GB1576421A - Quenching oil and quenching process - Google Patents

Description

(54) QUENCHING OIL AND QUENCHING PROCESS (71) We, EXXON RESEARCH AND ENGINEERING COMPANY, a Corporation duly organised and existing under the laws of the State of Delaware, United States of America, of Linden, New Jersey, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a quenching oil and a process for quenching metals, especially the mar-quenching of alloy through-hardened steel, and low alloy case hardened steel.

With ever-increasing competition many industries, especially the motor car industry, have been seeking ways to cheapen their process of producing high quality hardened components such as gears, or pinions. In particular, attention has been directed towards the production of high quality products from the cheaper and more readily available low alloy steels such as B.S.En 42, 44, 351, 352, 353, 363 and SAE 1019, 4620, 8615, 8617 and 8620. These products are nearly always produced by forming accurately, then hardening by heating, the metal, e.g. steel, to high temperature and then plunging the metal rapidly into a bath of a liquid maintained at a certain temperature or within a certain temperature range. In order to reach the required degree of hardness with minimum distortion, cracking or variation in hardness from batch to batch, and to obtain a hardened metal of consistent and satisfactory hardness, and to obtain satisfactory oil life, it is necessary that the process be carefully controlled and that the quenching liquid should meet fairly stringent requirements. The liquid should have a high flash point, good thermal stability, long life, very high cooling rate over the critical temperature range, good metal hardening characteristics, and not leave deposits on the metal after removal from the quenching bath. The liquid should also be capable of rapidly absorbing heat from the hot metal so that the quenching time is reduced.

In accordance with this invention, a quenching oil composition suitable for quenching or press quenching metals comprises a major proportion by weight of a synthetic oil or hydrocarbon oil, a minor proportion by weight of at least one phenol-based detergent (as hereinafter defined) and a minor proportion by weight of at least one dicarboxylic acid or anhydride thereof having a molecular weight of at least 250, and having a saponification number greater than 80.

Preferably the saponification number is above 90 and very preferably in excess of 100. However, the upper limit will not normally be greater than 150. A value of 110 to 150 is preferred, 110 to 120 being especially preferred. In all cases saponification number is measured in terms of mg KOH/gram.

The oil may be a synthetic oil, e.g. a polyglycol ether or ester, but is generally a hydrocarbon oil. The hydrocarbon oil is preferably a distillate mineral oil of medium viscosity.

For cold quenching, naphthenic, paraffinic or mixed base distillates of medium to low viscosity are suitable. For mar-quenching, especially suitable mineral oils are parafEnic distillates having a kinematic viscosity at 2100F of between 9.0 and 16.0, e.g. about 12.0 to 14.0, a viscosity index of between 80 and 105, e.g. about 100 and a flash point of at least 2500C, e.g. about 280"C. The flash point will not normally exceed 3 < 0 C, a preferred upper limit being 32()OC.

In general it has been found that close cut high flash point (e.g. above 2500C and preferably above 2700C) middle distillates are the most suitable hydrocarbon oils.

The phenol-based detergent additive contained as a minor proportion in the oil is defined as the reaction product of sulphur or a phosphosulphurised-hydrocarbon compound with either (A) an alkyl phenol or alkyl phenol sulphide, and an alkali metal base or alkaline earth metal base, or (B) an alkali metal alkyl phenate or alkyl thiophenate or an alkaline earth metal alkyl phenate or alkyl thiophenate.

The more preferred type of phenol-based detergent additive is that prepared by reacting either (1) an alkali metal base or an alkaline earth metal base with an alkyl phenol or alkyl phenol sulphide and a phosphosulphurised hydrocarbon in the presence of a diluent oil, or (2) an alkali metal alkyl phenate or alkyl thiophenate or an alkaline earth metal alkyl phenate or alkyl thiophenate with a phosphosulphurised hydrocarbon in the presence of a diluent oil. In both cases (1) and (2) it is preferable if carbon dioxide is blown into the reaction mixture whilst the reaction takes place.

Suitable alkyl phenols or alkyl phenol sulphides include mono or polyalkyl compounds in which each of the alkyl groups contains between 5 and 30, e.g. 7 to 26, preferably 7 to 10 carbon atoms. Particularly suitable phosphosulphurised hydrocarbons are phosphosulphurised polyolefins, e.g. polybutene, having a molecular weight of from 100 to 50,000, suitably from 500 to 1,500, e.g. 750 to 900. Methods of preparing these phenolbased detergent additives are described in U.K. Patent Specifications 921,124, 94G,175; 958,520; 970,786; 867,800 and 887,334.

