Quench oils, quench oil concentrates, method of heat treating a ferro-metal and articles made therefrom

Abstract

 An improved quench oil for use in heat treating fer- rometals comprises a major amount of mineral oil, an olefinic polymer, an ashless antioxidant, and, optionally, an alkaline earth metal or an alkali metal detergent.

Description

[0001] Properties of steel can be varied by heat treatment to obtain desired microstructures such as martensitic microstructure. Quenching and tempering is the heat treatment commonly used to obtain such microstructures. It involves heating steel to an austenitizing temperature such as 800°C, and then cooling through the martensite transformation temperature range at a rate rapid enough to minimize transformation at temperatures above the martensite range. This is accomplished by quenching the heated steel. The first requisite of a quenching medium is therefore a sufficient cooling rate to obtain the desired results. The temperature gradient caused by the quenching operation results in relatively high thermal and transformation stresses which may if excessive lead to cracking or distortion. In the prevention of these problems, the maximum quenching rate is limited by the nature of the component being heat treated.

[0002] Quenching media commonly used are water, oil and brine. Brine quenching is the most severe. Water approaches it in severity. Oil quenching is much less drastic. It has been proposed to add to various mineral oils to be used as quench oils an ashless dispersant such as an alkenyl succinimide. See for instance United States Patent Specification No. 3866603.

[0003] A need remains however for a quench oil having improved chemical stability and less tendency to deposit material on work pieces quenched therein.

[0004] According to the present invention, quench oil is provided which comprises a major amount of a mineral oil and contains effective amounts of olefinic polymer, ashless antioxidant, and, optionally, alkaline earth metal or alkali metal detergent.

[0005] A preferred embodiment of the invention is a quench oil for use in the heat treatment of ferro-metals, said composition comprising a major amount of mineral oil and (a) about 0.3 to 7.5 weight percent of at least one olefinic polymer of a lower mono-olefin and (b) about .01 to 2.5 weight percent of an ashless antioxidant which is one or more of (i) a sterically hindered phenol, (ii) an alkylated aromatic amine, or (iii) a sulfurized alkylphenol.

[0006] In another embodiment of the invention, there is provided a quench oil for use in the heat treatment of ferro-metals, which comprises a major amount of mineral oil and (a) about 0.3 to 7.5 weight percent of at least one olefinic polymer of a lower mono-olefin; (b) about .01 to 2.0 weight percent of an ashless antioxidant which is one or more of (i) a sterically hindered phenol, (ii) an alkylated aromatic amine, or (iii) a sulfurized alkylphenol and (c) about 0.02 to 2.5 weight percent of alkaline earth metal or an alkali metal detergent which is one or more of an alkaline earth metal arylsulfonate, alkali metal arylsulfonate, alkaline earth metal alkylphenate, alkaline earth metal sulfurized alkylphenate or an alkaline earth metal phosphonate phenate.

[0007] The base mineral oil is suitably a liquid hydrocarbon obtained by conventional petroleum refining methods including hydrocracking, hydrotreating and the like. A useful viscosity range is about 1.5 to 20cSt at 100°C and more preferably 4 to l2cSt at 100°_C.

[0008] Polymers contemplated for use in this invention include homopolymers or copolymers of lower mono-olefins, i.e., a C₂ to C₁₀ olefin, as for example, ethylene, propylene, n-butylene, isobutylene; copolymers and terpolymers of the lower mono-olefins and higher mono-olefins and diolefins having up to 2,000,000 or higher molecular weight, preferably 200 to 50,000 molecular weight. In a highly preferred embodiment, the polymers are those of isobutylene having a molecular weight of up to 10,000 or higher. In an even more preferred embodiment, the polymer is polyisobutylene having a molecular weight of about 700 to 5,000 and most preferably from about 900 to 2,000. As indicated above, the amount of olefinic polymer can vary from about 0.3 to 7.5 weight percent when present in a mineral oil containing an ashless antioxidant and more preferably from about 0.5 to 5.0 weight percent.

[0009] A very useful class of ashless antioxidants includes the hindered phenols. These are phenolic compounds having at least one tert-alkyl group substituted at a nuclear position ortho to a phenolic hydroxyl group. Representative examples of these are:

2,6-di-tert-butyl-4-methylphenol

2,6-di-tert-butyl-4-ethylphenol

2,6-di-tert-butylphenol

4,4'-methylenebis(2,6-di-tert-butylphenol)

4,4'-bis(2,6-di-tert-butylphenol)

2,6-di-tert-butyl-a-(dimethylamino)p-cresol

2,2'-methylenebis(4-methyl-6-tert-butylphenol)

2,2'-ethylidenebis (4,6-di-tert-butylphenol)

1,3,5-tri(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene

octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate

tetra-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionatelpentaerythritol

0,0-di-octadecyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate and the like.

