introduction to welding area: ag mechanics unit: arc welding

Introduction to Welding

Area: Ag Mechanics

Unit: Arc Welding

OAW

• Oxyacetylene– Tank of Oxygen – Tank of Acetylene– Striker– Goggles

GMAW

• Gas Metal Arc– Tank of C25 (Oxygen/ Argon Mix)– Mig Gun

SMAW

• Shielded Metal Arc– Electrode

GTAW

• Gas Tungsten Arc– Rods / Spool Gun

(filler Metal)– Pedal– Non Consumable

Electrode– Aluminum / Softer

Metals

OAC

• Oxyacetylene cutting– Cutting Attachment– Different O2 & Acet.

Settings– Striker– Goggles

PAC

• Plasma Arc Cutting– Air Supply– Cutting Torch– Clamp

Objectives:To identify approved clothing for Arc WeldingTo determine the proper safety equipment

needed for Arc Welding.To identify the parts of an Arc Welder.To identify how an Arc Welder works.

Behavior

• Most accidents are caused by carelessness

• Caused by human error

• Refrain from getting involved in poor

shop behavior:scuffling playing with tools

tripping running

pushing hurrying projects

disobeying shop rules loud talking

What are the approved safety clothing and gear for Arc Welding?

• Do not wear clothes that you do not want to get dirty.

• Body Protection– Tight woven cotton or denim fabrics are most

common and inexpensive.– Leather is the most effective but is more

expensive.

• Foot Protection– Leather shoes that cover the entire foot and

have a high top.

Approved safety clothing and gear cont’• Hand Protection

– Gauntlet type leather gloves that are heavy enough to protect hands from the heat.

• Welding Helmet– Most made of lightweight, heat resistant materials– Protection for the head and face

• Welding Lens– Fitted to the helmet– At least a # 10 shade

• Safety Glasses– MUST be worn at all times

• Here’s a good example of a welder wearing all the proper welding protection

• “An ounce of prevention is worth a pound of cure” when it comes to eye protection

• Always wear proper eye protection when working in the shop

• A welder must be protected from harmful light radiation given off by the welding process

• For welding you will be using chipping goggles and a welding helmet

SAFETY: Eye Protection

Here are

examples of

proper eye

protection

What are some safety practices used in Arc Welding?

• Safety First– Always check equipment for warn or damaged

parts– Make sure all safety gear is on and in proper

working order.– WEAR YOUR SAFETY GALSSES!!!

Safety practices cont’

• Good Ventilation– Welding fumes can be harmful to the welder causing

implications such as:– Irritation of the respiratory tract– Metal fume fever– A condition known as siderosis– Slightly increase the risk of lung cancer

• For these reasons, one should take precaution with welding fumes

Welding Fumes

• Welding should be done in a well ventilated area

• Should attempt to control fumes at the source– Common ways

• Extracted benches

• Local exhaust ventilation

Common Ventilation Practices

Extracted bench method Local exhaust ventilation

What are some ways to prevent/protect ourselves from fire?

• Discard frayed cords and wires• Don’t wear auto clothes in the welding shop• Keep flammable liquids away from heat• Class C fire extinguishers

– for electrical and chemical fires

• Fire Blanket– Use on people before trying to use a fire

extinguishers.

Examples of Welding Practices

What is Arc Welding?

• Arc Welding is the process of fusing metal together using the heat of an electric arc.– Done by sending an electric current through a

coated metal rod called an electrode– Creates temperatures greater than 90000 F.

What are the common terms used in Arc Welding?

• Arc Welder– Machine that supplies power for the welding

process

• Electrode– Metal rod with a flux coating that carries the

current to the base metal

• Base Metal– The metal to be welded on

• Arc Length– Distance from electrode to the base metal

Common terms cont’• Voltage

– Measure of the electrical pressure.

• Amperage– Measure of the electrical current flowing

through a circuit.

• Resistance– The opposite to the flow of current which

converts energy into heat.

• Open Circuit Voltage– Constant amount of current flowing between

electrode and base metal

What are the parts of a SMAW welder?

• Welder– The power supply unit.– 2 types Alternating Current (AC) and Direct

Current (DC)

• Cables– 2 cables the electrode (+) and the grounding (-)

that carry the electrical current

Parts of a welder cont’

• Electrode Holder– Spring loaded clamp with insulated handles

attached to the electrode cable.– Holds the electrode.

• Grounding clamp– Spring loaded clamp attached to the grounding

cable.– Attaches to the welding table or project to carry

the current back to the welder.

How does electricity flow in a welder?

• Electricity flows from the POSITIVE cable holding the electrode, to the Base Metal and through the grounding clamp back through the NEGATIVE cable to the machine

Positive Cable

Negative Cable

Base Metal

Electrode

AC vs. DC Current

Parts of the SMAW Welder

Parts of a GMAW Welder

A B C D E F1. Welding current too low.2. Welding current too high.3. Arc too long.4. Welding speed too fast.5. Welding speed too slow.6. Proper amperage, voltage, and speed.

Parts of OAW

Oxygen• Colorless

• Odorless

• Promotes combustion (Not a flammable gas)

Acetylene

• Colorless

• Odor

• Flammable

• Unstable(explosive above 15psi)

• Left Handed Thread

• Acetone in a “sponge” = consistent

3 Types of Flames• Carbonizing

– Too much acetylene– Metal turns black and you

can’t control the puddle

• Neutral– equal amounts of

O2 and acetylene

• Oxidizing– too much O2– Dirty and bubbling, lots of

sparks

Problems with OAW• Torch pops, whistles, or goes out.

– If this happens you have experience backfire or a flashback

Backfire vs Flashback

Black smoke comes out the tip, handle gets hot.

Flashback is when gases burn in the TIP

-Turn off torch valves-- Turn off Tanks

- Let Ms. Haslam Know-Check Equipment

Other Problems

• Too cold – bead sits on metal

• Too Hot- bead sags through the metal *holes

• Filler Rod Sticks – just wave the flame over it to get it unstuck.

• Dirty tips- get it cleaned

Acetylene Side1.Acetylene cylinder2.Cylinder valve3.Red cylinder pressure gauge4.Regulator 5.Hose pressure gauge6.Red hose7.Acetylene valve on torch

Oxygen SideOxygen cylinderCylinder valveGreen cylinder pressure gaugeRegulatorHose pressure gaugeGreen hoseOxygen valve on touch

Parts of a OAW Setup

Torches Cutting vs. Welding

• Cutting– Oxygen blaster– 3 torch valves

• Oxygen

• Acetylene

• Oxygen Blaster

• Welding– 2 torch valves

• Oxygen & Acetylene

• Rose Bud

• Heat Up

Regulators

What are the two gauges on the regulator used for?– Tank Pressure

– Hose Pressure

Setting Up the OxyFuel1.Check regulator thumb screws2.Turn on the oxygen valve all the way3.Set the correct oxygen working pressure4.Open acetylene cylinder valve one half turn5.Set the correct acetylene working pressure6.Light the flame7.Shut down the flame (Fuel first)8.Turn of the acetylene cylinder valve9.Empty acetylene hoses until gages register zero10.Turn off the oxygen cylinder valve11.Empty the oxygen hose until gages register zero12.Loosen regulator thumbscrews. ***Shut down:***To shut of a torch correctly, first close the acetylene valve on the torch then close the oxygen valve

Misc Safety Info

• Hood Shades– Arc / Mig = #10– OxyFuel = #5

• Potential Hazards

• Shock

• Fumes

• U rays

• Spark spatter

• Fire and explosion

Questions??

Review for the Test