Useful and decorative, this hanging outdoor lantern requires only a few sections of metal angle and a piece of sheet metal to be made. On the other hand, to get started, you have to master the basics of arc welding.
Arc welding makes it possible to assemble parts of the same type by fusion. It is an autogenous welding. The heat required for melting, between 4000 and 4500° C, is produced by the electric arc that forms between the parts to be welded and the electrode. The high intensity of electric current is provided by the welding station: generator of current, it transforms that of a normal network, for example of voltage 230 V and of intensity 16 A, in current of low tension (45 V) and high intensity (up to 200 A for a single-phase substation). Before buying an electric welding machine, make sure that the installation (subscription and circuit breaker) can support the request. For work requiring a high intensity, it is preferable to use a station powered with 380 V three-phase.
To weld, several tools and accessories are essential: a ground clamp, an electrode holder (these two elements being integral with the device), a hammer to stitch welds, electrodes of different diameters, specific gloves and a mask protection (with special tinted glass). A cast iron plate of great thickness and good size (called "marble"), placed on the bench, constitutes the work plan. The choice of the diameter of the electrode, its coating and the intensity adjustment are a function of the thickness of the parts to be assembled. After placing the pieces on the worktop, the clamp is attached to the "marble".
Find the right speed for a homogeneous weld
The end of the electrode is slightly rubbed on the part to be welded: the sparks which appear testify to the beginning of the arc. By slightly moving the electrode away from the workpiece (2 to 5 mm), the arc is formed. Before carrying out the welding itself, it is necessary to carry out pointing (or fastening welds) to immobilize the parts, as for torch welding. To achieve the weld bead, the electrode is oriented perpendicular to the metal, a little inclined in the direction of progression. The bead should be as regular as possible, maintaining a constant arc length and lowering the electrode holder as the electrode melts. A too slow progression associated with a too high intensity produces a curved cord, presenting risks of cracks. Too slow a speed and too large a gap give a collapsed cord, not welding properly parts.
After measuring and cutting the angles, place each piece between the jaws of a vise and file the ends.
By scouring the metal, it will be prepared for welding.
Fix the first piece with a clamp on the edge of the "marble".
Install the second in the assembly position with a square and clamp it as well.
Attach the ground clamp to the workpiece and rub the electrode onto the metal.
Lift it a few millimeters and then tilt slightly in the direction of the advance of the weld.
Weld the other two pieces to form the upper square of the lantern, then remove the slag (film covering the weld seam) with the hammer.
Secure the square on the worktop with a clamp.
With a portable angle grinder, sand the outer surfaces of the welds.
Finish eventually with the file.
The body of the lantern is formed of two U connected to their base by angles. They are also manufactured by welding.
Make a weld bead in the corners and eliminate the slag.
Bridle the upper square to the rest of the "frame".
Weld inside the corners without forgetting to fix the clamp of mass.
Remove the slag and grind the outer surface of the welds.
Cut out four triangles in a jigsaw from the metal sheet and file the gripping zones.
Weld the triangles together and then on the frame.
Finish the realization by welding the stem.
Tips for DIYers
• The strong heat generated by the arc expands the metal parts. While cooling, they retract and some deformations can occur. Before soldering, spread the plates a little more at one end than the other: this preliminary correction avoids the clamping effect, the most common deformation.
• In industry, arc welding tends to be replaced by laser welding. But there is still no mobile and consumer equipment for this type of welding.