什么情况下容易产生熔接痕（熔合线的不良形式是哪些因素造成的）

（1）粗熔合线。

在焊接速度和挤压力保持不变的情况下，如果线能量过大，板边会有更多的金属熔化，金属表面脱碳增加，熔合线可能变宽。

(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.

当线能量和挤压力保持稳定时，焊接速度越慢，焊缝金属在高温下的停留时间越长，金属表面脱碳深度和面积增加，熔合线宽度明显增加。

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.

大多数情况下，熔合线过宽主要与挤压力过小有关。同时，由于挤压力不足，容易使熔合线形状变差，熔合线中心常出现明显的“灰斑”或“氧化物夹杂物”。严重时，超声波探伤可能出现“喷标”现象，甚至导致焊缝开裂。

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）细熔合线。

熔合线过细，通常是挤压力过大造成的，板材边缘的大量熔融金属被过度挤出，焊缝容易出现“冷焊”，金属晶粒间的结合强度大大降低，焊缝脆性增大，容易导致焊缝压扁试验不合格。

(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”融合线。

在金属流线的分析中，经常会发现融合线忽上忽下，忽左忽右，有不同程度的倾斜。这些异常现象主要是挤压力不平衡造成的，板边V型开口角的中心位置和尺寸不合理对此也有很大影响。如果在生产中发现这种情况，应及时调整，以保证熔合线的垂直度。

(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”熔合线。

熔合线呈“S”形，有大有小。这种“扭曲”状态也是挤压力高度不平衡的表现。这种熔合线形式热变形复杂，内应力明显较高，对焊管质量影响很大。

(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“氧化物夹杂”的熔合线。

这是熔合线的常见缺陷，主要是板边平行度差，焊接时挤压力小造成的。当挤压力不足时，板边氧化的金属表层无法有效挤压，金属淬火后形成点、直链、线等氧化物夹杂物，滞留在熔合线内。焊缝中大量“灰斑”或“氧化物夹杂”的存在，往往成为焊缝开裂的裂纹源。

(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.