• Proceedings of the KSME Conference
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• 2003.04a
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• pp.72-77
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• 2003

In order to develop ASTM A302 grade C type steel plate with excellent weldability, several steels with different chemistry have been manufactured and evaluated their mechanical properties and weldability. Trial A302-C steels have revealed tensile strength in the range of $61-67kg/mm^2$ and elongation in the range of $27{\sim}32%$, depending on chemical compositions within the ASTM specification range. In case of impact toughness, trial steels showed in the range of 58-70J at $0^{\circ}C$. From the weldability test, the minimum preheat temperature was found to be about $150^{\circ}C$, and automatic welding condition satisfied the requirements of both ASTM specification and users.

• Analytical Science and Technology
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• v.22 no.4
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• pp.302-306
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• 2009

A trace amount of boron in steel significantly influences its mechanical and physical properties. A prompt gamma ray activation analysis (PGAA) method is used to measure boron in low alloy steel samples of KRISS 101-01-C21~C26. NIST SRMs of 362, 364, 1761 and 1767 serve as the control standards to validate the measurement method. The measured values of the NIST SRMs are consistent with their certified values within the expected uncertainties, except for that of NIST SRM 362. Experimental uncertainties are evaluated according to the guidelines given by the International Organization for Standardization (ISO). The expanded uncertainties are calculated with a coverage factor of 2, at approximately 95% confidence level. The calculated relative expanded uncertainties of boron mass fractions are between 3% and 7% at the mg/kg level. The results are compared with the results measured by the solvent extraction-inductively coupled optical emission spectrometry (ICP/OES) method.

• Journal of Powder Materials
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• v.5 no.4
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• pp.299-302
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• 1998

Dimensional accuracy is one of the most important issues in the production of sintered parts. The iron-copper-carbon system is commonly used alloys in sintered structural parts production. The dimensional control of these alloys, however, is not easy because of their complex sintering behavior. This study is an effort to clarify the influence of common factors on dimensional change of Fe-Cu-C sintered structural parts. We determined the effect of such various parameters as chemical composition, particle diameter, compact density, sintering temperature and sintering time on dimensional changes. Consequently, we obtained a useful formula to predict the final dimension in function of these parameters. The effect of typical impurities in copper powder on the dimensional change of sintered parts has also been described.

• Transactions of Materials Processing
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• v.23 no.5
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• pp.297-302
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• 2014

The current paper introduces work that was conducted during the development of a stamping die for a reinforce center pillar made from high strength steel. In the current study, the Bauschinger effect on the springback analysis was studied by comparing simulation results with real panels, which are currently in production. For a complicated part shape, quantitative measurements of the deformed shape are not easy in general to obtain. An adjustment procedure of the shape data for some chosen sections has been suggested to improve the accuracy of the quantitative measurements. The results show that the kinematic hardening model provides more accurate results.

• Journal of Ocean Engineering and Technology
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• v.9 no.2
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• pp.141-148
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• 1995

Fatigue tests were carried out by a rotary bending testing machine of cantilever type. M.E.F.(ferrite encapsulated islands of martensite) materials were made by a series of heat treatment from a low carbon steel(SM 20 C). The fatigue tests were conducted at stress levels of 302 MPa and with frequencies of 25Hz, 2.5 Hz and 0.5 Hz in 3% NaCl solution. The fatigue strength increased with frequency got higher. The microcracks and corrosion pits were generated at the boundary between the matrix and the 2nd phase. The cracks generated by the corrosion pits were coalesced with the pits around the notch and became the initial crack. The $N_i/N_f$ ratio increased as the frequency and stress level decreased. The interference phenomenon increased with stress level and frequency gots higher. The crack propagation rate was delayed as the stress level lowers and the frequency gets higher, however, the range of the stress intensity factor depended only on a stress level.

• Journal of the Korean institute of surface engineering
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• v.51 no.5
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• pp.297-302
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• 2018

The important drawback of hardware fasteners consisted of 304 stainless steel (STS) is a frequent galling caused by a combination of friction and adhesion between the sliding surface. To improve the anti-galling effect, Sn-Al coatings by a thermal diffusion have been developed. The thermal diffusion by pack cementation with an $AlCl_3$ activator at $250^{\circ}C$ for 1 hour produced an Sn-Al alloy coating layer with an average thickness of $9.9{\pm}0.5{\mu}m$ on the surface of 304 STS fasteners. Compared with the galling frequency of the 304 STS fasteners, Sn-Al coatings on the surface of 304 STS fasteners demonstrated about 2.8-time reduction of the galling frequency.

