Small diameter pipe butt horizontal fixed bottom welding technology

(1) Arc starting -- arc welding

When using alkaline electrode welding, in the arc initiation process, due to less slag, less protective gas in the arc, and other reasons, the welding pool protection effect is not good, the weld very easy to appears dense porosity, mostly N2 porosity.

In order to prevent the occurrence of this kind of phenomenon, the arc of the alkaline electrode is mostly scratched. After the arc starts 10mm in front of the 6-point clock position at the beginning of welding, pull the arc to the beginning of welding, that is, arc preheating at the 6-point clock position, when the groove root is found to have "sweating" phenomenon, the welding electrode is sent to the top of the groove gap, after hearing the "pupu" sound, stop a little, so that each side of the blunt edge is melted 1-2mm and the first melting hole is formed, then the arc starting work is completed.

An alkaline electrode requires about 10% less current than an acid electrode of the same diameter. To this end, the arc starting process requires the welder's hand steady, high technology, arc starting and arc back action to be fast and accurate.

(2) Arc breaking welding

At the 6-5 point position of the clock, that is, the upside-down welding position, the arc is preheated with a long arc. When the end of the electrode is in a state of melting, the first and second drops of the end of the electrode are thrown off with the wrist force.

At the same time, observe the preheating "sweating" phenomenon, quickly and accurately into the welding electrode melting drops into the gap at the beginning of the welding end, a little swing at the same time, the electrode back above a little push, and then inclined below the arc, arc out, the first molten pool is formed, arc work end.

(3) Electrode Angle

1) Starting welding spot, that is, 5-6 points of the clock, the Angle between the welding rod and the tangent line of the welding direction tube is 80-85°.

2) Upward climbing welding is done at the 7-8 point of the clock, and the Angle between the electrode and the tangent line of the welding direction tube is 100-105 °.

3) At the vertical welding position, that is, the 9 o 'clock position of the clock, the Angle between the electrode and the tangent line of the welding direction tube is 90°.

4) The Angle between the electrode and the tangent line of the welding direction tube is 85-90° during the welding process at the vertical climbing welding position, that is, 10-11 o 'clock of clock.

5) When welding at the flat welding position, that is, at 12 o 'clock of the clock, the Angle between the electrode and the tangent line of the welding direction tube is 75-80°.

The Angle of the electrode at each point is shown in Figures 3-6-4 and 3-6-5. The welding position corresponds to the first half of the ring and the second half of the ring, the Angle of the electrode is the same.

Small diameter pipe butt horizontal fixed cover layer welding technology

1. Clean up the slag

Carefully clean the slag at the Angle between the bottom weld and the base material on both sides of the groove, the slag at the superposition of the solder joint, and the solder joint.

2. Transportation method

At 5-6 o 'clock of clock, that is, after arc initiation at the upside-down welding position, the long arc preheats the upside-down welding position to shake off the first and second molten drops, because the temperature of the molten drops at this time is low and the fluidity is not good.

Then the droplet is sent upward in a short arc and welded by a crescent or transverse sawtooth.

Keep the short arc all the time in the welding process, and stop slightly when the welding rod swings to both sides. Melt the edge of the groove on both sides by 1-2mm, so that the weld metal and the base metal smooth transition, and prevent edge-biting defects.

During the welding process, the molten pool should always be elliptical in shape and of the same size. The molten pool should be bright and clear. When the first half circle is closed, the arc pit should be slightly filled with molten metal, so that the arc pit into a sloped shape, to create conditions for the end of the weld in the second half circle.

Before welding the second half of the turn, the welding slag of the first half of the turn should be knocked off 10-15 mm, and pay attention to filling the arc pit at the end of the weld. When the covering layer is welded with the alkaline electrode, the short arc is always used to preheat and weld, and the scratching method is used to initiate the arc.

3. Electrode Angle

Because the bottom weld of the root has been welded, the cover layer weld has nothing to do with the root penetration, the main technical problem is that the cover layer weld should be well-formed, the residual height should meet the technical regulations, the weld and the base metal smooth transition, no edge bite. For this reason, the Angle of the tangent line between the welding electrode and the pipe welding direction should be slightly larger than the bottom welding about 5°.

(1) The Angle between the electrode and the tangent line of the welding direction tube is 85°-90° at the upside-down welding position, that is, the 6-7 position of the clock.

(2) Upward climbing welding position, that is, the 7-8 position of the clock, the Angle between the electrode and the tangent line of the welding direction tube is 105°-110°.

(3) At the vertical welding position, that is, at the 9 o 'clock position of the clock, the Angle between the electrode and the tangent line of the welding direction tube is 95°.

(4) Vertical climbing welding position, that is, 10-11 o 'clock position of the clock, the Angle between the welding electrode and the tangent line of the welding direction tube is 90°-95°.

(5) At the flat welding position, namely the 12 o 'clock position, the included Angle between the electrode and the tangent line of the welding direction tube is 75°-80°

Steps and precautions

1) Familiar with the pattern, clean the groove surface, and trim the blunt edge.

2) Assemble the specimen according to the assembly requirements, conduct positioning welding, and fix the specimen horizontally at the height of the welding support 800-900mm from the ground to be welded.

3) Start welding with an arc from the upside-down welding position of the pipe, weld the right half circle counterclockwise first, and weld to the flat welding position by arc breaking method.

4) Clean the welding slag and grind the joint of the upward and flat welding position into a gentle slope.

5) Change the welding position, weld the left half circle, start the head at the gentle slope of the reverse welding position, or cut the head into a gentle slope by arc, and finish the bottom welding with the same operation method as the right half circle.

6) Clean up welding slag and splash, welding cover layer, still use the two-half ring welding method, welding used crescent shape or transverse sawtooth strip welding, pay attention to the arc pit filling.

7) After welding, clean the welding slag and spatter in the inner and outer welds of pipe fittings, and check the positive and reverse welds.