We investigated the effects of annealing temperature on the
microstructure and mechanical properties of dual phase steel (*) at
temperatures of 790C, 820C, and 850C in order to simulate the conditions
during hot-dipped galvanizing. At each temperature, we tested the
mechanical properties and observed the microstructures with both an
optical microscope and transmission electron microscopy.

Increasing the annealing temperature results in an increase of the
martensite volume fraction, and a reduction in both intergranular
carbide and ferrite intragranular carbide. With an annealing temperature
of 790C, most of martensite is distributed in the intergranular region.
As the annealing temperature increases, so does the amount of
intragranular island martensite. At an annealing temperature of 820C,
twin martensite appears in the room temperature microstructure.

The flow curve changes with the annealing temperature. At 790C, there
is obvious yield point elongation. When the annealing temperature is
820C, yield point elongation disappears. At the same time, tensile
strength fluctuates with the annealing temperature changes.

* (0.15wt%C 0.1wt%Si 1.7wt%Mn)

Comments: I$B!G(Bm not an english teacher. What happens to the martensite
fraction / percentage at 850C? Can you extrapolate the effect of
temperature on the formation of martensite? What temperature gives you
the desired fractions of martensite for the application?

You mention that the yield point returns to normal at 820C. But you say
that the tensile strength fluctuates. At what temperature do the
fluctuations in tensile strength negate the improvements in the yield point?


wrote:
English is a little trouble for me .so ,there are maybe some errors in
my writting.
so I hope someone who is kind help me check the syntax error (grammar
mistakes)
-------------------------------------------------------------------------------

Different microstructures and mechanical properties can be developed
in a variety of annealing temperature. An investigation was undertaken
to examine effect of annealing temperature on microstructure and
mechanical of dual phase steel under simulated hot-dipped galvanizing.
The steel (of composition 0.15wt%C 0.1wt%Si 1.7wt%Mn) was obtained at
three different heating temperatures (790$B!n(B, 820$B!n(B, 850$B!n(B) by continuous
annealing experiment thermal simulator. The microstructures were
observed by the optical microscope and transmission electron
microscopy, and the mechanical properties were tested. Under hot-dip
galvanizing condition, the effect of annealing temperature on
microstructure and the relationship of microstructure and mechanical
properties have been investigated. Increasing the annealing
temperature, martensite volume fraction increases, and intergranular
carbide reduces and ferrite intragranular carbide becomes small. When
the annealing temperature is 790$B!n(B, most of martensite distributes
intergranular region. Increasing the annealing temperature,
intragranular island martensite increases. When the annealing
temperature reaches 820$B!n!$(Btwin martensite appears in the room
temperature microstructure. The influence of annealing temperature on
the flow curve is significant. When the annealing temperature is 790$B!n(B,
there is obvious yield point elongation. When the annealing
temperature is 820$B!n(B, yield point elongation disappears. At the same
time, tensile strength fluctuates with the annealing temperature
changes.

On Dec 14, 4:27 am, Louis Ohland wrote:
We investigated the effects of annealing temperature on the
microstructure and mechanical properties ofdualphasesteel (*) at
temperatures of 790C, 820C, and 850C in order to simulate the conditions
during hot-dipped galvanizing. At each temperature, we tested the
mechanical properties and observed the microstructures with both an
optical microscope and transmission electron microscopy.

Increasing the annealing temperature results in an increase of the
martensite volume fraction, and a reduction in both intergranular
carbide and ferrite intragranular carbide. With an annealing temperature
of 790C, most of martensite is distributed in the intergranular region.
As the annealing temperature increases, so does the amount of
intragranular island martensite. At an annealing temperature of 820C,
twin martensite appears in the room temperature microstructure.

The flow curve changes with the annealing temperature. At 790C, there
is obvious yield point elongation. When the annealing temperature is
820C, yield point elongation disappears. At the same time, tensile
strength fluctuates with the annealing temperature changes.

* (0.15wt%C 0.1wt%Si 1.7wt%Mn)

Comments: I'm not an english teacher. What happens to the martensite
fraction / percentage at 850C? Can you extrapolate the effect of
temperature on the formation of martensite? What temperature gives you
the desired fractions of martensite for the application?

You mention that the yield point returns to normal at 820C. But you say
that the tensile strength fluctuates. At what temperature do the
fluctuations in tensile strength negate the improvements in the yield point?



wrote:
English is a little trouble for me .so ,there are maybe some errors in
my writting.
so I hope someone who is kind help me check the syntax error (grammar
mistakes)
--------------------------------------------------------------------------------

Different microstructures and mechanical properties can be developed
in a variety of annealing temperature. An investigation was undertaken
to examine effect of annealing temperature on microstructure and
mechanical ofdualphasesteel under simulated hot-dipped galvanizing.
The steel (of composition 0.15wt%C 0.1wt%Si 1.7wt%Mn) was obtained at
three different heating temperatures (790$B!n(B, 820$B!n(B, 850$B!n(B) by continuous
annealing experiment thermal simulator. The microstructures were
observed by the optical microscope and transmission electron
microscopy, and the mechanical properties were tested. Under hot-dip
galvanizing condition, the effect of annealing temperature on
microstructure and the relationship of microstructure and mechanical
properties have been investigated. Increasing the annealing
temperature, martensite volume fraction increases, and intergranular
carbide reduces and ferrite intragranular carbide becomes small. When
the annealing temperature is 790$B!n(B, most of martensite distributes
intergranular region. Increasing the annealing temperature,
intragranular island martensite increases. When the annealing
temperature reaches 820$B!n!$(Btwin martensite appears in the room
temperature microstructure. The influence of annealing temperature on
the flow curve is significant. When the annealing temperature is 790$B!n(B,
there is obvious yield point elongation. When the annealing
temperature is 820$B!n(B, yield point elongation disappears. At the same
time, tensile strength fluctuates with the annealing temperature
changes.- Hide quoted text -

- Show quoted text -



due to Fe-C phase-diagram, there must be a limit of martensite.
At 850C, the martensite fraction / percentage is around 17%

with special conditions,change the heating temperature, we can obtain
different volume of austenitite at high temperature. when it is
cooled down to the room temperature, the steel obtained different
fraction martensite.


You mention that the yield point returns to normal at 820C. But you say
that the tensile strength fluctuates. At what temperature do the
fluctuations in tensile strength negate the improvements in the yield point?

'fluctuations in tensile strength' --- my mean is that tensile
strength is not line with the temperature.

of course, lots of work need to be done to investigated other circs
and the rule.

wrote:
Increasing the annealing temperature results in an increase of the
martensite volume fraction, and a reduction in both intergranular
carbide and ferrite intragranular carbide.
due to Fe-C phase-diagram, there must be a limit of martensite.
At 850C, the martensite fraction / percentage is around 17%

// -------- Comment ---------------- //

What would make your data easier to conceptualize would be a graphic
showing the martensite, carbide, and ferrite levels changing as the
annealing temperature increases.


with special conditions,change the heating temperature, we can obtain
different volume of austenitite at high temperature. when it is
cooled down to the room temperature, the steel obtained different
fraction martensite.


You mention that the yield point returns to normal at 820C. But you say
that the tensile strength fluctuates. At what temperature do the
fluctuations in tensile strength negate the improvements in the yield point?

'fluctuations in tensile strength' --- my mean is that tensile
strength is not line with the temperature.

of course, lots of work need to be done to investigated other circs
and the rule.


// ------------- Comment ---------------- //

Adding a tensile strength curve to the above graph may show the
relationship between tensile strength, yield point, and the other
properties.