Microstructure and High Temperature Properties of the Dissimilar Weld between Ferritic Stainless Steel and Carbon Steel

김정길,강정윤,홍승갑,강기봉 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.5

Dissimilar joints between STS441, a ferritic stainless steel, and SS400, a carbon steel, were welded by GMAW (Gas Metal Arc Welding) using STS430LNb as a welding wire. The fracture behavior of the dissimilar weld was analyzed by a microstructural observation and thermo-mechanical tests. Martensite was formed at the region between SS400 and the weld metal because the Cr and Nb content in this region decreased due to the dilution of SS400 carbon steel during welding. According to results from a high temperature tensile test with a specimen aged at 900 °C, it was found that the tensile strength of the dissimilar weld at high temperature was equal to that of STS441 base metal and the formation of martensite had little influence on tensile strength of the dissimilar weld at high temperature. However, in the case of thermal fatigue resistance, the dissimilar weld had an inferior thermal fatigue life to STS441 because of the presence of martensite and the softened region around the interface between the dissimilar weld metal and SS400. Dissimilar joints between STS441, a ferritic stainless steel, and SS400, a carbon steel, were welded by GMAW (Gas Metal Arc Welding) using STS430LNb as a welding wire. The fracture behavior of the dissimilar weld was analyzed by a microstructural observation and thermo-mechanical tests. Martensite was formed at the region between SS400 and the weld metal because the Cr and Nb content in this region decreased due to the dilution of SS400 carbon steel during welding. According to results from a high temperature tensile test with a specimen aged at 900 °C, it was found that the tensile strength of the dissimilar weld at high temperature was equal to that of STS441 base metal and the formation of martensite had little influence on tensile strength of the dissimilar weld at high temperature. However, in the case of thermal fatigue resistance, the dissimilar weld had an inferior thermal fatigue life to STS441 because of the presence of martensite and the softened region around the interface between the dissimilar weld metal and SS400.

A Review on Welding of Dissimilar Metals in Car Body Manufacturing

Md. Abdul Karim,Yeong-Do Park 대한용접·접합학회 2020 대한용접·접합학회지 Vol.38 No.1

This paper presents a comprehensive study of the metallurgical challenges of welding dissimilar metals. It also describes the important factors in dissimilar welding which need to be considered for automotive applications. It further investigates effective approaches to overcome these present challenges. Steels, aluminum alloys, and magnesium alloys are widely used metals in car bodies. However, it is difficult to weld these dissimilar metals and achieve good joint quality, due to their inherent disparate properties. The formation of brittle, crack sensitive and corrosion susceptible intermetallic phases is the main obstacle to dissimilar weld quality. Various approaches have been attempted by many researchers to enhance the performance of dissimilar welds. The most notable efforts include the application of interlayers, cover plate, least heat input, a combination of welding and mechanical joining, and alloying elements of filler metals. Based on considerations of joint performance, production cost and time, present industry infrastructure, and so on, the most effective and feasible approaches were identified which required the least amount of heat input, and the appropriate filler metal alloying elements.

보수용접부 폭에 따른 용접잔류응력의 변화 및 재분배 거동 평가

박치용(Chi-Yong Park),이휘승(Hwee-Sueng Lee),허남수(Nam-Su Huh) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.2

본 논문에서는 보수용접부 폭 변화에 따른 이종금속 맞대기 용접부(Dissimilar metal butt weld) 용접잔류응력의 분포 및 동종금속용접/기계적 하중에 의한 재분배 거동을 평가하였다. 이를 위해 5가지 다른 보수용접부 폭을 고려한 상세 2차원 유한요소 열해석 및 응력해석을 수행하였다. 유한요소해석 결과를 바탕으로 보수용접에 의한 용접잔류응력 분포를 평가하였으며, 동종금속용접 및 기계적 하중에 의한 응력 재분배 특성을 평가하였다. 보수용접에 의해 배관 내면에서는 큰 인장 용접잔류응력이 축방향과 원주방향에 대해 발생하는 것으로 나타났으며 보수용접부 폭이 특정값 이상이 되면 용접잔류응력 분포가 변하는 것으로 나타났다. 그러나 동종금속용접과 기계적 하중을 고려하면 인장잔류응력값이 크게 감소하였으며 그 경향은 보수용접부 폭에 무관한 것으로 나타났다. In this study, we investigated the variations in welding residual stresses in dissimilar metal butt weld due to width of repair welding and re-distribution behaviors resulting from similar metal welding (SMW) and mechanical loading. To this end, detailed two-dimensional axi-symmetric finite element (FE) analyses were performed considering five different repair welding widths. Based on the FE results, we first evaluated the welding residual stress distributions in repair welding. We then investigated the re-distribution behaviors of the residual stresses due to SMW and mechanical loads. It is revealed that large tensile welding residual stresses take place in the inner surface and that its distribution is affected, provided repair welding width is larger than certain value. The welding residual stresses resulting from repair welding are remarkably reduced due to SMW and mechanical loading, regardless of the width of the repair welding.

