1-10احمد وسمير وحسام Al-Khwarizmi Engineering Journal,Vol. 13, No. 1, P.P. 1 The Effects of Long-Term Operation Material Properties of Ahmed Naif Al-Khazraji Husam Ahmed Al *,**,*** Department of *Email: ** Email: *** Email: (Received 3 August https://doi.org/10.22153/kej.2017.11.00 Abstract Changes in mechanical properties of material as a result of service in different conditions can be provided by mechanical testing to assist the estimation of current internal situation of these materials, or the degree of deterioration may exist in furnaces serviced at high temperature and exceed their design life. Because of the rarity works on austenitic stainless steel material type AISI 321H, in this work, ultimate tensile strength, yield strength, elongation, hardness, and absorbed energy by impact are Samples of tubes are extracted from furnace belong to used to make comparisons between these properties. temperature increases; the trend of properties decreasing for the samples of un used material. The trend of stress-strain curve will not change due to elevated temperature exposure for long time of service, except the yield strength will be higher in this diagram. The yield strength increased under these conditions, but the ability of material which is elongated will respectively when the material is aged for long time under effect of Keywords: Hardness, Impact, Mechanical Properties Tube Furnace. 1. Introduction Austenitic stainless steels are widely used in engineering applications; these types of alloy selected to serve at high temperature due to high tensile strength and good creep resistance Furnaces in reforming units are the core of these units provided by heat to produce hydrogen from hydrocarbons. The nominal life design for furnaces is 100000hr on the basis of standard 530[1]. Assessment of damage in these furnaces is an important factor in determining their remaining safe life. Components in service at elevated temperatures for long term can fail due to excessive creep deformation or cracking. Khwarizmi Engineering Journal,Vol. 13, No. 1, P.P. 1- 10 (2017) Term Operation and High Temperature of Austenitic Stainless Steel Type 321H Khazraji* Samir Ali Amin** Husam Ahmed Al-Warmizyari*** Department of Mechanical Engineering/ University of Technology Email:Dr_ahmed53@yahoo.com Email: alrabiee2002@yahoo.com Email: husamahmed75@yahoo.com August 2016; accepted 2 November 2016) https://doi.org/10.22153/kej.2017.11.005 Changes in mechanical properties of material as a result of service in different conditions can be provided by mechanical testing to assist the estimation of current internal situation of these materials, or the degree of deterioration s serviced at high temperature and exceed their design life. Because of the rarity works on austenitic stainless steel material type AISI 321H, in this work, ultimate tensile strength, yield strength, elongation, evaluated based on experimental data obtained from mechanical testing. Samples of tubes are extracted from furnace belong to hydrotreaterunit, also samples from un-used tube material are used to make comparisons between these properties. Tensile properties of stainless steel (AISI 321H) were temperature increases; the trend of properties decreasing for the samples of un-used tube material is the same for the ex strain curve will not change due to elevated temperature exposure for long time of will be higher in this diagram. The yield strength increased under these conditions, but elongated will decrease. Hardness and absorbed energy increased by 11.28 and 14% l is aged for long time under effect of high temperature accompanied with creep effect Mechanical Properties, Stainless Steel 321H, Mechanical Properties, Austenitic stainless steels are widely used in of alloys are due to their high tensile strength and good creep resistance. are the core of these produce hydrogen from design for such standard API ssessment of damage in these furnaces is an important factor in determining their remaining at elevated can fail due to excessive creep deformation or cracking. Therefore, improvement of material strength other properties for these components is the key to resist such failures. The assessment of properties, such as hardness, impact energy tensile strength near the end of design life or beyond that is vital