本文選題：鎳基高溫合金 + 熱擠壓��； 參考：《北京科技大學(xué)》2017年博士論文

【摘要】：鎳基高溫合金管材因其優(yōu)異的性能,在石油化工、能源等民用領(lǐng)域的用量逐漸增加。因?yàn)楣懿男枰趪?yán)苛的環(huán)境下長(zhǎng)期安全服役,所以對(duì)管材質(zhì)量提出了更高的要求。但鎳基高溫合金管材的生產(chǎn)流程較長(zhǎng)、組織控制困難,如何生產(chǎn)組織穩(wěn)定的優(yōu)質(zhì)鎳基高溫合金管材成為一大難題。因此,對(duì)鎳基高溫合金管材生產(chǎn)過程組織控制規(guī)律和機(jī)理的研究為提高管材質(zhì)量具有重要的理論和工程應(yīng)用意義。本研究以617B合金管材生產(chǎn)流程為主線,對(duì)生產(chǎn)過程中的組織控制問題展開研究。通過對(duì)均勻化程度與動(dòng)態(tài)再結(jié)晶之間關(guān)聯(lián)性的研究,提出了低溫均勻化的設(shè)計(jì)思路,利用低溫均勻化處理后合金中殘余的枝晶為動(dòng)態(tài)再結(jié)晶提供形核點(diǎn),使得動(dòng)態(tài)再結(jié)晶增加的同時(shí)控制了晶粒度的長(zhǎng)大。通過等溫?zé)崮M壓縮實(shí)驗(yàn),得到了熱變形參數(shù)對(duì)617B合金動(dòng)態(tài)再結(jié)晶過程的影響規(guī)律。采用多種組織觀察手段對(duì)其動(dòng)態(tài)再結(jié)晶機(jī)制進(jìn)行了研究,證明了617B合金以非連續(xù)動(dòng)態(tài)再結(jié)晶機(jī)制為主、連續(xù)動(dòng)態(tài)再結(jié)晶機(jī)制為輔的形核機(jī)制：闡明了高應(yīng)變速率促進(jìn)動(dòng)態(tài)再結(jié)晶的本質(zhì)是存儲(chǔ)能升高、位錯(cuò)密度和孿晶的增加使形核作用更為強(qiáng)烈,彌補(bǔ)了高速率變形導(dǎo)致的動(dòng)態(tài)再結(jié)晶時(shí)間不足。因此也就明確了絕熱溫升并非高速率變形時(shí)動(dòng)態(tài)再結(jié)晶被促進(jìn)的唯一因素�；趯�(shí)驗(yàn)數(shù)據(jù)分析繪制了617B合金的熱加工圖,實(shí)現(xiàn)了熱變形參數(shù)與組織演變規(guī)律之間的半定量表征；同時(shí)建立了617B合金的動(dòng)態(tài)再結(jié)晶和晶粒長(zhǎng)大模型,將組織演變模型與DEFORM-2D有限元模擬軟件相結(jié)合,實(shí)現(xiàn)了擠壓工況對(duì)擠壓參數(shù)和組織演變過程的準(zhǔn)確預(yù)測(cè)。在給定荒管晶粒尺寸要求和設(shè)備承載能力條件下,可提供617B管材熱擠壓的優(yōu)化工藝范圍。對(duì)熱擠壓后的荒管進(jìn)行固溶和冷軋退火研究,得到了617B合金主要工藝參數(shù)：荒管固溶制度1190--1210℃/1 h,冷軋中間退火制度1200℃/30～60 min。長(zhǎng)期時(shí)效實(shí)驗(yàn)結(jié)果表明,740H合金在720℃時(shí)效至10000 h時(shí)無有害相析出,但MC碳化物在時(shí)效200 h時(shí)即開始發(fā)生元素的再分配,成為其他相演變過程中合金元素的“源泉”,而617B合金在720℃時(shí)效至5000 h左右時(shí)有μ相析出：通過組織觀察和定量的相分析,構(gòu)建了近服役條件下主要析出相之間的元素再分配規(guī)律�？傊�,本文對(duì)617B合金管材制備過程中的均勻化、熱擠壓、冷軋退火等關(guān)鍵環(huán)節(jié)的組織演變過程進(jìn)行了系統(tǒng)性的研究和深入的理論分析,對(duì)管材制備過程中的組織演變和控制原則提供了實(shí)驗(yàn)和理論指導(dǎo)依據(jù)。
[Abstract]:Because of its excellent properties, nickel-based superalloy pipes have been used in petrochemical, energy and other civil fields. Because the pipe needs to serve in strict environment for a long time, the quality of the pipe is required to be higher. However, the production process of nickel-based superalloy pipe is long and the structure control is difficult. How to produce high-quality nickel-base superalloy pipe with stable microstructure becomes a big problem. Therefore, the study of microstructure control law and mechanism in the production process of nickel-base superalloy pipes has important theoretical and engineering application significance for improving pipe quality. The main line of this study is 617B alloy pipe production process. Based on the study of the relationship between homogenization degree and dynamic recrystallization, the design idea of low temperature homogenization is put forward. The residual dendrites in the alloy after low temperature homogenization treatment provide nucleation point for dynamic recrystallization. The dynamic recrystallization increases and the grain size growth is controlled. The effect of thermal deformation parameters on the dynamic recrystallization process of 617B alloy was obtained by isothermal thermal simulation compression experiment. The dynamic recrystallization mechanism of 617B alloy was studied by various means of microstructure observation. It was proved that the main mechanism of dynamic recrystallization of 617B alloy was discontinuous dynamic recrystallization. Nucleation mechanism supplemented by continuous dynamic recrystallization mechanism: the essence of high strain rate promoting dynamic recrystallization is the increase of storage energy, and the increase of dislocation density and twin makes nucleation more intense. It makes up for the shortage of dynamic recrystallization time caused by high rate deformation. Therefore, it is clear that adiabatic temperature rise is not the only factor to promote dynamic recrystallization during high rate deformation. Based on the analysis of experimental data, the hot working diagram of 617B alloy has been drawn, and the semi-quantitative characterization between the thermal deformation parameters and the microstructure evolution law has been realized, and the dynamic recrystallization and grain growth model of 617B alloy has also been established. By combining the microstructure evolution model with the DEFORM-2D finite element simulation software, the accurate prediction of extrusion parameters and microstructure evolution process under extrusion conditions is realized. Under the condition of grain size requirement and equipment carrying capacity, the optimum technological range of hot extrusion for 617B pipe can be provided. The solid solution and cold rolling annealing of the hot extruded tube were studied. The main technological parameters of 617B alloy were obtained: the solution system of the waste tube was 1190--1210 鈩，

本文編號(hào)：1886416