• Title/Summary/Keyword: Hardness Distribution of HAZ

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Prediction Study of Heat-Affected Zone (HAZ) Properties in ERW Pipes using Hardness Distribution and Reverse Engineering Techniques (경도분포 및 역설계 기법을 활용한 ERW 파이프 열영향부(HAZ) 물성 예측 연구)

  • S. Lee;D. Hyun;S. Hong
    • Transactions of Materials Processing
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    • v.32 no.6
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    • pp.321-328
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    • 2023
  • To ensure driver safety, high-strength steel pipes are utilized in the chassis and internal structures design of automobiles. ERW(electric resistance welding) pipes, fabricated through welding at joints using electrical resistance, form a Heat-Affected Zone (HAZ) during the welding process. Due to characteristics such as increased hardness and reduced ductility compared to the base material, HAZ poses challenges in finite element analysis (FEA) for pipe shapes. In this study, for FEA considering HAZ properties, mechanical properties were measured through uniaxial tensile testing and digital image correlation (DIC) techniques after specimen fabrication. These measurements were validated using reverse engineering methods. Furthermore, hardness measurements and gaussian functions were employed to ascertain the hardness distribution within the HAZ, serving as a basis for subdividing the HAZ and modeling the pipe shape. To validate the effectiveness of the HAZ modeling approach, models were interpreted incorporating only base material properties and models incorporating average-calculated HAZ properties. Comparative analysis was performed, revealing that the model subdividing the HAZ based on hardness measurements closely approximated experimental values. This validation offered a methodology for HAZ modeling in FEA.

Statistical Properties of Vickers Hardness of Post Weld Heat Treated Friction Welded Parts in Alloy718 (Alloy718 마찰용접 후열처리재의 비커스 경도의 통계적 성질)

  • Kong, Yu-Sik;Kwon, Hyeok-Yong;Kim, Seon-Jin
    • Journal of Ocean Engineering and Technology
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    • v.23 no.6
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    • pp.105-110
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    • 2009
  • The objective of this paper is to investigate the statistical properties of Vickers hardness (HV) for friction welded parts in a Ni-based super alloy (Alloy718). In the case of post weld heat treatment (PWHT) parts, hardness tests were repeated for three different applied loads, 100, 200, and 300 g, with a duration time of 10 seconds. The arithmetic means of the Vickers hardness in heat affected zone (HAZ) materials were smaller than those of the base metal (BM) in all of the applied loads. The coefficient of variation (COV) for the BM and HAZ decreased by increasing the applied load. The probability distribution of the Vickers hardness followed the Weibull distribution well. The distribution of the Vickers hardness was not found to be symmetric. The shape parameter and scale parameter increased by increasing the applied load at both the BM and HAZ.

A Study on Statistical Properties of Vickers Hardness of Friction Welded Parts in Alloy718 Steel (Part 1. As-welded) (Alloy718 마찰용접재의 비커스 경도의 통계적 성질에 관한 연구 (As-welded 재의 경우를 중심으로))

  • Kwon, Hyeok-Yong;Choi, Sung-Yoong;Lee, Sang-Yeal;Kong, Yu-Sik;Kim, Seon-Jin
    • Journal of Ocean Engineering and Technology
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    • v.22 no.5
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    • pp.87-93
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    • 2008
  • The objective of this paper is the investigation of the statistical properties of Vickers hardness (HV) of friction welded parts in nickel based super resisting steel, alloy 718 steel. First, we examine the statistical properties on the case of as-welded parts. Several Virkers indentations were made under same nominal conditions. This was repeated for three different applied loads, 100, 200 and 300g with a duration time, 10 second. The arithmetic mean of Vickers hardness in base metal (BM) materials is larger than that of HAZ in all applied loads. The measure of dispersion, that is, the coefficient of variation (COV) for BM and HAZ is decreased by increasing with the applied load. The distribution of Vickers hardness was not found to be symmetric type. The probability distribution of Vickers hardness was well followed Weibull distribution. The shape parameter and the scale parameter (characteristic hardness) are increased by increasing with the applied load, as both BM and HAZ.

Hardness Distribution and Microstructures of Electric Resistance Spot Welded 1GPa Grade Dual Phase Steel (1GPa급 DP강 전기저항점용접부의 경도분포와 미세조직의 상관관계)

  • Na, Hye-Sung;Kong, Jong-Pan;Han, Tae-Kyo;Chin, Kwang-Geun;Kang, Chung-Yun
    • Journal of Welding and Joining
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    • v.30 no.2
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    • pp.76-80
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    • 2012
  • In this study, the effect of the welding current on the hardness characteristics and microstructure in the resistance spot welding of 1GPa grade cold-rolled DP steel was investigated, Also, correlation between the hardness and microstructure was discussed. In spite of the change in the welding current, the hardness distributions near weld was similar. the hardness in the HAZ and the fusion zone was higher than that of the base metal and the hardness in the fusion zone was variated with the location. Especially, the hardness of HAZ adjacent to the base metal showed maximum value, and softening zone in the base metal adjacent to HAZ was found. With the increasing of welding current, there were no difference in maximum hardness and average hardness in the fusion zone were, but the hardness of the softening zone reduced. The difference in the hardness in each location of weld due to grain size of prior austenite. The softening of the base metal occurred by tempering of the martensite.