to provide a safe working life for the unit and prevent a catastrophic failure Hardness measurements are the best ways to detect if there are metallurgical changes Recent developments in the technique have shown that it can be used in a predictive sense to estimate the remnant life based approach is used to evaluate strength of superheater tubes of boiler impact test also has been used in testing of steel Al-Khwarizmi Engineering Journal Temperature on Type 321H Changes in mechanical properties of material as a result of service in different conditions can be provided by mechanical testing to assist the estimation of current internal situation of these materials, or the degree of deterioration s serviced at high temperature and exceed their design life. Because of the rarity works on austenitic stainless steel material type AISI 321H, in this work, ultimate tensile strength, yield strength, elongation, evaluated based on experimental data obtained from mechanical testing. used tube material are were decreased as used tube material is the same for the ex- strain curve will not change due to elevated temperature exposure for long time of will be higher in this diagram. The yield strength increased under these conditions, but by 11.28 and 14% accompanied with creep effect. Tensile Strength, Therefore, improvement of material strength and for these components is the key to e assessment of material impact energy, and near the end of design life or provide a safe working life prevent a catastrophic failure. Hardness measurements are the best ways to detect if there are metallurgical changes [2,3]. ecent developments in the technique of hardness shown that it can be used in a predictive remnant life [4], a hardness based approach is used to evaluate the creep of boilers [5]. The n testing of steel PDF created with pdfFactory trial version www.pdffactory.com https://doi.org/10.22153/kej.2017.11.00 mailto:Dr_ahmed53@yahoo.com mailto:alrabiee2002@yahoo.com mailto:husamahmed75@yahoo.com https://doi.org/10.22153/kej.2017.11.00 http://www.pdffactory.com http://www.pdffactory.com Ahmed Naif Al-Khazraji Al-Khwarizmi Engineering Journal, Vol. 13, No. 2, P.P. 1- 10 (2017) 2 products which is related to the behavior of metal, and in some cases, making the tests at properly chosen temperatures other than room temperature [6]. The remaining life of furnaces tubes can be predicted based on fracture toughness and mechanical properties, also a suggestion to pay more attention to avoid the excessive impact during starting up and shutdowns because of the decrease in material ductility [7]. A comparison of both mechanical properties at different temperatures and the roles of these properties to resist creep [8], can be useful to give good indications for the degree of internal damage due to prolonged exposure to temperature, when these comparisons are made between the un-used and ex-used material. Austenitic Stainless steel AISI 321 is stabilized by titanium addition. This grade of steel is used in engineering applications under high temperature, because of its high strength and good creep resistance. While, stainless steel AISI 321H is modified to stainless steel AISI 321 with higher carbon contains, it was developed to enhance the creep resistance and the higher strength at temperature above 537oC. Many researches cover the stainless steel material type 321 from different viewpoints [9, 10, 11, 12, 13, 14, 15], on the other hand, there is a gap in the published researches about the modified stainless steel material type 321H. Because of the rare work on austenitic stainless steel material type 321H, the present work investigates a furnace tube (O.D. 141.3 mm, thickness 6.55 mm) made from this type of steel and served in complex reformer/naphtha hydrotreater unit for more than 290000hr, the design tube wall temperature is 570oC. This investigation uses the mechanical properties, such as hardness, impact energy, yield strength, and tensile strength at different temperatures to make a comparison between an ex-used tube with un- used one of the same dimensions and material. Tensile tests were done at four different temperatures 25oC, 300oC, 500oC, and 700oC, while impact tests were conducted at room temperature and at the maximum service temperature 466oC. 2. Experimentation 2.1. Chemical Analysis of Tube Samples In this work, two different ages of austenitic stainless steel samples were investigated, namely un-used SS321H and ex-used SS321H. The ex- used samples are belongs to a Stripper Reboiler furnace / Naphtha Hydrotreater Unit, these samples are made according to ASTM standard A-312TP321H. Their compositions with the limitations for the elements percentage according to the standard are given in table 1. 