激光焊接參數對1.2 mm TC4鈦合金薄板焊縫的影響

張穎云,陳素明,李 波

(航空工業西安飛機工業(集團)有限責任公司,西安710089)

摘 要:為了研究激光焊接參數對鈦合金焊縫的影響,對厚度1.2 mm 的TC4 鈦合金板材進行光纖激光焊接。分別采用單因素試驗和正交試驗研究了不同的激光工藝參數對焊縫形貌及力學性能的影響。單因素試驗結果表明:焊縫熔寬隨著激光功率的升高大體呈上升趨勢,焊縫背寬比隨著激光功率的升高先增大然后趨于穩定; 焊縫熔寬隨著離焦量的增大逐漸減小,當離焦量達到4 mm 時,出現未焊透現象; 焊縫尺寸隨著焊接速度波動變化,當焊速大于1.5 m/min 時,焊縫尺寸呈現減小趨勢。正交試驗結果表明:激光功率對抗拉強度的影響較大; 而對于延伸率,相較于激光功率,離焦量和焊接速度對延伸率的影響水平相當。

關鍵詞: 激光焊接; TC4 鈦合金; 焊縫; 宏觀形貌; 力學性能

0 引 言

鈦合金具有密度低、比強度高、比模量高、耐腐蝕性好等優良特性,被廣泛應用在航空航天、能源、海洋工程等領域[1-2]。目前,鈦合金的焊接方式有釬焊、固相焊和熔化焊[3]。由于釬焊焊縫的疲勞性能較差,固相焊在實際工況中限制條件較多,因此在目前的工業生產中鈦合金主要焊接方式是熔化焊。在目前航空工業生產中,鈦合金主要利用傳統的熔化焊方式進行焊接,以用于環控管路、燃油通道等異型導管的制造,生產效率低,焊接變形大,給后期安裝帶來諸多不便[4-5]。激光焊相對于傳統的熔焊焊接方式,具有能量密度高、焊接速度快、熱輸入小、焊后變形小等優點[6-9],適合鈦合金薄板的焊接。

國內外對鈦合金的激光焊接開展了大量的研究工作。英國焊接研究所 (TWI)應用 4 kW YAG 激光器實現6 mm 的Ti-6Al-4V 鈦合金的一次焊透,有些鈦合金激光器進行的鈦合金焊接,焊接速度快,接頭質量好,殘余應力小[10]。梁春雷等[11]對TC4 鈦合金薄板的焊接接頭進行了疲勞性能研究,明確了焊接接頭的拉伸和疲勞斷裂行為,為激光焊接結構件的設計、制造和安全評估提供了依據。由于激光器技術的發展,光纖激光器成為第三代激光器的代表,擴展了激光焊的發展空間,許飛等[12-13]進行了TC4 鈦板光纖激光焊和YAG 激光焊的焊接接頭性能差異分析,獲得了焊接熱輸入對光纖激光焊接接頭宏觀形貌與拉伸性能的影響規律。目前,關于光纖激光焊接鈦合金方面的報道較少,而關于焊接參數與焊縫的宏觀形貌及力學性能的關系方面的研究更少。

本研究分別從單因素試驗和正交試驗及試驗結果分析入手,探究了厚度1.2 mm 薄板鈦合金光纖激光焊接參數對焊縫宏觀形貌和力學性能的影響。

1 試驗材料及設備

試驗材料為TC4 鈦合金板材,厚度1.2 mm,狀態為退火態 (M),其化學成分見表1,力學性能指標見表2。

表1 TC4 鈦合金板材化學成分 %

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表2 TC4 鈦合金板材力學性能

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采用單因素試驗方法在不同的焊接功率、焊接速度、離焦量及對接間隙下對1.2 mm 鈦合金試板進行光纖激光焊接試驗,研究焊接參數對焊縫宏觀形貌的影響。單因素試驗參數見表3。采用正交試驗極差分析和方差分析方法探究激光焊接參數對焊接接頭力學性能的影響,正交試驗參數見表 4。焊后,采用 LEICA M125 型體式顯微鏡對焊縫的上下表面進行觀察,采用AG-250KNG 型電子拉力試驗機測試其力學性能。

