VARIABLES IN SMAW (Stick) WELDING
THE VARIABLES OF SMAW (STICK) WELDING:
INTRODUCTION
Welding is a practical skill that requires continual practice and careful attention to the variables that the welder controls to improve. The old golden rule “practice makes perfect” applies to welding in that the more you do, as long as you or someone evaluates your welds, the better you become.
The term variable as used in this text means something the welder has control of either before welding or during welding.
1. Welding Current
2. Arc Length
3. Angle of Electrode.
4. Speed of Travel.
5. Selection of Electrode.
1. WELDING CURRENT
The welding current or amperage is essential to producing welds with good appearance and the required strength characteristics. The welder controls the amperage variable by setting the amperage on the welding machine prior to welding.
Welding Current increases with increase in electrode size. The current increases with coating thickness. Too low current produces an unstable arc and results in lack of fusion and lack of penetration in the melted joint.
The amperage is set from recommended ranges according to the size of the electrode, the type of electrode, and the type of current AC, DCEN or DCEP you are using.
2. ARC LENGTH
When electricity is made to jump across a gap it is said to arc across the gap. In Shielded Metal Arc Welding (Stick) it is this arcing effect that creates the intense heat required for melting the electrode and the base metal together.
The Arc is the term used to describe the distance from the tip of the electrode to the base metal and can be varied from lightly touching the metal at an angle sufficient to maintain an arc to a distance far enough from the base metal to extinguish the arc.
Arc length should be as short as possible. Too long arc dissipates the heat into the air, increases spatter & slows down the speed of welding. It also results in Nitrogen pick up by the weld metal. In DC welding a long arc is more susceptible to arc blow than a short arc.
3. ANGLE OF ELECTRODE
In the Shielded Metal Arc Welding (STICK) process there are two electrode angles that the welder must control. The first angle is the one formed between the electrode and the base metal, called the work angle. The second angle is the angle the electrode is held at relative to the direction of travel, called the travel angle.
The travel angle for the flat, horizontal and overhead can be either pulled or pushed and the travel angle for the vertical can be either upward or downward.
The angle determines the uniformity of fusion & weld bead contour & freedom from undercut & slag inclusions.
4. SPEED OF TRAVEL
The rate of travel across the joint is controlled by the welder during welding and greatly affects the appearance and strength characteristics of the weld.
The amount of weld metal deposited (weld deposition rate) and the travel speed may vary with the type and size of electrode being used. The correct weld speed will result in a well formed weld bead that shows good fusion, penetration and a gradual transition of weld metal into the corners of the joint.
Since the travel speed is not timed in stick welding, the welder must be able to read the molten weld pool as the electrode is manipulated across the joint. A weld speed that is too fast results in a thin stringy weld with poor strength and it result in undercutting and lack of penetration. A weld bead that is too slow a speed will result in a heavy weld that has too much convexity and result in over lapping. The travel speed should be somewhere between the maximum without under welding & minimum without over welding.
5. SELECTION OF ELECTRODE
There are a variety of electrodes available for welding a wide range of metals. The electrode for a given application must be selected carefully to provide the strength characteristics required for the weld joint. One of the most useful tools for electrode selection is the Electrode. In general the electrode weld metal must be matched to the type and composition of the base metal being welded.
The size of the electrode to be used is determined by joint thickness,edge preparation, & welding positions. Thicker materials require large diameter electrodes to ensure efficient melting of the base plate & the electrode. Use of current above the range the range of the electrode will cause the covering to overheat & breakdown, resulting in increased spatter & inferior quality.
For Vertical & Overhead welding a smaller diameter electodes have to be used to restrict the size of the weld puddle, Since there is a tendancy for the molten metal to flow out due to force of gravity.
INTRODUCTION
Welding is a practical skill that requires continual practice and careful attention to the variables that the welder controls to improve. The old golden rule “practice makes perfect” applies to welding in that the more you do, as long as you or someone evaluates your welds, the better you become.
The term variable as used in this text means something the welder has control of either before welding or during welding.
1. Welding Current
2. Arc Length
3. Angle of Electrode.
4. Speed of Travel.
5. Selection of Electrode.
1. WELDING CURRENT
The welding current or amperage is essential to producing welds with good appearance and the required strength characteristics. The welder controls the amperage variable by setting the amperage on the welding machine prior to welding.
Welding Current increases with increase in electrode size. The current increases with coating thickness. Too low current produces an unstable arc and results in lack of fusion and lack of penetration in the melted joint.
The amperage is set from recommended ranges according to the size of the electrode, the type of electrode, and the type of current AC, DCEN or DCEP you are using.
2. ARC LENGTH
When electricity is made to jump across a gap it is said to arc across the gap. In Shielded Metal Arc Welding (Stick) it is this arcing effect that creates the intense heat required for melting the electrode and the base metal together.
The Arc is the term used to describe the distance from the tip of the electrode to the base metal and can be varied from lightly touching the metal at an angle sufficient to maintain an arc to a distance far enough from the base metal to extinguish the arc.
Arc length should be as short as possible. Too long arc dissipates the heat into the air, increases spatter & slows down the speed of welding. It also results in Nitrogen pick up by the weld metal. In DC welding a long arc is more susceptible to arc blow than a short arc.
3. ANGLE OF ELECTRODE
In the Shielded Metal Arc Welding (STICK) process there are two electrode angles that the welder must control. The first angle is the one formed between the electrode and the base metal, called the work angle. The second angle is the angle the electrode is held at relative to the direction of travel, called the travel angle.
The travel angle for the flat, horizontal and overhead can be either pulled or pushed and the travel angle for the vertical can be either upward or downward.
The angle determines the uniformity of fusion & weld bead contour & freedom from undercut & slag inclusions.
4. SPEED OF TRAVEL
The rate of travel across the joint is controlled by the welder during welding and greatly affects the appearance and strength characteristics of the weld.
The amount of weld metal deposited (weld deposition rate) and the travel speed may vary with the type and size of electrode being used. The correct weld speed will result in a well formed weld bead that shows good fusion, penetration and a gradual transition of weld metal into the corners of the joint.
Since the travel speed is not timed in stick welding, the welder must be able to read the molten weld pool as the electrode is manipulated across the joint. A weld speed that is too fast results in a thin stringy weld with poor strength and it result in undercutting and lack of penetration. A weld bead that is too slow a speed will result in a heavy weld that has too much convexity and result in over lapping. The travel speed should be somewhere between the maximum without under welding & minimum without over welding.
5. SELECTION OF ELECTRODE
There are a variety of electrodes available for welding a wide range of metals. The electrode for a given application must be selected carefully to provide the strength characteristics required for the weld joint. One of the most useful tools for electrode selection is the Electrode. In general the electrode weld metal must be matched to the type and composition of the base metal being welded.
The size of the electrode to be used is determined by joint thickness,edge preparation, & welding positions. Thicker materials require large diameter electrodes to ensure efficient melting of the base plate & the electrode. Use of current above the range the range of the electrode will cause the covering to overheat & breakdown, resulting in increased spatter & inferior quality.
For Vertical & Overhead welding a smaller diameter electodes have to be used to restrict the size of the weld puddle, Since there is a tendancy for the molten metal to flow out due to force of gravity.