[0010] Another useful class of ashless antioxidants are the aromatic amines. Examples of these are N,N'-di- octylphenylenediamine, N-isopropylphenylenediamine and the like.

[0011] The most preferred of these are the alkylated diphenylamines such as

di-(octylphenyl)amine

di-(dodecylphenyl) amine

octylphenyl dodecylphenylamine

and the like. Of the sub-class the most preferred is di-(nonylphenyl)amine.

[0012] Sulfurized alkylphenols can also be used as the ashless antioxidant. These can be made by reacting an alkylphenol with elemental sulfur at elevated temperature. This forms sulfur bridging groups between alkylphenol molecules. The phenols are preferably para- alkylated. Examples of alkylphenols which make useful sulfurized products are:

p-dodecylphenol

p-octadecylphenol

p-eicosylphenol

p-isobutylphenol

and the like. The most preferred is sulfurized p-nonylphenol.

[0013] The amount of ashless antioxidant in the quench oil should be an amount that provides the required amount of stabilization. A useful range is about .01 to 2.5 weight percent when used in combination with the olefinic polymer only and from about .01 to 2.0 weight percent when used in combination with both olefinic polymer and detergent.

[0014] The more preferred alkaline earth or alkali metal detergents are the alkaline earth or alkali metal arylsulfonates. These include both the so-called natural sulfonates derived by sulfuric extraction of petroleum as well as the synthetic sulfonates made by sulfonating synthetic alkylbenzenes. The alkaline earth metal sulfonates include both neutral and over based sulfonates. The term "alkaline earth metal" as used herein includes calcium, barium and magnesium. The term "alkali metal" as used herein includes sodium.

[0015] The most preferred alkaline earth metal arylsulfonates are the calcium salts of alkylbenzene sulfonic acids in which the alkylbenzenes have an average molecular weight of about 300-700.

[0016] Another useful class of alkaline earth metal detergents includes the alkaline earth metal alkyl phenates (e.g. US 2,228,671; US 2,252,663; US 2,280,419; US 2,412,903; US 2,610,982; US 3,779,920; US 3,691,076) and alkaline earth metal sulfurized alkyl phenates. (e.g. US 2,249,626; US 2,331,448; US 2,336,074; US 2,342,887; US 2,346,826; US 2,362,292; US 2,366,874; U_S 2,406,564). These are made by reacting alkaline earth metal hydroxide or oxide (e.g. CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂) with an alkylphenol or sulfurized alkylphenol.

[0017] The alkyl substituent preferably contains about 4-20 carbon atoms such as in isobutylphenol, 2-ethyl- hexylphenol, nonylphenol, 1-ethyldecylphenol and the like. The corresponding sulfurized detergent is made by well-known methods such as by heating a mixture of alkylphenol and sulfur and then reacting the sulfurized phenols with an alkaline earth metal base.

[0018] Alkaline earth metal phosphonate phenates are typically made by the coneutralization of a mixture of a phosphosulfurized polyolefin and an alkyl phenol or an alkyl phenol sulfide. Co-neutralization may be carried out using, for example barium oxide, barium hydroxide, calcium oxide or calcium hydroxide or an alkoxide of magnesium or a carbonated alkoxide of magnesium in an alkanol, such as described in British Patent 1303048.

[0019] The alkylphenol sulfide (that is to say a compound containing two or more alkylphenol residues linked by one or more sulfur atoms) or the alkylphenol is preferably one which has an aromatic nucleus that is substituted by an alkyl group having from 5 to 20 carbon atoms, especially from 7 to 12 carbon atoms. An alkyl group having 9 carbon atoms is often particularly satisfactory.

[0020] It is often preferable to use an alkylphenol sulfide rather than the alkylphenol itself. The sulfide can be a monosulfide, but disulfides, trisulfides, tetra- sulfides, pentasulfides and other polysulfides are also very useful. A suitable alkylphenol sulfide can in fact be made from an appropriate alkylphenol by reaction with sulfur dichloride, the composition of the product depending on the molar ratio of alkylphenol to sulfur dichloride used and the alkylphenol residues being linked in general by monosulfide links.

