Effect of Low Transformation Temperature Welding Consumable on Microstructure, Mechanical Properties and Residual Stress in Welded Joint of A516 Carbon Steel

최성기,이준상,이재익,강승균,김영천,이승준,권동일 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.8

The microstructure, mechanical properties and residual stress of flux-cored arc welded ASTM A516-70N carbon steel using a Mn-based low-temperature transformation (LTT) welding consumable were investigated. Microstructural analysis with X-ray diffraction, an electron backscattered diffractometer and a field-emission scanning electron microscope showed that the LTT weld metal was made up of ferrite, austenite, martensite, and bainite with phase fractions 50.5%, 0.2%, 40.2% and 9.1%, respectively. The increase in hardness and the decrease in absorbed impact energy of the LTT weld metal compared with conventional consumable welds were confirmed to be due to the relatively high fraction of martensite phase in the weld metal. The welding residual stress distributions in three coupons (LTT, conventional and postweld heat-treated conventional weld) were compared by the results using instrumented indentation testing. The LTT weld coupon showed compressive residual stress distributed in the weld metal and heat-affected zone (HAZ), confirming previous studies in which this residual stress was attributed to a martensitic phase transformation at relatively low temperature. PWHT in the conventionally welded coupon considerably reduced the tensile residual stress distributed in the weld metal and HAZ. The LTT consumable, however, showed a significant advantage in welding residual stress, even compared with the heat-treated conventional consumable.

세계 용접재료 및 용접로봇시장 현황 (Ⅱ)

김병진,강민정,천현필 대한용접접합학회 2023 대한용접·접합학회지 Vol.41 No.3

This study analyzed the market trends of welding consumables and welding robots from international welding industries using data reported by SHIMPO CORPORATION. Recently established companies are planning to use automation to achieve high performance with cheap labor. In this context, welding robots are commonly used in manufacturing facilities to perform high-quality welds at a faster rate than with manual welding. In addition, most welding procedures exhaust welding consumables such as rods and wires. Therefore, it is possible to estimate the trends of the overall welding market and related application industry market through the market trends of welding robots and welding con- sumables. From 2009 to 2021, the sales of welding consumables grew at a compound annual growth rate (CAGR) of 2.17%, whereas those of welding robots grew at a CAGR of 11.17%. The higher growth rates in developing countries have lifted up the overall market growth, whereas the rates in leading markets such as the US and China have tended to slow down. In conclusion, the increasing demands for manufacturing and construction in developing countries such as India and Southeast Asia are expected to drive the market growth in the coming years.

통계를 이용한 국내 용접산업 현황 분석 (V)

Minjung Kang,Won-Ho Choi,김철희 대한용접접합학회 2023 대한용접·접합학회지 Vol.41 No.2

In this study, the revenue and import/export status of the domestic welding industry between 2017 and 2022 was analyzed using statistics provided by the Korea International Trade Association (KITA) and Korea Statistical Information Service (KOSTAT). The welding industry can be categorized into the welding equipment/consumables industry and welding process industry, which is part of the manufacturing process in the welding application industry. The welding process industry statistics are difficult to extract from the welding application industry statistics; therefore, they were calculated using the ratio of the welding-related expenditure to the total application industry expenditure. The welding industry's revenue, exports, and imports have recently recovered after hitting a low point during the COVID-19 pandemic. Moreover, the increase in the welding process industry imports and exports in the electronics industry offset the decrease in those of the shipbuilding and offshore industry for the specified investigation period.

EGW 용접재료 및 용접부 특성에 관한 연구

이정수,윤진오,정상훈,박철규,안영호,Lee, Jeong-Soo,Yun, Jin-Oh,Jeong, Sang-Hoon,Park, Chul-Gyu,An, Young-Ho 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.2

In this study, newly developed welding consumables for EGW were welded in EH 36 TM steel plates and their welded joints were evaluated in point of mechanical properties and microstructures compared with imported consumables. Newly developed welding consumables were evaluated as good arc stability and slag fluidity, substantially the same with imported products. The tensile strength of all welded joints were sufficient to meet the requirements specified in a ship’s classification(490~640MPa) and all areas of fracture were heat affected zone(HAZ). Charpy absorbed energy values of all EG welded metals were sufficient to meet the requirements of classification(min. 34J) and those of newly developed wires were evaluated to be better than those of imported wires. As a result observing microstructures of single and tandem EG welded metals through optical and scanning electron microscope (OM&SEM), no grain boundary ferrite(PF(G)) were created in a prior austenite grain boundary and a volume fraction of a fine acicular ferrite were observed very high.

Development of Creep and Mechanical Properties for SMAW Cr-Mo-X Steel Welds

Sanghyun Bae,Yongchul Kim,Stephen Liu 대한용접·접합학회 2024 대한용접·접합학회지 Vol.42 No.1

This research describes the development of new welding materials with high strength and high heat resistance for Cr-Mo-X type steels. Through thermodynamic simulation, the newly designed welding electrode had excellent mechanical properties, especially in high temperature tensile testing at 600℃ with 393.2 ㎫ tensile strength, 385.3 ㎫ yield strength and 23.5% elongation. Refinement of second phase particles were key to the success of the newly designed electrodes. Presence of M23C6 is noticeable in the new electrode welds which contributed to the high temperature strength and creep properties. Compared to conventional products, it was confirmed that the amount of M23C6 precipitates, measured in area fraction, increased substantially, from 5.9 to 11.9%. Z-phase, known to degrade weld mechanical properties, was reduced through adjusting chemical composition of the experimental welds. The reduction in Z-phase precipitates improved the brittle fracture resistance.

