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通过化学相分析手段测试了EAF-CSP流程Nb(C,N)析出规律,结果表明:连铸出坯后,Nb大部分已析出,析出量为79%,平均尺寸为60.7nm;铸坯均热后,Nb(C,N)明显回溶并发生Ostwald熟化,回溶比例为56.3%,平均尺寸为69nm,此时析出量为总量的34.7%;经连轧、加速冷却和卷取后,Nb又重新诱导析出,析出量为71%,平均尺寸减少为54.5nm。利用Gleeble3500热模拟实验机研究了EAF-CSP流程原始奥氏体静态再结晶规律,结果表明含0.045%Nb铸坯均热后晶粒尺寸达到700μm,1050℃变形50%后保温10s仍不能完全再结晶,这是导致混晶的根本原因。合理设计成分,调整铸轧工艺,可成功地解决EAF-CSP生产含Nb钢的混晶问题并有效细化晶粒。基于EAF-CSP流程Nb微合金化技术,开发出X52、X56、X60系列管线钢。
The analysis of Nb (C, N) precipitation in EAF-CSP process was carried out by means of chemical analysis. The results showed that most of Nb had been precipitated after the billet was cast and the amount of precipitation was 79% and the average size was 60.7nm. After heat, the Nb (C, N) is obviously dissolved and Ostwald maturation occurs, with the ratio of 56.3% and the average size of 69 nm, the amount of precipitation is 34.7% of the total amount. After the continuous rolling, accelerated cooling and coiling , Nb re-induced precipitation, the amount of precipitation was 71%, the average size reduction of 54.5nm. The static recrystallization of austenite in EAF-CSP process was studied by Gleeble3500 thermal simulation machine. The results show that the grain size of 0.045% Nb billet after soaking is 700μm, and the 10% Crystallization, which is the root cause of mixed crystals. Reasonable design of components, adjust the casting process, can successfully solve the EAF-CSP production of Nb-containing mixed crystal problems and effectively refine the grain. Based on Nb micro-alloying technology of EAF-CSP process, X52, X56 and X60 series pipeline steel have been developed.