©
COPYRIGHT 2000 THE ESAB GROUP, INC. LESSON
IV
APPENDIX B
LESSON IV - GLOSSARY
OF TERMS Quench
- The
rapid cooling of steel from a temperature above the transformation
temperature.
This results in hardening of the steel. Temper
- Reheating
of steel to a temperature below the transformation temperature
following
the quenching of steel. This usually lowers the hardness and
strength
and increases the toughness of the steel. Stress
Relieved
- The
reheating of a weldment to a temperature below the transformation
temperature and
holding it for a specified period of time. A frequently used
temperature and
time is 1150°F. for 1 hr. per inch of thickness. This
reheating removes
most of the residual stresses put in the weldment by the
heating and cooling
during welding. Transformation
Temperature
- The
temperature at which the crystal structure of the steel changes,
usually about 1600°F.
Heat
Affected Zone
- The
area of the base metal that did not become molten in the welding
process, but did undergo a microstructure
change as a result of the heat induced
into that area. If the HAZ in hardenable steels is cooled rapidly, the
area becomes excessively brittle.
Underbead
Cracking
- A
weld defect that starts in the heat affected zone and is caused by
excessive molecular hydrogen trapped
in that region. It is sometimes referred
to as cold cracking, since it occurs after the weld metal has cooled.
Low
Hydrogen Electrodes
- Stick
electrodes that have coating ingredients that are very low in
hydrogen content. The low hydrogen
level is achieved primarily by keeping the
moisture content of the coating to a bare minimum. Weathering
Steel
- Low
alloy steel that is specially formulated to form a thin tightly adhering
layer of rust. This initial layer
prevents further rusting and thus, the need to paint
the steel is eliminated. The main alloys in this steel are copper and
chromium. Toe
Cracking
- A
weld defect that occurs at the toe of the weld metal. The cracking
occurs when the weld metal does not
stretch with the base metal because the
yield and tensile strength of the weld metal is greater than the steel.
