本文選題：堆焊 + Inconel��； 參考：《西南石油大學》2017年博士論文

【摘要】：隨著天然氣工業(yè)的不斷發(fā)展,高含H2S/CO2酸性氣田逐漸步入全面開發(fā)階段,在這類氣田開采過程中,若選材或防腐工藝不當,腐蝕介質會造成金屬材料的嚴重腐蝕。Inconel 625合金具有良好的綜合性能,其耐腐蝕性能滿足API 6A、NACE MR0175/ISO 15156等標準所推薦的用于酸性氣田惡劣腐蝕環(huán)境的材料要求。然而Inconel 625合金的價格約為普通抗硫鋼的10-15倍,材料成本嚴重地制約了其單獨大量使用。因此開展Inconel 625合金的堆焊表面改性研究,具有重要的理論意義和工程應用前景。本文針對熱絲脈沖 TIG(Hot-wire pulsed tungsten inert gas,HPTIG)堆焊 Inconel 625合金所涉及的焊縫成形質量控制、微觀組織與殘余應力調控、微觀組織與耐腐蝕性能的關聯(lián)性以及焊后熱處理工藝等關鍵問題進行了系統(tǒng)地研究,并提出了合理的堆焊工藝和熱處理工藝。研究所得的焊件具有較好的力學性能,而且堆焊層具有良好的耐H2S/CO2腐蝕性能。針對HPTIG工藝焊縫成形質量不易控制的問題,采用中心復合試驗設計(Central composite design,CCD)法進行堆焊試驗,結合響應面法(Response surface method,RSM)建立了工藝參數(shù)與焊縫成形質量之間的回歸模型,并對模型進行了顯著性檢驗、擬合度檢驗、殘差分析和試驗驗證。結果表明:所建立的模型能夠反映工藝參數(shù)與焊縫成形質量之間的關系,能夠用于焊縫成形質量的預測。同時揭示了工藝參數(shù)對焊縫成形質量的影響規(guī)律,主效應對焊縫高度的影響大小依次為:VsδfIpIb,主效應對焊縫寬度和稀釋率的影響大小依次為:δVsfIpIb;交互效應對焊縫高度的影響大小依次為:IpδIbδIpI邱;對于稀釋率,Ibδ的交互影響較大,而Ipδ的交互影響則較弱�；谒⒌幕貧w模型,以焊縫的高度、寬度和稀釋率為優(yōu)化目標,對工藝參數(shù)進行了優(yōu)化,優(yōu)化后焊縫的稀釋率明顯降低。采用優(yōu)化所得的工藝參數(shù)進行多道焊試驗,以建立焊件的幾何模型;在此基礎上以Abaqus軟件為平臺,結合Fortran和Python編程軟件,采用生死單元法模擬焊縫單元的逐步填充,建立了堆焊溫度場和應力場的三維耦合有限元模型,并對模型進行了有效性驗證。結果表明:所建立的模型是可靠的,能夠準確地反映堆焊溫度和應力的分布與變化。為了改善堆焊層的微觀組織,并降低焊件的殘余應力,分析了焊縫間隔時間和堆焊路徑對冷卻速率、溫度梯度和殘余應力的影響規(guī)律。研究表明:合理地控制間隔時間和優(yōu)選堆焊路徑,能夠提高堆焊層微觀組織的均勻性,并降低殘余應力。根據(jù)優(yōu)化得到的工藝參數(shù)和仿真得到的堆焊方案,進行多焊縫單層和兩層堆焊。采用掃描電子顯微鏡(Scanning electron microscope,SEM)、X 射線衍射(X-ray diffraction,XRD)和能譜分析(Energy dispersive spectrometer,EDS)等方法研究了所得堆焊層的微觀組織演變和析出相分布規(guī)律,結果表明:自熔合界面至堆焊層表面的微觀組織演變依次為平面晶、胞狀晶、柱狀晶和等軸晶;堆焊層主要由γ-Ni固溶體、分布在晶間的Laves相和MC相組成,而且晶體形態(tài)對Laves相的分布特征有顯著影響。利用電化學阻抗譜(Electrochemical impedance spectroscopy,EIS)、動電位掃描技術和浸泡試驗,并結合腐蝕微觀形貌,研究了堆焊層的耐點蝕性能和耐晶間腐蝕性能。結果表明:單層Inconel 625堆焊層受母材稀釋的影響,其耐腐蝕性能明顯低于第二層堆焊層;由于第二層堆焊層的微觀組織與成分存在梯度,其不同厚度處的耐點蝕性能和耐晶間腐蝕性能存在差異,大的晶粒尺寸、少的析出相對堆焊層的耐點蝕性能和耐晶間腐蝕有利。為了改善堆焊層的耐腐蝕性能和焊件的力學性能,在考慮母材與堆焊層異種材料的基礎上,研究了相同保溫時間條件下,熱處理溫度對堆焊層微觀組織、耐腐蝕性能和力學性能的影響規(guī)律。結果表明:經(jīng)750℃熱處理后,有部分Laves發(fā)生了溶解,并在晶界處析出了 δ相;隨著熱處理溫度的升高,δ相含量增多、尺寸增大。采用電化學測試、浸泡試驗和掛片試驗,結合腐蝕微觀形貌與腐蝕產(chǎn)物,揭示了熱處理溫度對耐腐蝕性能的影響規(guī)律,即隨著δ相的增多,堆焊層的耐晶間腐蝕性能和耐H2S/CO2腐蝕性能顯著惡化。結合拉伸試驗和斷口形貌,揭示了熱處理溫度對堆焊層力學性能的影響規(guī)律。發(fā)現(xiàn)少量的δ相對堆焊層的屈服強度和抗拉強度有利,然而隨著δ相的增多,堆焊層的屈服強度和抗拉強度明顯降低。綜合熱處理對耐腐蝕性能、力學性能的影響,得到了合理的熱處理工藝。
[Abstract]:With the continuous development of the natural gas industry, the high H2S/CO2 acid gas field has gradually entered the comprehensive development stage. In the process of exploitation of this kind of gas field, if the material selection or the anticorrosion technology is improper, the corrosive medium will cause serious corrosion of metal material to.Inconel 625 alloy, and its corrosion resistance meets API 6A, NACE MR0175/ISO 151. The material requirements for the harsh corrosive environment of acid gas field recommended by the 56 standards are required. However, the price of Inconel 625 alloy is about 10-15 times as high as that of ordinary sulfur resistant steel. The material cost seriously restricts its use alone. Therefore, it is of great theoretical significance and engineering application prospects to carry out the study of the surface modification of the surfacing surface of Inconel 625 alloy. In this paper, the quality control of weld forming, microstructure and residual stress control, the correlation between microstructure and corrosion resistance, and heat treatment process after welding are systematically studied for the welding of Inconel 625 alloy by hot wire pulse TIG (Hot-wire pulsed tungsten inert gas, HPTIG), and a reasonable pile is put forward. Welding and heat treatment process. The welded parts obtained have good mechanical properties, and the surfacing layer has good H2S/CO2 corrosion resistance. In view of the problem that the weld quality of the HPTIG process is not easy to control, the central composite test design (Central composite design, CCD) is used to carry out the surfacing test, and the response surface method (Response Su) is combined with the response surface method (Response Su). Rface method, RSM) established the regression model between the process parameters and the weld forming quality. The model was tested by the significance test, the fitting degree test, the residual analysis and the test verification. The results show that the model can reflect the relationship between the process parameters and the weld forming quality, and can be used for the prediction of the weld forming quality. The influence of process parameters on weld forming quality is revealed. The main effect of main effect on weld height is Vs [delta] fIpIb. The influence size of main effect on weld width and dilution rate is: Delta VsfIpIb, and the influence of interaction effect on weld height is Ip Delta Ib Delta IpI