal heat treatment process quenching oil is applied in order to achieve a specific quality of materials and also decrease the risk of tensile stresses, cracking and workpiece distortion. The quenching oil contains base oil and different types of additives according to application requirements. High-performance quenching oils must have very high oxidation and thermal resistance, high flash point, low sludge formation, must be non-staining and possess acceptable heat-transfer characteristics. That can be achieved by proper components selection, both base oils and additives. In this study the results of investigation of physical and chemical properties of new quenching oils are presented. Also, in this paper quenching oils performance characteristics were tested. Quenching experiments according to ISO 9950 standard were performed in order to investigate various methods of heat transfer enhancement. Three sets of experiments were conducted. First, still quenching oil at two temperature levels, 20 and 60 °C was tested. Then, titanium oxide nanoparticles were added to the oil in order to increase its thermal properties. Last set of experiments was conducted under ultrasonic agitation at three different levels of power. The cooling curve analysis showed that temperature had almost no effect in still conditions, while the addition of nanoparticles caused increase in heat transfer at all phases of quenching. Using ultrasonic agitation caused elimination of full film phase and increase in cooling rate. All of the mentioned test sets were used to compare the effect different enhancement methods that would have on quenching of real work pieces.

At metals heat treatment processes quenching media are applied in order to achieve specific materials quality. Adequate selection of quenching media decreases the risk of tensile stresses, and also of cracking and workpiece distortion. The quenching oil contain a base oil and different types of additives according to application requirements. During metal cooling process quenching oil is exposed to high temperatures in the presence of metals and air which has an adverse impact on the working life of oil. Because of that high-performance quenching oils must have very high oxidation and thermal resistance and low sludge formation, must be non-staining and have a high flash point and acceptable heat-transfer characteristics. There are numerous compounds available for use but, besides their functional and safety properties, the tribology effects have to be considered in the selection of components. Mineral oils, synthetic and natural oils, used separately or in combination, may be used as base oils. Mineral base oils are widely used because of their advantages with respect to stability in comparison to natural oils, or lower prices in comparison to synthetic oils. By proper components selection for quenching oils production, both base oils and additives, working life can be extended. In this study are presented the results of investigation of physical and chemical properties of new quenching oils and also oils from application.

Quenching is the most common method of hardening metals, which involves continuous cooling from a given austenite temperature to achieve full transformation into martensite structure to produce optimal mechanical properties. The quenching media contain base oil and different types of additives according to application requirements. The cooling rate mainly depends on thermal characteristics of metals, section thickness of workpieces and the quenching medium heat-removal properties. As the base oil, it is possible to use mineral oils, synthetic and natural oils separately or in combination. Mineral base oils are widely used because of their advantages in stability in comparison to natural oils, or lower prices in comparison to synthetic oils. There are numerous compounds available for use but, besides of functional properties, the environmental and safety requirements have a strong influence on the components selection. Based on that the barium additives must be replaced with less harmful compounds. Petroleum derivatives should be changed with renewable base stocks that are biodegradable, as general trend in lubricant development. By changing the composition of quenching oils, base oils or additives, heat transfer characteristics are also changed. In this study are presented the examination results of physical-chemical properties and also cooling characteristics of quenching oils formulations with different types of additives. Cooling curves of tested oils have been evaluated according to ISO 9950 standard.

Adequate selection of quenching media decreases the risk of tensile stresses, and also of cracking and workpiece distortion. High-performance quenching oils must have very high oxidation and thermal resistance and low sludge formation, must be non-staining and have a high flash point and acceptable heat-transfer characteristics. The quenching media contain a base oil and different types of additives according to application requirements. Mineral oils, synthetic and natural oils, used separately or in combination, may be used as base oils. Mineral base oils are widely used because of their advantages with respect to stability in comparison to natural oils, or lower prices in comparison to synthetic oils. There are numerous compounds available for use but, besides their functional properties, the environmental and safety requirements have to be considered in the selection of components. Based on that, barium additives must be replaced with less harmful compounds. Petroleum derivatives should be replaced with renewable base stocks that are biodegradable, which is a general trend in lubricant development. By changing the composition of quenching oils, base oils and additives, heat transfer characteristics are also changed. In this study, the results of investigation into physical and chemical properties and also cooling characteristics of new quenching oils with different compositions are presented. Cooling curves for different compositions have been evaluated according to the ISO 9950 standard.

