DE1551391A1 - Cooling liquid and its method of use - Google Patents

Description

UMHTANWALf OIPUINO. Λ CC

, GORTZ ^ March 29 * 1967 4 Frankfurt am Main 70 /

27-TW.41707 »

UNION CARBIDE CORPORATION, New York 17, N ₀ Y ₀ (V.St.A.) Coolant and method of its use

The invention relates to a cooling liquid with improved heat absorption and heat transfer. The invention also relates to a method for using such a liquid sub rapid and controllable cooling of objects »The cooling liquid according to the invention is particularly suitable for quenching Metals »However, the invention is not limited to this ·

There are already different quenching media to get through quenching to improve the properties of metals »Here you want obtain optimal properties of the quenched articles, e.g., improved yield strength, improved tear strength, improved ductility, and improved resistance to corrosion, without warping of the quenched article and without cracking stand"

A method for hardening steels is already known, where < they are first heated to a higher temperature and then by means of a stream of air or by quenching in oil or water When it cools, it is also known that when quenching Objects made of aluminum are treated with cold water. throw occurs. The difficulty can be at least partially be overcome by sealing one to quench

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Used mist of v / aaser droplets in air. Here arise but again the difficulty that the inner parts, especially of intricately built objects, do not come into contact with the Fog koianas; thereby germ ei »rejection occur. because the Heat is not removed quickly and evenly from all parts « It is also known that residual stresses in objects made of alloys of aluminum and magnesium are thereby eliminated can eliminate, since (3 these objects are first heated, then in a common quenching medium, ζοB. Water and then Cools in liquid nitrogen to about -75 C or below, and they are finally heated to room temperature with steam

A method for quenching hot metal sheets is described in US patent specification No. 3 »185» 600. Here, the hot metal sheets are immersed directly in a liquid, eg liquid nitrogen, the sheets being brought to a temperature below -45 as quickly as possible ⁰ C. The disadvantage of this method is that the cooling of the hot objects can not be controlled, and that are quenched as a result the Abkühlungegeschwindigkeit suitable only for a limited number of alloys is to Furthermore, after this V _e rfahren only thin objects such as sheet metal ^ "

» Sa eats known to be objects made of different metals and alloys bit very specific speeds within must cool down in certain temperature ranges in order to optimally Bolichen su received; these cooling rates are from *

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depending on the respective composition of the objects. Bas means that a different cooling rate occurs for each alloy This requires a well-adapted deterrent medium lift, which guaranteed a very specific cooling rate within certain temperature ranges

Some of the problems outlined have been solved by the known methods for quenching metals. More difficulties However, there are still some problems, achieved when quenching with water

* ■ - s I

one is a very fast one. But cooling, this type of quenching »^ leads to the discard of the chilled goods, as the thinner and thicker parts at different speeds are cooled ₀ ^ With liquid nitrogen warping does not occur, but the method can only ^ Sünnen articles or sheets are applied, and only for those alloys for which the cooling rate by liquid nitrogen is suitable ₀ In other words, water _{quenching too quickly, liquid nitrogen quenching too slowly o} There is also no known oil for quenching which, when used, increases the strength. is increased, | without warping, _etc.

All these difficulties are overcome by the invention. The cooling liquids according to the invention have a particularly good one Heat transfer. Their composition can be regulated in such a way that entirely determined within a certain temperature range © Ab * » cooling speeds can be achieved. Those with these Euhlfl'Js objects deterred by candy do not warp and

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Strength is not significantly decreased

The invention relates to a cooling liquid, in particular for quenching heated metal objects, which contains one or more cryogenic substances boiling ^{below 0 ° C. as an essential component.} The cooling liquid is characterized in that it contains at least one in its dispersed solid material, the melting point ψ between the boiling temperature of the cryogenic substance and the temperature Dess cooled object is located, and the part forming a liquid phase within this temperature range at least.

