The document discusses various heat treatment processes that can be applied to welded materials and structures to relieve stress and improve properties. It describes processes like annealing, normalizing, stress relieving, quenching, and tempering, and explains how they work to soften metals, reduce stresses, and achieve desired material properties. Several studies are summarized that examine the effects of post-weld heat treatment on the microstructure, hardness, residual stresses and mechanical properties of welded materials like titanium alloys, TRIP steel, and low-carbon steel. The studies found that heat treatment helped relieve stresses, refine grains, improve strength and ductility, and in some cases extend the life of welded components.

1. STRESS RELIEVING HEAT
TREATMENT OF
WELDMENTS
BY
MOHAMMED NOUFIL

2. WHY HEAT TREATMENT
• Alter physical & chemical properties. Mostly concentrating on metallurgical properties
• To achieve desired hardening or softening of materials

3. SOME OF THE COMMON HEAT TREATMENT
PROCESSES
• Annealing – Heating a material to specific temperature & cooling at slower rates. Annealing
is most often used to soften a metal for cold working, to improve machinability, or to
enhance properties like electrical conductivity.
• Normalising -Normalizing is a technique used to provide uniformity in grain size and
composition throughout an alloy. Normalizing of iron not only produces pearlite, but also
martensite and sometimes bainite, which gives harder and stronger steel, but with less
ductility for the same composition than full annealing.
• Stress relieving -Stress relieving is a technique to remove or reduce the internal stresses
created in a metal. These stresses may be caused in a number of ways, ranging from cold
working to non-uniform cooling. Stress relieving is usually accomplished by heating a metal
below the lower critical temperature and then cooling uniformly

4. • Quenching -Quenching is a process of cooling a metal at a rapid rate. This
is most often done to produce a martensite transformation. In ferrous
this will often produce a harder metal, while non-ferrous alloys will usually
become softer than normal.
• Tempering -Tempering consists of heating steel below the lower critical
temperature, (often from 400 to 1105 ˚F or 205 to 595 ˚C, depending on the
desired results), to impart some toughness. Higher tempering temperatures
(may be up to 1,300 ˚F or 700 ˚C, depending on the alloy and application)
sometimes used to impart further ductility, although some yield strength is
lost.

5. A NEW HEAT TREATMENT TECHNOLOGY FOR
ON-SITE LIFE EXTENSION OF HIGH ENERGY PIPE
WELDMENTS DEGRADED BY CREEP DAMAGE
• Induction heating to high energy pipe weldments having experienced degradation
due to creep
• Regenerative kind of heat treatment is applied
• Life of the pipe was increased from 63,000hrs before treatment to 200,000hrs after
treatment, confirming that life can be extended by approximately 130,000hrs

7. EFFECT OF POST-WELD HEAT TREATMENT ON
MICROSTRUCTURE AND MECHANICAL PROPERTIES OF
LASER BEAM WELDED TIAL-BASED ALLOY
• Post-weld heat treatment is carried out on the laser beam welded gamma-TiAl-
based alloy (Ti-48,Al- 1,Cr-1.5,Nb-1,Mn-0.2,Si-0.5)
• The residual stresses are largely relieved after the heat treatment.
• After heat treatment specimen has balanced mechanical properties of strength and
ductility.
• The diffraction shows that the phase transformation from alpha to gamma takes
place under tensile load at 1023 K (750 C), and the grain size and lamellar spacing
are refined in the weld zone.

8. INFLUENCE OF POST WELD HEAT TREATMENT ON THE
MICROSTRUCTURE & HARDNESS OF LASER WELD
SEAMS ON HOT ROLLED TRIP 800 STEEL
• The transformation induced plasticity (TRIP) steel effect occurs because of the
martensitic transformation of retained austenite during plastic deformation, & it
provides the steel with excellent strength & ductility
• Weldability of TRIP steels is problematic, & this prevents its adoption for many
applications in the automotive industry
• Hardness test revealed that fusion zone hardness decreased with increasing of
temperatures in the post weld heat treatment on the laser weld seam

10. HARDNESS, MICROSTRUCTURE, AND RESIDUAL STRESSES
IN LOW CARBON STEEL WELDING WITH POST-WELD
HEAT TREATMENT AND TEMPER BEAD WELDING
• A weld bead placed at a specific location in or at the surface of a weld for the
purpose of affecting the metallurgical properties of the heat affected zone or
previously deposited weld metal.
• Effects of post-weld heat treatment (PWHT) and temper bead welding (TBW) on
hardness, microstructure and residual stresses in multi-layer welding on low carbon
steel specimens
• It was found that the PWHT technique gave overall lower hardness than the TBW
technique, but the hardness values in both techniques were acceptable
• Microscopy analysis showed that the TBW technique was more effective in
tempering the heat affected zone as the grain size decreased slightly at the fusion
line in spite of the higher temperature at the fusion line

11. • Residual stresses measured using the hole-drilling method showed that the residual
stress is not reduced below yield stress near the last bead solidified in TBW. Only
PWHT gives low residual stress results
• High tensile residual stresses may result in sensitivity to fatigue loading.

13. THANK YOU