A synthetic liquid (5 % water solution) was used during the coarse and fine grinding of single- crystal Si and fused SiO2. In order to characterize the synthetic liquid, its physical and chemical properties, corrosion protection, foaming, coolant and lubricant properties were determined. These parameters were determined before machining and after coarse and fine grinding. The liquid contains particles of the treated material after coarse and fine grinding. Therefore, the particle size distribution was determined in order to select a method for removing solid particles before the liquid is reused. Results of investigation indicated that the physical and chemical properties of the used synthetic liquid did not change after machining, which means that the liquid can be reused after an adequate solid-liquid separation method has been applied.

Quenching is the most common method of hardening metals, which involves continuous cooling from a given austenite temperature to achieve full transformation into martensite structure. The cooling rate mainly depends on thermal characteristics of metals, section thickness of workpieces, and the quenching medium heat-removal properties. Oils as quenching media contain a base oil and different types of additives according to application requirements. As the base oil, it is possible to use mineral oils, synthetic and natural oils, either separately or in combination. Mineral base oils are widely used because of their advantages in stability in comparison to natural oils, or lower prices in comparison to synthetic oils. There are numerous additives available for use but, besides functional properties, the environmental and safety requirements have to be considered in the selection of additives, e.g. barium additives must be replaced with less harmful compounds. Petroleum derivatives should be replaced with renewable base stocks that are biodegradable, which is a general trend in lubricant development. By changing the composition of quenching oils, base oils and additives, heat transfer characteristics are also changed. This study presents results of the analysis of physical and chemical properties, as well as of cooling characteristics of new quenching oils with different compositions. Cooling curves for different compositions have been evaluated according to ISO standard 9950.

A synthetic liquid (5 % water solution) was used during the fine grinding of alumina (Al2O3) ceramics. In order to characterize the synthetic liquid, its physical and chemical properties, corrosion protection, foaming, coolant and lubricant properties were determined. These parameters were determined before machining and after fine grinding. The liquid contains particles of the treated material after fine grinding. Therefore, the particle size distribution was determined in order to select a method for removing solid particles before the liquid is reused. Results of investigation indicated that the physical and chemical properties of the used synthetic liquid did not change after machining, which means that the liquid can be reused after an adequate solid-liquid separation method has been applied.

Correct selection of quenching media decreases the risk of tensile stresses, and also cracking and workpiece distortion. High-performance quenching oil must have excellent oxidation and thermal resistance and low sludge formation, must be non- staining and have an elevated flash point and acceptable heat-transfer characteristics. The quenching media contain base oil and different types of additives according to application requirements. As the base oil, it is possible to use mineral oils, synthetic and natural oils separately or in combination. Mineral base oils are widely used because of their advantages in stability in comparison to natural oils, or lower prices in comparison to synthetic oils. There are numerous compounds available for use but, besides functional properties, the environmental and safety requirements have a strong influence on components selection. Based on that the barium additives must be replaced with less harmful compounds. Petroleum derivatives should be changed with renewable base stocks that are biodegradable, as the general trend in lubricant development. By changing the composition of quenching oils, base oils and additives, heat transfer characteristics are also changed. In this study the examination results of physical-chemical properties and also cooling characteristics of new quenching oils with different compositions are presented. Cooling curves for different compositions have been evaluated according to ISO 9950 standard.