2.2. Mechanical Tests Macro-hardness according to Vickers scale were done using a device (Nemesis 9000) with a load of 10 Kgf, the tests are supported by the relevant standard ISO-6507-1[17]. Groups of five hardness measurements were taken at room temperature for each sample (un-used material and ex-used material). Samples of these tubes were cut and prepared according to the requirement of adopted standard. Any individual of hardness measurement made in the lab will lack perfect precision that often leads to take multiple measurements. So, no one of these measurements is likely to be more precise than any other, this group of values will cluster about the true value to be measured. This distribution of data values is often represented by showing a single data point, representing the mean value of the data, and error bars to represent the overall distribution of the data. The standard error for hardness measurement was calculated (2.5008, 0.8792) for samples of the materials un-used and ex-used, respectively. Standard charpy v-notch impact specimens were prepared according to the American Standard ASTM E23[6]. Due to tube thickness restriction, specimens with sub size dimensions were prepared, as shown in figure 1. All impact specimens were tested using a universal impact test machine (Brooks – Model IT3U). The impact tests for specimens of each type of material were performed in two different temperatures, at room temperature and at furnace service temperature (maximum wall temperature) 466oC. PDF created with pdfFactory trial version www.pdffactory.com http://www.pdffactory.com http://www.pdffactory.com Ahmed Naif Al-Khazraji Al-Khwarizmi Engineering Journal, Vol. 13, No. 2, P.P. 1- 10 (2017) 3 Table 1, Composition of material tubes samples. Materials C Si Mn Ni Cr Ti P S Fe A-312TP321H (standard)[16] 0.04- 0.1 1.0 A 2.0 A 9 –12 17–19 H 0.045A 0.03A Rem. Un-Used Tube Samples 0.04 0.49 0.61 9.24 15.87 0.29 0.033 0.004 Rem. Ex-Used Tube Samples 0.061 0.3 1.66 11.34 15.94 0.43 0.016 0.016 Rem. A:Maximum, H:The Titanium content shall be not less than four times the carbon content and not more than 0.60%. Table 2, Mechanical properties for austenitic stainless steel 321H at different test temperatures. Temperature (oC) 25 300 500 700 Specimen Type Un Used Ex Used Un Used Ex Used Un Used Ex Used Un Used Ex Used Yield Strength0.2% (MPa) 190 219 135 191 109 182 93 153 Tensile Strength (MPa) 606 584 401 417 381 376 237 242 Elongation32% (%) 69 49 40 32 37 28 56 55.6 Fig. 1. Specimen's classification for Impact test. Changes in strength between the un-used material and the ex-used one at a temperature range (from room temperature up to 700oC) can be found by performing a uniaxial tensile test using tensile machine "Shimadzu AG-25TC". Flat dog bone type specimens with thickness 3mm for this purpose were prepared according to the standard, see figure 2. Different test machine speeds were used to distinguish between the elastic and plastic zones, also these values are different either at room temperature tensile tests or for hot tensile tests. The values of yield strength (taken at 0.2% engineering strain), tensile strength, and elongation were recorded for each test temperature for both un-used material and ex- used material of austenitic stainless steel 321H, see table 2. Fig. 2. Dimensions of Flat Specimen for the Uniaxial Tensile Test. 3. Results and Discussion 3.1. Hardness Behavior As known, the easy way to sense that there is a metallurgical change happened in the metals due to temperature exposure is the hardness PDF created with pdfFactory trial version www.pdffactory.com http://www.pdffactory.com http://www.pdffactory.com Ahmed Naif Al-Khazraji Al-Khwarizmi Engineering Journal, Vol. 13, No. 2, P.P. 1- 10 (2017) 4 measurement, but the behavior of hardness depends on steel alloy, and its carbide type precipitated. As example, the hardness