이종 마찰용접 강봉재의 기계적 특성(2. PWHT)

권상우(S. W. Kwon),정원택(W. T. Jeong),공유식(Y. S. Kong),김영식(Y. S. Kim),김선진(S. J. Kim) 한국동력기계공학회 2004 한국동력기계공학회 학술대회 논문집 Vol.- No.-

Dissimilar friction welding were produced using 15㎜ diameter solid bar in chrome molybedenum steel(KS SCM440) to carbon steel(KS S45C) to investigate their mechanical properties. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Virkers hardness surveys of the bond of area and HAZ and macrostructure investigations. The specimens were tested as-welded and post-weld heat-treated. The tensile strength of the friction welded steel bars was increased up to 100% of the S45C base metal under the condition of all heating time. Optimal welding conditions were n=2,000(rpm), P₁=60(MPa), P₂=100(MPa), t₁=4(s), t₂=5(s) when the total upset length is 5.4(㎜).

Analysis of residual stress relief mechanisms in post-weld heat treatment

Dong, P.,Song, S.,Zhang, J. Applied Science Publishers ; Elsevier Science Ltd 2014 The International journal of pressure vessels and Vol.122 No.-

This paper presents a recent study on weld residual stress relief mechanisms associated with furnace-based uniform post-weld heat treatment (PWHT). Both finite element and analytical methods are used to quantitatively examine how plastic deformation and creep relaxation contribute to residual stress relief process at different stages of PWHT process. The key contribution of this work to an improved understanding of furnace based uniform PWHT can be summarized as follows:(1)Plastic deformation induced stress relief during PWHT can be analytically expressed by the change in material elastic deformation capacity (or elastic deformation limit) measured in terms of material yield strength to Young's modulus ratio, which has a rather limited role in overall residual stress relief during furnace based uniform PWHT. (2)The most dominant stress relief mechanism is creep strain induced stress relaxation, as expected. However, a rapid creep strain development accompanied by a rapid residual stress reduction during heating stage before reaching PWHT temperature is shown to contribute to most of the stress relief seen in overall PWHT process, suggesting PWHT hold time can be significantly reduced as far as residual stress relief is concerned. (3)A simple engineering scheme for estimating residual stress reduction is proposed based on this study by relating material type, PWHT temperature, and component wall thickness.

토션바材의 摩擦熔接에 관한 硏究(Ⅱ)

吳世奎(Sae-Kyoo Oh),李鍾斗(Jong-Doo Lee) 한국해양공학회 1990 韓國海洋工學會誌 Vol.4 No.2

This paper deals with investigating experimentally the effects of PWHT on the weld quality such as strength, toughness, hardness and micro-structure of the welded joints in friction welding of torsion bar material SUP9A bar to bar.<br/> The results obtained are summarized as follows ;<br/> 1) It was certified that the condition of the post-weld heat treatment(PWHT) for the friction welded joints was very satisfactory because both strength and toughness of the joints were improved as almost same as those of the base metal or better by the PWHT.<br/> 2) The peak of hardness distribution of the friction welded joints can be eliminated by PWHT, resulting in being almost equalized at the weld interface, the HAZ(heat affected zone) and the base metal.<br/> 3) The micro-structure of the base metal, HAZ and weld interface(WI) of friction welded joints welded at the optimum welding condition consists of the same sorbite structure obtained by PWHT and fined sorbite at WI, resulting in increasing toughness as well as strength, and no micro structural defect has been found at the friction welded zone.

해양구조물용 RE36강의 용접부 부식거동에 관한 전기화학적 특성 연구

김성종,김진경,문경만 대한용접접합학회 2000 대한용접·접합학회지 Vol.18 No.5

The effect of Post Weld Heat Treatment(PWHT) of RE36 steel for marine structure was investigated with parameters such as micro-vickers hardness, corrosion potential and corrosion current density of weld metal(WM), base metal(BM) and heat affected zone(HAZ), and both Al alloy anode generating current and Al alloy anode weight loss quantity etc. Hardness of post-weld heat treated BM, WM and HAZ is lower than that of As-welded condition of each region. However, hardness of HAZ was the highest among those three parts regardless of PWHT temperature and corrosion potential of WM was the highest among those three parts without regard to temperature and corrosion potential of WM was the highest among those three parts without regard to PWHT temperature. The amplitude of corrosion potential difference of each other three parts at PWHT temperature $550^{\circ}C$, $650^{\circ}C$ are smaller than that of three parts by As-welded condition and corrosion current density obtained by PWHT was also smaller than that of As-welded condition. Eventually, it was known that corrosion resistance was increased by PWHT. However both Al anode generating current and anode weight loss quantity were also decreased by PWHT compare to As-welded condition when RE36 steel is cathodically protected by Al anode. Therefore, it is suggested that the optimum PWHT temperature with increasing corrosion resistance and cathodic protection effect is $550^{\circ}C$.

기계구조용 탄소강 중공축의 마찰 용접후 열처리의 기계적 특성

선신규,조창주,김종희 한국기계기술학회 2017 한국기계기술학회지 Vol.19 No.4

In this study, SM45C-STKM13B hollow shaft of different thickness was joined by friction welding. After friction welding, we treated to specimen of annealing(post-weld heat treatment). The specimens were tested as-welded and post-weld heat treatment(PWHT). The mechanical properties including tensile test and vickers micro-hardness were examined. And then, the mechanical properties were compared for as-welded and PWHT in SM45C to STKM13B. Microstructure of joining part were examined in the weld interface and weld region and heat affected zone and base metal of weld parts.

