Improper Heat Treatment Research Articles

Failure Analysis of Bypass Rupture of Flowmeter in Steam Pipeline

Abstract A petrochemical company’s pipeline ruptured in the flowmeter bypass of the main steam pipeline during a steam blowdown before commissioning, resulting in material failure and inoperability. The cause of the pipe rupture needed to be detected experimentally. To study the failure in the steam pipeline of a flowmeter of bypass rupture, visual inspection, mechanical properties testing, chemical composition analysis, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Mechanical property. The experiments confirmed the reason for the bypass rupture of the 15CrMoG steam pipeline: improper heat treatment transforms the material’s structure, and the pearlite spheroidization (PC) leads to the deterioration of the material’s mechanical properties. The main manifestations are as follows: the grains in the superheated zone of the welding exhibit a coarse morphology, and a distinctive superheated Widmanstatten structure is formed due to rapid cooling, resulting in a significant reduction in material plasticity and impact toughness. High-temperature oxidation occurs, accompanied by localized enrichment of Cr-element in certain areas, while other regions experience Cr depletion, resulting in the deterioration of material properties.

Fracture failure analysis of high-strength bolts in power plant steel structures

The high-strength bolts of a power plant steel structure fractured and failed in many places. To find the cause of the failure, this paper analyzed the failure reasons of fractured bolts through macroscopic inspection, chemical composition analysis, mechanical performance test, metallographic inspection, and fracture microscopic analysis. The results show that the main cause of bolt fracture is that improper heat treatment leads to a carburized layer on the surface of the bolt, which makes the surface of the bolt sensitive to hydrogen. At the same time, there is a certain amount of hydrogen in the material matrix, which leads to hydrogen accumulation and cracks in the bolt at the stress concentration. Eventually, the cracks propagate and lead to fracture failure.

The fracture reason of high-pressure outer cylinder bolt

The power plant experienced a cylinder bolt fracture accident during the power generation process of the unit. This study conducted fracture research and analysis on fractured bolts through a series of macroscopic and microscopic detection methods. The analysis results indicated that the cause of the bolt fracture accident of the high-pressure outer cylinder of the 5th steam turbine this time was the improper heat treatment process during the bolt material processing stage, which resulted in coarse grain size and severe insufficient impact toughness of the bolt material. Finally, the crack occurred at the position with the largest load and gradually expanded in a brittle manner until the overall fracture failure.

Fracture Failure Assessment Analysis and Process Improvement of Vessel Bending Test

The high-purity ethylene dichloride (EDC) head tower is an important pressure vessel in the vinyl chloride production process. During the manufacturing process, the bending test of 2 product specimens broke. In this paper, the failure analysis of the bending test fracture of the welding test plate was carried out, and a systematic analysis, including chemical composition, mechanical properties, and microstructure, was carried out. The causes of fracture of welded test plates during the manufacturing process of the head tower were studied. The results show that the incorrect heat treatment process leads to the extension strength, hardness, and impact performance, being lower than the standard requirements. The combined fracture analysis shows that the material is brittle, which makes the welding test board brittle fracture. At the same time, metallographic analysis shows that the steel is tempered. The comprehensive performance of duplex stainless steel in the tempered state is significantly lower than the original solid solution heat treatment performance. Thus, the bending test fracture of the welding test board of the equipment is caused by the improper heat treatment process, resulting in the microstructure and performance of the material not meeting the relevant requirements. According to the cause of the fracture, the heat treatment and welding process are improved. The heat treatment was carried out first, and then the duplex steel was welded to prevent the heat treatment state of the duplex steel supply from changing. Finally, a qualified specimen was obtained.

