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Quenching Process |
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High-velocity water sprays are useful for parts formed from clad sheet and for large sections of almost all alloys. This type of quench also minimizes distortion and alleviates quench cracking. However, many specifications forbid the use of spray quenching for bare 2017 and 2024 sheet materials because of the effect on their resistance to corrosion. Lag Between Soaking and Quenching The time interval between the removal of the material from the furnace and quenching is critical for some alloys and should be held to a minimum. When solution heat treating 2017 or 2024 sheet material, the elapsed time must not exceed 10 second. The allowable time for heavy sections may be slightly greater.
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Quenching Process |
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Lag Between Soaking and Quenching The time interval between the removal of the material from the furnace and quenching is critical for some alloys and should be held to a minimum. When solution heat treating 2017 or 2024 sheet material, the elapsed time must not exceed 10 second. The allowable time for heavy sections may be slightly greater. Allowing the metal to cool slightly before quenching promotes re-precipitation from the solid solution. The precipitation occurs along grain boundaries and in certain slip planes causing poorer formability. In the case of 2017,2024, and 7075 alloys, their resistance to integranular corrosion is adversely affected. Re-heat Treatment The treatment of material which has been previously heat treated is considered a re-heat treatment. The unclad heat-treatable alloys can be solution heat treated repeatedly without harmful effects. The number of solution heat treatments allowed for clad sheet is limited due to increased diffusion of core and cladding with each re-heating. Existing specifications allow one to three re-heat treatments of clad sheet depending upon cladding thickness. Straightening After Solution Heat Treatment Some warping occurs during solution heat treatment, producing kinks, buckles, waves, and twists. These imperfections are generally removed by straightening and flattening operations. Where the straightening operations produce and appreciable increase in the tensile and yield strengths and a slight decrease in the percent of elongation, the material is designated - T3 temper, the material is designated - T4 temper.
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