不(bu)銹鋼(gang)管(guan)渦(wo)流檢(jian)(jian)(jian)測(ce)(ce)是以交流電(dian)(dian)磁(ci)線圈在金屬(shu)(shu)構件(jian)表面感應產生渦(wo)流的(de)無損(sun)檢(jian)(jian)(jian)測(ce)(ce)技術(shu)，它適用(yong)于導電(dian)(dian)材料(liao)，可以檢(jian)(jian)(jian)測(ce)(ce)鐵磁(ci)性(xing)和(he)非(fei)鐵磁(ci)性(xing)金屬(shu)(shu)構件(jian)中的(de)缺陷(xian)。由于渦(wo)流檢(jian)(jian)(jian)測(ce)(ce)在檢(jian)(jian)(jian)測(ce)(ce)時不(bu)要求線圈與構件(jian)緊密接(jie)觸(chu)，也不(bu)需要耦合劑，容易實現自動化。但渦(wo)流檢(jian)(jian)(jian)測(ce)(ce)僅適用(yong)于導電(dian)(dian)材料(liao)，只(zhi)能檢(jian)(jian)(jian)測(ce)(ce)表面或近表面層(ceng)的(de)缺陷(xian)，不(bu)便使用(yong)于形狀復雜(za)的(de)構件(jian)。

  將不銹鋼管放置在通以交流電的線圈中時，不銹鋼管表面會感生出周向電流。渦流磁場方向與外加電流的磁化方向相反，因此將抵消一部分外加電流，從而使線圈的阻抗、通過電流的大小、相位均發生變化。不(bu)銹鋼管的直徑、厚度、電導率和磁導率的變化以及有缺陷存在時，均會影響線圈的阻抗。若保持其他因素不變，僅將缺陷引起阻抗的變化信號取出，經儀器放大并予檢測，就能達到無損檢測的目的。

  照檢(jian)測線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)的(de)使用(yong)(yong)方(fang)式(shi)(shi)，可分為(wei)絕對線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)式(shi)(shi)、標準比(bi)較(jiao)(jiao)(jiao)(jiao)線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)式(shi)(shi)和自比(bi)較(jiao)(jiao)(jiao)(jiao)式(shi)(shi)等(deng)形式(shi)(shi)。只用(yong)(yong)一(yi)個檢(jian)測線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)的(de)稱為(wei)絕對線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)式(shi)(shi)。用(yong)(yong)兩個檢(jian)測線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)接(jie)成差動(dong)形式(shi)(shi)，稱為(wei)標準比(bi)較(jiao)(jiao)(jiao)(jiao)線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)式(shi)(shi)。采(cai)用(yong)(yong)兩個線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)放于同一(yi)被檢(jian)構(gou)件(jian)的(de)不同部位，作為(wei)比(bi)較(jiao)(jiao)(jiao)(jiao)標準線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)，稱為(wei)自比(bi)較(jiao)(jiao)(jiao)(jiao)式(shi)(shi)，是(shi)標準比(bi)較(jiao)(jiao)(jiao)(jiao)線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)式(shi)(shi)的(de)特例。基本電(dian)(dian)路(lu)(lu)由振蕩器、檢(jian)測線(xian)(xian)圈(quan)(quan)(quan)(quan)(quan)信號(hao)輸出電(dian)(dian)路(lu)(lu)、放大器、信號(hao)處理器、顯(xian)示器和電(dian)(dian)源等(deng)部分組成。

  為使無縫鋼管和焊接鋼管在整個圓周面上都能進行無損檢測，可使用穿過式線圈渦流檢測技術，或者使用扁平式線圈檢測技術。當使用穿過式線圈對鋼管進行檢測時，如圖1-2所示，被檢不銹鋼管的最大外徑一般不超過180mm。當使用旋轉鋼管扁平式線圈檢測技術時，為實現對鋼管表面的全覆蓋檢測，需要形成線圈與不(bu)銹鋼管表面之間的相對移動掃描，如圖1-3所示。