Qiu, and the interaction effect of Ib Delta on dilution ratio is larger. And the interaction of Ip delta is weak. Based on the established regression model, the optimization of the weld seam height, width and dilution rate is optimized and the dilution rate of the weld is reduced obviously. The multi pass welding test is carried out with the optimized process parameters to establish the geometric model of the weld. On this basis, Abaqus The software is used as a platform, combining the Fortran and Python programming software, using the life and death element method to simulate the gradual filling of the weld unit. The three-dimensional coupling finite element model of the temperature field and stress field of the surfacing welding is established, and the validity of the model is verified. The results show that the model is reliable and can accurately reflect the temperature and stress of the welding. In order to improve the microstructure of the surfacing layer and reduce the residual stress of the weld, the influence of the interval time of the weld and the welding path on the cooling rate, the temperature gradient and the residual stress are analyzed. The research shows that the reasonable control of the interval time and the optimum welding path can improve the uniformity of the microstructure of the surfacing layer and reduce the microstructure. Low residual stress. On the basis of the optimized process parameters and the simulated welding scheme, multi weld single layer and two layer surfacing are carried out. Scanning electron microscope (Scanning electron microscope, SEM), X ray diffraction (X-ray diffraction, XRD) and energy spectrum analysis (Energy dispersive spectrometer, EDS) are used to study the surfacing welding. The microstructure evolution and precipitation phase distribution of the layer show that the microstructure evolution of the self fusion interface to the surface of the surfacing layer is the plane crystal, the cell crystal, the columnar crystal and the equiaxed crystal, and the surfacing layer mainly consists of the solid solution of gamma -Ni, which is distributed in the intercrystalline Laves phase and the MC phase, and the crystal morphology has a significant shadow on the distribution of the Laves phase. The corrosion resistance and intergranular corrosion resistance of the surfacing layer were studied by electrochemical impedance spectroscopy (Electrochemical impedance spectroscopy, EIS), dynamic potential scanning and immersion test, and the corrosion micromorphology was combined. The results showed that the corrosion resistance of the monolayer Inconel 625 surfacing layer was significantly lower than second. Layer surfacing layer; due to the gradient of microstructure and composition of the second layer surfacing layer, the corrosion resistance and intergranular corrosion resistance at different thickness are different, the large grain size, less precipitation relative overlay resistance and intergranular corrosion resistance are favorable. In order to improve the corrosion resistance and mechanical properties of the welding parts, the mechanical properties of the surfacing layer are improved. The influence of heat treatment temperature on the microstructure, corrosion resistance and mechanical properties of the surfacing layer under the same holding time was studied on the basis of the dissimilar material of the parent material and the surfacing layer. The results showed that after heat treatment at 750 C, some Laves was dissolved, and the delta phase was precipitated at the grain boundary, with the rise of heat treatment temperature. The effect of heat treatment temperature on corrosion resistance is revealed by electrochemical testing, immersion test and hanging test. The effect of heat treatment temperature on corrosion resistance is revealed. That is, with the increase of the delta phase, the intergranular corrosion resistance and H2S/CO2 corrosion resistance of the surfacing layer are significantly worse. The fracture morphology reveals the influence of the heat treatment temperature on the mechanical properties of the surfacing layer. It is found that the yield strength and tensile strength of a small amount of delta are favorable, but with the increase of the delta phase, the yield strength and tensile strength of the surfacing layer are obviously reduced. The effect of comprehensive heat treatment on corrosion resistance and mechanical properties is reasonable. Heat treatment process.
【學位授予單位】：西南石油大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TG444.74

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