【摘要】：隨著經(jīng)濟(jì)的發(fā)展和工業(yè)技術(shù)的進(jìn)步,高放廢物也隨之大量增加。為了安全有效必須妥善處理高放廢物,有學(xué)者提出將高危高放廢物高溫熔融后澆注到容器中密封然后做填埋處理。310S奧氏體耐熱鋼具有良好的加工性能和力學(xué)性能,是接收容器的首選材料,但310S鋼在高溫下僅依靠固溶強(qiáng)化,強(qiáng)度不足。為了提高310S鋼高溫力學(xué)性能,本研究提出在310S鋼中的基礎(chǔ)上添加Nb元素來(lái)提高其高溫強(qiáng)度的思路。為此,本文首先利用Thermo-Calc熱力學(xué)軟件設(shè)計(jì)了一系列含Nb新型奧氏體耐熱鋼,對(duì)不同Nb含量的奧氏體耐熱鋼的顯微組織、力學(xué)性能以及熱加工性能進(jìn)行了系統(tǒng)研究。論文主要研究?jī)?nèi)容和結(jié)論如下:(1)利用熱力學(xué)計(jì)算軟件Thermo-Calc,設(shè)計(jì)了一系列不同Nb含量的新型奧氏體耐熱鋼。在此基礎(chǔ)上,通過真空感應(yīng)爐和氣體保護(hù)澆注制備了Nb含量為0、0.036 wt.%、0.12 wt.%、0.32wt.%和0.54 wt.%的新型奧氏體耐熱鋼,通過金相顯微鏡和掃描電鏡對(duì)鍛后組織觀察表明熱力學(xué)計(jì)算和實(shí)驗(yàn)結(jié)果吻合良好。(2)對(duì)不同Nb含量新型奧氏體耐熱鋼進(jìn)行固溶處理后,測(cè)試了不同Nb含量新型奧氏體耐熱鋼的室溫和高溫力學(xué)性能。結(jié)果表明:隨著Nb含量增加材料室溫強(qiáng)度變化不大,但高溫強(qiáng)度逐漸提高,達(dá)到了通過添加Nb元素來(lái)提高材料高溫強(qiáng)度的目標(biāo)。同時(shí),Nb的添加會(huì)略微降低材料的室溫沖擊韌性。(3)采用Gleeble熱模擬壓縮實(shí)驗(yàn),研究不同Nb含量奧氏體耐熱鋼的在900~1200℃溫度范圍內(nèi)和0.001-1~10s-1應(yīng)變速率下的熱變形特征。根據(jù)雙曲正弦模型建立Z參數(shù)與峰值應(yīng)力的關(guān)系,發(fā)現(xiàn)隨著Z值的增加,材料的峰值應(yīng)力也增加,同時(shí)材料的動(dòng)態(tài)再結(jié)晶也越難發(fā)生。利用Laasraoui和jonas模型建立高溫應(yīng)力-應(yīng)變模型,發(fā)現(xiàn)在相同應(yīng)變速率和相同溫度條件下,材料的峰值應(yīng)力、穩(wěn)態(tài)應(yīng)力以及飽和應(yīng)力隨著Nb含量升高而提高;同時(shí)Nb會(huì)抑制動(dòng)態(tài)再結(jié)晶,提高材料熱變形激活能。結(jié)合動(dòng)態(tài)材料模型和連續(xù)失穩(wěn)判據(jù),繪制了不同Nb含量的奧氏體耐熱鋼的熱加工圖。(4)以0.32wt.%Nb材料為載體,研究了材料中Nb(C,N)對(duì)動(dòng)態(tài)再結(jié)晶抑制機(jī)制。使用ECCI觀察熱壓縮變形試樣組織,發(fā)現(xiàn)Nb(C,N)析出相有效釘扎了材料在熱變形中位錯(cuò)的運(yùn)動(dòng)。
[Abstract]:With the development of economy and the progress of industrial technology, the high-level radioactive waste also increases greatly. In order to be safe and effective, high-level radioactive waste must be properly treated. Some scholars have proposed that high-risk high-level radioactive waste should be melted at high temperature and then sealed in a container and then landfill. 310S austenitic heat-resistant steel has good processing and mechanical properties. It is the first choice material for receiving container, but 310S steel only depends on solid solution strengthening at high temperature, and its strength is insufficient. In order to improve the high temperature mechanical properties of 310S steel, the idea of adding Nb element to 310S steel to improve its high temperature strength is put forward in this paper. In this paper, a series of new austenitic heat-resistant steels containing Nb were designed by using Thermo-Calc thermodynamic software. The microstructure, mechanical properties and hot-working properties of austenitic heat-resistant steels with different Nb contents were studied systematically. The main contents and conclusions of this paper are as follows: (1) A series of new Austenite heat-resistant steel with different Nb content were designed by using thermodynamic calculation software Thermo-Calc,. On this basis, a new type of Austenite heat-resistant steel with Nb content of 0, 0. 036 wt.%,0.12 wt.%,0.32wt.% and 0. 54 wt.% was prepared by vacuum induction furnace and gas-protected pouring. The microstructure observation after forging by metallographic microscope and scanning electron microscope shows that the thermodynamic calculation and experimental results are in good agreement with the experimental results. (2) the new austenitic heat-resistant steels with different Nb content are treated by solid solution treatment. The mechanical properties of new austenitic heat resistant steels with different Nb content at room temperature and at high temperature were tested. The results show that the room temperature strength of the material does not change much with the increase of Nb content, but the high temperature strength increases gradually, which achieves the goal of improving the high temperature strength of the material by adding Nb element. At the same time, the addition of Nb will slightly reduce the impact toughness of the material at room temperature. (3) the Gleeble thermal simulation compression experiment is used. The thermal deformation characteristics of austenitic heat resistant steels with different Nb content at 900 鈩，

本文編號(hào)：2472317