of material A-213T91 decreases during creep at elevated temperature [3]. For austenitic stainless steel type 321H as seen in figure 3, the hardness increased about (11.27%) compared to the un-used material, that raising happen during the material service under operating temperature about 466oC for this long time. It is thought that this increase is related the fine titanium carbide TiC precipitated in grains at the temperature range of furnace operation, where the fine TiC precipitation increases the hardness of austenitic stainless steel type 321 up to temperature 850oC, while the coarsening of TiC precipitation softens this type of stainless steel more than 850oC [9]. Fig. 3. Comparison between hardness of un-used and ex-used tubes of stainless steel material A- 312TP321H. 3.2. Impact Energy A comparison between the results of impact test at room temperature and at 466oC for specimen dimension (10x5x55 mm) can be seen in figures 4 (a) and 4(b) for both un-used and ex- used stainless steel 321H material. The impact energy value is directly related to the cross- sectional area of the specimens, and to make a double check for the accuracy of the measurements, another sub-size dimension (5x5x55 mm) for the specimens with 50% reduction in specimen cross section was used, see Figure 4 (c). a. Impact test at room temperature for specimens with dimensions 10x5x55 mm b. Impact test at temperature 466 oC for specimens with dimensions 10x5x55 mm c. Impact test at room temperature for specimens with dimensions 5x5x55 mm Fig. 4 Impact energy comparison between un-used and ex-used stainless steel tube samples (SA-312TP321H) PDF created with pdfFactory trial version www.pdffactory.com http://www.pdffactory.com http://www.pdffactory.com Ahmed Naif Al-Khazraji Al-Khwarizmi Engineering Journal, Vol. 13, No. 2, P.P. 1- 10 (2017) 5 When stainless steel type 321H is aged for long time under the effect of elevated temperature exposure accompanied with creep effect in general, it shows a rising in bearing energy before break can happen, this can be measured either under room temperature impact test or at elevated temperature test, see figures 4(a) and 4(b), also the reduced specimen size (5x5x55 mm) depicts similar behavior as seen in figure 4(c). This energy increased by a percentage 14% in figures 4(a) and 4(b), as well by about 10% in figure 4(c), this is most likely due to the thermal effect occurred during the material service at the furnace operation temperature. The temperature effect on the amount of the impact energy was also examined for the two types of stainless steel type 321H, the un-used and ex-used material, as shown in figure 5. This figure shows decreases by a percentage about 10% for each type of this material, this is most probably ascribed to the precipitation hardening effect by chromium carbides formation within the structure. This means that this decrease is due to thermal influence only, indicating that operating at this temperature for long period of time leads to increase this absorbed energy. Fig. 5. Relation between impact energy and test temperature for austenitic stainless steel 321H. 3.3. Tensile Properties The results of uniaxial tensile tests for austenitic stainless steel type 321H under different test temperatures (25oC, 300oC, 500oC, 700oC) were drawn on the same stress-strain diagram for comparison, the resulted diagram for the un-used material can be seen in figure 6, while figure 7 shows the resulted diagram for the ex-used material. The plastic deformation seems to fade with increased temperature, the maximum stresses decrease with increased temperature for the two types of samples as expected. Tensile properties of SS321H, such as 0.2% offsite of yield and tensile strength, generally decrease as temperature increases, as seen in figure 8. The trend of this decreasing in properties for un-used material is the same for the ex-used material. This reduction is related to the formation of carbides at grain boundaries. Fig. 6. Stress-strain curve under different temperatures for un-used austenitic stainless steel 321H. Fig. 7. Stress-strain curve under different temperatures for ex-used stainless steel 321H. Fig. 8. Yield and tensile strength versus temperature for austenitic stainless steel 321H. PDF created with pdfFactory trial version