烘烤硬化钢的音频内耗研究

用音频内耗仪，在加与不加磁场(磁场强度为300Oe)的不同条件下，测量了H180钢热轧及烘烤不同时间试样的290~630K内耗.在Q-1-T谱中出现了两个较明显的内耗峰，一个在362K附近，另一个在474K附近(测量频率2300~2150Hz)；随着时效时间的增加，第一个峰不断减小，第二个峰不断增大.分析得出，第一个峰为Snoek峰，第二个峰为B峰.对比加与未加磁场测量的内耗看出，加磁场后的“背景”内耗反而比未加磁场时的“背景”内耗要高，而且音频测量引起的这种加磁场“背景”内耗比未加磁场时增强，却随温度升高下降.

Study of Audio Frequency Internal Friction in Bake Hardening Steel

The internal frictions from 290 to 630K in the H180 steel specimens hot rolled or baked for various time were measured under different conditions with and without a magnetic field (magnetic field strength is 300Oe) using an audio frequency internal friction instrument. It is found that there are two clear peaks of internal friction in all the Q-1 T curves， and that the first peak appears at about 362K， while the other one occurs at about 474K (measurement frequencies are 2300~2150Hz). With increasing baking time， the first peak continuously decreases but the second peak increases. Analysis demonstrates that the first peak is the Snoek peak and the second one is the B peak. A comparison of the internal frictions measured with and without a magnetic field shows that the background internal friction measured under a magnetic field is higher than that measured without a magnetic field. Such a background internal friction is enhanced under the present audio frequency measurements， but it decreases with increasing the measurement temperature.