• Title/Summary/Keyword: Medium Carbon Steel

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A Study on the Influence of Atmospheres in Frictional Machining(Part II) (摩찰加工 에 있어서의 零圍氣 영향 에 관한 硏究 제2보)

  • 손명환
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.6 no.2
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    • pp.113-120
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    • 1982
  • In the previously reported Part I, the experimental results in frictional machining that finished medium carbon steel SM 50 C under 6 kinds of liquid atmospheres by using ceramic tip as a frictional tool was described. The present study reports the experimental results that all the machining conditions are same in the Part I except tool material changed ceramics into tungsten carbide. The ceramic tool material is a stable oxide and a non-metallic material, but the tungsten carbide has the metallic characteristics that adhere to carbon steel at about 750.deg.C. The present study shows th comparison of the experimental results for the above 2 kinds of frictional tool material.

Charactrerization of microstructure, hardness and oxidation behavior of carbon steels hot dipped in Al and Al-1% Si molten baths (Al과 Al-1% Si 용융조에서 용융 도금된 탄소강의 경도, 산화 및 미세조직의 특성)

  • Hwang, Yeon-Sang;Won, Seong-Bin;Chunyu, Xu;Lee, Dong-Bok
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2013.05a
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    • pp.109-110
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    • 2013
  • Medium carbon steel was aluminized by hot dipping into molten Al or Al-1%Si baths. After hot-dipping in these baths, a thin Al-rich topcoat and a thick alloy layer rich in $Al_5Fe_2$ formed on the surface. A small a mount of FeAl and $Al_3Fe$ was incorporated in the alloy layer. Silicon from the Al-1%Si bath was uniformly distributed throughout the entire coating. The hot dipping increased the microhardness of the steel by about 8 times. Heating at $700-1000^{\circ}C$ however decreased the microhardness through interdiffusion between the coating and the substrate. The oxidation at $700-1000^{\circ}C$ in air formed a thin protective ${\alpha}-Al_2O_3$ layer, which provided good oxidation resistance. Silicon was oxidized to amorphous silica, exhibiting a glassy oxide surface.

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Study on Atmospheric Corrosion for Two Different Marine Environments in India

  • Saha, Jayanta Kumar
    • Corrosion Science and Technology
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    • v.6 no.3
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    • pp.120-127
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    • 2007
  • In any developing nation major investment goes for infrastructure and it is not exception in India. Good numbers of buildings, bridges, shopping malls, car parks etc. are coming up with steel for sustainable development. Thus protecting the structures from corrosion are the challenges faced by professionals for all types of steel structures. About 3% of GDP is accounted for loss due to corrosion. To combat this up to date corrosion map is called for as the country has wide variation of climatic zones with vastcoastline. Logically organic paint system can be prescribed based on the corrosion rate on bare steel with respect to environment. Present paper will emphasis on the study conducted on two types of structural steel coated with organic paint located in twomarine environment having been exposed for three years, Test coupons made from steels both bare and coated are deployed at two field stations having marine (Digha) and industrial marine (Channai) environments. Various tests like AC impedance DC corrosion, polarisation, salt spray test, $SO_2$ chamber and Raman spectroscopy were carried out both in laboratory on fresh as well as coupons collected from exposure sites. Rust formed on the bare and scribed coated coupons are investigated. It is found that normal marine environment at Digha exhibits higher corrosion rate than polluted marine environment in Channai. Rust analysis indicates formation of ${\propto}$-FeoOH protects or reduces corrosion rate at Channai and formation of non-protective ${\gamma}$-FeoOH increases corrosion rate at Digha. The slower corrosion rate in Channai than at Digha is attributed due to availability of $SO_2$, in the environment, which converts non‐protective rust ${\gamma}$-FeoOH to protective rust ${\propto}$-FeoOH. While comparing the damage on the coated panels it is found that low alloy structural steel provides less damage than plain carbon steel. From the experimentations a suitable paint system specification is drawn for identical environments for low medium and high durability.

Fatigue Crack Growth Rate Equation by Crack Closure (균열닫힘현상을 고려한 피로균열전파식)

  • 김용수;강동명;신근하
    • Journal of the Korean Society of Safety
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    • v.6 no.4
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    • pp.81-87
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    • 1991
  • We propose the crack growth rate equation which will model fatigue crack growth rate behavior such that constant stress amplitude fatigue crack growth behavior can be predicted. Constant stress amplitude fatigue tests are conducted for four materials under three stress ratios of R=0.2, R=0.4 and R=0.6. Materials which have different mechanical properties i.e. stainless steel, low carbon steel, medium carbon steel and aluminum alloy are used. Through constant stress amplitude fatigue test by using unloading elastic compliance method, it is confirmed that crack closure is a close relationship with fatigue crack propagation. We describe simply fatigue crack propagation behavior as a function of the effective stress intensity factor range ($\Delta$ $K_{eff}$=U .$\Delta$K) for all three regions (threshold region, stable region). The fatigue crack growth rate equation is given by da / dN=A($\Delta$ $K_{eff}$­$\Delta$ $K_{o}$ )$^{m}$ / ($\Delta$ $K_{eff}$­$\Delta$K) Where, A and m are material constants, and $\Delta$ $K_{o}$ is stress intensity factor range at low $\Delta$K region. $K_{cf}$ is critical fatigue stress intensity factor.actor.