表3 單因素試驗參數

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表4 正交試驗參數

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2 試驗結果及討論

2.1 單因素試驗分析

2.1.1 激光功率對焊縫形貌的影響

表5 顯示了不同激光功率作用下的焊縫成形數據,圖1 顯示了正面熔寬和背面熔寬隨激光功率升高的變化趨勢。從圖1、表5 可以看出,正面熔寬依次增大,但是在1.1~1.2 kW 范圍內,尺寸變化不大,說明在該焊接功率條件下焊接熱輸入正好滿足薄板焊透,且處于穩定狀態,焊縫正面、背面形貌如圖2 所示。

表5 不同激光功率下焊縫成形數值

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圖1 焊縫正面熔寬、背面熔寬及背寬比隨激光功率的變化趨勢

焊縫的背寬比隨功率增大先增加,然后趨于穩定,再稍有增加。焊縫尺寸的均勻度隨功率增大稍有變化,從表5 數據可知,激光功率在1.0~1.1 kW 的情況下,焊縫的寬度尺寸變化在同一水平,正面均勻度優于背面,此區間焊縫邊緣形貌呈均勻的 “波紋狀”,而在1.2 kW 功率下,焊縫外形更平滑連續,當功率為1.3 kW 時,背面均勻度優于正面。從焊縫的宏觀形貌看,焊縫呈銀亮色,焊縫寬度均勻,未見燒穿和焊縫堆積等缺陷。

圖2 1.1 kW 和1.2 kW 功率條件下焊縫正、背面形貌

2.1.2 離焦量對焊縫形貌的影響

不同離焦量下的焊縫形貌特征數據見表6。正面熔寬和背面熔寬隨離焦量的變化趨勢如圖3所示。從圖3 可知,正面熔寬和背面熔寬隨離焦量的增大而減小,但是在1~2 mm 范圍內,焊縫尺寸變化不大,當離焦量達到4 mm 時,出現未焊透現象,說明薄板激光焊選用正離焦方式時,離焦量應控制在一定范圍,當超出了最大范圍就會出現未焊透現象,也說明離焦量對激光焊接的質量影響較大。這是因為改變離焦量會影響試件表面光斑尺寸,并改變了到達試件表面及小孔內的能量密度[14],隨著焦點位置上移,光束聚焦位置遠離工件表面,激光能量密度逐步降低,這樣主要的激光能量集中在工件的上表面,試件下表面能量密度不夠,無法實現穿透焊,從而導致未焊透[15]。從表6 中的均勻度數據也可看出,離焦量為1 mm 時,正面均勻度相對于背面較差; 離焦量為2 mm 時,正面和背面的均勻度相當; 隨著離焦量再增大,背面出現了鏈狀的斷續焊縫形貌,甚至未焊透,焊縫形貌如圖4所示。因此可以得出,離焦量在 2 mm 時焊接過程最穩定。

表6 不同離焦量下焊縫成形數值

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圖3 焊縫正面熔寬、背面熔寬及寬背比隨離焦量的變化趨勢

圖4 離焦量為3 mm 時焊縫的正、背面形貌

2.1.3 焊接速度對焊縫形貌的影響

焊縫正面熔寬、背面熔寬及背寬比隨焊接速度的變化趨勢如圖5 所示。從圖5 可以看出,焊縫尺寸隨焊接速度波動變化,當焊接速度提高至1.5 m/min 時,焊縫尺寸有減小趨勢,這是因為在一定的激光功率下提高焊接速度,熱輸入能量密度值下降,焊縫寬度減小。當速度降低時,可增大熔深,但是速度過低,熔深不增反而增加熔寬,這主要是因為:①激光深熔焊接時,維持小孔存在的主要動力是金屬蒸汽的反沖壓力,在焊接速度低至一定程度時,熱輸入增加,熔化金屬越來越多,當金屬汽化所產生的反沖壓力不足以維持小孔的存在時,小孔不僅不加深,甚至會崩潰,焊接過程蛻變成為傳熱型焊接,因而熔深不會增大; ②隨著金屬汽化的增加,小孔區溫度上升,等離子體的濃度增加,對激光吸收增加[16]