MS Point 저감 용접재에 적용한 냉각시 용접부 열변형률 분석에 관한 연구

하윤석,남성길,박세진,권창길,Ha, Yunsok,Nam, Seongkil,Park, Sejin,Kwon, Changgil 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.6

This study targets to make clear the connection between MS (Martensite start) point and welding shrinkage. We approved that a Martensite-transformed weldment may not yield state under low MS point, but also admitted the limitation of numerical calculation by inherent strain approach or thermal strain approach. Therefore, new thermal strain formulae during cooling stages were made. As a thermal strain is obtained by integrating thermal extension coefficient, a constant of integration should be decided. In our suggested formulae, the origin was based on totally remained austenite, and added strain from volume changes in Martensite transformation was based on totally transformed ferrite. Through the suggested methodology, It is verified that an MS point under a critical temperature can let weld shrinkage relax and the critical value can be obtained. For supporting this process, 15 weld-consumables were made, were tested by fillet type and were measured. As a result, a positive correlation between MS point and level of weld-distortion was obtained, but it was rather weak.

항복강도 690MPa급 전자세용 FCA 용접와이어 개발에 있어 용접 입열의 영향 평가

조영주(Young-Ju Jo),서대곤(Dae-Gon Seo),신용택(Yong-Taek Shin) 대한용접·접합학회 2016 대한용접·접합학회지 Vol.34 No.6

YP 690MPa grade steels are used as the main structural steel for offshore structure such as Jack-up Rig and WTIV(Wind Turbine Installation Vessel). Most of welding consumables applied to YP 690MPa grade steels are basic type flux cored wires that shows the poor weldability and not suitable for all position welding. For this reason, welding consumables with rutile type flux system is required. Rutile type flux cored wires show excellent weldability and apply to all position welding. This paper presents the mechanical properties of weld metal with rutile type flux cored wire developed and finally assessed the possibility for application.

Low Temperature Impact Toughness of Structural Steel Welds with Different Welding Processes

신현섭,박기태,이진형,장경호,Vuong Nguyen Van Do***** 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.5

Influence of welding process and welding consumable on the impact toughness at low temperatures of the Heat Affected Zone (HAZ) and the weld metal in a structural steel weldment was investigated. A comparison of the low temperature impact toughness was made between the welded joints fabricated by Shielded Metal Arc Welding (SMAW) and Flux Cored Arc Welding (FCAW) processes, respectively. The Charpy impact tests along with the microstructural observations and the hardness measurements were carried out to derive the effective welding method to guarantee the higher impact toughness of the HAZ and the weld metal at low temperatures. Standard V-notch Charpy impact specimens were prepared and tested under dynamic loading condition. Variation of the Charpy impact energy with respect to the test temperature and that of the hardness across the welds were presented and correlated with the microstructure and the welding process. Analysis of the results unveiled that the weld metal of the FCAW joint has a little higher low temperature impact toughness owing to the higher nickel content, whilst the HAZ of the SMAW joint has much superior impact toughness at low temperatures attributed to the lower heat input; thus the efficient welding method to ensure higher low temperature impact toughness of the HAZ and the weld metal is to employ a low heat input welding process using a welding consumable with high nickel content.

세계 용접재료시장 현황 (II)

이승재,김철희 대한용접접합학회 2019 대한용접·접합학회지 Vol.37 No.4

In this paper, global and regional market trends for welding consumables were summarized using market analysis reports from 2005 to 2017. In the analysis, welding consumables were classified as rods, solid wire, flux cored wire, and submerged arc welding consumables and others. The global welding material market is on an increasing trend, and the markets of other countries are growing faster than those of the five conventional major countries (China, EU, USA, Japan and Korea). Due to the growing automation of welding processes, the market for solid wire and flux core wire markets is increasing and the market for welding electrodes is stagnating or declining. Sales in each country and types of welding consumable were influenced by major application industries such as shipbuilding/heavy industry and automobile industry.

고경도 장갑판재의 TACOM 규격 평가를 통한 다양한 용접재료의 특성분석에 관한 연구

손휘준(Hwi Jun Son),정영철(Young Cheol Jeong),박태원(Tae Won Park),김석(Seok Kim),조영태(Young Tae Cho) 한국생산제조학회 2021 한국생산제조학회지 Vol.30 No.3

A very thick single-armor material is generally used for bulletproof performance in combat vehicles; as a result, the combat capability is greatly reduced by the heavy weight. The armor plate of a combat vehicle is manufactured by applying a welding process to the joints of high-hardness steel. However, when applying the welding process to the high-hardness armor plate, the hardness decreases owing to hot softening in the heat-affected area, resulting in deterioration of the bulletproof performance. In this study, three different welding materials were selected, and their weld strengths were evaluated according to the TACOM standard. The mechanical properties and microstructures of the welded parts of the three materials were analyzed through tensile, bending, impact, and hardness tests. Finally, the most suitable welding material was selected for the high-hardness armor plate.