• Journal of Power System Engineering
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• v.8 no.3
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• pp.30-35
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• 2004

In the steel making industries, the continuous casting process has been applied to the number of company because of its economical benefit. Casting rolls are utilized for frictional drive and transport of solidifying slap. Dimensional tolerances, mechanical stability and surface condition of the cast roll can affect both the surface and internal quality of the product being cast. To overcome these problems, the industry is accelerating on the rate of technology improvements. Samples were overlaid on the S45C steel by submerged arc welding process. And the hardness, wear, electrochemical corrosion and oxidation tests were carried out. Test results were that all these materials were satisfying basic requirements of caster rolls. By these results, the addition of 0.1%Nb and 0.15%V increase mechanical properties and tempering resistance by its superior carbide forming characteristics in low carbon $12{\sim}13%Cr$ martensitic stainless steels.

• Journal of Welding and Joining
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• v.14 no.2
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• pp.19-27
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• 1996

재료의 표면개질은 표면층의 조직변화에 대한 개질법과 표면피복에 의한 개질 법으로 나눌 수 있다. 조직변화에 의한 개질법으로는 침탄, 질화, 이온주입 및 금속 확산 등이 있고, 표면피복에 의한 개질법으로는 도장, 도금, 육성용접, 물리증착(PVD) 및 화학증착(CVD) 등이 있는데, 용사법은 표면피복에 의한 개질법에 속한다. 용사기술 은 비교적 최근에 발달된 표면피복 기술로서 그림1과 같이 플라즈마, 가스화염 또는 아크열원을 이용하여 금속 또는 비금속 재료를 용융 혹은 반용융 상태로 모재에 고속 도로 분사하여 충돌 적층시켜 피복하는 공정으로 다른 표면개질기술에 비해서 여러 가지 잇점을 가지고 있다. 이것은 거의 모든 재질의 모재(금속, 세라믹, 유기재료 등) 에 대해 피막의 형성이 가능하고, 용사재료의 종류도 다양하다(금속, 합금, 각종 세라 믹, 플라스틱, 각종 복합재료 등). 또한 노재크기의 제한이 없고, 대형의 재료에 대해 서 한정된 부위의 피복이 가능하며, 모재의 열영향이 적고, 피막의 형성속도가 다른 피막법에 비해 빠른 장점을 가지고 있다. 그 예로 알루미나(Al$_{2}$O$_{3}$)를 피복할 경우 화학증착(CVD)법에 의해서는 피막형성 속도가 약 2 * $10^{-4}$mm/min 인데 비해 용사법에 의해서는 약 7.5 * $10^{-1}$mm/min로 매우크다. 이와같은 많은 장점을 갖고있는 용사법을 이용한 표면개질에 대해 본 기술보고에서 서술하고자 한다.

• Journal of Ocean Engineering and Technology
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• v.5 no.1
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• pp.97-105
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• 1991

In this paper, the fatigue strength and the fatigue crack propagation behaviors of the round bar specimens which were spirally built up by welding and subsequently hardened by quenching were investigated. The material used was SF60 which was whdely employed in mechanical components, especially shafts. Fatigue tests were conducted at the fully reversed condition(R=-1) and axial and load control in the room temperature ahd air environment. The experimental results were expressed by both the range of stress intensity factor ($\Delta{K}$) and the effective range of stress intensity factor ($\Delta{K}_{eff}$). It was clarified that applying of quenching after the building up welding process improved the fatigue strength and the gatigue crack propagation property in the low range of $\Delta{K}$ of the built up round bar specimen.

• Journal of Welding and Joining
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• v.26 no.2
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• pp.50-54
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• 2008

The wearplate with Cr-C has been used in condition of severe abrasion. Recently, the demand of wearplate made by hardfacing with Cr-C has increased in the world, but it is lack of supply and expensive due to low productivity. CMAW (Compound Metal Arc Welding) is very useful process of several welding methods to make wearplate. In this paper, twin torch CMAW to use twin torch at the same time was developed to improve productivity and to ensure quality of wear plate. When the distance between two touches was smaller than 30mm, arc blow was occurred. However when the distance was larger than 35mm, there was no arc blow any more. If the oscillation path of each torch was overlapped together, the melt through at the overlapped zone was occurred due to concentrated heat input in substrate. On the other hand, the turning point of each torch was open more than 5mm, separated bead was generated. Therefore twin torch CMAW which has adequate conditions was able to make wearplate having flatter surface at the bead connection than single torch.

