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2014 Vol. 32 No. 4
Published: 2014-08-15
Test and Research
Measuring Technology
Defect Analysis
Subject Discussion
Test and Research
6
YUAN Da, WANG Bing-xing, WANG Zhao-dong, WU Di
Technology of Material Tracking for Ultra-Fast Cooling System
In order to improve the accuracy and instantaneity of ultra fast cooling material tracking system, the speed of pre-straightening machine replaces the speed of roll table, effectively eliminates relative displacement between plate and roll table. A device for position correction in the cooling zone is developed. The problem of position detection device can not be used in the cooling zone is solved. The accuracy of ultra-fast cooling material tracking system is increased effectively by the two methods.
2014 Vol. 32 (4): 6-8 [
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LI Kai, CEN Feng
Effect of Machining on Tensile Properties of Round Bar Metal Samples
Effect of machining on the mechanical properties of round bar metal tensile samples was investigated. According to machining requirements of tensile samples in the national standard, four aspects were discussed, respectively, i.e. dimension deviation, shape deviation, surface roughness and transition arc radius of round rod tensile samples. The tensile strength and the elongation after fracture become smaller as the shape tolerance becomes bigger. When size deviation is positive, the elongation after fracture becomes bigger as the positive size tolerance becomes bigger. But when size deviation is negative, the elongation after fracture becomes smaller as the negative size deviation becomes bigger. As the surface roughness is bigger, the downturn of tensile strength and section shrinkage become more obvious, as the surface roughness becomes smaller, tensile strength and section shrinkage become bigger, and the increase gradually tends to be slow. As the transition arc [R] of round bar tensile samples becomes bigger, upper yield strength increases gradually, but when [R≥0.75 d0], the increase is slower.
2014 Vol. 32 (4): 9-14 [
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CHEN Lei, HU Lei, LIU Bo, LI Xiao-meng, DING Hong-sheng, PAN Li-qing
Study on Magnetic Flux Leakage Effect of Seamless Rail Under Static Tension Test
Based on the metal magnetic memory testing, using static tension to simulate the formation of defects of the seamless rail, a metal magnetic memory diagnostic instrument (EMS-2000) is applied to study the magnetic flux leakage effect of PD3 seamless rail. The normal component of magnetic strength[Hp(y)]and the gradient value [K] on the surface of PD3 seamless rail are tested at different loads under static tension condition. The results show that the magnetic field strength and the gradient value of the specimen change regularly as the load increases. The zero-crossing point of[Hp(y)] and the peak value point of [K] are corresponding to the stress concentration area, and the variation of the amplitude of[Hp(y)]and [K] is related to the degree of stress concentration. The experiments show that the position and level of the stress concentration of seamless rail can be effectively tested by magnetic memory method.
2014 Vol. 32 (4): 15-19 [
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MA Yong-qing , LIANG Yu-fen, ZHANG Xiao-jing
Microstructure and Properties of Weld Joint and Base Materials of Machinery Knives by Hot Rolling-Jointing
The microstructure and properties of weld joint and base materials of machinery knives by hot rolling-jointing were researched. The results show that the metallurgy jointing of the blade steel and knife body already have been completed by hot rolling-jointing and heat treatment. The microstructure of the blade steels is fine and uniform owing to the best heat treatment. The microstructure of Q235 steel knife body is complicated depending on both hot rolling-jointing process and heat treatment process. The shear strength of the weld joint generally is 196-343 MPa and the carbon diffusion layer of the weld joint is very deep, and the key of increasing welding strength is decreasing the impurity and air hole in the weld joint. The analysis based on hot rolling-jointing mechanism discussion show that the raising temperature and increasing press ratio are both advantageous to increase welding strength, but appropriate temperature and rational press ratio are not only the request of excellent microstructure but also the need to debase dissipative hot energy and rolling mill power.
2014 Vol. 32 (4): 20-23 [
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TIAN De-xin, WU Qing-song, ZHU Hong-chuan, LEI Ze-hong
Effect of Holder Force on Limit Drawing Ratio of IF Steel
The deep drawing test on IF steel is carried out under various holder forces. The relationship between limit drawing ratio and holder force is discussed. The mathematical relationship between limit drawing ratio and holder force for IF steel is obtained. This result indicates that the relationship between limit drawing ratio and holder force can be divided into two stages. In the first stage, while the limit drawing ratio increases, the holder force drops sharply; in the second stage, while the limit drawing ratio increases, the holder force gently declines, thus gradually tends to a certain value.
2014 Vol. 32 (4): 24-27 [
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LIU Yi-min
Study on Dynamic Recrystallization Behavior of 310S Austenitic Stainless Steel Under Different Heat Deformation Conditions
The dynamic recrystallization behavior of 310S austenitic stainless steel was analyzed by microstructure observation and micro-hardness test. The hot compression tests of 310S steel were carried out at temperatures ranging from 900 ℃ to 1 150 ℃ and strain rates from 0.1 s–1 to 1 s–1 using a Gleeble-3800 thermal simulator. The results show that the flow stress of 310S steel decreases with increasing deformation temperature. The complete dynamic recrystallization temperature is about 1 000 ℃ at stain rate of 0.1 s–1. When the strain rate reaches 1 s–1, the complete dynamic recrystallization temperature increases sharply to 1 100 ℃, and higher stain rate can significantly refine the recrystalized grains.
