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1. Technology and Livelihood Education—Industrial Arts Shielded Metal Arc Welding
IA –SMAW: Prepare Weld Materials
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Learning Material, Learning Guide, Learning Module | PDF
Published on 2014 September 15th
Description
This module contains information and suggested learning activities on Preparing Weld
Materials. It includes instruction and procedure on how to prepare the materials for welding.
Objective
1. Discuss cutting equipment used in welding
2. Set-up cutting equipment in conformity with the acceptable occupational health and safety
standards.
3. Check cutting equipment fittings, connection, and power source in accordance with
workplace procedure
4. Cut materials according to specified dimensions/specifications.
5. Prepare edge of materials according to specified dimensions/specifications.
6. Clean surfaces and edges based on the job requirements.
7. Use correct tools and equipment for cleaning surfaces and edges in accordance with the job
requirements.
8. Use appropriate Personal Protective Equipment (PPE)
9. Perform proper housekeeping (5S)
10. Identify welding electrodes according to classification and specifications.
11. Maintain and keep electrodes in electrode oven based on prescribed temperature.
12. Prepare specified consumable gases based on job requirements
13. Select correct materials in accordance with job requirements
14. Prepare Personal Protective Equipment (PPE) in accordance with the occupational health
and safety standards.
15. Check welding protective equipment in accordance with safety procedures.
16. Answer the activities accurately.
17. Participate actively in class activities
Curriculum Information
Education Type
K to 12
Grade Level
Grade 9
Learning Area
Technology and Livelihood Education
Content/Topic
Industrial Arts Shielded Metal Arc Welding
Intended Users
Competencies
Perform tack welding Weld butt joint close in flat and horizontal position Weld b
Cutting and Grinding Equipment <<<
Not infrequently, a welder has to cut metal for a repair job or prepare some
fresh stock for welding. Oxy-Fuel cutting has stepped up to the task for more
than a half century, but today you have other choices to get the job done.
Even grinders can cut metal. Here's a look at several common processes:
Oxy-Acetylene Cutting
Cutting metal with a gas torch is accomplished by pressing a lever on the
torch that shoots a stream of pure O2 into preheated metal. This triggers a
chemical reaction, causing the metal in its path to rust away instantly. For that
reason, oxy cutting only works on steel and other ferrous metals. You'll need
an alternate cutting process for aluminum, titanium, copper, and other nonferrous metals.
By all accounts, the oxy-acetylene "kit" remains the cheapest, all-purpose
welding-cutting combination on the market today. Acetylene gas mixed with
oxygen produces nearly 7000 degrees farenheit. The high heat is necessary
to generate the chemical reaction described above. Other fuels, like propane
and Mapp gas, may also be used in the oxy-fuel cutting.
In addition, with a special tip called a rosebud the oxy torch allows you to heat
metal for forming or annealing purposes. A rosebud is routinely used to loosen
tight bolts and nuts. Some welding applications that require pre-heating can
likewise be accomplished with the oxy torch.
Heating up metal with a torch
An oxy-acetylene kit should include a torch handle, welding tip (hopefully
more than one size), a cutting tip and a rosebud (heating) tip. Unfortunately,
many inexpensive kits skip the rosebud (and even the welding tip in some
cases), so pay close attention when you're shopping around. The torch handle
should be outfitted with flashback arrestors and check valves. These prevent
flames from traveling up through the hoses, and the two gases from mixing
inside the hoses. Refillable gas cylinders that fuel the torch should come with
protective caps, as shown in the photo below right. (Since lots of safety
protocols apply to pressurized tanks, be sure to review the literature on this
subject before setting up a welding shop.)
---A good kit also includes high-quality regulators for both the oxygen and
acetylene (or alternative fuel) tank, as well as a gas hose for each (red and
green). Most kits come with tip cleaners, a flint striker and set of goggles.
You'll have to supply your own gloves and a suitable work area for welding,
which typically means purchasing fire clay bricks, either from a ceramics shop
or company that sells fireplace and other refractory supplies.
The diagram above illustrates the basic set-up of an oxy-acetylene cutting
operation.
Plasma Cutting
Plasma Cutting works on all metals, ferrous and non-ferrous, thin or thick. It's
particularly effective for gouging holes into aluminum or stainless steel,
leaving behind no trace of carbon contamination. However, it's less effective
on dirty metal and aluminum oxide build-up.
