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2014 Vol. 32 No. 3
Published: 2014-06-15
Test and Research
Measuring Technology
Defect Analysis
Subject Discussion
Test and Research
1
LI Feng-yan, WANG Zhi-gang, WU Gui-lin, PAN Hui-jun
Microstructure and Property Control of Small Rolling Bars of GH698 Alloy
The problem of unqualified tensile property of small rolling bars of GH698 alloy (≤Φ20 mm) at 750 ℃ was deeply investigated. The results show that for Φ180 mm ingots melted with VIM+VAR, Mg content is controlled between 0.004% and 0.008%; the rolling deformation is controlled between 50% and 80%, and heating temperature is controlled between 1 140~1 180 ℃, the alloy can get complete recrystallized grains of grade 2-6 after standard heat treatment, and the elevated temperature tensile property of the samples passes the initial test.
2014 Vol. 32 (3): 1-3 [
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LU Jun-hui,, WANG Xiao-chun, LIU Jia-qi, ZHANG Cheng-wu,QIU Sheng-tao, PIAO Feng-yun
Analysis of Corrosion Resistance About High Strength Q450NQR1 Steel for Railway Truck
In order to investigate the corrosion resistantance of Q450NQR1 developed steel, alternative immersion test and atmospheric exposure test were carried out in laboratory and Zhoushan, respectively. The results show that along with the corrosion time, the corrosion rate of Q450NQR1 decreases 1/3 compared with Q345B, and the rust layer of Q450NQR1 is stable. In atmospheric exposure test, when corrosion is beginning, the corrosion rate of Q450NQR1 was slightly higher than that of Q345B, but when the rust layer become stable on the surface, its corrosion resistantance appears.
2014 Vol. 32 (3): 4-8 [
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ZHOU Chao, , HUI Wei-jun , WANG Mao-qiu, WANG Lei
Effect of Cleanliness on Ductile-Brittle Transition of Medium Carbon Low-Alloy Steels
The effect of cleanliness on the ductile-brittle transition of 38CrMoAl steel was studied by optical microscopy, scanning electron microscopy and series impact test. The results show that for the low purity of electric furnace steel and the high purity of double vacuum steel, the ductile-brittle transition temperature is both –60 °C. Nevertheless, in the entire scope of series impact test, toughness of DV (double vacuum) specimens is higher than that of EF (electric furnace) specimens. For the upper platform of ductile-brittle transition, the toughness of DV specimens is about 25 J higher than that of EF specimens, and with decreasing temperature, the gap is shrunk. Between the upper platform and the lower platform, the former is about 5–10 J higher than the latter. In the scope of the lower platform, the gap become less and less. The lower S, P elements contents and the less amounts of MnS and AlN are the main reason for that the toughness of DV steel is higher than that of EF steel.
2014 Vol. 32 (3): 9-13 [
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14
JIANG Sui-he, MAO Wei-min,, YANG Ping, YE Feng
D03 Ordering of Fe-6.5Si Alloy and Its Effect on Magnetic Properties
When direct comparison method by X-ray diffraction was used to characterize the D03 ordering reaction of Fe–6.5%Si alloy, diffraction intensity is affected by crystallography texture and overlapping of a great many diffraction peaks, which make it difficult to quantitatively analyze D03 ordering. {111} characteristic peak of D03 and overlapping peaks including {444} peak of D03 and {222} peak of A2 and B2 were selected to make comparison. Because the two diffraction planes are both {111} crystal plane on the basis of cubic structure, combined with analysis on characteristics of order transformation, the effect of texture can be avoided by this method. Ratio of the two peaks is the product of volume fraction of D03 and parameter indicating its ordering degree of the next nearest neighbor position. The D03 ordering reaction in the process of aging was characterized by this method, and the results show that metastable D03 ordering takes place after annealing and air cooling; B2 ordering and phase separation with increased degree of D03 ordering happened in the process of aging. It can be seen through analysis that, magnetic properties of Fe-6.5%Si alloy are affected by volume fraction of B2 and D03, ordering level and microstructure of two phases.
2014 Vol. 32 (3): 14-19 [
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Measuring Technology
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XUE Fei, LIU Jun-liang
Application of FIB Technique on the Surface Failure Analysis of Pre-Coating Nickel-Steel Cans
FIB technique was applied to reveal the cross sections of pre-coating-nickel steel cans, combined with scanning electron microscopy and X-ray diffraction methods. The results indicated that single-beam FIB system could be an important quasi-situ characterization technique. It is sensitive to the contrast of elemental, grain deformation and orientation, provided more evidence of the defect developing during the forming process.
2014 Vol. 32 (3): 20-24 [
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ZHOU Ji-lei, WANG Yan-feng
Two Methods for Measuring Gravitational Acceleration
Simple pendulum and free fall experimental instrument are used for measuring the acceleration of gravity. In the simple pendulum experiment, the origin and establishing conditions of cycle formula are stated systematically. In the free fall experiment, Timing method by two optical switch is used and the result is satisfactory. The results of the two different experiments validate each other very well.
