On 2018-08-08 14:48:54
Hazard of under-welded pressure vessel and undercut
A description of the hazards of incomplete welding and undercut of pressure vessels
Between the base material, between the base material and the weld metal and the multilayer welding layer is not melted, leaving visible space or slag inclusion is called incomplete welding. This kind of defect can be divided into three kinds according to the position and the reason of forming, the root is not welded thoroughly, the groove part is not fused and the layer is not fused. Causes: welding current is too small; Welding speed is too fast; Improper welding Angle or arc blowing; Groove Angle or clearance is too small; Welding heat dissipation is too fast; Oxides and slag prevent adequate fusion between metals.
Bite edge is a defect to reduce the cross-sectional area of base metal and reduce the bearing section.
Pressure vessel pressure elements are not allowed to contain unwelded structure. The lack of penetration and edge bite destroys the continuity of welding, reduces the mechanical properties of welded joints, and causes stress concentration. When the defect exceeds the standard, it will affect the bearing sectional area and endanger the safety.
Pressure vessels made of steel with the lower limit of tensile strength rated at or above 540MPa and chromium-Molybdenum low alloy steel, pressure vessels made of austenitic stainless steel, titanium and nickel, low-temperature pressure vessels, spherical pressure vessels and pressure vessels with weld coefficient of 1.0 shall have no edge on the weld surface; The seam depth on the weld surface of other pressure vessels shall not be greater than 0.5mm, and the continuous length of the seam shall not be greater than 100mm. The total length of the bite on both sides of the weld shall not exceed 10% of the length of the weld.