Aqueous quenching media and use thereof in quenching metal substrates

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.

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.