本文關(guān)鍵詞：SW400鋼預(yù)熱閃光對(duì)焊接頭組織及性能的研究　出處：《吉林大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 預(yù)熱閃光對(duì)焊 熱輸入 熱循環(huán) 微觀組織 力學(xué)性能

【摘要】：隨著人們環(huán)保意識(shí)的提高,低能耗、環(huán)境友好型經(jīng)濟(jì)模式逐漸成為未來(lái)發(fā)展的潮流。在汽車行業(yè),各大生產(chǎn)商都在積極尋求節(jié)能發(fā)展的新方向。在影響汽車油耗的各個(gè)因素中,車體自重占有很大的比例,車體輕量化成為車輛開(kāi)發(fā)的熱點(diǎn)。作為車身的重要部件,車輪在車體輕量化中占據(jù)著重要地位。國(guó)內(nèi)車輛,尤其是中低端車型和商用車型,車輪依舊以使用鋼材為主。提高、優(yōu)化車輪鋼材強(qiáng)度等級(jí)和結(jié)構(gòu)設(shè)計(jì),成為國(guó)內(nèi)車輪生產(chǎn)商實(shí)現(xiàn)輕量化的發(fā)展方向。SW400鋼是本鋼新研制的一種車輪生產(chǎn)專用鋼,具有良好的承載性能與安全性能優(yōu)勢(shì),是生產(chǎn)輪輞的主要材料之一。輪輞焊接常使用閃光對(duì)焊,但SW400鋼閃光對(duì)焊接頭仍面臨很多問(wèn)題。輪輞焊縫易在隨后的加工中開(kāi)裂,很難修補(bǔ),導(dǎo)致車輪生產(chǎn)廢品率居高不下。預(yù)熱工藝可以有效改善接頭組織,提高輪輞的力學(xué)性能,是優(yōu)化車輪生產(chǎn)工藝的的一種有效手段。本文主要研究了SW400鋼預(yù)熱閃光對(duì)焊的熱循環(huán)特征及預(yù)熱工藝參數(shù)對(duì)熱循環(huán)的影響;預(yù)熱閃光對(duì)焊接頭的宏、微觀組織特點(diǎn);預(yù)熱參數(shù)對(duì)接頭組織及力學(xué)性能的影響和閃光留量對(duì)接頭組織及力學(xué)性能的影響。研究結(jié)果表明,預(yù)熱可以改變焊接過(guò)程中接頭的熱循環(huán),預(yù)熱電流和預(yù)熱時(shí)間共同決定預(yù)熱階段接頭的熱輸入量,增加兩者或其中之一均會(huì)增大熱輸入,導(dǎo)致接頭溫度梯度變緩,各區(qū)域峰值溫度和加熱速度升高,冷卻速度降低,焊縫激冷效應(yīng)減弱。閃光對(duì)焊接頭可分為界面區(qū)(WZ)、過(guò)熱區(qū)(OZ)、重結(jié)晶區(qū)(RZ)和不完全重結(jié)晶區(qū)(PZ)。SW400鋼對(duì)焊接頭界面區(qū)由于脫碳、高溫和熱變形等因素主要由塊狀鐵素體、上貝氏體和針狀鐵素體組成;過(guò)熱區(qū)主要是粗大的上貝氏體,并有少量珠光體生成;重結(jié)晶區(qū)晶粒得到細(xì)化,主體為塊狀鐵素體和珠光體;不完全重結(jié)晶區(qū)組成與重結(jié)晶區(qū)一致,但晶粒大小不均。隨著預(yù)熱電流和預(yù)熱時(shí)間的增加,SW400鋼接頭加熱速度上升,冷卻速度下降;接頭的微觀組織經(jīng)歷了塊狀鐵素體增多、長(zhǎng)大,上貝氏體和針狀鐵素體粗化,微觀組織均勻化這一過(guò)程。合適的預(yù)熱電流和預(yù)熱時(shí)間有利于改善接頭組織,但其一或兩者過(guò)大會(huì)導(dǎo)致接頭晶粒粗化嚴(yán)重,明顯降低接頭力學(xué)性能。這個(gè)規(guī)律在接頭力學(xué)性能測(cè)試中得到驗(yàn)證。閃光對(duì)焊過(guò)程中的閃光留量對(duì)接頭組織及力學(xué)性能具有明顯影響,加入預(yù)熱工藝后,應(yīng)適當(dāng)采用較小的閃光留量值,否則,接頭組織會(huì)因預(yù)熱工藝帶來(lái)的額外熱輸入而嚴(yán)重粗化,力學(xué)性能降低。降低閃光留量同時(shí)可以節(jié)省鋼材,節(jié)約閃光時(shí)間。
[Abstract]:With the improvement of people's awareness of environmental protection, low energy consumption, environment-friendly economic model has gradually become the trend of future development, in the automotive industry. Major manufacturers are actively looking for a new direction of energy conservation development. In the various factors that affect the fuel consumption of cars, the weight of the car body occupies a large proportion. As an important part of the body, the wheel occupies an important position in the body lightweight. Domestic vehicles, especially low-end models and commercial models. The wheel still mainly uses steel. Improves, optimizes the wheel steel strength grade and the structure design. SW400 steel, which has become the development direction of domestic wheel manufacturer to realize lightweight, is a new kind of special steel for wheel production in Benxi Iron and Steel Co., which has the advantages of good bearing capacity and safety performance. Flash butt welding is often used in rim welding, but the SW400 steel flash butt welding joint still faces many problems. The weld seam of rim is easy to crack in the subsequent processing, and it is difficult to repair. The preheating process can effectively improve the joint structure and improve the mechanical properties of the rim. This paper mainly studies the thermal cycle characteristics of SW400 steel preheating flash butt welding and the influence of preheating process parameters on thermal cycle. Macrostructure and microstructure of preheated flash butt welding joint; The effect of preheating parameters on the microstructure and mechanical properties of the joints and the effect of flash retention on the microstructure and mechanical properties of the joints. The results show that preheating can change the thermal cycle of the joints during welding. Preheating current and preheating time jointly determine the heat input of the joint in the preheating stage. Increasing both or one of them will increase the heat input, resulting in the joint temperature gradient becoming slower, and the peak temperature and heating speed of each region increasing. The flash butt welding joint can be divided into interfacial zone (WZ) and superheated zone (OZ). Recrystallization zone (RZ) and incomplete recrystallization zone (PZN. SW400) are mainly composed of bulk ferrite, upper bainite and acicular ferrite due to decarburization, high temperature and hot deformation. The superheated zone is mainly composed of coarse upper bainite and a small amount of pearlite. The grains in recrystallization region are refined, and the main grains are block ferrite and pearlite. The composition of the incomplete recrystallization zone is consistent with that of the recrystallization zone, but the grain size is uneven. With the increase of preheating current and preheating time, the heating rate increases and the cooling rate decreases with the increase of preheating current and preheating time. The microstructure of the joints experienced a process of increasing and growing up, coarsening of upper bainite and acicular ferrite, and homogenization of microstructure. Proper preheating current and preheating time were beneficial to improve the microstructure of the joints. But one or both of them lead to serious grain coarsening. The mechanical properties of the joints were obviously reduced. This rule was verified in the testing of the mechanical properties of the joints. The flash retention during flash butt welding had a significant effect on the microstructure and mechanical properties of the joints, and the preheating process was added. The smaller flash retention should be used properly, otherwise, the microstructure of the joint will be coarsened seriously because of the extra heat input brought by the preheating process, and the mechanical properties will be reduced, and the steel and flash time can be saved by reducing the flash retention at the same time.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：U466

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