후열처리에 따른 A105/A312 배관재의 이종 마찰용접 최적화

공유식,박영환 대한용접접합학회 2019 대한용접·접합학회지 Vol.37 No.2

A study on dissimilar friction welded joints were performed using 22 mm diameter tube-to-bar in forging bar steel(ASTM A105) to stainless pipe steel(ASTM A312) for piping materials. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Virkers hardness surveys of the bond of area and HAZ, and macrostructure investigations. The specimens were tested as-welded and post-weld heat treated(PWHT). The tensile strength of the friction welded joints was increased up to 100 % of the A105 base metal under the condition of heating time(HT). Optimal welding conditions were n=2,000 rpm, HP=50 MPa, UP=100 MPa, HT=5 sec and UT=10 sec when the total metal loss(Mo) is 11 mm. The peak of hardness distribution of the friction welded joints can be eliminated by PWHT. Two different kinds of materials are strongly mixed to show a well-combined structure of macroparticles without any molten material and particle growth or any defects. In addition, the results of the radiological examination(RT) showed that there was no blowhole in the friction welding area.

해양 수송용 호스니플 제작을 위한 마찰용접 조건의 최적화

김동규(Dong-Gyu Kim),김역란(Yeuk-Ran Kim),공유식(Yu-Sik Kong) 한국해양공학회 2016 韓國海洋工學會誌 Vol.30 No.1

In this study, for the tube-to-tube friction welding of hose nipple materials, the main parameters of friction welding were investigated using tensile tests, Vickers hardness surveys of the bond area (HAZ), and observations of the microstructure to increase the quality of friction welding based on visual examination. As-welded and post weld heat treated (PWHT) specimens were tested. The optimal welding conditions were found to be n = 1000 rpm, HP = 10 MPa, UP = 15 MPa, HT = 9 s, and UT = 5 s when the metal loss (Mo) was 7.5 mm. Furthermore, the peak of the hardness distribution of the friction welded joints could be eliminated by PWHT. Moreover, the two materials of the friction weld were thoroughly mixed with a well-combined structure of micro-particles, without any molten material, particle growth, or defects.

Variation of Microstructures and Mechanical Properties in the Post-Weld Heat-Treated HAZ of Cu Containing HSLA Steel Welds

Sanghoon Kim,Jongho Lee,이창희,황병철,Chang Gil Lee 대한금속·재료학회 2011 METALS AND MATERIALS International Vol.17 No.1

The present study focuses on the effect of Cu and post-weld heat treatment (PWHT) on the microstructure and mechanical properties in the coarse grained heat affected zone (CGHAZ) of Cu containing high strength low alloy (HSLA) steel welds. For this study, HSLA steels with and without Cu were prepared in laboratory. Mechanical properties were estimated by Vickers hardness and Charpy impact tests. As a result, despite PWHT,the Vickers hardness did not change noticeably; however, the impact toughness deteriorated significantly with increasing PWHT time. In case of Cu added steel, intergranular brittle fractures occurred after PWHT, due to the strengthening of the grain interior by precipitation of Cu particles. Additionally, the formation of a soft denuded grain boundary zone also played a significant role in lowering the fracture toughness during PWHT.

Behavior of Cu Precipitates During Thermo-Mechanical Cycling in the Weld CGHAZ of Cu-Containing HSLA Steel

Sanghoon Kim,이창희 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.5

The behavior of Cu precipitates in the weld coarse-grained heat-affected zone (CGHAZ) of 1.5 wt% Cucontaining high strength low-alloy (HSLA) steel subjected to a thermal/thermo-mechanical welding cycle and post-weld heat-treatment (PWHT) was evaluated. The welding cycles of CGHAZ and PWHT were simulated by the Gleeble system. The hardness was measured at each PWHT condition, and observation and analysis of the Cu particles were performed using HRTEM. The hardness decreased initially with an increasing PWHT time at 550 °C. However, the peak hardness resulting from precipitation of Cu particles occurred after about 60 min at 550 °C. In the thermo-mechanical cycle, the peak hardness appeared at an earlier PWHT time. These results correspond with the HRTEM observations in which Cu particles were observed at an earlier PWHT time and larger Cu particles were observed at the same given PWHT time after the thermo-mechanical cycle. Thus, this paper confirms that the kinetics of Cu precipitation can be accelerated by an intrinsic mechanical cycle during the welding cycle.

수송차량 안전벨트용 모터축재의 마찰용접 최적화(1)

공유식(Yu-Sik Kong),안석환(Seok-Hwan Ahn) 한국해양공학회 2012 韓國海洋工學會誌 Vol.26 No.1

Dissimilar friction welds were produced using 15-mm diameter solid bars of chrome molybdenum steel (KS SCM440) and carbon steel (KS SM20C) to investigate their mechanical properties. The main friction welding parameters were selected to ensure good quality welds on the basis of visual examination, tensile tests, Vickers hardness surveys of the bond area and HAZ, and macro-structure investigations. The specimens were tested as-welded and post-weld heat treated (PWHT). The tensile strength of the friction welded steel bars was increased to 100% of the SM20C base metal under the condition of a heating time of more than four seconds. Optimal welding conditions were n = 2,000 (rpm), HP = 60 (MPa), UP = 100 (MPa), HT = 5 (s),and UT = 5 (s), when the total upset length was 7.8 (mm). The hardness distribution peak of the friction welded joints could be eliminated using PWHT. The two different kinds of materials were strongly mixed to show a well-combined structure of macro-particles, with no molten material, particle growth, or defects.