The overhead welding is one of the most difficult welding positions.During welding, the weld pool is located above the combustion arc, and the welder has poor vision in the upward position of welding. The welding arm is from near to far (low to high), which increases the difficulty of operation.In addition, people from the height of the workpiece should be moderate, low inconvenient to observe weld pool, high when welding arm more and more high, reduce stability, increase labor intensity.When backing welding, due to the effect of metal gravity of welding rod droplet, will hinder the droplet transition, easy to appear welding rod phenomenon;The molten pool is suspended upside down under the welding piece without the support of solid metal. The molten metal flows easily under the action of gravity.Only by relying on the surface tension and arc blowing force of the metal solution can the dissolution pool exist continuously.The higher the temperature of molten pool, the less the surface tension.Therefore, the shape and size of the dissolving pool are not easy to control, and defects such as slag inclusion, incomplete welding, bottom depression, surface bulge and undercut are easy to occur, making it difficult to form welding seams.Therefore, short arc welding should be used for operation.During overhead welding, the diameter of welding rod and welding current should be correctly selected. The diameter of welding rod should not exceed 4mm.Welding current is 15%-20% less than flat welding current.The welding rod diameter is large, the welding rod droplet transition is difficult;If the welding current is large, the temperature of the molten pool will be high, the volume will increase, and the fluidity of molten metal will increase, which will easily cause the metal in the molten pool to drip downward, making the bottom weld hole large, the weld seam concave, and the filling and cover surface layer convex.If the welding current is too small, the root is not easy to penetrate, resulting in defects such as slag inclusion and poor weld forming.Vertical welding: the basic operation process is the same as that of horizontal welding, but the following problems should be paid attention to:

1. Under the same conditions, the welding power supply is 10% ~ 15% smaller than the flat welding current.

2. Short arc welding, arc length is generally 2 ~ 3mm.

3. The welding rod Angle is determined according to the welding part thickness.The thickness of the two welding parts is the same, and the included Angle between the electrode and the electrode in the left and right directions is 45°.When the thickness of two welding parts is different, the Angle between the electrode and the thicker welding part should be greater than that of the thinner part.The welding rod should form a 60° ~ 80° Angle with the vertical plane, making the arc slightly upward, blowing to the center of the molten pool.

4. Arc closing: when welding to the end, fill the arc pit with arc discharging method, and move the arc to the center of the weld pool to stop the arc.Do not swing the arc pit aside.In order to prevent meat bite, arc should be lowered to change welding electrode Angle.