US2013153090A1PendingUtilityA1
Method for thermal treatment of articles from iron-based alloys (variants)
Assignee: DOVATELSKO T TS AUSFERR OBSCHESTVO S OGRANICHENNOI OTVETSTVENNOSTYU ISSLEPriority: Aug 10, 2010Filed: Feb 14, 2013Published: Jun 20, 2013
Est. expiryAug 10, 2030(~4 yrs left)· nominal 20-yr term from priority
Inventors:Vladimir Nikolaevich UrtsevYury Nikolaevich GornostyrevMikhail Iosifovich KatsnelsonAnton Vladimirovich ShmakovDim Maratovich KhabibulinVasily Nikolaevich DegtyarevEvgeny Dmitrievich MokshinVladimir Leonidovich KornilovSergey Iosifovich PlatovGennady Vasilievich SamokhvalovSergey Anatolievich MurikovAlexandr Vasilievich KorolevVladimir Ivanovich VoroninNikolay Vladimirovich Urtsev
C21D 6/00C21D 9/525
42
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Claims
Abstract
The invention relates to the field of thermal processing of articles consisting of steel and iron-based alloys with a carbon content of up to 4.3% by weight. In order to reduce the duration of the technological processes used for producing articles consisting of iron-based alloys with a set structural state, the first variant of the method comprises heating the articles so as to form austenite and then cooling, which is performed under conditions which ensure the formation, in the structure of the alloy, of regions of austenite with a chemical composition similar to eutectoid with the subsequent formation in said regions of marinite and a set structural state so as to produce perlite with a different degree of dispersion and/or hardened structures. The second variant of the method comprises heating the article, which is performed under conditions which ensure the formation, in the structure of the alloy, of marinite and then cooling with the formation a set structural state so as to produce perlite with a different degree of dispersion and/or hardened structures. When implementing the methods, pulsed cooling and plastic deformation are used.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1 . A method for the heat treatment of articles made of iron-based alloys having carbon contents of up to 4.3% by weight, comprising: heating to provide the formation of austenite and subsequent cooling according to schedules that provide the formation of the desired structural state, wherein cooling is carried out according to schedules that provide the occurrence of austenite regions having near-eutectoid chemical compositions, followed by forming marinite therein, and wherein the desired structural state is formed so as to obtain therein pearlite in various degrees of dispersion and/or quenched structures.
2 . The method according to claim 1 , wherein cooling is carried out according to schedules that provide the formation of the desired fraction of austenite regions having near-eutectoid chemical compositions, followed by forming therein the desired marinite fraction.
3 . The method according to claim 2 , wherein the schedules that provide the formation of the desired fraction of austenite regions having near-eutectoid chemical compositions, followed by forming therein the desired marinite fraction, are determined by calculations or experimentally.
4 . The method according to claim 1 , wherein the desired structural state is formed so as to obtain therein the desired pearlite fractions in various degrees of dispersion and/or quenched structures.
5 . The method according to claim 3 , wherein, when the schedules that provide the formation of marinite from austenite regions with a near-eutectoid chemical composition are determined by calculations, the temperature range of marinite formation is set such that satisfies the condition that
T TEX <T<T C loc , wherein T C loc is the local ferromagnetic ordering temperature in austenite in the vicinity of a carbon atom, determined by quantum-chemical calculations and T TEX is the temperature selected with account for technological limitations, and the cooling rate is selected such that the cooling temperature versus time T(t) satisfies the condition that T(t)<θ(t), wherein the θ(t) function is given by the starting lines of the pearlite and bainite transformations in the thermokinetic diagram.
6 . The method according to claim 3 , wherein in the experimental determination of the schedules that provide the formation of marinite from austenite regions with a near-eutectoid chemical composition, samples are quenched from fixed temperatures with various exposure times at these temperatures, and the occurrence of marinite is judged from the occurrence of rutite in the quenched sample.
7 . The method according to claim 1 , wherein the determination of the schedule for cooling from the prior-formed marinite to form the desired amount of pearlite in the desired structural state comprises quenching of experimental samples followed by the determination of the structural state thereof.
8 . The method according to claim 1 , wherein the determination of the schedule for cooling from the prior-formed marinite to form the desired structural state, comprises: measuring temperature at selected sites of the volume of a model alloy sample having a simple shape upon cooling at rates that lead to the formation of the required structural state in the alloy sample, determining the values of thermokinetic constants that provide (for known heat flows on the sample surface) the coincidence of the temperature versus time dependence obtained in the course of the model experiment with the one obtained as a result of solving the set of equations comprising:
the heat conductivity equation
H
(
r
,
t
,
T
)
t
=
∇
→
·
Q
→
(
r
,
t
)
+
ρ
∑
i
f
i
(
r
,
t
,
T
)
t
q
i
,
wherein
the operator
∇
→
=
∂
∂
r
has a dimension of m −1 ,
r is the radius-vector of the point to which the calculations refer,
ρ is density, measured in kg/m 3 ,
q i is specific enthalpy of formation of the ith phase, measured in J/kg,
f i (r,t,T) is the dimensionless weight fraction of the ith phase in the vicinity of point r at moment of time t at temperature T,
{right arrow over (Q)}(r,t) is the heat flow, measured in J/(m 2 ·s),
H(r,t,T) is the enthalpy distribution, measured in J/m 3 , over the volume of the sample,
the energy conservation equation
H
(
r
,
t
,
T
)
=
ρ
∑
i
f
i
(
r
,
t
,
T
)
∫
0
T
C
p
i
(
T
′
)
T
′
,
wherein
C p i (T) is the specific heat capacity ith phase at a fixed pressure as a function of temperature, measured in J/(kg·K), and
the kinetic equation
f
i
(
r
,
t
,
T
)
t
=
∑
k
≠
i
∫
0
t
M
ik
(
T
,
f
k
(
τ
)
,
(
t
-
τ
)
)
τ
,
wherein
M ik (T,f k (τ),(t−τ)) is the function that defines the variation rate of change of the weight fraction f i of the ith phase, determined for each phase transformation, and
then calculating the heat flow as a function of time across the surface of the alloy article, using the above equations and the thermokinetic constants thus found, so as to provide the trajectory of temperature variation with time that would lead to the formation of the desired structural state.
