120201c SMAW Fillet Welds on Mild Steel (Information Deck) Flashcards
Practical Welding Applications
Key Concepts:
- Welding involves various techniques; no single method is universally best.
- Personal development of unique welding techniques is important.
- Focus on the end result of the weld, rather than the specific technique used.
Guidance for Learners:
* Use proven procedures as a guide in developing your technique.
* Listen to instructors for basic, easily mastered techniques.
Welding Technique Considerations:
* Includes variables like electrode inclination, angle, arc length, bead type, and pass type.
* Evaluate techniques based on weld quality, speed, cost, stress/distortion, position effectiveness, and learning time.
Safety Reminder:
* Always prioritize safety for yourself and others.
* Review safety guidelines for equipment before starting.
Cover Pass
Definition:
* A cover pass, also known as cap or wash coat, is a thin weave or series of passes.
Purpose:
* Applied as the final layer over a fill pass or passes in welding.
* Intended to eliminate undercut and enhance the weld’s appearance.
Characteristics:
* Provides a finish that is pleasing to the eye.
* Often built up slightly higher than the parent metal for reinforcement.
Electrode Angle
Definition:
* The electrode angle is the position of the electrode relative to the angle of the parts being joined.
Standard Angles:
* Usually one half of the included joint angle.
* Perpendicular for butt joints, 45° for fillet welds.
Purpose and Application:
* Used to achieve the desired bead contour and direct weld metal placement.
* Utilizes arc force to prevent undercut and ensure good bead contour.
Adjusting for Undercut:
* Point heat towards undercut areas to correct issues, ensuring metal flows to the hottest point.
Considerations:
* Be mindful of gravity and electrode behavior.
* Adjust angle to compensate for sag and undercut.
Electrode Inclination
Definition:
* Electrode inclination is the angle of the electrode relative to the workpiece and travel direction.
Types of Inclination:
* Forehand: Electrode points in the direction of travel.
* Backhand: Electrode points back at the puddle.
Inclination Angles:
* Measured in degrees from the perpendicular.
* Common range for SMAW: 5° to 30°, either forehand or backhand.
Impact on Welding:
* Inclination affects weld profile size, shape, and penetration depth.
* Forehand: Flatter, wider beads with less penetration, suitable for finishing and thin materials.
* Backhand: Deeper penetration and narrower beads, ideal for heavy beads.
Factors Influencing Inclination:
* Bead type, bead size, electrode type, and work position.
Inclination for Flat Position
Recommended Inclination:
* Range from 5° forehand to 15° backhand.
Purpose:
* Achieves beads of acceptable shape and size for flat position welding.
Inclination for Vertical Position
Uphand (Uphill) Welding:
* Specific inclination not detailed; adapt based on position and technique.
Downhand (Downhill) Welding:
* Requires more electrode inclination to control weld metal flow.
Inclination for Overhead Position
Recommended Inclination:
* Same as flat position: 5° forehand to 15° backhand.
Purpose:
* Ensures effective welding in the overhead position.
Inclination for Uphill Pipe Welding
Recommended Inclination:
* Square to the pipe surface or pointing to the pipe’s axis.
Variations:
* 5° backhand in the overhead position and 5° forehand in other positions.
Fill Pass
- A second or filling bead in welding, sometimes called the hot pass.
- Used to fill, melt out slag, and undercut from the root bead.
- May require multiple passes for heavy welds.
- Can be stringer or weave beads.
Finish Pass
- The final pass that finishes the surface, also known as the cap pass.
- It fills the groove and produces a finished surface, sometimes doubling as a fill pass in thinner materials.
Fillet Weld
- A weld with a triangular cross-section, used to join parts typically at 90° to each other.
Groove Weld
- A weld placed between two mating surfaces that usually lie in the same plane.
Manipulative Welding Technique
- A technique involving a back and forth motion with cellulose-coated electrodes.
- Involves short arc length for penetration and metal deposit, and longer arc for more metal flow and blending.
Polarity
- Refers to the pole of a DC power source to which an electrode or work lead is attached.
- Reverse polarity (DCEP) attaches to the positive pole, straight polarity (DCEN) to the negative.