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An Experimental Equation on the Fatigue Crack Growth Rate Behavior (피로 균열 전파 거동에 대한 실험식)

  • Kim, Sang-Chul;Kang, Dong-Myeong;Woo, Chang-Gi
    • Journal of the Korean Society for Precision Engineering
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    • v.8 no.2
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    • pp.27-35
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    • 1991
  • We propose the crack growth rate equation which applied over three regions (threshold region, stable region, unstable region) of fatigue crack propagation. Constant stress amplitude fatigue tests are conducted for four materials under three stress ratios of R=0.05, R=0.2 and R=0.4. Materials which have different mechanical properties i.e. stainless steel, low carbon steel, medium carbon steel and aluminum alloy are used. The fatigue crack growth rate equation is given by $da/dN={\beta} (1-R)^{\delta}\({\DELTA}K-{\DELTA}K_t)^{\alpha} / (K_{cf}-K_{max})$${\alpha}, {\beta}$ , and ${\delta}$ are constants, and ${\Delta}K_t$ is stress intensity factor range at low ${\Delta}K$ region. The constants are obtained from nonlinear least square method. $K_{ef}$is critical fatigue stress intensity factor. The relation between half crack length and number of cycles obtained by integrating the crack growth rate equation is in agreement with the experimental data. It is also experimented with constant maximum stress and decreasing stress ratios, and the fatigue growth rate of each material is in accord with the proposed equation.

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Study on Characteristics of Laser Surface Transformation Hardening for Rod-shaped Carbon Steel (I) - Characteristics of Surface Transformation Hardening by Laser Heat Source with Gaussian Intensify distribution - (탄소강 환봉의 레이저 표면변태경화 특성에 관한 연구 (I) - 가우시안 파워밀도 분포의 레이저 열원을 이용한 표면변태경화 특성 -)

  • Kim, Jong-Do;Kang, Woon-Ju
    • Journal of Welding and Joining
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    • v.25 no.3
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    • pp.78-84
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    • 2007
  • Laser Material Processing has been replaced the conventional machining systems - cutting, drilling, welding and surface modification and so on. Especially, LTH(Laser Transformation Hardening) process is one branch of the laser surface modification process. Conventionally, some techniques like a gas carburizing and nitriding as well as induction and torch heating have been used to harden the carbon steels. But these methods not only request post-machining resulted from a deformation but also have complex processing procedures. Besides, LTH process has some merits as : 1. It is easy to control the case depth because of output(laser power) adjustability. 2. It is able to harden the localized and complicated a.ea and minimize a deformation due to a unique property of a localized heat source. 3. An additional cooling medium is not required due to self quenching. 4. A prominent hardening results can be obtained. This study is related to the surface hardening of the rod-shaped carbon steel applied to the lathe based complex processing mechanism, a basic behavior of surface hardening, hardness distribution and structural characteristics in the hardened zone.

A Study in the Heat Resistance Properties of STD61 Steel using the Surface Hardening Method (STD61 강의 내열특성향상을 위한 표면경화에 관한 연구)

  • Lee, Gu-Hyeon
    • 연구논문집
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    • s.26
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    • pp.121-132
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    • 1996
  • The carburising surface modification treatment of the die steel has been used for improving wear resistance and heat cycle strength of the die and preventing a pitting on the surface because the carbides are forming in the matrix during carburising. Generally, the hot forging die was used after quenching-tempering treatment or nitriding after quenching-tempering treatment. The nitriding after carburising on the surface of a hot die steel and a wear resistance die steels was suggested by SOUCHARD, JACQUOT. and BUVRON. This surface modification treatment improved the adhesive and abrasive wear resistance and friction coefficient. The process was introduced to the forging die of stainless steel, titanium alloy steel, alloy and medium carbon steel and the physical properties of the die after the treatment were improved. The surface hardening treatment of the nitriding, the carburising, the boriding, and TD process were used to improved the life time of the forging die. Also, the coating process of PVD, CVD and PCVD were used and the hard chromium plating was occasionally used. Therefore, this study analyzed the effects of the carburising time and the conditions of nitriding on STD61 steel. The case depth, the surface hardness, the forming carbide size and shape during overcarburising process on the die steel were also examined.

