本文選題：Mn　切入點(diǎn)：等溫淬火溫度　出處：《武漢紡織大學(xué)》2017年碩士論文

【摘要】：ADI(Austempered Ductile Iron),即等溫淬火球墨鑄鐵,因具有優(yōu)良的力學(xué)性能和耐磨性能,已成為當(dāng)今最熱點(diǎn)的材料之一。該材料是球墨鑄鐵通過等溫淬火處理得到的以針狀鐵素體和富碳奧氏體為主要基體的高性能鑄造合金。本課題設(shè)計(jì)的Mn含量有三組,等溫淬火工藝參數(shù)有4組,通過對不同的試樣進(jìn)行金相組織分析、X射線衍射分析、掃描電子顯微鏡分析、摩擦磨損試驗(yàn)、表面硬度測量、磨損形貌觀察和能譜分析,研究了Mn及等溫淬火溫度對ADI組織與磨損性能的影響。ADI的鑄態(tài)組織主要包括:石墨球、珠光體、碳化物及極少量的鐵素體。Mn主要以碳化物的形式存在,Mn含量的多少對石墨球化作用影響不明顯,都能使球化率達(dá)到2級,石墨球大小等級達(dá)到6級。但Mn能影響鑄態(tài)組織中石墨球的均勻程度和珠光體、碳化物的體積分?jǐn)?shù),Mn含量越高,石墨球分布不均,珠光體和碳化物含量增多。ADI的基體組織主要由針狀鐵素體和富碳奧氏體組成。隨著Mn含量的增加,組織中原有的針狀鐵素體逐漸粗化,數(shù)量增多。且組織中殘余奧氏體的含量和奧氏體中碳含量隨Mn的增加而增加,這使得高M(jìn)n量的ADI受應(yīng)力作用時(shí),發(fā)生加工硬化明顯,表面硬度因Mn含量增加而增大,提高了材料的耐磨性。在所研究的等溫淬火溫度(280℃~370℃)范圍內(nèi),等淬溫度低的鐵素體呈細(xì)針狀,等淬溫度高的鐵素體呈粗針狀。同一試樣的表面硬度隨磨損的進(jìn)行逐漸增高;相同Mn含量,不同試樣的表面硬度隨等淬溫度的升高而降低,總磨損量增多,但磨損中,磨損量的幅度逐漸變小;同一等淬溫度,ADI的表面硬度隨Mn量的增加而升高,總磨損量減小,耐磨性增強(qiáng)。通過掃描電鏡觀察磨損形貌組織發(fā)現(xiàn)等溫淬火溫度為280℃時(shí),微切削磨損是其主要磨損機(jī)制,切削痕淺,耐磨性好;等溫淬火溫度為310℃和340℃時(shí),微切削磨損是材料的主要磨損機(jī)制,表面存在少許犁溝,切削痕加深,磨損量增加,耐磨性降低;等溫淬火溫度為370℃時(shí),材料磨損表面有明顯深度的切削痕,伴隨少量物料剝落,材料的磨損以犁溝為主,還有少量微觀切削。相同等溫淬火溫度下的ADI,當(dāng)Mn含量為0.2%~0.5%時(shí),犁溝及微觀剝落是材料的主要失效形式;當(dāng)Mn含量為0.8%時(shí),失效形式以犁溝及切削為主。通過對試樣磨損后的物相分析發(fā)現(xiàn),ADI在摩擦應(yīng)力的作用下發(fā)生了加工硬化,殘余奧氏體轉(zhuǎn)變成了馬氏體增加了表面硬度。能譜分析發(fā)現(xiàn)ADI組織中的石墨球會(huì)脫落到摩擦副表面,形成減磨層,提高ADI耐磨性。
[Abstract]:ADI(Austempered Ductile iron, or isothermal quenched ductile iron, has excellent mechanical properties and wear resistance. This material is a kind of high performance cast alloy with acicular ferrite and carbon-rich austenite as the main matrix, which is obtained by isothermal quenching of ductile iron. There are three groups of mn content designed in this paper. There are 4 groups of isothermal quenching process parameters. X-ray diffraction analysis, scanning electron microscope analysis, friction and wear test, surface hardness measurement, wear morphology observation and energy spectrum analysis were carried out on different samples. The effects of mn and isothermal quenching temperature on the microstructure and wear properties of ADI. The presence of carbides and ferrite. Mn mainly in the form of carbides has no obvious effect on the spheroidization of graphite, and the spheroidization rate can reach 2 order. However, mn can affect the homogeneity of graphite spheroids and pearlite in as-cast structure. The higher the content of mn in carbides is, the more uneven the distribution of graphite spheroids is. The matrix structure of pearlite and carbides increased. ADI was mainly composed of acicular ferrite and carbon-rich austenite. With the increase of mn content, the acicular ferrite in the microstructure gradually coarsened. The amount of residual austenite and the content of carbon in austenite increase with the increase of mn, which makes the ADI with high mn content work hardening obviously, and the surface hardness increases with the increase of mn content. The wear resistance of the material is improved. In the range of isothermal quenching temperature of 280 鈩，

本文編號(hào)：1668941