Those cooling fluids are particularly suitable in which the Solid matter dispersed in the cryogenic substance is one which is between the boiling point of the cryogenic substance and the Temperature of the object to be cooled at least partially formed a vapor phase

The cooling liquid can contain various quantities of the dispersed solid matter. The best results are achieved if the cooling liquid contains 10 to 70, preferably 30 to 60, parts of the dispersed solid matter _a

Of some importance let the particle size of the disperse solid material. In fact, it has a particle size ifon 0.05 to 6, preferably from 0.25 to 0.85 mm »

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A number of different substances can be used as cryogenic liquids and as substances dispersed therein. Has proven itself well as a cryogenei? Fabric liquefied stick _r fabric., As üisper§ierten solid material can be used with success Mb. ·.

The invention can be used Ktilüflüssigkeiten of objects from Alurainiumlegierungen with excellent success for cooling-objects, in particular eum quenching here- _c ^ j can be in so doing, treating the heated objects with the located at its boiling temperature of the cooling liquid ,. ZoBo dipped the objects in the coolant

The drawings ue3 explain the following description by way of example further objects and advantages of the invention "

The figure 1 shows the cooling curves of graphieeh copper counter "stands that were in pure liquid nitrogen in liquid nitrogen i with various amounts of ice particles and water Xn immersed"

FIG. 2 shows curves similar to those when the copper gogon stands are immersed was obtained in liquid nitrogen and dispersions of various finely divided substances in liquid nitrogen

'· * · ■
the*

3 shows the Ablühlungskürven that upon immersion of 166 ⁰ Cf-hot objects in liquid nitrogen and containing in 50 $> solid ovum fLdssi ^ s nitrogen were obtained ''

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Figure 4 shows the same with the difference _f that the temperature of the immersed objects was 107 ⁰ C »

FIG. 5 also shows the same thing, with the difference that the temperature of the immersed objects was 63 ^° C. «

The inventive method may sum cooling of all objects are used, the fast New York Convention / controlled rate to be cooled from a relatively high temperature _β .Xn Hegel it is check are metals, in particular alloys that have been heat treated. The process can also be used to cool non-metallic material, S ₀ B * of cermet, ceramic substances, cement-like substances, natural or synthetic rubber or plastics. The material to be cooled can have any shape, gB it can be Bleoh ^,? all rods, plates, fibers or a compiled built object are present «,

The heat transfer of known oryogenic liquids or mixtures. them is improved by the invention. The expression “cryogenic liquid ¹ * denotes substances that boil below ⁰ ° C. at normal pressure. Examples of such cryonic liquids are liquid air and the substances contained in table 1.

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Table I.

cryogenic
Pl üß sjLjg kel t Ji ¹ sleeve Boiling point ⁰ C helium Hey -269 Y / aasörrtoff - H ₂ -253 neon Hey -246 nitrogen N ₂ -196 argon A. -186 oxygen ° 2 -183 Möthasf = CH ₄ -162 krypton Kr -153 Tetrafluoromethane CP ₄ -128 xenon Xe -118 λ than ⁰ A ~ 89 Irifluoromethane CHP ₃ - 84 Chlorotrif1aomethane CGlP ₃ - 81 propane C ₃ H ₈ - 42 Chlordifluoriethan GHClP ₂ - 40 Diclorodifluoromethane GCl ₂ P ₂ - 31 Ohlortrif.luoräthen C ₂ ClP ₃ - 28 Ilethyl chloride GH ₃ Cl - 24th Bi diethyl ether CH ₃ OCH ₃ - 23

The finely divided wet substance dispersed in the cryogenic Plus8igle © it must be at least partially stable within the temperature range between the boiling point of the cryogenic liquid and the temperature of the object to be cooled

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Form liquid phases _o All substances corresponding to these conditions are suitable according to the invention as additives.

Are .Bevorzugt such finely divided solid substances, the de3 cooled object at least in part a vapor phase form "Solid substances in the meaning of the invention are also those" within the Teioperaturbereiches between the boiling point of the cryogenic liquid and the temperature, the \ are not solid at room temperature k, but pass into the solid state when introduced into the cryogenic liquid. Water is a preferred solid additive because it solidifies in the cryogenic liquid to form ice.