Welding Residual Stress Analysis and Fatigue Strength Assessment at Elevated Temperature for Multi-Pass Dissimilar Material Weld Between Alloy 617 and P92 Steel

Juhwa Lee,Jeongho Hwang,Dongho Bae 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.4

In this paper, welding residual stress analysis and fatigue strength assessment were performed at elevated temperature formulti-pass dissimilar material weld between Alloy 617 and P92 steel, which are used in thermal power plant. Multi-passwelding between Alloy 617 and P92 steel was performed under optimized welding condition determined from repeated pretestwelding. In particular, for improving dissimilar material weld-ability, the buttering welding technique was applied onthe P92 steel side before multi-pass welding. Welding residual stress distribution at the dissimilar material weld joint wasnumerically analyzed by using the fi nite element method, and compared with experimental results which were obtained bythe hole-drilling method. Additionally, fatigue strength of dissimilar material weld joint was assessed at the room temperature(R.T), 300, 500, and 700 °C. In fi nite element analysis results, numerical peak values; longitudinal (410 MPa), transverse(345 MPa) were higher than those of experiments; longitudinal (298 MPa), transverse (245 MPa). There are quantitativelybig Differences between numerical and experimental results, due to some assumption about the thermal conductivity, specifi cheat, Effects of enforced convection of the molten pool, dilution, and volume change during phase transformation caused byactual shield gas. The low fatigue limit at R.T, 300 °C, 500 °C and 700 °C was assessed to be 368, 276, 173 and 137 MParespectively.

Optimization of welding current waveform for dissimilar material with DP590 and Al5052 by Delta-spot welding process

Ji-Sun Kim,In-Ju Kim,김영곤 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.6

The automotive industry has a target goal to improve fuel consumption due to restricted exhaust gas regulation. For this reason, the applicability of lightweight material, Al alloys, Mg alloys is also being expanded. In this concept, high strength steel, DP590 and light alloy, AL5052 are joined in the right place of the car body. However, it is difficult to join to steel and aluminum by conventional fusion welding. Generally, in respect to dissimilar metal joining by fusion welding, intermetallic compound layer is formed at the joint interface, hot cracking is generated. In this study, the effect of the current waveform on the mechanical characteristics and microstructure in Delta spot welding process of dissimilar metal was investigated. As results, Intermetallic compound (IMC) layer was reduced from 2.355 μm to 1.09 μm by using Delta spot welding process; also the welding current range improved by 50% in the delta spot welding, higher than in the inverter resistance welding. To conclude, the delta spot welding process adopting the process tapes contributes to improving the welding quality for dissimilar metals (Al5052 and DP590) due to a decrease in IMC layer.

A Study on Dissimilar Welding of Aluminum Alloy and Advanced High Strength Steel by Spot Welding Process

김영곤,조범지,김지선,김인주 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.1

Recently, Car makers have required a light weight of vehicles in relation to fuel efficiency. In that respect, dissimilar welding method is very important in the car body assembly process. In this study, resistance spot welding was performed to evaluate the welding quality and mechanical properties for dissimilar materials of the cold rolled DP590 and Al 5052. The welding experiment was carried out changing with the welding current and the other process parameters such as electrode force, weld time, squeezing time and holding time were fixed with the basic welding condition of the ISO18278-2 standard. Especially, the shear tensile strength was evaluated at each condition and the cross-sectional observation for weld zone such as nugget diameter was performed. As a result, the thickness of IMC (Intermetallic Compound) layer at 11.5 kA was thinner than those of 9.5 kA and 10.5 kA conditions. On the other hand, Delta-spot welding experiment was performed using various process tapes at welding current of 11.5 kA. The other conditions were same with that of the conventional spot welding. Sound welds was formed by applying to the optimum welding conditions in the Delta-spot process due to the thermal balance of dissimilar materials.

