焊接方管變形主要是焊縫收縮力大于母材強度造成的。著色探傷法基本上和熒光探傷法相類似，所不同的是用顯象劑來顯示焊接方管缺陷的圖象。著色探傷法的原理是利用毛細管滲透吸附現象來實現的。檢驗時，先將焊接方管表面用清洗劑洗凈、除去塵土、油污、氧化物及其它影響滲透的臟物。然后，將焊接方管浸沒在滲透劑中，或將滲透劑涂抹(或噴涂)在所需探傷的部位上。如果方管焊縫表面有缺陷存在時，那末滲透劑便會滲透到缺陷中去。其后，將焊接方管焊縫表面的滲透劑擦拭干凈或洗凈，但在缺陷縫隙內仍會有滲透劑存在。均勻地涂上顯象劑，這樣就會把表面缺陷里的滲透劑吸附出來，從而在白色的顯象劑底層上顯示出紅色的缺陷圖象。

The deformation of welded square pipe is mainly caused by the shrinkage force of weld seam greater than the strength of base metal. Coloring method is basically similar to fluorescence method, but the difference is that the image of welding square tube defect is displayed by imaging agent. The principle of colouring flaw detection is realized by capillary osmotic adsorption. During inspection, the surface of the welded square pipe should be cleaned with detergent to remove dust, oil, oxides and other dirt affecting penetration. Then, the welded square pipe is immersed in the penetrant, or the penetrant is smeared (or sprayed) on the required flaw detection site. If there is a defect on the surface of square pipe weld, the penetrant will penetrate into the defect. Thereafter, the penetrant on the weld surface of the welded square pipe will be wiped clean or washed, but there will still be penetrant in the defect gap. Apply the developer evenly, so that the penetrant in the surface defect can be adsorbed out, so that the red defect image can be displayed on the bottom of the white developer.

這種方法可以檢驗鋼、銅、鋁等金屬零件或焊接方管焊縫的表面缺陷，不受不銹鋼管的性能、形狀、尺寸的限制。探傷時操作簡便、經濟，不需要專用的設備和裝置，可在無水、無電的高空或野外場所作業。對于大型不銹鋼焊接方管的局部檢驗，或返修處焊補后的重復檢驗特別適用。著色探傷法在機車車輛上應用也較多，例如內燃機車柴油機上進、排氣門堆焊層等的檢驗。

This method can be used to inspect the surface defects of metal parts such as steel, copper and aluminum or welded square pipes, which are not limited by the properties, shape and size of stainless steel pipes. It is easy to operate and economical in flaw detection. It does not need special equipment and equipment. It can work in high altitude or field without water or electricity. It is especially suitable for local inspection of large stainless steel square welded pipes or repeated inspection after repair. Coloring flaw detection method is also widely used in locomotives and vehicles, such as inspection of inlet and exhaust valve surfacing layers of diesel locomotives.

1、只有單面一條焊縫的，采用從中部開始分段退焊，即：第二段焊縫收弧在第一段起弧處。

1. If there is only one weld on one side, the second weld is retracted from the middle, i.e. the first arc is retracted from the second weld.

2、采取較小的焊接線能量，(焊接線能量與電流大小成正比，而與焊接速度成反)，即：用較小焊接電流、較快的焊速。

2. Take a smaller welding line energy (welding line energy is proportional to the current, but inverse to the welding speed), that is, use a smaller welding current, faster welding speed.

3、有對稱的兩條、四條焊縫的，從一端開始焊，采用對稱越前法兩條交錯焊。比方：第一次焊150mm長仃止，再焊對稱方300mm，越過前面150mm，隨后每次焊300mm，就每次越過150mm。

3. If there are two or four symmetrical welds, they should be welded from one end, and two staggered welds with symmetrical advance method are adopted. For example, the first welding is 150 mm long, then 300 mm symmetrical, crossing the front 150 mm, then 300 mm each time, crossing 150 mm each time.