Effect of heat treatment on mechanical properties (breaking torque) of leaded brass of temperature oil sensor body

In this case study, failure analysis of engine oil temperature sensor (OTS) is conducted. The OTS usually consist of three parts: brass body, thermistor unit and a coupler unit. For continuous temperature monitoring, the brass body is continuously in contact with the engine oil that are based on sulphates and ammoniate, under high pressure and elevated temperature. This sensor is mounted on the vehicle engine using torque gauge/ wrench during the final vehicle assembly. For this, the brass body is designed to withstand a torque of 44 Nm and should have a design torque between the ranges of 70–80 Nm.In present study, we observed cracks on the OTS brass body during assembly process. The product was failing at a much lower value than the design torque i.e. less than 44 Nm. For failure analysis, vehicle assembly conditions were simulated and the failed parts were analyzed using microstructural, morphological and elemental analyses. Lead segregation was identified as the root cause of the failure which occurred due to improper heat treatment temperature (annealing conducted at 300 °C for 1 h). Lead segregation resulted in making the component brittle which acted as a crack initiation zone and failed at low torque values. The design torque value of T-Oil Sensor is improved by reduction in Pb content and providing annealing heat treatment to brass at 550 °C for 2 h which leads to even distribution of Pb and beta refinement.

Microstructural investigation on a rail fracture failure associated with squat defects

Squats, observed in numerous railway networks worldwide, are a significant concern for rail track maintenance. This work presents a specific case study of a rail fracture failure associated with squat defects. A detailed microstructural analysis was conducted to investigate the causes of squat formation, subsequent crack propagation, transverse defects, and fracture. According to the findings, the initiation of squats can be attributed to the presence of White Etching Layers on the rail surface and rolling contact fatigue. After the initiation of Squats, the cracks extended downwards into the bulk rail at a shallow angle until reaching a sizeable martensitic island located in the subsurface of the rail along the path of crack propagation. The brittleness of the undesired martensitic structure triggered rapid crack development, facilitated transverse cracking, and ultimately resulted in rail fracture failure. Transmission electron microscopy examination confirmed that the abnormal defects are plate martensite with a twin substructure and high carbon content, which could be generated as a result of improper heat treatment during the manufacturing of rails.

Evaluation of hydroxymethylfurfural content in commercial and artisanal bee honey from Los Ríos-Babahoyo

Hydroxymethylfurfural (HMF) is a compound that is produced after heat treatment of honey; that is, they are not present in the initial raw materials and can present a potential health hazard; they are known as chemical processing contaminants. This compound is an indicator parameter of the quality of honey produced spontaneously. Its concentration increases with time and other factors, such as improper heat treatment during processing, storage temperature and mode of transportation. The objective of this research is focused on evaluating the content of HMF present in 6 types of bee honey, 3 commercial brands and three artisanal brands; the honey was from eucalyptus and citrus flowering, and the place where the honey was acquired is in the Province of Los Ríos, since being a geographical area with abundant flora, the primary pollinators are bees (Apis Mellifera). In addition, the honey was heated at different temperatures and time intervals to evaluate whether Hydroxymethylfurfural increases when heat is added to the honey. The present work was carried out at the Technical University of Babahoyo; the commercial and artisanal bee honey were acquired between 1 and 5 days before the assay. For HMF analysis, a UV spectrophotometer was used, as specified in INEN 1637 standards, to determine the absorbance of the standard sample at 284 and 336 nm. The HMF values obtained for the three commercial brand honey and the artisanal brand honey are within limits allowed by INEN 1572 Technical Standard, which is 4_mg HMF/100_g of honey (40 mg HMF/kg of honey) as a maximum limit. The mean values ranged from 0.08 to 1.77 mg HMF-/g honey, while the honey subjected to heating had mean values ranging from 0.08 to 4.43 mg HMF/100_g honey. A high HMF content was determined, which exceeded the maximum limit, leading to the conclusion that commercial and artisanal honey does contain Hydroxymethylfurfural. Still, in small quantities, it is important to use good handling and preservation methods to prolong the product's shelf life. Keywords: spectrophotometer ; Apis Mellifera ; radiation

Evaluation of hydroxymethylfurfural content in commercial and artisanal bee honey from Los Ríos-Babahoyo

