未焊透是指母材间未熔化，焊缝金属未能进入接头根部而产生的缺陷。根据焊接方式，可以区分为中间未焊透和根部未焊透。
Incomplete penetration refers to the defect that the base metal is not melted and the weld metal fails to enter the root of the joint. According to the welding method, it can be divided into intermediate incomplete penetration and root incomplete penetration.
根部未焊透是由于液态焊缝金属多存在于V型或U型坡口单面焊中，没有进入根部钝边，中间未焊透多存在于双U型或双V型坡口双面焊中，是由于液态金属没有进入中间。
The root incomplete penetration is due to the fact that the liquid weld metal mostly exists in the single-sided welding of V-shaped or U-shaped groove and does not enter the blunt edge of the root. The middle incomplete penetration mostly exists in the double-sided welding of double-u-shaped or double-V-shaped groove because the liquid metal does not enter the middle.
焊缝未焊透缺陷
Incomplete penetration defect of weld
焊缝未熔透会减少其有效面积，严重降低焊件的强度和其他机械性能。未焊透还会严重降低焊缝的疲劳强度，引起应力集中此外。当焊件处于载荷应力下，未焊透可能发展成裂纹，这可能最终导致焊缝开裂。
Incomplete penetration of the weld will reduce its effective area and seriously reduce the strength and other mechanical properties of the weldment. Incomplete penetration will also seriously reduce the fatigue strength of the weld and cause stress concentration. When the weldment is under load stress, incomplete penetration may develop into cracks, which may eventually lead to weld cracking.
未焊透比气孔、夹渣、夹钨等缺陷危害更大，属于危害较大的缺陷。
Incomplete penetration is more harmful than porosity, slag inclusion, tungsten inclusion and other defects, which belongs to more harmful defects.
未焊透的原因
Causes of incomplete penetration
- 钝边过大，坡口角度小，选用的焊条直径过大，装配间隙小或边缘错边，使熔敷金属达不到根部。
1) The blunt edge is too large, the groove angle is small, the diameter of the selected electrode is too large, the assembly gap is small or the edge is staggered, so that the deposited metal can not reach the root.
2）焊接电流太小，焊接速度太快，电弧熔深减少，熔池变浅。
2) The welding current is too small, the welding speed is too fast, the arc penetration is reduced, and the molten pool becomes shallow.
3）由于操作不当，由于电弧的磁偏吹造成热能损失，电弧不能在此处发挥作用，或熔敷金属不能输送到预定位置，或由于电弧燃弧时间短或未能在坡口根部形成一定尺寸的熔洞，导致单面焊双面成形的击穿焊接不完全。
3) Due to improper operation, the arc cannot play a role here due to the heat loss caused by the magnetic bias blowing of the arc, or the deposited metal cannot be transported to the predetermined position, or due to the short arc burning time of the arc or the failure to form a certain size of weld hole at the root of the groove, resulting in incomplete breakdown welding formed by one side welding and two sides.
预防措施
preventive measure
- 选择合适的坡口角度、钝边尺寸和装配间隙，防止错边。
1) Select appropriate groove angle, blunt edge size and assembly clearance to prevent misalignment.
2）选择合适的焊接电流、运输角度和焊条直径。如果焊条药皮厚度不均匀造成局部电弧，应及时更换。
2) Select appropriate welding current, transportation angle and electrode diameter. If the uneven thickness of electrode coating causes local arc, it shall be replaced in time.
3）掌握正确的焊接操作方法，稳定准确地送进手工电弧焊带和氩弧焊丝。熟练的分解合适尺寸的熔孔，应把熔敷金属送到坡口根部。
3) aster the correct welding operation method and send the manual arc welding belt and argon arc welding wire stably and accurately. Skillfully decompose the weld hole with appropriate size, and send the deposited metal to the root of the groove.
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