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| THE PROPERTIES OF NICHROME 80 Ni-20Cr UNDER MECHANICAL WORKING |
| CHANG TSO-MEI;MAN SHOO-SHAN;GAU TZE-MING Institute of Metal Research; Academia Sinica |
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Cite this article:
CHANG TSO-MEI;MAN SHOO-SHAN;GAU TZE-MING Institute of Metal Research; Academia Sinica. THE PROPERTIES OF NICHROME 80 Ni-20Cr UNDER MECHANICAL WORKING. Acta Metall Sin, 1957, 2(1): 41-63.
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Abstract In order to find out the properties of Nichrome 80 Ni-20 Cr under mechanicalworking, a systematic research has been conducted on the workability, forging, roll-ing, wire-drawing and heat-treatment of this material. Wires of 1 mm diameterhave also been successfully drawn from rolled rod that has been made from ingotsunder laboratory conditions. These have been tested for life in accelerated lifetest apparatus of our own make and have been found to possess satisfactory pro-perties as a heating element. The following are the chief results obtained: 1. From the results of the various workability tests and also results from forg- ing and rolling tests, this alloy has best hot-working properties within the tem-peratures of 1100℃ and 1300℃, Between 800℃ and 1000℃, there exists a brittletemperature range. It is best to avoid this brittle temperature range duringmechanical working. 2. The resistance to deformation of this material lowers gradually with therise in temperature. Even at the high temperatures of 1000—1300℃, there ismarked increase in resistance to deformation with the increase in reduction byrolling. When flat specimens are rolled, linear relationship exists between reduc-tion and the resistance to deformation between temperatures of 800℃ and 1300℃.The lateral spread also increases rapidly with the increase in reduction by rolling.When the reduction is below 30%, a rise in temperature increases the value oflateral spread. 3. With a view to obtaining products of good quality, the anvils of hammersused should have well-rounded edges in order to avoid the occurrence of folds.Similarly, in roll pass designs, the lateral spread should be carefully consideredin order to eliminate the occurrence of ears and consequently the folds producedfrom it. The drawing dies should have smooth working surfaces and the lubricantused should be clean. 4. According to the degree of cold work, the best results could be obtainedin heat-treating this material within the temperatures of 900℃ and 1050℃ whenthe soaking time is kept between 20 to 30 minutes. 5. The well-treated alloys have good cold-drawing properties. During experi-ments, the greatest reduction per pass permissible for a single drawing operationreached 35.4%; while in successive drawing, as much as 90%, reduction in cross-sectional area was recorded.
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Received: 18 January 1957
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