CC BY
28
SRSTI 53.49.21:50.53.15
https://doi.org/10.48081/RLYO5699
A. A. Zinger1, A. N. Zhakupov2, *A. V. Bogomolov3
Toraighyrov University, Republic of Kazakhstan, Pavlodar
predicting steel mechanical properties using computer modeling in deform 3D
This article presents the results of heat-treated low-alloy steel microstructure research using the Deform 3D program, which allows determining the optimal technological parameters of steel hardening. The object of research is pipe steel grade 12CrMoV. To determine and evaluate the heat treatment parameters affecting the increase in mechanical properties, the results of modeling in the specified program were used. To compare the results, we used the method for determining the mechanical properties during tensile testing (GOST1497-84).
In order to determine the technological parameters of heat treatment for obtaining pipes of a high strength group, the mode of thermal cyclic hardening of steel was simulated, followed by low-temperature tempering, which allows obtaining properties at the level of: tensile strength — not less than 931 MPa, yield strength — in the range 862—1034 MPa, elongation — not less than 9.0 %.
The values of the mode parameters were selected according to the recommendations: heating temperature — 860 °C; tempering temperature — 150 °C. The results of modeling the heat treatment process were confirmed by tensile tests, as a result of which mechanical properties were obtained: tensile strength — 1093 MPa, yield point — 937 MPa and relative elongation — 11.4 %, corresponding to the property values of the Q125 strength group.
Keywords: Thermal cyclic treatment, modeling, hardening, microstructure, mechanical properties.
Introduction
Heat treatment of steels is a complex process that requires the determination of the following technological parameters: heating temperature, holding time, tempering temperature, cooling rate. The optimal mode of heat treatment makes it possible to save energy and time resources of the plant. To increase the efficiency and confirm the reliability of the proposed technological parameters, simulation is used in computer simulation systems such as Deform, Simufact Forming, Q-Form.
In this research, the Deform program was used for modeling, as the most reliable one [1-2]. The specified program uses the Heat Treatment module, which outputs the results of mechanical properties, phase composition, grain size, and structure inhomogeneity in the postprocessor.
The aim of this work is to determine the dependence of the structure formation and mechanical properties on temperature parameters, as well as to determine the optimal
heat treatment mode for the production of the Q125 strength group according to the API standard for steel grade 12CrMoV.
Materials and methods
The object of research is pipe steel grade 12CrMoV with indicators according to [3]. To determine and evaluate the heat treatment parameters affecting the increase in mechanical properties, the results of modeling in the specified program were used. To compare the results, we used the method for determining the mechanical properties during tensile testing (GOST 1497-84) [4-7].
In order to determine the technological parameters of heat treatment for obtaining pipes of a high strength group, the mode of thermal cyclic hardening of steel was simulated, followed by low-temperature tempering, which allows obtaining properties at the level of: tensile strength - not less than 931 MPa, yield strength - in the range 862-1034 MPa, elongation - not less than 9.0 %.
The values of the mode parameters were selected according to the recommendations: heating temperature - 860 °C (critical point of phase transformation Ac3) [3]; tempering temperature - 150 °C (temperature of preservation of the martensite structure for steel 12CrMoV) [3]; heating time - according to the recommendations [8]; holding time during heating for hardening - 1.5-2 minutes per 1 mm of section [3]; holding time during vacation - 1 hour [9]; cooling rate during quenching - 150 °C/s (thermokinetic diagram for steel 12CrMoV); cooling time in air after tempering - according to [10].
Results and discussion
As a result of modeling, according to the scheme shown in Figure 1, the following results were obtained (where i is the number of quenching cycles):
Microstructure. Figure 2 shows the microstructure at different heat treatment modes: from one quenching cycle and higher, followed by low tempering.
Figure 1 - Heat treatment scheme
Analyzing the microstructures, it can be seen that the largest amount of martensite was recorded during three quenching cycles. The values of the graphs indicate that during one quenching cycle followed by tempering from the pipe core to the surface, the amount of martensite is from 72.3 to 98.7 %, with increasing cycles, this amount accordingly increases from 78.3 to 98.8 % of martensite and further at three cycles from 85.4 to 99.2 %. However, with four cycles, a gradual decrease occurs - from 81.9 to 99.0 %, which tentatively suggests a decrease in strength properties, since a decrease in the martensite phase causes an increase in troostite, which has a lower hardness and, accordingly, the strength of steel. In addition, a decrease in the amount of the martensite phase with four quenching cycles gives a recommendation that it is unreasonable to further increase the cycles of thermal cycling.
Hardness. Figure 3 shows the hardness results for various thermal cycling modes. It can be seen that the average value of hardness between the center and the surface of the pipe is 53.0 HRC, which is the maximum, which is revealed during three quenching cycles. At the same time, an increase in hardness from one cycle to three is confirmed by the analysis of the results of the microstructure in terms of the number of phase components.
