3. Operands#
3.1. Keyword HIST_EXP#
♦ HIST_EXP =
An occurrence of the keyword factor HIST_EXP makes it possible to define the evolutions of ferrite, pearlite and bainite associated with a thermal history upon cooling and given austenitization conditions.
3.1.1. Operand VALE#
♦ VALE = lval
List of values defining austenitization, thermal history \(T(t)\) and evolutions of ferrite, pearlite, and bainite.
The first value is the value of the derivative of the \(T(t)\) function (i.e. the cooling rate) when \(T\) is equal to \(700°C\).
The second value is the grain size (i.e. their diameter) resulting from the austenitization conditions associated with TRC.
The following 6 values define the thermal history between \({\mathrm{AR}}_{3}\) and \(\mathrm{TMF}\) (temperature at the beginning of decomposition of austenite under « quasi‑static » cooling and temperature at the end of martensitic transformation respectively). These values are the respective coefficients of the monomials of degrees 0 to 5 such that the polynomial of order 5 thus constructed is the interpolation between \({\mathrm{AR}}_{3}\) and \(\mathrm{TMF}\) in the least squares sense of the function \(F(T)\) deduced from the thermal history and such that:
\(F(T)=\mathrm{ln}(t(T))\)
In the case where the experimental thermal history to be defined is an affine function of time (i.e. where the cooling rate is constant) these six values will be entered as all equal to zero.
The following values (necessarily in groups of 4) define the respective proportions of ferrite, pearlite and bainite present at a given temperature for the experimental thermal history defined by the first 8 values.
The ferritic, pearlitic and bainitic transformations associated with a thermal history are defined by the set of final proportions in each of the phases (\({Z}_{1}\) final, \({Z}_{2}\) final, \({Z}_{3}\) final) and the corresponding temperatures, for each of the transformations at:
the temperature at which transformation begins,
the temperature at which 1% of a new phase is formed,
the temperature at which \({Z}_{\mathrm{final}}\) — 1% of a new phase is formed,
the temperature at which the transformation is finished (with \({Z}_{\mathrm{final}}\) of phase formed).
The set of « points » \(({Z}_{\mathrm{1,}}{Z}_{\mathrm{2,}}{Z}_{\mathrm{3,}}T)\) defining an experimental story is therefore as follows:
Note: it is necessary to be consistent between the value of the temperature at the start of ferritic transformation and that corresponding to AR3 in DEFI_MATERIAU. Beyond a difference of 10°C, an alarm will be issued and it is considered that the results could be false.
3.2. Keyword TEMP_MS#
♦ TEMP_MS
This key word factor makes it possible to define the law of evolution of temperature \(\mathrm{Ms}\) according to the quantities of ferrite, pearlite and bainite already formed according to the law:
\(\begin{array}{ccc}\mathrm{Ms}=\mathrm{Ms0}& \text{si}& {Z}_{1}+{Z}_{2}+{Z}_{3}\le \text{SEUIL}\\ \mathrm{Ms}=\mathrm{Ms0}+\mathrm{AKM}({Z}_{1}+{Z}_{2}+{Z}_{3})+\mathrm{BKM}& \text{si}& {Z}_{1}+{Z}_{2}+{Z}_{3}>\text{SEUIL}\end{array}\)
where \(\mathrm{Ms0}\) is the « classical » temperature at the start of martensitic transformation when it is total (it is defined under the keyword factor META_ACIER of DEFI_MATERIAU).
3.2.1. Operand SEUIL#
♦ SEUIL = zs,
\({z}_{s}\) is the quantity of austenite transformed below which \(\mathrm{Ms}\) is invariant.
3.2.2. Operand AKM#
♦ AKM = akm,
\(\mathrm{akm}\) is the proportionality factor between the decrease in temperature \(\mathrm{Ms}\) and the quantity of austenite transformed \(({Z}_{1}+{Z}_{2}+{Z}_{3})\).
3.2.3. Operand BKM#
♦ BKM = bkm,
\(\mathrm{bkm}\) is the ordinate at the origin of the affine equation relating the decrease in \(\mathrm{Ms}\) to the quantity of austenite transformed.
3.2.4. Operand TPLM#
♦ TPLM = Vc,
\(\mathrm{Vc}\) is the slowest cooling rate at \(700°C\) in the experimental history, which allows a little bit of martensite to be formed.
These four keywords define the values of the \(\mathrm{SEUIL},\mathrm{AKM},\mathrm{BKM}\) quantities involved in the law of evolution of \(\mathrm{Ms}\) that are assumed to be independent of the grain size.
3.3. Keyword GRAIN_AUST#
Allows you to define the influence of grain size on metallurgical transformations during cooling defined by diagram TRC.
3.3.1. Operand DREF#
◊ DREF = do,
\(\mathrm{do}\) is the grain size (i.e. its diameter) associated with the diagram defined under the keyword factor HIST_EXP.
3.3.2. Operand A#
◊ A = a,
\(a\) is a material parameter that makes it possible to characterize the effect of grain size on the TRC diagram of a steel (cf. [R4.04.01]).