• Title/Summary/Keyword: Weld Metal HAZ

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Effect of Preheat Temperature on Diffusible Hydrogen Content in Weld Metal Deposited using Flux Cored Wire (시편 예열 온도가 FCW 용착금속의 확산성 수소량에 미치는 영향)

  • Kim, Dong Yoon;Hwang, In Sung;Kim, Dong Cheol;Kang, Moon Jin
    • Journal of Welding and Joining
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    • v.32 no.2
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    • pp.18-21
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    • 2014
  • Cold cracking of weldment is one of the most serious welding problems. A sufficient quantity of diffusible hydrogen, a residual stress, and a sensitive microstructure are the causes of cold cracking. Removal of any one of these factors can be used to prevent cold cracking. Application of flux cored arc welding process is increasing due to high productivity and easiness of welding. In addition, to prevent cold cracking in the HAZ or weldment, preheat temperature and interpass temperature have to be controlled. In this study, the effect of preheat temperature on the levels of diffusible hydrogen in the weld metal deposited using flux cored wire was examined. The levels of preheat temperature of base metal specimen were ambient temperature, 50, 100 and $150^{\circ}C$ respectively. The result showed that the increase of preheat temperature was a linear relationship with reduction of diffusible hydrogen content in weldment.

The study on dynamic fracture toughness of friction-welded M.E.F. dual phase steel (복합조직강의 마찰용접부에 대한 동적파괴특성)

  • 오세욱;유재환;이경봉
    • Journal of Welding and Joining
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    • v.7 no.3
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    • pp.19-27
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    • 1989
  • Both the SS41 steel and the M.E.F(martensite encapsulated islands of frrite) dual phase steel made of SS41 steel by heat treatment were welded by friction welding, and then manufactured machinemade Vnotch standard Charpy impact specimens and precracked with a fatigue system at BM(base metal), HAZ(heat affected zone) and WZ(weld interface Zone). The impact test of them was performed with an instrumented impact test machine at a number of temperatures in constant loading velocity and the dynamic fracture characteristics were studied on bases of the absorbed energy, dynamic fracture toughness and fractography from the test. The results obtained are as follows; At the room temperature, the absorbed energy is HAZ.geq.WZ.geq.BM in case of the M.E.F. dual phase steel: BM.geq.HAZ.geq.WZ in case of the SS41 steel, HAZ.geq.BM.geq.WZ at the low temperature. The absorbed energy is decreased markedly with the temperature lowering; it is highly dependent on the temperature. The dynamic fracture toughness of the M.E.F. dual phase steel is HAZ.geq.WZ.geq.BM at the room temperature; BM.geq.WZ.geq.HAZ below-60.deg. C. Therefore the reliability of friction welding is uncertain at the low temperature(below-60.deg. C). The dynamic fracture toughness of the SS41 steel; HZA.geq.WZ.geq.BM at overall temperature region. The flaw formed by rotational upsetting pressure was shown y SEM; in this region. The absorbed energy per unit area and dynamic fracture toughness were low relative to other region.

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The Effect of Heat Input on Fracture Toughness(CTOD) in Submerged Arc Offshore Steel Weldments (해양구조용강재의 SA용접부에서 입열량이 파괴인성에 미치는 영향에 관한 실험적 연구)

  • Kang, Sung-Won;Kim, Myung-Hyun;Shin, Yong-Taek;Lee, Hae-Woo
    • Journal of the Society of Naval Architects of Korea
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    • v.41 no.6
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    • pp.40-47
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    • 2004
  • The influence of heat input on fracture toughness was investigated in SAW weldments, which were prepared at two different welding conditions in API 2W Gr.50 and EN10225 5420. By examining the fracture initiation point, refined areas(ICHAZ and SCHAZ) in weld metal was identified as local brittle zone, in which M-A constituents and coarsed grain size were observed. Impact values showed the most significant difference at root portion, and CTOD transition temperature was related with impact values obtained at root portion. Hardness values in refined area were less than columnar microstructure about 20 HV5.

