本文選題：噴射成形　切入點：高速鋼　出處：《北京科技大學》2016年博士論文　論文類型：學位論文

【摘要】：M3型高速鋼具有高硬度、高耐磨性、良好的強韌性,被廣泛應用于刀具和冷作模具,其制備方法主要有傳統(tǒng)鑄造及粉末冶金。傳統(tǒng)鑄造冷速慢,形成的組織中含有大量網(wǎng)狀共晶碳化物,直接影響其產(chǎn)品性能的提升。粉末冶金冷速快,生產(chǎn)的高速鋼組織性能優(yōu)良,但其復雜的制備工藝及過高的生產(chǎn)成本限制了其產(chǎn)品應用范圍。此外,合金設計也是改善組織性能的重要途徑,采用強碳化物形成元素提高耐磨性并結(jié)合快速凝固技術改善強韌性是高速鋼的主要研發(fā)趨勢�；谡n題組開展的結(jié)合鈮合金化與噴射成形技術制備M3型高速鋼的相關研究,本文主要對噴射成形高速鋼組織性能調(diào)控機理及應用展開相關研究,獲得主要結(jié)論如下：通過研究關鍵工藝參數(shù)對沉積坯質(zhì)量的影響規(guī)律,確定了噴射成形M3型高速鋼的制備工藝：過熱度160-180℃,霧化壓力0.45-0.5MPa,氣液比0.7-0.75。利用Gleeble熱模擬研究了噴射成形M3型高速鋼的熱變形行為,建立了實驗鋼的本構(gòu)方程、動態(tài)再結(jié)晶動力學方程、熱加工圖,確定出致密化處理工藝為：變形溫度1050-1150℃,變形速率0.001-0.1 s-1,鍛造比6.25。并最終制定了適合刀具應用的強韌化熱處理工藝：淬火1200℃,回火560℃。發(fā)現(xiàn)噴射成形M3型高速鋼沉積態(tài)的組織具有等軸晶及微觀孔隙兩個特征,其平均晶粒尺寸約為45μm,且晶界上分布著以釩為主的塊狀MC及以鉬、鎢為主的片層狀M2C。熱變形借助動態(tài)再結(jié)晶及機械破碎等機制使晶粒尺寸細化至10μm,并將片層狀M2C分解破碎成均勻細小的顆粒狀M6C與MC�；鼗鸲斡不饕啥蜯2C和MC碳化物析出所致,其中M2C呈針狀,長約5-10nm,厚度約2nm。MC呈顆粒狀,約3-5nm。鈮能有效細化沉積態(tài)M2C共晶片層尺寸,并通過減少M2C中鎢、釩、鉬等強碳化物形成元素的含量降低其熱穩(wěn)定性,從而促進M2C分解,使含鈮鋼熱變形后可獲得更均勻細小的M6C,淬火時更易溶入基體提高過飽和度,從而提高二次硬化能力。同時,鈮也提高了沉積態(tài)中一次MC的數(shù)量及其所含鎢、鉬元素的含量,并代替部分釩進入MC中,使含鈮鋼中MC硬度和穩(wěn)定性提高,耐磨性增強。此兩方面的作用是含鈮鋼刀具壽命提升的主要原因�？偨Y(jié)而言,本文研究所得噴射成形高速鋼制備、致密化及強韌化三個工藝與組織調(diào)控及鈮合金化作用兩個機理可為噴射成形含鈮M3型高速鋼在刀具上的應用提供工藝及理論支持。
[Abstract]:M3 high speed steel has high hardness, high wear resistance, good strength and toughness. It is widely used in cutting tools and cold working dies. The main preparation methods are traditional casting and powder metallurgy. The resulting microstructure contains a large number of reticular eutectic carbides, which directly affects the improvement of the properties of the products. However, its complex preparation process and high production cost limit its application scope. In addition, alloy design is also an important way to improve microstructure and properties. It is the main research trend of high speed steel to improve wear resistance by means of strong carbide forming element and to improve strength and toughness by combining rapid solidification technology. Based on the related research on the preparation of M3 type high speed steel by combining niobium alloying and spray forming technology carried out by our research group. In this paper, the control mechanism and application of microstructure and properties of spray forming high speed steel are studied. The main conclusions are as follows: the influence of key process parameters on the quality of deposition billet is studied. The preparation process of spray formed M3 high speed steel was determined: superheat 160-180 鈩，

本文編號：1561230