本文選題：鈦微合金鋼 + 靜態(tài)再結(jié)晶�。� 參考：《江蘇大學(xué)》2017年碩士論文

【摘要】：中國鈦資源豐富,價格優(yōu)勢明顯,而且鈦的析出物在鋼中有明顯的細化晶粒和沉淀強化作用,采用Ti微合金化技術(shù)是開發(fā)高強鋼的有效途徑。本文從生產(chǎn)現(xiàn)場取鑄坯樣(主要成分為0.051%C-0.96%Mn-0.104%Ti),在實驗室采用物理熱模擬方法,研究鈦微合金鋼的靜態(tài)再結(jié)晶和相變規(guī)律,在此基礎(chǔ)上,分析了TMCP工藝對其組織和性能的影響,得到以下主要結(jié)論:(1)同樣道次間隔時間內(nèi),不同實驗參數(shù)下的再結(jié)晶軟化率表明:高溫、大變形量將促進靜態(tài)再結(jié)晶的發(fā)生,而應(yīng)變速率和原始奧氏體晶粒尺寸對靜態(tài)再結(jié)晶的影響相對較小;變形溫度在980℃以上,變形量超過30%時,當(dāng)?shù)来伍g隔時間小于1s時,以靜態(tài)回復(fù)為主并伴有少量再結(jié)晶,1s到10s之內(nèi),靜態(tài)再結(jié)晶軟化率迅速升高,超過30s之后,再結(jié)晶軟化率上升緩慢。(2)在950℃變形之后,道次間隔時間為1s時,形變誘導(dǎo)TiC粒子析出量較少,隨著道次間隔時間延長至100s時,TiC粒子數(shù)量顯著增加,這些析出粒子沿位錯線隨機分布,對位錯產(chǎn)生強烈的釘扎作用,將會明顯抑制靜態(tài)再結(jié)晶發(fā)生。(3)隨著冷卻速率的增加,相變開始溫度和結(jié)束溫度都呈現(xiàn)下降趨勢,晶粒尺寸逐漸細化;當(dāng)冷速為20℃/s時,動態(tài)相變的溫度區(qū)間為513.4~717.8℃;變形使CCT曲線向上移動,提高鈦微合金鋼的相變溫度,促進鐵素體相變,加快相變轉(zhuǎn)變速率,細化貝氏體晶粒。(4)由于實驗鋼含碳量較低,靜態(tài)CCT曲線上不存在珠光體轉(zhuǎn)變區(qū)間,當(dāng)冷卻速率5℃/s時,先共析鐵素體相變受到抑制,組織以粒狀貝氏體為主。當(dāng)冷卻速率1℃/s時,動態(tài)CCT曲線上存在珠光體轉(zhuǎn)變區(qū)間,當(dāng)冷卻速率10℃/s時,先共析鐵素體相變受到抑制,組織以粒狀貝氏體為主。隨著冷速進一步提升,粒狀貝氏體向板條貝氏體轉(zhuǎn)變。(5)對比不同壓縮變形和冷卻工藝下的室溫組織強度。在1050℃和900℃先后進行30%的變形,并在600℃保溫60min和直接采用空冷的實驗鋼DW和DA,其強度值分別為636.0MPa和514.4MPa,組織為先共析鐵素體和粒狀貝氏體;在1050℃進行50%變形,保溫和空冷下的實驗鋼SW和SA,其強度值分別為537.9MPa和482.6MPa,組織為先共析鐵素體和粒狀貝氏體,伴有少量針狀鐵素體。實驗鋼DW的屈服強度值最高,其強化方式為細晶強化和沉淀強化。壓縮變形后的冷卻工藝對實驗鋼屈服強度提升幅度最大。(6)分析表明:600℃處于鈦微合金鋼的相變溫度區(qū)間,在該溫度下保溫,TiC粒子會發(fā)生相間析出,尺寸為納米級,能夠釘扎位錯,發(fā)揮顯著的沉淀強化作用,而直接進行空冷,由于冷卻速率大,會抑制TiC的析出。對納米碳化物相間析出的研究是發(fā)開鈦微合金鋼的關(guān)鍵。
[Abstract]:China is rich in titanium resources and has obvious price advantages, and titanium precipitates have obvious effect on grain refinement and precipitation strengthening in steel. The use of Ti microalloying technology is an effective way to develop high strength steel. In this paper, the static recrystallization and phase transformation of titanium microalloyed steel were studied by physical thermal simulation method, and the effect of TMCP process on the microstructure and properties of the steel was analyzed based on the sample of casting billet (0.051C-0.96Mn-0.104Ti) taken from the production site, and the physical thermal simulation method was used to study the effect of TMCP process on the microstructure and properties of titanium microalloyed steel. The main conclusions are as follows: (1) in the same interval, the recrystallization softening rate under different experimental parameters shows that high temperature and large amount of deformation will promote the occurrence of static recrystallization. However, the effect of strain rate and original austenite grain size on static recrystallization is relatively small, and when the deformation temperature is above 980 鈩，

本文編號：2093907