9 . The method according to claim 1 , wherein after marinite is formed, cooling is carried out according to the schedules that provide the formation of desired fractions of ferrite and iron carbide phases in the desired structural state either without formation of quenched structures or with formation of fractions thereof not exceeding the desired values.
10 . The method according to claim 1 , wherein cooling is carried out in pulses.
11 . The method according to claim 1 , wherein after alloy articles are heated to temperatures that provide the formation of the desired austenite fraction in the alloy, the alloy articles are subjected to plastic strain.
12 . A method for the heat treatment of articles made of iron-based alloys having carbon contents of up to 4.3% by weight, comprising: heating and subsequent cooling according to schedules that provide the formation of the desired structural state, wherein the heating is carried out according to schedules that provide the formation of marinite, and wherein the desired structural state is formed to obtain therein pearlite having various degrees of dispersion and/or quenched structures.
13 . The method according to claim 12 , wherein heating is carried out according to the schedules that provide the formation of the desired marinite fraction.
14 . The method according to claim 13 , wherein the schedules that provide the formation of the desired marinite fraction, are determined by calculations or experimentally.
15 . The method according to claim 12 , wherein the desired structural state is formed so that to obtain therein desired pearlite fractions in various degrees of dispersion and/or quenched structures.
16 . The method according to claim 14 , wherein in the determination of the schedules that provide the formation of marinite by calculations, the temperature range of marinite formation is set such that satisfies the condition that
T X <T<T C loc , wherein T C loc is the local ferromagnetic ordering temperature in austenite in the vicinity of a carbon atom, determined by quantum-chemical calculations, T X is the eutectoid temperature for an alloy of the appropriate chemical composition, and exposure time t in seconds, necessary for the required cementite fraction f C , is derived from the equation
f C =1.05 f C0 exp(− kt n ), wherein
f C0 is the dimensionless cementite fraction in the initial moment of time, n is an exponent, 4>n>3, and k is the parameter that determines the cementite dissolution rate in the alloy of the appropriate chemical composition at temperature T, in s −n .
17 . The method according to claim 14 , wherein in the experimental determination of the schedules that provide the formation of marinite from austenite regions with a near-eutectoid chemical composition, samples are quenched from fixed temperatures with various exposure times at these temperatures, and the occurrence of marinite is judged from the occurrence of rutite in the quenched sample.
18 . The method according to claim 12 , wherein the determination of the cooling schedule from the prior-formed marinite to form the desired amount of pearlite in the desired structural state comprises quenching experimental samples followed by the determination of the structural state thereof.
19 . The method according to claim 12 , wherein the determination of the schedule for cooling from the prior-formed marinite to form the desired structural state, comprises: measuring temperature at selected sites of the volume of a model alloy sample having a simple shape upon cooling at rates that lead to the formation of the required structural state in the alloy sample; determining the values of thermokinetic constants that provide (for known heat flows on the sample surface) the coincidence of the temperature versus time dependence obtained in the course of the model experiment with the one obtained as a result of solving the set of equations comprising the heat conductivity equation:
the heat conductivity equation
H
(
r
,
t
,
T
)
t
=
∇
→
·
Q
→
(
r
,
t
)
+
ρ
∑
i
f
i
(
r
,
t
,
T
)
t
q
i
,
wherein
the operator
∇
→
=
∂
∂
r
has a dimension of m −1 ,
r is the radius-vector of the point to which the calculations refer,
ρ is density, measured in kg/m 3 ,
q i is the specific enthalpy of formation of the ith phase, measured in J/kg,
f i (r,t,T) is the dimensionless weight fraction of the ith phase in the vicinity of point r at moment of time t at temperature T,
{right arrow over (Q)}(r,t) is the heat flow, measured in J/(m 2 ·s),
H(r,t,T) is the enthalpy distribution, measured in J/m 3 , over the volume of the sample;
the energy conservation equation
H
(
r
,
t
,
T
)
=
ρ
∑
i
f
i
(
r
,
t
,
T
)
∫
0
T
C
p
i
(
T
′
)
T
′
,
wherein
C p i (T) is the specific heat capacity of the ith phase as a function of temperature at a fixed pressure, measured in J/(kg·K); and
the kinetic equation
f
i
(
r
,
t
,
T
)
t
=
∑
k
≠
i
∫
0
t
M
ik
(
T
,
f
k
(
τ
)
,
(
t
-
τ
)
)
τ
,
wherein
M ik (T,f k (τ),(t−τ)) is the function that defines the variation rate of change of the weight fraction f i of the ith phase, determined for each phase transformation, and
calculating the heat flow as a function of time across the surface of an alloy article, using said equations and the thermokinetic constants thus found, so as to provide the trajectory of temperature variation with time that would lead to the formation of the desired structural state.
20 . The method according to claim 12 , wherein after marinite is formed, cooling is carried out according to the schedules that provide the formation of desired fractions of ferrite and iron carbide phases in the desired structural state without formation of quenched structures or with formation of fractions thereof not exceeding the desired values.
21 . The method according to claim 12 , wherein cooling is carried out in pulses.
22 . The method according to claim 12 , wherein alloy articles are subjected to plastic strain during heating, either prior to or in the course of marinite formation.Join the waitlist — get patent alerts
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