introduction to shielded metal arc welding

INTRODUCTION TO SHIELDED METAL

ARC WELDING

OBJECTIVESIdentify Shielded Metal Arc Welding?

List the safety precautions for arc welding?

List the equipment needed for shielded arc welding.

List some basic welding joints and positions.

Label the different parts of the arc

welding equipment.

•Shielded Metal arc welding (SMAW) is a fusion process where heat is obtained from an electric arc which is formed between a base metal and an electrode.

Safety precautions are:

• Don't strike arc until helmet is in place

• Wear proper clothing

• Hold electrode holder by insulated handle

• Proper ventilation is needed

• Avoid welding near combustible material

• Always wear safety glasses

• Never stand in water when welding

• Never weld on closed containers

Some basic welded joints are Butt, Tee, Lap, Corner

Two types of Butt Joints: Square and Beveled

Square: used to weld light pieces of metal (1/16 to 3/16 inch)

Beveled: used to weld heavier pieces of metal

3/8 to 1/2 inch metal can be welded by using a single V or U joint 1/2 inch metal and above can be welded by using a double V or U joint

Tee Joint: used to weld two pieces of metal that are approximately 90 degrees to each other.

Lap Joint: used to join two overlapping pieces of metal

1. Single lap joint welded on one side

2. Single lap joint welded on two sides (develops full strength)

3. Offset lap joint is used to weld two pieces of metal that need to be joined in the same plain

CORNER JOINT: USED TO JOIN METAL THAT ARE RIGHT ANGLES TO EACH OTHER.1. CLOSED CORNER JOINT- USED ON LIGHTER SHEETS OF METAL WHERE STRENGTH IS NOT REQUIRED AT THE JOINTS.

2. HALF OPEN CORNER JOINT- USED ON HEAVIER METAL WHEN ONLY ONE SIDE CAN BE WELDED.

3. OPEN CORNER JOINT- USED ON HEAVY METAL. IT IS THE STRONGEST OF CORNER JOINTS

1. 2. 3.

Types of welds: fillet and groove

A. Fillet- used when joining two pieces of metal together without preparing the surface of the metal first.

B. Groove- used when preparing the metal before welding it into place.

Fillet Welds

GROOVE WELDS

Some equipment:

(A) Grinder (E) Chipping Hammer

(B) Helmet (F) long sleeves

(C) Vice (G) Pliers

(D) Wire brush (H) Closed toed shoes

Welding positions: Flat, Horizontal, Vertical, Overhead

The amperage setting is determined by the rod size and thickness of the work

Parts of the Arc Welder AC/DC switch (polarity switch) Amperage adjustment dial Positive cable lug Electrode holder Electrode Amperage scale Ground clamp Ground cable lug Power cord Air vents Power switch

REVIEW• What equipment is needed?

• List the basic welding joints

• List the different welding positions

• Identify the parts of an arc welder