本文選題：非調(diào)質(zhì)鋼 + 熱成形　； 參考：《重慶理工大學(xué)》2015年碩士論文

【摘要】：非調(diào)質(zhì)鋼是一種通過控鍛-控冷技術(shù)而使鋼材不需要經(jīng)過調(diào)質(zhì)處理就能達(dá)到力學(xué)性能的材料。38MnVTi非調(diào)質(zhì)鋼作為汽車前軸和轉(zhuǎn)向節(jié)鍛件的常用材料,對(duì)它鍛造性能要求很高。本文通過熱模擬壓縮試驗(yàn)研究了該材料在熱變形中的變形行為,運(yùn)用了本構(gòu)方程、神經(jīng)網(wǎng)絡(luò)及顯微組織等手段獲得了Parasd和Murty判據(jù)的加工圖,論文的主要研究?jī)?nèi)容及成果有:(1)分析了38MnVTi非調(diào)質(zhì)鋼應(yīng)力-應(yīng)變曲線的特征。達(dá)到峰值應(yīng)力的快慢與變形溫度的大小有關(guān),變形溫度越高達(dá)到峰值應(yīng)力的時(shí)間越短;此外,應(yīng)力達(dá)到峰值后曲線的平緩或下降與材料的軟化機(jī)制有關(guān),動(dòng)態(tài)回復(fù)和動(dòng)態(tài)再結(jié)晶能使材料發(fā)生軟化,因而影響應(yīng)力-應(yīng)變曲線的走勢(shì)。(2)研究了變形參數(shù)與流變應(yīng)力的關(guān)系。通過回歸分析的方法建立了峰值應(yīng)力的本構(gòu)方程,用于描述材料在變形過程強(qiáng)度量的最大屬性;為了拓展本構(gòu)方程的適用性,采用應(yīng)變量的多項(xiàng)式表示材料常數(shù),對(duì)Arrhenius雙曲正弦形式的表達(dá)式通過引入應(yīng)變進(jìn)行修正,得到帶應(yīng)變的本構(gòu)方程。(3)對(duì)比了本構(gòu)方程與BP神經(jīng)網(wǎng)絡(luò)模型預(yù)測(cè)應(yīng)力的精度。以應(yīng)變、變形速率和變形溫度作為輸入信息并將應(yīng)力作為輸出信息,進(jìn)行神經(jīng)網(wǎng)絡(luò)模型建模。訓(xùn)練后的神經(jīng)網(wǎng)絡(luò)模型其應(yīng)力的預(yù)測(cè)精度比本構(gòu)方程預(yù)測(cè)精度高。利用訓(xùn)練好的神經(jīng)網(wǎng)絡(luò)對(duì)變形溫度為1050℃和1150℃下不同應(yīng)變速率的應(yīng)力進(jìn)行預(yù)測(cè)。(4)構(gòu)建了Parasd和Murty兩種失穩(wěn)判據(jù)的加工圖并對(duì)其適用性進(jìn)行了驗(yàn)證。對(duì)不同應(yīng)變的加工圖通過功率耗散系數(shù)及失穩(wěn)區(qū)特征的分析,結(jié)合顯微組織、硬度、拉伸測(cè)試對(duì)加工圖進(jìn)行驗(yàn)證。結(jié)果表明:制作加工圖的應(yīng)變必須選取穩(wěn)態(tài)階段,非穩(wěn)態(tài)階段的應(yīng)變不能保證加工圖的準(zhǔn)確性;兩種判據(jù)的加工圖具有相似性,且Parasd判據(jù)的加工圖失穩(wěn)區(qū)與低的功率耗散系數(shù)有關(guān),工藝設(shè)計(jì)時(shí)應(yīng)綜合考慮二者的失穩(wěn)區(qū)及功率耗散系數(shù)特征。對(duì)于38MnVTi非調(diào)質(zhì)鋼,不能在高應(yīng)變速率進(jìn)行高應(yīng)變量的成形,否則會(huì)導(dǎo)致組織失穩(wěn)。經(jīng)工藝優(yōu)化后,該材料的最佳工藝參數(shù)為溫度1100~1200℃,應(yīng)變速率0.1~1s-1。
[Abstract]:Non quenched and tempered steel is a material of.38MnVTi non quenched and tempered steel which can achieve mechanical properties without quenching and tempering through controlled forging and controlled cooling technology. The non quenched and tempered steel is used as a common material for the front axle of the car and the forgings of the steering knuckle. It has a high requirement for its forging performance. This paper has studied the deformation of the material in the thermal deformation by thermal simulation test. Parasd and Murty criteria are obtained by using constitutive equations, neural networks and microstructures. The main contents and results of this paper are as follows: (1) the characteristics of stress strain curves of 38MnVTi non quenched and tempered steel are analyzed. The speed of reaching the peak stress is related to the size of the deformation temperature, and the higher the deformation temperature is to the peak stress. The time is shorter; in addition, the slow or decrease of the curve is related to the softening mechanism of the material. Dynamic recovery and dynamic recrystallization can soften the material and affect the trend of the stress-strain curve. (2) the relationship between the deformation parameters and the rheological stress is studied. The peak stress is established by the regression analysis method. The structure equation is used to describe the maximum properties of the strength of the material in the deformation process. In order to extend the applicability of the constitutive equation, the polynomial of the strain is used to express the material constant. The constitutive equation with strain is obtained by modifying the expression of the Arrhenius hyperbolic sine form by introducing strain. (3) comparing the constitutive equation with the BP neural network model. The precision of stress is predicted. The neural network model is modeled by the strain, deformation rate and deformation temperature as the input information and the stress as the output information. The prediction accuracy of the stress is higher than the constitutive equation after training. The trained neural network is used for the deformation temperature of 1050 and 1150. The stress of the strain rate is predicted. (4) two kinds of Instability Criteria of Parasd and Murty are constructed and their applicability is verified. The analysis of the power dissipation coefficient and the characteristics of the instability zone for different strains of the strain is verified by the microscopic structure, hardness and tensile test. The results show that the processing chart is made. The strain must be selected in the steady state. The strain of the unsteady state can not guarantee the accuracy of the processing diagram; the processing diagram of the two criteria has the similarity, and the instability zone of the Parasd criterion is related to the low power dissipation factor. The process design should take into account the instability zone and the power dissipation factor of the two parties. For the non tuning of the process design, the characteristics of the power dissipation factor should be taken into consideration. The high strain rate of high strain rate can not be formed in high strain rate, otherwise the structure will be unstable. The optimum process parameters of the material are temperature 1100~1200 C and the strain rate 0.1~1s-1. after optimization.
【學(xué)位授予單位】：重慶理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG142.1

【共引文獻(xiàn)】

相關(guān)期刊論文 前6條

1 王進(jìn);褚忠;李君飛;張琦;;F35MnVN非調(diào)質(zhì)鋼高溫本構(gòu)模型對(duì)比研究[J];材料科學(xué)與工藝;2012年05期

2 王進(jìn);褚忠;張琦;;38MnVS6非調(diào)質(zhì)鋼兩種高溫本構(gòu)模型的對(duì)比[J];材料工程;2014年02期

3 陳元芳;江華德;湯萌;;38MnVTi鋼本構(gòu)方程及加工圖[J];材料導(dǎo)報(bào);2014年22期

4 何沂桂;滿廷慧;譚利;詹肇麟;雍岐龍;包耀宗;;鍛造工藝對(duì)鈮-釩微合金非調(diào)質(zhì)鋼顯微組織的影響[J];機(jī)械工程材料;2015年01期

5 地力木拉提·希爾尼牙孜;李Z，

本文編號(hào)：1922734