连续冷却过程中含Cu相在钢中析出行为的研究

STUDY ON PRECIPITATION BEHAVIOR OF PHASES CONTAINING Cu IN THE Cu-BEARING STEEL IN CONTINUOUS COOLING PROCESS

利用热模拟技术研究了一系列含Cu钢在不同冷速下的硬度变化.借助金相和高分辨透射电镜研究了连续冷却过程中的含Cu相析出行为及其对硬度的影响.结果表明:在连续冷却过程中Fe-Cu合金中会发生第二相析出,从而造成硬化.第二相析出为富Cu过渡相,以相让沉淀方式析出,析出行为与冷速和Cu含量有关,当冷却速率为0.1—1℃/s时,随着冷却速率的增加第二相析出物变得更加细小且密度更大,当冷却速率为1℃/s时析出物密度最大.当冷却速率超过1℃/s后,随着冷却速率的增加析出物逐渐减少.当样品以10℃/s冷速冷却时,几乎没有析出物产生.富Cu相析出状况对合金起明显的强化作用.当Cu含量低于1%时,析出现象并不明显.

The hardening behavior of five Cu-bearing steels during continuous cooling has been studied with the aid of thermo-simulation technique.Optical microscope（OM） and high resolution transmission electron microscopy（HRTEM） were employed to investigate the influence of cooling rate on the precipitation behavior in these steels and their hardness.The results show that during the continuous cooling the second phase precipitates occur in these steels and cause the precipitation hardening.These precipitates are proved to be Cu-rich phases and formed by the way of inter-phase precipitation.The precipitation behavior and hardening effect could be affected by cooling rate and copper content in these steels.When the steels are cooled at a cooling rate between 0.1—1℃/s,the second phase precipitates become finer and denser with the increase of cooling rate.Only when the cooling rate is 1℃/s the density of the second phase precipitates is the largest.When the cooling rate is quicker than 1℃/s,increasing the cooling rate leads to the precipitates being finer and fewer.When the samples are cooled at a rate of 10℃/s,there are few precipitates in samples.The Cu-rich phase is the main cause to strengthen these steels.It is also found that when the copper content is less than 1%,the precipitation behavior is unobvious.