The process utilizes an inert gas (nitrogen, argon, or oxygen) that streams
through a narrow tube insde a nozzle. An electrical arc strikes the gas,
ionizing it, and that in turn generates plasma, which physicists like to refer to
as the "fourth state of matter". (If you're wondering what plasma looks like,
think of the Sun. )The concentrated heat produced by this chemistry is
sufficient to blow through hard metal like it's a piece of paper.
Air Carbon Arc Cutting
Air carbon-arc cutting is a process of cutting, piercing, or gouging metal by
heating it to a molten state and then using compressed air to blow away the
molten metal. In terms of what you hold in your hand, it has a similar set-up to
stick welding. There's an electrode holder and a "stick". In this case, the stick
is made of graphite and carbon. This is coated with copper to help maintain an
electrical connection through the holder into the machine.
In the air carbon-arc process, a stream of compressed air is aimed at the point
of contact with the base metal. There's a valve in the holder for turning the
compressed air on and off. Unlike a welding machine, this equipment includes
an air compressor and hose. The size of the compressor ranges between one
and ten horsepower, depending on the electrode sizes, amperage and duty
cycle at which the machine operates.
U.S. Navy
You can use this process to cut metal, gouge out defective metal or bad
welds, or to bevel a groove for welding. (You'll probably have to do some
grinding and other clean-up afterward.) The cuts made are generally not as
precise and pretty as plasma cutting, but the cost is far cheaper. Using
compressed air also saves you the hassle and cost of filling acetylene and
oxygen tanks. In addition, since the area affected is small and the process
quick, the surrounding base metal does not reach a high enough temperature
to potentially alter its mechanical properties.
Air carbon arc cutting can be either a manually operated venture (as shown in
the photo above) or hooked up to a travel carriage for long, even cuts. The
manual process can be used in all positions, but overhead cutting is difficult.
You can cut aluminum, copper, cast iron, magnesium, and stainless steels.
Holders are available in several sizes depending on the duty cycle of the work
performed, the welding current, and size of carbon electrode used. For extra
heavy duty work, water-cooled holders are needed.
For more info on CAC, read the overview posted at WeldGuru.com
Grinders
After welding a joint, it's a common practice to grind a weld bead down, using
an angle grinder. (Cover weld beads are usually kept in tact, but root and fill
passes in pipe welding are frequently grinded.) So an angle grinder is a
standard tool of the trade. In addition to finishing surfaces, they're also used to
create beveled edges for plate or pipe joints, or to prepare base metal
surfaces prior to grinding. The tool easily removes rust and other oxides.
Nowadays, the most widely used angle grinder handles 4 1/2 inch diameter
grinding discs. Larger grinders use discs up to 9 inches and are ideal for
beveling thick-walled pipe. The other variable to consider when shopping for a
grinder is the motor's amperage. More amps means more power and the
ability to grind faster. A 10-amp angle grinder is standard in industry, while
students and hobbyists may buy a 6 to 7.5 amp grinder.
-Angle grinders accommodate a variety of abrasive discs, which are divided
into five categories:
grinding discs - These eliminate material, like excess weld metal, weld spatter,
burrs, and the rough edges of oxy-cut material.
cutting discs - These work like a mini-circular saw to cut through metal.
flap discs - These polish and smooth metal in advance of a paint job, powder
coating or bend test.
wire brush discs - These are used to remove weld spatter and slag from welds
without altering the surface of the base or weld metal.
sanding discs - This requires a special spindle adapter to handle flat, rounded
sheets of sandpaper.
Flap disc
Smaller types of grinders and deburring tools are powered by an air
compressor rather than an electrical outlet. Since they don't contain a motor or
battery, these tools are designed to fit in tight spaces, like corners and
interiors.
Deburring tool
You'll also find a stationary (aka bench) grinder set up in most shops. This
equipment is used to sharpen tools, smooth out bevels cut in metal stock, or
for quick rust-removal of small plates before welding. Home improvement
stores generally sell affordable models for consumers, so be sure to consider
one if you're setting up a shop.
----A tungsten grinder (left) and a bench grinder.
For TIG welding, a special tungsten grinder is also a necessity. Both portable
and stationary models are available to grind this exceptionally hard metal
down to a sharp point. (And both are expensive.) During welding, the tungsten
tip will occasionally come in contact with the molten puddle, losing its point.
That's why the grinder must always be closeby. In the field, the portable
version is plugged into an outlet on the welder- generator. See the Guides and
Video page for a good look at this on YouTube.