• Journal of Welding and Joining
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• v.18 no.6
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• pp.102-107
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• 2000

It was attempted to improve the wear resistance of Al alloy under the load condition by making a formation of the thick surface hardening alloy layers. The thick surface hardening alloy layers were formed on 6061 Al alloys overlayed by MIG welding process with WC-12%Co powder addition. Effects of the dispersion of WE-12%Co powders on hardness and wear characteristics of alloys were investigated. The following results were obtained. Most of WE-12%Co powders are dispersed nearly uniform as unmelted particles in the matrix alloy. A part of WC-12%Co powders are melted in the molten pool, and during solidification {TEX}$Al_{9}Co_{2}${/TEX} appeared. With increasing addition of WC-12%Co powders, the hardness and specific wear resistance of the overlay weld alloys increased and reached Hv450 at WC-12%Co powder addition rate of 54g/min. It is considered that excellent wear resistance of the overlayed alloys was due to dispersed WC-12%Co powders and increased 10 times at WC-12%Co powder addition rate of 54 g/min than that of the WC-free overlaying layers.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.56-60
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• 2008

Laser cladding technology was studied as a method for upgrading the present repair procedures of damaged tubes in a nuclear steam generator and Doosan subsequently developed and designed a new Laser Cladding Repair System. One of the important features of this newly developed Laser Cladding Repair System is that molten metal can be deposited on damaged tube surfaces using a laser beam and filler wire without the need to install sleeves inside the tube. Laser cladding qualification tests on the steam generator tube material, Alloy 600, were performed according to ASME Section IX. Residual stress analyses were performed for weld metal and heat affected zone of as-welded and PWHT with SYSWELD software.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.1
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• pp.36-41
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• 2003

The purpose of this study was to find a way to lengthen the life of hot closed forging die. The fluid interpretation on the plastic deformation of billet of billet was performed by finite element method. And design modification on the impression shape was also performed. The defaced part on the impression surface was mended by the developed build-up welding method. The die life was 3,000 units but alter the procedure it was lengthened up to 5,000.

• Journal of Welding and Joining
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• v.28 no.3
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• pp.79-85
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• 2010

Hardfacing is one of the frequently applying method to increase surface hardness in hot forging die. Recently, hardfacing receives great attention due to it's repair availability and low cost. In hot forging die, crack resistance and thermal shock resistance have been considered as major properties, However there are few studies for the assessment of these properties. So, it is necessary to establish the assessment method for crack resistance and thermal shock resistance in hardfacing for hot forging die. In this study, flux cored arc welding was applied to make hardfacing welds. Three point bending test was carried out to assess hardfacing weld's crack resistance, and high temperature bending test using salt bath was developed for thermal shock resistance. Consequently, it was possible to assess crack resistance and thermal shock resistance of hardfacing welds for hot forging die quantitatively.

• Journal of Welding and Joining
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• v.15 no.5
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• pp.134-143
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• 1997

The formation of thick alloyed layer with high Si content have been investigated on the surface of Al alloy (A5083) plate by PTA process with Si powder. Hardening characteristics and wear resistance of alloyed layer was examined in relation to the microstructure of alloyed layer. Thick hardened layer in mm-order thickness on the surface of A5083 plate can be formed by PTA process with wide range of process condition by using Si powder as alloying element because of eutectic reaction of Al-Si binary alloy. High temperature and rapid solidification rate of molten pool, which are features of PTA process, enable the formation of high Si content alloyed layer with uniform distribution of fine primary Si paticle. High plasma arc current was beneficial to make the alloyed layer with smooth surface appearance in wide range of powder feeding rate, because enough volume of molten pool was necessary make alloyed layer. Uniform dispersion of fine primary Si particle with about 30${\mu}{\textrm}{m}$ in particle size can be obtained in layer with Si content ranging from 30 to 50 mass %. Hardness of alloyed layer increased with increasing Si content, but increasing rate of hardness differed with macrostructure of alloyed layer. Wear resistance of alloyed layer depended on $V_{si}$(volume fraction of primary Si) and was remarkably improved to two times of base metal at 20-30% $V_{si}$ without cracking, but no more improvement was obtained at larger $V_{si}$.

• Journal of Welding and Joining
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• v.23 no.6
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• pp.72-76
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• 2005

Friction surfacing of STS304 consumable rod on S45C substrate was investigated by microstructural observation and mechanical tests. STS304 layer formed a strongly-bonded thick layer under a wide range of surfacing conditions. The highest coating eefficiency was obtained in the condition of 1000rpm-2.5mm/sec-2.5mm/sec. The hardness distribution showed the peak value in the boundary layer and as the consumable rotation speed increased, the boundary layer also hardness increasing. As the consumable rotation speed and the traveling speed increased, the coating efficiency tended to decrease. On the other hand, as the feeding speed increased, the coating efficiency appeared to be increased. The new Fe-Cr-Ni alloy layer is showed in the interface layer on $5\~15{\mu}m$ width. After friction surfacing, corrosion resistance of STS 304 surfacing layers were equaled to that of STS304 consumable rod.