中碳鋼晶粒控制技術之建立

Fine Tuning Technology of Grain-size to Improve the Hardenability of Medium Carbon Steel

蔡大和(D.H. Tsai) ； 林鴻榮(H.R. Lin)

《鑛冶：中國鑛冶工程學會會刊》 47卷2期 (2003/06) Pp. 22-32

https://doi.org/10.30069/MM.200306_47(2).0003

摘要

本研究經由鋼中Al、N含量與軋延條件最適化的方式，並且應用第二相析出物對晶界之固著效應（Pinning Effect），發展出晶粒控制在ASTM＃5-＃8之有效成份設計，以改善晶粒過細導致螺栓淬不硬問題。首先經由熱加工模擬實驗証實含0.047%Al-0.006%N之中Al鋼，最易生成＃9-＃11之過細晶粒，其晶粒過細之機構係因中Al鋼材之AlN析出物介於100－400nm之間，對晶界會產生固著作用（Pinning Effect），因而易生成過細晶粒。並發現Al，N成份最適化到Al＞ 0.06%及N＞0.007%的水準，可控制析出物大於600nm以上，是生成＃5-＃8合適細晶的關鍵。進一步的試驗得知，當散置溫由900℃降至820℃時，低Al鋼之淬火晶粒度將由＃9-＃11提升到＃5-＃8合適水準，此乃因低溫散置冷卻有利於促進部份AlN之先行析出，可防止再淬火時AlN大量微細析出所導致之晶粒過細現象。

關鍵字

固著效應 ； 晶粒粗化曲線 ； 硬化能曲線

並列摘要

To improve the hardenability insufficiency owing to inadequate grain size, this study describes how the fine -tuning technology of austenite grain size on medium carbon wire rod was established via optimization of Al, N contents and rolling conditions and the pinning effect of second-phase precipitates on grain boundary. Firstly, thermomechanical simulation test were carried out. The results reveal that the mechanism of excess-fine grain of ASTM #9-#11 steel with 0.047%Al-0.006%N content is due to the pinning force exerted by the precipitates with size ranging from 100 to 400 nm. And the steel with precipitate size over 600 nm has a appropriate fine-grain of ASTM #5-#8 by optimizing the contents of Al and N to a level of Al＞0.06% and N＞0.007%. Further investigation result also shows a proper fine-grain of ASTM #5-#8 was achieved by adjusting laying temperature from 900℃ to 820℃ to facilitate partial precipitation of AlN and to avoid the formation of excess-fine grains during quenching.

並列關鍵字

Pinning effect ； Grain-coarsening curves ； Hardenability curves