•Allthread—This is rod stock threaded end-to-end and useful where clamping or positioning action is needed.
•Hinges—There are three main hinge designs:
•Leaf hinges for welding—These hinges are not plated and have no screw holes.
•Cylindrical weld hinges—These are made in a wide variety of sizes and can support heavy loads.
•Piano hinges—Provide continuous support along a door or cover.
•Casters and Wheels—These are better purchased than shop-made.
Cu = Copper Sn=Tin Zn = Zinc Al = Aluminum Si =Silicon
Cleaning Metals
Some welding processes are fairly tolerant of mill scale and small amounts of rust and paint, so it is possible to make good welds on most steel rolled goods—flats and shapes—as they come from the mill. However, the metal must not be greasy and for this reason most hollow products like pipe, tubing, and hollow rectangular shapes that are shipped from the factory well oiled must be degreased before welding.
Household cleaners like Simple Green® or Formula 409® All Purpose Cleaner will work; industrial degreasers like denatured alcohol and acetone can also be used. Paint stores, metal supply houses, hardware stores, and pool supply stores often carry phosphoric acid (dilute in 4 to 10 parts water). These stores may carry tri-sodium phosphate (TSP), also a good cleaner. Do not clean hollow steel shapes too far in advance of welding or they will rust. Do not use compressed air to dry them off as this will re-introduce oil contamination from the compressor. Use a plastic bristle brush or a stainless-steel brush since copper, brass, or aluminum brushes will contaminate the weld.
Thorough Prep Work
•Grind, wire brush with a grinder, use flap wheels, or emery cloth to remove all mill scale, rust, paint, and dirt and get down to fresh metal.
•Wipe cleaned weld area with alcohol or acetone to remove residual grease.
•Avoid getting your fingerprints on the area just cleaned.
•Remember not to cross-contaminate your wire brush, emery cloth, and flap wheels by using the same ones on both steel and stainless steel. Hint: If you will be working with both steel and stainless steel, paint the handles of stainless steel brushes red for use on steel, and green for use on stainless. This prevents cross-contamination.
Figure 2-11 As a final prep step, clean the area with alcohol or acetone
Protecting Metal
Preparation for welding removes mill scale, grease, and paint, thus exposing fresh, bare metal to the atmosphere, an ideal condition for rapid corrosion. This is particularly true for most steels and for aluminum in a salt atmosphere. A protective finish will prevent corrosion and enhance the part’s appearance.
The most common protective finishes for welded products include:
•Painting for all metals—No specialized equipment is needed, but spray painting may be best for complex shapes to reduce labor expense. Several coats may be needed to make the item weatherproof.
•A red Rust-oleum® brand primer and two more finish coats will provide at least five years of rust-free service outdoors. In general, products which are supplied in aerosol cans are less durable than those supplied in conventional cans.
•Powder coating for steel and aluminum—Provides a durable, professional-looking surface with many colors and surface textures available. May be nearly as inexpensive as painting for complex shapes as it is sprayed on. Holds up well outdoors.
•Anodizing for aluminum only—This coating is durable and very thin, typically from 0.5 to 6 thousandths of an inch (0.013 to 0.154 mm). Colors are available but tend to fade in the sun. Red is the least stable color, black is much more stable. A non-colored, clear anodizing is the most stable. This is not a do-it-yourself process; leave it to specialists.
Protective coatings should go on promptly after welding (or final surface prep) so the metal does not have a chance to react with the atmosphere. Ideally only a few hours should elapse.
Figure 2-12 After welding, metal should be protected with paint or some other type of coating
What are some basic safety requirements?
Safe Welding Areas
Some welding processes have specific safety requirements. But in general the welding area should
•Be clean and comfortable to work in.
•Allow you to position the work to avoid welding on the floor unless absolutely necessary; you will not do you best work there.
•Be free of drafts on the work from fans, wind, windows, and doors, yet still have adequate change of air ventilation to reduce weld fume inhalation.
•Provide bright light; welding in sunlight is better than in dim light as the non-glowing parts of the weld show up better.
•Be between 70 to 80°F (21 to 27°C) because better welds will result than welds made in cold temperatures; however, acceptable welds can be made at ambient temperatures in the 40 to 50°F (4 to 10°C) range except where the weld specifications call for preheating.
•Have tools positioned within easy reach of the weldor.
•Be clear of combustibles, puddles, and tripping hazards.
•Provide all necessary personal safety equipment for the processes to be used.
Figure 2-13 A welding fume extractor removes potentially harmful vapors from the welding area without contaminating the weld
Photo courtesy of Lincoln Electric.
Personal Safety
In addition to providing a safe working environment, the weldor should also take steps toward personal protection for themselves or anyone else in the welding area. Those steps include:
•Protection of face and eyes from sparks and radiation with a helmet and lens of appropriate shade number (darkness).
•Protection of all of the welders skin from arc and weld material radiation by covering it with cotton, wool, specially treated canvas jackets, or leather garments; ultra violet radiation is carcinogenic.
•Personnel in the welding area must be protected from the welding arc and sparks by protective screens. Never view the welding being performed through the protective screens alone; the only way to safely view welding is through the proper shade lens and welding helmet or goggles.
•Beware of hazards from gases and ensure adequate ventilation; inert shielding gases may cause suffocation in confined areas.
•Provide adequate ventilation from welding process smoke and the metal vapors, particularly heavy metals like zinc and cadmium that are toxic; keep your head out of the welding plume.
•Leathers or specially treated canvas jackets