[0021] Examples of suitable alkylphenol sulfide and alkylphenol starting materials are nonylphenol and dodecylphenol and the product of reacting from three to five moles of an alkylphenol in which the alkyl group has from 7 to 11 carbon atoms with from two to four moles of sulfur dichloride. A particularly preferred example is the reaction product of four moles of nonylphenol and three moles of sulfur dichloride.

[0022] The polyolefin that is used in phosphosulfurized form is preferably one of relatively low molecular weight; it can be for example a polypropylene, polybutene or polyisobutylene, for instance one that has an average molecular weight between 500 and 2500, for example 1100. It can for instance have been phosphosulfurized by reacting it with a phosphorus sulfide such as for example P₄^s_3l P₄S₇, or more preferably P₂S₅. The phosphosulfurized polyolefin can be used as such that is to say in the form in which it is produced by phospho- sulfurization.

[0023] The alkylphenol sulfide or alkylphenol and the phosphosulfurized polyolefin can be used in any desired relative proportion, but usually it is preferred to employ these in a weight ratio between 1: 12 and 6: 1 especially between 1: 9 and 4: 1 and more preferably between 3: 7 and 1: 1.

[0024] The amount of alkaline earth or alkali metal detergent can vary from about .02 to about 2.5 weight percent. A preferred range is about .05 to 2.0 weight percent and a most preferred range is about 0.1 to 1.0 weight percent.

[0025] The invention also includes a quench oil concentrate cocprising a mineral oil solvent and (a) olefinic polymer and (b) ashless antioxidant, and, optionally, an alkaline earth metal or alkali metal detergent.

[0026] In commerce a convenient way to prepare the quench oil is to add a quench oil concentrate to the mineral oil base. The concentrate contains the proper amount of each additive such that when blended in the mineral oil base the resultant quench oil will contain the proper amount of each additive. In concentrates containing olefinic polymer in combination with ashless antioxidant, a useful concentration range of each class of additive is 25 to 90 weight percent olefinic polymer and 2.0 to 30 weight percent ashless antioxidant. In concentrates containing olefinic polymer, ashless antioxidant and alkaline earth or alkali metal detergent, a useful concentration range of each additive is 25 to 90 weight percent olefinic polymer, 1.0 to 20 weight percent ashless antioxidant and 2.0 to 15 weight percent alkaline earth or alkali metal detergent.

[0027] The invention will be illustrated by the following Examples.

Examples

[0028] Initially tests were conducted to compare the cooling rate of the present quench oil according to the invention with the cooling rate of the base oil. The method used was the Wolfson Heat Treatment Centre Test Method. In this test a specified stainless steel probe of length 60mm and diameter 12.5mm and containing a thermocouple is soaked at 850°C in a furnace and then rapidly transferred to a 2 litre sample of the quench oil held at 40°C. The temperature vs time and the rate of temperature change vs temperature as measured by the thermocouple are recorded.

[0029] The test method is described in detail in "Laboratory Test for Assessing the Cooling Characteristics of Industrial Quenching Media" ISBN 0 9507768 2 3 available from the Wolfson Heat Treatment Centre, The University of Aston in Birmingham, Gosta Green, Birmingham _B4 7ET England.

[0030] First, a quench oil concentrate "A" according to the invention was prepared containing:

13.0 weight percent mineral oil

70 weight percent polyisobutylene (molecular weight = 1,000)

17.0 weight percent sulfurized p-nonylphenol

[0031] Next, a quench oil concentrate "B" according to the invention was prepared containing

7.0 wt % mineral oil

74.4 wt % polyisobutylene (molecular weight = 1000)

7.0 wt % Ca phosphonate phenate

11.6 wt % Di-(nonylphenyl)amine

[0032] 1. Calcium phosphonate phenate having a calcium content of 3.3%, a phosphorus content of 2.2%, a sulfur content of 6.0% and a total base number (IP method 276) of 92.

[0033] The test results were as follows:

[0034] These test results show that the present additive packages provide a significant increase in quenching rate.

[0035] Further tests were conducted to measure the thermal stability of the quench oil. In the Panel Coker test the oil sample was splashed against a heated (315°C) aluminum plate intermittently (45 sec splash - 15 sec no splash) while air was circulated through the test cell at the rate of 2.3 litre per hour. The test duration was 14.75 hours. Test criteria was the amount of deposit formed on the heated aluminum plate. The results were as follows:

[0036] These results show that not only is the quenching rate improved but also the deposition tendency is much reduced.

