High-frequency Heat Treatment Research Articles

Failure analysis of the rotating shaft in the rail grinding car

Rail grinders belonging to special vehicles have fewer accidents than general railroad vehicles and parts, and the causes are diverse. Therefore, there is a lack of basic data for inspection methods and preventative measures necessary for accident prevention, and the collection and analysis of accident cases are also necessary. In this paper, a failure analysis of the recently derailed rail grinding car's rotating shaft was conducted. Various analyses, including fractography, chemical analysis, metallography and hardness measurement, were performed on the failed shaft. In the fracture surface of the shaft, ratchet marks and fatigue striations indicative of fatigue failure were observed. Consequently, it was confirmed that the failure of the shaft was attributed to fatigue, with the primary cause being identified as the cracks found on the fillet area surface. Chemical analysis of the observed inclusions in the sample revealed manganese (Mn) at 6.16 wt% and sulfur (S) at 1.35 wt%. These are attributed to non-metallic MnS inclusions, which are presumed to have adversely affected the fatigue strength of the material. Additionally, hardness deficiency due to heat treatment defects on the shaft surface was identified. The surface hardness measured approximately HV400, suggesting that it is desirable to achieve a surface hardness of HV600 or HRC55 or higher during high-frequency heat treatment. Lastly, the finish state of the fillet area surface was not smooth. Given that the fillet area is a region where stress concentration occurs, the presence of such machining traces raises the possibility of progressing into fatigue cracks. Finite element analysis revealed that the von-Mises stress was less than the yield strength of the material, and a safety factor based on the yield strength was calculated to be 3.5. The results confirmed that fatigue cracks in the fillet area were caused by the hardness deficiency due to the poor heat treatment, the rough surface finish, and the presence of non-metallic inclusions.

코일전류 계산 및 AISI 1552 상변태를 고려한 주차기어의 고주파 열처리 시뮬레이션

This study performed high-frequency heat treatment experiments and simulations of the park gear of an automobile transmission. The heating temperature and hardening depth were measured during high-frequency heat treatment. Moreover, by applying the resonance RCL circuit, the current value of the coil during high-frequency heat treatment, the electromagnetic and heat transfer material properties dependent on the temperature, and the phase transformation function were all applied to the simulation. In the high-frequency heat treatment experiment, the heating temperature was 977.4℃ and the 1st direction hardening depth was 1.5 mm, the 2nd direction hardening depth was 3 mm, and the 3rd direction hardening depth was 2.5 mm, and the reliability was verified by comparing the simulation heating temperature of 1,097℃ and the 1st direction predicted hardening depth of 1.6 mm, the 2nd direction predicted hardening depth of 2.8 mm, and the 3rd direction predicted hardening depth of 2.7 mm. The error rate of the heating temperature results was 12.2% whereas that of the hardening depth results was 7.1%.

Study on rheological behaviors and rheokinetics of urushiol/MDI resin system during curing process

The gelation and curing process of urushiol and MDI system were studied by dynamic rheology. Rheometer was used to monitor the changes of rheological parameters (storage modulus G', loss modulus G", complex viscosity η* and loss tangent tanδ) during continuous heating, isothermal aging and high-frequency heat treatment. And track the gelation and structural evolution of the curing process system. The results showed that the combination of isothermal aging, heating and high frequency were expected to be a simple strategy for low temperature curing or shortening the curing time of resin. The conversion α of the curing process was described by the evolution of storage modulus G'. The curing process can be described by autocatalytic model, and the fitting data are in good agreement with the experimental data. The model can be used for process optimization and further development of urushiol based materials.

중소기업 제조 공정 혁신 기술 도입 활성화를 위한 디지털 트윈 기술 적용 - 협동 로봇 적용 사례 -

This study is to provide a simulation environment by applying only the minimum technology based on digital twin and to provide an easier decision-making environment for SMEs to introduce the innovative manufacturing process. A framework that utilizes a combination of resource library, layout design, and simulation algorithm based on digital twin technology was proposed. In order to verify the applicability and limitations of the proposed methodology, a comparison of productivity performance indicators was performed when the manual process part was replaced with a collaborative robot in the high frequency heat treatment process for saw blade manufacturing.

Effect of Sn addition on the Microstructure and Friction–wear Properties of a Nodular Graphite Cast Iron

Nodular graphite cast iron is used in the railway and automobile industries because of its excellent workability, abrasion resistance, mechanical strength, and hardenability. To use nodular graphite cast iron in harsh environments, it is essential to examine their friction–wear properties in conjunction with the surface hardness of the materials. Therefore, in this study, a pin–on–disk type method was used to investigate specimens whose surface hardness was improved by the addition of Sn alloying element, followed by high-frequency heat treatment. The results revealed that Sn inhibited the growth of nodular graphite by acting as a barrier to the movement of carbon and promoted the transformation of some matrix from ferrite to pearlite. In contrast, most of the matrix of the high-frequency heat treated specimen was transformed into pearlite. Consequently, the specimens prepared using both methods achieved higher surface hardness than the as-cast state. With regards to the friction–wear properties, the Sn added alloy exhibited a relatively weak matrix, and therefore, delamination of the surface and spalling on the nodular graphite occurred, with significant wear width and depth. In contrast, surface delamination was not observed in the specimen after high-frequency heat treatment.