Plane
- A flat surface on which a straight line joining any two points would lie.
Postheat Treatment
- Applied heat treatment of the weldment after the completion of welding.
Preheat
- Heat applied to the weldment before starting any welding.
Root Face
- Area of metal removed from the root edge to form a square face at the root of a butt joint.
Root Pass
- The first or penetrating bead made at the root of the joint.
Stringer Bead
- A single passweld performed with no side-to-side motion, involving only forward movement.
- Size depends on various factors like electrode size, current setting, and speed of travel.
Stringer Padding
Method:
* Using stringer beads to build up a surface uniformly.
Application:
* Each bead partially overlaps the previous one, maintaining level crowns without valleys.
Cleaning:
* Advisable to deslag between passes, except in vertical positions where slag runs downward.
Stringer Fill
Purpose:
* To blend into a finished contour using overlapping stringer beads.
Technique:
* Start at the bottom of the joint, with each pass applied over the previous one.
Considerations:
* Adjust current settings, bead size, electrode angle, and arc length for optimal results.
Tack Weld
Definition:
* A short weld used to hold parts together and in alignment until final welding.
Usage:
* Ensures stability and alignment during the welding process.
Weave Bead
Description:
* A bead made with side-to-side motion in addition to the forward travel.
Characteristics:
* Leads to higher localized heat and slower cooling in the weld zone.
Guidelines:
* Width based on electrode size and current setting, with side motion ideally 2-3 times the electrode diameter.
Weave Padding
Technique:
* Utilizes weave beads to build up wear surfaces.
Application:
* Beads are placed to blend smoothly with previous ones, creating an even, solid layer of weld metal.
Herringbone Weave
Description:
* Cross the center with a longer arc and faster travel, depositing little metal. Pause at edges after shortening the arc for blending.
Application:
* Eliminates undercut at weld toes, covers craters of previous passes.
Versatility:
* Suitable for flat, vertical, and overhead positions, and as a fill, fill and finish, or cover pass.
Crescent Weave
Characteristics:
* Small forward progression compared to side movement. Adjust forward progression for lighter or heavier beads.
Suitability:
* Usable for all positions, but watch for undercut in vertical and overhead positions.
Use:
* Ideal for fill or fill and finish passes.
Lazy L Weave
Technique:
* Diagonal weave resembling an ‘L’, overlapping with previous passes.
Application:
* Used as a cover pass over stringer fill passes, mainly in horizontal position.
Considerations:
* Requires skill for successful application, may not be allowed in all welding procedures.
Sawtooth Weave
Description:
* A variation of stringer bead with side motion limited to half the electrode’s diameter.
Purpose:
* Prevents undercutting on cap layers of multi-pass welds or root beads in open gap horizontal welds.
Application:
* Acts as a gravitational correction, especially along the top edge of the weld.
Weld Procedure Specifications (WPS)
Definition:
* A detailed document specifying the necessary variables for a specific welding application to ensure consistent quality by trained welders.
Purpose:
* Ensures repeatability and quality of welds; includes variables proven through destructive tests.
Key Variables in WPS:
1. Project Identification: No thickness limit for SMAW process joints.
1. Material Selection: Match filler metal to base material properties.
1. Weld Position: Determine the placement of the weld.
1. Process Selection: Choose the appropriate welding process.
1. Material Preparation: Varies based on material thickness and welding side.
1. Weld Size: Calculate for load capacity, considering contour and leg length.
1. Pass Sequence: Plan for fusion and penetration, avoiding slag traps.
1. Technique: Stringer beads, weave beads, or combinations.
1. Procedure Parameters: Current, polarity, electrode type, and size for joint type and position.
Setting the Current and Polarity
Initial Steps:
* Select the correct polarity for the electrode.
* Adjust the machine to the recommended current setting for the chosen electrode.
Amperage Adjustment:
* Start with a range provided by manufacturers or use general rules:
* Imperial: Electrode diameter in thousandths of an inch as the amperage. (e.g., 1/8” = 0.125” = 125 amps)
* Metric: Multiply electrode diameter by 40. (e.g., 3.2 mm × 40 = 128 amps)
Fine-Tuning:
* These are starting points. Fine-tune the current based on arc characteristics and puddle reactions.
