Welding Tips for practice
1 Mild steel electrodes:E 6010,E6011,E6012,E6013
2.Use DCEP for E6010 when used for mild steel and
low alloy steels required for ship building,construction,bridges,tanks,piping.
3.AC/DC can be used for E6012 for flat and horizontal positions.
4.Use E6012 when fitup is a problem.
5.E6013 can be used with AC/DC and has very good
slag detachability.Sheet metals are welded very well.
6.E7016 is used for hardenable steels when preheat and stress relieving cannot be performed.
7.E7018 which is a low hydrogen iron powder all position electrode can be used for radiograph quality welds.
8.Arc striking with scratch method in the direction of welding is to followed.
9.Use AC to prevent arc blow problem.
10.Use short arc and low current for horizontal position welding.
11.Use whipping motion in the direction of welding for vertical uphill welding.
12.Use constant current power source with 60%duty cycle at maximum current.
13.Transformer sets are useful for all types of structural fabrication.
14.Arc blow problem can be avoided by using AC transformer sets.
15.Motor Generator sets are useful for all types of fabrication in workshops and site work.
16.Inverter sets are highly portable and can be used for all types of fabrication.
Factors to be understood for cooling rate control for weld,HAZ
- Preheat and interpass temperature
- Material thickness
- Heat sinks – presence of chill bars or other ways to drive heat away from the welded part
- Heat input from welding – certain process, such as submerged arc welding, can have high enough heat inputs that make preheat not necessary
- Use of cooling blankets
- Ambient conditions (ambient temperature)
- Quenching (air, water, oil, furnace).
Electrode wrong polarity will result in:
– excess spatter and poor penetration
– improper fusion of the electrode
– heavy brownish deposition on the face of the weld metal
– difficulty in manipulation of the arc
– abnormal sound of the arc
– poor weld bead appearance with surface defects and more spatter.
Arc blow control techniques in DC
1. Placing workpiece lead connections as far as possible from the joints to be welded;
2. If back blow is the problem, placing the work- piece connection at the start of welding, and welding toward a heavy tack weld;
3. If forward blow is causing trouble, placing the workpiece connection at the end of the joint to be welded;
4. Positioning the electrode so that the arc force counteracts the arc blow;
5. Using the shortest possible arc consistent with good welding practice to help the arc force coun- teract the arc blow;
6. Reducing the welding current;
7. Welding toward a heavy tack or runoff tab;
8. Using the backstep sequence of welding;
9. If backing is used, welding the entire length of
the backing to each base plate;
10. Changing to alternating current, which may
require a change in electrode classification; and
11. Wrapping the workpiece lead around the work- piece in a direction so that the magnetic field it sets up will counteract the magnetic field causing
the arc blow.