Mixtures of solid substances can also be used, as well as frozen aqueous solutions, such as saline solutions. One or more solid substances can be used in finely divided form in the cryogenic

Liquid disperses its

* Table II contains, for example, various according to the invention solid additives, which also include metals, salts, acids and organic compounds. But this table is natural not complete

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Table II boiling point Freezing ~
point ⁰ C ueoignej 1180 650 Pein distributed feate
Fabrics te solid additives 930 617 Manganch1ο rid Pormel 922 420 Cadmium chloride MnCl ₂ 767 321 zinc CdCl ₂ 711 378 cadmium Zn 622 246 Cadniium iodide CD 460 218 Tin chloride CdI ₂ 445 113 Uismuthbromld SnCl ₂ 441 23Ο sulfur 'BiBr ₅ 331 - 39 Wianuth chloride S. 314 282 mercury BiOl ₅ 193-254 --- Perrichloride Ed 151 - 55 Kerosene PeCl ₅ 114 - 32 Monan —— " 100 0 Tin chloride ^C 9 ^H 20 65 - 97 water SnCl ₄ 23 -111 Methyl alcohol H ₂ O - 40 »160 Trichlorofluoromethane CH ₅ OH -128 -184 Chlorodifluoromethane CCl ₅ P Tetrafluoromethane OHOlP ₂ CP,

The effectiveness of the finely divided substances is also dependent on Their particle size. Table IS shows the effect of the particle size of air particles in liquid nitrogen on the cooling rate. Here were 15 cm long copper cylinders

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~ 10 -

with a diameter of 1.1 cm cooled from a temperature of 482 C to 27 ⁰ C by immersion in liquid nitrogen. The nitrogen contained 10 $> ice particles in various particle sizes, respectively. Table III shows that the fastest cooling rates are achieved when the ice particles diameter of 0.8 to 0.4 mm & aben ₀ When exceeding this range downwards or upwards also increases the time required for cooling,

Table JCII

on the cool-down, speed Effect of particle size Cooling down time in seconds Particle size 42 6.0 - 3t5 mm 34 3.5-0.8 mm 29 0.8 - Ό.4 mm 34 0.4-0.25 mm 54 0.25-0.15 mm 62 less than 0.15 mn 78 no ^ ia

The amount of solids dispersed in the cryogenic liquid is also important. With a mixture of ice in liquid nitrogen, the best results are obtained with an ice content of 50%. The above-mentioned copper cylinder wttrden innerr · half of 16 seconds "of a temperature of 482 ⁰ C to 27 ⁰ C cooled In comparison, you needed when using pure flüiiigem nitrogen 78 sec" The Pig "1 shows the differences in Abkühlungageschwindigkeiten when using liquid fabric

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with a salary of 5 #. 10 #, 30 #, 50 #, 60 # and 65 ft Sia. The corresponding curves for liquid water and pure nitrogen are also plotted for comparison. FIG. 1 shows that the cooling capacity of a dispersion τοη ice in liquid nitrogen is far greater than that of liquid nitrogen alone. If you take the content of solids, the cooling rate approaches that has liquid pure nitrogen "The small addition of 10 ^ ovum but already a significant effect on the Abkühlungegeechwindigkeit" J

The maximum permissible solids content depends on the fluidity of the mixture. In order to be useful, the cooling liquid of the invention must be fluid. This pluidity depends on various circumstances, to which the diets of cryogenic pluses and finely divided solid substances also belong, and also on the average particle size of the pesticides. Numerical information on the permissible upper limit can therefore not be given «. When dispersions of Eisteilohen with a diameter of 0.05 mm to 6 mm in a liquid nitrogen content of 70 i> Peststoffen forms the upper allowable limit ₀