[0037] An Oxidative Stability Test was conducted by bubbling air through a test oil at 150°C for 72 hours at 10 l/hr. A small amount of iron acetylacetonate (40ppm) was added to the test oil to promote oxidation. Test criteria were the increase in total acid number (TAN), percent insolubles and percent viscosity increase measured at 40°C. Results were as follows:

[0038] These results attest to the excellent oxidative stability of the quench oil containing the present additive combinations.

Claims

1. A quench oil which comprises a major proportion of a mineral oil and an effective amount of (a) olefinic polymer and (b) ashless antioxidant.

2. A quench oil for use in the heat treatment of ferro-materials and comprising a major amount of mineral oil and (a) about 0.3 to 7.5 weight percent of at least one olefinic polymer and (b) about .01 to 2.5 weight percent of ashless antioxidant which is one or more of (i) a sterically hindered phenol, (ii) an alkylated aromatic amine or (iii) a sulfurized alkylphenol.

3. A quench oil as claimed in which claim 1 or claim 2, wherein said olefinic polymer has an average molecular weight of 200 to 2,000,000.

4. A quench oil as claimed in claim 1 or claim 2, wherein said olefinic polymer has an average molecular weight of 200 to 50,000.

5. A quench oil as claimed in any one of claims 1 to 4, wherein said olefin polymer is a homopolymer or a copolymer of a C₂ to C₁₀ mono-olefin.

6. A quench oil as claimed in claim 5, wherein the olefin polymer is polyisobutylene.

7. A quench oil as claimed in any one of claims 1 to 6, wherein said antioxidant is an alkylated diphenylamine.

8. A quench oil as claimed in claim 7, wherein said alkylated diphenylamine is di(nonylphenyl)amine.

9. A quench oil as claimed in any one of claims 1 to 6, wherein said antioxidant is sulfurized p-nonylphenol.

10. A quench oil as claimed in any one of claims 1 to 9 also comprising an alkaline earth metal or alkali metal detergent.

11. A quench oil as claimed in claim 10 comprising about .01 to 2.0 weight percent of said ashless antioxidant and about .02 to 2.5 weight percent of said alkaline earth metal or alkali metal detergent.

12. A quench oil as claimed in claim 10 or claim 11, wherein said alkaline earth metal or alkali metal detergent is one or more of alkaline earth metal arylsulfonate, alkali metal arylsulfonate, alkaline earth metal alkylphenate, alkaline earth metal sulfurized alkylphenate or an alkaline earth metal phosphonate phenate.

13. A quench oil as claimed in claim 12, wherein said alkaline earth metal detergent is a calcium arylsulfonate or a calcium phosphonate phenate.

14. A quench oil concentrate comprising a mineral oil solvent and (a) olefinic polymer and (b) ashless antioxidant.

15. A quench oil concentrate comprising a mineral oil solvent containing (a) 25 to 90 weight percent of olefinic polymer and (b) 2.0 to 30 weight percent ashless antioxidant which is one or more of (i) a sterically hindered phenol, (ii) an alkylated aromatic amine or (iii) sulfurized alkylphenol.

16. A quench oil concentrate as claimed in claim 14 or claim 15 and further defined by the specific feature of any one of claims 3 to 13.

17. A quench oil concentrate comprising a mineral oil solvent containing (a) 25 to 90 weight percent of at least one olefinic polymer, (b) 1.0 to 20 weight percent of ashless antioxidant which is one or more of (i) a sterically hindered phenol, (ii) an alkylated aromatic amine or (iii) sulfurized alkylphenol and (c) 2.0 to 15 weight percent of an alkaline earth or alkali metal detergent which is one or more of an alkaline earth metal aryl sulfonate, alkali metal aryl sulfonate, alkaline earth metal alkylphenate, alkaline earth metal sulfurized alkylphenate or an alkaline earth metal phosphonate phenate.

18. A concentrate as claimed in claim 17 and further defined by the specific feature of any one of claims 3 to 9 or 13.

19. A method of heat treating a ferro-metal, said method comprising heating said metal to an elevated temperature and then quenching the heated metal in a quench oil as claimed in any one of claims 1 to 13.

20. Articles fabricated at least in part from a metal which has been quenched from an elevated temperature in a quench oil as claimed in any one of claims 1 to 13.