Hydroxymethylfurfural (HMF) is a compound that is produced after heat treatment of honey; that is, they are not present in the initial raw materials and can present a potential health hazard; they are known as chemical processing contaminants. This compound is an indicator parameter of the quality of honey produced spontaneously. Its concentration increases with time and other factors, such as improper heat treatment during processing, storage temperature and mode of transportation. The objective of this research is focused on evaluating the content of HMF present in 6 types of bee honey, 3 commercial brands and three artisanal brands; the honey was from eucalyptus and citrus flowering, and the place where the honey was acquired is in the Province of Los Ríos, since being a geographical area with abundant flora, the primary pollinators are bees (Apis Mellifera). In addition, the honey was heated at different temperatures and time intervals to evaluate whether Hydroxymethylfurfural increases when heat is added to the honey. The present work was carried out at the Technical University of Babahoyo; the commercial and artisanal bee honey were acquired between 1 and 5 days before the assay. For HMF analysis, a UV spectrophotometer was used, as specified in INEN 1637 standards, to determine the absorbance of the standard sample at 284 and 336 nm. The HMF values obtained for the three commercial brand honey and the artisanal brand honey are within limits allowed by INEN 1572 Technical Standard, which is 4_mg HMF/100_g of honey (40 mg HMF/kg of honey) as a maximum limit. The mean values ranged from 0.08 to 1.77 mg HMF-/g honey, while the honey subjected to heating had mean values ranging from 0.08 to 4.43 mg HMF/100_g honey. A high HMF content was determined, which exceeded the maximum limit, leading to the conclusion that commercial and artisanal honey does contain Hydroxymethylfurfural. Still, in small quantities, it is important to use good handling and preservation methods to prolong the product's shelf life.

Fracture Analysis of Butt Welding Area of 5″ Drill Pipe Internal Thread End in an Oilfield

This paper tested fracture morphology analysis, mechanical properties and chemical, metallographic analysis and micro analysis to find out the factors of fracture in the butt welding area of the internal thread of the 5″ drill pipe, which is made of S135 in the casing pulling process of an oilfield. The results show that the chemical element, tensile strength and yield strength, impact performance, metallographic structure, inclusions in microstructure and grain size of the Fracture drill pipe meet the relevant data of the oilfield and industry standards, but the hardness of the fracture does not meet the requirements of the national standard. The important reason of the fracture of the drill pipe is that the oxide skin was not cleaned before the drill pipe joint was welded with the body. During welding, the oxide skin entered the molten weld metal, and large slag inclusions formed in the weld resulted. The secondary cause is improper subsequent heat treatment of drill pipe weld, which leads to increased weld brittleness and accelerated crack growth. This paper puts forward corresponding countermeasures to improve the quality of the drill pipe’s weld and prevent the failure accidents of drill pipe.

Fracture analysis on involute spline of large tunnel boring machine

The main drive spline shafts of two large tunnel boring machines were broken after service of less than 150 h. The failure located at the section flush with the end of the spline sleeve. Different from the gear fracture occurred at the tooth roots of the working side, the spline fracture started from the tooth roots of the non-working side. The non-working side cracks were wider and longer than these of working side, and their damage were more serious. At the failed roots, there were obvious fan-shaped shellfish lines which these were significant fatigue characteristics. Through chemical composition test and metallographic analysis, the spline shaft material was speculated to be 17CrNiMo6, and quenched and tempered heat treatment. The microstructure was mainly bainite with tempered martensite and retained austenite. The micro-hardness was uneven and fluctuated between 31 and 43HRC. Sulfide inclusion was grade 2 and alumina inclusion was 2.5. The calculation by finite element method (FEM) showed that the maximum stress was located at the tooth root of the non-working side. The safety factors calculated by three methods were less than 1.0. Therefore, the root cause of spline failure is improper design and heat treatment. Failure analysis, theoretical calculation and simulation test show that the failure mode was torsion fracture.