Cryogenic liquids are generally poor heat exchangers « This is probably because a boiling layer forms between the liquid and the surface to be cooled when the surface temperature is more than 20 ° above the boiling point of the Liquid lies. The effect of the invention may be due to this be explained that the heat transfer from the warm

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Area to the cryogenic liquid is improved by the finely divided solids with the properties according to the invention will «If you come into contact with the warm surface, you will find it instead, which probably extended over three zones. The first zone consists of the material to be cooled, the second Zone contains in contact with the surface to be cooled Gas and also solid and molten additives »The third zone consists of the bulk of the cryogenic liquid with the

L in it disperse solid additives. The second zone is

So between the first and the third Zoneρ When the cryogenic liquid boils away, those in the third zone become. F _e etteilchen to the warm surface driven forth * This movement of the solid particles through the zone 2 is dependent on the pressure exerted on the solid particle forces you "are directed to the heat source out '' because the evaporation dor cryogenic liquid large volume" held changes. After entering the second zone, at least four forces act on each particle. The force of gravity acts vertically downwards, acting in the opposite direction

"Forces that move the solid particle in the resulting gas upwards In the horizontal direction there is a force that moves the solid particles against the warmer surface. «The viscosity of the liquid acts in opposition to this force» The path of the solid particles is determined by the resultant of these forces. With larger solid particles, gravity is strongest and moves the particles durci the gas space below NaOH before si "di · warm surface have reached, d _{o o} h before the material cooled istο Very fine particles are formed by the

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Gas flow ruptured upwards without reaching the warm surface. This theory is supported by the data in Table III. These indicate that very fine particles with diameters below 0.15 ram and very coarse particles with diameters above 3.5 mm die Practically influencing the cooling rate of the cryogenic mixture, and that an optimal cooling speed foresees an optimal particle diameter. Medium-sized particles reach the warm surface, click there and cool the surface by absorbing the latent ones. Heat of fusion , This theory also corresponds to the data in FIG. 2, which indicate that a finely divided solid additive such as solid carbon dioxide is not effective because it does not form a stable liquid phase at normal pressure.

The quench mixes can be prepared as follows. If a substance is used as an additive which is liquid at room temperature and Hbr = painting pressure, it is atomized and the droplets are sprayed into the cryogenic liquid in an insulated vessel. The liquid can be dispensed under pressure by means of an atomizer nozzle atomize of about 3.5 kg / cm. The mouthpiece of the nozzle is then held about 2.5 cm above the surface of the cryogenic liquid. The droplets freeze when they come into contact with the cryogenic liquid. The mixture may be stirred continuously with a stirrer with two impellers to the formation of a solidified crust on the surface of the mixture to veihinderno The mixtures used in the tests were approximately 2 kg in amounts of from ₀ per Faessen prepared in Dewar G ·

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-H-

Are the additives solid at room temperature, such as sulfur? and ferric chloride, so sieve · !; one up to the appropriate size and gives it then directly in front of the dryogonic fluid. When using solid »carbon dioxide, * solid pieces were ground and before the Sifted addition o

Pieces of copper were used to determine the cooling rates used. Each piece is cylindrical with a length of about

L 15 cm and a diameter of 1.1 cm. In the middle of each P _r obe-piece thermocouple from Ghromel and alumel was welded "The cold junction is maintained at a temperature of" 196 ° G Temj> eraturen ^ on ge draws with a millivolt recorder, with a port speed of movement of 2 , 5 cm within 10 seconds. the mixture was heated the cooled pieces in a salt bath, to a uniform temperature of 482 ° or '166 ⁰ C, 107 ⁰ C and 6J ⁰ C was reached _o remote Then, the copper pieces from the salt bath, and immediately plunged into the stirred cooling mixture. This mixture was left in until a thermal equilibrium

Was "weight reached ° The quenched objects but can of course also be treated so that they besprühtο m ± \ of the cooling liquid