www.pdffactory.com http://www.pdffactory.com http://www.pdffactory.com Ahmed Naif Al-Khazraji Al-Khwarizmi Engineering Journal, Vol. 13, No. 2, P.P. 1- 10 (2017) 6 Comparisons were made between the results of uniaxial tensile tests represented by stress-strain curves as shown in figures (9 to 12) for different test temperatures, each diagram compares the tensile properties of stainless steel 321H at specific temperature between the un-used and ex- used samples. In general, stainless steel 321H lost its ability to elongate, which represents a reflection to the deterioration happened in this material due to the exposure to elevated temperature (466oC) for long time of service. On the contrary, the yield strength 0.2% offset of stainless steel 321H enhanced at each test temperature as seen in table 2, while the curves for each test temperature are in the same trend between the ex-used and un-used stainless steel 321H, but the curves for the ex-used samples are higher than the un-used ones. The ultimate tensile stress of stainless steel 321H is changed after its long service life in this case study for stripper re-boiler furnace under maximum tube wall temperature about 466oC, this change is fluctuating, it is varying in a manner depends on the test temperature, where it is decreased at temperatures 25 and 500oC and increased at temperatures 300oC and 700oC, as shown in table 2 and in figures (9-12). So that, it is not accredited parameter to judge that the deterioration or damage due to high temperature exposure does or doesn't exist in the structure of the material. The stress-strain curves in figures 6 and 7 reveal signs of dynamic strain aging effect for the SS321H material; this is due to alloy content, test temperature, and past service life. The common feature of dynamic strain aging is that it increases the ultimate tensile strength (UTS) and causes strengthening in a specific temperature range which depends on the strain rate as shown in table 2 for this material which is aged for long life time; this is repeated for the uniaxial tensile tests at 500oC and at 700oC, figures 10 and 12. The level of strengthening depends on the aging time and on the aging temperature. A typical characteristic of dynamic strain aging is the formation of serrated yielding. This is often called the Portevin- LeChatelier (PLC) effect. Different serration types of stress-strain curves for the austenitic stainless steel 321H are marked on the curves of figures (9-11). The most common serration types were A, B, and D appeared on the curves up to test temperature 500oC, while at the test temperature 700oC, they didn't appear, because the material at this temperature is near the recovery and recrystallization temperatures which will decrease the dynamic strain aging due to the extermination of dislocations. Type A is considered as locking serrations, it is abrupt rise and then drop to a stress level below the general level. Type B has an irregular movement and is characterize by small oscillations about the general level of the curve. Type D is characterized by plateaus on the curve, it can also appear mixed with the type B [18]. Changes in mechanical properties of material as a result of service in different conditions from load, temperature, environment, etc., can be provided easily if we adopt usual examination techniques such uniaxial tensile tests to have a data or figures aid the estimation of the current internal situation of these materials, or the degree of deterioration may exist. 4. Conclusions The following results of this work can be used for the tubes of furnaces operated at high temperatures for long time as a supportive technique to give a good indication about the remaining life estimation in short time, which could be used as a routine inspection activity during the period of scheduled shutdowns, especially when the operation life is near or overcome the design life. (i) Changes in mechanical properties of material as a result of service in different conditions from load, temperature, environment, etc., can be provided easily if we adopt available examination techniques to have a data or figures assist to estimate the current internal situation of these materials, or the degree of deterioration may exist. (ii) Hardness of austenitic stainless steel type 321H increased