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Corrosion of Steel Rebar in Concrete: A Review

  • Akib Jabed;Md Mahamud Hasan Tusher;Md. Shahidul Islam Shuvo;Alisan Imam
    • Corrosion Science and Technology
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    • v.22 no.4
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    • pp.273-286
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    • 2023
  • Rebar is embedded in concrete to create reinforced concrete (RC). Rebar carries most of the tensile stress and gives compressively loaded concrete fracture resistance. However, embedded steel corrosion is a significant cause of concern for RC composite structures worldwide. It is one of the biggest threats to concrete structures' longevity. Due to environmental factors, concrete decays and reinforced concrete buildings fail. The type and surface arrangement of the rebar, the cement used in the mortar, the dosing frequency of the concrete, its penetrability, gaps and cracks, humidity, and, most importantly, pollutants and aggressive species all affect rebar corrosion. Either carbonation or chlorides typically cause steel corrosion in concrete. Carbonation occurs when carbon dioxide in the atmosphere combines with calcium within the concrete. This indicates that the pH of the medium is falling, and the steel rebar is corroding. When chlorides pass through concrete to steel, corrosion rates skyrocket. Consideration must be given to concrete moisture. Owing to its excellent resistance, dry concrete has a low steel corrosion rate, whereas extremely wet concrete has a low rate owing to delayed O2 transfer to steel surfaces. This paper examines rebar corrosion causes and mechanisms and describes corrosion evaluation and mitigation methods.

Effects of Heat Treatment Condition on the Mechanical Properties in Fe-0.4%C-2.3%Si Steel (Fe-0.4C-2.3Si강의 기계적 성질에 미치는 오스템퍼링 열처리 조건의 영향)

  • Son, Je-Young;Song, June-Hwan;Kim, Ji-Hun;Ye, Byung-Joon
    • Journal of Korea Foundry Society
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    • v.32 no.2
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    • pp.104-108
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    • 2012
  • The effect of heat treatment on mechanical properties of 0.4C-2.3Si(wt%) steel with bainitic ferrite matrix were investigated. This steel has been synthesized intergrating concepts from TRIP(Transformation Induced Plasticity) steel & Austempered Ductile Cast Iron(ADI) technology. The low alloy medium carbon (0.4 %C) steel with high silicon (2.3 %Si) was initially annealed for 60 min at $800^{\circ}C$, $820^{\circ}C$ and $840^{\circ}C$ respectively in the intercritical region and then subsequently austempered at various temperatures at $260^{\circ}C$, $320^{\circ}C$ and $380^{\circ}C$ for 30 min in a salt bath. The mechanical properties were measured by using a tensile test. A detailed study of the microstructure of this steel after heat treatment was carried out by means of electron back scattering diffraction (EBSD) technic. In this study, a new low alloy steel with high strength (780~1,050MPa) and exceptionally high ductility (20~40%) was obtained.

Effect of Microstructural Factors on Room- and Low-Temperature Impact Toughness of Hypoeutectoid Steels with Ferrite-Pearlite Structure (페라이트-펄라이트 조직 아공석강의 상온 및 저온 충격 인성에 미치는 미세조직적 인자의 영향)

  • Lee, Seung-Yong;Jeong, Sang-Woo;Hwang, Byoungchul
    • Korean Journal of Materials Research
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    • v.25 no.11
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    • pp.583-589
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    • 2015
  • This paper presents a study on the room- and low-temperature impact toughness of hypoeutectoid steels with ferrite-pearlite structures. Six kinds of hypoeutectoid steel specimens were fabricated by varying the carbon content and austenitizing temperature to investigate the effect of microstructural factors such as pearlite volume fraction, interlamellar spacing, and cementite thickness on the impact toughness. The pearlite volume fraction usually increased with increasing carbon content and austenitizing temperature, while the pearlite interlamellar spacing and cementite thickness mostly decreased with increasing carbon content and austenitizing temperature. The 30C steel with medium pearlite volume fraction and higher manganese content, on the other hand, even though it had a higher volume fraction of pearlite than did the 20C steel, showed a better low-temperature toughness due to its having the lowest ductile-brittle transition temperature. This is because various microstructural factors in addition to the pearlite volume fraction largely affect the ductile-brittle transition temperature and low-temperature toughness of hypoeutectoid steels with ferrite-pearlite structure. In order to improve the room- and low-temperature impact toughness of hypoeutectoid steels with different ferrite-pearlite structures, therefore, more systematic studies are required to understand the effects of various microstructural factors on impact toughness, with a viewpoint of ductile-brittle transition temperature.