Correct selection of quenching media decreases the risk of tensile stresses, and also cracking and workpiece distortion. High-performance quenching oil must have excellent oxidation and thermal resistance and low sludge formation, must be non-staining and have an elevated flash point and acceptable heat-transfer characteristics. The quenching media contain base oil and different types of additives according to application requirements. As the base oil, it is possible to use mineral oils, synthetic and natural oils separately or in combination. Mineral base oils are widely used because of their advantages in stability in comparison to natural oils, or lower prices in comparison to synthetic oils. There are numerous compounds available for use but, besides of functional properties, the environmental and safety requirements have a strong influence on the components selection. Based on that the barium additives must be replaced with less harmful compounds. Petroleum derivatives should be changed with renewable base stocks that are biodegradable, as general trend in lubricant development. By changing the composition of quenching oils, base oils and additives, heat transfer characteristics are also changed. In this study are presented the examination results of physical-chemical properties and also cooling characteristics of new quenching oils with different compositions. Cooling curves for different compositions have been evaluated according to ISO 9950 standard.

Kaljenje je najrašireniji postupak toplinske obradbe metala a sastoji se od odgovarajućeg gašenja s određene temperature austenitizacije da bi se postigla martenzitna struktura. Sposobnost ohlađivanja sredstva za gašenje uglavnom ovisi o toplinskim svojstvima metala, debljini oblika obradaka te o svojstvima odvođenja topline sredstva za gašenje. Pravilnim izborom odgovarajućeg sredstva za gašenje smanjuje se opasnost od nastajanja napetosti, eventualnih pukotina i deformacija obratka. Za gašenje čelika najčešće se primjenjuju voda, biljna i mineralna ulja, otopine polimera, solne kupke, fluidizirane kupke, inertni plinovi te zrak. Voda je oštro sredstvo za gašenje dok ulja hlade znatno sporije od vode ali je njihov glavni nedostatak opasnost od požara. Primjenom vodomješivih tekućina za gašenje kombiniraju se pozitivna svojstva ova dva tipa sredstava za gašenje, vode i ulja. U ovom radu prikazana su fizikalno kemijska svojstva vodomješivih tekućina kao sredstva za gašenje kod toplinske obradbe metala. Pripremljeno je više vrsta tekućina s vodom u različitim koncentracijama. Za pojedine koncentracije ispitivanih sredstava za gašenje snimljene su krivulje hlađenja, određene brzine ohlađivanja i značajke H sredstva za gašenje prema standardu ISO 9950., Quenching is the most common procedure of metal heat treatment, which involves adequate cooling from given austenite temperature to achieve full transformation into martenzite structure. The cooling rate of quenching media mainly depends on thermal characteristics of the metals, section thickness of the workpieces, and the quenching medium heat-removal properties. Correct selection of adequate cooling media decreases risk of tension formation, possible cracking, and deformation of workpieces. The most commonly used cooling media for quenching steel are water, vegetable and mineral oils, polymer solutions, molten salts, fluidized baths, gases, and air. Water is a severe quenchant while oils cool more slowly than water but their main disadvantage is high fire hazard. Using watermiscible fluids combines positive properties of those two types of quenchant media, the water and the oils. In this work are presented physical and chemical properties of watermiscible metalworking fluids as cooling media. Several fluid mixtures were prepared with water in different concentrations. Cooling curves for every concentration of test cooling fluids are plotted with determined cooling rates and H-values using ISO 9950 standard.

Quenching media are applied on heat treatment processes of materials in order to achieve specific properties. By correct selection of adequate quenchant the risk of tensile stresses, and also of cracking and workpiece distortions, is decreased. By a constant development of quenchants, environment and human protection and safety requirements are the factors, which directly influence the quenching medium composition. The composition of modern formulations is becoming more and more sophisticated so that a great deal of usual components is changing with new less harmful substances. High-performance quench oil must have oxidation and thermal resistance, be nonstaining, and have an elevated flash point, decreased volatility and acceptable heat-transfer characteristics. By changing quenching oils composition, base oils and additives, cooling rate also is changing. In this paper are presented examination results of physical-chemical properties of new quenching oil formulations and also their cooling rates.