Direct Reading Spectrometer Research Articles

The fracture and perforation failure analysis of downhole tubes

：The downhole tubes were fractured and perforated after 5 years of shut-in due to high water cuts. This study employs a comprehensive array of analytical techniques to investigate the mechanisms behind fractures and perforations. Utilizing non-destructive testing (NDT), direct reading spectrometer, tensile strength testing machine, impact testing machine, optical microscope (OM), macroscopic fracture morphology observation, scanning electron microscope (SEM) and energy spectrum analysis (EDS), and sulfide stress corrosion cracking (SSCC) was studied. The reason for the fracture of the tubing is that under the condition of low pH value, high hydrogen sulfide environment, the tubing is fractured due to stress concentration caused by cracks in the outer thread relief groove. The perforation of the inner tube wall was caused by gradual wall thickness reduction under the influence of H2S, CO2, and Cl−, resulting in fouling and eventual perforation. To prevent tube corrosion during long-term shut-in, it is recommended to inject crude oil or diesel into the well.

Failure analysis and heat treatment process optimization of NOS525 rotary flat binaural hot forging die

A NOS525 steel rotary flat binaural hot forging die frequently failed too early due to collapse and wear in service. In this paper, the rotating planar binaural failure die was taken as the research object. Firstly, the sample design and sample processing of the failure die with different depths and directions were carried out. The material composition, hardness and metallographic structure of the samples were analyzed, and the tensile and impact properties were tested by direct-reading spectrometer, Rockwell hardness tester, optical microscope, scanning electron microscope, MTS testing machine and impact testing machine, etc. Meanwhile, with the help of Deform-HT software and JMatPro software, the coupling simulation of hardness, temperature and structure of the heat treatment of NOS525 steel was realized, and the hardness change of the material after heat treatment was predicted and verified by heat treatment test. The research results show that the composition of the die material is abnormal, especially the excessive P and C elements, at the same time, there is a phenomenon of quenching overheating and insufficient tempering, resulting in insufficient strength, toughness and hardness of the die material, in addition, the die surface is subjected to the cold and hot alternating load, and finally, the die surface collapses and wear too soon, resulting in its failure. Through the combination of heat treatment simulation optimization and test, the optimal heat treatment temperature of NOS525 steel was finally determined, that is, the quenching temperature of 1090℃, the first tempering temperature of 560℃, the second tempering temperature of 600℃, the third tempering temperature of 600℃, so that the mechanical properties of the material have been significantly improved.

Effect of Silicon–Manganese Deoxidation on Oxygen Content and Inclusions in Molten Steel

In order to improve the cleanliness of steel, non-aluminum deoxidation processes have begun to replace aluminum deoxidation processes. Although the aluminum deoxidation process can reduce the oxygen content in steel to <10 × 10−6, this deoxidation method causes fatigue failure resulting from the formation of large-grained spherical (Ds-type) inclusions composed of calcium–aluminate. It also tends to lead to nozzle blockage during casting. Given the above problems, this study conducted an in-depth investigation of silicon–manganese deoxidation. Thermal experiments and thermodynamic calculations were used to assess the impact of different Mn–Si ratios on the oxygen content and inclusion characteristics during the deoxidation process of molten steel with different initial oxygen contents. The experimental samples were analyzed using an oxygen–nitrogen–hydrogen analyzer, a direct reading spectrometer, and an automatic scanning electron microscope. After that, the samples were electrolyzed to observe the 2D morphology and 3D morphology of the inclusions using scanning electron microscopy. Finally, thermodynamic calculations were carried out using FactSage to verify the experimental results. The results indicated that, regardless of the initial oxygen content, silicon–manganese deoxidation maintained the total oxygen content at 35 × 10−6. It effectively managed the plasticization of inclusions in molten steel, predominantly yielding spherical silicates while minimizing Al-containing inclusions. Nevertheless, as the initial content of [O] increased, the size and density of the silicate inclusions in the steel also increased. An optimal point in the number and size of inclusions was observed with an increased Mn–Si ratio. Moreover, the combined utilization of silicon–manganese deoxidation, diffusion deoxidation, and vacuum deoxidation enabled ultra-low oxygen content control of molten steel.