Phosphorus contents can range from, for example, 1 to 10 wt.%, preferably 2 to 5 wt.%; sulphur contents from 1 to 10 wt.%, preferably 5 to 8 wt.%. This type of phenolbased detergent additive, i.e. prepared by a reaction involving a phosphosulphurised hydrocarbon, is preferably highly basic, e.g. having an alkalinity index greater than 50. This, of course, may be achieved by ensuring that there is excess base in the reaction mixture. Generally, it is preferable if these additives are derived from alkaline earth metal base, especially from barium hydroxide pentahydrate or barium hydroxide octahydrate.

The quantity of phenol-based detergent additive incorporated in the quenching oil is preferably iess than 20% by weight, and a suitable amount has been found to be between 1 and 10% by weight, based on the total weight of the quenching oil composition.

Particularly suitable for use as the dicarboxylic acid or anhydride constituent are those having a molecular weight of above 500, the upper limit being set in practice by the requirement that the saponification number must be above 80. These carboxylic acids are conveniently derived from a polymer of a mono-olefin, e.g. a C2 to C mono-olefin, such as polyethylene, polypropylene or polyisobutene.

Dicarboxylic acid anhydrides having a relatively long chain may be conveniently made by the reaction of maleic anhydride with a long-chain olefin or a halogenated long-chain olefin. The preferred olefins are polymers of mono-olefins. Thus, one may react a polyisobutene, or the halogenated derivative thereof, with maleic anhydride to give an alkenyl succinic anhydride. ?'he two reactants may be merely heated together at a temperature of 1500C to 2000 C. However, only those reaction products having a molecular weight of at least 250 and a saponification number greater than 80 are suitable for use in the compositions of the present invention.

The corresponding acids can, of course, be made by hydrolysis of the anhydride. A particular example of a long chain dicarboxylic acid is polybutenyl succinic acid of MW approximately 1,000.

Most preferred are substituted succinic anhydrides of the formula.

where R and Rl are either alky; or alkenyl radicals or hydrogen, provided at least one of them is alkyl or alkenyl.

R and Rl can be straight-chain or branched, the total number of carbon atoms in both groups R and R2 preferably being from 25, the upper limit being governed by the necessity for the compound to have a saponification value above 80. Although the alkenyl group can be polypropenyl or polyisoamylenyl it is preferably polyisobutenyl. Thus a particularly preferred anhydride is polyisobutenyl succinic anhydride of molecular weight of from 200 to 1,200, e.g. about 1,000.

The quantity of dicarboxylic acid or anhydried incorporated in the quenching of composition is normally up to 20% by weight, and it is preferred to use from 1 to 15% by weight, more preferably from 1 to 10% by weight, suitably 1 to 5% by weight, based on the total weight of the quenching oil. A major advantage of the compositions of this invention is that such acid or anhydride additives are ashless. This marks a fundamental departure from the majority of the special additives previously employed in mar-quenching oils, as these are metal-containing e.g. overbased alkali or alkaline earth sulphonates, and hence not ashless. Such prior proposals are disclosed, for example in British Patent Specification 1,137,187. In addition, the acid or anhydride is the simple component, not a derivative such as an ester or imide; and hence is relatively inexpensive and is more stable at the elevated temperatures initially met in quenching processes.

A quenching oil composition according to this invention may, if desired, also include minor amounts of one or more additives, such as antioxidants and/or emulsifiers. Thus, one can employ up to about 1 wt.% of phenylthiazines, substituted phenylthiazines, sub stituted phenols, bisphenols, catechols, aromatic amines. One can employ up to 4 wt.% of emulsifiers, such as the sorbitan monolaurate and polyoxyethylene-sorbitan monolaurate types; and the fatty acid-, or alkaryl-, polyglycol ether types.

The oil compositions of this invention can be used to quench or press quench a metal by a process comprising heating the metal to an elevated temperature, and thereafter transferring the metal into a bath or mould comprising said quenching oil maintained at a temperature lower than the elevated temperature.