圖5 焊縫正面熔寬、背面熔寬及背寬比隨焊接速度的變化趨勢

不同焊接速度下焊縫成形數值見表7。從表7可見,隨著焊接速度的增大,焊縫正面和背面的均勻度變化不大,說明焊接速度對焊縫形狀無明顯影響。而焊縫邊緣起伏均勻性隨焊接速度增大而更趨于均勻。從焊縫的宏觀形貌看,焊縫呈銀亮色,焊縫寬度均勻,未見燒穿和焊縫堆積等缺陷。

表7 不同焊接速度下焊縫成形數值

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2.1.4 焊縫間隙對焊縫形貌的影響

不同焊縫間隙下焊縫形貌特征數據見表8。正面熔寬、背面熔寬和背寬比隨焊縫間隙的變化趨勢如圖6 所示。從圖6 可知,焊縫間隙對焊縫外形的影響不大,從焊縫的宏觀形貌看,焊縫呈銀亮色,焊縫寬度均勻,未見燒穿和焊縫堆積等缺陷。焊接過程會形成熔池,當焊接間隙大于0.3 mm 時,焊接熔池經熔化和凝固補充不足造成焊接焊縫不連續、不均勻,甚至出現塌陷,因此當對接間隙較大時自熔焊已不適應,應采用填絲焊工藝進行焊接。

表8 不同焊接間隙下焊縫成形數值

images/BZ_36_283_1965_404_2096.pngimages/BZ_36_404_1965_562_2096.pngimages/BZ_36_562_1965_721_2096.pngimages/BZ_36_721_1965_876_2096.pngimages/BZ_36_876_1965_1012_2096.pngimages/BZ_36_1012_1965_1202_2096.pngimages/BZ_36_283_2096_404_2166.pngimages/BZ_36_404_2096_562_2166.pngimages/BZ_36_562_2096_721_2166.pngimages/BZ_36_721_2096_876_2166.pngimages/BZ_36_876_2096_1012_2166.pngimages/BZ_36_283_2166_404_2236.pngimages/BZ_36_404_2166_562_2236.pngimages/BZ_36_562_2166_721_2236.pngimages/BZ_36_721_2166_876_2236.pngimages/BZ_36_876_2166_1012_2236.pngimages/BZ_36_283_2236_404_2306.pngimages/BZ_36_404_2236_562_2306.pngimages/BZ_36_562_2236_721_2306.pngimages/BZ_36_721_2236_876_2306.pngimages/BZ_36_876_2236_1012_2306.pngimages/BZ_36_283_2306_404_2376.pngimages/BZ_36_404_2306_562_2376.pngimages/BZ_36_562_2306_721_2376.pngimages/BZ_36_721_2306_876_2376.pngimages/BZ_36_876_2306_1012_2376.pngimages/BZ_36_1012_2096_1202_2376.png

圖6 焊縫正面熔寬、背面熔寬和背寬比隨焊縫間隙的變化趨勢

2.2 正交試驗分析

2.2.1 極差分析

表9 顯示了正交試驗得到的拉伸結果,表10為極差分析結果,因素 A (離焦量)、B (激光功率)、C (焊接速度)的主次關系可由極差大小決定。從表10 極差值可以看出,對于抗拉強度指標,ΔkB>ΔkA>ΔkC,因此影響抗拉強度的主要因素是激光功率,離焦量和焊接速度影響水平相當; 對于延伸率指標,ΔkA>ΔkC>ΔkB,因此離焦量和焊接速度對延伸率的影響水平相當,而激光功率的影響較小。

