JPH0637665B2 - Method for correcting cooling capacity of aqueous solution for quenching metal alloy - Google Patents

Abstract

Process for modifying the cooling power of an aqueous solution of at least one water-soluble organic polymer which has a lower critical solubility temperature (LCST) with a view to its use for quenching metal alloys, characterised in that a water-soluble additive which modifies the said critical temperature is introduced into the said solution. To lower the LCST of the solution, an inorganic salt of an inorganic or organic acid is preferably employed as an additive in a concentration of between 0.1 and 200 grams per litre, this salt being chosen from the salts of alkali and alkaline-earth metals, including magnesium and zinc. To raise the LCST of the solution, a water-soluble organic derivative is added, in a concentration of between 0.1 and 200 grams per litre, chosen from aliphatic compounds containing at least one functional group chosen from alcohols, acids, aldehydes, amides and amines. <IMAGE>

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention is used for quenching a metal alloy having a so-called inverse solubility and composed of a water-soluble organic polymer which precipitates with an increase in temperature. To improve the cooling capacity of the aqueous solution. The invention also relates to a quenching aqueous solution whose cooling capacity is improved by the addition of water-soluble additives.

Prior art Quenching oils have many drawbacks, and it is known that attempts have been made for many years to use aqueous solutions instead of quenching oils. For example, French Patent 1384244 proposes the use of a solution of polyalkylene glycol having a molecular weight of 60,000 or less, optionally containing 0.1 to 30% of a polymer, for quenching steel. In addition, U.S. Pat.
865642 (polyvinyl alcohol), US Patent 39029
A number of documents have proposed aqueous solutions for quenching, including 29 (polyvinylpyrrolidone) and US Pat. No. 4087290 (polyacrylate). Also French patent 2507209
No. 2538002 (polyoxyalkylene glycol containing an anticorrosive agent that also acts on quenching quenchability), French Patents 2537997 and 2537998 (polyvinyl containing various additives that also act on quenching quenchability. (Pyrrolidone) is also proposed.

The main component of the quenching liquid in the quenching method described in European Patent Application No. 206347 is a water-soluble polymer which is made hydrophobic by appropriately selecting substituents so as to lower the cloud point by a predetermined value. . Aqueous solutions of organic polymers of this type precipitate at high temperatures (especially in contact with the article to be hardened) but redissolve at low temperatures. “Journal of Applied Polymer
Science ", 1959, Vol. 1, No. 1, pp. 56-62, FE Bailey and RW Callard, entitled" Properties of Polyethylene Oxide in Aqueous Solution, "
The relationship between the cloud point of these polymers and the amount of inorganic salt added is reported. However, the application to quenching is not mentioned in this paper. The same goes for the “Journal of
This also applies to the paper by EA Boucher and PM Hines in "Polymer Science", Vol. 14, 1976, pp. 2421-2251, where the "turbidity point" of a polymer solution is the physical constant of the solution. It should be pointed out that what can be regarded and that the cloud point can be determined by measuring the extinction coefficient against temperature using a cell containing the solution. At this cloud point, the permeability over several tens of K (Kelvin) is suddenly interrupted.

For the purposes of understanding the present invention, it should be noted that quenching a metal article into an aqueous solution usually involves three steps. About 850
For example, a steel article preheated to a temperature of ° C is as follows.

The first step is the heating step. The article is surrounded by a coating of steam that shields the article from the liquid and slows the cooling action. However, depending on the working conditions, this step either does not exist or can be omitted by using various means known to those skilled in the art.

The second step is the nucleate boiling process, i.e. the formation of a large number of vapor bubbles on the article.

The third stage corresponds to conduction by direct contact between the article and the quenching liquid and cooling by convection.

If the objects to be quenched have the same initial temperature, a curve showing the time-temperature relationship and the time or temperature-cooling rate relationship (derivative curve), ie often the "quenching cooling curve" A curve known as "" can be plotted for each quench. Considering the properties of the alloy to be quenched, the quenching liquid slows down the cooling in the high temperature region or in the region below 300 ° C (critical region of martensitic transformation) where deformation or "quenching crack" may occur. Or it is chosen to accelerate. However, this requires a large number of coolants, depending on the type of alloy.
Therefore, a fluid in which the quenching and cooling properties of a certain fluid can be adapted to all cases by adding a properly selected specific additive is desired from the viewpoint of industrial convenience. However, hitherto no completely satisfactory solution has been obtained for this problem.

