【摘要】：包殼與端塞焊接是我國(guó)鈉冷快堆堆芯組件制造的重要組成部分。15Cr-15Ni含Ti單相奧氏體不銹鋼(15-15Ti),具有良好的高溫強(qiáng)度、耐腐蝕性能以及輻照性能,是我國(guó)鈉冷快堆燃料主要候選包殼材料。該材料在焊接時(shí)易出現(xiàn)焊接熱裂紋和晶間腐蝕等問題,且目前與其相匹配的端塞材料尚未實(shí)現(xiàn)國(guó)產(chǎn)化應(yīng)用。本文針對(duì)15-15Ti奧氏體不銹鋼焊接中容易出現(xiàn)的問題,在現(xiàn)有文獻(xiàn)和資料基礎(chǔ)上,設(shè)計(jì)一種與之相匹配的含Nb、Si的16Cr-15Ni改進(jìn)型奧氏體不銹鋼(16-15NbSi)作為端塞材料,采用氬弧焊(TIG)將6組不同合金成分的16Cr-15Ni與15-15Ti進(jìn)行自熔焊接,并研究Nb、C、Si含量對(duì)焊接接頭時(shí)效前后組織性能的影響,考察焊接接頭的熱裂紋敏感性和晶間腐蝕性能,對(duì)確定端塞的合金成分范圍,實(shí)現(xiàn)端塞材料的國(guó)產(chǎn)化具有重要意義。本文研究工作與成果如下:(1)采用Thermo-Calc軟件對(duì)設(shè)計(jì)的6組16-15NbSi合金成分進(jìn)行熱力學(xué)平衡相圖計(jì)算。結(jié)果表明,隨著Nb元素的增加,NbC由從γ相中析出,轉(zhuǎn)變?yōu)橹苯訌囊合嘀形龀�。C含量的增加可促進(jìn)NbC的形成,Si元素可擴(kuò)大Laves相的析出溫度區(qū)間,降低σ相的析出溫度和析出量。(2)對(duì)時(shí)效前后焊接接頭組織性能進(jìn)行分析可知,隨Nb元素和C元素含量增加,NbC析出量和尺寸均增加,Si元素含量增加使晶界處析出相的析出現(xiàn)象更為顯著。時(shí)效后焊接接頭組織中Nb、C含量較低時(shí)NbC析出相的析出量和尺寸幾乎無變化,當(dāng)Nb和C含量分別達(dá)到0.9wt.%和0.09wt.%時(shí)焊縫組織中析出相尺寸長(zhǎng)大嚴(yán)重。時(shí)效前后焊接接頭的拉伸性能幾乎沒有變化,其中,0.6wt.%Nb、0.03wt.%C和0.09wt.%C時(shí)焊接接頭具有較高的抗拉強(qiáng)度和延伸率。時(shí)效后焊接接頭硬度與時(shí)效前相比略有下降,且6組焊接接頭中,只有0.6wt.%Nb、0.03wt.%C時(shí)效前后焊縫硬度均高于母材硬度。(3)6組焊接接頭在熱裂紋敏感性試驗(yàn)中未發(fā)現(xiàn)裂紋。晶間腐蝕試驗(yàn)中,只有0.6wt.%Nb和0.09wt.%C時(shí)發(fā)生了晶間腐蝕開裂,其余5組均未發(fā)現(xiàn)晶間腐蝕傾向。(4)綜合焊接接頭時(shí)效前后的組織性能,優(yōu)選出端塞的最佳合金成分范圍為:C含量0.02-0.04wt.%,Nb含量0.5wt.%-0.7wt.%,硅含量小于0.4wt.%.
[Abstract]:Shell and end plug welding is an important part of the manufacture of sodium cold fast reactor core assembly in China. 15Cr-15Ni contains Ti single phase Austenite stainless steel (15-15Ti), which has good high temperature strength, corrosion resistance and irradiation performance, and is the main candidate coating material for sodium cooled fast reactor fuel in China. The material is prone to welding hot crack and intergranular corrosion, and the matching end plug material has not yet been made in China. In order to solve the problems in welding of 15-15Ti Austenite stainless steel, based on the existing literature and data, an improved 16Cr-15Ni stainless steel (16-15NbSi) containing Nb,Si was designed as end plug material. Six groups of 16Cr-15Ni and 15-15Ti with different alloy composition were self-fluxing welded by argon arc welding (TIG), and Nb,C, was studied. The effect of Si content on the microstructure and properties of welded joints before and after aging is of great significance to determine the alloy composition range of end plugs and to realize the localization of end plug materials. The research work and results of this paper are as follows: (1) the thermodynamic equilibrium phase diagram of six groups of 16-15NbSi alloys is calculated by Thermo-Calc software. The results show that with the increase of Nb element, NbC precipitates from gamma phase to precipitates directly from liquid phase. The increase of C content can promote the formation of NbC. Si element can expand the precipitation temperature range of Laves phase and decrease the precipitation temperature and precipitation amount of 蟽 phase. (2) the microstructure and properties of welded joints before and after aging show that the precipitation amount and size of NbC increase with the increase of Nb element and C element content. The precipitation of precipitated phase at grain boundary is more obvious with the increase of Si element content. After aging, the precipitation amount and size of NbC precipitated phase were almost unchanged when the content of Nb,C in welded joint was low. When the content of Nb and C reached 0.9wt.% and 0.09wt.%, respectively, the precipitated phase size in weld microstructure grew up seriously. There is little change in the tensile properties of the welded joints before and after aging, in which the welded joints have higher tensile strength and extensibility when 0.6wt.% NB, 0.03wt.% C and 0.09wt.%C. The hardness of the welded joint after aging is slightly lower than that before aging, and only 0.6 wt.% NB in the six groups of welded joints, and the hardness of the weld before and after aging is higher than that of the base metal. (3) No cracks were found in the hot crack sensitivity test of the 6 groups of welded joints. In the intergranular corrosion test, intergranular corrosion cracking occurred only in 0.6wt.%Nb and 0.09wt.%C, and no intergranular corrosion tendency was found in the other five groups. (4) the optimum alloy composition range of end plug was 0.02 wt.%, 0.5 wt.% and 0. 7 wt.%, respectively, and the silicon content was less than 0. 4 wt.%, 0. 02 wt.%, 0. 7 wt.%, and 0. 4 wt.%, 0. 4 wt.%, 0. 02 wt.%, 0. 5 wt.%, 0. 7 wt.% and less than 0.4 wt.%, respectively.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG407

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本文編號(hào)：2507866