本文關(guān)鍵詞：基于CMT的不銹鋼電弧增材制造溫度場、應力場及成型工藝研究　出處：《南京理工大學》2017年碩士論文　論文類型：學位論文

  更多相關(guān)文章： 電弧增材制造 成型路徑 溫度場及應力場 數(shù)學模型 組織及力學性能

【摘要】：電弧增材制造是以電弧為熱源,均勻送入的焊絲為熔覆材料,直接快速成型致密度高、力學性能優(yōu)良的金屬復雜結(jié)構(gòu)件,可極大提高材料的利用率、生產(chǎn)效率和制造技術(shù)的核心競爭力。課題基于CMT的不銹鋼增材制造技術(shù),以成型直壁件為研究對象,對增材制造過程中的溫度場、應力場、增材制造工藝及成型件組織性能開展了研究。首先對不銹鋼CMT增材制造過程中的溫度場及應力場進行了研究。建立了基于SYSWELD的增材制造有限元模型,對比了同向連續(xù)增材制造、S形連續(xù)增材制造及S形間隔時間增材制造三種常用的電弧增材制造路徑下溫度場及應力場,其結(jié)果表明,基板對前四層熔覆層的冷卻速率影響較大,且基板能夠影響的層數(shù)與增材制造方式無關(guān);熔覆層的溫度在其上熔覆一定層數(shù)后趨于穩(wěn)定,穩(wěn)定后的溫度在奧氏體不銹鋼敏感化溫度區(qū)間以下,且控制層間溫度可以獲得較小的穩(wěn)定溫度值;CMT在連續(xù)熔覆時熱累積作用不明顯。奧氏體不銹鋼增材制造后殘余應力大于屈服強度;同向增材制造時出現(xiàn)較大的殘余應力及變形;S形連續(xù)增材制造時殘余應力分布特點為較大的應力分布在較小的區(qū)域,而控制層間溫度時表現(xiàn)為較小的應力分布在較大的區(qū)域,且都呈現(xiàn)對稱分布;增材制造過程中的重熱作用相當于進行回火熱處理,減小了熔覆層中的殘余應力。其次利用MATLAB軟件建立了增材制造過程中保護氣流量、送絲速度及熔覆速度與成型壁厚的數(shù)學模型。該模型表明,送絲速度越大,成型壁厚越大,且當送絲速度超過4.0m/min時,壁厚增加速度明顯變慢;保護氣流量當與送絲速度交互作用時對成型壁厚影響較為明顯;三個因素對成型壁厚影響順序大致如下:送絲速度=熔覆速度保護氣流量。最后對比了S形連續(xù)增材制造及S形間隔時間增材制造成型直壁件顯微組織和力學性能。成型直壁件中組織按照經(jīng)歷的熱循環(huán)過程的不同主要分為六個區(qū)域,其中Ⅰ區(qū)與Ⅱ區(qū)為底部及底部過渡區(qū)域,含有較多枝晶狀的殘余鐵素體,Ⅲ區(qū)為熔覆層之間熔合形成的含有少量奧氏體柱狀晶區(qū)域,Ⅳ區(qū)為中部穩(wěn)定成型區(qū)域,鐵素體較少,呈現(xiàn)較小樹枝晶,Ⅴ區(qū)及Ⅵ六為頂部過渡區(qū)域及頂部區(qū)域,鐵素體含量較多�？刂茖娱g溫度時增加了相應區(qū)域的殘余鐵素體含量。成型直壁件抗拉強度達到了 304冷軋后退火不銹鋼基板的70%,且均高于鑄造態(tài)及熱軋狀態(tài),抗沖擊性能達到基板的65%,硬度與基板相當;橫向與縱向的拉伸強度、抗沖擊性能及塑性表現(xiàn)為不明顯的差異性;控制層間溫度對不銹鋼成型直壁件力學性能影響較小。
[Abstract]:The arc is to increase timber manufacturing arc as the heat source, evenly into the wire as cladding materials, direct rapid prototyping of high density and excellent mechanical properties of the metal complex structure, can greatly improve the material utilization and production efficiency and core competitiveness of manufacturing technology. The subject of CMT stainless steel increased material manufacturing technology based on the molding straight wall parts as the research object, on the temperature increasing material manufacturing process, stress field, microstructure and properties of additive manufacturing process and molding are studied. Firstly, CMT stainless steel material manufacturing process to increase the temperature field and stress field are studied. A material increase in manufacturing SYSWELD finite element model based on the comparison with the continuous increase in material manufacturing, S shaped and S shaped continuous increasing material manufacturing interval increasing material manufacturing three kinds of arc material manufacturing growth path under the temperature field and the stress field, the results show that the substrate of four layer of cladding layer The cooling rate has great influence, is irrelevant and can affect the substrate layers and increasing material manufacturing method; cladding temperature tends to be stable in the cladding layers, stable temperature on austenitic stainless steel sensitive temperature range, and the control layer temperature can obtain stable temperature of the lower value of CMT in continuous; cladding heat accumulation effect is not obvious. The austenitic stainless steel material manufacturing increased residual stress is greater than the yield strength; with the increasing material manufacturing occurs when large residual stress and deformation; S type continuous increasing material manufacturing residual stress distribution of stress distribution in a small area is larger, and the control layer when the temperature stress distribution is larger in the small area, and showed a symmetrical distribution; heavy heat increasing material in the manufacturing process of equivalent heat treatment, reduce the residual stress in the cladding layer. The utilization of MATLAB Software to establish a gas flow protection additive manufacturing process, the mathematical model of wire speed and feeding speed and the thickness of cladding forming. The model shows that the wire feeding speed is larger, forming wall thickness increases, and when the wire feeding speed is more than 4.0m/min, the wall thickness increases much slower when the amount of air protection; and the wire feeding speed interaction effect on the forming of wall thickness is obvious; three factors as follows for forming wall thickness influence order: the wire feeding speed = cladding speed protection gas flow. Finally compared the S type continuous increasing material manufacturing and S interval increasing material manufacturing straight wall parts and mechanical micro organization the performance of forming straight wall parts in the organization. According to the different thermal cycling process is divided into six regions, in which area I and II for the bottom and the bottom of the transition region, the residual iron containing more dendritic ferrite, III fusion formed between the cladding layer containing a small amount of The austenite columnar crystal region, Central District IV forming stable region, ferrite is less, a small dendrites, and the top six District V VI for the transition region and the top region, the ferrite content is more. The control layer temperature increases the residual iron ferrite content. The forming of straight wall parts the tensile strength reached 304 annealing of cold rolled stainless steel substrate 70%, and higher than that of casting and hot rolling state, impact resistance to substrate 65%, the hardness and the substrate; transverse and longitudinal tensile strength, impact resistance and ductility performance difference is not obvious; the control layer temperature of stainless steel straight the mechanical properties of the wall a little effect.

【學位授予單位】：南京理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG142.71;TP391.7

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