Aqueous quenching media and use thereof in quenching metal substrates
Aqueous media for quenching metal substrates are provided and contain (i) a polyvinylpyrrolidone/polyvinylcaprolactam copolymer and (ii) one or more of a second polymer, which is selected from (a) a substituted oxazoline polymer; (b) a poly(oxyethylene-oxyalkylene)glycol; or (c) a polyvinylpyrrolidone polymer. The quenching bath provides reduced cooling rates through the martensite temperature ranges. Also provided are processes for quenching metal substrates using these quenching media.
1. A quenching concentrate for heat-treating metal substrates, said concentrate consisting of
(a) water;
(b) at least 5% by weight of a mixture of
(i) a non-ionic, water-soluble or water-dispersible polyvinylpyrrolidone/polyvinylcaprolactam copolymer; and
(ii) a non-ionic, water-soluble or water-dispersible vinylpyrrolidone polymer having a molecular weight of at least 500,000; and
(c) at least one additive which is a bacteriocidal agent or biocide, a preservative, a corrosion inhibitor, a buffer, a metal deactivator, a dye, a fragrance, a caustic agent, a wetting agent, a sequestering agent, a fungicide, or a defoamer.
2. The concentrate according to claim 1 comprising about 5% to 70% by weight of components (i) and (ii).
3. The concentrate according to claim 1 comprising about 5% to about 20% of components (i) and (ii).
4. The concentrate according to claim 1 , wherein component (i) is of formula I:
wherein:
R is a caprolactam; and
n and m are, independently, integers, provided that said polymer of component (i) has a molecular weight of about 5,000 to about 2,000,000 and a K-value of about 60 to about 70.
5. The concentrate according to claim 4 , said copolymer (i) comprising about 75% of n and about 25% of m.
6. The concentrate according to claim 1 , wherein said polyvinylpyrrolidone/polyvinylcaprolactam copolymer (i) has a molecular weight of about 50,000 to about 1,000,000.
7. The concentrate according to claim 1 , wherein said vinylpyrrolidone polymer (ii) is of formula IV:
wherein:
z is an integer, provided that said vinylpyrrolidone polymer has a molecular weight of at least 500,000 and a K-value of about 26 to 130.
8. The concentrate according to claim 7 , wherein said vinylpyrrolidone polymer (ii) has a molecular weight of at least 1,000,000.
9. The concentrate according to claim 7 , wherein said vinylpyrrolidone polymer (ii) has a molecular weight of about 750,000.
10. The concentrate according to claim 7 , wherein said vinylpyrrolidone polymer (ii) has a molecular weight of about 1,500,000.
11. The concentrate according to claim 7 , wherein said vinylpyrrolidone polymer (ii) has a molecular weight of about 2,000,000.
12. The concentrate according to claim 7 , wherein said vinylpyrrolidone polymer (ii) has a molecular weight of about 2,500,000.
13. The concentrate according to claim 1 , wherein the ratio of component (i) to component (ii) is about 90:10 to about 10:90.
14. The concentrate according to claim 1 comprising:
(i) a vinylpyrrolidone/vinylcaprolactam copolymer having a molecular weight of about 50,000 to about 1,000,000; and
(ii) a vinylpyrrolidone polymer having a molecular weight of about 1,000,000, and
wherein the concentration of the vinylpyrrolidone/vinylcaprolactam copolymer and the vinylpyrrolidone polymer in the concentrate is about 5% to 70% by weight.
15. The concentrate according to claim 1 comprising:
(i) a vinylpyrrolidone/vinylcaprolactam copolymer having a molecular weight of about 100,000 to about 200,000; and
(ii) a vinylpyrrolidone polymer having a molecular weight of about 1,000,000,
wherein the concentration of the vinylpyrrolidone/vinylcaprolactam copolymer and the vinylpyrrolidone polymer is about 5% to about 20% by weight.
16. A concentrate for preparing an aqueous quenching medium useful in the heat treatment of metal substrates comprising in water at least 5% by weight, of a mixture of one copolymer (i) and one homopolymer (ii), wherein:
(i) the copolymer is a nonionic, water-soluble or water-dispersible substituted vinylpyrrolidone/vinylcaprolactam copolymer of formula I:
wherein:
R is a caprolactam;
n and m are independently integers, provided that said polymer of component (i) has a molecular weight of from about 5,000 to about 1,000,000 and a K-value of about 60 to about 70; and
wherein said vinylpyrrolidone/vinylcaprolactam copolymer has a vinylpyrrolidone component of about 10 to about 90 mol %, said copolymer has a vinylcaprolactam component of about 90 to about 10 mol %, and the sum of said vinylpyrrolidone and vinylcaprolactam components is 100 mol %; and
(ii) the homopolymer is a vinylpyrrolidone polymer having formula IV:
wherein:
z is an integer, provided that said vinylpyrrolidone polymer has a molecular weight of at least 500,000 and a K-value of about 26 to 130.
17. A quenching concentrate for heat-treating metal substrates, said concentrate consisting of two polymers and an aqueous medium,
wherein said polymers consist of at least 5% by weight of a mixture of
(i) a non-ionic, water-soluble or water-dispersible polyvinylpyrrolidone/polyvinylcaprolactam copolymer; and
(ii) a non-ionic, water-soluble or water-dispersible vinylpyrrolidone polymer; and
wherein said aqueous medium consists of water and at least one additive which is a bacteriocidal agent or biocide, a preservative, a corrosion inhibitor, a buffer, a metal deactivator, a dye, a fragrance, a caustic agent, a wetting agent, a sequestering agent, a fungicide, or a defoamer.
18. A method for quenching a heated metal substrate, said method comprising:
I. mixing the concentrate of claim 1 with a carrier, additional water, or a combination thereof; and
II. quenching said heated metal substrate with the product of step I.