회주철의 마찰용접 특성에 관한 연구 - 입열량 이론식을 중심으로 -

정호신,방국수,Jeong, Ho-Shin,Bang, Kook-Soo 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.3

Joining of grey cast iron by fusion welding has much difficulties for its extremely low ductility and low toughness because of the flake form of the graphite. And the brittle microstructure, i.e. ledeburite may be formed during fusion welding by its rapid cooling rates. By these kinds of welding problem, preheat and post heat treatment temperature must be increased to avoid weld crack or welding problems. In order to avoid these fusion welding problem, friction welding of cast iron was carried out for improving joint soundness, establishing friction welding variables. There is no factor for evaluating friction weldability in continuous drive type friction welding. In this point of view, this study proposed the parameters for calculating friction weld heat input. The results obtained are as follows ; 1. There was a close relationship between tensile strength and flash appearance of friction welded joint. 2. Tensile strength was decreased and flash was severely oxidized as increasing frictional heating time. 3. As increased forging pressure $P_2$, flash had a large crack and tensile strength was decreased. 4. As powdered graphite by rotational frictional force induced flat surface and hindered plastic flow of metal, tensile strength of welded joint was decreased. 5. Heat input for continuous drive type friction welding could be calculated by the factors of $P_1$, $P_2$ and upset distance(${\delta}$).

오스테나이트계 스테인리스강의 용접성과 내식성에 미치는 합금원소의 영향(I) - 응고균열 감수성을 중심으로 -

정호신,이윤용,배동수,Jeong, Ho-Shin,Lee, Yun-Young,Bae, Dong-Soo 대한용접접합학회 2012 대한용접·접합학회지 Vol.30 No.3

The interest of austenitic heat resistant stainless steels containing high Si has increased because they have higher resistance of oxidation and higher strength at high temperature than STS 310. This study carried out Varestraint test for evaluation of solidification cracking sensitivity of 14 different stainless steels. As a result of Varestraint test, all specimens solidified as primary ferrite, and solidification crack sensitivity increased with adding $N_2$ to shielding gas. Nb and W had beneficial effect on solidification crack resistance in case of less than FN 2 containing, but crack sensitivity increased with Nb and W in case of more than FN 2. Ce had beneficial effect on solidification crack resistance but impaired weld bead appearance.

스테인리스강의 용접특성과 균열방지대책

정호신 ( Ho Shin Jeong ),정호신 ( Ho Shin Jeong ),김기철 ( Ki Chul Kim ) 대한금속재료학회 1989 大韓金屬學會會報 Vol.2 No.2

회주철 용접부 금속조직의 특성에 관한 연구

정호신(Ho-Shin Jeong),방국수(Kook-Soo Bang),오창수(Chang-Soo Oh) 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.1

The purpose of this study is evaluation of proper welding condition in order to solve the problems such as cast iron weld cracking, HAZ embrittlement. The formation of martensite in welding of the gray cast iron by arc welding is related to weld cracking. The effect of pre-heating and post-heating to microstructure and hardness of weld joint were examined. Main results obtained were as follows. In case of autogenous welding by GTAW, the number of crack was significantly decreased with increasing welding heat input and pre-heat temperature. But crack sensitivity was increased by martensite formation due to increasing cooling rate with increasing of base metal thickness. In case of bead on plate welding by GTAW, crack sensitivity was increased with increasing welding current, and welding current exhibiting no crack was increased with pre-heat temperature. The most of cracks formed at deposited weld metal were solidification crack in the case of 316L buttering. The main cause of GTAW deposited metal cracking was martensitic transformation. The GTAW range for crack free was very severe and narrow. To minimize the welding crack sensitivity, buttering gray cast iron by 316L welding electrode was very effective and the application of preheating made welding range broad.

구리-알루미늄 이종재료의 브레이징 특성 향상에 관한 연구

정호신(HO-SHIN JEONG),배동수(DONG SU BAE),고성우(SUNG WOO KO) 한국해양공학회 2001 韓國海洋工學會誌 Vol.15 No.3

One of the most important considerations to braze Cu-Al dissimilar materials is control of brittle metallic compound which makes it difficult to obtain a sound brazed joint. Nowdays, several attempts were made to control the metallic compound. But effective method for controlling metallic compound was not established. In this point of view, commercially pure aluminum and copper were used as base metal and Al-Si-X and Zn-Al-X alloy systems were developed as filler metal. Brazing was carried out to find optimum conditions for Cu-Al dissilmilar joint.<br/> The results obtained in this study were summarized as follows:<br/> 1) The joint brazed by Al-Si-X filler metal showed good brazeability and mechanical properties. The tensile strength of the joint brazed over solidus temperature was more than 90% of Al base metal. Especially, the joint brazed at liquidus temperature was fractured in the Al base metal.<br/> 2) Fluorides fluxes(a mixture of potassium fluoro-aluminates) were used to improve surface cleanliness of base metal and wettability of Al-Si-X filler metal. It was melted at the temperature about 10℃ lower than that of the filler metal, and made appropriate brazing environment. Therefore, it could be a proper selection as flux.