SUMMARY OF THE INVENTION The present invention is directed to overcoming the problems set forth above. It has the reverse solubility of the present invention and has a lower melting temperature (lower critic
A method of modifying the cooling capacity of at least one organic polymer having an al solution temperature (usually abbreviated as LCST) is to add a predetermined amount of a water-soluble additive to the aqueous solution of the polymer, It is characterized in that the lower limit temperature is raised or lowered depending on the agent to be corrected.

These additives are selected from the following:

-A certain water-soluble inorganic salt for lowering LCST;
However, certain organic compounds also have this property.

-Some organic compounds that are water-soluble and relatively hydrophobic when increasing (or optionally decreasing) LCST.

These additives are added at a rate of 0 to 200 g per quenching liquid.

The present invention relates to an aqueous solution for quenching a metal alloy having at least one water-soluble organic polymer having reverse solubility and having an LCST point, said aqueous solution raising or lowering its LCST point in a controlled manner. It is also characterized in that it also comprises at least one additive which can be modified according to the above, thereby forming a cooling curve.

DESCRIPTION OF THE INVENTION From the above mentioned Bailey and Callard reference, it is known to modify the cloud point or LCST of a solution of a polymer having reverse solubility by adding a salt to the solution. However, the relationship between the cloud point and the quenching and cooling property of the solution was not recognized. Several subsequent publications point out the adverse effects of introducing salt into the quenching fluid. Page 19 of the chapter "Quenching of Steels" in the "Metal Handbook", Vol. The effects of pollution are described. An article consisting of an aluminum-based alloy preheated to about 500 ° C. in a nitrite-nitrate bath is illustrated. The above-mentioned patent specification as prior art also describes that a small amount of an inorganic salt is added. However, these inorganic salts are usually added in small amounts to give a secondary effect, mainly an anticorrosive effect. For example, in US Pat. No. 3902929 or French Patent No. 1384244, 0.8 g as a corrosion inhibitor
/ Borax and 0.2 g / sodium nitrite are listed.

Therefore, by controlling the use of certain additives that affect the cloud point (LCST) of the aqueous polymer solution having reverse solubility, the quenching cooling curve can be used to determine the properties and structure of the quenched alloy. The Applicant's findings, which made it possible to modify it to adjust as accurately as possible, were truly surprising.

The present invention is particularly applicable to an oxyethylene polymer, trade name "EM
KAROX "Imperial Chemical Industries) known as" KAROX "oxyethylene-oxypropylene copolymer having a propylene oxide (PO) / ethylene oxide (EO) ratio of 0 to 1, PVME (polyvinyl methyl ether)
It applies to quenching solutions based on polymers and PDME (polydimethoxyethylene) polymers, but is not necessarily limited to these. The product used in the examples of the present invention is EMKAROX known as FC31-165000 (QO / PO ratio = 3). This copolymer has the following properties.

Average molecular weight: M = 32500 Intrinsic viscosity: n = 38.65 cm · g LCST (turbidity point): 74.2 ° C. FIGS. 1 to 10 are curves showing the effect of the present invention.

The Applicant has found that additives capable of modifying the cloud point of water-soluble polymers with reverse solubility are of two types: a-LCST lowering, alkali metal or alkali of inorganic or organic acids. Those belonging to the group of earth metal (including magnesium) salts and zinc salts, and those containing other certain organic derivatives, those which increase (or decrease in some cases) b-LCST, and contain water-soluble organic compounds It was found that it is classified into a group, in particular, one belonging to a group containing at least one functional group selected from alcohol, acid, aldehyde, amide and amine.

It was found that in the first group of inorganic salts, the effect of lowering the LCST on the concentration of the polymer solution was significantly changed depending on the types of cations and anions.

The order of effects of cations, anions and salts is as follows (listed in order of decreasing effect):

As the same molar concentration: K ⁺ , Na ⁺ , Ca ⁺ , Mg ²⁺ , Zn ²⁺ , Li ⁺ ; B ₄ O ₇ ²⁻ , PO ₄ ³⁻ , CO ₃ ²⁻ , Si.
O ₃ ²⁻ , SO ₄ ²⁻ , F ⁻ , Cl ⁻ , CH ₃ CO
O ⁻ , Br ⁻ , ClO ₃ ⁻ , I ⁻ ; Na ₃ PO ₄ , Na ₂ B ₄ O ₇ , Na ₂ CO ₃ , Na _{2
SiO 3, K 2 SO 4,} MgSO 4, ZnSO 4, Li
₂ SO ₄ , KF, NaCH ₃ CO ₂ , KCl, NaC
1, CaCl ₂ , MgCl ₂ , KBr, KClO ₃ , L
iC, KI: - as the same anhydrous salt weight _{concentration: KOH, Na 2 CO 3,} Na 2 B 4 O 7, Na 3 P
O ₄ , K ₂ CO ₃ , MgSO ₄ , Na ₂ SiO ₃ , K
F, K ₂ SO ₄ , Li ₂ SO ₄ , NaCl, ZnS
O ₄ , KCl, NaCH ₃ CO ₂ , LiCl, MgCl
₂ , CaCl ₂ , KClO ₃ , KBr, KI. In the group containing the second water-soluble organic compound, the effect on the cloud point depends on the type and number of polar groups and the length of paraffin chains.