Failure analysis and numerical drive structure optimization design of Cr12Mo1V1 electrical connection die

A type of Cr12Mo1V1 electric connection die occured brittle fracture after 200 times of service, and its life was much lower than the design life of the die. In this paper, the 5M1E failure analysis method was adopted, combined with the characteristics of Cr12Mo1V1 cold-work die steel, scanning electron microscopy, direct reading spectrometer, Rockwell hardness tester, metallographic microscope and other means were used to analyze and test the macro fracture morphology, material composition, mechanical properties and microstructure of Cr12Mo1V1 electric connection die. The crimping process of the die was simulated by Deform software. The results show that the material composition is not up to standard, the strength is too low, the internal eutectic carbide is not uniform, the size of carbide exceeds the standard and so on are the root causes of the short life and brittle fracture of the die. In addition, the unreasonable designs of the crack slot and round hole of the die lead to excessive stress concentration in the crimping process of the die, which is too the main reason for the brittle fracture failure of the die. In view of the above factors, the paper puts forward some measures to prolong the life of the electric connection die from the aspects of raw materials, heat treatment, forging process and die structure design.

Corrosion Analysis and Prevention of Tubing Nipples in Four Wells

A high-temperature and high-pressure gas field in an oil field requires the use of super 13 chromium material due to corrosive environments. In the recent production process, there have been four consecutive cases of corrosion, fracture, and perforation of tubing nipples, which have brought enormous economic losses to the oilfield. This article analyzes the failure causes of these four tubing nipples and proposes preventive measures. In this paper, the macroscopic morphology, chemical composition, mechanical properties, metallography, and microscopic morphology of four failed tubing nipples have been analyzed. Combined with the field service conditions and string structure of the tubing nipples, it is believed that the failure of the tubing nipples is mainly due to the connection of carbon steel and stainless steel materials, forming a typical galvanic corrosion galvanic cell. The geometric and environmental factors of the materials exacerbate this corrosion. Eventually, severe galvanic corrosion occurred on the inner surface of the tubing nipple, resulting in severe wall thinning or partial perforation, and four tubing nipples failed. The failed tubing nipples in Wells A, B, and C have erosion marks, which are caused by the action of high pressure and high flow rate fluids in the well; The inner surface of the tubing nipple in Well D is rusty yellow, mainly due to the corrosion of its inner wall caused by the acid fracturing fluid injected earlier. At the same time, the string structure of four wells shows that the tubing nipple is located at the variable diameter node of the string. When the fluid in the well flows from the large hole into the smaller hole, the fluid in the well will change there, and its flow rate and pressure will also increase, further exacerbating the erosion in this area. With the development of deep wells containing carbon dioxide in oil fields and the application of carbon dioxide injection secondary oil recovery technology, the use of 13Cr martensitic stainless steel is also increasing. In order to avoid the occurrence of similar accidents that will bring huge economic losses to the oil field, it is recommended that the material of the pipe string (including accessories) of such wells be confirmed using a portable direct reading spectrometer before entering the well.

The analysis of the jump ring on the surface of a thin wall copper tube by drawing with a floating plug

The defect of the jump ring on the surface of the thin wall copper tube by drawing with a floating plug was analyzed, experiment was based on a direct reading spectrometer, metallographic microscope, SEM, and 3D surface topography instrument. Research shows that: when the plug position was over the extreme for-most position, the copper tube was extruded between the drawing die and mandrel, forming a localized necking state; when the plug position was over the extreme rear-most position, the copper tube was drawing in the empty sinking state. The plug does not play a finishing affection, which causes local projections of surface materials. The jump ring macro showed a ring bamboo section scar with bright and dark, micro performance for the uneven wall thickness.