A study on the fatigue and fracture characteristics of localized nuclear reactor vessel material (국산 원자로용기 재료의 피로 및 파괴특성 연구)

  • Jeong, Sun-Eok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.10
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    • pp.1626-1635
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    • 1997
  • It is important to ensure the reliability of the first localized reactor vessel steel. To satisfy with this purpose, a study on the impact/hardness, low cycle fatigue(LCF), crack growth rate(da/dN) and fracture toughness( ) of base material(BM) and weld metal(WM) were performed under room temperature air and corrosion conditions. A summary of the results is as folows : (1) Charpy impact absorbed energy of BM was the highest value, heat affected zoon(HAZ) and the lowest, WM. The hardness of BM was similar to HAZ. (2) Coefficients of Manson equation using the monotonic tensile test data were obtained for the present material. (3) The effects of stress ratio and ambient (120.deg. C and NaCl) condition on da/dN were investigated, da/dN with NaCl condition expressed the highest value. (4) The results of Charpy V-notch impact test had good correlation with $K_{IC}$ characteristics and the lowest curve of $K_{IC}$ for BM was derived, more researches about WM and HAZ are required hereafter.

Ultimate Compressive Strength Analysis of TMCP High Tensile Steel Plates with HAZ Softening(2nd Report) (HAZ 연화부를 가진 TMCP형 고장력강판의 압축최종강도에 관한 연구 - 제 2 보)

  • 백점기;고재용
    • Journal of Welding and Joining
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    • v.9 no.2
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    • pp.44-50
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    • 1991
  • The use of high tensile steel plates is increasing in the fabrication of ship and offshore structures. The softening region which has lower yield stress than base metal is located to prevent cracking in the conventional high tensile steel. Also, thermo mechanical control process(TMCP) steel with low carbon equivalent has the softening region which occurs in the heat affected zone when high heat input weld is carried out. The softening region in the high tensile steel gives rise to serious effect on structural strength such as tensile strength, fatigue strength and ultimate strength. In order to make a reliable structural design using high tensile steel plates, the influence of the softening on plate strength should be evaluated in advance. In the previous paper, the authors discussed the ultimate compressive strength of 50HT steel square plates with softening region. In this paper, the ultimate compressive strength with varying the yield stress of softening region and the aspect ratio of the plate is investigated by using the elasto-plastic large deformation finite element method.

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Evaluation of Fracture Toughness on High Frequency Electric Resistance Welded API 5LB Steel Pipe (API 5LB강관의 고주파전기저항용접부에 관한 파괴인성 평가)

  • 오세욱;윤한기;안계원
    • Journal of Ocean Engineering and Technology
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    • v.1 no.1
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    • pp.127-137
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    • 1987
  • The evaluation of the elastic-plastic fracture toughness $J_{1C}$ was performed on the center of weld metal(CWM), the heat affected zone (HAZ) and the base metal (BM) of API 5LB steel pipes welded by the high frequency electric resistance welding. The $J_{1C}$ was evaluated by the JSME R-Curve and JSME SZW methods using the smooth and side-grooved specimens. The results are as follows; (1) The $J_{1C}$ values by the SZW method are overestimated as compared with those by the R-curve method, because the micro-crack is formed as SZW increase with the deformation at SZ after initiation of the ductile crack. (2) The everage of $J_{1C}$ values by the the R-curve and the SZW methods in side-grooved specimens tended to decrease in comparison with smooth specimens 9.42% at CWM, 4.2% at HAZ, 23.2% at BM, respectively. (3) The boundary of the fatigue pre-crack, stretched zone, and dimple regions appeared more clearly in side-grooved specimens, for the slight change of SZW in the direction of the plate thickness, as compared with smooth specimens.

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A Study on Mechanical Properties and Friction Weldability of SKH51 and SM45C (SKH51/SM45C의 마찰용접특성에 관한 연구)

  • Lee, Se-Gyoung;Min, Byung-Hoon;Choi, Su-Hyun;Shim, Do-Ki;Min, Taeg-Ki
    • Journal of Welding and Joining
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    • v.25 no.6
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    • pp.53-58
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    • 2007
  • The present study examined the mechanical properties of the friction welding of shaft made of SKH51 and SM45C, of which the diameter is 12mm. Friction welding was done at welding conditions of 2,000rpm, friction pressure of 104MPa, upset pressure of 134MPa, friction time of 0.5sec to 2.5sec by increasing 0.5sec, upset time of 2 seconds. Under these conditions, a tensile test, a bending test, a shear test, a hardness test and a microstructure of weld interface were studied. When the friction time was 1.0 second under the conditions, the maximum tensile strength of the friction weld observed to be 963MPa, which is 89% the tensile strength of SKH51 base metal and 101% of the tensile strength of SM45C base metal. When the friction time was 1.0 seconds under the conditions, the maximum bending strength of the friction weld happened to be 1,647MPa, which is 78% the bending strength of SKH51 base metal(2,113MPa) and 87% of the bending strength of SM45C base metal(1,889MPa). When the friction time was 1.0 seconds under conditions, the maximum shear strength of the friction weld was observed to be 755MPa, which is 92% the shear strength of SKH51 base metal and 122% of the shear strength of SM45C base metal. According to the hardness test, the hardness distribution of the weld interface varied from Hv282 to Hv327. HAZ was formed from the weld interface to 1.2mm of SKH51 and 1.6mm of SM45C. Upon examination it was found that the microstructure became finer along with increase of friction revolution radius.