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Figure 2 - Microstructure of 12CrMoV steel at 1-3 hardening cycles (a - one cycle; b - two cycles; c - three cycles)
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Figure 3 - Hardness of 12CrMoV steel at 4 hardening cycles
Mechanical properties. To determine the parameters normalized by the API 5CT standard, namely the tensile strength, yield strength and relative elongation, the tensile stress of a standard 12CrMoV steel sample made was modeled in Deform 3D Forming, as shown in Figure 4. At the same time, the material was used from the thermal cooling database at the last step in each mode. As a result, the data were obtained, the values of which are indicated in Table 1.
Figure 4 - Simulated tensile test of a 12CrMV steel sample
Table 1 - Simulated tensile test results
Indicator 1 cycle 2 cycles 3 cycles 4 cycles
Tensile strength, MPa 925 997 1080 975
Yield strength, MPa 745 848 928 825
Elongation,% 10,1 10,8 11,1 9,8
To confirm the results of computer simulation of heat treatment in the Deform 3D HT program, samples were cut from a tubing with a diameter of 88.9 mm and a wall thickness of 12 mm from 12CrMoV steel, obtained using the current production technology of «KSP Steel» LLP. that is, from one quench cycle followed by low tempering to four cycles, three specimens were processed according to the heat treatment scheme in Figure 1. After the treatment, all specimens were tensile tested to determine mechanical properties. At the same time, the results shown in Figure 5 were obtained (0 cycles corresponds to the initial state of the metal).
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Figure 5 - Tensile test of steel 12CrMV
As can be seen from Figure 5, the maximum mechanical properties, namely the tensile strength equal to 1093 MPa, the yield strength - 937 MPa and the relative elongation - 11.4 % are observed during three quenching cycles followed by tempering. Three samples were used for each mode and the graph shows average values, the results obtained correspond to the Q125 strength group according to API 5 CT standard. The relative error of the calculated and experimental data ranges from 0.96 to 4.04 %. This confirms the sufficient accuracy and efficiency of computer modeling in the Deform 3D HT environment for predicting mechanical properties during heat treatment of steel.
Conclusions
1 Computer modeling in the Deform 3D HT environment makes it possible to effectively predict the mechanical properties of steels, depending on the technological parameters and heat treatment modes for steel hardening;
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2 Comparing the results of tensile tests of computer simulation in Deform 3D and the actual, the relative calculation error does not exceed 4.04 %;
3 The results of computer modeling and the performed mechanical tests confirm the effectiveness of the thermal cycling modes use for obtaining pipes of strength group Q125 from steel 12CrMoV: the number of cycles - 3, heating temperature - 860 °С, tempering temperature - 150 °С, cooling rate - 150 °C/sec.
СПИСОК ИСПОЛЬЗОВАННЫХ ИСТОЧНИКОВ
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2 Iyengar, S. Heat Treatment of Low-Alloyed Steel up to Grade Q125 / Iyengar S., Bogomolov A. V., Zhakupov A. N. [Text] // Solid State Phenomena. - 2017. - V. 265. - P. 981-987.
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6 Журавлев, Л. Г. Физические методы исследования металлов и сплавов / Л. Г. Журавлев, В. И. Филатов [Text]. // Челябинск : изд-во ЮУрГУ, 2004. - 165 с.
7 Итыбаева, Г. Т. Методы прогнозирования качества сварных труб / Г. Т. Итыбаева, А. К. Акылбеков, Л. Р. Мусина // Наука и техника Казахстана. -2019. - № 2. - С. 13-27.
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9 Смирнов, М. А. Влияние структуры на деформационное старение низкоуглеродистой стали /М. А. Смирнов, И. Ю. Пушминцев, О. В. Барнак и А. Н. Мальцева [Текст] // Деформация и разрушение материалов. - 2014.- No. 8. - C. 9-15.
10 Tanigawa, H. Irradiation effects on precipitation and its impact on the mechanical properties of reducedactivation ferritic/martensitic steels / H. Tanigawa [et al.] // Journal of Nuclear Materials. - 2007. - № 367-370. - P. 42-47.
REFERENCES
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3 Sedov, Yu. E. Spravochnik molodogo termista [ Handbook of a young thermist ] / Sedov Yu. E., Adaskin A. M. [Text] // Moscow : Higher school, 1986. - 239 p.
4 Fedyukin, V.K. Termotsiklicheskaya obrabotka stalei i chugunov [Thermo-cyclic treatment of steels and cast irons] / V.K. Fedyukin. [Text]. // Leningrad : Mashinostroyenie, 1977. - 384 p.
5 Prilhodko, V. M. Metallofizicheskiye osnovy uprochnyayuchshikh tekhnologiy [ Metal physical principles of strengthening technologies ] / V. M. Prikhodko, L. G. Petrova, O. V. Chudina. [Text]. // Moscow : Mashinostroyenie, 2003. - 381 p.
