Arc Welding

By: John Templeton

Objectives

Identify and explain safety practices and procedures as related to electric and oxy fuel welding Identify equipment used in SMAW welding Explain the SMAW process Identify the 2 types of welding current and machines

Arc Welding

The process of fusing two or more pieces of metal together by using the heat produced from an electric arc welding machine.

Otherwise known as SMAW (shielded metal arc welding) – The electrode produces a gas which shields the arc from the atmosphere as the electrode melts.

SMAW Advantages

Scrap metal can used make repairs Repairs can be made quickly before a problem becomes severe Metal repair and construction can be accomplished more economically Arc welders can be used to accomplish jobs like cutting, piercing, gouging and beveling

Welding Equipment

Welding hood Welding gloves Electrodes Welding machine Chipping hammer Wire brush

Welding Equipment

Welding leads Electrode holder Ground clamp

Alternating Current Welding

AC (alternating current) – Most common – 180 Ampere or 225 Ampere between 220 240 volts – Can handle most agriculture and construction jobs – Alternating flow of electrons

SMAW

Direct Current Welding

DC (direct current) – Can produce direct current of both straight (negative) and reverse (positive) polarity. – Polarity is the direction in which the current flows across the arc.

– Makes a continuous flow of electrons

Straight/Reverse Polarity

Straight Polarity (DC-) – Work is positive and electrode is negative – Used to weld thinner metals – Shallow penetration Reverse Polarity (DC+) – Work is negative and electrode is positive – Used to weld thicker metals – Deeper penetration

Types of Welding Machines

AC machine – Only works on alternating current (+-)

Types of Welding Machines

AC/DC – Can run on three different types of current Alternating Direct current + (reverse polarity) Direct current – (straight polarity) This machine will have a rectifier switch which will allow it to switch between the three Or the leads will need to be placed in certain parts of the machine.

Types of Welding Machines

AC/DC Machines – Are capable of handling most agriculture and construction.

– Are the most popular.

– Allow the operator to weld metal of all thickness.

Types of Welding Machines

Machines can either be gasoline engine driven or they can be powered be electricity.

Duty Cycle

Tells the operator how long his machine can operate without causing damage to the machine.

It is how long a machine can run in ten minute intervals, and is measured by a percentage.

Duty Cycle

If a machine has a duty cycle of 25%, for every ten minutes the machine is operated you can only weld for 2.5 minutes.

The remaining 7.5 minutes must be spent letting the machine idle.

Electrodes

All major manufacturers of welding electrodes use the American Welding Society (AWS) code of specifications. Each company makes basically the same quality which is established by the AWS.

Electrodes

Electrodes are classified according to type of coating, composition of the weld metal and operating characteristics.

The numbering system is started with “E” for electrode and then followed by a four digit number

Electrodes

Each number in the four number sequence has a specific meaning.

60XX = Tensile Strength in pounds (X 1,000) 60,000 lbs per square inch XX1X = Welding Position 1 =All 2 = Flat and Horizontal XXX1 = Polarity 1,3,4,8=AC or DC Reverse 2 = AC or DC straight 0 = DC Reverse 3 = Flat

Electrodes

What is the classification of an E 7018? – E – 70 – 1 – 8

Electrode Diameter

Electrodes are also measured by their diameter (the diameter of the electrode without including the flux.

The diameter is measured in thirty-seconds of an inch.

Always use an electrode ½ the size of you base metal – What does this mean?

Electrodes

What diameter electrode should you use if your base metal is ½ in thick?

1/8 inch?

¼ inch?

Electrodes

When selecting an electrode you need to consider the following: – How thick is your base metal?

– What condition is your metal in?

– What type of machine do you have access to?

– Welding position?

Welding Safety

Electrical shock – Make sure the machine is grounded.

– Make sure the cables are not cut or frayed.

– Do not stand in wet surfaces.

– Wear leather gloves.

– Wear rubber-soled shoes

Radiant Energy

Radiant Energy can cause burn – Make sure you helmet is in good repair and lenses are not cracked.

– Make sure all skin is covered with cotton material – Say cover before welding, so that everyone can protect themselves from radiant energy

Eye Protection

Make sure you are welding with a shade of 12-14 lens Make sure your helmet has a Z87 clear lens with a shaded 12-14 lens on top.

Ventilation

Make sure you are welding in a well ventilated area If you become sick do not continue and drink milk.

Use fans to blow out smoke

General Safety

Keep work area clean and free from hazards.

– Welding leads – Flammables – Cover eyes while chipping slag

What to do and what not to do

Review

What are the types of welding current?

What are the types of welding machines?

Describe proper ventilation when welding.