The process of the invention can be applied to the quenching of any metal or metal alloy, but is especially suitable for quenching through or case hardened steels, e.g. a steel having a carbon content at least at the surface, of about 0.9% by weight. Other suitable metals include aluminum alloys.

The elevated temperature to which the metal is first heated and soaked will depend on the nature of the metal and the final properties required, but generally this temperature will be at or above the temperature where the impurities or alloying elements are in solid solution. Thus, in the case of carbon steel this elevated temperature will be above 8000C and often about 9000 C, whereas with aluminum alloys, e.g. Duralumin (the word DURALUMIN is a registered Trade Mark), this elevated temperature will be about 5000 C.

The temperature of the quenching oil in the bath into which the metal is plunged will vary according to the treatment it is desired to give to the metal. Thus, in the case of carbon steel (e.g. 0.9 to 1.2% by weight carbon) if it is desired to mar-quench the steel, the temperature of the oil in the bath will be maintained at about 1500C to 2500C, e.g. about 200 depending upon the Ms point of the particular steel; Ms point being the temperature at which the onset of martensite formation occurs. tf, however, it is desired to "cold" quench the steel the temperature of the oil will be from ambient to about 800 C.

"Cold" quenching of steel will normally result in a more rapid quench than marquenching, but there will be more difference in mechanical properties between the core and case of the metal. For warm quenching of steels the temperature of the liquid will usually b e from 80"C to 1500C. When quenching aluminum alloys, the temperature of the oil in the bath will often be about ambient.

The metal should be transferred or plunged into the bath as quickly as possible. The bath may be a tank or any receptacle suitable for containing the quenching oil and also large enough to accommodate the metal which is being quenched.

Generally, the metal will be completely immersed in the oil whilst it is being quenched until the case/core temperature differential is small enough to prevent internal stresses being set up during subsequent conversion to martensite (in the case of steel) or mixed structures on cooling in air or by water spray to ambient temperature. The quench bath may be covered or uncovered, and may be maintained under an inert atmosphere preferably an endothermic gas.

In the examples given hereafter the products of the following preparations were employed: Preparation 1.

The phenol based detergent additive which was used was the reaction product obtained as follows: 14.5 wt.% of a phosphosulphurised polybutene of molecular weight 750 to 900 having a sulphur content of 6.1 to 6.5 wt.% and a phosphorus content of 3.2 to 3.7 wt.% was mixed with 7.4 wt.% of a mixture of C7 to C9 alkyl phenols in 46.7 wt.% of a mineral hydrocarbon diluent oil. This mixture was purged with nitrogen from 90 to 130/133cm and contained at a temperature of 127 to 1350C 26.9 wt.% of barium hydroxide pentahydrate was added over 3 to 6 hours. Half an hour after the start of the barium hydroxide pentahydrate addition, carbon dioxide was blown in. The blowing in of CO2 was continued for about half an hour after the last of the barium hydroxide pentahydrate had been added and in all 14.5 wt.% of CO2 was added. Finally, the reaction product obtained by filtering.

Preparation 2.

A polyisobutenyl succinic anhydride having a saponification number of 80 (mg KOH/ gram) was prepared by reaction, at a temperature between 1500C and 200eC of polyisobutylene of about 900 molecular weight with maleic anhydride.

Preparation 3.

A polyisobutenyl succinic anhydride having a saponification number of 112 was prepared by chlorinating polvisobutylene of about 950 molecular weight to a 4.5 wt.% chlorine content and then condensing the chlorinated poly isobutylene with maleic anhydride at a temperature between 1SO"C and 200"C.

Preparation 4.

This product was a commercially available calcium alkyl benzene sulphonate having a TBN of 300 and made in the normal manner for such products.

Preparation 5.

Employing the general technique of Preparation 3, but using polyisobutylene of about 1,300 molecular weight, a polyisobutenyl succinic anhydride having a saponification number of 103 was prepared.

Preparation 6.

A polyisobutylene succinic anhydride having a saponification number of 140 was prepared by the general technique of Preparation 3.

Preparation 7.

A polyisobutenyl succinimide of tetraethylenepentamine was prepared by reacting the said amine with the product of Preparation 3.

The following non-limitative examples illustrate the invention: Example 1.

In this Example, quenching oils were tested for their oxidation stability and thermal stability. The base oil for the tests was a phenol treated hydrorefined paraffinic oil of approximately 12 cSt viscosity at 2100F and having a Viscosity Index of approximately 95.

