• 대한금속재료학회지
• /
• 제49권11호
• /
• pp.831-838
• /
• 2011

Effects of spangle size and crystallographic characteristics on the surface appearance, galling properties, and adhesive strength of hot-dip galvanized steel sheets have been investigated. Both spangle size and crystallographic orientation measured by optical microscopy, scanning electron microscopy, and X-ray diffraction were identified as critical factors influencing the galvanized coating performance. By decreasing the spangle size, surface appearance and galling properties related to the friction coefficient were significantly improved. However, low temperature adhesive-strength with small spangle galvanized steel sheets showed lower values compared to commercially used galvanized coating. The variation of adhesive strength in terms of spangle size has been clarified.

• 한국토양동물학회지
• /
• 제8권1_2호
• /
• pp.23-26
• /
• 2003

고구마뿌리혹선충(Meloidogyne incognita)에 대하여 멀구슬나무(Azadirachta indica) 부산물인 Suneem-G와 요소의 억제효과를 연구하였다. 폿트 당 살균토양을 2kg씩 넣고 M. incognita 2령기 유충 2,000마리를 접종한 후 오크라를 심고 Suneem-G를 처리하였다. Suneem-G의 처리량에 따라 유충 밀도 및 형성은 유의성 있게 차이가 있었고, Suneem-G와 요소를 동시에 처리하였을 때 그 효과는 상승하였으며, 선충 밀도가 낮을수록 오크라 식물체의 생장이 좋았다. 요소와 Suneem-G를 함께 처리한 조합에서 가장 높은 효과를 보였으며, 처리량의 증가에 따라 억제 효과도 증가하였다. 폿트 당 Sueem-G 6g과 요소 25g 조합의 처리에서 최대의 식물생육과 뿌리혹의 최대감소를 보였는데, 식물체 엽육과 뿌리의 길이가 84%와 58%나 높았으며, 뿌리혹은 58%나 감소하였다. Suneem-G의 최저 처리인 폿트 당 2g 처리에서 식물체의 엽육과 뿌리의 길이는 25.7과 17%까지 증가하였으며, 뿌리혹은 24% 감소하였다. 그러나, 요소 25g 처리에서 가장 낮은 효과를 나타내었으며, 식물의 엽육과 뿌리의 길이는 증가하였으며 뿌리혹은 14% 감소하였다.

• 한국재료학회지
• /
• 제12권8호
• /
• pp.608-612
• /
• 2002

The sliding wear behavior of an iron-base NOREM 02 hardfacing alloy was investigated in the temperature range of $25～250^{\circ}C$ under a contact stress of 103MPa (15ksi). With increasing temperature, the wear loss of Norem 02 in water increased slightly up to $180^{\circ}C$ at which Norem 02 showed the wear loss of 2.1mg. The wear resistance of Norem 02 resulted from the surface hardening due to the strain-induced phase transformation from austenite to $\alpha$'martensite during sliding wear. The wear loss of Norem 02 was smaller in water compared to air at same temperature because the water could be served as a sort of lubricant. The wear mode of NOREM 02 changed abruptly to severe adhesive wear at $190^{\circ}C$ and galling occurred above $200^{\circ}C$. It was caused that the strain- induced phase transformation took place below $180^{\circ}C$ while not above $190^{\circ}C$. Therefore, Norem 02 was considered to be inadequate at high temperature service area.