Analysis and investigation of the failure elevator induced by dual effects of cyclic alternating load and improper heat treatment

Aiming at the deformation and fracture of slope elevator caused by the cyclic alternating load in service, analyzes and studies the failure reasons and mechanisms from microstructure, physical and chemical properties, and service state. The microstructure of the elevator was lower bainite that preserves the intact of the laths orientation, with high P element content, a certain amount of low harmful low-melting-point elements, and presence of D-type non-metallic inclusions, led to low impact toughness. It indicated that failure of the elevator can be attributed to dual effects of load and improper heat treatment, caused dislocation glide to occur in the crystals, eventually resulting in a mixed-crystal-type brittle fatigue fracture. It was advised to strictly control the content of trace elements, rationally optimize the heat treatment process, and select microstructure with good resistance to fatigue impact and alternating load, to improve the deformation resistance and critical fracture toughness of the elevator.

Failure of hydraulic lathe chuck assembly

Present work provides a detailed failure investigation of a hydraulic lathe chuck assembly that comprises a plunger, three jaws, and three jaw-carriers that are made of carburized, tempered and sub-zero treated EN36C steel. The chuck assembly suffered premature failure of the plunger and one of the jaw carriers during the service in a CNC lathe. The investigation comprises a detailed metallurgical failure analysis involving: visual inspection, fractography, metallography, and hardness measurements. The analysis concludes that plunger failed first by fatigue fracture that is originated at a sharp corner of a T-slot. The mating jaw-carrier failed in the next event due to instant misalignment and overstressing during the lathe operation. The investigation concludes that design flaw and improper heat treatment cycle as the reasons for the premature failure of the assembly. Through experimental simulation of the heat-treatment cycles using EN36C specimens, the work suggests that carburizing, cryogenic treatment and then tempering is the proper sequence for achieving the best combination of mechanical properties that should extend the service life of the chuck-assembly.

Failure analysis of heat exchange tubes in hydrogenation unit

The leakage failure of the austenitic stainless steel tubes in the hydrogenation unit of a petrochemical company was analyzed. The causes of the failure were investigated by visual examination, chemical compositions analysis of the tube, microscopic examination, metallographic examination and scale layer analysis. The results showed that the directly reason of the failure is pitting corrosion and stress corrosion cracking. We concluded that the improper heat treatment of the austenitic stainless tubes and existence of the corrosive substances including wet hydrogen sulfide and hydrogen chloride in the working medium, result in the occurrence of the corrosion, and the complex flowing conditions accelerate the corrosion process. Proposals were put forward in this paper.

Failure investigation of a 304 stainless steel geothermal tube

The investigation of this paper aimed at finding the failure cause of a heavily cracked geothermal water convection tube, utilizing electron backscattered diffraction, double loop potentiodynamic polarization test, and energy-dispersive X-ray spectroscopy. Results show the failure was attributed to stress corrosion cracking (SCC). Chloride in the service environment has induced the initiation of SCC cracks. The sensitization of matrix increased the susceptibility to intergranular cracking, which may result from improper heat treatment before service. The residual stress arising from the manufacturing process promoted the failure process. The SCC cracks originated from the internal tube. In the early stage, the cracks propagated along austenite grain boundaries. Thereafter, they transformed into a coexisting mode of intergranular cracking and transgranular cracking. The failure was attributed to the synthetical effect of sensitization, chloride, and residual stress.

Failure Analysis of Drive Axle Shaft failed under Torsional Stress

Drive axles are an essential component for power transmission in any automobile. It transfers the power from the differential to the hub of the wheels which drives the vehicle. The axles are subjected to torsional stresses due to the torque from the differential and the resisting torque present due to the frictional resistance from the ground on the wheels. Hence, they are prone to torsional failures under fatigue with and without shock loading. In this paper, a comprehensive engineering failure analysis of the failed drive axle shaft of material EN 24-T, custom designed for a 200kg BAJA SAE all-terrain vehicle was performed. Destructive, non-destructive testing and material analysis along with finite element simulations using Ansys were carried out to better understand the nature and cause of the failure. Failure analysis data hints at the flaws in design considerations and scanning electron microscopy (SEM) images reveal the formation of bainitic microstructures within the component due to improper heat treatment which lowers the ultimate tensile strength of the material.

