Preheat and Welding Heat Input

TB9-2510-240-40

To control moisture contamination, keep electrodes in hermetically sealed containers. Upon opening

container, place electrodes into a holding oven at 250-300 degrees F. Follow manufacturer's instructions for

electrodes which have been exposed to the atmosphere for longer periods. When welding, do not remove

more than 1/2 hour's worth of electrodes at a time.

In the event that electrodes are exposed to the atmosphere for longer than 1/2 hour, they must be placed in

a ventilated baking oven set at 800 degrees F for 1 1/4 hours. In some cases, the electrode manufacturer

may specify different exposure and baking time periods. Manufacturer guidelines shall be the governing

document.

3.1.5 Preheat and Welding Heat Input . Excessive preheat and welding heat causes T-1 steel to become brittle

resulting in a severe loss of strength. It is desirable to use a low total heat input and allow the base metal to cool quickly.

This results in a small increase in hardness without the brittleness. Heat generated in the base metal weld area should

be monitored by the use of temperature-indicating crayons or their equivalent to avoid excessive heat input and resultant

brittleness and loss of properties.

Closely controlled preheat and inter pass temperatures must be maintained. When frame members are below the

minimum temperature they shall be preheated for a distance equal to the thickness of the part being welded, but not less

than 3 inches in all directions from the point of welding. (See Table 2). The following are general guidelines for

preheating and total heat input.

a. Preheat and Interpass Temperatures. A weld bead, due to its high heat, shrinks faster than the surrounding

base metal. This results in high stresses around the weld. By applying preheat, the weld bead will shrink more

uniformly with the surrounding base metal thus minimizing the risk of cracks due to shrinkage. The thicker the

base metal or the more restrained a joint, the higher the preheat temperature must be. The minimum/maximum

preheat and Interpass temperatures listed in Table 2 have been established for all materials conforming to ASTM

A514, which includes all T-1 steel types.

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