1. Shielded Metal Arc Welding of Plate
Chapter 4
Shielded Metal Arc Welding of Plate

2. Objectives Demonstrate safe work practices
Demonstrate the ability to strike an arc at a specific point
List the problems that can result if the welding current is set too low or too high
Discuss how to select the correct diameter of welding electrode for a weld
Describe the effects of overheating a weld by comparing the bead’s shape for width, reinforcement, and appearance

3. Objectives (cont'd.)
Define arc length, and describe the effects of using too short or too long an arc length
Compare a leading electrode angle to a trailing electrode angle
Tell what characteristics of the weld bead can be controlled by the movement or weaving of the welding electrode
Demonstrate ten weave patterns for weld beads
Discuss the importance of positioning the welder and the plate properly before starting to weld

4. Objectives (cont'd.)
Give the characteristics of the three filler metal groups E6010 and E6011, E6012 and E6013, and E7016 and E7018
Define stringer beads and tell how they are used
Demonstrate a vertical up stringer bead and a horizontal stringer bead
Demonstrate how to make a welded square butt joint in the flat, vertical up, and horizontal positions

5. Objectives (cont'd.)
On an edge joint, demonstrate how to make a flat weld, a vertical down weld, a vertical up weld, a horizontal weld, and an overhead weld
On an outside corner joint, demonstrate how to make a flat weld, a vertical down weld, a vertical up weld, a horizontal weld, and an overhead weld

6. Objectives (cont'd.)
Demonstrate how to make a welded lap joint in the flat position, a welded horizontal lap joint, a vertical up-welded lap joint, and an overhead-welded lap joint
Demonstrate how to make a welded tee joint in the flat, horizontal, vertical, and overhead positions

7. Introduction Shielded metal arc welding (SMAW)
Common method used to join plate
Also called stick welding
Provides high temperature and heat concentration
Allows a weld pool to be built up quickly
Filler metal from the electrode increases strength
Minimum equipment required
High-quality welds can be consistently produced

8. Figure 4-1 Striking an arc and running short beads
Figure 4-1 Striking an arc and running short beads. © Cengage Learning 2012

9. Effect of Too High or Too Low Current Settings
Each welding electrode must be operated in a specific current range
Current set too low results in poor fusion and poor arc stability
Arc length is very short
Results in frequent shorting and sticking of the electrode
Weld bead at a high amperage is wide and flat with deep penetration
Spatter is excessive
Causes electrode to discolor, crack, low red, or burn

10. Electrode Size and Heat
Welding electrode size depends upon:
Welder skill and welding codes or standards
Metal thickness and size
Small diameter electrodes
Require less skill, but more time
Large diameter electrodes
May overheat: can cause a burn-through
Chill plate
Large piece of metal that absorbs excessive heat

11. Figure 4-9 The effect on the shape of the molten weld pool caused by the heat input.
© Cengage Learning 2012

12. Arc Length
Distance the arc jumps from the end of electrode to the plate or weld pool surface
To maintain a constant arc length: electrode must be lowered continuously
Narrow range for the arc length to remain stable
Higher settings must be within the amperage range for the specific electrode

13. Figure 4-11 Welding with too long an arc length. Larry Jeffus.

14. Electrode Angle Measured from electrode to surface of the metal
Leading electrode angle: pushes molten metal and slag ahead of the weld
Flat position: caution must be taken to prevent cold lap and slag inclusion
Rapid cooling: prevents the metals from fusing together

15. Electrode Angle (cont'd.)
Preventing cold lap and slag inclusions:
Use as little leading angle as possible
Ensure arc melts the base metal completely
Use a penetrating-type electrode
Move arc back and forth across molten weld pool to fuse both edges

16. Electrode Angle (cont'd.)
Trailing electrode angle
Pushes molten metal away from leading edge of pool
Solidifies toward the back
Molten metal is forced away from bottom of weld
Arc melts more of the base metal
Reinforces weld

17. Figure 4-21 Welding with a trailing angle. Larry Jeffus.

18. Electrode Manipulation
Weaving the welding electrode
Controls several bead characteristics
Penetration
Buildup
Width
Porosity
Undercut
Overlap
Slag inclusion

19. Electrode Manipulation (cont'd.)
Weave pattern for each weld
Personal choice of the welder
Some patterns are especially helpful for specific welding situations
Many weave patterns are available

20. Figure 4-23 Weave patterns.
© Cengage Learning 2012

21. Position of the Welder and the Plate
Should be in a relaxed, comfortable position before starting to weld
Welding helmet is down
Welder is blind to surroundings
Several factors led to swaying
Lean against or hold a stable object
Find most comfortable angle

22. Practice Welds Grouped according to: Instructor or welder Students
Type of joint
Type of welding electrode
Instructor or welder
Selects order in which welds are made
Students
Find it easier to start with butt joints
Flat position allows welder to build skills slowly

23. Electrodes
Arc welding electrodes used for practice welds are grouped into three filler metal classes
F3 E6010 and E6011 electrodes
Cellulose-based flux
F2 E6012 and E6013 electrodes
Rutile-based flux
F4 E7016 and E7018 electrodes
Mineral-based flux
Should be the last choice

24. Stringer Beads Characteristics
Straight weld bead with little or no side-to-side electrode movement
Used to practice maintaining arc length and electrode angle
Should be straight
Easily made once the welder develops the ability to view the entire welding zone

25. Square Butt Joint
Made by tack welding two flat pieces of plate together
Root opening: space between the plates
Changing the root opening affects penetration
Excessively large openings can cause burn-through

26. Figure 4-43 Square butt joint in the flat position.
© Cengage Learning 2012

27. A B
FIGURE 4-44 (A) After the arc is established, hold it in one area long enough to establish the size of molten weld pool desired. (B) Weld back over the arc strike to melt it into the weld.
A & B Larry Jeffus.

28. Edge Weld Made by placing the edge of the plate evenly
Plates should be clamped tightly together
Make tack welds to hold the plates together
Size of weld should equal the thickness of the plate being joined
Weld bead should have a slight buildup

29. FIGURE 4-49 Make tack welds at the ends of the joint.
© Cengage Learning 2012

30. Outside Corner Joint
Made by placing the plates at a 90 degree angle to each other
Make small tack welds
Weld bead should completely fill the V-groove formed by the plates
Slightly convex surface buildup
Back side can be used to practice fillet welds

31. Lap Joint Made by overlapping edges of the two plates
Can be welded on one side or both sides with a fillet weld
Buildup should equal the thickness of the plate
Good weld has smooth transition from the plate to the surface of the weld

32. FIGURE 4-69 Lap joint.
© Cengage Learning 2012

33. Tee Joint
Made by tack welding one piece of metal on another piece of metal at a right angle
Heat is not distributed uniformly between both plates
Most heat should be directed toward the base plate
Can be strong if welded on both sides
Flat or slightly concave appearance

34. Figure 4-83 Tee joint in the flat position.
© Cengage Learning 2012

35. Summary Shielded metal arc welding
Referred to as stick welding
Stick shape of electrode
Tendency of electrode to stick to the workpiece
Difficult to view entire welding zone
Developing visual skill is essential
Takes time and practice
Objectively inspecting work
Enhances skills