• Title/Summary/Keyword: Laser heat treatment

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A Study on the Properties of Laser-Welded Boron Steel for Hot Stamping According to the Heat-Treatment Conditions (핫스탬핑용 보론 강판의 레이저 용접부에 대한 열처리 조건에 따른 특성 연구)

  • Hwang, Seok-Hwan;Nam, Ki-Woo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.3
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    • pp.319-324
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    • 2012
  • The hot-stamping technique is a forming method for manufacturing high-strength parts, in which the part is cooled rapidly after press forming above the austenite transformation temperature. Boron steel, which contains a very small amount of boron, is one of the materials used for hot stamping. The purpose of this study is to investigate the microstructure and mechanical properties according to the heat-treatment conditions. Die-quenching from various temperatures was conducted for different elapsed heat-treatment times. Laser-welded boron steel after quenching has a tensile strength of 1454 MPa and an elongation of 6 %. It has 94 % of the tensile strength of the base metal (1522 MPa). These properties can provide practical information for the use of boron steels for hot stamping.

A Study on 40Cr Alloy steel of Laser Surface Hardening (40Cr 강의 Laser Surface Hardening 에 관한 연구)

  • Ryu, Nung-Hee;Kang, Sung-Goon
    • Korean Journal of Materials Research
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    • v.11 no.11
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    • pp.1001-1005
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    • 2001
  • In this study, the surface of 40Cr steel was hardened by $CO_2$Laser, and then the microstructural transformations and the hardness distributions of the laser surface hardened layer were observed. The experimental results showed the surface hardening layer was consisted of three parts, which is outmost surface layer of needle martensite, middle layer of martensite and remained pearlite, and transitory boundary layer. In hardness distributions, the surface hardeness of the surface hardening layer had Hv 800~1000, that was 2 to 4 times of matrix's hardness. The hardeness distribution of laser hardening layer that of surface layer hardened by general heat treatment.

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Porosity Reduction in Laser Welding of Nitrided Carbon Steel (질화처리된 저탄소강 레이저 용접부의 기공 감소)

  • Ahn, Young-Nam;Kim, Cheolhee;Lee, Wonbeom;Kim, Jeonhan
    • Journal of Welding and Joining
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    • v.31 no.6
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    • pp.71-76
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    • 2013
  • Gas nitriding is a surface hardening process where nitrogen is introduced into the surface of a ferrous alloy. During fusion welding of nitrided carbon steel, the nitride inside weld metal is dissolved and generates nitrogen gas, which causes porosities - blow holes and pits. In this study, several laser welding processes such as weaving welding, two-pass welding, dual beam welding and laser-arc hybrid welding were investigated to elongate the weld pool to enhance nitrogen gas evacuation. The surface pits were successfully eliminated with elongated weld pool. However blowholes inside the weld metal were effective reduced but not fully disappeared.

Effect of Laser Surface Hardening Factors on the Wear Resistance of Medium Carbon Low Alloy Steel Surface-hardened by Using CO2 Laser Technique (CO2 레이저 표면경화처리된 중탄소 저합금강의 내마모 특성에 미치는 레이저 표면경화 인자의 영향)

  • Park, K.U.;Roh, Y.S.;Han, Y.H.;Lee, S.Y.
    • Journal of the Korean Society for Heat Treatment
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    • v.5 no.2
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    • pp.122-132
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    • 1992
  • This study has been performed to investigate into some effects of the power density and traverse speed of laser beam on the optical microstructure, hardness and wear characteristics of medium carbon low alloy steel treated by laser surface hardening technique. The results obtained from the experiment are summarized as follows : (1) Optical micrograph has shown that finer lath martensite is formed and the amount of undissolved complex carbides increases as the traverse speed increases under the condition of a given power density, whereas the coarsening of lath martensite and the reduction of undissolved complex carbides occur with increasing the power density at a given traverse speed. (2) Hardness measurements have revealed that as the traverse speed increases, hardness values of outermost surface layer more of less decrease under low power densities, but are uniformly distributed under high power densities, also showing that they are uniformly distributed at low traverse speeds and more or less decrease at high traverse speeds with increasing the power density. (3) The effective case depth has been found to decrease from 0.26 mm to 0.17 mm with increasing the traverse speed from 1.5 m/min to 3.0 m/min at a given power density of $25.48{\times}10^3w/cm^2$ and to increase from 0.20 mm to 0.36 mm with increasing the power density from $19.11{\times}10^3w/cm^2$ to $38.22{\times}10^3w/cm^2$ at a given traverse speed of 2.0 m/min. (4) Wear test has exhibited that the amount of weight loss of laser surface hardened specimen with respect to sliding distance at a given load increases with increasing traverse speed at a given power density and decreses with increasing power density at a given traverse speed.