The values obtained are shown in Figures 1 and 2. The results of FIG. 1 have already been discussed above. Figure 2 shows cooling curves in pure liquid nitrogen, in 10-50 jSigen dispersions of finely divided methanol ^ and Kerosene reed parts, from 10 # dispersions of frozen SaIs

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were obtained solutions containing 10 ^c ß> NaCl in water, with 10 #igen dispersions of sulfur "with 10bigen dispersions of ferric chloride in liquid nitrogen" These curves show how to change the KUhlgeschwindigkeit of a submerged object by the type and composition of Kühlgemischeβ "

Figures 3-4 and 5 show the influence of different starting temperatures of the objects to be cooled. In any case, will when using a 50 # dispersion of ice in liquid nitrogen, a shorter cooling time is achieved than when using of pure liquid nitrogen. When the starting temperature is reduced, the differences become smaller wants to cool down to the temperature of the coolant at high temperature.

The use of cooling liquids according to the invention for removing corners of the aluminum alloy 7075 was also investigated. This alloy contains .1.5 # copper, 2.5 # magnesium, 2.5 # zinc, small amounts of silicon, iron and manganese, the remainder being aluminum This alloy is very difficult to work with by heat, as its properties depend largely on the quenching speed The alloy 7075 is one of the strongest and has a tensile strength of 5 810 kg / cm in the forged state. 6 state reached. For this purpose, the alloy is heated in a bath to 490 to 500 ^° C. and then quenched in water. Aa-

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closing taper ^ 4 hours at 120 ⁰ C. Upon quenching with water often arise distortions of Aluminiumgegenatändeo

The mechanical properties of test specimens from aluminum alloy 7075 were tested after quenching in various coolants, the starting temperature being 490 to 500 ^° C. and afterwards the objects were tempered to achieve the D-6 condition. The test specimens had a length of 2.5 cm. From these bodies, disks about 3 mm thick were cut perpendicular to the longitudinal axis. Two specimens were used for quenching. Table IV contains the results obtained in this way

Table e IV

Mechanical properties of 7075 heat treated aluminum alloy articles after quenching in various coolants

water

liquid nitrogen liquid argon liquid aron + 40 i> ice

liquid nitrogen + 50 Jt ice

liquid nitrogen + 10 # ice

liquid nitrogen + 50 # kerosene

liquid nitrogen + 50 # methanol

liquid nitrogen + $ 50> GO ₂

liquid nitrogen + 40 <> Graphite flakes

Stretch limit
kg / cm Hotgrenae 5,250 5 ο 964 3,920 5.110 3,570 4,900 4,550 5,481 4,550 5,495 4,200 5,306 4,270 5 376. 3,976 5.110 3,290 5.110 3,395 4,830 10/2036 'BAD ORIGINAL

The test pieces quenched in water had a yield strength of 5,250 kg / cm, -The test pieces quenched in liquid nitrogen had a yield strength of 5,290 kg / cm _9, which means a decrease of 25 μg compared to the quenching in water. Specimens quenched in dispersions of liquid nitrogen and 50% and of liquid argon and 40 % ice had yield strengths of 4 * 550 kg / cm. This value lies roughly in the middle between those with water and with liquid nitrogen alone obtained values. Liquid nitrogen with an addition of 50 fi kero-

% / 2

sin resulted in a yield point of 4 * 270 kg / cm, somewhat more fluid Nitrogen with an addition of 50 liters of " methanol" resulted in a yield point of 3β976 kg / cm. These differences can be explained by comparing the curves contained in FIG. The cooling with kerosene causes faster cooling in the temperature interval between 290 and 400 ° G than the mixtures with methanol In order to achieve optimal properties of certain alloys, one must use precisely matched cooling mixtures, which bring about the appropriate cooling rates precisely in the critical temperature range. This is the main meaning of the invention.