2014 Vol. 32 (4): 28-31 [
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Measuring Technology
32
WANG Yong-feng, LIU Tao
Design and Achievement of Tube-End Ultrasonic Flaw Detection System
In order to eliminate the untested area and avoid added artificial detection, a tube-end ultrasonic flaw detection system is designed. The scanning method of this detection system is using roller device drives the steel pipe to spin around and the probe group moves along the axial of the steel pipe. A tube-end UT without blind spot is carried out through inverter drive the steel pipe to spin around and servo motor drive the movable probe group to move back and forth, which are both controlled by PLC. So the quality of the steel pipe and production efficiency are both improved.
2014 Vol. 32 (4): 32-34 [
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Defect Analysis
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ZHANG Kai-guang, TONG Ming-wei, CHEN Yan-tang, LIU Wen-bin
Causes Analysis of the Unqualified Elongation of Q420B Steel
To the problem of unqualified elongation of rolled Q420B steel, the fractography, microstructure and inclusions of the tensile specimens were studied by optical microscopy and scanning electron microscopy. The results showed that lots of pores, serious stratification and band structure existed in the fracture site, and the initiation and growth of the cracks and pores happened at segregated band. Inclusions were concentrated on the fracture site. The inclusions beseparated and extended from matrix interface under tension, which will result in crack at last under tension. So the band structures and inclusions were thought to be the major causes of the unqualified elongation of the plate steel.
2014 Vol. 32 (4): 35-38 [
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WANG Zhao-yang, WANG Zhi-yi, HE Jian-zhe, GONG Wen-xu
Cause Analysis of Cracks on the Surface of P110 Grade Oil Casing
Aiming at the cracks on the surface of P110 grade oil casing, which produced by 27MnCr6,the characteristics and causes of the micro-cracks were analyzed by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and spectrography. The macroscopic characteristics and microscopic morphology of the defect in different processing were elaborated. The analysis results show that the cause of the defects is due to star cracks generated on the surface of billet. By taking some effective technical measures, star cracks on the surface of billet can be eliminated basically, and furthermore, the micro-cracks on the surface of steel pipe can be eliminated. This work plays an important guiding role in improving product quality, reducing scrap quantity and reducing the production cost.
2014 Vol. 32 (4): 39-43 [
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SUN Yi-qiang, WU Chao, LU Xiu-yu, GUI Jiang-bing
Early Failure Analysis of 55SiCr Automobile Suspension Spring
A 55SiCr automobile suspension spring fractured after 5 000 km service. The early failure analysis of 55SiCr automobile suspension spring was carried out by means of scanning electron microscopy and optical microscopy to find the failure reason, verifie the safety of the same batch spring and seek prevention measures. The fatigue curve was found on the surface of the fracture, and the mechanical damage was found at the fatigue source. The results showed that the fracture was fatigue fracture and the fatigue source was the mechanical damage on the inner surface.
2014 Vol. 32 (4): 44-46 [
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LIU Yu-zhang
Studies on the Filiform Spot Stain on the Surface of Cold Rolled Steel Sheet After Annealing by Bell Type Annealing Furnace
The filiform spot stain on the surface of low carbon aluminium-killed cold-rolled steel sheet which heat-treated by bell annealing furnace(BAF) was studied by analyzing microstructure and chemical component. The results showed the surface of the steel sheet without filiform spot stain was uniformly shining and no carbon enrichment. However, the surface of the steel sheet with filiform spot stain was black and taking on island-like and line-like. The abnormal element causing the surface filiform spot stain was graphite. The carbon percentage in certain depth range of surface layer was higher than its substrate.
2014 Vol. 32 (4): 47-50 [
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LIU Hong-lan
Fracture Cause Analysis of Intake Valve of Automobile Engine
Taking the broken intake valve of automobile engine as an example, the chemical composition, hardness, microstructure, nonmetallic inclusions, carbides and fracture morphology were analyzed. The results showed that the reason for intake valve break was class B alumina inclusions, which reduce its using performance. The valve classis breaks when overloaded.
2014 Vol. 32 (4): 51-53 [
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Subject Discussion
54
KANG Lun
Analysis and Treatment of Abnormal Vibration of No. 3 Round Billet Step Cooling Bed in Panzhihua Iron and Steel Group
Stress calculation of step cooling bed for No.3 round billet cooling was carried out in Panzhihua Iron and Steel Group. It was found that the real work load of step cooling bed was 5 times larger than theoretical load. By measuring and comparing the installation size on site, it was found that the basic frame of step cooling bed was deviated. Through correcting the foundation frame of step cooling bed, improving the stability of the structure, avoiding cooling bed excess working and decreasing start acceleration of the step cooling bed, the harmful vibration of the cooling bed was eradicated.
2014 Vol. 32 (4): 54-57 [
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JIANG Zhen-ya, XU Jian-yong, PAN Hui-ying
Quartile Calculation in the Laboratory Proficiency Test
Robust statistical techniques are commonly used to conduct statistical analysis and evaluation on the experimental data. This method involves the calculation of the normalised interquartile range and quartile. There are different calculating models used for quartiles calculation. Different computational models cause different results which affect the laboratory proficiency test to keep impartiality. The four typical quartile calculation models are analyzed. Based on the successful cases of the existing proficiency test activities, model 2 is suitable for applying on the laboratory proficiency test schemes.
2014 Vol. 32 (4): 58-61 [
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