本文關鍵詞：鋼中殘余元素錫與銻析出行為的基礎研究　出處：《北京科技大學》2016年博士論文　論文類型：學位論文

  更多相關文章： 錫 銻 二維錯配度 異質形核 力學性能

【摘要】：隨著煉鋼生產中廢鋼循環(huán)利用的比例越來越大,錫、銻等殘余元素在鋼中的富集問題將日益嚴峻。錫、銻等殘余元素在鋼中不斷的富集,會因其易在晶界和表面偏聚而嚴重惡化鋼材的高溫塑性、低溫沖擊韌性等。目前生產中解決鋼中殘余元素超標的主要方法為采用優(yōu)質原料進行稀釋,然而這并不能從根本上解決鋼中殘余元素循環(huán)富集的問題。本文通過系統(tǒng)研究錫、銻在鋼中的析出規(guī)律,錫、銻異質形核析出所需的冶金條件,以及錫、銻彌散析出前后對鋼性能的影響規(guī)律,期望在不降低鋼中錫、銻含量的前提下,通過改變其在鋼中的析出行為,減輕甚至消除其在晶界和表面的偏聚,改善其對鋼性能的危害。應用點陣錯配度理論,對鋼中常見夾雜物Si02、A1203、MnS和TiN與殘余元素錫、銻以及鐵錫、鐵銻金屬問化合物之間的二維錯配度進行了計算。結果表明,在二維錯配度值小于12%作為基體對形核相具有較好異質形核效果的判別標準下,Si02可作為FeSn、Fe3Sn2的有效異質形核核心；A1203可成為FeSn、Fe3Sn2、Fe5Sn3、Sb的有效異質形核核心；MnS可作為Sn、FeSn、 FeSb2、FeSb的有效異質形核核心。利用掃描電鏡和透射電鏡對含Sn(Sb)量分別為0.5%、1.5%和5.0%的Fe-Sn合金和Fe-Sb合金中的Sn、Sb析出行為進行了研究,并對析出相的類型進行了鑒定。結果表明,對Sn含量為5.0%的Fe-Sn合金,1600℃水冷的試樣中有含Sn相析出,該冶煉條件下,Sb含量為5.0%的Fe-Sb合金中也有含Sb相析出；但是Sn(Sb)含量為0.5%和1.5%的Fe-Sn(Sb)合金中在同樣條件下并沒有觀察到含Sn(Sb)相析出,線掃描的能譜分析發(fā)現其主要在晶界偏聚。對于Sn(Sb)含量為0.5%、1.5%和5.0%的Fe-Sn(Sb)合金,在1200℃和600℃分別水冷的試樣中沒有發(fā)現含Sn(Sb)相的析出,能譜分析結果表明Sn(Sb)在晶界有富集。利用碳復型萃取技術對1600℃水冷的Sn(Sb)含量為5.0%的Fe-Sn(Sb)合金中的Sn(Sb)析出相進行研究,透射選區(qū)衍射標定結果表明,Fe-5.0%Sn合金中析出的含Sn相為FeSn2,Fe-5.0%Sb合金中析出的含Sb相為ε-FeSb。根據錫、銻在鋼中的析出相類型及其與鋼中常見夾雜物的二維錯配度計算結果,本文選取MnS夾雜物作為錫、銻異質析出的形核質點。計算了實驗鋼中MnS夾雜物的生成熱力學條件,對能成為含Sn、Sb相有效異質形核核心的MnS夾雜的形狀和尺寸進行了研究。結果表明,當凝固分率達到0.9464以后,鋼中MnS夾雜物開始析出,此時析出溫度為1689.9K。鋼中直徑2-4gm的球形硫化錳夾雜物可以成為殘余元素錫異質析出的形核核心,鋼中殘余元素銻則可以在直徑1-10μm的硫化錳夾雜物上異質形核析出,添加0.03wt%Ti能明顯提高MnS夾雜物上含Sn(Sb)相的形核率,Sn和Sb的異質形核率分別由8.8%和13.21%提高到17.14%和36.02%。選區(qū)電子衍射結果表明MnS夾雜物上異質析出的含錫相為FeSn2,含銻相為ε-FeSb相,該結果與Fe-Sn(Sb)二元合金中的含Sn(Sb)析出相種類相一致。應用Gleeble 1500熱模擬機對含錫、銻C-Mn鋼的高溫熱塑性以及MnS變質處理改善其熱塑性進行了研究。結果表明,隨著錫、銻含量的增加,C-Mn鋼的熱塑性逐漸惡化。當錫含量為0.04wt%和0.10wt%時,C-Mn鋼第三脆性溫度區(qū)700℃～900℃范圍內熱塑性明顯下降；銻含量為0.046wt%和0.13wt%時,主要表現為顯著降低C-Mn鋼奧氏體單相區(qū)850℃～900℃溫度范圍內的熱塑性。電子探針(EMPA)分析表明殘余元素錫和銻的晶界偏聚是鋼熱塑性惡化的原因。對于MnS改善含錫、銻實驗鋼的熱塑性,研究結果表明,含0.10wt%Sn和含0.13wt%Sb的C-Mn鋼中添加0.02wt%S和0.03wt%Ti后,含錫C-Mn鋼700℃-900℃以及含銻C-Mn鋼700℃～1100℃的熱塑性明顯得到改善。測定了不同Sn和Sb含量實驗鋼的常溫拉伸以及室(低溫)沖擊性能。結果表明,常溫拉伸時,隨著殘余元素錫含量由0%增加到O.10wt%、銻含量由0%增加到0.13wt%,C-Mn鋼的屈服強度和屈強比小幅提高,斷面收縮率明顯降低。對于沖擊韌性,常溫時,當實驗鋼中Sn含量從0%增加到0.017wt%時,沖擊功急劇減少,Sn含量超過0.040wt%時,沖擊功減少速度變緩。低溫(-20℃和-40℃)時,當實驗鋼中Sn含量從0%增加到0.0068wt%時,沖擊功急劇減少,Sn含量超過0.0068wt%時,沖擊功減少速度變緩。同時,殘余元素Sb也嚴重影響實驗鋼的沖擊韌性。添加少量的Sb(0%-0.006wt%)時,實驗鋼的常溫沖擊功和低溫(-20℃和-40℃)沖擊功急劇減少。當Sb含量超過0.046wt%后,常溫沖擊功緩慢減少；當銻含量超過0.015wt%以后,低溫(-20℃和-40℃)沖擊功基本保持不變。含0.10wt%Sn和含0.13wt%Sb的C-Mn鋼中添加0.02wt%S和0.03wt%Ti后,MnS變質處理的試樣常溫和低溫沖擊韌性得到明顯改善。
