| 摘要 |
Materials such as tool steel, plastics and natural fibres are treated at low temperatures to enhance their performance. An economical process provides for first cooling the material down to about -70.degree.C for a predetermined time followed by an intense cooling step down to about -190.degree.C for a short duration. The materials are allowed to warm up in two stages pausing between stages at about -70.degree.C. The specific time/temperature program utilizes liquid carbon dioxide and liquid nitrogen and may be varied for the materials to be treated.
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