Читать книгу The Art of Welding - William Galvery - Страница 10

GENERAL TOOLS, MATERIALS AND SAFETY EQUIPMENT

Each welding process requires specialized equipment to do the job. But welding, whether you use it for hobby purposes or to make home repairs, requires a number of common hand and power tools. Many of these tools you may already have in your toolbox, others you may need to purchase. One thing is certain, you will need a wide assortment of clamps to hold the work in position—both to keep the work steady while you weld and to reduce weld-induced distortion. The metals you will be working with all have different characteristics and react differently under the intense heat of the welding torch. This chapter will look at some of the properties of those metals. And, finally, you will also require specialized safety equipment.

WHAT HAND TOOLS ARE USED IN WELDING?

WHAT POWER TOOLS ARE USED IN WELDING?

WHAT TYPES OF CLAMPS ARE USED IN WELDING?

WHAT ARE THE MOST COMMON STEEL PRODUCTS USED IN WELDING?

WHAT ARE SOME BASIC SAFETY REQUIREMENTS?

What hand tools are used in welding?

A welder removes slag after a welding pass

You may already own many of these tools because they are commonly used for general carpentry and household repair. Some tools that you should have to facilitate your welding include:

•Builder’s and torpedo levels—Use the larger builder’s level whenever possible; it is more accurate and measures over a longer span; use the torpedo level wherever the builder’s level won’t fit.

•Framing, carpenter’s, cabinet maker’s, and combination squares—Use the largest square that fits the work. The combination square is convenient for layout of 45° corner cuts and parallel lines.

•Cold chisel and ball peen hammer—Handy for breaking tack welds when they must be repositioned; also useful for removing material between a series of drilled holes (chain drilling).

•Center Punch—Marks hole centers and cutting lines.

•Compass and dividers—For scribing circles or stepping off a series of equal intervals.

•Files—For bringing an oversized part down to exact dimension or removing a hazardous razor/burr edge.

•Hack saw—For slow, but accurate metal cutting.

•Tape measures—16- and 24-foot tapes are the most convenient sizes. Useful for measuring on curved surfaces too.

•Precision steel rules—Available in lengths from 6 to 72 inches (150 to 1000 mm).

•Protractor—For finding angles.

•Trammel points—These points fit on and adjust along a wood or metal beam and scribe circles or arcs with 20- to 40-foot (6 to 12 m) diameters. See Figure 1-2.

Figure 2-1 Here is a selection of typical hand tools used in welding, including an assortment of hammers, wrenches, screwdrivers, and pliers (top), as well different types of squares, such as carpenter’s squares, speed squares, and combination squares. You will find uses for both builder’s levels and smaller torpedo levels (below)

Figure 2-2 This page contains an assortment of common hand tools, including hammers, pliers, wrenches, and levels. At left are trammel points for scribing large circles

Metal Marking Tools

There are a variety of tools used to mark metal layout lines. They include

•Chalk line snap

•Weldor’s chalk, also called soapstone

•Ball point metal marker

•Single center punch mark or a line of punch marks

•White lead or silver lead pencil

•Felt-tip pen

•Aerosol spray paint

•Scriber on bare metal

•Scriber on layout fluid

Use weldor’s chalk for marking rough dimensions or to indicate cutting lines that will hold up under cutting torch heat. A line of center punch marks can be more accurate and will also withstand torch heat. For very accurate layout lines, spray paint the metal in the area of the layout lines and use a scriber to scratch through the paint to make the layout lines. Alternatively, machinist’s layout fluid (Dykem® is the major brand, and available in red or blue) can be used to make the scribed lines more visible. These lines will not hold up under torch heat, but can be essential to laying out non-torch cutting lines. A black felt-tip pen can also be used in place of spray paint or layout fluid to darken the metal and show up scriber lines. Do not use scribe marks to designate bend/fold lines since they will be stress raisers and the part will eventually fail along the scribed line. Metal markers are available. They put down a 1/16 inch width line, come in several colors, and are excellent for applying lettering to metals. The are rated at 700°F (370°C) so cannot be used for torch cutting lines. Note that some marking materials’ residues may contaminate GTAW welds.

Figure 2-3 This yellow marker is used for drawing layout lines

Figure 2-4 Soapstone applicators and refills mark metals. Soapstone is also called welder’s chalk

Both Photos courtesy of Hobart Welders.

Specialized Hand Tools

Here are some tools most welders will find necessary. They include:

•Chipping hammer to remove welding slag.

•Wire brush for cleaning welds.

•Hammer and cold chisel to break tack welds.

•Pliers for moving hot metal safely.

•Wire cutters to trim electrode wire.

Figure 2-5 Here is a group of specialized welder’s hand tools

Photo courtesy of Hobart Welders.

What common power tools are used in welding?

Many of the power tools used by welders are also used for carpentry and other tasks. They include:

•Reciprocating saw—Excellent for rough cuts of bar stock, shapes, pipe, and plate.

•Hand-held band saw—Capable of accurate cuts and following scribed lines; excellent for both pipe and tubing. Its throat is too small for most plate cutting.

•Electric drill, drill bits—For starter holes to begin oxyfuel cutting, holes toinstall hardware, and for chain drilling.

•Abrasive cutoff saw—Good for rod and pipe. Not good for shapes and tubing. Difficult to make accurate cuts.

•Portable grinder with abrasive and wire wheels and abrasive flapwheels—To remove mill scale, rust, and paint before welding. It is also good for smoothing rough edges and removing bad welds.