表9 抗拉強度和延伸率正交試驗結果

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2.2.2 方差分析

方差分析不僅可以討論試驗誤差,還可以進一步明確各獨立因素及其交互作用對試驗結果的影響程度。方差分析的基本原則,即設用正交表Ln (pm)安排試驗,總試驗次數 N=n,表的縱列數為m,因素的水平數為p,則每一水平的試驗次數為n/p。

表10 抗拉強度和延伸率極差分析結果

images/BZ_37_272_407_455_465.png images/BZ_37_822_407_1006_465.pngimages/BZ_37_455_407_639_465.pngimages/BZ_37_639_407_822_465.png images/BZ_37_1006_407_1190_465.pngimages/BZ_37_272_465_455_868.pngimages/BZ_37_455_465_639_522.pngimages/BZ_37_639_465_822_522.pngimages/BZ_37_822_465_1006_522.pngimages/BZ_37_1006_465_1190_522.pngimages/BZ_37_455_522_639_580.pngimages/BZ_37_639_522_822_580.pngimages/BZ_37_822_522_1006_580.pngimages/BZ_37_1006_522_1190_580.pngimages/BZ_37_455_580_639_637.pngimages/BZ_37_639_580_822_637.pngimages/BZ_37_822_580_1006_637.pngimages/BZ_37_1006_580_1190_637.pngimages/BZ_37_455_637_639_695.pngimages/BZ_37_639_637_822_695.pngimages/BZ_37_822_637_1006_695.pngimages/BZ_37_1006_637_1190_695.pngimages/BZ_37_455_695_639_752.pngimages/BZ_37_639_695_822_752.pngimages/BZ_37_822_695_1006_752.pngimages/BZ_37_1006_695_1190_752.pngimages/BZ_37_455_752_639_810.pngimages/BZ_37_639_752_822_810.pngimages/BZ_37_822_752_1006_810.pngimages/BZ_37_1006_752_1190_810.png images/BZ_37_455_810_639_868.pngimages/BZ_37_639_810_822_868.pngimages/BZ_37_822_810_1006_868.pngimages/BZ_37_1006_810_1190_868.pngimages/BZ_37_272_868_455_1271.pngimages/BZ_37_455_868_639_925.pngimages/BZ_37_639_868_822_925.pngimages/BZ_37_822_868_1006_925.pngimages/BZ_37_1006_868_1190_925.pngimages/BZ_37_455_925_639_983.pngimages/BZ_37_639_925_822_983.pngimages/BZ_37_822_925_1006_983.pngimages/BZ_37_1006_925_1190_983.pngimages/BZ_37_455_983_639_1040.pngimages/BZ_37_639_983_822_1040.pngimages/BZ_37_822_983_1006_1040.pngimages/BZ_37_1006_983_1190_1040.pngimages/BZ_37_455_1040_639_1098.pngimages/BZ_37_639_1040_822_1098.pngimages/BZ_37_822_1040_1006_1098.pngimages/BZ_37_1006_1040_1190_1098.pngimages/BZ_37_455_1098_639_1156.pngimages/BZ_37_639_1098_822_1156.pngimages/BZ_37_822_1098_1006_1156.pngimages/BZ_37_1006_1098_1190_1156.pngimages/BZ_37_455_1156_639_1213.pngimages/BZ_37_639_1156_822_1213.pngimages/BZ_37_822_1156_1006_1213.pngimages/BZ_37_1006_1156_1190_1213.pngimages/BZ_37_455_1213_639_1271.png images/BZ_37_639_1213_822_1271.pngimages/BZ_37_822_1213_1006_1271.pngimages/BZ_37_1006_1213_1190_1271.png

對抗拉強度的結果進行方差分析,得到的結果見表11。從表11 可以看到,3 個因素對抗拉強度的影響均不顯著。這可能是由于鈦合金較好的焊接性所導致的。由于鈦合金接頭均表現出較高的力學性能,導致了試樣在不同參數下接頭的力學性能相差不大。