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Dental Co-Cr alloys fabricated by selective laser melting: A review article (선택적 레이저 용융 방법으로 제작한 치과용 코발트 크롬 합금에 대한 문헌고찰)

  • Kang, Hyeon-Goo
    • The Journal of Korean Academy of Prosthodontics
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    • v.59 no.2
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    • pp.248-260
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    • 2021
  • Cobalt-chromium alloys are used to fabricate various dental prostheses, and have advantages of low cost and excellent mechanical properties compared to other alloys. Recently, selective laser melting, which is an additive manufacturing method, has been used to overcome the disadvantages of the conventional fabrication method. A local rapid heating and cooling process of selective laser melting induces fine microstructures, grain refinement, and reduction of porosities of the alloys. Therefore, it can improve mechanical properties compared to the alloys fabricated by the conventional method. On the other hand, layering process and rapid heating and cooling cause accumulation of a large amount of residual stresses that can adversely affect the mechanical properties. A heat treatment for removing residual stresses through recovery and recrystallization process caused complicated changes in mechanical properties induced by phase transformation, precipitate and homogenization of the microstructures. The purpose of this review was to compare the manufacturing methods of Co-Cr alloys and to investigate the characteristics of Co-Cr alloys fabricated by selective laser melting.

A Study on the $CO_2$ Laser Beam Welding of Thin Steel Sheets and Tailored Blanks - Between Similar Thin Sheet Materials - (박판의 $CO_2$레이저 빔 용접과 소재접합일체성형에 관한 연구- 동질 박판재간 -)

  • 이희석;배동호
    • Journal of Welding and Joining
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    • v.15 no.2
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    • pp.54-63
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    • 1997
  • For the purpose of establishing laser welding condition (laser power, welding speed and beam focus) and of evaluating tailored blanks for two kinds of thin steel sheets SPCC and SK5M using in the thin plate structure such as automobile, train, and so on, investigated their $CO^2$ laser weldability under various initial welding conditions. SPCC thin sheet showed good weldability under some welding conditions. But, high carbon steel sheet SK5M needed heat treatment after welding to obtain ductility of the welded joint. And next, tailored blank was tested through deep drawing to evaluate reliability of their obtained laser welding conditions. The forming depths by tailored blank were SPCC+SPCC=22-25mm and SK5M+SK5M=13-25mm.

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Wear characteristics of High Carbon 9CrSi Alloy Steel of Laser Surface Cladding (Laser Surface Cladding 고탄소 9CrSi 합금강의 마모 특성)

  • Yu, Neung-Hui;Gang, Seong-Gun
    • Korean Journal of Materials Research
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    • v.11 no.10
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    • pp.813-819
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    • 2001
  • The microstructure and the distribution of hardness of Co and A1 alloy powder cladding layer in high carbon 9CrSi alloy steel for roll materials cladded by laser surface cladding were investigated. And, for the evaluation of soundness as the roll materials, we examined the wear resistance of the cladding materials with the wear appratus of pin on disc type. The experimental results showed that the microstructure of laser cladding layer was constituted with the clad surface layer, the alloy layer, the heat treatment layer with base metal. The wear resistance of Ni alloy Powder cladding material was superior to that of Co alloy powder cladding material both at the low speed (0.46m/s) and the high speed(0.92m/s). It seemed that the behavior of wear showed the abrasive wear at the early stage and the adhesive wear at the late stage.

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A Study on the CO $_2$Laser Beam Welding of Thin Steel Sheets and Tailor Welded Blank (박판 $CO_2$레이져 빔 용접과 소재접합일체성형에 관한 연구)

  • 이희석
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1996.03a
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    • pp.159-164
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    • 1996
  • For the purpose of establishing laser welding condition(laser power, welding speed and beam focus) and of evaluating tailor welded blank for three kinds of thin steel sheets of SPCC, SK5M and SUS304 using in the thin plate structure such as automobile, train and so on. Their $CO_2$ laser weldability were primarily tested under various welding condition. SPCC and SUS304 thin sheets showed good weldability under some welding condition. But, high carbon steel sheet SK5M needs heat treatment after welding to obtain higher tensile strength and ductility of the welded joint. And next, laser welding condition. Butt-welded specimens were not nearly broken at weld bead. However, base material were ruptured in the direction of circumference. The forming depths by tailor weld bead. However, base material were ruptured in the direction of circumference. The forming depths by tailor welded blank were SPCC+SPCC=22~25mm, SUS304+SUS304=25~43mm and SK5M+SK5M=13~17mm.

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The in vivo photothermal treatment of gold nanorod in the mouse ear model

  • Liu, Bruce Yao Wen;Chen, Cheng-Lung;Lee, Shin-Yu;Chang, Fu-Hsiung;Lin, Win-Li;Chia, Chih-Ta;Chen, Yang-Yuan
    • Biomaterials and Biomechanics in Bioengineering
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    • v.1 no.1
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    • pp.41-50
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    • 2014
  • Gold nanorod's exceptional light to heat transduction is a robust phonomenon that has been extensively verified. The phenomenon is a trait from which many novel applications across disciplines have been proposed. In this investigation, the feasibility of utilizing heat harvested from such photothermal method to combat cancer is presented. Using non-invasive laser methods, an in vivo study is conducted on mouse ear tumors administered with gold nanorods (Au NRs). An emphasis is placed on monitoring the tumor developments after photothermal treatments, over time. The findings reveal significant tumor growth surpression at a threshold laser power of $0.6W/cm^2$ lasting 2 minutes; this energy also brought about dramatic size reduction in treated tumors. Furthermore, the apparent formation of an eschar over the laser treated region indicates extensive hemorrhagic necrosis of the tumor tissue; a phenomenon implicative to the inhibition of angiogenesis.