2014 Vol. 32 (3): 25-27 [
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Defect Analysis
28
YANG Yong
Analysis on Tensile Fracture of HRB400 Rebar Welding Joint
By means of optical microscopy and scanning electron microscopy (SEM) the tensile fracture of HRB400 rebar after welding joint was analysed. Experimental results showed that the partially unwelded joint is the main reason of tensile fracture. Through strictly conducting welding process, eliminating or reducing gap part, the tensile fracture of HRB400 rebar joint could be effectively prevented.
2014 Vol. 32 (3): 28-31 [
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32
YUE Hua
Analysis on Yield Strength Disqualification of Q390E H-Beam Steel
The causes of unqualified strength of Q390E were researched. According to technology contrast and samples testing, it was found that the rolling and high finishing rolling temperature increased the steel internal grains size and decreased the steel strength. The high final cooling temperature was the main reason for less dislocation and vacancy in the matrix. It was not beneficial for the refinement of microstructure. It was also the main reason for unqualified strength of the steel.
2014 Vol. 32 (3): 32-34 [
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JIANG He, YANG Guo-bin, ZHANG Xian-feng, MA Fang-wu, FENG Qing-feng
Failure Analysis of Automotive Front Beam Under Crash Condition
There are two typical cases of front beam crash test: in one case, there is serious crooking after heavy crash, but no cracking; in the other one, there is cracking with slight crooking after slower crash. By failure analysis, such as visual check, scan electron microscope analysis, elongation measurement, mechanics deduction, material examination, metallographic inspection, the root causes of rupture of front beam are revealed.
2014 Vol. 32 (3): 35-40 [
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41
AN Lei, SHEN Lin
Analysis and Repair of Cracking of Nitrogen Storage Tank
The large number of cracks in the head butt welds were found when the first comprehensive inspection was ma-de on a company’s nitrogen storage 16MnR tank. The cause of this tank cracking was analyzed from the aspects of material, manufacturing, welding quality and so on. The results showed that hardening microstructure occurred at welding joint due to the improper control of welding quality. At the same time, large residual stress of welded joints was formed due to the existence of hydrogen diffusion, eventually, leading to the cold cracking. In view of the above problems, the repair process for this container was put forward, which can guarantee the safe operation of the container.
2014 Vol. 32 (3): 41-45 [
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ZHAO Ya-juan, TAO Tao, TIAN Li
Fracture Analysis on Weld of 23MnNiMoCr54 Steel Chain
23MnNiMoCr54 chain steel fractured at the weld joints in using process, the fracture phenomenon was analyzed in detail. By using spectrometer, oxygen nitrogen analyzer, scanning electron microscope and electron probe instrument, the samples were observed. The results show that the chemical composition, morphology at low magnifications, hardness can meet the national standard requirements, the reason for fracture at weld seam is that the foreign Cu leads to weakness of grain boundaries, and the grain boundary strength decrease sharply, thus fracture happens. So the welding process should be strictly controlled to improve the quality of weld seam.
2014 Vol. 32 (3): 46-49 [
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YU Zhao-bin, ZHONG Zhen-qian, ZHAO Yun-geng, SONG Jian-fei, WEI Zhong-kai
Analysis of Six Hexagon Head Bolt Fracture
A broken bolt was analyzed by macro analysis, chemical composition analysis, mechanical properties testing, fracture analysis, metallographic analysis and hardness testing, the results show that the bolt is unidirectional bending fatigue fracture at surface of thread boot. It is mix fracture of transcrystalline and a few intergranular rupture in initiation zone. In extension zone it is transcrystalline fatigue fracture. The bolt splitting process is influenced by the bending fatigue stress and hydrogen, the bending stress is slight when the bolt broken. The main reasons for bolt fatigue rupture are higher remain H after zinc plating and vibration in working process.
2014 Vol. 32 (3): 50-53 [
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Subject Discussion
54
PENG Wen-jie, YU Li, CHEN Yi-ming, ZHANG Yan-wen
Application and Research of Ultrasonic Fatigue Testing Technology
Characteristic and application of ultrasonic fatigue testing technology, as well as the difference of ultrasonic fatigue testing between the conventional fatigue testing are illuminated. The main problems, i.e. the thermal effect and frequency effect due to the high frequency is briefly reviewed and discussed.
2014 Vol. 32 (3): 54-58 [
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ZHANG Zhi-wei
Establishment Ideas of Automatic Mechanical Laboratory
Based on the development status of testing equipment and information system in mechanical laboratory，the tentative idea for establishing a automatic mechanical laboratory was put forward. Around the development of test software and management systems in laboratory, applied summaries were provided for future lab construction by combining with test mode, test equipment, sample identification, sample transfer and practical application in TISCO technology center.
2014 Vol. 32 (3): 59-61 [
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