The order of effects in the product studied by the applicant is as follows (listed in order of decreasing effect).

-As equimolar concentrations: Positive effect (elevation of LCST): 1,3-butanediol, acetamide, propylene glycol, ethanol, methanol, formamide, ethylene glycol.

Negative effect (LCST drop): Butanol, propanol.

-At the same weight concentration: Positive effect: acetamide, 1,3-butanediol, methanol, propyne glycol, ethanol, formamide, ethylene glycol.

Negative effect: butanol, propanol.

Generally, in the practice of the present invention, the most effective additives are preferred in order to strictly limit the salt concentration of the quenching liquid for a definite reason.

The effects of substances in the two groups (groups that increase or decrease LCST) are algebraically added, that is, the increasing effect of LCST obtained with, for example, an organic derivative is reduced or offset by addition of an inorganic salt, or reversed. Turned out to be even. This effect is achieved by using LC additives added for the purpose of anticorrosion, sterilization, defoaming or other effects.
It can be used to offset the undesired effects on ST.

Also, as clearly shown in FIGS.
The effect obtained with ethylene oxide-propylene oxide copolymers with an EO / PO ratio of 1/1 is exactly reproducible using copolymers with EO / PO ratios of 2/1 and 5/1. There was found.

FIG. 1 shows the effect of the two groups of additives. By increasing the amount of inorganic salt added, the cloud point drops substantially linearly. Sodium carbonate Na _{2 at the} same concentration
CO ₃ is more effective than sodium metaborate (borax). Propylene glycol and acetamide raise the cloud point more effectively than their lower homologues ethylene glycol and formaldehyde, but the effect of potassium iodide is less pronounced as already mentioned.

Table 1 shows the properties of the solutions used to measure quench quenchability. In either case, the basic solution is EMKARO
It is a 4% by weight solution of XFC31-165000.

FIG. 2 shows the effect of the sodium carbonate additive in Table 1 on the cooling curve when the initial temperature of the steel article to be quenched is 850 ° C. This effect, which is not significant in the nucleate boiling region, is also increased by conduction / convection in the cooling region below 300 ° C, where a significant decrease in cooling temperature is observed.

In Fig. 4 which corresponds to the same conditions as in Fig. 2 when the additive is propylene glycol, the quenching cooling curve is corrected at 850 ° C.
It shows that the effect is reversed at temperatures below about 300 ° C. It is clear that the addition of Na ₂ CO ₃ increases the transition temperature between nucleate boiling and natural convection, while the addition of propylene glycol has the opposite effect. Thus, by carrying out these various tests, it is possible to modify the cooling curve of a polymer or polymers as a function of the quenching conditions required by the article to be heat treated.

The change is clearly shown in Figs. 3 and 5,
The derivative curve (cooling rate as a function of temperature) is drawn here.

FIG. 3 shows Na ₂ at concentrations of 0.76, 1.52 and 3.04% by weight.
The derivative curve for CO ₃ is plotted. The derivative curves for equal numbers of 5 to 20% propylene glycol are shown in FIG. Two temperature ranges are distinguishable: -between about 850 and 300 ° C., the cooling rate for a certain temperature increases with increasing concentration of Na ₂ CO ₃ and decreases with increasing concentration of propylene glycol.

Between about 300 and 25 ° C, the cooling rate for a temperature decreases with sodium carbonate addition and increases with propylene glycol.

6 to 9 have already been described.

Fig. 10 shows three temperatures in the range of about 25 to 300 ℃: 1
00, 150 and 200 ℃ and various concentrations of sodium carbonate,
3 shows the relationship between cooling rate and cloud point for sodium phosphate, ethylene glycol, propylene glycol and potassium iodide.

It is known that the higher the viscosity in this type of aqueous solution, the slower the cooling process. In the case of a solution containing propylene glycol, the overall viscosity of the solution (overal
l viscosity) increases with concentration (see Table 1), whereas in the case of Na ₂ CO ₃ containing solutions the overall viscosity decreases. Therefore, d in the range of 850-300 ° C
The change in T / dt can be represented by the change in viscosity.

