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LHT-318 N

Unitor LHT-318 N is a heavily coated basic electrode for welding low alloy steel and cast steel with up to approx. 1% Chromium and 0.5% Molybdenum, used for working temperatures up to 550°C. Such type of steel is normally found in boilers, plates or pipes. The basic coating is of extra moisture resistant type, but as for all basic electrodes, they should be protected against humidity. See section on afterdrying of basic electrodes. For best results on Chromium alloyed materials thicker than 8–10 mm, pre-heating of the welding area to 200–250°C is recommended.

Electrode for heat resistant steels, e.g. boiler plate and boiler tubes

The electrodes may be used in all positions, with DC positive or negative polarity.

Vertical welding should be carried out upwards.

Boiler tubes welded to boiler tube plate

3.01

As for all basic electrodes the arc should be kept short.

For root pass in open joints DC negative polarity is preferable. For filling the joint use DC+ polarity. Note that for root passes, TIG welding with Icromo-216 may be an advantage. V-groove with 60° angle is recommended for butt welding of ship plates up to 12 mm thickness. Root opening should be 1–2 mm, and nose thickness should be 0.5–1 mm.

In cases where stress relieving is demanded, the temperature should be between 620°C and 720°C. As a general rule the temperature should be maintained for 1 hour per inch plate thickness (30 minutes for 1/2" plate) to ensure full effect.

V-groove for plates up to 12 mm thickness: 60° 0.5–1 mm t < 12 mm

1–2 mm

For t >12 mm welding from both sides is recommended

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