A comparative study on Sn macrosegregation behavior of ternary Al-Sn-Cu alloys prepared by gravity casting and squeeze casting

A comprehensive study on Sn macrosegregation behavior in ternary Al-Sn-Cu alloys was carried out by comparative analysis between gravity casting and squeeze casting samples. The microstructure and Sn distribution of the castings were characterized by metallography, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and a direct reading spectrometer. Results show that there are obvious differences in Sn morphology between gravity casting and squeeze casting alloys. Under squeeze casting condition, the grain size of the casting is smaller and the distribution of β(Sn) is uniform. This effectively reduces the segregation of triangular grain boundary as well as the segregation of Sn. The segregation types of Sn in gravity casting and squeeze casting samples are obviously different. The upper surfaces of gravity casting samples show severe negative segregation, while all the lower surfaces have positive segregation. Compared with gravity casting, squeeze casting solidifies under isostatic pressure. Due to the direct contact between the upper surface of the casting and the mold, the casting solidifies faster under higher undercooling degree and pressure. Consequently, the uniform distribution of Sn reduces the segregation phenomenon on the surface of the casting.

Optical Design of an Integrated Paschen–Runge Spectrometer by Using a Multigrating Structure

An integrated direct-reading spectrometer scheme using seven concave gratings is proposed. At present, the optical design simulation has been completed, and the subsequent physical design may be carried out according to the simulation results. Ray-tracing software (Zemax) is used to divide the spectrum on the grating into seven bands, and an area array detector is used to receive the spectral signals simultaneously, which reduces the volume of the spectrometer and improves the spectral consistency. Using this method, a spectrometer covering 230–440 nm is designed, and the spectral resolution of the center wavelength corresponding to the seven grating windows of 230–260 nm, 260–290 nm, 290–320 nm, 320–350 nm, 350–380 nm, 380–410 nm, and 410–440 nm can reach 0.0974 nm, 0.0652 nm, 0.0361 nm, 0.0157 nm, 0.0838 nm, 0.0872 nm, and 0.1471 nm.

Wire Arc Additive Manufactured CuMn13Al7 High-Manganese Aluminium Bronze

In this work, high-manganese aluminium bronze CuMn13Al7 samples were prepared by arc additive manufacturing technology. The phase composition, microstructure, and crystal structure of the high-manganese aluminium bronze CuMn13Al7 arc additive manufactured samples were analysed using direct-reading spectrometer, metallographic microscope, scanning electron microscope, and transmission electron microscope. The micro-hardness tester, tensile tester, impact tester, and electrochemical workstation were also used to test the performance of the CuMn13Al7 samples. By studying the microstructure and properties of the CuMn13Al7 samples, it was found that preparation of the samples by the arc additive manufacturing technology ensured good forming quality, almost no defects, and good metallurgical bonding inside the sample. The metallographic structure (α + β + point phase) mainly comprises the following: the metallographic structure in the equiaxed grain region has an obvious grain boundary α; the metallographic structure in the remelting region has no obvious grain boundary α; the thermal influence on the metallographic structure produced a weaker grain boundary α than the equiaxed grain region. The transverse and longitudinal cross sections of the sample had uniform microhardness distributions, and the average microhardness values were 190.5 HV0.1 and 192.7 HV0.1, respectively. The sample also had excellent mechanical properties: yield strength of 301 MPa, tensile strength of 633 MPa, elongation of 43.5%, reduction of area by 58%, Charpy impact value of 68 J/cm2 at – 20 ℃, and dynamic potential polarisation curve test results. Further, it was shown that the average corrosion potential of the sample was – 284.5 mV, and the average corrosion current density was 4.1×10–3 mA/cm2.

Failure Analysis on Cracked Cr8Mo2SiV Mold Parts

Cr8Mo2SiV cold work die parts cracked early during machining process. In order to find out the reason of cracking failure of the die parts, the macro crack analysis, chemical composition analysis, hardness test and microstructure analysis of the parts were carried out by stereo microscope, direct reading spectrometer, digital Vickers hardness tester, metallographic microscope and scanning electron microscope. Some results are obtained: the chemical composition of cracked parts was tested and found similar to Cr8Mo2SiV, compared with standard Cr8Mo2SiV, it contains 3.81%W, and its hardness is 229 HV1, means that the cracked parts are not hardened. By observing the micro morphology of the crack, there are oxide and decarburization layer on the crack surface of the parts. It proves that the crack was formed before spheroidizing annealing. It is a typical raw material crack.

