Welding Butt Joints - Miller Shielded Metal Arc Welding Manuallines

3-11. Welding Butt Joints

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1
2
°
30
1/16 in.
(1.6 mm)
Types Of Butt Joint Welds
1 Tack Welds
Prevent butt joint distortion by tack weld-
ing the materials in position before final
weld.
Workpiece distortion occurs when heat
is applied locally to a joint. One side of a
metal plate will "curl" up toward the weld.
Distortion will also cause the edges of a
butt joint to pull together ahead of the
electrode as the weld cools.
2 Square Groove Weld
3 Single V-Groove Weld
4 Double V-Groove Weld
Materials up to 3/16 in (5 mm) thick can
often be welded without special prepara-
tion using the square groove weld. How-
ever, when welding thicker materials it
may be necessary to prepare the edges
(V-groove) of butt joints to ensure good
welds.
The single or double V-groove weld is
good for materials 3/16 − 3/4 in (5-19
mm) thick.
groove is used on materials up to 3/4 in
(19 mm) thick and when, regardless of
thickness, you can weld from one side
only. Cut the bevel with oxyacetylene or
plasma cutting equipment. Remove
scale from material after cutting. A grind-
er can also be used to prepare bevels.
Create a 30 degree angle of bevel on ma-
terials in V-groove welding.
Butt Joint Training Procedure
Practice welding butt joints on 1/8 in (4
mm) or thicker material. (Avoid thinner
materials since they require greater
skill.) Separate the squared edges of the
material about 1/16 in (1.6 mm) and
make a butt weld all the way through with
a 1/8 in electrode. (You may need to ad-
just the weld current and travel speed to
obtain the desired weld.) Perform a simi-
lar exercise on 1/4 in (6 mm) material, de-
4
positing a bead on each side of the joint
and fusing one to the another (no bevel
needed).
Practice making a single V-groove weld
on 1/4 in (6 mm) plate beveled 30°. Start
with a 1/8 in electrode for the first bead
and finish with a 5/32 in (4 mm) elec-
trode. Be sure to penetrate about 1/32 in
(1 mm) beyond the bottom of the "V" or
root. Perform a similar exercise on thick-
er materials. Generally, deposit a bead
for each 1/8 in (3mm) of material thick-
ness, cleaning the joint between layers.
On heavier plates, it may be necessary
to weave the top layers to fill the groove.
After completing the practice welds, test
them as described in Section 3-18.
Generally, the single V-
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