在與VOGT Ultrasonics GmbH的合作中，設(shè)計(jì)了一個用于電子束焊接WCu部件和坯料的無損測試的試驗(yàn)臺，通過超聲波相控陣技術(shù)在批量生產(chǎn)條件下進(jìn)行檢測。通過用戶的設(shè)置和軟件分析，可以清晰、容易地識別WCu觸頭的焊接區(qū)質(zhì)量，提高了工藝穩(wěn)定性。超聲波測試臺的一個基本特性是可以根據(jù)定義的質(zhì)量標(biāo)準(zhǔn)立即在線對工件進(jìn)行分類。該測試的最大挑戰(zhàn)是生產(chǎn)中高頻次地掃描粉末冶金工藝生產(chǎn)的WCu復(fù)合材料組件，并評估焊接區(qū)質(zhì)量。WCu部分通常是焊接到銅合金或鋼材上。由于種種原因，超聲波束在任何情況下都無法穿過均勻的材料。因此對不均勻的WCu部件進(jìn)行測量，我們面臨的挑戰(zhàn)是如何避免由于WCu復(fù)合材料的微觀結(jié)構(gòu)在密度、重量和均勻性方面存在較大差異而引起的超聲反射或偏轉(zhuǎn)。

01

高壓電弧觸頭的工作原理

Figure 1 shows a sketch how an arcing contact component system, consisting of a pin and a so calledtulip, works.It is shown that by means of the design of the tulip a minimum spring force has to be achieved to get an optimized and reliable contact to the pin surface. Therefore a maximum of energy transmission can be guaranteed and arcing between the two components can be avoided.

圖1是由觸指和梅花觸頭組成的弧觸頭系統(tǒng)的工作簡圖。事實(shí)證明，通過對梅花觸頭進(jìn)行優(yōu)化設(shè)計(jì)，可以實(shí)現(xiàn)以最小的彈力獲得與觸指表面最佳和可靠的接觸。因此，可以保證最大限度的電能傳輸，并避免兩個觸頭之間起弧。

圖1 電弧觸點(diǎn)系統(tǒng)在閉合、導(dǎo)電位置的功能示意圖

02

WCu材料

A cross section of a typical WCu microstructuregained by sintering and infiltrating with copper is shown in figure 2. Typical compositions are 60 to 80wt.-% W and 20 to 40 wt.-% Cu.

圖2中顯示了通過燒結(jié)和熔滲獲得的典型WCu微觀組織，其組成成分是60～80wt.%的W和20～40wt.-%的Cu。

圖2典型WCu (80/20)微觀結(jié)構(gòu)的截面

The inhomogeneous microstructure is caused by the very low solubility of W and Cu.The combination of the excellent electrical conductivity of Cu together with the good arcing resistanceand high melting temperature as well as high arcing resistance of W, see Table I, results in the usage ofcontact material for energy transmission up to voltages of 1200kV.

鎢和銅的溶解度極低，導(dǎo)致了微觀結(jié)構(gòu)的不均勻性。由于Cu具有優(yōu)良的導(dǎo)電性，加上W具有良好的耐燒蝕性和較高的熔點(diǎn)（見表1），鎢銅觸頭材料適用于特高壓的斷路器滅弧室中。

03

超聲相控陣原理

In general the ultrasonic device transmits electrical pulses to the probe where these pulses areconverted to ultrasound waves. After transmitting the waves the probe receives the reflected echoswaves as well. All received waves are converted to electrical pulses again and are evaluated by thesoftware. Phased Array probes are composed of several piezoelectric crystals that can transmit/receiveindependently at different times [5]. To focus or to steer the ultrasonic beam, time delays are applied tothe elements to create constructive interference of the wavefronts. Due to this the ultrasonic beam canbe steered within a range of angle and/or the energy can be focused at any depth in the test specimen(see Fig. 3).

一般情況下，超聲波設(shè)備將電脈沖傳送到探頭，這些脈沖被轉(zhuǎn)換成超聲波。在發(fā)射超聲波后，探頭也會收到反射的回波。所有接收到的波再次轉(zhuǎn)換為電脈沖，并由軟件進(jìn)行評估。相控陣探頭由多個壓電晶體組成，可以在不同時間獨(dú)立發(fā)射/接收[5]。為了聚焦或引導(dǎo)超聲波束，對元件施加時間延遲，以產(chǎn)生波束的建設(shè)性干擾。因此，超聲波波束可以被控制在一定的角度范圍內(nèi)，并且/或者能量可以在測試樣品的任何深度聚焦（見圖3）。

圖3波束控制和聚焦原理

04

相控陣超聲波試驗(yàn)臺

The task of the ultrasonic scanning system is to test the weld of the tulip within the production cycle withan offline system. Thereby it detects non connected areas in the weld seam, measures the sizes andclassifies the tulips in “good” or “bad” according to given guidelines. The inspection is done by immersiontechnique.

超聲波掃描系統(tǒng)的任務(wù)是在檢測周期內(nèi)用離線系統(tǒng)檢測梅花觸頭的焊縫。因此，它檢測焊縫中的非連接區(qū)域，測量尺寸，并根據(jù)給定的準(zhǔn)則將梅花觸頭分為"好 "或 "壞"。檢測是通過浸入式技術(shù)完成的。

Depending on the type of tulip there are two possible probe positions to insert the ultrasonic beamperpendicular to the welding. Inspecting the 45 degree weld requires a probe position along the body.The 90 degree weld needs to be inspected from above (see figure 4).

根據(jù)梅花觸頭的類型，超聲波束檢測位置有兩種：檢查45度焊縫需要沿著焊縫主體的探頭位置，90度焊縫需要從上方檢查（見圖4）。

圖4 典型梅花觸頭的剖面圖（圖中標(biāo)明了超聲束方向）

05

相控陣測試示例

Figure 7 (right picture) shows the C-Scan image recorded with a Phased Array system, the result of theconventional immersion inspection is shown in figure 6 as a linear illustration and in figure 7 (leftpicture) as a round illustration. Comparing both C-Scan images it is to be seen clearly the same resultsbut the way of recording is different. Using Phased Array technique the whole data acquisition and scanimaging lasts no longer than 10 seconds, while the conventional inspection method needs about 2minutes. Due to the limited capability of the chosen probe in this case the resolution is slightly worsecompared to the immersion probe, but it is no effort to get the same resolution like in figure 9 by usinganother probe.

圖7（右圖）為相控陣系統(tǒng)記錄的C-Scan圖像，圖6為線性圖，圖7（左圖）為圓形圖。比較兩個C-Scan圖像，可以看到記錄方式不同，但結(jié)果相同。使用相控陣技術(shù)，整個數(shù)據(jù)采集和掃描成像的時間不超過10秒，而傳統(tǒng)的檢測方式需要2分鐘左右。由于所選探頭的能力有限，在這種情況下，分辨率比浸入式探頭稍差，但要想得到圖6那樣的分辨率，可以使用另一個探頭。

圖7LS系統(tǒng)記錄的圓形圖像（左）和相控陣手持裝置記錄的圖像（右）

原文標(biāo)題：輸配電用的W-Cu觸頭的無損超聲檢測過程控制

文章出處：【微信公眾號：掌知視通訊技術(shù)】歡迎添加關(guān)注！文章轉(zhuǎn)載請注明出處。

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