When quenching in a mixture of liquid nitrogen with 50 i "COG same values were achieved as in the pure quenching in liquid nitrogen. The comparison of the cooling rates of these two cooling liquids according to Figure 2 shows the same cooling

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ventilation speeds. The experiments also show that it is necessary for the solid additive to have at least in part a stable liquid phase forms within the temperature range between the boiling temperature of the cryogenic liquid and the temperature of the material to be cooled. The dispersed solid must melt and thereby the surface ·; of the object to be cooled cool.

At. Using a dispersion of 40 # graphite flakes in liquid nitrogen and using liquid argon, poorer properties were obtained than with liquid nitrogen alone. In use of these mixtures gives slower cooling rates than with liquid nitrogen _o too shows only that just the 7075 must be cooled within a temperature range of about 290 ⁰ C to 400 ⁰ C with a specific speed ₀ The cooling medium used has this allow a certain cooling rate without the object from the aluminum compound warping, as is the case when using water.

However, good moisture properties alone are not enough. Ss is It is also important that the objects do not warp or warp when quenched. Objects made of aluminum are often very Complicated assembly and manufactured within very tight tolerances »These objects not only have to be feet, but they mustn't be warped either. Until now, ee was often necessary to apply additional costly procedures to

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to eliminate any distortions and distortions that have arisen. To test these circumstances, the 8th edition of the book "The American Society for Testing Metals Handbook", Volume 2, page 24 was _t-described method used for this purpose ite 0.32 cm thick aluminum plates were used. The test arrangement was modified inasmuch as the support ,, had no cut-outs, the gap has a \ / eite vcn 1.27 cm and the P _r obestücke a diameter of 9.52 cm were. The shaped by the 'rules l'beauty pieces were heated in einejji salt bath at 482 ⁰ G and then / * versohiedenen coolants "quenched the gap width was carefully measured before heat treatment and after quenching. The amount of change made here is a measure of the warpage during quenching. The values shown in Table 5 below have an accuracy of + 0.005 cm "

modification in different solutions Table V 0.0071 Closing of the gap after quenching
from a temperature of 4-82 C. 0.0008 0.56 Abs chreclMcedium 0.0008 0.06 water 0.06 liquid nitrogen liquid nitrogen
+ 50.S * ice cream

The values in the table are mean values of five tests each. As you can see, the strongest warped leg

Reticulated corners found in water. The specimens * warped very little when using liquid nitrogen or a Miachujg of liquid nitrogen with 50 # ice. So you can see that the

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sate of tein dispersed ice crystals to liquid nitrogen
not only enables better control of the cooling rate and thus better mechanical properties of the quenched material, but also that very little warping or warping takes place or discard ο

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Claims (1)

Patent claims: 1 _β cooling liquid, in particular for quenching heated metal objects, which contains one or more cryogenic ^{substances boiling below O 0} C as an essential component, characterized in that it contains at least one solid substance dispersed in it _% its melting point between the boiling point = - temperature of the cryogenic substance and the temperature of the object to be cooled, and which within this temperature range at least partially forms a liquid phase. 2ο coolant according to claim 1, characterized in that the solid matter dispersed in the cryogenic material is one which is between the boiling temperature of the cryogenic material and the Temperature of the object to be cooled, at least in part · .... forms a vapor phase " 3 »Cooling liquid according to claim 1 or 2, characterized in that that they have 10 to 70, preferably 30 to 60 # of the dispersed contains solid matter, 4. Cooling liquid according to one of claims 1 to 3, characterized in that that the dispersed solid substance has a particle size clay 0.05 to 6, preferably 0.25 to 0.85 mm. £. A cooling fluid according to any one of claims 1 to 4 characterized marked _f "eichnet 'that they contain as the dispersed solid material containing you 109810/2036 Cooling liquid according to one of Claims 1 to 51, characterized in that i! ai3 they liquefied nitrogen as a cryogenic substance contains, 7. Method sum cooling of objects inabesondere for quenching articles of aluminum alloys encryption "application of a cooling fluid according to any one of claims 1 to 6, characterized _(by treating the object with the located at its boiling temperature of the cooling liquid" SAD ORIGINAL 109810/2036