表11 抗拉強度方差分析結果

images/BZ_37_272_1822_393_1881.pngimages/BZ_37_393_1822_592_1881.pngimages/BZ_37_592_1822_693_1881.pngimages/BZ_37_693_1822_797_1881.pngimages/BZ_37_797_1822_924_1881.pngimages/BZ_37_924_1822_1061_1881.pngimages/BZ_37_1061_1822_1190_1881.pngimages/BZ_37_272_1881_393_1940.png images/BZ_37_393_1881_592_1940.pngimages/BZ_37_592_1881_693_1940.pngimages/BZ_37_693_1881_797_1940.pngimages/BZ_37_797_1881_924_1940.pngimages/BZ_37_924_1881_1061_1940.pngimages/BZ_37_1061_1881_1190_1940.pngimages/BZ_37_272_1940_393_1999.png images/BZ_37_393_1940_592_1999.pngimages/BZ_37_592_1940_693_1999.pngimages/BZ_37_693_1940_797_1999.pngimages/BZ_37_797_1940_924_1999.pngimages/BZ_37_924_1940_1061_1999.pngimages/BZ_37_1061_1940_1190_1999.pngimages/BZ_37_272_1999_393_2058.png images/BZ_37_393_1999_592_2058.pngimages/BZ_37_592_1999_693_2058.pngimages/BZ_37_693_1999_797_2058.pngimages/BZ_37_797_1999_924_2058.pngimages/BZ_37_924_1999_1061_2058.pngimages/BZ_37_1061_1999_1190_2058.pngimages/BZ_37_272_2058_393_2117.pngimages/BZ_37_393_2058_592_2117.pngimages/BZ_37_592_2058_693_2117.pngimages/BZ_37_693_2058_1190_2117.png

3 結 論

本研究采用光纖激光焊接方法對1.2 mm 厚TC4 鈦合金薄板進行了單因素試驗和正交試驗,并根據試驗過程分析了焊接參數對焊縫宏觀形貌和力學性能的影響,得到了如下結論:

(1)單因素試驗結果表明,焊縫熔寬隨著激光功率的升高大體呈上升趨勢,焊縫背寬比隨著激光功率的升高先增大然后趨于穩定; 焊縫熔寬隨著離焦量的增大逐漸減小,當離焦量達到4 mm 時,出現未焊透現象; 焊縫尺寸隨著焊接速度波動變化,當焊速大于1.5 m/min 時,焊縫尺寸呈現減小趨勢。

(2)正交試驗結果表明,影響抗拉強度的主要因素是激光功率,離焦量和焊接速度影響相當; 而對于延伸率,離焦量和焊接速度對延伸率的影響水平相當,而激光功率的影響較小。

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Influence of Laser Welding Parameters on the Weld of TC4 Titanium Alloy with 1.2 mm Thickness

ZHANG Yingyun, CHEN Suming, LI Bo
(Avic Xi’an Aircraft Industry (group) Co., Ltd., Xi’an 710089, China)

Abstract: In order to study the influence of laser welding parameters on the weld of titanium alloy, TC4 titanium alloy sheet with thickness of 1.2 mm was welded by optical fiber laser.The influences of different laser processing parameters on the weld morphology and mechanical properties were studied by single factor test and orthogonal test.The single factor test results show that the weld width increases with the increase of laser power, and the weld back width ratio increases first and then stabilizes with the increase of laser power.The weld width decreases gradually with the increase of defocusing amount, and when the defocusing amount reaches 4 mm, the weld unpenetrated phenomenon occurs.The weld size varies with the fluctuation of welding speed.When the welding speed is greater than 1.5 m/min, the weld size tends to decrease.The results of orthogonal experiment show that the laser power has a great influence on the tensile strength, and the influence of defocusing and welding speed on the elongation is comparable to that of laser power.

Key words: laser welding; TC4 titanium; weld; macroscopic morphology; mechanical property

中圖分類號: TG456.7

文獻標識碼: A

DOI: 10.19291/j.cnki.1001-3938.2019.9.005

作者簡介: 張穎云 (1968—),男,陜西臨潼人,高級工程師,現主要從事金屬材料焊接工藝研究。

收稿日期:2019-04-05

編輯:黃蔚莉

排列五50期走势图