Common Welding Defects

Welded steel pipe, also known as welded pipe, it is through the process with steel plate or steel belt crimp made of welded steel pipe after forming. Language is simple, the welded pipe production type specification, less equipment investment, but ordinary strength below seamless steel tube. Since the 1930 s, with the fast development of excellent steel strip rolling and welding and test techniques to go forward, gradually improve the weld quality, increasing the types of welded steel pipe specifications, and in the scope of more and more replaced the seamless steel tube. In the form of welded steel pipe according to the weld seam welded pipe and spiral welded pipe.

The rapid development of straight seam welded pipe manufacturing, Jane. The strength of the spiral welded pipe is generally higher than structural steel pipe, use a narrow billet create larger diameter welded pipe, or also use the same width of billet make welded pipe diameter of differences. However, compared with the same length of straight seam pipe, weld length add 30 ~ 100%, and the production speed is low. Therefore, a relatively small diameter welded pipe most straight seam welded pipe, large diameter welded pipe for the most part for spiral welded pipe. Steel pipe before leaving the factory inspection link will not less, is also equally important.

The shortcoming of common in the general mild steel pipewelds are: porosity, slag inclusion, incomplete fusion, incomplete fusion and crack, etc., only in accordance with the phosphor screen for the appearance of the disadvantages of the wave and reflected wave height variation analysis of the location of the breaks and welder comprehensive estimate of error. Deal with internal flaws of the essence of the gauge and the drawback of the notice and prevent measures roughly summed up the following:

stomatal

Spiral steel pipe in a single porosity low echo height, waveform for single slit, relatively stable. From each be partial to detect, reflected wave in contrary, but slightly move deeper into the probe is, dense hole will emerge a bunch of reflection wave and wave height along with the size of the hole, when the probe for fixed-point rotation, arise the circumstances of each other. Attacks of this kind of defect reason first is not according to delimit the drying temperature, welding material covering metamorphosis drops, welding core rust, welding wire cleaning not clean, manual when the welding current is too large, the arc is too long; Submerged arc welding when the voltage is too high or the network voltage stable too big; Cherish when welding spare gas purity elementary. With the porosity in the spiral steel pipe weld, both the density of the poor weld metal, and makes useful weld cross-sectional area cuts, low the machine performance, additional are linear porosity, bending to contrast clearly with the attack toughness will float in the sky.

To prevent the defects prevent order: don't use medicine skin crack, flake, metamorphosis and welding core corrosion of the electrode, rust, the wire must be used after derusting technique. The welding material should be used according to delimit the baking temperature, on both sides of groove and clean up clean, and should choose appropriate welding current, arc voltage and welding speed, etc.

slag

Dot slag in steel tube echo a standard lights similar to dot porosity, slag strip echo signal is more jagged wave amplitude is not high, waveform is dendritic, some small by the side of the main peak, probe translational amplitude changes, from all directions to detect when the reflection amplitude does not repel. The cause of the problem occurred are: welding current is too small, speed through faster, slag to rivers, by the liquidation is not clean edges and the layers of welding, its wrong with this metal and welding material chemical composition, containing more sulfur, phosphorus, etc. Prevent pace: correct selection of welding current, welding parts don't matters and the slope of the short length is too small, must put before welding groove clean up the dirty, multi-layer welding must be layers of the eradication of slag; And reasonable decision stretch Angle welding rate and so on.

Lack of penetration

High reflectivity, volatility is higher also, probe translation, the waveform is stable, the birds, the weld flaw detection on both sides can get similar reflection amplitude. Such flaws not only fit the welding machine's performance, and in the lack of penetration of gap and end stress convergence, bearing cracks tend to provoke up after, is a kind of harmful ills. | it happen because breeding reason is usually: pure edge clearance groove is too small, the welding current is too small, or stretch speed through faster, small black and white degree of slope, stretch Angle errors and arc blow. To prevent order are: reasonable selection of groove type, assembling clearance and adopt correct welding strength.