• Corrosion Science and Technology
• /
• 제23권4호
• /
• pp.296-301
• /
• 2024

Steels have excellent mechanical properties and weldability. They are also economically producible. Thus, they are widely applied in various industries. However, they have a disadvantage in that rust can occur after a certain period of time. To compensate for this, Zn, which has excellent sacrificial corrosion resistance, can be coated on steels. With global zinc consumption increasing at the current rate, depletion is expected in the near future. Recently, POSCO has developed innovative Al-Zn-Si alloy coated steel sheets with better corrosion resistance than Zn coating. In this study, corrosion resistance, weldability, friction characteristics, and so on were evaluated compared to GI steel sheets to evaluate their applicability to automotive steel sheets. It showed excellent corrosion resistance even at a lower coating weight compared to GI steel sheet. It was also excellent in terms of galling and welding LME. Its spot welding life, electrodeposition coating, and bendability were equally excellent. This is presumed to be related to the formation of the Al-Zn-Si alloy phase at the interface of the coating layer.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2018년도 춘계학술대회 논문집
• /
• pp.86-86
• /
• 2018

볼트, 너트 등의 파스너는 건축 재료나 기계부품을 고정하는 데 사용하는 기계요소로, 건축, 철도, 조선 등 전 산업분야에 걸쳐 사용되고 있다. 그 중 스테인리스 소재의 볼트, 너트는 뛰어난 내식성과 저렴한 가격으로 널리 사용되고 있는데, 소재의 특성 및 작업현장의 상황, 온도의 변화 등의 원인에 의해 고착현상(galling)이 발생한다. 고착현상이란 성분 혹은 표면경도가 비슷한 금속의 나사산을 조이는 과정에서 발생하는 압력의 증가 및 마찰력에 의해 냉간 용접(cold welding)이 일어나는 것으로 나사산의 표면이 눌어붙게 된다. 이러한 고착현상은 스테인리스 소재에서 많이 발생하는데, 한번 발생한 후에는 비파괴 해소가 불가능한 상태가 되어 경제적 손실을 야기한다. 이러한 고착현상의 해소를 위해 본 연구에서는 주석과 알루미늄을 사용한 새로운 열 확산 코팅 기술을 개발하고 이를 304 스테인리스강에 적용하여 열처리 온도에 따른 특성변화를 확인하였다. 열 확산 코팅을 위해 팩 세멘테이션 방법을 이용하여 아르곤 분위기 하에서 열처리 하였고, 온도는 $200{\sim}250^{\circ}C$에서 코팅을 수행하였다. 이에 따른 코팅 전과 후의 표면 및 단면 분석을 통해 성공적으로 코팅층이 형성됨을 확인하였고, 온도가 증가함에 따라 코팅성분의 양이 증가하는 현상을 보임을 알 수 있었다. 또한, 고착방지성능을 확인하기 위하여 ASTM G196-08 시험을 통해 코팅조건에 따른 고착현상을 분석하였으며, 그 결과 기존에 코팅되지 않은 304 스테인리스강보다 고착현상이 개선됨을 확인하였다. 따라서 304 스테인리스강 소재의 볼트, 너트 제품에 주석-알루미늄 코팅층을 적용시키면 기존의 고착현상을 개선하고 서비스 품질을 향상시킬 수 있을 것으로 판단된다.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2008년도 추계학술대회 논문집
• /
• pp.87-90
• /
• 2008

Since fastener bolt for airplane require high specific strength and corrosion resistance, Ti-6Al-4V alloy is widely used. However, the Ti-6Al-4V bolt is generally manufactured by cutting and rolling because of their poor workability. The aim of present work is to develop hot forming technology for high strength Ti-6Al-4V. Various heat-treatments were applied to specimen in order to increase hot-workability and prevent galling with die Multiple forging were simulated with FE code to determine optimum process parameters including specimen temperature, strain rate, local strain, and thermal shrinkage. Forged samples were heat-treated again to increase their mechanical properties.