Fracture analysis of a pulley shaft for the linear motor oil pumping unit in western oilfield of China

The main objective of the present study is to investigate the fatigue failure in the pulley shaft of the linear motor pumping unit after 25 months of service in the western oilfield of China. In order to analyze the fracture mechanism systematically, different testing methods, including the microstructure observation, fluorescent magnetic powder detector, direct-reading spectrometer, material testing machine, pendulum impact testing machine and Brinell hardness test, are applied in the present study. The obtained results showed that under the action of a cyclic load, the fracture of the pulley shaft appears mainly because of the multi-source fatigue. Meanwhile, it is found that quality of the base material highly affects the impact energy, hardness, and resultant microstructure. Besides, it is demonstrated that fatigue cracks originate from the heat-affected zone of the outer surface of the pulley shaft. Then, these cracks grow simultaneously under the action of the cyclic load. When cracks reach the intersections, the brittle fracture occurs finally. In addition, efficient precautions were provided to avoid fracture.

Cracking analysis of a newly built gas transmission steel pipe

A longitudinal crack was found in the welding seam during the X-ray inspection of a newly built L245NS gas transmission pipeline in China western oilfield. The crack causes were analyzed by the nondestructive tester (NDT), direct-reading spectrometer, tensile strength test machine, impact test machine, Vickers hardness tester, optical microscope (OM), macroscopic fracture morphology, scanning electron microscopy (SEM) and energy spectrum analysis(EDS) in this paper. The results show that the crack is caused by the original defect. First, the fracture surface of the crack is characterized by multi-source cracking, and the origin of the crack is containing foreign matters. Second, the surface of crack fracture is blue, which indicates that the crack fracture has experienced high-temperature burning, so the crack may be formed before heat treatment. The main reason for steel pipe crack is the low stress cracking at the pipe end by the “slag inclusion” formed in the pipe body when the pipe is processing.

The Role of Ti in the Preparation of SiC/7075 Aluminum Matrix Composite

SiC/7075 aluminum matrix composites were prepared by a liquid stirring method. The role of Ti facilitating the preparation of SiC/7075 aluminum matrix were studied by means of direct-reading spectrometer, scanning electron microscope, energy dispersive spectrometer, X-ray diffraction and the sessile drop method. The results show that the SiC content in the SiC/7075 composite increases with an increase of Ti addition. The addition of Ti can significantly improve the wettability of SiC/Al system, there is a critical value of above 0.5% of Ti content in improving the wettability of the Al/SiC system at 1 173 K. The temperature of the “non wetting-wetting” transition for the (Al-2Ti)/SiC system is about 1 123 K, the contact angle decreases to 88 ° at 200 seconds and reaches a stable contact angle of 28 ° at 2 100 seconds.

Effect of Ultrasonic Bending Vibration Introduced by the L-shaped Ultrasonic Rod on Solidification Structure and Segregation of Large 2A14 Ingots.