[Abstract]:With the proportion of scrap recycling in steel production is more and more big, tin, antimony and other enrichment of residual elements in steel will become increasingly grim. Tin, antimony and other residual elements in the steel continuously enriched, due to high temperature at grain boundary and the surface segregation and the serious deterioration of steel plastic, low temperature impact toughness in the current production. The main method to solve the problem of residual elements in steel exceed the standard for the use of high-quality raw materials for dilution, but this does not solve the problem of circulation and enrichment of residual elements in steel fundamentally. This paper makes a systematic research on Precipitation in steel, tin, antimony in tin, antimony metallurgical conditions, heterogeneous nucleation precipitation required the influence of steel and tin, antimony precipitation before and after the performance, expectations can reduce the steel tin, antimony content under the premise, by changing the precipitation behavior in the steel, reduce or even eliminate the segregation in the grain boundary and the surface, improve the Harm the performance of steel. Application of lattice disregistry, A1203 of the common inclusions in steel, Si02, MnS and TiN and Sn, antimony and iron tin antimony, iron metal Q disregistry between compound degree were calculated. The results show that in the two-dimensional misfit value is less than 12% as the base of the body the nucleation phase has a good criterion for heterogeneous nucleation effect, Si02 can be used as FeSn, Fe3Sn2 effective heterogeneous nucleation; A1203 is FeSn, Fe3Sn2, Fe5Sn3, Sb effective heterogeneous nucleation; MnS can be used as Sn, FeSn, FeSb2, FeSb of the effective heterogeneous nucleation of heart. Sn using scanning electron microscopy and transmission electron microscopy (Sb) were 0.5%, 1.5% and 5% of the Fe-Sn alloy and Fe-Sb alloy in the Sn, Sb precipitation behavior was studied, and the precipitation types were identified. The results showed that the Sn content of Fe-Sn alloy 5%, with Sn of 1600 samples in the cold water temperature 鍑，

本文編號：1433613