Failure analysis of phase B pull rod of HGIS circuit breaker operating mechanism in 220 kV Substation

The B-phase pull rod of HGIS circuit breaker operating mechanism in a 220kV substation was broken at the root. The broken pull rod was analyzed by macro examination, metallographic examination, chemical composition analysis, fracture morphology analysis and impact test to find out the reason for the fracture. The results showed that: 1. Due to the improper heat treatment in the manufacturing process, the metallographic structure of B-phase pull rod appeared network ferrite and widmanstatten structure, which made the material brittle and impact toughness lower than the standard requirements; 2. The content of alloy elements Cr, Ni and Ni were significantly higher than the standard requirements, which reduced the plasticity and toughness of the material; 3. The low temperature of substation environment led to the decrease of material toughness and the viscosity of the lubricant decreased, causing the transmission parts to jam. The joint action of three factors led to cleavage fracture of B-phase pull rod in the stress concentration area.

Failure analysis of a secondary driving helical gear in transmission of electric vehicle

The failure cause of a secondary driving helical gear in transmission system of electric vehicle (VE) was analyzed in this paper. The macroscopic fractography, microscopic metallographic observation, hardening depth and hardness and chemical composition inspection, non-metallic inclusions analysis were carried out to evaluate the gear failure mechanism. The stress distributions of the tooth flank using static and dynamic contact finite element simulation were obtained based on ANSYS Workbench software. The results showed that the fracture surfaces of the failed gear originate from the tooth root and exhibit the intergranular brittle fracture, the main reason was low Ti content of the material, hardening depth and hardness in the root region and a number of large carbides on the on the matrix of martensite due to improper heat treatment, also FE simulation results revealed that the high contact stress in the root position and high impact load at the initial stage of gears meshing during the reducer in service possibly led to the fatigue failure.

Failure analysis on tee pipe of duplex stainless in an oilfield

During the hydraulic test in the station of an oil field, a tee-pipe of S32205 duplex stainless burst into several fragments without reaching the target pressure. In order to clarify the failure cause, visual inspection, chemical composition, mechanical test, hardness test, Charpy impact test, heat treatment, and finite element analysis were carried out in this paper. The results show the chemical composition of tee meets the requirements of the standard for S32205 duplex stainless steel, and the tensile property, hardness, Charpy impact and content of harmful phase do not meet the requirements of reference standard. The presence of sigma phase in the tee which induced by the improper heat treatment after cold forming makes the material hard and brittle. In the case of micro defects, the pressure bearing capacity of tee joint will be reduced, resulting in brittle cracking. Therefore, the quality control of tee should be strengthened, the heat treatment should be implemented strictly and nondestructive inspection of tee can be carried out such as field micro-hardness test and metallographic examination. Considering the burst failure case of tee pipe was rarely reported so far, the findings of this paper would provide useful quality control advice in the future.

The Corrosion of Al–Cu-Based Alloys and Comments on the Paper “Effect of Solidification Time on Microstructure, Wettability and Corrosion Properties of A205-T7 Aluminum Alloys” by Amir Kordijazi et al.

Al–Cu-based casting alloys have very high strength, but improper heat treatment will create a material susceptible to stress corrosion failure. A review of this problem is provided and discussed regarding a recent study of A205-T7 alloy castings.

Failure Analysis of Shipping Container Handler Twistlock Pin

During operation of a shipping container handler, a twistlock pin supporting one side of two stacked shipping containers fractured, causing the shipping containers to fall. An investigation revealed that the alloy steel pin had a ferritic/bainitic microstructure with an average hardness of 29.5 HRC and a typical Charpy V-notch impact energy of 17 J at room temperature. Examination of the fracture surface revealed a cleavage fracture that initiated from a quench crack. It was determined that the primary cause of the failure was improper heat treatment.