In order to achieve long-term and stable ultrasonic treatment in the direct chill semi-continuous casting process, a new L-shaped ceramic ultrasonic wave guide rod is designed to introduce ultrasonic bending vibration into 2A14 aluminum alloy melt. The effect of ultrasonic bending vibration on the solidification structure and composition segregation of large 2A14 aluminum alloy ingots (φ 830 mm × 6000 mm) in the process of semi-continuous casting were studied by means of a direct reading spectrometer, scanning electron microscope, metallographic microscope, and hardness test. The ultrasonic ingot treated by bending vibration was compared with the ingot without ultrasonic treatment and the ingot treated by the traditional straight-rod titanium alloy wave guide rod. The results show that, during the solidification of 2A14 aluminum alloy, ultrasonic treatment can significantly refine the grain, break up the agglomerated secondary phase, and make its distribution uniform. The macro-segregation degree of solute including the negative segregation at the edge of the ingots and the positive segregation in the center can be reduced. Through comparative analysis, the macrostructure of the ingot, treated by the L-shaped ceramic ultrasonic wave guide rod, was found to be better than that of the ingot treated by the traditional straight-rod titanium alloy wave guide rod. In particular, the grain refinement effect at the edge of the ingot was the best, the secondary phase was smaller, more solute elements can be dissolved into the α-Al matrix, and the ability of the L-shaped ultrasonic wave guide rod to restrain segregation was stronger at the edge of the ingot.

Failure analysis of a sucker rod fracture in an oilfield

The sucker rod was fracture after 729 days’ service in an oilfield. The fracture position is located at the welding seam that is connecting the sucker rod’s upsetting end and the polished rod end. The failure causes were analyzed by the nondestructive test (NDT) of penetration detection, direct-reading spectrometer, tensile strength test machine, impact test machine, vickers hardness tester, optical microscope (OM), macroscopic fracture morphology, scanning electron microscopy (SEM) in this paper. The process of the fracture is under cyclic loading and the stress concentration, the sucker rod’s outside weld was brittle cracking in the first fracture at the beginning. Then the crack in first facture is passed to the inside welding residual, which is corresponding to the source area of the second fracture. Finally, the crack in the second fracture propagation along the weld seam and connected with the first fracture surface lead the rod broke completely. The causes of sucker rod breaking for the sucker rod did not meet the requirements of the HL grade rod material and the friction welding defects.

Fracture analysis of a connecting rod for oil pumping unit in China western oilfield

The connecting rod of the pumping unit is fracture after 95 days' service in China western oilfield. The failure causes were analyzed by macroscopic fracture morphology, fluorescence magnetic particle detector, impact testing machine, direct-reading spectrometer, optical microscope(OM), scanning electron microscopy(SEM), energy dispersive spectrometer(EDS) in this paper. The direct cause of the fracture of the sample is the fatigue fracture of the connecting rod under the action of cyclic load, and the fundamental cause of the fatigue fracture of the sample is the material quality itself, including the impact energy of sample varies greatly, the substandard chemical composition of the material, the heterogeneity of the microstructure, the coarse grain, the influence of inclusion.The fracture process of the sample was as follows: under cyclic load, the root of the thread formed a fatigue crack source, and then the crack expanded from slow and fast fatigue, and finally under cyclic load, the crack expanded further until brittle fracture.

Failure analysis of the 13Cr valve cage of tubing pump used in an oilfield

Abstract The 13Cr valve cage of a tubing pump fractured after 191 days service in an oilfield in China. The failure causes were analyzed by direct-reading spectrometer, Rockwell hardness tester, optical microscope, scanning electron microscopy, energy dispersive spectrometer, electrochemical method and finite element method in this paper. The results showed that the failure reason was typical corrosion fatigue fracture initiating at the root of the last thread next to the thread relief groove, where numerous corrosion pits and cracks were observed. In general, co-effect of two factors occurred to cause the valve cage to corrosion fatigue fracture. The downhole medium with high CO2 and Cl− concentrations was the environmental factor of the failure. Alternating stress caused by pumping cyclic motion was the main stress factor of the failure, while the high stress concentration on thread connection further induced cracking.

