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造成直缝焊管的焊缝容易产生气孔的因素

发布时间:2019-02-12人气:10

大家都知道,焊缝的好坏决定了直缝焊管质量的优劣,一旦直缝焊管焊缝产生气孔,那不仅影响管道焊缝致密性,造成管道泄漏,而且会成为腐蚀的诱发点,严重降低焊缝强度和韧性。一般来说焊剂中的水分、污物、氧化皮和铁屑,焊接的成份及覆盖厚度,钢板的表面质量以及钢板边板处理,焊接工艺及钢管成型工艺等都可能是焊缝产生气孔的原因。所以,在焊接时,焊接温度高,则使焊缝过烧,形成穿孔,含有适量的CaF2和SiO2时,会反应吸收大量的H2,生成稳定性很高且不溶于液态金属的HF,从而可以防止氢气孔的形成;焊缝的成型系数过小,焊缝的形状窄而深,气体和夹杂物不容易浮出,易形成气孔和夹渣;直缝直缝焊管 钢板板边应设置铁锈和毛刺清除装置,以减少产生气孔的可能。

As we all know, the quality of longitudinal welded pipe depends on the quality of the welded seam. Once the gas hole is produced in the weld of the longitudinal welded pipe, it not only affects the compactness of the pipeline weld and causes the leakage of the pipeline, but also becomes the corrosion induction point, which seriously reduces the strength and toughness of the weld. Generally speaking, the moisture, dirt, oxide scale and iron scraps in flux, the composition and thickness of welding, the surface quality of steel plate, the treatment of steel plate edge, welding process and steel tube forming process may all be the reasons for the porosity in the weld. Therefore, when the welding temperature is high, the welding seam will be overheated and perforated. When the welding seam contains appropriate amount of CaF2 and SiO2, it will react and absorb a large amount of H2 to form HF which is stable and insoluble in liquid metal, thus preventing the formation of hydrogen pore. The forming coefficient of the welding seam is too small, the shape of the welding seam is narrow and deep, gas and inclusions are not easy to emerge, and gas and slag are easy to form. Rust and burr removal devices should be installed at the edge of longitudinal welded pipe steel plate to reduce the possibility of air hole.

焊接温度是影响焊缝质量的关键参数,清除装置的位置最好安装在铣边机和圆盘剪后,装置的结构是一边2个上下位置可调整间隙的主动钢丝轮,上下压紧板边;焊剂的堆积厚度一般为25-45mm,焊剂颗粒度大、密度小时堆积厚度取最大值,反之取最小值;大电流、低焊速堆积厚度取最大值,反之取最小值,此外,夏天或空气湿度大时,回收的焊剂应烘干后再使用;为了减少磁偏吹的影响,应使工件上焊接电缆的连接位置仅可能远离焊接终端,避免部分焊接电缆在工件上产生次级磁场;应适当降低焊接速度或增大电流,从而延迟焊缝熔池金属的结晶速度,以便于气体逸出,同时,如果带钢递送位置不稳定,应及时进行调整,杜绝通过频繁微调前桥或后桥维持成型,造成气体逸出困难;为避免开卷矫平脱落的氧化铁皮等杂物进入成型工序,应设置板面清扫装置。

Welding temperature is the key parameter affecting weld quality. The location of clearance device is best installed after milling machine and disc shear. The structure of the device is an active steel wheel with adjustable clearance in two upper and lower positions on one side, and the upper and lower edges of the plate are pressed tightly. In addition, in summer or when the air humidity is high, the recovered flux should be dried and reused; in order to reduce the influence of magnetic bias blowing, the connection position of welding cable on workpiece should be only far away from the welding terminal, so as to avoid the secondary magnetic field produced by some welding cable on workpiece; the welding speed should be reduced or the current should be increased appropriately, so as to delay the welding seam. At the same time, if the delivery position of strip steel is unstable, it should be adjusted in time to avoid the difficulty of gas escaping through frequent fine-tuning of the front or rear axles. In order to avoid unwinding, leveling off iron oxide sheet and other debris entering the forming process, a plate cleaning device should be set up. 


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