熔合線的不良形式是哪些因素造成的？

（1）粗熔合線。

在焊接速度和擠壓力保持不變的情況下，如果線能量過大，板邊會有更多的金屬熔化，金屬表面脫碳增加，熔合線可能變寬。

（1） Thick fusion line。

When the welding speed and extrusion force remain unchanged， if the line energy is too large， more metal will melt at the plate edge， decarburization on the metal surface will increase， and the fusion line may become wider。

當線能量和擠壓力保持穩定時，焊接速度越慢，焊縫金屬在高溫下的停留時間越長，金屬表面脫碳深度和麵積增加，熔合線寬度明顯增加。

When the line energy and extrusion force remain stable， the slower the welding speed， the longer the residence time of weld metal at high temperature， the decarburization depth and area of metal surface increase， and the fusion line width increases obviously。

大多數情況下，熔合線過寬主要與擠壓力過小有關。同時，由於擠壓力不足，容易使熔合線形狀變差，熔合線中心常出現明顯的“灰斑”或“氧化物夾雜物”。嚴重時，超聲波探傷可能出現“噴標”現象，甚至導致焊縫開裂。

In most cases， the too wide fusion line is mainly related to the too small extrusion force。 At the same time， due to insufficient extrusion force， the shape of fusion line is easy to deteriorate， and obvious “gray spots” or “oxide inclusions” often appear in the center of fusion line。 In case of serious， ultrasonic flaw detection may appear “spray mark” phenomenon， and even lead to weld cracking。

（2）細熔合線。

熔合線過細，通常是擠壓力過大造成的，板材邊緣的大量熔融金屬被過度擠出，焊縫容易出現“冷焊”，金屬晶粒間的結合強度大大降低，焊縫脆性增大，容易導致焊縫壓扁試驗不合格。

（2） Fine fusion line。

The too thin fusion line is usually caused by excessive extrusion force。 A large amount of molten metal at the edge of the plate is over extruded， and the weld is prone to “cold welding”。 The bonding strength between metal grains is greatly reduced， and the brittleness of the weld is increased， which is easy to lead to the disqualification of the weld flattening test。

（3）“歪”融合線。

在金屬流線的分析中，經常會發現融合線忽上忽下，忽左忽右，有不同程度的傾斜。這些異常現象主要是擠壓力不平衡造成的，板邊V型開口角的中心位置和尺寸不合理對此也有很大影響。如果在生產中發現這種情況，應及時調整，以保證熔合線的垂直度。

（3） “Crooked” fusion line。

In the analysis of metal streamline， it is often found that the fusion line is up and down， left and right， with varying degrees of inclination。 These abnormal phenomena are mainly caused by unbalanced extrusion force。 The unreasonable central position and size of the V-shaped opening angle at the plate edge also have a great influence on it。 If this situation is found in production， it shall be adjusted in time to ensure the perpendicularity of the fusion line。

（4）“S形”熔合線。

熔合線呈“S”形，有大有小。這種“扭曲”狀態也是擠壓力高度不平衡的表現。這種熔合線形式熱變形複雜，內應力明顯較高，對焊管質量影響很大。

（4） S-shaped fusion line。

The fusion line is in an “s” shape， large and small。 This “twisted” state is also a manifestation of the high imbalance of extrusion force。 This form of fusion line has complex thermal deformation and significantly high internal stress， which has a great impact on the quality of welded pipe。

（5）有“灰斑”或“氧化物夾雜”的熔合線。

這是熔合線的常見缺陷，主要是板邊平行度差，焊接時擠壓力小造成的。當擠壓力不足時，板邊氧化的金屬表層無法有效擠壓，金屬淬火後形成點、直鏈、線等氧化物夾雜物，滯留在熔合線內。焊縫中大量“灰斑”或“氧化物夾雜”的存在，往往成為焊縫開裂的裂紋源。

（5） Fusion lines with “gray spots” or “oxide inclusions”。

This is a common defect of fusion line， which is mainly caused by poor parallelism of plate edge and small extrusion force during welding。 When the extrusion force is insufficient， the oxidized metal surface at the plate edge cannot be extruded effectively， and oxide inclusions such as point， straight chain and line are formed after metal quenching and remain in the fusion line。 The existence of a large number of “gray spots” or “oxide inclusions” in the weld often becomes the crack source of weld cracking。