鍍鋅鋼管因為它有著耐腐蝕性能和使用壽命長的雙重優(yōu)點，并且鍍鋅管價格相應(yīng)的也比較低廉，所以現(xiàn)在它的使用率也是越來越高了，但是的使用者在焊接鍍鋅管時并不注意，導(dǎo)致了一些不必要的麻煩，那么鍍鋅管在焊接時我們都應(yīng)該注意些什么問題呢?那就讓濟南鍍鋅管的廠家小編來帶大家了解一下

Galvanized steel pipe because it has the dual advantages of corrosion resistance and long service life, and the price of galvanized pipe is also relatively low, so now its utilization rate is higher and higher, but the users do not pay attention to the welding of galvanized pipe, resulting in some unnecessary trouble, so what problems should we pay attention to when welding galvanized pipe? Let Jinan Galvanized pipe manufacturers to take you to understand

濟南鍍鋅鋼管

Jinan galvanized steel pipe

一、前提就要打磨

1、 The premise must be polished

必須把焊接處的鍍鋅層打磨掉，否則會產(chǎn)生氣泡、沙眼、假焊等。還會使焊縫變脆，剛性下降。

It is necessary to grind off the zinc coating at the welding position, otherwise bubbles, sand holes and false welding will be produced. It will also make the weld brittle and rigid.

二、鍍鋅鋼的焊接特點

2、 Welding characteristics of galvanized steel

鍍鋅鋼一般是在低碳鋼外鍍一層鋅，鍍鋅層一般在20um厚。鋅的熔點在419°C，沸點908°C左右。在焊接中，鋅熔化成液體浮在熔池表面或在焊縫根部位置。鋅在鐵中具有較大固溶度，鋅液體會沿晶界深入浸蝕焊縫金屬，低熔點鋅形成“液體金屬脆化”。

Galvanized steel is generally coated with a layer of zinc on low carbon steel, and the zinc coating is generally in the thickness of 20um. The melting point of zinc is 419 ° C and the boiling point is about 908 ° C. In welding, zinc melts into liquid and floats on the surface of molten pool or at the root of weld. Zinc has a large solid solubility in iron, and liquid zinc can deeply etch the weld metal along the grain boundary, resulting in "liquid metal embrittlement" of low melting point zinc.

同時，鋅與鐵可形成金屬間脆性化合物，這些脆性相使焊縫金屬塑性降低，在拉應(yīng)力作用下而產(chǎn)生裂紋。如果焊接角焊縫，尤其是T形接頭的角焊縫容易產(chǎn)生穿透裂紋。鍍鋅鋼焊接時，坡口表面及邊緣處的鋅層，在電弧熱作用下，產(chǎn)生氧化、熔化、蒸發(fā)以至揮發(fā)出白色煙塵和蒸汽，極易引起焊縫氣孔。由于氧化而形成的ZnO，其熔點較高，約1800°C以上，若在焊接過程中參數(shù)偏小，將引起ZnO夾渣，同時。由于Zn成為脫氧劑。產(chǎn)生FeO-MnO或FeO-MnO-SiO2低熔點氧化物夾渣。其次，由于鋅的蒸發(fā)，揮發(fā)出大量的白色煙塵，對人體有刺激、傷害作用，因此，必須把焊接處的鍍鋅層打磨處理掉。

At the same time, zinc and iron can form intermetallic brittle compounds. These brittle phases reduce the plasticity of the weld metal and cause cracks under tensile stress. If the fillet weld is welded, especially the fillet weld of T-joint, it is easy to produce through crack. During the welding of galvanized steel, the zinc layer on the surface and edge of the groove will oxidize, melt, evaporate and even volatilize white smoke and steam under the action of arc heat, which will easily cause weld porosity. The melting point of ZnO formed by oxidation is higher than 1800 ° C. if the parameters are too small during welding, it will cause slag inclusion in ZnO. Because Zn becomes the deoxidizer. FeO MnO or feo-mno-sio2 low melting point oxide inclusions are produced. Secondly, due to the evaporation of zinc, a large amount of white smoke and dust will be emitted, which will stimulate and damage the human body. Therefore, the zinc coating on the welding joint must be polished off.

三、焊接工藝控制

3、 Welding process control

鍍鋅鋼的焊前準備與一般的低碳鋼是相同的，需要注意的是要認真處理好坡口尺寸和附近的鍍鋅層。為了焊透，坡口尺寸要適當，一般60~65°，要留有一定的間隙，一般為1.5~2.5mm;為了減少鋅對焊縫的滲透，在焊之前，可將坡口內(nèi)的鍍鋅層清除以后再焊。

The preparation before welding of galvanized steel is the same as that of ordinary low carbon steel. It is necessary to carefully handle the groove size and the nearby zinc coating. In order to weld through, the groove size should be appropriate, generally 60 ~ 65 ° and a certain gap should be reserved, generally 1.5 ~ 2.5mm; in order to reduce the penetration of zinc to the weld, the zinc coating in the groove can be removed before welding.

在實際工作中，采用了集中打坡口，不留鈍邊工藝進行集中控制，兩層焊接工藝，減少了未焊透的可能性。焊條應(yīng)根據(jù)鍍鋅剛管的基體材質(zhì)選用，一般低碳鋼由于考慮易操作性，選用J422較為普遍。焊接手法：在焊多層焊的層焊縫時，盡量使鋅層熔化并使之汽化、蒸發(fā)而逸出焊縫，可大大減少液體鋅留在焊縫中。

In the actual work, the centralized beveling process without blunt edge is adopted for centralized control, and the two-layer welding process reduces the possibility of incomplete penetration. Welding rod shall be selected according to the base material of galvanized steel pipe. J422 is generally used for low carbon steel due to easy operation. Welding method: when welding the first layer weld of multi-layer welding, try to make the zinc layer melt and make it vaporize and evaporate out of the weld, which can greatly reduce the liquid zinc remaining in the weld.

在焊角焊縫時，同樣在層盡量使鋅層熔化并使之汽化、蒸發(fā)而逸出焊縫，其方法是先將焊條端部向前移出約5~7mm左右，當使鋅層熔化后再回到原來位置繼續(xù)向前施焊。再橫焊和立焊時，如選用短渣焊條如J427，咬邊傾向會很小;如果采用前后往返運條技術(shù)，更可以得到無缺陷的焊接質(zhì)量。

In the welding of fillet weld, the zinc layer shall be melted in the first layer as much as possible and vaporized and evaporated out of the weld. The method is to move the end of the welding rod forward about 5 ~ 7mm, and then return to the original position after melting the zinc layer and continue to weld forward. If short slag electrode such as J427 is selected for horizontal and vertical welding, undercut tendency will be very small; if back and forth rod transportation technology is adopted, the welding quality without defects can be obtained.