about (11.28%) during service for long time under temperature about 466oC, this increase is related to chromium carbide Cr23C6 and the fine titanium carbide TiC precipitated in grains at the temperature range of service. (iii) The absorbed energy due to impact by austenitic stainless steel 321H increased about (14%) when the material is aged for long time under the effect of elevated temperature exposure accompanied with creep effect, this is most likely due to thermal effect happened during material service at the furnace operation temperature. Also, this behavior can be recorded by the impact test with different specimens’ dimensions. (iv) The absorbed energy due to impact by austenitic stainless steel 321H decreased about (10%) when the temperature increased up to 466oC, this behavior can be recorded if the sample PDF created with pdfFactory trial version www.pdffactory.com http://www.pdffactory.com http://www.pdffactory.com Ahmed Naif Al-Khazraji Al-Khwarizmi Engineering Journal, Vol. 13, No. 2, P.P. 1- 10 (2017) 7 for impact test is taken from un-used material or ex-used material; this is most probably ascribed to the precipitation hardening effect by chromium carbides formation within the structure. (v) The trend of stress-strain curve of austenitic stainless steel 321H will not change due to the exposure to elevated temperature (466oC) for long time of service and/or creep effect takes place, but the curves will be higher. The yield strength 0.2% offset increased under these conditions, but the ability of material to be elongated under the action of axial load will decrease. The ultimate tensile stress is fluctuating in these conditions and depends on the service temperature. (vi) Tensile properties of austenitic stainless steel 321H decrease as the temperature increases, the trend of this decreasing in properties for un-used material is the same for the ex-used material. Fig. 9 Stress-strain curve at room temperature for un-used and ex-used stainless steel 321H. Fig. 10. Stress-strain curve at 300oC temperature for un-used and ex-used stainless steel 321H. Fig. 11 Stress-strain curve at 500oC temperature for un-used and ex-used stainless steel 321H. PDF created with pdfFactory trial version www.pdffactory.com http://www.pdffactory.com http://www.pdffactory.com Ahmed Naif Al-Khazraji Al-Khwarizmi Engineering Journal, Vol. 13, No. 2, P.P. 1- 10 (2017) 8 Fig. 12 Stress-strain curve at 700oC temperature for un-used and ex-used stainless steel 321H. 5. Acknowledgements The authors gratefully acknowledged Midland Refineries Company-Daura Refinery (MRC) for providing the needed samples for experiments and for the support for this work. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. 6. References [1] API 530 (2004) Calculation of Heater Tube Thickness in Petroleum Refineries, Fifth Edition, American Petroleum Institute. [2] Fernando Vicente (2013) Defining The Optimal Life Management Strategy for Gas Heater Tubes., Inspectioneering Journal,Vol. 19, Issue 3. [3] Takao Endo; Fujimitsu Masuyama; and Kyu- Seop Park (2003) Change in Vickers Hardness and Substructure during Creep of a Mod.9Cr– 1Mo Steel. Materials Transactions, Vol. 44, No. 2, pp. 239 - 246. [4] David J. Allen and Simon T. Fenton (2007) A Hardness-Based Creep Rupture Model for New And Service Aged P91 Steel. International Conference on Life Management and Maintenance for Power Plants (BALTICA VII), Helsinki, pp.156–170. [5] Shimpei Fujibayashi; Yuuji Ishikawa; and Yoshiaki Arakawa (2006) Hardness Based Creep Life Prediction for 2.25Cr–1Mo Superheater Tubes in a Boiler. ISIJ International, Vol. 46, No. 2, pp. 325–334. [6] ASTM E23 (2002) Standard Test Methods for Notched Bar Impact Testing of Metallic Materials. ASTM International. [7] Yong Jiang; Jianming Gong; Zhongzheng Zhang; Ruisong Zhu; and Dongxing Xi (2008) Remaining Life and Fracture Evaluation of Incoloy800H Furnace Tubes Serviced at High Temperature For 100000 h. Journal of Pressure Equipment and System 6, pp. 52-55. [8] Josip Brnic and Marino Brcic (2015) Comparison of Mechanical Properties and Resistance to Creep of 20MnCr5 Steel and X10CrAlSi25 Steel. Procedia Engineering 100, pp. 84 – 89. [9] V. Moura; Aline Yae Kina; Sérgio Souto; L. D. Lima; and Fernando B. Mainier (2008) Influence of stabilization heat treatments on