• 제목/요약/키워드: Heat Input

검색결과 532건 처리시간 0.188초

아크 스폿 용접의 입열효율 계산 방법에 관한 연구 (A Study on the Calculating Method of the Heat Input Efficiency in Arcspot Welding)

  • 장경복;조상명
    • 대한기계학회논문집A
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    • v.27 no.7
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    • pp.1065-1070
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    • 2003
  • In arc spot welding process, the arc is not moving and heat input is concentrated in one spot so that the heat input efficiency of arc is higher than that of GMAW. In other words, the heat input efficiency of arc change during weld time because arc start is done in spot and weld metal is filled. Therefore, the heat input model of arc spot welding should be different from that of general GMAW. In present study, the calculating model of heat input efficiency in arc spot welding was suggested by temperature monitoring near spot in arc spot welding of copper plate. The result showed that the heat input efficiency of arc was changed three times during weld time. The accuracy of calculating method of heat input efficiency was verified by heat transfer analysis of arc spot welding process using finite element method.

오스테나이트계 스테인레스강의 육성 용접부에서 고온균열 감수성에 미치는 용접입열의 영향

  • 김대영;김희진
    • Journal of Welding and Joining
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    • v.6 no.2
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    • pp.40-46
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    • 1988
  • The effect of heat input on the content of residual .delta.-ferrite and the hot cracking susceptibility in the austenitic stainless steel overlaid on the carbon steel was studied in the range of heat input from 7.5 to 15.1 KJ/cm. Present study shows that residual .delta.-ferrite content in the overlay is mainly determined by the dilution of the base metal (carbon steel) which is in turn affected by heat input, i.e. the amount of dilution decreases as heat input increase. Accordingly, higher heat input results in a substantial increase in Cr equivalent but a little increase in Ni equivalent due to the less dilution of carbon from base metal. This fact can explain the result obtained in this study, i, e, the higher content of .delta.-ferrite in the weld deposit made with higher heat input. This in turn causes more resistant overlaying weld metal to hot cracking.

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가스 메탈 아크 용접에서 토치 위빙 중 표면 입열 분포 해석에 관한 연구 (A Study of Heat Input Distribution on the Surface during Torch Weaving in Gas Metal Arc Welding)

  • 김용재;이세현
    • 한국정밀공학회:학술대회논문집
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    • pp.316-319
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    • 2001
  • In weaving welding where a V groove exists, the heat input distribution is an important factor that determines the defectiveness of the bead shape, undercut and over-lap. In this study, the amount of heat input, which is determined by the welding current, voltage, speed and weaving conditions is calculated through numerical methods. Furthermore, the heat input distribution as a two- dimensional heat source was observed when applied to each groove. Therefore, a heat input control algorithm is suggested to prevent the defects generated from undercut or over-lap, which was verified through an analysis of the heat input distribution.

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A Study of Heat Input Distribution on the Surface during Torch Weaving in Gas Metal Arc Welding

  • Kim, Y.;Park, H.
    • International Journal of Korean Welding Society
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    • v.4 no.1
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    • pp.23-29
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    • 2004
  • In weaving welding where a V groove exists, the heat input distribution is an important factor that determines the defectiveness of the bead shape, undercut and over-lap. In this study, the amount of heat input, which is determined by the welding current, voltage, speed and weaving conditions is calculated through mathematical development and numerical methods. Furthermore, the heat input distribution as a two- dimensional heat source was observed when applied to each groove.

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Low Heat Input Welding to Improve Impact Toughness of Multipass FCAW-S Weld Metal

  • Bang, Kook-soo;Park, Chan;Jeong, Ho-shin
    • 한국해양공학회지
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    • v.28 no.6
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    • pp.540-545
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    • 2014
  • Multipass self-shielded flux cored arc welding with different heat inputs (1.3–2.0 kJ/mm) was conducted to determine the effects of the heat input on the proportion of the reheated region, impact toughness, and diffusible hydrogen content in the weld metal. The reheated region showed twice the impact toughness of the as-deposited region because of its fine grained ferritic-pearlitic microstructure. With decreasing heat input, the proportion of the reheated region in the weld metal became higher, even if the depth of the region became shallower. Accordingly, the greatest impact toughness, 69 J at −40℃, was obtained for the lowest heat input welding, 1.3 kJ/mm. Irrespective of the heat input, little difference was observed in the hardness and diffusible hydrogen content in the weld metal. This result implies that low heat input welding with 1.3 kJ/mm can be performed to obtain a higher proportion of reheated region and thus greater impact toughness for the weld metal without the concern of hydrogen cracking.

다층용접한 저합금 용접금속의 강도와 인성에 미치는 입열량 및 예열/패스간 온도의 영향 (Effects of Heat Input and Preheat/interpass Temperature on Strength and Impact Toughness of Multipass Welded Low Alloy Steel Weld Metal)

  • 방국수;정호신;박찬
    • 한국해양공학회지
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    • v.29 no.6
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    • pp.481-487
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    • 2015
  • The effects of the heat input and preheat/interpass temperatures on the tensile strength and impact toughness of multipass welded weld metal were investigated and interpreted in terms of the recovery of the alloying elements and microstructure. Increases in both the heat input and preheat/interpass temperatures decreased the tensile strength of the weld metal. A lower recovery of alloying elements, especially Mn and Si, and smaller area fraction of acicular ferrite in the weld metal were observed in higher heat input welding, resulting in a lower tensile strength. In contrast, only a microstructure difference was observed at a higher preheat/interpass temperature. The impact toughness of the weld metal gradually increased with an increase in the heat input because of the lower tensile strength. However, it decreased again when the heat input was larger than 45 kJ/cm because of the much smaller area fraction of acicular ferrite. No effect of the preheat/interpass temperature on the impact toughness was observed. The formation of a weld metal heat-affect zone showed little effect on the impact toughness of the weld metal in this experiment.