無酸素銅의 마찰 용접 특성에 관한 연구

정호신(Ho-Shin Jeong),篠田 剛(Takeshi Shinoda) 한국해양공학회 1997 韓國海洋工學會誌 Vol.11 No.1

Copper and its alloy had been used widely because of its pronouncing characteristics on their high thermal and electrical conductivity. Various fusion welding methods, such as SMAW, SAW, GTAW, GMAW, Electroslag welding and so on are applied to weld copper and its alloy. But fusion welding of copper has so many welding problems. The most serious problems were poor penetration and high thermal contraction stress due to its high thermal conductivity and porosity could be formed by rapid cooling rate of fusion welding.<br/> In order to avoid such fusion welding problems, preheating, peening and heat treatment must be applied to obtain sound weld joint of copper.<br/> But preheating induce another welding problem such as grain coarsening of weld heat affected zone. This grain coarsening reduces ductility and strength of weld joint.<br/> As described above, there are so many problems in fusion welding of copper.<br/> In this view of point, friction welding of copper is tried to obtain sound weld joint of copper by reducing metallurgical problems.<br/> This study introduced new concept of heat input for evaluating the friction weldability of copper. As a result, weldability of copper could be evaluated by this new concept of heat input.

스테인리스강의 용접 특성에 미치는 합금원소의 영향

정호신(Ho-Shin Jeong),배동수(Dong-Su Bae),엄동석(Dong-Suk Um) 한국해양공학회 1997 韓國海洋工學會誌 Vol.11 No.1

Stainless steels are widely applicable in various engineering fields for its exellent corrosion and impact resistance. Austenitic weld metal has some ferrite for preventing solidification cracking by ASME specification. Several family of austenitic stainless steel contains varying ferrite contents. But ferrite in austenitic stainless steels is adversely affect weld metal toughness and since fully austenitic grades are known to have good toughness.<br/> Austenitic stainless steel has various alloying addition for improving corrosion resistance, impact toughness and solidification crack resistance. The effect of various alloying elements are not found to be clear in present.<br/> From this view of point, this study tried to establish the criteria of alloy design for austenitic stainless steels by controlling primary solidification mode and clarifying the effect of several alloying elements.

초정응고(初晶凝固) 형식(形式) 제어(制御)에 의한 오스테나이트계(系) 스테인리스 신강종(新鋼鍾)의 개발(開發)

정호신 ( Ho Shin Jeong ) 한국어업기술학회 1991 수산해양기술연구 Vol.27 No.2

오스테나이트계 스테인리스강의 확산접합 특성에 관한 연구

정호신(Ho-Shin Jeong),방국수(Kook-Soo Bang) 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.5

This study was conducted by using type 304 austenitic stainless steel as experimental material to clarify the diffusion characteristics of diffusion bonding and diffusion brazing. The bonding variables such as the bonding pressure, bonding time and surface roughness affecting the tensile behavior of joints. The main results obtained were as follows: 1. The tensile strength of diffusion bonded joint was almost equivalent to that of the base metal, and the joint efficiency of almost 100%. 2. Although the surface roughness did not have significant influence on the tensile strength of diffusion bonded joints, it shows notable difference in terms of the fracture appearance. The fracture occurred in the interface of bonded joints when the surface roughness was not so smooth. However, all of the tensile specimen fractured at base metal and showed typical a cup and cone fracture, when the surface was smooth. 3. The pressure was an extremely critical factor when conducting diffusion brazing. It was observed that as the pressure became higher, the better interface was produced, showing high quality interface with the tensile strength of the joints amounting to nearly 500MPa. 4. The homogenization heat treatment after diffusion brazing had some influence on the strength of joints.

시효한 STS304 모재부의 기공형성과 조사유기편석에 미치는 He 사전 주입의 영향

배동수 ( Dong Su Bae ),정호신 ( Ho Shin Jeong ),( Heishichiro Takahashi ) 대한금속재료학회(구 대한금속학회) 2014 대한금속·재료학회지 Vol.52 No.7

The matrix part of aged STS304 has been irradiated up to 5.4 dpa at 673 K using 1,250 keV highvoltage electron-microscopy (HVEM) connected with an ion accelerator, to study the effect of He pre-injection on microstructural evolution. Two types of irradiation modes were used in this study. The first mode used single electron-beam irradiation and the second mode used electron-beam irradiation after He pre-injection. Thin-disc samples were prepared from the matrix part of STS304 aged at 673 K for 1,000 h. Irradiationinduced- segregation analyses were carried out by an energy-dispersive X-ray analyzer (EDX) in a 200 keV field- emission transmission electron microscopy (FE-TEM) with a beam diameter of about 0.5 nm. The mean size of voids increased considerably and their distribution was bi-modal, when the electron-beam was used after He-injection. Void-number density, sink strength and swelling percentage of samples subjected to electron-beam irradiation after He-injection were larger than those subjected to single electron-beam irradiation. Compared to single electron-beam irradiation, the amount of grain boundary segregation was suppressed for electron-beam irradiation after He-injection. †(Received October 29, 2013)