microstructure, hardness and intergranular corrosion resistance of the AISI 321 stainless steel. Journal of Materials Science, Vol. 43, Issue 2, pp. 536-540. [10] M. Anderson; F. Bridier; J. Gholipour; M. Jahazi; P. Wanjara; P. Bocher; and J. Savoie (in revision from January 19 2016) Mechanical and Metallurgical Evolution of Stainless Steel 321 in a Multi-step Forming Process. Journal of Materials Engineering and Performance. [11] Mehdi Haj; Hojjatollah Mansouri; Reza Vafaei1; Golam Reza Ebrahimi; and Ali Kanani1 (2013) Hot compression deformation behavior of AISI 321 austenitic stainless steel. International Journal of Minerals, Metallurgy and Materials, Vol. 20, No. 6, Page 529. [12] J. G. González-Rodríguez; A. Luna-Ramírez; and A. Martínez-Villafañe (1999) Effect of hot corrosion on the creep properties of types 321 and 347 stainless steels. Journal of Materials Engineering and Performance, Vol. 8, Issue 1, pp. 91-97. [13] K. Kurihara; H. Kokawa; S. Sato; Y. S. Sato; H. T. Fujii; and M. Kawai (2011) Grain boundary engineering of titanium-stabilized 321 austenitic stainless steel. Journal of PDF created with pdfFactory trial version www.pdffactory.com http://www.pdffactory.com http://www.pdffactory.com Ahmed Naif Al-Khazraji Al-Khwarizmi Engineering Journal, Vol. 13, No. 2, P.P. 1- 10 (2017) 9 Materials Science, Vol. 46, Issue 12 , pp. 4270-4275. [14] Regina C. De Sousa; Jose C. C. Filho; Auro A. Tanaka; Ayana C. S. De Oliveira; and Wilman E. I. Ferreira (2006) Effects of solution heat treatment on grain growth and degree of sensitization of AISI 321 austenitic stainless steel. Journal of Materials Science, Vol. 41, Issue 8 , pp. 2381-2386. [15] P. Rozenak and D. Eliezer (1989) Behavior of Sensitized AISI Types 321 and 347 Austenitic Stainless Steels in Hydrogen. Metallurgical Transactions A, Vol. 20a, pp. 2187-2190. [16] Designation: A 312/A 312M (2010) Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes. ASTM International. [17] ISO 6507-1 (2005) Metallic materials - Vickers hardness test, Part 1: Test method. International Organization for Standardization. [18] Mattias Calmunger (2011) Effect of Temperature on Mechanical Response of Austenitic Materials, Linköping University, Sweden. PDF created with pdfFactory trial version www.pdffactory.com http://www.pdffactory.com http://www.pdffactory.com )2017( 1-12، صفحة 2، العدد13دجلة الخوارزمي الھندسیة المجلماحمد نایف الخزرجي 10 تأثیر العمر التشغیلي لفترات زمنیة طویلة على الخصائص لسبیكة الفوالذ المقاوم للصدأ والتي تعمل بدرجات حرارة عالیة 321Hاالوستنایتي من النوع **سمیر علي امین *احمد نایف الخزرجي ***حسام احمد الورمزیاري التكنولوجیةالجامعة /المیكانیكیةقسم الھندسة ***، **، * Dr_ahmed53@yahoo.com : االلكتروني البرید* alrabiee2002@yahoo.com البرید االلكتروني: ** husamahmed75@yahoo.com : االلكتروني البرید*** الخالصة االختبارات المیكانیكیة، عن طریقخدمتھا یمكن الحصول علیھا أثناءفي التغیرات الحاصلة في الخصائص المیكانیكیة للمواد نتیجة للظروف المختلفة األفران أنابیببحیث یمكن االستعانة بالتغیرات الحاصلة للخصائص في تقدیر حالة ھذه المواد ودرجة الضرر المتولدة فیھا وكمثال للجانب التطبیقیة الفوالذ المقاوم للصدأ االوستنایتي ولندرة البحوث التي تستخدم سبیكة . عمریة تتجاوز العمر التصمیمي لھا لمدةرجات حراریة عالیة ودالحراریة التي تعمل ب 321H الصدمة باالعتماد على نتائج أثناءمتانة الشد، االستطالة، الصالدة، والطاقة الممتصة ھذه الخصائص مثل متانة الخضوع، فقد تم دراسة دراستھافي للحصول على فرن حراري عائد لوحدة ھدرجة النفثا في مصفى الدورة أنابیبنماذج من ھذه السبیكة مستخدمة في صناعة فقد تم تقطیع . االختبارات العملیة اختبار الشد لحالتي النماذج الجدیدة بزیادة درجة حرارة. المقارنة بین النتائج ألغراضنفسھا دراسة نماذج جدیدة من نوع السبیكة فضال عن، عینات اختباریة االختبار تصرف متماثل لمنحني نفسھا حرارة الدرجة بوظھرت عینات حالتي المعدن المستخدم ، وقد اوالمستخدمة سابقا اظھرت نقصان في متانة الشد صان في القدرة على االستطالة نتیجة التحمیل في حالة العینات ذات العمر قنمع زیادة في متانة الخضوع لحالة المعدن المستخدم سابقة، مع االنفعال - االجھاد و %) ١١,٢٨(بمقدار الصالدة والطاقة الممتصة من قبل المعدن قبل حدوث الكسر وحصول زیادة في كل من التشغیلي الطویل عنھا في العینات الجدیدة، .یل مقارنتا مع العینات الجدیدةالة العینات ذات العمر التشغیلي الطوعلى التوالي لح%) ١٤( PDF created with pdfFactory trial version www.pdffactory.com mailto:Dr_ahmed53@yahoo.com mailto:alrabiee2002@yahoo.com mailto:husamahmed75@yahoo.com http://www.pdffactory.com http://www.pdffactory.com