WELDING HEAT-INPUT LIMIT OF ROLLED STEELS FOR BUILDING STRUCTURES (SN400BAND SN490B) BASED ON SIMULATED HAZ TESTS

  • Sakino, Yoshihiro;Horikawa, Kohsuke;Kamura, Hisaya
    • 대한용접접합학회:학술대회논문집
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    • pp.714-719
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    • 2002
  • In The Great Hanshin-Awaji Earthquake, the general yield brittle fractures were observed in beam-column connections of steel building frames. Among many influencing factors which affect the general yield brittle fracture, it can be considered that fracture toughness has substantial effects. Some studies are making clear the required toughness for the base metal and the weld metal, but general values are not proposed. Moreover, it seems that it is also important to pay attention to the toughness decrease in the weld heat affected zone (weld HAZ), because the toughness decrease occurs in the HAZs of mild steel. In this paper, the relationship between toughness of simulated HAZs of "the rolled steels for building structures (SN)" and the weld heat-input limit of the SN steel are investigated, in an attempt to provide the required toughness for HAZs. The relationships between the increase of the hardness value and toughness, and changes of microstructure after weld heat-input are also discussed. The main results are summarized as follows. 1) The SN400B can keep its toughness at higher heat-inputs compare to the SN490Bs. 2) The steel grade, which becomes harder than other steel grades at the same heat-input, has smaller absorbed energy and smaller limit of heat-input. 3) The weld heat-input limit of the SN400B and the SN490B are proposed separately for some required toughness values.

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일렉트로 가스 용접부의 기계적 성질에 미치는 Mn 및 입열량의 영향 (Effects of Mn and Heat-input on the Mechanical Properties of EGW Welds)

  • 김남인;정상훈;이정수;강성원;김명현
    • 대한금속재료학회지
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    • v.47 no.3
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    • pp.195-201
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    • 2009
  • This paper is concerned with effects of Mn and heat-input on the mechanical properties of EGW welds. Four different kinds of welding consumables were fabricated by varying Mn contents such as 1.3, 1.5, 1.7, 2.0%Mn and each consumable was welded for EGW on four heat-input conditions between 190 and 340 KJ/Cm. Mn contents were decreased as heat-input increases and alloy elements (C, Si, Ti, B, Al) to deoxidize easily also revealed similar tendency to Mn. Their microstructure, Charpy impact property and strength were investigated, and it is found that Charpy impact property and strength exhibit a strong dependence on change of microstructure by Mn contents and heat-input. The increase of Mn contents or the decrease of heat-input made the microstructure fine and increase volume fraction of acicular ferrite, thereby leading to the great improvement of Charpy impact property and strength. In case of single EGW, optimum Mn contents are over 1.7% for the toughness and strength.

용접구조용 고장력강의 용접부 인성에 미치는 미세 조직과 용접 입열량의 영향 (Effects of microstructure and welding heat input on the toughness of weldable high strength steel weldments)

  • 장웅성;방국수;엄기원
    • Journal of Welding and Joining
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    • v.7 no.3
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    • pp.44-54
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    • 1989
  • This study was undertaken to evaluate the allowable welding heat input range for high strength steels manufactured by various processes and to compare the weldability of TMCP steel for high heat input welding with that of conventional Ti-added normalized steel. The allowable welding heat input ranges for conventional 50kg/$mm^2$ steel to guarantee D or E grade of ship structural steel were below 150 and 80kJ/cm respectively. Such a limit in welding heat input was closely related with the formation of undesirable microstructures, such as grain boundary ferrite and ferrite side plate in the coarse grain HAZ. In case of 60 and 80kg/$mm^2$ quenched and tempered steels, for securing toughness in weldments over toughness requirements for base metal, each welding heat input had to be restricted below 60 and 40kJ/cm, that was mainly due to coarsened polygonal ferrite in weld metal and lower temperature transformation products in coarse grain HAZ. The TMCP steel could be appropriate as a grade E ship hull steel up to 200kJ/cm, but the Ti-added normalized steel could be applied only below 130kJ/cm under the same rule. This difference was partly owing to whether uniform and fine intragranular ferrite microstructure was well developed in HAZ or not.

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大入熱 高張力鋼 熔接部 의 機械的 特性 變化 에 關한 硏究 (A study on the Mechanical Properties in High Heat Input Welds of High Strength Steels)

  • 김영식;배차헌
    • Journal of Welding and Joining
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    • v.1 no.1
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    • pp.47-55
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    • 1983
  • The mechanical and microstructural properties in high heat input welds of home-made SM 50 high strength steels were investigated and compared with the manual shielded metal arc welds. Also, the fracture toughnesses of the simulated weld-bonds with various thermal cycles were quantatively examined in order to provide the basic data for further development of the high strength steels for high input welding. Main results obtained are as follows. (1) The embrittlement degree and the coarse grained region in high heat input welds appear to be extraordinarily large compared with the manual shielded metal arc welds, while the difference in change of nicrohardness is not so large in both welds. (2) The embrittleness in high heat input weld-bonds is mainly affected by the size of coarse grain rather than the microstructure. (3) The fracture toughness in high heat input weld-bonds can be improved by controlling the cooling rate from 800.deg.C to 500.deg.C rapidly.

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