电镀膜钝化

在焊接过程中遇到的气孔问题是很常见的，焊接材料干燥、母材和焊接耗材的腐蚀、焊接过程中油和杂质不够稳定以及保护能力差都会出现不同程度的气孔。焊缝气孔分类，气孔产生的根本原因是由于高温熔融金属中溶解了大量气体，这部分气体在焊缝结晶时逸出，形成气孔。

根据所产生气体的组成，焊接后焊缝金属中的气孔主要是气孔中的氢气和CO。对于低碳钢焊接，氢气孔在焊缝表面的情况下，气孔的截面大部分呈螺旋形，从焊缝表面看光滑壁呈喇叭口状。由于温度较高，氢在熔槽和金属液滴中的溶解度较高，焊接过程中焊缝金属迅速凝固，氢来不及逸出，就在焊缝中形成气体。孔洞CO的产生主要是由于冶金反应产生CO气体残留在焊缝内部结晶。气孔沿晶体方向呈虫状分布。影响气孔的因素是冶金和工艺造成的。主要影响冶金方面的有焊接材料在焊接过程中的冶金反应、保护气氛的性质、待焊材料在焊接前的原始状态，例如湿气的影响、腐蚀对焊缝气孔产生的影响。焊接工艺作为一种冶金工艺，由于具有不同于普通冶金工艺的特点，反应时间短，保护气氛差，使焊缝金属与母材在组织微观上存在差异。炉渣气孔的氧化敏感性对焊缝的耐氧化性有很大的影响，实验表明，无论是酸性电极还是碱性电极CO气孔倾向都随着炉渣抗氧化性的增加而增加。但氢孔的趋势却恰恰相反。 Than the CO due to the hydrogen in the metal structure of Compliance Compliance so often taken suppressed in order to achieve to maintain slag appropriate oxidizing hydrogen. It is also used in the actual welding production such methods. Added with strong oxidizing acid electrode composition. Hydrogen generation of the hole can be prevented. The alkaline electrode was added fluorite, often contain a certain amount of carbonate. During the welding process, the welding arc heating effect of Fe203 decomposition emits O generated Fe30 Fe | 0 HO reaction at a high temperature to regenerate Fe20, and H, elemental Fe and HO FeO and H is generated at high temperatures, can be seen rust for the formation of two types of pores have a greater impact. Normal welding operation welding specification for the formation of weld porosity have a certain impact, but to take appropriate specifications for operation, welding current, welding voltage have little impact on the formation of pores in the low-carbon steel welding.

在低碳钢焊接中，焊缝熔合区夹杂物会引起焊缝金属韧性下降，增加热裂和层状撕裂的倾向。焊缝中的夹杂物主要是氧化物、氮化物和硫化物。氧化物夹杂物多以硅酸盐、二氧化硅的形式存在;氧化物夹杂物主要是由于焊接过程中冶金反应产生的，实际焊接过程中在焊接材料和选择合适的情况下由于焊接操作不当混合产生的焊缝氧化物夹杂物是少量的。低碳钢焊接中氮化物主要以N混合，时效时Fe4N焊接金属析出，呈针状分布在晶界或穿过晶界，导致焊缝金属韧性下降。低碳钢焊接时，氮气的来源为周围大气，即从周围大气渗入焊缝水坑而产生的氮气是由夹杂物引起的，焊接过程中保护不良主要是由于形成氮化物夹杂物。硫化物中的硫主要来自焊接材料，如焊条涂层、焊剂、焊缝硫化物MnS和FeS。焊缝夹杂物造成实际焊接生产的原因一般有:焊缝选择不正确或不合理;焊接规范不当，如焊接电流、焊接电压不当导致熔渣难以上浮;粘焊和多焊，焊缝不清渣; welding, the angle of the electrode and the transport bar inappropriate molten metal and slag mixed together; the poor weld pool protection operation, the air intrusion welding protective atmosphere.

防止低碳钢管焊缝缺陷的技术措施

焊接材料的选择直接影响焊接金属的性能和组成，这对于预防和控制焊接缺陷具有非常重要的意义。工艺因素包括焊接规格、电流类型和焊接操作等方面。为焊接材料选择合适的焊接电源是预防焊接缺陷的前提。焊接设备的更换速度非常快，由于电子技术的飞速发展，焊接电源也正在发生着深刻的变革。对于普通低碳钢管焊接材料，采用普通焊接设备施工。但设备运行带来的良好性能也不容忽视。必须在准备合理设备条件的前提下，有针对性地制定焊接工艺措施。包括焊接规范、电流类型、焊接操作、坡口及层清洁工艺要求。焊接规格包括焊接电流、焊接电压、焊接速度等参数。焊接操作应按正常规范进行。 In the case of the welding voltage. The welding current increases will lead to the increase of the depth of penetration of the molten bath; in the case of welding current, welding voltage increases will lead to the increase in the width of the bath melt; but the current increases. Result in the arc transition molten metal particles decreases. Ratio of the surface area increases, the gas absorbed by the transition of molten metal particles Multiple increased stomatal tendency; arc voltage caused by increased the welding protective atmosphere decreased, outside air easily penetrated; welding speed increases, so that the crystallization speed is increased, but also easy to make the residual gas The increased tendency to cause holes in the weld metal. Therefore, as far as possible to maintain the normal construction norms conducive to the generation of defects.