EFFECTS OF THE INVENTION The present invention provides a solution to the problem that a large number of quenching fluids are required for the heat treatment of various articles made of different alloys and requiring different quenching rates in a particular temperature range. It is possible to modify the cooling curve as desired by the user, based on a single water-soluble polymer solution giving a given value of cloud point.

Secondly, the invention makes it possible to correct the influence of auxiliary additives such as germicides, defoamers and anticorrosive agents on the cloud point.

Finally, the LCST point can be tentatively restored in a solution that has begun to change due to degradation due to extended use, for example to complete a series of quenching operations before the solution has been completely replaced.

[Brief description of drawings]

Figure 1 shows EMKAROX for various additive concentrations.
The change in the cloud point of a 4% by weight aqueous solution of FC31-16500 is shown. 2 to 5 show cooling curves when various additives of the present invention were added to a 4 wt% aqueous solution of EMKAROX FC31-1650000. The curves in FIGS. 2 and 4 show changes in temperature with time, and FIGS. 3 and 5 show changes in cooling rate with temperature (derivative curve). Figures 6-9 show that the effect of adding an inorganic salt to the LCST does not depend on the type of polymer. FIG. 10 shows the change in cooling rate for various concentrations of various additives and LCST at various temperatures.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jeanne Francois France, 67000 Strasbourg, Lieu Chott, 21 (72) Inventor Gilbert Pole France, 73490 La Lavoir, Lieu Giynute, 7 (72) Inventor Jean-Paul Betan, France, 73008 Syanberg Sedex, Abunyu Dou Comte Vale 355

Claims (13)

[Claims] 1. A method for correcting the cooling ability of a quenching aqueous solution of a metal alloy containing at least one water-soluble organic polymer having a lower limit solution temperature (LCST), the method comprising modifying the LCST by lowering or raising the LCST. When a predetermined amount of the volatile additive is introduced into the solution, the fluctuation of the LCST due to the presence of at least one compound that changes (decreases or increases) the LCST in a certain direction causes the LCST to change in a direction opposite to the certain direction. A method characterized by being offset by the addition of one compound. 2. The method according to claim 1, wherein an inorganic acid or an inorganic salt of an organic acid is used as an additive at a concentration of 0.1 to 200 g / in order to lower the LCST of the solution. 3. The method according to claim 2, wherein the inorganic salt is selected from salts of alkaline earth metals including alkaline metals and magnesium and zinc salts. 4. The anion of the inorganic salt is B ₄ O ₇ ²⁻ , PO ₄
^3- , CO ₃ ²⁻ , SO ₄ ²⁻ , SiO ₃ ²⁻ , F ⁻ ,
The method according to claim 2, wherein the method is selected from among Cl ⁻ , CH ₃ COO ⁻ , Br ⁻ , ClO ₃ ⁻ , I ⁻ . 5. The inorganic salt is selected from the group consisting of disodium carbonate, trisodium phosphate, borax, sodium silicate and disodium sulfate.
The method described in any one of. 6. The method according to claim 1, wherein the water-soluble organic derivative is added at a concentration of 0.1 to 200 g / to increase or decrease the LCST of the solution. 7. The method according to claim 6, wherein the organic derivative is selected from aliphatic compounds having at least one functional group selected from alcohols, acids, aldehydes, amides and amines. 8. An organic derivative which increases LCST is 1,3
Method according to claim 7, characterized in that it is selected from butanediol, acetamide, propylene glycol, ethanol, methanol, formamide, ethylene glycol. 9. The method according to claim 7, wherein the organic derivative that lowers LCST is propanol or butanol. 10. The water-soluble polymer having LCST is selected from oxyethylene polymer, ethylene oxide-propylene oxide copolymer having a propylene oxide / ethylene oxide ratio of 0 to 1, polyvinyl methyl ether and polydimethoxyethylene. The method according to claim 1, wherein the method is performed. 11. An aqueous solution for quenching a metal alloy, comprising at least one water-soluble organic polymer having LCST and at least one additive for modifying (increasing or decreasing) LCST, wherein LCST is in the above-mentioned modifying direction. An aqueous solution, characterized in that it also contains at least one compound which changes in the opposite direction. 12. The additive for lowering LCST is 0.1 to 2
12. Aqueous solution according to claim 11, characterized in that it is selected from water-soluble salts and water-soluble zinc salts of alkali metals and alkaline earth metals (including magnesium) of inorganic or organic acids at a concentration of 00 g /. . 13. The additive for increasing LCST is 0.1 to 2
12. Aqueous solution according to claim 11, characterized in that it is selected from among water-soluble aliphatic organic derivatives with a concentration of 00 g / having at least one functional group selected from alcohols, acids, aldehydes, amides and amines.