The test was conducted at a temperature of 200"C as follows: 250g of the oil was placed in a 400 ml tall, uncovered beaker, which was then placed in an oven maintained at 2000 C. The oven was fitted with a fan to provide a forced draught in the oven. A 45g sample was taken at the end of the first, second, third, etc.

weeks, its viscosity measured and its percentage viscosity increase calculated.

The results are shown in Table 1 hereafter.

It can be seen that the composition in accordance with the invention is equal or superior to a composition not having the component of Preparation 3.

Example 2.

In this Example, quenching oils were tested in a steel probe quenching test. The apparatus employed comprised a probe 1" long by 0.5" diameter, constructed of 18/8 stainless steel. The probe was threaded and welded to a 0.125" o.d., 24" long stainless steel sheath or tube in which was disposed a thermocouple and carrying a stop to locate the tube and probe during heating and quenching. The temperature at the centre of the probe, as determined by the thermocouple, was recorded on a continuous recorder.

In each test the probe was heated for 15 minutes in a tube furnace at 850"C and then immersed in 400 ml of quenching oil, initially at 1800C, contained in a 600 ml tall beaker.

The base oil of the quenching oil was that same as for Example 1.

The results are shown in Table 2 hereafter.

It will be seen that the compositions in accordance with the invention (the two marked with an asterisk in the Table) have superior quenching time properties.

Example 3.

This Example was conducted in the same way as Example 2 but using also the products of Preparations 5 to 7. The results are shown in Table 3. Again it will be seen that the compositions in accordance with the invention (the three marked with an asterisk in Table 3) have superior quenching time properties.

The use of the product of Preparation 7, as shown in the last result in Table 3, gives a similar result. However that product is a relatively costly one and, in practice, was found not to be so stable in use as the compositions in accordance with the present invention.

TABLE 1 BASE OIL plus

% Increase 2 wt. % Preparation 1 5 wt. % Preparation 1 of Initial 2100F Plus Plus Plus Pius Viscosity Prepn. 1 Prepn. 3 2 wt. % of 2 wt. % of 5 wt. % of 5 wt. % of after 4 wt. % 4 wt. % Prepn. 2 Prepn. 3 Prepn. 2 Prepn. 3 1 Week 15neo 9% 5% 7% 10% 13% 2 Weeks 30% 20% 15% 14% 20% 22% 3 Weeks 55% 30% 20% 20% 25% 28% 4 Weeks 95% 40% 30% 30% 32% 35% TABLE 2

Base Oil Probe Temp. ( C) plus After Quench Time (Secs.) (wt. %) 0 5 10 15 20 25 4% prepn. 1 850 542 429 388 361 340 4% prepn. 1 850 542 429 388 361 340 4% prepn. 3 850 548 466 425 394 366 4% prepn. 4 850 568 431 388 362 344 2% prepn. 1 + 2% prepn. 2 850 531 437 400 370 347 2% prepn. 1 + 2% prepn. 3* 850 531 424 382 355 332 5% prepn. 1 + 2% prepn. 4 850 563 424 385 359 34;4 5% prepn. 1 + 5% prepn. 2 850 512 388 343 319 304 5% prepn. 1 + 5% prepn. 3* 1 850 531 389 333 310 290 5% prepn. 1 + 5% prepn. 4 850 640 412 348 319 304 TABLE 3

Base Oil plus Probe Temp. ( C) after Quench Time (Secs) (wt. %) 0 5 10 15 20 25 Nil 850 601 570 418 379 350 3% prep. 1 850 579 420 375 345 317 3% prepn. 2 850 564 438 393 359 330 3% prepri. 5 850 562 434 390 356 327 3% prepn. 3 850 565 441 395 362 332 3% prep. 6 850 557 427 382 349 319 3% prepn. 7 850 562 432 386 352 322 /2% prepn. 1 + 1h% prepn. 2 850 562 420 375 344 325 1h% prepn. 1 + l'h%.prepn. 5* 850 568 419 -370 340 312 llh% prepn. 1 + 1% prepa. 3* 850 551 407 363 332 304 llh% prepn. 1 + 1'h% prepn. 6* 850 561 414 368 336 307 1% prep. 1 + F/2% prepn. 7 850 553 411 367 335 309 WHAT WE CLAIM IS: 1. A quenching oil composition comprising a major proportion by weight of a synthetic oil or hydrocarbon oil, a minor proportion by weight of at least one phenol-based detergent (as herein defined) and a minor proportion by weight of at least one dicarboxylic acid or anhydride thereof having a molecular weight of at least 250 and having a saponification number greater than 80.