• 소성∙가공
• /
• 제7권5호
• /
• pp.439-444
• /
• 1998

Recently many automotive parts have been made with stainless steels by deep drawing processes, But there are various problems occurred in deep drawing works of stainless steels compared with low carbon steels. For the severe deep drawing of complex cylindrical housing optimum process planning is required to eliminate intermediate annealing improve shape accuracy and maintain surface integrity without drawing defects such as tears wrinkles and scratches or galling. Therefore in this study a sample process planning of the severe of the severe deep drawing process is applied to a complex cylindrical housing needed for a 6 multi-stepped deep drawing of type STS 305 . A series of experiments are performed to investigate optimum process variables such as drawing rate radius and clearance. Through experiments the variations of the thickness strain distribution and hardness distribution in each drawing step are observed. Also the effects of other factors on formability such as drawing oil, blank holding force and die geometry are examined and discussed.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2002년도 춘계학술대회 논문집
• /
• pp.206-208
• /
• 2002

Metalworking fluids (MWFs) are fluids used during machining and grinding to prolong the life of the tool , carry away debris, and protect the surfaces of work pieces. These fluids reduce friction between the cutting tool and the work surface, reduce wear and galling, Protect surface characteristics, reduce surface adhesion or welding and carry away generated heat. Workers can be exposed to MWFs by inhaling aerosols (mists) and by skin contact with the fluid. Skin contact occurs by dipping the hands into the fluid, splashes, or handling workpieces coated with the fluids. The amount of mist generated (and the result ins level of exposure) depends on many factors. To reduce the potential health risks associated with occupational exposures to MWFs, it is required to establish optimum MWFs supply method and condition with minimum Quantity in all over the mechanical machining field including high speed type heavy cult ing process.

• International Journal of Industrial Entomology and Biomaterials
• /
• 제8권2호
• /
• pp.175-179
• /
• 2004

Trichoderma harzianum-THN1 parasitising the egg masses of root knot nematode Meloidogyne incognita was isolated from galled mulberry roots and evaluated for its potential to control root knot disease. In pot experiments root galling was reduced and leaf yield increased significantly following soil treatment with T. harzianum-THN1. The extracts obtained from the soils inoculated with T. harzianum-THN1 drastically inhibited the hatching of nematode eggs and the effect was irreversible even after the eggs were transferred to fresh water. The fungus was equally effective in controlling the disease in nematode infested mulberry garden under field conditions which was significant over the most commonly used egg parasitic fungus Paecilomyces lilacinus. The disease reduction recorded with T. harzianum was on par with the plants treated with the nematicide Carbofuran. The results suggest that T. harzianum- THN1 could be used as a potent ecofriendly biocontrol agent against M. incognita in mulberry without any residual toxicity to silkworms. T. harzianum- THN1 can form an important component of integrated disease management package in mulberry cultivation.

• Tribology and Lubricants
• /
• 제9권2호
• /
• pp.1-8
• /
• 1993

기어가 비교적 큰 하중과 고속의 운전상태에서 사용되는 경우 되풀이 응력에 의한 피로를 대상으로 하는 면압이나 굽힘강도 이외에 치면에서 발생되는 긁힘이나 융착(瀜着) 또는 용착(溶着)을 대상으로 한 스코어링(scoring) 강도를 고려하여야 한다. 스코어링은 주로 치의 이끝 부분에서 접촉방향으로 긁힘이 나타나는 손상으로 특징지워진다. 미국기어제조협회(AGMA)에서는 윤활막 파손에 의한 금속과 금속과의 접촉에 기인하여 발생되는 여러형태의 손상, 예를 들면 scuffing, seizing, galling 등을 광범위하게 스코어링으로 통칭하고 있다. 미국계통의 기술분야에서는 스코어링을 고온 스코어링(hot scoring)과 저온 스코어링(cold scoring)으로 구분하고 있다. 고온 스코어링은 고속 운전시 표면의 섬광온도(flash temperature)에 기인한 용착과 접촉방향으로 재료를 이탈시키는 형태를 나타내고, 저온 스코어링은 저속의 기어에서 윤활막 파단으로 표면에 줄질(filing)한 듯한 손상이 발생되는 것을 나타낸다. 유럽에서는 고온 스코어링 손상은 스커핑이라 하고 저온 스코어링손상만을 스코어링이라 부르고 있다.