Submerged arc welding molding defects and prevention measures

Submerged arc welding molding process is the use of a large welding current carcass liner on the back by way of the molding conditions, the weldment welded thoroughly to thereby obtain double-sided weld. Efficient welding method has been widely used. However, in the welding process. Welding parameters to select the unreasonable malpractice and other process factors will have defects. Common defects are undercut, overflow, burn, lack of fusion, slag the pores and weld the back of the molding defects.

Undercut
Undercut along weld toe base metal parts, welded shut to form a depression or groove phenomenon. 8 mm plate. 750A welding current, arc voltage 38V, welding speed 34m / h gap 2.5mm welding parameters, Undercuts after welding. Defects because one too welding current, welding speed is too fast. The welding current is adjusted to 700A. The welding speed was adjusted to 32m / h, is not generated Undercuts. The liner plate shaped slot size is too small. The misalignment installation groove center back seam will produce undercut. Proved side the oars village pad pad than arc-shaped village not easy to produce undercut; the arc size large liner board smaller than the arc size liner board is not easy to produce undercut undercut weld stress concentration affect the strength of the weld build. Can be prevented by choosing the right welding parameters and process measures.

Burn through
The molten metal flowing from the back seam, the to form perforation phenomenon called burn-through. Plate thickness 8 mm, welding current 800A, arc voltage 38V, welding speed 30m / h the groove gap of 2.5 mm when the welding parameters to produce burn-through defects. If the above parameters are adjusted to the welding current is 700A, the welding speed is 32m / h, and will not produce burn through. Obviously. Burn-through is not allowed, usually guarantee the back seam meet the requirements of the premise, should try to reduce the welding current, on the one hand, to prevent burn-through, on the other hand to prevent coarse grains in the fusion zone and overheating, produce widmanstatten.

Overflow
Refers to the molten metal from flowing out of the welding pieces with the gasket between the phenomenon. Due to the the welding the l pieces with liner board not snapping the molten pool of metal in the Arc force and metal gravity flow from the gap caused by the weldment group generated when high and low dislocation weldment clamping force is not enough, will form gap, thereby generated during welding overflow defect, molding defects caused by the back seam. Weldment assembly not only to ensure the accuracy and need to have enough clamping force.

Weld positive depression
Weld the front I high too low or collapsed, said depression. Defects the weldment assembly smell gap large weldments and liner board not snapping due. The gap is too big. Molten iron flow molten pool of metal is too late to supplement, the weldment Village pad gap also make the molten pool metal indecent excessive. Obviously, the weld recessed will reduce the weld strength. Just adjust the gap between weldments and weldment and liner board. You can avoid this pitfall.

Weld the back of the mouth
The back seam depression defects. Shaped slot village pads to tie it at the flux is too wet, the edge of the weldment dirty reason generates more gas can not escape timely the forming groove weld pool metal, making the back of the molten pool of metal is the gas boosting the floating formation cavity removal into the back of the depression. Such defects as long as the edge of the weldment clean up, the flux drying, the gap between the the weldment liner board can relax properly solve.

Stoma
The stomatal is a serious defect. Due to the wet flux of the molding grooves of the liner plate, in the welding process, steam is decomposed into oxygen and hydrogen, so that increased the amount of hydrogen in the weld seam, in iron decreased solubility of hydrogen in the cooling, in the water-cooled backing plate under the action of molten pool cooling is fast, the formation of pores within the weld. Strict the hydrogen too late to escape before welding, the formation of pores within the weld. Strict drying flux before welding to prevent blowholes.