Evaluation of Characteristic for SS400 and STS304 steel by Weld Thermal Cycle Simulation - 2nd Report: Corrosion Characteristics (용접열사이클 재현에 의한 SS400강 및 STS304강의 특성 평가 -제2보: 부식특성)

  • Ahn, Seok-Hwan;Choi, Moon-Oh;Kim, Sung-Kwang;Son, Chang-Seok;Nam, Ki-Wook
    • Journal of Ocean Engineering and Technology
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    • v.21 no.5
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    • pp.33-38
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    • 2007
  • The welding methods have been applied in the most structural products from multi-field of automobile, ship construction and construction, and so on. The structure steel must have enough strength of structure. In this study, SS400 steel and STS304 steel were used to estimate the corrosion characteristics of the weld thermal cycle simulated HAZ. To evaluate the corrosion characteristics, also, the materials with two conditions were used in 3.5% NaCl. The one is to the drawing with diameter of ${\Phi}10$ and the other is to the residual stress removal treatment. The electrochemical polarization test and immersion test were carried out. From test results, corrosion potential, corrosion current density, weight loss ratio and corrosion rate were measured. In the kinds of SS400 steels, corrosion potential of weld thermal cycle simulated specimens after the heat treatment showed somewhat the direction of noble potential. And in the base metal to be drawing weight loss ratio and corrosion rate occurred higher than the other kinds. In the kinds of STS304 steels, the result of base metal to be drawing was similar to results of SS400 steels, too. Two kinds of $750^{\circ}C$ and $1300^{\circ}C$ of weld thermal cycle simulation after the heat treatment were rather higher than the other kinds in weight loss ratio and corrosion rate.

Evaluation of the Applicability of Structural Steels to Cold Regions by the Charpy Impact Test (샤르피 충격시험을 통한 구조용강재의 극한지 적용성 검토)

  • Lee, Chin-Hyung;Shin, Hyun-Seop;Park, Ki-Tae;Yang, Seunng-Hyun
    • Journal of Korean Society of Steel Construction
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    • v.23 no.4
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    • pp.483-491
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    • 2011
  • The fabrication of steel structural members always involves welding process such as flux cored arc welding. Therefore, for the application of structural steels to cold regions, it is a prerequisite to clarify the service temperature of the welded joints in order to ensure the structural integrity of the welded parts. In this study, the Charpy impact test was conducted to evaluate the service temperature of structural steel weld. The Charpy impact test is a commercial quality control test for steels and other alloys used in the construction of metallic structures. The test allows the material properties for service conditions to be determined experimentally in a simple manner with a very low cost. Standard V-notch Charpy specimens were prepared and tested under dynamic loading condition. The service temperatures of the weld metal, HAZ (heat affected zone) and base metal were derived by the absorbed energy and the impact test requirements; thus the applicability of the structural steels to cold regions was discussed in detail.

Nondestructive Evaluation on Hydrogen Effect of TIG Welded Stainless Steel for Component Design of Pressure Vessel

  • Lee, Jin-Kyung
    • Journal of Power System Engineering
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    • v.21 no.3
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    • pp.102-107
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    • 2017
  • A tungsten inert gas (TIG) welding method was used for the bonding of stainless steel. TIG welding using inert gas (He or Ar gas) is a method to prevent oxidation and nitriding of materials and to combine non-ferrous metals. This method has the advantage of obtaining a smooth weld surface. In this study, the welding characteristics of 304 stainless steel welded by TIG welding method were analyzed by using nondestructive technique. Ultrasonic and Acoustic Emission (AE) was applied to evaluate the micro-damage of TIG welded 304 stainless steel. The velocity and damping coefficient of ultrasonic wave showed a slight difference in HAZ, which is the welding part of stainless steel. The AE parameters of average frequency, rise time and event were analyzed for the dynamic behavior of stainless steel during loading. Optimal AE parameters for evaluating the degree of damage to the specimen have been derived. Fractograph and metal structures of 304 stainless steel using SEM and optical microscope were discussed.