• Transactions of Materials Processing
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• v.20 no.4
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• pp.296-302
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• 2011

The objective of this paper is to determine the effect of process parameters on the behavior of a 18Cr-10Mn-$0.44N_2$ nitrogen steel sample deformed by hot rolling. Compression tests were carried out at high temperatures to determine the flow stresses needed for a finite element(FE) analysis. The strain rate, ranging from 0.1 to $1.0s^{-1}$, significantly affected the flow stress at temperatures higher than $1,000^{\circ}C$. Non-isothermal rolling simulations and laboratory rolling tests were performed with plate specimens 14.5mm thick, 135mm wide and 226mm long. A rolling reduction of 15% per pass leading to a cumulative rolling reduction of 60% was determined as optimal. The extension ratio of 176.5% in the length direction was about 30.4 times greater than the extension ratio of 5.8% in the width direction. Isotropic properties for tensile strength, microstructure and grain size were measured after mock-up hot rolling tests. The results from the mockup tests were found to be in good agreement with those of the simulations.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.302-317
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• 1995

After initial structure of AISI 9260 steel is changed into pearlite and martensite, one is isothermally annealed at $700^{\circ}C$ below of $A_1$ transformation point and the other is isothermally annealed at the same condition after 3 cycles of heating and cooling between $680^{\circ}C$ and $780^{\circ}C$ of $A_1$ transformation point. Analyzing the changes of microstructure, mechanical properties and fractography of tension test, we obtained result as follows. The fastest spheroidization rate by changes of initial structure and heat treatment cycles is appeared at the heat treatment cycle which is isothermally annealed after 3 cycles of heating and cooling at below and above $A_1$ transformation point for martensite. At the above condition, the perfect spheroidization structure is appeared after 60hrs and after then, globular carbide is being coarsened. The mean diameter of globular carbide is $2.4{\times}10^{-3}mm$ after 90hrs. The changes of tension strength during spheroidization heat treatment follows Orwan function, ${\sigma}_o={\sigma}_i+Gb/l$, where l is interspacing of carbide particles and at the above condition, ${\sigma}_o=70.48+2.5{\times}10^{-3}/l(kg/mm^2)$. Fractography of fracture of spheroidization structure in tension test is appeared as dimple which is ductile rupture type by nucleation and growth of void, size of dimple is larger and deeper with increasing of heat treatment time.

• Journal of Korea Soil Environment Society
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• v.5 no.2
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• pp.55-66
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• 2000

A U.S EPA Synthetic soil matrix was used for reference neat soil and pyrene contaminated soil. For the contaminated soil, 4.79 wt.% pyrene was dissolved completely into the djchlorornethane, and the soil was evenly soaked with the pyrene solution. The contaminated soil samples(50$\pm$0.5mg) were heated in a modified electrical screen heater reactor which consisted of a thin stainless foil (3.5cm$\times$13cm$\times$0.00254cm, 302 stainless steel shim), two electrodes, and a 20cm dia. $\times$30cm tall cylindrical Pyrex chamber sealed at both ends by aluminum flanges. The heating rate and time conditions were selected as $455^{\circ}C$ @ $1137^{\circ}C$ /s, $760^{\circ}C$ @ $950^{\circ}C$ /s and $977^{\circ}C$ @ $977^{\circ}C$/s. Tar samples after heating the soils were collected on the aluminum foil funnel and a glass filter paper (25mm dia. filter paper) The tar sample and remnant soil on the reactor were extracted with dichloromethane covering the filters, foils and soil by sonicating each in the waterbath for 10 minutes. The extractions were run on a HPLC. At the low peak temperature(about $455^{\circ}C$ @ $1137^{\circ}C$/s) the color of tar was "white", at the middle peak temperature (about 76$0^{\circ}C$ @ 95$0^{\circ}C$/s) the color of tar was "pink brown", at the high peak temperature (about 977$^{\circ}C$ @ 977$^{\circ}C$/s) the color of tar was "dark brown". Cyclopeta(cd)pyrene (CPEP) , which is an interesting species due to mutagenic effect on human cells, was detected in tar samples only above the middle peak temperature. This species was not detected at the low peak temperature. Six isomers of bipyrene were detected. Phenanthrene(C$_{14}$ $H_{10}$) and cyclopenta(def)phenanthrene(C$_{15}$ $H_{10}$) were also detected, but their content was very small relative to the other listed compounds.to the other listed compounds.

• Journal of Powder Materials
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• v.25 no.4
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• pp.302-308
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• 2018

A lean alloy is defined as a low alloy steel that minimizes the content of the alloying elements, while maintaining the characteristics of the sintered alloy. The purpose of this study is to determine the change in microstructure and mechanical properties due to the addition of silicon or tin in Fe-Mo-P, Fe-Mn-P, and Fe-Mo-Mn-P alloys. Silicon- or tin-added F-Mo-P, Fe-Mn-P, and Fe-Mo-Mn-P master alloys were compacted at 700 MPa and subsequently sintered under a $H_2-N_2$ atmosphere at $1120^{\circ}C$. The sintered density of three alloy systems decreases under the same compacting pressure due to dimensional expansion with increasing Si content. As the diffusion rate in the Fe-P-Mo system is higher than that in the Fe-P-Mn system, the decrease in the sintered density is the largest in the Fe-P-Mn system. The sintered density of Sn added alloys does not change with the increasing Sn content due to the effect of non-dimensional changes. However, the effect of Si addition on the transverse rupture strengthening enhancement is stronger than that of Sn addition in these lean alloys.