* Test on scrap metal similar in thickness to the weld piece.
* Adjust for a stable arc, minimal spatter, and a smooth bead with the correct profile.
Polarity Check
Context:
* Essential for setting the right polarity in DC welding.
Polarity Switching:
* Some machines have a control panel switch, others require manual cable switching.
Quick Polarity Check Procedure:
1. Use a cellulose type electrode (e.g., E4310 / E6010).
2. Weld a bead on scrap material at normal settings, observe the puddle and listen to the arc.
3. Switch cables and repeat. Compare puddle reactions and arc sounds:
* Electrode Positive (EP): Normal puddle reactions with a smooth, crisp sound, like bacon frying.
* Electrode Negative (EN): More violent puddle reactions, longer arc, higher fume emission, and a hissing sound, like rushing air.
Body Position in Welding
Importance of Comfort and Visibility:
* Find a position that is comfortable while ensuring clear visibility of the weld puddle.
Using the Booth Anchor Post:
* Use the booth anchor post for support. It helps you stay steady and relaxed while welding.
Movement and Support:
* Your body should be able to move freely yet remain supported by the anchor post.
Direction of Welding:
* Typically weld across your body.
* For right-handed people, from left to right; reverse for left-handed individuals.
Tapping Method for Starting an Arc
Procedure:
* Hold the electrode perpendicular to the work surface.
* Strike the arc by tapping the electrode’s end near the welding point, then quickly withdraw to establish the arc.
Key Points:
* Immediate withdrawal after contact prevents electrode fusion to the metal.
* Be cautious not to raise the electrode too far, or the
arc will break.
Caution:
* Avoid stray arc strikes outside the weld zone to prevent metal brittleness and cracks.
Scratch Method for Starting an Arc
Procedure:
* Use a motion similar to striking a match.
* Strike the arc by scratching the electrode across the surface, then quickly withdraw to the desired arc length.
Key Points:
* Ensure smooth and controlled scratching to start the arc effectively.
Caution:
* Stray arc strikes outside the weld area are serious
faults, as they can weaken the metal.
* Avoid striking the arc outside the designated weld zone.
Stops and Restarts in SMAW Welding
Context:
* Necessary when changing electrodes or pausing the welding process.
Crater Management:
* Stopping leaves a deep crater; ensure uniformity when restarting to avoid weld faults.
Preparation for Restart:
* Clean the original bead and crater area with a chipping hammer and wire brush to remove slag.
Restart Procedure:
* Start the arc within the weld zone but not in the original crater.
* Move the arc backward into the crater to blend the new weld pool with the previous crater’s edge.
* Continue forward to complete the weld.
Key Point:
* Ensure the restart integrates seamlessly with the previous weld to maintain uniformity and strength.
Arc Length in Welding
General Rule:
* Normal arc length is typically the same as the electrode core wire diameter. (e.g., 3.2 mm electrode = 3.2 mm arc length).
Influence on Weld Bead:
* Arc length affects penetration, deposition rate, weld height and width, and finished appearance.
Types of Arc Length:
Short Arc (Choked Arc):
* Deeper penetration, higher deposition rate,
narrower puddle with build-up.
Long Arc:
* Shallow penetration, lower deposition rate, wider puddle with good edge blending.
Normal Arc:
* Balances characteristics of short and long arcs for versatile application.
Crucible Cup Effect in Welding
Definition:
* The cup-like shape formed by the flux coating at the end of some electrodes.
Impact on Arc Length:
* Heavier flux coatings create deeper cups, allowing the electrode to be held closer to the metal.
Examples:
* E4914 (E7014) electrodes have greater cupping than
* E4310 (E6010) and should be held as if touching the metal.
* E4924 (E7024) electrodes, with heavy flux coating, are designed for the drag technique, maintaining normal arc length by contacting the metal surface.
Significance:
* Electrodes with high iron powder coatings, or “contact electrodes,” use this effect for effective welding.