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9 Smirnov, M. A. Vliyaniye struktury na deformatsionnoye stareniye nizkouglerodistoy stali [Influence structure on stress aging of low-alloyed steel]/ М. А. Smirnov, I. Yu. Pyshmintsev, O. V. Barnak, A. N. Maltseva [Text] // Deformation and rupture of materials [Deformatsiya i razrusheniye materialov]. - 2014. - No. 8. -P. 9-15.
10 Tanigawa, H. Irradiation effects on precipitation and its impact on the mechanical properties of reducedactivation ferritic/martensitic steels / H. Tanigawa [et al.] // Journal of Nuclear Materials. - 2007. - № 367-370. - P. 42-47.
Материал поступил в редакцию 17.03.22.
А. А. Зингер1, А. Н. Жакупов2, *А. В. Богомолов3
1,2,3TopaÜFbipoB университет^ Казахстан Республикасы, Павлодар к.
Материал баспаFа 17.03.22 TY^i.
DEFORM 3Б-ДЕ КОМПЬЮТЕРЛ1К МОДЕЛЬДЕУД1 ЦОЛДАНА ОТЫРЫП БОЛАТТЫЦ МЕХАНИКАЛЫЦ ЦАСИЕТТЕР1Н БОЛЖАУ
Болатты ныгайтудыц оцтайлы технологиялъщ параметрлерт анъщтауга мумктдж беретт Deform 3D багдарламасын цолдана отырып, термиялыц вцделген темен цосындыланган болаттыц микроцурылымын зерттеу нэтижелерi усынылган. Зерттеу нысаны 12ХМФ маркалы цубырлы болат. Механикалыц цасиеттердщ жогарылауыта эсер ететт термиялыц ецдеу параметрлерт аныцтау жэне багалау ушт осы багдарламада модельдеу нэтижелерi цолданылды. Нэтижелердi салыстыру ушт ГОСТ 1497-84 сэйкес созылу сынагы кезтде механикалыц цасиеттердi аныцтау эдс цолданылды.
Бержтшш жогары топтагы цубырларды алу ушт термиялыц ецдеудщ технологиялыц параметрлерт аныцтау мацсатында болатты темен температуралы жасытумен термоциклдi берiктендiру тэртiптемесi модельдендi, бул келеd децгейде цасиеттер алуга мумктдж бередi: созылудыц бержтж шегi — 931 Мпа кем емес, аццыштыц шегi — 862—1034 МПа диапазонында, салыстырмалы узаруы — 9,0 % кем емес.
Модельдеу параметрлертщ мэндерi болаттыц химиялыц цурамын ескере отырып тацдалды: цыздыру температурасы — 860 °C, жасыту температурасы — 150 °C. Термиялыц ецдеу процест модельдеу нэтижелерi созылу сынацтарымен расталды, нэтижестде келеd механикалыц цасиеттер алынды: созылудыц бержтж шегi —1093 МПа, аццыштыц шегi — 937 МПа жэне салыстырмалы узаруы —11,4 %, Q125 бержтж тобы цасиеттерШц мэндерте сэйкес келедi.
Кiлттi сездер: термоциклдi ецдеу, модельдеу, берiктендiру, микроцурылым, механикалыц цасиеттерь
А. А. Зингер1, А. Н. Жакупов2, *А. В. Богомолов3
1,2,3Торайгыров университет, Республика Казахстан, г. Павлодар.
Материал поступил в редакцию 17.03.22.
ПРОГНОЗИРОВАНИЕ МЕХАНИЧЕСКИХ СВОЙСТВ СТАЛИ С ИСПОЛЬЗОВАНИЕМ КОМПЬЮТЕРНОГО МОДЕЛИРОВАНИЯ В DEFORM 3D
Представлены результаты исследования микроструктуры термообработанной низколегированной стали с использованием программы Deform 3D, позволяющей определить оптимальные технологические параметры упрочнения стали. Объектом исследования является трубная сталь марки 12CrMV. Для определения и оценки параметров термообработки, влияющих на повышение механических свойств, были использованы результаты моделирования в указанной программе. Для сравнения результатов использовали
метод определения механических свойств при испытании на растяжение по ГОСТ 1497-84.
С целью определения технологических параметров термообработки для получения труб группы высокой прочности был смоделирован режим термоциклического упрочнения стали с последующим низкотемпературным отпуском, который позволяет получить свойства на уровне: предел прочности при растяжении — не менее 931 МПа, предел текучести — в диапазоне 862—1034 МПа, относительное удлинение — не менее 9,0 %. Значения параметров моделирования были выбраны в соответствии с учетом химического состава стали: температура нагрева — 860 °С , температура отпуска — 150 °С. Результаты моделирования процесса термообработки были подтверждены испытаниями на растяжение, в результате которых были получены механические свойства: предел прочности при растяжении — 1093 МПа, предел текучести — 937 МПа и относительное удлинение — 11, 4%, соответствующие значениям свойств группы прочности Q125.
Ключевые слова: термоциклическая обработка, моделирование, упрочнение, микроструктура, механические свойства.
