Production methods and large diameter spiral steel pipe spiral steel pipe weld zone defects of
Production methods and large diameter spiral steel pipe spiral steel pipe weld zone defects of Bending hot-rolled steel strip according to form, followed by use of automatic submerged-arc welding the inner seam and outer seam welding, making a spiral steel pipe (also known as spiral welded pipe, spiral pipe). Through a variety of factors make it widely used in the production of large diameter spiral pipe:
A, by change angles, we can use the same width of strip steel pipe of various caliber; B, due to continuous bending, so the exact length of the spiral pipe without restriction; C, weld spiral is evenly distributed over the entire pipe circumference, spiral steel pipe precision high intensity is high; D, and easy to change size, suitable for small quantity and variety of spiral pipe production. Spiral steel pipe weld longer than straight-seam pipes, conduit length is l, the weld length is L/cos (8) disputed the spiral steel pipe and straight-seam pipes, especially compared with the UOE steel tube of anyone else's problems. The steel pipe manufacturing technology today, we should comprehensively and correctly evaluated and compared to reconsider the problem of steel pipe weld.
Because the defects in parallel with the weld, so the spiral steel pipe and welded seam defect as "oblique flaw." In the course of using, the principal stress direction of steel tubes, the axis of the pipe equivalent defect length smaller than a straight seam pipe and, secondly, because of pipeline steel for rolling steel plate, impact toughness have larger anisotropy, along the rolling direction CVN CVN value is 3 times higher than perpendicular to the rolling direction. Straight-seam pipes of principal stress directions perpendicular to the pipe resistance minimum, while spiral steel pipe staggered tube direction of impact resistance minimum, make long spiral steel pipe weld's disadvantages into advantages.
Spiral steel pipe weld zone defects of Spiral steel pipe weld zone defects of porous, thermal cracking, and undercut. Spiral steel pipe weld porosity affects compactness for pipeline welds, resulting in leakage and corrosion-induced, significant degradation of strength and toughness of weld. Weld porosity factors: in the flux of moisture, dirt, oxide and iron filings, welding the composition and thickness of cover, surface quality of the steel plate and steel plate processing, welding and pipe forming process. Flux compositions. When welding with the right amount of CaF2 and SiO2, will react to absorb large quantities of H2, generates a very high stability and does not dissolve in liquid HF of metal, which can prevent the formation of hydrogen porosity. The bubbles. Bubble in the Center bead, is the main reason remains hidden as a bubble of hydrogen in the weld metal, so measures to eliminate this defect is first must clear the wire and weld materials such as rust, oil, moisture and humidity, then must be dry solder remove moisture. In addition, increased current, reduce speed, slow down the speed of solidification of molten metal is also very effective.
Source: http://www.gblsteel.com/