Novel Magnetic Attachment System Manufactured Using High-Frequency Heat Treatment and Stamp Technique: Introduction and Basic Performance

Recently, a novel magnetic attachment with extremely low cost and high performance was developed. This article aims to introduce a novel magnetic attachment and to evaluate its basic eligibility for denture retention in clinical practice. The novel magnetic attachment system used in this study was the direct-bonding root-keeper-type Magteeth™ MT800 (MagneDesign, Nagoya, Japan). The retentive force without displacement (position 0) and after horizontal displacement to positions 0.5, 1, 1.5, 2, 2.5, and 3 mm were measured. The values relative to the retentive force without displacement were gradually decreased to 82.7 ± 16.3%, 68.8 ± 17.1%, 62.4 ± 15%, 47.2 ± 13.1%, 35.7 ± 9.9%, and 20.7 ± 6.5%, respectively. The retentive force and magnetic field strength did not change significantly after the load test (100 N load, 10,000 times). No new gap between the metal and resin was found in the root keeper- and magnet assembly-embedded blocks after the load test. Some scratches on magnetic assembly and root keeper surface, while no change in the resin texture after the load test were observed. Based on the findings of this preliminary study, this novel low-cost magnetic attachment exhibited favorable retention, strength, and durability for clinical use.

High-Frequency Heat Treatment of AISI 1045 Specimens and Current Calculations of the Induction Heating Coil Using Metal Phase Transformation Simulations

AISI 1045 specimen was compared through a high-frequency heat treatment simulation and experiment considering metal phase transformation. Hardening zone predictions were confirmed through cooling and metal phase transformation simulations after obtaining the results from electromagnetic heat transfer simulations. The cooling process was modeled by applying the cooling coefficient of the cooling water in the same way as the actual heat-treatment process. To obtain the current flowing through the coil during high-frequency induction heating, the voltage was measured and applied using the resistance–inductance–capacitance circuit calculation method. Experimental and simulated results of the heating temperature and curing depth of an AISI 1045 specimen with a carbon content of 0.45% were compared; the comparison indicated good agreement between the two. Using the simulation results, we established a method for obtaining the current flowing through the induction coil for predicting the extent and depth of the hardening zone during high-frequency induction heat treatment.

Effect of High Frequency Heat Treatment on the Microstructure and Macroscopic Properties of WC-50Ni+Stellite 1 Coating Layer Fabricated by HVOF Spray Process

Effect of High Frequency Heat Treatment on the Microstructure and Macroscopic Properties of WC-50Ni+Stellite 1 Coating Layer Fabricated by HVOF Spray Process

NDE Characterization on the Heat Treatment in Piston Rods for a Use of Shock Absorbers Using a Simple Automatic Ultrasonic System

Piston rods are key components that absorb shock and vibration energy, and provide handling stability while automotive wheels are rolling. A high-frequency heat treatment process guarantees the surface-hardening durability of piston rods. The Rockwell hardness test is performed to evaluate the degree of surface heat treatment. However, this test does not determine the hardening of the whole surface because only a part of the piston rod surface is tested. Thus, a proper nondestructive method was developed for inspecting the whole surface. The beam profile behavior was predicted by measuring the 360° full profile surface ultrasonic behavior using Rayleigh ultrasonic waves. We implemented a contact-type jig to measure the hardness, developed a simple automated operating system, and data signals were processed with LabVIEW. Finally, we implemented the ultrasonic behavior and optimal test conditions through FEM 3D simulation to produce Rayleigh ultrasonic waves.

Effect of High Frequency Heat Treatment on the Microstructure and Wear Properties of Ni based Self Fluxing Composite Coating Layer Manufactured by HVOF Spray Process

Effect of High Frequency Heat Treatment on the Microstructure and Wear Properties of Ni based Self Fluxing Composite Coating Layer Manufactured by HVOF Spray Process

쇼크옵소버용 피스톤로드의 열처리 NDE탐상을 위한 자동화시스템 개발

In general, piston rods can absorb both the shock and vibration to maintain the stability of moving automotive wheels; a high-frequency heat treatment is performed to guarantee their quality. Appropriate nondestructive techniques are required to monitor the degrees of this treatment. It is possible to quantitatively predict the beam profile behavior and the degree of heat treatment for the outer diameter of the piston rods by measuring the ultrasonic behavior of the rods through an automated ultrasonic system.BRThe results of this study demonstrated that the specimens underwent this treatment had a longer time-of-flight (TOF) than the specimens without it, indicating that it is possible to lower the surface ultrasound velocity. It was determined that the shock observer piston rod surface particles become both enlarged and oxidized owing to this treatment and that the surface wave velocity is affected by thermal oxidation.