•Bench grinder/pedestal grinder with abrasive and wire wheels—Same as portable grinder, but here the operator holds the parts.

Figure 2-6 Welders find that portable power saws and grinders come in handy

Figure 2-7 Bench grinders are one way to sharpen TIG electrodes before welding

What types of clamps are used in welding?

Clamps play a critical role in holding the parts to be welded in the proper position to make the weld and in preventing weld-induced distortion. Welders use a variety of general purpose clamps and clamps specifically designed for welding projects.

Figure 2-8 This page shows a variety of clamps used in welding, including locking clamps in various shapes and sizes and common C clamps. The clamp shown directly above is an angle clamp; to the left is a group of magnetic clamps

Photo courtesy of Hobart Welders.

Welding Tables

A welding table places the work at a comfortable height and allows weldors to concentrate on their work, rather than their discomfort. A welding table allows some welds to be made sitting down. Also, it provides a stable, flat surface to position and clamp work prior to welding. In some applications the work itself may be tack-welded to the table. Later these weld-tack beads can be ground off.

Figure 2-9 A portable welding table is useful when working in remote locations.

Photo courtesy of Miller Electric.

What are the most common steel products used in welding?

Low carbon, hot rolled solid shapes, sheet goods, plate, pipe, and tubing are the most often used fabrication materials. Large steel distributors stock a wide variety of shapes and sizes. Additional sizes and shapes of steel as well as other materials like alloy steels, stainless steel, brass, copper, and bronze are also available on order. These materials are substantially more expensive than carbon steel.

When planning projects, remember that one size of tubing (either round, square, or rectangular) is dimensioned to telescope or slide smoothly into the next larger size. This can be very helpful and a design shortcut.

Large steel distributors usually have a variety of remnant material that is sold by the pound. A tape measure and calipers can also help you determine if a particular remnant will be useful. This can be both economical and convenient for many projects. Bring work gloves to handle the greasy and sharp remnants.

Usually for a small charge, or often at no charge, the distributor will cut the material to make it easier to transport since many products come in 20 foot lengths. With good planning, cuts made on the distributor’s huge shears or band saws can save you a lot of cutting time, particularly on heavy plate goods.

Fig.2-10 Common steel products used in welding projects

Other Hardware Items

Common hardware items used by welders include

•Nuts—By welding a nut over an existing hole, we can add threads without tapping them; this facilitates adding leveling jacks, adjustment members, and clamps.

•Bolts—These can be used for leveling jacks, axels, swivel points, and locating pins. Bolts can also be cut to provide just the threaded portion for threaded studs, or just the rod section.

•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 must be worn when welding vertically or overhead to protect the welder from the falling hot metal, sparks and slag.

•A welder’s hat will prevent both radiation burns to the head and hot sparks, falling slag, and hot metal burns.

•High-top boots can prevent hot sparks and slag from burning your feet.

•Never weld with pant cuffs; sparks falling into cuffs will burn pants.

•Make sure your welding gloves are dry and have no holes.

•Keep hands and body insulated from both the work and the metal electrode holder.

•Do not change the polarity switch position while the machine is under welding current load.

•Welding machines must be turned off when not attended.

•Do not stand on a wet surface when welding to prevent electric shock.

•Welding cables and electrode holders must be inspected for broken insulation regularly to prevent electric shock.

•Welding power supplies on AC lines must be properly grounded and emergency shut-off switch location known and accessible.

•Welding area must be dry and free of flammable materials.

•Protect your ears from welding and grinding noise with ear plugs or ear protectors.

•Any compressed gas cylinders must be properly secured and out of the spark stream.

•Avoid wrapping welding cable around your arm or body in case a vehicle snags the cables.

•Never cut or weld on containers without taking precautions.

•In shielded metal arc welding, the welder must plan for disposal of electrode stubs: they are hot enough to cause burns and to start fires and must not be dropped from heights because of the hazard to others.

Basic Safety Equipment

Welding helmet with the proper lens shade for the process and amperage.

Leather capes and sleeves or jacket called skins or leathers, to protect the welder’s clothing from sparks, especially while welding overhead.

Welder’s cap to protect from sparks getting behind the welding helmet and into the welder’s hair.

Welding safety equipment

Breathing apparatus to provide the welder with fresh air in confined spaces with inadequate ventilation. Safety glasses under the welding helmet.

Figure 2-14 Here’s a sample of safety equipment. From top left going clockwise: goggles worn under welding helmet; welding caps to be worn under helmet; welding jacket; and gloves

Photo courtesy of Lincoln Electric and Hobart Welders.

Table 2-3 Recommended lens shade by amperage and welding process

courtesy of Hobart Welders.

Auto-darkening Faceplates

An electronic faceplate or lens is one of the most recent and important safety devices developed in the welding industry. These devices are designed to be clear, or nearly clear, then darken the instant arc is established; when purchasing be aware of the time the lens takes to darken 1/25.000 of a second or faster is recommended. Advantages of auto-darkening faceplates include:

•The welder does not need to raise and lower his helmet when performing a series of welds: he can always see where he is with the helmet down.

•The beginner does not have to master holding his electrode steady when he drops his helmet. This permits beginners to perform better welds earlier in their training.

•Electronic faceplates offer continuous eye protection from infrared radiation coming off red-hot metal even when they are not in the darkened mode. It is just easier on the eyes and the welder is less likely to incur eye injury from inadvertent arc strikes.

Figure 2-15 Auto-darkening faceplates darken almost immediately as soon as the arc is established

Photo courtesy of Hobart Welders.