本文選題：P91鋼　切入點(diǎn)：補(bǔ)焊　出處：《江蘇科技大學(xué)》2017年碩士論文

【摘要】：P91鋼(9Cr1Mo,V,Nb)是一種新型的馬氏體耐熱鋼,在長(zhǎng)期服役過(guò)程中往往會(huì)出現(xiàn)局部裂紋等問(wèn)題。補(bǔ)焊具有操作簡(jiǎn)單、成本低和修復(fù)質(zhì)量高等優(yōu)點(diǎn),從而成為修復(fù)耐熱鋼管缺陷的主要手段。補(bǔ)焊所產(chǎn)生的焊接殘余應(yīng)力往往是焊接接頭裂紋產(chǎn)生的首要原因,因此,為確保補(bǔ)焊工藝的成功實(shí)施以及補(bǔ)焊部位的各項(xiàng)性能得到有效控制,必須對(duì)焊接殘余應(yīng)力進(jìn)行全面系統(tǒng)的分析。傳統(tǒng)的殘余應(yīng)力檢測(cè)方法大多只能測(cè)量焊件表層殘余應(yīng)力,而焊接數(shù)值模擬能快速對(duì)不同焊接工藝參數(shù)下殘余應(yīng)力作出定量化描述。通過(guò)數(shù)值模擬的方法,可以全面了解影響殘余應(yīng)力分布規(guī)律的因素,為制定合理的焊接工藝和預(yù)測(cè)焊接殘余應(yīng)力提供指導(dǎo)依據(jù)。本文采用同質(zhì)和異質(zhì)兩種填充材料對(duì)60mm厚P91鋼進(jìn)行補(bǔ)焊試驗(yàn),采用小孔法對(duì)補(bǔ)焊后試件殘余應(yīng)力進(jìn)行測(cè)量�；跓釓椝苄岳碚�,利用ANSYS建立P91鋼多層多道補(bǔ)焊三維數(shù)值分析模型,計(jì)算了P91鋼補(bǔ)焊的殘余應(yīng)力,并探究了補(bǔ)焊的殘余應(yīng)力分布特征,確定補(bǔ)焊的危險(xiǎn)位置。結(jié)果表明:模擬結(jié)果和試驗(yàn)結(jié)果吻合較好,證明了模型的準(zhǔn)確性。對(duì)于同質(zhì)補(bǔ)焊,在焊接過(guò)程中,由于后序焊縫對(duì)前序焊縫具有熱處理作用,每層焊縫表面的縱向應(yīng)力峰值逐漸減小。焊接結(jié)束后,焊縫及其近縫區(qū)域表現(xiàn)出較高的縱向殘余拉應(yīng)力,峰值為532MPa,高于材料室溫下屈服強(qiáng)度,離焊縫稍遠(yuǎn)處,縱向殘余拉應(yīng)力迅速降為壓應(yīng)力。橫向拉應(yīng)力較大值位于最后一層焊道先施焊?jìng)?cè),峰值為444MPa。Von-mises等效應(yīng)力在起弧及熄弧端較大,達(dá)到屈服強(qiáng)度,沿厚度方向殘余應(yīng)力數(shù)值相對(duì)較小可以忽略。在坡口輪廓區(qū)域,縱向殘余應(yīng)力沿厚度方向呈增大趨勢(shì),峰值出現(xiàn)在距焊縫上表面5-7mm處,且后施焊?jìng)?cè)坡口輪廓區(qū)域應(yīng)力峰值較先焊?jìng)?cè)大,峰值為589MPa。對(duì)于異質(zhì)補(bǔ)焊,施焊后在焊縫及其附近區(qū)域表現(xiàn)出較大的縱向拉應(yīng)力,應(yīng)力峰值為482MPa,隨著距焊縫中心距離增大,拉應(yīng)力迅速降為壓應(yīng)力;橫向拉應(yīng)力較大值位于焊縫上表面兩側(cè),峰值為333MPa;最高等效應(yīng)力區(qū)位于上表面焊縫區(qū)域周圍,峰值為470MPa,小于母材室溫時(shí)屈服強(qiáng)度;在坡口輪廓區(qū)域,縱向殘余應(yīng)力隨著補(bǔ)焊厚度的增加,呈先減小后增大趨勢(shì),且較大值位于焊縫的根部,峰值為424MPa。在真實(shí)服役條件下,殘余應(yīng)力整體有較大下降幅度,在坡口輪廓區(qū)域,縱向殘余應(yīng)力隨著補(bǔ)焊厚度的增加而增大,較大應(yīng)力區(qū)位于焊縫中部。
[Abstract]:P91 steel is a new type of martensite heat-resistant steel, which often has local cracks in the long service.Repair welding has the advantages of simple operation, low cost and high repair quality.Welding residual stress produced by welding is often the primary cause of welding joint cracks. Therefore, in order to ensure the successful implementation of the repair welding process and the effective control of the properties of the repair welding site,Welding residual stress must be comprehensively and systematically analyzed.Most of the traditional residual stress detection methods can only measure the residual stress in the surface layer of the welding piece, but the numerical simulation of welding can quickly quantify the residual stress under different welding process parameters.By means of numerical simulation, the factors affecting the distribution of residual stress can be fully understood, and the guidance basis for making reasonable welding process and predicting welding residual stress can be provided.In this paper, two filling materials, homogeneous and heterogeneous, are used to weld 60mm thick P91 steel, and the residual stress of post-weld specimens is measured by small hole method.Based on thermoelastic-plastic theory, a three-dimensional numerical analysis model of multi-layer and multi-pass repair welding for P91 steel was established by using ANSYS. The residual stress of P91 steel was calculated, and the distribution characteristics of residual stress were investigated, and the dangerous position of repair welding was determined.The results show that the simulation results are in good agreement with the experimental results, and the accuracy of the model is proved.For homogeneous repair welding, the longitudinal stress peak value of each layer of weld decreases gradually because of the heat treatment effect of the post-sequence weld on the pre-sequence weld during the welding process.At the end of welding, the longitudinal residual tensile stress of the weld and its near seam shows a relatively high peak value of 532 MPA, which is higher than the yield strength of the material at room temperature, and the longitudinal residual tensile stress decreases rapidly to compressive stress at a little distance from the weld.The larger transverse tensile stress is located at the first welding side of the last layer of welding pass, and the peak value of 444MPa.Von-mises equivalent stress is larger at the starting and extinguishing end of arc, reaching the yield strength, and the value of residual stress along the thickness direction is relatively small and can be neglected.In the groove contour region, the longitudinal residual stress increases along the thickness direction, and the peak value appears at 5-7mm from the upper surface of the weld, and the peak value of the stress in the groove profile region of the post-weld side is larger than that of the first welding side, and the peak value is 589 MPA.For heterogeneous welding, the longitudinal tensile stress is larger in the weld and its adjacent area after welding, the peak value of the stress is 482MPa, and the tensile stress decreases rapidly to compressive stress with the increase of distance from the center of the weld.The larger transverse tensile stress is located on both sides of the upper surface of the weld, the peak value is 333MPa, the maximum equivalent stress zone is located around the weld area of the upper surface, the peak value is 470MPa, which is smaller than the yield strength of the base metal at room temperature.The longitudinal residual stress decreases first and then increases with the increase of welding thickness, and the larger value is located at the root of the weld, and the peak value is 424 MPA.Under the real service condition, the residual stress decreases greatly. In the groove contour, the longitudinal residual stress increases with the increase of the welding thickness, and the larger stress zone is located in the middle of the weld.
【學(xué)位授予單位】：江蘇科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG457.11

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