2. A composition as claimed in claim 1, wherein the dicarboxylic acid or anhydride

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   TABLE 2

   Base Oil Probe Temp. ( C) plus After Quench Time (Secs.) (wt. %) 0 5 10 15 20 25 4% prepn. 1 850 542 429 388 361 340 4% prepn. 1 850 542 429 388 361 340 4% prepn. 3 850 548 466 425 394 366 4% prepn. 4 850 568 431 388 362 344 2% prepn. 1 + 2% prepn. 2 850 531 437 400 370 347 2% prepn. 1 + 2% prepn. 3* 850 531 424 382 355 332 5% prepn. 1 + 2% prepn. 4 850 563 424 385 359 34;4 5% prepn. 1 + 5% prepn. 2 850 512 388 343 319 304 5% prepn. 1 + 5% prepn. 3* 1 850 531 389 333 310 290 5% prepn. 1 + 5% prepn. 4 850 640 412 348 319 304 TABLE 3

   Base Oil plus Probe Temp. ( C) after Quench Time (Secs) (wt. %) 0 5 10 15 20 25 Nil 850 601 570 418 379 350 3% prep. 1 850 579 420 375 345 317 3% prepn. 2 850 564 438 393 359 330 3% prepri. 5 850 562 434 390 356 327 3% prepn. 3 850 565 441 395 362 332 3% prep. 6 850 557 427 382 349 319 3% prepn. 7 850 562 432 386 352 322 /2% prepn. 1 + 1h% prepn. 2 850 562 420 375 344 325 1h% prepn. 1 + l'h%.prepn. 5* 850 568 419 -370 340 312 llh% prepn. 1 + 1% prepa. 3* 850 551 407 363 332 304 llh% prepn. 1 + 1'h% prepn. 6* 850 561 414 368 336 307 1% prep. 1 + F/2% prepn. 7 850 553 411 367 335 309 WHAT WE CLAIM IS: 1. A quenching oil composition comprising a major proportion by weight of a synthetic oil or hydrocarbon oil, a minor proportion by weight of at least one phenol-based detergent (as herein defined) and a minor proportion by weight of at least one dicarboxylic acid or anhydride thereof having a molecular weight of at least 250 and having a saponification number greater than 80.
2. 2. A composition as claimed in claim 1, wherein the dicarboxylic acid or anhydride

   thereof has at least one polyalkenyl group.
3. 3. A composition as claimed in claim 2, wherein the acid or anhydride is a polysiobutenyl succinic acid or anhydride.
4. 4. A composition as claimed in any preceding daim wherein the saponification number is in the range 100 to 150.
5. 5. A composition as claimed in any preceding claim, wherein there is present from 1 to 10% of said acid or anhydride.
6. 6. A composition as claimed in claim 5, wherein there is present from 1 to 5% of said acid or anhydride.
7. 7. A composition as claimed in any preceding claim, wherein the phenol-based detergent is that obtained by the reaction of (1) an alkali metal base or alkaline earth metal base with an alkyl phenol or alkyl phenol sulphide and a phosphosulphurised hydrocarbon in the presence of a diluent oil, or (2) an alkali metal alkyl phenate or alkyl thiophenate or the ccrresponding alkaline earth metal compounds with a phosphosulphurised hydrocarbon in the presence of a diluent oil.
8. 8. A composition as claimed in claim 7, wherein the phenol-based detergent is that obtained from a barium base, a phosphosulphurised polybutene of 750 to 900 molecular weight and a mixture of C7 to C,0 alkyl phenols.
9. 9. A composition as claimed in claim 7 or claim 8, wherein there is present from 1 to 10 wt.% of the phenol-based detergent.
10. 10. A composition as claimed in any preceding claim, wherein the oil is a paraffinic petroleum middle distillate oil.
11. 11. A composition as claimed in any preceding claim and substantially as herein described.
12. 12. A composition as claimed in claim 1 and substantially as herein described with reference to any one of the Examples.
13. 13. A mental quenching process whenever employing as the, or as a, quenching oil a composition as claimed in any preceding claim.