本文關(guān)鍵詞：鈦合金激光填粉焊接粉末燒損研究　出處：《湖南大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 激光焊接 粉末輸送 光粉耦合 粉末燒損 數(shù)學(xué)模型 鈦合金

【摘要】：鈦合金以其優(yōu)良的機(jī)械性能,廣泛地應(yīng)用于飛機(jī)蒙皮中。但在鈦合金激光焊接中因焊接裝配間隙過大或者高能激光束對焊縫金屬的輻射汽化,易出現(xiàn)焊縫塌陷現(xiàn)象。焊縫塌陷對飛機(jī)蒙皮隱身涂層涂裝及整體的隱身性能具有直接影響。而激光填粉焊接技術(shù)可以有效抑制焊縫塌陷,同時(shí)可以提高焊縫力學(xué)性能。在焊接過程中,激光束與粉末束的能量耦合作用對于作為激光填粉焊接的核心技術(shù)之一的粉末有效輸送具有直接影響。因此,本文采用模擬與試驗(yàn)分析相結(jié)合的方法研究了激光束與粉末束的能量耦合作用以及粉末填充對于鈦合金焊縫塌陷的補(bǔ)償作用。首先,以傳熱學(xué)、概率學(xué)理論為基礎(chǔ),本文通過對粉末顆粒空間密度分布與單位傳輸距離粉末顆粒數(shù)的求解,建立了粉末束與激光束能量耦合的數(shù)學(xué)模型,并將通過模型計(jì)算出的單位傳輸距離上粉末吸收的激光功率與粉末汽化潛熱的比值轉(zhuǎn)化為粉末燒損摩爾量。該模型考慮了粉末顆粒直徑,粉末顆粒速度,激光功率密度分布,送粉量等主要因素。其次,本文搭建了粉末束與激光束能量耦合試驗(yàn)觀測平臺,拍攝了在激光輻照作用下粉末束灰度圖。依據(jù)圖像灰度與粉末質(zhì)量的相關(guān)函數(shù)以及所建數(shù)學(xué)模型,對比有無激光輻照作用的粉末質(zhì)量分布,測量得到了粉末在激光功率為1000W、2000W時(shí)的吸收率。并討論了各參數(shù)對于粉末束中粉末顆粒燒損的影響。結(jié)果表明:粉末質(zhì)量峰值隨著激光功率的增加而減小;隨著載粉氣流量的增加,粉末燒損率呈先下降再上升的趨勢,并且在6L/min時(shí)燒損率達(dá)到最小值15.10%;在相同激光功率下,直徑較大的粉末顆粒的燒損量較小。最后,依據(jù)上述粉末燒損規(guī)律,計(jì)算了鈦合金填粉焊接中純鈦粉末顆粒的填充量,并使用激光填粉焊接工藝對TC4鈦合金進(jìn)行了焊接試驗(yàn)。試驗(yàn)結(jié)果顯示:填充粉末的鈦合金激光焊接焊縫無明顯塌陷,與普通激光焊接相比,組織、力學(xué)性能基本相同,延伸率略有增加。光粉耦合粉末顆粒燒損量的研究探討了以激光填粉焊接技術(shù)為代表的激光增材制造技術(shù)中激光束能量在粉末束上的分布關(guān)系,為焊縫高度和元素組織的調(diào)控提供了設(shè)計(jì)理論依據(jù)。
[Abstract]:Titanium alloys are widely used in aircraft skin because of their excellent mechanical properties, but in laser welding of titanium alloys, the welding gap is too large or the radiation vaporization of weld metal by high energy laser beam. Welding seam collapse is easy to occur. The seam collapse has a direct impact on the coating of aircraft skin stealth coating and the overall stealth performance. Laser powder filling welding technology can effectively suppress the seam collapse. At the same time, the mechanical properties of welding seam can be improved. In the process of welding, the coupling of laser beam and powder beam has a direct impact on the effective transportation of powder as one of the core technology of laser powder filling welding. In this paper, the energy coupling between laser beam and powder beam and the compensation effect of powder filling on weld collapse of titanium alloy are studied by means of simulation and experimental analysis. Firstly, heat transfer is used to study the effect of laser beam and powder beam on the weld collapse of titanium alloy. Based on the theory of probability, the mathematical model of energy coupling of powder beam and laser beam is established by solving the spatial density distribution of powder particles and the number of powder particles per unit transmission distance. The ratio of the laser power absorbed by the powder to the latent heat of vaporization is converted to the molar amount of the powder burning in the unit transmission distance calculated by the model. The model takes into account the particle diameter and particle velocity. The main factors such as laser power density distribution, powder feeding amount and so on. Secondly, the experimental observation platform of energy coupling of powder beam and laser beam is built in this paper. According to the correlation function between image grayscale and powder mass and the established mathematical model, the powder mass distribution with or without laser irradiation was compared. The laser power of the powder is 1000W. The absorptivity of 2000W and the influence of various parameters on the burning loss of powder particles in the powder beam are discussed. The results show that the peak value of powder mass decreases with the increase of laser power. With the increase of the flow rate of the carrier gas, the burning loss rate of the powder decreased first and then increased, and the burning rate reached the minimum value of 15.10 at 6L / min. At the same laser power, the amount of burning loss of the larger diameter powder particles is smaller. Finally, according to the law of the above powder burning, the filling amount of pure titanium powder particles in titanium alloy powder filling welding is calculated. The welding test of TC4 titanium alloy was carried out by using laser powder filling welding technology. The results showed that there was no obvious collapse in the welding seam of titanium alloy filled with powder, and the microstructure was compared with that of conventional laser welding. The mechanical properties are basically the same. The research on the burning loss of photo-powder coupling powder particle has discussed the distribution of laser beam energy on powder beam in laser material augmentation manufacturing technology represented by laser powder filling welding technology. It provides a theoretical basis for the control of weld height and element structure.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG456.7

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