A Study on the Rupture and Crack Propagation Dharacteristics in the Material Friction-Welded with Hetrogeneous Steels of SM40C and STS304 (SM40C와 STS304 이종재료 마찰용접재의 파단특성 및 크랙전파특성의 연구)

  • 오세욱;허정원;유재환;김재철
    • Journal of Welding and Joining
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    • v.10 no.4
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    • pp.230-239
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    • 1992
  • The specimens of two base metals and material friction-welded with hetrogeneous steels of SM40C and STS304 have been prepared and the characteristics of rupture and crack propagation of them have been examined. In the friction-welded material, the width of HAZ is 3.0mm for STS304 and 3.4mm for SM40C. The hardness distribution in HAZ of SM40C is decreased gradually as being getting off interface, but that in HAZ of STS304 is decreased remarkedly and the value of hardness becomes a little lower than that of the base metal in region of 1mm from interface and becomes a little higher than that of the base metal. The tensile strength of the friction-welded material appeared a little lower than that of the base metal and rupture by tensile load is developed in HAZ of STS304 and the position of rupture is at region of low hardness(1mm from interface). The crack propagation rates(da/dN) in both HAZ of the friction-welded material are a little higher than those in both base metals, but the difference are less except for the case of SM45C in low .DELTA. K value. It has been ascertained that the crack in the interface propagates selectively along the HAZ of SM40C and consequently the crack propagation rate is almost similar to that in the HAZ of SM40C.

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Study on Friction Welding of Torsion Bar Material(II) - Effect of PWHT on Friction Weld Quality- (토션바재의 마찰용접에 관한 연구(II) -용접 후열처리가 마찰용접 품질에 미치는 영향-)

  • Oh, Sae-Kyoo;Lee, Jong-Du
    • Journal of Ocean Engineering and Technology
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    • v.4 no.2
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    • pp.244-244
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    • 1990
  • 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. The results obtained are summarized as follows; 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. 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. 3) The micro-structure of the base meta., 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.

Study on Friction Welding of Torsion Bar Material(II) - Effect of PWHT on Friction Weld Quality- (토션바재의 마찰용접에 관한 연구(II) -용접 후열처리가 마찰용접 품질에 미치는 영향-)

  • Oh, Sae-Kyoo;Lee, Jong-Du
    • Journal of Ocean Engineering and Technology
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    • v.4 no.2
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    • pp.94-99
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    • 1990
  • 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. The results obtained are summarized as follows; 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. 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. 3) The micro-structure of the base meta., 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.

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Microstructure and Mechanical Properties of Clad(A4045/A3003) Al Alloy by Gas Tungsten Arc Welding (가스텅스텐아크 용접한 클래드(A4045/A3003) 알루미늄 합금의 기계적성질 및 미세조직)

  • Kim, Ki-Bin;Gook, Jin-Seon;Yoon, Dong-Ju;Kim, Byung-Il;Lee, Il-Cheon
    • Journal of Welding and Joining
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    • v.26 no.4
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    • pp.73-78
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    • 2008
  • In this paper, research was the variation of microstructure and mechanical properties of clad(A4045/A3003) Al alloy sheet by gas tungsten arc welding. Tensile properties of the gas tungsten arc welding joint decreased because of the softened heat affected zone(HAZ). The hardness of HAZ was lower than that of base metal, because relieved the work hardening effect of the welding heat. Hardness distribution of the weld zone with the base metal appears similarly, but the hardness of HAZ decreased remarkably. The microstructure in the weld zone of A4045 clad layer was formed a coarse columner grains of Si-rich. In the case of large weld heat input, the Si of the A4045 were diffused and until A3003 weld zone they decreased the strength.

The TRC Test for Cold Crack Susceptibility of Welded Zone for ABS EH32 Steel (인장구속 균열시험에 의한 ABS EH 32강 용접부 저온 균열 감수성 시험)

  • 정수원;박동환;김대헌
    • Journal of Welding and Joining
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    • v.2 no.2
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    • pp.62-69
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    • 1984
  • In this study, cold crack susceptibility of high strength steel (ABS EH32 Steel) welded zone with shielded metal are welding was investigated by tensile restraint cracking test method. Effects of diffusible hydrogen content on root cracking, lower critical stress, crack initiation and fracture mode, hardness value distribution of welded zone and fractograph were mainly investigated. Following conclusions are made: 1. In the view of the lower critical stress level, wet electrode, containing much diffusible hydrogen content shows lower value than dried electrode. 2. Hardness value(Hv 5kg) in Heat Affected Zone of wet electrode is higher than that of dried electrode caused by hydrogen embrittlement. 3. In the case of wet electrode, root crack is initiated and propagated in Heat Affected Zone and then propagated to weld metal, but using of dried electrode, root crack is initiated in Heat Affected Zone and propagated to weld metal without propagating in HAZ. 4. For wet electrode, quasi-cleavage fracture mode is majorly observed on the fracture surface of HAZ and partially of weld metal due to hydrogen embrittlement.

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A Study on fatigue Strength in the Friction Welded Joints of HSS-Co to SM55C Carbon Steel(I) (HSS-Co와 SM55C 이종 마찰용접재의 피로강도에 관한 연구(1))

  • 서창민;서덕영;이동재
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.4
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    • pp.918-928
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    • 1995
  • This paper deals with the various mechanical properties and fatigue strength in the FRW1 (friction welded interface) of high speed steel (HSS-Co) to SM55C through the tensile test, hardness test and fatigue test. The data of FRW specimens are also compared with those of the base materials (HSS-Co and SM55C steel). Three kinds of specimens used in this study are the friction welded joints, HSS-Co and SM55C carbon steel with circumferential notch, saw notch and smooth, respectively. It is confirmed that the applied welding conditions are optimum methods in order to minimize the heat affected zone (HAZ) and hardness distribution at the HAZ. The fatigue strengths at N = 10$^{6}$ cycles of smooth, circumferential notch and saw notch specimens in the FRW joints are about 299.2 MPa, 123.8 MPa and 247.5 MPA, respectively. The fatigue strength of the friction welded joints is almost equal to that of the SM55C carbon steel in the optimum welding conditions. The fatigue cracks initiated at the welded zone are propagated along the side of SM55C steel.