Heat Treatment Terms
Stress Relieving (Post Weld Heat Treatment)
- Is the heating of steel to a relatively high temperature e.g. (590
C -700C) shortly after welding, and maintaining that temperature for
a specific period of time. The purpose is to reduce internal stresses,
caused by welding, quench hardening or by cold working. It also has
an advantageous effect on the elasticity, ductility and strength of
Pre - Heating
- Is a very effective means of preventing weld metal or base metal
from cracking? It is the application of heat to the base metal prior
to a welding or cutting operation. It does not change the properties
of the steel, but it is advisable under certain conditions to drive
off moisture and help to ensure even expansion to eliminate undesirable
stresses. Concurrent heating during welding (also referred to as pre
- heating) retards the cooling thus preventing the formulation of
an under bead crack.
Solution Heat Treatment
- Is performed on certain types of authentic stainless steel to prevent
decay in WELDMENT. This is done by the high temperatures (e.g. 1050C)
and the cooling is very rapid.
- Is much like annealing, but the cooling process is much faster.
This result is in increased strength but less ductility in the metal.
It also produces higher yield strength with greater tensile strength,
and in most instances, a higher impact resistant.
- Is employed after steels have been fully hardened and are too brittle
to be of any practical use. Tempering reduces the brittleness and
relieves internal stresses. Tempering is actually a heating and slow
cooling process. The cooling is accurately controlled to impact certain
characteristics to the base metal.
- Was the first form of heat treatment applied to the ferrous metals.
It is essentially the softening of the base metal to make it more
malleable. The process is involves a controlled heating and slow cooling
which includes softness. Additionally, the process removes gasses,
relieves stresses and enhances the mechanical properties in alloyed
steels. This is generally performed at temperatures up to 700C
- Is process of cooling heated metal to room temperature by immersion
in liquid or gaseous cooling medium. This method provides greater
strength and hardness than slow cooling, but it is accompanied by
Post-weld heat treatment
- Heat treatment carried out after welding in order to decrease residual
welding stress and/or change the micro structure.
Post-forming heat treatment
- Heat treatment carried out after forming in order to regain the
original properties of the material or reduce stresses caused by the
- The holding temperature is the temperature range in which the product
or component is kept in order to achieve specified properties. The
holding temperature depends on the type of heat treatment and material.
Normally it is expressed as a temperature range (580C - 620 C).
- Holding time is the time the product or component is kept at the
holding temperature. The holding time starts when the temperature
at all the measuring points has reached minimum value of the range
of the holding temperature and stops when one of the measuring points
falls below that temperature. The duration of the holding time depends
on the type of heat treatment, material and material thickness.
- The temperature of the product or component when it is taken out
e.g. of a furnace or when any other heat treatment is finished.