Anti-carburizing Coating for Resin Sand Casting of Low Carbon Steel Based on Composite Silicate Powder Containing Zirconium

This paper studied the structure and properties of anticarburizing coating based on composite silicate powder containing zirconium by X-ray diffraction analyzer, thermal expansion tester, digital microscope and other equipment. It is introduced that the application example of the coating in the resin-sand casting of ZG1Cr18Ni9Ti stainless steel impeller. The anti-carburizing effect of the coating on the surface layer of the cast is studied by using direct reading spectrometer and spectrum analyzer. The change of the micro-structure of the coating after casting and cooling is observed by scanning electron microscope. The analysis of anti-carburizing mechanism of the coating is presented. The results indicate that the coating possesses excellent suspension property, brush ability, permeability, levelling property and crackresistance. The coating exhibits high strength and low gas evolution. Most of the coating could be automatically stripped off flakily when the casting was shaken out. The casting possesses excellent surface finish and antimetal penetration effect. The carburizing layer thickness of the stainless steel impeller casting with respect to allowable upper limit of carbon content is about 1mm and maximum carburizing rate is 23.6%. The anticarburizing effect of casting surface is greatly improved than that of zircon powder coating whose maximum carburizing rate is 67.9% and the carburizing layer thickness with respect to allowable upper limit of carbon content is greater than 2mm. The composite silicate powder containing zirconium coating substantially reduces the zircon powder which is expensive and radioactive and mainly dependent on imports. The coating can be used instead of pure zircon powder coating to effectively prevent metal-penetration and carburizing of resin-sand-casting surface of low carbon steel, significantly improve the foundry production environment and reduce the production costs.

Anti-carburizing Coating for Resin Sand Casting of Low Carbon Steel Based on Composite Silicate Powder Containing Zirconium

This paper studied the structure and properties of anticarburizing coating based on composite silicate powder containing zirconium by X-ray diffraction analyzer, thermal expansion tester, digital microscope and other equipment. It is introduced that the application example of the coating in the resin-sand casting of ZG1Cr18Ni9Ti stainless steel impeller. The anti-carburizing effect of the coating on the surface layer of the cast is studied by using direct reading spectrometer and spectrum analyzer. The change of the micro-structure of the coating after casting and cooling is observed by scanning electron microscope. The analysis of anti-carburizing mechanism of the coating is presented. The results indicate that the coating possesses excellent suspension property, brush ability, permeability, levelling property and crackresistance. The coating exhibits high strength and low gas evolution. Most of the coating could be automatically stripped off flakily when the casting was shaken out. The casting possesses excellent surface finish and antimetal penetration effect. The carburizing layer thickness of the stainless steel impeller casting with respect to allowable upper limit of carbon content is about 1mm and maximum carburizing rate is 23.6%. The anticarburizing effect of casting surface is greatly improved than that of zircon powder coating whose maximum carburizing rate is 67.9% and the carburizing layer thickness with respect to allowable upper limit of carbon content is greater than 2mm. The composite silicate powder containing zirconium coating substantially reduces the zircon powder which is expensive and radioactive and mainly dependent on imports. The coating can be used instead of pure zircon powder coating to effectively prevent metal-penetration and carburizing of resin-sand-casting surface of low carbon steel, significantly improve the foundry production environment and reduce the production costs.

Failure analysis of an oil pipe wall perforated by pitting corrosion

Failures of underground oil pipes caused by pitting perforation are investigated in this paper. The chemical composition of the failed oil pipe was analyzed by the direct reading spectrometer, which is in accordance with China national standard GB/T699‐1999 for 20 steel. The failed parts were investigated by means of visual observation, optical microscope (OM) and scanning electron microscope (SEM). Energy‐dispersive X‐ray spectroscopy (EDS) of the inner pits were conducted. The results indicate that the pit on the failed oil pipe is composed of three smaller circular pits, on which a fatigue striation‐like pattern suggests a repetitionary pitting corrosion process, while pitting corrosion in the vertical direction is more serious. The failed position was located in the underground ditch where carbon dioxide (CO2) deposited and underwent wetting and drying cycles with an alternative of rainy and sunny days. Combined with the environment of the oil pipe, the simulation experiment, and corresponding mechanism analysis was conducted to evolve the mechanism of pitting corrosion, initiated by the synergistic effect of CO2 and chloride ions (Cl−), and impelled the production of FeCO3 corrosion agents providing an isolated space in a short time, meanwhile chloride ions proceed to propagate continuously into the inner pit, which could explain pitting corrosion is more serious in the vertical direction.