Study of poly (N-isopropyl acrylamide) electrospinning magnetic fiber as a cell attach/detach substrate

In this study, we used electrospinning technology to develop a novel composite material with temperature and magnetic responsive characteristics which physical and chemical parameters were verified. Poly(N-isopropylacrylamide), PNIPAAm polymer was chosen as the main material for the spinning process, to prepare the temperature-responsive material with a hydrophobic/hydrophilic fiber structure. The fibers prepared by the electrospinning method resulted in high pores and high volume-surface area that can serve as substrates for cell tissue engineering applications. The material was then integrated with magnetic nanoparticles which led to composite materials of magnetic temperature-responsive spinning fibers and can further be used as a substrate material in the biomedical engineering field. Field-scanning emission electron microscopy (FSEM) and transmission electron microscopy (TEM) were used to characterize the spinning fibers diameter and surface morphology. The superconducting quantum interference device (SQUID) and thermogravimetric analyzer (TGA) were used to analyze the amount of magnetic nanoparticles confined in the magnetic temperature-responsive spinning fiber. The proportion of magnetic particles in magnetic temperature-responsive spinning fiber from SQUID and TGA analysis was 3.44% and 4.07%, respectively. This study successfully established the preparation of temperature-responsive spinning fiber with extracellular matrix structure through an electrospinning technique. In the future, this composite material with the advantage of switchable hydrophilic/hydrophobic temperature-responsive and magnetic induction properties can further be used in the field of biomedical engineering applications, such as drug-carrier, drug release, skin wound healing, and magnetic high-frequency heat treatment.

Automated control system to monitor dielectric losses in polymers

The basic property of the processed polymers when it comes to high-frequency heat treatment is their dielectric losses. The purpose of the present study is elaboration of automated control system to monitor dielectric losses in polymers during heating. The technique developed in the given paper implies linear uniform heating of the studied material by contact method with the given velocity and when heating is off, periodic short-term action of high-frequency electric field on the polymer after each temperature growth of polymer per preset degree. The studies conducted in the automatic mode allowed obtaining new knowledge on changing electro-physical properties of polymers during heat treatment; and determining the new parameter to control polymer state while high-frequency processing; distinguishing and identifying different relaxation transitions of polymer materials during heating and thus broadening applicability of high-frequency heat treatment.

A Study on Piston Surface Defect by High Frequency Heat Treatment

This study is a study on the cracking of the main piston surface which is generated in the injection molding machine to generate mold force. The main piston machining process consists of high frequency heat treatment, grinding and super finishing after lathe turning. Scale, defect size, and fracture texture were observed for four cracks on the surface of the piston during the tempering process after high frequency heat treatment using a metallurgical microscope. In this study, it was confirmed that the cracked structure of the piston structure was ferrite and pearlite structure. It was confirmed that cracks progressed to 480 ㎛ and scale layer of 3 ㎛ or less. Surface hardening layer and hardness were min 2.0mm/HRc 58±2 spec 1.6 mm/HRc 56.5~57.5 In addition, cracks on the surface of the piston appear perpendicular to the rolling process. Therefore, it can be assumed that the crack occurred in the low temperature tempering process at 200°C or less after the high frequency heat treatment, not the material defect. Therefore, the temperature should be maintained at 200°C or higher during tempering after high-frequency heat treatment, and the cracking defect on the surface of the piston can be prevented by setting the feed rate to 1.3 mm/s or less during heat treatment.

Study on the High Frequency Heat Treatment Characteristics with the Distance between Coil and SCM440 Parts

Study on the High Frequency Heat Treatment Characteristics with the Distance between Coil and SCM440 Parts

시험평가법을 이용한 IRB 면진장치 롤러 설계 : Part 2. 소재 열처리

This paper presents a subsequent research work on the roller design of IRB(isolation roller bearing) seismic isolation device presented in Part 1 by focusing on heat treatment. The hardness and friction factor are very important factors of material and after-treatment process selection. Normally, roller bearing consists of roller and retainer. The roller gets high pressure constantly, while the retainer gets tensile and compressive stress. Therefore, sensitive material selection and heat treatment of each part is quite important. In this experimental evaluation, carbon steel, chrome special steel and others are employed and their characteristics after heat treatment are identified. Each material is prepared by refining high frequency heat treatment. The friction factor and static load capacity of manufactured material are experimentally identified and destructive test of material is processed. Optimal material and heat treatment conditions for IRB roller bearing are determined based on experiment results.

A Study on Tribology Characteristics of SM53C by High Frequency Heat Treatment

The Cam nose part of the Automobile's Cam shaft is strongly bumped with rocker arm or valve-lift. Therefore abnormal wear such as unfair-wear and early-wear occur in the surface. This abnormal wear causes a defect that bad timing open and close actions of the engine valve happen in the combustion chamber so the fuel gas will be combustion imperfect. Therefore, the Cam shaft has to be high hardness and wear resistance. In this study, high frequency heat treatment method was accomplished for wear test for material SM53C.

Library of the high frequency heat treatment engineer

Library of the high frequency heat treatment engineer

Mechanized high-frequency heat treatment of truck transmission gears made of steel with low hardenability

Mechanized high-frequency heat treatment of truck transmission gears made of steel with low hardenability