유전자알고리즘에 의한 자동차용 이종강판 최적 점용접 설계

이은옥(Eun-ok Lee),이철민(Chul-min Lee),기창두(Chang-Doc Kee),유효선(Hyu-sun Yu),양성모(Sung-mo Yang) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Welding conditions in process of spot welding must become optimum and need to guarantee stability and reliability of vehicle body considering dynamic load history. Because welding parameters in process of spot welding are various, it is difficult that the quality of spot weldment was included in the optimum levels. In this paper, we found the optimum welding conditions satisfying KS spot welding qualities using genetic algorithm and spot welding experiments of high tensile strength steel and galvanized steel. Those experiments were dissimilar weld and 2-lap spot welding. Genetic algorithm created random welding condition after that, selected optimum individuals by probability concept.

유한요소해석을 이용한 노즐 이종금속용접부의 용접잔류응력 예측

허남수(Nam-Su Huh),김종욱(Jong-Wook Kim),최순(Suhn Choi),김태완(Tae-Wan Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

The primary water stress corrosion cracking (PWSCC) of dissimilar metal weld based on Alloy 82/182 is one of major issues in material degradation of nuclear components. It is well known that the crack initiation and growth due to PWSCC is influenced by material’s susceptibility to PWSCC and distribution of welding residual stress. Therefore, modeling the welding residual stress is of interest in understanding crack formation and growth in dissimilar metal weld. Currently in Korea, a numerical round robin study is undertaken to provide guidance on the welding residual stress analysis of dissimilar metal weld. As a part of this effort, the present paper investigates distribution of welding resisual stress of a ferritic low alloy steel nozzle with dissimilar metal weld using Alloy 82/182. Two-dimensional thermo-mechanical finite element analyses are carried out to simulate multi-pass welding process on the basis of the detailed design and fabrication data. The present results are compared with those from other participants, and more works incorporating physical measurements are going to be performed to quantify the uncertainties relating to modelling assumptions.

이종용접에서 풀림 열처리가 용착금속에 미치는 영향에 관한 연구

김중호(Jung-Ho Kim) 산업기술교육훈련학회 2008 산업기술연구논문지 (JITR) Vol.13 No.4

In this study, this research analyzed and studied the result of executing annealing heat treatment at specific temperatures after welding the dissimilar materials of SS41 and STS304, for the purpose of studying the effect of annealing heat treatment on weld metal in dissimilar welding. The conclusion of this research is as follows. As for the tensile strength, in case of annealing the dissimilar welding of SS41 and STS304 at 1100℃, the maximum value showed at 46.5㎏/mm2. and in case of annealing at 870℃, the lowest value showed as 32.3㎏/mm2. As for the elongation, in case of annealing the dissimilar welding of SS41 and STS304 at 1100℃, maximum value showed as 29.5%. and in case of annealing at 870℃, the lowest value showed as 14.8%. As for the hardness, in case of annealing the dissimilar welding of SS41 and STS304 at 1100℃, maximum value showed as HV385 around SS41 bond.

Al/Fe 이종재의 마이크로 마찰교반 맞대기용접 적용성 평가

유현정(Hyeonjeong You),안영남(Youngnam Ahn),이성(Sung Yi),현승균(Soongkeun Hyun),김철희(Cheolhee Kim) 대한용접·접합학회 2021 대한용접·접합학회지 Vol.39 No.3

In the automobile industry, there is an increasing demand for Al/Fe dissimilar metal joining. Friction stir welding (FSW) is an efficient solid-state welding method to achieve high-quality Al/Fe dissimilar metal welding. Here, we reviewed the previous studies on butt FSW of thin Al/Fe sheets and conducted feasibility tests to investigate the applicability of micro FSW with a base material thickness of 1 mm or less. Most of the past literature, except for one study that adopted 1.12 mm-thick specimens, has worked with a base metal thickness of 1.5 mm or more. Selecting appropriate parameters can lead to a weld strength that is more than 90% of the base metal strength. Through feasibility tests on 2 mm-thick specimens, we could derive the welding conditions to obtain sound welds and the required joint strength. An adequate range (0.5-0.75 mm/rev) of advance per revolution was recommended to ensure the weld strength. A feasibility test on 1 mm-thick specimens revealed the possibility of melting of Al base metal during FSW of 1 mm-thin sheets; moreover, a low tool rotation speed was found to be crucial in ensuring the weld joint strength. The maximum weld strength for 1 mm-thick specimens was 200 MPa, which is 117% of the required weld strength.